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ROS Navigation Stack について2 ~ Odometry生成ノードの作成 ~

Week of 2017/2/6

先ほどのmove_base生成のエントリに引き続き,Odometryを生成するノードを作成します.コードはほぼROSのチュートリアルのままです.

引用:http://wiki.ros.org/navigation/Tutorials/RobotSetup/Odom

1. Odometry生成ノード用のパッケージ作成

Odometry生成ノード用のパッケージを生成します.ここでは,simple_odom_generatorとします.

cd ~/reps/catkin_ws/src
catkin_create_pkg simple_odom_generator tf nav_msgs
roscd simple_odom_generator
mkdir src

2. Odometryノードのソース作成

下記,ほぼチュートリアルのコードのままですが,ロボットの土台の座標系をbase_linkからbase_footprintに変えてあります.あと,簡単のために速度も位置も常に0にしてあります.
Publish Rateは10にしてます.デフォルトだと1なのですが,move_baseのデフォルトの設定だとタイムアウトしてしまうので,変えました.

#include <ros/ros.h>
#include <tf/transform_broadcaster.h>
#include <nav_msgs/Odometry.h>

int main(int argc, char** argv){
  ros::init(argc, argv, "odometry_publisher");

  ros::NodeHandle n;
  ros::Publisher odom_pub = n.advertise<nav_msgs::Odometry>("odom", 50);
  tf::TransformBroadcaster odom_broadcaster;

  double x = 0.0;
  double y = 0.0;
  double th = 0.0;

  double vx = 0.0;
  double vy = 0.0;
  double vth = 0.0;

  ros::Time current_time, last_time;
  current_time = ros::Time::now();
  last_time = ros::Time::now();

  ros::Rate r(10);
  while(n.ok()){

    ros::spinOnce();               // check for incoming messages
    current_time = ros::Time::now();

    //compute odometry in a typical way given the velocities of the robot
    //double dt = (current_time - last_time).toSec();
    double dt = 0;
    double delta_x = (vx * cos(th) - vy * sin(th)) * dt;
    double delta_y = (vx * sin(th) + vy * cos(th)) * dt;
    double delta_th = vth * dt;

    x += delta_x;
    y += delta_y;
    th += delta_th;

    //since all odometry is 6DOF we'll need a quaternion created from yaw
    geometry_msgs::Quaternion odom_quat = tf::createQuaternionMsgFromYaw(th);

    //first, we'll publish the transform over tf
    geometry_msgs::TransformStamped odom_trans;
    odom_trans.header.stamp = current_time;
    odom_trans.header.frame_id = "odom";
    odom_trans.child_frame_id = "base_footprint";

    odom_trans.transform.translation.x = x;
    odom_trans.transform.translation.y = y;
    odom_trans.transform.translation.z = 0.0;
    odom_trans.transform.rotation = odom_quat;

    //send the transform
    odom_broadcaster.sendTransform(odom_trans);

    //next, we'll publish the odometry message over ROS
    nav_msgs::Odometry odom;
    odom.header.stamp = current_time;
    odom.header.frame_id = "odom";

    //set the position
    odom.pose.pose.position.x = x;
    odom.pose.pose.position.y = y;
    odom.pose.pose.position.z = 0.0;
    odom.pose.pose.orientation = odom_quat;

    //set the velocity
    odom.child_frame_id = "base_footprint";
    odom.twist.twist.linear.x = vx;
    odom.twist.twist.linear.y = vy;
    odom.twist.twist.angular.z = vth;

    //publish the message
    odom_pub.publish(odom);

    last_time = current_time;
    r.sleep();
  }
}

3. CMakeLists.txtの生成

次にcatkinビルドのためにCMakeLists.txtを変更します.

cmake_minimum_required(VERSION 2.8.3)
project(simple_odom_generator)

find_package(catkin REQUIRED COMPONENTS
  nav_msgs
  tf
)

catkin_package(
  CATKIN_DEPENDS nav_msgs tf
  DEPENDS system_lib
)

include_directories(
  ${catkin_INCLUDE_DIRS}
)

add_executable(simple_odom_generator_node src/simple_odom_generator.cpp)

target_link_libraries(sample_odom_generator_node
   ${catkin_LIBRARIES}
)

4. ノードの起動

roscore
rosrun simple_odom_generator simple_odom_generator_node

5. move_baseノードの起動

rosrun sample_odom_generator sample_odom_generator_node

ここまで来ると,move_baseがエラー・警告をはかなくなります.以下,実行した時のログ.
次は,このmove_baseにたいして,目的地を指定するプログラムを作ります.といっても,位置・速度は永遠に0なので,目的地に対して進むことはないプログラムですが...

core service [/rosout] found
process[navigation_velocity_smoother-1]: started with pid [14221]
process[kobuki_safety_controller-2]: started with pid [14222]
process[move_base-3]: started with pid [14228]
[ INFO] [1486805952.117027681]: Using plugin "obstacle_layer"
[ INFO] [1486805952.137293082]:     Subscribed to Topics: scan bump
[ INFO] [1486805952.167710860]: Using plugin "inflation_layer"
[ERROR] [1486805952.176414612]: You must specify at least three points for the robot footprint, reverting to previous footprint.
[ INFO] [1486805952.217033572]: Using plugin "obstacle_layer"
[ INFO] [1486805952.233590024]:     Subscribed to Topics: scan bump
[ INFO] [1486805952.261528950]: Using plugin "inflation_layer"
[ERROR] [1486805952.270706401]: You must specify at least three points for the robot footprint, reverting to previous footprint.
[ INFO] [1486805952.304290698]: Created local_planner dwa_local_planner/DWAPlannerROS
[ INFO] [1486805952.306532365]: Sim period is set to 0.20
[ INFO] [1486805952.509251511]: Recovery behavior will clear layer obstacles
[ INFO] [1486805952.528223121]: Recovery behavior will clear layer obstacles
[ INFO] [1486805952.551962298]: odom received!