What’s the best option to sufficiently power 2 of these D6374 motors? I have ordered the 56v variant of the ODrive. Mains voltage in Canada is 120v and will be powering them with a PSU connected to the wall.
I plan on using the 2 motors for force feedback so they will be running intermittently, but I would like to power them to get the most torque for short periods at a time.
I was thinking of running a single 48v 1000W power supply with a small bank of capacitors to handle the short current spikes the motors could draw. Would there be a better option?
EDIT: I’ve found 2 topics that might have covered this here:
This is all to be part of an open source force feedback joystick I’m working on. Old design was to use electromagnets but will be changing it over to use BLDC motors instead.
At zero rpm, you only need enough power to run the current you want through the phase resistance. For the D6374, that means you’re looking at something like P = I^2 * R = 100A * 100A * 0.1\Omega = 1000W peak.
Worst case, you need high braking force when the user is slamming the stick from one side to the other against the force, but I can’t imagine that rpm will actually be all that high.
Cool project - might want to consider some gearboxes like the VersaPlanetary + a smaller motor. Not sure where price vs performance will work out.
Thank you very much. Calculating this has been so confusing to me!
So for the D6374: motors they could handle ~70amps * 2 motors 140amps for the purpose of what I’m using them for, the voltage will be far less important. I think it’s also unlikely I would need to drive both motors at 70amps so could get away with a 100amp power supply like this 12V 100A one.
I’ve thought about running gears but from hearing similar setups people have done, the feel of the gears meshing together becomes undesirable.
I have thought about using belts because you wouldn’t feel them. I think an easy setup would be to just take some electric skateboard motor mounts (they have the belts, pulleys already). Another benefit with them is I could offset/raise the motors as the pitch axis might be pushing the motor into the base too much as that axis pivots.
I’m not sure how the motor cogging will come into play with all this or if it’ll become an issue. I guess cogging would be less in a direct-drive setup.
Finally some good active cooling fans on these motors will probably be a big “must” with high currents!?
Hmm, I don’t think you quite understood. The motor phase current != power supply current.
Motor power ~= psu power
Motor Power = Torque * Speed
For your application, where you have zero speed, you can instead calculate motor power as I^2 * R (resistive heating loss)
70A * 70A * 0.1ohm = 490 Watts (per motor)
Your 12V 100A supply is good for 1200Watts, so it’s nearly three times too big.
A 24 or 48V, 1000W supply will be way more than enough. That’s 40A at 24V or 20A at 48V. The lower current supplies are much less expensive, and the Higher voltage is better for ODrive too
Edit: whoops, realized I did my math wrong in the last post, that probably didn’t help lol
And specifically on the issue of power supply for this application:
The D6374 and the CUI encoder might not be the best choice of motor for a force-feedback system - this motor is designed for high power-density only - it is not meant as a servo and so has high cogging and other torque ripple effects, meaning you might not get a high fidelity force feedback feeling from it; there will be a certain amount of torque variation with any movement, even where the torque setpoint is held constant.
A better choice might be a large “gimbal motor”.
It’s possible to compensate some of this out in software; but for that, you ideally want an absolute encoder (with the highest available resolution).
For a joystick, you might need an absolute encoder, because you can’t easily detach the motor from the mechanism to perform calibration on start-up.
