Design and application of a wire-driven bidirectional telescopic mechanism for workspace expansion with a focus on shipbuilding tasks

Various products and patents have been established with regard to telescopic mechanisms over a long period of time. However, to the best of our knowledge, with reference to motional characteristics, few studies have been reported on a telescopic mechanism that is capable of bidirectional extension. Moreover, as we wish to point out here, such a kind of mechanism has received little attention due to the absence of practical applications. However, in the case of blast-cleaning and painting in double-hulled structures in shipbuilding, the bidirectional-extension mechanism seems to be a worthwhile subject for investigation since it will be of great help in the execution of suggested tasks for the entire transverse web floor with a range of 2-3 m. Since the self-traveling robotic platform is located on longitudinal stiffeners whose heights range from 400 to 800 mm, the manipulator to be installed on the robotic platform should have a bidirectional stroke to continuously approach the upper and lower sections of the transverse web floor. Further, with the rapid progress of the shipbuilding industry in South Korea, the importance of the bidirectional-extension mechanism in the automation of double-hulled structures has been increasingly recognized. Thus, for the design of a new mechanism, this paper describes a new type of telescopic mechanism that is capable of bidirectional strokes; the paper focuses on the mechanical design, analysis, manufacture and experimentation. Further, a customized pulley with a cylindrical-helix groove is designed to prevent the problem of overlapping steel wires since it leads to inaccurate position control with respect to the motor's rotation. In particular, experiments have been conducted in terms of the positional repeatability of the manufactured telescopic manipulator and the quality of blast-cleaning of an upper section of a transverse web floor in a double-hulled structure. Throughout the experiments, the manufactured mechanism has demonstrated an amazing bidirectional translating stroke that has ranged from -500 to +2000 mm in field testing. Further, the repeatability of the manufactured bidirectional manipulator with the suggested motor-pulley system has been clearly identified as ±0.84 mm in the descending direction and ±0.63 mm in the ascending direction.