Control of continuously-operated high temperature furnaces

The paper describes the motivation for, and the development and implementation of, a bilinear retrofitable compensator which is cascaded with an existing PID controller to produce improved performance over a wider operating range. The resulting controller, which has a bilinear structure, exploits the fact that local bilinearisation holds for a wider range about a given operating point than the conventional local linearisation approach. In situations where the standard linear PID controller is either required to be retuned to provide optimum performance or detuned to provide satisfactory performance over a given range, the nonlinear PID controller which arises from the inclusion of a bilinear compensator is able to maintain performance without the need for retuning.