Simulating prosthetic devices with human-inspired hybrid control

A method is proposed which enables testing of prosthetic devices in simulation. A hybrid model is used to represent human walking—the combination of continuous and discrete dynamics motivates the use of hybrid systems. A human walking experiment is analyzed and mathematical functions on the kinematics of the collected data are found which capture some of the fundamental behaviors associated with human walking. One model is considered in which these behaviors are fully tracked using feedback linearization; the intent of this is to simulate healthy human walking. Then, a second model is considered: this model is assumed to be a human with a transfemoral prosthesis; PD control is used on the prosthesis. All models considered demonstrate locally exponentially stable periodic orbits when simulated for four separate test subjects, or, in other words, the models exhibit stable walking even with a prosthetic lower extremity. The methods used in this paper are a stepping stone toward a process capable of rapidly prototyping potential prosthesis designs and controllers.