Analysis of the self-excited vibration and dynamics modification for rolling mills

The rolling mills are the complex mechatronics systems controlled by computer. Improper design and some other reasons may result in continuous vertical vibration of the mill stand. This vertical vibration that badly influences product quality is occurred due to self-excited vibration of the hydraulic AGC (auto-gauge control) system. This paper provides an integrated method to analyze design defects, and avoid self-excited vibration of the hydraulic AGC system effectually. This method includes synthesized online measurement and test, system identification, experiment modal analysis, combination modeling and simulation, and structural dynamic modification etc. There is different delay-time in identified mathematic models of mill hydraulic AGC system for different operation conditions. When delay-time oversteps a limit, self-excited vibration is occurred. The long delay-time can arise due to improper design of the mounted structures for mill roller gap displace transducer. Through dynamics modification of the mounted structures, the delay-time of displace feedback signal is reduced to minimum in the engineering case of this paper. And self-excited vibration is eliminated.