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Odometry的发布和发布odom到base_link的tf变换

作者：互联网

这里面我觉得重要的话，而且我还看到了twist，这不正是前阵子普罗米修斯群里问的T265发布的带不带速度信息所说到的twist？

导航包使用tf来确定机器人在世界中的位置，并将传感器数据与静态地图相关联。然而，tf不提供关于机器人的速度的任何信息。因此，导航包要求任何odometry源通过ROS发布包含速度信息的transform和nav_msgs/Odometry消息。

 

摘自：https://www.cnblogs.com/gary-guo/p/7215284.html

Odometry的发布和发布odom到base_link的tf变换

转载自http://www.ncnynl.com/archives/201702/1328.html

ROS发布nav_msgs/Odometry消息，以及通过tf从“odom”坐标系到“base_link”坐标系的转换。

在ROS上发布Odometry信息

导航包使用tf来确定机器人在世界中的位置，并将传感器数据与静态地图相关联。然而，tf不提供关于机器人的速度的任何信息。因此，导航包要求任何odometry源通过ROS发布包含速度信息的transform和nav_msgs/Odometry消息。

nav_msgs/Odometry消息

nav_msgs/Odometry信息存储在自由空间的机器人的位置和速度的估计：

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# This represents an estimate of a position and velocity in free space.  
# 这表示对自由空间中的位置和速度的估计
# The pose in this message should be specified in the coordinate frame given by header.frame_id.
# 此消息中的姿势应在由header.frame_id给定的坐标系中指定
# The twist in this message should be specified in the coordinate frame given by the child_frame_id
# 这个消息中的twist应该在由child_frame_id给出的坐标系指定
Header header
string child_frame_id
geometry_msgs/PoseWithCovariance pose
geometry_msgs/TwistWithCovariance twist

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下面是更详细的消息类型

std_msgs/Header header
string child_frame_id
geometry_msgs/PoseWithCovariance pose
geometry_msgs/TwistWithCovariance twist

该消息中的姿势(pose)对应于机器人在世界坐标系中的估计位置以及该姿势估计特定的可选协方差。

该消息中的速度(twist)对应于机器人在子坐标系的速度，通常是移动基站的坐标系，以及该速度估计特定的可选协方差。

使用tf发布Odometry变换

如变换配置教程中所讨论的，“tf”软件库负责管理与变换树中的机器人相关的坐标系之间的关系。

因此，任何odometry(里程)源都必须发布其管理的坐标系的相关信息。

编写代码

我们将编写一些用于通过ROS发布 nav_msgs/Odometry消息的示例代码，以及使用tf的虚拟机器人的变换。

catkin_create_pkg Odom tf nav_msgs roscpp rospy

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#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 = 0.1;
  double vy = -0.1;
  double vth = 0.1;

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

  ros::Rate r(1.0);
  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 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_link";

    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_link";
    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();
  }
}

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代码解释：

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

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 = 0.1;
 double vy = -0.1;
 double vth = 0.1;

ros::Rate r(1.0);

//compute odometry in a typical way given the velocities of the robot
double dt = (current_time - last_time).toSec();
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_link";

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_link";
odom.twist.twist.linear.x = vx;
odom.twist.twist.linear.y = vy;
odom.twist.twist.angular.z = vth;

CMakeLists.txt

 add_executable(Odom_exam src/Odom_exam.cpp)
target_link_libraries(Odom_exam ${catkin_LIBRARIES})

 

分类: ROS

标签：Odometry,msgs,double,pose,base,link,odom,th,tf
来源： https://blog.csdn.net/sinat_16643223/article/details/113919768