DE102015108960A1 - Device with negative stiffness - Google Patents

Abstract

A negative stiffness device includes a fluid filled bellows disposed between a first surface and a second surface, the bellows and the first and second surfaces having a substantially equilibrium orientation between the first and second surfaces. The bellows and the first and second surfaces comprise other orientations, the first and second surfaces being out of substantial equilibrium orientation, and the bellows exerting an adjustment force to drive the first and second surfaces farther away from the substantially equilibrium orientation

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from US provisional Application No. 62 / 009,416, filed Sep. 6, 2014, which is incorporated herein by reference.

TECHNICAL AREA

This disclosure relates to a device with negative stiffness.

BACKGROUND

The notes in this section are merely background information associated with the present disclosure. Accordingly, such remarks are not intended to constitute an acknowledgment of the state of the art.

Negative stiffness devices are known that achieve their performance goals by, for example, mechanical buckling or electromagnetism. However, negative stiffness mechanical devices require joints that exhibit wear and friction. In addition, mechanical implementations that require vertical springs may suffer from installation disadvantages. Electromagnetic implementations may take the form of linear motors that are massive and expensive, or solenoid attractors that are limited to small adjustments. In addition, electromagnetic implementations require energy input, including holding.

SUMMARY

A negative stiffness device includes a fluid filled bellows disposed between a first surface and a second surface, the bellows and the first and second surfaces having a substantially equilibrium orientation between the first and second surfaces. The bellows and the first and second surfaces comprise other orientations, the first and second surfaces being displaced from substantially equilibrium orientation, and the bellows exerting an adjustment force to drive the first and second surfaces farther away from the substantially equilibrium orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

1 shows an embodiment of a device with negative stiffness and linear motion in equilibrium orientation according to the disclosure;

2-A to 2-C certain key components of the device with negative rigidity and linear motion of 1 according to the disclosure;

3-A and 3-B the device with negative rigidity and linear motion of 1 which is out of equilibrium orientation, according to the disclosure;

4-A and 4-B the device with negative rigidity and linear motion of 1 according to the disclosure, applied to a hydropneumatic strut;

5 Figure 4 shows force versus displacement data from Table 1 according to the disclosure;

6-A and 6-B show an embodiment of a device with negative stiffness with rotational movement in equilibrium orientation according to the disclosure; and

7-A and 7-B the device with negative stiffness with rotational movement of 6-A and 6-B which is out of equilibrium orientation, according to the disclosure show.

DETAILED DESCRIPTION

Referring now to the drawings wherein the illustrated is for the purpose of illustrating certain example embodiments only and not for the purpose of limiting the same, FIG 1 a device 100 with negative stiffness that works linearly, ie a device with negative stiffness and linear motion. The device 100 with negative stiffness and linear motion has three main components: an outer tube or an outer guide 1 , an inner tube or inner guide 3 and a flexible, substantially toroidal bellows 2 , Thus, in the general case, a negative stiffness and linear motion device according to the present disclosure has a substantially toroidal bellows disposed between a first surface and a second surface.

The bellows 2 is generally between and in contact with the inner surface 8th the outside guide 1 and the outer surface 7 the inner guide 3 arranged. The general section of the bellows 2 in contact with the inner surface 8th the outside guide 1 can as an outer wall 19 be designated, and the general section of the bellows 2 in contact with the outer surface 7 the inner guide 3 can as an interior wall 17 be designated. End walls of the bellows can generally the axially opposite portions of the bellows 2 affecting the interior and exterior walls. Since the position and contact relationship of the bellows varies between and with the surfaces of the inner and outer guides in operation, it should be understood that the inner, outer and end walls are relative descriptors and do not relate to absolute portions of the bellows. The bellows 2 is flexible, being made of rubber or elastomeric material and filled with a fluid, either gas or liquid.

The inner guide 3 is elongate and cylindrical and longitudinal along an axis of linear motion (longitudinal center line 200 ). The exterior guide 1 is elongated and longitudinally aligned along the axis of linear motion, but generally has convex cross-sectional walls when intersected by the longitudinal centerline 200 , In a section perpendicular to the longitudinal center line 200 are the cross sections of the outer guide 1 circular with a centrally located minimum circumference and circumferences that are monotone to each end of the outer track 1 away from the minimum amount. While the inner and outer guides 3 respectively. 1 are shown symmetrically in the longitudinal direction, the applicants take asymmetric geometries into consideration, for example an arrangement of the minimum circumference of the guide 1 closer to one end, generally convex cross-sections of different curvature, or tubular structures that expand or collapse, as may be the case only at one end thereof. In addition, while the inner guide 3 is cylindrical, the inner guide 3 own other geometries. For example, the inner guide 3 have a maximum central circumference and circumferences that reduce from the maximum central circumference to each end. While the inside guide 3 alternatively, as shown as an empty hollow cylinder, the guide may be completely solid, hollow with a filled core, or of any construction apparent to one skilled in the art. Material that can be used to guide the interior 3 and outdoor tour 1 can be a suitable material for any application depending on such considerations as mass, strength, operating environment, design to manufacture, etc. Exemplary materials may include conventional steel material tubing. Techniques for expanding and reducing the tubing are known to those skilled in the art and may include, for example, plunger shapes, rotational molding and hydroforming.

