动载体成像系统底座无角位移减振器的设计

详细分析了由动载体振动引起的角位移和线位移对成像系统的影响。角位移是影响成像质量的主要因素。对成像底座减振系统的要求既要满足减振效率,又要控制减振过程中产生的角位移。设计了一种三向等刚度无角位移减震器,它既能满足减振要求,又能控制减振过程中产生的角位移,从而提高了动载体摄像系统的清晰度,同时又不影响视轴的指向精度,是一种比较理想的减振器。     

随机振动对星载TDICCD影响分析

研究了星载TDICCD的成像机理,着重分析卫星扰动引起TDICCD随机振动,造成图像质量下降,给出了典型的振动传递率和可行的振动抑制方法.为了提高TDICCD减振的能力,对TDICCD实施隔振和阻尼抑振控制技术.同时分析了振动控制的基本原理和设计原则,给出了相关的设计.     

高频振动模糊图像仿真与分析

研究了运动模糊图像在空间域和频域上的数学模型,根据运动图像的模糊原理,提出了时间等分运动模糊图像的仿真方法,仿真了高频振动模糊图像.理论分析指出,物体做高频谐波振动时运动模糊成像的频谱会由于Bessel函数的零点的存在而形成系列条纹,对振动模糊图像的频谱做两次Radon变换能检测出振动的方向和振幅,从而得到高频振动模糊...     

磁悬浮－气囊主被动混合隔振装置理论和实验

为了更有效地控制舰船动力机械宽频和低频线谱振动的传递,提出了一种将磁悬浮作动器与气囊隔振器集成应用的磁悬浮-气囊主被动混合隔振装置。通过对磁悬浮作动器机电耦合特性和混合隔振系统动力学特性的分析研究,确定了满足线谱振动控制要求和满足混合隔振装置性能要求的参数设计方法。针对主动控制时,FxLMS (filtered-x least mean square)算法在小阻尼系统上需用高阶FIR滤波器建模,运算量大的问题,提出了分频段控制的改进FxLMS算法,并有效地解决了作动器的非线性效应问题。样机实验结果表明:理论分析是正确的,该项技术控制力需求小,装置稳定性好,具有优良的宽频隔振和低频线谱振动控制效果。      

斯特林制冷机振动输出转动分量测试的必要性

通过振动对成像质量影响的理论分析,阐明了振动的转动分量是影响成像质量的主要因素。在此基础上,采用目前测试斯特林制冷机振动输出量值准确度最高的方法——悬挂法,对振动输出的各方向数据进行测量。从各组测量数据中,筛选出量值最大的一组数据,据此计算振动输出转动分量和平动分量对制冷机成像质量影响的程度,从而得出振动输出转动分量是影响制冷机成像质量的主要因素。     

光学移相干涉仪抗振系统的鲁棒控制系统仿真分析

将被动抗振和主动抗振相结合的混合控制技术应用于解决光学移相干涉仪抗振系统的不确定性问题,其中主动抗振采用鲁棒控制策略.该方法克服了由模型和干扰所引起的不确定性,使得控制系统能够有效地抑制抗振模型的不确定性和外部振动的干扰.仿真结果表明,该方法使光学移相干涉仪在振动的干扰下具有较好的鲁棒稳定性和控制准确度.     

基于主动悬架的模糊神经网络控制的研究

传统的被动悬架由于阻尼参数不可任意选择和调节,减振性能不好,不能满足乘客的乘坐舒适性;而主动悬架可通过改变减振器的阻尼特性而适应不同的道路和行驶状况,改善乘坐舒适性和操纵稳定性;以汽车主动悬架为研究对象,建立了汽车二自由度1/4车体模型,提出了一种汽车主动悬架模糊神经网络控制方法,设计了模糊神经网络控制器;以B级路面作为随机路面输入,并利用Matlab进行仿真;通过动态仿真对被动悬架和主动悬架的特性进行了对比,仿真结果表明,该模糊神经网络控制器对车身加速度、悬架动挠度和轮胎动载荷都有很好的抑制。     

基于超磁致致动器的车削振动主动控制

设计了一种基于模糊PID控制器和超磁致伸缩致动器的车削振动主动控制系统,推导了超磁致伸缩致动器和专用刀架的数学模型,并在Matlab环境下进行建模仿真,当振动频率在50~100 Hz时,仿真结果表明该控制系统能抑制振幅达50%以上;在现场车削试验中,以普通45#钢为车削工件,分别在转速1 500 r/min、车削深度为0.07 mm和转速3 000 r/min,车削深度为0.04 mm下,对车削振动进行主动控制,结果证明所设计的车削振动控制系统能够抑制振动幅度达30%以上。     

