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A three-wheeled vehicle for in-pipe monitoring tasks is described. The vehicle is basically composed of two hinged arms building what is hereafter referenced as a scissor structure. The arms are joined at one end. Another joint connects the middle points of the lower parts, called links. A wheel located at the pivot of the scissor structure is driven by an electric dc motor. Two other wheels located at the ends of the links (sphere bearings) are not actuated and can roll freely in any direction. Since the force of the arm mechanism pushing against the pipe wall is generated mechanically by an extension spring combined with levers, the vehicle rests in the pipe by pressing its wheels in the direction of maximum pipe cross section. The vehicle moves automatically by action of the driving wheel in the direction in which the pipe extends. The relation between the stretch force and the configuration of the vehicle is analyzed to optimize the lengths of the levers and the direction in which the levers should be attached for force generation. The geometric and kinematic conditions of the vehicle are investigated to make it move stably. Results of a simulation of locomotion proved the capability of self-adjustment of the vehicle to different pipe shapes and sizes. The resulting vehicle mechanism, called MOGRER, was built to carry a CCD video camera attached to its body for in-pipe monitoring tasks. Experimental results show that MOGRER can monitor while moving in an inclined pipe with a heavy angle, overcoming the effects of gravity and changes in pipe size and shape.
Okada et al. (Tue,) studied this question.