The Direct Torque Control Of Brushless DC Motor Considering Torque Ripple Minimization

Permanent magnet brushless dc motor(PMBLDCM)is a kind of special motor thatconquer the disadvantages of mechanical commutation and adopt electronic commutation,it has the advantages of simple structure, high power density and high efficiency. It keepsthe advantages of DC motor, which have high operating efficiency and speed regulationcharacteristics. It is widely used in the filed of industrial automation, transportation. Thetorque ripple of BLDCM is obviously because of non-ideal trapezoidal back EMF,non-ideal square wave current, the stator cogging torque and so on. So suppress the torqueripple is the object that widely concerned by scholars at home and abroad.The application of BLDCM is limited because of its torque ripple problems. Sohigher requirements are put forward to the torque adjusting effect that regulate by thecontrol methods of BLDCM, that is to say, a small torque ripple and smooth quick fourquadrant operation can be achieve together. On the basis of instantaneous torque controlmethod of BLDCM by current control, through controlling the conducting phase currentof BLDCM, tracking given shaping reference current and adopting new switching mode,the torque ripple of BLDCM is restrained. The implementation strategy of PMBLDCMthat consider torque ripple minimization is put forward at last.Firstly, the basic structure and working principle of PMBLDCM and the controltechnology of four quadrant operation to brushless dc motor are introduced; the basicmathematical model of motor is set up.Secondly, the control system of BLDCM considering the torque ripple minimizationis put forward, to the obvious torque ripple problem of brushless dc motor. Theelectromagnetic torque ripple of BLDCM is overcome by adopting new switch mode andcontrolling conductive phase current of motor to track the given shaping reference current.The access method of shaping reference current and the theory analysis of adopting newswitch mode to improve the commutation torque ripple are given.Finally, through M-file comes from Matlab and the system platform withTMS320LF28335DSP as the core, the control system of PMBLDCM considering the torque ripple minimization is simulated and tested, and the results of Matlab simulationand DSP experiment are given to verify the validity and feasibility.