An object detection method and system based on a microwave sensor array

Abstract

The present invention discloses an object detection method and system based on a microwave sensor array, including constructing a spatial radiation field through the microwave sensor array to achieve non-contact detection of the object to be measured, analyzing the resonant frequency and amplitude change amounts before and after the object to be measured is placed, characterizing the thickness of the object to be measured according to the resonant amplitude change amount, then calculating the resonant frequency change amount caused by the thickness, and then removing the resonant frequency change amount caused by the thickness from the resonant frequency change amount to obtain the resonant frequency change amount caused by the dielectric constant, and finally determining the material of the object according to the dielectric constant of the object; simulating the three-dimensional shape of the object to be measured through the thickness values of multiple groups of microwave sensor array units. The present invention uses a non-contact method to detect the material, shape and thickness of an object, which is beneficial to improving the safety during the object detection process.

Description

Technical Field

[0001] The present invention relates to the technical field of sensor detection, and particularly to an object detection method and system based on a microwave sensor array. Background Art

[0002] In recent years, the application and research of robot technology have penetrated into various fields. However, with the development of artificial intelligence technology, humans have put forward higher requirements for robots in terms of structure, perception, control, and intelligence. Therefore, robots are developing towards networking and intelligence to adapt to new environments, new tasks, and new demands.

[0003] For the three-dimensional shape recognition of an object by a robot, it is currently mainly achieved through image recognition technology, which requires a large amount of data set collection and feature extraction in the early stage, and is combined with algorithms in the later stage to achieve the recognition of the object and the reproduction of the three-dimensional shape. In addition, by means of a pressure sensor array, the pressure information and pressure data of different array units are transmitted to a processor and / or a memory connected to an electronic skin, and the pressure data is calculated and compared with the stored object shape data one by one to determine the shape of the object. However, the above detection technologies cannot accurately identify the material of the object while detecting the three-dimensional shape. Image recognition technology cannot give an accurate judgment for objects with similar appearances and small sizes, and the pressure sensor array not only needs to contact the object to achieve the recognition of its three-dimensional shape, but also cannot identify the material of the object.

[0004] In summary, it can be seen that how to provide a non-contact object detection method for intelligently identifying the shape, material, and thickness of an object is a problem to be solved at present. Summary of the Invention

[0005] The purpose of the present invention is to provide an object detection method and system based on a microwave sensor array, which solves the drawback in the prior art that the shape and other information of an object must be recognized by relying on contact.

[0006] To solve the above technical problems, the present invention provides an object detection method based on a microwave sensor array, including:

[0007] Placing an object to be detected into a spatial radiation magnetic field established by exciting multiple groups of microwave sensor array units with a radio frequency signal source;

[0008] Obtaining the change amount of the resonant frequency and the change amount of the resonant amplitude of each group of microwave sensor array units before and after placing the object to be detected into the spatial radiation magnetic field;

[0009] Characterizing the thickness of the object to be measured in each group of microwave sensor array units according to the change in the resonance amplitude of each group of microwave sensor array units, and performing comprehensive modeling based on the thickness of the object to be measured in each group of microwave sensor array units to obtain a three-dimensional shape of the object to be measured;

[0010] Calculating the resonant frequency variation of each group of microwave sensor array units caused by the thickness effect according to the thickness of the object to be measured in each group of microwave sensor array units;

[0011] According to the resonant frequency change of each group of microwave sensor array units and the resonant frequency change caused by the thickness effect, the resonant frequency change of each group of microwave sensor array units caused by the dielectric effect is calculated, and the dielectric constant detected by each group of microwave sensor array units is calculated;

[0012] The dielectric constants detected by all groups of microwave sensor array units are averaged and weighted to obtain the target dielectric constant of the object to be measured, and the material of the object to be measured is determined.

[0013] Preferably, the obtaining of the resonant frequency change and the resonant amplitude change of each group of microwave sensor array units before and after the object to be measured is placed in the spatial radiation magnetic field comprises:

[0014] collecting microwave signals of the plurality of groups of microwave sensor array units when they are unloaded;

[0015] After the object to be tested is placed, target microwave signals of the multiple groups of microwave sensor array units are collected;

[0016] Calculating the difference between the microwave signals of the plurality of groups of microwave sensor array units when they are unloaded and the target microwave signals to obtain microwave change signals of the plurality of groups of microwave sensor array units;

[0017] Converting the microwave change signals of the plurality of microwave sensor array units into electrical signals, and converting the electrical signals into waveform graphs;

[0018] The resonant frequency change and the resonant amplitude change of each group of microwave sensor array units are obtained according to the waveform diagram.

