【作者】 王世勇；

【导师】 李迪；

【作者基本信息】 华南理工大学 ， 机械电子工程， 2010， 博士

【摘要】 激光加工是利用高能量密度的激光束在物质表面产生光化学效应或使表层物质蒸发的先进加工技术,由于具有非接触、工件无变形、切缝质量好、加工速度快、容易与数控技术结合等诸多特点,已广泛地应用于汽车、航空、化工、轻工、电器与电子、石油和冶金等工业部门。高性能的运动控制是提高数控系统加工精度和加工效率的前提。对于激光加工数控系统来说,高精度、高灵敏度的激光功率控制以及激光功率与运动的精确同步控制对提高加工精度和加工效率也具有重要的作用。复杂轨迹的插补是高速高精运动控制的核心问题和热点问题,因而得到了大量的研究,但仍然存在速度波动较大、速度曲线不光滑,存在非常大的加加速度等不足,从而降低了系统的动态性能,难以实现高精度与高速度的统一。为了实现高性能的激光加工控制,研究并开发了连续小线段和NURBS(非均匀有理B样条)曲率适应前瞻插补算法,闭合NURBS轮廓的激光清扫算法,高精度的激光功率控制算法以及激光功率与运动的精确同步控制算法。并且在上述算法的基础上,实现了面向激光加工领域的高性能激光控制系统。主要研究内容和研究成果如下:1)针对由连续小线段描述的复杂轨迹,提出了一种曲率适应前瞻插补算法。研究了复杂连续小线段轨迹的曲率变化描述方法,并在此基础上优化了小线段衔接点速度,以使得速度跟随曲率变化。并且在能量最小原理约束下,研究了小线段轨迹三次样条插值处理,生成了多项式三次样条曲线。该样条曲线插补计算简单、速度曲线连续光滑、加加速度受限,既可保证加工精度又提高了加工效率。2)针对由NURBS描述的复杂轨迹,提出了一种曲率适应前瞻插补算法。研究了复杂曲线轨迹的曲率变化描述方法,并在此基础上进行了NURBS曲线的速度规划,以使得速度跟随曲率变化,而且速度曲线连续光滑,加加速度受限,从而既保证了加工精度又提高了加工效率。采用二阶泰勒展开建立参变量求解函数,不仅简单化了算法计算、截断误差小,而且使得加工速度曲线匹配规划的速度曲线。3)针对由NURBS描述的闭合轮廓,研究了高速、高精的激光清扫算法。建立了有理多项式形式的NURBS表达式,解决了迭代形式定义难以进行清扫计算的问题,从而实现了激光启闭控制点计算、激光启闭延时补偿、激光清扫路径生成、实时激光启闭控制等功能,实现了复杂NURBS闭合轮廓的高速、高精激光清扫加工。4)研究了高精度的激光功率控制算法以及激光功率与运动的精确同步控制算法。在分析材料激光加工特性和激光器功率控制特性的基础上,采用分段线性近似的方法建立了材料切割质量与激光能量密度以及激光器输出功率与控制信号间的定量描述。设计开发了激光功率闭环控制算法,保证了高精度的激光功率输出;研究了激光功率与运动的关系,在插补周期内同步更新激光功率与运动位置,实现了激光功率与运动的精确同步。5)在分析多种激光加工设备对控制系统需求的基础上,开发了面向激光加工领域的控制系统。控制系统的硬件具有可配置、可重构的特点,支持在不改变硬件电路的前提下对硬件功能,特别是控制接口进行重新定义。控制系统软件具有模块化、可配置的特点,各功能单元抽象为具有互操作性和可互换性的软件模块。由于该控制系统的软、硬件均具有较高的可配置性,所以能够针对不同的激光加工设备,实现快速的客户化定制。高性能激光加工控制若干关键技术的研究与突破,有利于提高激光加设备性能,提高加工质量和加工效率,提升行业竞争力,具有良好的经济效益和社会效益。更多还原

