CN102620638B - Aviation-specific displacement sensor measuring method - Google Patents

Abstract

The invention discloses an aviation-specific displacement sensor measuring method, which includes the following steps: (1) establishing a measurement circuit with a magnetic induction sensor composed of an internal resistor r and an inductor L; (2) establishing a lookup table, and using an ADC (analog-to-digital converter) for measuring inductor discharge voltage values U1 and U2 corresponding to two fixed delay times T1 and T2 respectively to acquire discharge voltage equations of the r-L circuit: U1 (T1, R, r, L) and U2 (T2, R, r, L); (3) compressing the lookup table, and measuring a displacement sensor according to the compressed lookup table . The aviation-specific displacement sensor measuring method has the advantages that the system can work in the army standard temperature ranges, the stability, the reliability and the real-time of the system measurement can be improved, no floating point arithmetic is required, and the CPU (central processing unit) or MCU (microprogrammed control unit) hardware resources are omitted.

Description

A kind of measuring method of aviation dedicated bit displacement sensor

Technical field:

The invention belongs to sensor field, relate to a kind of driving and detection method of passive sensor, especially a kind of driving and detection method of passive electrical perception non-contact displacement transducer (Aerospace Inductive Proximity Sensors) of aviation field, and use look-up table to calculate the optimization method of inductance value, be particularly useful for carrying out the r-L circuit charging and discharging curve look-up table calculating of sample with look-up table and compress.

Background technology:

Because non-contact displacement transducer possesses the reliability higher than mechanical shift switch and MTBF (average no-failure operation hourage), be applied to more and more in the Mechatronic Systems of aviation field.Comprise the undercarriage of all kinds of aircrafts, passenger-cargo hatch door, aileron, trhrust-reversal device etc.The aircraft type relating to comprises large-scale airline carriers of passengers, transporter etc.

The non-contact displacement transducer using in industrial circle is normally active, and volume is large, and coil-winding is thick, detects by strong current drive, externally exports digital switch signal, and it is relatively convenient to use.But the driving of the large electric current of this sensor and control mode cannot meet the general electromagnetic compatibility standard of aviation field.In aviation field, cannot adopt the sensor of industrial circle.

The main devices of the non-contact displacement transducer that aviation field uses is at present provided by two companies, is respectively Crane (U.S.) and Crouzet (France).Their principle of products is identical with inner structure, major parameter index is similar.Sensor is passive sensor, and its internal circuit is simple in structure, is formed by one group of coil winding.As shown in Figure 1, the equivalent-circuit model of proximity displacement transducer is in series by pure resistance r and inductance L.Its inductance value and coil through-current capability be all much smaller than industrial sensor, inductance maximal value is no more than 10mH, coil the is through-flow 20mA of being no more than.

Driving and the detection method of the passive electrical perception non-contact displacement transducer that industry is popular at present mainly contain two kinds: analogy aerotriangulation and digital photogrammetry.

Analogy aerotriangulation is that cell winding is applied after pulse excitation, realizes the test to inductance value thereby contrast R-L discharge curve threshold value by comparer.Further near the judgement of inductance value being judged to sensor, whether there is target object to approach.This way is the most frequently used means of current industry, and circuit is simple, reliable.But because sensor internal resistance temperature is floated greatly, cause measuring system operating temperature range little, have the contradiction between working temperature to be solved and measuring accuracy.

Digital photogrammetry applies sine-wave excitation to sensor circuit conventionally, by voltage and current waveform sampling, utilizes Fast Fourier Transform (FFT) (FFT) algorithm to obtain voltage and current phase differential, calculates the inductance value L of sensor.Eliminate the temperature of sensor internal resistance by calculating and float, eliminate the measuring error that environment temperature is brought, extended operating temperature range.But the method Measurement sensibility is poor, be subject to that external electromagnetic is bothered, real-time is poor.

