Robust control of a DC motor

This paper presents an observer-based active disturbance rejection control (ADRC) structure which achieves robust tracking performance, effective regulatory control, and negligible internal uncertainty for a separately-excited DC motor. The approach is primarily founded on the opportunity of online estimation of all the disturbance inputs – known and unknown – which affects a DC motor utilizing suitable observers, and proceeding to reject them through an appropriate feedback control law. The critical tuning parameters for this controller are the observer and controller bandwidths; the higher values of which will result in enhanced disturbance-rejection performance. A frequency response analysis demonstrates that the observer-based controller significantly improves the robustness of the DC motor to external disturbances, and remarkably maintains its bandwidth and stability margin regardless of the unknown dynamics and parametric variations existing in the motor. A thorough comparison is made between the proposed control strategy and previous model-based strategies used via control simulations to validate its effectiveness.