Basic principle of torque motor control

1. Control principle of Brushless DC motor :

        Brushless electric regulator , The input is DC , Stabilize the voltage through a filter capacitor . Then it is divided into two ways , All the way is electrically adjusted BEC Use ,BEC It is used to supply power to the single chip microcomputer of the receiver and the electric regulator , The power line output to the receiver is the red line and black line on the signal line , The other way is to intervene MOS Tube use , ad locum , Power on , The SCM starts , drive MOS Tube vibration , Make the motor make a dripping sound . Standby after startup , Some electric regulators have throttle calibration function , Before entering standby, it will monitor whether the throttle position is high, low or middle , If it is high, enter the electric adjustment travel calibration , In the middle, it starts to send an alarm signal , The motor will make a dripping sound , If it is low, it will enter the normal working state . When everything is ready , The single chip microcomputer in the electric regulator will be based on PWM The signal on the signal line determines the output voltage and frequency, as well as the driving direction and angle to drive the motor speed , to turn to . This is the principle of brushless electrical regulation . When the drive motor is running , There are 3 Group MOS Management work , Each group 2 Geji , A control positive output , A control negative output , When the positive pole is output , Negative pole does not output , Negative output , Positive pole does not output , In this way, alternating current is formed , Again , All three groups work like this , Their frequency is 8000HZ. When it comes to this , Brushless electric regulator is also equivalent to the frequency converter or governor used on the motor in a factory .
 

2. PWM Control torque motor ：

        PWM The duty cycle of determines the average voltage output to the torque motor .

        PWM Not regulating the current ,PWM Pulse width modulation , That is, adjust the time ratio of square wave high level and low level , One 20% Duty cycle waveform , There will be 20% High level time and 80% Low level time , The larger the duty cycle , The longer the high level lasts , The higher the output pulse amplitude , The higher the voltage . By adjusting the duty cycle , It can adjust the output voltage , And the output voltage can be adjusted steplessly and continuously .

        For example Duty ratio 50% That's half the high-level time , Half the low-level time , At a certain frequency , You can get the simulated 2.5V Output voltage that 75% Duty cycle of The resulting voltage is 3.75V.

PWM Is at the right signal frequency , The effective voltage of the output is changed by changing the duty cycle in one cycle .

 

PWM Example of output breathing lamp ：

Usually people's eyes are for 80Hz The above refresh rate has no flicker at all .

If the frequency is too small It looks like it flashes

So what we usually see LED The lamp , When its frequency is greater than 50Hz When , The human eye will produce a visual persistence effect , Basically, there is no flicker , It's a constant light LED The lamp .

you are here 1 Seconds , High level 0.5 second , Low level 0.5 second ,( frequency 1Hz) So again and again , Then the light you see will flash ;

But if it is 10 In milliseconds ,5 Open in milliseconds ,5 Millisecond off ,( frequency 100Hz) At this time, the light on and off speed can not catch up with the switch speed (LED The light went out again before it was completely on ), Because vision is reserved for use The human eye doesn't feel the light flashing , But feel the brightness of the lamp is less Due to high level time ( Duty cycle ) by 50% The brightness is the same as before 50% .

When the frequency is very high , No flicker is visible , The larger the duty cycle ,LED The brighter ;
When the frequency is very low , Flashes can be seen , The larger the duty cycle ,LED The brighter .
therefore , Under certain frequency , It can be changed with different duty cycle LED The brightness of the light . Make it reach the effect of a breathing lamp

3. Three loop control of torque motor ：

3.1 Innermost PID The ring is the current ring , This ring is completely carried out inside the servo driver , The output current of each phase from the driver to the motor is detected by the hall device , Negative feedback to current setting PID Adjust the , So that the output current is as close as possible to the set current , The current loop controls the torque of the motor , Therefore, the calculation of the driver is minimal in torque mode , The fastest dynamic response .

3.2 The second loop is the speed loop , Negative feedback is carried out by detecting the signal of the motor encoder PID Adjust the , Inside its ring PID The output is directly the setting of the current loop , Therefore, speed loop control includes speed loop and current loop , In other words, any mode must use a current loop , Current loop is the basis of control , While controlling the speed and position, the system is actually carrying out current （ torque ） To achieve the corresponding control of speed and position .

3.3 The third ring is the position ring , It is the outermost ring , It can be built between the driver and the motor encoder , It can also be built between the external controller and the motor encoder or the final load , It depends on the actual situation . Because the internal output of the position control ring is the setting of the speed ring , In the position control mode, the system performs all three ring operations , At this time, the system has the largest amount of computation , The dynamic response speed is also the slowest .