Summary of the invention:

The object of the invention is to overcome the shortcoming of above-mentioned prior art; a kind of measuring method of aviation dedicated bit displacement sensor of digital-to-analogue mixing is provided; the method compatibility the advantage of two kinds of traditional measurement method mensurations: guarantee that system works in army mark temperature range; improve stability, reliability and the real-time of systematic survey simultaneously; and there is not floating-point operation, saved CPU or MCU hardware resource.In order to ensure the accurate enforcement of above method, the present invention has designed the appraisal procedure of concrete grammar, the loop up table quantization error of calculating two-dimensional look-up table and has significantly compressed the method for look-up table size.

The object of the invention is to solve by the following technical programs:

A measuring method for aviation dedicated bit displacement sensor, in accordance with the following steps:

(1) set up metering circuit: magnetic induction sensor is made up of internal resistance r and inductance L, wherein internal resistance r changes with variation of ambient temperature, and inductance L is relevant with near the metal target degree of closeness of sensor; With current-limiting resistance R, magnetic induction sensor, the controlled switch formation displacement sensor circuit of series connection; Voltage measurement Nodes between current-limiting resistance R and internal resistance r arranges analog to digital converter (ADC).

(2) set up look-up table: use ADC to measure the first voltage measuring value U1 that the first fixed delay time T1 is corresponding; Use ADC to measure the second voltage measured value U2 that the second fixed delay time T2 is corresponding; Obtain sparking voltage equation U1 (T1, R, r, L) and the U2 (T2, R, r, L) of r-L circuit; Wherein T1, T2, R is constant, two establishing equation internal resistance r of simultaneous and inductance L are about the look-up table of sparking voltage sampled value U1 and U2.

(3) compression look-up table, utilizes the look-up table after compression to carry out the measurement of displacement transducer: taking 12 ADC as example, complete two-dimensional look-up table is of a size of 2 ¹²× 2 ¹², memory space 16M unit.For making the present invention possess practicality, must find effective compressing way of look-up table just can make this method possess practicality.The distribution characteristics that makes full use of sampled value in side circuit [U1, U2] can effectively be compressed look-up table.

Described step (2) is:

Between the first fixed delay time T1 and the second fixed delay time T2, controlled switch is in opening, and inductance L is slowly discharged by inside and outside resistance; Initial time T0 controlled switch closure, inductance L starts charging afterwards, and its electric current is:

$i=\frac{U_{\max }}{R+r}[1-e^{-\frac{R+r}{L}\×T}]---\left(1\right)$

The voltage of voltage measurement node is:

U＝U _max-i×R (2)

Through and obtain:

$U=\frac{U_{\max }}{R+r}[r+R\×e^{-\frac{R+r}{L}\×T}]---\left(3\right)$

The first fixed delay time T1 and the second fixed delay time T2 control ADC and sample, and corresponding the first voltage measuring value U1 and second voltage measured value U2 are respectively:

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_1=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T_1}]\\ {\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA0000146058760000051.png,HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_2=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T_2}]\end{array}\right.---\left(4\right)$

Described formula (4) adopts optimization method to solve, and process is as follows:

Set up objective function:

min：(U ₁-U ₁(L，r)) ²+(U ₂-U ₂(L，r)) ²

s.t.1：r＞0 (5)

s.t.2：L＞0

Through and obtain:

$\min :{(U_1(R+r)-U_{\max }(r+R\&times;e^{-\frac{R+r}{L}\&times;T_1}))}^2+{(U_2(R+r)-U_{\max }(r+R\&times;e^{-\frac{R+r}{L}\&times;T_2}))}^2$

s.t.1：r＞0 (6)

s.t.2：L＞0

Wherein voltage max U _max(2 ⁿ-1, n by the figure place of use ADC), current-limiting resistance R, the first fixed delay time T1 and the second fixed delay time T2 be constant.

Can prove, the sampled value [U1, U2] that one group of T1 of every acquisition and T2 moment obtain, substitution equation (4), equation has and only has unique solution [L, r].Utilize equation (6) can obtain the numerical solution of [L, r].

Travel through all scopes of sampled value [U1, U2], obtain successively the numerical solution of each [U1, U2] corresponding [L, r], just obtained look-up table.

