Robotic spring-mass walkers – potential and limitations

As spring-like leg behaviour in human running was observed in a number of studies [1] the spring loaded inverted pendulum (SLIP) model was initially proposed as a template model for running and hopping [2]. Based on the model behaviour a number of predictions were made concerning the ability to reproduce dynamics of walking gaits [3], stability measures and stabilisation strategies [4] as well as energetics of gait [5]. Compliant monoand bipedal robot hoppers and runners have been around since the the 1980ies [6] and there have been attempts to implement SLIP-behaviour in running robots. To the best of our knowledge there had been no bipedal robotic spring-mass walker so far. This study presents experiments made with a bipedal walking robot mimicking the SLIP-model gait and testing model predictions on CoM-motion and acting forces. The implementation of similar tests on the advanced biped ATRIAS is discussed.