Some Issues in Control Engineering Practice

In the last years a lot of papers appearing in the control literature introduced elaborated control design algorithms. Most of them contain mathematical approaches that apparently solve control problems. However in many cases the engineering perspective is lost. Some case-dependent conclusions are proposed to be of general use and some properties are considered as universal, even they can fail under some specific situations. In this paper, a critical perspective based on some illustrative results suggests the need of a final review of any control solution according to the control engineering good practice. Delays in the feedback control loop are not always bad, multirate control not always leads to rippled behaviour and feedback of the actual process output is generally better than inferential control. Key-Words: Discrete-time systems, multirate systems, sampled-data systems, time delay, inferential control.