Abstract
This study is inspired by the passive walking mechanisms which show that stable walking can be realized simply. The passive walkers can only walk on shallow slopes because they use gravitational potential energy in order to recover the energy lost mainly thorough the swing-leg impacts with the ground. The walking speed decreases with the slope angle and it is almost impossible to walk on level ground. We propose a level-ground walking method for a biped walker based on passive walking mechanisms, however two actuators are added at the hip in order to walk on level ground. The torso is added to the biped walker and the torque required to hold the leaning torso is used to walk on level ground. A swing- leg control is introduced to modify the free pendulum motion of the swing-leg in order to avoid falling forward. Numerical simulations show that ankle stiffness helps the walker to walk more efficiently.
