FR2848700A1 - Acoustic signal transmitter and receiver includes supporting plate carrying set of independent piezoelectric sensors - Google Patents

Abstract

The transmitter-receiver has five piezoelectric sensors (PZT0- PZT4) glued to a plate. These are able to operate independently in audible frequency or ultrasound frequency range, either for transmission or reception. The device is used to provide remote control of an appliance, such as a video camera or projector. The transmitter-receiver for acoustic signals comprises a set of piezoelectric sensors (PZT0- PZT4) glued to a plate. The sensors are able to operate independently as transmitters or receivers for acoustic waves propagated within the plate. The device includes a filter defining at least two separate spectral bands, one in the audible range and one in the ultrasound range. At least three of the piezoelectric sensors within the group (PZT0 - PZT3) operate in reception mode in the audible and ultrasonic bands, providing a microphone facility. At least one of the sensors within this same group (PZT0 - PZT3) operates in transmission or reception mode in the ultrasonic band, whilst one further sensor (PZT4a) operates in simultaneous transmission mode within the audible band.

Description

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The present invention generally relates to interactive communication devices between a user and a machine.

More specifically, the invention relates to a device for collecting, transmitting and processing acoustic waves transmitted by a user or a sensor to a plate serving as an interface with a machine, said device being provided with functionalities enabling it, d on the one hand, to analyze acoustic wave propagation times in the plate, in particular for measuring the xr, yr impact coordinates, on the other hand, to emit or receive an audible sound, in particular the voice, by using the plate as a microphonic membrane or as a speaker. Thus, the fact of being able to locate small impacts made with objects such as fingernail, key, ring or pen makes it possible to transform the plate into a giant impact surface, the term impactile being a neologism created by analogy with the tactile word and whose meaning throughout this description will be that reacts to an impact.

Patent WO 96/11378 discloses a device for acquiring xr, yr coordinates from the point of a rigid plate from which a source occasionally emits wave packets, by analyzing the propagation time of the waves in the plate in two directions. x and y of the plate.

French patent 9816229 of 22 December 1998 also discloses an acquisition device in which two pairs of transducers are respectively associated with each direction x, y, the position of the source in each direction being determined by the measurement of the differential arrival of the wave packets on the two pairs of respective transducers of said direction.

These two acquisition devices are particularly well suited to the selective detection of a Lamb acoustic mode in an isotropic glass plate. In particular, the device of patent FR9816229 proposes a method for collecting the voice of a user who mechanically excites the glass plate. The present invention shows how to further improve this result by transforming the plate into an audio, half duplex and programmable transceiver using one or more sensors stuck on the plate as acoustic wave transmitters in the ambient air which is equivalent to using the plate as a loudspeaker in a frequency band limited to a portion of the audible band while simultaneously using other sensors in receiver mode in a different spectral band, especially in the ultrasound frequency spectrum, in order to simultaneously detect the position of a possible impact on the plate controlling for example the stopping of the current emission in the audible spectrum and the subsequent emission of another sound message.

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 In addition, the devices described in the patents cited above lack flexibility during the transformation of a glazing interactive screen simply by that the gains of the receiver amplifiers must be optimized from one device to another and d. one way to another depending on the type and quality of the bonding of the sensors or the dispersion of the properties of the electronic components used generating a variation of the analog noise on each amplification channel. The present invention therefore proposes the following improvement consisting in introducing a numerically programmable gain range for each of the channels and independently of the other channels, as well as an optimal automatic gain search algorithm for each detection channel.

Furthermore, the plate having a number of sensors that can be damaged during an installation or after several years of use, it may be necessary to be able to check the state of the electrical connections and easily identify the one or more faulty connections. For this, the invention shows a method of checking the state of the electrical connections of the sensors by measuring the equivalent capacitance of the piezoelectric sensors.

Another object of the present invention is to also improve the electroacoustic bandwidth of the glass plate when it is used as a loudspeaker, in particular to correct the bandwidth of the glass plate at low frequencies and to enable it to using a dynamic compression function to emit an acoustic sound of sufficient amplitude and quality to hear correctly, even in urban areas where there is in practice a relatively high ambient acoustic noise.

To achieve these aims, the invention proposes a device for acquiring interaction point coordinates of an acoustic source with the surface of the plate, of finite dimensions, comprising a set of acoustic sensors each formed of two piezoelectric transducers. located opposite one another on the plate, or on a transducer in the form of a piezoelectric wafer with alternating polarization, glued to the edge of the plate, the device comprising processing means for determining the coordinates said interaction point by analyzing the propagation time difference of the acoustic waves emitted by the source to the different sensors, characterized in that the processing means comprise in association with each sensor a respective electronic circuit comprising in cascade means for performing a wideband pre-amplification with four bit digital gain control, ie 16 values of possible gains, means

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 selective amplification centered on a determined first frequency, means for detecting the head of the wave packet and means for switching the sensors into transmitter or receiver so as to automatically determine the distance separating the different sensors, starting from knowledge of the sound velocity of acoustic waves in the plate, and also perform a plate integrity check by regularly making a new measurement of this distance that is compared to the values measured during the first configuration of the plate. plate. The device also comprises at least one piezoelectric transducer intended for producing sound in the ambient air by using the plate as a coupling surface, the said coupling surface acting as a speaker membrane, the interesting feature being that the mechanical excitation of the plate produced by a small piezoelectric transducer propagates in the plate at a speed 10 times greater than the speed of propagation of sound in the air, which makes it possible to distribute the sound to be transmitted on a surface of large transmission, typically of several square meters. The effect produced is then a sensation of uniformity of the sound produced regardless of the position of the user in front of the plate, as well as the absence of decay of the signal when the user moves away from the plate.

