Question on Electric Motors?

zekester

I am trying to implement an electric motor as a generator at the end of a steering wheel shaft. The motor would be used to apply a resistance torque to the shaft. What type of motor would you recommend?

Danger

This sounds like a rather odd project. Is the purpose of the motor specifically to generate electricity, or to dampen the motion of the shaft, or what?

zekester

the purpose of the motor is to apply a small resistance (4-7 N*m) to the steering wheel shaft. The shaft itself will be turned by a steering wheel. this should allow the motor to run as a generator creating a voltage.

marcusl

Why not use friction? Wrap the shaft with a piece of leather and put a clamp around the whole thing...

zekester

sorry, i should have said this before, but the resistance needs to be able to vary from no resistance to around 7 N*m

marcusl

tighten the clamp to vary the torque...

Seriously, a generator is complicated. Doesn't the torque depend on the speed? Also athe armature poles in a generator will give you funky results if you turn your steering wheel only a little (like 30 degrees). Mechanical systems are easy. Look at the simple brake on an exercise bike--you turn a screw that squeezes two pads onto the turning wheel. The knob has a pointer that indicates the relative drag. Once you calibrate the torque or drag (which you'd have to do your way too), you're done.

Danger

And if you have to have something that varies on the fly, without manual input, you might look into using the motor as a motor, instead of a generator. Check into how force-feedback joysticks work.

KleptoPanda

A generator wouldn't be that hard to do. You would just use an MCU controlled digital potentiometer to apply resistance to the motor windings. Then it is just a matter of measuring the change in voltage to determine speed. Make sure you have a set of diodes in place at least equal to the sample rate of you MCU to prevent any damage in case Vin Diesel gets in your car.