Academic literature on the topic 'Continuum robot'
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Journal articles on the topic "Continuum robot"
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Luo, Kelan. "Modeling of continuum robots: A review." Journal of Physics: Conference Series 2634, no. 1 (November 1, 2023): 012029. http://dx.doi.org/10.1088/1742-6596/2634/1/012029.
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Abstract Continuum robots offer good environmental adaptability and superior safety in human-robot interaction. This paper describes the state of the art in continuum robot modeling and summarizes and evaluates the mainstream continuum robot modeling approaches in the current community through three different classifications: continuum models, geometric models, and data-driven models. Finally, the paper provides a summary of existing research approaches and provides future research opportunities in continuum robot modeling.
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Ji, Kenneth, and Yuyu Fang. "A review of continuum robot." Applied and Computational Engineering 36, no. 1 (January 22, 2024): 265–70. http://dx.doi.org/10.54254/2755-2721/36/20230460.
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This paper comprehensively reviews continuum robots and their application in medical domains. Unlike traditional rigid robots, continuum robots possess continuous, flexible structures that enhance dexterity and adaptability. Their compliant nature allows safer human-robot collaboration, while their deformability permits navigation through confined spaces and conformance to anatomy. These advantages make continuum robots promising for medical applications like minimally invasive surgery. The paper discusses continuum robots' fundamental principles, including kinematics, dynamics, mechanical design, modelling, and control strategies. It highlights the unique benefits of continuum robots compared to rigid counterparts, especially for medical use. Challenges such as design optimization, accurate control and modelling, sensing, miniaturization, and technology integration are also addressed. Enhancing manipulation capabilities, developing miniaturized continuum robots, achieving autonomous operation, integrating imaging modalities, and validating safety and efficacy through clinical trials are suggested for future work. This review offers valuable insights into continuum robotics technology and its immense potential to transform medical interventions through precise, minimally invasive procedures.
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Walker, Ian D. "Continuous Backbone “Continuum” Robot Manipulators." ISRN Robotics 2013 (July 16, 2013): 1–19. http://dx.doi.org/10.5402/2013/726506.
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This paper describes and discusses the history and state of the art of continuous backbone robot manipulators. Also known as continuum manipulators, these robots, which resemble biological trunks and tentacles, offer capabilities beyond the scope of traditional rigid-link manipulators. They are able to adapt their shape to navigate through complex environments and grasp a wide variety of payloads using their compliant backbones. In this paper, we review the current state of knowledge in the field, focusing particularly on kinematic and dynamic models for continuum robots. We discuss the relationships of these robots and their models to their counterparts in conventional rigid-link robots. Ongoing research and future developments in the field are discussed.
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Li, Yunfei, Qiuhao Wang, and Qian Liu. "Developing a Static Kinematic Model for Continuum Robots Using Dual Quaternions for Efficient Attitude and Trajectory Planning." Applied Sciences 13, no. 20 (October 14, 2023): 11289. http://dx.doi.org/10.3390/app132011289.
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Kinematic modeling is essential for planning and controlling continuum robot motion. The traditional Denavit Hartenberg (DH) model involves complex matrix multiplication operations, resulting in computationally intensive inverse solutions and trajectory planning. Solving position and orientation changes in continuum robots using the double quaternion rule can reduce computational complexity. However, existing dual quaternion methods are direct equational transformations of DH rules and do not give a complete modeling process. They usually require more interpretability when applying continuum robot kinematic modeling. This paper uses the dual quaternion method to establish a kinematic model of a continuum robot. It uses a two-section continuum robot model to compare the advantages of dual quaternion and traditional modeling methods. In addition, this paper proposes a five-polynomial interpolation algorithm based on the dual quaternion method for trajectory planning of continuum robots. This method accurately models spatial bending and torsional motions of singularity-free continuum robots.
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Wooten, Michael, and Ian Walker. "Vine-Inspired Continuum Tendril Robots and Circumnutations." Robotics 7, no. 3 (September 18, 2018): 58. http://dx.doi.org/10.3390/robotics7030058.
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Smooth-backboned “continuum” robot structures offer novel ways to create robot shapes and movements. In this paper, we show how circumnutation, a motion strategy commonly employed by plants, can be implemented and usefully exploited with continuum robots. We discuss how the kinematics of circumnutation, which combines local backbone growth with periodic backbone bending, can be created using extensible continuum robot hardware. The underlying kinematics are generated by adapting kinematic models of plant growth. We illustrate the effectiveness of that approach with experimental results with a tendril-like robot exploring a congested environment.
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Liu, Zhipeng, Linsen Xu, Xingcan Liang, and Jinfu Liu. "Stiffness-Tuneable Segment for Continuum Soft Robots with Vertebrae." Machines 10, no. 7 (July 18, 2022): 581. http://dx.doi.org/10.3390/machines10070581.
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In addition to high compliance to unstructured environments, soft robots can be further improved to gain the advantages of rigid robots by increasing stiffness. Indeed, realizing the adjustable stiffness of soft continuum robots can provide safer interactions with objects and greatly expand their application range. To address the above situation, we propose a tubular stiffening segment based on layer jamming. It can temporarily increase the stiffness of the soft robot in a desired configuration. Furthermore, we also present a spine-inspired soft robot that can provide support in tubular segments to prevent buckling. Theoretical analysis was conducted to predict the stiffness variation of the robot at different vacuum levels. Finally, we integrated the spine-inspired soft robot and tubular stiffening segment to obtain the tuneable-stiffness soft continuum robot (TSCR). Experimental tests were performed to evaluate the robot’s shape control and stiffness tuning effectiveness. Experimental results showed that the bending stiffness of the initial TSCR increased by more than 15× at 0°, 30× at 90°, and 60× in compressive stiffness.
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Li, Minhan, Rongjie Kang, Shineng Geng, and Emanuele Guglielmino. "Design and control of a tendon-driven continuum robot." Transactions of the Institute of Measurement and Control 40, no. 11 (March 1, 2017): 3263–72. http://dx.doi.org/10.1177/0142331216685607.
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Continuum robots are suitable for operating in unstructured environments owing to their intrinsic compliance. This paper presents a novel tendon-driven continuum robot equipped with two modules and a compliant backbone formed by helical springs. Each module is driven by four parallel arranged tendons to implement a redundant actuation system that guarantees dexterous motions of the robot. A position feedback controller for the continuum robot is then developed, and a quadratic programming algorithm is incorporated into the controller to achieve a smooth configuration of the robot. Experiments results show that the control method has good trajectory tracking performance against external disturbances.
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Zhong, Yong, Luohua Hu, and Yinsheng Xu. "Recent Advances in Design and Actuation of Continuum Robots for Medical Applications." Actuators 9, no. 4 (December 19, 2020): 142. http://dx.doi.org/10.3390/act9040142.
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Traditional rigid robot application in the medical field is limited due to the limited degrees of freedom caused by their material and structure. Inspired by trunk, tentacles, and snakes, continuum robot (CR) could traverse confined space, manipulate objects in complex environment, and conform to curvilinear paths in space. The continuum robot has broad prospect in surgery due to its high dexterity, which can reach circuitous areas of the body and perform precision surgery. Recently, many efforts have been done by researchers to improve the design and actuation methods of continuum robots. Several continuum robots have been applied in clinic surgical interventions and demonstrated superiorities to conventional rigid-link robots. In this paper, we provide an overview of the current development of continuum robots, including the design principles, actuation methods, application prospect, limitations, and challenge. And we also provide perspective for the future development. We hope that with the development of material science, Engineering ethics, and manufacture technology, new methods can be applied to manufacture continuum robots for specific surgical procedures.
