Research On Several Issues Of BLDC Motor Control System

Permanent magnet brushless dc motors are widely used for its high efficiency and simple control method,and tend to be applied to some special military-industrial areas.The research is based on two special military-industrial occasions:one is to improve the torque in a short time with a large inductance and heavy load;the other one aims at achieving emergent stop and locking the rotor with load.To solve these issues,this paper focuses on the torque degradation caused by phase current shift and a strategy for controlled braking torque and locking.First,this paper analyzes the motor's phase current during commutation based on PWM_ON modulation with current loop,and presents a particular PWM duty cycle increment which could eliminate the non-commutation phase current ripple at a low speed.The simulation and experiment result show the theory's fesibility.Second,to increase the torque in a short time with a large inductance,this dissertation chose to start the trigger signal earlier so that the midlines of the phase current and the back emf could overlap,which could contribute to the improvement of the unit current torque.The simulation and experiment result prove that taking the trigger signal in advance could promot output torque.Third,this paper presents cycle-by-cycle current limit method to make sure the braking torque is under control.After the rotor speed decreases to some proper rate,the asymmetry following-and-locking method could offer asymmetry braking torque to lock the rotor,which adjusts over HALL signals.The simulation result indicates the theory's validity.Besides,this paper introduces driver control hardware platform based on TMS320F28069 in detail,on which the experiments were completed in this paper.More over,upper computer could monitor the motor's running state and send commands to the controlled motor with eCAN on this hardware platform.