Fradkov Theorem-Based Control of MIMO Nonlinear Lurie Systems

Consideration was given to the problem of adaptive output control of the class of MIMO (Multiple Input Multiple Output) systems that are functionally and parametrically uncertain. An approach to the design of the control law ensuring stabilization of the MIMO nonlinear Lurie system, that is, a system consisting of the linear part (strictly minimum-phase unit) and nonlinear static feedback unit, was proposed on the basis of the Fradkov theorem on feedback passification of linear systems.     

基于多变量广义预测控制的不稳定系统控制结构选择方法

对于多输入多输出系统, 在控制系统设计时首先要对被控变量和操纵变量进行控制结构选择. Bristol提出的相关增益矩阵(Relative gain array, RGA)法, 以及学者们后来提出的各种改进方法, 都只适用于稳定系统. 本文针对不稳定系统, 基于多变量广义预测控制(Generalized predictive control, GPC)的闭环控制律提出了一种控制结构的变量匹配准则. 通过对预测时域、控制时域等各个参数的优化选择, 使系统闭环稳定; 由闭环控制律得到被控变量期望值与操纵变量的相关性矩阵, 以此得出控制结构的变量配对方案. 通过实例研究表明, 对于开环不稳定系统, 该方法可以得出正确的变量配对结果.     

基于软件无线电的并行多输入多输出均衡技术

针对3GPP-LTE协议中多输入多输出(MIMO)均衡算法的高复杂度和高吞吐率问题,提出了一种面向软件无线电的并行MIMO均衡处理器,该处理器采用单指令流多数据流(SIMD)和超长指令字(VLIW)技术同时开发子载波间MIMO均衡和子载波内矩阵运算的并行性,并且每一个SIMD功能单元能够支持16 bit定点和20 bit伪浮点复数向量运算和矩阵运算,满足不同天线配置的MIMO均衡算法对处理精度、延迟和功耗的要求。实验结果表明,MIMO均衡处理器的4×4矩阵逆运算吞吐率达到了95 MInversion/s,满足3GPP-LTE协议的要求,并且其灵活可编程性和可配置性能够支持不同的均衡算法。     

Development of a fractional order based MIMO controller for high dynamic engine testbeds

Testbed are used to tune and assess automotive engines. As more High Dynamic (HD) scenarios need to be simulated, the testbeds require Multi Input Multi Output (MIMO) and robust control systems. A cooperation involving a major testbed manufacturer and two university laboratories was therefore set up. This paper presents the Control-System Design (CSD) methodology developed from system identification to the design and assessment of the MIMO robust controller for a HD testbed coupled with a spark-ignition engine. It is specially highlighted how the entire process has been automated and simplified and how the fractional order based MIMO CRONE CSD has been parameterized to obtain the best performance. Experimental results show that the proposed fractional order based MIMO control system is able to improve robustness and decoupling.     

MIMO技术在无线通信领域的应用研究

在第4代移动通信技术（4G）飞速发展的今天,MIMO（MultipleInputMultipleOutput,多输入多输出）技术由于其在通信领域的先天技术优势,被广泛的应用于无线通信技术中。文章从MIMO从无线通信技术的发展引出MIMO的概念,详细介绍了MIMO的系统原理、关键技术应用研究、发展前景等。     

A GGP approach to solve non convex min-max predictive controller for a class of constrained MIMO systems described by state-space models

This paper proposes a new method to solve non convex min-max predictive controller for a class of constrained linear Multi Input Multi Output (MIMO) systems. A parametric uncertainty state space model is adopted to describe the dynamic behavior of the real process. Moreover, the output deviation method is used to design the j-step ahead output predictor. The control law is obtained by the resolution of a non convex min-max optimization problem under input constraints. The key idea is to transform the initial non convex optimization problem to a convex one by means of variable transformations. To this end, the Generalized Geometric Programming (GGP) which is a global deterministic optimization method is used. An efficient implementation of this approach will lead to an algorithm with a low computational burden. Simulation results performed on Multi Input Multi Output (MIMO) system show successful set point tracking, constraints satisfaction and good non-zero disturbance rejection.     

