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The Development of Neural Network Based System Identification ...

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7.3 EXPERIMENTAL RESULTS 201<br />

Yaw Rate (deg/s)<br />

30<br />

20<br />

10<br />

0<br />

−10<br />

−20<br />

Reference<br />

NNAPC−Online<br />

NNAPC−Offline<br />

−30<br />

0 50 100 150 200 250 300 350 400 450 500<br />

Sample (k)<br />

Tail Rotor Collective Pitch<br />

0.5<br />

0<br />

−0.5<br />

0 50 100 150 200 250 300 350 400 450 500<br />

Sample (k)<br />

Figure 7.12 <strong>The</strong> yaw controllers response comparison under changes in the collective pitch and<br />

throttle curve settings.<br />

Table 7.8 <strong>The</strong> controllers’ performance comparison under changes in the collective pitch and throttle<br />

curve settings.<br />

θ<br />

φ<br />

r<br />

Tuning parameter MSE Settling Time (s) Overshoot (%) Rise Time (s)<br />

NNAPC-Online 0.08 1.00 13.52 0.32<br />

NNAPC-Offline 0.29 14.16 26.57 3.91<br />

NNAPC-Online 0.05 n/a n/a n/a<br />

NNAPC-Offline 0.21 n/a n/a n/a<br />

NNAPC-Online 8.19 n/a n/a n/a<br />

NNAPC-Offline 9.34 n/a n/a n/a<br />

the helicopter carries. <strong>The</strong> compensation response comparison between the controllers<br />

under consideration is given in Figure 7.13 with the performance analysis for the test<br />

given in Table 7.9. <strong>The</strong> NN weights used in the NNAPC-Offline controller is trained<br />

based on the data measured with the original counterbalance weight (5 kg). <strong>The</strong> same NN<br />

weights obtained in the <strong>of</strong>f-line training are also used in the NNAPC-Online controller<br />

as the network’s initial weights. <strong>The</strong> NNAPC-Online controller is found to be superior<br />

in terms <strong>of</strong> compensation performance compared with the NNAPC-Offline controller.<br />

An overshoot about 16.41% occurs in the NNAPC-Online controller response due to the<br />

inertia effect <strong>of</strong> the counterbalance weight. Even with the changes in counterbalance

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