Walking gait of a planar bipedal robot with four-bar knees

Abstract

The design of a knee joint is a key issue in robotics and biomechanics to increase the compatibility between prostheses and human movements and to improve the performances of the bipedal robot. We propose a novel design for the knee joint of a planar bipedal robot, based on a four-bar linkage. The advantage of this structure is to produce a translation of the Instantaneous Center of Rotation (ICR) of the knee joint like in the human case. We propose to study the sthenic criterion of a bipedal robot using four-bar knee joint during a walking gait. This walking gait is a succession of finite time double support phases, single support phases and impacts. During the double support phase, both feet rotate. This phase is ended by an impact on the ground of the toe of one foot, the other foot taking off. The single support phase is ended by an impact of the swing foot heel, the other foot keeping contact with the ground through its toe. A parametric optimization problem is presented for the determination of the parameters corresponding to the optimal cyclic walking gait. The main contribution of this paper is to show the influence of double support phases for cyclic stable walking gaits with this novel bipedal robot.