FR3099260A1 - Method for calibrating a haptic actuator and haptic actuator - Google Patents

Abstract

The invention relates to a method for calibrating the distance between the stator (110) and the moving part (120) of a haptic actuator (100), said stator comprising a coil designed to generate a magnetic field when it is traversed by an electric current, said moving part being designed to be attracted, along a longitudinal axis (A1), towards the stator by said magnetic field. According to the invention, the method comprises the following steps: a) installing at least one wedge (140) between the movable part and the stator, b) pinching the wedge between the movable part and the stator and fixing the stator to a base (130), c) removing the wedge. The invention also relates to such a haptic actuator in which the stator is glued to the base. Figure. 2

Description

Calibration method of a haptic actuator and haptic actuator

Technical field to which the invention relates

The present invention generally relates to the field of haptic actuators.

It relates more particularly to the calibration of these actuators.

Technology background

There are haptic actuators comprising a stator and a moving part. The stator is designed to generate a magnetic field thanks to a coil and this magnetic field has the function of attracting the moving part, generally made of ferromagnetic material. The mobile part can be connected to a touch surface; the role of the actuator is for example to make the touch surface vibrate to transmit haptic feedback to a user.

An important step in the design of these haptic actuators is the calibration of the distance between the moving part and the stator. This distance is subsequently called the magnetic air gap. Improper calibration of this distance can drastically reduce the performance of the actuator. Calibration also ensures a consistent haptic effect from one product to another.

Currently, the magnetic air gap is calibrated by measuring the distance between the stator and the moving part, for example optically using lasers, and bringing the stator closer to the moving part until the magnetic air gap corresponds to the expected distance.

The disadvantages of this technique are the difficulty of setting up the measurement of the magnetic air gap, the cost of the measuring devices, and the accuracy of the measurement.

Object of the invention

In this context, the invention proposes a method for calibrating the distance between the stator and the moving part of a haptic actuator, said stator comprising a coil designed to generate a magnetic field when it is traversed by an electric current. , said movable part being designed to be attracted, along a longitudinal axis, towards the stator by said magnetic field, the method comprising the following steps:

a) installation of at least one wedge between the moving part and the stator,

b) pinching of the spacer between the mobile part and the stator and fixing of the stator to a base,

c) removal of the chock.

Thus, thanks to the invention, the calibration of the magnetic air gap is freed from a measurement step and its intrinsic errors. In addition, this makes it possible to gain in efficiency by reducing the number of iterations (one iteration including the displacement of the stator then the measurement of the magnetic air gap) in the calibration and to dispense with complex and expensive measuring devices.

Advantageously, step b) comprises bonding the stator to the base with an adhesive. This makes it possible to compensate for tolerances and/or defects in the mechanical parts in order to guarantee the magnetic air gap set by the shim(s). For example, if the moving part is linked to a surface which is not strictly parallel to the base, the resulting lack of parallelism between the stator and the base is compensated by the glue.

Other non-limiting and advantageous characteristics of the calibration method in accordance with the invention, taken individually or according to all the technically possible combinations, are the following:

• a gap, located between the base and the stator along the longitudinal axis, is filled with glue;
• the glue is a “UV glue” which hardens under the action of ultraviolet rays;
• the glue is an epoxy or acrylate-based resin;
• the thickness of the wedge is equal to the said distance to be calibrated;
• the wedge has a rectangular section along a plane parallel to the longitudinal axis;
• the wedge has a rectilinear profile along an axis orthogonal to the longitudinal axis;
• in step a), a pair of wedges is used;
• the haptic actuator has a plane of symmetry and, in step a), the wedge(s) are arranged symmetrically with respect to this plane of symmetry;
• in step b), the wedge is pinched by attracting the stator and the moving part towards each other by means of an electromagnetic force;
• said electromagnetic force is generated by means of an electromagnet, positioned opposite the moving part with respect to the stator;
• said electromagnetic force is generated the coil of the stator;
• at least part of the surface of the stator is tapped to be screwed into the base and in step b), the stator is screwed in until the stator is butted against the shims and the shims are butted against the moving part.

The invention also proposes a haptic actuator comprising a stator and a mobile part, said stator comprising a coil designed to generate a magnetic field when it is traversed by an electric current, said mobile part being designed to be attracted, along a longitudinal axis , towards the stator by said magnetic field, said haptic actuator comprising a base and said stator being bonded to said base.

It is possible to provide for a gap, located between the stator and the base along the longitudinal axis, to be filled with hardened glue.

Detailed description of an example of realization

The following description with reference to the accompanying drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

Of course, the different characteristics, variants and embodiments of the invention can be associated with each other in various combinations insofar as they are not incompatible or exclusive of each other.

