The Influence of Centrifugal Force on the Interference Fit of High-Speed Electric Spindle

The letter presents an analysis of interference fit of the electric spindle at different rotor speeds due to the influence of centrifugal force and provides a theoretical formula showing the relationship of the speed, stress on the rotation speed. The letter also established a finite element model of the interference fit. The study found that as the rotation speed increases, the interference and contact stress between the spindle and the rotor gradually decrease, and the reduced speed is proportional to the square of the rotation speed.

Thermal Model of High-Speed Spindle Units

For the purpose to facilitate development of high-speed Spindle Units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.

Model of Rotation Accuracy of High-Speed Spindles on Ball Bearings

For the purpose to improve a design quality of high-speed spindle units, we have developed mathematical models and software to simulate a rotation accuracy of spindles running on ball bearings. In order to better understand the mechanics of ball bearings, the dynamic interaction of ball bearings and spindle unit, and the influence of the bearing imperfections on the spindle rotation accuracy, we have carried out computer aided analysis and experimental studies. When doing this, we have found that the spindle rotation accuracy can vary drastically with rotational speed. The influence of bearing preload has a secondary importance. Comparison of the results of these studies has demonstrated adequacy of the models developed to the real spindle units.

Research Progress of Key Technology of High-Speed and High Precision Motorized Spindles

High speed machining and high precision machining are two tendencies of themanufacturing technology worldwide. The motorized spindle is the core component of the machine toolsfor achieving the high speed and high precise machining, which affects the general developmentlevel of the machine tools to a great extent. Progress of the key techniques is reviewed in thispaper, in which the high speed and high precision spindle bearings, the dynamical and thermalcharacteristics of spindles, the design technique of the high frequency motors and the drivers, theanti-electromagnetic damage technique of the motors, and the machining and assembling technique areinvolved. Finally, tha development tendencies of the motorized spindles are presented.

Temperature prediction model for a high-speed motorized spindle based on back-propagation neural network optimized by adaptive particle swarm optimization

To predict the temperature of a motorized spindle more accurately,a novel temperature prediction model based on the back-propagation neural network optimized by adaptive particle swarm optimization(APSO-BPNN)is proposed.First,on the basis of the PSO-BPNN algorithm,the adaptive inertia weight is introduced to make the weight change with the fitness of the particle,the adaptive learning factor is used to obtain different search abilities in the early and later stages of the algorithm,the mutation operator is incorporated to increase the diversity of the population and avoid premature convergence,and the APSO-BPNN model is constructed.Then,the temperature of different measurement points of the motorized spindle is forecasted by the BPNN,PSO-BPNN,and APSO-BPNN models.The experimental results demonstrate that the APSO-BPNN model has a significant advantage over the other two methods regarding prediction precision and robustness.The presented algorithm can provide a theoretical basis for intelligently controlling temperature and developing an early warning system for high-speed motorized spindles and machine tools.

MECHANICAL-ELECTRIC COUPLING DYNAMICAL CHARACTERISTICS OF AN ULTRA-HIGH SPEED GRINDING MOTORIZED SPINDLE SYSTEM

On the basis of the traditional mechanical model of a grinding wheel rotor and the mechanical-electric coupling model with ideal sinusoidal supply, taking high-frequency converting current of inverter power switches into further consideration, a modified mechanical-electric coupling model is created. The created model consists of an inverter, a motorized spindle, a grinding wheel and grinding loads. Some typical non-stationary processes of the grinding system with two different supplies, including the starting, the speed rising and the break in grinding loads, are compared by making use of the created model. One supply is an ideal sinusoidal voltage source, the other is an inverter. The theoretical analysis of the high-order harmonic is also compared with the experimental result. The material strategy of suppressing high-order harmonic mechanical-electric coupling vibration by optimizing inverter operating parameters is proposed.

