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Plantenberg, Detlef Holger. "Adaptive motion control for a four wheel steered mobile robot." Thesis, Nottingham Trent University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341262.
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For adaptive motion control of an autonomous vehicle, operating in a generally structured environment, position and velocity feedback are required to ascertain the vehicle location relative to a reference. Whilst the literature offers techniques for guiding vehicles along external references, autonomous vehicles should be able to navigate between despatch locations without the need to rely on external guidance systems. Considerations of the vehicle stability and manoeuvrability favour a vehicle design with four independently steered wheels. A new motion control methodology has been proposed which utilises the geometric relationship of the angular displacements and the rotations of the wheels to estimate the longitudinal and lateral motions of the vehicle. The motion controller consists of three building blocks: the motion control system comprising the position tracking and the motion command generation; the electronic system comprising a data acquisition system and proprietary power electronics; the mechanical system which includes an undercarriage enabling permanent contact of the wheels with the floor. The components have been designed not only to perform optimally in their specific functions but also to ensure full compatibility within the integrated system. For reliable deduction of the wheel rotations with a high degree of accuracy a dedicated data acquisition interface has been developed, which enables data to be captured in parallel from four optical encoders mounted directly on the wheel axles. Parallel sampling of the angular wheel position and parallel actuation of all steering motors improves the accuracy of the system state and gives a higher degree of certainty. Considering only circular motion of the vehicle, a method for calculating the steering angles and wheel speeds based on the complex notation is presented. By cumulating the displacement vectors of the vehicle motion and the location of the centre of rotation between consecutive samples of the controller, the path of the vehicle is estimated. The difference between the nominal and the deduced centre of rotation is determined to minimise deviations from the reference trajectory and to allow the controller to adapt to changes in the road/tyre interface characteristics. The individual mechanical and electronic components have been assembled and tested. Additionally, the performance of the electronic interface has been evaluated on a purpose built test-bed. For the experimental validation of the methodology, a simple method of mapping the centre of curvature with a pen mounted at the nominal centre of rotation has been proposed. Experiments have been conducted with both the steering angles fixed to their theoretical values for the nominal centre of rotation and with the proportional steering controller enabled. The results from the latter method have shown a significantly reduced deviation from the nominal centre of rotation. The data captured of the angular wheel positions and steering angle settings has been analysed off-line. Good agreement is obtained between the deduced and the actual centres of rotation for the measurements averaged over 1.5 seconds. A number of different centres of rotation have been investigated and the required steering angles to compensate for the deviation have been plotted to form a control surface for the motion controller. The deviation between the estimated and the actual centre of curvature was less than 1.6% and adequate results could be obtained with the proportional steering controller.
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Gandhi, Yogesh. "Motion planning and control for Differential Drive Wheel Mobile Robot (DDWMR)." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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This thesis proposes algorithms for motion planning to navigate robot in cluttered environment and a robust velocity-based tracking controller for Differential Drive Wheel Mobile Robot (DDWMR).
First, the thesis presents, an offline A* path planning algorithm is used to find sequence of optimal waypoints in a two-dimensional occupancy grid also taking in account obstacle avoidance minimum distance criteria and using these waypoints, reference trajectory is generated based on the constraints on DDWMR.
Second, the design of online non-linear back-stepping tracking controller for DDWMR, based on PSO algorithm in the selection of optimal controller gains.
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Arrizabalaga, Aguirregomezcorta Jon. "MPC based Caster Wheel Aware Motion Planning for Differential Drive Robots." Thesis, KTH, Mekatronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281702.
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The inherited rotation in a caster wheel allows movement in any direction, but pays at the expense of reaction torques. When implemented in a mobile robot, these forces have a negative impact in its performance. One approach is to restrict rotations on the spot by attaching a filter to the output of the motion planner. However, this formulation compromises the navigation’s completion in critical scenarios, such as parking, taking curves in narrow corridors or navigating at the presence of a high density of obstacles. Therefore, in this thesis we consider the influence of caster wheels in the motion planning stage, commonly presented as local planning. This work proposes a Model Predictive Control (MPC) based local planner that integrates the caster wheel physics into the motion planning stage. A caster wheel aware term is combined with a reference tracking based navigation, which leads to the formulation of the Caster Wheel Aware Local Planner (CWAWLP). Since this method requires knowing the caster wheel’s state and there is no sensor that provides this information, a caster wheel state observer is also formulated. In order to evaluate the impact of the caster wheel aware term, CWAWLP is compared to a Caster Wheel based Agnostic Local Planner (CWAGLP) and a Caster Wheel based Agnostic Planner Local Planner with Path Filter (CWPFLP). After running simulations for three case studies in a virtual framework, two experimental case studies are conducted in an intra-logistics robot. These are evaluated according to the navigation’s quality, motor torque usage and energy consumption. According to the patterns observed in the evaluation, CWAWLP covers a longer distance than CWAGLP wihout decreasing the navigation’s quality. At the same time, its motor torques are similar to the ones of CWPFLP. Therefore, CWAWLP is capable of considering caster wheel physics without sacrificing navigation capabilities. The formulated caster wheel aware term is compatible with any MPC based navigation algorithm and inherits the derivation of an observer capable of estimating caster wheel rotation angles and rolling speeds. Even if the caster wheel awareness has been implemented in a differential driven robot, this approach is also applicable to vehicles with an alternative drivetrain, such as car-like robots.Den ärvda rotationen i ett hjul möjliggör rörelse i vilken riktning som helst, men fås på bekostnad av reaktionsmoment. När de implementeras i en mobil robot har dessa krafter en negativ inverkan på dess prestanda. Ett tillvägagångssätt är att begränsa rotationer på plats genom att applicera ett filter på rörelseplannerns utgång. Denna formulering komprometterar dock navigeringens slutförande i kritiska scenarier, såsom parkering, kurvor i smala korridorer eller navigering i närheten av höga hinder. Därför beaktar vi i denna avhandling påverkan av hjul på hjulplaneringen, som ofta presenteras som lokal planering. Detta arbete föreslår en Model Predictive Control (MPC) -baserad lokal planerare som integrerar svängbara länkhjuls fysik i rörelseplaneringsstadiet. En kugghjulmedveten term kombineras med en referensspårningsbaserad navigering, vilket leder till formuleringen av Caster Wheel Aware Local Planner (CWAWLP). Eftersom denna metod kräver kunskap om svängbara länkhjuls tillstånd och det inte finns någon sensor som ger denna information, formuleras också en hjulhjulstillståndsobservatör. För att utvärdera effekten av det medvetna begreppet svängbara änkhjul jämförs CWAWLP med en Caster Wheel-baserad Agnostic Local Planner (CWAGLP) och en Caster Wheel-baserad Agnostic Planner Local Planner with Path Filter (CWPFLP). Efter att ha kört simuleringar för tre fallstudier i ett virtuellt ramverk genomförs två experimentella fallstudier i en intra-logistikrobot. Dessa utvärderas enligt navigeringens kvalitet, vridmomentanvändning och energiförbrukning. Enligt de mönster som observerats i utvärderingen når CWAWLP ett längre avstånd än CWAGLP utan att sänka navigeringens kvalitet. Samtidigt liknar motorns vridmoment dem som CWPFLP. Därför kan CWAWLP ta hänsyn till svängbara länkhjuls fysik utan att offra navigationsfunktionerna. Den formulerade medhjulningsmedveten termen är kompatibel med vilken MPC-baserad navigationsalgoritm som helst och ärver härledningen av en observatör som kan uppskatta hjulets rotationsvinklar och rullningshastigheter. Även om hjulhjälpmedvetenheten har implementerats i en differentierad robot, är detta tillvägagångssätt också tillämpligt på fordon med ett alternativt drivsystem, såsom billiknande robotar.
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Tsinias, Vasileios. "A hybrid approach to tyre modelling based on modal testing and non-linear tyre-wheel motion." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/17852.
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The current state-of-the-art tyre models tend to be demanding in parameterisation terms, typically requiring extensive and expensive testing, and computational power. Consequently, an alternative parameterisation approach, which also allows for the separation of model fidelity from computational demand, is essential. Based on the above, a tyre model is introduced in this work. Tyre motion is separated into two components, the first being the non-linear global motion of the tyre as a rigid body and the second being the linear local deformation of each node. The resulting system of differential equations of motion consists of a reduced number of equations, depending on the number of rigid and elastic modes considered rather than the degrees of freedom. These equations are populated by the eigenvectors and the eigenvalues of the elastic tyre modes, the eigenvectors corresponding to the rigid tyre modes and the inertia properties of the tyre. The contact sub-model consists of bristles attached to each belt node. Shear forces generated in the contact area are calculated by a distributed LuGre friction model while vertical tread dynamics are obtained by the vertical motion of the contact nodes and the corresponding bristle stiffness and damping characteristics. To populate the abovementioned system of differential equations, the modal properties of the rigid and the elastic belt modes are required. In the context of the present work, rigid belt modes are calculated analytically, while in-plane and out-of-plane elastic belt modes are identified experimentally by performing modal testing on the physical tyre. To this end, the eigenvalue of any particular mode is obtained by fitting a rational fraction polynomial expression to frequency response data surrounding that mode. The eigenvector calculation requires a different approach as typically modes located in the vicinity of the examined mode have an effect on the apparent residue. Consequently, an alternative method has been developed which takes into account the out-of-band modes leading to identified residues representing only the modes of interest. The validation of the proposed modelling approach is performed by comparing simulation results to experimental data and trends found in the literature. In terms of vertical stiffness, correlation with experimental data is achieved for a limited vertical load range, due to the nature of the identified modal properties. Moreover, the tyre model response to transient lateral slip is investigated for a range of longitudinal speeds and vertical loads, and the resulting relaxation length trends are compared with the relevant literature.
