时间延迟系统用 LambertW函数分析和控制

时间延迟在工程学和科学系统中十分常见，它将会影响系统的稳定性、精准度等从而限制和降低控制系统的性能。本书综合介绍了当前在时滞系统分析和控制中的最新发展成果，

考虑统计过程控制影响的时间延迟生产系统预防维修优化模型

针对时间延迟生产系统,研究考虑了统计过程控制影响的预防维修优化问题。首先,根据导致停机维修的原因不同,分析和建立了时间延迟生产系统在考虑统计过程控制时可能存在的运行状态;然后在对各种运行状态发生概率分析基础上,通过对周期期望更新成本和更新周期长度的研究,利用更新过程理论建立了以系统长期运行单位时间期望费用最小为目标的预防维修优化数学模型。最后,针对具体算例将本文模型同没有考虑统计过程质量监控的维修决策模型进行了比较分析,结果表明本文模型由于进一步综合考虑和利用了质量控制图监测结果对系统运行状态的反应信息和知识,能减少系统性能退化运行质量损失和延长预防维修周期,因此在节约成本方面更具经济性。

定量超声骨密度测量系统中系统延迟时间的测量研究

骨超声传导速度是定量超声骨密度测量系统的主要参数之一,主要反映骨骼的矿物质密度。精密测量骨骼的超声传导速度,就必须测得系统延迟时间。为了探索高精度的测量方法,得到准确的系统延迟时间,本研究提出了最小二乘线性回归拟合测量法,并将其测量效果与传统直接法进行对比。实验证明,该方法能避免直接法测量中的系统误差,得到准确的系统延迟时间。在特定实验条件下,可明显减小超声传导速度的测量误差。

用滤波反馈信号控制时间延迟混沌系统

利用幅频特性具有凹槽型的反馈信号控制一类时间延迟(或时滞)混沌系统,使其到达周期态.基于延迟系统的Hopf分支理论推算出系统可控性的必要条件.数值模拟及PSPICE仿真平台上的电路实验结果均很好地验证了理论分析的正确性以及该方案控制延迟混沌系统的有效性.

带时间延迟工业最优控制问题扩展控制变量参数化算法

为了进一步提升控制变量参数化(CVP)算法在工程优化控制上的应用,提出一种求解带时间延迟最优控制问题的扩展CVP算法。该方法首先采用分段常量控制变量参数化和不等式路径约束光滑化处理技术将带时间延迟最优控制问题近似转化为非线性优化问题;定义辅助状态变量分析时间延迟状态变量扩展变分系统,并以此为基础推导目标函数和约束条件梯度信息;最后,针对两个典型工业过程时间延迟最优控制问题进行测试。结果显示,相较其他控制变量参数化直接法,提出方法能在更少优化参数下取得相近甚至更优的结果,表明所提出方法的有效性和正确性。

预估模型的烟气氨法脱硫控制系统

对于火力发电厂而言,加大控制SO_2的排放量显得非常紧迫和必要。氨法脱硫技术是采用氨(NH_3)作为吸收剂除去烟气SO_2的工艺,是控制酸雨和SO_2污染最为有效和环保的湿法烟气脱硫技术。在氨法脱硫技术的设备中,由于存在传感器检测过程的延时问题,传统的脱硫控制系统采取PID控制无法解决该问题。运用一种预估方法能补偿延迟时间,仿真实验验证了该算法的正确性,在负荷变化中实现了氨投放量的精确控制。显著地改善了烟气氨法脱硫控制系统的动态性能,有较好地应用价值。

延迟时间生产系统预防维修策略和X-bar控制图联合经济设计

针对生产过程输出质量特性服从正态分布的单部件延迟时间生产系统,研究了预防维修策略和X-bar控制图联合经济设计问题.首先,在将延迟时间系统界定为受控、失控、故障3种结果状态基本内容前提下,根据维修时系统可能存在的实际状态和控制图监测结果关系,分析构建了生产系统维修方式和控制图监测的耦合机制;在此基础上,以期望单位时间最小成本为目标,以系统维修成本、产品质量抽检成本、不合格品的生产费用、维修停机生产损失为考虑成本内容,利用更新过程理论建立了生产系统预防维修策略和X-bar控制图联合决策数学模型;然后基于数值仿真示例,利用遗传算法对模型的求解进行了分析验证.实例分析结果表明,文章模型可行有效.最后,利用部分因子试验设计方法对模型参数进行了敏感性分析.

Delay-dependent Stability Criteria for Systems with Differentiable Time Delays

This paper studies the problem of stability for continuous-time systems with differentiable time-varying delays.By using the information of delay derivative,improved asymptotic stability conditions for time-delay systems are presented.Unlike the previous methods,the upper bound of the delay derivative is taken into consideration even if this upper bound is larger than or equal to 1.It is proved that the obtained results are less conservative than the existing ones.Meanwhile,the computational complexity of the presented stability criteria is reduced greatly since fewer decision variables are involved.Numerical examples are given to illustrate the effectiveness and less conservatism of the obtained stability conditions.

史密斯预估器的鲁棒调整方法

提出了模型不确定时史密斯预估器的鲁棒PID调整。引入了等效增益脉冲时间延迟(EGPTD)的概念 ,并用于史密斯预估器的PID调整中的鲁棒稳定性控制。由于二阶脉冲时间延迟(SOPTD)系统广泛地用于描述工业过程 ,特别地开发了鲁棒调整在该系统中的应用。推荐的调整方法可以处理模型的所有参数同时不确定的情况。另一个重要的特点是本方法可以利用有效的PID调整规律。

Property Analyses and Experiment Studies of a Kind of PWM System

The properties and the design of PWM systems are discussed. The relations among the orifice areas of the valves, initial times and the rate of piston areas are deduced. Also a PWM system is designed and some experiments are done. The experiment results agree with those of theory analyses. It can be shown that the relations are correct and the conclusion of theory analyses is reasonable.

