【作者】 王威远；

【导师】 邹振祝；

【作者基本信息】 哈尔滨工业大学 ， 固体力学， 2008， 博士

【摘要】 20世纪90年代以来,随着航空航天、机械、建筑、船舶等众多领域的飞速发展,结构的大型化、柔性化趋势日益显著,由之而来的结构振动破坏、失效以及干扰等问题已经成为工程设计过程中不可忽视的客观因素之一。结构的振动控制研究是国内外工程界和学术界所面临的一项重要而又充满挑战的课题。目前国内外航天工程中的卫星适配器多采用金属锥壳结构,该结构本身的阻尼特性较差,无法有效控制发射过程中的振动载荷对卫星结构的影响。此外,截顶锥壳结构也是其他工程领域应用非常广泛的一种薄壁承载结构,发动机喷嘴、连接单元、各种适配器以及整流罩外壳等都可以看作锥壳结构。对这一类结构的振动动控制问题进行研究具有重要的现实意义,因此,本文以某卫星适配器锥壳模型为研究对象,以结构的振动控制为目标进行了理论推导、数值仿真和实验验证工作。首先,从控制器是否需要外界能量输入角度,振动控制可以分为主动控制、被动控制两类。本文中的结构振动的被动控制研究主要包括三个部分:1、通过两自由度简化模型分析了各个系统参数对结构隔振效能的影响;2、采用复合材料蜂窝结构对卫星适配器截顶锥壳模型进行结构改进,并用等效法进行了建模计算;3、应用模态应变能法对附加约束阻尼层的铝制适配器截顶锥壳模型进行了数值模拟研究。将后面两部分计算所得到的动力学特性与未改进的铝制卫星适配器锥壳模型的相关数据进行对比分析,可以证明文中卫星适配器结构改进方案的优越性。其次,本文中的振动主动控制研究主要围绕压电智能结构的应用展开。在系统建模方面,通过利用四节点Mindlin层合板单元进行有限元建模过程的推导,对目前所普遍采用的压电结构的建模方法进行了分析,并针对这一类方法难以对复杂压电结构进行建模的问题,提出了一种基于通用有限元软件的等效建模方法:即利用通用有限元软件(Patran/Nastran)导出结构的动力学方程;然后根据弹性力学和压电方程,得到压电结构的作动方程;最后将压电元件的作动力等效为载荷边界条件加入动力学方程中完成建模。该方法是一种基于通用有限元软件的计算机辅助建模(Computer Aided Modeling)方法,是进行复杂结构动力学分析与主动控制研究最为可靠和快捷的手段。仿真结果对比证明了等效法建模的正确性与有效性。第三,基于结构的有限元模型和动力学方程,利用独立模态空间控制对卫星适配器模型结构振动的主动控制进行了仿真研究。该方法是目前结构振动控制当中应用较为广泛的一种方法,能够使复杂结构的控制器设计得到简化。在控制律方面则主要针对比例反馈控制和LQR最优控制进行了控制器设计。从结构振动控制效果及对比分析可以看出,主动控制能够有效抑制结构的振动,而LQR控制具有更高的控制效率。本文还对卫星适配器模型振动主动控制中压电作动器的位置优化设计进行了研究,提出了一种基于结构模态阻尼比最大化的优化准则。优化过程中采用了累积法进行优化计算。数值仿真结果证明优化后的作动器布置能够获得最佳的阻尼特性,从而更加有效地控制结构的振动。最后,根据相关研究内容设计了不同的测试实验来验证理论分析和数值仿真结果:利用LMS系统对复合材料蜂窝结构卫星适配器模型进行了模态测试,实验结果与前文中的相关仿真结果吻合较好;应用振动台实验对上述模型的振动传递特性进行了测试,从结果中可以看出改进后的卫星适配器结构具有良好的隔振效能;基于MATLAB软件中的xPC实时控制平台,利用压电作动器对锥壳结构的低频振动进行了控制,控制前后的结果对比证明了主动控制方法的有效性和可行性。更多还原

【Abstract】 Since 1990’s, the structures had become larger and more flexible with the development of aeronautic, aerospace, mechanical, architecture and marine. Then, the problems which caused by the vibration and resonance such as destroy, disable and disturb can’t be neglected during engineering design process. Investigation on vibration control of structures becomes an important and challenge issue for academia and engineering.At present, many satellite adapter used in aerospace engineering over the world were made up with the metal truncated conical shell structures with small damping ratios. So, it can not control the vibration effect during the launch by the adapte itself. In addition, the truncated conical shell structures, as a special thin walled braced structure, are wildly used in some other engineering fields. Nozzles, joint elements, adapters and fairings can be seen as conical shell structures. Then, the investigations on vibration control of this structure have important practical significance. Then, the investigation subject of this paper is a conical shell satellite adapter model in aerospace application. Theoretical derivations and experiment on active and passive vibration control for the conical shell model have been performed.There are two types of structures vibration control method: active control and passive control. The passive control needs no control energy input and has a simply form with good stability. The inefficient for low frequencies vibration control is the main shortage of passive control method. The active control method can supply the gap of the passive control. Low frequencies vibration can be controlled effective by using active control method and the controller design becomes more flexible.The main contents of the paper are as follows:The passive control of structure vibration research in this paper includes three aspects. Firstly, the parameter variations affect for vibration isolation system is analyzed by a simplified model with two degree of freedoms. Secondly, composite honeycomb structures were applied for structural modifications of the truncated conical shell satellite adapter model. The mathematical modeling of the structure above is based on equivalence method. Thirdly, an aluminum conical shell model with constrained damping layer was simulated by using modal strain energy method. The calculation results of the second and third part above were compared with the relevant data of untreated aluminum conical shell model. Comparison results proved that the adoption of composite and honeycomb structure could improve the effect of vibration isolations and reductions.Based on the piezoelectric equations and Hamilton principle, four nodes Mindlin plate element is applied for finite element modeling. But it is difficult for the modeling of complex piezoelectric structures by the method above. Then, in this paper, an equivalent modeling method based on the universal finite element software is present. Commercial softwares Patran/Nastran are used for derivations of structural dynamic equations. The control force of piezoelectric actuator is considered as boundary conditions in dynamic equations. The actuating equations are derived from piezoelectric equations and electrodynamics. Numerical examples show that this method is efficient and accurate.Active control of vibration for the truncated conical shell satellite adapter model is simulated with the independent modal space control method base on the finite element model and dynamic equations. The method has an extensive application in structure vibration control and the controller design is simplified with it. Two control laws are used for the simulations and comparisons. One is the proportional feedback control and the other is LQR optimal control. Vibration control results prove the availability of actice control method and the LQR control has a high performance.Optimal placement of actuators is investigated with the optimization criterion of modal damping ratios maximization. Accumulation method is used for optimization calculations. Numerical results show that actuators located at the optimal place can control the vibtaion effectively.Several relevant experiments were performed to validate the results of theoretical analysis and simulations. Firstly, modal test was accomplished for the composite honeycomb conical shell adapter model by using LMS system. The experiment results were in good agreement with the calculations. Secondly, vibration table experiment was conducted to test the vibration transmissibility of the model above. The results show that the model has favorable vibration isolation effect. Finally, based on the xPC real-time control platform in MATLAB, active vibration control experiment for conical shell adapter model was developed by using piezoelectric actuators. Feasibility and effectiveness of the active method were verified by control results comparisions.更多还原