WO2017055222A2

WO2017055222A2 - Conformable structural element

Info

Publication number: WO2017055222A2
Application number: PCT/EP2016/072871
Authority: WO
Inventors: Jens-Peter WULFSBERG; Robert Weidner; Tobias Meyer
Original assignee: Helmut-Schmidt-Universität, Universität Der Bundeswehr Hamburg
Priority date: 2015-10-02
Filing date: 2016-09-26
Publication date: 2017-04-06
Also published as: WO2017055222A3

Abstract

A conformable structural element (100, 200, 300, 400) is provided. The conformable structural element (100, 200, 300, 400) comprises a stack (60) or the bundle (160) of layer elements (61, 62, 63, 64; 161, 162, 163, 164) of a flexible sheet or rod material, a force application means, which is configured to exert a force on the stack (60) or the bundle (160) such that super-imposed surfaces of the flexible sheet or rod material are subjected to a force such that the conformable structure element thereby obtains an increased distortion stiffness.

Description

Conformable structural element

TECHNICAL FIELD

The invention relates to the field of conformable structural elements. More specifically, the invention relates to a flexible, conformable structural element with controllable stiffness by using vacuum or overpressure.

BACKGROUND OF THE INVENTION Despite the increasing degree of automation many tasks are still performed manually, especially in production of individualized, sensitive or quality critical products. The spectrum of production tasks is very broad. The tasks can have different characteristics, e.g., low or high process or product accuracy/precision as well as small or big dimension and light or heavy weight of components, products and tools that have to be handled. Exemplary activities are the handling of loads, assembling something in or above head level as well as high precision manufacturing and assembly in micro production. Despite the numerous efforts to increase automation, in these and other fields of application, a number of tasks are still performed manually. Therefore, the employee represents an important factor of success within the production process, which must be supported in an adequate manner. The support for employees and organizations can have different forms and structures. Nowadays, a lot of technical systems exist in order to support production tasks. These include tools like screw drivers, lifting aids, industrial robots, system based on human-machine cooperation, assistance systems and exoskeletons. All these systems have in common that they support, assist or help the employees in order to produce relief or to increase the overall productivity in producing organizations. Nevertheless, these systems may have different forms, structures and core characteristics. Such system can support manual tasks during surgery or can entirely replace human activity. Not all systems are suitable for direct human- machine interaction or integration, e.g., due to hard structures or other objectives.

SUMMARY OF THE INVENTION

There may therefore be a need for a system of flexible conformable elements with controllable stiffness to support employees during working tasks.

The present invention is defined by the subject-matter of the independent claims, wherein further embodiments are incorporated in the dependent claims and the following description.

According to a first aspect of the invention, a conformable structural element is provided, comprising a stack of at least two superimposed layer elements of a flexible sheet material and a force application means, which is designed to exert a force on the stack increasing a static friction between adjacent surfaces of the superimposed layer elements, whereby the conformable structure element thereby obtains an increased distortion stiffness.

Thus, in the operating state of the present invention, the force application means applies a force on the stack of layer elements and presses the layer elements together. Therefore, the friction between the surfaces of the sole layer elements is increased and the distortion stiffness of the conformable structural elements is increased. Furthermore, the shape of the conformable structural element is conserved. Without force application on the stack of layer elements, named the initial state, there may be space between the sole layer elements of the stack of layer elements. Therefore, the friction between the sole layer elements is low, and thus, the sole layer elements can be moved in respect of each other. In result a 3D-shaped structure can be formed. The achievable distortion stiffness of the conformable structural element depends on a variety of parameters. The most important parameters may be the size of the contact surfaces between the sole layer elements, the used materials for the layer elements, the stiffness of the used materials, the roughness of the used materials, the number of layers and the dimension of the applied force by the force application means. The layer elements may be made out of a flexible sheet material e.g. paper, plastic, metal, fibre plastic, styrofoam and / or a compound thereof. The geometry of the flexible sheet material can be freely chosen e.g. squares, triangles, rectangles, circles, etc. The used materials depending on the application of the conformable structural element. E.g. a material can be used that offers low friction during the initial state and high friction during the operating state. On one side, the low friction during the initial state is useful for modelling the shape of the conformable structural element. On the other side, a high friction between the sole layers in the operating state is necessary to achieve a high distortion stiffness of the conformable structural element. The resulting conformable structural element can handle tensile force, compression force, bending and torsion. Force application means is a means configured to apply a force on the stack of superimposed layer and/or rod elements.

According to an embodiment of the invention, the force application means of the conformable structural element is a flexible, airtight sheath provided with an opening for introducing or discharging air into or from the airtight sheath, wherein the stack of layer elements of the flexible sheet material is located within the flexible sheath, and wherein the force is applied on the super-imposed layer elements of the flexible sheet material by evacuating the air out of the airtight sheath over the opening.

Thus, the force generated by the force application means results to the differences of pressure between inside and outside the flexible, airtight sheath. During the initial state of the conformable structural element the pressure inside the sheath is equal to the environmental pressure outside the sheath. So there is no force applied on the stack of layer elements by to force application means. In the operating state, the air within the sheath is evacuated and a vacuum is generated inside the flexible, airtight sheath. The pressure of the environmental air is higher than the air pressure of the applied vacuum inside the sheath. Therefore, the resulting force applied on the stack of layer elements presses the sole layer elements together. The friction between the sole layer elements increases, thus, the distortion stiffness increases and the formed shape of the conformable structural element is conserved. The applied force is proportional to the generated vacuum and can be controlled. The sheath may refer to a flexible, airtight material, such as plastic, a foil and / or rubber. Airtight also includes gas tight. Air also includes other gases, in particular when applying overpressure to the airtight sheath. In case the conformable structural element is used in other than air atmospheres, the sheath is tight with respect to the type of gas of that particular atmosphere.

