Research On Dynamic Detection Method Of Track Line Condition Based On Strap-down Inertia Technology

In view of track line deformation, a non contact dynamic detection method based onstrap down inertia technology is investigated. This method applys strap down inertiatechnology: firstly, three accelerations on the axis of x, y, z are measured withaccelerometers; secondly, the attitude matrix is updated timely according to the angularvelocity information from gyroscopes, then the accelerations on three axis are transferedinto the geographic coordinate; finally, the position of objective in three dimensional spaceis obtained by integrating the transformed accelerations. The track line deformationcondition is gained from comparative analysis of the data which acquired in differentperiods but on the same reference point of measurement.The basic principle of strap down inertia technology, especially the algorithm ofupdating attitude matrix, is researched in depth. A strap down inertia system including thenertial measurement unit, wireless transmitting module and computer for detecting trackline condition is designed. A kind of digital integrator for detecting track line condition isdesigned with linear programming method, thus timely transformation from accelerationinformation to displacement information is realized. A high pass filter with low cut offfrequency is designed to overcome integral saturation phenomenon resulted by extremelylow frequency composition in digital integration;when the cut off frequency of filter is1/1024, it can remove low frequency components. The model for gyro drift error isestablished. With root mean square error and signal to noise ratio as evaluation parametersfor denoising effect, the wavelet parameters such as the wavelet base, waveletdecomposition level, threshold function and threshold estimation method are selected. Thisscheme effectively controls gyro drift error. At the same time, the software for detectingtrack line condition is programmed in Labview. This program consists of modules such as serial communication, data extraction, attitude matrix update, acceleration integral etc.The theory of applying strap down technology into detecting track line condition isproved to be corrected by practical application. Experiments show that the detection errorfor track line deformation is lower than5%, meeting the test requirements.