Method for detection of soil heavy metal pollution using unmanned aerial vehicle (UAV) and X-ray fluorescence (XRF) technology

Patent metadata

Field	Value
Publication number	US-12339240-B2
Application number	US-202217719859-A
Country	US
Kind code	B2
Filing date	Apr 13, 2022
Priority date	May 8, 2021
Publication date	Jun 24, 2025
Grant date	Jun 24, 2025

Abstract

The present disclosure provides a method for detection of soil heavy metal pollution using an unmanned aerial vehicle (UAV) and an X-ray fluorescence (XRF) technology. Based. Based on hardware equipment such as the UAV, XRF analyzer, and embedded equipment, the present disclosure develops an altitude hold module of the system and a ground-contact monitoring module, and assists the UAV to achieve safe and accurate fixed-point hovering, and develops a driving device for data acquisition to replace manual control and realize the automatic acquisition of XRF data. The data inversion method is realized by using embedded equipment, and after the data is acquired by the portable XRF analyzer near the ground, the algorithm research of inversion processing of contents of heavy metal elements in soil is realized, such that the portable XRF analyzer can automatically and accurately detect the contents of heavy metals in soil at a certain distance.

First claim

What is claimed is:

1. A method for detection of soil heavy metal pollution using an unmanned aerial vehicle (UAV) and an X-ray fluorescence (XRF) technology, comprising the following steps:
Step 1 , uniformly selecting enough sampling points in an area to be detected using an XRF analyzer, and detecting each sampling point respectively near ground and on the ground to obtain content data of a set of metal elements to be detected;
Step 2 , performing data check and data preprocessing, wherein after data acquisition is completed, a scatter plot is drawn from known data for data check, wrong data is eliminated, and a fitting degree n of a polynomial (or similar model) is determined according to preliminary data;
Step 3 , calculating polynomial fitting functions with highest degrees of n−1 and n and a sum of squared errors successively;
Step 4 , if a reduction amount of the sum of squared errors of a last fitting function compared with the sum of squared errors of a previous fitting function is greater than a set threshold, continuing to calculate the fitting function with a highest order greater than n successively until a reduction amount of a final sum of squared errors compared with the sum of squared errors of the previous fitting function is less than a set threshold;
Step 5 , recording and saving a fitting function corresponding to a minimum sum of squared errors as a final inversion model; and
Step 6 , controlling the UAV to hover at an altitude of h 2 accurately acquiring, by the XRF analyzer carried or the UAV, soil data near the ground, and detecting, by the XRF analyzer accurate content data of heavy metal elements in soil by performing inversion on the soil data based on the final inversion model, wherein h 2 is the altitude for acquiring the soul data near the ground.

2. The method for detection of soil heavy metal pollution using an UAV and an XRF technology according to claim 1 , wherein in step 6 , a method for controlling the UAV when the XRF analyzer carried on the UAV acquires the soil data is as follows:
Step 1 . 1 , initializing and self-checking each module of a system to ensure that each module of the system works normally;
Step 1 . 2 , planning an UAV flight task route for soil heavy metal pollution monitoring, and constructing a task queue;
Step 1 . 3 , enabling the UAV to take off: when the task queue is valid, enabling the UAV to take off to a specified altitude H, wherein H is the set plane flight altitude of the UAV;
Step 1 . 4 , performing automatic control of plane flight of the UAV: controlling the UAV to fly over a next task point, wherein a flight path of an operation plane of the UAV is a straight line from a point A to a point B, and the altitude remains unchanged at the flight altitude H;
Step 1 . 5 , performing automatic control of a descending process of the UAV: in order to acquire valid data, controlling the UAV to descend to a predetermined altitude and hover for completion of data acquisition;
Step 1 . 6 , enabling the UAV to hover and performing data acquisition: keeping the UAV hovering at the altitude of h 2 accurately until the data acquisition is completed, and repeating step 1 . 4 until the data acquisition is completed for all task points in the task queue; and
Step 1 . 7 , enabling the UAV to return and land: automatically controlling the UAV to return to coordinates of a take-off point and land.

3. The method for detection of soil heavy metal pollution using an UAV and an XRF technology according to claim 1 , wherein step 3 is specifically as follows:
assuming that there are n+1 linearly independent continuous functions:
φ 0 (x), φ 1 (x) . . . φ n (x), wherein φ k (x)=x k , k=1, 2, . . . , n,

p
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(
x
)

=

∑

k
=
0

n

a
k

⁢

φ
k

(
x
)

is recorded, namely: p(x)=a 0 +a 1 x+ . . . +a n x k , then a function p(x) is a linear function with respect to a coefficient dx, and for a set of known discrete data points (x 0 , y 0 ), (x 1 , y 1 ), . . . , and (x m , y m ), a set of ax satisfying the following formula is solved:

I
=

∑

i
=
0

m

[

p
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(

x
i

)

-

y
i

]

2

then a least square fitting function of this set of discrete data is the function p(x), and to obtain a minimum I, conditions for an extreme value of a multivariate function are obtained:

∑

k
=
0

n

(

∑

i
=
0

m

φ
j

(

x
i

)

⁢

φ
k

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)

·

a
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0

Assignees

• Univ Electronic Sci & Tech China

Inventors

• Huang Fang
• Peng Shuying
• Yang Hao
• Chen Shengyi

Classifications

• G05D1/46

  Control of position or course in three dimensions [3D] · CPC title

• B64U2101/00

  UAVs specially adapted for particular uses or applications · CPC title

• G01S19/45

  by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement · CPC title

• G01N2223/616

  earth materials · CPC title

• G01N2223/507

  secondary-emission detector · CPC title