According to another embodiment of the invention, the force application means of the conformable structural element is a double sheath envelope comprising an inner sheath envelope and an outer sheath envelope, wherein an intermediate space between the inner sheath envelope and the outer sheath envelope is airtight and has an opening for introducing or discharging air into or from the intermediate space, wherein the stack of layer elements of the flexible sheet material is located inside the inner sheath envelope, and wherein the force is applied on the super-imposed surfaces of the sheet material by pressurizing the intermediate space via the opening.

Thus, during the operation state, air is introduced in the space between the inner sheath envelope and the outer sheath envelope. Therefore, an overpressure is generated in the intermediate space between the inner sheath envelope and the outer sheath envelope. The air inside the inner sheath envelope is discharged through an opening within the inner sheath envelope by the overpressure in the intermediate space. The pressure in the intermediate space between the outer sheath envelope and the inner sheath envelope is higher than the air pressure inside the inner sheath envelope. Therefore, the resulting force applied on the stack of layer elements presses the sole layer elements together. The friction between the sole layer elements increases, thus, the distortion stiffness increases and the formed shape of the conformable structural element is conserved. The applied force is proportional to the generated pressure difference between inside the outer sheath envelope and the inner sheath envelope and can be controlled. The inner and the outer sheath envelopes may refer to a flexible, airtight material, such as plastic, a foil and / or rubber. According to an embodiment of the invention, the conformable structural element comprise a first group of layer elements of the flexible sheet material and a second group of layer elements of flexible material, wherein the layer elements of the first group and the layer elements of the second group mutually overlap, wherein the first group with respect to the second group without application of force on the stack is movable along a trajectory, so the amount of overlap and thus the extent of the stack along this trajectory can be varied.

Thus, the conformable structural element is able to vary its length along the longitudinal trajectory. Therefore, an adaption at the needs of the use case is provided. The stack of layers may be divided into two or more groups, at least a first group and a second group. The layer elements of each side may be arranged alternately mutually in the overlapping. During the initial state, without force application, the stack can vary its length along the longitudinal axis by sliding together or pulling apart. In result of the length variation, the overlapping area enlarges or decreases. After evacuating or filling in the air, the conformable structural element contains the applied structure and the applied dimension along the longitudinal trajectory. The longitudinal dimension of this embodiment of the conformable structural element is between the length of either the left side or the right side (depending on which of the two sides is longer) and the sum of the length of the left side and the right side of the stack of layer element. The resistance of the conformable structural element against tensile stress is proportional to the size of the overlapping area. Thus, there may be a minimal size of overlapping area specified to guarantee a certain resistance against tensile stress. Overlap or mutually overlap may include an immediate overlap, however may also include intermediate layers between overlapping layers of the first and second group respectively. Not only two groups of layer elements, but also three or more groups of layer elements, in particular when there is a need for complex 3D structures.

According to an embodiment of the invention, the conformable structural element comprise a first group of layer elements of the flexible sheet material and a second group of layer elements of flexible material wherein at least one of the first group of layer elements and the second group of layer elements each in a non- overlapping area are connected with each other, so that a displacement of the layer elements within said respective group of layer elements in an area averted from the overlap area is avoided. Thus, it can be ensured that the sole layer elements of the stack of layer elements persist in one of the two groups, the layer elements of the first group may be connected apart the overlapping area between each other and the layer elements of the second group may be connected apart the overlapping area between each other. Therefore, the first group of layer elements and the second group of layer elements may move respectively altogether and only along the longitudinal trajectory of the conformable structural element.

According to an embodiment of the invention, the conformable structural element comprise at least a first group of layer elements of the flexible sheet material and a second group of layer elements of flexible material, wherein the layer elements of the first group and the layer elements of the second group mutually overlap, wherein the first group with respect to the second group without application of force on the stack are rotatable around a rotation axis, so that the angular position of the first group can be varied with respect to the second group.

Thus, the conformable structural element allows an adaption around a rotation axis. Therefore, an adaption at the needs of the use case is provided. In the initial state, without force application, the stack can vary his angle continuously around the rotation axis. As result of the rotation, the angle between the first group of layer elements and the second group of layer elements may vary. After evacuating or filling in the air, the conformable structural element contains the applied structure and angle. The resistance of the conformable structural element against torque is proportional to the size of the overlapping area within the pivot joint. Thus, there may be a minimal size of overlapping area specified to guarantee a certain resistance against torque. Overlap or mutually overlap may include an immediate overlap, however may also include intermediate layers between overlapping layers of the first and second group respectively. Not only two groups of layer elements, but also three or more groups of layer elements, in particular when there is a need for complex 3D structures. Three or more groups can be rotated around the rotation axis or the conformable structural element contains more than one rotation axis. According to an embodiment of the invention, the conformable structural element comprises a first group of layer elements of the flexible sheet material and in a second group of layer elements of flexible material, wherein the layer elements of the first group of layer elements and the layer elements of the second group of layer elements are connected in the axis of rotation by a connecting axle block, so that a displacement of the material in relation to the rotation axis is avoided.

Thus, the element offers a defined rotation axis. The two groups of layer elements may be connected in the overlapping area by an axle block. This axle block relates to a pivot joint with a defined rotation axis. The axle block may refer to wood, metal, and / or plastic. Further, the pivot joint may be realised by a long slot and a pin. Thus, a conformable structure element with a wandering fulcrum can be realised.

According to another embodiment of the invention, the conformable structural element comprise at least a first group of layer elements of the flexible sheet material and a second group of layer elements of flexible material, wherein the first group with respect to the second group is connected with an elastic element, wherein moving the first group of layer elements with respect to the second group of layer elements biases the elastic element, wherein the biased condition of the elastic element is fixable by applying the force to the stack of layer elements, wherein the first group of layer elements with respect to the second group of layer elements is returnable into a defined position by the biased elastic element when withdrawing the force application on the stack.

Thus, during the initial state, without force application by the force application means, the elastic element may withdraw the first group of layer elements in respect to the second group of layer elements into a previously defined position. A flexible element e.g. a spring or a rubber band may be mounted between the connection point of the first group of layer elements and the connection point of the second group of layer elements.

