WO2004074797A1 - Structure for shear force sensing - Google Patents

Structure for shear force sensing

Info

Publication number
WO2004074797A1
WO2004074797A1 PCT/DK2004/000122 DK2004000122W WO2004074797A1 WO 2004074797 A1 WO2004074797 A1 WO 2004074797A1 DK 2004000122 W DK2004000122 W DK 2004000122W WO 2004074797 A1 WO2004074797 A1 WO 2004074797A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
plane
structure
shear
force
sensor
Prior art date
Application number
PCT/DK2004/000122
Other languages
French (fr)
Inventor
Mohamed Yahia Benslimane
Peter Gravesen
Original Assignee
Danfoss A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01LMEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00Measuring force or stress in general
    • G01L1/14Measuring force or stress in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators
    • G01L1/142Measuring force or stress in general by measuring variations in capacitance or inductance of electrical elements, e.g. by measuring variations of frequency of electrical oscillators using capacitors

Abstract

This invention relates generally to elastomeric sensors of the type where two electrodes are placed on opposite sides of an elastomeric corrugated core. More specifically, this invention relates to the application of such sensors as a shear force sensor structure. It is a task of this invention to disclose a device, by means of which elastomeric sensors can be used for sensing shear forces.

Description

Structure for shear force sensing

This invention relates generally to elastomeric sensors of the type where two electrodes are placed on opposite sides of an elastomeric corrugated core. More specifically, this invention relates to the application of such sensors as a shear force sensor structure .

Examples of such sensors exist, where the basic elements often are a strain gauge consisting of resistive elements composing each side of a bridge formation, like a Wheat- stone bridge circuit. The resistive elements are characterized by a change in resistance, when forces, like a shear force, are applied thereto. In the application DE

100 40 287 Al four such strain gauges are placed plane and orthogonal to each other on a sheet, and each consists of two connected bridges placed mutual diagonal on the sheet . The idea to place several strain gauges in such a forma- tion, is to eliminate the influence of parasitic forces and moments on the measurements .

It is the subject of this invention to eliminate the need of strain gauges, and to produce a cheap and easily manu- factured shear force sensor, based on the fact that the capacity alters when the distance between the to electrodes and/or the area of the two electrodes of a capacitor are changed.

Elastomeric actuators with a corrugated core, and having anisotropic properties, are known from DE 100 54 247 C2. The actuator described in DE 100 54 247 C2 has an elastomeric corrugated core, onto which an electrode is deposited by for example physical vapor deposition processes. The electrode, evaporated onto opposite sides of the core, onto which an electrode is vaporised. The electrode, vaporised onto opposite sides of the core, will follow the corrugation, and will therefore give the actuator a higher ability of deformation in a direction across the corruga- tion, than in a direction along the corrugation. Consequently, when an electrical field is applied to two opposite electrodes, forcing the two electrodes towards each other, the thickness of the core will decrease, and convert into an extension only in the direction across the corrugation.

The actuator of DE 100 54 247 C2 will also work as a ca- pacitive sensor, described in PCT/DK02/00861. Mechanical deformation or influence in one direction across the cor- rugation will be converted into a variation in thickness and the area, and this will change the distance to area ratio, and thus the capacitance, between the two electrodes on opposite sides.

It is an object of this invention to disclose a device, by means of which elastomeric sensors can be used for sensing shear forces. This object could be achieved in that the shear force sensor is made as a structure comprising a base plate, at least one pair of planes positioned around a centre plane, said centre plane raised as a normal to said base plate, each of said pair of planes comprising:

- a first plane inside the structure having defined on it a first and a second endline, said two endlines placed at different vertical distances relative to said base plate and different horizontal distances relative to said centre plane,

- a second plane inside the structure opposing said first plane through said centre plane and having defined on it a first and a second endline, said two endlines placed at different vertical distances relative to said base plate and different horizontal distances relative to said centre plane, where the first and second planes do not necessarily have identical profiles, and where the first plane and the sec- ond plane are provided with similar elements, each element consisting of an elastomeric core with a compliant electrode on each side. The corrugation of the elastomeric sensors runs along the base plate and the centre plane, deformations across the centre plane being converted into dimension variations in each of the two elements.

