面向胶囊机器人驱动原理的小肠环境摩擦模型研究

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题名	面向胶囊机器人驱动原理的小肠环境摩擦模型研究
作者	张诚
学位类别	博士
答辩日期	2013-11-20
授予单位	中国科学院沈阳自动化研究所
导师	李洪谊
关键词	冲击式胶囊机器人小肠交互摩擦模型 “内力-摩擦”驱动原理非线性粘弹性本构
其他题名	Friction Model of Intestinal Environment for the Drive Principle of the Capsule Robot
学位专业	模式识别与智能系统
中文摘要	目前，在世界范围内胃肠道疾病发病率处于上升趋势，对于胃肠道疾病的诊断和治疗，胶囊内窥镜在减轻患者检查痛苦方面相比于传统内窥镜具有显著优势，然而被动式的胶囊内窥镜尚存在漏检、耗时等缺陷，因此研究具有自主运动能力的胶囊机器人是国际医疗器械研究的前沿和重点之一。本研究在国家高技术研究发展计划的资助下，基于机械电子原理、微加工和微驱动方法、材料学理论、生物力学理论及临床医学实验方法，开展了胶囊机器人驱动原理及与小肠交互摩擦特性研究。本文研制了一种新颖的冲击式胶囊机器人，利用“内力-摩擦”式驱动原理，该胶囊机器人可以实现单自由度前后运动，由于驱动器无爪、轮等外部机构，因此具有较高的安全性。驱动器基于音圈电机的原理进行设计，选择钕铁硼材料作为永磁体，根据体积及功耗的限制制定尺寸参数，并通过计算优化参数信息。根据运动学分析结果和仿真分析结果，研制了三款驱动原理样机，并制作了驱动电路。二代样机直径8mm，长30mm，在硬质平面上的平均速度可达45.8mm/s；三代样机可实现在剖开小肠表面以3.6mm/s的平均速度运动。为了模拟胶囊机器人在不同速度下的运动状态，测得其在小肠内运动时受到的摩擦阻力，本文设计并搭建了低速和高速两种物理仿真平台，低速实验平台在牺牲输出力和运动速度的前提下加强了低速运动的稳定性，而高速实验平台更加注重于输出力和冲击速度，另外为了测得小肠在胶囊振动情况下特殊的材料力学特性我们选用DMA测试平台开展实验研究。在标准化小肠样本制备流程后，我们通过实验发现在冲击条件下随着胶囊直径增大，受到的摩擦阻力也随之增大，而胶囊质量对摩擦阻力的影响不十分显著；通过详细的实验分析发现胶囊运动速度增大则摩擦阻力也随之增大，但在速度约20mm/s处出现阶跃变化。利用真空负压吸附夹具测得胶囊模型与小肠之间的滑动摩擦系数，约为0.082。在分析小肠材料力学性质的基础上，本文建立了胶囊机器人与小肠之间的交互摩擦模型。首先明确了小肠的形态及结构特征，以现有的五元件线性粘弹性模型为基础分析小肠材料的力学性质，我们发现传统的线性粘弹性本构不能合理描述小肠材料的蠕变和松弛特征，通过分析实验结果对五元件线性粘弹性模型进行优化，建立了非线性的粘弹性模型。利用DMA实验机分析小肠材料对于不同频率应变的响应，进一步完善了小肠材料模型，并发现小肠材料沿轴向自由振动过程表现为过阻尼振动。结合小肠材料性质，建立了胶囊机器人在不同速度下与小肠的交互摩擦模型，胶囊机器人启停阶段与小肠的交互摩擦模型及胶囊机器人匀速运动时与小肠的交互摩擦模型。胶囊机器人在小肠内受到的摩擦阻力包括环境阻力、粘滞摩擦力和库伦摩擦力，其中环境阻力所占比重最大且受到速度影响也最大。摩擦阻力与速度的关系近似于对数曲线，但是在速度约20mm/s时，摩擦阻力会发生阶跃变化，其原因主要是胶囊机器人较快的冲击速度使小肠材料的力学性质发生改变。胶囊机器人启停阶段受到的摩擦阻力与匀速运动阶段完全不同，本文从摩擦阻力变化的持续时间、变化趋势及初始状态三个方面进行分析，根据实验结果拟合得到启停阶段摩擦阻力变化的解析表达式。胶囊机器人匀速运动时受到的摩擦阻力是类正弦的波动曲线，本文基于小肠材料的超弹性模型建立了改状态下的交互摩擦模型，通过仿真分析验证了该模型的有效性。交互摩擦模型的建立是对胶囊机器人在小肠内运动受力情况的定量描述，有助于胶囊机器人驱动方式的研究和控制方法的优化，特别是对启停和匀速阶段摩擦阻力细微变化的分析将使胶囊机器人在小肠内具有更平稳的运动状态并更有效的节约能源。由于基于“内力-摩擦”驱动原理的冲击式胶囊机器人在小肠内运动效率不高，在详细研究胶囊机器人和小肠交互摩擦特性的基础上，对冲击式胶囊机器人的驱动原理进行了优化。首先在保持现有胶囊机器人驱动器结构不变的前提下，提出一种“秋千”式驱动原理，该驱动方式利用小肠的形变能的储存来增大胶囊机器人在小肠内振动的幅度，从而使胶囊机器人一个运动周期内的位移大于小肠的伸长量，达到运动的目的。此外，从理论层面提出了一种新型的冲击式胶囊机器人驱动模式，并对其进行了运动学分析。利用本文提出的胶囊机器人匀速运动阶段与小肠的交互摩擦模型，通过控制驱动力均值的阶跃变化，可实现胶囊机器人在小肠内的平稳匀速运动。本文对胶囊机器人的驱动原理、驱动器设计、小肠材料力学实验、小肠环境摩擦模型建立、动物实验等方面进行了深入的研究。这些工作为胶囊机器人系统临床化奠定了基础，建立适用于胶囊机器人的消化道环境模型及对现有驱动原理的优化是下一步的研究方向。
索取号	TP242/Z31/2013
英文摘要	For the moment, the morbidity of the gastrointestinal disease is increasing in the worldwide. Capsule endoscopy has advantages over the traditional endoscopy in the way of easing the pain of the patient when the patient receives testing and treatments of gastrointestinal disease. However, the passive capsule endoscopy has some defects, such as missing inspection, time-consuming and so on. So the active capsule robot with independent movement ability will be one of the scientific frontier and research emphasis in the research of medical apparatus and instruments. Based on the principle of machinery and electronics, micro machining and micro driver, materials science, biomechanics and clinical/medical laboratory science, the research of the drive principle of the capsule robot and the interactive friction characteristics are carried out under the support of the National High Technology Research and Development Program ("863" Program) of China. A novel vibro-impact capsule robot was developed based on “internal force-static friction” drive principle. The capsule robot could move forward and backward and had good security performance because it had no external structure, such as claws or wheels. The actuator was designed based on the principle of voice coil motor. The rare earth (NdFeB) was chosen as the material of the permanent magnet. The dimension parameters of the actuator were decided by the constraint of volume and power consumption and optimized by calculation. Three types of prototypes and drive circuit were developed according to the results of kinematics analysis and simulated analysis. The diameter and length of the secondary generation prototype was 8mm and 30mm, respectively. Its average velocity on a hard surface could reach up to 45.8mm/s. The third generation prototype could move on an open intestinal surface at a speed of 3.6mm/s. Two types of physical simulation platforms were set up for the use of simulating the motion of the capsule robot at different velocities. The frictional resistance of the capsule could also be measured with these platforms. The lower-speed platform had a low speed stability at the expense of output force and speed, while the higher-speed platform made up for the faults of the former. In addition, we used DMA apparatus to measure the material mechanics property of the intestine in the condition of vibration. After the process of standardized preparation of intestine, the