(A) study on robust digital control for brushless DC motor under disturbance and parameter variation

Abstract

The PMSM is widely used because of high power density, low electric noise, high torque and high efficiency. However, there are some limitations to solve the disturbance and parameter variation effects using conventional controller especially in high resolution position control. One effort was done by compensating the load torque with a torque estimator. But, it is not systematic and included noise effect caused by speed sensor. A several new control method for the robust position control of a brushless DC(BLDC) motor is presented. The linear quadratic controller plus 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 design is simply done in the state space. Finally, the overall system is controlled by using the microprocessor and the performance of each control algorithm is compared through 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. Furthermore, a new control method for the robust position control of a brushless DC(BLDC) motor using the adaptive load torque observer is presented. To overcome the problem of the unknown parameter or the parameter variation such as a flux linkage, an adaptive mechanism is employed. As a result, the robustness can be obtained without affecting the overall system response. The load disturbance is detected by the adaptive 0-observer of an unknown and inaccessible input, and is compensated by feedforwarding the equivalent current having the fast response. Next, another control method...