Construction of central pattern generator for quadruped locomotion control

Central pattern generators (CPGs) inspired from neural system of animal are widely used for the control of locomotion in robots. Such systems present special characteristics like limit cycle behavior, synchronization, entrainment and to be modulated by external signals. However, one drawback of this kind of CPG is that most of the time these CPGs have to be tailored made for a specific application, and there are very few methodologies to modulate the shape of the rhythmic signals, in particular for online trajectory generation. In this paper, we illustrate a method for generating the rhythmic movement patterns with nonlinear dynamical systems. Using the phase angle of a canonical oscillator with limit cycle properties, we drive a perturbed dynamical system by means of embedding arbitrary smooth target signal, however, without losing the stability properties of the canonical system. The shape of target signal can be adjusted on line by internal parameters. The new kind of CPG is constructed by the coupling of oscillators with locked phase difference and synchronization. The outputs of perturbed dynamical system are used to control the walking of a quadruped robot with 12-DOF. The result of experiment shows the new kind of CPG is suitable for the control of multi-joint robot.