【作者】 尹航；

【导师】 杨唐文；

【作者基本信息】 北京交通大学 ， 电子与通信工程（专业学位）， 2013， 硕士

【摘要】 柔性针软组织穿刺相互作用机理建模是机器人辅助穿刺系统及穿刺手术虚拟培训系统研究中的关键问题,开展相关理论与仿真研究具有重要的意义。本文主要完成了以下的研究工作：首先,基于Okamura刚性针穿刺受力分析方法,以软组织膜皮刺穿为界,将柔性针穿刺过程分为三个阶段,全面分析了穿刺过程中针的受力,并建立了穿刺力的分段模型。软组织膜皮刺穿前,采用了弹簧模型,推导针与软组织之间的相互作用。在膜皮刺穿后的模型中,摩擦力采用了改进的Karnopp公式。同时,利用欧拉-伯努利梁理论,推导了柔性针的挠曲变形模型。其次,利用约束Delaunay三角化算法,实现软组织与针的四面体网络划分,并以人体肝穿刺为例,利用有限元仿真工具SOFA,进行柔性针穿刺仿真,采集不同模型参数下穿刺力的仿真数据。然后,对仿真数据进行分析,建立柔性针软组织穿刺相互作用模型。鉴于软组织的非线性特性,提出用多项式建立膜皮刺穿前的模型。刺穿膜皮后,穿刺力具有周期性与波动性。这里,利用傅里叶变换,分别得到摩擦力与切割力的频谱特征,从中提取主要频谱,再经傅里叶逆变换,建立了柔性针刺穿膜皮后的穿刺力模型。对于柔性针的挠曲变形,则采用了三次多项式进行拟合。最后,对依据理论与仿真数据建立的穿刺相互作用模型,进行对比研究,以考察前面提出的穿刺作用建模方法的可行性。论文完成了柔性针软组织穿刺有限元仿真与相互作用建模。首先基于理论分析,建立了柔性针软组织穿刺力的分段模型,然后,与基于仿真数据建立的穿刺力模型进行了比较研究。论文工作将为进一步开展机器人辅助外科系统研究打下基础,具有重要意义。更多还原

【Abstract】 It is an important issue to model and simulate the interaction of flexible needle insertion into soft tissue, and the development of relevant theoretic and simulation work is significant for robot-assisted needle insertion systems and virtual reality simulators for needle insertion training. The work done in this thesis is given below.First, the forces of the flexible needle insertion into soft tissue are analyzed based on Okamura’s method for rigid needle. Flexible needle insertion process is divided into three phases, and force models are correspondingly derived. Stiffness force occurs before the penetration of the tissue capsule, and is computed with mass-spring model. Friction and cutting forces occur after the penetration. As the needle completely penetrates the soft tissue, there is only friction force left, and it is modeled with a modified Karnopp formulation. Simultaneously, the deformation of the flexible needle is computed using Euler-Bernoulli beam theory.Second, a generic tetrahedral method is proposed to mesh the flexible needle and soft tissue, based on constrained Delaunay triangulation algorithm. The finite element models of a flexible needle and a soft tissue (say liver from human being) are created through a biomedical simulation tool SOFA, and the interaction between the flexible needle and the liver is simulated, and interaction forces are acquired.Third, an interaction model of flexible needle insertion into soft tissue is obtained from the simulation force data. A polynomial formulation is used to model the stiffness force due to the nonlinear characteristics of needle-tissue interaction. Fourier transform is used to analyze the frequency spectrum of the force data obtained after capsule penetration, and the dominant frequencies are used to model the stiffness and cutting forces via inverse Fourier transform. A third-order polynomial is used to fit the deformation of the flexible needle.Finally, comparison study is made to the two sorts of interaction models respectively obtained from biomechanical theory and simulation data, and they are proved feasible to model the interaction of a flexible needle insertion into soft tissue.In this thesis, flexible needle-tissue interaction modeling and simulation are investigated. The outcome of this work will contribute significantly to robot-assisted surgery systems.更多还原