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Kim, Bumsoo. "Motion control of an autonomous vehicle with loss of wheel-ground contact avoidance using dynamic model based predictive control." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ58286.pdf.
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Seegmiller, Neal A. "Dynamic Model Formulation and Calibration for Wheeled Mobile Robots." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/460.
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Advances in hardware design have made wheeled mobile robots (WMRs) exceptionally mobile. To fully exploit this mobility, WMR planning, control, and estimation systems require motion models that are fast and accurate. Much of the published theory on WMR modeling is limited to 2D or kinematics, but 3D dynamic (or force-driven) models are required when traversing challenging terrain, executing aggressive maneuvers, and manipulating heavy payloads. This thesis advances the state of the art in both the formulation and calibration of WMR models We present novel WMR model formulations that are high-fidelity, general, modular, and fast. We provide a general method to derive 3D velocity kinematics for any WMR joint configuration. Using this method, we obtain constraints on wheel ground contact point velocities for our differential algebraic equation (DAE)-based models. Our “stabilized DAE” kinematics formulation enables constrained, drift free motion prediction on rough terrain. We also enhance the kinematics to predict nonzero wheel slip in a principled way based on gravitational, inertial, and dissipative forces. Unlike ordinary differential equation (ODE)-based dynamic models which can be very stiff, our constrained dynamics formulation permits large integration steps without compromising stability. Some alternatives like Open Dynamics Engine also use constraints, but can only approximate Coulomb friction at contacts. In contrast, we can enforce realistic, nonlinear models of wheel-terrain interaction (e.g. empirical models for pneumatic tires, terramechanics-based models) using a novel force-balance optimization technique. Simulation tests show our kinematic and dynamic models to be more functional, stable, and efficient than common alternatives. Simulations run 1K-10K faster than real time on an ordinary PC, even while predicting articulated motion on rough terrain and enforcing realistic wheel-terrain interaction models. In addition, we present a novel Integrated Prediction Error Minimization (IPEM) method to calibrate model parameters that is general, convenient, online, and evaluative. Ordinarily system dynamics are calibrated by minimizing the error of instantaneous output predictions. IPEM instead forms predictions by integrating the system dynamics over an interval; benefits include reduced sensing requirements, better observability, and accuracy over a longer horizon. In addition to calibrating out systematic errors, we simultaneously calibrate a model of stochastic error propagation to quantify the uncertainty of motion predictions. Experimental results on multiple platforms and terrain types show that parameter estimates converge quickly during online calibration, and uncertainty is well characterized. Under normal conditions, our enhanced kinematic model can predict nonzero wheel slip as accurately as a full dynamic model for a fraction of the computation cost. Finally, odometry is greatly improved when using IPEM vs. manual calibration, and when using 3D vs. 2D kinematics. To facilitate their use, we have released open source MATLAB and C++ libraries implementing the model formulation and calibration methods in this thesis.
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Miranda, La Hera Pedro Xavier. "Contributions to Motion Planning and Orbital Stabilization : Case studies: Furuta Pendulum swing up, Inertia Wheel oscillations and Biped Robot walking." Licentiate thesis, Umeå : Umepå universitet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1874.
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Kimmel, Shawn Christopher. "Considerations for and Implementations of Deliberative and Reactive Motion Planning Strategies for the Novel Actuated Rimless Spoke Wheel Robot IMPASS for the Two-Dimensional Sagittal Plane." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/32324.
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IMPASS is a novel spoke-wheel robot invented by researchers at the Robotics and Mechanisms Lab (RoMeLa) at Virginia Tech. The robot is driven by a rimless spoke wheel which can alter the length of any given spoke in the hub. This form of novel locomotion combines the efficiency of a wheeled robot and the mobility of a legged robot, arriving at a very practical mobility platform. A highly mobile robot such as IMPASS could prove very valuable in applications where the terrain is complex and dangerous, such as search and rescue, reconnaissance, or anti-terror response. A prototype has been constructed that effectively demonstrates the actuated spoke wheel concept using two wheels containing six spokes each.
Manually controlling the motion of two wheels and twelve spokes would be a daunting task for any operator. Due to this inherent complexity, automated motion control is a necessity for the IMPASS platform. The work presented here will discuss two different approaches to the motion planning problem for the two-dimensional sagittal plane. The first approach is deliberative in nature and depends on fairly accurate terrain sensing. The motion planning first decides on a set of contact points based on obstacle configurations and a Lagrangian interpolation of the terrain. A lower level motion planning component then executes the movements that guide the spoke ends to the contact points. The second motion planning approach is reactive in nature. Proprioceptive and tactile sensors are used to determine the robot's pose and immediate surroundings. These sensors directly affect the motion profile of the robot. The reactive approach follows much simpler logic, which theoretically will make it more robust.
Motion planning strategies were tested in simulation and on the IMPASS prototype. Both strategies proved to be well suited for different applications. The deliberative control was very successful in a structured environment, whereas the reactive control was able to cross a wider variety of terrain. The results from the testing also provided some insight into variables introduced by the hardware. Future improvements to the motion planning control include accounting for these variables in the hardware and eventually developing three-dimensional motion planning algorithms based on the lessons learned from the two-dimension case.Master of Science
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Grönlund, Arthur, and Christos Tolis. "Riderless self-balancing bicycle : Derivation and implementation of a time variantlinearized state space model for balancing a bicycle in motion by turning the front wheel." Thesis, KTH, Maskinkonstruktion (Inst.), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230169.
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Självkörande fordon börjar bli en allt större verklighet isamhället, där bussar och bilar snart kan komma att implementeraspå större skala. Självkörande tvåhjuliga fordonkan vara en möjlig lösning på mindre fordon i städer därutrymme blir mer och mer sparsamt.Syftet med detta projekt har varit att ta fram och implementeraen linjäriserad tidsvarierande tillståndsmodell förbalansreglering av en elcykel genom vridning av framhjulet.För att testa modellen konstruerades en liten demonstratormed vilken experiment och tester utfördes.Den slutsats som drogs var att modellen mycket väl skullekunna vara en lösning för balansering av en elcykel, menatt fortsatta undersökningar bör genomföras på en större skala för att en mer definitiv slutsats skall kunna dras.Self-driving vehicles are becoming more and more prevalentin society, with buses and cars close to being implementedin the public domain. Self-driving two-wheeled vehiclescould be a solution for space-efficient transportationin cities, where space is becoming a larger issue.The purpose of this project was to develop and implement alinearized time variant state space model for balancing sucha two-wheeled vehicle in the form of a bicycle by turningits front wheel. To test the derived model a small demonstratorwas built and experimented with.The final conclusion was that the model could be a simplesolution for balancing an electric bicycle. However, furtherexperimentation on a bigger scale would have to be doneto reach a more decisive conclusion.
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Hosseinipour, Milad. "Electromechanical Design and Development of the Virginia Tech Roller Rig Testing Facility for Wheel-rail Contact Mechanics and Dynamics." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82542.
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The electromechanical design and development of a sophisticated roller rig testing facility at the Railway Technologies Laboratory (RTL) of Virginia Polytechnic and State University (VT) is presented. The VT Roller Rig is intended for studying the complex dynamics and mechanics at the wheel-rail interface of railway vehicles in a controlled laboratory environment. Such measurements require excellent powering and driving architecture, high-performance motion control, accurate measurements, and relatively noise-free data acquisition systems. It is critical to accurately control the relative dynamics and positioning of rotating bodies to emulate field conditions. To measure the contact forces and moments, special care must be taken to ensure any noise, such as mechanical vibration, electrical crosstalk, and electromagnetic interference (EMI) are kept to a minimum. This document describes the steps towards design and development of all electromechanical subsystems of the VT Roller Rig, including the powertrain, power electronics, motion control systems, sensors, data acquisition units, safety and monitoring circuits, and general practices followed for satisfying the local and international codes of practice.
The VT Roller Rig is comprised of a wheel and a roller in a vertical configuration that simulate the single-wheel/rail interaction in one-fourth scale. The roller is five times larger than the scaled wheel to keep the contact patch distortion that is inevitable with a roller rig to a minimum. This setup is driven by two independent AC servo motors that control the velocity of the wheel and roller using state-of-the-art motion control technologies. Six linear actuators allow for adjusting the simulated load, wheel angle of attack, rail cant, and lateral position of the wheel on the rail. All motion controls are performed using digital servo drives, manufactured by Kollmorgen, VA, USA.
A number of sensors measure the contact patch parameters including force, torque, displacement, rotation, speed, acceleration, and contact patch geometry. A unified communication protocol between the actuators and sensors minimizes data conversion time, which allows for servo update rates of up to 48kHz. This provides an unmatched bandwidth for performing various dynamics, vibrations, and transient tests, as well as static steady-state conditions.
The VT Roller Rig has been debugged and commissioned successfully. The hardware and software components are tested both individually and within the system. The VT Roller Rig can control the creepage within 0.3RPM of the commanded value, while actively controlling the relative position of the rotating bodies with an unprecedented level of accuracy, no more than 16nm of the target location. The contact force measurement dynamometers can dynamically capture the contact forces to within 13.6N accuracy, for up to 10kN. The instantaneous torque in each driveline can be measured with better than 6.1Nm resolution. The VT Roller Rig Motion Programming Interface (MPI) is highly flexible for both programmers and non-programmers. All common motion control algorithms in the servo motion industry have been successfully implemented on the Rig. The VT Roller Rig MPI accepts third party motion algorithms in C, C++, and any .Net language. It successfully communicates with other design and analytics software such as Matlab, Simulink, and LabVIEW for performing custom-designed routines. It also provides the infrastructure for linking the Rig's hardware with commercial multibody dynamics software such as Simpack, NUCARS, and Vampire, which is a milestone for hardware-in-the-loop testing of railroad systems.Ph. D.
