微步长位移法在机械式可重构反射器形面优化中的应用与改进

从作动器作动力阀值和作动器间刚度耦合影响角度出发,建立了可重构反射器计算模型,对微步长位移法计算流程进行了改进,并通过仿真试验对改进后的算法进行了验证,最后对仿真结果进行了分析。仿真结果表明,改进后的微步长位移法可满足各作动器最大作动力小于作动器作动力阀值,重构后反射器形面精度保持不变。

接口前处理在光机系统动力学分析和面形优化中的应用

为了解决光机系统动力学分析与面形优化过程中由于光机接口程序后处理方式所引起的计算数据量大或接口处理失效的问题,提出将光机接口处理过程移到有限元前处理中,并进行了光机系统的集成分析与优化。首先,为了解决标准Zernike多项式在环形离散点域内的非正交性,引入了节点面积加权因子和环域Zernike多项式。提出了通过对镜面施加均匀压强求节点支反力的方式求取节点面积加权因子的计算方法。然后采用最小二乘法推导出镜面刚体位移和拟合镜面变形的Zernike多项式系数与镜面各节点变形量之间的线性关系式。最后,编写接口程序将这些线性表达式以多点约束(MPC)的方式导入到有限元模型中,在前处理过程中完成系统的光机接口处理过程。通过对非稳态风载引起的某1.2m地基望远镜视轴抖动和液压whiffletree支撑下的主镜镜面高阶变形量进行结构动力学随机响应分析,验证了光机前处理方法对解决光机系统动力学问题的有效性。此外,还以镜面面形为优化目标对1.2m轻量化主镜的镜体结构和尺寸进行敏感度分析,证明了光机前处理方法可以有效地简化镜面面形的优化分析过程。

KDP晶体面形控制夹持方案的分析及优化

本文提出了一种能较大程度优化大口径晶体面形的夹持方案,同时分析对比了优化方案与常规方案下重力作用对KDP晶体面形和三倍频转换效率的影响。研究结果表明:优化方案能极大的改善重力对KDP晶体面形的影响;同时当基频光光强为5.5GW/cm2时,优化方案较之三种常规方案的三倍频转换效率分别提高了6.2%、9.5%和6.5%。

大口径空间反射镜的重力卸载优化方法

针对某Φ1550 mm口径高轻量化反射镜在轨面形误差RMS优于1/50λ(λ=632.8 nm)的高精度要求,为模拟在轨失重状态,降低反射镜光轴水平状态面形检测时重力的影响,对反射镜进行了多点主动支撑式重力卸载参数优化。首先,在反射镜分区的基础上,提出了卸载力大小、支撑点数量及轴向初始位置的确定原则;随后,建立反射镜的有限元模型,以重力与卸载力共同作用下主镜面形RMS优于0.002λ为目标,以卸载力轴向位置为参数进行仿真优化,通过对参数的影响规律分析总结出快速优化要点,实现优化过程的简化;最终使重力引起的面形误差RMS值减小至0.00145λ。将优化后参数应用于反射镜光轴水平状态的面形检测中,测得绕轴0°、120°、240°时面形RMS分别为0.0157λ、0.0161λ及0.0159λ,且面形分布较为一致,说明经卸载后重力对面形的影响被有效消除。所提出的重力卸载优化方法灵活高效,为实现大口径反射镜的高精度光学加工及在轨使用提供保障。

多电极静电拉伸薄膜反射镜的面形优化

为了提高多电极静电拉伸薄膜反射镜的面形精度,基于Henky-Campbell圆薄膜平衡方程分析了薄膜均布载荷作用下的拉伸成形和面形误差。采用ANSYS软件一阶优化法,建立了以薄膜屈服强度为状态变量,镜面3个同心环形区域上施加的载荷为设计变量,以反射镜面形与理想面形的最小均方根误差(RMS)为目标的优化模型,对口径300 mm、中心挠度分别为0.5、1.0和1.5 mm的薄膜反射镜面形进行了优化。实验中优化后的最佳镜面面形RMS为7.73μm,PV值为50.69μm,较优化前分别减少了30.2%和23.7%。

重力作用下大口径薄型光学元件面形的优化方法

高功率固体激光装置的频率转换系统中,大口径薄型KDP晶体附加面形的产生,直接影响了高功率激光的频率转换效率和光束质量.针对非垂直放置状态下的大口径平面光学元件,提出了一种用于改变并优化光学元件因重力作用产生附加面形的"杠杆式"夹持方法,并据此设计了适用于大口径超薄Ⅰ/Ⅱ类KDP晶体的夹持系统.利用ANSYS分析软件,建立了相应的有限元分析模型,仿真计算了晶体在夹持前后的附加面形变化,讨论了支撑条长度及加工误差对晶体面形优化效果的影响.研究结果表明:提出的"杠杆式"夹持方法在加工无误差时,对晶体附加面形的优化率达到了90%以上;在支撑条存在加工误差时,对晶体附加面形的优化率也达到了74%以上.

