Method for detecting touch on a steering wheel, and vehicle steering wheel system

Abstract

In a method for detecting touch on a steering wheel (12) by means of a touch sensor (36) arranged in the steering wheel (12) and having an electrical sensor conductor, the following steps are carried out: the capacitance of the sensor conductor is determined by applying an input signal to the sensor conductor and detecting an output signal at the sensor conductor; the steering wheel temperature of the steering wheel (12) is determined; correction data are generated on the basis of the steering wheel temperature; and potential touch on the steering wheel (12) is determined on the basis of the correction data and the output signal. Furthermore, a vehicle steering wheel system (10) having a control unit (14) for carrying out such a method is provided.

Description

[0001] Method for detecting a touch of a steering wheel and vehicle steering system

[0002] The invention relates to a method for detecting a touch on a steering wheel by means of a touch sensor arranged in the steering wheel. Furthermore, the invention relates to a vehicle steering wheel system comprising a steering wheel and a control unit configured to perform such a method.

[0003] Methods for detecting a touch of a steering wheel, also known as hand touch detection, and vehicle steering wheel systems that perform such a method are known.

[0004] To detect a touch on the steering wheel, the change in capacitance, induced, for example, by a hand gripping the steering wheel, is usually detected by means of an electronic sensor in the steering wheel.

[0005] These types of sensors have a complex design, especially if the steering wheel is heated. Furthermore, temperature changes can impair the accuracy of hand touch detection.

[0006] The object of the invention is to provide a method for detecting a touch on a steering wheel that exhibits a particularly high degree of accuracy in hand touch detection. A further object of the invention is to provide a vehicle steering wheel system that is configured to perform such a method.

[0007] The problem is solved by a method for detecting a touch of a steering wheel using a touch sensor arranged in the steering wheel with an electrical sensor conductor, with the following steps:

[0008] a) The capacitance of the sensor conductor is determined by applying an input signal to the sensor conductor and detecting an output signal at the sensor conductor,

[0009] b) The steering wheel temperature is determined using a sensor conductor voltage and a sensor conductor current of the sensor conductor or using a heating wire voltage and a heating wire current of a heating wire arranged in the steering wheel for heating the steering wheel,

[0010] c) Correction data is generated based on the steering wheel temperature, sensor conductor voltage and sensor conductor current, or based on the steering wheel temperature, heating wire voltage and heating wire current, and

[0011] d) A potential contact of the steering wheel is determined based on the correction data and the output signal.

[0012] It was recognized according to the invention that, based on the generated correction data, a temperature compensation of the touch measurement can be carried out with little effort and thus a hand touch detection of particularly high quality can be provided in an efficient manner.

[0013] According to one aspect, all information required for the process is obtained by means of the sensor conductor and / or the heating wire, so that no information from further sensors is required.

[0014] In one embodiment, step b) determines the temperature of the steering wheel based on the electrical resistance and the temperature coefficient of the sensor conductor or heating wire. This allows the temperature of the sensor conductor or heating wire to be determined quickly and with minimal effort.

[0015] Furthermore, the sensor conductor can be configured to heat the steering wheel. In this configuration, the sensor conductor operates alternately in a touch measurement mode, in which step a) is performed, and a heating mode, in which the steering wheel is heated by means of the sensor conductor. Step b) is performed in the touch measurement mode and / or the heating mode. This design has the advantage that the sensor conductor combines both a sensor functionality and a heating functionality. In other words, the sensor conductor also forms a heating wire for heating the steering wheel. Thus, no separate heating wire is required to heat the steering wheel. In another embodiment, in which the steering wheel temperature is determined by means of the heating wire in step b), step b) is performed in parallel with step a), i.e., at least partially simultaneously and therefore particularly efficiently.

[0016] Additionally or alternatively, in step c), the correction data can be determined using one or more state diagrams, an artificial neural network, linear algebra, or one or more characteristic map tables. This allows for a particularly reliable determination of the correction data.

[0017] In one embodiment, in step d), an intensity value is determined based on the correction data and the output signal, which is used to determine the potential contact with the steering wheel. According to the invention, the intensity value can comprise a plurality of values ​​and can alternatively be referred to as an intensity signal. The intensity value represents a signal strength that exceeds a reference value or reference signal and allows for particularly reliable detection of contact with the steering wheel, regardless of the steering wheel temperature.