In a prefered embodiment of the invention, the shear force sensor consists of multiples of such pairs of first and second planes, where the first plane of a second pair is following in succession of the second plane of a first pair.

Preferably the structure can be formed as a massive elastomeric body, moulded with the two elements inside. This will give the structure a high degree of deformation, depending on the elastomeric material, and thus the shear force sensor could be useful in applications with a low level of forces, but at high relative deformation.

In one specific embodiment the structure could be moulded as only one unit, where only the two elements are forming the first and second plane inside the structure. This will provide a very simple structure, which in production will be easy to handle.

In another specific embodiment of the invention the elastomeric body can be formed by a bottom part and a top part, where the geometry of the bottom and top part forms the first and the second plane. Further specific, the bot- torn and the top part are separate sub-structures, which are assembled with the two elements between them in a way that provides an interlock of the two sub-structures. Hereby a multi-element structure is provided, and the shear force sensor is formed upon assembly of the sub- structures .

As the structure is a sensor element, it is preferable that the capacitance of each of the elements is detectable. Detection of the capacitance difference could give the sensor signal, depending on the level of shear forces and shear deformation. An advantage obtained through difference sensing, is that influences from temperature variations, influences from force or deformations in other directions than pure shear force, or the like will have same impact on both elements, and therefore have no influence on the difference detection.

In a specific embodiment of the invention, the two elements could be mounted or fixed in a loaded position, when the structure is in an unstressed situation, meaning that an increase as well as a decrease in capacitance is detectable. When an element is in an unloaded position, the capacitance can only be increased through an extension of the element across the direction of the corrugation, as a reduction of the element beyond the no-load position is impossible. This could be overcome by pre-loading each element .

It is preferable that only deformations in said shear force direction is detectable. This could reduce detection errors from forces in other directions than the pure shear forces. Despite this the invention is not to be limited to detecting shear forces alone. The sensor may measure shear force by detecting a change in the capitance difference, or a normal force by detecting a change in the sum of capacitances .

In yet another specific embodiment of the invention, the structure could further comprise an electronic circuit, and yet further the electronic circuit could be connected with each element to perform the force detection. Hereby is achieved that the structure exposes a complete sensor unit, where the output signal corresponds directly to the shear force.

Now having described the invention in general terms, a detailed embodiment of the invention will be described with reference to the drawings, showing:

Fig. 1: An exploded view of a multi-element structure Fig. 2: The multi-element structure of figure 1 assembled Fig. 3: The shear force sensor block in a sensing position Fig. 4: The shear force sensor block in another sensing position Fig. 5: The shear force sensor made of two blocks. Fig. 6: Sideview of a second embodiment of the shear force sensor. Fig. 7: Sideview of a third embodiment of the shear force sensor.

Figure 1 shows a structure, generally indicated as position 1, in an exploded view. The structure comprises a bottom part 2, a top part 3 and elements 4 and 5, each formed as an elastomeric sensor with a corrugated core. Two axes 6 and 7 are indicated on figure 1, by means of which the geometry of the structure is to be explained. The bottom part 2 has a base plate 8, and on the opposite surface a first plane 9 and a second plane 10 are formed. The two planes 9 and 10 in this embodiment are facing each other through a centre plane, the centre plane being the plane with the axes 6 and 7.

The top part 3 has a bottom surface with a geometry similar to that of the top surface of the bottom part 2 , and between the top part 3 and the bottom part 2, the two ele- ments 4 and 5 are placed on the two planes 9 and 10. Putting the elements of figure 1 together will give figure 2 as result .

On each plane is defined a first endline 14 and a second endline 15, where it is seen that the first endline 14 is placed above the second endline 15, and the first endline 14 is placed closer to the normal plane 7 than the second endline 15.

The structure of figure 2 has been explained through an exploded view in figure 1, simply for the explanation. The preferred embodiment is a homogenous structure, moulded in one piece with the two elements 4 and 5 fixed in position before the structure is moulded. This will give the struc- ture of figure 2, with the two elements 4 and 5 inside the structure. Wiring between an electronic circuit and the electrodes on each element of 4 and 5 are not shown in figures 1 and 2, and the electronic circuit itself is not shown either. Applying this is simply a matter of using known techniques, and shall therefore not be subject to further explanation.

