Open channel online early warning system and method based on ultrasonic electromagnetic technology

Abstract

The invention relates to an open channel on-line early warning system and method based on an ultrasonic electromagnetic technology. An ultrasonic liquid level sensor is installed on a contraction section of a Parshall groove, and a flow sensor is installed on a connecting pipeline; the image acquisition module comprises a camera; the control module is in communication connection with the flow measurement module and the image acquisition module, the control module is used for calculating a measurement difference value between flow data measured by the ultrasonic liquid level sensor and the flow sensor, and if the measurement difference value exceeds a preset flow threshold value, online calibration is carried out and an alarm is given out; and the control module is also used for judging the volume of the interferent according to the image data acquired by the camera, and giving an alarm if the volume of the interferent exceeds a preset volume threshold. According to the technical scheme, interference of interferents on the ultrasonic liquid level sensor is avoided, the measurement accuracy and stability of the ultrasonic liquid level sensor are guaranteed, and the accuracy and reliability of flow measurement in the open channel are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of open channel online early warning, and in particular to an open channel online early warning system and method based on ultrasonic electromagnetic technology. Background Art

[0002] The Parshall flume is a device used for open channel flow measurement. Its working principle is based on the energy conservation principle of open channel steady gradual flow and the characteristics of critical flow. However, in actual use, due to the complex open channel environment in the field, ultrasonic waves will be affected by interferences such as leaves, branches, aquatic plants, plastic bottles, and plastic bags in the Parshall flume when propagating in the fluid. As a result, in complex water systems, the ultrasonic level sensor has low measurement accuracy and poor stability, which affects the accuracy and reliability of flow measurement in the open channel. Summary of the invention

[0003] To this end, it is necessary to provide an open channel online early warning system and method based on ultrasonic electromagnetic technology to solve the technical problem that when ultrasonic waves propagate in the fluid, they will be affected by interferences in the Parshall cell, resulting in low measurement accuracy and poor stability of the ultrasonic liquid level sensor, thereby affecting the accuracy and reliability of flow measurement in the open channel.

[0004] To achieve the above objectives, in a first aspect, the present invention provides an open channel online early warning system based on ultrasonic electromagnetic technology, comprising:

[0005] An open channel, the open channel includes a Parshall flume and a connecting pipe, the outlet of the Parshall flume is connected to the inlet of the connecting pipe;

[0006] A flow measurement module, the flow measurement module includes an ultrasonic level sensor and a flow sensor, the ultrasonic level sensor is installed at the contraction section of the Parshall trough, and the flow sensor is installed on the connecting pipe. The ultrasonic level sensor is used to measure the real-time flow of the contraction section of the Parshall trough, and the flow sensor is used to measure the real-time flow of the connecting pipe;

[0007] An image acquisition module, the image acquisition module includes a camera, the camera is installed at the contraction section of the Parshall trough, the acquisition end of the camera is aimed at the contraction section of the Parshall trough, and the camera is used to acquire the image of the contraction section of the Parshall trough in real time;

[0008] The control module is communicatively connected with the flow measurement module and the image acquisition module. The control module is used to calculate the measurement difference between the flow data measured by the ultrasonic liquid level sensor and the flow data measured by the flow sensor. If the measurement difference exceeds a preset flow threshold, online calibration is performed and an alarm is issued. The control module is also used to determine the volume of the interference object based on the image data collected by the camera. If the volume of the interference object exceeds a preset volume threshold, an alarm is issued.

[0009] As an implementation mode of the present invention, the image acquisition module includes two cameras, and the two cameras are respectively installed on both sides of the contraction section of the Parshall cell.

[0010] As an implementation manner of the present invention, the preset flow rate threshold is ±2%.

[0011] As an implementation manner of the present invention, the preset volume threshold is 1 / 10 of the width of the ultrasonic beam emitted by the ultrasonic liquid level sensor or 10% of the area of ​​the contraction section of the Parshall cell.

[0012] As an implementation manner of the present invention, the diameter of the connecting pipe is D, and the distance between the ultrasonic liquid level sensor and the flow sensor is 10D.

