Navigation Functionalities for an Autonomous UAV Helicopter

3.4. THE AUGMENTED RMAX DYNAMIC MODEL 19
3.4 The augmented RMAX dynamic model
The RMAX helicopter model presented in this thesis includes the bare helicopter
dynamics and the YACS control system dynamics. The code of the
YACS is strictly Yamaha proprietary so the approach used to build the relative
mathematical model has been that of black-box model identification.
With the use of this technique, it is possible to estimate the mathematical
model of an unknown system (the only hypothesis about the system is that
it has a linear behavior) just by observing its behavior. This is achieved in
practice by sending an input signal to the system and measuring its output.
Once the input and output signals are known there are several methods to
identify the mathematical structure of the system.
The YACS model identification is not part of this thesis and details
can be found in [4]. In the following section the transfer functions of the
augmented attitude dynamics will be given. These transfer functions will
be used to build the augmented RMAX helicopter dynamic model used in
the simulator.
3.4.1 Augmented helicopter attitude dynamics
As previously stated the YACS and helicopter attitude dynamics have been
identified through black-box model identification.
The equations 3.3 represent the four input/output transfer functions in
the Laplace domain:
∆Φ =
∆Θ =
∆R =
∆AZ =
2.3(s 2 + 3.87s + 53.3)
(s 2 + 6.29s + 16.2)(s 2 + 8.97s + 168) ∆AIL
0.5(s 2 + 9.76s + 75.5)
(s 2 + 3s + 5.55)(s 2 + 2.06s + 123.5)
9.7(s + 12.25)
(s + 4.17)(s2 + 3.5s + 213.4) ∆RUD
0.0828s(s + 3.37)
(s + 0.95)(s2 ∆T HR
+ 13.1s + 214.1)
∆ELE (3.3)
where ∆Φ and ∆Θ are the roll and pitch angle increments (deg), ∆R