A bilinear controller with PID structure

This paper describes the development of a bilinear compensator which may be either retrofitted with an existing PID controller or integrated to produce a bilinear structured PID scheme. Motivation for the approach stems from the need for improved performance of industrial processes and plant over wider ranges of their operation. Essentially, the resulting controller exploits the fact that local bilinearisation holds for a wider range about a given operating point than the conventional approach in which local linearisation is assumed. The nonlinear PID controller which arises from the inclusion of a bilinear compensator, has been found to produce a more consistent performance without the need for retuning. The paper also discusses issues relating to the design of an auto-tuning facility for the bilinear controller.