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
1 #include "pose_sensormanager.h"
2
3 int main(int argc, char** argv)
4 {
5 ros::init(argc, argv, "msf_pose_sensor");
6 msf_pose_sensor::PoseSensorManager manager;
7 ros::spin();
8 return 0;
9 }
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>
1 PoseSensorManager(ros::NodeHandle pnh = ros::NodeHandle("~/pose_sensor"))
2 {
3 bool distortmeas = false; //< Distort the pose measurements.
4 imu_handler_.reset(new msf_core::IMUHandler_ROS<msf_updates::EKFState>(*this, "msf_core", "imu_handler"));
5 pose_handler_.reset(new PoseSensorHandler_T(*this, "", "pose_sensor", distortmeas)); AddHandler(pose_handler_);
6
7 reconf_server_.reset(new ReconfigureServer(pnh));
8 ReconfigureServer::CallbackType f = boost::bind(&PoseSensorManager::Config, this, _1, _2);//回调
9 reconf_server_->setCallback(f);
10
11 init_scale_srv_ = pnh.advertiseService("initialize_msf_scale",
12 &PoseSensorManager::InitScale, this);
13 init_height_srv_ = pnh.advertiseService("initialize_msf_height",
14 &PoseSensorManager::InitHeight, this);
15 }
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。
1 IMUHandler_ROS(MSF_SensorManager<EKFState_T>& mng,
2 const std::string& topic_namespace, const std::string& parameternamespace)
3 : IMUHandler<EKFState_T>(mng, topic_namespace, parameternamespace)
4 {
5 ros::NodeHandle nh(topic_namespace);
6 subImu_ = nh.subscribe("imu_state_input", 100, &IMUHandler_ROS::IMUCallback, this);
7 subState_ = nh.subscribe("hl_state_input", 10, &IMUHandler_ROS::StateCallback, this);
8 }
PoseSensorHandler构造，同时查看PoseSensorHandler::MeasurementCallback回调函数。
1 template<typename MEASUREMENT_TYPE, typename MANAGER_TYPE>
2 PoseSensorHandler<MEASUREMENT_TYPE, MANAGER_TYPE>::PoseSensorHandler(
3 MANAGER_TYPE& meas, std::string topic_namespace,
4 std::string parameternamespace, bool distortmeas)
5 : SensorHandler<msf_updates::EKFState>(meas, topic_namespace, parameternamespace),
6 n_zp_(1e-6),
7 n_zq_(1e-6),
8 delay_(0),
9 timestamp_previous_pose_(0)
10 {
11 ros::NodeHandle pnh("~/" + parameternamespace);
12
13 MSF_INFO_STREAM(
14 "Loading parameters for pose sensor from namespace: "
15 << pnh.getNamespace());
16
17 pnh.param("pose_absolute_measurements", provides_absolute_measurements_,
18 true);
19 pnh.param("pose_measurement_world_sensor", measurement_world_sensor_, true);
20 pnh.param("pose_use_fixed_covariance", use_fixed_covariance_, false);
21 pnh.param("pose_measurement_minimum_dt", pose_measurement_minimum_dt_, 0.05);
22 pnh.param("enable_mah_outlier_rejection", enable_mah_outlier_rejection_, false);
23 pnh.param("mah_threshold", mah_threshold_, msf_core::kDefaultMahThreshold_);
24
25 MSF_INFO_STREAM_COND(measurement_world_sensor_, "Pose sensor is interpreting "
26 "measurement as sensor w.r.t. world");
27 MSF_INFO_STREAM_COND(
28 !measurement_world_sensor_,
29 "Pose sensor is interpreting measurement as world w.r.t. "
30 "sensor (e.g. ethzasl_ptam)");
31
32 MSF_INFO_STREAM_COND(use_fixed_covariance_, "Pose sensor is using fixed "
33 "covariance");
34 MSF_INFO_STREAM_COND(!use_fixed_covariance_,
35 "Pose sensor is using covariance "
36 "from sensor");
37
38 MSF_INFO_STREAM_COND(provides_absolute_measurements_,
39 "Pose sensor is handling "
40 "measurements as absolute values");
41 MSF_INFO_STREAM_COND(!provides_absolute_measurements_, "Pose sensor is "
42 "handling measurements as relative values");
43
44 ros::NodeHandle nh("msf_updates/" + topic_namespace);
45 subPoseWithCovarianceStamped_ =
46 nh.subscribe < geometry_msgs::PoseWithCovarianceStamped
47 > ("pose_with_covariance_input", 20, &PoseSensorHandler::MeasurementCallback, this);
48 subTransformStamped_ = nh.subscribe < geometry_msgs::TransformStamped
49 > ("transform_input", 20, &PoseSensorHandler::MeasurementCallback, this);
50 subPoseStamped_ = nh.subscribe < geometry_msgs::PoseStamped
51 > ("pose_input", 20, &PoseSensorHandler::MeasurementCallback, this);
52
53 z_p_.setZero();
54 z_q_.setIdentity();
55
56 if (distortmeas)
57 {
58 Eigen::Vector3d meanpos;
59 double distortpos_mean;
60 pnh.param("distortpos_mean", distortpos_mean, 0.0);
61 meanpos.setConstant(distortpos_mean);
62
63 Eigen::Vector3d stddevpos;
64 double distortpos_stddev;
65 pnh.param("distortpos_stddev", distortpos_stddev, 0.0);
66 stddevpos.setConstant(distortpos_stddev);
67
68 Eigen::Vector3d meanatt;
69 double distortatt_mean;
70 pnh.param("distortatt_mean", distortatt_mean, 0.0);
71 meanatt.setConstant(distortatt_mean);
72
73 Eigen::Vector3d stddevatt;
74 double distortatt_stddev;
75 pnh.param("distortatt_stddev", distortatt_stddev, 0.0);
76 stddevatt.setConstant(distortatt_stddev);
77
78 double distortscale_mean;
79 pnh.param("distortscale_mean", distortscale_mean, 0.0);
80 double distortscale_stddev;
81 pnh.param("distortscale_stddev", distortscale_stddev, 0.0);
82
83 distorter_.reset( new msf_updates::PoseDistorter(meanpos, stddevpos, meanatt, stddevatt, distortscale_mean, distortscale_stddev));
84 }
85 }
3.reconf_server_->setCallback(f)绑定了一个回调，回调函数PoseSensorManager::Config(xx).
1 virtual void Config(Config_T &config, uint32_t level)
2 {
3 config_ = config;
4 pose_handler_->SetNoises(config.pose_noise_meas_p,
5 config.pose_noise_meas_q);
6 pose_handler_->SetDelay(config.pose_delay);
7 if ((level & msf_updates::SinglePoseSensor_INIT_FILTER)
8 && config.core_init_filter == true)
9 {
10 Init(config.pose_initial_scale);
11 config.core_init_filter = false;
12 }
13 // Init call with "set height" checkbox.
14 if ((level & msf_updates::SinglePoseSensor_SET_HEIGHT)
15 && config.core_set_height == true)
16 {
17 Eigen::Matrix<double, 3, 1> p = pose_handler_->GetPositionMeasurement();
18 if (p.norm() == 0)
19 {
20 MSF_WARN_STREAM(
21 "No measurements received yet to initialize position. Height init "
22 "not allowed.");
23 return;
24 }
25 double scale = p[2] / config.core_height;
26 Init(scale);
27 config.core_set_height = false;
28 }
29 }
参考文献：
多传感器卡尔曼融合框架 Ethzasl MSF Framework 编译与使用
