Parabolic and hyperbolic flexure hinges: flexibility, motion precision and stress characterization based on compliance closed-form equations

The parabolic and hyperbolic flexure hinges are introduced as new rotation joints to be utilized in two-dimensional monolithic mechanisms. Closed-form equations are formulated for compliances to characterize both the active rotation and all other in- and out-of-plane parasitic motions. The stress levels are also evaluated in terms of compliances. Checked against finite element analysis and experimental measurement data, the model predictions are within 8% error margins. Further simulation is performed to compare geometrically-equivalent parabolic and hyperbolic flexure hinges. The results indicate that the parabolic flexures are more rotation-compliant and induce less stress, while the hyperbolic flexures are less sensitive to parasitic effects.     

Design and analyze of flexure hinges based on triply periodic minimal surface lattice

The triply periodic minimal surface lattice structure is innovatively introduced into the design of flexure hinges in this paper. Four types of triply periodic minimal surface lattices are generated by approximate mathematical expressions. The compliance characteristics of these four lattices are simulated by finite element analysis (FEA), and it is found that the primitive lattice (P-lattice) is the most suitable lattice for flexure hinges. Simplified model of single P-lattice and one-dimensional parallel structure composed of several P-lattices are proposed. Finally, the P-lattice is integrated into the beam portion of flexure hinges by Boolean operation, and this new type of flexure hinge is additively manufactured. The FEA and experimental results show that the compliance and compliance ratio of this new type of leaf flexure hinges are greatly improved.     

具有应力和厚度约束的平面弹性体结构拓扑优化设计

研究了具有应力和厚度约束的弹性平面体结构拓扑优化问题。这类问题不同于一般意义的拓扑优化问题 ,其优化结果不仅得到最优拓扑 ,而且得到最优形状和尺寸。建立了这类问题的数学模型 ,给出了求解策略 ,算例表明算法是有效的     

具有力约束的多体系统动力学优化方法的研究

本文以Ｋａｎｅ方程为基础，建立了具有力约束的多体系统动力学方程，以能量最小为优化目标，实现了动力学解算。以工业机器人为例，进行了动力学分析和解算。     

具有等厚主片变截面钢板弹簧优化设计

建立了具有等厚主片少片变截面钢板弹簧优化设计模型,探讨了利用最优化方法进行具有等厚主片少片变截面钢板弹簧设计可靠性,并以某轻型客车前悬架刀例,设计了变截面钢板弹簧。     

基于MATLAB的优化模型几何描述

利用MATLAB出色的数据可视化功能,以几何图形描述优化问题的形态及其要素,以获得对优化模型的直观认识和深入理解。     

基于混沌映射与差分进化自适应教与学优化算法的太赫兹图像增强模型

为消除功率起伏效应引起的太赫兹(THz)图像局部伪影,构建了基于同态滤波的THz图像增强模型.然而,模型各参数取值差异大且耦合性强,给其参数确定带来了困难.为此,本文提出了混沌映射与差分进化自适应教与学优化算法以求解增强模型最优参数.首先,改进了标准Logistic混沌映射,提高了种群多样性.其次,引入适应度更新率,构...     

Adaptive synchronization and parameter identification of chaotic system with unknown parameters and mixed delays based on a special matrix structure

In this paper, we investigate the synchronization and parameter identification of chaotic system with unknown parameters and mixed delays. A new approach is proposed for designing a controller and a update rule of unknown parameters based on a special matrix structure, and the synchronization and the parameter identification are realized under the controller and the update rule. Numerical simulations are carried out to confirm the effectiveness of the approach. A significant advantage is that the process of designing a controller and a update rule become very clear and easy by the proposed approach.     

