Design of a helicopter automatic flight control system using adaptive control

Due to the complexity of the equations of motion governing the dynamics of the helicopter, the design of automatic flight control systems has proven to be difficult, time consuming task, often employing ad hoc methods to reach a solution. There is a need for a systematic control system design procedure. Since handling quality specifications are often given in terms easily interpreted for Linear Time Invariant system design, it is convenient to construct a reference model that exhibits satisfactory performance and design the control system such that the actual helicopter behaves like this reference model. One method of control system design that follows this approach is known as Adaptive Model Following Control.;There is an established theory for the stability of Adaptive Model Following Control systems. However, this theory has the restriction that the helicopter (plant) dynamics are Linear Time Invariant. In this work, the effects of considering nonlinearities (due to kinematics and aerodynamics) and unmodeled high frequency dynamics (due to the rotor dynamics) are considered. Two different mathematical models of the helicopter are used. One model calculates the aerodynamic forces and moments as functions of the control positions and vehicle velocities and uses Euler's equations. The other model uses the same structure except that it includes a transfer function approximation to the rotor dynamics at the inputs to assess the impact of unmodeled high frequency rotor dynamics on the performance of the control system. The helicopter models are based on the McDonnell Douglas Helicopter Company's Apache AH-64.