Development and Validation of a Coupled Numerical Wrap Model for Pressure Distribution and Comfort Prediction in...

Exoskeletons have shown significant promise in rehabilitation by assisting patients with motor dysfunction. However, the design of wraps remains predominantly empirical, requiring extensive experimentation and prolonged timelines. This study aims to present a coupled numerical model of a lower leg wrap system, which is capable of predicting pressure distributions on the skin to provide mechanical indicators for inferring user comfort. The coupled lower leg wrap model integrated a reconstruction of a lower leg, derived from Magnetic Resonance Imaging (MRI) data, with a geometric model of the wrap. The application process of the wrap was simulated by applying prescribed displacement loads on multiple reference points (RP) of the wrap model. Pressure at 12 predetermined measurement points, distributed across three height levels (ankle, shank, and calf) along four anatomical directions on the subject's lower leg, was recorded using flexible pressure sensors. These experimental measurements were then compared with pressures predicted by the simulation to validate the numerical model. The simulation results demonstrated a strong correlation with the experimental pressure measurements, yielding a correlation coefficient of 0.88 (p < 0.05, the 95% Confidence Interval (CI): 0.61 - 0.97). Additionally, the strain and pressure distributions across various cross-sections also demonstrated a good correlation, with coefficients consistently more than 0.75 (p < 0.05). Notably, areas of high contact pressure were localized in areas with thin soft tissue, such as near the tibia and fibula, whereas areas characterized by thicker soft tissue exhibited lower or negligible pressures. In conclusion, this study successfully developed and validated a coupled numerical model of the lower leg wrap. This model provides deeper insights into the complex biomechanical interactions between wrap and lower leg. As a result, this validated framework provides quantitative mechanical indicators to infer the potential wear comfort of soft exosuit wraps and serves as a critical tool for guiding improvements in wrap design.