The BLDC motor consists of a motor body and a driver, and is a typical mechatronic product. The control methods of BLDC motors mainly include square wave control and sine wave control. The basic rules include left-hand rule, right-hand rule, and right-hand spiral rule. The following describes "control methods and basic rules of BLDC motors" in detail.
1. Square wave control, also known as six-step control.
2. Sine wave control is called SPWM drive. Strictly speaking, Foc is also called sine drive, but the control object of SPWM is voltage, while the control object of FOC is current. According to the complexity of the control, the sine wave control of brushless DC motor can be divided into: simple sine wave control and complex sine wave control.
Simple sine wave control: Apply a certain voltage to the winding of the BLDC motor, so that the phase voltage of the motor is a sine wave. Since the winding of the BLDC motor is an inductive load, the phase current of the BLDC motor is also a sine wave. By controlling the amplitude and phase of the phase voltage of the motor to control the phase and amplitude of the current, it is a voltage loop control, and the implementation is relatively simple.
Complex sine wave control: Different from simple sine wave control, the target of complex sine wave control is the phase current of the BLDC motor, and a current loop is established to achieve the purpose of controlling the motor by directly controlling the phase and amplitude of the phase current. Since the phase current of the BLDC motor is a sinusoidal signal, the decoupling operation of the current is required, which is relatively complicated, and the common ones are field-oriented control (FOC) and direct torque control (DTC).
1. Left-hand rule: The basis of BLDC motor rotation force analysis, simply put, is that the current-carrying conductor in the magnetic field will be affected by force. Let the magnetic induction line pass through the front of the palm, the direction of the finger is the direction of the current, and the direction of the thumb is the direction of the magnetic force.
2. Right-hand rule: the basis for generating induced electromotive force, contrary to the left-hand rule, the conductor in the magnetic field cuts the magnetic induction line due to the force to generate electromotive force. Let the magnetic induction line pass through the palm, the direction of the thumb is the direction of movement, and the direction of the finger is the direction of the generated electromotive force.
3. Right-hand spiral rule: Hold the energized solenoid with your right hand, and make the four fingers bend in the same direction as the current, then the end pointed by the thumb is the N pole of the energized solenoid. This rule is the basis for judging the polarity of the energized coil, and the direction of the red arrow is the direction of the current.