Mismatched Parameter Uncertainties Research Articles

Distributed fuzzy fault-tolerant consensus of leader-follower multi-agent systems with mismatched uncertainties

In this paper, the distributed fuzzy fault-tolerant tracking consensus problem of leader-follower multi-agent systems (MASs) is studied. The objective system includes actuator faults, mismatched parameter uncertainties, nonlinear functions, and exogenous disturbances under switching communication topologies. To solve this problem, a distributed fuzzy fault-tolerant controller is proposed for each follower by adaptive mechanisms to track the state of the leader. Furthermore, the fuzzy logic system is utilized to approximate the unknown nonlinear dynamics. An error estimator is introduced between the mismatched parameter matrix and the input matrix. Then, a selective adaptive law with relative state information is adopted and applied. When calculating the Lyapunov function's derivative, the coupling terms related to consensus error and mismatched parameter uncertainties can be eliminated. Finally, a numerical simulation is given to validate the effectiveness of the proposed protocol.

New Second-Order Sliding Mode Control Design for Load Frequency Control of a Power System

The implementation of the sliding mode control (SMC) for load frequency control of power networks becomes difficult due to the chattering phenomenon of high-frequency switching. This chattering problem in SMC is extremely dangerous for actuators used in power systems. In this paper, a continuous control strategy by combining a second-order mode and integral siding surface is proposed as a possible solution to this problem. The proposed second-order integral sliding mode control (SOISMC) law not only rejects chattering phenomenon in control input, but also guarantees the robustness of the multi-area power network, which has an effect on parametric uncertainties such as the load variations and the matched or mismatched parameter uncertainties. Moreover, the reporting of the simulation indicates that the proposed controller upholds the quality requirement by controlling with operating conditions in the larger range, rejects disturbance, reduces the transient response of frequency, eliminates the overshoot problem, and can better address load uncertainties compared to several previous control methods. The simulation results also show that the proposed SOISMC can be used for practical multi-area power network to lessen high parameter uncertainties and load disturbances.

Adaptive Fault-Tolerant Compensation Control for T–S Fuzzy Systems With Mismatched Parameter Uncertainties

This paper is concerned with the adaptive fault-tolerant compensation control problem for a class of Takagi–Sugeno (T–S) fuzzy systems with mismatched parameter uncertainties and actuator faults. A matrix transformation technique is introduced to relax the restriction regarding the input matrices of T–S fuzzy systems considered in the existing results. Moreover, by combining backstepping-like technique and adaptive control method, a new adaptive fault-tolerant control scheme with compensation mechanism is proposed to achieve the desirable control performance. In addition, it is proved that the states of the resulting closed-loop fuzzy system converge to zero asymptotically even in the presence of actuator faults and mismatched parameter uncertainties. Finally, two simulation examples are given to verify the effectiveness of the presented control scheme.

An Improved Sliding Mode Control Technique to Mitigate Mismatched Parameter Uncertainties of Three-Phase Voltage Source Inverters

This paper proposes a theoretical and experimental implementation of an advanced sliding mode control (SMC) for a three-phase voltage source inverter (VSI) to achieve robustness against the unknown uncertainties of an LC filter. The significant contributions of the proposed SMC are summarized as considerations for the matched and mismatched uncertainties of the LC filter, more relaxed norm-bounds, dynamic characterization of sliding surface, and unique stability analysis. Unlike the conventional SMC techniques with matched uncertainties, the mismatched uncertainties in the state matrix are taken for the design of the proposed SMC. Also, the relaxed norm-bound designed for matched and mismatched uncertainties allows a wide range of variations in the values of LC filter. The voltage tracking errors are significantly reduced and the total harmonic distortions (THDs) are highly suppressed by characterizing the sliding surface in terms of flexible linear matrix inequalities (LMIs). Next, the stability analysis and reachability conditions are given using the Lyapunov criterion. The authenticity of the proposed SMC method is proved by TMS320LF28335 DSP based experimental results with a prototype 1-kVA test-bed. The comparative experimental results and analysis for the proposed SMC scheme, the conventional SMC scheme, and the conventional PI-PI control scheme are presented under the load step change, unbalanced load, and non-linear load step change with the parameter uncertainties to demonstrate the excellent performance of the proposed controller such as fast transient response, small steady-state error, and low THD.

