Direct torque control method of brushless DC motor based on segmented sliding mode variable structure

Abstract

The invention provides a direct torque control method based on a sectional sliding mode variable structure for a brushless direct current motor. A sectional sliding mode variable structure state observer is used for refactoring counter electromotive force of the motor, and then a space vector switch state selector is used for controlling on and off of six switching tubes of a three-phase inverter power supply, so that direct torque control of the brushless direct current motor is solved. According to the relation of electromagnetic torque with the counter electromotive force and magnetic flux linkage, a voltage space vector control method is adopted for realizing direct torque control of the brushless direct current motor. Since sliding mode variable structure control is unrelated to system parametric variation and external interference, robustness of a sliding mode variable structure system is higher than that of a conventional continuous system. Experimental results prove that buffeting of the system can be improved by sectional sliding mode variable structure control, and rapidness and robustness of the system are further improved.

Description

Technical field [0001] The invention belongs to the field of mechanical engineering, and relates to a direct torque control method of a brushless DC motor based on a segmented sliding mode variable structure. Background technique [0002] Under normal circumstances, when analyzing the permanent magnet brushless DC motor (BLDCM), we always assume that its back-EMF waveform is a trapezoidal wave and the flat top width is 120°. Due to process problems such as insufficient rotor magnetization and asymmetric windings during the manufacturing process of the motor, it is difficult for the actual back-EMF waveform of the permanent magnet brushless DC motor to achieve an ideal trapezoidal wave. Therefore, if double closed-loop control of current and speed is adopted, large low-frequency torque ripple and poor dynamic performance will be produced. As a high-performance brushless DC motor control strategy, direct torque control can effectively suppress low-frequency torque ripple. At the s...

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Problems solved by technology

[0004] The above studies have difficulties in extracting the back EMF or have not considered the adverse effects of chattering on the system when the sliding mode input error is within a small range in the sliding mode variable structure control.

Therefore, the actual application effect is not ideal

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