[0013] As an implementation mode of the present invention, the ultrasonic liquid level sensor is installed at one third of the contraction section of the Parshall cell, and the camera is located at the front end of the ultrasonic liquid level sensor.

[0014] As an implementation manner of the present invention, the control module includes a control panel and a display screen, and the display screen is installed on the control panel.

[0015] As an implementation mode of the present invention, the open channel online early warning system based on ultrasonic electromagnetic technology also includes a host computer, which is communicatively connected with the control module.

[0016] As an implementation mode of the present invention, the control module is installed on the side of the open channel.

[0017] To achieve the above purpose, in a second aspect, the inventor provides an open channel online early warning method based on ultrasonic electromagnetic technology, including any open channel online early warning system based on ultrasonic electromagnetic technology provided by the inventor above, and further comprising the following steps:

[0018] S01: An ultrasonic level sensor and a camera are installed at the contraction section of the Parshall trough, and a flow sensor is installed on the connecting pipe;

[0019] S02: Initialize the open channel online early warning system based on ultrasonic electromagnetic technology, including inputting geometric parameters of the open channel, setting a preset flow threshold, and setting a preset volume threshold;

[0020] S03: When the open channel operates normally, the ultrasonic level sensor and the flow sensor collect flow data in real time and transmit the collected flow data to the control module. The control module calculates the measurement difference using the error discrimination algorithm. When the measurement difference is within the normal range, normal measurement continues. When the measurement difference exceeds the preset flow threshold, the calibration program is started to perform online calibration on the flow measurement module and trigger an alarm. At the same time, the camera collects image data of the contraction section of the Parshall trough in real time and transmits the collected image data to the control module. The control module preprocesses and extracts features from the collected image data and determines the volume of the interference object based on the recognition results. When the volume of the interference object is within the normal range, normal collection continues. When the volume of the interference object exceeds the preset volume threshold, an alarm is issued.

[0021] Different from the prior art, the technical solution of the present application is provided with a flow sensor and an ultrasonic level sensor, and when the measurement difference between the two exceeds the preset flow threshold, online calibration will be performed and an alarm will be triggered, thereby enabling real-time calibration to meet the needs of online continuous measurement. On the other hand, an image acquisition module is provided to specifically acquire images of the contraction section of the Parshall flume, under the action of the image acquisition module, interferences in the contraction section of the Parshall flume can be effectively monitored to avoid interference of interferences with the ultrasonic level sensor, thereby ensuring the measurement accuracy and stability of the ultrasonic level sensor, and thus ensuring the accuracy and reliability of flow measurement in the open channel.

[0022] The above-mentioned records related to the invention content are only an overview of the technical solution of the present application. In order to enable ordinary technicians in the field to more clearly understand the technical solution of the present application, and then implement it according to the text of the specification and the contents recorded in the drawings, and to make the above-mentioned purpose and other purposes, features and advantages of the present application easier to understand, the following is an explanation in combination with the specific implementation mode and drawings of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings are only used to illustrate the principles, implementation methods, applications, characteristics and effects of the specific embodiments of the present application and other related contents, and shall not be considered as limitations of the present application.

[0024] In the drawings of the specification:

[0025] Figure 1 The structure of an open channel online early warning system based on ultrasonic electromagnetic technology according to an embodiment of the present application is shown in FIG. Figure 1 ;

[0026] Figure 2 The structure of an open channel online early warning system based on ultrasonic electromagnetic technology according to an embodiment of the present application is shown in FIG. Figure 2 ;

[0027] Figure 3The structure of an open channel online early warning system based on ultrasonic electromagnetic technology according to an embodiment of the present application is shown in FIG. Figure 3 ;

[0028] Figure 4 This is a schematic diagram of the structure of a control module according to an embodiment of the present application;

[0029] Figure 5 This is a system block diagram of an open channel online early warning system based on ultrasonic electromagnetic technology according to an embodiment of the present application;

[0030] Figure 6 This is a flow chart of an open channel online early warning method based on ultrasonic electromagnetic technology according to an embodiment of the present application.

