William Garrard - Academia.edu (original) (raw)

Papers by William Garrard

Journal of Guidance, Control, and Dynamics, 2009

Stochastic observability refers to the existence of a filter for which the errors of the estimate... more Stochastic observability refers to the existence of a filter for which the errors of the estimated state mean vector have bounded variance. In this paper, we derive a test to assess the stochastic observability of a Kalman filter implemented for discrete linear time-varying stochastic systems. This test is derived with the assumptions that the system matrices

Journal of Guidance, Control, and Dynamics, 1997

The dynamic response characteristics of modern aircraft vary substantially with ight conditions. ... more The dynamic response characteristics of modern aircraft vary substantially with ight conditions. These changes require scheduling of the ight control system with variables such as dynamic pressure and Mach number. This scheduling can be accomplished easily for simple controllers but is much more di cult for complex controllers which result from the use of most modern control design techniques. On the other hand these complex controllers can yield signi cant performance improvements when compared with simple controllers. Recently Linear Parameter Varying (LPV) techniques have been developed which provide a natural method for scheduling for Hinf based controllers. In this paper LPV techniques are combined with mu synthesis methods to develop a self-scheduled longitudinal controller for a high performance aircraft. The ability of this controller to achieve speci ed handling qualities over a wide range of ight conditions is demonstrated by non-linear simulations.

11th Aerodynamic Decelerator Systems Technology Conference, 1991

International Journal of Control, 1969

... GARRARD, W. L., MCCL ~ OOH , NH, and CLARK, LG, 1967, Int. J. Control, 5,425. liA~nm~, R. E.,... more ... GARRARD, W. L., MCCL ~ OOH , NH, and CLARK, LG, 1967, Int. J. Control, 5,425. liA~nm~, R. E., 1960, Boln Soc. mat. mex., 5, 102. LEE, EB, and MARKUS, L., 1967, Foundations of Optintul Control Theory (John Wiley). LURES, D., 1967, Ph.D. Thesis, University of Minnesota. ...

22nd Atmospheric Flight Mechanics Conference, 1997

Recently there has been considerable interest in the development of aircraft which have reduced v... more Recently there has been considerable interest in the development of aircraft which have reduced vertical tail size compared with conventional aircraft. The tail of an aircraft produces a large radar signature and the requirement for stealth in new military aircraft necessitates the design of ...

Aiaa Atmospheric Flight Mechanics Conference, 1992

This paper proposes the use of piecewise constant control in aeroassisted orbital transfers. Aero... more This paper proposes the use of piecewise constant control in aeroassisted orbital transfers. Aeroassisted orbital transfers can be achieved in practice through direct lift modulation or bank angle modulation. Practical implementation prefers constant lift coefficients. On the other hand, controls need to vary in order to cope with uncertainties in the atmosphere. As a result, piecewise constant lift or bank modulation presents a practically useful form. In this paper, several related problems in using piecewise constant lift control are discussed. In particular, the energy is used as the independent variable, and maps of state variables achievable with constant lift controls are provided.

1985 American Control Conference, Jun 19, 1985

Eigenspace techniques allow the control system designer to use feedback to place eigenvalues and ... more Eigenspace techniques allow the control system designer to use feedback to place eigenvalues and shape eigenvectors so as to modify closed loop dynamic response characteristics to achieve performance objectives. In this paper the theory of eigenspace design is reviewed, extended and applied to several aircraft control problems.

Recent results in multivariable robust control synthesis for linear parameter-varying (LPV) syste... more Recent results in multivariable robust control synthesis for linear parameter-varying (LPV) systems are applied to the control of a turbofan engine over a wide range of power codes. Seven linear, time-invariant models are used in the control design. The resulting LPV ...

36th AIAA Aerospace Sciences Meeting and Exhibit, 1998

Guidance, Navigation, and Control Conference, 1995

34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, 1998

Recent results in multivariable robust control synthesis for linear parameter-varying (LPV) syste... more Recent results in multivariable robust control synthesis for linear parameter-varying (LPV) systems are applied to the control of a turbofan engine over its entire range of operation. Ten linear, time-invariant models are used in the control design. An LPV model of the turbofan ...

Proceedings. The First IEEE Regional Conference on Aerospace Control Systems,, 1993

This paper describes a method for design of a flight control system for a high performance helico... more This paper describes a method for design of a flight control system for a high performance helicopter. This mlethod uses H, techniques to provide inner loop control laws which decouple the roll, pitch, and yaw rates and vertical velocity, and provide desired bandwidth in those channels. The design is an implicit model following approach in which the H, norm between the actual system outputs and outputs of desired handling quality models is minimized. Stability robustness is investigated by using a nonlinear simulation. This controller provides excellent performance when the control inputs are small and the system is essentially linear.

Guidance, Navigation and Control Conference, 1993

Guidance, Navigation, and Control Conference, 1994

International Journal of Control - INT J CONTR, 1972

In many cases of interest, systems described by non-linear differential equations are modelled by... more In many cases of interest, systems described by non-linear differential equations are modelled by linear equations for purposes of synthesizing feedback controllers. A theorem relating the stability properties of the linear model and the non-linear system is presented and discussed.

Journal of the American Helicopter Society, 1990

Journal of Guidance, Control, and Dynamics, 1999