Estimation of random information sets of multistep systems

The estimation problems for the linear multistep controlled system under mixed perturbations are considered. It is assumed that deterministic perturbations are bounded by convex and compact constraints and random perturbations are Gaussian. Random information sets, called multiestimes for brevity, are defined. In the absence of random components, the introduced multiestimates coincide with information sets in the theory of guaranteed estimation. The multiestimate structure is considered. It is shown that multiestimates can be represented as the sum of a random vector and a deterministic set, which depend on several parameters. In turn, this set of parameters determines uniquely both conditional and unconditional probability of inclusion of the multiestimate in the covering set. Several special cases are analyzed, and the form of the covering set is discussed. A modification of the problem under communication constraints is proposed. This modification takes into account the limited capability of the digital data transfer channel. Relations between the accuracy of multiestimate parameters identification and the length of the transmitted word are obtained. A number of the obtained results are illustrated by examples.     

基于小波域滤波的电子通信信道恶意干扰信号分离方法

针对电子通信信号与恶意干扰信号严重重叠的现象,设计了基于小波域滤波的电子通信信道恶意干扰信号分离方法。在分析信道特征并划分噪声种类后明确噪声信号形式,然后利用小波域滤波算法合理设置分解层数,对信号做分解重构与降噪,再利用极限学习机建立神经网络学习模型。根据干扰信号模型与信道衰减程度提取干扰信号特征,并将特征样本输入到神经网络中,直到输出分离结果。仿真结果表明：该方法能够有效去除信道噪声、降低通信误码率、均衡信道负载。     

Linear filtering with adaptive adjustment of the disturbance covariation matrices in the plant and measurement noise

For filtering a nonstationary linear plant under the unknown intensities of input signals such as plant disturbances and measurement noise, a new algorithm was presented. It is based on selecting the vectors of values of these signals compatible with the observed plant output and minimizing the error variances of the last predicted measurement. The measurement prediction is determined from the Kalman filter where the input signals are assumed to be white noise and the covariance matrix coincides with the empirical covariance matrix of the selected vectors. Numerical modeling demonstrated that the so-calculated filter coefficients are close to the optimal ones constructed from the true covariance matrices of plant disturbances and measurement noise. The approximate Newton method for minimization of the prediction error variance was shown to agree with the solution of the auxiliary optimal control problem, which allows to make one or some few iterations to find the point of minimum.     

Observer-based tracking controller design for networked predictive control systems with uncertain Markov delays

This paper is concerned with a tracking controller design problem for discrete-time networked predictive control systems. The control law used here is a combined state-feedback control and integral control. Since not all the states are available in practice, a local Luenberger observer is utilised to estimate the state vector. The measured output and estimated state vector are packed together and transmitted to the tracking controller via a communication channel with a limited capacity. Meanwhile, the control signal is also transmitted through a communication network.Network-induced delays on both links are considered for the signal transmission and modelled by Markov chains. Moreover, it is assumed that the elements in Markov transition matrices are subject to uncertainties. In order to fully compensate for network-induced delays, the controller generates a sequence of control signals which are dependent on each possible delay in the feedforward channel. By taking the augmentation twice, we obtain delay-free stochastic closed-loop systems and the controlled output is chosen as the tracking error. Sufficient conditions are provided for the energy-to-peak performance of the closed-loop systems. The feedback gains of the controller can be derived by solving a minimisation problem. Two examples are illustrated to demonstrate the effectiveness of the proposed design method.     

Stabilization for nonlinear systems via a limited capacity communication channel with data packet dropout

This paper addresses the stabilization problem for a class of nonlinear systems. It is assumed that the controller can only receive the transmitted sequence of finite coded signals via a limited digital communication channel. Both state and output feedback coder-decoder-controller procedures are proposed. Stabilization conditions involving the size of coding alphabet, the sampling period, system state growth rate and data packet dropout rate are obtained. Finally, an example is given to illustrate the design procedures and effectiveness of the proposed results.     