[0031] The reference numerals in the above drawings are described as follows:

[0032] 100-Open channel online early warning system based on ultrasonic electromagnetic technology; 1-Open channel; 11-Parshall flume; 12-Connecting pipe; 2-Flow measurement module; 21-Ultrasonic liquid level sensor; 22-Flow sensor; 3-Image acquisition module; 31-Camera; 4-Control module; 41-Control panel; 42-Display screen; 43-Button; D-Diameter of connecting pipe. DETAILED DESCRIPTION

[0033] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0034] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0035] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0036] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0037] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0038] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0039] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0040] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0041] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0042] According to some embodiments of the present application, please refer to Figures 1 to 5 The present embodiment relates to an open channel online early warning system 100 based on ultrasonic electromagnetic technology, comprising an open channel 1, a flow measurement module 2, an image acquisition module 3 and a control module 4; the open channel 1 comprises a Parshall trough 11 and a connecting pipe 12, the water outlet of the Parshall trough 11 is connected to the water inlet of the connecting pipe 12; the flow measurement module 2 comprises an ultrasonic liquid level sensor 21 and a flow sensor 22, the ultrasonic liquid level sensor 21 is installed at the contraction section of the Parshall trough 11, the flow sensor 22 is installed on the connecting pipe 12, the ultrasonic liquid level sensor 21 is used to measure the real-time flow of the contraction section of the Parshall trough 11, and the flow sensor 22 is used to measure the real-time flow of the connecting pipe 12; the image acquisition module 3 comprises a control module 4, and the control module 4 comprises a control module 4; the open channel 1 comprises a Parshall trough 11 and a connecting pipe 12, the water outlet of the Parshall trough 11 is connected to the water inlet of the connecting pipe 12; the flow measurement module 2 comprises an ultrasonic liquid level sensor 21 and a flow sensor 22, the ultrasonic liquid level sensor 21 is installed at the contraction section of the Parshall trough 11, and the flow sensor 22 is installed on the connecting pipe 12, the ultrasonic liquid level sensor 21 is used to measure the real-time flow of the contraction section of the Parshall trough 11, and the flow sensor 22 is used to measure the real-time flow of the connecting pipe 12; the image acquisition module 3 comprises a control module 4, and the control module 4 comprises a control module 4; the control module 4 comprises a control module 4, and the control module 4 comprises a control module 4; the control module 4 comprises a control module 4, and the control module 4 comprises a control module 4; the control module 4 The collection module 3 includes a camera 31, which is installed at the contraction section of the Parshall trough 11. The acquisition end of the camera 31 is aimed at the contraction section of the Parshall trough 11, and the camera 31 is used to acquire the image of the contraction section of the Parshall trough 11 in real time; the control module 4 is communicated with the flow measurement module 2 and the image acquisition module 3, and the control module 4 is used to calculate the measurement difference between the flow data measured by the ultrasonic liquid level sensor 21 and the flow data measured by the flow sensor 22. If the measurement difference exceeds the preset flow threshold, online calibration is performed and an alarm is issued; the control module 4 is also used to determine the volume of the interference object based on the image data collected by the camera 31. If the volume of the interference object exceeds the preset volume threshold, an alarm is issued.

[0043] The Parshall flume 11 comprises a contraction section, a throat section and a diffusion section. Water flows sequentially from the contraction section to the throat section, then to the diffusion section, and finally flows from the diffusion section into the connecting pipe 12 .

[0044] The flow sensor 22 is an electromagnetic flow sensor 22, which is used to measure the instantaneous flow rate and volume flow rate of the conductive liquid and the slurry. Among them, the ultrasonic liquid level sensor 21 is used to measure the real-time flow rate of the contraction section of the Parshall trough 11, and the electromagnetic flow sensor 22 is used to measure the real-time flow rate of the connecting pipe 12, ensuring that the flow measurement module 2 can accurately obtain the flow information in the open channel 1.

[0045] The camera 31 is a high-definition camera 31 and can rotate 360 ​​degrees. The camera 31 can obtain the visual information inside the water tank in real time and provide raw data for subsequent identification. The acquisition end of the camera 31 needs to be aimed at the contraction section of the Parshall tank 11, and in particular, the position and angle of the camera 31 need to ensure that it can cover the contraction section area in the Parshall tank 11 that may disrupt the accurate measurement of the ultrasonic liquid level sensor 21.

