EP2480289A2

EP2480289A2 - Device using a membrane suitable for supporting and moving a load

Info

Publication number: EP2480289A2
Application number: EP10769022A
Authority: EP
Inventors: Eric Belmon
Original assignee: AMPLISENS
Current assignee: AMPLISENS
Priority date: 2009-09-23
Filing date: 2010-09-23
Publication date: 2012-08-01
Also published as: WO2011036412A2; FR2950329B1; FR2950329A1; WO2011036412A3

Abstract

The invention relates to a device (1) for moving a load (2), including a frame (3), a membrane (7) for supporting the load and a motor (8), designed to move the membrane relative to the frame, characterised in that the device includes a means (9) for rigidifying at least one portion of the membrane. The membrane advantageously includes a magneto-rheological material and the device includes a magnetic means (9) for rigidifying the membrane, in particular in a load application area (11). Such a device is particularly well suited for producing a virtual reality mat, with a user moving about on the membrane.

Description

Device using a membrane adapted to carry and move a load.

The present invention relates to the field of moving mats for moving a load carried by a membrane. The invention relates more particularly, but not only, to the field of carpets intended to move under the steps of a user who travels a virtual reality.

The membranes used are generally flexible and elastically deformable membranes. However, carpets include a motorization generally distant from the place where the load is applied to the carpet. However, the distance between the place of application of the load and the motorization is likely to induce an elastic deformation of the membrane. As a result, there is no linear relationship between a displacement of the load and a movement of the motor. In particular, a gradual acceleration of the motorization can induce a delayed and sudden displacement of the load. In the case of a virtual reality mat, the load is essentially a user standing on the membrane, and a sudden displacement of the carpet can cause the fall of this user. In addition, especially for a virtual reality mat, it is important that the displacement of the membrane, at the place where the user is, be controlled, both in position, speed and acceleration, to make Realistic and consistent, moving the user into virtual reality.

The aim of the invention is to propose a device and a method that make it possible to solve the disadvantages previously described, and in particular to ensure a controlled transmission of a movement where the load is carried by the membrane.

According to the invention, such a device for moving a load, comprising a frame, a membrane and a motor, said membrane being provided for carrying said load, said motor being designed to move said membrane relative to the frame, is characterized in that the device comprises means for stiffening at least a portion of the membrane.

The stiffening means may be arranged to stiffen the membrane when said membrane traverses a rigidification zone fixed relative to the frame. This stiffening zone may be an area of application of the load on the membrane.

Advantageously, the membrane comprises a magnetorheological material, preferably a polymer, and the stiffening means comprise magnetic means for generating a magnetic field in the stiffening zone. The polymer may be an elastomer. The magnetic means are advantageously arranged so that the magnetic field varies gradually in the stiffening zone, preferably decreasing when moving away from a center of said stiffening zone. The magnetic means may comprise at least one permanent magnet and / or at least one electromagnet disposed near the membrane in the stiffening zone.

When the magnetic means comprise at least one electromagnet, it may be a flat coil, each turn of which is further apart from its neighbors as one moves away from a center of the stiffening zone.

When the magnetic means comprise at least one electromagnet, it may be a flat coil, each turn of which is further away from the membrane as one moves away from a center of the stiffening zone. The magnetic means may also include several permanent magnets distributed near the membrane.

The device can be a virtual reality mat, that is to say, be provided to move in a virtual reality, and comprise a substantially rigid chassis core, and the membrane forming an envelope arranged to be able to move in all directions. the directions around the core, the envelope forming with an upper face of said core a surface adapted for the displacement of a person, the assembly formed by the core and its envelope resting on appropriate support means. The core of such a device is advantageously substantially of revolution about a substantially vertical axis, the stiffening zone extending above the core.

In addition, a method according to the invention for stiffening the membrane of a device intended to move a charge placed on said membrane, for example a virtual reality mat, is characterized in that:

a membrane comprising a magneto-rheological material is used; and

a suitable magnetic field is created which defines an area in which a part of the membrane, which runs through the area or which is situated thereon, must be rigidified.

Several embodiments of the invention will be described below, by way of non-limiting examples, with reference to the appended drawings in which:

- Figure 1 schematically illustrates the principle of the invention;

- Figure 2 schematically illustrates a first embodiment;

FIG. 3 is a schematic top view of a virtual reality mat comprising a membrane according to the invention; and

FIG. 4 is a diagrammatic view, in vertical section, of the carpet of FIG. 3.

Figure 1 illustrates an endless belt 1 for moving a load 2. The endless belt 1 comprises a frame 3 extending horizontally. Two opposite ends of the frame each carry a roll 4.6. Each roller 4,6 is rotatably mounted about a respective axis X4, X6. The axes X4, X6 of the rollers are fixed relative to the frame 3. A first roll 4 is mounted free to rotate about its axis X4. The second roller is connected to a motor 8 adapted to drive the second roller in rotation along R6 about its axis X6.

