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CN114647968B - A method for formulating thermal control indicators of aerospace remote sensors based on thermal coupling algorithm - Google Patents

A method for formulating thermal control indicators of aerospace remote sensors based on thermal coupling algorithm Download PDF

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CN114647968B
CN114647968B CN202210372465.4A CN202210372465A CN114647968B CN 114647968 B CN114647968 B CN 114647968B CN 202210372465 A CN202210372465 A CN 202210372465A CN 114647968 B CN114647968 B CN 114647968B
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张刘
郑潇逸
张帆
吕雪莹
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Jilin University
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Abstract

本发明公开了一种基于力热耦合算法的航天遥感器热控指标制定方法，包括：建立四种力热耦合的假设工况；根据力热耦合弹性变形理论，以及光机结构变形与光学系统转换关系，计算MTF的值用于定量的评价成像质量；根据成像质量的整体指标与分系统指标的关系，确定遥感器热控子系统和机械子系统耦合情况下对应的综合成像质量指标；对耦合工况进行迭代计算并以达到成像质量阈值时对应的温度作为热控指标，完成光学指标到热控指标的转换。本发明的指标可保证在轨时的遥感器成像质量满足指标的前提下，降低约20%的热控系统功耗并在一定程度上的缩短了遥感器研制周期。

The present invention discloses a method for formulating thermal control indicators of aerospace remote sensors based on a force-heat coupling algorithm, including: establishing four hypothetical working conditions of force-heat coupling; calculating the MTF value for quantitative evaluation of imaging quality based on the elastic deformation theory of force-heat coupling and the relationship between the deformation of the optomechanical structure and the conversion of the optical system; determining the corresponding comprehensive imaging quality indicator under the coupling condition of the thermal control subsystem and the mechanical subsystem of the remote sensor based on the relationship between the overall imaging quality indicator and the subsystem indicator; iteratively calculating the coupling working condition and using the temperature corresponding to the imaging quality threshold as the thermal control indicator to complete the conversion from the optical indicator to the thermal control indicator. The indicators of the present invention can reduce the power consumption of the thermal control system by about 20% and shorten the development cycle of the remote sensor to a certain extent, while ensuring that the imaging quality of the remote sensor on orbit meets the indicator.

Description

Space remote sensor thermal control index formulation method based on force-heat coupling algorithm
Technical Field
The invention relates to a space remote sensing technology, in particular to a space remote sensor thermal control index formulation method based on a force thermal coupling algorithm.
Background
With the rapid development of the aerospace industry, optical remote sensing technology has been applied to various fields, and development of optical remote sensors with high performance (high imaging quality, strong maneuverability, etc.) and low cost (low energy consumption, small volume, light weight, etc.) is one of the demands of industrial development. The imaging quality of the optical remote sensor is very sensitive to temperature, and the temperature of the remote sensor needs to be maintained in a proper range through a thermal control system in order to ensure that the space observation task is successfully completed. The remote sensor thermal control index is a precondition for designing and formulating a thermal control system, and the thermal control index requirement is too low, so that the thermal control system design cannot meet the requirement of imaging quality index on temperature, and the thermal control index requirement is too high, so that a series of adverse effects such as increased power consumption of the thermal control system, increased design difficulty of the thermal control system, increased development period and the like can be brought. Therefore, a more reasonable thermal control index formulation method is urgently needed in engineering application to accurately predict the proper temperature level of the remote sensor when in orbit.
At present, the research on the method for formulating the thermal control index of the remote sensor is less, and in the early development stage of the aerospace industry, experienced designers can formulate a stricter index for the whole temperature level of the remote sensor, so that the thermal control system is ensured to have a high enough security domain. However, the method lacks enough theoretical basis, and the severe index of the thermal control system can lead to the energy consumption redundancy of the thermal control system and the increase of the development period. Along with the development of the aerospace industry, a new remote sensor thermal control index formulation method is put forward through computer aided engineering. The method is characterized in that thermal deformation analysis is carried out by adopting finite element software through supposing the temperature load in the on-orbit process, polynomial fitting is carried out on the optical surfaces under the action of different thermal loads, analysis is carried out through optical software, and finally, the temperature corresponding to the optical index threshold is used as a thermal control index. The thermal control index of the remote sensor is constrained by the imaging quality index during preparation, but the origin of the imaging quality index is not clear enough in the method, and the influence of gravity release on the imaging quality after the remote sensor is in orbit is not considered in the preparation process of the thermal control index, so that the calculated thermal control index is not accurate enough due to the factors.
