WO2023237942A1

WO2023237942A1 - A haptic device for applying sensor stimuli

Info

Publication number: WO2023237942A1
Application number: PCT/IB2023/053525
Authority: WO
Inventors: Giovanni SPAGNOLETTI; Mirko AURILIO; Fabio PIZZATO; Biagio FORESTIERI; Mattia De Santis; Guido GIOIOSO
Original assignee: Weart S.R.L.
Priority date: 2022-06-08
Filing date: 2023-04-06
Publication date: 2023-12-14

Abstract

This disclosure illustrates a haptic device having a thermal bridge composed of thermally conductive material, comprising: a central portion having a shape corresponding to a support surface, installed between a vibration or pressure actuator and a thermally conductive element so as to transmit the movement of vibration or pressure generated by the vibration or pressure actuator to the thermally conductive element; at least one first intermediate portion integral with the central portion, having an undulated profile configured to elastically deform when the central portion is vibrated or moved by the vibration or pressure actuator; at least one first end portion integral with the first intermediate portion and in contact with a heat sink.

Description

A HAPTIC DEVICE FOR APPLYING SENSOR STIMULI

TECHNICAL FIELD

This disclosure relates to devices for applying sensory stimuli.

BACKGROUND

Haptic interfaces, i.e. devices that provide tactile sensations to users, are increasingly widespread in robotics and in virtual reality applications. These interfaces must be properly controlled to generate on the skin of the users the same tactile sensations as they would receive by touching the surface of a real object.

Ring-shaped haptic interfaces are known, such as for example the one described in Italian patent application 102018000003965 entitled "Haptic ring", wearable by a user and connected via wireless or wired connection to systems which supply the signals to control them.

To make realistic a reconstruction of tactile sensations, it would be necessary to sample the tactile sensations using devices equipped with sensors organized to obtain a set of data which, suitably processed, allow the haptic interfaces to be driven so as to reproduce the same tactile sensation as faithfully as possible.

Said devices can also be used in research fields for study purposes on manipulation, or they can be used during rehabilitation sessions having curative purposes, such as during treatments of traumas due to a stroke. Using these devices it is also possible to provide thermal stimuli to the skin of a user.

An example of a known device is described in W02017029406A1. In particular, this device is used for the treatment of patients after a stroke, but it can also be used in the entertainment sector or in the sports sector during training programmes. The device contemplates the possibility of being worn on one or more fingers of a hand, and comprises a Peltier cell element for the administration of thermal stimuli, a vibration actuator for providing mechanical stimuli at high frequency values, a pneumatic element configured to vary its volume and thus applying pressure stimuli to the user.

A limitation of haptic devices that include a Peltier cell element is the fact that, in order to make the sensations of hot/cold realistic, it is necessary to be able to rapidly heat/cool the conducti ve surface in contact with the skin of a user, as well as to transfer energy with the external environment via a heat exchange interface. The document US2019/339783 discloses a tactile sensation presenting device includes: a vibrating element configured to present vibration information; a warmth/coldness presenting element provided above the vibrating element and configured to present warm/cold information to a tactile sensation presentation surface; a pressure detecting unit configured to detect a pressure corresponding to a contact state of an operating part with respect to the tactile sensation presentation surface; and an adjusting unit configured to adjust a presentation condition based on a detection result by the pressure detecting unit.

SUMMARY

In the cited prior documents, the Peltier cell element is configured to directly heat/cool the user's skin. Such haptic devices have shown the unexpected and unsuspected problem of not being able to reproduce hot/cold thermal sensations in relatively rapid succession using the Peltier cell elements typically used in haptic devices. Currently, relatively powerful Peltier cell elements must be chosen to increase the speed of the sequences of hot/cold transitions, but this would cause a significant energy consumption of the haptic device battery, which is normally relatively small.

Studies carried out by the Applicant have shown that it is possible to make the hot/cold transitions very fast while using Peltier cell elements with relatively low power and therefore low consumption, compatible with the limited capacity of the batteries of portable or wearable haptic devices.