Adaptive Backstepping Controller of PMLSM

In this paper, a nonlinear adaptive speed controller for permanent magnet linear synchronous motors based on a newly developed adaptive recursive Backstepping control approach for a permanent magnet synchronous motor drive is discussed and analyzed. The Backstepping technique provides a systematic method to address this type of problem. It combines the notion of Lyapunov function and a controller procedure recursively. The adaptive Backstepping control approach is utilized to obtain the robustness for mismatched parameter uncertainties. The overall stability of the system is shown using Lyapunov stability theorem. The simulation results clearly show that the proposed scheme can track the speed reference.

New observer-based control design for mismatched uncertain systems with time-delay

Abstract In this paper, the state estimation problem for a class of mismatched uncertain time-delay systems is addressed. The estimation uses observer-based control techniques. The mismatched uncertain time-delay systems investigated in this study include mismatched parameter uncertainties in the state matrix and in the delayed state matrix. First, based on a new lemma with appropriately choosing Lyapunov functional, new results for stabilization of mismatched uncertain time-delay systems are provided on the basis of a linear matrix inequality (LMI) framework and the asymptotic convergence properties for the estimation error is ensured. Second, the control and observer gains are given from single LMI feasible solution which can overcome the drawback of the bilinear matrix inequalities approach often reported in the literature. Finally, a numerical example is used to demonstrate the efficacy of the proposed method.

Sliding mode control design for mismatched uncertain systems using output feedback

This paper develops an output feedback sliding mode control law for linear MIMO systems having mismatched parameter uncertainties along with disturbances and matched perturbations. Both quadratic stabilization and static output feedback control techniques are introduced into the sliding mode controller. The proposed output-dependent sliding surface can guarantee robust stability of the closed-loop system and achieve disturbance attenuation when the system is in the sliding mode. The existence condition of the sliding surface is determined by solving the coupled algebraic Riccati equations which involve the original system parameters. The developed output feedback control law can guarantee that the system globally reaches and is finally maintained on the sliding surface in finite time.

Distributed adaptive fault‐tolerant consensus tracking of multi‐agent systems against time‐varying actuator faults

This study considers the distributed fault-tolerant consensus problem for uncertain multi-agent systems using adaptive protocol. A more general time-varying actuator fault model is given, which includes loss of effectiveness, stuck, bias and outage fault. A new distributed adaptive control scheme is developed to compensate the effect of fault, multiple delayed state perturbations, mismatched parameter uncertainties and external disturbances on leader-follower multiagent systems. Based on the local state information of neighbouring agents, the adaptive updating protocol gains are adjusted online, which remove the assumption that the upper bounds of unknown uncertainty, delayed state perturbation and external disturbances should be known. Moreover, the consensus errors of leader-follower systems can asymptotically converge to zero. Finally, a simulation example is given to show the effectiveness of the theoretical analysis. c The Institution of Engineering and Technology 2016.

Novel Adaptive Sliding Mode Control with Nonlinear Disturbance Observer for SMT Assembly Machine

This paper presents a novel adaptive sliding mode control based on nonlinear sliding surface with disturbance observer (ANSMC-DOB) for precision trajectory tracking control of a surface mount technology (SMT) assembly machine. A two-degree-of-freedom model with time-varying parameter uncertainties and disturbances is built to describe the first axial mode of the pick-place actuation axis of the machine. According to the principle of variable damping ratio coefficient which makes the system have a nonovershoot transient response and a short settling time in the second-order system, the nonlinear sliding surface is designed for the sliding mode control (SMC). Since the upper bound value of the disturbances is unknown, the adaptive gain estimation is applied to replace the switching gain in the SMC. In order to settle the problem of SMC unrobust to the mismatched parameter uncertainties and disturbances, the nonlinear disturbance observer is introduced to estimate the mismatched disturbances and form the novel controller of ANSMC-DOB. The stability of sliding surfaces and control laws are verified by the Lyapunov functions. The simulation research and comparative experiments are conducted to verify the improvement of positioning accuracy and robustness by the proposed ANSMC-DOB in the SMT assembly machine.

