The control of industrial processes is set up in a hierarchial mode. At the bottom are the regulators which handle short term, random, rapid fluctuations, in the middle are control actions to maintain stability in response to changes in set point, feed, etc., and above all this is long term, production planning, etc. The PI's work falls in the middle of the control hierarchy: he plans to develop a high-level surveillance and corrective system that can sustain control system and process operability when abnormal situation arise. There are hundreds of feedback/feedforward control loops in a process plant that are supposed to function in concert, yet reports of practicing engineers over the years claim that half of them are out of commission at any one time reason or another. Malfunction of control system components, human operator decisions and actions, unusual process conditions, and control system design deficiencies are some of the reasons. The focus of this work is to synthesize and develop a surveillance system capable of assessing the operational status of multiloop control systems and the integrity of operation of the process they control in continually changing, such a surveillance system will need redetermine the current structure each time a change in status is detected. Status changes can occur owing to failure of sensors, failure of actuators, unrelieved saturation of process manipulatable inputs, breaking of signal continuity in multilevel cascade systems, and operators, unrelieved saturation of process manipulatable inputs, breaking a signal continuity in multilevel cascade systems, and operator actions. The system will incorporate the following components: 1. Determination of the current control system structure. 2. Identification of the changes that have occurred. 3. Assessment of prospective control system modifications needed to address the exigencies of the moment. 4. Development of a procedure for implementing the structural changes in a coordinated and safe manner.
