Design of H_∞ Robust Controller for Electro-hydraulic IGC System of Four-high Mill

The two degrees stand-roll system model of four-high mill was built, the electro-hydraulic IGC servo system was further built. The closed loop controller of roll gap was designed with the H∞ mixed sensitivity robust control theory based on simplified algorithm because of the parameter uncertainty of the IGC model. Simulation results and comparison with the effect of PID control show that the robust controller designed has better disturbance attenuation performance for parameter uncertainty and external disturbance. The dynamics performances and stability of the electro-hydraulic IGC system were improved significantly.