CN104458833A - Method for analyzing test data of humidity sensor based on time domain reflection principle - Google Patents

Abstract

The invention relates to a method for analyzing test data of a humidity sensor based on a time domain reflection principle. The method comprises the following steps: designing iterative program to calculate electromagnetic characteristic parameters epsilon, TauL and sigma of a roadbed material based on a system identification method, soil mass dry density gamma d and volume moisture content theta w, and calculating mass moisture content w. According to the method for analyzing test data of the humidity sensor based on the time domain reflection principle disclosed by the invention, the relevance between the soil medium dry density and the moisture content of the soil medium of the roadbed material and the like is considered, the system errors can be effectively eliminated. Moreover, the method can be used for improving the reliability and the accuracy of the test data, and laying good foundation for the development of humidity automatic monitoring technology of engineering structures in industries such as roads, municipal administration, land, water conservancy and mines.

Description

A kind of humidity sensor test data analytic method based on Time Domain Reflectometry principle

Technical field

The present invention is specifically related to a kind of humidity sensor test data analytic method based on Time Domain Reflectometry principle.

Background technology

Subgrade soil moisture measurement method can be divided into direct method and the large class of indirect method two, as shown in table 1, the water cut test method specified in highway industry standard is mainly the weighting method after dried that fetches earth, the classic methods such as alcohol combustion method, although the classic methods such as oven drying method have the advantages such as reliable test result, but shortcoming is obvious equally: can soil structures be destroyed during sampling, original position cannot be carried out, in real time, Continuous Observation etc., therefore, from the nineties in 20th century, there is test speed fast, precision is high, the new method of testing that can realize automatic monitoring is applied in road engineering circle, wherein time domain reflection technology (TDR, Time Domain Reflectometry) be exactly representative humidity measurement new technology, Fig. 4 is the TDR Test instrument structural map that Bureau of Public Road (FHWA) recommends to adopt.

TDR is owned by France in soil body moisture indirectly testing method, utilize TDR technical testing soil moisture content, electromagnetic property parameters need be set up (as relative dielectric constant, be normally defined the ratio of material dielectric constant absolute value and permittivity of vacuum absolute value, can referred to as specific inductive capacity) and water percentage index between relation, current existing data analysis method is all by measuring soil body electromagnetic property parameters, water percentage is inquired into again by calibration equation, calibration or conversion process often adopt experimental means, and application has sizable limitation.

Therefore, the invention provides a kind of humidity sensor test data analytic method based on Time Domain Reflectometry principle, the method considers to have relevance between a few person of soil body electromagnetic property, water status and packing, from system perspective, utilize the data that TDR directly records, propose that there is the electromagnetic property parameters of several power theoretical foundation, water percentage index and the bearing calibration of packing index.

Summary of the invention

In view of this, the object of the present invention is to provide a kind of humidity sensor test data analytic method based on Time Domain Reflectometry principle, the method considers the relevance of the rock soil medium dry densities such as roadbed material and its water percentage, propose the electromagnetic property parameters computing method effectively can eliminating systematic error, and then calculate volumetric water content and the quality water percentage of the soil body, improve reliability and the degree of accuracy of test data.

For achieving the above object, the invention provides following technical scheme:

Based on a humidity sensor test data analytic method for Time Domain Reflectometry principle, the method comprises the following steps:

S1: calculate roadbed material electromagnetic property parameters DIELECTRIC CONSTANT ε, reflectioncoefficientг based on System identification _lwith conductivityσ;

S2: adopt System identification to calculate volumetric water content θ _wwith dry density γ _d;

S3: pass through formula calculated mass water percentage w, wherein, γ _wfor the density of water; γ _dfor soil body dry density; γ _dmaxfor soil body maximum dry density under certain pressing power; K is compactness, K=γ _d/ γ _dmax.

