Applications of State Estimators in Industrial Process Control

This paper describes the successful application of state estimation in the control of commercial chemical process operations. From a theoretical standpoint, it appears straightforward to use state estimation for detecting faulty measurements, for estimating unmeasured variables, and for obtaining improved estimates when redundant information is available. However, despite a widespread need, there are few such applications documented in the chemical process control literature. By using a time-invariant observer feedback gain matrix, the estimator and control algorithms lend themselves to a physical interpretation which can be more readily understood by operating personnel. In addition the on-line computational load is much reduced from that required with a time-varying Kalman filter. A specific case involving the estimation and control of a flow rate based on vessel weigh cell measurements is discussed.