阅读说明：本技术 一种电磁无损质量检测方法及其检测电路和系统 (Electromagnetic nondestructive quality detection method and detection circuit and system thereof ) 是由 胡舟逸 于 2020-06-22 设计创作，主要内容包括：本发明公开了一种电磁无损质量检测方法及其检测电路和系统,通过对一阶RL电路交替进行直流激励响应和零输入响应,使其电感元件磁化线圈产生的直流磁场的磁场强度随电流大小的变化而交替变化,将检测对象置于此磁场强度交替变化的直流磁场中后,检测对象被磁化的同时也引起磁场电感的变化,可通过检测磁化线圈的电感来判断检测被检测对象的电磁特性是否变化,从而判断是否有如钢丝裂纹、钢丝绳断丝等质量缺陷,或者通过检测磁化线圈的电感来分析被检测对象与电磁特性相关的截面积、或锌层厚度等特性；本发明适应于实时、在线、连续、自动地对电磁敏感的检测对象检测或产品性能标定,从而及时发现质量问题,减少次品率,提高产品质量性能。(The invention discloses an electromagnetic nondestructive quality detection method and a detection circuit and a system thereof.A first-order RL circuit is subjected to alternating direct current excitation response and zero input response to ensure that the magnetic field intensity of a direct current magnetic field generated by a magnetizing coil of an inductance element of the RL circuit is changed alternately along with the change of the current magnitude; the invention is suitable for real-time, online, continuous and automatic detection of electromagnetic sensitive detection objects or product performance calibration, thereby finding quality problems in time, reducing defective rate and improving product quality performance.)

1. An electromagnetic nondestructive quality detection method is characterized in that: the method comprises the following steps:

s1, using the first-order RL circuit as the magnetizing circuit of the magnetizing coil and the magnetizing coil as the inductance element of the first-order RL circuit, automatically controlling the electronic switch to preset the maximum current I of the magnetizing coil_maxAnd minimum current I_minMaking the first-order RL circuit alternately perform direct current excitation response and zero input response;

when the direct current excitation response is carried out, the direct current passing through the magnetizing coil is increased regularly, and when the zero input response is carried out, the current of the magnetizing coil is decreased regularly;

s2, under the direct current excitation response and the zero input response of the first-order RL circuit, the magnetizing coil which is electrified with direct current with alternating current magnitude generates a direct current magnetic field with alternating magnetic field intensity;

s3, placing an electromagnetically sensitive detection object in the direct-current magnetic field with the alternating magnetic field intensity of S2, wherein on one hand, the detection object is magnetized by the magnetic field with the alternating magnetic field intensity, and on the other hand, the detection object also causes the change of the magnetic induction intensity or the magnetic flux of the magnetizing coil, so that the change of the inductance of the magnetizing coil is caused; when the detected object is subjected to differential change, the change of magnetic induction intensity or magnetic flux can be caused, and the inductance of the magnetizing coil is further caused to change along with the differential change of the detected object;

s4, detecting the inductance of the magnetizing coil in the RL circuit to detect the difference change of the detected object, thereby determining whether a quality defect occurs, or detecting the inductance of the magnetizing coil to analyze the electromagnetic characteristics of the detected object, thereby analyzing the related characteristics of the detected object.

2. The electromagnetic non-destructive quality inspection method of claim 1,the method for detecting the inductance of the magnetizing coil in the RL circuit in S4 is characterized by comprising the following steps: the first-order RL circuit which takes the magnetizing coil as an inductance element is controlled by the automatic control electronic switch to circularly enter a direct current excitation response state and a zero input response state, and the current of the magnetizing coil is increased in an exponential law when the magnetizing coil is in the direct current excitation response state; when the current of the magnetizing coil is in a zero input response state, the current of the magnetizing coil is reduced in an exponential law; presetting the maximum current I of the magnetizing coil_maxAnd minimum current I_minWhen other parameters in the circuit are kept unchanged, the time of the current change process of the magnetizing coil is in a linear relation with the inductance of the magnetizing coil, and the time of each response state current change process or the frequency of the two response state cyclic changes can be sampled to amplify the inductance change signal of the magnetizing coil in the RL circuit.

3. The electromagnetic nondestructive quality inspection method according to claim 2, wherein the time when the first-order RL circuit having the magnetizing coil as the inductance element is in the dc excitation response state, the time when the first-order RL circuit having the magnetizing coil as the inductance element is in the zero input response state, or the sum of the two state times can be sampled to linearly characterize the inductance of the magnetizing coil.

