Controller Design for Automatic Diameter-Adjusting and Driving of a Wheel Type Pipe Inspection Robot

Abstract

Recently, various pipeline inspection robots have been researched. However, there are few control methods of the pipeline inspection robots (PIRS). Therefore, a few control methods of the pipeline inspection robot are needed. This thesis proposes a controller design for a wheeled type of pipe inspection robot to adjust its diameter atomically and drive inside the pipelines with diameters from 300 to 500 mm using fuzzy logic control. The developed pipeline inspection robot can be used to inspect the sea-water in pipelines. To do this task, the followings are done. Firstly, mechanical design of a wheel type pipe inspection robot is proposed. The proposed PIR consists of driving part and sensor part. The driving part is composed of two modules and universal joint: passive module and active module that produces pressing force and universal joint connecting them. The sensor part is composed of ultrasonic sensors, angle sensor and camera sensor. Ultrasonic sensors are used for detecting curvature of pipe line and wheel positions, whereas the camera sensor is used for detecting the inside of the pipeline obtaining its inner state data in real time. Both the active and passive modules consist of a body, 3 driving modules and 3 4-bar linkage that are spaced at an angle 120 each other. The 4-bar linkages in the active and passive modules are extended and shrunk by expansion DC motor and compression spring, respectively. Each driving module of the proposed PIR consists of driving wheel DC motor, motor case, double type wheel, and is connected to the 4-bar linkage. The body of the active module consists of front body, rear body, rotating thread shaft, gear motor and expansion DC motor, whereas the body of the passive module consists of front body, rear body, spring and shaft. Secondly, for system modeling of the active module, kinematic modeling of 4-bar linkage of the proposed PIR and dynamic modeling of the expansion DC motor to track the reference diameter are proposed. In addition, kinematic modelings of the proposed PIR are proposed and dynamic modelings of the driving DC motor for driving inside the pipelines are proposed. Thirdly, a driving algorithm for driving the proposed PIR in a curved pipelines and straight pipelines is proposed. This driving algorithm is used to design reference wheel velocities and reference PIR linear velocity by detecting curvatures of curved pipelines, straight pipelines and wheel position depending on the posture of the proposed PIR using 3 ultrasonic sensors for the curve pipeline and 2 ultrasonic sensors to the straight pipeline. Fourthly, a conventional proposed PI controller and a fuzzy logic controller based on the kinematic modeling of the 4-bar linkage and the dynamic modeling of expansion the DC motor are designed for the proposed PIR to track given reference diameters of pipelines with different diameters by making the tracking errors. Fifthly, based on the kinematic modeling and the dynamic modeling of the driving wheel DC motor of the PIR, a conventional PI controller and a fuzzy logic controller are designed to track the wheel reference velocities and the reference PIR linear velocity obtained from the proposed drive algorithm in order to drive well in the curved pipeline with different diameters. Sixthly, a control system using computer, ATmega8 microcontroller, RS232 communication channel, ultrasonic sensors, camera, and angle sensor is developed for the proposed PIR to track the reference diameter and reference wheel velocities and reference PIR linear velocity in order to move along the wall of the pipeline. Finally, the simulation and experimental results are show that the proposed fuzzy logic controllers make PIR track the reference diameter and drive with the reference wheel velocities and the reference PIR linear velocity inside a given pipeline better than the conventional PI controllers. To prove the effectiveness and the applicability of the designed driving algorithm and the proposed controllers during driving experimental results of the proposed PIR in the pipeline, detected images of the pipeline wall are obtained from camera sensor.