Preliminary study of the electrospray DPE peculiarities from the liquid surface in the presence of the CSWs

The Ultrasonic Electric Propulsion(UEP)system is a cutting-edge propulsion technology that is mostly used on platforms for small satellites(less than 10 kg).The characteristics of droplet partial emissions(DPEs)in the UEP system are investigated using a high-speed imaging technique(an ultra-high speed camera(NAC HX-6)and a long-distance microscope)in this work.The experiments demonstrate that there are a few partial emission modes,including left-side emission,double-side emission,and right-side emission,that are present in the droplet emission process of the UEP system.These modes are primarily caused by the partial formation of capillary standing waves(CSWs)on the emission surface of the ultrasonic nozzle.The emission rate for single-and double-sided emissions varies at different times,indicating that there are different CSWs engaged in droplet emission due to variations in the liquid film thickness and charge state of the liquid cones.Additionally,as the droplets emit continuously,a raised area on the emission surface appears,with several droplets emitting there as a result of charge accumulation.Additionally,photos of the CSWs with emitting droplets are obtained,which highlights the CSWs'distinctive wave morphology.

Lightweight design of 45000r/min spindle using full factorial design and extreme vertices design methods

Factors for determining the spindle size are the shaft diameter, positions of bearing and motor, and entire length of the spindle. Then, it is important to find the assembling of the optimal design variables, which satisfy the stiffimss and rotational speed required to the spindle. A general full factorial design method was used to verify some factors that affect the natural frequency of a spindle. It is verified that the shorter shaft length and bearing span length represent the higher natural frequency, and there are some effects according to the change in the levels of factors. The detailed spindle dimension is determined by applying an EVD method, which can define the optimal bearing position through considering the limiting condition. Based on the estimated regression model, the optimal spindle size and bearing distance that can improve the primary natural frequency are obtained, and the influence of design factors on the natural frequency is also analyzed.

Fuel Saving and Emissions Cut Through Shore-Side Power Concept for High-speed Crafts at the Red Sea in Egypt

The progress of economic globalization,the rapid growth of international trade,and the maritime transportation has played an increasingly significant role in the international supply chain.As a result,worldwide seaports have suffered from a central problem,which appears in the form of massive amounts of fuel consumed and exhaust gas fumes emitted from the ships while berthed.Many ports have taken the necessary precautions to overcome this problem,while others still suffer due to the presence of technical and financial constraints.In this paper,the barriers,interconnection standards,rules,regulations,power sources,and economic and environmental analysis related to ships,shore-side power were studied in efforts to find a solution to overcome his problem.As a case study,this paper investigates the practicability,costs and benefits of switching from onboard ship auxiliary engines to shore-side power connection for high-speed crafts called Alkahera while berthed at the port of Safaga,Egypt.The results provide the national electricity grid concept as the best economical selection with 49.03 percent of annual cost saving.Moreover,environmentally,it could achieve an annual reduction in exhaust gas emissions of CO2,CO,NOx,P.M,and SO2by 276,2.32,18.87,0.825 and 3.84 tons,respectively.

Plasma-Assisted Chemistry in High-Speed Flow

Fundamental problems related to the high-speed combustion are analyzed. The result of plasma-chemical modeling is presented as a motivation of experimental activity. Numerical simulations of the effect of uniform non-equilibrium discharge on the premixed hydrogen and ethylene-air mixture in supersonic flow demonstrate an advantage of such a technique over a heating. Experimental results on multi-electrode non-uniform discharge maintenance behind wallstep and in cavity of supersonic flow are presented. The model test on hydrogen and ethylene ignition is demonstrated at direct fuel injection to low-temperature high-speed airflow.

High-speed imaging observation on molten bridges of AgNi10 electrical contact material

The electrical contact-high-speed imaging experimental system was developed to investigate the molten bridge phenomena of AgNi10 electrical contact material.The dimension of molten bridges was measured along with the measurement of waveforms in the contact voltage under the load of direct current(DC) 6 V(8-20 A)and breaking speed of 50.0 mm·s^(-1).A part of the observed results was presented as well as surface morphology of the contacts after electrical contact behavior,which shows some interesting and new phenomena.Molten bridges and arc could exist simultaneously.The stable molten bridge looks like cylindrical shape and then becomes needle tip at its rupture,the diameter and length of molten bridges both increase with the increase in current and the growth gradient of the diameter is larger than that of the length.The morphology and elemental distribution of the contact surface are changed by the behavior of electrical contact.

