【作者】 易新华；

【导师】 钱晋武；

【作者基本信息】 上海大学 ， 机械电子工程， 2008， 博士

【摘要】 由于工作环境的复杂性和自身形状不可视等缺点,结肠内窥镜在介入过程中会发生镜体缠绕、非预期结襻等情况,给病人带来痛苦和危险。因此,用智能传感器技术、可视化技术对传统内窥镜系统进行改进并实现其形状显示和手柄部的姿态检测是急需解决的。基于光纤光栅传感理论,本文对光纤光栅传感阵列的设计、封装方法进行了分析,并对内窥镜柔性杆形状重建方法进行了研究。考虑到光纤光栅波长的变化受温度和应变两个参数的影响,通过传感阵列的设计来消除温度对形状重建的影响。在形状重建算法上,利用柔性杆上检测到的光栅点的应变信息,推导从平面曲线到空间曲线的重建方法,并通过仿真实验和实物实验进行对比分析,验证了算法的可行性。由于传感器实际封装位置与理论位置存在差异,为了精确重构内窥镜的形状和测得每个传感点相对于内窥镜手柄部的位置,对传感器的每个检测点进行了修正,修正后的重建结果相对于前期研究有了很大的提高。考虑到柔性杆曲线形状的多样性,提出了两检测点之间的空间曲率的非线性拟合方法—逐次中值分隔算法,从与线性分隔方法对比分析可以看出,重建精度得到了提高。由于基于光纤光栅的柔性杆形状重建方法是假定内窥镜手柄部在固定条件下重建的,而在实际的应用中,手柄是医生用来对柔性杆前端进行定位操作和进镜用的,因此,手柄姿态的变化会影响整个内窥镜柔性杆空间姿态的变化,为此提出了利用双目视觉及外加标志点的方法对端部姿态进行检测,并深入的探讨了检测误差对整个形状的影响。在内窥镜手柄部分的位姿检测方面,主要从视觉系统的构建,标志点的设计入手,对摄像机的标定、坐标系的建立作了详细的分析与论述,建立了同时对两摄像机进行标定来推导两摄像机位姿关系的方法。为了提高视觉跟踪速度及姿态检测的实时性,在Rosenfeld的邻域标记算法基础上,提出了一种快速的邻域标记算法来提取标志点在图像中的中心位置,该方法比较原始的邻域标记算法在检测速度上得到了很大的提高。利用图像点及摄像机的标定参数求解空间点的位置,是根据两摄像机之间的位姿关系,把图像点在左右摄像机坐标系下的坐标值转化为同一坐标系下的坐标值,从而简化了空间点的求解问题。空间点的精确度由于受诸多因素的影响,得到的每个标志点相对于全局坐标系的坐标值是有误差的,这种误差对内窥镜手柄姿态的影响非常大。本文从姿态的求解开始分析,对目前常用的求解方法进行了分析和总结,提出了基于主元分析法与最小二乘法的位姿估计方法。在内窥镜显形系统集成实验中,分别探讨了内窥镜端部的仰俯、偏转和横滚对内窥镜柔性杆形状、姿态的影响分析及内窥镜端部柔性杆形状的修正问题。本文在Windows XP平台上采用VC++.NET平台开发了一套实验系统,该显形系统能够满足实验测试的需要。实验结果表明该系统能够在内窥镜手柄部姿态检测的基础上实时显示内窥镜镜体的形状。更多还原

【Abstract】 Loop formation of colonoscope often happens in diagnosis of colon because of complexity of working condition and non-visualization of shape of flexible rod and it brings a great pain and danger to the patient. So it is necessary to use intelligent sensor and visualization technique to innovate performance of traditional colonoscope and realize shape display of flexible rod and pose detetion of handling part of colonoscope.Shape reconstruction theory, design and packing method of flexible rod based on Fiber Brag Grating sensing theory was adopted in this paper. Considering shift of wavelength was affected by temperature and strain, it is necessary to compensate temperature by using layout of FBG sensor array. The shape reconstruction algorithm based on strain information about flexible rod was derived from plannar curve to spatial curve, simulation experiment and real experiment has demonstrated that it is feasible. Because actual packing position of FBG point isn’t consitent with ideal packing position, good accuracy of shape reconstruction of flexible rod was obtained by rectifing packing position of FBGs.Considering multiformity of flexible rod, nonlinear fitting method named median segment algorithm was proposed to solve the curvature between two FBGs. Experiment results shows that accuracy of reconstruction was improved comparing with linear fitting method.However, shape reconstruction of colonoscope is on the assumption that handling part of colonoscope is fastened, but in actual manipulation it is used to advance into the body and control direction of tip and orientation of handling part of colonoscope, so it would change the shape and orientation of colonosope. In this paper a detecting method was proposed to detect the orientation of handling part of colonosope based on binocular vision of markers and estimate the detection error how to affect shape of colonoscope was discussed deeply.For pose detection of handling part of colonoscope, this research mainly describes visual-tracking principle, layout of markers, camera calibration and setting up of coordination sytem. A method was proposed about solving the pose relation between two cameras. To improve the tracking speed, a fast Connected Components Labeling (CCL) algorithm based on Rosenfeld’s method was proposed and the speed about extracting the markers was impoved greatly. Using markers in image coordinates system, calibration parameters of two cameras and the pose relation about two cameras, image points about two cameras in left and right coordinate system can be converted into the same coordinate system, so solving of the spatial point can be simplified.Because many factors have an effect on accuracy of spatial point, position of markers relative to global coordinate system has an error which will degrade the pose accuracy relative to global coordinate system. This paper describes traditional solving method and proposes a method about pose estimation and error propagation based on principal component analysis and least square method.In the integration display system of colonoscope, this paper discuss the pitch, yaw and roll of handling part how to affect shape and pose of flexible rod. It is solved that how to rectify the flexible rod shape when pose of handling part of colonoscope is changing.An experimental system has been written using VC++.NET developing platform in Windows XP operation system. The experimental result indicates that the system can realize shape real time display of flexible rod on the basis of pose detetion of handling part of colonoscope.更多还原