Airplane stability and control: A history of the technologies that made aviation possible

This paper describes a multi-disciplinary design optimization approach to the conceptual design of a commercial aircraft with relaxed static stability. Longitudinal flight dynamics analysis and control design are performed concurrently with other disciplinary analysis to augment and improve handling qualities. The developed methodology enables control-configured designs providing higher freedom of change at the conceptual design stage. A design example demonstrates the effectiveness of the proposed integrated approach to improve performance goals.

Relaxed Static Stability Aircraft Design via Longitudinal Control-Configured Multi-disciplinary Design Optimization Methodology

This paper demonstrates a practical approach in designing a longitudinal command stability augmentation system for unstable combat aircraft. The unaugmented aircraft is originally unstable configuration in order to gain fast response for agility. The flight control system was designed in compliance with MIL-F-8785C and Gibson Criterion for the corresponding flight case. The design case study is based on pitch rate command control system using I controller. The design evaluation is based on time response analysis of simulated results using Matlab and Simulink. The pole-placement method was used to determine the augmented feedback gain. Second order actuator dynamics model was introduced to see its effect on overall design. This design case study offers a better understanding, an easier and practical approach implementation based on aircraft longitudinal pitch rate command.

Longitudinal command stability augmentation system design for unstable aircraft using flying and handling qualities specifications

A Nonsingular Fast Terminal sliding mode flight controller with power rate reaching law for a subscale aircraft is presented in this paper. The stability and convergence characteristics of the proposed controller are demonstrated for a nonlinear aircraft model. Non-Singular Fast Terminal sliding mode control has an improved convergence rate, thereby making the system state in the sliding stage to converge in finite time. The fast terminal sliding mode combines the advantages of terminal sliding mode and a hyperplane-based conventional sliding mode, thereby enabling a fast transient convergence of the states at close range and as well as at a distance from the equilibrium. Power Rate Reaching law is used in combination with the proposed controller, which improves the tracking performance and decreases time to reach the sliding manifold, and mitigates chattering in a better manner when compared to classical sliding mode reaching law. The proposed controller is evaluated numerically for attitude command tracking under nominal and turbulent conditions in comparison with the classical sliding mode controller. Also, the performance of the proposed flight controller for a variety of controller parameters is studied in the present work. 

Nonsingular Fast Terminal Sliding Mode Flight Control of a Subscale Aircraft

There exists an enormous wealth of published material describing the application of so called, 'modern control methods' to the design of fliglat control systems for piloted aeroplanes. It is also evident, with the exception of a very small number of recent applications, that there is a conspicuous lack of enthusiasm on the part of the airframe manufacturers to adopt this design technology, especially for the design of command and stability augmentation systems for piloted aeroplanes. It is possible to speculate on the reasons for this apparent lack of interest, but to do so might well result in a misplaced condemnation of modern control methods. Since evidence exists to suggest that some modern control system design strategies have overlooked important flight dynamics considerations, the discussion is turned around here by drawing attention to some of the more important considerations in command and stability augmentation system design. The object is, therefore, to inform the designer, of whatever persuas...

M.V. Cook

Papers

On the design of command and stability augmentation systems for advanced technology aeroplanes