无线网络化系统自适应能量调度与协同控制

无线网络化系统（wireless networked control system,WNCS）中节点能量受限是影响系统性能的重要因素．本文提出了一种自适应能量调度方法解决节点能量与控制需求问的矛盾,在采样周期与能量消耗之间关系的基础上,利用动态采样周期实现能耗的实时调节,满足节点生存时间的需求．进而,将自适应采样的WNCS建模为一类具有短暂不确定切换信号的离散切换系统,采用切换状态反馈控制律,利用切换系统理论分析了系统的稳定性,给出了系统渐近稳定时控制器增益与滞留时间需要满足的约束条件．最后在Truetimel．5和MATLAB仿真平台上验证了文中提出的方法和结论．     

Consensus Control in Linear Multi‐Agent Systems with Current and Sampled Partial Relative States

This paper studies consensus in linear multi‐agent systems with current and sampled partial relative states. A distributed linear consensus protocol is designed, where both current and sampled relative states are utilized. A necessary and sufficient condition for consensus in this setting is established. The notion of the consensus region is then introduced and analyzed for third‐order systems, provided that each agent can only know its relative positions and velocities. It is shown that the consensus regions are stable to control gains and sampling period. Additionally, how to choose the control gains and the sampling period is given for consensus in third‐order systems. Finally, an example is given to verify and illustrate the analysis.     

Sampling period scheduling of networked control systems with multiple-control loops

This paper addresses the sampling period scheduling of Networked Control Systems (NCSs) with multiple control loops. The generalized exponential function is employed to describe Integral Absolute Error (IAE) performance versus sampling period by Truetime toolbox under Matlab environment, and the sampling periods are scheduled to obtain the optimal integrated performance based on Kuhn–Tucker Theorem, which are subject to the stability of every control loop and the bandwidth on available network resource. Numerical examples are given to show the effectiveness of our method.     

机器人非线性连续变增益H∞控制器设计

本文针对n关节的刚性机器人,提出了一种设计连续变增益控制器的新方法．这种方法结合 了变增益和H∞理论,通过在平衡点附近线性化系统,利用具有极点配置的状态反馈H∞ 技术,对应每个运动区域,设计满足H∞性能和动态特性的状态反馈增益,这些增益通过 泰勒级数展开拟合成与运动点有关的连续函数．随着系统状态的变化,拟合成的增益函数可 使控制器获得连续的增益,使得所设计的控制器同样适合系统状态变化较快的对象,而且系 统随状态的变化始终具有很高的动态性能,克服了传统变增益控制器中存在的不足．仿真结 果验证了此控制器的有效性．     

Global Robust Stabilization via Sampled‐Data Output Feedback for Nonlinear Systems with Uncertain Measurement and Control Gains

This paper studies the problem of using a sampled‐data output feedback controller to globally stabilize a class of nonlinear systems with uncertain measurement and control gains. A reduced‐order observer and a linear output control law, both in the sampled‐data form, are designed without the precise knowledge of the measurement and control gains except for their bounds. The observer gains are chosen recursively in a delicate manner by utilizing the output feedback domination approach. The allowable sampling period is determined by estimating and restraining the growth of the system states under a zero‐order‐hold input with the help of the Gronwall–Bellman Inequality. A DC–DC buck power converter as a real‐life example will be shown by numerical simulations to demonstrate the effectiveness of the proposed control method.     

Digital versus analog control of bilateral teleoperation systems: A task performance comparison

Controller discretization has the potential to jeopardize the stability of a bilateral teleoperation system. As reported in the literature, stability conditions impose bounds on the gains of the discrete-time controller and the sampling period and also a trade-off between the two. This paper shows a choice of task for which large sampling periods, necessitating low control gains for maintaining stability, lead to low teleoperation transparency and unacceptable task performance. It continues to show that users can successfully perform the same task if the controller is implemented using analog components. This highlights the advantages of analog haptics in tasks involving the display of highly stiff environments. The paper also highlights the constraints in designing analog haptic teleoperation controllers and proposes design guidelines to address them.     

无抖振离散准滑模控制

基于对常规离散准滑动模态及其抖振的分析,提出将离散趋近等效控制相结合的控制策略,既保证了趋近模态具有良好品质,又降低了准滑动模态带。该控制策略可避免系统状态步步反向穿越滑动面的抖振运动,从面消除了控制的抖振,并以较少的控制能量获得较好的系统性能。     

Sensitivity of linear time invariant sampled data systems to sampling period

A technique for generation of sampling-period sensitivity functions for cyclic linear time-invariant sampled data systems is presented. The method uses some results of Rozenvasser to form the sensitivity models. The sensitivity functions are discontinuous at sampling times. Using some aspects of controllability, it is shown that integration of the model equations over one period only is sufficient to generate the sensitivity functions for all additional periods.     

