Prediction of quality characteristics of laser drilled holes using artificial intelligence techniques

Micro-drilling using lasers finds widespread industrial applications in aerospace, automobile, and bio-medical sectors for obtaining holes of precise geometric quality with crack-free surfaces. In order to achieve holes of desired quality on hard-to-machine materials in an economical manner, computational intelligence approaches are being used for accurate prediction of performance measures in drilling process. In the present study, pulsed millisecond Nd:YAG laser is used for micro drilling of titanium alloy and stainless steel under identical machining conditions by varying the process parameters such as current, pulse width, pulse frequency, and gas pressure at different levels. Artificial intelligence techniques such as adaptive neuro-fuzzy inference system (ANFIS) and multi gene genetic programming (MGGP) are used to predict the performance measures, e.g. circularity at entry and exit, heat affected zone, spatter area and taper. Seventy percent of the experimental data constitutes the training set whereas remaining thirty percent data is used as testing set. The results indicate that root mean square error (RMSE) for testing data set lies in the range of 8.17–24.17% and 4.04–18.34% for ANFIS model MGGP model, respectively, when drilling is carried out on titanium alloy work piece. Similarly, RMSE for testing data set lies in the range of 13.08–20.45% and 6.35–10.74% for ANFIS and MGGP model, respectively, for stainless steel work piece. Comparative analysis of both ANFIS and MGGP models suggests that MGGP predicts the performance measures in a superior manner in laser drilling operation and can be potentially applied for accurate prediction of machining output.

     

Linear energy control of laser drilling and its application in the repair of TFT-LCD bright pixels

Laser drilling is an energy dependent process in which energy consumption is linearly proportional to the thickness of the material being drilled. Thus, providing linear output power from the laser can provide considerable advantages in the repair of devices such as TFT-LCD pixels. Unfortunately, the non-linear energy characteristics of lasers require compensation to achieve linear power output. Conventional compensation schemes use laser power meters that require repeatedly switching the laser system off and on again. This study developed a software-based energy compensation method to provide optimized energy output and continuous linear laser energy. This software solution enables the measurement of laser energy in a fixed period and its manipulation using a compensation table, which eliminates the need for a laser power meter and enables the system to remain in operation during laser power calibration. The proposed method provides linear output in which the linear energy proportion (R ²) reaches 0.9988 and provides a very stable power source. We applied this method to repair bright pixels in LCD panels, achieving a success rate of 86?%. In addition, the proposed method eliminates the need to remove the LCD casing from the fabrication module, thereby increasing the efficiency of production.     

基于ARM和CPLD的水松纸激光打孔控制系统设计

针对现阶段香烟水松纸激光打孔控制系统的打孔精度差、监控能力不足等问题,设计了一种新型的打孔控制系统.控制系统采用ARM和CPLD相结合的控制方式,配合外围各种控制模块实现了本系统的硬件设计.ARM实现触摸屏实时数据通信和高速激光打孔功能,CPLD辅助ARM完成对香烟位置检测传感器输入信号的滤波、延时输出等功能.运行测试表明:本控制系统运行稳定、可靠、抗干扰能力强,并且打孔脉冲精度高达100 ns,能够满足目前香烟水松纸激光打孔控制系统的要求.     

Accurate positioning of a drilling and riveting cell for aircraft assembly

Modern aircraft assembly demands assembly cells or machines with higher machining efficiency and accuracy. Thus, a dual-machine drilling and riveting cell is developed in this paper. We firstly discuss its physical design, as well as the automatic drilling and riveting process. With the automatic drilling and riveting cell, drilling and riveting production line of aircraft panels can be expected. The frame chain of the drilling and riveting cell is constructed to link the assembly cell to its task space, which is the kinematics base. System calibrations, including task space calibration, the sensor calibration of an orientation alignment unit, the floating calibration of the implicit hand-eye relationship, are explored. For high positioning accuracy, a multi-sensor servoing method is proposed for cell positioning. An orientation-based laser servoing strategy, which uses the feedback of the orientation errors measured by laser displacement sensors, is used to align drilling direction and camera shooting direction. Besides, A single-camera-based visual servoing is applied to align the tool center point (TCP) to reference holes, to obtain their coordinates for drilling position modification. Experiments of multi-sensor servoing for cell positioning are performed on an automatic drilling and riveting machine developed for the panel assembly of an aircraft in China. With the cell positioning method, the automatic drilling and riveting cell can approximately achieve an accuracy of 0.05 mm, which can adequately fulfill the requirement for the assembly of the aircraft.     