In actual engineering, the rationality of the thermal control index is indirectly checked by simulating and experimental the thermal control system, and many scholars have studied this aspect. The space thermal environment of the remote sensor is subjected to numerical analysis, and the change condition of the external heat flow density under the corresponding orbit parameter is calculated. And calculating transient temperature distribution of the remote sensor through track thermal simulation, comparing the transient temperature distribution with corresponding thermal control indexes according to simulation results, and further making a thermal control system design. The method is used for calculating the thermal deformation of the optical machine structure when the remote sensor is on-orbit by taking the temperature distribution result of the thermal analysis of the orbit as an input condition. After the surface shape fitting is carried out on the deformed surface of the optical element, each mirror surface shape meets the tolerance requirement of optical design. And then, verifying that the imaging quality of the remote sensor under the unidirectional gravity condition meets the requirement through a thermal vacuum test, and verifying the effectiveness of the thermal control system design through the combination of simulation and experiments. The effectiveness of the thermal control design is verified according to the fact that the thermal balance experimental result is consistent with the simulation result.
However, in the above simulation verification study, only the tolerance of a single optical element is considered, but the performance of the whole optical system is ignored, and whether the imaging quality in on-orbit meets the index cannot be accurately judged. In addition, the thermal balance experiment and the thermal vacuum experiment under the unidirectional gravity condition can not detect the imaging quality of the remote sensor under the coupling condition of gravity release and temperature change, and are insufficient to prove the rationality of the thermal control index and the effectiveness of the thermal control system design.
Disclosure of Invention
The invention mainly aims to provide a remote sensor thermal control index formulation method based on force-thermal coupling, which researches the coupling influence mechanism of gravity release and temperature change on the imaging quality of a system by analyzing the environmental difference between space and the ground, takes the requirement of the imaging quality index on the temperature as a constraint condition, and effectively reduces the power consumption of the thermal control system, reduces the design difficulty of the thermal control system and shortens the development period on the premise of ensuring that the design of the thermal control system meets the requirement of the imaging quality index.
The technical scheme adopted by the invention is that the method for formulating the thermal control index of the space remote sensor based on the force thermal coupling algorithm comprises the following steps:
Establishing four hypothetical conditions of force thermal coupling;
calculating the value of MTF for quantitatively evaluating imaging quality according to the force thermal coupling elastic deformation theory and the conversion relation between the optical-mechanical structure deformation and the optical system;
Determining a corresponding comprehensive imaging quality index under the coupling condition of a remote sensor thermal control subsystem and a mechanical subsystem according to the relation between the integral index of the imaging quality and the subsystem index;
And carrying out iterative computation on the coupling working conditions, and taking the corresponding temperature when the imaging quality threshold is reached as a thermal control index to finish the conversion from the optical index to the thermal control index.
Further, the assumed working conditions for establishing the four force thermal couplings include:
Before the establishment of the thermal control index, the force and heat environment of the remote sensor during on-orbit operation is described and assumed, a unified temperature range is generally defined for the whole system during the establishment of the thermal control index of the remote sensor, and four temperature working conditions are established from two aspects of uniform temperature load and uniform gradient change temperature load;
And carrying out gravity working condition assumption on the remote sensor according to the gravity direction of actual assembly and debugging, and combining the assumed four temperature working conditions with one gravity working condition to establish four coupling working conditions which are respectively (delta T) and G, X (delta T) and G, Y (delta T) and G and Z (delta T) and G.
