Development of a knee joint assist suit with a velocity-based mechanical safety device (Frequency response analysis of the safety device and experiments)

Abstract

Safety is a crucial issue in rehabilitation assist suits. We have proposed and developed a rehabilitation assist suit equipped with a velocity-based mechanical safety device (VBMSD). The assist suit assists a patient's knee joint. The VBMSD switches off the assist suit's motor if it detects an unexpected high joint angular velocity. The VBMSD works even when the assist suit's computer breaks down, because it consists of only passive mechanical components without controllers, actuators, or batteries. However, the VBMSD may resonate with a walking cycle (0-1Hz) in a gait exercise because it has a bar, a rotary damper, and two tension springs, that is, it is a mass-spring-damper system. In this paper, we check whether the VBMSD resonates with the walking cycle by using the frequency response analysis of the VBMSD. Firstly, we review the assist suit equipped with the VBMSD. Secondly, we analyze the VBMSD and examine whether it resonates with the walking cycle. Finally, we present experimental results to verify the effectiveness of the VBMSD.

Keywords

• robot
• design
• mechanism
• rehabilitation assist suit
• mechanical safety device
• frequency response analysis