Design, Optimization and Fabrication of a Sensorized-Insole using Taguchi Method

The human foot plays a vital role during locomotion, being the primary point of contact with the environment. Detecting foot-related issues early is crucial for injury prevention and well-being. Assessing foot irregularities requires measuring parameters like pressure, center of pressure, and force. The Ferdowsi University of Mashhad Center of Advanced Rehabilitation and Robotics (FUM-CARE) developed an insole with eight Force-Sensing Resistor (FSR) sensors to address these needs. The FUM insole optimized sensor placement to accurately detect the standard gait pattern. Experiments, following the Taguchi methodology, were conducted on the insole, considering three cost functions to determine two sensor arrangements. The cost functions attempted to follow the various aspects of the vertical ground reaction force, vGRF, of a gait cycle. The two sensor arrangements aimed to mimic different aspects of the vertical ground reaction force (vGRF) during a gait cycle. The first arrangement attempted to track magnitudes of valleys and peaks of a standard vGRF diagram, with the first, third, and seventh factors as key influencers. The second configuration, targeting precise vGRF replication, was influenced primarily by the first, third, and sixth factors. Remarkably, the first sensor placement had a 2.4% error at detection of peaks and valleys magnitude. The second arrangement exhibited a 97% cross-correlation with the standard vGRF diagram, confirming its alignment. Additionally, the FUM Insole’s construction employed a lamination method, which offered resistance to surface scratches and shear forces. This strategic approach significantly enhanced sensor durability for prolonged functionality.