非均匀采样系统的修正与补偿

提出一种针对非均匀采样失真的修正补偿方法.用正弦波激励与波形拟合,获得各子A/D的增益、直流偏移和相对于参考子A/D的延迟时间差.将各子A/D的采样序列叠加直流偏移修正因子使各直流偏移一致,补偿偏移采样失真,将各子A/D的样本序列乘以增益修正因子使各增益一致,补偿增益采样失真,通过等间隔采样插值运算,补偿采样延迟失真,获得均匀采样结果.在一组16个子A/D的仿真数据上的补偿实验验证了方法的正确性.在具有8个子A/D的一个数据采集系统的实测数据上的补偿实验,验证了方法的可行性.     

拒绝服务攻击下网络化非线性系统的采样数据控制

本文研究了在拒绝服务攻击下网络化非线性系统的采样数据输出反馈控制问题.首先,为了避免使用完整的状态信息,在存在拒绝服务攻击的情况下设计了一种新颖的切换观测器.其次,同时考虑两个采样周期和拒绝服务攻击的影响,建立了一个新的切换增广系统模型,包括系统本身和误差系统.利用该模型和分段Lyapunov-Krasovskii泛函方法推导出保证切换增广系统是指数稳定的充分条件.进一步,利用线性矩阵不等式的解给出了观测器和控制器增益的共同设计方案.最后,通过仿真验证所提出控制方法的有效性.     

Asynchronous sampled-data consensus of singular multi-agent systems based on event-triggered strategy

This paper is concerned with sampled-data consensus for multi-agent systems with singular dynamics. It is assumed that the sampling period of each agent is independent of the other's. Based on event-triggered sampled-data transmission strategy, a distributed consensus protocol is presented. The consensus of singular multi-agent system is transformed into the stability of singular systems with multiple time-varying delays. By employing the Lyapunov-Krasovskii functional method, a sufficient condition on the consensus of multi-agent singular system is derived. Based on the obtained condition, an algorithm to design consensus controller gains is presented in terms of linear matrix inequalities. Two numerical examples are given to show the effectiveness of the proposed method.     

Stochastic bounded consensus tracking of second-order multi-agent systems with measurement noises based on sampled-data with general sampling delay

This paper investigates the stochastic bounded consensus tracking problems of second-order multi-agent systems, where the control input of an agent can only use the information measured at the sampling instants from its neighbours or the virtual leader with a time-varying reference state, the measurements are corrupted by random noises and the signal sampling process induces the general sampling delay. First, the stochastic bounded consensus tracking protocol based on sampled-data with the general sampling delay is presented by using the delay decomposition technique. Second, the augmented matrix method, the probability limit theory and some other techniques are employed to derive the necessary and sufficient conditions guaranteeing the mean square bounded consensus tracking. The theoretical results show that the convergence of the proposed protocol simultaneously depends on the constant feedback gains, the network topology, the sampled period and the sampling delay, and that the static consensus tracking error depends on not only the above-mentioned factors, but also the noise intensity and the upper bound of the velocity and the acceleration of the virtual leader. The obtained results cover no sampling delay and the small sampling delay as two special cases. Simulations are provided to demonstrate the effectiveness of the theoretical results.     

Energy‐efficient distributed control of large‐scale systems: A switched system approach

This paper is concerned with the sensor‐network‐based distributed control of large‐scale systems with the power constraint. In the underlying system, the measurement is firstly sampled under nonuniform sampling periods, which are varying in a given set. Then, the measurement size reduction technique and communication rate reduction method are used to save the constrained power in sensor networks. Specifically, only one element of sampled measurement is chosen at each sampling time instant, and it is then quantized and transmitted to the neighbouring controllers. Based on the switched system approach, a unified model is presented to capture the nonuniform sampling, the measurement size reduction, the transmission rate reduction and the controller failure phenomenon. A new sufficient condition is obtained such that the filtering error system is exponentially stable in the mean‐square sense with a prescribed H_∞ performance level. Based on this condition, the controller gains are designed by using the cone complementarity linearization algorithm. Finally, a simulation study is given to show the effectiveness of the proposed new design technique. Copyright © 2015 John Wiley & Sons, Ltd.     

