Research On Tracking Control Of Vibration Displacement Of Continuous Casting Mold Under The Constraint Of One-Direction Rotation Of Motor

Continuous casting mold is the casting equipment in the process of iron and steel production.Non-sinusoidal vibration of the mold is one of the important technologies to develop high-efficiency continuous casting and improve production efficiency.Continuous casting mold driven by a servo motor is a new non-sinusoidal vibrating device.The servo motor rotates in one direction with varying angular velocity to drive the mold vibrated in non-sinusoidal form through mechanical transmission mechanism.The device has the advantages of compact structure,energy saving and easy maintenance.However,there are some problems in the vibration displacement system,such as the non-linear periodic function relationship between motor angle(or speed)and vibration displacement of mold,constraint of one-direction rotation of motor(the speed control value is always positive and has an upper limit value,which has asymmetric saturation characteristics),the fast time-varying load and system uncertainties,which have a negative impact on the stability and accuracy of the control system.Therefore,this paper focuses on the tracking control of the vibration displacement of mold with non-linear periodic function and the constraint of one-direction rotation of motor.Firstly,aiming at the constraint problem of one-direction rotation of motor and non-linear periodic function in the forward channel of mold vibration displacement system,the feed-forward and feedback compound control based on the reference mold vibration displacement and compound control scheme considering feedforward compensation through disturbance observer are put forward respectively.In the feedforward-feedback control scheme,the feedforward control is realized by constructing the nonlinear function relationship between the expected motor speed and the expected mold vibration displacement with its first derivative,and the feedback control is realized by repetitive PI controller.On this basis,the disturbance observer is used to estimate the influence of the system uncertainty on the vibration displacement of the mold,and it is converted into the speed difference for feedforward compensation to improve the robust stability and tracking control accuracy of the mold vibration displacement system.Secondly,in order to solve the problem that the load torque of servo motor has a large fast time-varying load due to the effect of gravity when the mold vibrates up and down,the active disturbance rejection controller(ADRC)and the sliding mode ADRC are designed respectively based on the one-to-one segment function relationship between mold displacement and angle displacement of servo motor.An extended state observer(ESO)is used to estimate the system states and overall uncertainty,and a parameter estimator is used to estimate the time-varying parameters in the ADRC controller.A hybrid approach law,which combines power approach law and constant speed approach law,is used to reduce the approach time of sliding mode surface,and construct the quantitative relationship between the approach law parameters and the uncertainty.The effectiveness of the two methods is verified by simulations.Thirdly,in view of the nonlinear periodic function from motor speed to mold vibration displacement in the forward control channel of the system and the time-varying load and system uncertainty,a sliding mode control scheme considering the one-direction rotation constraint is proposed.In this scheme,the tracking error of mold vibration displacement is transformed into the corresponding angle error of servo motor.Based on the switching function,an observer is designed to estimate the overall uncertainty,and then a sliding mode controller is designed to achieve the uniform and bounded tracking error of mold vibration displacement.Finally,the main contents of this paper are studied by the simulation vibration device of continuous casting mold built in laboratory,based on the SIMOTION D425 controller.According to the characteristics that the servo controller integrates the controllers of motor speed loop and current loop,this paper mainly studies the feed-forward and feedback compound control method based on the reference mold vibration displacement under the constraint of one-direction rotation of motor.