Synchronizing Virtual Constraints and Preview Controller: a Walking Pattern Generator for the Humanoid Robot COMAN In this paper we propose a novel hybrid walking pattern generator which combines results from the virtual constraints and the preview control theories for bipedal locomotion. This choice is motivated by findings in biomechanics that show how the dynamic motion of the human walk is mainly generated by the sagittal component of the stepping. Thus, we choose the conservative preview control to generate the lateral motion while we pick a more dynamical framework such as the virtual constraints for the sagittal motion. We investigate how the timedependent preview control and the timeindependent virtual constraints approach can be integrated together in a humanoid locomotion and finally we show promising results on COMAN, the new humanoid robot from Istituto Italiano di Tecnologia.

A programmable central pattern generator with bounded output Abstract   Despite extensive studies on cyclic tasks in robotics, definitive solutions for the problem of trajectory generation for periodic motions have not been achieved so far. In this paper, we present an approach for online trajectory generation from a library of desired periodic trajectories. The proposed approach consists of a Central Pattern Generator (CPG) architecture ensuring entrainment of any periodic trajectory, smooth motion modulation and observing position and velocity limits of the robot. The proposed CPG is composed of a synchronized network of novel bounded output oscillatory systems. Every oscillatory system is a threedimensional dynamical system encoding a onedimensional periodic function as a stable limit cycle. We also use the state transformation method to bound the oscillatorxe2x80x99s output and its first time derivative. Finally, we present a synchronization technique to construct a synchronized network of the proposed oscillators for generating multi dimensional periodic functions. Using Lyapunov based arguments, we prove that the proposed CPG ensures stability, convergence, and synchronization of the desired trajectory. The soundness of the proposed oscillator and the resulting CPG are validated both in simulations and experiments on the humanoid robot iCub.