Three Unrequited Loves in Retirement

I have used the Three Unrequited Loves several times in the past years to express three (to date) failings, of myself, academia, industry, and the company I worked for, to get with it on three basic technologies and problems of varying importance to the Process Control industry's effective execution of its responsibilities (as I see it).

Unrequited Love #1: ICL

Idioms and ICL are the top level focus of the site, adequately covered in its body. The industry mess, in design, documentation, and human communication and understanding of control designs and technology, is getting worse and is unforgivable.

Unrequited Love #2: A More General and Fundamental Understanding of the PID

The PID has three basic critical claims to fame:

As basic as it is, we have no understanding adequate with which to teach and communicate it without interminable debate, argument, and error. This being the case, we need to admit that we do not, at least at a formal level, really understand the PID. Part of the difficulty is that PID control is inherently a matter of approximation. All this does is make explicit what is true of any real control of any real process. I believe that this situation/problem/whatever can be overcome.

Unrequited Love #3: Developing a More Intuitive and General Understanding of Multivariable Effects

The RGA has done yeoman service making multivariable processes accessible to Process Control. But it is inherently incomplete. The author's unused thinking on pinned zeros provides an intuitive connection through the basic impact of right half plane zeros, but it is also incomplete. Part of the problem is the eigenvalue style issues of sensitivity expressed in the RGA and the singular values, which are not integrated with the kind of Gaussian elimination style of the pinned zeros. And there is the possibility also examined in the reference of a general related analysis of nonlinear right half plane zeros. Somewhere in all this -mess- there is a pony.