含间隙齿轮传动系统的非线性动力学特性的研究

含间隙齿轮传动系统存在着丰富的非线性动力学行为,建立了两自由度齿轮传动系统的动力学模型,首先利用数值方法分析了齿轮传动系统的分岔和混沌动力学行为,然后将非光滑的间隙函数用光滑函数拟合,通过对系统进行多尺度摄动分析和计算,得到间隙函数拟合后的齿轮传动系统的非线性动力学现象,并与无拟合非光滑系统的数值结果进行比较分析,为含间隙齿轮传动系统的研究奠定了基础.     

含间隙同步锥齿轮锁定后的非光滑动力学分析

针对周边环形桁架天线展开锁死后,分析齿轮副间隙由于空间冷—热环境交替对天线所产生的影响.因为整个桁架结构复杂,间隙种类众多,所以文中只研究一对同步直齿锥齿轮锁定后间隙的非光滑动力学行为.文中首先介绍了三种碰撞力模型,即恢复系数模型、Hertz接触力模型和非线性弹簧—阻尼模型,然后对物理模型进行简化得到动力学模型,最后建立了动力学方程.由于动力学方程中存在分段,直接求得解析解难度过大,文中直接采用数值仿真的方法进行分析,从仿真结果中得知含间隙的同步锥齿轮在外力的作用下整个系统会出现单倍周期、倍周期分岔和混沌等复杂的非线性响应.     

考虑含间隙与润滑平面机构的简化算法

为了更快速、高效地确定含润滑铰间间隙对机构动态特性的影响,文中建立了一种新的计算思路.首先,通过理想机构与含间隙机构的运动学模型求出间隙力,进一步把间隙力以主动力的形式带入动力学方程,得到机构的相应动态特性.然后,以含间隙与润滑的曲柄滑块机构为例,基于二状态接触模型与流体润滑模型,对比分析该模型与干摩擦模型,来进一步验证该方法的正确性与可行性.Simulink仿真数据表明,文中建立的模型能有效地抑制机构的振动,动态特性更接近于理想模型,符合实际情况.     

基于接触碰撞理论的锭子动力学仿真研究及实践

为减小锭杆顶端振幅对纺纱质量的影响，分析了基于接触碰撞理论的锭子动力学仿真中的分离－接触－碰撞三状态，建立了非变形经典碰撞模型和接触变形模型。建立切换点判定方程计算状态切换点，求解动力学微分方程以获得接触力和碰撞冲量作为失空输入求得模态振型和不平衡响应。比较两类多体动力学仿真结果，提出用碰撞耗能来研究锭子振动控制问题的方法。     

汽车转向机构间隙运动副的碰撞接触分析

应用多体动力学分析方法及仿真技术研究了某汽车转向机构间隙运动副在转向过程中的碰撞接触特性.首先应用ADAMS软件创建了该车的仿真模型.由悬架系统、转向系统、行驶系统等系统纰成.其次研究了『H]隙运动副的碰撞接触特性,包括转向横拉杆与转向梯形臂之间的运动副及转向梯形臂与悬架之间的运动副.根据实际工作特征,前者运动副采用空间圆柱铰模型,后者运动副采用平面圆柱铰模型.最后对模型进行了仿真分析.仿真结果表明,转向过程中,两问隙运动副的碰撞接触力与间隙大小成非线性关系,多个运动副间隙共存状念下各间隙运动副的碰撞接触力发生变化.这些研究结果为转向机构零部件设计、动力学特性分析提供了更为准确的实验依据.     

含间隙非线性的Wiener-Hammerstein系统复合补偿控制

针对含非对称间隙环节的Wiener-Hammerstein系统提出了一种新的由输出反馈和间隙动态逆补偿构成的复合控制方案.首先应用参数化分段线性表达式设计了未知参数的整体估计模型,可同时估计线性参数和间隙的特征参数,然后提出了一种新的误差有界的间隙动态逆模型,该模型可使得驱动信号能在间隙的不同线性段之间快速切换,在此基础上设计了鲁棒补偿控制律,同时对输入线性环节采用输出反馈控制构建了复合控制器,通过李亚普诺夫方法证明了闭环系统的稳定性.带减速器的单电机伺服系统模型的仿真结果表明该方法在跟踪精度良好的同时可使系统动态响应满足要求.     

