WO2010037379A1 - Artificial muscle - Google Patents

Abstract

The invention relates to an artificial electric muscle with two endpieces (12, 14) lying opposite each other, with two electrode element groups (16, 24) made up of flexible electrode elements (18) which are arranged next to one another along a surface (F1, F2) and are secured via their ends to the endpieces (12, 14) and make contact with, respectively, an anode or cathode (20, 32), and with a deformable  dielectric (26), which is arranged between the first electrode element group (16) and the second electrode element group (24) such that it cannot penetrate the electrode element groups (16, 24), wherein the electrode elements (22, 18) are elastic in a longitudinal direction (A), and the dielectric (26) is incompressible, such that when a voltage is applied between the anode (20) and the cathode (32), the electrode elements (22, 18) deform in such a way that the first endpiece (12) and the second endpiece (14) move relative to each other.

Description

 Artificial muscle

The invention relates to an artificial electrical muscle. Artificial muscles are components in which the application of an electrical voltage directly, that is without the interposition of an electric motor, leads to a force.

From the article "Biominetics Using Electroactive Polymers (EAP) as Artificial Muscles - a Review" by Yoseph Bar-Cohen, Journal of Advanced Materials, Volume 38, No. 4, October 2006, muscles are known that are made up of polymers that are used in the A disadvantage of this is that a relatively complicated construction is necessary if only a shortening of the artificial electrical muscle is to be achieved.

Various concepts of dielectric contraction actuators are described in the article "Contractile dielectric elastomer actuator with a folded shape" by F. Carpi and D. De Rossi, Proceedings of SPIE Vol 6168, 61680 D-1, in addition to a stack arrangement of thickness transducers which swells on actuation A shortened electrical muscle is known, and when a voltage is applied, the bending moments of a meander-folded polymer add up to a linear contraction movement, which is disadvantageous in that it is always necessary to use polymers which develop a bending moment when a voltage is applied to them.

Also known are artificial electrical muscles that contain carbon nanotubes. The disadvantage of this is the elaborate production, which also does not succeed yet reliably at the present time. This also leads to a high price for such artificial muscles.

The invention has for its object to propose a structurally particularly simple artificial electrical muscle. The invention solves the problem by an artificial electrical muscle having (a) a first end piece, (b) a second end piece opposite the first end piece, (c) a first electrode element group of electrode elements arranged side by side along a first closed surface have first end with which they are attached to the first end piece, have a second end, with which they are attached to the second end piece, which are contacted with an anode and which are flexible, (d) a second electrode element group of electrode elements, side by side a second closed surface, having a first end with which they are attached to the first end piece, having a second end with which they are attached to the second end piece, which are contacted with a cathode and flexible, and (e) to a deformable dielectric, between the first electrode element group and the second electrode nelementgruppe is arranged so that it can not or not substantially penetrate the electrode element groups, wherein the electrode elements are so inelastic in a longitudinal direction and the dielectric is so incompressible but elastic, that the E lektrodenelemente so when applying a voltage between the anode and cathode deform, that the first end piece and the second end piece to move towards each other. The dielectric is compressed and bulges due to the volume constancy of the dielectric preferably in the middle. Due to the deflection of the almost strain-free electrode elements, there is a shortening of the distance of the electrode element ends from one another, as a result of which the end pieces are moved toward one another. The electrode element groups are designed as tensile force-transmitting elements, so that the force transmission takes place substantially parallel to the longitudinal extent of the electrode elements. This avoids that by a tensile force transmission perpendicular to the electrode plane, the electrodes are lifted or detached from the dielectric or from an adjacent electrode. In a thread-like configuration of the electrode elements, the dielectric can be pressed in slightly between the electrodes. The invention is based on the idea of arranging the dielectric between the electrode element groups such that application of an electrical voltage between the two electrode element groups leads to an increase in a hydrostatic pressure in the dielectric. The electrode element groups are also arranged so that the first surface and the second surface are different in size. The dielectric desires to avoid the increased hydrostatic pressure by increasing the area between the electrodes. Since this is suppressed in the longitudinal direction due to the configuration of the electrode elements, the circumference increases and the artificial muscle deforms. It is a simple mechanism that can be implemented with simple design and easy to manufacture.

