Self-excitation Pneumatic Soft Actuator Inspired by Vocal Cords

Abstract Pneumatic actuators afford advantages such as flexibility, low weight, and explosion-proofness. However, increasing the number of pressure supply tubes and using solenoid valves in a multi-degree-of-freedom system may negate these advantages. Therefore, this study proposes a soft actuator that uses self-excited vibrations realized by using an airflow between two flexible plates to open and close a valve in a manner similar to vocal cords. This valve can be fabricated using simple and flexible materials, unlike those used in conventional self-excited vibration valves and robots, and it can expand the applications of pneumatically driven soft robots. A prototype actuator was constructed, and its operation was verified. Further, a model was developed to analyze the characteristics of the proposed actuator, and the results of simulations based on the analytical model and experiments with the prototype were compared. The simulation successfully predicted that a minimum flow rate is required for producing oscillations and that the plate thickness mainly affects the driving frequency. The results show that the proposed actuator can increase the degree of freedom of a pneumatic soft actuator without requiring the use of a valve.