Such an interface can thus be installed on store windows, or bus shelters but also on the glazing components partitions, glass doors, flat windows or slightly curved such as those that can be found in the window windows of passengers of motor cars.

Preferred but nonlimiting aspects of the device according to the invention are the following: the sensors are four in number and consist of an assembly of two piezoelectric transducers of square, rectangle, disk, half-disk or quarter disc of piezoelectric ceramics glued on both sides of the plate, so that four sensors form the vertices of a rectangle whose center constitutes the origin of the coordinates. A sensor is formed of two half-disks when it is glued to more than three diameters of the corner of a rectangular plate, the edge of the half-disk being collinear and in line with the edge of the plate, while the connections electrical devices are made of antiparallel. It is formed of two quarters of discs when glued in the corner of a plate, the two perpendicular slices of each quarter disc being aligned with those of the corners of the plate. The shape of the piezoelectric transducer is arbitrary

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 when it is intended to mechanically excite the plate so that it transmits in the ambient air an audible sound.

 The sensors are four in number and are in the form of a rectangular piezoelectric wafer glued to the polished edge of the plate, the width of a wafer being equal to the thickness of the wafer, while the length of a wafer is chosen. so that the fundamental longitudinal resonance of the wafer along this length is close to 100 kHz, which corresponds in practice to a length of the order of 20 mm. In addition, the wafer is alternately polarized, the plane delimiting the polarization inversion being coplanar with the median plane of the plate, so that the wafers will be particularly well suited to the detection of antisymmetric Lamb waves, in particular in the case of double glazed glass plates. In this case, the four sensors are glued to the edges of the plate intended to serve as a user interface, that is to say intended to receive the impacts. These sensors are particularly well suited to glass plates at least 10 mm thick.

The rectangle whose vertices correspond to the location of the four sensors is divided into four quadrants, each quadrant being associated with the triplet of sensors closest to the center of the quadrant responsible for detecting the coordinates of an impact in this quadrant. accuracy of the measurement being theoretically better than that which would be obtained by other triplets, - The piezoelectric ceramic discs have a return of silvering making it possible to make the electrical connections on the same face of the disc, - In the case of sensors stuck on the faces, the electrical connections of the two piezoelectric transducers of each sensor are connected in antiparallel, the polarization vectors being mounted symmetrically with respect to the median plane of the plate so that the symmetrical modes, faster, are discriminated and the antisymmetric modes , slower, privileged, - The location of an impact point on a plate of one of the four quadrants defined by the pair of bits (gy, gx) consists of measuring the difference in flight times between two sensors, taken from a triplet of sensors, defining a first direction and two sensors, taken from the same triplet of sensors, defining a second direction perpendicular to the first, such that the Cartesian coordinates of the point of impact (xr, yr) on the plate are given by the formula:

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Atx q p2v (p-vAtxg) 9P2 aq-aZ atcg-Atyg)2)Atr, q- etY ) p2 At ~ c + atYg(-At. AtYgl ) ( ~ 1)gu 4pAtN(q"Y'Atxg2 +Y (-4q"+Y'At")) !l''' Ataq (-4 p2 +". At:zg (Ab;g- tN" At!9+"'p2 v" (4p2 -Y' At>C!l") (4 p2 +4q" -v" (Atxg-AtN)2) At" (4e - V2 ÀtW) Yr = (-1) 4(q2v2Atxg2 + p2(-4q2 + v2 #tyg2)) - Où, p et q sont des nombres positifs représentant respectivement l'abscisse et l'ordonnée de la position des capteurs par rapport au centre du rectangle défini par les capteurs, v la célérité du mode acoustique de plaque détecté, c'est-à-dire, pour un verre isotrope, celle du mode de Lamb Ao, #txg, (respectivement Atyg) la différence des temps de propagation du paquet d'ondes engendré par l'impact, entre les capteurs de la première paire située dans le demi-rectangle gx (respectivement de la deuxième paire située dans le demi rectangle gy),
La détermination du triplet de capteurs associé à un impact donné s'effectue selon un algorithme recherchant la plus grande différence de temps de vol disponible entre les capteurs dans deux directions perpendiculaires, - Les circuits électroniques associés aux capteurs pour la localisation d'un impact comprennent en cascade un étage préamplificateur large bande, un étage d'amplificateur programmable numériquement sur quatre bit, un étage amplificateur sélectif réglable dans une bande ultrasonore située entre 20 kHz et 150 kHz, un étage élévateur au carré, un étage détecteur de crête avec résistance de décharge, un étage intégrateur à amplificateur opérationnel avec pont résistif à fortes impédances de polarisation d'entrée pour que l'intégrateur soit saturé à un niveau inverse de celui vers lequel il saturerait en présente d'un signal positif, un étage d'adaptation à un niveau logique constituant un signal de synchronisation destiné au calcul de la position d'un impact, - Les circuits électroniques associés aux capteurs pour l'enregistrement du son audio récupéré par la plaque baignant dans l'air ambiant et fonctionnant en mode microphone comprennent une dérivation en sortie des amplificateurs à gains programmables vers un étage suiveur haute impédance d'entrée, un étage amplificateur sommateur des voies sélectionnées, un filtre passe-haut du premier ordre de fréquence de coupure 30 Hz, un filtre passe-bas du 6eme ordre de fréquence de coupure 5000 Hz, un interrupteur analogique vers une sortie audio sur connecteur Jack mono 3,5 mm destinée à être connectée sur l'entrée microphone