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Russo, Matteo, Elie Gautreau, Xavier Bonnet, and Med Amine Laribi. "Continuum Robots: From Conventional to Customized Performance Indicators." Biomimetics 8, no. 2 (April 6, 2023): 147. http://dx.doi.org/10.3390/biomimetics8020147.
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Continuum robots have often been compared with rigid-link designs through conventional performance metrics (e.g., precision and Jacobian-based indicators). However, these metrics were developed to suit rigid-link robots and are tuned to capture specific facets of performance, in which continuum robots do not excel. Furthermore, conventional metrics either fail to capture the key advantages of continuum designs, such as their capability to operate in complex environments thanks to their slender shape and flexibility, or see them as detrimental (e.g., compliance). Previous work has rarely addressed this issue, and never in a systematic way. Therefore, this paper discusses the facets of a continuum robot performance that cannot be characterized by existing indicator and aims at defining a tailored framework of geometrical specifications and kinetostatic indicators. The proposed framework combines the geometric requirements dictated by the target environment and a methodology to obtain bioinspired reference metrics from a biological equivalent of the continuum robot (e.g., a snake, a tentacle, or a trunk). A numerical example is then reported for a swimming snake robot use case.
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He, Bin, Shoulin Xu, and Zhipeng Wang. "Research on Stiffness of Multibackbone Continuum Robot Based on Screw Theory and Euler-Bernoulli Beam." Mathematical Problems in Engineering 2018 (2018): 1–16. http://dx.doi.org/10.1155/2018/6910468.
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Continuum robots have become a focus for extensive research, since they can work well in complex and confined environments. The main contribution of this paper is to establish a stiffness model of a single section multibackbone continuum robot and analyze the effect of the structural parameters of continuum robot on the overall rotation and translation stiffness. First, a stiffness model which indicates the end configuration of continuum robot under external load is deduced by the screw theory and Euler-Bernoulli beam. Then, the stiffness elements are fully analyzed, therefore, obtaining the influence of the structural parameters of continuum robot on the stiffness elements. Meanwhile, a numerical analysis of stiffness elements is given. Furthermore, the minimum and maximum rotation/translation stiffness are introduced to analyze the effect of the structural parameters of continuum robot on the overall rotation and translation stiffness. Finally, the experiments are used to validate the proposed stiffness model. The experimental results show that the proposed stiffness model of continuum robot is correct and the errors are less than 7%.
Dissertations / Theses on the topic "Continuum robot"
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Thorapalli, Muralidharan Seshagopalan, and Ruihao Zhu. "Continuum Actuator Based Soft Quadruped Robot." Thesis, KTH, Mekatronik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286348.
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Quadruped robots can traverse a multitude of terrains with greater ease when compared to wheeled robots. Traditional rigid quadruped robots possess severe limitations as they lack structural compliance. Most of the existing soft quadruped robots are tethered and are actuated using pneumatics, which is a low grade energy source and lacks viability for long endurance robots. The work in this thesis proposes the development of a continuum actuator driven quadruped robot which can provide compliance while being un-tethered and electro-mechanically driven. In this work, continuum actuators are developed using mostly 3D printed parts. Additionally, the closed loop control of continuum actuators for walking is developed. Linear Quadratic Regulator (LQR) and pole placement based methods for controller synthesis were evaluated and LQR was determined to be better when minimizing the actuator effort and deviation from set-point. These continuum actuators are composed together to form a quadruped. Gait analyses on the quadruped were conducted and legs of the quadruped were able to trace the gaits for walking and galloping.Fyrfotarobotar kan lättare korsa en mängd olika terränger jämfört med hjulrobotar. Traditionella styva fyrfotarobotar har kraftiga begränsningar då de saknar strukturell följsamhet. De flesta befintliga mjuka fyrbenta robotar är kopplade till en eller flera kablar och drivs av pneumatik, vilket är en lågkvalitativ energikälla och lämpar sig inte för robotar med lång uthållighet. Arbetet i denna avhandling föreslår utvecklingen av en continuum ställdonsdriven fyrfotarobot, som ger följsamhet samtidigt som den ¨ar frånkopplad och elektromekaniskt driven. I detta arbete framställs continuum ställdon med mestadels 3D-printade delar. Dessutom utvecklas dessa ställdons slutna kontrolloop för gång. Linjärkvadratisk regulator (LQR) och metoder baserade på polplacering utvärderades för styrsyntes, och det fastställdes att LQR presterade bättre när man minimerar ställdonets ansträngning samt avvikelse från referensvärde. Continuum ställdon sammansattes för att bilda en fyrbent robot. Gånganalyser utfördes på roboten och dess ben kunde följa gång- och galopprörelser.
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Iqbal, Muhammad Sohail. "Continuum robot modeling with guaranteed approach." Thesis, Paris Est, 2010. http://www.theses.fr/2010PEST1027.
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Contrairement aux robots conventionnels, les robots continuums ne possèdent ni de liaisons discrètes, ni de corps rigides. Leur courbure est continue, similaire à celle des trompes ou des tentacules animales. Le développement de ce type de robots pour les applications médicales soulève plusieurs problèmes : optimisation de la conception, modélisation cinématique, choix des capteurs et commande en temps réel. Les techniques actuelles pour la modélisation des robots continuums ne tiennent pas compte les incertitudes inhérentes au système. La prise en compte de ces incertitudes est d'une importance cruciale pour la certification de tels robots utilisés pour les gestes chirurgicaux. Dans cette thèse, nous considérons un micro robot continuum à 3 actionneurs. Ce robot a été développé au laboratoire LISSI pour le traitement des anévrismes de l'aorte abdominale par chirurgie mini-invasive. Dans ce type de chirurgie, il est important de disposer d'un modèle cinématique garanti du robot continuum prenant en compte différents types d'incertitudes. Pour traiter ce problème, nous utilisons les techniques d'analyse par intervalles. Ces techniques permettent de résoudre des problèmes d'optimisation globale sous contraintes tout en prenant en compte des incertitudes aussi bien aléatoires que systématiques. La contribution de cette thèse porte sur la proposition d'un modèle cinématique d'un robot continuum prenant en compte des incertitudes liées à différents facteurs comme les erreurs d'arrondis, les erreurs paramétriques et les erreurs dues aux hypothèses de modélisation. Tout d'abord, nous développons les modèles géométriques direct et inverse du robot continuum sous forme de solutions de formes fermées. Ces solutions sont utilisées pour caractériser les différentes propriétés du robot comme la manipulabilité. Pour calculer la cinématique inverse garantie et optimale, nous appliquons une version améliorée de l'algorithme par séparation et évaluation (Branch and Bound). En considérant l'orientation du robot, la cinématique inverse est ramenée à la formulation et à la résolution par intervalles d'un problème d'optimisation sous contraintes. Les approches proposées sont validées par des simulations. Les résultats de cette thèse constituent un cadre général pour la modélisation garantie de la classe des robots continuums dont la forme est décrite par des actionneurs en flexion continueUnlike conventional robots, continuum robots do not contain any rigid link or any rotational joint but present a continuous bending in the structure through smooth motion. Development of this class of robot for their medical application presents a common set of problems : optimization of design, kinematic modeling, sensing choice, and their control in real time. Existing techniques for the modeling of continuum robots do not take system uncertainties into account. A proper handling of these uncertainties becomes of crucial importance for the certification of such robots used as medical devices. For our research, we consider a continuum robot that has been developed for the treatment of aortic aneurysm by Minimal Invasive Surgery (MIS), in LISSI Lab. In the context of MIS, it is very important to develop a guaranteed kinematic model of robot taking into account the different types of un-certainties. To handle this problem, we use the techniques of interval analysis. These techniques are capable of performing the global optimization and solving CSPs while taking into account the different uncertainties ; no matter, whether these uncertainties are random or systematic. Contribution of this thesis is proposal of a continuum robot's kinematic model that can take system uncertainties due to different factors such as rounding errors, parametric errors, and errors due to modeling assumptions. Initially, we develop the forward and inverse kinematics of the continuum robot in closed-form formulas. These derived formulas are used for the characterization of different properties of the robot such as manipulability. To find optimized guaranteed kinematics, we retained and applied an enhanced version of branch and bound algorithm. The inverse kinematics was formulated and resolved as a constrained optimization problem for robot's orientation. The proposed approaches are validated through simulations. The results of this thesis give rise to a general framework that is valid to handle the system uncertainties for the entire class of continuum robot that are shaped by continuously bending actuators
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Sherrod, Vallan Gray. "Design Optimization for a Compliant,Continuum-Joint, Quadruped Robot." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7766.
