CN100429515C - Eddy current inspection device based on resistance transducer of gigantic magnetism - Google Patents

Abstract

A vortex detection device based on huge magnetic resistance transducer is prepared as generating vortex by detected element when excitation coil is near to detected conduction structure based on electromagnetic induction principle and conversely influencing magnetic field generated by excitation coil by vortex, using probe of huge magnetic resistance transducer to detect out variation of magnetic field, sending said variation signal to two phase sensitive rectifiers and making output signal of said rectifier be close relation with parameter of detected element then driving out value of parameter to be detected.

Description

Eddy current testing device based on giant magnetoresistance sensor

Technical field

The present invention relates to a kind of eddy current testing device based on giant magnetoresistance sensor.

Background technology

Current dual-use aviation development is very rapid.Need under the situation that guarantees safety, increase the service life at the labour aircraft in a large number as far as possible.Therefore to the challenge problem of carrying out in time at aircrafts such as using as a servant aircraft, safety assessment quick and robotization becomes a urgent need solution.

As everyone knows, long-term its fuselage of aircraft that uses tends to occur burn into air gap, splitting, takes off number of drawbacks such as riveting, crackle.In above-mentioned defective, corrosion and the crackle hidden in the corrosion of fuselage and crackle, especially the multilayer bridging arrangement can cause that the many places of fuselage are damaged, and then influence the safe flight of aircraft.Therefore developing the fatigue crack that a kind of low cost, can detecting of changing fast and automatically hide in the multi-layered conductive structure and the system of corrosion presses for.

Detection technique at fatigue crack and corrosion default has a lot.Consider accessibility, detection speed and detection cost, selecting eddy detection technology for use is rational selection.

Conventional eddy current testing instrument adopts coil as detection probe, it can solve problems such as some top layers and subsurface stratum defective, thickness measure, but be difficult to be applied to detect darker defective, especially defectives such as the small size crackle hidden of multi-layered conductive structure deep layer such as airframe and corrosion, its subject matter is that the coil type detection probe is all not high enough for the susceptibility and the spatial resolution of sandwich construction inherent vice.In order to detect deep zone defect, need to adopt the excitation frequency (low frequency) that reduces detection system, the diameter measures such as (big probes) that strengthens magnetic test coil, but it is very low to do the sensitivity that can cause magnetic test coil like this, resolution is not high, the local detection signal distortion increases, less than the problems such as defective omission of magnetic test coil diameter.Based on the eddy current testing device of giant magnetoresistance sensor detection probe, then can solve an above-mentioned difficult problem well.

Summary of the invention

Purpose of the present invention just provides a kind of high sensitivity, high-resolution eddy current testing device based on giant magnetoresistance sensor, it not only can solve the soluble problem of conventional coil type detection probe eddy current instrument, and be used for detecting nexine and the defectives such as deep layer fatigue crack and corrosion that multi-layered conductive structure is hidden, detect the degree of depth and can reach 15mm, have remarkable superiority.

Hardware ingredient and annexation based on the eddy current testing device of giant magnetoresistance sensor are: PC and singlechip controller, signal generating circuit I, power amplification circuit, probe I, differential amplifier circuit, phase-sensitive detector (PSD) I, the system balancing circuit I, amplifying circuit I, data collecting card, PC connects, power amplification circuit and probe II, differential amplifier circuit, phase-sensitive detector (PSD) II, system balancing circuit I I, amplifying circuit II, the data acquisition card connection, probe II and XY scanner, the XY scanning monitor connects, signal generating circuit I and waveform transformation circuit I, phase-sensitive detector (PSD) I connects, singlechip controller and signal generating circuit II, waveform transformation circuit I I, phase-sensitive detector (PSD) II connects.

Described eddy current testing device based on giant magnetoresistance sensor, its probe has drive coil, is fixed with giant magnetoresistance sensor in coil.

