Research And Design On PMBLDCM Controller

Permanent magnet brushless DC motor (PMBLDCM), using electronic commutation instead of DC motor’s mechanical commutation, not only has DC motor’s advantages such as high running efficiency, good speed regulation performance, but also has AC motor’s series advantages such as simple structure, reliable operation, easy maintenance. The rotor of is excited by permanent magnet, without excitation loss. The appearance and development of high performance permanent magnetic materials, such as Nd Fe B, has greatly promoted the production and application of PMBLDCM. At present, many fields use PMBLDCM, including aerospace, military equipment, industrial automation, medical equipment, household appliances, electric vehicles, etc. Due to high running efficiency, wide range of speed regulation, high power density, large output torque, PMBLDCM is particularly suited as driving motor of electric vehicle.As mechanical and electrical integration of motor products, PMBLDCM and its matching controller are an organic whole. In this paper, the basic structure and working principle of PMBLDCM are introduced; the phase-commutation logic controlling principle of six-phase asymmetrical PMBLDCM is explained; the mathematical model is derived and builded, including voltage equation, back EMF equation, electromagnetic torque equation and motion equation. After those, the simulation model of six-phase asymmetrical PMBLDCM control system is builded in MATLAB/Simulink. The simulation analysis demonstrates the correctness of the control system, which provides theoretical basis for the research on the causes and restraining strategies of commutation torque ripple.Torque ripple? the prominent problem of PMBLDCM, seriously restricts the appliance of PMBLDCM to low ripple speed regulation system and high accuracy servo system, and it also can make motor produce great operational noise. The cause of commutation torque ripple is detailedly analyzed in the paper, which comes to the following conclusion:during commutation, because the falling rate of turning off phase’s current isn’t equal to the rising rate of opening phase’s current, the non-commutation phase current generates ripple, so that torque ripple appears. In consideration of different ripple performance when motor running in low middle speed and high speed, two restraining strategies are presented, non-commutation phase current hysteresis control based on pwm-on-pwm and overlapping commutation control. Through simulation, the correctness and availability of two strategies is demonstrated.Finally, on the basis of the above theory and simulation, PMBLDCM controller based on DSP&CPLD is designed, including hardware circuit design, software program design and Labview program design of principal computer. After the establishment of the controller hardware platform, some certain experiment testing is done, and the expected results is achieved. The results show that the designed PMBLDCM controller works properly, and has good operational performance, and that the stator current waveform of the motor is relatively good.