Journal of Advanced Mechanical Design, Systems, and Manufacturing (Oct 2020)
Development of a new compact and light velocity-based mechanical safety device for a rehabilitation assist suit
Abstract
Safety is an important requirement in rehabilitation assist suits. We have developed a velocity-based mechanical safety device (VBMSD) for an assist suit to aid in the flexion and extension of a patient’s knee joint. The VBMSD is attached to the assist suit. The VBMSD stops the suit’s motor when the angular velocity of the knee joint matches or exceeds a preset threshold level. This level is called the “detection velocity level (DVL)” and it is adjustable based on the specification of each patient’s gait training. Since the VBMSD is composed only of passive mechanical elements such as a rotary damper, it works even when the suit’s computer has stopped working. In view that portability is equally important as safety in wearable assist devices, the size and the weight of the VBMSD must be reduced for practical use. This paper presents the design and development of a new compact and light VBMSD. First, we describe the problems in the previous VBMSD. Second, we present the requirements and design specifications in the new VBMSD. The requirements and design specifications in the new VBMSD’s size are determined by considering International Organization for Standardization (ISO) 13482 and Advanced Industrial Science and Technology (AIST) human body dimensions data. Third, we propose the structure and the mechanism of the new VBMSD. Fourth, we explain the design process of the new VBMSD. In the design process, the frequency response and the transient response of the new VBMSD are also considered. Fifth, experimental results to check whether the new VBMSD achieves the necessary function are presented. Lastly, the possibility of installing the new VBMSD to an ankle joint assist suit and a wrist joint assist suit is discussed using AIST human body dimensions data, etc.
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