The device 100 with negative stiffness is in 1 with a longitudinally symmetrical arrangement between the outer guide 1 and the bellows 2 shown, ie the bellows 2 is centered with respect to the minimum cross-sectional circumference of the outer guide 1 arranged. The bellows 2 is between the inner surface 8th the outside guide 1 and the outer surface 7 the inner guide 3 limited. Even at the narrowest part of the guide 1 can be an open channel on the inside of the bellows 2 be there for a fluid connection. In the component orientation of 1 is the brat 2 compressed to a nearly uniform thickness from wall to wall from end to end, and due to the symmetrical arrangement with respect to the outer guide 1 are the longitudinal forces (if according to the profiles of the inner surface 8th and the outer surface 7 available) balanced. Thus, the orientation of 1 is referred to as a substantially equilibrium orientation or as an equilibrium state. Such a position may also be referred to as a nominal or coordinated position. The bellows 2 is on the inside guide 3 and the outside guide 1 attached to the respective surfaces where they meet at one or more locations in alignment with the section passing through the center of symmetry (ie the section perpendicular to that through the smallest circumference of the outer guide 1 extending longitudinal axis). Such attachment may be effected by means of adhesives or co-acting positive and negative bead features, for example bead.

There will be an additional contextual reference to the 3-A and 3-B taken. When the inner guide 3 relative to the outer guide 1 moves, the restricted bellows rolls 2 between the inner surface 8th and the outer surface 7 , The bellows 2 adapts in shape to the changing gap between the inner surface 8th and the outer surface 7 and a resulting change in trapped volume. The shape of the outer guide 1 , the interior guide 3 or both may be designed to achieve a desired volume constraint change at different positions between the inner and outer guides and resultant axial forces acting on the guides.

W

inkrementelle Arbeit ist, die bei der Bewegung der Innen- und Außenführungen von der ersten Positionsbeziehung zu der zweiten Positionsbeziehung verrichtet wird;

P₁

der Balgdruck in der ersten Positionsbeziehung ist;

V₁

das Balgvolumen an einem ersten Ablenkpunkt δ₁ (eine erste Positionsbeziehung zwischen der Innen- und Außenführung) ist; und

V₂

das Balgvolumen an einem zweiten Ablenkpunkt δ₂ (eine zweite Positionsbeziehung zwischen der Innen- und Außenführung) ist.

The volume change results in a pressure change according to the gas rules assuming adiabatic or isothermal processes. This volume / pressure change results in work passing through the device 100 is performed, resulting in a force acting between the inner and outer guide linear force. Performed work can be estimated (for an isothermal process) according to the following relationship: W = P ₁ * V ₁ * ln (V ₂ / V ₁ ) [1] in which

W

incremental work performed on the movement of the inner and outer guides from the first positional relationship to the second positional relationship;

P ₁

the bellows pressure is in the first positional relationship;

V ₁

the bellows volume at a first deflection point δ ₁ (a first positional relationship between the inner and outer guides); and

V ₂

the bellows volume at a second deflection point δ ₂ (a second positional relationship between the inner and outer guides).

W

inkrementelle Arbeit ist, die bei der Bewegung der innen- und Außenführungen von der ersten Positionsbeziehung zu der zweiten Positionsbeziehung verrichtet wird;

F

die durchschnittliche Kraft ist, die entlang der relativen Bewegung zwischen den Innen- und Außenführungen von der ersten Positionsbeziehung zu der zweiten Positionsbeziehung wirkt; und

δ_2-1

die Auslenkung aus der ersten Positionsbeziehung zu der zweiten Positionsbeziehung ist.

This work is equal to the work performed by the force acting along the relative movement between the inner and outer guides according to the following relationship. W = F · δ _2-1 [2] in which

W

incremental work performed on the movement of the inner and outer guides from the first positional relationship to the second positional relationship;

F

the average force acting along the relative movement between the inner and outer guides from the first positional relationship to the second positional relationship; and

δ _2-1

is the displacement from the first positional relationship to the second positional relationship.

From the equations [1] and [2], a performance of force depending on the adjustment by a person skilled in the art can be designed.

