Parallel robot - IK mode

Typically: "How do I... ", "How can I... " questions
Post Reply
fede
Posts: 2
Joined: 11 Sep 2019, 13:36

Parallel robot - IK mode

Post by fede » 16 Sep 2019, 22:22

Hi there!
We are two italian guys trying to create a movimentation of a parallel robot.
We understand that we have to use IK mode but we don't know how to set it up correctly.
Our robot is similar to the irb360 that is already built in V-REP.
In our robot thanks to the three actuators the platform can translate remaning parallel to the floor.

If someone can help us with IK mode we will be very happy.

We leave our scene!
Feel free to say anything about our robot...be gentle we are only beginners :)

https://drive.google.com/file/d/1ashn6t ... sp=sharing

We leave also the video of the real robot moving in our LAB.

https://drive.google.com/file/d/1a_TI1f ... sp=sharing

coppelia
Site Admin
Posts: 7330
Joined: 14 Dec 2012, 00:25

Re: Parallel robot - IK mode

Post by coppelia » 18 Sep 2019, 06:10

Hello,

how you build the kinematics of your robot will depend how you want to operate it. If you want to operate it in IK mode, then this is pretty straightforward: you simply need to have 3 branches that link together at the platform. So each branch should be:

Code: Select all

prismaticJoint --> sphericalJoint --> revoluteJoint --> revoluteJoint --> tipDummy
and you would have the platform with:

Code: Select all

platform --> targetDummy1
         --> targetDummy2
         --> targetDummy3
If you want to operate the robot in FK, or in FK & IK, then it becomes more complicted, since you would need something like:

Code: Select all

base --> branch1 --> platform --> invertedBranch2 --> tipDummy2
                              --> invertedBranch3 --> tipDummy3
     --> targetDummy2
     --> targetDummy3
Have a look at the various simple examples in scenes/ik_fk_simple_examples

Cheers

fede
Posts: 2
Joined: 11 Sep 2019, 13:36

Re: Parallel robot - IK mode

Post by fede » 18 Sep 2019, 15:46

Thank you very much! Now our robot moves correcly!
Just one more question: how can we avoid this type of collision(photo)?
https://drive.google.com/file/d/1skSg8Y ... sp=sharing

Thank you again :)

coppelia
Site Admin
Posts: 7330
Joined: 14 Dec 2012, 00:25

Re: Parallel robot - IK mode

Post by coppelia » 19 Sep 2019, 08:40

this collision happens because the red joint's range is not large enough. You can detect this if one of the joints is very close to its limit. Or when IK doesn't fulfill precision requirements.
If your IK group doesn't fulfill precision requirements, you can configure your IK group to revert to the configuration prior to calculations.
If you flag your IK group as explicit handling, and call sim.handleIkGroup upon it on a regular basis, then the return value of that function will tell you whether IK was successful or not. Then you could react differently based on that.

Cheers

Post Reply