MRAC load torque observer for position control of a brushless DC motor

Abstract

A new control method for the robust position control of a brushless DC (BLDC) motor using the adaptive load torque observer is presented. For a BLDC motor system, approximately linearized using the held-orientation method, it is shown that the augmented state variable feedback can be applicable to this system. To overcome the problem of the unknown parameter, or of parameter variation such as a flux linkage, a model following adaptive control mechanism is employed for the load torque observer. Stability analysis is carried out using the Lyapunov stability theorem. As a result, the robustness can be obtained without affecting the overall system response. The load disturbance detected by the adaptive O-observer is compensated for by feedforwarding the equivalent current having the fast response.