Development and implementation of an automated micrometric bone distraction system based in a fuzzy logic controller for an Aybar-type external fixator.

Bone distraction is a widely applied orthopedic procedure based on Ilizarov's tension-stress principle, which requires high precision and accuracy to guarantee successful bone regeneration. In many low resource locations, the Aybar-type external fixator is the only viable treatment option due to its low cost and accessibility. However, its manual procedure introduces human error, reduces precision, and compromises treatment outcomes. To address this problem, this study develops and implements an automated micrometric distraction system for an Aybar-type fixator, aiming to provide a low cost yet highly accurate alternative, particularly focused on pediatric patients, for whom precision is critical to ensure proper callus formation and bone growth. Four control strategies were designed and evaluated: an ON-OFF controller, a Proportional-Integral (PI) controller, a Linear Quadratic Integrator (LQI), and a Fuzzy Logic Controller (FLC). The mechanical platform integrates a Direct Current (DC) motor, encoder, and worm gear with 1.25 mm pitch, while simulations and experimental tests were performed under two distraction regimens: 1 mm/day in four increments and 1 mm/day in sixty increments. Results indicate that the FLC achieves the best performance in coarse step elongation, while the LQI provides superior results in high-resolution protocols. These findings demonstrate that it is possible to enhance the precision and reproducibility of the Aybar external fixator through low cost automation. The proposed solution contributes to improving treatment quality for pediatric patients in contexts where advanced imported systems are unavailable, filling a critical gap between affordability and clinical efficacy.