Model discrimination by optimal frequency. A] Bode plot determining the optimal input frequency for model discrimination. The Bode magnitude plot shows the output amplitude gain, g
, versus frequency ω (in decibel; that is in 20 log(g
)). Here, the gain corresponds to the ratio of the difference between the outputs of the blue and the red model, and the input amplitude (sinusoidal input); in other words, the maximum denotes at which frequency one can expect to see the largest difference between the models. The aim was to determine the optimal input frequency to apply to the system. This was determined to have a period of 4 minutes. B] Outputs of the simulation for the behaviour of the models with this optimal frequency applied as the input frequency demonstrating that the best input perturbation alone is not enough to discriminate between the two models. The coloured lines represent the models defined in Figure 2.