Giant magnetoresistance sensor is that core constitutes with SS501A, the 1st pin of SS501A connects positive 5v power supply, the 2nd pin of SS501A is connected with the 3rd pin of INA118, the 3rd pin of SS501A connects simulation ground, the 4th pin of SS501A is connected with the 2nd pin of INA118, the 1st pin of INA118 is connected with the 8th pin of INA118 by first resistance, the 4th pin of INA118 connects negative 5v power supply, the 7th pin of INA118 connects positive 5v power supply, the 5th pin of INA118 connects simulation ground, and the 6th pin of INA118 is connected with the input end of differential amplifier circuit.

Signal generating circuit is to be that core constitutes with AD9832, the 1st pin of AD9832 connects simulation ground by first resistance, the 2nd pin of AD9832, the 3rd pin connects simulation ground by first electric capacity, the 4th pin of AD9832 connects positive 5v power supply, the 5th pin of AD9832 connects digitally, the 7th pin of AD9832, the 8th pin respectively with the SCLK of single-chip microcomputer SPI module, the SDATA pin connects, the 9th pin of AD9832, the 10th pin, the 11st pin, the 12nd pin is connected with 4 pins of single-chip microcomputer IO mouth respectively, the 13rd pin of AD9832 connects simulation ground, the 14th pin of AD9832 is connected with simulation ground by second resistance, the 15th pin of AD9832 and positive 5v, first pin of the 3rd electric capacity connects, the 16th pin of AD9832 is by second electric capacity and positive 5v, first pin of the 3rd electric capacity connects, the crus secunda of the 3rd electric capacity connects simulation ground, the 6th pin of AD9832 is connected with the 3rd pin of active clock, the 4th pin of active clock connects positive 5v power supply, and the 2nd pin of active clock connects digitally, and the 1st pin of active clock is unsettled.

The circuit connecting relation of system balancing circuit is: trigger button is connected with monostable circuit I, binary counter, D/A converter, voltage amplifier, instrumentation amplifier, zero-crossing comparator, monostable circuit III, square-wave generator, binary counter; Monostable circuit II is connected with square-wave generator, binary counter.

Advantage of the present invention:

1, adopted detection probe, greatly improved sensitivity and spatial resolution when eddy current testing device detects deep zone defect based on giant magnetoresistance sensor.The magnetic field sensor formulas such as traditional coil type and HALL of comparing are popped one's head in, the probe of using giant magnetoresistance sensor has the following advantages: (1), because giant magnetoresistance sensor is directly to detect magnitude of field intensity, and the not influence of excited target frequency still has high sensitivity under low frequency; (2), sensor can do very for a short time, because of defective exists the detection signal distortion that causes also very little; (3), temperature stability is good, thereby make that the measurement result temperature influence is little, can adapt to all temps and change big condition of work; (4) compare with numerous magnetic field sensors such as SQUID, FLUXGATE, AMR, HALL, the giant magnetoresistance sensor cost is low, can measure that magnetic field range is wide, signal to noise ratio (S/N ratio) is high, low in energy consumption, thereby cost performance is the highest.

2, introduced the system balancing circuit,, effectively eliminated the detection error that zero point drift causes, improved accuracy of detection with the zero point drift of restraining device.

3, signal generating circuit has adopted the DDS technology, and frequency of operation is easy to adjust, has improved the stability of pumping signal simultaneously.

Description of drawings

Fig. 1 is based on the eddy detection system theory diagram of giant magnetoresistance sensor;

Fig. 2 is a sonde configuration schematic cross-section of the present invention;

Fig. 3 is a sonde configuration vertical view of the present invention;

Fig. 4 is giant magnetoresistance sensor output circuit figure of the present invention;

Fig. 5 is signal generating circuit figure of the present invention;

Fig. 6 is system balancing circuit theory diagrams of the present invention;

Fig. 7 is a system software process flow diagram of the present invention.

Embodiment

Apparatus of the present invention have adopted the high sensitivity based on giant magnetoresistance sensor, high-resolution detection probe, and its frequency of operation can be regulated in the 0-10KHz scope continuously, can be used for the detection of the multi-layered conductive structure deep zone defect of key areas such as Aero-Space.

