• Title, Summary, Keyword: linear time-varying system

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Static Output Feedback Robust $H\infty$ Fuzzy Control of Discrete-Time Nonlinear Systems with Time-Varying Delay (시변 지연 이산 시간 비선형 시스템에 대한 정적 출력 궤환 $H\infty$ 퍼지 강인 제어기 설계)

  • Kim Taek Ryong;Park Jin Bae;Joo Young Hoon
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • pp.149-152
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    • 2005
  • In this paper, a robust $H\infty$ stabilization problem to a uncertain discrete-time fuzzy systems with time-varying delay via static output feedback is investigated. The Takagi -Sugeno (T-S) fuzzy model is employed to represent an uncertain nonlinear systems with time-varying delayed state. Using a single Lyapunov function, the globally asymptotic stability and disturbance attenuation of the closed-loop fuzzy control system are discussed. Sufficient conditions for the existence of robust $H\infty$ controllers are given in terms of linear matrix inequalities.

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Time-varying modal parameters identification of large flexible spacecraft using a recursive algorithm

  • Ni, Zhiyu;Wu, Zhigang;Wu, Shunan
    • International Journal of Aeronautical and Space Sciences
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    • v.17 no.2
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    • pp.184-194
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    • 2016
  • In existing identification methods for on-orbit spacecraft, such as eigensystem realization algorithm (ERA) and subspace method identification (SMI), singular value decomposition (SVD) is used frequently to estimate the modal parameters. However, these identification methods are often used to process the linear time-invariant system, and there is a lower computation efficiency using the SVD when the system order of spacecraft is high. In this study, to improve the computational efficiency in identifying time-varying modal parameters of large spacecraft, a faster recursive algorithm called fast approximated power iteration (FAPI) is employed. This approach avoids the SVD and can be provided as an alternative spacecraft identification method, and the latest modal parameters obtained can be applied for updating the controller parameters timely (e.g. the self-adaptive control problem). In numerical simulations, two large flexible spacecraft models, the Engineering Test Satellite-VIII (ETS-VIII) and Soil Moisture Active/Passive (SMAP) satellite, are established. The identification results show that this recursive algorithm can obtain the time-varying modal parameters, and the computation time is reduced significantly.

Adaptive control of time varying system (시변시스템의 적응제어에 관한 연구)

  • 곽유식;양해원
    • 제어로봇시스템학회:학술대회논문집
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    • pp.264-267
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    • 1988
  • One of the major reasons of Adaptive Control is to control time varying systems. In this paper new adaptive algorithms are suggested for a class of linear time varying systems that satisfy certain assumptions. These algorithms consist of three modules, modeling, parameter estimation and control. The key feature of this paper is that power series of time varying parameters are used for estimation.

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Robust $H_{\infty}$ FIR Sampled-Date Filtering for Uncertain Time-Varying Systems with Unknown Nonlinearity

  • Ryu, Hee-Seob;Byung-Moon;Kwon, Oh-Kyu
    • Transactions on Control, Automation and Systems Engineering
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    • v.3 no.2
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    • pp.83-88
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    • 2001
  • The robust linear H(sub)$\infty$ FIR filter, which guarantees a prescribed H(sub)$\infty$ performance, is designed for continuous time-varying systems with unknown cone-bounded nonlinearity. The infinite horizon filtering for time-varying systems is systems is investigated in therms of two Riccati equations by the finite moving horizon.

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Mixed Control of Agile Missile with Aerodynamic Fin and Thrust Vectoring Control (공력 및 추력을 이용한 유도탄의 혼합제어기 설계(I))

  • 이호철;최용석;최재원;송택렬;송찬호
    • Journal of the Korea Institute of Military Science and Technology
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    • v.6 no.3
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    • pp.122-130
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    • 2003
  • This paper is concerned with a control allocation strategy using the dynamic inversion and the pseudo inverse control which generates the nominal control input trajectories, and autopilot design using time-varying control technique which is time-varying version of pole placement of linear time-invariant system for an agile missile with aerodynamic fin and thrust vectoring control. Control allocation of this paper is capable of extracting the maximum performance from each control effector, aerodynamic fin and thrust vectoring control, by combining the action of them. Time-varying control technique for autopilot design enhance the robustness of the tracking performance for a reference command. The main results are validated through the nonlinear simulation.