太阳帆航天器展开机构柔性动力学建模

研究了大型太阳帆航天器展开机构的柔性动力学建模问题。首先对结合模态综合法和混合坐标法介绍了太阳帆展开机构柔性动力学一般模型建立过程。根据工程需要对展开机构进行模态分析,给出了工程实用的各耦合系数的计算表达式,并计算出各耦合系数。     

时滞系统非线性动力学研究进展

综述了近年来时滞系统非线性动力学的研究进展,重点阐述了时滞系统的稳定性与分岔、时滞系统的混沌及其控制、时滞系统随机动力学研究、时滞网络系统的动力学方面的一些理论和方法的研究结果,结合研究现状展望了若干值得关注的问题.     

间隙引发的变载非线性及其闭环辨识

阐明了齿轮传动位置伺服系统间隙除产生熟知的前向迟滞非线性之外,还将因系统往复运动中加卸载相交替的反向调制致使驱动电机动力学参数同步跳变所出现的变载非线性现象.推导建立了这类非线性在一阶谐波意义下的串联式等效频域模型及其近似计算公式,分析了相应的幅相特性.进一步面向服役中系统提出了直接通过闭环弱自激振荡控制所实现的间隙辨识新方法,给出了控制器的结构及其参数整定策略.此外,文中还给出了含高斯白噪声测量的仿真算例,充分验证了闭环间隙辨识方法的有效性和便捷性.     

刚杆非定点碰撞的几何学及动力学模拟

两刚性杆件在运动过程中其接触碰撞点的位置是不确定的.本文给出了此模型接触碰撞时的两种接触碰撞模式,分析了寻找接触碰撞点位置的方法,由此得出判断接触碰撞模式的方法,并通过MATLAB对此模型进行了几何学及动力学模拟.     

A Continuous Analysis Method for Planar Multibody Systems with Joint Clearance

Clearance from manufacturing tolerances or wear is likely to degrade the dynamic performance of connected machine parts. When joint clearance is introduced, the dynamic response of the mechanical system is substantially changed, seen as high acceleration and force peaks and dissipation of energy. Looking at contact models, the simpler ones, such as the linear Kelvin–Voigt or the nonlinear Hertz model, are characterized by a set of parameters. These include material parameters, coefficient of restitution and possibly a coefficient of friction. The analysis models can be divided into two groups – continuous and dis-continuous, related to whether integration is carried out through the period of contact, or stopped and restarted after the impact.Based on the equations of motion for a multibody system of rigid bodies, it is suggested that the continuous analysis approach is combined with a contact force model to describe joint clearance in rotational joints. Performing simulations with this methodology allows not only to quantify the overall mechanism behaviour, but also in-depth analysis of the impact mechanics in the clearance joint. Experimental data from a double pendulum impacting a rigid plate is used to verify the suggested continuous analysis method.     

一类含间隙结构振动特性分析

为分析一类含间隙结构的振动特性及为保护特定子结构而预留间隙的合理性,根据其振动试验结果,采用假设模态法的思想,将该类带间隙的非线性结构按其子结构的一阶弯曲模态简化为带间隙的单自由度与二自由度弹簧-质量系统,分析了不同激励条件下间隙对系统动力学响应的影响.分析结果表明:此类结构中,间隙具有阻碍振动传递的性质,预留间隙是合理的.     

Dynamic Analysis for Planar Multibody Mechanical Systems with Lubricated Joints

The dynamic analysis of planar multibody systems with revolute clearance joints, including dry contact and lubrication effects is presented here. The clearances are always present in the kinematic joints. They are known to be the sources for impact forces, which ultimately result in wear and tear of the joints. A joint with clearance is included in the multibody system much like a revolute joint. If there is no lubricant in the joint, impacts occur in the system and the corresponding impulsive forces are transmitted throughout the multibody system. These impacts and the eventual continuous contact are described here by a force model that accounts for the geometric and material characteristics of the journal and bearing. In most of the machines and mechanisms, the joints are designed to operate with some lubricant fluid. The high pressures generated in the lubricant fluid act to keep the journal and the bearing surfaces apart. Moreover, the lubricant provides protection against wear and tear. The equations governing the dynamical behavior of the general mechanical systems incorporate the impact force due to the joint clearance without lubricant, as well as the hydrodynamic forces owing to the lubrication effect. A continuous contact model provides the intra-joint impact forces. The friction effects due to the contact in the joints are also represented. In addition, a general methodology for modeling lubricated revolute joints in multibody mechanical systems is also presented. Results for a slider-crank mechanism with a revolute clearance joint between the connecting rod and the slider are presented and used to discuss the assumptions and procedures adopted.     

