Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrati...Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrations are not well understood.To clarify the vibration transfer function and its characteristics,four basic input vectors are defined,and an analytical method is proposed.The vibration transfer functions of the vehicle system are solved,and their spatial coherence is analyzed.The results show that there are two spatial scales and four coherent modes in the vehicle system.The track irregularity wavelengths are combined with two spatial scales to alter the proportions of basic input vectors and then show the characteristics of spatial coherence.Four coherent modes are involved in wheel-rail force and primary suspension force;two coherent modes are involved in bogie vertical motion;and their dominant modes vary with the input frequency.On the other hand,the coherent modes involved in the bogie pitching motion and vehicle body motion are single and fixed over the whole range of frequency.This study presents an analytical method for the rapid solution of dynamic responses in vehicle systems and systematically analyzes the coherence behavior of vibration transfer functions with respect to tracking irregularity wavelengths.展开更多
This paper investigates the applicabilitles of pole-zero model and wave propagation theory in estimating the phase characteristics of vibrating systems. The measured phase spectra are compared with the estlmated rever...This paper investigates the applicabilitles of pole-zero model and wave propagation theory in estimating the phase characteristics of vibrating systems. The measured phase spectra are compared with the estlmated reverberant phase limit and wave propagation phase. The relations between transfer function phase and frequency, damping, and separation distance are described. The present results show that the pole-zero model provides a reasonable estimation of the reverberant phase limit in low frequency band below an identified transition frequency.The reverberant phase is linearly dependent on frequency in this band, but from the transition frequency and onwards the phase increases only with the square root of frequency. This behavior is characteristic for free propagating waves展开更多
Although the performance of space cameras has largely improved, the micro vibration from flywheel disturbances still significantly affects the image quality of these cameras. This study adopted a passive isolation met...Although the performance of space cameras has largely improved, the micro vibration from flywheel disturbances still significantly affects the image quality of these cameras. This study adopted a passive isolation method to reduce the negative effect of flywheel disturbance on image quality. A metal-rubber shock absorber was designed and installed in a real satellite. A finite element model of an entire satellite was constructed, and a transient analysis was conducted afterward. The change in the modulate transfer function was detected using ray tracing and optical transfer function formulas. Experiments based on real products were performed to validate the influence of the metal-rubber shock absorber. The experimental results confirmed the simulation results by showing that the negative effects of flywheel dis- turbance on the image quality of space cameras can be diminished significantly using the vibration isolation method.展开更多
基金Supported by Fundamental Research Funds for the Central Universities(Grant No.2024QYBS031)Fundamental Research Funds for the Central Universities(Grant No.2022JBQY007)。
文摘Current research on rail vehicle system vibrations primarily relies on numerical methods,with vibration transfer functions commonly derived through data fitting.However,the physical mechanisms underlying these vibrations are not well understood.To clarify the vibration transfer function and its characteristics,four basic input vectors are defined,and an analytical method is proposed.The vibration transfer functions of the vehicle system are solved,and their spatial coherence is analyzed.The results show that there are two spatial scales and four coherent modes in the vehicle system.The track irregularity wavelengths are combined with two spatial scales to alter the proportions of basic input vectors and then show the characteristics of spatial coherence.Four coherent modes are involved in wheel-rail force and primary suspension force;two coherent modes are involved in bogie vertical motion;and their dominant modes vary with the input frequency.On the other hand,the coherent modes involved in the bogie pitching motion and vehicle body motion are single and fixed over the whole range of frequency.This study presents an analytical method for the rapid solution of dynamic responses in vehicle systems and systematically analyzes the coherence behavior of vibration transfer functions with respect to tracking irregularity wavelengths.
文摘This paper investigates the applicabilitles of pole-zero model and wave propagation theory in estimating the phase characteristics of vibrating systems. The measured phase spectra are compared with the estlmated reverberant phase limit and wave propagation phase. The relations between transfer function phase and frequency, damping, and separation distance are described. The present results show that the pole-zero model provides a reasonable estimation of the reverberant phase limit in low frequency band below an identified transition frequency.The reverberant phase is linearly dependent on frequency in this band, but from the transition frequency and onwards the phase increases only with the square root of frequency. This behavior is characteristic for free propagating waves
文摘Although the performance of space cameras has largely improved, the micro vibration from flywheel disturbances still significantly affects the image quality of these cameras. This study adopted a passive isolation method to reduce the negative effect of flywheel disturbance on image quality. A metal-rubber shock absorber was designed and installed in a real satellite. A finite element model of an entire satellite was constructed, and a transient analysis was conducted afterward. The change in the modulate transfer function was detected using ray tracing and optical transfer function formulas. Experiments based on real products were performed to validate the influence of the metal-rubber shock absorber. The experimental results confirmed the simulation results by showing that the negative effects of flywheel dis- turbance on the image quality of space cameras can be diminished significantly using the vibration isolation method.
