Hopping Gait Generation for a Biped Robot with Hill-Type Muscles

This work presents a novel gait generation method for biped hopping with point feet. The investigated biped model consists of a kneed massless leg and a trunk with two Hill-type muscles at the hip and knee joints. The dynamic equations of the system are derived using Lagrange method. Since the most important phase to stabilize bipedal running and hopping motion is stance phase, this paper deals only with the stance phase and develops a control law for the actuators to generate an arbitrary trajectory for hip of the underactuated biped robot. Without loss of generality, a forth order curve with properly chosen parameters has been used as the desired robot trajectory in stance phase. This curve has similarities to the Spring Loaded Inverted Pendulum gait, and can generate the desired initial and final position and velocity of the stance phase. Hill-type muscles are used as the actuators of our model, because being simple it includes fundamental elements that are necessary for biped running efficiency. The proposed control law calculates the needed actuators inputs and gets the robot to undergo the desired trajectory. The designed control law is verified in simulation. Keywords—biped hopping; gait generation; Hill-type muscle