Modeling Of Material Handling System Based On Modelica And Balance Analysis Of Mixed Flow Assembly Line

As an indispensable part of the manufacturing field,the material handling system not only occupies a large amount of industrial production costs,but also obviously affects the balance of the production system.It has become more and more negligible during the optimization of the production system.On the other hand,the material handling system is a typical discrete event system,and it is difficult to describe and calculate with a simplified mathematical model.Therefore,this paper adopts the discrete event system simulation modeling idea based on the system modeling language Modelica,models and modularizes the basic objects of the material handling system and constructs a reusable and extensible material handling model library to support rapid establishment of system models,simulation and design verification of optimization schemes.First of all,this article classifies the basic objects of the material handling system according to the functions and derived relationships to determine the common components of the material handling library.The applicability of finite state machine modeling to material handling system is analyzed.The basic theory of finite state machine,the state machine component expressed by Modelica and the Modelica grammatical structure support for discrete modeling are introduced.Based on the functional principle,the common state and transition logic of typical components such as material storage area,conveyor belt,and AGV transportation are analyzed.The state transition diagram is drawn and implemented using the state machine component.Modelica programming defines the key algorithm logic to complete the construction of the material handling model library.The system simulation model established by the model library provides a verification platform for the simulation optimization schemes to be studied later.Secondly,taking the material handling system of a vehicle body-in-white mixed flow welding line as a research object,the welding production process and material handling process of the system are analyzed.Combined with the production situation,the material distribution model used to control AGV scheduling is constructed using the material handling model library components,and then the process of establishing the system simulation model is described in detail from the aspects of model layout,production process,and simulation parameter settings.The simulation results are analyzed in terms of system status,welding line balance,and material demand waiting to evaluate the overall performance of the system.Finally,this paper analyzes the necessity of system optimization for a reasonable production sequence for the problem of assembly line imbalance found in the simulation of the material handling system of the mixed flow welding line.The necessity of optimization based on simulation model is determined by the complexity of assembly work affected by material handling in actual production.A multi-objective optimization model is established with the minimum function of idle time and overload time as the objective function,the production sequence as the optimization variable,production process,material handling rules and AGV control scheduling as constraints.An optimization method using genetic algorithm combined with simulation model is proposed,and the genetic algorithm chromosome coding is designed to save simulation optimization time.The optimization plan is imported into the model for re-simulation,and the simulation results before and after system optimization are compared to further verify the optimization effect.The research results show that the discrete event system simulation modeling ideas adopted in this paper are feasible,and they have achieved good results in the simulation and optimization of material handling systems.They can provide reference ideas for the modeling and simulation research of discrete event systems like material handling systems in industrial enterprises.