阅读说明：本技术 一种平面式的电容层析成像系统及检测方法 (A kind of capacitance tomography system and detection method of plane formula ) 是由 萧鹏 史倩竹 丁雨谢 殷丽娟 于 2019-09-06 设计创作，主要内容包括：本发明公开了一种平面式的电容层析成像系统及检测方法,所述电容层析成像系统包括上位机、单片机、电容测量电路、开关电路、阵列式电容传感器,其中：单片机分别与上位机、电容测量电路和开关电路连接；开关电路分别与阵列式电容传感器和电容测量电路连接；单片机控制开关电路对阵列式电容传感器进行电极切换,实现不同电极间的电容连接,以便能用电容测量电路进行测量,电容测量电路的数据单向传递到单片机,利用单片机对数据进行采集后与上位机的数据采集通信系统通信将数据传入电脑,然后图像重建系统对数据进行处理与重建。该电容层析成像系统结构简单,成本低,能够实现大面积的快速检测,从而能实现对缺陷的快速检测与定位。(The invention discloses a kind of capacitance tomography system of plane formula and detection methods, the capacitance tomography system includes host computer, single-chip microcontroller, capacitance measurement circuit, switching circuit, capacitive array sensor, in which: single-chip microcontroller is connect with host computer, capacitance measurement circuit and switching circuit respectively；Switching circuit is connect with capacitive array sensor and capacitance measurement circuit respectively；Single-chip microcontroller control switch circuit carries out electrode switching to capacitive array sensor, realize the capacitance connection between Different electrodes, to be measured with capacitance measurement circuit, the data of capacitance measurement circuit are passed uni-directionally to single-chip microcontroller, data are acquired to communicate with the Data Acquisition and Communication System of host computer afterwards using single-chip microcontroller, data are passed to computer, then image re-construction system is handled and rebuild to data.The Structure of Electrical Capacitance Tomography Systems is simple, at low cost, can be realized the quick detection of large area, to be able to achieve the quick detection and positioning to defect.)

1. a kind of capacitance tomography system of plane formula, it is characterised in that the capacitance tomography system include host computer, Single-chip microcontroller, capacitance measurement circuit, switching circuit, capacitive array sensor, in which:

The single-chip microcontroller is connect with host computer, capacitance measurement circuit and switching circuit respectively；

The switching circuit is connect with capacitive array sensor and capacitance measurement circuit respectively；

The host computer includes Data Acquisition and Communication System and image re-construction system；

The single-chip microcontroller control switch circuit carries out electrode switching to capacitive array sensor, realizes the capacitor between Different electrodes Connection, to be measured with capacitance measurement circuit, the data of capacitance measurement circuit are passed uni-directionally to single-chip microcontroller, utilize monolithic Machine, which is acquired data to communicate with the Data Acquisition and Communication System of host computer afterwards, is passed to computer for data, then image reconstruction system System is handled and is rebuild to data.

2. the side that a kind of capacitance tomography system using plane formula described in claim 1 carries out material internal defect detection Method, it is characterised in that the described method comprises the following steps:

Step 1: capacitance measurement circuit is motivated using the AC signal of 20KHz；

Step 2: electrode switching is carried out to capacitive array sensor using single-chip microcontroller control switch circuit, realizes Different electrodes Between capacitance connection, to be measured with capacitance measurement circuit, single-chip microcontroller acquire capacitance measurement circuit data, pass through string Port communications program passes data to host computer again；

Step 3: utilize image re-construction system to collected after collecting data using the Data Acquisition and Communication System of host computer Data carry out image reconstruction, obtain material internal defect situation.

3. the side that the capacitance tomography system according to claim 2 using plane formula carries out material internal defect detection Method, it is characterised in that the AC signal is generated by signal generator, and the peak value of signal is 5V.

4. the side that the capacitance tomography system according to claim 2 using plane formula carries out material internal defect detection Method, it is characterised in that the capacitance measurement circuit uses the measurement method of ac-excited formula, passes through sinusoidal excitation in testing capacitance After signal excitation, the signal of generation is as follows:

In formula, V₀₁For output signal, V_iFor input signal, C₀For testing capacitance, C_fFor feedback reference capacitor.