Further, described S1 comprises the following steps:

S11: set parameter ε to be asked, Г _lestablish value with the first of σ, introduce constant ε ₀, ω, wherein, ε ₀for the specific inductive capacity absolute value of vacuum, unit F/m, farad/rice, ε ₀=(1/36 π) × 10 ^-9f/m; ω is angular frequency;

S12: adopt TDR method to obtain magnitude of voltage V not measuring in the same time _m(t _i), t _i(i=1,2 ..., n);

S13: calculate magnitude of voltage V by following correction equation for transmission line _c(t _i);

$V_c\left(t_i\right)=(e^{-\frac{\mathrm{\σ}}{2\mathrm{\ϵ}}\·\frac{1}{\sqrt{{\mathrm{\ϵ}}_0}}{t}_i}+{\mathrm{\Γ}}_L{e}^{+\frac{\mathrm{\σ}}{2\mathrm{\ϵ}}\·\frac{1}{\sqrt{{\mathrm{\ϵ}}_0}}{t}_i})\cos \left(\mathrm{\ω}\frac{t_i}{\sqrt{{\mathrm{\ϵ}}_0}}\right)$

Wherein, t _i(i=1,2 ..., n) be the travel-time of signal in TDR probe, unit sec, second; ε ₀for the specific inductive capacity absolute value of vacuum, unit F/m, farad/rice; ε ₀=(1/36 π) × 10 ^-9f/m; ω is angular frequency;

S14: design iteration program, the β=[F of computing formula ^tf] ^-1f ^tthe value of r, β ₁~ β ₃for the element of change vector β, when element each in β is less than or equal to 1%, the calculating of termination of iterations program, obtains ε, Г _lwith the value of σ; When β is greater than 1%, reset ε, Г _lwith the value of σ, σ ⁱ⁺¹=(1+0.6 β ₁) σ ⁱ, ε ⁱ⁺¹=(1+0.6 β ₂) ε ⁱ, Γ _l ⁱ⁺¹=(1+0.6 β ₃) Γ _l ⁱ, jump to step S13,

Wherein, F is sensitivity matrix, $F=\left(\begin{array}{ccc}\frac{\∂V_c\left(t_1\right)}{\∂\mathrm{\σ}}\·\frac{\mathrm{\σ}}{V_c\left(t_1\right)}& \frac{\∂V_c\left(t_1\right)}{\∂\mathrm{\ϵ}}\·\frac{\mathrm{\ϵ}}{V_c\left(t_1\right)}& \frac{\∂V_c\left(t_1\right)}{\∂{\mathrm{\Γ}}_L}\·\frac{\mathrm{\Γ}}{V_c\left(t_1\right)}\\ .& .& .\\ .& .& .\\ .& .& .\\ \frac{\∂V_c\left(t_n\right)}{\∂\mathrm{\σ}}\·\frac{\mathrm{\σ}}{V_c\left(t_n\right)}& \frac{\∂V_c\left(t_n\right)}{\∂\mathrm{\ϵ}}\·\frac{\mathrm{\ϵ}}{V_c\left(t_n\right)}& \frac{\∂V_c\left(t_n\right)}{\∂{\mathrm{\Γ}}_L}\·\frac{{\mathrm{\Γ}}_L}{V_c\left(t_n\right)}\end{array}\right);$

R is residual vector, $r=\left(\begin{array}{c}\frac{V_m\left(t_1\right)-V_c\left(t_1\right)}{V_c\left(t_1\right)}\\ .\\ .\\ .\\ \frac{V_m\left(t_n\right)-V_c\left(t_n\right)}{V_c\left(t_n\right)}\end{array}\right).$

Further, described S2 comprises the following steps:

S21: set parameter soil body dry density γ to be asked _dwith volumetric water content θ _wjust establish value, introduce constant γ _w, ε ₃, ε ₃=1, γ _wfor the density of water, ε ₁, ε ₂, ε ₃be respectively the specific inductive capacity of grogs, water and air;

S22: the soil body is considered as three-phase body: grogs, water, air, draws following relational expression,