This exceptional result is obtained with a haptic device according to claim 1. This haptic device, which can be made for example in the form of a wearable ring, or a bracelet, or still like a computer mouse or any object that can be held, having a thermoelectric actuator, which for example can be a Peltier cell, thermally coupled to a thermal bridge composed of thermally conductive material, comprising: a central portion having a shape corresponding to a support surface, installed between a vibration or pressure actuator and a thermally conductive member so as to transmit the vibration or pressure motion generated by the vibration or pressure actuator to the thermally conductive member; at least one first intermediate portion integral with the central portion, having a undulated profile configured to deform elastically when the central portion is vibrated by the vibration actuator and/or set in motion to apply pressure; at least one first end portion integral with the first intermediate portion and in contact with a heat sink.

According to an optional aspect, the thermal bridge is configured such that the central portion is sandwiched between the vibration or pressure actuator and the thermally conductive member, so as to vibrate when the vibration or pressure actuator vibrates and to transmit mechanically by contact the vibration or pressure movement from the vibration or pressure actuator to the thermally conductive element, with the thermoelectric actuator (which may be for example a Peltier cell) which is placed in contact with the first end portion of the thermal bridge.

According to another optional aspect, the thermal bridge is configured so that the central portion is sandwiched between the vibration or pressure actuator and the thermoelectric actuator, with the thermoelectric actuator (which can be for example a Peltier cell ) which is placed between the central portion and the thermally conducting element so as to vibrate when the vibration or pressure actuator vibrates and to mechanically transmit by contact the vibration or pressure movement from the vibration or pressure actuator to the thermally conducting element.

Further embodiments are defined in the attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Characteristics and/or advantages of the present invention will become clearer with the ensuing description of an embodiment thereof, given as non-limiting example, with reference to the attached drawings in which:

Figure 1 is a sectional view of a device of this disclosure in the form of a ring/thimble.

Figure 2 shows the device of figure 1 without the upper part of the body, to show the compartment containing an actuator configured to move the thermally conductive element which comes into contact with the user's skin in order to apply pressure.

Figure 3 shows the device of Figure 1 with the part that contacts the skin in the maximum pressure/excursionposition .

Figure 4 shows the device of Figure 1 seen in section from behind.

Figure 5a shows the assembly of the part of the device of figure 1 which contains the actuator, a Peltier cell, the thermal bridge and the thermally conductive element.

Figure 5b is an exploded view of figure 5a.

Figure 6 is a basic diagram showing a device of this disclosure with a vibrating Peltier cell installed below the thermally conducting element in contact with a fingertip and connected via two end portions of a thermal bridge to two heat sinks.

Figure 7 shows a device of this disclosure with a Peltier cell installed in the upper part in order to reduce the encumbrance of the block placed under the fingertip.

Figure 8 shows a device of this disclosure with the upper rigid body used as a heat sink. Figure 9 is a basic diagram showing a device of this disclosure with two Peltier cells connected to two heat sinks and connected via two end portions of a thermal bridge below a thermally conducting contact element with a fingertip.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

A device for reproducing tactile sensations 1 according to one aspect of the present disclosure is illustrated in figures 1 to 4 and 7 to 8. It has an annular shape to be worn preferably as a ring, or possibly as a bracelet or even as a thimble, and is configured to give tactile sensations on the skin of the user who wears it or on any part of the body of a living being. For simplicity, reference will be made to the illustrated case in which the device for reproducing tactile sensations 1 is a ring in which a user can insert a finger of a hand, but what will be said can be repeated mutatis mutandis if the reproduction device is a bracelet or a thimble, or a device on which a finger can be placed, such as a mouse for computer or another interactive object. Furthermore, for simplicity reference will be made to the case in which the thermoelectric actuator is a Peltier cell, but what will be said can be repeated mutatis mutandis also for thermoelectric actuators of different types provided they are configured to receive a relative command signal and to heat up or cool down according to this command signal.

According to a general aspect, any device of this disclosure, whether made in the form of a ring or in any other form, comprises: a thermally conductive element 2, defining a support surface suitable for being touched, for example with a fingertip or other sensitive parts of the user's body, configured to move so as to be alternately pressed against and away from the fingertip or other sensitive part of a user's body resting on the support surface of the thermally conductive element 2; a vibration or pressure actuator 3 located below the thermally conductive element 2, configured to generate a vibration or pressure movement, which is transmitted to the fingertip or other sensitive part of the user's body through the thermally conductive element 2; at least one thermoelectric actuator, for example a Peltier cell 4, which heats up or cools down according to the received relative command signal; at least one thermal bridge 8a, 8b, 8c, composed of thermally conductive material for exchanging thermal energy between the thermally conductive element 2 and the Peltier cell 4 or between the Peltier cell 4 and a heat sink 5; at least one heat sink 5 functionally connected to the Peltier cell 4 or to the thermal bridge 8a, 8b, 8c, so as to rapidly dissipate the absorbed heat, as schematically indicated by the wavy arrows.

