Angular sector detection system, in particular for a gyro-stabilized platform on an aircraft-type vehicle

Abstract

The invention relates, according to a first aspect, to a system (1) for detecting angular sectors, comprising a non-magnetic disc or portion of disc (5), the disc (5) comprising at least one main track (2) arranged on a part of a circumference of the disc (5), the detection system (1) comprising a first Hall effect sensor (6) arranged opposite the main track (2) in a direction orthogonal to a plane in which the disc (5) is included, each main track (2) consisting of several permanent magnets (4) of North or South polarity, each main track (2) comprising at least one magnet of North polarity and at least one magnet of South polarity, so as to define angular sectors (7) along the circumference part of the disc (5) as a function of the polarity of the permanent magnets (4). Figure for abstract: Fig. 2

Description

Title of the invention: Angular sector detection system, in particular for a gyro-stabilized platform on an aircraft-type vehicle FIELD OF THE INVENTION

[0001] The invention relates generally to the field of magnetic encoder type angular sector detection systems, and more particularly to magnetic encoders for defining no-fire zones, for example no-fire zones of a laser. It advantageously finds application for detecting the position of a gyro-stabilized platform (optronic platform for example) placed on a vehicle, in particular of the aircraft type. STATE OF THE ART

[0002] Gyro-stabilized platforms are devices used in particular on vehicles and in particular aircraft (helicopters, airplanes, drones), which allow optronic equipment (camera, laser sight, etc.) to be stabilized, so that they maintain a specific orientation relative to the earth, despite the movements or vibrations of the vehicle. These platforms operate using gyroscope-type systems, in particular mechanical ones, which allow decoupling of the orientation of the equipment from the movements of the vehicle.

[0003] When such a gyro-stabilized platform carries a laser transmitter on board an aircraft, it is desirable to define so-called "no-fire" zones, corresponding to angular sectors of the field that can be scanned by the platform in which the laser transmitter is not authorized to fire. For example, it is appropriate to prevent the laser from being directed towards the pilot of the vehicle, in order to avoid any risk of blinding.

[0004] To define such no-fire zones, it is necessary to be able to know the angular positions of the equipment around their axes of rotation relative to the fixed platform. Several technologies of encoders or angular sector sensors are known from the state of the art in order to carry out this monitoring of the angular position of the equipment of the gyrostabilized platform.

[0005] Firstly, we can cite differential angular detectors, which are encoders exploiting a variation in electromagnetic coupling between, on the one hand, a ferromagnetic stator provided with three windings or coils, and on the other hand, a ferromagnetic rotor which does not have any windings. The shape of the rotor makes it possible to vary the air gap between it and the stator according to the angular position of the rotor, thus modifying the electromagnetic coupling. We can thus deduce from the variations in this coupling the angles traveled by the rotor on its rotational trajectory.

[0006] Resolvers can also be mentioned. These encoders also comprise a rotor and a stator, both made up of a stack of ferromagnetic sheets. The rotor comprises a single winding, called the reference winding, while the stator comprises two windings placed at 90° intervals along the circumference of the stator. In operation, the reference winding is excited and the rotor begins to rotate, inducing a voltage across each of the two stator windings. The ratio between these two voltages makes it possible to deduce an absolute position of the rotor - that is, even if the angular position of the rotor is changed when the device is stopped, the exact position of the rotor remains known thanks to this voltage ratio.

[0007] These two types of encoders unfortunately have certain drawbacks. First of all, they have a non-negligible bulk in the gyro-stabilized platform, of the order of a few centimeters, which is unacceptable for certain platforms in which the maximum space available for the position detector device is restricted to a few millimeters. When the gyro-stabilized platform is on board an aircraft, although it may include encoders making it possible to know precisely the direction of the line of sight, safety requirements do not allow the information obtained by these encoders to be used to define no-fire zones. These encoders are in fact not designed for this nor are they compatible with the requirements of reliability of the components, use of software / digital processing, and redundancy of the information. It is therefore necessary to add additional devices to the existing equipment.Another disadvantage of these encoders is that they do not allow redundant position information to be obtained, which may be desirable for the purpose of reliability of the position detection carried out. When such redundancy of information is desired, it is necessary to provide two separate devices. Alternatively, for the purpose of increasing measurement reliability, a two-speed resolver can be used, comprising a first resolver indicating the angular position within a revolution, and a second, slower resolver, which makes it possible to indicate which revolution one is in among a plurality of revolutions. However, the use of a double detector further increases the space requirement in the gyro-stabilized platform. Two-speed resolvers also have the disadvantage of being particularly expensive.

