(496b) From Stability to Performance-Driven Control Configurations for Multi Delay Systems

Most dead-time compensation (DTC) schemes developed to-date can be regarded as stability driven since their predictive elements are conventionally structured to eliminate delays from the closed-loop characteristic equation. In the single-delay case this approach happens to also agree well with a number of optimization-based design methods. This, however, is no longer true in the multiple-delay case, where stability driven DTCs might yield poor closed-loop performance. In fact, there appears to be no clear choice of the DTC configuration and conventional wisdom even suggests that in certain situations it may be advantageous to add artificial loop delays to control channels with shorter delays to equalize input dead times. In this talk, given in memory of my mentor for many years the late Professor Reuel Shinnar, I will show  that DTC structures should be performance driven. To simplify the exposition, systems with multiple input delays will be considered and used to show how performance analysis can lead to a novel DTC configuration termed FASP (feedforward action Smith predictor). Alongside the conventional internal feedback, this configuration contains novel  interchannel feedforward controllers and never adds artificial loop delays. The structure of FASP has an intuitive explanation and effectively prompts a paradigm shift in DTC for systems with multiple loop delays. Application of the FASP to an upgraded version of the quadruple tank process with multiple delays laboratory set-up confirms the potential superiority of the FASP over existing state of the art dead-time compensators.