In the figures, reference is made to the exemplifying case in which the thermally conductive element 2 is a flat plate, but it is understood that it can assume any shape as long as it defines a support surface suitable for coming into contact with a part of a user's body. For example, the thermally conducting element 2 could alternatively be made as a concave plate shaped so as to define an anatomical support surface for a fingertip, or still so as to define a convex support surface for making a haptic mouse for computers.

In the particular embodiment shown in figure 1, the device 1 is configured as a ring and therefore comprises an annular band 6, defining an opening suitable for inserting a fingertip, and a rigid body 7. Typically, in the haptic ring illustrated in the figures from 1 to 4 and from 7 to 8, the body 7 defines an internal compartment which encloses the upper part of the annular band and a microprocessor electronic board, not shown in the drawings. The annular band 6 has a lower part which supports the vibration or pressure actuator 3 from below', which is in turn placed below the thermally conductive element 2 intended to come into contact wi th a fingertip. The upper part of the annular band 6, which can be made of deformable material, for example silicone, is visible in figure 1 and is in the upper internal compartment of the device, which also houses an electronic board having at least one microprocessor functionally configured to control the vibration or pressure actuator 3 and the Peltier cell 4 and the motor which moves the block with the thermally conductive element 2 to apply pressure.

According to a general aspect, any device of this disclosure has a thermal bridge 8a, 8b, 8c, composed of thermally conductive material, comprising:

-a a central portion 8a having a shape corresponding to the support surface of the fingertip. installed between the vibration or pressure actuator 3 and the thermally conducting element 2 so as to transmit, in a direction orthogonal to the support surface, the vibration or pressure movement generated by the vibration actuator or pressure 3 to the thermally conductive element 2;

- at least a first intermediate portion 8b, integral with the central portion 8a, having an undulated profile configured to deform elastically when the central portion 8a is vibrated by the vibration or pressure actuator 3 and to allow a displacement of the central portion 2 to exert a pressure;

- at least one first end portion 8c integral with the first intermediate portion 8b, in contact with a heat sink 5.

As illustrated in particular in figures 5a, 5b, 6 and 9, the thermal bridge 8a, 8b, 8c is configured so as to transmit thermal energy from the thermally conductive element 2 and from the Peltier cell 4 to the first heat sink 5 and at the same time it is structured so that its central portion 8a transmits, by contact, the vibration or pressure movement from the vibration or pressure actuator 3 to the thermally conducting element 2. As will be better understood below, the fact that this central portion 8a is used to simultaneously transmit mechanical vibration or pressure and thermal energy to the thermally conducting element 2, allows optimizing the size, below the fingertip, of a device 1 of this disclosure. This allows to make sensations of gripping an object more realistic by squeezing two fingers, which can approach almost touching each other while remaining separated only by the thickness of the device below the fingertip.

The central portion 8a of the thermal bridge of any device of this disclosure is able to transmit thermal energy and vibrations or pressures without breaking thanks to the undulated intermediate portion 8b which, thanks to its shape, can oscillate allowing the central portion 8a of the thermal bridge to vibrate or in any case to move with an alternate back and forth movement perpendicularly to the thermally conductive element 2 and to transmit the vibration or pressure to it without interrupting the thermal connection with the Peltier cell 4 and the heat sink 5.

In the embodiment shown in figures 1 to 9, the undulated profile of the intermediate portion 8b of the thermal bridge substantially consists of a single half-wave. Thanks to the undulated profile, the central portion 8a of the thermal bridge can vibrate while the end portion 8c remains fixed, with the intermediate portion 8b, integral with the central portion 8a and the end portion 8c, which acts as a connection and which absorbs the vibrations without breaking.

Suitable materials for making such a thermal bridge are known. For example, the material described in document US20150211815, or in document US10806054 can be used, or again the thermal bridge 8a, 8b, 8c can be made with a flexible multilayer structure of graphene. For example, a thermal bridge 8a, 8b, 8c in graphite could be used, made with 10 superimposed sheets with a thickness of 0.1 mm, configured to transmit heat from the point of generation and to bring it externally to two heat sinks 5 in aluminum which exchange heat with the external environment by natural convection.

