Gait Pattern Design for a Modular Snake Robot Moving on a Straight Pipe with Varying Diameter

Abstract

Modular snake robots are highly redundant mechanisms with small cross-section, which can move in confined and complex real-world environments. Due to higher degrees of freedom and small modular structures, they have the flexibility to move on the planar surface as well as the rough, unstructured environment. Apart from ground locomotion, they can also Gait Pattern Design for a Modular Snake Robot Moving on a Straight Pipe with Varying Diameter in three dimensions i.e. pipe locomotion, tree climbing, stairs or ladder locomotion for surveillance or inspection tasks in hazardous or hard to reach environments. Along with benefits which come from hyper redundancy, it is also difficult to control and coordinate between joints of the robot. The interaction between the world and shape of the modular snake robot is also very complex and the structure is less reliable due to serial connection between joints. To achieve complex tasks in three dimensions, Gait Design is one of the well known and effective approaches for modular snake robot. The main contribution of this thesis is to design a gait for a modular snake robot to move on a varying diameter pipe. While moving on the outer pipe, a gait is designed based on a spiral curve along with shift control and rolling motion to effectively move from one pipe to another pipe with varying diameter, which can not be done by using helical rolling motion only. The desired joint angles for a modular snake robot are calculated based on curvature and torsion of the backbone curve, using Bellow’s model. The proposed idea is validated using the physical simulator Open Dynamics Engine (ODE) on a thirty joints modular snake robot.