TIME-OPTIMAL SLIDING MODE CONTROL IMPLEMENTATION FOR ROBUST TRACKING OF UNCERTAIN FLEXIBLE STRUCTURES/

An improvement strategy in robust control is proposed for uncertain li near or nonlinear systems. This two-stage control scheme first modifie s the original desired trajectory, and then imposes robustness against uncertainties in tracking the new trajectory. For the trajectory modi fication stage, two different schemes are considered: Time Optimal-Rig id Body Motion (TO) and Shaped Input (SI). The robustness stage is per formed using Sliding Mode Control with Perturbation Estimation (SMCPE) , an advanced form of SMC. This routine brings some strong features as demonstrated by examples. A rotating hub with flexible beam attachmen t is taken as the first example, and an undercontrolled two-mass syste m with a linear spring as the second. The comparative studies show sup erior results for the combination of TO-SMCPE over SI-SMCPE. Moreover, this two-stage control exhibits stable and highly advantageous perfor mance even for cases where H-proportional to type robust control struc ture is declared unstable. (C) 1998 Elsevier Science Ltd. All rights r eserved.