Version: QTrobot V2

Controlling QTrobot arms using MoveIt

Overview

Level: Advanced
Goal: learn how to control QTrobot arms using MoveIt
Requirements:

This advanced tutorial demonstrate how to use ROS MoveIT to control QTrobot arms. The examples draw some shapes (i,e. rectangle and spirals) on the XY plane in robot frame.

Preparation and requirements

Before running the example, please ensure that following setups of your QTrobot and the machine which you are running the example.

QTrobot motors setup

By default QTrobot motors interface runs in 'normal' mode. in normal mode, the motors control loop and joints state publisher run in low frequency (2-5Hz). More importantly the joint position values are in degree. To be able to use MoveIt with QTrobot, you need to configure it to run in 'advanced' mode:

joints position value is in radian
motors main controller loop and joints state publisher runs in 30hz.
required interfaces and controller such as robot_state_publisher and JointTrajectoryController are available

To run qt_motor interface in advanced mode:

first ssh to QTRP and switch to qtrobot user:

ssh developer@QTRP 
su qtrobot 

stop the qt_motor.service and launch the advanced motor interface from the command line:

sudo systemctl stop qt_motor.service
roslaunch qt_motor qt_motor_advanced.launch

Note: When running qt_motor_advanced.launch if face this error No such file or directory: '/opt/ros/noetic/share/qt_motor/model/qtrobot.urdf', follow the foll steps on QTRP:

sudo mkdir -p /opt/ros/noetic/share/qt_motor/model
sudo wget -O /opt/ros/noetic/share/qt_motor/model/qtrobot.urdf https://raw.githubusercontent.com/luxai-qtrobot/software/refs/heads/master/models/qtrobot.urdf
sudo wget -O /opt/ros/noetic/share/qt_motor/model/qtrobot.srdf https://raw.githubusercontent.com/luxai-qtrobot/software/refs/heads/master/models/qtrobot.srdf

Check if the advanced mode is running:

After rebooting the reboot, you can check (from QTPC or QTRP) if the motor interface is running in the advanced mode:

joint state publisher frequency:

rostopic hz /qt_robot/joints/state
...
average rate: 30.041
	min: 0.029s max: 0.047s std dev: 0.00391s window: 29

joints value should be in radian:

rostopic echo /qt_robot/joints/state
...
position: [0.015707962851830046, 0.0, -0.6073745663782212, 1.569051024174513, -0.9896016991965904, -0.5689773095185405, -0.3455751785790718, -0.8360127383368947]

trajectory controller is running:

rostopic type  /qt_robot/left_arm_controller/follow_joint_trajectory/goal
...
control_msgs/FollowJointTrajectoryActionGoal

MoveIt setup on QTPC:

After checking and updating the motor setup, you can install MoveIt and the iKfast solver plugin for MoveIt on QTPC:

Ensure ros-noetic-moveit is installed on QTPC:

sudo curl -s https://raw.githubusercontent.com/ros/rosdistro/master/ros.asc | sudo apt-key add -
sudo apt update
sudo apt install ros-noetic-moveit

Update the QTrobot software and tutorial repositories:

# software repository
cd ~/robot/code/software
git pull

# tutorials repository
cd ~/robot/code/tutorials
git pull

build the plugins:

cd ~/catkin_ws/src
ln -s ~/software/plugins/qtrobot_ikfast_right_arm_plugin .
ln -s ~/software/plugins/qtrobot_ikfast_right_left_plugin .
cd ~/catkin_ws
catkin_make

Build the motors_moveit

cd ~/catkin_ws/src
ln -s ~/robot/code/tutorials/examples/motors_moveit ./
cd ~/catkin_ws
catkin_make

How to run the examples

Launch moveit_qtrobot.launch to start move_group planner and rviz:

roslaunch motors_moveit moveit_qtrobot.launch

wait until rviz shows up, then run one of the following demos:

Drawing rectangle

rosrun motors_moveit draw_rectangle.py joint_states:=/qt_robot/joints/state

Drawing spiral

rosrun motors_moveit draw_spiral.py joint_states:=/qt_robot/joints/state

Preparation and requirements​

QTrobot motors setup​

MoveIt setup on QTPC:​

How to run the examples​

Drawing rectangle​