Design and motion analysis of Compliant Omnidirectional Spherical Modular Snake Robot (COSMOS)

Control, state estimation and motion planning of highly articulated snake robots have been challenging tasks for researchers. As a result, formulating gaits for the modular structure, for motion on flat trajectories as well as overcoming obstacles is mathematically complicated. This paper presents a novel design of a Compliant Omni-directional snake robot (COSMOS) consisting of mechanically and software linked spherical robot modules. This design eliminates the problems of planar snake robots to handle versatile motions with complex gait analysis, by leveraging Omni-directional motion capabilities of spherical robots. The robot is also capable of climbing smooth obstacles by introducing compliant joints in the links interconnecting adjacent modules. This paper also presents the basic robot gaits and their motion analysis which clearly demonstrate the robot design advantages such as fast turn speed and simpler motion planning strategies. Experimental results that verify the effectiveness of this robot architecture and gaits that have been designed to traverse flat terrain are included. Also, the spring stiffness of the passive joints which provide the vertical compliance in the links joining the modules is calculated and simulation results for obstacle climbing are included.