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Need motor for certaint force regardless of motion

Need motor for certaint force regardless of motion

(OP)
I have a rotating shaft that I need to apply a rotational force to which varies depending upon the shaft position. However, the shaft will be rotated back and forth, or all the way around, randomly, at any speed, by forces much larger than the motor applies. In other words, the motor is not expected to successfully control the position or movement of the shaft, just apply a given rotational force in either direction, depending on the shaft position. I have successfully accomplished this with air cylinders, but that solution is overly complex for production. Can anyone think of a motor type that can handle this?

RE: Need motor for certaint force regardless of motion

It depends. If you are OK with a torque that varies quite a lot, a DC motor in series with an incandescent lamp works well.
If you need better precision (more constant torque) you will need a motor with a torque controller. The torque controller is the inner loop of most drives today and there are motors with torques from mNm to kNm.

If all you need is a torque in the "Human Hand" range and can accept some variation, like 10 or 20 percent, then a small 12 V DC motor usually can be used. A transmission (not worm) can often be used to get the desired force. But may be a problem if the load fights back and needs to drive the motor in reverse.

Then, there are more elaborate solutions with/without force or torque sensors and PM servos or asynchronous motors (high rotor resistance or slip ring rotor) which can be surprisingly simple if you use a piezo-resistive sensor. A slip ring motor can often be used without any controller or sensor. Look for cable reel motors.

More input needed. Torque, maximum speed, acceptable torque variation, environment, cost restraints, expected life etcetera are important parameters.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Need motor for certaint force regardless of motion

If you just need retarding consider an eddy current brake.
Google "Torque Motor" (Used on hose and cable take-up reels.)
A wound rotor motor with a lot of resistance in the rotor circuit.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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