Atx q p2v (p-vAtxg) 9P2 aq-aZ atcg-Atyg) 2) Atr, q- and Y) p2 At ~ c + atYg (-At AtYgl) (~ 1) gu 4pAtN (q "Y'Atxg2 + Y (-4q "+ Y'At"))! "Ataq (-4 p2 +". At: zg (Ab; g; tN "At! 9 +"'p2 v "(4p2 -Y'At> C! L ") (4 p2 + 4q" -v "(Atxg-AtN) 2) At" (4th - V2 AttW) Yr = (-1) 4 (q2v2Atxg2 + p2 (-4q2 + v2 # tyg2)) - Where, p and q are positive numbers respectively representing the abscissa and the ordinate of the position of the sensors relative to the center of the rectangle defined by the sensors, v the speed of the sensed plate acoustic mode, that is to say, for isotropic glass, that of the Lamb Ao mode, #txg, (respectively Atyg) the difference in propagation times of the wave packet generated by the impact, between the sensors of the first pair located in the half-wave. rectangle gx (respectively of the second pair located in the half rectangle gy),
The determination of the sensor triplet associated with a given impact is carried out according to an algorithm seeking the greatest difference in available flight time between the sensors in two perpendicular directions. The electronic circuits associated with the sensors for the location of an impact comprise in cascade a broadband preamplifier stage, a digitally programmable four-bit amplifier stage, a tunable selective amplifier stage in an ultrasonic band located between 20 kHz and 150 kHz, a squaring stage, a peak detector stage with resistance of discharge, an integrator stage with an operational amplifier with a resistive bridge with high input bias impedances so that the integrator is saturated at a level opposite to that to which it would saturate in the presence of a positive signal, a stage of adaptation to a logic level constituting a synchronization signal for the calculation of the position of an impact, - The electronic circuits associated with the sensors for the recording of audio sound recovered by the plate bathing in the ambient air and operating in microphone mode include an output bypass of the programmable gain amplifiers to a follower stage high input impedance, one summing amplifier stage of the selected channels, a high-pass filter of the first order of cut-off frequency 30 Hz, a low-pass filter of the 6th order of cut-off frequency 5000 Hz, an analog switch to an output audio on 3.5 mm mono jack connector to be connected to the microphone input

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 a sound card from a PC. The analog switch is in high impedance mode when the plate is operating in speaker mode.

 - The electronic circuits associated with the sensor intended for the production of sound by the plate comprise an amplifier stage, a first-order low-pass filter stage with a cut-off frequency around 2.3 KHz, a 6th-order low pass stage with a cutoff frequency of 5 kHz, a signal dynamics compression stage with a square root function, a high-voltage output amplifier stage to an RCA-type output connector, a tap to a logic level adapter stage, under high impedance the output switch of the microphone function.

 At least one of the sensors is able to be switched into a transmitter of an ultrasonic wave packet detected by the other sensors whose positions are to be determined in order to trigger a test of integrity of the plate, by measurement of the difference in the propagation time of the wave packet between the different sensors, - The management of all the measurement, processing and data transfer steps via a serial communication interface, either to an LCD display, or to an interface for musical instruments (MIDI interface), either to a more powerful computer such as a microcomputer via its RS232 or USB port is governed by a microcontroller, - The device constitutes a peripheral interface with a machine that receives the signals from the processing means and which according to said signals commands the execution of files contained in the computer by various peripherals of known types connected to the computer, such as, for example, However, a video projector, a video camera, loudspeakers, a modem, an intercom, a printer, or an automatic control unit controlling a mechanical action such as the closing of a curtain of protection, the orientation of Another aspect of the present invention will become more apparent from the following detailed description of preferred embodiments thereof, given by way of nonlimiting example. and with reference to the accompanying drawings, in which: FIG. 1 is a schematic view of a rectangular impactile plate with a speaker function and a reduced active surface, giving the location and the coordinates of the sensors

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 in the particular case where they are in the form of half-disk and form the vertices of a rectangle. The actual landmark, the identification of the four quadrants, the propagation times of the acoustic waves, and the real coordinates (xr, yr) of an impact on the plate are also given.

FIG. 2 comprises a schematic view from above and in section of a rectangular impact plate giving the location and the positioning of four quarter-disc-shaped sensors glued in facing relation and intended for the measurement of the coordinates of impacts brought to the plate.

FIG. 3 comprises a schematic view from above and in section of a rectangular plate rendered impactile on only a portion of its total surface, the portion also being in the form of a rectangle whose vertices are given by the location and positioning of four Half-disc shaped sensors glued in facing relation and intended for the measurement of the impact coordinates carried on the plate.

FIG. 4 is a diagrammatic sectional view from above of the placement and the electrical connections connecting two quarter-disc-shaped silver-plated piezoelectric return transducers, mounted facing each other in the square corner of a plate; .

Figure 5 is a schematic sectional view from above of the placement and electrical connections connecting two piezoelectric transducers back of silvering, in the form of half-disc, mounted vis-a-vis at the edge of a plate.