According to an embodiment of the invention, the conformable structural element is comprising a pressure sensor being configured to control the force applied by the force application means and therewith the mobility of the layer elements to each other.

Thus, the control of the stiffness of the conformable structural element can be realised over a pressure sensor within the sheath. The pressure sensor may measure the pressure within the sheath and hand over the measurement signals to a control unit. The control unit may control the vacuum or overpressure inside the sheath or the intermediate space. The applied force by the force application means is proportional to the applied pressure difference between the environment and the sheath. As mentioned above, the distortion stiffness of the conformable structural element depends on several parameters. As the material properties and the number of used layers cannot be changed during the use of the conformable structural element, the control of the distortion stiffness occurs over the applied force by the force application means. This force is proportional to the pressure difference between the environment and the pressure within the sheath. Therefore, a pressure sensor in conjunction with a control unit and a pump may be used to control the force applied by the force application means. According to a second aspect of the invention, a conformable structural element is provided, comprising a bundle of elongate elements of a flexible material, a force application means, which is configured to exert a force on the bundle of elongate elements increasing a static friction between adjacent surfaces of the bundled elongate elements, whereby the conformable structure element thereby obtains an increased distortion stiffness.

Thus, without force application on the bundle of elongate elements, named the initial state, there may be space between the sole elongate elements of the bundle of elongate elements. Therefore, the friction between the sole elongate elements is low, and thus, the sole elongate elements can be moved in respect of each other. In result a 3D-shaped structure can be created. In the operating state of the present invention, the force application means may apply a force on the bundle of elongate elements and may press the elongate elements together. Therefore, the friction between the sole elongate elements may be increased and the distortion stiffness of the conformable structural elements may be increased. Furthermore, the shape of the conformable structural element may be conserved. The achievable distortion stiffness of the conformable structural element may depend on a variety of parameters. The most important parameters may be the size of the contact surfaces between the sole elongate elements, the used materials for the elongate elements, the stiffness of the used materials, the roughness of the used materials, the number of rods and the dimension of the applied force by the force application means. The used materials depending on the application of the conformable structural element. E.g. a material can be used that offers low friction during the initial state and high friction during the operating state. On one side, the low friction during the initial state is useful for modelling the shape of the conformable structural element. On the other side, a high friction between the sole elongate elements in the operating state is necessary to achieve a high distortion stiffness of the conformable structural element. The resulting conformable structural element can handle tensile force, compression force, bending and torsion. The use of elongate elements offers another degree of freedom for the conformable structural element in view of the flexile sheet material. The conformable structural element can further be realised by using elongate flexible materials. The bundle elements may be made out of a flexible long material e.g. paper, plastic, metal, fibre plastic, styrofoam and / or a compound thereof. The cross section of the elongate elements may be round, rectangular, triangular, hexagonal or any polygonal shape.

According to an embodiment of the invention, the elongate elements are rod elements. The rod elements are characterised by a restoring force, if no force is applied on the bundle of rod elements (elastic deformation).

Thus, the rod will return into their original shape, if the force application tool does not apply force on the bundle of rod elements. The elongate elements are may be made out of rods. The cross section of the rod elements may be round, rectangular, triangular, hexagonal or any polygonal shape. Further, the sole rods may contain a restoring force, so that if no force is applied on the rods, the rods return into their original shape. The rods may extend in all three dimensions of space.

According to an embodiment of the invention, the elongate elements are wire elements. The wire elements are characterised by bending under their dead weight, if no force is applied on the bundle of wire elements (including plastic deformation).

Thus, as wire elements are, compared to their cross section long, without force application on the stack of wire elements the wire elements will bend under their own dead weight. The elongate elements are may be made out of wires. The cross section of the wire elements may be round, rectangular, triangular, hexagonal or any polygonal shape. The wire elements may have a small cross section. Further, the wire elements may have no or little restoring force, so that the wire elements are very flexible.

According to an embodiment of the invention, the conformable structural element can be made out of a ball-shaped material. The structural element is provided, comprising a quantity of ball elements, a force application means, which is configured to exert a force on the quantity of ball elements increasing a static friction between adjacent surfaces of the quantity of ball elements, whereby the conformable structure element thereby obtains an increased distortion stiffness. Without force application on the quantity of ball elements, named the initial state, there may be space between the sole ball elements of the quantity of ball elements. Therefore, the friction between the sole ball elements is low, and thus, the sole ball elements can be moved in respect of each other. In result a 3D-shaped structure can be created. In the operating state of the present invention, the force application means may apply a force on the quantity of ball elements and may press the ball elements together. Therefore, the friction between the sole ball elements may be increased and the distortion stiffness of the conformable structural elements may be increased. Furthermore, the shape of the conformable structural element may be conserved. The achievable distortion stiffness of the conformable structural element may depend on a variety of parameters. The most important parameters may be the size of the contact surfaces between the sole ball elements, the used materials for the ball elements, the roughness of the used materials and the dimension of the applied force by the force application means. The used materials depending on the application of the conformable structural element. E.g. a material can be used that offers low friction during the initial state and high friction during the operating state. On one side, the low friction during the initial state is useful for modelling the shape of the conformable structural element. On the other side, a high friction between the sole ball elements in the operating state is necessary to achieve a high distortion stiffness of the conformable structural element. The resulting conformable structural element can handle tensile force, compression force, bending and torsion. The use of ball elements offers another degree of freedom for the conformable structural element in view of the flexile elongate material. The conformable structural element can further be realised by using ball flexible materials. The quantity of ball elements may be made out of e.g. paper, plastic, metal, fibre plastic, styrofoam and / or a compound thereof.

According to an embodiment of the invention, the force application means of the conformable structural element is a flexible, airtight sheath provided with an opening for introducing or discharging air into or from the airtight sheath, wherein the bundle of rods of the flexible rod-shaped material is located within the flexible sheath, and wherein the force is applied on the rods of the flexible rod-shaped material by evacuating the airtight sheath over the opening.

