Study On The Structural Input Identification Of The Nonlinear System

As the important part of health monitoring, force identification is widely concerned by the scholars. In many practical engineering, the external force in unknown. So the correct estimation of the external force directly determines the accuracy of the system identification. On the other hand, the systems are nonlinear subject to normal load, using linear analysis to the nonlinear numerical model inevitably introduces errors. Therefore, the structural input force identification of the nonlinear system is studied.The typical nonlinear properties are studied in this paper. First, this paper introduces a method to transform the nonlinear system to be an equivalent linear system. The dynamic responses of the equivalent linear system are studied. Secondly, the paper investigates two kinds of material nonlinear systems: the stiffness is nonlinearly related to the displacement and the stress is in a nonlinear relation with the strain. Examples are used to verify the accuracy and precision. A tunnel model is established. The affection of nonlinear soil to the tunnel is studied.The paper also introduces a method of force identification based on finite element model updating. In the state space domain, the moving force is transformed to the Chebyshev orthogonal polynomial. The force identification is solved by the identification of Chebyshev orthogonal coefficients. Take the nonlinear systems to this method, complete the indentification under the nonlinear condition.According to the practical structure of nonlinear characteristics, the external force indentification under the nonlinear condition is studied. This method avoids the errors from the linear simulation, provides a new way for the engineering structural system identification.