Research On Torsional Vibration Control Strategy For Rolling Mill Main Drive System With Unknown Parameters

In the steel industry,the rolling mill main drive system is a vital part of the rolling equipment,whose frequent torsional vibration phenomenon directly affects the quality of steel products.The dynamic characteristics of the rolling mill main drive system and the quality of steel products can be improved by using effective control strategies to suppress torsional vibration.In this paper,we present the following studies for the vibration problem of the rolling mill main drive system.Firstly,we establish the mathematical model of the rolling mill main drive system.According to the concentrated mass method,the rolling mill main drive system can be simplified by the motor,roll through the elastic connection shaft connected to form a twodegree-of-freedom system.On this basis,considering the load disturbance,the mathematical model with matched uncertainty of the rolling mill main drive system is established;we give a continuously differentiable saturation function to approximate the control input saturation characteristic of the rolling mill main drive system,translating the latter into the matched uncertainty and unknown time-varying gain in the system.Then,comprehensively considering the presence of control input saturation,actuator faults,sensor measurement error,and parameter perturbation,the rolling mill main drive system mathematical model with unmatched uncertainty and unknown time-varying gain is developed.Secondly,to address the problem that a rolling mill main drive system is prone to torsional vibration under the impact of load disturbance,this paper proposes a fractionalorder continuous nonsingular fast terminal sliding mode control method based on an adaptive finite-time composite disturbance observer(AFTCDO-FOCNFTSMC).To compensate for the load disturbance,AFTCDO-FOCNFTSMC uses an adaptive finite-time composite disturbance observer(AFTCDO)as the load disturbance estimation unit,which improves the estimation accuracy and rate.AFTCDO has the capability to estimate steptype disturbances by a novel two layers adaptive law and reduces the requirements to be satisfied by the load disturbance.Then,based on the AFTCDO reconstructing the load disturbance information,the fractional-order operational structure is applied to the continuous nonsingular fast terminal sliding mode controller to enhance the anti-disturbance capability of the latter,thus suppressing the load-induced torsional vibration while improving the convergence speed of the controller.Again,AFTCDO enhances the antidisturbance capability of the fractional-order continuous nonsingular fast terminal sliding mode controller(FOCNFTSMC)and suppresses its control input chattering.The simulation results verify the superiority of the proposed AFTCDO-FOCNFTSMC in suppressing torsional vibration.Finally,we investigate an anti-saturation fault-tolerant adaptive torsional vibration control method with fixed-time prescribed performance for the rolling mill main drive system,which is affected by control input saturation,actuator faults,sensor measurement error,and parameter perturbation.Based on the established mathematical model,an error transformation model of the roll speed tracking is constructed by the equivalent error transformation method.According to the error transformation model,a barrier Lyapunov function(BLF)and a novel adaptive controller are studied to ensure that the roll speed tracking error always evolves inside an asymmetric constraint.Through the above processes,the proposed control method achieves fixed-time prescribed performance control for the rolling mill main drive system in presence of control input saturation,actuator faults,sensor measurement error,and parameter perturbation,which has good torsional vibration suppression.Furthermore,numerical simulations verify the effectiveness and superiority of the proposed control method in suppressing the rolling mill main drive system torsional vibration.