Figure 6 is a schematic top view in section of a rectangular plate with reduced active surface area, the sensors being alternating polarization ceramics glued to the polished edges of the plate.

Referring firstly to Figure 1, there is shown a PLQ plate comprising four PZTO sensors, PZT1, PZT2, PZT3 formed pairs of piezoelectric transducers.

As shown in FIG. 4, the two transducers of each pair are identified by the indices t for the upper face and b for the lower face. They are shaped half-disk, indicated by the index s and are fixed vis-à-vis the two opposite faces of the plate, for example by gluing, to collect the acoustic waves flowing in the plate. The choice of the shape of the transducer is imposed by the reflection of the acoustic waves on the sides of the plate. Indeed, the reflection of an elastic wave, in a solid, at the interface of a free surface results in a superposition of the incident wave and reflected waves, reflected waves can be very different in nature because of the phenomenon of conversion of

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 fashion, which however and despite conversions produces almost a doubling of the mechanical movement collected by the ceramic. Thus, a quarter disc will be chosen when the sensors are glued in the square corners of a plate, according to the assembly of FIG. 3, and in the form of a half-disc when glued away from a corner, in practice. to more than three sensor diameters. The direction of the electric polarizations and electrical connections are respectively symmetrical with respect to the median plane of the plate and antiparallel so as to discriminate any symmetrical propagation mode and to favor any antisymmetric propagation mode. The realization of the electrical connections is facilitated by a return of silvering RA from one side to the other of the half-disks so as to have the two electrodes on the same side. The four sensors are the vertices of a rectangle. An orthogonal reference x, y of origin 0 is associated with the plate PLQ, the origin 0 being physically located at the point of intersection of the diagonals of the rectangle defined by the four sensors. The x and y axes intersect the middle of the sides of the rectangle defined by the sensors. The sensors PZTO, PZT1, PZT2, PZT3 have respective coordinates (-p, -q) and (p, -q), (-p, q), (p, q).

The acoustic waves can be generated by the shock of an object on the plate or by compression waves propagating in the ambient air and mechanically exciting the surface of the plate, such as the voice. The plate is an isotropic material, for example glass, having optionally undergone a quenching process to increase its impact resistance. When the material is monolithic glass, an impact of the plate of the nail on the surface of the plate generates essentially two acoustic modes, one corresponding to an elastic deformation of the glass due to the shock wave, antisymmetric with respect to the median plane of the plate, the other corresponding to a symmetrical elastic deformation wave with respect to the median plane of the plate. These modes are respectively the modes AO and SO of Lamb. The relative proportions of the two modes depend on the frequency, the nature of the impact and the materials colliding. In the case of an impact carried by a fingernail of the hand, for example that of the index finger, struck flat on a plate, which will be described by the term flick, the mode AO is generated in a predominant way compared to in the SO mode in a monolithic glass plate. The use of a pair of transducers glued face-to-face on both sides of the plate and electrically connected in antiparallel makes it possible to selectively detect the antisymmetric mode AO, which is slower to propagate in the plate than the symmetrical mode SO . The plate may be in a material other than glass. This can be an aluminum or steel sheet or made of a metal alloy. The plate may also be plastic, for example plycarbonate or polymethylmethacrylate. In the case of

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 plastics, the relative proportion of modes generated by flicking changes in favor of the SO mode. In addition, while acoustic propagation velocities are comparable between glass and a metal such as aluminum, it is quite different for plastics that have acoustic propagation velocities two to four times lower and a much lower acoustic attenuation. great. In the case of plastics, such as polycarbonate, it is preferable to detect the fast mode SO rather than the slow mode AO. To do this, simply paste the transducers on one side of the plate without vis-à-vis on the other side. The plate also comprises a fifth sensor PZT4a, shown in FIG. 1 in the form of a piezoelectric silver-return disk, but which may be of any shape, its function being to mechanically excite the plate only in the spectral band. audible used in telephony, typically 300 Hz-3300 Hz, so that it becomes a giant speaker, but not hinder the operation of the plate as slab impactile. The fifth PZT4a sensor may also be in the form of two piezoelectric transducers mounted vis-à-vis according to Figures 4 or 5, the advantage being to increase the transverse excitation power of the plate.

The useful impact surface is within the rectangle defined by the location of the four sensors. This rectangle can cover only a portion of the total area of the plate.

In the case of showcases of shops whose total surface easily exceeds ten square meters, the impactile surface may be limited to the surface that can reach a user in a standing position, that is to say a little more than two meters in height. The sensors will preferably be concealed and protected from moisture and aggression. This is achieved by using metal profiles with glazing beads and silicone joints incorporating the sensors. The dormant profiles and the glazing beads may be made of an electrically conductive material such as aluminum. The sandwiching of the sensors constitutes a Faraday cage, that is to say an electromagnetic shielding, protecting the input amplifiers of certain unwanted capacitive couplings with other devices such as plasma screens, LCD screens or other electronic or electrical devices.

The aim of the present invention is thus to show how these three functionalities, that is to say impactile slab, microphone and loudspeaker coexist and make it possible to transform the plate into a consumer communication terminal.

For this, if we stick to the signal processing described in the French patent 98/16229 mentioning a broadband amplification followed by a square elevation followed by a peak detection and integration , it appears that this process lacks flexibility on the

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 tuning the gains of the amplifiers. Indeed, there is some dispersion on the values of the electrical components used, as well as on the quality of the bonding so that the optimum gain can vary from one channel to another and from one device to another.

