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Impacts of time-varying Channel Spreading Function on the OTFS Modulation system

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2024年第7期73卷 10744-10749页

作者： Ma, Yiyan Ma, Guoyu Ai, Bo Wang, Ning Zhong, Zhangdui Beijing Jiaotong Univ Sch Elect & Informat Engn Beijing 100044 Peoples R China PengCheng Lab Shenzhen 518052 Peoples R China Zhengzhou Univ Henan Joint Int Res Lab Intelligent Networking & D Zhengzhou 450001 Peoples R China Zhengzhou Univ Sch Informat Engn Zhengzhou 450001 Peoples R China

The channel spreading function (CSF) could be time-varying due to the interference and "birth and death" of inseparable propagation paths, whose impacts need to be considered when designing delay Doppler (DD) domain multiplexing systems. In this correspondence, the digital input/output (I/O) relationship under rectangle and bi-orthogonal pulses for one of the DD domain multiplexing schemes, orthogonal time frequency space (OTFS) modulation, is derived considering the time-varying CSF with off-grid delay and off-grid Doppler shift. Therein, the time-varying CSF is modeled by the first-order autoregressive random process (AR(1)). The impacts of time-varying CSF on OTFS are studied regarding the sparsity of effective DD domain channel, the achievable bit rate, and the bit error rate (BER) under different equalizers. Through simulation, it is revealed that time-varying CSF reduces the bit rate under least square (LS) and zero-forcing decision feedback equalization (ZF-DFE) equalizers, but decreases BER with higher multipath diversity.

关键词： OTFS modulation Channel spreading function linear time-varying system OTFS modulation Channel spreading function linear time-varying system

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Parity space-based fault detection for linear discrete time-varying systems with unknown input

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AUTOMATICA 2015年 59卷 120-126页

作者： Zhong, Maiying Song, Yang Ding, Steven X. Beihang Univ Dept Inertia Technol & Nav Guidance Instrument Beijing 100191 Peoples R China Univ Duisburg Essen Inst Automat Control & Complex Syst D-47057 Duisburg Germany

In this paper, a new approach to parity space-based fault detection (FD) is put forward for linear discrete time-varying (LDTV) systems. The focus of our study is on solving the problem with heavy online computational burden. The main contributions are two folds. Firstly, the problem of parity space-based FD is formulated as finding a minimum of quadratic form of unknown input. Secondly, by applying projection in Krein space, a solution of optimal parity space-based FD is obtained via recursively computing innovations. It is shown that the reduction of computation cost is achievable, especially with the increase of parity space order. Finally, a numerical example is given to demonstrate the application of the proposed method. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Parity space Fault detection linear time-varying system Krein space Projection

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Adaptive filter of non-linear systems with generalised unknown disturbances

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IET RADAR SONAR AND NAVIGATION 2014年第4期8卷 307-317页

作者： Qin, Yuemei Liang, Yan Yang, Yanbo Wang, Zengfu Yang, Feng Northwestern Polytech Univ Sch Automat Xian 710072 Peoples R China

This study presents the state estimation problem of discrete-time non-linear stochastic system with generalised unknown disturbance (GUD) in the measurements. To the best of our knowledge, there is no research result on the filter design dealing with such estimation problem. Here, an upper-bound filter is designed for the linear time-varying system with the GUD existing in the measurement equation, and optimal parameters are derived so that the minimum upper-bounds filter is obtained. The result is further extended to the non-linear case via the iterative optimisation of joint state estimation and parameter identification (the linearised measurement matrix). The simulation about tracking a target via one biased radar and one biased electronic support measure (ESM) shows the effectiveness and robustness of the proposed filter.

关键词： adaptive filters discrete time filters iterative methods nonlinear filters optimisation parameter estimation state estimation stochastic processes target tracking time-varying filters adaptive filter state estimation problem discrete-time nonlinear stochastic system generalised unknown disturbance GUD filter design upper-bound filter linear time-varying system measurement equation optimal parameter iterative optimisation parameter identification linearised measurement matrix target tracking biased radar biased electronic support measure

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Stability Criteria for Uncertain linear time-varying systems

Stability Criteria for Uncertain Linear Time-Varying Systems

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IEEE Annual Conference on Decision and Control

作者： Amit P. Pandey Martin A. Sehr Mauricio C. de Oliveira Department of Mechanical and Aerospace Engineering University of California San Diego La Jolla CA 92093-0411

ISBN: (纸本)9781467360890

In this paper robust stability of continuous linear time-varying systems is addressed based on Lyapunov functions which are constructed by max-composition of continuously differentiable functions. The resulting Lyapunov functions are continuous but not necessarily differentiable and no individual component needs to be positive definite. When the components are quadratic functions it will be possible to prove robust stability of systems which fail the classic quadratic stability test. The resulting conditions are matrix inequalities which are linear after choosing a set of tuning parameters. The robust stability condition is also extended to provide upper-bounds on integral performance measures.

