Human-machine interface with magnetorheological braking module

Abstract

A human-machine interface (1) comprising a control element (2) mounted on a base (3), the base (3) comprising a rotating element (12) whose rotation is a function of a displacement of the lever (2), and a braking module (14) configured to be coupled to the base (3) and to brake the rotation of the rotating element (12), the braking module (14) comprising: a stator (20) defining a braking cavity (22) filled with a magnetorheological medium, a coil (20) configured to generate a magnetic field in the braking cavity (22), a rotor (16) which includes a braking element (24) disposed in the braking cavity (22), the rotor (16) being configured to be coupled to the rotating element (12) to lock the rotor (16) and the rotating element (12) coaxially about an axis of rotation (Ω), and having a rotational asymmetry with respect to the axis of rotation (Ω). Figure for the abbreviation: 1

Description

Title of the invention: Human-machine interface with magnetorheological braking module Technical field

[0001] The present invention relates to a human-machine interface comprising a joystick mounted on a base, the joystick being adapted to be moved by a user according to two degrees of freedom to control an apparatus. Technological background

[0002] A human-machine interface is an electromechanical device adapted to transmit a command exerted by a user on a mobile element, such as a joystick for example, to a device coupled to said mobile element. A joystick is a device projecting from a base and movable relative to this base according to at least two degrees of freedom to control a device according to the movement (in inclination, translation or rotation) of the joystick.

[0003] The base comprises at least two rotating members, generally taking the form of shafts but which may also be a rotating bore such as a sleeve, the rotation of which is a function of the movement of the handle according to a respective degree of freedom. The movement of the handle generates by mechanical drive the rotation of the rotating members.

[0004] It is interesting to provide such a human-machine interface with several haptic feedbacks, that is to say kinesthetic stimulations aimed at informing the user about a state of the device, or more generally translating information intended for the user. Such haptic feedback can be provided by a brake, controlled by a control unit as a function of the position of the joystick determined by a sensor.

[0005] For example, patent application WO2018 / 055295 proposes a lever equipped with a brake for braking a rotating member as described in patent application WO2016 / 050717. These magnetorheological brakes are capable of generating kinesthetic stimulations.

[0006] However, such a system is complex, in particular when, in order to achieve high braking torques, it becomes necessary to use gears between the rotating member and the brake or other reduction systems or geared motors (chains, belts, etc.). This complexity results in a high cost, and a lack of mechanical robustness, even though such levers are intended to be used in environments with high mechanical constraints, both in terms of vibrations, temperatures, intensity of use and service life.

[0007] In addition, these braking systems are bulky, and their integration into spaces restricted spaces such as vehicle interiors, can be difficult, especially when it is necessary to leave the base of the controller free for the user to rest their hand or arm on when using the controller.

[0008] Finally, haptic transparency can be affected over time due to phenomena of wear, friction, pollution by particles at the level of the transmission of movements, phenomena which are all the more important as the system is complex. PRESENTATION OF THE INVENTION

[0009] The invention aims to remedy at least in part these drawbacks, and to propose a human-machine interface provided with one or more brake(s), which is of a simple design, less expensive, more robust, less bulky and easier to integrate.

[0010] For this purpose, a human-machine interface is proposed comprising: - a control member adapted to be moved by a user according to a degree of freedom to control a device; - a base on which the control member is mounted, the base comprising a rotary member whose rotation is a function of a movement of the control member according to the degree of freedom; - a braking module configured to be coupled to the base and to brake the rotation of the rotating member, the braking module comprising: - a stator defining a braking cavity, - a rotor which comprises a braking part arranged in the braking cavity, - a coil configured to generate a magnetic field in the braking cavity, - a magnetorheological medium in the braking cavity and sensitive to the magnetic field, wherein the rotor is configured to be coupled to the rotating member to rotationally secure the rotor and the rotating member coaxially about an axis of rotation, and in that the braking part extends radially relative to the axis of rotation in the braking cavity and has rotational asymmetry relative to the axis of rotation.

