Analysis of EALQR control design methodology

EALQR (linear quadratic regulator with an eigenstructure assignment capability), a control design methodology previously developed by the authors, performs better than a conventional LQR or an eigenstructure assignment. However, it has a constraint on the weighting matrix, that is, the weighting matrix can be indefinite for some high-order systems. This paper analyzes the effects of an indefinite weighting matrix in EALQR on the frequency domain properties. The robustness criterion and the quantitative frequency domain properties are presented. The frequency domain properties of EALQR with an indefinite weighting matrix have been analyzed by applying them to a flight control system as a design example.