This month's column is not what I initially planned it to be. I had originally decided to set aside our current thread temporarily and to look at something completely different - the process of software development itself. This is a vitally important topic and so I've decided to treat it as the next stage of these essays instead of as an aside. Consequently we will be charging ahead with learning how to make an adaptive PID controller.
You may recall that all of the adaptive filters that we described last time involved the phrase ``least squares''. For adaptive PID controllers the concept will also show up. This month we will take a look at just what a least squares estimation is and how it can be used.