[0011] The invention is advantageously supplemented by the following characteristics, taken alone or in any of their technically possible combinations: - the braking part is flat and extends along a braking plane perpendicular to the axis of rotation; - at least 75% of the braking part is confined in an angular portion of the braking cavity less than 180° relative to the axis of rotation; - the braking part extends from the axis of rotation over at least 20 mm in a first direction in a braking plane perpendicular to the axis of rotation, and extends over less than 10 mm in a second direction opposite to the first direction; - the rotation axis is eccentric relative to the braking part and relative to the braking module - the rotor and the rotating member have a rotational transmission ratio of 1: - the braking part comprises on one surface a plurality of cavities; - the stator comprises in an active zone a first part in a first material, and a second part in a second material outside the active zone, the first material having a magnetic permeability greater than a magnetic permeability of the second material, the coil being arranged in the active zone - the braking part comprises a first face and a second face, each face being separated from a coil by a thickness of magnetorheological medium; - the braking module is configured so that magnetic flux lines generated by the coil transversely pass through the magnetorheological medium and the braking part in two opposite directions.

[0012] The human-machine interface may comprise an additional braking module mounted on the braking module, the additional braking module being configured to brake the rotation of the rotating member and comprising: - a stator defining a braking cavity, - a rotor which comprises a braking part arranged in the braking cavity, - a coil configured to generate a magnetic field in the braking cavity, - a magnetorheological medium in the braking cavity and sensitive to the magnetic field, wherein the rotor is configured to be rotationally secured to the rotating member, and the braking part extends radially relative to the axis of rotation in the braking cavity and has rotational asymmetry relative to the axis of rotation. Presentation of figures

[0013] The invention will be better understood, thanks to the following description, which relates to embodiments and variants according to the present invention, given as non-limiting examples and explained with reference to the appended schematic drawings, in which:

[0014] - [Fig.l] schematically shows a lever mounted on a base on which couple two braking modules according to a possible embodiment of the invention

[0015] - [Fig.2] shows the spreader bar integrated into the base according to one embodiment possible of the invention;

[0016] - [Fig.3] shows a side view of a handle and a base, with several braking modules coupled to the same rotating member, according to a possible embodiment of the invention;

[0017] - [Fig.4] shows an external view of a braking module, according to a method of rea possible use of the invention;

[0018] - [Fig.5] is an exploded view of a braking module according to one embodiment possible of the invention;

[0019] - [Fig.6] is a sectional view of a braking module according to a method of rea possible use of the invention;

[0020] - [Fig.7] shows a detail of a sectional view of a braking module centered on the active zone, with the flux lines of the magnetic field;

[0021] - [Fig.8a] shows a front view of a braking part in its cavity of braking, in the absence of rotation of the rotary member according to a possible embodiment of the invention;

[0022] - [Fig.8b] shows a front view of a braking part in its cavity of braking when the braking part reaches a maximum rotational travel, according to a possible embodiment of the invention. Detailed description

[0023] In the following non-limiting example, the control member adapted to be moved by a user according to one degree of freedom to control a device is a joystick, adapted to be moved by a user according to two degrees of freedom to control a device. However, the control member could be for example a lever, a wheel (or "roller" in English), or any other device whose positioning can be modified (by rotation, translation, inclination) by a user relative to a base to control a device.

[0024] With reference to [Fig.l], 2 and 3, the human-machine interface 1 comprises a joystick 2 and a base 3 on which the joystick 2 is mounted. The human-machine interface 1 is intended to be mounted on or in a control panel of a device and connected to one or more components of the device, in order to allow a user to perform one or more tasks. There are a large number of types of devices capable of using such a human-machine interface. Among these devices, mention may be made, but are not limited to: construction vehicles, agricultural vehicles, forestry vehicles, forklifts, autonomous vehicles, game consoles, etc.

[0025] The joystick 2 is adapted to be moved by a user according to at least two degrees of freedom relative to its base 3 to control the device. The movement of the joystick 2 is done by translation, inclination or rotation of the joystick 2 relative to the base 3. Conventionally, an inclination is assimilated to a translation in the same direction, and the same will be done here.

