Control structure selection based on attainable performance

In this paper, numerical optimisation in combination with a suitable parametrisation of all stable closed-loop systems is proposed as a tool for control structure selection. The key benefit is that the suitability of a control structure can be assessed without a priori information about the desired closed-loop behaviour or the controller structure. Thus, it constitutes an effective tool to explore different control structures and to integrate the performance of the controlled plant into the plant optimisation process. In the control structure selection process, robustness properties are screened using the robust performance number (RPN) as a controllability index. The advantage of our approach is demonstrated for the example of an air separation plant.