Thus, the above described principle of using the pressure difference between the environment and inside the sheath to generate a force can also be adapted for rod- shaped materials. According to an embodiment of the invention, the force application means of the conformable structural element is a flexible, airtight double sheath comprising an inner sheath envelope and an outer sheath envelope, wherein an intermediate space between the inner sheath envelope and the outer sheath envelope is airtight and has an opening for introducing or discharging air into or from the intermediate space, wherein the bundle of rods of the flexible rod-shaped material is located inside the inner sheath envelope, and wherein the force is applied on the bundle of rods of the rod-shaped material by a pressurizing the intermediate space via the opening.

Thus, the above described principle of using a double sheath as a force application means to generate a force can also be adapted for a bundle of elongate elements of a flexible rod-shaped material.

According to a third aspect of the invention, a system of conformable structural elements is provided, comprising a control unit, a pump arrangement, a input unit and one or more conformable structural elements, wherein the control unit is configured to control the pump arrangement upon user request to evacuate or fill in air from or into the respective intermediate spaces of the respective conformable structural elements, wherein each one of the conformable structural elements can be controlled independently or in combination with one or more of the one or more conformable structural elements.

Thus, one or more conformable structural elements can be combined in a system. The system contains a control unit to control the one more conformable structural elements, an input unit for e.g. to trigger a setting or a target value and a pump arrangement. The pump arrangement may create the vacuum or generates the overpressure inside the sheath of the conformable structural elements. Each conformable structural element of the system may be controlled separately or in combination with other conformable structural elements. The different type of mentioned conformable structural elements can be combined to a variety of shapes for different purposes. The stiffness of each conformable structural element is controlled individually by the control unit and ensures an optimum of flexibility of the system. The system of conformable structural elements may contain one pump and a controllable valve block to switch between the sole conformable structural elements or the system may contain for each conformable structural element a different pump. The system can be used to support both, humans and machines. According to an embodiment of the system, an exoskeleton can be constructed for supporting humans during work. The different body shapes of humans can be respected by adapting the exoskeleton via the conformable elements with constant length, variable length and variable angle.

According to an embodiment of the invention, the system further comprises a pressure sensor in each of at least two conformable structural elements, wherein the control unit controls the pump arrangement to evacuate or fill in the air from or into the conformable structural element based on determined pressures of the pressure sensor upon user set up of a desired configuration of the at least two conformable structural elements. Systems, which are constructed entirely of such soft materials and structures, have a significantly higher complexity, e.g., for designing. Hybridization with rigid components as well as conformable structural elements with other elements are approaches for reducing complexity. As a result, a passive and active support may be a possible outcome, but without completely renouncing soft structures. The modular design enables different system designs. The described technology can also be used for other applications. On the one hand, it can also be used for stabilization and fixation of other body parts during ergonomic or quality critical tasks, e.g., stabilizing the lower body or the head. On the other hand, it can be used for stabilizing technical joints, e.g., in soft robots.

The following describes various exemplary embodiments, features, and aspects of the present invention in detail with reference to the accompanying figures. Same reference signs in the accompanying figures indicate components that have same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, unless otherwise specified, the accompanying figures do not need to be drawn to scale.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject-matter of the invention will be explained in more detail in the following with reference to exemplary embodiments which are illustrated in the attached figures, wherein:

FIG. la is a schematic diagram of a conformable structural element, including a side view, front view of layers and front view of elongate elements; FIG. lb is a schematic diagram of a conformable structural element without force application according to an embodiment of the present invention, including a side view, front view of layers and front view of elongate elements;

FIG. lc is a schematic diagram of a conformable structural element with force application according to an embodiment of the present invention, including a side view, front view of layers and front view of elongate elements;

FIG. 2a is a schematic diagram of a conformable structural element without force application according to an embodiment of the present invention, including a side view, front view of layers and front view of elongate elements; FIG. 2b is a schematic diagram of a conformable structural element with force application according to an embodiment of the present invention, including a side view, front view of layers and front view of elongate elements; FIG. 3a is a schematic diagram of a conformable structural element according to an embodiment of the present invention with length variation with short overlap;

FIG. 3b is a schematic diagram of a conformable structural element according to an embodiment of the present invention with length variation with long overlap;

FIG. 4a is a schematic diagram of a conformable structural element according to an embodiment of the present invention with angle variation, in a side view;

FIG. 4b is a schematic diagram of a conformable structural element according to an embodiment of the present invention with angle variation, in a top view;

FIG. 5 is a schematic diagram of a system comprising one or more conformable structural elements according to an embodiment of the present invention; FIG. 6 is a schematic diagram of a conformable structural element according to an embodiment of the present invention, during the process of shape changing;

FIG. 7 is a table of different structures, arrangement, materials and linkage of conformable structural elements;

FIG. 8 is an overview of different possibilities to control two or more conformable structural elements within a system;

Fig. 9 is a close up of the conformable structural element. The adhesion between the surfaces of the layer and /or rod elements is shown.

DETAILED DESCRIPTION OF EMBODIMENTS This invention relates to a novel concept for a modular and wearable technical support system for reducing musculoskeletal stress. The support system, based on the approach of Human Hybrid Robot (HHR), which can be adapted easily to different users and activities. The system emphasis on modularity and use of soft materials for kinetic elements in order to gain higher flexibility and increased human safety. The basic idea can be applied to various applications. This invention focuses on the development of technologies for supporting human being individually by performing tasks without replacing by technical systems. Based on main resulting stress during manual tasks, the general approach for support system as well as an approach for a general technology for soft and wearable support systems is described.

In consideration to the approach of HHR, a modular approach is chosen in order to adapt the system ad hoc to different tasks and users by using pre-developed modules of a construction kit. So, technical functionalities will support the human abilities. The basic principle of this approach concentrates on the use of soft chamber elements with different geometry, which are structured or non-structured and including elastic or rigid elements.

The conformable structural elements can be used as parallel kinematic elements for stabilizing and fixation of bio mechanical and technical kinematic chains like human extremities or other body parts, up to joints in (soft) robots.

