Device and method for hand contact detection and heating of steering wheel of motor vehicle

Abstract

The invention relates to a method and a device (2) for hand contact detection and for heating a steering wheel (3) of a motor vehicle. For this purpose, a heating element (9) for heating the steering wheel (3) and a sensor element (8) for hand contact detection on the steering wheel (3) are provided. The heating element (9) and the sensor element (8) are assigned to a general function group (7) for integration in the steering wheel (3). The electronic control unit (4) is designed to alternately activate heating elements (9) in a heating routine (H) for heating the steering wheel (3) and sensor elements (8) in a measuring routine (M) for hand contact detection on the steering wheel (3) in a time division multiplexing method (TDM). The electronic control unit (4) is further designed to check whether the sensor element (8) is subjected to the interference signal (N) in a check program (P) before the corresponding measuring routine (M) is executed. According to the invention, only if the interference signal (N) exceeds a predetermined limit value, a predetermined measure for adjusting the measurement routine (M) is carried out for a subsequent measurement routine (M) in the time division multiplexing method (TDM), thus at least reducing the influence of the interference signal (N) on the hand contact detection.

Description

Technical Field

[0001] The present invention relates to a device and a method for detecting hand contact and heating a steering wheel of a motor vehicle. Background Art

[0002] For today's standards for assisting or guiding the driving of motor vehicles (abbreviated as vehicles), it is important that the driver can control the vehicle at any time. This particularly includes the fact that the driver keeps at least one hand or both hands on the steering wheel during driving. To detect hand contact, i.e., grasping on the steering wheel, there are various systems in motor vehicles that can perform the corresponding hand contact detection, namely the hand detection or hand on / off detection (abbreviated as HoD) hereinafter. Popular systems include, for example, systems that detect hand contact based on impedance measurement or capacitance measurement.

[0003] For example, US 11,145,996 B2 shows a device for detecting hand contact. A grip sensor is integrated in the steering wheel rim, which can be used to determine the grip around the steering wheel. By means of a control circuit, the signal output by the grip sensor according to the grip on the steering wheel can be determined. The capacitance of the grip sensor changes according to whether the driver grasps the steering wheel.

[0004] For example, a possibility of capacitance contact detection is also known from US 9,823,798 B2. Here, a capacitance sensor system is described, by means of which the capacitance change of a variable capacitance in the system can be determined according to a predetermined measurement principle. The measurement principle is also referred to as the charge / discharge method hereinafter.

[0005] However, in modern vehicles, in addition to detecting hand contact, the steering wheel can also be heated. For this purpose, in addition to the sensor element for detecting hand contact, a heating element for heating the steering wheel can be integrated in the steering wheel.

[0006] However, integrating these two elements in the steering wheel results in feedback or mutual influence. In particular, the heating element in the heating mode couples interference such as electromagnetic interference into the sensor element for detecting hand contact. When hand contact is detected, this interference causes the interference signal to be misinterpreted as a grip on the steering wheel. The measurement result is a false positive. Therefore, for such a system, the hand contact detection function is unreliable. Summary of the Invention

[0007] The object of the present invention is to provide a possible method to make the hand contact detection of an integrated system for detecting hand contact and heating a steering wheel of a motor vehicle reliable.

[0008] This object is achieved by the corresponding subject matter of the independent claims. Advantageous developments and preferred embodiments are the subject matter of the dependent claims, the description and the drawings.

[0009] In order to make the hand detection of an integrated system with hand contact detection and steering wheel heating functions reliable, according to one aspect, the present invention provides a device for detecting hand contact and for heating a steering wheel of a motor vehicle. The device includes a heating element for heating the steering wheel. Thus, the heating element is designed to heat or control the temperature of the steering wheel during operation. In addition, the device includes a sensor element for detecting hand contact on the steering wheel. Thus, the sensor element is designed to detect, for example, the grasping or holding of the steering wheel by the vehicle driver or operator with a hand.

[0010] The heating element and the sensor element are assigned to a common functional group for integration into the steering wheel. This means that the heating element and the sensor element can be installed together in the steering wheel. They can form an integrated system.

[0011] The device further includes control electronics. These are designed to alternately control the heating element in a heating routine for heating the steering wheel and the sensor element in a measurement routine for detecting hand contact on the steering wheel in a time-division multiplexing method. This means that the control electronics can control or operate the heating element and the sensor element such that the steering wheel heating and the hand contact detection are carried out continuously in time.

