Dunstan Graham

Bio: Dunstan Graham is an academic researcher. The author has contributed to research in topics: Feedback linearization & Nonlinear control. The author has an hindex of 9, co-authored 10 publications receiving 1255 citations.

Aircraft Dynamics and Automatic Control

Abstract: From the Publisher: Aeronautical engineers concerned with the analysis of aircraft dynamics and the synthesis of aircraft flight control systems will find an indispensable tool in this analytical treatment of the subject. Approaching these two fields with the conviction that an understanding of either one can illuminate the other, the authors have summarized selected, interconnected techniques that facilitate a high level of insight into the essence of complex systems problems. These techniques are suitable for establishing nominal system designs, for forecasting off-nominal problems, and for diagnosing the root causes of problems that almost inevitably occur in the design process. A complete and self-contained work, the text discusses the early history of aircraft dynamics and control, mathematical models of linear system elements, feedback system analysis, vehicle equations of motion, longitudinal and lateral dynamics, and elementary longitudinal and lateral feedback control. The discussion concludes with such topics as the system design process, inputs and system performance assessment, and multi-loop flight control systems.

Manual control of single-loop systems: Part II

Abstract: The c. 1959 mathematical model for human operator control dynamics has been validated and extended to produce a practically complete mathematical description of manual control dynamics for single-loop systems. This model is essential to the analytical design of closed-loop man-machine systems, and it facilitates understanding of the human as a control device. An extensive number of selected experiments using 9 subjects, 4 forms of plant dynamics of general applicability, and 3 principal forcing functions, yielded definitive describing function data over a frequency range of two decades including system crossover. Models were constructed at three levels of detail: 1) a crossover model which is easily and usefully applied; 2) an extended crossover model which accounts more adequately for low frequency lags and plant dynamics; and 3) a precision model which provides a description so detailed that inferences can be drawn about neuromuscular functions. The resulting adaptive, optimalizing c. 1965 human operator mathematical model is presented, with a detailed summary of its adjustments for proper application.

Retrospective essay on nonlinearities in aircraft flight control

Abstract: Preface and Introduction F years ago the structures of a linearized theory of servomechanisms and a linearized theory of aircraft dynamics were substantially complete. Combination and extension of the two subjects, accumulation of favorable experimental evidence, an increased general understanding, and the continuing challenge of complex and stringent requirements have made aircraft flight control a useful predictive science and a recognized engineering specialty. This much is no news to readers of the Journal of Guidance, Control, and Dynamics. Before we begin to congratulate ourselves, however, the editors have thought it appropriate to reflect on the perennial question from the floor: "What about nonliriearities?" The question is often facile and impertinent. A considered response is, of necessity, complicated, extensive but not comprehensive, and invariably controversial. No general response is possible^ Nevertheless, we may hope that reconsideration of specific topics will elucidate the matter and we have been persuaded to make the attempt. Our approach is historical. No new research results are presented, but our interpretation may disturb the conventional wisdom. The earliest, more or less successful, automatic flight control systems were highly nonlinear in their sensing and actuating elements (see Fig. 1, taken from Ref. 1). Analysis, however, was at that time disdained, and performance was achieved by cut and try methods. We have told elsewhere the story of the synthesis of the art of the " tinker er-in vent or" and the science of the "theoretician" in connection with aircraft flight control.' The confluence of techniques was well developed by about 1952.' This included the experimental and theoretical study of significant nonlinearities. But the litera-

A Review of Quasi-Linear Pilot Models

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.

Disturbance attenuation and rejection for systems with nonlinearity via DOBC approach

Abstract: In this paper the disturbance attenuation and rejection problem is investigated for a class of MIMO nonlinear systems in the disturbance-observer-based control (DOBC) framework. The unknown external disturbances are supposed to be generated by an exogenous system, where some classic assumptions on disturbances can be removed. Two kinds of nonlinear dynamics in the plants are considered, respectively, which correspond to the known and unknown functions. Design schemes are presented for both the full-order and reduced-order disturbance observers via LMI-based algorithms. For the plants with known nonlinearity, it is shown that the full-order observer can be constructed by augmenting the estimation of disturbances into the full-state estimation, and the reduced-order ones can be designed by using of the separation principle. For the uncertain nonlinearity, the problem can be reduced to a robust observer design problem. By integrating the disturbance observers with conventional control laws, the disturbances can be rejected and the desired dynamic performances can be guaranteed. If the disturbance also has perturbations, it is shown that the proposed approaches are infeasible and further research is required in the future. Finally, simulations for a flight control system is given to demonstrate the effectiveness of the results. Copyright © 2005 John Wiley & Sons, Ltd.

Automatic Flight Control Systems

Abstract: Aircraft flight control the equations of motion of an aircraft aircraft stability flexibility upon aircraft motion disturbances which affect aircraft motion flying and handling qualities control system design methods I control system design methods II stability augmentation systems attitude control systems flight path control systems adaptive flight control systems.

Strategies for the control of voluntary movements with one mechanical degree of freedom

Abstract: A theory is presented to explain how accurate, single-joint movements are controlled. The theory applies to movements across different distances, with different inertial loads, toward targets of different widths over a wide range of experimentally manipulated velocities. The theory is based on three propositions. (1) Movements are planned according to “strategies” of which there are at least two: a speed-insensitive (SI) and a speed-sensitive (SS) one. (2) These strategies can be equated with sets of rules for performing diverse movement tasks. The choice between SI and SS depends on whether movement speed and/or movement time (and hence appropriate muscle forces) must be constrained to meet task requirements. (3) The electromyogram can be interpreted as a low-pass filtered version of the controlling signal to the motoneuron pools. This controlling signal can be modelled as a rectangular excitation pulse in which modulation occurs in either pulse amplitude or pulse width. Movements to different distances and with loads are controlled by the SI strategy, which modulates pulse width. Movements in which speed must be explicitly regulated are controlled by the SS strategy, which modulates pulse amplitude. The distinction between the two movement strategies reconciles many apparent conflicts in the motor control literature.

Mathematical Models of Human Pilot Behavior

Abstract: : The use of mathematical models of the human pilot in analyses of the pilot/vehicle system has brought a new dimension to the engineering treatment of flying qualities, stability and control, pilot/vehicle integration, and display system considerations. As an introduction to such models, elementary concepts and specific physical examples are used to set the stage for a step-by-step development of what is known about the human pilot as a dynamic control component. In the process, quasi-linear models for single-loop systems with visual stimuli and multiloop systems with visual stimuli are presented and then extended to cover multiloop, multi-modality situtations. Empirical connections between the pilot dynamics and pilot ratings are also considered. Some of the most important nonlinear features of human pilot behavior in adapting to changes in the character of the stimuli are described and tied to the quasi-linear models.