New tuning strategy for series cascade control structure

Abstract

In the presence of disturbances associated with the manipulated variable, performance of a single loop control structure can be improved with the help of a series cascade control. A design approach for a series cascade control system is proposed in this paper. The secondary controller is tuned by finding the centroid of the convex stability region to quickly attenuate the disturbances arising in the inner loop before they influence the controlled variable, whereas the primary controller is tuned by magnitude optimum criterion to achieve improved servo response in the outer loop. Servo and regulatory responses for the nominal model, as well as for the perturbed model of the plant obtained by the proposed method are compared with some recently reported tuning strategies. Simulation results show that the proposed tuning strategy yields improved closed-loop performance.