Described step (3) is:

In order to make the present invention possess practicality, need to make full use of sampled value [U1, U2] and be subject to the various constraints of metering circuit physical model, look-up table is compressed.Above-mentioned constraint comprises:

1.T1 and T2 are artificial definite, so there is the constraint condition of T1 < T2.Provable U (T) is monotone decreasing function, so U1 is greater than U2.

2.[L, r] be the distribution parameter in actual physics model, can only be arithmetic number.Can prove under the constraint of equation (1), can cause [L, r] to comprise even plural number of negative from arithmetic number [U1, U2] space to [L, r] spatial mappings.Being combined in actual samples of these [U1, U2] there will not be.

U1 in look-up table can be less than to U2, and [L, the r] that can make to obtain point of comprising negative or plural number removes and can reduce look-up table scale.

By U _maxand sampled value (U1, T1) and (U2, T2) substitution equation (4) and do arrange obtain:

$\left\{\begin{array}{c}L=-\frac{(R+r)\&times;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HDA0000146058760000061.png"\; state="\{\{state\}\}">T</figure-callout>}}_1}{\log [\frac{U_1}{(2^n-1)R}(R+r)-\frac{r}{R}]}\\ L=-\frac{(R+r)\&times;{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000146058760000051.png,HDA0000146058760000061.png"\; state="\{\{state\}\}">T</figure-callout>}}_2}{\log [\frac{U_2}{(2^n-1)R}(R+r)-\frac{r}{R}]}\end{array}\right.---\left(7\right)$

Through and

${[\frac{U_1}{(2^n-1)R}(R+r)-\frac{r}{R}]}^{\left(\frac{T_2}{T_1}\right)}=[\frac{U_2}{(2^n-1)R}(R+r)-\frac{r}{R}]---\left(8\right)$

In above formula, R, r are arithmetic number and T1 < T2, are arithmetic numbers if separate [L, r], will satisfy condition:

$1>[\frac{U_1}{(2^n-1)R}(R+r)-\frac{r}{R}]>[\frac{U_2}{(2^n-1)R}(R+r)-\frac{r}{R}]>0---\left(9\right)$

That is:

$(2^n-1)>U_1{>U}_2>\frac{(2^n-1)r}{R+r}---\left(10\right)$

According to the constraint condition of above formula, adopt the method for traversal to determine the scope of [U1, U2], method is as follows:

In actual conditions, r follows temperature variation in wire and the distributed resistance that changes, gets its minimum value r in system allows working range _minsubstitution formula (X2), determines sampled value U1, the minimum value U1 that may occur _min.

By U1 _minafter substitution formula (8), arrange and obtain:

${\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA0000146058760000051.png,HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_{2\min }=\frac{{[\frac{{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_{1\min }}{(2^n-1)R}(R+r)-\frac{r}{R}]}^{\left(\frac{T_2}{T_1}\right)}+\frac{r}{R}}{(R+r)}\&times;(2^n-1)R---\left(11\right)$

Regard above formula as U2 _minabout the function of r, obtain corresponding U2 in distributed resistance r span _mincodomain scope.

[U1, U2] is the positive integer obtaining through ADC sampling, and the above method of Reusability obtains U1 successively _min, U1 _min+ 1, U1 _min+ 2, U1 _min+ 3...... is until (2 ⁿ-1) U2 codomain scope corresponding to difference.The set of these points is exactly the field of definition scope of look-up table.

To in the point in the field of definition of look-up table successively substitution equation (6), solve the solution [L, r] of its correspondence, just obtained the look-up table after compression.The extraneous point of field of definition of look-up table can not obtain in actual sampling, so without record.

By being carried out to mathematical analysis, formula (11) can obtain as drawn a conclusion:

The value of the main and divider resistance R of the scale of the look-up table after T1, T2 are selected after compression, and the variation size of distributed resistance r in system efficient working range is relevant.