Sampled‐data control of a class of uncertain switched nonlinear systems in nonstrict‐feedback form

This paper investigates the stabilization problem of sampled‐data output feedback for a class of uncertain switched nonlinear systems in nonstrict‐feedback form. An observer is designed to estimate the unmeasured states, and a sampled‐data controller is obtained by discretizing the virtual controller that is constructed via the dynamic surface control method. It is proved that the designed sampled‐data controller can render all states of the resulting closed‐loop system to converge to a neighborhood of the origin for the arbitrary switching signal, and an allowable sampling period is also given. Finally, 2 examples are presented to illustrate the effectiveness of the proposed method.     

Multi-rate digital redesign of cascaded and dynamic output feedback systems

In this paper, a new indirect digital redesign method is presented for multi-rate sampled-data control systems with cascaded and dynamic output feedback controllers. These analogue controllers are often pre-designed based on desirable frequency specifications, such as bandwidth, natural angular frequency, etc. To take advantage of the digital controller over the analogue controller, digital implementation of these analogue controllers are often desirable. As only measured input-output signals are available, an ideal state reconstructing algorithm is utilised to obtain the multi-rate discrete-time states of the original continuous-time system. Based on the Chebyshev quadrature method, the gains of the multi-rate cascaded and the output feedback digital controllers are determined from their continuous-time counterparts according to the different sampling rates employed in the different parts of the closed-loop system. As a result, the respective analogue controllers with the high-frequency and low-frequency characteristics can be implemented using the respective fast-rate sampling and slow-rate sampling digital controllers. Unlike the classical direct bilinear transform method, which is an open-loop direct digital redesign method, the proposed digital controllers take into account the state-matching of the original continuous-time closed-loop system and the digitally redesigned sampled-data closed-loop system. To further improve the state-matching performance, an improved digital redesign approach is also developed to construct the multi-rate cascaded and dynamic output feedback digital controllers. Illustrative examples are given to demonstrate the effectiveness of the developed methods.     

Optimal discretization of continuous-data control system

Two methods of simulating continuous-data systems by sampled-data models are presented. Sample-and-hold devices are inserted in an otherwise continuous-data system, and the input and the feedback gains are modified to make the response of the sampled-data model as close to that of the original system as possible. A point-by-point comparison method matches the state variables of the two systems at the sampling instants. Another method relies on the optimization of the sampled-data system with a quadratic performance index.     

基于周期抽样的通信网性能测量方法

通信网性能测量技术能够通过采集有限的网络性能数据反映网络运行状态的主要特征。该文提出了一种基于周期抽样的通信网性能测量方法,该方法能够根据网络运行状态的变化特征自适应地调整抽样周期,并根据抽样结果重建网络运行状态。经实验验证,采用该方法的测量结果可以描述网络运行状态的变化过程。     

Global decentralized sampled‐data output feedback stabilization for a class of large‐scale nonlinear systems with sensor and actuator failures

In this paper, we investigate global decentralized sampled‐data output feedback stabilization problem for a class of large‐scale nonlinear systems with time‐varying sensor and actuator failures. The considered systems include unknown time‐varying control coefficients and inherently nonlinear terms. Firstly, coordinate transformations are introduced with suitable scaling gains. Next, a reduced‐order observer is designed to estimate unmeasured states. Then, a decentralized sampled‐data fault‐tolerant control scheme is developed with an allowable sampling period. By constructing an appropriate Lyapunov function, it can be shown that all states of the resulting closed‐loop system are globally uniformly ultimately bounded. Finally, the validity of the proposed control approach is verified by using two examples.     

基于电流预测的三相感应电机矢量控制

在分析三相感应电机离散化的电流预测控制模型的基础上,本文提出了一种新的基于电流预测的三相感应电机矢量控制的算法。该算法不同于传统的SVPWM调制方式,而是在每个采样周期内,对三相逆变器的8个电压矢量进行在线评估,并选择使目标函数最小的电压矢量作为下一个周期的施加矢量。该方法控制策略简单,且具有较好的动静态性能,实现了对M轴和T轴给定电流的快速跟踪。在MATLAB／Simulink仿真软件平台下建立仿真模型,仿真结果验证了本文所提出控制策略的正确性和有效性。     

Metropolis–Hastings thermal state sampling for numerical simulations of Bose–Einstein condensates

We demonstrate the application of the Metropolis–Hastings algorithm to sampling of classical thermal states of one-dimensional Bose–Einstein quasicondensates in the classical fields approximation, both in untrapped and harmonically trapped case. The presented algorithm can be easily generalized to higher dimensions and arbitrary trap geometry. For truncated Wigner simulations the quantum noise can be added with conventional methods (half a quantum of energy in every mode). The advantage of the presented method over the usual analytical and stochastic ones lies in its ability to sample not only from canonical and grand canonical distributions, but also from the generalized Gibbs ensemble, which can help to shed new light on thermodynamics of integrable systems.