The control decisions are made based on the fuzzified variables in the Table II. The inference
involves a set of rules for determining the output decisions. As there are 2 input variables & 7
fuzzified variables, the controller has a set of 49 rules for the ANFIS controller. Out of these
49 rules [Fig. 9], the proper rules are selected by the training of the neural network with the
help of back propagation algorithm & these selected rules are fired.Further, it has to be
converted into numerical output, i.e., they have to be de-fuzzified. This process is what is
called as defuzzification,which is the process of producing a quantifiable result in fuzzy
logic.The defuzzifcation transforms fuzzy set information into numeric data information. There
are so many methods to perform the defuzzifcation, viz., centre of gravity method, centre of
singleton method, maximum methods, the marginal properties of the centroid methods & so on. In
our work, we use the centre of gravity method. The output of the defuzzification unit will
generate the control commands which in turn is given as input(called as the crisp input) to the
plant through the inverter. If there is any deviation in the controlled output (crisp output),
this is fed back & compared with the set value & the error signal is
generated which is given as input to the ANFIS controller which in turn brings back the output to
the normal value, thus maintaining stability in the system. Finally, the controlled output
signal, i.e., y is given by Eq. (21) as