长焦距斜视航空相机图像拖影与扭曲补偿技术研究

	长焦距斜视航空相机图像拖影与扭曲补偿技术研究
	刘志明
学位类型	博士
导师	朱明
	2014-07
学位授予单位	中国科学院大学
学位专业	机械电子工程
摘要	航空成像与测量技术是20世纪发展起来的一个新学科，它利用航空机载光学系统和光电耦合器件来遥测和侦察地面景物信息，主要应用于战前军事侦察和战后军事打击评估，对我国国防发展具有相当重要的意义。机载光电设备与星载航天光电设备的不同之处在于，飞机的机动性大，飞行振动和姿态不平稳，造成遥感器光轴指向产生晃动，在曝光时间内光轴无法指向固定目标，造成同一景物在CCD的不同像元上成像，产生像拖影及扭曲现象，导致了飞行分辨率的降低。虽然航空相机与载机平台之间安装有减震器，但是一般被动减振只能大幅抑制较高频率的扰动，对于低频扰动减振效果不明显，不能完全满足长焦距光学系统的隔振要求。针对图像拖影问题，本文分析像拖影产生原因并建立了数学模型，定量分析了像拖影对调制传递函数的影响。针对图像扭曲问题，建立了飞行速度、高度及目标水平倾角与俯仰轴补偿速度之间的几何模型，分析了外界扰动对图像扭曲的影响。通过模型建立和参数分析，得出了俯仰轴控制系统的动态和稳态性能指标及鲁棒性要求。针对正弦扰动构建了动态补偿器，得到扰动抑制控制律，并证明了最优扰动抑制控制器解的存在性。通过仿真试验，对没有干扰反馈的LQR法、具有干扰反馈的LQR法和动态反馈算法进行了对比，结果表明动态反馈算法对外部正弦扰动具有较强的抑制性，输出更加平稳。将飞机前向飞行引起的视轴运动补偿问题归结为近似最优输出跟踪问题，构建动态补偿器，求解矩阵方程得到近似最优控制律，通过仿真及部分试验，对状态反馈法、前馈-反馈法和动态反馈算法进行了对比，结果表明在外部正弦扰动的作用下，采用动态反馈算法，系统的输出干扰量最小。分析了空域-频域同步性对摆扫方向的像拖影和扭曲的影响。介绍了三种行转移信号产生的方法：1、基于光电轴角编码器细分抗微扰动法；2、基于希尔伯特黄变换的陀螺信号滤波抗扰法；3、结合光电轴角编码器及陀螺优化处理法。并分析了每种方法的适用性和抗干扰效果。当俯仰运动0.8°/s做0.2Hz低频正弦运动时，动态补偿反馈法使正弦信号干扰量对输出的标准差为0.0688°/s，相机分辨率为58.4lp/mm；在量级为2G(重力加速度)的振动环境下成像，采用动态补偿算法进行扰动抑制，俯仰轴上的速度残差为0.14°/s，相机分辨率为43.89lp/mm。振动台以0.5G量级微振动，基于编码器鲁棒设计的行转移信号发生器输出不受该量级的振动影响，相机分辨率为58.4lp/mm。振动台以2G量级振动后，该方法无法抑制干扰。振动台输入量级为2G时，基于希尔伯特-黄变换的行转移信号发生器使陀螺的输出波动范围大幅减小，峰峰值被削弱到0.12°/s，行转移信号的频率波动范围缩小到2KHz，稳速滤波效果非常的明显，相机分辨率为49.3lp/mm。采用优化行转移信号发生器法，提高了信号对外界振动的环境适应性、鲁棒性及实时性，图像上也不会出现压缩、拉伸现象及拖影现象。相机分辨率为55.2lp/mm。通过飞行试验验证，飞行海拔高度15863米，遥感图像可以分辨铁道枕木，(枕木间距约0.3m),航空遥感器的焦距为1.5m，其分辨率优于45lp/mm。本论文研究工作表明，论文提出的研究方法有效补偿干扰造成的图像拖影和扭曲现象，对于提高该相机成像质量具有重要的意义。
其他摘要	As one of new discipline developed in the 20th century, aerial imaging and measurement techniques are used to detect ground telemetry and scene information by airborne optical system and optical coupling device. It is used in pre-war and post-war military strike military reconnaissance assessment. The significance is very important for the development of our defense. The differences between spaceborne optical equipment and aerospace equipment are large aircraft maneuverability, flight vibration and attitude instability which cause remote sensor axis to sway. Axis can not point to a fixed target in the exposure time, and so the same scene image in different CCD pixels. That produces smear and distortion resulting in a lower flight resolution. Although shock absorbers are equipped between the aerial camera and carrier aircraft, generally the effect of passive damping is obvious for high-frequency disturbance, but unobvious for low-frequency disturbance. The isolation requirement of long focal length optical system cannot be meeted. For smear problem, this paper not only analyzes the causes of smear and builds a mathematical model, but also analyzes quantitatively the effects of smear on modulation transfer function. For distortion problem, this paper builds a mathematical model to indicate the relationship betweenlight speed, altitude, target angle and pitch axis compensation speed, and analyzes the effect of image distortion on the outside disturbance. The dynamic and steady-state performance indicators and the robust of pitch axis control system