---
title: Usage of virtual_wall
---
***Usage***: By publish two points to create a virtual wall that prevents a robot can go through.

download link: https://github.com/DylanLN/virtual_wall
required packages:
+ navigation: https://github.com/ros-planning/navigation
+ turtlebot3: https://github.com/ROBOTIS-GIT/turtlebot3 -- for simulation.

move_base package inside navigation is the brain of our program that can be read file config of our map
such as : global and local costmap yaml file.
for example:
<!-- move_base -->

<node pkg="move_base" type="move_base" respawn="false" name="move_base2" output="screen">
    <param name="base_local_planner" value="dwa_local_planner/DWAPlannerROS" />
    <rosparam file="$(find turtlebot3_navigation)/param/costmap_common_params_$(arg model).yaml" command="load" ns="global_costmap" />
    <rosparam file="$(find turtlebot3_navigation)/param/costmap_common_params_$(arg model).yaml" command="load" ns="local_costmap" />
    <rosparam file="$(find turtlebot3_navigation)/param/local_costmap_params.yaml" command="load" />
    <rosparam file="$(find turtlebot3_navigation)/param/global_costmap_params.yaml" command="load" />
    <rosparam file="$(find turtlebot3_navigation)/param/move_base_params.yaml" command="load" />
    <rosparam file="$(find turtlebot3_navigation)/param/dwa_local_planner_params_$(arg model).yaml" command="load" />
    <remap from="cmd_vel" to="$(arg cmd_vel_topic)"/>
    <remap from="odom" to="$(arg odom_topic)"/>
    <param name="DWAPlannerROS/min_vel_x" value="0.0" if="$(arg move_forward_only)" />
  </node>

***Note: change to our real path of yaml file***

we use turtlebot3 for example of adding virtual wall.Two files that we need to modify include globalcostmapparams.yaml && localcostmapparams.yaml

change detail of two files inside
+*catkinws/src/turtlebot3/turtlebot3navigation/param/globalcostmapparams.yaml*

global_costmap:
  global_frame: map
  robot_base_frame: base_footprint

  update_frequency: 10.0
  publish_frequency: 10.0
  transform_tolerance: 0.5

  static_map: true
  plugins:
    - {name: static_layer,            type: "costmap_2d::StaticLayer"}
    - {name: obstacle_layer,          type: "costmap_2d::VoxelLayer"}
    - {name: virtual_wall,    type: "virtual_wall::VirtualWall"}
    - {name: inflation_layer,         type: "costmap_2d::InflationLayer"}

+*catkinws/src/turtlebot3/turtlebot3navigation/param/localcostmapparams.yaml*

local_costmap:
   global_frame: odom
   robot_base_frame: base_footprint
   
   update_frequency: 10.0
   publish_frequency: 10.0
   transform_tolerance: 0.5

   static_map: false
   rolling_window: true
   width: 3.0
   height: 3.0
   resolution: 0.05
   plugins:
    - {name: static_layer,            type: "costmap_2d::StaticLayer"}
    - {name: virtual_wall,    type: "virtual_wall::VirtualWall"}
    - {name: obstacle_layer,      type: "costmap_2d::VoxelLayer"}
    - {name: inflation_layer,     type: "costmap_2d::InflationLayer"}

**Step1**:
cd catkin_ws
export TURTLEBOT3_MODEL=burger
source devel/setup.bash
roslaunch turtlebot3_gazebo turtlebot3_world.launch

**Step2**:
cd catkin_ws
export TURTLEBOT3_MODEL=burger
source devel/setup.bash
roslaunch turtlebot3_navigation turtlebot3_navigation.launch

OR: roslaunch turtlebot3_navigation turtlebot3_navigation.launch map_file:=$HOME/map.yaml(FOR SPECIFIC SCANED MAP)

use QMTT to publish two points with topic as :
/clicked_point

# **Note: Add Maker in rviz to see the wall + to publish points to create a wall please use the command : **

rostopic pub /clicked_point geometry_msgs/PointStamped '{header: {stamp: now, frame_id: map}, point: { x: -0.951733231544, y: -1.90567553043, z: 0.00247192382812}}'


rostopic pub /clicked_point geometry_msgs/PointStamped '{header: {stamp: now, frame_id: map}, point: { x: 0.367253124714, y: -1.8252556324, z: 0.00247192382812}}'

format of json we can take a look : http://library.isr.ist.utl.pt/docs/roswiki/ROS(2f)YAMLCommandLine.html

# To list all ids of walls please command:
`rostopic echo virtual_wall_list`
each wall will be index from 0
To delete a wall:

`rostopic pub /delete_wall std_msgs/Int32 '0'`

# *The way to create an layer plugin, please take a look at* : http://wiki.ros.org/costmap_2d/Tutorials/Creating%20a%20New%20Layer
Idea: Amap contain many layers such as static_layer map, obstacle map and inflation_layer
The static map layer: the map is scan by SLAM
The obstacle layer: tracks the obstacles as read by the sensor data
The inflation layer: is an optimization that adds new values around lethal obstacles
Robots will avoid to move through by read each layer; therefore, you can add one layer such as virtual wall.

# Result: