I am trying to use a 24v DC motor in conjunction with a rotational to linear drive (rack and pinon) to drive the clamping force to hold a workpiece in position. So when the clamp is forced up against workpiece, the idea is that i can control the current input into the motor and therefore keep a constant force against the workpiece. (using the fact that current and motor torque have a linear relationship so by fixing the current to say 0.3amps I will know what the motor output torque is and therefore know the clamping force on the workpiece.)
My problem is I do not know what i need to do to build a control circuit to keep the current at a constant set value. Because motor driving against workpiece and therefore not rotating anymore it will look for more current and i need this current to stay at a set value. From discussing with others it was suggested I use a proportional controller where i can input my referance current and have a current monitor feed the actual current from the motor into the controller. And then put some more control cricuitry like a pulse with modulator to drive a two quadrent chopper to modulate voltage to the motor which will then in turn control the current. All ideas welcome....