Research On Information Processing Technology Of Underground Pipeline Detector

Underground pipeline is an important lifeline to maintain the normal operation of the city.Regular inspection can prevent accidents.Due to the shielding effect of the environment,the conventional electromagnetic detection has many limitations.In this paper,an underground pipeline detector based on Inertial Measurement Unit(IMU)and laser is designed.In the process of the instrument moving in the pipeline,the IMU module is used to obtain the motion attitude,and the offset of the laser spot on the imaging screen is fused to obtain the spatial distribution of the underground pipeline.According to the device characteristics of the speedometer and gyroscope in the IMU module,error compensation models were established respectively to correct the measured data.The accelerometer fitted the regression equation to compensate the noise,the gyroscope smoothed the noise with Kalman filter,and the Allen variance analysis verified the effectiveness of the error correction.Then,the extended Kalman method and quaternion Picard approximation method were used to fuse IMU data,calculate the attitude Angle of the instrument probe under the motion state,and give the velocity curve under the navigation coordinate system.Design and realize the laser spot image processing module,realize the complete extraction of coordinates of calibration hole under different working conditions,and locate the laser spot.Firstly,the camera was calibrated and the pre-processed image was obtained by adaptive median filtering.Then,adaptive threshold segmentation is used to obtain binary image,detect and screen the contour of scaling hole,seed filling is used to obtain connected domain,and center of mass is extracted to establish coordinate system.Finally,the laser spot profile is fitted and located in the coordinate system to obtain the offset of the laser on the imaging screen.The results show that the spatial distribution of the pipeline given by the instrument is basically consistent with the actual situation.For the short pipe whose height change is not obvious and the position deviation of the measuring point is small,the error of the instrument is within the acceptable range.The z-axis data of the lowest point of the measured pipeline is-0.1582 m,the lowest value of the reconstructed pipeline is-0.1493 m,the highest point of the z-axis of the measured pipeline is 0.156 m,and the highest point of the z-axis of the reconstructed data is 0.160 m,which is roughly consistent,with an average error of 5.6%.