Flexible haptic interface, method for generating a haptic effect, and method for manufacturing the flexible haptic interface

Abstract

The invention relates to a flexible haptic interface (1) defining a touch surface (S) capable of being touched by a user, the interface comprising: - a plurality of rigid tactile elements (3) joined by a flexible carrier (4), and - in contact with each rigid tactile element (3), at least one actuator (5), the actuators (5) being arranged to transmit a mechanical excitation to the rigid tactile elements (3) in order to drive the flexible carrier (4) in contact with the rigid tactile elements (3) to vibrate with a tactilely detectable flexible-carrier vibration amplitude (f), the ratio e / L of the thickness e of the flexible carrier to the spacing L between at least two adjacent tactile elements being less than or equal to 002.

Description

[0001] Description

[0002] Title: FLEXIBLE HAPTIC INTERFACE, METHOD FOR GENERATING A HAPTIC EFFECT AND METHOD FOR MANUFACTURING THE FLEXIBLE HAPTIC INTERFACE

[0003] Technical field

[0004] The present invention relates to human-machine interfaces, and more particularly those producing haptic effects, in particular multi-point haptic effects.

[0005] Prior art

[0006] A haptic interface allows the user to interact with the environment through the sense of touch. The haptic effect is increasingly used in many applications today, for example on a smartphone, when it generates a slight vibration when a key displayed on the screen is pressed to simulate the impression of pressing a button. Haptic applications also exist for virtual or augmented reality devices, particularly to allow better immersion in video games. Haptic interfaces such as touchscreens, generating a haptic effect on a tactile surface when a user contacts it, can be integrated into many technologies such as computers, tablets and / or smartphones.

[0007] It is known to generate varied and relatively complex haptic effects on a rigid tactile surface using ultrasonic transducers emitting ultrasonic waves which propagate on the rigid surface.

[0008] With the emergence of flexible commercial products, such as foldable mobile phones and rollable televisions, there is a desire to have flexible haptic interfaces that can be integrated into such products.

[0009] The use of a simple flexible support carrying ultrasonic transducers is however limited because the waves emitted by the transducers are partly absorbed by the flexible material; the haptic effect generated is then difficult to perceive by a user applying pressure with his finger or hand on such a support.

[0010] It is also known to use pneumatic actuation to generate haptic effects on a flexible structure. Patent US10240688B2 discloses a flexible haptic interface comprising pneumatic actuators for generating a topology effect. The article by Yu et al. “Skin-integrated wireless haptic interfaces for virtual and augmented reality” (Nature, 2019) discloses a flexible haptic interface comprising magnetic actuators for generating various haptic effects. However, the spatial resolution of the haptic effects obtained with such an interface is relatively low, and the use of magnetic actuators results in high power consumption.

[0011] Finally, non-Newtonian fluids have already been used to generate simple haptic effects such as button effects and relief effects. Lochtefeld's article "Towards real organic user interfaces - using non-Newtonian fluids for self-actuated displays" (CHI13 workshop, 2013) describes a haptic device using a shear-thickening non-Newtonian fluid sandwiched between two flexible sheets placed on a fixed array of loudspeakers. A finger-perceptible topology is generated when a sound wave propagates through the fluid and locally hardens it.

[0012] Furthermore, a multi-touch haptic device can recognize simultaneous and multiple contact points. It typically includes a haptic interface and software that interprets simultaneous contacts. To be sufficiently effective, multi-touch haptic devices require good localization of haptic effects on the haptic interface, for example via localized friction modulation.

[0013] Patent FR3064504 describes a non-flexible and non-conformable interface providing localized friction modulation.

[0014] Applications FR3124617 and FR3125144 describe non-flexible and non-conformable tactile simulation interfaces comprising acoustic wave confinement zones delimited by acoustic mirrors made of acoustic metamaterials. These applications do not describe multi-point haptic interfaces.

[0015] Application US2012293441 describes non-flexible touch interfaces.

[0016] Application FR31128546 describes haptic interfaces with flexible hinges.

[0017] Application US 2017 / 005077 describes a flexible device, comprising electrical components including vibrators for providing haptic feedback and tactile sensors, the components being mounted on a flexible substrate.

[0018] Application EP 3 401 763 describes a computing device comprising a touch-sensitive surface comprising touch sensors, the device further comprising a plurality of haptic output devices. Application US 2012 / 229401 describes a haptic user interface comprising a flexible surface layer and a haptic substrate, the surface layer comprising, for example, a plurality of regions each capable of accepting touch input, and the substrate comprising a plurality of actuators.

[0019] Application US 2017 / 068318 describes a device comprising a foldable screen, a foldable housing, and input-output devices, including touch sensors and a haptic output device.

[0020] Statement of the invention

[0021] There is a need to improve flexible haptic interfaces, in particular to have a tactile interface, preferably conformable, capable of generating varied haptic effects, presenting a good spatial resolution over the entire interface, and making it possible to generate well-localized multi-point haptic effects.

[0022] Summary of the invention

[0023] The invention aims to meet this need, and it achieves this, according to a first of its aspects, thanks to a flexible haptic interface defining a tactile surface capable of being contacted by at least one user, the interface comprising:

[0024] - a plurality of rigid tactile elements connected by a flexible support, and

[0025] - superimposed on each rigid tactile element, at least one actuator, the actuators being arranged to transmit mechanical excitation to the rigid tactile elements in order to cause the flexible support to vibrate, the ratio e / L of the thickness e of the flexible support to the spacing L between at least two adjacent rigid tactile elements being less than or equal to 0.02.

[0026] By "tactile detectable" it is meant that the vibration amplitude of the hinge typically exceeds an amplitude of 1 micron under a load of between 0.05 and 0.5 N.

[0027] By "transmitting mechanical excitation to the elements" is meant inducing a vibration of the elements with a tactilely detectable amplitude, the vibration amplitude of the rigid tactile elements possibly being different from that of the flexible support, in particular lower. Thanks to the invention, it is possible to obtain haptic effects having a satisfactory spatial resolution, because the vibration of the flexible support contributes, in addition to that of the excited rigid tactile elements, to the haptic effect generated by the haptic interface.

