Nonlinear sliding surface based adaptive sliding mode control for industrial emulator

The control of an industrial emulator is one of the interesting problems to look into. In this paper, a high performance nonlinear sliding surface based strategy is combined with an adaptive tuning algorithm to achieve low overshoot, short settling time, robustness against disturbance, chattering reduction, as well as minimum control effort where the prior knowledge of uncertainty bound is not required. The designed sliding surface increases the damping ratio of the closed-loop system as the states approach the setpoint. Initially the system is lightly damped resulting in a quick response and as the states approach the setpoint, the system is overdamped to avoid overshoot. In adaptive sliding mode strategy, control gain is dynamically adapted, to be as small as possible but sufficient enough to counteract the uncertainties. Since chattering magnitude is proportional to the controller gain, using the adaptive gain, chattering can be further reduced. Effectiveness of the proposed method is validated in simulation as well as by experiment.