Human leg adjustment in perturbed hopping

Robots can help to demonstrate and prove concepts on human locomotion such as concepts based on springlike leg behavior. Hopping is a fundamental requirement for running in two basic functions: bouncing and balancing. In addition, for robust hopping against perturbations, swinging the leg in flight/swing phase is observed. These three elements need to be integrated for stable/robust locomotion in bipeds. Unlike running [1] and walking [2], stable hopping cannot be achieved with a fixed angle of attack with respect to the ground. So, finding an appropriate leg direction during the flight phase is needed for stable hopping in place. In this study, different methods of leg adjustment during swing phase are compared both in simulation with SLIP (Spring Loaded Inverted Pendulum) model and in human experiment. Because of the lack of space and since we reported the simulation results previously [3], in this paper, it is just reported with a few sentences. Our presented method called VBLA (Velocity Based Leg Adjustment) shows better performance in modeling and is also closer to what humans do.