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In TwinCAT3 or Codesys, is it possible to control a bi-directional servo with 0-10v and direction pin? Or, is it possible to decouple the analog output from a PTP Axis at runtime, and control it from the program?

I am trying to do a software work-around for a 'missing of appropriate hardware' problem.

I want to jog a servo backward, while my interface to it is: Enable, 0-10v and Direction. Normally, the machine has to run only forward, but there are special cases when jog backward is needed.

Now, the controller outputs 0v for 0 speed, and 10v for max speed. Ideally, I would have an analog card which can output -10/+10v, and I would have no issues to run backward. Is it possible to control a bi-directional servo with 0-10v and direction pin?

I tried to call MC_Jog_instance.JogBackwards, but the output would be 0v, as I limited the 'Position and Velocity Scaling'.'Minimum drive output limitation [-1.0 ... 1.0] ' to 0.0

I tried to call MC_Jog_instance.JogForward, and change manually the Direction pin, but the Axis motion controller would get into error, as it expects motion forward, and servo runs backward.

All motion tasks in forward direction are running fine.

More context: Structured Text application in TwinCAT3 (based on Codesys), PLCopen Motion Control standard, like MC_Power, MC_Jog. Target IPC is a Beckhoff CX5020, and for analog I use an EL4004. Servo: LS apd, does not allow offset bigger than 1v. It is set for velocity control. The machine is unwinding some plastic foil.

Dexter
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  • Could you potentially put back the drive output to -1.0 ...1.0, then manually ABS the output and use the direction pin? – chrisbeardy Jun 29 '23 at 10:14
  • I mean you could just ditch the MC blocks. Jogging is simple enough, no? Doesn't the external drive take care of positioning? You are using wires to control the drive, so I would assume so. I use LS drives (L7N series), I don't use NC since its bonkers expensive (other reasons as well), but interfacing to it is pretty simple, I don't see why you couldn't do the same with external setpoint (I use CoE). – ziga Jun 29 '23 at 14:37

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