Research On Key Technology Of Erection Operation Scheduling On Dock In A Shipyard

Erection operation scheduling on dock (EOS), differing from both job-shop and flow-shop, is a kind of new type one, whose special and complex characteristics include large scale, existing occupying multiple machines simultaneously, unbalance load of machine. And its production mode is order oriented style. Under the complex and change chaos circumstance, the control system of EOS is nonlinear. The production scheduling and control methods, based on traditional production operation theory, can't meet the need of the control of EOS. In order to solve this problem, supported by the Key Item Program of S&T Committee, Shanghai City, China project'Research on material flow in shipbuilding enterprise'(Grant No.04DZ11004), the thesis'topic is research on the intelligent coordinated scheduling technologies of EOS and its key technologies. The paper discussed from different points, and expected gain breakthrough in theory, method, supporting technologies and engineering application. The following are the main works in this paper:(1) Block Erection in Shipyard is a complex process. A method based on sharing synthesis of timed colored Petri net for modeling of block erection process in shipyard is proposed. A min-max algebra algorithm is used to calculate the time. The information of erection constraints, facilities, space and time consuming are involved and expressed clearly in this model. The approach can be employed to model the erection process of single vessel or multi-vessel. Finally, a case study of the modeling and optimization of erection process of two 74,500 DWT bulk carriers is given and the result shows that this modeling method is effective.(2) A method based on modified genetic algorithm for optimization of block erection process is proposed. Firstly, the constraints of erection network and the production ability of block are analyzed and the objective function to minimize the makespan on dock is given. Then, a modified genetic algorithm is used to optimize this problem, and the coding approach and a crossover operator are introduced in details. Finally, a case study of the optimization of erection process of a 74500 DWT bulk carrier is given and the result shows that this optimization method is effective. The convergence rate of modified genetic algorithm with integer coding was analyzed. Firstly, a diversity of population of genetic algorithm is defined which can formally express the degree of premature for this kind of genetic algorithm. Then the formalized equation is given about the relationship between diversity and crossover rate, mutation rate and population size. Finally, a simulation experiment about block assembly sequence scheduling in a shipyard is introduced to verify the above opinions.(3) A new Lagrangian Relaxation approach is developed to schedule the erection operations to minimize the inventory cost of blocks. It corresponds to a parallel machine problem with the precedence constraints of tasks, the capacity constraints of machines and the situation that some tasks must occupy multiple machines simultaneously. The objective is to minimize the weighted total completion time. A mathematical formulation of the problem is presented firstly. Then the task precedence constraints rather than crane machine capacity constraints are relaxed by Lagrangian relaxation method and the subgradient method is used to solve the Lagrangian dual problem. Finally the results are modified by some heuristic operation. A practical example of container vessel that includes 65 blocks is solved by the proposed approach, and the results show that the Lagrangian relaxation method is able to solve industrial-dimensioned problems within reasonable time and accuracy.(4) The disturbance types of erection time were analyzed and a rescheduling method was proposed. A novel fuzzy neural network based algorithm for analyzing disturbance of erection time was proposed. The learning samples for FNN were setup by simulation evaluation. The relation between the input parameters of block and erection time was built by FNN. The branch and bound algorithm is used to rescheduling the erection operations. The construction of feasible tree and the branch fathom rules were given. The nodes-including rule and lower-bound rule were used to cut the invalid branches.(5) A simulation platform based on HLA was proposed. This platform can help user to simulation their scheduling results dynamically. The architecture and function modules of this platform were analyzed and defined. The data and time management methods were discussed and the prototype of this platform was developed. In 3D simulation module, a method about navigation path multi-resolution planning based on wavelets was proposed to eliminate the vision dither phenomenon and enhance the immerse feeling in virtual environment of shipbuilding. The theory and realization of constructing navigation path were introduced in details and an example about block erection is given.