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Author Topic: Linear scales in dual loop feedback system  (Read 783 times)

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Linear scales in dual loop feedback system
« on: July 19, 2019, 09:42:10 AM »
I posed this question directly to VitalSystems but got no reply....

"I have a system running Mach4 connected to a CM106ESS Smoothstepper breakout board via LAN with SureServo AC Servos using Step & Direction pulses, as if they were Stepper motors. However, I have Linear scales on all three axes and I'd like to close the loop with those instead of just having the closed loop on the leadscrew.
Do you have a solution that would allow me to take the output from Mach4 and feedback from the Linear encoders and feed the AC Servos with Step & Direction pulses or Modbus?

So to recap, the PC talks to the CM106ESS board which handles the I/O for the drives, spindle and limit switches. The SureServo AC servo takes the Step & Direction pulses and closes the loop with the rotary encoder which is integral to the drive motor.
I have Newall microsyn 1micron linear scales on each of the 3 axes but these are currently unused.

The aim is to use the linear scales to overcome the backlash issues which limit the accuracy of the current setup, even though backlash compensation is enabled.

I've attached the manuals of the components mentioned above so you can see in more detail what I'm currently running. (note:- I can't include these here because they're too big for the Forum)

Ideally I'd just plug a board in place of the CM106ESS which would take the commands from Mach4 via Ethernet and allow me to connect the AC Servos via Step & Direction or Modbus as well as the Linear encoders to close the position loop.

Perhaps you can tell me if this is feasible and what I would need to buy to implement it."

I've been communicating with the suppliers of the Galil motion controller and that does look like they might be able to help, but it's mighty expensive. Their solution involves controlling the SureServo using +/-10V analogue signals so they can control each element of the control loop without the SureServo controlling the motor position. In other words, the SureServo would be a torque control system, with the position being controlled by the outer loop and the linear scales.

Any assistance would be greatly appreciated