bubbleRob moving weird

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ssj
Posts: 12
Joined: 27 Feb 2017, 15:40

bubbleRob moving weird

Postby ssj » 27 Feb 2017, 17:43

hello

I m new to vrep. i have started with the tutorial bubbleRob. i ve followed the tutorial religiously. everything is working fine except bubbleRob. in any case it rotates and does not move straight . either i set velocity to one of the wheel or both.

coppelia
Site Admin
Posts: 5901
Joined: 14 Dec 2012, 00:25

Re: bubbleRob moving weird

Postby coppelia » 28 Feb 2017, 08:32

Hello,

can you post the scene? It will be easier to find out what is going on.

Cheers

ssj
Posts: 12
Joined: 27 Feb 2017, 15:40

Re: bubbleRob moving weird

Postby ssj » 27 Apr 2017, 08:31

hey i solved that. thanks.
i am try to build my own multi platform robot now. but whenever i start simulation it disintegrates into components. please help :(
how can i send you my scene file?

coppelia
Site Admin
Posts: 5901
Joined: 14 Dec 2012, 00:25

Re: bubbleRob moving weird

Postby coppelia » 28 Apr 2017, 07:49

Please post a link to a dropBox file (or similar).

If your robot desintegrates, it either has many self-collisions, or it is not build according to this page.

Cheers

ssj
Posts: 12
Joined: 27 Feb 2017, 15:40

Re: bubbleRob moving weird

Postby ssj » 28 Apr 2017, 09:17


coppelia
Site Admin
Posts: 5901
Joined: 14 Dec 2012, 00:25

Re: bubbleRob moving weird

Postby coppelia » 02 May 2017, 07:41

Looking at your model... your platforms are way too light (1 gram) (and have a too small inertia), compared with the wheels (1.23 Kg). Simply multiply the mass and inertia of those platforms by approximately 1000 and things will be much better.
Make sure to carefully read this page when designing dynamic simulations.

Cheers

ssj
Posts: 12
Joined: 27 Feb 2017, 15:40

Re: bubbleRob moving weird

Postby ssj » 12 May 2017, 08:04

Thank you for your response. I ve tried to manage the weight of robot platform and wheels. it is relatively stable now. but when i start simulation, wheels rotate but the body does not move forward. additionally it tilts towards one side. please help.
here is the link of my file https://drive.google.com/open?id=0B6Fmg ... 3ZGQTEtMDA

coppelia
Site Admin
Posts: 5901
Joined: 14 Dec 2012, 00:25

Re: bubbleRob moving weird

Postby coppelia » 15 May 2017, 15:25

This is perfectly normal: you have two wheels (left and right) and two contact points (front and back). So you basically have 4 contact points and you have a hyperstatic situation. On top of that you managed to place the 4 items (2 wheels and 2 spheres) so that their contact with the floor does not lie on one plane.

You have two possibilities:

  • Move one of the spheres slightly up, so that the two wheels touch the floor at all times. YOu will then have some slight tilting from back to front.
  • The better solution is to perform above point 1, and to attach one of the spheres to a spring-damper. This way you won't have a hyperstatic situation anymore.

Cheers

ssj
Posts: 12
Joined: 27 Feb 2017, 15:40

Re: bubbleRob moving weird

Postby ssj » 16 May 2017, 06:20

hey it works. Thanks.
now I have attached another base above the existing base using 4 joint between them. unfortunately when i start simulation, the upper layer falls down on the lower layer :( moreover the icons appear against these 4 joints, showing message that joints are not dynamically enabled.
what should i do?

coppelia
Site Admin
Posts: 5901
Joined: 14 Dec 2012, 00:25

Re: bubbleRob moving weird

Postby coppelia » 20 May 2017, 05:36

Please post your scene.

Cheers


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