Study of dynamic load identification under unknown initial conditions

Abstract

Dynamic load identification belongs to the second inverse problem of structural dynamics, i.e. the inversion of the load history in the real state by collecting the measured data of structural vibration. Some traditional dynamic load identification methods do not consider the initial conditions, i.e. the initial conditions of the structure are assumed to be zero, however, the structure is not always at rest during the process of collecting the vibration response, which leads to a large error between the identified force and the actual force using traditional methods. Since the measurement of initial conditions is very difficult, in order to solve the influence brought by the initial conditions to the dynamic load identification process, this paper proposes a method based on sparse regularization to identify the load history under unknown initial conditions. Firstly, the unknown force is represented using basis functions, and the vibration response of the structure is divided into two parts: forced vibration caused by the force and free vibration under the initial conditions, and finally sparse regularization is used to solve the ill-conditioned equation. The experimental and simulation results also further verify the applicability and robustness of the method proposed in this paper in dealing with the load identification problem under unknown initial conditions.