气动八作动器隔振平台的主动隔振研究

多自由度隔振平台可以有效地隔离运载器传递到卫星的振动载荷。本文采用气动八作动器隔振平台实现卫星的六自由度隔振。首先应用牛顿欧拉法建立了气动八作动器隔振平台的动力学模型,设计了平台的主动控制律,然后对平台的主、被动隔振特性进行了仿真分析。仿真分析和实验结果显示主动隔振使平台各方向的低频隔振性能均得到改善。     

一种基于SMR主动隔振模型的功率流控制方法

用功率流指标描述主动隔振系统中能量的传输，以传输到接受性的功率流最小为最优化控制目标，推导主动隔振系统中功率流传递的最优控制表达式，提出一种基于SMR主动隔震模型的主动功率流的最优化控制策略，对比分析了被动和主动模型下总功率流的传递特性以及主动控制时传递到基础的各功率流分量的分布特征。针对工程实际中的柔性安装问题，对四边筒支矩形薄板扩动隔振进行了研究。     

基于菱形压电作动器和内模控制策略的微振动隔振研究

提出了一种以菱形压电作动器为隔振元件,并结合内模控制策略的微振动主动隔振方法。首先设计并分析了菱形压电作动器,分析其力电耦合特性;以单自由度主动隔振系统为例,建立了隔振系统的动力学模型。在此基础上,设计了基于内模控制的主动隔振策略,进行了含有模型误差、迟滞等多工况的数值仿真分析。仿真结果表明,隔振位移传递率最大可达94%。菱形压电作动器结合内模控制策略的振动主动控制技术具有较好的隔振能力,为进一步微振动平台的主动隔振设计与实验研究奠定了基础。     

主动约束层阻尼对超声速梁结构颤振特性的影响

本文采用主动约束层阻尼技术研究超声速梁的颤振特性,利用Hamilton原理和假设模态方法建立结构的运动方程,采用活塞理论模拟超声速梁的气动压力,采用速度负反馈控制获得主动阻尼,求解本征值问题得到复特征值,进而得到结构的固有频率和损耗因子.计算结构的固有频率随无量纲气动压力的变化曲线,得到颤振点,分析了主动阻尼和被动阻尼对颤振速度的影响.计算结果表明主动阻尼可以影响梁的气动弹性特性,并增大超声速梁的颤振速度.本文研究结果对超声速飞行器结构的颤振分析和气动设计具有重要意义.     

非线性被动隔振的若干进展

工程中航空航天、船舶与海洋结构物及其上装备和精密仪器易受极端环境干扰和破坏,使得非线性隔振理论在近十年来迅猛发展;针对日益严峻的隔振和抗冲击等要求,工程师和科学家们已发展出各种不同的非线性隔振系统,包括主动、半主动、被动和复合隔振.利用非线性改善的被动隔振兼具传统被动隔振的鲁棒性和主动隔振的高效性成为振动控制领域的先进技术.本文主要综述了非线性隔振理论和应用的近十年进展,包括非线性隔振设计、建模、分析、仿真和实验.在隔振系统的构建中,既考虑了刚度非线性又考虑了阻尼非线性;动力学响应的研究中,既有确定性分析又有随机分析.首先提出了适用于非线性隔振系统改进的评价方式;其次综述了高静态低动态刚度隔振及其加强形式非线性阻尼加强和双层非线性隔振,混沌反控制技术、内共振影响、非线性能量阱应用等振动机制利用型隔振和非线性隔振功能材料.最后,对非线性隔振研究发展的热点和关键性问题进行了分析和展望.     

车载系统主被动联合振动控制研究

针对车载系统行进过程中产生的结构振动,提出被动隔振和主动减振相结合的方法对结构弹性振动和刚体振动进行抑制．一方面,针对结构弹性振动,在车载结构和车体之间安装隔振装置,选择合适的隔振器参数,对车载结构的弹性振动进行隔离．另一方面,结合刚体振动抑制的需求,进一步研究小阻尼隔振器带来的结构低频刚体振动．对隔振器和车载结构形成的新系统采用主动控制方法设计最优控制器,对这一类过驱动控制系统进行主动控制研究．通过主被动控制结合,实现车载结构全频段范围内的振动抑制,能够将系统刚体振动的位移均方根值抑制到无控制时的5%以下．     

主动控制翼板抑制悬索桥颤振的研究

主动控制翼板是一种新型桥梁气动措施。本文基于非定常气动力理论，推演了安装主动控制翼板后作用在整个桥梁主梁单位长度上气动力表达式，从增加系统扭转阻尼的角度，研究了翼板主动扭转振动参数的选取。在此基础上，对某大跨悬索桥方案进行了二自由度颤振分析，结果表明：合理选取翼板的主动扭转振动参数，主动控制翼板能够有效地提高该桥的颤振稳定性。     

