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111 lines
7.0 KiB
Markdown
111 lines
7.0 KiB
Markdown
# 광류 센서
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_Optical Flow_ uses a downward facing camera and a downward facing distance sensor for velocity estimation.
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It can be used to determine speed when navigating without GNSS — in buildings, underground, or in any other GNSS-denied environment.
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The video below shows PX4 holding position using the [Ark Flow](../dronecan/ark_flow.md) sensor for velocity estimation in [Position Mode](../flight_modes_mc/position.md):
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<lite-youtube videoid="aPQKgUof3Pc" title="ARK Flow with PX4 Optical Flow Position Hold"/>
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<!-- ARK Flow with PX4 Optical Flow Position Hold: 20210605 -->
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The image below shows an optical flow setup with a separate flow sensor ([PX4Flow](../sensor/px4flow.md)) and distance sensor ([Lidar-Lite](../sensor/lidar_lite.md)):
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## 설정
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An Optical Flow setup requires a downward facing camera and a downward facing [distance sensor](../sensor/rangefinders.md) (preferably a LiDAR).
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These can be combined in a single product, such as the [ARK Flow](../dronecan/ark_flow.md), [ARK Flow MR](../dronecan/ark_flow_mr.md) and [Holybro H-Flow](https://holybro.com/products/h-flow), or they may be separate sensors.
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The sensor(s) can be connected via MAVLink, I2C or any other bus that supports the peripheral.
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:::info
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If connected to PX4 via MAVLink the Optical Flow camera sensor must publish the [OPTICAL_FLOW_RAD](https://mavlink.io/en/messages/common.html#OPTICAL_FLOW_RAD) message, and the distance sensor must publish the [DISTANCE_SENSOR](https://mavlink.io/en/messages/common.html#DISTANCE_SENSOR) message.
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The information is written to the corresponding uORB topics: [DistanceSensor](../msg_docs/DistanceSensor.md) and [ObstacleDistance](../msg_docs/ObstacleDistance.md).
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:::
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다른 방향으로 이동할 때의 흐름 출력은 다음과 같아야합니다.
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| 기체 이동 | 통합 흐름 |
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| ----- | ----- |
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| 전방 | + Y |
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| 후방 | - Y |
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| 우측 | - X |
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| 좌측 | + X |
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:::info
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The integrated flow values are **angular measurements** (radians) representing rotation of the image about the sensor's body axes using the right-hand convention.
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They are _not_ translational displacements along those axes, which is why forward vehicle movement (along X) appears in the Y flow axis, and rightward movement (along Y) appears in the X flow axis.
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Specifically, forward movement causes the ground image to rotate about the Y axis (+ Y), while rightward movement causes a negative rotation about the X axis (- X).
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:::
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광류 데이터는 다른 속도 데이터 소스와 융합됩니다.
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The approach used for fusing sensor data and any offsets from the center of the vehicle must be configured in the [estimator](#estimators).
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### Scale Factor
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For pure rotations the `OPTICAL_FLOW_RAD.integrated_xgyro` and `OPTICAL_FLOW_RAD.integrated_x` (respectively `integrated_ygyro` and `integrated_y`) have to be the same.
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If this is not the case, the optical flow scale factor can be adjusted using [SENS_FLOW_SCALE](../advanced_config/parameter_reference.md#SENS_FLOW_SCALE).
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:::tip
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The low resolution of common optical flow sensors can cause slow oscillations when hovering at a high altitude above ground (> 20m).
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Reducing the optical flow scale factor can improve the situation.
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:::
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## 유량 센서/카메라
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### ARK Flow & ARK Flow MR
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[ARK Flow](../dronecan/ark_flow.md) is a [DroneCAN](../dronecan/index.md) optical flow sensor, [distance sensor](../sensor/rangefinders.md), and IMU.
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It has a PAW3902 optical flow sensor, Broadcom AFBR-S50LV85D 30 meter distance sensor, and Invensense ICM-42688-P 6-Axis IMU.
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[ARK Flow MR](../dronecan/ark_flow_mr.md) is a [DroneCAN](../dronecan/index.md) optical flow sensor, [distance sensor](../sensor/rangefinders.md), and IMU, for mid-range applications.
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It has a PixArt PAA3905 optical flow sensor, Broadcom AFBR-S50LX85D 50 meter distance sensor, and Invensense IIM-42653 6-Axis IMU.
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### Holybro H-Flow
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The [Holybro H-Flow](https://holybro.com/products/h-flow) is a compact [DroneCAN](../dronecan/index.md) optical flow and [distance sensor](../sensor/rangefinders.md) module.
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It combines a PixArt PAA3905 optical flow sensor, a Broadcom AFBR-S50LV85D distance sensor, and an InvenSense ICM-42688-P 6-axis IMU.
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An all-in-one design that simplifies installation, with an onboard infrared LED enhances visibility in low-light conditions.
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### PMW3901 기반 센서
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[PMW3901](../sensor/pmw3901.md) is an optical flow tracking sensor similar to what you would find in a computer mouse, but adapted to work between 80 mm and infinity.
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Bitcraze, Tindie, Hex, Thone 및 Alientek의 일부 제품을 포함하여 여러 제품에 사용됩니다.
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### 기타 카메라 / 센서
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카메라 통합 보드를 사용할 수 있습니다.
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For this the [Optical Flow repo](https://github.com/PX4/PX4-OpticalFlow) can be used (see also [snap_cam](https://github.com/PX4/snap_cam)).
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## 거리 측정기
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You can use any supported [distance sensor](../sensor/rangefinders.md).
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그러나 견고성과 정확성 측면에서는 음향 센서보다 LIDAR를 사용하는 것이 좋습니다.
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## 추정기
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추정기는 광학 흐름 센서 및 기타 소스의 데이터를 융합합니다.
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융합 방법 설정과 차량 중심에 대한 상대적 오프셋이 사용되는 추정기를 지정하여야합니다.
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오프셋은 아래와 같이 차량 방향 및 중심을 기준으로 계산됩니다.
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Optical Flow based navigation is enabled by both [EKF2](#ekf2) and LPE (deprecated).
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### Extended Kalman Filter (EKF2) {#ekf2}
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For optical flow fusion using EKF2, set [EKF2_OF_CTRL](../advanced_config/parameter_reference.md#EKF2_OF_CTRL).
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광류 센서가 차량 중앙에서 오프셋된 경우 다음 매개변수를 사용하여 설정합니다.
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| 매개변수 | 설명 |
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| ----------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------ |
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| <a id="EKF2_OF_POS_X"></a>[EKF2_OF_POS_X](../advanced_config/parameter_reference.md#EKF2_OF_POS_X) | 바디 프레임에서 광류 초점의 X 위치 (기본값은 0.0m). |
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| <a id="EKF2_OF_POS_Y"></a>[EKF2_OF_POS_Y](../advanced_config/parameter_reference.md#EKF2_OF_POS_Y) | 바디 프레임에서 광류 초점의 Y 위치 (기본값은 0.0m). |
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| <a id="EKF2_OF_POS_Z"></a>[EKF2_OF_POS_Z](../advanced_config/parameter_reference.md#EKF2_OF_POS_Z) | 바디 프레임에서 광류 초점의 Z 위치 (기본값은 0.0m). |
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See [Using PX4's Navigation Filter (EKF2) > Optical flow](../advanced_config/tuning_the_ecl_ekf.md#optical-flow) for more information.
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