Autonomous alert device and associated alert system

Abstract

Mechanical bell for generating an alert signal. A person monitoring system equipped with a bell, the system comprising a microphone and a central unit for analyzing the sound detected by the microphone. Figure 1

Description

Title of the invention: Autonomous alert device and associated alert system Technical field

[0001] The technical field of the invention is the monitoring of people. PREVIOUS ART

[0002] Currently, monitoring of people, for example elderly people, disabled people, or hospitalized people, is carried out using alert systems, often activated by pressure on an electronic circuit, and sending an alert signal to a wired or wireless network.

[0003] The object of the invention is a particularly simple-to-use bell, and making it possible to send an alert signal, not an electric one, but an audible one, to request assistance. Another object of the invention is an alert system, based on a bell, or a mechanical cricket, making it possible to alert a person to the need for assistance. Statement of the invention

[0004] A first object of the invention is a bell, comprising a housing, configured to be held between the palm and the fingers of a user, from which emerges a button, in particular a push button, arranged to be activated by a finger of the user, in particular the thumb, the bell being such that: - the push button is movable relative to the housing, in particular in translation, so as to be brought closer to the housing to activate the bell, the push button being connected to a first spring, maintaining the push button in an equilibrium position in the absence of pressure exerted on the push button; - the push button is connected to a member, extending into the housing, so that the movement of the push button, in particular translation, causes a displacement of the member; - the organ has a spur;

[0005] the bell also comprising: - a hammer, connected to a second spring; - a bell, configured to emit a sound when struck by the hammer, the hammer being movable relative to the bell, the second spring being configured to keep the hammer away from the bell, in the absence of stress exerted on the hammer;

[0006] the bell being characterized in that: - the hammer has a contact portion, arranged facing the organ, so that that when the push button occupies the equilibrium position, the lug extends between the contact portion and the push button, the contact portion occupying an initial position; - under the effect of pressure exerted on the push button, the contact portion is pushed by the lug, until it reaches a limit position in which the contact portion is no longer in contact with the lug;

[0007] so that - the thrust exerted by the lug on the contact portion causes the hammer to move back relative to the bell, and the second spring to compress, until the contact portion reaches the limit position; - after the limit position is reached, under the effect of the second spring, the contact portion returns to the equilibrium position, causing the hammer to move to the bell.

[0008] According to one possibility, the push button is movable in translation.

[0009] According to one possibility: - the housing extends around a longitudinal axis, being configured to be held between the palm of a user's hand and fingers; - the push button extends, parallel to the longitudinal axis, through an opening made in the housing, so that it can be activated by a thumb of the user.

[0010] The member may be movable in translation, for example of the rod type, or movable in rotation, for example a wheel or a portion of a wheel or a trigger.

[0011] According to one possibility: - the hammer is mobile in rotation relative to the bell, around an axis of rotation; - under the effect of the pressure exerted on the push button, the contact portion is configured to tilt, around the axis of rotation, being pushed by the lug, so that the contact portion gradually moves away from the member during its tilting.

[0012] According to one possibility: - the member is movable in translation along a first translation axis; - the hammer is movable in translation along a second translation axis secant of the first translation axis; - under the effect of pressure exerted on the push button, the contact portion is configured to gradually move away from the lug, up to the limit position.

[0013] According to one possibility: - the bell delimits an internal space; - all or part of the hammer extends into the internal space, in particular a striking end intended to strike the bell.

[0014] According to one possibility: - the hammer has a striking end, configured to strike the bell; - in the initial position, the striking end is arranged less than 5 mm or less than 3 mm or less than 2 mm from the bell.

[0015] A second object of the invention is a system for monitoring a person, comprising: - an acoustic transmitter, configured to be activated by the person, so as to emit a sound, preferably audible; - a microphone, arranged in a room likely to be occupied by a person, the microphone being configured to detect a sound and produce a detection signal dependent on the detected sound; - a central unit, configured to receive the detection signal and to analyze said detection signal;

[0016] the system being characterized in that: - the central unit is programmed to recognize, from the detection signal, the sound emitted by the acoustic transmitter, and to generate an alert signal when the sound emitted by the acoustic transmitter is recognized.

[0017] The acoustic transmitter may be a mechanical doorbell, the doorbell comprising a bell and a hammer, the bell being configured to emit a sound when struck by the hammer.

