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作者： Pouyanfar, N. Brno University of Technology

A compact multi-band multi-input multi-output (MIMO) antenna with high isolation is proposed for C and X bands applications. The antenna consists of two trapezoidal-shaped patches printed on FR-4 substrate with a thickness of 1.6 mm and compact size of 17 mm×42 mm. Defected ground structure (DGS) is wisely embedded in antenna body to reduce the mutual coupling between the antenna elements. This modification suitably enhances the isolation by 30dB in C-band extended from 6.6 GHz to 7.6 GHz and by 17 dB in X-band between 8.3 GHz to 10 GHz. Moreover, five meander line rectangular patches are properly included to further improve the mutual coupling and eliminate the antenna size increment, simultaneously. The aforementioned meander lines also improve impedance bandwidth of the antenna as well as impedance matching over the entire frequency band. Close agreement of simulated and measured results confirm the antenna outperformance. Design, simulation, and performance analysis of the proposed antenna is discussed in detail.

关键词： multi-input multi-output Defected Ground Structure (DGS) mutual coupling C band X band

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A relationship between fatigue damage estimation under multi-axis and single-axis random vibration

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2024年 215卷

作者： Proner, Enrico Mucchi, Emiliano Tovo, Roberto Univ Ferrara Engn Dept Via G Saragat 1 I-44122 Ferrara Italy

Random vibration testing is traditionally performed by means of single -axis testing. However, real operational environment are in general characterized by multi -axis vibration. As a consequence, single -axis testing is incapable of reproducing the actual damaging process of a component in the laboratory. In this work the damage inflicted to a cantilever beam by multiaxis and sequential single -axis random excitation is compared. A fatigue testing campaign is carried out to establish the fatigue properties of the specimen under different types of vibration environment. The results of the fatigue testing campaign are used to define a relationship between the damage inflicted by multi -axis and sequential single -axis excitations. In particular, a correction factor is defined that allows to calculate the fatigue damage under multi -axis vibration environment knowing the damage inflicted by single -axis excitations. The correction factor takes into account the different activation of the vibrating modes of the specimen caused by different types of excitations. The correction factor for multi -axis vibration environments may allow to estimate the damage caused by multi -axis vibration with the use of a single -axis shaker, as well as allowing to calculate the required testing time for a multi -axis test starting from single -axis testing procedures, improving laboratory testing in terms of costs and realism.

关键词： multi-axis vibration teasing Sequential single-axis testing Fatigue Random vibration multi-input multi-output

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Fault-tolerant virtual synchronous generator control of inverters in synchronous generator-based microgrids

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ELECTRIC POWER SYSTEMS RESEARCH 2023年第1期218卷

作者： Khajesalehi, Jasem Afjei, Seyed Ebrahim Shahid Beheshti Univ Dept Elect & Comp Engn Tehran Iran

Virtual synchronous generator (VSG) control approach which mimics the behavior of conventional synchronous generator (SG) is an attractive solution to integrate low inertia inverter-based distributed energy resources into SG-based microgrids (MGs). As a result, parallel operation of VSGs and SG is a common practice to guarantee the stability of the MGs. Induction motors (IMs) with heavy reactive power demand during acceleration in post-fault condition heighten the risk of instability of SG-based MGs in islanding subsequent to faults. In this paper a novel VSG control system based on the concept of VSG is developed for inverters operating in parallel with SG to improve the voltage and frequency stability of MG with high penetration of IM loads during faults. For this purpose, a fault tolerant enhancement (FTE) module is added to the core of the VSG control system. Accurate reference power tacking in grid-connected (GC) mode, the capability of forming a MG in stand-alone (SA) mode when the SG is out of service and resistance against the grid disturbance are other merits of employing the proposed control system. A current limiting strategy is adopted to restrict the inverter current during fault without devastating control system operation and causing instability. Moreover, a systematic approach for design of a robust dual loop multi-input multi-output (MIMO) control system for inverters is proposed. A new dynamic modeling approach is developed in order to analyze the behavior of the proposed control system and design control parameters. Extensive simulations conducted in MATLAB/Simulink are used to substantiate the effectiveness of the proposed control. It is concluded in simulations that, unlike conventional VSG control, the proposed VSG maintains the voltage and frequency stability of the overall MG in islanding subsequent to a 140 ms fault. Furthermore, the proposed MIMO control and associated current limiting strategy improves the stability when a 140 ms fault occ

关键词： virtual synchronous generator inverter synchronous generator microgrid Induction motor multi-input multi-output

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A simplified modelling and analysis of six degree of freedom random vibration test

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MECHANICAL SYSTEMS AND SIGNAL PROCESSING 2021年 150卷 107304-107304页

