Intrinsic safety type GHz radar liquid level meter and use method thereof

Abstract

The invention discloses an intrinsic safety type GHz radar liquid level meter and a using method thereof, and relates to the technical field of industrial automation instruments.The intrinsic safety type GHz radar liquid level meter comprises a machine shell cavity, a circuit board assembly is arranged in the machine shell cavity, a flange assembly is arranged at the lower end of the machine shell cavity, and a lens is arranged at the bottom end of the flange assembly; the flange assembly and the edge of the lens are sealed through epoxy resin glue. A window cover assembly is installed at the top end of the machine shell cavity. The end, close to the lens, of the circuit board assembly is electrically connected with a transceiving circuit board, and the end, close to the window cover assembly, of the circuit board assembly is provided with a display panel. According to the intrinsic safety type GHz radar liquid level meter, high-precision liquid level measurement is achieved through the 120 GHz millimeter wave technology, the explosion-proof requirement is met through the intrinsic safety type circuit design, a dynamic threshold value filtering algorithm and a temperature compensation model are integrated, the measurement reliability under the complex working condition is effectively improved, and the intrinsic safety type GHz radar liquid level meter is compact in structure, low in power consumption and suitable for petrochemical engineering and other dangerous environments.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial automation instruments, and specifically relates to an intrinsically safe GHz radar level gauge and its usage method. Background Technique

[0002] The radar level gauge belongs to a general-purpose radar level gauge. It is a measuring instrument based on the time-of-flight principle. The radar wave travels at the speed of light, and the running time can be converted into a level signal by electronic components. The probe emits high-frequency pulses that propagate in space at the speed of light. When the pulse encounters the surface of the material, it is reflected back and received by the receiver in the instrument, and the distance signal is converted into a level signal.

[0003] Currently, most of the radar level gauges commonly used in the industrial field adopt low-frequency bands (such as 6 GHz, 26 GHz) or 80 GHz high-frequency technology. Although they can meet the basic level measurement requirements, they have deficiencies in the following aspects: Insufficient explosion-proof performance: Traditional radar level gauges rely on external flameproof enclosures to achieve explosion protection, which are large in size, high in cost, and complex to maintain; Weak anti-interference ability: Low-frequency radars are easily interfered by media such as dust, steam, and foam, resulting in an increase in measurement errors; Limited accuracy and resolution: Below the 80 GHz frequency band, due to the longer wavelength, the measurement accuracy for small containers or complex liquid surface forms is relatively low; High power consumption: Existing intrinsically safe devices are difficult to meet the low-power requirements due to redundant circuit designs, affecting long-term stability; The present invention aims to solve the above problems and proposes an intrinsically safe radar level gauge based on 120 GHz millimeter-wave technology, which has high precision, low power consumption, and strong anti-interference ability. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides an intrinsically safe GHz radar level gauge and its usage method, which solves the problems raised in the above background technique.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: An intrinsically safe GHz radar level gauge includes a housing cavity. A circuit board assembly is provided inside the housing cavity. A flange assembly is provided at the lower end of the housing cavity. A lens is provided at the bottom end of the flange assembly. The flange assembly and the lens edge are sealed with epoxy resin glue; A window cover assembly is installed at the top end of the housing cavity; One end of the circuit board assembly close to the lens is electrically connected to a transceiver circuit board, and a display board is provided at one end of the circuit board assembly close to the window cover assembly; The circuit board assembly includes a signal processor for performing spectral analysis and refinement on the received echo signals. The signal processor includes time-domain accumulation, spectral analysis, filter tracking, constant false alarm rate detection, and distance estimation. The distance estimation is performed using Kalman filtering to determine the position of the medium surface as follows: Estimate the state at the current time ( time) based on the posterior estimate value at the previous time ( time) to obtain the prior estimate value at time; and based on the state transition matrix predict the posterior state estimate value at time to obtain the prior state estimate value at time ; Update the error covariance matrix to obtain the prior estimate covariance at time ; The distance estimation also includes using the measurement value at the current time to correct the estimated value in the prediction stage to obtain the posterior estimate value at the current time, specifically including: Based on the prior estimate covariance at time , the conversion matrix from the state variable to the measurement and the measurement noise covariance calculate the Kalman gain ; and use the Kalman gain , the measurement value at the current time and the prior state estimate value at time to calculate the posterior state estimate value at time ; update the error covariance matrix to obtain the posterior estimate covariance at time .

[0006] Optionally, the signal processor further includes a Bluetooth communication module.

