Electrical field tomography detection system and method with adjustable electrode plate distance

Abstract

The application provides an electric field tomography detection system and method with adjustable electrode plate distance, which comprises a cylindrical shielding layer (1), a plate electrode array (2), a control module (3), a sinusoidal excitation voltage module (4), a multi-channel electronic switch module (5), a stepping motor transmission module (6), a voltage detection module (7), a Fourier phase extraction module (8) and an electrical impedance tomography module (9). The stepping motor transmission module (6) can accurately move the electrode plate to a suitable position, and the Fourier phase extraction module (8) is used for fast Fourier transform to simplify the phase offset calculation in the electric field tomography system. The application solves the problem of fixed electrode plate in the electric field tomography detection system, and the high accuracy of the stepping motor can accurately adjust the positions of the plate electrode array and the target object, which is beneficial to signal detection.

Description

Technical Field

[0001] This invention belongs to the field of electrical impedance tomography detection systems, and specifically relates to an electric field tomography detection system and method with adjustable electrode distance. Background Technology

[0002] Electrical Impedance Tomography (EIT) utilizes the significant differences in the electrical impedance distribution of biological tissues under different physiological and pathological conditions. By generating electrical excitation within the biologically permissible range through electrodes placed on the surface of the biological tissue, an electric field is generated within the biological tissue. Then, the electrical signals are measured using the electrodes attached to the surface of the biological tissue, and combined with relevant imaging algorithms, an image of the electrical impedance distribution within the biological tissue can be reconstructed.

[0003] Most current electrical impedance tomography (EIT) systems use contact electrodes. When these electrodes come into contact with the object, they generate contact impedance that interferes with the test signal. Solving the inverse problem is difficult, leading to poor imaging results. Furthermore, the need for contact with biological tissue places high demands on the electrodes. To address the problems of contact EIT, experts and scholars both domestically and internationally have proposed non-contact EIT methods, mainly including magnetic induction tomography (MIT) and electric field tomography. MIT, which emerged in 1997, uses induction coils to map the electromagnetic properties of an object. As a non-invasive technique, it has many potential applications. However, because the secondary induction signal in MIT is weaker than the primary excitation signal, and according to the eddy current detection principle, both primary and secondary induction signals are detected simultaneously, making it difficult to distinguish between the two signals.

[0004] Russian researchers have proposed a non-contact impedance imaging method—electric field tomography (EDT). This method uses fixed, circularly arranged electrode plates for non-contact electric field excitation and employs a lock-in amplifier to obtain the phase shift between the excitation and detection potentials, thus retrieving the impedance distribution information. In EDT, the distance between the detector and the electrode plates is a crucial parameter affecting the detection phase signal; the closer the distance, the greater the phase shift, which is more beneficial for detecting impedance anomalies. The fixed-electrode method used by the Russian researchers yields good results for larger anomalies located close to the plates, but performs poorly for smaller anomalies. Furthermore, the detection data accuracy is low when the anomaly is far from the plates, causing significant interference during image reconstruction. Additionally, the phase calculation method employed by the Russian researchers uses lock-in amplification, which is challenging due to the large difference in amplitude between the excitation and detection signals, making signal jumps highly likely, and the calculation steps are quite complex. Summary of the Invention

[0005] This invention addresses the problems of existing electric field tomography systems by proposing a detection system and method with adjustable electrode spacing. Existing electric field tomography systems suffer from issues such as non-adjustable electrode spacing and difficulty in phase-locked detection. This invention proposes a detection system and method with adjustable plate-type electrode arrays and phase shift calculation using fast Fourier transform, thus solving the problems of existing systems.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An electric field tomography detection system with adjustable electrode spacing includes a cylindrical shielding layer, a plate electrode array, a control module, a sinusoidal excitation voltage module, a multi-channel electronic switch module, a stepper motor drive module, a voltage detection module, a Fourier transform phase extraction module, and an electrical impedance tomography module.

