FIXED – ORDER AND STRUCTURE H∞ CONTROL WITH MODEL BASED FEEDFORWARD FOR ELASTIC WEB WINDING SYSTEMS

In web transport systems, the main concern is to control independently speed and tension in spite of perturbations such as radius variations and changes of setting point. This paper presents the application of nonsmooth nonconvex optimization techniques to design centralized fixed order and decentralized fixed order and fixed structure H∞ controllers with model based feedforward for web winding systems. The approach provides improved web tension and velocity regulation. First, mathematical models of fundamental elements in a web process line are presented. A state space model is developed which enables calculation of the phenomenological model feedforward signals and helps in the synthesis of H∞ controllers around the set points given by the reference signals. The H∞ control strategies with additive feedforward have been validated on a nonlinear simulator identified on a 3-motor winding test bench.