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Control Law (control + law)
Kinds of Control Law Selected AbstractsDeployable Truss Operation by ETS-VII Robot Arm Using Force Accommodation ControlCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 3 2001Masahiro Nohmi An experiment for teleoperating a truss structure has been performed as part of a space robotics mission on Engineering Test Satellite No. 7 (ETS-VII). This article reports the results from truss experiments conducted by means of the ETS-VII robot arm using force accommodation control, which is a specific control law developed for the ETS-VII robot arm. With this control function, the robot arm moves toward the point where the external force becomes the command value, which is sent from the ground. This control technique is useful especially in the case of teleoperation with time delay, since excessive force and torque can be avoided, and in addition, no a priori trajectory information is required. However, the robot arm cannot attain the desired configuration for itself. These characteristics can be used for deployable and assembly truss operation, making full use of merits and avoiding demerits. The effectiveness is confirmed through an ETS-VII onboard experiment. [source] Protection of seismic structures using semi-active friction TMDEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2010Chi-Chang Lin Abstract Although the design and applications of linear tuned mass damper (TMD) systems are well developed, nonlinear TMD systems are still in the developing stage. Energy dissipation via friction mechanisms is an effective means for mitigating the vibration of seismic structures. A friction-type TMD, i.e. a nonlinear TMD, has the advantages of energy dissipation via a friction mechanism without requiring additional damping devices. However, a passive-friction TMD (PF-TMD) has such disadvantages as a fixed and pre-determined slip load and may lose its tuning and energy dissipation abilities when it is in the stick state. A novel semi-active-friction TMD (SAF-TMD) is used to overcome these disadvantages. The proposed SAF-TMD has the following features. (1) The frictional force of the SAF-TMD can be regulated in accordance with system responses. (2) The frictional force can be amplified via a braking mechanism. (3) A large TMD stroke can be utilized to enhance control performance. A non-sticking friction control law, which can keep the SAF-TMD activated throughout an earthquake with an arbitrary intensity, was applied. The performance of the PF-TMD and SAF-TMD systems in protecting seismic structures was investigated numerically. The results demonstrate that the SAF-TMD performs better than the PF-TMD and can prevent a residual stroke that may occur in a PF-TMD system. Copyright © 2009 John Wiley & Sons, Ltd. [source] Active tendon control of cable-stayed bridges: a large-scale demonstrationEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2001Frédéric Bossens This paper presents a strategy for active damping of cable structures, using active tendons. The first part of the paper summarizes the theoretical background: the control law is briefly presented together with the main results of an approximate linear theory which allows the prediction of closed-loop poles with a root locus technique. The second part of the paper reports on experimental results obtained with two test structures: the first one is a small size mock-up representative of a cable-stayed bridge during the construction phase. The control of the parametric vibration of passive cables due to deck vibration is demonstrated. The second one is a 30 m long mock-up built on the reaction wall of the ELSA test facility at the JRC Ispra (Italy); this test structure is used to demonstrate the practical implementation of the control strategy with hydraulic actuators. Copyright © 2001 John Wiley & Sons, Ltd. [source] Smooth switching control for transfer from the Automatic Traveling Mode to the Power Assist Mode of the Skill-AssistIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 4 2007Suwoong Lee Non-member Abstract The objective of this study is to verify a smooth switching control method for transfer from the automatic traveling mode (ATM) to the power assist mode (PAM) of Skill-Assist. A control law including time-varying impedance parameters is utilized to attain the objective. The experimental result shows that the transfer from ATM to PAM was successfully performed by the smooth switching control method. © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Optimal solid shell element for large deformable composite structures with piezoelectric layers and active vibration controlINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 15 2005X. G. Tan Abstract In this paper, we present an optimal low-order accurate piezoelectric solid-shell element formulation to model active composite shell structures that can undergo large deformation and large overall motion. This element has only displacement and electric degrees of freedom (dofs), with no rotational dofs, and an optimal number of enhancing assumed strain (EAS) parameters to pass the patch tests (both membrane and out-of-plane bending). The combination of the present optimal