Modelling, design, and control of a robotic running foot for footwear testing with flexible actuator

Abstract

Footwear effects on the human feet have been widely studied to prevent injuries, improve sports performance, and human health through running exercise. Due to the dynamics of human joints and passive imitative feet, current automatic footwear testing systems reported in the literature are not very realistic, are limited in the imitation of running gaits, and still use the passive prosthetic foot. In addition, many studies on humanoid walking robots, orthotic ankles, and prosthetic foot for amputees only focus on the human ankle joint and walking gaits. In this project, the design and control of a realistic robotic running foot-leg testing of shoes are introduced. The designed robotic foot possesses a higher number of degrees of freedom compared to other robotic systems in the literature and have abilities to mimic accurately biomechanical patterns of the human foot as well as to replicate the plantar pressure distribution under the foot sole in running in the sagittal plane. Because of lightweight, flexibility, and ease of power transmission, the Bowden-cable or the tendonsheath mechanism (TSM) is used in this project for the actuation of the robotic joints. However, nonlinear friction and backlash hysteresis in such mechanisms vary with the change of cable configuration and they degrade the system performances. In this project, novel nonlinear and adaptive schemes for controlling the position of the ankle and metatarsophalangeal joints will also be presented. The control schemes consider the nonlinear and backlash hysteresis as uncertainties and are able to deal with unexpected disturbances due to the change of the cable configuration and the unknown environments. In addition, no knowledge of the model parameters is required. To validate the design systems and control approaches, simulations are also introduced. There are good agreements between the proposed approaches and simulation results.