[0018] Here, the output signal can be mathematically combined with the correction data, for example by addition or subtraction, before the intensity value is determined. Such a correction of the output signal is particularly simple.

[0019] Furthermore, the intensity value can be determined using one or more state diagrams, an artificial neural network, linear algebra, or one or more characteristic curve tables. This allows for a particularly reliable determination of the intensity value.

[0020] According to one embodiment, the intensity value is used to determine the state of the touch sensor, which is then used to determine the potential contact with the steering wheel. The state of the touch sensor reflects the state of the steering wheel and all objects relevant for hand touch detection, such as hands. This has the advantage of providing particularly high-quality hand touch detection.

[0021] The state of the touch sensor can be determined using one or more state diagrams, an artificial neural network, linear algebra, or one or more characteristic map tables. This allows for a particularly reliable determination of the touch sensor's state.

[0022] According to a further embodiment, the type of touch is determined based on the state of the touch sensor and the state of a second touch sensor arranged in the steering wheel, which is connected to an additional electrical sensor conductor. The state of the second touch sensor is determined analogously to the state of the first touch sensor. In other words, two touch sensors are used for hand touch detection. This allows for plausibility checks of the temperature compensation of the touch measurement based on the two data sets, thereby further improving the accuracy of hand touch detection. Furthermore, the two data sets allow for a more precise determination of how the steering wheel is touched.

[0023] The type of contact can be determined using one or more state diagrams, an artificial neural network, linear algebra, or one or more characteristic map tables. This allows for a particularly reliable determination of the type of contact.

[0024] According to the invention, to solve the above-mentioned problem, a vehicle steering wheel system is also provided comprising a steering wheel, a touch sensor arranged in the steering wheel which has an electrical sensor conductor, and a control unit which is designed to carry out the inventive method with the aforementioned advantages.

[0025] Further advantages and features will become apparent from the following description and the accompanying drawings. These show:

[0026] - Figure 1 shows a schematic representation of a vehicle steering wheel system according to the invention,

[0027] - Figure 2 shows a perspective view of a steering wheel of the vehicle steering wheel system according to the invention from Figure 1, and

[0028] Figure 3 shows a flowchart of a method according to the invention. The detailed description below, in conjunction with the accompanying drawings, in which identical numbers refer to identical elements, is intended as a description of various embodiments of the disclosed subject matter and is not meant to represent the only embodiments. Each embodiment described in this disclosure serves only as an example or illustration and should not be interpreted as preferred or advantageous over other embodiments.

[0029] All features disclosed below with reference to the exemplary embodiments and / or the accompanying figures can be combined alone or in any subcombination with features of the aspects of the present disclosure, including features of preferred embodiments, provided that the resulting combination of features is meaningful to a person skilled in the art.

[0030] Figure 1 shows a vehicle steering wheel system 10 for a vehicle, comprising a steering wheel 12 and a control unit 14.

[0031] The steering wheel 12 is designed for steering the vehicle and has a steering wheel hub 16 (see Figure 2), a steering wheel rim 18 and several spokes 20 that connect the steering wheel hub 16 and the steering wheel rim 18.

[0032] Furthermore, the steering wheel 12 has an internal steering wheel skeleton (not shown) and a foam covering 22 that surrounds the steering wheel skeleton at least in the area of ​​the steering wheel rim 18 on the outside, for example completely in the circumferential direction.

[0033] The foam covering 22 is surrounded on the outside by a sheathing 24, which forms a gripping surface 26 in the form of an outer surface of the steering wheel rim 18.

[0034] The covering 24 is made of leather or imitation leather, for example. The steering wheel frame forms a core of the steering wheel rim 18 and is made of a solid material, for example a light metal alloy.

[0035] The foaming 22 consists, for example, of polyurethane foam (PUR). Several electrical sensor conductors 28 are provided in the foaming 22, which are connected to the control unit 14 for signal transmission, for example via an electrical connection (not shown) on one of the spokes 20.

[0036] Furthermore, several heating wires 30 are provided in the foam covering 22, which are electrically connected to the control unit 14 or a separate heating control unit, for example via an electrical connection (not shown) on one of the spokes 20.

[0037] Naturally, the vehicle steering wheel system 10 or the steering wheel 12 can only have one heating wire 30, which extends, for example, several times around the steering wheel rim 18 in the direction of rotation D of the steering wheel 12.

