Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering.This study proposes a novel method for constructing the surface design of space reflector antennas base...Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering.This study proposes a novel method for constructing the surface design of space reflector antennas based on polar scissor units.The concurrency and deployability equations of the space scissor unit with definite surface constraints are derived using the rod and vector methods.Constraint equations of the spatial transformation for space n-edge polar scissor units are summarized.A new closed-loop deployable structure,called the polar scissor deployable antenna(PSDA),is designed by combining planar polar scissor units with spatial polar scissor units.The overconstrained problem is solved by releasing the curve constraint that locates at the end-point of the planar scissor mechanism.Kinematics simulation and error analysis are performed.The results show that the PSDA can effectively fit the paraboloid of revolution.Finally,deployment experiments verify the validity and feasibility of the proposed design method,which provides a new idea for the construction of large space-reflector antennas.展开更多
Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This st...Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This study makes a comprehensive investigation of random manufacturing errors during constructing the mesh reflector antennas,and analyze its influence on reflector surface accuracy.Firstly,the sensitivity of reflector surface accuracy with respect to the random errors of the unstressed cable length is mathematically deducted.Secondly,a non-button connecting method is proposed and analyzed to reduce manufacturing errors.Thirdly,two physical experiment models based on 2.62-meter mesh reflector antenna are made.Finally,numerical examples and experimental tests are given to demonstrate the effectiveness of the proposed method.Compared with the traditional method,the proposed method can effectively reduce the influence of the manufacturing errors on the reflector surface accuracy.Moreover,the reduction in the sizes of the nodes also reduces the risk of entanglement of the mesh reflector antenna during the deployment process,and thereby improves the deployment reliability.展开更多
Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher sur...Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher surface accuracy. However, low accuracy and low effi- ciency are the common disadvantages for traditional panel alignment and adjustment. In order to improve the surface accuracy of large reflector antenna, a new method is pre- sented to determinate panel adjustment values from far field pattern. Based on the method of Physical Optics (PO), the effect of panel facet displacement on radiation field value is derived. Then the linear system is constructed between panel adjustment vector and far field pattern. Using the method of Singular Value Decomposition (SVD), the adjustment value for all panel adjustors are obtained by solving the linear equations. An experiment is conducted on a 3.7 m reflector antenna with 12 segmented panels. The results of simulation and test are similar, which shows that the presented method is feasible. Moreover, thediscussion about validation shows that the method can be used for many cases of reflector shape. The proposed research provides the instruction to adjust surface panels efficiently and accurately.展开更多
Acting as a pilot of the Square Kilometer Array (SKA), a Five hundred meter Aperture Spherical Telescope (FAST) project puts forward many innovative ideas, among which the design of the active main reflector shows fas...Acting as a pilot of the Square Kilometer Array (SKA), a Five hundred meter Aperture Spherical Telescope (FAST) project puts forward many innovative ideas, among which the design of the active main reflector shows fascinating potential. The main spherical reflector is to be composed of thousands of small spherical panels, which can be adjusted to fit a paraboloid of revolution in real time. For the construction and performance, the rms of the fit must be optimized, and so appropriate dimensional limits for the panels need to be determined. The issue of how to divide the spherical reflector mathematically is addressed in this paper. The advantages and drawbacks of various segmenting methods are discussed and an optimum one is suggested.展开更多
A new type and easy-to-fabricate metal-insulator-metal(MIM) waveguide reflector based on Sagnac loop is designed and investigated.The transfer matrix theoretical model for the transmission of electric fields in the re...A new type and easy-to-fabricate metal-insulator-metal(MIM) waveguide reflector based on Sagnac loop is designed and investigated.The transfer matrix theoretical model for the transmission of electric fields in the reflector is established,and the properties of the reflector are studied and analyzed.The simulation results indicate that the reflectivity strongly depends on the coupling splitting ratio determined by the coupling length.Accordingly, different reflectivities can be realized by varying the coupling length.For an optimum coupling length of 750 nm, the 3-dB reflection bandwidth of the MIM waveguide reflector is as wide as 1.5 μm at a wavelength of 1550 nm, and the peak reflectivity and isolation are 78%and 23 dB, respectively.展开更多
