Movement along path supported by rotary tilting table

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tumsimon
Posts: 8
Joined: 17 Jul 2014, 11:28

Movement along path supported by rotary tilting table

Post by tumsimon » 24 Sep 2014, 12:05

Hi coppelia,

the problem I am facing is the following: I have a robot which is following a defined path via IK at the moment. I connected that path to the rotary tilting table which is positioned in front of the robot. So when the table moves, the path will move as well.
Now what I want to achieve is, that the movement of the table "supports" the robot. When it's easier for the table to just turn by 180 degrees instead of the robot moving a long way, that should happen.For example, if the path is a circle on the surface of the table, it's probably easier for the table to turn one joint by 360 degrees instead of the robot moving lots of joints.
I imagine it kind of like in this video: https://www.youtube.com/watch?v=ar14v7P16zA

Is that in any way possible and if yes, how would I start?

Thank you very much for your help!

Cheers, Simon

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

Re: Movement along path supported by rotary tilting table

Post by coppelia » 24 Sep 2014, 12:41

Hello Simon,

if I understood you correctly, you can do following:

Build your set-up in order to have your welding part not mobile. Then, configure the base of the part in order to have V-REP think it is part of the robot (i.e. this will effectively add additional DoFs to your robot (the welding part orientation joints will be seens as part of the kinematic chain of your robot)).
Then, mount the camera to the intermediate base of the robot (i.e. its real base) so that the robot's base appears as immobile.
You can also use a similar approach when doing motion planning.

What you now have:

Code: Select all

world --> robot
      --> revoluteJoint --> weldingPart
And what you should do:

Code: Select all

world --> weldingPart --> revoluteJoint --> robot
i.e.:

Code: Select all

world --> weldingPart --> revoluteJoint --> robotBase --> robotJoint1 --> link1 --> robotJoint2 --> link2 --> ...
Be aware that the revoluteJoint object in above example will have to be built upside-down, and be controlled in opposite direction.

Cheers

tumsimon
Posts: 8
Joined: 17 Jul 2014, 11:28

Re: Movement along path supported by rotary tilting table

Post by tumsimon » 25 Sep 2014, 13:19

Hi coppelia,

thanks for the suggestions. I think I need some more explanations though:)
Build your set-up in order to have your welding part not mobile.
I don't really have a welding part, it's just a path, as in here: viewtopic.php?f=9&t=1747&p=6919&hilit=m ... path#p6913
Does that make a difference? How can I make it not mobile?
Then, configure the base of the part in order to have V-REP think it is part of the robot (i.e. this will effectively add additional DoFs to your robot (the welding part orientation joints will be seens as part of the kinematic chain of your robot)).
To do that, is it enough to put all of the parts in one tree in the scene hierarchy? Is that what you mean by
world --> weldingPart --> revoluteJoint --> robotBase --> robotJoint1 --> link1 --> robotJoint2 --> link2 --> ...
Then, mount the camera to the intermediate base of the robot (i.e. its real base) so that the robot's base appears as immobile.
To do that, I chose the base of the robot and then go add->camera, right? Is the point of view then from the base of the robot and can I not see the rest of the scene from an external observer's point of view? Will the real base move from an external point of view?
Be aware that the revoluteJoint object in above example will have to be built upside-down, and be controlled in opposite direction.
What you call revoluteJoint (my table) is actually more than just one joint. How can I build that upside down? If you want to take a look at the scene, it's uploaded here https://www.dropbox.com/s/1d0mqnkr22lz9 ... _.ttt?dl=0

I am so sorry for all those questions, for me as a student who's never really worked with anything similar to this, it's hard to implement all instructions and make this work. Thank you!

Cheers, Simon

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

Re: Movement along path supported by rotary tilting table

Post by coppelia » 25 Sep 2014, 16:14

See this corrected scene. You will however have to install a newer V-REP version. The beta version of V-REP 3.1.3 can be found here.

Cheers

tumsimon
Posts: 8
Joined: 17 Jul 2014, 11:28

Re: Movement along path supported by rotary tilting table

Post by tumsimon » 29 Sep 2014, 01:08

Thanks so much for your help! You really helped me out on this one. I appreciate your effort a lot!

Cheers, Simon

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