On New Detecting Method Of 3D Curve Of Trenchless Information Pipelines

Traditional on-site measurement for trenchless information pipeline made use of the electro-magnetic sensing method, the accuracy of which will be interfered by electro-magnetic noises or the depth of earth above pipelines. This dissertation investigates on the theoretical method of spaticl curve reconstruction from either the tangeat angle of the curve or the curvature of the curve. The new techniques developed include measuremen devices of pipeline tangent angle based on either an angular sensor or a PSD component, a curvature sensing device based on FBG sensors, and a mobile robot inside piplines. And furthermore, a prototype of inserted-type detecting system for trenchless information pipelines is developed. The detailes of chapters are as follows.In Chaper 1, the research goal of a new method for obtaining spatial curvature or tangent angle information of pipeline curves is proposed. Based on this methed, a detecting system for 3D information of trenchless pipeline is to be developed. To reach is goal, the research contents and key techniques are listed briefly.In Chaper 2, after analysis of geometrical dimension and shape of pipelines to be detected, the configuration design of the pipeline detecting system is conducted based on either curvature or tangent angle information of the pipeline. The system is composed of a probe to detect curvature or a probe to detect tangent angle, a traction subsystem to pull the sensing probe along the pipeline, and a control/visnalization subsystem, which collects the information detected by the probe and calculates a 3D curve from the data of discrete curvatures or discrete tangent angles.In Chapter 3, a new algorithm is proposed for 3D curve reconstruction based on curvatures of discrete points of the curve. The variation method and numerial integration are employed in the algorithm, which is verified to be feasible by an example of helix. Furthermore, another new algorithm is put forward for 3D curve fitting from the discrete data of tangent angles from a curve. The method begins with the coordinates of a given point (starting point), length of curve segment, and the tangent angle on the curve, and deduces the coordinates of the next point, using recurrence formulae to calculate all points on the curve. It is also verified by examples.Chapter 4 deals with the design of a FBG sensing system for curvature data. After analysing the principles of curvature detection for the central axis of a pipeline using FBG sensor, a relationship formulae is established between the curvature of the central axis of a pipeline and the modulated wave length of FBG. The characteristics of a flexible core material for sticking FBG on and the method of transmitting the curvature of a pipeline to the flexible core are proposed. Polyurethane is selected for the flexible core, annular holding stands with diameter adaption for transmiting curvature are designed. The whole Set-up to detect the curvature of the central axis of a pipeline is integrated with its components and experiments are conducted.Chapter 5 deals with the design of two apparatus to detect tangent angle of pipeline, one is based on an electronic compass and the other on a PSD component. With an centering mechanism of diameter adaptation, the electronic compass will be located along the central axis of a pipeline, thus the tangent angle on discrete points of a pipeline will be obtained. To overcome the disadvantage of magnetic noise effect on the electronic compass, laser alignment method is used on tangent angle measurement with the help of the PSD component. The relationship is established between the tangent angle of pipeline and position of laser spot on PSD. Two prototypes of detecting systems based on the above principles are constructed and tested for technological feasibility.In Chapter 6, the design of the experimental platform is accomplished. A traction robot is developed to pull the sensing apparatus inside the pipeline, which employes worm-planet gear train for driving and adapting to the diameter of pipe. A dead-reckoning module is also developed to record the distance the robot covered, which is quite useful in the reconstruction of the pipeline curve. Control sub-system is established using two-layer control architecture.Chapter 7 discusses the experiments of the detecting system of pipeline both in lab or on the field. Experimental data shows the system can do its job quite well, with less electro-magnetic noise interruption.Finally conclusions are given for the whole dissertation, and further research aspects are discussed.