Sensor and method for ultrasonic detection of thickness of oil spilled on sea surface

Abstract

The invention relates to a sea surface oil spill thickness ultrasonic detection sensor and method, and belongs to the technical field of marine environment monitoring. The sensor transmits an ultrasonic signal to the water surface and receives upper and lower surface reflection signals of spilled oil, and the thickness of the spilled oil is accurately measured by calculating the time difference of the upper and lower surface reflection signals of an oil layer and multiplying the time difference by the propagation speed of ultrasonic waves in the oil layer. The ultrasonic sensor comprises a plurality of modules such as an ultrasonic transducer, an ultrasonic signal transmitting and receiving module, a master control MCU module, a signal processing module and a data transmission module, can be integrated on various underwater and aerial platforms, can be used for accurately measuring the thickness of spilled oil at a fixed point in a small range in real time, and can also be used for drawing the thickness distribution of spilled oil in a large range. The method has the advantages of high measurement precision, high environmental adaptability, low cost and the like, can be widely applied to the fields of offshore oil operation, ship transportation, oil spill emergency response and the like, and provides reliable technical support for marine environment protection.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic sensing technology, and mainly to an ultrasonic sensor that is adapted to a variety of underwater and aerial unmanned platforms and can accurately detect the thickness of oil spills on the sea surface. Background Art

[0002] With the rapid development of the offshore oil industry, the pollution problem caused by offshore operations has become increasingly prominent. Offshore oil wells, loading and unloading operations, and ship accidents are the main causes of oil spills. These spills not only cause significant economic losses, but also seriously damage the marine ecological environment. The measurement of the amount of oil spilled on the sea surface is crucial for the selection of oil spill disposal solutions, and the measurement of the amount of oil spilled requires the knowledge of the thickness of the oil spill. Therefore, accurate detection of the thickness of the oil spilled on the sea surface is crucial for the effective disposal of the oil spilled on the sea surface.

[0003] At present, the detection of the thickness of oil spills on the sea surface mainly relies on a variety of detection technologies such as ultraviolet / infrared spectroscopy, microwave radiation measurement, satellite and aviation synthetic aperture radar detection, buoy detection and resistance measurement. These technologies have their own limitations: Ultraviolet / infrared spectroscopy: It is more effective when measuring thin oil films, but it is easily disturbed by natural phenomena such as temperature and sea conditions, and the measurement accuracy is low. In addition, this method relies on optical sensors and is easily affected by lighting conditions, especially at night or in bad weather conditions, its performance will be significantly reduced. Microwave radiation measurement: Although it can penetrate clouds and smoke, its accuracy is greatly affected by sea conditions and sunshine conditions. The reflection and scattering characteristics of microwave signals make its measurement results in complex sea conditions not stable enough, and the equipment cost is high. Satellite and aviation synthetic aperture radar detection: It can cover a large area of ​​sea, but its resolution is limited, and it is difficult to accurately measure the thickness of oil spills in local areas. In addition, the operating costs of satellite and aviation equipment are high and are greatly affected by weather conditions. Buoy detection: It is limited to a specific location and cannot achieve large-scale, real-time detection. The deployment and maintenance costs of the buoy detection system are high, and it is easily affected by the marine environment, such as storms and waves. Resistance measurement: Direct contact measurement is used, with limited detection range and easy to corrode. The resistance measurement method requires the sensor to be in direct contact with the oil film, which is easily affected by oil pollution and seawater corrosion, resulting in reduced measurement accuracy and shortened sensor life.

[0004] As an emerging detection technology, ultrasonic detection technology can work stably under various climatic conditions and is not affected by natural factors such as temperature, light, and sea conditions, ensuring the accuracy and reliability of the measurement results. Ultrasonic detection uses a non-contact measurement method to avoid direct contact between the sensor and the oil, reduce the risk of corrosion and contamination, and extend the service life of the sensor. Therefore, the development of an ultrasonic detection sensor for sea surface oil spill thickness that is suitable for multiple underwater and aerial platforms is currently a major demand in this field. Summary of the invention

[0005] The purpose of the present invention is to solve the problem that the existing oil spill detection technology is greatly affected by marine environmental factors such as sea conditions and temperature, has low detection accuracy and limited detection range, and to provide an ultrasonic detection sensor for sea surface oil spill thickness. The ultrasonic sensor can be used for accurate measurement of sea surface oil spill thickness, and has high resolution and sensitivity. At the same time, the ultrasonic sensor can be adapted to a variety of underwater and aerial unmanned platforms, and can be used for real-time and accurate measurement of oil spill thickness at a small fixed location, and can also be used for mapping the distribution of oil spill thickness over a large area. It can be widely used in offshore oil exploitation, transportation and other fields, and provides strong technical support for marine environmental protection and oil spill emergency response.

