Haptic interface providing improved control of the haptic sensation

TECHNICAL AREA AND PRIOR ART

The present invention relates to a haptic interface offering improved control of haptic feeling.

A haptic interface can take the form of a rotary button manipulated by a user, in this case the interface opposes a torque resistant to the user depending on the angular position of the actuation button and the displacement applied by the user. , allowing to define haptic patterns that will be felt by the user when he turns the button.

The resisting torque can be transmitted to the button via a magneto-rheological fluid whose apparent viscosity is modified by the application of a magnetic field in order to define the predefined haptic patterns.

Certain haptic patterns include numerous variations of the resistive torque in a relatively narrow angular zone. In this case, there is a decrease in the haptic feeling perceived by the user when the speed of actuation of the button increases.

The document <patcit id="pcit0001" dnum="FR2930655A1"><text>FR 2 930 655 A1</text></patcit> discloses a haptic interface according to the preamble of claims 1 and 2.

STATEMENT OF THE INVENTION

It is therefore an object of the present invention to provide a haptic interface offering improved control of haptic feeling.

The previously stated object is achieved by a haptic interface according to claim 1 or claim 2.

Thanks to the invention, by applying a haptic pattern which is dependent on the speed of actuation of the element of interaction with the user, it is possible to modulate, for example to accentuate the haptic feeling as a function of the actuation speed of the user interaction element. This modulation can relate to amplitude or shape modifications of the pattern. Thus by taking into account the actuation speed in the selection of the haptic pattern value, the control of the haptic feeling is improved. This prevents, for example, a decrease in haptic feeling when the actuation speed is high.

Particularly advantageously, a slow speed pattern and a fast speed pattern are used and an interpolation is carried out between a value of a pattern at zero or low speed and a value of a pattern at fast speed for the measured position.

In one embodiment, a slow speed pattern and a fast speed pattern are used and a threshold is fixed below which the actuation speed of the interaction element is considered to be slow and beyond which one considers that the actuation speed of the user interaction element is high, and one or the other of the patterns is applied depending on whether the actuation speed is considered to be high or low.

In other words, for each current position, provision is made to apply at least two stimulus values ​​whose intensities may or may not be different in order to take account of the speed of actuation of the element of interaction with the user. , whereas in the haptic interfaces of the prior art only one stimulus value is applied for each current position regardless of the actuation speed. Advantageously, a stimulus value is determined for each actuation speed value according to a predetermined law or calculation algorithm taking the speed as an input parameter.

According to an additional characteristic, provision may be made for implementing a device for determining the intention of action of the user before the movement applied to the element of interaction with the user becomes perceptible to the user. user and for the position measurement sensor, to determine the direction of movement that the user intends to apply to the user interaction element, which further improves the haptic rendering .

For example, the means for determining the intention of action of the user on the element of interaction with the user comprise:<ul id="ul0001" list-style="dash" compact="compact"><li>means for detecting the torque exerted by a user on the element of interaction with the user, in the case of an element of interaction with the user mobile in rotation, in order to know the direction of the torque and if 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 information obtained on the torque at least when a zero or low speed of the element of interaction with the user is detected, or</li><li>means for detecting the force exerted by a user on the element of interaction with the user, in the case of an element of interaction with the user mobile in translation, in order to know the direction of the force and if the force 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 force at least when a zero or low speed of the element of interaction with the user is detected.</li></ul>

The means for detecting the torque or the force applied by the user to the element for interaction with the user may comprise at least one force sensor, preferably mounted in prestressing mode or at least one sensor for the deformation caused by the torque or force to one of the elements of the haptic interface.

The haptic interface may include a test body which is arranged so as to be deformed by the torque or the force applied by the user to the element of interaction with the user, the means for detecting the torque or the force being in contact with said test body. Preferably, the test body is made of a material such that its deformation is not perceptible to the user.

Advantageously, the means generating the orders implement an interpolation, for example a linear interpolation, between a value of the first database and a value of the second database or between a value of the third database and a value from the fourth database.

