Space-expandable pod rod structure shape inversion method

Abstract

The invention discloses a shape inversion method for a space deployable pod rod structure, and belongs to the field of space deployable structure deformation measurement and deformation state monitoring. The implementation method comprises the following steps: utilizing the surface density lt; the 7 / m < 2 > sensor array realizes shape real-time measurement of the pod rod structure in the out-of-plane bending and in-plane curling processes; the bendable flexible sensor, the light-weight signal wireless acquisition device and the pod rod structure are integrated, accurate measurement and wireless transmission of surface strain in the pod rod structure deformation process are achieved, and real-time measurement of pod rod structure deformation is achieved by processing sensor signals. The position of the sensor is the junction of each section of pod rod structure; the pod rod structure is segmented in the in-plane length direction according to the curl radius, and the length of each segment is 2 pi times of the average radius of the area in the curl state. The measuring direction of the sensor is the out-of-plane bending deformation direction and is perpendicular to the unfolding direction of the pod rod structure. The method has the advantages of low cost, accurate result, wide applicability and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of space deployable structures, and relates to a space deployable pod pole structure shape inversion method. BACKGROUND

[0002] The traditional space deployment device cannot perceive the bending deformation of the inter-joint rod and itself. When facing the deformation state monitoring demand, an optical sensor or a camera is often installed for deformation detection, which significantly increases the system weight and complexity. Using strain to obtain full-field displacement information is an accurate, simple, and convenient testing method that does not require any external device assistance and does not damage the structure itself. The method uses a sensor array to provide characteristic signals of key deformation positions, uses a resistance-strain conversion relationship to obtain key point strain values, inputs a strain-displacement relationship to obtain full-field strain, obtains displacement data of the entire surface of the structure through strain data, and realizes real-time reconstruction of the three-dimensional morphology of the deformation structure with a continuous curved surface feature through surface fitting, so as to realize a work state monitoring system that does not depend on cameras and other visual objective external devices and can be highly integrated with the deformation mechanism body. The system can customize flexible sensors according to the target to be measured, and the adjustable sensitivity flexible sensing unit can be applied to various large and small deformation working conditions, and has the advantages of wide application range, high deformation feedback precision, etc.

[0003] Through the above analysis, the problems and defects of the prior art are:

[0004] (1) The existing method can measure the displacement data of the structure surface, but it needs to rely on external equipment assistance, and is easily blocked by the structure itself, so it cannot accurately test the real-time deformation of the structure surface.

[0005] (2) The existing method of obtaining structure surface deformation data through a sensor is only applicable to hard plates and shells with flat surfaces and simple deformation structures, and cannot reconstruct complex surface deformation.

[0006] The difficulty of solving the above problems and defects is:

[0007] (1) When measuring the strain of the structure surface using a sensor, it is necessary to strictly ensure the safe operation of the equipment under non-stop conditions, and the measuring device has high requirements. The measurement accuracy should be as high as possible and the size of the measurement equipment should not affect the safe operation of the equipment.

[0008] (2) The existing measurement method needs to paste sensors on the upper and lower surfaces of the structure, and cannot measure the deformation of the external closed structure surface. In addition, the applicability to different structures is poor, and it is difficult to find a unified measurement method for different structures. SUMMARY

[0009] In view of the problems in the prior art, the core purpose of the present application is to provide a space deployable pod structure shape inversion method, which realizes real-time shape measurement of the out-of-plane bending and in-plane curling processes of the pod structure by using a sensor array with a surface density of less than 7 / m 2 The present application is suitable for the deformation inversion requirements of spacecraft components such as satellite solar panels, space manipulators, space telescope support arms and the like that need to accurately control the deployment morphology, and can realize digital reconstruction of the three-dimensional morphological deformation of continuous complex surfaces.