[0038] The heating wires 30 are optional and can be completely omitted in an alternative embodiment, i.e. the vehicle steering wheel system 10 has no heating wires 30 in this case, which are exclusively intended for heating the steering wheel 12.

[0039] The sensor conductors 28 and heating wires 30 are arranged, for example, in incisions in the foam covering 22, which extend essentially radially inwards from the outside.

[0040] The heating wires 30 are designed to heat the steering wheel 12 by applying an electric current to the heating wires 30 via the control unit 14 (see Figure 1), which heats them due to their electrical resistance.

[0041] Additionally or alternatively, the sensor conductors 28 can be configured to heat the steering wheel 12 by applying an electric current to the sensor conductors 28 via the control unit 14 in a heating mode, which heats them due to their electrical resistance.

[0042] In this case, where each sensor conductor 28 additionally provides a heating function, all conductors can be arranged at the same depth or in a single layer with respect to a steering wheel rim surface. The heat emitted to the steering wheel 12 via the heating wires 30 and / or the sensor conductors 28, and thus the temperature of the grip surface 26, can be controlled and / or regulated via the control unit 14.

[0043] The sensor conductors 28 are part of a sensor unit 32, by means of which a touch of the steering wheel 12, more precisely the grip surface 26, can be detected by the control unit 14 using the procedure described below.

[0044] In this context, the vehicle steering wheel system 10 or the steering wheel 12 has a first sensor conductor 34 (with several steering wheel windings, see Figure 2), which forms a first touch sensor 36 (see Figure 1) of the sensor unit 32, and a second sensor conductor 38 (with several steering wheel windings, see Figure 2), which forms a second touch sensor 40 (see Figure 1) of the sensor unit 32.

[0045] In the present embodiment, the first sensor conductor 34 is arranged closer to the outer circumference 42 than to the inner circumference 44 of the steering wheel rim 18, while the second sensor conductor 38 is arranged closer to the inner circumference 44 than to the outer circumference 42 of the steering wheel rim 18.

[0046] Accordingly, the first touch sensor 36 is assigned to the outer circumference 42, which forms a first sensor zone 46 of the steering wheel 12, while the second touch sensor 40 is assigned to the inner circumference 44, which forms a second sensor zone 48 of the steering wheel 12. This means that, due to the proximity of the first sensor conductor 34 to the grip surface 26 on the outer circumference 42, the first touch sensor 36, and the second touch sensor 40, due to the proximity of the second sensor conductor 38 to the grip surface 26 on the inner circumference 44, can detect a touch on the outer circumference 42 or inner circumference 44 particularly effectively. In Figure 1, the first and second sensor zones 46 and 48 are separated by a dashed line. In this way, for example, a gripping of the steering wheel rim 18 can be distinguished from a point contact with the steering wheel.

[0047] In principle, each touch sensor 36, 40 can have any number of sensor conductors 28, but at least one that extends, for example, at least sectionally or multiple times in the direction of rotation D of the steering wheel 12 around the steering wheel rim 18.

[0048] Furthermore, the sensor unit can have 32 additional touch sensors, for example a third touch sensor 50 assigned to the left half L of the steering wheel 12, and a fourth touch sensor 52 assigned to the right half R of the steering wheel 12. In this way, it is possible, for example, to distinguish whether the steering wheel rim 18 is touched by one hand or by both hands.

[0049] Of course, the sensor unit 32 can in principle have any number of touch sensors of any design, each assigned to a corresponding sensor zone of the steering wheel 12, for example a single touch sensor 36, 40, 50, 52 with at least one sensor conductor 28.

[0050] The other touch sensors also each have, for example, at least one sensor conductor 28.

[0051] The method for detecting a touch of the steering wheel 12 using the sensor unit 32 is described below with reference to Figure 3.

[0052] In a first step S1, the capacitance of the first sensor conductor 34 is determined by applying an input signal to the first sensor conductor 34 and detecting an output signal at the first sensor conductor 34.

[0053] The input signal includes at least one frequency and is generated, for example, by means of a signal generator 54 (see Figure 1) of the control unit 14.

[0054] In a step S2, which can take place before or after step S1, a sensor conductor voltage and a sensor conductor current of the sensor conductor 34 are determined, for example by means of an input signal of the signal generator 54.

