Research On Modeling Of System Behavior Of Complex Assembly Lines During Transients

The modern manufacturing mode has transformed into product variety and the small-batch production.Manufacturers are generally pursuing more flexible assembly systems to delivery customized products to the market.The organization and the elemental factors of assembly systems have become more complex.The transient behavior of production systems refers to the system performance before reaching the steady-state.Compared to the stable performance measures at the steady-state,the transient behavior changes dynamically over time.Since the measures of transient system behavior are usually less than the steady-state measures,the production system has an unavoidable production loss during transients.Due to the highcoupling and uncertainty of complex assembly systems,the duration of transients is much longer than other manufacturing systems,which contributes to a significant production loss.Therefore,it is crucial to perform the transient analysis of complex assembly systems.In this paper,we propose a description model of transient states of complex assembly systems,based on which the modeling method of transient behavior for homogeneous assembly systems and inhomogeneous assembly lines are proposed,respectively.The content of this thesis is summarized as follows:1)A description model of transient states of complex assembly systems is established,which is the basis of assembly system modeling.First,the origin and characteristics of manufacturing complexity in complex assembly systems are explored considering the assembly process.Second,the measurement of process complexity is built through the analysis of the standard assembly steps.This model can evaluate the uncertainty during assembly,based on which the distribution of the reliability model for each workstation is formulated.Third,the representation method of transient states of complex assembly systems is defined,based on which the transient state scale is estimated theoretically.Inspired by the Markov process,the description model of transient states of complex assembly systems is proposed.The model can represent the mapping relationship of numerous transient system states.2)A new modeling method of transient behavior for complex homogeneous assembly lines is proposed.First,the general layout and the modeling consumptions of complex homogeneous assembly systems are introduced.Second,according to the organization of the complex assembly line and the principle of system running,the functional states of workstations are defined.The mapping relationship of transient system behavior is formulated from the perspective of buffer states.Third,the reverse analysis of transient states of workstations is conducted considering the transferring of transient buffer states.The mapping matrix representing the transmission of transient system behavior is built.Forth,the mathematical model of transient behavior of homogeneous assembly systems and its solution are introduced.The feasibility of the solution is proven theoretically.The performance of the presented modeling method is illustrated through the numerical studies.3)A new modeling method of transient behavior for complex inhomogeneous assembly systems is proposed.First,the general system layout and the modeling consumptions of complex inhomogeneous assembly lines are introduced.The principle of the split-based analysis is explained by transforming the inhomogeneous assembly system as a homogeneous one.Second,the virtual homogeneous assembly system is constructed,which not only can inherit all the production attributes of the original inhomogeneous system,but also satisfy the requirements of Markov process.The functional states of workstations are re-defined in the transformed system.Third,the reverse analytical model of transient states of workstations is executed considering the transferring of transient states of buffers,based on which the mapping matrix representing the transmission of transient system behavior is formulated.Forth,the mathematical model of transient behavior of inhomogeneous assembly lines and its solution are introduced.The existence of the solution is proven theoretically.The feasibility of the modeling method is illustrated through the numerical cases.