钢板激光打孔打标机计算机控制的研究

该项目根据宝钢钢板打孔和打标的实际需要出发,研制出新型脉冲调Q Nd：YAG激光打孔和打标两用激光加工系统所用的计算机操作系统;开发应用软件,并辅助以硬件设备,可利用多功能数字输入输出计数器/定时器PCL-836（A）产生频率、幅值、脉冲宽度、脉冲组数等均可自由调整的控制脉冲信号,能够满足现场各类打孔打标需要,脉冲输出准确率100%.     

High-precision and ultrafast UV laser system for next-generation flexible PCB drilling

Since conventional mechanical punching technology for Flexible Printed Circuit Board (FPCB) drilling has restricted via-hole size and depth control for multi-layer circuit boards, CO₂ and Ultra Violet (UV) laser drilling technologies have been developed. However, the FPCBs for mobile phones and Personal Digital Assistants (PDAs) require smaller via-hole diameters, since the development of thinner and higher circuit density devices is demanded. Currently, UV laser systems are widely used for FPCB drilling of 75–105 μm diameter via-holes and inspectors performs quality test manually using microscopes. We developed a high-precision UV laser microfabrication system for next-generation FPCB drilling of 15 μm diameter via-holes. The degrees of the precision of the microfabricated via-holes of 15, 35, 50 and 85 μm were mean absolute error rate of 4.4, 2.2, 2.3, and 2.2 which was fully satisfied with industrial inspection specification ±10%. The drilling speed of the system of 2800 via-holes per second at stationary state was achieved. In addition, we applied modified Greedy 2-opt algorithm to find out optimal drilling path which reduced the total time of via-hole fabrication. We successfully reduced the production time by 25% compared with the result obtained in the normal Greedy 2-opt algorithm. Moreover, we designed very accurate inspection method using Canny edge detection and geometric pattern matching algorithms and successfully applied it to the Automated Optical Inspection (AOI) module for the inspections of 15 μm diameter via-hole which was required for the fabrication of high density FPCB.     

Performance improvements of IGZO and ZnO thin‐film transistors by laser‐irradiation treatment

Abstract— Zinc oxide (ZnO) and indium gallium zinc oxide (IGZO) thin films subjected to laser irradiation were investigated. The structural, optical, and electrical properties of the as‐deposited and laser‐irradiated films at different laser dosages were studied. The crystallinity of the structure increased after laser treatment. The transmittances without/with laser irradiation had a net rise of 85–92% and 80–95% (@550 nm) for 250‐nm ZnO and IGZO films, respectively. Thin‐film transistors (TFTs) with ZnO and IGZO as the active layer were fabricated. The as‐deposited ZnO/IGZO TFT devices had a field‐effect mobility of 0.19 and 1.3 cm²/V‐sec, respectively. The electrical characteristics increased by more than 2.8 times for ZnO and by 5.8 times for IGZO with laser treatment. The field‐effect mobility of ZnO and IGZO are 0.5 and 7.65 cm²/V‐sec.     

Numerical investigation on the dynamics of cavitation nanobubbles

The dynamics of cavitation nanobubbles, generated after irradiation of a single-spherical gold nanoparticle with laser pulses in water, were investigated numerically to obtain a better understanding of the physical mechanisms involved in plasmonic photothermal therapy. The significant parameters of this study are the nanoparticle radius, laser pulse duration, and laser pulse fluence F. For laser fluences close to the fluence threshold for bubble formation, the maximum bubble radius is in the nanometer range, and the maximum pressure inside the bubble is smaller than 1.5 MPa. For laser fluences larger than the fluence threshold for bubble formation, the maximum bubble radius scales with the square root of laser fluence, and the maximum pressure inside the bubble during its first collapse is proportional to F ^0.25. The oscillation time of nanobubbles is smaller than that predicted by the Rayleigh formula. The numerical results are in good agreement with the available experimental data. The calculations of bubble dynamics can cover a large parameter range and may thus serve as a tool for the optimization of laser parameters in medical laser applications.     

Micromachining of biocompatible polymer substrate for cancer cell separation applications

Isolation of circulating tumor cells from human blood plays a significant role in diagnosis and treatment of cancer. The most effective way of isolating cells is the use of lab on-chip microfluidic devices. This paper presents the development of cyclic olefin polymer membrane with an array of micropores for separating circulating tumour cells using ultrashort laser ablation process. Initially, the substrate is tested for its cell viability. The laser Fluence is varied from 1–12 J/cm² and its observed that at a fluence of 2.5 J/cm² the desired diameter of 12 μm with ablation depth of 1 μm is obtained which is necessary for CTC separation. The treated and untreated structure is characterized using Fourier transform infrared spectrometer and it shows that the treated region shows no significant shift in the spectrum after femtosecond laser ablation.

