Hi DAB, Thanks a lot for your comments. First of all I want to clarify that, this is not an on-off controller. The control is by actuator variation. In case of temperature control if the temperature falls for a certain cause, a voltage variable resistor will allow more current to flow in the coil and more heating. In the block diagram I did not close the loop with VVR and thats why confusion took place. But I am happy that you have gone through the document. In fuzzy controller the mathematical foundation is quite inadequate to choose the fuzzy function and the parameters.( I am familiar with the research done till 1994.) PID stands on a firm mathematical basis. Here integrator takes care of hysteresis.
How accurate are you trying to make your temperature control?
I always find that simple state machines work very well with MCU implementations and they let you use a little fuzzy logic to set up a nice hysteresis zone to keep the system from toggleing from on to off due to noise in the signal.
