ATV underwater ultrasonic tomography section flowmeter

1、 Background of the plan

1.1 Hydrological National Examination Section

Hydrology: refers to various phenomena such as changes and movements of water in nature. It is a discipline that studies the different temporal and spatial distributions and changes in nature. According to a report by People's Daily on January 23, 2020, China's hydrological monitoring stations have grown from 353 in New China to 121000, and the overall density of the station network has reached the level of a moderately developed country. Play a role in flood prevention, drought resistance, disaster reduction, water resource management, and ecological protection.

With the advancement of technology, the Internet of Things technology has quietly entered us and has been applied in various fields. Things such as hydrology and water conservancy, industrial monitoring, smart cities, smart water management, etc. are connected to cloud servers through the Internet of Things, which improves production efficiency, flexibility, and responsiveness through big data analysis and processing.

On March 16, 2016, the Ministry of Ecology and Environment announced the "13th Five Year Plan" for the establishment of a national surface water environmental quality monitoring network. The plan includes 2767 national control sections (points), of which 717 trend research sections are not subject to assessment, and the remaining 2050 sections are national surface water assessment sections (hereinafter referred to as "national assessment sections").

The national examination section belongs to the evaluation, assessment, and ranking monitoring sections (points) of the national surface water environment monitoring network, with the core of improving water environment quality, meeting the current environmental management needs such as the assessment of basin water pollution prevention and control goals and the ranking of urban water environment quality. Characteristics of the national examination section: wide section, operating under low flow conditions throughout the year.

Against the backdrop of the substantive operation stage of the river chief system at all levels of the basin, the management bureaus of each basin have begun to actively play a role in coordinating and coordinating the basin, such as joint meetings of river chief systems, floating object monitoring, cross-border river and lake management, ecological flow scheduling and other water control mechanisms. Each unit should attach great importance to achieving the ecological flow and flow guarantee goals of the Ministry of Water Resources, especially in the scheduling during the dry season. The river chief offices of each basin will fully play the role of basin coordination, continuously improve the supervision and coordination capabilities of rivers and lakes in the basin, further deepen and improve the "basin+region" collaborative water management mechanism, coordinate the promotion of upstream and downstream, left and right banks, and main and tributary collaborative management, collaborate with various cities in the basin to solve the difficult and blocking problems in river and lake management and protection work, and jointly promote the smooth and clean water in the basin.

1.2 Common measurement methods for cross-sectional flow rate

1: Cableway flow measurement

2: Acoustic Doppler velocity ADV

3: Acoustic Doppler Profile Analyzer ADCP, HADCP

4: Traditional ultrasonic time difference method

5: Calculation of flow rate for hydraulic structures (culverts and gates)

6: Calculation of flow rate using water level gradient method

7: Radar surface wave velocity measurement to calculate flow rate

8: New visual recognition flowmeter

9: New Acoustic tomography sectional FLOW METER ATV

For wide cross-section and low flow velocity measurement sections, there have always been significant issues with flow measurement. In order to meet the above measurement requirements, attention should also be paid to simple installation, real-time measurement, and not interfering with the normal use of the river channel. The cross-sectional flow rate of ATV acoustic tomography is a specialized product designed based on the above definition.

2、 Scheme Introduction

2.1 Acoustic tomography technology

Acoustic technology used to play an important role in marine environmental observation, and with the expansion of its applications, it has also become one of the important means in the measurement of other water bodies. Acoustic tomography technology, especially the application of 15-88K frequency acoustic tomography, has also shifted from river mouths and coasts to the measurement of surface water, groundwater and other water bodies.

The Autai Automated ATV Acoustic Tomography Section Flow Meter utilizes underwater acoustic reciprocity transmission (also known as bidirectional acoustic transmission) for acoustic tomography (temperature flow) inversion calculation, and uses Fourier models to reconstruct the sound velocity, temperature field, and flow field in two dimensions.

Sound waves have superior propagation characteristics in water and are an effective radiation form for long-distance transmission of energy and information in surface water. Due to the stratification, peak surface, internal waves, reflection, scattering, absorption, and boundary between water surface and bottom, sound waves carry a large amount of propagation path information during their propagation in water. By analyzing the frequency, phase, time, and multi-path structure of acoustic signals, a lot of water information can be inferred.

