Research On Scheduling Optimization Of The Tractors In The Tractor-and-semitrailer Transportation Under Multiple Modes

In the Lu-Liao tractor-and-semitrailer transportation network,the tractor dispatching problem under various modes closely related to the actual operation has not been studied in theory.In order to make up for this shortage,and to rationally arrange the order of the tractor's tasks under the corresponding resources and time constraints,improve the effective utilization rate of tractors,as well as reduce the overall operating cost of the system,in this dissertation,the scheduling optimization of tractors in the tractor-and-semitrailer transportation is studied under four modes,the details are as follows:(1)A mixed integer programming model is established for the tractor scheduling under the roll-on-roll-off tractor-and-semitrailer transportation mode.A lower bound of the objective function is derived.By adopting the hybrid simulated annealing algorithm,numerical solutions are obtained under two conditions:overlapping ship turnaround time and non-overlapping ship turnaround time.Results show that the model and the algorithm are effective,and the algorithm performs better when the ships' turnaround time has no overlap.(2)In road network,with uncertain empty-semitrailer tasks,an optimization model on the tractor-and-semitrailer transportation scheduling is established,and a two-stage heuristic algorithm to solve it is developed.The results show that when it comes to tractor-and-semitrailer transportation scheduling with uncertain empty-semitrailer tasks,the policy,minimizing total surplus of laden-semitrailer tasks' OD points,has obvious superiority.(3)A scheduling optimization model for tractors of the crossed tractor-and-semitrailer transportation with multiple vehicles is established.According to the characteristics of the model,a hybrid simulated annealing algorithm is developed to solve the numerical examples based on operation data and to solve the converted Solomon classic numerical examples.The results indicate the superiority of the multiple tractor-and-semitrailer crossed transportation.The effect of the distribution of customers on the objective function value is analyzed as well.(4)Under the midway semitrailer-uncoupling operation mode,a mixed integer programming model for the tractor scheduling is established,and a hybrid simulated annealing algorithm is adopted.The influence of changing the proportion of the mainline task/subline task and the influence of changing the total number of tasks on the results is analyzed.Moreover,the results under the three modes are compared,the three modes refer to "the tractor can uncouple the semitrailer halfway","the tractor cannot uncouple the semitrailer halfway but the mainline tasks and the subline tasks can be mixed conducted",and "the tractor cannot uncouple the semitrailer halfway,the mainline tasks and the subline tasks cannot be mixed conducted neither".The superiority of the mode "the tractor can uncouple the semitrailer halfway" is reflected.The research results of this dissertation can promote the exploration and popularization of the new modes of the tractor-and-semitrailer transportation,and provide decision-making support for the corresponding managers in operation and scheduling.