Dynamic Simulation and Experimental Validation of a Single Stage Thermocompressor for a Pneumatic Ankle-Foot Orthosis

Abstract

The mechanical design, modeling, and partial experimental validation of a prototype Stirling thermocompressor is presented in this paper. The thermocompressor is intended to serve as a compact and quiet, untethered 50 W, pneumatic power supply for an ankle foot orthosis. The goal of high efficiency at the target power density is pursued through the use of novel heat exchangers and high operating temperature and frequency. The motion of the displacer piston is controlled utilizing a brushless DC motor driving a continuous linear reciprocating screw. This paper presents the experimental validation of the heat transfer and pressure dynamics portions of the thermocompressor, leaving the modeling and validation of mass transfer to future work.

System Dynamic Model and Design of a Stirling Pump

“…The rationale for the design of the proposed device result in large part from results and observations from a previous Stirling Thermocompressor device that was designed, fabricated, and experimentally tested by our research group [10]. The previous (generation 1) device was a multi-stage, true thermocompressor ( Fig.1).…”

“…A dynamic simulation of the multi-stage thermocompressor [10] showed that more than four compression stages would be needed to reach the target output pressure. With respect to the multi-stage architecture, the prospect of having at least four compression stages to reach a target output pressure of 80 psig (for pneumatics reservoir) becomes untenable in the face of the mechanical complexity encountered in our single stage prototype.…”