WO2013007950A1

WO2013007950A1 - Instrumented steering wheel for a motor vehicle

Info

Publication number: WO2013007950A1
Application number: PCT/FR2012/051639
Authority: WO
Inventors: Michèle MOESSINGER; Bertrand MASSOT
Original assignee: Renault S.A.S.
Priority date: 2011-07-11
Filing date: 2012-07-11
Publication date: 2013-01-17
Also published as: FR2977852A1; FR2977852B1

Abstract

The invention relates to a generally ring-shaped steering wheel for a motor vehicle, comprising electrodes (80a, 80b, 82a, 82b) arranged thereon. The electrodes are connected to a power supply circuit (M₁, M₂) in order to supply a signal to a computer, on the basis of signals emitted by the electrodes (80a, 80b, 82a, 82b), said signal being representative of the physiological condition of the driver when the driver places his/her hands on the electrodes (80a, 80b, 82a, 82b). When the vehicle steering angle is zero, the steering wheel comprises two portions each forming a half-ring in relation to a vertical plane passing through its axis of rotation. The invention is characterised in that one part of the electrodes is arranged on all or part of one of the portions of the steering wheel in at least two measuring circuits (M₁, M₂), while the other part of the electrodes is arranged on all or part of the other portion of the steering wheel in at least two other measuring circuits.

Description

WHEEL INSTRUM ENTÉ FOR MOTOR VEHICLE

The present invention relates to a steering wheel for a motor vehicle, and more particularly to a steering wheel comprising electrodes for measuring electrical parameters of the driver.

In this field, it is known from document FR 2 880 166, means for measuring the resistance or cutaneous potential of the driver when he has hands on the steering wheel, the latter being equipped with electrodes for generating a signal measurement unit providing a computer, via a conditioner, with a signal representative of the physiological state of the driver.

It is indeed known that the measurement of cutaneous electrical resistance, reflecting the electrodermal activity, makes it possible to estimate various physiological parameters. The short-term variations in these measurements reflect the influence of the demands on the driver's environment, while the long-term variations reflect the driver's state of alertness and vigilance.

However, the implementation and in particular an effective implementation of the measuring electrodes on the steering wheel can be complex, in particular by the great diversity of grip behavior of the steering wheel by the drivers, as well as by the diversity of pressure exerted by the driver on the wheel.

Indeed, the principle of measurement is based on Ohm's law, applied from continuous or alternating signals. It is thus necessary to have at least two electrodes in contact with the skin and between which the electrical resistance is measured. During electrode implantation tests at the steering wheel, it appears that the pressure exerted by the driver on the steering wheel, as well as the gripping zone has an influence on the measurement, essentially through the contact impedance, which causes a signal instability.

The present invention aims to improve the quality and reproducibility of the signal without introducing any noticeable change in the structure and handling of the steering wheel, or hindering its grip.

The present invention is achieved with the aid of a motor vehicle steering wheel having a generally toroidal shape and comprising electrodermal measuring electrodes disposed on said flywheel, said electrodes being connected to a power supply circuit for supplying a computer, from the signals from the electrodes, a value of the electrical impedance between the electrodes representative of the physiological state of the driver when the latter places his hands on said electrodes, said flywheel having, when the steering angle of the vehicle is zero , two portions each forming a half-torus relative to a vertical plane passing through its axis of rotation, characterized in that a portion of the electrodes is disposed on all or part of one of the portions of the flywheel in at least two circuits measuring the other part of the electrodes being disposed on all or part of the other portion of the steering wheel in at least two other circu its of measure.

Thus, it is proposed to make the cutaneous electrical measurement (impedance or resistance between electrodes) for each of the hands by two specific measuring circuits, in order to limit the noise due to the movements of the hands.

Advantageously, each measuring circuit has an alternation of electrodes regularly spaced by a distance h, two successive electrodes forming a pair of measuring electrodes of said circuit. This arrangement makes it possible to increase the density of the measurement points. According to a first embodiment of the invention, each half-toroidal portion of the flywheel has two measuring circuits, the circuits being interleaved in such a way as to present an alternation of electrodes of each circuit separated from each other. a distance h / 2. This configuration allows a simple implementation, compact and therefore not intrusive.

Advantageously, the electrodes of each half-toroid portion of the flywheel are arranged on one of the parallel circles of the torus forming the flywheel, on the upper part thereof. The upper part of the steering wheel is normally the one that has the most stable contact with the hands of the driver, and in this case the palm, rather than the fingers, which increases the number and / or the measurement time.

According to a second embodiment of the invention, each half-toroid portion of the flywheel comprises two measurement circuits, and the electrodes of each half-torus have an implantation, both in parallel circles of the torus forming the flying, and according to meridians of said torus, to improve the probability of contact between a portion of the hand and the electrodes.

