Help Needed: Cracking the Code on LinuxCNC Servo Homing Setup!

The final word from Delta on Gantry axis control.

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This gantry mode, intended for our EtherCAT controllers  did die.   However; they left some features in the drive that can help you accomplish this.
 
There is no substitute for the upper EtherCAT CNC control to have a gantry mode.  If the two controllers mentioned below don’t have a gantry mode, then you may be able to use some extra features in the B3A-E
(example part number for 400W, 220V ASD-B3A-0421-E) that can help. There can be two methods.

 

The B3A-E servo drive has “pulse train” mode.  Meaning when you use it, the drive is not in EtherCAT mode.  It can be set up to follow the encoder of
another drive – the slave of the gantry.  The position of the send drive can be monitored via EtherCAT and the other general operational status can be monitored via General Purpose I/O .If you can put both on the network, and use the control’s gantry mode, you can connect the encoder output of each into the other and EtherCAT can monitor
it.   

You may need to sacrifice (swap out) a PDO for this extra encoder into each of the gantry drives.Extra logic for the machine will need to be written to monitor for skew.It would be better to do this with Absolute encoders, correct skew on power up and make sure it does not go out of skew during operation.


 
Above is just an overview.  There is not white paper because the next step of control was supposed to be implemented in our EtherCAT controls, but never was. 

However, because the drive can be set-up to monitor and send the secondary pulse input over EtherCAT, it is possible for a third-party control to use it for gantry mode

I think the framework is already there in Linuxcnc but will need to be ported to the custom homing module
if home sequence < 0 then find the other joint(s) and home together.
Once both homed, if a home_offset exists, move each joint by the home offset

So if a gantry needs to be squared, the home_offset for each side will be different and account for the squaring.

I have not looked at the various homing modes again but it might be possible to do this internally by setting the parameters in the drive accordingly. without linuxcnc involvement.

 

Parts turned up on Friday and my homing lab is slowly taking shape. I just have to bolt the linear guide down.

 

I have a rtelligent closed loop ethercat stepper to mount up to this.
Then testing the custom homing module
 

Hi Paul,
I could not run with el8_homecomp. I can run with cia402_homecomp of rodw.
I tested with both Leadshine + JMC:
- Homing is ok. But speed is too fast.
- HM (homing mode): not switching to, and of course "opmode" is still 8
- I set homing velocity: 6099-01h and 6099-02h to reduce homing speed, but not effective