167 research outputs found

    Feedforward control for lightweight motion systems

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    Automatic Flight Control Systems

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    The history of flight control is inseparably linked to the history of aviation itself. Since the early days, the concept of automatic flight control systems has evolved from mechanical control systems to highly advanced automatic fly-by-wire flight control systems which can be found nowadays in military jets and civil airliners. Even today, many research efforts are made for the further development of these flight control systems in various aspects. Recent new developments in this field focus on a wealth of different aspects. This book focuses on a selection of key research areas, such as inertial navigation, control of unmanned aircraft and helicopters, trajectory control of an unmanned space re-entry vehicle, aeroservoelastic control, adaptive flight control, and fault tolerant flight control. This book consists of two major sections. The first section focuses on a literature review and some recent theoretical developments in flight control systems. The second section discusses some concepts of adaptive and fault-tolerant flight control systems. Each technique discussed in this book is illustrated by a relevant example

    Identifying Position-Dependent Mechanical Systems: A Modal Approach Applied to a Flexible Wafer Stage

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    Increasingly stringent performance requirements for motion control necessitate the use of increasingly detailed models of the system behavior. Motion systems inherently move, therefore, spatio-temporal models of the flexible dynamics are essential. In this paper, a two-step approach for the identification of the spatio-temporal behavior of mechanical systems is developed and applied to a lightweight prototype industrial wafer stage. The proposed approach exploits a modal modeling framework and combines recently developed powerful linear time invariant (LTI) identification tools with a spline-based mode-shape interpolation approach to estimate the spatial system behavior. The experimental results for the wafer stage application confirm the suitability of the proposed approach for the identification of complex position-dependent mechanical systems, and its potential for motion control performance improvements

    Deterministic and stochastic responses of smart variable stiffness and damping systems and smart tuned mass dampers

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    Semi-active control algorithms are developed and examined for a variety of civil engineering applications subjected to a wide range of excitations. Except two control algorithms based on continuous variable structure control and Lyapunov control, the semi- active controllers developed in this study are based on real-time estimation of instantaneous (dominant) frequency and the evolutionary power spectral density by time-frequency analysis of either the excitation or the response of the structure. Time-frequency analyses are performed by either short-time Fourier transform or wavelet transform. The semi-active strategies are applied to three categories of structures: (1) smart single- and multi- degree-of-freedom (sSDOF/sMDOF) systems subjected to pulse-type and random ground excitations, (2) single/multiple smart tuned mass dampers (sTMD/sMTMD) subjected to random wind and ground excitations, and (3) smart tuned liquid column dampers (sTLCD) subjected to random wind and ground excitations. For sMDOF/sMDOF systems, nonlinear control algorithms developed to independently vary stiffness (continuous variable structure control) and damping (Lyapunov control) are examined against near-fault earthquakes and pulse type of excitations fitted to them. Another semi-active (time-frequency) controller is developed based on minimizing the instantaneous H2 norm of the response of the structure. Two time-frequency controllers (feedforward and feedback) are developed for single/multiple smart tuned mass dampers (sTMD/sMTMD) subjected to either force or base excitation. In the feedforward control, the smart tuned mass damper stiffness and damping are varied based on the instantaneous (dominant) frequency of the excitation, whereas in the feedback control the smart tuned mass damper stiffness is varied based on the instantaneous (dominant) frequency of the response. The developed algorithms are also extended to semi-active smart tuned liquid column dampers (sTLCD) subjected to either force or base excitation. The performance of the control algorithms are evaluated by studying the deterministic and stochastic responses of the examined semi-active structures. Stochastic responses are computed from Monte Carlo simulations of various target evolutionary spectra. It is shown that smart variable stiffness and variable damping systems and smart tuned mass/liquid column dampers lead to significant response reduction over a broad frequency range and under a wide set of excitations

    Development of an Apparatus for Wind Tunnel Dynamic Experiments at High-alpha

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    A unique experimental apparatus that allows a wind tunnel model two degrees of freedom has been designed and built. The apparatus was developed to investigate the use of new methods to augment aircraft control in the high angle of attack regime. The model support system provides a platform in which the roll-yaw coupling at high angles of attack can be studied in a controlled environment. Active cancellation of external effects is used to provide a system in which the dynamics are dominated by the aerodynamic loads acting on the wind tunnel model

    Optimal control and approximations

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    Optimal control and approximations

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