Updating of Finite Element Models for Controlled Multibody Flexible Systems Through Modal Analysis

Abstract

Model updating is widely used for the estimation of the correct parameters of finite element models. Indeed, model accuracy should be as high as possible to synthesize controllers and observers, as well as for fault detection. Model updating based on experimental measurements is hence necessary to ensure model correctness.

A procedure tailored for updating dynamic models of flexible-link multibody systems (FLMSs) modelled through ordinary differential equations is proposed in this paper. The aim is to correct mass, stiffness matrices for modeling accurately the main vibrational modes in the frequency range of interest. Once consistency between the model coordinates and the modal data is obtained through a suitable transformation, model updating will be solved an optimization problem that also accounts for bounds on the feasible values. The method exploits model linearization, since it allows for modal analysis.

The paper also discusses some issues in performing experimental analysis in the presence of FLMSs that are not in an asymptotically stable equilibrium configuration. First of all, it is proposed, and also validated experimentally, the use of balancing springs. Then, it is discussed theoretically and numerically the use of active control to set the mechanism in an asymptotically stable equilibrium configuration, by tackling the issues of spillover due to the controller.