基于小肠力学本构模型的胶囊机器人动力学研究 | |
Alternative Title | Reaserch on Dynamics of the Capsule Robot based on the Mechanical Constitutive Model of Small Intest |
谭人嘉1,2 | |
Department | 机器人学研究室 |
Thesis Advisor | 王越超 ; 李洪谊 |
Classification | TP242 |
Keyword | 胶囊机器人 粘弹性本构 小肠 动力学 摩擦系数 |
Call Number | TP242/T18/2014 |
Pages | 95页 |
Degree Discipline | 模式识别与智能系统 |
Degree Name | 博士 |
2014-06-03 | |
Degree Grantor | 中国科学院沈阳自动化研究所 |
Place of Conferral | 沈阳 |
Abstract | 本研究拟通过建立动力学方程来刻画胶囊机器人在肠道中的运动，定量回答上述问题，为胶囊驱动器的优化设计提供理论基础。研究内容按思路划分，大致包括两大部分：第一部分是对小肠组织的材料力学行为的研究，包括通过实验确定粘弹性本构模型，和通过实验寻找小肠组织与胶囊外壳发生相对滑移的临界条件；第二部分是对胶囊与小肠之间的力学交互行为进行理论分析，包括胶囊的尺寸、外形与临界阻力的数量关系，以及胶囊启动过程中的动力学问题。第二部分研究结论的得出充分利用了第一部分的研究成果，而且这两部分的核心内容都是原创性的贡献。各项研究的具体内容及其间的内在联系如下： 首先是建立小肠的粘弹性本构模型。由于小肠对胶囊运动的阻力与时间相关，即小肠组织具有粘弹性，因此，本研究安排了两个实验对此进行研究。一是DMA(Dynamicas Machanical Analysis)测试，结果显示小肠的粘弹性具有非线性的特点。通过实验作出的应力-应变滞回曲线的倾斜角随应变幅度发生了变化，说明小肠在受迫作剪切振动时，其粘弹性非常复杂，仅用一组线性粘弹性参数无法刻画其粘弹性的全貌。二是应力松弛实验。为了得到可靠的实验数据，该实验经历了一次方案的改进，最终结果得到了空肠和回肠组织经受剪切加载时的五元件粘弹性模型参数表，这些参数被直接使用在后续研究的动力学计算中，确保研究结果具有现实的工程意义。应力松弛实验的结果同样显示了小肠组织具有非线性粘弹性。 其次是研究胶囊与肠壁之间发生滑移的临界条件。胶囊刚开始运动时，肠壁的剪切形变较小，胶囊外壳与肠壁之间仍然保持接触状态，而维持接触状态的原因是由于二者之间存在摩擦力。该摩擦力的最大值是确定两者发生相对运动的临界条件，而计算最大静摩擦力的关键是确定接触面上的静摩擦力系数。为了得到尽可能精确的结果，本研究先后安排了两个实验，分别独立地对静摩擦系数进行了测试。最终结果显示空肠和回肠的表面摩擦性质区别不大，去除肠液后，肠壁与聚碳酸酯材料之间的静摩擦系数大约为0.03。 上述实验的开展为关于胶囊机器人在肠道中的运动性能的研究提供了可靠的基础。随后，本文分别就胶囊机器人在准静态下的受力情况和启动过程中的动力学问题进行了深入研究。 理论上，胶囊机器人在一段确定的肠段中作准静态运动时，所受到的阻力由其外部形状和尺寸大小确定。本文提供了一种计算该阻力的严谨分析方法：首先采用Cialleta超弹模型，列出胶囊外壳各接触面上的环向应力分布表达式，然后将该应力对接触面积分，分别求解接触面上的张力和摩擦力，并将其相加得到总的阻力。结果显示，影响阻力的主要因素是胶囊长度与胶囊外径-小肠管内径之比，而胶囊头部的摩擦力对总阻力的贡献非常小，以至于可以忽略不计。这就为胶囊外形的优化设计提供了理论依据。 最后，通过建立动力学方程，对胶囊的启动问题进行了深入的研究。该方程中的应力项以前文所得的五元件粘弹性本构模型来表示，方程的成立范围以前期研究得到的滑移临界条件为判别标准。将动力学方程改写为状态方程之后，借助“速度-位移”相平面来观察胶囊的启动的方法，为研究带来了方便。考虑到粘弹性材料的加载历史对应力的影响，研究给出了迭代计算应力的方法。案例计算的结果显示了驱动力的大小和力脉冲宽度与胶囊启动加速过程之间的数量关系。应用该分析方法提出的安全控制的策略，同时也是能量最省的控制方案。 本研究所包含的内容，构成了关于胶囊机器人外形设计及运动能力之研究的完整系统。本文的研究方法和结论，初步回答了关于胶囊机器人驱动器的优化设计问题，具有较强的工程实践意义，其中，有关小肠组织的力学建模和器械交互摩擦系数的实验研究，本身也具有独立的科学探索价值。 |
Other Abstract | This study intends to give a quantitative explain of the above question, describe the capsule robot’s motion inside the intestine through establish the dynamic equation, and provide theoretical basis for the optimized design of the capsule robot. The research comprises two parts: the first part is the research on the material mechanical behavior of the intestine tissue, include the confirmation of the tissue viscoelasticity by experiments, and the exploration of the critical condition when the slip happens bewteen the capsule shell and the intestinal inner surface; the second part is the theretical analysis for the mechanial interation , include the quatitative relationship between the critical resistance and the shape and size of the capsule, and the dynamics of the capsule’s start. The second part makes use of the results of the first part, and the conclusions of the two parts are both original. The specific contents of the researches and their inner relation are as follows: First, the small intestine’s viscoelastic constitutive model is established. As the intestinal resistance to the capsule’s movement is time dependent, that is the intestinal tissue is of viscoelasticity, two experiments are arranged for the research of the viscoelasticity. One is the DMA (Dynamicas Machanical Analysis) test, and the result demonstrated the nonlinear viscoelasticity of the small intestine. The incline degree of the experiment-original stress-strain hysteresis curves changes as the strain magnitude, and that demonstrats that the viscoelasticity of the intestinal tissue is so complicated that only one set of parameters cannot describe the viscoelasticity in linear theroy. Another one is the stress relaxation experiment. In order to obtain reliable data, the experiment was improved in design, and finally the parameter tables of the five-element viscoelastic model were concluded, which were obtaind by regression of the shear load for jejunum and ileum respectively, and the parameters were used in the subsequent dynamical calcultion, ensuring the results are engineering significance. The results of the stress relaxation experiments have also shown the nonlinear viscoelasticity in the