## 1 Introduction
Although EMU have been in operation for years, such as the TGV (Train a Grande Vitesse) in France, the ICE (Inter-City Express) in Germany, the Shinkansen in Japan and the CRH (China Railways High-Speed) in China, the identification of the best solution regarding the suspension of the equipment in order to lower the level of carbody vibration and to improve the ride comfort is still the subject of many studies [39; 40; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 52; 53; 54; 55; 56; 57; 58]. Two conventional passive methods are frequently used to reduce the vibrations of the flexible carbody of EMU, one based on the vibration isolation theory and the other on the dynamic vibration absorber theory. The active vibration reduction methods can also be added to these, but they are not applicable due to the high cost of implementation and maintenance [59]. Although several studies based on experimental research have been identified on this topic [40; 42; 43; 44; 45; 47; 48; 49; 51; 52; 53; 54], their number is relatively small compared to the large number of published papers. Carrying out experimental research in the laboratory on special test vehicles requires a large investment of time and a considerable financial effort for the development of complex stands equipped with specialized systems and equipment for simulating real traffic conditions and measuring, controlling, and acquiring data. Thus, it can be explained that the small number of studies in which the vibration reduction methods of flexible carbody of railway vehicles are investigated based on both numerical simulation results and experimental results. A less expensive alternative to experimental research on full-scale test vehicles is laboratory research on experimental systems that have as their main structure the scale model of the vehicle carbody [60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73]. Such systems have been used to verify the results of some methods of passive or active damping of flexible vibrations of the carbody of the railway vehicles [60; 61; 62; 63; 64; 65; 66; 67; 68; 72; 73], in the experimental study of a method of increasing the structural damping of the light carbody of the high-speed trains [67], or in evaluating the influence of some elements of the vehicle on the flexible vibrations of the carbody [74]. Section 2 of the paper describes these experimental systems, which include different scale models (1:5, 1:6, 1:10; 1:12; 1:24.5) of the vehicle carbody. Section 3 of the paper presents the structure and dimensioning elements of a new demonstrative experimental system, specially designed by the authors of the present pa  
Figure 2: The commuter type test vehicle [35]. per for experimental testing the functionality of an original method of reducing vertical bending vibration of the carbody of the railway vehicles. This method, proposed by one of the authors of this paper, relies on an innovative approach that implies the use of a passive system [29]. This system consists of two bars, hereafter referred to as anti-bending bars, which are rigidly mounted on the longitudinal beams of the carbody underframe. When the carbody bends, the anti-bending bars act as elastic elements developing at the clamping ends two opposing longitudinal forces that act below the neutral axis of the carbody and create two bending moments which oppose the bending of the carbody. The couples corresponding to these forces limit the rotation of the cross-sections of the carbody caused by vertical bending vibration. The advantage of the method being proposed consists in the fact that the anti-bending bars parameters are determined from the requirement to achieve a frequency of the first vertical bending mode of the carbody, advantageous from the ride comfort. In other words, the eigenfrequency of the carbody vertical bending can be increased and taken out of the frequency interval of sensitivity to vertical vibrations of the human body.