利用ADAMS的泵车臂架连杆机构优化设计与模拟

针对泵车臂架常用连杆机构的运动过程,建立目标力的数学模型,得到目标优化参数。在ADAMS软件中对其进行动力学仿真,获取连杆机构的最恶劣工作姿态,然后进行优化计算,得到典型工况下连杆结构参数的最优值。     

基于可靠性原理的质量成本模型及其动态优化

为了进一步研究质量管理与质量成本的关系,提升质量管理水平.引入质量管理可靠性,来定量评价产品寿命周期内的质量管理工作,并依据质量管理可靠性与质量成本存在的关系,建立了新的质量成本模型,给出了该模型动态优化流程,实现了质量成本优化与质量改进的统一.实例验证表明,该模型是可行的和有效的.     

Design and optimization for the occupant restraint system of vehicle based on a single freedom model

Throughout the vehicle crash event, the interactions between vehicle, occupant, restraint system (VOR) are complicated and highly non-linear. CAE and physical tests are the most widely used in vehicle passive safety development, but they can only be done with the detailed 3D model or physical samples. Often some design errors and imperfections are difficult to correct at that time, and a large amount of time will be needed. A restraint system concept design approach which based on single-degree-of-freedom occupant-vehicle model (SDOF) is proposed in this paper. The interactions between the restraint system parameters and the occupant responses in a crash are studied from the view of mechanics and energy. The discrete input and the iterative algorithm method are applied to the SDOF model to get the occupant responses quickly for arbitrary excitations (impact pulse) by MATLAB. By studying the relationships between the ridedown efficiency, the restraint stiffness, and the occupant response, the design principle of the restraint stiffness aiming to reduce occupant injury level during conceptual design is represented. Higher ridedown efficiency means more occupant energy absorbed by the vehicle, but the research result shows that higher ridedown efficiency does not mean lower occupant injury level. A proper restraint system design principle depends on two aspects. On one hand,the restraint system should lead to as high ridedown efficiency as possible, and at the same time, the restraint system should maximize use of the survival space to reduce the occupant deceleration level. As an example, an optimization of a passenger vehicle restraint system is designed by the concept design method above, and the final results are validated by MADYMO, which is the most widely used software in restraint system design, and the sled test. Consequently, a guideline and method for the occupant restraint system concept design is established in this paper.     

Independent continuous and mapping method of structural topology optimization based on the global stress approach

There are three difficulties in topology optimization of continuum structures. 1) The topology under multiple load case is more difficult to be optimized than under single load case, because the former becomes a multiple objective based on compliance objective functions. 2) With local constraints, such as an elemental stress limit, the topology is more difficult to be solved than with global constraints, such as the displacement or frequency limits, because the sensitivity analysis of the former has very expensive computation. 3) With the phenomenon of load illness, which is similar with stiffness illness in the structural analysis, it is not easy to get the reasonable final topological structure, because it is difficult to consider different influences between the loads with small forces and big forces, and some topology paths of transferring small forces may disappear during the iteration process. To overcome difficulties above, four measures are adopted. 1) Topology optimization model is established by independent continuous mapping (ICM) method. 2) Based on the von Mises strength theory, all elements’ stress constraints are transformed into a structural energy constraint. 3) The phenomenon of load illness is divided to classify into three cases. 4) A strategy based on strain energy is proposed to adopt ICM method with stress globalization, and the problems of the above mentioned three cases of load illness are solved in terms of different complementary approaches. Several numerical examples show that the topology path of transferring forces can be obtained more easily by substituting global strain energy constraints for local stresses constraints, and the problem of load illness can be solved well by the weighting method that takes the structural energy as a weighting coefficient.     