[0028] Localized haptic effects can also be obtained, allowing the haptic interface to be used to create multi-touch haptic effects, for example.

[0029] This is made possible when some actuators of the interface are electrically powered, while other actuators of the interface are not electrically powered. Thanks in particular to the e / L ratio defined above, the rigid tactile elements in contact with the unpowered actuators act as acoustic mirrors and / or waveguides and can reflect the acoustic waves emitted by the rigid tactile elements propagating in the flexible support.

[0030] These reflected acoustic waves can interact with the incident acoustic waves in constructive interference, increasing the amplitude of the acoustic waves at the level of the active rigid tactile elements, i.e. excited by corresponding electrically powered actuators. Furthermore, since the acoustic waves are reflected by the passive rigid tactile elements, i.e. in contact with actuators not electrically powered, the vibration amplitude at the level of these elements remains limited; this allows good localization of the vibrations at the level of the active rigid tactile elements. Due to these localized haptic effects, it is possible to obtain good quality multipoint haptic effects.

[0031] This provides a haptic interface with a certain flexibility, conformability and suppleness, while offering varied and localized haptic effects with good spatial resolution.

[0032] By "conformable haptic interface" we mean a haptic interface that is adaptable to a non-planar support and capable of substantially conforming to its shape.

[0033] Preferably, the interface comprises a control circuit configured to modulate the signals sent to the actuators in order to mechanically induce a vibration of the elements and the flexible support and generate a haptic sensation on the touch surface. The control circuit is preferably configured so as to allow the modulation of each actuator to be individually controlled. The control circuit can control the signal voltage, the signal frequency, the signal phase and / or the ultrasonic frequency of each actuator individually. It can thus comprise a network of electronic switches allowing each of the actuators to be selectively activated, according to the desired excitation pattern.

[0034] The vibration of the elements and the flexible support can generate a variation in friction that can be perceived tactilely by a user moving their finger over the touch-sensitive surface. This effect, also called the "squeeze-film" effect, can give the user the impression of touching a surface with reliefs or different textures.

[0035] The vibration of the elements and the flexible support can also generate an impulse that can be perceived tactilely by a user exerting static contact on the touch surface. This effect can, for example, give the user the impression of pressing a button.

[0036] Rigid tactile elements

[0037] The invention is not limited to the excitation of individual tactile elements of a particular material, or having a particular shape. However, certain shapes and materials may facilitate the manufacture of the interface.

[0038] Thus, at least some of the rigid tactile elements, better all of the rigid tactile elements, may have a general polyhedral shape, preferably parallelepiped. The rigid tactile elements may in particular be in the form of rectangular, in particular square, blades, in front view. Alternatively, the rigid tactile elements may be in the form of circular blades.

[0039] At least some of the rigid tactile elements, more preferably all of the rigid tactile elements, are preferably made of a relatively rigid, hard and / or widespread material, such as glass, preferably borosilicate glass, silicon, a metal, for example aluminum, copper or stainless steel, or a hard polymer, in particular a polymer with a Young's modulus greater than the Young's modulus of the flexible support, for example greater than 10 GPa.

[0040] At least two rigid tactile elements may have different rigid supports from each other.

[0041] At least some of the rigid tactile elements, more preferably all of the rigid tactile elements, preferably have a substantially constant thickness, preferably between 50 microns and 5 mm, more preferably between 200 and 700 microns. At least some of the rigid tactile elements, more preferably all of the rigid tactile elements, may have a surface area of ​​at least 1 cm 2 , for example a surface with dimensions of at least 10 mm by at least 15 mm, when the elements have a rectangular blade shape in front view.

[0042] All rigid touch elements may be identical. Alternatively, individual rigid touch elements of different sizes may be combined within the same interface, depending, for example, on their location relative to the touch surface and / or the application.

[0043] Soft support

[0044] The term "support" refers to any single- or multi-layer structure that ensures the rigid tactile elements are held in position and cohesive within the haptic interface. The flexible support is preferably formed from one or more polymeric materials, which can facilitate manufacturing and the achievement of the desired flexibility for the haptic interface, while generating deformation with the desired amplitude.

[0045] The flexible backing may include polycarbonate (PC), polyethylene terephthalate (PET), poly(ethylene naphthalate) (PEN), polyetheretherketone (PEEK), KAPTON, a green polymer, or any other suitable material.

[0046] The choice of the thickness of the flexible support can be made according to its flexibility; the softer the flexible support, the greater its thickness can be while still maintaining the desired flexibility.

[0047] Preferably, the flexible support is of substantially constant thickness, the thickness preferably being between 25 and 200 microns. This low thickness allows good propagation of vibrations on the surface of the flexible support.

[0048] The flexible support may have an equivalent Young's modulus greater than or equal to 1.5 GPa, in particular less than or equal to 10 GPa.

[0049] By "equivalent Young's modulus" is meant, for a flexible multi-layer support, the average of the Young's moduli of the different layers weighted by the thicknesses of said layers.

[0050] The rigid tactile elements are advantageously made of a material that is more rigid than that or those of the flexible support. The ratio of the Young's modulus of each rigid tactile element to that of the flexible support is, for example, greater than or equal to 8, better still greater than or equal to 20, even better still greater than or equal to 50, more preferably between 80 and 90, in particular equal to approximately 85.

[0051] Rigid tactile elements can be integrated into the flexible support in different ways, depending on the structure of the flexible support.

[0052] The flexible support can consist of one or more layers.

[0053] The flexible support may in particular comprise a carrier layer and a compensation layer for the thickness of the elements. This compensation layer may extend between the rigid tactile elements, above the carrier layer.

[0054] The compensation layer and the carrier layer, when linked together at their interface between two adjacent rigid tactile elements, form multi-layer hinges, in particular bi-layer hinges, between these elements.

[0055] The carrier layer can also act as a protective layer for the rigid tactile elements and / or the actuators with which they are equipped.

[0056] Preferably, the flexible support or, in the case of a carrier layer and a compensation layer, the carrier layer, has a substantially constant thickness, preferably between 50 nm and 500 microns, better still between 25 and 100 microns, for example 75 pm.