OPCL控制方法在准零刚度隔振系统中的应用研究

为了降低船舶动力机械的振动噪声和线谱信号,解决常见线谱控制方法存在的小能量控制混沌化、变工况下持续混沌化和小振幅混沌化的难题,采用开环加闭环(OPCL)控制方法进行了两自由度准零刚度隔振系统的吸引子迁移控制和广义混沌同步化研究。首先,建立了两自由度准零刚度隔振系统的动力学模型,进行了全局性态分析;然后,利用OPCL控制方法将系统从大振幅吸引子迁移至小振幅吸引子,从而减小了系统振幅;最后,在单向耦合系统中,利用OPCL控制方法施加主动控制,实现了系统在大参数范围内的小振幅广义混沌同步化。结果表明,将OPCL控制方法应用于两自由度准零刚度隔振系统的吸引子迁移控制和广义混沌同步化,能够同时实现隔振系统的线谱控制和振动隔离,从而进一步扩大了OPCL控制方法的应用范围。     

实验建模方法在金属橡胶隔振系统分析中的应用

本文结合金属橡胶隔振系统的性能特点，利用静态实验数据建立数学模型，求解隔振系统的运动微分方程，并根据方程的数值解分析金属橡胶隔振系统的动静态特性，该建模方法减少了理论误差，提高了建模业度，为金属橡胶隔振系统的动静态特性研究提出了一种新思路。     

回滞非线性结构的瞬态最优控制

本文对一种国滞非线性基础隔振的主从结构模型用瞬态最优控制法进行振动控制研究。利用四阶Ｒｕｎｇｅ－Ｋｕｔｔａ积分格式统一处理最优控制方程，可直接逐步积分求出系统在瞬态最优控制下的最优控制力与系统响应。分别对主从结构无主动控制及有主动控制时的两种情况（包含或不包含ｖｂ反馈）进行计算。结果表明瞬态最优控制可有效地抑制振动。     

A model reference robust multiple-surfaces design for tracking control of radial pneumatic motion systems

A robust model reference backstepping (multiple-surfaces) controller is proposed for radial pneumatic motor motion systems with variable inlet pressure and mismatched uncertainties (time-varying payload). A radial pneumatic motor is first modeled by a non-autonomous equation with consideration of a ball screw table. A practical integral action and robust action are included in the backstepping design to compensate for the disturbance, mismatched uncertainty, and to eliminate the steady state error. The motion system is proved to have asymptotically stable performance and the experimental results show that the proposed controller is able to track the reference model output signal and maintain steady-state error.     

Determination of slug permeability factor for pressure drop prediction of slug flow pneumatic conveying

Current models for pressure drop prediction of slug flow pneumatic conveying in a horizontal pipeline system assume some type of steady state conditions for prediction, which limits their capability for increased predictive accuracy relative to experimental data. This is partly because of the nature of slug flow pneumatic conveying system, which, as a dynamic system, never becomes stable. By utilising conservation of mass （airflow）, a dynamic pressure analysis model is proposed on the basis of the derivative of the upstream pressure behaviour. The rate of air permeation through slug, one of the important factors in the conservation model, is expressed as a function of a slug permeability factor. Other factors such as slug velocity, slug length and the fraction of stationary layer were also considered. Several test materials were conveyed in single-slug tests to verify the proposed pressure drop model, showing good agreement between the model and experimental results.     

Determination of slug permeability factor for pressure drop prediction of slug flow pneumatic conveying

Current models for pressure drop prediction of slug flow pneumatic conveying in a horizontal pipeline system assume some type of steady state conditions for prediction,which limits their capability for increased predictive accuracy relative to experimental data.This is partly because of the nature of slug flow pneumatic conveying system,which,as a dynamic system,never becomes stable.By utilising conservation of mass (airflow),a dynamic pressure analysis model is proposed on the basis of the derivative of the upstream pressure behaviour.The rate of air permeation through slug,one of the important factors in the conservation model,is expressed as a function of a slug permeability factor.Other factors such as slug velocity,slug length and the fraction of stationary layer were also considered.Several test materials were conveyed in single-slug tests to verify the proposed pressure drop model,showing good agreement between the model and experimental results.     

Robust tracking control method based on composite nonlinear feedback technique for linear systems with time-varying uncertain parameters and disturbances

In this paper, the composite nonlinear feedback control method is considered for robust tracking and model following of uncertain linear systems. The control law guarantees that the tracking error decreases asymptotically to zero in the presence of time varying uncertain parameters and disturbances. For performance improvement of the dynamical system, the proposed robust tracking controller consists of linear and nonlinear feedback parts without any switching element. The linear feedback law is designed to allow the closed loop system have a small damping ratio and a quick response while the nonlinear feedback law increases the damping ratio of the system as the system output approaches the output of the reference model. A new collection of different nonlinear functions used in the control law are offered to improve the reference tracking performance of the system. The proposed robust tracking controller improves the transient performance and steady state accuracy simultaneously. Finally, the simulations are provided to verify the theoretical results.     