Through a higher stiffness of the conformable structural element during operating state, forces and torques can be transmitted. Evacuating the sheaths may lead to shrinkage of the sheaths, e.g., due to the properties of the layer elements, the size of the air gap or the arrangement of the layer elements.

The use of corresponding conformable structural elements or a systems of conformable structural elements (serial or parallel arrangement of several conformable structural elements) can have different objectives. The overall objective is to increase the stiffness of joints as well as to stabilize or fixate flexible structures. Specifically, this means that the conformable structural elements are designed for at least one up to four kinds of force and torque transmission: tensile force,

compression force, bending and torsion. The sheaths, the integrated stack of layer elements as along with the interaction can be designed entirely different. Main distinguishing criteria for the conformable structural element properties, e.g., stiffness, are the geometry, the material, e.g., stiffness and surface finish, the elements structure as well as the type of connectivity between the sole conformable structural elements and between the sole layer elements and the sheath. It is assumed that the sheath (inclusive material of sheath) does not affect the property of the layer elements on its inside. If possible or necessary, a distinction in respect to the properties for evacuated and non-evacuated sheath is carried out. These distinctions are important for the system design. Based on the basic principle described above, but maybe with different geometry, designs and paths for force redirection, without power reinforcement, for wearable support and several applications can be realized, especially in order to support the upper body, shoulder and upper extremities of a human. The elements are suitable for different loading conditions. The system is designed for force redirection in order to decrease musculoskeletal stress. The components used for this purpose are soft and can be integrated into clothes. During the initial state, the range of motion is only slightly reduced. The word "exemplary" for exclusive use herein means, "used as an example or embodiment or for a descriptive purpose". Any embodiment described herein for an "exemplary" purpose does not need to be explained as being superior to or better than other embodiments. In addition, to better describe the present invention, many specific details are provided in the following specific implementation manners. A person skilled in the art should understand that the present invention can still be implemented without these specific details. In some other instances, well-known methods, means, components, and circuits are not described in detail, so that a main purpose of the present invention is highlighted. In Fig. la a schematic diagram of a conformable structural element 100 comprising a stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 of a flexible sheet material is shown. A force application means applies a force F on the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 such that the superimposed surfaces of the flexible sheet material are pressed together and thereby an increased distortion stiffness is obtained. Further, also a front view of a stack 60 of layer elements 61, 62, 63, 64 and front view of a stack 160 of rod or wire elements

161, 162, 163, 164 is shown. The cross section of a rod element can be round, rectangle, triangle, hexagonal or any other kind of a polygon. Fig. lb shows a schematic diagram of a conformable structural element 100 during the initial state, without force application by the force application means. The conformable structural element 100 comprises a stack 60, 160 of two or more layer elements 61, 62, 63, 64, 161, 162, 163, 164 of a flexible sheet, wire-shaped or rod- shaped material arranged in a super- imposed manner, a force application means, wherein the force application means is a sheath 10. The stack 60, 160 of the layer elements 61, 62, 63, 64, 161, 162, 163, 16 is within the sheath 10. The sheath 10 further comprises an opening 20 and a pressure sensor 30. During the initial state, as shown in Fig. lb, there are spaces 50 within air 40 between the sole layer elements 61, 62, 63, 64, 161, 162, 163, 164 of the flexible sheet, wire-shaped or rod-shaped material. The word "spaces" signifies not literal space, but rather that the sole layer elements 61, 62, 63, 64, 161, 162, 163, 164 can be moved in respect to each other with low exertion. The pressure sensor 30 is integrated inside the sheath 10 to measure the pressure inside the sheath 10. During the initial state of the invention, no force is applied by the force application means on the flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 of the stack 60, 160 of layer elements 61, 62, 63, 64, 161,

162, 163, 164. Further, also a front view of a stack 60 of layer elements 61, 62, 63, 64 and front view of a stack 160 of rod or wire elements 161, 162, 163, 164 is shown.

Fig. lc shows a schematic diagram of a conformable structural element 100 during the operating state, with force application by the force application means. The conformable structural element 100 comprises a stack 60, 160 of two or more layer elements 61, 62, 63, 64, 161 , 162, 163, 164 of a flexible sheet, wire-shaped or rod- shaped material arranged in a super- imposed manner, a force application means, wherein the force application means is a sheath 10. The stack 60, 160 of the layer elements 61, 62, 63, 64, 161 , 162, 163, 164 is within the sheath 10. The sheath 10 further comprises an opening 20 and a pressure sensor 30. During the operating state, as shown in Fig. lc, the adhesion between the sole layer elements 61, 62, 63, 64, 161, 162, 163, 164 of the flexible sheet, wire-shaped or rod-shaped material is increased and therefore the distortion stiffness is increased. The air 40, inside the sheath 10, has been evacuated through the opening 20. In the operating state of the invention, force is applied on the flexible layer elements 61, 62, 63, 64, 161 , 162, 163, 164 of the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164. The applied force results through the difference of pressure between the environment and inside the sheath 10. If the air 40 from inside the sheath 10 is evacuated, the ambient pressure applies a force on the flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 and presses the layer elements together. Through the friction between the sole flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 the stiffness is increased of the conformable structural element 100 and the shape is conserved. This state is maintained until the air 40 returns into the sheath 10 through the opening 20. If the pressure inside the sheath 10 and outside the sheath 10 is equal, the applied force on the stack 60, 160 of layers is lower or zero and the conformable structural element 100 can be reformed into another 3D-shape. A pressure sensor 30 may be integrated inside the sheath 10 to measure the pressure inside the sheath 10, in case the system underlies an automatic control. Further, also a front view of a stack 60 of layer elements 61, 62, 63, 64 and front view of a stack 160 of rod or wire elements 161, 162, 163, 164 is shown. Fig. 2a shows a schematic diagram of a conformable structural element 200 during the initial state, without force application. The conformable structural element 200 comprises a stack 60, 160 of two or more layer elements 61, 62, 63, 64, 161, 162, 163, 164 of a flexible sheet, wire-shaped or rod-shaped material arranged in a super- imposed manner, a force application means wherein the force application means is a double sheath. The double sheath comprises an outer sheath 10 and an inner sheath 11, wherein the inner sheath 11 is inside the outer sheath 10 and inside the inner sheath 11 the stack 60, 160 of flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 is located. Further, the sheaths comprise an opening 20, an opening 21 and an optional pressure sensor 30. During the initial state, as shown in Fig. 2a, the sole layer elements 61, 62, 63, 64, 161, 162, 163, 164 of the flexible sheet, wire- shaped or rod-shaped material can be moved in respect to each other with low exertion. The pressure sensor 30 is integrated inside the outer sheath 10 to measure the pressure inside the outer sheath 10. During the initial state of the invention, there is no force applied by the force application means on the flexible layer elements 61,

