WO2014131562A1

WO2014131562A1 - Device for measuring static pressure, tracking system comprising such a device and method of tracking of said system

Info

Publication number: WO2014131562A1
Application number: PCT/EP2014/051516
Authority: WO
Inventors: Eric WILLEMENOT DE NANC; Alexandre HOUEE
Original assignee: Move'n See
Priority date: 2013-02-27
Filing date: 2014-01-27
Publication date: 2014-09-04

Abstract

The invention relates to a device for measuring a static pressure on an object or an individual, said device being characterized in that it comprises a bearing surface (4), a pressure sensor (1), a power supply (2) suited to powering the pressure sensor (1), a measurement duct (3) a first end of which is intended to contain the pressure sensor (1) on the walls of said measurement duct (3) and a second end that opens onto the bearing surface (4), a protective means (5) placed in front of the measurement duct (3) and wider than the said measurement duct (3).

Description

Static pressure measuring device, tracking system comprising such a device and method of tracking said system

Technical field and state of the art

The present invention relates to the altimetric measurement by pressure, that is to say to a device that measures the static atmospheric pressure with sufficient precision to deduce the altitude.

The reliability of a pressure measurement by means of a static pressure measuring device depends on the relative wind conditions. If the pressure sensor is facing a relative speed wind v, it measures, in addition to the static pressure representative of the altitude, a dynamic stop value pressure ½ * Rho * v ² , where Rho is the density air. For example, at a constant altitude if a wind of 20 m / s is facing the pressure sensor, the theoretical error of altitude measurement is 260 m.

Another perturbation comes from the venturi effect. If the sensor is in an area where the airflow is locally accelerated due to the local geometry, as is the case on the top of an airplane wing, then the total pressure is lower. a term proportional to ½ * Rho * v ² , and thus affects the measurement of static pressure which is no longer representative of altitude.

EP0677798 discloses a pressure sensor protected by a device having holes to allow air and water to come into contact with the sensor to communicate their pressure.

However, this document does not describe how to measure an atmospheric pressure without being disturbed by the contact of the water with the sensor or with the small holes, on which menisci of water can be formed, and to alter the measurement of pressure. because of their weight and surface tension. The weight and the surface tension of the water menisci deform the water surface which is on the side of the pressure sensor, thus modifies the air volume on the pressure sensor side or directly exerts pressure on said sensor, and therefore modifies its atmospheric pressure measurement by an uncontrolled error term.

Moreover, any difference in altitude between a static pressure tap and the pressure sensor itself generates a pressure difference directly related to the mass of the element present in the duct connecting the pressure tap to the sensor itself. . For example, the pressure sensor is subject to external conditions and sometimes a liquid, such as water, can penetrate the conduit; the presence of this water leads to an alteration of the pressure measurement.

The object of the present invention is to overcome these disadvantages and to propose a device for measuring the static pressure of reduced sensitivity to the undesirable effects described above.

Description of the invention

The invention aims to overcome the disadvantages of the prior art and for this purpose concerns a device for measuring a static pressure on an object or a person, said device comprises:

a support surface, a pressure sensor,

a power supply adapted to the supply of the pressure sensor,

a measurement duct, of which a first end is provided for containing the pressure sensor on the walls of said measuring duct and a second end opening on the bearing surface;

a protection means arranged in front of the measurement duct and wider than said measuring duct.

Surprisingly, this device improves the reliability of the pressure measurement. Without being bound to any theory, it is assumed that the protective means guides the flow of air in a laminar direction and parallel to the surface of the pressure sensor, and limits the venturi effect and the effect of the dynamic pressure. stopping, or that the average protection advantageously venturi effects and stop dynamic pressure.

According to an exemplary embodiment, the device is a sealed housing. The seal is achieved by an elastic seal such as rubber between a first portion and a second portion. The bearing surface may be on the first part or the second part of the device.

According to an exemplary embodiment, the bearing surface (in which there is the measurement duct) is the flat surface below the device.

The term object is to be understood as a garment of a natural person, the skin of a person or animal, or a land, sea, rail or air vehicle.

According to an exemplary embodiment, the pressure sensor comprises a sealing means positioned between the pressure sensor and the measurement duct of the device. According to non-limiting exemplary embodiments, the sealing means is a seal or glue. In this way, there is no pressure error between the pressure inside the device and the pressure outside the device. The term measuring pipe is a pipe that includes an end plugged by the pressure sensor.

The invention is advantageously implemented according to the embodiments described below, which are to be considered individually or in any technically operative combinations.

According to embodiments, the device comprises a fastening element, such as a cuff, adapted to orient the bearing surface of the device on the object or the person.

According to embodiments, the length of the measurement duct is from 0.5 to 10 mm, preferably from 1 to 5 mm.

