HYBRID HAPTIC INTERFACE WITH IMPROVED HAPTIC FEEDBACK

Description

TECHNICAL FIELD AND STATE OF THE PRIOR ART

[0001] The present invention relates to a hybrid haptic interface with improved haptic rendering.

[0002] A haptic interface can take the form of a rotary button manipulated by a user, in which case the interface opposes a resistive torque to the user depending on the angular position of the actuating button and the displacement applied by the user, thus making it possible to define varied haptic patterns that will be felt by the user when turning the button.

[0003] The resistive torque can be transmitted to the button via a magnetorheological fluid whose apparent viscosity is modified by the application of a magnetic field in order to define the predefined haptic patterns.

[0004] Such an interface is called passive because it only opposes an effort generated by the user. It cannot provide more energy than that provided by the user.

[0005] Furthermore, despite the richness of haptic patterns that can be generated by an interface using only a magnetorheological material fluid, it cannot perfectly generate certain specific haptic patterns such as a spring effect. When the user forces on the "spring", the passive interface correctly opposes the movement. On the other hand, when the user releases the "spring", he cannot feel the spring's restoring force and the interface does not return to the "spring's" rest position.

[0006] There are also so-called active haptic interfaces that use an electric motor capable of providing force.

[0007] However, a large motor is required to provide a resistive force equivalent to that of a magnetorheological fluid interface, such as when the interface needs to reproduce the haptic sensation of a virtual stop or wall.

[0008] The motor size can be reduced, but a reduction stage is necessary to obtain an equivalent braking force. Such a reduction stage is detrimental to the haptic perception felt, due to the inertia and parasitic forces generated and it degrades the "transparency" of the interface.

[0009] In addition, the implementation of an electric motor poses difficulties in translating rapid or fine variations in force. Vibrations or instability of the control appear.

[0010] Finally, this type of interface can be potentially dangerous for a user if the forces generated by the motor are significant.

[0011] EP 1698 538 describes a hybrid haptic interface comprising an output element that can be, for example, directly manipulated by the user, an electric motor, a double magnetorheological fluid clutch between the electric motor and the output element, and a magnetorheological fluid brake. The motor rotates at a constant speed. Gears are used to generate two opposite directions of movement. Each magnetorheological clutch and the magnetorheological brake have their own sealing system, each introducing parasitic friction that impairs the transparency of the interface. In addition, the clutches generate friction. In addition, the motor and gears rotate continuously, which generates continuous operating noise. The interface's footprint is also important.

[0012] US 2006 / 054427 describes a haptic system in which a first braking surface of a first member is in contact with a second braking surface of a second member. At least one actuator is configured to exert a force on at least one of the first and second members. A flexure device is coupled to at least one of the following: the first member, the second member, a housing, a manipulator, and a shaft coupled to the manipulator. The flexure provides a degree of rotational flexibility to the manipulator when the at least one actuator exerts the force.

[0013] JP 2012 155674 discloses a camera having a drive unit having a rotation shaft as an output shaft, an operating member connected to the rotation shaft, an angle detection unit for detecting a rotation angle of the rotation shaft, and a torque detection unit for detecting a rotation torque of the rotation shaft; a control unit performs control to give a click feeling to the operation of the operating member by driving the drive unit based on the detection results of the angle detection unit and the torque detection unit. STATEMENT OF THE INVENTION

[0014] It is therefore an aim of the present invention to provide a hybrid haptic interface offering improved haptic rendering, in particular a haptic interface capable of reproducing a greater diversity of haptic patterns with a high-quality feel and reasonable size.

[0015] The previously stated aim is achieved by a rotary hybrid haptic interface comprising a member for interaction with the user and a member for interaction with a fluid whose viscosity varies as a function of a control stimulus, the two members being integral at least in rotation or at least in translation, means for generating a variable stimulus by modifying the viscosity of the fluid, a rotary electromechanical actuator coupled directly with the member for interaction with the user, so that the electromechanical actuator can apply a rotational force to the element for interaction with the user.The interface also comprising means for detecting the user's intention to act before the movement applied to the user interaction element becomes perceptible to the user and to the position measurement sensor, in order to determine the direction of movement that the user intends to apply to the user interaction element.

[0016] The electromechanical actuator, for example an electric motor, is active when the haptic pattern to be reproduced requires it; when it is not active, very few parasitic effects are transmitted to the user. The inertia of the interface is therefore slightly increased compared to that of a haptic interface with rheological fluid alone.

[0017] Furthermore, since the electromechanical actuator is directly coupled to the user interaction element, the interface has a certain compactness.

[0018] The electromechanical actuator can advantageously be sized to generate low-torque movements, which saves space. Indeed, the dissipation of significant forces obtained thanks to the magnetorheological brake and the generation of low forces obtained by a small motor are sufficient to produce a good quality haptic sensation. There is no need to restore a significant force to the user by a haptic interface when it must simulate an element having stored energy.

[0019] Advantageously, the coupling of a passive brake and an electromechanical actuator makes it possible to reproduce new patterns, such as the "spring" pattern. For example, the brake opposes movement when the user forces on the spring and the electromechanical actuator simulates the return action of a spring when the force is released.

[0020] In addition, the variable viscosity fluid brake has seals that confine the variable viscosity fluid in a chamber and exert a pressure on the moving parts that induces a residual cut, also called no-load torque. The electromechanical actuator can be advantageously controlled to compensate for this torque.