[0057] The carrier layer alone can ensure the rigid tactile elements are held within the haptic structure. The thickness compensation layer can also play this role, in association with the carrier layer.

[0058] The rigid tactile elements can all be located on the same side of the substrate or carrier layer.

[0059] When present, the compensation layer is preferably of substantially constant thickness, preferably between 25 microns and 300 microns, preferably between 25 and 100 microns, for example 75 microns.

[0060] The flexible support may extend continuously over the entire extent of the touch surface, the rigid elements being covered by the support, the latter preferably being of constant thickness.

[0061] Alternatively, at least a portion of the rigid touch-sensitive elements, preferably all of the rigid touch-sensitive elements, may have an outer surface opening onto the touch-sensitive surface. This outer surface of the rigid touch-sensitive elements may be flush with the outer surface of the compensation layer, the outer surface of the elements and that of the compensation layer then defining a substantially smooth surface which may serve as a touch-sensitive surface for the interface.

[0062] The user then comes directly into contact with the rigid tactile elements when he brings his finger into contact with the tactile surface.

[0063] Alternatively, the rigid tactile elements and the compensation layer may be covered with a protective layer, which may or may not be identical to the carrier layer of the flexible support. This may result in a flexible support having three layers between the rigid tactile elements, when the vibration of the protective layer is mechanically coupled with that of the underlying layers. The thickness of the protective layer is preferably relatively small, so as not to unduly affect the feeling of the tactile effect at the rigid tactile elements.

[0064] The flexible support may comprise housings in which the rigid tactile elements extend at least partially, the latter being for example continuously covered by a flexible sheet defining the tactile surface.

[0065] In an exemplary embodiment, the support comprises a layer for receiving the touch elements, the receiving layer forming bowl-shaped housings, the support also comprising a layer for covering the elements, defined for example by the aforementioned flexible sheet.

[0066] The cover layer makes it possible in particular to standardize the externally tactile surface, and to avoid parasitic tactile sensations which could otherwise occur if the user were in direct contact with the rigid tactile elements and / or the neighboring regions, the latter being able to form a heterogeneous surface to the touch.

[0067] The flexible support may include notches, additions of material(s), reliefs, and / or any other structure allowing the vibrations of the flexible support and thus the haptic feeling to be modified.

[0068] Arrangement of tactile elements

[0069] The rigid tactile elements can be distributed in different ways on the support, depending in particular on the application, while respecting a spacing in accordance with the invention.

[0070] The spacing between two adjacent rigid tactile elements can be chosen according to the flexibility of the flexible support and its thickness, so as to obtain the desired vibration amplitude for the flexible support and the desired location for the vibrations in the case of a multi-point tactile effect, while preserving the flexibility of the assembly.

[0071] The softer the flexible support and / or the thinner its thickness, the closer the elements can be brought together while maintaining a vibration amplitude of the flexible support sufficient to be tactilely detectable.

[0072] Preferably, the spacing between two adjacent rigid tactile elements (measured edge to edge) is greater than 10 mm. This minimum distance of 10 mm must be large enough to allow good flexibility of the flexible support, despite the use for the flexible support of a material having the required rigidity.

[0073] Preferably, the spacing between two adjacent elements (measured edge to edge) is less than 100 mm, better still less than 50 mm, even better still less than 20 mm. This spacing is chosen so that the vibration amplitude does not attenuate excessively between two rigid tactile elements.

[0074] At least some of the rigid tactile elements may be arranged in rows and / or columns, in particular on the same plane when the flexible support is laid flat, preferably in a regular network.

[0075] Alternatively, the rigid tactile elements are arranged in a concentric or other distribution.

[0076] Actuators

[0077] Each rigid touch element may be provided with at least one actuator, for example on its face located on the side of the flexible support and / or its opposite face, preferably the face opposite the flexible support.

[0078] Each actuator can be arranged on a vibration antinode of the associated rigid tactile element.

[0079] Each actuator may be of the piezoelectric, ferroelectric, electromagnetic or thermal type, preferably of the piezoelectric type. In particular, each actuator may be ceramic piezoelectric, for example PZT ceramic piezoelectric, or AIN piezoelectric.

[0080] The actuators may be in the form of a thin layer, for example in the form of a thin layer of PZT. Preferably, the shape and arrangement of the actuators are chosen so as to obtain the desired vibration mode(s) on the rigid tactile element.

[0081] The actuator(s) associated with a rigid tactile element may each have an elongated shape, preferably according to the width of the rigid tactile element in contact with which it is located in the case where the latter has a rectangular shape.

[0082] The actuator(s) may be arranged on either side of a median plane of the rigid tactile element. The actuator(s) may be arranged at vibration nodes or antinodes.

[0083] Actuators can be of various shapes; for example, they each have a general polygonal shape, notably rectangular or square, or a circular or annular shape.

[0084] It is also possible to combine several forms of actuators on the same rigid tactile element in order to be able to generate several different vibration modes, for example alternately, which makes it possible to obtain varied haptic effects.

[0085] Ancillary systems

[0086] The interface may comprise a system for detecting a user's contact on the touch-sensitive surface, in particular a capacitive detection structure, which is, where appropriate, integrated into the haptic structure. Alternatively, the system for detecting a user's contact on the touch-sensitive surface is an impedance tracking or voltage tracking structure.

[0087] The interface may include a system for superimposing an image at least partially on the touch surface. The interface may thus include a screen, preferably a screen integrating the haptic structure. The screen may in particular include OLED-type pixels.

[0088] The interface may comprise at least one actuator for selectively conforming the interface to at least two distinct shapes. This may be useful, for example, for changing the shape of the interface depending on the tactile sensation to be reproduced, for example to improve the quality of the simulation.

[0089] The invention also relates to a clothing item equipped with a haptic interface according to the invention, as defined above. The invention also relates to a mobile device equipped with a haptic interface according to the invention, as defined above.

[0090] Alternatively, the haptic interface according to the invention is integrated into a fabric, a bracelet, a display or any other curved surface.

[0091] In particular, the haptic interface according to the invention can be integrated into a dashboard. Indeed, the haptic effects created by the interface make it possible to interact with the dashboard by touching it, without having to look at it.

[0092] Haptic interface can be used for braille surfaces.

