How to fine tune the BLDC startup period?

[Daniel Husztikd]

Posted on June 19, 2017 at 15:28

HI!

I am evaluating a bldc driver setup for a golf caddy with the stspin3201 eval board. The motor has Hall sensor, so I would like to use it, as the main (and preferably) only sensor. Is it a good idea not to use FOC, only just Hall sensor feedback? 

I am having problem with the motor startup period. I use speed control, and the  controller have a serious overshoot and a very long setting time. I need the lowest overshoot and the smallest setting time for this application.  I have reduced the setting time with increasing Ki constant of the PID controller, but it still overshoots, so I need some advice for the fastest startup with the minimal swing. Can anybody help me? I have attached the datasheet of the motor, and the system parameter headers. 

Thank you!#stspin32f0 #bldc #eval #power-stage #rev-up #brushless

[Muhammad Yaacob Hasan]

Posted on September 11, 2017 at 08:08

Hello, I also have the same problem.

Just out of curiosity, can you handle high speed on that motor of yours? I'm using hall sensor as main sensor. 

Sometimes my motor is skipping intermittently and sometimes it goes to overvoltage.

Thank you and good luck on your endavour

[Daniel Husztikd]

Posted on September 18, 2017 at 13:43

Hi! 

For me, Hall sensors did not work at all somehow. Does it work correctly for you? Did you used the motor control workbench?  I use FOC. I am struggling with the start up period. It usually starts, but sometimes gives speed fedback error. I would like to start my motor with absolutely no error at all, ever.  

Good luck for you too

Daniel

[Hani Chahine]

Posted on September 21, 2017 at 13:06

Just adding my experience with this.

I also have this issue. I can run OK with Hall sensors in torque control mode but in speed control the motor overshoots to back emf limit and then comes back down to set point after some time. This behaviour is not good. No amount of speed or current PI tuning is helping fix this. I also have the same issue in sensorless speed control.

The motor is quite large and needs a decent amount of current to get going. I suspect the output of the speed PI is saturating before motor actually starts. Something is definitely wrong with this behaviour.

Smaller RC drone motor don't seem to suffer from this issue. I usually run larger motors with large inertias and startup on these is terrible (sensored or sensorless) they always overshoot and take some time to settle. I'm probably going to have to implement my own startup and speed loop around torque control to overcome this unless ST can do some testing and fix it on their end.

[Daniel Husztikd]

Posted on October 03, 2017 at 13:05

Dear Hani! 

Could you share your schematic with me? I am very interested with the wiring of the Hall -sensor. 

Thank you 

Daniel

[Hani Chahine]

Posted on October 14, 2017 at 17:02

I don't have my schematic on hand but you can reference any one of the ST dev kits that support hall sensor input. The basic simple connection is just a pull up resistor on each hall sensor output and a small cap to ground. I think I used 4.7k and 470pf. 

On another note I drastically improved my start up and running performance with hall and even in sensorless by properly tuning the speed PI controller gains. The gains were way to low for my large motor / custom drive. I had to reduce the gain divisors by quite a bit untill I found the right range for my setup. After this my motor runs really well using the halls and starts smoothly everytime.