An adaptive backstepping approach is used to control the longitudinal dynamics of an Unmanned Air Vehicle (UAV). The nonlinear controller designed makes the system follow references in the aerodynamic velocity and flight path angle, using the elevator deflections and the thrust as actuators. Moreover, the (global) solution is valid for all the flight envelope, since it is based on a general nonlinear model. The adaptation scheme proposed allowed us to design an explicit controller with a minimal knowledge of the aircraft aerodynamics. Simulations are included for a realistic UAV model that includes actuator saturation.
This work presents a model predictive controller (MPC) that is able to handle linear time-varying (LTV) plants with PWM control. The MPC is based on a planner that employs a PAM or impulsive approximation as a hot-start and then uses explicit linearization around successive PWM solutions for rapidly improving the solution by means of linear programming. As an example, the problem of rendezvous of spacecraft for eccentric target orbits is considered. The problem is modeled by the LTV Tschauner-Hempel equations, whose transition matrix is explicit; this is exploited by the algorithm for rapid convergence. The efficacy of the method is shown in a simulation study.
An output-feedback control law is designed for the longitudinal flight dynamics of an aircraft. The proposed control law is designed using the adaptive backstepping method and does not require any knowledge of aircraft aerodynamics beyond well-known qualitative physical properties. The resulting feedback controller is able to follow given references in both airspeed and flight-path angle by actuating elevator deflections and aircraft engine thrust. Engine physical limits are incorporated into the design by using a Lyapunov function analysis that includes saturation, obtaining a novel hybrid adaptation law that guarantees closed-loop system stability. Simulation results show good performance of the feedback law and, in particular, demonstrate that the hybrid adaptation law improves the behavior of the closed-loop system when saturations are present. A degraded scenario (a sudden cargo displacement that renders the aircraft statically unstable) is also considered to show the adaptation capabilities of the control law. The simulations are carried out using a realistic aircraft model that is also developed in the paper.
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