Metallic nanotextured reflectors have been widely used in light emitting diodes(LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structu...Metallic nanotextured reflectors have been widely used in light emitting diodes(LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structure is often neglected. Here, the influence of absorption loss of metallic nanotextured reflectors on the LED optoelectronic properties were studied. Two commonly used metal reflectors Ag and Al were applied to green GaN-based LEDs. By applying a Ag nanotextured reflector, the light output power of the LEDs was enhanced by 78% due to the improved light extraction. For an Al nanotextured reflector, however,only a 6% enhancement of the light output power was achieved. By analyzing the metal absorption using finite-difference timedomain(FDTD) and the metal reflectivity spectrum, it is shown that the surface plasmon(SP) intrinsic absorption of metallic reflectors with nanotexture structure play an important role. This finding will aid the design of the high-performance metal nanotextured reflectors and optoelectronics devices.展开更多
Based on the works of Greve and Rahmat-Samii, theelectromagnetic (EM) performance of the reflector antenna withnon-uniform surface errors along radius is further addressed. Amathematical model is developed to descri...Based on the works of Greve and Rahmat-Samii, theelectromagnetic (EM) performance of the reflector antenna withnon-uniform surface errors along radius is further addressed. Amathematical model is developed to describe the weighting functionfor the non-uniform surface errors along radius. Then, somediscussions on the peak gain loss (PGL) and the first sidelobelevel increase (SLLI) caused by the non-uniform surface errors arepresented and several significant radiation characteristics of thereflector with non-uniform errors are pointed out. Last, based onthe proposed model, the weighted root mean square (RMS) valueof the surface errors is produced to evaluate the EM performanceand several representative cases with different non-uniform errorsare presented with good results. Results show that the weightedRMS value should be taken into account for a better quality evaluationof the reflector surface.展开更多
This paper discusses the basic principle and design m ethod for light distribution of car lamp, introduces an important development: h igh efficient and flexible car lamp with reflecting light distribution-segmente d ...This paper discusses the basic principle and design m ethod for light distribution of car lamp, introduces an important development: h igh efficient and flexible car lamp with reflecting light distribution-segmente d reflector (multi-patch) car lamp, and puts out a design method for segmented reflector based on error analysis. Unlike classical car lamp with refractive lig ht distribution, the method of reflecting light distribution gives car lamp desi gn more flexibility. In the case of guarantying the lightness of car lamp and sa tisfying the standard demand for the light distribution, the design of the exter ior of the car lamp has more freedom. The high gradient of car lamp is more suit able for the demand of streamline of the car exterior. The shape of segmented re flector obtained by theory calculating of car lamp reflecting light distribution is only an ideal shape, which usually has considerable differences with the fin al shape and will influences light distribution. There exist difference between the calculated reflector and manufactured reflector. Owing to light reflecting c haracter, the small diversification of the reflector will reduce the big diver sification of the light distribution shape on light distribution screen in 25 -meter place, so light distribution quality can’t be ensured. To ensure the re flector by light distribution calculation accordance to reflector by practical m anufacture, the error effect of surface shape must be reasonably considered name ly the error effect of manufacture tache. The paper establishes error-analyzing model for segmented reflector according to the analysis of error of making proc ess for segmented reflector. Based on this error-analyzing model and by use of the analyzing software developed for segmented reflector light distribution, it could reasonably consider reflector errors made by manufacturing, such as reflec tor surface spray-painting and plating aluminum, which could give out shapes of reflector patches for segmented reflector well and truly, and direct the plan o f making process efficiently. The method put by the paper has successfully appli ed to develop segmented reflector lamp for several type cars and obtained good e ffect for the factory.展开更多
