| Since the vast territory and complicated geological conditions, some high-speedrailways inevitably adopt subgrade-type. Subgrade, as the foundation of railway tracks,has to undertake the static load of the upper structures and receive the repeated dynamicload from trains, so its dynamic response is extraordinarily complex. The speeding-up oftrains will increase vibration frequency and dynamic stress to the subgrade, thus weakenits dynamic stability and directly threaten trains’ security.The current theoretical analysis and researches are far from satisfying the needs onthe design, construction and maintenance of high-speed railway due to the deficiency oftest technology and methods for rail subgrade’s dynamic response, that it can not predictethe dynamic stability of the subgrade under long-term load before the train lines are built.This situation severely restricts the depth and width of the researches on the railsubgrade’s dynamic response.Combined with the contents of track dynamic and hydraulic servo control, the systemfor subgrade dynamic response in-situ test based on the electro-hydraulic servo excitingtechnology has been detailed studied. The following researches are included.1. In view of the deficiencies (poor universality, over-simplification of excitingsource, et al.) in current research methods on subgrade dynamic response, this dissertationputs forward a multi-body dynamics–finite element combined simulation technology forthe research on the dynamic response in the huge train–rail–subgrade system, i.e.,giving full play to the advantages of the two kinds of software. Firstly, the vehicle–railmulti-body dynamics model is built in ADAMS/Rail software to explore the wheeltrack’sforces with track irregularity spectrum as the external incentive. Then after beingconverted, the forces are input to the track–subgrade multi-layered finite element modelestablished in Patran for simulating.2. This dissertation takes CRH2high-speed train and CRTS II ballastless track asexample to carry out simulation research, concluding stress, strain, velocity, accelerationand other dynamic responses of each layer of track and subgrade’s structures. Then, thedynamic response laws of track and subgrade at different speeds are investigated. Thecomparison to the actually measured data verifies the accuracy of the modeling andsimulation technology and clarifies the design indicators for the research onelectrohydraulic servo exciting system.4. Multiple plans for hydrauservo cylinder design are proposed, then each plan is analyzed respectively, and finally an actively controllable exciting hydrauservo cylinderwith static and dynamic pressure is designed through combining the advantages of eachplan. The static pressure is controlled by the proportional valve and used for simulatingthe static load on the subgrade. The dynamic pressure is controlled by the electrohydraulicservo valve and used for constituting force or position double closed-loop system,outputting controllable waves and simulating trains’ dynamic load. They are controlledrespectively without mutual intervention and can satisfy the requirements of subgrade’sdynamic response test. To meet the demands of minimum friction force and great lateralforce resistance of servo hydraulic cylinder, flow field characteristics of hydrostaticbearing guide sleeve with I-section oil cavity are also studied for the relationship betweeneccentric distance and friction force, supporting force and leakage.5. Combined with the nonlinear feedback transformation and adaptive modelfollowing control, the referential model with the same characteristics to the controlledobject is constructed. Besides, with the help of non-linear feedback, the referential modelcan be linearized so as to realize the model following adaptive control for complexelectrohydraulic systems. The purpose is to generate ideal output which can follow theinput signals and provide relevant non-linear compensation information for the controlledobject. The simulation and test technologies are adopted and the parameters are optimizedso as to realize accurate wave forms, quick and automatic following without distortion.6. The counterforce framework is designed for the test and its modal and transient areanalyzed to avoid resonance from affecting the test results. Besides, the software to testthe rail subgrade’s dynamic response based on Labview is developed, which can collectand analyze signals from sensors automatically. Through the embedded correctionalgorithm, the output parameters of the system can be controlled in real time. Therefore,visibility, adjustability and controllability of the vibration system are achieved. Finally thelaboratory tests of the exciting system are carried out. The results show that the designedin-situ test equipment for subgrade’s dynamic response satisfies the working demands andlaids a good foundation for further field test study. |
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