I have a project which involves taking up the slack on a 300 ft. long 1/8" thick wire and wrapping it around a spool as it is pulled in or out. The far end of the cable is attached to a robot with enough torque to pull the cable out. The other end is wound on a spool and is kept taut using a motor. As more or less line is paid out, I am able to manually vary the amount of pull (torque) of the take-in motor using a motor speed controller to vary the voltage. I do this with a potentiometer attached to the analog input of the motor controller. This all works well at low voltage/low torque.
I almost never need full power from the motor (in this case Dayton 4z144 from grainger, 24 V, brushed), and using the potentiometer, I usually feed the motor between 2-5 volts DC. But when I do need the full 24 volts, my motor controller and power source are unable to handle the motor's load. This is because the motor is almost always in a stalled state (as it is just keeping the wire taut, not consistently turning and spooling wire). Stalled, the motor draws over 75 Amps.
My question is then what to do about this situation. Find a motor with a lower stall current, but the same torque curve? Control it differently? Someone suggested a feedback loop that would dynamically control voltage, but I can't see this working..
Any advice would be appreciated.