Adaptive optics are becoming a valuable tool for laser processing,providing enhanced functionality and flexibility for a range of systems.Using a single adaptive element,it is possible to correct for aberrations intro...Adaptive optics are becoming a valuable tool for laser processing,providing enhanced functionality and flexibility for a range of systems.Using a single adaptive element,it is possible to correct for aberrations introduced when focusing inside the workpiece,tailor the focal intensity distribution for the particular fabrication task and/or provide parallelisation to reduce processing times.This is particularly promising for applications using ultrafast lasers for threedimensional fabrication.We review recent developments in adaptive laser processing,including methods and applications,before discussing prospects for the future.展开更多
Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological (MR) fluids is desig...Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological (MR) fluids is designed to investigate the regenerative chatter suppression during the machining. Based on the analysis of typical structural components in the aerospace industry, a general complex thin-walled workpiece with fixture and damping constraint can be equivalent as a rectangular cantilever beam. On the basis of the equivalent models, natural frequency and mode shape function of the thin-walled workpiece is obtained according to the Euler-Bernoulli beam assumptions. Then, the displacement response function of the bending vibration of the beam is represented by the product of all the mode shape function and the generalized coordinate. Furthermore, a dynamic equation of the workpiece-fixture system considering the external damping factor is proposed using the Lagrangian method in terms of all the mode shape function and the generalized coordinate, and the response of system under the dynamic cutting force is calculated to evaluate the stability of the milling process under damping control. Finally, the feasibility and effectiveness of the proposed approach are validated by the impact hammer experiments and several machining tests. (C) 2016 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.展开更多
The milling stability of thin-walled components is an important issue in the aviation manufacturing industry, which greatly limits the removal rate of a workpiece. However, for a thin-walled workpiece, the dynamic cha...The milling stability of thin-walled components is an important issue in the aviation manufacturing industry, which greatly limits the removal rate of a workpiece. However, for a thin-walled workpiece, the dynamic characteristics vary at different positions. In addition, the removed part also has influence on determining the modal parameters of the workpiece. Thus,the milling stability is also time-variant. In this work, in order to investigate the time variation of a workpiece＇s dynamic characteristics, a new computational model is firstly derived by dividing the workpiece into a removed part and a remaining part with the Ritz method. Then, an updated frequency response function is obtained by Lagrange＇s equation and the corresponding modal parameters are extracted. Finally, multi-mode stability lobes are plotted by the different quadrature method and its accuracy is verified by experiments. The proposed method improves the computational efficiency to predict the time-varying characteristics of a thin-walled workpiece.展开更多
The workpiece frames relative to each robot base frame should be known in advance for the proper operation of twin-robot nondestructive testing system. However, when two robots are separated from the workpieces, the t...The workpiece frames relative to each robot base frame should be known in advance for the proper operation of twin-robot nondestructive testing system. However, when two robots are separated from the workpieces, the twin robots cannot reach the same point to complete the process of workpiece frame positioning. Thus, a new method is proposed to solve the problem of coincidence between workpiece frames. Transformation between two robot base frames is initiated by measuring the coordinate values of three non-collinear calibration points. The relationship between the workpiece frame and that of the slave robot base frame is then determined according to the known transformation of two robot base frames, as well as the relationship between the workpiece frame and that of the master robot base frame. Only one robot is required to actually measure the coordinate values of the calibration points on the workpiece. This requirement is beneficial when one of the robots cannot reach and measure the calibration points. The coordinate values of the calibration points are derived by driving the robot hand to the points and recording the values of top center point（TCP） coordinates. The translation and rotation matrices relate either the two robot base frames or the workpiece and master robot. The coordinated are solved using the measured values of the calibration points according to the Cartesian transformation principle. An optimal method is developed based on exponential mapping of Lie algebra to ensure that the rotation matrix is orthogonal. Experimental results show that this method involves fewer steps, offers significant advantages in terms of operation and time-saving. A method used to synchronize workpiece frames in twin-robot system automatically is presented.展开更多
