Command- and Stability Systems for Aircraft: A New Digital Adaptive Approach

Abstract

Ensuring good handling qualities of aircraft in the whole flight envelope is a difficult and time consuming task because aircraft parameters are subjected to drastic changes. Adaptive control is a very promising technique to solve these problems and to improve the performance deficiencies of conventional stability systems with preprogrammed control gains. The approach used in this paper is based on digital control and on a special stabilization concept which requires only three dynamic parameters of the aircraft to meet standard handling qualities criteria. These three parameters cannot be measured directly. Therefore a recursive, weighted least squares algorithm is used which delivers sufficient fast and accurate on-line— parameter estimates. The adaptive control system has proven its very satisfactory performance in several digital and hybrid simulations including fast parameter variations and turbulence conditions. Real flight test data have been used to verify the performance of the identification process.