[0006] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0007] An ultrasonic detection sensor for sea surface oil spill thickness comprises an ultrasonic transceiver module, a main control MCU, a signal processing unit, a data transmission module, and a battery for powering various components of the sensor, which are connected in sequence;

[0008] An ultrasonic transceiver module, the front end of which is connected to an ultrasonic transducer, transmits ultrasonic waves to the sea surface and receives ultrasonic echo signals reflected by the oil spill layer;

[0009] The main control MCU sets the operating parameters of each component according to the background instructions of the host computer and controls the ultrasonic transmission and reception;

[0010] A signal processing unit is used to enhance and filter the ultrasonic echo signal;

[0011] The data transmission module uses wireless communication technology to transmit instructions and oil spill detection data to the host computer in real time.

[0012] The ultrasonic transceiver module includes one or more channels, each channel independently transmits and receives ultrasonic signals in parallel to avoid signal interference between channels, and the front end is connected to ultrasonic transducers of different frequencies;

[0013] The transmitting module is used to transmit high-voltage negative square wave pulses to the oil spill area on the sea surface, and to control the transmitting voltage, pulse width, and damping parameters of the square wave pulses to adapt to ultrasonic transducers of different frequencies;

[0014] The ultrasonic receiving module receives a plurality of ultrasonic signals reflected from the upper and lower surfaces of the oil layer.

[0015] The signal processing unit comprises:

[0016] The signal filtering module uses an FPGA microcontroller to filter out environmental noise;

[0017] The signal amplification module uses VGA variable gain control to enhance the strength of the reflected signal;

[0018] The oil spill thickness calculation module calculates the oil spill thickness based on the propagation time and reflection intensity of the ultrasonic signal and adopts the signal processing algorithm program module.

[0019] The signal processing algorithm program module includes an empirical mode decomposition noise reduction module, a convolutional neural network signal classification module and a quadratic correlation thickness calculation module.

[0020] The components of the ultrasonic detection sensor for sea surface oil spill thickness are built into the shell, and an underwater sealing joint directly connected to various detection platforms is provided on the outside of the shell for carrying a variety of detection platforms; the ultrasonic transducer is connected to the ultrasonic transceiver module through a Ramo connector, and the frequency range is 1MHz to 10MHz, which is used to achieve high-precision detection of the oil film.

[0021] A method for ultrasonic detection of sea surface oil spill thickness comprises the following steps:

[0022] The main control MCU receives the background command of the remote host computer and controls the ultrasonic transmitting module to transmit ultrasonic signals to the water surface;

[0023] The main control MCU controls the ultrasonic receiving module to collect the reflected ultrasonic echo signal;

[0024] The signal processing unit filters and enhances the ultrasonic echo signal; and calculates the oil spill thickness through an algorithm based on the propagation time and reflection intensity of the ultrasonic signal;

[0025] The detection results are transmitted to the remote host computer background monitoring system in real time through the data transmission module. The host computer background monitoring system renders the three-dimensional oil spill distribution data in real time according to the detected water surface oil film thickness for intuitive display.

[0026] It uses empirical mode decomposition denoising method, convolutional neural network signal classification method and quadratic correlation thickness calculation method to achieve accurate calculation of oil layer thickness.

[0027] The empirical mode decomposition noise reduction method is to decompose the ultrasonic signal into several modal components with frequencies from high to low, select the high-frequency components to remove and reduce noise, and reconstruct the signals of the subsequent components.

[0028] The convolutional neural network signal classification method uses a one-dimensional convolutional neural network method to screen and remove unusable signals from the denoised ultrasonic signals, retains the available ultrasonic signals, and then uses the available signals to calculate the oil layer thickness.

