Adaptive Sliding Mode Control For The Oscillation Displacement Sysrem Of Continuous Casting Mold Driven By Servo Motor

The continuous casting mold is an important equipment for solidification and forming of molten steel.The oscillation of the mold can prevent the steel water from adhering to the mold,which can effectively improve the surface quality of the slab.The non-sinusoidal oscillation technology of continuous casting mold has been recognized as one of the key technologies in the development of continuous casting.Whether the mold can oscillate according to the given non-sinusoidal waveform is an important factor affecting the surface quality of the slab.This paper mainly studied the high-precision tracking control of the continuous casting mold oscillation displacement system driven by the servo motor with time-varying disturbance and uncertain parameters.The main work of this paper is as follows:Firstly,to ensure that the servo motor rotates in one direction to save energy,a mapping function from the angle of eccentric shaft to the displacement of the mold is introduced by the piecewise function method,thus the mold displacement tracking control problem is transformed into the problem of eccentric shaft angle tracking control,which simplifies the complexity of controller design and lays a foundation for subsequent research.Secondly,aiming at the time-varying load torque existing in the system and considering the unmeasurable condition of the motor speed,a backstepping sliding mode controller based on extended state observer(ESO)is designed.Firstly the ESO is constructed to estimate load disturbance and unmeasurable state,then backstepping controller based on ESO and sliding mode control method is designed,and disturbance estimation value into the controller is introduced to compensate to improve output tracking control accuracy.Thirdly,considering the existence of parameter uncertainty in the reduction ratio,time-varying load disturbance and eccentric shaft mechanical zero offset in the system,The time-varying load disturbance and the parameter uncertainty can be regarded as the matched disturbance and mismatched disturbance of the system respectively.For the oscillation displacement system with matched disturbance and mismatched disturbance,a sliding mode control method based on ESO is designed.Two ESOs are used to estimate the matched disturbance and mismatched disturbance of the system respectively,and a new sliding surface is designed based on the disturbance estimations.Under the new controller,the anti-interference ability of the system is greatly improved.At the same time,the dither phenomenon is effectively reduced.Finally,an adaptive backstepping sliding mode control method based on ESO is proposed for continuous casting mold displacement tracking system with mismatched disturbances.This method uses the backstepping technique and transforms the mismatched disturbances into matched disturbances to process,and introduces the upper bound of the estimation error of the ESO estimation by the adaptive gain,so as to reduce the influence of the ESO estimation error on the system control accuracy,thereby realizing the high-precision tracking of mold displacement.At the same time,this method relaxes the limitations of existing methods on mismatched disturbances.