For example, the second given speed can be set as the maximum actuation speed in the first actuation direction and the given fourth speed is set as the maximum actuation speed in the second actuation direction

In an advantageous embodiment, the fluid is a magneto-rheological fluid, the stimulus being a magnetic field and the orders generated are intensities of current.

The means for determining the actuation speed can for example calculate the derivatives of the information supplied by the means for determining the current position.

In an exemplary embodiment, the element of interaction with the user is movable in rotation and is integral with a rotation shaft of longitudinal axis of which is integral in rotation with the element of interaction with the fluid, the means for measuring the angular position being an angular position sensor.

In another exemplary embodiment, the element of interaction with the user is movable in translation.

The present invention also relates to a method for controlling a haptic interface according to the invention, comprising the steps:<ol id="ol0001" compact="compact"><li>a) determining the current position of the user interaction element,</li><li>b) determining the speed of the user interaction element,</li><li>c) determination of the direction of actuation,</li><li>d) determination, for the determined actuation direction, of a value of a haptic pattern for the determined actuation speed,</li><li>e) generation of an order to the system for generating said stimulus.</li></ol>

During step d), the value of a haptic pattern can be determined from a first value of a haptic pattern for an actuation speed lower than a first given value and not zero and a second value of a haptic pattern for an actuation speed at least equal to a second given value.

For example, step d) is a step of calculating said value of a haptic pattern for the actuation speed determined by means of a threshold function, the value of the pattern for the determined actuation speed being either the first value of a haptic pattern for an actuation speed lower than a first given value, or the second value of a haptic pattern for an actuation speed at least equal to a second given value.

Advantageously, the method may include the step prior to step d) of determining the intention of action of the user on the element of interaction with the user. During step d), the value of a haptic pattern can be determined from a first value of a haptic pattern for an actuation speed less than or equal to a first given value possibly zero and of a second value of a haptic pattern for an actuation speed at least equal to a second given value.

Step d) can be a step of calculating said value of a haptic pattern for the actuation speed determined by interpolation, for example by linear interpolation.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood on the basis of the description which follows and of the appended drawings in which:<ul id="ul0002" list-style="dash" compact="compact"><li>the <figref idref="f0001">figure 1A</figref> is a sectional view of an exemplary embodiment of a rotary haptic interface which can be implemented in the present invention,</li><li>the <figref idref="f0001">figure 1B</figref> is a schematic representation of a rotary interface according to the invention,</li><li>the <figref idref="f0001">figure 2</figref> a graphic representation of the variation of the braking stress applied by a magneto-rheological brake as a function of the angular position of an element of interaction with the user for a pattern in a given direction and for a given speed,</li><li>the <figref idref="f0002">figure 3</figref> is a graphic representation of the braking level applied by the magneto-rheological brake as a function of the speed of actuation of the element of interaction with the user,</li><li>the <figref idref="f0002">figures 4</figref> and <figref idref="f0003">5</figref> represent examples of haptic interface control algorithms according to the invention,</li><li>the <figref idref="f0003">figure 6</figref> is a cross-sectional view along the plane AA of the interface of the <figref idref="f0001">figure 1</figref>,</li><li>the <figref idref="f0004">figure 7</figref> is a perspective view of an exemplary embodiment of a test body implemented in the interface of the <figref idref="f0003">figure 6</figref>,</li><li>the <figref idref="f0004">figure 8</figref> is a perspective view of another embodiment of a test body which can be implemented in the interface of the <figref idref="f0003">figure 6</figref>,</li><li>the <figref idref="f0005">figure 9</figref> is a side view of another example of a haptic interface,</li><li>the <figref idref="f0005">Figures 10A to 10C</figref> are different views of the test body implemented in the interface of the <figref idref="f0005">figure 9</figref>,</li><li>the <figref idref="f0006">figure 11</figref> is an exploded view of an example of a linear haptic interface that can be implemented in the invention,</li><li>the <figref idref="f0006">figure 12</figref> represents an example of an algorithm for controlling the haptic interface according to the invention,</li><li>the <figref idref="f0007">figures 13</figref> and <figref idref="f0008">14</figref> represent variants of the algorithm of <figref idref="f0002">figures 4</figref> and <figref idref="f0003">5</figref> respectively, taking into account the knowledge of the user's intended action.</li></ul>

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

In the description which follows, the example of a haptic interface with a rotary button will be described in detail, but it will be understood that the invention also applies to a haptic interface with linear displacement of the cursor type. In addition, the described interface implements a magneto-rheological fluid, ie whose apparent viscosity varies according to the magnetic field applied, but the implementation of an electro-rheological fluid, ie a fluid whose apparent viscosity depends on the electric field applied, does not depart from the scope of the present invention.