Adaptive fault-tolerant control of a class of nonaffine nonlinear systems with mismatched parameter uncertainties and disturbances

This paper studies the problem of robust adaptive fuzzy fault-tolerant tracking control for a class of nonaffine nonlinear systems with mismatched parameter uncertainties, external disturbances and actuator faults. Without using complicated backstepping technique, a direct adaptive fuzzy tracking control approach is used to achieve the fault-tolerant control objective. First, to overcome the obstacle for the nonaffine nonlinear term with actuator faults, a nonaffine compensation term is constructed to eliminate the effect of the nonaffine fault parameters. Then, based on the implicit function theorem and the mean value theorem, a novel design scheme that converts the nonaffine system into the corresponding affine system is developed, and two effective fuzzy logic systems, which are introduced to approximate the appropriate nonlinear functions, are constructed to compensate the effect on mismatched parameter uncertainty and disturbance, respectively. Furthermore, with the help of Lyapunov stability analysis, it is also proved that all the closed-loop system error signals are uniformly ultimately bounded. Finally, a numerical example is given to verify the efficiency of the presented adaptive fuzzy fault-tolerant tracking design approach.

Cooperative adaptive fault‐tolerant tracking control for a class of multi‐agent systems with actuator failures and mismatched parameter uncertainties

This study addresses the cooperative fault-tolerant tracking control problem for a class of multi-agent systems subject to mismatched parameter uncertainties, external disturbances and actuator faults including loss of effectiveness, outage and stuck. The communication network is undirected connected graph with a fixed topology. It is assumed that the actuator efficiency factors, the upper bounds of the unparametrisable time-varying stuck faults and disturbance, are unknown. Different from the traditional centralised fault-tolerant tracking control problem, only part of the follower nodes can obtain the information of leader directly. On the basis of the local state information of neighbouring agents, a novel cooperative fault-tolerant tracking control scheme by using adaptive mechanism is proposed. By introducing the estimates of controller parameters driven by neighbourhood tracking errors, it is shown that not only the actuator faults in the follower nodes can be compensated, but also the global tracking objective can be achieved. Furthermore, it is proved that all closed-loop signals are bounded and all follower nodes asymptotically tracking to the leader can be achieved in the presence of actuator faults, external disturbances and mismatched parameter uncertainties. Finally, a numerical example is given to show the effectiveness of the proposed control scheme.

Output feedback high-gain proportional integral control for minimum phase uncertain systems

This study examines the problem of designing a high-gain proportional integral controller for minimum-phase linear systems with mismatched parameter uncertainties and matched perturbations. The proposed method can efficiently eliminate the matched disturbance when the control gain is high enough and uses the static output feedback control technique to stabilize the closed-loop system. By using the singular perturbation theory, the system states are finally constrained in a bounded region. Simulation results show the effectiveness of the proposed method.

FPGA-Based Implementation Nonlinear Backstepping Control of a PMSM Drive

In this paper, we present a new contribution of FPGAs (Field-Programmable Gate Array) for control of electrical machines. The adaptative Backstepping control approach for a permanent magnet synchronous motor drive is discussed and analyzed. We present a Matlab&Simulink simulation and experimental results from a benchmark based on FPGA. The Backstepping technique provides a systematic method to address this type of problem. It combines the notion of Lyapunov function and a controller procedure recursively. First, the adaptative and no adaptative Backstepping control approach is utilized to obtain the robustness for mismatched parameter uncertainties. The overall stability of the system is shown using Lyapunov technique. The simulation results clearly show that the proposed scheme can track the speed reference. Secondly, some experimental results are demonstrated to validate the proposed controllers. The experimental results carried from a prototyping platform are given to illustrate the efficiency and the benefits of the proposed approach and the various stages of implementation of this structure in FPGA. DOI: http://dx.doi.org/10.11591/ijpeds.v4i1.4645

Robust adaptive fault‐tolerant tracking control of multiple time‐delays systems with mismatched parameter uncertainties and actuator failures

SummaryThis study deals with the problem of robust adaptive fault‐tolerant tracking for uncertain systems with multiple delayed state perturbations, mismatched parameter uncertainties, external disturbances, and actuator faults including loss of effectiveness, outage, and stuck. It is assumed that the upper bounds of the delayed state perturbations, the external disturbances and the unparameterizable time‐varying stuck faults are unknown. Then, by estimating online such unknown bounds and on the basis of the updated values of these unknown bounds from the adaptive mechanism, a class of memoryless state feedback fault‐tolerant controller with switching signal function is constructed for robust tracking of dynamical signals. Furthermore, by making use of the proposed adaptive robust tracking controller, the tracking error can be guaranteed to be asymptotically zero in spite of multiple delayed state perturbations, mismatched parameter uncertainties, external disturbances, and actuator faults. In addition, it is also proved that the solutions with tracking error of resulting adaptive closed‐loop system are uniformly bounded. Finally, a simulation example for B747‐100/200 aircraft system is provided to illustrate the efficiency of the proposed fault‐tolerant design approach. Copyright © 2014 John Wiley & Sons, Ltd.

