Overview

In this tutorial, we'll describe how to interact with the simulated RobotiQ hand, as well as how to read its state and visualize it in rviz.

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 it from your .bashrc file when it is not needed anymore.

Running the Simulation and controlling the gripper

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

roslaunch drcsim_gazebo atlas_robotiq_hands.launch

If the initial hand configuration does not match your robot's configuration, you can edit the file atlas_robotiq_hands.urdf.xacro. Note that there are different versions of this file for Atlas V3 and Atlas V4.

Once your configuration is correct you can look for ROS nodes controlling the RobotiQ hands by typing:

rostopic list | grep hand

Note the RobotiQ hand messages:

/left_hand/command
/left_hand/state
/right_hand/command
/right_hand/state
/robotiq_hands/left_hand/joint_states
/robotiq_hands/right_hand/joint_states

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

rostopic info /right_hand/command

You should see something like this:

Type: atlas_msgs/SModelRobotOutput

Publishers: None

Subscribers:
 * /gazebo (http://turtlebot:54036/)

The message type is atlas_msgs/SModelRobotOutput which contains all the different registers for controlling the behavior of the hand:

rosmsg show SModelRobotOutput

uint8 rACT
uint8 rMOD
uint8 rGTO
uint8 rATR
uint8 rICF
uint8 rICS
uint8 rPRA
uint8 rSPA
uint8 rFRA
uint8 rPRB
uint8 rSPB
uint8 rFRB
uint8 rPRC
uint8 rSPC
uint8 rFRC
uint8 rPRS
uint8 rSPS
uint8 rFRS

Open a separate terminal and make sure to source the environment setup.sh files as we explained at the beginning of the tutorial. Then, invoke the next command to send a ROS message for closing the right hand halfway:

rostopic pub --once right_hand/command atlas_msgs/SModelRobotOutput {1,0,1,0,0,0,127,255,0,155,0,0,255,0,0,0,0,0}

You can send the next ROS message to fully open the hand:

rostopic pub --once right_hand/command atlas_msgs/SModelRobotOutput {1,0,1,0,0,0,0,255,0,155,0,0,255,0,0,0,0,0}

The hand supports different grasping modes and uses multiple registers to control the position of the fingers, as well as other parameters. Check out Section 4.4 of the instruction manual for a full list of features and a description of each control register.

As an example, you can execute the following command to change the grasping mode to pinch and close the gripper:

rostopic pub --once right_hand/command atlas_msgs/SModelRobotOutput {1,1,1,0,0,0,255,255,0,155,0,0,255,0,0,0,0,0}

Or switch to wide mode and fully open the hand:

rostopic pub --once right_hand/command atlas_msgs/SModelRobotOutput {1,2,1,0,0,0,0,255,0,155,0,0,255,0,0,0,0,0}

Or you can change to scissor mode and close the fingers:

rostopic pub --once right_hand/command atlas_msgs/SModelRobotOutput {1,3,1,0,0,0,255,255,0,155,0,0,255,0,0,0,0,0}

And open the fingers:

rostopic pub --once right_hand/command atlas_msgs/SModelRobotOutput {1,3,1,0,0,0,0,255,0,155,0,0,255,0,0,0,0,0}

Showing the gripper state

The gripper state is periodically published via ROS messages and is available at:

/left_hand/state
/right_hand/state

Open a separate terminal and make sure to source the environment setup.sh files as we explained at the beginning of the tutorial. Then, execute the next command for visualizing the output of the right hand:

rostopic echo /right_hand/state

You should see something similar to:

---
gACT: 1
gMOD: 3
gGTO: 1
gIMC: 3
gSTA: 2
gDTA: 1
gDTB: 1
gDTC: 1
gDTS: 3
gFLT: 0
gPRA: 0
gPOA: 1
gCUA: 0
gPRB: 0
gPOB: 1
gCUB: 0
gPRC: 0
gPOC: 1
gCUC: 0
gPRS: 0
gPOS: 3
gCUS: 0
---

Now, come back to the terminal that you are using for sending joint commands and close the hand by typing:

rostopic pub --once right_hand/command atlas_msgs/SModelRobotOutput {1,0,1,0,0,0,255,255,0,155,0,0,255,0,0,0,0,0}

You should see how the different state registers change according to the target position specified, the current finger position, velocities, etc. Check out Section 4.5 of the instruction manual for a detailed description of the state registers.

Visualizing the gripper in rviz

The simulated RobotiQ gripper publishes its state using ROS, so it is possible to graphically visualize its state using rviz. Go to the terminal where you were visualizing the hand state and press CTRL-C.

Open rviz:

rosrun rviz rviz

Let's start by adding Atlas to the visualization by pressing the Add button, and then, RobotModel. Change the property Fixed Frame to pelvis.

Now, you should be able to visualize the hands in real-time.

Known limitations

The following features are not yet available in drcsim:

• Speed/torque control
• Individual Control of Scissor

We will update this tutorial when these features become available.