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1
Ali, Imran. "Spacecraft nonlinear attitude control with bounded control input." Thesis, University of Glasgow, 2010. http://theses.gla.ac.uk/1717/.
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The research in this thesis deals with nonlinear control of spacecraft attitude stabilization and tracking manoeuvres and addresses the issue of control toque saturation on a priori basis. The cascaded structure of spacecraft attitude kinematics and dynamics makes the method of integrator backstepping preferred scheme for the spacecraft nonlinear attitude control. However, the conventional backstepping control design method may result in excessive control torque beyond the saturation bound of the actuators. While remaining within the framework of conventional backstepping control design, the present work proposes the formulation of analytical bounds for the control torque components as functions of the initial attitude and angular velocity errors and the gains involved in the control design procedure. The said analytical bounds have been shown to be useful for tuning the gains in a way that the guaranteed maximum torque upper bound lies within the capability of the actuator and, hence, addressing the issue of control input saturation. Conditions have also been developed as well as the generalization of the said analytical bounds which allow for the tuning of the control gains to guarantee prescribed stability with the additional aim that the control action avoids reaching saturation while anticipating the presence of bounded external disturbance torque and uncertainties in the spacecraft moments of inertia. Moreover, the work has also been extended blending it with the artificial potential function method for achieving autonomous capability of avoiding pointing constraints for the case of spacecraft large angle slew manoeuvres. The idea of undergoing such manoeuvres using control moment gyros to track commanded angular momentum rather than a torque command has also been studied. In this context, a gimbal position command generation algorithm has been proposed for a pyramid-type cluster of four single gimbal control moment gyros. The proposed algorithm not only avoids the saturation of the angular momentum input from the control moment gyro cluster but also exploits its maximum value deliverable by the cluster along the direction of the commanded angular momentum for the major part of the manoeuvre. In this way, it results in rapid spacecraft slew manoeuvres. The ideas proposed in the thesis have also been validated using numerical simulations and compared with results already existing in the literature.
2
Kaliora, Georgia. "Control of nonlinear systems with bounded signals." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397289.
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Ntumy, Emmanuel. "Active sound control in 3D bounded regions." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/active-sound-control-in-3d-bounded-regions(45886d75-5437-464a-95c6-27cfc9613567).html.
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Active sound control (ASC) based on surface potentials is one of two methods of noise control using potential-based method. The method does not require detailed knowledge of the noise source parameters, boundary conditions, characteristics of the acoustic medium or the transmission path. It allows significant volumetric noise cancellation inside the shielded region using only the knowledge of the total acoustic field which includes the wanted sound at the boundary of the shielded region(s) to obtain additional secondary sound sources known as controls which are distributed at the boundary of the shielded region. It allows the presence of a wanted sound inside the shielded region, which it preserves while canceling the noise. In contrast, other methods require various detailed knowledge. In many cases, they do not allow the wanted sound to be generated inside the protected region. The aim of this thesis is to implement numerically the ASC method in 3D bounded regions and confirm its theoretical predictions. The theoretical framework for the method has already been established in previous related literature. Experimental work in this area is mostly limited to laboratory experiments in one dimensional settings. The algorithm was tested in 3D numerical test cases in the frequency domain involving single and composite regions. The Helmholtz equation was used to model the wave propagation. In both single and composite regions, volumetric noise cancellation of over 20 dB was achieved at most areas of the shielded regions. Outside the shielded region, the field remained practically unchanged during noise cancellation. On the other hand, in test cases involving wanted sound, the noise inside the shielded region was canceled while the wanted sound was preserved. However, outside the shielded region, the field was amplified. Moreover in composite regions, the selective cancellation/propagation of the wanted sound was demonstrated successfully in regions having two and three sub-regions by allowing the wanted sound to propagate to one region but not to the other. To enforce selective propagation of the wanted sound, additional steps are required to obtain the separate field of the wanted sound in addition to the total field. A study on the effect of the number of controls on noise cancellation showed that in both single and composite regions, as the number of controls fell there was a corresponding decrease in the level of noise cancellation. A doubling of the number of controls yields about ~3 dB of noise cancellation, and vice versa. The independence of the operation of the algorithm on characteristics or number of noise sources, shape, size or position of shielded region is also demonstrated via further test cases. In all test cases considered, the results confirmed the theoretical predictions. However, at resonance modes the method did not provide noise cancellation, though at near-resonance modes a lower level of noise cancellation was obtained. Although this work considered only monochromatic waves, the method is applicable to broadband noise. In real-time application of the method, the assumption in the thesis that only the field of the noise source(s) is known does not hold and therefore its implementation is more complicated.
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Hoepffner, Jerome. "Control and estimation of wall bounded flow systems." Licentiate thesis, KTH, Mechanics, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1805.
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<p>This thesis focuses on the application of linear feedback control and estimation to channel flow. Both the initial stage of the transition and the low Reynolds number turbulent cases are studied. From sensors at the wall, the state of the flow is estimated, using a stochastic description of the flow disturbances. The estimated state is in turn fed back to the flow system in order to achieve a control objective. This model based scheme uses the linearised Navier-Stokes equations as a dynamic model for the flow evolution. The emphasis is here put on the estimation procedure, that was so far the limiting factor for the overall control performance. We show that the estimation performance rely on a correct description of the flow disturbances. We apply model reduction on the controller, and show that we can maintain the control performance even with a highly truncated system. We then introduce a representation of the feedback by means of transfer functions, and discuss the implication of the transfer function for the interpretation of the feedback, and for possible implementation of the control loop.</p>
5
Wu, Dong-Nan. "Active bounded-state vibration control for structural applications." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12326.
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Hogg, Lisa Marie Jean. "Control of social reasoning in resource bounded agents." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251682.
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Shan, Xu Yi. "Bounded feedback and structural issues in linear multivariable systems." Thesis, City University London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316131.
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Jamak, Anes. "Stabilization of Discrete-time Systems With Bounded Control Inputs." Thesis, University of Waterloo, 2000. http://hdl.handle.net/10012/765.
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In this paper we examine the stabilization of LTI discrete-time systems with control input constraints in the form of saturation nonlinearities. This kind of constraint is usually introduced to simulate the effect of actuator limitations. Since global controllability can not be assumed in the presence of constrained control, the controllable regions and their characterizations are analyzed first. We present an efficient algorithm for finding controllable regions in terms of their boundary hyperplanes (inequality constraints). A previously open question about the exact number of irredundant boundary hyperplanes is also resolved here. The main result of this research is a time-optimal nonlinear controller which stabilizes the system on its controllable region. We give analgorithm for on-line computation of control which is also implementable for high-order systems. Simulation results show superior response even in the presence of disturbances.
9
Arora, Sumit. "Online regulations of low order systems under bounded control." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/376.
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Time-optimal solutions provide us with the fastest means to regulate a system in presence of input constraints. This advantage of time-optimal control solutions is offset by the fact that their real-time implementation involves computationally intensive iterative techniques. Moreover, time-optimal controls depend on the initial state and have to be recalculated for even the slightest perturbation. Clearly time-optimal controls are not good candidates for online regulation. Consequently, the search for alternatives to time-optimal solutions is a very active area of research. The work described here is inspired by the simplicity of optimal-aim concept. The "optimal-aim strategies" provide online regulation in presence of bounded inputs with minimal computational effort. These are based purely on state-space geometry of the plant and are inherently adaptive in nature. Optimal-aim techniques involve aiming of trajectory derivative (or the state velocity vector) so as to approach the equilibrium state in the best possible manner. This thesis documents the efforts to develop an online regulation algorithm for systems with input constraints. Through a number of hypotheses focussed on trying to reproduce the exact time-optimal solution, the diffculty associated with this task is demonstrated. A modification of optimal-aim concept is employed to develop a novel regulation algorithm. In this algorithm, aim directions are chosen in a special manner to generate the time-optimal control approximately. The control scheme thus developed is shown to be globally stabilizing for systems having eigenvalues in the CLHP (closed left half-plane). It is expected that this method or its modifications can be extended to higher dimensional systems as a part of future research. An alternative control algorithm involving a simple state-space aiming concept is also developed and discussed.
