【作者】 叶东东；

【导师】 颜国正；

【作者基本信息】 上海交通大学 ， 精密仪器及机械， 2009， 博士

【摘要】 目前,国内外对胃肠道疾病的诊断和治疗主要采用胃肠道内窥镜。因此,研究机器人系统来诊查胃肠道疾病是国际生物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,利用微加工技术、微驱动技术、微电子技术、无线通信和能量传输技术以及临床医学技术,开展了胃肠道微型仿生机器人诊查系统及运动相容性研究。在对人体胃肠道的生理特征进行详细分析的基础上,研制成胃肠道微型仿生机器人诊查系统。组装完成的第一代胃肠道诊查微型机器人样机实现了无缆化要求,其外径12.1mm,长165.5mm。由1个头舱、3个驱动单元、1个尾舱共五个运动单元组成,可以实现前进、后退、停止等功能。位于头舱中的视频摄像模块采集到的胃肠道内部图像经无线通信模块发送至体外,视频传输约3帧/秒,功耗约120mW。无线能量接收模块为机器人的各个部分提供能量。第二代全覆膜式胃肠道诊查微型机器人样机在第一代样机的基础上研制而成。硅胶波纹管覆盖在整个机器人样机的外表,在保护机器人的同时减少了胃肠道黏弹性对机器人运动的负面影响。利用电磁耦合原理设计并研制了无线能量传输系统。这种无线能量传输方式需要两个线圈。其中发射线圈为螺线管线圈,布置在人体表面,由E类放大器或开关电路驱动。接收线圈安放于机器人的头舱。为提高无线能量传输电路的电磁耦合能效,发射和接收回路均采用谐振补偿技术,即在发射和接收回路串联或者并联谐振电容。通过调节谐振电容使发射端谐振,产生一定频率的正弦波激励电流,形成一个交变磁场。此时,处于交变磁场中的接收端线圈感生电动势。经过后续整流稳压电路,转换成直流电压为胃肠道诊查微型机器人提供稳定能量。在将无线能量传输系统应用于胃肠道微型仿生机器人诊查系统的同时,人体也将暴露于无线能量传输系统的电磁场当中。为此,建立了一个有限长密绕螺线管电磁场模型,推导了电场强度和生物组织中SAR值以及电流密度值之间的关系。并进行了SAR值和电流密度值的仿真试验。结果表明,供能480mW、工作频率36 kHz的无线能量传输系统对人体的电磁影响非常小,属安全范围内。研制成基于直流电动机的微型直线驱动器,具有体积小、体重轻、功重比高、控制简单等优点。考虑到系统的稳定性,建立了微型直线驱动器的有限元模型,根据有限元模态分析结果设计并优化了微型直线驱动器,避免了系统共振的产生。并建立了该微型直线驱动器的数学模型,进行了动力学分析。仿真和试验表明,该微型直线驱动器的阶跃响应时间短,受负载变化影响小,在额定电压工作时驱动力达可到2.55N,温升在36℃以下。该研究为胃肠道诊查微型机器人在人体胃肠道运行的安全性和可行性提供了保障。研究了胃肠道生物组织的黏弹性力学行为,提出了一般三维情况的准线性黏弹性模型。引入了拟应变能函数的指数形式,并利用最小平方的方法拟合试验曲线得到了待定的材料常数C1和C2。为了得到最低阶应变,利用应变能函数指数的二次方程形式推导出了黏弹性体的一般表达式。对于单轴拉伸试验系统,推导了黏弹性体一般表达式中各个部分的具体形式,并引用了fung的连续谱归一化松弛函数表达式,将准线性黏弹性模型简化成一维模型。利用一维黏弹性简化模型,结合两个模拟肠道应变情况的应变变形函数,求出了黏弹性组织变形时的应力-时间关系和应变-应力关系,并分析了不同参数的松弛函数对模型的影响。在机器人的运动时效性分析中,得到了在一定的应变率范围内,加载时应力响应对加载速度的不敏感性这一重要结论。从牵引效率的角度出发,分析了机器人临界步距和机器人的质量、摩擦系数、直径、初始接触长度之间的关系,得到了胃肠道诊查微型机器人运动单元需要具有较轻的重量、光滑的表面和较大的直径以及较小的接触长度的结论。根据这些结论研制成的全覆膜式胃肠道诊查微型机器人的理论临界步距由原先的6.45mm减小到了1.6mm。机器人外表覆盖的波纹管能够起到减黏降阻的作用,是依据仿生学的原理设计并加工制造。通过测试波纹管变形-力之间的关系,发现波纹管产生的弹性力最大不会超过0.12N,很容易被微型直线驱动器所克服。当微型直线驱动器伸长时,波纹管因自身的弹性恢复功能,将会助推动微型直线驱动器的挡板做伸长运动。研究比较了本文研制的两种胃肠道诊查机器人样机的牵引力、运动性能和离体肠道试验结果。通过牵引力和运动性能试验,分别测量了两种机器人在不同环境中的牵引力和运动速度,验证了机器人的运动模型和驱动原理。进行了离体肠道爬行试验,进一步验证了机器人模型,并对比了这两种机器人离体试验结果,发现将硅胶波纹管应用于胃肠道诊查机器人之后,机器人的运动效率得到了明显的提高。本文对胃肠道微型仿生机器人诊查系统的样机集成、无线能量传输、驱动技术、模型建立和离体试验等方面进行了深入的研究。这些工作为机器人诊查系统的实用化奠定了基础,系统的进一步能量供应优化和机构优化等是下一步的研究方向。更多还原