According to embodiments, the protection means is a porous material.

According to embodiments, the protection means is a pierced protection cap comprising a space without material completely covering the measurement conduit, said space without material includes a disc with a diameter greater than or equal to 1 cm and greater thickness or equal to 1 mm. In this way the water contained in the protective cap flows freely with reduced retention inside the protective cap. Bores or through holes are used for the free circulation of air and water. According to embodiments, the protective cap comprises two bores, one of which has a surface area greater than 10 mm ² .

According to embodiments, a flexible membrane plugs the measurement duct, the flexible membrane being fixed to the bearing surface and sealed, said measuring duct contains a volume of a gaseous fluid.

The flexible membrane in contact with the device is watertight and reduces the adverse effects related to external elements such as wind, water, and water menisci that could form on the pressure sensor or in the immediate vicinity of it. this.

According to embodiments, the protection means comprises a protective cap which is porous. This porosity attenuates the disturbances of the venturi effect and the effect of the dynamic stop pressure by averaging these effects on a surface greater than that of the measurement duct.

The protective cap is a cover covering the measurement duct while allowing the air to pass through so that the sensor is subjected to atmospheric pressure. According to one embodiment, holes (or holes) are on the sides (edges) of the protective cap or on most of the surfaces of the protective cap.

According to embodiments, the volume of the gaseous fluid contained in the measuring pipe is less than S * 10 ^-3 M, where S is the surface of the flexible membrane.The flexible membrane is free to deform under the effect of a pressure change on the outside of the device.

For the measurement of the surface S, the flexible membrane is the part of the membrane which remains flexible after all the possible stages of assembly.

In fact, the trapped water modifies by its weight the measurement of the volume of the measurement pipe and thus the measurement of the pressure. The inventors have discovered that the holes on the sides or on the surface of the cap are useful for passing air, and hence influence the measurement. Said holes allow air to pass while protecting the flexible membrane from contact with an external solid. The cap also makes it possible to protect the membrane from any contact with an external element, capable of generating a contact pressure which distorts the measurement of the atmospheric pressure.

According to embodiments, the device comprises a differential measurement pipe positioned on a surface other than the bearing surface, the differential measurement conduit opening on a wall of the measuring pipe.

Due to the pressure difference between the measuring pipe and another measuring pipe, the pressure measurement is an average of several pressure measurements. The inventors have discovered an improvement in the accuracy of the measurement.

The invention also relates to a tracking system comprising a static pressure measuring device according to one of claims 1 to 9, said tracking system comprising a tracking means and n means for transmitting the relative or absolute position, characterized in that said system comprises means for calculating the relative position of the device disposed on the device or on the tracking means, a means for receiving the static pressure measurement and the relative or absolute position of said static pressure device, a processing means adapted to orient said tracking means as a function of the relative position and the static pressure of the device.

Depending on the size of the device, it will be preferable in some cases to have the means for calculating the relative position inside the device while in other cases it will be preferable to have the means for calculating the device. relative position in the tracking means or in the system incorporating the tracking means.

The invention also relates to a method for tracking a tracking system comprising the following steps:

- setting up the pressure measuring device on an object or a person,

positional data transmission of the device and measurement of static pressure,

orienting the tracking means to said device as a function of the relative position and the static pressure measurement.

Brief description of the figures

Other features and advantages of the invention will become apparent in the light of the following description, made on the basis of the accompanying drawings. These examples are given in a non-limiting manner. The description is to be read in conjunction with the appended drawings in which:

FIG. 1 represents an example of the invention for cutting along the transverse axis of the device

FIG. 2 represents an example of the invention in a view from above,

FIG. 3 represents another example of an invention of the invention for cutting along the transverse axis of the device,

FIG. 4 represents another example of the invention for cutting along the transverse axis of the device,

- Figure 5 shows another example of the invention for cutting along the transverse axis of the device. Description of Embodiments of the Invention

Figures 1 and 2 show two views of the static pressure measuring device. The device is in the form of a rectangular parallelepiped, but it can also be in another form such as, for example, pyramidal, ovoid, pyramid trunk, ...

The static pressure measuring device comprises a bearing surface 4, a pressure sensor 1 positioned in front of a measurement duct 3 and a supply 2. The supply 2 serves the needs of the various elements of the device. The measurement duct 3 extends from a first end adjacent to the pressure sensor 1 to a second end adjacent to the bearing surface 4. The measurement duct 3 allows measurement of pressure by the pressure sensor. The section of the measurement duct is substantially equal to the measurement section of the pressure sensor 1. The supply 2 supplies the various elements of the device, in particular the pressure sensor 1.

The measurement of the pressure sensor 1 can be processed directly by the device by means of a pressure sensor measurement processing means for, for example, display it on the device.