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Iourtchenko, Daniil V. "Optimal bounded control and relevant response analysis for random vibrations." Link to electronic thesis, 2001. http://www.wpi.edu/Pubs/ETD/Available/etd-0525101-111407.
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Thesis (Ph. D.)--Worcester Polytechnic Institute.<br>Keywords: Stochastic optimal control; dynamic programming; Hamilton-Jacobi-Bellman equation; Random vibration. Keywords: Stochastic optimal control; dynamic programming; Hamilton-Jacobi-Bellman equation; Random vibration; energy balance method. Includes bibliographical references (p. 86-89).
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Pfaff, Sebastian [Verfasser]. "Optimal Control of Hyperbolic Conservation Laws on Bounded Domains with Switching Controls / Sebastian Pfaff." München : Verlag Dr. Hut, 2015. http://d-nb.info/1080754601/34.
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Tahir, Furqan. "Robust feedback model predictive control of norm-bounded uncertain systems." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/24749.
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This thesis is concerned with the Robust Model Predictive Control (RMPC) of linear discrete-time systems subject to norm-bounded model-uncertainty, additive disturbances and hard constraints on the input and state. The aim is to design tractable, feedback RMPC algorithms that are based on linear matrix inequality (LMI) optimizations. The notion of feedback is very important in the RMPC control parameterization since it enables effective disturbance/uncertainty rejection and robust constraint satisfaction. However, treating the state-feedback gain as an optimization variable leads to non-convexity and nonlinearity in the RMPC scheme for norm-bounded uncertain systems. To address this problem, we propose three distinct state-feedback RMPC algorithms which are all based on (convex) LMI optimizations. In the first scheme, the aforementioned non-convexity is avoided by adopting a sequential approach based on the principles of Dynamic Programming. In particular, the feedback RMPC controller minimizes an upper-bound on the cost-to-go at each prediction step and incorporates the state/input constraints in a non-conservative manner. In the second RMPC algorithm, new results, based on slack variables, are proposed which help to obtain convexity at the expense of only minor conservatism. In the third and final approach, convexity is achieved by re-parameterizing, online, the norm-bounded uncertainty as a polytopic (additive) disturbance. All three RMPC schemes drive the uncertain-system state to a terminal invariant set which helps to establish Lyapunov stability and recursive feasibility. Low-complexity robust control invariant (LC-RCI) sets, when used as target sets, yield computational advantages for the associated RMPC schemes. A convex algorithm for the simultaneous computation of LC-RCI sets and the corresponding controller for norm-bounded uncertain systems is also presented. In this regard, two novel results to separate bilinear terms without conservatism are proposed. The results being general in nature also have application in other control areas. The computed LC-RCI sets are shown to have substantially improved volume as compared to other schemes in the literature. Finally, an output-feedback RMPC algorithm is also derived for norm-bounded uncertain systems. The proposed formulation uses a moving window of the past input/output data to generate (tight) bounds on the current state. These bounds are then used to compute an output-feedback RMPC control law using LMI optimizations. An output-feedback LC-RCI set is also designed, and serves as the terminal set in the algorithm.
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Menéndez, Gómez José María. "Computational Methods for Control of Queueing Models in Bounded Domains." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/28036.
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The study of stochastic queueing networks is quite important due to the many applications including transportation, telecommunication, and manufacturing industries. Since there is often no explicit solution to these types of control problems, numerical methods are needed. Following the method of Boué-Dupuis, we use a Dynamic Programming approach of optimization on a controlled Markov Chain that simulates the behavior of a fluid limit of the original process. The search for an optimal control in this case involves a Skorokhod problem to describe the dynamics on the boundary of closed, convex domain. Using relaxed stochastic controls we show that the approximating numerical solution converges to the actual solution as the size of the mesh in the discretized state space goes to zero, and illustrate with an example.<br>Ph. D.
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Tamaddoni, Seyed Hossein. "Optimal Vehicle Stability Control with Driver Input and Bounded Uncertainties." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77238.
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For decades vehicle control has been extensively studied to investigate and improve vehicle stability and performance. Such controllers are designed to improve driving safety while the driver is still in control of the vehicle. It is known that human drivers are capable to learn and adapt to their built-in vehicle controller in order to improve their control actions based on their past driving experiences with the same vehicle controller. Although the learning curve varies for different human drivers, it results in a more constructive cooperation between the human driver and the computer-based vehicle controller, leading to globally optimal vehicle stability.
The main intent of this research is to develop a novel cooperative interaction model between the human driver and vehicle controller in order to obtain globally optimal vehicle steering and lateral control. Considering the vehicle driver-controller interactions as a common two-player game problem where both players attempt to improve their payoffs, i.e., minimize their objective functions, the Game Theory approach is applied to obtain the optimal driver's steering inputs and controller's corrective yaw moment. Extending this interaction model to include more realistic scenarios, the model is discretized and a road preview model is added to account for the driver's preview-time characteristic. Also, a robust interaction model is developed to stabilize the vehicle performance while taking bounded uncertainty effects in driver's steering behavior into consideration using the Integral Sliding Mode control methodology.
For evaluation purposes, a nonlinear vehicle dynamics model is developed that captures nonlinear tire characteristics and includes driver steering controllability and vehicle speed control systems such as cruise control, differential braking, and anti-lock braking systems. A graphical user interface (GUI) is developed in MATLAB to ease the use of the vehicle model and hopefully encourage its widespread application in the future.
Simulation results indicate that the proposed cooperative interaction model, which is the end-product of human driver's and vehicle controller's mutual understanding of each other's objective and performance quality, results in more optimal and stable vehicle performance in lateral and yaw motions compared to the existing LQR controllers that tend to independently optimize the driver and vehicle controller inputs.<br>Ph. D.
15
LaClare, Jeanette M. "VHF air to ground communications in bounded oceanic airspace." Master's thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-02162010-020322/.
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Saraf, Nilay. "Bounded-variable least-squares methods for linear and nonlinear model predictive control." Thesis, IMT Alti Studi Lucca, 2019. http://e-theses.imtlucca.it/296/1/Saraf_phdthesis.pdf.
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This dissertation presents an alternative approach to formulate
and solve optimization problems arising in real-time model
predictive control (MPC). First it has been shown that by
using a quadratic penalty function, the linear MPC optimization
problem can be formulated as a least-squares problem
subject to bounded variables while directly employing
models in their input/output form. A theoretical analysis
on stability and optimality is included with a comparison
against the conventional condensed approach based on linear
state-space models. These concepts are straightforwardly
extended for fast nonlinear MPC with bounded variables.
An active-set algorithm based on a novel application of linear
algebra methods is proposed for efficiently solving the
resulting box-constrained (nonlinear) least-squares problems
with global convergence, numerical robustness, and easy deployability
on industrial embedded hardware platforms. Finally,
new methods and tools are devised for maximizing
efficiency of the solution algorithm considering the numerically
sparse structure of the non-condensed MPC problem.
Based on these methods, the problem construction phase in
MPC design is systematically eliminated by parameterizing
the optimization algorithm such that it can adapt to real-time
changes in the model and tuning parameters while significantly
reducing memory and computational complexity with
a potentially self-contained matrix-free implementation. Numerical
simulation results included in this thesis testify the
potential, applicability, numerical robustness and efficiency
of the proposed methods for practical real-time embedded
MPC.
17
Stroh, Alexander [Verfasser]. "Reactive Control of Turbulent Wall-Bounded Flows for Skin Friction Drag Reduction / Alexander Stroh." Karlsruhe : KIT Scientific Publishing, 2019. http://www.ksp.kit.edu.
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Hwang, Yongyun. "Large-scale streaks in wall-bounded turbulent flows: amplication, instability, self-sustaining process and control." Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00564901.
