/*
adjust altitude target depending on mode
*/
void Plane::adjust_altitude_target()
{
if (control_mode == FLY_BY_WIRE_B ||
control_mode == CRUISE) {
return;
}
if (flight_stage == AP_SpdHgtControl::FLIGHT_LAND_FINAL) {
// in land final TECS uses TECS_LAND_SINK as a target sink
// rate, and ignores the target altitude
set_target_altitude_location(next_WP_loc);
} else if (flight_stage == AP_SpdHgtControl::FLIGHT_LAND_APPROACH ||
flight_stage == AP_SpdHgtControl::FLIGHT_LAND_PREFLARE) {
setup_landing_glide_slope();
adjust_landing_slope_for_rangefinder_bump();
} else if (reached_loiter_target()) {
// once we reach a loiter target then lock to the final
// altitude target
set_target_altitude_location(next_WP_loc);
} else if (target_altitude.offset_cm != 0 &&
!location_passed_point(current_loc, prev_WP_loc, next_WP_loc)) {
// control climb/descent rate
set_target_altitude_proportion(next_WP_loc, 1.0f-auto_state.wp_proportion);
// stay within the range of the start and end locations in altitude
constrain_target_altitude_location(next_WP_loc, prev_WP_loc);
} else {
set_target_altitude_location(next_WP_loc);
}
altitude_error_cm = calc_altitude_error_cm();
}
/*
adjust altitude target depending on mode
*/
void Plane::adjust_altitude_target()
{
Location target_location;
if (control_mode == FLY_BY_WIRE_B ||
control_mode == CRUISE) {
return;
}
if (landing.is_flaring()) {
// during a landing flare, use TECS_LAND_SINK as a target sink
// rate, and ignores the target altitude
set_target_altitude_location(next_WP_loc);
} else if (landing.is_on_approach()) {
landing.setup_landing_glide_slope(prev_WP_loc, next_WP_loc, current_loc, target_altitude.offset_cm);
landing.adjust_landing_slope_for_rangefinder_bump(rangefinder_state, prev_WP_loc, next_WP_loc, current_loc, auto_state.wp_distance, target_altitude.offset_cm);
} else if (landing.get_target_altitude_location(target_location)) {
set_target_altitude_location(target_location);
} else if (reached_loiter_target()) {
// once we reach a loiter target then lock to the final
// altitude target
set_target_altitude_location(next_WP_loc);
} else if (target_altitude.offset_cm != 0 &&
!location_passed_point(current_loc, prev_WP_loc, next_WP_loc)) {
// control climb/descent rate
set_target_altitude_proportion(next_WP_loc, 1.0f-auto_state.wp_proportion);
// stay within the range of the start and end locations in altitude
constrain_target_altitude_location(next_WP_loc, prev_WP_loc);
} else {
set_target_altitude_location(next_WP_loc);
}
altitude_error_cm = calc_altitude_error_cm();
}
/*
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)
{
float total_distance = get_distance(prev_WP_loc, next_WP_loc);
// If someone mistakenly puts all 0's in their LAND command then total_distance
// will be calculated as 0 and cause a divide by 0 error below. Lets avoid that.
if (total_distance < 1) {
total_distance = 1;
}
// 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;
}
// calculate slope to landing point
bool is_first_calc = is_zero(auto_state.land_slope);
auto_state.land_slope = (sink_height - aim_height) / total_distance;
if (is_first_calc) {
gcs_send_text_fmt(MAV_SEVERITY_INFO, "Landing glide slope %.1f degrees", (double)degrees(atanf(auto_state.land_slope)));
}
// 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;
}
// 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);
// now calculate our aim point, which is before the landing
// point and above it
Location loc = next_WP_loc;
location_update(loc, land_bearing_cd*0.01f, -flare_distance);
loc.alt += aim_height*100;
// calculate point along that slope 500m ahead
location_update(loc, land_bearing_cd*0.01f, land_projection);
loc.alt -= auto_state.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);
}