Feature Request: Add a separate variable for the back-off distance after sensorless homing

[nielsvz]

Sensorless homing is a bit tricky with high current low impedance motors (LDO 2804AH). I find they're most reliable when using the following steps, per axis:

1. Lower the run_current to the home_current
2. Home the axis
3. Back off 5mm
4. Raise the run_current back to the configured value
5. Back off the axis to a minimum of 0.5-1.0x the rotation distance (20-40mm in my case)

It would be nice if the good sensorless feature had an additional setting, such as sensorless_minimum_dist, that value could be compared to the distance moved as well (currently using homing_retract_dist).

Homing would then follow this process, per axis:

1. Lower the run_current to the home_current
2. Home the axis
3. Back off by homing_retract_dist
4. Raise the run_current back to the configured value
5. Back off the axis to the endstop position minus sensorless_minimum_dist
6. Check if the distance moved is at least sensorless_minimum_dist and re-home if required

[numanair]

Duplicate of #86? #78

[nielsvz]

I believe the difference between this and #78 (I think you meant that issue?) is that this request doesn't change the homing process, but it would add a second variable to distinguish between the backoff distance (homing retract) and the minimum distance required to reliably home with sensorless.

[numanair]

Yep, mixed up my tabs, thanks!

It sounds like they are achieving the same goal, but I like the additional flexibility of this one.

[lraithel15133]

I believe the difference between this and #78 (I think you meant that issue?) is that this request doesn't change the homing process, but it would add a second variable to distinguish between the backoff distance (homing retract) and the minimum distance required to reliably home with sensorless.

#78 is mostly asking for built-in checks for sensorless homing failures. Seems you just want a separate configurable variable for minimum homing distance. I think this would be an easy change. Make it default to retract distance, but make it configurable

[nielsvz]

#78 is mostly asking for built-in checks for sensorless homing failures. Seems you just want a separate configurable variable for minimum homing distance. I think this would be an easy change. Make it default to retract distance, but make it configurable

Correct, without a minimum distance I find sometimes it doesn't trigger at all.

[bwnance]

@nielsvz is the problem that if you set the retract distance to 20-40, it backs off too much after a successful home? because other than that, it should result in the behavior you want

[bwnance]

#90 will resolve this

[rogerlz]

#90 has been merged now