piezoelectric solid-shell element and the optimal solid-shell element previously developed allows for efficient and accurate analyses of large deformable composite multilayer shell structures with piezoelectric layers. To make the 3-D analysis of active composite shells containing discrete piezoelectric sensors and actuators even more efficient, the composite solid-shell element is further developed here. Based on the mixed Fraeijs de Veubeke,Hu,Washizu (FHW) variational principle, the in-plane and out-of-plane bending behaviours are improved via a new and efficient enhancement of the strain tensor. Shear-locking and curvature thickness locking are resolved effectively by using the assumed natural strain (ANS) method. We also present an optimal-control design for vibration suppression of a large deformable structure based on the general finite element approach. The linear-quadratic regulator control scheme with output feedback is used as a control law on the basis of the state space model of the system. Numerical examples involving static analyses and dynamic analyses of active shell structures having a large range of element aspect ratios are presented. Active vibration control of a composite multilayer shell with distributed piezoelectric sensors and actuators is performed to test the present element and the control design procedure. Copyright © 2005 John Wiley & Sons, Ltd. [source] Two-dimensional transonic aeroservoelastic computations in the time domainINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2001L. Djayapertapa Abstract A computational method to perform transonic aeroelastic and aeroservoelastic calculations in the time domain is presented, and used to predict stability (flutter) boundaries of 2-D wing sections. The aerodynamic model is a cell-centred finite-volume unsteady Euler solver, which uses an efficient implicit time-stepping scheme and structured moving grids. The aerodynamic equations are coupled with the structural equations of motion, which are derived from a typical wing section model. A control law is implemented within the aeroelastic solver to investigate active means of flutter suppression via control surface motion. Comparisons of open- and closed-loop calculations show that the control law can successfully suppress the flutter and results in an increase of up to 19 per cent in the allowable speed index. The effect of structural non-linearity, in the form of hinge axis backlash is also investigated. The effect is found to be strongly destabilizing, but the control law is shown to still alleviate the destabilizing effect. Copyright © 2001 John Wiley & Sons, Ltd. [source] Neural network-based adaptive attitude tracking control for flexible spacecraft with unknown high-frequency gainINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 6 2010Qinglei Hu Abstract Adaptive control design using neural networks (a) is investigated for attitude tracking and vibration stabilization of a flexible spacecraft, which is operated at highly nonlinear dynamic regimes. The spacecraft considered consists of a rigid body and two flexible appendages, and it is assumed that the system parameters are unknown and the truncated model of the spacecraft has finite but arbitrary dimension as well, for the purpose of design. Based on this nonlinear model, the derivation of an adaptive control law using neural networks (NNs) is treated, when the dynamics of unstructured and state-dependent nonlinear function are completely unknown. A radial basis function network that is used here for synthesizing the controller and adaptive mechanisms is derived for adjusting the parameters of the network and estimating the unknown parameters. In this derivation, the Nussbaum gain technique is also employed to relax the sign assumption for the high-frequency gain for the neural adaptive control. Moreover, systematic design procedure is developed for the synthesis of adaptive NN tracking control with L2 -gain performance. The resulting closed-loop system is proven to be globally stable by Lyapunov's theory and the effect of the external disturbances and elastic vibrations on the tracking error can be attenuated to the prescribed level by appropriately choosing the design parameters. Numerical simulations are performed to show that attitude tracking control and vibration suppression are accomplished in spite of the presence of disturbance torque/parameter uncertainty. Copyright © 2009 John Wiley & Sons, Ltd. [source] Indirect adaptive control of a class of marine vehiclesINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 4 2010Yannick Morel Abstract A nonlinear adaptive framework for bounded-error tracking control of a class of non-minimum phase marine vehicles is presented. The control algorithm relies on a special set of tracking errors to achieve satisfactory tracking performance while guaranteeing stable internal dynamics. First, the design of a model-based nonlinear control law, guaranteeing asymptotic stability of the error dynamics, is presented. This control algorithm solves the tracking problem for the considered class of marine vehicles, assuming full knowledge of the system model. Then, the analysis of the zero-dynamics is carried out, which illustrates the efficacy of the