Moving Switching Surfaces for High Precision Position Control of Electrical Drives

In this paper, a variable structure position control law for electrical drive is proposed. The algorithm based on a time-varying switching line guarantees the existence of the sliding mode since the beginning of the shaft motion. Indeed, the surface is initially designed to pass through the initial representative point and subsequently moved towards a predetermined desired surface via shifting. By this mean, the reaching phase is eliminated and the motor behavior is insensitive to unknown mechanical configuration changes. This algorithm has been first applied to a DC machine and then to an induction machine. The experimental results show that the position evolution is the same whatever the mechanical configuration of the drive and whatever the electrical machine.