According to this second mode, advantageously, the electrodes of each half-toroid portion of the flywheel have an implantation according to three parallel circles of the torus forming the flywheel, the three electrodes located on each meridian comprising two electrodes of the same measurement circuit forming a measuring torque, between which is disposed an electrode of the other measuring circuit, the electrodes implanted on the same circle being interwoven in such a way as to present an alternation of electrodes of each circuit, as previously mentioned.

According to characteristics peculiar to the invention, each measuring circuit advantageously comprises an insulation galvanic independent, especially to avoid crossing currents.

According to another complementary feature of the invention, the electrodes are made of a conductive material, for example Ag / AgCl, which makes it possible to reduce the contact resistance between the hands and the electrodes.

Advantageously, the electrodes are circular and have a radius of between 4 and 6 mm to facilitate the production of such a wheel while limiting the intrusion of these electrodes for the driver.

Other characteristics and advantages of the invention will become clear from reading the detailed description of various embodiments taken as non-limiting examples, and illustrated by the appended drawings, in which:

FIG. 1 is a view of a steering wheel portion according to the invention,

FIGS. 2a and 2b are diagrams illustrating the implantation of the electrodes on the steering wheel,

FIG. 3 diagrammatically shows the implantation of the electrodes according to a first implementation of the invention,

FIG. 4 schematically represents the implantation of the electrodes according to a second implementation of the invention,

FIG. 5 diagrammatically shows the implantation of the electrodes according to a third implementation of the invention,

Figure 6 shows the measurement results made actual condition of use of a vehicle with a steering wheel according to the invention. Figure 1 shows a steering wheel 1 of a motor vehicle seen from the front, and more particularly the left part of such a steering wheel, this part being del imitated by a vertical plane P.

The position of the steering wheel as shown, corresponds, when mounting the volum nt in a vehicle, to a straight position of the wheels of the vehicle, that is to say with a possibility of rotation of the steering wheel substantially equal in the clockwise direction or counter-clockwise.

The vola nt 1 consists of a central hub 2 connected, by substantially radial portions 4, to a tubular portion 6 closed ring-shaped.

This tubular portion, which corresponds to the main gripping zone of the steering wheel, can be likened to a torus of major diameter noted Di, corresponding to the diameter of the flywheel 1, and of minor diameter noted D ₂ , corresponding to the diameter of the tubular zone grip 6.

The plane P thus cuts the volum nt according to the diameters Di and D ₂ . This plane P is, according to the example of real isation, the vertical plane when the steering wheel is mounted on the steering column of a vehicle, where the steering wheel has a certain inclination to the ground assumed horizontal.

According to the invention, the vola nt is equipped with electrodermal measuring electrodes 8, these electrodes being of circular shape and made of an electrically conductive material, for example Ag / AgCl or copper. The radius of these electrodes is between 4 and 6 mm. These electrodes are connected to a connection and measurement circuit making it possible to determine the electrical impedance, or the electrical resistance in a simple measurement version, of the portion of mai n situated between two measurement electrodes, this impedance or resistance being a reflection of the physiological state of the driver. According to the invention, these electrodes are disposed on the upper face of the steering wheel, according to one of the parallel circles of the torus, as shown in FIG.

The parallel circles of a torus are the sections by planes perpendicular to the axis of the torus, which, in the present case, is substantially the axis of rotation of the flywheel.

In the same way, we define the meridians of the torus as the different generating circles of the torus.

The electrodes may be disposed on a sleeve attached to the steering wheel, or molded with the sleeve. It is also conceivable, in the context of the invention, to directly mold the electrodes with the insulating coating surrounding the frame of the steering wheel during manufacture of the latter.

The explanation of the implantation of the electrodes on the steering wheel will be facilitated by the following schematization and shown in FIGS. 2a and 2b.

The implantation of the electrodes according to FIG. 1 and FIG. 2a, corresponds to that shown in the patent FR2880166, with a distribution of the electrodes 8 in a uniform manner over a portion of the tubular gripping zone 6 according to one of the parallel circles. torus schematizing the steering wheel. Figures 2a and 2b show only a portion of length L of this gripping zone.

The notion of uniformity is understood as the distance between the electrodes, combined with the distance between the electrodes and the center of the steering wheel, which corresponds to the positioning of the electrodes on the grip area.

Figure 2b illustrates this positioning. This figure is obtained by unwinding the tubular gripping zone 6, so as to form a rectangular surface S of length L and width t with = = π * ϋ ₂ . It is, in geometry, the equivalent of a boss, except for the representation of the diameter profiles D ₂ of the tubular zone.

