The Research Of Dynamic Loading Identification In Time Domain Based On System Total Decoupling

With the development of engineering design and technology, the identification of dynamic load is becoming an urgent problem to be solved in engineering practice. The traditional dynamic load identification method can be divided into frequency domain method and time domain method. The former is earlier and the precision is higher, and the calculation method is more mature. The latter is developed in the middle of 1980s, which directly identify time course process of unknown source according to the response time course process of structure instead of the transformations between frequency domain and time domain, and it has potential in identifying all kinds of loads whatever it is steady or non-steady. So it has a very wide prospect in engineering application.At present,a load identification method in time domain transforms the differential equation of multi-degree of freedom system into a non-coupled system by using the modal coordinate transformation at the beginning of the model design, and then a specific inversion formula is established. Under the condition of the three matrices referred to the quadratic system, the thought that it uses the coordinate transformation to diagonalize the three matrices simultaneously can be realized only when the system is proportional damping or classical damping, which limits the application of algorithm. In the field of numerical algebra,quadratic system decoupling are researched usually by building the structure of Lancaster, and it has been proved that almost all the quadratic system could be decoupled.In the paper, we first used the quadratic system decoupling algorithm based on the spectral information to realize the diagonalization of three matrices, and obtained the corresponding decoupling transformations by utilizing the method on the basis of the Sylvester equation. Secondly, upon the decoupling problem which were involved in present load identification methods, we applied quadratic system decoupling of the Lancaster structure to system dynamics equation decoupling,then we used the decoupling transformations to propose a load identification mathematical model which was based on the total decoupling system by the mathematical theoretical derivation. Then, on the assumption of the step force and linear force in tiny time, we obtained the specific load identification formula by taking advantage of the precise step integration method and established a new load identification model. Finally, we calculated it and got the time course by structural dynamic response. On the one hand, it was verified by numerical experiments that the load identification accuracy of the model was higher than that of the load identification method based on modal method, on the other hand, the proposed model was suitable for the non-proportional damping system and it was the focus of the method.