Bipedal Walking Based on Improved Spring Loaded Inverted Pendulum Model with Swing Leg (SLIP-SL)

This paper proposes a new template model called Spring Loaded Inverted Pendulum with Swing Legs (SLIP-SL) which improves on the popular SLIP model by adding passive swing leg dynamics. It is shown that SLIP-SL can be used to realize cyclic walking on multi-body bipedal systems using the proposed controller. SLIP model has some excellent properties for realizing a natural locomotion but it doesn’t have swing leg dynamics. Thus, SLIP requires additional methods to find a swing foot trajectory. This might cause difficulties since adding this dynamics later on might prove difficult to synchronize with SLIP model and even be considered as disturbance. In this paper, we present the dynamics of the SLIP-SL model which is passive and actuated only by springs. We show how to find proper spring parameters using Direct Collocation methods, which is key for realizing cyclic gait with SLIP-SL. Then, a feedback linearization controller is described that can track the trajectories obtained from the template model. Finally, we present numerical simulation results that illustrate a 5 link fully actuated bipedal robot model’s gait based on the the proposed SLIP-SL model.