[0010] The purpose of the present application is achieved by the following technical solutions:

[0011] The space deployable pod structure shape inversion method disclosed by the present application realizes accurate measurement and wireless transmission of surface strain during deformation of the pod structure by integrating a bendable flexible sensor, a lightweight signal wireless acquisition device and the pod structure, realizes real-time measurement of deformation of the pod structure by processing the sensor signals.

[0012] In the above method, the sensor position is the junction of each pod structure segment; the pod structure is segmented in the in-plane length direction according to the curling radius, and the length of each segment is 2π times the average radius of the region in the curled state, i.e. one turn.

[0013] In the above method, the sensor measurement direction is the out-of-plane bending deformation direction, which is perpendicular to the deployment direction of the pod structure.

[0014] In the above method, the surface strain during deformation of the structure is measured by a highly integrated sensor array, the number of sensing units in the sensor array is n, the sensor signal changes are collected and transmitted by a small wireless acquisition card, and the strain value is calculated from the sensor measurement data.

[0015] In the above method, the strain value is obtained by the following formula:

[0016] ;

[0017] In the formula, is the strain value at the sensor measurement position, is the sensor strain coefficient, is the initial resistance of the i th sensor, is the real-time resistance of the i th sensor after deformation of the structure; the sensor represented by R1 is located at the edge of the pod structure.

[0018] In the above method, the configuration of the pod structure is obtained by the following method,

[0019] Step 1: according to Establish the strain-curvature transformation relationship caused by out-of-plane bending of the pod stalk structure:

[0020]

[0021] Where h is the structural thickness and ρ is the average curvature at the sensor;

[0022] Step 2: Based on ρ from Step 1, obtain the spatial coordinates (x, y) of the sensor. i , y i ):

[0023]

[0024] Wherein, the local rotation angle at the i-th sensor , ρ i Let be the average curvature at the i-th sensor; ΔL is the distance between the two sensing units.

[0025] By fitting the coordinates of n test points, the interface shape at the junction of each segment in the in-plane direction of the pod stem structure can be obtained at this moment:

[0026]

[0027] Where x ri Let y be the global x-coordinate of node i. ri Let x be the global ordinate of node i. i Let y be the local x-coordinate of node i. i Let θ be the local ordinate of node i. ri-1 The global rotation angle of node i-1 is equal to θ. i-2 +θ i-1 .

[0028] Step 3: Obtain the coordinates of the non-sensor locations based on the interface shape at the sensor location obtained in Step 2.

[0029]

[0030] In the formula, and Let be the x and y coordinates of the node position at distance m from the sensor. The distance from this node to the edge of the pod stalk structure is the same as the distance from the i-th sensor to the edge of the pod stalk structure; m is the distance between this node and the sensor; l is the unfolded length of the i-th segment of the pod stalk structure. i Represented as:

[0031]

[0032] In the formula, 'a' is the correlation coefficient, and 'v' is a constant determined in the previous period. The maximum change of the resistance of the No. 1 sensor of the pod stem structure end sensor in the whole pod stem structure deformation process, The real-time change of the resistance of the No. 1 sensor, The initial resistance value of the No. 1 resistance;

[0033] The configuration of the pod stem is finally obtained by interpolating and fitting the coordinates (x i , y i ) and (x , y ).

[0034] In the above method, the sensor substrate material is polyimide, the sensing material and the wire are both Karma alloy, and the preparation is carried out by etching method; by changing the type of sensing functional material and the two-dimensional pattern of the sensor, the adjustment of the range and sensitivity of the sensor is realized.

[0035] In the above method, the adjustment of the range and sensitivity of the sensor is realized by changing the type of sensing functional material and the two-dimensional pattern of the sensor, which is realized by the following method:

[0036] The sensing functional material is replaced by constantan, the sensor range is reduced from 0-4% to 0-2%, the sensitivity is reduced from 10-15 to 2-6; by modifying the line width of the serpentine wire, the sensitivity of the sensor is adjusted, and the adjustment formula is as follows:

[0037]

[0038] Wherein, S is the sensitivity, l is the line width, and n is a constant, which is obtained by calibrating the sensor.

