My application requires maintaining constant tension on a fiber production line and I’m considering using an O-Drive kit in torque/current control mode as a direct drive to achieve this. I’ve searched the documents and see only cursory references to how to set current control.
I would like to know what are the ranges of torques I can achieve with this mode, the resolution and if I will get constant torque or if torque amplitude will have some temporal (or positional ripples)? I’m particularly interested in a low-speed domain (0.1 to 5 RPMs) and low torque values (<0.001 Nm).
Can anyone comment if they have used these motors in a constant current/torque mode and what are the performance ranges?
The torque is of course a function of the torque constant of the motor. With some modifications, you can get ODrive to run pretty low current motors, but I’m not sure about 0.001Nm, that’s very low. The ODrive D5065 motor available in the webshop theoretically produces 2.14Nm at 70A, so to hit 0.001Nm you’d need 32mA. That’s ~3 orders of magnitude below the point where ODrive starts to have trouble measuring (without modifications). Are you sure 0.001Nm is right? Do you know what motors you would use for this?
There will be some torque ripple unless you go with very expensive motors. You can also try our anti-cogging algorithm, which can reduce that torque ripple at low speeds.