Variable Structure Model Reference Adaptive Control Research Articles

A novel reconfigurable control method for an aircraft with potential actuator failures

This paper presents a novel reconfigurable control method for an aircraft with potential actuator failures. A Variable Structure Model Reference Adaptive Control (VS-MRAC) scheme is deployed to counteract the adverse effects when the actuator failure occurs. Combined with exponential reaching law, the convergence rate is improved and the chattering is reduced. This approach ensures that the reference input value can be tracked rapidly and accurately. The safety and stability of the aircraft is much improved during the event of actuator failures. Finally, the simulation results are given to show the effectiveness and performance of the developed method.

A novel reconfigurable control method for an aircraft with potential actuator failures

This paper presents a novel reconfigurable control method for an aircraft with potential actuator failures. A Variable Structure Model Reference Adaptive Control (VS-MRAC) scheme is deployed to counteract the adverse effects when the actuator failure occurs. Combined with exponential reaching law, the convergence rate is improved and the chattering is reduced. This approach ensures that the reference input value can be tracked rapidly and accurately. The safety and stability of the aircraft is much improved during the event of actuator failures. Finally, the simulation results are given to show the effectiveness and performance of the developed method.

BLDC Multi-Motor Speed Synchronization by Leader Following Multi-Agent and Hybrid Control

In this article, a unique and innovative design for addressing the speed synchronization problem in a multi-motor system using Brush less DC (BLDC), motors is presented by utilizing motor back emf equation and rotor position commonly called sensor less technique. In the proposed method, the system is modelled as a consensus problem of leader following multi-agent system (MAS), and a hybrid controller is designed by using Model Reference Adaptive Control (MRAC) along with Variable Structure (VS) control technique of Sliding Mode Control (SMC), herein called Variable Structure Model Reference Adaptive Control (VS-MRAC). The consensus algorithm of MAS (reformed w.r.t motor speed data), is fused with the hybrid controller to reach consensus on speed regulated by proposed hybrid controller. The stability of a system is endorse by designing a Lyapunov function. The efficiency of the proposed methodology is proven by simulations performed in MATLAB and the acquired results validate the success of proposed design methodology.

From adaptive control to variable structure systems – seeking harmony

From adaptive control to variable structure systems – seeking harmony

Model‐reference impedance and admittance control of linear systems

SummaryA variable structure model‐reference adaptive control (VS‐MRAC) of impedances and admittances (driving‐point (DP) functions) is proposed. Only voltage and current measurements are required to implement the controllers. The inclusion of a prefilter in the reference model allows the synthesis of quite general DP functions, even with nonminimum phase zeros and unstable poles. It is shown that the stability of the closed‐loop system depends only on the source DP function and the chosen reference model. The VS‐MRAC guarantees global exponential stability properties, robustness to parameter uncertainties, disturbances, and unmodelled dynamics. Simulation results illustrate the performance and robustness of the VS‐MRAC. Copyright © 2016 John Wiley & Sons, Ltd.

MRAC-based Fault Tolerant Control of a SISO Real Process Application

In this paper, a modified version of Variable Structure Model Reference Adaptive Controller (VS-MRAC) scheme is developed for an application in Fault Tolerant Control (FTC) of a Single Input-Single Output (SISO) process. As a result of steady state error and oscillations when faults are induced in sensor and actuator of the process, the original VS-MRAC is modified by adding a Saturation Function and a PI controller (VS-MRAC-SAT-PI). The new scheme performance is compared against a classical PID and two other MRAC-based FTC schemes in a Coupled-Tank System. Different types of additive faults (abrupt and gradual faults) were induced in the process and results showed better fault accommodation capabilities of the VS-MRAC-SAT-PI.

Back-to-back converter state-feedback control of DFIG (doubly-fed induction generator)-based wind turbines

Control of DFIG (doubly-fed induction generator) is traditionally based on PI (proportional-integral) controllers and recently many papers have proposed sliding-mode based controllers. However, such controllers may excite unmodeled high-frequency system transients due to chattering, resulting in oscillations or even in unforeseen instability. In order to overcome these drawbacks, this paper proposes a internal model state-feedback control strategy for regulation of rotor direct and quadrature currents for wind driven DFIG, which can keep the smooth control signal of the classical PI controller and, at the same time, provides robustness to external disturbances. The currents are controlled in order to accomplish reactive power support to the grid and MPPT (maximum power point tracking). The proposed state-feedback control strategy as well as the classical PI and the VS-MRAC (variable-structure model reference adaptive control) sliding-mode strategy were discretized and implemented in a digital signal processor in order to interact with a real-time digital simulation of the DFIG-based wind energy conversion system. The proposed control structure achieved the fastest and the most robust dynamic response without stressing the converters or deteriorating the power quality.

