Optimal variable-structure controller for DC motor speed control

A new technique, based on the theory of variable-structure systems, is proposed for the speed control of a separately excited DC motor. A systematic procedure for selection of the switching hyperplane in the design of variable-structure controllers is developed, by minimising a quadratic performance index in the sliding-mode operation. The proposed control scheme is illustrated by digital simulation of a separately excited DC motor. It is shown that use of optimal variable-structure controllers can greatly improve the transient performance of the system, while still keeping the steady-state error at zero.