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The work herein proposes the use of the data-driven Loewner-framework for reduced order modeling as applied to dynamic Finite Element Models (FEM) of thermally morphing structures. The Loewner-based modeling approach is computationally efficient and accurately constructs reduced models using analytical output data from a FEM. This paper details the two-step process proposed in the Loewner approach. First, a random vibration FEM simulation is used as the input for the development of a Single Input Single Output (SISO) data-based dynamic Loewner state space model. Second, an SVD-based truncation is used on the Loewner state space model, such that the minimal, dynamically representative, state space model is achieved. For this second part, varying levels of reduction are generated and compared. The work herein can be extended to model generation using experimental measurements by replacing the FEM output data in the first step and following the same procedure. This method will be demonstrated on two thermally morphing structures, a rigidly fixed hexapod in multiple geometric configurations and a low mass anisotropic morphing boom. This paper is working to detail the method and identify the benefits of the reduced model methodology. [ABSTRACT FROM AUTHOR]

Abstract Conventionally, the dynamic modeling of H-type gantry stage(HGS) assumes that the stiffness of mid-beam is extremely high so that its deformation is ignorable. This assumption apparently simplifies the study, but unavoidably compromises the modeling precision as it is not consistent with the real working status especially at high frequency motion. Comparing with similar studies on moving mass problems, the beam vibration of HGS is excited not only by the moving mass and system acceleration but also by the non-synchronized motion of the two moving ends of mid-beam. Therefore, the objective of this paper is to propose an assumed mode method based on simplified mode shapes(AMM-SMS) by simultaneously considering the lateral flexibility and the motion of the ends of mid-beam. The proposed AMM-SMS adopts the mode shapes of a simplified system, which has the same geometry boundary condition(BC) with the investigated system, to discretize the nonlinear kinematic equations of the proposed system. This method improves the modeling precision with low complexity, and can be applied in different BCs of FHGS. The proposed method is verified by various comparisons with the finite element method. Based on the AMM-SMS, the first three natural frequencies and mode shapes are studied. The open-loop responses of the system are obtained to analyze the effects of different BCs, of the motion of end-effector and of the external exciting force on the vibratory behavior. [ABSTRACT FROM AUTHOR]

• A dual rotor experimental rig of an aero-engine is designed and manufactured. • Nonlinear dynamic model of the test rig is established based on finite element method. • Reduced-order model of dual rotor-bearing system is obtained by CMS method. • Local blade-casing rubbing fault feature is revealed by numerical simulation and experiments. In order to reveal the nonlinear vibration characteristics of an actual dual-rotor-aero-engine with blade-casing rubbing, a dual-rotor-bearing-coupling misalignment system with blade-casing rubbing are investigated based on numerical simulation and experimental measurement in this paper. A dual-rotor experimental rig is designed and manufactured, that is a simplified structure according a dual-rotor-aero-engine. The dynamic model of the dual- rotor-bearing system of the test rig is established based on the finite element method (FEM) taking into account the coupling misalignment, blade-casing rubbing and the nonlinearities of all of the supporting rolling element bearings. The component mode synthesis (CMS) method is applied to the model order reduction of the high-degrees of freedom (DOFs) dynamic model. The numerical and experimental nonlinear vibration responses of the dual-rotor system are compared with each other at different rotational speeds at different rotational speed ratios. The numerical results are in agreement with the experiment. These results reveal the nonlinear vibration characteristics of the dual-rotor-bearing-coupling misalignment system with local blade-casing rubbing fault. [ABSTRACT FROM AUTHOR]