Skip to main content
Version: QTrobot V1

ROS motor controller for QTrobot

Overview

 Level:  Advanced
 Goal:  learn how to implement ROS motor controller for QTrobot
 Requirements:

This example shows how to write a new ROS controller for QTrobot on QTRP. Before getting into that, make sure you know and understand what is ROS Control.

What it does?​

this controller simply play a predefined trajectory directly by commanding the QTrobot motors at hardware level. You can use it as a simple template to implement more sophisticate controllers.

Compilation and build​

  • copy motors_custom_controller to the ~/catckin_wson the RPI of QTrobot

  • build the example code:

cd ~/catckin_ws
catkin_make --pkg motors_custom_controller

Configuration and launching​

  • modify the qt_motor config file to define your new controller. to do that open /opt/ros/noetic/share/qt_motor/config/qtrobot-controller.yaml file and add the following lines to the end of the file.
  custom:
    type: motors_custom_controller/QTCustomController
    myparam: bar

  • modify qt_motor launch file to load and run your controller. to do that, open /opt/ros/noetic/share/qt_motor/launch/qt_motor.launch and add /qt_robot/custom controller to controller_manager node. it should look like this:
<!-- load the controllers -->
 <node pkg="controller_manager" name="controller" type="spawner" launch-prefix="bash -c 'sleep 15; $0 $@' " respawn="false"
       output="screen" clear_params="true"  args="/qt_robot/head_position
                             /qt_robot/right_arm_position
                             /qt_robot/left_arm_position
                             /qt_robot/joints_state
                             /qt_robot/motors
                             /qt_robot/gesture
                             /qt_robot/custom"/>

Re-launch qt_motor node​

you can simply reboot the robot or launch the qt_motor node from terminal to see its output.

  • stop the running instance:
ps -aux | grep qt_motor | grep SCREEN
...
kill xxx
  • launch qt_motor node
roslaunch qt_motor qt_motor.launch

you should see your controller (QTCustomController) running by checking the terminal output:

...
[INFO] [1576498210.924577]: Controller Spawner: Loaded controllers: /qt_robot/head_position, /qt_robot/right_arm_position, /qt_robot/left_arm_position, /qt_robot/joints_state, /qt_robot/motors, /qt_robot/gesture, /qt_robot/custom
[ INFO] [1576498210.984396566]: QTMotorsController: starting
[ INFO] [1576498210.985034385]: QTGestureController: starting
[ INFO] [1576498210.985518609]: QTCustomController: starting
...

Testing​

your custom controller implement a service to Start/Stop it.

  • to start the trajectory player, open another terminal and
rosservice call /qt_robot/custom/startstop "command: true"
  • to stop the trajectory player:
rosservice call /qt_robot/custom/startstop "command: false"