基于视觉伺服的柔性组织操控技术研究

发布时间：2018-05-09 13:57

本文选题：柔性组织变形 + 柔性针穿刺　；参考：《哈尔滨工业大学》2015年硕士论文

【摘要】：经皮穿刺术是微创介入手术中一种重要的方法。传统的经皮穿刺术使用刚性针作为穿刺工具,但刚性针通常难以满足穿刺过程中的避障要求,由此产生斜角柔性针。尽管柔性针轨迹十分灵活,但大曲率圆弧轨迹易造成人体组织撕裂,且针尖反复转向产生的直线轨迹会造成组织挫伤。本文针对此问题,对柔性组织操控技术进行研究,通过控制柔性组织变形使穿刺目标靶点发生偏移,从而简化穿刺轨迹并降低伤害。通常的柔性体变形控制方法要先对柔性体建模,这需要大量变形参数,而人体组织通常是无先验知识目标。对此,本文使用基于无标定视觉伺服的柔性组织控制理论估计变形模型并进行变形控制:通过对包含未知的柔性组织变形特征及摄像机投影模型的变形雅克比矩阵进行估计,得到系统的预估雅克比矩阵,并由预估矩阵通过速度控制器生成系统的变形控制速度使柔性组织变形,通过视觉检测出实际变形特征与理论变形特征的误差,反馈给估计器来修正预估雅克比矩阵。本文由李雅普诺夫第二法验证算法的稳定性,并通过仿真实验分析算法各项指标。本课题提出了针对柔性针穿刺的柔性组织变形控制方案。本文通过对柔性针进行轨迹规划,逆向推导出柔性组织靶点位移从而变形控制方案。柔性针穿刺轨迹种类较多,为解决平面的变形控制问题,本文对均匀组织中的平面圆弧穿刺轨迹进行分析,提出复数障碍物约束条件下的轨迹求解方案,并建立评价函数来对穿刺轨迹进行分级。考虑到这是一个多目标优化问题,本文使用改进的NSGA2遗传算法求解,通过种群最优面对于评价函数进行修正,并最终通过权重系数将多目标合成为单一评价函数并得到最优穿刺轨迹,从而确立柔性组织变形控制方案。最后,本文对现有的图像处理方法进行分析比较,使用Open CV实现目标检测与跟踪,并编写了变形控制的软件平台,包括视觉系统、机器人系统、控制系统等。本文提出的变形控制分为两部分:一是根据具体环境,通过轨迹优化求得目标靶点位移方案,二是通过变形控制系统控制柔性材料达到预定变形目标。通过对实验数据进行分析,进一步检验控制理论,并验证变形控制系统的可行性。
[Abstract]:Percutaneous puncture is an important method in minimally invasive interventional surgery. The traditional percutaneous puncture uses rigid needle as puncture tool, but rigid needle is usually difficult to meet the requirements of obstacle avoidance in the process of puncture, resulting in oblique flexible needle. Although the flexible needle trajectory is very flexible, the arc trajectory with large curvature can easily lead to the tear of human tissue, and the straight line track caused by the repeated turning of the needle will cause tissue contusion. Aiming at this problem, this paper studies the flexible tissue manipulation technology, which makes the target deviation by controlling the deformation of the flexible tissue, thus simplifies the puncture trajectory and reduces the injury. The common deformation control method of flexible body is to model the flexible body first, which requires a large number of deformation parameters, while human tissue is usually no prior knowledge of the target. In this paper, the theory of flexible organization control based on uncalibrated visual servo is used to estimate the deformation model and control the deformation. The prediction Jacobian matrix of the system is obtained, and the deformation control speed of the system is generated by the predictive matrix through the velocity controller. The errors between the actual deformation characteristics and the theoretical deformation characteristics are detected by vision. Feedback is given to the estimator to modify the estimated Jacobian matrix. In this paper, the stability of the algorithm is verified by Lyapunov's second method, and the indexes of the algorithm are analyzed by simulation experiments. In this paper, a flexible tissue deformation control scheme for flexible needle puncture is proposed. In this paper, the target displacement of flexible tissue is derived by trajectory planning of flexible needle, and the deformation control scheme is derived. There are many kinds of flexible needle puncture trajectory. In order to solve the problem of plane deformation control, this paper analyzes the plane arc puncture trajectory in uniform organization, and puts forward the trajectory solution scheme under the condition of complex obstacle constraint. An evaluation function was established to grade the puncture track. Considering that this is a multi-objective optimization problem, an improved NSGA2 genetic algorithm is used to solve the problem. Finally, the multi-objective is synthesized into a single evaluation function through the weight coefficient, and the optimal puncture trajectory is obtained, thus the flexible tissue deformation control scheme is established. Finally, this paper analyzes and compares the existing image processing methods, uses Open CV to realize target detection and tracking, and compiles the software platform of deformation control, including vision system, robot system, control system and so on. The deformation control proposed in this paper is divided into two parts: one is to obtain the target target displacement scheme by trajectory optimization according to the specific environment, and the other is to control the flexible material to achieve the predetermined deformation target through the deformation control system. Through the analysis of experimental data, the control theory is further tested and the feasibility of deformation control system is verified.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：R616;TP273

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