为满足高通量卫星对反射面高精度型面和低成本要求,从碳纤维蜂窝夹层结构反射面在固化成型过程中的固化收缩变形角度出发,根据模具型面补偿原理,提出了反射面模具型面补偿设计方法,并基于六面体单元有限元模型和三维正交各项异性材料属...为满足高通量卫星对反射面高精度型面和低成本要求,从碳纤维蜂窝夹层结构反射面在固化成型过程中的固化收缩变形角度出发,根据模具型面补偿原理,提出了反射面模具型面补偿设计方法,并基于六面体单元有限元模型和三维正交各项异性材料属性及三点边界约束方法进行了试验验证。试验结果表明,通过型面补偿后的铸铁模具加工得到的两米口径反射面型面精度达到0.096 mm均方根(root mean square,RMS),为模具型面补偿和高精度反射面提供了参考。展开更多
角反射器是一种宽角域的常见无源干扰设备,常被用于保护关键目标.但传统金属角反射器特性固定,需借助新型电磁材料实现角反射器的特性优化.有源频率选择表面(adaptive frequency selective surface,AFSS)是在单元间加载一系列可变有源...角反射器是一种宽角域的常见无源干扰设备,常被用于保护关键目标.但传统金属角反射器特性固定,需借助新型电磁材料实现角反射器的特性优化.有源频率选择表面(adaptive frequency selective surface,AFSS)是在单元间加载一系列可变有源器件而构成的具有可调电磁特性的新型结构.为拓展角反射器的适用范围、分析电磁材料角反射器的散射特性以更好地保护关键目标,本文设计了一种基于单面AFSS的电控角反射器,并仿真计算分析了该电控角反射器的散射特性.仿真结果表明设计的电控角反射器的散射特性可灵活调控,即不同偏置电流下AFSS单元可对入射电磁波能量产生不同反射效果;同时验证了该电磁调控角反射器的宽角域特性,其调控角域在方位向、俯仰向均大于60°,实现了基于无源散射体的宽角域实时调控效果.相较于传统角反射器和平面电磁材料,所设计电控角反射器兼具实时调控性和宽角域特性,拓展了角反射器的应用场景和适用范围.展开更多
The surface temperature of casting slab is an important parameter in the metallurgy field. Because the surface emissivity is uncertain and also unknown, it is difficult to measure the slab surface temperature accurate...The surface temperature of casting slab is an important parameter in the metallurgy field. Because the surface emissivity is uncertain and also unknown, it is difficult to measure the slab surface temperature accurately. A method based on preceded reflector and multi-wavelength was put forward to deal with the difficulty in surface temperature measurement of casting slab. On the premise of preceded reflector and non-preceded reflector, the method establishes the radiation energy equations and works out the emissivity and temperature in the equations. Also, the multilayer modeling of casting slab surface and multiple reflection-absorption process modeling were built by Monte Carlo method. The temperature measuring method had been applied in the continuous casting field. In order to verify the measured result, the thermal imaging method was adopted when the slab surface emissivity was set by repeated tests. Finally, the measured and verified temperature curves keep a same tendency and the error of the values is lower than 5℃. The comparison result shows that the method can measure temperature accurately.展开更多
基金Supported by National Key R&D Program of China(Grant No.2018YFB1304600)National Natural Science Foundation of China(Grant No.51775541)+1 种基金CAS Interdisciplinary Innovation Team of China(Grant No.JCTD-2018-11)Hundred-Talent Program(Chinese Academy of Sciences)(Grant No.Y8A3210304).
文摘Space-deployable mechanisms can be used as supporting structures for large-diameter antennas in space engineering.This study proposes a novel method for constructing the surface design of space reflector antennas based on polar scissor units.The concurrency and deployability equations of the space scissor unit with definite surface constraints are derived using the rod and vector methods.Constraint equations of the spatial transformation for space n-edge polar scissor units are summarized.A new closed-loop deployable structure,called the polar scissor deployable antenna(PSDA),is designed by combining planar polar scissor units with spatial polar scissor units.The overconstrained problem is solved by releasing the curve constraint that locates at the end-point of the planar scissor mechanism.Kinematics simulation and error analysis are performed.The results show that the PSDA can effectively fit the paraboloid of revolution.Finally,deployment experiments verify the validity and feasibility of the proposed design method,which provides a new idea for the construction of large space-reflector antennas.
基金supported by the National Natural Science Foundations of China(Nos.52022075,U1937202,&52175246)the Fundamental Research Funds for the Central Universities(Nos.QTZX2188&QTZX2173)。
文摘Cable-net structures are of substantial importance in the construction of large mesh reflector antennas.Owing to the inevitable errors in their manufacturing process,the reflector surface accuracy deteriorates.This study makes a comprehensive investigation of random manufacturing errors during constructing the mesh reflector antennas,and analyze its influence on reflector surface accuracy.Firstly,the sensitivity of reflector surface accuracy with respect to the random errors of the unstressed cable length is mathematically deducted.Secondly,a non-button connecting method is proposed and analyzed to reduce manufacturing errors.Thirdly,two physical experiment models based on 2.62-meter mesh reflector antenna are made.Finally,numerical examples and experimental tests are given to demonstrate the effectiveness of the proposed method.Compared with the traditional method,the proposed method can effectively reduce the influence of the manufacturing errors on the reflector surface accuracy.Moreover,the reduction in the sizes of the nodes also reduces the risk of entanglement of the mesh reflector antenna during the deployment process,and thereby improves the deployment reliability.