On the <figref idref="f0001">figure 1A</figref>, we can see a longitudinal sectional view of an embodiment of a rotary haptic interface I1 according to the invention.

The haptic interface I1 comprises an element 1 intended to be manipulated by a user and which will hereinafter be designated "button", this button is integral in rotation with a shaft 2 movable in rotation about the axis X, and a resistant force generation device 4 or magneto-rheological brake opposing the rotation of the shaft 2.

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 magneto-rheological liquid. The assembly comprising the housing, the fluid and the system for generating a magnetic field forms a magneto-rheological brake.

The housing 8 defines a sealed chamber 9 containing the magneto-rheological fluid. All or part of this chamber being subjected to a magnetic field generated by the system 6. The housing 8 has a side wall 8.1, a lower bottom 8.2 and an upper bottom 8.3.

The shaft 2 crosses the upper bottom 8.3, crosses the chamber 9 and crosses the lower bottom 8.2. The end 2.1 of the shaft 2, opposite to that carrying the button 1, is housed in the lower bottom of the housing 8 and is guided in rotation by means of a bearing 11 mounted in the lower bottom 8.2. Seals 13, for example O-rings, seal between the shaft and the bottom and top bottoms.

The housing 8 defines a sealed chamber confining the magneto-rheological fluid.

The brake 4 also includes an element 12 integral in rotation with the shaft 2 and housed in the sealed chamber 10. This element is capable of interacting with the magneto-rheological fluid, the rotation of the element 12 being more or less braked by the magneto-rheological fluid as a function of its apparent viscosity.

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

Alternatively, the element 12 may have only one side wall or more than two concentric side walls. In another variant, the element 12 could be formed by a disc. Furthermore, the interaction element could include lights and / or protruding or recessed portions in order to increase the resistance to displacement.

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 amount of fluid required. In the example shown, a cylindrical element 13 of 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 magneto-rheological fluid when the side walls 12.1 and 12.2 are rotated.

The side walls 12.1, 12.2 of the element 12 can be made of magnetic or non-magnetic material.

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

The interface also includes 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 is in the example shown the current angular position. It may for example be an incremental optical encoder.

The haptic interface also comprises a frame 16 in which the housing 8 is disposed. 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 rotating shaft. The position sensor 14 is fixed to the first flange of the frame.

The brake is intended to exert a resistant force opposing the movement of the element of interaction with the user. This resistant effort is determined from predefined haptic patterns as a function of the haptic rendering which it is desired to reproduce, these patterns are recorded in a database.

A pattern is defined by a braking force to be applied according to the following data:<ul id="ul0003" list-style="dash" compact="compact"><li>the current angular position of the button,</li><li>the current direction of rotation of the button,</li><li>the speed of rotation of the button.</li></ul>

A haptic pattern is therefore a set of braking force values ​​to be applied to the button, ie a set of values ​​defining the pattern, each value of the haptic pattern is associated with a given angular position of the button and with a direction of rotation of the button. . Each braking force value corresponds to an apparent viscosity value which corresponds to a magnetic field value which corresponds to a current intensity supplying the system generating the magnetic field, for example a coil.

It is understood that the same value of the pattern can be assigned for different angular positions, or several different linear positions in the case of a linear interface.

On the <figref idref="f0001">figure 2</figref>, we can see a graphic representation of any haptic pattern. We represent the braking stress CF applied by the brake as a function of the angular position in degree Θ. Each angle value corresponds to a braking stress value.

The haptic interface comprises a control unit UC intended to generate orders with said magnetic field generation system so that it applies the values ​​of the pattern to be reproduced. On the<figref idref="f0001">figure 1B</figref>, we can see a schematic representation of the interface I1.