$\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}\frac{{\mathrm{\ϵ}}_1-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_1+2{\mathrm{\ϵ}}_{\mathrm{cc}}}+{\mathrm{\θ}}_w\frac{{\mathrm{\ϵ}}_2-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_2-2{\mathrm{\ϵ}}_{\mathrm{cc}}}+(1-\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}-{\mathrm{\θ}}_w)\frac{{\mathrm{\ϵ}}_3-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_3+2{\mathrm{\ϵ}}_{\mathrm{cc}}}=0$

Wherein, γ _dfor soil body dry density; G _sfor specific gravity of soil partical; γ _wfor the density of water; θ _wfor the volume accounting of volumetric water content and water; ε ₁, ε ₂, ε ₃be respectively the specific inductive capacity of grogs, water and air; ε _ccfor the complex phase dielectric constant of soil body obtained based on volume mixture theory calculate; be respectively the volume accounting of grogs and air;

S23: design iteration program, the β=[F of computing formula ^tf] ^-1f ^tthe value of r, when element each in β is less than or equal to 1%, the calculating of termination of iterations program, obtains γ _dand θ _wvalue; When β is greater than 1%, reset γ _d, θ _wvalue, γ _d ⁱ⁺¹=(1+0.6 β ₁) γ _d ⁱ, θ _w ⁱ⁺¹=(1+0.6 β ₂) θ _w ⁱ, jump to step S22, wherein, $F=\left[\begin{array}{cc}\frac{\∂{\mathrm{\ϵ}}_{\mathrm{cc}}}{\∂{\mathrm{\γ}}_d}\left(\frac{{\mathrm{\γ}}_d}{{\mathrm{\ϵ}}_{\mathrm{cc}}}\right)& \frac{\∂{\mathrm{\ϵ}}_{\mathrm{cc}}}{\∂{\mathrm{\θ}}_w}\left(\frac{{\mathrm{\θ}}_w}{{\mathrm{\ϵ}}_{\mathrm{cc}}}\right)\end{array}\right],r=\left[\frac{{\mathrm{\ϵ}}_c-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_c}\right].$

Beneficial effect of the present invention is: the present invention proposes a kind of humidity sensor test data analytic method based on Time Domain Reflectometry principle, the method considers humidity sensor (TDR) the test data analytical optimization method of roadbed material comprehensive electromagnetic characteristic and each phase volume accounting, overcomes now methodical following defect: the relevance that 1. have ignored the rock soil medium dry densities such as roadbed material and its water percentage; 2. the experimental regression relation often of the calibration equation between electromagnetic property parameters and water percentage, between the water cut value causing calibration to obtain and actual value, error is comparatively large, and in addition, the scope of application of empirical formula is also subject to larger restriction.Method provided by the present invention a kind ofly has universality, TDR Test data inversion method that precision is higher, for the industry engineering structure humidity automatic monitoring technical development such as highway, municipal administration, territory, water conservancy, mine are had laid a good foundation.

Accompanying drawing explanation

In order to make the object, technical solutions and advantages of the present invention clearly, below in conjunction with accompanying drawing, the present invention is described in further detail, wherein:

Fig. 1 is the process flow diagram of the method for the invention;

Fig. 2 is electromagnetic property parameters calculation process;

Fig. 3 is volumetric water content and dry density calculation process;

Fig. 4 is the TDR Test instrument that FHWA recommends to adopt,

Wherein (a) is vertical view, and (b) is outboard profile, and (c) is end-view.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 1 is the process flow diagram of the method for the invention; Based on a humidity sensor test data analytic method for Time Domain Reflectometry principle, the method comprises the following steps:

S1: calculate roadbed material electromagnetic property parameters DIELECTRIC CONSTANT ε, reflectioncoefficientг _lwith conductivityσ;

S2: calculate volumetric water content θ _wwith dry density γ _d;

S3: calculated mass water percentage w.

Electromagnetic wave at free space or open Propagation, and can not only be propagated in the finite space with conductive border, now, electromagnetic wave limit by border, be formed with the propagation of guiding.The coaxial transmission line that TDR adopts is a kind of like this carrier of ripple.

