Search-Based Functional And Temporal Testing For The Onboard Interlocking Software Of The New Train Control System

With the rapid economy gross of our country,people's demand on the railway transportation has increased gradually in the recent years.The train control system as the key point of ensuring the safe operation of the trains and improving the transport efficiency,the researches of which have drawn more and more attentions.In the traditional “ground-centric” train control system,the ground equipment takes care of almost all the core functionalities,and thus has led to some problems.The vehicle-tovehicle communication-based train control system as one of the possible solutions,reduces a significant amount of ground equipment and moves the traditional ground interlocking system to the vehicle,to achieve the autonomous control and operation of trains.The new onboard interlocking is based on distributed “vehicle-to-vehicle communication” control principle,which is quite different from the traditional Interlocking system.Also,its temporal performance will be affected by more factors.Thus,it is of significant importance to guarantee both the functional and temporal correctness of the new onboard interlocking system.The traditional researches of automatic testing for train control systems use model checking techniques to automatically generate test cases.However,this kind of methods will be limited by the scale of the system,which makes it very hard to test exhaustively.Thus,this paper has proposed a new testing method that combines the heuristic search and timed automata together,using the dynamic characteristics of the heuristic search to deal with the state space explosion problems caused by the system scale,while using the model to abstract the system to reduce search space and replace real time with abstract time.The main works in the paper have been summarized as following:(1)While focusing on the core route-control functionality of the new onboard interlocking system,this paper has proposed functional testing requirements and the temporal testing indicator WCET(Worst Case Execution Time),by analyzing the structure and typical scenarios of the new train control system,as well as the control principle and time-affecting factors of the route control function of the interlocking system.On this basis,this paper has studied and summarized the related works about train control system testing.(2)This paper has studied the testing methods based on heuristic search and then proposed a modified genetic algorithm which can combine with time.By using the timed input trace as individuals,this paper has proposed a new encoding method as well as new crossover and mutation operators,new fitness functions,etc.The functional testing generates test cases covering typical faults automatically by using timed automata mutation models.The temporal testing generates WCET test cases based on model,which solves the problem of the traditional methods that test directly on real systems,leading to a very long consuming time.(3)This paper has proposed a modified heuristic-search-based testing structure for the new onboard interlocking system,mainly including: the modelling method for the new onboard interlocking system based on timed automata,the functional and temporal test case generation techniques,the test execution and test environment developing method based on software fault injecting techniques,and the testing evaluation method based on conformance relation scores.(4)This paper has carried out a real case study on the route control function of the new onboard interlocking system.Based on Rail ML data structure and pathfinding algorithms,the simulation software of the system was developed,and its corresponding models were constructed.The functional testing generated mutation models using mutation operators designed,and generated test cases using the modified genetic algorithm,and finally covered 61.1% of the real faults by executing test cases on the real system.The temporal testing generated the WCET test case of the route setting function based on the testing model,and gained the actual WCET of 2072 ms via executions on the real system.By comparing with the unmodified genetic algorithm,k-Bounded model checking method,online heuristic search method,and random search method,the method proposed in this paper shows a certain level of advantages regarding to the test case generation efficiency and time consumption,the effectiveness of which on the functional and temporal testing of the new onboard interlocking system is thus proved.This paper has 44 figures,16 tables and 80 references.