Tomography technology is an inversion observation method that can use acoustic radiation to penetrate the measured medium from different angles, and invert the properties of the measured medium by measuring the differences in its absorption and propagation time characteristics. Acoustic tomography is a technique that uses measured changes in propagation time to invert temperature and flow field parameters. The inversion will take into account the parameter changes of temperature, salinity, and depth.

The measurement of cross-sectional flow only requires critical velocity data, so it is not necessary to obtain accurate flow field distribution of each profile, and therefore there is no need to invert through multidimensional monitoring acoustic data. By relying on the time variation of acoustic direct waves and multipath wave reverberation at two points, the two-dimensional cross-sectional average flow velocity can be inverted. By utilizing the high-frequency (1 second cross reciprocity) reciprocity transmission acoustic tomography principle, rapid measurement can be achieved with limited investment, and the system has a small measurement cycle of 5 seconds.

After the ultrasonic signal is emitted from the host, within a 65 degree angle range, the acoustic direct wave and multipath wave reverberation are obtained by the slave to obtain a complete signal; After mutual exchange, the slave sound waves are received by the host through the same channel sound waves; The sound signal can basically reflect the velocity field properties of the entire water crossing section, representing the average acoustic characteristics of the water crossing section. The back and forth sound information is inverted through tomography to obtain time variation data, thereby converting the average flow velocity value of the cross-section. (As shown in the following figure:)

2.2 Other special algorithms

Data Pool Management: Based on the application experience of actual installation cases, we have discovered many practical algorithms

Spare tire algorithm: The host has built-in powerful self-learning ability. When the measurement quality (sound wave: feature matching) reaches the set threshold, the device will continuously learn the relationship between flow rate, flow rate, and water level, and record the adaptation for a long time. When the measurement quality is lower than the set value and the duration reaches the set time, the device will enter automatic correction mode based on self-learning data.

2.3 Patent Declaration

The patented technologies applied to this product include (as of July 2021, excluding patents in the application stage during this period):

1: Installation Structure of Acoustic Tomography Section Velocity Meter; ZL20201960851.8

2: A high-precision time delay estimation system for underwater ultrasonic waves; ZL202022032230.X

3: An underwater ultrasonic acoustic tomography cross-sectional flowmeter; ZL202022094871.8

4: Ultrasonic Level gauge Shell (Integrated); ZL202130086557.2

5: Flow meter probe housing; ZL202030043609.3

6: A Two Line ultrasonic level gauge; ZL202020142207.3

7: A battery powered ultra-low power IoT instrument based on NB IoT; ZL201921790068.9

8: A segmented energy adaptive liquid level difference meter; ZL201921790067.4

9: A multifunctional display unit; ZL201920347290.5

10: An Intelligent Energy Controlled Ultrasonic Level Gauge Measuring Instrument; ZL201920350123.6

11: A type of instrument switch power supply; ZL200920138383.3

2.4 Software Copyright Declaration

The software copyright applied to this product includes (up to April 2021, excluding patents in the application stage during this period):

1: Aotai Automation Cloud Data Platform [referred to as IoT Platform] V1.02019SR0363471

2: ATV Ultrasonic Acoustic Tomography Flow Meter Software V1.02020SR1107703

2.5 Acoustic tomography and time difference method

When the river width is small (within 20 meters): the sound wave time is short, the direct wave is strong, and conventional time difference measurement becomes possible (dual machine wired connection is easier to achieve);

When the river width is medium (20-200 meters) and large (over 200 meters): The complex and variable multi-path structure of underwater acoustic signals and strong random fading problems have a fatal impact on conventional time difference (single channel, multi-channel) methods, coupled with the problem of dual machine wireless communication.

2.6 Acoustic tomography and other measurement methods

In the flow measurement of rivers and waterways, it is necessary to achieve long-term and real-time measurement.

Other shore based measurements: good real-time performance, insufficient cross-sectional representativeness, difficult to establish relationships;

Aerial survey: Poor real-time performance, good cross-sectional representativeness, single measurement cycle. When there is a significant change in flow velocity during the measurement cycle, it is difficult to close and the cost is high;

3、 Product composition

3.1 Basic components

1: Power supply system, capable of mains electricity and solar energy (one master station and one slave station)

Note: Solar panel: 200W, battery: 150AH

2: Master station system, slave station system

3: Attachment: Ultrasonic water level gauge, water temperature conductivity sensor and installation bracket (main station side)

4: Outdoor instrument box (one master station and one slave station)

5: Base, can be cement-based or steel structure (one for main station and one for slave station)

3.2 Core Components

1: ATV host, ATV slave

The application of 7-inch large screen color LCD display provides a better human-computer interaction experience for waveform diagrams and menus;

2: Broadband antenna for 5G frequency band (dedicated for wireless data link)

Long distance wireless high-speed data link: The application of a new type of bridge expands the communication distance to 5 kilometers, with a working frequency of 5.8G and an error free communication capacity of 38K for master and slave data every 5 seconds (with a measurement value refresh cycle). This technology does not rely on public communication 4G5G stations, allowing devices to operate independently without communication costs.

