A Detailed Nonlinear Dynamic Model of a 3-DOF Laboratory Helicopter for Control Design

This work investigates the model of a 3-DOF laboratory helicopter, which constitutes a highly nonlinear system. For this model, advanced control concepts are developed and applied. In the beginning, the equations of motion are derived from a physical modeling approach. The modeling procedure yields highly nonlinear differential equations, from which linear state space systems are derived for arbitrary operating points. The major part of this work consists of the development of different linear and non-linear control architectures. At first, a classic state vector feedback controller with integration of the control error is implemented. Based on the system parameters of the linearized model, a gain scheduling approach is developed using one of the degrees of freedom as scheduling parameter. The gain scheduling application uses both discrete operating points as well as one possible continuous scheduling through interpolation. Additionally, a flatness-based feedforward controller architecture is added for transient set point changes using linear and nonlinear inverse dynamics. The control performance is validated in its dynamical and steady-state behavior. Finally, the previously derived approaches are tested on the actual helicopter.