On the attached drawings:

is a block diagram of a sequence of steps allowing the calibration of the distance between the stator and the moving part of a haptic actuator,

is a schematic view of a method for calibrating a haptic actuator according to a first embodiment of the invention,

is a schematic view of a method for calibrating a haptic actuator according to a second embodiment of the invention.

To fully understand the calibration method proposed by the invention, it is necessary to briefly describe the essential parts of a haptic actuator and its operation.

As shown for example in Figure 2, a haptic actuator 100 conventionally comprises a stator 110, a movable part 120 connected to a touch surface 121, and a base 130. The stator 110 further comprises a coil of electric wire for generating a magnetic field when an electric current passes through it. When the actuator 100 is operational (at the end, moreover, of the calibration described below), the stator 110 is fixed with respect to the base 130. The base 130 is fixed with respect to the touch surface 121 at least rest, that is to say when the latter is not set in motion by the haptic actuator 100 or moved under the pressure of a user's finger. Typically, in a motor vehicle, base 130 may be included in the dashboard in which touch surface 121 is included. Mobile part 120 is preferably made of ferromagnetic material to be attracted towards stator 110 by the magnetic field. The touch surface 121, rigidly linked to the mobile part 120, is therefore set in motion relative to the base 130, along a longitudinal axis A1, when the magnetic field is activated. This mechanism is the basis of the vibration of the touch surface 121. The force with which the movable part 110 is attracted towards the stator 120 is a function of the distance between the stator 110 and the movable part 120. In order for the stator 110 to exert on the moving part 120 the programmed force, the distance between the stator 110 and the moving part 120, called the magnetic air gap, must be precisely calibrated.

To determine when and how to vibrate the touch surface 121, the haptic actuators can also measure the force exerted by the user, for example with his finger, on the touch surface 121. The distance between the stator 110 and the moving part 120 is for example measured capacitively, using a dedicated electronic circuit, or inductively by directly measuring the inductance of the coil. In both cases, the magnetic air gap must be precisely calibrated since it serves as a reference distance (case of zero force exerted on the tactile surface 121).

Figures 2 and 3 show two embodiments of the calibration method according to the invention.

In these two embodiments it is a method of calibrating the distance between the stator 110 and the moving part 120, called the magnetic air gap, comprising the three steps, a), b), and c), presented in figure 1.

In step a), at least one wedge 140 is interposed in the space located between the stator 110 and the moving part 120.

In step b), the stator 110 is clamped against the wedge 140, the wedge 140 is then compressed between the stator 110 on one side and the moving part 120 on the other; subsequently or at the same time, the stator 110 is fixed to the base 130.

In step c), the wedge 140 is removed from the space located between the stator 110 and the moving part 120.

Step a) is identical for both embodiments. As already indicated, it includes the placement of at least one wedge 140 between the stator 110 and the moving part 120.

The wedge 140 has a dimension 141, along the longitudinal axis A1, which is strictly equal to the magnetic air gap to be calibrated. This dimension 141 is called the thickness of the wedge 140. By strictly equal, is meant the maximum precision that a person skilled in the art, specialized in the design of mechanical parts, can bring to the dimensions of the wedge 140, for example by molding, cutting or by 3D printing. Preferably, dimension 141 of wedge 140 is accurate to ten micrometers.

As shown in Figures 2 and 3, provision may be made for the wedge or wedges to preferably have a rectangular section along a plane parallel to the longitudinal axis A1. According to this plan, the opposite sides of a wedge 140 are parallel and of the same length. Here, this plane is for example the cutting plane according to which the actuator 100 is represented in FIGS. 2 and 3. In this way, when in step b) the wedge 140 is clamped between the stator 110 and the part mobile 120, the parallelism between the stator 110 and the mobile part 120 is facilitated. This parallelism is desirable so that the moving part 120 is attracted towards the stator 110 by the magnetic field in the most balanced way possible. This parallelism corresponds to what is called the stability of the magnetic air gap, that is to say the fact that the expected magnetic air gap is respected for all points of the two flat surfaces 111, 122 facing each other and belonging respectively to the stator 110 and to the moving part 120. A magnetic air gap which would not be stable would correspond to certain zones of these two flat surfaces 111 and 122 which are closer to each other.

Alternatively, the shim(s) can have a circular section along a plane parallel to the longitudinal axis A1.