The defined endlines 14 and 15 are seen to have different vertical distances to the base plate 26, and different horizontal distances to the center plane defined by the axis 6 and 7.

Figure 3 shows the shear force sensor 1 in a sensing posi- tion, where pure shear forces are applied as a couple indicated as positions 12 and 12'. The couple 12 and 12' will increase element 4 and decrease element 5, whereby the capacitance of element 4 is increased and the capacitance of element 5 is reduced. Figure 4 shows another sensing position where a couple 13 and 13' are applied as pure shear force. In figure 4, the element 4 is decreased and element 5 is increased, whereby the capacitance of element 4 is reduced and the capacitance of element 5 is increased.

On figure 5 a shear force sensor is illustrated comprising two pairs of planes of the type shown in figure 1. The view is here from the side and the electrodes are not shown. A first pair 20 consists of the two planes 21 and 22, the second pair 23 consists of the two planes 24 and

25. The pairs are positioned so that the first plane 24 of the second pair 23 follows in succession of the second plane 22 of the first pair 20. Any number of such pairs as 20 and 23 may be used in the shear force sensor.

Figure 6 shows a sideview of a second embodiment of the invention, dimensions not being correct, where the two opposing planes 16 and 17 are facing each other through the center plane, the black parts 18 and 19 being the elec- trodes (the corrugations not shown) . Here the profile takes on a curved shape. The two planes 16 and 17 are shown not to be symmetrical around the normal plane.

Figure 7 shows a sideview of a third embodiment of the in- vention, where endpoints 30 and 31 of the first plane 33 are at the same vertical level as the endpoints 34 and of the second plane 36.

Claims

Claims
1. Shear force sensor made as a structure comprising a base plate, at least one pair of planes positioned around a centre plane, said centre plane raised as a normal to said base plate, each of said pair of planes comprising:
- a first plane inside the structure having de- fined on it a first and a second endline, said two endlines placed at different vertical distances relative to said base plate and different horizontal distances relative to said centre plane,
- a second plane inside the structure facing said first plane through said centre plane and having defined on it a first and a second endline, said two endlines placed at different vertical distances relative to said base plate and different horizontal distances relative to said centre plane, where said first plane and said second plane are supplied with similar elements, each element consisting of an elastomeric core with a compliant electrode on each side.
2. Structure in accordance with claim 1, characterised in that it forms a massive elastomeric body, moulded with said pairs of elements inside.
3. Structure in accordance with claim 2, characterised in that said pairs of elements are forming said first and second plane inside said structure.
4. Structure in accordance with claim 1, characterised in that said body is formed by a bottom part and a top part, and where the geometry of said bottom and top part forms said first and second plane.
5. Structure in accordance with claim 4, characterised in that said bottom and said top part are separate sub-structures, which are assembled with said two elements between them in a way that provides an in- terlock of the two sub-structures .
6. Structure in accordance with claim 1, characterised in that the capacitance of each of said elements is detectable .
Structure in accordance with claim 6, characterised in that shear forces relative to said centre plane induce deformations, which will influence said capacitance .
Structure in accordance with claim 7, characterised in that said influence on said capacitance is detectable.
9. Structure in accordance with claim 8, characterised in that an increase as well as a decrease in capacitance is detectable.
10. Structure in accordance with claim 7, characterised in that only deformations in said shear force direction is detectable.
11. Structure in accordance with claim 1, characterised in that it further comprises an electronic circuit.
12. Structure in accordance with claims 11 and 6, characterised in that said electronic circuit is connected with each element to perform said detection.
13. Structure in accordance with claim 7, characterised in that said structure is formed of an elastomeric material with characteristics in accordance with the magnitude of the mechanical stress in the application.
PCT/DK2004/000122 2003-02-24 2004-02-24 Structure for shear force sensing WO2004074797A1 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DKPA200300275 2003-02-24
DKPA200300275 2003-02-24

Publications (1)

Publication Number Publication Date
WO2004074797A1 true true WO2004074797A1 (en) 2004-09-02

