Search

This paper is devoted to the observer-based adaptive robust control for fractional-order Takagi–Sugeno (T-S) fuzzy systems with input uncertainties and output disturbances. By combining system states and output perturbations as new state variables, an augmented fuzzy system whose state variables are unknown is built. Furthermore, an observer is devised to simultaneously estimate unmeasurable system states together with unknown external disturbances. Two stability theorems are derived to prove the asymptotic stability of the error system based on linear matrix inequalities and Lyapunov stability theory. Finally, simulation results are provided to demonstrate the effectiveness of the designed method. [ABSTRACT FROM AUTHOR]

This paper presents a new approach of fault-tolerant control (FTC) for the transmission line as a neutral variable time-delay system. The main goal of this work guarantees faulty neutral variable time delay system stabilization using the state feedback control design based on Lyapunov function and the Linear Matrix Inequality resolution. The use of the FTC method is to achieve actuator and sensor fault compensation. This method is based on two steps. The first one is the synthesis of a nominal control, which remains to maintain the closed-loop system stability. The second step is based on adding a new control law to the nominal one to compensate the fault effect on system behaviour and maintain the desired performance in the closed loop system. Then, a conception of an adaptive observer is used to detect and estimate the fault. Finally, the developed approach is applied for the transmission line. The given results are presented to prove the effectiveness of this approach. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive sensorless control based on sliding mode approach for Interior Permanent Magnet Synchronous Motor (IPMSM) using the method of the angular position estimation error extraction. The proposed strategy combines a novel Adaptive Super-Twisting Controller (ASTWC) with a novel Adaptive Observer High-Order Sliding Mode (AOHOSM), where: (i) The control and observer gains are parameterized in terms of a single parameter simplifying its implementation and reducing the tuning time. (ii) By using an auxiliary system, which does not depend on machine parameters, an AOHOSM is designed for estimating the angular position, speed and acceleration in a wide speed range of the IPMSM, (iii) and these are used in an ASTWC to track a desired reference of speed and direct-axis current. (iv) Sufficient conditions are given to ensure the stability of the closed-loop system using a Lyapunov approach. Furthermore, the proposed strategy is validated throughout experimental set-up in order to show its effectiveness. Finally, a comparative study between the proposed strategy and other strategies published in the literature is addressed. • An extraction of the angular error allows to design a parameter-free observer • A parameter-free observer is able to overcome the issues of parametric uncertainties • Adaptive sliding mode avoids overestimation of gains and reduces chattering • Closed-loop analysis of the system is easier due to separation principle [ABSTRACT FROM AUTHOR]

With unknown leader parameters and false or immeasurable tracking paths, the leader–follower tracking problem via adaptive control becomes more complex and challenging. Different from the existing work in the literature and in line with real-world applications, this challenging issue is solved in this paper for multi-agent networks with different kinds of unknown uncertainties in the followers such as partially known parameters, nonlinearities, external disturbances, communication weights, and sensor faults. The solution of this challenging issue is obtained in three steps. Firstly, the tracking path is estimated by designing distributed adaptive observers at all agents that have direct communication edges with the leader. Next, by designing local adaptive observers for all followers, the estimates of all followers' states can be obtained. Then, distributed adaptive controllers for all followers are designed using the estimated states of both followers and their neighbors in addition to the estimated tracking path. The tracking performances are provided via sufficient conditions for both the adaptive observers and the adaptive controllers. The proposed methods are evaluated through two examples that are commonly used in the literature. The obtained results prove the efficacy of the recommended adaptive approaches. • The leader–follower tracking problem for general nonlinear MASs is solved with an uncertain leader and false tracking paths. • Local-based adaptive observers with partially known system parameters, disturbances, and sensor faults are investigated. • The weighted graphs with unknown weights for nonlinear MASs described by different dynamics are considered. • The asymptotic stabilities of the estimation and the tracking errors are guaranteed based on the Lyapunov stability method. • The proposed approach is examined efficiently by applying it to a numerical example plus a group of Volkswagen GOLF V. [ABSTRACT FROM AUTHOR]