[0008] The aforementioned encoders have a geometry which must be adapted to the no-firing zones which one wishes to define, the shape of the rotor and the stator as well as the winding of the coils defining the variation of electromagnetic coupling between the stator and the rotor and therefore the defined zones. Such encoders are therefore not modular: if one wishes to modify the angular no-firing zones, it is necessary to use a different encoder geometry.

[0009] Finally, most angular position encoders require digital post-processing of the electromagnetic coupling variation between the rotor and the stator, in order to deduce the angular position information that is desired. The complexity of such a digital post-processing process can compromise the reliability of the encoder. Statement of the invention

[0010] An aim of the invention is to provide an angular sector detection system for a gyro-stabilized platform, in particular intended to be mounted on a vehicle, particularly on an aircraft, which has a small footprint in the platform while allowing reliable and precise detection of an angular position of the platform relative to the aircraft.

[0011] Another aim of the invention is to avoid any digital processing for obtaining the position data of the gyro-stabilized platform.

[0012] Another aim of the invention is to provide a modular detection sensor, which can be adapted both to the geometry of the platform and to the angular sectors that one wishes to define.

[0013] To this end, according to a first aspect of the invention, there is proposed a system for detecting angular sectors, comprising a non-magnetic disk or portion of disk, the disk comprising at least one main track arranged on a part of a circumference of the disk, the detection system comprising a first Hall effect sensor arranged opposite the main track in a direction orthogonal to a plane in which the disk is included, each main track consisting of several permanent magnets of North or South polarity, each main track comprising at least one magnet of North polarity and at least one magnet of South polarity, so as to define angular sectors along the circumference part of the disk as a function of the polarity of the permanent magnets.

[0014] According to one embodiment, the permanent magnets are circular in shape.

[0015] According to one embodiment, the disk comprises a redundancy track for at least at least one of the main tracks, preferably for each main track, the redundancy track consisting of permanent magnets located on the same circumferential position of the disk as the magnets of the corresponding main track, the detection system comprising a second Hall effect sensor arranged opposite the redundancy track.

[0016] According to one embodiment, each permanent magnet of the redundancy track is of opposite polarity to that of the permanent magnet of the main track located on the same circumferential position of the non-magnetic disk.

[0017] According to one embodiment, the detection system comprises the same number of permanent magnets of North polarity as permanent magnets of South polarity.

[0018] According to one embodiment, the detection system further comprises a support sheet comprising a ferromagnetic material, the support sheet being interposed between the non-magnetic disk and the permanent magnets.

[0019] According to one embodiment, the detection system comprises at least two main tracks, the magnets of the two main tracks not being arranged on the same circumferential position of the disk, so as to define an angular sector of circumferential dimension less than that of a permanent magnet, or of circumferential dimension which is not a multiple of the dimension of a permanent magnet.

[0020] Another aspect of the invention relates to a gyrostabilized platform comprising an angular sector detection system as defined previously.

[0021] According to one embodiment, the gyro-stabilized platform comprises two separate detection systems, the detection systems being respectively arranged around a site axis and a bearing axis of the platform.

[0022] Another aspect of the invention relates to an aircraft comprising a gyrostabilized platform as defined previously. DESCRIPTION OF FIGURES

[0023] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0024] [Fig.l] schematically illustrates an angular sector detection system for a gyrostabilized platform comprising a single main track, according to a first aspect of the invention;

[0025] [Fig.2] schematically illustrates a detection system for a gyro-stabilized platform comprising two redundant main tracks;

[0026] [Fig.3a] schematically illustrates an arrangement of magnets on tracks of a detection system according to a first embodiment.

[0027] [Fig.3b] schematically illustrates an arrangement of magnets on tracks of a detection system according to a second embodiment.

[0028] [Fig.4] schematically illustrates a gyrostabilized platform comprising a detection system, according to a second aspect of the invention.

[0029] [Fig.5] schematically illustrates a vehicle, and more specifically an aircraft, equipped with a gyro-stabilized platform, according to a third aspect of the invention.

