Touch sensor in the form of a ring and associated human-machine interface

Abstract

The invention relates to a sensor assembly (R) in the form of a ring, the assembly comprising an annular element (ANN) having a substantially cylindrical shape; at least two deformation sensors (SENS1, SENS2, SENS3) mounted on the annular element on at least two radii thereof, respectively, the two radii being angularly separate from one another, so that the at least two sensors are sensitive to an overall deformation of the annular element; and an electronic module (EL) configured so as to produce a detection signal representative of the overall deformation of the annular element in response to the step of processing at least two signals transmitted by the at least two deformation sensors (SENS1, SENS2, SENS3), respectively.

Description

RING-SHAPED TOUCH SENSOR AND ASSOCIATED HUMAN-MACHINE INTERFACE TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a ring-shaped sensor, and extends to human-machine interfaces, systems allowing a user to control interactive systems, and is therefore in the field of human-machine interactions sometimes referred to by the acronym HMI. TECHNOLOGICAL BACKGROUND

[0002] Human-machine interfaces come in many forms that allow a user to interact with an electronic system, whether it is, for example, a computer, a robot, a television, a sound reproduction system, or a game console. These interfaces are designed to i) generate control signals from a user action, and then ii) transmit these signals to the electronic system.

[0003] The wide variety of actions possible for a user to control the electronic system has been used to design various types of interfaces: it can be a keyboard, a mouse, a touch screen, an optical detection system, a microphone or even a joystick, all equipped with sensors (contact, infrared, magnetometer, optical, camera, accelerometer, gyroscope, etc.) whose function is to detect a specific action by the user (movement, gesture, speech, actuation, etc.).

[0004] Among these various types of interfaces, development efforts have focused on devices in the form of a ring, generally intended to be worn around a user's finger, as described in US patent 9,582,076 B2 and in patent application US 2017 / 0242496 A1. Such devices have the advantage of minimal bulk, being able to be worn without bothering the user, but require complex sensors such as cameras intended to analyze the immediate environment of the ring and generating signals whose processing involves heavy calculations, requiring high-performance electronics, which are expensive and compromise the autonomy of these interfaces. In addition, this complexity negatively impacts the reliability of the control.

[0005] Still regarding ring-shaped devices, there are simpler design schemes, such as a ring with eight outer faces described in the article by Hyunchul Lim et al., "OctaRing: Examining pressure-sensitive multi-touch input on a finger ring device," UIST 2016 Adjunct - Proceedings of the 29th Annual Symposium on User Interface Software and Technology, Association for Computing Machinery, Inc., pages 223-224. Each of the eight faces is equipped with a pressure sensor intended to be directly pressed by the user. Various control signals can be generated depending on the pressure sensors pressed simultaneously.

[0006] Along the same lines, patent application US 2020 / 0150715 A1 describes ring-shaped systems intended to be worn on a finger. Each of these systems is equipped with one or more sensors that may be intended to detect an action of the wearer of the ring performed by the hand wearing it or to detect an action applied to it by the wearer's other hand.

[0007] Another device, a ring intended to be grasped with two hands by the user at two diametrically opposed zones, is described in patent application US 2022 / 0212112 A1. It comprises a flexible ring mounted on a base provided with a deformation sensor, the assembly being configured to generate a signal representative of the amplitude of deformation of the flexible ring when the user deforms the ring by bringing his hands closer together.

[0008] However, a human-machine interface having a general ring shape, of simple design while allowing the generation of varied control signals from equally varied user actions remains to be defined.

[0009] The applicant's objective is to propose, on the one hand, a ring-shaped deformation sensor, and, on the other hand, an application of this deformation sensor to a human-machine interaction device taking the form of a ring sensitive to the deformation of an annular element of the ring caused by a user.

[0010] To achieve this aim, a first aspect of the invention is a sensor assembly in the form of a ring, comprising an annular element of substantially cylindrical shape, at least two deformation sensors mounted on the annular element at levels of at least two radii thereof, respectively, the two radii being angularly distinct from each other, so that the at least two sensors are sensitive to an overall deformation of the annular element, and an electronic module configured to generate a detection signal representative of the overall deformation of the annular element, in response to processing of at least two signals respectively emitted by the at least two deformation sensors.

[0011] Such a sensor assembly allows the detection of a wide variety of actions on the annular element forming its mechanical structure. More specifically, mechanical actions such as pressures, taps or frictions applied to the annular element itself cause its deformation and, thanks to the presence of at least two sensors, this deformation can be characterized spatially and monitored over time. The annular element is not a simple passive support for the sensors, but participates, through its deformation, in the detection of a user action, more specifically a mechanical action causing a deformation of the annular element.

[0012] Thus, this sensor assembly allows the detection and characterization of a large number of actions, in a manner not limited to a binary detection logic of an action or to a measurement of a one-dimensional deformation amplitude. This sensor in fact makes possible the spatio-temporal monitoring of a deformation imposed on the annular element, as will be developed in more detail in the rest of the description.

[0013] It is notable that the actions do not have to be applied directly to the sensors, but can be applied at any point of the annular element, possibly at a plurality of points of this element, regardless of the presence or absence of sensors at this or these points. Furthermore, the point(s) of application of the action on the annular element do not have to be fixed, but can be movable on the surface of this annular element.

[0014] The very structure of the sensor assembly, with essentially sensors permanently fixed on an annular element, remains simple and does not include any moving parts, guaranteeing the reliability and robustness of the assembly.

[0015] According to additional non-limiting characteristics of the sensor according to the invention, considered individually or in any technically feasible combination:

[0016] - the annular element may have a monolithic structure;

[0017] - the annular element may be formed of metal;

[0018] - the at least two distinct spokes may be angularly spaced apart from each other by an angle of between 20° and 160°;

[0019] - the at least two deformation sensors may be piezoelectric type sensors;

[0020] - the at least two deformation sensors may comprise at least one thin monocrystalline piezoelectric element in the form of a plate extending in an extension plane defined by a first direction and a second direction normal to the first direction, with dimensions in the first direction and the second direction each greater than 100 µm and with a thickness less than 50 µm, a ratio of the thickness to the dimension in the first direction or the dimension in the second direction being less than 0.1.

[0021] A second subject of the invention is a human-machine interface comprising the sensor assembly according to the invention, the electronic module being further configured so as to generate a control signal for a device external to the human-machine interface in response to the detection signal.

[0022] Such an interface makes it possible to characterize in a simple, precise and time-monitored manner, a global or localized deformation of the annular element on the basis of local deformations measured by the sensors. Various control signals from an external device can be associated with the occurrences and variations in time of the deformation, which allows great flexibility of use compared to the simplicity of the device.

[0023] Indeed, the deformations of the annular element are not evaluated using a single sensor, or using a single sensor independently of any other sensors, but using at least two sensors, a minimum number sufficient to detect and characterize a wide variety of deformations of the annular element.

[0024] The deformations can in particular be deformations considered as global, that is to say that they can be detected by all the sensors. The deformation amplitudes detected by each of the sensors, of relative values ​​and respective temporal evolutions specific to each of the sensors, depend on the deformation actually applied to the annular element and allow a very fine characterization of the deformation and to associate it with an action applied on the annular element by the user. Thus, very diverse mechanical actions of the user on the annular element can be associated with as many control signals from the external device. This gives a very versatile control interface, capable of generating a very large number of control signals despite a very simple hardware architecture: a ring, two sensors and measurement and control electronics.

[0025] Furthermore, it is an interface that does not infringe on the user's privacy since it does not rely on the acquisition and processing of video or sound signals, which may contain personal information. This interface is very suitable for integration into classic-looking jewelry, including small ones.

[0026] According to additional non-limiting characteristics of the sensor according to the invention, considered individually or in any technically feasible combination:

[0027] - the interface can be configured to keep awake only a first part of the acquisition module associated with the detection and to activate second parts of the acquisition module only when it is determined that respective activations of these second parts are necessary for an analysis of the signals emitted by the at least two deformation sensors;

[0028] - the calculator can be configured to (i) classify events represented by the signals emitted by the at least two deformation sensors and (ii) generate the control signal of a device external to the human-machine interface in response to this classification;

[0029] - the control signal may be representative of at least one action chosen from a tightening, a short tightening or a long tightening of the annular element between two fingers or between three fingers, repeated or not, in a centripetal direction to the annular element; a tightening of the annular element, repeated or not, parallel to an axis of revolution of the annular element; a closing of a hand of which one finger carries the annular element or the closing of a finger carrying the annular element; and a rotation of the annular element between two fingers of a first amplitude belonging to an angular interval or of a second amplitude greater than an upper limit of the angular interval;

[0030] - the control signal may be representative of at least one action selected from a touch of the annular element by a finger; a tap of a surface by a finger carrying the annular element; a tap of a surface directly with the annular element; the application of pressure to the annular element at a point moving on the annular element around a finger carrying the annular element; a sliding of the annular element on a surface, a sliding of a finger of a first hand on the annular element in a direction parallel to a finger of a second hand carrying the annular element; a localization of any one of the preceding actions; and a snap of a finger carrying the annular element;

[0031] - the acquisition module can be configured to detect a rotation of the annular element on the basis of the signals emitted by the at least two deformation sensors; and in response to the detection step, generate a signal representative of the occurrence of a rotation of the annular element;

[0032] - the signal is representative of a rotation having exceeded an incremental angular value;

[0033] - the interface may further comprise a wireless transmission module configured to transmit signals generated by the acquisition module to the external device and a source of electrical power supply to the wireless transmission module and the acquisition module;

[0034] - the interface may further comprise a feedback device configured to signal to a user a generation of a detection signal by the acquisition module; and

[0035] - the interface may be configured to be threaded onto a part of a user or a rod of a control device of the external appliance.

[0036] The interface according to the invention can be compact, passive when piezoelectric type deformation sensors are used, and the processing of the signals generated by these sensors can be simple and light from the point of view of computational intensity, resulting in a high autonomy of the device. In addition, the detection of deformation of the ring, or, more specifically, of the annular element, can be of high sensitivity and can therefore operate without difficulty even with very rigid rings such as thick metal rings, such as commonly worn jewelry.

[0037] The invention extends to a kit comprising a human-machine interface according to the invention as well as an external device configured to be controlled by means of the human-machine interface. BRIEF DESCRIPTION OF THE FIGURES

[0038] Other characteristics and advantages of the invention will emerge from the detailed description of the invention which follows with reference to the appended figures in which:

[0039] It represents a human-machine interface according to the invention, taking the form of a ring equipped with sensors;

[0040] It represents ways of using the ring;

[0041] It represents structural features of the ring;

[0042] This is a functional diagram of elements constituting the ring;

[0043] Illustrates signals generated by the ring in response to pressure on a first sensor of the ring;

[0044] Illustrates signals generated by the ring in response to pressure on a second sensor on the ring;

[0045] Illustrates signals generated by the ring in response to pressure on a third sensor on the ring;

[0046] Illustrates signals generated by the ring in response to two successive presses on the ring's sensors;

[0047] La represents signals generated by the ring in response to long and short ring tightenings;

[0048] Illustrates the signals generated by the ring during rotational actions in opposite directions;

[0049] Laest is a representation of signals generated by the ring during a rotation action;

[0050] Illustrates signals generated by the ring in response to a strike of a finger wearing the ring on a table;

[0051] Illustrates signals generated by the ring in response to the ring being struck on a table;

[0052] It represents signals generated by the ring in response to taps on the sensors;

[0053] La represents a first and a second block of a ring usage algorithm;

[0054] Illustrates the location of a point on the ring;

[0055] It represents a third block of the ring usage algorithm;

[0056] La represents a fourth block of the ring usage algorithm; and

[0057] It represents variations in the structure of the human-machine interface of the.

