To enhance the accuracy of robotic drilling in aircraft structures, numerous methods for detecting reference holes have been proposed. However, these methods are often ineffective in the presence of occlusions or high noise levels. In this paper, we propose a coarse-to-fine method for detecting multiple types of reference holes. At the coarse localization stage, a gradient-based template matching method is used to efficiently and accurately identify candidate regions. For the precise detection stage, a hybrid method is proposed to extract contours within candidate regions by integrating edge-following and iterative techniques. By leveraging template information iteratively, the proposed method enhances accuracy while substantially reducing computational costs. The experimental results demonstrate that the proposed method achieves a maximum detection error of less than 0.4 pixels and maintains a recall rate above 94% across different types of reference holes. Furthermore, in comparative experiments using reference hole images, our method consistently achieves the highest recall rate among all tested approaches, validating its effectiveness and robustness in complex industrial environments.

The level of automation and precision in aircraft assembly determines the effectiveness and quality of aircraft manufacturing. In contrast, the unstable localization accuracy resulting from the layout pattern of flexible track drilling robot has limited their further development and applications in domains with high machining accuracy requirements, such as aircraft assembly. This study begins by presenting the paradox between the need for high-precision drilling tasks during aircraft construction and the accuracy of automated drilling equipment. The problem of precision loss due to flexible track drilling devices is examined in a new application scenario where the overall position and pose layout change with the location of the process station. Then, the characteristics of the weak rigidity of the transmission system of the flexible track drilling robot at the joint surface and the variation of the transmission axial load due to variations in the position and pose of the drilling process station are examined. In addition, an equivalent stiffness model is developed to predict the incremental error of the entire process station, and the incremental error conjecture due to the elastic deformation of the coupling surface of the transmission system is proposed as an optimization algorithm for global position accuracy compensation. Finally, experimental results showed that the incremental error compensation method optimized 68.67% of the total error.

针对航空密封胶与预装配紧固件等因素对自动化装配系统基准检测的干扰问题以及系统对多类型装配基准检测的需求,分析了工业环境装配基准特点以及目前检测算法的局限性,提出了一种基于单目视觉的多类型装配基准椭圆特征稳健检测方法.该方法以弓弦比与弦长为依据选取最优弧,通过分析剩余弧段与最优弧的关联凸性,实现对弧段的快速筛选.借助改进的基于存在概率的圆检测算法拟合装配基准近似圆,并通过设定的距离阈值实现对圆弧的快速精确聚类.最后,采用直接最小二乘法拟合装配基准椭圆轮廓,并通过参数约束对拟合结果进行去伪.通过现场测试与精度验证,算法对装配场景常见干扰因素具有显著的抑制作用,对基准孔的检测精度(孔径)与定位精度(孔距)分别为0.10 mm与0.09 mm,对铆钉、靶标点、通孔以及含穿心夹基准孔的检测准确率为97.9%、98.3%、99.1%和91.1%,能够满足自动化装配系统对多类型装配基准的检测需求.

With the development of aviation industry, more stringent demands are put forward for the performance and manufacturing level of aircraft. Moreover, the automation and precision of aircraft assembly determine the efficiency and quality of aircraft production. In order to improve the positioning precision of the flexible track hybrid robots which are applied to the flexible automatic assembly of aircraft , a precision compensation method based on response surface methodology was proposed in this paper. Firstly, the global positioning error model, optimized by characteristics of error data, was constructed to predict the positioning errors of the flexible track hybrid robot. Secondly, the predicted errors are utilized to realize the compensation of the target points at drilling workspace on nose and front fuselage assembly areas. Finally, a series of experiments of the flexible track hybrid robot with no-load and drilling scenarios are implemented to validate the proposed precision compensation method. The experiment of a hybrid robot for aircraft assembly shows that the mean value of the absolute positioning precision of the end-effector was promoted from 0.081 mm to 0.025 mm, maximum error reduced from 0.143 mm to 0.039 mm, respectively, which means that the position accuracy of the robot is increased by 69.1% and 72.7% for two experimental conditions.

Workpiece pose deviation is inevitable during automatic drilling and riveting in aircraft assembly, and it either leads to increased time cost or decreased position accuracy with the present methods. This study aims to propose a quick modification method to modify the coordinates of assembly holes based on online detection of the position of pre-assembly holes considering the effect of abnormal data caused by workpiece pose deviation. In the case of hole-making in the double curvature skin region of three pre-assembly holes, the space transformation matrix is determined using the unit quaternion method in accordance with the on-line detection of the hole position coordinates. In the case of more than three assembly holes with abnormal data, a new modification method using a random sampling consistency RANSAC algorithm is used to optimize the spatial transformation matrix and eliminate the abnormal data effectively. This method has been integrated into automatic drilling and riveting systems. Numerical simulation and experiment tests were conducted, and the result comparison showed that the method has obvious positive effect dealing with the abnormal data considering component pose deviation, which proves the effectiveness of the method.

