Decoupled kinematic control of terrestrial locomotion for an ePaddle-based reconfigurable amphibious robot

In this paper we present a decoupled control method based on kinematic models of an amphibious reconfigurable robot called ePaddle-based quadruped robot (eQuad). The locomotion mechanism of eQuad is a novel eccentric paddle mechanism (ePaddle) that can perform wheeled, legged and paddling actions in both terrestrial and aquatic environments. We first introduce five terrestrial and aquatic gaits. A duty factor of up to 1.0 can be achieved for the legged walking. Therefore, the proposed robot eQuad can walk with a unique gait by eliminating the swing phase of the legs, and it has a large stable margin because all its legs are in contact with ground during walking. Kinematic models of this robot suggest that with this unique gait the reconfigurable ePaddle mechanism has the potential to achieve both legged and wheeled locomotion with the aid of a simple controller. A decoupled controller adapted from the wheeled robot is then built to evaluate this idea. Finally, simulations are performed to verify our proposed decoupled control and gait sequence planning methods.