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Wall-bounded turbulent flows such as plane Couette flow, channel, pipe flows and boundary layer flows are fundamental problem of interest that we often meet in many scientific and engineering situations. The goal of the present thesis is to investigate the origin of large-scale streaky motions observed in the wall-bounded turbulent flows. Under a hypothesis that the large-scale streaky motions sustain with a process similar to the well-known near-wall self-sustaining cycle, the present thesis have pursued on four separate subjects: (i) non-modal amplification of streaks, (ii) the secondary instability of the finite amplitude streaks, (iii) existence of a self-sustaining process at large scale and (iv) turbulent skin friction reduction by forcing streaks. First, using a linear model with turbulent mean flow and the related eddy viscosity, it is shown that the streaks are largely amplified by harmonic and stochastic forcing. The largely amplified streaks undergo the secondary instability and it has been associated with the formation of the large-scale motions (bulge). The existence of a self-sustaining process involving the amplification and instability of streaks at large scale is proved by quenching the smaller-scale energy carrying eddies in the near-wall and logarithmic regions. Finally, it is shown that artificially forcing of large-scale streaks reduce the turbulent skin friction up to 10\% by attenuating the near-wall streamwise vortices.
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Hwang, Yongyun. "Large-scale streaks in wall-bounded turbulent flows: amplification, instability, self-sustaining process and control." Palaiseau, Ecole polytechnique, 2010. http://pastel.archives-ouvertes.fr/docs/00/56/49/01/PDF/Thesis_final.pdf.
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Sur la plateforme de thèses en ligne Tel on trouve le résumé suivant en anglais : Wall-bounded turbulent flows such as plane Couette flow, channel, pipe flows and boundary layer flows are fundamental problem of interest that we often meet in many scientific and engineering situations. The goal of the present thesis is to investigate the origin of large-scale streaky motions observed in the wall-bounded turbulent flows. Under a hypothesis that the large-scale streaky motions sustain with a process similar to the well-known near-wall self-sustaining cycle, the present thesis have pursued on four separate subjects: (i) non-modal amplification of streaks, (ii) the secondary instability of the finite amplitude streaks, (iii) existence of a self-sustaining process at large scale and (iv) turbulent skin friction reduction by forcing streaks. First, using a linear model with turbulent mean flow and the related eddy viscosity, it is shown that the streaks are largely amplified by harmonic and stochastic forcing. The largely amplified streaks undergo the secondary instability and it has been associated with the formation of the large-scale motions (bulge). The existence of a self-sustaining process involving the amplification and instability of streaks at large scale is proved by quenching the smaller-scale energy carrying eddies in the near-wall and logarithmic regions. Finally, it is shown that artificially forcing of large-scale streaks reduce the turbulent skin friction up to 10 % by attenuating the near-wall streamwise vortices.
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Jahromizadeh, Soroush. "Join rate control and scheduling for providing bounded delay with high efficiency in multihop wireless networks." Thesis, City University London, 2013. http://openaccess.city.ac.uk/11790/.
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This thesis considers the problem of supporting traffic with elastic bandwidth requirements and hard end-to-end delay constraints in multi-hop wireless networks, with focus on source transmission rates and link data rates as the key resource allocation decisions. Specifically, the research objective is to develop a source rate control and scheduling strategy that guarantees bounded average end-to-end queueing delay and maximises the overall utility of all incoming traffic, using network utility maximisation framework. The network utility maximisation based approaches to support delay-sensitive traffic have been predominantly based on either reducing link utilisation, or approximation of links as M/D/1 queues. Both approaches lead to unpredictable transient behaviour of packet delays, and inefficient link utilisation under optimal resource allocation. On the contrary, in this thesis an approach is proposed where instead of hard delay constraints based on inaccurate M/D/1 delay estimates, traffic end-to-end delay requirements are guaranteed by proper forms of concave and increasing utility functions of their transmission rates. Specifically, an alternative formulation is presented where the delay constraint is omitted and sources’ utility functions are multiplied by a weight factor. The alternative optimisation problem is solved by a distributed scheduling algorithm incorporating a duality-based rate control algorithm at its inner layer, where optimal link prices correlate with their average queueing delays. The proposed approach is then realised by a scheduling algorithm that runs jointly with an integral controller whereby each source regulates the queueing delay on its paths at the desired level, using its utility weight coefficient as the control variable. Since the proposed algorithms are based on solving the alternative concave optimisation problem, they are simple, distributed and lead to maximal link utilisation. Hence, they avoid the limitations of the previous approaches. The proposed algorithms are shown, using both theoretical analysis and simulation, to achieve asymptotic regulation of end-to-end delay given the step size of the proposed integral controller is within a specified range.
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Stroh, Alexander [Verfasser], and B. [Akademischer Betreuer] Frohnapfel. "Reactive Control of Turbulent Wall-Bounded Flows for Skin Friction Drag Reduction / Alexander Stroh ; Betreuer: B. Frohnapfel." Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1119243025/34.
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Józsa, Tamás István. "Drag reduction by passive in-plane wall motions in turbulent wall-bounded flows." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/33155.
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Losses associated with turbulent flows dissipate a significant amount of generated energy. Such losses originate from the drag force, which is often described as the sum of the pressure drag and the friction drag. This thesis sets out to explore the hypothesis that passive wall motions driven by fluid mechanical forces are able to reduce the friction drag in fully developed turbulent boundary layers. Firstly, the streamwise and spanwise opposition controls proposed by Choi et al. (1994, Journal of Fluid Mechanics) are revisited to identify beneficial wall motions. Near-wall streamwise or spanwise velocity fluctuations are measured along a detection plane parallel to the wall (sensing). For streamwise control, the wall velocities are set to be equivalent to the measured streamwise velocity fluctuations, whereas for spanwise control, the wall velocities are set to have the same magnitude but opposite direction as the measured spanwise velocity fluctuations (actuation). Direct numerical simulations of canonical turbulent channel flows are carried out at low (Reτ ≈ 180) and intermediate (Reτ ≈ 1000) Reynolds numbers to quantify the effect of the distance between the wall and the detection plane. The investigation reveals the primary differences between the mechanisms underlying the two active in-plane controls. The modified flow features and turbulence statistics show that the streamwise control amplifies the most energetic streamwise velocity fluctuations and damps the near-wall vorticity fluctuations. In comparison, the spanwise control induces near-wall vorticity in order to counteract the quasi-streamwise vortices of the near-wall cycle and suppress turbulence production. Although, the working principles of the active controls are fundamentally different, both achieve drag reduction by mitigating momentum transfer between the velocity components. Secondly, two theoretical passive compliant wall models are proposed, the aim being to sustain beneficial wall motions identified by active flow control simulations. In the proposed models, streamwise or spanwise in-plane wall motions are governed by an array of independent one-degree-of-freedom damped harmonic oscillators. Unidirectional wall motions are driven by local streamwise or spanwise wall shear stresses. A weak coupling scheme is implemented to investigate the interaction between the compliant surface models and the turbulent flow in the channel by means of direct numerical simulations. A linear analytical solution of the coupled differential equation system is derived for laminar pulsatile channel flows allowing verification and validation of the numerical model. The obtained analytical solution is utilised to map the parameter space of the passive controls and estimate the effect of the wall motions. It is shown that depending on the control parameters, the proposed compliant walls decrease or increase the vorticity fluctuations at the wall similarly to the active controls. This is confirmed by direct numerical simulations. On the one hand, when the control parameters are chosen appropriately, the passive streamwise control damps the near-wall vorticity fluctuations and sustains the same drag reduction mechanism as the active streamwise control. This leads to modest, 3.7% and 2.3% drag reductions at low and intermediate Reynolds numbers. On the other hand, the spanwise passive control is not capable of increasing the near-wall vorticity fluctuations as dictated by the active spanwise control. For this reason, passive spanwise wall motions can increase the friction drag by more than 50%. The results emphasise the necessity of anisotropy for a practical compliant wall design. The present work demonstrates for the first time that passive wall motions can decrease friction drag in fully turbulent wall-bounded flows. The thesis sheds light on the working principle of an active streamwise control, and proposes a passive streamwise control exploiting the same drag reduction mechanism. An analytical model is developed to give a ready prediction of the statistical behaviour of passive in-plane wall motions. Whereas streamwise passive wall motions are found beneficial when the control parameters are chosen appropriately, solely spanwise passive wall motions lead to a drag penalty.
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ABDALLA, TALAL ALMUTAZ ALMANSI. "Recursive Algorithms for Set-Membership Estimation." Doctoral thesis, Politecnico di Torino, 2022. https://hdl.handle.net/11583/2972788.
