An integrated approach to controls and diagnostics using the four parameter controller

A foundation for an integrated approach to the design of controls and diagnostics in reliable control systems is presented. The control module and diagnostic module of the control system are designed together, instead of independently, thereby accounting for the interactions which occur between these two modules in a functioning control system. The four-parameter controller, a generalization of the two-parameter controller, is used. This controller has two vector inputs and two vector outputs, and, correspondingly, is composed of four matrix parameters. The additional controller output may be viewed as a diagnostic output which is monitored to detect and isolate sensor and actuator faults. A parameterization of all four parameter controllers is developed. The fundamental limitations and inherent tradeoffs governing the design of controls and diagnostics are delineated. Special attention is given to the issues of control/diagnostic interaction and uncertainty. Several means for resolving these design tradeoffs are proposed and illustrated by an example involving a jet engine.<>