WO2016020868A1

WO2016020868A1 - Actuator for haptic devices

Info

Publication number: WO2016020868A1
Application number: PCT/IB2015/055963
Authority: WO
Inventors: Michele ANTOLINI
Original assignee: Haways S.R.L.
Priority date: 2014-08-06
Filing date: 2015-08-06
Publication date: 2016-02-11

Abstract

A device (1) is described, able to generate a torque due to gyroscopic effect, comprising at least one mass (M) rotalable around a first rotation axis (R-R), means for generating the rotation (2) of said at least one mass (M) around said first rotation axis (R-R) and orientation means (5) for rotating said first rotation axis (R-R) around a second rotation axis (O-O), characterized in that said means (2) for generating the rotation make a reciprocating rotation of said at least one mass (M) around said first rotation axis (R-R)- It is also described a method for generating a torque due to gyroscopic effect.

Description

"ACTUATOR FOR HAPTIC DEVICES"

Field of the Invention

The present invention concerns a device that is able to generate a torque due to gyroscopic effect. More in particular, the present invention relates to an actuator for haptic devices.

Known previous art

In general, a haptic device can be defined as an interface, by means of which an operator can control a particular device or tool by receiving tactile sensation as feedback signal.

Haptic devices are devices nowadays used in some advanced robotic fields, such as surgery robotics, the space one and those related to virtual reality, such as the remote manipulation or the training with simulated operations in which vision alone of what is happening is not enough for an operator to ensure a correct control of a particular device.

In addition to the robotic field, haptic devices are useful where an interaction between computer and operator is required, such as in the field of the solid modeling where the haptic interface allows the user exploiting his/her own manual skills and holding the sense of touch.

Haptic devices are known, by means of which an operator can receive a tactile sensation in response to a certain command. For example, such devices can comprise an eccentric mass rotated in order to generate a vibration in response to the occurrence of a particular event. However such devices generate, as feedback signal for an operator, a tactile sensation in which information contained is a temporal indication related only to a given event occurring or not (such as, for example, the force feedback in a joypad or the vibracall in a cellphone).

Other haptic devices can transmit to an operator a tactile sensation containing spatial indications, such as for example a direction to follow. In particular, such devices generate a torque acting on the musculoskeletal system of the operator so that he/she can perceive, as a tactile sensation, which direction the generated torque has. In other words, the device indicates to the operator a specific direction to follow, which has the form of a tactile sensation produced by a torque generated by gyroscopic effect, for example.

The gyroscopic effect rises due to the conservation law of angular momentum, whereby a rotating mass tends to keep the orientation of its own rotation axis in a fixed direction. When such a rotation axis is biased to move, i.e. is tilted by means of a torque acting on one of the planes containing the rotation axis, a precession torque appears and is perpendicular both to the rotation axis and torque that has generated the tilt of the rotation axis.

Haptic indicators are known in which, by tilting the rotation axis of two or more masses (flywheels) rotated by means of electric motors, a torque acting on the musculoskeletal system of an operator is generated due to gyroscopic effect. The torque generated by the device is perceived by the operator as a tactile sensation adapted to denote a determined direction to follow. In particular, flywheels' rotation axes are tilted at a given angular velocity by rotating them by means of further electric motors. The torque generated due to gyroscopic effect is proportional both to angular velocity related to flywheels' rotation and to angular velocity at which flywheels' rotation axes are tilted. In general, haptic devices exploiting the gyroscopic effect thus require electric motors in order to rotate one or more masses (flywheels) and to divert their rotation axes. Such devices can be therefore hardly miniaturized since electric motors with size in the order of centimeter and able to provide high angular velocities, are able to provide torques inadequate to accelerate the flywheels in times useful for the application (lower than 1 second).

In order to miniaturize haptic devices exploiting the gyroscopic effect, high rotation velocities are required whereby the precession torque generated by the deviation of the rotation axis is perceivable by the operator.

Summary of the invention

Object of the present invention is to provide a device able to generate a torque due to gyroscopic effect. Further object of the present invention is to realize an actuator for haptic devices that can be easily miniaturized and that is able to produce a torque due to gyroscopic effect perceivable by a user even without the aid of electric motors.

These and other objects are solved by the present invention by means of a device according to claim 1 , and the respective dependent claims.

In particular, the device according to the present invention comprises at least one mass rotatable around a first rotation axis, means for generating the rotation of such a mass and orientation means for rotating such a first rotation axis.

