【作者】 郑慧峰；

【导师】 周晓军；

【作者基本信息】 浙江大学 ， 机械制造及其自动化， 2009， 博士

【摘要】 当前超声无损检测方法被广泛应用于材料的内部缺陷探测,在产品全面质量控制中占有举足轻重的作用。特别针对复杂型面构件在航空、船舶、汽车、医疗器械等行业中的大量应用,如何设计一个适用范围广、精度高、效率高的曲面自动化超声检测系统,是近年来国内外超声无损检测领域研究的前沿课题。本文结合复合材料曲面工件自动超声检测项目的实际需要和具体实现方案,对系统的运动学与动力学建模、运动轨迹规划、多工件超声检测中模板定位以及变厚度曲面工件的灵敏度补偿与底波跟踪等问题进行了系统深入的研究。第一章阐述了课题的背景和研究的重要意义,分析了曲面数据测量、机器人动力学建模和轨迹规划、曲面匹配、复合材料超声检测等相关技术的国内外研究现状,最后给出了本论文主要的研究内容和章节安排。第二章对超声检测机器人建立了运动学与动力学模型,首先以五自由度超声机器人为研究对象,利用D-H表示法和齐次变换矩阵方法进行运动学建模,给出其运动学正逆解;然后分析了超声检测机器人各杆件速度与关节力的递推关系,利用Newton-Euler递推方法建立了检测机器人的动力学模型。第三章对超声检测系统的运动轨迹规划进行了研究。根据曲面超声检测的特点,正确进行超声检测系统的运动轨迹规划,是实现高效超声探伤检测的关键。首先,给出了曲面工件的测量、重建和采样点生成方法;然后,从检测的动态特性出发,在满足运动学和动力学约束条件下,针对点对点和连续轨迹两种任务下分别采用五次多项式和4-3-4多项式来对超声检测的运动轨迹进行时间优化,保证检测机器人终端的探头能够平稳快速地采集信号,最后给出实例来验证该算法的有效性,并为提高超声检测系统的性能提供了依据。第四章对多工件超声检测中模板定位进行了研究。提出了一种分级匹配的定位算法来保证基于检测模板的多工件超声检测机器人轨迹可靠性:首先以待测工件与检测模板工件的包围盒的中心为原点分别建立坐标系来进行匹配,使得待测工件趋向检测模板,然后通过质心匹配来使得待测工件实际位姿基本与检测模板吻合,再通过点到曲面最小距离寻优的完全匹配来实现检测工件的最终定位。最后通过仿真与实例分析了各级匹配的精度与效果,验证了此分级匹配定位算法的可行性,并给出超声C扫描实例。此算法同样可应用在其他装配生产线上的软件定位方法上。第五章对曲面变厚度工件超声检测中灵敏度的自适应调节和波形跟踪进行了研究。针对曲面型复合材料工件衰减率大和厚度变化不均匀连续的特点,导致其超声自动化探伤中灵敏度调节困难,介绍了变厚度工件的超声C扫描的原理,阐述了灵敏度补偿的原理,提出了基于BP神经网络的方法来获取灵敏度与曲面位置信息之间的映射关系,用此来实现灵敏度的补偿与实时控制,并且结合生成的灵敏度模板提出了一种新的超声检测底波跟踪算法。最后通过扫查实例来验证该方法的满足检测需要,大大提高了对类似的变厚度高衰减率工件的超声检测的自动化程度和准确性。最后对全文工作进行了总结,并对将来进一步的工作作出展望。更多还原

【Abstract】 Nowadays ultrasonic non-destructive inspection method is widely used for detecting internal flaws in materials and very significant in products all-sided quality control. With large use of parts of complex surfaces in many fields such as aviation, shipping, automobile and medicine, how to design an ultrasonic detection system with flexibility, high precision, high efficiency and acceptable cost is a frontal research to realize automated ultrasonic inspection for the complex surface parts in recent years. Combined with the actual requirements in the automated ultrasonic inspection and its realization scheme, some key problems and algorithms in relation to automated such as dynamic modeling, ultrasonic inspection trajectory planning, the loclization of template in ultrasonic inspection for multi-parts and sensitivity compensation and wave tracking in various thickness of curved surface parts are systematically studied in this dissertation.In chapter 1, the background of the research work and important significance of the dissertation were discussed. Some crucial techniques involved with the research project, such as surface measurement, dynamic modeling, ultrasonic inspection trajectory planning, trajectory reliability of multi-parts based on testing templet and sensitivity compensation and wave tracking in various thickness of curved surface parts and etc. In finial part of this chapter, detailed research contents and chapters arrangement were given.In chapter 2, the kinematic equation of ultrasonic inspection system was presented and its dynamic modeling was set up. Firstly the 5-DOF automatic ultrasonic system for curved surface work-pieces was treated as the research subject, kinematic was analysed by using D-H denotation and transfer matrices. The direct and inverse solution was given.Then the recursive relation of the velocity and joint’s force between each link of ultrasonic system was deduced. Finally the dynamic modeling of ultrasonic inspection system was set up by Newton-Euler recursive method.In chapter 3, the trajectory plannning in ultrasonic automatic inspection for curved surface work-pieces was studied. According to the features of ultrasonic inspection for curved surface work-pieces, planning the trajectory of the inspection system rightly was key to realize the ultrasonic inspection for flaws. Firstly, the methods of measurement、reconstruction and sampling points generation for curved surface work-pieces was given. Then onsidering the dynamic characteristic of ultrasonic inspection quintic polynomial and 4-3-4 polynomial were respectively adopted to optimize run time of the trajectory of inspection system to solve the point to point and continuous trajectory between points with the constraints in kinematics and dynamics. The method guaranteed the ultrasonic detector to keep stable and rapid to acquire the signal. Finally, experiments showed the validity of algorithm for trajectory planning, which is also the according to improve the performance of ultrasonic inspection system.In chapter 4, the loclization of template in ultrasonic inspection for multi-parts was studied. One kind of graduation match localization algorithm was proposed: firstly the coordinate whose origin was surrounding box’s center was established on both testing work-pieces and template separately to make the orient of testing work-piece to trend the template one. Then the center of mass matching was used to cause actual pose of testing work-piece to tally basically with the template. Finally the final localization was completely realized through the entireness mass matching, in which the shortest distance from the space point to the curved surface was searched. Finally all levels of match precision were analyzed through the simulation and the C scanning example was given to confirm this graduation match localization algorithm feasibility. This algorithm can be also applied in the other surveying domains beside ultrasonic inspection.In chapter 5, the sensitivity compasation and waveform tracking in ultrasonic inspection for curved surface workpieces with varying thickness was studied. For the difficulties in sensitivity adjustment of automated ultrasonic inspection caused by the Surface-based composite materials for the workpiece with high decay rate and uneven thickness changes, the principle of ultrasonic C Scanning for workpieces with varying thickness and sensitivity compensation were firstly introduced. Then the method based on BP NN was proposed to access the mapping between the sensitivity of ultrasonic inspection and the surface locations. The method was used to the real-time control and compensation of sensitivity and applied to propose an algorithm to track the bottom waveform of ultrasonic inspection. Finally, scanning examples were given to validate the method satisfy the inspect needs, which was greatly increasing the automation and accuracy of ultrasonic inspection for similar workpieces.In the chapter 6, main results and conclusions of this dissertation were systematically summarized; the prospects and study emphases of the future research work were discussed and forecast.更多还原