[0019] Preferably, the step of calculating the resonant frequency change amount caused by the dielectric effect of each group of microwave sensor array units according to the resonant frequency change amount of each group of microwave sensor array units and the resonant frequency change amount caused by the thickness effect, and calculating the dielectric constant detected by each group of microwave sensor array units comprises:

[0020] According to the formula Δf rn (t) = A Tn x mn +B TnCalculate the change in resonant frequency caused by the thickness effect for each group of microwave sensor array units;

[0021] The induced relationship between the change in resonant frequency of each group of microwave sensor array units and the dielectric constant and thickness parameters of the object to be measured is:

[0022] Δf rn =Δf rn (ε r )+Δf rn (t)

[0023] Based on the change in resonant frequency of each group of microwave sensor array units and the change in resonant frequency caused by the thickness effect, calculate the change in resonant frequency caused by the dielectric effect for each group of microwave sensor array units;

[0024] According to the relationship formula Δf rn (ε r ) = A εn x εn +B εn between the change in resonant frequency caused by the dielectric effect of each group of microwave sensor array units and the dielectric constant of the object to be measured, calculate the dielectric constant of the object to be measured detected by each group of microwave sensor array units;

[0025] Among them, A Tn , B Tn , A εn and B εn are the radio frequency constants of the nth microwave sensor array unit, x mn is the thickness detected by the nth microwave sensor array unit, Δf rn is the change in resonant frequency of the nth group of microwave sensor array units, Δf rn (t) is the change in resonant frequency caused by the thickness effect of the nth group of microwave sensor array units, Δf rn (ε r ) is the change in resonant frequency caused by the dielectric effect of the nth group of microwave sensor array units, x εn is the dielectric constant detected by the nth microwave sensor array.

[0026] Preferably, after calculating the change in resonant frequency caused by the dielectric effect of each group of microwave sensor array units according to the change in resonant frequency of each group of microwave sensor array units and the change in resonant frequency caused by the thickness effect of each group of microwave sensor array units, and calculating the dielectric constant of each group of microwave sensor array units, it further includes:

[0027] Screen out the abnormal dielectric constants among all groups of dielectric constants and determine the microwave sensor array units of the abnormal dielectric constants;

[0028] Extract the attenuation value and phase shift value of the abnormal dielectric constant array unit;

[0029] According to the relationship between the attenuation constant, phase shift constant and material dielectric constant, construct the relationship between the attenuation value, the phase shift value and the material dielectric constant directly;

[0030] Query the defect type table according to the relationship between the attenuation value, the phase shift value and the material dielectric constant, and obtain the defect of the object to be measured.

[0031] Preferably, the step of placing the object to be measured into the spatial radiation magnetic field established by exciting multiple groups of microwave sensor array units by a radio frequency signal source includes:

[0032] Collect the harmonic amplitude values of multiple groups of microwave sensor array units after placing the object to be measured;

[0033] Judge whether the harmonic amplitude value of each group of microwave sensor array units is lower than the preset amplitude;

[0034] When the harmonic amplitude value of a group of microwave sensor array units is lower than the preset amplitude, increase the power of the radio frequency signal source until the harmonic amplitude value of each group of microwave sensor array units is greater than or equal to the preset amplitude.

[0035] The present invention also provides an object detection system based on a microwave sensor array, including:

[0036] A microwave sensor array, including a plurality of sensor units, each of the sensor units generates a radiation field with a specific frequency for realizing microwave detection;

[0037] A radio frequency signal source for exciting the microwave sensor array;

[0038] A microwave parameter reading circuit, arranged at the output port of the microwave sensor array, for reading the spatial radiation field information of the microwave sensor array;

[0039] An upper computer communication serial port circuit, connected to the microwave parameter reading circuit, for transmitting the information read by the microwave parameter reading circuit;

[0040] An upper computer, connected to the upper computer communication serial port circuit, for implementing the steps of the above-mentioned object detection method based on a microwave sensor array when executing the computer program.

[0041] Preferably, the microwave sensor array includes:

[0042] A top metal layer, on the upper surface of which a microwave sensor unit structure of a transmission line and a circular inductor is etched;

[0043] A bottom metal layer, and the bottom metal layer is a ground layer;

[0044] An intermediate dielectric layer for carrying the top metal layer and the bottom metal layer.

[0045] Preferably, the RF signal source includes:

[0046] An RF circuit using a fourth-order type-II wideband fractional-N phase-locked loop, the fourth-order type-II wideband fractional-N phase-locked loop including:

[0047] A phase-frequency detector with its input terminal connected to an input signal source;

[0048] A charge pump with its input terminal connected to the output terminal of the phase-frequency detector,

[0049] A loop filter with its input terminal connected to the output terminal of the charge pump for filtering;

[0050] A voltage-controlled oscillator with its input terminal connected to the output terminal of the loop filter, and the operating scanning frequency of the voltage-controlled oscillator is matched with the operating frequency of the microwave sensor array.