基于ANSYS的磁瓦压机支座有限元性能分析与优化设计

磁瓦压机是磁瓦生产的一种重要的毛坯生产设备,压机支座的性能会对毛坯制造质量和支座寿命产生较大的影响。针对企业开发CS150Q全自动压机的设计需要,提出了一种通过Solidworks创建支座三维模型并导入ANSYS进行有限元性能分析相结合的方法。静力学分析找出了其最大形变和最大应力,拓扑分析显示了其材料分配情况。在不改变安装尺寸的前提下,基于静力和拓扑分析结果,优化了支座局部结构。对比了优化前后结构的性能,优化后支座质量有所减少,静力学性能和前2阶固有频率均有所提高,表明结构优化方案是可行的。     

Computation of a turbulent natural convection in a rectangular cavity with the low-reynolds-number differential stress and flux model

A numerical study of a natural convection in a rectangular cavity with the low-Reynoldsnumber differential stress and flux model is presented. The primary emphasis of the study is placed on the investigation of the accuracy and numerical stability of the low-Reynolds-number differential stress and flux model for a natural convection problem. The turbulence model considered in the study is that developed by Peeters and Henkes (1992) and further refined by Dol and Hanjalic (2001), and this model is applied to the prediction of a natural convection in a rectangular cavity together with the two-layer model, the shear stress transport model and the time-scale bound model, all with an algebraic heat flux model. The computed results are compared with the experimental data commonly used for the validation of the turbulence models. It is shown that the low-Reynolds-number differential stress and flux model predicts well the mean velocity and temperature, the vertical velocity fluctuation, the Reynolds shear stress, the horizontal turbulent heat flux, the local Nusselt number and the wall shear stress, but slightly under-predicts the vertical turbulent heat flux. The performance of the model is comparable to that of the low-Reynolds-number differential stress and flux model except for the over-prediction of the horizontal turbulent heat flux. The two-layer model predicts poorly the mean vertical velocity component and under-predicts the wall shear stress and the local Nusselt number. The shear stress transport model predicts well the mean velocity, but the general performance of the shear stress transport model is nearly the same as that of the two-layer model, under-predicting the local Nusselt number and the turbulent quantities.     

采用人体树图与混合粒子群聚类的行人检测

为提升辅助驾驶系统的可靠性及安全系数,实现更高精度的行人检测,基于人体树图模型提出了一种改进的离线训练、在线检测的行人检测方法。首先,定义人体部件间的共生关系,得到对应父子部件对,结合K-means算法对其位置关系进行聚类获得部件类型。为兼顾类内紧密性与类间分离性,采用MSE和DBI构建具有两阶段适应度函数的混合粒子群聚类算法,在有效估计各部件最优聚类中心数量的同时,消除随机初始化对聚类准确率造成的影响。其次,将优化聚类得到的部件类型作为隐藏变量,通过求解隐结构SVM获取改进后的人体检测模型。最后,通过动态规划算法求解状态转移方程,在多个尺度上有效估计人体部件位置及检测包围盒,并结合非极大值抑制思想得到最终的行人检测结果。实验结果表明,所提方法在检测性能上明显优于5种行人检测方法,并且相比于原始Pose-original方法,在INRIA和ETH数据集上的丢失率分别下降了8.14%和5.05%。实验证明该方法检测性能良好且具有较高的准确性和鲁棒性。     

个体眼结构的横向色差随外置光阑偏心和视场的变化

由角膜地形图计算了8只人眼视轴与光轴的夹角。依据实际测得的角膜地形图数据、人眼波像差、眼轴数据以及计算的视轴与光轴间夹角,运用ZEMAX光学设计软件构建了考虑视轴方向的个体化眼模型。基于这些眼模型,研究了外置人工光阑相对视轴偏移在中心凹附近所引入的横向色差变化规律。研究表明,横向色差随人工光阑的偏移量线性增加;8只人眼存在一定的个体差异,横向色差随人工光阑偏移量增加的速率在5.46 arcmin/mm ~5.95 arcmin/mm 范围之间,平均值为5.7 arcmin/mm。然后研究了在420 nm至700 nm波段边缘横向色差随入射视场角的变化规律。在鼻侧和颞侧20°视场范围内,8只人眼的横向色差平均以0.36 arcmin/deg 的速率随视场角增加而增加, 不同个体的增长速率有所差别,变化范围在0.32 arcmin/deg~0.44 arcmin/deg 之间。同时横向色差在长波段的变化要比短波段处缓慢。 关键词：视觉光学;横向色差;个体化眼模型