The device is characterized in that the means for generating the rotation of the rotatable mass produce a reciprocating rotation, preferably continuous during the operation of the device, of the rotatable mass around the first rotation axis.

By "reciprocating rotation" is meant a succession of rotations of the same mass, around the same axis with alternately reverted way (sense).

In other words, with the term "reciprocating rotation" herein is substantially meant an oscillation made by the rotatable mass, for example and preferably with a preset finite angular amplitude and/or frequency, around the aforesaid first rotation axis.

Note that, in the device object of this patent right, during the operation of the haptic device the aforesaid rotatable mass does not rotate continuously around its own "first" rotation axis, but rather it oscillates (i.e. reciprocally rotates) around such an axis and such an oscillation has the purpose of allowing the generation of the desired torque due to gyroscopic effect, as it will be better explained in the following.

Therefore, according to the present invention, the means for generating the rotation are such that, at first, the mass is rotated around its own rotation axis in a way and then in the opposite way - i.e. it is biased to oscillate around its own axis - for a certain angular amplitude and/or with a given frequency.

In order to generate a torque due to gyroscopic effect the mass rotation axis is tilted, i.e. rotated around a second rotation axis by means of orientation means producing a rotation, which is reciprocating too and preferably continuous during the device operation, of the first rotation axis around the second rotation axis.

Note that also in this case the term "reciprocating rotation" substantially takes the meaning of oscillation of the first rotation axis around the second rotation axis, preferably with a predetermined angular amplitude and/or frequency.

Peculiar aspect of the present invention is that reciprocating rotations of mass and rotation axis around which the mass is rotated have finite angular amplitude; thus such rotations, or oscillations, can be made also without the aid of electric motors. In particular, reciprocating rotations can be made starting from a reciprocating straight movement generated, for example, by a linear strain or by attraction and repulsion forces of an electric or magnetic field. The reciprocating straight movement is therefore turned into reciprocating rotations - oscillations - through means known in the art, for example by means of the so called "compliant mechanisms" or by means of levers and/or in general gears transforming the straight motion into rotatory motion. There is no need for the reciprocating rotations to perform a whole revolution, in particular, according to an aspect of the present invention, the maximum angular amplitude of the reciprocating rotations is lower than 360°, preferably lower than 45°, more preferably lower than 1° with a frequency higher than 1 kHz.

In practice, the reciprocating rotations can be assimilated to a sort of "vibrations" of the rotatable mass which are controlled in amplitude and frequency, preferably around the two afore mentioned axes, in order to generate a torque of desired amplitude and direction due to gyroscopic effect. In this way, the device can be miniaturized while obtaining high angular velocities and a torque due to gyroscopic effect not negligible also for masses having reduced sizes.

According to a particular aspect of the present invention, the means for the rotation of the mass and for the orientation of the rotation axis make reciprocating rotations, i.e. oscillations, of the mass and of the rotation axis respectively that are phased or in phase opposition one to another. In this way, due to gyroscopic effect, a torque can be produced in a direction orthogonal to the first and second rotation axis and with a specific way depending whether reciprocating rotations of the mass are in-phase or in phase opposition with the reciprocating rotations of the rotation axis.

In particular, the torque due to gyroscopic effect is made by reciprocally rotating a mass around a first rotation axis for a given angular amplitude, simultaneously to such a rotation, the device orientates the rotation axis by reciprocally rotating the same axis around a second rotation axis by a determined angular amplitude, then both the mass and the first rotation axis are rotated in the way opposite to the above one.

The device according to the present invention can be therefore implemented, for example, in MEMS technology and can be integrated in multiple common use devices, such as for example smartphones, navigation devices and in general all haptic devices. Furthermore, by making the device with several and suitably-positioned rotatable masses, possible vibrations produced by the afore said reciprocating rotations of each mass, which could disturb the perception of the torque generated due to gyroscopic effect, can be reduced and/or eliminated.

Brief Description of the Drawings

Further aspects and advantages of the present invention will be more evident from the following description, made for illustration purposes only and without limitation referring to the accompanying schematic drawings, in which:

- figures 1 A and IB are perspective views of two possible embodiments of the device according to the present invention, referring in particular to the means for generating the reciprocating rotation around the first rotation axis;

- figure 2 is a perspective view of a particular embodiment of the device according to the present invention, referring in particular to the orientation means for the reciprocating rotation of the first rotation axis around a second rotation axis;

- figure 3 is a three-dimensional perspective view of the arrangement of four rotatable masses of a particular embodiment of the device according to the present invention;

- figure 4 is a perspective view of an embodiment of the device according to the present invention in which there are four masses arranged as shown in figure 3.