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Legged robots have the potential to cover terrain not accessible to wheel-based robots and vehicles. This makes them better suited to perform tasks, such as search and rescue, in real-world unstructured environments. Pneumatically-actuated, compliant robots are also more suited than their rigid counterparts to work in real-world unstructured environments with humans where unintentional contact may occur. This thesis seeks to combine the benefits of these two type of robots by implementing design methods to aid in the design choice of a 16 degree of freedom (DoF) compliant, continuum-joint quadruped. This work focuses on the design optimization, especially the definition of design metrics, for this type of robot. The work also includes the construction and closed-loop control of a four-DoF continuum-joint leg used to validate design methods.We define design metrics for legged robot metrics that evaluate their ability to traverse unstructured terrain, carry payloads, find stable footholds, and move in desired directions. These design metrics require a sampling of a legged-robot's complete configuration space. For high-DoF robots, such as the 16-DoF in evaluated in this work, the evaluation of these metrics become intractable with contemporary computing power. Therefore, we present methods that can be used to simplify and approximate these metrics. These approximations have been validated on a simulated four-DoF legged robot where they can tractably be compared against their full counterparts.Using the approximations of the defined metrics, we have performed a multi-objective design optimization to investigate the ten-dimensional design space of a 16-DoF compliant, continuum-joint quadruped. The design variables used include leg link geometry, robot base dimensions, and the leg mount angles. We have used an evolutionary algorithm as our optimization method which converged on a Pareto front of optimal designs. From these set of designs, we are able to identify the trade-offs and design differences between robots that perform well in each of the different design metrics. Because of our approximation of the metrics, we were able to perform this optimization on a supercomputer with 28 cores in less than 40 hours.We have constructed a 1.3 m long continuum-joint leg from one of the resulting quadruped designs of the optimization. We have implemented configuration estimation and control and force control on this leg to evaluate the leg payload capability. Using these controllers, we have conducted an experiment to compare the leg's ability to provide downward force in comparison with its theoretical payload capabilities. We then demonstrated how the torque model used in the calculation of payload capabilities can accurately calculate trends in force output from the leg.
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Santoso, Junius. "Toward Deployable Origami Continuum Robot: Sensing, Planning, and Actuation." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/582.
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Continuum manipulators which are robot limbs inspired by trunks, snakes, and tentacles, represent a promising field in robotic manipulation research. They are well known for their compliance, as they can conform to the shape of objects they interact with. Furthermore, they also benefit from improved dexterity and reduced weight compared to traditional rigid manipulators. The current state of the art continuum robots typically consists of a bulky pneumatic or tendon-driven actuation system at the base, hindering their scalability. Additionally, they tend to sag due to their own weight and are weak in the torsional direction, limiting their performance under external load. This work presents an origami-inspired cable-driven continuum manipulator module that offers low-cost, light-weight, and is inherently safe for human-robot interaction. This dissertation includes contributions in the design of the modular and torsionally strong continuum robot, the motion planning and control of the system, and finally the embedded sensing to close the loop providing robust feedback.
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Su, Hao. "Force Sensing and Teleoperation of Continuum Robot for MRI-Guided Surgery." Digital WPI, 2013. https://digitalcommons.wpi.edu/etd-dissertations/156.
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Percutaneous needle placement, a minimally invasive procedure performed dozens of millions in the U.S. each year, relies on dedicated skill and long-term training due to difficult control of needle trajectory inside tissue and mental registration of images to locations inside the patient. Inaccurate needle placement may miss cancer tumors during diagnosis or eradicate healthy tissue during therapy. MRI provides ideal procedure guidance with the merit of excellent soft tissue contrast and volumetric imaging for high spatial resolution visualization of targets and surgical tool. However, manual insertion in the bore of an MRI scanner has awkward ergonomics due to difficult access to the patient, making both training and intervention even harder.
To overcome the challenges related to MRI electromagnetic compatibility and mechanical constraints of the confined close-bore, a modular networked robotic system utilizing piezoelectric actuation for fully actuated prostate biopsy and brachytherapy is developed and evaluated with accuracy study. To enhance manipulation dexterity, two kinds of steerable continuum needle robots are developed. The asymmetric tip needle robot performs needle rotation and translation control to minimize tissue deformation, and increase steering dexterity to compensate placement error under continuous MRI guidance. The MRI-guided concentric tube robot is deployed to access delicate surgical sites that are traditionally inaccessible by straight and rigid surgical tools without relying on tissue reaction force. The master-slave teleoperation system with hybrid actuation is the first of its kind for prostate intervention with force feedback. The teleoperation controller provides the feel and functionality of manual needle insertion. Fabry- Perot interferometer based fiber optic force sensor is developed for the slave manipulator to measure needle insertion force and render proprioception feedback during teleoperation.
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Mauzé, Benjamin. "Triskèle-Bot : étude et développement d'un robot parallèle continu pour le micro-positionnement." Thesis, Bourgogne Franche-Comté, 2021. http://www.theses.fr/2021UBFCD006.
