## 5 Conclusions and Prospection  
The dynamic design methodology should be actively recommended and introduced to the high-tech manufacturing industries, such as HSRS, so that the development of large-scale complex nonlinear dynamic systems becomes one of its basic works. Moreover, PODA and MMRT are used as effective tools for big data mining to remove and eliminate the singularities of complex constraints and their negative impacts on related interfaces. The following two criteria must be addressed clearly: (i) proper modeling needs to pay very much attention to the premise for investigating engineering problems, e.g., singularity of complex constraints; (ii) the transaction strategy of the flexible body to MBS interface is very crucial, which is closely related to the ESL safety of lightweight structures. In short, no matter what causes the roll and rock of the service car body, it will lead to the improper use of anti-roll torsion bar devices, which has become one of the most common technical problems. Consequently, the central hollow tread wear is then the highest probability event in Chinese HSR practices, with almost no flange root wear or flange side wear. Onthe first fluttering phenomenon of the service car body, the contrastive analyses of line tracking tests and rigid-flex coupling simulations show that stability, wear, and vibration are closely related to each other, and the internal lateral coupling resonance of such a traction converter has been one of the main restrictive factors that determine the operation and maintenance costs. With the technical support of relevant analysis software, this paper proposes a large-scale MDO flow chart for HSRS. After defining the key problems to be solved, the self-adaptive improved design solution and associated technical features were formulated and verified for the next-generation HSRS with higher speed requirements. Through these works on paper, three main conclusions can be drawn as follows:  
(1) Only under the rational conditions of wheel-rail matching can the limit and construction speeds be scientifically promoted. By referring to relevant experiences at home and abroad, the rational condition of wheel-rail matching can be determined as follows: \(0.10\geq\lambda_{eN}>\lambda_{emin}\) and \(\lambda_{emin}\) = (0.03-0.06), which is taken as one of the necessary conditions to establish the large-scale MDO technical platform. (2) Compared with the improved design of the wheel-rail relationship for HSR, the self-adaptive improved design of higher speed bogies is one of the more preferable options. The comprehensive evaluation shows that this self-adaptive improved design solution can solve the car body instability problem at a low cost according to the principle of momentum conservation, making Chinese HSR come back to the rational conditions of wheel-rail matching. By contrast, the steel rail profession unilaterally initiated the improved design of the wheel-rail relationship for Chinese HSR practices, which can neither achieve the uniform wear stage at low conicity nor obtain the stable wear stage at high conicity. For the running mileage of ca. \(20\times 10^{4}\) km only left thereby, Chinese HSR practices prove that the \(\lambda_{e}\) variation from 0.10 to 0.35 has so many uncertain factors, e.g., service car body shaking phenomenon occurs when high speed running at low conicity of \(\lambda_{e}<\) (0.10-0.12), or more serious fluttering phenomenon takes place when \(\lambda_{e}\) is approaching to (0.30-0.35). This is one of the radical reasons for the high costs of Chinese HSR operations and maintenance. (3) The successful commercial application of high-tech manufacturing industries such as HSRS requires the support of the MDO technical platform. However, the dynamic design methodology plays an active role in developing the large-scale complex nonlinear dynamic system, leading and steering the system design in a more preferable direction, i.e., a self-adaptive, improved design solution for higher speed bogies.