[0058] Illustrates a variance curve taken from signals emitted by the sensors of the;

[0059] Illustrates a step in determining the occurrence of an event from sensor signals;

[0060] Illustrates a method of controlling the human-machine interface;

[0061] It represents a table gathering test results of the process of the;

[0062] It represents a table gathering test results of the process of the;

[0063] Illustrates actions applied to the ring of the and recognized by the process of the;

[0064] Illustrates the determination of the amplitude of a rotation of the ring;

[0065] It represents various variance profiles depending on the type of actions applied to the ring;

[0066] It represents a thin piezoelectric element; and

[0067] Illustrates a strain sensor incorporating a thin piezoelectric element; DETAILED DESCRIPTION OF THE INVENTION

[0068] An embodiment of the present invention is described by means of Figures 1 to 19 and the associated passages below. Figures 1 to 4 and 19 give information on the structure, use and operating principle of the human-machine interaction ring.

[0069] Figures 5 to 18 detail a first option for exploiting the signals generated by the deformation sensors following manipulation of the ring by a user.

[0070] Figures 20 to 27 detail a second option for exploiting the signals generated by the deformation sensors following manipulation of the ring by the user.

[0071] Figures 28 and 29 illustrate a piezoelectric element that can be used to form a deformation sensor integrated into the human-machine interface according to the invention.

[0072] Illustrates the structure and the general operating principle of the ring according to the invention, with in (A) a perspective view of a sensor assembly R according to the invention, comprising an annular element ANN instrumented by three sensors SENS1, SENS2 and SENS3. The sensor assembly R may subsequently also be designated as the ring R. The sensors may be conventional deformation sensors, for example resistive gauges, the electrical resistance of which varies with their deformation, or piezoelectric type sensors. The latter are deformation sensors based on a piezoelectric measuring element, that is to say, taking advantage of the piezoelectric behavior of a material to transform into an electrical signal a deformation that it undergoes under the effect of external forces, for example when it is stuck to a surface and the latter deforms.The annular element ANN can be made of any material capable of forming a self-supporting structure capable of being passed around a finger or a rod. The annular element can have a composite structure. Preferably, the annular element has a monolithic structure, i.e. formed from a single piece and a single material. Thus, the annular element can be formed from a metal part. This latter configuration has the advantages of a simple, robust and reliable structure.

[0073] This instrumentation of the annular element, and therefore of the ring, allows it to be coupled with an EL electronic module to form a human / machine interface in order to control, for example, an electronic device such as a computer, a smartphone, a television or even a multimedia player. In this example, three piezoelectric deformation sensors SENS1 to SENS3 are glued to the annular element, on which the EL electronic module is mounted, configured to measure the electrical charges or the electrical voltage generated by the sensors, analyze them, and return, using a wireless technique, the information to an external device such as those mentioned above.

[0074] As illustrated in (B) of the, when the ring R is taken between two fingers F1 and F2, a pressure force F is applied on either side of the ring by the fingers (the pressure force therefore being applied to the annular element ANN), which will create an overall deformation of the ring that can be characterized using the three sensors SENS1 to SENS3. More generally, and as will be detailed below, the detection of this deformation, single or repeated, and the profile of this deformation, corresponding for example to pressure between the fingers or to a strike, can be used to generate a control signal for an external device APP. Indeed, the sensors make it possible to detect the locations of the support points on the annular element, the temporal evolution of these locations, as well as the temporal evolution of the amplitude of the applied force.

[0075] As illustrated in (C) of the, when the ring is rolled between the fingers in a rotational movement Rot caused by the combination of the pressure force F and the displacements Dplt of the fingers F1 and F2, the position at which this force is applied to the annular element moves significantly, and this displacement can be measured by comparing the signals of the three sensors.

[0076] Various user actions on the ring can thus be detected and associated with predetermined actions, such as (i) a single squeeze between the fingers associated with a validation action, (ii) a double press associated with a backing up action in a menu of an application controlled by the ring, (iii) a rotation in one direction or the other associated with the control of scrolling up or down in a list or with the control of the volume of a music player, and (iv) a tap of the finger wearing the ring on a hard surface such as a table or (v) a direct tap of the ring on a hard surface such as the table associated with validation actions equivalent to a single click or a double click of a computer mouse. It is also possible to associate the intensity of the squeeze or taps, or the speed of rotation with particular commands to control the external device.Other actions may be considered, such as those listed in Tab. 1 below. In this document, when rotations are mentioned, and unless otherwise stated, it is a rotation of the ring around its axis of revolution Ax, illustrated by the. A direction of rotation may be that of the counterclockwise direction around this axis of revolution, or a direction opposite to the counterclockwise direction. An axis of revolution is here considered as an axis of revolution allowing to describe the general shape of the annular element, which extends parallel to the axis of revolution and has an overall shape having a symmetry of revolution around this axis, which includes the examples of figures 1, 3 and 19.

[0077] It should be noted that the ring taken as an example in this embodiment is equipped with three sensors, but a ring equipped with two sensors, the minimum number to spatially characterize the deformation of the ring, would also work. Using three sensors brings redundancy and an additional measurement allowing discrimination in the event of an ambiguous situation. It is also possible to use a larger number of sensors, with the disadvantages of an increase in the integration and cost of the ring, as well as a complexity of the electronic processing system to be integrated on the annular element, with an increase in the electrical contact tracks and signal processing channels, and as an advantage of better robustness of event detections.An event is here understood as a deliberate action by the user on the ring with the aim of producing a control signal from an external device, the sensors generating signals in response to this action.

[0078] Also, the sensors SENS1, SENS2 and SENS3 are shown located on the outer surface of the ring, but they could also be located on its inner surface, or even integrated into the volume of the annular element, for example by being sandwiched between two concentric rings.

[0079] In (C), a ring is illustrated equipped with two sensors SENS1 and SENS2 arranged on the inner surface of the ring, substantially at 90° to each other (the respective radii r1 and r2 make an angle of substantially 90° to each other).

[0080] The respective positions of the sensors on the ring are identified by means of rays, the center of one of the sensors defining a reference radius, the positions of the other sensors being identified by the angles made by the rays passing through their respective centers (in a sectional view along the axis of revolution Ax of the ring) with the initial radius. In the example of laen (A), the three sensors are arranged substantially homogeneously around the ring, at angular intervals of approximately 120°. In this case, the radius r1 associated with the sensor SENS1 can be considered as the reference radius, the radii r2 and r3 associated respectively with the sensors SENS2 and SENS3 being located respectively at approximately 120° and 240° from the radius r1.

[0081] There is no strict obligation to respect in the relative positioning of the sensors, with the exception of the fact that it is advisable to avoid placing two sensors in diametrically opposed positions if one wishes to spatially characterize the deformation linked to a pressure exerted at two diametrically opposed points, for example between two fingers of the user: such a symmetrical positioning of the two sensors limits the spatial characterization capabilities of the deformation. It is also preferable to space two sensors sufficiently apart from each other to facilitate this spatial characterization, which is all the easier since the deformations measured by the sensors will have different amplitudes.

[0082] Thus, it is preferable that the spokes defining the positions of the sensors are angularly spaced at angles between 20° and 160°, more preferably between 40° and 140°. Of course, the angles chosen may depend on the number of sensors integrated on the ring.

[0083] The ring may also be provided with a feedback device (FB), informing the user that their manipulation of the ring by squeezing, tapping, or rotating it has been taken into account. The FB device may be of any type conventionally used for this purpose, such as a light, sound, or haptic device.

[0084] The ring may be manipulated while it is threaded onto a part of a user, and in particular onto a finger F6 of a hand H as illustrated in (A) of the, or threaded onto a rod or wand RD of an external apparatus control system as in (B) of the. It is of course possible to construct the ring so that it is worn for example on a wrist, an arm or a leg of the user. Alternatively, the ring may be used "free" without being threaded onto any element, as illustrated by the.

[0085] The ring preferably has dimensions making it suitable for being put on a finger as would be a piece of jewelry such as a ring, with for example for the annular element ANN an internal diameter f in , illustrated in (A) of the, between 1 and 3 cm and a length L, illustrated in (B) of the, along its axis of revolution Ax between 2 mm and 2 cm. The radial thickness Thck of the annular element, defined for example by (fin - f ext ) / 2 for a perfectly cylindrical annular element with external diameter f ext , as illustrated in (A) and (B) of the, may be greater than 0.1 mm, preferably 0.4 mm, and less than 3 mm, preferably 1 mm. Such thicknesses provide sufficient rigidity for the annular element to be self-supporting while allowing deformations imposed manually by the user to be detectable, even if the annular element is formed of metal. Among the metals from which the annular element may be formed, a metal that is not very susceptible to corrosion and is hypoallergenic will preferably be chosen. This may, for example, be a metal conventionally used in jewelry such as gold, silver, stainless steel, brass, titanium, solid or plated.

[0086] Furthermore, the ring is not necessarily a closed ring, but can also be an open ring with a cut C, as shown in (C) of the. Even without rotational symmetry in the strict sense, the ring is considered to have a rotationally oriented axis Ax, shown in (B) of the and perpendicular to the plane of the page in (B) and (C) of the, located at the center of the ring and along which the ring extends. The orientation of the axis Ax is indicated by the arrowhead in the figure.

[0087] The ring element is considered to be substantially cylindrical in shape in the sense that it is suitable for being slipped onto a finger. However, the substantially cylindrical shape of the ring element can encompass various shapes, the important thing being that it can be comfortably worn on the finger by a user and that sensors can be integrated into it.

[0088] Illustrates the elements integrated on a ring R and the functional relationships between the elements composing it and with an external device. Thus, the ring R comprises, in a two-sensor configuration, two sensors SENS1 and SENS2 connected to an electronic module EL for processing the signals from the sensors.

[0089] The electronic module EL includes an acquisition module ACQ in which an analog-to-digital converter CONV receives the analog signals from the sensors SENS1 and SENS2 and converts them into digital signals processed by a digital computer CALC. The digital computer processes the digital signals, generates detection signals in response to the digital signals, generates control signals S Conof an external device APP based on the detection signals, and sends these control signals to a communication module COM. The communication module COM has the function of transmitting by conventional methods, preferably wirelessly, the generated control signals to the external device APP, remote from the ring R.

[0090] The CALC calculator is also configured to, if necessary, control the FB feedback device and trigger an action indicating to the ring user that his action on the ring has been taken into account to send a control signal to the external device APP.

[0091] A BAT battery provides the energy needed to operate the analog-to-digital converter CONV, the digital calculator CALC, the communication module COM and the feedback device FB. If the sensors are resistive gauges, the battery can also be used to power them with electrical current.

[0092] Optionally, the battery may be charged by means of an EH energy harvesting device, or "Energy Harvesting" in English terminology, such as a miniature electromechanical device configured to conventionally harvest energy from ambient vibrations or movements of the user of the ring R.

[0093] With regard to the structure of the sensor assembly, the invention is not limited to the examples mentioned above and the annular element and the sensors can be implemented in various ways, illustrated by Figures 1, 3 and 19 as described below.

[0094] Thus, the sensor assembly or ring R may comprise an open or closed annular element ANN formed from a block as illustrated in A) of the, an annular element formed from two coaxial elements ANN 1 / 2C and ANN 2 / 2C as illustrated in B) of the, or formed from two angularly complementary parts ANN 1 / 2A and ANN 2 / 2A connected by assembly elements AE, preferably rigidly to each other so as to transmit a deformation applied to one element to the other, as illustrated in C) of the.