数控机床电动主轴WPD-TSNE-SVM模型故障诊断

为了提高数控机床电动主轴故障诊断效率,设计了一种WPD-TSNE-SVM组合模型。利用小波包方法分解主轴振动信号,并完成样本集TSNE降维的过程,利用SVM完成重构特征的故障分类。构建数控机床主轴信号混合特征空间向量,并进行故障诊断分析。研究结果表明:TSNE方法训练样数据形成规律分布特点,采用非线性SVM多故障分类器实现小波包混合特征的故障准确分类。根据径向基核函数建立的非线性SVM诊断方法获得更高准确率。该方法诊断轴承运行故障,获得更高维护效率,确保数控机床主轴运行稳定性。

高速电主轴瞬态热特性实验研究

热变形是影响高速机床加工精度的重要因素。为了研究高速电主轴热特性,搭建了包含多组温度传感器、多通道无知记录仪、激光位移传感器、涡电流传感器、高频数据采集卡、工控机的高速机床温度场和热变形实时检测平台。测试结果表明,电主轴定子的温度随转速增加而升高,转速超过3000转/分后温升更显著。电主轴系统产生的大部分热量被冷却水吸收,底座、水套、轴承外圈温升不大。主轴因热变形引起的位置偏差随转速增大而增大,主轴端面跳动却随转速增大而减小。该研究为高速机床热误差控制和补偿建模提供依据。

缺血性神经阻滞状态下神经肌肉电刺激诱发感觉皮层活动的研究

目的基于缺血性神经阻滞(INB)技术能够成功剥离出运动阈值上神经肌肉电刺激(NMES)前臂肌肉诱发的肌梭感觉传入信息,本文旨在探究INB状态下感觉运动皮层如何感知运动阈值上NMES所诱发的肌梭感觉传入信息。方法本文设计了一个2×2因素(INB:前、后;NMES强度:运动阈值上、下)的实验任务方案,任务期间记录健康受试者大脑64通道脑电信号,并利用脑电beta频段的事件相关去同步化(beta ERD)量化感觉运动皮层区域的激活水平。通过心理物理学测试评估血压袖带施加于右手腕处后受试者右手感觉与运动的变化。结果在INB状态下,运动阈值上NMES诱发的对侧感觉运动皮层脑电beta ERD显著减弱,并且在INB施加前,运动阈值上、下NMES诱发的对侧感觉运动皮层脑电beta ERD幅值差异具有统计学意义(P<0.05),但是此差异在INB状态下消失。此外,阻滞成功后NMES诱发的感觉运动皮层脑电beta ERD的对侧优势转移到了同侧。结论INB导致运动阈值上NMES诱发的皮层活动显著减弱,对侧感觉运动皮层对NMES刺激强度的感知减弱,这可能由INB引起感觉运动皮层产生快速功能重塑造成。

基于激光测振技术的铣床电主轴振动特性研究

采用激光测振技术获取了机床不同转速下的振动信号,并分析研究了其振动特性。使用激光测振仪采集机床电主轴的振动速度信号,避免了传统传感器带来的附加质量问题,提高了测量的准确性。完成电主轴在不同位置测点和不同转速运转状态下的振动信号采集实验,对采集到的原始振动速度信号和原始振动速度信号,经积分得到的振动位移信号,并进行时域分析。结果表明:在所测转速范围内机床电主轴的振动位移平均幅值稳定在1μm范围内;在所测转速范围内,随着转速的增加,电主轴各个测点的振动烈度是先缓慢增加再减小再快速增加的趋势,在14 000 r/min振动烈度局部最小,该结果可指导实际加工过程中的加工参数选择;电主轴上测点轴向方向位置距离主轴端部越近,振动烈度越大,检测主轴振动状况是否异常时应选取靠近主轴端部的测点来代表电主轴的振动状况。