In actual applications, measured to liking the inductance with plain conductor coiling, the temperature of its distributed resistance r is floated coefficient and is caused more greatly its span larger, is unfavorable for look-up table compression.But the numerical value of r conventionally can be very not large, can select high-accuracy, low temperature ticket divider resistance R much larger than r span, can obtain good look-up table ratio of compression.Concrete numerical value can reference example.

The present invention is for systems such as the undercarriage of all kinds of Aeronautics and Astronautics devices, passenger-cargo hatch door, aileron, trhrust-reversal devices.Along with opening gradually of civil aviaton and military market, the present invention is widely used, and possesses larger economic benefit and social benefit.Compared to existing technology and product, the present invention's advantage that possesses skills, improves no-failure operation hourage, can improve the market share of non-contact displacement transducer series products and secondary development product thereof.Meanwhile, multidimensional lookup table compression method, can effectively reduce scale and the cost of relevant control detection system, improves system stability.Application prospect is extensive, and economic benefit and social benefit are large.

Brief description of the drawings:

Fig. 1 is sensor equivalence circuit model figure;

Fig. 2 is that sensor drives and detection module theory diagram;

Fig. 3 is sensor drive driving circuit signal output waveform figure;

Fig. 4 is the response wave shape figure of sensor during near target;

Response wave shape figure when Fig. 5 is sensor wide;

Response wave shape figure when Fig. 6 is sensor distance target 1mm～2mm;

Fig. 7 is discharge curve;

All curves that Fig. 8 puts by (U1, T1);

All curves that Fig. 9 puts by (U2, T2);

Figure 10 r-L restriction relation;

Figure 11 r-U2 restriction relation;

The curve of Figure 12 and selected U1 has the curve family of the U2 of arithmetic number focus;

The mapping of Figure 13 coordinate system;

The mapping of Figure 14 coordinate system;

The effective table area of Figure 15;

The solution of Figure 16 function L (U1, U2) in effective field of definition.

Embodiment:

Below in conjunction with accompanying drawing, the present invention is described in further detail:

The internal circuit configuration of sensor involved in the present invention is simple, is only formed by one group of wire coil coiling.As shown in Figure 1, its equivalent-circuit model is by the internal resistance r in telefault and inductance L (stray capacitance can be ignored) in series.Wherein internal resistance r changes with variation of ambient temperature; Inductance L is relevant with near the metal target degree of closeness of sensor.If sensor outside has metal target close, make near its electromagnetic field distribution marked change, sensor equivalence inductance increases, and can judge by driving and detecting inductance value whether outside has metal target to approach.

Taking Crouzet company product sensor as example, inductance changing value be 4.5mH (away from) to 5.5mH (approaching), substantially do not vary with temperature.Electrical resistance temperature variation, term of reference be 10 Ω to 15 Ω, substantially not with degree of closeness change change.

Driving sensor, and the induction reactance that detects its equivalent inductance just can be determined the degree of closeness of this sensor.

In order to reach target effect of the present invention, drive and detection method requirement:

1). drive current peak value is no more than 15mA, crosses the requirement that cannot meet by force industry EMC test; Also should not be less than 10mA, a little less than crossing, easily be subject to external electromagnetic environmental interference;

2). sensor mutual inductance rate of change is 2%, needs 5% quantitative measurment index, requires system inductance detection precision 0.1%;

3). the rate of change of sensor internal resistance in army's mark temperature range exceedes 60%.Must consider the warm impact on inductance measurement of floating;

4). in order to improve system reliability, do not use the hardware resources such as CPU, MCU or DSP.

Basic test principle of the present invention as shown in Figure 2.FPGA controls the pulse signal of driving circuit output 0～5V.Through the driving signal of driving circuit output amplitude 0～5V, positive frequency range 2ms, cycle 200Hz, as shown in Figure 3.Fig. 3 has provided sensor drive driving circuit signal output waveform output signal through bleeder circuit, wave filter, sensor, via wave filter ground connection.

If sensor approaches target, in measured node, measured waveform is shown in Fig. 4.If sensor wide, in measured node, measured waveform as shown in Figure 5.If sensor distance target 1mm～2mm, in measured node, measured waveform as shown in Figure 6.

