Researches On The Method Of The Sensorless Brushless DC Motors Torque Control

The performance of Brushless DC motor is very outstanding,especially in the field of industrial automation.In view of the problem of the BLDC control field,it is given a detailed description of the research of sensor-less and the analysis of motors' torque control.Firstly,according to the electronic control system,it is introduced its basic composition,internal model,algorithm and the current focus in the future.It is believed that BLDCM should been smoothly controlled based on the condition of Sensor-less and the importance of torque control.Secondly,aiming at some problems,such as the sensors' insufficient precision,the error of phase change and the environmental influence,it is analyzed the BLDCM based on the condition of Sensor-less control mode,which has the advantages of more reliable commutation and lower external interference.As a result,it has already established some improvements in sensor-less control technology.And it used a fully equipped simulation platform to test and verify strictly.Then,aiming at the large torque ripple of the motor,it is designed an improved DTC strategy electrical control system.In the system,it could stably generate continuous torque with ideal trapezoidal back EMF.When brushless DC motor works,the commutation current will fluctuate to a certain extent,and the torque ripple will increase.In order to decrease the torque-ripple in commutation period,it put forward a variable current device,which is a Quasi-Z-Source network.When the circuit is compensated,the drop rate of the off phase current of the brushless DC motor can be consistent with that of the open phase.Finally,aiming at the instability of open loop system,it is designed the speed closed loop and the torque closed loop.The frequency information of the position signal is generated by the observed back EMF,and the speed closed loop controller outputs the signal as the input signal of the torque hysteresis control.And the output signal of the closed-loop controller is used as the input signal of the torque hysteresis control.In this system,the torque vector selection module is used as the basis of the system,and the Direct-Torque-Control is carried out according to the change of the torque vector of the BLDCM.In the experiment,the motor speed regulation,commutation,torque and current output-signals are stable,and meet the expected goals.