12 research outputs found

    A survey of adaptive control technology in robotics

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    Previous work on the adaptive control of robotic systems is reviewed. Although the field is relatively new and does not yet represent a mature discipline, considerable attention has been given to the design of sophisticated robot controllers. Here, adaptive control methods are divided into model reference adaptive systems and self-tuning regulators with further definition of various approaches given in each class. The similarity and distinct features of the designed controllers are delineated and tabulated to enhance comparative review

    Continuous-time self-tuning algorithms

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    This thesis proposes some new self-tuning algorithms. In contrast to the conventional discrete-time approach to self-tuning control, the continuous-time approach is used here, that is continuous-time design but digital implementation is used. The proposed underlying control methods are combined with a continuous-time version of the well-known discrete recursive least squares algorithms. The continuous-time estimation scheme is chosen to maintain the continuous-time nature of the algorithms. The first new algorithm proposed is emulator-based relay control (which has already been described in a paper by the author). The algorithm is based on the idea of constructing the switching surface by emulators; that is, unrealisable output derivatives are replaced by their emulated values. In particular, the relay is forced to operate in the sliding mode. In this case, it is shown that emulator-based control and its proposed relay version become equivalent in the sense that both give the same control law. The second new algorithm proposed is a continuous-time version of the discrete-time generalized predictive control (GPC) of Clarke et al (which has already been described in a paper by the author). The algorithm, continuous-time generalized predictive control (CGPC), is based on similar ideas to the GPC, however the formulation is very different. For example, the output prediction is accomplished by using the Taylor series expansion of the output and emulating the output derivatives involved. A detailed closed-loop analysis of this algorithm is also given. It is shown that the CGPC control law only changes the closed-loop pole locations leaving the open-loop zeros untouched (except one special case). It is also shown that LQ control can be considered in the CGPC framework. Further, the CGPC is extended to include some design polynomials so that the model-following and pole-placement control can be considered in the same framework. A third new algorithm, a relay version of the CGPC, is described. The method is based on the ideas of the emulator-based relay control and again it is shown that the CGPC and its relay version become equivalent when the relay operates in the sliding mode. Finally, the CGPC ideas are extended to the multivariable systems and the resulting closed-loop system is analysed in some detail. It is shown that some special choice of design parameters result in a decoupled closed-loop system for certain systems. In addition, it is shown that if the system is decouplable, it is possible to obtain model-following control. It is also shown that LQ control, as in the scalar case, can be considered in the same framework. An illustrative simulation study is also provided for all of the above methods throughout the thesis

    Adaptive control of plants with input saturation: an approach for performance improvement

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    In this work, a new method for adaptive control of plants with input saturation is presented. The new anti-windup scheme can be shown to result in bounded closed-loop states under certain conditions on the plant and the initial closed-loop states. As an improvement in comparison to existing methods in adaptive control, a new degree of freedom is introduced in the control scheme. It allows to improve the closed-loop response when actually encountering input saturation without changing the closed-loop performance for unconstrained inputs.Diese Arbeit prĂ€sentiert eine neue Methode fĂŒr die adaptive Regelung von Strecken mit StellgrĂ¶ĂŸenbegrenzung. FĂŒr das neue anti-windup Verfahren wird gezeigt, dass die ZustĂ€nde des Regelkreises begrenzt bleiben, wenn dessen initiale Werte und die Regelstrecke bestimmte Bedingungen erfĂŒllen. Eine Verbesserung im Vergleich zu existierenden Methoden wird durch die EinfĂŒhrung eines zusĂ€tzlichen Freiheitsgrades erzielt. Dieser erlaubt die Verbesserung der RegelgĂŒte des geschlossenen Regelkreises, wenn das Eingangssignal sich in der Limitierung befindet, ohne diese sonst zu verĂ€ndern

    Adaptive load frequency control of electrical power systems

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    The thesis describes Load Frequency Control techniques which may be used for real-time on-line control of large electrical power systems. Traditionally the frequency control of power systems has been carried out using standard fixed parameter control schemes, which give control over the immediate steady- state error and the long term accumulated frequency error, but do not account for the fact that system conditions can alter due to the change in consumer load and generating patterns. The thesis presents a method of controlling the system frequency using adaptive control techniques, which ensure that optimal control action is calculated based on the present system conditions. It enables the system operating point to be monitored so that optimal control may continue to be calculated as the system operating point alters. The proposed method of frequency control can be extended to meet the problems of system interconnection and the control of inter-area power flows. The thesis describes the work carried out at Durham on a fixed parameter control scheme which led to the development of an adaptive control scheme. The controller was validated against a real-time power system simulator with full Energy Management software. Results are also presented from work carried out at the Central Electricity Research Laboratories under the C.A.S.E award scheme. This led to the development of a power system simulator, which along with the controller was validated on-line with the Dispatch Project used by the Central Electricity Generating Board