Detailed description of some embodiments of the invention

Referring to the figures, the device 1 according to the present invention comprises at least one mass M that is rotatable around a first rotation axis R-R and means 2 for generating a rotation of the mass M around the axis R-R.

The mass M shown in the figures has the shape of a circular sector but, as it will be better explained hereinafter, the shape of the mass M does not affect particularly the torque generated due to gyroscopic effect by the device 1 according to the present invention.

Referring in particular to figure 1 A, the device 1 comprises a mass M that is rotatable around a first rotation axis R-R. The rotation axis R-R shown in figure 1 A has direction perpendicular to the sheet direction and passes through a center of rotation C.

The device 1 comprises means 2 for generating a reciprocating rotation, i.e. an oscillation preferably having finite angular amplitude, of the mass M around the rotation axis R-R. In the embodiment shown in figure 1A, the means 2 comprise a lever L whose fulcrum corresponds to the center of rotation C. In particular, the lever L comprises an arm 3 integral with the mass M and pivoted at the center of rotation C. In order to produce a reciprocating rotation of the mass M, the arm 3 is moved from the end opposite with respect to the mass M by means of at least one element 6 in order to generate a straight movement. In the embodiment shown in figure 1 A, the means 2 for generating the reciprocating rotation of the mass M comprise a piezoelectric element 6. By applying an electric field to the piezoelectric element 6, a deformation of the latter and the consequent generation of a straight movement are obtained. In particular, the piezoelectric element 6 is provided with a first end 6a integral with a supporting structure 10, only partially visible in the figures, and a second end 6b integral with the arm 3. By applying an alternating electric field to the element 6, the piezoelectric element 6 is deformed by shrinking and stretching itself as depicted by the arrows 6c. Therefore, through the lever L, the reciprocating straight movement of the piezoelectric element 6 is turned into a reciprocating rotation of the mass M around the axis R-R.

In general, the means 2 for generating the reciprocating rotation (oscillation) can comprise one or more mechanisms or gears, per se known in the art, for turning a straight motion into a rotary motion.

For example, further embodiments can provide for the use of the so called compliant mechanisms thanks to which a (preferably straight) movement acting on an input portion of the compliant mechanism can be turned into a (preferably rotary) movement acting on an output portion of the compliant mechanism, without using gears or pins, but rather exploiting the deformation of elements having different elastic coefficients. Figure 1 B shows a preferred embodiment of means 2 for generating the rotation of the mass M. In this embodiment, the means 2 for generating the rotation of the mass M comprise a lever L whose fulcrum is made without the aid of a pin, but rather by constraining the arm 3 at the center of rotation C by means of two deformable bars 4. Each deformable bar comprises a first end 4a constrained to the supporting structure 10 and a second end 4b constrained to the arm 3 of the lever L at the center of rotation C. The bars 4 hold the fulcrum of the lever L at the center of rotation C, by moving the arm 3 of the lever L by means of at least one element 6 for generating a straight movement, the bars 4 are deformed and allow the rotation of the lever L around the center of rotation C.

The arm 3 is integral with the mass M and, similarly to the embodiment shown in figure 1A, the reciprocating straight movement of the element 6 is turned into a reciprocating rotation of the lever L around the center of rotation C thereby generating the reciprocating rotation of the mass M around the rotation axis R-R. In this way, the fulcrum of the lever L can be realized more easily than the pin-equipped solution shown in figure 1 A, especially in case the device 1 is to be realized with reduced size, for example in MEMS technology.

The configuration of the lever shown in the figures has been selected for a larger ease of implementation and illustration of the present invention. Further embodiments can provide for the use of one or more compliant mechanisms having configurations different from the one shown in the figures, such that a straight movement acting on its own input portion can be turned into a rotary motion of an output portion. The inlet portion is integral with at least one element 6 for generating the straight movement, whereas the outlet portion is integral with the mass M so that to obtain a reciprocating rotation of the mass M around the axis R-R.