[0021] Very advantageously, the motor can be used to reposition the user interaction element to an absolute position after, for example, a power failure of the device.

[0022] Furthermore, the above-mentioned undesirable vibrations due to the implementation of an electric motor control having to control very high torque dynamics do not appear in the interface according to the invention, since only the magnetorheological fluid brake is used to control very high torque dynamics.

[0023] The present invention then relates to a haptic interface comprising: an element for interaction with a user capable of moving in a first direction and in a second direction, an element for interaction with a fluid whose viscosity varies as a function of an external stimulus, the element for interaction with the fluid being integral at least in translation or at least in rotation with the element for interaction with the user, means for measuring a current angular position of the element for interaction with the user, means for determining the direction of rotation of the element for interaction with the user, a brake comprising a fluid whose apparent viscosity varies as a function of an external stimulus and a system for generating said stimulus on command in said fluid, the element for interaction with the fluid being arranged in the fluid, rotary electromechanical means comprising a shaft integral in rotation with the element for interaction with the user,a control unit capable of generating orders to said system for generating said stimulus to modify the value of the stimulus, and to the electromechanical means, means for detecting the torque exerted by a user on the user interaction element, in the case of a rotating user interaction element, in order to know the direction of the torque and whether the torque is greater than a given value for a given direction, the control unit controlling the system for generating said stimulus on the basis of the information obtained on the torque at least when a zero or low speed of the user interaction element is detected.

[0024] In an advantageous example, the electromechanical means comprise an electric motor.

[0025] Preferably, the means for determining the direction of rotation of the user interaction element are formed by the means for detecting the torque exerted by a user on the user interaction element or use temporal variations of the means for measuring a current angular position of the user interaction element,

[0026] The means for detecting the torque applied by the user to the user interaction element may comprise two sensors of the deformation caused by the torque to one of the elements of the haptic interface, said deformation sensors being arranged so that one deformation sensor detects the deformation when the torque is applied in the first direction and the other deformation sensor detects a deformation when the torque is applied in the second direction.

[0027] In another exemplary embodiment, the means for detecting the torque applied by the user to the user interaction element comprise at least one sensor for detecting the deformation caused by the torque to one of the elements of the haptic interface. Preferably, the means for detecting the torque applied by the user to the user interaction element comprise two sensors for detecting the deformation caused by the torque to one of the elements of the haptic interface, said deformation sensors being arranged so that one deformation sensor detects the deformation when the torque is applied in the first direction and the other deformation sensor detects a deformation when the torque is applied in the second direction.

[0028] Preferably, the test body is made of a material such that its deformation is not perceptible by the user.

[0029] The force sensor(s) may be in point contact with the test body.

[0030] The haptic interface may comprise a frame on which means for detecting the torque or force are fixed, the test body being on the one hand integral with the brake and on the other hand integral with the frame so as to be deformed when a torque or a force is applied to the element of interaction with the user.

[0031] The force sensor(s) or the deformation sensor(s) are advantageously arranged relative to the test body so that the measurement sensitivity of the force sensors with respect to the torque or force is maximized.

[0032] In an exemplary embodiment, the user interaction element is rotatable and is integral with a rotation shaft with a longitudinal axis to which the fluid interaction element is rotationally integral, the rotation torque being determined. The brake may then comprise a cylindrical housing of circular section coaxial with the axis of the rotation shaft, the test body being cylindrical with a coaxial circular section and arranged coaxially around the housing and in which the force sensor(s) or the deformation sensor(s) are arranged on a circle centered on the axis of rotation of the rotation shaft.

[0033] In an exemplary embodiment, the control unit is configured to generate orders to the electromechanical means to return the user interaction element to at least one given position.

[0034] The control unit can be configured to generate orders to the electromechanical means and to the system for generating said stimulus so that they act simultaneously on the element of interaction with the user.

[0035] According to an additional feature, the control unit is configured to generate orders to the electromechanical means so that they apply a torque to the user interaction element compensating for friction applied to the user interaction element.

[0036] According to another additional feature, the control unit is configured to generate orders to the electromechanical means and to the system for generating said stimulus so that, from at least one given angular position of the user interaction element, the system for generating said stimulus acts and / or the electromechanical means act on the user interaction element, when the user interaction element rotates in a first direction and in a second direction opposite to the first direction, to oppose the rotation of the user interaction element, and so that the electromechanical means assist the rotation of the user interaction element at least when the latter is pivoted in the first direction or the second direction towards the given angular position.

[0037] The control unit can then be configured so that, when the user interaction element is at the given angular position, it generates orders to the electromechanical means and / or to the system for generating said stimulus to apply a non-zero force to the user interaction element. Alternatively, the control unit is configured so that, when the user interaction element is in an angular zone on either side of the given angular position, it generates orders to the electromechanical means and / or to the system for generating said stimulus to apply no force to the user interaction element.For example, the control unit is configured so that, when the user interaction element is located at ends of the angular zone, it generates orders to the electromechanical means and / or to the system for generating said stimulus to apply a force to the user interaction element.

[0038] The means for detecting the torque or force applied by the user to the user interaction element comprise, for example, at least one force sensor, preferably mounted in prestress.

[0039] Alternatively, the means for detecting the torque may comprise at least one sensor of the deformation caused by the torque or the force to one of the elements of the haptic interface.

