Flight Dynamics Modeling For Rotorcraft Flying Quality Evaluation

A mathematical model is developed for an articulated helicopter. It is especially suitable to flight quality analysis and flight control system design. This model is formulated as a non-linear state-space representation of helicopter flight dynamics, incorporating with blade element unsteady aerodynamics, a finite state dynamic inflow wake model, and flapping/lead-lag blade dynamic model. The formulation of the coupled rotor and fuselage equations enables the use of common solution techniques for trim and linearization in arbitrary steady flight condition as well as control response calculations. Besides, a flying quality evaluation code of the military rotorcraft is developed, and the quality levels in hover/low speed flightwere calculated according ADS-33D(3.3). The principal contributions of this dissertation are:1. A high fidelity and real-time rotor wake inflow model was built up. Based on Peters-He finite states wake theory, a new influence coefficient matrix for high speed flight was derived, The modified wake model is better suitable for the flight state with a large wake skew angle.2. An unsteady, nonlinear state-space airfoil aerodynamics model was developed with ONERA dynamic stall model.3. A high fidelity real-time mathematical model of a turboshaftengine was developed and included in the helicopter flight dynamics mathematical model.4. An effective trim solution for first order state-space unsteady aerodynamics formulation was obtained.5. The integration technology for solving the flight dynamics equations was investigated and applicable code was compiled.6. The flight quality levels of the sample helicopter were caculated according to ADS-33D.At first, the model validation work was done with the available experiment data from NASA and our key lab. Results and analysis are presented in chapter 2. For the validation of the total model, the comparison of trim results in hover/forward flight was made with the popular software of FLIGHTLAB, and linearization matrixes were compared with HELISIM, they both show the coordination results.