[LinuxCNC/linuxcnc Issue#45] ja: Command isn’t tracking feedback in machine-off About GRBL HAL

Issue #45 | 状态: 已关闭 | 作者: samcoinc | 创建时间: 2016-03-10

Here are the steps I follow to reproduce the issue:

1.On a servo machine with encoder feedback – after machine is up / homed
2.Toggle machine back off
3.Physically move axis
5.Toggle machine back on
6.You instantly get a following air for that axis and machine powers back off.
7.Currently no way to fix this state

On sim
1.Power up and home
2.Open halcmd
3.unlink joint.0.motor-pos.fb
4.setp joint.0.motor-pos-fb 5
5.Toggle machine back on.
6.At this point – fb should equal commanded.. It doesn’t and you get a following error.

This is what I expected to happen:

The machine should turn on and the fb should equal cmd position

This is what happened instead:

Following error

It worked properly before this:

If you do the exact same sequence in 2.7 – when you toggle power on – the machine turns on as expected.

#1 – samcoinc 于 2016-03-10

Ok – so the above directions seem to not work 100% of the time. What does seem to work 100% of the time is
1. power up – home machine
2. open halcmd
3. unlink joint.0.motor-pos-fb
4. jog X axis -> get a following error
5. toggle machine on. – > following error -> machine turns off.

#2 – jepler 于 2016-03-11

I think another connected issue is how ja doesn’t update cartesian feedback position from joint feedback position while in “machine off” mode.
1. power on, home all, machine off
2. open halcmd
3. unlink joint.0.motor-pos-fb
4. setp joint.0.motor-pos-fb various values

Steps 3/4 are emulating the case where you have a servo machine where you can turn the motor shafts with the amplifiers off, or if you have a nice big machine where the Z axis droops measurably with amplifiers off.

Expected: cartesian feedback position tracks changes in joint feedback, as it does in 2.7

I think that if this cartesian-tracks-joints behavior were happening, then the fix at 3cd7b92 would not be needed (but is probably harmless)

#3 – jepler 于 2016-03-15

I tested at the tip of ja12 and the steps I described in my previous comment now work as I expect. @samcoinc also says things are better for him.

原始Issue: https://github.com/LinuxCNC/linuxcnc/issues/45

Here are the steps I follow to reproduce the issue:

This is what I expected to happen:

This is what happened instead:

It worked properly before this:

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