Bouncing hinged wheel vehicle (robot)

[mandor]

Hi,
I'm trying to build a model of a wheel-leg hybrid robot like this one:

(in a few words, each wheel is put at the end of a leg to get a reconfigurable robot).

So far, I used bullet boxes, cylinders and hinges to get this model :


Then, I tried to move the wheels by setting their angular velocity... and the robot is bouncing, front to back, while moving forward.

Maybe it's caused by the absence of tires (the wheels are too rigid); anyway, how should I proceed to get a realistic simulation ? I think I can't use a btRaycastVehicle because the wheels can be freely moved (by moving the legs).

Thank you for your ideas.

--
Mandor

[sparkprime]

Even if you can't use the btRaycastVehicle class, you should be able to use the principles behind it to do what you want. Do the wheels have suspension? If not, possibly the tyres alone are acting as "suspension".

[mandor]

Thanks for your reply.

I will dig into the vehicle code but I'd like to use the current code as much as possible (and I'm as lazy as any programmer)

May be it would be possible to define a vehicle for each leg ?

[sparkprime]

You could probably define a vehicle for each leg and use constraints to hold everything together. There is the DynamicControlDemo which has spider-like objects, if you have not seen it?

[mandor]

OK, that's exactly what I did. I set up a vehicle for each leg and hold everything together with hinge constraints. The vehicle is made of only one box, which is linked by a hinge to the leg.

Here is what I get : the robot is falling on the side by bending the leg's constraint. Everything looks fine for a few time step then it falls on the side until it has the four wheels on the top.

What could explain this weird behavior ?

btw, setting a mass < 1 for my vehicles led to a wheel that go trough the ground, is it a "normal" behavior ?

Thanks for your help.

--
Mandor