[0093] The interface may include additional means of vibration, for example a small local vibrator, or fluidic technology enabling vibration.

[0094] Method for generating a haptic effect

[0095] The invention also relates to a method for generating a haptic effect, in particular a multi-point haptic effect, with a flexible haptic interface according to the invention, as defined above, a method in which at least one rigid tactile element is mechanically excited using one or more actuators superimposed on this rigid tactile element, in order to cause the flexible support to vibrate with a tactilely detectable vibration amplitude.

[0096] The features of the flexible haptic interface described above apply to the method in combination or independently of each other.

[0097] The method according to the invention may comprise the prior detection of the position(s) of a user's contact(s) on the haptic interface using a detection system, then the modulation, using a control circuit, of the signals sent to the actuator(s) as a function of the detected position(s) in order to mechanically induce a vibration of the rigid tactile elements and the flexible support and generate a haptic sensation on the tactile surface.

[0098] This allows the desired haptic effect to be generated in the detected contact area.

[0099] The method may comprise the selective excitation of a single actuator or only some of the actuators, according to a predefined excitation pattern; the excitation may be carried out so as to excite a given actuator without exciting any of the closest actuators, or without exciting any of the actuators surrounding the one being excited; the excitation may also be carried out by exciting several actuators aligned with each other, without exciting the closest actuators located on the same side of the line connecting the excited actuators or on either side of this line. Other actuator excitation patterns are possible, depending on the desired result.

[0100] Excitation of rigid tactile elements

[0101] The invention is not limited to a particular mechanical excitation of the rigid tactile elements. However, certain types of excitation, and in particular certain vibration modes of the tactile elements, facilitate the vibration of the flexible support and make it possible to generate haptic effects in a relatively reliable manner.

[0102] Thus, rigid tactile elements can be mechanically excited according to a first vibration mode called “bending mode”.

[0103] Alternatively, the rigid tactile elements can be mechanically excited in an antisymmetric Lamb mode.

[0104] The rigid tactile elements are mechanically excited at a frequency preferably between 20 and 250 kHz, better still between 20 and 100 kHz, in particular to make each rigid tactile element vibrate at a mechanical resonance frequency.

[0105] Rigid tactile elements are preferably chosen to enter into resonance at a co frequency greater than or equal to 20 kHz. The resonant co frequency of rigid tactile elements can be defined by the following formula: a> = with Prigtde the density of rigid tactile elements, h rigide the thickness of the rigid tactile elements, E rigide Young's modulus of rigid tactile elements, has rigide the characteristic dimension of a rigid tactile element, v rigide Poisson's ratio of rigid tactile elements and fi a coefficient characteristic of the shape of the rigid tactile element, various examples of which are given in Harris's book, Shock and Vibration Handbook.

[0106] The flexible support is chosen so that the acoustic wave propagating on its surface is tactilely detectable by a user, i.e. the wavelength 2 of the acoustic wave propagating on the surface is preferably greater than 2 mm. The wavelength 2 can be defined by the following formula: 2 = 2TT with p flexible support the density of the flexible support, h-soft support the thickness of the soft support, co the vibration frequency of the rigid tactile elements defined above, and D the bending rigidity of the soft support, such that D = a vec E soft support æ Young's modulus of the soft support and h-soft support the thickness of the soft support.

[0107] The signals sent to the actuators can be modulated at a frequency lower than 1000 Hz, particularly to modulate friction. This modulation of the signals sent to the actuators enables ultrasonic lubrication, among other things. By "ultrasonic lubrication," we mean the reduction of friction due to the squeeze film and intermittent contact when a finger passes over the surface, for example. This can improve the haptic feel.

[0108] At least one actuator of a rigid touch element located in the vicinity of an energized rigid touch element may not be electrically powered.

[0109] In the remainder of this document, the assembly consisting of an actuator, an associated rigid tactile element and a part of the flexible support superimposed on the rigid tactile element is called a haptic resonator.

[0110] The assembly composed of a rigid tactile element, one or more non-electrically powered actuators, and a part of the flexible support superimposed on these elements, is called a passive haptic resonator, as opposed to an active haptic resonator.

[0111] An active haptic resonator can enable ultrasonic vibration of the soft media in a specific mode, which enables ultrasonic lubrication.

[0112] A passive haptic resonator may reflect and / or guide ultrasonic waves generated by one or more neighboring active haptic resonators and / or act as a barrier to ultrasonic waves generated by one or more neighboring active haptic resonators.

[0113] One actuator of a given first rigid tactile element can be excited, without exciting all the actuators of the rigid tactile elements surrounding this first rigid tactile element. Passive haptic resonators in the vicinity of an active haptic resonator can be considered as acoustic mirrors. Indeed, they can reflect the ultrasonic waves emitted by one or more neighboring active haptic resonators, due to the difference in acoustic impedance.

[0114] The waveguides and / or acoustic mirrors created by passive haptic resonators allow the ultrasonic waves emitted by active haptic resonators to be confined and / or amplified, and allow for good localization of the ultrasonic vibrations at the active haptic resonators. This also allows the use of the flexible haptic interface to create multi-point haptic effects. Due to the localization of the vibrations generated by the resonators, the sensations can be localized.

[0115] At least two active resonators can be excited with different signals, particularly with signals having modulations at different frequencies and / or amplitudes, so as to create a multi-point haptic effect. This can make it possible to obtain different sensations on the tactile surface.

[0116] Preferably, the reflection coefficient by a passive haptic resonator of the ultrasonic waves emitted by an active haptic resonator is greater than 50%, better still greater than 70%, even better still greater than 90%.

[0117] By "coefficient of reflection by a passive haptic resonator of ultrasonic waves emitted by an active haptic resonator" we mean the value of R given by the formula: 1 imp redance acoustics of the soft support and Z act +rigide+soupie the acoustic impedance of the assembly composed of an actuator, a rigid tactile element and the flexible support in contact with the rigid tactile element, this latter impedance being substantially equal to the acoustic impedance of a rigid tactile element Z rigide , Or

[0118] Z support flexible the P support flexible XC support flexible? P support flexible being the density of the flexible support and csupport SOupie the speed of the acoustic wave in the flexible support, and

[0119] Zrigid = Pngid x Rigid, where Pngid is the density of the rigid tactile element and Crigid is the speed of the acoustic wave in the rigid tactile element, with c = l 2p (-1 + the speed of an acoustic wave in a material with Young's modulus E, density p and Poisson's ratio v.