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Song, Zhuoyue. "Robust analysis and synthesis for uncertain negative-imaginary systems." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/robust-analysis-and-synthesis-for-uncertain-negativeimaginary-systems(9de4af43-983c-42a2-bafe-062970a738be).html.
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Negative-imaginary systems are broadly speaking stable and square (equal number of inputs and outputs) systems whose Nyquist plot lies underneath (never touches for strictly negative-imaginary systems) the real axis when the frequency varies in the open interval 0 to ∞. This class of systems appear quite often in engineering applications, for example, in lightly damped flexible structures with collocated position sensors and force actuators, multi-link robots, DC machines, active filters, etc. In this thesis, robustness analysis and controller synthesis methods for uncertain negative-imaginary systems are explored. Two new reformulation techniques are proposed that facilitate both the robustness analysis and controller synthesis for uncertain negative-imaginary systems. These reformulations are based on the transformation from negative-imaginary systems to a bounded-real framework via the positive-real property. In the presence of strictly negative-imaginary uncertainty, the robust stabilization problem is posed in an equivalent H∞ control framework; similarly, a negative-imaginary robust performance analysis problem is cast into an equivalent μ-framework. The latter framework also allows robust stability analysis when the perturbations are a mixture of bounded-real and negative-imaginary uncertainties. The proposed two techniques pave the way for existing H∞ control and μ theory to be applied to robustness analysis and controller synthesis for negative-imaginary systems. In addition, a static state-feedback synthesis method is proposed to achieve robust stability of a system in the presence of strictly negative-imaginary uncertainties. The method is developed in the LMI framework, which can be solved efficiently using convex optimization techniques. The controller synthesis method is based on the negative-imaginary stability theorem: a positive feedback interconnection of two negative-imaginary systems is internally stable if and only if the DC loop gain is contractive and at least one of the systems in the interconnected loop is strictly negative-imaginary. Also, in order to handle non-strict negative-imaginary uncertainties, a strongly strictly negative-imaginary lemma is proposed that helps to ensure the strictly negative-imaginary property of the nominal closed-loop system for robustness. To this end, a state-space characterization for strictly negative-imaginary property is given for non-minimal systems where the conditions are convex and hence numerically attractive. The results in this thesis hence facilitate both the robustness analysis and controller synthesis for negative-imaginary systems that quite often arise in practical scenarios. In addition, they can be applied to quantify the worse-case performance for this class of systems. Therefore, the proposed results have important implications in controller synthesis for uncertain negative-imaginary systems that achieve not only robust stabilization but also robust performance.
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Tugluk, Ozan. "Direct Numerical Simulation Of Pipe Flow Using A Solenoidal Spectral Method." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614293/index.pdf.
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In this study, which is numerical in nature, direct numerical simulation (DNS) of the pipe flow is performed. For the DNS a solenoidal spectral method is employed, this involves the expansion of the velocity using divergence free functions which also satisfy the prescribed boundary conditions, and a subsequent projection of the N-S equations onto the corresponding dual space. The solenoidal functions are formulated in Legendre polynomial space, which results in more favorable forms for the inner product integrals arising from the Petrov-Galerkin scheme employed. The developed numerical scheme is also used to investigate the effects of spanwise oscillations and phase randomization on turbulence statistics, and drag, in turbulent incompressible pipe flow for low to moderate Reynolds numbers (i.e. $mathrm{Re} sim 5000$) ).
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Bedford, Stephen James. "Calculus of variations and its application to liquid crystals." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:a2004679-5644-485c-bd35-544448f53f6a.
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The thesis concerns the mathematical study of the calculus of variations and its application to liquid crystals. In the first chapter we examine vectorial problems in the calculus of variations with an additional pointwise constraint so that any admissible function <strong>n</strong> ε W<sup>1,1</sup>(ΩM), and M is a manifold of suitable regularity. We formulate necessary and sufficient conditions for any given state <strong>n</strong> to be a strong or weak local minimiser of I. This is achieved using a nearest point projection mapping in order to use the more classical results which apply in the absence of a constraint. In the subsequent chapters we study various static continuum theories of liquid crystals. More specifically we look to explain a particular cholesteric fingerprint pattern observed by HP Labs. We begin in Chapter 2 by focusing on a specific cholesteric liquid crystal problem using the theory originally derived by Oseen and Frank. We find the global minimisers for general elastic constants amongst admissible functions which only depend on a single variable. Using the one-constant approximation for the Oseen-Frank free energy, we then show that these states are global minimisers of the three-dimensional problem if the pitch of the cholesteric liquid crystal is sufficiently long. Chapter 3 concerns the application of the results from the first chapter to the situations investigated in the second. The local stability of the one-dimensional states are quantified, analytically and numerically, and in doing so we unearth potential shortcomings of the classical Oseen-Frank theory. In Chapter 4, we ascertain some equivalence results between the continuum theories of Oseen and Frank, Ericksen, and Landau and de Gennes. We do so by proving lifting results, building on the work of Ball and Zarnescu, which relate the regularity of line and vector fields. The results prove to be interesting as they show that for a director theory to respect the head to tail symmetry of the liquid crystal molecules, the appropriate function space for the director field is S BV<sup>2</sup> (Ω,S<sup>2,/sup>). We take this idea and in the final chapter we propose a mathematical model of liquid crystals based upon the Oseen-Frank free energy but using special functions of bounded variation. We establish the existence of a minimiser, forms of the Euler-Lagrange equation, and find solutions of the Euler-Lagrange equation in some simple cases. Finally we use our proposed model to re-examine the same problems from Chapter 2. By doing so we extend the analysis we were able to achieve using Sobolev spaces and predict the existence of multi-dimensional minimisers consistent with the known experimental properties of high-chirality cholesteric liquid crystals.
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Achour, Walid. "Estimation à erreurs bornées et guidage pilotage des aéronefs autonomes en milieu perturbé." Phd thesis, Supélec, 2011. http://tel.archives-ouvertes.fr/tel-00795270.
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L'objectif principal du travail de recherche présenté dans ce mémoire est l'amélioration de la sécurité et les performances du vol des mini drones soumis à des perturbations atmosphériques. Pour ce faire, un couplage entre un estimateur ensembliste à erreurs bornées et une stratégie de guidage pilotage est mise en œuvre. L'estimateur ensembliste a été utilisé pour restituer l'état du modèle dynamique du drone en présence de perturbations et de bruits de mesure supposés bornés. L'utilisation de ces techniques avait pour objet tout d'abord de détecter l'occurrence d'une perturbation atmosphérique par estimation de l'état du drone puis d'estimer l'amplitude et la direction du vent agissant sur le véhicule. Des expérimentations dans le générateur de rafale B20 à Lille ont été ainsi présentées afin de valider ces approches et d'évaluer leurs performances. La stratégie de guidage pilotage développée favorise le déplacement du véhicule dans une direction qui tient compte de l'évolution de la perturbation atmosphérique et du prochain point de passage désigné au véhicule. Cette loi de guidage est basée sue la loi de guidage par navigation proportionnelle et a été adaptée pour tenir compte des perturbations dans le déplacement du véhicule. Les résultats obtenus montrent qu'il est possible d'améliorer la sécurité du vol des mini-drones en présence de perturbations atmosphériques transversales, en modifiant en ligne la trajectoire.
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Haberkamp, Angela Maria. "Julgamento e tomada de decisão dos contadores no processo de controle do ativo imobilizado." Universidade do Vale do Rio dos Sinos, 2018. http://www.repositorio.jesuita.org.br/handle/UNISINOS/7179.
