微型柔性机构的多目标计算机辅助拓扑优化设计

提出了基于结构整体柔度最小化和结构输出位移最大化的多目标拓扑优化设计方法,建立了微型柔性机构的多目标拓扑优化设计模型.提出了适用于微型柔性机构多目标拓扑优化设计的伴随矩阵敏度分析方法,并将广义收敛移动渐进算法用于多目标多约束微型柔性机构拓扑优化问题的求解.最后通过数值计算验证了优化模型的有效性.     

基于传递函数法的带外挂大柔性机翼颤振分析

基于带外挂大柔性机翼结构和气动特点,使用带有半解析半数值特性的传递函数方法进行处理.首先,将变形后的柔性机翼视为曲梁,基于曲梁的运动微分方程,结合传递函数方法,将曲梁运动微分方程整理成状态空间方程形式.然后,借鉴有限元方法的思想将单元进行组集,组集时结合机翼挂载处内力平衡和位移协调条件,得到了机翼整体平衡方程,结合求解复特征值的方法,完成了带外挂大展弦比大柔性机翼的动气动弹性稳定性分析.对比通过有限元方法得到的仿真结果,证实了文章提出计算方法的准确性和高效性.文章结尾,分析了外挂质量、转动惯量、位置分布及数量等变量对带外挂大展弦比大柔性机翼的动气动弹性稳定性的影响.     

并联三钳指柔性压电微夹钳的设计与分析

为增大柔性微夹钳可操作物体的范围、增加操作过程中的稳定性、降低对可操作物体的损伤、消除垂直于输出位移方向的耦合位移,基于二级杠杆位移放大机构、桥式位移放大机构、位移导向机构,设计了一种单压电执行器驱动并联三钳指的柔性微夹钳.首先,描述了并联三钳指微夹钳的结构特征与工作原理;然后,根据微夹钳的柔性特征构建其输出位移放大倍...     

柔性桥式微位移机构位移放大比特性研究

为了分析柔性桥式微位移放大机构的位移放大比特性,利用桥式微位移放大机构的结构全对称性,建立了微位移放大机构的1/4数学模型.采用矩阵法建立了其柔度矩阵,进而推导了桥式位移放大机构的输出位移公式及位移放大比公式.采用ANSYS 11.0软件进行了有限元仿真,并与理论模型进行了分析比较.最后,设计加工了一个实验样件,对理论...     

飞机机翼垂尾壁板制孔系统孔位自动校正方法

飞机机翼垂尾壁板制孔系统孔位容易受到随机波动干扰产生误差,提出基于电控机械式误差调节的飞机机翼垂尾壁板制孔系统孔位自动校正方法,构建飞机机翼垂尾壁板制孔系统孔位校正的执行机构控制模型,采用位移传感器进行垂尾壁板制孔系统孔位的误差偏移测量,在执行机构中进行误差的自适应调节和输出稳定性控制,结合迭代学习控制方法进行飞机机翼垂尾壁板制孔系统孔位自动校正过程中的误差偏移修正,采用电控式的机械误差调节方法,实现机翼垂尾壁板制孔系统孔位自动校正优化。仿真结果表明,采用该方法进行机翼垂尾壁板制孔系统孔位校正的自动性较好,误差修正能力极强,提高了飞机机翼垂尾壁板制孔系统孔位主动调节和误差自适应修正性能。     

六自由度微动机构的运动分析

本文对作者设计的一种六自由度微动机进行位移分析，该机构由３条ＰＰ－Ｒ－Ｓ支链并联而成，为消除间隙，每条链的运动副都设计柔性铰链，本文用坐标变换方法求出了机构的输入输出微位移关系，由于柔性铰链的运动范围受到材料强度的限制。文中还建立了柔性铰链微小角位移与机构输出位移的关系，以上关系式为六自由度微动机构的结构设计提供了计算依据。     

一种检测钢轨温度应力的电容式传感器

介绍了一种用于钢轨温度应力检测的电容式位移传感器。该传感器采用柔性铰链作为位移放大机构,并通过ANSYS软件对结构进行有限元建模。分析了该机构对传感器的灵敏度、线性度等参数的影响,以实现对传感器的参数优化设计。     

