Nonlinear Phase Shift Compensator for Pilot-Induced Oscillations Prevention
01 Oct 2015-pp 225-231
TL;DR: A novel phase shift compensator based on nonlinear correction technique is presented and numerical comparative study for two models of a pilot for PIO prevention during the flight is given, demonstrating that the proposed method increases the admissible gain of the "airplane-pilot" loop as compared with non-corrected system.
Abstract: The pilot-induced oscillation (PIO) is denoted as unintended steady fluctuation of the piloted aircraft, generated due to the efforts of the pilot to control the aircraft. The main non-linear factor leading to the PIO is, generally, rate limitations of the aircraft control surfaces, resulting in a delay in the response of the aircraft to pilot commands. Due to the tight relationship between magnitude and phase frequency responses for linear systems, applicability of the linear compensator for mentioned aim is highly restricted. This leads to the idea of employing the nonlinear phase shift compensator. In the control theoretic literature, various nonlinear corrective devices (NCD) are elaborated, which make it possible to change the phase-frequency and amplitude-frequency responses independently on each other. In the paper, a novel phase shift compensator based on nonlinear correction technique is presented and numerical comparative study for two models of a pilot for PIO prevention during the flight is given. The results obtained demonstrate that the proposed method in several times increases the admissible gain of the "airplane-pilot" loop as compared with non-corrected system.
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TL;DR: Simulation and experiment results verify that the PI controller tuned by Skogestad internal model control (SIMC) method is less sensitive to the rate limit variation and is more suitable for processes which have severe actuator rate limit.
Abstract: The control performance can be worsened by actuator rate limit, which can result in amplitude attenuation and phase delay in process control. In some extreme situations, actuator rate limit may bring about the system non-convergence. This paper focuses on the control difficulties and solutions of first-order plus time-delay (FOPTD) systems caused by rate limit. The influence of rate limit on stability regions of proportional–integral (PI) controller is analysed. Results show that a small rate limit value can reduce stability regions of PI parameters greatly. The negative correlation between the integral gain and the onset frequency, and the positive correlation between the proportional gain and the onset frequency are conducted. Moreover, the control performance of different PI tuning rules such as Skogestad internal model control, integral gain maximization, delay robustness-constrained optimization and Tyreus–Luyben tuning rules is evidently affected by rate limit. Simulation and experiment results verify that the PI controller tuned by Skogestad internal model control (SIMC) method is less sensitive to the rate limit variation and is more suitable for processes (the normalized dead-time is from 0.03 to 1) which have severe actuator rate limit. Tyreus–Luyben tuning rule is another optional method. In addition, the reasons why SIMC is not sensitive to rate limit variation are analysed. These analytical results can offer a guideline for practical applications.
13 citations
TL;DR: In this article, the existence of the hidden attractor in pitch motion of the piloted aircraft is demonstrated and the nonlinear phase shift compensator is designed, which increases the admissible gain of the "airplane-pilot" loop as compared with non-corrected system.
11 citations
TL;DR: This study proposes both graphical method and curve fitting method to identify the first-order plus time-delay (FOPTD) systems with consideration of the actuator rate limit effect whose limit value is unknown.
Abstract: Actuator rate limit phenomenon is ubiquitous in control systems, but it has always been neglected in practical engineering. Especially, few papers are published to investigate the system identification while considering the rate limit. Step function is commonly used in parameter estimation and its first-order derivative at the step time goes to infinity, which is not affordable by real actuators. As a result, the rate limit slows down the system response speed, misleads the parameter identification, and subsequently affects the controller design and deteriorates the control performance. This study proposes both graphical method and curve fitting method to identify the first-order plus time-delay (FOPTD) systems with consideration of the actuator rate limit effect whose limit value is unknown. Quantitative analyses of the parameter mismatch in the traditional FOPTD model and parameter sensitivity analyses are also carried out. Both simulation results and experimental results have shown the necessity and feasibility of defining a new model structure which includes the rate limit value.
6 citations
TL;DR: In this paper, a new identification framework for first-order plus time-delay (FOPTD) systems affected by actuator rate limit is presented, where the rate limit can lead to an illusory delay in system reaction curves.
Abstract: While actuator rate limit is common and counted in practical engineering, it has not drawn enough attention in control synthesis especially system identification. In this note, it aims to construct a new identification framework for first-order plus time-delay (FOPTD) systems affected by actuator rate limit. It is found that the rate limit can lead to an illusory delay in system reaction curves. Furthermore, necessary quantitative analyses are given to validate that excessively estimated or illusory delay significantly influences estimation accuracy of other parameters and subsequently degrades control performance. Two illustrative examples and experimental results are provided to demonstrate the adverse effect of actuator rate limit on system identification and the effectiveness of the proposed model structure on control performance.
4 citations
DOI•
13 Sep 2021TL;DR: In this article, a pseudo-linear correcting device is used to prevent oscillations in the angular motion of a piloted aircraft by the pseudolinear correcting devices. But the human influence on the piloting process is not considered.
Abstract: The paper is devoted to preventing oscillations in the angular motion of piloted aircraft by the pseudo-linear correcting device. The prime cause of this event is the unfavorable interaction between the pilot and the vehicle or the so-called pilot-induced oscillations. In this connection, it becomes necessary to consider the human influence on the piloting process to preserve the formation.
