体内超声碎石机的换能器设计及频率跟踪研究
文献类型：学位论文
| 作者 | 李小雪 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-05-23 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 体内超声碎石 阶梯形变幅杆 过渡段 夹心式压电换能器 频率跟踪 |
| 其他题名 | Study on Transducer Designing and Frequency Tracing of the Intracorporeal Ultrasonic Lithotripter |
| 学位专业 | 信号与信息处理 |
| 中文摘要 | 体内超声碎石（简称超声碎石）因其安全有效而被广泛应用于结石治疗中。和其他的功率超声应用设备一样，超声换能器的设计和频率跟踪是影响设备性能的两个关键问题，也是该领域研究的两个重要课题。根据超声碎石机对换能器的要求，应采用由变幅杆与夹心式压电换能器组成的组合换能器。本文采用理论分析与实验相结合的方法，研究了用于超声碎石的组合换能器设计（包括变幅杆的设计及组合换能器整体设计）以及夹心式压电换能器的频率跟踪问题。 首先，文中分析和总结了阶梯形变幅杆常用过渡段的设计方法，比较了它们的性能，发现它们对阶梯形变幅杆性能的影响有如下规律：即悬链线<指数<圆锥，也就是过渡段母线与轴线及两端面半径所围面积越小对阶梯形变幅杆性能的改变越小。在此基础上提出一种新的以三次函数为母线的阶梯形变幅杆过渡段。分析表明，当过渡段长度固定时，可以找到一条与悬链线母线有共同端点并单调下降的三次函数曲线，该曲线与轴线所围面积比悬链线所围面积还小。通过对实例所做的ANSYS分析表明，当过渡段长度固定，其他条件相同时，带三次函数过渡段的阶梯形变幅杆放大系数最大，与阶梯形的固有频率偏离最小。将这种带三次函数过渡段的阶梯形变幅杆用于超声碎石设备，设计为1/4波长变幅杆，与夹心式压电换能器也设计为1/4波长振子，二者组成1/2波长的组合换能器。阻抗分析仪测量结果说明这种组合换能器频率一致性良好，同时离体碎石实验说明其辐射声功率、输出端振幅达到碎石要求。 此后，本文深入讨论了夹心式压电换能器频率跟踪问题。鉴于传统的基于相位方式的跟踪方案的不足，提出了一种基于DDS的频率跟踪方案，该方案中采用直接数字合成器（DDS）作为频率调整和信号产生的器件；采用可编程逻辑器件（CPLD）完成相位比较和DDS控制；采用单片机作为系统的控制核心，对反馈电流进行实时监测，在此基础上实现了先扫频后跟踪的策略以及自动解锁控制。由于采用了先扫频后跟踪的策略，使得系统有良好的适应性；通过增加解锁控制，使得系统在死锁或误跟踪时能自动回到频率搜索状态，工作可靠；由频率跟踪实验可见，该系统实现了快速、高精度频率跟踪。 |
| 英文摘要 | Intracorporeal ultrasonic lithotripsy（ultrasonic lithotripsy for short）is safe and effective thus widely used in the fragmentation and removal of calculi. Just like other power ultrasonic application equipment, the designing of the ultrasonic transducer and frequency tracing are two key points that related to the performance of the lithotripter, and two important subjects in the research on this field. According to the requirement of the lithotripter on transducer, combined transducer which consists of an ultrasonic horn and an sandwich piezoelectric transducer should be used. In a method that combine theory with experiment, the designing of the lithotripter’s combined transducer (including the designing of the horn and the designing of the combined transducer as a whole) and frequency tracing of the sandwich piezoelectric transducer are studied in this paper. Firstly, the designing of the stepped ultrasonic horns with usual transitional sections is analyzed, the performance of stepped ultrasonic horns with different transitional sections are compared, the rule of the influence of different transitional sections on stepped ultrasonic horn is found: catenary transition < exponential transition < taper transition, which can be summarized into that the smaller the area of the generatrix of the transitional section encircle with the axes of the horn and two head faces, the smaller the influence of the transitional section on the performance of the stepped ultrasonic horn. Based on this rule, cubic function transition for the stepped ultrasonic horn is proposed. Analyzes shows that, when the length of the transitional section is fixed, a cubic function who has the same endpoints with catenary and declines monotonously and encircles smaller area with the axes and two head faces than catenary does can be found. Analysis with ANSYS shows that when the length of transitional sections are fixed, and other conditions stay the same, the magnification coefficient of stepped ultrasonic horn with cubic function transition is the biggest and the difference with stepped horn is the smallest. 1/4 wave length stepped horns with cubic function transitions are designed, which form 1/2 wave length combined transducers together with 1/4 wave length sandwich piezoelectric transducers, for using in the ultrasonic lithotripter. These combined transducers are measured by the Impedance analysis equipment, and they show good frequency consistency. Excised calculi fragmenting experiment shows that the combined transducer radiates enough acoustic power and vibration amplitude for fragmenting calculi. Then, frequency tracing of sandwich piezoelectric transducer is studied. In view of the inadequacy of present frequency tracing schemes using phase locking method, a frequency tracing scheme based on DDS is proposed. This scheme utilizes direct digital synthesizer (DDS) to adjust the frequency and generate driving signal; utilizes CPLD to detect phase difference and to control DDS; utilizes micro control unit (MCU) as the control center of the system, and monitoring the feedback current in real time, based on which realizes a strategy of weeping frequency before tracing and an unlock function. The strategy of sweeping frequency before tracing renders the system more adaptable, and the unlock function makes the system back to frequency sweeping when dead locking or error locking occurred, thus makes the system more reliable; According to the results of frequency tracing experiments, high speed and high resolution frequency tracing is realized by this system. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 62 |
| 源URL | [http://159.226.59.140/handle/311008/392]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 李小雪. 体内超声碎石机的换能器设计及频率跟踪研究[D]. 声学研究所. 中国科学院声学研究所. 2008. |
入库方式： OAI收割
来源：声学研究所
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