[0012] The control electronics are also designed to check, in a test routine, whether the sensor signal is affected by interfering signals, also referred to hereinafter as noise or interference, before executing the corresponding measurement routine. In particular, the control electronics are designed to (temporarily) execute the test routine before each measurement routine in the time-division multiplexing method. In addition, the control electronics are designed to execute a predetermined measure for adjusting the measurement routine only when the interfering signal exceeds a predetermined limit value according to the test routine for the immediately following or subsequent measurement routine in the time-division multiplexing method. In the present case, the immediately following measurement routine is used to denote the measurement routine that is assigned a time interval in the time-division multiplexing method, and this time interval directly follows the time interval of the test routine. Adjusting the measurement routine at least reduces, preferably completely suppresses, the influence of the interfering signal on the hand contact detection.

[0013] In other words, before executing the measurement routine for detecting hand contact, the state or absence of interfering signals from the device (especially the sensor element) can be checked by means of the control electronics. Thus, the interference of the device, for example, interference attributable to electromagnetic interference, can be checked.

[0014] The advantage resulting from this is that when detecting hand contact, only interference-free data is evaluated. This is because such an evaluation is complex and generally requires a large amount of time and computing power. Overall, if only relevant or interference-free data is evaluated, the processing time of the raw data provided by the sensor element can thus be reduced. In addition, hand contact can be reliably detected. Data that can be attributed to interference signals and output by the sensor element will not be misinterpreted as hand contact.

[0015] In this case, the steering wheel is particularly used to represent a control device for steering or guiding a motor vehicle. The control device can be directly operated by the vehicle driver, i.e., the driver. In the present application, the steering wheel can be used to represent a traditional steering wheel or another suitable control device that performs the same function, such as a joystick.

[0016] Of course, the described device can also be used for components other than the steering wheel. For example, all systems for performing hand contact detection can be considered. These include, for example, touch-sensitive operating elements, such as displays or touchpads, or other previously known operating elements, such as those used in the automotive field. Instead of a heating element, for example, another sensor element can be provided, such as an illumination element for illuminating the relevant system or a radio element for radio transmission, such as an antenna.

[0017] The sensor element and the heating element can be designed as a sensor and / or actuator in the form of an antenna, for example. For example, it can be a wire. Further configuration examples will be described in more detail later.

[0018] For heating, for example, a current can be applied to the heating element in a heating routine. Due to the resistance provided or possessed by the heating element, the heating element can become hot when powered on, depending on the selected current intensity. The heating element can preferably include a temperature sensor. The temperature sensor can monitor, i.e., measure or record, the temperature of the heating element and can provide the measured temperature to the control electronics for temperature control. The control electronics can perform temperature control as part of the heating routine. This means that the heating routine can include measuring the current temperature, evaluating the measured temperature, and adjusting it to a target temperature based on the measured temperature.

[0019] As mentioned at the beginning, the measurement routine for detecting hand contact itself is known. The measurement routine can be based on, for example, the determination of predetermined characteristics, such as the capacitance, resistance, and / or impedance of the sensor element. In particular, the sensor element has variable characteristics. Variable here means especially based on the characteristics or attributes of hand contact, preferably whether the hand is on or at least near the steering wheel.

[0020] To detect hand contact, for example, a predetermined reference signal can be applied to the sensor element during a measurement routine. The reference signal can be, for example, an alternating current signal, in particular, for example, a clock-controlled DC voltage or AC voltage. Depending on the characteristics of the sensor element, the sensor element can affect or change the reference signal. The changed reference signal can be provided by the sensor element as a measurement signal, for example, and read out by the control electronics. The measured value of the measured signal that has been read out can provide information about the characteristics of the sensor element. For this purpose, the measurement signal can be evaluated using the control electronics during the measurement routine. For example, the evaluation can include comparing the signal curve of the measurement signal with a previously known comparison measurement signal or checking it. The comparison measurement signal can be a signal representing a predetermined change in the characteristics of the sensor element, that is, for example, an increase or decrease in impedance, capacitance, or resistance. Thus, by checking the comparison signal, the presence or absence of a hand on the steering wheel can be inferred. Here, for example, a pattern recognition algorithm or other evaluation methods known per se can be used for the evaluation. In particular, it can be checked, for example, whether the voltage value of the measurement signal is below or exceeds a predetermined limit value. The limit value represents the transition between hand contact (hand on) and no hand contact (hand off).

[0021] In summary, the measurement routine can thus include measuring or recording the measurement signal and evaluating the measurement signal. In addition, the measurement routine can include generating an alarm signal for controlling a vehicle alarm device based on the evaluation result. The alarm device can be, for example, an emergency stop or braking assistance device or an optical display device for the driver. For example, if no hand is detected on the steering wheel in the autonomous driving mode, an emergency stop maneuver can be performed or an optical warning can be output to the driver.