At first, probe 1 and probe 2 are separately fixed at as requested the top of standard component and measured piece; Press the triggering zero-setting button, make instrument be output as zero; Determine controlled variable such as excitation frequency, gain, and be downloaded to singlechip controller under inciting somebody to action; The sweep velocity of scanner is set, and starts the scanner controller.The motion of scanner controller gated sweep instrument makes probe 2 scan measured piece as requested.

Thereafter, signal generating circuit I, II produce the two-way orthogonal sinusoidal wave, and wherein the output signal of exiting signal generating circuit I is through power amplification rear drive probe I, probe II.Contain the probe I of giant magnetoresistance sensor, the variation that probe II detects magnetic field.The two-way output signal of probe I, probe II is divided into two-way behind differential amplifier circuit: the one tunnel sends into phase-sensitive detector (PSD) I with reference to square-wave signal I and carries out multiplying with probe I, probe II pumping signal same frequency are synchronous, another road and probe I, probe II pumping signal same frequency but the reference square-wave signal II of quadrature sends into phase-sensitive detector (PSD) II carries out multiplying.Because the effective constituent of the differential output signal of probe I, probe II is and the sinusoidal signal of reference signal same frequency that the difference frequency of the two product partly is a direct current signal.And the product of various noise signals and reference signal is a high-frequency signal, can effectively suppress The noise by the low-pass filter circuit in the phase-sensitive detector (PSD).This shows that the noise of being introduced by the sensor amplifying circuit can not worsen the signal to noise ratio (S/N ratio) of metering circuit output signal.

If be respectively through the sensor output signal and the reference signal of amplifying:

S(t)＝x(t)+N(t)＝Asin(ωt+θ+φ)+N(t) (1)

y(t)＝Bsin(ωt+θ) (2)

Then their cross correlation function is:

$R_{\mathrm{sy}}\left(0\right)=\frac{1}{T}\underset{0}{\overset{T}{\∫}}S\left(t\right)y\left(t\right)\mathrm{dt}=\frac{1}{2}\mathrm{AB}\cos \left(\mathrm{\φ}\right)---\left(3\right)$

From (3) formula as can be seen, noise contribution is not owing to having correlativity with reference signal, to the not influence of result of related operation.Phase-sensitive detector (PSD) is exactly by relevant link of introducing in signal processing circuit, thereby greatly improves the noise inhibiting ability of circuit.Because interchannel noise that amplifying circuit is introduced and reference signal do not have correlativity yet and are fully suppressed by phase-sensitive detector (PSD), so can improve the resolution of system by the gain that improves amplifying circuit and need not worry that amplifying circuit introducing noise effect detects the precision of data.

As shown in Figure 1, the probe that has metering circuit plate and embedded giant magnetoresistance sensor based on the eddy current testing device of giant magnetoresistance sensor.Hardware ingredient and annexation based on the eddy current testing device of giant magnetoresistance sensor are: PC and singlechip controller, signal generating circuit I, power amplification circuit, probe I, differential amplifier circuit, phase-sensitive detector (PSD) I, the system balancing circuit I, amplifying circuit I, data collecting card, PC connects, power amplification circuit and probe II, differential amplifier circuit, phase-sensitive detector (PSD) II, system balancing circuit I I, amplifying circuit II, the data acquisition card connection, probe II and XY scanner, the XY scanning monitor connects, signal generating circuit I and waveform transformation circuit I, phase-sensitive detector (PSD) I connects, singlechip controller and signal generating circuit II, waveform transformation circuit I I, phase-sensitive detector (PSD) II connects.The frequency of operation of apparatus of the present invention can be regulated in the 0-10KHz scope continuously, can be used for the detection of the multi-layered conductive structure deep zone defect of key areas such as Aero-Space.

The present invention adopts the phase sensitive detection technology of the feeble signal extraction that is specifically designed under the strong noise background can improve system signal noise ratio more than the 80db.Phase-sensitive detector (PSD) is made up of multiplier and low-pass filter.Multiplier can be realized by on-off circuit, analog multiplier and digital information processing system.It is that core constitutes that phase-sensitive detection circuit of the present invention has adopted with AD835 and OP07.

