CN113129433B - Flexible optical fiber attitude sensing method, device and sensor - Google Patents
Flexible optical fiber attitude sensing method, device and sensor Download PDFInfo
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Abstract
The invention relates to the technical field of flexible optical fiber sensing. The flexible optical fiber attitude sensing method comprises the following steps: establishing a forward model, wherein the forward model is used for obtaining two-dimensional spatial distribution image information of flexible optical fiber output light according to flexible optical fiber three-dimensional attitude data and flexible optical fiber input light information; establishing a reverse model based on an inversion algorithm, wherein the reverse model comprises the forward model, and takes flexible optical fiber input light information and flexible optical fiber output light two-dimensional space distribution image information as input and flexible optical fiber three-dimensional attitude data as output; processing light spots received by light measuring equipment in the flexible optical fiber attitude sensing process to obtain two-dimensional space distribution image information of the output light of the flexible optical fiber; and inputting the two-dimensional spatial distribution image information of the output light of the flexible optical fiber in the flexible optical fiber attitude sensing process to the reverse model to obtain the three-dimensional attitude data of the flexible optical fiber in the flexible optical fiber attitude sensing process.
Description
Technical Field
The invention relates to the field of flexible optical fiber sensing, in particular to a flexible optical fiber attitude sensing technology using an optical line tracking technology.
Background
Flexible optical fibers have many excellent properties, such as: the material has the performances of electromagnetic and atomic radiation interference resistance, small diameter, soft quality, light weight, mechanical performance, insulation, no induction and the like. Because the flexible optical fiber is thin in soft diameter, the flexible optical fiber is often used for manufacturing sensors, and has important application in the fields of electronic skin, biological medicine, wearable electronic products, aerospace and the like.
One type of flexible optical fiber attitude sensing technology mainly utilizes a flexible optical fiber grating method, a Brillouin effect (BOTDA, BOFDA, BOTDR and the like) and the like to obtain flexible optical fiber local strain data, and then uses data processing modes such as fitting, interpolation and the like to process discrete data points to obtain the attitude of the flexible optical fiber, wherein the accuracy of the flexible optical fiber attitude sensing technology is limited by the number of monitoring points. For example, based on fresnel reflection law, a white light scanning demodulation system is adopted to measure interference arm length change of an interferometer array in four fiber cores of a spiral four-core flexible optical fiber generating a thermal diffusion effect, measured data are transmitted to a computer for processing, the value of the strain is calculated through the difference of the arm lengths, further parameters such as curvature and deflection rate of each point of the interferometer array are calculated by an interpolation method, a cubic spline interpolation method is adopted for the discrete curvature and the bending direction to interpolate the curvature and the bending direction of the whole flexible optical fiber, inversion is carried out on the three-dimensional shape of the whole multi-core flexible optical fiber, coordinate fitting and coordinate fusion are carried out, and finally real-time display is carried out by using a 3D graph.
Another type of flexible optical fiber attitude sensing technology is to install a stereoscopic vision positioning tag on the surface of a flexible optical fiber, obtain a vision positioning tag image by using a camera, and calculate the position and the attitude of each vision positioning tag by a computer so as to obtain the shape of the flexible optical fiber; and then fitting the corresponding relation between the input light and the output light of the flexible optical fiber and the shape of the flexible optical fiber by using a deep learning method, thereby obtaining the shape sensing model of the flexible optical fiber.
The first flexible optical fiber attitude sensing technology obtains the flexible optical fiber attitude by measuring local strain data and processing discrete data points by using data processing modes such as fitting, interpolation and the like. Selecting measuring points for measuring local strain data, wherein the accuracy of data processing results is reduced due to the fact that the number of the measuring points is too small; too many measurement points may lead to an increase in processing cost and processing error, and may extend the time for reconstructing the posture, and decrease the synchronization of posture sensing. In addition, interpolation and fitting methods are used for processing data for many times, so that deviation is necessarily introduced, and the accuracy of a measurement result is reduced.
The second type of flexible optical fiber attitude sensing technology has the problem of self-shielding when using a visual positioning label, and in order to obtain different samples, the arrangement scheme of the label and a camera needs to be changed, so that the samples are obtained by the method, the number and diversity of the samples are limited, the efficiency is low, the cost is high, the measurement precision is limited, and the precision of sample data is limited.
Accordingly, in view of the above deficiencies, there is a need to provide a new flexible fiber optic attitude sensing technique.
Disclosure of Invention
The invention aims to solve the technical problem that the existing flexible optical fiber attitude sensing technology is difficult to consider the problems of sample number, data processing time and measurement precision, and provides a novel flexible optical fiber attitude sensing method, device and sensor aiming at the defects in the prior art.
