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 = LAND_DETECTOR_TRIGGER;  // we assume we are landed
static bool land_with_gps;

static uint32_t land_start_time;
static bool land_pause;

// 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.init_loiter_target(stopping_point);
    }

    // initialize vertical speeds and leash lengths
    pos_control.set_speed_z(wp_nav.get_speed_down(), wp_nav.get_speed_up());
    pos_control.set_accel_z(wp_nav.get_accel_z());

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

    land_start_time = millis();

    land_pause = false;

    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.relax_bf_rate_controller();
        attitude_control.set_yaw_target_to_current_heading();
        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 && (ap.throttle_zero || failsafe.radio)) {
            init_disarm_motors();
        }
#else
        // disarm when the landing detector says we've landed
        if (ap.land_complete) {
            init_disarm_motors();
        }
#endif
        return;
    }

    // relax loiter target if we might be landed
    if (land_complete_maybe()) {
        wp_nav.loiter_soften_for_landing();
    }

    // process pilot inputs
    if (!failsafe.radio) {
        if (g.land_repositioning) {
            // 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(ekfGndSpdLimit, ekfNavVelGainScaler);

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

    //pause 4 seconds before beginning land descent
    float cmb_rate;
    if(land_pause && millis()-land_start_time < 4000) {
        cmb_rate = 0;
    } else {
        land_pause = false;
        cmb_rate = get_throttle_land();
    }

    // update altitude target and call position controller
    pos_control.set_alt_target_from_climb_rate(cmb_rate, G_Dt, true);
    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.relax_bf_rate_controller();
        attitude_control.set_yaw_target_to_current_heading();
        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 && (ap.throttle_zero || 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) {
        if (g.land_repositioning) {
            // 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());

    //pause 4 seconds before beginning land descent
    float cmb_rate;
    if(land_pause && millis()-land_start_time < LAND_WITH_DELAY_MS) {
        cmb_rate = 0;
    } else {
        land_pause = false;
        cmb_rate = get_throttle_land();
    }

    // call position controller
    pos_control.set_alt_target_from_climb_rate(cmb_rate, G_Dt, true);
    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 CONFIG_SONAR == ENABLED
    bool sonar_ok = sonar_enabled && sonar.healthy();
#else
    bool sonar_ok = false;
#endif
    // if we are above 10m and the sonar does not sense anything perform regular alt hold descent
    if (current_loc.alt >= LAND_START_ALT && !(sonar_ok && sonar_alt_health >= SONAR_ALT_HEALTH_MAX)) {
        return pos_control.get_speed_down();
    }else{
        return -abs(g.land_speed);
    }
}

// land_complete_maybe - return true if we may have landed (used to reset loiter targets during landing)
static bool land_complete_maybe()
{
    return (ap.land_complete || ap.land_complete_maybe);
}

// update_land_detector - checks if we have landed and updates the ap.land_complete flag
// called at 50hz
static void update_land_detector()
{
    // detect whether we have landed by watching for low climb rate, motors hitting their lower limit, overall low throttle and low rotation rate
    if ((abs(climb_rate) < LAND_DETECTOR_CLIMBRATE_MAX) &&
        (abs(baro_climbrate) < LAND_DETECTOR_BARO_CLIMBRATE_MAX) &&
        motors.limit.throttle_lower &&
#if FRAME_CONFIG != HELI_FRAME
        (motors.get_throttle_out() < get_non_takeoff_throttle()) &&
#endif
        (ahrs.get_gyro().length() < LAND_DETECTOR_ROTATION_MAX)) {
        if (!ap.land_complete) {
            // increase counter until we hit the trigger then set land complete flag
            if( land_detector < LAND_DETECTOR_TRIGGER) {
                land_detector++;
            }else{
                set_land_complete(true);
                land_detector = LAND_DETECTOR_TRIGGER;
            }
        }
    } else {
        // we've sensed movement up or down so reset land_detector
        land_detector = 0;
        // if throttle output is high then clear landing flag
        if (motors.get_throttle_out() > get_non_takeoff_throttle()) {
            set_land_complete(false);
        }
    }

    // set land maybe flag
    set_land_complete_maybe(land_detector >= LAND_DETECTOR_MAYBE_TRIGGER);
}

// land_do_not_use_GPS - forces land-mode to not use the GPS but instead rely on pilot input for roll and pitch
//  called during GPS failsafe to ensure that if we were already in LAND mode that we do not use the GPS
//  has no effect if we are not already in LAND mode
static void land_do_not_use_GPS()
{
    land_with_gps = false;
}

// set_mode_land_with_pause - sets mode to LAND and triggers 4 second delay before descent starts
static void set_mode_land_with_pause()
{
    set_mode(LAND);
    land_pause = true;
}

// landing_with_GPS - returns true if vehicle is landing using GPS
static bool landing_with_GPS() {
    return (control_mode == LAND && land_with_gps);
}