Research On Sensorless BLDC Motor Control System For Electric Fork Lift

It is a new direction in electric fork lift development that the sensorless brushless DC(BLDC) motor is used as driving motor. First the status of brushless DC motor research and development is introduced in this paper. Compared with several types of motors which used for electric fork lift, it can be found that the brushless DC motor is one of the best drive motors for electric fork lift and this motor has good foreground. The math model of BLDC is introduced based on the principle of BLDC, and the simulation model is established, too. The methods of sensorless rotor position detection are introduced in the third chapter. And, a proper method is choosed. Regenerative braking and PWM mode are dissertated in detail. The control methods have been testified by the simulation results. Then the hardware and software of the motor control system are introduced in the fifth chapter. On the basis of the foregoing chapters, in the sixth chapter some experiments results are given and also the results analysis is included.The main works and conclusions in this paper are as follows:①A simulation model of brusless DC motor for electric fork lift based on BLDC principle is established, and its good operation performance is proved by simulation. Also, the subsystems are introduced in detail in the paper. The reasonability and validity have been testified by the simulation results.②The effects on the torque ripples induced by the PWM methods are studied.A novel torque suppression, PWM_ON_PWM, is used. The novel PWM mode not only can reduce the commutation torque ripples but also can reduce or eliminate the non-commutation torque ripple.③Regenerative braking of BLDC at low speed for electric forklift is analyzed and researched based on electric braking principle, and the braking method is improved for its disadvantage that there is not enough braking force at low speed. A mixed braking method, which can implement electric braking effectively, is proposed.④A method of field weakening based instantaneous reactive power theory is used.⑤According to the electric fork lift characteristic and requirement, hardware and software of BLDC control system based on dsPIC30F6010 is designed. The IPM as the main circuit, the testing table is established to testify the motor control system.