4. The electromagnetic nondestructive quality inspection method according to claim 1 or 2, wherein the change in inductance of the magnetizing coil is detected in the magnetizing circuit having the magnetizing coil as the inductance element of the first-order RL circuit in S4 by:

according to a predetermined maximum current I of the magnetizing current through the magnetizing coil_maxAnd minimum current I_minAutomatically controlling the electronic switch to be switched on to enable the first-order RL circuit to enter a direct current excitation response state;

in the DC excitation response state, the magnetizing current of the magnetizing coil rises, and when the magnetizing current of the magnetizing coil rises to reach the preset maximum current I_maxWhen the circuit is in a zero-input response state, the electronic switch is automatically controlled to be turned off so that the first-order RL circuit is switched to the zero-input response state.

In the zero input response stateThe magnetizing current of the magnetizing coil is reduced, when the current of the magnetizing coil is reduced to a preset minimum current I_minWhen the circuit is in a direct current excitation response state, the electronic switch is automatically controlled to be switched on, so that the first-order RL circuit is switched to the direct current excitation response state, and the process in the direct current excitation response state is repeated;

next, cycling the first order RL circuit alternately between a dc stimulus response state and a zero input response state;

when the detected object is not subjected to difference change and the inductance of the magnetizing coil is not changed, the time when the magnetizing coil is in a direct current excitation response state and the time when the magnetizing coil is in a zero input response state are constant during cyclic repetition;

when the detected object is subjected to differential change to cause the change of the inductance of the magnetizing coil, the time of the two response states changes along with the change of the inductance of the magnetizing coil, and the time of the two response states, or the time of any one of the two response states, or the frequency of the cyclic change of the two response states is detected, so that the change of the inductance of the magnetizing coil can be sensitively detected.

5. The electromagnetic non-destructive quality inspection method according to claim 1, wherein the inspection object continuously running in real time in the production line is placed in a direct current magnetic field having a magnetic field intensity continuously alternating at S3, thereby realizing real-time continuous on-line automatic inspection of the inspection object.

6. The electromagnetic non-destructive quality testing method of any one of claims 1-5, characterized in that: maximum current I of magnetizing coil_maxAnd minimum current I_minDifferent values can be set according to the actual detected object, so that the magnetic field intensity for magnetizing the detected object and the time of the process that the magnetizing coil is in the direct current excitation response state and the zero input response state or the frequency of the cyclic change of the two response states can be adjusted.

7. A detection circuit for electromagnetic non-destructive quality testing, characterized by: the circuit comprises a direct current stabilized voltage power supply, a first-order RL circuit consisting of a magnetizing coil and a current-limiting resistor, and a loop of an excitation current electronic switch, wherein the direct current stabilized voltage power supply is connected with the magnetizing coil;

the exciting current electronic switch is used for controlling a first-order RL circuit formed by the magnetizing coil and the current-limiting resistor to be connected with or disconnected from the direct current power supply voltage-stabilized power supply and controlling the first-order RL circuit to enter or exit a direct current excitation response state;

when the exciting current electronic switch is switched on, magnetizing current flows into the magnetizing coil from the positive electrode of the direct current power supply voltage-stabilized power supply through the current-limiting resistor and is connected to the negative electrode of the direct current power supply voltage-stabilized power supply through the exciting current electronic switch;

the first-order RL circuit enters a direct current excitation response state, and the magnetizing current of the magnetizing coil reaches a set maximum current I_maxWhen the current is cut off, the exciting current electronic switch is switched on;

when the exciting current electronic switch is switched off, the follow current loop provides a follow current channel of the magnetizing coil, the first-order RL circuit enters a zero-input response state, and the magnetizing current decreases according to an exponential law; until the magnetizing current reaches the set minimum current I_minAnd the exciting current electronic switch is conducted again, and the direct current excitation response and the zero input response of the magnetizing coil are performed in an alternate cycle mode.

8. The circuit of claim 7, wherein when the first-order RL circuit is enabled to perform a dc excitation response, a voltage of a dc regulated power supply for supplying power to the first-order RL circuit is adjustable, and a current limiting resistor of the first-order RL circuit is independently selectable with the magnetizing coil, so that a rate of change of a current and thus a rate of change of a magnetic field intensity for magnetizing the object to be inspected can be adjusted to be suitable for different objects to be inspected.

9. A detection system using an electromagnetic nondestructive detection method is characterized by comprising a detection circuit, wherein the detection circuit comprises a first-order RL circuit consisting of a magnetizing coil and a current-limiting resistor, and is connected with a direct-current power supply voltage-stabilized power supply and a loop of an exciting current electronic switch, and the magnetizing coil is also independently connected with a follow current loop;

the exciting current electronic switch is used for controlling a first-order RL circuit formed by the magnetizing coil and the current-limiting resistor and a loop of the direct-current power supply voltage-stabilized power supply;

when the exciting current electronic switch is switched on, magnetizing current flows into the magnetizing coil from the positive electrode of the direct current supply voltage-stabilized power supply through the current-limiting resistor, is connected to the negative electrode of the direct current supply voltage-stabilized power supply through the exciting current electronic switch, and carries out direct current excitation response on the magnetizing coil when the magnetizing current of the magnetizing coil reaches the set maximum current I_maxWhen the current is cut off, the exciting current electronic switch is switched on;

when the exciting current electronic switch is switched off, the follow current loop provides a follow current channel of the magnetizing coil, the magnetizing coil performs zero input response, and the magnetizing current decreases according to an exponential law until the magnetizing current reaches a set minimum current I_minAnd the exciting current electronic switch is conducted again, and thus the direct current excitation response and the zero input response of the magnetizing coil are alternately circulated.