Controlador em modo dual adaptativo robusto para plantas com grau relativo arbitrário

Neste artigo é apresentado o Controlador em Modo Dual Adaptativo Robusto (DMARC). O DMARC é um sistema de controle que combina as estratégias de Controle Adaptativo por Modelo de Referência (MRAC) com leis integrais de adaptação e o Controle Adaptativo por Modelo de Referência e Estrutura Variável (VS-MRAC) com leis chaveadas de acordo com a teoria de sistemas com estrutura variável. A idéia básica é incorporar as vantagens de desempenho transitório de um VS-MRAC, com as propriedades de regime permanente de um MRAC convencional. Desta forma, obtém-se um sistema de controle robusto a incertezas paramétricas e perturbações externas, com desempenho rápido e pouco oscilatório durante o transitório e um sinal de controle suave em regime permanente.

A DUAL-MODE ADAPTIVE ROBUST CONTROLLER APPLIED TO THE SPEED CONTROL OF A THREE-PHASE INDUCTION MOTOR

This work presents a Dual-Mode Adaptive Robust Controller applied to the angular shaft speed control of a three-phase induction motor. A liaison between a Model Reference Adaptive Controller (MRAC) and a Variable Structure Model Reference Adaptive Controller (VS-MRAC) through a tuning parameter is obtained using fuzzy logic. The basic idea of the Dual-Mode controller is adding both the advantages of the VS-MRAC transient behavior with the steady-state properties of the conventional MRAC.

Robust sliding mode control of a robot manipulator based on variable structure-model reference adaptive control approach

A model reference adaptive-sliding mode control is presented and applied for a variable stiffness actuated (VSA) system. The VSA is a flexible stiffness machine with two coupled actuators in each link, and its safety during the movement can be guaranteed by varying both stiffness and the angular variables. Realisation of precise control of two coupled actuators poses a considerable challenge, however, because of uncertain time-varying parameters and unknown variation bounds. In this paper a neuro-sliding mode approach based on model reference adaptive control (MRAC) is proposed. The proposed MRAC control structure induces the VSA to follow its nominal dynamics with help of sliding mode control efforts. The sliding gain, implemented by a simple neural network (NN), is adaptively updated based on the Lyapunov criterion. A control law and adaptive laws for the sliding mode control as well as the weights in the NN are established so that the closed-loop system is stable in the sense of Lyapunov. The tracking errors of both the angular variables and stiffness are managed to guarantee the system to be asymptotically stable rather than uniformly ultimately bounded. And, the feasibility of the proposed control approach is demonstrated by means of experimental results as well as computer simulations.

Controlador em modo dual adaptativo robusto para plantas com grau relativo unitário: prova de estabilidade

Neste artigo é apresentada uma prova de estabilidade para o controlador em Modo Dual Adaptativo Robusto (DMARC) para plantas com grau relativo unitário. O DMARC é um controlador que interpola as estratégias de Controle Adaptativo por Modelo de Referência (MRAC) e o Controle Adaptativo por Modelo de Referência e Estrutura Variável (VS-MRAC) com o intuito de incorporar as vantagens de desempenho transitório de um VS-MRAC, com as propriedades de regime permanente de um MRAC convencional. Desta forma, deseja-se obter um sistema de controle robusto a incertezas paramétricas e perturbações externas, com desempenho rápido e pouco oscilatório durante o transitório e um sinal de controle suave em regime permanente.

A variable structure MRAC with expected transient and steady-state performance

A new output feedback variable structure model reference adaptive control (VS-MRAC) scheme is proposed in this paper for uncertain plants with relative degree one. The scheme is based on the existing VS-MRAC structure together with a high gain switching mechanism to adjust the variable structure control signal. The main features of the scheme are that (1) the pre-specified transient and steady-state performance specifications for tracking error can be guaranteed, (2) it does not require the plant high frequency gain sign to be known a priori, (3) the usual assumption for MRAC system that the reference model is strictly positive real (SPR) is not needed and (4) the plant input disturbance, which is assumed to be unknown but bounded, can be completely rejected.

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.

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.

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.

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.

Decentralized variable-structure model-reference adaptive control of linear time-varying large-scale systems with bounded disturbances

Abstract The problem of model-reference control is considered for a large-scale variable-structure adaptive control system in the presence of interconnected terms, system parameter variations and external disturbances. Based on the technique of parameter estimations and the theory of the variable-structure systems, this paper presents a new and feasible design algorithm to synthesize a decentralized variable-structure adaptive controller which can easily tackle the model-reference control problem of linear time-varying large-scale systems subjected to interconnected terms, system parameter variations and bounded disturbances. In contrast with previous results, the restrictive condition that the exact value of the parameter about the input gain must be known can be relaxed. A series of computer simulations are also included to illustrate the proposed design algorithm.

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...