Robot IK mode problem

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sumi_boss
Posts: 33
Joined: 21 Sep 2020, 11:44

Robot IK mode problem

Post by sumi_boss »

Hello Coppelia

I have a UR5 robot in my scene, attached to a cuboid. I want to control it in IK mode. I made the tip and target dummies, added the tip/target link, the Ik group everything as you explained. All the joints are in inverse kinematics mode, with hybrid operation checked as well. I added a third dummy, the desired position of the robot tip. I wanted to programmatically make a path to that desired position. The sim.followPath is called from a threaded child script of the UR5. So, as the simulation starts a path is created from the target dummy to the desired position dummy. The path is visible as a red line. However, as soon as the simulation starts, the robot starts behaving unexpectedly. Its moves are very jerky and unnatural and it does not follow the path at all. It doesn't even matter where the desired position dummy is placed, the robot behaves in the same way. I even tried putting the desired position very close to the tip, where it can certainly be reached, but the same thing happened.

Do you have any idea as to why this is happening and how I could find the error and fix it?
Thanks in advance
Cheers

coppelia
Site Admin
Posts: 8446
Joined: 14 Dec 2012, 00:25

Re: Robot IK mode problem

Post by coppelia »

Hello,

please post a minimalistic version of your scene that illustrates the problem.

Cheers

hajs
Posts: 5
Joined: 20 Nov 2019, 10:18

Re: Robot IK mode problem

Post by hajs »

Hey
'
I read your query. I was facing almost the same issue in my project. I thought there are possibly two issues:

For making it follow your designed path, You should work on your scripts, extract angle positions from IK mode and put those angle positions in your programming code.
Read vrep user manual Ik tutorial 2-3 times thoroughly. and yes, posting your scene will clear if this is the problem.
Regards

sumi_boss
Posts: 33
Joined: 21 Sep 2020, 11:44

Re: Robot IK mode problem

Post by sumi_boss »

Hello,

The is the Google drive link to the folder with the scene.
https://drive.google.com/drive/folders/ ... sp=sharing

The robot in question is the 'UR5#1'

Cheers

coppelia
Site Admin
Posts: 8446
Joined: 14 Dec 2012, 00:25

Re: Robot IK mode problem

Post by coppelia »

I don't have access to the file...

Cheers

sumi_boss
Posts: 33
Joined: 21 Sep 2020, 11:44

Re: Robot IK mode problem

Post by sumi_boss »

Here is the github link, the file is dualArmUR5ver2

https://github.com/sumiboss95/coppelia

coppelia
Site Admin
Posts: 8446
Joined: 14 Dec 2012, 00:25

Re: Robot IK mode problem

Post by coppelia »

Your arm is in a singular configuration... it is fully extended and this makes IK unstable. Select a damped resolution method for your IK.

Cheers

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