[0046] The control module 4 can be installed externally. In some embodiments, such as Figure 1 As shown, the control module 4 is installed on the side of the open channel 1. Preferably, the control module 4 is installed on the side of the diffusion section of the Parshall trough 11. The control module 4 can be connected to the ultrasonic level sensor 21, the flow sensor 22 and the camera 31 through wires. In actual use, the alarms of the flow measurement module 2 and the image acquisition module 3 are separate alarms.

[0047] On the one hand, the technical solution of the present application is provided with a flow sensor 22 and an ultrasonic level sensor 21. When the measurement difference between the two exceeds a preset flow threshold, an online calibration is performed and an alarm is triggered. Thus, real-time calibration can be performed to meet the needs of online continuous measurement. On the other hand, an image acquisition module 3 is provided to specifically acquire the image of the contraction section of the Parshall flume 11. Under the action of the image acquisition module 3, interferences in the contraction section of the Parshall flume 11 can be effectively monitored to avoid interference of interferences with the ultrasonic level sensor 21, thereby ensuring the measurement accuracy and stability of the ultrasonic level sensor 21, thereby ensuring the accuracy and reliability of the flow measurement in the open channel 1.

[0048] According to some embodiments of the present application, optionally, Figure 2 As shown, the image acquisition module 3 includes two cameras 31 , and the two cameras 31 are respectively installed on both sides of the contraction section of the Parshall cell 11 .

[0049] By arranging two cameras 31 to cooperate with each other, the image of the contraction section of the Parshall cell 11 can be more completely collected. In addition, when one of the cameras 31 fails, the other camera 31 can be guaranteed to collect normally.

[0050] According to some embodiments of the present application, the preset flow threshold is optionally ±2%. Preferably, the preset flow threshold is set to ±2%. In other embodiments, the preset flow threshold can be set according to the size of the open channel 1 and the installation position of the flow measurement module 2.

[0051] According to some embodiments of the present application, optionally, the preset volume threshold is 1 / 10 of the width of the ultrasonic beam emitted by the ultrasonic liquid level sensor or 10% of the area of ​​the contraction section of the Parshall cell 11 .

[0052] When the diameter (or maximum linear dimension) of a single object exceeds 1 / 10 of the width of the ultrasonic beam emitted by the ultrasonic level meter, larger floating objects will block or scatter the ultrasonic signal, changing the direction and intensity of the reflected wave; when the area occupied by the floating object exceeds 10% of the area of ​​the contraction section of the Parshall cell 11, the probability of the ultrasonic signal being disturbed during the reflection process will greatly increase, resulting in an increase in the liquid level measurement error. Therefore, it is preferred to set the preset volume threshold to 1 / 10 of the width of the ultrasonic beam emitted by the ultrasonic level sensor or 10% of the area of ​​the contraction section of the Parshall cell 11.

[0053] According to some embodiments of the present application, optionally, Figure 3 As shown, the diameter of the connecting pipe is D, and the distance between the ultrasonic liquid level sensor 21 and the flow sensor 22 is 10D.

[0054] By setting the distance between the ultrasonic liquid level sensor 21 and the flow sensor 22 to 10D, the influence of the upstream flow field disturbance on the downstream electromagnetic flow sensor 22 is reduced.

[0055] According to some embodiments of the present application, optionally, Figures 1 to 3 As shown, the ultrasonic liquid level sensor 21 is installed at one-third of the contraction section of the Parshall cell 11 , and the camera 31 is located at the front end of the ultrasonic liquid level sensor 21 .

[0056] By installing the camera 31 at the front end of the ultrasonic liquid level sensor 21 , the acquisition end of the camera 31 can cover the contraction section area in the Parshall cell 11 that may disturb the accurate measurement of the ultrasonic liquid level sensor 21 .

[0057] According to some embodiments of the present application, optionally, Figure 4 As shown, the control module 4 includes a control panel 41 and a display screen 42 , and the display screen 42 is mounted on the control panel 41 .