The measured value that uses ADC to obtain twice fixed delay time obtains two voltage measuring value U1 and the U2 of corresponding fixed delay T1 and T2, obtains sparking voltage equation U1 (T1, R, r, L) and the U2 (T2, R, r, L) of r-L circuit.Wherein T1, T2, R (current-limiting resistance) is constant, two equations of simultaneous are obtained internal resistance r and inductance L.

Set up the process of equation:

As shown in Figure 1, between twice measurement, controlled switch is in opening, and inductance L is slowly discharged by inside and outside resistance.T0 moment controlled switch closure, inductance L starts charging afterwards, and its electric current is:

$i=\frac{U_{\max }}{R+r}[1-e^{-\frac{R+r}{L}\&times;T}]---\left(1\right)$

The voltage of voltage measurement node is:

U＝U _max-i×R (2)

Through and obtain:

$U=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T}]---\left(3\right)$

T1 and T2 moment are controlled ADC and sample, and relevant voltage U1 and U2 are respectively:

$\left\{\begin{array}{c}{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_1=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T_1}]\\ {\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA0000146058760000051.png,HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_2=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T_2}]\end{array}\right.---\left(4\right)$

Parameter is selected:

The scope of inductance L is [4.5,5.5] mH; The scope of internal resistance r is [10,15] Ω.

With numeric representation U1 and the U2 of 12 ADC samplings, U _maxbe exactly 4095.

According to limiting condition, the value of current-limiting resistance R is 230 Ω.

As shown in Fig. 7 discharge curve, get internal resistance r scope and inductance L scope intermediate value is set up a discharge curve.In the time that inductance L is discharged to 30%, being the T1 moment, is the T2 moment while being discharged to 60%.T1 value is 10.284 μ s, and T2 value is 24.287 μ s.

Can prove that system of equations (4) has and only have unique solution:

After ADC quantizes, obtain:

$U(R,T,r,L)=\frac{4095}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T}]---\left(5\right)$

U (R, T, r, L) is the monotone decreasing function about R and T, is also the monotonic increasing function about r and L.

Because U (R, T, r, L) is dull continuously, just there is corresponding inverse function, system of equations (4) has solution.

Given one group of (U1, T1) numerical value, formula (4) becomes the restriction relation of r and L.Definition p space is (rp, Lp) set of all curve negotiating points (U1, T1) that can make function U-T, as Fig. 8.

Definition q space is (rq, Lq) set of all curve negotiating points (U2, T2) that can make function U-T, as Fig. 9.

P space and q space are drawn respectively in r-L coordinate, as Figure 10.Article two, the U-T curve that the intersection point of curve is corresponding can pass through point (U1, T1) and point (U2, T2) simultaneously, is solution of equation.L (r) is dull, and both only have at most an intersection point, and system of equations (4) only has at most a solution.

To sum up, system of equations (4) has and only has unique solution.

Equation is that group (4) is transcendental equation, is difficult to obtain the computing formula that counts and separate.Since but prove that it has and only have unique solution, just can use the computing method of iteration to be met the numerical solution that engineering precision needs.

Use optimization method solving equation:

min：(U ₁-U ₁(L，r)) ²+(U ₂-U ₂(L，r)) ²

s.t.1：r＞0 (6)

s.t.2：L＞0

Through and obtain:

$\min :{(U_1(R+r)-U_{\max }(r+R\&times;e^{-\frac{R+r}{L}\&times;T_1}))}^2+{(U_2(R+r)-U_{\max }(r+R\&times;e^{-\frac{R+r}{L}\&times;T_2}))}^2$

s.t.1：r＞0 (7)

s.t.2：L＞0

Travel through all scopes of sampled value [U1, U2], obtain successively the numerical solution of each [U1, U2] corresponding [L, r], just obtained look-up table.In practice, find L numerical value by U1, U2, can determine the state of sensor of interest.

