/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
#include "Plane.h"
/*
landing logic
*/
/*
update navigation for landing. Called when on landing approach or
final flare
*/
bool Plane::verify_land()
{
// we don't 'verify' landing in the sense that it never completes,
// so we don't verify command completion. Instead we use this to
// adjust final landing parameters
// If a go around has been commanded, we are done landing. This will send
// the mission to the next mission item, which presumably is a mission
// segment with operations to perform when a landing is called off.
// If there are no commands after the land waypoint mission item then
// the plane will proceed to loiter about its home point.
if (auto_state.commanded_go_around) {
return true;
}
float height = height_above_target();
// use rangefinder to correct if possible
height -= rangefinder_correction();
/* Set land_complete (which starts the flare) under 3 conditions:
1) we are within LAND_FLARE_ALT meters of the landing altitude
2) we are within LAND_FLARE_SEC of the landing point vertically
by the calculated sink rate (if LAND_FLARE_SEC != 0)
3) we have gone past the landing point and don't have
rangefinder data (to prevent us keeping throttle on
after landing if we've had positive baro drift)
*/
#if RANGEFINDER_ENABLED == ENABLED
bool rangefinder_in_range = rangefinder_state.in_range;
#else
bool rangefinder_in_range = false;
#endif
if (height <= g.land_flare_alt ||
(aparm.land_flare_sec > 0 && height <= auto_state.sink_rate * aparm.land_flare_sec) ||
(!rangefinder_in_range && location_passed_point(current_loc, prev_WP_loc, next_WP_loc)) ||
(fabsf(auto_state.sink_rate) < 0.2f && !is_flying())) {
if (!auto_state.land_complete) {
if (!is_flying() && (millis()-auto_state.last_flying_ms) > 3000) {
gcs_send_text_fmt(PSTR("Flare crash detected: speed=%.1f"), (double)gps.ground_speed());
} else {
gcs_send_text_fmt(PSTR("Flare %.1fm sink=%.2f speed=%.1f"),
(double)height, (double)auto_state.sink_rate, (double)gps.ground_speed());
}
}
auto_state.land_complete = true;
if (gps.ground_speed() < 3) {
// reload any airspeed or groundspeed parameters that may have
// been set for landing. We don't do this till ground
// speed drops below 3.0 m/s as otherwise we will change
// target speeds too early.
g.airspeed_cruise_cm.load();
g.min_gndspeed_cm.load();
aparm.throttle_cruise.load();
}
}
/*
when landing we keep the L1 navigation waypoint 200m ahead. This
prevents sudden turns if we overshoot the landing point
*/
struct Location land_WP_loc = next_WP_loc;
int32_t land_bearing_cd = get_bearing_cd(prev_WP_loc, next_WP_loc);
location_update(land_WP_loc,
land_bearing_cd*0.01f,
get_distance(prev_WP_loc, current_loc) + 200);
nav_controller->update_waypoint(prev_WP_loc, land_WP_loc);
// check if we should auto-disarm after a confirmed landing
disarm_if_autoland_complete();
/*
we return false as a landing mission item never completes
we stay on this waypoint unless the GCS commands us to change
mission item or reset the mission, or a go-around is commanded
*/
return false;
}
/*
If land_DisarmDelay is enabled (non-zero), check for a landing then auto-disarm after time expires
*/
void Plane::disarm_if_autoland_complete()
{
if (g.land_disarm_delay > 0 &&
auto_state.land_complete &&
!is_flying() &&
arming.arming_required() != AP_Arming::NO &&
arming.is_armed()) {
/* we have auto disarm enabled. See if enough time has passed */
if (millis() - auto_state.last_flying_ms >= g.land_disarm_delay*1000UL) {
if (disarm_motors()) {
gcs_send_text_P(SEVERITY_LOW,PSTR("Auto-Disarmed"));
}
}
}
}
/*
a special glide slope calculation for the landing approach
During the land approach use a linear glide slope to a point
projected through the landing point. We don't use the landing point