[0120] Realization

[0121] The invention also relates to a method for producing a haptic interface as defined above, comprising the steps consisting of:

[0122] (a) Manufacture an assembly comprising rigid actuators and tactile elements,

[0123] (b) Producing the haptic interface with said assembly. Step (a) may include:

[0124] (al) the production of a lower electrode by depositing, preferably by photolithography or by screen printing, at least a first layer of a conductive material on the upper face of a rigid support, preferably a glass or silicon support,

[0125] (a2) depositing a conductive glue on the lower electrode,

[0126] (a3) placing the actuators, preferably piezoelectric, on the first layer thus formed by the lower electrode and the conductive glue, so as to establish a first electrical connection with the actuators,

[0127] (a4) depositing a layer of an insulator on the previously deposited layers, for the insulation of the lower electrode,

[0128] (a5) thinning, for example by chemical or laser etching, by abrasion, by compression, or by dissolution, of the insulating layer in order to expose the upper face of each actuator,

[0129] (a6) the production of an upper electrode by depositing, preferably by evaporation or by screen printing, a layer of a conductive material on the actuators thus exposed, so as to establish a second electrical connection with the actuators,

[0130] (a7) cutting or engraving the rigid support, for example into a square or rectangle, so as to obtain tactile elements each equipped with one or more actuators.

[0131] The method of step (a) makes it possible in particular to simply manufacture several tactile elements from the same support, for example a glass plate.

[0132] Alternatively, steps (a2) and (a3) ​​may be replaced by a step corresponding to the deposition of lead zirconate titanoates (PZT) in a thin layer on the lower electrode, by a conventional thin layer deposition technique, in particular by vacuum evaporation.

[0133] The rigid actuator / touch element assemblies obtained in step (a) can then be attached to a flexible support to form a haptic interface according to the invention. Step (b) can thus comprise:

[0134] (bl) the deposition, in particular the lamination, of a separation film, in particular thermal, on a manufacturing support,

[0135] (b2) the deposition, in particular the lamination, of a layer of flexible material, preferably polymer, on the separation film,

[0136] (b3) the deposition, in particular by screen printing, of electrical tracks on the layer of flexible material,

[0137] (b4) the deposition, in particular by screen printing, of a conductive glue on the layer of flexible material,

[0138] (b5) the installation of the previously produced tactile elements, equipped with one or more actuators, on the layer of conductive adhesive thus deposited, the actuators being arranged on the outer face of the tactile elements,

[0139] (b6) electrically connecting each lower electrode to the electrical tracks, preferably by masking and spraying a conductive material,

[0140] (b7) the release of the haptic interface from the manufacturing support, in particular by heating the separation film when it is thermal, this can also allow the manufacturing support to be recycled and / or recovered,

[0141] (b8) cutting the haptic interface according to the desired design.

[0142] Step (b) may further comprise an additional step, in particular between steps (b6) and (b7), corresponding to the addition of a passivation layer, in particular an insulating varnish, to electrically insulate the lower part of the haptic interface, the lower part of the haptic interface corresponding to the surface comprising the rigid tactile elements and the actuators, opposite the tactile surface.

[0143] The conductive adhesive used in step (a) and / or step (b) may be an epoxy adhesive. Brief description of the drawings

[0144] The invention may be better understood by reading the detailed description which follows, non-limiting examples of its implementation, and by examining the attached drawing, in which:

[0145] [Fig IA] is a schematic and partial longitudinal sectional view of an example of a haptic interface according to the invention,

[0146] [Fig IB] is a partial, schematic top view of the haptic interface of Figure 1 A,

[0147] [Fig 2A] is a perspective view of the haptic interface of Figure 1B,

[0148] [Fig 2B] is a bottom view of the haptic interface of Figure 2A,

[0149] [Fig 3 A] is a simulation of the displacement field of an active haptic resonator without (left) and with (right) neighboring passive haptic resonators, on a regular array of nine resonators as on the haptic interface of Figures 1 A to 2B,

[0150] [Fig 3B] and [Fig 3C] are laser vibrometer measurements of the displacement field of the interface of Figure 1B with a central active haptic resonator and neighboring passive haptic resonators,

[0151] [Fig 4] is an experimental measurement of the vibration amplitude of an active haptic resonator with a neighboring passive haptic resonator,

[0152] [Fig 5] is a simulation of the displacement field of the haptic interface of Figure 1B with multi-point haptic effects,

[0153] [Fig 6] is an experimental measurement of the displacement field of the haptic interface of Figure 1B with multi-point haptic effects,

[0154] [Fig 7] is an experimental measurement of the displacement field of the haptic interface of Figure 1B with other multi-point haptic effects,

[0155] [Fig 8] is an experimental measurement of the displacement field of the haptic interface of Figure 1B with other multi-point haptic effects,

[0156] [Fig 9A] and [Fig 9B] illustrate vibration modes of a rigid tactile element according to the invention,

[0157] [Fig 10A], [Fig 10B] and [Fig 10C] represent steps of an example of a method for producing a flexible haptic interface according to the invention.

[0158] Detailed description In the drawings, the actual proportions have not always been respected, for the sake of clarity.

[0159] Figures 1A to 2B illustrate an example of a flexible haptic interface 1 according to the invention. The interface 1 comprises a haptic structure 2 defining a tactile surface S capable of being contacted by a user and on which a haptic effect can be generated.

[0160] The haptic structure 2 comprises rigid tactile elements 3, only two of which are shown in FIG. 1 A, carried by a flexible support 4. The rigid tactile elements 3 are for example made of glass, in particular borosilicate glass, or silicon. The rigid tactile elements 3 are for example fixed to the flexible support 4 using a layer of conductive adhesive 46, in particular a layer of epoxy adhesive.

