Output Feedback Sliding Mode Control Research Articles

Dynamic output feedback RBF neural network sliding mode control for robust tracking and model following

A dynamic output feedback radial basis function (RBF) neural network sliding mode control (SMC) scheme is proposed to realize the problem of robust tracking and model following for a class of uncertain time-delay systems. The algorithm is based on dynamic output feedback SMC, RBF neural network and adaptive control. The design of sliding surface and the existence of sliding mode have been addressed. The proposed robust tracking controller guarantees the stability of overall closed-loop system and achieves zero-tracking error in the presence of state delays, input delays, time-varying parameter uncertainties and external disturbances. Moreover, the knowledge of upper bound of uncertainties is not required, and chattering phenomenon is eliminated. Both theoretical analysis and illustrative examples demonstrate the validity of the proposed scheme.

Design of Adaptive Sliding Mode Controllers for Linear Systems via Output Feedback

This paper considers the problem of designing adaptive output feedback sliding mode controllers for a class of linear systems with matched external disturbances, where the norm bound of the external disturbance is unknown. First, we derive a new design approach of linear sliding surface in the singular system framework, and propose an adaptive output feedback sliding mode controller such that the motion of the closed-loop system is uniformly ultimately bounded stable. Second, to improve the transient performance, a memory-based adaptive output feedback sliding mode controller is also proposed. Finally, an illustrative example is utilized to demonstrate the design procedures proposed in this paper. It is shown that the memory-based adaptive output feedback sliding mode control approach provides a better transient performance.

Memoryless Static Output Feedback Sliding Mode Control for Nonlinear Systems With Delayed Disturbances

In this technical note, a local stabilization problem for nonlinear systems with disturbances which are dependent on time-varying delay phenomena, is studied. An appropriate transformation is introduced to express the system in regular form which facilitates both design and analysis. Then, sufficient conditions are developed based on a Lyapunov-Razumikhin approach such that the sliding motion is uniformly asymptotically or exponentially stable. A static output feedback control law, independent of the time delay, is synthesized to guarantee reachability of the sliding mode. The accessible bounds on the disturbances are fully used in the control design to reduce the conservatism. A simulation example shows the effectiveness of the approach.

DYNAMIC OUTPUT FEEDBACK SLIDING MODE CONTROLLER DESIGN FOR CHATTERING AVOIDANCE

For a class of linear MIMO uncertain systems, a dynamic output feedback sliding mode control algorithm that avoids the chattering problem and high gain control is proposed in this paper. Without using any differentiator, we develop a modified asymptotically stable second order sliding mode control law in which the developed controller can guarantee the finite time convergence to the sliding mode and the system states asymptotically approach to zero. Finally, a numerical example is explained for demonstrating the applicability of the proposed scheme.

Sliding mode output feedback control based on tracking error observer with disturbance estimator

For a class of systems who suffers from disturbances, an original output feedback sliding mode control method is presented based on a novel tracking error observer with disturbance estimator. The mathematical models of the systems are not required to be with high accuracy, and the disturbances can be vanishing or nonvanishing, while the bounds of disturbances are unknown. By constructing a differential sliding surface and employing reaching law approach, a sliding mode controller is obtained. On the basis of an extended disturbance estimator, a creative tracking error observer is produced. By using the observation of tracking error and the estimation of disturbance, the sliding mode controller is implementable. It is proved that the disturbance estimation error and tracking observation error are bounded, the sliding surface is reachable and the closed-loop system is robustly stable. The simulations on a servomotor positioning system and a five-degree-of-freedom active magnetic bearings system verify the effect of the proposed method.

Output feedback sliding mode control for a linear multi-compartment lung mechanics system

In this paper, we develop a sliding mode control architecture to control lung volume and minute ventilation in the presence of modelling system uncertainties. Since the applied input pressure to the lungs is, in general, nonnegative and cannot be arbitrarily large, as not to damage the lungs, a sliding mode control with bounded nonnegative control inputs is proposed. The controller only uses output information (i.e., the total volume of the lungs) and automatically adjusts the applied input pressure so that the system is able to track a given reference signal in the presence of parameter uncertainty (i.e., modelling uncertainty of the lung resistances and lung compliances) and system disturbances. Controllers for both matched and unmatched uncertainties are presented. Specifically, a Lyapunov-based approach is presented for the stability analysis of the system and the proposed control framework is applied to a two-compartment lung model to show the efficacy of the proposed control method.