[0058] The display screen 42 can display the measurement data of the flow measurement module 2 and the image data collected by the image acquisition module 3 in real time. The control module 4 also includes a data processing center, which can process the data measured by the flow measurement module 2 and the image data collected by the image acquisition module 3. In some embodiments, the control module 4 also includes a button 43, through which a preset flow threshold, a preset volume threshold, or switching different interfaces can be adjusted. In other embodiments, the control module 4 also includes an alarm, and the control module 4 issues an alarm through the alarm.

[0059] According to some embodiments of the present application, optionally, the open channel online warning system 100 based on ultrasonic electromagnetic technology also includes a host computer, which is communicatively connected to the control module 4.

[0060] The host computer can be a computer or a remote monitoring center. The alarm issued by the control module 4 can be notified to the staff through the host computer, and the staff can take measures according to the alarm. Optionally, the alarm issued when the measured difference exceeds the preset flow threshold is different from the alarm issued when the volume of the interference exceeds the preset volume threshold, which can be different lights or different broadcast contents.

[0061] According to some embodiments of the present application, please refer to Figure 6 This embodiment also relates to an open channel 1 online early warning method based on ultrasonic electromagnetic technology, including an open channel online early warning system 100 based on ultrasonic electromagnetic technology, and further comprising the following steps:

[0062] S01: An ultrasonic level sensor 21 and a camera 31 are installed at the contraction section of the Parshall cell 11, and a flow sensor 22 is installed on the connecting pipe 12;

[0063] S02: Initializing the open channel online early warning system 100 based on ultrasonic electromagnetic technology, including inputting geometric parameters of the open channel 1, setting a preset flow threshold, and setting a preset volume threshold;

[0064] S03: When the open channel 1 operates normally, the ultrasonic liquid level sensor 21 and the flow sensor 22 collect flow data in real time and transmit the collected flow data to the control module 4. The control module 4 calculates the measurement difference using an error discrimination algorithm. When the measurement difference is within a normal range, normal measurement continues. When the measurement difference exceeds a preset flow threshold, the calibration program is started to perform online calibration on the flow measurement module 2 and trigger an alarm. At the same time, the camera 31 collects image data of the contraction section of the Parshall trough 11 in real time and transmits the collected image data to the control module 4. The control module 4 preprocesses and extracts features from the collected image data and determines the volume of the interference object based on the recognition results. When the volume of the interference object is within a normal range, normal collection continues. When the volume of the interference object exceeds the preset volume threshold, an alarm is issued.

[0065] After step S03, step S04 is also included: the control module 4 transmits the processed flow data to the host computer through the communication module, and the host computer stores and analyzes the data after receiving the data.

[0066] In step S03, it should be emphasized that the image collected by the camera 31 will be affected by factors such as illumination, water wave reflection, and image noise. Therefore, the image needs to be preprocessed. The preprocessing process includes grayscale processing (because the original image collected by the camera is a color image, it needs to be converted into a grayscale image to simplify subsequent processing and reduce the amount of data) and contrast enhancement operations to improve image quality and make the features of the interference objects in the image more obvious. Afterwards, computer vision technology is used to extract features from the preprocessed image. Specifically, the shape features, edge contours, and texture features of objects (bottle caps, branches and leaves, plastic bags, duckweed, etc.). For shape feature extraction, the shape feature extraction algorithm uses Hu moment invariants. When identifying different shapes of interference objects in the sink, Hu moment invariants can help distinguish between round plastic bottles and square foam boards, etc.; edge detection algorithms are used, and Canny edge detection is used to obtain the edge contours of objects; surface texture features can use the grayscale co-occurrence matrix method to describe textures, and a variety of texture features can be extracted from the co-occurrence matrix, such as contrast, correlation, energy, and entropy. These texture features can be used to distinguish different texture patterns, and to distinguish smooth water surfaces from water surfaces with debris. Finally, the control module 4 determines the volume of the interference object based on the recognition result. When the volume of the interference object is within the normal range, normal collection continues; when the volume of the interference object exceeds the preset volume threshold, an alarm is issued. Among them, the alarm information can be sent to the on-site staff or the host computer so that cleaning or other countermeasures can be taken in time.

