基于虚拟样机技术的步进链传动系统动力学仿真研究

以步进链传动系统为研究对象,分析了该类系统的动力学特性及影响因素,构建了步进链传动系统虚拟样机模型,分析了该类系统采用不同步进运动规律及在不同预紧力状态下动力学特性的变化规律。通过计算机仿真,验证了虚拟样机模型的合理性与正确性,研究结果可为以链传动为执行机构的一类步进传动系统的动力学分析与设计提供借鉴。     

Dynamic Modeling of a Roller Chain Drive System Considering the Flexibility of Input Shaft

Roller chain drives are widely used in various high-speed, high-load and power transmission applications, but their complex dynamic behavior is not well researched. Most studies were only focused on the analysis of the vibration of chain tight span, and in these models, many factors are neglected. In this paper, a mathematical model is developed to calculate the dynamic response of a roller chain drive working at constant or variable speed condition. In the model, the complete chain transmission with two sprockets and the necessary tight and slack spans is used. The effect of the flexibility of input shaft on dynamic response of the chain system is taken into account, as well as the elastic deformation in the chain, the inertial forces, the gravity and the torque on driven shaft. The nonlinear equations of movement are derived from using Lagrange equations and solved numerically. Given the center distance and the two initial position angles of teeth on driving and driven sprockets corresponding to the first seating roller on each side of the tight span, dynamics of any roller chain drive with two sprockets and two spans can be analyzed by the procedure. Finally, a numerical example is given and the validity of the procedure developed is demonstrated by analyzing the dynamic behavior of a typical roller chain drive. The model can well simulate the transverse and longitudinal vibration of the chain spans and the torsional vibration of the sprockets. This study can provide an effective method for the analysis of the dynamic characteristics of all the chain drive systems.     

重力影响下滚子链传动的横向振动分析

基于多自由度系统的振动理论,建立了竖直拉伸下滚子链传动系统横向振动动力学模型。考虑了链条重力及张力对链传动系统横向振动固有特性的影响,并利用M atlab软件对该系统横向振动固有频率进行了数值分析。在此基础上研究了不同边界激励条件对该链传动系统横向振动稳定性的影响。所得结论可为用于生产实践中的机械传动装置的动态分析与设计提供参考。     

进给系统振动特性研究及新型加减速控制策略

不平滑的运动指令导致数控机床进给过程中产生振动。本研究基于滚珠丝杠进给系统集中质量动力学模型,建立了伺服电机扭矩激励与进给系统响应的理论模型,分析了运动指令加速度曲线功率谱与进给系统振动响应的相关关系。针对加减速策略中存在的加加速曲线开始点和结束点不连续而引入振动激励的问题,提出一种类余弦加加速加减速控制策略,实现了加加速全过程的平滑过渡。以某滚珠丝杠进给实验台架为例,建立并实验验证了该台架的集中质量动力学模型,在此基础上建立了加减速控制策略激励特性分析的仿真模型,对加减速控制策略的激励特性进行了对比分析。仿真结果表明,类余弦加加速策略的激励特性最小,其工作台响应的功率密度是有限加加速策略的万分之一,是正弦加加速策略的1%。     

Rigid-flexible coupling dynamic modeling and characteristic analysis of the chain ramming mechanism

The previous studies on the dynamic characteristics of chain ramming mechanism have ignored the linkage effect of factors such as the elastic deformation of components, transmission clearance, stiffness of support body. In the model established in this paper, of which the effectiveness is verified by comparing with the experimental data, the influence of the main factors such as the elastic deformation of the chain link, the transmission clearance, the stiffness of the support body of the dynamic component and the linkage effect are all considered. The results show that the support stiffness of the sprocket shaft and the transversal support stiffness of the oil cylinder affect the longitudinal vibration of the chain. The chain link/roller clearance affects the longitudinal vibration of the chain. The track/roller clearance affects the transversal vibration of the chain at the beginning time of the ramming process and during the deceleration of the projectile.

     

Modeling and simulation of joint clearance effects on mechanisms having rigid and flexible links

In this study, kinematic and dynamic characteristics of a planar four-bar mechanism having joint clearance and link flexibility are investigated. Assuming that joint clearance as a virtual massless link, artificial clearances are developed at crank-coupler and coupler-follower joints. Contact model in joints with clearance is established using the nonlinear spring-damper model and the friction effect is considered using the Coulomb friction model. Then the simulation is implemented and the kinematic and dynamic characteristics of model mechanism are investigated. The computational methodology can predict the effects of clearance on planar mechanism having rigid and flexible links. The results are evaluated for the case of stationary phase, and naturally show that extreme values occur in output of the mechanism with clearances. Due primarily to the suspension effect of the flexible link, values of these peaks in the flexible mechanism decrease relative to that of the rigid mechanism. In addition, the flexibility has a significant effect on the vibration response of the mechanism with joint clearance.     

