Autonomous gait transition and galloping over unperceived obstacles of a quadruped robot with CPG modulated by vestibular feedback

The aim of this paper is to demonstrate, based on robot results, the effectiveness and practicability of vestibular feedback to central pattern generators (CPG) employed for the locomotion of quadruped robots. We build a new quadruped robot with mechanisms enabling walking to running and apply CPGs modulated by simple vestibular sensory feedback (a body tilt multiplied by a fixed gain). As a result, the robot safely locomotes at a variety of speeds by autonomously changing the gait from walking to trotting to galloping according to speed, despite the fact that the walk and gallop are not preprogrammed. In addition, as this paper's major contribution, we discover and demonstrate that the robot robustly runs with an emergent gallop while stepping on and over several types of unperceived obstacles, while being suddenly pulled forward, and while the physical balance is changed (i.e., a weight is put forward on the robot), by autonomously modifying the phase differences between the four legs from the basic gallop. To our knowledge, no other galloping robots have been reported that can adapt to an unperceived obstacle. We conclude that CPGs modulated by vestibular feedback is effective and practical as a gait generator for bio-inspired robots that are expected to have both the abilities of speed-based autonomous gait transition and autonomous robust running. (C) 2018 Elsevier B.V. All rights reserved.