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161.
162.
ZHAO Zheying 《声学学报:英文版》1995,(1)
I.IntroductionThcthickncssvibrationsofahomogeneous-anisotropicpiezoclectriccrystalplatewithanexcitingficldparallcltothemajorsurfacesofthep1ate,andalsototheplanewavefront(calledasthepara11e1fic1dcxcitatloninbricO,havebccnana1yzedI'1.Theprimarybehaviourofthick-nessvibrationshasbecnobtaincdasthepIatewitharbitraryorientationisexcitedbythepara11elfield.Inthispapcr,wcwillgofurthcrtogivcancwformu1aofthemechanicalresonantfrequen-cyequation.ILqformisthesameasthercsonantequationofthepuremodeandiseasyt… 相似文献
163.
Command profiles are required to move a dynamical system from rest to rest without residual vibration in a minimum time. The unity-magnitude (UM) input shaper is one of the faster input shaping techniques. However, analytical solution of the impulse time locations is impossible due to the dependent residual vibration constraint equations. Many researchers solve these by using curve fitting. In this paper, the characteristics of the UM shaping coefficients as a function of system parameters are investigated. An analysis procedure to obtain UM input shaper impulse time sequences is presented. Finally, the proposed technique is compared to the zero vibration (ZV) shaper in both response and robustness to modeling error. 相似文献
164.
Hopf-flip bifurcations of vibratory systems with impacts 总被引:2,自引:1,他引:1
Two vibro-impact systems are considered. The period n single-impact motions and Poincaré maps of the vibro-impact systems are derived analytically. Stability and local bifurcations of single-impact periodic motions are analyzed by using the Poincaré maps. A center manifold theorem technique is applied to reduce the Poincaré map to a three-dimensional one, and the normal form map associated with Hopf-flip bifurcation is obtained. It is found that near the point of codim 2 bifurcation there exists not only Hopf bifurcation of period one single-impact motion, but also Hopf bifurcation of period two double-impact motion. Period doubling bifurcation of period one single-impact motion is commonly existent near the point of codim 2 bifurcation. However, no period doubling cascade emerges due to change of the type of period two fixed points and occurrence of Hopf bifurcation associated with period two fixed points. The results from simulation shows that there exists an interest torus doubling bifurcation occurring near the value of Hopf-flip bifurcation. The torus doubling bifurcation makes the quasi-periodic attractor associated with period one single-impact motion transit to the other quasi-periodic attractor represented by two attracting closed circles. The torus bifurcation is qualitatively different from the typical torus doubling bifurcation occurring in the vibro-impact systems. 相似文献
165.
Vijay Raj Singh Jianmin Miao Zhihong Wang Gopalkrishna Hegde Anand Asundi 《Optics Communications》2007,280(2):285-290
In this paper dynamic characterization of a MEMS diaphragm is investigated using lens-less time averaged in-line digital holography. The analysis and capability of the numerically reconstructed amplitude and phase information from in-line time averaged holograms as applied to MEMS vibration are presented. Particularly the effect of mean static state on the phase in time averaged digital holography is explored. A novel double exposure method is also demonstrated using a diverging object wave suitable for dynamic characterization of small size objects. A phase jump in the static deformation fringes in the vibrating regions is observed and described and can be used for precise analysis of vibration mode shape under simultaneous presence of mean static deformation. A simple and robust tool for dynamic optical metrology of MEMS devices and micro-objects using time averaged in-line digital holography is thus proposed. 相似文献
166.
Carlos Prez Lpez Fernando Mendoza Santoyo Ramn Rodríguez Vera Marcelo Funes-Gallanzi 《Optics and Lasers in Engineering》2002,38(3-4)
In industrial and other types of non-controlled environments, an unbalanced rotating object may present characteristic out-of-plane vibration amplitude at a specific frequency. For this type of cases and as a first step towards a complete evaluation, it is only desired to visualize the effect of the vibration on the rotating object, or vice versa, for instance to achieve object balancing. Real time optical non-intrusive measurement techniques such as pulsed electronic speckle pattern interferometry (ESPI), are well suited to study this rotating-vibrating object. The advantage offered by ESPI is that real-time fringe data is qualitatively analyzed while being observed on a TV monitor. The present paper proposes a qualitative method, based on pulsed ESPI, to separate rotation fringes from fringes solely related to vibration. The method relies on a high precision scheme that synchronizes and fixes an object point during rotation, without the use of an optomechanical object derotator. 相似文献
167.
168.
This paper aims at addressing the active control effort of the active-shunted hybrid piezoelectric absorber for structural vibration suppression. Both active control efforts of the integrated and separated hybrid piezoelectric absorbers are analyzed by using a simple cantilevered beam example. It is recognized that a new hybrid piezoelectric absorber based on a switching operation is capable of reducing the active control effort. A switching type of the hybrid piezoelectric absorber can be developed by the simple combination of integrated and separated hybrid piezoelectric absorbers. It is demonstrated that the switching type of the absorber has the capability of the trade-off between the active control effort and the damping performance. 相似文献
169.
This paper demonstrates a methodology for detecting cracks in a metal spindle, which is housed within a military vehicle wheel
end assembly. A finite element model is used to estimate the undamped natural frequencies of the raw spindle. Additional mass
and stiffness is then added to a simplified model of the spindle to simulate sources of variability within the assembly. Spindles
are tested outside the wheel end assembly to compare the responses of undamaged and cracked spindles. A hypothesis testing
approach is developed to detect the presence of a crack based on damage indices involving the summation and multiplication
of spectral energies. Experiments on wheel assemblies mounted on a vehicle with the vehicle lifted off the ground are performed
to demonstrate that the wheel assemblies can be nondestructively evaluated to identify cracks of varying depths despite sources
of variability due to the presence of the brake drum, lack of repeatability in the sensor attachment, and other issues. 相似文献
170.
Indoor testing of road vehicle suspensions 总被引:1,自引:0,他引:1
The paper presents a method for the indoor testing of road vehicle suspension systems. A car suspension is positioned on a
rotating drum located in the Laboratory for the Safety of Transport at the Politecnico di Milano and it is excited as the
wheel passes over a cleat fixed on the drum. The wheel accelerations, displacements and the forces/moments acting at the suspension-chassis
joints are measured in the frequency range 0–120 Hz. Five special six-axis load cells have been designed and used. Transient
wheel motions have been recorded. The influence of the running conditions on the relevant performance indexes related to the
vibration behavior of the tire/suspension system has been assessed. 相似文献