ardupilot/ArduCopter/control_land.pde

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

// counter to verify landings
static uint16_t land_detector;
static bool land_with_gps;

// land_init - initialise land controller
static bool land_init(bool ignore_checks)
{
    // check if we have GPS and decide which LAND we're going to do
    land_with_gps = GPS_ok();
    if (land_with_gps) {
        // set target to stopping point
        Vector3f stopping_point;
        wp_nav.get_loiter_stopping_point_xy(stopping_point);
        wp_nav.set_loiter_target(stopping_point);
    }

    // initialise altitude target to stopping point
    pos_control.set_target_to_stopping_point_z();
    return true;
}

// land_run - runs the land controller
// should be called at 100hz or more
static void land_run()
{
    if (land_with_gps) {
        land_gps_run();
    }else{
        land_nogps_run();
    }
}

// land_run - runs the land controller
//      horizontal position controlled with loiter controller
//      should be called at 100hz or more
static void land_gps_run()
{
    int16_t roll_control = 0, pitch_control = 0;
    float target_yaw_rate = 0;

    // if not auto armed or landed set throttle to zero and exit immediately
    if(!ap.auto_armed || ap.land_complete) {
        attitude_control.init_targets();
        attitude_control.set_throttle_out(0, false);
        wp_nav.init_loiter_target();

#if LAND_REQUIRE_MIN_THROTTLE_TO_DISARM == ENABLED
        // disarm when the landing detector says we've landed and throttle is at minimum
        if (ap.land_complete && (g.rc_3.control_in == 0 || failsafe.radio)) {
            init_disarm_motors();
        }
#else
        // disarm when the landing detector says we've landed
        if (ap.land_complete) {
            init_disarm_motors();
        }
#endif
        return;
    }

    // process pilot inputs
    if (!failsafe.radio) {
        // apply SIMPLE mode transform to pilot inputs
        update_simple_mode();

        // process pilot's roll and pitch input
        roll_control = g.rc_1.control_in;
        pitch_control = g.rc_2.control_in;

        // get pilot's desired yaw rate
        target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
    }

    // process roll, pitch inputs
    wp_nav.set_pilot_desired_acceleration(roll_control, pitch_control);

    // run loiter controller
    wp_nav.update_loiter();

    // call attitude controller
    attitude_control.angle_ef_roll_pitch_rate_ef_yaw(wp_nav.get_roll(), wp_nav.get_pitch(), target_yaw_rate);

    // update altitude target and call position controller
    pos_control.set_alt_target_from_climb_rate(get_throttle_land(), G_Dt);
    pos_control.update_z_controller();
}

// land_nogps_run - runs the land controller
//      pilot controls roll and pitch angles
//      should be called at 100hz or more
static void land_nogps_run()
{
    int16_t target_roll = 0, target_pitch = 0;
    float target_yaw_rate = 0;

    // if not auto armed or landed set throttle to zero and exit immediately
    if(!ap.auto_armed || ap.land_complete) {
        attitude_control.init_targets();
        attitude_control.set_throttle_out(0, false);
#if LAND_REQUIRE_MIN_THROTTLE_TO_DISARM == ENABLED
        // disarm when the landing detector says we've landed and throttle is at minimum
        if (ap.land_complete && (g.rc_3.control_in == 0 || failsafe.radio)) {
            init_disarm_motors();
        }
#else
        // disarm when the landing detector says we've landed
        if (ap.land_complete) {
            init_disarm_motors();
        }
#endif
        return;
    }

    // process pilot inputs
    if (!failsafe.radio) {
        // apply SIMPLE mode transform to pilot inputs
        update_simple_mode();

        // get pilot desired lean angles
        get_pilot_desired_lean_angles(g.rc_1.control_in, g.rc_2.control_in, target_roll, target_pitch);

        // get pilot's desired yaw rate
        target_yaw_rate = get_pilot_desired_yaw_rate(g.rc_4.control_in);
    }

    // call attitude controller
    attitude_control.angle_ef_roll_pitch_rate_ef_yaw_smooth(target_roll, target_pitch, target_yaw_rate, get_smoothing_gain());

    // call position controller
    pos_control.set_alt_target_from_climb_rate(get_throttle_land(), G_Dt);
    pos_control.update_z_controller();
}

// get_throttle_land - high level landing logic
//      returns climb rate (in cm/s) which should be passed to the position controller
//      should be called at 100hz or higher
static float get_throttle_land()
{
    // if we are above 10m and the sonar does not sense anything perform regular alt hold descent
    if (current_loc.alt >= LAND_START_ALT && !(g.sonar_enabled && sonar_alt_health >= SONAR_ALT_HEALTH_MAX)) {
        return pos_control.get_speed_down();
    }else{
        return -abs(g.land_speed);
    }
}

// update_land_detector - checks if we have landed and updates the ap.land_complete flag
// returns true if we have landed
static bool update_land_detector()
{
    // detect whether we have landed by watching for low climb rate and minimum throttle
    if (abs(climb_rate) < 20 && motors.limit.throttle_lower) {
        if (!ap.land_complete) {
            // run throttle controller if accel based throttle controller is enabled and active (active means it has been given a target)
            if( land_detector < LAND_DETECTOR_TRIGGER) {
                land_detector++;
            }else{
                set_land_complete(true);
                land_detector = 0;
            }
        }
    }else{
        // we've sensed movement up or down so reset land_detector
        land_detector = 0;
        if(ap.land_complete) {
            set_land_complete(false);
        }
    }

    // return current state of landing
    return ap.land_complete;
}