关键词： Stability criteria Liapunov function linear time-varying system system stability Robust stability Continuously differentiable Quadratics Positive definite Plant uncertain

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A Generalization of Chang Transformation for linear time-varying systems

A Generalization of Chang Transformation for Linear Time-Var...

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2010 49th IEEE Conference on Decision and Control

作者： Xiaojing Yang J. Jim Zhu School of Electrical Engineering and Computer Science Ohio University Athens OH 45701 USA

ISBN: (纸本)9781424477456

Chang transformation was introduced for decoupling the slow and fast dynamics of a singularly perturbed linear time Invariant (LTI) system, and it was subsequently extended to linear time-varying (LTV) systems under the slowly-varying assumption by way of frozen-time eigenvalues. This paper extends Chang transformation from slowly-varying LTV systems to LTV systems, when the singularly perturbed system has a semi-proper coefficient matrix A_(22)(t) and LTV system w(t) velence A_(22)(t)w(t) is exponentially stable. Instead of using frozen-time eigenvalues based on slowly time-varying conditions, PD-eigenvalues for LTV systems are employed to characterize the exponential stability, thereby circumventing the slowly-varying constraint. Our results provide a larger bound on epsilon, which is a gauge on the validity of the Chang transformation, in some situations than using previous techniques. We have also recast the original Chang transformation so as to provide more insight into the decoupled subsystems. The insight will be useful in subsequent investigation on estimate of the Singular Perturbation Margin (SPM) for LTV systems. An equivalence relationship has recently been established for LTI system between the SPM and the Phase Margin (PM). The new results in this paper will facilitate the development of a PM-type stability margin metric for LTV systems, and for nonlinear, time-varying systems in the future.

关键词： linear time-varying system DECOUPLING Nonlinear time-varying system singularly perturbed systems LTI exponential stability. Insight Coefficient Matrix

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A time Domain Approach to Robust Fault Detection of linear time-varying systems

A Time Domain Approach to Robust Fault Detection of Linear T...

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Proceedings of the 46th IEEE Conference on Decision and Control, Pages 919-1382

作者： Xiaobo Li Kemin Zhou Department of Electrical and Computer Engineering Louisiana State University Baton Rouge LA USA

ISBN: (纸本)9781424414970;1424414970

This paper gives the optimal solutions to several robust fault detection problems such as H_(-)/H_(infinity), H_(2)/H_(infinity) and H_(infinity)/H_(infinity) problems for linear time varying systems in time domain, which extends the previous results on linear time invariant systems in frequency domain. It is shown that all three problems have the same optimal detection filter and the filter is a simple observer by solving a standard differential Riccati equation. Finally, an example is given to illustrate our results.

关键词： time-DOMAIN linear time-varying system Defect detection time invariant systems Riccati equations Filters optimal solution Frequency-domain analysis optimum detection

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An adaptive observer for joint estimation of states and parameters in both state and output equations

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INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING 2011年第9期25卷 831-842页

作者： Li, Xiuliang Zhang, Qinghua Su, Hongye INRIA F-35042 Rennes France Zhejiang Univ Inst Adv Proc Control Hangzhou 310027 Zhejiang Peoples R China

An adaptive observer is a recursive algorithm for joint state-parameter estimation of parameterized state-space systems. Previous works on globally convergent adaptive observers consider unknown parameters either in state equations or in output equations, but not in both of them. In this paper, a new adaptive observer is designed for linear time-varying systems with unknown parameters in both state and output equations. Its global convergence for simultaneous estimation of states and parameters is formally established under appropriate assumptions. A numerical example is presented to illustrate the performance of this adaptive observer. Copyright (C) 2011 John Wiley & Sons, Ltd.