[0029] The quadratic correlation method is to perform autocorrelation on the ultrasonic reflection signal of the lower surface of the oil layer, perform cross-correlation on the signals of the upper and lower surfaces of the oil layer, and then perform a quadratic cross-correlation on the autocorrelation and cross-correlation signals. The time point corresponding to the peak value of the obtained quadratic correlation signal is the propagation time Δt of the ultrasonic wave in the oil layer for one round trip.

[0030] The present invention has the following beneficial effects and advantages:

[0031] 1. The present invention uses ultrasonic technology to avoid direct contact between the sensor and oil, reducing the risk of corrosion and pollution;

[0032] 2. The present invention measures the thickness of the oil layer from underwater, which can achieve real-time and accurate measurement of the thickness of the oil spill on the sea surface;

[0033] 3. The present invention adopts corrosion-resistant materials and waterproof design to adapt to complex marine environments;

[0034] 4. The present invention has low cost and high measurement accuracy, can be equipped with a variety of detection platforms, and is suitable for large-scale deployment and scanning;

[0035] 5. The present invention supports real-time data transmission and remote monitoring, making it easy to take timely countermeasures. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the structural block diagram of the ultrasonic detection sensor for the thickness of oil spill on the sea surface;

[0037] Figure 2 Ultrasonic signals collected by ultrasonic sensors for oil spills on the sea surface;

[0038] Figure 3 A schematic diagram of using underwater robots and aerial drones as platforms to integrate ultrasonic sensors for oil spill thickness, conduct small-scale fixed-point sea surface oil spill thickness detection, and large-scale sea surface oil spill thickness distribution imaging;

[0039] Figure 4 It is a schematic diagram of the structure of the autonomous underwater robot platform AUV integration;

[0040] Figure 5 Schematic diagram of the structure of integrating an ultrasonic sensor for oil spill thickness into an aerial drone platform;

[0041] In the figure: 1. Oil spill layer, 2. Water surface, 3. Ultrasonic transducer, 4. Ultrasonic signal reflected from the lower surface of the oil layer, 5. Ultrasonic signal reflected from the upper surface of the oil layer, 6. Secondary reflection signal of ultrasonic wave in the oil layer, 7. Cable-controlled underwater robot platform system, 8. Autonomous unmanned underwater robot platform system, 9. Aerial drone platform system, 10. Mother ship computer, 11. Ultrasonic detection sensor for oil spill thickness, 12. Underwater robot controller, 13. Underwater power supply system, 14. Rigid signal transmission cable. DETAILED DESCRIPTION

[0042] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation method of the present invention is described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the invention, so the present invention is not limited by the specific implementation disclosed below.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The present invention is further described in detail below in conjunction with the accompanying drawings and examples.

[0044] like Figure 1 As shown, the present invention provides an ultrasonic detection sensor for sea surface oil spill thickness, which includes an ultrasonic transducer, an ultrasonic signal transceiver module, a main control MCU module, a signal processing unit, a data transmission module, a power management module, etc.; the ultrasonic transducer is connected to the ultrasonic signal transceiver module, the ultrasonic signal transceiver module is connected to the main control chip, the main control chip is connected to the signal processing unit, and the signal processing unit is connected to the data transmission module.

[0045] The ultrasonic detection sensor for sea surface oil spill thickness works in the following way: the host computer sends instructions through software, which are transmitted to the main control MCU module through the data transmission module; the main control chip controls the ultrasonic transmitting module to transmit ultrasonic signals to the water surface through the ultrasonic transducer, and the ultrasonic signals are reflected on the upper and lower surfaces of the oil layer; the receiving module receives the ultrasonic reflection signal from the surface of the oil layer, and the signal processing unit enhances and filters the signal; the data transmission module transmits the processed signal to the host computer in real time, and the host computer calculates the oil spill thickness through the signal processing algorithm.

