Square wave sensorless brushless DC motor debugging steps

The square wave sensorless BLDC is mainly divided into three steps:

1. Rotor positioning.

Second, force dragging.

3. Cut the closed loop.

Problem:

1. The closed loop is not smooth when forced to cut, and it will lose step. 1. Frequency. 2. The waiting time is not enough, and the zero-crossing detection is unstable and the circuit is cut.

2. Adjust the switching frequency

There are two kinds of phenomena when the motor loses step: 1. Stuck. 2. Vibration.

If you are adjusting the initial forced PWM, the correct value is between these two values. If it is stuck, adjust it down. If it is vibrating, adjust it up.

If you are adjusting PH_TIME, then the stuck one will adjust it down, and the vibration one will adjust it up. What is the essence of this? It is worth thinking about it.

Now there is a problem that PH_TIM has been adjusted to a very small value. Although the initial PWM has been adjusted upwards, the load starting capability has increased, but the load capacity still feels weak. Maybe something is not adjusted correctly.

The above problem has been solved. The strong drag load is a bit weak. If you press it hard, it will lose step. Constant voltage and frequency may not be enough. Try frequency and voltage increase later.

As far as my code is concerned, I mean my code. The biggest difference between the sensor and the sensorless is the start-up time. The sensor should have a stronger load start capability. There should be something wrong with my code. I haven't fully understood the sensorless square wave start.

Just taking this as a note.

The following are just to make up the word count, don’t read them.

The position estimation method of brushless DC motor without position sensor can be discussed from many aspects. This article focuses on the back-EMF rotor position detection technology.

In a brushless DC motor, the rotor rotates continuously in a certain direction due to the synthetic magnetic field generated by the stator winding. The armature winding is placed on the motor stator. Therefore, once the rotor rotates, a conductor cuts the magnetic lines of force in space. According to the law of electromagnetic induction, when a conductor cuts the magnetic lines of force, an induced potential is generated in the conductor. Therefore, when the rotor rotates, an induced potential, i.e., a motion potential, is generated in the stator winding, generally called back electromotive force or back electromotive force.

When the back EMF of a phase winding of the BLDCM passes through zero, the rotor direct axis coincides with the axis of the phase winding. Therefore, as long as the zero-crossing point of the back EMF of each phase winding is detected, several key positions of the rotor can be obtained. Then, based on these key rotor position signals, the BLDCM commutation is controlled after corresponding processing to achieve continuous operation of the BLDCM. This is the "back EMF method" BLDCM control.

The zero-crossing point of the back-EMF of the brushless DC motor winding strictly reflects the position of the rotor pole. Therefore, as long as the zero-crossing signal of the winding back-EMF can be accurately detected, the key position of the rotor can be determined. After a 30° electrical angle delay, it can be used as the phase change moment of the winding. Then, according to the conduction sequence of the power tube, the corresponding power tube is triggered to realize the phase change operation of the brushless DC motor, ensuring that the motor rotates continuously in a fixed direction. In this way, the motor phase change can meet the "optimal phase change logic" and reduce torque pulsation.