In order to solve the technical problems, the invention provides a flexible optical fiber attitude sensing method, which comprises the following steps:
Establishing a forward model, wherein the forward model is used for obtaining two-dimensional spatial distribution image information of flexible optical fiber output light according to flexible optical fiber three-dimensional attitude data and flexible optical fiber input light information;
Establishing a reverse model based on an inversion algorithm, wherein the reverse model comprises the forward model, and takes flexible optical fiber input light information and flexible optical fiber output light two-dimensional space distribution image information as input and flexible optical fiber three-dimensional attitude data as output;
processing light spots received by light measuring equipment in the flexible optical fiber attitude sensing process to obtain two-dimensional space distribution image information of the output light of the flexible optical fiber;
And inputting the two-dimensional spatial distribution image information of the output light of the flexible optical fiber in the flexible optical fiber attitude sensing process to the reverse model to obtain the three-dimensional attitude data of the flexible optical fiber in the flexible optical fiber attitude sensing process.
Optionally, the method further comprises, after the building of the forward model:
inputting flexible optical fiber input light information and flexible optical fiber three-dimensional posture data to the forward model, and taking the flexible optical fiber input light information and flexible optical fiber three-dimensional posture data and two-dimensional space distribution image information of flexible optical fiber output light output by the forward model according to the flexible optical fiber input light information and the flexible optical fiber three-dimensional posture data as training samples;
And training the reverse model by using the training sample.
Optionally, the processing the light spot received by the light measurement device in the flexible optical fiber attitude sensing process, and obtaining the two-dimensional spatial distribution image information of the output light of the flexible optical fiber includes:
Calculating the tangential direction of the flexible optical fiber at the output end according to the light spot received by the light measuring equipment;
Calculating an included angle theta mn and an included angle theta mn between each pixel on the light measuring device and the connecting line of the output end of the flexible optical fiber relative to the tangent line under a spherical coordinate system M and n represent the row and column numbers of the pixel in the pixel matrix, respectively;
Vector As an element of an nth row and an nth column in the two-dimensional spatial distribution image matrix of the light output by the flexible optical fiber, I mn represents a ratio of light intensity incident on the pixel to incident light intensity.
Optionally, the obtaining, by the forward model, two-dimensional spatial distribution image information of the flexible optical fiber output light according to the three-dimensional posture data of the flexible optical fiber and the input light information of the flexible optical fiber includes:
Emitting photons according to a preset emitting point and emitting direction;
In the process of tracking, when the photon is positioned on the inner surface of the flexible optical fiber cladding layer, the photon is totally reflected or reflected according to the Fresnel law, and when the photon is positioned on the end face of the flexible optical fiber emergent end, the position and the emergent direction of the photon on the end face of the flexible optical fiber emergent end are recorded, and the position of the photon on a receiving surface of light measuring equipment is calculated according to the position and the emergent direction;
When the number of photons received by the light measuring device reaches a preset value, calculating two-dimensional space distribution image information on the receiving surface of the light measuring device according to the position of each photon on the receiving surface of the light measuring device.
The invention also provides a flexible optical fiber attitude sensing device, which comprises:
The forward model building module is configured to build a forward model, and the forward model is used for obtaining two-dimensional space distribution image information of the flexible optical fiber output light according to the three-dimensional attitude data of the flexible optical fiber and the input light information of the flexible optical fiber;
A reverse model building module configured to build a reverse model based on an inversion algorithm, the reverse model including the forward model, the reverse model having flexible optical fiber input light information and flexible optical fiber output light two-dimensional spatial distribution image information as inputs and flexible optical fiber three-dimensional attitude data as outputs;
the light spot processing module is configured to process light spots received by the light measuring equipment in the flexible optical fiber attitude sensing process, and two-dimensional space distribution image information of the flexible optical fiber output light is obtained; and
The sensing module is configured to input two-dimensional space distribution image information of the flexible optical fiber output light in the flexible optical fiber attitude sensing process to the reverse model, and obtain flexible optical fiber three-dimensional attitude data in the flexible optical fiber attitude sensing process.
Optionally, the apparatus further comprises:
The training sample acquisition module is configured to input flexible optical fiber input light information and flexible optical fiber three-dimensional posture data to the forward model, and takes the flexible optical fiber input light information and flexible optical fiber three-dimensional posture data and two-dimensional space distribution image information of flexible optical fiber output light output by the forward model according to the flexible optical fiber input light information and the flexible optical fiber three-dimensional posture data as a training sample; and
A training module configured to train the inverse model using the training samples.
Optionally, the light spot processing module includes:
A first calculation module configured to calculate a tangential direction of the flexible optical fiber at an output end thereof from the light spot received by the light measurement device;
A second calculation module configured to calculate an included angle θ mn and an included angle θ mn between a line connecting each pixel on the light measurement device and the output end of the flexible optical fiber and the tangent line in a spherical coordinate system M and n represent the row and column numbers of the pixel in the pixel matrix, respectively; and
A third calculation module configured to calculate a vectorAs an element of an nth row and an nth column in the two-dimensional spatial distribution image matrix of the light output by the flexible optical fiber, I mn represents a ratio of light intensity incident on the pixel to incident light intensity.