基金Supported by National Natural Science Foundation of China(Grant Nos.51490661,51490660,51205301)National Key Basic Research Program of China(973 Program,Grant No.2015CB857100)Special Funding for Key Laboratory of Xinjiang Uygur Autonomous Region,China(Grant No.2014KL012)
文摘Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher surface accuracy. However, low accuracy and low effi- ciency are the common disadvantages for traditional panel alignment and adjustment. In order to improve the surface accuracy of large reflector antenna, a new method is pre- sented to determinate panel adjustment values from far field pattern. Based on the method of Physical Optics (PO), the effect of panel facet displacement on radiation field value is derived. Then the linear system is constructed between panel adjustment vector and far field pattern. Using the method of Singular Value Decomposition (SVD), the adjustment value for all panel adjustors are obtained by solving the linear equations. An experiment is conducted on a 3.7 m reflector antenna with 12 segmented panels. The results of simulation and test are similar, which shows that the presented method is feasible. Moreover, thediscussion about validation shows that the method can be used for many cases of reflector shape. The proposed research provides the instruction to adjust surface panels efficiently and accurately.
文摘Acting as a pilot of the Square Kilometer Array (SKA), a Five hundred meter Aperture Spherical Telescope (FAST) project puts forward many innovative ideas, among which the design of the active main reflector shows fascinating potential. The main spherical reflector is to be composed of thousands of small spherical panels, which can be adjusted to fit a paraboloid of revolution in real time. For the construction and performance, the rms of the fit must be optimized, and so appropriate dimensional limits for the panels need to be determined. The issue of how to divide the spherical reflector mathematically is addressed in this paper. The advantages and drawbacks of various segmenting methods are discussed and an optimum one is suggested.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61827815 and 61775142)
文摘A new type and easy-to-fabricate metal-insulator-metal(MIM) waveguide reflector based on Sagnac loop is designed and investigated.The transfer matrix theoretical model for the transmission of electric fields in the reflector is established,and the properties of the reflector are studied and analyzed.The simulation results indicate that the reflectivity strongly depends on the coupling splitting ratio determined by the coupling length.Accordingly, different reflectivities can be realized by varying the coupling length.For an optimum coupling length of 750 nm, the 3-dB reflection bandwidth of the MIM waveguide reflector is as wide as 1.5 μm at a wavelength of 1550 nm, and the peak reflectivity and isolation are 78%and 23 dB, respectively.
基金supported by the National Key Research and Development Program of China (No. 2017YFB0402900)the National Natural Science Foundation of China (No. 61504132, 61505197)
文摘Metallic nanotextured reflectors have been widely used in light emitting diodes(LEDs) to enhance the light extraction efficiency. However, the light absorption loss for the metallic reflectors with nanotexture structure is often neglected. Here, the influence of absorption loss of metallic nanotextured reflectors on the LED optoelectronic properties were studied. Two commonly used metal reflectors Ag and Al were applied to green GaN-based LEDs. By applying a Ag nanotextured reflector, the light output power of the LEDs was enhanced by 78% due to the improved light extraction. For an Al nanotextured reflector, however,only a 6% enhancement of the light output power was achieved. By analyzing the metal absorption using finite-difference timedomain(FDTD) and the metal reflectivity spectrum, it is shown that the surface plasmon(SP) intrinsic absorption of metallic reflectors with nanotexture structure play an important role. This finding will aid the design of the high-performance metal nanotextured reflectors and optoelectronics devices.
基金supported by the National Basic Research Program of China(973 Program)(2015CB857100)the Foundation for Key Laboratory of Xinjiang Uygur Autonomous Region(2014KL012)+2 种基金the National Natural Science Foundation of China(514906605147534951522507)
文摘Based on the works of Greve and Rahmat-Samii, theelectromagnetic (EM) performance of the reflector antenna withnon-uniform surface errors along radius is further addressed. Amathematical model is developed to describe the weighting functionfor the non-uniform surface errors along radius. Then, somediscussions on the peak gain loss (PGL) and the first sidelobelevel increase (SLLI) caused by the non-uniform surface errors arepresented and several significant radiation characteristics of thereflector with non-uniform errors are pointed out. Last, based onthe proposed model, the weighted root mean square (RMS) valueof the surface errors is produced to evaluate the EM performanceand several representative cases with different non-uniform errorsare presented with good results. Results show that the weightedRMS value should be taken into account for a better quality evaluationof the reflector surface.
