 M=5(4,11)runlength limited code for multi-level data |
| The present invention is directed toward an M=5 (4,11) runlength-limited code for multi-level data ... |
|
| Cursor control system |
| Based on the above background, it is an object of the present invention to provide a cursor ... |
|
| Computer mouse pad |
| I claim: 1. A computer mouse pad made of a laminate consisting of three discrete layers, an upper ... |
|
| Variable resistance switch |
| There are claimed: 1. Variable resistance switch of a continuously-variable resistance pressure-... |
|
| Post-termination apparatus and process for thick film resistors of printed circuit boards |
| Referring now to FIG. 1A, there is shown a portion of a printed circuit board 10 including a layer ... |
|
| Reduction of comparator power requirement in a switched capacitor ADC |
| It is an objective of the invention to reduce the power requirement of ADC devices of the kind ... |
|
| amplifying signals in switched capacitor environments |
| An embodiment of an amplification circuit of the present invention is implemented in the context of ... |
|
| Device for handling game pieces |
| What is claimed is: 1. A unitary device for handling game pieces comprising four uniform one piece ... |
|
| Radar detector arrangement |
| In accordance with the present invention, a radar detector is equipped with a positional tracking ... |
|
| Wide band radar detector with three-sweep input stage |
| The present invention provides a police radar detector that takes advantage of the sensitivity ... |
|
|
Apparatus for passive damping of a structure
| Details |
Inventors: Bicos, Andrew S.;
Assignee: McDonnell Douglas Corporation (Long Beach, CA)
Primary Examiner: Stephan; Steven L.
Assistant Examiner: Haszko; D. R.
Attorney, Agent or Firm: Stout; Donald E., Scholl; John P.
An apparatus for controlling the motion of a structural member on a space platform truss structure, launch vehicle, automobile, building, or the like is comprised of a first driving piezoelectric element and a second constraining piezoelectric element. The first piezoelectric element is embedded in or bonded onto the structural member. The second piezoelectric element is bonded onto the structural member, with a viscoelastic material (VEM) layer sandwiched between the structural member and the second piezoelectric element. The first and second piezoelectric elements are electrically connected in opposite phase. When the structural member is deformed by an applied force, the first driving piezoelectric element is correspondingly deformed, generating an electrical field. The electrical field is then applied in an opposite sense to the second piezoelectric element through the electrical connections, thereby oppositely deforming the second piezoelectric element with respect to the first piezoelectric element. This opposite deformation induces a large shear strain in the VEM layer, giving the apparatus a large damping capacity. Because the system is passive, it has great advantages over prior art systems, because of its greater simplicity, lower cost, easier maintainability, and lower weight. |
|
DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings, FIG.
1 shows a preferred passive damping system for a structural member 10, which includes a constraining piezoelectric element 12, an embedded piezoelectric element 14, and a viscoelastic material (VEM) layer 16 positioned between the piezoelectric element 12 and the structural member 10.
Each piezoelectric element is electroded on its upper and lower surface.
Piezoelectric elements 12 and 14 are electrically coupled by means of electrical connections 18, in an opposite phase relationship.
Connectors 18 are preferably flat leads, because they are easier to embed, but may be any other known connector type.
The structural member 10 may be employed in any type of structure, such as a space vehicle, building, ground vehicle, aircraft, machine, or the like.
The VEM layer 16 may be formed of any known VEM, such as one or more layers of damping tape, for example.
The piezoelectric element 12 must be of a material which has a high enough modulus to serve as a relatively stiff constraining layer to the VEM layer 16, and both of the piezoelectric elements 12 and 14 are preferably formed of a piezoelectric ceramic, such as Lead Zirconate Titanate (PZT).
FIGS.
2 and 3 both show the embodiment of FIG.
1, with the structural member 10 under an oscillating load F which would be typical when the member is subjected to a vibration, a change in motion of the structure, or the like.
When the load F is applied to the structural member 10, part of the load is applied to the piezoelectric element 14, which is embedded in the member 10.
This causes the piezoelectric element 14 to deform by elongating, as shown in both of the FIGS.
2 and 3.
This deformation of element 14 in turn causes an electric field to be generated in the material of element 14, because of its piezoelectric properties.
FIG.
2 represents the case in which the two piezoelectric elements 12 and 14 are not electrically connected.
With no electrical connections between these two elements, the inventive device acts in much the same manner as in the classical damping approach discussed in the Background of the Invention portion of this specification, wherein a VEM layer is sandwiched between the structural member and a rigid constraining layer
|
|
Coded 