[0051] A power amplifier with its input terminal connected to the voltage-controlled oscillator and its output terminal connected to the microwave sensor array.

[0052] Preferably, the output power of the RF signal source can be adjusted through the voltage-controlled oscillator.

[0053] Preferably, the microwave parameter reading circuit includes:

[0054] An RF detection circuit for converting the high-frequency microwave signal output by the microwave sensor array into a DC analog signal;

[0055] A high-speed analog-to-digital converter for converting the DC analog signal into a digital signal;

[0056] A waveform generator for converting the digital signal into a waveform diagram and interacting with a host computer through a host computer serial communication circuit.

[0057] An object detection method based on a microwave sensor array provided by the present invention constructs a spatial radiation field through the microwave sensor array to achieve non-contact detection of the object to be measured and the sensor array. Analyze the change amount of the resonant frequency and the change amount of the resonant amplitude after being affected, extract the change amount of the resonant amplitude, characterize the thickness of the object to be measured according to the change amount of the resonant amplitude, and then calculate the change amount of the resonant frequency caused by the thickness effect according to the thickness of the object to be measured. Then, according to the change amount of the resonant frequency of each group of microwave sensor array units and the change amount of the resonant frequency caused by the thickness effect, calculate the change amount of the resonant frequency caused by the dielectric effect of each group of microwave sensor array units, obtain the dielectric constant detected by each group of microwave sensor array units according to the change amount of the resonant frequency caused by the dielectric effect, and finally determine the material of the object according to the dielectric constant of the object; simulate the three-dimensional shape of the object to be measured through the thickness detected by multiple groups of microwave sensor array units. The present invention uses non-contact detection of the material, three-dimensional shape and thickness of the object, which is beneficial to improving the safety during the object detection process. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions of the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0059] Figure 1 It is a structural block diagram of an object detection system based on a microwave sensor provided by an embodiment of the present invention

[0060] Figure 2 It is a flowchart of the first specific embodiment of an object detection method based on a microwave sensor array provided by the present invention;

[0061] Figure 3 It is a schematic diagram of non-contact detection using a microwave sensor array in an embodiment of the present invention;

[0062] Figure 4 It is a schematic diagram of the change of microwave signals at different distances between a microwave sensor array and a target object in an embodiment of the present invention;

[0063] Figure 5 It is a schematic diagram of the change of microwave signals when a microwave sensor array detects target objects of different materials in an embodiment of the present invention;

[0064] Figure 6 It is a flowchart of the second specific embodiment of an object detection method based on a microwave sensor array provided by the present invention;

[0065] Figure 7Schematic diagram of detecting the thickness of an object using the microwave sensor array unit in an embodiment of the present invention;

[0066] Figure 8 Schematic diagram of the microwave signal change of the microwave sensor array unit in an embodiment of the present invention for detecting target objects with different thicknesses. Specific implementation manners

[0067] The core of the present invention is to provide an object detection method and a detection system based on a microwave sensor array, realizing a non-contact object recognition method, and analyzing the material, shape, and thickness of an object through the change amount of microwave signals.

[0068] In order to enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0069] The object detection method provided by the present invention adopts an object detection system based on a microwave sensor array. Please refer to Figure 1 , Figure 1 The structural block diagram of an object detection system based on a microwave sensor provided in an embodiment of the present invention is specifically as follows:

[0070] A microwave sensor array, including a plurality of sensor units, and each of the sensor units generates a radiation field with a specific frequency for realizing microwave detection;

[0071] A radio frequency signal source for exciting the microwave sensor array;

[0072] A microwave parameter reading circuit is arranged at the output port of the microwave sensor array for reading the spatial radiation field information of the microwave sensor array;

[0073] An upper computer serial communication circuit is connected to the microwave parameter reading circuit for transmitting the information read by the microwave parameter reading circuit;

[0074] An upper computer is connected to the upper computer serial communication circuit for executing a program for calculating the thickness, material, and shape of the object to be measured.

[0075] Among them, the microwave sensor array includes:

[0076] A top metal layer, on the upper surface of which a microwave sensor unit structure of a transmission line and a loop inductor is etched;

[0077] A bottom metal layer, and the bottom metal layer is a ground layer;

[0078] An intermediate dielectric layer, which is used to carry the top metal layer and the bottom metal layer.

[0079] In the microwave sensor array described above, a plurality of resonant units with different electrical lengths are arranged on both the upper and lower sides of each transmission line along the vertical direction of the transmission line, and resonant modes RM1-9 at 2.89 GHz, 3.25 GHz, 3.67 GHz, 3.96 GHz, 4.27 GHz, 4.56 GHz, 4.82 GHz, 5.13 GHz, and 5.41 GHz are generated at 2-6 GHz respectively. The difference between each frequency point is at least 200 MHz or more, ensuring a good penetration depth while preventing crosstalk and overlap between frequency points.

