# US 2022/0036744 A1 · System to automate a non-destructive test for stress or stress change using unmanned aerial vehicle and ultrasound

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- Number: US 2022/0036744 A1
- Document ID: US20220036744A1
- Status: Published application
- Kind: A1
- Application number: 16/945,873
- Filed: 2020-08-02
- Published: 2022-02-03
- Earliest claimed: 2020-08-02
- Inventors: Yoshikazu Yokotani
- Web page: https://patentgrep.com/patent/US20220036744A1

## CPC

- G08G 5/34: for flight plan modification
- B64D 17/80: in association with aircraft, e.g. for braking thereof
- G01K 13/00: Thermometers specially adapted for specific purposes
- G01N 29/07: by measuring propagation velocity or propagation time of acoustic waves
- G01N 29/225: {Supports, positioning or alignment in moving situation}
- G01N 29/24: Probes {(transducers for acoustic waves B06B, G10K; for measuring G01H)}
- G01N 29/2412: {using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]; (investigating the presence of flaws using eddy currents G01N27/90, magnetostrictive transducers B06B1/08, measuring magnetostrictive properties G01R33/18)}
- G01N 29/265: by moving the sensor relative to a stationary material
- G01N 29/326: {compensating for temperature variations}
- G01S 7/521: Constructional features
- G01S 7/539: using analysis of echo signal for target characterisation; Target signature; Target cross-section
- G01S 13/08: Systems for measuring distance only (indirect measurement G01S13/46)
- G01S 13/933: of aircraft or spacecraft
- G01S 15/88: Sonar systems specially adapted for specific applications (seismic or acoustic prospecting or detecting G01V1/00)
- G01S 15/89: for mapping or imaging
- G05D 1/104: {involving a plurality of aircrafts, e.g. formation flying (traffic control systems for aircraft G08G5/00)}
- G08G 5/55: for a single aircraft
- G08G 5/57: for unmanned aircraft
- G08G 5/727: {from a ground station}
- B64U 10/14: with four distinct rotor axes, e.g. quadcopters
- B64U 70/83: using parachutes, balloons or the like
- B64U 2101/26: for manufacturing, inspections or repairs
- B64U 2201/10: autonomous, i.e. by navigating independently from ground or air stations, e.g. by using inertial navigation systems [INS]
- G01N 2291/011: Velocity or travel time
- G01N 2291/0234: Metals, e.g. steel
- G01N 2291/044: Internal reflections (echoes), e.g. on walls or defects
- G01N 2291/045: External reflections, e.g. on reflectors
- G01N 2291/101: one transducer
- G01N 2291/106: one or more transducer arrays
- G08G: TRAFFIC CONTROL SYSTEMS (guiding railway traffic, ensuring the safety of railway traffic B61L; arrangement of road signs or traffic signals E01F9/00; radar or analogous systems, sonar systems, lidar systems specially adapted for traffic control G01S13/91, G01S15/88, G01S17/88; {radar or analogous systems, sonar systems, lidar systems specially adapted for anti-collision purposes G01S13/93, G01S15/93, G01S17/93})
- B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- B64U: UNMANNED AERIAL VEHICLES [UAV]; EQUIPMENT THEREFOR

## Abstract

This invention discloses a system to automate a non-destructive test (NDT) for measuring stress or stress change developed within an object during a certain time period by using unmanned aerial vehicles (UAV) and ultrasound technique. The system comprises a ground control station (GCS), UAVs and reference positioning modules as its basis. Given a test plan containing test points over a surface of a test object in 3D point coordinates, UAVs can fly autonomously to the points and perform ultrasound measurements on them with a single or a plurality of ultrasound transducers in an automated manner. Moreover, after receiving trigger signals from the GCS, a UAV can also perform the flight and the measurement synchronously with other UAVs. After a measurement, an acquired ultrasound echo signal is taken with another echo signal acquired at a different time point to compute stress or stress change.

## Claims

### Claim 1

A system to automate a non-destructive test for stress or stress change developed within an object, comprises:
ground control station;
wherein the station comprises the following properties:
1. the station transmits a test plan, including a single or a plurality of autopilot flight control commands, to a single or a plurality of unmanned aerial vehicles;
2. the station receives the flight state of a single or a plurality of unmanned aerial vehicles;
3. the station receives and stores ultrasound echo signals or a stress map from a single or a plurality of unmanned aerial vehicles;
4. the station retrieves ultrasound echo signals acquired at different time points from a storage and computes stress or stress change from the temporal ultrasound velocity changes with the signals for creating a stress map;
a single or a plurality of unmanned aerial vehicles;
wherein the vehicle comprises the following properties:
1. the vehicle comprises a single or a plurality of ultrasound transducers for a non-destructive test;
2. the vehicle flies autonomously to a hold point located near above a surface of a test object;
3. the vehicle comprises a single or a plurality of distance sensors to measure distances of ultrasound transducers of the vehicle to an object, and the sensors are used for a vehicle to autonomously move and contact or nearly contact the object;
4. the vehicle carries out a single or a plurality of ultrasound measurements while contacting or nearly contacting a test object to acquire a single or a plurality of ultrasound echo signals;
5. the vehicle stores the acquired ultrasound echo signals locally or transmits them to the ground control station;
a single or a plurality of reference positioning modules;
wherein the modules transmit signals to the vehicles, so that the vehicles, as the receivers, correct or calculate their positions with the signals.

### Claim 2 (depends on 1)

The system of claim 1,
wherein the ground control station further comprises the following properties:
1. the station transmits a flight trigger to a single or a plurality of unmanned aerial vehicles, so that each of the vehicles move to a hold point synchronously;
2. the station transmits a measurement trigger to a single or a plurality of unmanned aerial vehicles, so that each of the vehicles carry out an ultrasound measurement synchronously.

### Claim 3 (depends on 1)

The system of claim 1,
wherein stress or stress change is computed by using the coda wave interferometry (CWI) method.

### Claim 4 (depends on 1)

The system of claim 1,
wherein stress or stress change is computed by using the time-of-flight (TOF) method.

### Claim 5 (depends on 1)

The system of claim 1,
wherein an unmanned aerial vehicle retrieves ultrasound echo signals acquired at different time points from a storage and computes stress or stress change from temporal ultrasound velocity changes with them for creating a stress map;
wherein stress or stress change is computed by the coda wave interferometry (CWI) method or the time-of-flight (TOF) method;
wherein the obtained stress map is transmitted to the ground control station;

### Claim 6 (depends on 1)

The system of claim 1,
wherein the vehicle further comprises a manually or electronically angle-controllable rod holding the ultrasound transducers;
wherein the angle is changeable from −90 degrees to +90 degrees, and they indicate a direction towards the bottom of the vehicle and its upright direction, respectively;
wherein a damper such as springs is installed between the transducers and the head of the rod.

### Claim 7 (depends on 1)

The system of claim 1,
wherein the vehicle further comprises a thermometer;
wherein, with this temperature measurement, ultrasound velocity variation due to a temperature change is compensated.

### Claim 8 (depends on 1)

The system of claim 1,
wherein the vehicle further comprises a parachute.

### Claim 9 (depends on 1)

The system of claim 1,
wherein the vehicle further comprises a propeller vertically installed to its frame on the opposite side of the rod, in order to hold its contact position on a test object.

### Claim 10 (depends on 1)

The system of claim 1,
wherein a reference positioning module is an RTK base station.

### Claim 11 (depends on 1)

The system of claim 1,
wherein a reference positioning module is an ultrasound stationary beacon.