Research On Multi-objective Cooperative Scheduling Optimization Of Berths And Tugboats In Ports

With the trend of global integration and the rapid development of domestic economy,ports are becoming an important part of the international logistics system,which can absorb people,logistics,capital,information and other factors of production in the world.The development of ports not only promotes the economy of coastal cities,but also promotes the economic chain to reach the hinterland and the prosperity of the whole region.Due to the continuous development of shipping market,the number of arriving ships is increasing,assuming a trend to large-scale.Tugboats are needed to guide them in and out of ports.However,berths and tugboats are scarce resources in ports.How to allocate the limited resources of berths and tugboats reasonably so that ships arriving at ports can be served as soon as possible and saving operating costs at the same time is an important problem that the port urgently needs to solve in order to improve its competitiveness.In this dissertation,berth and tugboat are jointly dispatched.All arriving ships are waiting at anchorage.When a suitable berth is available,tugboat tows the ship to berth through the channel.After the ship is loaded or unloaded on the berth,tugboat tows the ship out of the port through the channel.Avoiding the situation that tugboats bring ships into the harbour without berths or that the berth will continue to be occupied after the completion of loading and unloading due to the absence of tugboats.The main work is as follows:Firstly,the mathematical model of cooperative scheduling problem is established.Describing the ship’s operation process in port,the characteristics of berth and tugboat cooperative dispatching operation are analyzed.Assuming that all arriving ships need enter and leave the port,and some ships need shift.Considering the influence factors of single channel and the decision of tugboat returning to base in time,the model is closer to the facts.The objective function is to minimize the total time of all ships in port and the total operation cost of berths and tugs.According to the characteristics of the model and the physical significance of each parameter and their relationship,the constraints that the mathematical model of cooperative scheduling must satisfy are obtained.Secondly,the algorithm is designed to solve the model.By analyzing and comparing the characteristics of scheduling algorithm and multi-objective optimization algorithm,NSGA-Ⅱ(a fast non-dominated sorting genetic algorithm with elite strategy)is selected to solve the multi-objective cooperative scheduling problem,and the shortcomings of the algorithm are improved.Then a reasonable way of code and decode and methods of crossover and mutation are designed which can effectively avoid the generation of illegal solutions.Finally,an example is selected to verify the effectiveness of the model and the algorithm,and the characteristics of the model are analyzed by design factor experiments.An example of cooperative scheduling of berths and tugboats is constructed by means of artificial experience and random generation.And the relevant parameters in the model are optimized,and the example is solved by programming.The effects of channel conditions,tugboat number and berth number on total time in port and total operating cost of ships are analyzed through experiments.The results obtained can provide decision-making reference for the scheduling of port tugboats and berths.