多采样率数字控制系统综述

本文给出了多采样率数字控制系统的发展和目前研究情况的综述．根据系统中各采样周期之间的关系，多采样率控制系统可以分为输入多采样率控制系统输出多采样率控制系统和广义多采样率控制系统等．它们又分别对应于采用广义保持器、广义采样器和周期时变控制器的数字控制系统．文中对这三类系统的特点和近期研究成果进行了系统的介绍与讨论．由于“因果条件”， 多采样率控制器具有结构约束．本文综述了几类满足这一结构约束的多采样率控制器的设计方法和各类多采样率控制系统．     

Stability analysis of explicit multirate methods

If stiff differential systems can be divided into stiff and nonstiff subsystems, each subsystem can be integrated with different step sizes. These methods are called multirate methods, and they have been successfully used in several practical problems, especially in real-time simulations.In this paper a new way to perform the stability analysis of multirate versions of linear multistep methods is presented. This stability analysis makes use of the multirate z-transform method.     

On the effect of multirate co-simulation techniques in the efficiency and accuracy of multibody system dynamics

Dynamic simulation of complex mechatronic systems can be carried out in an efficient and modular way making use of weakly coupled co-simulation setups. When using this approach, multirate methods are often needed to improve the efficiency, since the physical components of the system usually have different frequencies and time scales. However, most multirate methods have been designed for strongly coupled setups, and their application in weakly coupled co-simulation is not straightforward due to the limitations enforced by commercial simulation tools used in mechatronics design. This work describes a weakly coupled multirate method intended to be a generic multirate interface between block diagram software and multibody dynamics simulators, arranged in a co-simulation setup. Its main advantage is that it does not enforce equidistant or synchronized communication time-grids and, therefore, it can be easily applied to set up weakly-coupled co-simulations using off-the-shelf commercial block diagram simulators while giving the user a great flexibility for selecting the integration scheme for each subsystem.     

多采样率数字控制系统的函数空间模型

采用函数空间的方法 ,利用提升 (lifting)技术 ,构造出多采样率数字控制系统的函数空间模型 .该线性时不变离散模型同时描述了被控对象在采样点上和采样点之间的动态行为 .根据这种模型所设计的多采样率数字控制系统 ,有望克服目前多采样率数字控制系统所存在的采样点之间存在有纹波或振荡等弊病 ,为多采样率数字控制系统的分析与综合提供了一个新的方法 .     

多采样率系统的辨识问题综述

在多率采样系统中, 采样间隔不均匀. 本文综述了文献中有关多率采样系统的数学模型, 如线性周期时变模型、频域模型和连续状态空间模型等. 同时对相应的辨识方法, 如提升、频域方法、子空间辨识方法等, 也进行了全面的综述. 对多率采样系统辨识中存在的一些问题, 包括辨识模型的选择、一致性问题、带约束条件的辨识方法和辨识收敛性等, 也作了深入的讨论.     

Adaptive dynamic programming for discrete-time linear quadratic regulation based on multirate generalised policy iteration

In this paper, we propose two multirate generalised policy iteration (GPI) algorithms applied to discrete-time linear quadratic regulation problems. The proposed algorithms are extensions of the existing GPI algorithm that consists of the approximate policy evaluation and policy improvement steps. The two proposed schemes, named heuristic dynamic programming (HDP) and dual HDP (DHP), based on multirate GPI, use multi-step estimation (M-step Bellman equation) at the approximate policy evaluation step for estimating the value function and its gradient called costate, respectively. Then, we show that these two methods with the same update horizon can be considered equivalent in the iteration domain. Furthermore, monotonically increasing and decreasing convergences, so called value iteration (VI)-mode and policy iteration (PI)-mode convergences, are proved to hold for the proposed multirate GPIs. Further, general convergence properties in terms of eigenvalues are also studied. The data-driven online implementation methods for the proposed HDP and DHP are demonstrated and finally, we present the results of numerical simulations performed to verify the effectiveness of the proposed methods.     

AMR mode selection enhancement in 3G networks

This paper describes methods for mode selection in multirate speech codecs, such as the AMR (Adaptive Multi-Rate), that is the mandatory speech codec selected in 3GPP (3rd Generation Partnership Project) defined mobile networks. Originally, the multirate functionality has been developed for coping with changing radio conditions. The algorithms described in this paper find applicability in IP-based mobile networks, where speech encoded data is encapsulated using the RTP (Real Time Protocol). The main advantages offered by these techniques are improved speech quality and congestion control along the network path between two mobile terminals.     