[0040] In an advantageous example, the haptic interface comprises a test body which is arranged so as to be deformed by the torque applied by the user to the user interaction element, the means for detecting the torque or force being in contact with said test body.

[0041] In a preferred example, the fluid is a magnetorheological fluid and the stimulus is a magnetic field.

[0042] The present invention also relates to a method for controlling a haptic interface according to the invention, comprising the steps Measuring the current position of the user interaction element, recording said current position in a non-volatile memory, Measuring the current position of the user interaction element, for example following an interruption in the power supply to the control unit, comparing the measured current position and the recorded current position, Controlling the electromechanical means so that the measured current position corresponds to the recorded current position.

[0043] The present invention also relates to a method for controlling a haptic interface according to the invention, with a view to reproducing a spring-type haptic pattern, comprising the steps: Measuring the current position of the user interaction element Determining the direction of rotation of the user interaction element Controlling the electromechanical means to apply a force in the direction of movement of the user interaction element, or Controlling the electromechanical means and / or the system for generating said stimulus to apply a force opposing the movement of the user interaction element.

[0044] The present invention also relates to a method for controlling a haptic interface according to the invention, comprising the steps: Control of electromechanical means for applying a force in the direction of movement of the user interaction element such that the electromechanical means apply a torque compensating for an idle torque exerted on the user interaction element

[0045] The present invention also relates to a method for controlling a haptic interface according to the invention, comprising the steps: determining the speed of the user interaction element from the information provided by the means for measuring the current position of the user interaction element, determining the torque applied to the user interaction element, determining the current position of the user interaction element, if the speed is greater than a given speed, the direction of rotation is that given by the speed and the stimulus generation system is controlled so as to apply the recorded haptic pattern for the determined current position and for the determined direction of rotation, if the speed is less than a given speed and if the torque or force is greater than a positive threshold value or less than a negative threshold value, the direction of movement of the user interaction element is deduced from the determined torque or force,and the stimulus generation system is controlled to apply a stimulus based on the recorded haptic pattern for this current position and for the deduced direction of movement.

[0046] For example, when the determined torque is less than a given value, no stimulus is applied to the fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will be better understood on the basis of the following description and the attached drawings in which: there figure 1 is a schematically represented longitudinal sectional view of an example of a haptic interface according to the invention, the figure 2 is a cross-sectional view along plane AA of the interface of the figure 1 , there figure 3 is a perspective view of an example of the realization of a test body implemented in the interface of the figure 1 , there figure 4is a perspective view of another example of the realization of a test body which can be implemented in the interface of the figure 1 , there Figure 5 is a side view of another example of a haptic interface, the Figures 6A to 6C are different views of the test body implemented in the interface of the Figure 5 , THE figures 7 to 11 are graphical representations of instructions as a function of angular position in degrees to produce different haptic patterns, the figure 12 is a front view of a ratchet wheel and its pawl, the movement of the pawl being reproducible by the haptic interface according to the invention. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0048] The following description describes the example of a rotating haptic interface implementing a magnetorheological fluid, i.e. one whose apparent viscosity varies depending on the applied magnetic field, but the implementation of an electrorheological fluid, i.e. a fluid whose apparent viscosity depends on the applied electric field, does not depart from the scope of the present invention.

[0049] On the figure 1 , we can see a longitudinal sectional view of an exemplary embodiment of a rotating haptic interface according to the invention.

[0050] The haptic interface comprises an element 1 intended to be manipulated by a user and which will be referred to hereinafter as a “button”, this button is integral in rotation with a shaft 2 movable in rotation around the X axis, a resistive force generation device 4 or magnetorheological brake opposing the rotation of the shaft 2 and a second force generation device M formed by an electromechanical actuator, for example a motor and referred to hereinafter as a “motor”. The shaft 2 will be referred to as an “actuating shaft 2” in the remainder of the description. The electromechanical actuator may for example be of the direct current electric machine type, or even of the synchronous electric machine, of the “brushless” type for example, which makes it possible to do without brushes and to reduce the inertia of the rotor.

[0051] The motor M comprises a motor shaft M1 which is aligned with the longitudinal axis. The shaft M1 comprises a free end arranged opposite a free end of the actuating shaft 2. The motor shaft M1 and the actuating shaft 2 are mechanically coupled so as to be integral with each other at least in rotation. A coupling part 42 of the shafts M1 and 2 is mounted around the free ends of the shafts. The coupling part may for example be a ring mounted on the end of the motor shaft M1 and on the end of the actuating shaft 2, each of the ends being provided with a flat cooperating with the ring. Alternatively, the shafts may be splined and the ring may have a complementary inner surface.

[0052] Alternatively, a single tree can form tree 2 and tree M1.

[0053] As a further variant, the motor may have a shaft emerging at each end, one end of the motor shaft being secured to the emerging end of the shaft 2. The button 1 is secured to the end of the motor shaft not secured to the brake shaft 2. This variant has the advantage of being able to implement a brake with an axis which only passes through one wall of the brake chamber, which makes it possible to reduce the number of brake seals ensuring the sealing of the chamber, and therefore to reduce parasitic friction.

[0054] The brake 4 comprises a fluid whose characteristics can be modified by means of a magnetic field and a system for generating a magnetic field 6 received in a housing 8. The fluid is, for example, a magnetorheological liquid. The assembly comprising the housing, the fluid and the system for generating a magnetic field forms a magnetorheological brake.

