ardupilot/ArduCopter/land_detector.pde

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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
// counter to verify landings
static uint32_t land_detector = ((float)LAND_DETECTOR_TRIGGER_SEC)*MAIN_LOOP_RATE; // we assume we are landed
// 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 MAIN_LOOP_RATE
static void update_land_detector()
{
// land detector can not use the following sensors because they are unreliable during landing
// barometer altitude : ground effect can cause errors larger than 4m
// EKF vertical velocity or altitude : poor barometer and large acceleration from ground impact
// earth frame angle or angle error : landing on an uneven surface will force the airframe to match the ground angle
// gyro output : on uneven surface the airframe may rock back an forth after landing
// range finder : tend to be problematic at very short distances
// input throttle : in slow land the input throttle may be only slightly less than hover
// check that the average throttle output is near minimum (less than 12.5% hover throttle)
bool motor_at_lower_limit = motors.limit.throttle_lower && motors.is_throttle_mix_min();
Vector3f accel_ef = ahrs.get_accel_ef_blended();
accel_ef.z += GRAVITY_MSS;
// lowpass filter on accel
accel_ef = land_accel_ef_filter.apply(accel_ef, MAIN_LOOP_SECONDS);
// check that the airframe is not accelerating (not falling or breaking after fast forward flight)
bool accel_stationary = (accel_ef.length() < 1.0f);
if ( motor_at_lower_limit && accel_stationary) {
if (!ap.land_complete) {
// increase counter until we hit the trigger then set land complete flag
if( land_detector < ((float)LAND_DETECTOR_TRIGGER_SEC)*MAIN_LOOP_RATE) {
land_detector++;
}else{
set_land_complete(true);
land_detector = ((float)LAND_DETECTOR_TRIGGER_SEC)*MAIN_LOOP_RATE;
}
}
} 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_SEC*MAIN_LOOP_RATE);
}
// update_throttle_thr_mix - sets motors throttle_low_comp value depending upon vehicle state
// low values favour pilot/autopilot throttle over attitude control, high values favour attitude control over throttle
// has no effect when throttle is above hover throttle
static void update_throttle_thr_mix()
{
if (mode_has_manual_throttle(control_mode)) {
// manual throttle
if(!motors.armed() || g.rc_3.control_in <= 0) {
motors.set_throttle_mix_min();
} else {
motors.set_throttle_mix_mid();
}
} else {
// autopilot controlled throttle
// check for aggressive flight requests - requested roll or pitch angle below 15 degrees
const Vector3f angle_target = attitude_control.angle_ef_targets();
bool large_angle_request = (pythagorous2(angle_target.x, angle_target.y) > 1500.0f);
// check for large external disturbance - angle error over 30 degrees
const Vector3f angle_error = attitude_control.angle_bf_error();
bool large_angle_error = (pythagorous2(angle_error.x, angle_error.y) > 3000.0f);
// check for large acceleration - falling or high turbulence
Vector3f accel_ef = ahrs.get_accel_ef_blended();
accel_ef.z += GRAVITY_MSS;
bool accel_moving = (accel_ef.length() > 3.0f);
// check for requested decent
bool descent_not_demanded = pos_control.get_desired_velocity().z >= 0.0f;
if ( large_angle_request || large_angle_error || accel_moving || descent_not_demanded) {
motors.set_throttle_mix_max();
} else {
motors.set_throttle_mix_min();
}
}
}