[0095] The sensors can be mounted on the same surface, inside or outside the ring as illustrated in figures 1 and 3, or they can be mounted on different surfaces of the ring. Illustrated in A) is a configuration where the sensors SENS1 and SENS3 are mounted on an outside surface S ext of the annular element and the SENS2 sensor on an inner surface S int of this annular element, in B) a configuration where the sensors SENS1 and SENS3 are mounted on an outer surface of the annular element and the sensor SENS2 is positioned between a first coaxial element ANN 1 / 2C and a second coaxial ANN element 2 / 2Cof the annular element, in D) a configuration similar to the configuration illustrated in A), except that the sensors are mounted in recesses or notches formed on the annular element. Placing the sensors in recesses has the advantage of protecting them from external aggressions when they are directly accessible from the outside or making the ring more comfortable to wear by the user when they are located on the inner surface in contact with the skin.

[0096] The sensors can also be mounted on other parts of the annular element than its outer or inner surfaces. Thus, E) illustrates a configuration where the sensors are mounted on a surface S t of the edge of the ring, so as to be positioned according to a plane intersecting the longitudinal axis of the ring.

[0097] The sensors are mounted on the annular element so as to be integral with its deformations and thus generate signals representative of these deformations. They can be glued to a surface of the annular element, crimped between two elements of the annular element, or integrated in any other manner considered adequate by a person skilled in the art.

[0098] Any combination of the sensor implementations illustrated by Figures 1, 3 and 19 is acceptable and falls within the scope of the invention described herein.

[0099] I. Analytical option for event detection

[0100] Several types of user actions can be applied to the ring, each type of action being able to be associated with a given command of the external device allowing it to be controlled. Each action causes a deformation event of the ring, which results in the generation of signals by the sensors. Each episode of signal generation corresponds to an event that we seek to characterize and which makes it possible to go back to the type of action exerted on the ring: tightening, rotation, tapping, or other.

[0101] Analytical methods for detecting these types of action through the signals generated by the sensors are explained below, using the ring illustrated by the, therefore equipped with 3 sensors distributed homogeneously around the periphery of the ring. Similar results would be obtained with a different number of sensors or sensors distributed differently. The explanations below are intended to explain the principles on which the practitioner can base himself to implement the ring according to the invention with configurations of sensors varied in number and location.

[0102] In the figures mentioned below, the references S1, S2 and S3 are associated respectively with the signals generated by the three sensors Sens1, Sens2 and Sens3 in response to an action S00 applied to the annular element by a user. The reference "S" represents the signals S2 and S3, the reference T represents the time. The references S, S1 and T are expressed respectively mV, mV and s.

[0103] I.1 Tightening

[0104] Here we call "tightening" the action of squeezing the ring between two fingers, as illustrated by laen (B). This figure illustrates a situation in which the SENS2 sensor undergoes elongation and the SENS1 and SENS3 sensors undergo compression.

[0105] A clamping action can be detected by exceeding a detection threshold THR0 by the amplitudes of the signals generated by the sensors.

[0106] It is also possible to detect not only the occurrence of the application of a tightening, but also its angular location on the ring. Indeed, depending on the location of the applied tightening, the three sensors will provide different signals. An analysis of the relationships between the signals makes it possible to trace the location of the applied tightening, either by ab initio simulation of the ring, or by a calibration of the latter. By tightening location, we mean the determination of an angle between 0° and 180° defining the position of one of the two fingers applying the tightening pressures with respect to a reference angle, for example defined by the radius r1 of the SENS1 sensor. It is assumed that the second applies pressure at a location diametrically opposite that of the first finger.

[0107] Figures 5, 6 and 7 illustrate the results of three experimental situations in which the ring is tightened so that one of the two fingers exerting the tightening is located at, respectively, the sensors SENS1, SENS2 and SENS3, the other finger being located diametrically opposite the first finger. In (A) are represented graphs of the amplitudes of the signals S2 and S3 generated respectively by the sensors SENS2 and SENS3 as a function of the amplitude of the signal S1 generated by the sensor SENS1. In (B) are represented graphs of the amplitudes of the signals generated by the sensors SENS1, SENS2 and SENS3 from the same data as the corresponding graphs in (A), but this time expressed as a function of time T.

[0108] When, as in, one of the fingers exerting the clamping is located on the SENS1 sensor, the two curves illustrated in (A) trace approximately straight lines of the same slope. This is due to the symmetry of the ring, which means that the mechanical load is distributed symmetrically at the levels of the SENS2 and SENS3 sensors.

[0109] When, as in, one of the fingers exerting the clamping is located on the SENS2 sensor, the curve corresponding to the SENS2 sensor approximately forms a straight line of negative slope while the curve corresponding to the SENS3 sensor approximately forms a straight line of positive slope.

[0110] When, as in, one of the fingers exerting the clamping is located on the SENS3 sensor, the curve corresponding to the SENS2 sensor approximately forms a straight line of positive slope while the curve corresponding to the SENS3 sensor approximately forms a straight line of negative slope.

[0111] The fact that the amplitudes of the signals generated by the sensors SENS2 and SENS3 expressed as a function of the amplitude of the signal generated by the sensor SENS1 form substantially straight lines is representative of the fact that the ratios of the amplitudes of the signals generated by the sensors SENS2 and SENS3 to the amplitude of the signal generated by the sensor SENS1 are substantially constant. This characteristic is due to the fact that the pressure application zones on the ring remain stationary during the application of the pressure.

[0112] Also, as illustrated in (B) of Figures 5, 7 and 6, the maximum amplitude among the signals generated by the three sensors is found in the signal generated by the sensor at which one of the fingers of the user exerting the tightening is located, indicating that this location of the ring presents a deformation greater than those of the locations of the other two sensors.

[0113] A clamping action produces two absolute value peaks in the signals generated by the sensors: a first peak caused by the application of clamping pressure to the ring, and a second peak due to the release of this pressure, identified respectively by Max1 and Max2 in (B) for the signal S1. The first peak and the second peak have opposite signs.

[0114] The analysis of curves such as those in figures 5, 6 and 7 makes it possible to trace the occurrence of a tightening action as well as a characterization of this tightening action, a characterization which is a function of the areas of application of the tightening forces.

[0115] For example, a tightening action without significant displacement of the pressure application zones may be considered to have been applied to the ring if a criterion is met, according to which a ratio between the amplitudes of two of the signals is constant to within 20% of the average value of the ratio during the duration of the action. The percentage may be adjusted by the user. Detection of such an action makes it possible to rule out the possibility that an action involving significant displacement of the pressure zones on the ring, such as rotation or sliding, has been applied. In other words, compliance with this criterion implies that a pressure action of substantially constant location has been applied to the ring by a user.In order to improve the reliability of the application of the criterion, it can be applied only to signal amplitude values ​​exceeding a certain level, in order to avoid the effect of relative noise which becomes very significant for small amplitude values ​​and / or adjust the percentage.

[0116] Thus, it is important to note that an analysis of the relationships between the signals generated by the different sensors makes it possible to characterize the clamping action according to a criterion linked to a location of the fingers applying the clamping, not only at a particular sensor, but also at an arbitrary position varying continuously between two sensors. The straight lines obtained by clamping actions gradually shifting from the situation of the to that of the would show a corresponding continuous variation in the slopes of the curves. With each slope or grouping of slopes, and therefore with each ratio of amplitudes of signals generated by two sensors, it is possible to associate a particular location of the action exerted on the ring and to associate with this location a particular command of the external device.

[0117] I.2 Double tightening

[0118] Double clamping is a variation of the clamping action described above, in which the clamping action is repeated within a predefined time interval, like double-clicking a computer mouse.

[0119] This action is detected by counting for each sensor the number of maxima taking place during the predefined time interval. Illustrated in (A), (B) and (C) are the signals S (in mV) generated by the sensors in response to the double clamping actions at the levels of the sensors SENS1, SENS2 and SENS3, respectively, expressed as a function of time T (in s). The amplitude maxima (in absolute value) clearly present four maxima identified Max1 to Max4 in (A) for the signal S1. We can thus associate the occurrence of a double clamping with the detection of four maxima in absolute value in the signal generated by a sensor over a given time interval, preferably of the order of a second or less.

[0120] I.3 Long tightening

[0121] A long tightening is distinguished from a tightening that can be described as short, such as those illustrated in Figures 5 to 7, in that the tightening is maintained for a certain duration exceeding a predetermined duration threshold value THR4.

[0122] During a tightening action, the signals generated by the sensors each comprise a first maximum Max1 in the form of a peak at the start of tightening and a second maximum Max2 of opposite sign to Max1 in the form of a peak of opposite orientation when tightening is released. An event corresponds to a long tightening action when two maximums are detected, each exceeding a predetermined threshold level, which are spaced apart by a duration exceeding the predetermined threshold value THR4, as illustrated in B) of the.

[0123] The profile of the curves in B) is explained by the fact that the voltage generated by a piezoelectric sensor will gradually return to zero after application of the deformation, even without the sensor returning to its initial physical state, according to a characteristic time depending on the sensor itself and the acquisition system, i.e. approximately 0.2 s for the system having generated the signals represented here.

[0124] I.4 Rotation – Method 1

[0125] Here, we call "rotation" the action of rotating the ring between two fingers while applying a tightening force to it using the two fingers. This user action results in a deformation of the ring moving with the rotation. It is a rotation of the ring according to this principle which makes it possible to move from configuration (B) to configuration (C). The sensors can characterize this deformation and its movement, and therefore the rotation imposed on the ring, as described below.

[0126] The figure shows graphs representing signals S1, S2 and S3 (in mV) experimentally generated by the piezoelectric sensors SENS1, SENS2 and SENS3 of the ring, respectively, as a function of time T (in s), in (A) for a rotation Rot in one direction going from the sensor SENS1 to the sensor SENS2 then the sensor SENS3 (direction 1-2-3) and in (B) for a rotation in the opposite direction going from the sensor SENS3 to the sensor SENS2 then the sensor SENS1 (direction 3-2-1), by rotating the ring between two fingers.

[0127] It is found that the sensor signals oscillate in an approximately sinusoidal pattern. The oscillation maxima, which correspond to the deformation maxima at the three sensors, appear in an order imposed by the direction of rotation. The latter can therefore be deduced from the analysis of the signals generated by the sensors, by finding the maxima and determining their order of appearance. Thus, it is possible to characterize the rotation in direction, angular amplitude and speed.

[0128] I.5 Rotation – Method 2

[0129] The first method for characterizing a ring rotation is based on the order of appearance of the maximums in the deformation amplitude. A second method, based on the same signals generated by the sensors, can be considered.

[0130] Lamontre in A) and B) graphs in which the signals S (in mV) generated by the sensors SENS2 and SENS3 are expressed as a function of the signal S1 (in mV) generated by the sensor SENS1, forming two distinct curves in the plane (S1, S) defined by the signal S1 and one or other of the signals S2 and S3. In these two graphs, we follow the progress of the curves over time by moving on them in the directions indicated by the arrows.

[0131] As regards the graph in A), in a zone ZSq-Start of the graph corresponding to the start of the application of the tightening by means of the two fingers of the, it is observed that the two curves move away from the origin of the graph along straight lines until they exceed a threshold level Thr represented by a circle centered on the origin of the graph. The ratios of the amplitudes of the signals remain substantially constant, due to the fact that the zones of application of pressures on the ring remain immobile: for the moment it is a simple tightening action, already described above. The distance of each curve from the origin of the graph is defined by the root of the quadratic sum of the amplitudes of the signals concerned: either a first pair of signals consisting of the signals from the sensors SENS1 and SENS2, or a second pair of signals consisting of signals from the sensors SENS1 and SENS3.The distance from each point on these curves to the origin point (0,0) of the graph represents the root of the quadratic sum of the coordinates of the curve at that point.