[0026] The handle 2 extends on the side of the control panel facing the user, the base 3 being able to be located at least partly on the side of the control panel opposite the user. The base 3 may comprise fixing means adapted to rigidly fix the base to the panel or to another element of the apparatus.

[0027] The joystick 2 can be moved in a plane substantially parallel to the surface of the base, defined by the X and Y axes. In certain embodiments, the joystick can also be pivotally moved about a Z axis orthogonal to the XY plane. Any combination of at least two degrees of freedom in translation and / or rotation and / or inclination can be implemented. The joystick 2 can further comprise one or more control buttons 4, for example of the push button, rocker, wheel, etc. type, making it possible to activate or deactivate a component of the device.

[0028] The movement of the lever 2 causes the movement of a rod 6 extending from the lever 2 into the base 3. This rod 6 enters slots 8a, 8b formed in two rudders 10a, 10b housed in the base 3 and which pivot about two respective axes. Each slot 8a, 8b of the rudders 10a, 10b has an oblong shape, extending in a direction perpendicular to the slot 8a, 8b of the other rudder 10a, 10b, so that the movement of the rod 6 in a direction along an X or Y axis causes only the movement of one rudder 10a, 10b, the rod moving freely in the slot 8a, 8b of the other rudder 10a, 10b. Rotating members 12 are coupled to each spreader bar 10a, 10b so that pivoting of a spreader bar 10a, 10b causes its rotating member 12 to rotate. The rotating members 12 are accessible from outside the base 3.In the illustrated example, the rotating member 3 is a shaft projecting out of the base 3, but the rotating member 3 could also be a rotating bore facing an opening in the housing of the base 3.

[0029] At least one position sensor makes it possible to detect the position and / or the movement of one of the components driven by the lever, such as for example the rod 6 or the rotating members 12. Any suitable sensor technology can be used, such as for example a Hall effect sensor.

[0030] A braking module 14 is configured to be coupled to the base 3. More specifically, the braking module 14 is configured to be fixed to the base 3, for example by screws or any other form of connector, and comprises a rotor 16 configured to be coupled to a rotating member 12. The braking module 14 is configured to brake the rotation of the rotary member 12 to which its rotor 16 is coupled. In the example illustrated, the rotary member 12 is a shaft, and the braking module 14 comprises a receiving cavity 18 (see [Fig.4]) into which the shaft 12 is inserted during the assembly of the braking module 14. When the rotary member 12 is a rotary bore, the rotor 16 of the braking module 14 may comprise a shaft engaging in the rotary bore.

[0031] Typically, the base 3 is provided with at least two rotating members 12 around two perpendicular axes, defining at least two sides against which braking modules 14 can be mounted, as in the example of [Fig. 1]. It is possible for a rotating member 12 to be integral with another rotating member 12, in particular when they are coupled to the same lifting beam 10a, 10b. This is typically the case for rotating members 12 located on opposite sides of the base 3. This is for example the case in the example of [Fig. 3], where braking modules 14, 14' are mounted on opposite sides of the base 3. In this case, the braking actions of the two braking modules 14, 14' are applied, via the rotating members 12 integral in rotation, to the same movement of the rudder 10a, 10b, and therefore add up. This arrangement makes it possible to increase (for example double) the maximum braking torque over one degree of freedom.

[0032] It is also possible to couple two braking modules 14 on the same side of the base 3, as on the left side of the base 3 in [Fig. 3]. To this end, a braking module 14 may provide a mechanical connection returning the effect of the rotary member 12 to its side opposite to that facing the base 3. For example, if the rotary member 12 is a sufficiently long shaft, a first braking module 14 may be crossed by the shaft 12, allowing the coupling of a second braking module 14" on the same shaft 12. Otherwise, the first braking module 14 may itself comprise an auxiliary rotary member integral in rotation with the rotor 16 of the first braking module 14 and which acts as a rotary member for the second braking module 14".For example, the first braking module 14 may extend the shaft 12 by an auxiliary shaft coupled to the shaft 12 of the base 3, the auxiliary shaft projecting from the first braking module 14 allowing the coupling of a second braking module 14" to the auxiliary shaft. The first braking module 14 may alternatively comprise a rotary bore coupled with the rotary member 12 of the base 3 or the rotor 16 of the first braking module 14, and the second braking module 14" may comprise a shaft configured to be coupled to the rotary bore. This arrangement makes it possible to increase (for example double) the maximum braking torque over one degree of freedom. It should be noted that as in these examples, the two braking modules 14, 14" may be different in terms of the rotational connection with the rotary member 12, but that they are preferably similar in other respects, in particular braking, which will now be described.