[0161] Throughout the description, including the claims, the expression "in contact" must be understood as including the possible presence of a thin layer of glue used to assemble the adjacent parts. Thus, the rigid elements 3 and the flexible support 4 are considered to be in contact.

[0162] The flexible support 4 forms hinges 40 extending between the tactile elements 3.

[0163] In the example considered, each tactile element 3 is provided with a single actuator 5, preferably a piezoelectric actuator, for example made of lead zirconate titanoate (PZT), the latter being for example fixed to the rigid tactile element 3 using a layer of glue 51, in particular epoxy. The actuator 5 is connected to a control circuit 6 visible in FIG. 1B using electrical connections 50. The electrical connection between the actuator 5 and the control circuit 6 is notably enabled by layers 26, 24, 36 and 46 of electrically conductive materials. Furthermore, a layer 58 of an electrically insulating material makes it possible to electrically insulate the electrodes of the actuator 5.

[0164] The actuators may further be covered on the side opposite the support 4 with a layer 48 of a protective material.

[0165] The control circuit 6 is configured to modulate the signals sent to each of the actuators 5 in order to mechanically induce vibrations therein and to selectively mechanically excite one or more rigid tactile elements 3. The excitation of a rigid tactile element 3 locally causes the flexible support 4 to vibrate.

[0166] The arrangement of the tactile elements 3 on the flexible support 4, and in particular the spacing L between two adjacent rigid tactile elements 3, is chosen so that when the tactile elements 3 are mechanically excited using the actuators 5, the resulting vibration amplitude of the flexible support is tactilely detectable.

[0167] The spacing Z between two rigid tactile elements 3 is also chosen so that the haptic interface allows the generation of localized, and optionally multi-point, haptic effects. The ratio e / L thus respects the relationship e / L <0.02, where e denotes the thickness of the flexible support.

[0168] The haptic structure 2 can be of any shape and size. Its dimensions are, for example, in the order of cm, dm or meters, depending on the application.

[0169] The rigid tactile elements 3 may have a varied shape when viewed from the front, for example rectangular, square, circular or other. Their largest dimension is for example between a few hundred microns to a few cm on each side, preferably from 2 mm to 1 cm on each side.

[0170] The rigid tactile elements 3 can be distributed on the support 4 according to various configurations.

[0171] For example, as illustrated in Figure 1B, the elements 3 are distributed in three rows and three columns on the support 4, according to a regular network.

[0172] In other embodiments (not illustrated), the interface 1 comprises rigid tactile elements 3 of different sizes and / or shapes, or even rigid tactile elements 3 arranged in a concentric or staggered distribution.

[0173] In particular, we can play on the size of the rigid tactile elements 3 in order to generate haptic effects tactilely simulating more or less large patterns.

[0174] The rigid tactile elements 3 are arranged on the support 4 in such a way that the haptic structure 2 retains overall flexibility in at least one direction, and better in all directions.

[0175] However, as mentioned above, this arrangement is subject to certain constraints to obtain an effect that is tactilely perceptible by the user. A vibration of the flexible support or of the tactile elements is considered to be tactilely perceptible when its amplitude typically exceeds 1 micron under a load of between 0.05 and 0.5 N.

[0176] The vibration amplitude of a rigid tactile element 3 depends, among other things, on its dimensions, its rigidity and the vibration mode in which it is activated.

[0177] The vibration amplitude of the flexible support depends on its thickness e, the characteristics of the material(s) constituting the flexible support 4, and the spacing L between two rigid tactile elements 3.

[0178] Figure 3A i) illustrates a numerical simulation, on the commercial software COMSOL, of a central active haptic resonator 77a surrounded by a large expanse of flexible support without other haptic resonators.

[0179] In comparison, Figure 3 A ii) illustrates a numerical simulation, on the commercial software COMSOL, of the same active haptic resonator 77a in a regular network of nine haptic resonators such as that of the interface of Figures 1A to 2B, the active haptic resonator 77a being the central resonator of the network and the other eight haptic resonators being passive haptic resonators 77b. This figure shows the effect of the acoustic mirror as well as the waveguide created by the passive haptic resonators 77b.

[0180] Figures 3B and 3C illustrate two experimental validations using a laser vibrometer of the observations in Figure 2A ii). A central zone of localized friction is always identified, corresponding to the active haptic resonator 77a, the waves being confined to the level of this resonator thanks to the eight passive haptic resonators 77b.

[0181] Figure 4 illustrates a similar experimental validation, comprising a single passive haptic resonator 77b adjacent to an active haptic resonator 77a. The attenuation of the acoustic wave is clearly observed at the hinge 40 between the two resonators 77a and 77b. This is an attenuation of type exp( — a X r), with r the distance to the active haptic resonator and a the damping coefficient of the amplitude of the wave, where a = - d —i —stan -ce . The esp rThe distance L between the rigid tactile elements 3 is determined in particular as a function of the damping coefficient a, or the quality factor i

[0182] Q = — of a resonator (a haptic resonator can be considered as a harmonic oscillator), because we seek not to have a total attenuation of the wave between two haptic resonators. Figure 5 illustrates a simulation with COMSOL software of a multipoint haptic effect on the haptic interface with nine rigid tactile elements arranged in a regular network excited at a frequency of 30.2 kHz; we observe two friction zones located at the level of two active haptic resonators 77a, while the other seven haptic resonators 77b are passive.

[0183] Figure 6 illustrates the experimental results obtained with two active haptic resonators 77a and seven passive haptic resonators 77b. The friction zones located at the level of the resonators 77a are clearly identifiable.

[0184] It is possible, thanks to the control circuit 6, to modulate differently the signals sent to the actuators 5 of the two active haptic resonators 77a in order to mechanically excite the resonators 77a differently. For example, the first active haptic resonator 77a can be modulated at 50 Hz to obtain a feeling of large vibrations, and the second active haptic resonator 77a at 250 Hz to obtain a feeling of fine vibrations.

[0185] Figures 7 and 8 illustrate experimental results obtained for excitation patterns where some resonators are active while others are passive.

[0186] In Figure 7, three active resonators 77a are identified on the top row and one active resonator 77a on the bottom right. The vibration amplitude at these resonators is significant, unlike that observable at the five passive resonators 77b.