Still further, the calculating the value of MTF for quantitatively evaluating imaging quality includes:
calculating the elastic deformation of the remote sensor under the coupling working condition by adopting a finite element analysis method of coupling elastic mechanics to ensure the formulating precision of a thermal control index, and obtaining the coordinate information of each deformed finite element node through the force-thermal coupling calculation of the remote sensor FEM, wherein the coordinate information can be used as the input condition of optical calculation;
The influence of the structural deformation of the remote sensor on the imaging quality can be analyzed through optical calculation, the optical surface nodes are rebuilt into a software usable form through a method of wavefront fitting based on Zrenike polynomials, and then all rebuilt optical surfaces are sequentially input into optical software to generate a new optical system, so that the change condition of MTF under the working condition of force-thermal coupling is analyzed;
Wherein Zrenike is mathematically described as:
Wherein K is a conic coefficient, c is a curvature, A i is a coefficient of a polynomial, Z i is a polynomial, In order to normalize the radius,Is the amplitude angle;
And comparing the calculated MTF with the MTF required by the imaging quality index, and taking the temperature corresponding to the coupling working condition when reaching the imaging quality threshold as a thermal control index.
The invention has the advantages that:
The index of the invention can reduce the heat control power consumption by about 20 percent and shortens the development period of the remote sensor to a certain extent. According to the prediction result of the MTF change condition of the remote sensor in orbit, the method can just ensure that the imaging quality in orbit meets the index, and has higher reliability compared with the index formulated by only considering the temperature.
In addition to the objects, features and advantages described above, the present invention has other objects, features and advantages. The present invention will be described in further detail with reference to the drawings.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application.
FIG. 1 is a flow chart of a method for formulating thermal control indexes of a space remote sensor based on a force thermal coupling algorithm in an embodiment of the invention;
FIG. 2 is a schematic diagram of a remote sensor optical design in accordance with an embodiment of the present invention;
FIG. 3 is a graph showing temperature fluctuations of the optical components of the remote sensor over 10 cycles in accordance with an embodiment of the present invention;
FIG. 4 is a graph showing the comparison of MTF at a certain moment in time with the initial MTF of the optical system when different indicators are on-track in accordance with an embodiment of the present invention;
fig. 5 is a schematic diagram of the systems according to the embodiments of the present invention respectively installed on a vacuum tank platform.
Reference numerals:
The system comprises an interferometer 1, a collimator 2, a vacuum tank 3, an infrared radiator 4, a remote sensor 5 and a satellite platform 6.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Thermal control index formulation method
The invention provides a thermal control index formulation method taking an imaging quality index as a requirement under the condition of force thermal coupling. Fig. 1 depicts the specific process of the method, firstly, because the space environment can cause the remote sensor to generate gravity release and temperature change, four hypothetical conditions of force-heat coupling are established. And secondly, calculating the MTF value for quantitatively evaluating the imaging quality according to the force-thermal coupling elastic deformation theory and the conversion relation between the optical-mechanical structure deformation and the optical system. And then, determining the corresponding comprehensive imaging quality index under the coupling condition of the remote sensor thermal control subsystem and the mechanical subsystem according to the relation between the integral index of the imaging quality and the subsystem index. And finally, carrying out iterative computation on the coupling working conditions, and taking the corresponding temperature when the imaging quality threshold is reached as a thermal control index to finish the conversion from the optical index to the thermal control index.
Working condition hypothesis
Because the on-orbit imaging quality of the remote sensor can be influenced by the coupling of temperature change and gravity release, the invention uses an optomechanical thermal integration analysis method to calculate the structural deformation of the remote sensor caused by the force-thermal coupling environment and the imaging quality of an optical system after deformation.
