How To Use the EPMC With ROS2

Learn how to test and integrate the Easy IMU (EIMU) in your ROS2 project

Before Using The EPMC in ROS2

• Firstly, ensure you have your Geared DC motors connected to the EPMC Module and the motor PID gains already set up. If not, follow the instructions here [link to the post]

• Also, before you start, it is worth knowing that you can use it with a PC, Raspberry Pi, or any microcomputer running Ubuntu OS and ROS2. You can also use docker (if you can).

• You should also have some experience with ROS2 as a beginner or intermediate user. (e.g. Installing ROS2, setting up ros workspace, building packages with colcon, rosdep, ros topics, rviz, ros transforms, e.t.c)

Using The EPMC in ROS2

• First clone and install the epmc harware plugin package - epmc_ros_hw_plugin.

• Next clone and install the demo_bot package - demo_bot. The demo_bot package is a test robot for testing the EPMC plugin package. I contains example on how to implement the EPMC ROS2 control on a differential drive robot. (It requires that the epmc hardware interface plugin be installed on your computer)

NOTE: you can use in place of the demo_bot your preferred robot where you have already implemented the EPMC ROS2 control. You can also make use of the demo_bot to build your preferred 2 or 4 wheeled differential drive robot.

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Basically, after cloning, installing necessary dependencies, compiling, and installing both packages using colcon build --symlink-install , you can quickly follow the steps below to test the EPMC.

• You need to first connect the EPMC Module to your PC (or microcomputer)

• Check the USB port the EPMC Module is connected to and give the port necessary permissions.

• Go to the epmc_ros2_control.xacro file found in the demo_bot/demo_bot_description/urdf/ folder

• change the port param file to the USB port found in the second step above <param name="port"> {discovered port value} </param>

• Then ensure the motorA_wheel_name and the motorB_wheel_name params properly indicates which port you connected your left and right motor wheel.

• Change the command interface velocity min and max parameter, to that of you Motor (i.e *W_MAX value during setup)

NOTE: at this point, you don't need to re-compile and build with colcon if you've built previosly using the --symlink-install

• open a new terminal (and source your workspace) and launch the demo_bot_base ros2 launch demo_bot_base robot.launch.py

• open another terminal (and source your workspace) and launch the demo_bot_rviz view file ros2 launch demo_bot_rviz robot.launch.py

• You can drive using the ros teleop package or the arrow_key_teleop_drive package

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Finally, please chekout and go through the demo_bot package to see proper sample of how combine the EIMU with the EPMC and ekf sensor-fusion in a mobile robot.