In other words, the electrode element groups are arranged on the end pieces such that the increase of the hydrostatic pressure when applying a voltage in the dielectric results in the dielectric not being able to expand in the longitudinal direction of the electrode elements and the electrode element groups thereby changing their shape, for example to the outside bulge.

It is a further advantage that the artificial muscle according to the invention is particularly robust. The artificial muscle can also be constructed so that external parts carry no tension, so that the artificial muscle is safe to handle.

In a preferred embodiment, the electrode elements are filiform or filamentary. A thread-like electrode element is understood in particular to mean electrode elements which have a constant cross-section over a longitudinal extent. This cross section is elliptical or circular, for example. However, it is also possible for the cross section to be rectangular, for example, so that the electrode elements are strip-shaped. A filament-type electrode element is to be understood as filament-shaped and strip-shaped electrode elements. Such electrode elements are particularly easy to manufacture and process and result in a high efficiency artificial electrical muscle. The thread-like electrode elements may be formed twisted, while Denelemente can be formed twisted, for example, twisted around a substantially cylindrical outer surface, whereby the length of the electrode elements increases and a reinforced bulge can be achieved.

In a preferred embodiment, the electrode elements are arranged along closed surfaces. This is to be understood in particular that the surfaces are orientable in a mathematical sense and thus separate an interior space from an exterior space, wherein each connection path between the interior space and the exterior space extends either through the area or through one of the two end pieces. It is possible, but not necessary, for the electrode elements to adjoin one another in each case. It is also possible that the electrode elements are spaced apart from each other.

In a preferred embodiment, the first surface and the second surface are cylinder jacket surfaces. Particularly preferably, these cylinder jacket surfaces are concentric with one another. This results in a symmetrical structure that is particularly easy to manufacture and also has a particularly simple Verkürzungskinetik.

It is particularly favorable if the first surface and the second surface extend equidistantly. When contracting the muscle then tilting of the first surface are avoided over the second surface.

Alternatively, it is possible that the first surface and the second surface are arranged spirally. In this case, the first surface and the second surface have at least one open end where they are bonded together so that the dielectric can not move out of the free end.

The artificial muscle can thereby be used as a pump or biased by the first electrode element group and / or the second electrode element group with the first end piece and the second end piece enclose a gas-tight cavity. This cavity is preferably sealed by a valve against an environment of an artificial muscle. Will the Artificial muscle contracts and there is an increase in volume by the bulge in the interior of the artificial muscle, a backflow of a fluid, such as air and a liquid can be made possible by the valve, so that a denting of the artificial muscle is prevented in the presence of a tensile load , The electrode element groups are thereby forced to expand outward and remain in this state, even when the tensile load on the end pieces is increased.

In order to avoid denting, the wall thickness of the artificial muscle can be selected, for example, by a corresponding design of the dielectric. It is also possible to form a Vorbombierung, so that even in the non-contracted, relaxed state, a slight bulge is present.

In order to increase the force density of the artificial muscle, additional electrode groups may be provided. Preferably, all electrode groups are then arranged so that there is a symmetrical, in particular a rotationally symmetrical, artificial muscle. It is also possible to connect several electrode groups in succession in order to increase the overall path of shortening.

An energetic improvement in a plurality of electrode groups concentric to each other is when the electrode spacings are different in size, that is, the layer thickness of the dielectric between the cathode and anode changes from layer to layer. The outer layers may be thicker than the inner layers to compensate for the differences in curvature since the curvature is greater inside than outside.

Also, different electrode spacings may be provided to produce different responses at the same applied voltage. Greater distances lead to a less great attraction of the electrodes, so that by adjusting the distance of the electrodes to each other different contractile strengths can be adjusted. The same can also be done by a variation of the dielectrics, so that with constant dimensions and different dielectrics different contraction strengths can be generated at the same applied voltage.