[0033] With reference to Figures 5 and 6, the braking module 14 comprises a rotor 16 and at least one stator 20, preferably composed of two parts or two stators 20a, 20b as in the illustrated example, which defines a braking cavity 22. The rotor 16 comprises a braking part 24 arranged in the braking cavity 22. The rotor 16 is configured to be coupled to the rotary member 12 to rotationally secure the rotor 16 and the rotary member 12 coaxially about an axis of rotation Q. The coupling between the rotor 16 and the rotary member 12 is done directly, that is to say without an intermediate moving part such as for example a gear, which allows greater simplicity and great robustness. The rotor 16 and the rotary member 12 rotate at the same speed. In other words, the rotor 16 and the rotating member 12 have a rotational transmission ratio of 1.The rotor 16 and the rotating member 12 may for example be coupled using a key, splines, flats, etc. Any form of coupling may be used. Preferably, the rotor 16 is in contact with the rotating member 12.

[0034] In this example, the rotary member 12 is a shaft 12, and the rotor 16 therefore comprises an opening 26, here in the braking part 24 for the passage of the shaft 12 with which the rotor 16 is coupled. For example, the opening 26 has a section with a rotational asymmetry complementary to a rotational asymmetry of the section of the shaft 12. In this example, the opening 26 comprises at least one flat side against which a flat side of the shaft 12 can cooperate to rotate the rotor 16. In order to allow the coupling between the rotor 16 and the shaft 12, the cover 28 of the housing 30 of the braking module 14 is provided with an opening defining the receiving cavity 18 to allow the shaft 12 to pass along the axis of rotation Q. The shaft 12 then passes through a seal 34 and a ball bearing 36, then passes through a first stator 20a, the coupling opening 26 of the rotor 16, the second stator 20b and a second ball bearing 38.This arrangement is only an example, in the case where the rotating member 12 is a shaft 12. For example, when the rotating member 12 is a rotating bore, the rotor 16 may comprise a shaft integral with the braking part 24, which extends along the axis of rotation Q through the opening 32 of the housing 30 to penetrate into the rotating bore of the base 3. .

[0035] The two stators 20a, 20b bear against each other and define the braking cavity 22 between them, in which the braking part 24 is housed. Centering pins 39 may be provided to connect the two stators 20a, 20b together.

[0036] The braking module 14 also comprises at least one coil 40 configured to generate a magnetic field in the braking cavity 22. The coil 40 is arranged as close as possible to the braking part 24 of the rotor 16, and preferably in the braking cavity 22. The coil 40 extends in a plane parallel to the braking part 24 of the rotor 16, i.e. perpendicular to the axis of rotation Q. The coil 40 forms a loop around the axis of rotation Q at the periphery of the braking cavity 22. Preferably, two coils 40a, 40b are arranged between the two stators 20a, 20b, each on one side of the rotor 16. The two coils 40a, 40b face each other and extend in planes parallel to the braking part 24 of the rotor 16. The coils 40a, 40b are spaced at least less than 5 mm apart in an active zone 41 where the braking part 24 is located in the braking cavity 22.

[0037] The braking module 1 comprises in the braking cavity a magnetorheological medium 42 sensitive to the magnetic field, and in which the braking part 24 is capable of rotating in the absence of a magnetic field. When a magnetorheological medium 42 is subjected to a magnetic field, its apparent viscosity increases with the intensity of the magnetic field. Typically, the magnetorheological medium 42 is a magnetorheological fluid, taking the form of a liquid in the absence of a magnetic field, but can also be a powder. For example, it is possible to use a magnetorheological fluid based on an insulating fluid such as an oil, loaded with ferromagnetic particles. The braking part 24, in use, is immersed in the magnetorheological medium 42. Preferably, the magnetorheological medium 42 fills the majority of the volume of the braking cavity 22, and more preferably the entirety of the braking cavity 22.

