CN104237561A - Spatial acceleration measuring method and device based on fiber grating curvature sensing network - Google Patents

Abstract

The invention relates to a spatial acceleration measuring technology based on a fiber grating curvature sensing network. A flexible spatial coordinate detection rod is attached to a mechanical component to be measured; when the mechanical component moves, strain information is measured by fiber gratings on the flexible spatial coordinate detection rod and demodulated into digital wavelength information through fiber grating demodulators to be input into a computer; the digital wavelength information is converted into curvature information first in the computer, spatial coordinate information is obtained through the curvature information by means of recursion, the acceleration is worked out through numerical difference calculation, and finally the acceleration is displayed in real time. Compared with the prior art, the spatial acceleration measuring technology based on the fiber grating curvature sensing network has the advantages of being high in measurement accuracy, good in real time performance, wide in application range and the like.

Description

Based on steric acceleration measuring method and the device of fiber bragg grating curvature sensing network

Technical field

The present invention relates to a kind of steric acceleration measuring technique, especially relate to a kind of steric acceleration measuring method based on fiber bragg grating curvature sensing network and device.

Background technology

The measurement of steric acceleration to engineering machinery accurately effectively control be of great significance, but can realize at present also not based on curvature measurement the system that whole audience steric acceleration measures in real time.The existing acceleration transducer based on fiber grating can only realize spot measurement, its mentality of designing mainly designs the sensing head with mass, mass produces inertial force when vibrating, under inertial force effect, transducing head structure can produce corresponding strain, corresponding strain is measured by sensitive elements such as fiber gratings, just can obtain inertial force by the stress-strain relation of structure again, and then try to achieve acceleration.

Summary of the invention

Object of the present invention be exactly in order to overcome above-mentioned prior art exist defect and a kind of steric acceleration measuring method based on fiber bragg grating curvature sensing network and device are provided.

Object of the present invention can be achieved through the following technical solutions:

Based on a steric acceleration measuring method for fiber bragg grating curvature sensing network, comprise the following steps:

1) demarcate process by arc-spline curve, determine the Proportional coefficient K between the strain signal of each check point on flexible space coordinate measurement bar and the curvature of curve of flexible space coordinate measurement bar;

2) flexible space coordinate measurement bar is close on mechanical component to be detected, by the fiber grating of each check point according to the flexibility of flexible space coordinate measurement bar, obtains strain signal:

3) strain signal of each check point converts digital wavelength signal to, by computer real-time acquisition through the fiber Bragg grating (FBG) demodulator device of correspondence:

4) computing machine is according to the digital wavelength signal of Real-time Collection, carry out arc-spline curve and demarcate process, obtain the corresponding relation between wavelength signals changing value and flexible space coordinate measurement bar curvature value, and calculate the curvature at each check point place on flexible space coordinate measurement bar according to this relation;

5) computing machine is according to the curvature information of multiple check point on flexible space coordinate measurement bar, and recursion goes out the spatial coordinated information of each check point on flexible space coordinate measurement bar;

6) computer disposal is by the spatial coordinated information of flexible space coordinate measurement bar, the coordinate in tri-directions of X, Y, Z in spatial coordinated information is carried out secondary diff backward to the time and calculates, obtain the acceleration in X, Y, Z tri-directions.

Step 1) in arc-spline curve demarcate process detailed process be: for the fiber grating of each check point, first measure the central wavelength lambda of the fiber grating of flexible space coordinate measurement bar under several known curvature radiuses ρ, obtain the scale-up factor under each radius-of-curvature ρ according to formula K=λ × ρ, then get the Proportional coefficient K of its mean value as the fiber grating of next measurement point.

