Novel mechanisms and simple locomotion strategies for an in-pipe robot that can inspect various pipe types Dongwoo Lee 1 , Jungwan Park, Dongjun Hyun 2 , GyungHwan Yook, Hyun-seok Yang ⁎ Department of Mechanical Engineering, Yonsei University, 262 Seongsanno, Seodaemun-ku, Seoul 120–749, Korea article info abstract Article history: Received 15 February 2011 Received in revised form 8 May 2012 Accepted 12 May 2012 Available online 19 June 2012 In this paper, we present a new design and simple locomotion strategies for a pipe inspection robot that can travel through various pipe configurations including vertical, elbow, and branch pipes. Two specific mechanisms in the robot are important for successful locomotion: the Adaptable Quad Arm Mechanism (AQAM) and the Swivel Hand Mechanism (SHM). The AQAM allows the robot to travel in reduced branch pipes and branch pipes with zero-radius of curvature, which are both common in real life but which pose a challenge to the previously developed in-pipe robots. The SHM enables the robot to change its orientation, and in particular, allows it to bypass bumps. Modeling and simulations were conducted to test the validity and practicality of the proposed design and strategies. The prototype was able to travel successfully through elbow and vertical pipes with a diameter of 305 mm and zero-radius of curvature reduced branch pipes of at least 305 mm × 259 mm to 305 mm × 290 mm or smaller. © 2012 Elsevier Ltd. All rights reserved. Keywords: In-pipe robot Zero-radius of curvature branch pipe Reduced branch pipe Adaptable Quad Arm Mechanism (AQAM) Swivel Hand Mechanism (SHM) 1. Introduction Pipelines are used to transport fluids such as water, oil, and gas, which are crucial to everyday life. However, repairing pipes has always been problematic due to geographical difficulties. In-pipe robots have thus received special attention as an effective solution to resolve this issue. In-pipe robots may be classified in several different ways. They may be categorized into wheel [1–12], track [13,14], inchworm [15,16], walking [17,18], and pig [19] types depending on their travelling mechanisms. They may also be categorized according to their structures: single-plane type [1,2], with arms 180° apart, or 3-plane [3–8] and 4-plane types [9], which have arms separated by 120° and 90°, respectively. While the 3-plane and the 4-plane types have a large traction force and exhibit stable performance in pipes, the single-plane type enjoys the advantages associated with its simple architecture. Another criterion for categorizing in- pipe robots is their method of adapting to a pipe's inner surface: passive [1–7,9,10] or active adaptation [8,13,14]. Many passively adaptable in-pipe robots adapt to a pipe's inner surface with springs only; no additional actuators are used. In-pipe robots that adapt to pipes actively, however, can travel more effectively than the robots with passive adaptation because the normal force between the robot and the pipe is controlled with additional actuators. Many of the developed in-pipe robots can traverse simple pipe configurations, such as straight pipes or pipes with no variation in diameter. Although some robots can travel through branched and elbow pipes, travelling in branched pipes is still regarded as a challenge in the field of in-pipe robotics. Even these robots that are designed to travel through branched pipes have difficulty in Mechanism and Machine Theory 56 (2012) 52–68 ⁎ Corresponding author at: School of Engineering, Yonsei University 50 Yonsei-ro, Seodaemun-gu, Seoul 120–749, Korea. Tel.: + 82 2 2123 2824. E-mail addresses: roboticsbylee@gmail.com (D. Lee), avarta99@yonsei.ac.kr (J. Park), dongjunn@kaeri.re.kr (D. Hyun), bcuzilovu@yonsei.ac.kr (G. Yook), hsyang@yonsei.ac.kr (H. Yang). 1 Dong Woo Lee was previously based in the Department of Mechanical Engineering, Yonsei University. He is now based in the School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA. 2 Dongjun Hyun was previously based in the Department of Mechanical Engineering, Yonsei University. He is now based in Decontamination & Decommissioning Reasrch Division, Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon, Korea. 0094-114X/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.mechmachtheory.2012.05.004 Contents lists available at SciVerse ScienceDirect Mechanism and Machine Theory journal homepage: www.elsevier.com/locate/mechmt