The Study Of Error Detection In The Forming Process Of The Large Spatial Bending Steel Pipe Based On Laser Ranging Principle

As the outstanding representative of the structural building, the large spatial bending steel pipe is used widely in the steel construction and its irregular spatial curve profile fully reflects the perfect combination of the architecture and the nature. However, the study of the forming technology of the large spatial bending steel pipe is immature. The accumulative error generated from each process of the forming tends to exceed the standard requirements, which leads to the difficulty of closure with other steel parts in the construction site and require forcible correction. Thus the spatial alignment and the internal forces of the pipe are affected.The current error detection method in the forming process of large spatial bending steel pipe is limited to the artificial contact measurement. Its large-span space and difficulty for on-site detecting result in the poor detecting accuracy, low efficiency and consuming much time, which are not conductive to controlling error effectively. Combining the present error detection method of forming process of the pipe, the special non-contact measurement system is developed in this thesis. The detection of the control parameters and the accumulative error in the forming process of the pipe are achieved, which contributes to the solution of the quality control in the forming process of the large spatial bending steel pipe.The main results of the paper include the discussion of the error source in the forming process of the large spatial bending steel pipe. The influence of the accumulative error in multi-processes is analyzed and the proper control model is proposed. In this way, the closure precision requirements are guaranteed. Also, the development of the special non-contact measurement system is completed based on the laser ranging principle, which realizes the detection of the control parameters of the accumulative error of the large spatial bending steel pipe. Then the post-process of the points cloud data from measurement is discussed. Through importing the preprocessed points cloud data to the reverse engineering software Imageware the surface fitting and model rebuilding are completed and the target parameters are extracted so that the detection purpose is reached. Finally, the scanning path planned reasonably is proposed and the automatic scanning process is achieved. Thus the efficiency of the scanning measurement is upgraded. Combining with the example, the measuring process of the large spatial bending steel pipe is fully accomplished and the source and the influence of the main errors in the measurement are discussed, then the relevant control measures are proposed.