【Abstract】 Laser processing is a kind of advanced processing technology which causes photochemicaleffect on the material surface or evaporates surface material with high-energy density laserbeam. The laser processing has been widely used in many industrial areas such as automotive,aerospace, chemical, light industry, electrical and electronics, oil and metallurgical industriesbecause of its many advantages such as no mechanical contact between work piece and tools,no deformation suffered by work piece, fine machining quality, high machining speed, easilyintegrated with numerical control technology.High-performance motion control is the prerequisites to improve the accuracy andefficiency of CNC system. For laser processing CNC system, the high-precision andhigh-sensitivity laser power control and accurate synchronization control between laser powerand motion plays an important role in improving the accuracy and efficiency. Theinterpolation of complex trajectory interpolation is the core issues and hot issues of highspeed and high precision motion control, which received a great deal of research. However,there are still drawbacks such as the feedrate is fluctuant, the feedrate profile is not smoothand the jerk is terribly high, which reduces the system’s dynamic performance and it isdifficult to achieve high precision as well as high-speed machining.To realize high-performance control of laser processing, curvature-adaptive look-aheadinterpolation schemes for CSLB (Continuous Small Line Blocks) and NURBS (Non-uniformRational B-Spline) are developed. In addition, three schemes are developed specially for thelaser processing applications, which are laser scan of closed NURBS contour, high precisionlaser power control scheme, as well as accurate synchronization control between laser powerand motion. Based on the above-mentioned schemes, a high-speed and high-precision flexiblemotion controller was developed for the field of laser processing. Main research contents andresearch results are as follows:1) Curvature-adaptive look-ahead interpolation scheme is developed for the complextrajectory expressed as CSLB. The curvature variation of complex CSLB trajectory isdescribed based on which feedrate of turning points is optimized. The turning feedratechanges following the curvature variation, that is, turning feedrate is high in low curvaturesections and low in high curvature sections. Under the constraint of Energy MinimizationPrinciple, the CSLB trajectory is cube fit into cube spline. The cube spline is continuous andsmooth, and it approaches to the original trajectory more closely than the CSLB trajectory.The cube spline is a third degree polynomial, so the interpolation calculation is easy to perform and the feedrate profile is smooth, the acceleration profile is continuous, which helpsto guarantee the accuracy meanwhile improve the efficiency.2) Curvature-adaptive look-ahead interpolation scheme is developed for the complextrajectory expressed as NURBS. The curvature variation of complex curve trajectory isdescribed based on which feedrate planning is performed. The feedrate changes following thecurvature variation, that is, turning feedrate is high in low curvature sections and low in highcurvature sections. The feedrate profile is smooth, the acceleration profile is continuous andthe jerk is limited, which helps to guarantee the accuracy meanwhile improve the efficiency.The function to calculate the parametric variable is formed with second-degree Taylorexpansion, which simplifies the interpolation calculation, minimizes the truncation error andthe generated feedrate profile matches the planned feedrate profile.3) High-speed and high-precision laser scan scheme is developed for the closed NURBScontour. An explicit rational polynomial NURBS expression is derived from the recurrencedefinition, based on which four essential modules involved are realized, namely calculatingintersection points of the scan line and the NURBS contour, compensating on-off delay,generating motion path, and real-time on-off control of laser. The laser scan of complexclosed NURBS contour fills the gaps at home and abroad.4) Laser power control scheme, as well as synchronization control between laser powerand motion scheme are developed. In laser processing, the constant laser energy density is animportant factor in guaranteeing the quality, which requires not only high-precision laserpower control, but also that laser power follows the processing speed by a constant rate ofchange in sync. With the analysis of material characteristic on laser processing and laserpower control features, the piecewise-linear approximation method is used to establish thequantitative between the material cutting quality and laser energy density as well as betweenlaser output power and control signals Then the closed-loop laser power control algorithm isdeveloped, ensuring high-precision laser power output. In addition, the relationship betweenlaser power and motion is studied and the laser power and motion position are renewedsynchronously in each interpolation cycle, which achieves the precise synchronization controlbetween the laser power and motion.5) The control requirements of a variety of laser processing equipment are analyzedbased on which the controller is developed for the field of laser processing. The hardware ofthe controller is configurable and reconfigurable. The hardware functions, in particular thecontrol interface can be redefined without changing the hardware circuitry. The software ofcontroller is modularized and configurable. All the functional units are abstracted into software modules with interoperability and interchangeability. Since the controller hardwareand software all have a high flexibility, rapid customization can be achieved for different laserprocessing equipment.Research and breakthrough of several key technologies of laser processing control helpsto improve performance of laser processing machine, to improve machining quality andmachining efficiency, to improve industrial competitiveness, which makes fine economic andsocial benefits.更多还原