[0080] Each resonant unit can generate a radiation field with a specific frequency and serves as a spatial detection unit for object detection. When an object is in the radiation field, it will change the microwave scattering parameters of the resonant unit. By integrating the radiation field information of multiple resonant units, the detection of physical information such as the material, shape, defect, and distance of the object to be measured can be achieved.

[0081] The RF signal source includes: an RF circuit that uses a fourth-order type-II wideband fractional-N phase-locked loop, and the fourth-order type-II wideband fractional-N phase-locked loop includes:

[0082] A frequency discriminator and phase detector, whose input terminal is connected to the input signal source;

[0083] A charge pump, whose input terminal is connected to the output terminal of the frequency discriminator and phase detector,

[0084] A loop filter, whose input terminal is connected to the output terminal of the charge pump and is used for filtering;

[0085] A voltage-controlled oscillator, whose input terminal is connected to the output terminal of the loop filter, and the operating scanning frequency of the voltage-controlled oscillator matches the operating frequency of the microwave sensor array.

[0086] A Sigma Delta modulator is also provided in the fourth-order type-II wideband fractional-N phase-locked loop to suppress fractional spurs;

[0087] The loop filter LF1 uses a third-order passive low-pass filter, and the third-order passive low-pass filter includes capacitors C1, C2, C3, resistors R1, and R2.

[0088] The RF signal source can adjust the output frequency of the power, and its adjustment range is -10 dBm to 100 dBm.

[0089] A power amplifier, whose input terminal is connected to the voltage-controlled oscillator and whose output terminal is connected to the microwave sensor array.

[0090] The microwave parameter reading circuit includes:

[0091] A radio frequency detection circuit for converting the high-frequency microwave signals output by a microwave sensor array into direct current analog signals:

[0092] A high-speed analog-to-digital converter, which uses a 12-bit high-speed analog-to-digital converter to convert analog signals into digital signals;

[0093] A waveform generator for converting digital signals into waveforms and interacting with a host computer through a host computer serial communication circuit.

[0094] The object detection method of this embodiment uses the object detection system provided in the above embodiment. Please refer to Figure 2 , Figure 2 which is the flowchart of the first specific embodiment of an object detection method based on a microwave sensor array provided by the present invention; the specific operation steps are as follows:

[0095] Step S21: Place the object to be detected in the space radiation magnetic field established by exciting multiple groups of microwave sensor array units with a radio frequency signal source;

[0096] First, the power of the radio frequency signal source is selected. According to the definition of penetration depth, increasing the power of the radio frequency signal source can increase the penetration depth of the microwave signal and establish a larger volume space detection field. Therefore, for objects of different volumes, the maximum coupling between the detection field and the object can be achieved by adjusting the power of the radio frequency signal source. The maximum detection thicknesses corresponding to different powers are: 1 cm (20 dBm), 2 cm (40 dBm), 3 cm (60 dBm), 4 cm (80 dBm), 5 cm (100 dBm). The initial power of the radio frequency signal source during the detection process is set to 40 dBm.

[0097] When the object is placed above the sensor array, the system first traverses from small to large power, and extracts and analyzes the resonant frequency and amplitude of the microwave array sensor at each power. The resonant frequency f r is mainly affected by the real part ε′ of the dielectric constant, while the sample volume mainly affects the dielectric loss ε″. If the sample volume is too large or the dielectric loss is high, the amplitude of the resonant frequency will be severely attenuated. Therefore, it is necessary to select an appropriate power for detection. Set thresholds S n (n = 20, 40, 60, 80, 100 dBm) for the amplitudes at each power. When the amplitude of the microwave array unit is lower than the set threshold S n after the object is placed, a higher power level is selected until the amplitude attenuation meets the requirements.

[0098] According to the above description, the maximum size of the object in the direction perpendicular to the microwave sensor array can be initially judged by the power selection level.

[0099] Placing the object to be measured into the spatial radiation field of the array will affect the microwave scattering parameters of the array, and thus can be detected. This microwave sensor array realizes non-contact detection. The detection schematic diagram is as Figure 3 shown.

[0100] Step S22: Obtain the change amount of the resonance frequency and the change amount of the resonance amplitude of each group of microwave sensor array units before and after placing the object to be measured into the spatial radiation magnetic field;

[0101] S221: Collect the microwave signals of the multiple groups of microwave sensor array units when they are unloaded;

[0102] S222: After placing the object to be measured, collect the target microwave signals of the multiple groups of microwave sensor array units:

[0103] S223: Calculate the difference between the microwave signals of the multiple groups of microwave sensor array units when they are unloaded and the target microwave signals to obtain the microwave change signals of the multiple groups of microwave sensor array units;

[0104] S224: Convert the microwave change signals of the multiple groups of microwave sensor array units into electrical signals, and convert them into waveform diagrams according to the electrical signals;

[0105] S225: Obtain the change amount of the resonance frequency and the change amount of the resonance amplitude of each group of microwave sensor array units according to the waveform diagrams.

