Research On Deformation Reconstruction Method For Wing Integrated Conformal Antenna Beam Structure

High-aspect-ratio,light structure and conformal antenna are becoming the future development tendency of Unmanned Aerial Vehicle(UAV).The integration of wing and antenna can not only increase antenna area,but also reduce the influence of antenna installation on UAV aerodynamic performance.However,in the service process,the wing integrated antenna is deformed by the influence of environmental loads,such as self weight,aerodynamic loads.The results seriously affects the antenna pointing accuracy.Therefore,real-time shape sense of wing deformation and active electrical compensation become an effective ways to ensure the communication ability of conformal antenna.The existing photo-electricity measurement methods,such as photogrametry,position sensing device,are easy to be affected by the service environment,so it is difficult to accurately measure deformation of the conformal antenna.To solve this problem,a real-time measurement method based on inverse Finite Element Method(iFEM)is proposed to realize the shape sense of conformal antenna structure deformation,The specific research contents include the following five aspects:1.Analysis of the wing structure component and shape sensing method for the constant cross-section beam.Initially,the component of the wing structure is introduced,and the then shape sensing model is established for constant cross-section beam.It is a inverse problem that the deformed displacements are reconstructed using the measurement strains in engineering.Hence,the improper strain sensor placements can cause the ill-condition of the strain-displacement transformation matrix,which leads to the failure of displacement reconstruction.For this problem,a Multi-Objective Particle Swarm Optimization(MOPSO)model is proposed for strain sensor placements.In this optimal model,the accuracy and stability of the reconstruction displacements are used as the optimization objectives,and the multiple working conditions are considered.Finally,a circular beam is used as case to establish the optimization model,and the optimal results are applied for loading experiments.The experimental results shows that shape sensing model can accurately and stably reconstruct the deformation displacements.2.Shape sense method proposed for variable cross-section beam.The section size of the wing structure decreases gradually along the spanwise direction,which leads to the section mechanical parameters not to be constant,and the section strains appearing "negative order" or "discontinuity".Therefore,the wing deformation is divided into two parts:the deformation of continuously variable cross-section beam in the element and the deformation of multi-element stepped beam.For continuously variable section beam,the axial displacements and rotation functions are derived by linearizing the section area and stiffness.Because the original functions of the rotation functions don’t exist and can’t be expressed as the product of the shape functions and the nodal degree of freedoms,the inverse finite element method can’t be used to establish the shape sensing model.Therefore,this papaer proposed to use the NURBS functions as the shape functions to approximate and replace the rotation functions,and then the displacement shape functions are determined and the shape sensing model is established.For multi-element stepped beam,a unified description method for section strain field is proposed.Based on this method,the transformation relationship between surface strains and section strains is derived,and the corresponding interpolation shape functions are constructed.The experimental results of UAV wing and stepped cantilever beam demonstrate that the displacement reconstruction accuracies of the proposed variable section beam reconstruction method are significantly higher than that of the constant section beam shape sensing method.3.Shape sensing method presented for composite and laminates beam.The composite sandwich beam is composed of different materials along the thickness direction,so the section distortion deformation can’t be ignored under shear forces.In order to accurately describe the deformed displacement fields,the Timoshenko beam theory is used as a frameworks and the additional zigzag kinematic variable is introduced to correct the cross-section distortion deformation.Based on the derived constitutive relations,the orders of section strain functions and displacement functions are determined,and the calculation method for section strain of composite beam is proposed.The shape sensing model is established for multilayer composite beam.The simulation and experimental results of three-layer composite beam show that the proposed reconstruction method is more accurate than the homogeneous beam shape sense method.4.Shape sensing method developed for airfoil beam.When the airfoil profile is subjected to shear loads or torsion loads,the shear strains on the beam section don’t remain a constant distribution,but a function distribution,which makes the section strain calculation method derived from constant section beam be not suitable for airfoil profile.In order to solve this problem,a novel method for calculating the section strain is presented,where the product of the maximum shear strain on the cross section and the position variation function is proposed to describe the shear strain distribution,and then the relation among the section strains,the variational functions and the shear strains is established.Based on the relations,the transformation relationship between the section strains and the measured strains is deduced,and the shape sensing model of the airfoil beam is established.The solving process of variational functions and related parameters is explained in detail by using the finite element analysis results of wing integrated antenna.The simulation results show that the displacement reconstruction accuracy of proposed shape sensing method is significantly higher than that of constant section beam method.5.Strain fields analysis subjected to multiple load types and shape sensing model established for airfoil composite beam.In the service process of UAV,the wing is subjected to concentrated loads,distributed loads,and concentrated-distributed loads.Hence,it is difficult to employ shape sensing model based on one load type to reconstruct the deformation displacements accurately under various load distribution forms.A strain field reconstruction method compatible with multi-load types is proposed by analyzing the strain fields under multi-load distribution.And combined with the section strain calculation method of airfoil beam,the shape sensing model of airfoil profile beam is established.The experimental results from wing integrated antenna loading case show that the establishedshape sensing model can accurately reconstruct the deformation displacements under three different load distribution forms.In addition,the proposed shape sensing method for the composite beam is coupled with the section strain calculation method of the airfoil beam to establish the reconstruction model for the airfoil composite beam.And then it is used to reconstruct the deformation displacements of wing integrated antenna.The results demonstrate that the deformation reconstruction error from the airfoil composite beam is decreased compared with the airfoil beam reconstruction model.