[ros-users] Spring simulation problem

Jim Rothrock jim.rothrock at wunderkammerlab.com
Wed Feb 2 03:51:00 UTC 2011

I am writing a package that simulates a Traxxas E-Maxx RC truck in 
Gazebo. Since springs (for the shock absorbers) cannot be specified in a 
URDF dynamics block, I've created a node that reads the shock absorber 
joint positions (they are prismatic joints), uses Hooke's law to compute 
spring forces, then applies the forces to the springs. The node also 
simulates damping. No matter what damping coefficient I use, the truck 
continues to oscillate. Sometimes it appears that Gazebo's ground 
contact force simulation is kicking the wheels into the air, but that's 
just a hypothesis. I've attached a test package to this message, and I'd 
really appreciate it if someone could take a look at it. To execute the 
test, run "roslaunch test test.launch" in one window, then run "rosrun 
test test.py" in another. The oscillating truck should be displayed in a 
Gazebo window.

Jim Rothrock | Wunderkammer Laboratory
jim.rothrock at wunderkammerlab.com

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