Optionally, the obtaining, by the forward model, two-dimensional spatial distribution image information of the flexible optical fiber output light according to the three-dimensional posture data of the flexible optical fiber and the input light information of the flexible optical fiber includes:
Emitting photons according to a preset emitting point and emitting direction;
In the process of tracking, when the photon is positioned on the inner surface of the flexible optical fiber cladding layer, the photon is totally reflected or reflected according to the Fresnel law, and when the photon is positioned on the end face of the flexible optical fiber emergent end, the position and the emergent direction of the photon on the end face of the flexible optical fiber emergent end are recorded, and the position of the photon on a receiving surface of light measuring equipment is calculated according to the position and the emergent direction;
When the number of photons received by the light measuring device reaches a preset value, calculating two-dimensional space distribution image information on the receiving surface of the light measuring device according to the position of each photon on the receiving surface of the light measuring device.
The invention also provides a flexible optical fiber attitude sensor, which comprises a flexible optical fiber, a light source, measuring equipment and data processing equipment;
Light emitted by the light source enters the flexible optical fiber from one end of the flexible optical fiber, exits from the other end of the flexible optical fiber and enters the measuring equipment, the measuring equipment outputs measured data to the data processing equipment, and the flexible optical fiber attitude sensing device is embedded in the data processing equipment.
The invention also provides another flexible optical fiber attitude sensor, which comprises a flexible optical fiber, a light source, a beam splitter, measurement equipment, a reflector and data processing equipment;
The light source, the beam splitter and the measuring equipment are positioned at one end of the flexible optical fiber, and the reversing mirror is positioned at the other end of the flexible optical fiber;
Light emitted by the light source enters the flexible optical fiber after passing through the beam splitter, exits from the flexible optical fiber, is reflected by the reflector and returns in the original path, and enters the measuring equipment after being refracted by the beam splitter, the measuring equipment outputs measured data to the data processing equipment, and the flexible optical fiber attitude sensing device is embedded in the data processing equipment.
The flexible optical fiber attitude sensing method, the device and the sensor have the following beneficial effects:
The sensor gesture (namely the flexible optical fiber gesture) can be reconstructed once after detection, and the real-time reconstruction sensor gesture is monitored in real time;
processing treatment on the flexible optical fiber is reduced, and processing errors are reduced;
the sample acquisition mode for simulating the light propagation physical process improves the efficiency of obtaining samples, reduces the cost and improves the number and diversity of the samples;
deviation caused by processing discrete data is avoided, and accuracy of a measurement result is improved;
The accuracy of the obtained three-dimensional attitude data of the flexible optical fiber can be ensured by optimizing the reverse model.
Drawings
FIG. 1 is a schematic flow chart of a flexible optical fiber attitude sensing method according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram of a hardware device arrangement adopted by a forward model according to a first embodiment of the present invention;
FIG. 3 is a schematic diagram of another hardware arrangement adopted by the forward model according to the first embodiment of the present invention;
FIG. 4 is a schematic flow chart of the forward model tracking light rays according to the first embodiment of the present invention;
FIG. 5 is a schematic diagram of a hardware device layout for performing flexible fiber pose reconstruction by using a reverse model according to the first embodiment of the present invention;
FIG. 6 is a schematic diagram of another hardware device arrangement situation for performing flexible fiber pose reconstruction by using a reverse model according to the first embodiment of the present invention;
FIG. 7 is a schematic flow chart of a genetic algorithm of the first embodiment of the present invention;
FIG. 8 is a block diagram of one embodiment of the present invention obtained B m×n or Is a schematic diagram of the principle of (a);
FIG. 9 is a schematic structural view of a flexible optical fiber attitude sensing device according to a first embodiment of the present invention;
FIG. 10 is a schematic diagram of a flexible optical fiber attitude sensor according to a first embodiment of the invention;
FIG. 11 is a schematic diagram of another flexible fiber optic attitude sensor according to a first embodiment of the invention;
fig. 12 is a schematic diagram of a method for using the flexible optical fiber attitude sensor according to the first embodiment of the invention.
In the figure: 1: simulating a light source; 2: a flexible fiber optic model; 3: a virtual surface; 4: simulating a beam splitter; 5: a simulated mirror; 6: a light source; 7: a flexible optical fiber; 8: a measuring device; 9: a beam splitter; 10: a reflecting mirror.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
As shown in fig. 1, the method for sensing the posture of the flexible optical fiber provided by the embodiment of the invention includes the following steps S1 to S4.
Step S1, establishing a forward model
The forward model is used for obtaining two-dimensional space distribution image information of the flexible optical fiber output light according to the three-dimensional attitude data of the flexible optical fiber and the input light information of the flexible optical fiber.
Parameterized representation of flexible fiber space three-dimensional pose: the flexible optical fiber is spatially positioned by taking the axis of the flexible optical fiber, which can be described by a Bezier curve phi. The parameter equation forms a curve phi, a point u i is selected on the curve phi to generate a sphere, a point u i hidden function expression f i (x, y, z) is given, a plurality of function isosurfaces are fused by using Boolean transformation, the fused isosurfaces are round pipes, and the pipe diameter is equal to the pipe diameter of a flexible optical fiber cladding (namely the inner diameter of the flexible optical fiber cladding):
fblinn(x,y,z)＝g(fi(x,y,z))
The Boolean transform is used for fusion between multiple functional isosurfaces, and the expression is as follows:
Wherein i is the hidden function number; n is the total number of hidden functions; f i (x, y, z) is a hidden function expression; a blinn,i is a Boolean factor for controlling the fusion condition between functions, namely the skeleton shape between nodes; c blinn,i is used for controlling the volume occupied by the hidden function isosurface, namely the skeleton volume. The aim of controlling the structural parameters can be achieved by coordinating the values of A blinn,i and C blinn,i.