Further embodiments can provide means 2 for generating the rotation, which comprise at least one element 6 for generating a straight movement in which such a straight movement is generated by exploiting the attraction and/or repulsion forces of an electric or magnetic field. For example, the element 6 can comprise an electromagnet able to generate such a variable magnetic field that a further electromagnet or permanent magnet can be attracted and/or repulsed. The electromagnets and/or the permanent magnets, being respectively integral with the supporting structure 10 and the arm 3 of the lever L, or vice versa, will produce a movement of the arm 3 and the consequent rotation of the mass M.

Referring to figure 2, the device 1 comprises orientation means 5 for reciprocally rotating, i.e. oscillating, the rotation axis R-R around a second rotation axis O-O. The rotation axis 0-0 is perpendicular to the axis R-R and, in the embodiment shown in the figures, intersects the axis R-R in a center of rotation C Other embodiments can provide for the rotation axis 0-0 not intersecting the rotation axis R-R, whereas in other embodiments the rotation axis 0-0 could intersect the rotation axis R-R in a center of rotation C coincident with the center of rotation C, still falling within the protection scope of the present invention.

The orientation means 5 are analogous to the means 2 for generating the rotation, which are shown in figure 1A and in figure IB. In particular, the orientation means 5 comprise at least one element 7 for generating a straight movement and a mechanism for turning such a straight motion into a rotary motion adapted to tilt the rotation axis R-R by rotating it around the axis 0-0.

In figure 2 a particular embodiment of the orientation means 5 is shown, in which the arm 3 of the lever L is constrained at the center of rotation C to an oscillating structure 1 1 integral with the supporting structure 10. The oscillating structure 1 1 comprises a portion 12 integral with the arm 3 and transversal to the same, so that to extend in a direction substantially coincident with the rotation axis R-R.

The oscillating structure comprises a further portion 13 opposed to the portion 12 and also integral with the arm 3 and transversal thereto so that to extend in a direction substantially coincident with the rotation axis R-R. The portion 13 is integral with an element 7 for generating a straight movement that, in this case, is a piezoelectric element. Such a piezoelectric element is interposed between the portion 13 and the supporting structure 10 so that the reciprocating straight movement generated by the piezoelectric element 7 is turned into a reciprocating rotary movement, i.e. an oscillation, of the portions 12, 13 around the axis 0-0. Since the portions 12 and 13 extend in a direction coincident with the axis R-R, also the rotation axis R-R is reciprocally rotated around the axis 0-0.

Further embodiments are provided in which the orientation means 5 can be realized differently with respect to the embodiment shown in figure 2. Further embodiments can provide orientation means 5 realized analogously to what above described for making the means 2 for generating the reciprocating rotation of the mass M, still remaining within the protection scope of the present invention.

In general, orientation means 5 such that a reciprocating rotation of the rotation axis R-R around the rotation axis 0-0 can be produced, still fall within the protection scope of the present invention.

In general, the means 2 for generating the rotation and the orientation means 5 respectively produce a reciprocating rotation - oscillation - of the mass M around a rotation axis R-R and a reciprocating rotation - oscillation - of the axis R-R around the axis O-O. Therefore, in case size of the device 1 is not a pressing specification, the means 2 for generating the rotation and/or the orientation means 5 can comprise one or more electric motors, still remaining in the protection scope of the present invention. As explained above, by "reciprocating rotation" is meant a succession of rotations with reciprocally inverted way (first in a way and subsequently in the opposite way) for a given angular amplitude and/or with a certain frequency.

For ease of calculation, both the elements 6, 7 for generating a straight motion can be assumed to be piezoelectric elements excited through an alternating electric field having a sinusoidal pattern at a determined frequency f. In particular, by defining Θ as the reciprocating rotation of the mass M around the rotation axis R-R, it will have a maximum angular amplitude β (shown in figure IB) and a time pattern of the type:

Where f is the excitation frequency of the electric field to which the piezoelectric element 6 is subjected.

The angular velocity oo(t) of the mass M is obtained as the time derivative of the function 0(t), i.e.:

o>(t) = 2npf cos(2nft)

Therefore, to the mass M an angular momentum having amplitude L = Ιω will be associated, where I is the moment of inertia of the mass M.

Similarly, by defining φ as the reciprocating rotation of the rotation axis R-R around the rotation axis O-O, a time function φ(ΐ) can be defined as the time pattern of the angular amplitude of the reciprocating rotation φ. In particular, by denoting with γ the maximum angular amplitude of the reciprocating rotation φ, it results that:

(p(t) = γ sin^ft)

Both the reciprocating rotations Θ and φ have the same frequency f.