Based on the self-dressing of ice fixed abrasive polishing (IFAP) by melting, a new method of subzero polishing was proposed in this paper as multi-layer ice fixed abrasive polishing (MIFAP). The multi-layer ice fixed abrasive polishing tool (MIFAPT) was designed as triple-layer and used to polishing single-crystal germanium (sc-Ge) wafer through "rough polishing-semi-fine polishing-fine polishing" (RP-SP-FP) by one time of clamping in subzero. The results show that the surface roughness Sa of sc-Ge wafer polished by MIFAPT is at the nanoscale as the same as by single-layer ice fixed abrasive polishing tool (SIFAPT). Compared with SIFAP, the machining efficient of MIFAP is increased by about 66.7 %.

针对大飞机上常用的四轮并列式起落架,给出了飞机在着陆准稳态阶段,其起落架焊接主起轮轴的受载数学模型。以伊尔-76飞机为研究对象,采用有限元分析软件ANSYS,模拟了其机轮着陆过程中焊接主起轮轴受力状况。结果表明,主起轮轴上两道焊缝处应力最大,断裂几率最高,最先着陆机轮的轴颈处由于受到循环载荷作用,易发生疲劳断裂。

The Ni-based WC composite(Ni-WC) coating on mould steel 2738 was prepared by CO2 laser cladding.The substrate 2738 steel and the Ni-based WCCC were tested under dry sliding friction conditions to investigate their friction and wear behavior.The wear volume of specimen was measured using a 3-D surface profilometer,and the worn surface topography was observed by the scanning electronic microscopy.The results show that the microhardness of the Ni-WC coating was enhanced significantly,its surface hardness exceeded 1200 HV,ensuring its wear resistance.The average friction factor was about 0.25,it decreased by about 44% in comparison with that of the substrate 2738 steel of 0.43.WC hard phase enhanced the bearing capacity of the friction surface,reduced the wear rate by 96.7%.The abrasive wear was the main wear mechanism for the Ni-WC coating.

The process performance of cold extrusion of Q460 high-strength-steel internal thread was studied by experiments.The effects of hole-diameter,extrusion speed and number of extrusions on the quality of the thread,such as surface morphology,residual stress and micro hardness were analyzed.High quality internal thread was obtained by optimization of the technological parameters.Results show that the optimized technological parameters are as follows,the hole-diameter is in the range of 21.20 mm to 21.30 mm,the rotation speed of the machine tool is from 20 r/min to 40 r/min,one-step cold extrusion forming is the best technology rather than multi-step extrusion.

Experimental study was carried out on the FSJ of 10mm thick 7022 aluminum alloy. The cross-section of jointing area was analyzed by the tool microscope. The results show that the plastic metal of seam in the ad- vancing side along the surface of the stirring pin was squeezed into the cavity clockwise and the plastic metal of seam in the retreating side along the surface of the stirring pin was squeezed into the cavity counterclockwise. In high rotation speed of the stirring head, the plastic metal soften by shaft shoulder friction stirring was generated vortex flow and squeezed into the cavity under the pressure of shaft shoulder. With the high speed of stirring pin, the plastic metal in the cavity squeezes the base metal to the surrounding, resulting in plastic deformation of base metal. At the same time, the part of plastic metal of the bottom was squeezed to the surface of base metal, which was squeezed to the surrounding and formed the ＂Flash＂ under the action of the pressure of shaft shoul- der. As the vortex flow, the metal layer of the middle was concave, and the middle position of the surface of seam was sunken. ＂Reduction effect＂ phenomenon was occurred in the jointing area. The model of ＂filling indi- rect squeeze - vortex flow＂ can accurately express the flow pattern of the plastic metal of jointing area and reduc- tion formed process.

Interfacial clearance could be controlled effectually through putting pressure on the skin of aircraft. when drilling a hole on the skin of airplane, It can only use one-side pressure. The effect of pressure on the interface is analyzed, and then three methods for pressure analysis are discussed. A typical docking location of middle-fuselage and middle-after fuselage sections is taken for example. The relationship between interfacial clearance and pressure is analyzed by using finite element method(FEM). Finally, a rational value of pressure is presented.

