PhD Thesis

Title: Walking control of biped robots / Contribution à la commande de robots marcheurs bipèdes

Advisor: Christine Chevallereau (DR CNRS)

Lab: LS2N, Ecole Centrale de Nantes

Defense: December, 2011.

Jury: Abba G, Alamir M, Aoustin Y, Bruneau O, Chevallereau C, Gelin R.

Abstract:

1. The objective of this thesis is to study the walking control of biped robots including imbalance walking phase. Thus we dedicated to the stability analysis of periodical walking with under-actuation. Firstly, a planar biped robot with point feet is studied. Some tools for stability analysis such as Poincaré return map, Zero Dynamics and Hybrid Zero Dynamics are discussed. Two control laws based on joint reference motion (common in robotics) are proposed and compared with a control law for tracking parameterized reference trajectory (free temporal evolution). Next a biped robot with feet moving in 3D is discussed. In view of the importance of ZMP (Zero Moment Point) for the walking stability, it is regulated to its desired values. Moreover, a feedback control of the orientation of the swing foot is used to ensure a proper landing. As a result, some controlled outputs have been defined, so the robot can be dealt with like an under-actuated system. The approaches developed previously are then taken to obtain a stable walking. In addition, a steering control law is proposed to control the walking direction of the robot to pass through a door and reach a destination with a mild curvature. Finally, the proposed controller is extended to a biped robot with arms and a foot rotation phase that describing the stance heel lifts from the ground and the stance foot rotates about the toe is included in the single support phase. The proposed control can be naturally extended to this imbalance phase due to the control of ZMP, and the simulation results validate it is effective to obtain stable walking.
2. The full thesis and the presentation slides are available below