Stability and efficiency of underactuated bipedal walker that generates non-instantaneous double-limb support motion

It was clarified that limit cycle walkers with redundant free joints generate the measurable periods of double-limb support (DLS) through numerical simulations and experiments. This paper then conducts numerical analyses to examine the effects of non-instantaneous DLS motion on the gait properties such as stability and energy efficiency. First, we divide the gait cycle into the collision and the stance phases and numerically evaluate their stability in terms of the convergence rate. Second, we analyze the stability in more detail by dividing the stance phase into the periods of DLS and single-limb support. The simulation results show that the energy efficiency monotonically worsens with the increase of the ratio of the period of DLS to the gait cycle but the convergence rate improves. Furthermore, we discuss the similarities between robot walking and human walking based on the analysis results obtained.