[0055] In step S3, the temperature of sensor conductor 34 is subsequently determined in a known manner based on its electrical resistance and temperature coefficient. For example, the electrical resistance of sensor conductor 34 is calculated using the sensor conductor voltage and current previously determined in step S2. Finally, the temperature of sensor conductor 34 is determined using the temperature coefficient stored in control unit 14 and the electrical resistance of sensor conductor 34.

[0056] The determined temperature of the sensor conductor 34 is also dependent on the temperature inside the steering wheel 12, which can be derived from the determined temperature of the sensor conductor 34.

[0057] In a further step S4, correction data is determined based on the steering wheel temperature, the sensor conductor voltage and the sensor conductor current using several characteristic map tables.

[0058] Alternatively, the correction data can be determined using one or more state diagrams, an artificial neural network, linear algebra, or a characteristic map table.

[0059] In an alternative embodiment, the steering wheel temperature of the steering wheel 12 is determined based on the heating wire voltage and current of at least one of the heating wires 30. For this purpose, an input signal is applied to the heating wire 30 and an output signal is detected at it. Steps S1 and S2 can be performed in parallel or simultaneously. Based on the output signal of the heating wire 30, the correction data is then determined analogously to the output signal of the first sensor conductor 34, as described above.

[0060] In a further embodiment, in which the sensor conductor 34 is configured to heat the steering wheel 12, the sensor conductor 34 is operated alternately in a touch measurement mode and a heating mode, in which the steering wheel 12 is heated by means of the sensor conductor 34. Step S1 is performed in touch measurement mode, while step S2 can be performed in touch measurement mode and / or in heating mode. The time intervals of the touch measurement mode and the heating mode can each have a cycle duration of less than one-tenth of a second. Furthermore, the time intervals of the touch measurement mode can be a multiple of the heating mode, for example, in an operating state of the vehicle steering wheel system 10 in which the steering wheel 12 is not heated or is heated only briefly. In step S5, corrected data is generated by subtracting the correction data from the output signal.

[0061] In principle, the correction data can be mathematically linked to the output signal in any way to generate the corrected data.

[0062] In a subsequent step, an intensity value S6 is determined using linear algebra based on the corrected data.

[0063] Alternatively, the intensity value can be determined using one or more state diagrams, an artificial neural network, or one or more characteristic map tables.

[0064] In a subsequent step S7, the state of the first touch sensor 36 is determined based on the intensity value using several state diagrams, since touching the steering wheel 12 leads to a significant change in the output signal, for example its amplitude.

[0065] The states of the first touch sensor 36 can include: no contact, light contact, medium contact, etc.

[0066] Alternatively, the state of the first touch sensor 36 can be determined using a state diagram, an artificial neural network, linear algebra or one or more characteristic map tables.

[0067] In parallel, in step S8, the state of the second touch sensor 40 is determined analogously to the first touch sensor 36 using the second sensor conductor 38.

[0068] Alternatively, step S8 can be performed before or after step S7.

[0069] Each type of touch on the steering wheel 12 affects the output signals of the sensor conductors 34, 38 in a characteristic way.

[0070] Types of contact with the steering wheel 12 can include: firmly gripped with both hands, gripped with one hand, point contact, for example with one or more fingers, etc. Using state diagrams, in a step S9, based on the determined state of the first touch sensor 36 and the determined state of the second touch sensor 38, it is determined whether and what type of contact with the steering wheel 12 is present.

[0071] Alternatively, the type of touch on the steering wheel 12 can be determined using a state diagram, an artificial neural network, linear algebra or one or more characteristic map tables.

[0072] If the sensor unit has 32 additional touch sensors, for example the third and fourth touch sensor 50, 52, then in step S9 the states of any number of the touch sensors 36, 40, 50, 52 can be measured by means of the control unit 14 and used accordingly in step S9 to determine the type of touch of the steering wheel 12.

[0073] In another embodiment, steps S8 and S9 can be omitted. For example, if the steering wheel 12 has only a single touch sensor 36, 40, 50, 52, or if no type of touch of the steering wheel 12 is to be determined and thus the one state of a touch sensor 36, 40, 50, 52 is sufficient to reliably detect a touch of the steering wheel 12.

