The optimization of the elevation rotation structure (ERS) is one of the critical problems in the design of a large submillimeter telescope (LST). Here, combining the super element model with topology optimization method and genetic algorithm (SEMTOMGA) is proposed for the ERS design of an LST. The SEMTOMGA has three key steps: (1) the super element model is applied to condensing all the degrees of freedom of the large structure elements, which needs no topology optimization, except for the connecting nodes and the objective structure elements; (2) the topology method is applied to optimizing the objective structure; (3) based on the optimization results of the second step, the further whole structure optimization with multiobjective genetic algorithm(GA) is performed. The SEMTOMGA, which exploits the complementary merits of the super element model, topology optimization method, and GA, solves the problem of the ERS design effectively. As an application, a 60-m submillimeter telescope is designed and optimized by SEMTOMGA. The results have shown that the SEMTOMGA not only obtains a lightweight design of the ERS but also has sufficient stiffness. Moreover, the performance of the whole structure has been improved, and the residual half-path length errors of the main reflector have declined from 263.7 to 135.6 μm, which is about half of the original 263.7 μm of the initial design.
We propose an analytical nonlinear hysteresis model of the bimorph beam bending piezoelectric actuator for a deformable mirror system. An explicit solution is derived from the analytic method based on the nonlinear elasticity. As an application example, the nonlinear hysteresis behaviors of a bimorph beam bending piezoelectric actuator, which is sandwich compounds consisting of a lower and an upper piezoelectric ceramic (PZT8-50) layer and a middle layer made of the aluminum alloy, are examined with the model. The numerical calculations based on the analytical solution are presented. The numerical simulations have shown that the nonlinear hysteresis behaviors of the bending actuator are depended on the start values of the exciting electric field and the geometric parameters of the metallic layer. In addition, the numerical results have also shown that the thickness of metallic layer has little influence on the relative hysteresis, and the relationships between relative hysteresis Δd / ΔD and the driving electric field | Estart | are linear.
In this paper, the finite element parameterized model of 1.2 meter terahertz antenna is established for near-field holographic measurement. The structure of 1.2m antenna, which consists of reflector body and tower base, is developed to a prototype of the 5-m Dome A Terahertz Explorer (DATE5). The reflector is made of carbon fiber-reinforced plastics, and tower base is made of steel. For the evaluation of the antenna performances, the gravity load effects of 1.2m antenna have been analyzed by the model. The numerical analysis results show that reflector surface RMS errors due to gravity load decrease with the increase of elevation angle, and the ranges of values of the surface RMS errors are from 0.14μm, to 0.81μm, which has been met the performance requirements of 1.2m antenna. Moreover, the mode shapes and the eigenfrequencies are also studied. The results suggest that the trends of the dependence of first three orders eigenfrequency upon elevation angles are well agreement with those of DATE5: the eigenfrequencies of the first and second orders of the model also decrease with the increase of elevation angle, while the eigenfrequencies of the third order increase with the increase of elevation angle.
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