The primary concern of this article is to stabilize the rotating speed of the permanent magnet DC (PMDC) motor driven by a DC-DC sepic converter under mismatched disturbances via higher order PID sliding surface (PIDSS) controller. This controller offers numerous benefits, including robustness, enhanced control performance, flexibility, simple implementation, and low cost. An algorithm for the above-said control is developed for the load torques such as: no-load, constant, frictional, and propeller types. Further, the features of PIDSS are compared with classical sliding surface, sliding mode control (SMC) and proportional integral controller (PIC) by taking into consideration of peak overshoot, steady-state error and settling time. Simulation and experimental results are obtained satisfactorily.