Utilize the equation for transmission line (such as formula (1) Suo Shi) in electrotechnics, introduce major parameter DIELECTRIC CONSTANT ε, the reflectioncoefficientг of reflection rock soil medium (i.e. roadbed material) electromagnetic property _lwith conductivityσ.

$\left\{\begin{array}{c}V\left(z\right)=V_{+}{e}^{-\mathrm{jkz}}+V_{-}{e}^{+\mathrm{jkz}}\\ {\mathrm{\Γ}}_L=V_{-}/V_{+}\\ V\left(z\right)=V_{-}(e^{-\mathrm{jkz}}+{\mathrm{\Γ}}_L{e}^{+\mathrm{jkz}})\end{array}\right.---\left(1\right)$

In formula, V (z) is the voltage of signal by producing during transmission line; Z is the distance that signal passes through in transmission line; V ₊for signal is along the amplitude of forward-propagating; V _-for the amplitude that signal is propagated along negative sense; K is propagation coefficient, k=k _r-jk _i, k _rfor the real part of propagation coefficient, k _ifor the imaginary part of propagation coefficient.Corresponding, voltage V (t) that a certain time-ofday signals produces in transmission line calculates by formula (2):

$v\left(t\right)=(e^{-\frac{\mathrm{\σt}}{2\mathrm{\ϵ}\sqrt{{\mathrm{\ϵ}}_0}}}+{\mathrm{\Γ}}_t{e}^{+\frac{\mathrm{\σt}}{2\mathrm{\ϵ}\sqrt{{\mathrm{\ϵ}}_0}}})\·\cos \left(\mathrm{\ω}\frac{t}{\sqrt{{\mathrm{\ϵ}}_0}}\right)---\left(2\right)$

In formula, t is the travel-time of signal in TDR probe (sec, second); ε ₀for the specific inductive capacity absolute value (F/m, farad/rice) of vacuum, ε ₀=(1/36 π) × 10 ^-9f/m; ω is angular frequency.

Adopt the electromagnetic property parameters of System identification determination roadbed material, on the basis of same input signal, design iteration program, by adjustment known variables (as ε, Г _l, σ, soil body dry density γ _dwith volumetric water content θ _w), system is exported with the error-reduction of model Output rusults in tolerance interval.

The magnitude of voltage V obtained by TDR measurement _m(t) (i.e. relative voltage V _r), correct the magnitude of voltage V that equation for transmission line calculates _ct (), adopts following formula:

$\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\left(\frac{\∂V_c{\left(t\right)}^n}{\∂X_i^n}\frac{X_i^n}{V_c{\left(t\right)}^n}\right)\left(\frac{\mathrm{\Δ}{X}_i^n}{X_i^n}\right)=\frac{\mathrm{\Δ}{V}_c{\left(t\right)}^n}{V_c{\left(t\right)}^n}---\left(3\right)$

In formula, m is known variables or parameter X to be asked _i ⁿnumber; V _ct () is the calculating voltage value (being tried to achieve by formula (2)) when n-th iteration; N is iterations; X _i ⁿfor known variables or parameter to be asked, be ε, Г herein _land σ; Δ X _i ⁿ=X _i ⁿ⁺¹-X _i ⁿ; Δ V _c(t) ⁿ=V _c(t) ⁿ-V _m(t).Above formula can be converted to matrix equation:

F＝βr

β＝[F ^TF] ^-1F ^Tr (4)

In formula, F is sensitivity matrix, for its element; β is change vector, for its element; R is residual vector, for its element.Patent each element in β is less than 1% as iterative program end condition.

