CoppeliaSim forums

Hello,

Again I'm trying to design a dynamic simulation for our robot, starting from the most complex part which is the tracked flipper-bogie-flipper body.

I believe I followed the recommendations for designing a dynamics simulation and here's the model tree during the simulation:



it consists only of pure non-static shapes. I carefully created and placed every shape/joint numerically, following a reference cad design. Every joint is revolute.

This is the model at design time:



Wheels weigh from 0.09 (smallest) to 3.7 (largest) and have the same density.

However, at simulation time, the links and/or the joints bend so badly:



Every shape is pure, non-static and respondable with complementary mask. Color indicates the mask, blue is:



and green is:



Is there some parameter to control how much a link will bend? Or how much a joint will bend along an axis other than its rotation axis?
Or more probably, I've done some mistake I'm not aware of.
I can send scene file if needed.

Hello,

you can try to check several things:

• turn on contact point display (in the general dynamics properties), to see if some objects that are not supposed to collide, collide anyway.
• during simulation, switch to the dynamic content visualization and verification mode (click the 14th toolbar button from the left). You could detect something suspect. Refer to the design consideration 3.
• you probably already made sure that design considerations 7 and design consideration 8 are respected.
• try to run the simulation with the Vortex engine. Do you notice the problems there too?

You can also post your scene.

Cheers

This is the dynamic content during simulation:



I cannot try with Vortex, but with ODE the bending effect is less prominent.

Here is the scene file

Is it relevant that joints do not physically touch the link object?

To me the link object for the bogie and the two flippers it was not relevant (I could have used a dummy if only it allowed maintaining dynamically enabled joints), so I created a 5cm x 5cm pure plane with mass 0.3 Kg.

Also, lowering the masses (I've changed them to 0.1, 0.15, and 0.2 respectivelly) seems to help a bit.
However the effect never goes away (both in Bullet and ODE).

If you increase the inertia of objects bogie_link, fli_1_link and fli_2_link, you can reach a much more stable situation. Vortex works fine also without those adjustments.

Cheers