作者： Zheng, Ronghui Chen, Huaihai Angeli, Andrea Vandepitte, Dirk Nanjing Univ Aeronaut & Astronaut Coll Aerosp Engn State Key Lab Mech & Control Mech Struct Nanjing 210016 Peoples R China Katholieke Univ Leuven Dept Mech Engn B-3001 Leuven Belgium Flanders Make Lommel Belgium

This paper deals with the modelling and analysis of six degree of freedom random vibration test. It involves an advanced multi-input multi-output random vibration test system where three translational and three rotational motions can be controlled simultaneously. In this work, a mechanical model of the six degree of freedom vibration test system is established such that eight exciters are modelled as spring damper pairs and the shaker table is assumed to be rigid. The acceleration properties of the test article undergoing such six degree of freedom base vibrations are analyzed and the relationships among the absolute acceleration, relative acceleration and base acceleration are derived. In practical applica-tions, typically there is no available angular acceleration sensor for high frequency measurements. Therefore, the three rotational accelerations are obtained from measured translational accelerations of three or more control sensors with a response coordinate transformation matrix. It is shown that the locations of the control points have a significant influence on the response spectral results, which is reflected in the condition number of the output coordinate transformation matrix. The general multi-input multi-output random vibration control method is applied to the 6-DOF random vibration test. A six degree of freedom random vibration test simulation is finally provided. (c) 2020 Elsevier Ltd. All rights reserved.

关键词： multi-input multi-output Six degree of freedom Random vibration Coordinate transformation Condition number

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Octagonal polarization-maintaining supermode fiber for mode division multiplexing system

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OPTICS COMMUNICATIONS 2022年 510卷 127897-127897页

作者： Chen, Hongyao Chen, Yijin Wang, Jianping Lu, Huimin Feng, Lifang Song, Weijun Univ Sci & Technol Beijing Shunde Grad Sch 2 Daliang Zhihui Rd Foshan 528300 Peoples R China Univ Sci & Technol Beijing 30 Xuanyuan Rd Beijing 100083 Peoples R China

We present a new type of polarization-maintaining supermode fiber which can separate adjacent modes from each other. The proposed polarization-maintaining supermode fiber features an octagonal core composed of multiple high-refractive-index circular holes. By using high refractive index cores and setting the angle subtly between the cores, the fiber proposed can support 22 modes with different polarization states under two parameters in the entire C-band. Through the finite element method simulation, we conducted simulation study to analyze the influence of the angle between the cores and the core diameter on the performance of the optical fiber. In addition, we analyzed effective refractive index difference (d(neff)) and effective modal area (A(eff)) of the fiber for each characteristic mode. The differential mode delay (DMD) under different cores angle is also calculated. Numerical results present that the minimum A neff of the octagonal polarization-maintaining supermode fiber in the entire C-band under the two parameters is greater than 1.1 x 10(-4). It was measured to have good tolerance under the condition of unsatisfactory structure. These results indicate that the proposed fiber is superior candidate for improving the optical transmission capacity in the transmission of the mode division multiplexing system.

关键词： Supermode fiber Mode division multiplexing multi-input multi-output

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Cooperative DF Protocol for MIMO Systems Using One-Bit ADCs

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SENSORS 2022年第20期22卷 7843页

作者： Kim, Tae-Kyoung Gachon Univ Dept Elect Engn Seongnam 13120 South Korea

This study considers a detection scheme for cooperative multi-input-multi-output (MIMO) systems using one-bit analog-to-digital converters (ADCs) in a decode-and-forward (DF) relay protocol. The use of one-bit ADCs is a promising technique for reducing the power consumption, which is necessary for supporting future wireless systems comprising a large number of antennas. However, the use of a large number of antennas remains still limited to mobile devices owing to their size. Cooperative communication using a DF relay can resolve this limitation;however, detection errors at the relay make it difficult to employ cooperative communication directly. This difficulty is more severe in a MIMO system using one-bit ADCs due to its nonlinear nature. To efficiently address the difficulty, this paper proposes a detection scheme that mitigates the error propagation effect. The upper bound of the pairwise error probability (PEP) of one-bit ADCs is first derived in a weighted Hamming distance form. Then, using the derived PEP, the proposed detection for the DF relay protocol is derived as a single weighted Hamming distance. Finally, the complexity of the proposed detection is analyzed in terms of real multiplications. The simulation results show that the proposed detection method efficiently mitigates the error propagation effect but has a relatively low level of complexity when compared to conventional detection methods.

