Fluid-based haptic device with deformable membranes

Abstract

The invention relates to a haptic device (1) adapted to interact with a user's hand (M), wherein a set of membranes (15-19) are in contact with the fingers of the hand (M). The device is equipped with control means (20-24) operatively associated with the membranes (15-19) to send and / or receive signals in order to issue commands or provide feedback. The control means comprise a pressure sensor (21) and a vibrating actuator (12) co-operating with an electropneumatic unit (20) in order to measure inputs from the device user and provide feedback by means of controlled force and vibration signals.

Description

[0001] TRANSLATION (RULE 12.3) 21 February 2025

[0002] Description of patent for industrial invention entitled:

[0003] “Fluid-based haptic device with deformable membranes”

[0004] Applicant: Politecnico Torino - (Torino)

[0005] Filed on No.

[0006] Appointed inventors:

[0007] COLUCCI Giovanni (c / o: Politecnico di Torino - DIMEAS Dept.)

[0008] QUAGLIA Giuseppe (c / o: Politecnico di Torino - DIMEAS Dept.)

[0009] DESCRIPTION

[0010] In a general aspect, the invention relates to a graspable haptic device for rehabilitation and alternative communication applications.

[0011] The invention falls within the field of haptic devices that can interact, and be grasped by, a user’s hand(s).

[0012] The notion of a haptic device initially referred to a system capable of using the sense of touch to permit bidirectional physical interaction for several purposes, such as interaction with virtual environments (virtual reality) or with real environments enriched with multimedia information (augmented reality); communication in non-verbal, alternative forms (augmented or alternative communication); telemedicine or, more generally, teleoperations; rehabilitation.

[0013] With a view to improving and increasing the functionality of such devices, the definition of a “haptic device” has been subsequently made to include also force exchange between user and device.

[0014] For the development of modern haptic systems, the scientific literature has identified the following design requirements:

[0015] - ability to track the movements of the limb to which the device has been applied;

[0016] - ability to provide multimodal haptic feedback, i.e. feedback combining vibration, force and temperature signals over multiple body areas, for the purpose of making virtual interaction as realistic as possible;

[0017] - a geometry that is compact, light and comfortable, i.e. that can be modified or re-configured to suit different sizes of the user’s limbs / body areas in contact with the device;

[0018] - a low-consumption, and preferably built-in, power supply unit; communication with a remotecontrol centre, preferably in wireless mode. As concerns the acquired input data, i.e. the data coming from the user and sent to the remotecontrol centre, it is generally necessary to track the position and orientation of the hand, as well as the position of one or more fingers.

[0019] Among haptic systems designed to interact with the user’s hand(s), the state of the art of commercial products or research prototypes shows a clear majority of devices that can be grasped or worn by the user.

[0020] This is due to their plain advantages in terms of ergonomics, simplicity and ease of transportation over alternative feedback devices.

[0021] The goal is, in this case, to provide combined feedback signals that can be summarized as follows:

[0022] - localized pressure at one or more points on the fingers and the palm; generally, this pressure is used to reproduce contact with an object in teleoperations, augmented / virtual reality and alternative communication applications;

[0023] - kinesthetic feedback, i.e. exertion of a force on the finger’s kinematic chain to allow for geometry recognition (augmented / virtual reality or teleoperations) for rehabilitation or alternative communication purposes;

[0024] - mechanical vibration, in localized form, e.g. at the fingertips, for alternative communication purposes, or distributed over the whole hand.

[0025] Note that the ability of providing kinesthetic feedback is the most powerful and useful function among those listed above, and for this very reason it is being paid much attention by developers of research prototypes and commercial systems.

[0026] A first category of developed devices makes use of traditional rigid actuators, whether fluidbased or electromechanical ones, in direct contact with one of more distal phalanxes of the hand. The most important limitation of these solutions lies in their large size and heavy weight, and also in the fact that the system is hardly adaptable to patients having very differently sized hands.