[0039] Advantages:

[0040] 1. The space deployable pod stem structure shape inversion method disclosed by the application designs a high-precision metal-based sensing unit according to a to-be-measured pod stem structure, and utilizes etching to high-integration package a plurality of sensing units, so that the use of wires is significantly reduced. The packaged sensing array is connected with a wireless data acquisition and transmission device, the change of the sensor array signal caused by the deformation of the to-be-measured target is acquired and transmitted at a high frequency; by comparison with a commercial sensor, the calibration of the sensor array is realized, and the relationship between strain and resistance change rate is established; based on the KO displacement theory, the mapping relationship between the structure surface strain and deformation is established, and the structure shape change is realized by using the sensor signal. The application can accurately obtain the structure surface displacement without the aid of external equipment, and can realize the purpose of real-time reconstruction of the structure 3D surface, so as to provide accurate measurement data for judging the structure operation state and maintenance.

[0041] 2. The shape inversion method of the space deployable pod beam structure disclosed in the application solves the problem that sensors cannot measure large deformation by integrating multiple sensors, increasing the test area and reducing the number of sensor wiring, increases the application range of the sensor, and has the ability to adapt to different monitoring targets.

[0042] 3. The shape inversion method of the space deployable pod beam structure disclosed in the application reduces the influence on the structure during the curling process by reducing the thickness of the sensor and the size of the wireless data acquisition card, avoids interference between the sensor device and the pod beam structure, and can measure the surface deformation of the structure without stopping the equipment. The surface deformation is tested while reducing the influence on the equipment, without stopping the equipment, and the safe operation of the equipment is ensured.

[0043] 4. The shape inversion method of the space deployable pod beam structure disclosed in the application solves the limitation that traditional deformation inversion methods must double-side paste sensors by segmenting the structure and correlating the local curvature and local strain value after the structure deformation. The purpose of accurately obtaining the deformation degree by single-side pasting sensors can be achieved, greatly saving the cost.

[0044] 5. The shape inversion method of the space deployable pod beam structure disclosed in the application can realize real-time and accurate reconstruction of the surface of non-flat structures and complex deformation structures by reducing the thickness of the sensor, allowing the sensor to follow the structure deformation and not affecting the deformation of the pod beam structure itself, and establishing a correlation between continuous strain and continuous curvature.

[0045] 6. The shape inversion method of the space deployable pod beam structure disclosed in the application has the characteristics of low cost, accurate results, and wide applicability compared with the existing optical measurement method. The resistance-strain-displacement relationship constructed can be applied to real-time reconstruction of the surface displacement of the service structure, providing accurate measurement data for judging the operation state and maintenance of the structure. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application.

[0047] Figure 1 It is a whole view of the pod beam structure and the strain measurement device of the present application.

[0048] Figure 2 It is a schematic view of the installation position of the sensing unit of the present application.

[0049] Figure 3 It is the resistance signal measurement principle of the sensing unit of the present application.

[0050] Figure 4 The local curvature, corner and displacement calculation method of the application is shown in the figure;

[0051] Figure 5 The global displacement calculation method of the application is shown in the figure;

[0052] Figure 6 The performance adjustment of the sensing unit of the application is shown in the figure;

[0053] Figure 7 The section of the pod structure obtained by inversion of the application is shown in the figure;

[0054] In the figure, 1 is the external frame of the device, 2 is the motor drum, 3 is the guide mechanism, 4 is the pod structure, and 5 is the sensing system. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical scheme and advantages of the application clearer and more apparent, the application will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and not to limit the application. In view of the problems existing in the prior art, the space deployable pod structure shape inversion method disclosed in the embodiment can realize real-time monitoring of the shape of the space deployable device and can be used for shape monitoring of the space deployable structure such as the pod structure, thereby providing data for precise control of equipment. The application will be described in detail below in combination with the drawings:

