基于双向渐进结构优化法的柔性机构设计

Design of Compliant Actuation Mechanisms by Evolutionary Structural Optimization Method

基于双向渐进结构优化法提出一种面向柔性机构的拓扑优化设计策略。由于采用0/1离散拓扑设计变量和启发式变量更新机制,双向渐进结构优化法一般适用于结构刚度相关的凸优化设计问题。柔性机构以最大化驱动端的位移为设计目标,属于典型的非凸优化问题,难以直接应用该方法开展相应的设计。针对于此,通过定义一种由驱动位移和刚度特性(柔顺度)加权平均的优化目标函数,实现基于双向渐进结构优化法的柔性机构设计。该优化目标函数具有双重功效:①通过逐步(设计迭代步)衰减刚度特性的贡献,实现优化问题由刚度设计向驱动设计的动态演化,可应用双向渐进结构优化法开展机构的拓扑构型设计;②通过调节加权系数,实现对设计机构的驱动性能和刚度特性的灵活匹配调控,可有效抑制铰链的形成、防止应力集中引起的失效。典型算例的设计结果显示,提出的发展的演化式设计策略可实现稳健且高效的柔性机构设计。

This research proposes a topology optimization design strategy for compliant actuation mechanisms using the evolutionary structural optimization(ESO) method. Because of the discrete nature of design variables(0/1) and heuristic update mechanism,ESO-type methods have been mainly applied for convex optimization problems such as structural stiffness maximization design.Compliant mechanisms design with maximized actuated displacements as the design objective is a typical non-convex problem and ESO methods cannot be applied directly. In this regard, a weighted objective function is proposed by combining actuated displacement and structural stiffness(in terms of compliance). The merits of the newly defined objective function are twofold. First,by gradually(design iterations) damping the stiffness contribution, the design objective dynamically evolves from stiffness to actuation, and thus ESO methods can be applied. Second, a flexible control on actuation and stiffness performances can be achieved by adjusting the weights, which assists in avoiding the appearance of fragile hinges and prevents failure due to stress concentration.By means of a series of benchmark design tests, the proposed evolutionary design strategy has been shown robust and high-efficient in designing compliant actuation mechanisms.