The space environment (microgravity and space thermal environment) where the remote sensor is located is different from the ground environment, and the difference can cause gravity release and temperature change when the remote sensor is on track. The influence of gravity release and temperature change on the imaging quality of the remote sensor is inseparable, so that the force-heat coupling effect is comprehensively considered to formulate a heat control index. Before the establishment of the thermal control index, the force-thermal environment of the remote sensor when in orbit needs to be described and assumed:
Assume 1 temperature regime
Because the temperature distribution of each node inside the remote sensor is irregular in the space environment, a uniform temperature range is generally defined for the whole system when the thermal control index of the remote sensor is formulated. The invention establishes four temperature conditions as shown in table 1 from two aspects of uniform temperature load and uniform gradient temperature load. The initial temperature for all conditions was set to 20 ℃ taking into account the actual temperature at ground machining and conditioning. No. 1 is a uniform temperature load working condition, and the temperature value (20+/-delta T) of the working condition is changed by changing the value of the variation delta T of the temperature. 2-4 is a temperature load working condition with uniform gradient change, and the temperature gradient change has directivity due to the asymmetry of a remote sensor structure, so that the working condition is described by adopting X, Y, Z directions of a Cartesian coordinate system, and the temperature value taking 20 ℃ as a symmetry center is 20-delta T/2-20+delta T/2, wherein the positive and negative of the temperature change quantity delta T represent the change trend.
Table 1 description of the working conditions
Let 2 be the gravity condition
The remote sensor can offset the deformation caused by gravity to the structure through assembly and debugging when on the ground, but after entering a rail, new structural internal stress can be generated due to the release of the gravity so as to cause the new deformation of the remote sensor structure, so that the gravity working condition assumption is needed to be carried out on the remote sensor according to the gravity direction of actual assembly and debugging. The direction of gravity of the remote sensor in the present invention is-Y, and the gravity condition is hereinafter designated G.
The invention combines the assumed four temperature working conditions with a gravity working condition to establish four coupling working conditions which are respectively (delta T) and G, X (delta T) and G, Y (delta T) and G and Z (delta T) and G. The invention uses the coupling symbol to name the working condition in a simplified way.
Determination of thermal control indicators
Since the imaging quality is very sensitive to deformations of the opto-mechanical structure of the remote sensor, an accurate method is needed to calculate the structural deformations. The result of the force-thermal coupling method for calculating the elastic deformation is more accurate than that of a method for respectively calculating the force and the thermal deformation and then superposing, so that the method adopts a finite element analysis method of coupling elastic mechanics to calculate the elastic deformation of the remote sensor under the coupling working condition to ensure the formulating precision of the thermal control index. And (3) obtaining coordinate information of each deformed finite element node through force-thermal coupling calculation of the remote sensor FEM, wherein the coordinate information can be used as an input condition of optical calculation.
The influence of the structural deformation of the remote sensor on the imaging quality can be analyzed through optical calculation. Considering that the optical software has no data interface of finite element discrete nodes, the invention reconstructs the optical surface nodes into a software usable form by a method of wavefront fitting based on Zrenike polynomials. And then sequentially inputting all reconstructed optical surfaces into optical software to generate a new optical system, and further analyzing the variation condition of MTF under the working condition of force-thermal coupling.
Wherein Zrenike is mathematically described as:
Wherein K is a conic coefficient, c is a curvature, A i is a coefficient of a polynomial, Z i is a polynomial, In order to normalize the radius,Is the argument.
By iterating the different coupling conditions, the corresponding MTF value can be obtained. And comparing the calculated MTF with the MTF which is not required by the imaging quality, and taking the temperature corresponding to the coupling working condition when the coupling working condition is brought to the imaging quality threshold as a thermal control index.
Example calculation
Description of the optical machine structure
The invention takes a coaxial reflection type remote sensor as a research object, the imaging range is within the visible light wave band range, and the structural components of the coaxial reflection type remote sensor comprise a load body (a main mirror component, a secondary mirror component, a three-mirror component, a reflecting mirror component, a focusing mechanism, a main bearing component, a light shield component and the like), an electronic system, a thermal control system and the like. As shown in FIG. 2, the optical design of the remote sensor uses the direction of the main optical axis as +Z axis, the refractive direction of the refractive mirror as +Y axis, a Cartesian coordinate system is established by the right hand rule, and the geometric model and the finite element model of the remote sensor use the same coordinate system.
Determination of imaging quality index
The imaging quality index of the remote sensor is a precondition for the formulation of a thermal control index, wherein each subsystem of the remote sensor has a corresponding imaging quality index, and the indexes are quantitatively described through respective MTF values. From the above, the effects of temperature and gravity on imaging quality are mutually coupled, and the imaging quality index corresponding to the thermal control or mechanical subsystem cannot be independently formulated, so the invention calculates the comprehensive imaging quality index (MTF D) corresponding to the coupling condition of the thermal control and mechanical subsystem according to the relation between the MTFs of the systems.