With reference to the 4-A and 4-B is an application to a hydropneumatic strut 200 shown. The device 100 with negative stiffness is a simple and cost effective way to implement a negative stiffness with a low inertia, virtually no friction controlled profile with simplicity and proven technologies while allowing concentric installation about the strut, thereby replacing the eliminated coil spring volume. Alternatively, the device 100 with negative stiffness between a damper and a coil spring, for example, be installed in more conventional passive suspensions. In any case, the tuned position can be determined by the relative height between the inner and outer guides, which is determined by the length of the connecting sleeve 400 is set to be adjusted. Those skilled in the art should be understood that a Abstimmpositionseinstellung can also be actively changed.

Table 1 shows the bellows volume (V), the bellows pressure (P), the volume / pressure change work (W), and the average force on the strut (F) at various displacements (δ) from the tuned position of the example application the device 100 with negative stiffness to the hydropneumatic strut 200 as in the 4-A and 4-B is shown. And 5 Figure 12 illustrates an average force (F) acting on the strut in response to displacements (δ) from the adjusted position of the exemplary application of the device 100 with negative stiffness to the hydropneumatic strut 200 as in the 4-A and 4-B is shown. Table 1 δ deflection of tuned position [mm] V bellows volume [cm ³ ] P bellows pressure [Atm] W Work performed by volume or pressure change [J] F average power [N] 80 191.80 4.25 5.67 1134.91 75 178.90 4:56 6:49 1298.62 70 165.20 4.93 5.83 1165.51 65 153.80 30.5 5.99 1198.18 60 142.90 5.70 5.79 1158.02 55 133.10 6.12 5.64 1128.08 50 124.20 6:56 5:43 1085.26 45 116.20 7:01 5.14 1027.68 40 109.10 7:47 4.77 953.67 35 102.90 7.92 4:39 878.66 30 97.50 8:36 3.85 770.22 25 93.00 8.76 3:40 680.01 20 89.20 9.14 2.79 557.64 15 86.20 9:45 2.20 440.83 10 83.90 9.71 1:53 305.93 5 82.34 9.90 0.84 167.14 0 81.50 10:00 - 00:00 -5 81.60 9.99 12:10 -19.99 -10 82.00 9.94 12:40 -79.71 -15 83.30 9.78 1.23 -256.39 -20 85.30 9:55 1.93 -386.73 -25 88.00 9.26 2:54 -507.95 -30 91.40 8.92 3:09 -617.91 -35 95.60 8:53 3.65 -732.32 -40 100.50 8.11 4:07 -814.75 -45 106.20 7.67 4:50 -899.21 -50 112.60 7.24 4.77 -953.84 -55 119.80 6.80 5:05 -1010.31 -60 128.20 6:36 5:52 -1104.62

The 6-A and 6-B show a device 100 ' with negative stiffness, which is in rotary motion, ie a device with negative stiffness and rotary motion. The device 100 ' with negative stiffness and rotary motion has three main components: an outer guide 1' , an inside guide 3 ' and a flexible bellows 2 ' , The bellows 2 ' is generally between and in contact with the inner surface 8th' the outside guide 1' and the outer surface 7 ' the inner guide 3 ' arranged. The general section of the bellows 2 ' in contact with the inner surface 8th' the outside guide 1' may be referred to as an outer wall, and the general portion of the bellows 2 ' in contact with the outer surface 7 ' the inner guide 3 ' can be referred to as an inner wall. End walls of the bellows may generally be the circumferentially opposed portions of the bellows 2 ' include, which connect the inner and outer walls. Since the position and contact relationship of the bellows varies between and with the surfaces of the inner and outer guides in operation, it should be understood that the inner, outer and end walls are relative descriptors and do not relate to absolute portions of the bellows. Thus, in the general case, a negative stiffness and rotary motion device in accordance with the present disclosure has a bellows disposed between a first surface and a second surface. The bellows 2 ' is flexible, being made of rubber or elastomeric material and filled with a fluid, either gas or liquid.

The inner guide 3 ' is cylindrical. The exterior guide 1' has a generally concave inner surface 8th' with a right-angled cut to the longitudinal center line 200 ' on. The inner surface 8th' has a radius of curvature or profile that is greater than that of the outer surface 7 ' the inner guide 3 ' is. A minimal distance between the outer surface 7 ' and the inner surface 8th' corresponds to an axis 210 that are normal to the longitudinal axis 200 ' is.

The bellows 2 ' is symmetrical with respect to the minimum distance between the outer surface 7 ' and the inner surface 8th' according to the axis 210 ' arranged. The bellows 2 ' is between the inner surface 8th' the outside guide 1' and the outer surface 7 ' the inner guide 3 ' limited. Even in the area of the narrowest space between the inner surface 8th' and the outer surface 7 ' can be an open channel on the inside of the bellows 2 ' be present for fluid communication therein. In the component orientation of 6-A and 6-B is the brat 2 ' compressed to a nearly uniform wall to wall thickness from end to end and due to the symmetrical arrangement with respect to the outer surface 7 ' and inner surface 8th' are the rotational forces ((if according to the profile of the inner surface 8th' and the outer surface 7 ' available) balanced. Thus, the orientation of 6-A and 6-B is referred to as a substantially equilibrium orientation or as an equilibrium state. Such a position may also be referred to as a nominal or coordinated position. The bellows 2 ' is with the inner guide 3 ' and outdoor tour 1' attached to the respective surfaces, where at one or more locations in alignment with the longitudinal axis 200 ' meet.