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Les robots parallèles continus (RPC) sont de nouvelles structures qui présentent un grand intérêt en termes de souplesse, d’espace de travail ou encore de miniaturisation, mais qui ne sont pas connus pour leur précision. Cette thèse étudie le potentiel des RPC pour le positionnement à haute précision demandant un espace de travail conséquent. Pour cela, un nouveau concept de RPC planaire à 3 degrés de liberté, nommé Triskèle-Bot, constitué d’une plateforme et de trois bras flexibles continument déformables actionnés en translations, est proposé. Pour étudier son comportement, un modèle géométrique directe et inverse sont établis à partir d’une résolution numérique d’un système d’équations aux dérivées partielles non-linéaires, fondées sur une modélisation de poutre de Kirchhoff, contraintes aux conditions limites. Un prototype est développé de manière à valider ces modèles tout en offrant une répétabilité intrinsèque et une manière innovante de mesurer les paramètres intrinsèques et extrinsèques au robot. Un protocole de mesure par vision est proposé pour réduire les nombreuses sources d’incertitudes inhérentes à l’échelle microscopique et obtenir, ainsi, des mesures de poses avec un bruit de mesure inférieur à la dizaine de nanomètres. Il est utilisé pour mesurer expérimentalement la répétabilité du Triskèle-Bot qui atteint 9,13 nanomètres en position et 0,71 microradians en orientation. Une étude de la justesse de pose, faisant suite à une stratégie originale d’étalonnage, est réalisée sur plusieurs trajectoires montrant des valeurs inférieures à 4 micromètres et 0,6 milliradians. L’ensemble de ces résultats démontre le potentiel des PCR pour des applications de micro-positionnementParallel Continuum Robots (PCR) are new structures that present great interest in terms of workspace or miniaturization, but they are not known for their precision. This thesis studies the potential of RPCs for high precision positioning requiring a consequent workspace. For this purpose, a new concept of planar RPC with 3 degrees of freedom called Triskèle-Bot, composed of a mobile platform and three flexible continuously deformable limbs driven by linear actuators, is proposed. To study its behavior, direct and inverse geometric models are created by a numerical resolution of a system of non-linear partial derivative equations (based on a Kirchhoff beam model) constrained to boundary conditions. A prototype is built to validate these models while offering intrinsic repeatability and an innovative way to measure the intrinsic and extrinsic parameters of the robot. A vision measurement protocol is proposed to minimize the numerous sources of uncertainty inherent to the microscopic scale, and thus obtain measurements of poses with less than ten nanometers of uncertainties. This protocol is used to experimentally measure the repeatability of the Triskele-Bot which reaches 9.13 nanometers in position and 0.71 microradians in orientation. A study of the robot’s accuracy, resulting from an original strategy of calibration, is performed on several trajectories exhibiting values lower than 4 micrometers and 0.6 milliradians. All these results demonstrate the potential of PCR for micro-positioning applications
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Dong, Xin. "Design of a continuum robot for in-situ repair of aero engine." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/31679/.
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Unlike conventional rigid-link robots, continuum robot, also known as elephant trunk and snake arm robot, has numerous numbers of degrees of freedom, which enables it to be used for accessing confined places in many fields, e.g. minimally invasive surgery, and safe robot/objective interactions, e.g. rapid handling. Up to now, most of the researches are driven to develop two kinds of continuum robots, i.e. flexible and rigid backbones, which can be structured with either small diameter but short length or long length but large diameter. Further, according to the observation of this work, the conventional flexible backbone has a twisting problem when bending in the horizontal plane with end load, rendering a poor position control. Therefore, designing a ‘slender’ continuum robot enabling to be employed in in-situ repair of gas turbine engine is still a challenge, since it requires a long length, small diameter, appropriate flexibility and variable stiffness simultaneously. In the research of this PhD thesis, two unique concepts of continuum robot designs were proposed, i.e. double- and twin-pivot compliant joint constructions. By employing compliant joints, the continuum robot was enabled to be built with small diameter/length ratio, appropriate flexibility, stiffness, and minimised twisting angle. Further, a variable stiffness system was developed in this research, which allows the robot arm able to be articulated in a relatively low stiffness state and dramatically enhance its stiffness in a relatively high stiffness state. With these features, this system was able to be navigated into gas turbine engine (Rolls-Royce Trent XWB) and activate inspection and in-situ repair tasks. Since the new continuum robot concepts were introduced, the fundamental modelling was developed for both design and control of the new structures. Firstly, position kinematics models were developed: one for double-pivot construction deployed a new derivation approach, which can simplify the procedure; the other for twin-pivot construction employed a two-sub bending plane model, due to unique construction of the robot, which is different to the conventional method. Secondly, the actuation force analysis was derived, enabling to calculate the action force of an arbitrary section in a multiple-section continuum robot with any bending angle. Further, buckling failure is a major obstacle for designing the compliant joints, since flexible structure can experience buckling. Hence, the analysis of compliant joint critical buckling load was introduced for guiding the hardware design. Also, a general approach for deriving Jacobian and stiffness matrix of continuum robot was presented in this work. According to the concept and modelling of the new concepts, four demonstrators of continuum robots were built and tested. Comparing with the conventional concept, the double-pivot and twin-pivot concept can decrease the twisting angle by 67% and 98.6%, respectively. Further, in the machining trails, it has been proven that a three-section twin-pivot backbone continuum robot can provide an appropriate stiffness, control accuracy (± 1mm error for sweeping in any ± 5º area in the work volume) and repeatability (± 0.5 mm error in the whole work volume), enabling the system to blend metal materials, e.g. aluminium and titanium, which are the materials widely employed in aerospace industry. Next, a two-section variable stiffness system was tested on this demonstrator and the TCP displacement caused by end load can be decreased by up to 69%. Finally, accessing in gas turbine engines has been realised by the final full length continuum robot (1266mm). It has been proven that the system has an appropriate control accuracy to be navigated to reach the first stage of LPC (low pressure compressor) of a gas turbine engine (Rolls-Royce XWB) by following a pre-planned path. Therefore, it can be concluded that the study of this PhD thesis provides a unique continuum robot design concept, which can be utilised for in-situ repair of gas turbine engine.
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Quach, Lucian. "Application of gestural guided continuum robots in orthopaedic surgery." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/208080/1/Lucian_Quach_Thesis.pdf.
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This thesis describes the design and control of snake like concentric tube robots for the purposes of minimally invasive, orthopaedic arthroscopic procedures, although similarities can be drawn in multiple surgical contexts. It analyses multiple aspects of delivering the technology, including different forms of robot hardware, the role of robots in surgery and different control modalities including gesture recognition. A prototype tube robot developed by the Australian Centre for Robotic Vision is tested and end user feedback provided to further refine its development.
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Gray, Jr Ricky Lee. "VERIFICATION OF A THREE-DIMENSIONAL STATICS MODEL FOR CONTINUUM ROBOTICS AND THE DESIGN AND CONSTRUCTION OF A SMALL CONTINUUM ROBOT (SCR)." MSSTATE, 2009. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11062009-155747/.
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Continuum robots are biologically inspired robots that capture the extraordinary abilities of biological structures such as elephant trunks, octopus tentacles, and mamma-lian tongues. They are given the term continuum robots due to their ability to bend conti-nuously rather than at specific joints such as with traditional rigid link robots. They are used in applications such as search and rescue operations, nuclear reactor repairs, colo-noscopies, minimal invasive surgeries, and steerable needles. In this thesis, a model that predicts the shape of a continuum robot is presented and verified. A verification system to verify the validity and accuracy of the model is presented which allows easy and accu-rate measurement of a continuum robot tip position. The model was verified against a flexible rod, the core component of a continuum robot, resulting in an accuracy of 0.61%. Finally, this thesis introduces a novel robot design, consisting of a single rod for the backbone which can be manipulated by applying external forces and torques.
