Control Variable Parameterization Based On Optimal Control Method Of Injection Speed In Injection Molding Process

Plastic products frequently appear in People’s Daily life and many industrial production.Injection molding machine is one of the main production equipment to complete plastic products production.Whether the controller design of injection molding machine is good or not and whether the control parameters are correct or not determines whether the plastic products can reach the production standard.At present,the traditional control system used in injection molding machine needs manual adjustment,which is highly demanding for the operator.The operator needs to repeatedly debug the control parameters according to the actual engineering experience and the external environment of the site,until the ideal control effect is achieved.But even so,after setting the best parameters of the control system,once the injection molding machine is fundamentally changed by external interference,such as pressure valve adjustment and cleaning,heating ring replacement,in order to ensure the effectiveness of the control system,it must be adjusted according to the needs of the best parameters.The quality of controller parameter setting of injection molding machine is affected by objective factors such as external environment disturbance and subjective factors of equipment adjuster,not only the process of control system parameter adjustment is not intelligent and efficient,but also the final control parameters can not be adjusted accordingly with the change of external disturbance,and the self-adaptability is poor.This thesis mainly studies the optimal control of injection speed in the process of injection molding.The method of parameterization of control variables is applied to the optimal control problem to improve the autonomy and adaptability of the system.By obtaining the optimal solution of the control system,the optimal trajectory tracking of injection speed is realized.The innovation of this thesis is to avoid the manual parameter adjustment in the traditional control system of injection molding machine,and to use an off-line parameter adjustment mode instead of manual online parameter adjustment,which improves the efficiency of parameter adjustment process and ensures the effectiveness and accuracy of the control system.The main contents of this thesis are as follows:（1）The existing injection molding and system control schemes at home and abroad were investigated.The injection screw speed control of injection molding machine was selected as the research point,and the advantages and disadvantages of injection speed control algorithms of different injection molding machines were summarized.（2）The work flow and system structure of injection molding machine are studied,and the characteristics and control system of injection speed are analyzed.Taking all-electric injection molding machine as the research object,simple modeling of servo motor is carried out,and the dynamic system model of injection speed is obtained.（3）Study the optimal control theory and its solving algorithm,mainly expounds the standard expression of the optimal control problem,and how to use the control parameterization method to approximate the original optimal control problem,so as to get the approximate optimal solution.（4）Control variable parametric method was applied to the injection speed of the optimal control problem,based on the optimal control problem of building transformation and nonlinear problems,get the injection speed optimal control problem of standard form,and based on the control variable parametric method,using the method of sensitivity for state variables and objective function of the gradient information,then the optimal control parameters.（5）Numerical simulation verifies that for different injection speed tracking curves,good control accuracy and tracking effect can be achieved by solving them through the parameterization method combined with control variables proposed in this thesis.