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.

State estimation of transient response flow in pneumatic pipelines is important for system design and phenomenon analysis. The purpose of this study is to investigate a one-dimensional numerical method by using a high-order finite upwind difference scheme that can calculate the transient response in a straight circular tube with turbulent transitions. In order to calculate such a flow by using a one-dimensional numerical model, the source term needs to be represented accurately. We propose an appropriate representation of the source term in the form of a switch between laminar and turbulent models with unsteady losses, depending on the critical Reynolds number. To validate the model, transient response experiments were conducted in a single closed-end circular tube with an inner diameter of 28 mm and a length of 4 m, up to an initial pressure difference of 7 kPa, and the closed-end pressure was measured. Comparison with experimental data showed that the transient response flow including turbulent transition can be calculated accurately by considering the pipe wall roughness and setting the critical Reynolds number between 12000 and 14000.

A swirl gripper, which uses a vane rotated by an electric motor to form a swirling flow, is known to be more energy- efficient than the conventional pneumatic vortex gripper. However, the effect of its design parameters on the lifting force has not been fully investigated. In this study, the design parameters of the intake of the swirl gripper, such as the ratio of the inlet radius to the swirl chamber radius and the ratio of the distance from the center of the cup to the center of the intake, are investigated to clarify how they affect the lifting force. The working fluid was air, and the design parameters were varied to experimentally investigate the lifting force and pressure distribution for two different vane speeds. The experimental results suggested that the inlet flow rate increased as the diameter of the intake increased and its position became closer to the center of the swirl chamber, and the gap thickness for the same lifting force increased accordingly. In addition, it was found that there was an optimum intake diameter to obtain the maximum lifting force for the intake position.