10. The inspection system according to claim 9, further comprising a magnetizing current sampling unit, a voltage comparing unit, a magnetizing current switching correspondence control voltage setting unit, a magnetizing current switching control logic and magnetizing current switching driving unit, and an inductance-sensitive signal processing and outputting unit;

a voltage sampling point is arranged between the magnetizing coil and the current-limiting resistor, and the current sampling unit collects the voltage to ground of the voltage sampling point and outputs the voltage to the voltage comparison unit after processing;

the magnetizing current conversion corresponding control voltage setting unit is connected with the maximum current I of the magnetizing coil according to preset magnetizing current information_maxAnd minimum current I_minDuring the DC excitation response phase of the first-order RL circuit, when the magnetization of the magnetizing coil is in the middleThe current reaches the maximum current I_maxWhen the current is in a zero-input response state, the magnetizing current switch conversion control logic and the magnetizing current switch driving unit turn off the exciting current electronic switch and turn on the follow current loop to enable the first-order RL circuit to enter the zero-input response state; the magnetizing current is decreased according to an exponential law until the magnetizing current reaches a set minimum current I_minThe exciting current electronic switch is conducted again, and thus the direct current excitation response and the zero input response of the magnetizing coil are alternately circulated;

the inductance sensitive signal processing and output unit is used for sampling the time of the direct current excitation response stage and the time of the zero input response stage or the cyclic variation frequency thereof, and processing and outputting the variation result of the inductance signal.

11. The inspection system using the electromagnetic nondestructive inspection method according to claim 10 or 9, further comprising a microprocessing unit including a magnetizing current setting unit, a system parameter setting unit, and an analyzing processing and outputting unit of defects and related quality indexes of the inspected product;

the magnetizing current setting unit is used for setting the maximum current I of the magnetizing coil_maxAnd minimum current I_minAnd outputs the signal to a magnetizing current conversion corresponding control voltage setting unit;

the system parameter setting unit is used for setting related operation data;

the analysis processing and output unit of the detected product defects and the related quality indexes is used for carrying out analysis processing and outputting according to the signals output by the inductance sensitive signal processing and output unit and by combining the characteristics of the detected object and the related parameter setting.

Technical Field

The invention belongs to the field of electromagnetic detection and related application, relates to a detection method for detecting whether an object contains difference change or not based on the inductance change of a magnetizing coil for sensitively detecting the direct current excitation response and the zero input response of a first-order RL circuit, a detection circuit and a system for realizing the electromagnetic nondestructive quality detection method, and particularly relates to online, automatic, continuous and detection electromagnetic detection application.

Background

With the progress and development of industrial technology, the demand and related quality requirements of metal wires or cables and their products are continuously increasing. The online detection of defects in high-speed production processes and the control of quality indicators, such as the thickness of a galvanized steel wire coating, are becoming increasingly important. Some of these defects or technical indicators may be visually detectable on the surface, while some may be imperceptible on the interior. The detection method related to electromagnetic detection, such as eddy current detection and magnetic flux related detection, is a suitable detection means because it can detect the change condition inside the material, and the theoretical basis of the detection method is mature, and the influence and relationship of the magnetized detection object (the characteristic of ferromagnetic or non-ferromagnetic conductive material) on the magnetic field are relatively clear.

However, the currently used electromagnetic detection schemes include magnetic particle detection, cross-sectional metal flux measurement, magnetic flux leakage detection, eddy current detection, and the like, and some of them have high accuracy and can be used for defect subdivision. But the method is widely applied to professional detection institutions or laboratories and is rarely seen in industrial fields. For the reasons, some signal generation and processing schemes are complex, the equipment requirement is high, and the price is high; some of the devices need to operate on a computer system platform and are not suitable for industrial field application; some rely on manual intervention to identify, do not meet the automatic continuous detection; some detection sensitivities are not satisfactory or the response is too slow.

The existing electromagnetic detection techniques:

in common electromagnetic detection applications, a metal cross-section magnetic flux measurement method (based on the principle that magnetic flux is substantially proportional to a metal cross-section area under a certain condition), a magnetic flux leakage detection method and an eddy current detection method for a non-ferromagnetic detection object are mainly applied to automatic detection, and different detection methods are respectively adopted to perform the detection at present.