A Singular System Approach to Output Feedback Sliding Mode Control for Time-delay Systems

摘要: 利用一种奇异系统方法讨论了时滞系统的输出反馈滑模控制问题. 时滞系统的非线性项满足范数有界约束.首先,将滑动模态与线性切换面作为一个奇异时滞系统,基于奇异时滞系统的稳定性理论, 给出滑动模态稳定及切换面存在的线性矩阵不等式(Linear matrix inequality, LMI)充分条件.然后,给出使得系统闭环渐近稳定的静态输出反馈滑模控制器的设计方法,此控制器保证闭环 系统有限时间到达切换面.最后,用数值算例验证本文方法的有效性和正确性. 关键词: 时滞系统 / 滑模控制 / 奇异系统方法 / 静态输出反馈 / 线性矩阵不等式

Dynamic Sliding Mode Control Design Based on an Integral Manifold for Nonlinear Uncertain Systems

An output feedback sliding mode control law design relying on an integral manifold is proposed in this work. The considered class of nonlinear systems is assumed to be affected by both matched and unmatched uncertainties. The use of the integral sliding manifold allows one to subdivide the control design procedure into two steps. First a linear control component is designed by pole placement and then a discontinuous control component is added so as to cope with the uncertainty presence. In conventional sliding mode the control variable suffers from high frequency oscillations due to the discontinuous control component. However, in the present proposal, the designed control law is applied to the actual system after passing through a chain of integrators. As a consequence, the control input actually fed into the system is continuous, which is a positive feature in terms of chattering attenuation. By applying the proposed controller, the system output is regulated to zero even in the presence of the uncertainties. In the paper, the proposed control law is theoretically analyzed and its performances are demonstrated in simulation.

Global Output Feedback Sliding Mode Control of Nonlinear Systems with Multiple Time Delays

This paper proposes a sliding-mode control scheme for a class of nonlinear systems with multiple time delays, in the state variables and in the output signal. The unmeasured state of the system is estimated by an asymptotic observer for the zero dynamics and high-gain observers connected in cascade for a chain of integrators with a nonlinear input disturbance which compose the complete state. The proposed control strategy guarantees global asymptotic stability of the closed-loop system using only output feedback. The use of observers prevents undesirable chattering phenomena. Simulation results illustrate the effectiveness of this scheme.

Robust dynamic output feedback second-order sliding mode controller for uncertain systems

This paper addresses the problem of designing a dynamic output feedback sliding mode control algorithm to stabilize a linear MIMO uncertain system having relative degree two. Introducing a suitable dynamic compensator into the sliding variable, the additional degree of freedom can be used to robustly guarantee the closed-loop system stability once the system is in the sliding mode. A modified asymptotically stable second-order sliding mode control is analyzed and the proposed controller can obtain the real second-order sliding mode. Finally, the feasibility of the proposed method is illustrated by a numerical example.

Second order sliding mode output feedback control with switching gains—Application to the control of a pneumatic actuator

This paper proposes a switching gains output feedback controller, which is a sample-based second order sliding mode one. First, constructive convergence conditions are established for the controller, in the unperturbed and perturbed cases. Then, a gain adjustment mechanism of the gain, based on the aforementioned convergence conditions, allows us to reduce gain magnitude, and then to reduce the chattering effect. This new algorithm is experimentally applied for the position control of an electropneumatic actuator.

Output‐feedback sliding‐mode control of multivariable systems with uncertain time‐varying state delays and unmatched non‐linearities

An output-feedback sliding-mode controller is proposed for multivariable uncertain systems with unknown time-varying state delays and unmatched non-linear terms. The non-linearities are allowed to depend not only on the system output, but also on its unmeasurable state, and can be polynomial. This scheme is based on model-reference unit vector control under a mild Hurwitz condition for the high-frequency gain matrix. To achieve global stability properties, the amplitude of the control signal is given by a norm observer for the unmeasured state. For the first time, the design of norm observers is applied to a class of time-delay systems. This approach guarantees finite-time convergence of the output-tracking error to zero. Simulation results illustrate the application of the developed control scheme.

Fractional‐Order Dynamic Output Feedback Sliding Mode Control Design for Robust Stabilization of Uncertain Fractional‐Order Nonlinear Systems

AbstractA robust fractional‐order dynamic output feedback sliding mode control (DOF‐SMC) technique is introduced in this paper for uncertain fractional‐order nonlinear systems. The control law consists of two parts: a linear part and a nonlinear part. The former is generated by the fractional‐order dynamics of the controller and the latter is related to the switching control component. The proposed DOF‐SMC ensures the asymptotical stability of the fractional‐order closed‐loop system whilst it is guaranteed that the system states hit the switching manifold in finite time. Finally, numerical simulation results are presented to illustrate the effectiveness of the proposed method.

Output feedback sliding mode control under networked environment

This article considers the problem of sliding mode output feedback control for networked control systems (NCSs). The key idea is to make use of not only the current and previous measurements, but also previous inputs for the reconstruction of the state variables. Using this idea, sliding mode controllers are designed for systems with constant or time-varying network delay. The approach is not only more practical but also easy to implement. To illustrate this, the design technique is applied to an inverted pendulum system.