This work addresses the problem of adaptive observer design for nonlinear systems satisfying incremental quadratic constraints. The output of the system includes nonlinear terms, which puts an additional strain on the design and feasibility of the observer, which is guaranteed under the satisfaction of an LMI, and a set of algebraic constraints. A particular case where the output nonlinearity matches the unknown parameter coefficient is also discussed. The result is illustrated through a numerical example for the chaos synchronization of the Rössler system. [ABSTRACT FROM AUTHOR]

The paper discusses the cooperative tracking problem of partially known cyber–physical multi-agent networked systems. In this system, there exist two cascaded chances for cyber-attacks. The local agent is of networked system type that is subjected to unknown false data-injection and replay cyber-attacks that are dissimilar in the sensor-controller and the controller-actuator network parts. The communication between any two agents, if they are connected, is accomplished via a communication network that is subjected to false data-injection cyber-attacks. The problem of the existing two cascaded chances for cyber-attacks is solved in three steps. First, with partially known system parameters and unknown false data-injection and replay cyber-attacks, the state estimates of all the local followers are evaluated by designing local adaptive observers. Second, a new technique is designed to compensate for the unmatched terms that result from the use of local adaptive observers. After that, distributed adaptive leader–follower security controllers are proposed based on the local estimated information in addition to the infected arrived information from the neighbors. Meanwhile, it is verified that the suggested security control method guarantees that all states of the followers under the considered cyber-attacks follow the given leader asymptotically. The efficacy of the developed adaptive leader–follower security controllers is verified via an illustrative example. • The adaptive leader-follower security control for CPMANSs is considered. • The challenges of considering two cascaded cyber-attacks are investigated. • The first is in the local networked agent; false-data injection and replay attacks. • The second is between the agents and their neighbors; false-data injection attacks. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive nonlinear observer for sensorless passivity based control applied to permanent magnet synchronous motor. The passivity based control approach is applied to a complex and coupled nonlinear mathematical model of permanent magnet synchronous motor without any approximation or cancellation of nonlinearities. A nonlinear adaptive observer is proposed to estimate the mechanical speed and the unmeasured load torque (unknown disturbance) that has an effect on the control performance; therefore, those estimated states are then used to improve the performance of the passivity based control for permanent magnet synchronous motor. The performance of the proposed controller-observer have been tested using MATLAB/SIMULINK, where those Simulation results show a perfect tracking of the mechanical speed and load torque. [ABSTRACT FROM AUTHOR]

This study investigates the challenge of designing a fault-tolerant control (FTC) for partially known nonlinear singular systems subjected to unmatched uncertainties in addition to actuator and sensor faults. The suggested technique is dependent on the neural network-based adaptive observer. The unknown system nonlinearities are approximated by making use of an adaptive neural network (NN) approximation technique. The parameters of the NN are unknown. A new methodology is proposed to transform the partially known singular system to a non-singular form with unknown uncertainties. Different from all previous work dealing with singular systems with partially known system parameters, an adaptive observer is proposed with the help of adaptive laws to obtain an estimation of the augmented states of the constructed descriptor system. Based on the estimated states, a new approach for dealing with unmatched disturbances and faults are proposed. Finally, an adaptive controller is designed to account for unmatched disturbances and faults. The asymptotic stability of the overall system is guaranteed via Lyapunov-stability functional. The designed method is applied efficiently to a satellite control system as a practical example in addition to another numerical example. • A new approach based on the ANN is proposed to deal with unknown singular system by transforming it to a nonsingular form with faults and uncertainties. • With sensors and actuators faults in addition to uncertainties, an adaptive observer with unknown system parameters based on adaptive laws is designed to estimate the system states. • A new adaptive controller is designed to account for matched and unmatched terms based on the estimated states. [ABSTRACT FROM AUTHOR]