A novel DLC film deposition method was proposed to realize the deposition of DLC film on the surface of complex shaped workpiece.Meanwhile,Si-DLC film was deposited on the surface of M2 high-speed steel(HSS M2)and 304...A novel DLC film deposition method was proposed to realize the deposition of DLC film on the surface of complex shaped workpiece.Meanwhile,Si-DLC film was deposited on the surface of M2 high-speed steel(HSS M2)and 304 stainless steel(304SS),and the microstructure,surface roughness,mechanical properties,corrosion resistance and tribological properties of Si-DLC films were characterized in detail.Results show that Si-DLC film at different axial positions of the auxiliary cathode possesses similar microstructure,film thickness and surface roughness,and the as-deposited Si-DLC film shows the low intrinsic stress of<0.3 GPa.Compared with the 304SS substrate,the Si-DLC film presents more noble corrosion potential,lower corrosion current density and higher polarization resistance,exhibiting higher corrosion resistance.Moreover,the Si-DLC film exhibits higher hardness,elastic factor and plastic factor than HSS M2 substrate and the corresponding adhesive strength is more than 10 N.The Si-DLC film sliding against GCr15 steel ball shows a lower friction coefficient than that of HSS M2 substrate and the wear rate of GCr15 steel ball sliding against the Si-DLC is lower than that of HSS M2 substrate.In addition,this novel method was used to deposit Si-DLC film on gears,drills and bearings without rotating sample racks.As a consequence,this method possesses great potential and can be generalized for the deposition of DLC film on the surface of complex shape workpiece.展开更多
In order to achieve active grinding control, a novel numerical controlmicropositioning workpiece table with a resolution of 6 nm has been developed. The table is drivenby three piezoelectric actuators mounted on the b...In order to achieve active grinding control, a novel numerical controlmicropositioning workpiece table with a resolution of 6 nm has been developed. The table is drivenby three piezoelectric actuators mounted on the base. An elastic structure with three half-notchflexure hinges is designed to apply preload to the piezoelectric actuators. The position of flexurebinges is also elaborately designed with consideration to reduce the bending deformation of themoving part. Three capacitive sensors are used to form close loop control system. Considering thetable as a damped 3-DOF mass-spring system, the models of static and dynamic stiffness and errorowing to the action of external forces have been established. In order to make the table have highresolution and positioning accuracy, an error compensation algorithm is implemented by using theestablished models. The experimental testing has been carried out to verify the performance of theworkpiece table and the established models of the micropositioning workpiece table.展开更多
The problem of chatter vibration is associated with adverse consequences that often lead to tool impairment and poor surface finished in a workpiece, and thus, controlling or suppressing chatter vibrations is of great...The problem of chatter vibration is associated with adverse consequences that often lead to tool impairment and poor surface finished in a workpiece, and thus, controlling or suppressing chatter vibrations is of great significance to improve machining quality. In this paper, a workpiece and an actuator dynamics are considered in modeling and controller design. A proportional-integral controller(PI) is presented to control and actively damp the chatter vibration of a workpiece in the milling process. The controller is chosen on the basis of its highly stable output and a smaller amount of steady-state error. The controller is realized using analog operational amplifier circuit. The work has contributed to planning a novel approach that addresses the problem of chatter vibration in spite of technical hitches in modeling and controller design. The method can also lead to considerable reduction in vibrations and can be beneficial in industries in term of cost reduction and energy saving. The application of this method is verified using active damping device actuator(ADD) in the milling of steel.展开更多
针对工业生产流水线中工件识别速度慢、精度低的问题,提出1种基于改进YOLOv5(You Only Look Once v5)的工件识别方法,称为YOLO_Meta。对YOLOv5原有的网络架构进行多个阶段的调整,包括利用双路注意力机制模块和深度可分离卷积改进主干特...针对工业生产流水线中工件识别速度慢、精度低的问题,提出1种基于改进YOLOv5(You Only Look Once v5)的工件识别方法,称为YOLO_Meta。对YOLOv5原有的网络架构进行多个阶段的调整,包括利用双路注意力机制模块和深度可分离卷积改进主干特征提取网络,可以更全面地提取特征;引入1种新型解耦头增强模型对各层级特征图的利用效率;利用聚类算法计算随机锚框相似度,对先验框进行过滤以及加入标签平滑算法等。基于MS COCO数据集和自制工件数据集进行实验并根据模型深度和宽度将模型分为大、中、小3款。实验结果表明:在MS COCO数据集上,大、中、小3款模型对比原模型的AP分别提高了3.4%、1.8%、6.9%。在自制工件数据集上,大模型对比原模型mAP提高了19.1%,F1分数提高了15.2%。文章提出的YOLO_Meta模型与原始模型相比,无论是稳定性还是准确率都有很大的提升,可为工件检测任务提供参考。展开更多
文摘Adaptive optics are becoming a valuable tool for laser processing,providing enhanced functionality and flexibility for a range of systems.Using a single adaptive element,it is possible to correct for aberrations introduced when focusing inside the workpiece,tailor the focal intensity distribution for the particular fabrication task and/or provide parallelisation to reduce processing times.This is particularly promising for applications using ultrafast lasers for threedimensional fabrication.We review recent developments in adaptive laser processing,including methods and applications,before discussing prospects for the future.
