Study On The Key Technologies Of The Multi-level Mixed Model Product Line Dynamic Scheduling System

The background of this dissertation is the multi-level mixed model product line in automobile plant. According to the sequence from single objective scheduling to multi-objective scheduling, from static scheduling to dynamic scheduling, a detailed study on the scheduling system framework model, objectives, strategy and algorithm for the multi-level mixed model product line scheduling problem, and method for the multi-objective scheduling decision making problem is carried out. The main contents and achievements of the dissertation are as follows:For the requirements of automobile plants, the mathematics model of the scheduling problem is presented in details under the considering of product cost, JIT and utility ratio of equipment etc. And a step optimized solution, which through the combination of multi-objective optimization and secondary optimization, is designed to solve the problem. At first an improved ant colony optimization (ACO) algorithm with two layers searching space is designed to solve the scheduling problem which minimize the paint purge times in paint shop and keep the constant usage of part in assembly shop. To the problem that the product order couldn't be executed correctly in some automobile plant due to ignoring the storage constraint, a resequencing algorithm with limited flexibility is designed based on the detailed analysis of kinds of storage structure. At last, a useful route control approach is presented, which can be used to address the product routing problem. Simulation result shows that the proposed strategy and the algorithm are effective and useful.A periodic and event-driven scheduling model is presented to deal with the changing mixed-model manufacture environment. The schedule strategy is designed to deal with the rush order or rework. Based on the two layers searching space ACO algorithm, a hierarchy searching space ACO algorithm is designed to address the multi-objective scheduling problem under structure constraint of multi-level mixed product line. Simulation results show that the proposed model and algorithm are feasible to the problem.To the multi-objective scheduling decision making problem, two solutions be presented, one is fuzzy analytic hierarchy process (F-AHP) and entropy theory method and the other is assistant objective decision making method. The first solution use F-AHP to get the subjective weight from the fuzzy information of decision-maker, and use entropy theory to get the objective weight from the result matrix. To the second solution, the conveyor stoppage time is used as the assistant object to the decision making problem. At first, a mathematics model of conveyor stoppage problem under the concept of extendable region(ER) is presented. Then combined with the ER concept, several useful properties, such as, necessary and sufficient condition that a conveyor stoppage occurs, lower and upper bounds of the objective function are described. And an algorithm for calculating the conveyor stoppage time is designed. Simulation result shows that the algorithm is effective, and the ER has important effect to the conveyor stoppage time.Finally, based on the Build Control System of Nanjing MG automobile plant, a multi level mixed-model product line scheduling prototype system is developed. Through the test run in Nanjing MG automobile plant, it verifies the feasibility of this system.