平面全柔性3-DOF过驱动并联机构的最优综合

以设计全柔性多自由度过驱动并联机构为目标，研究了平面3-DOF 4RRR过驱动并联机构的最优综合问题．从一般四分支3-DOF平面并联机构出发，建立了机构的运动学模型；给出了机构的4种可能拓扑结构分类，对不同拓扑结构类型机构的运动学和力学性能进行了分析比较．建立了并联机构全工作空间操作性改善优化模型，采用遗传算法进行优化设计并给出了实例，根据优化实例的结果设计制造了平面全柔性三自由度过驱动并联机构．以上方法对其它全柔性并联机构的优化设计具有参考价值．     

新型离散蝙蝠算法求解柔性流水车间调度问题

针对以最小化完工时间为目标的柔性流水车间调度问题,提出了一种新型离散蝙蝠算法。介绍了蝙蝠算法的基本思想,重新定义速度与位置的加法操作来实现粒子的位移,给出了算法的具体实现方案。通过实例仿真和算法比较验证了算法的优化性能,实验结果表明该算法可以有效地求解柔性流水车间调度问题。     

基于LQG自校正器的机翼颤振主动抑制

研究了一种基于LQG自校正器的机翼颤振主动抑制设计方法.以带有后缘控制面的柔性机翼为研究对象,采用在线辨识来获取系统的时变参数,利用Kalman滤波器重构状态,通过求解离散时间代数Riccati方程得出机翼颤振主动控制律.在Simulink仿真平台上实现了上述方法,仿真结果表明,该控制器能够有效抑制机翼颤振的发生并具有一定的鲁棒性.     

Design of distributed compliant micromechanisms with an implicit free boundary representation

In this paper, a parameterization approach is presented for structural shape and topology optimization of compliant mechanisms using a moving boundary representation. A level set model is developed to implicitly describe the structural boundary by embedding into a scalar function of higher dimension as zero level set. The compactly supported radial basis function of favorable smoothness and accuracy is used to interpolate the level set function. Thus, the temporal and spatial initial value problem is now converted into a time-separable parameterization problem. Accordingly, the more difficult shape and topology optimization of the Hamilton–Jacobi equation is then transferred into a relatively easy size optimization with the expansion coefficients as design variables. The design boundary is therefore advanced by applying the optimality criteria method to iteratively evaluate the size optimization so as to update the level set function in accordance with expansion coefficients of the interpolation. The optimization problem of the compliant mechanism is established by including both the mechanical efficiency as the objective function and the prescribed material usage as the constraint. The design sensitivity analysis is performed by utilizing the shape derivative. It is noted that the present method is not only capable of simultaneously addressing shape fidelity and topology changes with a smooth structural boundary but also able to avoid some of the unfavorable numerical issues such as the Courant–Friedrich–Levy condition, the velocity extension algorithm, and the reinitialization procedure in the conventional level set method. In particular, the present method can generate new holes inside the material domain, which makes the final design less insensitive to the initial guess. The compliant inverter is applied to demonstrate the availability of the present method in the framework of the implicit free boundary representation.     

Optimal design of compliant mechanisms using functionally graded materials

This research applies topology optimization to create feasible functionally graded compliant mechanism designs with the aim of improving structural performance compared to traditional homogeneous compliant mechanism designs. Converged functionally graded designs will also be compared with two-material compliant mechanism designs. Structural performance is assessed with respect to mechanical/geometric advantage and stress distributions. Two design problems are presented – a gripper and a mechanical inverter. A novel modified solid isotropic material with penalization (SIMP) method is introduced for representing local element material properties in functionally graded structures. The method of moving asymptotes (MMA) is used in conjunction with adjoint sensitivity analysis to find the optimal distribution of material properties. Geometric non-linear analysis is used to solve the mechanics problem based on the Neo-Hookean model for hyperelastic materials. Functionally graded materials (FGMs) have material properties that vary based on spatial position. Here, FGMs are implemented using two different resource constraints – one on the mechanism’s volume and the other on the integral of the Young’s modulus distribution throughout the design domain. Tensile tests are performed to obtain the material properties used in the analysis. Results suggest that FGMs can achieve the desired improvements in mechanical/geometric advantage when compared to both homogeneous and two-material mechanisms.     

