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International Conference on Automation and Computing (ICAC)

作者： Hang Zhang Zi Qiang Lang Yun Peng Zhu Department of Automatic Control and Systems Engineering University of Sheffield Sheffield UK

The Nonlinear Output Frequency Response Functions (NOFRFs) are concepts proposed for the frequency analysis of nonlinear systems, and they have been essential for applications of damage detection in mechanical and civil engineering, etc. Although they have been evaluated by the Least-Square method and the associated linear equations based method, there is little research about the comparative study of these two methods. This paper describes the comparative study of the LS method and the ALEs based method in an application of the NOFRFs based mechanical damage detection. The two methods are respectively introduced and employed to evaluate the NOFRFs, which are capable of indicating the growth of damage in the mechanical system; then, the two methods are compared using the damage evolution results of the corresponding NOFRFs. A series of comparative experiments with different system input amplitudes are carried out. The experiment results expose limitations of both methods for the NOFRFs based damage detection.

关键词： Frequency response Mathematical model Nonlinear systems Fourier transforms Harmonic analysis Frequency-domain analysis systems engineering and theory

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Output feedback quasi-distributed MPC for linear systems coupled via dynamics and constraints

Output feedback quasi-distributed MPC for linear systems cou...

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UKACC International Conference on control (control)

作者： P. R. Baldivieso Monasterios P. A. Trodden Department of Automatic Control & Systems Engineering University of Sheffield Sheffield UK

In this paper, we present a non-centralized approach to the output-feedback variant of tube-based model predictive control of dynamically coupled linear time-invariant systems with shared constraints. The proposed algorithm achieves guaranteed recursive feasibility and closed-loop asymptotic stability of the overall system. The approach combines decentralized and distributed MPC, hence the name quasi-distributed MPC. Local controllers, which are deployed among subsystems of the system, solve model predictive control problems in a decentralized fashion (i.e. without communication) in order to regulate their respective subsystems; the output-feedback variant of tube-basedPC is employed in order that controllers may reject the mutual disturbances induced by the coupled dynamics and the state estimation errors arising from having only noisy output measurements. On the other hand, shared constraints are handled in a distributed fashion: in order to satisfy shared constraints between systems, the controllers share predicted trajectories and take remedial action (by adjusting the optimized control inputs) only when a constraint violation is predicted.

关键词： Couplings Output feedback Observers Electron tubes Noise measurement Trajectory

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Distributed model predictive control using a chain of tubes

Distributed model predictive control using a chain of tubes

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UKACC International Conference on control (control)

作者： Bernardo Hernandez Paul Trodden Department of Automatic Control and Systems Engineering The University of Sheffield Sheffield UK

A new distributed MPC algorithm for the regulation of dynamically coupled subsystems is presented in this paper. At each time instant, the control action is computed via two robust controllers working in a nested fashion. The inner controller provides local reference trajectories computed on a fully decentralized framework. The outer controller uses this information to take into account the effects of the dynamic coupling and implement a distributed control action. The tube-based approach to robustness is employed. A supplementary constraint is included in the outer optimization problem to provide recursive feasibility of the overall controller.

关键词： Electron tubes Trajectory Robustness Couplings Optimization Algorithm design and analysis Heuristic algorithms

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Compressive phase retrieval via reweighted amplitude flow

arXiv

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arXiv 2017年

作者： Zhang, Liang Wang, Gang Giannakis, Georgios B. Chen, Jie Digital Technology Center Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States State Key Laboratory of Intelligent Control and Decision of Complex Systems Beijing100081 China School of Automation State Key Laboratory of Intelligent Control and Decision of Complex Systems Beijing Institute of Technology Beijing100081 China

The problem of reconstructing a sparse signal vector from magnitude-only measurements (a.k.a., compressive phase retrieval), emerges naturally in diverse applications, but it is NP-hard in general. Building on recent advances in nonconvex optimization, this paper puts forth a new algorithm that is termed compressive reweighted amplitude flow and abbreviated as CRAF, for compressive phase retrieval. Specifically, CRAF operates in two stages. The first stage seeks a sparse initial guess via a new spectral procedure. In the second stage, CRAF implements a few hard thresholding based iterations using reweighted gradients. When there are sufficient measurements, CRAF provably recovers the underlying signal vector exactly with high probability under suitable conditions. Moreover, its sample complexity coincides with that of the state-of-the-art procedures. Finally, substantial simulated tests showcase remarkable performance of the new spectral initialization, as well as improved exact recovery relative to competing alternatives. Copyright © 2017, The Authors. All rights reserved.