chosen set of tracking errors in stabilizing the internal dynamics. Finally, an indirect adaptive technique, relying on a partial state predictor, is used to address parametric uncertainties in the model. The resulting adaptive control algorithm guarantees Lyapunov stability of the errors and parameter estimates, as well as asymptotic convergence of the errors to zero. Numerical simulations illustrate the performance of the adaptive algorithm. Copyright © 2009 John Wiley & Sons, Ltd. [source] Improved adaptive control for the discrete-time parametric-strict-feedback formINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 12 2009Graciela Adriana González Abstract Adaptive control design for a class of single-input single-output nonlinear discrete-time systems in parametric-strict-feedback form is re-visited. No growth restrictions are assumed on the nonlinearities. The control objective is to achieve tracking of a reference signal. As usual, the algorithm derives from the combination of a control law and a parameter estimator (certainty equivalence principle). The parameter estimator strongly lies on the regressor subspace identification by means of an orthogonalization process. Certain drawbacks of previous schemes are analyzed. Several modifications on them are considered to improve the algorithm complexity, control performance and numerical stability. As a result, an alternative control scheme is proposed. When applied to the proposed class of systems, global boundedness and convergence remain as achieved objectives while improving the performance issues of previous schemes. Copyright © 2009 John Wiley & Sons, Ltd. [source] Longitudinal auto-landing controller design via adaptive backsteppingINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 7 2009Hann-Shing Ju Abstract This paper presents an auto-landing controller for glide-slope tracking and the flare maneuver via adaptive backstepping design and describes a flight path command generator for indirect altitude control in order to provide precise altitude trajectories for auto-landing of unmanned aerial vehicles (UAVs). Using the adaptive backstepping procedure to synthesize a glide-slope tracking and flare maneuver control law is being used differently from designing the guidance and control loops separately in autopilot. An adaptive controller is proposed to control aircraft from glide-slope to flare by following the flight path angle command for indirect altitude control via elevator and maintaining the constant airspeed control via throttle. Simulation results demonstrate that the adaptive auto-landing controller is capable of effectively guiding the UAV along the flight path angle command under the presence of the wind turbulence. Copyright © 2008 John Wiley & Sons, Ltd. [source] Adaptive synchronization for nonlinear FitzHugh,Nagumo neurons in external electrical stimulationINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 9 2008Chung-Wen Lai Abstract This paper investigates the synchronization problem for FitzHugh,Nagumo (FHN) neurons in external electrical stimulations. Using the sliding mode control technique, an adaptive control law is established that guarantees synchronization even when the parameters of the master and slave FHN neurons are fully unknown. A proportional-integral switching surface is introduced to simplify the task of assigning the stability of the closed-loop error system in the sliding mode. Furthermore, the proposed synchronization scheme is then applied to a secure communication system. Computer simulations are provided to verify the effectiveness of the proposed adaptive synchronization scheme. Copyright © 2007 John Wiley & Sons, Ltd. [source] Passification-based adaptive control of linear systems: Robustness issuesINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 6 2008Dimitri Peaucelle Abstract Passivity is a widely used concept in control theory having led to many significant results. This paper concentrates on one characteristic of passivity, namely passification-based adaptive control. This concept applies to multi-input multi-output systems for which exists a combination of outputs that renders the open-loop system hyper-minimum phase. Under such assumptions, the system may be passified by both high-gain static output feedback and by a particular adaptive control algorithm. This last control law is modified here to guarantee its coefficients to be bounded. The contribution of this paper is to investigate its robustness with respect to parametric uncertainty. Time response characteristics are illustrated on examples including realistic situations with noisy output and saturated input. Theoretical results are formulated as linear matrix inequalities and can hence be readily solved with semi-definite programming solvers. Copyright © 2007 John Wiley & Sons, Ltd. [source] Adaptive backstepping control for a class of time delay systems with nonlinear perturbationsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2008Chang-Chun Hua Abstract The sliding mode control method has been extensively employed to stabilize time delay systems with nonlinear perturbations. Although the resulting closed-loop systems have good transient and steady-state performances, the designed