[0022] The test routine includes, for example, evaluating a test signal output or provided by the sensor element. The test signal can be a signal obtained or generated when the sensor element is subjected to, for example, electromagnetic interference or, for example, when there is residual capacitive charge in the sensor element. Electromagnetic interference can occur, for example, when using radio, especially mobile radio or radio broadcasting, from the magnetic field transmitted from a heating element and / or wires of the device and / or other elements in the device environment to the sensor element.

[0023] For the purpose of evaluation, the test signal can be compared with the aforementioned limit value. The limit value represents the transition at which the test signal is interpreted as an interference signal. For example, if the limit value is exceeded, the test signal is classified or identified as an interference signal. The interference signal used here means that the signal distorts the measurement signal, such that hand contact detection provides a false positive result (hand contact is confirmed even when the hand is not on the steering wheel). Preferably, the sensor element (measurement routine) is only controlled in the time-division multiplexing method when no interference is detected, i.e., the interference signal is below the limit value. On the other hand, if interference is detected, the measurement routine is adjusted. For example, adjustment means that the interference signal is compensated or filtered. This will be discussed in more detail later.

[0024] The time-division multiplexing method is a method known per se, in which multiple signals are transmitted in a time-shifted manner relative to each other. For example, this can be achieved by time-interleaved (transmission) channels. Each channel is processed in a fixed pattern within a specific time. Each channel is assigned a fixed time window or time interval (time slot). The time windows can be synchronous and of equal length, or asynchronous and demand-based. Within the specified time window, the entire bandwidth of data transmission is available for each transmission channel. In the current case, for example, the first channel can be assigned to the measurement routine, while a second channel different from the first channel can be assigned to the heating routine. For example, the test routine can also be integrated into the time-division multiplexing method. For example, a third channel different from the first and second channels can be provided for the test routine.

[0025] In this case, the control electronics are used to specifically denote the circuitry for processing data. For example, the circuitry can include at least one computing unit or control unit. Preferably, the control electronics include two or more computing units. A computing unit can be understood as particularly referring to a data processing device containing processing circuitry. A computing unit can thus process data, especially for performing computational operations. Optionally, these also include operations for performing indexed access to data structures, such as lookup tables (LUTs). In addition, the computing unit can generate and provide, for example, control data for controlling coupled components for their control.

[0026] The computing unit can in particular comprise one or more computers, one or more microcontrollers and / or one or more integrated circuits, such as one or more application-specific integrated circuits (ASICs), one or more field-programmable gate arrays (FPGAs) and / or one or more systems-on-chip (SoCs). The computing unit can also comprise one or more processors, such as one or more microprocessors, one or more central processing units (CPUs), one or more graphics processing units (GPUs) and / or one or more signal processors, especially one or more digital signal processors (DSPs). The computing unit can also comprise a set of physical or virtual computers or other types of the aforementioned units.

[0027] In various exemplary embodiments, the computing unit includes one or more hardware and / or software interfaces and / or one or more storage units. The storage unit may be configured as a volatile data memory, such as a dynamic random access memory (DRAM) or a static random access memory (SRAM), or a non-volatile data memory, such as a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a flash memory or flash EEPROM, a ferroelectric random access memory (FRAM), a magnetoresistive random access memory (MRAM), or a phase change random access memory.

[0028] Other advantages and configurations of the present invention are described in more detail in the following embodiments.

[0029] In one embodiment, the control electronic device is designed to adjust at least one relevant signal characteristic or signal property of a reference signal based on at least one determined signal characteristic or signal property of an interference signal according to the measure, and the reference signal can be supplied to a sensor element for performing a measurement routine. This has the advantage of compensating or eliminating the interference signal in advance, i.e., before evaluating the measurement signal.

[0030] In this case, the adjustment may mean that when generating the reference signal, the determined signal characteristic of the interference signal is removed or omitted. Thus, the reference signal is calculated or determined and output without the signal characteristic of the interference signal. The signal characteristic of the interference signal can be verified or determined by the control electronic device, for example. In the present case, as described above, the reference signal is the signal output to the sensor element, and its change is measured by the sensor element based on hand contact to detect hand contact.

[0031] The signal characteristic of the interference signal is used herein and hereinafter to denote, for example, frequency, amplitude, and / or edge steepness. The signal characteristic of the reference signal can be similarly understood herein and hereinafter as, for example, frequency, amplitude, or baseline or threshold, i.e., the so-called zero line. For example, if an interference signal with a specific frequency and / or amplitude is now measured, then this frequency and / or amplitude can be avoided when generating the reference signal. For example, the bandwidth of the reference signal can be limited. Conversely, for example, different signal characteristics are selected, preferably differing from the signal characteristic of the interference signal by a predetermined limit amount. Thus, it is possible to prevent the interference signal from affecting the reference signal, for example, within the relevant range, and thus, for example, distorting the measurement signal and the measurement result when reading out the sensor element.