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Previous issue date: 2018-03-07<br>CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>Esta pesquisa analisou quais são as variáveis individuais e ambientais que influenciam o julgamento e a tomada de decisão (JDM) de contadores em empresas que adotam as International Financial Reporting Standards (IFRS) e como o fazem, no que se refere ao controle do imobilizado. Este estudo defende que elementos individuais e pressões ambientais influenciam o JDM dos contadores, demandado em maior grau desde a adoção das IFRS no Brasil, em 2010. A perspectiva individual foi estudada à luz da Teoria da Racionalidade Limitada (limitações cognitivas, situacionais e informacionais impedem a decisão ótima); já a ambiental utiliza os pressupostos da Teoria Institucional (as organizações tendem à similaridade, em função de pressões coercitivas, normativas e miméticas). Para a coleta de dados, foi utilizado um questionário semiestruturado, aplicado a 28 contadores que atuam em organizações que adotam as IFRS. Os resultados mostram que tanto as variáveis individuais, quanto as pressões institucionais influenciam o JDM dos contadores estudados. Os elementos individuais referem-se a limitações cognitivas (uso de facilitadores de decisão e excesso de variáveis); informacionais (informação indisponível e custo-benefício de obtê-la); e situacionais (tempo); sendo a limitação cognitiva a mais frequente. As pressões ambientais identificadas são as coercitivas (legislação, auditoria, detentores de capital, gestores e entidades regulamentadoras), as normativas (graduação, outros contadores, formação complementar, professores e auditoria) e as miméticas (consultoria). Destas, a pressão coercitiva é a mais presente no JDM dos contadores. A análise em relação a como elementos individuais e ambientais influenciam o JDM mostra que: a) as limitações cognitivas influenciam com maior intensidade o JDM dos contadores nas decisões operacionais, enquanto as pressões coercitivas influenciam mais o JDM nas decisões relacionadas à gestão do imobilizado (adotar a IFRS de forma integral ou parcial e como atender - ou não - a tudo que a norma demanda); b) há eventos em que Racionalidade Limitada e as Pressões Institucionais influenciam o JDM dos contadores de forma conjunta (como no cálculo da depreciação, teste de impairment e controles complementares), quando isso ocorre, as pressões coercitivas são determinates da decisão.<br>This research analyzed the individual and environmental variables that influence the judgment and decision making (JDM) of accountants in companies that adopt International Financial Reporting Standards (IFRS), and how they do it, in terms of asset control. This study argues that individual elements and environmental pressures influence the accountants JDM, demanded to a greater degree since the adoption of IFRS in Brazil in 2010. The individual perspective was studied in light of the Bounded Rationality Theory (cognitive, situational and informational limitations prevent the optimal decision); and the environmental uses the presuppositions of the Institutional Theory (the organizations tend to the similarity, due to coercive, normative and mimetic pressures). For the data collection, was used a semi-structured questionnaire, applied to 28 accountants who work in organizations that adopt the IFRS. The results show that individual variables and institutional pressures influence the JDM of the studied accountants. The individual elements are related to cognitive limitations (use of decision facilitators and excess variables), informational limitations (information unavailable and cost-effective to obtain it) and situational limitations (time); where the cognitive limitation is the most frequent. The environmental pressures identified are coercive (legislation, audit, capital holders, managers and regulators), normative (graduation, other accountants, supplementary training, teachers and auditing) and mimetics (consulting). Of these, the coercive pressure is the most present in the JDM of the accountants. The analysis of how individual and environmental elements influence the JDM shows that: a) Cognitive limitations influence the accountant’s JDM more strongly in operational decisions, while coercive pressures influence the JDM more in decisions about the management of fixed assets (adopt IFRS in whole or in part and how to meet - or not - all that the standard demands). b) There are events in which Limited Rationality and Institutional Pressures influence the accountant’s JDM jointly (as in the calculation of depreciation, impairment test and complementary controls), when this occurs, coercive pressures are determinate to the decision.
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Date, Paresh. "Identification for control : deterministic algorithms and error bounds." Thesis, University of Cambridge, 2000. https://www.repository.cam.ac.uk/handle/1810/251751.
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This dissertation deals with frequency domain identification of linear dynamic systems in a deterministic set-up. Various untuned algorithms are suggested, including one which is robustly convergent and asymptotically optimal (in n-width sense) for a finite model order. The suggested algorithms can easily be implemented in commercially available software for convex optimization.
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Iyogun, Paul Omolewa. "Lower bounds for production/inventory problems by cost allocation." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27323.
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This thesis presents a cost allocation method for deriving lower bounds on costs of feasible policies for a class of production/inventory problems. Consider the joint replenishment problem where a group of items is replenished together or individually. A sequence of reorders for any particular item will incur holding, backorder and set-up costs specific to the item, in addition whenever any item is replenished a joint cost is incurred. What is required of the total problem is the minimization of a cost function of the replenishment sequence or policy.
The cost allocation method consists of decomposing the total problem into sub-problems, one for each item, by allocating the joint cost amongst the items in such a way that every item in the group receives a positive allocation or none. The result is that, for an arbitrary feasible cost allocation, the sum of the minimum costs for the subproblems is a lower bound on the cost of any feasible policy to the total problem. The results for the joint replenishment problem follows:
For the constant and continuous demand case we reproduce the lower bound of Jackson, Maxwell and Muckstadt more easily than they did. For the multi-item dynamic
lot-size problem, we generalize Silver-Meal and part-period balancing heuristics, and derive a cost allocation bound with little extra work. For the 'can-order' system, we use periodic policies derived from the cost allocation method and show that they are superior to the more complex (s,c,S) policies. The cost allocation method is easily
generalized to pure distribution problems where joint replenishment decisions are taken at several facilities. For example, for the one-warehouse multi-retailer problem, we reproduce Roundy's bound more easily than he did. For the multi-facility joint replenishment problem (a pure distribution system with an arbitrary number of warehouses),
we give a lower bound algorithm whose complexity is dr log r where d is the maximum number of facilities which replenish a particular item and r is the number of items.<br>Business, Sauder School of<br>Graduate
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Giacometti, Simone. "CBC bound proteins and RNA fate." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTS028.
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Le complexe de liaison de la coiffe des ARN (CBC) joue un rôle essentiel dans leur maturation et déclenche une variété de réactions biochimiques, via son interaction avec différents partenaires. Deux complexes, CBC-ARS2-PHAX (CBCAP), et CBC-ARS2-ZC3H18-NEXT (CBCN), ont récemment été montré comme important pour cibler les ARN vers l'export (CBCAP) ou la dégradation (CBCN). Cependant, les mécanismes par lesquels la sélection se fait pour l'une voie ou l'autre reste mystérieuse. Ainsi, une question majeure qui reste à résoudre est de savoir quand et comment ces complexes sont recrutés sur les ARN. Dans ce travail, j'ai utilisé la procédure du iCLIP (Cross-Linking and Immuno-Precipitation), afin d'identifier les cibles de ces complexes sur l'ensemble du transcriptome humain. J'ai réalisé un iCLIP sur cinq composants de CBCAP et CBCN, et j'ai comparé les résultats à ceux obtenus avec RBM7, un composant de NEXT précédemment étudié par iCLIP. Mes résultats indiquent que: (i) CBP20, ARS2, PHAX et ZC3H18 se lient près de la coiffe des ARN, tandis que RBM7 et MTR4 se lient partout; (ii) CBP20, ARS2, PHAX et ZC3H18 s'associent à un large ensemble d'ARN transcrits par l'ARN polymérase II et montrent une faible sélectivité; (iii) la liaison de ces protéines varie avec l'état de maturation des ARN, avec le CBC enrichi sur les ARN matures, tout comme ARS2/PHAX/ZC3H18 et MTR4 (bien que dans une moindre mesure), tandis que RBM7 est préférentiellement lié sur les pre-mRNAs non épissés; (iv) une liaison différentielle de RBM7 et MTR4 sur les ARN, avec RBM7 enrichi sur les introns et les PROMPTs, et MTR4 plus présent sur les ARN mature. Bien que des expériences additionnelles soient requises, nous proposons que le CBCAP et le CBCN se lient à un même ensemble d'ARN, ce qui indique à la fois une compétition entre ZC3H18 et PHAX pour la liaison à ces ARN, et l'absence de voies de routage bien déterminées qui ciblerait les ARN vers l'une ou l'autre de ces protéines. Le devenir des ARN pourrait ainsi être déterminé par d'autres caractéristiques des ARN, ou encore par des protéines additionnelles. Ces facteurs pourraient s'allier aux protéines liées à la coiffe afin de favoriser la formation du CBCAP ou du CBCN. Dans le but d’identifier des facteurs additionnels, j'ai réalisé un screen d'interaction par