The identical signal generating circuit I of circuit, II are that core realizes with a slice based on the AD9832 of DDS technology respectively.Two AD9832 adopt same active clock to drive, singlechip controller writes identical frequency control word to two AD9832, but the phase control words difference of write signal generation circuit I, II, the phase control words of the two will make that the signal phase difference that produces is 90 °, the 9th pin (FSYNC) by AD9832 makes two AD9832 work synchronously, thereby not only frequency is identical for the two-way sine wave that guarantee to produce, and phase place is 90 °, i.e. the two paths of signals quadrature.The output of signal generating circuit I provides excitation for behind power amplification circuit probe I, probe II.

Sonde configuration schematic cross-section and vertical view based on giant magnetoresistance sensor are distinguished as shown in Figures 2 and 3.Probe has coil, is fixed with giant magnetoresistance sensor in coil.

A very crucial problem of eddy detection technology practicability is the measurement in magnetic field.The sensor that a variety of measurements magnetic field is arranged at present.Based superconductive quantum interference (SQUID) is though the magnetic field sensor sensitivity of principle is very high, and its complex structure, bulky and cost an arm and a leg is used for medical treatment and magnetism of material research field at present more; That the magnetic field sensor of coil type is made is simple, cost is low, but aspect static state or low frequency magnetic field measurement scarce capacity; Magnetic field sensor based on the fluxgate principle has higher resolution and good robustness, but volume big, cost an arm and a leg, frequency response is poor; Anisotropic magnetoresistive sensor (AMR) remolding sensitivity is higher, and response is fast, but that the AMR magnetic field sensor can be measured magnetic field range is little, poor anti jamming capability; Though the Hall element cost is low, to use very extensively, the remolding sensitivity of Hall element is lower, the skew big, temperature stability is low; Nearest business-like giant magnetoresistance sensor is then not only highly sensitive, temperature stability is good, and cost is also lower, and antijamming capability is strong, and it is big to measure magnetic field range.Dissimilar magnetic field sensor performance comparative control tables as shown in Table 1 and Table 2.

	GMR	HALL	AMR
				Size	Little	Little	Greatly
Signal level	Greatly	Little	In
				Sensitivity	High	Low	High
Temperature stability	High	Low	In
				Power consumption	Low	Low	High
Cost	Low	Low	High

The comparison of the dissimilar magnetic field sensors of table 1

The detectable magnetic field range of table 2 different magnetic field sensor and the market price

The magnetic field sensor formulas such as traditional coil type and HALL of comparing are popped one's head in, the probe of using giant magnetoresistance sensor has the following advantages: (1), because giant magnetoresistance sensor is directly to detect magnitude of field intensity, and the not influence of excited target frequency still has high sensitivity under low frequency; (2), sensor can do very for a short time, the detection signal distortion that is caused is also very little; (3), temperature stability is good, thereby make that the measurement result temperature influence is little, can adapt to all temps and change big condition of work; (4) compare with numerous magnetic field sensors such as SQUID, FLUXGATE, AMR, HALL, the giant magnetoresistance sensor cost is low, can measure that magnetic field range is wide, signal to noise ratio (S/N ratio) is high, low in energy consumption, thereby cost performance is the highest.

As shown in Figure 4, giant magnetoresistance sensor is that core constitutes with SS501A, the 1st pin of SS501A connects positive 5v power supply, the 2nd pin of SS501A is connected with the 3rd pin of INA118, the 3rd pin of SS501A connects simulation ground, the 4th pin of SS501A is connected with the 2nd pin of INA118, the 1st pin of INA118 is connected with the 8th pin of INA118 by first resistance R 1, the 4th pin of INA118 connects negative 5v power supply, the 7th pin of INA118 connects positive 5v power supply, the 5th pin of INA118 connects simulation ground, and the 6th pin of INA118 is connected with the input end of differential amplifier circuit.

Probe 1 based on giant magnetoresistance sensor is identical with the structure and the circuit theory of probe 2.