[0007] Optionally, the transceiver circuit board includes a microwave transmitter and a microwave receiver.

[0008] Optionally, the microwave transmitter includes a transmitting front-end circuit and a lens for transmitting narrowband radio frequency signals with a transmission frequency range of 119 - 125 GHz, and a linear frequency modulated continuous wave is transmitted within this frequency range.

[0009] Optionally, the transmitting front-end circuit includes a modulation signal generator, a voltage controlled oscillator (VCO), a power divider, and a power amplifier. ​

[0010] Optionally, the microwave receiver includes a receiving front-end circuit and a lens for receiving the echo signal reflected from the surface of the medium to be measured.

[0011] Optionally, the receiving front-end circuit includes a low-noise amplifier (LNA), a quadrature mixer, a low-pass filter, and a zero-IF amplifier.

[0012] A method for using an intrinsically safe GHz radar level gauge includes the following specific steps: Step 1: The microwave transmitter emits a 120 GHz signal that propagates to the surface of the medium to be measured. Step 2: The microwave receiver receives the reflected GHz signal, performs quadrature demodulation, zero-IF amplification, A / D sampling on the echo signal, and sends the A / D sampled signal to the signal processor. Step 3: The signal processor processes the zero-IF signal to extract the liquid level information. Among them, the signal processing flow is as follows: (1) Time-domain accumulation is used to improve the signal-to-noise ratio. (2) Spectrum analysis is used to analyze the influence of the environment on the spectrum of the echo signal. (3) Filter tracking is used to resist interference and improve stability. (4) Constant false alarm rate detection, by introducing machine learning and data fusion technologies, realizes the improvement of the target recognition accuracy, thereby dynamically adjusts the false alarm threshold, performs real-time optimization according to the changes in the environment, and calculates the detection curve to extract the target distance information. (5) The distance estimation is specifically as follows: State prediction: According to the state transition matrix For The posterior state estimate value at time Is predicted to obtain The prior state estimate value at time , and the formula is ; Among them Is the matrix that converts the input into the state, Is the new external control quantity; Error covariance prediction: Update the error covariance matrix to obtain The prior estimate covariance at time , and the formula is ; Among them Is the process excitation noise covariance; Update step: Use the measurement value at the current time to correct the estimated value in the prediction stage to obtain the posterior estimated value at the current time, which specifically includes: Calculate the Kalman gain: The formula is ; Update the state estimate: The formula is ; Update the error covariance: The formula is ; where is the identity matrix; (6) Determine whether there is clutter interference; If there is, return to step two for A / D sampling operation; If not, output the measurement result; Step four: Implement Bluetooth communication between the signal processor and the mobile client through the Bluetooth communication module, and display, set, and modify the parameters of the radar level gauge through the mobile client.

[0013] The present invention provides an intrinsically safe GHz radar level gauge and its usage method, having the following beneficial effects: The intrinsically safe GHz radar level gauge and its usage method emit a linear frequency modulated continuous wave (FMCW) through a transmitter, and the receiver receives in real time the linear frequency modulated continuous wave (FMCW) reflected from the surface of the medium; the transmitted linear frequency modulated wave and the received linear frequency modulated wave are orthogonally mixed, and a zero intermediate frequency signal is obtained through low-pass filtering. The frequency of the zero intermediate frequency signal reflects the interface position between two materials with different dielectric constants; an advanced algorithm is adopted to perform signal processing on the echo, automatically suppressing false echoes and interference clutter caused by the environment, making the measurement of the liquid level of the measured medium more accurate; Specifically as follows: 1) High precision: The GHz characteristic is combined with the frequency modulation bandwidth design to achieve high-precision liquid level measurement; 2) High reliability: Advanced signal processing algorithms and anti-interference designs achieve the stability and reliability of the measurement results; 3) Non-contact measurement: There is no need to directly contact the measured liquid material, avoiding the pollution and corrosion of the radar level gauge by chemical liquid materials; 4) Intrinsic safety: An intrinsically safe circuit design is adopted, eliminating the need for an external explosion-proof box, and significantly reducing the volume. Description of the Drawings

[0014] Figure 1 is the front view full-section structural schematic diagram of the invention; Figure 2 is the schematic block diagram of the hardware composition of the invention; Figure 3 is the schematic diagram of the signal processing flow in the invention.

