Concerted Control Framework for Gait Generation Across Models of Varying Complexity

Human rhythmic motor patterns require proper coordination of all the degrees of freedom (DoF) that contribute to the output motor task. Walking, for instance, is a biomechanically complex motor pattern with many moving parts. In human walking, coordination of the stance (axial leg function), swing (rotational leg function), and balance (posture control) — which are known as locomotor subfunctions (LSF) - is pivotal to generating an efficient gait. Despite plenty of empirical studies on human walking behavior, the coordination processes that regulate human locomotion are still not well-understood. In this regard, this work aims to contribute to understanding more about coordination in human locomotion. This work hypothesizes that coordination between LSFs during a gait stems from a correlated signal distributed among different DoFs, analogous to the beats of an internal metronome that brings harmony to different DoFs for accomplishing a specific task. It is hypothesized that if all the contributing DoFs to a motor task have access to the same sensory signal, they can be implicitly synchronized. From a control engineering perspective, the idea is to consider one common global sensory information to orchestrate all contributors of the motion task in an outer-loop feedback circuitry, along with local feedback from each contributor. This control methodology - termed concerted control hereinafter - does not dictate desired trajectories to different DoFs; instead, it uses universal feedback to enable task-specific synchronization among DoFs. Furthermore, some levels of robustness to external perturbations might be expected due to the information from the peripheral sensors (i.e., global and local feedback) that continuously modulate the patterns during locomotion.