set redundancy information for LBR IIWA

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OliRMD
Posts: 5
Joined: 17 Jul 2018, 07:51

set redundancy information for LBR IIWA

Post by OliRMD » 27 Jul 2018, 12:43

Hello !

Does anyone here know a simple way to set the redundancy information for a redundant robot like LBR IIWA ?
My goal is to be able to set the elbow angle of the robot while maintining the endPoint in both position and orientation.
For exemple : robot goes to desired frame, then we change the elbow angle and a new motion is launched : the redundant motion.

Any ideas on how to do it in V-REP ?
I already looked into the motions methods, but they don't seems to be fine for that type of motion :
- sim.setJointTargetPosition()
- simSetJointPosition ()
- simRMLPos()
- simRMLMoveToJointPositions()

Thanks in advance,
OliRMD,

coppelia
Site Admin
Posts: 6736
Joined: 14 Dec 2012, 00:25

Re: set redundancy information for LBR IIWA

Post by coppelia » 27 Jul 2018, 14:18

Hello,

if I understood you correctly, you want to lock one of the joints, for the second part of the movement?
In that case you can use sim.setJointMode to temporarily switch to a passive joint mode.

Cheers

OliRMD
Posts: 5
Joined: 17 Jul 2018, 07:51

Re: set redundancy information for LBR IIWA

Post by OliRMD » 30 Jul 2018, 07:43

Hello coppelia,

The action i'm searching is to block the endPoint in position and orientation to re-create the redundancy motion of the LBR-iiwa. Here a video of what i want. Indeed i want to lock a joint (the number 3, corresponding to the elbow angle) while the others ones use IK to realised the motion. Or mostly, i want to make others joints dependent of the n°3 while keeping the current position and orientation at the endPoint.
https://www.youtube.com/watch?v=sZYBC8Lrmdo

Is it possible to do it in V-REP ?

Thanks in advance,
OliRMD,

coppelia
Site Admin
Posts: 6736
Joined: 14 Dec 2012, 00:25

Re: set redundancy information for LBR IIWA

Post by coppelia » 31 Jul 2018, 06:05

The motion showed in the video can easily be performed in a similar way as previously explained:

Imagine your robot end-effector has the desired position and orientation. Then, keep the IK target in place, and set the first joint in your robot in passive mode. If the IK group for the robot is handled now, the robot should not move. Next, increment the angular position of your first joint (the one that is now passive) by, e.g. 1 degree. Handling the IK group for the robot now, the first joint won't move, but all the other joints will appropriately adjust so that the end-effector remains in place and orientation.

Putting above in a loop, then you will have the same type of motion as in the video.

Cheers

OliRMD
Posts: 5
Joined: 17 Jul 2018, 07:51

Re: set redundancy information for LBR IIWA

Post by OliRMD » 31 Jul 2018, 09:17

Hello coppelia,

It worked perfectly ! Thanks a lot !

Have a good day,
OliRMD,

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