iCub "falling" in Gazebo

[jimmybaraglia]

Hi,

I am migrating from iCub_SIM to Gazebo, but the iCub appears to "fall" whenever I send a command to the Cartesian controller in Gazebo.

I am using the command goToPose(xd, od) to set the right end-effector to:

xd = -0.4 : 0.1 : 0.2
od = -0 : 0.707107 : -0.707107

It works very well with the iCub_SIM, but not with Gazebo (see enclosed screen-shots)

I tried to start the wholeBodyDynamics or/and the gravityCompensator with the "robot" variable set to icubGazeboSim, but it still does the same thing (i.e. falling down).

Any idea why this is happening?

Best,
Jimmy Baraglia

[traversaro]

I think that the problem is that in Gazebo simulation the velocity control is not properly tested/tuned (see robotology/gazebo-yarp-plugins#240).

This is happening because simCartesianControl is using velocity control by default; you can try to make it use the POSITION_DIRECT mode by setting the PositionControl option of the simCartesianControl to on.

[jimmybaraglia]

I changed the option PositionControl to "on" in simCartesianRightArm.ini and simCartesianLeftArm.ini.
It worked perfectly, thank you.

Cheers,
Jimmy

[tkelestemur]

I still have the falling problem even though I change PositionControl to on in both simCartesianRightArm.ini and simCartesianLeftArm.ini. I am running tutorial_cartesian_interface from icub-tutorials. After two second running the code iCub falls backwards.

[traversaro]

By default no balancing controller is running on icub when simulated on Gazebo. To simulate the robot
as if it was fixed on a fixed base, can you try to launch the iCub (fixed) model?
If that model is without hands we need to updated it, it is not a big problem.

[tkelestemur]

Thank you very much @traversaro, with iCub (fixed) it is working now. I wonder why same code causes falling in Gazebo but not in default simulator? From your point is some kind of balancing controller running when we run iCub_SIM ?

[pattacini]

@tkelestemur there's no balancing in iCub_SIM, and be also careful because fixed_hip is on by default in iCub_SIM; that's why usually you don't see any fall of the iCub therein.

That being said, it would be normal any how to get different results with different simulators.