Delay-dependent robust control for uncertain discrete singular systems with time-varying delay

The design problem of delay-dependent robust control for uncertain discrete singular systems with time-varying delay is addressed in this paper. The uncertainty is assumed to be norm-bounded. By establishing a finite sum inequality based on quadratic terms, a new delay-dependent robust stability condition is derived and expressed in terms of linear matrix inequalities (LMIs). A suitable robust state feedback control law is presented, which guarantees that the resultant closed-loop system is regular, causal and stable for all admissible uncertainties. Numerical examples are given to demonstrate the applicability of the proposed method.

Robust Predictive Control of Uncertain Systems with Time-delay Using Tight Sets of Predicted States

A robust model predictive control (MPC) algorithm for discrete time linear systems with time-delay (RPC-TDS) subjected to constrained input control is presented, where the polytopic uncertainties exist in state matrices and input matrices. In the algorithm the standard optimization of quadratic objective function has been transformed into optimization of sum of N+1 upper bounds of the quadratic objective function with respect to N control moves and a state feedback control law, where N is the control horizon. The feasibility of the optimization problem guarantees that the algorithm is robustly stable. The simulation results verify the effectiveness of the proposed algorithm.

Transient Properties of a Bistable System with Delay Time Driven by Non-Gaussian and Gaussian Noises:Mean First-Passage Time

The mean first-passage time of a bistable system with time-delayed feedback driven by multiplicative non-Gaussian noise and additive Gaussian white noise is investigated. Firstly, the non-Markov process is reduced to the Markov process through a path-integral approach; Secondly, the approximate Fokker-Planck equation is obtained by applying the unified coloured noise approximation, the small time delay approximation and the Novikov Theorem. The functional analysis and simplification are employed to obtain the approximate expressions of MFPT. The effects of non-Gaussian parameter （measures deviation from Gaussian character） r, the delay time τ, the noise correlation time to, the intensities D and a of noise on the MFPT are discussed. It is found that the escape time could be reduced by increasing the delay time τ, the noise correlation time τ0, or by reducing the intensities D and α. As far as we know, this is the first time to consider the effect of delay time on the mean first-passage time in the stochastic dynamical system.

Guaranteed cost sampled-data control for uncertain nonlinear time-varying delay system

The robust guaranteed cost sampled-data control was studied for a class of uncertain nonlinear systems with time-varying delay. The parameter uncertainties are time-varying norm-bounded and appear in both the state and the input control matrices. By applying an input delay approach, the system was transformed into a continuous time-delay system. Attention was focused on the design of a robust guaranteed cost sampled-data control law which guarantees that the closed-loop system is asymptotically stable and the quadratic performance index is less than a certain bound for all admissible uncertainties. By applying Lyapunov stability theory, the theorems were derived to provide sufficient conditions for the existence of robust guaranteed cost sampled-data control law in the form of linear matrix inequalities (LMIs), especially an optimal state-feedback guaranteed cost sampled-data control law which ensures the minimization of the guaranteed cost was given. The effectiveness of the proposed method was illustrated by a simulation example with the asymptotically stable curves of system state under the initial condition of x(0)=[0.679 6 0].

Stabilization of a class of nonlinear discrete time systems with time varying delay

The stability and stabilization of a class of nonlinear discrete time delayed systems(NDTDS) with time-varying delay and norm-bounded nonlinearity are investigated. Based on discrete time Lyapunov–Krasovskii functional method, a sufficient delaydependent condition for asymptotic stability of nonlinear systems is offered. Then, this condition is used to design a new efficient delayed state feedback controller(DSFC) for stabilization of such systems. These conditions are in the linear matrix inequality(LMI) framework. Illustrative examples confirm the improvement of the proposed approach over the similar cases. Furthermore, the obtained stability and stabilization conditions will be extended to uncertain discrete time delayed systems(UDTDS) with polytopic parameter uncertainties and also with norm-bounded parameter uncertainties.

H_∞ Control Based on LMIs for a Class of Time-delay Switched Systems

The problem of H∞ stability analysis and control synthesis of switched systems with delayed states under arb/trary switchirg laws is considered. By means of Lyapunov function and linear matrix inequality tools, sufficient ctmdition of H∞ stability is presented in terms of linear matrix inequalities. Furthermore, the robust H∞ control synthesis via state feedback and output feedack is studied. Finally, a numerical example is given to demonstrate the effectiveness of the proposed method.

Robust Stability and Performance Comparison of PID and PPI Control

Predictive PI (PPI) control form, capable of time delay compensation, has been put forward recently. This control algorithm is essentially a PI controller with enhanced derivative action, which is not only suitable for long time delay process, but also of simple structure and excellent robust stability. The performance of PPI controller was demonstrated and compared with that of traditional PID controller by different tuning methods.

Online Delay-Evaluation Control for Networked Control Systems

This paper presented an evaluation approach of time delays for networked control systems (NCS). An improved scheme based on optimal LQG control was designed to achieve desired performance despite the uncertain delays in the system. The experimental results illustrate the effectiveness of the proposed control design and satisfactory performance of the closed loop system.