Electromagnetic property parameters calculation process, as shown in Figure 2, these computing method effectively can eliminate systematic error, comprise with step:

S11: set parameter ε to be asked, Г _lestablish value with the first of σ, introduce constant ε ₀, ω, wherein, ε ₀for the specific inductive capacity absolute value of vacuum, unit F/m, farad/rice, ε ₀=(1/36 π) × 10 ^-9f/m; ω is angular frequency; For reducing iterative computation number of times, patent By consulting literatures roughly determines the scope of parameter to be asked: ε generally changes between 3 to 80, gets 10 herein for just to establish value; Г _lgeneral variation between-1 to 1, gets 0.1 herein for just to establish value; σ mobility scale is not fixed, and gets 0.5 herein for just to establish value.

S12: adopt TDR method to obtain magnitude of voltage V not measuring in the same time _m(t _i), t _i(i=1,2 ..., n);

S13: calculate magnitude of voltage V by following correction equation for transmission line _c(t _i);

$V_c\left(t_i\right)=(e^{-\frac{\mathrm{\σ}}{2\mathrm{\ϵ}}\·\frac{1}{\sqrt{{\mathrm{\ϵ}}_0}}{t}_i}+{\mathrm{\Γ}}_L{e}^{+\frac{\mathrm{\σ}}{2\mathrm{\ϵ}}\·\frac{1}{\sqrt{{\mathrm{\ϵ}}_0}}{t}_i})\cos \left(\mathrm{\ω}\frac{t_i}{\sqrt{{\mathrm{\ϵ}}_0}}\right)$

Wherein, t _i(i=1,2 ..., n) be the travel-time of signal in TDR probe, unit sec, second; ε ₀for the specific inductive capacity absolute value of vacuum, unit F/m, farad/rice; ε ₀=(1/36 π) × 10 ^-9f/m; ω is angular frequency;

S14: design iteration program, the β=[F of computing formula ^tf] ^-1f ^tthe value of r, β ₁~ β ₃for the element of change vector β, when element each in β is less than or equal to 1%, the calculating of termination of iterations program, obtains ε, Г _lwith the value of σ; When β is greater than 1%, reset ε, Г _lwith the value of σ, σ ⁱ⁺¹=(1+0.6 β ₁) σ ⁱ, ε ⁱ⁺¹=(1+0.6 β ₂) ε ⁱ, Γ _l ⁱ⁺¹=(1+0.6 β ₃) Γ _l ⁱ, jump to step S13,

Wherein, F is sensitivity matrix, $F=\left(\begin{array}{ccc}\frac{\∂V_c\left(t_1\right)}{\∂\mathrm{\σ}}\·\frac{\mathrm{\σ}}{V_c\left(t_1\right)}& \frac{\∂V_c\left(t_1\right)}{\∂\mathrm{\ϵ}}\·\frac{\mathrm{\ϵ}}{V_c\left(t_1\right)}& \frac{\∂V_c\left(t_1\right)}{\∂{\mathrm{\Γ}}_L}\·\frac{\mathrm{\Γ}}{V_c\left(t_1\right)}\\ .& .& .\\ .& .& .\\ .& .& .\\ \frac{\∂V_c\left(t_n\right)}{\∂\mathrm{\σ}}\·\frac{\mathrm{\σ}}{V_c\left(t_n\right)}& \frac{\∂V_c\left(t_n\right)}{\∂\mathrm{\ϵ}}\·\frac{\mathrm{\ϵ}}{V_c\left(t_n\right)}& \frac{\∂V_c\left(t_n\right)}{\∂{\mathrm{\Γ}}_L}\·\frac{{\mathrm{\Γ}}_L}{V_c\left(t_n\right)}\end{array}\right);$

R is residual vector, $r=\left(\begin{array}{c}\frac{V_m\left(t_1\right)-V_c\left(t_1\right)}{V_c\left(t_1\right)}\\ .\\ .\\ .\\ \frac{V_m\left(t_n\right)-V_c\left(t_n\right)}{V_c\left(t_n\right)}\end{array}\right).$

TDR Test Data Analysis optimization method is when determining roadbed material humidity, the soil body is considered as three-phase body: grogs, water, air, this kind of way discrimination can often plant the impact of component dielectric property on soil body water status, and the relation in volume mixture theory between three-phase dielectric material character and single item grouping volume adopts formula (5) quantitative description:

$\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}\frac{{\mathrm{\ϵ}}_1-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_1+2{\mathrm{\ϵ}}_{\mathrm{cc}}}+{\mathrm{\θ}}_w\frac{{\mathrm{\ϵ}}_2-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_2-2{\mathrm{\ϵ}}_{\mathrm{cc}}}+(1-\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}-{\mathrm{\θ}}_w)\frac{{\mathrm{\ϵ}}_3-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_3+2{\mathrm{\ϵ}}_{\mathrm{cc}}}=0---\left(5\right)$

In formula, γ _dfor soil body dry density; G _sfor specific gravity of soil partical; γ _wfor the density of water; θ _wfor the volume accounting of volumetric water content and water; ε ₁, ε ₂, ε ₃be respectively the specific inductive capacity of grogs, water and air, by standard test method or consult pertinent literature and determine; ε _ccfor the complex phase dielectric constant of soil body obtained based on volume mixture theory calculate; γ _d/ (G _sγ _w), 1-γ _d/ (G _sγ _w)-θ _wbe respectively the volume accounting of grogs and air.

Adopt the physical parameter (volumetric water content and dry density) of System identification determination roadbed material, volumetric water content and dry density calculation process as shown in Figure 3, comprise the following steps:

S21: set parameter soil body dry density γ to be asked _dwith volumetric water content θ _wjust establish value, introduce constant γ _w, ε ₃, ε ₃=1, γ _wfor the density of water, ε ₁, ε ₂, ε ₃be respectively the specific inductive capacity of grogs, water and air;

S22: the soil body is considered as three-phase body: grogs, water, air, draws following relational expression,

$\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}\frac{{\mathrm{\ϵ}}_1-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_1+2{\mathrm{\ϵ}}_{\mathrm{cc}}}+{\mathrm{\θ}}_w\frac{{\mathrm{\ϵ}}_2-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_2-2{\mathrm{\ϵ}}_{\mathrm{cc}}}+(1-\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}-{\mathrm{\θ}}_w)\frac{{\mathrm{\ϵ}}_3-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_3+2{\mathrm{\ϵ}}_{\mathrm{cc}}}=0$

Wherein, γ _dfor soil body dry density; G _sfor specific gravity of soil partical; γ _wfor the density of water; θ _wfor the volume accounting of volumetric water content and water; ε ₁, ε ₂, ε ₃be respectively the specific inductive capacity of grogs, water and air; ε _ccfor the complex phase dielectric constant of soil body obtained based on volume mixture theory calculate; be respectively the volume accounting of grogs and air; By the parameter ε that experimental test obtains ₁, ε ₂, G _sand ε _c.

S23: design iteration program, the β=[F of computing formula ^tf] ^-1f ^tthe value of r, when element each in β is less than or equal to 1%, the calculating of termination of iterations program, obtains γ _dand θ _wvalue; When β is greater than 1%, reset γ _d, θ _wvalue, γ _d ⁱ⁺¹=(1+0.6 β ₁) γ _d ⁱ, θ _w ⁱ⁺¹=(1+0.6 β ₂) θ _w ⁱ, jump to step S22, wherein, $F=\left[\begin{array}{cc}\frac{\∂{\mathrm{\ϵ}}_{\mathrm{cc}}}{\∂{\mathrm{\γ}}_d}\left(\frac{{\mathrm{\γ}}_d}{{\mathrm{\ϵ}}_{\mathrm{cc}}}\right)& \frac{\∂{\mathrm{\ϵ}}_{\mathrm{cc}}}{\∂{\mathrm{\θ}}_w}\left(\frac{{\mathrm{\θ}}_w}{{\mathrm{\ϵ}}_{\mathrm{cc}}}\right)\end{array}\right],r=\left[\frac{{\mathrm{\ϵ}}_c-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_c}\right].$

Try to achieve volumetric water content θ _wbasis on, by formula (6), inquire into the humidity index-quality water percentage w of widespread use in Practical Project:

$w=\frac{{\mathrm{\γ}}_w}{K{\mathrm{\γ}}_{d\max }}{\mathrm{\θ}}_w---\left(6\right)$

In formula, γ _wfor the density of water; γ _dfor soil body dry density; γ _dmaxfor soil body maximum dry density under certain pressing power; K is compactness, K=γ _d/ γ _dmax.

