系留气球平台动力学仿真研究

研究系留气球平台设计问题,随着人类探索太空技术的不断进步,空间任务也变的越来越复杂.以空间绳网为柔性部件是最近发展起来的空间概念,在空间任务中发挥越来越大的作用,而柔性部件研究是当今世界学术研究的重点技术,需要通过大量的试验分析绳网的性能.根据绳网地面试验的需要,建立了系留绳气球平台动力学模型,分析了不同构建方式下的系留气球平台的稳定性,同时分析地面环境下风力干扰作用对系留气球平台稳定性的影响,提出了构建稳定系留气球平台的方法,并将仿真结果与地面试验结果进行对比,结果一致.     

基于ANSYS的兆瓦级风力发电机组机舱罩分析仿真

通过有限元分析能对极限风载下机舱罩结构强度进行有效分析仿真.本文首先研究了某新型机舱罩关键部件--上机舱罩在极限风速条件下的受力分析理论模型,以及ANSYS三维有限元分析的基本步骤,并在此基础上介绍了利用ANSYS软件建立上机舱罩三维有限元模型,设定有限元分析参数,约束边界条件,施加外部载荷等具体操作方法,从而构建了一种基于ANSYS的大型兆瓦级风电机组机舱罩受极限风载时的三维有限元分析仿真方法.     

系留气球压差与球体应力变化关系研究

针对系留气球球体压差变化和球体应力变化之间的关系进行研究.对球体受力情况进行简化,采用微元受力分析的方法进行应力分析,得出球体应力的理论解.采用有限元软件对无附加结构的球体进行应力分析并同球体应力的理论解进行对比,验证了有限元软件计算结果的可靠性.利用有限元方法在不同压差情况下对球体应力进行分析,确定了其高应力区域的范围和数值.需要指出的是采用膜单元比采用通常的薄壳单元进行应力分析更贴近实际情况.上述结果为球体气囊的结构设计、强度设计提供依据.     

小型系留气球尾翼构型对气动特性的影响北大核心

针对小型系留气球尾翼设计周期长、参数调整复杂的问题,使用了建模仿真的方法:逐个改变决定系留气球尾翼构型的几个参数(弦长、高度、相对位置及尾翼夹角),建立了不同尾翼构型下的系留气球模型;并使用Fluent对这些模型进行了仿真计算。得到了小型系留气球气动特性随几个决定尾翼构型的关键参数变化的规律以及变化幅度。计算结果表明,修改尾翼构型时应该优先调整弦长、尾翼相对位置应该尽量接近球尾、下尾翼夹角90°较为合适。     

基于ANSYS的某活塞热应力分析

结合虚拟样机技术和有限元分析技术,使用SolidWorks建立活塞的虚拟样机后,通过SolidWorks与ANSYS的接口,将温度载荷施加在活塞的有限元模型上,得到温度场分布;在对某发动机活塞组进行了结构介绍和理论分析的基础上,采用ANSYS软件建立了活塞组三维有限元模型;基于有限元理论对有限元模型进行仿真计算,确定了热应力和变形集中部位.通过对有限元仿真结果进行分析可以看出,该研究验证了分析的可行性和准确性,能够为活塞进一步的优化设计提供理论依据.     

系留旋翼平台建模与控制技术研究

文章提出了一种系留旋翼平台,首先介绍了系留旋翼平台与普通旋翼飞行器之间在结构和控制方式的异同点,其次针对系留旋翼平台进行动力学分析并建立其动力学模型,然后依据所建立模型采用PID控制方法对姿态、偏航以及位置进行控制,最后对系统进行了Simulink仿真,仿真结果证明系统采用模型和控制器,控制效果良好,对实际设计具有指导作用。     

大气模型对高空气球运动特性和热特性的影响

气球放飞前的蒙皮温度和充气质量计算是保障气球安全的重要手段.以高空气球为研究对象,建立了高空气球的动力学模型和热平衡模型,对气球放飞后的运动特性和热特性模型进行了仿真研究.采用用四阶龙格-库塔格式计算了不同大气模型下气球上升过程的高度和氦气温度的变化曲线,分析了大气模型对高空气球载荷、氦气充气质量、驻空高度氦气温度昼夜变化、蒙皮温度分布以及蒙皮极值温差的影响,为完善高空气球运动特性和热特性分析提供了依据.     

海缆铠装结构锚固性能有限元分析

基于有限元显式算法,通过预紧、加载载荷作用次序,研究海缆铠装层的锚固结构在工作载荷和破断力下的承载能力,并对影响锚固性能的参数进行敏感性分析.数值仿真结果显示：在破断力作用下,法兰内壁与钢丝接触位置产生明显压痕,钢丝断裂位置发生在钢丝在锚固出口位置.增加锥形锚固的内锥角可降低钢丝轴向拉伸量,减缓法兰的不利应力.同时.在较低摩擦因数下具有较大内锥角的接头盒依旧具有良好的机械性能.所设计的内锥形锚固维修接头盒能满足施工过程中的最大拉伸载荷要求.     

