This paper presents a coaxial integrated macro-micro composite actuator. The macro-actuator of the macro-micro composite actuator is similar to a moving coil type voice coil motor, and a giant magnetostrictive actuator is installed coaxially inside it as a micro-actuator. In this work, kinetic models are established for both the macro-actuator and micro-actuator, and based on the models, an automatic disturbance rejection controller is adopted to control the macro-actuator, and a fuzzy sliding mode controller is adopted for the micro-actuator. In order to verify the actual performance of the proposed macro-micro composite actuator, a prototype was fabricated, and experimental results show that the macro-actuator can achieve a 10 mm step positioning error of 9 mu m and a 30 mm step positioning error of 11 mu m under a load of 1 kg. The resolution of the minimum PWM square wave change identification of the controlled micro-actuator is 0.047 mu m, and the minimum displacement resolution of the micro-actuator is 0.15 mu m. The micro-actuator is capable of achieving 1 mu m steps with no displacement overshoot. In addition, when the positioning distance is 5 mu m, there is a small amplitude overshoot of 0.18 mu m. The final positioning accuracy of macro-micro composite positioning is within 350 nm.

Bolted connections are widely used under impact loading conditions, and the detection of the bolts loosening is important. Although previous studies have utilized triboelectric nanogenerators (TENGs) for detecting bolt loosening, they have predominantly concentrated on the state of individual bolts. In this work, a self-powered Polyimide/Copper TENG (PC-TENG) sensor was proposed for the real-time monitoring of multiple bolts under impact loading. By incorporating LED indicators into each PC-TENG and measuring the output voltage, it is a simple and straight way to detect the presence of loose bolts and to identify their specific locations. Moreover, the possibility by only measuring the combined output voltages of TENG sensors was studied, and it was found that the TENG sensors with different output voltages were suitable for the multiple bolts detection, while the ones with similar output voltages cannot be employed for the multiple cases. The inconsistence of TENGs output results was often seen as a disadvantage, but in this work, we innovatively leveraged this behavior to enable multiple bolts loosening detection. By creatively utilizing distinct voltage outputs and integrated LED indicators, this PC-TENG system achieves simple, real-time identification of loose bolts in multi-bolt setups, offering a novel strategy for structural health monitoring in practical applications.

Purpose - The purpose of this study is to detect the bolt loosening under conditions of impact loading with a low-cost self-powered triboelectric nanogenerator sensor. Design/methodology/approach - In this work, an Al/PTFE-based triboelectric nanogenerator (AP-TENG) is used as a sensor. A pendulum impact device and a force hammer were used to apply the impact loads. The bolt status and the applied torque can be monitored under impact loading conditions by using the output voltage results of the AP-TENGs. Findings - The output voltage results of the current AP-TENG sensor under five different bolt torques, i.e. from 0.5 to 2.5 N m, were measured. The measurements revealed that a thicker buffer layer significantly contributed to the generation of higher voltages. Besides, the AP-TENG was also used to light ten commercial green LEDs in series, and the brightness of the LEDs was high enough even for the daytime, which showed that it can be used as the alarm device. In addition, a sudden loose test was also carried out, and the obvious voltage spikes can be seen without the external impact. The force hammer impact tests have expanded the application scope of the AP-TENG in the bolt loosening detection. Originality/value - The bolt loosening monitoring is important and useful for the safe operation. The application of TENG technology for detecting bolt loosening remains relatively unexplored. In addition, ten commercial green LEDs can be driven by the AP-TENG sensor, which can be used for the early warning of the bolted loosening status.

A coaxially integrated macro-micro composite actuator (MMCA) with large stroke and high accuracy is proposed by combining a voice coil motor (VCM) with the giant magnetostrictive actuator (GMA). The magnetic circuit model of the macro-motion part is established based on the driving principle of VCM, and the multi-field coupling model of the micro-motion part is established based on the Jiles-Atherton model. The finite element method was used to analyze the relationship between displacement, output force, velocity, acceleration, and time of the macro-motion part under different currents, the magnetic flux density, output force, and displacement curves of the micro-motion part, and the mutual influence between the macro and micro motion parts were analyzed. The prototype of the MMCA was developed, and an experimental test platform was built. The results show that the MMCA macro-motion displacement curve can fit the simulation curve well during open-loop positioning, and when the current size of the input macro-motion coil is 4 A, the experimental curve of the MMCA is the most consistent with the simulation curve. When closed-loop control, the motion curve of the drive can well follow the set displacement curve, in which the maximum stroke of the prototype developed is 50 mm, the positioning error of the macro-motion part is less than 20 μm, the maximum stroke of the micro-motion part is 40 μm, and the overall positioning accuracy of the MMCA is 0.14 μm. The research results provide a new idea and theoretical basis for further optimization and development of precision positioning platform with high precision and large stroke.

