A Fluid Self-excited Oscillation Peculiar to Flat Ring Tube and its Application to Wearable Robots

A novel fluid power actuator called flat ring tube (FRT) is introduced in this paper. The mechanism of FRT is so simple that it only needs a urethane flat tube and some water pressure. No valves or switches are required. Applying constant water pressure results in periodic oscillation of the tube. The frequency is proportional to the flow rate of the water and inversely proportional to the tube length. By contacting the tube with a motor shaft, the motor rotates due to the periodic tube oscillation. Thus, we succeeded in rotating the motor without using any electricity. There are many possible applications with FRT, and we are developing a wearable massage device which makes people feel comfortable and improves their circulation of the blood.