Close-loop torque control

[Muzzer]

The Lichuan, DMM and Yaskawa AC servos all support torque mode although the Lichuan seems to only support analogue (+/-10V) inputs. The others seem to support serial / digital comms etc as well. Step/dir isn't an obvious mode for controlling torque but I suppose the pulse frequency would indicate the torque demand.

My Leadshine closed loop servo only supports position control with step/dir inputs, so I'm guessing this "closed loop stepper in torque mode" function seems to be a bit of a minority sport. I suspect the norm is just to use servos for torque control.

Unless you need true 4 quadrant operation, there are iron powder clutches and brakes that generate a (drag) torque that is proportional to control current. For things like coil winders and tensioners, this may be a much simpler solution but it's not clear what the OP is actually after. https://www.aliexpress.com/w/wholesa...der-brake.html

[alanambrose]

>>> "closed loop stepper in torque mode" function seems to be a bit of a minority sport.

Yeah, I think so. And I didn't realise the preference for servos for this application although that makes sense, so thanks everyone for that.

>>> it's not clear what the OP is actually after

I should have said: the application is a clamping one - needing to produce a given clamping force in the 1-5Kg (~10-50 Nm) range and constant over a variable distance of ~5mm or so. There is a requirement to start at a particular distance (hence my 'stepper thinking') but after that it's a 'closed-loop clamping application'.

Alan