62, 63, 64, 161, 162, 163, 164 of the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164. Further, also a front view of a stack 60 of layer elements 61, 62,

63, 64 and front view of a stack 160 of rod or wire elements 161, 162, 163, 164 is shown.

Fig. 2b shows a schematic diagram of a conformable structural element 200 during the operating state, with force application by the force application means. The conformable structural element 200 comprises a stack 60, 160 of two or more layer elements 61, 62, 63, 64, 161 , 162, 163, 164 of a flexible sheet, wire-shaped or rod- shaped material arranged in a super- imposed manner, a force application means wherein the force application means is a double sheath. The double sheath comprises an outer sheath 10 and an inner sheath 11, wherein the inner sheath 11 is inside the outer sheath 10 and inside the inner sheath 11 the stack 60, 160 of flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 is located. Further, the sheaths comprise a first opening 20, a second opening 21 and a pressure sensor 30. In the operating state, as shown in Fig. 2b, the adhesion between the sole layer elements 61, 62, 63,

64, 161, 162, 163, 164 of the flexible sheet, wire-shaped or rod-shaped material is increased and therefore the distortion stiffness is increased. Inserting compressed air 40 through the opening 20 generates an overpressure in the outer sheath 10. The air 40 within the inner sheath 11 has been displaced through the opening 21. In the operating state of the invention, force is applied on the flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 of the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164. The applied force results through the difference between pressure of the space between the outer sheath 10 and the inner sheath 11 on the one hand, and the atmosphere, where the layer elements are located on the other hand. Thus, the pressure of the air 40 in the outer sheath 10 displaces the air 40 from inside the inner sheath 11. Therefore, a force is applied on the flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 and presses them together. Through the friction between the sole flexible layer elements 61, 62, 63, 64, 161, 162, 163, 164 the stiffness is increased and the shape is conserved of the conformable structural element 200. This state is contained until air 40 returns into the sheath 11 through the opening 21. If the pressure inside the inner sheath 11 and outer the sheath 10 is equal, the applied force on the stack 60, 160 of layers is zero and the conformable structural element 200 can be reformed into another 3D-shape. The pressure sensor 30 is integrated inside the outer sheath 10 to measure the pressure inside the outer sheath 10. Further, also a front view of a stack 60 of layer elements 61, 62, 63, 64 and front view of a stack 160 of rod or wire elements 161, 162, 163, 164 is shown.

Another embodiment of the invention is shown in Fig. 3a. The stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 is divided into two groups, the first group 61, 63, 161, 163 and the second group 62, 64, 162, 164. The sole layer elements 61, 62, 63, 64, 161 , 162, 163, 164 are overlapping alternately mutually in an overlapping area. In this embodiment the layer elements 61, 63, 161, 163 of the first group of the stack 60, 160 are jointed in the non-overlapping area through the connection element 70. The layer elements 62, 64, 162, 164 of the second group of the stack 60, 160 are jointed in the non-overlapping area through the connection element 71. The two connection elements 70, 71 may be optionally connected through an elastic element 80. Thus, a flexible element 80 e.g. a spring or a rubber band is mounted between the connection point 70 of the first group of layer elements 61, 63, 161, 163 and the connection point 71 of the second group of layer elements

62, 64, 162, 164. During the initial state, without force application by the force application means, the elastic element 80 withdraws the first group of layer elements

61, 63, 161, 163 in respect to the second group of layer elements 62, 64, 162, 164 into a previously defined position. In the initial state, where no force is applied to the layer elements 61, 62, 63, 64, 161, 162, 163, 164 the first group 61, 63, 161 , 163 and the second group 62, 64, 162, 164 of the stack 60, 160 can be displaced along the longitudinal trajectory x. The two groups are slidden together or pulled apart. After evacuating the air 40 or applying an overpressure, a force is generated on the stack 60, 160 of layers 61, 62, 63, 64, 161, 162, 163, 164 and the sole layer elements 61,

62, 63, 64, 161, 162, 163, 164 are detained to move along the longitudinal trajectory x and the shape of the conformable structural element 300 is provided. To change the length of the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 of the conformable structural element 300 the pressure difference between inside and outside of the sheath 10 is equated. Thus, there is no more force applied on the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164. Therefore, the conformable structural element 300 has a variable length.

Fig. 3b shows the conformable structural element 300 in another length configuration. The two groups of the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 are slidden together in view of Fig. 3a. The overlapping area increases compared to Fig. 3a and, therefore, the length of the conformable structural elements is smaller. Fig. 4a and 4b shows another embodiment of the present invention. The first group and the second group of the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 are connected in the overlapping area with an axle block 90 to form a pivot joint. The axis of rotation 91 is located in the middle of the axle block 90. It should be noted that it is not mandatory to provide an axle block 90. The two groups of layer elements can also be rotated and/or shifted without an axle block. In this case the degree of freedom is higher, as it allows a combined shifting and rotation. The optional elastic element 80 is connected between the connection elements 70, 71 of the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 and the axle block 90 of the pivot joint. During the initial state, where no force is applied on the stack 60, 160 of layer elements 61, 62, 63, 64, 161, 162, 163, 164 the first group 61, 63, 161, 163 of the layer elements 61, 62, 63, 64, 161, 162, 163, 164 and the second group 62, 64, 162, 164 of the layer elements 61, 62, 63, 64, 161, 162, 163, 164 can be rotated around the rotation axis 91 by the angle a. After the air 40 is evacuated or the overpressure is applied, the pivot functionality is blocked and the conformable structural element 400 maintains the shape including the angle a and increases the stiffness of the conformable structural element 400.