[0056] The space deployable pod structure shape inversion method disclosed in the embodiment is used for measuring the configuration during the folding and unfolding of the foldable pod structure, as shown in the figure. Figure 1 The space deployable pod structure disclosed in the embodiment includes an external frame 1, a motor drum 2, a guide mechanism 3, a pod structure 4 and a sensing system 5. The external frame 1 is in the form of a closed rectangular box structure as a whole, and the size can be determined according to specific conditions. The motor drum 2 is fixed to the inner wall of the frame structure 1 through a motor mounting platform. The pod structure 4 is fixed to the motor drum 2 through bolts, and the other end extends out of the external frame 1 through the guide mechanism 3. The guide mechanism 3 is arranged on the left upper side inside the external frame and clamps the extended part of the pod structure 4. Multiple sensing systems 5 are attached to the surface of the pod structure 4 to collect and transmit the changes in the sensor signals caused by the deformation of the pod structure 4. The width of the pod structure 4 is not less than 60 cm, the thickness is 0.5 mm, and the total length of the unfolded pod structure 4 is not less than 1000 cm. The length of the sensor in the sensing system 5 is half of the width of the pod structure 4, and the thickness is less than 60 μm. In this embodiment, the width of the pod structure 4 is 60 cm, the length of the sensor is 30 cm, and the thickness is 48 μm.

[0057] The winding contraction and rotary elongation of the pod rod structure 4 is driven by clockwise and counterclockwise rotation of the motor winding drum 2.

[0058] The upper left side of the outer frame 1 is provided with an outlet, and the end of the pod rod structure 4 is extended out of the outlet. The guide mechanism 3 is installed at the outlet of the outer frame 1, and the compression and alignment of the pod rod structure 4 to the outlet of the outer frame 1 are realized through the guide of the guide mechanism 3, realizing the extension and recovery from the outlet of the outer frame 1.

[0059] The pod rod structure 4 is made of carbon fiber material, and the cross section in the initial state is "Ω" shape, at this time the axial bending stiffness is larger. First, one end of the pod rod structure is passed through the guide mechanism 3, at this time the pod rod structure is flattened, and the flattened end is fixed on the surface of the guide structure 3 by bolts. Subsequently, by rotating the motor winding drum 2, the entire pod rod structure 4 can be automatically wound.

[0060] When the pod rod structure 4 needs to be rotated and elongated, the motor winding drum 2 rotates counterclockwise, and the pod rod structure automatically expands to an Ω-shaped structure through the guide mechanism 3.

[0061] The sensing system 5 includes a flexible sensor and a data acquisition and transmission device. The material of the sensing unit of the flexible sensor is Karma alloy, the base material is polyimide film, and the total thickness is less than 60μm. The sensor is pasted on the surface of the pod rod structure 4 by glue. During the elongation stage of the pod rod, the surface of the pod rod structure 3 is wiped with acetone-impregnated non-woven fabric for 3 times to remove the residual release agent, and then polished along the axial direction with 1200 grit sandpaper to ensure that the surface is free of contamination. According to the position in the Figure 2 , the end of the sensor is located at the center of the pod rod structure 4, and one sensor array is pasted on each circle. The flexible sensor gold finger (left end) is thickened and gold-plated to ensure the connection strength and signal stability of the data acquisition and transmission device.

[0062] When the pod rod shape needs to be inverted, the motor winding drum 2 is first rotated to drive the pod rod structure 4 to elongate or retract. At this time, the cross-sectional shape of the pod rod structure 4 changes from "Ω" to "1" (elongation process) or from "1" to "Ω" (retraction process), and the change of the cross section will cause the resistance of the sensor to change. The sensing system 5 collects the changed signal and transmits it to the upper computer through the signal receiving device in Figure 5 , and processes the data through the built-in program.