The method mainly applies to the cross-sectional area change detection of the ferromagnetic detection object, such as steel wire rope, firstly, the steel wire rope is saturated magnetically, then the magnetic flux change caused by the cross-sectional area change is detected by a detection coil or a sensor, and the magnetic flux change is converted into a voltage current signal for analysis and processing.

Similarly, for ferromagnetic detection objects, the magnetic flux leakage detection method firstly magnetically saturates a steel wire rope, then detects magnetic flux leakage caused by wire breakage by a magnetic pick-up coil, converts the magnetic flux leakage into a voltage and current signal, analyzes and processes the voltage and current signal, and uses the voltage and current signal as a detection basis for determining wire breakage.

In the eddy current detection method for a non-ferromagnetic detection object, impedance analysis is generally used to detect differences in reactance caused by eddy currents of different detection objects, and thereby analyze the characteristics of the detection objects.

The methods are complex, large in size, high in price and difficult to adapt to continuous and online universal application.

The technical problem to be solved by the technical requirement of electromagnetic detection is as follows:

how to make the electromagnetic detection simpler, and continuous, online, automatic and sensitive detection can be carried out. The device is particularly suitable for detecting the condition that an object runs at high speed in the high-speed production process, such as a wire rod, a pipe or a strand made of the wire rod.

The existing inductance sensitive method and the existing defects thereof are as follows:

the existing methods commonly used for measuring or sensing inductance mainly include impedance analysis, alternating current bridge method and LC oscillation method.

The impedance analysis method is that an alternating current power supply with a certain frequency is connected to an inductor to be measured through a resistor, the voltage and the current on the inductor to be measured are measured, and the inductive reactance is calculated. For the condition of small change, the voltage and current change on the inductor to be measured is very weak, the change of the impedance angle is very small, and particularly, the phase delay detection difficulty is high during high-frequency detection. In addition, the electromagnetic interference on the industrial site is uncertain, and the detection result is easily influenced by various interferences, so that the method is not suitable for relevant online automatic detection of electromagnetic detection.

The ac bridge method is usually used to connect the inductor to be tested to the ac bridge, adjust the adjustable resistance and the adjustable inductor in the ac bridge to balance the bridge, and calculate the inductor to be tested according to the resistance and the inductance of each bridge arm during balancing.

LC oscillation method adopts LC transduction oscillation principle, fixes C, and passes through F ═ 1/[2 pi (LC)^1/2]Detecting FAnd calculating L. The method adopts a three-point oscillation method, so that more elements are used in the actual application circuit, and the oscillation frequency is influenced by a plurality of elements, so that the data fluctuation is larger. And the inductance change is not sensitive enough to the influence of frequency and sensitive to electromagnetic interference, so that the method is difficult to meet the requirement that the electromagnetic detection is sensitive to small change reliably during automatic online continuous detection.

Disclosure of Invention

The invention provides an online, continuous and automatic electromagnetic nondestructive testing method, a testing circuit and a system using the electromagnetic nondestructive testing method, which enable the electromagnetic nondestructive testing application technology to meet the application of industrial fields and are suitable for online, continuous and automatic sensitive defect or quality index testing of production fields to realize the control of product quality.

In order to achieve the purpose, the invention provides the following technical scheme:

an electromagnetic nondestructive quality detection method comprises the following steps:

an electromagnetic nondestructive quality detection method is characterized in that: the method comprises the following steps:

s1, using the first-order RL circuit as the magnetizing circuit of the magnetizing coil and the magnetizing coil as the inductance element of the first-order RL circuit, automatically controlling the electronic switch to preset the maximum current I of the magnetizing coil_maxAnd minimum current I_minMaking the first-order RL circuit alternately perform direct current excitation response and zero input response;

when the direct current excitation response is carried out, the direct current passing through the magnetizing coil is increased regularly, and when the zero input response is carried out, the current of the magnetizing coil is decreased regularly;

s2, under the direct current excitation response and the zero input response of the first-order RL circuit, the magnetizing coil which is electrified with direct current with alternating current magnitude generates a direct current magnetic field with alternating magnetic field intensity;

s3, placing an electromagnetically sensitive detection object in the direct-current magnetic field with the alternating magnetic field intensity of S2, wherein on one hand, the detection object is magnetized by the magnetic field with the alternating magnetic field intensity, and on the other hand, the detection object also causes the change of the magnetic induction intensity or the magnetic flux of the magnetizing coil, so that the change of the inductance of the magnetizing coil is caused; when the detected object is subjected to differential change, the change of magnetic induction intensity or magnetic flux can be caused, and the inductance of the magnetizing coil is further caused to change along with the differential change of the detected object;

s4, detecting the inductance of the magnetizing coil in the RL circuit to detect the difference change of the detected object, thereby judging whether quality defects such as steel wire cracks, surface defects, material changes, steel wire rope breakage, incorrect arrangement and the like occur or analyzing the electromagnetic property of the detected object by detecting the inductance of the magnetizing coil, thereby analyzing the relevant property of the detected object. Such as the cross-sectional area of the wire in relation to the magnetic flux, the thickness of the zinc layer of the coated wire, etc.