The invention also relates to prostheses or orthoses equipped with an artificial muscle as described above.

In the following, an exemplary embodiment of the invention is explained in more detail with reference to the accompanying drawings. It shows

Figure 1 shows an electrical muscle according to the invention in a relaxed

Position,

FIG. 2 a shows a cross section through the artificial muscle according to FIG. 1 in a tension-free state,

FIG. 2 b shows the cross section according to FIG. 2 a, in which an electrical voltage is applied between the two electrode element groups, and

FIG. 3 shows a contracted electrical muscle. The

Figures 4a, 4b show a section through an elementary cell of the electrical

muscle,

FIG. 5 shows a cross section through an electrical muscle composed of a plurality of electrode element groups in a schematic view,

FIG. 6 shows a schematic view of an electrical muscle

Electrode element groups arranged along spiraling surfaces, and FIG. 7 shows a further embodiment of an electrical muscle according to the invention with partial muscles connected in series. In

FIG. 8 shows an alternative electrical muscle according to the invention.

FIG. 1 shows an artificial electrical muscle 10 having a first end piece 12 and a second end piece 14, which are both disc-shaped and arranged opposite one another. Between the first end piece 12 and the second end piece 14, a first electrode element group 16 is arranged, which has a plurality of electrode elements 18.1, 18.2,. In the following reference numerals without Zählsuffix each denote the object as such. All of the electrode elements 18 are fixedly connected at a first end to the first end piece 12 and at a second end to the second end piece 14 so that the two end pieces 12, 14 are not spaced apart along a longitudinal axis A extending along an x-axis are.

The electrode elements 18 of the first electrode element group 16 are arranged along a cylinder jacket surface F ₁ , which represents a closed surface. The end faces associated with the cylindrical surface Fi are formed by the end pieces 12 and 14. The electrode elements 18 are substantially inelastic in their longitudinal direction A (x-direction). That is, forces occurring during operation of the electrical muscle 10 are so small that the resulting relative elongation of the electrode elements 18 is, for example, below 5%. The electrode elements 18 are flexible, so that the two end pieces 12, 14 in the y- and z-direction can be easily shifted against each other.

2 a shows a cross section in the y / z direction through the artificial muscle 10 according to FIG. 1. It can be seen that the electrode elements 18 are electrically connected to a first electrode in the form of an anode 20, which is penetrated by the first end piece 12 passes through (see Figure 1). About the anode 20 may be a electrical voltage to the electrode elements 18 of the first electrode element group 16 are applied.

The electrode elements 18 are arranged on the cylinder jacket surface Fi around a circle center point M. Concentrically, second electrode elements 22.1, 22.2,..., Are arranged along a second cylinder jacket surface F ₂ , which form a second electrode element group 24. It is possible, but not necessary, for each of a first electrode element 18 to be opposed by exactly one second electrode element 22. Between the first electrode element group 16 and the second electrode element group 24, a hollow-cylindrical dielectric is arranged. The dielectric 26 may be constructed, for example, of a sheath 28 and a dielectric jelly 30.

The dielectric 26 is constructed so that it is always between the two cylinder jacket surfaces Fi and F ₂ and the cylinder jacket surfaces Fi, F ₂ can not traverse. For this purpose, for example, the sheath 28 is designed to be dense and stiff.

The second electrode elements 22 of the second electrode elements 24 are contacted electrically with a second electrode in the form of a cathode 32, via which an electrical voltage can be applied to it. The anode 20 and the cathode 32 are electrically isolated from each other by the dielectric 26.

Figure 2a shows the floating state. That is, there is no potential difference between the anode 20 and the cathode 32. It should be noted that it is not necessary for the first electrode elements 18 to be arranged radially outside the second electrode elements 22. It would accordingly be possible to exchange the designations for anode and cathode. The term anode or cathode is for convenience only.

