Device, method and system for determining flight height of unmanned aerial vehicle

Patent metadata

Field	Value
Publication number	US-2022044434-A1
Application number	US-202117159676-A
Country	US
Kind code	A1
Filing date	Jan 27, 2021
Priority date	Aug 10, 2020
Publication date	Feb 10, 2022
Grant date	—

Abstract

A method and system for determining flight height of an unmanned aerial vehicle (UAV) includes a determining device that includes a camera at bottom of the is UAV carried on a three-axis self-stabilizing tripod head; and a carrier phase difference satellite positioning system (CPDSPS), a graphics processing computer (GPC) and a power supply system provided on top of the UAV The GPC is connected with the CPDSPS, the power supply system and the camera, respectively. An attitude and heading reference system (AHRS) is provided at the bottom of the three-axis self-stabilizing tripod head and connected with the GPC The GPC is configured to determine relative height of the UAV from a canopy of farmland surface crops according to position information acquired by the CPDSPS, attitude information acquired by the AHRS and ground orthographic image acquired by the camera, and determine flight height of the UAV according to the relative height.

First claim

1 . A device for determining the flight height of an unmanned aerial vehicle, comprising:
an unmanned aerial vehicle; a three-axis self-stabilizing tripod head; a carrier phase difference satellite positioning system; an attitude and heading reference system; a graphics processing computer; and a power supply system, wherein; a camera at the bottom of the unmanned aerial vehicle is carried on the three-axis self-stabilizing tripod head, and the three-axis self-stabilizing tripod head is used to maintain an optical axis of the camera; the carrier phase difference satellite positioning system, the graphics processing computer and the power supply system are all provided on top of the unmanned aerial vehicle; the graphic processing computer is connected with the carrier phase difference satellite positioning system, the power supply system and the camera, respectively; the attitude and heading reference system is provided at bottom of the three-axis self-stabilizing tripod head and is connected with the graphics processing computer; the graphic processing computer is configured to determine a relative height of the unmanned aerial vehicle from a canopy of farmland surface crops according to position information acquired by the carrier phase difference satellite positioning system, attitude information acquired by the attitude and heading reference system and a ground orthographic image acquired by the camera, and determine the flight height of the unmanned aerial vehicle according to the relative height.

2 . The device for determining the flight height of an unmanned aerial vehicle according to claim 1 , wherein the camera is a high-resolution visible light camera.

3 . A method for determining the flight height of an unmanned aerial vehicle, wherein the determining method is applied to the device for determining the flight height of an unmanned aerial vehicle according to claim 1 , and the determining method comprises:
acquiring a plurality of ground orthographic images in an agricultural operation area and position data and attitude data of an unmanned aerial vehicle at time of acquiring the plurality of ground orthographic images; constructing a Gaussian difference pyramid according to pixel points in any two adjacent ground orthographic images; determining feature points in any two adjacent ground orthographic images according to the Gaussian difference pyramid; matching the feature points in two adjacent ground orthographic images to determine a matching feature point pair; determining a position of the matching feature point pair in space according to the matching feature point pair; determining the position of the unmanned aerial vehicle in space according to the position data and attitude data of the unmanned aerial vehicle; determining the relative height of the unmanned aerial vehicle from the canopy of farmland surface crops according to the position of the unmanned aerial vehicle in space and the position of the matching feature point pair in space; and determining the flight height of the unmanned aerial vehicle according to the relative height.

4 . The method for determining the flight height of an unmanned aerial vehicle according to claim 3 , wherein prior to constructing a Gaussian difference pyramid according to pixel points in any two adjacent ground orthographic images, the method further comprises:
calibrating pixel points in the ground orthographic image by using formulas x corrected =x(1+k 1 r 2 +k 2 r 4 +k 3 r 6 ), y corrected =y(1+k 1 r 2 +k 2 r 4 +k 3 r 6 ), x corrected =x+[2p 1 xy+p 2 (r 2 +2x 2 )] and y corrected =y+[p 1 (r 2 +2y 2 )+2p 2 xy]; wherein k 1 , k 2 , and k 3 are radial distortion factors, p 1 and p 2 are tangential distortion factors, x and y are pixel point coordinates, x corrected and y corrected are the coordinates of the calibrated pixel points, and r is the distance from the pixel point to the image center point.