Disturbance Decoupling of Time Delay Systems

A necessary and sufficient condition is derived for the solvability of the disturbance decoupling problem by a pure shift dynamic compensator. It corrects previously obtained results for multi‐input multi‐output (MIMO) systems. Also, necessary and sufficient conditions are given for the solvability of the problem by a dynamic compensator for single input single output (SISO) systems.     

EVOLUTIONARY SEARCH FOR LIMIT CYCLE AND CONTROLLER DESIGN IN MULTIVARIABLE NONLINEAR SYSTEMS

A feature of many practical control systems is a Multi‐Input Multi‐Output (MIMO) interactive structure with one or more gross nonlinearities. A primary controller design task in such circumstances is to predict and ensure the avoidance of limit cycling conditions followed by achieving other design objectives. This paper outlines how such a system may be investigated using the Sinusoidal Input Describing Function (SIDF) philosophy quantifying magnitude, frequency and phase of any possible limit cycle operation. While Sinusoidal Input Describing function is a suitable linearization technique in the frequency domain for assessment of stability and limit cycle operation, it can not be employed in time domain. In order to be able to incorporate the time domain requirements in an overall controller design technique, the appropriate linearization technique suggested here is the Exponential Input Describing Function (EIDF). First, an evolutionary search based on a multi‐objective formulation is employed for the direct solution of the harmonic balance system matrix equation. The search is based on Multi‐Objective Genetic Algorithms (MOGA) and is capable of predicting specified modes of theoretically possible limit cycle operation. Second, the design requirements in time as well as frequency domain are formulated by a set of constraint inequalities. A numerical synthesis procedure also based on Multi‐Objective Genetic Algorithm is employed to adjust the initial compensator parameters to meet the imposed constraints. Robust stability and robust performance are investigated with respect to linearization uncertainty within the context of multiobjective formulation. In order to make the Genetic Algorithm (GA) search more amenable to design trade‐off between different and often contradictory specifications, a weighted sum of the functions is introduced. This criterion is subsequently optimized subject to the nonlinear system dynamics and a set of design requirements. Examples of use are given to illustrate the effectiveness of the proposed approach.     

Performance analysis of ordered CFAR detectors for MIMO radars

Ordered statistics is one of the proposed solutions to improve the detection in a multiple target environment. Some variants of this technique have been proposed for the SISO (Single Input Single Output) radars such as the OS-CFAR (Ordered Statistics CFAR), the GOSCA-CFAR (Generalized Ordered Statistics, Cell Averaging CFAR), the OSGO-CFAR (Ordered Statistics Greatest Of CFAR) and the OSSO-CFAR (Ordered Statistics Smallest Of CFAR) to deal with multiple target situations. In this paper, we generalize these CFAR detectors for the MIMO (Multi Input Multi Output) radars with three different schemes. We derive closed-form expressions of the probability of false alarm (Pfa) and the probability of detection (Pd) in a homogeneous environment for two schemes. The performance of these detectors for a non-homogeneous clutter environment (presence of interfering targets and clutter edge) has been assessed and compared. The results obtained showed that the best performance is obtained by the OSSO-CFAR.     

时间选择性衰落信道下的空时多普勒编码

利用分层的代数方法,提出了一种新型的应用于时间选择性平坦衰落信道下的多输入多输出系统的空时多普勒码字,该码字能在符号速率达到Nt的情况下同时获得最大分集增益NtNrNb（Q+1）,也就是发送天线数Nt、接收天线数Nr、编码符号块的数目Nb以及信道复指数基的个数（Q+1）的乘积。仿真结果表明,与已有空时多普勒码字相比,所设计的码字可以获得更高的分集增益。     

