Overview

In this tutorial, we'll send desired grasp pose to Sandia hands mounted on an Atlas robot in simulation through the use of a simple ROS topic publisher. Please note that this is a tremendously simplistic implementation of grasping, and is not in any way attempting to be a "reference" implementation of any sort. The controller is just a strawman to demonstrate motion of the hands into several canonical grasps.

Setup

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

If you haven't done so, make sure to source the environment setup.sh files with every new terminal you open:

source /usr/share/drcsim/setup.sh

To save on typing, you can add this script to your .bashrc files, so it's automatically sourced every time you start a new terminal.

echo 'source /usr/share/drcsim/setup.sh' >> ~/.bashrc
source ~/.bashrc

But remember to remove them from your .bashrc file when they are not needed any more.

Running the Simulation

In terminal, source the DRC simulator setup script and start the DRC robot simulation:

roslaunch drcsim_gazebo atlas_sandia_hands.launch

Look for ros nodes controlling Sandia hands by typing

$ rosservice list | grep sandia_hand

In particular, note the output should contain Sandia hands services for simplified grasps:

/sandia_hands/l_hand/simple_grasp
/sandia_hands/r_hand/simple_grasp

To get more information on the type of service offered, type

rosservice info /sandia_hands/l_hand/simple_grasp

with the following output:

Node: /sandia_hands/l_hand/simple_grasp_left
URI: rosrpc://lcp1:37083
Type: sandia_hand_msgs/SimpleGraspSrv
Args: grasp

The service type is sandia_hand_msgs/SimpleGraspSrv which contains a SimpleGrasp message, to see what it is, do:

rosmsg show SimpleGrasp

with the following output:

[sandia_hand_msgs/SimpleGrasp]:
string name
float64 closed_amount

The name string may take the value of "cylindrical", "prismatic", or "spherical" and refers to the type of grasp. The closed_amount value should be between 0 and 1, with 0 being an open hand and 1 being a closed grasp. The source code for this controller is in simple_grasp.py in the sandia_hand_teleop package.

In a separate terminal, invoke the service call to close left hand half way by executing:

rosservice call /sandia_hands/l_hand/simple_grasp ' { grasp: { name: "spherical", closed_amount: 0.8 } }'