cartograhper 中IMU 消息发布需要注意的东西

const imu_data_t* imu = &info->imu_data;
//这里除以100 是由协议规定的，因为芯片为了防止传输浮点型数据，先乘以100后再传输的，
//因此在stm32上获取数据后，需要除以100.0 才是真是的数据
float yaw = imu->yaw/100.0f;  
float roll = imu->roll/100.0f;
float pitch = imu->pitch/100.0f;
//imu 芯片数据中的坐标系是左手定则，而ros 的数据是右手定则，因此乘以-1 进行转换
float yaw_rate = -1*imu->yaw_rate/100.0f;
float roll_rate = -1*imu->roll_rate/100.0f;
float pitch_rate = -1*imu->pitch_rate/100.0f;

sensor_msgs::Imu imu_data;
imu_data.header.stamp = ros::Time::now();
imu_data.header.frame_id = imu_frame_id;
imu_data.orientation_covariance[0] = 1000000;
imu_data.orientation_covariance[1] = 0;
imu_data.orientation_covariance[2] = 0;
imu_data.orientation_covariance[3] = 0;
imu_data.orientation_covariance[4] = 1000000;
imu_data.orientation_covariance[5] = 0;
imu_data.orientation_covariance[6] = 0;
imu_data.orientation_covariance[7] = 0;
imu_data.orientation_covariance[8] = 0.000001;
geometry_msgs::Quaternion imu_quaternion;

/*这是欧拉角与四元数的转换公式， 理论是
x = 0.0;
y = 0.0;
z = sin(th/2.0); //th 为yaw 角，单位为弧度
w = cos(th/2.0);
*/
imu_quaternion.x = 0.0;
imu_quaternion.y = 0.0;
imu_quaternion.z = sin(-1*yaw*3.1416/(180 *2.0));
imu_quaternion.w = cos(-1*yaw*3.1416/(180 *2.0));
imu_data.orientation = imu_quaternion;
/*
这是线加速度，理论z 为重力加速度为9.8
然后根据你陀螺仪安装的位置(坐标系)调试(ROS坐标系下)x 方向数据和y 方向数据
*/
imu_data.linear_acceleration.x = -1*imu->yacc/100.0;
imu_data.linear_acceleration.y = -1*imu->xacc/100.0;
imu_data.linear_acceleration.z = -1*imu->zacc/100.0;
imu_data.linear_acceleration_covariance[0] = 1000000;
imu_data.linear_acceleration_covariance[4] = 1000000;
imu_data.linear_acceleration_covariance[8] = 0.000001;

imu_data.angular_velocity_covariance[0] = 0.000001;
imu_data.angular_velocity_covariance[4] = 0.0;
imu_data.angular_velocity_covariance[8] = 0.0;

imu_data.angular_velocity.x = DEG2RAD(roll_rate);
imu_data.angular_velocity.y = DEG2RAD(pitch_rate);
imu_data.angular_velocity.z = DEG2RAD(yaw_rate);
imuPub.publish(imu_data);
std_msgs::Float32 imuAngle;
imuAngle.data = -1*DEG2RAD(yaw);
imuAnglePub.publish(imuAngle);