In recent years, interest in in-pipe robot research has been steadily increasing. This phenomenon reflects the necessity and urgency of pipe inspection and rehabilitation as several pipe networks have become outdated around the globe. In-pipe robots can be divided into several groups in accordance with their locomotion principles, each with its own advantages and best suited application scope. Research on the screw drive in-pipe robot (SDIR) has had a rising trend due to the robot's simple driving mechanism design and numerous advantages. This study compares and analyzes the characteristics of various SDIRs from the aspects of mechanism design, driving principle, and motion and mechanical behaviors. Each SDIR has its own advantages and disadvantages depending on its design requirements and intended applications. A number of prototypes have been fabricated to verify their functionality and efficiency in inspection tasks. This study can provide an up-to-date reference for researchers to conduct further analysis on SDIRs.
Modern pipelines are often very long, having bends, branches and even variable diameters. Moving inside such pipelines to perform certain tasks has not been easy. There are various design concepts for traction inside a pipe. Screw drive is one of the concepts for in-pipe traction. This article presents a general description and analysis of available screw drives that have been used for in-pipe drives. The main focus is on the characteristic analysis of a novel variable radius screw drive mechanism that is proposed by the authors. The proposed mechanism is a two-stage planetary gearing system driven by a single motor. Major parameters of the mechanism, including helical angle, pitch and forward velocity, are derived. Furthermore, by conducting a force analysis, it is found that the proposed mechanism has much larger thrust force compared with that of the existing screw drive mechanism. A larger thrust force means that the proposed mechanism can carry more devices, thus perform more tasks inside pipes. To demonstrate the effectiveness of the proposed mechanism, thrust force measurement experiments have been conducted.
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