激光距离选通技术在微光成像系统中的应用

激光距离选通技术提高了微光条件下的远距离观测的视距,有效的克服了大气的后向散射对微光成像系统成像质量的影响。采用改进的同步控制技术解决了距离选通技术中激光器与摄像机的同步问题。实验结果表明,采用同步控制技术的距离选通技术对提高成像的质量和探测距离起到了关键的作用。     

光电成像系统动态调制传递函数测量装置

在光电成像系统中,动态调制传递函数受到光学系统波像差、探测组件信号分辨率及传递特性以及载体运动引起图像模糊等环节对图像质量的综合影响,成为光电成像系统的重要参数之一。论文基于光电成像系统动静态调制传递函数的测试原理,研制一种动态调制传递函数测量装置,其中光学准直系统焦距为10 000 mm,运动目标速度控制范围达到30 mm/s～5 000 mm/s,满足长焦距光电成像系统的动态调制传递函数测试。利用该装置进行了一系列的实验研究,结果表明,动态调制传递函数测量重复性优于0.01,测量不确定度达到U=0.05（k=2）。     

Restoration of images degraded by extreme mechanical vibrations

A method of numerically calculating the optical transfer function appropriate to any type of image motion and vibration, including random, has been recently developed. This method has been verified experimentally with real vibrations, and the close agreement justifies implementation in image restoration from blur deriving from any type of image motion, including random displacement. Here, image restorations of actual physically degraded images are presented, based on a constrained least squares improvement of the original Wiener filter. Even for extreme vibrations where the blur extent is much larger than the blurred detail, restoration is quite complete. The key to restoration is the determination of the optical transfer function unique to the particular image motion and vibration causing the blur. Results are also presented for low vibration frequency motion of random blur extent, as well as for high vibration frequencies.     

Semi-active on–off damping control of a dynamic vibration absorber using Coriolis force

A passive dynamic vibration absorber (DVA) moving along a pendulum can cause the nonlinear Coriolis damping to reduce the pendulum swing. This paper proposes a simple semi-active on–off damping controller to improve the passive Coriolis DVA. The aim of the on–off damping control is to amplify the DVA resonance motion to increase the energy dissipated. Moreover, the paper finds the analytical solution of the harmonic vibration of semi-active controlled system. The accuracy of the analytical formulas and the superior performance of the semi-active DVA are verified by numerical simulations.     

Interlaced scan CCD image motion deblur for space-variant motion blurs

Motion blur is caused by camera shakes or object motions during exposure when the shutter speed is relatively slow. As for the object motion blur, the degradation of a CCD image is often characterized by space-variant motion blurs, since objects are often moving in different directions at different speeds. But most image restorations for space-variant motion blurs are addressed only for progressive scan CCD images. To address the space-variant image restorations for interlaced scan images, we propose a novel image restoration scheme. First, one interlaced scan image frame is required, which is divided into the odd field and the even field images. These two field images are further segmented into rectangular blocks. The motion vectors are computed in these rectangular blocks using an efficient block matching algorithm. Second, image restoration is performed in these rectangular blocks using a constrained least square algorithm in the odd or even field image, which can both preserve edge structures and remove noises. Our novel scheme is illustrated by restoring a space-variant blurred moving boat image and a synthetic blurred image.     

Passive and active interior noise control of box structures using the structural intensity method

This paper presents passive and active vibro-acoustic noise control methods for attenuating the interior noise level in box structures which can be an analogy of cabins of vehicle and aircraft. The structural intensity (SI) approach is adopted to identify the predominant vibration panels and interior noise sources for box structures. In the study, the finite element method is used to determine the structural vibration and structural intensity in the box surfaces. According to structural intensity vectors plot and structural intensity stream lines presentation, the possible effective control positions where the dampers may be attached and the active control forces may act to reduce vibration and interior noise, are identified. From the study, it can be demonstrated that the structural intensity approach and stream line presentation are possible methods for identifying the vibro-acoustic interior noise source and predominant panels which may be modified to reduce the interior noise level. The structural intensity methodology, passive and active noise control results can be extended to the further study of the vibration and interior noise control of actual cabins of vehicles and aircraft.     