[0055] The housing 8 delimits a sealed chamber 9 containing the magnetorheological fluid. All or part of this chamber is subjected to a magnetic field generated by the system 6. The housing 8 comprises a side wall 8.1, a lower base 8.2 and an upper base 8.3.

[0056] The shaft 2 passes through the upper base 8.3, the chamber 9 and the lower base 8.2. The end 2.1 of the shaft 2, opposite that carrying the button 1, passes through the lower base 8.2 of the housing 8 and is guided in rotation by means of a bearing 11. Seals 13, for example O-rings, ensure the seal between the shaft and the chamber. In the example shown, the bearing is arranged outside the sealed area delimited by the seals 13.

[0057] The housing 8 delimits a sealed chamber confining the magnetorheological fluid.

[0058] The brake 4 also comprises an element 12 integral in rotation with the shaft 2 and housed in the sealed chamber 9. This element is capable of interacting with the magnetorheological fluid, the rotation of the element 12 being more or less braked by the magnetorheological fluid depending on its apparent viscosity.

[0059] In the example shown, the element 12 comprises two concentric side walls 12.1, 12.2 of circular cross-section secured to a base 12.3, itself secured in rotation with the shaft.

[0060] Alternatively, the element 12 may comprise only one side wall or more than two concentric side walls. Alternatively, the element 12 could be formed by a disc. Furthermore, the interaction element could comprise slots and / or projecting or recessed portions in order to increase the resistance to movement.

[0061] In the example shown, the lower bottom 8.2 of the housing 8 has a shape such that the interior volume of the sealed chamber 9 has a shape which corresponds to that of the interaction element 12, which makes it possible to reduce the quantity of fluid required. In the example shown, a cylindrical element 15 with a circular section integral with the housing is interposed between the two side walls 12.1, 12.2, this contributes to the shearing effect of the magnetorheological fluid when the side walls 12.1 and 12.2 are rotated.

[0062] The side walls 12.1, 12.2 of the element 12 may be made of magnetic or non-magnetic material.

[0063] In the example shown, the system for generating a variable magnetic field 6 comprises a coil fixed to the housing and arranged inside the interaction element 12, and a current supply (not shown) controlled by a control unit as a function of the manipulation of the button and pre-recorded patterns.

[0064] The interface also comprises a position sensor 14 which is, in the example shown, located outside the housing and partly secured to the shaft 2. The position sensor 14 makes it possible to measure the current position of the button, which in the example shown is the current angular position. It may be, for example, an incremental optical encoder.

[0065] The interface also comprises means for detecting the direction of rotation of the user interaction element, these means are for example formed by the processing of the position information provided by the angular position sensor, which makes it possible to determine the direction of actuation by performing for example a calculation of the difference between an angular position measured at a time T and a position measured at time T+deltaT. In the case where the position sensor is an encoder providing digital signals in quadrature, for example an incremental optical encoder, the direction of actuation can be determined directly by analyzing the relative phase of the quadrature signals. The direction of actuation of the button is used for controlling the magnetorheological brake as well as for controlling the motor.As we will see later, the interface also includes a sensor for the torque exerted on the user interaction element; the torque measurements can be used to determine the direction of rotation.

[0066] The haptic interface also comprises a frame 16 in which the housing 8 is arranged. The frame 16 comprises a first and a second end flange 18, 20 and a side wall 22 fixed to the two flanges 18, 20, the first flange 18 is crossed by the rotary shaft and the second flange is crossed by the motor shaft. The position sensor 14 is fixed on the first flange of the frame.

[0067] The interface also includes means for detecting the user's intention to act, these means detecting the torque exerted by the user on the button before a movement of the button perceptible by the user and by the position sensor is applied to it.

[0068] In the example shown, the means for detecting the user's intention to act comprise a test body 26, the deformation of which caused by the torque applied by the user will be detected, and force sensors. The test body is shown alone on the figure 3 The test body 26 is fixed by one longitudinal end 26.1 to the frame 16 and by the other longitudinal end 26.2 to the magnetorheological brake, i.e. to the housing 8 in the example shown. The force sensors are in contact with the test body at its longitudinal end 26.2 secured to the housing 8.

[0069] In the example shown on the figures 1 , 2 and 3 , the test body 26 comprises a cylindrical body with a circular section closed by a bottom 28 at the longitudinal end 26.2. An annular collar 30 extends radially outwards at the other longitudinal end 26.1.

[0070] The inner diameter of the test body corresponds to the outer diameter of the housing 8, increased by an operating clearance. The bottom of the test body is arranged between the housing and the second flange 20 of the frame 16.

[0071] The test body is secured to the frame by means of at least one screw 32 passing through the flange 18 and the collar 30. In the example shown, the screws 32 also serve to connect the flange 18 to the side wall 28.

[0072] The bottom 28 of the test body is fixed to the housing 8 by at least one screw 34.

[0073] The test body 26 also comprises an element 36 projecting from its longitudinal end 26.2 opposite that in contact with the housing. The element 36 is received in a cavity 38 formed in the flange 20 of the frame.

[0074] In the example shown, the projecting element 36 has the shape of an angular portion centered on the longitudinal axis. As can be seen in the figure 2, the angular portion 36 is delimited by two faces 36.1, 36.2. The cavity 38 has a shape corresponding to that of the angular portion 36 and is delimited by two faces 38.1 38.2 each facing a face 36.1, 36.2 of the angular portion 36. A force sensor 40.1 is mounted on the face 38.1 of the cavity in contact with the face 36.1 of the angular portion and a force sensor 40.2 is mounted on the face 38.2 of the cavity in contact with the face 36.2 of the angular portion 36. A point-type mechanical contact is ensured between each force sensor 40.1, 40.2 and the test body 26. The force sensors 40.1, 40.2 are advantageously mounted prestressed.