[0074] Of course, the procedure is not limited to determining the state of the first touch sensor 36 to detect the touch. Similarly, the state of the second, third, and fourth touch sensors 40, 50, 52 can be determined to detect a touch of the steering wheel 12.

[0075] For example, the different touch sensors 36, 40, 50, 52 can be alternately controlled with an input signal, for example with a clock duration of less than one tenth of a second, in order to further improve hand touch detection.

[0076] In this procedure, the temperature of the steering wheel 12 is determined using the sensor conductors 28 or the heating wires 30 in order to perform temperature compensation.

[0077] Thus, the steering wheel 12 can be designed without a dedicated temperature sensor, for example without an NTC thermistor. In all embodiments, a method for detecting a touch of a steering wheel 12 and a vehicle steering wheel system 10 for carrying out such a method are provided, by means of which touches of the steering wheel 12 can be detected with particularly high quality.

[0078] Compared to conventional vehicle steering wheel systems, certain types of touch can also be determined.

[0079] The vehicle steering wheel system 10 is designed to be compact and has very few components.

[0080] Furthermore, it is possible to verify the plausibility of the temperature compensation of the touch sensors 36, 40, 50, 52 among themselves without requiring additional hardware.

Claims

Patent claims 1. Method for detecting a touch of a steering wheel (12) by means of a touch sensor (36) arranged in the steering wheel (12) with an electrical sensor conductor (34), comprising the following steps: a) The capacitance of the sensor conductor (34) is determined by applying an input signal to the sensor conductor (34) and detecting an output signal at the sensor conductor (34), b) the steering wheel temperature of the steering wheel (12) is determined on the basis of a sensor conductor voltage and a sensor conductor current of the sensor conductor (34) or on the basis of a heating wire voltage and a heating wire current of a heating wire (30) arranged in the steering wheel (12) for heating the steering wheel (12), c) Correction data is generated based on the steering wheel temperature, sensor conductor voltage and sensor conductor current, or based on the steering wheel temperature, heating wire voltage and heating wire current, and d) a potential contact of the steering wheel (12) is determined based on the correction data and the output signal.

2. Method according to claim 1, wherein in step b) the temperature of the steering wheel (12) is determined on the basis of the electrical resistance and the temperature coefficient of the sensor conductor (34) or the heating wire (30).

3. Method according to claim 1 or 2, wherein the sensor conductor (34) is configured to heat the steering wheel (12), wherein the sensor conductor (34) is operated alternately in a touch measurement mode in which step a) is performed and a heating mode in which the steering wheel (12) is heated by means of the sensor conductor (34), wherein step b) is performed in the touch measurement mode and / or in the heating mode.

4. A method according to claim 1 or 2, wherein in step b) the steering wheel temperature is determined using the heating wire (30), wherein step b) is performed in parallel with step a).

5. A method according to any of the preceding claims, wherein in step c) the correction data are determined using one or more state diagrams, an artificial neural network, linear algebra or one or more characteristic map tables.

6. Method according to one of the preceding claims, wherein in step d) an intensity value is determined on the basis of the correction data and the output signal, on the basis of which the potential contact of the steering wheel (12) is determined.

7. The method of claim 6, wherein the output signal is mathematically linked with the correction data before the intensity value is determined.

8. Method according to claim 6 or 7, wherein the intensity value is determined by means of one or more state diagrams, an artificial neural network, linear algebra or one or more characteristic map tables.

9. Method according to one of claims 6 to 8, wherein a state of the touch sensor (36) is determined on the basis of the intensity value, on the basis of which the potential touch of the steering wheel (12) is determined.

10. Method according to claim 9, wherein the state of the touch sensor (36) is determined by means of one or more state diagrams, an artificial neural network, linear algebra or one or more characteristic map tables.

11. Method according to claim 9 or 10, wherein a type of touch is determined based on the state of the touch sensor (36) and a state of a further touch sensor (40, 50, 52) arranged in the steering wheel (12) with a further electrical sensor conductor (38).

12. Method according to claim 11, wherein the type of contact is determined by means of one or more state diagrams, an artificial neural network, linear algebra or one or more characteristic map tables.

13. Vehicle steering wheel system (10) comprising a steering wheel (12), a touch sensor (36) arranged in the steering wheel (12) which has an electrical sensor conductor (34), and a control unit (14) configured to perform the method according to one of the preceding claims.

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