Liu Chih-Hsing, Chen Yang, Yang Sy-Yeu
Department of Mechanical Engineering, National Cheng Kung University, Tainan, Taiwan.
Soft Robot. 2022 Oct;9(5):837-849. doi: 10.1089/soro.2020.0212. Epub 2021 Oct 7.
This study presents a multimaterial topology optimization method for design of multimaterial compliant mechanisms. Traditionally, the objective function in topology optimization for design of structures is to minimize the strain energy (SE). For synthesis of compliant mechanisms, the objective function is usually to maximize the mutual potential energy (MPE). To design an adaptive compliant gripper for grasping size-varied objects, a multicriteria objective function considering both the SE and MPE at two different output ports is proposed in this study. In addition, based on the fact that different infill densities in three-dimensional (3D) printing leads to prototypes with different equivalent mechanical properties, this article proposes that a multimaterial design can be approximated by varying the values of infill densities in different portions of a 3D-printed component, which enables the multimaterial designs to be prototyped using the general low-cost, single-material fused deposition modeling 3D printing machines. The proposed method is used to design and prototype a bi-material compliant finger which is 3D printed using a flexible thermoplastic elastomer with infill densities of 30% and 100%. The experimental results demonstrate that the bi-material finger is a better design in terms of reducing the driving force while increasing the output displacement at the fingertip comparing to the single-material finger design with the same volume and weight. Furthermore, a two-finger gripper with two identical multimaterial-like compliant fingers is prototyped and installed on a six-axis industrial robot. The experimental tests are performed to demonstrate the effectiveness of the presented design.
本研究提出了一种用于多材料柔顺机构设计的多材料拓扑优化方法。传统上，结构设计拓扑优化中的目标函数是使应变能（SE）最小化。对于柔顺机构的综合设计，目标函数通常是使互能（MPE）最大化。为了设计一种用于抓取尺寸变化物体的自适应柔顺夹具，本研究提出了一种在两个不同输出端口同时考虑SE和MPE的多准则目标函数。此外，基于三维（3D）打印中不同的填充密度会导致具有不同等效机械性能的原型这一事实，本文提出可以通过改变3D打印部件不同部分的填充密度值来近似多材料设计，这使得多材料设计能够使用普通的低成本单材料熔融沉积建模3D打印机制作原型。所提出的方法用于设计并制作一个双材料柔顺手指，该手指使用填充密度为30%和100%的柔性热塑性弹性体进行3D打印。实验结果表明，与具有相同体积和重量的单材料手指设计相比，双材料手指在降低驱动力的同时增加指尖输出位移方面是一种更好的设计。此外，制作了一个具有两个相同的类似多材料柔顺手指的双指夹具，并将其安装在六轴工业机器人上。通过实验测试来证明所提出设计的有效性。
