Adaptive walking with compliant ankle joints based on ROS

Pneumat-BT had circular feet based on the foot design of passive dynamic walkers. This design has disadvantages to realize humanoid robot that can not only walk but also various locomotion. In this study, we have replaced the circular feet with flat feet and investigated the control to stabilize its walking by adjusting ankle stiffness. In order to search a fine parameter of ankle stiffness, we¸ considered Roll-Over Shape(ROS) as an indicator of walking behavior. ROS is defined as a shape of center of pressure (COP) of stance foot from a shank-based coordinate system while walking. There is interesting literature that reports ROS is invariant while human walking even when walking condition is varied. In this study, we have investigated experimentally the relationship between an ankle stiffness, a ROS, and a stability of the walking robot. As a result, We found the suitable stiffness of the ankle joint of the biped robot. This study is reported in [narioka2009].