Research On Deformation Measurement And Displacement Reconstruction Theory For Wing Based On Strain Information

With the rapid development of air transport industry, as well as the concept of low-carbon aviation, unmanned aerial vehicles, big airplane, new energy aircraft and other transportation equipment had become hot topics in the field of sophisticated technology. High-altitude long-endurance aircraft is the direction of its development, while high-altitude long-endurance aircraft generally use lightweight, flexible, and high aspect ratio wing. The higher the wing aspect ratio, the more oustanding the drag reduction effect. Large flexible features of high aspect ratio and large size wing make great elastic deformation of the wing during flight. Great deformation affect the safety of the flight and the reliability of the wing structure. Meanwhile, the wing is also the carrier of antenna. Flight loads lead to antenna amplitude and phase error, leading to a sharp decline in the electrical performance of the antenna. Problems include pointing error caused, risen sidelobe level and gain reduction. Real-time perception and reconstruction of the wings deformed can be used to assess the safety of the aircraft, reduce deformation by active controling methods, or ensure the antenna electrical performance by means of compensating. Therefore, detection and reconstruction of the wing deformation are the problems needed to be solved firstly.This thesis, starting from the structural deformation measurement technique, combines deformation measurement technique with deformation reconstruction theory, elaborates the existing mature technology and theory, and studies the new deformation reconstruction theory. Using deformation measurement technology, three deformation reconstruction theorys are applied to a actual wing model.1) The Ko displacement theory, based on piecewise linearization, sets up mathematical model for the strain at linear or quadratic distribution. It uses the partial derivative relation between the deformation function the displacement function, calculates shape function coefficients and thus calculates displacement. The modal method based on modal information establishes the transformation matrix between strain and displacement using modal superposition principle, through strain mode and displacement mode. A simple cantilever beam is taken for example to verify the deformation reconstruction effects of Ko displcement theory and modal method.2) Inverse finite element method based on Timoshenko beam theory builds relationships between section strain and displacement through the least squares of the measured strain and the estimated strain, with the deformation function and strain function. Section strain was obtained by surface strain. It takes cantilever beam as an example, reconstruct the cantilever six displacement components using inverse finite element method, and verifies its deformation reconstruction effect.3) Refer to the actual wing structure, design the wing model, use Ansys finite element analysis software to build wing FEA model for simulation of three deformation reconstruction method to obtain the simulation accuracy. Process wing model, build experimental platform, strain measurement system and displacement measurement system. The actually measured strain informations are substituted into the three reconstruction theory to obtain the displacement variables. According to the actual wing shape function, fit the strain data into the calculation, effectively improve the deformation reconstruction precision of the inverse finite element method.Inverse finite element method does not require sufficiently accurate loading and material information. The same set of strain information reconstruct six displacement components, and Ko displacement theory and modal method can only reconstruct displacement in one direction, for trusses type and other complex structures have limitations, and inverse finite element method is more flexibe if applied to complex structures.