Theoretical Research On Wheel/Rail Contact Force Identification And Its Application

Wheel rail contact force is an important indicator to evaluate railway safety. Therefore, it is very important to monitor the wheel rail contact force and to evaluate the safety of track-vehicle system by using the monitoring data during high speed railway operation. Given economic reasons and maintenance complexities, a wheel rail contact force identification based on the responses of vehicles is necessary, and it provides great theoretical significance and practical value.Based on the Duhamel’s Integral, an identification method is derived in time domain, then a wheel identification model and a wheelset identification model are built. From these two models, wheel rail vertical contact force is identified. The verification results show that the correlation coefficients between the two identified forces (i.e. vertical force identified by the wheel identification model and the force identified by the wheelset identification model) and the simulation force are 0.81 and 0.9 respectively.Based on Creep Theory and Dynamic Theory, a new model called Identification Model Based on Rolling Contact (RC Model) is built. The model is discretized by Newark method and is solved by Chord Intercept method. Then the lateral contact force is identified. The results of the identification are compared to the simulation results, and the verification results show that the correlation coefficient between identified lateral force and simulation force is 0.71. With RC Model, wheel rail contact parameters such as contact angle and contact radius can also be identified.Based on optimal control theories, an optimal control force identification model (OC Model) is built. First, dynamic equations are converted to space state equations. Then the inspection acceleration is regarded as the target output and an optimal control strategy is designed. The optimal control strategy is the contact force to be identified. The solution of the OC model is an ill posed problem, so SVD decomposition technique is used to solve the OC model. In addition, Kalman filtering technology is introduced to OC model to improve identification accuracy.Due to the characteristics of the wheel/rail dynamic system, only the integrated lateral force of the wheelset can be obtained, and left and right contact force cannot be obtained separately from OC model. Thus, the RC contact force identification model above is combined with OC model, and left/right contact force can be identified. A new identification model is established and called as Rolling Contact Force Identification Model with Optimal Control Method (RCOC Model). Based on the state space equation, with the RCOC Model, the identification model of vehicle system is built and solved subsequently. The results of the identification are compared to simulation results, and the verification results show that the correlation coefficients between the identified forces (i.e. identified lateral force and identified vertical force) and simulation force are 0.65 and 0.8 respectively.Based on Adams/rail software, a dynamic simulation model of CRH3 is also established, and it is validated by WuGuang/ZhengXi High Speed Railway inspection data. Identification contact force is validated by the dynamic simulation model. As mentioned above, the correlation coefficients between identified lateral force/vertical force and simulation force can reach 0.65 and 0.8 respectively. Identification contact force is also validated by PanYing High Speed Railway inspection data, and the verification results show that the correlation coefficients between identified lateral force/vertical force and inspection force are 0.51 and 0.69 respectively.Safety evaluation methods for the rail-vehicle system are summarized. Developing comprehensive evaluation method is a direction to evaluate the safety of the rail-vehicle system. Derailment mechanism is studied by the dynamic simulation of the single wheelset. A comprehensive evaluation index based on the derailment coefficient and the vertical displacement of wheel are proposed. Finally, the safety of the rail-vehicle system is evaluated by the index proposed above.