[0046] The ultrasonic transceiver module can excite high-voltage square wave pulses, transmit ultrasonic waves through the ultrasonic transducer to propagate to the oil spill on the sea surface, and collect reflection signals from the upper and lower surfaces of the oil spill on the sea surface through the ultrasonic transducer;

[0047] The main control MCU module can control the parameters of each module, including ultrasonic excitation voltage, transmission frequency, gain adjustment, filter setting, etc.;

[0048] The signal processing unit can process the collected ultrasonic signals, which mainly includes a signal filtering module and a signal amplification module; the signal filtering module is mainly used to filter the ultrasonic signals, filter out background noise, and improve the signal-to-noise ratio; the signal amplification module is mainly used to adjust the gain of the ultrasonic signals and enhance the strength of the ultrasonic signals.

[0049] The data transmission module integrates wired and wireless communication technologies (such as 4G / 5G, satellite communication or LoRa communication) to achieve real-time transmission of ultrasonic data, support remote monitoring and data storage, and facilitate subsequent analysis and emergency response;

[0050] The power management module is equipped with a low power consumption design, which prolongs the working time of the sensor and provides a stable power supply for the sensor.

[0051] Further, as a preferred embodiment of the present invention, the ultrasonic transceiver module includes one or more channels, each of which can be used for transmitting and receiving ultrasonic signals separately, and can be connected to ultrasonic transducers of different frequencies; the transmitting module is used to transmit high-voltage negative square wave pulses, and the transmitting voltage, pulse width, damping and other parameters of the square wave pulses are individually controlled to adapt to ultrasonic transducers of different frequencies; the ultrasonic receiving module receives multiple ultrasonic signals reflected from the upper and lower surfaces of the oil layer; the ultrasonic transducer is connected to the ultrasonic transceiver module and extended to the outside of the shell through the Ramo connector; as a preferred embodiment, the ultrasonic transmitting module includes four transmitting channels, each of which has a pulse repetition frequency of 100 to 2000Hz, a transmitting voltage of -50V to -400V, and a pulse width range of 25μs to 500μs. The ultrasonic receiving module has a receiving sensitivity of -80dB and a dynamic range of 60dB. It adopts a multi-channel self-transmitting and self-receiving mode to avoid interference between transmitting signals and receiving signals between different channels.

[0052] As a preferred implementation, the ultrasonic transducer uses a water-immersed non-focused piezoelectric transducer with a diameter of 16 mm, a length of 30 mm, a center frequency range of 1.0 MHz to 20 MHz, and can emit and receive signals autonomously.

[0053] As a preferred embodiment, the signal processing unit includes a processor using a Xilinx FPGA ZYNQXC7Z045 microcontroller with a main frequency of 500MHz, supporting high-speed parallel data processing, the filtering module is configured with a 15-channel programmable filter group, covering the 20MHz frequency band, and adapting to ultrasonic transducers of different frequencies, and the signal amplification module is based on a variable gain amplifier (VGA), and the gain range can be dynamically adjusted (-24dB to +124dB) to match the signal strength requirements under complex sea conditions.

[0054] The host computer receives the signal and calculates the oil spill thickness. The processed signal is analyzed and the oil spill thickness is calculated mainly through signal processing algorithm, empirical mode decomposition noise reduction method, convolutional neural network signal classification method and quadratic correlation method.

[0055] Furthermore, as a preferred embodiment of the present invention, the signal processing algorithm includes an empirical mode decomposition denoising method, a convolutional neural network signal classification method and a quadratic correlation thickness calculation method. By analyzing and processing the ultrasonic signal, the propagation time of the ultrasonic wave in the oil layer can be accurately measured, and the thickness of the oil layer can be accurately calculated. The ultrasonic signal, oil layer thickness and the position information of the detection platform can be visualized and displayed in real time.

[0056] Furthermore, as a preferred embodiment of the present invention, the empirical mode decomposition noise reduction method is to decompose the ultrasonic signal into several modal components with frequencies from high to low, and remove the high-frequency components to achieve the effect of noise reduction, and reconstruct the signals of subsequent components.

[0057] Furthermore, as a preferred embodiment of the present invention, the convolutional neural network signal classification method is to use a one-dimensional convolutional neural network method to screen and remove unusable signals from the denoised ultrasonic signals, retain available ultrasonic signals, and then use the available signals to calculate the oil layer thickness.