Preferably, the piezoelectric elements 6 and 7 are connected to a synchronization circuit (not shown) that excites both the piezoelectric elements 6, 7 with the same frequency f and with a certain phase difference.

The angular velocity Ω, at which the rotation axis R-R is rotated around the axis O-O, is obtained as the time derivative of φ(ΐ), therefore:

Due to gyroscopic effect, a precession torque τ appears with amplitude QL.

In particular, the torque generated due to gyroscopic effect will have a time pattern x(t) of:

x(t) = Ω(ι) I co(t) = I 2πγί cos(2irft) 2πβί cos(2itft) As explained above, the shape of the mass M does not affect particularly the calculation of the torque generated due to gyroscopic effect, in fact the moment of inertia I of the mass M can be generalized by applying the Huygens-Steiner theorem, by which I = I_m + Md², where I_m is the inertia of the mass M calculated at its center of mass (referred to an axis parallel to the axis R-R) and d is the distance between the center of mass and the center of rotation C. The resulting torque is therefore approximated by the following formula:

τ(ΐ) = 4βγ (πί)² (Im + Md²) cos²^ft)

The direction of the torque τ will be perpendicular to both the axes R-R and O-O and have a way depending on the phase difference at which the piezoelectric elements 6 and 7 are excited. In particular, in order to obtain a torque having constant way during time, i.e. with always-positive way or always-negative way, the piezoelectric elements 6 and 7 are in-phase or in phase-opposition excited.

In order to determine the sign of the way of the torque generated due to gyroscopic effect, the right hand rule is followed by arranging the device 1 on a Cartesian axes system.

The generated torque τ has a pulsating time pattern whose amplitude reaches the maximum value when both the angular velocities (in absolute value) co(t) of the mass M and Ω(ΐ) of the axis R-R reach the maximum value.

In practice, the generated torque τ has amplitude with a time pattern having twice the frequency with respect to the excitation frequency at which the piezoelectric elements 6, 7 are deformed.

The maximum angular amplitudes γ and β in the embodiment shown in the figures are lower than 10° but, depending on the configuration of the means 2 for generating the rotation and of the orientation means 5, they can have higher amplitudes. In particular, the maximum amplitudes of the reciprocating rotations will be lower than 360°, preferably lower than 45°, in other words the reciprocating rotations have angular amplitude lower than a whole revolution, and thus a torque can be generated due to gyroscopic effect also without the aid of electric motors.

The minimum torque perceivable by a human being is 0.02 Nm, but this is the inferior limit. In order to make the torque more clearly perceivable, it has to be higher than 0.06 Nm or more preferably higher than 0.1 Nm.

By way of example, considering a steel mass M of 1 cm³ (7.8 g/cm³ density) reciprocating rotated through an arm 3 of 1 cm length, with angular amplitudes γ and β of grade 1 and frequency 2.5 kHz, the generated torque is in first approximation 0.068 Nm. A suitable optimization of the parameters allows recognizing the optimal selection of the angular frequencies γ, β of the reciprocating rotations, the frequency f, the mass M and the length of the arm 3, so that to minimize the size and allow obtaining the maximum energy efficiency.

In particular, figures 3 and 4 show a further embodiment of the device Γ according to the present invention comprising four masses denoted by Ma, Mb, Mc, Md and arranged so that to be able to compensate possible vibrations produced by the reciprocating rotations.

In figure 3 the four masses of the device 1 ' are shown as arranged on a Cartesian axes system xyz. In order to determine the way of the torque generated due to gyroscopic effect by each mass, the right hand rule is followed. The rotation axis R-R of each mass is parallel to the axis z, whereas each axis 0-0 around which the respective axis R-R is rotated, is parallel to the axis y. The torque generated due to gyroscopic effect acts around an axis A-A parallel to the axis x.

The reciprocating rotations of each mass are actuated similarly to what described for the device 1 shown in figures 1A, IB and 2, i.e. through the means 2 and the means 5 even if not shown in figure 3. By taking into account for example the mass Ma, it is rotated in the positive way (unit vector +z) during a first half-period of the period T and in the negative way (unit vector -z) during the next half-period. In order to obtain a torque due to gyroscopic effect in the positive way (unit vector +x), the rotation axis R-R is rotated around the axis 0-0 in the positive way (unit vector +y) during the first half-period and in the negative way (unit vector -y) during the following half-period. In other words, the reciprocating rotations of the mass Ma around the axis R-R and the reciprocating rotations of the axis R-R around the axis 0-0 are phased. This is obtained by exciting the respective piezoelectric elements 6 and 7 with the same alternating electric field. Similarly, in order to generate a torque due to gyroscopic effect in the negative way (unit vector - x), the reciprocating rotations are generated in phase opposition, thus exciting the respective piezoelectric elements 6 and 7 with respective alternating electric fields in phase opposition.

