Research On Mems Strapdown Inertial Navigation System Aided Pipeline Inspection And Location Techniques

Pipeline has been widely used in oil,gas,water and chemical substances transportation because of its efficiency,economy and reliability.Pipeline transportation safety is an important prerequisite to ensure the resources are transported to the destination safely.Pipeline exceeds the designed life-expectancy,natural disasters and human being caused damages are the main reasons that affect its safety transportation.Using the Pipeline Inspection Gauge(PIG)regularly to inspect the pipeline defects such as cracks and notches,to localize and maintenance these defects accurately could improve the pipeline operation safety rate to 99.99%.Inertial Navigation System(INS)aided pipeline inspection and location techniques play a key role in pipeline defects location,which is mainly because its priorities of high accuracy and reliability,immune to pipeline materials,provide accurate 3D pipeline coordinates information and so on.Limited by the diameter and surrounding environments of the inspected pipeline,the positioning precision of pipeline inspection and location system in the small diameter(D<30cm)pipeline or complex marine environments is far away from the requirements of engineering application.Therefore,the Micro-Electro-Mechanical System(MEMS)based Strapdown INS(SINS)aided pipeline inspection and location techniques are studied to realize the high-precision location in small diameter pipeline.Meanwhile,the related research results could be utilized in the study and application of pipeline inspection and location techniques in complex marine environments.The SINS aided pipeline inspection and location system is introduced comprehensively in this research at first.It includes the strapdown inertial navigation technique of pipeline inspection and location system.In addition,the pipeline inspection and location related strapdown inertial navigation aided techniques are also introduced with details.These introductions would provide a good beginning for the depth research of this work.Due to the error parameters of low-cost MEMS Inertial Measurement Unit(IMU)are vulnerable to temperature and other environmental factors,a Novel Artificial Fish Swarm Algorithm(NAFSA)based MEMS IMU error parameters infield identification technique is proposed.NAFSA enhanced the feasibility of AFSA in IMU error parameters identification by improving its execution speed and precision when it compared with the Optimal AFSA(OAFSA).In addition,the IMU error parameters identification accuracy implemented by NAFSA is similar to the conventional high-precision and expensive turntable,and it reduces the cost during IMU error parameters identification process.Hence the proposed method canbe used to optimize the low-cost MEMS IMU error parameters accurately infield before it conducts the pipeline surveying mission and to ensure the completeness of this mission.The PIG spiral motion is dominated by the conventional travelling motion and rotation motion along the pipeline longitudinal direction,which would affect the positioning precision of SINS aided pipeline inspection and location system.Generally,the tangential resistances of PIG are different when it rotating in various transported substances,so its rolling rates and directions are also different.This study starts from analyzing the error propagation characteristics of gyroscope biases and scale factor errors,accelerometer biases and scale factor errors of PIG carried IMU and deriving the positioning precision of SINS aided pipeline inspection and location system when PIG exhibiting the rolling motion.Consequently,the corresponding experiments are designed to verify the positioning accuracy of SINS aided pipeline inspection and location system in different PIG rolling rates and directions.Moreover,the study results could provide theoretical and practical guidelines for designing and choosing the IMU when SINS aided pipeline inspection and location system is used in different transportation pipelines.Pipeline Junction(PJ),such as girth weld ring,flange and bend pipeline,is adopted to connect two straight pipelines,and the PIG azimuth and pitch are invariant in each straight pipelines.The azimuth error of low-cost MEMS SINS based PIG location system presents a divergent property in small diameter pipeline,which would induce large positioning error in long-term pipeline inspection mission.Two types of PJ detection methods are studied in this research,namely Complex Continuous Wavelet Transform(CCWT)and Fast Orthogonal Search(FOS).The inspected pipeline is divided into the pipeline junction components and the straight pipeline components by analyzing MEMS surveying data by these two methods respectively.The PJ detection result could provide azimuth and pitch errors correction for MEMS SINS aided pipeline inspection and location system in straight pipeline,and hence to improve the positioning accuracy of long-term pipeline inspection mission in small diameter pipeline.Finally,a MEMS IMU based SINS/AGM/Odometer/PJ pipeline inspection and location system is proposed based on the PJ detection result.This system adds continuous azimuth and pitch errors correction in straight pipeline segment to reduce the positioning error that caused by the accumulated PIG azimuth error.However,the conventional SINS aided pipeline inspection and location system only used continuous 3D velocity error and discrete 3D position error correction to improve its positioning precision.The verification experiments demonstrated that the pipeline defects positioning precision of the MEMS SINS aidedpipeline inspection and location system could improve about 50% after adding the azimuth and pitch errors correction.