The mathematical meaning of the Boolean transform is to control the range of influence of each node hidden function. The function value of the node hidden function is related to the distance of the node from the hidden function iso-surface. Outside the equivalent surfaces, the function value approaches infinity along with the increase of the distance, which is unfavorable for the fusion among the equivalent surfaces of a plurality of nodes. Whereas the brin transformation constrains the value of the function whose out-of-surface variation range is infinite to a certain range (the farther from the surface, the closer to a certain value the function value is) by bringing this hidden function into the negative exponential function of e. That is, the value of the hidden function of each node only changes within a certain distance around the node, and the function value is unchanged after the distance is exceeded. The Boolean transform thus constrains the range of influence of each node's implicit function. This region of rapid change in the off-surface function value is called the brin region, the size of which is controlled by parameter a blinn,i. The nature of the brin region determines the fusion of isosurfaces between nodes, including the magnitude of the brin region and the rate at which the function values approach a constant value in the brin region. For the same node hidden function expression, the larger the Boolean region (i.e., the smaller A blinn,i), the node isosurface may be fused with the further other isosurfaces. For different node hidden function expressions, under the condition that the sizes of the Boolean areas are the same, the function value approaches to a fixed value faster, and the influence range of the node hidden function is larger, so that the function value can be fused with a more distant isosurface.
The present embodiment uses only the brin transformation between two nodes, and the node hidden function expression uses the square of the euclidean distance function of node i.
The forward model is used for tracking the light rays, and the simulated hardware is arranged as shown in fig. 2 or 3. In fig. 2, a simulated light source 1 is located at one end of a flexible optical fiber model 2, and light emitted by the simulated light source 1 enters the flexible optical fiber model 2 from one end of the flexible optical fiber model 2, exits from the other end of the flexible optical fiber model 2, and then enters a detection surface of a measuring device, wherein the detection surface is represented by a virtual surface 3. In fig. 3, a simulated light source 1, a simulated beam splitter 4 and measurement equipment are located at one end of a flexible optical fiber model 2, a simulated mirror 5 is arranged at the other end of the flexible optical fiber model 2, light emitted by the simulated light source 1 enters the flexible optical fiber model 2 from one end of the flexible optical fiber model 2 after being transmitted by the simulated beam splitter 4, and returns to the flexible optical fiber model 2 after being reflected by the simulated mirror 5 at the other end of the flexible optical fiber model 2, exits from the flexible optical fiber model 2 and is refracted by the simulated beam splitter 4, and then is incident on a detection surface of the measurement equipment.
The principle of the forward model for tracking the light is as follows: the light source emits quantitative photons, the emitting point and the emitting direction of the photons are recorded, the photons enter the flexible optical fiber from the incident end of the flexible optical fiber, when encountering an isosurface in the internal transmission process of the flexible optical fiber, the photons are reflected according to the total reflection law or the Fresnel reflection law according to the difference of the incident angles, finally, the direction vector and the emitting position of the photons emitted from the emitting end of the flexible optical fiber are recorded, a certain quantity of photons are accumulated, and the relative light intensity distribution matrix A m×n/vector at a certain distance l from the emitting end face (namely, the position of the receiving surface of the light measuring device) is calculated according to the direction vector and the emitting position of the photonsThe shape of the curve phi is changed for a plurality of times to track the optical fiber, and a mapping p is established, wherein the mapping p is phi-A m×n or mapping/>The forward model may also be optimized according to the actual usage scenario.
The specific method of ray tracing is not limited in the present application. The method shown in fig. 4 may be employed:
Firstly, controlling a light source to emit a certain number of photons according to a preset emergent point and a preset emergent direction, and advancing the photons according to a preset step length after entering a flexible optical fiber;
the current position of the photon is judged every time a step length is passed:
If the photon is currently in the cavity (i.e., inside the core, not the core boundary), then the photon proceeds one step;
If the photon is currently positioned on the surface of the skeleton (namely the inner surface of the cladding), judging whether the photon generates total reflection according to the direction of the photon, if the photon generates total reflection, calculating the direction vector of reflected light according to the law of total reflection, if the photon does not generate total reflection, calculating the reflectance according to the law of Fresnel, judging whether the photon is reflected or absorbed, if the photon is reflected, calculating the direction vector of the reflected light, taking the position of the photon on the surface of the skeleton as a new emergent point, then continuing to advance according to a preset step length, and if the photon is absorbed, recording the position and vector of an absorption point;
If the photon is currently at the space boundary (namely the end face of the emergent end of the flexible optical fiber), the current direction vector and emergent position of the photon are recorded, and the relative light intensity distribution at the position l (namely the position of the receiving surface of the virtual light measuring device) can be calculated according to the current direction vector and emergent position.