关键词： multi-input multi-output cooperative communication pairwise error probability one-bit ADCs

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Modeling a 5-DOF Haptic Interface for Isotropic Force Control *

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IFAC Proceedings Volumes 2002年第2期35卷 523-529页

作者： Christopher D. Lee Dale A. Lawrence Y. Lucy Pao Electrical & Computer Engineering Department University of Colorado Boulder CO 80309-0425 Aerospace Engineering Sciences Department University of Colorado Boulder CO 80309-0429

This paper describes a multivariable modeling and control strategy that increases the bandwidth of isotropic force transmission in multi-degree of freedom haptic interfaces. The controller structure leads to a straightforward model identification procedure and yields a simple control law that can be easily implemented. Experimental results show that this technique significantly improves force tracking performance on a 5 degree-of-freedom in-parallel haptic interface.

关键词： force control modeling haptic interfaces multi-input multi-output parameter identification weighted least squares

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Improved State-Space Model Identification Using input and output Data with Steady State Values

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IFAC Proceedings Volumes 2004年第11期37卷 215-220页

作者： Manabu Kosaka Hiroshi Uda Eiichi Bamba Hiroshi Shibata Dept. of Mechanical Engineering Faculty of Science and Engineering Kinki Univ. 3-4-1 Kowakae Higashiosaka Osaka 577-8502 JAPAN Faculty of Engineering Doshisha University 1-3 Tatara Tsudani Kyotanabe Kyoto 610-0394 JAPAN

In this paper, we improve the deterministic off-line identification method (Kosaka et. al., 2002) that obtains a state-space model from input and output data with a constant steady state response. The method is composed of determining the parameters by zeroing the 0 ~ N -tuple integral values of output error between the plant and the model (Kosaka et. al., 2000) and by using Ho-Kalman's method (Zeiger et. al., 1974). The method theoretically has an assumption that plant system matrix A satisfies | A | < 1 because the method utilizes Taylor series expansion. But the method can be applied to plants without the assumption | A | < 1. The feature is that the method is performed by using a step response, which is suitable to a mechnical system where noise and vibration are undesirable, and that the identification result is accurate at low frequency range. Numerical simulations of multi-input multi-output system identification are illustrated.

关键词： Identification state-space model step response multi-input multi-output mechanical system

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MIMO modeling and multi-loop control based on neural network for municipal solid waste incineration

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CONTROL ENGINEERING PRACTICE 2022年 127卷

作者： Ding, Haixu Tang, Jian Qiao, Junfei Beijing Univ Technol Fac Informat Technol Beijing 100124 Peoples R China Beijing Lab Smart Environm Protect Beijing 100124 Peoples R China

The Municipal solid wastes incineration (MSWI) process with complex mechanism and strong nonlinearity is an important part of resource cycle. It is a challenge to design its multivariable controlled object model and control strategy. To solve this problem, a multi-input multi-output (MIMO) data-driven model and a multi-loop PID controller are proposed in this paper. Firstly, a feature selection method based on Pearson correlation coefficient (PCC) and expert knowledge is used to analyze the relationship between the manipulated variable and the controlled variable of MSWI process. Secondly, a MIMO Takagi-Sugeno fuzzy neural network (TSFNN) based on multi-task learning (MTL) is designed to construct the multivariable controlled object model. Thirdly, a multi-loop PID controller based on quasi-diagonal recurrent neural network (QDRNN) is constructed, which has self-feedback channel and interconnection channel, and can adjust the control parameters automatically. Next, the stability of control strategy is proved by Lyapunov second method. Finally, the modeling effect and control performance are confirmed on the simulation experiments based on the real MSWI process data.

关键词： Municipal solid wastes incineration Quasi-diagonal recurrent neural network multi-loop PID controller multi-input multi-output multi-task learning

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Fault-tolerant output-constrained control of unknown Euler-Lagrange systems with prescribed tracking accuracy

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AUTOMATICA 2020年 111卷 108606-000页

作者： Zhang, Jin-Xi Yang, Guang-Hong Northeastern Univ Coll Informat Sci & Engn Shenyang 110819 Liaoning Peoples R China Northeastern Univ State Key Lab Synthet Automat Proc Ind Shenyang 110819 Liaoning Peoples R China

This paper explores the output-constrained tracking control problem for unknown Euler-Lagrange systems subject to actuator faults, in the case where the reference trajectory is unknown in advance. The presence of actuator faults may lead to the loss of strong controllability of the system assumed in the existing literature on robust control of multi-input multi-output nonlinear systems. The lack of a priori knowledge on the reference trajectory renders the current constraint-handling techniques to achieve prescribed tracking accuracy infeasible. To conquer the above obstacles, a novel fault compensation scheme is designed in this paper, and a new-type error boundary is introduced to the control design. It is proved that the proposed approach guarantees output tracking with prescribed accuracy and constraint satisfactions simultaneously, even if actuator faults occur. A comparative simulation on a robot manipulator is conducted to further illustrate the established theoretical findings. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Nonlinear systems multi-input multi-output Actuator faults output constraints Prescribed accuracy

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