System designers have had only limited success in regulating these environments using techniques based on linear control theory. Today, however, a number of designers are exploring other approaches to achieving more precise control, including fuzzy logic. This branch of logic is based on approximate reasoning. There is no middle ground. This flexibility is useful in coping with the imprecision of real-world situations, such as designing precision environmental control systems.
Fuzzy logic makes it possible to express a control system with a set of fuzzy rules.
Any number of fuzzy rules can be used to express the total system control action. They can use any number of variables and may be as complex as desired. The controller can consider as many system inputs and outputs as desired. This means that 1.5 degrees has a membership of .4 in the set of large values. At the same time, 1.5 degrees may have a membership of .9 in the set of small values.