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_msfmsf_updatessrcpose_msfmain.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 }
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