[0132] In a second step, the ring is rolled between the two fingers, the amplitudes of the signal pairs remaining such that the roots of their quadratic sums remain greater than the threshold value, if not constant. This behavior is representative of a tightening exerted on the ring by a human being: it is difficult to maintain a constant tightening on the ring while rolling it between two fingers, but it is possible to maintain a certain level of tightening. The rolling results in displacements over time in opposite directions of rotation along the two curves, clockwise for the SENS2 sensor, counterclockwise for the SENS3 sensor, these two directions depending on the direction of rotation imposed on the ring. The ratios between the amplitudes of the signals generated by the SENS sensors 2et SENS3et l’amplitude du signal généré par le capteur SENS1changent continûment en raison du déplacement continu des zones de pressions appliqués sur l’anneau. La détection de ces changements est indicative de l’occurrence d’une action de rotation. L’amplitude de ces changements est représentative de l’angle de la rotation. On peut suivre la courbe et y faire correspondre une amplitude angulaire de rotation W entre deux instants donnés, par calibration ou calculs ab initio.

[0133] At the end of rotation, the finger grip is released, the signal amplitudes return to zero, which means that the curves simultaneously return to the perimeter defined by the threshold level Thr and then fall back to the point of origin of the graph, at the levels of the ZSq-End2 and Zsq-End3 zones of grip release, for the curves resulting from the signals generated by the Sens2 and Sens3 sensors, respectively. At the moment of grip release, the rotation is stopped, the pressure application points are fixed, the curves form straight lines, as for the case of a grip described above using figures 5 to 7.

[0134] The analysis of the graph in A), whether we consider a single curve or both curves, allows us to go back to the detection of a rotation action of the ring and to the characteristics (angle, duration) of this rotation by correspondence between the points of crossing of the threshold level by these curves at the beginning and at the end of the rotation action and a rotation of the ring, correspondence determined by simulation calculations or calibrations of the ring.

[0135] In practice, it may be advantageous to initiate an analysis of the curve as soon as the threshold level Thr is reached, analyze the curve continuously, generate a rotation detection signal each time the rotation angle exceeds one of a series of thresholds (for example spaced at intervals of 10° or any other predetermined value), and stop the analysis when the curves fall back below the threshold Thr.

[0136] This is illustrated in B), with the tracking of the curve representing the signal S2 expressed as a function of the signal S1, signals respectively generated by the sensors Sens2 and Sens1. The curve representing the signal S2 leaves the Thr threshold visualization circle at a point A, turns clockwise around the origin point of the graph while remaining outside the circle, then crosses it at a point B. Points A and B are angularly separated by a total rotation angle W tot During rotation, the increase in rotation angle exceeded several thresholds indicated by the values ​​W1 and W2.

[0137] I.6 Finger tap

[0138] Tapping the finger wearing the ring, preferably on a hard surface such as a table, generates a signal with a higher frequency content than the actions of squeezing or rotating the ring. The following illustrates the signals S1, S2 and S3 detected during a tap of the finger wearing the ring. The frequency components of the signals generated during a tap of the finger therefore make it possible to distinguish this action from a squeezing or rotating action.

[0139] A method for detecting a tap from the finger wearing the ring may include as a first step a sum of the signals generated by the sensors during an event to obtain a sum signal. A high-pass filter is applied to the sum signal, then a first effective RMS value H of this filtered sum signal is calculated. A low-pass filter is applied to the same sum signal, then a second effective RMS value Lof this filtered sum signal is calculated. The ratio of these two effective values ​​is then compared to a predetermined threshold value THR1. The cut-off frequencies of the applied filters can be, for example, 10 Hz. If the RMS ratio H / RMS L is greater than or equal to the threshold value THR1, then the ring deformation event is considered to have been generated by a finger tap. If the RMS ratio H / RMS L is less than the threshold value THR1, then the event is classified as a clamping. The sum of the signals can be a weighted sum, with each signal being associated with a given weighting coefficient. It is thus possible to choose the coefficients in order to choose the sensor(s) used for detection. An effective value can be defined as the square root of the average of the square of the signal value over a period of time.

[0140] I.7 Ring Tap

[0141] The approach taken for the finger tap can be applied to the ring when it is tapped directly on a surface, preferably a hard one, such as a table. The difference is that the signals generated by the sensors have a higher frequency component content than when only the finger wearing the ring is tapped on the hard surface. For example, we can compare the curves of the signals S1, S2 and S3 of the, generated when the ring is tapped directly on a table to the. Thus, this time we can compare the RMS ratio H / RMS L at a threshold value THR2 preferably higher than THR1. If the RMS ratio H / RMS L is greater than or equal to the threshold value THR2, then the event is considered to have been generated by a tap of the ring.

[0142] I.8 Tap on a sensor

[0143] Sensor tapping is an action that involves directly tapping the ring at the location of one of the sensors with a finger. The difference with clamping is that the force is applied to only one side of the ring, not both sides. In the case of the configuration illustrated in the, the sensors are tapped directly and the measured amplitudes of the signals S (in mV) generated in response by the sensors are illustrated by means of the graphs in the, with in (A), (B) and (C) the measurement results for taps on the sensors SENS1, SENS2 and SENS3, respectively.

[0144] For each of the situations (A), (B) and (C), we note that the maximum amplitude among all the signals generated by the sensors is that corresponding to the sensor at which the tap is made, and that it corresponds to the maximum amplitude of a peak.

[0145] Thus, we can identify a tap event on a given sensor by identifying the sensor whose generated signal has a peak with the highest amplitude, calculate the ratio of this amplitude to the maximum amplitudes of each of the other sensors, and, if these ratios are all greater than a threshold value THR3, consider the event as having been generated by a tap at the sensor having generated the signal having the peak with the highest amplitude, therefore the maximum amplitude.

[0146] I.9 Example algorithm

[0147] As illustrated above, several types of ring deformation events can be detected by analyzing the signals from the sensors mounted on it.

[0148] Figures 15 to 18 illustrate a method of using a ring R equipped with at least two sensors SENS1 and SENS2, according to an algorithm allowing the detection of several types of events each characterized by the signals generated by the sensors following an action by the user on the ring.

[0149] Upon user action on the ring, two digital signals S1 and S2 are generated by the two sensors SENS1 and SENS2, respectively, and the analog-to-digital converter CONV, according to the algorithm illustrated by the.

[0150] A first calculation block Bl1a has the function of discriminating background noise or accidental or purposeless manipulations from a voluntary action by the user. In the first calculation block Bl1, the CALC calculator performs the quadratic sum of the amplitudes of the signals S1 and S2 during a summation operation Bl 1-10 . During a Bl test operation 1-15, the calculator determines whether the quadratic sum Q of the signal amplitudes exceeds a predetermined threshold value Thr, indicating that an action has been deliberately performed on the ring. This test operation has a function of detecting an event measured by the ring sensors. In response to this determination, in the event that the sum exceeds the threshold value, a signal S Act action detection signal is generated and, in response to this signal, a second calculation block Bl2 is implemented and the signals S1 and S2 are recorded in a computer memory MEM in functional communication with the computer CALC during an operation Bl 1-20 . The recorded signals will be used in the following operations. Recording is stopped when the quadratic sum falls below the THR threshold value.

[0151] More generally, the amplitude of a signal representative of a sum of unaveraged signals generated by the sensors or the amplitude of a single signal, averaged or not, representative of a signal generated by a single sensor, could be used as the amplitude of the signal Q and compared to the threshold value to determine the occurrence of a voluntary action. In all cases, it is a matter of comparing the amplitude of a signal or a combination of signals, reprocessed or not, representative of a deformation of the ring, to a predefined threshold and determining that a voluntary action has been exerted on the ring when this amplitude exceeds this predefined threshold, such as the threshold level Thr represented on the. Averaging over a combination (a sum in particular) of several signals representative of signals generated by the sensors allows for better reliability in this determination.

[0152] Alternatively, in order to discriminate background noise or accidental or purposeless manipulations from voluntary user action, the test operation Bl 1-10 could relate to a variance in the amplitudes of the signals emitted by the sensors. This variance can, for example, be calculated over a sliding period of a signal or the sum, weighted or not, of several signals generated by the sensors, and can be considered as an event detection signal when it exceeds a predetermined threshold, set for example by a user: the variance of the signals becomes in fact greater when the user takes action on the ring.

[0153] The Bl test step 1-15thus has the function of detecting an exceedance of a threshold by a quantity representative of an amplitude of a signal or of a combination of signals each representative of a deformation of the annular element and generated by one or more of the deformation sensors mounted on the annular element in response to an action of the user, whether the quantity in question is derived directly from the amplitudes of the signal(s) considered, from a variance of this or these signals, or is representative of any other information derived from the signal(s) considered.

[0154] The Bl1 block is advantageous from the point of view of the autonomy of the human-machine interface: except for the detection of an event exceeding a certain threshold level, only a part of the ACQ acquisition module associated with the Bl1 block needs to be supplied with voltage, which greatly limits the power consumption of the entire device. Indeed, a comparator, an electronic device consuming very little energy, can be sufficient to implement the Bl1 block, in particular when piezoelectric sensors are used, the voltages they generate being sufficient to operate the comparator without requiring amplification.

[0155] The second calculation block Bl2 has the function of carrying out a first analysis of the signals S1 and S2, intended to detect whether or not a rotation is exerted by the user on the ring and to characterize this rotation, if applicable. When block Bl2 is implemented, the CALC calculator carries out the operations described below. In preliminary steps, (i) a counter of the CALC calculator initializes to 0 a counting variable n for incrementing rotation, at a step Bl 2-1 0, and the CALC calculator determines and assigns, to a rotation angle variable W0, the exit angle of the circle of radius Thr in the plane (S1, S2) by the signal S2 as determined according to method 2 of characterizing a rotation on the basis of the signals S1 and S2, at a step Bl 2- 15. For illustration, we can refer to the ZSq-Start zone in A) of the. In the graph in B) of the, this exit angle corresponds to the orientation of the line passing through the origin of the graph and point A located on the circle of radius Thr.

[0156] A Bl test operation 2-20 ensures that as long as the quadratic sum of the signals remains above the threshold Thr, as indicated by the filled test condition indicator Y, the next calculation loop is continuously implemented by the computer. A current rotation angle W is calculated based on the signals S1 and S2 according to method 2 during an operation Bl 2-25 . A difference W-W0 is calculated at an operation Bl 2-30 , and the result of this difference is compared during two test operations Bl 2-35 and Bl 2-45 at a positive angular threshold value Thr Ang and its opposite -Thr Ang , respectively. If the test operation Bl 2-35returns a positive result, indicated by Y in the figure, then a ROT- event determination signal is generated, representative of the fact that i) there has been rotation of the ring by an angle defined by the value of Thr Ang , and ii) this rotation is done in a direction defined as negative. Conversely, if the test operation Bl 2-45 returns a positive result, indicated by Y in the figure, then a ROT+ event determination signal is generated, representative of the fact that i) there has been rotation of the ring by an angle defined by the value of Thr Ang , and ii) this rotation is in a direction defined as positive. The ROT- and ROT+ signals can be generated in succession when the user continues a rotation. Each of these signals is generated in response to an incremental increase in this rotation imposed on the ring by the user, each of which can be associated with a control signal from the external device APP.

[0157] In response to positive results from Bl testing operations 2-35 and Bl 2-45 , the rotation increment count variable n is incremented by 1 during a Bl operation 2-55 and the current rotation angle W is assigned to the rotation angle variable W0. The count value n therefore indicates the number of times the ring has been rotated by a value Thr Ang during the rotation being analyzed and is therefore representative of a total rotation amplitude, corresponding to the sum of the n rotation increments. By repeating these operations, rotations can be followed in both directions, according to amplitude increments defined by the value of Thr Ang .

[0158] This algorithm implements method 2 of characterizing a ring rotation, but method 1 could be applied, or any other suitable method.

