A Flexible Mechanical System Using a Hydrostatic Skeleton : Comparison of Driving Forces and Avoidance of Stress Concentrations Based on Nonlinear Finite Element Analysis

Abstract

The purpose of this study is to develop a design method of a fl exible mechanical system using a hydrostatic skeleton driving mechanism. The system consists of two types of fl exible bags in order to separate the roles into a structural part and an actuator part. One is a constant pressure bag as a structural part, and the other is a pressure tunable bag as an actuator part. There are remarkable advantages of using this system as listed below: i) Because of the fl exibility, the system can be applied safely to various kinds of workspaces where living beings and mechanical systems work together. ii) Because of using two types of bags, driving effi ciency of the system is higher than that of other fl exible systems using only one type of bag. The theoretical design method of the system is required to realize these advantages. In order to realize the design method, it is important to calculate the structural strength of the structural part and driving force generated by the actuator part. In this paper, strength evaluation of the structural part is performed by nonlinear FEA. From the comparison between the analytical result and measurement results, defl ection of the structural part is obtained. On the other hand, the driving force that is generated by the actuator part is also analyzed. Based on the analytical results, an empirical equation about the driving force is induced. The validity of the empirical equation is confi rmed by the comparison between measurement values and the values of the empirical equation. These results will contribute to an optimum design of the proposed fl exible mechanical system.