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speed controller at low RPM

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hagoston
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Last seen: 2 years 9 months ago
Joined: 2021-03-08 13:39
Posts: 7
speed controller at low RPM

Hi all,

my setup is a hall-sensored BLDC Maytech 6374 90KV motor with SUPERFOC6.8 VESC on 10s battery and I would like to use it with speed control mode from a ROS node.
After successful FOC setup, the motor is not able to run under ~300 ERPM in speed mode without coughing / oscillation. Duty cycle works fine at low speed but without enough tourqe.
I also tried foc_openloop command from the vesc tool console which is ok at lower rpm but for me the speed controller interface would be ideal.

Is there anything I miss to be able to use the speed controller with high torque at low speed?
Would I get better results if I attached an encoder instead of the hall sensors?

Any advice would be appreciated.
Thanks
/Ágoston

salviador
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Last seen: 1 year 7 months ago
Joined: 2021-09-08 11:37
Posts: 3

I have the same problem, no one has experience on how to fix it?

 

lurch
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Last seen: 2 months 1 day ago
VESC Free
Joined: 2021-10-05 18:56
Posts: 33

try to reduce flux linkage by 1 point manually ... 

halls have good efficieny at low speed .

 

Elwin
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Last seen: 2 months 2 weeks ago
VESC Free
Joined: 2021-09-30 16:41
Posts: 76

There are multiple things I think of the can cause something like that.

1. Motor cogging. This is simply the attraction force between the magnets and the steel in the motor. Feedback can be too weak to compensate.

2. Operation on hall sensors of motor with sinusoidal back emf. I have no checked hpe the VESC uses the hall sensors exactly, but if you operate a motor with sinusoidal back EMF with 6 step commutation which is typically used with hall sensors you get a torque ripple of almost 15 percent.

For more options, see https://www.sciencedirect.com/science/article/pii/S2352146519302388/pdf?...