To overcome this drawback, the present invention proposes a modification of the broadband amplifier stage by replacing the fixed gain wideband amplifier with a programmable gain amplifier. Each of the four sensors is thus connected to a programmable gain amplifier, the gain value being defined by four bits allowing 16 possible gain values. The gain of the programmable amplifiers is then determined experimentally by an automated gain search procedure consisting of, for each channel, from the maximum gain and decreasing it in successive steps until the background noise of the channel is reached. the absence of any interactivity on the glass is sufficiently low to no longer inadvertently trigger the switching of the synchronization and adaptation transistors to a logic level.

The determination of the coordinates of an impact according to the assembly of FIG. 1, requires only three sensors taken from PZTO, PZT1, PZT2, PZT3. Several configurations with 3 sensors forming a right triangle can be extracted from the 4-sensor configuration of Figure 1. The four configurations described below lead to identical mathematical solutions, with the sign close, for the coordinates of an impact (xr , yr). In addition, each of these configurations is more suitable than the others, from the point of view of the accuracy of the measurement, if it is used only on a given quadrant of the active surface. A quadrant corresponds to a quarter of the active area and represents the intersection of one of the two positive or negative x-coordinate demiplans with one of the two positive or negative y coordinate half-planes.

Thus, for a given impact, we first determine the quadrant to which it belongs, then we calculate the coordinates (xr, yr) according to the formula associated with this quadrant.

The Cartesian coordinates of the sensors PZTO, PZT1, PZT2, PZT3 are respectively (-p, -q), (p, -q), (-p, + q), (+ p, + q). The acoustic waves move at the speed v of the mode detected by the sensors (i.e. antisymmetric or symmetrical). The propagation times to the sensors of a wave packet generated by an impact at (xr, yr) are respectively t00, t10, t01, t11.

The coordinates (xr, yr) are obtained by solving a system of equations, valid for a given quadrant. The four systems of equations are:

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v(ti i-tio)=vAtXg=vAtxi=A/(xr-p)2+(yr-q)r # \j(xr+pf+{yt-qf [v(too-tio)=vAtyg=vAtyo=-NxH-p)r+(yr+q)2 -(xr+p)2 +(yi-qf (gy, gx). (1,0). xr > 0 et yr < 0

v(too-to!)=vAtxg=vAtxû=(xr+p)+(yr+q)#J(xr-p)+(yr+q) v(ti i-toi)=vAtyg =vAtyi =A/(xr-p)2+(yr-q7 -yjfa-vf+(yr+qf (gy, gx). = (1,1). xr > 0 et yr > 0 v (t10-t11)=v#txg=v#tx1=#(xr+p)2+(yr-q)2-#(xr-p)2+(yr-q)2

v(tot-t)t)=vAtyg=vAtyi=-J(xr-p)+(yr+q #J(xr-p+(yr-q) j v (t01-t11)=v#tyg=v#ty1=#(xr-p)2+(yr+q)2-#(xr-p)2+(yr-q)2 Les formules suivantes donnent la position de l'impact (xr, yr). Il suffit de remplacer gx et gy par la valeur 1 ou 0 correspondant au quadrant concerné.

(gy, gx). = (0,0). xr <0 and yr <0 v (t01-t00) = v # txg = v # tx0 = # (xr-p) 2+ (yr + q) 2 - # (xr + p) 2+ (yr + q) 2 # # v (t10-t00) -v # tyg = v # ty0 = # (xr + p) 2+ (yr-q) 2 - # (xr + p) 2+ (yr + q) 2 (gy, gx). = (0,1). xr <0 and yr> 0

v (ti i-tio) = vAtXg = vAtxi = A / (xr-p) 2+ (yr-q) r # \ j (xr + pf + {yt-qf [v (too-tio) = vAtyg = vAtyo = -NxH-p) r + (yr + q) 2 - (xr + p) 2 + (yi-qf (gy, gx). (1.0) xr> 0 and yr <0

v (too-to!) = vAtxg = vAtxu = (xr + p) + (yr + q) #J (xr-p) + (yr + q) v (ti i-you) = vAtyg = vAtyi = A / (xr-p) 2+ (yr-q7 -yjfa -vf + (yr + qf (gy, gx). = (1,1). xr> 0 and yr> 0 v (t10-t11) = v # txg = v = # # tx1 (xr + p) 2 + (yr-q) 2 - # (p-xr) 2+ (q-yr) 2

v (tot-t) t) = vAtyg = vAtyi = -J (xr-p) + (yr + q #J (xr-p + (yr-q) jv (t01-t11) = v # tyg = v # ty1 = # (xr-p) 2+ (yr + q) 2 - # (xr-p) 2+ (yr-q) 2 The following formulas give the position of the impact (xr, yr). gx and gy by the value 1 or 0 corresponding to the quadrant concerned.

