Ethzasl MSF源码阅读(1)：程序入口和主题订阅

关于IMU融合知乎上的一篇问答：有哪些开源项目是关于单目+imu做slam的？

Ethz的Stephen Weiss的工作，是一个IMU松耦合的方法。

1.程序入口：ethzasl_msf\msf_updates\src\pose_msf\main.cpp

 #include "pose_sensormanager.h"

 int main(int argc, char** argv)
 {
   ros::init(argc, argv, "msf_pose_sensor");
   msf_pose_sensor::PoseSensorManager manager;
   ros::spin();
   return ;
 }

PoseSensorManager类，查看构造函数。PoseSensorManager继承自msf_core::MSF_SensorManagerROS，继承自msf_core::MSF_SensorManager<EKFState_T>

 PoseSensorManager(ros::NodeHandle pnh = ros::NodeHandle("~/pose_sensor"))
 {
     bool distortmeas = false;  //< Distort the pose measurements.
     imu_handler_.reset(new msf_core::IMUHandler_ROS<msf_updates::EKFState>(*this, "msf_core", "imu_handler"));
     pose_handler_.reset(new PoseSensorHandler_T(*this, "", "pose_sensor", distortmeas)); AddHandler(pose_handler_);

     reconf_server_.reset(new ReconfigureServer(pnh));
     ReconfigureServer::CallbackType f = boost::bind(&PoseSensorManager::Config, this, _1, _2);//回调
     reconf_server_->setCallback(f);

     init_scale_srv_ = pnh.advertiseService("initialize_msf_scale",
                                            &PoseSensorManager::InitScale, this);
     init_height_srv_ = pnh.advertiseService("initialize_msf_height",
                                             &PoseSensorManager::InitHeight, this);
   }

2. 注意其中的imu_handler_和pose_handler_，分别是IMUHandler_ROS对象和PoseSensorHandler模板类对象。IMUHandler_ROS继承自IMUHandler。

typedef PoseSensorHandler<msf_updates::pose_measurement::PoseMeasurement<>,
      PoseSensorManager> PoseSensorHandler_T;

（msf_updates::pose_measurement::PoseMeasurement<>是模型类PoseSensorHandler的类参数，这是一个观测量参数。）

注意IMUHandler和PoseSensorHandler最终都继承自msf_core::SensorHandler<typename msf_updates::EKFState>类。

这两个类对象构造的时候都传入了*this指针，即PoseSensorManager对象自身。这很重要，两个类中都调用了PoseSensorManager的成员函数。

可以进入这两个类进行查看构造函数，这2个构造函数都进行了一些主题的订阅。

IMUHandler_ROS构造，同时查看IMUHandler_ROS::IMUCallback回调函数。

 IMUHandler_ROS(MSF_SensorManager<EKFState_T>& mng,
                  const std::string& topic_namespace, const std::string& parameternamespace)
        : IMUHandler<EKFState_T>(mng, topic_namespace, parameternamespace)
 {
     ros::NodeHandle nh(topic_namespace);
     subImu_ = nh.subscribe("imu_state_input", , &IMUHandler_ROS::IMUCallback, this);
     subState_ = nh.subscribe("hl_state_input", ,   &IMUHandler_ROS::StateCallback, this);
 }

PoseSensorHandler构造，同时查看PoseSensorHandler::MeasurementCallback回调函数。

 template<typename MEASUREMENT_TYPE, typename MANAGER_TYPE>
 PoseSensorHandler<MEASUREMENT_TYPE, MANAGER_TYPE>::PoseSensorHandler(
     MANAGER_TYPE& meas, std::string topic_namespace,
     std::string parameternamespace, bool distortmeas)
     : SensorHandler<msf_updates::EKFState>(meas, topic_namespace, parameternamespace),
       n_zp_(1e-),
       n_zq_(1e-),
       delay_(),
       timestamp_previous_pose_()
 {
   ros::NodeHandle pnh("~/" + parameternamespace);

   MSF_INFO_STREAM(
       "Loading parameters for pose sensor from namespace: "
           << pnh.getNamespace());

   pnh.param("pose_absolute_measurements", provides_absolute_measurements_,
             true);
   pnh.param("pose_measurement_world_sensor", measurement_world_sensor_, true);
   pnh.param("pose_use_fixed_covariance", use_fixed_covariance_, false);
   pnh.param("pose_measurement_minimum_dt", pose_measurement_minimum_dt_, 0.05);
   pnh.param("enable_mah_outlier_rejection", enable_mah_outlier_rejection_, false);
   pnh.param("mah_threshold", mah_threshold_, msf_core::kDefaultMahThreshold_);