Thus, in this figure, the electrodes 8 are arranged aligned along an axis xx 'which represents one of the parallel circles of the torus schematizing the steering wheel, which corresponds to an implantation of the different electrodes equidistant from the center of the steering wheel, on the same side of the gripping zone 6, in this case the upper face of this zone, as shown in FIGS. 1 and 2a. In addition, the electrodes are arranged at equal distances from each other.

According to a first embodiment of the invention, illustrated in FIG. 3, in a representation similar to that of FIG. 2b, the supply and measurement device 20, represented here in part, comprises electrodes 80a, 80b, 82a, 82b also aligned, and belonging to two independent measuring circuits each having electrodes between which the measurement will be performed.

Thus, one of the measuring circuits or channels, denoted Mi, has alternating electrodes 80a, 80b, the other measuring circuit or channel, denoted M ₂ , having alternating electrodes 82a, 82b.

The electrodes are arranged alternately, in each measurement circuit, but also between the two measurement circuits, so as to perform an interlacing of the electrodes of the two measuring circuits. In the example proposed in FIG. 3, the following alternation of electrodes is thus obtained: 80a, 82a, 80b, 82b. Alternation 80a, 82b, 80b, 82a is also possible.

Preferably, the electrodes are implanted regularly, leaving a distance h / 2 between two successive electrodes, which corresponds to a distance h between two electrodes of the same measuring circuit. According to this first mode of implementation, the electrodes are disposed at an equal distance from the center of the steering wheel, on one of the parallel circles of the torus schematizing the steering wheel which is materialized in FIG. 3, like the FIG. 2b, to an alignment of the electrodes along the axis xx 'previously defined. The electrodes are preferably arranged on the upper surface of the gripping zone, slightly at the periphery of the steering wheel, which corresponds to the most frequent gripping zone of the steering wheel by the driver.

According to a second embodiment of the invention, it is illustrated in FIG. 4, the supply and measurement device 20 also comprises two circuits M i and M ₂ , but the implantation of the electrodes is this time according to a matrix distribution in the representation of Figure 2b. More specifically, the electrodes of the same measurement circuit are arranged along different axes yy 'parallel to the width ί of the surface S, this width ί corresponding to the meridian of the torus schematizing the steering wheel. Such an arrangement makes it possible to increase the density of the electrodes and thus to increase statistically the number of possible measurements and therefore the reliability of the measuring device.

This exemplary implementation shows the possibility of a more complex implantation than implantation in a single ring of the electrodes.

The distribution as shown may have many variants, each pair of electrodes may be arranged along a slightly inclined axis relative to the yy 'axes shown, depending on the handling models of the steering wheel used in observed driving habits.

Although FIG. 4 shows a substantially homogeneous distribution of the different electrodes, the implantation can be more complex and refined according to experimental data, while remaining within the scope of the invention. It is possible to further densify in electrodes frequent gripping zones of the steering wheel, and to space temporary gripping zones, such as the zones A and B shown in FIG. 1.

Figure 5 shows a more complex implantation of the electrodes in a preferred embodiment of the invention. The electrodes are arranged in different parallel circles of the torus schematizing the steering wheel (x-x 'axes) and on different meridians (y-y' axes). As compared with FIG. 4, on each meridian equipped with electrodes are arranged three electrodes: two electrodes of one of the measuring circuits, for example M i, the electrodes forming a measurement torque, the third electrode being a the other measuring circuit, M ₂ . The following implantation, i.e. the next three electrodes immediately comprise two electrodes of the measurement circuit M ₂ and one of the electrodes of the measuring circuit M i.

In order to offer a homogeneous coverage of the electrodes, on each parallel circle of implantation of the electrodes, there is an alternation of electrodes identical, in principle, to that which it shines in FIG. 3, that is to say say with an interlacing of the electrodes of the two measuring circuits.

Thus, if we take the three electrodes figura nt ga uche in Figure 5, the electrodes located at the top and bottom respectively are the electrodes 80a and 80b belonging to the measuring circuit M i. An electrode 82b is disposed between these two electrodes.

In this way, the following three electrodes, referring to FIG. 3, are respectively (from top to bottom): an electrode 82a, an electrode 80a, and an electrode 82b.

This repetition continues for the other implantations. Note that in the explanatory diagram starting, between the two electrodes 80a and 80b may be arranged an electrode 82a.

Thus, the periodic repetition of the implantation of four electrodes along x-x 'axes, with an implantation of three electrodes along yy' axes, creates a mesh of the electrodes of the same series which is more complex, by the offset as well. generated.

FIG. 5 shows, in solid lines, the connections between the electrodes 80a, in solid double lines the connections between the electrodes 82a, in full dashed lines, the connections between the electrodes 80b, in double dashed lines full the connections between the electrodes 82b. .

