| City gas is an important part of urban energy. With the widely use of clean energy and the accelerating pace of urbanization, city gas is developing in a golden period. However, as the main delivery vehicle of city gas pipelines are facing unprecedented challenges because of the increasing usage time and physical and chemical damages; therefore, it’s an urgent need to develop an intelligent robot for inspecting or maintaining gas pipeline network regularly.This paper gives a summary and analysis about present researches of pipeline robots home and abroad. Supporting-wheeled gas pipeline robots have the advantages of efficient movement, strong pipe-adaptability, good performance to carry instrumentation, etc. On that basis a gas pipeline robot was designed, used to carry a CCD camera and an electromagnetic ultrasonic testing equipment.The robot’s overall structure takes use of two driving modules and an intermediate steering module which are connected by 2 DOF steering knuckles between them. This frame effectively improves the load capacity and the ability of adapting to the pipe. Meanwhile, the dynamic characteristics of adjusting mechanism are analyzed by means of theoretical analysis and simulation. In addition, the robot’s other key mechanisms are designed. Multidisciplinary optimization theory is introduced for optimizing the robot’s wheel-frames. Firstly, key structural parameters of a typical wheel-frame are determined through DOE. Secondly, the spatial characteristics of the quality, the maximum equivalent stress and the first natural frequency are analyzed by second-order response surface model. Finally, lightweight design of the wheel-frame is completed through the combining Algorithm of multi-island genetic algorithm and sequential quadratic programming algorithm. This paper also includes the modular robot’s motion characteristics based on the theory of rigid body kinematics. Dynamic equations and theoretical ratio relationship of the robot’s wheels in confined pipe-space are established and will provide a reference for robot’s motion control.A robot prototype is manufactured based on the design optimization result. Series tests are accomplished including the speed test of wheels, adjustable range of adjusting mechanism, angle calibration of steering knuckle as well as traction test. The experimental data show that the robot achieves the desired design specifications. Compared with the first generation of robot, this new one has more complete functions. And its running in pipeline is more smoothly. |
