Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F41—WEAPONS
  • F41J—TARGETS; TARGET RANGES; BULLET CATCHERS
  • F41J5/00—Target indicating systems; Target-hit or score detecting systems
  • F41J5/04—Electric hit-indicating systems; Detecting hits by actuation of electric contacts or switches
  • F41J5/056—Switch actuation by hit-generated mechanical vibration of the target body, e.g. using shock or vibration transducers

Definitions

• the present invention relates to a method for manufacturing an impact location device with at least three transducers fixed against an interactive surface. BACKGROUND OF THE INVENTION It also relates to an impact location device resulting from such a manufacturing method.
• an impact locating device comprising an interactive surface having an impact receiving front face and at least three transducers, to be distributed and fixed against the front face or a rear face of the impact surface.
• the interactive surface designed to capture the progressive mechanical waves propagating in the interactive surface from the impact and turn them into electrical signals, the manufacturing process comprising the following steps:
• each transducer fixing each transducer around its central positioning point, each transducer having a lower conductive layer forming a first electrode by which it is fixed against the front or rear face of the interactive surface, a piezoelectric intermediate layer and a free upper conductive layer; intended to form a second electrode.
• Many interactive surface devices are known, such as display devices, mobile phones or other portable digital personal assistance devices. Their interface is usually a flat and rectangular screen with which a user can interact with a projectile, a stylus or even a finger.
• an amusement or sports shooting facility with automatic location of impacts may include such a device, with a target representation displayed on an interactive surface or plate, in particular on its front or rear face.
• the invention applies more generally to any type of object having an interactive surface capable of propagating progressive mechanical waves from an impact, this surface not necessarily being flat, nor of rectangular contour. .
• Interactive surface means a three-dimensional or three-dimensional surface, having a certain thickness, capable of changing its shape in the sense of the static and dynamic elasticity of the materials when it is subjected to an impact such as a touch, a force of contact, a mechanical pulse or a shock, thus allowing the propagation of progressive mechanical waves detectable using transducers, including surface acoustic waves such as Lamb waves, from the place of impact.
• the surface deformation can be submillimetric not visible to the naked eye. Plastic, glass or metal surfaces are suitable.
• Each of the known interactive surface devices comprises means for locating impacts using one or more detection techniques.
• a strong trend toward reducing manufacturing cost and reducing clutter is to retain only the simplest technologies using a limited number of piezoelectric transducers.
• a first solution is disclosed in US Pat. No. 7,345,677 B2. It is based on a recognition of the position of an impact by learning.
• the method implemented cross-correlates at least one measured acoustic signal resulting from the detection of an acoustic wave generated by an impact on the interactive surface of the object and a reference set called "set of signatures" consisting of prerecorded impulse acoustic responses, each relating to a predefined position that one wishes to associate with a function and recognize when an impact is carried on this position.
• a second solution for example disclosed in US Pat. No. 8,330,744 B2, consists in measuring the perturbation of an impact on the propagation of progressive mechanical waves emitted regularly in the interactive surface independently of this impact.
• This solution is known to be more precise and reliable than the previous one, especially for qualifying or monitoring the impact, but it is also based on recognition of the position of an impact by learning.
• a third, older solution is based on the measurement of a transit time difference of a wave packet generated by an impact to a plurality of piezoelectric detectors and on the analytical calculation by triangulation, to using a mathematical formula pre-established according to the assumed position of the detectors, the position of a source emitting the wave packet.
• An example of an analytical calculation is for example detailed in US Pat. No. 6,933,930 B2.
• this solution requires an impact location device comprising:
• an electronic central unit connected to the transducers for receiving their electrical signals, programmed to locate the impact in the interactive surface by analyzing the propagation time differences of the progressive mechanical waves resulting from the impact towards the transducers on the basis of the impact detection instants identified in the received electrical signals.
• any mispositioning of at least one of the transducers generates location errors due to the difference between the actual position of the transducers and the theoretical one which served as a basis for calculating the preset mathematical formula. It is thus shown, for example, that for an impact surface of 200 mm ⁇ 200 mm with four transducers arranged in a square, a bad positioning of 100 ⁇ of each leads to errors of offset and linearity. In terms of offset, that of the center of view can reach under these conditions up to 100 ⁇ in abscissa and ordinate.
• the error is a function of the position of the impact, increasing from the center of measurement to the periphery of the impact surface, and can thus reach up to 340 ⁇ at the periphery under the aforementioned conditions.
• these errors are added resolution errors due to the quantification of the measurements returned by the transducers at a given clock rate. With a clock of 80 Mhz, an interactive plate made of sheet steel involving a propagation speed of Lamb waves close to 0.53 mm ⁇ s, the resolution errors can reach +/- 50 ⁇ .
