相位校正器补偿能力的频域特性仿真分析

在自适应光学系统仿真分析中,通常用变形镜对Zernike像差的拟合精度来评价,但不易反映变形镜参数变化和补偿能力的关系。采用高斯型面形影响函数,并用最小二乘法以及Householder变换法,把系数矩阵正交三角化,直接求解拟合系数,计算出各驱动器驱动权重。通过傅立叶变换,得出拟合波前和入射波前对应频率关系。可将变形镜视作空间滤波器,进行入射波前的补偿。结果表明,变形镜对低空间频率波前具有较好的补偿能力,且驱动器密度是波前补偿能力的决定因素,截止频率的变化与波前类型密切相关。     

相位校正器波前拟合误差仿真分析

在自适应光学系统中,波前拟合误差直接影响到相位校正器的校正效果。在仿真分析中,作为相位校正器的变形镜,其面形影响函数通常采用高斯函数近似。以高斯型面形影响函数为基础,利用最小二乘法,通过仿真计算分析了波前拟合误差与入射波前空间频率、驱动器密度、高斯指数、交连值等变形镜主要参数的关系。结果表明,变形镜对低空间频率波前具有较好的补偿能力,且驱动器密度是波前补偿能力的决定因素,增大高斯指数和交连值一定程度上有利于波前的补偿,并对其原因进行了阐释。存在一类特殊情况,当入射波前的零点恰好通过各变形镜所在位置,补偿拟合基本失效,应注意避免。     

电活性聚合物致动器机电响应特性研究

电活性聚合物(EAP)致动器是一类极具发展潜力的智能材料。通过对尺寸为10 mm×2 mm离子型聚吡咯致动器施加阶跃电压、方波、正弦波、斜波电压,研究分析致动器位移响应与驱动电压波形、幅值和频率的关系。阶跃电压下,致动器位移响应经过5s左右达到稳定状态,仅1 V驱动电压就可使致动器稳态弯曲位移变化值达2. 22 mm。在幅值为±1 V方波驱动电压下,致动器稳定状态位移变化值则为1. 96 mm。试验结果表明:驱动电压增加,迁进迁出致动聚合物层的离子增多引起聚合物层的氧化还原加剧,致动器位移响应滞后于驱动电压变化;其位移响应幅值随驱动电压增加而增大,呈线性关系。当驱动电压波形与幅值相同时,致动器位移变化幅值随驱电压频率的增高而减小,且呈非线性关系。该致动器机电响应特性试验为微阀、微型机器人、生物医学设备、人工肌肉、电化学传感器、贮能材料等领域的实际应用提供了理论参考。     

一种基于平面控制直线约束的非量测相机检校方法

光束法自检校为一种经典的适合于非量测相机的检校算法,但其解算精度易受到大量像点坐标观测值的影响.本文讨论一种基于平面控制直线约束的非量测相机检校方法.该方法利用平面格网控制场中的直线特征对格网像点坐标及畸变参数进行直线几何约束.详细推导了该方法的直线约束方程,对检校实验结果从控制场格网点直线性、构像残差等方面进行分析.经实验验证,相较传统的光束法自检校,该附加直线约束的检校方法可有效提高检校结果精度.     

汽车燃油喷射系统用磁致伸缩驱动构件的 建模与特性研究

针对传统发动机喷射系统存在的非无级控制及喷射量难于精确最小化的问题,论文提出一种利用磁致伸缩致动器直接驱动喷嘴针控制燃油喷射过程的磁致伸缩喷射系统.通过调整磁致伸缩材料变形量以快速无级控制喷射器开合尺寸及喷射量.以基于多值函数算子现象学方法的磁滞理论为基础,结合对致动器系统的动力学特性分析,建立了包含磁滞损耗特性的位移模型.结果表明,模型可较准确描述磁致伸缩驱动构件的位移幅值及频率特性,位移预测平均相对误差约为5.6%;系统一阶谐振频率和位移峰值分别为380 Hz和50μm.研究结果为改善喷射系统性能提供一种新方法.     

介电弹性体材料致动器的非线性动态行为研究

介电弹性体材料(Dielectric Elastomer,简称DE),是制造柔性智能致动器最有潜力的电活性聚合物(Electroactive polymer,缩写EAP)材料之一,可在电压驱动下产生大幅度的厚度与面积变形,最大面积应变高达1600%.由于DE材料的固有阻尼特性,从而使其变形具有时间依赖性,因此动态变形中,其能量转换、宏观变形等特性也必然受到阻尼的影响.借助热力学自由能理论,考虑DE材料致动器面内动态变形过程中的惯性力和阻尼力,构建平面DE材料致动器的非线性动力学模型.研究了交变电载荷下DE系统的非线性动态特性,包括其幅频曲线、位移响应和相平面图.研究表明,存在阻尼的时候,DE系统的振动会随着时间的增加出现锁频现象,最后变成一种具有恒定振幅的振动.相平面图和Poincaré映射图研究表明,考虑阻尼后DE系统的稳态相平面图是一条闭合的曲线,其Poincaré映射点集是有限的,代表其产生周期性运动.研究成果为DE材料致动器在各种动态驱动器或传感器中的应用提供理论依据.     