基金supported by the National Basic Research Program of China (Grant No. 2013CB035802)the 111 Project of China (Grant No. B13044)
文摘Milling of the thin-walled workpiece in the aerospace industry is a critical process due to the high flexibility of the workpiece. In this paper, a flexible fixture based on the magnetorheological (MR) fluids is designed to investigate the regenerative chatter suppression during the machining. Based on the analysis of typical structural components in the aerospace industry, a general complex thin-walled workpiece with fixture and damping constraint can be equivalent as a rectangular cantilever beam. On the basis of the equivalent models, natural frequency and mode shape function of the thin-walled workpiece is obtained according to the Euler-Bernoulli beam assumptions. Then, the displacement response function of the bending vibration of the beam is represented by the product of all the mode shape function and the generalized coordinate. Furthermore, a dynamic equation of the workpiece-fixture system considering the external damping factor is proposed using the Lagrangian method in terms of all the mode shape function and the generalized coordinate, and the response of system under the dynamic cutting force is calculated to evaluate the stability of the milling process under damping control. Finally, the feasibility and effectiveness of the proposed approach are validated by the impact hammer experiments and several machining tests. (C) 2016 Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.
基金co-supported by the National Natural Science Foundation of China (No.51575319)the Young Scholars Program of Shandong University (No. 2015WLJH31)+1 种基金the Major National Science and Technology Project (No. 2014ZX04012-014)the Tai Shan Scholar Foundation (No. TS20130922)
文摘The milling stability of thin-walled components is an important issue in the aviation manufacturing industry, which greatly limits the removal rate of a workpiece. However, for a thin-walled workpiece, the dynamic characteristics vary at different positions. In addition, the removed part also has influence on determining the modal parameters of the workpiece. Thus,the milling stability is also time-variant. In this work, in order to investigate the time variation of a workpiece＇s dynamic characteristics, a new computational model is firstly derived by dividing the workpiece into a removed part and a remaining part with the Ritz method. Then, an updated frequency response function is obtained by Lagrange＇s equation and the corresponding modal parameters are extracted. Finally, multi-mode stability lobes are plotted by the different quadrature method and its accuracy is verified by experiments. The proposed method improves the computational efficiency to predict the time-varying characteristics of a thin-walled workpiece.
基金Supported by International S&T Cooperation Program of China(Grant No.2012DFA70260)High-end CNC Machine and Basic Manufacturing Equipment of Chinese Key National Science and Technology(Grant No.2011ZX04014-081)
文摘The workpiece frames relative to each robot base frame should be known in advance for the proper operation of twin-robot nondestructive testing system. However, when two robots are separated from the workpieces, the twin robots cannot reach the same point to complete the process of workpiece frame positioning. Thus, a new method is proposed to solve the problem of coincidence between workpiece frames. Transformation between two robot base frames is initiated by measuring the coordinate values of three non-collinear calibration points. The relationship between the workpiece frame and that of the slave robot base frame is then determined according to the known transformation of two robot base frames, as well as the relationship between the workpiece frame and that of the master robot base frame. Only one robot is required to actually measure the coordinate values of the calibration points on the workpiece. This requirement is beneficial when one of the robots cannot reach and measure the calibration points. The coordinate values of the calibration points are derived by driving the robot hand to the points and recording the values of top center point（TCP） coordinates. The translation and rotation matrices relate either the two robot base frames or the workpiece and master robot. The coordinated are solved using the measured values of the calibration points according to the Cartesian transformation principle. An optimal method is developed based on exponential mapping of Lie algebra to ensure that the rotation matrix is orthogonal. Experimental results show that this method involves fewer steps, offers significant advantages in terms of operation and time-saving. A method used to synchronize workpiece frames in twin-robot system automatically is presented.