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GRÖNLUND, ARTHUR, and CHRISTOS TOLIS. "Riderless self-balancing bicycle : Derivation and implementation of a time variant linearized state space model for balancing a bicycle in motion by turning the front wheel." Thesis, KTH, Mekatronik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-232995.
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Self-driving vehicles are becoming more and more prevalent in society, with buses and cars close to being implemented in the public domain. Self-driving two-wheeled vehicles could be a solution for space-efficient transportation in cities, where space is becoming a larger issue. The purpose of this project was to develop and implement a linearized time variant state space model for balancing such a two-wheeled vehicle in the form of a bicycle by turning its front wheel. To test the derived model a small demonstrator was built and experimented with. The final conclusion was that the model could be a simple solution for balancing an electric bicycle. However, further experimentation on a bigger scale would have to be done to reach a more decisive conclusion.Självkörande fordon börjar bli en allt större verklighet i samhället, där bussar och bilar snart kan komma att implementeras på större skala. Självkörande tvåhjuliga fordon kan vara en möjlig lösning på mindre fordon i städer där utrymme blir mer och mer sparsamt. Syftet med detta projekt har varit att ta fram och implementera en linjäriserad tidsvarierande tillståndsmodell för balansreglering av en elcykel genom vridning av framhjulet. För att testa modellen konstruerades en liten demonstrator med vilken experiment och tester utfördes. Den slutsats som drogs var att modellen mycket väl skulle kunna vara en lösning för balansering av en elcykel, men att fortsatta undersökningar bör genomföras på en större skala för att en mer definitiv slutsats skall kunna dras.
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Du, Wenqian. "Motion generation of four-limb robots using whole-body torque control." Thesis, Sorbonne université, 2020. http://www.theses.fr/2020SORUS067.
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Cette thèse présente la génération de mouvements de deux robots quadrupèdes : la génération du mode roulement d’un robot quadrupède sur roues, et la génération du mode trot d’un robot quadrupède avec mécanisme en parallélogramme. Ces deux générateurs de mouvement sont développés en utilisant des modèles de dynamiques généralisées et de dynamiques centroidales. Nous introduisons le concept de contrôleur en impédances priorisées et nous proposons un nouveau modèle de dynamiques qui incorpore une hiérarchie de contrôle multitâche. Nous l’intégrons dans le nouveau modèle dynamique pour améliorer quatre différents cadres de travail pour le contrôle hiérarchisé. Puis, nous proposons deux générateurs de mouvements pour le mode roulement de TowrISIR. Le mouvement des roues est extrait selon les mouvements des pattes et de la base. Le premier générateur de mouvement des roues est développé en combinant le modèle cinématique et le modèle dynamique et de moments centroidaux. Le deuxième générateur de mouvements est plus général et permet de franchir des terrains accidentés avec différences d’altitude. Un générateur de mouvements corps complets est développé en combinant un modèle de mouvements centré sur roues et un modèle proposé de contrôle d’altitude. Enfin, nous proposons un nouveau principe de locomotion à pattes pour notre robot quadrupède, QuadISIR, qui peut générer les mouvements des pattes automatiquement en utilisant les propriétés centroidales, sans nécessiter l’approximation de pattes sans masse. La position des pattes suit le mouvement de la base sans interférer avec les contraintes de contact. Le balancement des pattes compense le délai généré par les pattes de postureThe thesis presents the whole-body motion generation of two four-limb robots, including the rolling-mode generation of a quadruped-on-wheel robot, TowrISIR, and the trotting-mode generation of a quadruped robot with parallelogram mechanisms, QuadISIR. Both the wheeled and legged motion generators are developed by using the generalized dynamics and centroidal dynamics models, and they are verified by our improved proposed torque controllers. We propose the concept called prioritized impedance controller, and we propose one new dynamics model to embody multi-task control hierarchy. We integrate it into the new dynamics model to improve four kinds of hierarchical operational-space torque control frameworks. Then, we propose two rolling-mode motion generators of TowrISIR. By given legged-suspension motion, the wheel motion is extracted out depending on base and legged motions, then the first wheel motion generator is developed by combining the kinematics model and centroidal momentum/dynamics model. The second whole-body motion generator is more general which enables the robot to cross rough terrains with much-altitude difference. Then the whole-body motion generator is developed by combining further the wheel-center motion model and a proposed altitude control model. Finally, we propose a new legged locomotion principle for one quadruped robot, QuadISIR, which can generate legged motion automatically using the centroidal properties without massless-leg assumption. The virtual joint between the base and each-leg CoM is used. The stance legs follow the base motion without conflicting the contact constraints. The swing legs compensate the delay influences by the stance legs
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Theron, Willem F. D. "Analysis of the rolling motion of loaded hoops." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/1206.
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Thesis (PhD (Mathematical Sciences. Applied Mathematics))--University of Stellenbosch, 2008.This dissertation contains a detailed report on the results of a research project on the behaviour of a dynamical system consisting of a hoop to which a heavy particle is fixed at the rim. This loaded hoop rolls on a rough surface while remaining in the vertical plane. The motion of the hoop consists of various, possibly alternating, phases consisting of rolling without slipping, spinning or skidding motion and in some cases ends by hopping off the surface. A general mathematical model is developed, consisting of a system of second order ordinary differential equations, one for each of the three degrees of freedom. Analytic solutions are obtained in some cases; otherwise numerical solutions are used. Three specific applications of the general model are dealt with. In the first application the problem of massless hoops is investigated. The main emphasis is on the somewhat controversial question of what happens after the normal reaction becomes zero in a position where the particle is still moving downwards. A new result shows that the hoop can continue to move horizontally in a motion defined as skimming. The second application deals with rigid hoops and a large number of detailed results are presented. Classification schemes for the different types of behaviour are introduced and summarised in the form of phase diagrams. Some emphasis is placed on the rather amazing number of different patterns of motion that can be obtained by varying the parameters. In the third application two elastic models are analysed, with the primary purpose of explaining one aspect of the reported behaviour of experimental hoops, namely hopping while the particle is moving downwards. A chapter on experimental models rounds off the project.
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Le, Marquer Nicolas. "Vers la synthèse d'une roue à rochet moléculaire." Thesis, Le Mans, 2015. http://www.theses.fr/2015LEMA1025/document.
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Dans le domaine des machines moléculaires, la recherche d'un système produisant un mouvement orienté fait l'objet d'intenses recherches. Des résultats ont déjà été obtenus en ce sens mais n'exploitant pas le mouvement brownien comme le font les systèmes trouvés dans la nature comme la myosine. Nous proposons donc la synthèse d'une roue à rochet avec pour but de mimer ce phénomène, si besoin avec une activation de faible énergie. La première partie de ce travail a consisté en la conception par modélisation de l'équivalent synthétique d'une roue à rochet, basiquement constituée d'une roue crantée et d'un cliquet en vue d'étudier si une telle molécule pourrait produire une rotation orientée. Ce système est constitué d'un motif bishomoinositol fonctionnalisé en tant que roue et d'un cycloadduit de l'anthracène comme cliquet, liés par des bras espaceurs. La synthèse d'un système modèle dans lequel un motif bicyclo[2.2.2]octane joue le rôle de roue simplifiée a été menée afin de valider les différentes stratégies de synthèse. A cette occasion, une méthode alternative de la synthèse du diacide bicyclo[2.2.2]octanoïque a été mise au point ainsi qu'une méthodologie d'estérification compatible avec cet acide ainsi que le diacide 9,10-anthracènedioïque. Nous sommes ainsi parvenus à obtenir le produit de macrolactonisation, avec de possibles application comme roue de nanovéhicules. La synthèse du modèle a été l'occasion de pointer certaines impossibilités synthétiques au niveau des espaceurs (éthers, amides, triazoles, tétrazoles, alcènes) dans le système original. Un nouveau travail de modélisation a permis d'aboutir à une cible accessible synthétiquement conservant le comportement de roue à rochet. Dans cette optique, la synthèse du bishomoinositol fonctionnalisé par des acides en tête de pont a été entreprise par une première voie incluant ces groupements au départ de la synthèse, une seconde voie introduisant ces groupements en fin de séquenceIn the field of molecular machines, systems producing an oriented motion have been intensely looked for. Results, obtained toward this goal, do not exploit Brownian motion whereas it happens in natural systems such as myosin. Hereby we propose the synthesis of a molecular ratchet aiming to mimic this phenomenon or to be able to act as a molecular motor through low energy activation. The first part of this work consisted in the design by modelisation of a synthetic equivalent of a ratchet, basically consisting of a toothed wheel and a pawl. This study aim at determining if such a molecule could produce an oriented motion by simple Brownian motion. This system is consisting of a functionalized bishomoinositol moiety as the wheel and a cycloadduct of anthracene as the pawl, linked by spacers allowing the adjustment of the energy barriers. The synthesis of a model where a bicyclo[2.2.2]octane moiety plays the role of a simplified wheel has been conducted in order to validate various synthetic strategies. This gave the opportunity to develop an alternative method of the synthesis of the bicyclo[2.2.2]octanedicarboxylic diacid as well as an esterification methodology compatible with the bulkiness or low solubility of both partners. The macrolactonization product could be obtained and opens some possible applications as nanovehicle wheels. The synthesis of the model was the occasion to highlight synthetic limitations concerning the spacers (ethers) in the original system. A new series of targets taking into account the synthetic restrictions while keeping the ratchet behavior were designed. The discovery of another synthetic difficulties (amides, triazoles, tetrazoles and alkenes) yielded a single refined target. Toward this goal, the synthesis of the bishomoinositol functionalized in the bridgehead position was engaged in a first pathway including these functions at the beginning of the synthesis, the second way introducing them on the bishomoinositol at the end of the sequence
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Moreno, Blanc Javier. "Improvement of the implementation of an Assistant Personal Robot." Doctoral thesis, Universitat de Lleida, 2017. http://hdl.handle.net/10803/457621.
