## 1 Introduction
### Theoretical Concept of the Method
vibration level of the carbody due to bending decreased significantly after increasing the bending frequency from 8 Hz to 12 Hz. Further increasing the bending frequency of the carbody to 14 Hz did not introduce any noticeable changes. The effect of the anti-bending bars on ride comfort (evaluated via the ride comfort index [78; 79]) at the reference points located in the centre of the carbody and above the two bogies is shown in Figure 11. A more important improvement in ride comfort was noticeable in the centre of the carbody, especially at high velocities. For example, at velocity of 270 km/h, the comfort index for the carbody without anti-bending bars was 2.68. At the bending frequency of the carbody at 12 Hz, the ride comfort index was reduced to 1.19, and at 14 Hz, the comfort index dropped to 1.06. It is worth noting that for carbody bending frequencies higher than 12 Hz, a significant improvement in ride comfort was no longer obtained. The ride comfort was also slightly increased above the bogies where, by increasing the bending frequency of the carbody to 14 Hz due to the anti-bending bar, at a velocity of 270 km/h, the comfort index drops from 2.11 to 1.67--above the front bogie, respectively to 2.25 to 1.85--above the rear bogie. Structure of the Demonstrative Experimental System for Laboratory Testing of the Method's Functionality  
Demonstrative experimental system for testing the functionality of the method of reducing vertical bending vibrations of the carbody of the railway vehicles based on a system consisting of two anti-bending bars is schematically represented in Figure 12.  
Figure 11: Influence of the anti-bending bars upon ride comfort: (**a**) at the carbody centre; (**b**) above the front bogie, and (**c**) above the rear bogie [29]. Figure 10: Effect of the anti-bending bars upon the carbody dynamic response at velocity of 270 km/h: (**a**) at the carbody centre; (**b**) above the front bogie, and (**c**) above the rear bogie [29]. The main element of the demonstrative experimental system was the scale model of the vehicle carbody, which was reduced to an aluminium beam, with the bending eigenfrequency close to the bending eigenfrequency of the real carbody. On either side of the carbody scale model, the anti-bending bars were attached. The carbody experimental model was supported on rubber elements (suspension elastic elements). The excitation force was generated with an electro-dynamic vibration generator (shaker) and measured by a load cell located between the shaker and the carbody experimental model. The vibrations measurement of the carbody experimental model was obtained with the accelerometers mounted on its middle and against the support points on the elastic elements. The demonstrative experimental system integrated more specialized components, meant for the acquisition and processing of the experimental data (the acceleration of the carbody model and the excitation force) or for generating the command signals of the shaker, controlled via dedicated software applications. It is about the ensemble comprising the NI cDAQ-9174 type chassis and three modules with specialized functions--the NI 9234 module for acquiring and synthesis of the data flow from the three accelerometers type 4514 Bruel and Kjaer, the NI 9263 module for generation the command signals of the shaker type of LDS V201 and the NI 9219 module meant for the measurements of voltage and current with applications in the resistive electric tensometry. This ensemble together with the three accelerometers, the shaker and the amplifier formed the measurement and control chain of the demonstrative experimental system. This was connected to a laptop.