In this paper, we discuss the application of a Single Network Adaptive Critic (SNAC) tracking controller on a morphing fighter aircraft modeled as a time-varying system. The performance of the aircraft is investigated from a flight dynamics perspective during a pull-up maneuver; and the time scale over which the morphing occurs is of the same order as the flight dynamics, due to which the influence of time-varying effects is significant. The time varying dynamical equations are adopted for a fighter aircraft which is assumed to be equipped with a variable-sweep wing. The SNAC controller is implemented on the longitudinal dynamic model of this aircraft. The neural network is trained to provide optimal tracking control over the aircraft flight envelope state space as the wing is swept along a specific morphing trajectory during the maneuver.
Nomenclaturek = discrete time index j = sweep angle trajectory index = state input = co-state = control = lift-curve slope = static longitudinal stability derivative coefficient = sweep angle = time = System matrix = Control matrix = longitudinal velocity = normal velocity = pitch rate = pitch angle S = solution of Joseph stabilized version of Riccati equation Q = State weighting matrix R = Control weighting matrix = sampling time tol = training tolerance
Abstract. This paper discusses active wing shaping control strategies for an elastic aircraft, with highly flexible wings. The objective of in-flight wing shaping is to ensure that the local angle of attack distribution on the wing is optimal at every flight condition so as to result in reduced drag during cruise. The wings are constructed using lightweight materials as a means to reduce aircraft weight -use of such materials ensures that strength and durability is retained, but results in reduced structural rigidity. This increase in structural flexibility leads to a significant increase in the effects of aeroelastic interaction forces and moments, which can lead to important aircraft stability and control issues.
In this paper, control design of an elastically shaped aircraft with highly flexible wings is discussed. The aircraft has the capability to actively change the wing twist and bending in flight so as to achieve a local angle of attack distribution that is optimal for the specific flight condition. The aircraft has 23 control surfaces and is longitudinally unstable in the open loop. Two design approaches are explored. In the first approach, a multi-objective performance index that includes an explicit drag minimization term is considered, and an optimal controller design is performed using this performance index. In the second approach, a decentralized controller that uses the elevator to control only the rigid body modes, and the wing flap and slat control surfaces to control the flexible modes, is developed. Simulation results demonstrate the validity of these controllers in stabilizing this elastic aircraft.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.