[0063] The sensor position is at the junction of each segment of the pod rod structure; the pod rod structure is segmented according to the in-plane length direction of the curling radius, and each segment has a length of 2π times the average radius of this area in the curled state, i.e. one circle. The measurement direction of the sensor is the out-of-plane bending deformation direction, which is perpendicular to the unfolding direction of the pod rod structure. As shown in Figure 2 .

[0064] The surface strain is measured by a highly integrated sensor array, the number of sensing units in the sensor array is 7, the sensor signal changes are collected and transmitted by a small wireless acquisition card, and the strain value is calculated by the sensor measurement data. When the pod structure is deformed, the surface sensor will be bent and deformed, at this time the resistance of the sensor unit inside the sensor will change due to deformation, as shown in Figure 3 At this time, the strain at the sensor can be calculated by the following formula:

[0065]

[0066] In the formula, is the strain value at the sensor measurement position, is the sensor strain coefficient, is the initial resistance of the i-th sensor, is the real-time resistance of the i-th sensor after structural deformation; R1 represents the sensor located at the edge of the pod structure.

[0067] The configuration of the pod structure is obtained by the following steps:

[0068] Step 1: According to , the strain-curvature conversion relationship generated by the out-of-plane bending of the pod structure is established:

[0069]

[0070] Where h is the thickness of the structure, and p is the average curvature at the sensing unit.

[0071] Step 2: According to the p of step 1, the spatial coordinates (x i , y i ) at the sensor are obtained:

[0072]

[0073] Where the local corner of the i-th sensor , as shown in Figure 4 , p i is the average curvature of the i-th sensor; ΔL is the distance between two sensing units, as shown in Figure 5 .

[0074] Fitting the coordinates of n test points can obtain the interface shape at the junction of each segment in the in-plane direction of the pod structure at this moment:

[0075]

[0076] Where x ri is the global horizontal coordinate of node i, and yri Xi is the global longitudinal coordinate of node i, x i Yi is the local lateral coordinate of node i, y i θi is the local longitudinal coordinate of node i, θ ri-1 θi-1 is the global rotation angle of node i-1, equal to θ i-1 + θ i-2 As shown in FIG. 2. Figure 6

[0077] Step 3: Obtain the coordinates at the non-sensor positions according to the interface shape in Step 2:

[0078]

[0079] In the formula, and are the lateral and longitudinal coordinates of the node position away from the sensor m, and the distance from this node to the edge of the pod rod structure is the same as the distance from the ith sensor to the edge of the pod rod structure; m is the distance between the node and the sensor at this position; the development length of the ith pod rod structure l i is expressed as:

[0080]

[0081] In the formula, a is the correlation coefficient, which is a constant determined in advance, is the maximum change of the resistance of the No. 1 sensor at the end of the pod rod structure during the entire deformation process of the pod rod structure, is the real-time change of the resistance of the No. 1 sensor, is the initial resistance value of the No. 1 resistance;

[0082] Through interpolation fitting of the coordinates (x i , y i ) and (x , y ), the configuration of the pod rod is finally obtained, as shown in FIG. 3. Figure 7

[0083] The data of the positions of all sensors at the same time are processed. If the resistance of the sensor does not change, it can be considered that no curling or uncurling deformation occurs at this position; if the resistance of the sensor changes, the position of the sensor at this time is in the uncurling or curling state. The displacement data obtained by inverting all the data passing through the sensor are interpolated, and the real-time shape of the entire pod rod structure is obtained;

[0084] ​​The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any modification, equivalent replacement and improvement within the technical range disclosed by the present application and within the spirit and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for shape inversion of a spatially deployable pod-like stem structure, characterized in that: Utilizing surface density <7 / m 2 The sensor array enables real-time shape measurement of the out-of-plane bending and in-plane curling processes of the pod stalk structure. By integrating a flexible sensor and a lightweight wireless signal acquisition device with the pod stalk structure, accurate measurement and wireless transmission of surface strain during the deformation process of the pod stalk structure are achieved. Real-time measurement of the deformation of the pod stalk structure is realized by processing the sensor signals.

