Design and Control of a Free-Liquid-Piston Engine Compressor for Compact Robot Power

  • Nithin Kumar Vanderbilt University-School of Engineering
  • Mark Hofacker Vanderbilt University-School of Engineering
  • Eric Barth Vanderbilt University-School of Engineering


This paper presents the design and control of a free-liquid-piston engine compressor (FLPEC). The FLPEC produces low temperature, high-pressure air for use as a high energy density power supply for untethered, compact robots. Internal combustion with a propane-air mixture in the engine combustion chamber drives a high inertance, low mass liquid piston, which compresses air into an onboard reservoir. A real time logical controller is implemented in Matlab to regulate the timings of the air and fuel injection, spark, and exhaust valve and to compensate for misfires. Experimental pressure data is overlaid with the logical state of the injectors, spark plug, and exhaust valve to demonstrate the efficacy of the controller to account for cycle-to-cycle pressure variations in the combustion chamber.

Author Biographies

Nithin Kumar, Vanderbilt University-School of Engineering
Undergraduate Department of Mechanical Engineering
Mark Hofacker, Vanderbilt University-School of Engineering
PhD student Department of Mechanical Engineering
Eric Barth, Vanderbilt University-School of Engineering
Associate Professor Department of Mechanical Engineering
How to Cite
KUMAR, Nithin; HOFACKER, Mark; BARTH, Eric. Design and Control of a Free-Liquid-Piston Engine Compressor for Compact Robot Power. Vanderbilt Undergraduate Research Journal, [S.l.], v. 9, aug. 2013. ISSN 1555-788X. Available at: <>. Date accessed: 20 aug. 2019. doi:
Engineering and Natural Sciences