Thus a fairly straightforward sensor system can provide the necessary inputs for our fuzzy controller. Before designing the controller, we must determine the range of possible values for the input and output variables. These are the membership functions used to translate real world values to fuzzy values and back. Figure 2 shows the labels of input and output variables and their associated membership functions. We can use fuzzy sets or singletons for output variables.
Singletons are simpler than fuzzy sets.
They need less memory space and work faster. If we could not be satisfied by the result when output values are given by singltons we could change them into fuzzy sets. Remember that when we use TVFI method for inference we can only use singltons as values of outputs. We should use Mandani's method for inference if we want to define output values as fuzzy sets. Details about TVFI and Mandani's method can be found in FIDE's User's Manual.