why my model seems to defy the gravity, and seems to be grabbed from the top when moving?
Dear all, I am new to ROS and Gazebo. I built a 4 wheeled model that I can control via a teleop program. I can also spawn the model with an arm on top of it, which includes a two finger gripper.
If I spawn the robot without the arm, then it would behave realistically (at least to my eyes) -aside from the fact the it seems to move by itself very little, and I confirmed this happens as well to the Husky model from Clearpath- therefore I believe this is normal. However, when I spawn the robot including the arm, and I command the robot to move forward or backwards, it behaves very strange:
It would seem as if someone is grabbing the arm, so the front or back wheels are lifted when moving to the front or to the back, accordingly. When I stop issuing the command, the vehicle will return slowly to full contact with ground. If I make the mass of the whole arm including gripper, minimal, the behavior disappears, but then another problem occurs: If I try to grab a beer can with the gripper, the fingers would vibrate, shake and the can would almost be thrown away.
There may be something with the modeled physical properties of the wheeled base and/or the arm and the gripper which I cannot seem to fine tune properly.
Any guidance appreciated.
Test: In Translation mode, select the robot, move it up, and drop it. It can be seen how it falls slowly as if it was hold from the arm. If I remove the arm, it falls ok.
Video showing my robot side by side with the husky. I have compared frictions, gravity, and other settings and cannot find what makes them behave different in the same world.
I noticed something strange also, which happens with or without loading the arm. If I lift my robot and drop it , gazebo shows first it going quickly to the ground and then brings it back to the position it was, and then it lets it fall. This does not happen with the Husky.
Any ideas where to look at? Thanks