The Design Of Servo Drive And Closed-loop Speed Control System Of BLDCM

BLDCM has high efficiency and high power density,and is widely used in many fields because of its excellent control and mechanical characteristics.Among them,the commutation circuit composed of inverter plays the role of electronic commutation,that is,changing the direction of synthetic magnetomotive force.In order to realize the commutation control,it is necessary to detect the rotor position information.The traditional driving technology of the position sensor BLDCM is complex and limited by the working environment,which limits the application of the BLDCM to a certain extent.Therefore,further research on the key technologies of sensorless BLDCM has important practical value and significance.In this paper,the sensorless technology is the main research content,and several key technical problems are discussed,including rotor position identification method,motor starting method,the cause of commutation error and commutation error compensation.Finally,the simulation and experiment are carried out to verify these problems.According to the voltage equation of the motor,this paper uses the line voltage difference method to detect the zero crossing point of the back EMF.This method does not need to reconstruct the neutral point of the motor,does not increase the hardware circuit of the motor,and has a wider range of application.Based on the method of detecting the zero crossing point of back EMF by on-line voltage difference,the reason of commutation error is analyzed.Starting from the continuous current process during commutation,the mechanism of leading commutation is analyzed by decomposing the line voltage difference signal.The mathematical relationship between the angle of commutation error and the integral value of line voltage difference is analyzed,and the influence of the continuous current process on the integral value of line voltage difference is considered.On this basis,a correction method of commutation error of sensorless BLDCM Based on the integral value of line voltage difference is proposed.According to the saturation effect of stator core,the relationship between the equivalent inductance of winding and the position of rotor is analyzed,and a method to judge the initial position of rotor is proposed.In the phase of synchronous acceleration outside the motor,the motor is driven by short pulse and long pulse and the sector of rotor is detected.The pulse acceleration motor also provides rotor position information dynamically,and this process will not produce reverse electromagnetic torque to interfere with the starting process of the motor.In the last step of motor starting scheme,the self synchronous switching stage,this paper proposes an effective synchronous switching strategy to switch the motor from the external synchronous stage to the self synchronous stage.In Matlab / Simulink,the simulation research of the control system of the sensorless BLDCM is completed,and the simulation of the control system of the sensorless BLDCM with position sensor and the sensorless BLDCM with position sensor and its commutation compensation strategy is built.At the same time,the commutation signal generated by the position sensor is compared with the commutation signal generated by the position sensor after compensation,which proves the effectiveness of the position sensor free method.