Figure 2b shows the state in which a voltage between the anode 20 and the cathode 32 is applied. This leads to a negative electrostatic charge of the second electrode elements 22 compared to the positively charged The unlike charged electrode elements attract each other, so that an internal pressure p of the dielectric 26 increases. The increased internal pressure p exerts a hydrostatic force on the first cylinder jacket surface Fi and the second cylinder jacket surface F ₂ . Since the first cylinder _{jacket surface} Fi is larger than the second cylinder _{jacket surface} F _{2, a} net force F _rac j i i acts radially outward. The bulging takes place, since an enlargement of the lateral surface occurs at a constant volume.

FIG. 3 shows that the radially outward force F _rad i _a i results in a bulging of the electrode elements 18 in the yz direction, ie, radially outward. This reduces a distance between the two end pieces 12, 14 of L _R in the relaxed state to L _k in the contracted state. When short-circuiting the two electrode element groups 16, 24, the bending stress of the electrode elements pushes the two end pieces 12, 14 apart again.

The dielectric 26 encloses a cavity in the form of an interior 34 (see FIG. 2b) which is sealed in a gas-tight manner with respect to an environment of the artificial muscle 10. Via a valve 36, which is shown schematically in Figure 1, a gas or liquid exchange between the interior 34 and the environment can be released or shut off. In this way, the electric muscle 10 can be used as a pump when the void volume is increased by the bulge and is reduced again by the relaxation.

FIG. 4a shows a section through an elementary cell of the artificial muscle. The electrode elements 18.1 and 18.2 of the first electrode element group 16 and the electrode elements 22.1, 22.2 of the second electrode element group 24 are shown schematically. The dielectric 26 surrounds the electrode elements in this embodiment in the form of an elastomer matrix.

FIG. 4b shows the basic principle of the electrical muscle according to the invention when a voltage is applied to the electrode elements 18.1, 18.2, 22.1, 22.2. In this case, the same named charged electrode elements 18.1, 18.2 of the first electrode element group 16 from each other and attract the second electrode elements 22.1 and 22.2 of the second electrode element group 24 electrostatically. Since an expansion in the x-direction, ie in the longitudinal direction A, is out of the question due to the inelasticity of the electrode elements 18, 22, the unit cell of the artificial muscle expands along the first surface Fi or the second surface F ₂ due to the volume constancy , This expansion is translated into movement of the end pieces relative to or away from each other.

FIG. 5 schematically shows a parallel connection of a plurality of electrode element groups. Besides the first electrode element group 16 and the second electrode element group 24, there is a third electrode element group 38 including electrode elements. The electrode elements of the third electrode element group 38 can not be seen in FIG. 5, since this is a cross section. The artificial muscle 10 further includes a fourth electrode element group 40, a fifth electrode element group 42, and a sixth electrode element group 44. The second, fourth, and sixth electrode element groups 24, 40, 44 are connected in common to the cathode 32. The first, third and fifth electrode element groups 16, 38, 42 are connected in common to the anode 20. By applying a voltage V between anode 20 and cathode 32, a contraction of the dielectric 26 occurs in a thickness direction D and an expansion in a circumferential direction U, which leads to bulging of the artificial muscle 10 (see FIG. 3).

FIG. 6 shows a further embodiment of an artificial muscle 10 according to the invention, in which, for the sake of clarity, the end pieces are omitted and the electrode element groups are shown partially unwound. The electrode element groups are now arranged along a spiral-shaped surface F ₁ or F ₂ .

FIG. 7 shows an embodiment according to the invention, in which a first artificial partial muscle 46.1 is arranged behind a second partial muscle 46.2. It can thus be arranged a plurality of partial muscles in a row. FIG. 8 shows a further alternative embodiment of an artificial muscle 10 according to the invention, in which the end pieces 12, 14 are formed as rings.

