Speed limitation close to software limit by traj planner

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15 Jan 2020 00:56 #154870 by Nico2017
Hi all,
I just want to confirm that the traj planner decreases the speed before reaching a software limit defined in the .ini file as Max or Min limits of a joint or axis. So if you jog manually towards a soft limit, it ramp down the vel cmd instead of going from the jog speed to 0 at the software limit location.

I did some test and it seems to be the case, the traj planner ramping down the speed, but I cannot remember why I use to think it was not the case. Maybe it was not the case in the past.

If someone could confirm this, that would be great.

Thank you

Nicolas

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15 Jan 2020 01:02 #154871 by Leon82
My speeds are about 110 or 120ipm in the ini and it always stops at .01 past the software limit's.

I haven't really tested it thoroughly, but I would assume it will use your acceleration setting to slow down at the limit

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15 Jan 2020 01:06 #154875 by andypugh
A keyboard jog is actually performed as a linear move to the soft limit.
Then, when you release, the move is aborted.

So the move will always stop smoothly and within limits at the soft limit.

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15 Jan 2020 01:14 #154877 by Shu

Leon82 wrote: My speeds are about 110 or 120ipm in the ini and it always stops at .01 past the software limit's.


I experienced that on some machines. If I remember correctly they were all closed loop. Are you running servos? A slight overshoot might be the culprit.

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15 Jan 2020 01:18 #154878 by Leon82
Steppers.

There is probably a parameter for acceptable overshoot. It has never gone past it.

Even in a fanuc you can set the distance past

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15 Jan 2020 04:18 #154888 by Nico2017
Hi,
I am using servos in position control so I would expect the machine to decelerate smoothly then get bang on the soft limit.

Thank you for your answers.
Nicolas

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23 Jan 2020 02:03 #155487 by Nico2017
Hi all,
regarding this topic,I obverse a different behaviour regarding if the motor is homed or not.
If it is homed, the axis min position limits the motion. If it is not homed, the joint min position does not seem to be effective.
Any idea why?

Thank you,
Nicolas

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23 Jan 2020 21:52 #155578 by tommylight
That is normal.
The machine should not be used without being homed first.
The following user(s) said Thank You: Nico2017

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23 Jan 2020 22:18 #155581 by Nico2017
Hi,
ok, that sounds perfectly normal. I am just wondering then why do you define min and max limit for the joints in the ini file?
Is it if the hard limit switch is triggered to get a value for the machine position, or is it for display reason of the machine limits in gremlin or axis?
Thank you,
Nicolas

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23 Jan 2020 22:51 #155589 by Leon82
The hard limits are to prevent machine damage from a faulty encoder or a large amount of lost steps or slippage of the coupling.

Ideally you would set them a little after home and min limit.

so in a perfect world you will never hit your hard limit switches only software limit

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