【作者】 王雯静；

【导师】 余跃庆；

【作者基本信息】 北京工业大学 ， 机械设计及理论， 2009， 博士

【摘要】 柔顺机构主要靠机构中柔性构件的变形来实现机构的运动和功能。与传统刚性机构相比,它具有减少机构重量、安装时间、间隙和摩擦磨损,提高机构精度、增加可靠性、减少维护等方面的优点,适应现代科技发展对机械设备的要求,引起了学者们的广泛关注。目前,柔顺机构的绝大部分研究都是围绕着结构和运动分析以及拓扑优化设计开展的,而在动力学方面却很少涉及。随着柔顺机构的应用范围和工作要求的不断提高,如何改善柔顺机构的动力学特性,提高柔顺机构设计水平,将成为柔顺机构领域的关键问题,此项研究具有重要的理论意义和应用价值。本文以平面柔顺机构为研究对象,重点研究柔顺机构动力学问题,主要包括建模与特性分析、优化设计和实验研究等方面的内容。首先,建立了以柔性铰链为主要特征的柔顺机构动力学模型。推导出四种常见柔性铰链的刚度计算公式,并分析柔性铰链各参数对其刚度的影响。在此基础上,针对平行导向柔顺机构和曲柄滑块柔顺机构,应用拉格朗日方程,建立了该柔顺机构动力学模型。其次,建立了以柔顺杆为主要特征的柔顺机构动力学模型。首先充分考虑杆件的大变形特性,分别采用数值拟合方法和有限元方法建立了以柔顺杆为主要特征的柔顺机构动力学模型,分析了两种模型的差别和适用范围。再次,深入分析了柔顺机构的动力学特性。计算了柔顺机构的固有频率;研究了机构参数对动力学性能的影响及其灵敏度问题;分析了柔顺杆的动态应力及应变,给出了杆件最大动应力以及发生的位置;基于动应力造成的累积疲劳损伤,预测了杆件的疲劳寿命;推导出以柔性铰链为主要特征的柔顺机构驱动力矩的计算公式,分析了柔性铰链刚度及未变形位置与驱动特性之间的内在关系。然后,进行了柔顺机构的优化设计。根据柔顺机构的特点,探讨了柔顺机构材料的选择准则;以固有频率、驱动力矩等为约束条件,以柔性铰链的刚度最小为优化目标,对以柔性铰链为主要特征的柔顺机构进行了优化设计;还分别以柔顺机构总质量最小、变形能最大为优化目标,以固有频率、动应力等为约束条件,优化设计出了以柔顺杆为主要特征的柔顺机构。最后,进行了柔顺机构的实验研究。设计、加工了一个平行导向柔顺机构。对该平行导向柔顺机构的固有频率及应变等问题进行了实验研究,通过实验结果与理论计算结果的对比和分析,相互验证了实验系统和理论模型的有效性和正确性。更多还原

【Abstract】 Compliant mechanisms gain their motion from the relative flexibility of their members. Compared with conventional rigid-body mechanisms, compliant mechanisms have many advantages such as part-count reduction, reduced assembly time, simplified manufacturing processes, increased precision, reduced wear, and reduced weight. At present, compliant mechanisms have attracted much attention and become the focus of mechanisms research. They have been developed rapidly in recent years due to their advantages as required in modern machinery. Most of these works are focused on the structural and kinematic analysis and design of compliant mechanisms. However, the study of the dynamics of compliant mechanisms is lacking. With the increasing requirements of task and application, the dynamic analysis to improving the dynamic characteristics and design of compliant mechanism is a new hot topic in mechanism research. The study of the dynamic analysis of compliant mechanisms has great theoretical significance and practical value.By taking the planar compliant mechanisms as subject investigated, the dynamics and synthesis of the compliant mechanisms are studied in aspects of dynamic modeling, dynamic analysis, optimal design and experiment verification in this dissertation.Firstly, the dynamic models of compliant mechanisms with flexure hinges are created. The stiffness of four flexure hinges are deduced respectively, and the effect of design parameters on stiffness of flexure hinge is studied. By taking the compliant parallel-guiding mechanism and compliant slider-crank mechanism as subject investigated, the dynamic model of compliant mechanisms with flexure hinges is created based on the Lagrange equation.Secondly, the dynamic models of compliant mechanisms with compliant links are developed. Considering the large deflection of compliant links, the numerical method and the finite element method are utilized respectively to generate the dynamic models of compliant mechanisms with compliant links. The difference and application of these models are discussed.Thirdly, the dynamic characteristics of compliant mechanisms are investigated. Based on the proposed dynamic models of the compliant mechanisms, the natural frequency is calculated. By using direct differential method for sensitivity analysis, the effect of design parameters on dynamic characteristics is discussed. The compliant link’s dynamic stress and strain are calculated,the value and position of maximal stress were derived. Based on the cumulative damage resulted from the alternate dynamic stress, the fatigue lives of the compliant links are predicted. A new method is obtained for calculating the driving torque, it shows that the flexure hinges have impact on the driving characteristics of compliant mechanisms.Fourthly, optimal design of compliant mechanisms is investigated. Based on the characteristics analysis, the material selection is studied. The stiffness of flexure hinge is taken as optimal design objective. The natural frequency and driving torque are taken as constraints. The optimal design of compliant mechanism with flexure hinges is performed. Then, the total compliant links mass and the total strain energy are taken as optimal design objective, respectively. The natural frequency and dynamic stresses are taken as constraints. The optimal design of compliant mechanism with compliant links is performed.Finally, the experimental study of compliant mechanism is performed. The compliant parallel-guiding mechanism is developed. The experimental studies of natural frequency and strain are performed. The comparison between the experiment results and the theoretical results verifies the validity of the experiment system and theoretical models.更多还原