Robust adaptive fault‐tolerant control for linear systems with actuator failures and mismatched parameter uncertainties

In this study, a direct adaptive control scheme is developed to solve the robust fault-tolerant control problem for linear systems with mismatched parameter uncertainties, disturbances and actuator faults including loss of effectiveness, outage and stuck. Although the unparameterisable time-varying stuck faults and the upper bounds of disturbances are unknown, the adaptive laws are proposed to estimate the unknown controller parameters online. Then, by using the information from the adaptive mechanism, a class of robust adaptive state feedback controllers are constructed for automatically compensating the actuator faults, external disturbances and mismatched parameter uncertainties. Moreover, on the basis of Lyapunov stability theory, it is proved that the resulting adaptive closed-loop system can be guaranteed to be asymptotically stable in the presence of actuator faults, disturbances and mismatched parameter uncertainties. Finally, simulation results are presented to illustrate the efficiency of the proposed fault-tolerant design approach.

Robust sliding control for mismatched uncertain fuzzy time-delay systems using linear matrix inequality approach

In this article, we propose a robust sliding control design method for uncertain time-delay systems that can be represented by Takagi–Sugeno fuzzy models. The uncertain fuzzy time-delay systems under consideration have mismatched parameter uncertainties in the state matrix and external disturbances. We derive existence conditions of linear sliding surfaces guaranteeing the asymptotic stability in terms of constrained linear matrix inequalities (LMIs). We present an LMI characterization of such sliding surfaces. Also, an LMI-based algorithm is given to design the switching feedback control term so that a stable sliding motion is induced in finite time. Finally, we give two numerical design examples to show the effectiveness of the proposed method.

Disturbance Observer Based Dynamic Output Feedback Controller Design for Linear Uncertain Systems

AbstractFor linear multiple input multiple output (MIMO) systems with mismatched parameter uncertainties and matched nonlinear perturbations, a compensator‐based controller based on the disturbance estimation algorithm is considered in this paper. We design a reduced‐order high‐gain observer to estimate the effect of matched perturbation, and introduce the estimation information into the controller design. Using singular perturbation theory, the proposed control law can guarantee robust stability of the closed‐loop system. Moreover, the peaking phenomenon in the control input during the transient time can be effectively avoided using our method. Finally, the feasibility of the proposed method is illustrated by a numerical example.

LMI‐based robust sliding control for mismatched uncertain nonlinear systems using fuzzy models

SUMMARYWe propose a robust sliding control design method for uncertain Takagi–Sugeno fuzzy models. The uncertain fuzzy systems under consideration have mismatched parameter uncertainties in the state matrix and external disturbances. We make the first attempt to relax the restrictive assumption that each nominal local system model shares the same input channel, which is required in the traditional VSS‐based fuzzy control design methods. We derive the existence conditions of linear sliding surfaces guaranteeing the asymptotic stability in terms of constrained LMIs. We present an LMI characterization of such sliding surfaces. Also, an LMI‐based algorithm is given to design the switching feedback control term so that a stable sliding motion is induced in finite time. Finally, we give two simulation results to show the effectiveness of the proposed method. Copyright © 2011 John Wiley & Sons, Ltd.

Dynamic output feedback integral sliding mode control design for uncertain systems

SUMMARYThis paper addresses the problem of designing a dynamic output feedback sliding mode control algorithm for linear MIMO systems with mismatched parameter uncertainties along with disturbances and matched nonlinear perturbations. Once the system is in the sliding mode, the proposed output‐dependent integral sliding surface can robustly stabilize the closed‐loop system and obtain the desired system performance. Two types of mismatched disturbances are considered and their effects on the sliding mode are explored. By introducing an additional dynamics into the controller design, the developed control law can guarantee that the system globally reaches and is maintained on the sliding surface in finite time. Finally, the feasibility of the proposed method is illustrated by numerical examples. Copyright © 2011 John Wiley & Sons, Ltd.

폴리토픽 모델을 갖는 시스템을 위한 적분 슬라이딩 모드 제어기의 LMI 기반 설계

This paper presents an LMI-based method to design an integral sliding mode controller for an uncertain system with a polytopic model. The uncertain system under consideration may have mismatched parameter uncertainties in the state matrix as well as in the input matrix. Using LMIs we derive an existence condition of a sliding surface. And we give a switching feedback control law.