Relative Degree Two Discrete Time Sliding Mode Speed Tracking Control of a DC Motor

This paper makes a study on the speed control of a DC motor by discrete time sliding mode control (DTSMC) technique with an objective to track a reference speed. DTSMC is chosen for this purpose to ensure the robustness due to uncertainty while considering digital implementation in practical scenarios. First, a sliding variable or an output is selected to be of relative degree one (RD1) to achieve the goal. Then the same task is done in the recently developed relative degree two (RD2) paradigm for DTSMC. Both these methods are implemented practically on a DC motor by giving different reference speeds. A comparative study is done for RD1 and RD2 and internal dynamics are found to be stable and yielding better robustness for the latter case.