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Cores, Vitor Finotto. "Robô contínuo telescópico para tarefas em alturas elevadas." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-07082009-102547/.
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Observando-se as diversas aplicações de robôs na área de serviços é possível perceber uma crescente busca por manipulação de ferramentas em lugares elevados utilizando dispositivos robóticos, visto que tais tarefas exigem a utilização de diversos equipamentos de segurança e apresentam um alto risco à presença humana. Os exemplos mais comuns desse tipo de tarefa são: inspeção de: máquinas de grande porte, tanques de armazenamento, silos, postes, linhas de transmissão e distribuição de energia elétrica, etc. Com o intuito de aplicar robôs a essas tarefas, e consequentemente aumentar a segurança e eficiência dessas operações, foi realizado, primeiramente neste trabalho, um estudo sobre as classes de robôs manipuladores existentes. Para tanto adotou-se uma classificação que separa os robôs de acordo com o número de juntas, o que gera uma divisão em três diferentes grupos, robôs discretos, robôs do tipo serpente e robôs contínuos. Ao analisar as três classes, observa-se que os robôs contínuos possuem mais graus de liberdade que os outros grupos, apresentando como estrutura uma coluna vertebral continuamente deformável, que em oposição aos tradicionais manipuladores robóticos elo/junta/elo, possuem mecanismos mais simplificados, controle menos complexo devido ao menor número de atuadores e podem interagir com obstáculos encontrados em seu ambiente sem criar grandes forças de contato. Ao utilizar configurações extrínsecas, ou seja, posicionando os atuadores fora da estrutura do robô, e transmitindo o movimento utilizando cabos, é possível construir robôs com alta isolação elétrica, o que é de grande utilidade para operações que envolvem tarefas nas proximidades de redes elétricas de alta tensão. Apesar das diversas vantagens, não foram encontradas na literatura aplicações de robôs contínuos na realização de tarefas em alturas elevadas. Levando em consideração as vantagens oferecidas pelos robôs contínuos, este trabalho propõe o estudo e a aplicação de um robô do tipo contínuo que possua uma arquitetura mais adequada para realizar trabalhos a alturas elevadas. Com o intuito de demonstrar as vantagens oferecidas por essa arquitetura, será realizado um estudo de caso no qual o objeto a ser inspecionado são as cruzetas de madeira em postes de distribuição de energia elétrica. Em uma segunda etapa, elabora-se o projeto mecânico do robô contínuo proposto, onde são detalhados os mecanismos propostos e são feitas simulações utilizando o método dos elementos finitos para analisar o comportamento da estrutura quando submetida a carregamentos. Em uma terceira etapa, adotando-se uma estratégia de controle seqüencial é elaborado o projeto de controle. Em uma ultima etapa, com o intuito de analisar o funcionamento do robô é construído um protótipo, com o qual são feitos os testes.Among several applications of robots in the service field, it is possible to percept an increasing interest in manipulate tools in higher positions using automatic devices, due to the fact that such activities are high risked operations and demands the use of several safety equipments. The most common examples of this kind of activity are the inspection of machines, silos, electrical distribution poles, etc. With the aim of apply robots to these activities and increase the safety and efficiency in these operations, as a first step in this work is done the study of different kinds of manipulators. Adopting a classification based on the number of joints, it is possible to separate robots in three different classes: discrete robots, snake-like robots and continuum robots. By analyzing these classes, it is possible to say that continuum robots have more degrees of freedom than the robots of others groups; Compared with the classic discrete robots, continuum robots have simplified mechanisms, simpler control scheme due to the small number of actuators and, in the case of an obstacle, they can contour the obstacle without generating high contact forces. By positioning the actuators out of the robot structure and transferring the motion using cables, i.e., adopting an extrinsic actuation, it is possible to build continuum robots with high electric insulation that is important in applications in which the robot must work near of an electrical distribution network. Despite these advantages, no previous works concerning the use of continuum robots to work in higher positions were found in the literature. Considering the advantages offered by continuum robots, this work proposes a study and application of a continuum robot that uses a more suitable architecture to work in higher positions. Aiming to demonstrate the advantages provided by this architecture, It will be used a case study, in which, the object to be inspected is the wood cross-arms of an electrical poles used in the electrical distribution networks. In a second step, it is done the mechanical project of the robot, where the proposed mechanisms are explained and structural simulations using the finite element method are performed in order to analyze how the structure would react to loads. In a third step, by adopting a strategy of sequential control, it is done the control project. In the last step, with the aim of analyze the robot in practical situation, a prototype is built, which is used to perform the tests.
Books on the topic "Continuum robot"
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Torrey, John G., and Lawrence J. Winship, eds. Applications of Continuous and Steady-State Methods to Root Biology. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-2237-2.
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G, Torrey John, and Winship Lawrence J. 1952-, eds. Applications of continuous and steady-state methods to root biology. Dordrecht: Kluwer Academic Publishers, 1989.
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Schnakenberg, George H. Computer-assisted continuous coal mining system-research program overview. Washington, D.C: U.S. Dept. of the Interior, Bureau of Mines, 1989.
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Hamann, Heiko. Space-time continuous models of swarm robotic systems: Supporting global-to-local programming. Berlin: Springer-Verlag, 2010.
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Capretti, Paolo, Cecilia Comparini, Matteo Garbelotto, and Nicola La Porta, eds. XIII Conference "Root and Butt Rot of Forest Trees" IUFRO Working Party 7.02.01. Florence: Firenze University Press, 2013. http://dx.doi.org/10.36253/978-88-6655-353-3.
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The present Proceedings comprise the contributions that were presented at the 13th International Conference of the IUFRO W. Party 7.02.01 “Root and Butt Rot of Forest Trees” that was held in Italy from the 4th to the 10th of September 2011. The Conference started in Firenze than moved to FEM Research Centre, S. Michele all’Adige, Trento and continued in San Martino di Castrozza, Dolomite region. Root and Butt Rot of Forest Trees have a high biological and economic impact in forestry. The Proceedings were organized under seven headings: Genomics and Plant-Pathogen Interactions; Systematics, Taxonomy and Phylogeography; Ecology; Population Genetics; Etiology and Epidemiology; Disease Management and Control; New Reports, Diagnostics and Research on the Application of new Diagnostic Methods.
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Tabarah, Edward. Trajectory planning for the coordinated continuous-path motion of two-robot systems. 1993.
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Winship, Lawrence J., and John G. Torrey. Applications of Continuous and Steady-State Methods to Root Biology. Springer, 2012.
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Torrey, John G. Applications of Continuous and Steady-State Methods to Root Biology. Springer, 2011.
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Hall, Richard A. Robots in Popular Culture. Greenwood, 2021. http://dx.doi.org/10.5040/9798216009559.
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Robots in Popular Culture: Androids and Cyborgs in the American Imagination seeks to provide one go-to reference for the study of the most popular and iconic robots in American popular culture. In the last 10 years, technology and artificial intelligence (AI) have become not only a daily but a minute-by-minute part of American life—more integrated into our lives than anyone would have believed even a generation before. Americans have long known the adorable and helpful R2-D2 and the terrible possibilities of Skynet and its army of Terminators. Throughout, we have seen machines as valuable allies and horrifying enemies. Today, Americans cling to their mobile phones with the same affection that Luke Skywalker felt for the squat R2-D2. Meanwhile, our phones, personal computers, and cars have attained the ability to know and learn everything about us. This volume opens with essays about robots in popular culture, followed by 100 A–Z entries on the most famous AIs in film, comics, and more. Sidebars highlight ancillary points of interest, such as authors, creators, and tropes that illuminate the motives of various robots. The volume closes with a glossary of key terms and a bibliography providing students with resources to continue their study of what robots tell us about ourselves.