线性盲信道系统的一种稳定控制策略

就通信系统而言,涉及到有线信道及非卫星无线信道的问题时,信道不再可以看成为恒参信道,信号往往是通过未知信道传播,通常把这样的信道称为盲信道。数据信号在盲信道传播,将在接收端引入线性失真,导致误码率。为了提高系统性能,收端通过均衡器或序列估计器改善信道失真。本文在传统的盲信道辨识与均衡技术的处理方法下,给出了一种前馈稳定控制方法,这种方法能解决传统均衡器设计在进行信道辨识时,在训练序列较短或者缺损的情况下,盲信道的辨识的一些弊端。考虑盲信道的信号的接收品质,给出了线性盲信道系统可稳的一种控制方法。     

陈-Mobius多路载波数字通信系统及性能仿真

将几种常用数字波形的陈-Mobius逆变换作为多路载波数字通信系统数字输入信号的编码波形函数族,由其对二进制输入信号进行调制后直接叠加在一起在一个物理信道上进行传输;在接收端,用与各调制编码波形对应的正交的数字波形对各路信号进行同步相干解调,从而构成新的相干调制解调系统;而调制编码波形与解调波形函数族这两个函数族内部本身却是非正交的;而后应用MATALAB平台对这种新型多路载波数字通信系统进行性能仿真,在大量仿真平均的基础上,绘出了使用各函数族的系统的位错率对信噪比曲线,并与传统的相干调制解调系统的仿真结果相比较;结果表明,该系统具有更优异的抗强噪声与干扰的性能,可实现多路载波数字通信的直接叠加,节约系统的初始投资与运行费用.     

Correction of motion under communication constraints

Consideration was given to the problem of correcting motion of a linear controlled system under deterministic perturbations straitened by joint integral constraints. The impact on the motion correction parameters of the additional communication constraints resulting from insufficient power of the digital data transmission channel was studied. Obtained were the relations between the accuracy of restoring the phase system vector and the optimal value of the functional, as well as the length of the transmitted word and transmission frequency. Some results were illustrated by an example.     

基于HART协议的储罐自动计量系统的设计

研究和探讨了储罐自动计量使用的核心技术:储罐计量方法和HART通信协议,给出了HART协议在储罐自动计量系统中的应用实例.HART协议是模拟系统向数字系统转变过程中唯一向后兼容的智能仪表解决方案,在发挥现代现场总线技术优势的同时,保留了对现有工业电流标准4～20 mA信号的兼容性.本文对HART协议作了全面的分析,阐述了HART总线通信功能的软、硬件工作原理.     

Totally blind channel identification by exploiting guard intervals

Blind identification techniques estimate the impulse response of a channel by exploiting known finite alphabet or statistical properties of the transmitted symbols. Alternatively, oversampling the output is known to introduce dependencies also exploitable for channel identification. This paper proves the feasibility of estimating the channel by relying instead on the short sequences of zeros, known as guard intervals or zero padding, introduced between transmitted blocks by a number of communication protocols. Since no property of the transmitted information symbols is assumed, the method is called totally blind channel identification. It is proved that totally blind channel identification requires only two received blocks to estimate the channel.     

Multichannel direct sequence spectrum signaling using code phase shift keying

In this paper, we have designed and realized multichannel direct sequence spread spectrum (DSSS) system using code phase shift keying (CPSK). In the transmitter, taking each bit from each channel, data word is made as a symbol for selecting PN sequence, which is modulated with frequency of 100 MHz as DSSS signals. At the receiver, the correlator, integrator and decoder are used for separation of the signal of respective channel after demodulation. Oscilloscope traces show that the transmitted signals are matched with the simulated signals at the receiver. The bit error rate (BER) variation with jamming signal is estimated by our proposed simulation model, matching well with experimental values of BER measured by BER meter.     

A subband coding approach to control under limited data rates and message losses

For the design of networked control systems, we employ a subband coding technique to efficiently use the available data rate. Such coding schemes have widely been used in signal processing for data compression. We take an approach suitable from the control perspective in that frequency characteristics of a controller are directly used. In particular, we propose a three-step design procedure for the overall controller having the following features: On the coder side, it uses a controller consisting of a filter bank whose outputs are subband signals of the control input. On the decoder side is another filter bank for reconstruction of the subband signals. This decoder is capable to account for random message losses that occur in communication and is designed via an H^∞-type method. For the quantizers in the coder, an efficient bit allocation scheme is also developed.     

Robust stabilization of linear uncertain discrete-time systems via a limited capacity communication channel

The paper considers the problem of robust stabilization of linear uncertain discrete-time systems via limited capacity communication channels. We consider the case when the control input is to be transmitted via communication channel with a bit-rate constraint. A constructive method to design a robustly stabilizing controller is proposed.     

