On 01/28/2011 05:44 PM, John Hsu wrote:
>
>     Is my understanding correct?
>
>
> yes, the forces applied are cumulative.  I've updated the wiki to 
> reflect so.
Thank you.
>
>     I tried to use gazebo/clear_joint_forces instead of applying a -0.01
>     effort, but it appears that clear_joint_forces is no longer in
>     ROS, even
>     though it is in the Gazebo package documentation in the ROS wiki.
>
>
> which release are you running?  I see the clear_joint_forces service 
> calls in both cturtle 
> <https://code.ros.org/svn/ros-pkg/stacks/simulator_gazebo/tags/cturtle/gazebo/src/gazeboros.cpp> 
> and unstable 
> <https://code.ros.org/svn/ros-pkg/stacks/simulator_gazebo/tags/unstable/gazebo/src/gazeboros.cpp>(diamondback 
> alpha) files.
I am running C-Turtle for Ubuntu. "rosnode info gazebo" shows 
/gazebo/clear_joint_forces in the service list, but "rossrv package 
gazebo" does not list gazebo/ClearJointForces.
"locate ClearJointForces" doesn't find anything, but "locate 
ApplyJointEffort" shows:

/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/src/gazebo/srv/_ApplyJointEffort.py
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/src/gazebo/srv/_ApplyJointEffort.pyc
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/srv/ApplyJointEffort.srv
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/srv/lisp/gazebo/.ApplyJointEffort.asd-dep
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/srv/lisp/gazebo/ApplyJointEffort.lisp
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/srv/lisp/gazebo/_package_ApplyJointEffort.lisp
/opt/ros/cturtle/stacks/simulator_gazebo/gazebo/srv_gen/cpp/include/gazebo/ApplyJointEffort.h

"ls /opt/ros/cturtle/stacks/simulator_gazebo/gazebo/srv" lists:

ApplyBodyWrench.srv     GetModelProperties.srv    SetLinkProperties.srv
ApplyJointEffort.srv    GetModelState.srv         SetLinkState.srv
BodyRequest.srv         GetPhysicsProperties.srv  SetModelConfiguration.srv
DeleteModel.srv         GetWorldProperties.srv    SetModelState.srv
GetJointProperties.srv  JointRequest.srv          SetPhysicsProperties.srv
GetLinkProperties.srv   lisp                      SpawnModel.srv
GetLinkState.srv        SetJointProperties.srv

This works:

rospy.wait_for_service("gazebo/apply_joint_effort")
_apply_joint_effort = rospy.ServiceProxy("gazebo/apply_joint_effort", 
gazebo.srv.ApplyJointEffort)

but this:

rospy.wait_for_service("gazebo/clear_joint_forces")
_clear_joint_forces = rospy.ServiceProxy("gazebo/clear_joint_forces", 
gazebo.srv.ClearJointForces)

results in this:

Traceback (most recent call last):
   File "truck.py", line 141, in <module>
     gazebo.srv.ClearJointForces)
AttributeError: 'module' object has no attribute 'ClearJointForces'

-- 
Jim Rothrock | Wunderkammer Laboratory
jim.rothrock@wunderkammerlab.com