2 citations
References
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Book•
01 Jan 1968
TL;DR: The theory of automatic control has been advanced in important ways during recent years, particularly with respect to stability and optimal control, but these theories do not, however, lay to rest all questions of importance to the control engineer.
Abstract: ABRAMSON Information theory and coding BATTIN Astronautical guidance BLACHMAN Noise and its effect on communication BREMER Superconductive devices BROXMEYER Inertial navigation systems GELB AND VANDER VELDE Multiple-input describing functions and nonlinear system design GILL Introduction to the theory of finite-state machines HANCOCK AND WINTZ Signal detection theory HUELSMAN Circuits, matrices, and linear vector spaces KELSO Radio ray propagation in the ionosphere MERRIAM Optimization theory and the design of feedback control systems MUUM Biological control systems analysis NEWCOMB Linear multiport synthesis PAPOULIS The fourier integral and its applications R. N. BRACEWELL) STEINBERG AND LEQUEUX (TRANSLATOR Radio astronomy WEEKS Antenna engineering PREFACE The theory of automatic control has been advanced in important ways during recent years, particularly with respect to stability and optimal control. These are significant contributions which appeal to many workers, including the writers, because they answer important questions and are both theoretically elegant and practically useful. These theories do not, however, lay to rest all questions of importance to the control engineer. The designer of the attitude control system for a space vehicle booster which, for simplicity, utilizes a rate-switched engine gimbal drive, must know the characteristics of the limit cycle oscillation that the system will sustain and must have some idea of how the system will respond to attitude commands while continuing to limit-cycle. The designer of a chemical process control system must be able to predict the transient oscillations the process may experience during start-up due to the limited magnitudes of important variables in the system. The designer of a radar antenna pointing system with limited torque capability must be able to predict the rms pointing error due to random wind disturbances on the antenna, and must understand how these random disturbances will influence the behavior of the system in its response to command inputs. But more important than just being able to evaluate how a given system will behave in a postulated situation is the fact that these control engineers must design their systems to meet specifications on important characteristics. Thus a complicated exact analytical tool, if one existed, would be of less value to the designer than an approximate tool which is simple enough in application to give insight into the trends in system behavior as a function of system parameter values or possible compensations, hence providing the basis for system design. As an analytical tool to answer questions such as these in a way …
1,244 citations
"Nonlinear Phase Shift Compensator f..." refers background in this paper
...Then the approximate frequency response representation for nonlinearity ψ(·) (the describing function [8]) may be written as...
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TL;DR: An essential feature of this theory is the use of quasi-linear analytical models for the human pilot wherein the models' form and parameters are adapted to the task variables involved in the particular pilot-vehicle situation.
Abstract: During the past several years, an analytical theory of manual control of vehicles has been in development and has emerged as a useful engineering tool for the explanation of past test results and prediction of new phenomena. An essential feature of this theory is the use of quasi-linear analytical models for the human pilot wherein the models' form and parameters are adapted to the task variables involved in the particular pilot-vehicle situation.
860 citations
"Nonlinear Phase Shift Compensator f..." refers background in this paper
...Consider now more complex (dynamical) model of the pilot, following the crossover pilot model considerations, given in [33], [34]:...
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...The following parameters of pilot describing function (22) are taken [33], [34]: τpilot = 0....
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TL;DR: The problem of investigating hidden oscillations arose in the second part of Hilbert's 16th problem (1900), and the first nontrivial results were obtained in Bautin's works, which revealed no similar transient processes leading to such attractors.
Abstract: From a computational point of view, in nonlinear dynamical systems, attractors can be regarded as self-excited and hidden attractors. Self-excited attractors can be localized numerically by a standard computational procedure, in which after a transient process a trajectory, starting from a point of unstable manifold in a neighborhood of equilibrium, reaches a state of oscillation, therefore one can easily identify it. In contrast, for a hidden attractor, a basin of attraction does not intersect with small neighborhoods of equilibria. While classical attractors are self-excited, attractors can therefore be obtained numerically by the standard computational procedure. For localization of hidden attractors it is necessary to develop special procedures, since there are no similar transient processes leading to such attractors. At first, the problem of investigating hidden oscillations arose in the second part of Hilbert's 16th problem (1900). The first nontrivial results were obtained in Bautin's works, which...
750 citations
TL;DR: An overview of anti-windup techniques for linear systems with saturated inputs can be found in this article, where the authors provide constructive LMI conditions for the synthesis of antiwindup compensators in both global and local contexts.
Abstract: The anti-windup technique which can be used to tackle the problems of stability and performance degradation for linear systems with saturated inputs is dealt with. The anti-windup techniques which can be found in the literature today have evolved from many sources and, even now, are diverse and somewhat disconnected from one another. In this survey, an overview of many recent anti-windup techniques is provided and their connections with each other are stated. The anti-windup technique is also explained within the context of its historical emergence and the likely future directions of the field are speculated. The focus is on so-called ‘modern’ anti-windup techniques which began to emerge during the end of the 20th century and which allow a priori guarantees on stability to be made. The survey attempts to provide constructive LMI conditions for the synthesis of anti-windup compensators in both global and local contexts. Finally, some interesting extensions and open problems are discussed, such as nested saturations, the presence of time delays in the state or the input, and anti-windup for non-linear systems.
539 citations
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TL;DR: In this article, the authors investigate the relationship between optimal control design and control allocation when the performance indexes are quadratic in the control input and show that for a particular class of nonlinear systems, they give exactly the same design freedom in distributing the control effort among the actuators.
340 citations