紫外非视距通信的MLSE均衡器

针对无线非视距紫外通信中的大气信道模拟问题,提出将最大似然序列估计均衡器应用于无线非视距紫外通信中.推导紫外通信中接收信号的概率密度函数,以此近似研究均衡器的输出误码率.理论分析与仿真结果表明,在短距离通信时,大气衰减系数与信道带宽的变化不影响均衡器性能.在接收信噪比不变的较长距离通信时,两者的变化对均衡器性能影响明显.信道记忆长度等因素对均衡器性能影响显著,而对调制方式不敏感.     

如何解决基不匹配问题:从原子范数到无网格压缩感知

压缩感知理论能够以远低于经典Nyquist速率进行采样, 采用非自适应线性投影获得了保留信号有用信息的少量观测点, 并通过求解最优化问题精确重构原始信号.压缩感知理论大大缓解了信号采样、存储和传输的巨大压力, 在计算机科学、电子工程和信号处理等领域具有广阔的应用前景.信号的稀疏表示是对信号进行压缩采样和重构的前提, 即假设信号在某个变换基(傅里叶基、小波基等)下是稀疏的, 这些基可以看作是用于描述信号参数空间的有限离散字典.然而在如雷达、阵列信号处理、通信等领域的应用中, 信号的参数空间是连续的, 在假定的离散变换基下并不稀疏, 这种基不匹配问题会严重影响信号重构精度.本文首先介绍了基不匹配产生的原因及其对重构精度的影响, 接着从原子范数出发, 综述了无网格压缩感知的理论框架和关键技术问题, 着重介绍了一维和多维无网格压缩感知的最新研究进展, 最后对其在信号处理等领域的应用进行了探讨.     

面向智能安全物流应用的无线传感器网络设计

传感器节点主要由CC2530射频模块、温湿度传感器DHT21、GSM模块以及串口上位机组成。以CC2530射频模块为系统的控制核心,在发送端模块负责采集温湿度传感器信号,通过RF射频端把现场的信息传送到接收端的CC2530模块,接收模块把接收到的温湿度数据通过串口通信把数据传送到上位机中,从而实现现场温湿度数据曲线的显示。GSM模块通过串口直接与上位机通信,该模块能通过手机通信网络把温湿度以短信的形式发送到指定用户的手机中,从而实现物流货品信息的远程监控。     

OFDM系统稀疏信道估计研究

由于许多通信系统的信道具有稀疏多径的特性,因此可以将信道估计问题归结为稀疏信号的恢复问题。提出一种新的基于压缩感知理论的正交频分复用系统信道估计方法,采用稀疏度自适应匹配追踪压缩感知算法对OFDM信道时域脉冲响应进行估计。克服了现有基于压缩感知理论的信道估计方法需要预先知道信道冲激响应稀疏度才能重构信道参数的不足,在信道稀疏度等信道先验知识未知情况下可得到较好的信道估计性能,降低系统复杂度。     

基于恒幅多频载波调制的频率分集

针对信号在无线时变信道传输时出现频率选择性衰落这种特性,频率分集是克服衰落的有效途径.目前常用的时频相调制方式造成信号频谱展宽,为此本文提出了几种利用恒幅多频载波实现频率分集的方法,使得调制后的分集信号具有恒幅特性和较高的频谱利用率,适用于多重频率分集的通信系统.     

Signal reconstruction in the presence of finite‐rate measurements: finite‐horizon control applications

In this paper, we study finite‐length signal reconstruction over a finite‐rate noiseless channel. We allow the class of signals to belong to a bounded ellipsoid and derive a universal lower bound on a worst‐case reconstruction error. We then compute upper bounds on the error that arise from different coding schemes and under different causality assumptions. When the encoder and decoder are noncausal, we derive an upper bound that either achieves the universal lower bound or is comparable to it. When the decoder and encoder are both causal operators, we show that within a very broad class of causal coding schemes, memoryless coding prevails as optimal, imposing a hard limitation on reconstruction. Finally, we map our general reconstruction problem into two important control problems in which the plant and controller are local to each other, but are together driven by a remote reference signal that is transmitted through a finite‐rate noiseless channel. The first problem is to minimize a finite‐horizon weighted tracking error between the remote system output and a reference command. The second problem is to navigate the state of the remote system from a nonzero initial condition to as close to the origin as possible in finite‐time. Our analysis enables us to quantify the tradeoff between time horizon and performance accuracy, which is not well studied in the area of control with limited information as most works address infinite‐horizon control objectives (e.g. stability, disturbance rejection). Copyright © 2009 John Wiley & Sons, Ltd.