Advantageously, the wedge 140 has a rectilinear profile, along an orthoradial axis A2 orthogonal to the longitudinal axis A1. Here, the orthoradial axis A2 is perpendicular to the cutting plane along which the actuator 100 is shown in Figures 2 and 3. The faces that extend along the orthoradial axis A2 are parallel to this axis. This shape makes it possible to place (step a) and remove (step c) the wedge 140 with a translational movement, simple to put in place on an assembly bench and using the least space possible between the stator 110 and the moving part. 120. Indeed, other elements not shown in the figures, such as a translation axis or an elastic joint, can be located between the stator 110 and the moving part 120.

Alternatively, wedge 140 could have a curved profile. It could for example have a profile similar to the geometry of the stator 110, such as a profile having the same radius of curvature as the stator 110 if the latter is cylindrical.

In the embodiments described below, a pair of wedges 140 are used.

The use of a pair of wedges 140 has the advantage of ensuring very precise parallelism between the moving part 120 and the stator 110, that is to say a very stable magnetic air gap. This also has the advantage of stabilizing the stator when it clamps the wedges 140 against the moving part 120.

Here, the actuator 100 has a plane of symmetry P1 which includes the axis A1 and which is parallel to the axis A2. This plane P1 is perpendicular to the cutting plane along which the actuator 100 is shown in Figures 2 and 3 and passes through the center of the actuator 100. The wedges 140 are placed on either side of the plane P1. Provision can be made, for example, for the wedges 140 to be placed symmetrically with respect to the plane P1. Thus, a very good balance of the stator 110 during step b) and a very good stability of the magnetic air gap are guaranteed.

Alternatively, more than two wedges could be used. This would increase the stability of the magnetic air gap and the balance of the stator 110 during step b) but would increase the complexity of steps a) and c).

Figure 2 shows a first embodiment of step b). Here, a pair of shims 140 is placed in step a).

Step b) includes pinching the wedges 140 between the stator 110 and the moving part 120.

Remarkably, the pinching is achieved by attracting the stator 110 and the moving part 120 towards each other by an electromagnetic force. Here, this electromagnetic force is generated by an electromagnet 150. Indeed, the stator 110 can comprise a magnetizable envelope surrounding the coil. The role of this envelope is to serve as a magnetic circuit for the magnetic field created by the coil. Thus, the stator 110 is likely to be attracted by a magnet.

As shown in Figure 2, the electromagnet 150 is located opposite the movable part 120 with respect to the touch surface 120. The electromagnet 150 is for example positioned against the touch surface 121. The movable part 120 is therefore interposed between the stator 110 and the electromagnet 150. The electromagnet 150 is first positioned off, that is to say when it is not powered by an electric current and it does not produce magnetic field. A surface can be positioned between the electromagnet 150 and the touch surface 121 to protect the latter.

When the electromagnet 150 is energized, that is to say when it is supplied with an electric current, the latter produces an electric field which attracts the stator 110. The stator 110 comes into abutment against the wedges 140 which are themselves in abutment against the mobile part 120. The mobile part 120 is also attracted by the electromagnet 150 because it is made of ferromagnetic material, however, as it is integral with the touch surface 121, it is not Put into motion. When the electromagnet 150 is energized, the shims 140 are therefore pinched between the stator 110 and the moving part 120. At this time, the magnetic air gap is equal to the dimension 141 of the shims 140.

Preferably, the center of the electromagnet 150 is placed on the longitudinal axis A1 which here passes through the center 113 of the stator 110 and which is orthogonal to the touch surface 121. In this way, when the electromagnet 150 attracts the stator 110, the movement of the latter is a translational movement along this axis A1. The risks of tilting of the stator 110 or of the wedges 140 are thus reduced.

Here, the axis A1 passes through the center 113 of the stator 110 and through the center 123 of the moving part 120. The wedges 140 are arranged symmetrically with respect to the axis A1. This configuration ensures very good stability of the assembly formed by the stator 110, the wedges 140 and the moving part 120, when the electromagnet 150 is energized.

As a variant, the magnetic field attracting the stator 110 towards the moving part 120 is created by the coil of the stator 110 by energizing it. As described above, in this variant, the pinching of the wedges 140 is also obtained by an electromagnetic force produced by a coil. When it is energized, the coil of the stator 110 generates a magnetic field which magnetizes and attracts the mobile part 120. The mobile part 120 being, at this moment, fixed with respect to the base 130, it is the stator 110 which moves towards it, which pinches the wedges 140. The steps described below implementing the electromagnet 150 can be transposed to the use of the coil of the stator 110 as a generator of an electromagnetic force.

Step b) also includes attaching the stator 110 to the base 130.

