Proposal of method for assessment of anterior position of cane tip for fall prevention during walking by elderly people based on model with dynamic pair

Abstract

In order to assess anterior position of a cane tip for prevention of anterior fall during walking with a cane by the elderlies, this paper presents an investigation of three evaluation indices for determination of the cane tip’s position based on analysis model with dynamic pair. The dynamic pair expresses moveable and spring-damper characteristics between a human hand and a cane in consideration of hand grip weakness of the elderlies. A human body and a cane were modeled as a planar 4-link mechanism with the dynamic pair. Using this model, dynamic simulation was conducted. From the results, energy dissipation by damping effect of dynamic pair and magnitude of force applied to a human hand from a cane were proposed as the evaluation indices. In addition to this proposal, the simulation result also suggested that an ability to perform negative work (ANW) depending on a margin to a limit of torque and angular displacement at each joint of a human body played an important role in fall prevention. Experiment of walking with a cane by three subjects under three conditions concerning cane tip’s positions had been conducted. Through the experiment, joint torque and angular displacement of each joint for calculating values of the ANW, and the result of organoleptic evaluation for safety were obtained. Since magnitude of the values of the ANW mostly corresponded with a level of the organoleptic evaluation for a subject according to the cane tip’s position, effectiveness of the ANW as the evaluation index was validated in the subject and thus the ANW was proposed as another index. Finally, it was shown that by using the proposed indices, an optimal anterior position of a cane tip from a human toe could be determined according to physical characteristics of each of the elderlies.