基于有限元法的滚珠丝杠传动过程中的温度场和热变形仿真

为减小精密机床进给传动过程中传动发热对机床进给精度的影响,考虑丝杠导程引起表面积变化及螺母移动对温度场的影响,建立滚珠丝杠传动过程中温度场和热变形的数学模型. 应用有限元法(Finite Element Method, FEM)对该模型进行数值模拟,得到滚珠丝杠传动过程中温度场的分布规律以及温度对丝杠变形的影响关系. 结果可为机床进给传动系统散热结构的设计和丝杠热变形误差补偿设计提供依据.     

机床滚珠丝杠温度场热特性分析

机床加工过程生成热导致滚珠丝杠热变形,影响加工精度.以往的研究主要通过传统的解析方法计算得到滚珠丝杠热变形量,并没有考虑机床运行过程生成热引起机件热变形的影响.考虑热源的温度场影响,应用有限元分析法建立模型,并进行仿真,从而得到滚珠丝杠的热变形量和热变形的影响因素.研究结果为分析滚珠丝杠热变形对加工精度的影响和提高机床加工精度的优化设计提供了参考,为机床加工的误差补偿提供了理论依据.     

数控机床位置精度的测试与补偿

一、床进给传动装置的结构 在数控机床进给传动装置中,一般由电动机通过联轴器带动滚珠丝杠旋转,由滚珠丝杠螺母机构将回转运动转换为直线运动.     

滚珠丝杠副热变形计算分析及可视化

以传热学原理为基础,探讨温升对滚珠丝杠副的影响。首先确定热流密度系数及对流换热系数,然后借助有限元分析软件ANSYS,建立滚珠丝杠副的有限元模型,计算求解温度场及热变形。仿真云图显示：滚珠丝杠以1350r/min旋转时,其温升达到3.8℃,引起8.32m的热变形。     

普通车床的数控改造

一、对在用的普通车床进行数控改造,应选择经济型数控系统,清华大学研制的GMT-CNC-02车床数控系统是车床改造的较佳选择;机床控制方式宜选择半闭环系统。二、伺服系统的选用。纵向进给系统采用减速齿轮副带动丝杠运动;横向进给系统由伺服电机通过十字滑块联轴结直接驱动丝杠,驱动件为SGMC系列交流伺服电机。滚珠丝杠及交流伺服电机设计计算详见论。三、在机床机械结构改造中①主传动通过加装变频器实现无级变速,并在车床主轴后端加装光电脉冲编码器使机床具有车削螺纹的功能。②进给传动系统改造后,纵向进给系统传动链为：交流伺服电机——齿轮减速箱——滚珠丝杠——大拖板;横向进给系统传动链为交流伺服电机——滚珠丝杠副——中拖板。机床部件安装调整时,应采取工艺措施保护其位置精度。③对改造后的机床应进行直线运动定位精度和重复定位精度的检验,同时要进行空载、负载的调试及加工精度检验。     

基于ANSYS的滚珠丝杠螺母副的动力学分析

滚珠丝杠螺母副是数控机床中将旋转运动转化为直线运动的常用传动机构,利用ANSYS Workbench软件对其进行动力学仿真,对滚珠丝杠螺母副的实际应用有很好的参考价值,并能对使用滚珠丝杠螺母副的数控机床样机试制提供可靠的依据。首先利用三维软件Solid Edge建立三维模型,导入有限元分析软件ANSYS Workbench前处理,定义约束和施加载荷,然后对其进行模态分析,依据前6阶固有频率,分析各频率下的振型,对避免发生共振提出依据;而后对其进行了谐响应分析,分析正弦函数对滚珠丝杠螺母副的影响程度。结果表明,利用动力学分析中的模态和谐响应分析对滚珠丝杆螺母副的机械动态特性进行仿真分析,对滚珠丝杠螺母副在数控机床中的实际应用的好坏,有很好的参考价值和理论依据。     

注塑机电动托模伺服控制系统研究

介绍一种注塑机电动托模的伺服控制技术,通过伺服运动控制卡、伺服驱动器、伺服电机和滚珠丝杠实现注塑机托模机构的伺服闭环运动控制。整个运动控制过程采用S曲线加减速运动控制算法,能够有效减少运动过程中的冲击,提高滚珠丝杠和托模机构的寿命。     