controllers are dependent on the time delays. But one knows that it is difficult to obtain the precise delay time in practical systems, especially when it is time varying. In this paper, we revisit the problem and use the backstepping method to construct the state feedback controller. First, a coordinate transformation is used to obtain a cascade time delay system. Then, a linear virtual control law is designed for the first subsystem. The memoryless controller is further constructed based on adaptive method for the second subsystem with the uncertainties bounded by linear function. By choosing new Lyapunov,Krasovskii functional, we show that the system state converges to zero asymptotically. Via the proposed approach, we also discuss the case that the uncertainties are bounded by nonlinear functions. Finally, simulations are done to verify the effectiveness of the main results obtained. Copyright © 2007 John Wiley & Sons, Ltd. [source] Finite-model adaptive control using an LS-like algorithm,INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 5 2007Hongbin Ma Abstract Adaptive control problem of a class of discrete-time nonlinear uncertain systems, of which the internal uncertainty can be characterized by a finite set of functions, is formulated and studied by using an least squares (LS)-like algorithm to design the feedback control law. For the finite-model adaptive control problem, this algorithm is proposed as an extension of counterpart of traditional LS algorithm. Stability in sense of pth mean for the closed-loop system is proved under a so-called linear growth assumption, which is shown to be necessary in general by a counter-example constructed in this paper. The main results have been also applied to parametric cases, which demonstrate how to bridge the non-parametric case and parametric case. Copyright © 2006 John Wiley & Sons, Ltd. [source] An indirect adaptive pole-placement control for MIMO discrete-time stochastic systemsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 7 2005Wen-Shyong Yu Abstract In this paper, an indirect adaptive pole-placement control scheme for multi-input multi-output (MIMO) discrete-time stochastic systems is developed. This control scheme combines a recursive least squares (RLS) estimation algorithm with pole-placement control design to produce a control law with self-tuning capability. A parametric model with a priori prediction outputs is adopted for modelling the controlled system. Then, a RLS estimation algorithm which applies the a posteriori prediction errors is employed to identify the parameters of the model. It is shown that the implementation of the estimation algorithm including a time-varying inverse logarithm step size mechanism has an almost sure convergence. Further, an equivalent stochastic closed-loop system is used here for constructing near supermartingales, allowing that the proposed control scheme facilitates the establishment of the adaptive pole-placement control and prevents the closed-loop control system from occurring unstable pole-zero cancellation. An analysis is provided that this control scheme guarantees parameter estimation convergence and system stability in the mean squares sense almost surely. Simulation studies are also presented to validate the theoretical findings. Copyright © 2005 John Wiley & Sons, Ltd. [source] Gain scheduling control of functional electrical stimulation for assisted standing up and sitting down in paraplegia: a simulation studyINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 5 2005Fabio Previdi Abstract This paper reports on a simulation study that concerns the design of a non-linear controller for the standing up and the sitting down of a paraplegic patient by means of functional electrical stimulation. The simulations refer to a specific experimental device developed at the Fondazione Don Gnocchi (Italy). This is a seesaw, with the patient on one side and a weight on the other side. The patient is seated so that its posture can be fully known in real-time by continuously monitoring the knee joint angle. By delivering a suitable electrical stimulation to the quadriceps muscles groups, the patient can be raised and made to sit via smooth movements. Hitherto, the only feedback control law, which has been implemented in this area, is based on a PID controller and usually provides poor tracking performances. Hence, in this work, a non-linear gain scheduling controller has been designed and tested in a series of simulation experiments. The controller is tuned following a gain scheduling strategy: a set of local linear quadratic controllers is designed using a set of linear tangent models. A global non-linear gain scheduled controller is then obtained via interpolation. The gain- scheduled controller is implemented following an advanced strategy that guarantees that the so-called linearization property holds. Copyright © 2004 John Wiley & Sons, Ltd. [source] Adaptive control of Burgers' equation with unknown viscosityINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 7 2001Wei-Jiu Liu Abstract In this paper, we propose a fortified boundary control law and an adaptation law for Burgers' equation with unknown viscosity, where no a priori knowledge of a lower bound on