hydra_ros

ROS integration for the Hydra multi-robot system. This ROS2 metapackage provides launch files and configuration for the Hydra multi-robot system. See this repository's branches for different variants of the multi robot system configuration.

Note

ros2 variant:

The ros2 branch contains the default setup: Three robots spaced evenly around a 1-DOF positioner table.

Contents

• Dependencies
• Installation
• Running the System

Dependencies

When running the multi-robot system on the physical hardware, it is recommended to build the Docker image and use the scripts provided in za_docker (on each robot computer). If you only plan to run the system in simualtion, this is not required.

Installation

Create a ROS 2 workspace and clone this package into a src directory.

Import package dependencies:

sudo apt update
rosdep update
cd src
vcs import < hydra_ros/hydra.repos
rosdep install -r --from-paths . --ignore-src --rosdistro $ROS_DISTRO -y

Build the packages:

cd <COLCON_WORKSPACE>
colcon build

Running the System

Visualizing the robot description

To view the system in Rviz, run the following command after sourcing your bash file:

ros2 launch hydra_bringup hydra_visualization.launch.py

Running the System in Simulation

There are two forms of simulation for the system. The first uses the sim_hw_interface from ros_control_boilerplate. The second uses the sim version of the hal_hw_interface from hal_ros_control. For more information on the differences between these hardware interface see the README in za_hardware.

Launch all hardware interfaces and controllers on the same computer using the sim_hw_interface:

ros2 launch hydra_bringup hydra_system_sim.launch.py rviz:=true

From here you can run any custom controllers or start MoveIt! to begin planning.

Alternatively, you can run the system in simulation using the hal_hw_interface. The hydra_robot.launch file wraps the normal Za6 bringup in a namespace. The launch file should be run in seperate Docker containers. This works on seperate robot computers or all on the same machine. Launch all hardware interfaces (hal_hw_interface) in seperate docker containers and visualize the system:

# docker container 1
ros2 launch hydra_bringup hydra_robot.launch.py hardware:=hal arm_id:=rob1

# docker container 2
ros2 launch hydra_bringup hydra_robot.launch.py hardware:=hal arm_id:=rob2

# docker container 3
ros2 launch hydra_bringup hydra_robot.launch.py hardware:=hal arm_id:=rob3

# host computer
ros2 launch hydra_bringup hydra_visualization.launch.py

The "motors" can be activated by publishing the following ROS messages to the hardware interface from the host computer:

ros2 topic pub /rob1/hal_io/state_cmd std_msgs/UInt32 "data: 2"
ros2 topic pub /rob2/hal_io/state_cmd std_msgs/UInt32 "data: 2"
ros2 topic pub /rob3/hal_io/state_cmd std_msgs/UInt32 "data: 2"

Running the System on Hardware

The only difference here is that the sim:=false argument should be passed to the robot launch when running the hardware interface that will actually connect to EtherCat. Note: See za_docker for instructions on running the containers in execution mode

# docker container 1 on robot 1 computer
ros2 launch hydra_bringup hydra_robot.launch.py hardware:=hal sim:=false arm_id:=rob1

# docker container 2 on robot 2 computer
ros2 launch hydra_bringup hydra_robot.launch.py hardware:=hal sim:=false arm_id:=rob2

# docker container 3 on robot 3 computer
ros2 launch hydra_bringup hydra_robot.launch.py hardware:=hal sim:=false arm_id:=rob3

# host computer
ros2 launch hydra_bringup hydra_visualization.launch.py

After engaging the motors with the commands listed above, you can begin planning with MoveIt!.

Planning in MoveIt

MoveIt! has limited functionality for coordinated planning in multi-robot systems. However, it still works for point-to-point collision-free motion. You can use MoveIt! to plan for the Hydra system using any of the runtime configurations listed above.

# host computer
ros2 launch hydra_bringup moveit_planning.launch.py