DYNAMIC BALANCE OF HUMANOID SYSTEMS IN REGULAR AND IRREGULAR GAITS: AN EXPANDED INTERPRETATION

Abstract

The development of humanoid robotics during the last decades has undoubtedly resulted in numerous successful realizations in this area. One of the most important tasks that have been in the research focus is bipedal walk, which, despite the progress that has been made, has still remained an intriguing research task. The problem is not only how to realize a sustainable walk in an unstructured environment, requiring on-line trajectory planning and changes of gait parameters (turning, stopping, acceleration and deceleration, switching from the walk on a flat ground to the walk on an inclined surface or staircases, etc.), but the gait realization that will allow some additional activities such as, e.g. manipulation tasks. A prerequisite for the fulfillment of such requirements is that the system is dynamically balanced. On the other hand, we are witnesses of the diverse realizations of locomotion systems, from those with human-like feet, aiming to mimic in full the human gait, passive walkers, which practically roll on specially profiled feet, to the footless locomotion systems. It is quite clear that any of these systems can realize a gait, but our present study shows that performances of such walking systems are essentially different. In this sense we consider the minimal conditions for the realization of a dynamically balanced gait, analyze some examples of irregular gaits, and indicate the conditions in which particular phases of such gates are dynamically balanced. We point out the fact that in the presence of disturbances the transition to a dynamically (or even statically) balanced mode of the gait may prevent the system from falling. Besides, it is shown that at the end of the single-support phase of a dynamically balanced gait it is possible to "allow" a temporary, preplanned beforehand, loss of the dynamic balance without jeopardizing the gait realization only if the system has been prepared in advance for such an event. Finally, the work points out the indispensability of the regular, fully dynamically balanced gait for the simultaneous realization of locomotion-manipulation activities, as well as for the walk in an unstructured environment.