Compression look-up table:

Taking 12 ADC as example, complete two-dimensional look-up table is of a size of 2 ¹²× 2 ¹², memory space 16M unit, practical difficulty.Must find effective compressing way of look-up table just can make this method possess practicality.The distribution characteristics that makes full use of sampled value in side circuit [U1, U2] can effectively be compressed look-up table.

Given (rx, Lx), calculates unique (U1x, U2x) by (7).Ask (rp, Lx) and engineering application is upper by given (U1x, U2x), have in theory and separate and only have unique solution, but can be subject to the constraint of the condition such as physical model and T1 < T2.

U (T) is monotone decreasing function, and T1 < T2 U1 is greater than U2.If given U1 is less than U2, in the solution of equation, at least comprise negative and could change its monotonicity, physically unreasonable.

(5) are converted to the inverse function of U about L:

$\frac{1}{L}=-\frac{\log [\frac{U}{4096R}(R+r)-\frac{r}{R}]}{(R+r)\&times;T}---\left(8\right)$

By upper, the solution of L is likely plural number, unless satisfied condition:

$[\frac{U}{4096R}(R+r)-\frac{r}{R}]>0---\left(9\right)$

That is:

$U>\frac{4096r}{R+r}---\left(10\right)$

If (U1x, U2x) is given improper, (rx, the Lx) solving may comprise even plural number of negative.In fact (U1, the U2) of physics sampling must be rational.Between U1, U2, have restriction relation, make (r, the L) value solving all belong to arithmetic number territory, the intersection point of two curves of Figure 10 is positioned at the first quartile of real number field coordinate system.(U1, the U2) that do not meet constraint there will not be in actual samples, also just without record.

Obtained by sampled value (U1, T1) and (U2, T2):

$\left\{\begin{array}{c}L=-\frac{(R+r)\&times;{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HDA0000146058760000061.png"\; state="\{\{state\}\}">T</figure-callout>}}_1}{\log [\frac{{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_1}{4096R}(R+r)-\frac{r}{R}]}\\ L=-\frac{(R+r)\&times;{\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="HDA0000146058760000051.png,HDA0000146058760000061.png"\; state="\{\{state\}\}">T</figure-callout>}}_2}{\log [\frac{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA0000146058760000051.png,HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_2}{4096R}(R+r)-\frac{r}{R}]}\end{array}\right.---\left(11\right)$

Through and

${[\frac{{\mathrm{<figure-callout\; id="1"\; label="U"\; filenames="HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_1}{4096R}(R+r)-\frac{r}{R}]}^{\left(\frac{T_2}{T_1}\right)}=[\frac{{\mathrm{<figure-callout\; id="2"\; label="U"\; filenames="HDA0000146058760000051.png,HDA0000146058760000061.png"\; state="\{\{state\}\}">U</figure-callout>}}_2}{4096R}(R+r)-\frac{r}{R}]---\left(12\right)$

The set that simultaneously meets (U1, the U2) of (10) and (12) condition makes equation have arithmetic number solution.

According to (12), given U1, the value of r at least will meet certain condition:

$r\&GreaterEqual;\frac{U_{1}R}{U_1-4096}---\left(13\right)$

Can determine r _min.

Determine after U1, and then obtain the restriction relation of U2 (r), as Figure 11.

U2 (r) is monotonic quantity, utilizes the field of definition of r to determine the codomain of U2, and the U2 in this scope and the combination of given U1 all make equation have arithmetic number solution.As shown in Figure 12.

As Figure 13, the essence of computation of table lookup, is the process that U1-U2 coordinate is tied to the mapping of r-L coordinate system.

A process is physics sampling process.In r-L coordinate system, a little can be mapped in U1-U2 coordinate system.

B process is the process of computation of table lookup.In U1-U2 coordinate system, some point can shine upon back in r-L coordinate system.In U1-U2 coordinate system, some point is mapped with to r-L coordinate system and may falls into other quadrant (having negative), or expands in four-dimensional complex number space.

