ardupilot/ArduPlane/landing.pde

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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
landing logic
*/
/*
update navigation for landing. Called when on landing approach or
final flare
*/
static bool 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
float height = height_above_target();
// calculate the sink rate.
float sink_rate;
Vector3f vel;
if (ahrs.get_velocity_NED(vel)) {
sink_rate = vel.z;
} else if (gps.status() >= AP_GPS::GPS_OK_FIX_3D && gps.have_vertical_velocity()) {
sink_rate = gps.velocity().z;
} else {
sink_rate = -barometer.get_climb_rate();
}
// low pass the sink rate to take some of the noise out
auto_state.land_sink_rate = 0.8f * auto_state.land_sink_rate + 0.2f*sink_rate;
/* Set land_complete (which starts the flare) under 2 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 (height <= g.land_flare_alt ||
height <= -auto_state.land_sink_rate * g.land_flare_sec) {
if (!auto_state.land_complete) {
gcs_send_text_fmt(PSTR("Flare %.1fm sink=%.2f speed=%.1f"),
height, auto_state.land_sink_rate, 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);
/*
we always 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
*/
return false;
}