A time-varying sliding surface for robust position control of a DC motor drive

In this paper, a new variable-structure position control law for a dc motor is proposed. The algorithm based on a timevarying switching line guarantees the existence of a sliding mode from the beginning of the shaft motion. Indeed, the surface is initially designed to pass through the initial representative point and subsequently moved toward a predetermined desired surface via shifting. By this means, the reaching phase is eliminated and the motor behavior is insensitive to unknown mechanical configuration changes. The algorithm has been tested in simulation and the experiment has been performed using a low-cost 16-bit microcontroller. Then, an advanced test bed is used in order to evaluate the tracking properties and the robustness capacities of the variable-structure control law with variations of the mechanical configuration.