What finally illustrate is, above preferred embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although by above preferred embodiment to invention has been detailed description, but those skilled in the art are to be understood that, various change can be made to it in the form and details, and not depart from claims of the present invention limited range.

Claims (3)

1., based on a humidity sensor test data analytic method for Time Domain Reflectometry principle, it is characterized in that: the method comprises the following steps:

S1: calculate roadbed material electromagnetic property parameters DIELECTRIC CONSTANT ε, reflectioncoefficientг based on System identification _lwith conductivityσ;

S2: adopt System identification to calculate volumetric water content θ _wwith dry density γ _d;

S3: pass through formula calculated mass water percentage w, wherein, γ _wfor the density of water; γ _dfor soil body dry density; γ _dmaxfor soil body maximum dry density under certain pressing power; K is compactness, K=γ _d, γ _dmax.

2. a kind of humidity sensor test data analytic method based on Time Domain Reflectometry principle according to claim 1, is characterized in that: described S1 comprises the following steps:

S11: set parameter ε to be asked, Г _lestablish value with the first of σ, introduce constant ε ₀, ω, wherein, ε ₀for the specific inductive capacity absolute value of vacuum, unit F/m, farad/rice, ε ₀=(1/36 π) × 10 ^-9f/m; ω is angular frequency;

S12: adopt TDR method to obtain magnitude of voltage V not measuring in the same time _m(t _i), wherein, t _ifor the travel-time of signal in TDR probe, i=1,2 ..., n;

S13: calculate magnitude of voltage V by following correction equation for transmission line _c(t _i);

$V_c\left(t_i\right)=(e^{-\frac{\mathrm{\σ}}{2\mathrm{\ϵ}}\·\frac{1}{\sqrt{{\mathrm{\ϵ}}_0}}{t}_i}+{\mathrm{\Γ}}_L{e}^{+\frac{\mathrm{\σ}}{2\mathrm{\ϵ}}\·\frac{1}{\sqrt{{\mathrm{\ϵ}}_0}}{t}_i})\cos \left(\mathrm{\ω}\frac{t_i}{\sqrt{{\mathrm{\ϵ}}_0}}\right)$

Wherein, t _ifor the travel-time of signal in TDR probe, unit sec, second; ε ₀for the specific inductive capacity absolute value of vacuum, unit F/m, farad/rice; ε ₀=(1/36 π) × 10 ^-9f/m; ω is angular frequency;

S14: design iteration program, the β=[F of computing formula ^tf] ^-1f ^tthe value of r, β ₁~ β ₃for the element of change vector β, when element each in β is less than or equal to 1%, the calculating of termination of iterations program, obtains ε, Г _lwith the value of σ; When β is greater than 1%, reset ε, Г _lwith the value of σ, σ ⁱ⁺¹=(1+0.6 β ₁) σ ⁱ, ε ⁱ⁺¹=(1+0.6 β ₂) ε ⁱ, Γ _l ⁱ⁺¹=(1+0.6 β ₃) Γ _l ⁱ, jump to step S13,

