Found this very interesting. I have been using PID control without uderstanding its operation fully and these links have broadened my horizon when it comes to proportional control
why use pid control, just switch on when too cold and switch off when too hot.
in most applications this just works fine.
btw
i do use fuzzy for heating and cooling as the demand on our ships is always different, from freezing cold -25 and very small load up to 14 celsius sailing bananas, with very high coolingload.