【作者】 司洪伟；

【导师】 李东旭；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2006， 博士

【摘要】 大挠性航天桁架结构的振动控制是航天器动力学与控制领域的挑战性课题。大挠性航天桁架结构是由杆、梁、铰链及其有效载荷等结构单元根据特定的航天任务需求而组成的大型离散结构,并因其具有集散简单、可靠性强、对任务的适应度大等特点而在航天结构中得到广泛应用;但是作为一种极具代表性的大型离散结构,其结构动力学特性也很复杂,基于经典控制理论和现代控制理论的控制方法已经难以适应这一复杂系统的控制要求;而模糊控制理论不需要精确的数学模型,适用于对复杂大系统的控制,本文正是在这样的背景下,展开大挠性航天桁架结构动力学研究,提出针对大挠性航天桁架结构的主动模糊控制的理论和方法,并进行深入的探讨和研究。本文主要包含两个方面的工作:大挠性航天桁架结构动力学建模、特性分析和计算;基于模糊控制方法对大挠性航天桁架结构的振动展开主动控制研究。概括地说,围绕上述两个方面开展的具体研究内容包括:1.针对大挠性航天桁架结构这一代表性的离散结构,明确了研究对象的背景和特点,并对其进行分类(桁架式空间站、空间外伸承载桁架结构、抛物面桁架天线、环形张紧桁架可展开天线、四面体桁架天线以及变几何桁架结构),综述了国内外大挠性航天桁架结构动力学及主动控制研究、模糊控制研究以及结构振动的主动模糊控制研究的进展。2.深入系统地对大挠性航天桁架结构动力学展开研究。(1)结合航天器在轨运行时大挠性航天桁架结构的振动为控制带来的问题和挑战,针对几种常见的材料,分析了在地面实验室建立与在轨航天器具有相同或相似动力学特性的缩尺模型的可行性。(2)分别对抛物面桁架天线、环形张紧桁架可展开天线、四面体桁架天线以及变几何桁架结构等几种常见的大挠性航天桁架结构进行动力学特性分析。(3)对桁架式空间站和空间外伸承载桁架结构进行有限元建模与计算,主要包括基于缩尺建模方法的大型分布挠性航天结构(桁架式空间站)、带有大挠性桁架结构的挠性航天器、智能航天桁架结构(空间外伸承载桁架结构)及其主动杆;由于主动杆优化配置是一个离散问题,本文设计了基于整数编码的遗传算法来优化主动杆位置。3.结合国内外模糊控制理论的研究现状,将模糊控制理论和经典控制理论、现代控制理论、智能控制理论相结合,设计几种较先进的模糊控制器。(1)在简明地阐述模糊控制系统基本原理的基础上,着重研究了现实可行的四种模糊控制方法:结合PID控制原理,采用模糊推理实现PID参数的在线自整定;为改善控制系统的动态性能,在输入变量模糊化的过程中,引入了变论域的概念;创造性地使用基于整数编码的遗传算法优化模糊控制规则库,从根本上改善模糊控制系统的控制律;为了减小稳态误差,设计了一种引入智能积分环节的模糊控制器。(2)迄今为止,模糊控制尚未形成完善和系统的理论,尤其是模糊控制系统的稳定性和鲁棒性,一直是研究的难题。针对航天器控制宜采用自适应模糊控制的特点,基于输入和输出隶属度函数的中心值,结合Lyapunov稳定性理论,解决了自适应变论域模糊控制系统的稳定性和鲁棒性问题。4.在结构动力学计算的基础上,使用设计的模糊控制方法(模糊PID控制方法、自适应变论域模糊控制方法、引入智能积分环节的模糊控制方法以及基于整数编码遗传算法优化规则库的模糊控制方法)对大挠性航天桁架结构振动模糊控制进行仿真研究;在仿真中,针对模糊推理的原理,选取一种较优的模糊推理方法;在构造规则库的过程中,采用了基于物理经验和知识的方法与基于遗传算法优化相结合的办法,设计了一种比较适合大挠性航天桁架结构振动控制的规则库;在解模糊过程中,对比各种解模糊方法的优缺点,选取较优的解模糊方法;并与经典PID控制、最优控制以及H∞输出反馈控制相比较,分析结果表明设计的模糊控制方法对大挠性航天桁架结构这一复杂大系统的主动控制具有较好的适应性和明显的优越性。更多还原

