Liner Fleet Planning Research Under Uncertainty Of Transportation Demand Based On The Robust Optimization Model

From the economic crisis in 2008,the global shipping market has been in a grim situation of oversupply.The growth rate of transport capacity is still higher than the growth of shipping demand.When will the global shipping industry get out of the continuous downturn is still a concern for shipping people.The planning of the fleet is an important strategic decision of the liner company,which is the key problem to determine the long-term stable development of the liner company.In the operation of the liner company,the uncertainty of various factors is large,and the transportation demand will inevitably deviate from the initial estimated value.The optimal scheme provided by the deterministic model is not necessarily applicable to the future uncertainty.Therefore,the decision-makers must consider the impact of uncertainty in order to make more appropriate decisions.On the existing fleet planning uncertainty research methods mainly include the robust optimization method of stochastic programming,fuzzy programming and scenario sets,but these methods have limitations in their use of probability distribution of stochastic programming and fuzzy programming method of the membership function is usually not easy to obtain,and the robust optimization method is also set the scene the need to determine the probability of each scenario.In this paper,a mixed integer programming model is established,firstly establishing a fleet planning model under the certain demand,then considering the uncertain transportation demand of various routes in each period,based on the deterministic model,introducing the budget parameters,establish two stage robust optimization model,considering the disturbance of the demand rate,uncertainty budget under the changes of model robustness and total cost.This paper uses CPLEX 12.4 software to solve the robust optimization model.Finally,through an example analysis of the model was evaluated by adjusting the values of uncertainty budgets and demand fluctuation level,the robust optimization model were tested to show the robustness of robust and effective control model understand through the compensation function optimization model of two stage robust.Thus,it is suitable to solve the uncertain demand liner fleet planning problem under the two stage robust optimization model,a certain degree of optimization of the cost of the system,and has a larger processing capacity for fluctuations in demand,can minimize the change due to demand surge contrary to expectation cost,overall practical applicability.