LandingTargetEstimator.cpp

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/*
 * @file LandingTargetEstimator.cpp
 *
 * @author Nicolas de Palezieux (Sunflower Labs) <ndepal@gmail.com>
 * @author Mohammed Kabir <kabir@uasys.io>
 *
 */

#include <px4_platform_common/px4_config.h>
#include <px4_platform_common/defines.h>
#include <drivers/drv_hrt.h>

#include "LandingTargetEstimator.h"

#define SEC2USEC 1000000.0f


namespace landing_target_estimator
{

LandingTargetEstimator::LandingTargetEstimator()
{
    _paramHandle.acc_unc = param_find("LTEST_ACC_UNC");
    _paramHandle.meas_unc = param_find("LTEST_MEAS_UNC");
    _paramHandle.pos_unc_init = param_find("LTEST_POS_UNC_IN");
    _paramHandle.vel_unc_init = param_find("LTEST_VEL_UNC_IN");
    _paramHandle.mode = param_find("LTEST_MODE");
    _paramHandle.scale_x = param_find("LTEST_SCALE_X");
    _paramHandle.scale_y = param_find("LTEST_SCALE_Y");

    _check_params(true);
}

void LandingTargetEstimator::update()
{
    _check_params(false);

    _update_topics();

    /* predict */
    if (_estimator_initialized) {
        if (hrt_absolute_time() - _last_update > landing_target_estimator_TIMEOUT_US) {
            PX4_WARN("Timeout");
            _estimator_initialized = false;

        } else {
            float dt = (hrt_absolute_time() - _last_predict) / SEC2USEC;

            // predict target position with the help of accel data
            matrix::Vector3f a{_vehicle_acceleration.xyz};

            if (_vehicleAttitude_valid && _vehicle_acceleration_valid) {
                matrix::Quaternion<float> q_att(&_vehicleAttitude.q[0]);
                _R_att = matrix::Dcm<float>(q_att);
                a = _R_att * a;

            } else {
                a.zero();
            }

            _kalman_filter_x.predict(dt, -a(0), _params.acc_unc);
            _kalman_filter_y.predict(dt, -a(1), _params.acc_unc);

            _last_predict = hrt_absolute_time();
        }
    }

    if (!_new_irlockReport) {
        // nothing to do
        return;
    }

    // mark this sensor measurement as consumed
    _new_irlockReport = false;

    if (!_vehicleAttitude_valid || !_vehicleLocalPosition_valid || !_vehicleLocalPosition.dist_bottom_valid) {
        // don't have the data needed for an update
        return;
    }

    if (!PX4_ISFINITE(_irlockReport.pos_y) || !PX4_ISFINITE(_irlockReport.pos_x)) {
        return;
    }

    // TODO account for sensor orientation as set by parameter
    // default orientation has camera x pointing in body y, camera y in body -x

    matrix::Vector<float, 3> sensor_ray; // ray pointing towards target in body frame
    sensor_ray(0) = -_irlockReport.pos_y * _params.scale_y; // forward
    sensor_ray(1) = _irlockReport.pos_x * _params.scale_x; // right
    sensor_ray(2) = 1.0f;

    // rotate the unit ray into the navigation frame, assume sensor frame = body frame
    matrix::Quaternion<float> q_att(&_vehicleAttitude.q[0]);
    _R_att = matrix::Dcm<float>(q_att);
    sensor_ray = _R_att * sensor_ray;

    if (fabsf(sensor_ray(2)) < 1e-6f) {
        // z component of measurement unsafe, don't use this measurement
        return;
    }

    float dist = _vehicleLocalPosition.dist_bottom;

    // scale the ray s.t. the z component has length of dist
    _rel_pos(0) = sensor_ray(0) / sensor_ray(2) * dist;
    _rel_pos(1) = sensor_ray(1) / sensor_ray(2) * dist;

    if (!_estimator_initialized) {
        PX4_INFO("Init");
        float vx_init = _vehicleLocalPosition.v_xy_valid ? -_vehicleLocalPosition.vx : 0.f;
        float vy_init = _vehicleLocalPosition.v_xy_valid ? -_vehicleLocalPosition.vy : 0.f;
        _kalman_filter_x.init(_rel_pos(0), vx_init, _params.pos_unc_init, _params.vel_unc_init);
        _kalman_filter_y.init(_rel_pos(1), vy_init, _params.pos_unc_init, _params.vel_unc_init);

