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FW LandDetector: disregard horizontal velocity if local_position.v_xy_valid is false #24133

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FW LandDetector: disregard horizontal velocity if local_position.v_xy_valid is false #24133

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5e0a392
Disregard horizontal velocity if local_position.v_xy_valid is false
mahimayoga Dec 19, 2024
f8718e3
Formatting
mahimayoga Dec 19, 2024
8a16289
Check for xy rotational velocity
mahimayoga Dec 20, 2024
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26 changes: 22 additions & 4 deletions src/modules/land_detector/FixedwingLandDetector.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -71,9 +71,18 @@ bool FixedwingLandDetector::_get_landed_state()

} else if (hrt_elapsed_time(&_vehicle_local_position.timestamp) < 1_s) {

// Horizontal velocity complimentary filter.
float val = 0.97f * _velocity_xy_filtered + 0.03f * sqrtf(_vehicle_local_position.vx * _vehicle_local_position.vx +
_vehicle_local_position.vy * _vehicle_local_position.vy);
float val;

if (!_vehicle_local_position.v_xy_valid) {
// set _velocity_xy_filtered to 0 if data is invalid
val = 0.0f;
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We may need to add some logic that makes the acceleration threshold tighter if we don't have ground speed and airspeed. Similar to what we already do for the ground speed check if there is no airspeed.
Otherwise it gets dangerous to fly planes without GPS and without airspeed sensor, as then they could detect "landing" in-air if flies very smoothly.


} else {
// Horizontal velocity complimentary filter.
val = 0.97f * _velocity_xy_filtered + 0.03f * sqrtf(_vehicle_local_position.vx * _vehicle_local_position.vx +
_vehicle_local_position.vy * _vehicle_local_position.vy);
}


if (PX4_ISFINITE(val)) {
_velocity_xy_filtered = val;
Expand Down Expand Up @@ -105,6 +114,14 @@ bool FixedwingLandDetector::_get_landed_state()
const float acc_hor = matrix::Vector2f(_acceleration).norm();
_xy_accel_filtered = _xy_accel_filtered * 0.8f + acc_hor * 0.18f;

// Check for angular velocity (disregard yaw)
float max_rotation_threshold = math::radians(_param_lndfw_rot_max.get());
val = _angular_velocity.xy().norm(); // TODO: check if this should be low pass filtered
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in MC landing detector the angular velocity is not filtered. Unsure if it might be necessary for FW - I don't know how noisy the data usually is in comparison.


if (PX4_ISFINITE(val)) {
_velocity_rotational = val;
}

// make groundspeed threshold tighter if airspeed is invalid
const float vel_xy_max_threshold = airspeed_invalid ? 0.7f * _param_lndfw_vel_xy_max.get() :
_param_lndfw_vel_xy_max.get();
Expand All @@ -113,7 +130,8 @@ bool FixedwingLandDetector::_get_landed_state()
landDetected = _airspeed_filtered < _param_lndfw_airspd.get()
&& _velocity_xy_filtered < vel_xy_max_threshold
&& _velocity_z_filtered < _param_lndfw_vel_z_max.get()
&& _xy_accel_filtered < _param_lndfw_xyaccel_max.get();
&& _xy_accel_filtered < _param_lndfw_xyaccel_max.get()
&& _velocity_rotational < max_rotation_threshold;

} else {
// Control state topic has timed out and we need to assume we're landed.
Expand Down
2 changes: 2 additions & 0 deletions src/modules/land_detector/FixedwingLandDetector.h
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Expand Up @@ -75,13 +75,15 @@ class FixedwingLandDetector final : public LandDetector
float _velocity_xy_filtered{0.0f};
float _velocity_z_filtered{0.0f};
float _xy_accel_filtered{0.0f};
float _velocity_rotational{0.0f};

DEFINE_PARAMETERS_CUSTOM_PARENT(
LandDetector,
(ParamFloat<px4::params::LNDFW_XYACC_MAX>) _param_lndfw_xyaccel_max,
(ParamFloat<px4::params::LNDFW_AIRSPD_MAX>) _param_lndfw_airspd,
(ParamFloat<px4::params::LNDFW_VEL_XY_MAX>) _param_lndfw_vel_xy_max,
(ParamFloat<px4::params::LNDFW_VEL_Z_MAX>) _param_lndfw_vel_z_max,
(ParamFloat<px4::params::LNDFW_ROT_MAX>) _param_lndfw_rot_max,
(ParamFloat<px4::params::LNDFW_TRIG_TIME>) _param_lndfw_trig_time
);
};
Expand Down
11 changes: 11 additions & 0 deletions src/modules/land_detector/land_detector_params_fw.c
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Expand Up @@ -102,3 +102,14 @@ PARAM_DEFINE_FLOAT(LNDFW_AIRSPD_MAX, 6.00f);
* @group Land Detector
*/
PARAM_DEFINE_FLOAT(LNDFW_TRIG_TIME, 2.f);

/**
* Fixed-wing land detector: max rotation
*
* Maximum allowed angular velocity around each axis allowed in the landed state.
*
* @unit deg/s
* @decimal 1
* @group Land Detector
*/
PARAM_DEFINE_FLOAT(LNDFW_ROT_MAX, 5.0f);
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I made up this default value - needs to be verified/adjusted.

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