基于AMEsim背压补偿对液压缸低速运行稳定的研究

为避免液压低速爬行现象对机械制造业的危害,从液压系统背压入手,通过对无背压系统及背压系统的系统刚度及运动学分析,得到系统刚度及临界爬行速度表达式。结果表明,相同工况下背压系统比无背压系统的系统综合刚度大,临界爬行速度小。在背压系统的基础上提出自适应背压系统,利用背压力补偿来消除液压缸低速爬行现象,并利用仿真技术验证系统的平稳性,为消除液压缸低速爬行现象提供了新思路。     

伺服液压缸低速特性研究

伺服液压缸要求具有低摩擦、高动态响应、低速无爬行等特性,普通接触型动密封伺服液压缸中密封件导向件的选用是关键因素之一。该文分析了伺服液压缸低速爬行原因,指出了克服爬行的措施,介绍了一种无油润滑导向件——DU套,搭建DU套伺服液压缸低速特性实验台,进行了直驱式泵控和伺服阀控两种低速实验,验证了DU套伺服液压缸良好的低速稳定性。     

基于摩擦补偿的交流伺服工作台爬行控制

低速工况下由摩擦引起的爬行现象是影响机械加工精度的重要因素。建立了XY交流伺服工作台爬行的数学模型。设计了一种变结构控制和基于摩擦模型前馈补偿相结合的综合控制策略,用于减小交流伺服工作台爬行对定位精度的影响。仿真和实验结果表明,采用提出的控制策略可以明显降低爬行产生的跟踪误差。     

数控机床工作台与导轨部件对进给爬行的影响

数控机床在低速进给时,产生非匀速爬行,对加工精度和工件表面质量非常不利。应用控制理论对机床进给系统的爬行现象进行了理论分析,建立了进给系统的数学模型,用有限差分法对模型进行了模拟。在此基础上,系统研究了各种因素对爬行的影响,着重分析了工作台与导轨的摩擦对爬行起的作用,并且对不同摩擦力工作状态下的系统进行了对比,最后进行了实际测试验证。     

普通外圆磨床怎样进行内孔高光洁度磨削

三、对机床的要求在高光洁度磨削中,影响表面光洁度的主要因素是砂轮表面磨粒的微刃性与微刃的等高性,因此应低速修整砂轮,即要求工作台低速稳定性好。否则,产生爬行或速度不均匀,将影响表面光洁度。首先,要消除机床爬行。液压系统内混入空气,是工作台产生爬行的主要原因,故应采取各种措施,防止空气进入油液内。通常空气由高压区或低压区进入液压系统。高压区如有泄漏,空气会进入油缸,而使工作台爬行,或低速时趋于停止。低压     

气缸低速爬行特性影响因素及补偿

通过建立气动模型并进行联合仿真,探讨了气缸低速爬行现象和系统定位误差的来源,具体分析了气源压力、负载质量、摩擦力差值对气缸爬行的影响。采用单神经元PID控制算法和叠加颤振信号的方法,代替传统PID控制。结果表明气源压力大、负载质量小、动静摩擦差值小时有利于阻止系统的爬行;采用单神经元控制和叠加颤振信号的方法解决了系统的低速爬行问题。仿真证明系统定位精度由±0.61mm提高到±0.25mm,为低速阶段气缸平稳运行提供了较理想的控制策略。     

克服磁粉制动器低速爬行的自动控制方法

理论分析磁粉制动器的低速爬行现象，探讨低速稳定性条件、用扭矩反馈控制制动器的激励电流来消除爬行的产生。在PID控制原理的基础上提出PIDD控制算法能有效消除低速爬行，保持低刚度系统中磁粉制动器低速稳定性。     

基于Recurdyn的滚子输送链爬行现象仿真与分析

爬行现象是一种常见的链传动不稳定现象。由于滚子输送链常用在低速重载和工作环境恶劣的条件下传递动力和输送物料,因此更容易产生爬行现象而影响输送链的正常工作。通过对滚子输送链进行动力学分析并建立输送链动力学模型,得出导轨与链条动静摩擦力差值、系统刚度和动载荷是导致滚子输送链爬行的主要原因。最后基于Recurdyn软件对滚子输送链传动过程进行仿真并验证了相应结论。     

磨床低速爬行现象的鱼刺图及其分析

本文利用鱼刺图的分析方法对磨床低速爬行现象产生的原因进行了系统的分析，为排除磨床低速爬行故障提供了理论依据及分析方法。     

气缸爬行现象的建模与仿真

气缸低速运动时会出现时走时停或时快时慢的“爬行”现象。文章阐述了气缸产生爬行的原因，分析了爬行现象的机理，建立了气缸爬行现象的数学模型。用MATLAB6．5对气缸爬行现象的数学模型进行了动态特性仿真，通过理论分析和仿真计算，分析了导致气缸产生爬行现象的影响因素。     

基于LuGre模型的气动位置伺服系统摩擦补偿控制

气动伺服系统的摩擦力/驱动之比较大,摩擦力模型复杂、受影响因素较多且存在一定的不确定性,导致精确建模比较困难;另一方面,摩擦力和气体的低刚度、弱阻尼特性相互作用导致爬行、黏滑振荡现象,严重影响了伺服系统的动态及稳态性能的提升。在综合考虑摩擦力特征、系统自身非线性、未建模动态不确定性及摩擦力和系统性能相互影响的基础上,结合LuGre摩擦模型,采用双观测器估计摩擦力模型中的部分不确定性参数,提出非线性自适应反步摩擦补偿控制方法。通过在低速和高速工况下分别进行试验验证,并与PID控制方法进行比较,结果表明非线性自适应反步摩擦补偿控制方法有效改善了起步阶段的动态滞后现象,减少了低速工况下爬行及高速工况下的黏滑振荡现象,提高系统的响应速度及跟踪精度。     

电液比例方向控制系统理论与实践研究

针对大惯量、大负荷、低速工况液压系统的滞环及爬行现象,研究了一种基于高速开关阀控制的方向比例控制系统,建立了该系统的数学模型,并进行了计算机仿真研究,在此基础上,提出了以脉冲宽度调制(PWM)技术为核心的电液数字控制方法.     