[0030] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0031] [Fig.l] represents a detection system 1 of angular sectors defining a plurality of angular sectors 7, the detection system of the figure specifically representing two sectors 7. It comprises a non-magnetic disk 5 arranged opposite a first Hall effect sensor 6. According to one embodiment, a support sheet 8 comprising a ferromagnetic material is interposed between the disk 5 and the permanent magnets 4.

[0032] The disc has a central recess 14 allowing in particular to receive its axis of rotation. The disc 5 can in a non-limiting manner be made of aluminum. It can also be a portion of disc, not covering 360° but only part of a circle. Arranged on the disc 5 is a main track 2 in an arc of a circle concentric with the disc 5, which comprises a plurality of permanent magnets 4. This main track 2 comprises at least two permanent magnets 4, as shown in [Fig.l], of respective North and South polarity, so as to define two distinct angular sectors 7. The main track 2 generates, due to the presence of the magnets 4, a positive or negative induction a few centimeters above it which can be detected by the Hall effect sensor 6. In other words, the Hall effect sensor 6 makes it possible to know the polarity of the magnet which is in front of it, depending on the angular position of the disc.Thus, one of these two sectors 7 can define a firing authorization zone, the other of the two sectors 7 defining a firing prohibition zone, for example of a laser generated by a gyrostabilized platform 10 in which the detection system 1 is located.

[0033] The main track 2 may comprise more than two permanent magnets 4, so as to define a given number of angular sectors 7 each comprising one or more permanent magnets 4 of identical polarity. In other words, for any angular position in which the disk 5 is located, the main track 2 indicates to the Hall effect sensor 6 a binary value corresponding to a North or South polarity, and the detection system 1 changes angular sector 7 each time the disk passes from a magnet 4 of one polarity to an adjacent magnet 4 of the opposite polarity. The use of several magnets 4 for each main track 2 allows a great modularity of the detection system 1, since it is possible to define, by simply choosing the positioning of the North or South magnets on the main track 2, a desired number of angular sectors 7.The size of each angular sector simply results from the number and size of the magnets 4 of the same polarity used in this angular sector 7. For a gyro-stabilized platform located on a vehicle such as an aircraft, it is therefore easy to adapt the angular sectors 7 defined to the specific needs of said vehicle, or possibly to the position of the platform on the vehicle.

[0034] The choice of the size of the magnets 4 is a compromise between, on the one hand, the size of the defined angular sectors 7, and on the other hand the ease of placement of the magnets 4 on the disc 5. Indeed, a reduction in the size of the magnets makes it possible to increase their number on the main track 2 and therefore to define smaller angular sectors 7, thus increasing the precision of the detection system 1 beyond what is possible with the encoders of the state of the art, but also contributes to lengthening the installation of the magnets 4 on the disc 5.

[0035] The proposed detection system has a reduced footprint compared to the systems of the state of the art, in a radial direction of the disk 5 as in a direction orthogonal to the plane in which the latter is inscribed.

[0036] According to one embodiment, shown in [Fig.2], the detection system 1 comprises a plurality of main tracks 2 arranged on the disk. The figure represents the case where the detection system 1 comprises two separate main tracks 2. The detection system 1 then comprises a first separate Hall effect sensor 6 for each main track 2, capable of detecting the North or South polarity of the permanent magnet 4 opposite which it is positioned. If the detection system 1 comprises a number N of main tracks 2, the first Hall effect sensors 6 taken as a whole detect, for a given circumferential position of the detection system 1, N binary values, each corresponding to a North or South polarity. It is thus possible to increase the number of angular sectors 7 defined on the detection system 1, without having to increase the number of permanent magnets 4 included in a given main track 2. Indeed, such an increase necessarily implies a reduction in the size of the magnets 4 used.However, there is a critical size of magnets 4 below which it becomes difficult to position magnet 4 on disc 5, and which it is therefore advantageous not to exceed.

[0037] For a disk comprising N main tracks 2, each defining two distinct zones - one polarized North and one polarized South - we define 2 x N distinct angular sectors.

[0038] Another advantage of providing several main tracks 2 is to allow the definition of angular sectors 7 of circumferential size less than the thickness of a magnet 4, or of circumferential size which is not a multiple of the size of the magnets 4. For the case of a detection system with two main tracks 2, when it is desired to define an angular sector 7 of size less than the thickness of a magnet, it is sufficient to provide an offset distance 9 in the circumferential direction between the magnets 4 which is less than the size of a magnet. Thus, according to an embodiment shown in [Fig. 3a], the angular sector 7 located in the center defines a South polarity for each of the two main tracks 2, while the other two sectors 2 are characterized by a North-South and South-North polarity, starting with the track arranged in the upper position in the figure. On the contrary, according to the embodiment shown in [Fig.3b], no offset exists between the magnets of the . two tracks, so that the central angular sector 7 does not exist, and the two tracks only define two angular sectors 7. It is naturally possible to thus define angular sectors 7 whose circumferential size is between that of one and two magnets, between that of two and three magnets, etc.