[0032] In one embodiment, the control electronic device is designed to filter the measurement signal that can be provided by the sensor element during the execution of the measurement routine according to this measure and based on at least one determined signal characteristic of the interference signal. The "providing" used here means that the measurement signal as described above can be tapped from the sensor or can be output by the sensor.

[0033] Additionally or alternatively, the control electronic device is designed according to the measurement result to adjust the sampling rate based on the determined signal characteristic, and through this sampling rate, the measurement signal can be sampled when the measurement routine is executed. Sampling is used in this case to represent digitization, that is, to acquire a continuous-time signal as a discrete-time signal, which is known per se.

[0034] Therefore, it is possible to subsequently compensate for the interference signal. Subsequently here means that the compensation is performed only based on the measurement signal (rather than the reference signal). The compensation can include adjustment, that is, for example, hiding or removing, or filtering. For filtering, for example, frequency filters known per se, such as high-pass filters, low-pass filters, or band-pass filters, can be applied to the measurement signal.

[0035] In one embodiment, the control electronic device is designed to skip the subsequent measurement routine in the time-division multiplexing method according to this measure when the interference signal exceeds a predetermined limit value. This means that the relevant measurement routine can be suspended or not executed. Instead, the time interval reserved for the measurement routine can be waited for, or for example, the heating routine can be directly executed.

[0036] This allows the device to enter a safe state. This can completely prevent the occurrence of hand detection. Instead, for example, the sensor element for detecting hand contact can be controlled only when the interference signal is below the predetermined limit value.

[0037] According to one embodiment, the control electronic device is redundantly designed and has at least two separate measurement modules for executing the measurement routine, especially independently of each other. Such a redundant design can bring advantages, for example, for functional safety or classification according to ASIL (Automotive Safety Integrity Level according to ISO standard 26262).

[0038] In the current case and hereinafter, one or more separate or discrete components of the control electronic device can be understood to refer to modules. Separation here means that the modules, in this case, for example, the measurement modules, are electrically insulated from each other. As described above, each module can form, for example, the computing unit of the control electronic device. Each module can form, for example, a separate channel or a separate connection to the corresponding elements of the device, such as the sensor element and the heating element. Therefore, the signal transmission of the modules can be carried out independently of each other, that is, in a multi-channel manner.

[0039] The modules used here and below refer specifically to hardware modules or software modules. Preferably, a module can also have hardware and software components implemented on the hardware. For example, the corresponding programs, such as measurement routines, test routines, and heating routines, can form such software or such software components.

[0040] In order to be able to perform heating and testing in such a configuration, for example, the heating routine can be assigned to one of the measurement modules, while the test routine can be assigned to the corresponding other measurement module. Otherwise, the heating and test routines can themselves be executed using the specified modules separately, which will be described in more detail later.

[0041] According to one embodiment, the control electronic device has at least one measurement module for executing measurement routines and / or heating routines and at least one test module separate from the measurement module for executing test routines, in particular independently of each other. This means that testing and measurement can be carried out in separate components. Preferably, compared with the measurement module, the test module can have improved evaluation characteristics. For example, the test module can allow an increased sampling rate and can thus be designed for so-called oversampling. Additionally or alternatively, the test module can be provided as a so-called scan IC (integrated circuit). In this case, the test module can be specifically designed for radio frequency signals in the megahertz or gigahertz range, for example. Additionally or alternatively, the test module can be frequency selective. This means that, for example, it can provide particularly good resolution for certain frequencies of interference signals typical or previously known in the field of hand contact detection.

[0042] According to one embodiment, the control electronic device has at least one measurement module for executing measurement routines and at least one heating module separate from the measurement module for executing heating routines. This means that the measurement module and the heating module can be independent components of the control electronic device.

[0043] Of course, any combination of the foregoing module configurations can also be provided. For example, three independent modules can be provided, namely a measurement module, a heating module, and a test module. However, these modules can also be implemented in any combination with each other.

[0044] If the heating module is formed in a separate module, then according to one embodiment, it is provided that the control electronic device is designed to execute the test routine at least partially during the heating routine. This means that the time period for executing the test routine can fall within the time period or time interval of the heating routine. Therefore, interference signals can be determined during the execution of the heating routine or when the heating routine is being executed. The advantage of this is that the electromagnetic interference generated by the heating of the heating element is accurately referred to as the interference signal. Later, when the measurement routine is executed, it can be very easy to determine such interference.

