The Development of Neural Network Based System Identification ...

130 CHAPTER 5 NN BASED SYSTEM IDENTIFICATION: RESULTS AND DISCUSSION
(a)
(b)
Figure 5.9 The 5 steps ahead prediction of MLP network model for (a) Pitch dynamics; and (b)
Roll dynamics. The solid blue line with ‘x’ marker is the measured output while the red dashed line
indicates the prediction from neural network model.
and measured output data. The plots of the k-steps predictions are given in 5.9(a) and
5.9(b). The corresponding error statistics of one step and k-step ahead predictions are
given in Table 5.2 for each individual prediction variable. From the error statistics, we
can conclude that the discrepancy between the k-step ahead prediction (k = 5) and the
measured data is insignificant. Both figures show that the trained neural network model
predictions are close to the measured values and that the neural network is properly
trained to mimic the rigid body dynamics of the helicopter.
The MLP based NN model produced different magnitude of weight values if the
NN training was conducted several times using random initial weight values at the
beginning of the training. This would result in many possible sets of weights that would