Walking control for a compass-like biped robot under variable gravity based on passive dynamic walking

Recently, biped robots are flourished all over the world. Japan, as a leading country of biped robots, plans to send them into the moon. The project is greatly magnificent, but there are lots of problems to operate biped robots on lunar surface. One of the biggest problems is the difference of gravity between the moon and the earth. Therefore, it is necessary to develop control methods concerning the reduced gravity. This paper proposes a novel control method to generate gait under variable gravity. Previous study shows a method to generate gait based on passive dynamic walking. Proposed method expands the previous study and enables to control robots' step length and velocity on any slope angle under variable gravity. The concept of the proposed method is to generate gait based on natural relativities of passive dynamic walking: the step length depends on the slope angle and the velocity depends on the gravity. To generate control inputs, we derive the passive dynamic walking that corresponds to the desired gait in terms of step length and velocity. Then we apply this referential passive dynamic walking to previous method and we obtain control inputs. With proposed method, it is shown that simulation results under variable gravity conform to the desired gait.