1. A method of tuning a feedback controller employing fuzzy logic, the controller having a set of inputs and at least one output, the output being the result of fuzzy logic applied to the inputs, the fuzzy logic having a plurality of input and output membership functions arranged in sets, each input membership function of a set being identified to a single one of the inputs and the membership functions of the set together being defined between domain limits, the method comprising the steps of: selecting at least one set; and tuning the gain of the fuzzy logic for the selected set by changing the domain limits to change the domain of the input membership functions associated with that set wherein the domain is changed incrementally by a predetermined expansion factor.