Global exact tracking for uncertain MIMO linear systems by output feedback sliding mode control

This paper presents a solution to the problem of global exact output tracking for uncertain MIMO (multiple-input–multiple-output) linear plants with non-uniform arbitrary relative degree using output feedback sliding mode control. The key idea to overcome the relative degree obstacle is to generalize our previous hybrid estimation scheme to a multivariable version by combining, through switching, a standard linear lead filter with a non-linear one based on robust exact differentiators, achieving uniform global exponential practical stability and exact tracking.

Output Feedback Sliding Mode Control for a Stewart Platform With a Nonlinear Observer-Based Forward Kinematics Solution

In this paper, an observer-based forward kinematics solution of a 6-6 Stewart platform is proposed and this algorithm is applied to implement an output feedback sliding mode control. The conventional forward kinematics solutions take too much computational load or are too complex to be carried out in the online control scheme. The proposed nonlinear observer-based algorithm provides a simple method to obtain a real-time forward kinematics solution. With this solution, 6-degrees-of-freedom posture control of the moving platform can be achieved without installation of any external sensor after applying an output feedback control. In contrast with the conventional control scheme which aims to control individual leg length in actuator domain, the output feedback controller is proposed here to control the posture in Cartesian domain directly. The stability of the whole system is thoroughly proved to ensure convergence of the control errors. Simulations and experimental results are presented to validate the feasibility of the hereby proposed results.

Robust synchronization of chaotic systems using adaptive sliding mode output feedback control

This paper presents an adaptive sliding mode output feedback control method for a class of master–slave chaotic synchronization systems using only output variables. Using a simple adaptation law, a modified sliding mode controller is derived to guarantee the existence of the sliding mode. The proposed scheme not only ensures global synchronization between the master and slave systems, but also can be implemented without requiring a priori knowledge of uncertainties and external disturbances. Moreover, the structure of the slave system is simple and need not be identical to that of the master system. An illustrative example of a six-order coupled Chua hyper-chaotic circuit is given to demonstrate the effectiveness of the proposed synchronization scheme.

Applying output feedback integral sliding mode controller to uncertain time-delay systems with mismatched disturbances

For time-delay systems with mismatched disturbances and uncertainties, this paper develops an integral sliding mode control algorithm using output information only to stabilize the systems. An integral sliding surface is comprised of output signals and an auxiliary full-order compensator. The proposed output feedback sliding mode controller can satisfy the reaching and sliding condition and maintain the system on the sliding surface from the initial moment. When two specific algebraic Ricca- ti inequalities have solutions, our method can guarantee the stability of the closed-loop system and sa- tisfy the property of robust disturbance attenuation. Moreover, the design parameters of controller and compensator can be simultaneously determined by solutions to the algebraic Riccati inequalities. Final- ly, two numerical examples illustrate the applicability of the proposed scheme.

Mixed H2/H∞ robust output feedback sliding mode control

SUMMARYThis paper presents an output feedback sliding mode control scheme for uncertain dynamical systems. The design problem is solved in two steps, involving first a state feedback and then an output feedback problem. First, using the null space dynamics, the sliding surface for the unmatched uncertainty is designed. Then, by tuning the sliding surface, a robust controller is constructed for the whole uncertainty; this problem takes the form of static‐output feedback. Based on this, a dynamic output feedback controller for the system augmented with the sliding surface is designed. The synthesis involves the solution of an Linear Matrix Inequality (LMI) and Bilinear Matrix Inequality (BMI) problem; the BMI problem is solved iteratively. The proposed approach is illustrated by applying it to a well‐known robust benchmark problem and also experimentally on a spring mass system with variable stiffness. Simulation and experimental results show that the proposed method outperforms previous approaches in terms of robust performance. Copyright © 2011 John Wiley & Sons, Ltd.

Output feedback integral sliding mode controller of time‐delay systems with mismatch disturbances

AbstractFor uncertain time‐delay systems with mismatch disturbances, this paper presented an integral sliding mode control algorithm using output information only. An integral sliding surface is comprised of output signals and an auxiliary full‐order compensator. The designed output feedback sliding mode controller can locally satisfy the reaching and sliding condition and maintain the system on the sliding surface from the initial moment. Since the system is in the sliding mode and two specific algebraic Riccati inequalities are established, the proposed algorithm can guarantee the stability of the closed‐loop system and satisfy the property of disturbance attenuation. Moreover, the design parameters of the controller and compensator can be simultaneously determined by solutions to two algebraic Riccati inequalities. Finally, a numerical example illustrates the applicability of the proposed scheme.Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society