Research On Adaptive Control For Hydrualic Servo Position System Of Cold Strip Rolling Mill

Hydraulic servo system is widely used in many industrial applications because of its small volume, light weight, fast response, et al. However, parameter perturbation, nonlinear term, un-modeled dynamics which exist in the control system restrict the close loop control system from improving the control performance. The theory of adaptive control of hydraulic servo systems is studied in this thesis to improve the quality of the steel strip products.Primarily, a mathematical model of the plant is established based on the working condition of the hydraulic servo position system. During the process of hydraulic screwing down, there exists parameter jump due to the fact that the piston rod extends to touch the load. A multi-model set is established based on the simplified math model of the hydraulic servo position system..Next, robust H^control method based on Backstepping is proposed to control the hydraulic servo position system with parameter perturbation and external disturbance to make the tracking error to satisfy the robust H∞performance. Thus the anti-interference performance of the system is improved. The uncertain parameter in the model of the system is replaced and a proper Lyapunov function is constructed to solve the nesting problem caused by the mutual inclusion of the control law and parameter adaptive law. Simulation results verify that the proposed controller enable the output of the close-loop to track the given signal at a faster speed by contrast with PID control method.Then multi-model switching theory is used to deal with the influence of parameter jump. A multi-model set is built according to different working conditions of the hydraulic servo system. Dynamic surface control method is combined with Backstepping approach to design the controller of each subsystem, through which the design process is simplified. The external disturbance is estimated through adaptive method. The stability of the close-loop is proved based on mutual Lyapunov function.In the end, in view of the problem of input saturation and parameter jump, the controller of the hydraulic servo position system is designed on the basis of multi-model switching adaptive variable structure method. The stability of the close-loop is guaranteed under the influence of input saturation and parameter jump. The fast speed, small tracking error and good robustness to parameter variety and external disturbance is proved by simulation results.