Enhancing adaptability with local reactive behaviors for hexapod walking robot via sensory feedback integrated central pattern generator

Abstract Local reactive behaviors endow animals the ability to exhibit agile and dexterous performance when traversing challenging terrains. This paper presents a novel locomotion control method based on the central pattern generator (CPG) concept for hexapod walking robot with local reactive behavior to cope with terrain irregularities. Firstly, a two-layered CPG-based single-leg controller is developed to generate the rhythmical movement for each leg executing tripod walking. The Van der Pol oscillator is employed on the high-layer to construct a coupled CPG network which serves as a phase regulator (PR) to produce rhythmic signals with prescribed phase relations amongst neurons. On the low-layer, an auxiliary linear converter (LC) transforms these signals into the desired joint trajectories. Subsequently, by embodying the proprioceptive sensing and external tactile information as the sensory feedback, two typical local reactive mechanisms including the elevator reflex and searching reflex are achieved by virtue of on-line adjusting the coupling scheme of the PR and the coefficients of the LC. A locomotion control framework for hexapod walking robot is further established by combining the single-leg controller with a finite state machine to allocate swing/stance commands for individual joints in dealing with terrain perturbations. The effectiveness of the proposed method has been verified through both virtual model simulation and experiments on a physical hexapod platform.