Research On Inventory Control Models For Non-stationary Stochastic Demand

Since the advance of science and technology as well as the development of economic globalization, enterprises are faces more and more external uncertainties, one of them is demand uncertainty. Influenced by technology condition, environmental changes, promotion policies and management styles, the demand of many products are non-stationary and stochastic, the distribution of which may change rapidly.So far, there are two main inventory control policies for non-stationary stochastic demand. One is to treat non-stationary stochastic demand as stationary stochastic demand, the other is to treat non-stationary stochastic demand as non-stationary deterministic demand. When the demand changes rapidly and fluctuates a lot, the above two policies are not applicable. There lack of effective inventory control methods.The background of this thesis comes from non-stationary stochastic inventory control problem of manufacturing business. The inventory control policy is studied from the perspective of combining theory with practice, with the aim to develop new inventory control policies, which can be applied to general problem with service level constraint and without any limitation on lead time.This paper is devided into 4 parts including 6 chapters, the main content are summaries as follow:PartⅠincludes the first chapter and the second chapter. The first chapter is the introduction of the whole paper and the second chapter is the literature review. Chapter one introduce the background and significance of the paper, the main research idea, the framework and the innovation. Chapter two review the current study from three aspects, which is inventory control for stationaty stochastic demand, inventory control for nonstationaty deterministic demand and inventory control for nonstationaty stochastic demand.PartⅡis the main body of this paper and includes the third chapter and the forth chapter. Chapter three is inventory control for non-stationary stochastic demand and chapter four is inventory control based on rolling plan for non-stationary stochastic demand. In chapter three, a static-dynamic uncertainty strategy is proposed for non-stationary stochastic demand with service level constraint and non-zero lead time. The order quantity of this strategy depends on the demand realization. In chapter four, considering the rolling demand forecasting, a static-dynamic uncertainty strategy based on rolling plan is proposed. This strategy implements only the decision of the first period. It then use the rolling horizon approach in the next periods when the inventory status is revised and demand forecasting is updated. This strategy can adjust the order point as well as the order quantity.PartⅢis emprical research including chapter five. According to the investigation of the specific enterprise, the products are classified into three types based on product demand characteristic. Then, two models of static-dynamic uncertainty strategy and tho models of static-dynamic uncertainty strategy baesd on rolling plan are simulated to manage inventory and the performance is analysed.PartⅣis the summary of the whole paper including chapter 6. It summarized the main work and gives some useful suggestions for future research. Main contributions of this paper are briefly summarized as follow:(1) A new general static-dynamic inventory control policy for non-stationary stochastic demand is developed with the service level constraint and nonzero lead time, and the order quantity can be adjusted based on demand realization.(2) When studing inventory control policy for non-stationary stochastic demand, special delivery time due to cost accounting is considered, thus the sevel level constraint is revised.(3) Since the control parameters of static-dynamic uncertainty strategy are not optimal after demand realizes, a new inventory control policy based on rolling horizon approach is studied.