A Pressure-Amplifying Monopropellant Engine for Actuator-Localized Pneumatic Power

Despite its various potential uses, untethered pneumatics have little practical use due to the speed, power, and controllability limitations of power systems, and system-design restrictions (dead volume contained in pneumatic circuits and hardware needed to handle high actuator pressures). In this work, we present a compact monopropellant engine that localizes pressure generation to actuators. Our approach minimizes dead volume by eliminating pneumatic circuitry and allows high-pressure actuation from a low-pressure fuel source. We introduce the architecture, present a hardware implementation, and prove our pressure-amplification working principle experimentally. We also experimentally demonstrate fast response time (<30ms), high-pressure capability (>100kPa), high flow rate capacity 140 SLM/kg), and the ability to control the rate of gas output and volume of produced gas. Finally, we interface the engine with two distinct soft actuators to demonstrate its plug-and-play ease of use, operating at both high speeds and high pressures, and estimating a promising power output range (~5-25W/kg). With this design, we hope to move closer towards self-contained pneumatic muscles that interface with low-pressure embodied energy storage, which may increase the viability of pneumatic actuation for untethered robotic applications.