SES-P ROS2 Arms Package

The SES-P-ROS2-Arms repository contains common packages that are used by both the physical and simulated SES PRO Arms (5DoF/6DoF & 550mm/900mm versions).

Table of Contents

• Prerequisites
• Package installation
• Description package
• MoveIt package
• Simulated examples (C++)
• Author
• Resources

Prerequisites

1. Ubuntu 22.04 (Jammy Jellyfish)
2. ROS2 Humble
3. ROS2 dev tools:

sudo apt install python3-pip
sudo pip install colcon-common-extensions
sudo pip install vcstool

4. Rosdep: Used to install dependencies when building from sources

sudo apt install python3-rosdep2
rosdep update

5. Gazebo Ignition Fortress

Package installation

sudo apt install git
git clone https://github.com/Lynxmotion/SES-P-ROS2-Arms.git
mkdir -p src
mv SES-P-ROS2-Arms/* src
mv src SES-P-ROS2-Arms

Install dependencies

cd SES-P-ROS2-Arms
rosdep install --from-path src -yi --rosdistro humble
cd src
vcs import < required.repos
cd ..

Build instructions

export GZ_VERSION=fortress
source /opt/ros/humble/setup.bash
colcon build --symlink-install

Initialization instructions

You will have to use this in every new session in which you wish to use these packages:

source install/setup.bash

Description package

The pro_arm_description package contains the URDF description & SDF model of the robot and the mesh files for each component.

It contains scripts that convert xacro into the required URDF and SDF files.

To generate the REQUIRED SDF file used for the simulation run:

bash src/pro_arm_description/scripts/xacro2sdf.bash

All the available sdf generation scripts have the following configuration options:

-d: Which PRO Arm version to use

• options: 5, 6
• default: 6

-s: Size of the model to use

• options: 550, 900
• default: 550

-g: Gripper model to use

• options: none, pge_5040, cge_1010
• default: none

-f: Finger model to use

• options: 20, 40, 60, 80
• default: 40

The script defaults to the 6DoF 550mm model without gripper.

To generate the SDF of the 6DoF 550mm model with the gripper PGE_5040, 60mm finger version run:

bash src/pro_arm_description/scripts/xacro2sdf.bash -g pge_5040 -f 60

To generate the SDF of the 5DoF 900mm model run:

bash src/pro_arm_description/scripts/xacro2sdf.bash -d 5 -s 900

Similarly, if you want to generate the URDF files (not required) you can run:

bash src/pro_arm_description/scripts/xacro2urdf.bash

or

bash src/pro_arm_description/scripts/xacro2urdf.bash -d 5 -s 900

The decription and moveit packages launch files have the following configuration options:

dof: Which PRO Arm version to use

• options: 5, 6
• default: 6

size: Size of the model to use

• options: 550, 900
• default: 550

gripper: Gripper model to use

• options: none, pge_5040, cge_1010
• default: none

finger: Finger separation model to use

• options: 20, 40, 60, 80
• default: 40

• The 20 model is only available for the cge_1010 gripper and the 80 is only available for the pge_5040 gripper

View Model in Rviz

ros2 launch pro_arm_description view.launch.py

size 550mm gripper none

size 550mm gripper pge_5040 finger 40

size 550mm gripper cge_1010 finger 20

size 900mm gripper none

size 900mm gripper pge_5040 finger 80

size 900mm gripper cge_1010 finger 60

View in Gazebo Ignition

ros2 launch pro_arm_description view_ign.launch.py size:=900 gripper:=pge_5040 finger:=60

• Note that the generated SDF model is required.

MoveIt package

The pro_arm_moveit package contains all the configuration and launch files for using the PRO Arm with the MoveIt2 Motion Planning Framework.

It offers different controller plugins for the manipulator ('fake', 'sim' and 'real')

If you want to generate the SRDF files (not required) you can run:

bash src/pro_arm_moveit/scripts/xacro2srdf.bash

or

bash src/pro_arm_description/scripts/xacro2urdf.bash -d 5 -s 900

The following launch files are available:

Base control launch file

ros2 launch pro_arm_moveit move_arm.launch.py

• Note: This also launches the emergency_stop_marker node that integrates an interactive marker to STOP/START the arm_trajectory_controller. This functions as an Emergency Stop button but the same behavior can be achieved by running the folowing commands on a different terminal:

ros2 run pro_arm_moveit trigger_emergency_stop.py start

ros2 run pro_arm_moveit trigger_emergency_stop.py stop

These commands are available for the rest of the pro_arm_moveit package.

Fake controllers (Rviz)

ros2 launch pro_arm_moveit fake_arm_control.launch.py

Simulated controllers (Rviz + Gazebo Ignition Simulation)

ros2 launch pro_arm_moveit sim_arm_control.launch.py

Real controller (RViz + Real Robot)

Before controlling the real robot first follow these steps:

1. Update the firmware on the servos using PRO Config

2. Follow the initial setup and make sure the IDs are configured correctly and the arm is calibrated

To control the arm:

1. Run the launch file

ros2 launch pro_arm_moveit real_arm_control.launch.py

• Note: If the servos light up Blue they have been configured correctly if not try running this first:

sudo chmod 666 /dev/ttyACM0

Example 1: Real time

Example 2: Speeded up 2x

• Note: The planner uses a velocity and acceleration scaling factor of 0.5, these can be adjusted through RViz. The custom hardware interface also supports setting maximum speed and acceleration values which are configured at the initial stage and can be adjusted in the pro_arm.ros2_control file.

PRO Simulation Examples

C++

Follow Goal Demo (Simulation)

The pro_sim_examples package includes the follow_target demo which simulates the LSS arm in Gazebo Ignition and allows the user to interact with a box in the virtual environment. This example includes a C++ implementation that makes the arm track the target (box) whenever you change its location.

ros2 launch pro_sim_examples ex_cpp_follow_target.launch.py

Note: The 5DoF version does not have enough degrees of freedom to achieve all desired end-effector poses (position + orientation). This implementation first attempts to move to the desired pose, if unsuccessful it sets a position only target, this allows it to plan a trajectory "ignoring" the orientation.

Move Object Example (Simulation)

The move_object example contains a C++ implementation to make the arm move a box from one table to another. The motions are simulated in Gazebo Ignition.

ros2 launch pro_sim_examples ex_cpp_move_object.launch.py

Author

• Geraldine Barreto

Resources

Read more about the PRO Robotic Arm in the Wiki.

Purchase the PRO arm on RobotShop.

Official Lynxmotion Smart Servo PRO (LSS-P) Hardware Interface available here.

If you want more details about the LSS-P communication protocol, visit this website.

Have any questions? Ask them on the RobotShop Community.