Multi-cracks detection of a beam-like structure based on the on-vehicle vibration signal and wavelet analysis

In this paper, a new method for detecting a multi-cracked beam-like structure subjected to a moving vehicle is presented. The crack model is adopted from fracture mechanics. The dynamic response of the bridge-vehicle system is measured directly from the moving vehicle. When moving along the structure, the moving vehicle causes small distortions in the dynamic response of the bridge-vehicle system at the crack locations. In general, these small distortions are difficult to detect visually. However, wavelet transform has recently emerged to be an effective method of detecting such small distortions. Large values (peaks) in the wavelet transform indicate the existence of the cracks. The locations of the cracks are pinpointed by positions of peaks of the wavelet transform and the velocity of the moving vehicle. Numerical results show that the method can detect cracks as small as 10% of the beam height. The proposed method is applicable for low velocity-movements while high velocity-movements are not recommended. The method presents an idea for measuring the vibration directly from the vehicle for crack detection problem in practice.     

Theoretical modeling and characteristic analysis of moving-train induced ground vibrations

An integrated train-track-subsoil dynamic interaction model of moving-train induced ground vibration is developed on the basis of vehicle dynamics, track dynamics and the Green's functions of subsoil. The model takes account of the vibrations of vehicle components, the quasi-static axle loads and the dynamic excitations between the wheels and track. The analyzed results from an example show that the ground vibration characteristics have a close relationship with train speed and soil properties; the dynamic responses excited by wheel-track irregularity have big influence on the high frequency components of ground vibration; with the increase of distance to the track, the ground acceleration has the tendency of decrease, and the relevance of acceleration curves and train excitation becomes less obvious; the intersections of moving load speed-lines and subsoil dispersion curves are some resonance frequencies that cause the amplification of ground vibrations; there exists a critical speed for moving train that is close to the minimum velocity of the Rayleigh's wave in the subsoil.     

Reduction of vibration and noise radiation of an underwater vehicle due to propeller forces using periodically layered isolators

Using periodic structure theory, the suppression of vibration and noise radiation from an underwater vehicle due to excitation from propeller forces is investigated. The underwater vehicle is modelled in two parts (the hull and the propeller/shafting system). A model of the propeller/shafting system is constructed using a modular approach and considers the propeller, shaft, thrust bearing, isolation structure and foundation. Different forms of isolator are considered – a simple spring-damper system, a continuous rod and a periodically layered structure. The dynamic properties of the underwater vehicle and the isolation performances of various isolators are compared and analysed. The stop band properties of the periodic isolator are used to enhance the passive control performance. Furthermore, an integrated isolation device is proposed that consists of the periodic isolator and a dynamic absorber, and its isolation performance is investigated. The effects of the absorber parameters on the performance of the integrated device are also analysed. Finally, the radiated sound pressure is calculated to verify the attenuation. The numerical results show that the vibration and noise radiation are greatly attenuated in the stop bands. By optimising the design of the periodic isolators and its integrated structures, the suppression of the vibration and noise radiation can be improved effectively.     

基于分时积分亚像元融合的地球静止轨道平台消颤振技术

相较于低轨卫星线阵扫描成像模式,地球静止轨道面阵成像的曝光时间相对更长,更容易受到平台颤振的影响而造成图像模糊.为了消除由平台颤振引起的像质退化,本文提出了基于分时积分亚像元融合的方法.由于地球静止轨道的凝视成像特性,相机观察区域在长时间内保持不变,因此分时短曝光可以获得多帧目标内容相同,但模糊尺度更低的短曝光图像.然后对多帧短曝光图像采用基于能量区域质心法的相位相关算法进行亚像元图像配准,计算相对偏移量并进行补偿,位移探测准确度可达0.1像元以内,满足卫星平台应用需求.再按亚像元偏移量对多帧图像进行融合,融合的过程可以提升由于曝光时间缩短而降低的单帧图像信噪比,最终可以获得图像清晰度更高、信噪比与原长曝光图像相当、信息辨识度更好的遥感图像.     

基于分时积分亚像元融合的地球静止轨道平台消颤振技术

相较于低轨卫星线阵扫描成像模式,地球静止轨道面阵成像的曝光时间相对更长,更容易受到平台颤振的影响而造成图像模糊.为了消除由平台颤振引起的像质退化,本文提出了基于分时积分亚像元融合的方法.由于地球静止轨道的凝视成像特性,相机观察区域在长时间内保持不变,因此分时短曝光可以获得多帧目标内容相同,但模糊尺度更低的短曝光图像.然后对多帧短曝光图像采用基于能量区域质心法的相位相关算法进行亚像元图像配准,计算相对偏移量并进行补偿,位移探测准确度可达0.1像元以内,满足卫星平台应用需求.再按亚像元偏移量对多帧图像进行融合,融合的过程可以提升由于曝光时间缩短而降低的单帧图像信噪比,最终可以获得图像清晰度更高、信噪比与原长曝光图像相当、信息辨识度更好的遥感图像.