Structure Model Reference Adaptive Control Research Articles

Active control of vehicle active suspension with preview, using a variable structure model reference adaptive controller

A Variable Structure Model Reference Adaptive Controller (VS-MRAC) is proposed for the active control of vehicle suspension with preview. A two DOF quarter car model has been considered. The reference model is also a two DOF vibrating system with a skyhook damper. The structure of the switching functions is designed, based on global exponential stability requirements, and shows perfect model following at a finite time. Sliding surfaces are independent of system parameters and, therefore, VS-MRAC is insensitive to system parameter variations. Simulation is presented for some road irregularities, and compares to active suspension with fixed structure MRAC, and passive suspension. VS-MRAC shows the best performance on ride and working space.

A dual-mode adaptive robust controller using the takagisugeno model applied to a three-phase induction motor

In this paper is presented the application of a control strategy that interpolates the Model Reference Adaptive Control (MRAC) and the Variable Structure Model Reference Adaptive Control (VS-MRAC) applied to an induction motor. The combination of these strategies is obtained with concepts from Fuzzy Logic, where is used the idea of error magnitude for activating each controller in correct time. We used the Takagi-Sugeno Inference Model to obtain an analytic expression for the adaptation law. The application to the induction motor shows that this new strategy adaptation incorporates the advantages of both MRAC and VS-MRAC.

Structured Model Reference Adaptive Control for a Class of Nonlinear Systems

A control design methodology for a particular class of nonlinear dynamic systems in the structured first-order form is presented. The differential equations are distinctly categorized as two sets, one representing exact kinematic differential equations and the other representing an uncertain dynamic model. The control law seeks exponential stability of the position errors for the known parameter case. For the uncertain parameter case, an adaptive controller is designed that guarantees bounded position tracking errors. The efficacy of the controller is supported through simulation examples.

Structured Model Reference Adaptive Control for a Wing Section with Structural Nonlinearity

The recently derived structured model reference adaptive control (SMRAC) method is considered for the active suppression of limit cycle oscillations for a typical wing section with a structural nonlinearity. The SMRAC method uses the specific structure of the equations of motion governing general mechanical systems. This adaptive control method is implemented and tested in wind tunnel experiments to validate the performance. For comparison, results obtained with adaptive feedback linearization are also presented. It is shown that the derived SMRAC is advantageous in that it suppresses limit cycle oscillations at higher velocities, and also it can rigorously treat actuator saturation a priori.

OUTPUT FEEDBACK ADAPTIVE VARIABLE STRUCTURE CONTROL OF CHAOS IN LORENZ SYSTEM

Based on the variable structure model reference adaptive control (VS-MRAC) theory, a new control system for the control of chaos in Lorenz system, using only the measured output variable, is designed. For the derivation of the control law, it is assumed that the parameters of the model are unknown. Moreover, it is assumed that a disturbance input is present in the system. It is shown that in the closed-loop system, the output variable tracks a given reference trajectory, and the state vector converges to the equilibrium state. Digital simulation results show that the closed-loop system has good transient behavior and robustness to the uncertainties and disturbance input.

Variable Structure Adaptive Force Tracking Control of a Cantilever Beam Using a Piezoelectric Actuator

This paper presents an adaptive force trajectory control of a flexible beam using a piezoceramic actuator. Based on the variable structure model reference adaptive control theory, a new force control system using only force measurement is designed. For the derivation of the control law, it is assumed that parameters of the beam and contact surface stiffness are unknown. It is shown that in the closed-loop system, the contact force tracks a given reference trajectory and the beam vibration is suppressed as well. Digital simulations results show that the closed-loop system has good transient behavior and robust performance in the presence of uncertainties in the parameters of the flexible beam and the contact surface, and unmodeled dynamics as well.

Grasping impact force control of a flexible robotic gripper using a piezoelectric actuator

This paper presents robust force tracking control of a flexible beam during a grasping operation using a piezoceramic actuator. Equations describing the motion of the gripper in conditions of contact and noncontact are derived based on the cantilever beam. In this study, contact force is regulated, in addition to the impact force generated at the instant of contact, based on variable structure model reference adaptive control theory using only force measurements. For the derivation of the control law, it is assumed that parameters of the beam and the stiffness of the object are unknown. Computer simulations show the effectiveness the controller.

Dynamic positioning of remotely operated underwater vehicles

The paper describes an automatic dynamic positioning system for remotely operated underwater vehicles (ROVs) using a mechanical passive arm for position measurement that is suitable for inspection and intervention tasks requiring precise positioning. Good dynamic performance in tracking was also attained, particularly with the variable structure model reference adaptive control strategy.

A fuzzy neural network based on fuzzy hierarchy error approach

This paper presents a novel fuzzy neural network which consists of an antecedent network and a consequent network. The antecedent network matches the premises of the fuzzy rules and the consequent network implements the consequences of the rules. In the network learning and training phase, a concise and effective algorithm based on the fuzzy hierarchy error approach is proposed to update the parameters of the network. This algorithm is simple to implement and it does not require as many calculations as some other classic neural network learning algorithms. A model reference adaptive control structure incorporating the proposed fuzzy neural network is studied. Simulation results of a cart-pole balancing system demonstrate the effectiveness of the proposed method.

Output feedback variable structure adaptive control of a flexible spacecraft

Based on the variable structure model reference adaptive control theory, a new control system for the control of an orbiting flexible spacecraft, using output feedback, is designed. The spacecraft consists of a main rigid body to which elastic appendages are attached. For the purpose of control, a moment generating device is located on the rigid hub. For the derivation of control law, it is assumed that the parameters and the structure of the nonlinear functions in the model are unknown. It is shown that in the closed-loop system including the variable structure model reference adaptive control system designed using bounds on uncertain functions, the pitch angle tracks given reference trajectory and the vibration is suppressed. Digital simulation results show that the closed-loop system has good transient behavior and robustness to the uncertainties, unmodeled dynamics, and disturbance inputs.