viscosity is needed. This control law is decentralized, i.e., implementable without the need for central computer and wiring. Using the Lyapunov method, we prove that the closed-loop system, including the parameter estimator as a dynamic component, is globally H1 stable and well posed. Furthermore, we show that the state of the system is regulated to zero by developing an alternative to Barbalat's Lemma which cannot be used in the present situation. Copyright © 2001 John Wiley & Sons, Ltd. [source] Stabilization of n integrators in cascade with bounded input with experimental application to a VTOL laboratory systemINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 10 2010G. Sanahuja Abstract This paper presents a global stabilization of a chain of n integrators in cascade. The control strategy is obtained using the Lyapunov approach and separated saturation functions. Moreover, the stability analysis is obtained using the recurrence theorem. This generalized control law is designed in order to quickly implement it on a system, as choosing a degree n gives all conditions to have a stable system. Moreover, in the proposed controller the saturation function bound only one state. This allows us to easily tune the control parameters. Simulations and real-time experiments are presented for the VTOL platform represented as a chain of two and four integrators in cascade. Copyright © 2009 John Wiley & Sons, Ltd. [source] Robust impedance control of a hydraulic suspension systemINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 8 2010Mohammad Mehdi FatehArticle first published online: 2 JUN 200 Abstract A novel robust impedance control approach is developed to control dynamic behavior of a vehicle subject to road disturbances. This behavior is predetermined as an impedance rule to achieve passenger comfort and vehicle handling by the use of a hydraulically actuated suspension system. Impedance control law is simple, free of model and efficient to apply for a broad range of road conditions. Moreover, it relates comfort to handling. This control approach can provide a desired comfort when passing a bump, and both desired comfort and handling after passing a bump. Robust position and force controls are used to implement the robust impedance control with the presence of uncertainties. A transformed proportional,integral,derivative control is proposed to perform the robust control. The system stability is analyzed and analytical results are confirmed by simulations. A quarter-car model of suspension system and a nonlinear model of hydraulic actuator are used to simulate the control system. Copyright © 2009 John Wiley & Sons, Ltd. [source] Switching contact task control in hydraulic actuators: Stability analysis and experimental evaluationINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 17 2009P. Sekhavat Abstract A switching contact task control for hydraulic actuators is proposed. The controller is built upon three individually designed control laws for three phases of motion: (1) position regulation in free space, (2) impact suppression and stable transition from free to constrained motion and (3) force regulation in sustained-contact motion. The position and force control schemes are capable of asymptotic set-point regulation in the presence of actuator friction and without the complexity of sliding mode or adaptive control techniques. The intermediate impact control scheme is included for the first time to dampen the undesirable impacts and dissipate the impact energy that could potentially drive the whole system unstable. The solution concept and the stability of the complete switching control system are analyzed rigorously using the Filippov's solution concept and the concept of Lyapunov exponents. Both computer simulations and experiments are carried out to demonstrate the efficacy of the designed switching control law. Copyright © 2009 John Wiley & Sons, Ltd. [source] Inf,sup control of discontinuous piecewise affine systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 13 2009J. Spjřtvold Abstract This paper considers the worst-case optimal control of discontinuous piecewise affine (PWA) systems, which are subjected to constraints and disturbances. We seek to pre-compute, via dynamic programming, an explicit control law for these systems when a PWA cost function is utilized. One difficulty with this problem class is that, even for initial states for which the value function of the optimal control problem is finite, there might not exist a control law that attains the infimum. Hence, we propose a method that is guaranteed to obtain a sub-optimal solution, and where the degree of sub-optimality can be specified a priori. This is achieved by approximating the underlying sub-problems with a parametric piecewise linear program. Copyright © 2008 John Wiley & Sons, Ltd. [source] H, fuzzy control design of discrete-time nonlinear active fault-tolerant control systemsINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 10 2009Huai-Ning Wu Abstract This paper is concerned with the problem of H, fuzzy controller synthesis for a class of discrete-time nonlinear active fault-tolerant control systems (AFTCSs) in a stochastic setting. The Takagi and Sugeno (T,S) fuzzy model