基于系数图法的多输入多输出系统控制器设计方法

多输入多输出系统的交互作用会限制适用于单输入单输出系统的多种先进设计方法的使用,且多数关于多输入多输出系统控制研究只重视消除交互作用的影响,忽略系统控制问题,这样不但弱化系统的鲁棒性,且设计过程复杂,解耦后系统阶次也较高.鉴于此,提出一种基于系数图法的多入多出系统的控制器设计方法,将多输入多输出系统解耦问题转化为参数优化问题.首先,给出目标函数和两个线性约束条件,通过在频域基于粒子群算法优化目标函数,从而设计补偿器实现解耦;其次,基于系数图法确定控制器结构及参数整定,兼顾系统的稳定性和鲁棒性;最后,通过仿真实验验证所提出方法的有效性.     

MIMO-GFDM系统中低复杂度动态禁忌搜索检测算法的改进

针对多输入多输出的广义频分复用（MIMO-GFDM）系统的等效信道矩阵维度极大，传统的MIMO检测算法复杂度高且性能不佳的问题，将大规模MIMO系统中的动态禁忌搜索（RTS）检测算法运用到MIMO-GFDM系统中，并解决了RTS算法初始值的求解复杂度高的问题。首先利用最小均方误差（MMSE）检测算法所用到矩阵的正定对称性将矩阵Cholesky分解，并结合Sherman-Morrison公式迭代计算初始值，降低了初始值求逆的高复杂度；然后以改进的MMSE检测结果作为RTS算法的初始值，从初始值逐步全局搜索最优解；最后通过仿真，对不同算法的迭代次数和误码率（BER）性能进行了研究。理论分析与仿真结果表明：在MIMO-GFDM中，所提改进RTS信号检测算法误码率远低于传统信号检测算法。在4QAM时，RTS算法大约有低于MMSE检测6 dB的信噪比性能增益（误码率在10^-3时）；在16QAM时，RTS算法大约有低于MMSE检测4 dB的信噪比性能增益（误码率在10^-2时）。与传统RTS算法性相比，所提改进算法在不影响误码率性能的同时降低了算法复杂度。     

Ultra‐compact 4‐port DR antenna for multi‐input multi‐output standards

Here, an ultra‐compact Multi‐Input‐Multi‐Output (MIMO) antenna system is presented for Wireless Local Area Network (WLAN) applications. The proposed antenna compactness approach is based on using Cylindrical‐Dielectric‐Resonator‐Antenna (CDRA) symmetry with the help of image theory to achieve the best size reduction of the resonators and maintain the resonance frequency of the original CDRA. The electric/magnetic walls approach is utilized to miniaturize the size by exploring the symmetry and antisymmetry of the resonant mode. First, a CDRA for MIMO system is designed and tested in terms of return loss and radiation efficiency. Then, two configurations of MIMO‐Antennas (two and four ports) are examined by using the same substrate size. The 2‐port‐MIMO antenna is built from two half‐CDRs (HCDRs) facing each other. Similarly, four‐quarter‐CDRs (QCDRs) are created to form a 4‐port MIMO antenna system. As a result, a 75% size reduction is achieved (size of 30 × 30 × 7.62 mm³). The measured impedance bandwidth for the 4‐port MIMO antenna is 5.4% (5.4‐5.7 GHz), with more than 15 dB isolation levels. Proper levels of Envelope Correlation Coefficients (ECCs) are also achieved (1 × 10^?2‐4 × 10^?2), with a channel capacity loss (CCL) of 0.04 bits/S/Hz. The proposed MIMO antennas are suitable for compact wireless communication systems.     

A novel inverted fuzzy decoupling scheme for MIMO systems with disturbance: a case study of binary distillation column

This paper presents a novel inverted fuzzy decoupling scheme for multi-input multi-output (MIMO) systems with disturbance via PI controller. The emphasis is to determine a decoupling control where specific inputs and outputs are paired. This decoupling control is achieved using fuzzy logic, to reduce the reliance on model-based analysis. The inverted decoupling approach allows more flexibility in choosing the transfer functions of the decoupled apparent process. In addition, the expressions of the inverted decoupling are presented for general \(n \times n\) processes, highlighting that the complexity of the decoupling elements is independent of the system size. The inverted fuzzy decoupling scheme is developed and compared with an ordinary inverted decoupling scheme. Based on the direct Nyquist array method, the stability conditions of the overall closed loop MIMO system in the presence of disturbance are formulated. A case study of Wood and Berry model of a binary distillation column is used to illustrate the applicability of the proposed schemes.     

