A very common ROS controller used to control a mobile ground robot is diff_drive_controller. This controller can be used for two types of mobile ground robots: Mobile ground robot with two wheels using differential drive Mobile ground robot with four wheels using skid steering This controller is basically a velocity controller as it commands the …

There are two ROS controllers commonly used to control manipulators: effort_controllers/JointPositionController This is commonly used to control individual joints of a manipulator. The configuration YAML file of the controller, let’s call it my_controller.yaml, looks like this: A launch file to launch the controller looks like this: To command a joint position from the terminal, the …

The Big Picture The following shows the big picture of how to use ros_control with either simulation or a real robot. It can be seen in the picture that the class “hardware_interface::RobotHW” should be implemented in a hardware interface node when ros_control is used with a real robot. On the other hand, the class “hardware_interface::RobotHWSim” …

In general, there are several types of control software. Some of them are available out of the box whereas some others are those you may write by yourselves. ros_control is among the out-of-the-box control software you can directly use (so that you don’t need to write one from scratch) which is compatible with third-party packages …

tf Broadcaster and Listener tf broadcaster node written in C++ can be found here: In the code above, the node is subscribing to the pose of robot given by “turtle_name” parameter. Upon receiving the pose topic, it will run “poseCallback” callback function which basically broadcast the transformation between the robot frame and the world frame. …

tf Broadcaster and Listener tf broadcaster node written in Python can be found here: In the code above, the node is subscribing to the pose of robot given by “~turtle” parameter. Upon receiving the pose topic, it will run “handle_turtle_pose” callback function which basically broadcast the transformation between the robot frame and the world frame. …

tf and tf2 are ROS packages that handles frame transformation in the time frame. This means, we can get information about “What is the relative pose of Frame B with respect to Frame A at 10 seconds ago.” Frame transformation is extremely important in robotics as a robot itself typically consist of several frames, such …

The URDF robot description can be used to simulate the robot in Gazebo. This can be done through the following steps. For the example below, the folders “urdf”, “config”, “rviz”, and “launch” used in the example are all inside “my_robot_description” package. Step 1: Install gazebo_ros_pkgs package which connect between Gazebo and ROS. Step 2: Install …

xacro is a language defined in ROS to be used to: simplify URDF; make URDF cleaner make it easier to change the URDF’s parameters create a modular URDF xacro:property Use case 1: Using xacro:property, we can use constants as variables so that it is easier to change them or to avoid redundancy (repetition) in their …

URDF is the description of your robot. It describes how your robot looks like (the number of links, properties of the links, types of joints, where the joints located, properties of the joints, etc) and how the links of the robot move relative to each other. The kinematics of your robot is based on the …