Logic-based switching controllers – A stepwise safe switching approach

The present work proposes a new logic-based safe switching technique, called here Stepwise Safe Switching. This technique is based on the description of the process with linear approximants which are valid in operating areas around a finite number of nominal operating points of the process. Switching takes place between common controllers for adjacent nominal operating points. Moreover, the switching between the controllers is allowed to take place only when the process has reached an operating point. The proposed technique guarantees stability and good performance for all transitions between operating points that lie in the neighborhoods of the nominal operating points of the process. This way a simple to design and easy to implement solution that provides good performance despite the drawback of lack of knowledge of the process dynamics can be derived. The proposed technique is successfully applied to control an isothermal CSTR process, described by three linear approximants around corresponding nominal operating points.