In the previous tutorial, we built a simulated mobile robot base from scratch. Now I want to create a robotic arm that I will eventually attach to this base so that I have a complete mobile manipulator. Here is what we will build:

This tutorial would not have been possible without Ramkumar Gandhinathan and Lentin Joseph’s awesome book ROS Robotics Projects Second Edition (Disclosure: As an Amazon Associate I earn from qualifying purchases). I highly recommend it if you want to learn ROS 1. Many of the files (URDF, configuration, and STL files), come from their book’s public GitHub page.

Table of Contents

Real-World Applications

This project has a number of real-world applications:

Indoor Delivery Robots
Order Fulfillment
Factories
Warehouses
Space Exploration
Power Plants

Let’s get started!

Prerequisites

You have completed this tutorial where you learned how to create a mobile robot base.

Build the Robot Arm

Open a new terminal window.

Move to the urdf folder of your package.

roscd mobile_manipulator_body/urdf/

Now create a file named robot_arm.urdf.

gedit robot_arm.urdf

Add the robot_arm.urdf code inside there.

Save and close the file.

Test the Robot Arm

Now let’s launch the robot arm.

Open a new terminal window, and go to the package.

roscd mobile_manipulator_body/urdf/

roslaunch urdf_tutorial display.launch model:=robot_arm.urdf

Change the Fixed Frame to world.

Here is how the robot looks.

Move the arm using the sliders.

Here are the active ROS topics.

rostopic list

Press CTRL + C in all open terminal windows to close everything down.

Now, let’s set up the configuration parameters for the controllers.

Open a new terminal window.

Go to the config file of your package.

roscd mobile_manipulator_body/config/

Now create a file named arm_control.yaml.

gedit arm_control.yaml

Add the arm_control.yaml code inside there.

Save and close the file.

Now create a file named joint_state_controller.yaml.

gedit joint_state_controller.yaml

Add the joint_state_controller.yaml code inside there.

Save and close the file.

Launch the Robot Arm

Now let’s launch the robot arm.

Open a new terminal window, and go to the package.

roscd mobile_manipulator_body/launch/

Create a new launch file.

gedit arm_gazebo_control.launch

Add the arm_gazebo_control.launch code inside there.

Save and close the file.

Now let’s launch the robot in Gazebo.

Open a new terminal window.

Move to your catkin workspace.

cd ~/catkin_ws/

roslaunch mobile_manipulator_body arm_gazebo_control.launch

Here is how the robot arm looks.

Here are the active ROS topics.

rostopic list

Open a new terminal, and type this command to move the robot arm a little bit:

rostopic pub /arm_controller/command trajectory_msgs/JointTrajectory '{joint_names: ["arm_base_joint","shoulder_joint", "bottom_wrist_joint", "elbow_joint","top_wrist_joint"], points: [{positions: [-0.1, 0.5, 0.02, 0, 0], time_from_start: [1,0]}]}' -1

Type this command to bring the robot back to the home position.

rostopic pub /arm_controller/command trajectory_msgs/JointTrajectory '{joint_names: ["arm_base_joint","shoulder_joint", "bottom_wrist_joint", "elbow_joint","top_wrist_joint"], points: [{positions: [0, 0, 0, 0, 0], time_from_start: [1,0]}]}' -1

References

ROS Robotics Projects Second Edition