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WO (1) WO2004074797A1 (en)

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7233097B2 (en) 2001-05-22 2007-06-19 Sri International Rolled electroactive polymers
US7320457B2 (en) 1997-02-07 2008-01-22 Sri International Electroactive polymer devices for controlling fluid flow
US7368862B2 (en) 1999-07-20 2008-05-06 Sri International Electroactive polymer generators
US7378783B2 (en) 2001-03-02 2008-05-27 Sri International Electroactive polymer torsional device
US7436099B2 (en) 2003-08-29 2008-10-14 Sri International Electroactive polymer pre-strain
US7492076B2 (en) 2006-12-29 2009-02-17 Artificial Muscle, Inc. Electroactive polymer transducers biased for increased output
US7521847B2 (en) 2005-03-21 2009-04-21 Artificial Muscle, Inc. High-performance electroactive polymer transducers
US7521840B2 (en) 2005-03-21 2009-04-21 Artificial Muscle, Inc. High-performance electroactive polymer transducers
US7567681B2 (en) 2003-09-03 2009-07-28 Sri International Surface deformation electroactive polymer transducers
US7595580B2 (en) 2005-03-21 2009-09-29 Artificial Muscle, Inc. Electroactive polymer actuated devices
US7626319B2 (en) 2005-03-21 2009-12-01 Artificial Muscle, Inc. Three-dimensional electroactive polymer actuated devices
US7750532B2 (en) 2005-03-21 2010-07-06 Artificial Muscle, Inc. Electroactive polymer actuated motors
US7915789B2 (en) 2005-03-21 2011-03-29 Bayer Materialscience Ag Electroactive polymer actuated lighting
US8054566B2 (en) 2005-03-21 2011-11-08 Bayer Materialscience Ag Optical lens displacement systems
US9195058B2 (en) 2011-03-22 2015-11-24 Parker-Hannifin Corporation Electroactive polymer actuator lenticular system
US9231186B2 (en) 2009-04-11 2016-01-05 Parker-Hannifin Corporation Electro-switchable polymer film assembly and use thereof
US9425383B2 (en) 2007-06-29 2016-08-23 Parker-Hannifin Corporation Method of manufacturing electroactive polymer transducers for sensory feedback applications
US9553254B2 (en) 2011-03-01 2017-01-24 Parker-Hannifin Corporation Automated manufacturing processes for producing deformable polymer devices and films
US9590193B2 (en) 2012-10-24 2017-03-07 Parker-Hannifin Corporation Polymer diode
US9761790B2 (en) 2012-06-18 2017-09-12 Parker-Hannifin Corporation Stretch frame for stretching process
US9876160B2 (en) 2012-03-21 2018-01-23 Parker-Hannifin Corporation Roll-to-roll manufacturing processes for producing self-healing electroactive polymer devices

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0756162A2 (en) * 1995-07-28 1997-01-29 Nippon Dyne-A-Mat Corporation Pressure sensor
DE10054247A1 (en) * 2000-11-02 2002-05-23 Danfoss As Actuating element and process for its preparation
WO2002057711A1 (en) * 2001-01-10 2002-07-25 Societe De Technologie Michelin Method and device for evaluating deformations and forces

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0756162A2 (en) * 1995-07-28 1997-01-29 Nippon Dyne-A-Mat Corporation Pressure sensor
DE10054247A1 (en) * 2000-11-02 2002-05-23 Danfoss As Actuating element and process for its preparation
WO2002057711A1 (en) * 2001-01-10 2002-07-25 Societe De Technologie Michelin Method and device for evaluating deformations and forces

