Achieving CSP with Target Position & Torque Offset via Python API

jsh

Hello,

I am currently working on controlling a single-axis motor using the Python API based on the MachineControl app.

So far, I have successfully implemented control through the following paths:

root/MachineControl/hostInJointAdditivePosition1/ch0
root/SetpointGenerators/SetpointGenerator01/input

However, I have encountered a limitation with these modes: they only allow providing a pure Target Position and do not support sending a Target Torque Offset command simultaneously. My ultimate goal is to achieve CSP (Cyclic Synchronous Position) control by providing both Target Position and Target Torque Offset at the same time.

I attempted to write values directly to the parameters in AxesControl, but I found that the path axesPositionsInput/ch0 is read-only and does not accept input values.

Could you please provide guidance on the following:

Which specific path(s) should I use in AxesControl to input both the Target Position and Target Torque Offset simultaneously?

What are the prerequisite settings required to activate and use the AxesControl mode? Specifically, are there mandatory configurations for Jog mode, Pause mode, or PVA limits that must be initialized beforehand?

I would appreciate any insights or documentation regarding the correct variable paths and the required state machine transitions for this specific control mode.

Thank you in advance for your help.

Philippe

Hi,
I am assuming that you are using the Machine App configuration as an example for your own configuration.
In your case you may not want to use the Machine Control module at all. In config.json you can disable the module:

  "MachineControl": {
    "Enable": false,

Then there also will be no links created towards the AxesControl Module, so you should be able to stream your setpoints there directly:

root/AxesControl/axesPositionsInput
root/AxesControl/axesTorquesInput

If the drive is in CSP mode, the axesTorqueInput is routed to the motorTorqueOffsetTarget (which should be linked to the drive torque input). Adjust the torqueOffsetTransformation parameters to convert between ENgineering units (Nm) to torque in ticks (or whatever the drive expects).

If you use the drives in Torque Mode (CST) the axesTorqueInput is added to the outputs of the Velocity Controller and Position Controller blocks and then routed to motorTorqueTarget. So then you can close the loop on the Motorcortex side and bypass the drive's velocity and position controller.

There may be some issues when Logic cannot switch modes, because there is no Machine Control any more. Let me know if you see warnings or errors in the logs, so we can figure out a way around this.

Good luck.