According to the invention, the control unit UC takes into account the value of the speed of actuation of the button, in addition to the direction of movement, to generate the order to the magnetic field generation system.

For this we define four reasons:<ul id="ul0004" list-style="dash" compact="compact"><li>an MPL pattern defined for the direction of actuation considered positive of the button and for a low speed of rotation;</li><li>an MPR pattern for the positive direction of actuation of the button and for a fast rotation speed;</li><li>an MNL pattern defined for the direction of actuation considered as negative of the button and for a low rotation speed;</li><li>an MNR pattern for the direction of actuation of the negative button and for a fast rotation speed.</li></ul>

Low speed is a speed whose value is less than or equal to a given threshold but is not zero.

Fast speed is considered the maximum speed with which the button can be operated. The fast speed in the positive direction can be equal to or different from the fast speed in the negative direction.

The actuation speed is advantageously approximated from the information provided by the position sensor, which makes it possible to offer a compact system. However, any other device other than the position sensor could be used to determine the speed of rotation.

On the <figref idref="f0002">figure 4</figref> a first algorithm is represented ensuring the choice of the values ​​of patterns to be taken into account.

During a first step 100, the position of the button, the actuation speed (variable SPEED) and the direction of actuation (variable DIRECTION) are determined from the information provided by the current position sensor. The DIRECTION variable can take the value +1 (direction of movement considered as positive), the value -1 (direction of movement considered as negative) or the value 0 when the speed is zero.

If the DIRECTION variable is equal to +1, then:<ul id="ul0005" list-style="dash" compact="compact"><li>we will search the low-speed positive pattern database BPL for the pattern value VPL (step 102), and</li><li>we will look in the database of positive pattern at high speed BPR for the value of VPR pattern (step 104).</li></ul>

Steps 102 and 104 can be simultaneous or sequential.

Otherwise, ie if the DIRECTION variable is equal to -1 or O, then:<ul id="ul0006" list-style="dash" compact="compact"><li>we will search the low-speed negative pattern database BNL for the pattern value VNL (step 106), and</li><li>the VNR pattern value will be searched in the fast-speed negative pattern database BNR (step 108).</li></ul>

At the end of the course of the first algorithm, there are two pattern values ​​either VPL and VPR, or VNL and VNR.

In Fig. 5, we can see an advantageous example of a second algorithm for determining the braking stress or the intensity of the current, these being considered proportional, to be applied to the magnetic field generation system.

During a first step 200, it is checked whether the DIRECTION variable is equal to 0, if this is the case, in this example the control unit generates a command to the brake to apply no constraint to the button, ie no magnetic field is only applied to the fluid. The algorithm is finished. Alternatively, it could be decided to maintain the last magnetic field applied. This step could take place before step 102.

If the DIRECTION variable is different from 0, ie if it is equal to +1 or - 1 then, during a next step 202, we calculate the coefficient ALPHA which is equal to: (abs (SPEED) - V_MIN) / ( V_MAX - V-MIN).

abs (SPEED) being the absolute value of the variable SPEED, V_MAX being the fixed value of the maximum actuation speed, this value is fixed for example at the usual maximum rotation speed with which a user usually actuates the button when he wishes to carry out rapid and coarse movements with the interface.

V_MIN being the fixed value of the minimum actuation speed, this value is fixed for example at the usual minimum rotation speed with which a user usually actuates the button when he wishes to carry out slow and precise movements with the interface.

V_MAX corresponds to the fast speed at which the MPR and MNR patterns are established without correction.

V_MIN corresponds to the slow speed at which the MPL and MNL patterns are established without correction.

During a next step 204, the coefficient ALPHA is advantageously limited to 0 and 1 to avoid aberrant calculation results, in fact it may happen that, exceptionally, the button is actuated at a speed greater than the maximum speed which has been fixed, ie that the calculation of the ALPHA value provides a result greater than 1 since nothing mechanically limits the speed of actuation. In the same way it can happen that, in an exceptional way, the button is actuated at a speed lower than the minimum speed which was fixed, ie that the calculation of the value ALPHA provides a result lower than 0 since it is possible to choose for V_MIN a non-zero value.