    A control system design technique for nonlinear discrete time systems

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    Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1988A new control methodology is proposed for use with a class of nonlinear, single-input discrete time systems. The technique is based on a discrete time approach that parallels existing continuous time sliding surface concepts. Modifications to the basic algorithm allow for system models with time-variant or uncertain parameters, time delays in the control input, and external disturbances. A major feature of the method is its straightforward extension to an adaptive control form which can be used to improve performance and maintain stability in the presence of large parametric uncertainty or time-variant behavior. Techniques are proposed for overcoming instabilities that frequently arise when using adaptive control schemes based on reduced order system models or in the presence of disturbances. A framework is provided for the practical application of the methodology to continuous time systems. The discrete time nature of the development makes it especially well suited to applications where sensor data is infrequently available or computational power is limited. An experimental study is performed using an underwater remotely operated vehicle to verify the validity of the approach. The ability of the method to use a nonlinear model and adapt to large parametric uncertainty is shown to result in improved performance over the use of a linear or time-invariant model.Finally, the United States Navy and the National Science Foundation are gratefully acknowledged for their financial support of my graduate education. This research was also sponsored in part by ONR Contract N00014-36-C-0038, ONR Grant N00014-87- J-1111 (formerly N00014-87-G-0111), NSF Grant 8611640-ECS, and NRL Contract N00014-88-K-2022

    Du pilotage d'une famille de drones Ă  celui d'un drone hybride via la commande adaptative

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    Les micro-drones sont des aĂ©ronefs sans pilotes de dimensions infĂ©rieures Ă  un mĂštre et de poids infĂ©rieur Ă  deux kilogrammes. Ils se distinguent des aĂ©ronefs classiques pour plusieurs raisons : un cycle de dĂ©veloppement plus court, un coĂ»t plus faible, leur facilitĂ© d'opĂ©ration et des configurations de vĂ©hicules spĂ©cifiques. L'ensemble de ces points attendent une rĂ©ponse spĂ©cifique dans le dĂ©veloppement des lois de commandes. Cette thĂšse s'y intĂ©resse Ă  travers deux problĂ©matiques : la commande d'une famille de drones quadrirotors et celle d'un drone hybride. Une famille de drones reprĂ©sente un mĂȘme concept de vĂ©hicule dĂ©clinĂ© en plusieurs tailles dont on peut faire varier la charge utile ou son emplacement. Les lois de commandes doivent assurer un mĂȘme niveau de performances malgrĂ© ses modifications. Un drone hybride se caractĂ©rise par sa capacitĂ© Ă  rĂ©aliser du vol stationnaire et du vol d'avancement. Ces deux modes de vol ont chacun une dynamique de vol spĂ©cifique Ă  laquelle les lois de commandes doivent s'adapter. Cette thĂšse prĂ©sente la modĂ©lisation de quadrirotors et d'un drone hybride puis dĂ©taille une approche de commande adaptative indirecte qui rĂ©pond aux problĂšmes introduits. La commande adaptative permet de garantir Ă  l'aide d'un correcteur unique les performances de commande pour de multiples systĂšmes. Les mĂ©thodes d'estimation de paramĂštres et de synthĂšse linĂ©aire Ă  paramĂštres variants du schĂ©ma de commande sont dĂ©crites, puis, finalement, des rĂ©sultats d'essais en vol montrent l'apport et les limites de cette approche.Micro Air Vehicle are pilotless aircrafts with dimensions not exceeding one meter and a maximum weight of two kilograms. They are different from classical aircrafts for multiple reasons: a shorter development cycle, a cheaper development, their ease of operation and specific vehicle configurations. All these points expect a specific answer in the development of the control laws of the vehicles. This thesis considers this topic through two particular issues: the control of a family of quadrotors and the control of hybrid micro air vehicle. A family of quadrotor represents a single concept of vehicle but with various sizes, payloads and payload configurations. Control laws must guarantee the same level of performance despite all these modifications. A hybrid micro air vehicle is able to both hover like a helicopter and fly forward like a plane. These two flight modes have specific flight dynamics that the control laws must adapt to. This thesis first presents a model of quadrotors and hybrid micro air vehicle and then details an indirect adaptive control method to tackle both issues. Adaptive control should guarantee performance of multiple controlled systems with a single controller. The parameter estimation and linear parameter varying synthesis method of the adaptive control scheme are described and finally flight test results show the contributions and limits of the approach.TOULOUSE-ISAE (315552318) / SudocSudocFranceF
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