Step 6) in adopt after secondary diff calculates backward, then have the acceleration of i-th t to be:

$\left\{\begin{array}{c}{A}_{\mathrm{itx}}=\frac{X_i\left(t\right)-2\·X_i(t-\mathrm{\Δt})+X_i(t-2\·\mathrm{\Δt})}{{\left(\mathrm{\Δt}\right)}^2}\\ A_{\mathrm{ity}}=\frac{Y_i\left(t\right)-2\·Y_i(t-\mathrm{\Δt})+Y_i(t-2\·\mathrm{\Δt})}{{\left(\mathrm{\Δt}\right)}^2}\\ A_{\mathrm{itz}}=\frac{Z_i\left(t\right)-2\·Z_i(t-\mathrm{\Δt})+Z_i(t-2\·\mathrm{\Δt})}{{\left(\mathrm{\Δt}\right)}^2}\end{array}\right\}$

In formula, Aitx, Aity, Aitz are respectively the acceleration in i-th t x, y, z direction in dimensional Cartesian coordinates system, and Xi (t), Yi (t), Zi (t) are respectively the coordinate of i-th t x, y, z axle in dimensional Cartesian coordinates system.

Based on a steric acceleration measurement mechanism for fiber bragg grating curvature sensing network, comprising:

Flexible space coordinate measurement bar: depend on mechanical component to be detected, and be close to the outer wall of this mechanical component, flexible space coordinate measurement bar inside is provided with multiple check point vertically, and each check point arranges fiber grating for obtaining strain signal;

Fiber Bragg grating (FBG) demodulator: obtain strain signal by check point, converts the strain signal of multiple discrete check point to digital wavelength signal;

Computing machine: obtain digital wavelength signals by fiber Bragg grating (FBG) demodulator, obtains the acceleration at each check point place.

Multiple check point is axially evenly arranged along flexible space coordinate measurement bar, and each check point all comprises 4 fiber gratings of two groups respectively, and 4 fiber gratings are uniformly distributed along the circular cross section along flexible space coordinate measurement bar.Compared with prior art, the present invention has the following advantages:

1., because whole acceleration measurement system is primarily of optical fiber grating sensing network, fiber Bragg grating (FBG) demodulator device and computing machine composition, do not need extra utility appliance, so the composition of whole system is simple, the not impact of the extraneous factor such as easy electromagnetic wave.

2. because this steric acceleration measuring system arranges multiple curvature measuring fiber grating on flexible space coordinate measurement bar, the curvature measuring of multiple spot is carried out in a parallel fashion simultaneously, therefore whole steric acceleration measuring system can realize full field real-time measurement, this measuring technique is applicable to the acceleration analysis of multi-rigid body mechanical arm and flexible elongate mechanical component, and can reach very high real-time responsiveness.

3. to have size little for optical fiber grating sensing mode, and the advantage that measurement range is large, can design suitable flexible space coordinate measurement bar according to the requirement of engineering machinery and measure.

4. the steric acceleration measuring system composition that the present invention is based on fiber grating is simple, and measuring method is easy, and layman also can be familiar with method of operating very soon.

Accompanying drawing explanation

Fig. 1 is structural representation of the present invention;

The fiber-optic grating sensor of Fig. 2 flexible space coordinate measurement bar arranges schematic diagram;

Fig. 3 is the partial enlarged drawing of flexible space coordinate measurement bar;

Fig. 4 is the reconstruction schematic diagram based on discrete point curvature information;

Fig. 5-Fig. 7 be the spatial coordinated information of each check point on recursion flexible space coordinate measurement bar exploded view;

In figure, 1 be computing machine, 2 be fiber Bragg grating (FBG) demodulator, 3 be flexible space coordinate measurement bar, 4 is mechanical component, 5 to be measured is fiber grating on each check point.

Embodiment

Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.

