PX4-Autopilot/src/modules/ekf2/EKF/aid_sources/fake_pos_control.cpp

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/**
 * @file fake_pos_control.cpp
 * Control functions for ekf fake position fusion
 */

#include "ekf.h"

void Ekf::controlFakePosFusion()
{
	auto &aid_src = _aid_src_fake_pos;

	// If we aren't doing any aiding, fake position measurements at the last known position to constrain drift
	// During initial tilt alignment, fake position is used to perform a "quasi-stationary" leveling of the EKF
	const bool fake_pos_data_ready = !isHorizontalAidingActive()
					 && isTimedOut(aid_src.time_last_fuse, (uint64_t)2e5); // Fuse fake position at a limited rate

	if (fake_pos_data_ready) {

		Vector2f obs_var;

		if (_control_status.flags.in_air && _control_status.flags.tilt_align) {
			obs_var(0) = obs_var(1) = sq(fmaxf(_params.pos_noaid_noise, 1.f));

		} else if (!_control_status.flags.in_air && _control_status.flags.vehicle_at_rest) {
			// Accelerate tilt fine alignment by fusing more
			// aggressively when the vehicle is at rest
			obs_var(0) = obs_var(1) = sq(0.01f);

		} else {
			obs_var(0) = obs_var(1) = sq(0.5f);
		}

		const Vector2f position(_last_known_pos);

		const float innov_gate = 3.f;

		updateAidSourceStatus(aid_src,
					 _time_delayed_us,
					 position,                                           // observation
					 obs_var,                                            // observation variance
					 Vector2f(_state.pos) - position,                    // innovation
					 Vector2f(getStateVariance<State::pos>()) + obs_var, // innovation variance
					 innov_gate);                                        // innovation gate

		const bool enable_conditions_passing = !isHorizontalAidingActive()
				&& ((getTiltVariance() > sq(math::radians(3.f))) || _control_status.flags.vehicle_at_rest)
				&& (!(_params.imu_ctrl & static_cast<int32_t>(ImuCtrl::GravityVector)) || _control_status.flags.vehicle_at_rest)
				&& _horizontal_deadreckon_time_exceeded;

		if (_control_status.flags.fake_pos) {
			if (enable_conditions_passing) {

				// always protect against extreme values that could result in a NaN
				if ((aid_src.test_ratio[0] < sq(100.0f / innov_gate))
				    && (aid_src.test_ratio[1] < sq(100.0f / innov_gate))
				   ) {
					fuseHorizontalPosition(aid_src);
				}

				const bool is_fusion_failing = isTimedOut(aid_src.time_last_fuse, (uint64_t)4e5);

				if (is_fusion_failing) {
					ECL_WARN("fake position fusion failing, resetting");
					resetFakePosFusion();
				}

			} else {
				stopFakePosFusion();
			}

		} else {
			if (enable_conditions_passing) {
				ECL_INFO("start fake position fusion");
				_control_status.flags.fake_pos = true;
				resetFakePosFusion();

				if (_control_status.flags.tilt_align) {
					// The fake position fusion is not started for initial alignement
					_warning_events.flags.stopping_navigation = true;
					ECL_WARN("stopping navigation");
				}
			}
		}

	} else if (_control_status.flags.fake_pos && isHorizontalAidingActive()) {
		stopFakePosFusion();
	}
}

void Ekf::resetFakePosFusion()
{
	ECL_INFO("reset fake position fusion");
	_last_known_pos.xy() = _state.pos.xy();

	resetHorizontalPositionToLastKnown();
	resetHorizontalVelocityToZero();

	_aid_src_fake_pos.time_last_fuse = _time_delayed_us;
}

void Ekf::stopFakePosFusion()
{
	if (_control_status.flags.fake_pos) {
		ECL_INFO("stop fake position fusion");
		_control_status.flags.fake_pos = false;
	}
}