Double Back-Calculation Approach to Deal with Input Saturation in Cascade Control Problems

This paper presents a solution to the saturation problem in cascade control schemes. When cascade control approaches work in linear mode without saturation influence, important improvements can be achieved in industrial control loops. The effect of disturbances and/or nonlinear actuator behaviours on the main process variables can be considerably reduced. However, when saturation arises in the inner loop, these improvements cannot be reached and even sometimes the saturated cascade control scheme gives worse results than a single control loop. Thus, this work analyzes this situation and introduces an alternative solution to solve this problem and to reduce the impact of the saturation effect.