[0027] With a view to overcoming this limitation, alternative solutions employ a cable transmission between the electric motor and the fingertip. As a further alternative, the modern soft robotics paradigm has been used to make actuators, joints or entire actuation and transmission kinematic chains which are pliable and adaptable to the geometry of the fingers. To such end, these solutions utilize a “soft”, fluid-based actuator mounted on an individual finger and extending throughout the length of the latter, or a mixed rigid-deformable structure provided with actuated soft joints and rigid connections.

[0028] As far as graspable systems are concerned, some solutions are known which employ deformable fluid-based membranes or bellows distributed over the outer cap of the device, and generally in contact with the distal phalanxes of one or more fingers. However, these solutions still require external fluid-based and electric auxiliary equipment for controlling and powering the device.

[0029] Lastly, deformable membranes that are similar to, but much smaller than, the above-described ones have been used to provide the user with contact feedback through localized pressure forces. These are referred to as “feelers”, and such devices can generally be worn and are equipped with a pressurized air / fluid source that may be either delocalized and stationary or mounted on a gilet wearable by the user.

[0030] From an analysis of the solutions disclosed in patent or scientific publications, it is apparent that a device providing various haptic feedback types, even of a different nature (mechanical, thermal, etc.) is clearly in contrast with the need for a light and compact system. Over the years, this has led to developing complex systems that are heavy and equipped with external power and control units, or systems that are too simple, and hence neither realistic nor easy to use.

[0031] In light of the above examination, it can be stated that the technical problem at the basis of the invention is to provide a haptic device having structural and functional characteristics that make it possible to overcome the drawbacks of the prior art, with particular reference to the known devices previously described herein.

[0032] Within the frame of this general technical problem, it is one object of the invention to provide a haptic device which can interact with the user in such a way as to operate as a control means while also providing feedback signals.

[0033] In particular, the invention aims at providing a haptic device which can supply to the user a plurality of control and feedback signals, according to different operating conditions or different intended applications of the device, e.g. physical rehabilitation, virtual or augmented reality applications, telemedicine, etc.

[0034] Basically, the improved and extended performance of the haptic device leads to a broader range of possible applications of the same, thus making it advantageous in this respect.

[0035] It is a further object of the invention to provide a device that can supply a plurality of haptic feedback signals, preferably also of a different nature (mechanical, thermal, etc.), while at the same time being light and compact, thus being easier to use.

[0036] The idea that solves the above-mentioned technical problem is to provide a haptic device that comprises deformable membranes and a control system to provide feedback stimulation on the user’s fingers.

[0037] Thus, when a single membrane is pressed, the antagonistic force can be adjusted by the integrated control system. Advantageously, according to a preferred embodiment of the invention, the device can be set up off-line with different operating ranges.

[0038] Preferably, the deformable membranes are integrated with an LRA (Linear Resonant Actuator) vibrating actuator to provide vibratory haptic feedback.

[0039] The features of the invention are specifically set out in the claims appended to this description. Such features, the effects deriving therefrom, and the advantages of the invention will become more apparent in the light of the following description of a non-limiting preferred embodiment thereof as shown in the annexed drawings, wherein:

[0040] Fig. l is a top view of a haptic device according to the invention, grasped by a hand;

[0041] Fig. 2 is a side view of the device of Figure 1, with a part thereof removed to make the interior visible;

[0042] Fig. 3 is a bottom view of the device of Figures 1 and 2;

[0043] Fig. 4 is a perspective view of the device of the preceding figures;

[0044] Fig. 5 is an exploded view of the device of the preceding figures;

[0045] Fig. 6 is a sectional view of a detail of the device of the preceding figures;

[0046] Fig. 7 is an exploded view of the detail of Figure 6;

[0047] Fig. 8 is a drawing that shows the geometry of a component of the device of the preceding figures;

[0048] Fig. 9 is a cross-sectional view of the component of Figure 8;

[0049] Fig. 10 is a diagram that shows the actuation circuit of the detail of Figures 6 and 7;

[0050] Figs. 11(a), (b) are diagrams that illustrate the adjustment circuit of the detail of Figures 6 and 7;

[0051] Fig. 12 schematically shows the device of the invention as a whole. With reference to the above-listed figures, reference numeral 1 designates as a whole a haptic device in accordance with the invention.