There will be an additional contextual reference to the 7-A and 7-B taken. When the inner guide 3 ' relative to the outer guide 1' moved (in 7-A clockwise), the restricted bellows rolls 2 ' between the inner surface 8th' and the outer surface 7 ' , The bellows 2 ' adapts in shape to the changing gap between the inner surface 8th' and the outer surface 7 ' and a resulting change in trapped volume. The shape of the outer guide 1' may be configured to achieve a desired volume constraint change at different positions between the inner and outer guides and resultant axial forces acting on the guides.

As with the device with negative stiffness and linear motion of 1 the volume change results in a pressure change according to the gas rules assuming adiabatic or isothermal processes. This volume / pressure change results in work passing through the device 100 ' is performed, resulting in a force acting between the inner and outer guide linear force.

The disclosure has described certain preferred embodiments and modifications thereto. Other modifications and changes may become apparent to others in reading and understanding the description. Therefore, it is intended that the disclosure not be limited to the particular embodiment (s) disclosed as the best mode contemplated for carrying out this disclosure, but that the disclosure encompass all embodiments described in U.S. Patent Nos. 5,312,309; fall within the scope of the appended claims.

Claims (10)

Negative stiffness device comprising: a fluid-filled bellows disposed between a first surface and a second surface, the bellows and the first and second surfaces having a substantially equilibrium orientation between the first and second surfaces, and wherein the bellows and the first and second surfaces comprise other orientations, wherein the first and second surfaces are displaced from substantially equilibrium orientation and the bellows exerts an adjustment force to drive the first and second surfaces farther away from substantially equilibrium orientation. The negative stiffness device of claim 1, wherein the device comprises a negative stiffness and linear motion device comprising: an elongate inner guide including the first surface, the inner guide being longitudinally aligned along an axis of linear motion and having respective first and second ends; an elongated outer guide comprising the second surface, the inner guide aligned longitudinally along the axis of linear motion and having respective first and second ends, the outer guide being coaxial with the inner guide such that the second surface of the outer guide is the first surface surrounding and facing the inner guide in spaced proximity; and wherein the bellows comprises a substantially toroidal flexible fluid housing disposed between and in contact with the first surface of the inner guide and the second surface of the outer guide. The negative stiffness device of claim 1, wherein the device comprises a negative stiffness and rotary motion device comprising: an inner guide comprising: the first surface being convex relative to an axis of rotational movement; an outer guide comprising the second surface being concave relative to the axis of rotational movement and facing the first surface of the inner guide in spaced-apart relationship; and wherein the bellows includes a flexible fluid housing disposed between and in contact with the first surface of the inner guide and the second surface of the outer guide. The negative stiffness device of claim 2, wherein the bellows includes an outer wall in contact with the second surface of the outer guide and an inner wall in contact with the first surface of the inner guide, further wherein the outer wall is fixedly secured to the second surface of the outer guide and the inner wall firmly attached to the first surface of the inner guide. The negative stiffness device of claim 3, wherein the bellows includes an outer wall in contact with the second surface of the outer guide and an inner wall in contact with the first surface of the inner guide, further wherein the outer wall is fixedly secured to the second surface of the outer guide and the inner wall firmly attached to the first surface of the inner guide. The negative stiffness device of claim 2, wherein the second surface of the outer guide is flared outwardly toward at least one end. The negative stiffness device of claim 6, wherein the second surface of the outer guide widens in a curved manner. The negative stiffness device of claim 7, wherein the first surface of the inner guide is cylindrical. The negative stiffness device of claim 2, wherein the first surface of the inner guide is tapered inwardly toward at least one end. Negative stiffness device comprising: an elongated inner member longitudinally aligned along an axis of linear motion and having opposite ends and an outer surface; an elongate outer member longitudinally aligned along the axis of linear motion and having opposite ends and an inner surface flared outwardly to at least one end, the outer member surrounding the inner member in spaced apart proximity; and a flexible toroidal fluid housing comprising an outer wall and an inner wall, the enclosure being disposed between the outer surface of the inner member and the inner surface of the outer member such that the outer wall is in conformal contact with the inner surface of the outer guide and the inner wall is in conformal contact with the outer wall Outside surface of the inner member is, and wherein the outer wall is fixedly secured to the inner surface of the outer member and the inner wall is fixedly secured to the outer surface of the inner member.

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