Wherein, F is sensitivity matrix, $F=\left(\begin{array}{ccc}\frac{{\∂V}_c\left(t_1\right)}{\∂\mathrm{\σ}}\·\frac{\mathrm{\σ}}{V_c\left(t_1\right)}& \frac{{\∂V}_c\left(t_1\right)}{\∂\mathrm{\ϵ}}\·\frac{\mathrm{\ϵ}}{V_c\left(t_1\right)}& \frac{{\∂V}_c\left(t_1\right)}{{\∂\mathrm{\Γ}}_L}\·\frac{{\mathrm{\Γ}}_L}{V_c\left(t_1\right)}\\ \·& \·& \·\\ \·& \·& \·\\ \·& \·& \·\\ \frac{{\∂V}_c\left(t_n\right)}{\∂\mathrm{\σ}}\·\frac{\mathrm{\σ}}{V_c\left(t_c\right)}& \frac{{\∂V}_c\left(t_n\right)}{\∂\mathrm{\ϵ}}\·\frac{\mathrm{\ϵ}}{V_c\left(t_n\right)}& \frac{{\∂V}_c\left(t_n\right)}{{\∂\mathrm{\Γ}}_L}\·\frac{{\mathrm{\Γ}}_L}{V_c\left(t_n\right)}\end{array}\right);$

R is residual vector, $r=\left(\begin{array}{c}\frac{V_m\left(t_1\right)-V_c\left(t_1\right)}{V_c\left(t_1\right)}\\ \·\\ \·\\ \·\\ \frac{V_m\left(t_n\right)-V_c\left(t_n\right)}{V_c\left(t_n\right)}\end{array}\right).$

3. a kind of humidity sensor test data analytic method based on Time Domain Reflectometry principle according to claim 1, is characterized in that: described S2 comprises the following steps:

S21: set parameter soil body dry density γ to be asked _dwith volumetric water content θ _wjust establish value, introduce constant γ _w, ε ₃, ε ₃=1, γ _wfor the density of water, ε ₁, ε ₂, ε ₃be respectively the specific inductive capacity of grogs, water and air;

S22: the soil body is considered as three-phase body: grogs, water, air, draws following relational expression,

$\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}\frac{{\mathrm{\ϵ}}_1-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_1+{2\mathrm{\ϵ}}_{\mathrm{cc}}}+{\mathrm{\θ}}_w\frac{{\mathrm{\ϵ}}_2-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_2+{2\mathrm{\ϵ}}_{\mathrm{cc}}}+(1-\frac{{\mathrm{\γ}}_d}{G_s{\mathrm{\γ}}_w}-{\mathrm{\θ}}_w)\frac{{\mathrm{\ϵ}}_3-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_3+{2\mathrm{\ϵ}}_{\mathrm{cc}}}=0$

Wherein, γ _dfor soil body dry density; G _sfor specific gravity of soil partical; γ _wfor the density of water; θ _wfor the volume accounting of volumetric water content and water; ε ₁, ε ₂, ε ₃be respectively the specific inductive capacity of grogs, water and air; ε _ccfor the complex phase dielectric constant of soil body obtained based on volume mixture theory calculate; be respectively the volume accounting of grogs and air;

S23: design iteration program, the β=[F of computing formula ^tf] ^-1f ^tthe value of r, when element each in β is less than or equal to 1%, the calculating of termination of iterations program, obtains γ _dand θ _wvalue; When β is greater than 1%, reset γ _d, θ _wvalue, γ _d ⁱ⁺¹=(1+0.6 β ₁) γ _d ⁱ, θ _w ⁱ⁺¹=(1+0.6 β ₂) θ _w ⁱ, jump to step S22, wherein, $F=\left[\begin{array}{cc}\frac{{\∂\mathrm{\ϵ}}_{\mathrm{cc}}}{{\∂\mathrm{\γ}}_d}\left(\frac{{\mathrm{\γ}}_d}{{\mathrm{\ϵ}}_{\mathrm{cc}}}\right)& \frac{{\∂\mathrm{\ϵ}}_{\mathrm{cc}}}{{\∂\mathrm{\θ}}_w}\left(\frac{{\mathrm{\θ}}_w}{{\mathrm{\ϵ}}_{\mathrm{cc}}}\right)\end{array}\right],r=\left[\frac{{\mathrm{\ϵ}}_c-{\mathrm{\ϵ}}_{\mathrm{cc}}}{{\mathrm{\ϵ}}_c}\right].$