Robust loopshaping for process control

Strong trends in chemical engineering and plant operation have made the control of processes increasingly difficult and have driven the process industry's demand for improved control techniques. Improved control leads to savings in resources, smaller downtimes, improved safety, and reduced pollution. Though the need for improved process control is clear, advanced control methodologies have had only limited acceptance and application in industrial practice. The reason for this gap between control theory and practice is that existing control methodologies do not adequately address all of the following control system requirements and problems associated with control design: •The controller must be insensitive to plant/model mismatch, and perform well under unmeasured or poorly modeled disturbances. •The controlled system must perform well under state or actuator constraints. •The controlled system must be safe, reliable, and easy to maintain. •Controllers are commonly required to be decentralized. •Actuators and sensors must be selected before the controller can be designed. •Inputs and outputs must be paired before the design of a decentralized controller. A framework is presented to address these control requirements/problems in a general, unified manner. The approach will be demonstrated on adhesive coating processes and distillation columns.