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Abstract

Aircraft having flexibility can develop large amplitude acceleration due to structural modes, in addition to that caused by the rigid body motion. Reduction of these loads by means of active control systems is an important problem in flight control. Load alleviation control by means of full state variable feedback, obtained as a solution to an eigen vectorleigen value assignment problem is demonstrated in this paper. The mathematical model of the aircraft used as an example, the C-5A, includes the linearised longitudinal equations of the rigid motion, the dynamics associated with the first flexural mode of the wing and the linear dynamics of the control surface actuators. Assessment of the degree of alleviation achieved is based on the calculated root mean square (RMS) values of both the bending and torsional moments at the wing root, these moments being represented by an output equation which is a linear combination of the state variables of the aircraft dynamics and the command signals to the control surface actuators,

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References

Ali, Q.R. 1987. Aircraft load alleviation by specifying the closed-loop eigenstructure, PhD thesis, Loughborough University, UK.

Bisplinghoff, R. 1955. Aeroelasticity, Addison-Wesley Publishing Co., Cambridge, Mass, USA.

Harvey, C.A. and Pope, R.E. 1977. Study of synthesis techniques for insensitive aircraft systems, NASA CR-2803, Honeywell Inc. Systems Research Center. Minneapolis, Minnesota. USA.

Holloway, R.B. 1973. Introduction of CCV technology into airplane design. AGARD.

Konar, A.F. , Stone, C.R. and Mahesh, J.K. 1976. 'Active control syntheses for flexible aircraft', AFFDL-TR-75-146, 1 & 2, WPAFB, Ohio, USA.

McLean, D. 1976. Gust load alleviation systems: A feasibility study, Report TT7606, Loughborough University, UK.

McLean, D. and Prasad, R.A. 1980. A structural load alleviation contol system for a large transport aircraft. Report TT8802, Loughborough University , UK.

Moore, B.C. 1976. 'On the flexibility offered by state feedback in multivariable systems beyond closed-loop eigenvalue assignment', Trans IEEE , AC-21, 689-692.

Noble, B. and Daniel, J.W. 1977. Applied linear algebra, (2nd edn). Prentice Hall, Englewood Cliffs, NJ, USA.

10.

Prasad, R.A. 1980. Application of optimal control to structural load alleviation control systems, PhD thesis, Loughborough University, UK.

11.

Shapiro, E.Y. and Chung, J.C. 1984. 'Flight control system synthesis using eigenstructure assignment', JOTA, 43, (3), 415-429.

12.

Stone, C.R. , Ward, M.D. , Harvey, C.A. et al. 1972. 'Studies of the compatibility of relaxed static stability and manoeuvre load control to C5-A type aircraft', AFFDL TR-72-38, 2, WPAFB, Ohio, USA.

Structural load alleviation

Abstract

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References