[0045] Alternatively, it is of course possible to provide that the test routine is integrated in a time-division multiplexing method and thus executed separately from the heating routine and the measurement routine.

[0046] According to one embodiment, the control electronic device has at least two test connections for executing a test routine. The first test connection is coupled to the input connection of the sensor element, and the second test connection is coupled to the output connection of the sensor element. The connections used herein and hereinafter refer in particular to pins or electrical contacts. The connections of the control electronic device, in particular the computing unit of the control electronic device, can be designed as, for example, a so-called GPIO (General Purpose Input / Output) or an ADC input (ADC: Analog-to-Digital Converter) or a DIO (Digital Input Output). These are interface types known per se, especially interface types related to an IC or a microcontroller.

[0047] The advantage of using two or more test connections is that interference signals can be determined particularly precisely. For this purpose, for example, the measurement signals that can be tapped or present at the input connection end and the output connection end of the sensor element can be compared. Based on this comparison, the interference signal can be determined.

[0048] Similarly, the control electronic device, in particular the corresponding measurement module, can have at least two measurement connections for executing a measurement routine. The first measurement connection is coupled or connected to the input connection, and the second connection is coupled or connected to the output connection of the sensor element. For example, a total of four connections can thus be provided for the test and measurement routines. Advantageously, the above-mentioned test connections and test modules can also be used, for example, to execute a measurement routine, in particular the evaluation of a measurement signal, for the purpose of checking hand detection.

[0049] According to one embodiment, the control electronic device is designed to determine an interference signal and / or hand contact detection based on the capacitance value and / or impedance value of the sensor element. Thus, a capacitance measurement can be determined, i.e., a capacitance change in the system, in order to execute an interference signal and / or hand contact detection. This makes it possible to determine the influence of electromagnetic interference on the system or device.

[0050] For example, if two connections (test connection or measurement connection) are used for measurement, the capacitance measurement can be performed, for example, according to the charging / discharging method mentioned at the beginning. In particular, the capacitance or impedance value of the capacitance divider provided by the device is determined. The capacitance divider can be realized, for example, by a reference capacitor having a predetermined capacitance value provided by the control electronic device and a variable capacitor having a variable capacitance value that is generated based on hand detection at the corresponding sensor element.

[0051] According to one embodiment, for determining interference signals and / or hand contact detection, the control electronic device is designed to perform humidity measurement and, in the process, determine at least the interference signal based on the resistance value of the sensor element. Here, the principle that the resistance part of the device, in particular the sensor element, varies according to the humidity in the environment is used. In this case, humidity is used in particular to represent a liquid, preferably a conductive liquid such as water.

[0052] Therefore, the resistance measurement or resistance change in the device can be determined. This makes it possible to determine, for example, the influence of humidity from the environment or air on the steering wheel. If two test connections or measurement connections are provided, humidity measurement can be performed, for example, according to the principle of a resistive voltage divider. The voltage divider can be formed by a reference resistor and a variable resistor, the reference resistor having a pre-known resistance value provided, for example, by the control electronic device, and the variable resistor depending on the ambient humidity of the sensor element.

[0053] According to one embodiment, the heating element and / or the sensor element are provided at least by a wire or a wire mesh. The wire or wire mesh extends around the steering wheel rim of the steering wheel in an integrated state. In this case, the wire is used in particular to represent an element made of a conductive material, especially a metal, whose length is much greater than its cross-section. The wire mesh can be a mesh or a connection of multiple such wires. Preferably, the wires can be connected to form a grid. Preferably, the sensor element and / or the heating element are in the form of a pad or a film made of wires. A pad is used to represent a flat component whose length and width are much greater than its thickness.

[0054] According to one embodiment, the heating element and the sensor element form a common component. This means that the heating element is part of the sensor element and vice versa. For example, the heating element and the sensor element can be formed by a common wire or a common wire mesh. Thus, two different functions, namely heating and hand contact detection, can be performed with one component.

[0055] Alternatively, the sensor element and the heating element can be separate components. Thus, for example, wires or wire meshes can be provided for each element. In a separated configuration, the sensor element and the heating element can be constructed, for example, in a functional group of a layer structure, where the layer having the heating element is separated from the layer having the sensor element by a shielding layer. The shielding layer can be composed of a material that can at least partially shield electromagnetic radiation or an electromagnetic field.

[0056] On the other hand, the present invention relates to a steering wheel system for a motor vehicle. The steering wheel system includes a steering wheel and the device as described above. The functional group including the sensor element and the heating element is integrated in the steering wheel, in particular in the steering wheel rim.