The manner in which photons are transmitted during ray tracing includes, but is not limited to, the step-wise progression described above. For the position and direction of photonsRepresentation of/>Coordinates representing the origin of the ray,/>Representing the direction vector of the ray, t represents the photon travel distance, e.g., t=1 represents the photon at/>Direction travel 1/>Is a distance of (3). The photon travels in the optical fiber and follows the Fresnel law, and the direction vector of the reflected photon is/> Is the direction vector of the reflected ray,/>Is the normal direction of the reflecting surface,/>Is the direction vector of the incident ray. After the primary reflection is completed, update/>And/>Will/>Value assignment/>Assigning/>, to a photon, position coordinates on a surface of a skeleton
And S2, establishing a reverse model based on an inversion algorithm, wherein the reverse model comprises the forward model, and the reverse model takes flexible optical fiber input light information and flexible optical fiber output light two-dimensional space distribution image information as input and flexible optical fiber three-dimensional attitude data as output.
The hardware arrangement corresponding to the inverse model is shown in fig. 5 or fig. 6. Fig. 5 and 6 show two hardware arrangements, in fig. 5, the light source and the light measuring device are respectively located at two ends of the flexible optical fiber, in fig. 6, the light source and the light measuring device are located at one end of the flexible optical fiber, and the reflector is arranged at the other end of the flexible optical fiber. Image recognition is carried out at the output end of the flexible optical fiber by using optical measurement equipment, and the recognized two-dimensional image information is processed to obtain a matrix B m×n or a vectorMatrix B m×n or vector/>Input into an inversion algorithm-based inverse model, and establish an objective function (or adaptation function) h (B m×n,Am×n) or/>The objective function is the difference between the output of the reverse model and actual measurement data, and the objective function is input into the reverse model for parameter optimization until the reverse model can output the flexible optical fiber space three-dimensional gesture meeting the accuracy requirement.
The reverse model can be implemented in a variety of ways, and the application is not limited in particular, and can be implemented by using a genetic algorithm, for example, and the flow is shown in fig. 7. For the measured image light intensity distribution information B m×n or(B m×n is a matrix,/>Vector), it is necessary to derive an expression for its corresponding flexible fiber pose, but there is no vector in the forward model with B m×n or/>The same sample, a completely new expression is needed to be found. Genetic algorithm first searches for and B m×n or/>, in a sample librarySeveral similar/>Or/>The number/>Or/>The expression Φ 1(1)、Φ2(1)、……Φi (1) … … of the corresponding flexible fiber morphology forms an initial population Φ' (1), the numbers in brackets represent the number of cycles, the initial number of cycles is 1, then the initial number of cycles is used to include B m×n or/>The objective function of the information calculates each/>Or/>According to the calculation result, judging whether the accuracy requirement is met or notOr/>If so, will meet the accuracy requirement/>Or/>The expression phi i (t) of the corresponding flexible optical fiber morphology is taken as the final flexible optical fiber attitude equation, if the accuracy requirement/>Or (b)Then for the number/>Or/>Selecting, intersecting and mutating operation is carried out, the group phi '(1) is updated according to the operation result to obtain a new group phi' (2), then the group phi '(2) is input into a forward model, and the forward model is calculated to obtain a plurality of light intensity distribution matrixes/>, which correspond to the group phi' (2)Or vector/>And calculates each matrix/>, using the objective functionOr vector/>According to the calculation result, judging whether a matrix meeting the accuracy requirement exists or notOr vector/>If so, the matrix/>, in phi' (2), of the sum meets the accuracy requirementOr vector/>The corresponding expression of the flexible optical fiber morphology is taken as a final flexible optical fiber attitude equation, and if not, the flexible optical fiber attitude equation is applied to the plurality of/>Or/>Selecting, intersecting and mutating operation, and updating the group phi '(2) according to the operation result to obtain phi' (3) … …, and repeatedly circulating until/>, which meets the accuracy requirement, can be foundOr/>Until then in Φ' (t) and/>, which meets the accuracy requirementOr/>The corresponding expression of the flexible fiber morphology serves as the final flexible fiber pose equation.
And S3, processing light spots received by the light measuring equipment in the flexible optical fiber attitude sensing process to obtain two-dimensional spatial distribution image information of the flexible optical fiber output light.
In the case of attitude sensing using a flexible optical fiber, the image light intensity distribution information B m×n or the image light intensity distribution information B m×n inputted into the inverse modelThe information measured by the light measuring device in this embodiment is processed as shown in fig. 8:
Firstly, the flexible optical fiber is equivalent to a curve, namely the axis of the flexible optical fiber, then the end face of the flexible optical fiber is equivalent to a point, the energy distribution of a light spot received by the light measuring equipment accords with Gaussian distribution, and the direction of a tangent A at the output end of the flexible optical fiber can be calculated according to the position of the central point of the light spot;
Then, taking CCD as light measuring device as an example, for any pixel point on CCD, for example, the pixel located in the mth row and the nth column in the pixel matrix, connecting the pixel point with the output end of the flexible optical fiber, marking the formed line segment as B, and calculating two included angles theta mn and a tangential line A under the spherical coordinate system
Finally, calculating the ratio I mn of the output light intensity to the incident light intensity of the flexible optical fiber on the pixel of the nth row and the nth column, and carrying out vectorAs the element of the nth row and the nth column in the two-dimensional space distribution image matrix of the light output by the flexible optical fiber, the calculation is carried out on each pixel of the CCD, so that the image light intensity distribution information B m×n or/>, on the CCD, can be obtained
And S4, inputting the two-dimensional spatial distribution image information of the flexible optical fiber output light in the flexible optical fiber attitude sensing process obtained in the step S3 into the reverse model, and outputting the flexible optical fiber three-dimensional attitude data by the reverse model according to the principle of the step S2.