Ultrasonic shot peening (USP) is widely used for materials surface strengthening and metal sheet forming as a novel mechanical surface treatment technology. The USP-caused surface roughness is usually viewed as an unfavorable factor influencing the service performance of the mechanical components treated by USP. Taking advantages of the experimental investigation, analytical calculation and finite element simulation, the correlation between the USP-caused surface roughness and the USP-induced metal sheet forming deformation is studied comprehensively. Firstly, the USP intensity was experimentally tested by USP of Almen strips. In accordance with the USP intensity, the experimental investigations on the evolutions of surface roughness caused by USP of 2024 aluminum alloy sheets with the thicknesses of 1mm, 2mm and 3mm were carried out, respectively. An analytical calculation model (ACM) was then proposed to account for the effects of the USP-induced metal sheet forming deformation on the USP-caused surface roughness. The analytically-calculated results are in good agreement with the experimentally-measured surface roughness caused by USP of 2024 aluminum alloy sheets. Lastly, linking the finite element simulation of the USP-induced metal sheet forming with the analytical calculation model, an innovative FEM-ACM coupling approach was presented for predicting the evolutions of surface roughness caused by USP of metal sheets. It has been experimentally validated with USP of 2024 aluminum alloy sheets, and would be of great significance for the development and industrial application of USP technology.

In order to study the drawability of AA5754 aluminum alloy blank, the numerical predictions of fracture failure behavior caused by cup drawing of metal sheet were carried out by using the GTN model and the thermodynamic-based continuous damage mechanics (CDM) model. The CDM model coupling the nonlinear isotropic and kinematic hardening laws with the isotropic ductile damage model was developed to carry out the numerical computation in the form of the user material subroutines. Although the forming limit curves predicted by GTN model and CDM model are distinctly different, but both of them are feasible to characterize the formability of metal sheets. The numerically predicted drawability of metal sheet is in good agreement with the experimental results in terms of strokes, sheet thinning and fracture failure location. The effects of sheet original thickness and friction coefficient between punch and sheet on the drawability of metal sheet were further investigated in detail.

Laser shock peening (LSP) has been frequently used in the aerospace industry for improving the fatigue performance of the load-bearing components by introducing the beneficial compressive residual stresses into the structural materials. By taking the advantages of finite element method (FEM) and artificial neural network (ANN), the FEM-ANN coupling dynamic prediction method is proposed to evaluate the in-depth residual stresses induced by LSP of TC4 titanium alloy. The Python program-based three-dimensional parametric modellings for the repeated LSP associated with the circular-shape laser spot and the multiple LSP associated with the squareshape laser spot are carried out, respectively. The LSP parameters are randomly generated within the given ranges and are treated as the input layer of ANN model, and the in-depth residual stresses induced by LSP are regarded as the output layer. The raw data resulting from FEM calculations are employed to train, test and validate ANN model. Once the test or validation for ANN model fails, the raw data in the test set or validation set would be transferred into the training set for further training the networks. As a result, the prediction accuracy of ANN model could become increasingly higher with the increase of the raw data in the training set. The FEM-ANN coupling dynamic predictions correlated with the dynamic prediction accuracy are well consistent with the FEM calculations as well as the experimental data, indicating that the FEM-ANN coupling dynamic prediction method is feasible and effective to evaluate the LSP-induced residual stresses. It therefore provides a new way to predict the LSP-induced residual stresses with high efficiency and low cost.

Surface mechanical rolling treatment (SMRT) is well documented as a novel and promising surface self-nanocrystallization technology. An experiment platform of air pressure-driven surface mechanical rolling treatment was established innovatively, and the gradient-structured 1060 aluminum rod samples were accordingly fabricated by air pressure-driven SMRT. The air pressure, rolling pass and rotation speed of rod sample are the three parameters used for controlling the SMRT process. A three-factor and five-level orthogonal experiment table was designed to study the effects of the process parameters on the results of air pressure-driven SMRT of 1060 aluminum rod samples in terms of the surface roughness and in-depth microhardness. The experimental results show that the different combination of the three process parameters could obtain almost the same surface roughness or in-depth microhardness. Both the surface roughness and in-depth microhardness induced by air pressure-driven SMRT of 1060 aluminum rod samples are relatively more sensitive to the air pressure. Based on the microstructure observations, the grain refinement mechanism of 1060 aluminum induced by air pressure-driven SMRT was discussed in detail. The friction and wear experiments were further conducted to investigate the influences of the surface roughness and in-depth microhardness on the dry sliding wear behavior of the air pressure-driven SMRTed 1060 aluminum rod samples. In comparison to the reduction of surface roughness, the increase of the in-depth mircohardness has the more significant impact on the dry sliding wear behavior of the SMRTed 1060 aluminum rod samples.

