The Design and Modeling of a Liquid-propellant-powered Actuator for Energetically Autonomous Robots

This paper describes the design of a liquid-propellant-powered hot-gas actuator appropriate for human-scale powerautonomous robots. The motivation for this work is the development of a lightweight actuation system with system energy and power densities significantly greater than a DC motor and battery combination. The proposed design of a liquid-fueled actuator is presented, followed by a thermodynamic model of the system. A single-degree of freedom manipulator prototype is presented, and closed-loop tracking control of the liquid-fueled actuator is demonstrated. The measured energy density of the system is presented, and this experimental result is followed by a discussion that correlates the theoretical energy density predicted by the model with the measured energy density of the prototype. The analysis presented in the discussion section indicates that heat flow in the uninsulated experimental prototype constitutes a significant loss of energy, and that if properly insulated, the system should demonstrate an energy density approaching the theoretically predicted case.