Describing function

About: Describing function is a research topic. Over the lifetime, 1742 publications have been published within this topic receiving 26702 citations.

Jet Engine Model for Control and Real-Time Simulations

Abstract: The main objective of this paper is development of a simple real-time transient performance model for jet engine control. A jet engine arrives to its most dangerous condition during transient operation that may be triggered by fast changes of the input fuel command signal. Thus, the control system specifications are formulated to specify the maximal variance of the fuel flow command (from idle to maximum power level) during transient maneuver. Linear and piecewise-linear techniques are not always convenient and appropriate for turbine engine controller design. An alternative quasilinear simple/ fast engine model is discussed in this paper. This model has maximum accuracy for maximal variance of the fuel flow input command in accordance to the jet engine control system specifications. The fast model is obtained using the Novel Generalized Describing Function, proposed for investigation of nonlinear control systems. The paper presents the Novel Generalized Describing Function definition and then discusses the application of this technique for the development a fast turbine engine simulation suitable for control and real-time applications. Simulation results are compared between the conventional and fast models and found to provide good agreement.

Nonlinear Control Systems

Abstract: Properties of nonlinear systems stability linearization methods operating modes and dynamic analysis methods phase trajectories in dynamic analysis of nonlinear systems harmonic linearization in dynamic analysis of nonlinear control systems operating in stabilization mode harmonic linearization in dynamic analysis of nonlinear control systems in tracking mode of operation performance estimation of nonlinear control system transient responses describing function method in fuzzy control systems. Appendices: harmonic linearization Popov diagrams.

An H-infinity-based control design methodology dedicated to the active control of vehicle longitudinal oscillations

Abstract: This paper deals with the problem of active damping of vehicle oscillations. A complete methodology based on an H/spl infin/ optimization is presented. Several dedicated analysis tools are used in order to analyze the behavior of the closed-loop system. Two tuning parameters allow the design of a controller managing the compromise between performance (in terms of oscillation attenuation and limit cycles) and robustness. Finally, a feedforward component is designed in order to improve the performance without changing the robustness properties or the controller complexity. Simulation results obtained with an experimentally validated model show the efficiency of the resulting controller.

Measurement of Driver-Vehicle Multiloop Response Properties with a Single Disturbance Input

Abstract: Multiloop response properties of controllers are, in general, very difficult to obtain because an independent forcing function is needed for each describing function to be measured, and interpolation procedures may be required to obtain intermediate describing functions at common frequencies. Even then, a certain amount of untangling is required before the final results are obtained. When the loops that are closed and the nature of the describing function forms adopted in each loop are known or hypothesized, matters can be made much simpler. Then, the quantitative values of the individual describing functions can be readily identified using appropriate closed-loop describing function measures and decomposition procedures. Two examples are provided for the measurement of driver-vehicle multiloop response properties using a single disturbance input. The validity of the procedure is based on current multiloop operator adjustment rules and is made plausible by comparison with experimental data.