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# Sine Wave Control of Brushless DC Motor

With the development of control technology and the improvement of energy conservation requirement by the society, as a new and efficient motor, brushless DC motor has been applied extensively. The traditional brushless DC motor adopts the square wave control means, which is simple in controlling and easy to be realized. However, it has the problems of torque pulsation, commutation noise and so on, thus having a certain limitation in the application fields with noise requirements. For these applications, sine wave control can solve this problem.

Sine wave control of brushless DC motor means that the motor winding generates the sine-wave current through exerting a certain voltage to the motor winding, so as to realize the purpose of controlling the motor torque by controlling the amplitude and phase of the sine-wave current. Compared with the traditional square wave control, the motor has sine-wave current, which changes continuously and has no phase-change current mutation, so the motor has quite low operation noise.

Based on the complexity degree of control, the sine-wave control of brushless DC motor can be divided into: simple sine-wave control and complicated singe-wave control.

The motor winding is exerted with a certain voltage, enabling the phase voltage of the motor to be sine wave. Because the motor winding is the inductive load, the phase current of the motor is sine wave as well. The phase and amplitude of the current is controlled through controlling the amplitude and phase of the motor phase voltage. It is the voltage loop control and has simple realization.

The simple sine-wave control means to realize the purpose of controlling the motor current through controlling the amplitude and phase of the sine phase voltage. Generally, the motor end line is exerted with the voltage of a certain form to have sine phase voltage to the two ends of the winding. The common generation means includes: Sine PWM and spece vector PWM. Because PWM has simple principle and easy realization, it is usually employed as the PWM generation means in simple sine-wave control.

Different from the simple sine-wave control, the purpose of the complicated sine-wave control is the phase current of the motor, and the establishment of the current loop, so as to realize the purpose of controlling the motor through controlling the phase and amplitude of the phase current. Because the phase current of the motor is the sine signal, it is required to conduct the decoupling operation of the current, which is rather complicated. The common ones include field-orientated control (FOC) and direct torque control (DTC) and so on.

Sine wave control of brushless DC motor means that the motor winding generates the sine-wave current through exerting a certain voltage to the motor winding, so as to realize the purpose of controlling the motor torque by controlling the amplitude and phase of the sine-wave current. Compared with the traditional square wave control, the motor has sine-wave current, which changes continuously and has no phase-change current mutation, so the motor has quite low operation noise.

Based on the complexity degree of control, the sine-wave control of brushless DC motor can be divided into: simple sine-wave control and complicated singe-wave control.

**Simple sine wave control**The motor winding is exerted with a certain voltage, enabling the phase voltage of the motor to be sine wave. Because the motor winding is the inductive load, the phase current of the motor is sine wave as well. The phase and amplitude of the current is controlled through controlling the amplitude and phase of the motor phase voltage. It is the voltage loop control and has simple realization.

The simple sine-wave control means to realize the purpose of controlling the motor current through controlling the amplitude and phase of the sine phase voltage. Generally, the motor end line is exerted with the voltage of a certain form to have sine phase voltage to the two ends of the winding. The common generation means includes: Sine PWM and spece vector PWM. Because PWM has simple principle and easy realization, it is usually employed as the PWM generation means in simple sine-wave control.

**Complicated sine wave control**Different from the simple sine-wave control, the purpose of the complicated sine-wave control is the phase current of the motor, and the establishment of the current loop, so as to realize the purpose of controlling the motor through controlling the phase and amplitude of the phase current. Because the phase current of the motor is the sine signal, it is required to conduct the decoupling operation of the current, which is rather complicated. The common ones include field-orientated control (FOC) and direct torque control (DTC) and so on.