基于多性能退化参数的电主轴可靠性研究

以数控机床磨削电主轴为研究对象,运用多性能退化参数可靠性理论对磨削电主轴进行研究。通过分析磨削电主轴的失效机制,选取性能退化参数,并在此基础上建立性能退化模型,提出一种基于多性能退化参数的电主轴可靠性评估方法。通过搭建试验台,采集性能退化参数试验样本数据,预测电主轴的可靠性变化规律,并将基于多性能退化参数的电主轴可靠性方法与基于单一性能退化参数中的贝叶斯法进行对比。结果表明:基于单一性能退化参数的方法往往高估电主轴的寿命,多性能退化参数的电主轴可靠性评估方法更加贴合实际。提出的方法可为数控机床电主轴可靠性评估提供参考。

面向铣削场景的电主轴数字孪生调试方法研究

数控机床电主轴作为机床关键功能部件之一,其工作性能直接影响数控机床的加工效果。电主轴加工前的调试工作,对于提升机床加工效率和工作性能具有重要意义。文章建立了面向铣削场景的电主轴数字孪生调试方法,针对控制效果受运行工况、敏感参数变化影响导致调试结果可靠性降低的问题,分析系统特性与运行场景特点,构建铣削场景模型,并将运行场景注入孪生模型内,结合基于模型的整定算法与手动调优策略,研究数字孪生驱动的虚拟调试方法。以主轴电机速度环控制参数为例,对PI参数进行虚拟调试优化,对比实验测试数据得出在缩短调试时间的同时也降低稳态误差48%、缩短响应时间13%,从而验证了所提方法的有效性和现场应用的可行性。

卧式五轴数控机床电主轴的动态特性分析及振动抑制优化

针对某卧式五轴数控加工中心电主轴动态特性较差、测试过程中振动量大的问题,对其建立动力学模型,利用Ansys Workbench对其进行模态分析,解得固有频率及模态振型。基于仿真结果及电主轴结构原理,诊断为电主轴后端悬伸量较大,外部连接法兰与主轴后轴承盖及冷却水套间隙量较大,导致机床固有频率低,动态特性差。针对上述原因对电主轴后端悬伸部增加辅助支撑优化设计,进行模态仿真分析,通过优化前后固有频率及临界转速数据对比验证其可行性。将优化设计应用于实际,并对电主轴进行振动测试,试验表明:电主轴振动量大幅减小,优化设计合理。研究结果为卧式五轴数控机床电主轴系统动态特性的改善,提供了优化思路和设计方法。

碳纤维-金属复合电主轴关键部件优化设计

为了进一步提升电主轴的加工性能,以常见的A02型电主轴为分析对象,使用热膨胀系数小以及减振性能优异的碳纤维材料替换芯轴的不同部位,以此设计4种碳纤维-金属复合芯轴,探讨其对A02型电主轴的影响。通过有限元分析,对4种碳纤维-金属复合芯轴和常规钢芯轴的动态特性和热特性进行评估。结果表明:全碳纤维芯轴的性能最佳,而心部碳纤维芯轴可以在避免使用大量碳纤维材料的基础上实现与全碳纤维芯轴相近的效果;外侧碳纤维芯轴具有成熟的加工工艺,可以直接进行加工试验。列举了几种碳纤维-金属复合芯轴已有或具备可行性的加工方案,为碳纤维材料与电主轴结构更好地结合提供参考。

高速电主轴轴承接触特性仿真研究

轴承是高速电主轴核心的回转部件,准确地进行接触特性分析计算和预测高速电主轴轴承的寿命,是保证高速电主轴可靠、稳定运行的关键。为此,研究了高速电主轴角接触球轴承的接触特性并进行仿真分析,考虑电主轴的高速及超高速运行工况因素,建立了高速电主轴角接触球轴承的三维几何模型、力学模型、受力模型和有限元分析模型。进行了角接触球轴承在载荷与约束下的等效应力、接触应力和径向变形等静力学仿真分析,结果说明内圈与滚动球体接触部位的总体变形量较小,轴承内圈的接触应力均大于外圈的接触应力,外圈的总体寿命稍高于内圈,滚动球体与内外圈非接触部位寿命高于其接触部位,能够满足实际使用要求,并且得到角接触球轴承接触特性规律,对进一步研究角接触球轴承疲劳寿命延长具有重要的理论意义和工程应用价值。