spectrométrie de masse après purification de ARS2 ou CBP80. Ceci a été fait dans des conditions natives ou après un cross-link des complexes à la formaldéhyde, afin de stabiliser les interactions transitoires. Ceci a permis d'identifier de nouveaux partenaires de ARS2 et de CBP80, dont la majorité sont impliqués dans l'épissage des ARN. Des expériences additionnelles seront nécessaires pour valider ces interactions<br>The cap-binding complex (CBC) plays a pivotal role in post-transcriptional processing events and orchestrates a variety of metabolic pathways, through association with different interaction partners. Two CBC sub-complexes, the CBC-ARS2-PHAX (CBCAP) and the CBC-nuclear exosome targeting (NEXT) complex (CBCN), were recently shown to target capped RNA either toward export or degradation, but the mechanisms by which they can discriminate between different RNA families and route them toward different metabolic pathways still remain unclear. A major question to be answered is how and when the different CBC subcomplexes are recruited to the RNP. Here, we used an individual nucleotide-resolution UV cross-linking and immunoprecipitation (iCLIP) approach to identify the transcriptome-wide targets for 5 different components of the CBCAP and CBCN complexes, and compared results to the previously analysed NEXT-component RBM7. We report that: (i) CBP20, ARS2, PHAX and ZC3H18 bind close to the cap, while RBM7 and MTR4 bind throughout the mRNA body; (ii) CBP20, ARS2, PHAX and ZC3H18 associate with a broad set of RNA polymerase II (PolII)-derived RNAs and have only mild species preferences; (iii) binding varies with the RNA maturation stage, with the CBC being highly enriched on mature mRNA, ARS2/PHAX/ZC3H18/MTR4 less so, and RMB7 preferentially bound to pre-mRNAs; (iv) MTR4 and RBM7 show different specificities, with RBM7 being highly enriched on introns and promoter upstream transcripts (PROMPTs), while MTR4 is additionally present on mature RNAs. Although more experimental work is needed to fully support our model, we propose that CBCAP and CBCN bind overlapping sets of RNAs, indicating a competition between the proteins ZC3H18 and PHAX, and the lack of a strict RNA sorting mechanism. RNA fate may therefore be determined by additional RNA features and/or by other RNA-binding proteins, which may synergize with the cap and drive the formation of one specific CBC subcomplex instead of another. In an attempt to identify yet unknown factors that may interact with cap-bound CBCAP and CBCN, we performed a protein interaction screen leveraging affinity capture-mass spectrometry (ACMS), using ARS2 and CBP80 as bait proteins. As a complementary approach, we also employed a formaldehyde-based chemical cross-linking strategy, aimed at stabilizing weak/transient interactions. Although we failed to detect any transient interactions involving the CBC, we identified several potential CBC80 and ARS2 interactors, the majority of which are involved in pre-mRNA splicing. Additional quantitative experiments are required to validate our ACMS results and confirm the existence of such protein interactions in vivo
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Pralx, Laurent. "Commande linéaire adaptative : solutions bornées et leurs propriétés." Paris 9, 1988. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1988PA090035.
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On est amené à modifier des lois d'adaptation en remarquant que les effets non modélisés par un modèle linéaire peuvent sous des hypothèses réalistes être majorées par une norme des signaux d'entrées-sorties. D'autre part, on propose une méthode d'analyse des portraits de phase des systèmes linéaires adaptatifs
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Thabet, Rihab El Houda. "Détection de défauts des systèmes non linéaires à incertitudes bornées continus." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0283/document.
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La surveillance des systèmes industriels et/ou embarqués constitue une préoccupation majeure en raison de l’accroissement de leur complexité et des exigences sur le respect des profilsde mission. La détection d’anomalies tient une place centrale dans ce contexte. Fondamentalement,les procédures de détection à base de modèles consistent à comparer le fonctionnement réel dusystème avec un fonctionnement de référence établi à l’aide d’un modèle sans défaut. Cependant,les systèmes à surveiller présentent souvent des dynamiques non linéaires et difficiles à caractériserde manière exacte. L’approche retenue dans cette thèse consiste à englober leur influencepar des incertitudes bornées. La propagation de ces incertitudes permet l’évaluation de seuils dedécision visant à assurer le meilleur compromis possible entre sensibilité aux défauts et robustesseaux perturbations tout en préservant une complexité algorithmique raisonnable. Pour cela, unepart importante du travail porte sur l’extension des classes de modèles dynamiques à incertitudesbornées pour lesquels des observateurs intervalles peuvent être obtenus avec les preuves d’inclusionet de stabilité associées. En s’appuyant sur des changements de coordonnées variant dans letemps, des dynamiques LTI, LPV et LTV sont considérées graduellement pour déboucher sur desclasses de dynamiques Non Linéaires à Incertitudes Bornées continues (NL-IB). Une transformationdes modèles NL-IB en modèles LPV-IB a été utilisée. Une première étude sur les non-linéaritésd’une dynamique de vol longitudinal est présentée. Un axe de travail complémentaire porte surune caractérisation explicite de la variabilité (comportement aléatoire) du bruit de mesure dansun contexte à erreurs bornées. En combinant cette approche à base de données avec celle à basede modèle utilisant un prédicteur intervalle, une méthode prometteuse permettant la détection dedéfauts relatifs à la position d’une surface de contrôle d’un avion est proposée. Une étude portenotamment sur la détection du blocage et de l’embarquement d’une gouverne de profondeur<br>The monitoring of industrial and/or embedded systems is a major concern accordingto their increasing complexity and requirements to respect the mission profiles. Detection of anomaliesplays a key role in this context. Fundamentally, model-based detection procedures consist incomparing the true operation of the system with a reference established using a fault-free model.However, the monitored systems often feature nonlinear dynamics which are difficult to be exactlycharacterized. The approach considered in this thesis is to enclose their influence through boundeduncertainties. The propagation of these uncertainties allows the evaluation of thresholds aimingat ensuring a good trade-off between sensitivity to faults and robustness with respect to disturbanceswhile maintaining a reasonable computational complexity. To that purpose, an importantpart of the work adresses the extension of classes of dynamic models with bounded uncertaintiesso that interval observers can be obtained with the related inclusion and stability proofs. Based ona time-varying change of coordinates, LTI, LPV and LTV dynamics are gradually considered tofinally deal with some classes classes of nonlinear continuous dynamics with bounded uncertainties.A transformation of such nonlinear models into LPV models with bounded uncertainties has beenused. A first study on nonlinearities involved in longitudinal flight dynamics is presented. A complementarywork deals with an explicit characterization of measurement noise variability (randombehavior of noise within measurement) in a bounded error context. Combining this data-drivenapproach with a model-driven one using an interval predictor, a promising method for the detectionof faults related to the position of aircraft control surfaces is proposed. In this context, specialattention has been paid to the detection of runaway and jamming of an elevator
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Ahlberg, John, and Wolter Håkansson Christoffer Cruz. "Identification, mapping and control of non-structure-bound materials." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-112101.
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I Saab Aerostructures tillverkning av flygplansdelar, används icke strukturbundet material, det vill säga material som inte har en angiven kvantifierad förbrukning per tillverkad enhet eller material vars angivna kvantifierade förbrukning per tillverkad enhet inte stämmer överens med verklig förbrukning. Personal på inköpsavdelningen vet i vissa fall inte var ett specifikt icke strukturbundet material förbrukas, alltså vilka tillverkningsavdelningar eller flygplansdelar som förbrukar materialet. Likaså saknas övergripande och gemensamma rutiner för hur material som klassas som icke strukturbundet material planeras och lagerstyrs. För att identifiera problemområden i materialförsörjningen genomfördes en flödeskartläggning för att identifiera vilka olika typer av icke strukturbundet material som används i Saab Aerostructures produktion samt hur dessa lagerstyrs mellan lager och buffertlager i produktion. Under flödeskartläggningen definierades sex olika materialgrupper tillhörande icke strukturbundet material. För att lagerstyra de identifierade materialgrupperna av icke strukturbundet material används idag åtta stycken lagerstyrningsmetoder. Saab Aerostructures har anlitat tredjepartslogistiker för att sköta merparten av dagens lagerstyrning. Lagerstyrningsmetoderna skiljer sig åt beroende på tredjepartslogistiker och materialgrupp av icke strukturbundet material. Resultatet från genomförd kartläggning och analys påvisar att det finns förbättringspotential i flera utav dessa lagerstyrningsmetoder, samt att det är möjligt att reducera antalet lagerstyrningsmetoder genom att använda samma lagerstyrningsmetod för snarlika materialgrupper av icke strukturbundet material. Genomförd analys påvisar även behovet av ett förbättrat informationsflöde mellan beredning, inköp och produktion, när det gäller hanteringen av icke strukturbundet material. Konkreta åtgärder i form av rekommendationer, för att förbättra lagerstyrningen av icke strukturbundet material, presenteras i slutet av denna rapport.
