help to set up the kinematics

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26 Jul 2011 19:50 #11881 by step4linux
andypugh wrote:

honey wrote:

"jointN following error". What means this?

This means that the axis in question can't keep up with the requested motion. With a stepper based system like yours it means that the stepgen can't move fast enough to keep up with the required speed (or that the stepgen isn't even enabled).

I believe for a non-trivial kinematic, a calculating problem in the kinematic modul can also cause a following error.
I find remarkable that all (?) joints are moving correctly (no errors?) in joint mode.
It makes me thinking that stepgen is working, motion is enabled, and the problem is solely in the kinematic, like Andy said

that the kinematics module couldn't find a solution to the requested movement commands


Gerd

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27 Jul 2011 08:11 #11908 by honey
Replied by honey on topic help to set up the kinematics
step4linux wrote:

I find remarkable that all (?) joints are moving correctly (no errors?) in joint mode.
It makes me thinking that stepgen is working, motion is enabled, and the problem is solely in the kinematic, like Andy said
Gerd


When I used Joint mode i haven't error in manual control. You say right...maybe the problem is the kinematics. I try to use dmesg when Emc2 run and i have only this message:

[ 1477.548560] ERR kI - compute_jinv (joints: %f %f %f %f %f %f), (iterations=0)

It is sure somethig about kinematics...but what?

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27 Jul 2011 08:20 #11909 by PKM
Replied by PKM on topic help to set up the kinematics
I guess that's about wrong kinematic parameters. Check it once more. Do you have a kinematic scheme for the robot, with DH parameters for each joint?

By the way, if you have kinematic relations for the robot, you could write your own kinematics file instead of using genserkins (but the inverse kinematics might be a problem).

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27 Jul 2011 09:19 #11911 by andypugh
honey wrote:

[ 1477.548560] ERR kI - compute_jinv (joints: %f %f %f %f %f %f), (iterations=0)
It is sure somethig about kinematics...but what?

I think it is saying that it can't compute the Inverse Jacobian for your current joint positions to solve into XYZ.
Are you sure that you have the D-H parameters correct for your robot?

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27 Jul 2011 10:18 #11913 by step4linux
I would try to find a set of correct parameters or an example somewhere, just to prove that everything else is OK.
Then honey, you can modify it, step by step.
Just make sure motors are not powered for this test.

Gerd

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27 Jul 2011 11:53 #11916 by honey
Replied by honey on topic help to set up the kinematics
andypugh wrote:
Are you sure that you have the D-H parameters correct for your robot?[/quote]

I think yes. My robot is very similar to Puma, i have changed A and D with the value of my robot. I have seen many documents about this.
I think that the problem is genserkins because i have made an experiment. I have used pumakins module (with puma parameters). The robot works in world mode (not so well really, there are following error yet but at least it moves! :) )

So, I could use pumakins for kinematics but i don't understand why there are this default values of A e D in pumakins.h:

DEFAULT_PUMA560_A2 300.0
DEFAULT_PUMA560_A3 50.0
DEFAULT_PUMA560_D3 70.0
DEFAULT_PUMA560_D4 400.0

are strange values for me. The A and D values of puma in genserkins are clear for me but not these!! why these are different?

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29 May 2017 05:40 - 29 May 2017 05:44 #93769 by Jozo132
Kinda late, but did you try using DEG or RAD for alpha values?
As the type of value could play a role.
(I'm new here)

edit: I suppose you did and I didn't research enough yet
Last edit: 29 May 2017 05:44 by Jozo132. Reason: New here and reading too fast

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