The Development of Neural Network Based System Identification ...

196 CHAPTER 7 FLIGHT CONTROL SYSTEM DESIGN: RESULTS AND DISCUSSION
Figure 7.7
The 4 DOF NNAPC controller with recursive NN training in action.
Table 7.6
The final controller settings for the hovering flight test.
Tuning Parameters Symbol Value
State Cost Q C T C
Control Cost r w 1.5
Control Horizon N c 3
Prediction Horizon N p 10
Roll-Pitch Amplitude Constraints u max,min ± 1
Yaw/Altitude Rate Constraints ∆u max,min ± 0.01
Yaw Rate Gain K Ψ 1.00
Altitude Speed Gain K w 0.75
in action. The step response is maintained for ∼600 samples, which equals 19.8 s at a
sample period time of 33 ms.
Figure 7.8 and 7.9 show the output responses of the 4 DOF controllers in term of
the pitch angle, roll angle, yaw rate and altitude speed, together with the corresponding
control signals. Table 7.7 summarises the performance indicators of the controller
responses. The MSE value is calculated in the period after the steady state condition
is obtained. The settling time is calculated after initiation of the step response with
settling threshold of 15 %. Again, the overshoot is determined as the percentage of the
highest peak compared with the settling point, and the rise time is calculated as the
time taken by the response signal to rise between 10 % and 90 % of the step input value.
It can be seen from visual inspection of the controller responses and the performance