Development of an Insole System for Real-time Capture of Ground Reaction Forces in Lower-limb Amputees

Current insole systems often require costly equipment and additionally exhibit large form factors and are often of limited in their range of activities that they can measure. These problems can be addressed if spatial resolution in the insole is sacrificed. In this study, a low-resolution smart insole system was designed and developed for the real-time determination of several gait parameters. Tekscan flexi-force sensors were selected to meet the required sensor properties: durability, sensitivity, precision and sensing-area. F-Scan system and PressureStat film were used to accurately position the sensors on the insole to capture the heel and metatarsals. Sensor data from the insole were acquired and wirelessly transmitted to a PC using an Arduino microcontroller with XBee radio. The insole was calibrated for pressure with a Kistler force plate system. Captured ground reaction forces were analyzed for symmetry in external work and gait phase transitions in unilateral lower-limb amputees on both anatomical and prosthetic feet in multiple ambulation tasks, including level-ground and ramp walking. The developed wireless instrumented insole system has the advantages of broadcasting real-time insole forces with minimal computational resources as well as being durable and portable.