[0057] Of course, it is also possible to provide a motor vehicle with a corresponding steering wheel system. The motor vehicle can preferably be designed as a passenger car or a truck or a minibus or a motorcycle.

[0058] On the other hand, the invention relates to a method for detecting hand contact and for heating a steering wheel of a motor vehicle. In this method, a heating element for heating the steering wheel and a sensor element for detecting hand contact on the steering wheel are alternately controlled or operated in a time-division multiplexing method using a control electronics during a heating routine and a measurement routine. The heating element and the sensor element are assigned to a common functional group for integration into the steering wheel. The control electronics is used to check in a test routine, in particular before performing the corresponding measurement routine, whether the sensor element is affected by interference signals. Only when the interference signal exceeds a predetermined limit value are predetermined measures for adjusting the measurement routine executed for the subsequent measurement routine in the time-division multiplexing method. The adjustment is performed so as to at least reduce the influence of the interference signal on the hand contact detection.

[0059] For application cases or application scenarios that can lead to this method and are not explicitly described herein, according to this method, it can be stipulated what error messages are to be output and / or requests for input user feedback and / or default settings to be set and / or predetermined initial states.

[0060] Unless otherwise specified, all steps of the method can be performed by a data processing device having at least one computing unit, in particular by the data processing device of a vehicle, in which case it is the control electronics. Specifically, at least one computing unit is configured or adapted to perform the steps of the (computer-implemented) method. For this purpose, at least one computing unit can store, for example, a computer program containing instructions that, when executed by at least one computing unit, cause at least one computing unit to perform the computer-implemented method.

[0061] According to another aspect of the invention, a computer program with instructions is specified. When the instructions are executed by at least one computing unit, the instructions cause at least one computing unit to perform the method according to the invention. The computer program can include the above-mentioned program. The instructions can exist as program code. The program code can be provided as binary code or assembly code and / or as source code of a programming language (such as C) and / or as a program script (such as Python).

[0062] Other embodiments of the method, the steering wheel system, and the computer program according to the invention directly result from the various embodiments of the device according to the invention, and vice versa. In particular, the device according to the invention can be configured to perform the method according to the invention, or to execute such a method.

[0063] Further features of the present invention emerge from the claims, the drawings and the description of the drawings. The features and combinations of features mentioned in the description and the combinations of features mentioned and / or shown in the drawings of the description can be included in the present invention not only in the combinations specified in each case, but also in other combinations. In particular, embodiments and combinations of features that do not have all the features of the claims in their original formulation can also be included in the present invention. In addition, embodiments and combinations of features that go beyond or are different from the combinations of features set forth in the back references of the claims can be included in the present invention. Description of the Drawings

[0064] In the drawings:

[0065] Figure 1 A schematic view of a steering wheel system according to an exemplary embodiment is shown, the steering wheel system having means for detecting hand contact and for heating the steering wheel; and

[0066] Figure 2 A schematic method flow diagram for operating the steering wheel system according to an exemplary embodiment is shown. Detailed Description of the Invention

[0067] The present invention will be explained in more detail below on the basis of specific exemplary embodiments and the associated schematic drawings. In the drawings, identical or functionally identical elements may have the same reference numerals. For different drawings, the description of identical or functionally identical elements need not be repeated.

[0068] Figure 1 A schematic view of an exemplary embodiment of a steering wheel system 1 is shown. The steering wheel system 1 includes a steering wheel 3 and means 2 for detecting hand contact and for heating the steering wheel 3. The steering wheel 3 includes a steering wheel rim 3a. The steering wheel rim 3a is connected to a central part 3c by spokes 3b. The central part 3c is for attaching the steering wheel 3 to the steering column of a motor vehicle. The steering wheel 3 is part of the steering system of a motor vehicle. A vehicle driver or operator can operate the steering wheel 3 so as to, for example, bring the vehicle tires to a desired steering position, thereby effecting a change of direction. The operation is carried out by hand, in particular with at least one hand. The steering wheel rim 3a serves as a gripping area or operating area for placing or gripping with one or more hands.

[0069] Device 2 is used to ensure that at least one hand of the driver remains on the steering wheel 3 during driving. Device 2 includes control electronics 4 and a functional group 7. The functional group 7 includes a sensor element 8 and a heating element 9. The sensor element 8 can be a sensor for detecting hand contact. The heating element 9 can be an actuator for heating the steering wheel 3. In the present exemplary embodiment, the sensor element 8 and the heating element 9 are implemented by a common component. The sensor and the heating elements 8, 9 are shown as wires, for example. For example, it can be a metal wire with high electrical conductivity, such as a copper wire or an aluminum wire. Preferably, the heating and sensor elements 9, 8 can also exist in the form of a pad as a wire mesh. This means that multiple wires can be interconnected in a flat cross-linked structure.