   MSF_INFO_STREAM_COND(measurement_world_sensor_, "Pose sensor is interpreting "
                        "measurement as sensor w.r.t. world");
   MSF_INFO_STREAM_COND(
       !measurement_world_sensor_,
       "Pose sensor is interpreting measurement as world w.r.t. "
       "sensor (e.g. ethzasl_ptam)");

   MSF_INFO_STREAM_COND(use_fixed_covariance_, "Pose sensor is using fixed "
                        "covariance");
   MSF_INFO_STREAM_COND(!use_fixed_covariance_,
                        "Pose sensor is using covariance "
                        "from sensor");

   MSF_INFO_STREAM_COND(provides_absolute_measurements_,
                        "Pose sensor is handling "
                        "measurements as absolute values");
   MSF_INFO_STREAM_COND(!provides_absolute_measurements_, "Pose sensor is "
                        "handling measurements as relative values");

   ros::NodeHandle nh("msf_updates/" + topic_namespace);
   subPoseWithCovarianceStamped_ =
       nh.subscribe < geometry_msgs::PoseWithCovarianceStamped
           > ("pose_with_covariance_input", , &PoseSensorHandler::MeasurementCallback, this);
   subTransformStamped_ = nh.subscribe < geometry_msgs::TransformStamped
       > ("transform_input", , &PoseSensorHandler::MeasurementCallback, this);
   subPoseStamped_ = nh.subscribe < geometry_msgs::PoseStamped
       > ("pose_input", , &PoseSensorHandler::MeasurementCallback, this);

   z_p_.setZero();
   z_q_.setIdentity();

   if (distortmeas)
  {
     Eigen::Vector3d meanpos;
     double distortpos_mean;
     pnh.param("distortpos_mean", distortpos_mean, 0.0);
     meanpos.setConstant(distortpos_mean);

     Eigen::Vector3d stddevpos;
     double distortpos_stddev;
     pnh.param("distortpos_stddev", distortpos_stddev, 0.0);
     stddevpos.setConstant(distortpos_stddev);

     Eigen::Vector3d meanatt;
     double distortatt_mean;
     pnh.param("distortatt_mean", distortatt_mean, 0.0);
     meanatt.setConstant(distortatt_mean);

     Eigen::Vector3d stddevatt;
     double distortatt_stddev;
     pnh.param("distortatt_stddev", distortatt_stddev, 0.0);
     stddevatt.setConstant(distortatt_stddev);

     double distortscale_mean;
     pnh.param("distortscale_mean", distortscale_mean, 0.0);
     double distortscale_stddev;
     pnh.param("distortscale_stddev", distortscale_stddev, 0.0);

     distorter_.reset( new msf_updates::PoseDistorter(meanpos, stddevpos, meanatt, stddevatt, distortscale_mean, distortscale_stddev));
   }
 }

3.reconf_server_->setCallback(f)绑定了一个回调，回调函数PoseSensorManager::Config(xx).

 virtual void Config(Config_T &config, uint32_t level)
 {
     config_ = config;
     pose_handler_->SetNoises(config.pose_noise_meas_p,
                              config.pose_noise_meas_q);
     pose_handler_->SetDelay(config.pose_delay);
     if ((level & msf_updates::SinglePoseSensor_INIT_FILTER)
         && config.core_init_filter == true)
     {
       Init(config.pose_initial_scale);
       config.core_init_filter = false;
     }
     // Init call with "set height" checkbox.
     if ((level & msf_updates::SinglePoseSensor_SET_HEIGHT)
         && config.core_set_height == true)
      {
       Eigen::Matrix<double, , > p = pose_handler_->GetPositionMeasurement();
       if (p.norm() == )
       {
         MSF_WARN_STREAM(
             "No measurements received yet to initialize position. Height init "
             "not allowed.");
         return;
       }
       double scale = p[] / config.core_height;
       Init(scale);
       config.core_set_height = false;
     }
 }

参考文献：

多传感器卡尔曼融合框架 Ethzasl MSF Framework 编译与使用