大口径主镜反射膜生长热应力及重力仿真

为了充分了解大口径主镜镀膜时热应力及自身重力的分布规律,达到控制反射镜面形变化、提高成膜质量的目的,采用有限元分析方法,对大口径主镜反射膜的生长热应力及重力对反射镜面形的影响进行了理论分析和研究。结果表明,大口径主镜反射膜更容易在靠近边缘位置处出现剥落和损坏情况;大口径主镜镀膜过程中,自身重力引起的反射镜面形变化对镀膜质量会产生较大影响,需要进行重力消除处理;3000 mm口径的主镜在采用镜面向上、向下蒸发膜料的方式镀膜时,需要对支撑方式进行优化设计。该研究为大口径反射镜镀膜时控制热应力及重力对反射镜面形的影响提供了参考。

基于UG的覆盖件压料面优化设计方法研究

对覆盖件压料面的设计过程进行分析和研究,从其工艺要求出发,基于最小二乘法的思想,提出了使用评价函数对压料面的质量进行定量评价的方式,并给出了求解评价函数最优解的算法,实现了规则类型压料面设计的定量优化。在基于UG/NX平台的PDCAPP系统中验证了算法的可行性,并在PDCAPP系统的压料面参数化设计模块基础上完成了以评价函数为标准计算规则压料面最佳参数的程序模块。以圆柱形压料面为例,给出了用模拟退火算法求解最佳轴向和用梯度法求解最佳拟合截面线的相关公式和算法以及完整优化程序流程。

The quadratic B-spline curve fitting for the shape of log cross sections

This paper describes a new method for simulation of the cross section shape of log. The self-developed MQK3102 log shape recognizing machine was used to acquire the finite discrete sampling points on the cross section of log and those points were fitted with the quadratic B-spline parametric curve. This method can clearly stimulate the real shape of the log cross section and is characterized by limited sampling points and high speed computing. The computed result of the previous curve does not affect the next one, which may avoid the graphic distortion caused by the accumulative error. The method can be used to simulate the whole body shape of log approximately by sampling the cross sections along the length direction of log, thus providing a reference model for optimum saw cutting of log.

Effects of AlN hydrolysis on fractal geometry characteristics of residue from secondary aluminium dross using response surface methodology

The effects of aluminium nitride(AlN)hydrolysis on fractal geometry characteristics of residue from secondary aluminium dross were studied using response surface methodology.The results show that the fractal dimensions of the residue can be significantly influenced by the AlN hydrolysis from secondary aluminium dross.The hydrolysis of AlN in the dross was spontaneous under temperatures of303-373K.The actual fractal dimensions of residue were significantly affected by the liquid-solid ratio(p<0.05)and changed from1.16to1.80,which accurately aligned with those from the calculations.Moreover,the fractal dimensions of residue were significantly affected by the interactions between hydrolysis temperature and hydrolysis time,liquid-solid ratio and hydrolysis time,respectively(p<0.01).The minimum fractal dimensions of the residue reached1.15under the optimized conditions,which included a hydrolysis temperature of30℃,liquid-solid ratio of5mL/g and hydrolysis time of10min.The results suggest that response surface methodology can guide in optimizing the conditions of AlN hydrolysis in order to obtain the minimum fractal dimensions of residue for improving the reutilization of the dross.

Bacterial graphical user interface oriented by particle swarm optimization strategy for optimization of multiple type DFACTS for power quality enhancement in distribution system

This study proposes a graphical user interface(GUI) based on an enhanced bacterial foraging optimization(EBFO) to find the optimal locations and sizing parameters of multi-type DFACTS in large-scale distribution systems.The proposed GUI based toolbox,allows the user to choose between single and multiple DFACTS allocations,followed by the type and number of them to be allocated.The EBFO is then applied to obtain optimal locations and ratings of the single and multiple DFACTS.This is found to be faster and provides more accurate results compared to the usual PSO and BFO.Results obtained with MATLAB/Simulink simulations are compared with PSO,BFO and enhanced BFO.It reveals that enhanced BFO shows quick convergence to reach the desired solution there by yielding superior solution quality.Simulation results concluded that the EBFO based multiple DFACTS allocation using DSSSC,APC and DSTATCOM is preferable to reduce power losses,improve load balancing and enhance voltage deviation index to 70%,38% and 132% respectively and also it can improve loading factor without additional power loss.

