Stability analysis for discrete-time switched systems with unstable subsystems by a mode-dependent average dwell time approach

This paper mainly intends to present new stability results of a discrete-time switched system with unstable subsystems. By adopting multiple Lyapunov functions? (MLFs?) method, new and less conservative stability conditions are derived in terms of a set of numerical feasible linear matrix inequalities (LMIs) with mode-dependent average dwell time (MDADT) techniques. Different from previous literatures, unstable subsystems are considered under two situations in this paper. It is shown that the discrete-time switched system can achieve exponential stability under a slow switching scheme and even in the presence of fast switching of unstable subsystems. Finally a numerical example is given to demonstrate the effectiveness of the proposed method.     

Asynchronous control of discrete-time impulsive switched systems with mode-dependent average dwell time

This paper mainly studies the asynchronous control problem for a class of discrete-time impulsive switched systems, where “asynchronous” means the switching of the controllers has a lag to the switching of system modes. By using multiple Lyapunov functions (MLFs), the much looser asymptotic stability result of closed-loop systems is derived with a mode-dependent average dwell time (MDADT) technique. Based on the stability result obtained, the problem of asynchronous control is solved under a proper switching law. Moreover, the stability and stabilization results are formulated in form of matrix inequalities that are numerically feasible. Finally, an illustrative numerical example is presented to show the effectiveness of the obtained stability results.     

Robust fault detection for switched positive linear systems with time-varying delays

This paper investigates the problem of robust fault detection for a class of switched positive linear systems with time-varying delays. The fault detection filter is used as the residual generator, in which the filter parameters are dependent on the system mode. Attention is focused on designing the positive filter such that, for model uncertainties, unknown inputs and the control inputs, the error between the residual and fault is minimized. The problem of robust fault detection is converted into a positive L₁ filtering problem. Subsequently, by constructing an appropriate multiple co-positive type Lyapunov–Krasovskii functional, as well as using the average dwell time approach, sufficient conditions for the solvability of this problem are established in terms of linear matrix inequalities (LMIs). Two illustrative examples are provided to show the effectiveness and applicability of the proposed results.     

Simultaneous fault detection and control design for switched systems with two quantized signals

The problem of simultaneous fault detection and control design for switched systems with two quantized signals is presented in this paper. Dynamic quantizers are employed, respectively, before the output is passed to fault detector, and before the control input is transmitted to the switched system. Taking the quantized errors into account, the robust performance for this kind of system is given. Furthermore, sufficient conditions for the existence of fault detector/controller are presented in the framework of linear matrix inequalities, and fault detector/controller gains and the supremum of quantizer range are derived by a convex optimized method. Finally, two illustrative examples demonstrate the effectiveness of the proposed method.     

进动气囊抛光的驻留时间优化

提出了一种新的进动气囊抛光驻留时间算法,用于实现高精度的光学玻璃零件的加工。首先,通过抛光工艺试验确定抛光去除率函数;在矩阵迭代算法的基础上,给定一个合适的驻留时间初值函数。然后,采用分层阈值去除法进行驻留时间的优化求解,并加上残余误差方差最小的判定条件,从而得到完整的驻留时间函数。该算法适用于非球面、自由曲面等光学玻璃元件的抛光加工。用MATLAB对残余面形误差进行了仿真,仿真结果表明残余误差精度PV值可以收敛到0.1μm左右。最后,对光学玻璃平面进行了抛光。实际抛光后,该玻璃表面粗糙度Ra从抛光前的0.159μm减小到0.024μm,面形精度PV值由抛光前的0.756μm减小到0.158μm。得到的结果验证了提出驻留时间算法的合理性,表明该算法可为以后进行复杂面形工件的气囊抛光研究提供理论基础。     

Finite-time stability and stabilization for stochastic markov jump systems with mode-dependent time delays

This paper is concerned with the problems of finite-time stability and stabilization for stochastic Markov systems with mode-dependent time-delays. In order to reduce conservatism, a mode-dependent approach is utilized. Based on the derived stability conditions, state-feedback controller and observer-based controller are designed, respectively. A new N-mode algorithm is given to obtain the maximum value of time-delay. Finally, an example is used to show the merit of the proposed results.     