[0106] Select different distances from the object to be measured to the microwave sensor array, and analyze the influence degree of the detection distance on the microwave sensor parameters. As Figure 4 shown, when the distance between the object to be measured and the array is between 0.5 mm and 2 mm, it has different degrees of influence on the microwave transmission parameters.

[0107] Step S23: Characterize the thickness of the object to be measured in each group of microwave sensor array units according to the change amount of the resonance amplitude of each group of microwave sensor array units, and perform comprehensive modeling based on the thickness of the object to be measured in each group of microwave sensor array units to obtain the three-dimensional shape of the object to be measured;

[0108] The dielectric characteristics of the object to be measured are mainly manifested in two aspects: one is the resonance frequency shift caused by the change of the sensitive MUT dielectric constant ε′ r due to the electric field perturbation; the other is the perturbation of the sample volume Vs on the field distribution, and the change of the dielectric loss ε″ of the loaded MUT caused by the field distribution loss, which leads to the change of the Q factor.

[0109] After loading objects with different shapes to be measured, the change of the resonance amplitude can be expressed as:

[0110]

[0111] where ΔQ r is the change in the Q factor, ε″ is the imaginary part of the dielectric constant of the object to be measured, E0 and H0 represent the electric and magnetic fields with the object to be measured unloaded, E1 and H1 define the field distribution after loading the object to be measured on the resonator, and Δμ represents the change in the magnetic permeability of free space. When the object to be measured is a pure dielectric medium, the perturbation of the sensing material only affects the electrical component and its dielectric constant. Therefore, the magnetic cross-section (H0, H1) can be ignored, and the change in the resonance amplitude is given by the following formula:

[0112]

[0113] As the height increases, the electric field lines become sparser and the electric field becomes weaker. Therefore, as the thickness and distance increase, the interaction intensity between the object to be measured and the electric field gradually decreases, resulting in a decrease in the infinite rate of change.

[0114] The proposed microwave sensor array unit is small enough that after loading the object, the change in the sample volume Vs of a single microwave resonator is mainly manifested as a change in the thickness t. Therefore, the relationship between the thickness and the change in the Q factor can be established:

[0115] ΔQ r = -∫∫∫ t (Δε″E0 × E1)dt

[0116] where the dielectric loss Δε″ of the object is proportional to the object volume, that is, for the same object, its dielectric loss change with volume can be approximately expressed as:

[0117] Δε″ = K t × Δt

[0118] So

[0119] ΔQ r = -∫∫∫ t (K t × Δt × E0 × E1)dt

[0120] Based on the above formula, the relationship between the thickness and the change in the Q factor can be simplified to

[0121] ΔQ r = At 4 + Bt 3 + Ct 2 + Dt + E

[0122] where A, B, C, D, and E are constants, K t is the relationship constant between the dielectric loss and the thickness, and Δt is the thickness change of the object to be measured.

[0123] Therefore, the Q factor can be used to characterize the thickness change of an object. By integrating the information of all array units, the shape of the object to be measured can be restored. By analyzing whether the microwave scattering parameters of different array units change, the shape of the two-dimensional plane of the object can be determined. Furthermore, by specifically analyzing the changed scattering parameters of different array units, the thickness of the object at the corresponding position can be determined. Thus, the thickness information of the object at different positions is determined, and the three-dimensional shape of the object can be restored after comprehensive modeling.

[0124] Step S24: Calculate the change in the resonant frequency caused by the thickness effect for each group of microwave sensor array units according to the thickness of the object to be measured in each group of microwave sensor array units:

[0125] Step S25: Calculate the change in the resonant frequency caused by the dielectric effect for each group of microwave sensor array units based on the change in the resonant frequency of each group of microwave sensor array units and the change in the resonant frequency caused by the thickness effect, and calculate the dielectric constant detected by each group of microwave sensor array units;

[0126] Step S27: Average and weight the dielectric constants detected by all groups of microwave sensor array units to obtain the target dielectric constant of the object to be measured and determine the material of the object to be measured.

[0127] The frequency shift represents the sensor response caused by the effective dielectric constant and the interrupted electric field when the object to be measured approaches the sensitive area. Therefore, an object to be measured with a high dielectric constant will disturb the sensor field distribution and exhibit a greater resonance frequency shift. The resonance frequency shift can be expressed by the following formula

[0128]

[0129] where Δf r is the frequency shift, f0 is the resonance frequency without a sample, and μ0 and ε0 are the magnetic permeability and dielectric constant of free space. When the object to be measured is a pure dielectric medium, its perturbation only affects the electric component and its dielectric constant. Therefore, the magnetic cross-section (H0 H1) can be ignored, and the resonance frequency shift is given by the following formula:

[0130]

[0131] The change in the dielectric constant ε′ of the object to be measured causes a shift in the resonant frequency, and the change in the dielectric constant ε′ is caused by the electric field perturbation. In addition, the uniformity of the object to be measured can also be analyzed. If there are cracks, bubbles or other defects inside, the corresponding units will show changes in microwave scattering parameters such as different frequencies and amplitudes.