• the four transducers must be fixed with an uncertainty of less than 100 ⁇ , which is very difficult to obtain with the processes known manufacture.
• a numerical method could be considered to determine the actual positioning of the transducers after fixation and to deduce the mathematical formula of triangulation or its numerical approximation. But such a calibration method after fixing is complex and expensive.
• transducers to be distributed and fixed against the front face or a rear face of the interactive surface, designed to capture progressive mechanical waves propagating in the interactive surface from the impact and transforming them into electrical signals
• the manufacturing process comprising the following steps: determining a central positioning point for each transducer on the front or rear face of the interactive surface,
• each transducer having a lower conductive layer forming a first electrode by which it is fixed against the front or rear face of the interactive surface, a piezoelectric intermediate layer and a free upper conductive layer; intended to form a second electrode,
• the method further comprising, following the attachment of each transducer, a step of machining the upper conductive layer free of at least one of the transducers using a machine tool at least until the piezoelectric intermediate layer of this transducer to form the second electrode of this transducer by centering it around its central positioning point as an upper conductive layer portion formed in the free upper conductive layer.
• the machining of the upper free conductive layer of said at least one of the transducers is made circularly to form the second electrode in the form of a disk centered on the central positioning point of this transducer.
• the machining step is performed on all the transducers fixed against the front or rear face of the interactive surface.
• the machine tool performing the machining is a laser machining device.
• the machining step includes drilling holes in the interactive surface for receiving reference pins in positioning a target carrier.
• the machining step includes a marking of a measuring center in the interactive surface.
• a method of manufacturing an impact locating device may include, following the machining step, a step of connecting by welding of two conducting wires to each transducer, the one to the first electrode formed in the lower conductive layer of this transducer and the other to the second electrode formed in the upper conductive layer portion of this transducer, for processing the signals provided by this transducer.
• an impact location device comprising:
• each transducer having a lower conductive layer forming a first electrode by which it is fixed against the front or rear face of the interactive surface, a piezoelectric intermediate layer and a free upper conductive layer for forming a second electrode,
• the upper free conductive layer of at least one of the transducers comprising a layer portion forming the second electrode centered on the central positioning point of this transducer and electrically isolated from another peripheral portion of the free upper conductive layer by a machining performed at least up to the piezoelectric intermediate layer of this transducer.
• an impact locating device furthermore comprising a central electronic processing unit for the electrical signals supplied by said at least three transducers, designed for an impact localization by a time difference analysis; propagation of the progressive mechanical waves resulting from the impact towards the transducers, and
• FIG. 1 is a diagrammatic front view of the general structure of a four transducer impact location device fixed against an interactive surface, according to one embodiment of the invention
• FIG. 2 illustrates the successive steps of a method of manufacturing the device of FIG. 1, according to one embodiment of the invention
• Figure 3 shows the device of Figure 1 in rear view.
• the impact locating device 10 shown in front view in FIG. 1 comprises an interactive surface in the form of a plate 12 having a front face A for receiving an impact P and a rear face B (illustrated on FIG. FIG. 3) against which four PT A , PT B , PT C and PT D piezoelectric transducers are distributed and fixed. These four transducers, of which only the functional part is delimited in short broken lines in FIG. 1, are centered on four respective central positioning points C A , C B , C c and C D. They are designed to capture the progressive mechanical waves propagating in the interactive plate 12 from the impact P and turn them into electrical signals.
• the device 10 further comprises a central processing unit 14 for the electronic processing of the electrical signals provided by the four piezoelectric transducers PT A , PT B , PT C and PT D , designed for impact localization by analysis of propagation time differences. progressive mechanical waves from the impact P to the piezoelectric transducers PT A , PT B , PT C and PT D.
• This central unit 14 is for example arranged against the rear face B of the interactive plate 12. Optionally, it can also provide an estimate of a power of each localized impact. Each detected impact can then be kept in memory with its location and power to form a history of impacts.
• the device 10 is, in the example of FIG. 1, used in a recreational or sports shooting facility that concerns both a sporting or recreational shooting activity with a weapon, rifle or pistol, with compressed air or with powder, that an activity of archery, crossbow, blowgun, dart or other.
• a target representation 16 is displayed in a plane of the interactive plate 12.
• this target representation 16 is reproduced on a cardboard 18 fixed against the front face A of the interactive plate 12 and correctly centered with respect to the PT A , PT B , PT C and PT D piezoelectric transducers with reference pins in position.
• the four piezoelectric transducers PT A , PT B , PT C and PT D are arranged at the four corners of a square and the reference pins 20 are arranged by manufacturing so as to place the aiming center of the target representation. 16 precisely on the center of measurement coinciding with the center of the square.
