SPECIAL FEATURE PID TUNING Bilinear controller with PID structure

The motivation for, and the implementation of, a bilinear control strategy having a PID structure is described. Improved consistency is automatically achieved by exploiting the fact that local bilinearisation holds for a wider range about a given operating point than a conventional approach in which local linearity is assumed. In terms of reduced activity of the control variable and tighter tracking of the process variable, the bilinear controller provides improved consistency of performance over a wider operating range. The benefits of employing the bilinear approach, which offers continuous scheduling of gains through an assumed bilinear controller model structure, are highlighted when the controller is applied to a continuously operated high-temperature furnace. Performance is compared to that of an optimally tuned industrial PID controller.