     

水平定向钻钻架有限元建模与分析

钻架是水平定向钻的主要承载部件,其强度和刚度对钻机能否正常工作影响很大.针对钻架传统设计方法存在的问题,提出利用有限元方法对设计进行校核.对水平定向钻钻进工况进行了分析,确定了有限元分析方案,并利用ANSYS软件建立了钻架有限元模型,在此基础上进行了应力应变分析.分析结果表明,钻架的强度能够满足要求,但部分结构需要改进,例如将单排链传动改为双排链传动.结构改进后重新进行分析,发现钻架强度和应力分布有了明显改善.该方法为钻架设计和优化提供了理论依据,有助于提高设计效率.     

基于OpenGL的钻井三维场景动态仿真

为能在脱离钻井现场的情况下向学员展示钻井操作的工艺流程,开发基于OpenGL的钻井三维场景仿真系统．利用3DSMAX构造复杂的钻井设备模型;在OpenGL平台中调用该模型,并利用双缓存技术控制各三维模型在场景中平滑的运动,实现钻井三维场景的动态仿真．该系统可以逼真地仿真正常钻进、起下钻、卸扣和上卡等多种钻井工艺流程．     

Effect of localized KrF excimer laser treatment on fracture behaviors of freestanding <110> and <100> single crystal silicon beams

Microscale silicon structures oriented along <100> and <110> orientations were laser treated with different conditions with the cross section shape and tensile strength investigated after the treatment. Finite element simulation was performed to examine the temperature distribution at different conditions during laser treatment. Using a low energy (1.2 J/cm²) and high tilt angle (65°) led to a more preserved cross section with a slight strength improvement. The strength improvement was limited due to other surfaces that were not affected by laser treatment. An improvement of 30 % in tensile strength was achieved with a higher energy (4 J/cm²) lower tilt angle (45°) treatment that was consistent for different sample orientations. The cross section of the samples treated at such condition was significantly changed however. The effect of sample orientation on fracture behaviour was studied and unstable crack propagation was observed for <100> oriented samples that was more significant after laser treatment.     

Positioning variation synthesis for an automated drilling system in wing assembly

Tight position tolerance is required for fastener holes in wing manufacturing. Automated drilling system with high positioning accuracy is the key to achieve the requirement. The paper seeks to determine allowable values of variation sources and guarantee the hole position tolerance. The process of reference hole positioning and the compensation of drilling positions are firstly explored and formalized for an automated drilling system integrated with an industrial camera. Based on this, a positioning variation model for automated drilling considering positioning error measurement and compensation is built. After that, positioning variation synthesis being imposed engineering constraints on is mathematically modeled based on the theory of mathematical statistics. In the positioning variation synthesis, imperfect camera installation, nonideal measurement conditions, equipment positioning error, etc. are included. The positioning variation model and involving synthesis strategy have been used to develop an automated drilling system for wing assembly. Experiments conducted on the developed drilling system show that the fastener holes’ desired position tolerance 0.3 mm will not be exceeded, which is a necessary condition of the satisfactory drilling quality of the aircraft wing.     

Measurement error analysis and accuracy enhancement of 2D vision system for robotic drilling

Robotic drilling for aircraft structures demands higher accuracy on industrial robots than their traditional applications. Positioning error measurement and compensation based on 2D vision system is a cost-effective way to improve the positioning accuracy in robotic drilling. In this paper, we first discuss the principle of error measurement and compensation with a 2D vision system for robotic drilling and the determination of tool center point of the vision system so that the Abbe errors are eliminated in the measurement process. Measurement errors due to nonideal measurement conditions, i.e. nonperpendicularity of the camera optical axis to the workpiece surface and incorrect object distance, are mathematically modeled and experimentally verified. A method utilizing four laser displacement sensors is proposed to ensure perpendicularity of the camera optical axis to the workpiece surface and correct object distance in the measurement process, and hence to achieve high accuracy in 2D vision-based measurement. Experiments performed on a robotic drilling system show that the 2D vision system can achieve an accuracy of approximately 0.1 mm with the proposed method.     