According to one aspect, illustrated in figures 1 to 6 and 9, a haptic device 1 of this disclosure can comprise a second heat sink 5. In this case, the thermal bridge 8a, 8b, 8c will advantageously comprise a second intermediate specular portion to the first intermediate portion 8b, as well as a second end portion 8c specular to the first end portion. To ensure an efficient thermal conduction, the second end portion 8c is integral with the second intermediate portion 8b, which in turn is integral with the central portion 8a of the thermal bridge, and the second end portion 8c i s in contact with the second heat sink 5.

According to one aspect, shown in figures 1 to 6, the Peltier cell is installed above the central portion 8 a of the thermal bridge and below the thermally conducting element 2, on which the user can rest a fingertip 10, so that the central portion 8a is sandwiched between the vibration or pressure actuator and the Peltier cell 4. In this way, the Peltier cell 4 is sandwiched between the central portion 8a and the thermally conducting element 2 and also vibrates when the vibration or pressure actuator 3 vibrates, mechanically transmitting by contact the vibration or pressure movement from the vibration or pressure actuator 3 to the thermally conducting element 2.

An advantage of this solution consists in the fact that the distance between the Peltier cell 4 and the thermally conductive element 2 is minimal, whereby it is possible to quickly alternate hot/cold sensations. However, the presence of the Peltier cell 4 increases the thickness of the device under the support surface of a fingertip and the inertia of the vibrating part of the device. According to one aspect shown in figure 7 to 9, the thermal bridge 8a, 8b, 8c, is configured so that the central portion 8a is sandwiched between the vibration or pressure actuator 3 and the thermally conducting element 2, so as to vibrate when the vibration or pressure actuator 3 vibrates and to mechanically transmit by contact the vibration or pressure movement from the vibration or pressure actuator 3 to the thermally conductive element 2. In this case, the Peltier cell 4 is placed in contact with the end portion 8c of the thermal bridge, so that it does not vibrate. This has the advantage of reducing the thickness of the device under the support surface of a fingertip and of reducing the inertia of the vibrating part of the device. However, the greater distance between the Peltier cell 4 and the thermally conductive element 2 slows down the heat exchange. To alleviate this drawback, it appears preferable to make the thermal bridge 8a, 8b, 8c, with a graphene multilayer structure, which has a relatively large thermal conductivity.

In the embodiment shown in figures 1 to 6 and 9, there are two heat sinks 5 and they are installed at the sides of the external rigid body 7. According to an alternative aspect, shown in figure 8, the upper rigid body is used as heat sink 5, in order to have more dissipation surface and move the disperser away from the user's fingers.

According to one aspect, the thermally conductive element 2 comprises a thermistor. The presence of the thermistor can enable closed-loop control of the perceived temperature and can limit the inrush current and thus protect both the cooling and/or heating circuit and to ensure that the safety temperature limits are not exceeded.

According to one aspect, the vibration or pressure actuator 3 is selected from: a voice coil, a vibrating eccentric mass, a piezoelectric vibrator, a resonator.

According to one aspect, the active surface as shown in Figs. 6 and 9 may contain temperature, force and vibration sensors 9 to allow calibration of haptic stimuli and closed-loop control of sensations.

In one aspect, a haptic device 1 of this disclosure comprises an electronic microprocessor board with a wired or wireless communication interface for causing the microprocessor board to receive external signals representative of hot/cold and vibrotactile or pressure sensations to be reproduced.

According to one aspect, the electronic board is powered by an internal battery of the device. The device of this disclosure, compared to the known solutions, is able to guarantee an excellent heat transfer while maintaining a very flexible and compact structure. The flexible thermal bridge 8a, 8b, 8c allows to thermally connect the heat generation point, which moves, to the heat sinks 5, which are fixed instead, and can be set in vibration without damping the vibrations thanks to the flexibility/lightness/low inertia.

Furthermore, the presence of the flexible thermal bridge 8a, 8b, 8c allows the heat dissipation systems - i.e. that part of the device that exchanges heat with the external environment - to be moved to an area distant from the thermally conducting element 2 of the active generation of the thermal stimulus, with the consequence that it is possible to considerably reduce the noise and vibrations generated by active heat dissipation systems

(fan). The vibrations generated by active heat dissipation systems represent a disturbance to be eliminated, because they modify the perception of the vibrations generated by a possible actuator predisposed to the generation of vibrational stimuli.