[0038] The braking part 24 is flat and extends along a braking plane perpendicular to the axis of rotation Q. For example, the braking part 24 may comprise a first face 24a and a second face 24b opposite the first face 24a in the direction of the axis of rotation Q. Preferably, the braking part 24 has a thickness between the first face 24a and the second face 24b of less than 5 mm, and more preferably less than 2 mm, in the direction of the axis of rotation Q. Each face 24a, 24b of the braking part 24 may be separated from a coil 40a, 40b by a thickness of magnetorheological medium 42, preferably less than 1 mm, and preferably less than 0.5 mm. The braking part 24 is made of ferromagnetic material and preferably has a high magnetic permeability, typically with a maximum relative permeability pr greater than 1000 at 20°C, and preferably greater than 5000 at 20°C.For example, the braking part 24 may be made of pure iron (i.e. purity greater than 99.50%, preferably greater than 99.80%). The stator 20 or the stators 20a, 20b are also made of a similar material, or less for a part of their volume.

[0039] More specifically, as illustrated in [Fig.7], the braking module comprises an active zone 41 in which the coils 40a, 40b generate a magnetic field. In this active zone 41, the stator 20 or the stators 20a, 20b have a first part 46a, 46b which is made of a first material, for example ferromagnetic, which preferably has a high magnetic permeability, typically with a per maximum relative permeability p, greater than 1000 at 20°C, and preferably greater than 5000, such as pure iron, while outside this active zone 41, the stator 20 or the stators 20a, 20b have a second part 48a, 48b which is, at least at the periphery of the active zone 41, formed of a second material having a second magnetic permeability lower than the first magnetic permeability, typically with a maximum relative permeability pr less than 10 at 20°C. The second material may be paramagnetic, and is for example aluminum. The first part 46a, 46b of a stator 20 is radially more external than the second part 46a, 46b of said stator 20.

[0040] The presence of two materials with different magnetic properties in a stator 20 makes it possible to define a magnetic circuit which concentrates the magnetic flux in the active zone 41 in which braking occurs. As shown in [Fig.7], the magnetic flux propagates in the first part 46a, 46b of each stator 20a, 20b, without significant propagation in the second part 48a, 48b of each stator 20a, 20b. The coils 40a, 40b are arranged in this active zone 4L. More precisely, each coil 40a, 40b is surrounded on three sides by the first material of a stator 20, the fourth side preferably being open to the braking cavity 22.

[0041] The braking module 14 is configured so that magnetic flux lines generated by the coil transversely pass through the magnetorheological medium 42 and the braking part 24 in two opposite directions. The magnetic flux lines are closed around the two coils 40a, 40b, and pass through the magnetorheological medium 42 in two different directions: - between the rotation axis Q and the two coils 40a, 40b facing each other, the magnetic flux lines pass through the braking cavity 22 and therefore the magnetorheological medium 42 and the braking part 24 which is immersed therein in a first direction, and - between the two coils 40a, 40b facing each other and the radial end of the braking part 24, the magnetic flux lines pass through the braking cavity 22 and therefore the magnetorheological medium 42 and the braking part 24 which is immersed therein in a second direction opposite to the first direction.

[0042] In both cases, the magnetic flux lines generated by the coils 40 are parallel to the axis of rotation Q, and therefore are perpendicular to the braking part 24. Thus, the magnetorheological medium 42 is traversed perpendicular to the direction of movement of the braking part 24 by the magnetic field, so as to strengthen the reaction of the magnetorheological medium 42 to the application of the magnetic field. Above all, the increase in the viscosity of the magnetorheological medium 42 requires a greater shear force from the braking part 24 to rotate in the braking cavity 22.

[0043] As illustrated in Figures 8a and 8b, the braking part 24 does not have a geometry of revolution, and in particular has an asymmetry by rotation by relative to the axis of rotation Q. For example, at least 75% of the braking part 24 is confined in an angular portion of the braking cavity less than 180° relative to the axis of rotation Q. In particular, at least 75% of the braking part remains in the part of the braking cavity 22 located below the axis of rotation Q.

