struct Encoder_{float d_left;float d_right;int enc_left; //wheel encoder readings int enc_right; int left; // actual values coming back from robot int right; }self; float d,th; #define ticks_meter 123077.0 //每米编码器的值 linear = 2.6 #define base_width 0.31f; //轴距 angule = 0.316 #define robot_timer 0.53f //周期  union Max_Value { unsigned char buf[12]; struct _Float_{ 　　　　　　　float hander; float _float_vx; float _float_vth; }Float_RAM; }Send_Data; extern int encoder_0; extern int encoder_1; void Updata_velocities_Data() { 　 　u8 i=0; self.right = encoder_0;//编码器的累计量 self.left = encoder_1; if(self.enc_left == 0) { self.d_left = 0; self.d_right = 0; } else { self.d_left = (self.left - self.enc_left) / ticks_meter; self.d_right = (self.right - self.enc_right) / ticks_meter; } self.enc_left = self.left; self.enc_right = self.right;  d = ( self.d_left + self.d_right ) / 2; //distance traveled is the average of the two wheels th = ( self.d_right - self.d_left ) / base_width; //this approximation works (in radians) for small angles  self.dx = d / robot_timer; //calculate velocities self.dr = th / robot_timer; 　　 Send_Data.Float_RAM.hander = 15.5; Send_Data.Float_RAM._float_vx = self.dx; Send_Data.Float_RAM._float_vth = self.dr; for(i=0;i<12;i++) 　　　　sendchar_usart1(Send_Data.buf[i]); }

#include <ros/ros.h>
#include <sensor_msgs/JointState.h>
#include <tf/transform_broadcaster.h>
#include <nav_msgs/Odometry.h>
#include <iostream>
#include <iomanip>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <math.h>using namespace std;
using namespace boost::asio;ros::Time current_time, last_time;
double x = 0.0;
double y = 0.0;
double th = 0.0;
double vx = 0.0;
double vy = 0.0;
double vth = 0.0;union _SPEED_
{unsigned char speed_buf[16];struct _speed_value_{float flag;float left_vel;float yspeed_vel;float right_vel;}Struct_Speed;
}Union_Speed;geometry_msgs::Quaternion odom_quat;void cmd_velCallback(const geometry_msgs::Twist &twist_aux)
{geometry_msgs::Twist twist = twist_aux;Union_Speed.Struct_Speed.flag = 15.5;Union_Speed.Struct_Speed.left_vel = twist_aux.linear.x;Union_Speed.Struct_Speed.yspeed_vel = 0.0;Union_Speed.Struct_Speed.right_vel = twist_aux.angular.z;
}double dt = 0.0; union _Data_
{unsigned char buf_rev[12];struct _value_encoder_{float Flag_Float;float VX_speed;float VZ_speed;}Struct_Encoder;
}Union_Data;int main(int argc, char** argv)
{unsigned char check_buf[1];unsigned char i;io_service iosev;serial_port sp(iosev, "/dev/ttyUSB0");sp.set_option(serial_port::baud_rate(115200));sp.set_option(serial_port::flow_control(serial_port::flow_control::none));sp.set_option(serial_port::parity(serial_port::parity::none));sp.set_option(serial_port::stop_bits(serial_port::stop_bits::one));sp.set_option(serial_port::character_size(8));ros::init(argc, argv, "base_controller");ros::NodeHandle n;ros::Subscriber cmd_vel_sub = n.subscribe("cmd_vel", 50, cmd_velCallback);ros::Publisher odom_pub = n.advertise<nav_msgs::Odometry>("odom", 50);tf::TransformBroadcaster odom_broadcaster;while(ros::ok()){current_time = ros::Time::now();ros::spinOnce();  dt = (current_time - last_time).toSec(); last_time = ros::Time::now();current_time = ros::Time::now();read(sp, buffer(Union_Data.buf_rev));if(Union_Data.Struct_Encoder.Flag_Float == 15.5){vx = Union_Data.Struct_Encoder.VX_speed;vth = Union_Data.Struct_Encoder.VZ_speed;ROS_INFO("msg_encoder.angular_z is %f",vth);ROS_INFO("msg_encoder.linear.x  is %f",vx);}else{    ROS_INFO("Fucking communication fails,The fuck can i hurry up to restart!");read(sp, buffer(check_buf));}    write(sp, buffer(Union_Speed.speed_buf,16)); 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;geometry_msgs::Quaternion odom_quat = tf::createQuaternionMsgFromYaw(th);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;odom_broadcaster.sendTransform(odom_trans);nav_msgs::Odometry odom;odom.header.stamp = current_time;odom.header.frame_id = "odom";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;odom.child_frame_id = "base_link";odom.twist.twist.linear.x = vx;odom.twist.twist.linear.y = vy;odom.twist.twist.angular.z = vth;odom_pub.publish(odom);last_time = current_time;}iosev.run(); 
}

roscore &
rosrun odom_tf_package tf_broadcaster_node
rviz
rosrun rbx1_nav timed_out_and_back.py  //此节点为turtlebot的damo