石油钻井物料清单的构造方法与系统实现

为有效控制石油钻井物料的供应,降低库存,应用企业资源计划系统申物料清单的方法,提出了适用于石油钻井物料管理与控制的石油钻井物料清单的概念.研究构建了钻井物料清单的结构模型,分析了模型中节点间的关系,给出了钻井物料清单的形式化定义.基于钻具可重复使用的特性,按钻井开次,以分阶段计算的方法,提出了钻井物料清单的数量模型.开发实现了一个钻井物料清单管理系统,为钻井物料供应的优化管理提供了辅助支持.     

Real-time prediction of horizontal drilling pressure based on convolutional Transformer

During horizontal drilling operations, real-time prediction of drilling pressure during the drilling process can help the drilling team cope with the complex and changing working environment downhole, adjust the parameters of the drilling rig promptly, make correct decisions, reduce the probability of drilling accidents, and avoid affecting the duration and cost of the project. This study provides a method for real-time prediction of the drilling pressure of horizontal drilling rigs. A deep learning model based on a convolutional Transformer is trained for accurate real-time prediction by extracting real-time operating data of the horizontal drilling rig from the data acquisition system. The method proposed in this study can be a useful tool to improve the performance of horizontal drilling rigs and can assist the drilling team in operating horizontal drilling rigs. The results of the case study show that: (1) the proposed convolutional Transformer model provides reliable real-time prediction with an MAE of 0.304 MPa and an RMSE of 0.508 MPa; (2) the proposed method can quickly and accurately predict the trend of drilling pressure change in the next period based on the current change of drilling pressure, and grasp the dynamics of drilling pressure of horizontal drilling rigs in advance. Further research could focus on assisted decision-making and intelligent optimization to provide solutions for preventing drilling accidents and improving horizontal rig performance based on the prediction.     

Quantum Computing vs. Coherent Computing

In this review article, we compare the performance of two computing systems: quantum computing and coherent computing. A layered architecture for circuit-model quantum computing, employing surface code quantum error correction, has been recently discussed. Using this concrete hardware platform, it is possible to provide resource analysis for executing the fault-tolerent quantum computing for prime number factoring and molecular eigen-energy calculation that cannot be solved by the present day computing systems. A particular quantum computing system could solve such problems on the time scale of 1-10 days by using 10⁸ – 10⁹ physical qubits. We discuss an alternative computing system based on an injection-locked laser network wnicn is called a coherent computing system here. A three-dimensional Ising model is mapped onto the mutually injection-locked slave laser network, while the independent injection signal from a master laser implements a Zeeman Hamiltonian. In this computing system, an Ising spin taking either up or down state is represented by the polarization degrees of freedom, right or left circular polarizations, of the lasing photons in each slave laser. A spin-spin coupling coefficient is implemented by simple linear polarization optics connecting the two slave lasers. We numerically study the scaling law of the proposed machine against the anti-ferromagnetic Ising model with varying problem size M. A transient time to reach a steady state polarization configuration is inversely proportional to the locking bandwidth and does not depend on the problem size strongly up to M=1000.     

Estimating above-ground biomass in young forests with airborne laser scanning

Total above-ground biomass of spruce, pine and birch was estimated in three different field datasets collected in young forests in south-east Norway. The mean heights ranged from 1.77 to 9.66 m. These field data were regressed against metrics derived from canopy height distributions generated from airborne laser scanner (ALS) data with a point density of 0.9–1.2 m^?2. The field data consisted of 79 plots with size 200–232.9 m² and 20 stands with an average size of 3742 m². Total above-ground biomass ranged from 2.27 to 90.42 Mg ha^?1. The influences of (1) regression model form, (2) canopy threshold value and (3) tree species on the relationships between biomass and ALS-derived metrics were assessed. The analysed model forms were multiple linear models, models with logarithmic transformation of the response and explanatory variables, and models with square root transformation of the response. The different canopy thresholds considered were fixed values of 0.5, 1.3 and 2.0 m defining the limit between laser canopy echoes and below-canopy echoes. The proportion of explained variability of the estimated models ranged from 60% to 83%. Tree species had a significant influence on the models. For given values of the ALS-derived metrics related to canopy height and canopy density, spruce tended to have higher above-ground biomass values than pine and deciduous species. There were no clear effects of model form and canopy threshold on the accuracy of predictions produced by cross validation of the various models, but there is a risk of heteroskedasticity with linear models. Cross validation revealed an accuracy of the root mean square error (RMSE) ranging from 3.85 to 13.9 Mg ha^?1, corresponding to 22.6% to 48.1% of mean field-measured biomass. It was concluded that airborne laser scanning has a potential for predicting biomass in young forest stands (> 0.5 ha) with an accuracy of 20–30% of mean ground value.