In this paper, a new robust adaptive estimation approach is designed for the inverted pendulum. The estimation scheme is composed by an auxiliary high gain observer in cascade with an adaptive sliding mode observer. The auxiliary high gain observer is designed to estimate auxiliary outputs in order to solve the dissatisfaction of observer matching condition related to the presence of disturbances. Then, using the estimated auxiliary outputs, the adaptive sliding mode observer is synthesized to estimate conjointly the states, the unknown parameter (the pendulum mass which appears nonlinearly in the dynamics of the pendulum model) and the unknown disturbances. The stability analysis is established using the Lyapunov approach. Numerical simulations are carried out to validate theoretical results. Furthermore, experimental tests are realized using a real pendulum setup (a product of Feedback Instruments) to highlight the good performances of the proposed estimation method in practice. • Joint unknown mass and disturbances estimation is solved for the inverted pendulum. • An adaptive sliding mode observer is developed for the inverted pendulum. • The proofs of convergence are based on a Lyapunov analysis and sliding modes theory. • The experimental validation is realized using a Feedback Instruments pendulum test-bed. [ABSTRACT FROM AUTHOR]

• A nonlinear observer has been designed for the system in the general strict feedback form. • Using the back-stepping technique, an observer based controller has been designed. • In the controller design input saturation has been taken into account. • The designed controller is singularity free. • Asymptotical stability of the closed-loop has been established in the presence of observer dynamics and input saturation. In this work, design of an observer-based nonlinear controller for a class of single input-single output (SISO) systems in the general strict feedback form subject to input saturation based on the back-stepping technique has been addressed. A full order adaptive observer is constructed to estimate the unknown states and system parameters simultaneously. The proposed control scheme is singularity free and can handle the input nonlinearity. Asymptotical stability of the closed-loop system in the presence of observer dynamics and input saturation has been established by the Lyapunov stability theorem. The effectiveness of the proposed controller is illustrated by applying the proposed scheme to a bioreactor and a mechanical system via simulation study. [ABSTRACT FROM AUTHOR]

This paper proposes a gain design methodology for adaptive observers applied to the estimation of rotor speed of permanent magnet synchronous machines (PMSM). First, a disturbance observer is used for estimation of the back-electromotive force (back-EMF) and avoid undesired nonlinearities in the adaptive observer design. The rotor speed is estimated by a back-EMF adaptive observer based on the PMSM linear model in stationary frame. Both feedback and adaptive gains are analyzed considering the full system in state space form. A pole placement technique is used to design the adaptive and feedback gains, and the mathematical behavior of the speed estimator is obtained. The desired pole locations of the observer are discussed aiming the implementation of a sensorless control scheme. Simulation and experimental results are presented to validate the proposed gain design method. [ABSTRACT FROM AUTHOR]

Abstract In this paper, an adaptive disturbance estimation-based control of a class of uncertain feedback linearizable systems with the presence of, both, external perturbations as well as non-modeled dynamics is considered. The aim of the control design was to solve the tracking trajectory problem for a class of output-based linearizable uncertain systems. An adaptive scheme is proposed for developing a state estimator of the uncertain dynamics. The estimation of both, the states and the uncertain dynamics is attained despite the limited knowledge of the plant and the information contained in the output signal. The uncertain section in the linearized system was approximated by a class of time-dependent combination of the system states. The observer implemented a parametric identifier to obtain the time varying parameters associated to the estimation of the uncertain section. This method ensured the adequate estimation process of the uncertainties/perturbations, measured in terms of the mean square error. Simultaneously, an adaptive gain associated to the observer adjusts its trajectories to provide the ultimate boundedness of the estimation error. Once the states of the uncertain system are obtained, a feedback controller rejects actively the perturbations that affect the system by a compensation scheme. Two numerical examples were developed to show the observer-based control performance. Highlights • The controller is based on an adaptive observer in order to estimate uncertainties. • The adaptive estimator uses a classic system identification procedure (LMS). • The stability analysis was based on an innovative Lyapunov theory. • A state observer and a time varying identifier formed the adaptive approach. • The Lyapunov analysis leads to find that origin is the practical stable equilibrium point. [ABSTRACT FROM AUTHOR]