基金financially supported by the National Key R&D Program of China(No.2018YFB0703801)the Sichuan Science and Technology Program(No.2019YFSY0012)the CAS"Light of West China"Program。
文摘A novel DLC film deposition method was proposed to realize the deposition of DLC film on the surface of complex shaped workpiece.Meanwhile,Si-DLC film was deposited on the surface of M2 high-speed steel(HSS M2)and 304 stainless steel(304SS),and the microstructure,surface roughness,mechanical properties,corrosion resistance and tribological properties of Si-DLC films were characterized in detail.Results show that Si-DLC film at different axial positions of the auxiliary cathode possesses similar microstructure,film thickness and surface roughness,and the as-deposited Si-DLC film shows the low intrinsic stress of<0.3 GPa.Compared with the 304SS substrate,the Si-DLC film presents more noble corrosion potential,lower corrosion current density and higher polarization resistance,exhibiting higher corrosion resistance.Moreover,the Si-DLC film exhibits higher hardness,elastic factor and plastic factor than HSS M2 substrate and the corresponding adhesive strength is more than 10 N.The Si-DLC film sliding against GCr15 steel ball shows a lower friction coefficient than that of HSS M2 substrate and the wear rate of GCr15 steel ball sliding against the Si-DLC is lower than that of HSS M2 substrate.In addition,this novel method was used to deposit Si-DLC film on gears,drills and bearings without rotating sample racks.As a consequence,this method possesses great potential and can be generalized for the deposition of DLC film on the surface of complex shape workpiece.
基金This project is supported by National Natural Science Foundation of China(No.50275104)
文摘In order to achieve active grinding control, a novel numerical controlmicropositioning workpiece table with a resolution of 6 nm has been developed. The table is drivenby three piezoelectric actuators mounted on the base. An elastic structure with three half-notchflexure hinges is designed to apply preload to the piezoelectric actuators. The position of flexurebinges is also elaborately designed with consideration to reduce the bending deformation of themoving part. Three capacitive sensors are used to form close loop control system. Considering thetable as a damped 3-DOF mass-spring system, the models of static and dynamic stiffness and errorowing to the action of external forces have been established. In order to make the table have highresolution and positioning accuracy, an error compensation algorithm is implemented by using theestablished models. The experimental testing has been carried out to verify the performance of theworkpiece table and the established models of the micropositioning workpiece table.
基金supported by National Natural Science Foundation of China(Grant No.51675440)Fundamental Research Funds for the Central Universities of China(Grant no.3102018gxc025)
文摘The problem of chatter vibration is associated with adverse consequences that often lead to tool impairment and poor surface finished in a workpiece, and thus, controlling or suppressing chatter vibrations is of great significance to improve machining quality. In this paper, a workpiece and an actuator dynamics are considered in modeling and controller design. A proportional-integral controller(PI) is presented to control and actively damp the chatter vibration of a workpiece in the milling process. The controller is chosen on the basis of its highly stable output and a smaller amount of steady-state error. The controller is realized using analog operational amplifier circuit. The work has contributed to planning a novel approach that addresses the problem of chatter vibration in spite of technical hitches in modeling and controller design. The method can also lead to considerable reduction in vibrations and can be beneficial in industries in term of cost reduction and energy saving. The application of this method is verified using active damping device actuator(ADD) in the milling of steel.
文摘针对工业生产流水线中工件识别速度慢、精度低的问题,提出1种基于改进YOLOv5(You Only Look Once v5)的工件识别方法,称为YOLO_Meta。对YOLOv5原有的网络架构进行多个阶段的调整,包括利用双路注意力机制模块和深度可分离卷积改进主干特征提取网络,可以更全面地提取特征;引入1种新型解耦头增强模型对各层级特征图的利用效率;利用聚类算法计算随机锚框相似度,对先验框进行过滤以及加入标签平滑算法等。基于MS COCO数据集和自制工件数据集进行实验并根据模型深度和宽度将模型分为大、中、小3款。实验结果表明:在MS COCO数据集上,大、中、小3款模型对比原模型的AP分别提高了3.4%、1.8%、6.9%。在自制工件数据集上,大模型对比原模型mAP提高了19.1%,F1分数提高了15.2%。文章提出的YOLO_Meta模型与原始模型相比,无论是稳定性还是准确率都有很大的提升,可为工件检测任务提供参考。