Full textAbstract:
Aquesta memòria presenta la investigació realitzada amb l'objectiu de millorar la implementació d'un Assistent Personal Robòtic (APR) basat en un robot mòbil per aplicacions en entorns domèstics. Aquesta implementació de noves tecnologies robòtiques ha permès el desenvolupament de noves aplicacions d'assistència personal contribuin a millorar la qualitat de vida de les persones.
La primera part de la memòria es centra en el desenvolupament mecànic, consistent en un sistema de mobilitat holonómic basat en l'ús de tres rodes omnidireccionals desfasades 120º.
Per l´objectiu de la millora sobre la ubicació del robot mòbil en el pla XY s'ha realitzat l'estudi i caracterització d'un sensor de baix cost basat en l'aplicació de l'efecte Doppler.
Tambe s'han explorat les possibilitats d'utilitzar una Tablet amb Google Android com a dispositiu de telecontrol, reunin en un únic dispositiu diversos sensors i elements d'interacció.
L'últim apartat de la memòria es centra en l'estudi d'una solució que permeti al robot desplaçarse per les habitacions d’una casa u oficina incorporan un accessori mecànic que li permeti obrir portes convencionals.Esta memoria presenta la investigación realizada con el objetivo de mejorar la implementación de un Asistente Personal Robótico (APR) basado en un robot móvil para aplicaciones en entornos domésticos. Esta implementación de tecnologías robóticas permite el desarrollo de nuevas aplicaciones de asistencia personal, contribuyendo a mejorar la calidad de vida de las personas. La primera parte de la investigación se centra en el desarrollo mecánico, presentando un sistema de movilidad holonómico basado en el uso de tres ruedas omnidireccionales desfasadas 120º. La mejorara de la ubicación del robot móvil en el plano XY se ha realizado a través del estudio y caracterización de un sensor de bajo coste, basado en la aplicación del efecto Doppler. También se han explorado las posibilidades de utilizar una Tablet con Google Android como sistema de control, reuniendo en un único dispositivo varios sensores y elementos de interacción. El último apartado de la memoria estudia el problema de la movilidad del robot por distintas habitaciones, incorporado al diseño básico un accesorio mecánico que le permite abrir puertas convencionales.
This memory presents the research carried out with the objective of improving the implementation of an Assistant Personal Robot (APR) based on a mobile robot for applications in domestic environments. This implementation allows the development of new assistance devices, which can be applied to significantly improve the quality of life of people. The first part of the research focuses on the mechanical development, which describes the holonomic mobility system based on the use of three omnidirectional wheels, shifted 120°. To the improvement of the location of the mobile robot in the XY plane, this research has been performed by means of the study and characterization of a low cost optical sensor based on the application of the Doppler Effect. One of the most characteristic elements of a care robot is its control unit. The research performed has explored the possibilities of a Tablet with Google Android as a control system, bringing together in a single body several sensors and interaction elements. The last section of the memory has been focused on the study of the problem of moving the mobile robot through closed rooms of the house, to this end, a mechanical accessory has been incorporated in order to mechanically open a conventional door.
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Corominas, Hife Kensell Kyle. "Four Wheel Steering : Comparison with two wheel steering." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153632.
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What are the differences between two wheel steering and four wheel steering? The aim of this project is to compare these two in terms of advantages gained from four wheel steering. A simulation is conducted on ADAMS Cars platform based on the RCV (Research Concept Vehicle) model, developed at KTH in Stockholm.
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Bott, M. P. "A new, robust, and generic method for the quick creation of smooth paths and near time-optimal path tracking." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2095.
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Robotics has been the subject of academic study from as early as 1948. For much of this time, study has focused on very specific applications in very well controlled environments. For example, the first commercial robots (1961) were introduced in order to improve the efficiency of production lines. The tasks undertaken by these robots were simple, and all that was required of a control algorithm was speed, repetitiveness and reliability in these environments. Now however, robots are being used to move around autonomously in increasingly unpredictable environments, and the need for robotic control algorithms that can successfully react to such conditions is ever increasing. In addition to this there is an ever-increasing array of robots available, the control algorithms for which are often incompatible. This can result in extensive redesign and large sections of code being re-written for use on different architectures. The thesis presented here is that a new generic approach can be created that provides robust high quality smooth paths and time-optimal path tracking to substantially increase applicability and efficiency of autonomous motion plans. The control system developed to support this thesis is capable of producing high quality smooth paths, and following these paths to a high level of accuracy in a robust and near time-optimal manner. The system can control a variety of robots in environments that contain 2D obstacles of various shapes and sizes. The system is also resilient to sensor error, spatial drift, and wheel-slip. In achieving the above, this system provides previously unavailable functionality by generically creating and tracking high quality paths so that only minor and clear adjustments are required between different robots and also be being capable of operating in environments that contain high levels of perturbation. The system is comprised of five separate novel component algorithms in order to cater for five different motion challenges facing modern robots. Each algorithm provides guaranteed functionality that has previously been unavailable in respect to its challenges. The challenges are: high quality smooth movement to reach n-dimensional goals in regions without obstacles, the navigation of 2D obstacles with guaranteed completeness, high quality smooth movement for ground robots carrying out 2D obstacle navigation, near time-optimal path tracking, and finally, effective wheel-slip detection and compensation. In meeting these challenges the algorithms have tackled adherence to non-holonomic constraints, applicability to a wide range of robots and tasks, fast real-time creation of paths and controls, sensor error compensation, and compensation for perturbation. This thesis presents each of the above algorithms individually. It is shown that existing methods are unable to produce the results provided by this thesis, before detailing the operation of each algorithm. The methodology employed is varied in accordance with each of the five core challenges. However, a common element of methodology throughout the thesis is that of gradient descent within a new type of potential field, which is dynamic and capable of the simultaneous creation of high-quality paths and the controls required to execute them. By relating global to local considerations through subgoals, this methodology (combined with other elements) is shown to be fully capable of achieving the aims of the thesis. It is concluded that the produced system represents a novel and significant contribution as there is no other system (to the author’s knowledge) that provides all of the functionality given. For each component algorithm there are many control systems that provide one or more of its features, but none that are capable of all of the features. Applications for this work are wide ranging as it is comprised of five component algorithms each applicable in their own right. For example, high quality smooth paths may be created and followed in any dimensionality of space if time optimality and obstacle avoidance are not required. Broadly speaking, and in summary, applications are to ground-based robotics in the areas of smooth path planning, time optimal travel, and compensation for unpredictable perturbation.
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Minda, Aditi. "The Wheel." Digital Commons at Loyola Marymount University and Loyola Law School, 2011. https://digitalcommons.lmu.edu/etd/70.
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Morini, Matteo. "Solar Wheel." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
L'elaborato tratta una particolare ruota solare prodotta da Marand, usata per le competizioni automobilistiche solari.
Dopo un'introduzione, che spiega chi è Marand, in cosa consiste la ruota a grandi linee e gli aspetti generali di cui tenere conto, segue una descrizione dei componenti principali che formano la ruota ed infine la procedura per smontarla/montarla.
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Silva, Seth F. "Applied System Identification for a Four Wheel Reaction Wheel Platform." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/328.
Full textAbstract:
Applied System Identification for a Four Wheel Reaction Wheel Platform
By
Seth Franklyn Silva
At the California Polytechnic State University, San Luis Obispo there is a four-wheel reaction wheel pyramidal simulator platform supported by an air-bearing. This simulator has the current capability to measure the wheel speeds and angular velocity of the platform, and with these measurements, the system identification process was used to obtain the mass properties of this simulator. A handling algorithm was developed to allow wireless data acquisition and command to the spacecraft simulator from a “ground” computer allowing the simulator to be free of induced torques due to wiring. The system identification algorithm using a least squares estimation scheme was tested on this simulator and compared to theoretical analysis. The resultant principle inertia about the z-axis from the experimental analysis was 3.5 percent off the theoretical, while the other inertias had an error of up to 187 percent. The error is explained as noise attributed to noise in the measurement, averaging inconsistencies, low bandwidth, and derivation of accelerations from measured data.
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LEJDEBY, ANGELICA, and KARL HERNEBRANT. "Omni wheel robot." Thesis, KTH, Maskinkonstruktion (Inst.), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-191520.
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This project is about building a three wheeled robot car with Omni wheels. Omni wheels can make a robot drive sideways without rotating first. They can make a robot rotate at the same time as it goes straight ahead. An Omni wheel robot can for example be good choice for a tracking robot, though it can drive more effective than a robot car with regular wheels. The thing that speaks against Omni wheels is that it has more friction and it takes more power to rotate the wheels. This robot car is an obstacles avoiding robot that should with help of Ultrasonic sensors and IR-sensors be able to drive around in a room without crashing in to objects or walls. With the help of Omni wheels the robot should drive without rotating much which makes it more effective than a robot car with regular wheels.Det här projektet handlar om att bygga en trehjulig robotbil med Omnihjul. Omnihjul kan göra det möjligt för en robot att köra i sidled utan att först rotera. De kan också möjliggöra för en robot att rotera samtidigt som den kör rakt fram i en rak linje. En Omnihjulrobot kan till exempel vara ett bra val som spårningsrobot. För att den kan köra mer effektivt än en robotbil med vanliga hjul. Det som talar mot Omnihjul är att de har mer friktion och det krävs mer kraft för att rotera hjulen. Den här robotbilen är en hinderundvikande robot som med hjälp av Ultraljudssensorer och IR-sensorer ska kunna köra runt i ett rum utan att krasha in i objekt eller väggar. Med hjälp av Omnihjul ska roboten kunna köra utan att rotera mycket, vilket gör den mer effektiv än en robotbil med vanliga hjul.
