Study On Several Vibration Control Technologies

In recent years, the vibration control technology has been gaining increasing attention in automobile, aerospace, and marine applications. Due to the mechanization and upsizing of producing tools, the vibration response is becoming more and more serious. Moreover, the vibration environment is an important consideration in the precision machining/measurement. These disadvantages confine the application of the traditional vibration control technology, which also stimulates the optimization of the traditional vibration control technology to meet the requirement of the engineering application. In view of the increasing applications of vibration attenuation, intense research has been carried out to explore novel vibration control technologies, such as the development of the adaptive tuned vibration absorption technology and nonlinear low-frequency vibration isolation technology. Although, some achievements have been done on these vibration control technologies, there is much work to be done before the applications of these vibration control technologies according to the complexity of the damping mechanism and the mild damping performance. Therefore, it’s essential to systematically investigate the novel applicable vibration control technology. The present study focuses on the adaptive tuned vibration absorber (ATVA), adaptive active resonant absorber (AARA), nonlinear low-frequency vibration isolation (NLFVI), which are applied in the vibration attenuation of shipping, based on a National Applicable Projects. The details are listed as follows.1. In this dissertation, by means of comparing the working principle, vibration characteristics and energy consumption of passive tuned vibration absorber (TVA), active vibration absorber (AVA), ATVA and AARA, the advantages and drawbacks of these vibration attenuations were systematically investigated, which can provide useful theoretic guide for the optimum design of vibration absorber and engineering application. Based on a universal calculation model, the characteristics of these four typical vibration absorbers were evaluated. The comparisons demonstrate that the TVA doesn’t consume energy in working mode while its vibration attenuation performance is not ideal. In addition, it can only work well when the excitation frequency around to its inherent frequency. Compared with TVA, the vibration attenuation performance of AVA is improved, but the vibration absorption bandwidth remains almost unchanged. Besides, it consumes a considerable amount of energy in working mode. For ATVA, the vibration absorption bandwidth of is extended, but the vibration attenuation performance doesn’t demonstrate significant improvement. In light of the comprehensive comparisons, the AARA is a good choice for vibration attenuation, which not only improves the vibration attenuation capacity but also extends the vibration absorption bandwidth, whose energy consumption is much lower than that in active absorber.2. In order to improve the vibration attenuation performance, the active force and lever structure were introduced in the design of ATVA, thus the AARA and pendulum-like ATVA were designed, respectively. It is noticed that the vibration attenuation capacity of ATVA is better when the damping is low. Furthermore, both of the active force and lever structure introduced into ATVA facilitate to reduce the damping of absorber, which play the same role in improving the vibration attenuation capacity. According to the theoretical and experimental results, both absorbers show attractive benefits on the dynamic performance and vibration attenuation capacity aspects, such as the extended vibration absorption bandwidth, lower damping, and significant vibration attenuation capacity. Therefore, both of them are promising for future applications.3. NLFVI technology is explored to meet the actual applications. Most of the traditional passive isolators were based on linearity theorem, i.e., in which the static stiffness equals to the dynamic stiffness, making it impossible for the application in low-frequency isolation. To solve this problem, a NLFVI system with high static stiffness and low dynamic stiffness was designed based on the nonlinearity theorem. From the experimental results, it is found that the NLFVI system has a low initial isolating frequency. The initial isolating frequency of this NLFVI system is below 5 Hz as the external load changes from 77.5kg to 105 kg. Clearly, this system is suitable for low-frequency isolation.4. The study on the response and vibration transmissibility of the NLFVI system is also conducted. Based on experiments, a mathematical model is developed to analyze the nonlinear isolating system, and nonlinear dynamic governing equations of the isolating system are proposed. Also the relationship between the non-damping free-vibration frequency and the vibration amplitude is obtained by utilizing immediate integration. It indicates that the isolating system is a classic hard spring isolating system. The steady response and vibration transmissibility are analyzed using harmonic balance method, and the influence of the system parameters on the vibration transmissibility is studied. They provide theoretical support for further optimization design. In addition, a two-dimensional vibration isolating platform is constructed to investigate the vibration transmission ratio of the prototype based on nonlinear vibration isolating system. It is indicated that the vibration transmission ratio is less than 1 when the excitation frequency is over 4.8 Hz, i.e., the initial isolating frequency of the vibration isolating system is 4.8 Hz. Overall, the experimental measurements agree well with the theoretical results.This dissertation has conducted a comprehensive analysis on several vibration control technologies, including ATVA, AARA, and NLFVI. Such a study enables a thorough understanding of the performance of the various vibration control technologies and can provide theoretical guide for the further development and engineering applications. Moreover, based on these new vibration controlling technologies, the corresponding damping devices are designed, and some valuable explorations have been made on the applications of these damping devices. This work has demonstrated the potential of using these novel vibration controlling technologies in the engineering.