| Pipeline transportation is the vein of the economy, and the safety of the pipeline is vital to economic development. Periodic testing and maintenance of the pipeline safety is the main method to prevent major accidents and ensure pipeline safety. Inner inspection is an internationally accepted method, pipeline geographic coordinate measurement based on inner inspection can provide the specific location of the pipeline, complete the test information of the pipeline, which has great importance to pipeline’s testing. To realize the technology, this paper study some key technical problems, it performs the following work and receives relevant conclusions:After the detailed analysis on the feasibility of various positioning methods at the inner inspected condition, it applies the SINS technique to the pipeline’s geographic measurement, and it realizes the whole pipeline geographic coordinate measurement in a closed environment. It selects the MEMS devices as the IMU according to the measurement conditions. It establishes the error model after the analysis on the error source of the IMU’s output signal. Dynamic signal error is much larger than the static signal, and its standard deviation is9times more than the static signal’s. Study the signal preprocessing algorithm to solve the dynamic signal noise problem. It utilizes the five points three times smoothing algorithm to remove high-frequency dynamic signal error, and the threshold method to remove impulse noise dynamic signal. Experimental results show that through the preprocessing algorithm the standard deviation of the dynamic signal is reduced to one-tenth of the original, and it does not affect one of the useful signal components.After analysis on the calculation principle of SINS algorithm, it utilizes the odometer speed correction kalman filtering estimation method to solve the algorithm’s calculated error accumulating problem. After analysis the algorithm of the kalman filtering, it utilizes the matrix factorization method to ensure the covariance matrix of non-negative qualitative, and finally solves the divergence problem caused by the iterative calculating. The paper designs the experimental platform simulated geographic coordinate measurement system. The experimental results show that the odometer correction kalman filtering method resolves the SINS error accumulated problem. In the case of using the lower precision inertial measurement devices and the measurement of the environment is relatively harsh, the measuring absolute error is5m every100meters distance of the pipeline. Paper design of the measurement system has a certain practicality. After analysis on the initial alignment principle of the inertial measurement unit, the paper utilizes the method that first process the coarse alignment then the fine alignment, it resolve the nonlinear problem caused by the too large alignment angle, as the fine alignment error angle is limited to a small range of angle; it utilizes the UPF to resolve the nonlinear model filtering problem in the fine alignment. The simulation results show that the alignment error angle of orientation can reach33second of arc through the method mentioned above. Alignment accuracy is higher than the UKF and the EKF, and the computation time is slightly longer than the two algorithms.The paper selects the before and after-two directions kalman smooth filtering termination point correction algorithm, that utilizes the offline features of the positioning calculation to resolve the calculated trajectory of the pipeline on the termination point deviating from the actual location problem. The algorithm smoothed estimates of all the measurement information, the actual termination point position is introduced into the positioning calculation. Experimental results show that the termination calculation point is coincident with the actual point after the algorithm. It improves positioning accuracy to a relative error of1.8%per100m, and the method has a certain practicality. |
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