针对某国六发动机进气流量(mass air flow,MAF)传感器在某转速升负荷后出现读数漂移现象,根据经验对增压器的进排气系统进行了噪声振动试验。试验结果表明,发动机涡轮增压器的BPF噪声振动影响了MAF传感器的读数。通过优化涡轮增压器压...针对某国六发动机进气流量(mass air flow,MAF)传感器在某转速升负荷后出现读数漂移现象,根据经验对增压器的进排气系统进行了噪声振动试验。试验结果表明,发动机涡轮增压器的BPF噪声振动影响了MAF传感器的读数。通过优化涡轮增压器压气机叶轮形状、在MAF传感器和增压器之间加消声器等降低BPF噪声振动的措施,解决了该发动机的MAF传感器读数漂移问题,满足了开发阶段的发动机性能及排放要求。展开更多
This work addresses the problem of self-excited vibration,which degrades the stability of the levitation control,decreases the ride comfort,and restricts the construction cost of maglev system.Firstly,a minimum model ...This work addresses the problem of self-excited vibration,which degrades the stability of the levitation control,decreases the ride comfort,and restricts the construction cost of maglev system.Firstly,a minimum model containing a flexible bridge and a single levitation unit is presented.Based on the simplified model,the principle underlying the self-excited vibration is explored.After investigations about the energy transmission between the levitation system and bridge,it is concluded that the increment of modal damping can dissipate the accumulated energy by the bridge and the self-excited vibration may be avoided.To enlarge the equivalent modal damping of bridge,the sky-hooked damper is adopted.Furthermore,to avoid the hardware addition of real sky-hooked damper,considering the fact that the electromagnet itself is an excellent actuator that is capable of providing sufficiently fast and large force acting on the bridge to emulate the influence of the real sky-hooked damper,the technique of the virtual sky-hooked damper is proposed.The principle underlying the virtual sky-hooked damper by electromagnet is explored and the vertical velocity of bridge is estimated.Finally,numerical and experimental results illustrating the stability improvement of the vehicle-bridge interaction system are provided.展开更多
This paper presents the knee-joint vibration signal processing and pathological localization procedures using the empirical mode decomposition for patients with chondrom alacia patellae.The artifacts of baseline wande...This paper presents the knee-joint vibration signal processing and pathological localization procedures using the empirical mode decomposition for patients with chondrom alacia patellae.The artifacts of baseline wander and random noise were identified in the decomposed monotonic trend and intrinsic mode functions (IMF) using the modeling method of probability density function and the confidence limit criterion.Then, the fluctuation parts in the signal were detected by the signal method turning for count. The results demonstrated that the quality of reconstructed signal can be greatly improved, with the removal of the baseline wander(adaptive trend) and the Gaussian distributed random noise. By detecting the turn signals in the artifact-free signal, the pathological segments related to chondrom alacia patellae can be effectively localized with the beginning and ending points of the span of turn signals.展开更多
文摘针对某国六发动机进气流量(mass air flow,MAF)传感器在某转速升负荷后出现读数漂移现象,根据经验对增压器的进排气系统进行了噪声振动试验。试验结果表明,发动机涡轮增压器的BPF噪声振动影响了MAF传感器的读数。通过优化涡轮增压器压气机叶轮形状、在MAF传感器和增压器之间加消声器等降低BPF噪声振动的措施,解决了该发动机的MAF传感器读数漂移问题,满足了开发阶段的发动机性能及排放要求。
基金Projects(11302252,11202230) supported by the National Natural Science Foundation of China
文摘This work addresses the problem of self-excited vibration,which degrades the stability of the levitation control,decreases the ride comfort,and restricts the construction cost of maglev system.Firstly,a minimum model containing a flexible bridge and a single levitation unit is presented.Based on the simplified model,the principle underlying the self-excited vibration is explored.After investigations about the energy transmission between the levitation system and bridge,it is concluded that the increment of modal damping can dissipate the accumulated energy by the bridge and the self-excited vibration may be avoided.To enlarge the equivalent modal damping of bridge,the sky-hooked damper is adopted.Furthermore,to avoid the hardware addition of real sky-hooked damper,considering the fact that the electromagnet itself is an excellent actuator that is capable of providing sufficiently fast and large force acting on the bridge to emulate the influence of the real sky-hooked damper,the technique of the virtual sky-hooked damper is proposed.The principle underlying the virtual sky-hooked damper by electromagnet is explored and the vertical velocity of bridge is estimated.Finally,numerical and experimental results illustrating the stability improvement of the vehicle-bridge interaction system are provided.
基金The Fundamental Research Funds for the Central Universities of Chinagrant number:2010121061 and 2010121062+3 种基金The Natural Science Foundation of Fujiangrant number:2011J01371The National Natural Science Foundation of Chinagrant number:81101115
文摘This paper presents the knee-joint vibration signal processing and pathological localization procedures using the empirical mode decomposition for patients with chondrom alacia patellae.The artifacts of baseline wander and random noise were identified in the decomposed monotonic trend and intrinsic mode functions (IMF) using the modeling method of probability density function and the confidence limit criterion.Then, the fluctuation parts in the signal were detected by the signal method turning for count. The results demonstrated that the quality of reconstructed signal can be greatly improved, with the removal of the baseline wander(adaptive trend) and the Gaussian distributed random noise. By detecting the turn signals in the artifact-free signal, the pathological segments related to chondrom alacia patellae can be effectively localized with the beginning and ending points of the span of turn signals.
