Research On Economic Model Predictive Control For The Molding Process With Large Time Delay

Molding industry is an important part of modern manufacturing industry,which is of great significance to the development of economy and society and the improvement of comprehensive national power.However,the time-delay phenomenon of molding system is prevalent.Meanwhile,the internal mechanism structure of molding system with external disturbances is complex.These lead to molding control facing problems such as system nonlinearity,multi-objective conflicting optimization,time delay,and external disturbances,which bring challenges to the stable control of molding systems.In addition,it is crucial to optimize the economic performance of the molding system.Therefore,based on the economic model predictive control(EMPC)algorithm,this thesis simultaneously considers the stability and economy of the molding system,adopts a Pareto multi-objective optimization method to deal with the conflicting multi-economic objectives,and accommodates the time delay and disturbance problems of the molding system in combination with a dual-mode control method.Finally,a experiment of a cooling molding process demonstrates the effectiveness and superiority of the proposed method to cope with the above multiple problems.The specific research work and results of this thesis are as follows.(1)For the modeling problem of molding system mechanism,a water bath cooling molding dynamic model is constructed,which leads to the time lag,nonlinearity and disturbance problems affecting the molding control effect,and lays the model foundation for the subsequent system economic model prediction and control research.(2)For the problems of strong nonlinearity and conflicting multiple objectives of the system in the molding process,a Pareto compromise multi-objective EMPC algorithm is proposed.This thesis combines the characteristics of the Pareto optimization algorithm to compromise multiple conflicting economic indicators with the ability of the EMPC algorithm to cope with nonlinear systems,which improves the convergence speed of the multi-objective optimization algorithm and reduces the steady-state oscillation of the closed-loop system compared with traditional optimization methods.Meanwhile,the stability of the proposed algorithm for nonlinear system control and its superiority in optimizing multiple conflicting economic indicators problems are demonstrated through theoretical analysis and numerical simulation experiments.(3)Further considering the coexistence of external disturbances and input time delay problems with system nonlinearity and multi-objective optimization in the molding process,a dual-mode EMPC method for bounded disturbances and large time delay is proposed.In this thesis,the EMPC algorithm its combined with the dual-mode control method to cope with disturbances;a new feedforward state compensator based on the nominal model is designed to accommodate the adverse effects of input time delays on the process control system by using the control capability of dual-mode control,which realizes the simultaneous treatment of strong disturbances and large time delay problems by the control algorithm.Finally,the comparison of experimental results under simulation conditions with different time delays and variable disturbances verifies that the proposed algorithm still has strong effectiveness and superiority...