MOVING SWITCHING SURFACES FOR ROBUST-CONTROL OF 2ND-ORDER VARIABLE-STRUCTURE SYSTEMS

Most of the switching surfaces proposed so far for a variable structur e control system (VSCS) have been determined independently of initial conditions. The VSCS with these typical switching surfaces may be sens itive to parameter variations and extraneous disturbances during the r eaching phase. To overcome this drawback, we propose a new switching s urface which is initially designed to pass arbitrary initial condition s, and subsequently move towards a predetermined switching surface by rotating or/and shifting. We call it a moving switching surface (MSS). Using the MSS a low sensitivity system is obtained through shortening the reaching phase. Furthermore, the system robustness is guaranteed during whole intervals of control action by eliminating the reaching p hase. To illustrate the advantages of the proposed method, a simple se cond-order linear system subjected to external disturbance is consider ed as a preliminary example followed by a two-link manipulator.