A first-order RL circuit is used as a magnetizing circuit, a changing magnetizing current is formed at the moment when a magnetizing coil is electrified or deenergized in direct current excitation response and zero input response, a changing magnetic field is generated, a detected object is magnetized as a magnetic medium in the magnetic field, and meanwhile, if the detected object is made of a conductive material, the eddy current phenomenon is generated in the detected object due to the change of the magnetic field.

As a detection object of a magnetic medium, a magnetic circuit, a magnetic resistance and a magnetic permeability thereof will affect a magnetic field therein; if the test object is a conductive material, eddy current phenomenon will be generated on the test object, and the property of the conductive material will also affect the magnetic field therein. These effects on the magnetic field cause, for the magnetizing circuit, an effect on the inductance of the magnetizing coil. The change in the electromagnetic characteristics of the detection object affects the change in the inductance of the magnetizing coil.

The electromagnetic property and its change of the detection object, including the material or shape of the detection object and its change, will cause the change of the related magnetic circuit, magnetic resistance, magnetic permeability, or cause the eddy current and its change, including but not limited to: surface defects, cracks, material doping, carbon content change and the like of the conductive ferromagnetic pipe and the rod wire; or the defects of broken wire, broken strand, rust , back wire and the like after the wire materials are stranded into a rope; or the thickness of the non-ferromagnetic conductive coating on the surface of the conductive ferromagnetic bar. The inductance of the magnetizing coil (including the influence of a detected object) and the change of the inductance can be detected by a magnetizing coil inductance sensing method based on a first-order RL circuit direct current excitation response and a zero input response.

The electromagnetic properties and changes of the detection object also include related magnetic circuits, magnetic resistance and magnetic permeability which are basically unchanged, and only the material or shape and changes of the material or shape which cause the changes of the eddy current include but are not limited to: surface variations of non-ferromagnetic conductive pipes, wires or cables. Can be detected by detecting the change of the inductance of the magnetizing coil (including the influence of a detected object) based on a first-order RL direct current excitation response and zero input response circuit

For example, when the detected object is a wire rod, a pipe or a strand made of the wire rod: in a metal cross section magnetic flux measurement method for a ferromagnetic detection object, for example, when the detection object is a steel wire rope, the cross section area changes when the detection object passes through a magnetizing coil, so that the change of magnetic flux passing through the magnetizing coil is caused, and the change of inductance of the magnetizing coil is also caused; when a detected object passes through the magnetizing coil, the broken wire causes magnetic leakage to generate, thereby causing the change of magnetic flux passing through the magnetizing coil and the change of inductance of the magnetizing coil; the eddy current itself also generates a magnetic field, which acts as a counter magnetic field to the magnetic field of the magnetizing coil, causing a change in the magnetic flux through the magnetizing coil and a change in the inductance of the magnetizing coil. When the detection object is placed in the alternating magnetic field of the magnetizing coil during eddy current detection, the change of the inductance of the magnetizing coil caused by the eddy current is unchanged when the detection object is unchanged, namely the inductance is constant; when the detected object is changed, the eddy current is changed, the action of the diamagnetic field is changed, and the inductance change of the magnetizing coil caused by the eddy current is also changed, namely, when the detected object is changed, the inductance change of the magnetizing coil is caused. Therefore, by detecting the inductance of the magnetizing coil, the condition of the objects can be detected. Especially, when the detected object is a wire rod, a pipe or a strand formed by the wire rods, the condition of the inductance of the magnetizing coil is detected through proper processing, and the condition of the product quality is also detected.

Further, in S4, the method for detecting the inductance of the magnetizing coil in the RL circuit is as follows: the first-order RL circuit which takes the magnetizing coil as an inductance element is controlled by the automatic control electronic switch to circularly enter a direct current excitation response state and a zero input response state, and the current of the magnetizing coil is increased in an exponential law when the magnetizing coil is in the direct current excitation response state; when the current of the magnetizing coil is in a zero input response state, the current of the magnetizing coil is reduced in an exponential law;

according to a predetermined maximum current I of the magnetizing current through the magnetizing coil_maxAnd minimum current I_minAutomatically controlling the electronic switch to be turned on to enable the first-order RL circuit to enter a DC excitation response state

The first-order RL circuit is in direct current excitation response, and the electronic switch is in a preset minimum magnetizing current I_minWhen the current is switched on, the magnetizing coil power supply loop is conducted, the first-order RL circuit responds to the direct current excitation, and the magnetizing current is increased;

from circuit theory analysis, the current response is as follows:

i_l(t)＝I_l(∞)+[I_l(0+)-I_l(∞)]e^(-t/τ)

