UPO: A Chair That Lifts Hips While Standing Up Using the Four-Link Mechanism

Abstract

Objective: The objective of the study is to develop a portable assistance device tohelp elderly users reduce strain on the knee and leg muscle while the elderly arestanding up. Background: The pose of standing up from a chair is a basic movement, but theelderly often have difficulty standing up due to their weak muscles. We focus ondesigning a solution that helps the elderly reduce physical problems and supportthem standing up. Method: This study consists of three parts. Part I explores the way to reduce therefrain of leg muscle while standing up from a chair. In the process of structuraldevelopment, we found that the moment is minimized when user pushes down thearmrests due to a decrease in the force acting on the center of mass. In part II, auser test of 20 participants was carried out to rank the order of comfort of twostimuli: the chair with fixed armrests and the chair with the four-link mechanism thatwe created-in three different ways; (1) to stand up without touching armrests, (2) tostand up by pushing down on fixed armrests, and (3) to stand up by pushing downon armrests and being supported by the mechanism. To examine the statisticallysignificant differences among the rank means, a Friedman test was conducted. Inpart Ⅲ, we analyze the results of the user test and interview feedbacks, focusingon establishing a design strategy from UPO and visualizing it in 1:1 scale. Results: In part I, we decided to develop the four-link mechanism. The bottom islifted up as the link rises. In part II, based on the rank data, we empirically foundthat UPO was assessed as the most comfortable during the stimuli. The thigh angleis smaller and the bottom of UPO is separated from a seat. In part III, after assessingthe results and feedbacks, we created a visualization strategy for UPO: light, friendly,and novel. Conclusion: The portable and non-mechanical UPO comprises a four-link systemthat lifts the user's hips while standing. It can help users avoid knee and leg musclestrain. Its universal design considers the elderly’s difficulties. Application: In a future study, combining light and durable material in UPO isexpected to increase its usability. And this study is an opportunity to design varioustypes of standing assistance devices.