[0132] By mathematically modeling the characteristics of the object to be measured in the early stage, an induced relationship is established between the scattering parameter changes at each frequency point of the sensor array and parameters such as the complex dielectric constant and thickness of the solid material:

[0133] Δf rn = Δf rn (ε r ) + f rn (t)

[0134] Δf rn (ε r ) = A εn x ε + B εn

[0135] Δf rn (t) = A Tn x mm + B Tn

[0136] Where x mn is the thickness detected by the nth microwave sensor array unit, Δf rn is the change in the resonance frequency of the nth group of microwave sensor array units, Δf rn (t) is the change in the resonance frequency of the nth group of microwave sensor array units caused by the thickness effect, Δf rn (ε r ) is the change in the resonance frequency of the nth group of microwave sensor array units caused by the dielectric effect, x εn is the dielectric constant detected by the nth microwave sensor array, A εn , B εn , A Tn , B Tn are the radio frequency constants of the nth microwave sensor array unit. By collecting data on dielectric constant blocks with the same dielectric constant but different volumes (1, 2, 3, 4, 5 cm 3 ) and collecting data on standard dielectric constant blocks with different dielectric constants, a machine learning training set based on this data set is established to obtain the constants required for later calculations.

[0137] By analyzing the Q factor, the influence of thickness on the frequency of the microwave sensor array unit is obtained. After removing the influence of thickness, only the influence of the object material on the microwave signal frequency of the microwave sensor is obtained, and the dielectric constant of the object is calculated to determine the object medium.

[0138] The detection results are as attached Figure 5As shown, the microwave sensor array has different responses to substances with different dielectric constants. When the dielectric constant of the object to be measured changes from 2 to 10, it has different degrees of influence on the transmission parameters of multiple frequency points. Through subsequent data analysis, the resonant frequency shifts from small to large respectively represent the dielectric constant values of the material as: 2, 4, 6, 8, 10, and the dielectric constant of the object is determined.

[0139] The proposed microwave sensor array detection method can calculate the dielectric constant of an object based on the microwave scattering parameters, thereby determining the material of the object. Table 1 shows the dielectric constants of common object materials. For materials with known dielectric constants, they can be directly compared in the existing database. For unfamiliar materials or composite materials, the dielectric constant needs to be deduced through the analysis of multiple frequency points and added to the database for later material identification. By comparing the calculation results of different frequency points, it is possible to detect the differences in the dielectric constants at different positions of the same object, thereby determining the defect position of the target object.

[0140] Table 1 is the relative dielectric constant of common object materials

[0141]

[0142]

[0143] When the size of the object is small, such as Figure 6 as shown, when the object is only located at the 9th resonant unit, the present invention can still analyze through the microwave scattering parameters of a single frequency point, thereby determining the thickness of the object. By judging the distance between the object and the microwave sensor, the material, thickness, and shape of the object are determined.

[0144] Such as in the appendix Figure 7 as shown, the object affects the resonant mode RM9 at the 9th resonant unit. When the thickness of the target object changes from 0.5 mm to 2 mm, RM9 changes to different degrees. Through subsequent data analysis, the thickness of the object can be quantitatively analyzed based on the change of RM9. The loaded object thicknesses are respectively: 1 mm, 3 mm, 4 mm, 5 mm, and the detection of the thickness of the target object is realized. And the present invention can also detect the shape, thickness, and material of small objects by adjusting the distance between the object and the microwave sensor.

[0145] In this embodiment, the object to be measured is placed in the spatial radiation magnetic field established by the microwave sensor array unit, and multiple groups of resonance frequency change amounts and resonance amplitude change amounts of the microwave sensor array unit are extracted and analyzed. The resonance amplitude change amount of each group of microwave sensor array units is used to characterize the thickness detected by each group of microwave arrays. According to the thickness detected by each group of microwave arrays, simulation is carried out through software to obtain the three-dimensional shape of the object to be measured. Based on the thickness detected by each microwave sensor array unit, the resonance frequency change amount caused by the thickness effect of each group of microwave sensor array units is calculated. According to the resonance frequency change amount of each group of microwave sensor array units and the resonance frequency change amount caused by the thickness effect, the resonance frequency change amount caused by the dielectric effect of each group of microwave sensor array units is calculated, and the dielectric constant of the object to be measured detected by each group of microwave sensor array units is obtained to determine the object material. In the present invention, non-contact detection is realized by using the microwave sensor array unit. By analyzing the resonance frequency change amount and resonance amplitude change amount before and after the object is placed, the thickness, material and shape of the object are determined.

