UR10 arm moves to a wrong direction

Hi, I try to attach the UR10 to a cube. I put the arm on the cube and set the Target Position of shoulder_lift_joint to -90. The robot turns up as expected. And then I set the rootJoint, attach the base_link to the cube, the robot turns up as expected too.
However, I set the cube’s rigid body then, and the robot turns down instead.
Could someone give me a solution to this situation? Or it is designed to be so?
Here is my usd file: wrong.usd (3.2 KB)

Hi @ddbw

A small question: is the goal to put the robot in a fixed position with respect to the cube as if it were on a wall?

If that is the case. You would just have to add the robot (rotate it and place it in the desired position) and that’s it, no need to link it to the cube. The robot will have its base fixed where it is placed in world coordinates (because it was probably created with the “Fix Base Link” set to true)

Actually, I want to put the robot on a wheeled robot, so it’s necessary to use the rootJoint. Using the cube simplify the question