(-1) "" At: zg (q "'P" v' (4P "-r At"! J ") (4P" + 4'1 "-r (Atxg-AtN) 1) AtH '" (4) '1 "- r AtH"') + p 'v' At! '! J "(-4q" + v' AtN (-At: zg + AtN)) x = t ~ i) 4pitY9ti, + (-4 q "+ Y 'At")). ## EQU1 ## where: ## STR2 ## ## STR2 ## where: ## STR2 ## AtX! F) (4 p2 + 4q "-v" (Atxg-At]! '! F) 2) AtJ! F (4 V' -v "AtJ! F) yx = (- 4 (q2v2 # txy2 + p2 (-4g2 + v2 # tyg2)) The method of determining the coordinates of an impact on a plate described above makes it possible to transform a shop window or any other glass or plastic or metal plate into an impactile surface. impact can be a flick, ie an impact made with the nail plate on the glass plate The impact has the characteristic of creating acoustic waves in a relatively wide spectral range and at an electronically level It can be used up to frequencies above 150 kHz Ultrasonic spectral components can be easily measured for differences in propagation time between different sensors, and when a glass or metal plate is used, the ultrasonic frequency the location of the impact to the nearest centimeter is between 80 kHz and 120 kHz. In the case of plastic such as polycarbonate the useful ultrasonic frequency

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 is between 20 kHz and 50 kHz. For this, the wave packet generated by an impact must be converted into an electrical signal for each of the PZTO sensors PZT3. Each of the four PZTO PZT3 sensors is thus associated with an electronic processing channel responsible for extracting the high-frequency components of the wave packet generated by the impact. This is done by subjecting the electrical signal to various processes including connection to a switching block defining the input or output mode of the channel, followed for the input mode of a programmable gain wide band amplifier stage, followed by a stage selective amplifier around a frequency of 100 kHz for glass or metal and 30 kHz for polycarbonate and other plastics, a squared level stage, a peak detector stage with slow discharge resistance, an active integrator with a positively saturated output level in the absence of a signal thanks to a bridge of bias resistors of values at least 10 times higher than the output impedance of the step-up stage, finally of a stage adaptation to a logical level. The result of this treatment is that an impact on the plate generates a wave packet that we will convert at the moment of its reception into a single logical transition for the whole head of the wave packet, which will allow us to accurately measure a difference in arrival time of the wave packet to the different sensors.

This treatment thus makes it possible to determine the coordinates of the impact thanks to the formula above. However, it is not enough to achieve a reliable interface that is to say that is triggered only when a human action consisting for example in a flick on the glass, metal, or plastic is performed. Indeed, acoustic noises in the band 30-150 kHz can reach the plate via the coupling by the ground and the chassis. To prevent such signals from triggering a position measurement, the device performs a simultaneous analysis of the wave packet on at least one other spectral component, in practice in the vicinity of the upper limit of the audible spectrum, for example 12 KHz. For this, the output of one of the four programmable broadband amplifiers is diverted to a selective filter of the frequency to be controlled, in this case 12 KHz, said filter being intended in combination with the selective filter at 100 kHz ( for the glass), to characterize the impact ie to define a frequency signature, by checking the simultaneous presence of energy around these two frequencies, in a given proportion characteristic of the impact and thus to discriminate the signals untimely in the form of a wave packet whose spectral content does not simultaneously exhibit the required levels.

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 We thus obtain a more reliable impactile slab. This is not enough, however. Indeed, it is common for electronic devices to fail after a certain number of hours of operation. It is often difficult and expensive to detect the failure. In addition, with the development of the complexity of the systems, it happens that a bad connection or a mistake is taken for a breakdown.

Another aspect of the present invention is to provide a system for assisting the identification of failures. The most important fault diagnosis is the state of the electrical connections at the sensor levels. Indeed, the installation of an interactive window is often carried out during the renewal of a storefront. The sensors are then integrated into the frame and it would be costly to have to completely dismount a storefront without knowing beforehand if the failure comes from a break of the electrical contact on one of the sensors. The fault diagnosis on one of the sensors can be achieved by using one of the characteristics of piezoelectric ceramics, ie their high dielectric permittivity which gives them a high static capacitance value, typically of several nanoFarads. The control of the state of the connections then consists of measuring the value of this static capacitance for each of the four PZTO PZT4 sensors. When the sensors consist of two transducers connected in parallel or antiparallel, the static capacitance measured is the sum of the two capacitors of the individual transducers. It is therefore very easy to identify the faulty sensor and if the failure simply concerns one or both transducers constituting the sensor. In practice, the measurement of the capacitance is carried out by measuring the discharge time of the static capacitance brought to a known potential, through a resistance of known value. For this purpose, the switching blocks placed at the inputs of the analog channels are fed into outputs. The sensors are then brought, for a short time, to a known potential difference. The charging current is limited by a resistance of a few hundred ohms. Once the load is completed, the switching blocks are put under high impedance, and the capacitors are slowly discharged through another resistance of the order of 100 kOhms while a timer is started. The timer stops when the voltage across the capacity falls below a preset threshold. For a static capacity of 10 nF, the discharge time is approximately equal to the product of the discharge resistance by the value of the static capacitance of the piezoelectric transducer, ie one millisecond. In case of breakage of the electrical connections at the sensors, there is a sharp decrease in the discharge time. It should be noted here that the linear capacitance of the coaxial cable connecting the sensors to the input amplifiers is only 100 picoFarad per meter. So the capacity

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 equivalent of 10 meters of coaxial cable, represents only a nanoFarad, barely 10% of the value of the static capacity of a piezoelectric sensor. It can never be confused between the static capacity of a sensor, and the capacity of the connecting cable.

