Unstable robot at simulation start

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paps1992
Posts: 2
Joined: 01 Dec 2017, 13:35
Location: Netherlands

Unstable robot at simulation start

Post by paps1992 » 06 Dec 2017, 12:04

Hi

I am new to V-REP and I am trying to build a robotic arm with 4 links. I import primitive shapes which are of STL type. I want to control the arm through MATLAB where I design my workspace controller (torque control). Having read through the design procedure and built the arm I am facing few problem. As soon as I start the simulation, the robot starts falling down (MATLAB not connected yet). I am not able to reason out as to why. I guess it is not because of the gravity as all the the links and joints are aligned properly.
Can any of you please help me out with this regard?

e2718
Posts: 33
Joined: 15 Nov 2015, 05:39

Re: Unstable robot at simulation start

Post by e2718 » 06 Dec 2017, 20:21

Could you be more specific on what you mean by falling down? If by falling down you mean falling through the simulation floor, it's might be because the body is not respondable (in the dynamic properties of an object). If by falling down you mean the robot is falling over, it might be because the body is dynamic (in the dynamic properties log of an object). Also if you're still stuck, there's example scenes in V-REP of moving robotic arms (motionPlanningAndGraspingDemo.ttt, forwardAndInverseKinematics1.ttt, and others). So you could check out those examples and see where your model is different. Hope this helps.

paps1992
Posts: 2
Joined: 01 Dec 2017, 13:35
Location: Netherlands

Re: Unstable robot at simulation start

Post by paps1992 » 07 Dec 2017, 14:07

HI

Thanks for the quick reply. The robot is falling over and not falling down (my mistake). I have gone through the tutorials and I am not able to see where I am going wrong. i am attaching the V-REp scene along with this post. Can you go through it and help me find my mistake?

PS : i am trying to give torque commands from MATLAB.

https://www.dropbox.com/s/eaf6x0env8afk ... F.ttt?dl=0

coppelia
Site Admin
Posts: 6612
Joined: 14 Dec 2012, 00:25

Re: Unstable robot at simulation start

Post by coppelia » 10 Dec 2017, 21:31

Hello,

you seem to have extremely large inertia values for your different robot links. Try reducing them. Then, you will of course also have to adjust the force/torque for each joints, and their target velocity (which is the upper limit velocity your joint can accelerate to).

Cheers

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