系留气球测控系统设计

系留气球是一种通用航空平台,测控系统是系留气球最重要的组成部分之一,其工程设计关系到系留气球运行的安全和性能.为了满足系留气球稳定可靠、能够长时间连续滞空工作的要求,对测控系统进行科学设计和有效配置,阐述了测控系统的功能、组成、关键技术等,给出了系留气球测控系统的设计方案.该方案可以直接应用于系留气球产品的工程设计中.     

平流层卫星轨道控制建模与仿真研究

平流层卫星由超压气球提供静浮力,气动帆提供轨道控制力,系绳传递各力.能够在一定纬度范围内沿东西方向缓慢运动,因此平流层卫星是一种良好的通信与对地观测平台.首先分析平流层风场特性,给出平流层卫星的组成与工作原理,采用"质量-集中弹性绳"模型,把气球和气动帆分别看作系绳节点,根据各部分动力学特性分别建模;采用Matlab软件平台进行动态仿真,利用不同海拔之间的风速差,产生侧向控制力进行南北方向轨道控制的方法.仿真结果证实气动帆轨道控制系统能够实现平流层卫星南北方向的稳定控制与机动调整.     

纳米级动态粘着接触的有限元模型与仿真

对纳米级动态粘着接触过程进行仿真,是为了研究微纳米尺度的机电系统(如MEMS)中所存在的纳米级表面接触和摩擦,对系统进行减粘附设计.利用商用有限元分析软件ANSYS建立的纳米尺度的动态粘着接触模型,采用原子间Len-nard-Jones作用势函数来描述表面力,用数值求解的方法来描述基本球-盘模型的接触-分离行为,最终得到接触过程的力-位移曲线和枯着接触的分离点和粘着力的大小.将有限元粘着接触模型仿真所得结果与常用的接触模型(DMT模型、JKR模型)解析解对比,证明了有限元粘着接触模型的适用性.由于有限元模型不受接触副几何形状和材料性质的限制,可以进一步对表面形貌修饰后的粘性接触过程和多峰粘着接触过程进行仿真.     

谐振式微加速度传感器的有限元分析

有限元分析用来评估一种新颖的谐振微加速度传感器,仔细分析新结构的几个主要振动模态,优化结构参数,证实这种硅基谐振式微加速度传感器的灵敏度高于1 000 Hz/gn.而且在有限元分析的基础上对实际制造的非完全匹配的双端固定音叉的特点和对于测量的不良影响进行分析.     

Intelligent health monitoring of aerospace composite structures based on dynamic strain measurements

This work presents a study on an intelligent system for structural health monitoring of aerospace structures based on dynamic strain measurements, in order to identify in an exhaustive way the structural state condition. Four fiber Bragg grating (FBG) optical sensors were used for collecting strain data, representing the dynamic response of the structure and the expert system that was developed was based on the collected response data. Multi-sensor data fusion in a feature-level approach was followed. Advanced signal processing and pattern recognition techniques such as discrete wavelet transform (DWT) and support vector machines (SVM) were used in the system. For the current analysis, independent component analysis (ICA) was additionally used for the reduction of feature space. The results showed that SVMs using non-linear kernel is a powerful and promising pattern recognition scheme for damage diagnosis.The system was developed and experimentally validated on a flat stiffened composite panel, representing a section of a typical aeronautical structure. Within the frame of the present work the flat stiffened panel was manufactured using carbon fiber pre-pregs. Damage was simulated by slightly varying the mass of the panel in different zones of the structure by adding lumped masses. The analysis of operational dynamic responses was employed to identify both the damage and its position. Numerical simulation with finite element analysis (FEA) was also used as a support tool.     

Shape optimizations and static/dynamic characterizations of deformable microplate structures with multiple electrostatic actuators

Micromirrors used in many optoelectronic devices can be considered as microplates. The functions and accuracy of the micromirrors depend on the static and dynamic deflection shapes of microplates. The objective of this study is to develop an efficient method for predicting the shapes of the microplates subjected to unsymmetrical electrostatic forces produced by electrostatic actuators such that micromirrors can be effectively optimized and controlled in their real time operation. The non-classical boundary conditions which result from the microfabrication process were modeled with artificial springs at the edges. A classical energy method using boundary characteristic orthogonal polynomials was applied to formulate the equations of motion of the microsystem. Based on this method, influence functions were built and least squares method was used to optimize the desired deflection under electrostatic forces from the electrostatic actuators. Softening effect of the electrostatic stiffness was also evaluated and considered in the simulation. Static deflections and dynamic responses were compared with those from finite element analysis (FEA) using Reduced Order Modeling (ROM) method. This study found that the static and dynamic responses of microplates predicted from the proposed method were highly consistent with those calculated from FEA. However, the proposed method is simpler and more efficient than FEA and can be conveniently used for any non-classical boundary condition situations. These features make the proposed method useful to effectively control and optimize the shape of a microplate with multiple electrostatic actuators.     

