Thread: PCM Brownout
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Unread 24-02-2016, 13:44
gpetilli gpetilli is offline
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Re: PCM Brownout

Quote:
Originally Posted by kan123 View Post
I can answer the questions also since I am also on this team.

We have check the 20 amp fuse.

We are 4 cim drive. For testing this issue we have been on blocks and have also removed breakers for 3 of the cims, so we are powering one cim while on blocks. The issue remains.

We will certainly look at the voltage ramp as a possible solution.

What is puzzling is this never happens when accelerating rapidly, it only occurs when decelerating rapidly.

We appreciate the assistance!!
It is hard to induce brownout while on blocks - especially with only one CIM fuse active. Decelerating rapidly makes sense since the drive needs to overcome the inertia of the robot - but not while on blocks.

If you are sure about brownout on blocks, it sounds like a mechanical binding. I would start by putting all fuses back and using the drive station software to plot out the current to each CIM independently. Is one current different than the others? Currents should be say 6A per CIM full speed on blocks and spike to maybe 30A when changing direction (more if driving). I am guessing at these numbers so if someone can try this on a working bot (ours is in the bag) and report back - that would be good.

Are your axles square with the frame? Belts, chains or gears? KOP chassis or custom? While on blocks, can you turn an unpowered wheel or is it bound up?

We did have a problem with one of four gearboxes once where one CIM had evidently been dropped on its output shaft and it had a slight bend which caused the gears to over engage. Disassembled that gearbox probably 10 times till we found the root cause. It does sound like some sort of assembly issue - maybe an extra spacer someplace binding things up?