[0044] Thus, the axis of rotation Q is eccentric relative to the braking part 24. The axis of rotation can then advantageously be eccentric relative to the braking module 14, which allows the braking module 14 not to require a large space in all directions. In particular, the braking module 14, as well as the rotor 16, can extend downwards more than upwards when it is mounted against the base 3 of the lever 2. On the other hand, the braking part 24 can have axial symmetry, around a median axis A of its travel.

[0045] In use, the travel of the braking part in the braking cavity is limited and less than + / - 40°, preferably less than + / - 30°, and more preferably less than or equal to 25°. [Fig. 8a] shows a braking part 24 positioned at the center of its possible travel, with a median or central axis A passing through the center of the braking cavity 22. [Fig. 8b] shows this braking part 24 after rotation of 20°, at the maximum of its travel in the braking cavity 22. It can be seen that the shape of the braking cavity 22 and the shape of the braking part 24 are optimized to allow rotations within the authorized travel, but do not allow a greater rotation, the stator 20 defining the braking cavity 22 preventing too great a rotation of the braking part 24.It is thus possible to limit the size of the braking cavity 22, and therefore to obtain a volume of the braking module 14 which is much smaller than if a complete rotation of the rotor 16 were permitted. It can also be seen that even at this extreme position, the greater part of the braking part 24 remains confined in the lower angular portion of the braking cavity 22.

[0046] In detail, the braking part 24 may extend over at least 20 mm, and preferably 30 mm in a first direction in a braking plane perpendicular to the axis of rotation Q, and may extend over less than 10 mm, and preferably 5 mm relative to the axis of rotation Q in a second direction opposite to the first direction. Typically, the first direction and the second direction are on the median axis A of the braking part.

[0047] This asymmetry and the fact that the braking part 24 extends radially relative to the axis of rotation Q in the braking cavity 22 allows, in addition to a simple, robust and compact structure, to increase the braking torque while limiting the size. Indeed, when a magnetic field is applied by the coil 40 in the braking cavity 22, the magnetization of the magnetorheological medium 42 increases the viscosity of this magnetorheological medium in the vicinity of this coil 40, and therefore increases the surface friction between the braking part 24 of the rotor 16 and the stator 20 in the vicinity of this coil 40, and therefore generates a higher resistance to the rotation of the rotor 16: the rotating member 12 coupled to the rotor 16 is braked in its rotation around the axis of rotation Q.

[0048] By making it possible to increase the distance between the effective braking zone in the vicinity of the coil 40 and the axis of rotation Q, it is possible to benefit from a large lever arm force, which makes it possible to achieve a significant braking torque on the axis of rotation Q, without needing intermediate parts such as gears, and without requiring an isotropic increase in the size.

[0049] In order to further improve the braking, the braking part 24 may comprise on at least one face 24a, 24b a plurality of cavities 44. These cavities 44 may be non-through, at least 0.5 mm deep, but are preferably through, and are then holes through the braking part, connecting the first face 24a to the second face 24b. These cavities 44 are essentially arranged in the active zone of the braking part 24, that is to say that near the coils 40 where the magnetic field is the most intense. For example, the braking part 24 may comprise at least 5 cavities, preferably at least 10 cavities and more preferably at least 15 cavities.

[0050] The braking action of the rotary member 12 is controlled by the intensity of the magnetic field generated by the coil(s) 40, which is a function of the current flowing through each coil 40. It is therefore sufficient to control the coil current 40 to obtain the desired braking torque. By means of determining the position of the lever 2, directly or via elements linked thereto such as the rod 6 or the rotary member 12, for example using a position or position indexing sensor, a microprocessor can determine a coil current intensity to be applied to this position of the lever 2 to obtain the desired braking.

