Research On Fast Calibration For Coordinate Frame Of Numerical Localizer

It is the support and assistance of numerical locator device and accurate measurement apparatus so that accuracy of positioning could be guaranteed in the digital assembly of large aircraft parts. Numerical localizer is the primary positioning device in the system of aircraft digital assembly, and its locator accuracy is under the influence of several factors such as manufacture accuracy, kinematic accuracy of movement axis, integral rigidity and deformation, abrasion loss and calibration of coordinate frame. The calibration of coordinate frame plays a pivotal role in keeping accurate positioning and adjustment in the system of numerical positioning, and then affects the establishment of zero point and coordinate axis of one localizer in the coordinate system of assembly and cooperative precision of loacalizer group which is composed by several localizers.Removable localizer, one kind of localizer, is widely applied on the system of aircraft digital assembly in which there is a lot of interference during pulling station in or out and in that positioning location may be changed after part joint. Support-foots of localizer are jointed with the support-holes on the foundation based by screw joint when the localizer is removed back to its configuration location on the foundation base. Primary support-foots joint with corresponding support-holes firstly and then keep them screw tighten, then secondary support-joints can be screwed tighten. It could incur that real fitting position deviates from its theoretical fitting position so that it would bring deviation of position every time for that matching order and fastening degree is different, support-foots develop abrasion with support-holes, and that there may be some fragment and sundries remained in the hole. So a method of calibration should be developed for coordinate frame of localizer in order to obtain the accurate fitting position of localizer after removed every time.Therefor, the model of least squares that is based on theoretical and measured coordinate of marker points on the localizer should be established. And then a method of initial calibration for numerical localizer based on SVD was researched to solve the problem of fast calibration and unification for the coordinate frame of numerical localizer which can be moved conveniently in aircraft digital assembly system. When the localizer was removed, the running position of three kinematic axis on localizer is unknow, so it could betreated as a black-box so the deviation of kinematic axis should be introduced into the model of least squares as new calibration parameters. Two methods of optimization theory, SQP and damping Gauss-Newton iteration algorithm, are used to develop fast calibration for coordinate frame of localizer. Meanwhile, a method that is based on the thought that data can be revised to apply SVD was researched to complete the calibration based on value revised by three-point method.Finally, a experimental system composed of numerical localizer, laser tracker and program of calibration and error analyzation was developed to analyze the result and error of initial and fast calibration. The calibration methods of SVD, SQP and damping Gauss-Newton iteration algorithm can obtain high accuracy so that it could catch up with the positioning accuracy that is 0.05mm of localizer. Results showed that the calibration accuracy based on the method of SQP was higher than damping Gauss-Newton iteration algorithm, but that stability of the former was lower. The method of calibration based on value revised by three-point method has a merit of simple and easy to be applied. However, its error is high and it also would become higher when the deviation of kinematic axis was large.