[0146] In this embodiment, the steps of detecting the defects of the object to be measured are described in detail. Please refer to Figure 8 , Figure 8 which is the flowchart of the second specific embodiment of an object detection method based on a microwave sensor array provided by the present invention; the specific steps are as follows:

[0147] Step S81: Screen the abnormal dielectric constants among all groups of dielectric constants and determine the microwave sensor array unit of the abnormal dielectric constant;

[0148] Step S82: Extract the attenuation value and phase shift value of the abnormal dielectric constant array unit;

[0149] Step S83: According to the relationship between the attenuation constant, phase shift constant and material dielectric constant, construct the relationship between the attenuation value, phase shift value and material dielectric constant directly;

[0150] Step S84: Query the defect type table according to the relationship between the attenuation value, phase shift value and material dielectric constant to obtain the defects of the object to be measured.

[0151] The attenuation A and phase shift φ of the microwave signal in the radiation field of the extracted resonant unit after passing through the object can be expressed as:

[0152]

[0153] φ = δ - 360n (deg);

[0154] where, |τ| is the modulus of the power transfer function, P in is the incident signal power of the object to be measured, P outis the outgoing signal power passing through the object under test, δ is the loss angle, and n is the degree of phase shift.

[0155] Practical dielectric materials are lossy, so the dielectric constant has a complex form, that is,

[0156] ε=ε′+jε″

[0157] Among them, ε′ is the relative dielectric constant, which represents the material dielectric energy storage characteristics, and ε″ is the loss factor, which represents the material energy consumption characteristics.

[0158]

[0159]

[0160] The above formula is the relationship between the attenuation constant α, the phase shift constant β and the dielectric energy storage characteristic ε′ and the energy dissipation characteristic ε″, tanδ is the loss tangent, and β0 is the original phase shift constant of the microwave signal.

[0161] Arrangement available

[0162]

[0163]

[0164]

[0165] After finishing, we can get:

[0166]

[0167] Right now

[0168]

[0169] Combine the above equations and solve the system of equations to get:

[0170]

[0171]

[0172] Where λ0 is the wavelength of the initial microwave signal in free space.

[0173] Thus, the relationship between the attenuation A and the phase shift φ and the dielectric constant ε of the object material can be established.

[0174] The dielectric constant of the object to be measured is calculated again by the method of attenuation A, phase shift φ and dielectric constant ε, and it is determined whether there is a calculation error in the previous and subsequent calculation methods. If there is an error, the dielectric constant of this time is used. If there is no error, the defect type table is queried to determine the defect type of the object to be measured.

[0175] The defect type table is obtained based on the detection of a large number of defective objects to be measured. Different dielectric constants are obtained according to different defects, and the defect size also affects the frequency change. Therefore, a large number of defect samples are required for training to obtain a large number of defect type tables.

[0176] In this embodiment, when an abnormal dielectric constant appears, the attenuation and phase shift are collected, the dielectric constant of the object to be measured is recalculated, whether there is a defect is judged, and then the defect type table is queried to determine the defect and location of the object to be measured. The present invention adopts non-contact detection. By analyzing the change amounts of the resonant frequency and amplitude before and after the object to be measured is placed, the recognition of the object material, thickness, and shape is carried out, and multiple array units are set. According to the differences in the detection data of each unit, it is possible to recognize whether there is a defect in the detected object and the type of the defect.

[0177] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0178] Those skilled in the art can further realize that the units and algorithm steps of each example described in combination with the embodiments disclosed in this article can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0179] The steps of the method or algorithm described in combination with the embodiments disclosed in this article can be directly implemented by hardware, a software module executed by a processor, or a combination of the two. The software module can be placed in a random access memory (RAM), memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, register, hard disk, removable disk, CD-ROM, or any other form of storage medium well-known in the technical field.

