Dear Christian:
the ideal PID equation is present in the net in plenty of sites and I know a little about it and methods to tune it (CDHW, ziegler-nichols,...). but do commercial PID controllers use this formula ? I found many variations some have d2Error/d2t, but I'm interested to know a very simple but effective variation. and certainly you misunderstand me I never ask anybody to solve my problems I usualy do it myself.I just posted a idea and waited to see comments.

regards