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Unable to get proper speed control

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New Member

Dear Sir,

I have exchaged emails with Francesco but he suggested that it is better to continue on your Forum. He have sent good tutorial material. My further experiments I have mainly done based on the video entitled "The Simplest way to drive your Brushless Motor Using SOLO".

The results are disappointing. MY BLDC motor is somewhat smaller than the one used in the video.

To start my BLDC motor with SOLO, I have to turn the speed and current potentiometers to about half or 2/3 of their range. By this start up the motor is jerking and drawing several ampers but starts continouos rotation with a little luck. After start up, the the motor speed follows the adjusments made by the speed potentiometers. The current drawn decreases with increase of speedand and vice versa. The current by its minimum is even higher (about doubled) than by my old BLDC driver.

If I force to stop the motor by hand by its highest speed, new start is possible only by turning back the two potentiomeres to their original position. Reversing shown in the video is impossible - the motor falls out if synchronism, new maual start is necessary. 

Adjusments of the Ki and Kp potentiometers have not given any usable improvements.

What I am doing wrong?

Best regards: Nandor



Topic starter Posted : 23/08/2021 10:17 am
Chief Member Moderator

Hi Nandor, 

Thanks for posting here, so as far as you mentioned before you are using SOLO in sensorless mode, but are you in closed-loop or open-loop mode?

Posted by: @nandorsolo

"The Simplest way to drive your Brushless Motor Using SOLO".

can you give a link to this article? we don't have an article with this exact name.

I believe you should read the article below and watch the video, to see how SOLO will operate properly in Sensorless mode

once you read the article and saw the video you need to make sure about the following things:

  1. Make sure you select Normal Brushless Motor type ( pin Number 1 Down, Pin Number 2 Up, on the Piano switch) as you are using SOLO in Analogue Mode
  2. Make sure you identify the Motor after the Motor type selection, so firstly select the Motor type, then Identify the Motor by pushing Pin Number 5 Down while it's UP and SOLO is powered ON. ( only 1 time needed, and pls keep pin Number 5 down to keep solo in closed-loop)
  3. Make sure you select the proper number of Poles for your motor in the Motion Terminal, by default it's at 8, but your motor might have different values, this is important to have the exact value set.
  4. Make sure you don't increase the Kp and Ki potentiometers very much, you need to increase them very slowly with very small rotations, maybe just 2 degrees for Kp and 1 degree for Ki in CCW direction while they are Zeroed by turning them fully in CW direction. ( increasing these gains can increase the current consumption for no good reason)

After doing the mentioned steps, now you can start to tune your system, for that, you need to connect SOLO to motion Terminal and adjust the following parameters to get some results:

  1. Try to reduce the PWM Frequency ( which is the output switching frequency) to values like 8kHz/10kHz/12kHz/16kHz and see what happens.
  2. Try to reduce the value you see in "Current Controller Kp*" to values like "0.1" or less and see if the behaviour changes ( after changing the current controller gains, to make them take effect you need to recycle the power of SOLO).

I believe after doing the mentioned points, we will be able to see noticeable differences in terms of performance, depending on your next report there are other tunings we can do to improve even further the control.

I'll be waiting for your update.




If you found the answers helpful and you could solve your problems, please kindly verify here to help others in the future.

Posted : 23/08/2021 10:47 am
Chief Member Moderator

Hi @nandorsolo

I hope you are doing well, just wondering if you had any luck with controlling better the speed by reducing the switching frequency to 8 or 10kHz?



If you found the answers helpful and you could solve your problems, please kindly verify here to help others in the future.

Posted : 25/08/2021 12:42 pm