During a following step 206, the variable MOTIF_COURANT is calculated from a linear interpolation on the basis of the values ​​of patterns selected by the first algorithm.<ul id="ul0007" list-style="none" compact="compact"><li>∘ MOTIF_COURANT = (1-ALPHA)^∗ VPL + ALPHA^∗ VPR if the direction of actuation is positive or</li><li>∘ MOTIF_COURANT = (1-ALPHA)^∗ VNL + ALPHA^∗ VNR if the direction of actuation is negative.</li></ul>

During a following step 208, the variable MOTIF_COURANT is applied to the brake.

In the algorithm of the <figref idref="f0003">figure 5</figref>, MOTIF_COURANT is calculated starting from a linear interpolation. On the<figref idref="f0002">figure 3</figref>, a representation of this pattern can be seen as a function of the actuation speed in the case of actuation in the positive direction.

Any other interpolation, for example a quadratic interpolation, can be used.

It can also be envisaged to use a threshold function, the MOTIF_COURANT taking a value for a speed less than or equal to a threshold value and taking another value for a speed greater than the threshold value.

In the algorithm of the <figref idref="f0003">figure 5</figref>, the braking force is increased with the actuation speed if one chooses to take VPR&gt; VPL (respectively VNR&gt; VNL for the other actuation direction).

On the contrary, it can be expected that the braking force decreases while the actuation speed increases or that the relationship between the CURRENT PATTERN and the speed is not monotonous.

The algorithms described above apply completely to a linear haptic interface, the position sensor would then determine longitudinal positions and not angular positions.

In a particularly advantageous embodiment, provision is made to implement a system for determining the intention of action of the user in order to further improve the general haptic rendering of the interface.

The system for determining the intention of action of the user detects the torque exerted by the user on the button in the case of a rotary interface or the force applied by the user on the button in the case of a linear interface, and this before a movement of the button perceptible by the user and by the position sensor is applied to it.

In the example shown on the <figref idref="f0001">Figures 1A</figref> and <figref idref="f0003">6</figref> such a system is implemented, it comprises a test body 26 of which we will detect the deformation caused by the torque applied by the user with force sensors. The test body is shown alone on the<figref idref="f0004">figure 7</figref>. The test body 26 is fixed by a longitudinal end 26.1 to the frame 16 and by the other longitudinal end 26.2 to the magneto-rheological brake, 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.

In the example shown on the <figref idref="f0001">figures 1</figref> and <figref idref="f0003">6</figref>, the test body 26 comprises a body of cylindrical shape with circular section closed by a bottom 28 at the longitudinal end 26.2. An annular flange 30 extends radially outward at the other longitudinal end 26.1.

The internal diameter of the test body corresponds to the external diameter of the housing 8, increased by a clearance of operation. The bottom of the test body is disposed between the housing and the second flange 20 of the frame 16.

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

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

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

In the example shown, the projecting element 36 has the shape of an angular portion centered on the longitudinal axis. 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 portion angular 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.

Thus, when a torque is applied to the button, the latter causes torsional deformation of the test body 26 by means of the housing 8 itself in interaction with the fluid, itself in interaction with the element interaction 12, itself linked to the shaft 2 This deformation is detected by one or the other of the force sensors 40.1, 40.2 according to the direction of rotation of the button.

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

The material of the test body and its geometry can be determined according to 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 to the user. For example, it could be considered that a deformation of the test body of a few microns is not perceptible by the user.

Alternatively, the forces could be measured directly on the housing 8 or on the rotary shaft, for this a torque sensor would be implemented. However, a torque sensor has a high cost and a large size compared to the 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.

The force sensor is for example produced 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 sufficiently high stiffness to limit displacement to a few tens of microns at full load. As a variant, 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.

On the <figref idref="f0004">figure 8</figref>, we can see another example of a test body 126, the general shape of which is identical to that of the test body 26, but also has longitudinal slots 127 in the side wall of the test body 126. From preferably, the lights 127 are distributed angularly in a regular manner. The test body has in this embodiment a greater ability to deformation. It is for example made of aluminum alloy.

