A dynamic bipedal walking method using coupled elastic actuation

The aim of this research is to find an actuated level ground walking method, which is analogous to the dynamics of a passive dynamic walker on a slope. We propose to take advantage of the coupled elastic to actuate legs. As a result, maintaining the character of passive dynamic and a simple control algorithm are achieved simultaneously. In our walking model, actuated bars are installed on each leg and connected with a linear spring at their ends. By properly swinging the bars forward and backward periodically, the spring is stretched to store potential energy at the walker's each stride. And after the heel strike the stored energy is transported to the whole system to compensate for the energy lost at the heel strike. By tuning three control parameters, namely the spring coefficient, the length and amplitude of the actuated bar, the walker exhibits stable periodical walking gait. While continuously changing these parameters, the gait of the walker also demonstrates period-doubling bifurcation and chaos. In some certain parameters, the gait can also evolves from chaos back to bifurcation. This gait evolution phenomenon has never been reported in the actuated walking robot before, it shows that the walker's dynamics is somewhat analogical to the passive dynamic walker. We also show this walker can walk over a wide range of speed, that have a reference value to build the actual robot.