1088 IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, VOL. 57, NO. 3, MARCH 2010 Development and Fuzzy Control of a Pipe Inspection Robot Han-Pang Huang, Member, IEEE, Jiu-Lou Yan, and Teng-Hu Cheng Abstract—A new pipe inspection robot, called the National Taiwan University (NTU) Navigator, is described in this paper. The NTU Navigator is lightweight, modularly designed, and easily manipulated and repaired. The robot consists of camera, steering, driving, and functional mechanism modules. Each module has its own control circuit and functions. In addition, a new stretch mech- anism is designed and optimized in order to adapt the robot to pipes of various radii. The robot can be easily controlled using GUI on a PC. A stable and smooth fuzzy steering controller for operat- ing inside the pipes is constructed. The stability and performance of the fuzzy controller are shown and compared with both the conventional proportional–integral–derivative controller and the flatness-based controller. Simulations and experiments further justify the performance of the NTU Navigator. Index Terms—Fuzzy control, modular design, pipe inspection robot. I. I NTRODUCTION P IPELINE systems are widely used in such industries as the chemical industry and nuclear power plants. The applica- tions of pipeline systems include carbon dioxide transportation, gas transmission and distribution, oil transmission, cable encap- sulation, and water transmission. The fluid in the pipelines is often subject to high pressure, high temperature, and condition change [19]. Therefore, in-pipe inspection is important for the pipelines’ operation under safe conditions. We can detect the conditions inside the pipelines through sensing devices, such as cameras, infrared sensors, and ultrasonic sensors. However, the pipes are not always located above the ground or in safe places [8], [19]. Sometimes they are even located at places that cannot be easily accessed [20]. In addition, the geometry of the pipe may vary and hence make inspection difficult. Considering the requirements and limitations, a properly designed pipe inspection robot should possess [8], [13], [15] the following properties: 1) lightweight; 2) modular structure; 3) a mechanism with reusability and expandability; 4) a quality camera for image viewing and recording; 5) variable lights to illuminate the interiors of pipes; Manuscript received April 15, 2008; revised August 24, 2009. First published September 22, 2009; current version published February 10, 2010. This work was supported in part by the Industrial Development Bureau, Ministry of Economic Affairs of the R.O.C., under Grant 97-EC-17-A-04-S1-054. The authors are with the Department of Mechanical Engineering, National Taiwan University, Taipei 10617, Taiwan (e-mail: hanpang@ntu.edu.tw). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIE.2009.2031671 6) a reliable method for moving and steering in the pipes; 7) an ability to operate in geometrically changing pipes; 8) a fail-safe method of manual retrieval; 9) stable communications and power supply; 10) a user-friendly control console for the operators. We can monitor the corrosion and abrasion inside the pipe with a pipe inspection robot. Furthermore, if there are welding and coating devices on the robot, pipe repair and other tasks can be performed by the robot. Many pipe inspection robots have been developed in recent years, but the steering control has not been emphasized [10], [11], [17], [23]. Okada and Sanemori [21] proposed a three- wheeled vehicle for in-pipe monitoring tasks. The vehicle, called MOGRER, can capture the images inside the pipes but cannot change its direction freely. In [7], a robot with six wheeled driving arms could stretch the arms against the pipe wall. The wheel, mounted directly at the end of each driving arm, can be driven by a single dc servomotor to obtain driving force. A robot with flexible bristles was developed by Aoyagi [1]. It consists of two vibrating units with flexible blades. By using the flexible blades, the robot slides forward easily, and it is self-locked in the backward direction. It acts simply, like an inchworm, but its traveling speed is too slow. When executing in-pipe tasks, the ability to adapt to different pipe geometries is very important. In terms of mechanism design differences, different pipe inspection robots possess different kinds of flexible motion [3], [9], [13]. Public Ser- vice Electric and Gas Company and Visual Inspection Tech- nologies, Inc. developed several products for pipe inspection [10], [17]. They propose three types of locomotion in pipes: a tractor/trunk type, a propulsion type, and a clamp-and-pull type, for various applications. However, those robots cannot pass through the elbow part of the pipes. In addition, the steering motions of most of the aforementioned pipe inspection robots are controlled with joysticks by humans rather than by steering controllers. In this paper, the development of a lightweight intelligent pipe inspection robot, called National Taiwan University (NTU) Navigator, is described. Its mechanism is optimally designed to comply with various pipes. Moreover, a fuzzy steering con- troller is constructed for the robot in order to achieve smooth steering motions. The performance of the fuzzy controller is compared with the proportional-integral-derivative (PID) controller and the flatness-based controller [22]. Simulations and experiments are conducted to justify the performance of NTU Navigator. 0278-0046/$26.00 © 2010 IEEE