Surface Precision Measurement, Space Thermal, Reliability And Clearance Effect Analysis Of Deployable Space Antennas

As a new kind of structure, deployable structures are more and more widely used in many fields recent years. They can be divided into space deployable structures and ground deployable structures by differentiations. Following the development of the aerospace technology, higher performance requirements are brought forward to deployable antennas on satellites from each relative field, which mainly focus on larger caliber and less surface error. And because of it, many kinds of space deployable antennas are studied and designed by research institutes from many countries. Measurement of surface precision, thermal analysis, structural analysis, reliability analysis, influence of clearance and deployment process for space deployable antennas have been studied systematically in this dissertation.Firstly, after referring a lot of pertinent literature worldwidely, applications of space deployable antennas are introduced and the research actuality on measurement of surface precision, thermal analysis, structural analysis, reliability analysis, influence analysis of clearance and deployment process analysis for space deployable antennas are summarized, then the research significance is presented.Factors which affect measuring accuracy of the system in photogrammetry are analyzed, and methods that can improve measuring accuracy of the system are analyzed systematically. Fitting formulas for the best fitting paraboloid are deduced, and numerical computation method on surface error of the reflector'RMS'is deduced based on Newton method, and the program is made. According to surface precision measurement of the reflector with large caliber, the method by which each part of the reflector is measured independently then combined together is proposed, measuring process of the method and some numerical computation methods in the measuring process are studied. A non-contact photogrammetric measure system is built on the base of Photomodeler software packages, and a surface precision experiment on a membrane inflatable antenna with 3.2m caliber is made. The method by which the whole reflector is measured once and the method by which each part of the reflector is measured independently then combined together are both used. And the two results obtained through the two methods are very close, and it is concluded that the method by which each part of the reflector is measured independently then combined together is precise enough for surface precision measurement of the antenna, and it can be used in surface precision measurement of antennas with large caliber. Then using the method by which each part of the reflector is measured independently then combined together, another surface precision experiment on a membrane inflatable antenna with 6.2m cal iber is made.Heat transfer, heat balance, computation of three kinds of space external thermal flow, external thermal flow of sun, external thermal flow of earth shine and external thermal flow of earth infrared radiation are discussed. And a numerical computation method on the three kinds of external thermal flow and shadow for an antenna in a sun-synchronous orbit is deduced based on geometric theory. Based on finite element theory, the transient conduction-radiation differential equation is established using one-dimensional bar element with two nodes and two-dimensional triangular element with three nodes. Corresponding functional formulas are obtained through introducing boundary conditions. Then iterative equations for temperature field computation of deployable antennas are established. Using FORTRAN, a finite element program based on the theory above is built. According to an example, temperature fields changing with time for an antenna in a sun-synchronous orbit in a cycle are calculated respectively at vernal equinox, summer solstice, autumn equinox and winter solstice. Time that is unfavorable for the antenna in the orbit is concluded through analysis, and it can be used for thermal controlling design.Mathematical models for coupling of many fields and coupling relationships are analyzed in detailed. According to characteristics of space deployable truss antennas, using non-liner finite element theory, formulations to analyze thermal deformation are established. Then the thermal analysis and structural analysis for deployable truss antennas are coupled, and a program is made based on FORTRAN. Direct conversion and coupling from thermal analysis to structural analysis for deployable truss antenna is real ized. An example is analyzed by the theory above, the reflector surface error RMS is used as the index to reflect the deformation. Temperature fields and reflector surface errors RMS changing with time for an antenna in a sun-synchronous orbit in a cycle are calculated respectively at vernal equinox, summer solstice, autumn equinox and winter solstice. Time that is unfavorable for the antenna in the orbit is concluded through analysis. Dynamic responses by temperature fields are analyzed. Accelerations of a joint changing with time in a cycle at four special times above are compared and the time obtained before that is unfavorable for the antenna in the orbit is verified.The failure probability function of an element is established. The antenna is a serial system made up of each element. The relationship between reliability degree of an element and that of the whole system in a serial system is deduced. Failure model of the truss deployable antenna is established using faulty tree theory, computational methods for failure probability and importance degree of basic events are analyzed and based on it failure probability formulations for the antenna are established using probability theory; deployment analysis formulations for deployable truss antenna are established using dynamic theory and deployment process of the antenna is analyzed when there are torsional spring failures at different positions, then those positions where the antenna could not deploy fully or the surface error is very high when torsional springs fail are obtained, and those positions where the antenna could deploy smoothly and the surface error is low when torsional springs fail are also obtained. These results and reliability analysis are combined. The reliability analysis on the antenna is made using conventional faulty tree theory and faulty tree theory based on fuzzy theory relatively.The clearance at the joint of the truss deployable antenna is calculated based on geometric theory. And combing probability theory, the probability distribution function of elongation of the rod caused by clearance is obtained. A model for random analysis is established based on Monte Carlo theory. The effect of clearance at the joint on reflector surface precision is analyzed through an example. And it is concluded that the effect of clearance on reflector surface precision is weak for a common antenna, it can be neglected. But the effect should be considered during design for antennas with high precision, and the effect should be reduced.Folding code of 2D paper-folding models is analyzed based on geometric theory. Based on rigid body kinematics, equations for motion analysis of deployable panel and shell structures are deduced using Moore-Penrose generalized inverse matrix theory. Two-dimensional deployable panel and shell structures based on a two-dimensional paper-folding models are analyzed. It is shown that there are elastic-plastic deformations between panels in these kinds of structures during folding and deployment process, and the deformations are simulated by corresponding constraint handling. The deployment process is simulated through an example.