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Sweeney, Robert John. "Static H [subscript infinity] Control of a Cantilevered Beam Using an Analytical Upper Bound Approach." Digital WPI, 2005. https://digitalcommons.wpi.edu/etd-theses/358.
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This paper considers the control of externally symmetric vector second order systems using an analytical upper bound method. The structural model is a cantilevered aluminum beam with a collocated pair of piezoceramic patches to serve as actuators and sensors. A computationally efficient method for approximating the H-infinity norm for externally symmetric systems is presented. The approximation method is then used to calculate a scalar output feedback controller to guarantee a closed-loop norm less than any user defined value. This method is tested with a finite-element representation of the beam, and then verified experimentally.
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McBride, John William. "Electrical contact bounce and the control dynamics of snap-action switches." Thesis, University of Plymouth, 1986. http://hdl.handle.net/10026.1/2477.
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Experimental and theoretical studies are made of a typical snap-action rocker switch, to establish the wear mechanisms in the pivoting contact. The rocker switch, used extensively in consumer goods, operates in the medium duty current range, (1 - 30 Amps). Highspeed photographic studies have shown that the main cause of wear is arcing, occurring during separation and bounce at the pivot contacts. To reduce the bounce a computer-based mathematical model of the system dynamics is developed and optimised; this results in recommended design changes. These changes are tested under full current endurance conditions, and show significant improvements in wear. The model of the switch dynamics relates the mathematics of motion to the bounce occuring at the pivot contact, without the influence of current. To show the effect of current and arcing, an automatic test system is developed for the controlled testing of electrical contacts. The system has the ability to evaluate arc energy, bounce times, and contact resistance. The results presented detail the influence of d.c current on contact bounce time, and identify the importance of the subsequent bounce time; which is defined for a single make operation, as the total duration of the bounces occurring after the first bounce. To compare the erosion profiles of the switch and test system, the system is operated under full load current endurance conditions, to evaluate wear. This comparison shows that the wear in the real switch contacts is greater, as result of the additional contact movement of slip and rolling.
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Ghafoor, Abdul. "Frequency-weighted model reduction and error bounds." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0118.
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This thesis investigates the frequency weighted balanced model reduction problem for linear time invariant systems. Both continuous and discrete time systems are considered, in one and two-dimensions. First the frequency weighted balanced model reduction problem is formulated, then a novel frequency weighted, balanced, model reduction method for continuous time systems is proposed. This method is based on the retention of frequency weighted Hankel singular values of the original system, and yields stable reduced order models even when two sided weightings are employed. An alternative frequency weighted balanced model reduction technique (applicable for controller reduction applications) is then developed. This is based on a parametrized combination of the frequency weighted partial fraction expansion technique with balanced truncation and the singular perturbation approximation techniques. This method yields stable models even when two sided weightings are employed. An a priori error bound for the model reduction method is derived. Lower frequency response errors and error bounds are obtained using free parameters and equivalent anti-stable weightings. Based on the same idea, a novel parameterized frequency weighted optimal Hankel norm model reduction method with a tighter a priori error bound is proposed. The proposed methods are extended to include discrete time systems. A frequency interval Gramians based stability preserving model reduction scheme with error bounds is also presented. In this case, frequency weights are not explicitly predefined. Discrete time system related results are also included. Several frequency weighted model reduction results for two-dimensional (2-D) systems are also proposed. The advantages of these schemes include error bounds, guaranteed stability and applicability to general stable (non-separable denominator) weighting functions. Finally, a novel 2-D identification based frequency weighted model reduction scheme is outlined. Numerically robust algorithms based on square root and balancing free techniques are proposed for frequency weighted balanced truncation techniques. Several practical examples are included to illustrate the effectiveness of the algorithms.
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Howe, Sei. "Upper and lower bounds for singularly perturbed linear quadratic optimal control problems." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/54758.
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The question of how to optimally control a large scale system is widely considered to be difficult to solve due to the size of the problem. This difficulty is further compounded when a system exhibits a two time-scale structure where some components evolve slowly and others evolve quickly. When this occurs, the optimal control problem is regarded as singularly perturbed with a perturbation parameter epsilon representing the ratio of the slow time-scale to the fast time-scale. As epsilon goes to zero, the system becomes stiff resulting in a computationally intractable problem. In this thesis, we propose an analytic method for constructing bounds on the minimum cost of a singularly perturbed, linear-quadratic optimal control problem that hold for any arbitrary value of epsilon.
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Rocha, Herbert Oliveira. "Verificação e comprovação de erros em códigos C usando bounded model checker." Universidade Federal do Amazonas, 2011. http://tede.ufam.edu.br/handle/tede/2965.
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Previous issue date: 2011-02-04<br>CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior<br>The use of computer-based systems in several domains has increased significantly over
the last years, one of the main challenges in software development of these systems
is to ensure the correctness and reliability of these. So that software verification now
plays an important role in ensuring the overall product quality, aimed mainly the
characteristics of predictability and reliability. In the context of software verification,
with respect to the use of model checking technique, Bounded Model Checkers have
already been applied to discover subtle errors in actual systems projects, contributing
effectively in this verification process. The value of the counterexample and safety
properties generated by Bounded Model Checkers to create test case and to debug
these systems is widely recognized. When a Bounded Model Checking (BMC) finds
an error it produces a counterexample. Thus, the value of counterexamples to debug
software systems is widely recognized in the state-of-the-practice. However, BMCs
often produce counterexamples that are either large or difficult to be understood and
manipulated mainly because of both the software size and the values chosen by the
respective solver. In this work we aim to demonstrate and analyze the use of formal
methods (through using the model checking technique) in the process of developing
programs in C language, exploring the features already provided by the model checking
as the counterexample and the identification and verification of safety properties. In
view of this we present two approaches: (i) we describe a method to integrate the
bounded model checker ESBMC with the CUnit framework. This method aims to
extract the safety properties generated by ESBMC to generate automatically test cases
using the rich set of assertions provided by the CUnit framework and (ii) a method aims
to automate the collection and manipulation of counterexamples in order to instantiate
the analised C program for proving the root cause of the identified error. Such methods
may be seen as a complementary technique for the verification performed by BMCs.
We show the effectiveness of our proposed method over publicly available benchmarks
of C programs.<br>A utilização de sistemas baseados em computador em diversos domínios aumentou
significativamente nos últimos anos. Um dos principais desafios no desenvolvimento
de software de sistemas críticos é a garantia da sua correção e confiabilidade. Desta
forma, a verificação de software exerce um papel importante para assegurar a qualidade
geral do produto, visando principalmente características como previsibilidade e confiabilidade.
No contexto de verificação de software, os Bounded Model Checkers estão
sendo utilizados para descobrir erros sutis em projetos de sistemas de software atuais,
contribuindo eficazmente neste processo de verificação. O valor dos contra-exemplos e
propriedades de segurança gerados pelo Bounded Model Checkers para criar casos de
testes e para a depuração de sistemas é amplamente reconhecido. Quando um Bounded
Model Checking (BMC) encontra um erro ele produz um contra-exemplo. Assim,
o valor dos contra-exemplos para depuração de software é amplamente reconhecido no
estado da prática. Entretanto, os BMCs frequentemente produzem contra-exemplos
que são grandes ou difíceis de entender ou manipular, principalmente devido ao tamanho
do software e valores escolhidos pelo solucionador de satisfabilidade. Neste
trabalho visamos demonstrar e analisar o uso de método formal (através da técnica
model checking) no processo de desenvolvimento de programas na linguagem C, explorando
as características já providas pelo model checking como o contra-exemplo e a
identificação e verificação de propriedades de segurança. Em face disto apresentamos
duas abordagens: (i) descrevemos um método para integrar o Bounded Model Checker
ESBMC como o framework de teste unitário CUnit, este método visa extrair as
propriedades geradas pelo ESBMC para gerar automaticamente casos de teste usando
o rico conjunto de assertivas providas pelo framework CUnit e (ii) um método que
visa automatizar a coleta e manipulação dos contra-exemplos, de modo a instanciar o
programa C analisado, para comprovar a causa raiz do erro identificado. Tais métodos
podem ser vistos como um método complementar para a verificação efetuada pelos
BMCs. Demonstramos a eficácia dos métodos propostos sobre benchmarks públicos de
código C.
