The Development of Neural Network Based System Identification ...

198 CHAPTER 7 FLIGHT CONTROL SYSTEM DESIGN: RESULTS AND DISCUSSION
Lateral Cyclic
Longitudinal Cyclic
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Tail Cyclic
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Collective Pitch
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Figure 7.9 The corresponding control signals from the 4 DOF NNAPC controller with recursive NN
training during hovering flight test.
weight, pitch and throttle curve setting or changes in the lift and drag forces acting on
the helicopter during different flight conditions [Samal, 2009]. It is important for the
flight controller design to perform adequately under these parameter variations. The
parameter variation test carried out by implementing the NNAPC controllers in the
roll, pitch and yaw channels. Two types of NNAPC controllers are used for comparison
in the test, i.e. the NNAPC controller with the off-line trained NN model (the NN
model obtained from off-line LM training or repeated rGN training) and the NNAPC
controller with the recursive NN training (rGN). For easy reference to the controllers,
the general term of ‘NNAPC-Offline’ and ‘NNAPC-Online’ will be used to represent the
NNAPC controller types respectively. The compensation performance of the controllers
is tested under different pitch and throttle curve setting from the one used in the NN
training. The value changes made to the original pitch and throttle curves are shown in
Figure 7.10. The collective pitch setting is created with lower throttle values in low and