ROBUST DIGITAL POSITION CONTROL OF BRUSHLESS DC MOTOR WITH ADAPTIVE LOAD TORQUE OBSERVER

A new control method for the robust position control of a brushless DC (BLDC) motor using the adaptive load torque observer is presented. It is shown that the augmented state variable feedback can be applied to the BLDC motor system approximately linearised using the field-orient ation method. To overcome the problem of an unknown parameter or a par ameter variation such as a flux linkage, an adaptive mechanism is empl oyed. As a result, the robustness can be obtained without affecting th e overall system response. The load disturbance is detected by the ada ptive 0-observer of an unknown and inaccessible input, and is compensa ted by feedforwarding the equivalent current having the fast response.