LIST OF REFERENCE NUMBERS

10 Artificial muscle

12 first tail

14 second tail

16 electrode element group

18 electrode element

20 anodes

22 second electrode elements

24 second electrode element group

26 dielectric

28 serving

30 jellies

32 cathode

34 interior

36 valve

38 third electrode element group

40 fourth electrode element group

42 fifth electrode element group

44 sixth electrode element group

46 partial muscle

A longitudinal direction

M center of the circle

Fi first cylindrical surface

F ₂ second cylinder jacket surface

P internal pressure

Fradial force

Claims

claims 1. Artificial electrical muscle, with (a) a first end piece (12), (b) a second end piece (14) opposite the first end piece (12), (c) a first electrode element group (16) of electrode elements (18) which (i) are arranged side by side along a first surface (Fi), (ii) have a first end with which they are attached to the first end piece (12) are fastened, (iii) have a second end with which they are attached to the second end piece (14) are attached, (iv) contacted with an anode (20) and, (v) are flexible, (D) a second electrode element group (24) of electrode elements, the (i) are arranged side by side along a second surface (F ₂ ), (ii) have a first end with which they are attached to the first end piece (12) are fastened, (iii) have a second end with which they are attached to the second end piece (14) are attached, (iv) contacted with a cathode (32) and (v) are flexible, and (e) a deformable dielectric (26) arranged between the first electrode element group (16) and the second electrode element group (24) such that it can not penetrate the electrode element groups (16, 24), (f) wherein the electrode elements (22, 18) are so inelastic in a longitudinal direction (A) and the dielectric (26) is incompressible so that the electrode elements (22, 18) upon application deforming a voltage between the anode (20) and the cathode (32) so that the first end piece (12) and the second end piece (14) move relative to each other. 2. Artificial muscle (10) according to claim 1, characterized in that the electrode elements (18, 22) along closed surfaces (Fi ₁ F ₂ ) are arranged. 3. Artificial muscle (10) according to any one of the preceding claims, characterized in that the electrode elements (18, 22) are thread-shaped. 4. Artificial muscle (10) according to any one of the preceding claims, characterized in that the first surface and the second surface are cylinder jacket surfaces (F ₁ , F ₂ ). 5. Artificial muscle (10) according to claim 4, characterized in that the first surface (F1) and the second surface (F ₂ ) are concentric. 6. Artificial muscle (10) according to any one of the preceding claims, characterized in that the first surface (F ₁ ) and the second surface (F ₂ ) are equidistant. 7. Artificial muscle (10) according to any one of claims 1 to 4, characterized in that the first surface (F ₁ ) and the second surface (F ₂ ) are arranged spirally. 8. Artificial muscle according to one of the preceding claims, characterized in that the electrode elements (18, 22) are arranged twisted in the longitudinal extent of the artificial muscle. 9. Artificial muscle (10) according to any one of the preceding claims, characterized in that the first electrode element group (16) and / or the second electrode element group (24) with the first end piece (12) and the second end piece (14) enclose a gas-tight cavity (34). 10. Artificial muscle (10) according to claim 9, characterized by a valve (36) which is arranged for reversibly closing the cavity (34). 11. Artificial muscle (10) according to any one of the preceding claims, characterized by (A) a third electrode element group (38) of electrode elements, the (i) are arranged side by side along a third surface, (ii) have a first end with which they are attached to the first end piece (12) are fastened, (iii) have a second end with which they are attached to the second end piece (14) are attached, (iv) contacted with the anode and, (v) are flexible, (b) a fourth electrode element group (40) of electrode elements, which (i) are arranged side by side along a fourth surface, (ii) have a first end with which they are attached to the first end piece (12) are fastened, (iii) have a second end with which they are attached to the second end piece (14) are attached, (iv) contacted with a cathode (32) and (v) are flexible, and (c) a deformable dielectric disposed between the first electrode element group (16) and the second electrode element group (24) such that it can not or substantially penetrate the electrode element groups (16, 24). 12. Artificial muscle according to one of the preceding claims, characterized in that the electrode element groups (18, 24, 38, 40) have different distances from each other. 13. Artificial muscle according to one of the preceding claims, characterized in that different dielectrics are arranged between different electrode element groups (18, 24, 38, 40). 14. prosthesis or orthosis with an artificial muscle (10) according to any one of the preceding claims.