Discrete sliding mode control to stabilize running of a biped robot with compliant kneed legs

Abstract

This paper investigates performance of two event-based controllers applied to an underactuated biped robot to stabilize its running gait in presence of uncertainties. Mechanism of the biped robot includes four links leg, one point mass at the hip, point feet, and three motors parallel to rotational springs. So it has one degree of underactuation during stance phase and three degrees of underactuation during flight phase. A discrete sliding mode controller (DSMC) in comparison with a discrete linear-quadratic regulator (DLQR) is examined in order to stabilize the fixed point of the corresponding Poincare map. Using numerical simulations, it is concluded that DSMC has a better performance regarding basin of attraction and convergence speed compared to DLQR, especially in presence of disturbances.