Hierarchical Optimal Production Control Policy For Production Systems In Processing Industry

With the rapid development and popularity of computer network techniques and digital communication techniques, information can be communicated in an increasingly convenient way in industrial enterprises, among each level ranging from production equipment to management scheduling. Optimal production control for production systems, as the core of the production planning and management, is paid priority to. Over the past ten years or so, a common paradigm for the analysis of the production control problem has been a fluid model characterizing parts production, punctuated by random jumps either in the production capacity (due to equipments failure or repair) or in the demand for products. But in past lectures on production control, most of which focus on the optimal production control for the flexible discrete manufacturing systems, though some features of the object have already been close to the nature of production systems in processing industry when the flow rate model is used, yet the optimal production control is mostly discussed based on the nature of discrete manufacturing systems. Hence the conclusion gotten by those lectures could not be directly applied to the production systems in processing industry. There are few works focused on the hybrid nature of the production systems in processing industry. Moreover since processing industry plays an important role in national economy, our work on its optimal production control is of practical significance.In this thesis, continue flow model, which is very meaningful, is used to describe the production systems in processing industry. Production systems in processing industry are studied being a set of failure-prone equipment. N different types of products can be produced by the production system consisting of a set of unreliable equipment, with only one at any given time. Moreover, a setup (with setup duration and setup cost) is required if production is to be switched from one type of product to another. And the equipment is subject to random failure and repairs. The objective of the optimal production control is to minimize the whole costs of setup, production, and inventory. The decision variables are a sequence of setups and the production plan. When preventive maintenance is considered, themaintenance cost must be introduced to the objective function and optimal maintenance rate must be included in the decision variables.Considering the nature of the production systems in processing industry and practical engineering, this thesis aims at studying and discussing optimal production control for production systems, based on the hierarchical rate control policy. The main contributions of this thesis are as follows: The understandings of production control for production systems are systematically set forth; the basic contents of production control are introduced; important lectures on the production control are classified and summarized in detail; the applications of production control in processing industry, especially based on flow rate model, are analyzed; the significance of the research in this thesis is pointed out. Based on the flow rate model, the optimal production control policies for flexible production systems and non-flexible production systems are discussed respectively in consideration of the aging of the equipment or preventive maintenance. A new framework of hierarchical production rate control policy for production systems with infrequent setup is constructed, and a receding optimal algorithm is given based on the critical events. Dynamic programming equation of production control for static optimization is put forward by way of introducing new hierarchical control policy. According to practical engineering, a new system state variable which is meaningful is defined, and the time horizon of the objective function is redefined. In this thesis the optimal production duration is introduced, which is different from the hedging point defined in past lectures and is more meaningful than the...