        _estimator_initialized = true;
        _last_update = hrt_absolute_time();
        _last_predict = _last_update;

    } else {
        // update
        bool update_x = _kalman_filter_x.update(_rel_pos(0), _params.meas_unc * dist * dist);
        bool update_y = _kalman_filter_y.update(_rel_pos(1), _params.meas_unc * dist * dist);

        if (!update_x || !update_y) {
            if (!_faulty) {
                _faulty = true;
                PX4_WARN("Landing target measurement rejected:%s%s", update_x ? "" : " x", update_y ? "" : " y");
            }

        } else {
            _faulty = false;
        }

        if (!_faulty) {
            // only publish if both measurements were good

            _target_pose.timestamp = _irlockReport.timestamp;

            float x, xvel, y, yvel, covx, covx_v, covy, covy_v;
            _kalman_filter_x.getState(x, xvel);
            _kalman_filter_x.getCovariance(covx, covx_v);

            _kalman_filter_y.getState(y, yvel);
            _kalman_filter_y.getCovariance(covy, covy_v);

            _target_pose.is_static = (_params.mode == TargetMode::Stationary);

            _target_pose.rel_pos_valid = true;
            _target_pose.rel_vel_valid = true;
            _target_pose.x_rel = x;
            _target_pose.y_rel = y;
            _target_pose.z_rel = dist;
            _target_pose.vx_rel = xvel;
            _target_pose.vy_rel = yvel;

            _target_pose.cov_x_rel = covx;
            _target_pose.cov_y_rel = covy;

            _target_pose.cov_vx_rel = covx_v;
            _target_pose.cov_vy_rel = covy_v;

            if (_vehicleLocalPosition_valid && _vehicleLocalPosition.xy_valid) {
                _target_pose.x_abs = x + _vehicleLocalPosition.x;
                _target_pose.y_abs = y + _vehicleLocalPosition.y;
                _target_pose.z_abs = dist + _vehicleLocalPosition.z;
                _target_pose.abs_pos_valid = true;

            } else {
                _target_pose.abs_pos_valid = false;
            }

            _targetPosePub.publish(_target_pose);

            _last_update = hrt_absolute_time();
            _last_predict = _last_update;
        }

        float innov_x, innov_cov_x, innov_y, innov_cov_y;
        _kalman_filter_x.getInnovations(innov_x, innov_cov_x);
        _kalman_filter_y.getInnovations(innov_y, innov_cov_y);

        _target_innovations.timestamp = _irlockReport.timestamp;
        _target_innovations.innov_x = innov_x;
        _target_innovations.innov_cov_x = innov_cov_x;
        _target_innovations.innov_y = innov_y;
        _target_innovations.innov_cov_y = innov_cov_y;

        _targetInnovationsPub.publish(_target_innovations);
    }
}

void LandingTargetEstimator::_check_params(const bool force)
{
    bool updated = _parameterSub.updated();

    if (updated) {
        parameter_update_s paramUpdate;
        _parameterSub.copy(&paramUpdate);
    }

    if (updated || force) {
        _update_params();
    }
}

void LandingTargetEstimator::_update_topics()
{
    _vehicleLocalPosition_valid = _vehicleLocalPositionSub.update(&_vehicleLocalPosition);
    _vehicleAttitude_valid = _attitudeSub.update(&_vehicleAttitude);
    _vehicle_acceleration_valid = _vehicle_acceleration_sub.update(&_vehicle_acceleration);

    _new_irlockReport = _irlockReportSub.update(&_irlockReport);
}

void LandingTargetEstimator::_update_params()
{
    param_get(_paramHandle.acc_unc, &_params.acc_unc);
    param_get(_paramHandle.meas_unc, &_params.meas_unc);
    param_get(_paramHandle.pos_unc_init, &_params.pos_unc_init);
    param_get(_paramHandle.vel_unc_init, &_params.vel_unc_init);

    int32_t mode = 0;
    param_get(_paramHandle.mode, &mode);
    _params.mode = (TargetMode)mode;

    param_get(_paramHandle.scale_x, &_params.scale_x);
    param_get(_paramHandle.scale_y, &_params.scale_y);
}


} // namespace landing_target_estimator