Measuring and testing – Vibration – Vibrator
Reexamination Certificate
2000-09-29
2003-01-07
Kwok, Helen (Department: 2856)
Measuring and testing
Vibration
Vibrator
C073S001820
Reexamination Certificate
active
06502464
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to vibrating systems and to an energy redistribution system for use in the vibrating system that functions to level the power spectral density of the vibrations and to redistribute vibrational energy among the three orthogonal linear and three rotational axes of vibration in a controllable manner.
PROBLEM
It is a problem in the field of vibrating systems to control the amplitude of vibrations as well as the spectral density of vibrations in each of the three orthogonal linear and three rotational axes of vibration. One such vibrating system consists of a mass of predefined shape and extent that responds to a series of impulses by vibrating as a function of the characteristics of the mass, as well as the frequency, pulse shape and magnitude of the impulses applied to the mass and the location of the site at which the impulses are imparted. These vibrating systems typically have very irregular spectrum in the above-noted six axes of vibration.
In the field of vibrating systems, there are impact driven vibration test systems that are used to test products to determine if design or process defects are present.
In these vibration test systems, it is desirable to excite all (or at least selected) frequencies of vibration as well as all six axes of vibration (three translation axes and three rotation axes) simultaneously and in a controllable manner. The present impact driven vibration test systems available for the vibration excitation of products lack reasonably flat spectra in the various axes and the balance among these axes (the overall level of vibration in each axis) is usually not very uniform. Exact uniformity is not required, but some commercially available impact driven vibration test systems have spectral density variations that leave some frequencies and axes of vibration essentially unexcited and some axes and frequencies of vibration excited to comparatively overly high levels. Additionally, the impact driven vibration test systems are usually very weak in the critical low frequency areas of vibration. The existing impact driven vibration test systems not only suffer from a lack of vibration in some frequencies and axes of vibration but also do not have any apparatus that allows the translation of energy from high frequencies to low frequencies of vibration.
The impact driven vibration test systems are typically implemented as a basic shaker table that includes a platform upon which the product is mounted. The platform is supported on flexible supports that permit the vibration of the table freely in all directions, independent of the environment. The shaker table generates vibration in six axes by providing either pneumatically driven or mechanically driven actuators, termed exciters or vibrators, that produce an impact to initiate the vibrations. The platform couples the vibrations from the actuators to the product. The typical actuator is an impact device that produces forces of high magnitude but very short duration, typically driven by air pressure. There are two effects that result from this input: the repeated impacts generate a line spectrum (equally spaced lines) in the spectral density domain, the shaker table is set into a quasi-resonance condition and all of its modes of vibration are excited. As a result, the spectral density of the shakers is not uniform and can vary by six or more decades. These variations are unacceptable for highly accelerated testing or for simulation applications.
The physical properties of the shaker table components cause the shaker table to respond to the different frequencies in the impact spectrum in different ways. The physical properties of the shaker table components typically resonate with certain vibration frequencies and suppress other vibration frequencies to result in selected modes of vibration. For example, resonation results in the vibrations remaining for a relatively long time compared to the duration of the input pulse, while suppression results in the quenching of the vibration in a relatively short time. The modes of vibration of the shaker table which are excited are also a function of the location, orientation and nature of the actuators as well as the dimensions and properties of the platform. Thus, by designing the shaker table to have relatively low resonant frequencies, the spectral response of the system can be shifted to fill up the low frequency end of the spectrum, but there is a tendency to have significant variation in spectral density.
This shaker table architecture is well known and the great difficulty facing the test engineers in this field is the implementation of the shaker table in a manner to precisely produce the desired vibration conditions in terms of the presence of selected vibration frequencies and regulation of their magnitude. There are obviously numerous variables, each of which affects the magnitude and frequency of the vibrations that are produced. These variables include but are not limited to: number of actuators, actuator placement, actuator characteristics, frequency of actuator operation, physical coupling of the actuator to the shaker table platform, coupling of the product to the shaker table platform, damping elements included in the shaker table, dimensions of the shakertable, shakertable implementation, including materials and intervening structures. A further complicating factor is that these variables can also be interactive, in that the variation of one variable can impact the effects produced by another variable. Thus, the design of a shaker table is a non-trivial task and typically represents a compromise that produces a crude emulation of the desired vibration characteristics. The quest for accuracy in this field is ongoing and has been relatively unsuccessful to date.
Thus, while there exist numerous variations of shaker tables, each implementation presents limitations that prevent the test engineer from effecting precise control over the vibration frequencies and magnitudes to thereby precisely emulate the environment that the product under test will encounter or the environment desired for simulation or stimulation.
The above-noted patent application titled: “Tuned Energy Redistribution System for Vibrating Systems” addresses this problem by selectively reducing discrete frequencies of vibration and translating them into frequency limited broad band vibrations. However, the system described in this patent application is limited in terms of not addressing the simultaneous redistribution of vibration among the six axes of vibration (three translation axes and three rotation axes).
U.S. Pat. No. 4,164,151 issued Aug. 14, 1979 to Douglas C. Nolan et al discloses a random vibration generator that includes a hollow table top for supporting equipment to be subjected to vibration and a sinusoidal reaction-type vibration machine connected to the tabletop to produce a sinusoidal vibration of adjustable frequency and amplitude. The hollow tabletop is divided into four sections, each containing a number of projectiles, such as heavy balls which roll and bounce around within these four sections, impacting the floor and ceiling of the four sections and each other in random fashion to produce random shocks over a wide band of frequency and amplitude, thereby subjecting equipment connected to the tabletop with every possible vibration failure mode that might occur in nature.
Therefore, the field of vibrating systems is devoid of any apparatus that is operable to controllably redistribute energy from axes and frequencies of high acceleration to axes and frequencies of low acceleration. Additionally, the impact driven vibration test systems are usually very weak in the critical low frequency areas of vibration. The existing impact driven vibration test systems not only suffer from a lack of vibration in some frequencies and axes of vibration but also do not have any apparatus that allows the translation of energy from high frequencies to low frequencies of vibration.
SOLUTION
The above-described problems are solved and a technical adva
Kwok Helen
Patton & Boggs LLP
LandOfFree
Energy redistribution system for a vibrating system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Energy redistribution system for a vibrating system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Energy redistribution system for a vibrating system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3001310