位移式阀门一旋转式阀门转换装置

位移式阀门－旋转式阀门转换装置实质上是大导程、大螺旋角多线滚珠丝杠副,它具有高效运行的可逆性,滚珠丝杠或滚珠螺母可作为主动件或从动件。当滚珠丝杠作为主动件,滚珠螺母作为从动件时,可以用滚珠丝杠很大的位移运动获得滚珠螺母较小的角位移运动。例如,在位移式阀门一旋转式阀门转换装置中,就是把滚珠丝杠的位移量（２５,４０,６０,１００ｍｍ）转换成旋转式阀门所需要的９０°或６０°的角位移量。角位移量可根据需要修正到所需要的数值,修正方法可以采用作图法和依据螺旋线公式计算法。当滚珠螺母做为主动件,滚珠丝杠做为…     

力士乐 滚珠丝杠系统

有了应用于直径为20、25、32以及40的滚珠丝杠系统的新型VSE前端润滑装置,力士乐大大降低了拥有滚珠丝杠的总成本。无需保养维护的同时还省去了中央润滑系统,这种新型前端润滑装置在正常工作条件下可实现高达3亿次的旋转或长达5年的最佳润滑效果。用于被驱动丝杠的塑料VSE将开孔泡沫与油箱相结合。接触区域内的微观运动确保流入滚珠丝杠轨道内的油量保持最小,并在轨道上覆盖一层极薄的油膜。     

舵机滚珠丝杠副测试系统的设计与实现

舵机滚珠丝杠副测试系统是导弹总装生产线上的重要设备．可为滚珠丝杠副提供一种自动化测试方法，本文介绍舵机滚珠丝杠副测试系统的硬件组成，功能测试项目和系统软件的设计。实践结果证明该系统工作良好，性能稳定。     

Dynamic reliability of thermally deduced positioning precision of ball screw systems based on random moving difference method

The positioning precision of a half-closed-loop feed system of machine tools is usually affected by the frictional heat of the system. The axial thermal errors of the working table exceeding the axial allowed tolerance is a type of failure mode of the ball screw system in positioning precision. At present, thermal error prediction and compensation methods have poor accuracy retention because they do not consider the randomness of the parameters. In order to solve the problem, we present a new random moving difference method of studying a tree-like heat transfer with thermally excited moving branches. Furthermore, based on the random moving difference method, a dynamic reliability prediction model (DRPM) of thermally deduced positioning precision is proposed, which was used in the study for predicting the dynamic variation performance of the heat boundaries in the ball screw feed drive system and the dynamic reliability of positioning precision of the system. Finally, the prediction performance of the presented method is verified under a CNC lathe. Our method provides the theoretical and practical foundation for a real-time monitoring positioning precision reliability index while describing the positioning precision accurately because it effectively takes into account the random parameters.     

Modeling and control of a feed drive with multiple mechanically coupled ball screws

This paper presents the modeling and control of a single‐axis feed drive that is jointly driven by three ball screw/motor units. These ball screws are bridged by a mechanical coupling, via which a joint thrust can be produced from the three drive units for high‐power output (e.g., injection molding machines). Synchronous positioning of these drive units can also be applied to the handling of large workpieces. For such a coupled system, a mathematical model is first derived and constructed using a system identification technique developed in this paper. A control scheme based on the master–slave control is then designed to improve the system performance with the mechanical coupling. To ensure synchronization of the three drive units, a synchronous compensator is also designed using the genetic algorithm. Finally, the performance of the entire control system is experimentally verified. Copyright © 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

螺旋理论在机器人解空间中的应用

本文首先提出了机器人解空间的概念,然后应用螺旋理论得到三自由度机器人位于解空间界面上的充分必要条件是表示三关节瞬时运动的螺旋与一过手部中心点且螺旋参量为零的螺旋互易。并推导出机器人解空间界面的母线方程。讨论了解空间界面与奇异点的关系。还举例绘制出一些解空间图形.     