is employed to exactly represent a nonlinear AFTCS. For this AFTCS, two random processes with Markovian transition characteristics are introduced to model the failure process of system components and the fault detection and isolation (FDI) decision process used to reconfigure the control law, respectively. The random behavior of the FDI process is conditioned on the state of the failure process. A non-parallel distributed compensation (non-PDC) scheme is adopted for the design of the fault-tolerant control laws. The resulting closed-loop fuzzy system is the one with two Markovian jump parameters. Based on a stochastic fuzzy Lyapunov function (FLF), sufficient conditions for the stochastic stability and H, disturbance attenuation of the closed-loop fuzzy system are first derived. A linear matrix inequality (LMI) approach to the fuzzy control design is then developed. Moreover, a suboptimal fault-tolerant H, fuzzy controller is given in the sense of minimizing the level of disturbance attenuation. Finally, a simulation example is presented to illustrate the effectiveness of the proposed design method. Copyright © 2008 John Wiley & Sons, Ltd. [source] A backstepping controller for path-tracking of an underactuated autonomous airshipINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 4 2009José Raul Azinheira Abstract In this paper we propose a nonlinear control approach for the path-tracking of an autonomous underactuated airship. A backstepping controller is designed from the airship nonlinear dynamic model including wind disturbances, and further enhanced to consider actuators saturation. Control implementation issues related to airship underactuation are also addressed, namely control allocation and an attitude reference shaping to obtain a faster error correction with smoother input requests. The results obtained demonstrate the capacity of an underactuated unmanned airship to execute a realistic mission including vertical take-off and landing, stabilization and path-tracking, in the presence of wind disturbances, with a single robust control law. Copyright © 2008 John Wiley & Sons, Ltd. [source] A new controller for the inverted pendulum on a cartINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 17 2008F. Gordillo Abstract This paper presents a complete solution to the problem of swinging-up and stabilization of the inverted pendulum on a cart, with a single control law. The resulting law has two parts: first, an energy-shaping law is able to swing and maintain the pendulum up. Then, the second part introduces additional control to stop the cart and it is based on forwarding control with bounded input. The resulting control law is the sum of both parts and does not commute between different laws although there exist switches inside the controller. Copyright © 2008 John Wiley & Sons, Ltd. [source] Robust discontinuous exponential regulation of dynamic nonholonomic wheeled mobile robots with parameter uncertaintiesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 9 2008B. L. Ma Abstract For regulating a dynamic nonholonomic WMR (wheeled mobile robot) with parameter uncertainties, we derive a simple robust discontinuous control law, yielding a global exponential convergence of position and orientation to the desired set point despite parameter uncertainties. The controller design relies on separating the error dynamics into two subsystems, followed by robust feedback control laws to stabilize the subsystems. The effectiveness of the proposed control laws is verified by simulation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Robust tracking control for a class of MIMO nonlinear systems with measurable output feedbackINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2008Ya-Jun Pan Abstract This paper proposes a robust output feedback controller for a class of nonlinear systems to track a desired trajectory. Our main goal is to ensure the global input-to-state stability (ISS) property of the tracking error nonlinear dynamics with respect to the unknown structural system uncertainties and external disturbances. Our approach consists of constructing a nonlinear observer to reconstruct the unavailable states, and then designing a discontinuous controller using a back-stepping like design procedure to ensure the ISS property. The observer design is realized through state transformation and there is only one parameter to be determined. Through solving a Hamilton,Jacoby inequality, the nonlinear control law for the first subsystem specifies a nonlinear switching surface. By virtue of nonlinear control for the first subsystem, the resulting sliding manifold in the sliding phase possesses the desired ISS property and to certain extent the optimality. Associated with the new switching surface, the sliding mode control is applied to the second subsystem to accomplish the tracking task. As a result, the tracking error is bounded and the ISS property of the whole system can be ensured while the internal stability is also achieved. Finally, an example is presented to show the effectiveness of the proposed scheme. Copyright © 2007 John Wiley & Sons, Ltd. [source] On delay-dependent LMI-based guaranteed cost control of uncertain neutral systems with discrete and distributed