[0039] The detection system 1 is of the analog type, each magnet 4 of the main track being able to indicate only two pieces of information (North or South). When the detection system comprises several main tracks 2, it is therefore possible to use simple logic gates to reconstruct the information relating to the angular sector 7 in which one is located on the basis of the binary value detected by the Hall effect sensor 6 of each main track 2. In comparison with the detection systems of the state of the art, one is therefore freed from the need for digital components to reconstruct the information, thus simplifying the electronic components necessary for processing the signal provided by the detection system 1, increasing the reliability of the detection system and reducing its bulk in the gyrostabilized platform in which it is located.

[0040] An example of logic gates that can be used to process information from two main tracks covering the same area, as shown in Figure 3A, is detailed in Table 1 below. Using these logic gates, output information 1 is returned here when the two tracks indicate the same binary value, and output information 0 when this is not the case.

[0041] [Tables 1] Area Main Track 1 Main Track 2 Logic Gate Output Binary Value 1 0 0 and + no 1 2 1 1 and 1 3 1 0 no(Main Track 1) + and 0 4 0 1 no(Main Track 2) + and 0

[0042] According to one embodiment, the permanent magnets 4 are circular, which has the advantage of allowing their positioning in any orientation on the disk 5 without affecting the polarization thereof. The fact of using circular magnets of the same dimension for the different magnets 4 of a given track 2, 3 also makes it possible to precisely control the place of passage from one zone of the track to an adjacent zone, this passage then being carried out at an equal distance from the two adjacent magnets 4 of different polarity.

[0043] According to one embodiment, a redundancy track 3 can be associated with the or each main track 2, each redundancy track 3 being opposite a second Hall effect sensor 11 in the direction orthogonal to the plane of the disk 5. This second Hall effect sensor 11 makes it possible to detect the polarity of the magnet 4 of the redundancy track 3 opposite which it is located. The redundancy track indicates the same information as the corresponding main track 2, either by polarity identity (each magnet 4 of the redundancy track 3 has the same polarity as the magnet 4 of the main track 2 arranged on the same circumferential position of the disk 5), or by polarity inversion (each magnet 4 of the redundancy track 3 has the opposite polarity to the magnet 4 of the main track 2 arranged on the same circumferential position of the disk 5). This second option has several distinct advantages.

[0044] First of all, for a main track 2 and a redundancy track 3 comprising the same number of magnets, an inverted polarity allows the assembly constituted by the main track 2 and the redundancy track 3 to present a neutral overall polarity from an observation point located at a distance from the tracks 2, 3.

[0045] The polarity inversion also makes it possible to desensitize the detection system 1 to an external magnetic disturbance. Let us take for example a magnetic disturbance going in the direction of a firing authorization, and affecting a firing prohibition zone. For a zone in which the main track 2 and the redundancy track 3 both have the same firing prohibition polarity, the prohibition signal of each track 2, 3 is weakened by the disturbance. On the other hand, for a zone in which the main track 2 has a prohibition polarity and the redundancy track 3 has an inverse polarity, the signal of the main track 2 is weakened by the disturbance, while the inverse signal of the redundancy track 3 is reinforced - the overall polarity modification of the two tracks 2, 3 for the zone concerned is therefore zero.

[0046] It can be provided that the detection system 1 comprises the same number of permanent magnets 4 of North polarity as of South polarity. Thus, the detection system has a neutral overall polarity, and does not risk destabilizing equipment located nearby which could be sensitive to a magnetic field. For example, when the detection system is included in a gyro-stabilized platform located on an aircraft, a compass placed on board the aircraft can be affected by the magnetic field of the detection system 1. For a stealth aircraft, it is also avoided to make the gyro-stabilized platform detectable due to a non-neutral magnetic field.

