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The Development of Neural Network Based System Identification ...

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58 CHAPTER 3 AERIAL PLATFORM AND CUSTOM-BUILT FLIGHT TEST SYSTEM<br />

Gyro<br />

Main Frames<br />

Main Drive Gear<br />

Tail Drive Gear<br />

Motor Battery<br />

Servo<br />

Brushless DC<br />

Motor<br />

7 Channel<br />

Receiver<br />

Receiver/Servo Battery<br />

Bottom<br />

Bracket<br />

Landing Gear Mounting Points<br />

Figure 3.2<br />

Side frame system and components attachment in TREX600 main structure.<br />

regarded as a secondary rotor attached to the shaft either below or above the main<br />

rotor position by an unrestrained teetering hinge. <strong>The</strong> stabiliser bar blade consists <strong>of</strong><br />

two simple paddles which are attached to a rigid rod. <strong>The</strong> stabiliser bar receives the<br />

same cyclic pitch and roll inputs from the swash-plate but no collective input. <strong>The</strong><br />

stabiliser mechanism introduces stability to the helicopter dynamics through the use<br />

<strong>of</strong> the gyroscopic effect <strong>of</strong> the stabiliser bar tip weights and the aerodynamic effect on<br />

the stabiliser bar paddles [Kim and Tilbury, 2004, Shim, 2000]. When the stabiliser<br />

bar rotates, the bar earns gyroscopic effect and it tends to remain in the same plane <strong>of</strong><br />

rotation. This would make the helicopter momentarily maintain the current roll and<br />

pitch angle for a substantial time. Considering the helicopter model in Figure 3.3, in a<br />

hovering condition, the stabiliser bar angle β is known to be zero (level). If a wind gust<br />

or other disturbance knocks the helicopter out <strong>of</strong> its equilibrium state, the stabiliser<br />

bar will continue to rotate in the same inertial plane [Kim and Tilbury, 2004]. This<br />

would subsequently help the helicopter back to equilibrium state through stabiliser bar<br />

action on the cyclic angle <strong>of</strong> the main blade.

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