I suggest start by making sure the mass and moment of inertias are close to realistic values. Then to get rid of the smooth-slow motion you are seeing, slowly increasing damping coefficients for the joints. Unfortunately, realistic damping coefficients are hard to come by, and for PR2 we got them by simply trying out different values and comparing joint responses when given a joint trajectory command. Note that when damping coefficient is too large, the joint may become unstable, at that point, you can optionally reduce time stepping size or increase quickStepW in your world file.
John
Ok. I'm having trouble getting a realistic behaviour for my model in
gazebo... It acts really really smoothly, with really slow movements
when I'm not sending commands to it. For example when the hand
hasn't received any command yet, it will close its fingers in maybe
10 seconds as if it were in oil or something.
Any idea on how to improve this?
Cheers
On 05/08/10 17:30, John Hsu wrote:
Hi Ugo,
Friction is not modeled in ode at this point, if it's something
you need, please file a feature request ticket here, and
set simulator_gazebo as the component. Modeling coulomb friction
at a joint is possible in ODE, but has not been tested.
thanks,
John
I'm currently trying to get a better control on
our gazebo model of the
Hand. I'm having trouble finding any kind of
documentation regarding the
parameters you can apply to a joint (e.g.
friction). Is there a place I
could start with?
For the time being, my joints look like this:
<joint name="trunk_rotation"
type="revolute">
<parent link="${parent}"/>
<child link="shadowarm_trunk"/>
<origin xyz="0 0 0.01" rpy="0 0 0" />
<axis xyz="0 0 1" />
<limit lower="-${M_PI/2}"
upper="${M_PI/4}"
effort="10" velocity="1.0"/>
<dynamics damping="1"/>
</joint>
You can add static friction to the dynamics
joint element. This link documents all the valid
elements for a URDF joint:
Robotics engineer
PAL ROBOTICS S.L http://www.pal-robotics.com
Tel. +34.93.414.53.47
Fax.+34.93.209.11.09
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