Research On Optimized Organization Theory And Method For Multi-Block Train

As one of the research hotspots for railway experts and scholars in operational research (OR) and management science at home and abroad, wagon flow organization plays an important role in train operation. Owing to the particularity of railway transportation operation and the large-scale network attribute, kinds of plans and schemes conducting transportation production are correlated and interchanged with each other, which makes this problem so extraordinarily difficulty and complicated that it has not been resolved completely so far.Multi-block train, awagon flow organization mode, is popular and widespread in U.S. and Canada representative of the countries with developed railway freight transportation. However, it’s difficult to fully applied abroad achievements to our country because of the difference in management system, transportation organization model, etc. In China, the research on wagon flow organization mainly focuses on one-block train (single group train) and rarely involves multi-block train, as well as the latter is of a very low proportion in practice and just adopted in traction destiny decline situation and "Five Scheduled" container trains at present. Therefore, theoretical achievements and practical experience of multi-block train are still scarce.Comparing with one-block train, the operation of multi-block train is more complex due to requiring the formation station with larger resorting capacity and more reclassification tracks, etc. However, it also has its own advantages, such as guaranteeing full train tonnagepunctuality and complying with train formation plan (TFP), shortening the transfer delay for long-distance wagon partly-resorting in intermediate block-swap station(s), reducing the load of technical stations along the route, etc. Considering the pros and cons of the two modes, it will be practically meaningful to improve efficiency and benefit of transportation by cooperating, maximizing the favorable factors and minimizing unfavorable ones. Moreover, one-block train and pick-up and drop train can be regarded as special multi-block trains in term of train’s constitution. From this point of view, multi-block train has wider extension, and the corresponding theoretical research is more universal. So it is valuable in both practice and academy to research the related problems of multi-block tram.Based on the analysis the principles of wagon flow organization and the summary of optimization theories and methods of TFP at home and abroad, following the guiding ideology of system engineering and micro-mechanism fusing with macro-mechanism, this paper systematically probed into the problems of operation characteristics, accumulation properties, operation conditions, train formation plan optimization, etc, by adopting qualitative and quantitative analysis together with deduction and simulation method. The main research work is as follows: (1) The comparative analysis of existing literature. On the basis of summing up related literature, the research status of TFP at home and abroad was introduced from the aspects of research object, modeling method and solution algorithm and their respective characteristics were contrasted and reviewed in terms of conducting process, composition content and modeling method.(2) Analysis of the operation features of multi-block train. Base on the overview of definition, content, operation scheme and experience of wagon flow organization, in China, some characteristics including technical operating traits, operation process in formation station, intermediate block-swap station(s) and destination, cars’ categorical attributes, advantages and disadvantages, operation conditions and various types of multi-block train mode were analyzed and contrasted with one-block mode.(3) Study on the accumulation properties of multi-block train. Taking double-block train with fixed weight as the object, qualitative analysis and quantitative measure were conducted aiming at the accumulation properties of multi-block train. Dividing the total aggregation cost into the inherent and additional aggregation cost, according to the uncertainty for arrival and the dynamics for aggregation process, the aggregation process of the fixed mode multi-block train at the formation station and intermediate block-swap station(s) were described by considering the size and interval time of the batch of cars as random variables and assuming them to independent and identical distribution. Furthermore, assuming that the size of the batch of cars obeys a Poisson distribution and the interval time follows an exponential one, the performance of aggregation process, i.e., aggregation batch, aggregation occupation time and aggregation cost were deduced applying stochastic processes theory. With the numerical method, estimation formulas of their mean were obtained while analyzing single parameter’s sensitivity and the coupling influence of double-parameter.(4) Study on the operation conditions of multi-block train. The double-block train with fixed weight was chosen as concern object yet whose operation conditions embrace the determination of train constitution and applicable operation conditions. The former was modeled as determinating the optimal proportion between basic-block (i.e. long-distance block) and complementary-block (i.e. short-distance block) to minimize the aggregation occupation time or aggregation cost given the arrival characteristics of the wagon flow. An Integer optimization model was established and solved though two phases. In phase I, the effect mechanism of optimal weights was mined using numerical calculation. In phase Ⅱ, the corresponding empirical regression formulas were respectively provided according to the explored information. Based on the analysis and comparison of aggregation cost between multi-block train with fixed weight and one-block train, applicable operation conditions of the latter was built by adopting the total net savings between the former and the latter as the measure of its comprehensive benefits and tested using discrete event system simulation (DESS) method.(5) The optimization parameters of multi-block train formation plan. This section studied the parameters for multi-block train formation plan optimization, including the traffic flow in schedule length (planning horizon), accumulation parameters of fixed and non-fixed pattern, two time-saving parameters about block swap that one is relative delay corresponding to passing through and the other is relative saving corresponding to resorting, the up-bound of reclassifi cation and maximum possible blocks in every station.(6) The optimization model of multi-block train formation plan. Taking the double-block train which has only one block-swap on its route as the research object in this section, under the framework by providing multi-block train and the one-block train services at the same time, the task of wagon flow organization has been reconstructed and the contents and features of the integrated train formation plan (ITFP) have been qualitatively analyzed according to the transitional linkage of blocks between cars and trains. Considering the decomposition of the above task and the actual situation of China, the block-to-train assignment plan (BTAP) was ignored, and then the block network design plan (BNDP), car-to-block assignment plan (CBAP) and train network design plan (TNDP) were taken as0-1decision variables.In order to minimize the total delay cost generated by aggregation, reclassification and transfer in all itineraries, an optimization model of integrated train formation plan (OMITFP) in the situation of giving car routing was constructed while satisfying the limitation in physical aspects, i.e., resorting capacity and reclassification tracks for every terminals, restriction on operational rules and regulations for wagon-flow, i.e., non-separation and consolidation (every railcar originating or re-blocked at a yard and destined for another must travel in a block to the same next re-blocking yard), as well as logical constraints among the decision variables, Considering the model’s characteristics, when two0-1decision variables corresponding to block plan and car-to-block assignment were introduced, a model to generating all possible CBAPs was developed with the constraints of non-circuit, maximum frequency of reclassification, cross relation and cutting off unfavorable plans. Besides, the method of scheme tree and backtracking algorithm was designed.