ROS中发布IMU传感器消息

　　下面使用SYD Dynamics的9轴AHRS(Attitude and heading reference system)，来发布sensor_msgs/Imu类型的消息。

　　将传感器用USB转串口接到Ubuntu系统上，可以用如下命令查看串口信息：

ls -l /dev/tty*

　　查询出串口名为“/dev/ttyUSB0”。根据官方给的传感器程序源文件和boost::asio库来实现串口发送request指令，并读取传感器返回的四元数信息。之后将其发送到/IMU_data的话题上：

// Step 1:  Include Library Headers:
#include "EasyObjectDictionary.h"
#include "EasyProfile.h"

#include <ros/ros.h>
#include <sensor_msgs/Imu.h>

#include <boost/asio.hpp>         // 包含boost库函数
#include <boost/bind.hpp>
using namespace boost::asio;

int main(int argc, char** argv)
{
    // Step 2: Initialization:
    EasyProfile_C_Interface_Init();

    ros::init(argc, argv, "imu");
    ros::NodeHandle n;  

    ros::Publisher IMU_pub = n.advertise<sensor_msgs::Imu>("IMU_data", );  

    io_service io;
    serial_port sp(io, "/dev/ttyUSB0");         // 定义传输的串口
    sp.set_option(serial_port::baud_rate());                                  // 波特率
    sp.set_option(  serial_port::flow_control( serial_port::flow_control::none ) ); // 流量控制
    sp.set_option(  serial_port::parity( serial_port::parity::none ) );             // 奇偶校验
    sp.set_option( serial_port::stop_bits(  serial_port::stop_bits::one ) );        // 停止位
    sp.set_option(  serial_port::character_size(  ) );                             // 数据位

    ros::Rate loop_rate();
    while(ros::ok())
    {
        // Step 3 and Step 4 are optional, only if you want to use the request-response communication pattern
        // Step 3: Request quaternion Data from TransdcuerM
        uint16 toId = ; // Node ID
        char*  txData;
        int    txSize;
        if(EP_SUCC_ == EasyProfile_C_Interface_TX_Request(toId, EP_CMD_Q_S1_E_, &txData, &txSize))
        {
            write(sp, buffer(txData, txSize));    // Step 4:  Send the request via Serial Port.
        } 

        char rxData[];
        boost::system::error_code err;  

        sp.read_some(buffer(rxData, ),err);  // Read from serial port buffer
        if (err)
        {
            ROS_INFO("Serial port read_some Error!");
            return -;
        }  

        Ep_Header header;                       // Then let the EasyProfile do the rest such as data assembling and checksum verification.
        if( EP_SUCC_ == EasyProfile_C_Interface_RX((char*)rxData, , &header))
        {
            // Quanternion received
            unsigned int timeStamp = ep_Q_s1_e.timeStamp;
            float q1 = ep_Q_s1_e.q[];              // Note 1, ep_Q_s1_e is defined in the EasyProfile library as a global variable
            float q2 = ep_Q_s1_e.q[];              // Note 2, for the units and meaning of each value, refer to EasyObjectDictionary.h
            float q3 = ep_Q_s1_e.q[];
            float q4 = ep_Q_s1_e.q[];
            ROS_INFO("Q: %f %f %f %f\n", q1, q2, q3, q4);

            sensor_msgs::Imu imu_data;
            imu_data.header.stamp = ros::Time::now();
            imu_data.header.frame_id = "base_link";
            imu_data.orientation.x = q3;
            imu_data.orientation.y = -q2;
            imu_data.orientation.z = -q1;
            imu_data.orientation.w = q4;

            IMU_pub.publish(imu_data);
        }

        io.run();
        ros::spinOnce();
        loop_rate.sleep();
    }

    return ;
}

　　在CMakeLists中添加：

add_compile_options(-std=c99)

aux_source_directory(./src  DIR_SRCS)
add_executable(imu   ${DIR_SRCS} )
target_link_libraries(imu  ${catkin_LIBRARIES})

　　使用catkin_make编译后，source ./devel/setup.bash，然后运行rosrun imu imu。这时可能会出现无法打开串口的错误，给串口添加权限后再次运行：

sudo chmod  /dev/ttyUSB0

　　无问题后可以输入下面的指令查看话题，转动IMU可以看到orientation的四个分量一直在变化：

rostopic  echo  /IMU_data

　　为了更形象的显示IMU姿态，可以下载rviz_imu_plugin插件并安装。The rviz_imu_plugin package is used to display sensor_msgs/Imu messages in rviz. Once you download and compile the package, it should be visible as a plugin. It displays the orientation of the IMU using a box as well as and coordinate axes. The acceleration can be visualized using a vector.

　　Make sure you have git installed:

sudo apt-get install git-core

　　Download the stack from our repository into your catkin workspace

git clone -b indigo https://github.com/ccny-ros-pkg/imu_tools.git

　　Compile the stack:

cd ~/catkin_ws
catkin_make

　　装好后打开rviz，可以看到rviz_imu_plugin与rviz中默认自带的rviz_plugin_tutorials并不一样：

　　在rviz_imu_plugin下添加imu，修改Fixed Frame为base_link，IMU下面的Topic选为/IMU_data，转动IMU rviz中的虚拟立方体和坐标轴会跟着转动（可以更改box三个方向尺寸的比例）：

参考：

IMU tools for ROS

CMake 入门实战

ROS Qt Creator Plug-in wiki

ROS下IMU串口通讯接口（通用版）

如何使用Qt插件在Qt中进行ROS开发

如何用Qt对ROS项目进行调试及创建GUI界面

Serial Cross-platform, Serial Port library written in C++