## 4 Next Generation HSRS with Higher Speed
### Self-Adaptive Improved Design of Higher Speed Bogies  
In order to overcome the primary hunting design default existing in the prototype of German ICE serial bogies, the analysis graphs of full-vehicle stability properties and variation patterns, as shown in Figure 10, clarify the correct direction of self-adaptive improved design for higher speed bogies, including the main reasons as follows:  
Figure 9: Lateral coupling resonances in equipment cabin under floor frame and associated influences on fatigue damage of aluminum alloy car body. (**a**) Rhombus modal coupling resonance in middle of service car body is accompanied by roof twisted modal vibration, ca. 17.40 Hz. (**b**) Crescent notch effect on one side of pantograph fairing and associated influences on fatigue damage at both ends of transverse weldline. (**c**) Relationship curve of vehicle speed influence on fatigue life at both ends of transverse weldline, in which roof is twisted and resonant when 450 km/h, and stronger resonance occurs again when 650 km/h. (**d–f**) Lateral and vertical vibrations of pantograph fairing and associated influences on fatigue life at both ends of transverse weldline when speed of (300–550) km/h. (**g–i**) Lateral and vertical vibrations of pantograph fairing and associated influences on fatigue life at both ends of transverse weldline when speed of (450–650) km/h.  
(1) There is a rational matching relationship between wheelset positioning constraint stiffness and anti-hunting dynamic features. Specifically, the longitudinal/lateral stiffness of wheelset positioning is ca. 15/6 MN/m, respectively. So, the novel anti-yaw dampers of ZF Sachs T60 and T70 are combined in parallel to establish the anti-hunting broadband energy-absorbing mechanism.  
Special attention: for ZF Sachs T60 \(\times\) 2, the rating values of linear damping and hydraulic stiffness need to be required to ca. 480 kN\(\cdot\)s/m and ca. 3 MN/m; whereas for ZF Sachs T70 \(\times\) 2, the parameters are the same as the original ones, i.e., ca. 18 MN/m and ca. 440 kN\(\cdot\)s/m. The radial stiffness of rubber joints at both ends is ca. 70 MN/m.  
(2) In order to avoid the rapid attenuation of the bogic yaw phase margin as much as possible, the lateral/vertical stiffness of motor hanging rubber joints is taken as ca. 380 kN/m, and the effects of detouring flow can be constructed thereby.  
Specifically, the lower the actual equivalent conicity, the greater the kinetic energy released in time by the modal vibration of traction motors swung laterally with hanging frames, thus ensuring the hunting motion stabilization. Whereas the actual equivalent conicity is increased, the lateral-swung of traction motors with hanging frames tends to self-stable vibration, thus reducing the wheel-rail dynamic interaction.  
Figure 10: Analysis graphs of stability properties and variation patterns for self-adaptive higher-speed bogic with anti-rolling torsion bar devices (in-) active. (**a**) When \(\lambda_{e}\) = 0.08–0.35 with anti-rolling torsion bar devices active. (**b**) When \(\lambda_{e}\) = 0.08–0.16 with anti-rolling torsion bar devices active. (**c**) When \(\lambda_{e}\) = 0.20–0.35 with anti-rolling torsion bar devices active. (**d**) When \(\lambda_{e}\) = 0.08–0.35 with anti-rolling torsion bar devices inactive. (**e**) When \(\lambda_{e}\) = 0.08–0.15 with anti-rolling torsion bar devices inactive. (**f**) When \(\lambda_{e}\) = 0.20–0.35 with anti-rolling torsion bar devices inactive.  
(3) Unlike the primary or secondary hunting phenomenon, the simple problem of car body instability is only related to the anti-roll torsion bar device, i.e., the self-excited vibration of car body up-swung or roll mode occurs within the range of vehicle speed (140-200) km/h at \(\lambda_{e}\) < 0.10. When the anti-roll torsion bar device is not activated, the above self-excited vibration will be converted into the modal vibration of car body yaw. Therefore, the self-adaptive improved design needs a low-cost solution to remove or eliminate the car body instability.