Fig. 5 shows a system 500 of conformable structural elements 100, 200, 300, 400 comprising, a control unit 501, an input unit 503 for e.g. triggering, a setting a target value etc., a pump arrangement 502 and one or more the conformable structural elements 100, 200, 300, 400. The control unit 501 receives pressure information from the pressure sensors 30 inside the sheaths 10 of the conformable structural elements 100, 200, 300, 400. With the pressure information and the input signal from the trigger unit 503, the control unit 501 controls a pump arrangement 502. The pump arrangement is able to deliver a specific vacuum or a specific overpressure according to the required stiffness of the conformable structural element 100, 200, 300, 400. The pump arrangement 502 is connected to the openings 20 of the sheaths 10 of each of the conformable structural elements 100, 200, 300, 400. The control unit 501 is able to control the conformable structural elements 100, 200, 300, 400 solely, two or more conformable structural elements simultaneous or two or more conformable structural elements in parallel with different force applications. The system 500 of conformable structural elements may contain one pump 502 and a controllable valve block to switch between the sole conformable structural elements 100, 200, 300, 400 or the system may contain for each conformable structural element 100, 200, 300, 400 a different pump 502. The basic design of systems with the presented technology is done by serial and/or parallel arrangement of the conformable structural elements. The elements can have different geometry, integrated elements, coupling modes etc. Three main types of conformable structural elements can be distinguished: an element with constant length, an element with variable length and an element with variable angle.

Nevertheless, there are still different variants when it comes to the connection between the conformable structural elements or between the elements and the sheath, the design of the elements and sheaths themselves as well as for used materials.

The control of the deflating process of the system, which consists of one or more conformable structural elements, can be achieved differently. A wide variety of different ways is possible, from manually controlled system by the user up to fully automatic control by e.g. measuring the musculoskeletal stress directly by sensors or indirectly by using force sensors.

The coupling between the conformable structural elements can be designed in various ways. Use only elements with constant length which are coupled serial to each other and are arranged parallel to human upper extremities. Use elements with constant length, but these elements are arranged by a helix structure. Use always elements with joints. The joints are arranged in that way that they are parallel to the human joints. Use elements with constant length, elements with joints and elements with flexible length together. All designs have different advantages and

disadvantages, e.g. in respect to stiffness.

Fig. 6 shows the process of the use of a conformable structural element.

During the initial state the conformable structural element is formable. The conformable structural element can be formed into the desired shape. If the force is applied by the force application means, the sole layer elements are pressed together and the stiffness is increased based on friction between the sole layer elements.

Therefore, the previously modelled shape is conserved.

As Fig. 7 shows, the variants have different advantages and disadvantages. The qualities that a system for direct human interaction should have are often different for individual cases of application. Aside from these requirements, the top priority must always lie within ensuring human safety as well as not restricting the range of motion during the use of the system. Thus, in case of this approach, the support effect should be very low for the initial state and very high for the operating state. However, an individual decision about every single conformable structural element and the whole system has to be made. The design not only depends on individual needs, but also highly to the occurring forces and torques. An approximate calculation thereof is possible by mechanical equation for friction force, tensile force as well as bending and torsion of a beam. Force and torque are mainly corresponding to the dimension, e.g., cross-sectional area of the elements, pressure difference (outside and inside the sheath), coefficient of friction between the elements, ultimate strength and Young's modulus. A comparison of different variants of conformable structural elements and the four loading conditions as mentioned above, are shown by Fig. 7. Therefore, a conformable structural element with different structured elements, serial arrangement of elements, materials as well as connections between the chamber and elements is considered.

Fig 8 shows the different possibilities to control a system of conformable structural elements. The user controls each conformable structural element separately, the user controls all conformable structural elements at the same time, a control sequence is controlled by the control unit, the control unit controls within a pressure sensor all conformable structural elements at the same time and the control unit controls based on sensors all conformable structural elements separately.

The basic idea of this principle is illustrated in Fig. 9 for an exemplary cuboid geometry with thin sheets as layer elements. During the initial state the sole layer elements 61, 62, 63, 64 are laying on top of each other and the adjacent surfaces 61b, 62a, 62b, 63a, 63a, 64a can move in respect of each other. During the operating state, a force is applied on the stack 60 of layer elements 61, 62, 63, 64 and the layer elements are pressed together. Thus, the adjacent surfaces 61b, 62a, 62b, 63a, 63a, 64a of the sole layer elements 61, 62, 63, 64 are pressed together and the friction between the adjacent surfaces61b, 62a, 62b, 63a, 63a, 64a of the layer elements 61, 62, 63, 64 increases. While the invention has been illustrated and described in detail in the figures and foregoing description, such illustration and descriptions are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawing, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.

Claims

C L A I M S

1. A conformable structural element (100, 200, 300, 400), comprising:

a stack (60) of at least two superimposed layer elements (61, 62, 63, 64) of a flexible sheet material,

a force application means, which is configured to exert a force on the stack (60) increasing a static friction between adjacent surfaces (61b, 62a; 62b, 63a; 63b, 64a) of the superimposed layer elements whereby the conformable structure element (100, 200, 300, 400) thereby obtains an increased distortion stiffness.

2. A conformable structural element (100, 200, 300, 400) according to claim 1, wherein the force application means is a flexible airtight sheath (10), provided with an opening (20) for introducing or discharging air (40) into or from the airtight sheath (10),

wherein the stack (60) of the at least two superimposed layer elements (61,

62, 63, 64) of the flexible sheet material is located within the flexible sheath (10), and

wherein the force is applied on the superimposed layer elements of the flexible sheet material (61, 62, 63, 64) by evacuating the air out of the airtight sheath (10) over the opening (20).

