版权声明:本文为博主原创文章,未经博主允许不得转载。 https://blog.csdn.net/kunyXu/article/details/71499944
ros中常见的坐标衔接关系为:map–>odometry–>base_link(base_footprint),所以随着机器人的移动,我们需要生成机器人的里程计信息,如此可以提供机器在map中大致的位置,一方面可以提供给相关算法(SLAM)减少搜索空间,另一方面如果没有SLAM也可以进行低精度的行走与导航。
odometry数据是由底盘的轮速与角速度结合起来计算并发布出来的,以下是ros官网的odometry数据生成源码。
#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); // 发布频率为1s
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;
// 计算累计行走的x,y,theta
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;
// 发布base_link与odom的坐标转换关系
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();
}
}
当要驱动自己的底盘移动时,需要通过某种协议获取两个轮子的速度,根据两个轮子的速度推算出底盘移动的线速度和角速度,此部分可参考,再输入到上述函数,即可完成底盘里程计数据的生成与分发。