R belongs to [10,15] Ω; L belongs to [4.5,5.5] mH, mapping relations as shown in figure 14:

Obtained the scope of U1 by formula (13), every given U1 numerical value just can utilize the restriction relation of formula (12), obtains the interval of corresponding U2 within the scope of the physical change of r.Obtain successively the scope of U2, determine U1-U2 coordinate system shadow region in Figure 14, draw Figure 15.

Look-up table unit narrows down to 9360 from 4096*4096, table compress 1792 times.

Beneficial effect:

According to Figure 15 (U1, U2) field of definition, utilize formula (4) to obtain successively corresponding L, set up look-up table.L is drawn as Z axis, obtain the image of function L (U1, U2) within the scope of this field of definition, as Figure 16.

Through traversal, the max quantization error of searching middle L is: 6.30153uH, is positioned at U1=2754, U2=1644.

Show that 12 ADC can reach 1.0 ‰ measuring accuracy.L belongs to [4.5,5.5] mH, within the scope of this, can obtain at least 33 grades of effective resolutions.

Based on the principle of the invention, exploitation is for driving and the detection system of non-contact displacement transducer, and system is at-55 DEG C within the scope of 125 DEG C after tested, and overall measurement error is below 1 ‰; All detections and evaluation work are directly sampled by programmable logic device (PLD) control, have avoided the hardware such as CPU or DSP, and retrieve one and be of a size of the look-up table of 10K and realize; This system, by the regulation of GB GJB151A-97, GJB152A-97, is carried out CS114, RE102, RS103 project testing simultaneously, and result meets GJB151A-97, GJB152A-97 requirement.

The above, it is only preferred embodiment of the present invention, not the present invention is done to any pro forma restriction, although the present invention discloses as above with preferred embodiment, but not in order to limit the present invention, any those skilled in the art, do not departing within the scope of technical solution of the present invention, when can utilizing the method for above-mentioned announcement and technology contents to make a little change or being modified to the equivalent embodiment of equivalent variations, in every case be the content that does not depart from technical solution of the present invention, any simple modification of above embodiment being done according to technical spirit of the present invention, equivalent variations and modification, still belong in the scope of technical solution of the present invention.

Claims (3)

1. a measuring method for aviation dedicated bit displacement sensor, is characterized in that, in accordance with the following steps:

(1) set up metering circuit: magnetic induction sensor is made up of internal resistance r and inductance L, wherein internal resistance value r changes with variation of ambient temperature, and inductance value L is relevant with near the metal target degree of closeness of sensor; With current-limiting resistance R, magnetic induction sensor, the controlled switch formation displacement sensor circuit of series connection; Voltage measurement Nodes between current-limiting resistance R and internal resistance r arranges analog to digital converter ADC;

(2) set up look-up table: use analog to digital converter ADC to measure the first fixed delay time T ₁the first corresponding voltage measuring value U ₁; Use analog to digital converter ADC to measure the second fixed delay time T ₂corresponding second voltage measured value U ₂; Obtain the sparking voltage equation U of r-L circuit ₁(T ₁, R, r, L) and U ₂(T ₂, R, r, L); Wherein T ₁, T ₂, R is constant, two establishing equation internal resistance r of simultaneous and inductance L are about sparking voltage sampled value U ₁and U ₂look-up table;

Concrete at the first fixed delay time T ₁with the second fixed delay time T ₂between controlled switch in opening, inductance L is slowly discharged by inside and outside resistance; Initial time T ₀controlled switch closure, inductance L starts charging afterwards, and its electric current is:

$i=\frac{U_{\max }}{R+r}[1-e^{-\frac{R+r}{L}\&times;T}]---\left(1\right)$

The voltage of voltage measurement node is:

U=U _max-i×R （2）

And then obtain:

$U=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T}]---\left(3\right)$

The first fixed delay time T ₁with the second fixed delay time T ₂control analog to digital converter ADC and sample, corresponding the first voltage measuring value U ₁with second voltage measured value U ₂be respectively:

$\left\{\begin{array}{c}{U}_1=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T_1}]\\ U_2=\frac{U_{\max }}{R+r}[r+R\&times;e^{-\frac{R+r}{L}\&times;T_2}]\end{array}\right.---\left(4\right)$

Wherein voltage max U _max, current-limiting resistance R, the first fixed delay time T ₁with the second fixed delay time T ₂for constant; Thereby calculate internal resistance value r and inductance value L;

(3) compression look-up table, utilizes the look-up table after compression to carry out the calculating in sensor measurement process.

