High efficient walking of compass-like biped robots with foot rotation

This paper investigates the high efficient walking problem of a planar compass-like biped robot with massless feet. The walking manner with the stance foot allowed to rotate about the toe, is considered. A latch attached to the hip is introduced to lock the hip joint, which works when the hip joint retracts to a desired angle, and spring devices are equipped at the ankle joints to reduce the inputs of the ankles. After modeling the walking robot as a hybrid system with multiple continuous state spaces, a high efficient walking gait limit cycle is found using the method of Poincare shooting with the objective of minimizing the dimensionless specific mechanical cost of transport. Then, an event-based feedback control law is proposed to stabilize the high efficient walking gait. The validity of our control strategies is illustrated by a series of numerical simulations.