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Logan, Jeffery Jay. "Control and Sensor Development on a Four-Wheel Pyramidal Reaction Wheel Platform." DigitalCommons@CalPoly, 2008. https://digitalcommons.calpoly.edu/theses/27.
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The Pyramidal Reaction Wheel Platform, or PRWP, is used to simulate three-axis controls in a torque free space-like environment. The primary purpose of the system will be to evaluate the effects of conjoining sensors to maximize pointing accuracy. Furthermore, the system will incorporate a star tracker in conjunction with a Simulated Star Field (SSF) to better estimate the PRWP orientation. For the sake of this document, however, the goal is to implement a gyroscope, wheel rate sensors, and a make-shift accelerometer—to the PRWP—and integrate a controls algorithm such that three-axis controls are achieved for the PRWP. Three sensors were either better integrated into the system or added altogether. Tachometers were created as a form of hardware circuitry to measure each wheel rate with an accuracy of approximately 2.5 Hz (nearly 15 radians per second). The TAC board circuitry converted each motors encoder output into a speed by use of a frequency to voltage converter. Additionally, although three gyroscopes had been implemented previously, the system was better incorporated into the model such that it was directly transformed via a ROBOSTIX ADC converter before being relayed to SIMULINK via a Bluetooth link. The MEMS gyroscopes allowed for very accurate rate measurements—with a minimum resolution of approximately 0.25 radians per second. Finally, a makeshift accelerometer was incorporated into the system for the purpose of system identification. The accelerometer was incorporated into the system by utilizing a discrete time derivative of the gyroscope readings. However, thankfully a system of two accelerometers can be later utilized to achieve an accuracy of approximately 6 degrees per second-second in the x-axis and 2-3 degrees per second-second in the y- and z-axes. A controls test was performed where the starting location was qo=[0, 0, sqrt(2)/2, sqrt(2)/2] and the target location was qc=[0, 0, 0, 1]. At 80 seconds, the pointing accuracy was 70 degrees around the target and the system was unable to settle during the 80 second trial. The inaccuracy was because of the low frequency of operation of the system—1 Hz. Additionally, the platform reacts slowly to sensor readings and commands. The coupling of these issues causes the pointing accuracy to high. Furthermore, through experimental testing, the maximum wheel rate was found to be approximately 6400 RPM at a duty cycle of 50% at an 8000Hz PWM application due to the Pololu MD01B design limitations: low voltage range (up to 16V), low limit current limiter (5A), and high susceptibility to overheating for large currents.
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Telliskivi, Tanel. "Wheel-rail Interaction Analysis." Doctoral thesis, KTH, Machine Design, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3532.
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A general approach to numerically simulating wear in rollingand sliding contacts is presented in this thesis. A simulationscheme is developed that calculates the wear at a detailedlevel. The removal of material follows Archards wear law,which states that the reduction of volume is linearlyproportional to the sliding distance, the normal load and thewear coefficient. The target application is the wheel-railcontact.
Careful attention is paid to stress properties in the normaldirection of the contact. A Winkler method is used to calculatethe normal pressure. The model is calibrated either withresults from Finite Element simulations (which can include aplastic material model) or a linear-elastic contact model. Thetangential tractions and the sliding distances are calculatedusing a method that incorporates the effect of rigid bodymotion and tangential deformations in the contact zone.Kalkers Fastsim code is used to validate the tangentialcalculation method. Results of three different sorts ofexperiments (full-scale, pin-on-disc and disc-on-disc) wereused to establish the wear and friction coefficients underdifferent operating conditions.
The experimental results show that the sliding velocity andcontact pressure in the contact situation strongly influencethe wear coefficient. For the disc-on-disc simulation, therewas good agreement between experimental results and thesimulation in terms of wear and rolling friction underdifferent operating conditions. Good agreement was alsoobtained in regard to form change of the rollers. In thefull-scale simulations, a two-point contact was analysed wherethe differences between the contacts on rail-head to wheeltread and rail edge to wheel flange can be attributed primarilyto the relative velocity differences in regard to bothmagnitude and direction. Good qualitative agreement was foundbetween the simulated wear rate and the full-scale test resultsat different contact conditions.
Keywords:railway rail, disc-on-disc, pin-on-disc,Archard, wear simulation, Winkler, rolling, sliding
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Gerasimoff, Steven (Steven A. ). "Open wheel racecar steering." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112590.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (page 36).
The steering system of a rear wheel drive open wheel racecar is the only directional control the driver possesses while driving. Steering linkages must be carefully designed to allow cars to navigate turns without exhausting the driver. Motorsports vehicles are designed to make tight turns while maximizing tire grip to maintain higher velocities in corners. Steering geometry must be optimized not only for car performance, but also to maximize driver comfort and improve the "feel" of the vehicle. In competitive motorsports, the steering system is critical to vehicle performance: an incorrectly designed system can at best cost a few fractions of a second on the track, and at worst cause severe driver injury. In the Formula SAE competition, student teams are tasked with designing and manufacturing all subsystems of a racecar for an annual competition while balancing safety, cost, and performance. This thesis will introduce fundamentals of steering system design, and will document in detail the design, analysis, manufacture, and testing of the 2017 MIT FSAE steering system.
by Steven Gerasimoff.
S.B.
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Gräsberg, Pontus, and Bill Lavebratt. "Reaction Wheel Stabilized Stick." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264481.
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Control theory can be used to make an unstable system stable. This thesis seeks to do this, where the system is a two DOF inverted pendulum with reaction wheels for stabilisation. The thesis also seeks to answer what is most important for making it stabilize for a longer period of time. It was decided that a state space controller was to be used with various sensors measuring the states. To be able to design a functioning demonstrator, a mathematical model of the system dynamics was developed. In the end the demonstrator proved to function as desired, being able to balance indefinitely. It was found that it is absolutely necessary to either give the controller a perfect set point or to implement an automatic set point.Reglerteknik kan användas för att göra ostabila system stabila. Målet med detta projekt var att göra detta med ett system i form av en inverterad pendel med två frihetsgrader som balanseras med hjälp av två svänghjul. Projektet söker att besvara frågan om vad som är de viktigaste faktorerna för att få systemet att vara stabilt över en längre tid. En tillståndsåterkoppling användes som regulator vilket innebar att flera olika sensorer behövdes för att mäta de olika tillstånden. För att kunna konstruera en fungerande prototyp utvecklades en matematisk modell av systemet vilken användes för simulering av systemet. Till slut konstruerades en fungerade prototyp som till synes kunde balansera över oöverskådlig tid. En av de faktorer som visade sig påverka huruvida systemet uppnår stabilitet över längre tid var hur bra referenspunkt som gavs till regulatorn, det vill säga det tillstånd som regulatorn reglerar systemet mot. Det visade sig vara möjligt att implementera en självjusterande referenspunkt som gjorde systemet stabilt över tid.
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Hwang, Choal Hee. "The wheel of rebirth." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1327603492.
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Hamnholm, Löfgren Teodor. "Wheel Brake Noise Analysis." Thesis, Linköpings universitet, Reglerteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-138011.
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The scope of this thesis is to investigate methods of recording, processing and analysing sound data from wheel brake testing in dynamometers with focus on detecting and measuring squeal. The desired outcome is a method that Scania can use to record and analyse brake sound. A literature study was made to find relevant methodologies and tools proposed in papers, books and industry standards. These methods were tried and evaluated by recording and analysing real sound data and other signals from one of Scanias dynamometers. The resulting method includes directions on what hardware to use, how to set it up and an algorithm that computes a spectral limit based on normal sound data. This limit is then used as reference when evaluating other recordings. To increase signal to noise ratio, an adaptive filter is proposed to attenuate background noise in the recordings, in particular from the dynamometer and ventilation system. The conclusion is that it is possible to find squeal using spectral limits based on normal data. The performance of the algorithm is a compromise between being very effective but rather complex, or slightly less effective but also less complex. Its performance is also highly dependent on how squeal is defined. A very narrow definition will only find certain types of squeal while a more broad definition will find more squeal, but also potentially mislabel some recordings.
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Navas, Medrano Samuel. "Autonomous Wheel Loader Simulator." Thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-38053.
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The usage of a robotic simulator hasprovidedthe advantages of the efficientdevelopment and testing of robotics applications, saving time and resources and making easier publics demonstrations. This thesis project consists on the simulation of a wheel loader at an industrial environment inthe cycle of material handling. For the development of the Project have been used the Robot Operating System (ROS) and Gazebo frameworks which allows to reproduce the 3D map of the work site as well as the robotic wheel loaderand simulate it in a realistic way. The developed softwarealsoprovidesthemechanism to drive the wheel loader throughthereproduced terrain, to controlthe movement of the different articulated joints of the robot, to recompile information of the environmentthroughdifferent sensors (Laser, Odometry, GPS, IMU, etc) and to provide of a waypoint routes to the robot. Furthermore the simulator will be able to reproduce and integrate an asphalt plant modelto the scenario. Allowing an interaction with the wheel loader, this will transport gravel from the piles of the terrain to the pocket of the asphalt plant.
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Fields, Travis D. "The development and optimization of a teleoperated four-wheel drive/four-wheel steer vehicle." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1472952.