[0052] While the device 1 is, for simplicity, schematically illustrated in the drawings as a single apparatus, it may nonetheless comprise also some separate elements to implement specific operating modes.

[0053] This may be the case, for example, when the haptic device 1 is intended for virtual or augmented reality applications and connected to equipment (e.g. robotic surgery arms, various machinery, displays, etc.) through remote communication systems (wired or wireless ones, as will become apparent below).

[0054] For convenience, reference will be made hereafter to the schematic configuration shown in the drawings. No other external elements will therefore be taken into account, but this should not be understood to be a limiting factor.

[0055] Furthermore, it must be pointed out that any reference to an “implementation”, an “embodiment”, or any other similar expressions that are typical of patent documents will indicate that a particular configuration, structure, action, operating phase or other feature is comprised in at least one example of embodiment of the invention.

[0056] Therefore, such expressions, which may be found in different parts of this description, will indicate elements not necessarily referring to a single implementation or embodiment.

[0057] In addition, those skilled in the art will recognize that the individual configurations, structures or features considered herein may be combined with each other in several appropriate ways to attain the described results of the invention.

[0058] Lastly, in compliance with an established practice in the patent field, the numerical or alphabetical references used in the drawings are provided only for clarity, without limiting the protection scope or extension of the invention.

[0059] With the above clarifications in mind, the device 1 comprises an external shell or enclosure 2, shaped substantially as a handle, which is preferably ergonomical so that it can be grasped by a hand M of a user.

[0060] The drawings show a right hand. The device 1 is, therefore, ergonomically suited for such hand, but of course devices may be provided which are suitable for being grasped by the left hand.

[0061] The shell 2 may be made either as one piece or, as shown in the drawings that illustrate the example considered herein, as two or more half-shells 2a, 2b j oined together by fastening means such as screws, brackets, welded or adhesive joints, etc.

[0062] In this embodiment, the shell 2 is closed laterally by a wall or flange 4, fastened by screws (not shown in the drawings) going through holes 5 and engaging seats 6 on the first half-shell 2a; in the configuration shown in Figure 5, the wall 4 is coupled to the other half-shell 2b by means of a set of protrusions 7 that fit into matching notches 8 on the edge of the half-shell 2b.

[0063] Of course, other solutions are also viable for fastening the wall 4 to the half-shells 2a, 2b, depending also on the materials and thickness of such components.

[0064] Preferably, the shell 2 and the wall 4 are made of semi-rigid plastic, such as PVC (polyvinyl chloride), EVA (ethylene-vinyl acetate), tetrafluoroethylene (Teflon), but of course other materials may be used as well.

[0065] In addition, in order to make the device 1 more anatomical and easier for a user to grasp, on the external shell 2 an insert 9 is preferably applied, which may be made of a material which is different from that of the shell 2.

[0066] For example, a deformable soft material may be used, such as synthetic rubber or foam (foam rubber, silicone, TPU, etc.) in the area of contact with the palm of the hand M. The insert 9 can preferably be replaced to fit the size of the user’s hand, and is secured to the shell 2, or part thereof, in any appropriate manner.

[0067] On the extrados of the shell 1 there is a series of (four) openings 10, arranged side by side and respectively positioned to match the distal phalanxes of the fingers of the hand M grasping the device; an additional opening 11 is present in the intrados of the shell 2, corresponding to the thumb of the hand M.

[0068] The openings 10, 11 are used as passages for respective deformable membranes 15, 16, 17, 18, 19, useful for operating the device 1; the membranes 15-19 are preferably installed by geometric interference fit into the openings 10 and 11 provided in the enclosure 2 of the device. The membranes 15-19 essentially consist of deformable hollow bodies made of rubber, latex or other natural or synthetic elastomers and configured substantially as a cap with a respective base or collar 15a- 19a, and perform a dual function as sensing and actuation units; to this end, each membrane 15-19 incorporates both a vibrating mini-actuator 12 of the LRA (Linear Resonant Actuator) type and a gauge pressure sensor 21, clearly shown in Figures 6 and 7.

[0069] In the example considered herein, the membranes 15-19 are all equal. For brevity’s sake, only one of them will be described herein, and the description provided shall be applicable to the other membranes as well.