[0187] In Figure 8, three active resonators 77a are identified, respectively at the top left, top right and bottom right. The vibration amplitude at these resonators is significant, unlike that observable at the six passive resonators 77b.

[0188] These observations confirm that the passive haptic resonators 77b act as acoustic mirrors to localize vibrations at the active haptic resonators 77a.

[0189] Thanks to the actuators 5, the tactile elements 3 can be made to vibrate according to vibration modes adapted to generate the desired haptic effects at their level.

[0190] Preferably, rectangular actuators are used to obtain a Lamb mode, illustrated in Figure 9B, and square and / or circular actuators are used to obtain an out-of-plane mode such as the bending mode, illustrated in Figure 9A. The flexible haptic interface 1 described above can be produced by the method comprising the steps illustrated in Figures 11A to 1IC, and described below.

[0191] In step i, a first layer 24 of an electrically conductive material, for example gold, is deposited on the upper face of a rigid plate (precursor of the elements 3), in particular a glass or silicon plate, the rigid plate being for example of a thickness substantially equal to 500 μm.

[0192] Layer 24 is, for example, gold deposited by photolithography or screen printing. Alternatively, layer 24 is silver ink deposited by screen printing, for example to a thickness of between 5 and 12 μm.

[0193] The layer 24 is discontinuous: for example, it comprises several separate sections 24a and 24b which form the electrical supply tracks of the actuators 5 which will come into contact with the tactile elements 3.

[0194] The thickness of layer 24 is for example 300 nm.

[0195] In step ii, a conductive adhesive 51, for example an epoxy adhesive, is deposited on the layer 24, for example to a thickness of 30 μm.

[0196] Then, in step iii, actuators 5 are put in place, comprising for example a lower electrode 52, a piezoelectric or ferroelectric layer 54 and an upper electrode 56. Alternatively, the actuators 5 only comprise the layer 54.

[0197] The lower electrode 52 of the actuators 5 is then connected to the track 24 by means of the conductive adhesive layer 51. The deformation of the layer 54 under the effect of a potential difference applied between the electrodes is transmitted to the element 3 by unimorphic effect in the layer 51.

[0198] Layer 54 is for example of lead zirconate titanoate (PZT) type. It can also be made of aluminum nitride (AIN), zinc oxide (ZnO) or any other suitable piezoelectric or ferroelectric material. Layer 54 can further be thinned and adjusted to the desired thickness.

[0199] In particular, a commercial piezoelectric ceramic can be used for the actuator 5, or the actuator 5 can be formed by depositing thin layers and shaping them on the rigid precursor plate of the elements 3, as described in patent FR3082997.

[0200] In step iv, each actuator 5 is then covered with an electrical insulation layer 58, for example made of a polymer material, in order to hold the actuator 5 and to insulate the electrodes 52 and 56. Only a portion of the power supply track 24 remains uncovered.

[0201] The insulating layer 58 is then thinned from above in order to uncover the electrode 56, with a view to depositing, in step v, a layer of conductive material 26 connecting the upper electrode 56 with the power supply track 24.

[0202] Layer 26 is in particular a titanium deposit, with a thickness of 20 nm or 500 nm for example, obtained by evaporation. Alternatively, layer 26 is silver ink obtained by screen printing, with a thickness of 5 to 12 microns for example.

[0203] The rigid precursor plate of elements 3 can then be thinned on the rear face, in particular by grinding, for example to a thickness of 400 microns.

[0204] The plate can finally be cut, in step vi, in order to obtain rigid tactile elements 3 of the desired size, square or rectangular for example, and equipped with the number of actuators 5 provided.

[0205] The rigid tactile elements 3 provided with their actuators 5, thus obtained, can subsequently be transferred and fixed on a flexible substrate 4 to form a haptic structure 2, for example following the production steps described below. In particular, a haptic structure 2 such as that previously described can be obtained according to the following steps.

[0206] In step vii, a thermal film 101, for example an adhesive tape which adheres strongly at room temperature and can be easily removed by heating it, in particular to 170°C, is laminated onto a manufacturing substrate, in particular a silicon wafer 100.

[0207] In step viii, a flexible layer 4 is formed on the thermal film 101, for example a layer of KAPTON or PEEK, in particular by lamination. The flexible layer

[0208] 4 must be able to withstand the temperature at which the thermal film 101 disintegrates, in particular 170°C.

[0209] Then, in step ix, a layer of an electrically conductive material 46 is deposited, for example silver ink deposited by screen printing to a thickness of between

[0210] 5 and 12 microns, in order to form the electrical connection between each actuator 5 and the control circuit 6. The layer 46 is discontinuous: it comprises several separate sections which form the electrical supply tracks of the actuators 5 which will come into contact with the tactile elements 3.

[0211] Then, in step x, the rigid tactile elements 3 are placed at the desired locations on the flexible layer 4. The tactile elements 3 are, for example, held in place by a layer 44 of rigid glue, for example of the epoxy type, deposited on the layer 24, for example by screen printing.

[0212] In step xi, a layer 36 of conductive material, for example silver ink, is deposited, making it possible to reestablish electrical contact between the upper electrode 56 and the layer 46.

[0213] It is then possible to continuously cover, in step xii, for example by lamination or bonding, all of the touch elements 3 and their actuators 5 with a layer 48, in particular a soft polymer film or a varnish, in order to protect the assembly on its face opposite the touch surface.

[0214] Finally, in step xiii, the manufacturing substrate 100 is removed by heating the assembly to at least the temperature at which the thermal film disintegrates, in order to expose the flexible layer 4, the exposed surface defining the tactile surface S of the flexible haptic interface 1.

[0215] The resulting flexible haptic interface 1 can be divided into several interfaces according to requirements.

[0216] The interface according to the invention may also include a detection system (not shown), for example a capacitive system known from the state of the art, allowing the detection of at least one point of contact of the user's finger with the surface S.

[0217] The interface 1 may also include one or more additional devices making it possible to improve the user experience, in particular to make it a multi-sensory experience.