[0008] The plate-shaped electrode array is uniformly distributed around the target object. A cylindrical shielding layer surrounds the target object and the plate-shaped electrode array. The output of the control module is connected to the input of the sinusoidal excitation voltage module, the input of the multi-channel electronic switch module, and the input of the stepper motor drive module. The output of the plate-shaped electrode array and the multi-channel electronic switch module is connected to the input of the voltage detection module. The output of the voltage detection module is connected to the input of the Fourier transform phase extraction module. The output of the Fourier transform phase extraction module is connected to the input of the electrical impedance tomography module. The output of the stepper motor drive module is connected to the rigid rod on the plate-shaped electrode array.

[0009] Furthermore, the plate electrode array consists of at least eight unconnected plate electrodes. The plate electrode array does not contact the target object under study. Each plate electrode has a front center terminal on its front side, which is used to connect the output terminal of the multi-channel electronic switch module and the input terminal of the voltage detection module. Under the control of the control module, the output terminal of the sinusoidal excitation voltage module is turned on. Each plate electrode has a fixed rigid rod on its back, which is connected to the output terminal of the stepper motor drive module. Under the control of the control module, the stepper motor drive module adjusts the position of the plate electrodes according to the size of the target object under study, thereby making it easier for the voltage detection module to measure the voltage signal on the plate electrodes.

[0010] Furthermore, the Fourier transform phase extraction module includes a window function unit, a fast Fourier transform unit, and a phase offset calculation unit; the same-frequency sinusoidal voltage digital signal output by the voltage detection module is subjected to synchronization signal interception by the window function unit, and then the phase information of the excitation signal and the detection signal is calculated by the fast Fourier transform unit, and then the required phase offset information is obtained by the phase offset calculation unit.

[0011] Furthermore, the cylindrical shielding layer is made of a non-ferromagnetic metal with good electrical conductivity.

[0012] Furthermore, the multi-channel electronic switch module controls the switching between the plate-type electrode and the sinusoidal excitation voltage module through the control signal of the control module.

[0013] Furthermore, the voltage detection module digitizes the analog signal and performs filtering processing on the signal.

[0014] Furthermore, the electrical impedance tomography module employs a joint algebraic iterative algorithm to invert the resistivity distribution image within the fault plane using phase shift.

[0015] The present invention also provides a detection method for an electric field tomography detection system with adjustable electrode distance, comprising the following steps:

[0016] First, based on the size of the target object, the control module controls the stepper motor drive module to position the plate electrode close to the target object. Simultaneously, the control module controls the frequency and amplitude of the excitation signal output by the sinusoidal excitation voltage module. The multi-channel electronic switch module receives the control signal generated by the control module according to the excitation detection rotation logic, controlling the on / off state of the center terminal on the front of the plate electrode and the sinusoidal excitation voltage module. The excitation detection rotation logic is determined based on the number of plate electrodes in the plate electrode array, with the number of rotations matching the number of plate electrodes. Each rotation allows only one plate electrode in the plate electrode array to be connected to the sinusoidal excitation voltage module; this plate electrode is called the excitation plate, and the remaining plate electrodes are called the detection plates. Under the shielding of a cylindrical shielding layer, the excitation signal applied by the excitation plate induces a corresponding sinusoidal electric field of the same frequency within the cylinder it surrounds. This electric field passes through the target object and is detected by the other detection plates. The voltage detection module collects the electric field signal on the detection plates and converts it into a digital signal, which is then sent to the Fourier Transform phase extraction module. The Fourier Transform phase extraction module performs synchronous truncation of the digitized signal using a window function and performs a Fast Fourier Transform to extract the phase information at the operating frequency. This allows for accurate calculation of the phase shift between the various signals, which is then sent to the electrical impedance tomography (EIT) module. The EIT module uses the phase shift to invert the electrical impedance distribution information of the tomographic plane where the center terminal of the plate-shaped plate is located, and displays the image.

[0017] Compared with the prior art, the advantages of this invention are mainly reflected in the following aspects:

[0018] 1) The detection system of this invention is mechanically connected to the electrode plate via a stepper motor transmission system. Due to the high control precision of the stepper motor, the movement of the electrode plate can be precisely controlled. When the size of the target object changes, the position of the electrode plate can be changed by controlling the stepper motor transmission system through the control module. Since the phase shift is theoretically related to the distance between the electrode plate and the target object, controlling the electrode plate to reduce the distance between it and the object being detected is more conducive to enhancing the detection signal and improving the resolution of electrical impedance imaging.