As shown in Figure 5, signal generating circuit I is that core constitutes with AD9832, the 1st pin of AD9832 connects simulation ground by first resistance R 1, the 2nd pin of AD9832, the 3rd pin connects simulation ground by first capacitor C 1, the 4th pin of AD9832 connects positive 5v power supply, the 5th pin of AD9832 connects digitally, the 7th pin of AD9832, the 8th pin respectively with the SCLK of single-chip microcomputer SPI module, the SDATA pin connects, the 9th pin of AD9832, the 10th pin, the 11st pin, the 12nd pin is connected with 4 pins of single-chip microcomputer IO mouth respectively, the 13rd pin of AD9832 connects simulation ground, the 14th pin of AD9832 is connected with simulation ground by second resistance R 2, the 15th pin of AD9832 and positive 5v, first pin of the 3rd capacitor C 3 connects, the 16th pin of AD9832 is by second capacitor C 2 and positive 5v, first pin of the 3rd capacitor C 3 connects, the crus secunda of the 3rd capacitor C 3 connects simulation ground, and the 6th pin of AD9832 is connected with the 3rd pin of active clock, and the 4th pin of active clock connects positive 5v power supply, the 3rd pin of active clock connects digitally, and the 1st pin of active clock is unsettled.

Signal generating circuit II is that core constitutes with AD9832, and its principle of work and circuit connect identical with signal generating circuit I.

The signal output of signal generating circuit I is through power amplification rear drive probe I, probe II.It is the BTL type power amplification circuit of core that power amplification circuit of the present invention has adopted with integrated power amplification chip TDA2030 and general amplifier NE5532.

The output of signal generating circuit I, II becomes square wave through the waveform transformation circuit with sine wave.Waveform transformation circuit of the present invention is that the AD8564 with TTL and CMOS level compatibility is that core realizes.

Signal through differential amplification probe I, II output divides two-way to send into phase-sensitive detector (PSD) I, II.Another road input signal of phase-sensitive detector (PSD) I be with the probe I, the probe II the synchronous square wave reference signal of pumping signal same frequency I; Another road input signal of phase-sensitive detector (PSD) II for the probe I, the probe II the pumping signal same frequency but phase differential is 90 ° square wave reference signal II.The difference frequency of two input signal products of phase-sensitive detector (PSD) is a direct current signal partly, and the product of various noise and reference signal is a HFS.After low-pass filter circuit in phase-sensitive detector (PSD) I, II was handled, the output signal of phase-sensitive detector (PSD) I, II was a direct current, and its amplitude size is corresponding with parameter to be detected in the measured piece.This two-way direct current signal is sent into PC after being converted to digital signal by data collecting card respectively after system balancing circuit I, II and amplifying circuit I, II handle.

The problem that often runs in the Analog Circuit Design is exactly zero point drift.The concrete manifestation of zero point drift is that the progressive of instrument working point changes slowly.It is a crucial factor that influences the instrument detecting precision, deals with improperly and will not reach design accuracy, serious even operate as normal that influence system.In general, the reason that produces zero point drift has two: one is that temperature is floated, the one, and in time, float.In above-mentioned two factors, it is the major part of system's zero point drift that temperature is floated.And the reason that causes zero point drift is a lot, for example the variation of the change of the variation of supply voltage, environment temperature, humidity and the aging circuit element parameter that causes etc.Zero point drift also exists in condenser coupling amplifier, but because the stopping direct current effect of coupling capacitance, this variation slowly can not be sent to next stage, and be little to influence circuit.So, should focus on the direct current amplifier section to what overcome circuit zero point drift, because at the direct current amplification stage, the drift of the dc point of previous stage, can be added to the next stage amplifier by coupled circuit, like this, drifting about after one-level is amplified has later just increased, and very big influence has been caused in the next stage working point.Based on this, we have designed inhibition zero point drift circuit, and its principle of work as shown in Figure 5.The circuit of system balancing circuit is: trigger button is connected with monostable circuit I, binary counter, D/A converter, voltage amplifier, instrumentation amplifier, zero-crossing comparator, monostable circuit III, square-wave generator, binary counter; Monostable circuit II is connected with square-wave generator, binary counter.

