
01-08-2016, 09:53
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no bag, vex only, final destination
AKA: Pinecone
 FRC #0228 (GUS Robotics); FRC #2170 (Titanium Tomahawks)
Team Role: Mentor
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Join Date: Dec 2008
Rookie Year: 2006
Location: Glastonbury, CT
Posts: 7,584
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Re: paper: 4 CIM versus 6 CIM theoretical calculations
Quote:
Originally Posted by GeeTwo
Another thing to consider if planning a drive train with current limiting is whether using some other motor will be more effective to your strategy than CIMs. A cursory review of the mini-CIM finds it to be inferior in most cases, as it has lower efficiency than the CIM at any given current draw, but there are probably cases where it is the proper choice, due to weight considerations or specific needs. If you're going to do proper current/speed and/or thermal monitoring, you may want to add the 775 pro or other low thermal mass motor to your considerations.
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The CIM versus mini-CIM case for the 6 motor drive is actually a lot closer of a comparison than you might think. The important thing to consider is that the more load the motors place on the electrical system, the greater the voltage drop, and the lower voltage in the system lowers the output torque / etc. There are diminishing returns on adding additional motors based on this. The performance jump from 2 to 4 CIMs is much greater than 4 to 6 CIMs. I think it was 234 that published some empirical data on this, which showed that 2 CIM + 1 mini-CIM has almost the same characteristics as a 3 CIM drive once you account for the decreased voltage drop on the entire system, and the 2+1 gearbox draws less overall current than a 3 CIM gearbox. Just some food for thought.
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