Hydrogen-absorbing alloy-based metal-hydride actuation for application in rehabilitative systems

BACKGROUND: A lightweight rehabilitation assisting system is required to help the aged and disabled with daily life activities, thereby improving the quality of their lives. OBJECTIVE: This paper discusses the development of a metal-hydride (MH) actuator, with excellent heat transfer performance, for application in a rehabilitative system incorporating an MH module. METHODS: The operating mechanism of MH actuators requires that the mechanical power of the pneumatic actuator only be generated via heat transfer through a Peltier element and the absorption/desorption of a hydrogen-contained MH module. To achieve this aim, a 3D model was first designed for two MH modules, and a thermal analysis was carried out according to the type of contact with the Peltier elements to fabricate an MH module with improved heat transfer performance. LabVIEW (National Instruments) was used for automatic temperature control of the Peltier element in the MH actuator driving experiment. Zr_0:9TI_0:1Cr_0:6Fe_1:4, which yields a pressure-composition-temperature (PCT) curve of appropriate pressure and temperature ranges for a rehabilitative system, was selected as the hydrogen-absorbing alloy. RESULTS: In addition, the temperature conditions of the MH actuator driving experiment were restricted by two temperature control ranges (30-40°C/30-50°C) of the Peltier element. Within these Peltier element temperature ranges of 30-40°C and 30-50°C, results showed that the MH actuator was driven in the ranges of 2-3 atm and 2.5-3.5 atm, respectively. CONCLUSIONS: These findings indicate that the MH actuator proposed in this paper can be utilized to drive a rehabilitative system for elbow and knee joint exoskeletons.