• each piezoelectric transducer identified by the general reference PT in FIG. 2, has a lower conductive layer 22 forming a first electrode by which it is fixed against the rear face B of the interactive plate 12, a piezoelectric intermediate layer 24 and a conductive layer. free upper 26 for forming a second electrode.
• each of the four piezoelectric transducers PT A , PT B , PT C and PT D is fixed, by its lower conductive layer 22, to the rear face B of the interactive plate 12.
• a central positioning point identified by the general reference C in FIG. 2 is precisely and previously determined for each transducer PT on the rear face B of the interactive plate 12.
• the currently known marking techniques make it possible to position such a central point C with micrometer scale accuracy.
• each piezoelectric transducer PT is fixed around its positioning center point C, for example by means of a glue layer 28, without particular precise adjustment. Note for example in Figure 2 that the transducer PT is not exactly centered on the central point C after bonding.
• the arrangement of each PT transducer glued can be examined to see if it is correctly centered in view of the accuracy requirements.
• each piezoelectric transducer PT that is not correctly centered, or by default each of the four transducers piezoelectric PT A , PT B , PT C and PT D if this verification was not made at the end of step 102, is placed in front of the machining tip 30 of a machine tool 32.
• Sa Free upper conductive layer 26 is then machined at least up to its piezoelectric intermediate layer 24 to form the second electrode of this piezoelectric transducer PT by centering it around the central point C as a portion 34 of upper conductive layer arranged in the conductive layer 26.
• the machining tip 30 is for example placed at a desired distance R from the axis of the central point C and the machining is carried out circularly around this axis to form the second electrode according to a disk. of radius R precisely centered on C.
• the precise positioning of the machine tool 32 is done for example by geometric reference from two edges at right angles to the interactive plate 12. Thanks to the machining performed, this disc is then electrically isolated from the remainder 36 of the upper free conductive layer 26 forming another portion located at the periphery of the latter.
• the piezoelectric transducer PT thus machined is thus functionally centered on C since it is only its cylindrical useful portion of radius R centered on the normal axis passing through C which fulfills the detection function.
• holes can be drilled by machining to define as precisely as possible the positioning of the reference pins 20 receiving them.
• the center of the square formed by the four piezoelectric transducers PT A , PT B , PT C and PT D , or center of measurement to coincide with the center of view of the target representation 16, can also be marked during this step.
• the first electrode consisting of the lower conductive layer 22 and the second electrode consisting of the upper conductive layer portion 34 are electrically connected, for example by soldering conductor wires, one to ground (or terminal -), the other to the central processing unit 14 (or + terminal) for processing the signals provided by the machined piezoelectric transducer PT.
• each upper free conductive layer 26 visible in FIG. 3 comprises a portion correctly centered (white) and electrically isolated from another inactive (textured) peripheral portion that becomes passive due to its isolation.
• the support could alternatively be a sighting jig made of a hard material to ensure very high positioning accuracy using the reference pins 20
• the target representation 16 may be formed on this support by etching, screen printing, etching or electrochemical by electroplating or electroplating, or color insert in the mass.
• the target representation could be a projected image or video, on screen or by video projector, and the positioning of the center of view on the measurement center could be provided by pixel alignment.
• it could be displayed against the rear face B, so as to protect it against impacts, in which case it is necessary that the interactive plate 12 is transparent.
• the interactive plate 12 may be chosen, depending on the intended applications, polycarbonate, possibly shielded glass, steel alloy, etc. It is advisable to choose one or another material according to its transparency and / or resistance to the projectiles expected.
• An interacted plate 12 has also been described, but any interactive surface, in particular non-planar, could more generally be suitable, such as for example a three-dimensional object shell.
• central processing unit 14 disposed on the rear face B of the interactive plate 12.
• the central processing unit 14 could be at least partially offset, in particular on a computer.
• Many other variants are possible for designing the set consisting of the interactive plate 12, the display support of the target representation 16 and the central processing unit 14.
• transducers It has also been described a set of four transducers, but three transducers may be sufficient to establish a location by analytical calculation of triangulation. More transducers can also be provided to improve the location by analytical calculation.

Landscapes

• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)
• Force Measurement Appropriate To Specific Purposes (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
• Mechanical Engineering (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=61187363

Family Applications (1)

Country Status (5)

Cited By (2)

Families Citing this family (1)

Family Cites Families (13)

• 2017
  • 2017-08-09 FR FR1757599A patent/FR3070080B1/fr not_active Expired - Fee Related
• 2018
  • 2018-07-19 CN CN201880064435.9A patent/CN111164369B/zh active Active
  • 2018-07-19 US US16/637,098 patent/US11231256B2/en active Active
  • 2018-07-19 WO PCT/FR2018/051839 patent/WO2019030438A1/fr unknown
  • 2018-07-19 EP EP18762571.0A patent/EP3665431B1/de active Active

Also Published As

Similar Documents

Legal Events