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 have all the same dimensions.

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 in the context of the invention, such as by example a radial stress which would be applied to the button in a parasitic way by the user. The detection sensitivity is thus improved and disturbances or false detections can be eliminated.

The example of a test body <figref idref="f0001">Figures 1A</figref>, <figref idref="f0003 f0004">6 at 8</figref> increases the sensitivity of the measuring device by placing the sensors on the largest possible diameter.

In the example shown and advantageously, the walls 36.1 and 36.2 of the projecting element are arranged at 90 ° relative 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 stress of deformation 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 a preferential assembly of the sensors with a load prestressing makes it possible to reduce to a certain extent the sensitivity to parasitic forces exerted parallel to the plane of the frame 16.

An example of operation of the device in which the intention of action of the user is determined will now be described.

The user turns the button 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 magneto-rheological fluid so that its variation in apparent viscosity generates a torque at the level of the element for interaction with the fluid simulating a stop at the button in the first direction of rotation.

If the user maintains his effort 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 element interaction 12, itself linked to tree 2

This deformation is measured by the force sensor arranged downstream in the first direction of rotation. Knowing which of the force sensors is used makes it possible to know the direction in which the user intends to turn the button. Preferably, the measurements from the two force sensors assembled can be combined with a load preload to determine the direction in which the user intends to turn the button. Detection of a minimum torque makes it possible to confirm that the user actually intends to rotate the button. It follows that the user intends to keep the button in abutment. The magnetic field is maintained so as to oppose a force to the movement of the interaction element 12 via the viscous magneto-rheological fluid.

If the user intends to rotate the button in a second direction opposite to the first direction, it is the force sensor disposed upstream considering the first direction of rotation, which will be requested. Preferably, the measurements from the two force sensors assembled can be combined with a load preload to determine the new direction in which the user intends to turn the button. We deduce the intention of the user, this intention is confirmed by the detection of a minimum torque. In this case, the magnetic field is canceled, the apparent viscosity of the fluid decreases sharply, the interaction element can therefore rotate in the second direction without feeling any sticking effect. We can thus reproduce thanks to the invention the operation of a freewheel.

On the <figref idref="f0005">Figures 9 and 10A to 10C</figref>, we can see another 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 of interaction with the user 201, the element of interaction with the fluid not being visible.

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

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

Two force sensors 240.1, 240.2 are disposed each bearing against a spoke 230 and arranged with respect to the spokes so that, when the test body 226 is biased in a direction of rotation, only one of the sensors is biased. The force sensors are fixed to the frame 216 and bear against a face with a radius 230. As a variant, the force sensors could be assembled with a prestressing load, or, as mentioned above, be replaced by elongation gauges placed on the test body and detecting the deformation, for example spokes under the effect of the torque. More generally, the force sensors can be replaced by deformation sensors.

The operation of this device is similar to that of the device of the <figref idref="f0001">figure 1A</figref> described above.

Means making it possible to apply mechanical stresses to the test body, such as means for guiding in rotation or in translation, can advantageously be added, which makes it possible to reduce the number of force sensors by assembling the latter with a preload of charge.

The data from these force or deformation sensors are processed by an electronic system to determine if 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.

As indicated above, knowledge of the actual value of the torque is not necessary, knowledge of the direction of torsion is sufficient. It is therefore possible to implement low-cost sensors making it possible to detect at least a binary threshold or a monotonic function of the force or the deformation, outside any specification of the linearity, dynamic, resolution, etc. type, to the extent where the sensor is sensitive enough to detect a minimum torque acting on the interface without there being any rotation of the latter. The sensor is also such that it is able to hold a maximum effort without degradation.

On the <figref idref="f0006">figure 11</figref>, an exploded view of an example shown diagrammatically of a linear interface according to the invention can be seen.

The device comprises a housing 308 in which is mounted an axis 302 movable axially along its axis X, the axis 302 being intended to carry an element of interaction with the user (not shown) at at least 1 'one of its longitudinal ends, means for generating a variable magnetic field 306 are arranged in the housing. The housing delimits a sealed chamber which contains magneto-rheological fluid and which is crossed by the axis 302. Seals 313 ensure a tight sliding of the shaft in the chamber.

