METHOD FOR DETECTING CONTACT WITH A MANUALLY ACTIVATED STEERING DEVICE, IN PARTICULAR A VEHICLE STEERING WHEEL, AND A DEVICE FOR CARRYING OUT THE METHOD

Abstract

A method for detecting contact with a manually activated steering or control device, in particular a vehicle steering wheel, comprises the following steps: applying an alternating voltage to at least one conductor arrangement (10) which is arranged on the steering or control device, and has at least one conductor line with a significant ohmic resistance; determining the current profile in the conductor arrangement (10); determining the real component and the virtual component of the instantaneous alternating current resistance of the conductor arrangement (10); determining the capacitance or the change in capacitance of the conductor arrangement (10); determining the phase shift; and evaluating the determined values. A device for carrying out the method comprises a steering or control device, in particular a vehicle steering wheel, a conductor arrangement (10) which is arranged on the steering or control device and which has at least one conductor line with a significant ohmic resistance, and a control and evaluation device which is configured to apply an alternating voltage to the conductor arrangement (10), to measure the current profile in the conductor arrangement (10) and to evaluate the determined values.

Claims

1. A method for detecting contact with a manually activated steering or control device, in particular a vehicle steering wheel, having the following steps: applying an alternating voltage to at least one conductor arrangement (10) which is arranged on the steering or control device, and has at least one conductor line with a significant ohmic resistance; determining the current profile in the conductor arrangement (10); determining the real component and the virtual component of the instantaneous alternating current resistance of the conductor arrangement (10); determining the capacitance or the change in capacitance of the conductor arrangement (10); determining the phase shift; and evaluating the determined values.

2. The method according to claim 1, wherein the method steps are carried out continuously.

3. The method according to claim 1, wherein the evaluation comprises at least one of the following steps: detecting whether the steering or control device is contacted over a large area; detecting whether the steering or control device is contacted at certain points; grip detection; detecting the number of simultaneous contacts; locating the positions of a plurality of contacts; determining the duration of a contact; identifying gestures.

4. The method according to claim 3, wherein certain functions are triggered as a function of the evaluation.

5. A device for carrying out the method according to claim 1, having a steering or control device, in particular a vehicle steering wheel, a conductor arrangement (10) which is arranged on the steering or control device and has at least one conductor line with a significant ohmic resistance, and a control and evaluation device which is configured to apply an alternating voltage to the conductor arrangement (10), to measure the current profile in the conductor arrangement (10), and to evaluate the determined values.

6. The device according to claim 5, wherein a plurality of conductor arrangements (10) distributed over the steering or control device are provided.

7. The device according to claim 5, wherein the conductor arrangement (10) is arranged under a surface of the steering or control device.

8. The device according to claim 5, wherein the conductor arrangement (10) has two substantially parallel electrical conductors (12, 14), of which at least one has a resistance which is significantly higher compared to a copper wire, preferably within a range of 10 Wm to 1 Mil/m.

9. The device according to claim 8, wherein the electrical conductors (12, 14) are each insulated.

10. The device according to claim 5, wherein the conductor arrangement (10) has a plurality of sensor fields (16) in the form of electrically conductive surfaces or regions and connected in series by means of electrical conductors (18), the electrical conductors (18) having a significant ohmic resistance between the sensor surfaces or regions.

11. The device according to claim 5, wherein the conductor arrangement (10) has one or more elongated electrical conductors (18) with a significant ohmic resistance which is or are laid in a specific manner such that RC elements are formed which can be evaluated in sequence.

12. The device according to claim 1, wherein the control and evaluation device is configured to trigger certain functions as a function of the evaluation.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further features and advantages of the invention will become apparent from the following description and from the accompanying drawings, to which reference is made. In the drawings:

[0040] FIG. 1 shows a first embodiment of a conductor arrangement for a device according to the invention for detecting contact with a manually activated steering or control device;

[0041] FIG. 2 shows a second embodiment of a conductor arrangement for a device according to the invention for detecting contact with a manually activated steering or control device;

[0042] FIG. 3 shows a third embodiment of a conductor arrangement for a device according to the invention for detecting contact with a manually activated steering or control device; and

[0043] FIG. 4 shows a fourth embodiment of a conductor arrangement for a device according to the invention for detecting contact with a manually activated steering or control device.

