There are a couple of ways to simulate a spring in gazebo. �One example in ros uses a transmission as a "spring-like controller" (see�http://ros-users.122217.n3.nabble.com/Flexible-amp-remote-transmission-td1929619.html#a1937295�for an example of a torsional spring). �Alternatively, you can use a joint constraint to do the same thing. �To simulate a linear spring, you can define a prismatic joint with both upper and lower limits equal to 0. �This means any constraint violation produces an error correction force which is essentially the amount of constraint violation (x) multiplied by ODE's ERP parameter / dt (k).

Note that using a joint constraint to simulate spring will actually update joint force and compute�equivalent�compression distance within the same time step, whereas using a transmission controller as given in the example above, the spring force applied is computed using spring stretch from the last time step.

John

On Sun, Jan 23, 2011 at 3:57 PM, Jim Rothrock <jimrothrock52@gmail.com> wrote:

I have created a URDF file for a four-wheel-drive vehicle and am beginning to use it with Gazebo. Each shock absorber is a prismatic joint. Simulating the damping of a shock is easy; just set the joint's damping factor in a dynamics block. However, I don't know how to simulate the spring component of a shock. My only idea so far is to write a ROS node that subscribes to the joint's position topic. The node's loop gets the position, computes a force via Hooke's law, then applies a corresponding wrench to the joint. Is there a better way to simulate a spring in Gazebo? It seems that someone would have needed to simulate a shock absorber by now, but my searches didn't turn up any examples.
--
Jim Rothrock | jimrothrock52@gmail.com
Sent from my Android phone

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