5. the side that the capacitance tomography system according to claim 4 using plane formula carries out material internal defect detection Method, it is characterised in that it is described it is ac-excited after signal by after band-pass filter using AD630 to sinusoidal signal progress Full-wave rectification, recycle low-pass filter the signal after this rectification is filtered, according to Fourier theory, finally obtain and The directly proportional d. c. voltage signal of capacitance.

6. the side that the capacitance tomography system according to claim 2 using plane formula carries out material internal defect detection Method, it is characterised in that the capacitive array sensor is be made using printed circuit 4 × 4 16 electrod-arrays, often A electrode is all the square electrode piece of 16mm, between adjacent electrode between be divided into 8mm.

7. the side that the capacitance tomography system according to claim 2 using plane formula carries out material internal defect detection Method, it is characterised in that the multiplexing chip that the switching circuit uses is 16 road bilateral analog switch CD4067, passes through monolithic Machine controls the measurement for 120 capacitors of total that two switch chips are realized between Different electrodes.

8. the side that the capacitance tomography system according to claim 2 using plane formula carries out material internal defect detection Method, it is characterised in that the single-chip microcontroller passes through the analog switch of digital I/O port control switch circuit, is received using analog input end The d. c. voltage signal of capacitance measurement circuit, and host computer is transmitted data to by serial ports.

9. the side that the capacitance tomography system according to claim 2 using plane formula carries out material internal defect detection Method, it is characterised in that the Data Acquisition and Communication System and image re-construction system are write using MFC and C++.

10. the capacitance tomography system according to claim 2 using plane formula carries out material internal defect detection Method, it is characterised in that the algorithm that described image reconstructing system uses is singular value decomposition algorithm.

Technical field

The invention belongs to technical field of nondestructive testing, are related to a kind of nondestructive detection system based on electrical capacitance tomography With method.

Background technique

Electrical capacitance tomography is being initially a kind of for detecting the non-destructive testing technology of multiphase flow in pipeline, is passed through Multiple electrodes are set on the outside of pipeline and carry out capacitance measurement to carry out reconstruction analysis to the case where pipeline inside multiphase flow.But with Variation has taken place in the development of technology, sensor structure, from 8 earliest electrodes to miscellaneous sensor, till now Three-dimensional chromatography imaging sensor and plane formula sensor.And its test object also changes from multiphase flow for others Nonmetallic substance makes it have certain detectability to the defect of material depths and damage due to the characteristic of its electrode, can be more Mend the deficiency of some other nondestructiving detecting means, such as infrared detection, ultrasound detection etc..

Summary of the invention

The present invention is not convenient to use other detection means to solve the problem of that material internal defect is deeper, provides one The capacitance tomography system and detection method of kind plane formula.The Structure of Electrical Capacitance Tomography Systems is simple, at low cost, Neng Goushi The quick detection of existing large area, to be able to achieve the quick detection and positioning to defect.

The purpose of the present invention is what is be achieved through the following technical solutions:

A kind of capacitance tomography system of plane formula, including host computer, single-chip microcontroller, capacitance measurement circuit, switching circuit, Capacitive array sensor, in which:

The single-chip microcontroller is connect with host computer, capacitance measurement circuit and switching circuit respectively；

The switching circuit is connect with capacitive array sensor and capacitance measurement circuit respectively；

The host computer includes Data Acquisition and Communication System and image re-construction system；

The single-chip microcontroller control switch circuit to capacitive array sensor carry out electrode switching, realize Different electrodes between Capacitance connection, to be measured with capacitance measurement circuit, the data of capacitance measurement circuit are passed uni-directionally to single-chip microcontroller, utilize Single-chip microcontroller, which is acquired data to communicate with the Data Acquisition and Communication System of host computer afterwards, is passed to computer for data, then image weight It builds system data are handled and rebuild.