双螺杆挤出机流场数值模拟中流道进出口边界条件的探讨

在对双螺杆挤出机流场的数值模拟中,流道进出口边界条件的设置一直是一个颇具争议的问题。由于事先无法获得计算域进出口平面上的真实边界条件,研究人员在进行双螺杆挤出机的流场分析时,大都采用放松边界条件。为了考察放松边界条件对双螺杆挤出机流场数值模拟结果的影响,本文采用聚合物流动分析软件POLYFLOW,在流量恒定的前提下对双螺杆挤出机流道进出口给定三种不同分布形式的速度边界条件,对其流场进行了数值模拟。数值计算结果表明,在体积流量恒定的条件下,流道进出口不同分布形式的速度边界条件对流场的影响主要集中在进出口附近区域,但对离进出口边界较远的流场影响很小。一般而言,当计算域所对应的螺杆较长时,可以忽略流道进出口的放松边界条件所引起的误差;当计算域较短时,不宜直接采用放松边界条件,而应根据螺杆的实际构型．在计算域的进出口增加适当长度的发展段。     

客车发动机舱热管理系统的数值仿真与实验验证

依据整车环境模拟实验,选取最大扭矩点、中间点和最大功率点（对应的发动机转速分别为1 800,2 800和3 450 r/min）作为发动机舱热管理系统分析的3个工况,应用FLUENT建立发动机舱热管理系统的三维仿真模型,根据实验边界条件,进行风速场和温度场的耦合仿真。采用稳态计算方法,获得发动机舱内外稳定的风速场和温度场分布。对比分析发现仿真结果与实验结果的均方根相对误差在合理范围内,从而验证该发动机舱热管理系统仿真模型的有效性。     

滚珠丝杠副加载试验台测控系统设计

一体化工业计算机系统目前在测控领域应用广泛.通过对滚珠丝杠副轴向力加载试验功能分析,拟定了滚珠丝杠副轴向力试验方案,构建了基于一体化工业计算机控制的测控系统,基于虚拟仪器技术平台和LabVIEW编程语言,设计了测控软件.实践验证与测试表明,一体化工业计算机结合虚拟仪器技术平台开发测控系统可以大大降低其软、硬件研发周期.     

强耦合双通道热分析炉温度跟随控制策略研究

量热仪作为化学品热危险性评估的主要工具之一,其热分析炉温度控制的准确性、通道间温度无差异性是保障样品放热量检测精度的前提.针对该类炉体纯滞后、大惯性及通道间强耦合的特性,提出了一种将功率补偿、模糊PID与跟随控制相结合的控制策略.此策略无需准确的数学模型,计算简单.实验结果表明,该控制策略相比于传统PID控制具有响应快、超调小、双通道温差小的特点,满足双通道热分析炉匀速升温控制中速率准确性和双通道温度一致性要求.     

Effects of slip on sheet-driven flow and heat transfer of a non-Newtonian fluid past a stretching sheet

The flow and heat transfer of an electrically conducting non-Newtonian fluid due to a stretching surface subject to partial slip is considered. The constitutive equation of the non-Newtonian fluid is modeled by that for a third grade fluid. The heat transfer analysis has been carried out for two heating processes, namely, (i) with prescribed surface temperature (PST-case) and (ii) prescribed surface heat flux (PHFcase) in presence of a uniform heat source or sink. Suitable similarity transformations are used to reduce the resulting highly nonlinear partial differential equations into ordinary differential equations. The issue of paucity of boundary conditions is addressed and an effective second order numerical scheme has been adopted to solve the obtained differential equations. The important finding in this communication is the combined effects of the partial slip, magnetic field, heat source (sink) parameter and the third grade fluid parameters on the velocity, skin friction coefficient and the temperature field. It is interesting to find that slip decreases the momentum boundary layer thickness and increases the thermal boundary layer thickness, whereas the third grade fluid parameter has an opposite effect on the thermal and velocity boundary layers.     

Prognostic study of ball screws by ensemble data-driven particle filters

The prognostic study of the ball screw is critical to increase the reliability of manufacturing system, which has drawn great attention in the field of Prognostics and Health Management (PHM). The particle filters (PF) method is a powerful tool for prognostic study because of its capability of robustly predicting the future behavior. However, lack of analytical ball screw measurement model limits the application of PF. In this paper, an ensemble GRU network is designed to extend PF to the case where the analytical measurement equation is not available. The proposed hybrid GRU-PF method integrates the data-driven model and the physical model into the particle filters network to realize the prognostic and remaining useful life (RUL) prediction of the ball screw. The effectiveness of the proposed method is validated by designing a ball screw accelerated degradation test (ADT), and the results of this experimental study demonstrate the satisfactory performances in terms of prognostic sensibility.