Analysis of Helicopter Flight Dynamics Through Modeling and Simulation of Primary Flight Control Actuation System

The work presented describes a hydraulic servo system consisting of nonlinear valve and actuator dynamics and its effect on rotorcraft dynamics. An empirical second order model is used to describe valve dynamics, and accounts for both internal friction and hysteresis. Pressure dynamics in the actuator are calculated using the continuity equation including the effects of fluid compressibility. Actuator dynamics are determined via Newton's second law and a force summation including chamber pressures, friction on the piston, and external forcing. The model is integrated with HeliUM, a state space nonlinear rotorcraft flight dynamics simulation model. A linearized dynamic analysis of coupled actuator and rotorcraft dynamics are carried out with models obtained using numerical linearization. Rotorcraft performance is quantified through the use of frequency response data and handling qualities metrics. The effects of nonlinearities such as displacement and rate saturation on the dynamics of the rotorcraft is studied.