A method of using the capacitance tomography system progress material internal defect detection of above-mentioned plane formula, including with Lower step:

Step 1: capacitance measurement circuit is motivated using the AC signal of 20KHz；

Step 2: electrode switching is carried out to capacitive array sensor using single-chip microcontroller control switch circuit, is realized different Interelectrode capacitance connection, to be measured with capacitance measurement circuit, single-chip microcontroller acquires the data of capacitance measurement circuit, leads to It crosses serial communication program and passes data to host computer again；

Step 3: utilize image re-construction system to acquisition after collecting data using the Data Acquisition and Communication System of host computer The data arrived carry out image reconstruction, obtain material internal defect situation.

Compared with the prior art, the present invention has the advantage that

1, the present invention utilizes the array electrode structure of print circuit plates making simple and strong interference immunity, detects imaging area Greatly, and material deep flaw can be detected.

2, the Exciting-simulator system capacitance measurement circuit that the present invention uses can detect small capacitance, and include in circuit Bandwidth-limited circuit and full-wave rectifying circuit can effectively reduce the interference of outer bound pair measurement result.

3, the switching circuit that the present invention uses can be gated and be measured to multiple electrodes.

4, the present invention uses Arduino single-chip microcontroller to carry out control to switching circuit and to the measurement result of capacitance measurement circuit Collection of simulant signal is carried out, realizes the selection of electrode and the measurement of capacitor.

5, for 4 × 4 array electrodes designed in the present invention, using finite element emulation software COMSOL to its sensitivity field into Row calculates, and is rebuild using singular value decomposition algorithm to image, can obtain better testing result.

6, the present invention can detect the damage of composite material deep part, and due to the row of its electrode array column The detection of large area may be implemented in cloth, while its structure is simple, and cost is relatively low, the detection suitable for various nonmetallic materials.

Detailed description of the invention

Fig. 1 is the schematic diagram of capacitance tomography system；

Fig. 2 is the schematic diagram of capacitive array sensor；

Fig. 3 is the schematic diagram of measuring circuit；

Fig. 4 is the simulation experiment result figure.

Specific embodiment

Further description of the technical solution of the present invention with reference to the accompanying drawing, and however, it is not limited to this, all to this Inventive technique scheme is modified or replaced equivalently, and without departing from the spirit and scope of the technical solution of the present invention, should all be covered Within the protection scope of the present invention.

As shown in Figure 1, present embodiment invention provide plane formula capacitance tomography system include host computer, Arduino single-chip microcontroller, capacitance measurement circuit, switching circuit, capacitive array sensor, in which:

The Arduino single-chip microcontroller is connect with host computer, capacitance measurement circuit and switching circuit respectively；

The switching circuit is connect with capacitive array sensor and capacitance measurement circuit respectively；

The host computer includes Data Acquisition and Communication System and image re-construction system；

The Arduino single-chip microcontroller control switch circuit carries out electrode switching to capacitive array sensor, realizes different Interelectrode capacitance connection, to be measured with capacitance measurement circuit, the data of capacitance measurement circuit are passed uni-directionally to Arduino single-chip microcontroller is acquired data using Arduino single-chip microcontroller and communicates afterwards with the Data Acquisition and Communication System of host computer Data are passed to computer, then image re-construction system is handled and rebuild to data.

The step of carrying out material internal defect detection using the capacitance tomography system of above-mentioned plane formula is as follows:

Step 1: motivating capacitance measurement circuit using the AC signal of 20KHz, this AC signal is sent out by signal Raw device generates, and the peak value of this signal is 5V.

In this step, capacitance measurement circuit uses the measurement method of ac-excited formula, and the schematic diagram of capacitance measurement circuit is such as Shown in Fig. 3.In testing capacitance after sinusoidal excitation signal motivates, the signal of generation is as follows:

In formula, V₀₁For output signal, V_iFor input signal, C₀For testing capacitance, ω is the angular frequency of pumping signal, C_fFor Feedback reference capacitor, R_fFor feedback resistance, j is imaginary number.If parameter ω, R_f、C_fMeet ω R_fC_f> > 1, then above formula can abbreviation are as follows:

Can thus capacitance be converted to the peak value of output signal, be convenient for subsequent measurement.

