一种直流力矩电机系统的滞滑摩擦补偿方法

陀螺漂移测试转台直流力矩电机系统中存在的非线性滞滑摩擦，使转台在PID控制下存在滞滑极限环。为提高转台定位精度，应用具有滞滑(stick-slip)摩擦的直流力矩电机系统模型，推导了一种补偿方法，对含有滞滑摩擦的PID控制转台直流力矩电机伺服系统进行滞滑摩擦补偿。在采用PID控制的转台电机系统定位工作状态下，这种滞滑补偿方法可以减小滞滑极限环的幅值。仿真结果证明了该补偿方法的有效性。     

粘滑混合边界条件下平面边界前的Stokes流动

对具有粘滑混合边界条件的平面边界,建立一个Stokes流动的一般性定理,利用双调和函数A与调和函数B,表示了3维Stokes流动的速度场和压力场.关于无滑动平面边界前Stokes流动的早期定理,成为该一般性定理的一个特例.进一步地,从一般性定理导出了一个推论,根据该Stokes流函数,给出了粘滑边界条件时刚性平面轴对称Stokes流动问题的解,得到了流体作用在边界上的牵引力和扭矩公式.给出了一个说明性的例子.     

An Approximate Analysis of Dry-Friction-Induced Stick-Slip Vibrations by a Smoothing Procedure

This paper deals with a systematic procedure to find both stable and unstable periodic stick-slip vibrations of autonomous dynamic systems with dry friction. In this procedure, the discontinuous friction forces are approximated by smooth functions. Using the simple shooting method with a stiff-ODE solver, in combination with a path following algorithm, branches of periodic solutions are computed for a changing design variable. For testing purposes, both 1 and 2-DOF autonomous block-on-belt models and a 1-DOF autonomous drill string model from literature are investigated. Comparison of the results shows that the smoothing procedure accurately describes the behavior of the discontinuous systems. The proposed procedure can also easily be applied to more complex MDOF models, as well as to nonautonomous dynamic systems.     

雨刮器非线性摩擦振动的稳定性与分岔特性

针对雨刮器建立2自由度非线性摩擦振动动力学模型,基于复模态理论计算复特征值并进行稳定性及其对刮刷速度的依赖性分析;通过数值计算分析摩擦振动对刮刷速度的分岔特性,并利用相轨迹、庞加莱映射、频谱特性分析不同刮刷速度下的非线性振动现象.研究发现:摩擦-速度特性的负斜率是导致系统不稳定的根本原因,增大刮刷速度有利于提高系统的稳定性;在高、低刮速区,随着刮刷速度的下降,系统振动形态遵循周期→准周期→混沌的演化规律,并会伴随显著的粘滑振动;仅高速区的周期振动和非振动条件下,刮刷时无附加的粘滑振动.     

Complex dynamics of an archetypal self-excited SD oscillator driven by moving belt friction

We propose an archetypal self-excited system driven by moving belt friction, which is constructed with the smooth and discontinuous(SD) oscillator proposed by the Cao et al. and the classical moving belt. The moving belt friction is modeled as the Coulomb friction to formulate the mathematical model of the proposed self-excited SD oscillator. The equilibrium states of the unperturbed system are obtained to show the complex equilibrium bifurcations. Phase portraits are depicted to present the hyperbolic structure transition, the multiple stick regions, and the friction-induced asymmetry phenomena. The numerical simulations are carried out to demonstrate the friction-induced vibration of multiple stick-slip phenomena and the stick-slip chaos in the perturbed self-excited system. The results presented here provide an opportunity for us to get insight into the mechanism of the complex friction-induced nonlinear dynamics in mechanical engineering and geography.     

Bifurcations in Nonlinear Discontinuous Systems

This paper treats bifurcations of periodic solutions indiscontinuous systems of the Filippov type. Furthermore, bifurcations offixed points in non-smooth continuous systems are addressed. Filippov'stheory for the definition of solutions of discontinuous systems issurveyed and jumps in fundamental solution matrices are discussed. It isshown how jumps in the fundamental solution matrix lead to jumps of theFloquet multipliers of periodic solutions. The Floquet multipliers canjump through the unit circle causing discontinuous bifurcations.Numerical examples are treated which show various discontinuousbifurcations. Also infinitely unstable periodic solutions are addressed.     

A new criterion for occurrence of strick-slip motion in drive mechanism

This paper, using Karnopp's model of friction force and phase plane method, studies the stick-slip motion of the flexble drive mechanism. It is explained that a sudden drop of friction force is the essential source of stick-slip motion when the sliding is impending. A new criterion for occurrence of stick-slip motion is established. The stick-slip region and the stable region in a parameter plane are separated by a critical parameter curve. Moreover, for the stick-slip motion of the flexible drive mechanism without viscous damping, a parameter expression is obtained. The results may be used in design of the flexible drive mechanism.     

Hysteresis and Stick-Slip Motion of Phase Boundaries in Dynamic Models of Phase Transitions

Summary. We investigate hysteretic behavior in two dynamic models for solid-solid phase transitions. An elastic bar with a nonconvex double-well elastic energy density is subjected to time-dependent displacement boundary conditions. Both models include inertia and a viscous stress term that provides energy dissipation. The first model involves a strain-gradient term that models interfacial energy. In the second model this term is omitted. Numerical simulations combined with analytical results predict hysteretic behavior in the overall end-load versus end-displacement diagram for both models. The hysteresis is largely due to metastability and nucleation; it persists even for very slow loading when viscous dissipation is quite small. In the model with interfacial energy, phase interfaces move smoothly. When this term is omitted, hysteresis is much more pronounced. In addition, phase boundaries move in an irregular, stick-slip fashion. The corresponding load-elongation curve exhibits serrations, in qualitative agreement with certain experimental observations in shape-memory alloys. Received August 4, 1998; revised December 11, 1998     

Analytical investigation of stick-slip motions in coupled brake-driveline systems

In this paper, we investigate the brake creep-groan problem by formulating the issues in terms of two dynamic sub-systems that are coupled at the friction interface, and thus, experience stick-slip motions. Thorough examination of the nature of discontinuous solutions using numerical methods is a useful prelude to analytical studies. We examine such dynamics through parametric studies for magnitude and rate of brake release, where the vehicle is initially at rest and under low constant drive torque. Dependency on the initial conditions and solution flow before reaching the orbit will thus be illustrated. Four types of motions (one steady sliding and three stick-slip) are found based on extensive studies. Our formulation and analysis should lead to a better understanding of the brake groan phenomenon and systems coupled by interfacial friction.     

在干摩革命擦和46号油润滑条件下滑动导轨副的爬行性能研究

针对金属切削机床（特别是数控机床）等机械设备中工作台沿着导轨低速运动时发生的爬行现象，建立了模拟滑动导轨副的试验台架．利用这种试验台架分别在于摩擦和４６号油润滑条件下，对滑动导轨副的爬行性能进行了模拟试验研究与考察，并且讨论了接触压力对具有固体润滑徐层的滑动导轨副防爬性能的影响．结果表明，摩擦引起法向接触振动导致摩擦系数随着滑动速度的增加而下降是产生爬行的直接原因，不同接触压力下固体润滑涂层滑动导轨副发生爬行的程度不同，在此基础上，提出用Ｌ＝μ静／μ动作为评价滑动导轨副防爬性能的准则：Ｌ＞１．００时的防爬性能差，Ｌ在０．９６－１．００之间时的防爬性能一般，Ｌ≤０．９５时的防爬性能良好．此外，还针对性地提出了防爬措施．