multi-robot systems with ros lesson 4

Multi-Robot Systems with ROS Lesson 4

Teaching Assistant: Roi Yehoshuaroiyeho@gmail.com

Summer 2015

Agenda• ROS navigation stack with multiple robots• Sending goals to robots

ROS Navigation Stack• http://wiki.ros.org/navigation• The navigation stack handles moving a robot

from one position to another position safely (without crashing or getting lost)

• It takes in information from odometry and the sensors, and a goal pose and outputs safe velocity commands

ROS Navigation Stack

Navigation Stack Main Componentscomponent

offers map data as a ROS Service map_server

provides laser-based SLAM (Simultaneous Localization and Mapping)

gmapping

a probabilistic localization system amcl

implementation of a fast global planner for navigation global_planner

implementations of the Trajectory Rollout and Dynamic Window approaches to local robot navigation

local_planner

links together the global and local planner to accomplish the navigation task

move_base

Navigation Stack with Multiple Robots• Download the navigation tutorials from git– https://github.com/ros-planning/navigation_tutorials

• This will create a navigation_stack package• In the launch directory of the package you will

find move_base_multi_robot.launch• This is an example launch file for running

the navigation stack with multiple robots in stage

$ cd ~/ros/stacks$ git clone https://github.com/ros-planning/navigation_tutorials.git

move_base_multi_robot.launch (1)

– Remove the first argument in the stage_ros node to make stage’s window visible

• Nodes that are common to all robots:

<group ns="robot_0"> <param name="tf_prefix" value="robot_0" /> <node pkg="move_base" type="move_base" respawn="false" name="move_base_node" output="screen"> <remap from="map" to="/map" /> <param name="controller_frequency" value="10.0" /> <rosparam file="$(find navigation_stage)/move_base_config/costmap_common_params.yaml" command="load" ns="global_costmap" /> <rosparam file="$(find navigation_stage)/move_base_config/costmap_common_params.yaml" command="load" ns="local_costmap" /> <rosparam file="$(find navigation_stage)/move_base_config/local_costmap_params.yaml" command="load" /> <rosparam file="$(find navigation_stage)/move_base_config/global_costmap_params.yaml" command="load" /> <rosparam file="$(find navigation_stage)/move_base_config/base_local_planner_params.yaml" command="load" /> </node>

• Nodes for controlling robot 0:

move_base_multi_robot.launch (3) <node pkg="fake_localization" type="fake_localization" name="fake_localization" respawn="false" output="screen"> <param name="odom_frame_id" value="robot_0/odom" /> <param name="base_frame_id" value="robot_0/base_link" /> </node> </group>

<group ns="robot_1"> <param name="tf_prefix" value="robot_1" /> <node pkg="move_base" type="move_base" respawn="false" name="move_base_node" output="screen"> <remap from="map" to="/map" /> <param name="controller_frequency" value="10.0" /> <rosparam file="$(find navigation_stage)/move_base_config/costmap_common_params.yaml" command="load" ns="global_costmap" /> <rosparam file="$(find navigation_stage)/move_base_config/costmap_common_params.yaml" command="load" ns="local_costmap" /> <rosparam file="$(find navigation_stage)/move_base_config/local_costmap_params.yaml" command="load" /> <rosparam file="$(find navigation_stage)/move_base_config/global_costmap_params.yaml" command="load" /> <rosparam file="$(find navigation_stage)/move_base_config/base_local_planner_params.yaml" command="load" /> </node>

• Nodes for controlling robot 1:

move_base_multi_robot.launch (5) <node pkg="fake_localization" type="fake_localization" name="fake_localization" respawn="false"> <param name="odom_frame_id" value="robot_1/odom" /> <param name="base_frame_id" value="robot_1/base_link" /> </node> </group>

</launch>

Fake Localization• This node is most frequently used during simulation as

a method to provide perfect localization in a computationally inexpensive manner

• It creates a link between the global /map frame and the robots /odom frames so they actually become equal – no localization error = pose of robot in its /odom frame

equals its pose in the global /map frame• Parameters:– odom_frame_id - the name of the odometric frame of the robot