Based on the configuration of the Stewart parallel mechanism (SPM), after analyzing the kinetostatic characteristic of a planar four-bar linkage with attached springs which works around the kinematic limb-singularity, a process of constructing a novel multi-degree of freedom (DOF) parallel passive compliant constant-force mechanism (CCFM) is presented. The kinematic limb-singularity of a rigid four-bar linkage with attached springs is obtained and then is applied to construct a constant-force compliant mechanism (CM) based on the pseudo-rigid-body-model by designing appropriate structure parameters to obtain appropriate equivalent spring stiffness of flexures. The CCFM is further used as the branches of the SPM and then a passive multi-DOF parallel mechanism (PM) is constructed. Here the method of replacing the original rigid branch of the PM with the CCFM is called the "Expanded Rigid-body Replacement Synthesis" (ERBRS). The multi-DOF parallel passive CCFM can generate a constant-force zone when makes a small pose transformation around a certain position, where each compliant branch is located at the constant-force zone. The proposed CCFM can be applied in practice such as the polishing machine which needs the constant contact-force between the polishing head and the workpiece. The proposed method of constructing a CCFM with one- or multi-degree of freedom mechanism has some important reference value on designing other types of CCFMs.

"一带一路"倡议和新工科建设理念对工科人才培养提出新的挑战.各工科院校需要改变传统教育理念,调整、改革及创新工科人才培养模式,以适应新时代对人才培养目标的需求.探讨工科专业的培养目标制定、协同育人保障体系构建和人才培养质量评价体系建立等,有望为培养并输出社会适应性强,具备多样化、个性化、可持续竞争力并兼具创新能力的新型复合型工科人才提供新思路.

针对目前多数微纳测头约束支撑机构刚度不可调的问题,基于柔性三角梁约束支撑原理,构造一种具有变刚度特性的新型微纳测头结构.利用压电叠堆器驱动柔顺机构以控制约束支撑梁所受轴向力,进一步调节梁的支撑刚度以及约束支撑机构的整体刚度.应用最小势能原理分别建立约束支撑机构的垂直刚度和横向刚度的理论模型,并利用有限元分析法获得支撑刚度随压电叠堆器输出轴向压力的刚度曲线.对比支撑刚度理论值和仿真值大小,结果表明建立的理论刚度模型正确.研究揭示了该新型微纳测头的变刚度机理,为其实际应用过程中的变刚度控制奠定了重要的理论基础.

在现代先进制造业中,特种加工技术是不可或缺的加工手段.针对工程实训教学中存在的问题,对特种加工实训方案进行教学改革和积极探索,对教学内容、教学模式和考核标准进行优化,提高学生的参与意识,激发学生的学习兴趣,最终达到提高实训教学效果的目的.

给出一种基于伪刚体模型的柔顺夹持器设计方法.基于附加弹簧双滑块四杆机构构造了一种具有恒力特性的柔顺夹持机构.建立了机构位置分析模型,利用虚功原理构建运动静力学方程,分析弹簧刚度对机构输出特性的影响,获得了具有一种恒力特性的柔顺夹持机构设计方法.基于伪刚体模型,将附加弹簧以柔性模块替代,得到一种新型柔顺恒力机构.利用有限元分析软件验证该机构理论模型建立柔顺恒力机构的可行性;构造了一种具有对称结构形式的新型柔顺恒力夹持器.该柔顺恒力夹持器的设计方法也可应用于其他类型附加弹簧机构的非线性刚度特性柔顺机构设计.

Being different from avoidance of singularity of closed-loop linkages, this paper employs the kinematic singularity to construct compliant mechanisms with expected nonlinear stiffness characteristics to enrich the methods of compliant mechanisms synthesis. The theory for generating kinetostatic nonlinear stiffness characteristic by the kinematic limb-singularity of a crank-slider linkage is developed. Based on the principle of virtual work, the kinetostatic model of the crank-linkage with springs is established. The influences of spring stiffness on the toque-position angle relation are analyzed. It indicates that corresponding spring stiffness may generate one of four types of nonlinear stiffness characteristics including the bi-stable, local negative-stiffness, zero-stiffness or positive-stiffness when the mechanism works around the kinematic limb-singularity position. Thus the compliant mechanism with an expected stiffness characteristic can be constructed by employing the pseudo rigid-body model of the mechanism whose joints or links are replaced by corresponding flexures. Finally, a tri-symmetrical constant-torque compliant mechanism is fabricated, where the curve of torque-position angle is obtained by an experimental testing. The measurement indicates that the compliant mechanism can generate a nearly constant-torque zone.