[0180] The above has introduced in detail a method and a system for object detection based on a microwave sensor array. In this article, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. An object detection method based on a microwave sensor array, characterized in that, include: The object to be tested is placed in a spatial radiation magnetic field established by stimulating multiple groups of microwave sensor array units by a radio frequency signal source; Obtaining the resonant frequency change and the resonant amplitude change of each group of microwave sensor array units before and after the object to be measured is placed in the spatial radiation magnetic field, including: collecting microwave signals of multiple groups of microwave sensor array units when they are unloaded; after the object to be measured is placed, collecting target microwave signals of multiple groups of microwave sensor array units; calculating the difference between the microwave signals of multiple groups of microwave sensor array units when they are unloaded and the target microwave signals to obtain microwave change signals of multiple groups of microwave sensor array units; converting the microwave change signals of multiple groups of microwave sensor array units into electrical signals, and converting them into waveform graphs according to the electrical signals; and obtaining the resonant frequency change and the resonant amplitude change of each group of microwave sensor array units according to the waveform graph; The thickness of the object to be measured in each group of microwave sensor array units is represented according to the change in the resonance amplitude of each group of microwave sensor array units, and a comprehensive model is performed based on the thickness of the object to be measured in each group of microwave sensor array units to obtain the three-dimensional shape of the object to be measured; Calculate the change in resonant frequency caused by the thickness effect for each group of microwave sensor array units based on the thickness of the object under test in each group of microwave sensor array units ; The induced relationship between the change in the resonant frequency of each microwave sensor array unit and the dielectric constant and thickness parameters of the object to be measured is as follows: ; Based on the resonant frequency change of each group of microwave sensor array units and the resonant frequency change caused by the thickness effect, the resonant frequency change of each group of microwave sensor array units caused by the dielectric effect is calculated; According to the relationship between the change in the resonant frequency caused by the dielectric effect of each group of microwave sensor array units and the dielectric constant of the object to be measured , the dielectric constant of the object to be measured detected by each group of microwave sensor array units is calculated; Among them, , , and are the radio frequency constants of the nth microwave sensor array unit, is the thickness detected by the nth microwave sensor array unit, is the change in the resonant frequency of the nth group of microwave sensor array units, is the change in the resonant frequency of the nth group of microwave sensor array units caused by the thickness effect, is the change in the resonant frequency of the nth group of microwave sensor array units caused by the dielectric effect, is the dielectric constant detected by the nth microwave sensor array; The dielectric constants detected by all groups of microwave sensor array units are averaged and weighted to obtain the target dielectric constant of the object to be measured, and the material of the object to be measured is determined.

2. The object detection method according to claim 1, wherein Placing the object to be measured into a spatial radiation magnetic field established by stimulating multiple groups of microwave sensor array units by a radio frequency signal source comprises: collecting resonance amplitudes of multiple groups of microwave sensor array units after the object to be measured is placed therein; Determining whether the resonance amplitude of each group of microwave sensor array units is lower than a preset amplitude; When the resonance amplitude of a group of microwave sensor array units is lower than the preset amplitude, the power of the radio frequency signal source is increased until the resonance amplitude of each group of microwave sensor array units is greater than or equal to the preset amplitude.

3. An object detection system based on a microwave sensor array, characterized in that, include: A microwave sensor array, comprising a plurality of groups of microwave sensor array units, each group of microwave sensor array units generating a radiation field of a specific frequency for realizing microwave detection; A radio frequency signal source, used to excite the microwave sensor array; A microwave parameter reading circuit is arranged at an output port of the microwave sensor array and is used to read the spatial radiation field information of the microwave sensor array; A host computer serial port communication circuit, connected to the microwave parameter reading circuit, for transmitting information read by the microwave parameter reading circuit; A host computer is connected to the host computer serial port communication circuit and is used to implement the steps of the object detection method based on a microwave sensor array as described in any one of claims 1 to 2 when executing a computer program.

4. The object detection system according to claim 3, wherein The microwave sensor array comprises: A top metal layer, a microwave sensor unit structure of a transmission line and a toroidal inductor is etched on an upper surface of the top metal layer; A bottom metal layer, wherein the bottom metal layer is a ground layer; An intermediate dielectric layer, wherein the intermediate dielectric layer is used to support the top metal layer and the bottom metal layer.

5. The object detection system according to claim 3, characterized in that, The radio frequency signal source comprises: RF circuit, adopting a fourth-order type-II wideband fractional-N phase-locked loop, the fourth-order type-II wideband fractional-N phase-locked loop comprising: Phase-frequency detector, with its input terminal connected to the input signal source; Charge pump, with its input terminal connected to the output terminal of the phase-frequency detector, Loop filter, with its input terminal connected to the output terminal of the charge pump for filtering; Voltage-controlled oscillator, with its input terminal connected to the output terminal of the loop filter, and the operating scanning frequency of the voltage-controlled oscillator being matched with the operating frequency of the microwave sensor array; Power amplifier, with its input terminal connected to the voltage-controlled oscillator and its output terminal connected to the microwave sensor array.

6. The object detection system according to claim 5, characterized in that, The RF signal source can adjust the output power through the voltage-controlled oscillator.

7. The object detection system according to claim 3, wherein The microwave parameter reading circuit comprises: RF detection circuit, for converting the high-frequency microwave signal output by the microwave sensor array into a DC analog signal; High-speed analog-to-digital converter, for converting the DC analog signal into a digital signal; Waveform generator, for converting the digital signal into a waveform diagram and interacting with the host computer through the host computer serial communication circuit.

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