On the dynamic characteristics and control of the ring rolling process

Abstract

In this thesis the dynamic characteristics of the radial axial ring rolling process were investigated, and an effective control algorithm for this process were presented. The investigations were performed for the growth of rolled ring and the relationships between the roll movements and the forming zone geometries brought about by these motions. The dynamics of the forming actions and guide roll motion were also analyzed. The results of this analysis shows that the ring rolling process reveals nonlinear characteristics and parameter variations in the dynamics. During the forming actions the yield shear stress of ring material which critically influences the deformed state varies considerably with the rolling time. The resulting yield shear stress variation affects the resultant forces applied to the pressure roll and conical roll, resulting in thevariation of these roll motions. In the guide roll dynamics, the ring stiffness is affected by the change of ring geometry and also largely uncertain during the rolling process due to the temperature variation of rolled ring. In order to deal with this parameter variations an adaptive controller for the pressure roll and concial roll motion has been developed to improve the final quality of the rolled ring products. This controller takes into account the relationships between the roll motions and the forming zone geometries as well as the uncertain parameters in the dynamics which arise from the yield shear stress variation. A similar adaptive algorithm has been applied for the force control of guide roll, taking into consideration the ring stiffness variation. In this adaptive control system, the ring stiffness is estimated by the force error signals, and the feedback gain in the force feedback block is changed by the force errors and current ring geometry. Simulation studies were performed to see the effectiveness of these controllers. The simulation results show that the process controller with the developed adaptiv...