Embodiment

The invention provides a kind of steric acceleration measuring method based on fiber bragg grating curvature sensing network, the method comprises the following steps:

Step one, demarcates process by arc-spline curve, determines the Proportional coefficient K between the strain signal of each check point on flexible space coordinate measurement bar and the curvature of curve of flexible space coordinate measurement bar.Wherein, arc-spline curve demarcates process detailed process: for the fiber grating of each check point, first measure the central wavelength lambda of the fiber grating of flexible space coordinate measurement bar under several known curvature radiuses ρ, obtain the scale-up factor under each radius-of-curvature ρ according to formula K=λ × ρ, then get the Proportional coefficient K of its mean value as the fiber grating of next measurement point.

Step 2, is close on mechanical component to be detected by flexible space coordinate measurement bar, by the fiber grating of each check point according to the flexibility of flexible space coordinate measurement bar, obtains strain signal.

Step 3, the strain signal of each check point converts digital wavelength signal to, by computer real-time acquisition through the fiber Bragg grating (FBG) demodulator device of correspondence.

Step 4, computing machine is according to the digital wavelength signal of Real-time Collection, carry out arc-spline curve and demarcate process, obtain the corresponding relation between wavelength signals changing value and flexible space coordinate measurement bar curvature value, and calculate the curvature at each check point place on flexible space coordinate measurement bar according to this relation.

Step 5, computing machine is according to the curvature information of multiple check point on flexible space coordinate measurement bar, and recursion goes out the spatial coordinated information of each check point on flexible space coordinate measurement bar.In this step, concrete recurrence method is as follows, and composition graphs 4 is specifically described it:

1, at coordinate system { B _iin carry out Vector modulation, the buckling vector k of synthesis to carrying out two component of curvature _i, size is:

$\left|k_i\right|=\sqrt{{k_{\mathrm{ai}}}^2+{k_{\mathrm{bi}}}^2}$

As shown in Figure 5, the plane that dotted line place represents is the osculating plane of an i, κ in figure _ibe the curvature of space of the some i of two orthogonal plane buckling vector synthesis, its direction is the normal direction of an i.

K _iwith k _aiangle α _ifor:

${\mathrm{\&alpha;}}_i=\left\{\begin{array}{c}{\tan }^{-1}(k_{\mathrm{bi}}/k_{\mathrm{ai}})+\mathrm{\&pi;}(k_{\mathrm{ai}}<0)\\ -\mathrm{\&pi;}/2(k_{\mathrm{ai}}=0,k_{\mathrm{bi}}<0)\\ 0(k_{\mathrm{ai}}=0,k_{\mathrm{bi}}=0)\\ \mathrm{\&pi;}/2(k_{\mathrm{ai}}=0,k_{\mathrm{bi}}>0)\\ {\tan }^{-1}(k_{\mathrm{bi}}/k_{\mathrm{ai}})(k_{\mathrm{ai}}>0)\end{array}\right.$

Specifically as shown in Figure 6.

2, linear interpolation is adopted to obtain continuous curvature from discrete curvature;

3, set up check point coordinate system { B _i+1;

4, at moving coordinate system { B _i+1middle recursion coordinate:

In moving coordinate system in coordinate recursion schematic thinking shown in geometric relationship just can in the moving coordinate system of an i calculation level i+1 relative to the increment of coordinate (dx of an i _i, dy _i, dz _i), (dx _i, dy _i, dz _i) can according to κ _iwhether the size of vector is zero.Because moving coordinate system is with an i for initial point, so the coordinate of some i in the moving coordinate system of an i is (0,0,0), therefore according to conclusion above, the coordinate of some i+1 in the moving coordinate system of an i is (0+dx _i, 0+dy _i, 0+dz _i)=(dx _i, dy _i, dz _i).Because the segment of curve that the segmental arc met between an i+1 and some i just must meet between an i+1 and some i in a plane and for circular arc is very small, thus each moving coordinate system only determine adjacent descend any coordinate.Namely the moving coordinate system putting i only determines the coordinate of an i+1, and the moving coordinate system of some i+1 is only determined just to go out the coordinate of each point in dimensional Cartesian coordinates system on curve by recurrence calculation by that analogy by the coordinate of an i+2.