一类异步多速率采样控制系统的近似问题

本文提出了一类异步多速率采样控制系统．针对这类非周期异步多速率系统分析、设 计困难这一问题，研究了其闭环系统性能关于采样器、保持器时间延迟的连续性问题．结果 表明，其闭环系统性能是采样器、保持器时间延迟的连续函数．据此连续性，在少许改变系 统性能的前提下，可以以任意给定精度将非周期异步多速率系统转变成周期异步多速率系统 ，再应用已有方法对其进行处理．     

A novel calibration approach of soft sensor based on multirate data fusion technology

In multirate chemical processes, soft sensor is commonly used for fast-rate quality estimations. As the kernel of soft sensor, modeling technique has drawn much attention from researchers. But most of the modeling methods have disadvantages of uncertain estimation errors and limited modeling capability. To these issues, soft sensor calibration is considered as an efficient alternative, which however is often ignored by researchers and the current application level is relatively low. A novel soft sensor calibration method is proposed in this paper. Under multirate sampling conditions, data fusion technology based on Kalman filter is introduced into soft sensor maintenance to integrate the soft sensor model estimations with process measurements. The performance of the algorithm is evaluated through simulations and a laboratory scale experiment. The factors that may influence the performance are also discussed in detail. The results demonstrate that the multirate Kalman filter approach is able to improve the accuracy and reliability of soft estimations, when the essential dynamics is included in the Kalman filtering model and the filter parameters are properly tuned.     

Monotone Routing in Multirate Rearrangeable Clos Networks

In this paper, we study monotone routing in the symmetric three-stage Clos network with general bandwidth, and propose a new approach to analyze the multirate rearrangeability. For networks with small size switches, we show that monotone routing is better than the previous methods.     

A new optimal multirate control of linear periodic andtime-invariant systems

The optimal multirate design of linear, continuous-time, periodic and time-invariant systems is considered. It is based on solving the continuous linear quadratic regulation (LQR) problem with the control being constrained to a certain piecewise constant feedback. Necessary and sufficient conditions for the asymptotic stability of the resulting closed-loop system are given. An explicit multirate feedback law that requires the solution of an algebraic discrete Riccati equation is presented. Such control is simple and can be easily implemented by digital computers. When applied to linear time-invariant systems, multirate optimal feedback optimal control provides a satisfactory response even if the state is sampled relatively slowly. Compared to the classical single-rate sampled-data feedback in which the state is always sampled at the same rate, the multirate system can provide a better response with a considerable reduction in the optimal cost. In general, the multirate scheme offers more flexibility in choosing the sampling rates     

多率系统Kalman滤波算法的鲁棒性分析

多率系统Kalman滤波算法是多率采样系统中对多源观测进行融合的重要手段. 基于化工过程的多率采样特点, 给出了多率Kalman滤波算法, 分析了该算法在模型失配情况下的鲁棒性. 在给定的假设条件下, 通过对滤波误差变化规律的分析, 给出了多率Kalman滤波稳定与发散的基本判定方法. 针对一类典型系统, 推导出了滤波稳定与发散判据. 通过仿真对该判据进行了验证, 仿真结果表明所提出的滤波鲁棒性分析方法可以用于算法的实际应用.     

多传感器单模型动态系统多尺度分布式融合估计

近几年来,小波理论和信号的多尺度表示方法都得到了迅速发展,并在包括信号处理和图像处理在内的众多领域中得到了成功的应用,而在这些领域中,目前一个较为活跃的分支是基于小波变换的多尺度表示的统计信号处理。运用多尺度分析的思想,将基于模型的动态系统分析方法与基于统计特性的多尺度信号变换方法相结合,建立起状态基于多源观测信息的多尺度分布式融合估计和单源观测信息的多尺度分布式估计两种新算法,用计算机仿真研究验证了算法效能。     

Sensitivity properties of multirate feedback control systems, basedon eigenstructure assignment

Some sampled-data systems, e.g., fly-by-wire control schemes, have a necessarily multirate structure, various input and/or outputs sampled at different rates. When considering a multirate system which has parameter uncertainty, it is important to examine ways in which the full freedom of the multivariable design can be utilized to minimize the sensitivity to parameter variations. Given the accompanying problems induced by intersample ripple disturbance. This note examines the design capabilities of a class of multirate systems with multiple input and fixed state sampling rates (MIFS), based on eigenstructure assignment. Although the use of eigenstructure assignment for continuous and single rate discrete systems is well understood, the eigenstructure assignment for the design of multirate feedback systems is an open topic of research. Accepting that the problems of intersample ripple are often magnified through multirate control, there are advantages in terms of increased freedom for minimizing sensitivity and optimizing robustness to parameter variations. A special feature of the MIFS class of multirate systems is the ability to introduce extra design freedom in the eigenproblem by a suitable choice of eigenstructure assignment and sample rates. The criteria for the selection of minimum sample rates to produce this extra freedom, and the implication that this has on the eigenstructure assignment problem, are outlined. The improved insensitivity properties are demonstrated using an example comparing the performance of multirate and corresponding single rate designs     

