Force adjustment of an active pipe inspection robot

This paper proposes an active pipe inspection robot with the wall-pressing force adjustment using DC motor. It is developed for long distance inspection of sea-water pipelines such as horizontal linear pipelines and slope linear pipelines with large variable diameters from 600mm to 800mm. Its mechanical design consists of two modules as driving module and control module. The driving module has three pantograph type links spaced in 120° with three caterpillar track wheels. This design makes it possible to realize the adaptation to pipe diameter and the adjustment of wall-pressing force. The control module consists of a micro controller, motor driver and sensor interface. An active pipe inspection robot is designed by 3D machine design program. To control the pipe inspection robot, firstly, the pipe inspection robot is considered as a mass-spring-damper system. The dynamic model of the system is obtained by process model identification method. Secondly, an observer is designed to estimate the unknown wall-pressing force to sustain the pipe inspection robot in pipeline. Thirdly, an algorithm of wall-pressing force generator is presented to find out an appropriate wall-pressing force, and the presented appropriate wall-pressing force is given as a reference value of wall-pressing force. Fourthly, PD controller is designed to make the estimated wall-pressing force track the reference wall-pressing force irrelatively to variable diameter of pipeline. Finally, the driving tests of the pipe inspection robot are performed in horizontal pipelines and slope pipelines of 30°. The test results are shown to prove the effectiveness of the developed pipe inspection robot.