[0051] Preferably, the maximum braking torque at the lever is at least 5 Nm, and preferably at least 10 Nm. It is then possible to prevent the movement of the lever 2 in certain angular ranges which are nevertheless part of the mechanical travel of the lever 2. It is then possible to make the operator physically feel limitations to the authorized movements. For example, in the case of a construction machine, the presence of a prohibited zone (presence of obstacles or dangerous zones) in which the movement of the controlled device is prohibited, it is possible to mechanically prevent the lever 2 from reaching a movement corresponding to this prohibited zone. Furthermore, it is possible to gradually increase the braking when approaching a prohibited zone, or to use particular braking in a defined angular portion to transmit information to the user.

[0052] The invention is not limited to the embodiment described and shown in the attached figures. Modifications remain possible, in particular from the point of view of the constitution of the various technical characteristics or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Claims

1. Human-machine interface (1) comprising: - a control member (2) adapted to be moved by a user according to a degree of freedom to control an apparatus, - a base (3) on which the control member (2) is mounted, the base (3) comprising a rotary member (12) whose rotation is a function of a movement of the control member (2) according to the degree of freedom, - a braking module (14) configured to be coupled to the base (3) and to brake the rotation of the rotary member (12), the braking module (14) comprising: - a stator (20) defining a braking cavity (22), - a rotor (16) which comprises a braking part (24) arranged in the braking cavity (22), - a coil (40) configured to generate a magnetic field in the braking cavity (22), - a magnetorheological medium (42) in the braking cavity (22) and sensitive to the magnetic field,characterized in that the rotor (16) is configured to be coupled to the rotary member (12) to rotationally secure the rotor (16) and the rotary member (12) coaxially about an axis of rotation (Q), and in that the braking part (24) extends radially relative to the axis of rotation (Q) in the braking cavity and has rotational asymmetry relative to the axis of rotation (Q).,

2. Human-machine interface according to the preceding claim, in which the braking part (24) is flat and extends along a braking plane perpendicular to the axis of rotation (Q).

3. Human-machine interface according to any one of the preceding claims, in which at least 75% of the braking part (24) is confined in an angular portion of the braking cavity (22) less than 180° relative to the axis of rotation (Q).

4. A human-machine interface according to any preceding claim, wherein the braking part (24) extends from the axis of rotation (Q) by at least 20 mm in a first direction in a braking plane perpendicular to the axis of rotation (Q), and extends by less than 10 mm in a second direction opposite the first direction.

5. Human-machine interface according to any one of the claims previous, in which the axis of rotation (Q) is eccentric relative to the braking part (24) and relative to the braking module (14).

6. A human-machine interface according to any preceding claim, wherein the rotor (16) and the rotating member (12) have a rotational transmission ratio of 1.

7. A human-machine interface according to any preceding claim, wherein the braking part (24) comprises on one surface a plurality of cavities (44).

8. Human-machine interface according to any one of the preceding claims, in which the stator comprises in an active zone (41) a first part (46a, 46b) in a first material, and a second part (48a, 48b) in a second material outside the active zone (41), the first material having a magnetic permeability greater than a magnetic permeability of the second material, the coil (40a, 40b) being arranged in the active zone (41).

9. Human-machine interface according to any one of the preceding claims, in which the braking part (24) comprises a first face (24a) and a second face (24b), each face (24a, 24b) being separated from a coil (40a, 40b) by a thickness of magnetorheological medium (42).

10. A human-machine interface according to any preceding claim, wherein the braking module (14) is configured so that magnetic flux lines generated by the coil transversely pass through the magnetorheological medium (42) and the braking part (24) in two opposite directions.

11. A human-machine interface according to any one of the preceding claims, comprising an additional braking module (14") mounted on the braking module (14), the additional braking module (14") being configured to brake the rotation of the rotary member (12) and comprising: - a stator (20) defining a braking cavity (22), - a rotor (16) which comprises a braking part (24) arranged in the braking cavity (22), - a coil (40) configured to generate a magnetic field in the braking cavity (22), - a magnetorheological medium (42) in the braking cavity (22) and sensitive to the magnetic field, wherein the rotor (16) is configured to be rotationally secured with the rotating member (12), and the braking part (24) extends radially relative to the axis of rotation (Q) in the braking cavity (22) and has a rotational asymmetry relative to the axis of rotation (Q).

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