Due to the diminished central pivot function in the elderly caused by venous motion, incidents such as dizziness and falls resulting from postural hypotension may occur when they rise quickly from a seated position. This paper introduces an air-operated spring-based stand assist chair designed to alleviate this issue. By conducting experiments on human pace analysis, the knee joint stress and torque during the standing process are obtained using statistical data from a simplified human body model, combined with principles of ergonomics and theoretical mechanics. These findings inform the design and parameters of the assistive chair. The actuating mechanism of the chair primarily consists of two air-operated springs and four roller wheels. Motion analysis of the actuating mechanism, taking into account motion constraints and the slight velocity variation of the air-operated springs during the standing process, demonstrates that the mechanism provides assistive torque that aligns with the knee joint torque, effectively aiding the elderly in standing up.

Recommended citation: Shi, C. and B. Lin (2007). Design of air-operated spring-based stand assist chair tracking knee joint torque for the elderly. Virtual and Physical Prototyping 2(3), 173-179.