微致动器在流动控制中的应用研究

基于MEMS技术,研制了一种微气泡型致动器.对前缘布置有微致动器的三角翼进行了数值模拟和风洞实验,结果表明:微致动器可以改变三角翼前缘的旋涡流状态,扰动边界层,改变三角翼前缘分离涡位置,合理布置微致动器可以获得一定的滚转力矩,利用微致动器可以进行流动控制,进而改变飞行器的动力性能.     

自校正信息融合Wiener预报器及其收敛性

对带相关观测噪声和未知噪声统计的多传感器系统,用相关方法得到噪声统计在线估值器.在按分量标量加权线性最小方差最优信息融合准则下,用现代时间序列分析方法,基于滑动平均(moving average)新息模型的辨识,提出了自校正解耦融合Wiener预报器.用动态误差系统分析(dynamic error system anallysis)方法证明了自校正融合wiener预报器收敛于最优融合Wiener预报器,因而它具有渐近最优性.它的精度比每个局部自校正Wienet预报器精度都高.它的算法简单,便于实时应用.一个目标跟踪系统的仿真例子说明了其有效性.     

相机一维标定的最优加权线性算法

为了进一步提高相机一维标定线性算法的精度,提出一种最优加权线性算法.首先对相对深度的约束方程进行一次最优加权得到其新的估计量,并指出一次最优加权具有与迭代最优加权相当的精度以及更少的计算量;然后对绝对二次曲线的像的约束方程也进行一次最优加权,并通过对最优权进行适当的近似以进一步减少计算量.实验结果表明,该算法的标定精度比现有的加权线性算法的精度更高,与光束法平差算法的精度相当.     

软体仿蛙游动机器人关节式气动致动器研制

为实现仿蛙游动机器人的微小型化,增强其环境适应能力,结合软体材料的优势特点和青蛙划动推进的游动方式,提出了一种关节式气动软体致动器,该致动器在满足软体仿蛙机器人游动过程中的运动性能和力学性能的同时,使得其肢体结构更加紧凑、轻量．利用Yeoh本构模型和虚功原理,结合关节式气动软体致动器的几何参数,建立了致动器的形变分析模型．进而,在致动器总体尺寸受约束的情况下,以一定弯曲角度下致动器输出恢复力矩最大为目标,确定了致动器的具体结构参数．融合3D打印、模塑成型等加工工艺方法,加工制备了关节式气动软体致动器,并通过对比分析,确定了采用纤维线限制致动器径向凸起效应时纤维线的绕线形式和绕线密度．最后经过实验测试分析,该致动器质量约7.5 g,可实现由180°弯曲状态至伸直状态的形态变化,并且在弯曲角度一定时通过调整充入气压的大小可以匹配一定范围内不同大小的负载力矩,从而验证了针对软体仿蛙游动机器人设计的关节式气动软体致动器的可行性．     

矩形孔径柱面镜面形拟合基底多项式研究

对矩形孔径柱面镜面形的拟合方法进行了研究，将矩形域的扩展Zernike多项式与Chebyshev多项式分别作为面形拟合基底，对导出面形数据进行波面复原，分析赛德像差与拟合基底的对应关系对比拟合结果，Chebyshev多项式较矩形域的扩展Zernike多项式有较好的像差分离能力。     

Large-stroke MEMS deformable mirrors for adaptive optics

Surface-micromachined deformable mirrors that exhibit greater than 10 /spl mu/m of stroke are presented. The segmented arrays described here consist of 61 and 85 hexagonal, piston/tip/tilt mirrors (three actuators each) with diameters of 500 and 430 /spl mu/m, respectively, and fill a 4 mm circular aperture. Devices were packaged in 208 and 256 pin-grid arrays and driven by a compact control board designed for turn-key operation. After metallization and packaging mirror bow is /spl sim/680 nm (/spl lambda//1), but a heat-treatment procedure is proposed for controlling mirror curvature to better than /spl lambda//10. An optical test bed was used to demonstrate basic beam splitting and open-loop aberration correction, the results of which are also presented.     