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Krishnan, Raj 1980. "Solving hybrid decision-control problems through conflict-directed branch & bound." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28429.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.<br>"February 2, 2004."<br>Includes bibliographical references (leaf 103).<br>There exists a large class of problems that incorporate both logical decision and algebraic constraints. For example, in cooperative path planning (CPP) problem, obstacle avoidance can be achieved by selecting a direction in which to avoid every obstacle, which in turn imposes an inequality constraint. Traditionally, these hybrid decision-control problems (HDCPs) are encoded in a binary integer program (BIP). These BIPs are solved using Branch and Bound (B&B) techniques. Two problems arise with this approach. First, binary arithmetic is not a natural representation for expressing complex logical choices. Propositional and higher order logics offer a more natural encoding, and computational methods exploit this encoding. Second, current BIP solution methods are to slow to solve large HDCPs online. To address these problems, this thesis introduces an approach that unifies representations and solution methods for logic and mathematical programming. To address representational adequacy, this thesis introduces the Clausal Linear Program (CLP) formulation, which encodes logical choice using propositional clauses and continuous control decisions using linear inequalities. CLPs offer a more compact and natural encoding than BIPs for many problems of logical choice. To address computational efficiency, this thesis introduces a branch and bound method for solving CLPs, analogous to BIP-B&B. This method is then unified with conflict-directed search and unit propagation. The resulting method, CDCL-B&B, searches in a best first order, while using conflicts to steer the search away from inconsistencies. Randomized experiments on CPP problems were performed using CDCL-B&B and a BIP-B&B algorithm. Results showed that CDCL-B&B improved time efficiency by<br>by Raj Krishnan.<br>M.Eng.
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Hart, Anastasios John 1979. "Chemical, mechanical, and thermal control of substrate-bound carbon nanotube growth." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38257.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.<br>Includes bibliographical references (p. 323-357).<br>Carbon nanotubes (CNTs) are long molecules having exceptional properties, including several times the strength of steel piano wire at one fourth the density, at least five times the thermal conductivity of pure copper, and high electrical conductivity and current-carrying capacity. This thesis presents methods of CNT synthesis by atmospheric-pressure thermal chemical vapor deposition (CVD), where effective choice of the catalyst composition and processing conditions enables growth of tangled single-wall CNTs or structures of aligned multi-wall CNTs, on bare silicon, microstructured silicon, and ceramic fibers. Applying mechanical pressure during growth controls the structure of a CNT film while causing significant defects in the CNTs. This mechanochemisty approach is used to "grow-mold" CNTs into 3D-shaped microforms. A new reactor apparatus featuring a resistively-heated suspended platform enables rapid ( 100 °C/s) temperature control and versatile in situ characterization, including laser measurement of CNT film growth kinetics, and imaging of stress-induced film cracking. By thermally pre-treating the reactant mixture before it reaches the substrate platform, aligned CNTs are grown to 3 mm length in just 15 minutes.<br>(cont.) A microchannel array is created for combinatorial flow studies of nanomaterials growth, having velocity range and resolution far exceeding those of conventional furnaces. A detailed design methodology considers compressible slip flows within the microchannels and flow leaks across the array, and the devices are fabricated by KOH etching of silicon. Initial experiments with this system demonstrate chemically-driven transitions in CNT yield and morphology along the microchannels, and flow-directed alignment of isolated CNTs and CNT strands. Applications of aligned CNTs in reinforced composites and electromechanical probes are enabled by the CNT synthesis technologies presented here, and show significant initial promise through collaborative research projects. Overall, controlling the packing density and matrix reinforcement of aligned CNTs gives material attributes spanning from those of energy-absorbing foams to stiff solids; however, significant increases in CNT length, growth rate, and packing density must be achieved to realize macroscopic fibers and films having the properties of individual CNTs. New machines can be created for studying the limiting aspects of growth reactions, for exploring new reaction regimes, and for producing exceptionally long nanostructures, looking ahead to fabrication of CNT-based materials in a continuous and industrially-scalable fashion.<br>by Anastasios John Hart.<br>Ph.D.
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Davies, Richard. "Bounds for the solution of algebraic matrix equations arising in mathematical control theory." Thesis, University of South Wales, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446089.
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Kurudamannil, Jubal J. "Improved Robust Stability Bounds for Sampled Data Systems with Time Delayed Feedback Control." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1419012522.
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Techakesari, Onvaree. "Filter and control performance bounds in the presence of model uncertainties with aerospace applications." Thesis, Queensland University of Technology, 2013. https://eprints.qut.edu.au/63956/1/Onvaree_Techakesari_Thesis.pdf.
Full textAbstract:
This thesis establishes performance properties for approximate filters and controllers that are designed on the basis of approximate dynamic system representations. These performance properties provide a theoretical justification for the widespread application of approximate filters and controllers in the common situation where system models are not known with complete certainty. This research also provides useful tools for approximate filter designs, which are applied to hybrid filtering of uncertain nonlinear systems. As a contribution towards applications, this thesis also investigates air traffic separation control in the presence of measurement uncertainties.
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Jonsson, Holm Erik. "Predictive Energy Management of Long-Haul Hybrid Trucks : Using Quadratic Programming and Branch-and-Bound." Thesis, Linköpings universitet, Fordonssystem, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-178224.
Full textAbstract:
This thesis presents a predictive energy management controller for long-haul hybrid trucks. In a receding horizon control framework, the vehicle speed reference, battery energy reference, and engine on/off decision are optimized over a prediction horizon. A mixed-integer quadratic program (MIQP) is formulated by performing modelling approximations and by including the binary engine on/off decision in the optimal control problem. The branch-and-bound algorithm is applied to solve this problem. Simulation results show fuel consumption reductions between 10-15%, depending on driving cycle, compared to a conventional truck. The hybrid truck without the predictive control saves significantly less. Fuel consumption is reduced by 3-8% in this case. A sensitivity analysis studies the effects on branch-and-bound iterations and fuel consumption when varying parameters related to the binary engine on/off decision. In addition, it is shown that the control strategy can maintain a safe time gap to a leading vehicle. Also, the introduction of the battery temperature state makes it possible to approximately model the dynamic battery power limitations over the prediction horizon. The main contributions of the thesis are the MIQP control problem formulation, the strategy to solve this with the branch-and-bound method, and the sensitivity analysis.
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Shi, Danni. "Robustness Issues of Run-time Leakage Control in Nano-scale Technologies." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282054251.
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Kratz, Jonathan L. "Robust Control of Uncertain Input-Delayed Sample Data Systems through Optimization of a Robustness Bound." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429149093.
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Mulay, Siddharth Pradeep. "Robustness Bounds For Uncertain Sampled Data Systems With Presence of Time Delays." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1365971507.
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Churches, Tim. "Estimation of a lower bound for the cumulative incidence of failure of female tubal sterilisation in NSW a population-based study /." Connect to full text, 2006. http://hdl.handle.net/2123/1968.
Full textAbstract:
Thesis (M. Phil.)--University of Sydney, 2007.<br>Title from title screen (viewed Oct. 16, 2007). Includes tables. Submitted in fulfilment of the requirements for the degree of Master of Philosophy to the School of Public Health, Faculty of Medicine. Degree awarded 2007; thesis submitted 2006. Includes bibliography. Also issued in print.
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Latess, Dennis R. "The effect of Outward Bound on health locus of control, health value, and wellness behavior /." The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487596807823003.
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