ardupilot/ArduCopter/baro_ground_effect.cpp

/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-

#include "Copter.h"

void Copter::update_ground_effect_detector(void)
{
    if(!g2.gndeffect_comp_enabled || !motors.armed()) {
        // disarmed - disable ground effect and return
        gndeffect_state.takeoff_expected = false;
        gndeffect_state.touchdown_expected = false;
        ahrs.setTakeoffExpected(gndeffect_state.takeoff_expected);
        ahrs.setTouchdownExpected(gndeffect_state.touchdown_expected);
        return;
    }

    // variable initialization
    uint32_t tnow_ms = millis();
    float xy_des_speed_cms = 0.0f;
    float xy_speed_cms = 0.0f;
    float des_climb_rate_cms = pos_control.get_desired_velocity().z;

    if (pos_control.is_active_xy()) {
        Vector3f vel_target = pos_control.get_vel_target();
        vel_target.z = 0.0f;
        xy_des_speed_cms = vel_target.length();
    }

    if (position_ok() || optflow_position_ok()) {
        Vector3f vel = inertial_nav.get_velocity();
        vel.z = 0.0f;
        xy_speed_cms = vel.length();
    }

    // takeoff logic

    // if we are armed and haven't yet taken off
    if (motors.armed() && ap.land_complete && !gndeffect_state.takeoff_expected) {
        gndeffect_state.takeoff_expected = true;
    }

    // if we aren't taking off yet, reset the takeoff timer, altitude and complete flag
    bool throttle_up = mode_has_manual_throttle(control_mode) && g.rc_3.get_control_in() > 0;
    if (!throttle_up && ap.land_complete) {
        gndeffect_state.takeoff_time_ms = tnow_ms;
        gndeffect_state.takeoff_alt_cm = inertial_nav.get_altitude();
    }

    // if we are in takeoff_expected and we meet the conditions for having taken off
    // end the takeoff_expected state
    if (gndeffect_state.takeoff_expected && (tnow_ms-gndeffect_state.takeoff_time_ms > 5000 || inertial_nav.get_altitude()-gndeffect_state.takeoff_alt_cm > 50.0f)) {
        gndeffect_state.takeoff_expected = false;
    }

    // landing logic
    Vector3f angle_target_rad = attitude_control.get_att_target_euler_cd() * radians(0.01f);
    bool small_angle_request = cosf(angle_target_rad.x)*cosf(angle_target_rad.y) > cosf(radians(7.5f));
    bool xy_speed_low = (position_ok() || optflow_position_ok()) && xy_speed_cms <= 125.0f;
    bool xy_speed_demand_low = pos_control.is_active_xy() && xy_des_speed_cms <= 125.0f;
    bool slow_horizontal = xy_speed_demand_low || (xy_speed_low && !pos_control.is_active_xy()) || (control_mode == ALT_HOLD && small_angle_request);

    bool descent_demanded = pos_control.is_active_z() && des_climb_rate_cms < 0.0f;
    bool slow_descent_demanded = descent_demanded && des_climb_rate_cms >= -100.0f;
    bool z_speed_low = abs(inertial_nav.get_velocity_z()) <= 60.0f;
    bool slow_descent = (slow_descent_demanded || (z_speed_low && descent_demanded));

    gndeffect_state.touchdown_expected = slow_horizontal && slow_descent;

    // Prepare the EKF for ground effect if either takeoff or touchdown is expected.
    ahrs.setTakeoffExpected(gndeffect_state.takeoff_expected);
    ahrs.setTouchdownExpected(gndeffect_state.touchdown_expected);
}