In this embodiment, the inverse model may also be trained to obtain an optimization model thereof. The training sample can have two sources, wherein one source is actually measured flexible optical fiber input light information, flexible optical fiber three-dimensional attitude data and flexible optical fiber output light two-dimensional space distribution image information, but the sample acquisition mode is long in time consumption, high in cost and relatively poor in diversity; another source is to obtain some sample data using a forward model, specifically: the method is characterized in that flexible optical fiber input light information and flexible optical fiber three-dimensional attitude data are input to the forward model, the forward model outputs two-dimensional space distribution image information of flexible optical fiber output light according to the input data, and the input and output of the forward model are used as training samples, so that a large amount of sample data can be obtained in a short time, the efficiency is high, the cost is low, and the variety of data is good. When training the reverse model, any one of the two samples can be used as a training sample to obtain an optimized model of the reverse model, and the two training samples can be used for cross verification at the same time. After training, the flexible optical fiber three-dimensional attitude data can be obtained by directly utilizing the optimization model of the reverse model during optical fiber sensing.
As shown in fig. 9, an embodiment of the present invention further provides a flexible optical fiber attitude sensing device, including:
The forward model building module is configured to build a forward model, and the forward model is used for obtaining two-dimensional space distribution image information of the flexible optical fiber output light according to the three-dimensional attitude data of the flexible optical fiber and the input light information of the flexible optical fiber;
A reverse model building module configured to build a reverse model based on an inversion algorithm, the reverse model including the forward model, the reverse model having flexible optical fiber input light information and flexible optical fiber output light two-dimensional spatial distribution image information as inputs and flexible optical fiber three-dimensional attitude data as outputs;
the light spot processing module is configured to process light spots received by the light measuring equipment in the flexible optical fiber attitude sensing process, and two-dimensional space distribution image information of the flexible optical fiber output light is obtained; and
The sensing module is configured to input two-dimensional space distribution image information of the flexible optical fiber output light in the flexible optical fiber attitude sensing process to the reverse model, and obtain flexible optical fiber three-dimensional attitude data in the flexible optical fiber attitude sensing process.
As a preferred embodiment of the present application, the apparatus further comprises:
The training sample acquisition module is configured to input flexible optical fiber input light information and flexible optical fiber three-dimensional posture data to the forward model, and takes the flexible optical fiber input light information and flexible optical fiber three-dimensional posture data and two-dimensional space distribution image information of flexible optical fiber output light output by the forward model according to the flexible optical fiber input light information and the flexible optical fiber three-dimensional posture data as a training sample; and
A training module configured to train the inverse model using the training samples.
As a preferred embodiment of the present application, the spot processing module includes:
A first calculation module configured to calculate a tangential direction of the flexible optical fiber at an output end thereof from the light spot received by the light measurement device;
A second calculation module configured to calculate an included angle θ mn and an included angle θ mn between a line connecting each pixel on the light measurement device and the output end of the flexible optical fiber and the tangent line in a spherical coordinate system M and n represent the row and column numbers of the pixel in the pixel matrix, respectively; and
A third calculation module configured to calculate a vectorAs an element of an nth row and an nth column in the two-dimensional spatial distribution image matrix of the light output by the flexible optical fiber, I mn represents a ratio of light intensity incident on the pixel to incident light intensity.
As a preferred embodiment of the present application, the obtaining, by the forward model, two-dimensional spatial distribution image information of the output light of the flexible optical fiber according to the three-dimensional posture data of the flexible optical fiber and the input light information of the flexible optical fiber includes:
Emitting photons according to a preset emitting point and emitting direction;
In the process of tracking, when the photon is positioned on the inner surface of the flexible optical fiber cladding layer, the photon is totally reflected or reflected according to the Fresnel law, and when the photon is positioned on the end face of the flexible optical fiber emergent end, the position and the emergent direction of the photon on the end face of the flexible optical fiber emergent end are recorded, and the position of the photon on a receiving surface of light measuring equipment is calculated according to the position and the emergent direction;
When the number of photons received by the light measuring device reaches a preset value, calculating two-dimensional space distribution image information on the receiving surface of the light measuring device according to the position of each photon on the receiving surface of the light measuring device.
The flexible optical fiber attitude sensing device provided by the embodiment of the invention can execute the steps of the flexible optical fiber attitude sensing method, and the principle and effects of the flexible optical fiber attitude sensing device are not repeated herein.
