Robust μ-Synthesis Control of the Lateral Web Shifting with Time Delay

Abstract

This paper deals with the robust control of the lateral movement of webs using a pivoting guiders. Lateral shifting is generally caused either by the changes in the physical properties of the materials being processed, or by the variations of mechanical conditions of the machine. The lateral motion of a web system is usually ignored1 however, to achieve high productivity and improve the product quality, the lateral position has to be controlled. A theoretical model is presented in this paper based on the assumption that the moving web is a beam with a very small, but finite, thickness. This leads to a sixth-order transfer function with a time delay. The time delay is the result of the non-colocation of the sensor and actuator. Since there are many sources of errors, a robust control technique is used to control the web lateral shifting. Several controllers were synthesized using the μ -synthesis control design technique which accounts for modeling imperfections as well as the time delay. Robust performance was achieved with the designed controllers and the closed-loop response was acceptable even under extreme conditions.