We thus have a first function to help in fault diagnosis. A second diagnostic assistance function also consists of switching the switching block of one of the four PZTO sensors PZT3 in output mode and applying an electrical pulse of the order of 45 V, for a very short time decomposing in 5 s rise time and 5 s return time. This has the consequence of generating a packet of acoustic waves in the plate. The other three sensors remaining in receiver mode, a measurement of the propagation time differences of the wave packet emitted by the excited sensor, for example PZT3, and the other sensors is simultaneously started. Knowing, then, the propagation velocity of the acoustic waves in the plate, v = 3350 m / s for the antisymmetric mode AO in the glass or v = 1500 m / s for the symmetrical mode SO in the polycarbonate, we obtain directly a measurement the length and width of the rectangle formed by the sensors. Indeed, the moment of excitation of the sensor PZT3 corresponds simultaneously to the instant of arrival of the wave which it generates at its location, so that t11 = 0. If the origin of the time is that corresponding to the moment of excitation of the transducer PZT3, then the length 2p and the width 2q of the rectangle formed by the four sensors are given by the formulas: {2p = v # t10 [2q = vxtoiJ We thus obtain a second very useful function which consists in the installation of the plate to measure the length and the width of the rectangle formed by the sensors and to periodically compare this saved value with other measurements carried out later, for example during an initialization process at each connection electrical impactile slab or as a result of each impact.

Another aspect of the present invention relates to the possibility of using the same PZTO PZT3 sensors to transform the plate into a microphonic membrane. This is achieved by deriving again the outputs of the four broadband programmable amplifiers to follower amplifiers, then to a summing amplifier stage of the signals from the follower amplifiers, a high pass filter stage of the first order of 30 Hz cutoff frequency, a low-pass filter stage of the first order of cut-off frequency 2 kHz, a high-order low-pass filter stage, such as a Bessel filter or Chebyshev of order 6, cut-off frequency of 5000Hz, an analog switch of the microphonic function, debiting on a

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 load impedance of 560 Ohms. This charging resistor arrives at the terminals of a 3.5mm audio jack connector, which can subsequently be connected to the microphone input of a sound card of a PC.

In addition to the microphone function, the plate can be used as a speaker. This function is provided by the PZT4a sensor. Since it is the same plate that serves as a microphone or loudspeaker, the two functions are exclusive of each other. In addition, one of the functions will take precedence over the other. In the case of this invention, priority is given to the speaker function which, when activated, disables the microphone function by putting the analog switch of the microphone function under high impedance. The speaker function is so-called master, while the microphone function is called slave.

One of the advantages of the present invention lies in the fact that it is possible to make sure that the loudspeaker function does not disturb the impactile slab function. For this, the audio sensor PZT4a is controlled by an electronic device with filtering functions. In particular, any audio signal coming from a high fidelity storage medium and, in general, any audio source intended to be retransmitted by the glass plate will undergo an electronic processing comprising at least one amplifier stage, a compression stage of dynamic consisting of a logarithmic amplification or an elevation at the square root of the signal, followed by a low-pass filtering stage of the 6th order of cut-off frequency 5000Hz, followed by a high-pass filter stage with 30Hz cut-off frequency, followed by a power amplifier stage for the mechanical excitation of the audio transducer PZT4a. Dynamic compression enhances some low-amplitude sounds that could only be heard in quiet environments where high-fidelity listening is possible. This is not the case of store windows that bathe most of the time in a noisy ambient noise. Dynamic compression by the square root function is constructed in such a way that the loudest sounds keep an unchanged level, while a weak sound will be amplified. For example, a recording in which the loudest sound is 1 volts peak-to-peak, but only lasts for one second over a total recording length of 30 seconds and contains virtually only sounds of 10 mV amplitude. after dynamic compression, still the same loudest 1 volt peak-to-peak sound, but the 10 mV sounds will have been amplified to 100 mV.

Thus, by making the speaker function independent of the impactile slab function, an impact at a given location of an impact plate can trigger an action implementing the loudspeaker function while the same speaker function can be used. stopped during

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 its execution by an impact on the plate made at another place on the plate. The impactile slab function will have priority and will be said master on the loudspeaker function that will be called slave.

For this, the process of calculating the impact coordinates, as well as impact characterization by simultaneous verification of the presence of energy in sufficient proportion to the two frequencies 12 KHz and 100 kHz (for glass or metal and 30 kHz). KHz for polycarbonate and other plastics), as well as the programmable gain, automatic gain optimization or fault diagnosis functions, are controlled by a microcontroller with an arithmetic and logical unit of several input ports. outputs capable of generating upstream or downstream edge interrupts, multiple timers, real-time clock, system clock, watchdog function, program memory and data, as well as communication functions of serial or parallel type allowing it to exchange commands and data with a master microcomputer.

The microcomputer itself will be provided with hardware and software means enabling it to execute certain computer files and the activation of certain peripherals such as, but not limited to, a video projector, an Internet video camera, a modem, a sound card, a printer, a compact disk drive, depending on the position of an impact on a predetermined area of the glass plate.

The microcomputer can itself be connected to the Internet Network via a service provider possibly implementing high-speed communication means and depending on a central server, so that a simple glass plate equipped with The invention may serve as a multimedia communication terminal.

