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Changing Viscous Damping Coefficients Over ROS Service

Overview

This tutorial will explain how to change Atlas robot and Sandia hand joint viscous damping coefficients.

Background

We assume that you've already done the installation step.

In this tutorial, we'll demonstrate how to call ROS services in command-line using rosservice.

After running Gazebo with Atlas, roslaunch drcsim_gazebo atlas_sandia_hands.launch, you can then use rosservice list to look for existing services:

rosservice list | grep damping

/atlas/get_joint_damping
/atlas/set_joint_damping
/sandia_hands/l_hand/get_joint_damping
/sandia_hands/l_hand/set_joint_damping
/sandia_hands/r_hand/get_joint_damping
/sandia_hands/r_hand/set_joint_damping

Each service is described in detail below:

  • To get Atlas robot model's current joint damping coefficients,
  • To set Atlas robot model's joint damping coefficients,
  • To get Sandia hand model's current joint damping coefficients (right hand),
  • To set Sandia hand model's joint damping coefficients,

Running the Tutorial

To run this tutorial, you'll need at least 2 separate terminals. Don't forget to execute following setup commands in each new terminal you open.

. /usr/share/drcsim/setup.sh

Start simulation of Atlas robot with Sandia hands:

roslaunch drcsim_gazebo atlas_sandia_hands.launch

To see information the current damping coefficients for Atlas, as well as the max and min values, open a separate terminal and run the following:

rosservice call /atlas/get_joint_damping

You should see output similar to the following:

damping_coefficients: [0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.2, 0.1]
damping_coefficients_min: [0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1]
damping_coefficients_max: [516.7333333333333, 861.8458333333333, 395.4583333333333, 20.833333333333336, 458.3333333333333, 750.0, 1083.3333333333335, 1666.6666666666667, 916.6666666666666, 375.0, 458.3333333333333, 750.0, 1083.3333333333335, 1666.6666666666667, 916.6666666666666, 375.0, 883.3333333333334, 708.3333333333333, 475.0, 475.0, 475.0, 250.0, 883.3333333333334, 708.3333333333333, 475.0, 475.0, 475.0, 250.0]
success: True
status_message: success

Here, the array of damping_coefficients should have exactly 28 elements for DRCSim < 4.2 and 30 elements for DRCSim >= 4.2, with each element corresponds to one joint as listed in atlas_msgs/AtlasState.msg. In this example, all joints will have a damping coefficient of 0.1 N*m*sec/rad, with the exception of r_arm_uwy with damping coefficient of 0.2 N*m*sec/rad.

To see the damping values for the Sandia hands, type the following:

rosservice call /sandia_hands/r_hand/get_joint_damping

You should see the following:

damping_coefficients: [1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
damping_coefficients_min: [1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
damping_coefficients_max: [30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
success: True
status_message: success

Here, each element of the damping_coefficients array corresponds to a joint as listed in SandiaHandPlugin.cc line 84 ~ 95. So for example, above rosservice call will set all joint damping values to 30 N*m*sec/rad with the exception of f3_j0, with damping coefficient of 5.0 N*m*sec/rad.

Change the Sandia hands model joint damping coefficients by typing:

  • For DRCSim < 4.2:

    . /usr/share/drcsim/setup.sh
rosservice call /sandia_hands/r_hand/set_joint_damping "damping_coefficients: [30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 5.0, 30.0, 30.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]"

  • For DRCSim >= 4.2+, the message sent over this service is two entries longer. You'll need to send the following command instead:

    . /usr/share/drcsim/setup.sh
rosservice call /sandia_hands/r_hand/set_joint_damping "damping_coefficients: [30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 30.0, 5.0, 30.0, 30.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]"

Similarly for the Atlas robot model:

  • For DRCSim < 4.2:

    . /usr/share/drcsim/setup.sh
rosservice call /atlas/set_joint_damping "damping_coefficients: [0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.2, 0.1]"

  • For DRCSim 4.2+:

    . /usr/share/drcsim/setup.sh
rosservice call /atlas/set_joint_damping "damping_coefficients: [0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.1, 0.2, 0.1, 0.1, 0.1]"