Prediction of vibration characteristics of a planar mechanism having imperfect joints using neural network

Clearance is inevitable in the joints of mechanisms due primarily to the design, manufacturing and assembly processes or a wear effect. Excessive value of joint clearance plays a crucial role and has a significant effect on the kinematic and dynamic performances of the mechanism. In this study, effects of joint clearances on bearing vibrations of mechanism are investigated. An experimental test rig is set up, and a planar slider-crank mechanism having two imperfect joints with radial clearance is used as a model mechanism. Three accelerometers are positioned at different points to measure the bearing vibrations during the mechanism motion. For the different running speeds and clearance sizes, this work provides a neural model to predict and estimate the bearing vibrations of the mechanical systems having imperfect joints. The results show that radial basis function (RBF) neural network has a superior performance for predicting and estimating the vibration characteristics of the mechanical system.     

计入运动副间隙的汽车制动摆振动态响应分析

建立了考虑制动过程中参数时变特性,并计入转向系运动副间隙耦合作用的七自由度非自治摆振系统的动力学模型。通过MATLAB数值算例,对制动过程中转向轮摆振的动态响应进行了分析。考察了轴荷转移、车速、间隙、轴距等因素对系统瞬态响应的影响。研究结果表明：制动过程中,轴荷转移等时变特性及运动副间隙的耦合作用对摆振系统动力学行为有重要影响,在建模时应予以考虑。相关规律与试验结果基本吻合,验证了模型的准确性。     

Fast drive of displacement magnification mechanism with flexure hinge using loading type impact damper

A displacement magnification mechanism which uses flexure motion guide using elastic hinges can realize smooth frictionless motion but has poor vibration damping capability. An impact damper is a damping mechanism which uses collision energy to dissipate vibration energy. If the damper is used for vibration control of the flexure mechanism, it may be able to dissipate unexpected vibration without killing the merits of the flexure mechanism. In the paper, a loading type impact damper is applied to settle down transient vibration of a displacement magnification mechanism. We investigate differences of damping effect by setting conditions of the damper. It is shown that the impact damper can eliminate residual vibration at step response effectively without steady state error. The experimental displacement magnification mechanism with impact damper can settle down less than 1/5 of the response without the damper under appropriate setting conditions. Influence of natural frequency ratio between damper and displacement magnification mechanism is investigated. Influences of indentation at impact point are also examined.     

多因素条件下单级齿轮系统的非线性特性

考虑啮合刚度、齿侧间隙和轴承支撑间隙等因素,运用集中质量法建立了三自由度直齿圆柱齿轮副弯扭耦合非线性振动模型,并据此研究了各参数对齿轮系统非线性振动特性的影响。结果表明：齿侧间隙一定时,随着频率的升高,系统由周期运动通过激变直接进入混沌,然后又由混沌通过激变变为周期运动;在周期运动中,系统经过倍周期分岔,由双周期运动变为四周期运动,然后又通过逆倍周期分岔,由四周期运动变为双周期运动,之后又由双周期运动变为单周期运动;不同的输入转频条件下,间隙变化使系统表现出不同分岔特性,在某些特定频率下,间隙变化只增加系统响应能量变化,并不改变其动力学特性。     

An experimental and analytical study of impact forces in elastic mechanical systems with clearancesEine experimentelle und analytische studie von stosskräften in einem elastischen mechanischen system mit spiel

Important performance limitations in mechanical systems results from clearances which cause rapid wear, increased noise and vibration. Relatively little experimental investigation has been performed in this area, although a number of analytical studies have been carried out. Recent studies of the latter kind show the effect of clearances is to amplify, greatly, connection forces, and that the introduction of link flexibility tends to reduce these impact forces significantly. This study shows experimentally the validity of the analytical studies and the mitigating effects of link flexibility on impact forces.     

消除柔性系统残留振荡有限冲击控制研究

将时滞滤波器用于具有刚性模态的柔性系统中，可以抑制残留振荡，但容易产生冲击运动。为了降低运动冲击，对控制信号的时间变化率加以限制，设计有限冲击指令，同时将最小最大优化思想引入时滞滤波器的设计中，提出一种新型控制器——有限冲击时滞控制器。计算机仿真和试验结果表明，这一控制器能降低振荡的最大幅值．在一个振荡周期内有效抑制残留振荡;在系统参数变化范围内，控制器的复数零点能有效抵消系统的极点，因此有更强的鲁棒性；与常用的时滞滤波器相比，能抑制控制信号的高频成分，降低未建模动态激励和运动冲击。     

Multibody contact dynamics on mechanisms with deep groove ball bearing joints

The dynamics of ball bearings are important to fatigue breakage, dynamic performance and motion precision of mechanisms connected by ball bearings joints with multi-clearances. In this study, a new method is proposed for multibody dynamics analysis on mechanisms under the effects of radial internal clearances and impact of balls/cage pockets interactions of ball bearings. Including balls/rings interactions and balls/cage pockets interactions, the three dimensional dynamics models of the crank slider mechanism are established and calculated by generalized-α algorithms on the basis of Hertzian contact theory and penalty function method. The rules of eccentric trajectories of inner and outer ring center for one ball bearing joint are verified with the results calculated by XU’s references. The results of dynamic errors, motion trajectories, dynamic forces are achieved under different speeds, radial clearances and number of ball bearings. The speeds and radial clearances are critical to the dynamic performances and motion precision of mechanisms, especially the number of ball bearings. The number of ball bearings is important to impact force and motion stability of the mechanism.     