关键词： Iterative methods

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On ${\mathcal H}_{\infty }$ Finite-Horizon Filtering Under Stochastic Protocol: Dealing With High-Rate Communication Networks

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IEEE Transactions on automatic control 2017年第9期62卷 4884-4890页

作者： Lei Zou Zidong Wang Jun Hu Huijun Gao College of Electrical Engineering and Automation Shandong University of Science and Technology Qingdao China Department of Computer Science Brunel University London Uxbridge U.K. Department of Applied Mathematics Harbin University of Science and Technology Harbin China Research Institute of Intelligent Control and Systems Harbin Institute of Technology Harbin China

This paper is concerned with the H ∞ filtering problem for a class of time-varying nonlinear delayed system under high-rate communication network and stochastic protocol (SP). The communication between the sensors and the state estimator is implemented via a shared high-rate communication network in which multiple transmissions are generated between two adjacent sampling instants of sensors. At each transmission instant, only one sensor is allowed to get access to the communication network in order to avoid data collisions and the SP is employed to determine which sensor obtains access to the network at a certain instant. The mapping technology is applied to characterize the randomly switching behavior of the data transmission resulting from the utilization of the SP. The aim of the problem addressed is to design an estimator such that the H ∞ disturbance attenuation level is guaranteed for the estimation error dynamics over a given finite horizon. Sufficient conditions are derived for the existence of the finite-horizon filter satisfying the prescribed H ∞ performance requirement, and the explicit expression of the time-varying filter gains is characterized by resorting toa set of recursive matrix inequalities. Simulation results demonstrate the effectiveness of the proposed filter design scheme.

关键词： Protocols Communication networks Symmetric matrices Time-varying systems Linear matrix inequalities Sensor phenomena and characterization

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Coordinated control strategy of reactive power for large-scale wind power transmission by LCC-HVDC links

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The Journal of engineering 2017年第13期2017卷 1082-1086页

作者： Wang Zhibing Xu Yang Wang Xitian State Key Laboratory of Operation and Control of Renewable Energy & Storage Systems China Electric Power Research Institute Beijing 100192 People's Republic of China Department of Electrical Engineering Shanghai Jiao Tong University Shanghai 200240 People's Republic of China

The intermittence and fluctuation of outputs of large-scale wind farms lead to significant problems in power transmission system by line-commuted converter high-voltage direct current (LCC-HVDC) links. Traditional reactive power compensation devices such as AC filters are not capable of adjusting reactive power balance continuously. This paper presents a coordinated reactive power control strategy to realise continuous adjustment. A synchronous condenser (SC) is applied in the DC converter station to cooperate with AC filters. The capacity of the SC is determined by the minimum capacity and dead zone of the AC filter unit, and cost saving is also taken into account. While power outputs of wind farms fluctuate, the setting value of DC power gets changed. The SC responses rapidly to reduce the reactive power exchange. When the reactive power demand is beyond the capacity of the SC, one AC filter unit operates and the SC readjusts to maintain the reactive power balance. The proposed control strategy is validated by simulation in PSCAD/EMTDC.

关键词： reactive power control wind power plants power transmission control HVDC power transmission HVDC power convertors commutation compensation power filters power generation control PSCAD-EMTDC reactive power balancing reactive power exchange reduction AC filter unit SC DC converter station synchronous condenser reactive power compensation device line-commuted converter high-voltage direct current link large-scale wind farm LCC-HVDC link large-scale wind power transmission system coordinated reactive power control strategy

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Bio-inspired evolutionary game dynamics on complex networks under uncertain cross-inhibitory signals

arXiv

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arXiv 2017年

作者： Stella, Leonardo Bauso, Dario Department of Automatic Control and Systems Engineering University of Sheffield Mappin St. SheffieldS1 3JD United Kingdom Dip. di Ing. Chimica Gestionale Informatica Meccanica Università di Palermo Palermo90128 Italy

Given a large population of players, each player has three possible choices between option 1 or 2 or no option. The two options are equally favorable and the population has to reach consensus on one of the two options quickly and in a distributed way. The more popular an option is, the more likely it is to be chosen by uncommitted players. Uncommitted players can be attracted by those committed to any of the other two options through a cross-inhibitory signal. This model originates in the context of honeybees swarms, and we generalize it to duopolistic competition and opinion dynamics. The contributions of this work include (1) the formulation of an evolutionary game model to explain the behavioral traits of the honeybees, (2) the study of the individuals and collective behavior including equilibrium points and stability, (3) the extension of the results to the case of structured environment via complex network theory, (4) the analysis of the impact of the connectivity on consensus, and (5) the study of absolute stability for the collective system under time-varying and uncertain cross-inhibitory parameter. Copyright © 2017, The Authors. All rights reserved.

关键词： Game theory

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Optimal distributed control for platooning via sparse coprime factorizations

Optimal distributed control for platooning via sparse coprim...