[0058] Furthermore, as a preferred embodiment of the present invention, the quadratic correlation method is performed by performing autocorrelation on the ultrasonic reflection signal of the lower surface of the oil layer, performing cross-correlation operation on the signals of the upper and lower surfaces of the oil layer, and then performing a quadratic cross-correlation operation on the autocorrelation and cross-correlation signals. The time point corresponding to the peak value of the obtained quadratic correlation signal is the round-trip propagation time Δt of the ultrasonic wave in the oil layer.

[0059] Then, according to the ultrasonic measurement principle, the time difference Δt between the ultrasonic reflection signals on the upper and lower surfaces of the oil spill on the sea surface is calculated, and multiplied by the propagation speed v of the ultrasonic wave in the oil layer, the thickness of the oil layer is calculated h=Δt*v / 2.

[0060] Furthermore, as a preferred solution of the present invention, the ultrasonic sensor housing is provided with an underwater sealing joint directly connected to various detection platforms, and a network cable is connected through the sealing joint to supply power to the power module;

[0061] Figure 2 The figure shows that the ultrasonic probe is below the oil layer. The ultrasonic probe emits ultrasonic waves. When the ultrasonic waves propagate to the interface between the oil layer and water and the interface between the oil layer and air, part of the energy will be reflected due to the difference in acoustic impedance. By measuring the time difference t1 and t2 of the reflected signals on the upper and lower surfaces of the oil layer, the propagation time of the ultrasonic wave in the oil layer can be calculated, and then combined with the propagation speed of the ultrasonic wave in the oil layer, the thickness of the oil layer can be accurately obtained.

[0062] The sea surface oil spill thickness ultrasonic sensor described in the present invention can be adapted to various unmanned platforms underwater and in the air. Figure 3 The cable-controlled underwater robot ROV platform system 7 is shown as an integrated ultrasonic detection sensor for the thickness of the oil spill on the sea surface, and a small-scale fixed-point accurate detection of the thickness of the oil spill on the sea surface is carried out. The ROV moves to the bottom of the oil spill area 1, and uses the ultrasonic transducer 3 to transmit and receive ultrasonic signals. The position information of the underwater platform, the received ultrasonic signal, and the oil spill thickness detection result are transmitted back to the mother ship computer 3 in real time through the underwater robot controller 12; in addition, the autonomous unmanned underwater robot AUV platform system 8 is integrated with a sea surface oil spill thickness sensor, and a large-scale sea surface oil spill thickness distribution scanning and detection is carried out, and the ultrasonic test data and the navigation information of the AUV platform are synchronously stored in the AUV computer in real time. After the detection is completed, the oil spill thickness distribution map is obtained by offline analysis of the ultrasonic data. The oil spill thickness ultrasonic detection sensor 11 of the present invention can also be integrated on the aerial drone platform 9, and the advantages of the drone platform 9 with fast speed and wide coverage are used to carry out the detection of the thickness of the oil spill on the sea surface in a fixed area, and the detection results are transmitted to the mother ship computer in real time by wireless.

[0063] Figure 4 The figure shows the integration method of the oil spill thickness ultrasonic sensor of the present invention on the autonomous underwater robot 8. The ultrasonic transducer 3 is installed on the back of the AUV platform. The power system 13 of the AUV system provides power to the ultrasonic detection sensor 11. The ultrasonic detection sensor 11 collects ultrasonic signals and transmits them to the AUV control system 12 in real time to process and collect the ultrasonic signals.

[0064] Figure 5 The figure shows the integration method of the oil spill thickness ultrasonic sensor of the present invention on the aerial drone platform 9, the ultrasonic detection sensor 11 is installed on the aerial drone platform 9, and the ultrasonic transducer 3 is vertically suspended below the oil layer through a rigid signal transmission cable 14. The detection data is transmitted back to the mother ship computer 3 at high speed through the wireless network on the aerial drone for data processing and analysis.

[0065] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. An ultrasonic sensor for detecting the thickness of oil spill on sea surface, characterized in that: It includes an ultrasonic transceiver module, a main control MCU, a signal processing unit, a data transmission module, and a battery for powering various components of the sensor, which are connected in sequence; An ultrasonic transceiver module, the front end of which is connected to an ultrasonic transducer, transmits ultrasonic waves to the sea surface and receives ultrasonic echo signals reflected by the oil spill layer; The main control MCU sets the operating parameters of each component according to the background instructions of the host computer and controls the ultrasonic transmission and reception; A signal processing unit is used to enhance and filter the ultrasonic echo signal; The data transmission module uses wireless communication technology to transmit instructions and oil spill detection data to the host computer in real time.