following conclusions were obtained from experimental results. The friction of smooth cylindrical capsule is smaller than other shapes. The influence of the capsule’s length on the friction is greater than that of the diameter. Capsule’s quality has no significant effect on the friction. The friction goes up with the velocity increasing, but a step change occurs at the velocity of about 20mm/s. The coefficient of sliding friction between the capsule and the intestine was measured to be about 0.082 with a negative pressure suction fixture. The interaction friction model is established based on the analysis of the material mechanics property of the intestine. After the analysis of the morphological and structural features, the material mechanics property of the intestine is described by five-element viscoelastic constitutive. I found that the traditional linear viscoelastic model could not describe the creep and relaxation characteristics of the intestinal material reasonably. The five-element model was optimized to be nonlinear viscoelastic constitutive with experimental results. The response of the intestinal material to different frequencies and strains was obtained with DMA apparatus. The model of intestinal material were perfected further. The free vibration of the intestinal material in the longitudinal direction was shown as a damped oscillation. Three interaction friction models are established based on the material mechanics property of the intestine. They are velocity-dependent frictional resistance model, frictional resistance model in the start-stop phase and that at a constant velocity. The frictional resistance consists of environmental resistance, viscous friction and Coulomb friction when the capsule robot moves in the intestine. The environmental resistance has the environmental resistance and affected most severely by the velocity. The relation between the frictional resistance and the velocity can be seen as frictional resistance approximately. However, a step change of the frictional resistance occurs when the velocity is about 20mm/s. The main reason is that the higher impact speed makes the material mechanics property of the intestine change. The frictional resistance in the start-stop phase is different from that in the uniform motion. The frictional resistance model in the start-stop phase is established with the analysis of duration, variation trend and initial state. The analytic expression of the model is obtained from the results of experiment data processing. The frictional resistance in the uniform motion can be seen as a sine curve. The model at a constant velocity is established based on the hyperelastic model of the intestinal material. The validity of the model is verified by a simulated analysis. The interaction friction models are quantitative description of the friction of the capsule robot in the intestine. They are useful to the optimization of the drive principle and the control strategy of the capsule robot. Especially, the analysis of the frictional resistance in the start-stop phase can make the capsule robot move in the intestine more smoothly and save more energy. The drive principle is optimized based on the interaction friction characteristic between the capsule robot and the intestine because of the poor efficiency of the vibro-impact capsule robot with “internal force-static friction” drive principle in the intestine. A “swing” drive principle is proposed on the premise that the structure of the capsule robot’s actuator is unchanged. The principle aims at increasing the amplitude of the capsule robot in the intestine with the storage of the intestinal deformation energy. Then the displacement of the capsule robot in one period is larger than the extension of the intestine. In addition, a novel drive mode of vibro-impact capsule robot is developed and kinematics analysis is carried out. The capsule robot with the new drive mode can move smoothly in the intestine by the step change of the drive force based on the interaction friction model. The drive principle and actuator design of the capsule robot, mechanics experiment of the intestinal material, interaction frictional model of the intestinal environment, animal experiment were studied thoroughly in the paper. They will lay a foundation for the clinic application of the capsule robot. Full gastrointestinal model for the capsule robot and the drive principle optimization should be studied in the future.
语种	中文
产权排序	1
页码	95页
分类号	TP242
内容类型	学位论文
源URL	[http://ir.sia.ac.cn/handle/173321/14841]
专题	沈阳自动化研究所_机器人学研究室
推荐引用方式 GB/T 7714	张诚. 面向胶囊机器人驱动原理的小肠环境摩擦模型研究[D]. 中国科学院沈阳自动化研究所. 2013.