Research On Tracking Control Of Vibration Displacement Of Continuous Casting Mold Driven By Motor With One-direction Rotation Constraint

As the key equipment of steel production,the tracking control precision of vibration displacement of continuous casting mold(CCM)is of great significance to improve the slab quality and casting speed.This paper focuses on the vibration displacement control system of CCM driven by servo motor,and the system can realize non-sinusoidal or sinusoidal vibration of the mold through continuous rotation of one-direction and variable angular speed of servo motor,and driving the reducer,the eccentric shaft and connecting rod mechanism.However,there are some difficulties in the system,such as the process constraint of servo motor with one-direction rotation,the non-uniqueness of the inverse solution of nonlinear periodic function between servo motor angular displacement and vibration displacement,the control current saturation control of servo motor,time-varying load disturbance,parameter perturbation and other uncertainties.These above problems not only reduce the control accuracy of the vibration displacement system to a certain extent,but also affect the improvement of slab surface quality.To solve the above problems,this paper takes the vibration displacement control system of CCM driven by servo motor as the research plant,and the tracking control of vibration displacement system of CCM is studied by using compound control method,active disturbance rejection control(ADRC),sliding mode control(SMC)and other control methods for improving the control accuracy and robustness of the system.Firstly,in view of the process constraints of one-direction rotation of servo motor and the non-uniqueness of the inverse solution of nonlinear periodic function in the forward channel of the system,a method of transforming vibration displacement control into servo motor angle control is proposed.Furthermore,aiming at the problems of time-varying load disturbance and other uncertainties in the system,the robust control method based on extended state observer(ESO),and the feedforward and feedback compound control method based on fractional power ESO are completed to achieve vibration displacement tracking control of CCM,respectively.Secondly,to tracking control problem of mold vibration displacement under the process constraints of one-direction rotation of servo motor and the operating changes of mold vibration frequency and time-varying load disturbance,a method of parameter self-adjusting active disturbance rejection controller based on ESO is proposed based on the discrete model of mold vibration displacement.In detail,a third-order discrete ESO is utilized to estimate the comprehensive item composed of time-varying load disturbance and other uncertainties,and the observed value is introduced into the ADRC controller for compensation.As the same time,the parameters of ADRC are optimized by genetic algorithm based on mismatched sorting.At last,simulation studies are carried out to verify the effectiveness of the proposed method.Thirdly,to be directed against the current input saturation problem of the servo motor of the mold vibration displacement system,and the system uncertainty problems of time-varying load disturbance,parameter perturbation and so on,a hyperbolic tangent function is utilized to approximate the saturation term of the control current input,and subsequently an adaptive finite-time super-twisting sliding mode controller(STSMC)based on ESO and a prescribe performance backstepping controller based on ESO are designed to improve the vibration displacement tracking control accuracy and robust stability of CCM system,respectively.Finally,aiming at the process constraints of one-direction rotation of servo motor and time-varying load disturbance in the system,a compound control strategy of CCM vibration displacement based on feedforward control and feedback control is proposed.At the same time,aiming at the parameters of feedback controller are difficult to be adjusted,an ameliorated moth-flame optimization(AMFO)algorithm is designed to optimize the parameters offline.After that,the optimized controller is used in system simulation and laboratory experiments to verify the effectiveness of the proposed control method.