[0075] Thus when a torque is applied to the button, this causes a deformation by torsion of the test body 26 via the housing 8 itself in interaction with the fluid, itself in interaction with the interaction element 12, itself linked to the shaft 2. This deformation is detected by one or other of the force sensors 40.1, 40.2 depending on the direction of rotation of the button.

[0076] The test body is, for example, made of plastic material, such as ABS.

[0077] The material of the test body and its geometry can be determined based on the minimum and maximum torque applied, the sensitivity of the force sensors and the desired detection threshold. In addition, the deformation of the test body is such that it is not perceptible by the user. For example, it can be considered that a deformation of the test body of a few microns is not perceptible by the user.

[0078] Alternatively, the forces could be measured directly on the housing 8 or on the rotating shaft, for which a torque sensor would be implemented. However, a torque sensor has a high cost and a large footprint compared to force sensors. Furthermore, a torque sensor provides a precise and calibrated torque value while this information is not useful in the context of the invention.

[0079] The force sensor is for example made using piezoresistive elements assembled in the form of a Wheatstone bridge, they allow a sensitivity of the order of a few tens of mV per Newton with a stiffness high enough to limit the displacement to a few tens of microns at full load. Alternatively, the force sensor(s) could be replaced by one or more deformation sensors formed, for example, by strain gauges directly applied to the test body to detect its deformation.

[0080] Since the motor M is mechanically linked to the second flange 16 of the frame, it does not disturb the measurement of the torque on the actuating shaft.

[0081] On the figure 4 , we can see another example of a test body 126 whose general shape is identical to that of the test body 26, but additionally comprises longitudinal slots 127 in the side wall of the test body 126. Preferably, the slots 127 are distributed angularly in a regular manner. The test body has in this embodiment a greater capacity for deformation. It is for example made of aluminum alloy.

[0082] Lights inclined relative to the longitudinal axis and / or having a shape other than rectilinear, for example a curved shape, do not depart from the scope of the present invention. Furthermore, the lights do not necessarily all have the same dimensions.

[0083] Advantageously, means may be provided for amplifying the deformation of the test body under an axial torsional stress while reducing the deformation of the test body for any other stress not relevant within the scope of the invention, such as for example a radial stress which would be applied to the button in a parasitic manner by the user. The sensitivity of the detection is thus improved and disturbances or false detections can be eliminated.

[0084] The example of the test body of the figures 1 to 4 allows the sensitivity of the measuring device to be increased by arranging the sensors over the largest possible diameter.

[0085] In the example shown and advantageously, the walls 36.1 and 36.2 of the projecting element are arranged at 90° to each other. This positioning associated with a point contact at the level of the force sensors 40.1 and 40.2 makes it possible to decompose the deformation stress of the test body and to favor the sensitivity to the forces according to two orthogonal components located in the plane of the frame 16. Thus, for example, the sensitivity is greatly reduced for parasitic forces exerted perpendicular to the plane of the frame 16. In addition, a computational or algorithmic processing on the components of the orthogonal forces measured by the sensors 40.1 and 40.2, such as for example a calculation based on the measurement difference between the two sensors weighted by the common measurement component of the two sensors in the case of a preferential assembly of the sensors with a load prestress, makes it possible to reduce to a certain extent the sensitivity to parasitic forces exerted parallel to the plane of the frame 16.

[0086] The haptic interface also includes a control unit UC to which the current position sensor, the means for determining the direction of rotation of the button, the torque sensor, the means for generating the magnetic field and the electric motor are connected. The control unit processes the signals transmitted by the sensors and generates orders to the means for generating the magnetic field and to the electric motor.

[0087] An example of the operation of the device will now be described.

[0088] The user rotates the knob around its axis in a first direction of rotation and brings it into an angular position defined as a stop. A magnetic field is applied to the magnetorheological fluid so that its apparent viscosity variation generates a torque at the level of the element interacting with the fluid simulating a stop at the level of the knob in the first direction of rotation.

[0089] If the user maintains his force on the button in the first direction of rotation, the test body 26 undergoes a torsional torque via the housing, itself in interaction with the fluid, itself in interaction with the interaction element 12, itself linked to the shaft 2.

[0090] This deformation is measured by the force sensor arranged downstream in the first direction of rotation. Knowing which of the force sensors is stressed makes it possible to know the direction in which the user intends to turn the knob. Preferably, the measurements from the two assembled force sensors can be combined with a load preload to determine the direction in which the user intends to turn the knob. The detection of a minimum torque makes it possible to confirm that the user actually intends to rotate the knob. It is deduced from this that the user intends to hold the knob in the stop position. The magnetic field is maintained so as to oppose a force to the movement of the interaction element 12 via the viscous magnetorheological fluid.

[0091] If the user intends to rotate the button in a second direction opposite to the first direction, it is the force sensor arranged upstream considering the first direction of rotation, which will be stressed. Preferably, the measurements from the two assembled force sensors can be combined with a load preload to determine the new direction in which the user intends to turn the button. The user's intention is deduced from this, this intention is confirmed by the detection of a minimal torque. In this case, the magnetic field is canceled, the apparent viscosity of the fluid decreases significantly, the interaction element can therefore rotate in the second direction without feeling any sticking effect. The invention can thus reproduce the operation of a freewheel.