Book chapters on the topic "Continuum robot"
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Hannan, M. W., and I. D. Walker. "Novel Kinematics for Continuum Robots." In Advances in Robot Kinematics, 227–38. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-011-4120-8_24.
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Altuzarra, Oscar, Diego Caballero, Quichen Zhang, and Francisco J. Campa. "Kinematic Characteristics of Parallel Continuum Mechanisms." In Advances in Robot Kinematics 2018, 293–301. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-93188-3_34.
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Geng, Shineng, Youyu Wang, Cong Wang, and Rongjie Kang. "A Space Tendon-Driven Continuum Robot." In Lecture Notes in Computer Science, 25–35. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-93818-9_3.
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Gotelli, Andrea, Federico Zaccaria, Olivier Kermorgant, and Sébastien Briot. "A Gazebo Simulator for Continuum Parallel Robots." In Advances in Robot Kinematics 2022, 248–56. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-08140-8_27.
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Wang, Long, and Nabil Simaan. "Investigation of Error Propagation in Multi-backbone Continuum Robots." In Advances in Robot Kinematics, 385–94. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-06698-1_40.
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Altuzarra, O., M. Urízar, K. Bilbao, and A. Hernández. "On Kinematics of Lower Mobility Planar Parallel Continuum Robots." In Advances in Robot Kinematics 2024, 222–29. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-64057-5_26.
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Altuzarra, Oscar, Mikel Diez, Javier Corral, Gennaro Teoli, and Marco Ceccarelli. "Kinematic Analysis of a Continuum Parallel Robot." In New Trends in Mechanism and Machine Science, 173–80. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-44156-6_18.
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Walker, Ian D. "Continuum Robot Surfaces: Smart Saddles and Seats." In Mechatronics and Robotics Engineering for Advanced and Intelligent Manufacturing, 97–105. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-33581-0_8.
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Davarpanah, Atoosa, Alireza Takolpour Saleh, and Amir Lotfavar. "Genetic Algorithm Application in Continuum Robot Optimization." In Springer Tracts in Nature-Inspired Computing, 269–87. Singapore: Springer Nature Singapore, 2024. http://dx.doi.org/10.1007/978-981-99-8107-6_14.
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Chikhaoui, Mohamed Taha, Kanty Rabenorosoa, and Nicolas Andreff. "Kinematic Modeling of an EAP Actuated Continuum Robot for Active Micro-endoscopy." In Advances in Robot Kinematics, 457–65. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-06698-1_47.
Full textConference papers on the topic "Continuum robot"
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Walker, I. D. "Robot strings: Long, thin continuum robots." In 2013 IEEE Aerospace Conference. IEEE, 2013. http://dx.doi.org/10.1109/aero.2013.6496902.
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Goergen, Yannik, Gianluca Rizzello, Stefan Seelecke, and Paul Motzki. "Modular Design of an SMA Driven Continuum Robot." In ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/smasis2020-2213.
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Abstract Due to their unique manipulation capabilities, continuum robots find applications in a variety of different areas, such as medical technology or maintenance and repair. When working with continuum robots, it is often necessary to bend the structure according to complex shapes. This is commonly achieved by arranging several individual modules in series. In this paper, a novel continuum robot concept is presented based on a serial arrangement of SMA (Shape Memory Alloy) wires actuated modules. The key advantage of the described modular continuum robot is the number of connection wires required to control the SMA wires, which is also independent of the number of modules. This feature makes it possible to virtually connect a very large number of serial modules, thus enabling to design continuum robots with arbitrary complexity. After outlining the concept, the mechanical and electrical components required to build one module of such an SMA driven continuum robot are introduced.
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Yang, Zhixiong, Xiangyang Zhu, and Kai Xu. "Continuum Delta Robot: a Novel Translational Parallel Robot with Continuum Joints." In 2018 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM). IEEE, 2018. http://dx.doi.org/10.1109/aim.2018.8452695.
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Zhang, Ketao, Chen Qiu, and Jian S. Dai. "An Origami Parallel Structure Integrated Deployable Continuum Robot." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46504.
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This paper presents a novel design for continuum robots in light of origami inspired folding techniques. The work of the present paper starts from design of a crease pattern, which consists of two triangular bases and three waterbomb bases, and folding process for creating an origami parallel structure in 3D from the crease pattern in 2D. Mapping the origami parallel structure to an equivalent kinematic model, the motion characteristics of the origami structure are unraveled in terms of kinematic principles. The analysis reveals that mixed rotational and translational motion of the origami parallel structure enables both axial contraction and bending motion. A novel multi-section continuum robot with integrated origami parallel structures and bias elements is then proposed to imitate not only bending motion but also contraction of continuum apparatus in nature. According to kinematics of the proposed continuum robot and features of the embedded helical spring in each module, three actuation schemes and their enabled two typical working phases with a tendon driven system are presented. A prototype of the continuum robot with six modules connected in serial is produced and tested. The functionality of the proposed continuum robot by integrating the origami parallel structure as its skeleton and helical springs as the compliant backbone is validated by the preliminary experimental results.
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Guo, Yong, Rongjie Kang, Lisha Chen, and Jian Dai. "Dynamic Modeling for a Continuum Robot With Compliant Structure." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-46683.
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Continuum robots have attracted increasing focus in recent years due to their intrinsic compliance and safety. However, the modeling and control of such robots are complex in comparison with conventional rigid ones. This paper presents the design of a pneumatically actuated continuum robot. A 3-dimensional dynamic model is then developed by using the mass-damper-spring system based networks, in which elastic deformation, actuating forces and external forces are taken into account. The model is validated by experiments and shows good agreement with the robotic prototype.
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Goergen, Yannik, Romol Chadda, Rouven Britz, Dominik Scholtes, Nataliya Koev, Paul Motzki, Roland Werthschützky, Mario Kupnik, and Stefan Seelecke. "Shape Memory Alloys in Continuum and Soft Robotic Applications." In ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/smasis2019-5610.
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Abstract Continuum robots are inspired by biological trunks, snakes and tentacles. Unlike conventional robot manipulators, there are no rigid structures or joints. Advantageous is the ease of miniaturization combined with high dexterity, since limiting components such as bearings or gears can be omitted. Most currently used actuation elements in continuum robots require a large drive unit with electric motors or similar mechanisms. Contrarily, shape memory alloys (SMAs) can be integrated into the actual robot. The actuation is realized by applying current to the wires, which eliminates the need of an additional outside drive unit. In the presented study, SMA actuator wires are used in variously scaled continuum robots. Diameters vary from 1 to 60 mm and the lengths of the SMA driven tentacles range from 75 to 220 mm. The SMAs are arranged on an annulus in a defined distance to the neutral fiber, whereby the used cores vary from superelastic NiTi rods to complex structures and also function as restoring unit. After outlining the theoretical basics for the design of an SMA actuated continuum robot, the design process is demonstrated exemplarily using a guidewire for cardiac catheterizations. Results regarding dynamics and bending angle are shown for the presented guidewire.
