Mechanical strain amplifying transducer
A transducer for assisting in measuring displacement or strain in an object of interest is described. A plate has at least two end sections for mounting the transducer. It comprises a flexible connection between the two end sections. The flexible connection comprises a plurality of rigid portions and flexible interconnections between the rigid portions for allowing relative movement of the rigid portions with respect to each other. The flexible connection has a central section substantially having a U-shape comprising two rigid portions spaced from each other over a distance and adapted for positioning a strain sensing element at the spacing in between said two rigid portions. The rigid portions and flexible interconnections are arranged so that a displacement applied to the end sections results in a relative displacement at the spacing in the central section that is larger than the relative displacement applied to the end sections.
1. A transducer for assisting in measuring displacement or strain in an object of interest, the transducer being a plate having at least two end sections for mounting the transducer to the object of interest,
the transducer comprising a flexible connection between the two end sections, the flexible connection comprising a plurality of rigid portions and flexible interconnections between the rigid portions for allowing relative movement of the rigid portions with respect to each other, the flexible connection having a central section being substantially U-shaped comprising two rigid portions spaced from each other over a distance and adapted for positioning a strain sensing element at the spacing in between said two rigid portions, the central section being connected to the remainder of the flexible connection via flexible interconnections,
wherein the rigid portions and flexible interconnections are arranged so that a first relative displacement applied to the end sections results in a second relative displacement at the spacing in the central section, the second relative displacement being larger than the first relative displacement applied to the end sections,
wherein the central section is connected to the remainder of the flexible connection via flexible interconnections at a position along the upstanding legs of the U-shape, on the rigid portions, away from a position of the spacing adapted for positioning a strain sensing element along the upstanding legs of the U-shape.
2. The transducer according to claim 1 wherein the transducer is configured for inducing a strain amplification in a same direction as a direction wherein a force is applied to the transducer.
3. The transducer according to claim 1 , wherein the plurality of rigid portions and flexible interconnections form more than 1 lever.
4. The transducer according to claim 1 , wherein the central section is connected to the remainder of the flexible connection via flexible interconnections at a position on the rigid portions away from a top side of the substantial U-shape being the opening of the U-shape.
5. The transducer according to claim 1 , wherein the central section is connected to the remainder of the flexible connection via flexible interconnections positioned at an intermediate position along the upstanding legs of the U-shape.
6. The transducer according to claim 1 , wherein the transducer plate is made of a single material.
7. The transducer according to claim 1 , wherein the plate has a uniform thickness.
8. The transducer according to claim 1 , wherein the ratio of the distance between the mounting points to the spacing between the spaced rigid portions of the central section is at least 2.
9. The transducer according to claim 1 , wherein the plate has a single symmetry axis or has two symmetry axes.
10. The transducer according to claim 1 , wherein the distance between the mounting points is at least 5 cm.
11. The transducer according to claim 1 , in which the eigenfrequencies of the structure are above 50 Hz.
12. The transducer according to claim 1 in which the thickness of the structure is between 1-10 mm.
13. The transducer according to claim 1 , in which the spring constant of the plate is below 107 N/m.
14. The transducer according to claim 1 , in which grooves are provided on the surface of the plate to mount the strain element at the central section.
15. The transducer according to claim 1 , wherein the transducer further comprises at least one rigid connection between the two end sections.
16. A system for measuring displacement or strain in an object of interest, the system comprising a transducer according to claim 1 and a strain element connected to the central section and provided with a strain sensor for measuring strain in the central section.
17. The system according to claim 16 , wherein the strain experienced by the strain sensor is amplified by the transducer with respect to the strain applied to the end sections of the plate, whereby the strain amplification is larger than 5.
18. The system according to claim 16 , wherein strain element is mounted under pre-strain and/or wherein the strain element comprises one or more of an optical fiber, a strain gauge or a fiber Bragg grating.