Optimization of transmission angle for slider-crank mechanism with joint clearances

In this study, kinematic analysis of a planar slider-crank mechanism having revolute joints with clearances was presented. Joint clearance was modelled as a massless virtual link, and Multi-Layered Neural Network (MLNN) structure was used for approximating the motion of this link with respect to the position of input link. Training and testing data sets for the neural network were obtained from mechanism simulation using the ADAMS software. A genetic algorithm was also used to optimize the design parameters for minimizing the deviations due to clearances. When two joint clearances at crank-pin and piston-pin centers were considered, the effects of these clearances on the kinematic characteristics and transmission quality of the mechanism were investigated using continuous contact model between the journal and bearing at a joint.     

带有不连续动力学的非线性多智能体系统固定时间一致性EI北大核心CSCD

本文研究了一类带有不连续动力学和有界扰动的非线性多智能体系统领导跟随固定时间一致性问题.首先,在不对称的有向拓扑图下,本文设计了一种辅助信号,该辅助信号用于观测领导者状态,且该辅助信号不在通信信道中传输,可以有效地减少系统计算代价.随后,基于辅助信号,本文设计了一种不连续控制协议,以实现多智能体系统固定时间收敛.然后,利用非光滑分析、Lyapunov稳定性理论及代数图论等证明系统可在任意初始状态下达到固定时间一致.最后,仿真实例进一步验证了理论结果的有效性.     

Robust adaptive observer for nonlinear systems with unmodeled dynamics

Unmodeled dynamics exist in almost all applications of observers due to the impossibility of using exact and detailed models. It is highly desired that the observers can dominate the effects of unmodeled dynamics independently to prevent the state estimations from diverging and to get the precise estimations. Based on adaptive nonlinear damping, this paper presents a robust adaptive observer for multiple-input multiple-output nonlinear systems with unknown parameters, uncertain nonlinearities, disturbances and unmodeled dynamics. The observer only has one adaptive parameter no matter how high the order of the system is and how many unknown parameters there are. With the proposed observer, neither estimating the unknown parameters or solving linear matrix inequalities is needed. It is shown that the state estimation error is uniformly bounded and can be made arbitrarily small.     

Game problems for systems with discontinuous dynamics

Differential games with discontinuous dynamics and a fixed termination time are considered. The operators describing the structure of a game are determined under certain conditions. The results obtained are illustrated by a model example. Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 183–187, July–August, 2000.     

Software for global dynamics evaluation of mechanisms

The paper deals with the multibody system software which implements the solution of the global dynamic problem for multibody systems described by redundant coordinates (DAE equations) and with a possibility of redundant number of actuators. The aim of the global dynamics evaluation is mainly the machine synthesis. The necessity of such formulation arises especially in robotics where the accessible velocities and accelerations on the given trajectory are important for the motion planning and for the design optimization of robots and manipulators. The analogical problem can be very important also for the design of any other machine type. The developed software is therefore one of the important tools for the multiobjective machine synthesis.     

Output consensus control of multi-agent systems with nonlinear non-minimum phase dynamics

This paper considers the output consensus problem in non-minimum phase nonlinear multi-agent systems. The main contribution of the paper is to guarantee achieving consensus in the presence of unstable zero dynamics. To achieve this goal, a consensus protocol consisting of two terms is proposed. The first term is a linear function of the states of each agent employed in order to overcome the non-minimum phase dynamics, and the second term is a function of the output of neighbouring agents which provides coupling among agents and guarantees output consensus in the network. The asymptotic stability of output consensus errors and the boundedness of the states of agents are also studied. A numerical example is presented to show the effectiveness of the proposed approach.