[0018] The acoustic transmitter may be a mechanical cricket, emitting an audible click upon manual activation. Thus, preferably, the doorbell is not connected to any power supply (battery or network).

[0019] The doorbell may be a doorbell according to the first object of the invention.

[0020] According to one possibility, the central unit is configured to produce a spectrogram of the detection signal, so that the analysis of the detection signal is carried out as a function of the spectrogram.

[0021] According to one possibility, the analysis comprises a determination of a spectral power in a previously determined spectral band, corresponding to a spectral band of emission of the doorbell.

[0022] According to one possibility, the analysis comprises an implementation of a supervised learning artificial intelligence algorithm, in particular a neural network, in particular a convolutional neural network.

[0023] The invention will be better understood upon reading the description of the exemplary embodiments presented in the remainder of the description, in conjunction with the figures listed below. FIGURES

[0024] [Fig.l] shows the main components of a doorbell according to a first embodiment of the invention

[0025] [Fig.2] shows one embodiment of the bell.

[0026] [Fig. 3] shows a spectrogram recorded with a bell as described in connection with Figures 1 and 2.

[0027] [Fig.4] shows the main components of a doorbell user monitoring system.

[0028] Figures 5A to 5H show the main components of a doorbell according to a second embodiment.

[0029] [Fig.6] shows a spectrogram recorded with a bell according to the second embodiment. PRESENTATION OF SPECIAL METHODS OF IMPLEMENTATION

[0030] [Fig.l] depicts an example of a doorbell particularly suitable for monitoring a person. In [Fig.l], only the main components have been shown.

[0031] The bell comprises a push button 10, movable, for example in translation, and capable of being returned to an equilibrium position by a first spring 12. The bell comprises a housing 5, in which the components shown in [Fig.l] are arranged, with the exception of the push button which emerges from the housing.

[0032] Preferably, the housing 5 is ergonomic. It extends around a longitudinal axis. It is configured to be held between the palm of the hand and the fingers of the hand. Preferably, the push button extends along the longitudinal axis, or parallel to the latter or substantially parallel to the latter. By substantially parallel, we mean parallel to + / - 10° or + / - 20°.

[0033] The doorbell is configured to emit a sound having constant spectral characteristics, or which can be considered as such, regardless of the pressure exerted on the push button 10.

[0034] The push button is connected to a member 11, extending in the housing 5, so that the translation of the button causes a movement of the member. In this example, the member is a rod, movable in translation. It can also be a member movable in rotation, for example a wheel or a portion of a wheel.

[0035] The member comprises a lug 13. The lug 13 is configured to come into contact with a hammer 15, as described below. The hammer 15 is intended to strike a bell 17 (or gong), so as to produce a sound. The hammer is rotatable relative to the bell, around an axis of rotation 19. A second spring 16 is configured to keep the hammer away from the bell, in the absence of stress exerted on the hammer.

[0036] The hammer comprises a contact portion 14, forming one end, arranged facing the member 11. When the push button occupies the equilibrium position, the lug 13 extends between the contact portion and the push button. The contact portion then occupies an initial position, the latter being shown in [Fig. 1]. The contact portion 14 extends a short distance from the member, typically a few mm.

[0037] In [Fig. 1], the arrow F1 represents pressure exerted on the push button. When it occupies the initial position, the contact portion is preferably at a distance of a few mm or 1 or 2 cm from the lug. Thus, after a short stroke of the push button, the lug comes into contact with the contact portion. Under the effect of the pressure exerted on the push button, the contact portion is configured to tilt, around the axis of rotation 19, being pushed by the lug. During its tilting, the contact portion gradually moves away from the member, until it reaches a limit position in which the contact portion is no longer in contact with the lug. In [Fig.l], the tilting of the contact portion is represented by an arrow F2. The limit position corresponds to a cross referenced by the letter P.

[0038] Under the effect of the tilting of the contact portion towards the limit position, the hammer moves back relative to the bell (arrow F3). More precisely, the rotation axis 19 is arranged between the contact end and a striking end 15' of the hammer, the latter being configured to strike the bell. Thus, under the effect of the tilting of the bell, the striking end moves back relative to the bell 17.

