Control of a DC Motor via SMC with Polynomial Reference Trajectories

DC motors remain a subject of significant interest due to their widespread use in industrial automation, robotics, and precision motion-control systems. In many industrial applications, such devices are regulated using PID controllers, though sliding mode control is a viable alternative. However, both approaches have inherent shortcomings. PID, while widespread and easy to tune, underperforms in systems subject to disturbances and model uncertainties. On the other hand, SMC offers excellent disturbance rejection, but typically cannot impose bounds on individual system states, which limits its applicability. To remedy these issues, this paper introduces a new sliding mode control strategy, which is then applied to a class of brushed DC motors. The proposed strategy involves applying a reference model-based SMC to drive the states of the DC motor alongside trajectories obtained from a particular polynomial. These trajectories are defined in a novel way, which always ensures a smooth convergence of each state to its target position while satisfying all necessary state and input constraints. Furthermore, since target states are tracked with the use of a robust sliding mode controller, the effect of uncertainties on system performance is effectively rejected.