一种基于子空间分解的认知MIMO传输机制

针对传统认知无线电中检测-避免机制无法保证认知用户通信质量的问题,利用多输入多输出(MIMO)在空域处理上的优势,提出一种基于子空间分解的认知MIMO传输机制。在信道检测阶段,通过对协方差矩阵进行子空间分解得到噪声空间,在数据传输阶段,结合预编码将发送信号投影到噪声空间上,并采用功率注水以优化系统性能。仿真结果表明,该算法可以实现认知用户与主用户的空间复用,有效地提高系统的频谱利用率。     

结合凸优化的宽带MIMO系统接收天线选择

研究宽带多输入多输出(MIMO)系统中的接收天线选择技术。基于添加循环前缀辅助的宽带MIMO系统数学模型,利用邻近子载波间的相关性,设计次优的天线选择准则,并对结合凸优化方法的接收天线选择算法进行改进。仿真结果表明,次优准则可以获得与最优准则几乎相同的性能,改进的接收天线选择算法以增加较少计算量为代价,提高了系统的容量性能。     

Isolation enhanced MIMO antenna for software defined networking (SDN) adapted ultrawide band (UBW) radio tech applications

In this paper four element, four-port “enhanced bandwidth reduced radius single stub annular ring slot” (EBRRSS-ARS) Multiple Input Multiple Output (MIMO) antenna with isolation enhancement structure is proposed. The prospective antenna with stub in annular slot reduces the mutual coupling has simple and compact structure. The EBRRSS-ARSA resonates at 4.4 GHz with a bandwidth of 0.9 GHz with minimum isolation of 10 dB between its elements. The parametric study for the proposed fabricated antenna agrees well with the measurements.     

基于双码本的多用户MIMO有限反馈预编码方法

针对多用户多输入多输出(MIMO)下行链路由有限反馈导致的性能缺失,提出一种基于双码本的有限反馈预编码方法。该方法首先在接收端根据期望用户最大信干比准则从预置码本中选取预编码码字及扰动码字反馈给发送端,然后利用矩阵线性变换特性对预编码码字进行线性变换扰动以达到容量最优,从而补偿由于有限反馈导致的容量性能缺失。仿真结果表明,所提出的方法在保证反馈链路开销与系统误码性能的情况下,有效地改善了系统吞吐量。     

基于信道分析的动态可重构MIMO检测器

在多输入多输出(MIMO)系统中分析信道增益对信号检测性能的影响,提出一种基于信道分析的智能MIMO信号检测算法,根据各对天线间的信道增益动态调整子节点扩展数,在检测性能接近最大似然算法性能的前提下,该算法比传统K-best算法减少54%的子节点扩展数。基于该算法设计并实现的动态可重构的超大规模集成电路MIMO检测器支持4×4天线阵列、QPSK/16-QAM调制信号,数据吞吐率达到800 Mb/s。     

Control configuration selection for multi input multi output processes

Traditionally, control configuration selection and controller design of MIMO systems are done using input/output information of direct loop while outputs of undesired or interactive loops go un-noticed that bears information on interactions. This paper describes the state of art in integration of manipulated variable and controlled variable by selecting an appropriate control configuration among the loops in MIMO systems using interactive responses. It is difficult to quantify the interactions among the control loops as the disturbance propagates from one loop to other loops and vice versa. This paper provides a technique to assess the control loop interactions and rank the loops accordingly. A novel method based on the comparison of areas of the undesirable responses has been proposed to calculate the interactions among the loops and subsequently input–output pairing. Simulation and experimental results shows the validity of the proposed methods.