激光微加工系统中若干关键技术的研究

【作者】 杨雷；

【导师】 姚建铨； 梁二军；

【作者基本信息】 郑州大学 ， 凝聚态物理， 2003， 博士

【摘要】 激光微加工具有加工条件较易满足、功率密度高、加工对象广泛、自动化程度高等特点，得到了广泛的应用。在激光微加工系统中，激光为能量提供者，被加工的工件为能量接受者。加工的过程是激光与物体表面相对运动，从而实现各种方式的加工。在研制的激光微加工系统中采用了工件运动、加工光源固定的方式。本文针对系统中运动控制系统部分提出了系统的设计方案，依据该方案完成了系统的设计、安装和调试工作。 1 控制系统组成。控制系统由设定器、数字控制器、输入通道(位置检测)、后向通道(执行机构)四部分组成。PC计算机作为设定器将控制的目标值(加工轨迹)下载至数字控制器，数字控制器是控制系统的核心部件，它由硬件电路和程序两部分组成，控制规律以及控制算法由数字控制器完成。数字控制器通过前向通道(光栅尺)完成对位置信号的采集，经数据处理，通过控制算法输出经执行机构(基于步进电机的X—Y平台)驱动完成闭环的运动控制。 2 执行机构和反馈部件的选择。运动控制是由电机带动X—Y平台来实现的，步进电机能够将控制器发出的脉冲信号变为X—Y平台的位移。相对于其他测长传感器而言，因为光栅尺具有精度高、响应速度快等优点，尤其是输出信号可以直接与数字电路接口且能方便地安装在X—Y平台上，很适合于本系统使用。因为步进电机具有积分的性能，在理论上能够实现无静差控制，但实际控制系统中，执行机构和反馈部件的分辨率决定了系统中存在着稳态误差。X—Y平台的步进分辨率与反馈部件的分辨率决定了系统的静态误差，在本系统中X—Y平台步进分辨率为1.25μm，光栅尺的分辨率为(经四细分)1μm，决定了静态误差能控制在2μm以内。 3 步进电机的驱动和光栅尺信号的处理。基于TA8435H步进电机驱动集成芯片完成了两相矢量步进电机驱动电路的设计与实现，整个驱动电路简洁可靠。本系统采用单片EPF10K10(FPGA芯片)完成了光栅尺信号处理模块的设计，包括X、Y两个方向的四细分辨向电路、18位的计数电路，锁存接口电路、地址译码电路，总线接口等功能单元。本系统采用了单片EPF10K10，如果用通用的逻辑集成电路设计，需要几十片。同时该模块响应速度快，与MCU接口时是直接的并行输入输出，访问的时间很短，为几个微秒。在系统中，可以认为延时时间为0，光栅尺信号处理模块的传递函数为H(z)=1，符合系统中的动态特性的要求。光栅尺的栅距为4μm，智能模块经四细分辨向后分辨率为1 pm，满足系统对反馈部件分辨率的要求。 4加工的运动轨迹文档的形成。PC计算机可以通过三种方式形成工件加工轨迹文档并下载至控制器:(l)利用被观察的工件的CCD图象的像素点的位置与工件在x一Y平台的坐标的对应关系形成加工轨迹在CRT上通过键盘(或鼠标)的移动形成加工轨迹;(2)利用在计算机上编辑的WORD、TXT、BMP文档经二值化转换形成的点阵图作为加工轨迹文档;(3)经各种图像输入设备得到的图像文件经图像处理和二值化转换形成的点阵图作为加工轨迹文档。 5运动控制的实现。在定位控制中，对步进电机采用闭环和加减速控制，通过算法可以将误差控制在2声m以内;在轨迹控制中，在速度低于2.5浏时s时(脉冲频率ZKHz)，基于光栅尺的闭环系统中，控制误差在2 pm以内。 6本系统采用的电磁兼容性措施(包括SMR抗干扰措施以及光电隔离等)和在设计安装过程中的采取的其他可靠性措施保证了控制系统安全、可靠地运行。、沙更多还原

【Abstract】 Laser micro-processing has been widely used due to its easy realization of processing conditions, high power dencity, broad processing objects and high automation. Laser is energy provider and processing objects are energy embracer in the laser micro processing system. The process is the relative movement between the laser spot and the surface of the object, so lots of processing modes can be realized. The method that laser beam is fixed and processing objects is movable is accepted in the system. The systemic design in the thesis is to the part of movement control system. The design, installation and realization are completed based on the design project.1. Components of the control system. The control system is composed of setting unit, digital controller, input channel and output channel. PC, the setting unit, downloads the setting value (processing track) to digital controller. Digital controller, the hardcore of the control system, is composed of hardware and software. It can realize the control arithmetic. Digital controller completed the closed loop movement control by getting grating scale signal, processing data and sending pulse to steeping motor.2. Selection of operater and feedback unit. Movement control realized by stepping motor drive X-Y table movement. Compared with other linear measure sensor, grating scale has the character of high precision and response speed, output signal be interfaced to digital circuit directly and installed on the X-Y table conveniently. These merits are very fit for the system. No static error control can be realized in theory because of integral character of stepping motor. But there is steady-state error in the practicable control system determined by operator and feedback unit’s distinguishability. Static error of system determined by X-Y table’s steeping distinguishability and feedback unit’sdistinguishability. In the system, X-Y table’s stepping distinguishability is 1.25//m and grating scale’s distinguishability (four folds subdivision) is 1 ?m, so the static error can belimited within 2.3. Drive of stepping motor and processing of grating scale signal. Diphase vector quantity stepping motor drive is designed based on TA8435H stepping motor drive 1C. Thecurcuit is brevity and credibility. In the system, the sigle chip EPF10K10 (FPGA)is used to complete the design of grating scale signal processing unit. The unit consists of some function units such as four folds subdivision direction judegment circuit of X and Y directions, 18 bits counter circuit, latch interface circuit, address decode circuit and bus interface. The sigle chip EPF10K10 instead tens of universual logic 1C in the system. The grating scale signal processing unit has high response speed and parallel input and output.And its access time is short to some ps. The time delay can be ignored in system. Transfer function of grating scale signal processing unit is H(z) = 1. It agrees the dynaimical property in system. The pitch of grating scale is 4 ?m. Intellect processing unitdistinguishability is 1 after four folds subdivision and direction judgement. Thisfeedback distinguishability is enough to system.4. Documentation of the processing tracks. There are three kinds of method for PC to obtain the processing movement track document. First, the coordinates of the object’s pixel in CRT and X-Y table are correspondingly correlated. Base on the correspondence relation, the processing track document can be made through the keyboard or mouse. Second, lattice binary picture transformed from Word, Txt and Bmp document edit in the PC. Third, lattice binary picture transformed from image document obtained by any other image device.5. Realization of movement control. In orientating control, stepping motor is accelerated and decelerated under the closed loop condition. The error can be limitedwithin 2?m through the arithmetic. In track control, based on the grating scale closed loop,the error can be limited within 2 when the stepping motor’s speed is under 2.5mm/s(pulse frequency 2KHz) .6.更多还原