ANSYS在腕力传感器结构设计中的应用

腕力传感器是一类重要的机器人传感器,腕力传感器的弹性体结构设计好坏直接影响到传感器的各项指标.由于腕力传感器结构复杂,各输出通道之间往往存在着干扰,通常采用实验的方法来进行标定,但标定的结果往往不够精确.利用所研制的一种新型机器人多维腕力传感器的结构,提出了一种利用有限元分析软件ANSYS对其维间干扰作定量分析的方法,分析结果证实了该传感器弹性体结构设计的合理性.     

Shape design sensitivity analysis and optimization of spatially rotating objects

Shape design sensitivity analysis (DSA) and optimization of spatially rotating objects is presented in this paper. Design sensitivity expressions are derived using a continuum DSA method for spatial objects rotating with angular velocity and angular acceleration, based on three definitions of the finite element mass matrix: consistent, lumped, and diagonalized. The design sensitivity expression derived using a diagonalized element mass matrix, which is consistent with the finite element analysis (FEA) method used in ANSYS, is implemented, although the method can work with other FEA codes, such as MSC/NASTRAN or ABAQUS. Since the continuum DSA method is used, sensitivity information can be computed outside the FEA codes by postprocessing finite element data. Rotating block and turbine blade examples are presented to validate the proposed DSA method. The turbine blade example is optimized using an integrated optimization module of the Design Sensitivity Analysis and Optimization (DSO) tool developed at the University of Iowa. The integrated module consists of ANSYS, MSC/NASTRAN, or ABAQUS for FEA; Design Optimization Tool (DOT) for nonlinear programming; and DSA and design model update programs developed in DSO.     

An efficient computational method for dynamic stress analysis of flexible multibody systems

This paper presents an efficient computational method of dynamic stress history calculation for a general three-dimensional flexible body by combining flexible multibody dynamic simulation and quasi-static finite element analysis (FEA). In the dynamic simulation of flexible multibody systems, flexible components can undergo nonsteady gross motion and small elastic deformation that is described with respect to the body reference frame by using the assumed mode method. D'Alembert inertia loads from the gross body motion and the elastic deformation are expressed as a combination of space-dependent and time-dependent terms that are obtained from the dynamic simulation. D'Alembert inertia loads that are associated with each unit value of the time-dependent terms are then distributed to all finite element nodes in order to compute a corresponding stress influence coefficient through quasi-static structural analyses. Total dynamic stresses due to D'Alembert inertia loads are obtained by multiplying actual magnitude of time-dependent terms with the associated stress influence coefficients. By the proposed method, it is shown that, for a general three-dimensional component, the required number of FEAs can be significantly reduced.     

基于dyna971的数控镗铣机床动态模拟仿真

落地式数控镗铣机床结构复杂,为保证机床具有良好的动态性能,在开发设计该类机床时要进行整机的动态模拟仿真分析。针对这一要求,提出一种实际设计中实用化程度较高的机床动态模拟仿真思路,首先对数控落地镗铣机床样机进行模态试验,获取床身〖CD*2〗滑座、滑座〖CD*2〗立柱、立柱〖CD*2〗主轴箱等结合面的模态参数,在对模态参数进行有限元方法优化识别后,利用COMBIN14单元模拟优化后的结合部参数建立机床整机有限元模型。在dyna971软件平台对整机有限元模型进行动态模拟仿真,从模拟仿真分析结果可以看出机床在受到外界作用力时,其输出的应力和应变变化波形平稳,说明经过上述分析而设计出的机床具有良好的动态性能。目前,该研究成果已应用于此类型机床的批量生产。     

Haptically integrated simulation of a finite element model of thoracolumbar spine combining offline biomechanical response analysis of intervertebral discs

In this paper, we first describe the construction of a finite element model of the human spine that may be used to assist the investigation of clinical problems by predicting its biomechanical behaviour. A beam finite element (FE) spine model for haptic interaction is built based on a solid FE spine model, which is created in an offline finite element analysis (FEA) software. The mechanical properties of the beam FE spine model are tuned so that its deformation behaviour is very similar to that of the offline solid spine model. Furthermore, the online beam FE spine model is greatly simplified as compared to the offline solid FEA model and hence more appropriate for real-time simulations. Haptic feedback is provided in the real-time simulation of the beam FE spine model, in order to enhance the human–computer interaction. Based on the results of spine deformation obtained from the haptic online FE simulator, the offline FEA spine model again is used to reproduce the same deformation and hence to provide more detailed deformation and vertebrae’s stress/strain information, which the haptic beam FE model is not capable to provide. Then, we present a tetrahedral mass–spring system to model intervertebral discs, which are interposed between vertebrae, and the offline simulation can be run to achieve deformation responses of these intervertebral discs. In our research, combining the haptic beam FE model and the intervertebral disc model can be useful for studying biokinematics of the spine as well as assessing medical conditions in the spine or the biomechanical behaviour of new designs of artificial intervertebral discs.