An Improved Qualitative Controller

The basic concepts cocerning the use of qualitative reasoning in process control are discussed. The method is applied to the control of single-input single-output (SISO) systems, using the two coupled-tanks system as an application example. We show here that a controller using a pure qualitative model of the process is inefficient for practical applications. Significant improvement in the performance of the controller can be achieved by combining the qualitative model with process-related quantitative knowledge.