The Research Of The Tramp Ship Routing And Scheduling Problem

Tramp shipping is the main transportation mode for dry bulk cargoes such as grain, iron ore, coal. Compared with the liner, it does not have fixed shipping lines, sailing schedule and the affiliated port, and transport with high flexibility, which is strongly influenced by policy makers. Tramp shipping is possible to be affected by 3 stochastic factors. Firstly, the transportation demand in the future is uncertain. There is spot cargoes in the tramp shipping market. Secondly, the freight rates of dry bulk cargoes show an obvious seasonality. Thirdly, the transportation is easily to be effected by the unseaworthy conditions. Therefore, for bulk shipping companies, it’s important to discuss when and where to make the ship in ballast, since a reasonable scheme can help to increase profit.This paper studies the tramp ship routing and scheduling problem (TPSRP) by taking into account spot cargo, seasonal fluctuation of demand and unseaworthy condition caused by weather factors. A mathematical model is proposed which attempts to maximize the total voyage profit of shipping company in the planning period. The freight rates of the cargos are set change in the model to simulate the characteristic of seasonal fluctuations. Delay cost is also introduced, which is mainly used to calculate the additional cost for the delays in the sea caused by the weather factors. And the demand uncertainty is mainly manifested in the process of solve the mathematical model. Since the problem is an NP-hard problem, a genetic algorithm-based heuristic is developed to solve the problem. In order to ensure that the length of the chromosome is equal and preserve the genetic diversity, the virtual ships are introduced in the algorithm, which are used to transport the cargos that actual ships can not transport. The planning cycle of one year is divided into four stages according to the quarter. At the beginning of each period, every ship route is adjusted according to updated cargo situation. So the other important function of the virtual ship is as follow. When the spot cargos appear on the market, the original ship routes may need to be changed. Under the new transport scheme, the cargos in virtual ships may could be transport by the actual ships. If this batch of cargos are give up in the early, the optimal transport scheme may can not be get. The operation data of a Chinese tramp shipping company are used to validate the model and method, and sensitivity analysis and algorithm evaluation were carried out.The empirical studies demonstrate the heuristic provides good ship routing and scheduling solutions to real-instances. It can consider both the uncertainty of transportation demands and the seasonal factors of shipping routes. Moreover, the results also show that the voyage arrangement with the consideration of seasonality and weather factors is an efficient way for tramp ship scheduling.