多采样率数字控制系统的零点与无纹波渐近跟踪

采用函数空间的方法,利用先后两次的提升技术,构造出多采样率数字控制系统的函数空间模型和相应的脉冲传递函数矩阵模型.在此基础上,给出了多采样率数字控制系统零点和零方向的定义及其计算方法.并利用零点和零方向的概念,得出了多采样率数字控制系统实现包括采样点上和采样点之间的整个连续时间区间内无纹波渐近跟踪的条件.     

Modeling and Identification of Multirate Systems

Multirate systems are abundant in industry; for example, many soft-sensor design problems are related to modeling, parameter identification, or state estimation involving multirate systems. The study of multirate systems goes back to the early 1950s, and has become an active research area in systems and control. This paper briefly surveys the history of development in the area of multirate systems, and introduces some basic concepts and latest results on multirate systems, including a polynomial transformation technique and the lifting technique as tools for handling multirate systems, lifted state space models, parameter identification of dual-rate systems, how to determine fast single-rate models from dual-rate models and directly from dual-rate data, and a hierarchical identification method for general multirate systems. Finally, some further research topics for multirate systems are given.     

一种新的IEEE 802.11自适应速率MAC协议——设计实现与性能测试

首先比较了现有的几种主要的自适应速率协议的特点,并详细阐述了一种新的自适应多速率协议AMARF的原理。其次,基于linux操作系统,通过修改设备驱动程序,在商业无线网卡上实现了ARF和AMARF两种自适应速率算法。最后,在实验室环境下,对各种速率自适应的算法进行了实际的性能测试,测试结果表明：在不同信道环境下,AMARF协议性能较优。     

Distributed multirate interacting multiple model fusion (DMRIMMF) with application to out-of-sequence GMTI data

This note develops a distributed approach for fusing ground moving target indicator data with out-of-sequence (OOS) measurements. A multirate interacting multiple model (MRIMM) fusion algorithm is developed for effectively fusing multirate information. The multirate approach provides an excellent framework for efficient information retrodiction and forward update. A multirate interacting multiple model filter is employed locally to track a target with or without maneuvering behavior. The combination of global MRIMM fusion and local MRIMM tracking proves to be powerful for tracking and fusing maneuvering and nonmaneuvering targets in an environment of OOS measurement reporting.     

多速率DS-CDMA系统中基于Kalman滤波的盲多用户检测

在讨论可变扩频增益多速率直接序列码分多址(DS-CDMA)系统信号模型的同时,为了保证该检测器能适用于多径衰落信道环境,提出了基于Kalman滤波的盲多速率多用户检测器,并给出了Kalman滤波算法的实现步骤与最大值合并过程.仿真结果表明,与现有的一些盲自适应多用户检测器相比,本文提出的检测器在多速率环境下具有更为好的抗多址干扰、抗多径干扰能力,且能更快地收敛.     

Some qualitative properties of multirate digital control systems

The authors consider multirate digital control systems which consist of an interconnection of a continuous-time nonlinear plant (described by ordinary differential equations), a digital controller (described by ordinary difference equations) which has quantizers (but is otherwise linear), along with the required interface elements (A/D and D/A converters). The input to the digital controller consists of the multirate sampled output of the plant. In the present paper, the authors show that when quantizer nonlinearities are neglected, then under reasonable conditions (which exclude the critical cases), the stability properties (in the Lyapunov sense) of the trivial solution of a nonlinear multirate digital control system can be deduced from the stability properties of the trivial solution of its linearization. For such systems we also present a result concerning the existence and construction of stabilizing multirate-output digital controllers. In the present paper, the authors also show that the solutions of a multirate digital feedback control system with nonlinear plant and quantizers are uniformly ultimately bounded if the trivial solution of the corresponding linear system consisting of the linearization of the plant and with the quantization removed from the digital controller is asymptotically stable. We also provide a result which compares the response of multirate digital control systems with nonlinear plant and quantizers in the controller with the response of the corresponding nonlinear multirate digital control systems without quantizers in the digital controller