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Jones, Emil. "All purpose physics wheel class." Thesis, University of Kalmar, School of Communication and Design, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hik:diva-902.
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Detta arbete beskriver hur processen för att skapa en generell hjulklass har gått till. Klassen skall skapas med hjälp av fysikmotorn Bullet. Den generella hjulklassen skall användas som en komponent i Craft Animations fordonssimuleringar. Det finns stöd för 3 olika former av hjulupphängning. Oberoende hjul medkollisionskroppar, Länkade hjul med kollisionskroppar samt Hjul med strålföljning. Rapporten visar hur konstruktionen av dessa hjulupphängningar går till. Slutligen görs en sammanställning där de olika teknikerna diskuteras och jämförs.
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Yeung, Nai Chi Psychology Faculty of Science UNSW. "Stereotype threat behind the wheel." Awarded by:University of New South Wales. School of Psychology, 2006. http://handle.unsw.edu.au/1959.4/26242.
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Stereotype threat refers to the pressure that individuals feel when they are at risk of confirming a demeaning stereotype about themselves. Research has found that stereotype threat impairs performance on cognitive-based tasks by inducing mental interference (e.g., Schmader & Johns, 2003). This thesis hypothesised that this finding would generalise to driving and that drivers who are better able to inhibit cognitive interference (i.e., with better inhibitory ability) would be less susceptible to the disruptive effect of stereotype threat than drivers who are less able (i.e., with poorer inhibitory ability). A series of three experiments conducted in a driving simulator tested the predictions using the gender stereotype of driving skills and investigated the interpretation of the results. The experiments revealed that stereotype threat exerted both a facilitative and debilitative influence on driving performance, as indicated by different performance measures. The facilitative effect diminished when drivers experienced increased mental demands or when they were assessed by an unexpected performance measure, while the debilitative effect was more likely observed among drivers who received negative feedback than drivers who received positive feedback. Moreover, the results supported the prediction that inhibitory ability would moderate the detrimental impact of stereotype threat as the performance of drivers with poorer inhibitory ability was impeded more than that of drivers with better inhibitory ability. Regarding the processes underlying the present findings, the experiments provided suggestive evidence that stereotype threat elicits cognitive interference and simultaneously motivates drivers to concentrate on particular performance areas in an attempt to refute the stereotype. In combination, these processes appear to be at least partly responsible for the performance deficits and boosts observed.
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Barlow, N. "High-rate grinding wheel design." Thesis, Liverpool John Moores University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380664.
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Eriksson, Kathryn O. "Red lustrous wheel-made ware /." Jonsered : Paul Åströms Förlag, 1993. http://catalogue.bnf.fr/ark:/12148/cb36210492b.
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Bengtsson, Erik. "Concept Development of Stroller Wheel." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Industriell produktutveckling, produktion och design, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-44610.
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Gharib, Alireza. "FOUR SIMULTANEOUSLY STEERABLE WHEEL ROBOT." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2500.
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Our whole purpose from this research is to come up with the best design of a robot which is capable of carrying the load and follow the most reliable and most efficient path in order to get to its destination. Previous research [1]is already done for a three and two wheel robot, however, we need a design which satisfies our specific requirement for higher reliability and ability to carry load in manufacturing environments or on different planets.
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Kienhöfer, Frank Werner. "Heavy vehicle wheel slip control." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609594.
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Beller, Philip. "FLUX : Rethinking two-wheel mobility." Thesis, Umeå universitet, Designhögskolan vid Umeå universitet, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-171771.
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This project has investigated how to reshape two-wheel mobility in a more functional driven way, without losing the thrill of riding a motorcycle. The intitial cue was offered by the current rise of electric powertrains in the market. The opportunity of finding new spaces in the existing motorcycle architecture that could increase it's functionality and safety served as inspiration for this project. By achieving these steps this project wishes to envision a product that can attract new audiences whilst making two-wheel mobility more accessible. The process involved a variety of techniques that range from concept creation to 3D visualisation. During the ideation phase digital and analogue sketching techniques were combined after benchmarking existing products and visualising through animations possible solutions. In a later step the design was refined using digital painting in addition to polygon modelling. It has been helpful to evaluate the product in VR through various steps of the process, this provided a better understanding of the volumes and enabled a more accurate design of certain components. The result of the project is Flux. Combining unusual materials, like silicone, with a new layout offered the possibility of creating a simple yet advanced solution that provides various benefits to riding in everyday life. These benefits range from an enhanced cargo capability to an easier way to swap or recharge the batteries. In addition, it features some seamlessly integrated technology improvements that are vowed to make riding safer, without compromising on the experience.
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Korhonen, Daniel. "Wheel alignment method feasibility study." Thesis, KTH, Fordonsdynamik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280555.
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Throughout the history of motor vehicles, the tyres have always been consideredas one of the most important components of the vehicle due to their interactionwith the road. One important aspect is the wheel alignment, with the purposeto adjust the static wheel angles that are essential for many reasons, such assafety and fuel consumption for instance. Despite the numerous methods forwheel angle measurements, there seems to be no existing technical solutionbased on computer vision, that is suitable for residential use, regarding bothcost and size of the equipment. The study aims to investigate the feasibility ofsuch a system.The proposed system is based on planar fiducial markers called ArUco.From images or video frames of the marker, the pose of the marker can beestimated. Thus, by placing such markers on the ground, on the wheel andon the vehicle, the estimated pose of the markers can be used to measure andcalculate the wheel alignment parameters. Only toe and camber angles aremeasured within the scope of this thesis, even if the system has the potential tomeasure other wheel alignment parameters as well.After camera calibration, simplified ArUco marker tests were done by measuringthe known displacement and inclination of a marker with respect to areference marker. The mean absolute error was 030400 and 0:024mm for theinclination angle and displacement, respectively. Furthermore, the toe and camberangles of a vehicle were measured and compared to reference measurementsperformed with a commercial wheel alignment system, giving mean absoluteerrors of 0520 and 0280 for the camber and toe angles, respectively. Despitethe relatively large errors for the toe and camber angle measurements, theresults from the initial inclination and displacement tests show the potential ofthe system. In addition, several error sources and suggestions for improvementcan be identified.As a conclusion, the proposed system can be considered a working firstprototype, which after improvement and optimisation has the potential tobecome a feasible alternative, especially for residential use and for mobileworkshops due to the low cost, size and usability of the system.Inom fordonstekniken har däcken alltid betraktats som en av fordonets viktigastekomponenter på grund av deras interaktion med vägen. En viktig aspektär hjulinställning, med syftet att justera de statiska hjulvinklarna som är viktigaav många anledningar, som exempelvis säkerhet och bränsleförbrukning.Trots flera metoder för mätning av hjulvinklar verkar det inte finnas någonbefintlig teknisk lösning baserad på datorseende, som är lämplig för privat brukbåde gällande kostnad och storlek på utrustningen. Syftet med studien är attundersöka genomförbarheten för ett sådant system.Det föreslagna systemet är baserat på plana ArUco-markörer. Från bildereller bildrutor i en video av markören kan dess läge uppskattas. Genom attplacera sådana markörer på marken, på hjulet och på fordonet, kan såledesmarkörernas uppskattade lägen användas för att mäta och beräkna hjulvinklarna.Endast toe- och cambervinklar mäts inom ramen för detta examensarbete, ävenom systemet också kan mäta andra hjulvinklar.Efter kamerakalibrering utfördes enkla ArUco-markörtester genom att mätaden kända förskjutningen och vinkeln av en markör i förhållande till en referensmarkör.De genomsnittliga absoluta felen var 030400 och 0:024mm förvinkeln respektive förskjutningen. Vidare mättes toe- och cambervinklar påett fordon och jämfördes med referensmätningar utförda med ett kommersiellthjulinställningssystem. De genomsnittliga absoluta felen var 0520 och 0280för camber- respektive toevinkeln. Trots de relativt stora felen i mätningarnaav toe- och cambervinklar visar resultaten från de första testerna systemetspotential. Dessutom kan flera felkällor och förslag till förbättringar identifieras.Som en slutsats kan det föreslagna systemet betraktas som en fungerandeförsta prototyp, som efter förbättring och optimering har potential att bli ettmöjligt alternativ, särskilt för hemmabruk och för mobila verkstäder på grundav låga kostnader, systemets ringa storlek och användbarhet.
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Villella, Matthew G. "Nonlinear Modeling and Control of Automobiles with Dynamic Wheel-Road Friction and Wheel Torque Inputs." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5198.
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This thesis presents a new nonlinear automobile dynamical model and investigates the possibility of automobile dynamic control with wheel torque utilizing this model. The model has been developed from first principles by applying classical mechanics. Inputs to the model are the four independent wheel torques, while the steer angles at each wheel are specified as independent time-varying signals. In this way, consideration of a variety of steering system architectures, including rear-wheel steer, is possible, and steering introduces time-varying structure into the vehicle model.
The frictional contact at the wheel-road interface is modeled by use of the LuGre dynamic friction model. Extensions to the existing two-dimensional LuGre friction model are derived and the steady-state of the friction model is compared to existing static friction models. Simulation results are presented to validate the model mathematics and to explore automobile behavior in a variety of scenarios.
Vehicle control with wheel torque is explored using the theory of input-output linearization for multi-input multi-output systems. System relative degree is analyzed and use of steady-state LuGre friction in a control design model is shown to give rise to relative degree singularities when no wheel slip occurs. Dynamic LuGre friction does not cause such singularities, but instead has an ill-defined nature under the same no-slip condition. A method for treating this ill-defined condition is developed, leading to the potential for the system to have relative degree.