A more complete outlook of the device Γ is shown in figure 4, in which also the means 2 for generating the reciprocating rotation of the four masses Ma, Mb, Mc, Md and the orientation means 5 for rotating the respective four rotation axes R-R of the afore said masses are shown.

The four masses of the device Γ are spatially arranged so that the rotation axes R-R of each mass are parallel one to another and the rotation axes 0-0 of the masses Ma and Mb coincide respectively with the rotation axes O-O of the masses Mc and Md (thus the rotation axes 0-0 are parallel one to another).

The reciprocating rotations of the masses around the respective rotation axes R-R are shown in figure 4 and, in particular, the rotations of the masses during a first half- period (as denoted by the arrows) are shown. By referring to the Cartesian axes system of figure 3, during the first half-period the masses Ma and Mc are rotated with positive way (thus they have the unit vector +z of the angular momentum), whereas the masses Mb and Md with negative way (thus they have the unit vector -z of the angular momentum). During such a half period, the rotation axes R-R of the masses Ma and Mc are rotated around the respective axes 0-0 with positive way (unit vector +y), whereas the rotation axes R-R of the masses Mb and Md are rotated around the respective axes O-O with negative way (unit vector -y). The torques made due to gyroscopic effect associated with each mass will have the same direction and way. In particular, for the masses Ma and Mc the torque way will be given by the vector product between the unit vector +z and the unit vector -y, thus the unit vector of the torque will be -x. For the masses Mb and Md the torque way will be given by the vector product between the unit vector -z and the unit vector -y, thus the unit vector of the torque will be -x.

During the following half period all the unit vectors will change sign and, therefore, the result does not change. The torque generated due to gyroscopic effect will have a direction parallel to the axis x, way -x and amplitude equal to four times the amplitude τ calculated for the device 1 comprising only one mass M. Therefore for the device 1 ', the amplitude of the torque τ will have a time pattern equal to:

x(t) - βγ (4πί ² (I_m + Md²) cos²^ft)

The embodiment shown in figure 3 and figure 4 has the advantage that possible vibrations produced by the reciprocating rotations of the masses Ma, Mb, Mc, Md around the respective rotation axes R-R and vibrations produced by the reciprocating rotations of the axes R-R around the respective axes O-O, can be mutually compensated. Such vibrations, by compensating themselves, reduce possible disturbances in perception of the generated torque. In addition, a torque generated due to gyroscopic effect is obtained with amplitude amplified by a factor four with respect to the torque obtained with a single mass.

Both the device 1 and the device can be however considered as base elements for the realization of actuators for more complex haptic devices. In fact, by virtue of their high level of miniaturization, haptic devices can be designed comprising a plurality of devices 1 or devices 1 in which the respective means 2 for the reciprocating rotation and the orientation means 5 can be suitably temporized in order to obtain a torque generated with nearly constant amplitude. For example, by grouping three devices 1 ' in a supporting structure, three torques τΐ, τ2, x3 can be produced due to gyroscopic effect, as described above. Such torques will have amplitude with a pattern pulsating at a frequency twice the frequency at which the piezoelectric elements are excited. By means of a timing circuit the three devices Γ can be controlled so that the generated torques τΐ , τ2, τ3 have a phase difference equal to one third of their pulse period. Thus, by adding the three generated torques, a resulting torque is obtained whose amplitude is nearly constant except for a ripple.

The resulting torque amplitude can be thus controlled by adjusting the frequency f with which the respective piezoelectric elements are excited or, in general, the frequency of the reciprocating rotations produced through the means 2 and the means 5.

In order to obtain a resulting torque with an adjustable direction lying on the xy plane, a further embodiment is provided in which at least two devices 1 or 1 ' are implemented on two or more layers (one above the other). Two layers are however enough to obtain a torque resulting as the sum of two components: a torque acting along the direction x generated by at least one device 1, V implemented on a first layer and a torque acting along the direction y generated by at least one device 1, 1' implemented on the other layer. By adjusting the amplitudes of the two components, a resulting torque acting along an adjustable direction lying on the xy plane can be obtained.

