A Soft Aquatic Actuator for Unsteady Peak Power Amplification

A soft hydraulic actuator is presented which uses elastic energy storage for the purpose of pulsed-jet propulsion of soft unmanned underwater vehicles. The actuator consists of a flexible membrane that can be inflated using a micropump and whose elastic potential energy may be released on demand using a controllable valve, in a manner inspired by the swimming of squids and octopuses. It is shown that for equivalent initial elastic energy, the drop in peak thrust is linearly proportional to the decrease in nozzle cross section. Peak hydraulic power amplification of the soft actuator of approximately 75% is achieved with respect to that of the driving pump, confirming that passive elasticity can be exploited in aquatic propulsion to replicate the explosive motion skills of agile sea-dwelling creatures.