In my application the motor maintains a constant torque regardless of which direction it is rotating. There is an input torque that can either be slightly higher than the motor’s output torque,causing it to rotate backwards (opposite the output torque vector), or it can be slightly less at which point the motor moves in the same direction of the torque vector. I call the first scenario “overdriving” and it tends to cause problems as it produces regenerative energy and the back EMF produces a voltage opposite the power supply and current increases. The scenarios are constantly alternating every second or so (kind of like an oscillating spring), so the motor is never overdriven for very long and it is always followed by the more typical scenario. The servo drive and power supply from my first prototype would error out if the motor was overdriven too fast (I used an Elmo servo, amp and power supply I got off Ebay) My current setup seems to handle it fine though. From what I can tell, this power supply stores the energy in capacitors and then dissipates it during the next normal move. Now to the question, do you think the Odrive could handle this? I see you have a terminal block for a resistor to handle regen, but I’d rather capture it and use it as my current setup does. Since my application will be very repetitive, I’d need a large resistor and it just makes more sense to reuse the energy if I can. I assume the resistor is there to protect the power supply, but if I leave the resistor out (or just but a jumper in) would the energy flow back to the power supply, assuming that the power supply can handle it?
Since my application requires minimal to no feedback for position and velocity, I’m not sure I need encoder feedback. Generally speaking, do you think you could commutate the motor in torque control mode using only hall sensors? If you think it’s possible, do you plan on adding hall feedback in the future? Not having encoders would be a nice simplification for my system. If you are planning on adding them, I’ve used this to quickly add hall feedback to an RC motor
http://e0designs.com/products/hall-effect-sensor-board/
Maybe it could help you prototype, rather than figuring out how to get hall sensors inside the motor.
What would it take to increase the voltage of the Odrive? My setup right now is running at 75 VDC. I realize that’s pretty specific and maybe higher than what your typical buyer would need, but is increasing it to 48V possible?
Does the PWM input you mention on the feature page control torque or position? Many industrial servo drives take a 0-10 V analog signal that controls the torque. The Teknic system I’m using takes a PWM or a variable frequency pulse train and varies torque relative to duty cycle or frequency. Having a way to vary torque without having to use a communication protocol would be nice.