A membrane 7 is mounted stretched between the rollers 4,6, so that it surrounds the frame, and, an upper part of the membrane, disposed above the frame, is provided to rest the mass 2 therein. Thus, a rotational movement of the second roll 6 along R tends to bring the mass 2 of the second roll 6, by traversing the upper, flat face of the frame 3.

The membrane 7 is made of a flexible, but nevertheless magnetorheological, polymeric material, that is to say able to stiffen as it passes through a suitable magnetic field. The chassis comprises means 9 for creating a magnetic field C9, in an area 11 located above the frame. Magnetic field C9 is illustrated in FIG. 1 by arrows. The zone 1 1 is crossed by the membrane 7 in its portion 7 A which carries the mass 2. Thus, it is possible to stiffen the upper portion 7A of the membrane 7, while retaining the necessary flexibility of the membrane in its parts which circumvent the rollers 4,6, or in its arranged portion, between the rollers, under the frame 3.

When it is not subjected to the magnetic field C9, the membrane 7 has a certain elasticity. Thus, without the application of the magnetic field C9, when the motor 8 accelerates or decelerates, this movement is transmitted with delay to the load by the membrane, located at a distance D from the axis X6 of the motor roller 6. This can cause brutal and unwanted movements of the load 2.

When, on the other hand, the magnetic field C9 is applied, in the zone 11 of stiffening, that is to say the volume where the magnetic field its effects, the whole part of the membrane which is situated there is stiffened. Thus, in the zone 1 1 of stiffening, the effects of the elasticity of the membrane are canceled. These effects remain only on a reduced part of the distance D, between the frame 2 and the second roller 6. Thus, the movement imposed by the motor 8 to the membrane is transmitted to the load with greater precision and with a reduced delay. .

A portion of the membrane is stiffened when it enters the stiffening zone 11 and then regains its flexibility and elasticity when it leaves the stiffening zone 11, allowing it in particular to wind around the rollers 4,6.

An application of the invention will now be described to a virtual reality mat, allowing a user to move horizontally in all directions. Such a belt 20 is illustrated in Figures 3 and 4. As particularly illustrated in Figure 3, in view from above the belt 20 has a circular shape. It is substantially symmetrical in rotation around a vertical axis X20. It comprises a base 21 designed to rest immobile on a substantially horizontal ground, a core 22 and a membrane 23. The core 22 forms a frame for the membrane 23, and it is intended to rest on the base 21.

The core 22 has a small thickness, measured vertically, relative to its diameter, and is rotatably mounted relative to the base 21, about the axis X20 of the belt 20. It has an upper surface 24 substantially flat and horizontal. It further comprises an axial appendix 26 extending downward and cooperating with a well 27 of the base 21 to maintain the core and the base coaxial about the axis X20.

The membrane 23 envelops the core and is mounted movably in all directions around the core. So that the belt 20 has constant characteristics regardless of the position of the membrane 23 around the core, the membrane is provided substantially isotropic. To guarantee the isotropism of the membrane, this one is carried out so that if it is freely inflated, it takes the form of a sphere. In addition, so that the membrane can freely deform as it moves around the core 22, it is made from a flexible material, preferably a polymer, preferably an elastomer.

The membrane 23 is mounted tightly around the core 22. However, the naturally "spherical" shape of the membrane 23, useful for its isotropism, makes that once placed around the core, each portion of the membrane has a tension which varies depending on the position of this portion relative to the core. Thus, at the upper surface 24 of the core, the membrane will be more taut along the peripheral circular edge 28 of the core 22 in the vicinity of the axis X20. Thus, at the upper surface 24 of the core, the membrane 23 will be progressively less stretched as one moves away from the edge 28 to approach the axis X20.

The base 21 comprises balls 29 arranged vis-à-vis a lower face 31, to allow substantially free movement of the membrane 23. Some of the balls 29 are motorized to control the position of the core 22 relative to the base 21, around axis X20.

The core 22 comprises balls 32, 33, arranged on its lower face 31, opposite the base 21, to allow the substantially free movement of the membrane 23. The balls 32, 33 comprise motorized balls 32 in order to driving the membrane 23 in motion around the core 22.

When a user uses the belt 20, he stands on the membrane pressing on the upper face 24 of the core. There is therefore a significant distance, with regard to the elasticity of the membrane, between the support of the user and the motor balls 32, arranged on the lower face 31 of the core 22. It is advisable that the displacement of the membrane is perfectly controlled so that the user's sensation of movement in the virtual reality is consistent with the vision given to it. In particular, there must be no delay or delay between what is seen by the user and the - - perceived displacement. However, for example, because of the distance between the support of the user and the motor balls 32, during an acceleration, the membrane tends to stretch over this distance, until the voltage is sufficient to transmit the movement, often brutally, which may cause a disruption of the user. Similarly, during a change of direction of the membrane, the movement of the membrane at the point of support tends to continue in the initial direction until the membrane is sufficiently stretched in the new direction to transmit the movement , sometimes brutally, which may cause an imbalance of the user.

