Comparative Analysis of ESAR Prosthetic Foot Designs Using Fiber Bragg Grating Sensors

Foot prostheses based on the Energy Storage and Return (ESAR) principle play a crucial role in improving gait dynamics for lower-limb amputees by optimizing energy efficiency and stability. However, despite advancements in prosthetic design, there is a lack of standardized methods to assess their mechanical and functional performance under real-world conditions. This study presents a novel approach for evaluating ESAR prostheses through the integration of Fiber Bragg Grating (FBG) sensors, enabling real-time monitoring of their mechanical behavior. Two different 3D-printed prosthetic foot designs, Prototype A (Prot. A) and Prototype B (Prot. B), were tested through mechanical tests following ISO 16955 standards. Tests were conducted in five different configurations to simulate different gait cycle phases. Strain distribution, stiffness variation, and energy return efficiency were the key performance parameters computed from the FBG sensors' strain measurements to compare the prosthetic feet. Moreover, data from dynamic mechanical tests were analyzed to access the variability in the prosthesis response under repeated dynamic loading. The results highlight how the integration of FBG sensors enables a detailed analysis of the prosthesis behavior, providing a more accurate method to compare different prosthesis designs. In particular, Prot. B showed a better balance in load distribution among structural components and an increase in heel stiffness, leading to an increase in energy efficiency of up to 15.5% under heel-strike conditions. These results confirm the potential of integrated FBG sensing technologies to assess the design and long-term performance of ESAR prostheses.