2. The method as described in claim 1, characterized in that: The sensor is located at the junction of each segment of the pod stalk structure; the pod stalk structure is divided into segments along its in-plane length direction according to the curling radius, and the length of each segment is 2π times the average radius of this area in the curled state, that is, one loop.

3. The method as described in claim 2, characterized in that: The sensor measures in the out-of-plane bending deformation direction, which is perpendicular to the unfolding direction of the pod-like stalk structure.

4. The method as described in claim 1, characterized in that: The surface strain during structural deformation is measured by a highly integrated sensor array. The number of sensing units in the sensor array is n. When the sensor signal changes, it is collected and transmitted by a small wireless acquisition card. The strain value is calculated from the sensor measurement data.

5. The method as described in claim 4, characterized in that: The strain value is obtained by the following formula: In the formula, ε mianwai k is used by the sensor to measure the positional strain value. sensor R is the strain coefficient of the sensor. i Let R be the initial resistance of the i-th sensor. i ′ represents the real-time resistance of the i-th sensor after structural deformation; R1 represents the sensor located at the edge of the pod stalk structure.

6. The method as described in claim 1, characterized in that: The configuration of the pod stalk structure is obtained by the following method. Step 1: Based on ε mianwai Establish the strain-curvature transformation relationship caused by out-of-plane bending of the pod stalk structure: Where h is the structural thickness and ρ is the average curvature at the sensing unit; Step 2: Based on ρ from Step 1, obtain the spatial coordinates (x, y) of the sensor. i ,y i ): x i =ρ i sin(θ i ) y i =ρ i (1-cos(θ) i )) Wherein, the local rotation angle of the i-th sensor ρ i Let be the average curvature of the i-th sensor; ΔL is the distance between the two sensing units. By fitting the coordinates of n test points, the interface shape at the junction of each segment in the in-plane direction of the pod stem structure can be obtained at this moment: Where x ri Let y be the global x-coordinate of node i. ri Let x be the global ordinate of node i. i Let y be the local x-coordinate of node i. i Let θ be the local ordinate of node i. ri-1 The global rotation angle of node i-1 is equal to θ. i-1 +θ i-2 ; Step 3: Obtain the coordinates of the non-sensor locations based on the interface shape from Step 2: In the formula, x im With y im Let be the x and y coordinates of the node position at distance m from the sensor. The distance from this node to the edge of the pod stalk structure is the same as the distance from the i-th sensor to the edge of the pod stalk structure; m is the distance between this node and the sensor; l is the unfolded length of the i-th segment of the pod stalk structure. i Represented as: In the formula, a is the correlation coefficient, is a constant determined in the previous period, and ΔR 1，max ΔR1 is the maximum change in resistance of sensor 1 at the end of the pod stalk structure during the entire deformation process of the pod stalk structure. ΔR1 is the real-time change in resistance of sensor 1, and R1 is the initial resistance value of sensor 1. By using coordinates (x) i ,y i ) and (x im ,y im Interpolation fitting is performed, and the configuration of the pod stem is obtained based on the fitting results.

7. The method as described in claim 1, characterized in that: The sensor described in step 2 has a substrate material of polyimide, and both the sensing material and the wires are made of Karma alloy, which is prepared by etching. The range and sensitivity of the sensor can be adjusted by changing the type of sensing functional material and the two-dimensional pattern of the sensor.

8. The method as described in claim 7, characterized in that: The adjustment of the sensor's range and sensitivity by changing the type of sensing material and the sensor's two-dimensional pattern is achieved through the following method: By replacing the sensing material with constantan, the sensor range was reduced from 0-4% to 0-2%, and the sensitivity was decreased from 10-15 to 2-6. The sensor sensitivity was adjusted by modifying the line width of the serpentine wire, using the following formula: Where S is the sensitivity, l is the line width, and n is a constant, obtained through sensor calibration.

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