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Pittiglio, Giovanni, Margherita Mencattelli, Abdulhamit Donder, Yash Chitalia, and Pierre E. Dupont. "Workspace Characterization for Hybrid Tendon and Ball Chain Continuum Robots." In THE HAMLYN SYMPOSIUM ON MEDICAL ROBOTICS. The Hamlyn Centre, Imperial College London London, UK, 2023. http://dx.doi.org/10.31256/hsmr2023.14.
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Continuum robots have attracted considerable attention for applications in minimally invasive diagnostics and therapeutics over the past decade [1]. The primary reason is their ability to navigate narrow and tortuous anatomical passageways, while guaranteeing safe inter- action with the anatomy. In designing such robots, an important goal is create a robot with a workspace appropriate for the clinical task. A significant limitation of many continuum designs re- lates to the minimum radius of curvature that a particular design can achieve. While multiple bending sections can be concatenated to provide more degrees of freedom, the orientations by which a point in the workspace can be approached are often limited. To overcome this limitation, this paper investigates a hybrid design that combines the advantages of tendon- actuated [2] and magnetic ball chain robots [3] as shown in Fig. 1. In this hybrid design, a proximal tendon- actuated section positions the robot with respect to the goal tip location while a distal ball chain section orients the robot tip with respect to the goal location. This abstract describes how the hybrid kinematics can be modeled and illustrates how the hybrid design possesses a dextrous workspace of finite extent.
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Aloi, Vincent, Caroline Black, and Caleb Rucker. "Stiffness Control of Parallel Continuum Robots." In ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-9112.
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Parallel continuum robots can provide compact, compliant manipulation of tools in robotic surgery and larger-scale human robot interaction. In this paper we address stiffness control of parallel continuum robots using a general nonlinear kinetostatic modeling framework based on Cosserat rods. We use a model formulation that estimates the applied end-effector force and pose using actuator force measurements. An integral control approach then modifies the commanded target position based on the desired stiffness behavior and the estimated force and position. We then use low-level position control of the actuators to achieve the modified target position. Experimental results show that after calibration of a single model parameter, the proposed approach achieves accurate stiffness control in various directions and poses.
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"EXPERIMENTS WITH A CONTINUUM ROBOT STRUCTURE." In 7th International Conference on Informatics in Control, Automation and Robotics. SciTePress - Science and and Technology Publications, 2010. http://dx.doi.org/10.5220/0002921501980205.
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Walker, Ian D., Darren M. Dawson, Tamar Flash, Frank W. Grasso, Roger T. Hanlon, Binyamin Hochner, William M. Kier, Christopher C. Pagano, Christopher D. Rahn, and Qiming M. Zhang. "Continuum robot arms inspired by cephalopods." In Defense and Security, edited by Grant R. Gerhart, Charles M. Shoemaker, and Douglas W. Gage. SPIE, 2005. http://dx.doi.org/10.1117/12.606201.
Full textReports on the topic "Continuum robot"
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Tatlicioglu, E., Ian D. Walker, and Darren M. Dawson. Dynamic Modelling for Planar Extensible Continuum Robot Manipulators. Fort Belvoir, VA: Defense Technical Information Center, January 2006. http://dx.doi.org/10.21236/ada462495.
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Braganza, D., D. M. Dawson, I. D. Walker, and N. Nath. Neural Network Grasping Controller for Continuum Robots. Fort Belvoir, VA: Defense Technical Information Center, January 2006. http://dx.doi.org/10.21236/ada462583.
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Graves, Kevin P. Continuous Localization and Navigation of Mobile Robots. Fort Belvoir, VA: Defense Technical Information Center, May 1997. http://dx.doi.org/10.21236/ada418467.
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Zhang, Xingyu, Matteo Ciantia, Jonathan Knappett, and Anthony Leung. Micromechanical study of potential scale effects in small-scale modelling of sinker tree roots. University of Dundee, December 2021. http://dx.doi.org/10.20933/100001235.
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When testing an 1:N geotechnical structure in the centrifuge, it is desirable to choose a large scale factor (N) that can fit the small-scale model in a model container and avoid unwanted boundary effects, however, this in turn may cause scale effects when the structure is overscaled. This is more significant when it comes to small-scale modelling of sinker root-soil interaction, where root-particle size ratio is much lower. In this study the Distinct Element Method (DEM) is used to investigate this problem. The sinker root of a model root system under axial loading was analysed, with both upward and downward behaviour compared with the Finite Element Method (FEM), where the soil is modelled as a continuum in which case particle-size effects are not taken into consideration. Based on the scaling law, with the same prototype scale and particle size distribution, different scale factors/g-levels were applied to quantify effects of the ratio of root diameter (𝑑𝑟) to mean particle size (𝐷50) on the root rootsoil interaction.
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Pellet, Philippe. Understanding the 2020-2021 Tigray Conflict in Ethiopia : Background, Root Causes, and Consequences. Külügyi és Külgazdasági Intézet, 2021. http://dx.doi.org/10.47683/kkielemzesek.ke-2021.39.
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The military offensive unleashed on 4 November, 2020 by the central government in Addis Ababa against the regional state of Tigray is the culmination of escalating tensions between Prime Minister Abiy Ahmed, in power since 2018, and the Tigray People’s Liberation Front (TPLF). Ethiopian federal troops, supported by the military forces of Amhara regional state and the Eritrean army, quickly occupied the main towns in Tigray by late November 2020, but Tigrayan forces retained control of large areas, particularly in the mountainous regions, where fighting continued. An offensive launched in June 2021 by the Tigrayan forces resulted in the recapture of the main towns, including Tigray’s capital Mekelle, leading the Ethiopian government to declare a unilateral ceasefire. There are numerous testimonies on major abuses and killings of civilians and clerics by the occupying forces, as well as looting of key infrastructure, leading to a major humanitarian crisis. Humanitarian aid has been hampered by continued fighting and access restrictions. The ceasefire raised hopes that massive humanitarian aid can finally be delivered, but statements made by Abiy Ahmed in June 2021, denying the existence of famine in Tigray and accusing aid organizations of supporting Tigrayan rebels, raise fears that the government’s strategy may be to maintain a blockade of Tigray, further exacerbating an already catastrophic humanitarian situation. In addition to analysing the immediate causes and consequences, this study also shows that this conflict has its roots in the long history of a country composed of more than 80 ethnic groups.
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Cardellina II, John. Turmeric Raw Material and Products Laboratory Guidance Document. ABC-AHP-NCNPR Botanical Adulterants Prevention Program, March 2020. http://dx.doi.org/10.59520/bapp.lgd/wcyh6498.
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Turmeric (Curcuma longa L.) dietary supplements, including standardized or partially purified extracts with high concentrations of curcumin, have enjoyed sustained sales growth in the United States over the past 5-6 years, while turmeric powder continues to be an important spice, flavor, and colorant in many regions of the world. There is considerable evidence that both powdered root and rhizome, as well as root and rhizome extracts, have been subjected to adulteration. This document should be viewed in relation to the corresponding Botanical Adulterants Prevention Bulletin on turmeric published by the ABC-AHP-NCNPR Botanical Adulterants Prevention Program.
