An optimized variable structure control for hydraulic AGC of cold rolling mill

The hydraulic automatic gauge control (AGC) of cold rolling mill is directly related to the quality and effectiveness of cold rolling aluminum sheet strips. Traditional PID control becomes difficult to satisfy the necessity of improving the control performance of cold rolling mill. A new variable structure control (VSC) based on a co-ordination optimization algorithm has been developed. Both steady state error and control switching frequency are used as the system coordination performance indexes in the co-ordination optimization, while the tuning rate of boundary layer width is employed as the optimized parameter. Based on steady state error in VSC, an optimized boundary layer width tuning rate is designed and added to the nonlinear control term of VSC. Simulation experiment results applied to the control of a hydraulic AGC system show the comprehensive superiority of dynamical and static state performance by using the proposed controller over that of by using VSC without optimized boundary layer width tuning rate. Chattering elimination and high-precision control are successfully coordinated in the hydraulic AGC system of cold rolling mill. The thickness precision of cold rolling aluminum strips may be improved.