Retrospective Cost Adaptive Control of Unstart in a Model Scramjet Combustor

Abstract

A data-enabled adaptive control strategy is developed to regulate the thrust produced by a scramjet engine under normal operating conditions as well as near unstart. Specifically, retrospective cost adaptive control is pursued. Retrospective cost adaptive control is a direct discrete-time adaptive control algorithm that is applicable to stabilization, command following, and disturbance rejection. Retrospective cost adaptive control uses minimal modeling information, past control inputs, and limited measurements to retrospectively optimize the controller coefficients. A two-dimensional computational fluid dynamics model of the Hyshot-II scramjet geometry is used with a heat-release model to represent the dynamics of the combustor. This representation involves coupled nonlinear partial differential equations with degrees of freedom. First, the open-loop dynamic response of the model is studied to estimate essential features of the system. Then, retrospective cost adaptive control is used to maintain the commanded thrust in the presence of a disturbance in the Mach number. Finally, a modified performance variable is defined and is shown to enable retrospective cost adaptive control to suppress unstart.