On the motion of the structure varying multibody systems with two-dimensional dry friction

In the present paper the dynamics of the structure varying multibody systems caused by stick-slip motion with two-dimensional dry friction are analyzed. The methods to determine friction force both in stick and slip states are described. The direct method of considering the wagon bogie system as a structure varying system was used to consider two dimensional friction at the wheelset-side frame connection. The concept of friction direction angle used to determine the friction force components of two-dimensional dry friction both in the stick and slip motion states was used. A speed depended friction coefficient was used and described approximately by hyperbolic secant function. All switch conditions were derived and friction forces both for stick and slip states. Some simulation results are provided.     

机械密封的黏滑分析

机械密封副磨损与黏滑引起的振动有关。以密封副动静环为摩擦副进行摩擦磨损试验,通过分析摩擦因数曲线的变化趋势以及机械密封副的磨损形貌,提出在动环与静环相对运动的过程中发生了黏滑振动。考虑动环刚度,构建密封副黏滑模型,通过仿真分析黏滑对密封副表面形貌的影响以及密封副的黏滑磨损机制。结果表明:动环在摩擦扭矩的作用下扭转导致黏滑;动环的最大转速在黏滑过程中达到转轴转速的2倍;黏滑在快速启动阶段并没有发生,仅在速度波动阶段出现,而当速度恢复稳定上升阶段,黏滑现象消失;黏滑最终造成密封副表面严重的黏着磨损。     

Pre-sliding Behaviour of Single Asperity Contact

The pre-sliding and static friction force behaviour at asperity level between a smooth ball and a smooth flat surface at different normal loads, as well as friction behaviour during full slip has been studied. The normal load dependence of the friction force and the preliminary displacement is discussed when the mean contact pressure is kept under 100 MPa. The theoretical model to calculate the shear stress and the preliminary displacement in the contact is discussed and the experimental data were used to verify the model. The results show that for low applied normal loads the adhesion force has an influence on the friction force measurements. Furthermore, the results for the friction force and preliminary displacement show good agreement with the theoretical trends. The experiments along with the model can be used to analyse the tangential traction in the contact and the behaviour of the stick–slip area. The measurement results along with the model were used to calculate the maximum shear stress at the point of sliding for different applied normal loads. It is also shown that at low applied normal loads the shear stress is not constant as compared to relatively high applied normal loads due to the presence of adhesion force.     

液晶降低机床爬行临界速度的研究

根据液晶的减摩作用，研究了液晶作为润滑添加剂在改善机床爬行状况，即降低其爬行临界速度方面的实际应用。选择了3种液晶，每种都按6种不同的浓度加入到N32（旧标准HJ20）机械油中，在M7130型平面磨床上进行了试验。试验结果表明，液晶作为润滑添加剂确实具有良好的防爬作用，且防爬效果与液晶种类及其添加浓度有关。     

Stick‐slip in the presence of a normal vibration

This paper presents a dynamic analysis of a contact system subjected to an applied normal vibration. The tangential motion of the system is found to exhibit stick‐slip behaviour dependent on the applied vibration, even in the absence of a difference in static and kinetic friction or a negative gradient in the friction‐velocity relation. The analysis leads to the development of a criterion for stick‐slip in the form of an equation defined in terms of the system and input parameters. This criterion is also presented graphically and is assessed through a series of experiments. The analysis and measurements show that stick‐slip occurs for a significantly wider drive velocity range when the normal vibration applied is near the natural frequency of the drive system. In addition, when stick‐slip occurs in the presence of a normal vibration, the frequency of stick‐slip is found to lock in to the frequency of the applied vibration.     

Parametric studies on drill-string motions

Experimental and numerical investigations are conducted into drill-string motions. The numerical efforts are carried out by using a reduced-order model with attention to stick–slip interactions between a drill string and an outer shell. These efforts are complemented by experimental studies conducted with a unique, laboratory scale model. Qualitative and quantitative changes in the system behavior are studied with respect to the rotation speed and mass imbalance. Comparisons are made between the numerical findings and the corresponding experimental results. In addition, the influence of contact conditions between the drill string and the outer shell on the drill-string dynamics is also examined. The findings of the work suggest that small changes in the system rotation speed can have a significant influence on the nature of drill-string motions and they also provide guidelines for steering the system out of regions of undesirable dynamics and maintaining drill-string motions close to the center of a borehole.     

Stick‐slip with the slip phase as the starting point

In the literature, the stick‐slip phenomenon is always explained and modelled as starting from an initial stick phase. However, stick‐slip can also occur after a decrease in the imposed velocity, commencing above the critical (stick‐slip‐free) velocity. In this paper, it will be shown how stick‐slip can originate from a situation of pure sliding (without stick phases), if the slope of the friction force‐relative sliding velocity relation (F‐v_rel gradient) is negative. The F‐v_rel gradient used to study stick‐slip must, because of the interaction between the friction force and the dynamic behaviour of the mechanical system, be derived from velocity changes with the same time‐constant as the mechanical system of which the friction interface is part. It will also be shown that steady‐state friction data, and dynamic (non‐stationary) friction results obtained for relatively large (but fast) velocity variations, can lead to completely false conclusions related to stick‐slip.