Helicopter control and its general models

Thèmes abordés

Helicopter control, helicopter simulations, aircraft nonlinear equations of motion, matlab, Helicopter Flight Dynamics

Résumé du document

The goal of this study is to describe the behavior of a helicopter during its flight through the equations of motions. Many parameters will be considered such as geometry, velocities, forces, torques or thrust. This document and the program are not definitive. They will be improved though more accurate theories and some hypothesis may probably change.

Extraits

[...] Holmgaard, Christian S. Jensen, Stefan L. Jakobsen, Martin Siegumfeldt, Autonomous Helicopter. Modelling and Control, AALBORG UNIVERSITY Frederico R. Garza, Eugene A. [...]

[...] Firstly, earth axes are still considered as inertial axes. The airplane rotation conventions are the usual righthand rule and each studied helicopter will be considered as a rigid body. The relative motion of the aircraft internal components is neglected and the mass as well as density are considered as constants. Gravity and its moments do not change with altitude. Moreover, helicopters are free to move in all directions degrees of freedom) and the thrust is assumed to act along the X body-axis and through the center of gravity. [...]

[...] The DRA Research Puma XW241 has been chosen as an example to complete the model. This helicopter is a twin-engine, medium-support helicopter in the 6-ton category, manufactured by Eurocopter France, and in service among civil operators and armed forces, to support battlefield operations. Figure simplified overview of the Matlab program As shown on figure each part of the helicopter has been modeled. In order to simplify calculations and to gain time, the main program had been separated in different parts (each one of them corresponds to a block) although they are all linked. [...]

[...] Along the X and Yaxis, the velocities remain are null as no other initial conditions have been implemented. As for this second test, a torque around the Z-axis is applied in addition to the force along this same axis. As the center of gravity of the helicopter is not exactly the same as the chosen frame center, the translational velocities vary cyclically. In this example, the translational velocity of the helicopter (the norm of the vector of translational velocities composed by in red, in blue and in green) is increasing cyclically but not linearly. [...]

[...] They are connected with aerodynamic and propulsion models using tables in a database. In some cases, analytic polynomial models have been used to model the aerodynamic and propulsion dependencies on state and control variables. The Newton's laws are applied to a system composed by the helicopter, which can itself be modeled as a combination of a large number of interacting subsystems. The forces generated by the various components of the aircraft are returned to the center of gravity through strong bonds between the points of application of these forces and the center of inertia. [...]