| Description |
This research explores the potential for an "intelligent" orthotic shoe sole to negate, or minimize, longitudinal slip by momentarily increasing friction force. The conceptual device takes the form of a rubberized shoe sole containing pockets of air that can be released via valves controlled by a microprocessor. During a slip event, the valves would be opened and the bladders would be collapsed by the weight of the user, which modulates contact and friction forces. The goal is to increase friction forces in this process, by creating an impact force between the user and ground surface, with the potential to achieve stiction and stop slip. The research first explores how design of the shoe sole can best compensate for longitudinal slip. Lumped parameter models of the system are developed to model bladder behavior and airflow through the system, which are then applied to optimize a prototype design. A friction model specific for two sliding surfaces is developed using basic coulombic friction equations. Simulations and experiments indicated flow rate was a limiting factor using existing valves, but experiments without valves confirmed that impact forces and friction forces can be increased by the system. The impulse created during impact creates a large spike in normal force, which translates into a spike in coulombic friction force that can be mathematically shown to reduce slipping velocity. The spike also causes an increase in Coefficient of Friction (COF) with the shoe and ground surface that, with surface specific testing, can be used to shift the sliding foot from a potentially dangerous kinetic COF range to a more stable static COF. Results of kinematic modeling are presented as well as empirical testing and future work. |