In the first embodiment described here, the fixing of the stator 110 corresponds to a bonding of the stator 110 to the base 130. During this bonding, the electromagnet 150 is kept under tension to guarantee that the magnetic air gap is equal to the dimension 141 of the wedges 140. Gluing the stator 110 to the base 130 makes it possible to compensate for the tolerances of the mechanical parts, for example a lack of parallelism between the base 130 and the touch surface 121 or of alignment of the parts along the longitudinal axis A1 . This also limits the effect of vibrations that the haptic actuator 100 will undergo during its operation. This method of fixing is more resistant and more durable than screwing or tight fitting.

To firmly glue the stator 110 to the base 130, a free space 131 is provided between the stator 110 and the base 130, here in the base 130. This free space 131 is adapted to receive one end 112 of the stator 110 and a layer of glue 160. The end 112 is opposite the axial end of the stator 110 facing the movable part 120. The dimensions of the free space 131 are slightly greater than the dimensions of the end 112 of the stator 110. Thus the stator 110 is glued to the base 130 over a wide contact surface of the stator 110 having at least one curvature and/or angles. Here, the stator 110 is glued on several faces, on some integrally and on others partially.

The depth of the free space 131 is such that the end 112 does not come out of this free space 131 when the stator 110 is attracted by the electromagnet 150, this taking into account the manufacturing processes.

The glue 160 is placed in the free space 131 before energizing the electromagnet 150 (step b). Prefilling the free space 131 with glue 160 before inserting the end 112 of the stator 110 there allows the glue 160 to be distributed evenly between the stator 110 and the base 130.

The glue 160 is therefore deposited in a gap located between the stator 110 and the base 130 along the longitudinal axis A1. Here, this interstice is part of the free space 131.

Here, the glue 160 is chosen so that its hardening time is greater than the time necessary to place the stator 110 in the free space 131 and to move the stator 110 attracted by the electromagnet 150 and in abutment against the wedges 140 .

An alternative way to proceed is to inject the glue 160, into the free space 131, between the base 130 and the end 112, once the stator 110 is in abutment against the wedges 140.

In practice, the glue 160 is a glue which is liquid when it is deposited. The fact that it is liquid allows it to spread easily, by gravity or by capillarity, in free space 131.

Advantageously, the glue 160 is of the "UV glue" type, that is to say a glue which polymerizes (hardens) under the action of ultraviolet rays. This type of glue makes it possible to decide when the glue 160 hardens, typically once the stator 110 has been attracted against the wedges 140 by the electromagnet 150.

Alternatively, the glue 160 could be an epoxy or acrylate based resin, for example "super glue". These glues harden quickly and have a high resistance. In addition, these adhesives are very liquid and spread easily into the interstices by capillarity.

The fixing step ends when the glue 160 has hardened sufficiently to hold the stator 110 in relation to the base 130. The electromagnet 150 can then be de-energized.

Alternatively, instead of and/or in combination with the glue 160, the fixing of the stator 110 to the base 130 could be carried out by means of a weld.

In step b), any means known to those skilled in the art for clamping one part against another can be considered for clamping the wedges 140 between the stator 110 and the moving part 120, instead of or in addition to the use of the 150 electromagnet.

Figure 3 shows a second embodiment of step b). Here again, a pair of shims 140 is placed in step a).

In this embodiment, at least part of the outer surface of the stator 110 and the base are threaded so that the stator 110 can be screwed into the base 130, along the axis A1 which here passes through the center 113 of the stator 110 and which is orthogonal to the tactile surface 121. This tapping can for example be made on the magnetizable envelope surrounding the coil of the stator 110.

In the example described below, as shown in FIG. 3, the stator 110 comprises an insertion part 170. This insertion part 170 and the base 130 are threaded in such a way that the insertion part 170 can be screwed into the base 130, along the axis A1 which here passes through the center 113 of the stator 110 and which is orthogonal to the touch surface 121.

The insertion part 170 has an outer surface 171 of cylindrical shape. The outer surface 171 is tapped so that the insertion part is screwed into the base 130.

At the center of the insertion part 170, a free space 172 is arranged to receive an end 112 of the stator 110 which is opposite the axial end of the stator 110 facing the movable part 120.

The free space 172 is dimensioned so that the end 112 of the stator 110 fits therein to within one clearance. The stator 110 is fixed with respect to the insertion part 170. Additional means can be provided to fix the stator 110 to the insertion part 170 such as clipping means.

The free space 172 is placed in the center of the insertion part 170 so that, when the insertion part 170 is screwed into the base 130, the movement of the center 113 of the stator 110 is a translational movement along of axis A1.