are educed from model establishment and parameter analysis. For sinusoidal disturbance, dynamic compensator is built and control law of disturbance rejection is got, then the optimal solution for the presence of disturbance rejection controller resistance is proved out. The law of LQR without interfere feedback, LQR with interfere feedback algorithm and dynamic feedback interference feedback are compared by simulation experiments. The results show that the dynamic feedback algorithm for external sinusoidal perturbation has a strong rubust. The issue of visual axis motion compensation comes down to the issue of approximate optimal output tracking. Dynamic compensator is built and control law of disturbance rejection is got by solving matrix. State feedback law, feedforward - feedback method and dynamic feedback algorithms were compared through simulation. The results show that external sinusoidal perturbation is minimal by the dynamic feedback algorithm. The effects of smear and distortion on synchronization of the space-time are analyzed in this paper. Three methods of line signal are introduced: 1. based on encoder subdivision method; 2. based on Hilbert-Huang Transform method; 3. encoders and gyro optimization method. The applicability of each method and interference effects are analyzed. When the pitch moves 0.8 ° / s, 0.2Hz sinusoidally, the dynamic compensation method depresses the standard output to 0.0688 ° / s by signal interference. The detector can distinguish 58.4lp/mm; When the camera image under the magnitude of the vibration input 2G, the dynamic compensation algorithm depresses the remains of pitch axis velocity to 0.14 ° / s. The detector can distinguish 43.89lp/mm. When vibration table vibrates 0.5G, the signal generator output of the robust of encoder is not the magnitude. The detector can distinguish 58.4lp/mm. When vibration table vibrates 2G, the method can not suppress interference. But under 2G vibrations, the output of gyro significantly reduces by Hilbert - Huang Transform, which weakens 0.12 ° / s. The transfer of the signal line frequency range narrows to 2 KHz. The filtering effect is very obvious. The detector can distinguish 49.3lp/mm. The optimized method improves the signal to external vibration environment adaptability, robustness, and real-time performance. It will not appear on the image compression, tension phenomenon and smear phenomenon. The detector can distinguish 55.2lp/mm. When flight altitude is 15,863 meters, railway sleepers ( ties spaced about 0.3m) can be distinguished by flight test. As the focal length is1.5m, the resolution is better than 45lp/mm. The work shows that the method in this paper compensates effectively the interference caused by image smear and distortion. It is important to improve the image quality of the camera.
语种	中文
文献类型	学位论文
条目标识符	http://ir.ciomp.ac.cn/handle/181722/41445
专题	中科院长春光机所知识产出
推荐引用方式 GB/T 7714	刘志明. 长焦距斜视航空相机图像拖影与扭曲补偿技术研究[D]. 中国科学院大学,2014.

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