[0092] On the Figures 5 and 6Aat 6C, we can see another example of embodiment of an interface I2 according to the invention comprising a frame 216, a brake 204, a test body 226 having the shape of a wheel and an element for interaction with the user 201, the element for interaction with the fluid not being visible.

[0093] The wheel has a hub 228, an outer ring 232 and spokes 230 connecting the hub 228 to the outer ring 232.

[0094] In this example, the hub 228 is secured to the interface housing, for example, by screws passing axially through the hub 228, and the outer ring 232 is secured to the frame, for example, by screws passing axially through the outer ring.

[0095] Two force sensors 240.1, 240.2 are arranged each bearing against a spoke 230 and arranged relative to the spokes such that, when the test body 226 is stressed in a direction of rotation, only one of the sensors is stressed. The force sensors are fixed on the frame 216 and bearing against a face of a spoke 230. Alternatively, the force sensors could be assembled with a load prestress, or, as mentioned above, be replaced by elongation gauges arranged on the test body and detecting the deformation, for example, of the spokes under the effect of the torsional torque. More generally, the force sensors can be replaced by deformation sensors.

[0096] The operation of this device is similar to that of the device of the figure 1 described above.

[0097] Means for applying mechanical constraints to the test body, such as rotational or translational guidance means, can advantageously be added, which makes it possible to reduce the number of force sensors by assembling the latter with a load prestress.

[0098] The data from these force or strain sensors are processed by an electronic system to determine whether the torque exerted by the user on the interface exceeds a predetermined threshold. The torque sign is also determined and makes it possible to know the direction in which the user intends to move the button.

[0099] As indicated above, knowledge of the actual value of the torsional torque is not necessary; knowledge of the direction of torsion is sufficient. It is therefore possible to implement low-cost sensors capable of detecting at least a binary threshold or a monotonic function of the force or deformation, without any specification such as linearity, dynamics, resolution, etc., provided that the sensor is sufficiently sensitive to detect a minimum torque acting on the interface without the latter being rotated. The sensor is also such that it is capable of withstanding a maximum force without degradation.

[0100] The motor M is intended to directly move the shaft 2 and therefore the button at low torque, without this representing a danger for the user. Indeed, the motor is not intended to apply very high torques. Thus the motor can have a small size which facilitates the integration of the motor in the interface and to create a small interface. In addition, since the motor is not intended to operate continuously, the power consumption of the interface is reduced compared to a haptic interface using only an electric motor.

[0101] Furthermore, the haptic interface according to the invention makes it possible to generate a large number of haptic patterns. For illustrative purposes, some of them will be described below, but this is not an exhaustive description of the haptic patterns that can be produced by the interface according to the invention.

[0102] As described above, the interface includes seals 13 to ensure the sealing of the chamber containing the magnetorheological fluid. These seals exert friction on the shaft 2, generating an idle torque which is detrimental to the haptic feeling.

[0103] The motor can be advantageously controlled to compensate for this no-load torque. For example, it is controlled to assist the rotational movement of the knob. The motor M can be activated to compensate for the no-load torque when no magnetic field is applied to the magnetorheological fluid. For example, when designing the interface, the no-load torque is measured or estimated, and the control unit is programmed to control the motor so that it compensates for this no-load torque.

[0104] Very advantageously, the haptic feeling can be significantly improved by controlling the motor based on knowledge of the user's intention. Indeed, as soon as this intention is detected, the motor is activated to compensate for the no-load torque, so the user may never feel this no-load torque inherent in the friction of the joints. Knowledge of the user's action intention is also beneficial in the case of operating modes implementing both the magnetorheological brake and the motor, the control of these elements being done in a more reactive manner, the transitions are less perceptible by the user.

[0105] The motor can also be operated to generate a vibration, which is transmitted to the actuating shaft since the two shafts are linked in rotation, this vibration giving for example a haptic indication of the alert type.

[0106] In addition, it is possible to reproduce the spring effect, for example the sensation felt when manipulating a spring, for example a spiral spring, on a rotating axis. One may wish to reproduce this effect, for example to return the button to a stable position

[0107] The interface is controlled to exert, depending on the direction of rotation and the angular position, a force against the rotation of the button or a restoring force on the button.

[0108] A spring is characterized by a stiffness k.

[0109] The control unit generates orders to the magnetic field generation means and to the motor in order to apply to the button the instruction shown on the figure 7 , the setpoint is a linear function whose zero value corresponds to a stable position of the spring whose action on the button we wish to simulate, i.e. its position at rest. The figure 7represents the variation of the setpoint C as a function of the rotation angle θ, which is here in degrees.

[0110] The 180° angle corresponds to the stable position or rest state of the spring to be simulated

[0111] The generated commands depend on the angular position of the button and the direction of rotation. Indeed, the further one deviates from the stable position E, the greater the force opposing the movement of the actuating shaft. When the direction of rotation brings the button closer to the stable position, a return force is felt by the user. The sign of the force to be applied to the user interaction element depends on the direction of rotation.

[0112] The haptic pattern of a spring can be achieved through different commands.