关键词： adaptive observer state and parameter estimation linear time-varying system fault detection and isolation

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Topology optimization of high-speed rail bridges considering passenger comfort

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STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION 2023年第10期66卷 1-16页

作者： Golecki, Thomas Gomez, Fernando Carrion, Juan Spencer Jr, Billie F. Univ Illinois Civil & Environm Engn 205 N Mathews Ave Urbana IL 61801 USA Univ San Francisco Quito Coll Sci & Engn Diego Robles & Via Interocean Quito Ecuador Skidmore Owings & Merrill LLP 224 S Michigan Ave 1000 Chicago IL 60604 USA Univ Cuenca Dept Civil Engn Cuenca Ecuador

Worldwide growth in high-speed rail (HSR) networks has brought a demand for improved structural performance of the bridges that make up a large portion of many of these HSR systems. While some improvement has been made via optimization either of the bridge or the passenger cars, the design criteria of passenger comfort has yet to be addressed in bridge optimization. The transient dynamics of vehicle-bridge interaction between a high-speed train and bridge make such structural optimization of these systems challenging. In this paper, we derive an approach for topology optimization of high-speed rail bridges including vehicle-bridge interaction that enables direct consideration of the passenger comfort in the objective function. Assuming constant contact between the vehicle's wheels and the bridge, the two systems are combined into a single-state space system. The resulting system matrices are time dependent, as they are a function of the wheel contact locations which change as the vehicles move over the bridge. The equations of motion and the adjoint sensitivities are derived and solved numerically in the time domain. Several numerical examples are provided based on high-speed rail applications that minimize a multi-objective function comprised of bridge and vehicle responses, including passenger comfort. These examples generate topologies that improve passenger comfort at only a small cost to the bridge response and demonstrate the dependence of optimal topology on train speed and length. The proposed method offers the potential for improving high-speed rail passenger comfort through optimization of bridge topology by accounting for the vehicle-bridge interaction effects.

关键词： Topology optimization Vehicle-bridge interaction linear time-varying system High-speed rail Sperling's ride comfort index

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Analytical Solutions to Aeroassisted Orbital Transfer Problem

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IEEE TRANSACTIONS ON AEROSPACE AND ELECTRONIC systemS 2020年第5期56卷 3502-3515页

作者： Yu, Wenbin Zhao, Penglei Chen, Wanchun Beihang Univ Sch Astronaut Beijing 100191 Peoples R China

In this article, the atmospheric flight of aeroassisted orbit transfer vehicle is investigated analytically. As the flight speed is greater than the first cosmic velocity, the centrifugal force is also larger than gravity. Due to this, the vehicle has to fly with a downward lift and the flight altitude is extremely unstable. To cope with this challenge, the high-precision formulae of altitude and flight-path angle for steady glide are deduced and used to develop the steady glide control technique to stabilize the flight altitude. Upon steady glide, the analytical solutions for 3-D aeroassisted maneuvering trajectory are derived. In the derivation, a reduced-order system with negative lift-to-drag ratio as control variable is obtained by subtly simplifying the nonlinear flight dynamics. To address the complex influence of Coriolis force, the regular perturbation method is used such that the system is further decomposed into two special linear time-varying systems, which can be solved analytically by the spectral-decomposition-based method. Due to the full consideration of the influence of the Earth's curvature and rotation, the analytical solutions can predict the downrange, crossrange, and heading angle of the 3-D trajectory accurately.

关键词： Orbits Trajectory Aerodynamics Atmospheric modeling Gravity Aeroassisted orbit transfer analytical solutions linear time-varying system regular perturbation method steady glide control technique

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Trajectory-Shaping Guidance with final speed and load factor constraints

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ISA TRANSACTIONS 2015年 56卷 42-52页

作者： Yu, Wenbin Chen, Wanchun Beihang Univ Sch Astronaut Beijing 100191 Peoples R China

This paper describes the design of a guidance law used for guiding a hypersonic gliding vehicle against a ground target from a near-vertical orientation with a specified final speed and a near-zero final load factor. The guidance law consists of two terms: one is Trajectory-Shaping Guidance (TSG) used for steering the vehicle to the target from the specified orientation;the other is Final-Speed-Control Scheme (FSCS) used for controlling the vehicle to perform lateral maneuver to adjust the final speed. Further, the generalized closed form solutions of TSG are obtained from a more general linearized engagement model, where the speed of the vehicle can be an arbitrary positive function of time. By analyzing these solutions, the stability domain of the guidance coefficients is obtained such that the final load factor is zero. This domain is not affected by the change rate of the speed. Thus, according to this analysis, the proposed guidance law can achieve a near zero final load factor by properly selecting the guidance coefficients in the stability domain. (C) 2014 ISA. Published by Elsevier Ltd. All rights reserved.

关键词： Trajectory-Shaping Guidance Final-Speed Control Scheme Generalized closed form solutions linear time-varying system Spectral decomposition

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