[0070] For simplicity, the collection of the heating element and the sensor element 9, 8 is hereinafter referred to as the functional group 7. As Figure 1 shown, the functional group 7 is integrated in the steering wheel rim 3a. In the integrated state, the wire extends once around the steering wheel rim 3a of the steering wheel 3. Thus, the sensor and the heating elements 8, 9 form an antenna. Due to the length of the wire, the sensor and the heating elements 8, 9 may therefore be particularly sensitive to electromagnetic interference (EMI).

[0071] For the electrical connection or attachment of the functional group 7, the functional group 7 includes two connections in the present case, which are led out from the steering wheel rim 3a as electrical contacts. One of the connections forms an input connection 7a, which is arranged at one end of the wire. The second connection forms an output connection 7b, which is formed at the opposite end of the wire.

[0072] The control electronics 4 is provided to operate the functional group 7 to perform corresponding functions. The control electronics 4 can be understood as a data processing device or a control device in the present case. In the present exemplary embodiment, the control electronics 4 includes a test module 5 and a measurement and heating module. The measurement and heating module is hereinafter referred to as the functional module 6. Modules 5 and 6 can be understood as hardware and software components in the present case. In particular, modules 5 and 6 are separate or distinct parts or components of the control electronics. Modules 5, 6 can be designed as, for example, computing units, especially microcontrollers or ICs (integrated circuits).

[0073] The measurement module is designed to implement the function of hand contact detection. This means that the sensor element 8 can be operated by the measurement module for hand contact detection. The heating module is designed to implement the function of steering wheel heating. This means that the heating element 9 can be operated or controlled to heat the steering wheel by the heating module. The test module is designed to implement the function of noise detection. This means that the test module can be used to determine whether the sensor element 8 is affected by an interference signal N (also called noise).

[0074] In the present case, the functional module 6 includes two connections, namely a measurement connection 6a and a measurement connection 6b. The measurement connection 6a is electrically connected to the input connection 7a. The measurement connection 6b is electrically connected to the output connection 7b. This connection provides a transmission channel between the functional group 7 and the functional module 6. An electrical signal can be transmitted through the transmission channel, that is, a line extending between the connections for making contact.

[0075] In the present exemplary embodiment, the test module 5 also includes two connections, namely a test connection 5a and a test connection 5b. The test connection 5a is electrically connected to the input connection 7a. The test connection 5b is electrically connected to the output connection 7b. This connection creates a transmission channel between the test module 5 and the functional group 7. This means that, as described above, an electrical signal can be transmitted through the line connecting the connections to each other.

[0076] In the present case, the connections 5a, 5b and 6a, 6b are designed as, for example, so-called GPIO (General-Purpose Input / Output) connections. Preferably, the test connections 5a, 5b are each coupled or assigned to the analog-to-digital converter function (ADC - Analog-to-Digital Converter) of the test module 5. The test module includes, for example, a first converter element ADC1 to which the test connection 5a is coupled and a second converter element ADC2 to which the test connection 5b is coupled. The converter elements ADC1, ADC2. Thus, the analog signals at the test connections 5a, 5b can be converted into binary signals, that is, digital signals. This analog-to-digital converter function enables the test module to read measurement values from an analog source and then perform digital processing on them.

[0077] As Figure 1 an alternative to the exemplary embodiment shown, for example, different combinations or divisions of the modules 5, 6 can be provided. For example, a common module, that is, for example, a common microcontroller, can be provided and used to implement the test module, the measurement module, and the heating module. Alternatively, the measurement module and the heating module can also be designed as separate modules. Particularly preferably, the test module can simultaneously act as a measurement module and thus perform hand contact detection.

[0078] Figure 1 The steering wheel system 1 shown by way of example is intended to enable reliable hand contact detection to be performed. In the present case, the hand contact detection is particularly based on the impedance evaluation of the steering wheel system 1, particularly based on the evaluation of the capacitive component of the impedance. The impedance used here and below particularly refers to the so-called AC resistance. In this case, the impedance can include, for example, resistive and capacitive components. The resistive component can be generated by the resistance (ohmic resistance) of the corresponding associated components. When the corresponding components act as capacitors or capacitances, the capacitive component can be attributed to the capacitance or capacitor.

[0079] For the sake of completeness, it should be noted that the impedance can also have, for example, an inductive component. For example, an inductive component is generated when the corresponding component acts as or has an inductor or coil.

