Key Technology For Laser Target Used In Shield Attitude Measurement

In order to ensure tunnel quality, shield attitude must be measured to control thedeviation of shield and DTA(designed tunnel axis). Considering the harsh environment intunnel construction, a shield attitude measurement system based on laser target with lowcomplexity and high vibration resistance is implemented in this article.This system accomplishes attitude measurement by combining inclinometer withCCD. Pitch and horizontal angle measurement is converted to distance measurement oflaser spot. To inhibit dark areas within the spot, gray-scale morphological image filteringtechnique with an appropriate size of filter template is utilized. Then, an algorithm usinggray-scale threshold method to detect rough edge, followed by gradient threshold methodto obtain more accurate edge, is conducted to detect spot center. Experiment shows thatthis algorithm can achieve pixel level accuracy.On the basis of space geometry, shield attitude calculation algorithm is analyzed. Theangle between laser and the axis of laser target is firstly computed according to laser-spotcenter. Then, shield attitude is calculated by taking azimuth and pitch of the laser intoaccount. Finally, calibration and error compensation of this system is also discussed andattitude measurement error is analyzed.At last, experiments of this system are carried out. The results verify that this systemcan meet the requirements of the shield attitude measurement accuracy.