The interface also includes a position sensor (not shown) for measuring the current longitudinal position of axis 302.

The interface also includes means for detecting the intention of action of the user, these means then detect a translational force applied by the user on the axis before a movement of the axis perceptible by the user and by the position sensor applied to it. These means comprise a test body (not shown), the deformation of which is measured by one or more force or deformation sensors, the test body being fixed on the housing and on the frame (not shown). If the user intends to move the axis in the first direction of translation, the test body undergoes a shearing force via the housing, itself in interaction with the fluid, itself in interaction with the interaction element, itself linked to axis 302.

We will now describe algorithms making it possible to operate the haptic interface according to the invention and taking into account the action intention of the user.

In the present case, we are particularly interested in cases where the speed of rotation of the button is zero or at least less than a value below which the movement of the button is considered to be imperceptible.

The control electronics jointly use the information from the angular position sensor and the information from the force sensors to determine the resistive torque to be generated by the brake 4.

The algorithm represented on the <figref idref="f0006">figure 12</figref> is applied to determine the direction of rotation in which the knob is rotated or in which the user intends to rotate it.

We use the variable TORSION which is an estimate of the torque. Knowledge of the precise torque value is not required. This estimate is obtained from the information provided by the force sensor which is requested by the test body in the embodiment of the<figref idref="f0001">Figures 1A</figref>, <figref idref="f0003 f0004">6 at 8</figref>. The estimation of the torque allows to know if it is higher or lower than threshold values ​​taking into account the direction in which the torque is applied.

During a first step 400, the speed of movement of the button is calculated. We get the SPEED variable.

It is considered that the speed is zero when it is lower than a given real value and therefore the approximation of the derivative of the information provided by the angular sensor sampled at a rate Te returns to a zero value.

During a next step 402, the function for estimating the torsional moment applied by the user is calculated from information supplied by the force sensors, this function is the TORSION variable.

During a next step 404, it is checked whether the variable SPEED is zero, if it is not zero, the variable DIRECTION is assigned the sign of speed (step 406).

If the SPEED variable is zero, the TORSION variable is used.

In a next step 408; it is checked whether the TORSION variable is greater than a threshold called "positive threshold", if this is the case, the variable DIRECTION is assigned the value +1 (step 410).

Otherwise, in a following step 412, it is checked whether the TORSION variable is less than a threshold called "negative threshold", if this is the case, the variable DIRECTION is assigned the value -1 (step 414).

Otherwise, ie if the speed is zero and the torque is greater than the negative threshold and is less than the positive threshold, then, during a next step 316, the DIRECTION variable takes the value zero. The system considers that no torque is applied to the button, it can for example be deduced therefrom that the user has released the button.

Thanks to this algorithm, it can be determined in the case where the speed of movement of the button is zero the direction in which the user intends to move the button without significant movement of the latter.

In fact, thanks to the information provided only by the force or deformation sensor (s), it is possible to determine in which direction the torque is applied, even without significant displacement of the button, and therefore to decide in which direction the user has l intention to move the button, and on this basis to control the system for generating a variable magnetic field accordingly.

Then; we apply a variant of the algorithm of the<figref idref="f0002">figure 4</figref>.

In this variant, the following four patterns are defined:<ul id="ul0008" list-style="dash" compact="compact"><li>an MPL 'pattern defined for the direction of actuation considered positive of the button and for a zero or low speed of rotation;</li><li>an MPR 'pattern for the positive direction of actuation of the button and for a fast rotation speed;</li><li>a pattern MNL 'defined for the direction of actuation considered as negative of the button and for a zero or low rotation speed;</li><li>a MNR 'pattern for the direction of actuation of the negative button and for a fast rotation speed.</li></ul>

The zero or low speed is a speed whose value is less than or equal to a given threshold. Since we determine the user's intention to act, we can define a zero speed in the positive direction and a zero speed in the negative direction. The user may not move the button, the SPEED variable is equal to 0 but the torque exerted in one direction or the other may be different from 0. The absence of user action intention is given when the DIRECTION = 0 variable.