The static MTF (MTF S) measured in the laboratory environment is a total indicator of the imaging quality of the remote sensor before emission, the present invention requires that MTF S be ≡0.12 at frequency=57.1 lp/mm. MTFs are considered to be the result of the combined actions of MTF D, process and tune transfer function (MTF m), and optoelectronic data transfer and process transfer function (MTF CCD), and have the following relationships.
In the case of a CCD device,The pixel size transfer function (MTF geometry, MTF G) and the electronic system transfer function (MTF E) are formed, and the relation is that:
MTF G can be expressed as:
Wherein f is the spatial frequency, f n is the Nyquist frequency, a is the CCD pixel size, and d is the CCD pixel spacing. When d=a, f=f n, MTF G =0.637 can be calculated.
Where MTF E =0.9 is given based on the study staff's statistics on the electronic system technology and the state of the art. MTF M was established empirically and through big data statistics, and MTF M =0.85 was obtained after the technician tested the remote sensor of the present invention.
In combination, the MTF D is more than or equal to 0.245, so that the imaging quality requirement can be met.
Determination of thermal control indicators
According to the glosser thermal integration analysis method, the step length of temperature change is 0.1 ℃, and after total iterative computation is carried out on 4 coupling working conditions for 580 times, the relation between MTF and temperature under the 4 coupling working conditions is obtained, wherein the threshold value of the MTF is 0.245. The temperature gradient sensitivity of the remote sensor to various working conditions is different, and the reasonability of the working condition type assumption is also proved. This type of assumption is reasonable because of the different sensitivity of the remote sensor to temperature gradients in different directions. The MTF of the edge view field in each working condition is most influenced by temperature change, and the threshold value of the MTF is reached first, which shows that the sensitivity of the edge view field to temperature is higher than that of other view fields, so that the temperature corresponding to the MTF=0.245 of the edge view field is used as a thermal control index.
Since the optical elements of the remote sensor are most spatially distributed along the Z direction, the maximum temperature difference between the optical elements occurs in the critical operating condition temperature distribution calculated by the total of force and thermal coupling in the G & Z (delta T) operating condition, and the maximum temperature difference between the optical elements is 4.44 ℃.
In summary, for the safety and reliability of the remote sensor, the thermal control index is formulated as follows:
a) The whole temperature range of the remote sensor is 17.3 < T < 22.6 ℃;
b) The temperature difference in the X direction is less than 5.6 ℃, the temperature difference in the Y direction is less than 6.6 ℃, and the temperature difference in the Z direction is less than 6.9 ℃;
c) The temperature difference between the optical elements is <4.4 ℃.
Simulation analysis and verification
Because the real space environment and the assumed temperature working condition are different, the temperature condition of the remote sensor during on-orbit needs to be simulated more accurately through the orbit thermal simulation analysis. The feasibility of remote sensor thermal control design and the rationality of the thermal control index formulation method can be checked by calculating and comparing the change conditions of the on-orbit imaging quality under different thermal control index formulation methods.
Rail environment analysis
The remote sensor can cause temperature change of the optical-mechanical structure due to the influences of vacuum, cold black, internal heat sources, heat radiation, heat conduction and other factors in the space. The temperature change can lead the optical element to generate displacement, distortion, thermal deformation and the like, thereby further reducing the imaging quality of the remote sensor, so that the remote sensor can perform normal imaging work only after reaching heat balance with the help of a heat control system.
The heat balance equation can be expressed as:
In the formula, Is solar radiation; is earth return; Infrared radiation of the earth; A heat source within the spacecraft; Heat radiated by the spacecraft to the space; the internal energy of the spacecraft can be changed.
