Counter electromotive force space vector-orientedinstantaneous torque control method for brushless direct current motor

Abstract

The invention discloses acounter electromotive force space vector-oriented instantaneous torque control method for a brushless direct current motor. The method comprises the steps of establishing a d-q rotating coordinate system which is orientated based on counter electromotive force; and deducing a torque computation formula under the d-q rotating coordinate system, thus proving that the actual torque Teof the motor is directly proportional to q-axis current. A, B and C three-phase current set values can be worked out through the given d-axis and q-axis current values, and the utilization rate of the winding is improved by using a three-phase breakover PWM modulation strategy applicable to the brushless direct current motor. As the control method adopts the three-phase breakover control mode, no commutation torque ripple occurs. The control mode is used during the whole operation period, separate division of a commutation region for control is not needed, the computation is simplified, and the implementation is simpler.

Description

technical field [0001] The invention relates to the field of brushless direct current motor control, in particular to a method for instantaneous torque control of a back EMF space vector oriented brushless direct current motor. Background technique [0002] Brushless DC motors are used in many fields due to their high working efficiency, simple structure, low maintenance costs, large output, long life, and wide speed range. Brushless DC motors usually work in a two-phase, three-phase, six-state working mode, which can make full use of the flat top part of the trapezoidal magnetic field of the brushless DC motor and increase torque stability. [0003] However, due to the production process, the magnetic field generated by the rotor of the brushless DC motor is not an ideal trapezoidal wave. The 120-degree square wave current will inevitably produce torque ripple; in the commutation area, the off-phase current and on-phase current cannot be ideally commutated, causing commuta...

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Problems solved by technology

[0003] However, due to the production process, the magnetic field generated by the rotor of the brushless DC motor is not an ideal trapezoidal wave. The 120-degree square wave current will inevitably produce torque ripple; in the commutation area, the off-phase current and the on-phase current cannot be commutated ideally, causing commutation torque ripple, which in turn limits its development in the high-precision field

At the same time, the brushless DC motor adopts two-phase conduction mode, the utilization rate of the winding is low, and the output is small

If the three-phase conduction method is adopted, due to the non-ideal back EMF of the brushless DC motor, the change of the back EMF of the brushless DC motor on the time axis is inconsistent with the change of the space axis of the rotor permanent magnet magnetic field, so that the brushless DC motor cannot Three-phase conduction control like a permanent magnet synchronous motor

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