As before, fast speed is considered to be the maximum speed with which the button can be operated. The fast speed in the positive direction can be equal to or different from the fast speed in the negative direction.

On the <figref idref="f0007">figure 13</figref>&gt; the variant of the algorithm of the <figref idref="f0002">figure 4</figref> ensuring the choice of pattern values ​​to be taken into account.

During a first step 100 ′, it is checked whether the DIRECTION variable is equal to +1, if this is the case then:<ul id="ul0009" list-style="dash" compact="compact"><li>we will search the low-speed positive pattern BPL 'database for the pattern value VPL' (step 102 '), and</li><li>we will look in the database of positive pattern at high speed BPR 'for the value of pattern VPR' (step 104 ').</li></ul>

Steps 102 ′ and 104 can be simultaneous or sequential.

Otherwise, ie if the DIRECTION variable is equal to 0 or -1, then:<ul id="ul0010" list-style="dash" compact="compact"><li>we will search the low-speed negative pattern database BNL 'for the pattern value VNL' (step 106), and</li><li>we will search the BNR 'fast-speed negative pattern database for the VNR pattern value (step 108).</li></ul>

At the end of the flow of the first algorithm, there are two pattern values ​​either VPL 'and VPR', or VNL 'and VNR'.

A variant of the algorithm of the <figref idref="f0003">figure 5</figref> represented on the <figref idref="f0008">figure 14</figref> is then applied to effectively determine the value of the braking constraint to be applied, ie the magnetic field to be applied, and therefore the intensity of the current which will supply the magnetic field generation system.

During a first step 200 ′, it is checked whether the DIRECTION variable is equal to 0, if this is the case, the control unit generates a command to the brake to apply no constraint to the button, ie no magnetic field is applied to the fluid. The algorithm is finished. In this algorithm, the fact that DIRECTION = 0 means that it has been determined that the user does not intend to press the button one way or the other. It can for example be deduced therefrom that the user has released the button. This step could take place before step 102 '.

If the DIRECTION variable is different from 0, ie if it is equal to +1 or -1 then, during a next step 202 ', the ALPHA coefficient is calculated which is equal to: abs (SPEED) / V_MAX.

abs (SPEED) being the absolute value of the current speed, PARAMETER V_MAX being the fixed value of the maximum actuation speed.

During a next step 204 ′, the coefficient ALPHA is advantageously limited to 0 and 1 to avoid calculation errors, in fact it may happen that, exceptionally, the button is actuated at a speed greater than the maximum speed which has been set, ie that ALPHA is greater than 1 since nothing mechanically limits the actuation speed.

During a next step 206 ′, the variable MOTIF_COURANT is calculated from a linear interpolation on the basis of the values ​​of patterns selected by the first algorithm.<ul id="ul0011" list-style="none" compact="compact"><li>∘ MOTIF_COURANT = (1-ALPHA)^∗ VPL '+ ALPHA^∗ VPR 'if the direction of actuation is positive or</li><li>∘ MOTIF_COURANT = (1-ALPHA)^∗ VNL '+ ALPHA^∗ VNR 'if the direction of actuation is negative.</li></ul>

During a following step 208 ′, the variable MOTIF_COURANT is applied to the brake.

As for the algorithm of the <figref idref="f0003">figure 5</figref>, the MOTIF_COURANT could be calculated with any other interpolation, for example a quadratic interpolation, can be used. It can also be envisaged to use a threshold function.

The algorithms described above apply completely to a linear haptic interface, the position sensor then determines longitudinal positions and not angular positions.

Knowing that there is no intention on the part of the user makes it possible, for example, to cut off the power supply to the system generating the magnetic field while being sure that the user does not intend to move the button. which improves haptic rendering. On the contrary, without this knowledge the current could be accidentally cut when the user has already applied a torque to the button not perceived by the system.

The haptic interface according to the invention is particularly suitable for application in motor vehicles, for example to form an on-board haptic interface assisting the car driver. It can allow the user to interact with different equipment or accessories of the vehicle such as GPS (Global Positioning System in English terminology or Global Positioning System), radio, air conditioning ...