itself as that leads to discontinuities close to the landing point,
which can lead to erratic pitch control
*/
void Plane::setup_landing_glide_slope(void)
{
Location loc = next_WP_loc;
// project a point 500 meters past the landing point, passing
// through the landing point
const float land_projection = 500;
int32_t land_bearing_cd = get_bearing_cd(prev_WP_loc, next_WP_loc);
float total_distance = get_distance(prev_WP_loc, next_WP_loc);
// height we need to sink for this WP
float sink_height = (prev_WP_loc.alt - next_WP_loc.alt)*0.01f;
// current ground speed
float groundspeed = ahrs.groundspeed();
if (groundspeed < 0.5f) {
groundspeed = 0.5f;
}
// calculate time to lose the needed altitude
float sink_time = total_distance / groundspeed;
if (sink_time < 0.5f) {
sink_time = 0.5f;
}
// find the sink rate needed for the target location
float sink_rate = sink_height / sink_time;
// the height we aim for is the one to give us the right flare point
float aim_height = aparm.land_flare_sec * sink_rate;
if (aim_height <= 0) {
aim_height = g.land_flare_alt;
}
// don't allow the aim height to be too far above LAND_FLARE_ALT
if (g.land_flare_alt > 0 && aim_height > g.land_flare_alt*2) {
aim_height = g.land_flare_alt*2;
}
// time before landing that we will flare
float flare_time = aim_height / SpdHgt_Controller->get_land_sinkrate();
// distance to flare is based on ground speed, adjusted as we
// get closer. This takes into account the wind
float flare_distance = groundspeed * flare_time;
// don't allow the flare before half way along the final leg
if (flare_distance > total_distance/2) {
flare_distance = total_distance/2;
}
// now calculate our aim point, which is before the landing
// point and above it
location_update(loc, land_bearing_cd*0.01f, -flare_distance);
loc.alt += aim_height*100;
// calculate slope to landing point
float land_slope = (sink_height - aim_height) / total_distance;
// calculate point along that slope 500m ahead
location_update(loc, land_bearing_cd*0.01f, land_projection);
loc.alt -= land_slope * land_projection * 100;
// setup the offset_cm for set_target_altitude_proportion()
target_altitude.offset_cm = loc.alt - prev_WP_loc.alt;
// calculate the proportion we are to the target
float land_proportion = location_path_proportion(current_loc, prev_WP_loc, loc);
// now setup the glide slope for landing
set_target_altitude_proportion(loc, 1.0f - land_proportion);
// stay within the range of the start and end locations in altitude
constrain_target_altitude_location(loc, prev_WP_loc);
}
/*
find the nearest landing sequence starting point (DO_LAND_START) and
switch to that mission item. Returns false if no DO_LAND_START
available.
*/
bool Plane::jump_to_landing_sequence(void)
{
uint16_t land_idx = mission.get_landing_sequence_start();
if (land_idx != 0) {
if (mission.set_current_cmd(land_idx)) {
set_mode(AUTO);
//if the mission has ended it has to be restarted
if (mission.state() == AP_Mission::MISSION_STOPPED) {
mission.resume();
}
gcs_send_text_P(SEVERITY_LOW, PSTR("Landing sequence begun."));
return true;
}
}
gcs_send_text_P(SEVERITY_HIGH, PSTR("Unable to start landing sequence."));
return false;
}
/*
the height above field elevation that we pass to TECS
*/
float Plane::tecs_hgt_afe(void)
{
/*
pass the height above field elevation as the height above
the ground when in landing, which means that TECS gets the
rangefinder information and thus can know when the flare is
coming.
*/
float hgt_afe;
if (flight_stage == AP_SpdHgtControl::FLIGHT_LAND_FINAL ||
flight_stage == AP_SpdHgtControl::FLIGHT_LAND_APPROACH) {
hgt_afe = height_above_target();
hgt_afe -= rangefinder_correction();
} else {
// when in normal flight we pass the hgt_afe as relative
// altitude to home
hgt_afe = relative_altitude();
}
return hgt_afe;
}