Force-finding analysis of cable-net deployable antenna considering shape constraints

The force-finding process of the cable-net in the deployable mesh reflector antenna,AstroMesh,is investigated to optimize the pretension distribution and satisfy surface accuracy.Since the geometry and topology of the mesh reflector antennas are given as a constraint with the boundary condition assumed to be fixed,the force-finding process can be performed on a constant equilibrium matrix to obtain a feasible set of forces.Then,the equilibrium matrix can be rewritten in terms of force modes after the singular value decomposition.The object of force design is to minimize the deviation of member forces and,therefore,the surface accuracy can be guaranteed by transforming an optimization of the distribution of prestresses into an optimization with multiple prestress modes.Finally,numerical examples solved by the sequential quadratic programming(SQP)algorithm and the genetic algorithm are given to validate the efficiency of the proposed method.The comparison results show that the genetic method can converge to the optimized point after approximately 50 iterations while the converging process of the sequential quadratic programming method depends largely on the initial points.

Optimization of press bend forming path of aircraft integral panel

In order to design the press bend forming path of aircraft integral panels,a novel optimization method was proposed, which integrates FEM equivalent model based on previous study,the artificial neural network response surface,and the genetic algorithm.First,a multi-step press bend forming FEM equivalent model was established,with which the FEM experiments designed with Taguchi method were performed.Then,the BP neural network response surface was developed with the sample data from the FEM experiments.Furthermore,genetic algorithm was applied with the neural network response surface as the objective function. Finally,verification was carried out on a simple curvature grid-type stiffened panel.The forming error of the panel formed with the optimal path is only 0.098 39 and the calculating efficiency has been improved by 77%.Therefore,this novel optimization method is quite efficient and indispensable for the press bend forming path designing.

Research on stability design of a bar-reinforced spherical bulkhead

In this paper, the stability of a concave spherical stem bulkhead under the pumping load when still lying at the slipway is analyzed. The stability of the spherical stem bulkhead with different shell thickness and reinforcing forms is discussed. According to the results of stability analysis, the optimization design of the spherical stem bulkhead stability is performed. On the basis of considering the machining technical requirements of the bulkhead, a rational design of the spherical stem bulkhead structure is obtained. This paper has a certain value to the design of submarine's spherical stem bulkhead.

Prediction of the Maximum Flow by the Model SASIS： Sensibility to the Empirical Parameters of the Shape of the Furrow

The model developed in this research presents effective mechanisms in simulations of a discharge strip understood between the minimum and the maximum allowable values, aiming to determine the relationship between discharge and water application efficiency, deep percolation and runoff rates, and consequently to optimize the performance of the furrow irrigation systems with continuous flow. The flow applied in each furrow must be adapted to the length, to the field slope and to the nature of the ground. The authors studied the maximum non erosive flow （Q,,,~）, in function of parameters obtained from the dimensions of the furrow, being Pl and/92, respectively, the linear and exponential parameters of the potential functions that described the relationship between the area of the cross section of flow （or wetted perimeter） and height of flow; in this way, the multiplicative effect of,01 on the area of the cross section of flow is linear, while ,02 is exponential. It verified a conjugated effect of,or and p20n the value of Q,,~. The results of this research point out for the importance of having an estimate of the parameters of the geometry of the cross section of flow （,01 and ,02） the most precise as possible, being known that the dimensions of this section can result in impracticable values of Qmax, outside of the acceptable strip in the literature, that is from 1.2 to 4.0 L.sl. This sensibility analysis was also of great benefit to create an interface in the software SASIS, capable to guide the user of this tool in the input of appropriate values for ,01 and P2 to the process of simulation of the irrigation for furrow with continuous flow and of the optimization of its performance.

Numerical study on the characteristics of natural supercavitation by planar symmetric wedge-shaped cavitators for rotational supercavitating evaporator

With the application of supercavitation effect, a novel device named rotational supercavitating evaporator(RSCE) was recently designed for desalination. In order to improve the blade shape of rotational cavitator in RSCE for performance optimization and then design three-dimensional blades, numerical simulations are conducted on the supercavitating flows(with cavitation number ranging from 0.055 to 0.315) around two-dimensional planar symmetric wedge-shaped cavitators with different wedge angles varied from 10 to 180 degrees. Proper numerical method for simulating supercavitating flows around planar symmetric cavitator is established, and assessment of k-ε-v2 -f turbulence model in simulating cavitating flows is conducted. It shows that the size of computational domain would affect the simulation result. Empirical formulae for supercavity dimensions about cavitation number at different wedge angles are obtained, which are of significant importance in the subsequent design of three-dimensional blade. The characteristics of resistance at different wedge angles are discussed, which, together with the characteristics of supercavity dimensions, play important roles in the optimal design of RSCE.