I’m new here. I have an EE degree from over a decade ago but have forgotten most things about motors and hoping to refresh myself via a little project.
I’m looking for a motor which I can control to act as a torsional spring. That is, if external forces move the shaft by, say, 5deg from 0 position, the system will respond with an opposing torque of, say .1Nm, if the shaft is moved an additional 5deg the opposing torque increases to .2Nm, etc. The system should have this behavior in both angular directions from the 0 position.
I don’t think I need a motor with super precise positioning control but I need to be able to vary the torque precisely based on a precise reading of the present angle of the shaft. Maybe that’s the same thing as precise positioning control lol, but my control system will not be seeking to control position if that makes sense.
The motor will need to be ok with having its shaft move in the opposite direction to the direction of torque it is applying, with about a 50% duty cycle, as shaft speed&direction will largely be determined by external forces. As I recall that’s exactly how you burn out a motor.
Is this feasible? What types of challenges can I anticipate?
If it is feasible, what type of motor is best suited to this application in both a small scale proof of concept setting as well as at larger scales?
If I’m looking for something with say, a max torque of about 2.5N*m to start playing with as a proof of concept, what would be a good product to purchase?
I first thought a Servo motor could be the product you are looking for but I’m not sure when reading all your post.
I believe that a geared DC brushed motor could do the job, it as a lot of torque and can be precise.
A good way to track the position of your motor would be to have an encoder on the rear shaft of the motor…
Concerning the opposite torque resistance, I think that the more the motor would be moving in a direction, the harder it would get for the motor to move? Am I right?
This means that the more the motor would turn, the more it would draw current from the Motor Driver.
I believe that you will need a microcontroller to track the position of the motor and apply the appropriate torque and direction to the motor.
Let me know if I’m in the right direction or if I’m wrong.
It is pretty hard to figure out the function of such a system without seeing it or having a schematic.
My only hesitation with a brushed motor is that I think I read they are not as long-lasting due to wear and tear. I’m hoping to use this eventually in an application that will be pretty long term. Would a brushless DC motor work as well?
I think you described the operation I have in mind accurately. The more the shaft turns clockwise (for example) the more opposing force the motor should exert counterclockwise. It is always pushing to have the shaft return to 0 position. If you turned the shaft 90 degrees and let go, it would oscillate back and forth from -90 to +90 degrees continuously (assuming an ideal motor with no friction/damping). The frequency of oscillation would depend on the shaft load.
Do I need to be concerned with burning the motor out since it will be operating at or near stall a lot of the time? Do I need a special motor like a torque motor to deal with this?