Generalization of the Spreading Function and Weyl Symbol for Time-Frequency Analysis of Linear Time-Varying Systems

  • Iem, Byeong-gwan
    • Journal of Korean Institute of Intelligent Systems
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    • v.11 no.7
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    • pp.628-632
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    • 2001
  • We propose time-frequency (TF) tools for analyzing linear time-varying (LTV) systems and nonstationary random processes. Obtained warping the narrowband Weyl symbol (WS) and spreading function (SF), the new TF tools are useful for analyzing LTV systems and random processes characterized by generalized frequency shifts, This new Weyl symbol (WS) is useful in wideband signal analysis. We also propose WS an tools for analyzing systems which produce dispersive frequency shifts on the signal. We obtain these generalized, frequency-shift covariant WS by warping conventional, narrowband WS. Using the new, generalized WS, we provide a formulation for the Weyl correspondence for linear systems with instantaneous of linear signal transformation as weighted superpositions of non-linear frequency shifts on the signal. Application examples in signal and detection demonstrate the advantages of our new results.

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Structural time-varying damage detection using synchrosqueezing wavelet transform

  • Liu, Jing-Liang;Wang, Zuo-Cai;Ren, Wei-Xin;Li, Xing-Xin
    • Smart Structures and Systems
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    • v.15 no.1
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    • pp.119-133
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    • 2015
  • This paper proposed a structural time-varying damage detection method by using synchrosqueezing wavelet transform. The instantaneous frequencies of a structure with time-varying damage are first extracted using the synchrosqueezing wavelet transform. Since the proposed synchrosqueezing wavelet transform is invertible, thus each individual component can be reconstructed and the modal participation factor ratio can be extracted based on the amplitude of the analytical signals of the reconstructed individual components. Then, the new time-varying damage index is defined based on the extracted instantaneous frequencies and modal participation factor ratio. Both free and forced vibrations of a classical Duffing nonlinear system and a simply supported beam structure with abrupt and linear time-varying damage are simulated. The proposed synchrosqueezing wavelet transform method can successfully extract the instantaneous frequencies of the damaged structures under free vibration or vibration due to earthquake excitation. The results also show that the defined time-varying damage index can effectively track structural time-varying damage.

Parameter Reduction in Digital Adaptive Flight Control System for Spaceplanes

  • Togasaki, Yoshihiro;Shimada, Yuzo;Uchiyama, Kenji
    • 제어로봇시스템학회:학술대회논문집
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    • pp.995-1000
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    • 2004
  • A digital adaptive flight control system is presented for a Japanese automatic landing flight experiment vehicle (ALFLEX). In previous adaptive control systems based on a linear-parameter-varying (LPV) form, the output behavior was excellent, while the behavior of the adjusted parameters was unsatisfactory. In the present study, to obtain a more appropriate parameter adjustment law, the relationship between the coefficient matrices in a continuous-time state equation and the coefficients of a pulse transfer function in a discrete system for conventional aircraft is investigated. As a result, it is revealed that the coefficients of the numerator can be treated as a linear function of dynamic pressure (linear-parameter-varying: LPV), while the coefficients of the denominator can be treated as constant (linear-time-invariant: LTI). From the above analysis, an improved parameter adjustment law is derived by reducing the number of the adjustment parameters. Simulation results also revealed both good output tracking and good parameter adjustment compared with the previous results.

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Static Output Feedback Robust $H_{\infty}$ Fuzzy Control of Nonlinear Systems with Time-Varying Delay (시변 지연이 있는 비선형 시스템에 대한 $H_{\infty}$ 퍼지 강인제어기 설계)

  • Kim, Taek-Ryong;Park, Jin-Bae;Joo, Young-Hoon
    • Proceedings of the KIEE Conference
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    • pp.379-381
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    • 2004
  • In this paper, a robust $H_{\infty}$ stabilization problem to a uncertain fuzzy systems with time-varying delay via static output feedback is investigated. The Takagi-Sugeno (T-S) fuzzy model is employed to represent an uncertain nonlinear systems with time-varying delayed state. Using a single Lyapunov function, the globally asymptotic stability and disturbance attenuation of the closed-loop fuzzy control system are discussed. Sufficient conditions for the existence of robust $H_{\infty}$ controllers are given in terms of linear matrix inequalities.

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Novel Results for Global Exponential Stability of Uncertain Systems with Interval Time-varying Delay

  • Liu, Yajuan;Lee, Sang-Moon;Kwon, Oh-Min;Park, Ju H.
    • Journal of Electrical Engineering and Technology
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    • v.8 no.6
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    • pp.1542-1550
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    • 2013
  • This paper presents new results on delay-dependent global exponential stability for uncertain linear systems with interval time-varying delay. Based on Lyapunov-Krasovskii functional approach, some novel delay-dependent stability criteria are derived in terms of linear matrix inequalities (LMIs) involving the minimum and maximum delay bounds. By using delay-partitioning method and the lower bound lemma, less conservative results are obtained with fewer decision variables than the existing ones. Numerical examples are given to illustrate the usefulness and effectiveness of the proposed method.