An fully-automated measurement system for identifying magnetization characteristics of switched reluctance motors

Precise understanding of knowledge and behavior of the SRM is needed for the development and verification of advanced control algorithm. An fully-automated measurement system is proposed in this paper to identify the magnetization characteristics of the SRM as functions of the winding current and rotor position. The proposed system can characterize the SRM automatically and take magnetic nonlinearity and static iron losses into account. The post-mortem data processing with a graphical user interface constitutes the measuring procedures and provides easy manipulation and clear presentation of the results. The theoretical sensitivity is derived; error sources and uncertainties of the measurement are also analyzed and discussed. Experimental results with good accuracy conducted on a four-phase SRM show the correctness and practicability of the presented system. Special emphasis is oriented on the suitability for the production line application to on-line determine the saturation behaviors of the SRMs.     

Decentralized output feedback stabilization for switched stochastic high-order nonlinear systems with time-varying state/input delays

This paper investigates decentralized output feedback stabilization problem for a class of switched stochastic high-order systems with time-varying state/input delays. With the help of coordinate transformations, a scaling gain is incorporated into the observers and controllers for the nominal system. Based on the homogeneous domination approach and stochastic Lyapunov–Krasovskii stability theorem, it is shown that global asymptotic stability in probability of the closed-loop system can be implemented by tuning the scaling gain. Two examples are given to demonstrate the feasibility of the proposed control method.     

H∞ mode-dependent fault detection filter design for stochastic Markovian jump systems with time-varying delays and parameter uncertainties

This paper deals with the problem of robust _H∞$H_{\infty }$ fault detection for a class of stochastic Markovian jump systems (SMJSs) The aim is to design a linear mode-dependent fault detection filter such that the fault detection system is not only stochastically asymptotically stable in the large, but also satisfies a prescribed _H∞-norm$H_{\infty }\mathrm{-}\mathrm{norm}$ level for all admissible uncertainties. By using Lyapunov stability theory and generalized Itô formula, some novel mode-dependent and delay-dependent sufficient conditions in terms of linear matrix inequality (LMI) are proposed to insure the existence of the desired fault detection filter. A simulation example and an industrial nonisothermal continuous stirred tank reactor (CSTR) system are employed to show the effectiveness of the proposed method.     

具有后台测量功能的水流量实时信息管理系统

本文介绍了一个水流量实时信息计算机管理的设计与实施,分析Ｗｉｎｄｏｗｓ与ＤＯＳ两种应用程序设计方法的区别,阐述了应用软件设计思想,设计要点及单相实现后台测量原理与方法;     

Decentralized adaptive neural prescribed performance control for high-order stochastic switched nonlinear interconnected systems with unknown system dynamics

In this paper, the problem of decentralized adaptive neural backstepping control is investigated for high-order stochastic nonlinear systems with unknown interconnected nonlinearity and prescribed performance under arbitrary switchings. For the control of high-order nonlinear interconnected systems, it is assumed that unknown system dynamics and arbitrary switching signals are unknown. First, by utilizing the prescribed performance control (PPC), the prescribed tracking control performance can be ensured, while the requirement for the initial error is removed. Second, at each recursive step, only one adaptive parameter is constructed to overcome the over-parameterization, and RBF neural networks are employed to tackle the difficulties caused by completely unknown system dynamics. At last, based on the common Lyapunov stability method, the decentralized adaptive neural control method is proposed, which decreases the number of learning parameters. It is shown that the designed common controller can ensure that all the signals in the closed-loop system are semi-globally uniformly ultimately bounded (SGUUB), and the prescribed tracking control performance is guaranteed under arbitrary switchings. The simulation results are presented to further illustrate the effectiveness of the proposed control scheme.     