[0067] It should be noted that, although the above embodiments have been described in this article, the patent protection scope of the present invention is not limited thereby. Therefore, based on the innovative concept of the present invention, changes and modifications made to the embodiments described herein, or equivalent structures or equivalent process changes made using the contents of the present invention specification and drawings, directly or indirectly applying the above technical solutions to other related technical fields, are all included in the patent protection scope of the present invention.

Claims

1. An open channel online early warning system based on ultrasonic electromagnetic technology, characterized in that: include: An open channel, the open channel comprising a Parshall flume and a connecting pipe, wherein the water outlet of the Parshall flume is connected to the water inlet of the connecting pipe; A flow measurement module, the flow measurement module comprising an ultrasonic level sensor and a flow sensor, the ultrasonic level sensor being mounted on the contraction section of the Parshall trough, the flow sensor being mounted on the connecting pipe, the ultrasonic level sensor being used to measure the real-time flow of the contraction section of the Parshall trough, and the flow sensor being used to measure the real-time flow of the connecting pipe; An image acquisition module, the image acquisition module comprising a camera, the camera is installed at the contraction section of the Parshall cell, the acquisition end of the camera is aimed at the contraction section of the Parshall cell, and the camera is used to acquire the image of the contraction section of the Parshall cell in real time; A control module, wherein the control module is communicatively connected with the flow measurement module and the image acquisition module, and the control module is used to calculate the measurement difference between the flow data measured by the ultrasonic liquid level sensor and the flow data measured by the flow sensor, and if the measurement difference exceeds a preset flow threshold, online calibration is performed and an alarm is issued; the control module is also used to determine the volume of the interference object based on the image data collected by the camera, and if the volume of the interference object exceeds a preset volume threshold, an alarm is issued.

2. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The image acquisition module includes two cameras, which are respectively installed on both sides of the contraction section of the Parshall cell.

3. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The preset flow rate threshold is ±2%.

4. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The preset volume threshold is 1 / 10 of the width of the ultrasonic beam emitted by the ultrasonic liquid level sensor or 10% of the area of ​​the contraction section of the Parshall cell.

5. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The diameter of the connecting pipe is D, and the distance between the ultrasonic liquid level sensor and the flow sensor is 10D.

6. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The ultrasonic liquid level sensor is installed at one third of the contraction section of the Parshall trough, and the camera is located at the front end of the ultrasonic liquid level sensor.

7. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The control module includes a control panel and a display screen, and the display screen is installed on the control panel.

8. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The open channel online early warning system based on ultrasonic electromagnetic technology also includes a host computer, which is communicatively connected with the control module.

9. The open channel online early warning system based on ultrasonic electromagnetic technology according to claim 1 is characterized in that: The control module is installed on the side of the open channel.

10. An open channel online early warning method based on ultrasonic electromagnetic technology, characterized in that: The open channel online early warning system based on ultrasonic electromagnetic technology as claimed in any one of claims 1 to 9 further comprises the following steps: S01: The ultrasonic liquid level sensor and the camera are installed at the contraction section of the Parshall cell, and the flow sensor is installed on the connecting pipe; S02: Initializing and setting the open channel online early warning system based on ultrasonic electromagnetic technology, including inputting geometric parameters of the open channel, setting a preset flow threshold, and setting a preset volume threshold; S03: When the open channel operates normally, the ultrasonic liquid level sensor and the flow sensor collect flow data in real time, and transmit the collected flow data to the control module. The control module calculates the measurement difference using an error discrimination algorithm. When the measurement difference is within a normal range, normal measurement continues. When the measurement difference exceeds a preset flow threshold, the calibration program is started to perform online calibration on the flow measurement module, and an alarm is triggered at the same time. At the same time, the camera collects image data of the contraction section of the Parshall trough in real time, and transmits the collected image data to the control module. The control module preprocesses and extracts features from the collected image data and determines the volume of the interference object based on the recognition results. When the volume of the interference object is within a normal range, normal collection continues. When the volume of the interference object exceeds the preset volume threshold, an alarm is sounded.

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