A ratio control scheme decoupling disturbance response from set-point response

In this paper a novel ratio control scheme is proposed for stable and unstable processes with time delay. The proposed ratio control system consists of two control loops with two-degrees-of-freedom control structure, which decouples the set-point response of each loop from its disturbance response. Two ratio controllers separately for the set-point and load disturbance changes are introduced between the two control loops, in order to achieve improved ratio control performance during the transients caused by the set-point and disturbance changes and to decouple the set-point response of the whole ratio control system from its disturbance response. For easy understanding and tuning, all the controllers in the ratio control system are designed analytically. As a result, the set-point and load disturbance responses of the ratio control system can be independently and conveniently tuned by a single control parameter. In addition, the proposed ratio control scheme can provide quantitative performance estimation. Simulation examples are included to illustrate the effectiveness of the proposed method.