针对传统微纳测量装置在测量过程中测头支撑机构刚度不可变化的问题,设计了一种基于悬丝约束支撑的变刚度微纳测头.利用压电装置驱动柔顺导向机构产生位移,以改变悬丝所受的轴向张紧力.基于应力刚化原理改变悬丝的横向刚度,进而改变测头支撑机构的整体刚度,以获得具有变刚度性能的新型微纳测头.根据测头支撑机构在测量过程中刚度的变化,分别建立刚性和柔性模式下微纳测头Z向和横向的刚度理论模型.根据有限元仿真和刚度理论模型,分别得到测头刚度随悬丝端面受力的变化曲线.对比测头刚度的仿真值和理论值,得到测头Z向和横向刚度的平均相对误差分别为2.41％ 和4.72％,结果表明理论模型具有较高的准确性.研究成果为该类型测头的变刚度控制奠定了前期理论基础.

机构静力学建模是机构学的基础,运用计算机辅助设计是提高学生综合应用知识能力的重要手段.本文以附加弹簧双滑块四杆机构为例,利用虚功原理,阐述基于Maple软件的机构位置闭环方程和运动静力学建模过程,并得到机构的力-位移模型;并利用Matlab软件,将重要模型以图形化描述,展示不同参数对力-位移曲线的影响情况.结果证明,附加弹簧机构的非线性特性扩展了学生的学习视野,有利于提高学生机构创新设计能力;采用的教学手段增强了教学过程的生动性,激发了学生的学习兴趣,提高了学生的实践能力.

The theory of nonlinear stiffness characteristic by employing the kinematic limb-singularity of planar mechanisms with attached springs is proposed.After constructing the position formula with closed-loop form of the mechanism, the kinematic limb-singularity can be identified.The kinetostatic model can be obtained based on the principle of virtual work.The influences of spring stiffness on the force-displacement or torque-angle curve are analysed.Different spring stiffness results in one of four types of stiffness characteristic, which can be used to design an expected stiffness characteristic.After replacing corresponding joints with flexures, the pseudo-rigid-body model of the linkage with springs is obtained.The compliant mechanisms with nonlinear stiffness characteristic can further be synthesised based on the pseudo-rigid-body model.

微纳测头是精密测量机的关键部件,其刚度特性直接影响坐标测量机的整体性能.基于压杆失稳原理,构造一种具有变刚度特性的新型微纳测头.利用压电装置驱动柔性机构变形以改变柔性支撑梁的轴向受力和横向刚度,从而改变约束支撑机构的整体刚度.综合考虑测头的刚度特性、结构稳定性和解耦性等因素,构造出基于十字交叉型悬臂梁支撑的变刚度微纳测头.利用最小势能原理构建微纳测头约束支撑机构的刚度模型,基于模型获得所需压电驱动力大小.通过有限元仿真得到测头刚度随压电驱动力变化的曲线.对比刚度理论计算值与仿真值,分别得到微纳测头约束支撑机构的轴向刚度及横向刚度的平均相对误差.仿真结果表明,建立的刚度理论模型具有较高的准确性.研究结果为该新型微纳测头的变刚度控制奠定了理论基础.

在复杂背景图像中,为准确识别垂直伸缩式刀闸状态,定义了新的绝缘子边缘特征,提出了垂直伸缩式刀闸检测与状态识别方法。采用改进的Freeman链码描述绝缘子波动点结构的边缘特征,利用提取的边缘特征在图像分割基础上定位刀闸位置。利用开合状态背景连通性的差异,通过区域语义分割实现对刀闸状态的正确识别。现场图片试验结果显示:采用该算法提取到的特征点主要分布在绝缘子周围,自动查找到的连通区域在开关状态下区别明显。改进的Freeman链码能有效描述绝缘子边缘连续波动特征,通过查找相应窗口即可准确定位刀闸区域。背景连通性的差异性适用于对各种型号垂直伸缩式刀闸开关状态的正确判断。

针对常模算法(CMA)对非常模高阶QAM信号均衡后收敛速度慢、稳态均方误差大的缺点,以T/4分数间隔均衡器为例,提出一种基于余弦代价函数的T/4分数间隔盲均衡算法(T/4-FSE-CCF),该算法将常模的代价函数用构造的余弦代价函数来替代,新算法摆脱了常数模算法对统计模值R的依赖.最后对算法性能进行了理论分析和仿真实验,结果表明,该算法对高阶QAM信号不仅提高了收敛速度而且降低了稳态均方误差.