DESCRIPTION

[0044] In the following, a device for detecting contact with a manually activated steering or control device is described using the example of a vehicle steering wheel.

[0045] According to a first embodiment of the device, a first conductor arrangement 10 having two parallel electrical conductors 12, 14 is arranged in the rim of the steering wheel, as shown symbolically in FIG. 1. More specifically, the conductor arrangement 10 is arranged under a decorative surface of the steering wheel, for example under a leather covering.

[0046] The conductor arrangement runs along the entire circumference or at least a substantial part of the steering wheel rim. Alternatively, a plurality of such conductor arrangements 10 are provided, each of which is arranged in a partial region of the steering wheel rim. In addition, a plurality of conductor arrangements 10 may be distributed over the toroidal circumference of the steering wheel rim.

[0047] The two conductors 12, 14 are provided with insulation, i.e. they are insulated from each other and from their environment.

[0048] The two conductors 12, 14 form a capacitance with respect to one another. In the case of two wires of the same thickness made of the same electrically conductive material, the capacitance C would be calculated as follows:

[00001]$C=\frac{\pi .Math..Math.\mathrm{.Math.}.Math..Math.l}{\mathrm{arcosh}\left(\frac{d}{2.Math..Math.R}\right)}$

[0049] where ε: dielectric constant between the conductors [0050] l: length of the conductors [0051] d: distance between the conductor central axes [0052] R: radius of the conductor cross sections

[0053] A special feature of the first conductor arrangement 10 provided for the device described here is that at least one line segment, i.e. at least one of the two conductors 12, 14 has a significant ohmic resistance compared to a copper wire, in particular within a range of 10 Ω/m to 1 MΩ/m. The total ohmic resistance or the specific resistance of the conductors 12, 14 is known to a control and evaluation device.

[0054] If an alternating voltage, i.e. a voltage having a profile based on an oscillation (such as a sinusoidal, square, triangular, or sawtooth oscillation) or a pulse voltage having successive voltage pulses is applied to the conductor arrangement 10, the total resistance consists of a real component and a virtual component. The real component is determined by the resistive conductor 12 or 14 and the virtual component by the capacitance that develops between the conductors 12, 14. A certain phase angle is set for the total resistance.

[0055] If a hand comes very close to the conductors, as is the case when contacting the steering wheel rim, the capacitance of the conductor arrangement changes significantly (C.sub.hand). This means that the virtual component of the total resistance changes and, as a result, so does the phase angle. If the alternating voltage is known, this detuning may be recognized and registered by measuring the current profile. In addition, a precise conclusion about the position of the hand on the steering wheel may be drawn in the control and evaluation device based on the change in the real component and the virtual component or the change in the phase angle.

[0056] In the context of permanent monitoring by the control and evaluation device, both contact per se and movement patterns (gestures) may be recognized in this way. The control and evaluation device may interpret certain gestures and trigger functions that are assigned to the gestures.

[0057] If a plurality of separate conductor arrangements 10 are distributed over the steering wheel, a plurality of simultaneous steering wheel contacts (two hands on the steering wheel) may be distinguished.

[0058] The arrangement of the conductor arrangement(s) 10 is not limited to the steering wheel rim, but can also extend to the spokes and the central part of the steering wheel. In addition, any course of the parallel conductors 12, 14 that is advantageous for the evaluation may be provided, for example a regular or irregular meandering course.

[0059] FIG. 2 symbolically shows a second conductor arrangement 10 that is provided for a second embodiment of the device for detecting contact with a manually activated steering or control device. The second embodiment is also described below using the example of a vehicle steering wheel.

[0060] The second conductor arrangement 10 consists substantially of a conductor line having a plurality of sensor fields 16 that are connected to one another in an electrically conductive manner. The sensor fields 16 are electrically conductive surfaces or regions that, for example may be formed from foils, conductive varnishes, wire meshes, wire mats or other wire structures. It is crucial for the sensor fields 16 to be electrically conductive and to be able to generate a significant capacitive field in relation to a hand.

[0061] The electrical conductors 18 between the sensor fields 16 in turn have an ohmic resistance that is significantly higher than the resistance, for example, of a copper wire or the like. Either the conductors 16 themselves may be resistive, or electrical components 20, conductor portions or the like with a significant ohmic resistance are connected in series.

