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Common motor control algorithms for BLDC brushless DC motors

Brushless DC motors are self-commutating (self-direction conversion), so they are more complex to control.
BLDC motor control requires an understanding of the rotor position and mechanism for rectification and steering of the motor.For closed loop speed control, there are two additional requirements that the rotor speed/or motor current and PWM signal be measured to control the motor speed and power.
Small brushless DC motor motors can use edge – or center-array PWM signals according to application requirements.Most applications require only velocity-varying operations and will use six independent edge arrays for the PWM signal.This provides the highest resolution possible.If the application requires server positioning, power braking, or power reversal, the use of a complementary center-array PWM signal is recommended.
In order to sense rotor position, the BLDC adopts Hall effect sensor to provide absolute position induction.This leads to the use of more lines and higher costs.Sensorless BLDC control eliminates the need for a Hall sensor and instead uses the back electromotive force (EMF) of the motor to predict rotor position.Sensorless control is essential for low-cost variable speed applications such as fans and pumps.In the use of BLDC motor, refrigerator and air conditioning compressor also need sensorless control.
Insertion and replenishment of no-load time
Most BLDC motors do not require complementary PWM, no-load time insertion, or no-load time compensation.The only BLDC applications that may require these characteristics are high-performance BLDC servo motors, sinusoidal excited BLDC motors, brushless AC, or PC synchronous motors.
Control algorithm
Many different control algorithms are used to provide control of BLDC motors.Typically, power transistors are used as linear regulators to control motor voltage.This method is not practical when driving high power motors.High power motors must be PWM controlled and require a microcontroller to provide starting and control functions.