[0015] In the figure: 1. Window cover assembly; 2. Display board; 3. Circuit board assembly; 4. Housing cavity; 5. Transceiver circuit board; 6. Lens; 7. Flange assembly. Detailed implementation

[0016] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0017] In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more; the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0018] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] Please refer to Figure 1 , an intrinsically safe GHz radar level gauge, including a housing cavity 4, a circuit board assembly 3 is provided inside the housing cavity 4, a flange assembly 7 is provided at the lower end of the housing cavity 4, a lens 6 is provided at the bottom end of the flange assembly 7, and the edge between the flange assembly 7 and the lens 6 is sealed with epoxy resin glue; A window cover assembly 1 is installed at the top end of the housing cavity 4; One end of the circuit board assembly 3 close to the lens 6 is electrically connected to a transceiver circuit board 5; the transceiver circuit board 5 includes a microwave transmitter and a microwave receiver; The microwave transmitter includes a transmitting front-end circuit and a lens 6, and is used to transmit a narrowband RF signal, and the transmission frequency range is 119~125 GHz, and a linear frequency modulation continuous wave is transmitted within this frequency range; the transmitting front-end circuit includes a modulation signal generator, a voltage-controlled oscillator VCO, a power divider, and a power amplifier; The microwave receiver includes a receiving front-end circuit and a lens 6 for receiving the echo signal reflected from the surface of the medium to be measured; the receiving front-end circuit includes a low-noise amplifier LNA, a quadrature mixer, a low-pass filter, and a zero-IF amplifier; One end of the circuit board assembly 3 close to the window cover assembly 1 is provided with a display board 2; the circuit board assembly 3 includes a signal processor for performing spectral analysis and refinement on the received echo signal; The signal processor includes time-domain accumulation, spectral analysis, filter tracking, constant false alarm detection, and distance estimation; the signal processor also includes a Bluetooth communication module.

[0020] Please refer to Figures 2 to 3 , a method for using an intrinsically safe GHz radar level gauge, including the following specific steps: Step 1: The microwave transmitter emits a 120 GHz signal that propagates to the surface of the medium to be measured; Step 2: The microwave receiver receives the reflected GHz signal, performs quadrature demodulation, zero-IF amplification, A / D sampling on the echo signal, and sends the A / D sampled signal to the signal processor; Step 3: The signal processor processes the zero-IF signal to extract the liquid level information therefrom; Among them, the signal processing flow is as follows: (1) Time-domain accumulation, used to improve the signal-to-noise ratio; (2) Spectral analysis, used to analyze the influence of the environment on the spectrum of the echo signal; (3) Filter tracking, anti-interference, improving stability; (4) Constant false alarm detection, by introducing machine learning and data fusion technologies, realizing an improvement in the target recognition accuracy, thereby dynamically adjusting the false alarm threshold, performing real-time optimization according to the changes in the environment, and calculating the detection curve to extract the target distance information; (5) Distance estimation module, using Kalman filtering for estimation to judge the position of the medium surface; Prediction step: Estimate the state at the current moment ( moment) based on the posterior estimate value at the previous moment ( moment) to obtain the prior estimate value at the moment; State prediction: According to the state transition matrix for the posterior state estimate value at the moment is predicted to obtain the prior state estimate value at the moment , and the formula is ; Among them is the matrix that converts the input to a state, is the new external control quantity; Error covariance prediction: Update the error covariance matrix to obtain the prior estimate variance at time , and the formula is ; where is the process excitation noise covariance; Update step: Use the measurement value at the current time to correct the estimated value in the prediction stage to obtain the posterior estimated value at the current time, which specifically includes: Calculate the Kalman gain: According to the prior estimate covariance at time , the transformation matrix from the state variable to the measurement and the measurement noise covariance calculate the Kalman gain , and the formula is ; Update the state estimate value: Use the Kalman gain , the measurement value at the current time and the prior state estimate value at time to calculate the posterior state estimate value at time , and the formula is ; Update the error covariance: Update the error covariance matrix to obtain the posterior estimate covariance at time , and the formula is ; where is the identity matrix; (6) Determine whether there is clutter interference; If there is, return to step two for A / D sampling operation; If not, output the measurement result; Step four: Implement Bluetooth communication between the signal processor and the mobile client through the Bluetooth communication module, and display, set, and modify the parameters of the radar level gauge through the mobile client.

[0021] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and all should be covered within the protection scope of the present invention.