A new level set method for systematic design of hinge-free compliant mechanisms

This paper presents a new level set-based method to realize shape and topology optimization of hinge-free compliant mechanisms. A quadratic energy functional used in image processing applications is introduced in the level set method to control the geometric width of structural components in the created mechanism. A semi-implicit scheme with an additive operator splitting (AOS) algorithm is employed to solve the Hamilton-Jacobi partial differential equation (PDE) in the level set method. The design of compliant mechanisms is mathematically represented as a general non-linear programming with a new objective function augmented by the high-order energy term. The structural optimization is thus changed to a numerical process that describes the design as a sequence of motions by updating the implicit boundaries until the optimized structure is achieved under specified constraints. In doing so, it is expected that numerical difficulties such as the Courant-Friedrichs-Lewy (CFL) condition and periodically applied re-initialization procedures in most conventional level set methods can be eliminated. In addition, new holes can be created inside the design domain. The final mechanism configurations consist of strip-like members suitable for generating distributed compliance, and solving the de-facto hinge problem in the design of compliant mechanisms. Two widely studied numerical examples are studied to demonstrate the effectiveness of the proposed method in the context of designing distributed compliant mechanisms.     

Aircraft morphing wing design by using partial topology optimization

A morphing wing concept has been investigated over the last decade because it can effectively enhance aircraft aerodynamic performance over a wider range of flight conditions through structural flexibility. The internal structural layouts and component sizes of a morphing aircraft wing have an impact on aircraft performance i.e. aeroelastic characteristics, mechanical behaviors, and mass. In this paper, a novel design approach is proposed for synthesizing the internal structural layout of a morphing wing. The new internal structures are achieved by using two new design strategies. The first design strategy applies design variables for simultaneous partial topology and sizing optimization while the second design strategy includes nodal positions as design variables. Both strategies are based on a ground structure approach. A multiobjective optimization problem is assigned to optimize the percentage of change in lift effectiveness, buckling factor, and mass of a structure subject to design constraints including divergence and flutter speeds, buckling factors, and stresses. The design problem is solved by using multiobjective population-based incremental learning (MOPBIL). The Pareto optimum results of both strategies lead to different unconventional wing structures which are superior to their conventional counterparts. From the results, the design strategy that uses simultaneous partial topology, sizing, and shape optimization is superior to the others based on a hypervolume indicator. The aeroelastic parameters of the obtained morphing wing subject to external actuating torques are analyzed and it is shown that it is practicable to apply the unconventional wing structures for an aircraft.     

Analytical model of displacement amplification and stiffness optimization for a class of flexure-based compliant mechanisms

The paper formulates an analytical method for displacement and stiffness calculations of planar compliant mechanisms with single-axis flexure hinges. The procedure is based on the strain energy and Castigliano’s displacement theorem and produces closed-form equations that incorporate the compliances characterizing any analytically-defined hinge, together with the other geometric and material properties of the compliant mechanism. Displacement amplification, input stiffness and output stiffness calculations can simply be performed for any serial compliant mechanism. The class of amplifying compliant mechanisms that contain symmetric corner-filleted or circular flexure hinges is specifically addressed here. A parametric study of the mechanism performance is performed, based on the mathematical model, and an optimization procedure is proposed, based on Lagrange’s multipliers and Kuhn-Tucker conditions, which identifies the design vector that maximizes the performance of these flexure-based compliant mechanisms. Independent finite element simulation confirms the analytical model predictions.     

