The High Inertance Free Piston Engine Compressor—Part I: Dynamic Modeling

Abstract

Free piston engine compressors have recently been investigated for the purpose of providing a high pressure air supply for untethered, pneumatically actuated robotic systems. Given that free piston engine performance is highly dependent on the dynamic characteristics of the piston, this paper presents the idea of incorporating a liquid piston whose geometry can be manipulated to achieve the desired piston dynamics while maintaining the compactness and light weight necessary for applications in the power output range of 100 W. An inertance-based dynamic model of the liquid piston is developed and validated experimentally. The piston model is incorporated into a complete system dynamic model of a proposed high inertance free liquid piston compressor (HIFLPC). Critical model parameters for individual components and subsystems of a proposed HIFLPC prototype are experimentally characterized. Simulation results for the proposed prototype are shown and discussed.