time-varying delaysINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 12 2007Jenq-Der Chen Abstract In this paper, the problem of designing robust guaranteed cost control law for a class of uncertain neutral system with a given quadratic cost function is considered. Based on Lyapunov,Krasovskii functional theory, a delay-dependent criterion for the existence of guaranteed cost controller is expressed in the form of two linear matrix inequalities (LMIs), which can be solved by using effective LMI toolbox. Moreover, a convex optimization problem satisfying some LMI constraints is formulated to solve a guaranteed cost controller which achieves the minimization of the closed-loop guaranteed cost. An efficient approach is proposed to design the guaranteed cost control for uncertain neutral systems. Computer software Matlab can be used to solve all the proposed results. Finally, a numerical example is illustrated to show the usefulness of our obtained design method. Copyright © 2006 John Wiley & Sons, Ltd. [source] Adaptive sensorless robust control of AC drives based on sliding mode control theoryINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 9 2007O. Barambones Abstract This paper focuses in the design of a new adaptive sensorless robust control to improve the trajectory tracking performance of induction motors. The proposed design employs the so-called vector (or field oriented) control theory for the induction motor drives, being the designed control law based on an integral sliding-mode algorithm that overcomes the system uncertainties. This sliding-mode control law incorporates an adaptive switching gain in order to avoid the need of calculating an upper limit for the system uncertainties. The proposed design also includes a new method in order to estimate the rotor speed. In this method, the rotor speed estimation error is presented as a first-order simple function based on the difference between the real stator currents and the estimated stator currents. The stability analysis of the proposed controller under parameter uncertainties and load disturbances is provided using the Lyapunov stability theory. The simulated results show, on the one hand that the proposed controller with the proposed rotor speed estimator provides high-performance dynamic characteristics, and on the other hand that this scheme is robust with respect to plant parameter variations and external load disturbances. Finally, experimental results show the performance of the proposed control scheme. Copyright © 2006 John Wiley & Sons, Ltd. [source] Further constructive results on interconnection and damping assignment control of mechanical systems: the Acrobot exampleINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 14 2006Arun D. Mahindrakar Abstract Interconnection and damping assignment passivity-based control is a controller design methodology that achieves (asymptotic) stabilization of mechanical systems endowing the closed-loop system with a Hamiltonian structure with a desired energy function,that qualifies as Lyapunov function for the desired equilibrium. The assignable energy functions are characterized by a set of partial differential equations that must be solved to determine the control law. A class of underactuation degree one systems for which the partial differential equations can be explicitly solved,making the procedure truly constructive,was recently reported by the authors. In this brief note, largely motivated by the interesting Acrobot example, we pursue this investigation for two degrees-of-freedom systems where a constant inertia matrix can be assigned. We concentrate then our attention on potential energy shaping and give conditions under which an explicit solution of the associated partial differential equation can be obtained. Using these results we show that it is possible to swing-up the Acrobot from some configuration positions in the lower half plane, provided some conditions on the robot parameters are satisfied. Copyright © 2006 John Wiley & Sons, Ltd. [source] Nonsingular path following control of a unicycle in the presence of parametric modelling uncertaintiesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 10 2006L. Lapierre Abstract A new type of control law is derived to steer the dynamic model of a wheeled robot of unicycle type along a desired path. The methodology adopted for path following control deals explicitly with vehicle dynamics and plant parameter uncertainty. Furthermore, it overcomes stringent initial condition constraints that are present in a number of path following control strategies described in the literature. This is done by controlling explicitly the rate of progression of a ,virtual target' to be tracked along the path, thus bypassing the problems that arise when the position of the virtual target is simply defined by the projection of the actual vehicle on that path. In the paper, a nonlinear adaptive control law is derived that yields convergence of the (closed-loop system) path following error trajectories to zero. Controller design relies on Lyapunov theory and backstepping techniques. Simulation results illustrate the performance of the control system proposed. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||