Missile Controlled by Lift and Divert Thrusters Using Nonlinear Dynamic Sliding Manifolds

Abstract

A new approach to the design of a kinetic-kill longitudinal autopilot steering the missile trajectory by the combination of aerodynamic lift and divert thrusters (dual-thrusters control) and with its attitude oriented by attitude thrusters is presented. The proposed approach may increase the total divert acceleration capability by up to 100%, improving the end-game intercept accuracy, when such capability is required. The pitch plane autopilot design is based on second-order sliding mode control using a nonlinear dynamic sliding manifold technique. A robust high-accuracy tracking of the missile normal acceleration guidance command is achieved in the presence of considerable model uncertainties created by the interactions between the airflow and the thrusters jets. Results of the computer simulation demonstrate excellent, robust, high-accuracy tracking performance of the proposed design.Nomenclature a α , a δ , a = distance from the center of gravity along the longitudinal axis of the aerodynamic center and application points of attitude and divert thrusters, m C Lα = lift coefficient gradient with respect to angle of attack α C Mq (C/V ) = moment coefficient gradient with respect to pitch rate q, s −1 C = reference length, m D α , D δ , D = distribution of multiplicative disturbances d α , d δ , d = multiplicative disturbance factors applied to aerodynamic lift, attitude, and divert thrusters e (·) = tracking error with respect to variable (·) e α , e γ = angle-of-attack and flight-path angle tracking errors, radacceleration of Earth gravity, m/s 2 I yy = moment of inertia around the pitch axis, kg · m 2 m = missile mass, kg T max δ , T max = maximum attitude and divert thrust, N . Associate Fellow AIAA. ‡ Senior Scientist, Applied Research Department; ishkolnikov@ ziimaging.com. T δ , T = attitude and divert thrust, N V = longitudinal velocity of a missile, m/s Z α , Z δ , Z = dimensional normal stability derivative with respect to α, δ, and , respectively, s −1 α, γ , q = angle of attack; flight-path angles, rad; and pitch rate, rad/s * = commanded normal acceleration, m/s 2 δ, = normalized attitude and divert thrusters forces ρ = air specific mass, kg/m 3 τ δ , τ = time constants of attitude and divert thrusters actuators, s , ω = characteristic frequencies of attitude and divert sliding surfaces, rad/s Subscript and Superscript δ; = value, variable associated to attitude and divert thrusters * = commanded, reference value of variable (·)

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