[advanced ROS] Lecture 9 robot model motion based on rviz and arbotix control

【ROS Advanced 】 About 9 be based on Rviz and Arbotix Controlled robot model motion

Preface

In the last blog section, we systematically learned about URDF File programming optimization method , namely Xacro, A kind of XML Optimization language , Through the basic concepts 、 Grammar explanation 、 The description of code examples shows how to improve URDF Reusability of documents 、 Security and efficiency , The article in this section mainly introduces Rviz How to use in the environment Arbotix Control the motion of the robot model .

One 、Arbotix Introduction to function package

• Problem introduction ：

In previous studies , We go through URDF The file realizes the static creation of robot model , And through visualization software Rviz Observe and implement basic operations , Then you want further simulation operations , It is necessary to complete the motion control of the robot model , Here we will introduce a corresponding function package to complete the target requirements .

1. Basic introduction ：

Arbotix：Arbotix It is a control motor 、 Steering gear control panel , And provide the corresponding ros Function pack , The functions of this feature pack can not only drive real Arbotix Control panel , It also provides a differential controller , Update the robot by receiving speed control commands joint state , So as to help us realize the robot in rviz Movement in .

notes ： This differential controller is located at python In the package , The complete package also includes a variety of controllers , Corresponding motor 、 Manipulator and gripper, etc ;

2. Installation tutorial ：

1. Command line calls directly ：

	sudo apt-get install ros-noetic-arbotix

2. git Installation source ：

	git clone https://github.com/vanadiumlabs/arbotix_ros.git

\qquad Call after downloading catkin_make After compiling ;

Two 、 Control the movement process

1. preparation

• Create Feature Pack , And write URDF file / adopt Xacro To optimize

• add to Arbotix To configure ： The configuration file control.yaml as follows

#  This file is the controller configuration file , A robot model may have multiple controllers , such as :  chassis 、 Mechanical arm 、 Gripper ( manipulator ).... #  therefore , root  name  yes  controller controllers: {
    
   #  Single controller settings  base_controller: {
    
          # type :  Differential controller 
       type: diff_controller,
       # Reference coordinates 
       base_frame_id: base_footprint, 
       # The distance between the two wheels 
       base_width: 0.2,
       # Control frequency 
       ticks_meter: 2000, 
       #PID Control parameter , Make the robot wheels reach the expected speed quickly 
       Kp: 12, 
       Kd: 12, 
       Ki: 0, 
       Ko: 50, 
       # Acceleration limit 
       accel_limit: 1.0 
    }
}

2. Write and start launch file

• To write launch file ：

\qquad The basic requirements ：
\qquad 1. Called arbotix_python Under the function package arbotix_driver node
\qquad 2. adopt file Load the configuration file to obtain the robot information in order to drive the movement
\qquad 3. To configure sim by true, Complete the simulation environment requirements

<launch>
    <!--1. Load in the parameter server urdf-->
    <!--<param name="robot_description" textfile="$(find urdf01_rviz)/urdf/xacro/demo05_car_base.urdf" />-->
    <param name="robot_description" command="$(find xacro)/xacro $(find urdf01_rviz)/urdf/xacro/car.urdf.xacro" />
    <!--2. start-up rviz-->
    <node pkg="rviz" name="rviz" type="rviz" args="-d $(find urdf01_rviz)/config/show_mycar.rviz"/>
 
    <!--3. Joint status publishing node -->
    <node pkg="joint_state_publisher" type="joint_state_publisher" name="joint_state_publisher"/>
    <!--4. Robot status publishing node -->
    <node pkg="robot_state_publisher" type="robot_state_publisher" name="robot_state_publisher"/>
 
    <!-- Integrate  arbotix  Motion control node , And load parameters -->
    <node pkg="arbotix_python" type="arbotix_driver" name="driver" output="screen">
        <rosparam command="load" file="$(find urdf01_rviz)/config/control.yaml" />
        <param name="sim" value="true" />
    </node>
</launch>

• start-up launch file ： Use roslaunch Command is enough
• To configure Rviz： modify Fixed Frame as well as TF、Odometry Under the Topic Set to odom etc.

• Control motion ： Topic at this time /cmd_vel appear , Therefore, we can complete motion control by publishing topic messages or entering commands , The effect is as follows ：

rostopic pub -r 10 /cmd_vel geometry_msgs/Twist '{linear: {x: 0.2, y: 0, z: 0}, angular: {x: 0, y: 0, z: 0.5}}'

Be careful ： If you want to further operate, you can modify Rviz Set up ：

1. Display the direction of trolley movement ： take Odometry Next status Under the topic It is amended as follows /odom;
2. Change the arrow represented by the direction of motion ： take Odometry Next shape Of shaft radius Make changes ;
3. Display the robot coordinate system ： Turn on TF arrow ;

summary

• Statement ： The blog section of this section refers to CSDN User zhaoxuzuo ROS course , The main content of this paper is to use Arbotix The function package is Rviz Complete the motion control of the static model of the robot in the environment , From the basic introduction 、 Install the tutorial to the final actual control example , Put it in simple terms from practice , Experience how to actually control robot movement . The next section will introduce in Gazebo Robot model simulation in , Coming soon .