DeltaV's Fuzzy Logic Controller (FLC) has three tuning parameters. I'm not sure about other manufacturers. They are:
% Error
% Change in Error
% Output
% Error: Very similar to P in PID. It looks at the error between setpoint and actual value. The parameter is in % of full scale of your process value.
% Change in error: How fast the process is approaching setpoint. This is also in % of full scale of your process value.
% Output: When the process value differs more than the "% Error" and the process value is heading in the 'wrong' direction (away from setpoint) by more than the "% change in error", then the output will change by the amount in this parameter. But, if the % Error or the %change in error is below the set parameters, the the fuzzy logic kicks in to determine how much and which direction the output will go.