[0019] 2) The acquired sinusoidal voltage signals of the same frequency are used for phase shift calculation using Fast Fourier Transform (FFT). The theory behind FFT for measuring phase difference is that the phase difference between two signals of the same frequency is equal to the phase difference of their discrete spectra at the maximum spectral line. This method has two main advantages: First, the two signals have identical transmission paths and identical deviations, so the system error introduced by the measurement system can be eliminated during subtraction. Second, since the signal at the electrode detected by electric field tomography is generated by field excitation, a lot of interference signals are introduced during transmission. Using FFT to measure phase deviation only uses the Fourier transform at the operating frequency, which is equivalent to performing a bandpass filter and is unaffected by interference signals.

[0020] Electric field tomography (EDT) and capacitance tomography (CTT) systems look similar, but the biggest difference is that CTT detects the capacitance value converted from the detection voltage amplitude, while the effective signal of EDT is the phase shift between the signals of the emitting and detecting plates rather than the amplitude change. They are completely different detection and imaging methods and systems. Attached Figure Description

[0021] Figure 1 Principle block diagram of the electric field tomography detection system of the present invention;

[0022] Figure 2 Schematic diagram of the plate-type electrode array of the present invention;

[0023] Figure 3 A structural diagram of a single plate electrode of the present invention;

[0024] Figure 4 The principle block diagram of the Fourier transform phase extraction module of the electric field tomography detection system of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0026] like Figure 1-3 As shown, the electric field tomography detection system with adjustable electrode distance of the present invention mainly includes a cylindrical shielding layer 1, a plate electrode array 2, a control module 3, a sinusoidal excitation voltage module 4, a multi-channel electronic switch module 5, a stepper motor drive module 6, a voltage detection module 7, a Fourier transform phase extraction module 8, and an electrical impedance tomography module 9.

[0027] The plate electrode array 2 is uniformly distributed around the target object. A cylindrical shielding layer 1 surrounds the target object and the plate electrode array 2. The output of the control module 3 is connected to the input of the sinusoidal excitation voltage module 4, the input of the multi-channel electronic switch module 5, and the input of the stepper motor drive module 6. The outputs of the plate electrode array 2 and the multi-channel electronic switch module 5 are connected to the input of the voltage detection module 7. The output of the voltage detection module 7 is connected to the input of the Fourier transform phase extraction module 8. The output of the Fourier transform phase extraction module 8 is connected to the input of the electrical impedance tomography module 9. The output of the stepper motor drive module 6 is connected to the rigid rod on the plate electrode array 2. This invention uses a stepper motor to precisely move the electrode plates to the appropriate position and utilizes Fast Fourier Transform to simplify the phase shift calculation in the electric field tomography system.

[0028] The cylindrical shielding layer 1 is made of a non-ferromagnetic metal with good conductivity, such as copper, silver, or aluminum. Its main function is to shield against external interference signals and prevent the excitation electric field from escaping, thus ensuring the signal-to-noise ratio. Figure 2 As shown, a three-dimensional schematic diagram of the cylindrical shielding layer 1 and the plate electrode array 2, as well as the cross-sectional plane S where the center terminal of the plate electrode array is located, is shown. The cylindrical shielding layer 1 surrounds the plate electrode array 2. There is no connection between the plate electrodes of the plate electrode array 2, and the cylindrical shielding layer 1 and the plate electrode array 2 are not in contact.

[0029] The plate electrode array 2 consists of at least eight unconnected plate electrodes. The plate electrode array 2 does not contact the target object. Each plate electrode has a center terminal 10 on its front side, used to connect the output of the multi-channel electronic switch module 5 and the input of the voltage detection module 7. Under the control of the control module 3, it connects to the output of the sinusoidal excitation voltage module 4. Each plate electrode has a fixed rigid rod on its back, connected to the output of the stepper motor drive module 6. Under the control of the control module 3, the stepper motor drive module 6 can adjust the position of the plate electrodes according to the size of the target object, making it easier for the voltage detection module 7 to measure the voltage signal on the plate electrodes. Figure 3As shown, the three-view diagram of the structure of each plate electrode in the plate electrode array 2 shows that the center terminal 10 on the front is used to connect the output terminal of the multi-channel electronic switch module 5 and the input terminal of the voltage detection module 7, and the rigid rod 11 on the back is connected to the output terminal of the stepper motor drive module 6.