2. measuring method as claimed in claim 1, is characterized in that, is proving given sampled value [U ₁, U ₂], system of equations (4) has and only has on the basis of unique solution [L, r], adopts optimization method to solve, and process is as follows:

Set up objective function:

min:(U ₁-U ₁(L,r)) ²+(U ₂-U ₂(L,r)) ²

s.t.1:r>0 （5）

s.t.2:L>0

And then obtain:

$\begin{array}{c}\min :{(U_1(R+r)-U_{\max }(r+R\&times;e^{-\frac{R+r}{L}\&times;T_1}))}^2+{(U_2(R+r)-U_{\max }(r+R\&times;e^{-\frac{R+r}{L}\&times;T_2}))}^2\\ s.t.1:r>0\\ s.t.2:L>0\end{array}---\left(6\right)$

Traversal sampled value [U ₁, U ₂] all scopes, obtain successively each [U ₁, U ₂] numerical solution of corresponding [L, r], just obtain look-up table.

3. measuring method as claimed in claim 2, is characterized in that, utilizes sampled value [U ₁, U ₂] be subject to the various constraints of metering circuit model, look-up table to be compressed, process is as follows:

By U _maxand sampled value (U ₁, T ₁) and (U ₂, T ₂) substitution equation (4) and arrange obtain:

$\left\{\begin{array}{c}L=-\frac{(R+r)\&times;T_1}{\log [\frac{U_1}{(2^n-1)R}(R+r)-\frac{r}{R}]}\\ L=-\frac{(R+r)\&times;T_2}{\log [\frac{U_2}{(2^n-1)R}(R+r)-\frac{r}{R}]}\end{array}\right.$

And then

${[\frac{U_1}{(2^n-1)R}(R+r)-\frac{r}{R}]}^{\left(\frac{T_2}{T_1}\right)}=[\frac{U_2}{(2^n-1)R}(R+r)-\frac{r}{R}]---\left(8\right)$

In above formula, R, r are arithmetic number and T ₁<T ₂, n by the figure place of use ADC, be arithmetic number if separate [L, r], must satisfy condition:

$1>[\frac{U_1}{(2^n-1)R}(R+r)-\frac{r}{R}]>[\frac{U_2}{(2^n-1)R}(R+r)-\frac{r}{R}]>0---\left(9\right)$

That is:

$(2^n-1)>U_1>U_2>\frac{(2^n-1)r}{R+r}---\left(10\right)$

According to above formula constraint condition, adopt the method for traversal to determine [U ₁, U ₂] scope, method is as follows:

In actual conditions, r follows temperature variation in wire and the distributed resistance that changes, gets its minimum value r in system allows working range _minsubstitution formula (10), determines sampled value U ₁, the minimum value U that can occur _1min;

By U _1minsubstitution formula obtains after (8):

$U_{2\min }=\frac{{[\frac{U_{1\min }}{(2^n-1)R}(R+r)-\frac{r}{R}]}^{\left(\frac{T_2}{T_1}\right)}+\frac{r}{R}}{(R+r)}\&times;(2^n-1)R---\left(11\right)$

Regard above formula as U _2minabout the function of r, obtain corresponding U in distributed resistance r span _2mincodomain scope;

[U ₁, U ₂] be the positive integer obtaining through analog to digital converter ADC sampling, the above method of Reusability obtains U successively _1min, U _1min+ 1, U _1min+ 2, U _1min+ 3 ... until (2 ⁿ-1) U corresponding to difference ₂codomain scope; The set of these points is exactly the field of definition scope of look-up table;

To in the point in the field of definition of look-up table successively substitution equation (6), solve the solution [L, r] of its correspondence, just obtained the look-up table after compression.

Images