Inverse kinematics not working for very simple robot

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gerosa
Posts: 3
Joined: 15 Nov 2016, 16:22

Inverse kinematics not working for very simple robot

Post by gerosa »

Hi to all,

For some reason a very simple model is not working for my very simple model.

I did the tutorial for the inverse kinematics and work flawlessly but now that I do it on my own on a very simple model it does not.

It is not dynamical, just kinematics, all built but it is not moving according to the target, not following.

Can you provide some help ?

This is the link to my scene. https://www.dropbox.com/s/eq2r2j78atvbo ... e.ttt?dl=0

Thanks in advance.

coppelia
Site Admin
Posts: 10339
Joined: 14 Dec 2012, 00:25

Re: Inverse kinematics not working for very simple robot

Post by coppelia »

Hello,

you have two problems:
  • You have a 2 DoF mechanism, but try to apply 6 constraints to it. Solution: make sure your IK element has only following constraints enabled: X and Z
  • You have your mechanism initially in a singular configuration. IK doesn't like that. Solution: either select a damped resolution method, or move a little bit away from the singularity (by initially setting the second joint angle to a small angle for instance)
Cheers

gerosa
Posts: 3
Joined: 15 Nov 2016, 16:22

Re: Inverse kinematics not working for very simple robot

Post by gerosa »

Thank you for your reply. I will try to do that.

I also found a solution myself and fits exactly with the solution proposed.

What I did was adding another joint at the base that is perpendicular to the other two. This make it work but with the condition of not moving in a different plane of the planar robot so it keeps on 0 degrees.

I will try your solution.

Best,

Juan

david07
Posts: 6
Joined: 22 Feb 2017, 14:43

Re: Inverse kinematics not working for very simple robot

Post by david07 »

Hello,

It can happen with imported robot from the library, that the joints are not in inverse kinematic mode :) It took me for a while to discover.

Regards,
david

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