[0030] The stepper motor drive module 6 uses a stepper motor to receive control signals from the control module 3, thereby generating rotation. This allows the plate-type motor array 2 to adjust the position of the plate-type electrodes according to the size of the target object being detected, and also makes it easier for the voltage detection module 7 to measure the voltage signal on the plate-type electrodes.

[0031] The sinusoidal excitation voltage module 4 is used to generate a sinusoidal excitation signal.

[0032] The control module 3 uses a microprocessor in conjunction with corresponding peripheral circuits to control the rotation of the stepper motor, generate control signals for the multi-channel electronic switch module 5, and control the frequency and amplitude of the sinusoidal excitation voltage source.

[0033] The multi-channel electronic switch module 5 controls the switching between the plate electrode and the sinusoidal excitation voltage module 4 through the control signal of the control module 3.

[0034] The voltage detection module 7 mainly digitizes analog signals and performs filtering on the signals.

[0035] like Figure 4 As shown, the Fourier Transform phase extraction module 8 consists of a window function unit A, a fast Fourier transform unit B, and a phase offset calculation unit C. The digital signal first undergoes synchronization signal extraction through the window function unit A, then the phase information between the excitation signal and the detection signal is calculated through the fast Fourier transform unit B, and finally, the required phase offset information is obtained through the phase offset calculation unit C.

[0036] The electrical impedance tomography module 9 employs a joint algebraic iterative algorithm to invert the resistivity distribution image within the fault plane using phase shift.

[0037] The detection method of the electric field tomography detection system of the present invention includes the following steps:

[0038] First, based on the size of the target object, the control module 3 controls the stepper motor drive module 6 to position the plate-shaped electrode plate close to the target object. Simultaneously, the control module 3 controls the frequency and amplitude of the excitation signal output by the sinusoidal excitation voltage module 4. The multiplexer module 5 receives the control signal generated by the control module 3 according to the excitation detection rotation logic and controls the on / off state of the center terminal 10 on the front of the plate-shaped electrode and the sinusoidal excitation voltage module 4. The excitation detection rotation logic is based on the number of plate-shaped electrodes in the plate-shaped electrode array 2, and the number of rotations is consistent with the number of plate-shaped electrodes. Each rotation allows only one plate-shaped electrode from the plate-shaped electrode array 2 to be connected to the sinusoidal excitation voltage module 4; this plate-shaped electrode is called the excitation electrode plate, and the remaining plate-shaped electrodes are called the detection electrodes. Under the shielding of the cylindrical shielding layer 1, the excitation signal applied by the excitation electrode plate will generate a corresponding sinusoidal electric field of the same frequency within the cylinder it encloses. This electric field passes through the target object and is detected by the remaining detection electrodes. The voltage detection module 7 collects the electric field signal on the plate-shaped electrode and converts it into a digital signal, which is then sent to the Fourier Transform phase extraction module 8. The Fourier Transform phase extraction module 8 performs synchronous window function truncation on the digitized signal, performs a Fast Fourier Transform, and extracts the phase information at the operating frequency. This allows for accurate calculation of the phase shift between each signal, which is then sent to the electrical impedance tomography module 9. The electrical impedance tomography module 9 uses the phase shift to infer the electrical impedance distribution information of the fracture plane where the front center terminal 10 of the plate-shaped electrode is located, and displays the image.

[0039] This invention overcomes the drawback of fixed electrode plates in electric field tomography detection systems. By utilizing the high precision of stepper motors, the positions of the plate electrode array and the target object can be precisely adjusted, facilitating signal detection. Simultaneously, a Fast Fourier Transform (FFT) is employed to calculate the phase shift. This eliminates system errors and, due to the FFT's bandpass filter-like characteristics, performs noise reduction, simplifying the calculation process.