Cited By (37)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7320457B2 (en) 1997-02-07 2008-01-22 Sri International Electroactive polymer devices for controlling fluid flow
US7368862B2 (en) 1999-07-20 2008-05-06 Sri International Electroactive polymer generators
US7378783B2 (en) 2001-03-02 2008-05-27 Sri International Electroactive polymer torsional device
US7705521B2 (en) 2001-03-02 2010-04-27 Sri International Electroactive polymer torsional device
US7456549B2 (en) 2001-03-02 2008-11-25 Sri International Electroactive polymer motors
US7233097B2 (en) 2001-05-22 2007-06-19 Sri International Rolled electroactive polymers
US8093783B2 (en) 2001-05-22 2012-01-10 Sri International Electroactive polymer device
US8042264B2 (en) 2001-05-22 2011-10-25 Sri International Method of fabricating an electroactive polymer transducer
US7761981B2 (en) 2001-05-22 2010-07-27 Sri International Methods for fabricating an electroactive polymer device
US7921541B2 (en) 2003-08-29 2011-04-12 Sri International Method for forming an electroactive polymer transducer
US7785656B2 (en) 2003-08-29 2010-08-31 Sri International Electroactive polymer pre-strain
US7436099B2 (en) 2003-08-29 2008-10-14 Sri International Electroactive polymer pre-strain
US8316526B2 (en) 2003-08-29 2012-11-27 Sri International Method for forming an electroactive polymer
US7567681B2 (en) 2003-09-03 2009-07-28 Sri International Surface deformation electroactive polymer transducers
US7787646B2 (en) 2003-09-03 2010-08-31 Sri International Surface deformation electroactive polymer transducers
US7750532B2 (en) 2005-03-21 2010-07-06 Artificial Muscle, Inc. Electroactive polymer actuated motors
US7679267B2 (en) 2005-03-21 2010-03-16 Artificial Muscle, Inc. High-performance electroactive polymer transducers
US7626319B2 (en) 2005-03-21 2009-12-01 Artificial Muscle, Inc. Three-dimensional electroactive polymer actuated devices
US7595580B2 (en) 2005-03-21 2009-09-29 Artificial Muscle, Inc. Electroactive polymer actuated devices
US7915789B2 (en) 2005-03-21 2011-03-29 Bayer Materialscience Ag Electroactive polymer actuated lighting
US7521840B2 (en) 2005-03-21 2009-04-21 Artificial Muscle, Inc. High-performance electroactive polymer transducers
US7923902B2 (en) 2005-03-21 2011-04-12 Bayer Materialscience Ag High-performance electroactive polymer transducers
US7990022B2 (en) 2005-03-21 2011-08-02 Bayer Materialscience Ag High-performance electroactive polymer transducers
US7521847B2 (en) 2005-03-21 2009-04-21 Artificial Muscle, Inc. High-performance electroactive polymer transducers
US8054566B2 (en) 2005-03-21 2011-11-08 Bayer Materialscience Ag Optical lens displacement systems
US8183739B2 (en) 2005-03-21 2012-05-22 Bayer Materialscience Ag Electroactive polymer actuated devices
US8283839B2 (en) 2005-03-21 2012-10-09 Bayer Materialscience Ag Three-dimensional electroactive polymer actuated devices
US8072121B2 (en) 2006-12-29 2011-12-06 Bayer Materialscience Ag Electroactive polymer transducers biased for optimal output
US7492076B2 (en) 2006-12-29 2009-02-17 Artificial Muscle, Inc. Electroactive polymer transducers biased for increased output
US7915790B2 (en) 2006-12-29 2011-03-29 Bayer Materialscience Ag Electroactive polymer transducers biased for increased output
US9425383B2 (en) 2007-06-29 2016-08-23 Parker-Hannifin Corporation Method of manufacturing electroactive polymer transducers for sensory feedback applications
US9231186B2 (en) 2009-04-11 2016-01-05 Parker-Hannifin Corporation Electro-switchable polymer film assembly and use thereof
US9553254B2 (en) 2011-03-01 2017-01-24 Parker-Hannifin Corporation Automated manufacturing processes for producing deformable polymer devices and films
US9195058B2 (en) 2011-03-22 2015-11-24 Parker-Hannifin Corporation Electroactive polymer actuator lenticular system
US9876160B2 (en) 2012-03-21 2018-01-23 Parker-Hannifin Corporation Roll-to-roll manufacturing processes for producing self-healing electroactive polymer devices
US9761790B2 (en) 2012-06-18 2017-09-12 Parker-Hannifin Corporation Stretch frame for stretching process
US9590193B2 (en) 2012-10-24 2017-03-07 Parker-Hannifin Corporation Polymer diode

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