Robust-decentralized tracking control for a class of uncertain MIMO nonlinear systems with time-varying delays

A new control design method based on signal compensation is proposed for a class of uncertain multi-input multi-output (MIMO) nonlinear systems in block-triangular form with nonlinear uncertainties, unknown virtual control coefficients, strongly coupled interconnections, time-varying delays, and external disturbances. By this method, the controller design is performed in a backstepping manner. At each step of backstepping procedure, a nominal virtual controller is first designed to get desired output tracking for the nominal disturbance-free subsystem, and then a robust virtual compensator is designed to restrain the effect of the uncertainties, delays involved in the subsystem, and the couplings among the subsystems. The designed controller is linear and time-invariant, so the explosion of complexity in the control law is avoid. It is proved that robust stability and robust practical tracking property of the closed-loop system can be ensured, and the tracking errors can be made as small as desired. Copyright (c) 2013 John Wiley & Sons, Ltd.