Decentralised variable structure control of uncertain large-scale systems containing a dead-zone

In order to deal with dead-zone nonlinearity in the input function through variable structure control theory, a new robust decentralised control scheme is proposed for a class of uncertain large-scale interconnected dynamic systems. Dead-zone characteristics are quite commonly encountered in actuators, such as electric servomotors and electronic circuits. Therefore, in addition to the uncertainties in the system, one must also be concerned with dead-zone nonlinearity in controller design. The proposed variable structure controller ensures the global reaching condition of the sliding mode of the uncertain composite system in the presence of input dead-zone nonlinearity. Also, in the sliding mode, the investigated uncertain composite system remains insensitive to the uncertainties and disturbances, and behaves like a linear system. Furthermore, it is shown that the proposed control law can be applied to uncertain large-scale systems with and without input nonlinearities. Nevertheless, this cannot be guaranteed by the traditional variable structure control design for the systems without dead-zone nonlinearity. Illustrative examples are given to verify the validity of the developed controller.