Quote:
Originally Posted by farmersvilleRob
But if you geared down one motor, when applying the ball to the system, one motor has more torque that gives more resistance to the ball's inertia. But at the same time, the other motor takes the same resistance to the ball's inertia, but has less torque than the geared down motor so it slows down more and gives the ball an odd trajectory and speed and backspin.
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FALSE.
If you mix two motors in a given system, and gear them appropriately, they will share the load.
Why?
Say I have a CIM (free speed say 5000rpm for this simplified example, with a torque of 1 units) and a FP (free speed say 20000rpm for this simplified example, with a torque of 0.2 units)
I gear the FP down 4:1 before mixing it with the CIM. The free speeds now match, but the FP only has an equiv. torque of 0.8 - the sum of the stall torques of the two motors geared together is now 1.8 units
When I apply a load to this system, the motors will slow down because there is a load. Say I apply a torque of 0.9 - half of our stall 1.8. Assuming everything is perfectly linear, the motors will slow down to half speed. Because they are geared together, they HAVE TO RUN AT THE SAME (relative) SPEED. Since, at a given speed, each contributes a different amount of power, the power they contribute is approximately correct, the sum of their power output is equal to the load, and given the power output of the motors, the larger motors will contribute more power than the smaller motors. - In this example, the CIM would contribute 0.5 torque units and the FP would contribute 0.4 after gearing (the FP sees 0.1).
You can effectively gear motors relative to one another and add their (geared) torques without much issue, and design the system as if it was a single super motor. To make things even better, most of the motors in the KOP come in pairs, and you can have up to 4 CIM or BB's, so you don't often need to mix motors of different types.
(as a side note, BJC and I wrote up some TI-84 equations/graphs for throwing a ball, and it wasn't as bad as you make it sound, balancing the ramp isn't very hard for a single human-driven robot, and if you are ever in the opposing alley it's a penalty under [G28], even if you were collecting balls)