Most pneumatic actuators used in robotics are controlled by valves that contain moving parts (e.g., spool or rotor) and electronics to change the direction or pressure of the air flow. Thus, the dynamic bandwidth and robustness of the system are limited by these elements. This article presents an oscillation-based pneumatic actuation method to remove the moving parts and electronics from the valve. The obtained bistable load-switched (LoS) oscillator utilizes two output attachment walls to generate the Coanda effect and internal flow field to control the pressure in different output channels. The bistable LoS oscillator is implemented on a soft fish and runner, achieving locomotion speed up to 1.68 and 1.97 BL/s (body length per second), respectively, which are faster than existing counterparts. Furthermore, a single-output LoS oscillator is demonstrated by slightly modifying the bistable one. It enables the development of a soft runner with higher load capacity, as well as a relief valve used for pressure regulation in soft robotic grippers. The presented actuation methods can be potentially extended to a variety of situations that require compact size, light weight, high dynamics, and robustness.
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