The remote sensor is set to run on the sun synchronous orbit, orbit parameters are shown in table 2, and the change trend of the sun illumination angle (beta angle) can be calculated through orbit information, so that the change of the external heat flow of the remote sensor can be calculated. The change in beta angle can be described as:
Wherein I is the inclination angle between the satellite orbit plane and the earth orbit plane, I is the included angle between the earth orbit plane and the earth orbit plane, The yellow meridian of the sun, omega is the red meridian of the ascending intersection point.
Rail thermal simulation analysis
The thermal control index according to the present invention is used for designing a thermal control system. And a thermal structure analysis model of the remote sensor and the satellite platform is established. And carrying out orbit thermal simulation analysis on the whole satellite by taking an orbit environment analysis result as an input condition and 20 ℃ as a thermal control target temperature, and carrying out iterative formulation on a thermal control system by taking the simulation result as a guide until the temperature meets the index requirement.
In an actual space environment, the external heat flow of a satellite, the temperature of a platform, the attitude of the satellite and other factors can be changed, and a thermal control coating and various lacquers can be degraded with time, so that two extreme working conditions of high temperature and low temperature can be generated. According to the invention, during simulation, two extreme working conditions are analyzed, and simulation of a plurality of track periods is performed, wherein the thermal control power consumption required by the high-temperature working condition and the low-temperature working condition is respectively 98.0w and 103.5w, and the thermal control power consumption of the low-temperature working condition is larger.
FIG. 3 shows the temperature fluctuation of each optical component of the remote sensor in 10 periods, and the temperature reaches equilibrium after 3 tracks and meets the thermal control index.
The threshold value (0.245) of the MTF D is used as the index requirement of the MTF when the remote sensor is on track, the coupling relation between gravity and temperature is comprehensively considered, the temperature of each finite element node of the remote sensor obtained in the rail thermal simulation analysis is used as a temperature working condition, and the coupling working condition is built by combining with the gravity working condition. The deformation condition of the optical-mechanical structure of the remote sensor during on-orbit can be calculated by the force-thermal coupling principle. And extracting deformed optical surface node data as surface shape fitting input conditions, loading fitting results into optical software, and calculating MTF (maximum transfer function) of the remote sensor at any moment in imaging time when the remote sensor is on track.
According to the task requirement, the imaging time of each rail of the remote sensor is less than 10min, and the data in the imaging time of the 8 th rail (40176-406 s) after the remote sensor reaches the heat balance are selected for research. Wherein fig. 4 shows the MTF at a point in time when different indicators are on track in comparison with the initial MTF of the optical system. And taking 20s as a step length, carrying out iterative computation on data in the imaging time for 60 times, and obtaining the MTF change condition of different indexes in-orbit as shown in figure 4.
As can be seen from fig. 4, the present index allows the MTF to meet the index during the imaging time, to reach a minimum value (0.248) at 40616s and 40716s and just meet the threshold. This means that the index can effectively ensure the imaging quality of the remote sensor in orbit and avoid the waste of the power consumption of the thermal control system.
Thermal vacuum experiments
Remote sensors require detection of MTFs by thermal vacuum experiments prior to transmission. The thermal vacuum experiment is to simulate the orbit environment by using a space environment simulator, and calculate the energy information of the target image by using optical test equipment to reflect the imaging quality of the remote sensor. The test system comprises a camera, a collimator system, an interferometer, an infrared radiator, a satellite mounting platform, a satellite platform simulation bin and the like, and as shown in fig. 5, the systems are respectively mounted on a vacuum tank platform. The vacuum tank can provide cold black temperature below 100k and vacuum environment of 1× -4 Pa to simulate real space environment. According to the actual scheme, the remote sensor is arranged on a satellite platform, and a heating system is arranged in a satellite platform simulation bin to simulate the real temperature change of the platform. The infrared heater can be used to provide external heat flow variation on each surface of the satellite. The interferometer is arranged on the focal plane of the collimation system, the emitted light outputs parallel light beams through the collimator, and the satellite is arranged on the high-precision turntable, so that MTFs S of different fields of view of the remote sensor can be detected. The experimental results are consistent with the overall temperature indexes (17.3 ℃ and 22.6 ℃) established by the method, and further prove the rationality of the method.