I_l(∞)＝U/R

I_l(0+)＝I_min

τ＝L/R

i_l(t)＝U/R-[U/R-I_min]e^(-t/τ)2-1

wherein

U: supply voltage of magnetizing circuit

L: magnetizing coil inductor

R: total equivalent resistance of magnetizing coil power supply loop

I_min：Minimum value of magnetizing current

τ: time constant of magnetizing coil power supply loop

In the DC excitation response state, the magnetizing current of the magnetizing coil rises, and when the magnetizing current of the magnetizing coil rises to reach the preset maximum current I_maxWhen the circuit is in a zero-input response state, the electronic switch is automatically controlled to enable the first-order RL circuit to be switched to the zero-input response state.

The first-order RL circuit has zero input response, and the magnetizing current is increased to a preset maximum magnetizing current I_maxWhen in use, the power supply loop of the magnetizing coil is cut off,then, the current in the magnetizing coil freewheels and decreases through the freewheeling loop;

from circuit theory analysis, the current response is as follows:

i_l(t)＝I_l(∞)+(I_l(0+)-I_l(∞))e^(-t/τ1)

I_l(∞)＝0,I_l(0+)＝I_max

τ1＝L/R1

i_l(t)＝I_maxe^(-t/τ1)2-2

wherein

L: magnetizing coil inductor

R1: total equivalent resistance of follow current loop

I_max：Maximum value of magnetizing current

τ 1: time constant of magnetization loop

In the zero input response state, the magnetizing current of the magnetizing coil is reduced, and when the current of the magnetizing coil is reduced to a preset minimum current I_minAnd automatically controlling the electronic switch to switch the first-order RL circuit to a direct current excitation response state, and repeating the process in the direct current excitation response state.

Thus, the first order RL circuit is cycled alternately between a DC stimulus response state and a zero input response state.

When the maximum and minimum magnetizing currents are preset and are unchanged and other parameters in the circuit are unchanged, the time of the transition process and the inductance of the magnetizing coil are in a linear relation:

will I_maxSubstituted into formula 2-1 i_lAt (t):

I_max＝U/R-(U/R-I_min)e^(-t/τ)

e^(-t/τ)＝(U/R-I_max)/U/R-I_min

t/τ＝Ln((U/R-I_min)/(U/R-I_max)) 2-3

when the current is I_maxTime t is I_minTo I_maxTime of transition T, visual T andτ is a linear relationship, and when the voltage and resistance are constant, T and L are linear relationships.

When the maximum and minimum magnetizing currents are preset and are unchanged and other parameters in the circuit are unchanged, the transition process time and the inductance of the magnetizing coil are in a linear relation:

will I_minSubstituted into formula 2-2 i_l(t):

I_min＝I_maxe^(-t/τ1)

e^(-t/τ1)＝I_min/I_max

t/τ1＝Ln(I_max/I_min) 2-4

When the current is I_minTime t is I_maxTo I_minThe transition time T1, see when I_max、I_minConstant, Ln (I)_max/I_min) Being constant, T1 and L are linear when the resistance is constant.

The maximum current Imax and the minimum current Imin of the magnetizing coil are preset, when other parameters in the circuit are kept unchanged, the time of the current change process of the magnetizing coil and the inductance of the magnetizing coil form a linear relation, and the time of each current change process in response states or the frequency of the cyclic change of the two response states can be sampled to represent the inductance change signal of the magnetizing coil in the RL circuit. Preferably, the time when the first-order RL circuit with the magnetizing coil as the inductance element is in the dc excitation response state, the time when the first-order RL circuit with the magnetizing coil as the inductance element is in the zero input response state, or the sum of the two state times can be sampled to linearly represent the inductance of the magnetizing coil.

In the above process, any one of the transition process time or the cycle period time and the inductance of the magnetizing coil are in a linear relationship, and T ═ K × L. Compared to the period time of a classical LC oscillation, T ═ K (L × C)^1/2When C is not changed, T ═ K × L^1/2. The magnetizing coil inductance detection method based on the first-order RL circuit direct current excitation response and the zero input response is more sensitive to the change of the inductance of the magnetizing coilAnd directly.

Further, in S4, the change in inductance of the magnetizing coil is detected in the magnetizing circuit having the magnetizing coil as the inductance element of the first-order RL circuit by the following method:

when the detected object is not subjected to difference change and the inductance of the magnetizing coil is not changed, the time when the magnetizing coil is in a direct current excitation response state and the time when the magnetizing coil is in a zero input response state are constant during cyclic repetition;

when the detected object is subjected to differential change to cause the change of the inductance of the magnetizing coil, the time of the two response states changes along with the change of the inductance of the magnetizing coil, and the time of the two response states, or the time of any one of the two response states, or the frequency of the cyclic change of the two response states is detected, so that the change of the inductance of the magnetizing coil can be sensitively detected.