To solve this problem, the membrane comprises a magnetorheological material, so that the membrane is able to stiffen when subjected to a magnetic field C9, illustrated by arrows pointing upwards in FIG. magnetic device is arranged so that it is active, in a stiffening zone 11 shown in dashed lines in FIG. 4, on a portion of the membrane traversing the upper surface 24 of the core 22. In addition, the magnetic field C9 is provided all the more intense as one moves away from the peripheral edge 28 of the core 22 while approaching axis X20, so that the membrane 23 is all the more stiffened by the field C9 that it is less tight on the core. Thus, in the zone 11 of stiffening, by the action of the magnetic field C9, the effects of the elasticity of the membrane are canceled. These effects remain only on a small part of the distance between the support of the user and the motor balls 32. Thus, the movement imposed by the motor balls to the membrane 23 is transmitted to the user with greater precision and with a reduced delay.

In the example illustrated in FIGS. 3 and 4, the magnetic field C9 is generated by means of a flat coil 36, in which the turns form a spiral substantially parallel to the upper face 24 of the core. In the example shown, each turn is further away from its neighbors, as one moves away from the axis X20. FIG. 2 is a diagram illustrating the electrical operation of the belt 20. The base is connected to a power supply 40 which feeds a first inductive coil 41. This first inductive coil is arranged around the well 27. A second coil 42 is arranged in the appendix 26, so that when the core 22 bears on the base 21, the second coil 22 is disposed coaxially with the first coil 21, between the turns thereof. Thus, the first coil 41 is provided to excite the second coil 22 by induction, so that it transmits energy from the power supply 40 to the equipment of the core 22. The core comprises, among these equipment, the flat coil 36 and a motor 43 for the driving balls 32, mounted in parallel.

Of course, the invention is not limited to the examples which have just been described.

In particular, the flat coil can be replaced by several coils disposed near the upper surface of the core, so that the winding axis of their coil is horizontal. Preferably, the density of these turns, measured with respect to a horizontal elementary surface, increases as one approaches the axis of the virtual reality mat, moving away from the peripheral circular edge of its core.

Also, rather than electromagnets, one can use permanent magnets.

In addition, several stiffening zones of the same membrane can be provided in a device according to the invention.

In addition, even if the magnetic field C9 has been shown vertical in FIG. 3, this field may be a horizontal magnetic field. Whatever the direction of the magnetic field C9, its intensity may nevertheless advantageously be of the type shown in dashed lines in FIG. 3, that is to say progressively weaker as one moves away from a center of the stiffening zone.

Claims

claims

1. Device (1,20) for moving a load (2), comprising a frame (3,22), a membrane (7,23) and a motor (8,43), said membrane being provided to carry said load, said motorization being designed to move said membrane relative to the frame, characterized in that the device comprises means (9,36) for stiffening at least a portion (7 A) of the membrane.

2. Device according to claim 1, characterized in that the stiffening means are used to stiffen the membrane when said membrane traverses a stiffening zone (11) fixed relative to the frame.

3. Device according to claim 2, characterized in that the membrane comprises a magneto-rheological material, preferably a polymer, and in that the stiffening means comprise magnetic means for generating a magnetic field in the stiffening zone.

4. Device according to claim 3, characterized in that the polymer is an elastomer.

5. Device according to one of claims 3 or 4, characterized in that the magnetic means are arranged so that the magnetic field varies gradually in the stiffening zone, preferably decreasing when moving away from a center (X20) of said stiffening zone.

6. Device according to one of claims 3 to 5, characterized in that the magnetic means comprise at least one permanent magnet and / or at least one electromagnet (36) disposed near the membrane in the stiffening zone.

7. Device according to claim 6, characterized in that the magnetic means comprise at least one electromagnet which comprises a flat coil (36) each turn of which is further apart from its neighbors as one moves away from a center of the stiffening zone.

8. Device according to claim 6, characterized in that the magnetic means comprise at least one electromagnet which comprises a flat coil which each turn is further from the membrane as one moves away from a center of the zone stiffening.

9. Device according to one of claims 6 to 8, characterized in that the magnetic means comprise a plurality of permanent magnets distributed in the vicinity of the membrane.

10. Device according to one of claims 2 to 9, characterized in that it is intended to move in a virtual reality, comprising a core (22) forming a frame, substantially rigid, and the membrane forming an envelope (23) disposed to be movable in all directions around the core, the shell forming with an upper face (24) of said core a surface adapted for the movement of a person, the assembly formed by the core and its envelope resting on appropriate means of support (21).

11. Device according to claim 10, characterized in that the core is substantially of revolution about a substantially vertical axis (X20), the stiffening zone extending above the core.

12. A method for stiffening the membrane of a device intended to move a charge placed on said membrane, characterized in that: a membrane (7, 23) comprising a magneto-rheological material is used; and

a suitable magnetic field is created which defines a zone (11) in which a part of the membrane, which traverses said zone or which is situated therein, must be rigidified.