Ecological Sign Stability and its use in robust control design for aerospace applications

Recently, the idea of using ecological sign stability approach for designing robust controllers for engineering systems has attracted attention with promising results. In this paper, continued research on this topic is presented. It is well known that, in the field of control systems, key to a good controller design is the choice of the appropriate nominal system. Since it is assumed that the perturbations are about this nominal, the extent of allowed perturbation to maintain the stability and/or performance very much depends on this dasianominalpsila system. In this paper, we propose that the stability robustness measures for parameter perturbation are considerably improved if the dasianominalpsila system is taken (or driven) to be a dasiasign stablepsila system. Motivated by this observation, a new method for designing a robust controller for linear uncertain time invariant state space systems using ecological sign stability approach is presented along with conditions under which such a controller exists. The resulting controller design method is illustrated with examples in the flight control area including aircraft lateral flight dynamics control and satellite formation flying control.