Due to the open by design of capacitor plate, the signal of interference can be inevitably introduced, so later use OP07 of the present invention The bandwidth-limited circuit for devising Butterworth low pass and high-pass filter cascade composition is filtered output signal, The cutoff frequency of middle high-pass filter is 8.7KHz, and the cutoff frequency of low-pass filter is 43KHz.Signal after ac-excited is logical It crosses after band-pass filter and full-wave rectification is carried out to sinusoidal signal using AD630, recycle the low-pass filter of OP07 design Signal after this rectification is filtered, according to Fourier's theory, can finally obtain the DC voltage directly proportional with capacitance Signal.

Step 2: switch electrode using Arduino single-chip microcontroller control switch circuit, and acquire the number of capacitance measurement circuit According to passing data to host computer by serial communication program.

In this step, as shown in Fig. 2, the capacitive array sensor is 4 × 4 to be made using printed circuit 16 electrod-arrays, the square electrode piece that each electrode is 16mm, between adjacent electrode between be divided into 8mm.

In this step, the multiplexing chip that the switching circuit uses is 16 road bilateral analog switch CD4067, is passed through Arduino single-chip microcontroller controls the measurement for 120 capacitors of total that two switch chips are realized between Different electrodes.

In this step, the Arduino single-chip microcontroller controls analog switch by digital I/O port, is received using analog input end The d. c. voltage signal of capacitance measurement circuit, and host computer is transmitted data to by serial ports.

Step 3: utilize image re-construction system to acquisition after collecting data using the Data Acquisition and Communication System of host computer The data arrived carry out image reconstruction, obtain material internal defect situation.

In this step, the Data Acquisition and Communication System and image re-construction system are write using MFC and C++.

In this step, described image reconstructing system mainly needs capacitance sensor to turn the dielectric distribution situation of testee Then the capacitance being changed between electrode pair solves the distribution situation of substance according to this capacitance.It can according to gauss flux theorem :

In formula:For capacitance, Q is the charge inducing in sensor plate, potential difference of the V between two electrode plates, ε (x, It y) is the dielectric distribution situation in testee section,For the field distribution situation in testee section.Every two pole plate Between capacitor:

In formula: i, j respectively indicate the number of source electrode and measuring electrode, C_i,jCapacitance size between Different electrodes, D Indicate the area of tested surface, S_i,j[x.y, ε (x, y)] is plates capacitance C_i,jDistribution function, i.e. C_i,jTo the electricity at point (x, y) The sensitivity of medium.

Generally for convenient for solution, it is assumed that sensitivity distribution function is influenced very little by dielectric distribution, can be ignored, then can table It is shown as:

In formula: S_i,j(x, y) capacitor C between pole plate_i,jSensitivity function, i.e. C_i,jTo dielectric quick at point (x, y) Sense degree.Discretization and normalization are carried out to it, further may be expressed as:

C=SG (6)；

Wherein, S is sensitive field matrix, and C is capacitance matrix, and G is normalization dielectric constant vector, it corresponds directly to rebuild The gray value of image.

For the ease of obtaining sensitive field matrix, the calculation formula of general sensitivity field is as follows:

Wherein, S_i,j(x, y) is sensitivity function, and p (x, y) is location information, E_i(x,y)、E_j(x, y) is single electrode energization When corresponding position electric field strength, V_i、V_jFor the voltage of single electrode.According to formula (7) different electricity can be exported using COMSOL The field distribution when independent role of pole, to solve sensitive field function.

In this step, algorithm used in described image reconstructing system is singular value decomposition algorithm.The principle of the algorithm is The matrix decomposition that one cannot be inverted using mathematically matrix singular value decomposition is multiple matrixes, acquires matrix with this Pseudoinverse.By this mathematical principle, sensitive field matrix is calculated using field distribution data derived from formula (7) and COMSOL Then S decomposes it, it can be resolved into:

S=QMZ^T；

Wherein, Q, Z are orthogonal matrix, and M is diagonal matrix.After inverting to it can and capacitance matrix C ask together Solve G.Solving result can correspond to the dielectric constant distribution situation of substance above sensor.The simulation experiment result such as Fig. 4 institute Show.It, can be by the image reconstructed when existing defects in sample thus, it is possible to carry out image checking to the sample above sensor Judged, defective locations can additionally be positioned by image processing techniques, reach the visual detection of automation, be each The non-destructive testing of kind material provides a kind of new means and method.