[0047] According to one embodiment, a support sheet 8 comprising a ferromagnetic material is interposed between the disc 5 and the permanent magnets 4. The The presence of such a sheet strengthens the magnetic field detected by the Hall effect sensors 6, 11 and consequently increases the accuracy of detecting the passage from one area of a given track to an adjacent area.

[0048] Another aspect of the invention, illustrated in [Fig.4], relates to a gyro-stabilized platform 10, comprising at least one detection system 1 as defined previously. The detection system 1 makes it possible in particular to define angular sectors 7 in which a firing authorization is or is not given, called respectively firing zones and no-firing zones. For example, the gyro-stabilized platform 10 can emit a laser and the no-fire zones can correspond to zones in which the laser risks blinding the pilot of a vehicle on which the gyro-stabilized platform 10 is positioned. The equipment included in the gyro-stabilized platform 10 is movable along two axes, called bearing axis 12 and elevation axis 13. The bearing axis 12 corresponds to an axis orthogonal to a horizontal plane of the vehicle, while the elevation axis 13 corresponds to an axis included in this plane and orthogonal to a longitudinal direction of the vehicle.

[0049] According to one embodiment, the gyro-stabilized platform 10 comprises two detection systems 1, respectively recording the rotation angle along the bearing axis 12 and along the elevation axis 13 relative to a reference position of the equipment in the gyro-stabilized platform 10.

[0050] Another aspect of the invention, illustrated in [Fig.5], relates to an aircraft 100 comprising a gyrostabilized platform 10 as defined in the preceding paragraph.

Claims

Claims

1. Detection system (1) of angular sectors, comprising a non-magnetic disc or portion of disc (5), the disc (5) comprising at least one main track (2) arranged on a part of a circumference of the disc (5), the detection system (1) comprising a first Hall effect sensor (6) arranged opposite the main track (2) in a direction orthogonal to a plane in which the disc (5) is included, each main track (2) consisting of several permanent magnets (4) of North or South polarity, each main track (2) comprising at least one magnet of North polarity and at least one magnet of South polarity, so as to define angular sectors (7) along the circumference part of the disc (5) according to the polarity of the permanent magnets (4), characterized in that the disc (5) comprises a redundancy track (3) for at least one of the main tracks (2), preferably for each main track (2),the redundancy track (3) being made up of permanent magnets located on the same circumferential position of the disc (5) as the magnets (4) of the corresponding main track (2) so that the redundancy track (3) indicates the same information as the main track (2), the detection system (1) comprising a second Hall effect sensor (11) arranged opposite the redundancy track (3).,

2. Detection system (1) according to the preceding claim, the permanent magnets (4) being circular in shape.

3. Detection system (1) according to any one of claims 1 and 2, each permanent magnet of the redundancy track (3) being of opposite polarity to that of the permanent magnet (4) of the main track (2) located on the same circumferential position of the non-magnetic disc (5).

4. Detection system (1) according to any one of claims 1 and 2, each permanent magnet of the redundancy track (3) being of the same polarity as that of the permanent magnet (4) of the main track (2) located on the same circumferential position of the non-magnetic disc (5).

5. Detection system (1) according to any one of claims 1 to 4, the detection system (1) comprising the same number of permanent magnets (4) of North polarity than of permanent magnets (4) of South polarity.

6. A detection system (1) according to any one of claims 1 to 5, further comprising a support sheet (8) comprising a ferromagnetic material, the support sheet (8) being interposed between the non-magnetic disc (5) and the permanent magnets (4).

7. Detection system (1) according to any one of claims 1 to 6, comprising at least two main tracks (2), the magnets (4) of the two main tracks (2) not being arranged on the same circumferential position of the disc (5), so as to define an angular sector (7) of circumferential dimension less than that of a permanent magnet (4), or of circumferential dimension which is not a multiple of the dimension of a permanent magnet (4).

8. Gyro-stabilized platform (10) comprising a detection system (1) of angular sectors according to any one of claims 1 to 7

9. 1 d. / . Gyrostabilized platform (10) according to the preceding claim, comprising two separate detection systems (1), the detection systems (1) being respectively arranged around a site axis (12) and a bearing axis (13) of the platform (10).

10. Method for controlling a laser, the laser being emitted by a gyro-stabilized platform (10) according to any one of claims 8 and 9, the control method comprising a step of authorizing or prohibiting a firing of the laser as a function of the angular sector (7) detected by the detection system (1).

11. An aircraft (100) comprising a gyrostabilized platform (10) according to any one of claims 8 and 9.

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