Hi, all!

I'm trying to simulate some tests in GAZEBO with robot. One of the tests is perfectly elastic and inelastic collision between robot and small sphere. The physic's engine is ODE.

Sphere is attached to the the stick that can be deflected by some angle and then falls back under gravity and hits my robot. There is no friction between soles of foots of the robot and floor.

I had setting and parameters in link -> collision -> surface -> friction -> ode to 0 in groundplane model and in model of my robot for foots. For bounce I had setting <restitutioncoefficient>, and , as described here: http://answers.gazebosim.org/question/678/a-simple-question-on-changing-bounce-properties/.

The experiments revealed that velocity of sliding of the robot after the hit not depends on the mass of the sphere. If I hit my robot with the 40 kg sphere and then with 4000 kg, it slides with the same velocity. But if I reduce mass of the sphere to some small value, for example 5 kg, then sliding speed is reducing.

Can you help me to resolve this problem and get any advice, please? Is there any examples of elementary physic's tests?