The high miniaturization degree allows embodying a plurality of devices 1 and/or devices V inside devices for medical use, in order to improve their control. For example, a scalpel provided with one or more devices according to the present invention inside the handle, in order to drive the user and follow a precise cutting line. Other applications of the present invention can be implemented on devices of common use, as smartphones or joypads, in which the addition of a feedback signal for the user, in the form of a tactile sensation, can show the way forward to several applications.

Claims

1. Device (1) able to generate a torque due to gyroscopic effect, comprising at least one mass (M) rotatable around a first rotation axis (R-R), means (2) for generating the rotation of said at least one mass (M) around said first rotation axis (R-R) and orientation means (5) to rotate said first rotation axis (R-R) around a second rotation axis (O-O) characterized in that said means (2) for generating the rotation produce a reciprocating rotation of said at least one mass (M) around said first rotation axis (R- R).

2. Device (1) according to claim 1, wherein said orientation means (5) produce a reciprocating rotation of said first rotation axis (R-R) around said second rotation axis

(O-O).

3. Device (1) according to claim 1 or 2, wherein said means (2) for generating the rotation produce a reciprocating rotation of said at least one mass (M) around said first rotation axis (R-R) with an angular amplitude lower than 360°.

4. Device (1) according to any one of the preceding claims wherein said orientation means (5) produce a reciprocating rotation of said first rotation axis (R-R) around said second rotation axis (O-O) with an angular amplitude lower than 360°.

5. Device (1) according to any one of claims 2 to 4 wherein said means (2) for generating the rotation and said orientation means (5) respectively produce a reciprocating rotation of said at least one mass (M) and a reciprocating rotation of said first rotation axis (R-R) phased or in phase opposition one to another.

6. Device (1) according to any one of the preceding claims, wherein said first rotation axis (R-R) is incident to said second rotation axis (O-O) in an instantaneous center of rotation (C).

7. Device (1) according to any one of the preceding claims wherein said means (2) for generating the rotation and said orientation means (5) comprise at least one element (6, 7) for generating a straight movement and at least one lever (L) or a compliant mechanism and/or means for turning said straight motion into rotary motion.

8. Device (1) according to claim 7, wherein said at least one element (6, 7) for generating a straight movement comprises at least one piezoelectric element.

9. Device (1) according to any one of the preceding claims wherein said reciprocating rotations made by said means (2) for generating the rotation and said orientation means (5) have angular amplitudes lower than 45°.

10. Device (Γ) according to any one of the preceding claims comprising at least two rotatable masses (Ma, Mb, Mc, Md), each mass (Ma, Mb, Mc, Md) being rotatable around its own rotation axis (R-R), said device (Γ) comprising means (2) for generating the reciprocating rotation of said masses (Ma, Mb, Mc, Md) and orientation means (5) for the reciprocating rotation of each rotation axis (R-R) around a respective second rotation axis (O-O), said at least two masses (Ma, Mb, Mc, Md) being arranged so that the vibrations made by the reciprocating rotations of said at least two masses (Ma, Mb, Mc, Md) and the respective rotation axes (R-R) can mutually cancel out.

11. Haptic interface comprising at least one device (1 , 1 ') according to one or more preceding claims.

12. Haptic interface according to claim 11 comprising at least two devices (1, Γ), a timing circuit adapted to adjust the amplitude phase difference of torques generated by said at least two devices (1 , ).

13. Haptic interface according to claim 11 or 12 wherein said timing circuit is adapted to adjust the frequency f of the reciprocating rotations of each of said at least two devices (1, Γ).

14. Method for generating a torque due to gyroscopic effect by means of a device (1, Γ) according to any one of claims 1 to 10 comprising the steps of:

a) generating a reciprocating rotation (Θ) of at least one mass (M) around a first rotation axis (R-R) with a determined angular amplitude (β) and a determined frequency (f);

b) generating a reciprocating rotation (φ) of said rotation axis (R-R) around a second rotation axis (O-O) with a determined angular amplitude (γ) and a determined frequency (f);

characterized in that said reciprocating rotation (Θ) generated during said step a) and said reciprocating rotation (φ) generated during said step b) have the same frequency (f) and that they are phased or in phase opposition one to another.