Finally, the device of this disclosure can be made in such a way as to have an external body without openings, protecting the internal parts from external factors (e.g. dust, water) and conferring greater reliability.

Claims

1. A haptic device (1) for applying sensory stimuli to a part of a user's body, said device comprising: a thermally conductive element (2) defining a support surface suitable to be touched by a fingertip or any other sensitive part of a user's body, configured to move so as to be alternately pressed against and removed from a user’s fingertip placed onto said support surface; a vibration or pressure actuator (3) located below said thermally conductive element (2), configured to generate a vibration movement or to apply pressure; at least one thermoelectric actuator (4) configured to receive a relative command signal and configured to heat or cool itself depending on said command signal; at least a first heat sink (5) functionally connected to the thermoelectric actuator

(4); a thermal bridge (8a, 8b, 8c) composed of a thermally conductive material, comprising:

- a central portion (8a) having a shape corresponding to said support surface, installed between said vibration or pressure actuator (3) and said thermally conductive element (2) so as to transmit in a direction orthogonal to the support surface said vibration or pressure movement generated by said vibration or pressure actuator (3) to said thermally conductive element (2), said thermal bridge (8a, 8b, 8c) being configured to conduct thermal energy among said thermally conductive element (2), said first heat sink

(5) and said thermoelectric actuator (4); characterized in that - at least a first intermediate portion (8b) integral with said central portion (8a), having an undulated profile configured to deform elastically when said central portion (8a) is moved along said orthogonal direction with said vibration or pressure movement by said vibration or pressure actuator (3),

- at least a first end portion (8c) integral with said first intermediate portion (8b), said first end portion (8c) being in contact with said first heat sink (5).

2. The device (1) according to claim 1, comprising a second heat sink (5) and said thermal bridge (8a, 8b, 8c) comprises: - a second intermediate portion (8b) specular to said first intermediate portion (8b), in which said second intermediate portion (8b) is integral with said central portion (8a);

- a second end portion (8c) specular to said first end portion (8c), in which said second end portion (8c) is integral with said second intermediate portion (8b), said second end portion (8c) being in contact with said second heat sink (5).

3. The device (1) according to one of the preceding claims, wherein:

- said thermal bridge (8a, 8b, 8c) is configured so that said central portion (8a) is sandwiched between said vibration or pressure actuator (3) and said thermoelectric actuator (4),

- said thermoelectric actuator (4) is placed between said central portion (8a) and said thermally conductive element (2), to vibrate when said vibration or pressure actuator (3) vibrates and to mechanically transmit by contact said vibration or pressure movement from said vibration or pressure actuator (3) to the thermally conductive element (2).

4. The device (1) according to one of claims 1 to 2, wherein: - said thermal bridge (8a, 8b, 8c) is configured so that said central portion (8a) is sandwiched between said vibration or pressure actuator (3) and said thermally conductive element (2), so as to vibrate when said vibration or pressure actuator (3) vibrates and to mechanically transmit by contact said vibration or pressure movement from said vibration or pressure actuator (3) to the thermally conductive element (2);

- said thermal actuator (4) is placed in contact with said first end portion (8c) of the thermal bridge (8a, 8b, 8c).

5. The device (1) according to one of the preceding claims, wherein said thermal bridge (8a, 8b, 8c) is composed of a flexible multilayer structure made of graphene.

6. The device (1) according to one of the preceding claims, characterized in that it is configured as a ring and comprises: an annular band (6) defining an opening suitable for inserting a fingertip, said band (6) having a lower part which holds from below said vibration or pressure actuator placed below said thermally conductive element (2), and an upper part configured to remain in an internal compartment of the device; a plurality of sensors (9) configured to monitor temperature, vibration, force / pressure to calibrate perception sensations of the user and to allow a closed-loop control of each individual stimulus given to the user; an electronic board, having at least one microprocessor functionally configured to acquire data from the sensors and to control said vibration or pressure actuator (3) and at least said thermoelectric actuator (4); a rigid body (7) defining at least one internal compartment that encloses the upper part of the annular band (6) and the electronic board; said at least one heat sink (5) being installed on one face of said rigid body (7).

7. The device (1) according to claim 2 and one of claims 5 or 6, wherein said first heat sink (5) and said second heat sink (5 ) are installed on opposite sides of said rigid body (7) comprised between the lower part and the upper part of said band (6).