Bank-to-Turn Control

Linear optimal control laws used for bank-to-turn missile guidance were investigated. The performance of these control laws was erratic because their development neglected attitude dependent constraints on the control variables. The effects of an inequality constraint on the control variable in a fixed final time, zero error controller were analyzed. This analysis led to the conclusion that the accepted technique of applying the constraint to the unconstrained optimal control solution is valid only if the control is saturated during the initial portion of the trajectory. Constraints during the terminal phase must be anticipated by adjusting intermediate boundary conditions. The nonzero set point optimal control law used for the analysis of inequality constraints was incorporated into a nonlinear Bank-to-turn attitude controller. This controller, which was evaluated on a six degree of freedom simulation, successfully eliminated the deficiencies of the linear controllers. (Author)