Research On Helicopter Flight Dynamics Model Identification

Modeling of helicopter flight dynamics is the foundation of helicopter flight controller and flight simulator development. This thesis systemically studies theories and methods of helicopter flight dynamics model identification. And concentrates on three correlative contents: transcendental information acquisition and adoption, identification methods and identification flight experiment technology. In the thesis, the analysis and study are mainly based on small-scaled single main rotor helicopter, and some conclusions are extended to the normal helicopter to solve the common problems on helicopters. This thesis pays attention to the utilization of prior knowledge, such as engineering experience and theoretical conclusions, so as to make the results capable of describe the helicopter flight dynamic natures correctly as well as of clear physical meaning and easy to be accepted by engineers.Firstly, in order to get the identification model group, the thesis researches the characters of helicopter flight dynamics and modeles helicopter flight dynamics using mechanism modeling method. The force and moments of the main aerodynamic components are considered. With these forces and moments the thesis built up the 6-DOF movement equations of the helicopter. Based on the 6-DOF equations the flapping motions of main rotor and Bell-Hiller bar are also modeled to analyse the influence to helicopter response. Through the analysis on helicopter flight dynamic characters and mechanism model the transcendental information is acquired, which is essential for the identification research in the next step.The helicopter is a multi-input multi-output non-linear unstable system with very high vibration. The characters make the identification of helicopter very difficult, since there are many problems during identification modeling. Aiming at solving these problems, the system identification method is researched in this thesis. A two step identification method is proposed, which firstly identify the initial model using subspace identification method and then identify the optimized model using frequency weighted prediction error method. With this identification method this thesis makes the simulation to identify the example helicopter flight dynamics model. The result shows that the method is efficient and accurate.In this thesis a helicopter flight dynamic identification experiment system is develop in order to carry out the flight experiments and research the problems encountered. According to the requirements of the experiment the subsystems are designed. Meanwhile, the navigation algorithm is researched and a multi-sensor data fusion method is proposed. Based on the system designed in the thesis, the common problems in experiment are also researched.At the end of the thesis, in order to verify the identification method and the experiment system the flight experiment is carried out with model-scaled helicopter. The 6-DOF and 8-DOF linear flight dynamics model of the helicopter are identified. The identification results are verified with the flight data which is not used in the identification calculation. Aiming at verifying the identified model further, the thesis designed the flight controller using identified result, and carried out flight test to verify the validity of the controller.