Longitudinal velocity control and combined longitudinal and angular vehicle velocity control are demonstrated in simulation using input-output linearization, and are shown to produce improved vehicle response as compared to the open-loop behavior of the automobile. Robustness of the longitudinal velocity control to friction model parameter variation is explored and little impact to the controller's ability to track the desired trajectory is observed.
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Karlsson, Jan. "Analyzes of a wheel loader usage." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-11240.
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The wheel loader is a very versatile machine hence the layout of the machine and the software has to be a compromise of all the possible application. If the machine could detect the application and adapt the software settings to optimize the machine for the current application more application unique settings would be possible. To make the application identification cost efficient and possible to implement over the whole product range a minimum of added product cost is preferred. Therefore only using existing sensors of a wheel loader and using a software algorithm for the identification is suggested. In the following chapters three common applications are described from a generic point of view. The identification can be divided into different sections days, series, cycles and phases. The declaration of the phases is meant to be consistent regardless of application, however some phases may not be present in some application, 18 phases are identified to cover all application. Algorithms are developed to identify three different applications, bucket, pallet, timber and two different material classes. It is stated that it is possible to differentiate at least two different material classes with the suggested algorithms.
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Berg, Johan. "Better design of wheel-loaded decks." Thesis, KTH, Marina system, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119766.
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This study treats the design of secondary structures for wheel-loaded decks. It concludes that significant savings in structural weight, overall cost and environmental impact can be obtained by an improved design. The rules of three classification societies are examined and their principle differences are discussed. Weight and cost optimal solutions of rule-based design are identified for a deck of a typical short-sea RoRo-vessel. The rule-optimal designs are assessed and further improved on the basis of FEcalculations and the economic and environmental benefits associated with the best solutions are approximated.
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Kunz, Jacob Andrew. "Probabilistic modeling of microgrinding wheel topography." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49118.
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This work addresses the advanced probabilistic modeling of the stochastic nature of
microgrinding in the machining of high-aspect ratio, ceramic micro-features. The
heightened sensitivity of such high-fidelity workpieces to excessive grit cutting force
drives a need for improved stochastic modeling. Statistical propagation is used to
generate a comprehensive analytic probabilistic model for static wheel topography.
Numerical simulation and measurement of microgrinding wheels show the model
accurately predicts the stochastic nature of the topography when exact wheel
specifications are known. Investigation into the statistical scale affects associated
microgrinding wheels shows that the decreasing number of abrasives in the wheel
increases the relative statistical variability in the wheel topography although variability in
the wheel concentration number dominates the source of variance. An in situ
microgrinding wheel measurement technique is developed to aid in the calibration of the
process model to improve on the inaccuracy caused by wheel specification error. A
probabilistic model is generated for straight traverse and infeed microgrinding dynamic
wheel topography. Infeed microgrinding was shown to provide a method of measuring
individual grit cutting forces with constant undeformed chip thickness within the grind
zone. Measurements of the dynamic wheel topography in infeed microgrinding verified
the accuracy of the probabilistic model.
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Zhu, Yi. "Adhesion in the wheel-rail contact." Doctoral thesis, KTH, Tribologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133342.
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To attract more customers and compete with other modes of transportation, railway transport needs to ensure safety, punctuality, high comfort, and low cost; wheel–rail adhesion, i.e., the transmitted tangential force in the longitudinal direction during driving and braking, plays an important role in all these aspects. Adhesion needs to be kept at a certain level for railway operation and maintenance. However, wheel−rail contact is an open system contact. Different contaminants can present between the wheel and rail surfaces, forming a third-body layer that affects the adhesion. Prediction of wheel–rail adhesion is important for railway operations and research into vehicle dynamics; however, this prediction is difficult because of the presence of contaminants. This thesis deals with wheel–rail adhesion from a tribological perspective. The five appended papers discuss wheel–rail adhesion in terms of dry conditions, lubricated conditions, leaf contamination, iron oxides, and environmental conditions. The research methodologies used are numerical modelling, scaled laboratory experiments, and field tests. The research objective is to understand the mechanisms of the adhesion loss phenomenon. A numerical model was developed to predict wheel–rail adhesion based on real measured 3D surfaces. Computer simulation indicates that surface topography has a larger impact on lubricated than on dry contacts. Plastic deformation in asperities is found to be very important in the model. Ball-on-disc tests indicate that water can give an extremely low adhesion coefficient on smooth surfaces, possibly due to surface oxidation. Investigation of lubricated contacts at low speed indicates that oil reduces the adhesion coefficient by carrying a normal load, while adhesion loss due to water depends on the surface topography, water temperature, and surface oxidation. A field investigation indicates that leaves reduce the friction coefficient because of the chemical reaction between leaves and bulk materials. The thickness of the surface oxide layer was found to be an essential factor determining adhesion reduction. Pin-on-disc experiments found a transition in the friction coefficient with regard to the relative humidity, due to a trade-off between the water molecule film and the hematite on the surface.QC 20131031
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Westbom, Daniel, and Petter Frejinger. "Yaw control using rear wheel steering." Thesis, Linköping University, Department of Electrical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-1463.
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The purpose of this project is to continue the work on a vehicle model developed in ADAMS/Car and applied with the concept of ACM (Autonomous Corner Module). The project is divided up in two parts. The objective of the first part is to setup a co-simulation environment between ADAMS/Car and MATLAB/Simulink, and evaluate the vehicle model. In the second part a yaw controller is developed using only the rear wheel steering possibilities. The controller will be evaluated when it is applied on the vehicle model.
The approach is to develop two models, one simpler in MATLAB/Simulink and one more complex in ADAMS/Car, and verify that they show similar behavior. The models will then be linearized and the control design will be based on the most appropriate linear model. Most of the work has been developing and evaluating the two vehicle models in ADAMS/Car and MATLAB/Simulink.
The result was a working co-simulation environment where an evaluation of two different controllers was made. Due to linearization of the ADAMS model was nsuccessful, the controllers were based on the simpler linear Simulink model. Both controllers show similar results. Tests on the ADAMS model showed that it is hard to control both the yaw rate and body slip only by rear wheel steering.
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Torstensson, Martin, and Hans Pettersen. "Optimization of front Wheel Arch Liner." Thesis, Linköping University, Department of Mechanical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5957.
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About ten years ago Volvo Cars could see that car manufactures began to introduce rear wheel arch liners made of non-woven fabrics or some kind of laminate which are mostly common today. Volvo Cars have also seen that competitors now are beginning to develop the front wheel arch liners more and more and expect a development equal to the one for the rear wheel arch liners. This is why we are set to optimize the front wheel arch liner.
For development of mechanical products such as car parts, a discursive method is most suitable to follow. For example systematical concept development which we have used in our work.
From a technical point of view, our results shows that the penta laminate used for the wheel arch liner on Mercedes Benz S-class is by far the best material. Unfortunately it is rather expensive which of course affects its result in a negative way when cost is taken in to consideration. When including cost, the solid plastic is actually rather economical.
After assessment of the result in total we are however convinced that Volvo Cars should concentrate on further research of penta laminate and open negotiations with different suppliers regarding a material of this kind.
Regarding the geometry, the tests and studies that Volvo Cars have performed earlier on splash shields clearly shows the usage of the part and further research done by our selves does not point at any problems with a splash shield integrated in the wheel arch liner.
För ungefär tio år sedan kunde Volvo Cars se att biltillverkare började introducera bakre hjulhus tillverkade av ”non-woven” fibrer eller någon form av laminat vilket idag är högst vanligt. Volvo Cars har också sett att konkurrenter nu börjar utveckla främre hjulhus mer och mer och räknar med en utveckling liknande den för bakre hjulhus. Detta är anledningen till att vi har fått uppgiften att optimera det främre hjulhuset.
För utveckling av mekaniska produkter så som bildelar, är en diskursiv metod mest lämpad att följa. Till exempel systematisk konceptutveckling som vi har valt att använda i vårt arbete.
Sett ur ett tekniskt perspektiv, visar våra resultat att pentalaminatet som används för hjulhusen på Mercedes Benz S-klass, är det överlägset bästa materialet. Tyvärr ar det ganska dyrt vilket naturligtvis påverkar dess resultat negativt när hänsyn tas till kostnader. När vi även ser till kostnaderna, är faktiskt den rena plasten mycket ekonomisk. Efter bedömning av det totala resultatet, är vi helt övertygade om att Volvo Cars borde koncentrera sig på fortsatta undersökningar av pentalaminat och inleda förhandlingar med olika underleverantörer angående material av denna typ.
Angående geometrin, visar Volvo Cars’ sedan tidigare genomförda tester och studier att en splash shield fyller en viktig funktion och vidare undersökningar genomförda av oss själva pekar inte på några problem med en i hjulhuset integrerad splash shield.
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Jenkins, Anne Elizabeth. "Operating the potter's wheel shaping faith /." Theological Research Exchange Network (TREN), 2006. http://www.tren.com/search.cfm?p068-0569.
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Garcia, Hector, and Emma Smith. "Wheel Induced Vibrations on Heavy Vehicles." Thesis, KTH, Skolan för teknikvetenskap (SCI), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-153927.
