High-Performance Tracking Controller for Discrete Plant Using Nonlinear Sliding Surface

A nonlinear sliding surface is proposed to improve the transient response for general discrete multiple-input-multiple-output linear systems with matched perturbations. The tracking case is analyzed, and it is shown that the scheme is able to achieve low overshoot and low settling time simultaneously; this is not possible with a linear sliding surface. The control law is based on the discrete-time sliding mode equivalent control and thus eliminates chattering. The control law is proposed based on two approaches: (1) reaching-law-based approach which needs only disturbance bounds and (2) disturbance-observer-based approach. Multirate output feedback is used to relax the need of the entire state vector for the implementation of the control law. A magnetic tape position control application is used to show the effectiveness of the proposed scheme.