Open Control Systems solution example

Two broad approaches to dynamic operability analysis are the use of so-called open-loop indicators, and the solution of a suitably formulated optimization problem. Characteristics of the former are that they are based on steady-state or linear dynamic models, are relatively easy to compute and seek to provide indications of potential plant-inherent control problems independent of the choice of control system. Examples are the minimum singular value and the plant condition number which reflect sensitivity to input constraints and model uncertainty respectively. More detail may be found in [1] with a good overview of these methods given in [2]. 

If the hazard cannot be designed out, because it is either impossible or cost-prohibitive, then the next best solution is to use fail-safe devices. An example is a valve that fails in a safe manner. In many chanical processes, it is CTitical that the temperature not exceed a certain level. If the control valve fails in an open position, then the system will still maintain cooling even if system power or control is lost for one reason or another. 

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