Abstract:

For the flight-path angle tracking control of fixed-wing unmanned aerial vehicles (UAVs) during the landing phase, a recursive sliding mode control method with nonlinear gains is proposed. By introducing a new function with nonlinear gains and developing recursive siding mode surface with integral action, the controller can guarantee precise tracking of flight-path angle as well as better dynamic transient performance of the control system, and it overcomes the troubles of conventional dynamic surface control (DSC) such as fragile to the measurement noise, and easy to cause actuator saturation. Theory analysis proves that all the signals of the resulting flight-path angle control system are semi-global uniform ultimately bounded; the tracking error of the flight-path angle can converge to an arbitrary small neighborhood of the origin and, for time invariant disturbance and constant reference command signal, there is no steady-state error. The numeric simulations on the YF-22 plant mode validate the effectiveness of the proposed approach.