A ROBUST DIGITAL POSITION CONTROL OF BRUSHLESS DC MOTOR WITH DEAD BEAT LOAD TORQUE OBSERVER

A new control method for the robust position control of brushless DC (BLDC) motor is presented. The linear quadratic controller pius load torque observer is employed to obtain the robust BLDC motor system approximately linearized using the field-orientation method for an ac servo. And the gains are obtained systematically from the discrete state space analysis. In addition, the robustness is also obtained without affecting the overall system response. The load disturbance is detected by a 0-observer of the unknown and inaccessible input, and is compensated by the feedforward without requiring the noisy current information. All these designs are done simply in the state space. Finally, the overall system is controlled by using the microprocessor and the performance of each control algorithm is compared with both the simulation and the experimental results for the two types of the machines, i.e., a BLDC motor and a brushless direct drive (BLDD) motor.