[0040] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electric field tomography detection system with adjustable electrode plate distance, characterized in that: The cylindrical shielding layer (1), the plate electrode array (2), the control module (3), the sinusoidal excitation voltage module (4), the multi-channel electronic switch module (5), the stepping motor transmission module (6), the voltage detection module (7), the Fourier phase extraction module (8) and the electrical impedance tomography module (9) are connected. The plate electrode array (2) is evenly distributed around the research target object, and the cylindrical shielding layer (1) surrounds the research target object and the plate electrode array (2). The output end of the control module (3) is connected with the input end of the sinusoidal excitation voltage module (4), the input end of the multi-channel electronic switch module (5) and the input end of the stepping motor transmission module (6), the output end of the plate electrode array (2) is connected with the output end of the multi-channel electronic switch module (5) and the input end of the voltage detection module (7), the output end of the voltage detection module (7) is connected with the input end of the Fourier phase extraction module (8), the output end of the Fourier phase extraction module (8) is connected with the input end of the electrical impedance tomography module (9), and the output end of the stepping motor transmission module (6) is connected with the rigid hard rod on the plate electrode array (2). Each plate electrode is provided with a fixed rigid hard rod at the back, which is connected with the output end of the stepping motor transmission module (6). The Fourier phase extraction module (8) comprises a window function unit, a fast Fourier transform unit and a phase offset calculation unit.

2. The electrode distance adjustable electroencephalogram tomography detection system of claim 1, wherein: Each plate electrode is provided with a fixed rigid hard rod at the back, which is connected with the output end of the stepping motor transmission module (6).

3. The electrode distance adjustable electroencephalogram tomography detection system of claim 1, wherein: The cylindrical shielding layer (1) is made of a non-ferromagnetic metal with good conductivity.

4. The electrode distance adjustable electroencephalogram tomography detection system of claim 1, wherein: The multi-channel electronic switch module (5) controls the on-off of the plate electrode and the sinusoidal excitation voltage module (4) through the control signal of the control module (3).

5. The electrode distance adjustable electroencephalogram tomography detection system of claim 1, wherein: The voltage detection module (7) digitizes the analog signal and filters the signal.

6. The electrode distance adjustable electroencephalogram tomography detection system of claim 1, wherein: The electrical impedance tomography module (9) adopts a joint algebra iterative algorithm to inversely calculate the electrical resistivity distribution image of the tomographic surface by using the phase offset.

7. A method of detecting an electric field tomography system with adjustable electrode plate distance according to one of claims 1 to 6, characterized in that The method comprises the following steps: First, according to the size of the object of study, by controlling the module (3) control stepper motor drive module (6) to make the plate electrode in the distance detection of the object of study is close to the position of the target object; While the control module (3) control sinusoidal excitation voltage module (4) output excitation signal frequency and amplitude; Multi-channel electronic switch module (5) receives control module (3) according to the control signal generated by the excitation detection wheel rotation logic, control plate electrode positive center terminal (10) and the on-off of sinusoidal excitation voltage module (4); Excitation detection wheel rotation logic according to the number of plate electrode array (2) in the plate electrode, rotation times and the number of plate electrode is consistent, each rotation only allows plate electrode array (2) of a plate electrode and the sinusoidal excitation voltage module (4) is connected, this plate electrode is called the excitation electrode plate, the rest of the plate electrode is called the detection electrode plate; Under the shielding of the cylindrical shielding layer (1), the excitation signal applied by the excitation electrode plate in the cylinder surrounded by the corresponding sinusoidal electric field of the same frequency, the electric field through the object of study, is detected by the rest of the detection electrode plate; Using voltage detection module (7) to collect the electric field signal on the detection electrode plate, and convert it into digital signal to deliver to the phase extraction module (8); Phase extraction module (8) of the digitized signal window function synchronous truncation, fast Fourier transform, extract the phase information under the working frequency, so as to accurately calculate the phase shift between the signal to deliver to the electrical impedance tomography module (9); Electrical impedance tomography module (9) using phase shift inversion of the plate electrode of the positive center terminal (10) in the tomographic plane of the electrical impedance distribution information, image display.

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