5, coordinate system { B _i+1be converted to Cartesian coordinates, as shown in Figure 7;

[I+1]=[D _i] [I] moving coordinate system is just transformed to the moving coordinate system of i+1 point, [D from the moving coordinate system of i point _i] be homogeneous coordinate system transition matrix.

$\left\{\begin{array}{c}{x}_{i+1}\\ y_{i+1}\\ z_{i+1}\\ 1\end{array}\right\}={\left[\mathrm{DI}\right]}^{-1}\left\{\begin{array}{c}{\mathrm{dx}}_i\\ {\mathrm{dy}}_i\\ {\mathrm{dz}}_i\\ 1\end{array}\right\}$

Namely above formula achieves the recursion of each point coordinate in dimensional Cartesian coordinates system on substrate deformation CB.

Step 6, the coordinate in tri-directions of X, Y, Z in spatial coordinated information, by the spatial coordinated information of flexible space coordinate measurement bar, is carried out secondary diff backward to the time and calculates, obtain the acceleration of i-th t by computer disposal:

$\left\{\begin{array}{c}{A}_{\mathrm{itx}}=\frac{X_i\left(t\right)-2\&CenterDot;X_i(t-\mathrm{\&Delta;t})+X_i(t-2\&CenterDot;\mathrm{\&Delta;t})}{{\left(\mathrm{\&Delta;t}\right)}^2}\\ A_{\mathrm{ity}}=\frac{Y_i\left(t\right)-2\&CenterDot;Y_i(t-\mathrm{\&Delta;t})+Y_i(t-2\&CenterDot;\mathrm{\&Delta;t})}{{\left(\mathrm{\&Delta;t}\right)}^2}\\ A_{\mathrm{itz}}=\frac{Z_i\left(t\right)-2\&CenterDot;Z_i(t-\mathrm{\&Delta;t})+Z_i(t-2\&CenterDot;\mathrm{\&Delta;t})}{{\left(\mathrm{\&Delta;t}\right)}^2}\end{array}\right\}$

In formula, Aitx, Aity, Aitz are respectively the acceleration in i-th t x, y, z direction in dimensional Cartesian coordinates system, and Xi (t), Yi (t), Zi (t) are respectively the coordinate of i-th t x, y, z axle in dimensional Cartesian coordinates system.

The acceleration in X, Y, Z tri-directions can be obtained thus.

Said method can adopt measurement mechanism as shown in Figures 1 to 3 to realize, and this device comprises flexible space coordinate measurement bar 3, fiber Bragg grating (FBG) demodulator 2, computing machine 3.Wherein, flexible space coordinate measurement bar 3 depends on mechanical component to be detected, and is close to the outer wall of this mechanical component, and flexible space coordinate measurement bar inside is provided with multiple check point vertically, and each check point arranges fiber grating for obtaining strain signal.These check points are axially evenly arranged along flexible space coordinate measurement bar, and each check point all comprises 4 fiber gratings of two groups respectively, and 4 fiber gratings are uniformly distributed along the circular cross section along flexible space coordinate measurement bar, each other in 90 °.Fiber Bragg grating (FBG) demodulator is used for obtaining strain signal from check point, converts the strain signal of multiple discrete check point to digital wavelength signal.Computing machine obtains digital wavelength signals for obtaining fiber Bragg grating (FBG) demodulator, finally obtains the acceleration at each check point place.

