a question about abnormal and large fluctuations in contact force between ball and the jump

[sanbens1234]

Hi,

I'm a student, tenghui wang. I'm trying to use MuJoCo for simulating a ball rolling on the slope and jumps.

I'm looking for some help with abnormal and large fluctuations in contact force between ball and the jump, see in fig. 2.

I have 2 questions. The first question is that at the junction of the geom “slope” and geom "jumps", the contact force is about 2000N(i.e. at the begining of the x-axis in fig.2), which is abnormally large. The secon question is that during the process of rolling on the jumps, the contact force varies largey( about ±200N, the gravity of ball about 670N). The second question might be caused by the discrete points of the hfiled, but i don't know how to improve it. Here is a model which explains my question:

minimal XML

```XML ```

since the file "generated_hfield.xml" is too long, i zip it as follows,

generated_hfield.zip

fig.1 the scene of the simulation

fig.2 the contact force Fz between geom"jumps" and geom "sph"

[yuvaltassa]

Not clear why you think they are "abnormally large". There is a corner at the beginning of your your slope geom, the ball hits the corner and you get a large force. In any case, looking at contact force magnitude in this situation is useless. This is a timestep-dependent quantity. You should be looking at the integral of the the impulse (force*dt). The actual size of the force is not something that can be judged to be small or large without knowing the time during which it was applied.