[0159] If the test operation Bl 2-20 returns a result N, indicating that the quadratic sum of the signals S1 and S2 has fallen below the value Thr, then another test operation Bl 2-70 is performed to check whether the count value n is 0, indicating that the analyzed event is not representative of a rotation. If this is the case, then a signal S No.Rot of detection of absence of rotation is generated and, in response, a third calculation block Bl3 is implemented during a step Bl 2-75 .

[0160] Alternatively, the test operation Bl 2-70 could be implemented independently of the count value n, by implementing the test principle described in the "Clamping" section. Thus, the test operation Bl 2-70could consist of testing whether a ratio between the signals S1 and S2 is substantially constant over the duration of the analyzed event, i.e. included in an interval defined by XX% around the average value of the ratio over the duration of the recorded event, XX% representing a percentage of the average value defined by the user, 20% for example, which constitutes a value allowing a relevant discrimination of the constancy of the ratio.

[0161] The third calculation block Bl3, illustrated by the, has the function of analyzing the signals generated by the sensors when it has been determined that this event is not generated by a rotation. More specifically, the function of block Bl3 is to discriminate the type of action among the ring tightening, finger tapping and ring tapping actions, and to characterize the tightening actions. For these purposes, the calculator implements the operations of block Bl3, the principles of which are explained in the sections Tightening, Finger Tapping and Ring Tapping described above.

[0162] First, the digitized signal S1 is filtered in parallel according to two filtering operations Bl 3-10 and Bl3 -15 employing a high-pass filter and a low-pass filter, respectively, so as to obtain two filtered signals. Each of the two signals filtered by the filtering operations Bl 3-10 and Bl 2-15 are averaged at the Bl averaging operations rates3-15 and Bl 3-25 to obtain the RMS averages H and RMS H of the two averaged filtered signals, respectively. The averaging period can be chosen by the user according to his preferences.

[0163] According to the principle explained above in the sections "Finger Tap" and "Ring Tap", a first test operation Bl 3-35 checks if the value of the RMS ratio H / RMS L is greater than a high threshold value ThrH. If a positive response, indicated by Y in the figure, is returned, then a Hit(R) detection signal is generated, representative of the fact that the event was caused by a tapping action of the ring on a rigid surface.

[0164] If a negative response to the test operation Bl 3-35 , indicated by N in the figure, is returned, then a test operation Bl 3-40 is implemented, checking whether the value of the RMS ratio H / RMS Lis greater than a low threshold value ThrL, with ThrL < ThrH.

[0165] If a positive response, indicated by Y in the figure, is returned, then a Hit(F) detection signal is generated, representative of the fact that the event was caused by a tapping action of the finger (F6) bringing the ring to a rigid surface.

[0166] If a negative response to the test operation Bl 3-40 , indicated by N in the figure, is returned, then it is determined that the event was caused by a clamping action, and a fourth calculation block Bl4 is implemented during an operation Bl 3-45 .

[0167] Bl operations 3-10 to Bl 3-40 constitute as a whole a Bl operation 3-FAanalysis of the frequency content of the signals emitted by the sensors, analysis on the basis of which is carried out a detection of the actions of tapping a finger Hit(F) and tapping the ring Hit(R), and a detection of the fact that the user's action is a tightening action, the latter being characterized more finely by the block Bl4 described below. The principle used is that the energy of a signal or of a sum of signals is distributed more predominantly in the high frequencies for the action Hit(R) than for the action Hit(F), and more predominantly in the low frequencies for tightening actions of the ring than for the action Hit(F). The block Bl3 of la illustrates a particular implementation of this principle, but other implementations could be considered by those skilled in the art to implement this principle.

[0168] Basically, it is a matter of carrying out an analysis of the energy distribution of the detected signals according to the frequencies. For example, it would be possible to carry out a Fourier transformation of the signals and to analyse the energy distribution in the frequency domain, for example by comparing the energy contained in the signals for frequencies above 10Hz and the energy contained in these same signals for frequencies below 10Hz.

[0169] The fourth calculation block Bl4, illustrated by the, has the function of analyzing the signals generated by the sensors when it has been determined that the event detected by block Bl1 is not caused by a rotation, nor by either a tap of the ring or a tap of the finger, as determined at the levels of blocks Bl2 and Bl3. More specifically, the function of block Bl4 is to characterize the type of tightening applied to the ring by the user: short tightening, long tightening, double tightening, and the location of the tightening. For these purposes, the calculator performs the operations of block Bl4 described in the sections Tightening, Finger Tap and Ring Tap described above.

[0170] Bl operations 4-10 , Bl 4-15 and Bl 4-20 of the Bl4 block allow the spatial characterization of the event being analyzed. The Bl operation 4-10 consists of calculating the ratio of signals S1 and S2, then averaging this ratio during an operation Bl4-20 averaging over the entire duration of the detected event. This average is compared to a calibration table prepared in advance and establishing a correspondence between averaged ratio values ​​and a location of a tightening applied to the ring. The calibration table can be stored in the MEM memory. Based on this comparison, a Loc signal representative of the location of the event being analyzed is generated.

[0171] Illustrates the local localization of the application of pressure (tightening, tapping) by a finger F1 on a ring R equipped with sensors SENS1 and SENS2. A table prepared in advance by calibrating the ring can indicate a correspondence between the ratio of the amplitudes of the signals generated respectively by the sensors SENS1 and SENS2 and a local localization identified by a radius r Loc angularly offset from a radius r refof reference. The same table, or a similar table taking into account the two diametrically opposed support zones existing during a tightening between two fingers, can be used to locate the start and the end of the tightening illustrated by the and therefore evaluate the angular amplitude of the rotation applied to the ring during a rotation action of the latter. In general, any action (tightening, rotation, tap) can be associated with a localization signal Loc representative of a Local localization of the action considered, on the basis of a ratio of the amplitudes of two signals generated simultaneously by two sensors located on two distinct radii of the ring.

[0172] Bl operations 4- 30 to Bl 4- 50 of block Bl4 allow to determine the type of tightening applied to the ring and having caused the generation of signals S1 and S2.

[0173] Operation Bl 4-30consists of detecting the number of peaks, i.e. the number of amplitude maxima, in absolute value, for each of the signals S1 and S2 and averaging the number of peaks detected. Alternatively, one can simply count the number of peaks detected for a signal. However, averaging over multiple signals makes the detection more robust.

[0174] Based on Operation Bl 4-30 , the test operation Bl 4-35 returns a positive response when the number of detected peaks is close to 4, for example in a range from 3.5 to 4.5 encompassing four to account for the averaging effect, as indicated by Y in the figure. In response to a positive response to the test operation Bl 4-35 , a detection signal D.Sq is generated, representative of a double tightening action (2 peaks per tightening action, therefore 4 peaks for a double tightening action, as explained in the “Double Tightening” section above).

[0175] Based on Operation Bl 4-30 , the test operation Bl 4-40 returns a positive response when the number of detected peaks is 2, as indicated by Y in the figure. In response to this detection, the time interval ΔT separating the two detected peaks is determined during operation Bl 4-45 . During a Bl test operation 4-50 , the time interval ΔT is compared to the predetermined duration threshold value THR4 as explained in the “Long tightening” section above.

[0176] If it is determined that ΔT is greater than THR4, as indicated by Y in the figure, then an L.Sq signal representative of a long clamping action is generated.

[0177] If it is determined that ΔT is not greater than THR4, as indicated by N in the figure, then a signal S.Sq representative of a short clamping action, or clamping, is generated.

[0178] Blocks Bl1 and Bl2 directly process the signals S1 and S2 generated by the sensors. Blocks Bl3 and Bl4 process the version of these signals recorded in the memory MEM during step Bl 1-20 .

[0179] An advantage of this algorithm is that it consumes minimal power, with the parts of the ACQ acquisition module associated with blocks Bl2 and Bl3 of the algorithm only being activated when it has been determined that it is necessary to use their respective functionalities.

[0180] When averaging operations are mentioned in this description, it will be understood that, unless otherwise indicated, this is averaging over time, over a duration that can be chosen by the user or the manufacturer of the human-machine interface according to the behavior desired for this interface. However, these may be durations of the order of a few tenths of a second.

[0181] Also, when we talk about a signal generated by the sensors, it could be a converted or processed signal and not only directly from the sensor, as long as it can be considered as representative of a deformation applied to the ring, that is to say as being able to be used to characterize this deformation.

[0182] Of course, those skilled in the art will be able to develop similar algorithms to enable the user to benefit from all the types of action described in this description.

[0183] Furthermore, it is entirely possible to detect actions other than those described above, such as a three-finger press, sliding a finger on the ring without rotating it ("swipe" in English terminology), flexion of the finger, extension of the hand, clenching of the fist, rotation around the finger without moving the pressure zones applied to the ring, etc.

[0184] Furthermore, those skilled in the art will understand that it is possible to implement algorithms other than those described here to exploit the signals generated by the sensors, including a so-called artificial intelligence approach, making it possible to classify the detected signals into different categories previously defined by carrying out automatic learning based on a database of signals measured during realistic actions by a user wearing the ring.

[0185] In response to the detection of events and therefore the generation of signals representative of particular actions applied to the ring, the computer can be configured to transmit these signals to the external device via the communication module COM in the form of a control signal S Con . Alternatively the control signal S Con can be a signal of a command associated with the type of action applied to the ring.

[0186] II. Learning option for event detection

[0187] The previous section presents a first option for the detection of actions applied to the ring, of the analytical type: each action applied to the ring causes a deformation of the latter, deformation resulting in the generation of signals by the sensors, which can be analyzed in order to determine the action exerted and therefore the control signal to be generated.

[0188] A second option for determining the type of action exerted on the ring is based on the classification of the event generated by this action by a computer system that has benefited from automatic learning, often referred to as "machine learning", or "deep learning" in the case of a neural network, in English terminology.

[0189] This approach can, for example, be based on the use of a neural network trained to classify events detected by sensors into different categories defined by a user or an agent responsible for the preparation and configuration of the ring. Alternatively, methods other than those of neural networks could be used, such as those of the K-nearest neighbor algorithm (sometimes abbreviated as k-NN) or decision tree forests, respectively "k-nearest neighbors" and "random decision forest" in English terminology.

[0190] For illustration purposes, this description will be based on the use of a neural network for processing sensor data. Regarding the use of neural networks for gesture detection, the following references can be referred to: (1) Nguyen-Trong, K., Vu, H.N., Trung, NN, & Pham, C. (2021), Gesture Recognition Using Wearable Sensors With Bi-Long Short-Term Memory Convolutional Neural Networks. IEEE Sensors Journal, 21(13), 15065-15079; (2) Kim, M., Cho, J., Lee, S., & Jung, Y. (2019), IMU Sensor-Based Hand Gesture Recognition for Human-Machine Interfaces. Sensors (Basel, Switzerland), 19(18), 3827; (3) Chuang, W.-C., Hwang, W.-J., Tai, T.-M., Huang, D.-R., & Jhang, Y.-J. (2019), Continuous Finger Gesture Recognition Based on Flex Sensors. Sensors (Basel, Switzerland), 19(18), 3986.

[0191] Figures 20, 21 and 22 illustrate the implementation of such an approach based on the use of a neural network, for the particular case where three sensors SENS1, SENS2 and SENS3 are used and deliver signals S1, S2 and S3, respectively. The approach consists of (i) detecting the occurrence of an event and (ii) classifying this event among a list of event classes prepared in advance. The classification is supported by the CALC computer of the, which includes a neural network that has been previously trained to classify events according to the profile of the signals delivered by the sensors.

[0192] II.1 Detection and isolation of an event

[0193] Before even considering the classification of an event, considered here as resulting from a deliberate action by the user on the ring with a view to generating a control signal from an external device, it is necessary to detect and isolate this event in a continuous flow of signals generated by the sensors in response, or not, to a deliberate action by the user.