[0113] According to a first operating mode, the motor is capable of delivering sufficient torque to simulate the spring effect, only the motor is then controlled. The haptic pattern is programmed so that the 180° angle is considered the stable position E or rest state of the spring. When the button is turned away from position E, the motor is controlled to generate a torque resisting this rotation. The intensity of this torque depends on the difference between the "rest" position and the current position of the button. The greater this difference, the greater the torque generated by the motor, thus simulating the elastic return. If the user releases the button, the torque exerted by the motor will tend to bring the button back to its rest position E. The closer it is to E, the less torque exerted by the motor.Ultimately, the button returns to the initial position E, the motor control becomes zero and the residual friction of the system immobilizes the interface.

[0114] In another mode of operation, the magnetorheological brake is controlled to generate the resistive torque when the knob is turned from its equilibrium position. The motor is controlled to return the knob to its equilibrium position, when the force on the knob is released, or when it is less than the restoring force of the spring.

[0115] It will be understood that the angle values ​​are given only as examples and are in no way limiting.

[0116] On the figure 8 , we can see a haptic pattern intended to reproduce the behavior of a three-position indexer type button considering an operating mode using the motor alone.

[0117] This button works as follows. When the user applies sufficient torque to the button, it moves up a notch and into the next equilibrium position.

[0118] The equilibrium positions are designated E1, E2, E3.

[0119] When the knob deviates for example from the equilibrium position E2, i.e. it is pivoted clockwise or counterclockwise from the angle of 120° without however pivoting to reach the angle 180° or 60° respectively, it returns to its second equilibrium position E2 under the action of the motor M. For example when the knob reaches the position of 180, a notch is simulated and the knob moves to the third equilibrium position E3 thanks to the action of the motor which is now controlled with a torque depending on the reference relative to the position E3, and which drives the knob towards the equilibrium position E3. This passage from the position at 180° to the position at 240° is shown diagrammatically by the arrow F.

[0120] Instabilities may occur around the stable position(s). For example, depending on the motor used, jerky movements or a lack of movement may appear when a small force is commanded which would be of the order of magnitude of the internal friction of the interface. By providing a jump in force or OFS offset (represented on the figure 9 ) sufficient at the equilibrium position, the motor is controlled to generate a force greater than the internal friction of the interface.

[0121] On the figure 10 , we can see the control of another haptic pattern in which, in addition to the OFS offset, an angular range ANG is provided around the equilibrium position E in which no force is generated by the motor and the brake. The stability of the interface around the equilibrium position is further improved compared to that controlled with the setpoint of the figure 9 .

[0122] On the figure 11 , we can see the instruction of a haptic pattern which applies to the motor and the brake. As explained above, the motor is preferably adapted to the application of low torques while the brake can apply high torques. It is then advantageous to provide for controlling the motor so that it applies alone over a first angular range P1 the resistive force, over the range [180°; 280°] in the example shown, then over a second angular range P2, the brake is also activated to apply an additional resistive force in addition to that generated by the motor.

[0123] The force applied by the motor is designated FM and the force applied by the brake is designated FF and the total force is designated FT.

[0124] The implementation of the motor and brake helps minimize abrupt transitions and increase the fluidity of haptic interaction. This improves haptic interaction and increases the transparency of the interaction.

[0125] It will be understood that this type of instruction cannot be applied in a perfectly symmetrical manner in the simulation of a spring, because the brake cannot simulate a return force on the second range P2. Despite the asymmetry of the profile obtained, since it is the force F 1 which is generated if the user moves the button against the spring, and it is the force FM which is generated if the user releases his action, the haptic feeling remains sufficient to be assimilated to a high stiffness spring.

[0126] The haptic interface according to the invention can also make it possible to reproduce the movement of a pawl CL along a ratchet wheel RR shown in the figure 12 .

[0127] The end of the pawl CL moves on the outer contour of the ratchet wheel RR which has alternating flat areas ZP and concave areas ZC, a concave area connecting to a flat area by a radial plane PR extending along a radius of the wheel. A flat area ZP connects to a concave area ZC by an acute angle. When the pawl moves on the contour of the ratchet wheel in a clockwise direction or the wheel moves in a counterclockwise direction relative to the pawl CL, it slides for example on a concave area ZC, for this the brake is controlled to create viscous friction. To reproduce the movement of the pawl on a flat area ZP, the motor and / or the brake are controlled to simulate a spring effect. If the pawl CL moves in a counterclockwise direction or the wheel moves in a clockwise direction, a virtual stop is to be simulated when the pawl comes into contact with the radial plane.For this, the brake and / or the motor are controlled to generate sufficient force to simulate a stop.

[0128] Very advantageously, the haptic interface according to the invention can be used to simulate a system requiring an absolute representation of the position. Indeed, the motor can be controlled to return the button to a desired position. For example, in the case of a rotary haptic interface simulating a rotary switch having different notches and comprising a button having a visual reference or marker. If the power supply to the interface is interrupted and the user operates the interface, when the power supply is resumed the motor can reposition the button to its position before the power supply was cut off. In the absence of a motor, the interface cannot reposition itself. This would then result in a discrepancy between the visual reference or marker of the button perceived by the user and the position of the interface expected by the haptic model.

[0129] The system could be controlled as follows. The current position of the button is stored regularly in the control electronics. This can be achieved by storing this information in a non-volatile memory. In the event of a power failure, the system thus has a memory of the last position of the button. When the power returns, the control electronics initializes and then compares the current position of the button with the last position stored in the non-volatile memory. The electric motor is then controlled, for example, at a constant speed, until the position of the button is equal to the stored position. The motor can then be stopped and the interface becomes operational. Alternatively, a "spring effect" type command can be generated whose stable position corresponds to the last position stored in the non-volatile memory.The button then returns to its last position as if it had been actuated by a return spring.