3. A conformable structural element (100, 200, 300, 400) according to any one of claims 1 and 2,

wherein said force application means is a double sheath (10, 11) comprising an inner sheath envelope (11) and an outer sheath envelope (10), wherein an intermediate space between the inner sheath envelope (11) and the outer sheath envelope (10) is airtight and has an opening (20, 21) for introducing or discharging air into or from the intermediate space,

wherein the stack (60) of the at least two superimposed layer elements (61, 62, 63, 64) of the flexible sheet material is located inside the inner sheath envelope (11), and wherein the force is applied on the superimposed layer elements (61, 62, 63, 64) of the fiexible sheet material by pressurizing the intermediate space via the opening (20).

4. A conformable structural element (100, 200, 300, 400) according to any one of claims 1 to 3,

wherein the superimposed layer elements (61, 62, 63, 64) of the flexible sheet material comprise a first group of layer elements (61, 63) of fiexible sheet material and a second group of layer elements (62, 64) of fiexible material,

wherein the layer elements of the first group (61, 63) and the layer elements of the second group (62, 64) mutually overlap,

wherein the first group (61, 63) with respect to the second group (62, 64) without application of force on the stack (60) is movable along a trajectory, so the amount of overlap and thus the extent of the stack along this trajectory can be varied.

5. A conformable structural element (100, 200, 300, 400) according to claim 4, wherein the layer elements of at least one of the first group of layer elements (61, 63) and the second group of layer elements (62, 64) in a non-overlapping area are connected with each other (70, 71), so that a displacement of the layer elements within said respective group of layer elements (61, 62, 63, 64) in an area averted from the overlap area is avoided.

6. A conformable structural element (100, 200, 300, 400) according to any one of claims 1 to 5,

wherein the superimposed layer elements (61, 62, 63, 64) of the flexible sheet material comprise a first group of layer elements (61, 63) of the flexible sheet material and a second group of layer elements (62, 64) of flexible sheet material, wherein the layer elements of the first group (61, 63) and the layer elements of the second group (62, 64) mutually overlap,

wherein the first group (61, 63) with respect to the second group (62, 64) without application of force on the stack (60) are rotatable around a rotation axis (91), so that the angular position of the first group (61, 63) can be varied with respect to the second group (62, 64).

7. A conformable structural element (100, 200, 300, 400) according to claim 6, wherein the layer elements of the first group of layer elements (61, 63) and the layer elements of the second group of layer elements (62, 64) are connected in the axis of rotation (91) by a connecting axle block (90), so that a displacement of the material in relation to the rotation axis (91) is avoided.

8. A conformable structural element (100, 200, 300, 400) according to any one of claims 4 to 7,

wherein the first group of layer elements (61, 63) and the second group of layer elements (62, 64) are connected with an elastic element (80), wherein moving the first group of layer elements with respect to the second group of layer elements biases the elastic element, wherein the biased condition of the elastic element is fixable by applying the force to the stack of layer elements, wherein the first group of layer elements (61, 63) with respect to the second group of layer elements (62, 64) is returnable into a defined position by the biased elastic element when withdrawing the force application on the stack (60).

9. A conformable structural element (100, 200, 300, 400) according to any one of claims 1 to 8,

wherein in the force application means comprises a pressure sensor (30) being configured to control the force application and therewith the mobility of the layer elements (61, 62, 63, 64) with respect to each other.

10. A conformable structural element (100, 200, 300, 400), comprising:

a bundle of elongate elements (161, 162, 163, 164) of a flexible material, a force application means, which is configured to exert a force on the bundle (160) of elongate elements (161, 162, 163, 164) increasing a static friction between adjacent surfaces (of the bundled elongate elements whereby the conformable structure element thereby obtains an increased distortion stiffness.

11. A conformable structural element (100, 200, 300, 400) according to claim 10, wherein the elongate elements (161, 162, 163, 164) are rod elements, wherein a rod element is characterised by a restoring force, if no force is applied on the bundle of rod elements.

12. A conformable structural element (100, 200, 300, 400) according to claim 10, wherein the elongate elements (161, 162, 163, 164) are wire elements, wherein a wire element is characterised by bending under their dead weight, if no force is applied on the bundle of wire elements.

13. A conformable structural element (100, 200, 300, 400) according to any one of the claims 10 to 12,

wherein the force application means is a flexible airtight sheath (10), provided with an opening (20) for introducing or discharging air (40) into or from the airtight sheath (10),

wherein the bundle (160) of elongate elements (161, 162, 163, 164) of the flexible elongate material is located within the flexible sheath (10), and

wherein the force is applied on the elongate material of the flexible elongate material (161, 162, 163, 164) by evacuating the air (40) out of the airtight sheath (10) over the opening (20).

14. A conformable structural element (100, 200, 300, 400) according to any one of claims 10 to 13,

wherein the bundle (160) of elongate elements (161, 162, 163, 164) of the flexible elongate material is located inside the inner sheath envelope (11), and wherein the force is applied on the bundled elongate elements (161, 162, 163, 164) of the elongate material by pressurizing the intermediate space via the opening (20).

15. A System of conformable structural elements (500), comprising:

a control unit (501),

a pump arrangement (502),

at least two conformable structural elements (100, 200, 300, 400) according to any one of claims 1 to 18,

wherein the control unit (501) is configured to control the pump arrangement (502) upon user request to evacuate or fill in air (40) from or into the respective intermediate spaces of the respective conformable structural elements (100, 200, 300, 400),

wherein each one of the conformable structural elements (100, 200, 300, 400) can be controlled independently or in combination with one or more of the other conformable structural elements (100, 200, 300, 400) upon user request.

16. System of conformable structural elements (500), according to claim 19, further comprising:

a pressure sensor (30) in each of at least two conformable structural elements (100, 200, 300, 400),

wherein the control unit (501) is configured to control the pump arrangement (502) to evacuate or fill in air (40) from or into the conformable structural elements (100, 200, 300, 400) based on determined pressures of the pressure sensors upon user set up of a desired configuration of the at least two

conformable structural elements (100, 200, 300, 400).