When the electronic switch is switched on after the maximum and minimum magnetizing currents are preset, the current in the magnetizing coil changes according to the direct current excitation response of the first-order RL circuit; when the electronic switch is turned off, the current in the magnetizing coil freewheels through the freewheeling loop and changes according to the zero-input response of the first-order RL circuit.

Thus, as the first-order RL circuit state cycles back and forth between the DC-stimulated response state and the zero-input response state, the time of the two state processes will change as the magnetizing coil inductance changes, the time of the two state processes described above will be detected, or either time will be detected, thereby sensing the magnetizing coil inductance. Moreover, when the maximum and minimum magnetizing current presets are unchanged and other parameters in the circuit are unchanged, when the detected object is unchanged and the inductance of the magnetizing coil is not changed, the time of the two state processes is unchanged, the cycle period time T is also unchanged, so that the detection process can be repeated and verified or other algorithms such as adaptive filtering calculation can be adopted, therefore, the detection result of the invention has high comparability and reliability.

Further, in S3, the inspection object continuously running in real time in the production line is placed in the dc magnetic field having the magnetic field intensity continuously alternating, thereby realizing real-time continuous on-line automatic inspection of the inspection object. The first-order RL circuit is in reciprocating circulation between a direct current excitation response state and a zero input response state, so that the detection process is continuous, and the real-time continuous online automatic detection can be performed on a detection object in operation.

Further, the maximum current I of the magnetizing coil_maxAnd minimum current I_minDifferent values can be set according to the actual detected object, so that the magnetic field intensity for magnetizing the detected object and the time of the process that the magnetizing coil is in the direct current excitation response state and the zero input response state or the frequency of the cyclic change of the two response states can be adjusted.

Maximum current I of magnetizing coil_maxAnd minimum current I_minThe maximum and minimum magnetizing currents can be set by means of independent programs, and the most suitable maximum and minimum magnetizing currents can be manually or automatically selected through experiments in practical application. Therefore, different detection objects are magnetized by different magnetic field strengths, and the method can adapt to different materials and different application purposes.

Furthermore, the voltage when the first-order RL circuit is subjected to direct current excitation response is adjustable, and the current-limiting resistor of the first-order RL circuit formed by the current-limiting resistor and the magnetizing coil is independently selectable, so that the current-limiting RL circuit is suitable for different detection objects. Maximum current I combined with magnetizing coil_maxAnd minimum current I_minThe settings of (a) and (b) may be selected to determine different rates of change of the current on the magnetizing coil, i.e. different rates of change of the magnetic field generated by the magnetizing coil. Therefore, different magnetic field change rates are selected, and the device can adapt to different application purposes or different materials and field requirements of detection objects.

A detection circuit for electromagnetic nondestructive quality detection comprises a direct current stabilized voltage power supply, a first-order RL circuit consisting of a magnetizing coil and a current-limiting resistor, and a loop of an exciting current electronic switch, wherein the magnetizing coil is connected to a follow current loop and is used for enabling the magnetizing coil to follow current when the exciting current electronic switch is switched off;

the exciting current electronic switch is used for controlling a first-order RL circuit formed by the magnetizing coil and the current-limiting resistor to be connected with or disconnected from the direct current power supply voltage-stabilized power supply and controlling the first-order RL circuit to enter or exit a direct current excitation response state;

when the exciting current electronic switch is switched on, magnetizing current flows into the magnetizing coil from the positive electrode of the direct current power supply voltage-stabilized power supply through the current-limiting resistor and is connected to the negative electrode of the direct current power supply voltage-stabilized power supply through the exciting current electronic switch;

the first-order RL circuit enters a direct current excitation response state, and the magnetizing current of the magnetizing coil reaches a set maximum current I_maxWhen the current is cut off, the exciting current electronic switch is switched on;

when the exciting current electronic switch is switched off, the follow current loop provides a follow current channel of the magnetizing coil, the first-order RL circuit enters a zero-input response state, and the magnetizing current decreases according to an exponential law; until the magnetizing current reaches the set minimum current I_minAnd the exciting current electronic switch is conducted again, and the direct current excitation response and the zero input response of the magnetizing coil are performed in an alternate cycle mode.

Preferably, when the first-order RL circuit is enabled to perform a dc excitation response state, the voltage of a dc regulated power supply for supplying power to the first-order RL circuit is adjustable, and a current limiting resistor of the first-order RL circuit formed by the first-order RL circuit and the magnetizing coil is independently selectable, so that the current change rate can be adjusted, and further, the change rate of the magnetic field intensity for magnetizing the detected object can be adjusted, so as to be suitable for different detected objects.