2. The ultrasonic detection sensor for sea surface oil spill thickness according to claim 1, characterized in that: The ultrasonic transceiver module includes one or more channels, each channel independently transmits and receives ultrasonic signals in parallel to avoid signal interference between channels, and the front end is connected to ultrasonic transducers of different frequencies; The transmitting module is used to transmit high-voltage negative square wave pulses to the oil spill area on the sea surface, and to control the transmitting voltage, pulse width, and damping parameters of the square wave pulses to adapt to ultrasonic transducers of different frequencies; The ultrasonic receiving module receives a plurality of ultrasonic signals reflected from the upper and lower surfaces of the oil layer.

3. The ultrasonic detection sensor for sea surface oil spill thickness according to claim 1 is characterized in that: The signal processing unit comprises: The signal filtering module uses an FPGA microcontroller to filter out environmental noise; The signal amplification module uses VGA variable gain control to enhance the strength of the reflected signal; The oil spill thickness calculation module calculates the oil spill thickness based on the propagation time and reflection intensity of the ultrasonic signal and adopts the signal processing algorithm program module.

4. The ultrasonic detection sensor for sea surface oil spill thickness according to claim 3 is characterized in that: The signal processing algorithm program module includes an empirical mode decomposition noise reduction module, a convolutional neural network signal classification module and a quadratic correlation thickness calculation module.

5. The ultrasonic detection sensor for sea surface oil spill thickness according to claim 1 is characterized in that: The components of the ultrasonic detection sensor for sea surface oil spill thickness are built into the shell, and an underwater sealing joint directly connected to various detection platforms is provided on the outside of the shell for carrying a variety of detection platforms; the ultrasonic transducer is connected to the ultrasonic transceiver module through a Ramo connector, and the frequency range is 1MHz to 10MHz, which is used to achieve high-precision detection of the oil film.

6. A method for ultrasonic detection of sea surface oil spill thickness, characterized in that: The following steps are involved: The main control MCU receives the background command of the remote host computer and controls the ultrasonic transmitting module to transmit ultrasonic signals to the water surface; The main control MCU controls the ultrasonic receiving module to collect the reflected ultrasonic echo signal; The signal processing unit filters and enhances the ultrasonic echo signal; and calculates the oil spill thickness through an algorithm based on the propagation time and reflection intensity of the ultrasonic signal; The detection results are transmitted to the remote host computer background monitoring system in real time through the data transmission module. The host computer background monitoring system renders the three-dimensional oil spill distribution data in real time according to the detected water surface oil film thickness for intuitive display.

7. The method for ultrasonic detection of sea surface oil spill thickness according to claim 6, characterized in that: It uses empirical mode decomposition denoising method, convolutional neural network signal classification method and quadratic correlation thickness calculation method to achieve accurate calculation of oil layer thickness.

8. The method for ultrasonic detection of sea surface oil spill thickness according to claim 7, characterized in that: The empirical mode decomposition denoising method is to decompose the ultrasonic signal into several modal components with frequencies from high to low, select the high-frequency components to remove them for denoising, and reconstruct the signals of the subsequent components.

9. The method for ultrasonic detection of sea surface oil spill thickness according to claim 7, characterized in that: The convolutional neural network signal classification method is to use the one-dimensional convolutional neural network method to screen and remove unusable signals from the denoised ultrasonic signals, retain the available ultrasonic signals, and then use the available signals to calculate the oil layer thickness.

10. The method for ultrasonic detection of sea surface oil spill thickness according to claim 7, characterized in that: The quadratic correlation method performs autocorrelation on the ultrasonic reflection signal from the lower surface of the oil layer, cross-correlation on the signals from the upper and lower surfaces of the oil layer, and then performs a quadratic cross-correlation operation on the autocorrelation and cross-correlation signals. The time point corresponding to the peak value of the quadratic correlation signal is the round-trip propagation time Δt of the ultrasonic wave in the oil layer.

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