Wei-Bing Gao

VSC coordinated control of two manipulator arms in the presence of environmental constraints

A variable structure control (VSC) method is developed for motion, internal force, and constrained force control of two manipulators grasping a common constrained object. Based on a transformed dynamic equation of the entire system in the joint space, a motion and force control are designed together via a VSC method with robustness to parametric uncertainties and external disturbances. The proposed controller guarantees the system with prescribed qualities in the sliding mode and during the reaching transient. Simulation results illustrate the method. >

Variable structure control of time-delay systems with a simulation study on stabilizing combustion in liquid propellant rocket motors

Abstract The dynamical model of combustion in liquid propellant rocket motors is an unstable time-delay system. When it is stabilized by a linear state feedback controller, the robustness of the closed-loop system is not satisfactory. In this paper a variable structure control approach to stabilize the combustion is presented. First, the concept of switching functional is introduced, and hence a systematic design method is established for the variable structure control of general time-delay systems. Secondly, the proposed theory is applied to the stabilization of combustion in liquid monopropellant rocket motors. Simulation results show that the robustness of the closed-loop system against variations in time lag δ and pressure exponent y is considerably improved. Specifically, the controller designed according to the nominal value δ = 1.0 can still stabilize the system with δ = 0, i.e. the system without time delay. This conclusion provides a powerful basis for the reliable design of rocket motor control systems.

Variable structure control of stochastic systems

Abstract In this paper, the problem of variable structure control of stochastic (SVSC) systems is proposed and the corresponding variable structure control strategies with complete and incomplete state information are established. The concepts of stochastic sliding mode and sliding motion band are introduced which may be regarded as the basic characteristics of SVSC systems. Robustness of SVSC systems is considered and a general design procedure for SVSC systems is presented. The effectiveness of the proposed control method is shown by simulation results.

Feedback stabilization of linear systems with distributed delays in state and control variables

Solving a generalized characteristic matrix equation (GCME) of a linear retarded system is the crux for stabilizing the system using a reduction technique. This note gives the solution of GCME under the general condition that the eigenvalues occur in the spectrum of the system with algebraic and geometric multiplicities being greater than or equal to one. The main idea is to transform the GCME into a group of linear algebraic equations. A sufficient condition for the existence of the solution to the linear algebraic equations is established. A key lemma for stabilizing the systems under the above general condition is also proved. >

Robust strict positive real stabilization criteria for SISO uncertain systems

Abstract This paper is devoted to the study of robust strict positive real stabilization criteria for SISO uncertain systems, i.e., considering the problem of when a single controller not only robustly stabilizes a plant with uncertainty under unity-feedback but also enables the closed-loop system to be robustly strictly positive real. The uncertain system models with both parameter variation and unstructured perturbation are considered and some necessary and sufficient conditions for the problem are derived.

Variable structure control of discrete-time stochastic systems

The problem of variable structure control of stochastic systems is proposed and the corresponding variable structure control strategies with complete and incomplete state information are established. The concepts of stochastic sliding mode and sliding motion band are introduced, which may be regarded as the basic characteristics of stochastic variable structure control (SVSC) systems. Robustness of (SVSC) systems is considered and a general design procedure of SVSC systems is presented. A comparison between SVSC and linear quadratic Gaussian (LQG) systems is given.<<ETX>>

Dynamics and control of robotic systems for assembly sets

Controlling an assembly set with a robotic system is discussed. The assembly set is formulated with a tree structure. Assembly tasks are treated as a tracking problem where the desired motion of the assembly set is described by the motion of one main body and the relative motions of other bodies with respect to the main body and others in series. Motion coordination and internal force regulation are solved simultaneously. Simulation results show that the suggested method is simple and plausible.<<ETX>>

Robust strict positive realness design of interval systems

The paper is devoted to the study of robust strict positive realness design of interval systems, i.e. considering the question of designing a single controller which both robustly stabilizes an interval denominator system by unity feedback and makes the closed-loop transfer function robustly strictly positive real. By establishing a new computationally checkable criterion for the strict positive realness of a rational function, the extreme point result for a class of interval denominator systems is obtained, which significantly simplies the controller design procedure.

Predictive supervisory control of real time discrete event systems

In this paper a predictive supervisor is proposed to deal with the supervisory control problem of discrete event systems subject to communication delays. Existence conditions of such supervisors are established. Related computational problems are discussed.<<ETX>>

Robust strict positive real stabilization and asymptotic hyperstability robustness

Abstract This paper is devoted to the study of robust strict positive real stabilization of SISO uncertain systems, i.e. finding a single controller that not only robustly stabilizes a plant with uncertainties under unity-feedback but also makes the closed-loop system robustly strictly positive real. It is proved that there must exist a stable controller achieving robust strict positive real stabilization of uncertain systems with both parameter variations and unstructured uncertainties under some reasonable assumptions. The propemess of the controller is guaranteed when the largest relative degree of an uncertain system is retricted. By applying these results to nonlinear systems, some significant conclusions on asymptotic hyperstability robustness are given.