Claims (16)

 1-acoustic wave transceiver device comprising a set of PZTO to PZT4 piezoelectric sensors bonded to a plate, said sensors being able to be independently transmitters or receivers of acoustic waves propagated in the plate and said device comprising means for filtering capable of defining at least two independent spectral bands, one in the audible range, the other in the ultrasound range, characterized in that a set of at least three sensors selected from four PZTO sensors PZT3 operates in reception mode in the audible and ultrasonic bands and allows operation of the device in impactile slab, at least one sensor taken from 4 PZTO sensors PZT3 operates in transmission mode or reception in the ultrasonic band while at least one PZT4a sensor operate in mode broadcast simultaneously and independently in the audible band. 2-Device according to claim 1 characterized in that the sensors operating in the ultrasonic band are used to determine the position of an impact applied to the plate by measuring the acoustic wave propagation time difference between the different sensors, said acoustic waves being generated by the impact of an object such as the dish of the nail, a key, the tip of a pen etc ... 3-Device according to claim 2 characterized in that the ultrasonic band is around 100 kHz for glass or metal plates and 30 KHz for plastics and in particular polycarbonate. 4-Device according to claims 2 to 3 characterized in that each sensor is associated with an electronic processing channel comprising a switching block defining the input or output mode of the channel, followed for the input mode of a broadband amplifier to Programmable gain, followed by a selective amplifier around a frequency of 100 kHz for glass and metals and 30 KHz for plastics, a squared floor, a peak detector stage with slow discharge resistance , of an active integrator with a positively saturated output level in the absence of a signal, and finally of an adaptation stage at a logic level and for the output mode, of a stage for applying to the terminals of the sensors and for a short time, a potential difference with load current limiting and discharge resistors, the measured discharge time being proportional to the product of the resistance of the <Desc / Clms Page number 18>  discharge, of known value, by the value of the static capacitance of the piezoelectric transducer and used to measure this value of static capacitance of the piezoelectric sensor and thus to check the good state of an electrical connection on the sensors. 5-Device according to claim 4 characterized in that the output of at least one programmable broadband amplifier is diverted to a selective filter of a predetermined frequency located in the upper part of the audible band, ie to 12 kHz, the said filter being intended in combination with the selective filter at 100 kHz for glass or metal and 30 KHZ for plastics, to characterize an impact by checking the simultaneous presence of energy around these two frequencies, in a proportion given, and thus to discriminate the unwanted signals in the form of wave packet whose spectral content does not simultaneously present the required levels of signals from impacts on the glass, only able to simultaneously produce the signal level required at both frequencies. 6-Device according to claims 2 to 5 characterized in that the gain of the programmable amplifiers is determined by an automated gain search procedure consisting for each channel to decrease in successive steps the value of the gain until the background noise the channel in the absence of any interactivity on the glass is low enough to no longer inadvertently trigger the switching of the matching transistors to a logic level. 7-Device according to claim 1 characterized in that the sensors operating in the audible band are adapted to the recording or the production of sound in the ambient air by coupling with the plate acting as a microphonic membrane receiving mode or speaker in transmit mode. 8-Device according to claim 7 characterized in that the audible band for the recording or the production of sound in the ambient air by coupling with the plate is limited by filtering at the band 30Hz-5000 Hz. 9-Device according to claim 7 characterized in that the plate is made of a transparent material such as glass or transparent plastics such as polycarbonate or <Desc / Clms Page number 19>  polymethylmethacrylate (trade name Plexiglas) and constitutes a coupling surface of several square meters. 10-Device according to claims 1 to 9 characterized in that the sensors are located on the periphery of the plate and are protected and concealed by a frame and glazing beads with silicone joints ensuring a splash-proof water or other liquids. 11-Device according to claims 1 to 10 characterized in that the application of a potential difference to the audio transducer PZT4a for the production of sound in the ambient air by the plate, puts under high impedance, and therefore deactivates the receiver audio filter for receiving sound by coupling with the plate, so that the speaker function is said master, while the microphone function is called slave. 12-Device according to claims 1 to 11characterized in that the production of an audio sound in the ambient air by the plate is optionally interrupted by an impact on the plate, said impact being validated by exceeding the threshold levels required by discrimination filters of 12 KHz and 100 kHz for glass or metal and 30 KHz for plastic, so that the plate in impactile interface mode is called master, while the production of audible sound is called slave. 13-Apparatus according to claim 7 characterized in that the plate is in a flat rectangular shape such as those that can be found in shop windows, partitions, glass doors, windows or slightly curved as those car window passengers or bus shelters or display furniture in commercial sales areas can be found in window panes. 14-Device according to claims 1 to 13 characterized in that for the monolithic plate glass and the monolithic plate metal, PZTO PZT4 piezoelectric sensors consist of two piezoelectric transducers PZTt and PZTb glued opposite part and other faces of the plate and are in the form of half-discs with return of silvering when they are glued on the side of a plate, the edge of the disc being collinear and in line with the edge of the plate or quarter-disc shape with silvering back when glued in the corners of the rectangular plate, both slices <Desc / Clms Page number 20>  perpendiculars being aligned with those of the plate, while the electrical connections are made in antiparallel, and for plastics such as polycarbonate, piezoelectric sensors PZTO to PZT4 consist of a single piezoelectric transducer, all glued on the same face or the face opposite to the face receiving the impact. 15-Device according to claims 1 to 14 characterized in that the sensors are piezoelectric ceramic plates with alternating polarization of rectangular shape, glued on the polished edge of the plate, the plane of separation of the alternating polarization being coplanar to the median plane of the glass plate. 16-Device according to claims 1 to 15 characterized in that audio recordings from high-fidelity media such as compact disc players and intended to be read using an interactive window in its speaker function, undergo a processing of signal consisting of a compression of the signal dynamics using a logarithmic amplifier or a square root type during which the low amplitude sounds are enhanced while the higher amplitude sounds remain unchanged.