CNC AXIS IN PARKING MODE

Good morning everyone.
I need to replace an old Siemens CNC.
I'd like to try Linux CNC, but the machine is a boring machine with a Z-axis that can be controlled manually or via CNC.
Let me explain. The Z-axis performs normal axis reference and moves in jog+ and jog- directions, with the position controlled by an optical scale.
However, the operator can press a mechanical selector, which allows the axis to be moved with a mechanical handwheel and, when desired, re-engage the axis in the CNC.
Clearly, the current CNC disables the axis drive when the mechanical handwheel is selected.
The axis on the current CNC goes into park mode, meaning the commanded position follows the feedback position, and when the mechanical handwheel is disengaged, the CNC does not enter a following error.
With Linux CNC, I could disable the drive and move the axis with the mechanical handwheel, but as soon as I disable the handwheel and enable the drive again, the CNC displays the following error because the commanded position doesn't follow the feedback position.

Is there a way to mimic the behavior of the Siemens CNC?

Thanks for support

Just to come up with something, doesn't necessarily mean it is practical
- set f-error-limit to a lot
- get feedback position
- fast forward to feedback position (servo off)
- reset f-error-lim and re-engage the servo
Maybe this can be done in a g-code macro.

You should be able to create  component that sets feedback = commanded pos when the handwheel is engaged. the cia402 component does this...

Thanks for the replies.
The solution of increasing the tracking value and resetting the axis is impractical and technically incorrect.

The servos are analog and controlled by Mesa boards.
Isn't there a component that creates the command position = position read by the transducer?
Or is there a way to modify the Trivkins kinematics?

Isn't there a component that creates the command position = position read by the transducer?

LinuxCNC does this (sets commanded position to actual position) when motion is disabled, but it's global (all joints)
It might require a modification of LinuxCNCs motion component to do this correctly on a joint by joint basis

Try the attached component

Untested. Probably has some typos but the logic should be sound.

Ooops, I did not set  pos_cmd_out but its not needed and could be removed from the component

You don't need a new component for connecting commanded to feedback position
when the joint is disengaged, and the mux component can already do this function.

That is not the tricky part anyway, the tricky part is returning to LinuxCNC control after
the hand motions  were completed.

Ideally there would be a per joint enable signal (that forced LinuxCNCs internal commanded
position to track the feedback position when disabled) but lacking that, a simple hal profile
generator (using limit3 for example) could be enabled to move to the original position
before control is handed back to LinuxCNC.

Good morning everyone and thanks for the replies.
It's clearly a machine axis, the Z axis.
The machine is old, and in some operations, it's more convenient to be able to drill manually. We're talking about a machine that works with enormous cast iron bases, 10 meters long, so it must have maximum flexibility.

Rown, basically, using your component, I would have:
net Zenable joint.2.amp-enable-out pid.2.enable isfreewheeling
net Zpos-cmd joint.2.motor-pos-cmd pid.2.command
net Zpos-fb joint.2.motor-pos-fb pid.2.feedback

But I don't understand where to connect: pos_fb_out

papagno-source wrote:

But I don't understand where to connect: pos_fb_out

Looks like from your hal it should be connected to pid.2.feedback You want the component to sit between the motor feedback and the pid

As far as the enable input, I wasn't sure. I thought it might be connected to a button on your GUI.

Another left field but more work idea would be to add a 100 ppr MPG wheel and manually jog the axis by hand. There are hale examples in the docs