Inverse Kinematics with LBR4p robot.

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Alex
Posts: 6
Joined: 27 Aug 2013, 10:50

Inverse Kinematics with LBR4p robot.

Post by Alex » 04 Sep 2013, 21:03

Hello!
I just finished reading the IK tutorial and managed to run this with 7 DoF robot.
I tried to repeat all the things, that were in the tutorial with the LBR4p robot and it doesn't work.
Here my actions:

I deleted the script that written for the LBR4p, created the tip-dummy and attached it to link_8, created a target-dummy (at the same position as the tip) and set as a base the LBR4p (the first line in the ierarchy). Can anyone tell me, please where I'm wrong?

coppelia
Site Admin
Posts: 7324
Joined: 14 Dec 2012, 00:25

Re: Inverse Kinematics with LBR4p robot.

Post by coppelia » 06 Sep 2013, 10:17

Hello Alex,

It is difficult to analyze what you did wrong with this little information. If possible, post your scene via dropBox or google drive.

Cheers

Alex
Posts: 6
Joined: 27 Aug 2013, 10:50

Re: Inverse Kinematics with LBR4p robot.

Post by Alex » 06 Sep 2013, 17:00

Hello, here is the link to the file with scene
https://docs.google.com/file/d/0B_o3lW0 ... sp=sharing.
The IK is working but it seems very strange. The 7 DoF robot moving smoothly and LBR4p is vibrating all the time, besides
I can't move the target dummy in 3 dimensions simultaneously (I believe i must change something in properties, please tell me what).
Thanks a lot!

coppelia
Site Admin
Posts: 7324
Joined: 14 Dec 2012, 00:25

Re: Inverse Kinematics with LBR4p robot.

Post by coppelia » 06 Sep 2013, 22:59

Initially, your robot is in a singularity, i.e. a configuration at the border of what is reachable. That's why it is jumping around. Try setting the Calculation method to DLS, which is a damped resolution method. Then, you should not forget that your robot has joint limits, and that the IK module will not perform motion planning (motion planning for kinematic chains should be supported from V-REP 3.0.5 on), so it will always try to reach the target configuration directly. If that is not possible, it will behave in a funny way (e.g. jump).

To move an object along other axes, hold down the ctrl key while in the position/orientation manipulation mode.

Cheers

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