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Some of the most significant comfort disturbances in heavy vehicles can often be related to the wheels. In those cases, the vibration of the vehicle is excited by for example force variations within the tire, ovality of the tire or imbalance in the wheel. The disturbances are dependent on vehicle speed and are often perceived as most unpleasant at cruising speed on a motorway, at around 90 km/h. Truck manufacturers want to increase the robustness against this type of disturbance, since this results in an improved operator comfort. But it also makes it possible to lower the requirements on the suppliers of tires and rims, and thereby there is a financial gain for both customer and manufacturer. The aim with this project is to increase the understanding of wheel induced vibrations. In order to achieve this a literature survey has been performed on the subject. Furthermore, the phenomenon has been studied analytically by using a quarter car model which includes a brush tire model. The model is scripted in MATLAB. Simulations have been performed to analyse the effect on the chassis when forces excited by mass imbalance and radial run out are introduced. When looking at the second harmonic radial run out imperfection the unsprung mass, i.e the wheel, starts to bounce during the settling time. Also when comparing two different weights of a mass imbalance the power increase of the vibration in the sprung mass is much larger than the power increase of the unsprung mass at the specific frequency. This implies that the excitation frequency, the wheel rotation frequency in this case, is a harmonic repetition of the sprung mass undamped natural frequency. To avoid this phenomenon the undamped natural frequency of the sprung mass must change either by adding a damper or by changing the weight or the spring stiffness. The simulation is run with a damper although without it the power increase would be much larger.
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Yang, Sichao. "In-wheel motors for electric vehicles." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/4054.
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The in-wheel motor technology as the source of traction for electric vehicles has been researched recently because it is compact and ease-to-integrate. The motor is housed in the wheel. Since the room for the motor is tightly defined by the size of the wheel and there is no gearing system, the motor must have a high torque density to drive the vehicle directly and a high efficiency to keep cool. The existing motor uses a surface-mounted magnet topology. To make it more cost-competitive, the magnet material needs to be reduced while maintaining the torque performance at the rated operating condition. It is the motive of this Ph.D. research. The thesis starts with a brief introduction on the background of the electric vehicle. Then the major challenges of the in-wheel motor technology are summarised. With the derived specifications, an induction machine and a switched reluctance machine are then simulated and analysed. Still, the permanent magnet synchronous machine is proved to have the highest torque density. Change from surface-mounted to interior topology, six new magnet topologies are investigated. The V-shaped interior magnet topology shows superior torque-to-magnet-mass ratio and is easy-to-manufacture. It gives 96% torque while using 56% of the magnet mass compared to the existing motor due to the assist from the additional reluctance torque and the lower magnetic circuit reluctance. The key to use less magnet mass while avoiding the demagnetisation is the front iron shielding effect. The analytical explanation on the better resistance to demagnetisation in the V-shaped motor is provided. The magnet loss mechanism is discussed for proper segmentation. Detailed design adjustments are made to compromise between the torque-to-magnet-mass ratio and the manufactural practicality. Issues regarding to lower mechanical rigidity occurred in initial assembly of the prototype and solutions are proposed. Followed by successful assembly, experimental tests were conducted and results show good agreement with the simulation. A specific form of torque ripple is found in the V-shaped motor and occurs generally in all fractional-slot concentrated-winding machines with saliency. It is explained by an analytical model. This model is also extended to explain the generally lower reluctance torque in vi fractional-slot concentrated-winding machines. Potential design improvements are suggested and simulated for future versions.
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Galas, Radovan. "Friction Modification within Wheel-Rail Contact." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-367508.
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Předložená disertační práce se zabývá experimentálním studiem modifikátorů tření a maziv pro temeno kolejnice, které jsou aplikovány do kontaktu kola a kolejnice za účelem optimalizace adheze a redukce hluku. Hlavním cílem práce bylo objasnit vliv aplikovaného množství a složení těchto látek na adhezi v kontaktu. Hlavní pozornost byla věnována zejména potencionálním hrozbám souvisejících s kriticky nízkou adhezí, která může nastat po aplikaci těchto látek. Experimentální studium probíhalo v laboratorních i reálných podmínkách, konkrétně v tramvajovém provozu. V případě laboratorních experimentů byl využit komerční tribometr a dvoudiskové zařízení umožňující simulovat průjezd vozidla traťovým obloukem. Kromě samotné adheze bylo při experimentech sledováno také opotřebení a míra hluku. Výsledky ukázaly, že maziva pro temeno kolejnice jsou schopna poskytovat požadované třecí vlastnosti, nicméně jejich chování je silně závislé na aplikovaném množství. V případě předávkování kontaktu dochází ke kriticky nízkým hodnotám adheze, které vedou k výraznému prodloužení brzdné dráhy. V případě modifikátorů tření bylo ukázáno, že chování těchto látek je výrazně ovlivněno odpařováním základního média. Výsledky také ukázaly, že nadměrné množství částic pro modifikaci tření může způsobit kriticky nízké hodnoty adheze. U obou výše zmíněných typů produktů byl prokázán pozitivní vliv na míru opotřebení a míru poškození povrchu, zatímco významná redukce hluku byla dosažena pouze v případech, kdy došlo ke značnému poklesu adheze. V závěru této práce jsou uvedena doporučení pro další výzkumné aktivity v této oblasti.
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Fagrell, William. "Optimization of a cutter wheel bearing." Thesis, Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-79051.
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This Master's thesis project was provided by Epiroc Rock Drills AB and conducted at Camatec Industriteknik AB in Karlstad, Sweden. The project is centered around the cutter wheel in the mechanical rock excavator Mobile Miner 40V. This cutter wheel is equipped with cutter discs that grind rock into debris as the wheel rotates and thrusts forward. The internal system consisting of a bearing constellation and the components in its vicinity has experienced a certain degree of wear in the form of scuffing and this was detected on the surfaces of some of the components in the system. The reasons for this occurrence are unknown and per the request of the thesis provider, this was to be determined. The thesis provider also requested a new Finite Element Analysis (FEA) model of the system along with feasible load cases that can be applied to said model. The project was deemed extensive and was therefore decided to be conducted by two students. This thesis covers the determination of the load cases as well as the optimization of the current design of the system inside the cutter wheel. During the pre-study, relevant background data was obtained for the cutter wheel and the internal system. Methods and models considered to potentially be useful were also gathered. The system in question was divided into two separate models; one consisted of a tribo-system with two components in sliding contact and the other consisted of the bearing constellation along with the outer-most section of the cutter wheel. The purpose of the first model was to use it to determine the contact pressure between the tribo-surfaces and by doing so, be able to determine the expected lubrication regime for the oil in the tribo-system. A material selection process was also conducted on the tribo-surface that had experienced the most severe surface damage. Additionally, minor reconstructions were made with the purpose of optimizing the system. The purpose of the second model was to apply the calculated load cases to the cutter disc attachments located on the outer-most section of the cutter wheel and then determine the contact pressures that develop on the bearing roller elements. The results of the thesis work consist of five potential material options, two reconstructions and 60 different load cases for the FEA model. With the load cases, the largest contact pressures on the bearing roller elements was determined. In addition, the cause of the severe surface damage that had occurred in the system is believed to have been identified. Further work on the project work is believed to be required. Future work of interest are determining load cases that incorporate multiple cutter discs simultaneously in contact with the rock, reconstruction solutions for the oil inlet and outlet pipes, a more thorough materials selection process and a criterion for the expected lubrication regime in the tribo-system based on tests performed with materials that are more identical to the ones in this project.Detta examensarbete tillhandahölls av Epiroc Rock Drills AB och genomfördes hos Camatec Industriteknik i Karlstad, Sverige. Projektet är centrerat kring cutterhjulet i maskinen Mobile Miner 40V som är avsedd för mekanisk bergavverkning. Cutterhjulet är utrustat med cutter discar som maler berget till mindre flisor genom att hjulet roterar och trycks framåt. Det inre systemet bestående av en lagring med närliggande komponenter har utsatts för en viss grad av nötning i form av scuffing och detta upptäcktes på ytorna hos vissa av komponenterna i systemet. De bakomliggande anledningarna för denna förekomst är okända och utifrån begäran från projektgivaren skulle dessa anledningar fastställas. Projektgivaren eftersökte även en ny FEM-modell av systemet tillsammans med rimliga lastfall som ska kunna appliceras på modellen i fråga. Projektet ansågs tämligen omfattande och det bedömdes därför att två studenter krävdes för att genomföra arbetet. Denna uppsats behandlar framtagningen av lastfallen såväl som optimeringen av den nuvarande designen av systemet inuti cutterhjulet. Under förstudien hämtades relevant bakgrundsdata för cutterhjulet och det interna systemet. Metoder och teorier som ansågs vara potentiellt användbara samlades även in. Systemet i fråga delades in i två separata modeller; en bestod av ett tribo-system bestående av två tribo-ytor i glidande kontakt och den andra bestod av lagringen tillsammans med den yttersta sektionen hos cutterhjulet. Syftet med den förstnämnda modellen var att använda den för att bestämma kontakttrycket mellan tribo-ytorna, och genom detta kunna fastställa den förväntade smörjningsregimen hos oljan i tribo-systemet. En materialvalsprocess utfördes även för tribo-ytan som hade utsatts för den mest allvarliga skadan. Även smärre omkonstruktioner utfördes med syftet att optimera systemet. Syftet hos den andra modellen var att kunna applicera de beräknade lastfallen på cutter discarnas infästningar som återfinns i den yttersta sektionen hos cutterhjulet och sedan bestämma kontakttrycken som uppstår på rullarna i lagren. Resultaten från arbetet består av fem potentiella materialval, två konstruktionsändringar och 60 olika lastfall för FEM-modellen. Genom att applicera lastfallen bestämdes de största kontakttrycken på lagrens rullar. Utöver detta anses det att anledningen för den allvarliga ytskadan som hade skett i systemet har identifierats. Det anses att fortsatt arbete krävs för projektet. Kompletterande arbete som anses vara av intresse är lastfall som inkluderar flera cutter discar i ingrepp samtidigt med berget, konstruktionslösningar för tillförsel och bortförsel av oljan, en mer djupgående materialvalsprocess och ett kriterium för förväntad smörjningsregim hos tribo-systemet baserat på tester utförda med material som är mer identiska med dem som förekommer i projektet.