Load Identification Technology For High-Speed Train Dynamic Force And Its Application

The relationship between excitation and time is very important for the design and analysis of engineering structures, and also impact on their use of process reliability. For high-speed vehicle, its operational stability is very high decided by the interaction between the wheel and rail in some extent. For the rail, with the improvement of train running speed, the wheel/rail interaction force will be dramatically worse, this would be serious influence the safety of high speed train. In addition, from the evaluation of high speed train dynamics characteristics, the vibration coupling relationship between the components, friction and wear performance, durability and so on, to controlling and analysis the real time of the wheel/rail force is also very necessary. Therefore, how to get the wheel/rail contact force is always a hot topic for researchers and engineers.In the high speed train operation, because of the high-speed relative motion between wheel and rail, structure complexity and load influence each other in each direction, it is very difficult to measure the wheel/rail excitation force in running state. So, we need to develop a kind of indirect force-time solution method, namely force inversion method. Based on the basis of theoretical derivation, with the engineering actual demand closely, the main works of this paper are as follows:(1) The domestic and foreign latest load inversion methods are comprehensively reviewed, and for the first time, we summarize the development and application of the load inversion methods which have been used in railway locomotive vehicles. From the present situation of the locomotive vehicle and high-speed train in our country, the importance of load inversion method for operation train to get high precision wheel/rail contact dynamic force is analyzed.(2) A non iterative load inversion time domain method which based on the dynamic programming is proposed. From the point of view of system, the structure input force evaluation mathematical model is established, and through the indirect measurement method, the relationship of the unknown excitation load and its response of the structure are also established, then the input excitation load in time domain is gotten. Because of the non iterative property of the inversion model, the initial condition dependence problem is solved effectively in the process of the load inversion. At the same time, the transfer and accumulation of the error are also avoided in the process of the method which makes the result have better numerical stability. Then the Bellman’s principle of optimality is used for the minimization of the objective function to estimate the excitation forces, which ensure to get the inverse forces and responses that make the objective function minimum in each time step, and effectively reduce the influence that caused by avoidless the ill-posed in the process of the load inversion, and get the inverse load which is very similar to the real load. (3) For the first time to systematically deduce and research the regularization parameter solution, and the generalized cross-validation (GCV) method calculation formula which is very suitable for the inversion model is obtained. Because the original measurement data is influenced by measuring instruments and external disturbance, and in the inverse problem of mathematical physics solving process, it often meets such as the insufficiency of known measuring data, improper values of boundary conditions, the noise disturbance of measuring response and the instability of the approximate solution, etc., the inversion solution process usually exists ill-posedness. Regularization method is a kind of effective methods to solve the ill-posedness problem. The regularization theory is introduced into the inversion mathematical model, based on the inversion model and the principle of GCV method, the GCV calculation formula which is very suitable for the inversion model is obtained. The regularization parameter is solved by GCV method and the L-curve method, and the method greatly reduces the influence that due to a calculation rounding measurement error and the signal noise during the load identification process, overcome the large fluctuation which is widespread existing in the current load inversion technology, and improve the anti-noise ability of the inversion mathematical model. At the same time, load drift is inhibited. In the above load inversion mathematical model, this paper further introduces characteristic value reduction technology, which is effectively used in the load inversion process of the large complex structure, especially when there are less number of inversion loads and measuring responses, and the control matrix solution efficiency is very low.(4) The load inversion method is used in the high-speed train. The load inversion mathematical model is introduced into the high-speed train wheel/rail contact force inversion,10degrees of freedom vertical vibration model and17degrees of freedom horizontal vibration model are established, respectively. First of all, the load inversion mathematical model is verified from the point of the SIMPACK dynamics simulation. Under100km/h and250km/h, longitudinal acceleration, transverse acceleration and vertical acceleration of the axle box from the SIMPACK dynamics simulation are used as the input of the inversion mathematical model, the wheel/rail contact forces and derailment coefficients are identified. From the time domain and frequency domain, inverse results are compared with SIMPACK simulation results. The results indicate that the vertical and horizontal wheel/rail forces had the same trend with SIMPACK simulation results, and in time domain, their correlation coefficients are greater than0.5, belongs to the moderate related and strong correlation. PSD analysis shows that, both in the low frequency range and in the high frequency range, from0.1Hz to500Hz, the PSD of the inverse forces is as the same as the simulation results, the inversion results are satisfactory.(5) The rolling and vibrating test-bed in TPL at Southwest Jiaotong University is used to verify the effectiveness of the load inversion mathematical method. Under280km/h, the car body vertical acceleration, two bogie frames accelerations and four axle boxes accelerations are measured using DDS32data acquisition system. Selecting four values in these measurement responses as the input of the inversion mathematical model, the wheel/rail vertical force and other parts of the inversion vertical vibration acceleration are gotten. The inversion vertical vibration acceleration is very close to the test value, at the same time, we also get the vertical contact force of the train.