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Unread 09-05-2015, 13:12
sanddrag sanddrag is offline
On to my 16th year in FRC
FRC #0696 (Circuit Breakers)
Team Role: Teacher
 
Join Date: Jul 2002
Rookie Year: 2002
Location: Glendale, CA
Posts: 8,502
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Re: pic: Small CIM in wheel swerve

On 696, we had a large 84T 20DP steering gear, and a 1:3.5 ratio between that and our MA3 absolute encoder. That is, the steering encoder would pass through 3.5 rotations for every one rotation of the swerve module. We had to physically set the wheels pointing straight at the start of each match (which is probably good practice anyhow), and there was a good bit of math and code involved, but we were able to very reliably track the position of our wheels at all times, resulting in fine control and operation.

Was it easy or friendly to do it this way? No. Is it possible? Yes. Would we run anything other than a 1:1 ratio to an absolute encoder again? Maybe not. It's kind of a pain. We likely will look into using a zeroing sensor and incremental encoder next time if we cannot maintain a 1:1 ratio with an absolute encoder.
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Teacher/Engineer/Machinist - Team 696 Circuit Breakers, 2011 - Present
Mentor/Engineer/Machinist, Team 968 RAWC, 2007-2010
Technical Mentor, Team 696 Circuit Breakers, 2005-2007
Student Mechanical Leader and Driver, Team 696 Circuit Breakers, 2002-2004
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