![Moving_Car](Moving_Car.mp4 "Moving_Car") Problem: 1. Collision not detected, robot car pass the ground. Potential resaons: Based on [the information provided by Webots](https://cyberbotics.com/doc/reference/solid) :"For consecutive solids, e.g., two solids attached to each other with a joint or a solid attached to the static environment with a joint, no collision detection is performed even if the physics field is set. The reason is that this type of collision detection is usually not wanted by the user, because a very accurate design of the bounding objects of the solids would be required. To prevent two consecutive solid nodes from penetrating each other, the minStop and maxStop fields of the corresponding joint node should be adjusted accordingly." However, when building the robot in Webots (not importing _.stl_), collision happens ... Weird ... ![Two_Wheel_Car](Two_Wheel_Car.mp4 "Two_Wheel_Car") Getting back to the "imported-stl" robot car, I changed car body from solid to shape (moved shape out to the top), here is the result, at least wheels did not collide... an improvement i guess ... ![Moving_Car_Body_Error](Moving_Car_Body_Error.mp4 "Moving_Car_Body_Error")