Another topic that I have only mentioned the existance of is how to make adaptive PID controllers. This type of PID controller can actually use the performance of the system to tune the gains while the controller is running. These controllers are implemented by combining aspects of PID controllers with adaptive digital filters. This is definitely a topic for the future since it requires an understanding of digital filtering, which is something that we have so far only covered in these columns in a cursory way.
My last column on measurement of frequency containing data got a lot of positive responses, including such comments like ``give us more math !'' (I actually spared you a bit on this request, a full analysis of PID controllers can be very mathematical). Thank you all for your input. If have comments, suggestions and criticisms for, please don't hesitate contacting me through Forth Dimensions or via e-mail at email@example.com. I receive about 100 e-mail messages per day, so I can't indivually answer it all, but I do read them all.
Skip Carter is a scientific and software consultant. He is the leader of the Forth Scientific Library project, and maintains the system taygeta on the Internet. He is also the President of the Forth Interest Group.