Bot moves on its own when I start simulation

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shreyas7738
Posts: 19
Joined: 30 Dec 2020, 15:32

Quadruped model moves irregularly when I start simulation

Post by shreyas7738 »

Hello!I have created a quadruped model in fusion 360 and exported it with fusion2urdf.I set the joint in control loop mode.I added a child script and set the angles to all the revolute joint to 0 rad.But when I play the simulation,the bot behaves anyhow.THe angle seems to works but the bot falls down.I have attached the here here.
https://drive.google.com/file/d/1HlFVn6 ... sp=sharing

shreyas7738
Posts: 19
Joined: 30 Dec 2020, 15:32

Bot moves on its own when I start simulation

Post by shreyas7738 »

I got this cad model from grabcad and converted it to urdf.For the quadruped,I enabled control loop for all the revolute joints and added a child script.I set all joints to 0 using sim.setJointTargetPosition.When I press play,I expect the bot to hold the current position but it start moving on its own and the joints move differently on their own.I am attaching the scene here.It would really help me if someone can explain me why it happens and a possible solution.

https://drive.google.com/file/d/1qD6sZS ... sp=sharing


shreyas7738
Posts: 19
Joined: 30 Dec 2020, 15:32

Re: Bot moves on its own when I start simulation

Post by shreyas7738 »

I fixed it by changing physics engine to Newton instead of pybullet.

fferri
Posts: 1193
Joined: 09 Sep 2013, 19:28

Re: Bot moves on its own when I start simulation

Post by fferri »

Newton is generally more stable (in terms of the simulation performing as expected).

But by following the recommendations in the tutorial, it is possible to make the model stable with any engine.

coppelia
Site Admin
Posts: 10339
Joined: 14 Dec 2012, 00:25

Re: Bot moves on its own when I start simulation

Post by coppelia »

Hello,

simply increase the mass and inertia of the various dynamics elements. Then it will hold its position with any physics engine. Make sure to carefully read this page, mainly the design considerations 7 & 8.

Cheers

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