[0070] Figures 8 and 9 show the geometric parameters of each membrane 15-19, wherein in the first quadrant of the <x, y> semi-plane three successive arcs of a circumference are drawn, imposing tangency between them and coincidence of the first section with the y axis and of the third section with the x axis.

[0071] Figure 9 is a view of the cross-section ST highlighted (in grey) in Figure 8. As shown, the geometry of the membrane body is then mirrored around y and extruded along z for a length of / . The same geometry is then extruded by revolution about the y axis to obtain a closed volume.

[0072] By appropriately selecting the geometry and material of the membranes 15-19, it is possible to modify the structure’s stiffness, which should however be reasonably irrelevant due to the following reasons.

[0073] The volume delimited by the membranes 15-19 is filled with incompressible fluid (e.g. oil, aqueous solution, or another liquid) or with compressible fluid (e.g. air), and has two ports or passages 30, 31 for connecting to an auxiliary unit 20 that comprises: a control valve 22; one or more auxiliary volumes 23 acting as liquid-air interfaces Ci, C2, . . ., CN; one or more non-retum valves 24.

[0074] In the diagram of Fig. 10, variable ^ represents the deflection of the membrane along the axis, VCn iis the air volume enclosed in the n-th cylinder when the membrane is not deflected, and Pt is the membrane pressure with null deflection. Assuming that the structural stiffness of the membrane 15 is negligible, the kinesthetic feedback perceived by the user while pressing the membrane 15 will be solely related to the relative internal pressure of the membrane itself and the contact area.

[0075] It is thus possible to generate an increasingly monotonic kinesthetic feedback signal on each finger of the user, for a deflection value equal to the height of the membrane. By appropriately setting the set-up parameters VCn iand Pt, one can adjust the initial point of the compression curve. As concerns the variation of VCn i, it can be achieved in the following two ways: - during the operation of the device 1, by connecting the membrane to a different auxiliary volume;

[0076] - while setting up the device 1, by changing the liquid volume in the chamber.

[0077] As far as Ptis concerned, it can only be adjusted during the set-up phase, by setting its value off-line through a connection to a suitable compressor.

[0078] One possible embodiment is shown in Figs. 11 (a)-(b), wherein, for construction simplicity and compactness, reference is made to a single auxiliary volume and the whole system is filled with pressurized gas. Note that the control accomplished by the directional valve 22 makes it possible to decide whether to connect the auxiliary volume or not, thus allowing, de facto, the creation of two possible volumes VCn i.

[0079] In order to acquire signals and provide kinesthetic and resonant haptic feedback signals, the device 1 is preferably integrated with (cf. Fig. 12):

[0080] - a control unit 35, preferably consisting of an on-board microcontroller;

[0081] - an inertial measurement unit (IMU) 36, for reconstructing the movement of the user’s hand while using the device;

[0082] - a power supply unit 37, preferably a rechargeable battery (a lithium polymer battery or the like);

[0083] - a communication module 38, preferably wirelessly connected to a remote-control unit 40.

[0084] The haptic device 1 operates as follows.

[0085] The deformable membranes 15-19 distributed on the external enclosure 2 are associated with a set of pressure sensors 21 and vibrating mini-actuators 12, which co-operate with an electropneumatic unit 20 in order to interact with the user and provide feedback by means of force and vibration signals. To this end, the device 1 preferably incorporates a controller or driver 41, connected to the control unit 35, for controlling the linear resonant actuator(s) 12.

[0086] The haptic device 1 is therefore a bidirectional one, since it operates both as an actuation controller and as a measurement apparatus, thanks to the integration of a vibrating mini-actuator 12 (preferably, of the LRA (Linear Resonant Actuator) type) and a gauge pressure sensor into its structure.

[0087] It should be noted that the device 1 can operate without needing any external electric and / or fluidic connections and without requiring the use of a compressor or a pump.

[0088] Furthermore, the combined use of the deformable membranes 15-19 in conjunction with the auxiliary electropneumatic unit 20 makes it possible to provide kinesthetic haptic feedback on the fingers of the hand M.