As shown in fig. 10, the embodiment of the present invention further provides a flexible optical fiber attitude sensor, which includes a light source 6, a flexible optical fiber 7, a measurement device 8, and a data processing device (the data processing device is not shown in the figure);
the light emitted by the light source 6 enters the flexible optical fiber 7 from one end of the flexible optical fiber 7, and enters the measuring equipment 8 after exiting from the other end of the flexible optical fiber, the measuring equipment 8 outputs measured data to the data processing equipment, the flexible optical fiber attitude sensing device is embedded in the data processing equipment, and the flexible optical fiber attitude sensing device is used for reconstructing the flexible optical fiber attitude according to the data measured by the measuring equipment 8.
As shown in fig. 11, the embodiment of the present invention further provides another flexible optical fiber attitude sensor, which includes a light source 6, a flexible optical fiber 7, a measuring device 8, a beam splitter 9, a reflecting mirror 10, and a data processing device (the data processing device is not shown in the figure);
The light source 6, the beam splitter 9 and the measuring device 8 are positioned at one end of the flexible optical fiber 7, and the reflecting mirror 10 is positioned at the other end of the flexible optical fiber 7;
light emitted by the light source 6 enters the flexible optical fiber 7 after passing through the beam splitter 9, exits from the flexible optical fiber 7 and returns to the flexible optical fiber 7 in a primary path through the reflector 10, exits from the flexible optical fiber 7 again and enters the measuring equipment 8 after being refracted by the beam splitter 9, the measuring equipment 8 outputs measured data to the data processing equipment, and the flexible optical fiber attitude sensing device is embedded in the data processing equipment and is used for reconstructing the flexible optical fiber attitude according to the data measured by the measuring equipment 8.
The flexible optical fiber posture sensor shown in fig. 11 is applied to the measurement of the posture of the human arm, and as shown in fig. 12 (the data processing device is not shown in the figure), the flexible optical fiber 7 is arranged along the arm, and the posture of the arm is obtained from the measured posture data of the flexible optical fiber.
In summary, the invention establishes a forward model based on a ray tracing method for simulating a light propagation process, wherein the model takes a flexible optical fiber three-dimensional posture and input light as input data and takes output light two-dimensional space distribution image information as an output result; taking input data and output results of the forward model as samples (namely, sample data is obtained only through a flexible optical fiber tracking method), establishing a machine learning algorithm for supervised learning, and training to obtain data for rapidly processing a large number of flexible optical fiber three-dimensional postures and input lights, so as to obtain an optimized model corresponding to the output light space distribution image information; the method comprises the steps of establishing a reverse model based on an inversion algorithm, obtaining two-dimensional spatial distribution image information of output light of a flexible optical fiber output end by combining optical measurement equipment measurement when the reverse model is used, defining the difference between numerical simulation data and actual measurement data as an objective function (or an adaptive function), inputting the objective function into the inversion algorithm to perform parameter optimization until parameterized representation of the three-dimensional spatial attitude of the flexible optical fiber meeting accuracy requirements (deviation is within a specified range) is output.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. A flexible optical fiber attitude sensing method, comprising:
Establishing a forward model, wherein the forward model is used for obtaining two-dimensional spatial distribution image information of flexible optical fiber output light according to flexible optical fiber three-dimensional attitude data and flexible optical fiber input light information;
Establishing a reverse model based on an inversion algorithm, wherein the reverse model comprises the forward model, and takes flexible optical fiber input light information and flexible optical fiber output light two-dimensional space distribution image information as input and flexible optical fiber three-dimensional attitude data as output;
processing light spots received by light measuring equipment in the flexible optical fiber attitude sensing process to obtain two-dimensional space distribution image information of the output light of the flexible optical fiber;
inputting two-dimensional spatial distribution image information of the output light of the flexible optical fiber in the flexible optical fiber attitude sensing process to the reverse model to obtain flexible optical fiber three-dimensional attitude data in the flexible optical fiber attitude sensing process;
Processing a light spot received by light measuring equipment in the flexible optical fiber attitude sensing process, and obtaining two-dimensional spatial distribution image information of the flexible optical fiber output light comprises the following steps:
Calculating the tangential direction of the flexible optical fiber at the output end according to the light spot received by the light measuring equipment;
Calculating an included angle theta mn and an included angle theta mn between each pixel on the light measuring device and the connecting line of the output end of the flexible optical fiber relative to the tangent line under a spherical coordinate system M and n represent the row and column numbers of the pixel in the pixel matrix, respectively;
Vector An element of an nth row and an nth column in a two-dimensional space distribution image matrix of the output light of the flexible optical fiber, wherein I mn represents a ratio of light intensity incident on the pixel to incident light intensity;
The forward model obtains two-dimensional space distribution image information of the flexible optical fiber output light according to the three-dimensional attitude data of the flexible optical fiber and the input light information of the flexible optical fiber, and the method comprises the following steps:
Emitting photons according to a preset emitting point and emitting direction;
In the process of tracking, when the photon is positioned on the inner surface of the flexible optical fiber cladding layer, the photon is totally reflected or reflected according to the Fresnel law, and when the photon is positioned on the end face of the flexible optical fiber emergent end, the position and the emergent direction of the photon on the end face of the flexible optical fiber emergent end are recorded, and the position of the photon on a receiving surface of light measuring equipment is calculated according to the position and the emergent direction;
When the number of photons received by the light measuring device reaches a preset value, calculating two-dimensional space distribution image information on the receiving surface of the light measuring device according to the position of each photon on the receiving surface of the light measuring device.
