Energy scattering of hybrid FE-SEA model with nonlinear joints

Nonlinearity in structures causes energy scattering between different frequency ranges. This paper proposes a new hybrid FE-SEA formulation to analyse complex structures with nonlinear deterministic components. The formulation is derived in two stages. First the governing equation for deterministic components in time domain is transformed to frequency domain using the method of harmonic balance and the Galerkin method. Equivalent stiffness method is then applied in frequency domain to linearise the nonlinear terms. The second process is regarded to the derivation of the hybrid model. Based on a proposed nonlinear energy transfer model and the linearisation in the first stage, the linearised hybrid FE-SEA governing equation is derived, and the iterative procedure is given. For validation purpose, nonlinear Lagrange–Rayleigh–Ritz method plus Monte Carlo simulation is used as the benchmark model. Two case studies are applied for validation and investigation of the coupling loss factor (CLF). The coupling between subsystems at different frequencies can be reflected by the CLF. Good agreements between the benchmark model and proposed hybrid model can be observed

A hybrid meshless–statistical energy analysis method for complex structure vibration analysis

AbstractA new hybrid deterministic–statistical energy analysis (SEA) formulation is presented by introducing a meshless method for modeling the deterministic components. Moving least square Ritz (MLSR) meshless method is applied, in which MLS is used to build the discrete model and the Ritz method allows to obtain variational formulation of the deterministic components of the governing equations. Such governing equations can be formulated via boundary conditions by penalty method and Lagrange multipliers. The hybrid model by penalty method keeps a similar formulation with the framework of the finite element SEA, while the model by the latter increases the size of the dynamic stiffness matrix and the expanded components are determined by the constraints. For validation purpose, three case studies are provided, including beam–coupled plates and plate–coupled plates built-up structure. The results by the hybrid MLSR-SEA model are compared with those by FE-SEA and Monte Carlo simulation. Good agreements of responses between the methods demonstrate the reliability of the MLSR-SEA formulation.</jats:p

ArticleGust Alleviation by Active–Passive Combined Control of the Flight Platform and Antenna Array for a Flying Wing SensorCraft

SensorCraft is an intelligence, surveillance, and reconnaissance (ISR) system that integrates unmanned flight platforms and airborne antenna arrays. Under gust loads, the high–aspect–ratio, light–wing structure of SensorCraft has considerable bending and torsion deformation, affecting the flight performance of unmanned flight platforms and leading to the loss of antenna arrays’ electromagnetic performance. Taking SensorCraft as the background, a wing conformal antenna array was designed, an aircraft model with a passive wingtip device was established, a control law was developed by the LQG/LTR method, and a gust alleviation active–passive combined control method of a “LQG/LTR active controller + passive wingtip device” was proposed. By constructing an unsteady aerodynamic reduced–order model (ROM) based on the Volterra series and a conformal array pattern fast method based on the modal form, the effectiveness of the gust alleviation active–passive combined control method on the aircraft platform and antenna array was analyzed. The results show that structural deformation of the wing conformal antenna leads to changes in the main lobe gain, beam direction, and sidelobe level. The active–passive gust alleviation method has obvious advantages. Compared with the LQG/LTR active gust alleviation method, the peak value of wingtip displacement is reduced by 15.6%, and the peak value of the gain loss is reduced by 0.72 dB, which is conducive to better performance of the airborne conformal antenna array