Microstructure and mechanical properties of the surface layer in cold-extruded internal thread of Q460 steel before and after heat treatment were investigated by means of FE-SEM,microhardness and tensile tests.The results show that the number and the width of the cracks formed along the elongated fibrous structure of the surface layer in the internal thread after heat treatment were all reduced,and the intensity of fiber streamline is increased and the grains are refined.Microhardness at crest,flank and root of the cold-extruded internal thread after heat treatment is improved evidently with slight decrease of the depth of hardened layer.The gradient of the microhardness curve in the hardened layer is decreased and its tensile strength is also improved evidently for the cold-extruded internal thread after heat treatment.The sustained maximum pulling force of the internal thread after heat treatment reaches to 202.68 kN,and increasing 9.24% compared with that before treatment.

Traditional cold extrusion process of internal thread is only fit for processing low-intensity and high plasticity metals such as non-ferrous metals and low-carbon steel.But the internal thread of the key parts such as airplane and high speed train is processed with high-strength steel.During cold extruding high-strength steel internal thread,the effects of lubricant,workpiece bottom hole diameter,extrusion speed and extrusion times on wear and fracture of the tap and manufacturing quality of the internal thread are great.The process of cold extrusion of Q460 high-strength steel internal thread is studied through experiments.The effects of lubricant,workpiece bottom hole diameter,extrusion speed and extrusion times on extrusion torque and extrusion temperature is analyzed.And the ideal internal thread is obtained through optimizing technological parameters.It provides a new basis for improving the surface quality and the fatigue property of internal thread.The test results show that Q460 high-strength steel internal thread is better formed by cold extrusion through one-step forming technology.The fluidic thin film lubricant whose viscosity number is between 10 and 12 is selected.The best range of workpiece bottom hole diameter is between 21.20 mm and 21.30 mm.And the generally selected extrusion speed is between 30 and 60 mm·min–1.

Aircraft automatic assembly becomes a king of trend and widely applied of all kinds of automatic system. Simulation is essential to studying which could meet the requirements of avoiding the investment risk. This paper describes the assembly process and simulation which include workflow and production line planning, which include the definition of automatic device, resource layout, panel-building process simulation, section assembly process simulation.

7022 aluminium alloy with a thickness of 10 mm was welded via the friction stir welding, and the influences of welding parameters on the microstructures and mechanical properties of the welded joint were investigated. The results show that, at a rotating speed of 400 r/min and a welding speed of 100 mm/min, the tensile strength and yield strength of the welded joint of 7022 aluminium alloy reach 615 MPa and 533 MPa, respectively, which are both greater than those of the base material, and that the microhardness of the welded joint is slightly lower than that of the base material. Moreover, it is found from the fracture surface analyses, it is found that the tensile fracture of the welded joint of 7022 aluminium alloy is ductile.

Experimental study is carried out on the friction stir welding of 10mm thick 7022aluminium alloy.The welded joint with smooth surface had been obtained.No welding crack and pore have been discovered by X-ray detection.The microstructure of friction welded joint is studied in different regions.The mechanical properties of welded joints are analyzed through tensile,impact and hardness tests.The results show that the organization of welded joint is small homogeneous isometric crystal.The tensile strength and yield strength of friction stir welded joints of 7022 aluminium alloy excess these of the base material when the rotating speed is 400r/min and the welding speed is 100mm/min.The impact toughness of welded joint is higher than the base material.The microhardness of welded joint is slightly lower than the base material.Welded joint has good mechanical properties.

An knowledge-based system (KBS) on aircraft assembly drilling should be develop because that assembly drilling requires much experience about process parameter, Tools, Equipments and fixtures to drill precisely and efficiently and the knowledge may update rapidly to suit the improvement of process. This paper lists the influence factor of aircraft assembly drilling which includes fastener, structure type and material. A Hierarchical case representation model presents to resolve the problem level by level in order to simplify the complexity. After discussing the Knowledge base (repository), Architecture of KBS and inference method, the KBS implement is introduced to explain its use.

The development history and situation of Chinese manufacturing enterprise informationization are reviewed in this paper. Based on practice, the problems of Chinese enterprise informationization are discussed on in view of understanding, methods and implementation, and difficulties are explained. At last, methods of Enterprise Information are proposed.

Aimed at the disadvantages of the lateral powder feeding and multi-lateral coaxial powder feeding process in laser cladding rapid prototyping process, a new process of hollow focusing laser, powder tube being medial and insidebeam powder feeding is applied in laser cladding direct manufacturing. The key process parameters, such as laser power density, beam of light mode and scanning speed, etc., are studied. In the multimode laser, the relation between different process parameters and cladding coat quality is found out, thus it can be used for shaping multilayer parts.