Discrete time H∞ control laws for a high performance helicopter

An application of the 2 Ricatti equation theory for discrete-time H^∞ optimization is presented. Two helicopter flight control laws are designed. The first design is based on a normalized coprime factor stabilization. The second uses a standard 2-block sensitivity and robustness formulation. The designs presented here are novel in that the problem is posed from the outset as a discrete-time (DT) problem which is solved using recent game-theoretic formulae for DT H^∞ optimization. It is shown that by suitable choice of weighting functions it is possible to obtain directly DT controllers that give good levels of performance and robustness