Limit cycle running based on flat-footed passive dynamic walking with mechanical impedance at ankles

To realize energy-efficient running of flat-footed biped robots, we propose novel running based on flat-footed passive dynamic walking with mechanical impedance at ankles. In recent years, ZMP-based running is popular as one of the running of humanoid robots. However, ZMP-based locomotion of the biped robots are not energy-efficient, and they require complicated trajectory planning and feedback control. Flat-footed passive dynamic walkers with mechanical impedance at ankles have been proposed as a biped robot achieving energy-efficient walking. Since they achieve energy-efficient walking without any control, we are interested in locomotion based on this passive walking. Therefore, we expect that flat-footed biped robots achieve energy-efficient running by taking advantage of the dynamics of the passive dynamic walker. In this paper, we show that the proposed method for a flat-footed biped robot achieves energy-efficient and high-speed limit cycle running.