Design of a Stirling Thermocompressor for a Pneumatically Actuated Ankle-Foot Orthosis

This paper presents the design, modeling, and simulated performance of a prototype Stirling thermocompressor. The thermocompressor is intended to be mounted on the back of a user’s lower leg and convert a hydrocarbon fuel source into 50 W of pneumatic power at 650 kPa to power an ankle foot orthosis. Consisting only of a displacer piston, the Stirling thermocompressor’s displacer piston motion is directly controlled by a brushless DC motor so that the frequency of operation can be tuned to output the maximum power. Simulation indicates that this operating frequency is influenced by the intended reservoir pressure and heat transfer properties of the thermocompressor.