Bursting-like motion induced by time-varying delay in an internet congestion control model

Time delay is an important parameter in the problem of internet congestion control. According to some researches, time delay is not always constant and can be viewed as a periodic function of time for some cases. In this work, an internet congestion control model is considered to study the time-varying delay induced bursting-like motion, which consists of a rapid oscillation burst and quiescent steady state. Then, for the system with periodic delay of small amplitude and low frequency, the method of multiple scales is employed to obtain the amplitude of the oscillation. Based on the expression of the asymptotic solution, it can be found that the relative length of the steady state increases with amplitude of the variation of time delay and decreases with frequency of the variation of time delay. Finally, an effective method to control the bursting-like motion is proposed by introducing a periodic gain parameter with appropriate amplitude. Theoretical results are in agreement with that from numerical method.     

A low-complexity tracker design for uncertain nonholonomic wheeled mobile robots with time-varying input delay at nonlinear dynamic level

A low-complexity design problem of tracking scheme for uncertain nonholonomic mobile robots is investigated in the presence of unknown time-varying input delay. It is assumed that nonlinearities and parameters of robots and their bounds are unknown. Based on a nonlinear error transformation, a tracking control scheme ensuring preassigned bounds of overshoot, convergence rate, and steady-state values of a tracking error is firstly presented in the absence of input delay, without using any adaptive and function approximation mechanism to estimate unknown nonlinearities and model parameters and computing repeated time derivatives of certain signals. Then, we develop a low-complexity tracking scheme to deal with unknown time-varying input delay of mobile robots where some auxiliary signals and design conditions are derived for the design and stability analysis of the proposed tracking scheme. The boundedness of all signals in the closed-loop system and the guarantee of tracking performance with preassigned bounds are established through Lyapunov stability analysis. The validity of the proposed theoretical result is shown by a simulation example.     

柔性机械臂的时滞最优跟踪控制

采用最优跟踪控制方法对柔性机械臂线性化主动控制中的时滞问题进行研究。首先采用一种积分变换,将包含时滞项的动力学方程转换成形式上不包含时滞项的标准形式,然后根据最优跟踪控制理论设计控制律。在每一步控制律的计算中,不但包含有当前步的状态反馈,而且包含有前若干步控制的线性组合。文中还给出了一个模态坐标的提取方法。仿真结果显示,若对时滞不处理,控制系统会在很小时滞量时出现发散;当控制系统中的时滞量不大时,本文的线性化时滞控制设计能够取得较好的控制效果;当系统存在较大时滞量时,线性化时滞控制设计的有效范围是有限的。     

存在关节力矩输出死区及外部干扰的漂浮基空间机械臂积分滑模神经网络自适应控制

探讨了载体位置和姿态都不受控时,漂浮基空间机械臂在带有关节力矩输出死区及外部干扰情况下轨迹跟踪的控制算法设计问题。死区与外部干扰影响系统的跟踪精度与稳定性。为此引入积分型切换函数,减少外部干扰引起的稳态误差,并利用径向基函数神经网络逼近动力学方程的未知部分,设计了一种积分滑模神经网络控制方案。控制算法的优点是,在死区斜率与边界参数不确定及最优逼近误差上确界未知的条件下,可以利用最优逼近误差、死区及干扰的补偿项来消除影响。李亚普诺夫稳定性分析证明了闭环系统的稳定性,且轨迹跟踪误差将收敛到0的某个小邻域内。仿真算例证实了该控制算法的有效性,实现了空间机械臂的轨迹跟踪控制。     

Discrete-time sliding mode control for robust tracking and model following of systems with state and input delays

This paper presents a novel robust tracking and model following control scheme for a class of linear systems with mismatched state and input delays. The algorithm is based on discrete-time sliding mode control (SMC) and time-delay control theory. The proposed scheme ensures the stability and robustness against time delays without state transformation, and achieves the ultimate boundedness of the tracking error. The selection of sliding surface and the existence of sliding mode are two important issues, which have been addressed. Chattering phenomenon and reaching phase are avoided. Simulation results demonstrate the validity of the proposed scheme.     

Simple, robust control and synchronization of the Lorenz system

Simple and robust techniques based on time delay estimation (TDE) are proposed to control and synchronize the Lorenz system. TDE provides a simple and easily applicable control input that does not require a precise system model and cancels a wide class of uncertainties. Both the tracking error and estimation error converge in finite time. Control and synchronization are achieved with a single control architecture, even in the presence of parameter variation and disturbance. Simulation results demonstrate fast convergence to the desired states and robustness to uncertainties and TDE error.