2. The method of claim 1, further comprising, after said establishing a forward model:
inputting flexible optical fiber input light information and flexible optical fiber three-dimensional posture data to the forward model, and taking the flexible optical fiber input light information and flexible optical fiber three-dimensional posture data and two-dimensional space distribution image information of flexible optical fiber output light output by the forward model according to the flexible optical fiber input light information and the flexible optical fiber three-dimensional posture data as training samples;
And training the reverse model by using the training sample.
3. A flexible optical fiber attitude sensing device, comprising:
The forward model building module is configured to build a forward model, and the forward model is used for obtaining two-dimensional space distribution image information of the flexible optical fiber output light according to the three-dimensional attitude data of the flexible optical fiber and the input light information of the flexible optical fiber;
A reverse model building module configured to build a reverse model based on an inversion algorithm, the reverse model including the forward model, the reverse model having flexible optical fiber input light information and flexible optical fiber output light two-dimensional spatial distribution image information as inputs and flexible optical fiber three-dimensional attitude data as outputs;
the light spot processing module is configured to process light spots received by the light measuring equipment in the flexible optical fiber attitude sensing process, and two-dimensional space distribution image information of the flexible optical fiber output light is obtained; and
The sensing module is configured to input two-dimensional space distribution image information of the output light of the flexible optical fiber in the flexible optical fiber attitude sensing process to the reverse model, so as to obtain flexible optical fiber three-dimensional attitude data in the flexible optical fiber attitude sensing process;
The light spot processing module comprises:
A first calculation module configured to calculate a tangential direction of the flexible optical fiber at an output end thereof from the light spot received by the light measurement device;
A second calculation module configured to calculate an included angle θ mn and an included angle θ mn between a line connecting each pixel on the light measurement device and the output end of the flexible optical fiber and the tangent line in a spherical coordinate system M and n represent the row and column numbers of the pixel in the pixel matrix, respectively; and
A third calculation module configured to calculate a vectorAn element of an nth row and an nth column in a two-dimensional space distribution image matrix of the output light of the flexible optical fiber, wherein I mn represents a ratio of light intensity incident on the pixel to incident light intensity;
The forward model obtains two-dimensional space distribution image information of the flexible optical fiber output light according to the three-dimensional attitude data of the flexible optical fiber and the input light information of the flexible optical fiber, and the method comprises the following steps:
Emitting photons according to a preset emitting point and emitting direction;
In the process of tracking, when the photon is positioned on the inner surface of the flexible optical fiber cladding layer, the photon is totally reflected or reflected according to the Fresnel law, and when the photon is positioned on the end face of the flexible optical fiber emergent end, the position and the emergent direction of the photon on the end face of the flexible optical fiber emergent end are recorded, and the position of the photon on a receiving surface of light measuring equipment is calculated according to the position and the emergent direction;
When the number of photons received by the light measuring device reaches a preset value, calculating two-dimensional space distribution image information on the receiving surface of the light measuring device according to the position of each photon on the receiving surface of the light measuring device.
4. A device according to claim 3, further comprising:
The training sample acquisition module is configured to input flexible optical fiber input light information and flexible optical fiber three-dimensional posture data to the forward model, and takes the flexible optical fiber input light information and flexible optical fiber three-dimensional posture data and two-dimensional space distribution image information of flexible optical fiber output light output by the forward model according to the flexible optical fiber input light information and the flexible optical fiber three-dimensional posture data as a training sample; and
A training module configured to train the inverse model using the training samples.
5. A sensor comprising the apparatus of any one of claims 3 to 4, comprising a flexible optical fiber, a light source, a measurement device, and a data processing device;
Light emitted by the light source enters the flexible optical fiber from one end of the flexible optical fiber, exits from the other end of the flexible optical fiber and enters the measuring equipment, the measuring equipment outputs measured data to the data processing equipment, and the flexible optical fiber attitude sensing device is embedded in the data processing equipment.
6. A sensor comprising the apparatus of any one of claims 3 to 4, comprising a flexible optical fiber, a light source, a beam splitter, a measuring device, a mirror, and a data processing device;
The light source, the beam splitter and the measuring equipment are positioned at one end of the flexible optical fiber, and the reflector is positioned at the other end of the flexible optical fiber;
the light emitted by the light source enters the flexible optical fiber after passing through the beam splitter, is reflected by the reflector and returns in the original path after exiting from the flexible optical fiber, then enters the measuring equipment after being refracted by the beam splitter, the measuring equipment outputs the measured data to the data processing equipment,
The flexible optical fiber attitude sensing device is embedded in the data processing equipment.
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