Precision Landing Not Working (using MAVLINK_MSG_ID_LANDING_TARGET)

ArduCopter Copter 4.0
41

Its working now . Seems like it needs rangefinder in order to work the precision land. I have enabled mavlink rangefinder. But I need to decent it at a constant velocity. Is there is any way to disable the rangefinder and do the precision landing?

42

Hello, after checking the source code of AC_PrecLand, if the PLND_TYPE = 1 (Companion)

void AC_PrecLand_Companion::handle_msg(const mavlink_landing_target_t &packet, uint32_t timestamp_ms)
{
    _distance_to_target = packet.distance;
    GCS_SEND_TEXT(MAV_SEVERITY_INFO, "handle msg %.3f", _distance_to_target);
    if (packet.position_valid == 1) {
        if (packet.frame == MAV_FRAME_BODY_FRD) {
            if (_distance_to_target > 0) {
                _los_meas_body = Vector3f(packet.x, packet.y, packet.z);
                _los_meas_body /= _distance_to_target;
            } else {
                // distance to target must be positive
                return;
            }
        } else {
            //we do not support this frame
            if (!_wrong_frame_msg_sent) {
                _wrong_frame_msg_sent = true;
                gcs().send_text(MAV_SEVERITY_INFO,"Plnd: Frame not supported ");
            }
            return;
        }
    } else {
        // compute unit vector towards target
        _los_meas_body = Vector3f(-tanf(packet.angle_y), tanf(packet.angle_x), 1.0f);
        _los_meas_body /= _los_meas_body.length();
    }

    _los_meas_time_ms = timestamp_ms;
    _have_los_meas = true;
}

the code show that your frame type should be MAV_FRAME_BODY_FRD distance >0 x y z >0 Position_valid == 1, and

void AC_PrecLand::check_ekf_init_timeout()
{
    if (!target_acquired() && _estimator_initialized) {
        // we have just got the target in sight
        if (AP_HAL::millis()-_last_update_ms > EKF_INIT_SENSOR_MIN_UPDATE_MS) {
            // we have lost the target, not enough readings to initialize the EKF
            _estimator_initialized = false;
            gcs().send_text(MAV_SEVERITY_CRITICAL, "PrecLand: Init Failed");
        } else if (AP_HAL::millis()-_estimator_init_ms > EKF_INIT_TIME_MS) {
            // the target has been visible for a while, EKF should now have initialized to a good value
            _target_acquired = true;
            gcs().send_text(MAV_SEVERITY_INFO, "PrecLand: Init Complete");
        }
    }
}
static const uint32_t EKF_INIT_SENSOR_MIN_UPDATE_MS = 500;

my mavlink_landing_target_t like that

mavlink_landing_target_t req = new mavlink_landing_target_t
            {
                x = 1,
                y = -1,
                z = 5,
                position_valid = 1,
                type = 0,
                distance = 30,
                frame = 12
                
            };

fast send the packet in LAND mode the your vehicle will move