(default = “odom”)– base_frame_id – the base frame of the robot (default =

“base_link”)

Running the Navigation Stack• To run this launch file type:

$ roslaunch navigation_stage move_base_multi_robot.launch

Running the Navigation Stack

Map in Stage and rviz

Map in Stage and rviz• By default the origin of the map is different in Stage

and rviz • In Stage the origin is by default at the center of the

map while in rviz it is at the lower-left corner• The map’s origin in Stage can be changed by

adjusting the floorplan pose in its world file• rviz reads the map from the /map topic that is

published by map_server• Its origin can be changed in the map’s yaml file

Map in Stage and rviz• Change the map’s pose in Stage world file so the

map’s origin will be adjusted to its origin in rviz• Also change the robots’ positions accordingly

# load an environment bitmapfloorplan( name "willow" bitmap "../maps/willow-full.pgm" size [58.4 52.6 0.5] #pose [ -26.300 29.200 0 90.000 ] pose [ 29.2 26.3 0 0 ] )# throw in a robot#pr2( pose [ -21.670 47.120 0 28.166 ] name "pr2_0" color "blue")#pr2( pose [ -21.670 48.120 0 28.166 ] name "pr2_1" color "green")#block( pose [ -24.269 48.001 0 180.000 ] color "red")pr2( pose [ 9.5 14.5 0 28.166 ] name "pr2_0" color "blue")pr2( pose [ 9.5 15.5 0 28.166 ] name "pr2_1" color "green")block( pose [ 12.5 15.5 0 180.000 ] color "red")

Map in Stage and rviz

Robot Footprint• To see the robot’s footprint in rviz change the

robot footprint topic to:/robot_N/move_base_node/local_costmap/footprint_layer/footprint_stamped

• In our case, the robots have a pentagon-shape– Defined in

move_base_config/costmap_common_params.yaml

Robot Footprint

TF• Add the TF display to watch the TF tree

Sending Goals• The 2D nav goal button allows you to send a goal

to the navigation by setting a desired pose for the robot to achieve

• By default the goal is published on the topic /move_base_simple/goal

• However, when having multiple robots, the topic is /robot_N/move_base_simple/goal

• To change the topic name, first enable the Tool Properties panel via the Panels menu

Sending Goals

Sending Goals• Change the 2D Nav Goal topic to

/robot_0/move_base_simple/goal• Click on the 2D Nav Goal button (or press G) and

select the map and the goal for the first robot• You can select the x and y position and the end

orientation for the robot

Sending Goals

Collision Avoidance• To avoid the robots from colliding into each

other, change the following definition in willow-pr2-multi.world:

define pr2 position( size [0.65 0.65 0.25] origin [-0.05 0 0 0] gui_nose 1 drive "omni” topurg(pose [ 0.275 0.000 -0.1 0.000 ]))

Using the Navigation Stack• We will now create a node that will make a given

robot to move to a specific location on the map• First create a package called navigation_multi that

depends on roscpp, rospy, tf, action_lib and move_base_msgs

• Build the package by calling catkin_make• Open the package in Eclipse and add a new

source file called print_location.cpp

$ cd ~/catkin_ws/src$ catkin_create_pkg navigation_multi roscpp rospy tf actionlib move_base_msgs

Integrating with move_base• Copy the following directories and files from the

navigation_stage package to your package:– Copy the entire directory move_base_config– From the launch directory copy

move_base_multi_robot.launch– From stage_config/maps copy willow-full.pgm– From stage_config/worlds copy willow-pr2-

multi.world– From the root directory copy multi_robot.rviz

Package Directory Structure

Integrating with move_base• move_base_config files:

• Fix move_base.xml to use the correct package:

Integrating with move_base

Integrating with move_base• Fix the package name also in the launch file:

Check Package Configuration• Test that all the configuration is correct by

running the launch file:$ roslaunch navigation_multi navigation_multi.launch

Sending Goals From Code• Open the project file in Eclipse• Under the src subdirectory, create a new file

called send_goal.cpp

Using the Navigation Stack• Open the package in Eclipse and add a new

source file called send_goal.cpp• Copy the following code into it

send_goal.cpp (1)#include <ros/ros.h>#include <move_base_msgs/MoveBaseAction.h>#include <actionlib/client/simple_action_client.h>#include <tf/transform_datatypes.h> typedef actionlib::SimpleActionClient<move_base_msgs::MoveBaseAction> MoveBaseClient; using namespace std; int main(int argc, char** argv) { if (argc < 2) { ROS_ERROR("You must specify leader robot id."); return -1; } char *robot_id = argv[1]; ros::init(argc, argv, "send_goals"); ros::NodeHandle nh; // Define the goal double goal_x = 7.45; double goal_y = 18.5; double goal_theta = 0;

send_goal.cpp (2) // Create the string "robot_X/move_base" string move_base_str = "/robot_"; move_base_str += robot_id; move_base_str += "/move_base"; // create the action client MoveBaseClient ac(move_base_str, true); // Wait for the action server to become available ROS_INFO("Waiting for the move_base action server"); ac.waitForServer(ros::Duration(5)); ROS_INFO("Connected to move base server"); // Send a goal to move_base move_base_msgs::MoveBaseGoal goal; goal.target_pose.header.frame_id = "map"; goal.target_pose.header.stamp = ros::Time::now(); goal.target_pose.pose.position.x = goal_x; goal.target_pose.pose.position.y = goal_y;

send_goal.cpp (3) // Convert the Euler angle to quaternion double radians = goal_theta * (M_PI/180); tf::Quaternion quaternion; quaternion = tf::createQuaternionFromYaw(radians); geometry_msgs::Quaternion qMsg; tf::quaternionTFToMsg(quaternion, qMsg); goal.target_pose.pose.orientation = qMsg; ROS_INFO("Sending goal to robot no. %s: x = %f, y = %f, theta = %f", robot_id, goal_x, goal_y, goal_theta); ac.sendGoal(goal); // Wait for the action to return ac.waitForResult(); if (ac.getState() == actionlib::SimpleClientGoalState::SUCCEEDED) ROS_INFO("You have reached the goal!"); else ROS_INFO("The base failed for some reason"); return 0;}

Compiling the Node• Change the following lines in CMakeLists.txt:

• Then call catkin_make• For example, to send a goal to robot no.1 type:

cmake_minimum_required(VERSION 2.8.3)project(tf_multi)…## Declare a cpp executableadd_executable(send_goal src/send_goal.cpp)…## Specify libraries to link a library or executable target againsttarget_link_libraries(send_goal ${catkin_LIBRARIES})

$ rosrun navigation_multi send_goal 1

Running send_goal node

Running send_goal node• Initial position:

Running send_goal node• In the middle of the path:

Running send_goal node• Final position:

send_goal Parameters• Now let us make the desired pose of the robot

configurable in a launch file, so we can send different goals to the robots from the terminal

• You can define parameters for a node by using the <param> tag in the ROS launch file

• Create the following send_goals.launch file

send_goal Parameters<launch>  <group ns="robot_0"> <param name="goal_x" value="6.32" /> <param name="goal_y" value="17.67" /> <param name="goal_theta" value="0" /> <node pkg="navigation_multi" type="send_goal" respawn="false" name="send_goal" output="screen" args="0"/> </group>

<group ns="robot_1"> <param name="goal_x" value="10.12" /> <param name="goal_y" value="12.97" /> <param name="goal_theta" value="45" /> <node pkg="navigation_multi" type="send_goal" respawn="false" name="send_goal" output="screen" args="1"/> </group> </launch>

send_goal Parameters• Now roslaunch send_goal.launch:

send_goal Parameters

ROS Graph• Graph of nodes running in the system:

multi-robot systems with ros lesson 4

pose of robot

launch 3c2015 roi yehoshua

robot default

mu 1c2015 roi yehoshua

base frame

navigation tutorials

link c2015 roi yehoshuarunning

navigation stackto

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