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From hybrid dynamics to motor control of human locomotion

I present a brief overview of my research on dynamics and control of human locomotion, which spans from modeling human running and walking as hybrid dynamical systems to building active leg prostheses whose control is derived from these mechanical and neuromechanical locomotion models. The overview is divided into two parts. First, I introduce the spring-mass model: a simple mechanical model that describes human locomotion as a hybrid system switching between stance and swing phases. With this model, I show that human walking and running dynamics can be combined in one theoretical framework, and that a swing-phase policy can be derived, which time-encodes a nearly deadbeat control of steady-state locomotion. The power of time-encoded control I demonstrate with a robot leg that blindly crosses over large obstacles. In the second part, I show how extending the simple spring-mass model to more complex neuromechanical models of the human leg led to a controller of an active leg prosthesis that doesn't need to track predefined joint motions. Central in this part is a usually fatal, positive force feedback during stance, which generates and stabilizes spring-like leg behavior in the hybrid locomotion system. Based on this positive feedback control, I present a human biped model, which doesn't know predefined joint motions, but walks and almost runs, and manages random ground and stairs. Finally, I show a self-adaptive, active foot prosthesis that uses the human biped model's foot control.

Type of Seminar:
IfA Seminar
Hartmut Geyer
Sep 13, 2007   11am

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