Claims

1. An intrinsically safe GHz radar level meter, comprising a housing cavity (4), characterized in that: A circuit board assembly (3) is provided inside the housing cavity (4), a flange assembly (7) is provided at the lower end of the housing cavity (4), a lens (6) is provided at the bottom end of the flange assembly (7), and the flange assembly (7) and the edge of the lens (6) are sealed with epoxy resin; A window cover assembly (1) is installed at the top of the housing cavity (4); One end of the circuit board assembly (3) close to the lens (6) is electrically connected to a transceiver circuit board (5), and one end of the circuit board assembly (3) close to the window cover assembly (1) is provided with a display panel (2); The circuit board assembly (3) includes a signal processor for performing spectrum analysis and refinement on the received echo signal, wherein the signal processor includes time domain accumulation, spectrum analysis, filter tracking, constant false alarm detection and distance estimation; Distance estimation uses Kalman filtering to estimate the surface position of the medium, as follows: According to the last moment ( moment) to estimate the current moment ( time), we get A priori estimate of the moment; And according to the state transfer matrix right The posterior state estimate at time Make a prediction and get The prior state estimate at time ; Update the error covariance matrix to get The prior estimate covariance of the moment ; Distance estimation also includes using the measured value at the current moment to correct the estimated value in the prediction phase to obtain the posterior estimated value at the current moment, including: according to The prior estimate covariance of the moment , the conversion matrix from state variables to measurements and the measurement noise covariance Calculate Kalman gain ; And using the Kalman gain , the measured value at the current moment and The prior state estimate at time calculate The posterior state estimate at time ; Update the error covariance matrix to get The posterior estimated covariance at time .

2. The intrinsically safe GHz radar level meter according to claim 1, characterized in that: The signal processor also includes a Bluetooth communication module.

3. The intrinsically safe GHz radar level meter according to claim 1, characterized in that: The transceiver circuit board (5) comprises a microwave transmitter and a microwave receiver.

4. The intrinsically safe GHz radar level meter according to claim 3, characterized in that: The microwave transmitter comprises a transmitting front-end circuit and a lens (6), and is used to transmit a narrowband radio frequency signal, wherein the transmitting frequency range is 119-125 GHz, and a linear frequency modulated continuous wave is transmitted within this frequency range.

5. The intrinsically safe GHz radar level meter according to claim 4, characterized in that: The transmitting front-end circuit includes a modulation signal generator, a voltage controlled oscillator (VCO), a power divider and a power amplifier.

6. The intrinsically safe GHz radar level meter according to claim 3, characterized in that: The microwave receiver comprises a receiving front-end circuit and a lens (6), and is used to receive an echo signal reflected from the surface of the measured medium.

7. The intrinsically safe GHz radar level meter according to claim 6, characterized in that: The receiving front-end circuit includes a low noise amplifier (LNA), an orthogonal mixer, a low-pass filter and a zero intermediate frequency amplifier.

8. A method for using the intrinsically safe GHz radar level gauge according to any one of claims 1 to 7, characterized in that: The specific steps include: Step 1: The microwave transmitter transmits a 120GHz GHz signal to the surface of the medium being tested; Step 2: The microwave receiver receives the reflected GHz signal, performs orthogonal demodulation, zero intermediate frequency amplification, A / D sampling on the echo signal, and sends the A / D sampling signal to the signal processor; Step 3: Process the zero intermediate frequency signal through a signal processor to extract the liquid level information; The signal processing flow is as follows: (1) Time domain accumulation, used to improve the signal-to-noise ratio; (2) Spectrum analysis, used to analyze the impact of the environment on the echo signal spectrum; (3) Filter tracking, anti-interference and improved stability; (4) Constant false alarm detection: by introducing machine learning and data fusion technology, the accuracy of target recognition is improved, thereby dynamically adjusting the false alarm threshold, optimizing in real time according to environmental changes, and calculating the detection curve to extract target distance information; (5) The distance estimation is as follows: State prediction: According to the state transfer matrix right The posterior state estimate at time Make a prediction and get The prior state estimate at time , the formula is ； in is the matrix that transforms input into state, is the new external control quantity; Error covariance prediction: Update the error covariance matrix to get The prior estimate covariance of the moment , the formula is ； in is the process excitation noise covariance; The update step uses the current measurement value to correct the estimated value in the prediction stage to obtain the posterior estimate value at the current moment, which includes: Calculate the Kalman gain: The formula is ； Update state estimate: The formula is ； Update error covariance: The formula is ； in is the identity matrix; (6) Determine whether there is clutter interference; If it exists, return to step 2 to perform A / D sampling operation; If it does not exist, output the measurement result; Step 4: Realize Bluetooth communication between the signal processor and the mobile client through the Bluetooth communication module, and display, set, and modify the parameters of the radar level meter through the mobile client.

Images