Changing Joint Limits in Simulation?

[Woolfrey]

I want to perform a certain action with the iCub in Gazebo, but the angle at the elbow is too large due to joint limits:

I have tried altering it with the yarp::dev::iControlLimits class:

this->limits->setLimits(i,lower,upper);

But if I force the joint beyond its default limits it will not move, and I get the following error message:

[ERROR] |gazebo-yarp-plugins.plugins.GazeboYarpControlBoard| An hardware fault occurred on joint  3  torque too big! (  -9999  )

Is it possible to alter this constraint, just for simulation purposes?

Thanks in advance,

Jon

[traversaro]

The setLimits interface can only change the so-called software limits, i.e. the limits imposed by the joint-level controller, both on the simulator and on the real robot. What can't be changed by the setLimits (both on simulation and on the real robot) are the hardware limits, i.e. the configuration where there it is not possible to move the joints due to some kind of hardware hardstop. Indeed, I am not sure if HW fault is the right behavior when setLimits outside the hardware limits are asked, and for that I opened #116 .

On the Gazebo-simulated robot, to change the hardware limits you need to modify the URDF model of the robot, i.e. the lower and upper limits of the limit tag, see

icub-models/iCub/robots/iCubGazeboV3/model.urdf

Line 636 in c73aa1d

<limit effort="50000" lower="-0.05235987755982989" upper="1.3089969389957472" velocity="120.0"/>

for r_elbow. If you modify the hardware limit, then you need to remember also to modify the corresponding default software limit, i.e. the value in

icub-models/iCub/conf_icub3/gazebo_icub_left_arm_no_hand_for_no_hand_model.ini

Line 70 in c73aa1d

[LIMITS]

.

In the case you are generating the models from icub-model-generator, the file to modify is https://github.com/robotology/icub-models-generator/blob/master/simmechanics/data/icub3/ICUB_3_joint_all_parameters.csv#L30 .

[Woolfrey]

Thanks for the information, @traversaro.

I wasn't sure if the setLimits function would also affect the Gazebo simulation, or if the constraints were set somewhere else. But modifying the URDF makes sense. I will give it a try!

Jon.

[traversaro]

Hi @Woolfrey, I will close this issue as the information has been provided. Feel free to re-open or open a new one if you still have problems.