5 . The method for determining the flight height of an unmanned aerial vehicle according to claim 3 , wherein matching the feature points in two adjacent ground orthographic images to determine a matching feature point pair specifically comprises:
constructing a feature description vector corresponding to each feature point according to the feature points in the ground orthographic image; determining a Euclidean distance between the feature points in one ground orthographic image and the feature points in another ground orthographic image according to the feature description vector corresponding to each feature point; taking the feature point pair whose Euclidean distance is less than the distance threshold as the matching feature point pair, wherein the matching feature point pair comprises two feature points and is located in different ground orthographic images.

6 . A system for determining the flight height of an unmanned aerial vehicle, comprising:
a data acquiring module configured to acquire a plurality of ground orthographic images in an agricultural operation area and position data and attitude data of an unmanned aerial vehicle at time of acquiring the plurality of ground orthographic images; a Gaussian difference pyramid constructing module configured to construct a Gaussian difference pyramid according to pixel points in any two adjacent ground orthographic images; a feature point determining module configured to determine the feature points in any two adjacent ground orthographic images according to the Gaussian difference pyramid; a matching feature point pair determining module configured to match the feature points in two adjacent ground orthographic images to determine a matching feature point pair; a position determining module of a matching feature point pair in space configured to determine the position of the matching feature point pair in space according to the matching feature point pair; a position determining module of an unmanned aerial vehicle in space configured to determine the position of the unmanned aerial vehicle in space according to the position data and attitude data of the unmanned aerial vehicle; a relative height determining module configured to determine the relative height of the unmanned aerial vehicle from a canopy of farmland surface crops according to the position of the unmanned aerial vehicle in space and the position of the matching feature point pair in space; a flight height determining module configured to determine the flight height of the unmanned aerial vehicle according to the relative height.

7 . The system for determining the flight height of an unmanned aerial vehicle according to claim 6 , further comprising:
a pixel point calibrating module configured to calibrate pixel points in the ground orthographic image by using formulas x corrected =x(1+k 1 r 2 +k 2 r 4 +k 3 r 6 ), y corrected =y(1+k 1 r 2 +k 2 r 4 +k 3 r 6 ), x corrected =x+[2p 1 xy+p 2 (r 2 +2x 2 )] and y corrected =y+[p 1 (r 2 +2y 2 )+2p 2 xy]; wherein k 1 , k 2 , and k 3 are radial distortion factors, p 1 and p 2 are tangential distortion factors, x and y are pixel point coordinates, x corrected and y corrected are the coordinates of the calibrated pixel points, and r is the distance from the pixel point to the image center point.

8 . The system for determining the flight height of an unmanned aerial vehicle according to claim 6 , wherein the matching feature point pair determining module specifically comprises:
a feature description vector constructing unit configured to construct a feature description vector corresponding to each feature point according to the feature points in the ground orthographic image; an Euclidean distance determining unit configured to determine the Euclidean distance between the feature points in one ground o

Assignees

• Univ Zhejiang

Inventors

• He Yong
• He Liwen
• Chu Bingquan

Classifications

• B64U2201/104

  using satellite radio beacon positioning systems, e.g. GPS · CPC title

• G06F18/22

  Matching criteria, e.g. proximity measures · CPC title

• B64U2101/30

  for imaging, photography or videography · CPC title

• B64U2101/40

  for agriculture or forestry operations · CPC title

• B64U20/87

  Mounting of imaging devices, e.g. mounting of gimbals · CPC title