Enhancing Operability of Glove-Type Power-Assist Systems: Descent-Assist Mechanism based on Human Centered Design

Abstract

Power assist devices can reduce the physical burden on factory workers; however, conventional control methods often induce hand pain and unstable operation during lowering tasks. Guided by human centered design (HCD), we adopted a design policy that does not require fine grip force modulation from operators during the most demanding phase. To this end, we developed and integrated a descent-assist switch (DAS) into the glove type interface of a traction type power-assist device (TPAD), enabling explicit switching of assistive behavior during lowering to improve operability and reduce physical/mental workload. We conducted comparative experiments with and without the DAS during lowering. Objective physical burden was assessed via lumbar joint torque, focusing on the peak value (maximum mechanical stress) and the time integral (sustained load). Subjective operability and perceived workload were measured using a Semantic Differential (SD) questionnaire, and factor analysis identified three latent dimensions: Sense of Security, Operability, and Fatigue. With the DAS, both the peak and time integral of lumbar joint torque during lowering were reduced relative to the no DAS condition, indicating lower physical burden. Questionnaire outcomes likewise showed higher ratings across Sense of Security, Operability, and Fatigue. Collectively, these findings demonstrate that the descent-assist switch reduces user burden and improves operability of the TPAD during lowering tasks.

Keywords: Human centered design, Power-assist device, Manual material handling, Glove type gripping interface, Workload reduction

DOI: 10.54941/ahfe1007255