[0130] It will be understood that the examples of haptic patterns described are non-limiting examples.

Claims

1. Haptic interface comprising: - an element (1) for interacting with a user and capable of moving in a first direction and in a second direction, - an element (12) for interacting with a fluid whose viscosity varies according to an external stimulus, the fluid-interaction element (12) being rigidly connected to the user-interaction element (1) at least for translation therewith or at least for rotation therewith, - means for measuring a current angular position (14) of the user-interaction element (1), - means for determining the direction of rotation of the user-interaction element (1), - a brake comprising a fluid whose apparent viscosity varies according to an external stimulus and a system (6) for generating said stimulus on command in said fluid, the fluid-interaction element (12) being disposed in the fluid, - rotary electromechanical means (M) comprising a shaft (M1) rigidly connected to the user-interaction element (1) for rotation therewith, - a control unit (UC) capable of generating commands for said system for generating said stimulus to modify the value of the stimulus, and to the rotary electromechanical means (M), the haptic interface being characterised in that it comprises - means for detecting the torque exerted by a user on the user-interaction element (1), in the case of a rotatable user-interaction element (1), in order to determine the direction of the torque and if the torque is greater than a given value for a given direction, the control unit controlling the generation system (6) of said stimulus based on the information obtained on the torque at least when a velocity of the user-interaction element (1) of zero is detected.

2. Haptic interface according to claim 1, wherein the electromechanical means (M) include an electric motor.

3. Haptic interface according to claim 1 or 2, wherein the means for determining the direction of rotation of the user-interaction element are formed by the means for detecting the torque exerted by a user on the user-interaction element or using time variations of the means for measuring a current angular position (14) of the user-interaction element (1),4. Haptic interface according to one of claims 1 to 3, wherein the control unit (UC) is configured to generate commands for the electromechanical means (M) to bring the user interaction element (1) back to at least one given position.

5. Haptic interface according to one of claims 1 to 4, wherein the control unit (UC) is configured to generate commands for the electromechanical means (M) and for the system for generating said stimulus such that they act simultaneously on the user-interaction element (1).

6. Haptic interface according to one of claims 1 to 5, wherein the control unit (UC) is configured to generate commands for the electromechanical means (M) so that a torque is applied thereby to the user-interaction element (1), which torque offsets friction applied to the user-interaction element (1).

7. Haptic interface according to one of claims 1 to 6, wherein the control unit (UC) is configured to generate commands for the electromechanical means (M) and for the system for generating said stimulus such that, from at least a given angular position of the user interaction element (1), the system for generating said stimulus acts and / or the electromechanical means (M) act on the user-interaction element (1), when the user-interaction element (1) rotates in a first direction and in a second direction opposite to the first direction, to oppose the rotation of the user-interaction element (1), and such that the electromechanical means (M) assist the rotation of the user-interaction element (1) at least when it is pivoted in the first direction or in the second direction towards the given angular position.

8. Haptic interface according to claim 7, wherein the control unit (UC) is configured so that, when the user-interaction element (1) is in the given angular position, it generates commands for the electromechanical means (M) and / or for the system for generating said stimulus to apply a non-zero force to the user-interaction element (1).

9. Haptic interface according to claim 7, wherein the control unit (UC) is configured so that, when the user-interaction element (1) is in an angular zone on either side of the given angular position, it generates commands for the electromechanical means (M) and / or for the system for generating said stimulus to apply no force to the user-interaction element (1).

10. Haptic interface according to one of claims 1 to 9, wherein the means for detecting the torque or force applied by the user to the user-interaction element (1) include at least one force sensor (40.1, 40.2, 240.1, 240.2), preferably mounted pre-stressed.

11. Haptic interface according to one of claims 1 to 10, wherein the means for detecting the torque include at least one sensor sensing the deformation caused by the torque or the force to one of the elements of the haptic interface.

12. Haptic interface according to one of claims 1 to 11, comprising a proof body (26, 126, 226) which is disposed so as to be deformed by the torque applied by the user on the user-interaction element (1), the means for detecting the torque or force being in contact with said proof body (26, 126, 226).

13. Haptic interface according to one of claims 1 to 12, wherein the fluid is a magneto-rheological fluid, the stimulus being a magnetic field.

14. Method for controlling a haptic interface according to one of claims 1 to 13, comprising the steps of: - determining the velocity of the user-interaction element (1) from the information provided by the means for measuring the current position of the user-interaction element (1), - determining the torque applied to the user-interaction element (1), - determining the current position of the user-interaction element (1), - if the velocity is greater than a given velocity, the direction of rotation is that given by the velocity and the system for generating a stimulus is controlled so as to apply the haptic pattern recorded for the determined current position and for the determined direction of rotation, - if the velocity is less than a given velocity and if the torque or force is greater than a positive threshold value or less than a negative threshold value, the direction of displacement of the user-interaction element (1) is deduced from the determined torque or force, and the system for generating a stimulus is controlled so as to apply a stimulus according to the haptic pattern recorded for that current position and for the deduced direction of displacement.

15. Method according to claim 14, wherein, when the determined torque is below a given value, no stimulus is applied to the fluid.