Actuator fault estimation and accommodation for switched systems with time delay: Discrete-time case

This paper investigates the problems of actuator fault estimation and accommodation for discrete-time switched systems with state delay. By using reduced-order observer method and switched Lyapunov function technique, a fault estimation algorithm is achieved for the discrete-time switched system with actuator fault and state delay. Then based on the obtained online fault estimation information, a switched dynamic output feedback controller is employed to compensate for the effect of faults by stabilizing the closed-loop systems. Finally, an example is proposed to illustrate the obtained results.     

分布式测量系统动态时间性能测度方法

在网络制造环境下,动态时间性能是分布式测量系统的重要指标.针对基于公共对象请求代理结构和尺寸测量接口规范的分布式测量系统,根据多用户非抢占优先排队网络静态性能模型,提出基于无穷小摄动分析的分布式测量系统动态性能评价算法.算法以分布式测量系统时间性能指标的在线变化为输入,动态调整排队网络系统服务台的窗口数量,从而实现对系统时间性能的动态调整.最后,在某制造工厂中进行了应用实验,证明了算法的有效性.     

针对纯滞后系统的RBF神经网络智能控制的研究

针对工业控制过程中普遍存在的大惯性、纯滞后、时变性、非线性对象的控制问题,采用传统的控制方法不能达到满意的控制效果,提出了基于RBF神经网络的PID自适应控制方案。采用神经网络辨识器在线辨识系统模型,自动调整PID控制器参数,从而实现系统的智能控制。仿真结果表明：该方法对于纯滞后控制系统能进行有效的控制并且具有很好的自适应性和鲁棒性。     

正压法音速喷嘴标准装置气源系统设计

为提高正压法音速喷嘴标准装置压力和流量稳定性能,提出了正压法气源系统设计的方法,设计包括气源及压缩气体净化系统,以及气源稳压系统。针对空压机出口气体特点,净化系统采用水冷型后置冷却器、高效除油器、精密过滤器、冷干机及吸干机组合的方式,并合理选择净化系统各部分参数,使得压缩空气达到-65℃左右的压力露点。系统采用自力式调压阀与稳压罐实现稳压功能,并用各个参量评估系统压力、流量稳定性能指标。最后通过实验验证设计效果,结果表明在同一流量点,滞止压力稳定性可以保持在0.2%以内,流量控制在0.03%以内,可以满足气体流量的检定需求。     

改进的最大-最小蚂蚁算法在有时间窗车辆路径问题中的应用

利用最大-最小策略,最大最小蚂蚁算法减小了蚂蚁算法陷入局部陷阱的可能性。基于对最大最小信息素策略和信息素更新方式的改进,结合快速产生初始解的算法,提出了一种新方法。把该方法应用于有时间窗车辆路径问题,试验结果表明该算法是有效的。     

管道导波时反聚焦检测系统的设计与实现

在分析管道中超声导波时反聚焦原理的基础上,设计并实现了一套适合激励压电换能器阵列,并对管道中超声导波能量在缺陷处进行时间-空间聚焦的时反聚焦检测系统.该系统实现的关键技术为:改进DDS( direct digital synthesis)结构,实现脉冲激励电路对时反特征信号进行合成发射;采用脉冲方式,实现小体积大输出功率的宽带线性功放电路;通过时反聚焦检测过程,实现管道中超声导波能量在缺陷处的时间-空间聚焦.采用该系统进行八通道时反聚焦检测实验,其结果表明,对于所用的含缺陷的管道而言,在特定的检测条件下,缺陷回波信号的幅值相对常规检测可提高246％,并且很好地抑制了导波的频散和多模态特性,提高了回波信号的信噪比.     

大时滞过程新型模糊控制策略研究进展

工业控制过程中普遍存在着大惯性、纯滞后对象的控制问题,而大时滞过程的控制依然是控制领域中的研究热点.该文就大时滞系统的各种改进型模糊控制策略的研究及其应用进行综述,并指出模糊控制与传统滞后控制方法的结合对大时滞过程的控制是有效的,可望在工业实践中得到广泛应用.