[0089] Therefore, when an individual membrane is pressed 15-19, the antagonistic force can be adjusted by the integrated control system 20.

[0090] Separately, by off-line set-up, it is possible to set the device to different operating intervals: in this manner, the performance range of the device 1 can be broadened without increased complexity.

[0091] Finally, it must be highlighted that, due to the control accomplished by the unit 20 and to the presence of the inertial measurement unit 36, the device of the invention can also track the user’s hand M, thus fulfilling one of the requirements for this type of equipment.

[0092] In this respect, it should be noted that the haptic device according to the invention needs no continuous pressure control, so that no electric power needs to be drawn for any connected pumps or compressors while the device is in operation. Because of its simple and compact architecture, the system is light and can be easily transported by the user.

[0093] The absence of any external physical connection prevents damage to remote units and connections during the installation and use of the device.

[0094] The device 1 according to the invention also permits tracking the movement of the limb, or anyway of the hand M that is grasping it. In addition, when the device 1 is equipped with other sensors in addition to the inertial one 36, such as, for example, a temperature sensor, multimodal haptic feedback can be provided by combining vibration, force and temperature signals over multiple body areas, for the purpose of attaining highly realistic virtual interaction. All these results are obtained through the use of a configuration that is compact, light and comfortable, i.e. which can be modified or re-configured for users having differently sized limbs or body areas in contact with the device.

[0095] All such features fall within the scope of the following claims.

Claims

CLAIMS1. Haptic device (1) that can be grasped to interact with a user’s hand (M), comprising at least one volume delimited by a membrane (15-19), which can be deformed by contact with the hand (M), and which internally contains an incompressible or compressible fluid, control means (20- 24) operatively associated with the membrane (15-19) to send and / or receive signals, thereby allowing the membrane (15-19) to issue a command and / or to operate in feedback, characterized in that the control means comprise at least one pressure sensor (21) and a vibrating actuator (12) co-operating with an electropneumatic unit (20), in order to interact with the user providing feedback by means of force and / or vibration signals.

2. Device according to claim 1, wherein, when the single membrane (15-19) is pressed, the antagonistic force can be adjusted by the control means (20).

3. Device according to claim 1 or 2, wherein the electropneumatic unit (20) comprises a control valve (22), one or more auxiliary volumes or chambers (23) acting as liquid-air interfaces (Cl, C2, . . . , CN) one or more non-retum valves (24).

4. Device according to claim 3, wherein, by acting upon the parameters of volume VCn iand pressure Ptof the auxiliary volumes (23), it is possible to adjust the feedback provided by the membrane (15-19).

5. Device according to claim 4, wherein the capacity VCn iof the auxiliary volume (23) can be changed in at least one of the following ways:- during the operation of the device, by connecting the membrane (15-19) to a different auxiliary volume (23);- during an inoperative set-up phase, by changing the liquid volume in the chamber.

6. Device according to any one of claims 3 to 5, wherein the pressure Pt can be adjusted during a set-up phase by setting its value off-line through a connection to a suitable compressor.

7. Device according to any one of the preceding claims, comprising an internally hollow external shell (2) housing the control means (20-24).

8. Device according to any one of the preceding claims, comprising an external shell (2) whereon an insert (9) is applied to adapt the device to the hand (M) of a user.

9. Device according to claim 8, wherein the insert (9) is made of a material which is different from that of the shell (2).

10. Device according to claim 8 or 9, wherein the shell (2) and / or the insert (9) comprise variable shapes and / or different types of materials, which may be rigid, semirigid, elastic, deformable, or the like.

11. Device according to any one of the preceding claims, wherein the membranes (15-19) essentially consist of deformable hollow bodies made of rubber, latex or other natural or synthetic elastomers, having substantially a cap-like shape.

12. Device according to any one of the preceding claims, comprising an internally hollow external shell (2) housing at least one of: power supply means (37) adapted to make the device independent when in use, control means (35) preferably comprising a microcontroller, a sensor (36) of the IMU (Inertial Measurement Unit) type or the like, for reading the position and orientation (36), wireless communication means (38) for communicating information with a remote-control system (40).

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