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Eslami, Keyvan, and Thomas M. Phelan. The Art of Temporal Approximation: An Investigation into Numerical Solutions to Discrete and Continuous-Time Problems in Economics. Federal Reserve Bank of Cleveland, May 2023. http://dx.doi.org/10.26509/frbc-wp-202310.
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A recent literature within quantitative macroeconomics has advocated the use of continuous-time methods for dynamic programming problems. In this paper we explore the relative merits of continuous-time and discrete-time methods within the context of stationary and nonstationary income fluctuation problems. For stationary problems in two dimensions, the continuous-time approach is both more stable and typically faster than the discrete-time approach for any given level of accuracy. In contrast, for convex lifecycle problems (in which age or time enters explicitly), simply iterating backwards from the terminal date in discrete time is superior to any continuous-time algorithm. However, we also show that the continuous-time framework can easily incorporate nonconvexities and multiple controls—complications that often require either problem-specific ingenuity or nonlinear root-finding in the discrete-time context. In general, neither approach unequivocally dominates the other, making the choice of one over the other an art, rather than an exact science. Code can be found at https://github.com/tphelanECON/The Art of Temporal Approximation WP.
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Orth. L51762 Investigation of Fatigue Properties of Girth Welds with Root Imperfections Allowed. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), January 1997. http://dx.doi.org/10.55274/r0010233.
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Fatigue analysis of welded components and structures according to established codes is based upon either S-N design curves or fracture mechanics principles. Fatigue damage in nominally sound joints is commonly estimated using an appropriate S-N curve in conjunction with a linear cumulative damage rule (i.e., Miner"s rule). By comparison, fracture mechanics is used to assess the growth of an imperfection during a period of cyclic loading, or to assess whether an imperfection will remain dormant under the applied cyclic loading condition. Thus, the S-N approach is used mostly during initial design, while the fracture mechanics approach is used mostly to justify the continued operation of existing structures. As the aim of this investigation is the rationalization of certain features of API-1104, an initial design code, the S-N approach was used here. The work described in this report was aimed at determining the effect of root imperfections allowed by API 1104 on the fatigue properties of girth welds, and to recommend a S-N curve appropriate for girth welds in pipelines. S-N curves were developed for single-sided girth welds without a backing strip using pipe strip specimens containing various sizes of incomplete root penetration and lack-of-root sidewall fusion.
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Shani, Uri, Lynn Dudley, Alon Ben-Gal, Menachem Moshelion, and Yajun Wu. Root Conductance, Root-soil Interface Water Potential, Water and Ion Channel Function, and Tissue Expression Profile as Affected by Environmental Conditions. United States Department of Agriculture, October 2007. http://dx.doi.org/10.32747/2007.7592119.bard.
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Constraints on water resources and the environment necessitate more efficient use of water. The key to efficient management is an understanding of the physical and physiological processes occurring in the soil-root hydraulic continuum.While both soil and plant leaf water potentials are well understood, modeled and measured, the root-soil interface where actual uptake processes occur has not been sufficiently studied. The water potential at the root-soil interface (yᵣₒₒₜ), determined by environmental conditions and by soil and plant hydraulic properties, serves as a boundary value in soil and plant uptake equations. In this work, we propose to 1) refine and implement a method for measuring yᵣₒₒₜ; 2) measure yᵣₒₒₜ, water uptake and root hydraulic conductivity for wild type tomato and Arabidopsis under varied q, K⁺, Na⁺ and Cl⁻ levels in the root zone; 3) verify the role of MIPs and ion channels response to q, K⁺ and Na⁺ levels in Arabidopsis and tomato; 4) study the relationships between yᵣₒₒₜ and root hydraulic conductivity for various crops representing important botanical and agricultural species, under conditions of varying soil types, water contents and salinity; and 5) integrate the above to water uptake term(s) to be implemented in models. We have made significant progress toward establishing the efficacy of the emittensiometer and on the molecular biology studies. We have added an additional method for measuring ψᵣₒₒₜ. High-frequency water application through the water source while the plant emerges and becomes established encourages roots to develop towards and into the water source itself. The yᵣₒₒₜ and yₛₒᵢₗ values reflected wetting and drying processes in the rhizosphere and in the bulk soil. Thus, yᵣₒₒₜ can be manipulated by changing irrigation level and frequency. An important and surprising finding resulting from the current research is the obtained yᵣₒₒₜ value. The yᵣₒₒₜ measured using the three different methods: emittensiometer, micro-tensiometer and MRI imaging in both sunflower, tomato and corn plants fell in the same range and were higher by one to three orders of magnitude from the values of -600 to -15,000 cm suggested in the literature. We have added additional information on the regulation of aquaporins and transporters at the transcript and protein levels, particularly under stress. Our preliminary results show that overexpression of one aquaporin gene in tomato dramatically increases its transpiration level (unpublished results). Based on this information, we started screening mutants for other aquaporin genes. During the feasibility testing year, we identified homozygous mutants for eight aquaporin genes, including six mutants for five of the PIP2 genes. Including the homozygous mutants directly available at the ABRC seed stock center, we now have mutants for 11 of the 19 aquaporin genes of interest. Currently, we are screening mutants for other aquaporin genes and ion transporter genes. Understanding plant water uptake under stress is essential for the further advancement of molecular plant stress tolerance work as well as for efficient use of water in agriculture. Virtually all of Israel’s agriculture and about 40% of US agriculture is made possible by irrigation. Both countries face increasing risk of water shortages as urban requirements grow. Both countries will have to find methods of protecting the soil resource while conserving water resources—goals that appear to be in direct conflict. The climate-plant-soil-water system is nonlinear with many feedback mechanisms. Conceptual plant uptake and growth models and mechanism-based computer-simulation models will be valuable tools in developing irrigation regimes and methods that maximize the efficiency of agricultural water. This proposal will contribute to the development of these models by providing critical information on water extraction by the plant that will result in improved predictions of both water requirements and crop yields. Plant water use and plant response to environmental conditions cannot possibly be understood by using the tools and language of a single scientific discipline. This proposal links the disciplines of soil physics and soil physical chemistry with plant physiology and molecular biology in order to correctly treat and understand the soil-plant interface in terms of integrated comprehension. Results from the project will contribute to a mechanistic understanding of the SPAC and will inspire continued multidisciplinary research.
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Neild, Rachel. The Role of the Police in Violence Prevention. Inter-American Development Bank, July 1999. http://dx.doi.org/10.18235/0008936.
Full textAbstract:
This document is one of a series of technical notes that describe the nature and magnitude of violence in the region, its causes and effects, and how it can be prevented and controlled. The notes provide useful information on designing programs and policies to prevent and deal with violence. This technical note discusses the roles of police in controlling and preventing violence and crime. These issues are the subject of much debate. Broadly, the debate breaks down into two opposing views that represent the two ends of a continuum of crime prevention programs: One view asserts the importance of the police role in controlling crime through effective law enforcement that removes criminals from the streets and increases the potential cost of committing crime, thus deterring potential offenders. The other viewpoint posits that police actions operate at the margins rather than at the root causes of crime and so have little impact on broad trends in crime rates, which are fundamentally driven by economic, demographic, social, and cultural factors.