[0039] After the contact portion has reached the limit position, under the effect of the second spring 16, the contact portion returns to the initial position (arrow F4), while the pressure on the push button continues. The contact portion is then arranged between the lug and the push button. The return of the contact portion to the initial position causes the hammer to rotate up to the bell (arrow F5). Under the effect of the stiffness of the second spring, the rotation of the hammer towards the bell causes the latter to be struck by the striking end. The closer the rotation axis 19 is to the contact portion 14, the more the striking effect is amplified, at the cost of increased pressure on the button to move the contact portion 14.

[0040] When the pressure on the push button ceases, the latter returns to the equilibrium position (arrow F6). The passage of the lug causes a slight displacement of the contact portion, which is not sufficient to move the striking end to the bell.

[0041] Preferably, the shape of the lug is adapted to allow support against the contact portion in the translation direction F1, while facilitating sliding of the lug against the contact portion in the translation direction F6.

[0042] [Fig.2] represents an integration of the components previously described in an ergonomic case 2.

[0043] [Fig. 3] shows an example of a spectrogram recorded by implementing such a doorbell. Abscissa axis: spectral power. Y axis: acoustic frequency. It can be seen that the spectrogram has a high spectral power in narrow frequency bands, for example between 2800 and 2900 Hz or between 7100 and 7400 Hz: this makes it easier for a processing unit to recognize the sound produced by the doorbell, as described below.

[0044] The doorbell is configured to be used in an environment occupied by a monitored person. This may in particular be a room 4, as shown diagrammatically in [Fig.4]. The room comprises a microphone 2. The microphone 2 is configured to generate a detection signal dependent on the detected sound.

[0045] The detection signal is addressed, by wired or wireless means, to a central unit 3, the latter comprising one or more microprocessors and a memory, in which instructions are stored allowing implementation of an algorithm for classifying or recognizing the sound produced by the doorbell. Preferably, the detection signal is addressed to the central unit by a Wi-Fi connection. The microphone 2 can be connected, by wired or short-range connection, to a local microprocessor, arranged in the room, in the event of a failure of the connection with the central unit 3. The local microprocessor can implement a classification based on a spectral analysis, which requires less memory capacity, as previously described.

[0046] The classification algorithm may include an analysis of the signal in the previously determined frequency band corresponding to the doorbell. Beyond a certain spectral power threshold, the sound of the doorbell is considered to be detected. An alert signal is sent to personal assistance personnel.

[0047] The advantage of the mechanical bell is that the spectral signature is characteristic and can be easily identified.

[0048] According to one possibility, a spectral filter targeting a particular harmonic is implemented, which makes it possible to limit the number of false positives, the latter being able to result from spectrally close noises, for example a noise from glass or cutlery. An advantage of a spectral analysis is that this can be implemented from an on-board analyzer. This type of analysis can be implemented on an analyzer whose performance is modest.

[0049] According to one possibility, the classification algorithm implements a supervised learning artificial intelligence algorithm. For example, a neural network, in particular a convolutional neural network. The algorithm is fed by one or more spectrograms. It has previously been trained, so as to identify the emission of the sound by the ringtone. The algorithm is, for example, a lightweight model of the mobilenet type, comprising convolution layers with 5.5 million weights.

[0050] The output of the algorithm corresponds to a probability of detecting the characteristic sound emitted by the doorbell. The output is binarized, so that above a threshold probability, it is considered that an alert has been issued. The threshold probability is defined according to the false positive rate and the false negative rate that we wish to obtain.

[0051] The training can be carried out by recording sounds only with the doorbell in use, without additional noise, and preferably by implementing different doorbells of the same design in order to take into account manufacturing variability. The recorded sounds are then randomly combined with recorded sounds corresponding to everyday activities. The algorithm is then trained to recognize the emission of a sound by the doorbell.

[0052] The use of other algorithms is possible, the convolutional neural network (or CNN) is nevertheless preferred in this invention because it constitutes an undeniably effective approach when one has to manage a massive database. Different architectural variants in this same class of models can be taken from the following reference: Review of deep learning: concepts, CNN architectures, challenges, applications, future directions - by Alzubaidi et al. In Journal of Big Data (2021) 8:53.

[0053] The previously described bell is advantageous because it is not connected to electrical means and does not include electronic means. It is therefore particularly robust and does not need to be recharged or powered electrically. It can withstand shocks without its operation being affected. It is therefore a robust design.