文摘This paper discusses the basic principle and design m ethod for light distribution of car lamp, introduces an important development: h igh efficient and flexible car lamp with reflecting light distribution-segmente d reflector (multi-patch) car lamp, and puts out a design method for segmented reflector based on error analysis. Unlike classical car lamp with refractive lig ht distribution, the method of reflecting light distribution gives car lamp desi gn more flexibility. In the case of guarantying the lightness of car lamp and sa tisfying the standard demand for the light distribution, the design of the exter ior of the car lamp has more freedom. The high gradient of car lamp is more suit able for the demand of streamline of the car exterior. The shape of segmented re flector obtained by theory calculating of car lamp reflecting light distribution is only an ideal shape, which usually has considerable differences with the fin al shape and will influences light distribution. There exist difference between the calculated reflector and manufactured reflector. Owing to light reflecting c haracter, the small diversification of the reflector will reduce the big diver sification of the light distribution shape on light distribution screen in 25 -meter place, so light distribution quality can’t be ensured. To ensure the re flector by light distribution calculation accordance to reflector by practical m anufacture, the error effect of surface shape must be reasonably considered name ly the error effect of manufacture tache. The paper establishes error-analyzing model for segmented reflector according to the analysis of error of making proc ess for segmented reflector. Based on this error-analyzing model and by use of the analyzing software developed for segmented reflector light distribution, it could reasonably consider reflector errors made by manufacturing, such as reflec tor surface spray-painting and plating aluminum, which could give out shapes of reflector patches for segmented reflector well and truly, and direct the plan o f making process efficiently. The method put by the paper has successfully appli ed to develop segmented reflector lamp for several type cars and obtained good e ffect for the factory.
文摘为满足高通量卫星对反射面高精度型面和低成本要求,从碳纤维蜂窝夹层结构反射面在固化成型过程中的固化收缩变形角度出发,根据模具型面补偿原理,提出了反射面模具型面补偿设计方法,并基于六面体单元有限元模型和三维正交各项异性材料属性及三点边界约束方法进行了试验验证。试验结果表明,通过型面补偿后的铸铁模具加工得到的两米口径反射面型面精度达到0.096 mm均方根(root mean square,RMS),为模具型面补偿和高精度反射面提供了参考。
文摘角反射器是一种宽角域的常见无源干扰设备,常被用于保护关键目标.但传统金属角反射器特性固定,需借助新型电磁材料实现角反射器的特性优化.有源频率选择表面(adaptive frequency selective surface,AFSS)是在单元间加载一系列可变有源器件而构成的具有可调电磁特性的新型结构.为拓展角反射器的适用范围、分析电磁材料角反射器的散射特性以更好地保护关键目标,本文设计了一种基于单面AFSS的电控角反射器,并仿真计算分析了该电控角反射器的散射特性.仿真结果表明设计的电控角反射器的散射特性可灵活调控,即不同偏置电流下AFSS单元可对入射电磁波能量产生不同反射效果;同时验证了该电磁调控角反射器的宽角域特性,其调控角域在方位向、俯仰向均大于60°,实现了基于无源散射体的宽角域实时调控效果.相较于传统角反射器和平面电磁材料,所设计电控角反射器兼具实时调控性和宽角域特性,拓展了角反射器的应用场景和适用范围.
基金Item Sponsored by National Natural Science Foundation of China(61004135)
文摘The surface temperature of casting slab is an important parameter in the metallurgy field. Because the surface emissivity is uncertain and also unknown, it is difficult to measure the slab surface temperature accurately. A method based on preceded reflector and multi-wavelength was put forward to deal with the difficulty in surface temperature measurement of casting slab. On the premise of preceded reflector and non-preceded reflector, the method establishes the radiation energy equations and works out the emissivity and temperature in the equations. Also, the multilayer modeling of casting slab surface and multiple reflection-absorption process modeling were built by Monte Carlo method. The temperature measuring method had been applied in the continuous casting field. In order to verify the measured result, the thermal imaging method was adopted when the slab surface emissivity was set by repeated tests. Finally, the measured and verified temperature curves keep a same tendency and the error of the values is lower than 5℃. The comparison result shows that the method can measure temperature accurately.