3: Installation bracket (including sonar transducer)

transducer

40KHZ: Suitable for 20-500 meters

25KHZ: Suitable for distances over 500 meters

4: GPS Beidou dual-mode positioning and high-precision timing antenna

High precision time service and positioning: through Beidou/GPRS/Gronas the third mock examination high-precision time service, the synchronization accuracy of master and slave computers is controlled below 20 nanoseconds, meeting the synchronization requirements of time difference measurement.

5: 4G NB IoT communication antenna

Built in IoT module, supports 4G/GPRS communication, has a built-in full network slot, and the application of 4G LET UserCAT. 1 module makes it extremely convenient to upload data to the Aotai Cloud platform or third-party cloud platforms;

6: Ultrasonic water level gauge

The integrated ultrasonic water level gauge is powered by 12VDC and communicates with the host via RS485. The installation height is set according to the elevation of the installation point, and the water level elevation signal is directly obtained. The acquisition of water level elevation data will be combined with the base elevation data to calculate the discharge area, thereby converting the flow velocity value into a flow rate value;

7: Water temperature/conductivity meter

External water temperature and conductivity sensors can accurately convert underwater sound velocity.

4、 Product Function Description

4.1 Base elevation

ATV can generate longitudinal profile description data for 50 points, inputting the offshore distance data (usually starting from the left bank to the right bank) and corresponding underwater terrain elevation data for each point. The base elevation of a river section is a necessary parameter for measuring the flow rate of various river channels. The water area can only be calculated by measuring the elevation and water level and the terrain of the section. Then, the flow rate data can be calculated by multiplying it with the flow velocity data measured by instruments and equipment.

4.2 Communication Terminal

The IoT multifunctional display terminal (hereinafter referred to as the terminal) needs to be used in conjunction with a primary instrument or digital sensor. The terminal provides 24V/12V power supply, which can supply power to sensors. By communicating with digital sensors through the 485 interface of the terminal's sensors, a measurement system with one terminal and multiple digital sensors can be realized.

The terminal power supply can be selected from 220AC, 24VDC, and 12VDC, and can be powered by mains or industrial power, or by various types of batteries or solar power systems. The terminal can easily interconnect with various wireless platforms, such as GPRS and WIFI, and upload the signal data transmitted by digital sensors to the cloud server.

Working principle

Input signals are collected through communication interfaces or AD, and measurement values are obtained through signal analysis. The measurement values are displayed on the LCD screen, and the signals are uploaded to the cloud through GPRS.

Main technical parameters

Usage conditions: Environmental temperature: 0~50 ℃; Relative humidity: £ 90% RH;

Power supply voltage: 90-265VAC or 24 ± 10% VDC or 12 ± 10% VDC;

Accuracy: ± 0.5% F.S+1 word;

Input characteristics: Current type: Input impedance<300W;

Output characteristics:

Relay capacity: 0.5A/240V AC, resistive;   

Current type transmitter output load impedance:<600W;

Power output: 12 ± 10% V DC/30mA;

Power consumption:<5W;

5、 Advantages of the plan

1: The master and slave dual machine data links can autonomously network and interact without relying on the public network or station;

2: Data is uploaded through the public network, and in case of a public network failure, Beidou Short Message Communication (RDSS) can also be selected;

3: Can be displayed in real-time on third-party large-scale display platforms;

4: Can be equipped with multiple IoT multi parameter display terminals to display data in real-time;

5: It can be equipped with telephone voice warning, SMS warning, and email warning functions;

6: Suitable for use in low flow, zero flow, and negative flow conditions;

7: Strong real-time measurement capability, fast measurement cycle: 5 seconds;

8: According to industrial instrument design standards, it has strong interference and lightning protection capabilities.

6、 Scheme configuration

6.1 Aotai Automation Supply Scope