The calculation of the altitude as a function of the pressure measurement p is given by known formulas such as, for example, altitude = 44330 * (1- (ρ / ρ0) ^Λ (1 / 5,255)) where p0 = 101325 Pa.

In another version of the device, the measurement of the pressure sensor is transmitted by means of transmission means to another device or to a system for analyzing the pressure measurement. For example, the means for transmitting the measurement of the pressure sensor is a means of wireless transmission such as a modem or a radio link.

The static pressure measuring device comprises a fixing element, the fastening element makes it possible to orient the fixing of the device on an object so that the bearing surface 4 of the device is in contact with the object. The bearing surface in contact with the object is not waterproof since the pressure measurement must be performed. The fact of having a bearing surface protected by the device makes it possible to limit the harmful effects related to an excess of air or liquid flow. For example, if the measuring pipe 3 is directly exposed to a wind of 20 m / s, the error of the calculation of the altitude from the pressure measurement is 120 m. This is the result of a practical measurement where the sensor is behind a flat surface which leads to a result different from the theoretical calculation seen previously since there is a turbulence regime. If the measuring pipe 3 is in the bearing surface 4 and is not exposed directly to the wind, the error of the calculation of the altitude from the pressure measurement is reduced to 50 m.

Figure 3 shows another example of the invention. In this case, a protection element 5 is positioned in front of the measuring conduit 3. The protection means 5 comprises at least one contact surface with the device. In a non-limiting example, the contact surface of the protection element 5 is in contact with the bearing surface 4 of the device. The protective element has a greater contact area than the section of the measuring conduit 3. The protective element 5 is positioned so as to completely cover the opening of the measuring conduit 3. In this way, the pressure is distributed in the volume of the protection element before reaching the duct, which increases the accuracy of the measurement since the effects related to external conditions are reduced by physical averaging before the measurement.

In another example, the protection means 5 is in a porous material. For example, it can be foam.

According to another example, the protection means 5 has a sealing surface 6 and an unsealed edge 7 adjacent to the sealing surface 6. For example, the protection means 5 is in the form of a disc whose first face is in contact with the support surface 4 of the device, a second face is sealed and has an unsealed edge. According to a variant of this example of the subject of the invention, the protection means has a planar shape whose smallest dimension is greater than 1 cm. The volume of this disc makes it possible to distribute the static pressure. In another example, the protection means 5 is of form pyramid. The base of this pyramid is in contact with the support surface 4 of the device, one of the surfaces is sealed and the edge corresponds to one or more surfaces adjacent to the sealed surface 6. In this way, if a device is positioned in the direction of a flow of air such as wind, normally the pressure increases, but thanks to the sealed surface 6, the problem related to the increase in pressure is avoided.

In another example, the protection means 5 is a disc whose diameter is greater than 1 cm.

In another example, the sealing surface 6 is of smaller dimension than the contact surface of the protection means. In this way, if the sealed surface is of dimension of the section of the measuring pipe 3, the influence of the relative wind is reduced while ensuring the good passage of the static pressure in the protection means.

According to any example comprising the protection element 6, if the device is subjected to a flow of air such as wind, the error of the calculation of the altitude is reduced. For example, for a wind of 20 m / s, the error of calculating the altitude from the pressure measurement is reduced to 16 m.

According to another example, the device comprises at least one differential measuring pipe positioned on a surface other than the bearing surface 4. The differential measuring pipe is another measuring pipe 3, which allows the pressure sensor to have a better measurement accuracy since the value of the pressure comes from at least two measuring ducts. In this way, the adverse effects related to external conditions are avoided. Indeed, if a measurement duct 3 undergoes a flow of air or liquid, as in the direction of the axis of the measuring duct 3, the differential measuring duct will not undergo the same constraints in the same direction, which will reduce the effects of external conditions.

According to one variant, a plurality of differential measurement conduits is connected to the pressure sensor, which makes it possible to refine the measurement. For example, for a device with six faces, each face has a measuring duct 3 or a differential measuring duct.

The differential measurement duct extends from a first end to a second end, the first end is adjacent to the measuring duct 3 of the pressure sensor and the second end is adjacent to the outer surface of the device.

In another example, the measurement of the pressure is transmitted to a tracking system so that it directs a tracking means (camera) according to the altitude of the device. The altitude is calculated from the pressure. The effect of having a better accuracy of pressure measurement will reduce the error of the calculation of the altitude and make it possible to optimize the operation of the tracking system. In this example, the static pressure measuring device also comprises means for calculating the relative position of the device and means for transmitting the relative position.