During step b), the insertion part 170 is screwed into the base 130, in the direction of the mobile part 120, until the stator 110 is in abutment against the wedges 140 and the wedges 140 are themselves in abutment against the moving part 120. The wedges 140 are thus pinched between the moving part 120 and the stator 110. Once the insertion part 170 has been screwed in this way, the magnetic air gap is equal to the dimension 141 of the wedges 140.

The thread of the insertion part 170 is fine so that the position of the stator 110 along the axis A1 is precise. The assembly of the insert part 170 in the base 130 is tight so that the stator 110 does not move due to the natural vibrations that the actuator 100 experiences during operation.

In this embodiment, the fixing of the stator 110 to a base is carried out at the end of screwing. Nevertheless, to perfect the fixing, additional means, such as notches, glue or welding, can be used to fix the insertion part 170 to the base 130.

Alternatively, an electromagnetic force, generated by an electromagnet 150 (not shown) or by the coil of the stator 110, can be used to pinch the wedges 140 between the stator 110 and the moving part 120, as described in the first mode of achievement. Here, the stator 110 is inserted into the free space 172 during the screwing of the insertion part 170. The fixing of the stator to a base then consists of screwing the insertion part 170 until the part of insertion 170 is in abutment against the stator 110, that is to say until the end 112 of the stator 110 is inserted into the free space 172. Fixing means, such as notches, of glue or solder may be provided to secure stator 110 to insert portion 170.

In both embodiments, step c) corresponds to the removal of the wedges 140.

Indeed, once the stator 110 is fixed relative to the base 130, the moving part 120 being fixed relative to the touch surface 121, the magnetic air gap is guaranteed. In addition, leaving the wedges 140 would prevent the moving part 120 from being moved towards the stator, which would therefore prevent the very operation of the actuator 100.

Of course, various other modifications may be made to the invention within the scope of the appended claims.

Claims (14)

Method for calibrating the distance between the stator (110) and the moving part (120) of a haptic actuator (100), said stator (110) comprising a coil designed to generate a magnetic field when it is traversed by a current electric, said movable part (120) being designed to be attracted, along a longitudinal axis (A1), towards the stator (110) by said magnetic field, the method beingcharacterized in thatthat it involves the following steps:
a) installation of at least one wedge (140) between the moving part (120) and the stator (110),
b) pinching the wedge (140) between the moving part (120) and the stator (110) and fixing the stator to a base (130),
c) removal of the wedge (140). Calibration method according to claim 1, wherein step b) comprises bonding the stator (110) to the base (130) with an adhesive (160). Calibration method according to claim 2, in which a gap, located between the base (130) and the stator (110) along the longitudinal axis (A1), is filled with the glue (160). Calibration method according to one of Claims 2 to 3, in which the glue (160) is a "UV glue" which hardens under the action of ultraviolet rays. Calibration method according to one of Claims 2 to 3, in which the glue (160) is an epoxy- or acrylate-based resin. Calibration method according to one of Claims 1 to 5, in which the thickness (141) of the wedge (140) is equal to the said distance to be calibrated. Calibration method according to one of Claims 1 to 6, in which the spacer (140) has a rectangular section along a plane parallel to the longitudinal axis (A1). Calibration method according to one of Claims 1 to 7, in which the wedge (140) has a rectilinear profile along an axis orthogonal (A2) to the longitudinal axis (A1). Calibration method according to one of Claims 1 to 8, in which in step a), a pair of wedges (140) is used. Calibration method according to one of Claims 1 to 9, in which the haptic actuator (100) has a plane of symmetry (P1) and in which, in step a), the wedge(s) (140) are placed symmetrically with respect to this plane of symmetry (P1). Calibration method according to one of Claims 1 to 10, in which in step b), the pinching of the wedge (140) is carried out by attracting the stator (110) and the movable part (120) towards one another. the other by means of an electromagnetic force. Calibration method according to one of claims 1 to 11, in which at least a part of the surface of the stator (110) is tapped to be screwed into the base (130) and in which, in step b), the stator (110) is screwed until the stator (110) is in abutment against the wedges (140) and the wedges (140) are in abutment against the mobile part (120). Haptic actuator (100) comprising a stator (110) and a movable part (120), said stator comprising a coil designed to generate a magnetic field when it is traversed by an electric current, said movable part (120) being designed to be attracted, along a longitudinal axis (A1), towards the stator (110) by said magnetic field,
characterized in that the haptic actuator 100 comprises a base (130),
and in that the stator (110) is bonded to said base (130). Haptic actuator (100) according to Claim 13, in which a gap, located between the stator (110) and the base (130) along the longitudinal axis (A1), is filled with hardened glue (160).