Sliding Mode Control Structure Research Articles

Variable structure sliding mode control for a class of uncertain distributed parameter systems with time-varying delays

This article considers sliding mode control of a class of parabolic linear uncertain distributed parameter systems with time-varying delays. The sliding mode controller design does not contain time delay terms and drives the state trajectory of the system to the sliding manifold in finite time. A sufficient condition of asymptotic stability for the sliding motion is derived. A simulation example is presented to illustrate effectiveness of the proposed method.

Nonlinear Synergetic Optimal Controllers

Optimality properties of synergetic controllers are analyzed using the Euler-Lagrange conditions and the Hamilton-Jacobi-Bellman equation. First, a synergetic control strategy is compared with the variable structure sliding mode control. The connections of synergetic control design methodology and the methods of variable structure sliding mode control are established. In fact, the methods of sliding surface design for the sliding mode control are essential for designing invariant manifolds in the synergetic control approach. It is shown that the synergetic control strategy can be derived using tools from the calculus of variations. The synergetic control laws have a simple structure because they are derived from the associated first-order differential equation. It is also shown that the synergetic controller for a certain class of linear quadratic optimal control problems has the same structure as the one generated using the linear quadratic regulator approach by solving the associated Riccati equation. The synergetic optimal control and sliding mode control methodologies are applied to the nonlinear control of the wing-rock suppression problem. Two different wing-rock dynamic models are used to test the design of the synergetic and sliding mode controllers. The performance of the closed-loop systems driven by these controllers is analyzed and compared.

Robust Nonlinear Control of a Miniature Autonomous Helicopter using Sliding Mode Control Structure

This paper presents an investigation into the design of a flight control system, using a robust sliding mode control structure, designed using the exact feedback linearization procedure of the dynamic of a small-size autonomous helicopter in hover. The robustness of the controller in the context of stabilization and trajectory tracking with respect to small body forces and air resistance on the main and tail rotor, is analytically proved using Lyapunov approach. Some simulation results are presented to illustrate the performance and robustness of such controller in the presence of small body forces and air resistance. Keywords—Robust control, sliding mode, stability, Lyapunov approach.

Sliding Mode Implementation of an Attitude Command Flight Control System for a Helicopter in Hover

This paper presents an investigation into the design of a flight control system, using a decoupled non-linear sliding mode control structure, designed using a linearised, 9th order representation of the dynamics of a PUMA helicopter in hover. The controllers are then tested upon a higher order, non-linear helicopter model, called RASCAL. This design approach is used for attitude command flight control implementation and the control performance is assessed in the terms of handling qualities through the Aeronautical Design Standards for Rotorcraft (ADS-33). In this context a linearised approximation of the helicopter system is used to design an SMC control scheme. These controllers have been found to yield a system that satisfies the Level 1 handling qualities set out by ADS-33.

Observer-Based Model Reference Sliding-Mode Control of Active Suspension Systems

In this paper a model reference variable structure controller (VSC) for an active suspension system is designed. A half vehicle model is used in which, the vertical and pitch motions of the mass supported by the suspension and the vertical motion of the suspension masses are considered. Sliding mode controller is applied for the purpose of disturbance attenuation. Unit vector approach, which is a sliding mode control structure for multivariable systems, is used and a robust adaptive nonlinear controller is designed. A reduced-order observer is designed to use only output information. Robust eigenstructure assignment method is implemented in the line of sliding surface design. Simulation results verify the effectiveness of the proposed nonlinear controller scheme in comparison with the passive suspension system and also H∞ technique. The output of the closed-loop system can also smoothly track a set point in a manner that the vertical position of vehicle may be regulated toward the desired point.

On discrete-time variable structure sliding mode control

The purpose of this paper is to show the limitations of discrete-time variable structure sliding mode control and that the equivalent control must be used in order to have sliding in a neighborhood of the switching surface. Conflicting requirements for the sliding mode controller behavior in the continuous and discrete-time domains are revealed and analyzed. A linear control law for an uncertain discrete-time linear plant, with bounded uncertainties, is analyzed and its superiority over nonlinear controllers is demonstrated. The conclusion of the obtained results is that in the discrete-time variable structure sliding mode controller design, unlike in the continuous-time, the designer may have limited flexibility in selecting controller architectures.

A variable structure static phase shifting transformer for power system stabilization

Abstract A variable structure sliding mode control system for controlling a static phase shifter is developed. The static phase shifter aims at introducing voltage phase shift between the terminals of transmission line. The voltage phase shift is controlled by adding to the voltage of one end of transmission line a quadrature voltage component. The thyristor switches is used to regulate that quadrature component, whereupon, the phase shift is changed. A sample power system model used for digital simulation is linearzied to design the variable structure control algorithm. To validate the power and robustness of the proposed controller for enhancing power system stability, the studied power system is subjected to different disturbances such as tie line power, frequency or synchronous machine speed disturbances. The power system dynamic responses for the above disturbances prove the effectiveness and superiority of the variable structure control system in terms of fast damping response with less settling time.

Multirate Implementation of a Quasi-Sliding Mode Control

In this paper a discrete time sliding-mode type controller is proposed and it is implemented by using a multirate output sampling scheme. This strategy avoids the use of state observers, the uncertainty in the model parameters and disturbances being counteracted by the robustness of the sliding mode control structure. This controller does not involve switching, and it is applied to control stable and unstable systems. Also by simulations, the controller has shown to be robust against changes in the plant model parameters.

Comments on "A new controller design for a flexible one link manipulator"

In the original paper of W.T. Qian and C.C.H. Ma (ibid., vol. 37, p. 132-7, 1992), a variable structure sliding mode controller (VSSMC) design for the tip position control of a flexible one-link manipulator has been presented, where a switching line constructed from the tip position and its derivative was employed for the design. The claim was that if the slope of this line is chosen positive and the system variables are made to stay on this line, they will converge to zero exponentially, thus yielding a stable system in sliding mode (SM). The purpose of this comment is to show that the choice of a positive constant as the slope for this switching line will not guarantee the stability of the system in SM because, in view of the functional relationship of the tip position with the generalized coordinates of the system through the mode shape functions, what is presented as a switching line is in fact a switching hypersurface. Hence, the stability of the system in SM is guaranteed only if the motion on this hypersurface is asymptotically stable. A positive value for the slope of the switching line employed by Qian and Ma will not guarantee this stability because variations in the mode shape functions due to varying payload conditions or other disturbances at the tip will lead to a varying switching surface. These variations can be such that the resulting sliding motion becomes unstable. Also, the varying switching surface implies that the controller will fail to maintain sliding mode motion.

Fuzzy Sliding Mode Control Application to Large time Varying Systems

This paper presents an application of fuzzy control techniques for large time varying systems. This study is based on an analogy between fuzzy control and sliding mode control techniques. First, special attention will be payed to the analysis of sliding mode control properties, next a generalization of sliding mode control structure to large time varying systems is presented and finally this concept will be extended to fuzzy controllers. Some application results are shown in the last section.

A new controller design for a flexible one-link manipulator

A novel controller design for noncollocated flexible one-link manipulator arm tip position control based on variable structure sliding mode control is presented. Using the assumed-mode method, the plant model is derived. The discontinuous control law based on the variable structure system theory for the noncollocated manipulator tip position control is then designed. The position state variables are obtained directly from the inversion of the output submatrix multiplied by the sensor measurements. The velocity state variables are estimated through decoupled estimators-a separate first-order observer for each of the system's modes under consideration. Different sampling periods are used for the estimator and the controller. The performance of the controller is evaluated through a series of simulations, followed by an analysis of the designed control system. >