ANFIS Identification applied to a reservoir level liquid system

This work applies a methodology for identification of a double tank system with conic shape by using an Adaptive-network-based fuzzy inference system (ANFIS). Considering that the cross section of the tank is no longer constant, it rather changes with the height of the liquid, a nonlinear modelling method becomes more suitable. A comparison is made with the phenomenological model, which shows that such approach does not show appropriate adherence to the data collected from the system, even for the nonlinear model obtained from geometry. ANFIS on the other hand, presents a considerable improved fitness as it captures far more modes of the system, being tested for five different regression vector structures and for three evaluation criteria, namely root mean square error (RMSE), the adjusted determination coefficient $R^{2}_{a\, j}$ and Akaike Information Criterion (AIC). A trade off between complexity and fitness was used to choose the ANFIS model 3 with ${RMSE}=0.0702, R^{2}_{aj} \quad =0.7135$ and ${AIC}=2147.2974$ for the validation collected data. The findings show the effectiveness of the presented methodology herein.