[0054] However, other bells can be used in the alert system, for example mechanical bells of a different design to that previously described, or electronic bells or buzzers or even whistles, or of the mechanical ratchet type.

[0055] Like the sounds produced by certain marine animals, mechanical clicks have the advantage of occupying a very wide frequency band given the temporal narrowness of their mechanical percussion. Thus, in an environment not conducive to propagation (walls of different materials, tortuous spaces, great distance, etc.), it may be advantageous to use such acoustic systems occupying a wide band, so that the vibration restored at the end of propagation remains available for detection. In this case, the "bell" may be a metal part that can be deformed by simple pressure and can return to its initial shape by emitting a brief click. Many clever mechanisms can produce useful and characteristic sounds in the context of this alert application and can offer various and varied advantages. The following may be cited, in a non-exhaustive manner: - D-Day crickets which produce a short and recognizable audible click (by rapid deformation followed by a return to the initial shape), broad spectrum, under the effect of manual activation. - ultrasonic whistles are used to emit sounds inaudible to the human ear, which can also present an advantage of discretion in an inhabited environment, but detectable with a microphone sensitive to this spectral band (by blowing into this type of ultrasonic whistle, a small membrane deforms, creating a vibration which generates a high-pitched sound), - push buttons on certain objects such as pens, but which can be used solely for this alert purpose, can be very inexpensive solutions. The monitoring system is then based on recognition of the audible click emitted following manual activation of the push button.

[0056] The detailed embodiments of bells in the present invention (spring pusher, hammer, bell) optimize the probability of detection of the sound and the ease of recognizing it among others as well as the multiplication of the effort to facilitate the support of a weakened person on this alert device.

[0057] Figures 5A to 5H describe another example of a doorbell 1' particularly suitable for monitoring a person. Only the main components have been shown.

[0058] The bell comprises a push button 20, movable, for example in translation, and capable of being returned to an equilibrium position by a first spring 22. The bell comprises a housing, in which the components shown in [Fig.l] are arranged, with the exception of the push button which emerges from the housing.

[0059] Preferably, the housing is ergonomic. It extends around a longitudinal axis. It is configured to be held between the palm of the hand and the fingers of the hand. Preferably, the push button 20 extends along the longitudinal axis, or parallel to the latter or substantially parallel to the latter. By substantially parallel, we mean parallel to + / - 10° or + / - 20°. The bell can also be used in the form of a pendant.

[0060] As in the first embodiment, the doorbell is configured to emit a sound having constant spectral characteristics, or which can be considered as such, regardless of the pressure exerted on the push button 20.

[0061] The push button is connected to a member 21, extending in the housing, so that the translation of the button causes a movement of the member. In this example, the member is a rod, movable in translation.

[0062] The member comprises a lug 23. The lug 23 is configured to come into contact with a hammer 25, as described below. The hammer 25 is intended to strike a bell (or gong) 27, so as to produce a ringing-type sound. The hammer 25 is movable in translation relative to the bell. A second spring 26 is configured to keep the hammer away from the bell, in the absence of stress exerted on the hammer.

[0063] The hammer comprises a contact portion 24, arranged facing the member 21. When the push button occupies the equilibrium position, the lug 23 extends between the contact portion 24 and the push button. The contact portion 24 then occupies an initial position, the latter being shown in [Fig.5A]. The contact portion 24 extends a short distance from the member, typically a few mm.

[0064] In Figures 5A to 5H, the arrow F1 represents the movement of the member 21. The arrow F2 represents the movement of the hammer 25.

[0065] When it occupies the initial position, the contact portion 24 is preferably at a distance of a few mm or 1 or 2 cm from the lug 23. Thus, after a short stroke of the push button, the lug 23 comes into contact with the contact portion 24. Under the effect of the pressure exerted on the push button 20, the contact portion 24 is configured to be moved in translation, being pushed by the lug, while moving away from the latter. The member 21 is movable in translation along a first translation axis AL. The contact portion is movable in translation along a second translation axis A2 secant from the first translation axis: see [Fig.5A]. Thus, under the effect of the translation of the member 21, the contact portion 24 gradually moves away from the member 21 (see [Fig.5B]) until reaching a limit position in which the contact portion 24 is no longer in contact with the lug 23: see [Fig.5C].

