Rearch On Control Methods Of Sensorless Brushless DC Motor

ii The paper introduces the application situation , the technique problems and the working principle of Brushless DC Motor(BLDCM), establishes the mathematic model and the simulation model of BLDCM, the simulation model is established based on simulation software matlab.And this paper pays more attention to the position sensorless techniques and torque ripple suppression techniques of BLDCM.The position phase error can seriously affect the operation performance of Sensorless BLDCM (SBLDCM), thus the method to correct position phase error is studied in this paper. The relationship between position phase error and freewheel current of silent phase is detailedly analyzed. It is noted that freewheel current error can exactly reflect position phase error. Based on the aforementioned analysis, a novel closed control method to correct position phase is proposed. Freewheel current error is inputted to PI controller in order to keep freewheel current of the silent phase symmetrical, and delaying angel after zero-crossing is adjusted in time through PI controller. Thus the phase error is corrected immediately.Commutation torque ripple is another important factor affecting the operation performance of BLDCM. In order to suppress the commutation torque ripple for BLDCM, this paper analyzes the reasons of the commutation torque ripple and proposes a novel control method, which keeps the un-commutated phase voltage during commutation the same with the one before commutation. Furthermore, this method combined with the PWM scheme'PWM_ON_PWM'can reduce the voltage compensation error caused by freewheel of silent phase during conduction. And the commutation torque ripple is suppressed further, conduction torque ripple is suppressed at the same time. Based on the aforementioned method, a strategy suited for wide speed range is given to suppress commutation torque ripple.Moreover, a control system based on DSP and CPLD is built to verify the validity of the proposed methods.Finally, this paper detailedly introduces the hardware composing of BLDCM speed regulation system,and explains the function of every component. And program flowcharts are also given.