These connections are made inside the steering wheel structure or on the surface, and do not appear to the driver.

Such an arrangement makes it possible to further increase the probability for the driver's hands to come into contact with at least one pair of electrodes of the same measurement circuit, and this, for a time sufficient for the performing a reliable measurement of the electro-dermal signal.

Figure 6 shows the gripping rate of the steering wheel according to the different measuring circuits. This is in fact the time during which a measurement is possible between electrodes of the same circuit, reduced to the total time of operation of the vehicle.

Channels 1 and 2 correspond to the two circuits arranged on the right side of the steering wheel, while channels 3 and 4 correspond to the measuring circuits arranged on the left side of the steering wheel. The results show that the two channels corresponding to electrodes located on the same side of the steering wheel give consistent results between them. The difference between the right side and the left side is mainly related to shifting and the controls of accessories that can be heating, air conditioning, car radio, ... Figure 6 also shows the grip rate of the steering wheel at least one hand, equal to 83.6%. This high rate thus makes it possible to obtain an electrodermal measurement for substantially the same rate of driving time.

The 16.4% of the time when the driver does not have at least one hand on the steering wheel that can correspond to the stopping time at a traffic light or a stop, the driver can then relax his grip on the steering wheel, as well as the moments transients where the hands are not sufficiently in contact with the steering wheel to generate a measurement signal.

Claims

REVEN DICATIONS

A motor vehicle flywheel (1) having a generally toroidal shape and having electrodermal measuring electrodes (8, 80a, 80b, 82a, 82b) disposed on said flywheel (1), said electrodes (8, 80a, 80b, 82a). , 82b) being connected to a power supply circuit for supplying to a computer, from the signals from the electrodes (8, 80a, 80b, 82a, 82b), a value of the electrical resistance between the electrodes representative of the physiological state of the driver when the latter places his hands on said electrodes (8, 80a, 80b, 82a, 82b), said flywheel (1) having, when the steering angle of the vehicle is zero, two portions (6) each forming a half-torus relative to a vertical plane (P) passing through its axis of rotation, characterized in that a part of the electrodes (8, 80a, 80b, 82a, 82b) is arranged on all or part of one portions of the steering wheel in at least two measuring circuits (M i, M ₂ ), the other part of the electrodes (8, 80a, 80b, 82a, 82b) being disposed on all or part of the other portion of the flywheel in at least two other measuring circuits.

2. Steering wheel (1) of a motor vehicle according to the preceding claim, characterized in that each measuring circuit (M i, M ₂ ) has an alternation of electrodes (80a, 80b, 82a, 82b) regularly spaced a distance h, two successive electrodes forming a pair of measuring electrodes of said circuit (M i, M ₂ ).

3. Flywheel (1) of a motor vehicle according to the preceding claim, characterized in that each portion (6) of the wheel has two measuring circuits (Mi, M ₂ ), and in that the circuits (Mi, M ₂ ) are intertwined in such a way as to present a alternating electrodes (80a, 80b, 82a, 82b) of each circuit (M i, M ₂ ) separated from each other by a distance h / 2.

4. Flywheel (1) of a motor vehicle according to one of the preceding claims, characterized in that the electrodes (80a, 80b, 82a, 82b) of each portion (6) flywheel are arranged on one of the parallel circles of torus forming the steering wheel (1) on the upper part thereof.

5. Flywheel (1) of a motor vehicle according to claim 1, characterized in that each portion (6) of the wheel has two measuring circuits (M i, M ₂ ), and in that the electrodes (80a, 80b, 82a , 82b) of each half-torus have an implantation, both along parallel circles of the torus forming the flywheel (1), and according to meridians of said torus.

6. Flywheel (1) of a motor vehicle according to the preceding claim, characterized in that the electrodes (80a, 80b, 82a,

82b) of each portion (6) of the flywheel have an implantation according to three parallel circles of the torus forming the flywheel, the three electrodes located on each meridian comprising two electrodes of the same measuring circuit (M i, M ₂ ) forming a pair measuring electrode, between which is disposed an electrode of the other measuring circuit (M ₂ , M i), the electrodes implanted on the same circle being in accordance with claim 3.

7. Steering wheel (1) of a motor vehicle according to one of the preceding claims, characterized in that each circuit (M i, M ₂ ) comprises an independent galvanic isolation.

8. Steering wheel (1) of a motor vehicle according to one of the preceding claims, characterized in that the electrodes (80a, 80b, 82a, 82b) are made of a conductive material, for example, Ag / AgCl.

9. Flywheel (1) of a motor vehicle according to one of the preceding claims, characterized in that the electrodes (80a, 80b, 82a, 82b) are circular and a radius of between 4 and 6 mm.