[0194] This is a graph representing the temporal evolution of the sum Var of the variances over a sliding window of the three signals S1, S2 and S3 in the form of a curve: the abscissa axis represents time and the ordinate axis the amplitude of the sum of the variances. In the present case, the signals and the sum of their variances are representative of a deformation of the ring in response to a double tightening action, i.e. two brief tightening actions of the ring close in time, carried out for example by the right hand of a user wearing the ring on his left hand. Each peak P1 and P2 of the curve is representative of an individual tightening action.

[0195] The graph shows two variance threshold values: V S and V E , which may be the same or different. Here, V S is greater than V E , but V S could be less than V E .

[0196] The first variance threshold V S is used to determine the start of the event: when the Var curve reaches and then exceeds the threshold value V S , we consider that an event has already started. The time T0 indicates the moment when the threshold V is reached S by the curve. We consider that the event started at a time T S = T0-dT S , dT S representing a safety duration determined by the practitioner in order to include a part of the amplitude curve lower than the threshold value V S , but which may be significant for the classification of the event.

[0197] Symmetrically, the second variance threshold V E is used to determine the end of the event: when the Var curve falls below the threshold value V E , the event is considered to end. Time T2 indicates the moment when threshold V is reached Eby the curve. We consider that the event ends at a time T E = T0+dT E provided that the curve remains below the threshold value for a duration dT E , dT E representing a safety duration determined by the practitioner in order to include a part of the amplitude curve lower than the threshold value V E , but which can be significant for the classification of the event, and which also makes it possible to include in the same event two parts of a Var curve separated by a portion of curve with an amplitude lower than the V threshold E .

[0198] Thus, in the case where the curve passes below the threshold value V E , at time T1 on the, for a duration less than the duration dT E, we consider that we have only a single event. The application here is to consider an event consisting of a double clamping, with two peaks of variance amplitude close together in time but separated by a brief period where the variance of the sum of the signals is low.

[0199] An advantage of choosing V S > V E is to combine a good level of selectivity regarding the detection of an event, selectivity conditioned by a value V S relatively high, with consideration of the entire event, consideration favored by a value V E relatively low.

[0200] Of course, this principle applies to any event including brief phases of ring release, during which no mechanical force is applied to the ring, or a mechanical force too weak for the curve of the sum of the variances of the signals to exceed the threshold V E .

[0201] From a practical point of view, the sensor signals can be kept in a buffer memory, possibly part of the MEM memory, for a duration at least equal to dT S , then, in case of detection of the occurrence of an event, the signals generated by the sensors from the beginning to the end of the event can be stored in the MEM memory for processing. The width of the variance calculation window, dT S and dT E can take identical or distinct values ​​adjustable by the practitioner, 50 ms for example.

[0202] By proceeding as explained above, the start and end times of an event are determined from the signals generated by the sensors.

[0203] Larepresents a diagram summarizing the above explanations. The diagram represents a step S00 of applying an action by the user to a ring R, causing an event at the detection signals S1, S2 and S3 generated by the sensors integrated into the ring. The step S00 of generating the signals is followed by a step S10 of determining the start times Start and end times End of the event, this step comprising steps S12, S14, 16 and S18.

[0204] At a step S12, the variances Var1, Var2 and Var3 of the three signals S1, S2 and S3 generated respectively by the three sensors Sens1, Sens2 and Sens3 are calculated over a sliding window.

[0205] At step S14, the variances are summed to give the summed variance Var illustrated by the.

[0206] At a step S16, the computer determines that the summed variance Var exceeds a given threshold and generates a Trig command to trigger the recording of the sensor signals in memory MEM. The recording of data predating the generation of the Trig command can be obtained by using a buffer memory recording the data according to a sliding window. Step 16 can also be used to exit a standby phase of the parts of the acquisition module, in a similar manner to the test step Bl. 1-15 written above in relation to the algorithm of the.

[0207] At step S18, the calculator determines that the event has ended, and returns the start times Start and the end times End of this event.

[0208] II.2 Actions to detect

[0209] Preparing a training program for a neural network involves first listing the classes into which this network will be tasked with classifying the data submitted to it.

[0210] The table Tab. 1 below lists the types of action that may be interesting to identify from the recorded data of ring deformation events.ActionDescriptionDirectionVariantsSqueezeSqueeze the ring between two fingers Single, Double, TripleShort, Long3 FingerssqueezeSqueeze the ring between three fingers Single, Double, TripleShort, LongLat SqueezeSqueezes the ring taken between two fingers along its axis of revolution Single, Double, TripleShort, LongRotRotate the ringPositive, NegativeShort, Long,Small, LargeFast, SlowTouchTouch the worn ring with a finger Single, Double, TripleShort, LongKnockTap a surface with a finger wearing the ring Single, Double, TripleRing KnockTap a surface directly with the ring Single, Double, TripleSlideApply pressure to a point moving on the ring around the fingerPositive, NegativeFast, SlowSurf SlideSlide the ring placed on a surfaceRight, LeftFast, SlowUp, DownShort,LongSwipeSwipe a finger across the ring in a direction parallel to the finger wearing the ringRight, Left Hand ClosureClose hand with the ring on one finger Single, Double, TripleFinger onlyFinger SnapFinger snap Trash ,

[0211] Tab. 1

[0212] The SQ “Squeeze” action corresponds to a radial tightening of the ring between two fingers, as illustrated in (B) of the.

[0213] The 3FS “3 Fingers Squeeze” action corresponds to a radial tightening of the ring between three fingers, as illustrated in (B) of the.

[0214] The “Lat Squeeze” action LS corresponds to a tightening of the ring R between two fingers F1 and F2 which apply forces F in a direction parallel to its axis of revolution, as illustrated in (C) of the.

[0215] The action "Rot" ROT corresponds to a rotation of the ring around the finger wearing it, as illustrated in (C) of the. To identify the direction of rotation, we consider that, when observing the ring with the axis oriented Ax directed towards the observer, the trigonometric direction, that is to say the counterclockwise direction of rotation, is the positive direction of rotation.

[0216] The “Touch” action TCH corresponds to the pressure of a finger F1 of one hand of the user exerting a force F on the ring R worn around a finger of the other hand of the user, as illustrated in (A) of the.

[0217] The "Knock" action corresponds to striking a rigid surface with a finger wearing the ring.

[0218] The "Ring Toc" action corresponds to tapping a rigid surface directly with the ring worn around a finger.

[0219] The “Slide” action SL corresponds to a radial centripetal force F applied at least partially towards the inside of the ring R at a point P moving on the periphery of the ring along a trajectory Traj so as to rotate around the finger F6 carrying the ring, as illustrated in (D) of the.

[0220] The “Surf Slide” action SS corresponds to the sliding of the ring R placed on a rigid Surf surface, such as the top of a table, for example in four directions Left, Right, Up and Down parallel to the rigid surface, opposite two by two, the Left and Right directions being normal to the Up and Down directions, as illustrated in (E) of the.

[0221] The "Swipe" action SW corresponds to a rubbing of the ring in a direction parallel to the finger wearing the ring. This situation can be described as the displacement of a point of application of a centripetal force F to the ring and / or to the finger wearing it along a trajectory Traj substantially parallel to the axis Ax of revolution of the ring, as illustrated in (F) of the.

[0222] The action "Hand closure" corresponds to the formation of a fist with a hand whose finger wears the ring. Alternatively, only the finger wearing the ring can be bent. The ring is deformed by the expansion of the finger wearing it due to the latter's muscular contraction, which results in a centrifugal force applied from the inside of the ring to the outside.

[0223] The “finger snap” action corresponds to a snap of the finger wearing the ring.

[0224] The "Trash" action corresponds to user actions not related to the intention of the external device executing a command: for example, it could be a gesture such as picking up a pen or a cup. These actions can be considered as parasitic actions that should not be taken into account for the control of the external device, and the events that they generate involuntarily can be classified as such so as not to cause the generation of control signals by the CALC computer.

[0225] Some of the actions listed above may have characteristic directions or meanings and / or variations.

[0226] The Slide and Rot actions, involving an angular displacement around the axis of revolution of the ring, can be applied in the trigonometric direction (positive direction) or in the opposite direction (negative direction).

[0227] The Rot action can have two variants: Small and Large, which are characterized by the angular amplitude α of the rotation imposed on the ring, illustrated by the. We can consider for example that a rotation of an angle α included in an angular interval between 20° and 40° is a rotation of small amplitude, therefore corresponding to the Small variant. Similarly, we can consider for example that a rotation of an angle α greater than the upper limit (40°) of the angular interval, for example greater than 90°, is a rotation of large amplitude, therefore corresponding to the Large variant.

[0228] The Swipe and Surf Slide actions can be performed by moving (either a finger applying pressure for slide or the ring itself for Surf Slide) from left to right (right direction) or from right to left (left direction), from the user's point of view.

[0229] The Surf Slide action can be performed in any direction, but the right and left directions described above and the forward (Up) and backward (Down) directions can be considered first.

[0230] The Slide, Surf Slide and Rot actions can have respectively higher or lower speeds of movement of a finger on the ring, of the ring on a surface, or of rotation, corresponding to relatively slow or relatively fast movements corresponding respectively to Slow and Fast variants.

[0231] Furthermore, with the exception of intrinsically short actions (Knock, Ring Knock, Swipe, Finger Snap), each of the actions in the table can have a relatively short duration or a relatively long duration. These durations can be illustrated, for example, by means of the variances of the corresponding events, as illustrated by the graphs in (A) and (C) of the (refer to the explanations concerning the graph of the). A short action corresponds to an applied force amplitude presenting a peak and will therefore generate only a peak of the variance Var as in (A) while a long action will generate a variance remaining of relatively large amplitude over a certain duration before falling back close to zero at the end of the event, illustrated in (C) by a plateau.

[0232] Also, the actions Touch, Toc, Ring Toc, Squeeze, 3 Fingers Squeeze, Lat Squeeze, Click and Hand Closure can be repeated during the same event (see the example of which represents a double action), thus creating variants of the basic event, as illustrated in (A), (B) and (D) of the (one can refer to the explanations concerning the graph of the). One, two and three occurrences of a basic action correspond respectively to the Single, Double and Triple variants of this action, for example repeating three times in rapid succession the action Toc corresponds to the Triple variant of this action Toc.

[0233] The curves in Figures 20 and 26 are, of course, simplified curves intended to explain the principle. Curves obtained during actual measurements will generally have much less regular, or even very irregular, profiles.

[0234] Of course, each action, direction of action and variant of action can be associated with a respective control signal to an external device to be controlled by means of the human-machine interface constituted by the ring R. A high speed or a high amplitude of an action can be used to perform to generate a command of a control signal of the same type as the same action having a lower amplitude or speed, or a command of another type.

[0235] A first application example is navigation within a drop-down menu of a computer interface by means of rotation actions. A small amplitude Rot rotation can allow you to move to an item in the menu immediately adjacent to or after the current item, depending on the direction of rotation, while a large amplitude rotation will move to a more distant item in the menu.

[0236] A second application example, still concerning rotations, is that of listening to a piece of music in a list. A low amplitude rotation can be associated with volume control while a high amplitude rotation can be associated with the choice of the piece in the list to play: the piece in the list following or preceding the piece currently playing, depending on the direction of rotation.

[0237] Among the actions detailed above, some will tend to globally deform the annular element, this is particularly the case for the so-called "global" actions of tightening, rotation and closing of a hand or finger wearing the ring. The detection of these actions by the sensors distributed on the annular element will be particularly effective.

[0238] Other actions will tend to deform the annular element more locally, less globally than the actions listed in the previous paragraph, such as for example the so-called "local" actions of touching, pressing, tapping, and sliding. However, the detection of these local actions remains possible, and this with the same sensor system as for the global actions, which allows for increased integration and simplification of the sensor and the human-machine interface described in this document.