[0066] Under the effect of the thrust exerted by the member 21, via the lug 23, the second spring 26 compresses, and the hammer 25 moves back relative to the bell.

[0067] After the contact portion has reached the limit position, shown in [Fig.5C], under the effect of the second spring 26, the hammer 25 is no longer pushed by the rod 23. The spring 26 relaxes, which causes a translation of the hammer towards the bell 27. Pressing the push button continues: see [Fig.5D]. Under the effect of inertia, the translation of the hammer continues until the striking end 25' of the hammer strikes the bell, which causes the latter to ring. The second spring 26 is then relaxed. See [Fig.5E]. The hammer 25 then undergoes a recoil movement, under the effect of a return force exerted by the second spring 26. See [Fig.5F].

[0068] Throughout the pushing of the push button 20, the first spring 22 tends to compress. When the pressure on the push button ceases, the member 21 returns to the equilibrium position. The passage of the lug 23 against the hammer 25 causes a temporary rotation of the hammer, as shown in [Fig.5G].

[0069] [Fig.5H] shows the hammer 25 in its initial position and the button 20 in its position equilibrium, similar to [Fig.5A].

[0070] [Fig.6] shows a spectrogram recorded using a bell as described in connection with Figures 5A to 5H. The axes are similar to those described in connection with [Fig.3]. Two peaks are observed at around 3700 Hz and 8000 Hz.

[0071] One of the advantages of the bell according to the second embodiment is that the bell 27 (or gong) describes a portion of a hollow ring. The term bell is to be taken in the broad sense: it is an element configured to produce a characteristic sound when struck by a hammer.

[0072] In the example described, the bell forms a portion of a ring describing a “C”, the internal diameter of which is 35 mm. The internal diameter is preferably between 20 mm and 50 mm, so as to be able to accommodate components in the internal space delimited by the bell, in this case the hammer and possibly all or part of the second spring. The compactness of the bell is increased. Compactness is an important criterion in the case of a bell intended to be used by being suspended from a pendant, so as to be easily accessible by a user.

[0073] It is also advantageous that the member 21, connected to the button 20, is movable in a plane parallel to a plane in which the ring described by the bell extends: this increases the compactness.

[0074] Advantageously, when the hammer is in the initial position, that is to say in the absence of manipulation of the push button, the spacing between the bell and the striking end 25' of the hammer is less than 10 mm, or 5 mm, or 3 mm or 2 mm. The spacing between the bell and the striking end 25' of the hammer, in the initial position, is preferably greater than 0.5 mm, to avoid striking the bell inadvertently. This also makes it possible to provide a safety margin to prevent the striking end 25' of the hammer from contacting the bell in the event of the second spring being released. A spacing of between 0.5 mm and 2 mm, for example 1 mm, is considered optimal. Indeed, this maximizes the use of the inertia of the hammer when it strikes the bell, under the effect of the release of the second spring. This increases the intensity of the bell's ringing.

[0075] Preferably, the striking end 25' of the hammer 25 is adjustable, so as to adjust the distance separating it from the bell in the initial position. The adjustment is preferably manual, using for example a screw thread, making it possible to move the striking end 25' closer to or further away from the bell 27.

[0076] The stroke of the button 20, and therefore of the member 21, is preferably short, less than 1 cm, typically between 5 mm and 8 mm. Too short a stroke encourages the triggering of false positives (unwanted alerts). The stroke is short enough to be able to be implemented by an elderly person or a person with a disability, whose strength is limited.

[0077] The device preferably combines a short stroke of the button 20 and a small distance between the end 25' of the hammer and the bell: this makes it possible to obtain a high intensity ringing by exerting a small push on the button 20.

[0078] The preceding characteristics (gap between the striking end and the bell, adjustment of this gap, stroke of the button) apply to the two embodiments described.

[0079] The monitoring system may be a sound monitoring system configured to detect other sounds emitted by the person, for the purpose of monitoring them, for example sounds generated by their daily activity. Thus, the central unit 3 may be configured to perform a classification of different sounds among different classes, corresponding respectively to normal noises and abnormal noises, for example a person falling or an object falling. The sound of the doorbell (or the cricket or the whistle) is then classified into a class corresponding to an abnormal noise.