[0218] The interface 1 may thus comprise a flexible screen (not shown) which makes it possible to superimpose an image on the touch surface S and, for example, to give the user the impression of virtually touching what he observes on the screen. The interface 1 may also comprise one or more loudspeakers (not shown) to add a sound effect. The touch elements 3 of the same group may be activated according to a vibration mode which is identical for all the touch elements of the group, or specific to each touch element, depending on the desired effect.

[0219] The interface 1 according to the invention can be integrated into a clothing item. It can alternatively be integrated into a mobile device, for example a flexible telephone.

[0220] The haptic structure 2 can also, in other examples, change shape depending on the desired haptic effect, the interface 1 being able, given its flexibility, to be a reconfigurable tangible object.

Claims

Claims 1. Flexible haptic interface (1) defining a tactile surface (S) capable of being contacted by at least one user, the interface comprising: - a plurality of rigid tactile elements (3) connected by a flexible support (4), and - superimposed on each rigid tactile element (3), at least one actuator (5), the actuators (5) being arranged to transmit mechanical excitation to the rigid tactile elements (3) in order to cause the flexible support (4) to vibrate, the ratio e / L of the thickness e of the flexible support to the spacing L between at least two adjacent tactile elements being less than or equal to 0.02, . ~ . . , , . > , , . , ' r» the reflection coefficient R being greater than 50%, or R = , with Z SU pp Or f flexible 1 acoustic impedance of the flexible support and Z ac t r igi dg measures the acoustic impedance of the assembly composed of an actuator, a rigid tactile element and the flexible support in contact with the rigid tactile element, this latter impedance being substantially equal to the acoustic impedance of a rigid tactile element Z rigide , Or Z soft support the P soft support XC soft support P soft support being the density of the soft support and c SU pp O rt flexible the speed of the acoustic wave in the flexible medium, and Zrigid = Pngid x Rigid, where Pngid is the density of the rigid tactile element and Crigid is the speed of the acoustic wave in the rigid tactile element, with c = the speed of an acoustic wave in a material with Young's modulus E, with density p and Poisson's ratio v.

2. Haptic interface according to claim 1, the flexible support (4) having an equivalent Young's modulus (E) greater than or equal to 1.5 GPa.

3. Haptic interface according to one of the preceding claims, the flexible support (4) being formed from a polymeric material.

4. Haptic interface according to any one of the preceding claims, the flexible support (4) being of substantially constant thickness (e), the thickness preferably being between 25 and 200 microns.

5. Haptic interface according to any one of the preceding claims, the spacing (L) being greater than 10 mm.

6. Haptic interface according to any one of the preceding claims, at least some of the rigid tactile elements (3), better all the rigid tactile elements (3), being of generally polyhedral shape, preferably parallelepiped, in particular of rectangular or square blade type.

7. Haptic interface according to any one of the preceding claims, at least two rigid tactile elements having rigid supports different from each other.

8. Haptic interface according to any one of the preceding claims, at least a portion of the rigid tactile elements (3) being arranged in rows and / or columns, in particular on the same plane when the interface is flat, preferably according to a regular network.

9. Haptic interface according to any one of the preceding claims, comprising a control circuit (6) configured to modulate the signals sent to the actuators (5) in order to mechanically induce a vibration of the rigid tactile elements (3) and of the flexible support (4) and generate a haptic sensation on the tactile surface (S), the control circuit (6) preferably being configured so as to allow the modulation of each actuator (5) to be individually controlled.

10. Haptic interface according to any one of the preceding claims, each actuator (5) being arranged on a vibration antinode of the associated rigid tactile element (3).

11. Haptic interface according to any one of the preceding claims, the actuators (5) being of the piezoelectric, ferroelectric, electromagnetic or thermal type, preferably of the piezoelectric type.

12. Method for generating a haptic effect, in particular a multi-point haptic effect, with a flexible haptic interface (1) according to any one of the preceding claims, method in which at least one rigid tactile element (3) is mechanically excited by means of one or more actuators (5) superimposed on this or these elements, in order to cause the flexible support (4) to vibrate with a vibration amplitude (f) detectable by touch.

13. Method according to claim 12, in which the rigid tactile elements (3) are mechanically excited at a frequency of between 20 and 250 kHz, in particular to make each rigid tactile element (3) vibrate at a mechanical resonance frequency.

14. Method according to one of claims 12 and 13, at least one actuator (5) of a rigid touch element (3) located in the vicinity of an excited rigid touch element (3) not being electrically powered.

15. Method according to any one of claims 12 to 14, in which an actuator (5) of a given first rigid tactile element (3) is excited, without exciting all the actuators (5) of the rigid tactile elements (3) surrounding this first tactile element (3).

16. Method according to any one of claims 12 to 15, in which at least two active resonators are excited with different signals, in particular with signals having modulations at different frequencies and / or amplitudes, so as to create a multipoint haptic effect.

17. Method of manufacturing a flexible haptic interface according to any one of claims 1 to 11, comprising: (al) the production of a lower electrode by depositing at least a first layer of a conductive material on the upper face of a rigid support, (a2) depositing a conductive glue on the lower electrode, (a3) placing the actuators on the first layer thus formed by the lower electrode and the conductive glue, so as to establish a first electrical connection with the actuators, (a4) depositing a layer of an insulator on the previously deposited layers, for the insulation of the lower electrode, (a5) thinning the insulating layer to expose the upper face of each actuator, (a6) the production of an upper electrode by depositing a layer of a conductive material on the actuators thus exposed, so as to establish a second electrical connection with the actuators, (a7) cutting the rigid support into a square or rectangle, so as to obtain rigid tactile elements each equipped with one or more actuators, (bl) the deposition of a separation film, in particular thermal, on a manufacturing support, (b2) the deposition of a layer of flexible material, preferably polymer, on the separation film, (b3) the deposition of electrical tracks on the flexible material layer, (b4) depositing a conductive glue on the layer of flexible material, (b5) the installation of the rigid tactile elements produced in step (a7), equipped with one or more actuators, on the layer of conductive adhesive thus deposited, the actuators being arranged on the outer face of the tactile elements, (b6) the electrical connection of each lower electrode to the electrical tracks, (b7) the release of the haptic interface from the manufacturing support, in particular by heating the separation film, when the latter is thermal, (b8) cutting the haptic interface according to the desired design.

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