[0239] Of course, it remains possible to combine (i) the sensor assembly described here in order to detect global actions and (ii) contact sensors (piezoelectric, capacitive or other) or actuation buttons in order to generate control signals sensitive to global deformations of the ring, local actions on it, and / or combinations thereof.

[0240] II.3 Training the neural network

[0241] Training the neural network involves providing it, during a learning phase, with a set of training data corresponding to events of identified classes, the classes being transmitted to the neural network associated with the corresponding data. Based on the data and associations provided, the neural network then "learns" to recognize the events and associate each with a given class, which correspond to a user action on the ring. Ideally, each user action on the ring corresponds uniquely to a particular event class that can be determined from the signals generated by the sensors and recorded in the memory.

[0242] Once the actions generating the events that the neural network must be able to process and classify have been defined, it is necessary to produce the corresponding training data. The actions can be chosen from the table Tab. 1 presented above. One solution to produce the training data for the chosen actions is to use the ring by applying these actions to it and recording the events generated in response.

[0243] Training data can thus be obtained by recording the signals generated by the sensors for, for example, 100 repetitions of a ring deformation event caused by a given user action, and performing this operation for each type of action to be identified.

[0244] Steps S00, S10, S20 and S30 of the flowchart can be used to illustrate this process of producing training data.

[0245] In step S10, detailed above, the calculator CALC determines the start and end of an event defined by the signals S1, S2 and S3 generated in response to an action by the user of the ring in step S00.

[0246] In a step S20, the signals generated during the duration of the event are sampled and recorded in the memory MEM during a recording operation Rec. It is preferable that the same number of measurements be associated with each detected event. If, for example, the sampling of the measurement signals is done at the frequency of 100 Hz and the number of samples of each of the signals S1, S2 and S3 is fixed at 100 for a given event, the signals are recorded for a duration of one second. If the event lasts less than one second, the data is completed with zeros to maintain the number of 100 samples.

[0247] At a step S30, the recorded data are preferably normalized by a conditioning Cond implemented by the calculation unit: the amplitude of this signal averaged over the duration of the event can be subtracted from each sample of a signal, then the result can be divided by the variance of the signal during the event.

[0248] This data conditioning allows for data sets to be stored in a single format, making them easier to process and classify using the neural network. In this example, each event is associated with a matrix of 3x100 samples.

[0249] Data conditioning can be adapted to the number of sensors, the use of the ring which can influence the length of the events to be recorded, the desired sampling rate, or even the processing capacity by the computer integrated into the ring.

[0250] Steps S00 to S30 are repeated until event recordings are obtained in a number and diversity considered sufficient by the practitioner.

[0251] The recorded data here is the neural network's training data: each data record is associated with the corresponding action. Part of the data can be used for the actual training, and another part for training validation; the latter is referred to as validation data.

[0252] Neural network training conventionally involves providing the neural network with the training data and the expected results, the class of each event in the training data. At the end of the training phase, the neural network's data processing is expected to be sufficiently reliable for use in real-world conditions. The level of reliability is estimated using validation data, which allows the network's performance to be tested.

[0253] The tables in Figures 23 and 24 illustrate the results of training a neural network. For each of these examples, a neural network was trained to classify events into a number of classes corresponding to given user actions. Following training, a test was performed, the table allowing a comparison between the classifications made by the neural network and the known classes from the validation data. The training and validation data consisted of a few dozen recordings of each action that were collected from about ten different users.

[0254] The table shows the classification test results for the following actions: Touch, Toc, Squeeze, Slide_pos and Slide_neg (Slide actions in a positive and opposite negative direction, respectively), Rot_pos and Rot_neg (Rot actions in the counterclockwise and opposite direction, respectively), Surf_slide_rl and Surf_slide_lr (Surf Slide actions to the left and to the right, respectively), and Swipe_rl and Swipe_lr (Swipe actions to the left and to the right, respectively).

[0255] The table shows the classification test results for the following actions: Single_squeeze and Double_squeeze (occurrence and two occurrences of the Squeeze action during one event, respectively), Rot_neg_small and Rot_neg_large (rot actions in the opposite direction to the counterclockwise direction for small and large amplitude rotations, respectively), Rot_pos_small and Rot_pos_large (rot actions in the counterclockwise direction for small and large amplitude rotations, respectively), and Trash.

[0256] The rows of the tables correspond to the true (known) classes of the validation data and the columns to the classifications of these data by the neural network. In an ideal case, the main diagonal of the tables would include only “1”s and the other boxes would include only “0”. Preliminary results show a classification reliability of 86% and 91% respectively for the tables in Figures 23 and 24. These scores largely validate the relevance of this approach to determine user actions on the ring from sensor measurement signals.

[0257] II.4 Event classification by the neural network

[0258] Once the neural network is trained, it can be used for practical use of the human-machine interface in the form of a ring illustrated for example by the.

[0259] This is a diagram summarizing the control process of an external APP device using the R ring.

[0260] Steps S00 to S30 are carried out in the same way as for the production of training data in the previous section.

[0261] Following the conditioning of the data in step S30, the conditioned data associated with an event are provided as input to the neural network of the CALC calculator, which performs a Class classification of the event in a step S40, which makes it possible to determine the type of action having generated this event and generate a signal S Class representative of the class of the event and the type of action that generated it. Each signal S Classcan be considered as a signal for detecting an action applied to the annular element, more specifically a mechanical action resulting in an overall deformation of the annular element. The neural network determines during this step to which class the event belongs. Step S40 can be considered as a step for detecting a particular event, and the signal S Class is also a signal for detecting a given event and therefore the action that generated it.

[0262] At step S50, the CALC calculator of the ACQ acquisition module generates a signal S Con control Con in response to signal S Class and therefore to the classification of data by the neural network. This operation can be carried out for example by searching in a table for a command associated with the class of the event, contained in the control signal. Alternatively, the signal S Class , can be used as an S signal Con. The S signal Con can be sent to the external device APP through the Com communication module.

[0263] An advantage of using a neural network is that the user, provided that the network is trained, can adapt the interface's response to his or her own gestures, and can even add new detection classes to the "vocabulary" understood by the interface. Thus, unlike the analytical option I, any type of action applied to the ring and leading to reproducible events in the ring element's deformation measurement signals can be used to control the external device. A user could thus "educate" the ring R to recognize a given manipulation of the ring, regardless of whether or not this manipulation was intended by its designer.

[0264] III. Piezoelectric strain sensors

[0265] Strain sensors are used to estimate the surface deformation that an element of any mechanical system undergoes when it is subjected to external forces (force and moments of force applied to it by external elements).

[0266] A sensor particularly suitable for the ring-shaped human-machine interface described above is a thin monocrystalline piezoelectric element in the form of a plate extending in an extension plane defined by a first direction and a second direction normal to the first direction, with dimensions in the first direction and the second direction each greater than 100 µm and with a thickness of less than 50 µm, a ratio of the thickness to the dimension in the first direction or the dimension in the second direction being less than 0.1. The piezoelectric element may have a first sensitivity S xto the deformation in the first direction and a second sensitivity S y to the deformation in the second direction, a crystalline orientation of the element being able to be such that abs(S y / S x ) < 0.1, corresponding to a so-called “unidirectional” sensitivity, abs((S y +S x ) / S x ) < 0.1, corresponding to a so-called “bidirectional” sensitivity, or for at least two first directions of the extension plane making an angle between them between 30° and 60°, abs((S x -S y ) / S x ) < 0.1, corresponding to a so-called “omnidirectional” sensitivity.

[0267] Such a thin piezoelectric element is suitable for forming the basis of a passive strain sensor, which can combine accuracy, sensitivity, conformability, flexibility, lightness, stability, linearity, directivity and applicability to wide strain ranges, as described in detail in French patent application FR2303635.

[0268] Thus, this piezoelectric element can measure deformations greater than 5000 micrometers per meter with a resolution of around 1 nanometer of deformation per meter. These figures compare with those of conventional resistive gauges which can measure deformations of up to 12000 micrometers per meter but with a much lower resolution, of around 1 micrometer of deformation per meter, or with those of piezoelectric gauges in a box which are only capable of measuring deformations limited to around 300 micrometers per meter with a resolution of 1 nanometer per meter.

[0269] This piezoelectric thin element may be provided with a pair of electrically conductive layers located respectively on two opposite faces of the piezoelectric thin element.

[0270] A strain sensor may include at least one thin piezoelectric element as described above, located on a flexible sheet.

[0271] According to additional characteristics, considered individually or in any technically feasible combination:

[0272] - the at least one thin piezoelectric element can be encapsulated between the flexible sheet and another flexible sheet;

[0273] - the sensor may comprise at least one charge amplifier connected to the at least one thin piezoelectric element;

[0274] - the at least one charge amplifier can be integrated on the flexible sheet;

[0275] - the sensor may comprise a plurality of thin piezoelectric elements as described above, oriented in different directions having at least a 30° separation between them;

[0276] - the sensor may comprise a first, a second and a third thin piezoelectric elements, each having the characteristic abs(S y / S x ) < 0.1, the first direction of the second piezoelectric thin element being able to make an angle of 90° with the first direction of the first piezoelectric thin element, the first direction of the third piezoelectric thin element being able to make an angle of 45° with the first direction of the first piezoelectric thin element;

[0277] - the sensor may comprise a first, a second and a third thin piezoelectric elements, each of which may have the characteristic abs(S y / S x) < 0.1, the first direction of the second piezoelectric thin element being able to make an angle of 120° with the first direction of the first piezoelectric thin element, the first direction of the third piezoelectric thin element being able to make an angle of 240° with the first direction of the first piezoelectric thin element;

[0278] - the sensor may comprise a plurality of charge amplifiers each connected to a respective one of the thin piezoelectric elements; and

[0279] - a sensor can combine at least two sensors according to the invention electrically connected in parallel.

[0280] Each of the sensors integrated into the R ring, such as the Sens1, Sens2 and Sens3 sensors, can consist of a sensor combining one or more of the characteristics listed above.

[0281] Indeed, the man-machine interface in the form of a ring, equipped with sensors sensitive to the deformation of the annular element as a whole, can advantageously use deformation sensors having as sensitive element the thin monocrystalline piezoelectric element described above. Its advantages are multiple, we can in particular cite the sensitivity and, possibly if it is sought, the directivity of a sensor based on such an element, but also the precision, conformability, flexibility, lightness, integrability and reduced dimensions, stability, linearity, directivity and applicability to wide ranges of deformations.

[0282] The R ring will benefit in particular from the integrability and sensitivity of the thin piezoelectric element. The sensitivity allows, for example, the ANN ring element to be formed in conventional materials and dimensions for manufacturing rings: lower sensitivities would require the use of more deformable and / or thinner materials, reducing their robustness and wearing comfort.

[0283] Indeed, a classic ring, made of metal, is rigid and deforms little under the action of forces applied by fingers, (usually of amplitudes less than 10 N. Such forces generate deformations of the order of 5 µdef, which are difficult to measure using conventional strain gauges.

[0284] Resistive gauges, for example, have insufficient sensitivity for the application in question. Even if they were mounted on a ring element flexible enough to measure user-induced deformations, their power consumption would disqualify them for the intended application. Furthermore, reducing the noise of the gauges by filtering to retain only the low frequencies of the measurement signals would induce a delay that would be prohibitive for a control interface.

[0285] It is preferable to consider sensors with low energy consumption, or even passive sensors. Piezoelectric sensors meet this criterion.

