Research On Commutation Torque Ripple Reduction And Sensorless Control Of Brushless DC Motor

Brushless DC motor (BLDCM), possessing excellent performance, has been widely used in all kind of areas, such as aerospace, industry, home appliances, and office automation. Due to the problems existed in BLDCM and current research for BLDCM, commutation torque ripple reduction and sensorless control of BLDCM is studied in this paper.To eliminate the torque ripple during commutation, a novel control strategy of commutation torque ripple reduction based on Finite-States model predictive control (FS-MPC) is proposed in this paper. The commutation process and conduction status of BLDCM is analyzed. And the optimal status of power switch is selected according to the established predictive model of non-commutated current and predefined cost function. The match of rising current and falling current during commutation is ensured by properly switching three conduction statuses. Research results demonstrate that the proposed method reduced commutation torque ripple effectively over the entire speed rank.A startup strategy was proposed based on fuzzy rules for BLDCM without position sensor. Based on the method of three-step starting, relationship between the characteristic of current response and commutation instant is analyzed. And the characteristic of phase current is obtained, when current lead, lag, or keep phase with EMF. Then, the conduction status is promptly adjusted online to avoid out of step in startup process. Research results show that the proposed approach improved the reliability of startup of BLDCM.Due to the problem in terminal voltage method, sensorless control of BLDCM based on second-order sliding mode observer is proposed. The commutation instant is directly determined by estimated value of line-EMF. Simulation and experiment results show that the proposed approach, which possesses good robustness, estimated the line-EMF correctly and improved the accuracy of sensorless control.To improve the performance of BLDCM drive system, active disturbance rejection control (ADRC) technique is implemented to design speed controller and current controller. In speed loop, extended state observer (ESO) is built up to estimate real-time disturbance, implement feedback control and compensate disturbance. Consequently, the linearization with dynamic compensation for mechanical inertia part is realized. In current loop, line-EMF is extracted by ESO, and the sensorless control of BLDCM is realized accompanying with linearization with dynamic compensation for electric inertia part. Research results show that the proposed approach realized sensorless control of BLDCM, and possess strong anti-disturbance to change of load torque, and achieve good performance both in dynamic and steady state.An experimental drive system for BLDCM is built up based on Texas Instruments (TI) float-point Digital Signal Controllers TMS320F28335. Experiments for commutation torque ripple reduction and sensorless control of BLDCM are implemented to verify the theoretical analysis and the proposed control strategy.