A detection system using an electromagnetic nondestructive detection method comprises the detection circuit, a magnetizing current sampling unit, a voltage comparison unit, a magnetizing current conversion corresponding control voltage setting unit, a magnetizing current switch conversion control logic and magnetizing current switch driving unit and an inductance sensitive signal processing and output unit;

a voltage sampling point is arranged between the magnetizing coil and the current-limiting resistor, and the current sampling unit collects the voltage to ground of the voltage sampling point and outputs the voltage to the voltage comparison unit after processing;

the magnetizing current conversion corresponding control voltage setting unit is connected with the magnetizing coil according to preset magnetizing current information to set the maximum current of the magnetizing coilI_maxAnd minimum current I_minWhen the magnetizing current of the magnetizing coil reaches the maximum current I in the DC excitation response stage of the first-order RL circuit_maxWhen the current is in a zero-input response state, the magnetizing current switch conversion control logic and the magnetizing current switch driving unit turn off the exciting current electronic switch and turn on the follow current loop to enable the first-order RL circuit to enter the zero-input response state; the magnetizing current is decreased according to an exponential law until the magnetizing current reaches a set minimum current I_minThe exciting current electronic switch is conducted again, and thus the direct current excitation response and the zero input response of the magnetizing coil are alternately circulated;

the inductance sensitive signal processing and output unit is used for sampling the time of the direct current excitation response stage and the time of the zero input response stage, processing and outputting the change result of the inductance signal.

Preferably, the detection system using the electromagnetic nondestructive detection method further comprises a microprocessing unit, wherein the microprocessing unit comprises a magnetizing current setting unit, a system parameter setting unit and an analysis processing and output unit for the defects and relevant quality indexes of the detected product;

the magnetizing current setting unit is used for setting the maximum current I of the magnetizing coil_maxAnd minimum current I_minAnd outputs the signal to a magnetizing current conversion corresponding control voltage setting unit;

the system parameter setting unit is used for setting related operation data;

the analysis processing and output unit of the detected product defects and the related quality indexes is used for carrying out analysis processing according to the signals output by the inductance sensitive signal processing and output unit and combining the characteristics of the detected object and related parameter setting, and outputting the signals in different forms such as pictures and texts, digital or analog quantity or communication.

Has the advantages that:

the electromagnetic nondestructive quality detection method provided by the invention has the advantages that the direct current excitation response and the zero input response are alternately carried out on the magnetizing coil by the first-order RL circuit, so that the magnetic field intensity of the direct current magnetic field generated by the magnetizing coil is alternately changed along with the change of the current; after an electromagnetic sensitive detection object is placed in a direct current magnetic field with the magnetic field intensity changing alternately, the inductance of the magnetizing coil changes, and the change of the inductance is in a linear relation with the time of the magnetizing coil in a direct current excitation response stage and the time of the magnetizing coil in a zero input response stage, so that the change of the inductance of the magnetizing coil caused by the performance parameters of the detected object can be detected skillfully and sensitively, and the defect that the electromagnetic detection cannot be detected online, automatically and continuously sensitively is overcome. The electromagnetic nondestructive quality detection method has the advantages of good real-time performance, high sensitivity and high reliability, can be suitable for online detection of defects in high-speed production processes of wires, bars or cables and the like and continuous, real-time and automatic detection of quality indexes, achieves the aims of improving quality and reducing unqualified products, can find problems in time in the production process, corrects the problems in time, reduces defective rate, reduces loss, saves resources, improves product quality performance and reduces potential safety hazards.

The invention is particularly suitable for detecting the defects of broken yarn, yarn lack, bulging, back yarn and the like of the strand structure in time in the production process by adopting proper working parameters without sudden change of the structure under normal conditions when the detected object is a strand formed by wire rods, tubes or wires thereof; and detecting the performance parameters of the defects of the wire and the bar, the thickness of the plating layer and the like on line. Because the production process of products such as bars, tubes and strand structures is usually continuous, quality problems often occur in batches. If the effective real-time online detection is lacked, the quality or performance change of the product is difficult to find in time, even the quality problem can not be found until the customer feeds back complaints, and a large amount of defective products are produced in the continuous production at the moment, so that great waste and potential safety hazards are caused.

Drawings

FIG. 1 is a block diagram of an inspection system utilizing an electromagnetic non-destructive inspection method according to the present invention;

FIG. 2 is a schematic diagram of an inspection circuit using an electromagnetic nondestructive inspection method according to the present invention;

FIG. 3 is an illustration of magnetization current waveforms in an embodiment of the present invention;

fig. 4 is an illustration of voltage waveforms of voltage sampling points in an embodiment of the invention.

Detailed Description

For the purpose of enhancing the understanding of the present invention, the present invention will be further described in detail with reference to the following examples and the accompanying drawings, which are only used for explaining the present invention and are not to be construed as limiting the scope of the present invention.