In order to ensure that the space observation task is successfully completed, the temperature of the optical remote sensor needs to be maintained in a proper range through a thermal control system, so that the imaging quality is prevented from being influenced by the space thermal environment. The design and formulation of the thermal control system need reasonable thermal control indexes for guidance, however, the existing thermal control index formulation method lacks enough theoretical basis and easily causes waste of resources and time, or only considers temperature change and ignores the influence of gravity release, so that the formulated thermal control indexes are inaccurate, and accurate pre-judgment of the proper temperature level of the whole machine when the remote sensor is in orbit is difficult to form. According to the invention, the coupling influence mechanism of gravity release and temperature change on the imaging quality of the system is researched by analyzing the environmental difference between space and ground, and the requirement of the imaging quality index on the temperature is taken as a constraint condition. The track thermal simulation result shows that compared with the empirical index, the index of the invention can reduce the thermal control power consumption by about 20 percent and shortens the remote sensor development period to a certain extent. In addition, the method can just ensure that the imaging quality in the on-orbit process meets the index and has higher reliability compared with the index formulated by only considering the temperature through the prediction result of the MTF change condition of the remote sensor in the on-orbit process. Then, the thermal vacuum experimental result shows that the temperature critical value of the remote sensor under the gravity release condition accords with the thermal control index formulated by the method, and the rationality of the method is further verified. Finally, through further verification, the method can be applied to remote sensors of various types (off-axis reflection type, transmission type and the like).
The invention establishes a remote sensor thermal control index formulation method based on force-thermal coupling by researching the comprehensive influence of optics, mechanics and heat on the imaging quality of the remote sensor. The method can accurately predict the proper temperature level of the remote sensor in orbit so as to guide the design of the thermal control system to meet the requirement of imaging quality on temperature. In addition, the power consumption of the thermal control system is reduced to a certain extent, the design difficulty of the thermal control system is reduced, and the development period is shortened. The main contents are as follows:
(1) 4 kinds of force-heat coupling assumption working conditions are established for the remote sensor according to the environmental difference between the space and the ground. And analyzing the change condition of the MTF of the remote sensor under the coupling working condition according to the force-heat coupling calculation method and the surface shape fitting method.
(2) According to the relation between the integral index of imaging quality and the subsystem index, the comprehensive imaging quality index corresponding to the condition of remote sensor thermal control and mechanical subsystem coupling is determined to be MTF D >0.245, and the temperature corresponding to the condition of reaching the imaging quality index is used as a thermal control index by carrying out iterative calculation on the coupling working condition.
(3) After different indexes are applied to the remote sensor, and simulation comparison is carried out, the method provided by the invention is verified to save about 20% of power consumption of a thermal control system and shorten the development period on the premise of meeting the requirement of imaging quality. The thermal vacuum experimental result accords with the index of the invention, and further illustrates the rationality of the method of the invention.
Through further research, the method is also applicable to other types of remote sensors (off-axis reflection type, transmission type and the like). However, a remote sensor with an active optical system can resist the effect of temperature on imaging quality by adjusting the wavefront of the optical element, and thus the thermal control index formulation of the present invention is not applicable to this type of remote sensor. In conclusion, the method for formulating the thermal control index has wide applicability, can be well applied to practical engineering, and provides a certain contribution and help for the development of the aerospace industry.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.