Claims

Claims

1. Doorbell (1, 1'), comprising a housing (5), configured to be held between the palm and the fingers of a user, from which a push button (10, 20) opens, arranged to be activated by a finger of the user, in particular the thumb, the doorbell being such that: - the push button is movable relative to the housing, so as to be brought closer to the housing to activate the bell, the push button being connected to a first spring (12, 22), maintaining the push button in an equilibrium position in the absence of pressure exerted on the push button; - the push button is connected to a member (11, 21), extending into the housing, so that a movement of the button causes a movement of the member; - the organ has a lug (13, 23); the doorbell also including: - a hammer (15, 25), connected to a second spring (16, 26), - a bell (17, 27), configured to emit a sound when struck by the hammer, the hammer being movable relative to the bell, the second spring being configured to hold the hammer away from the bell, in the absence of stress exerted on the hammer; the bell being characterized in that: - the hammer comprises a contact portion (14, 24), arranged facing the member (21), so that when the push button occupies the equilibrium position, the lug extends between the contact portion and the push button (10, 20), the contact portion occupying an initial position; - under the effect of pressure exerted on the push button, the contact portion is pushed by the lug, until it reaches a limit position (P) in which the contact portion is no longer in contact with the lug; so that - the thrust exerted by the lug on the contact portion causes the hammer to move back relative to the bell, and the second spring to compress, until the contact portion (14) reaches the limit position; - after the limit position is reached, under the effect of the second spring, the contact portion returns to the equilibrium position, causing the hammer to move towards the bell.

2. A doorbell according to claim 1, wherein the push button is movable in translation.

3. A doorbell according to claim 1, wherein - the housing extends around a longitudinal axis, being configured to be held between the palm of a user's hand and fingers; - the push button extends, parallel to the longitudinal axis, through an opening in the housing, so as to be able to be activated by a thumb of the user.

4. A bell according to any preceding claim, wherein the member (11) is movable in translation, for example of the rod type, or movable in rotation, for example a wheel or a portion of a wheel or a trigger.

5. Bell according to any one of the preceding claims, in which: - the hammer is movable in rotation relative to the bell, around an axis of rotation (19); - under the effect of the pressure exerted on the push button, the contact portion is configured to tilt, around the axis of rotation, being pushed by the lug, so that the contact portion gradually moves away from the member (11) during its tilting.

6. A doorbell according to any one of claims 1 to 4, wherein: - the member is movable in translation along a first translation axis (Al); - the hammer is movable in translation along a second translation axis (A2) intersecting the first translation axis; - under the effect of pressure exerted on the push button (20), the contact portion (24) is configured to gradually move away from the lug, up to the limit position.

7. A bell according to any preceding claim, wherein: - the bell defines an internal space; - all or part of the hammer extends into the internal space.

8. A bell according to any preceding claim, wherein: - the hammer comprises a striking end (15', 25'), configured to strike the bell; - in the initial position, the striking end is arranged less than 5 mm or less than 3 mm or less than 2 mm from the bell.

9. System for monitoring a person, comprising: - an acoustic transmitter, configured to be activated by the person, so as to emit a sound; - a microphone (2), arranged in a room likely to be occupied by a person, the microphone being configured to detect a sound and produce a detection signal dependent on the detected sound; - a central unit (3), configured to receive the detection signal and to analyze said detection signal; the system being characterized in that: - the central unit is programmed to recognize, from the detection signal, the sound emitted by the acoustic transmitter, and generate an alert signal when the sound emitted by the transmitter acoustics is recognized.

10. The system of claim 9, wherein the acoustic transmitter is a mechanical doorbell, the doorbell comprising a bell and a hammer, the bell being configured to emit a sound when struck by the hammer.

11. A system according to claim 9, wherein the acoustic transmitter is a mechanical cricket, emitting an audible click upon manual activation.

12. The system of claim 10, wherein the doorbell is a doorbell according to any one of claims 1 to 8.

13. A system according to any one of claims 9 to 12, wherein the central unit is configured to produce a spectrogram of the detection signal, such that the analysis of the detection signal is carried out as a function of the spectrogram.

14. System according to any one of claims 9 to 13, in which the analysis comprises a determination of a spectral power in a previously determined spectral band, corresponding to a spectral band of emission of the doorbell.

15. System according to any one of claims 9 to 13, wherein the analysis comprises an implementation of a supervised learning artificial intelligence algorithm, in particular a neural network, in particular a convolutional neural network.

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