Optical flow: compute velociy from corrected flow data for logging (#920)

This is really useful when debugging optical flow data

EKF/ekf.h

@@ -105,6 +105,12 @@ public:
 
 	void getFlowInnovRatio(float &flow_innov_ratio) const override;
 
+	Vector2f getFlowVelBody() const override;
+	Vector2f getFlowVelNE() const override;
+	Vector2f getFlowCompensated() const override;
+	Vector2f getFlowUncompensated() const override;
+	Vector3f getFlowGyro() const override;
+
 	void getHeadingInnov(float &heading_innov) const override;
 
 	void getHeadingInnovVar(float &heading_innov_var) const override;
@@ -437,6 +443,8 @@ private:
 	Vector2f _flow_innov;		///< flow measurement innovation (rad/sec)
 	Vector2f _flow_innov_var;	///< flow innovation variance ((rad/sec)**2)
 	Vector3f _flow_gyro_bias;	///< bias errors in optical flow sensor rate gyro outputs (rad/sec)
+	Vector2f _flow_vel_body;	///< velocity from corrected flow measurement (body frame)(m/s)
+	Vector2f _flow_vel_ne;		///< velocity from corrected flow measurement (local frame) (m/s)
 	Vector3f _imu_del_ang_of;	///< bias corrected delta angle measurements accumulated across the same time frame as the optical flow rates (rad)
 	float _delta_time_of{0.0f};	///< time in sec that _imu_del_ang_of was accumulated over (sec)
 	uint64_t _time_bad_motion_us{0};	///< last system time that on-ground motion exceeded limits (uSec)

EKF/ekf_helper.cpp

@@ -708,6 +708,31 @@ void Ekf::getFlowInnovRatio(float &flow_innov_ratio) const
 	flow_innov_ratio = _optflow_test_ratio;
 }
 
+Vector2f Ekf::getFlowVelBody() const
+{
+	return _flow_vel_body;
+}
+
+Vector2f Ekf::getFlowVelNE() const
+{
+	return _flow_vel_ne;
+}
+
+Vector2f Ekf::getFlowCompensated() const
+{
+	return _flow_compensated_XY_rad;
+}
+
+Vector2f Ekf::getFlowUncompensated() const
+{
+	return _flow_sample_delayed.flow_xy_rad;
+}
+
+Vector3f Ekf::getFlowGyro() const
+{
+	return _flow_sample_delayed.gyro_xyz;
+}
+
 void Ekf::getHeadingInnov(float &heading_innov) const
 {
 	heading_innov = _heading_innov;

EKF/estimator_interface.h

@@ -91,6 +91,11 @@ public:
 	virtual void getFlowInnov(float flow_innov[2]) const = 0;
 	virtual void getFlowInnovVar(float flow_innov_var[2]) const = 0;
 	virtual void getFlowInnovRatio(float &flow_innov_ratio) const = 0;
+	virtual Vector2f getFlowVelBody() const = 0;
+	virtual Vector2f getFlowVelNE() const = 0;
+	virtual Vector2f getFlowCompensated() const = 0;
+	virtual Vector2f getFlowUncompensated() const = 0;
+	virtual Vector3f getFlowGyro() const = 0;
 
 	virtual void getHeadingInnov(float &heading_innov) const = 0;
 	virtual void getHeadingInnovVar(float &heading_innov_var) const = 0;

EKF/optflow_fusion.cpp

@@ -102,6 +102,12 @@ void Ekf::fuseOptFlow()
 	// Note the sign convention used: A positive LOS rate is a RH rotation of the scene about that axis.
 	const Vector2f opt_flow_rate = _flow_compensated_XY_rad / _flow_sample_delayed.dt + Vector2f(_flow_gyro_bias);
 
+	// compute the velocities in body and local frames from corrected optical flow measurement
+	// for logging only
+	_flow_vel_body(0) = -opt_flow_rate(1) * range;
+	_flow_vel_body(1) = opt_flow_rate(0) * range;
+	_flow_vel_ne = Vector2f(_R_to_earth * Vector3f(_flow_vel_body(0), _flow_vel_body(1), 0.f));
+
 	if (opt_flow_rate.norm() < _flow_max_rate) {
 		_flow_innov(0) =  vel_body(1) / range - opt_flow_rate(0); // flow around the X axis
 		_flow_innov(1) = -vel_body(0) / range - opt_flow_rate(1); // flow around the Y axis