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Unread 01-05-2009, 18:13
vamfun vamfun is offline
Mentor :Contol System Engineer
AKA: Chris
FRC #0599 (Robodox)
Team Role: Engineer
 
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Re: Sensorless back_emf speed controller

Quote:
We used encoders for the back emf estimation this year with great success in implementing out traction control and anti-skid braking.

The most difficult issues were the centering of the KOP (read bearingless) US Digital encoders. US Digital FAE recommended staying below 0.010" bearing radial runout and maintaining the spacing between encoder wheel and the optics by the same tolerance.

The radial runout is not hard to comply with if you are on a shaft supported by 2 bearings and have a decent mount for the encoder. Sadly the $2 mount was not not supplied in KOP and likely lead to the destruction of many KOP encoders because of incorrect mounting
.

I envy your success. We had the right and left gear box and reference wheel encoders and supporting traction control sw but one gear box encoder was inop so the traction control was trashed as usual. Seems building your software house on a foundation of encoders is risky business....and the last three years many hrs of software development have been dumped due to said culprits.

We built the $2 mounts not supplied in KOP and I'm sure that the encoders were scratched due to pulling them off by forcing the disc against the xmission housing. The spacing was not too hard due to the supplied spacer from US digital. We did have an issue with shaft tolerance from AM. Also we have purchased SuperShifters which came with encoder mounting shafts about 1/8 in too short. The encoders fingers had to be crimped slightly to make them hold. AM knows of this problem and have corrected it. They will replace any short shafts if you send them back.

I look forward to any scope results...it will be a few weeks before we can look at some wave forms. Everyone is in Dallas today.