Abstract
In a home-based rehabilitation device, a soft mechanism that has a large moving area is attractive. An inexpensive pneumatic driving system using a low-cost control valve is also attractive because the valve is the most heavy and expensive device in the pneumatic driving system. The purpose of the study is to develop an inexpensive and compact pneumatic drive rehabilitation device with a three-dimensional large moving area. In this study, based on the concept that a tetrahedron is a minimum element required to construct a solid body, the tetrahedral-type soft actuator that includes six reinforced extension type flexible pneumatic actuators (EFPAs) and four connectors for vertices was proposed and tested. Each EFPA was set at the position of the side of the tetrahedral frame. Both ends of each EFPA were connected to the connectors in the vertices. The pneumatic driving system using on/off valves and an embedded controller was also proposed and tested. Consequently, it was observed that the tested actuator deformed to various tetrahedral shapes with various sizes by changing the pressure of the EFPA. In addition, a simple analytical model of the device was proposed to perform the tracking control of the top end of vertices. The tracking position control system using a novel pressure-control-type low-cost servo valve and an embedded controller with a D/A converter was also proposed and tested. The low-cost servo valve developed in our earlier study was used as a pressure control valve. Consequently, it was confirmed that the top end of the tested actuator could trace the desired position based on the simple model.
