paper: 4 CIM versus 6 CIM theoretical calculations

[MichaelBick]

Originally Posted by thatprogrammer

Are you saying that a 4 CIM drive should be limited to 38% per a motor in order to keep your robot below 200amps of power usage?

He is saying that @ 0 RPMs you need to provide 38% of full voltage to draw 200 amps total. At higher RPMs you will need to provide more voltage to draw the same 200 amps. Similarly you need to provide even less voltage if the robot is traveling backwards initially.

Originally Posted by thatprogrammer

2. Would limiting the current draw of a motor be similar to limiting voltage? I.e. would limiting max current have a similar effect to limiting a CIM's output to .5

Halving voltage halves no-load speed, halves torque, and results in 25% mechanical power. On the other hand, limiting current limits torque and thereby limits acceleration. This by itself is very helpful, even without the power increase that is mentioned in the paper, because it causes robots to be much more stable.

Originally Posted by thatprogrammer

3. Why not simply control the Max RPM of the CIM in code rather than using a current PID?

If you only control velocity, you will still draw high amounts of current at stall. For example, a 4 CIM drive will draw 524 amps at stall, and 1048 amps going from full forward to full reverse. This is what causes brownouts.