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Unread 05-12-2003, 15:43
Joe Johnson's Avatar Unsung FIRST Hero
Joe Johnson Joe Johnson is offline
Engineer at Medrobotics
AKA: Dr. Joe
FRC #0088 (TJ2)
Team Role: Engineer
 
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Redundancy is a 2 edged sword...

One thing about redundancy: It can hurt you some times too.

On several occassions we have had one of our multiple motors fail or partially fail and not discover it for several matches.

The machine works, but it works at a lower level of performance.

This year, our team is planning on putting in a "diagnostic mode" in which every motor is tested while monitoring sensors (current, speed, etc.) for out of range values. We are also planning on having sensors similarly checked automatically.

I don't suppose that it will find 100% of the problems, but it could help us avoid a full speed crash into the wall during autonomous simply because of an unpluged cable (this really happened last year).

Joe J.

P.S. Breaker ratings have safety factors in them. Essentially, they can carry the rated current for infinite time. At some percentage above that rating, they trip after some time depending on the percentage of over current.

Bottom line, I estimate that a robot could probably dead short the battery for 5 or 10 seconds before it would actually trip the 120 Amp battery (don't try this at home as batteries do not like such dead shorts). Given our current battery, with the motors we have and the required secondary breakers, I think it would be hard to trip that main breaker.

Last edited by Joe Johnson : 05-12-2003 at 15:47.
 


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