The tracking system includes tracking means such as a camera, data receiving means, and processing means adapted to orient said tracking means in accordance with the relative position and the static pressure of the device. The data receiving means makes it possible to receive the data of the device such as the measurement of static pressure or directly that of altitude calculated from the device, as well as the relative position of the static pressure measuring device.

The operation is as follows: the device is placed on an object according to the bearing surface 4 of the device, the data is then transmitted to the tracking system, such as the data relating to the position of the device and the measurement of static pressure, then the tracking system directs the tracking means to the static pressure measuring device according to the relative position and measurement of static pressure.

In another variant, it may be envisaged, without departing from the scope of the invention, to adapt the proportions, the shapes of the static pressure measuring device such as those described above by simple constructive arrangements which will appear directly and effortlessly. excessive to the skilled person, so that it can be used in areas such as aeronautics, mobile device tracking, freefall, indoor or outdoor positioning devices, watchmaking ...

Figure 4, according to an exemplary embodiment, said protection means 5 is a flexible membrane. Said flexible membrane is sealed with respect to the outside and the inside of the measuring duct 3. It is the pressure inside the measurement duct 3 which is measured by the pressure sensor. Advantageously, the measuring pipe 3 is sealed with respect to the inside of the device and the outside of the device. Under the effect of the external pressure the flexible membrane expands and the pressure inside the measuring duct 3 increases. Conversely, if the external pressure decreases, the flexible membrane expands and the pressure inside the measurement pipe 3 decreases. In this example of measurement, having a flexible and waterproof membrane avoids the formation of meniscus. Conventionally, because of moisture, a meniscus of convex or concave shape appears at the edge of the pressure sensor 1. This is why this solution is advantageous since there is no meniscus formation as the membrane is waterproof. .

In another embodiment, the membrane is flexible only at the measurement pipe 3, and rigid on the support surface of the device.

Figure 5, according to another embodiment, said protection means 5 also comprises a protective cap which covers the measuring pipe 3. The protective cap is perforated so as to let the pressure of the air on the flexible membrane .

The mechanical protection cap is larger than the flexible membrane. This mechanical protection is pierced on both sides to let the air. All are on the top or on the sides (not shown).

Advantageously, the protective cap avoids the formation of meniscus at the level of the flexible membrane and if something bears near the measuring conduit, the protective cap prevents pressing on the flexible membrane and avoids distorting the pressure measurements.

Advantageously, the thickness of the protective cap is greater than one mm so as to allow the water contained in the protective cap to flow.

Claims

claims

1. Device for measuring a static pressure on an object or a person, said device characterized in that it comprises

a support surface (4),

a pressure sensor (1),

a power supply (2) adapted to supply the pressure sensor (1),

a measurement duct (3) whose first end is provided to contain the pressure sensor (1) on the walls of said measurement duct (3) and a second end opening on the bearing surface (4),

- a protection means (5) disposed in front of the measurement duct (3) and wider than said measuring duct (3).

2. Device according to claim 1, comprising a fixing element, such as a cuff, adapted to orient the bearing surface (4) of the device on the object or the person.

3. Device according to one of claims 1 to 2, wherein the length of the measuring duct (3) is 0.5 to 10 mm, preferably between 1 to 5 mm.

4. Device according to one of claims 1 to 3, wherein the protective means (5) is a porous material.

5. Device according to one of claims 1 to 4, wherein the protection means (5) is a pierced protection cap comprising a space without material completely covering the measurement conduit

(3), said space without material includes a disk with a diameter greater than or equal to 1 cm and a thickness greater than or equal to 1 mm.

6. Device according to claim 5, wherein the protective cap comprises two bores, one of which has a surface area greater than 10 mm ² .

7. Device according to one of claims 1 to 6, wherein a flexible membrane plugs the measuring duct (3), the flexible membrane being fixed to the bearing surface and sealed, said measuring duct (3) contains a volume of a gaseous fluid.

8. Device according to claim 7, wherein the volume of the gaseous fluid contained in the measuring pipe (3) is less than S * 10-3M, where S is the surface of the flexible membrane.

9. Device according to one of claims 1 to 9, wherein said device comprises a differential measuring conduit positioned on a surface other than the bearing surface (4), the differential measuring conduit opening on a wall of the duct. measure (3).

10. tracking system comprising a static pressure measuring device according to one of claims 1 to 9, said tracking system comprising a tracking means and n means for transmitting the relative or absolute position, characterized in that said system comprises means for calculating the relative position of the device disposed on the device or on the tracking means, means for receiving the static pressure measurement and the relative or absolute position of said static pressure device, adapted processing means for orienting said tracking means according to the relative position and the static pressure of the device.

11. The method of tracking a system according to claim 10, said method comprising the following steps:

setting up the pressure measuring device on an object or a person, transmitting position-related data of the device and measuring the static pressure,