Claims (5)

1., based on a steric acceleration measuring method for fiber bragg grating curvature sensing network, it is characterized in that, comprise the following steps:

1) demarcate process by arc-spline curve, determine the Proportional coefficient K between the strain signal of each check point on flexible space coordinate measurement bar and the curvature of curve of flexible space coordinate measurement bar;

2) flexible space coordinate measurement bar is close on mechanical component to be detected, by the fiber grating of each check point according to the flexibility of flexible space coordinate measurement bar, obtains strain signal;

3) strain signal of each check point converts digital wavelength signal to, by computer real-time acquisition through the fiber Bragg grating (FBG) demodulator device of correspondence;

4) computing machine is according to the digital wavelength signal of Real-time Collection, carry out arc-spline curve and demarcate process, obtain the corresponding relation between wavelength signals changing value and flexible space coordinate measurement bar curvature value, and calculate the curvature at each check point place on flexible space coordinate measurement bar according to this relation;

5) computing machine is according to the curvature information of multiple check point on flexible space coordinate measurement bar, and recursion goes out the spatial coordinated information of each check point on flexible space coordinate measurement bar;

6) computer disposal is by the spatial coordinated information of flexible space coordinate measurement bar, the coordinate in tri-directions of X, Y, Z in spatial coordinated information is carried out secondary diff backward to the time and calculates, obtain the acceleration in X, Y, Z tri-directions.

2. a kind of steric acceleration measuring method based on fiber bragg grating curvature sensing network according to claim 1, it is characterized in that, step 1) in arc-spline curve demarcate process detailed process be: for the fiber grating of each check point, first measure the central wavelength lambda of the fiber grating of flexible space coordinate measurement bar under several known curvature radiuses ρ, obtain the scale-up factor under each radius-of-curvature ρ according to formula K=λ × ρ, then get the Proportional coefficient K of its mean value as the fiber grating of next measurement point.

3. a kind of steric acceleration measuring method based on fiber bragg grating curvature sensing network according to claim 1, step 6) in adopt after secondary diff calculates backward, then have the acceleration of i-th t to be:

$\left\{\begin{array}{c}{A}_{\mathrm{itx}}=\frac{X_i\left(t\right)-2\&CenterDot;X_i(t-\mathrm{\&Delta;t})+X_i(t-2\&CenterDot;\mathrm{\&Delta;t})}{{\left(\mathrm{\&Delta;t}\right)}^2}\\ A_{\mathrm{ity}}=\frac{Y_i\left(t\right)-2\&CenterDot;Y_i(t-\mathrm{\&Delta;t})+Y_i(t-2\&CenterDot;\mathrm{\&Delta;t})}{{\left(\mathrm{\&Delta;t}\right)}^2}\\ A_{\mathrm{itz}}=\frac{Z_i\left(t\right)-2\&CenterDot;Z_i(t-\mathrm{\&Delta;t})+Z_i(t-2\&CenterDot;\mathrm{\&Delta;t})}{{\left(\mathrm{\&Delta;t}\right)}^2}\end{array}\right\}$

In formula, Aitx, Aity, Aitz are respectively the acceleration in i-th t x, y, z direction in dimensional Cartesian coordinates system, and Xi (t), Yi (t), Zi (t) are respectively the coordinate of i-th t x, y, z axle in dimensional Cartesian coordinates system.

4., based on a steric acceleration measurement mechanism for fiber bragg grating curvature sensing network, it is characterized in that, comprising:

Flexible space coordinate measurement bar: depend on mechanical component to be detected, and be close to the outer wall of this mechanical component, flexible space coordinate measurement bar inside is provided with multiple check point vertically, and each check point arranges fiber grating for obtaining strain signal;

Fiber Bragg grating (FBG) demodulator: obtain strain signal by check point, converts the strain signal of multiple discrete check point to digital wavelength signal;

Computing machine: obtain digital wavelength signals by fiber Bragg grating (FBG) demodulator, obtains the acceleration at each check point place.

5. a kind of steric acceleration measurement mechanism based on fiber bragg grating curvature sensing network according to claim 4, it is characterized in that, multiple check point is axially evenly arranged along flexible space coordinate measurement bar, each check point all comprises 4 fiber gratings of two groups respectively, and 4 fiber gratings are uniformly distributed along the circular cross section along flexible space coordinate measurement bar.