## 1 Introduction  
With the continuous development of high-speed trains, carriage and seat vibration characteristics have become very important factors affecting the ride comfort of high-speed trains [1]. Studies of ride comfort concern not only the dynamics of rail vehicles but also those of the seats and passengers as well as subjective psychology.  
The establishment of the train model is helpful in analyzing the transmission characteristics of vibration and its influence on comfort. [PERSON] et al. [2] established a vertical model of the carriage to study the influence of train body elasticity on comfort and found that the elastic resonance of the body mainly came from the bogie space filtering effect. Increasing the stiffness and damping of the primary suspension helps to avoid the elastic resonance, but this may worsen the wheel-rail contact. [PERSON] et al. [3] compared the rigid train body and the elastic train body and found that the elasticity of the body had different effects on different positions of the body. Reducing the rigidity of the suspension can improve ride comfort. [PERSON] et al. [4] studied the elastic resonance and filtering effects of the train body based on the rigid-flex coupled model and analyzed the factors affecting comfort. [PERSON] et al. [5] established an analytical three-dimensional model of the carriage in which the train body was a box structure built with beams and plates. The modal frequency, modal shape, and power spectral density of the acceleration of carriage all agreed well with the test results within 0.5\(-\)20 Hz, while the shear mode of the body section was still far from the actual situation. [PERSON] et al. [6] established a three-dimensional finite element model of the full-trimmed carriage and verified the accuracy of the model by making comparisons with the results of modal tests. [PERSON] et al. [7] found that ignoring orbital dynamics behavior led to serious overestimation of oscillation and stability. Therefore, choosing the appropriate orbital model is important for evaluating comfort. [PERSON] et al. [8] established a carriage model containing a simple vertical model of seat-human body to study the impact of train-human interaction on train body dynamics and found that passengers had the effect of increasing train body damping, which greatly affected ride comfort.  
Therefore, in order to conduct a more accurate theoretical analysis and research on ride comfort, the introduction of the seat-human body system is very necessary. Although several studies on the seat-human body coupled system have been published recently [9; 10; 11], the train seat-human body coupled system of high-speed trains has rarely been reported, and the models proposed by previous research are limited to simplified multidynamics model [12; 13; 14].  
This paper proposes a train seat-human body coupled dynamics model to predict the ride comfort of high-speed trains. The rest of the paper is organized as follows. Section 2 describes the experiment on ride dynamic characteristics of the CRH380 series high-speed train under different speed conditions. In Section 3, the rigid-flex coupled model of the carriage of the high-speed train is established and verified by comparing the predicted and measured vibration of the carriage floor. In Section 4, the seat-human body coupled dynamics model is established and calibrated. In Section 5, the train seat-human body coupled dynamics model is established based on the two models mentioned above, and the predicted seat vibration is verified by the test results. The evaluation method for ride comfort based on BS EN 12299:2009 [15] is described. Finally, the ride comfort distribution and the effect of seat cushion stiffness and damping on ride comfort are analyzed.