As shown in Figure 7, in PC, at first image data is carried out pre-service, because in the multi-layered conductive structure eddy current scanning testing of reality, may be because of contactless detection, probe signal is more weak, lift from that distance (probe bottom is to the distance on measured piece surface) changes, the difference of material properties and the factor affecting such as noise of industrial processes, faint useful signal and noise are mingled in the data of collection.Apparatus of the present invention have adopted based on analysis method of wavelet packet carries out signal noise silencing.

According to pretreated " totally " data, call the measured data of master body in the database then, select least square, support vector machine (Support Vector Machine) scheduling algorithm to carry out Inversion Calculation, draw the parameter to be detected of measured piece.According to inversion result measured piece carried out Performance Evaluation, determine whether to send warning message according to assessment result thereafter.

Claims (4)

1, a kind of eddy current testing device based on giant magnetoresistance sensor, it is characterized in that, PC successively with singlechip controller, signal generating circuit I, power amplification circuit, probe I, differential amplifier circuit, phase-sensitive detector (PSD) I, the system balancing circuit I, amplifying circuit I, data collecting card, PC is connected, power amplification circuit successively with the probe II, differential amplifier circuit, phase-sensitive detector (PSD) II, system balancing circuit I I, amplifying circuit II, data collecting card is connected, probe II and XY scanner, the XY scanning monitor connects, signal generating circuit I and waveform transformation circuit I, phase-sensitive detector (PSD) I connects, singlechip controller successively with signal generating circuit II, waveform transformation circuit I I, phase-sensitive detector (PSD) II is connected, probe has coil, be fixed with giant magnetoresistance sensor in coil, in eddy current testing device, comprise standard component, and will pop one's head in I and the probe II that pops one's head in is separately fixed at above standard component and the measured piece when detecting.

2, a kind of eddy current testing device according to claim 1 based on giant magnetoresistance sensor, it is characterized in that, described giant magnetoresistance sensor is that core constitutes with SS501A, the 1st pin of SS501A connects positive 5v power supply, the 2nd pin of SS501A is connected with the 3rd pin of INA118, the 3rd pin of SS501A connects simulation ground, the 4th pin of SS501A is connected with the 2nd pin of INA118, the 1st pin of INA118 is connected with the 8th pin of INA118 by first resistance R 1, the 4th pin of INA118 connects negative 5v power supply, the 7th pin of INA118 connects positive 5v power supply, and the 5th pin of INA118 connects simulation ground, and the 6th pin of INA118 is connected with the input end of differential amplifier circuit.

3, a kind of eddy current testing device according to claim 1 based on giant magnetoresistance sensor, it is characterized in that, described signal generating circuit is to be that core constitutes with AD9832, the 1st pin of AD9832 connects simulation ground by first resistance R 1, the 2nd pin of AD9832, the 3rd pin connects simulation ground by first capacitor C 1, the 4th pin of AD9832 connects positive 5v power supply, the 5th pin of AD9832 connects digitally, the 7th pin of AD9832, the 8th pin respectively with the SCLK of single-chip microcomputer SPI module, the SDATA pin connects, the 9th pin of AD9832, the 10th pin, the 11st pin, the 12nd pin is connected with 4 pins of single-chip microcomputer IO mouth respectively, the 13rd pin of AD9832 connects simulation ground, the 14th pin of AD9832 is connected with simulation ground by second resistance R 2, the 15th pin of AD9832 and positive 5v, first pin of the 3rd capacitor C 3 connects, the 16th pin of AD9832 is by second capacitor C 2 and positive 5v, first pin of the 3rd capacitor C 3 connects, the crus secunda of the 3rd capacitor C 3 connects simulation ground, the 6th pin of AD9832 is connected with the 3rd pin of active clock, the 4th pin of active clock connects positive 5v power supply, the 2nd pin of active clock connects digitally, and the 1st pin of active clock is unsettled.

4, a kind of eddy current testing device according to claim 1 based on giant magnetoresistance sensor, it is characterized in that the circuit of described system balancing circuit is: trigger button is connected with monostable circuit I, binary counter, D/A converter, voltage amplifier, instrumentation amplifier, zero-crossing comparator, monostable circuit III, square-wave generator, binary counter successively; Monostable circuit II is connected with square-wave generator, binary counter successively.

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