Study Of Applying Strap Down Fiber Optic Gyro On The Deformation Measurement Of Structure

Since it is so important to detect the deformation of large structure to guarantee the performance and quality and assure the system safety, a kind of effective and feasible method is necessary. But because of the formidable natural environment, it is hard to put present methods into practice. For instance, the upstream slope deflection of dam and the deformation of dam body will affect the security of dam. The present measuring method must determine the reference points to detect corresponding measuring points. So it is hard fix the instruments underwater and to detect continuously. The same case happens to the deformation measurement of underwater pipeline, which is longer and deeper in water.To solve the above problems existing in detection approach, a new way to detect the structure deformation based on strap down Fiber Optic Gyro is presented in the paper. Fiber Optic Gyro (FOG) inertial system provides angular velocity and acceleration measurement of measurement body along three axes, based on the attitude matrix refreshed by outputs angular velocity to transform the acceleration from the body frame to the earth frame, finally through acceleration integral we can get the position of the measurement body in the space. FOG is popular in the navigation field for many advantages, such as wide dynamic range, high resolution and all solid components. In this article, we take advantage of the specialty of the FOG inertial system to apply it on deformation measurement of large structure, especially the three axes measurement of structure deformation.The basic principle of the new approach is described in this paper. Firstly, the measuring device assembled the FOG inertial system is driven along the curve to detect, such as the upstream slope or the tunnel. And then after data processing and analysis the moving trail of FOG inertial system can be obtained. At last, the shape and deflection of the curve can be measured. Comparing withthe different measuring result, the shape change, i.e., deformation is gotten. We bring forward the wavelet transform to eliminate the noises. Without more reference points and fixing place, the continuous and accurate measurement can be implemented regularly. At the end of this paper, some suggests of applying the strap-down FOG inertial system in the actual detects is given. Much work has been done in this paper:(1) Have analyze the principle of fiber optic gyro(FOG) and strap-down inertial system, and investigate the typical arithmetic of the attitude matrix.(2) Have settled a set of platform to do experiment, have programmed the data logging and processing software, have done experiment to analyze the properties of applying the FOG inertial system in the measurement.(3) Have processed and analyzed the experimental data, and according to the properties of no stationary and no normal distribution of bias drift of FOG, the wavelet transform is used to eliminate the noises.(4) Base on the properties of actual structure measurement; have summarized several rules to reduce error.