Reduction of the joint clearance effect for a planar flexible mechanism

When the operating speed of mechanical systems is increased, unpredictable dynamic problems are induced due to joint clearances and link elasticity. To solve these problems, quantitative prediction of the effects of joint clearance and link flexibility on the system is needed. This study has two principal objectives. The first is to develop a design method for eliminating the loss of contract at joints with clearance. The method utilizes three dimensionless parameters which govern the dynamic behavior at the instance when contact loss is predicted. These parameters are determined to maintain joint contacts throughout the operating cycle. The links in this mechanism are assumed to be rigid. The second objective of this study is to investigate the influence of the flexibility of the links. Using a finite element method, we found that link flexibility decreases the possibility of contact loss as well as the impact force at joints with clearance.     

滚子链传动振动特性的研究

提出了滚子链传动的横向振动新模型，依据新模型导出了滚子链传动时横向动力响应的表达式     

CSP轧机振动的测试与抑制

针对某CSP生产线F3轧机在轧制薄规格集装箱板时出现的严重振动问题，测试了主传动系统扭振、机座轧辊振动、齿轮座减速器振动等参数，通过对测试结果和所有可能的外激励分析后，表明该轧机振动的主要形式是横向振动。主要振因是当工作辊轴承座与牌坊之间间隙过大时，接轴弧形齿的啮合冲击将激起轧辊横向振动。试验表明，消除该间隙后振动得到了很好的抑制。     

数控运动中加加速度连续的加减速方法

为保证机床运动的平滑性,减少数控机床冲击与振动的影响,研究了数控机床动力学数学模型,从理论上分析造成机床冲击与振动的根源;提出一种加加速度连续的加减速方法,推导了运动轮廓不同阶段的运动表达式;对该加减速算法进行了合理简化,以满足数控系统实时性要求;利用搭建的数控试验台对S曲线加减速方法和本文所研究加减速方法作进行了对比。结果表明,所研究方法可使轮廓运动更加平滑,更具柔性,但运行时间略长。     

输入转矩对驱动桥系统动力学特性的影响

在驱动桥系统中,滚子轴承是连接轴系与壳体的关键部件,其刚度具有各向耦合性和非线性特性,且与输入转矩有关。为准确高效地分析输入转矩对驱动桥系统动力学特性的影响,基于非线性轴承理论、有限元法和模态综合方法,建立包含主减速器总成、差速器总成、轮毂总成和桥壳等部件的完整驱动桥系统动力学分析模型,根据输入转矩大小的不同,定义轻载、中载和重载三种典型工况,分别计算各工况下的非线性轴承刚度,分析轴承刚度随输入转矩大小变化的特点,对驱动桥系统进行单位谐波传动误差激励下的动力学分析,研究输入转矩对驱动桥系统动力学特性的影响,分析不同工况下准双曲面齿轮动态啮合力的频响特性。计算结果表明,驱动桥系统动力学特性随输入转矩大小变化具有一定规律,能有效指导驱动桥系统的减振降噪设计,避开危险工况。     

Wear-induced vibration in a radial roller bearing

A dependence of elastic deformation on the load in the linear contact of hardened steel parts obtained on the basis of experimental data is presented. A method for calculating the load in a radial roller bearing at various clearances and numbers of rollers, as well as with various arrangements of the rollers relative to the external load vector is described. It is shown that, at a regulated radial clearance, almost no vibration in the bearing resulting from load redistribution during its rotation occurs; the vibration increases proportionally to the clearance caused by wear. Some possibilities of reducing the vibrations are discussed.     

A new method for polygon effect analysis of saw chain

The polygon effect is a major factor affecting the dynamic characteristics of chain drive in oil saw chain system. It causes impact, noise and dithering of the saw chain and significantly affects the lifespan of oil saw. A simple analytical method is proposed for analyzing the dynamic response resulting from the polygon effect of an oil saw chain system by using the difference method for numerical approximation. A MATLAB program is implemented and then applied for the polygon effect analysis of a specific saw chain drive. Numerical results such as velocities and dynamic loads due to polygon effect are compared with experimental data to demonstrate the effectiveness of the new method. A good agreement is obtained. The proposed polygon effect analysis method can provide guidelines for oil saw chain design for better dynamic performance.