[0062] As in the first embodiment, the second conductor arrangement 10 is also arranged under a decorative surface of the steering wheel, for example under a leather covering. The conductor arrangement 10 runs along the entire circumference or at least a substantial part of the steering wheel. Alternatively, a plurality of such conductor arrangements 10 are provided, each of which is arranged in a partial region of the steering wheel rim.

[0063] If a hand comes very close to a sensor field of the second conductor arrangement 10, as is the case when the steering wheel rim is contacted, a capacitance is formed or the capacitance (Oland) changes with respect to the capacitance between the conductor arrangement 10 and the environment without a hand in the immediate vicinity. The presence of the hand in turn determines or changes the virtual component of the total resistance of the conductor arrangement 10. A certain phase angle is set depending on the position of the hand. Similar to the first embodiment, if the applied alternating voltage is known, an evaluation in the control and evaluation device is possible by measuring the current profile, which allows a precise conclusion to be drawn about the position of the hand on the steering wheel.

[0064] The accuracy of the position determination (resolution) in the second embodiment depends in particular on the number, shape, size and arrangement of the sensor fields 16.

[0065] In principle, the same applies to the second embodiment with regard to the arrangement of the second conductor arrangement 10 (steering wheel rim, steering wheel spokes, steering wheel center part), to the provision and distribution of a plurality of second conductor arrangements 10 and to gesture detection as in the first embodiment.

[0066] The sensor fields 16 may be generated and sampled (measured) not only capacitively, but also inductively, resistively, digitally (switch), magnetically and optically. Combinations are also possible, such as capacitive-resistive sensor fields 16.

[0067] The sampling of the sensor fields 16 may take place sequentially or in parallel, it being possible for the sensor fields 16 to be sampled individually or in groups.

[0068] FIGS. 3 and 4 symbolically show two further conductor arrangements 10 that are provided for a third or fourth embodiment of the device for detecting contact with a manually activated steering or control device.

[0069] In the conductor arrangement 10 shown in FIG. 3, the sensor fields 16 are formed by elongated electrical conductors 18 that are tightly curved or twisted in certain regions or have some other very strongly curved course that deviates significantly from a straight course. Because the electrical conductors 18 have such a specific course, the sensor surfaces 16, together with the intermediate (straight) conductor portions that have a significant ohmic resistance and/or with interposed components 20 (electrical resistance elements or the like), form individual RC elements. Said RC elements are evaluated in sequence.

[0070] The conductor arrangement 10 shown in FIG. 4 largely corresponds to that of FIG. 3. However, no resistors in the form of components or the like are inserted between the sensor fields 16. Instead, when the measured current profile is evaluated in the control and evaluation device, the known total resistance R of the electrical conductor 18 is taken into account.

[0071] With all embodiments, it is possible to distinguish between different types of contact, such as prolonged contact at a localizable point, knocking movements, stroking movements (including the direction), etc. by means of a suitable evaluation algorithm. This makes it possible to carry out functions that go beyond the detection of steering wheel contact per se in the context of safety and driver assistance systems and possibly the knowledge of whether the steering wheel is being gripped safely. In particular, grip detection is possible, i.e. the type of grip with which the driver grips or grasps the steering wheel may be recognized.

[0072] The most important differentiation possibilities and some of the functions that are introduced with them (assuming suitable placement and design of the conductor arrangements 10) are listed again as examples below: [0073] generally recognizing whether the steering wheel is fully grasped manually or whether the steering wheel is only touched selectively with a finger, etc.; [0074] detecting a contact at certain points (e.g. knocking) interpretation as a keystroke; [0075] detecting the positions of contacts at certain points interpretation as different keystrokes; [0076] detecting the number of simultaneous contacts conclusion about one-handed or two-handed steering wheel contact and/or multi-touch inputs; [0077] detecting the duration of a certain contact use for stepless setting of parameters; [0078] detecting certain gestures triggering assigned functions such as setting turn signals (left, right), turning on windshield wipers, radio control, in general within applications: “forward,” “back” etc.

[0079] The two embodiments described or certain aspects thereof can of course also be combined with one another.

[0080] The invention was explained using the example of a vehicle steering wheel, but is not restricted to this application. The contact detection according to the invention may in principle be used with any manually activated steering or control devices of motor vehicles, trains, machines, etc.