Claims (2)

1.一种基于力热耦合算法的航天遥感器热控指标制定方法，其特征在于，包括：1. A method for formulating thermal control indicators of aerospace remote sensors based on a force-heat coupling algorithm, characterized by comprising: 建立四种力热耦合的假设工况；Establish four hypothetical working conditions of mechanical and thermal coupling; 根据力热耦合弹性变形理论，以及光机结构变形与光学系统转换关系，计算MTF的值用于定量的评价成像质量；According to the elastic deformation theory of mechanical and thermal coupling, as well as the relationship between the optical-mechanical structure deformation and the optical system transformation, the MTF value is calculated to quantitatively evaluate the imaging quality. 根据成像质量的整体指标与分系统指标的关系，确定遥感器热控子系统和机械子系统耦合情况下对应的综合成像质量指标；According to the relationship between the overall imaging quality index and the subsystem index, the corresponding comprehensive imaging quality index under the coupling condition of the remote sensor thermal control subsystem and mechanical subsystem is determined; 对耦合工况进行迭代计算并以达到成像质量阈值时对应的温度作为热控指标，完成光学指标到热控指标的转换；Iteratively calculate the coupling conditions and use the temperature corresponding to the imaging quality threshold as the thermal control index to complete the conversion from optical index to thermal control index. 所述计算MTF的值用于定量的评价成像质量包括：The calculated MTF value is used to quantitatively evaluate the imaging quality including: 采用耦合弹性力学的有限元分析方法计算遥感器在耦合工况下的弹性变形保证热控指标的制定精度，通过对遥感器FEM的力-热耦合计算，得到变形后的各有限元节点的坐标信息，其可作为光学计算的输入条件；The finite element analysis method of coupled elastic mechanics is used to calculate the elastic deformation of the remote sensor under coupled working conditions to ensure the accuracy of the thermal control index. Through the force-heat coupling calculation of the remote sensor FEM, the coordinate information of each finite element node after deformation is obtained, which can be used as the input condition of optical calculation. 通过光学计算可分析遥感器结构变形对成像质量的影响，通过基于Zrenike多项式的波前拟合的方法将光学表面节点重建为软件可用形式，再将所有重建后的光学表面依次输入光学软件中生成新的光学系统，进而分析力-热耦合工况下MTF的变化情况；The influence of the deformation of the remote sensor structure on the imaging quality can be analyzed through optical calculation. The optical surface nodes are reconstructed into a software-usable form through the wavefront fitting method based on Zrenike polynomials. Then all the reconstructed optical surfaces are input into the optical software in sequence to generate a new optical system, and then the change of MTF under the force-heat coupling condition is analyzed. 其中Zrenike失高数学描述为：The Zrenike loss mathematical description is: ‘ ' 式中K为圆锥系数，ｃ为曲率, A i 为多项式的系数，Z i 为多项式，为归一化半径，为幅角；Where K is the cone coefficient, c is the curvature, Ai is the coefficient of the polynomial, Zi is the polynomial, is the normalized radius, is the argument; 通过对不同耦合工况进行迭代，可得到相对应的MTF值；通过将计算的MTF与成像质量所要求否MTF对比，将耦合工况中带到成像质量阈值时所对应的温度作为热控指标。By iterating different coupling conditions, the corresponding MTF value can be obtained; by comparing the calculated MTF with the MTF required for imaging quality, the temperature corresponding to the imaging quality threshold in the coupling condition is used as the thermal control index. 2.根据权利要求1所述的基于力热耦合算法的航天遥感器热控指标制定方法，其特征在于，所述建立四种力热耦合的假设工况包括：2. The method for formulating thermal control indicators of aerospace remote sensors based on a force-heat coupling algorithm according to claim 1 is characterized in that the establishment of four hypothetical working conditions of force-heat coupling includes: 在热控指标的制定前需要先对遥感器在轨时的力热环境进行描述和假设，在对遥感器热控指标的制定时通常对整个系统定义统一的温度范围，从均匀的温度载荷和均匀梯度变化的温度载荷两个方面考虑，建立四种温度工况；Before formulating the thermal control index, it is necessary to describe and assume the mechanical and thermal environment of the remote sensor when it is in orbit. When formulating the thermal control index of the remote sensor, a unified temperature range is usually defined for the entire system. Four temperature conditions are established from two aspects: uniform temperature load and uniform gradient temperature load. 根据实际装配和调试的重力方向对遥感器进行重力工况假设，将假设的四种温度工况与一种重力工况进行组合后建立了四种耦合工况，分别为(ΔT) ＆G , X(ΔT) ＆G ,Y(ΔT) ＆G and Z(ΔT) ＆G。According to the gravity direction of actual assembly and debugging, the gravity working condition of the remote sensor is assumed. After combining the four assumed temperature conditions with one gravity condition, four coupling conditions are established, namely (ΔT) ＆G, X(ΔT) ＆G, Y(ΔT) ＆G and Z(ΔT) ＆G.
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