Abstract The work of this paper addresses the study and application of control strategies based on the passivity of a sensorless induction motor (IM) in order to guarantee a high performance operation and to increase reliability at a lower cost. This control approach based on the passivity or the energy formulation is generally simple and physically meaningful. It achieves the control objective by reshaping the system natural energy and then injecting a damping term. A full-order adaptive observer is also considered to estimate the IM rotor flux and mechanical speed. These estimated quantities are then used in the control scheme. The observer gain is synthesized in the way that it minimizes the instability zone in the regenerative mode to a line in the torque–speed plane. The control-observer set is tested on the trajectories of the various operating modes (motor mode, regenerating mode and low speed mode). Highlights • The control based on the passivity without a speed sensor dedicated to the Induction motor, was not mathematically motivated procedure but by considering physical properties such as energy conservation and passivity. • Our goal is to submit the system behavior to a desired dynamics; leaving the closed loop system nonlinear; without cancelling the dynamics or introducing the controller singularities. • An adaptive observer is proposed for estimate the rotor flux that is inaccessible to measurement and speed. • The stability is studied using necessary condition to determine the observer gain in the line torque/speed in regenerative mode. [ABSTRACT FROM AUTHOR]

Abstract This paper deals with the design of adaptive observer for a class of bilinear time delay systems. First, this problem is investigated in the full order case and it is then extended to the reduced order one. The proposed observers allow the joint estimation of the state and the unknown parameter vectors. A Lyapunov–Krasovskii approach is used to deduce the stability conditions, given in terms of the solvability of Linear Matrix Inequalities (LMIs) on the vertices of a convex polytope. A relevant example is provided to show the feasibility and the high performances of our results. [ABSTRACT FROM AUTHOR]

A global fast terminal sliding mode (GFTSM)-based model predictive torque control (MPTC) strategy is developed for permanent magnet synchronous motor (PMSM) drive system with only one phase current sensor. Generally two phase-current sensors are indispensable for MPTC. In response to only one phase current sensor available and the change of stator resistance, a novel adaptive observer for estimating the remaining two phase currents and time-varying stator resistance is proposed to perform MPTC. Moreover, in view of the variation of system parameters and external disturbance, a new GFTSM-based speed regulator is synthesized to enhance the drive system robustness. In this paper, the GFTSM, based on sliding mode theory, employs the fast terminal sliding mode in both the reaching stage and the sliding stage. The resultant GFTSM-based MPTC PMSM drive system with single phase current sensor has excellent dynamical performance which is very close to the GFTSM-based MPTC PMSM drive system with two-phase current sensors. On the other hand, compared with proportional-integral (PI)-based and sliding mode (SM)-based MPTC PMSM drive systems, it possesses better dynamical response and stronger robustness as well as smaller total harmonic distortion (THD) index of three-phase stator currents in the presence of variation of load torque. The simulation results validate the feasibility and effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper addresses an adaptive output-feedback tracking problem of arbitrarily switched pure-feedback nonlinear systems with time-varying output constraints and unknown control directions. In this work, the tracking problem of switched non-affine nonlinear systems with output constraints is transformed into the stabilization problem of switched unconstrained affine systems. The main contribution of this paper is to present a universal formula for constructing an adaptive state-observer-based tracking controller with only two adaptive parameters by using the common Lyapunov function method. These adaptive parameters in the proposed control scheme are derived using the function approximation technique and a priori knowledge of the signs of control gain functions is not required. The theoretical analysis is presented for the Lyapunov stability and the constraint satisfaction of the resulting closed-loop system in the presence of arbitrary switchings. [ABSTRACT FROM AUTHOR]

