Combustion-Cylinder Optimization for an Active Ankle-Foot Orthosis

Sarah M. Swanson


Working from a previously-synthesized design concept, this research focuses on the optimization of a spark-ignition, internal-combustion actuator, intended to provide direct actuation for ankle plantarflexion in an active ankle-foot orthosis (AAFO). Optimization of the cylinder design was focused on meeting pressure and force loading requirements, through the gas-power cycle. Both, the designable (dynamic design space) and non-designable (fixed) geometries were generated using SolidWorks®, and were then imported into solidThinking Inspire® for optimization. The fixed geometry was used for load applications, and to establish certain necessary design features. Dynamic design space was created around the fixed geometry, within which the software algorithm performed its morphological optimization process, dependent on the connections and setup specified. In order to establish the loads for the setup, it was necessary to correlate the gait cycle to the power cycle, and determine the pressure-volume relationship for the design. The desired result was a combustion-cylinder design optimized for the projected loading during the power cycle required to provide full gait assistance. Future work will include the thermal-management requirements in the cylinder optimization. These include, but are not limited to, external surface temperature, as mandated by the Food and Drug Administration (FDA), flame quenching considerations, and further material considerations.


AFO; Internal Combustion; Optimization

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