[0286] A first type of piezoelectric deformation sensors is based on the use of a crystal of piezoelectric material with relatively good sensitivity to deformation and stable over time, but thick and rigid, often housed in a metal case to which it is mechanically integral, these latter characteristics making it difficult to integrate into a structure having the dimensions of the ring R and poorly suited to installation on a curved surface like that of the annular element ANN.

[0287] A second type of piezoelectric strain sensors is based on the use of composite structures comprising PZT (or lead zirconate titanoate) bars located between sheets of polymer materials, or on polymer piezoelectric films called "PVDF" for poly(vinylidene fluoride) in English terminology.

[0288] These structures are relatively flexible, but too unstable over time and sensitive to temperature for an application such as those targeted for the R ring, intended among other things to be worn around a user's finger.

[0289] On the other hand, the thin monocrystalline piezoelectric element described above meets all the criteria necessary for good integration into the ring and good functionality for it: dimensions, flexibility and sensitivity. The integrability of the piezoelectric element (ease of placing it in intimate contact with a rounded structure such as the annular element) is essential here, and its sensitivity makes it possible to detect deformations even simply applied to the finger to an annular element of comparable rigidity to a traditional metal ring.

[0290] The piezoelectric element can be formed from lithium tantalate LiTaO3 in monocrystalline form, which belongs to the 3m space group, but also from lithium niobate LiNbO3 (group 3m), lead magnesium niobate MgNb2(PbO3)3 (group P1), aluminum nitride AlN (group P63mc), barium titanate BaTiO3, potassium niobate KNbO3 or lead titanate TiPbO3 (all three from the P4mm group). Sensors

[0291] Illustrates in (A) a cross-sectional view of a SENS piezoelectric sensor based on a thin piezoelectric element PIEZO of extension plane chosen to exhibit a particular behavior, unidirectional, omnidirectional or bidirectional to a unidirectional deformation applied to it in its extension plane. The sensitivity behavior of the thin piezoelectric element (unidirectional, omnidirectional or bidirectional) is transferred to the sensor integrating this thin piezoelectric element. Such sensors can be particularly adapted to specific situations as illustrated by figures 10 to 12 commented below, but they can also be used in the context of more general applications, as will become apparent later.

[0292] In order to benefit from the thinness and therefore the flexibility and conformability of the PIEZO thin element, the SENS sensor comprises a flexible SH1 sheet on which the PIEZO thin element is fixed. The sheets are preferably made of flexible materials chosen according to the intended application, and may be made, for example, of metal, polyvinyl chloride (PVC), polyimide (PI), polyethylene terephthalate (PET), biaxially oriented polyethylene terephthalate (Mylar®) or a composite material of epoxy resin and glass fibers. The PIEZO thin element may be fixed to the SH1 sheet by means of a flexible adhesive such as an anisotropic conductive film (ACF) which further allows electrical contact as described in patent document FR 3 122 985. In use, the SENS sensor may be fixed to a surface to be characterized by means of an adhesive, for example a cyanoacrylate glue or an epoxy resin.

[0293] In addition to the thin PIEZO element, in the example of the, a charge amplifier C.AMP is also fixed on the sheet SH1 and functionally connected to two conductive layers EL1 and EL2 acting as electrodes, respectively formed on two opposite faces of the thin PIEZO element. The function of the charge amplifier is to produce a voltage corresponding to the charge applied at the input and which corresponds to the charge generated by the PIEZO element during its deformation, for the purpose of electronic processing of the generated electrical potential and to carry out an effective measurement of the deformation of the PIEZO element. Although not shown, a wire connection element, such as a cord in the form of a ribbon, is connected to the charge amplifier to connect the sensor to an external measuring device.

[0294] Illustrates in (B) a sensor similar to that of the configuration illustrated in (A), but also comprising a second sheet SH2, which may be of the same nature as the sheet SH1, which makes it possible to encapsulate the thin PIEZO element and charge amplifier C.AMP by sandwiching it between the sheets SH1 and SH2.

[0295] The thin piezoelectric element PIEZO preferably has a thickness of less than 50 µm, more preferably less than 25 µm, even more preferably less than 10 µm. Considering a piezoelectric element defined as illustrated in, a ratio of the thickness of the PIEZO element to its dimension L X in a first direction of its extension plane, and / or of a dimension Ly in a second dimension of its extension plane normal to the direction Lx, is less than 0.1, preferably less than 0.05, more preferably less than 0.01.

[0296] The SH1 sheet and, where applicable, the SH2 sheet, may have a thickness between 5 and 300 µm.

[0297] However, it is preferable that the SENS piezoelectric sensor considered as a whole be sufficiently flexible to fit the surface of the annular element to which it is to be fixed and capable of following its deformations. The practitioner will be able to decide for each application the characteristics of the thin piezoelectric element PIEZO, its support, and other elements such as the electrode layers or the means of making electrical contacts.

[0298] The flexibility of the thin piezoelectric element is advantageously exploited to fix the entirety of one of its faces in intimate contact with the curved surface of the annular element ANN (through an electrode and a possible adhesive film). In this way, this piezoelectric element is integral with the annular element, undergoes the same deformations as those undergone by the annular element where the piezoelectric element is fixed, and its deformation is therefore representative of that of the annular element.

[0299] The SH1 sheet may be made of or replaced by a flexible support such as a flexible printed circuit called "flex PCB", composed of layers of electrically insulating polymer and layers of copper, allowing the signals to be routed between the different components of an electronic circuit. Each sensor assembly may comprise a plurality of piezoelectric PIEZO elements, each having its own support, just as the electronic module controlling them may have its own. Alternatively, a single flex PCB support may accommodate all the PIEZO elements and the electronic module controlling these elements. Alternatively, a first flex PCB support may be common to all the PIEZO elements and a second flex PCB support may be dedicated to the electronic control module.

[0300] The exact type of sensor(s) to be integrated into the ANN annular element will depend on the type of action to be detected and the constraints imposed (autonomy, sensitivity, etc.), according to the designers' intentions.

[0301] The invention is not limited to the embodiment described above and variant embodiments may be made without departing from the scope of the invention as defined by the claims.

Claims

Sensor assembly (R) in the form of a ring, comprising:- an annular element (ANN) of substantially cylindrical shape;- at least two deformation sensors (SENS1, SENS2, SENS3) mounted on the annular element at levels of at least two radii (r1, r2, r3) thereof, respectively, the two radii being angularly distinct from each other, so that the at least two sensors are sensitive to an overall deformation of the annular element; andan electronic module (EL) configured to generate a detection signal (ROT-, ROT+, Loc, S.Sq, L.Sq, D.Sq, Hit(F), Hit(R), S Class ) representative of the overall deformation of the annular element, in response to processing of at least two signals (S1, S2, S3) respectively emitted by the at least two deformation sensors (SENS1, SENS2, SENS3). Sensor assembly (R) according to claim 1, wherein the annular element (ANN) has a monolithic structure. Sensor assembly (R) according to claim 2, wherein the annular element (ANN) is formed of metal. Sensor assembly (R) according to any one of claims 1 to 3, in which the at least two distinct rays (r1, r2, r3) are angularly spaced apart from each other by an angle of between 20° and 160°. Sensor assembly (R) according to any one of claims 1 to 4, in which the at least two deformation sensors (SENS1, SENS2, SENS3) are piezoelectric type sensors. The sensor assembly (R) according to claim 5, in which the at least two deformation sensors (SENS1, SENS2, SENS3) comprise at least one thin monocrystalline piezoelectric element (PIEZO) in the form of a plate extending in an extension plane (xy) defined by a first direction (x) and a second direction (y) normal to the first direction, of dimensions (L X , L Y) in the first direction and the second direction each greater than 100 µm and of thickness (L Z ) less than 50 µm, a ratio of the thickness to the dimension (L X ) in the first direction or dimension (L y ) in the second direction being less than 0.

1. Human-machine interface (R) comprising the sensor assembly according to any one of claims 1 to 6, the electronic module (EL) being further configured to generate a control signal (S Con ) of a device (APP) external to the human-machine interface (R) in response to the detection signal (ROT-, ROT+, Loc, S.Sq, L.Sq, D.Sq, Hit(F), Hit(R), S Class ). Human-machine interface (R) according to claim 7, configured to keep awake only a first part of the acquisition module (ACQ) associated with the detection (Bl 1-15) and only activate the second parts of the acquisition module when it is determined that respective activations of these second parts are necessary for an analysis of the signals (S1, S2) emitted by the at least two deformation sensors (SENS1, SENS2, SENS3). Human-machine interface (R) according to claim 7 or 8, in which the electronic module (EL) comprises a calculator (CALC) configured to (i) classify (S40) events represented by the signals (S1, S2, S3) emitted by the at least two deformation sensors (SENS1, SENS2, SENS3) and (ii) generate (S50) the control signal (S Con ) of a device (APP) external to the human-machine interface (R) in response to this classification. Human-machine interface (R) according to any one of claims 7 to 9, in which the control signal is representative of at least one action (S00) chosen from a tightening (SQ, 3SQ), a short tightening or a long tightening of the annular element (ANN) between two fingers (F1, F2) or between three fingers (F1, F2, F3), repeated or not, in a centripetal direction to the annular element (ANN); a tightening (LS) of the annular element (ANN), repeated or not, parallel to an axis (Ax) of revolution of the annular element (ANN); a closing of a hand of which one finger carries the annular element (ANN) or the closing of a finger carrying the annular element (ANN); and a rotation (ROT) of the annular element (ANN) between two fingers (F1, F2) of a first amplitude (α) belonging to an angular interval or of a second amplitude greater than an upper limit of the angular interval. Human-machine interface (R) according to any one of claims 7 to 9, in which the control signal (S Con ) is representative of at least one action (S00) selected from a touch (TCH) of the annular element (ANN) by a finger (F1); a tap of a surface by a finger carrying the annular element (ANN); a tap of a surface directly with the annular element (ANN); the application (SL) of pressure on the annular element (ANN) at a point moving on the annular element (ANN) around a finger (F6) carrying the annular element (ANN); a sliding (SS) of the annular element (ANN) on a surface (Surf), a sliding of a finger of a first hand on the annular element (ANN) in a direction parallel to a finger of a second hand carrying the annular element (ANN); a localization of any one of the preceding actions; and a snap of a finger carrying the annular element (ANN). Human-machine interface (R) according to any one of claims 7 to 11, in which the acquisition module is configured to:- detect (Bl 2-35 , Bl 2-45 , S40) a rotation (Rot, Rot_pos, Rot_neg, Rot_pos_small, Rot_pos_large, Rot_neg_small, Rot_neg_large) of the annular element on the basis of the signals (S1, S2) emitted by the at least two deformation sensors (SENS1, SENS2, SENS3); and- in response to the detection step, generating a signal (ROT-, ROT+, S Class ) representative of the occurrence of a rotation of the annular element (ANN). Human-machine interface (R) according to claim 12, in which the signal (ROT-, ROT+) is representative of a rotation having exceeded an incremental angular value (-Thr Ang , Thr Ang ). Human-machine interface (R) according to any one of claims 7 to 13, further comprising a wireless transmission module (COM) configured to transmit signals generated by the acquisition module (ACQ) to the external device (APP) and a power source (BAT) for supplying electrical energy to the wireless transmission module (COM) and the acquisition module (ACQ). Human-machine interface (R) according to any one of claims 7 to 14, further comprising a feedback device (FB) configured to signal to a user a generation of a detection signal (ROT-, ROT+, Hit(R), Hit(R), Loc, S.Sq, L.Sq, D.Sq, S Class ) by the acquisition module (ACQ). Human-machine interface (R) according to any one of claims 7 to 15, configured to be threaded onto a part (F6) of a user or a rod (RD) of an external apparatus control device (APP). Kit comprising a human-machine interface (R) according to any one of claims 7 to 16 as well as an external device (APP) configured to be controlled by means of the human-machine interface (R).

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