A CAD-based design parameterization for shape optimization of elastic solids

In this paper a CAD-based design sensitivity analysis (DSA) and optimization method using Pro/ENGINEER for shape design of structural components is presented. The CAD-based design model is critically important for multidisciplinary shape design optimization. Only when each discipline can compute the design sensitivity coefficients of the CAD-based design model, can a true multidisciplinary what-if study, trade-off analysis, and design optimization be carried out. The proposed method will allow the design engineer to compute design sensitivity coefficients of structural performance measures such. as stress and displacement, evaluated using existing finite element analysis (FEA) tools, both h- and p-versions, with respect to design variables defined in the parameterized CAD model. The proposed method consists of (i) a CAD-based design parameterization technique that ties the structural DSA and optimization to a CAD tool; (ii) a design velocity field computation that defines material point movement due to design change in CAD geometry, satisfies linearity and regularity requirements, and supports both hand p-version FEA meshed using existing mesh generators; and (iii) a design optimization method that supports structural geometric and finite element model updates in Pro/ENGINEER during the optimization process.     

全柔性机器人机构的结构构型研究

本文对全柔性机器人机构的结构构型问题进行了系统的讨论：首先从应用层面上对 全柔性机器人机构进行了分类，着重讨论了并联机构与全柔性机器人机构之间存在的有机联 系．通过对并联机构的结构及柔性铰链的几何模型进行系统的总结，为全柔性机器人机构“ 型”的选择与构筑提供了丰富的素材．此外，还重点讨论了对全柔性机器人机构的性能产生 较为显著影响的结构布局问题．     

A strain based topology optimization method for compliant mechanism design

The Energy based topology optimization method has been used in the design of compliant mechanisms for many years. Although many successful examples from the energy based topology optimization method have been presented, optimized configurations of these designs are often very similar to their rigid linkage counterparts; except using compliant joints in place of rigid links. These complaint joints will endure large strain under the applied forces in order to perform the specified motions which are very undesirable in a compliant mechanism design. In this paper, a strain based topology optimization method is proposed to avoid a localized high strain of the compliant mechanism design, which is one of the drawbacks using strain energy formulation. Therefore, instead of minimizing the strain energy for structural rigidity, a global effective strain function is minimized. This is done in order to distribute the strain within the entire mechanism while maximizing the structural rigidity. Furthermore, the physical programming method is adopted to accommodate both flexibility and rigidity design objectives. Design examples from both the strain energy based topology optimization and the strain based method are presented and discussed.     

Development of a Flying Robot With a Pantograph-Based Variable Wing Mechanism

We develop a flying robot with a new pantograph-based variable wing mechanism for horizontal-axis rotorcrafts (cyclogyro rotorcrafts). A key feature of the new mechanism is to have a unique trajectory of variable wings that not only change angles of attack but also expand and contract according to wing positions. As a first step, this paper focuses on demonstrating the possibility of the flying robot with this mechanism. After addressing the pantograph-based variable wing mechanism and its features, a simulation model of this mechanism is constructed. Next, we present some comparison results (between the simulation model and experimental data) for a prototype body with the proposed pantograph-based variable wing mechanism. Both simulation and experimental results show that the flying robot with this new mechanism can generate enough lift forces to keep itself in the air. Furthermore, we construct a more precise simulation model by considering rotational motion of each wing. As a result of optimizing design parameters using the precise simulation model, flight performance experimental results demonstrate that the robot with the optimal design parameters can generate not only enough lift forces but a 155 gf payload as well.      

Unified synthesis of compact planar path-generating linkages with rigid and deformable members

A unified procedure for the synthesis of planar linkages that may take the form of rigid body, fully compliant or partially compliant mechanisms is presented. The procedure automates the selection of mechanism topology as characterized by the number and connectivity of the links as well as the nature of the connections between them, the mechanism shape as characterized by the shapes of the individual links, and the mechanism dimensions which include the locations of the joints and the cross-sectional dimensions of the links. The synthesis task is posed as a constrained optimization problem and is solved by a hybrid, elite-preserving genetic algorithm. Three examples of compact mechanisms that trace different non-smooth paths in response to a single, monotonic and bounded force input are used to illustrate the synthesis capability of the procedure. Prototypes of the designs are built and tested to verify their performance. It is observed that in all three examples, partially compliant mechanism designs offer better conformance with design intent than either rigid body or fully compliant mechanisms.