【Abstract】 Active control of Large Flexible Space Truss (LFST) is a challenging subject in the domain of the dynamics and control of spacecrafts. LFST is a kind of large discrete structures made of structural elements, such as bars, beams, joints, its payloads and so on, according to given specific needs of space missions. LFST is widely used in space structures for its excellence of easily loading and unloading, high reliability, good suitability to missions. However, as a typical kind of large discrete structures, LFST is of complex dynamic characteristics, and the control methods based on custom and modern control theories are difficult to suit the control problem of this large complex system. However, fuzzy control theory doesn’t depend on the accurate mathematical model and it is suitable to the control of the large complex system. From this point of view, this dissertation researches the dynamics of LFST and brings forward the research topic of active fuzzy control for LFST, which are deeply studied and discussed in this dissertation.This dissertation mainly covers two aspects of works. One is the topic of the dynamic modeling, characteristics analysis and computation of LFST, and the other is the topic of active control of LFST based on fuzzy control methods. In a word, based on the two aspects, this dissertation includes:1. Aiming at LFST, a typical kind of discrete structures, this dissertation nails down the background and characteristics of the researched object, and LFST is classified as several kinds of structures, such as truss type of space station, stretched-out support truss, paraboloid truss antennas, ring-tension truss deployable antennas, tetrahedral truss antennas and variable geometry truss. This dissertation reviews three aspects of the research topics: (1) dynamics and active control of LFST; (2) fuzzy control; (3) active fuzzy control of structures.2. The dynamics of LFST is researched thoroughly and entirely.(1)Considering the problem and challenge brought by the vibration when spacecrafts with LFST in orbit, and aiming at several general materials, this dissertation analyses the feasibility to building a scaled model of LFST in lab, which is of the same or near dynamic characteristics as the LFST in orbit.(2)The dynamic characteristics based on modal analysis of some general types of space truss structures, such as paraboloid truss antennas, ring-tension truss deployable antennas, tetrahedral truss antennas and variable geometry truss, are researched.(3)Truss type of space station and stretched-out support truss structures are modeled and computed by finite element method, which mainly includes large distributed type of flexible structures for truss type of space station, flexible spacecraft with LFST, intelligent space truss model for stretched-out support truss and its active members. Because the optimal location of active members is a discrete problem, this dissertation designs Integer Coded Genetic Algorithms (ICGA) for the discrete problem.3. According to the research actuality of fuzzy control theory domestic and overseas, and combining fuzzy control theory with the custom control theory, modern control theory and intelligent control theory, this dissertation designs some advanced fuzzy controllers.(1)Based on the explanation of fuzzy control concisely, this dissertation emphasizes four kinds of advanced fuzzy controllers. Combining to the PID control principle, this dissertation adopts fuzzy inference mechanism to tune PID parameters. To improve the dynamic capability, the conception of Scaling Universes of Discourse (SUD) is inducted during the fuzzification of input parameters. Based on ICGA to the optimization of the fuzzy rules base, the control law of the fuzzy controller could be improved radically. To reduce the stable error, this dissertation designs a kind of fuzzy controller with intelligent integral introduced.(2)Now days, fuzzy control theory has not get the perfect and systemic theory, especially in the aspects of stableness and robustness. This dissertation aims at the characteristics that the control of spacecrafts gets better to adopt the self-adaptive control, and basing on the center values of input and output membership functions, adopting the analysis method of Lyapunov function, designs the stableness and robustness of self-adaptive fuzzy control system based on SUD.4. Based on the dynamic computation of LFST, several advanced fuzzy controllers (fuzzy PID controller, fuzzy controller with intelligent integral introduced, self-adaptive fuzzy controller based on SUD, fuzzy control based on ICGA to the optimization of the fuzzy rules base) are simulated for the active control of LFST. This dissertation chooses a kind of fuzzy inference mechanism according to the principle of fuzzy inference during simulation, adopts the method that combines the rules got from experience and knowledge with the rules got from ICGA for the optimization of fuzzy control of LFST, and finally chooses a kind of defuzzification method by comparison during the simulation. Furthermore, fuzzy controllers are compared with the custom PID controller, optimal controller and H∞output feedback controller for the active control of LFST, respectively. The simulation results show that the fuzzy control methods designed in the dissertation are much more suitable and superior than custom and modern control methods for the LFST.更多还原