Design of a Free Piston Pneumatic Compressor as a Mobile Robot Power Supply

The design of a free piston compressor (FPC) intended as a pneumatic power supply for pneumatically actuated autonomous robots is presented in this paper. The FPC is a proposed device that utilizes combustion to compress air into a high-pressure supply tank by using the kinetic energy of a free piston. The device is configured such that the transduction from thermal energy to stored energy, in the form of compressed gas, is efficient relative to other small-scale portable power supply systems. This efficiency is achieved by matching the dynamic load of the compressor to the ideal adiabatic expansion of the hot gas combustion products. The device proposed exploits this fact by first converting thermal energy into kinetic energy of the free piston, and then compressing air during a separate compression phase. The proposed technology is intended to provide a compact pneumatic power supply source appropriate for human-scale robots. The design and implementation of the FPC is shown, and preliminary experimental results are presented and discussed with regard to efficiency and energetic characteristics of the device. Most significantly, the device is shown to operate nearly adiabatically.