A non-linear adaptive guidance algorithm for last-stage launcher control

Abstract

On-line adaptive guidance algorithms are currently difficult to implement since algorithms involving trial and error are needed to solve the two-point boundary value problems related to the optimization process. These routines may require an unpredictable number of iterations to converge to a solution; moreover convergence itself cannot be assured a priori. This problem can be circumvented by linearizing the control strategy about the nominal trajectory. However, since the system to be controlled is intrinsically non-linear, the linearization may have a limited accuracy. In this paper an adaptive guidance method is presented which drives the launcher to the target in an optimal way even if the deviations from the nominal trajectory are so large that the variations of the guidance parameter become non-linear. The adaptive guidance proposed avoids iterative algorithms or convergence routines, shows good accuracy and a computational time suitable for current on-board computers.