空间望远镜主镜的主动支撑面形校正分析

大型空间望远镜的主镜由于受重力、温度和装配等因素的影响,会产生面形误差,影响光学系统的成像效果。为了提高空间望远镜主镜对重力、温度的适应性,采用400mm弯月镜进行了主动支撑面形校正研究。主动支撑方案由3个固定支撑和7个主动支撑构成,利用Zernike系数和最小二乘法计算力促动器的校正力大小。使用有限元仿真软件分析了镜子在重力工况和稳态温度工况下,校正前后的面形结果。分析结果显示,采用本文的主动支撑方案,各工况下被校正后的主镜面形精度达到均方根(RMS)值<λ/20的设计指标,面形质量有明显的提高。同时,在重力工况中引入了实际装调中可能存在的安装误差等因素,仿真结果显示装配误差对校正结果影响较小,说明主动支撑系统具有较高稳定性。     

Development of piezoelectric MEMS deformable mirror

This paper reports on piezoelectric micro-electro-mechanical systems deformable mirrors with high-density actuator array for low-voltage and high-resolution retinal imaging with adaptive optics. The deformable mirror was composed of unimorph structure of lead zirconate titanate (PZT) thin film deposited on Pt-coated silicon on insulator substrate and a diaphragm of 10?mm in diameter formed by backside-etching the Si handle wafer. 61 hexagonal electrodes were laid out on the PZT thin film for the high-density actuator array. In order to reduce the dead space for the lead lines between the electrodes and connecting pads, a polyimide layer with through holes on the electrodes was patterned as an electrical insulator. To confirm the application feasibility of the fabricated DMs, displacement profiles of the actuators were measured by a laser Doppler vibrometer. Independent applications of voltages on individual actuators were confirmed.     

Optical performance of fully and partially compensated adaptive optics systems using least-squares and minimum variance phase reconstructors

Adaptive optics systems have been proposed as a means of compensating for the effects of atmospheric turbulence on optical imaging systems. Many previously studied adaptive optics systems process measurements acquired from slope sensors to generate commands for the actuators in a deformable mirror. The act of generating actuator commands is referred to as reconstruction. Two types of phase reconstructor have been proposed for use in such systems: (1) the least squares reconstructor; and (2) the minimum variance reconstructor. The mean square phase error performance of these two reconstructors has been previously analyzed. However, the impact of the choice of reconstructor on the average optical transfer function and image signal-to-noise ratio in the spatial frequency domain have not been addressed. In this paper the optical performance of the two reconstructors is explored using the single frame signal-to-noise ratio as a function of spatial frequency as a comparative performance measure. The average optical transfer function and the second moment of the optical transfer function are computed. Performance is analyzed for fully and partially compensated systems. It is shown through theoretical calculations and simulation that the minimum variance reconstructor provides superior performance.     

Design of novel deformable mirror with large displacement

A stabilized zoom system with deformable mirrors (DMs) was designed for continuous optical zoom. In order to adjust the focal length and expand the field angle, the characteristic surface shapes of the DMs composed of the low-order and high-order Zernike polynomials were provided. The maximum peak-to-valley (PV) value at the center of the surface shape is 80 μm. This work presents a piezoelectrically-actuated deformable mirror (PADM) with large displacement for a stabilized zoom system. The COMSOL simulation was conducted to obtain the desired design by matching and optimizing structural parameters. The maximum displacement of PADM was more than 80 μm. The fitting results by the steepest descent algorithm (SD) showed that the RMS values of the residual surface shapes were 1 of 7 to 1 of 4 of their PV values, and the PV values of the residual surface shapes were less than 1 of 10 of the PV values of the target surface shapes.     

基于同轴回归激光传感器的水表误差检测系统

设计一种针对水表始动元件转速测量的激光传感器检测系统。在传感器光学结构中加入半透半反镜使光路同轴回归,从而对目标准确瞄准定位。处理系统由FPGA和DSP组成进行激光回波信号数字化处理和阈值选取,减小虚预警概率。实验证明:检测系统在校准之后具有较高的检测效率和准确度,能够实现水表实时误差检测。     

Estimating the contribution of different parts of the atmosphere to optical wavefront aberration

Current adaptive optical telescope designs use a single deformable mirror (DM), usually conjugated to the aperture plane, to compensate for the cumulative effects of optical turbulence. The corrected field of view (FOV) of an adaptive optics system could theoretically be increased through the use of multiple DMs conjugated to a like number of corresponding planes which sample the turbulence region in altitude. Often, the atmospheric turbulence responsible for the degradation of long-exposure telescope images is concentrated in several relatively strong layers. The logical location for the planes of correction in a multiconjugate adaptive optics (MCAO) system would be the same as these “seeing layers.” Each DM would correct for the component of the total wavefront contributed by its associated turbulent layer. However, there is no known method of isolating a particular layer so that its component may be measured. Somehow, the individual components must be estimated using available measurements of the cumulative wavefront at the aperture of the telescope. This paper presents a theoretical analysis of a signal processing technique for determining these phase contributions. The method takes advantage of the spatial diversity of wavefront sensor (WFS) measurements from two or more reference sources. These separate wavefront sensor measurements are processed via minimum mean square error filtering to yield an estimate of the phase perturbation caused by a particular turbulent layer of the atmosphere. Our results indicate that multiple wavefront corrector adaptive optics systems will require much brighter reference sources than single wavefront corrector systems.