【Abstract】 At the present day, the diagnose and therapy of the diseases of the gastrointestinal tract mainly depend on the means of gastrointestinal endoscopes. Therefore, the research on the gastrointestinal robotic examination system is the fornter and central issue in the international medical apparatus and instruments fields. Based on the micro machining technology, micro actuation technology, microelectrionics technology, wireless communication technology, wireless power transfer technology and clinical medical technology, this study focused on the system design and the locomotion compatibility of a miniature biomimetic robotic examination system for gastrointestinal tract under the support of the National High Technology Development Program.A miniature biomimetic robotic examination system for gastrointestinal tract was developed based on the detailed analysis of the physiological characteristics of human gastrointestinal tract. The first assembled miniature robotic prototype for gastrointestinal examination achieved the characteristics of being wireless. It’s outer dimension is 12.1mm in diameter and 165.5mm in length and comprised one head cabin, three driver units and one tail cabin. The robot may execute instructions including forwards, backwards and halt. The images of the inner gastrointestinal tract collected by the video camera module were transmitted to the outside by the wireless communication module. The image streams at rate of 3 frames per second with power consumption of 120mW. The wireless power receiving module supported each part of the robot with energy. The second whole tectorial membrane miniature robotic prototype was developed based on the first robotic prototype, The silicone bellows were laid over the whole robotic prototype. It reduced negative influence of the gastrointestinal viscoelastic behavior and protected the robot at the same time.The wireless transfer systerm was developed using the electromagnetic coupling principle. This power transfer means needed two coils. The launching coil was a solenoid, which was drived by the E class amplifier or switch circuit, and would surround the human trunk. The receiving coil was embedded in the the robot. For a power-efficient realization of an inductive link, the resonance compensation technology was adopted. That is to say, the inductance at the launching and receiving side were commonly cancelled by a parallel-resonant or series-resonant capacitor. The sine exciting current with a certain frequency, which was produced by the resonant lauching coil through adjusting the resonant capacitor, generated a alternating magnetic field. Here, the inductive electromotive force was produced in the receiving coil located in the alternating magnetic field. Through the following commutation and voltage regulation circuit, the inductive electromotive force was transformed to be direct voltage which would support the robot with steady power. At the time of applying the wireless power transfer system to the miniature biomimetic robotic examination system for gastrointestinal tract, the human would exposed to the electromagnetic field. Therefore, the limited close-wound solenoid electromagnetic model was build, the relationships between the electric intensity and the specific absorption rate and current density were deduced and the simulation experiments was done. Experimental results showed that the values of the SAR and the current density related to different tissue catalogs were all very small and not exceed their own limits, respectively, when the supplying power was 480mW and the resonance frequency of operation was 36 kHz.A miniature linear actuator based on the direct current motor was deceloped. It had many advantages such as small volume, light weight, high power-weigth ratio and easy control, etc. Finite element model of the miniature linear actuator was built for optimizing the linear actuator to avoid the sympathetic vibration of system. The mathematics model was also built to the analysis of the dynamics of the miniature linear actuator. The simulation and experimental results showed that the step response of miniature linear actuator was short and the infection of load was small. The driving force of miniature linear actuator could reach to 2.55N and the temperature rise was under 36℃. This research had laid a theory foundation for the motion security and feasibility of the miniature robot in the human intestines lumens.The viscoelastic mechanical behaviors of the gastrointestinal biological tissues were studied and the general three dimension quasi-linear viscoelastic model was introduced. The exponential format of the pseudo-strain energy function was used and the material constants C1 and C2 were determined by using the least-square method to fit the experimental curve. To achieve the lowest order of the strains, the general expression of the viscoelastic bodies was deduced by using the quadratic equation of the exponential format of the pseudo-strain energy function. For a uniaxial extension system, the concrete form of the the general expression of the viscoelastic bodies was deduced and the reduced relaxation function with a continuous spectrum of Fung was cited to reduce the quasi-linear viscoelastic model to be one dimension model. The relationships of the stress-time and the stress–strain of the deforming viscoelastic tissues were solved by using the one dimension quasi-linear viscoelastic model and two deformation functions which simulated the strain of the intestine. The influence by the relaxation function with the different parameters to the model was analyzed. In the analysis of the time-availability, an important conclusion was achieved, that was the stress response had insensitivity with the load rate in a certain range of the strain ratio. The influencing factors, such as the quality of robot, the friction coefficient, the diameter, and the original touching length, to the critical pace were analyzed. The analysis results showed that the locomotion units of the robot should have the lesser weight, the smooth surface, the bigdish diameter and the lesser touching length. Based on these results, a new whole tectorial membrane miniature robot prototype for the gastrointestinal tract examination was developed. According the quasi-linear viscoelastic model, the theoretical critical pace of the new robot was minished from the former 6.45mm to 1.6mm. The bellows could play the role to reduce the adhesion and was fabricated based on the bionic principle. The relationship between the distortion and the force was tested and the maximal elasticity force of the bellows was not exceeding 0.12N which would be conquered by the miniature linear actuator easily. When the miniature linear actutor elongated, the bellows would promote the baffle of the miniature linear actuator depending itself elasticity restoration function.The towing test, the locomotion capability and the in-vitro experimental results were researched and compared. The towing force and locomotion rates of the two robots were measured in the different condictionss, which validated the locomotion model and the driver principle. The in-vitro experiments were done and the results showed that the locomotion efficiency of the whole tectorial membrane miniature robot was promoted obviously.The prototype inegration, the wireless power transfer, the driver technology, the model foundation and the in-vitro experiments were studied thoroughly. All above researches laid the solid foundation to the robot examination system applying in clinic. The power supply and mechanism optimization should be studied in the future.更多还原