Help getting carousel to continue rotation after encoder position reached

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27 Aug 2023 20:13 #279113 by kinghpole
Hi I’m trying to get the tool turret of an Emco PC Turn 120 working using the carousel component the PC Turn 120 uses from I can tell a fairly unique "encoder" to measure the turret position it uses a ring with a 90 degree cut out that rotates through 4 optical limit switches measure the position of the turret I've attach a picture to help visualize it. I set up a carousel instance to read the encoder as a binary encoder and then use the remap to convert the called pocket to the binary value for the encoder to have carousel rotate to. The problem I'm running into is to lock the turret it needs to rotate slightly past when the encoder reads its in the correct position and then rotate back to engage the ratchet type locking mechanism. I’m currently looking for a way to get carousel to do that. I'd appreciate any insights into the problem and help with fixing it thanks.
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28 Aug 2023 13:28 #279169 by andypugh
Which version of linuxCNC are you using?
The latest version of carousel (in the pre-release 2.9 version) has some extra pins:
carousel.N.align-dc float in
Use this pin to set the speed of a slower alignment move once the changer is in position. Such a system almost certainly needs decel-time setting too
carousel.N.decel-time float in
Time to wait for carousel to stop before final alignment and position check

These might help.

If you are running the 2.8 version then you can download the carousel.comp file from 2.9 and compile/install it with the "halcompile" utility.

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28 Aug 2023 18:30 #279191 by kinghpole
I'm using version 2.9.0~pre1. I tried changing the carousel.N.decel-time but didn't see any change in operation could you possibly explain how to use those pins?

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28 Aug 2023 20:38 - 28 Aug 2023 20:38 #279207 by andypugh
Looking at the code, I think I see two possible ways to do this:

github.com/LinuxCNC/linuxcnc/blob/master...s/carousel.comp#L391

If either will work will depend on how you are controlling the motor. If you are only using motor_vel and ignoring motor-fwd and motor-rev then setting a timed reverse pulse with a _forward_ duty cycle might do the trick.
However you do need a reverse pulse with your changer, so then it is a question of whether the hold-dc will do that part.

The other option seems to be to have a very long debounce time.
Last edit: 28 Aug 2023 20:38 by andypugh.

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30 Aug 2023 04:17 #279343 by kinghpole
Trying to change the debounce time, I got an error saying the parameter was not editable. After that, I looked at the .comp file and realized adding a new forward pulse pin and having it trigger before the reverse pulse was achievable so I recompiled the .so file with a forward pulse and now it works.

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30 Aug 2023 08:52 - 30 Aug 2023 08:58 #279356 by andypugh

Trying to change the debounce time, I got an error saying the parameter was not editable.


It should be a read/write parameter that can be "setp" in the HAL file:

param rw unsigned debounce "How many thread cycles to wait for the position to stabilise";


Glad you got it working, but I would have preferred to find an answer that works for everyone. 
 

(edit) Though mis-using the debounce probably isn't a great solution
Last edit: 30 Aug 2023 08:58 by andypugh.

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31 Aug 2023 00:21 #279426 by kinghpole
Debounce was not editable for me it gave me an error when I tried to change it in the halfile. This is probably not the place to make a feature request, but having a forward pulse would be really useful for any ratcheting tool turrets that use an encoder that has the same resolution as positions.

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