Stability and control of a frontal four-link biped system.

A conceptual model for studying the involvement of the central nervous system (CNS) in the performance of lateral swaying movements is described. The model is based on a four-link planar biped that approximates gross human locomotion in the frontal plane. The viscoelastic function of the musculoskeletal system provides a linear controller for the system. Such an intrinsic controller can effectively duplicate simple well-learned tasks in the absence of higher level CNS feedback. This hypothesis is supported by comparing the proposed controller with two neurophysiologically involved linear decoupling schemes. Reference trajectories for swaying commands are recorded from experiments conducted in the Gait Analysis Laboratory of the Ohio State University Hospitals. These reference trajectories are inputs to all three controllers. The viability of intrinsic feedback scheme in the execution of swaying tasks is demonstrated via comparison of responses from the three controllers.