A Three-Wheeled Self-Adjusting Vehicle in a Pipe, FERRET-1

Abstract

This paper describes three-wheeled vehicles that can move inside a pipe and adjust to the shape and size of the pipe. We propose two types of vehicles: tractive and nontractive. Both types are based on two hinged arms. The tractive vehicle has a driving wheel at a hinge and two sphere bearings at the ends of the arms. The driving wheel rotates about the axis perpendicular to the plane in which the two arms move. The wheel can freely move sideways. The sphere bearings can move in all directions like ball casters. Since the stretch force of the arm to the pipe wall is generated mechanically by pulleys and a spring, the vehicle rests in the pipe by pressing the two arms in opposite directions where the diameter is the biggest and it moves according to the action of the driving wheel. Three wheels of the nontractive vehicle are sphere bearings. We analyze the shape geometry of the pipe to obtain sta bility conditions under which the vehicle can move, and we consider friction and gravity bringing the vehicle to rest in the pipe. We also analyze the kinematics and dynamics of lo comotion, and we simulate locomotion of the vehicle in the plane in which the biggest diameter of the pipe is measured. The results of the simulation prove the self-adjustability of the vehicle to the shape and size of the pipe. Experimental results show that the vehicle can move and self-adjust in an inclined or twisted pipe with a deep angle.