Output Feedback Variable Structure Adaptive Control of an Aeroelastic System

The paper presents an application of the variable structure model reference adaptive control theory to control of aeroelastic systems with structural nonlinearity. Interestingly, the design approach does not require any knowledge of the parameters of the system and the nonlinear functions, and only output feedback is used for the synthesis of the control systems. Control laws for the trajectory tracking of pitch angle and plunge displacement are derived. In the closed-loop system, the state vector asymptotically converges to the origin. Control laws are discontinuous functions of the tracking error, and modulation functions of the relays are generated on-line using bounds on uncertain functions and certain auxiliary signals. Digital simulation results are presented which show that in the closed-loop system, pitch angle and plunge displacement are smoothly regulated to zero in spite of the uncertainty and unmodeled functions in the system using only output feedback.

Robustness and Alleviation of Chattering by New Modified Update Laws and Sigmoid Function in Variable Structure Adaptive Control

A generalised applied of two modified update laws to plant model of relative degree greater than one, for variable structure model reference adaptive control, is presented in this paper. A type of augmented error is involved as identifier error. A k-sigmoid function, in parameter update laws, is used for to avoid stability analysis of the closed loop described by differential equations with discontinuous right-hand side. A forgetting term, that does not require any prior information, is enclosed in parameter update laws of the control input for to improve the transitory response and robustness to disturbances and unmodeled dynamics. Stability proof of the closed loop and on-line identifier is given together with the condition for system evolution in sliding mode.

Output Feedback Adaptive Variable Structure Control of Chaos in Lorenz System

Based on the variable structure model reference adaptive control (VS-MRAC) theory, a new control system for the control of chaos in Lorenz systems, using only output measurement, is designed. For the derivation of the control law, it is assumed that the parameters of the nonlinear functions in the model are unknown. Moreover, it is assumed that disturbance input is present in the system. It is shown that in the closed-loop system the output tracks a given reference trajectory and the chaos is suppressed. Numerical simulation results show that the closed-loop system has good transient behavior and robustness to the uncertainties and disturbance input.

Variable Structure Adaptive Control of Wing-Rock Motion of Slender Delta Wings

Based on the variable structure model reference adaptive control (VS-MRAC) theory, a new control system for the control of wing-rock motion of slender delta wings, using only roll angle measurement, is designed. For the derivation of the control law, it is assumed that the aerodynamic parameters and the structure of the nonlinear aerodynamic nonlinear functions in the model are unknown. Moreover, it is assumed that disturbance input is present in the system. It is shown that in the closed-loop system including the VS-MRAC system designed using bounds on uncertain functions, the roll angle tracks given reference trajectory and the wing-rock motion is suppressed. Digital simulation results show that the closed-loop system has good transient behavior and robustness to the uncertainties and disturbance input.

Robustness in Variable Structure and Compound Adaptive Control by Two New Modified Update Laws

Are proposed two new modified update laws for variable structure and compound model reference adaptive control with k-sigmoid function. Only, the adaptive control of the plant model with relative degree one is presented. In compound adaptive control, both components of the control law have enclosed adaptive modifications in parameter update laws. These new adjustment laws assure robustness of the adaptive loop in the presence of external bounded disturbances and unmodeled dynamics. No, any prior information is needed about the norm of the controller parameters or the upper bound of the disturbances. The Lyapunov functions are used to proof global stability of the adaptive loops.

New results on output-feedback variable structure model-reference adaptive control: design and stability analysis

The variable structure model-reference adaptive control(VS-MRAC) redesign and stability analysis, presented previously by the authors (1993) for the case of plants with relative degree n*/spl les/2, is generalized to the case of arbitrary n*/spl ges/1. This paper presents a complete stability analysis in the general case. The redesign is based on the explicit consideration of input disturbances which may include the disturbance originated by the uncertainty of the plant high-frequency gain. This leads to a considerably simpler and less restrictive stability analysis as well as to a systematic controller design for external disturbance rejection. The overall error system is globally exponentially stable with respect to a small residual set. Robustness to unmodeled dynamics is also discussed.

Variable structure model reference adaptive control with integration

Variable structure model reference adaptive control with integration

Finite-dimensional VS-MRAC of distributed parameter systems with boundary inputs

A design method is proposed for actual finite-dimensional VS-MRAC (variable structure model reference adaptive control) of asymptotically stable distributed systems with bounded disturbances, bound...

Robust variable structure model reference adaptive control

A new variable structure model reference adaptive control scheme is proposed in this paper to achieve robustness to bounded disturbance. A key feature of this scheme is that the knowledge of neither the upper bound on the disturbance nor the upper bound on the norm of the matching controller parameters is required. Another advantage of the scheme is its zero output error tracking

Analysis and design of I/O based variable structure adaptive control

This paper presents an overview of a technique for the design of variable structure model reference adaptive control (VS-MRAC) systems, using only input-output data. The main ideas underlying the design and the analysis, as well as the main properties of the controller, are described having as point of departure a well known parameter adaptive MRAC scheme. Then, asymptotic properties of the VS-MRAC system are established taking into account the effect of the averaging filters necessary to implement some equivalent control signals. In particular, global exponential stability of the associated error system with respect to a small residual set is demonstrated. The effect of linear zones in the relay functions is assessed showing that they can alleviate the chattering phenomena. This is related with the fact that the VS-MRAC has a high-gain stability property. A procedure for noise sensitivity reduction is also proposed. Simulations illustrate the very satisfactory performance of the VS-MRAC in adverse operating conditions.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>