Study of Dynamic Walk Control of a Biped Robot on Rugged Terrain – Derivation and Application of the Linear Inverted Pendulum Mode –
Shuuji Kajita and Kazuo Tani
Robotics Department Mechanical Engineering Laboratory, Namiki 1-2, Tsukuba, Ibaraki, 305 Japan
This paper introduces a control method for biped walking on rugged terrain. We assume a biped robot which has a mass body and massless legs, and which is restricted to move in a vertical plane. We apply constrain control to the body of the robot so that it moves on a particular straight line and rotates at a constant angular velocity. As the result of such control, the dynamics of the center of mass of the body becomes completely linear. We also notice that the dynamics of the body does not depend on the slope of the line on which the center of mass of the body is constrained. We call such motion of the ideal model “Linear Inverted pendulum Mode”. The limitation of the condition under which this method works is also discussed. After these consideration, we have developed the control scheme of the biped walking on rugged terrain. Under the control based on the linear inverted pendulum mode, walking on a particular rugged terrain is shown to be equivalent to walking on a level surface. Finally, it is shown that by using ankle torque, our method becomes robust and can be applied to a real biped robot with mass legs. This is ascertained by simulation.