Commutation torque ripple restraining method and system for brushless DC (Direct Current) motor driving system

Abstract

The invention discloses a commutation torque ripple restraining method and a commutation torque ripple restraining system for a brushless DC (Direct Current) motor driving system. The method comprises the following steps: (1) when T*-T is more than AT, carrying out PWM (Pulse Width Modulation) on a switching tube of an off phase, enabling a switching-in phase to be constantly communicated with a non-conducting phase, enabling the PWM duty cycle dhigh of the off switch to meet the condition and ensuring that a current rise speed of the switching-in phase is equal to a current fall speed of the off phase so as to restrain generation of a commutation torque ripple; and (2) when T-T* is more than delta T, carrying out PWM on switching tubes of the switching-in phase and the non-conducting phase, still switching off the off phase and enabling the PWM duty cycle dlow of the switching tubes of the switching-in phase and the non-conducting phase of the off phase to meet the condition. The method uses a torque ripple deviation as a feedback quantity and is matched with PWM to implement torque ripple restraint, has an excellent effect and is easy to implement.

Description

technical field [0001] The invention belongs to the field of mechanical engineering, and relates to a commutation torque ripple suppression method and system for a brushless DC motor drive system. Background technique [0002] When analyzing the permanent magnet brushless DC motor, it is always assumed that its back EMF waveform is a trapezoidal wave with a flat top width of 120°. However, during the manufacturing process of the motor, technological problems such as insufficient rotor magnetization and asymmetrical windings may occur, and it is difficult to achieve an ideal trapezoidal wave in the actual back EMF waveform of the permanent magnet brushless DC motor. Therefore, the traditional current and speed double closed-loop control will produce larger torque ripple and poor dynamic performance. In addition, many factors such as cogging design process, current commutation, and armature reaction will also cause torque ripple of brushless DC motors, among which current com...

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Problems solved by technology

[0003] In the prior art, some control the terminal voltage of each winding during commutation to make the current rising speed of the off phase and the access phase equal, but the chopping time is not easy to grasp; some propose an improved bipolar The permanent PWM brushless DC motor control method uses four switching tubes to perform PWM control at the same time, but this method increases the frequency of switching tubes; some documents use current sensors and torque observers to determine the three-phase PWM modulation range, but this method is extremely sensitive to motor parameters and lacks universal applicability; some literature proposes a method for calculating the current commutation interval through motor parameters, but this method needs to calculate the inductance value of the motor stator winding; some literature proposes a hysteresis loop current control method, but no specific solution is given for torque ripple suppression in high-speed areas; some literature proposes a three-phase PWM modulation strategy within the full speed range to suppress torque ripple during commutation, which simplifies the control process, but Ignoring the essential characteristics of torque ripple in the high and low speed range, the control effect is not good in the extreme speed range; some literatures have introduced a novel three-stage PWM commutation torque ripple suppression strategy, by switching off phase, The PWM modulation strategy with different duty ratios connected to the phase can achieve the effect of suppressing torque ripple

However, the introduction of two parameters that need to be adjusted makes the system complex and difficult to control; many documents in the prior art have proposed good control methods for suppressing the commutation torque, but the control methods are relatively complicated, commutation torque Difficult to determine the phase time and other issues

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