intestinal tissue. Second, the critical condition of silp between the capsule and the intestinal wall is researched. At the initial stage of the capsule’s motion, the shear deformation of the intestinal wall is small, so the capsule shell and intestinal wall remain in contact, and the friction is the cause that the contact can be kept. The maximum value of the friction is right the critical condition which confirms the slip happens in between, and the key point for the calculation of the maximum static friction is the confirmation of the static frictional coefficient. In order to obtain accurate results as possible as much, two experiments were arranged in the study, which tested the static frictional coefficient independently. The final result demonstrates that for the frictional property of surfaces, there is no significant difference between jejunum and ileum, and the coefficient of static friction between intestinal wall and polycarbonate is about 0.03. with the intestinal juice removed out. The experiments above provide reliable foundation for the study on the motion performance of capsule robots in the intestine. Then, the paper conducted deep researches, respectively on the resistance of the capsule robot’s motion under quasi-static condition and the dynamics of the capsule’s start progress. Theoretically, the resistance is determined by the shape and size of the capsule, when the capsule robot moves in quasi-static way, inside a certain segment of intestine tube. This paper provides a rigorous analysis method for calculating the resistance: first, Cialetta’s hyperelastic model was applied, and the expression of the hoop stress on various region of the contact surface was provided, then the integration about the hoop stress were conducted around the contact surface, and the tension and the friction on the contact surface were calculated respectively, and the total resistance was obtained by addtion. The results display that the main factor that affects the resistance is the capsule length and the ratio of the external diameter of the capsule and the inner diameter of the intestine tube ratio, and the friction from the capsule’s head part accounts for a very small propotion in the total resistance, so the friction can be neglected. This provides a theoretical basis for the design of the capsule’s shape. At last, a deep research on the start progress of the capsule’s motion was conducted through establishing the dynamic equation. The stress item in the equation was discribed with the five-element viscoelastic model mentiond above, and the effective region of the equation was judged by the critical condition which was obtaind in former research. The meathod of observing capsule’s start progress through “velocity-displacement”phase is a convenient meathod, which is plotted after rewriting the dynamic equation into the formulation of state equation. Considering the impact of load history of the viscoelastic material on the stress, the research provided an iterative method to calculate the stress. The results of the calculation display the quatitative relationship between the acceleration of the start progress and the magnitude of the drive force, along with its pulse width. The safe control strategy, which is proposed based on the analytical methods, is also the minimum energy control strategy. The content included in this study constitutes a complete system of the research on the design of the capsule robot’s shape and its motion capacity. The research method and conclusions of this paper provide a preliminary answer about the question of optimal design of the capsule robot’s driver, and the practical significance is important. The experimental studies on intestinal tissue’s mechanical modelling and on the frictional coefficient of instrument-tissue intraction are with independent scientific value. |
Language | 中文 |
Contribution Rank | 1 |
Document Type | 学位论文 |
Identifier | http://ir.sia.cn/handle/173321/14836 |
Collection | 机器人学研究室 |
Affiliation | 1.中国科学院沈阳自动化研究所 2.中国科学院大学 |
Recommended Citation GB/T 7714 | 谭人嘉. 基于小肠力学本构模型的胶囊机器人动力学研究[D]. 沈阳. 中国科学院沈阳自动化研究所,2014. |
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