• A fault-tolerant control strategy is applied to an innovative heat-exchanger/reactor. • The active fault-tolerant control method is based on adaptive observers and backstepping technique. • Both dynamic faults and sensor faults are considered for the heat-exchanger/reactor. • A backstepping control law is designed for the hear-exchanger/reactor to maintain the output temperature. • Adaptive observers are designed to detect and diagnose the fault of the proposed system. In this paper, an active fault tolerant control system is proposed and applied to a new intensified heat exchanger/reactor system. This method consists of an adaptive observer-based fault detection, isolation, and identification scheme and a control law redesign method based on the backstepping approach. The objective of the application of the fault tolerant control system is to ensure the safety and productivity of this intensified heat exchanger/reactor even in the presence of a fault. Both parameter and sensor faults are considered. The effectiveness of the fault tolerant control method based on adaptive observers is validated by simulations on the heat exchanger/reactor system. [ABSTRACT FROM AUTHOR]

This paper presents a modified structure of the backstepping nonlinear control of the induction motor (IM) fitted with an adaptive backstepping speed observer. The control design is based on the backstepping technique complemented by the introduction of integral tracking errors action to improve its robustness. Unlike other research performed on backstepping control with integral action, the control law developed in this paper does not propose the increase of the number of system state so as not increase the complexity of differential equations resolution. The digital simulation and experimental results show the effectiveness of the proposed control compared to the conventional PI control. The results analysis shows the characteristic robustness of the adaptive control to disturbances of the load, the speed variation and low speed. [ABSTRACT FROM AUTHOR]

This paper presents the synthesis of an adaptive observer which is used for the improvement of the direct torque control of induction motor drives. The observer detects stator flux components in two-phase stationary reference frame, rotor speed and stator resistance by measure of the stator terminal voltages and currents. The observer is adapted using a simple algorithm which does not imply a high computational load. Stability analysis based on Lyapunov theory is performed in order to guarantee the closed loop stability. Simulation tests under load disturbance and stator resistance variation are provided to evaluate the consistency and performance of the proposed control technique in the low and high speeds. [ABSTRACT FROM AUTHOR]

Copyright of Universidad & Ciencia is the property of Universidad Juarez Autonoma de Tabasco and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: This paper studies the problem of fault estimation of neutral delay systems using adaptive observer. A novel fast adaptive fault estimation (FAFE) algorithm based on adaptive observer is first proposed to enhance the performance of fault estimation including rapidity and accuracy. Meanwhile, a delay-dependent criterion is established to reduce the conservatism of design procedures especially for small delay systems. Then, comprehensive analysis is presented to discuss the calculating steps using linear matrix inequality (LMI) technique. Finally, simulation results are presented to illustrate the efficiency of the proposed algorithm. [Copyright &y& Elsevier]

Abstract: The goal of this work is to provide a method for monitoring performance degradation in counter-flow double-pipe heat exchangers. The overall heat transfer coefficient is estimated by an adaptive observer and monitored in order to infer when the heat exchanger needs preventive or corrective maintenance. A simplified mathematical model is used to synthesize the adaptive observer and a more complex model is used for simulation. The reliability of the proposed method was demonstrated via numerical simulations and laboratory experiments with a bench-scale pilot plant. [Copyright &y& Elsevier]

In this paper, a switched adaptive observer for a class of switched uncertain nonlinear systems is designed by using an average dwell time (ADT) method. Due to that switching unknown parameters lead to different coordinates transformation for different subsystems, some new dwell-time conditions are provided by an improved ADT method. Also, the boundedness of all signals is ensured by a well defined persistent excitation condition under a class of switching signals with ADT. Finally, the effectiveness of the theoretical results in this paper is demonstrated through a simulation example. [ABSTRACT FROM AUTHOR]