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2016 American control Conference, ACC 2016

作者： SabǍu, Şerban OarǍ, Cristian Warnick, Sean Jadbabaie, Ali Electrical and Computer Engineering Dept. Stevens Institute of Technology HobokenNJ United States Automatic Control Dept. University Politehnica Bucharest Romania Information and Decision Algorithms Laboratories Faculty of the Computer Science Department Brigham Young University United States Electrical and Systems Engineering Dept. University of Pennsylvania United States

ISBN: (纸本)9781467386821

We introduce a novel distributed control architecture for disturbances attenuation in heterogeneous platoons of linear and time-invariant autonomous agents that inherits the performance achievable by the leader-follower control policies. We provide a Youla-like parameterization for the class of all distributed controllers such that the sparsity constraints are imposed on the controllers' left coprime factors, outlining a new concept of structural constraints in distributed control. The proposed scheme lends itself to optimal controller design via norm based costs, it guarantees string stability and completely eliminates the accordion effect from the behavior of the platoon. The distributed controller is proven to attain global optimality for heterogeneous platoons and H2 costs and can easily reconfigure such as to remain optimal during formation merging/exiting maneuvers. The scheme is amenable to a GPS time base synchronization mechanism, allowing for the exact compensation of the time delays induced by the wireless communications. © 2016 American automatic control Council (AACC).

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Solving almost all systems of random quadratic equations

arXiv

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arXiv 2017年

作者： Wang, Gang Giannakis, Georgios B. Saad, Yousef Chen, Jie Digital Technology Center Department of Electrical and Computer Engineering University of Minnesota MinneapolisMN55455 United States State Key Lab of Intelligent Control and Decision of Complex Systems Beijing Institute of Technology Beijing100081 China Department of Computer Science and Engineering University of Minnesota MinneapolisMN55455 United States

This paper deals with finding an n-dimensional solution x to a system of quadratic equations of the form yi = jhai;xij2 for 1 ≤ i ≤ m, which is also known as phase retrieval and is NP-hard in general. We put forth a novel procedure for minimizing the amplitude-based least-squares empirical loss, that starts with a weighted maximal correlation initialization obtainable with a few power or Lanczos iterations, followed by successive refinements based upon a sequence of iteratively reweighted (generalized) gradient iterations. The two (both the initialization and gradient flow) stages distinguish themselves from prior contributions by the inclusion of a fresh (re)weighting regularization technique. The overall algorithm is conceptually simple, numerically scalable, and easy-to-implement. For certain random measurement models, the novel procedure is shown capable of finding the true solution x in time proportional to reading the data f(ai;yi)g1≤i≤m. This holds with high probability and without extra assumption on the signal x to be recovered, provided that the number m of equations is some constant c > 0 times the number n of unknowns in the signal vector, namely, m > cn. Empirically, the upshots of this contribution are: I) (almost) 100% perfect signal recovery in the high-dimensional (say e.g., n ≥2;000) regime given only an information-theoretic limit number of noiseless equations, namely, m = 2n - 1 in the real-valued Gaussian case;and, ii) (nearly) optimal statistical accuracy in the presence of additive noise of bounded support. Finally, substantial numerical tests using both synthetic data and real images corroborate markedly improved signal recovery performance and computational efficiency of our novel procedure relative to state-of-the-art approaches. Copyright © 2017, The Authors. All rights reserved.

关键词： Computational efficiency

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Development of animated facial expressions to express emotions in a robot: RobotIcon

Development of animated facial expressions to express emotio...

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IEEE Ecuador Technical Chapters Meeting (ETCM)

作者： Lukáš Danev Marten Hamann Nicolas Fricke Tobias Hollarek Dennys Paillacho Facultat d‚ Informática de Barcelona Universitat Politécnica de Catalunya (UPC) Barcelona Spain Department of Automatic Control Universitat Politécnica de Catalunya Barcelona Spain Electrical and Computer Engineering Department Escuela Superior Politécnica del Litoral (ESPOL) Guayaquil Ecuador

ISBN: (纸本)9781538638958

Robotics is a field which does not only become more and more important in industry and production but is becoming part of many peoples every day life and as such, the interaction between robots and humans is an essential field of research. In this work, we present a face - being an important part of a natural communication - and show that animated facial expressions can be used to express the robot's emotions. To do so, we developed a set of animated facial expressions to be shown on the screen of the MASHI robot, a telepresence robot with a wide-screen display mounted on top. A survey was conducted to evaluate the recognition value of the facial expressions as well as to evaluate whether displaying the full face or rather just the eye-region affects this recognition rate. The evaluation of this survey shows that most of our emotions are recognized better if a mouth is provided. Yet, the recognition rate is still acceptable without displaying the mouth. In summary, all emotions were well recognized and therefore, displaying these on robots like MASHI will contribute to a more natural human-robot interaction.

关键词： Face Mouth Service robots Emotion recognition Shape Face recognition

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