[0080] However, the inductive component of the impedance is irrelevant to the steering wheel system 1 described for achieving the desired function in the present case. Hand contact detection is particularly based on the capacitive component of the impedance of the steering wheel system 1. In this case, the following fact is utilized: The functional group 7, in particular the sensor element 8, as Figure 1 shown, has a variable impedance Zx. The impedance Zx is generated by the sensor element 8 with respect to a predetermined reference potential GND (such as the vehicle chassis). A variable is used to represent the impedance value, and in particular, the capacitance value of the impedance Zx can be changed. This change depends on whether a hand is on the steering wheel. In particular, when a hand is placed on the steering wheel 3, that is, grasping or holding the steering wheel, or when the hand is removed from the steering wheel 3, that is, releasing the grasp, the capacitance changes, that is, decreases or increases.

[0081] According to a predetermined measurement routine M for detecting hand contact, such a change in capacitance can be determined by means of a measurement module. For this purpose, the measurement module can apply a reference signal R to the sensor element 8. The reference signal R can preferably be an alternating current signal (alternating current or clock-controlled direct current) with a predetermined signal characteristic. The signal characteristic can specify, for example, the frequency, amplitude, and / or another signal attribute, such as the duty cycle. For example, in the present case, the reference signal R can be a 5-volt square wave pulse. If the reference signal R passes through the sensor element 8, the shape or characteristic of the reference signal R changes based on the impedance Zx of the sensor element 8. The changed reference signal R can be output from the sensor element 8 as a measurement signal S and can be used by the measurement module. The measurement module can evaluate the measurement signal S and, based on its signal characteristic, can infer the impedance or impedance change of the sensor element 8.

[0082] This method for hand-off detection, that is, for hand contact detection, is known per se. For example, an example of a known method operating according to the capacitance measurement principle is the so-called charge / discharge method. This method can be learned from the patent specification US 9,823,798 B2. In this case, the measurement connections 6a and 6b are first switched to a high level and a low level, and then both are switched to a high-impedance state. In the high-impedance state, an inspection is then carried out to determine the degree of difference in the voltage values of the signals present on the measurement connections 6a and 6b. The voltage value depends in particular on the capacitance value of the capacitive component of the impedance Zx relative to the capacitance value of a reference capacitance provided by the measurement module. This is because the reference capacitance and the capacitive component of the impedance form a so-called capacitive voltage divider.

[0083] To heat the steering wheel 3, the heating module can execute a heating routine H. For this purpose, the heating module can, for example, apply a current of a predetermined current intensity to the heating element 9. Depending on the resistance provided by the heating element 9, the heating element gets hot. For temperature monitoring, the heating module can monitor, for example, the resistance of the heating element 9. The resistance is a temperature-dependent variable and can thus be calculated. For example, depending on the determined temperature, the current intensity for heating can be adjusted or set in a control loop.

[0084] Advantageously, heating and hand contact detection are decoupled in an integrated system, as Figure 1 shown. This means that heating and hand contact detection can be specifically switched and thus only occur alternately or continuously in time. However, due to the impedance Zx of the functional group 7, parasitic signals or currents occur in the steering wheel system 1 even after the heating routine H has been completed. If the measurement routine M is then executed, the parasitic signals will affect the hand contact detection as interference signals N. For example, hand contact may be confirmed even if the hand is not on the steering wheel 3.

[0085] For noise detection, i.e., to determine the interference signal N, a test routine P can be executed by the test module 5. Depending on the result provided by the test routine P, corresponding measures for adjusting the measurement routine M can then be executed. Possible measures here will be described in more detail later. To perform the measurement, the test module 5 can, for example, provide a trip signal to the measurement module.

[0086] To determine the interference signal N, the test module 5 can, for example, acquire test signals at corresponding test connections 5a, 5b and can digitize them. If two test connections 5a, 5b are used in the current case, the digitized measurement data can be compared in order to make the interference signal test more precise. The test signals can then be evaluated, as described in more detail below.

[0087] For example, according to the above charging / discharging method, the interference signal N can be determined, as already described for the measurement routine M. Figure 1 By way of example, reference impedances Z1, Z2, Z11, Z12, Z21, Z22 are shown, each having a reference capacitance, which can be taken into account for this method. Z1 and Z2 represent the impedances of the lines forming the transmission channel between the test module 5 and the functional group 7. The impedances Z11, Z12, Z21 and Z22 are shown as the impedances generated between the respective transmission channels and the reference potential GND, i.e., for example, the vehicle chassis. The impedances Z1, Z2, Z11, Z12, Z13, Z14 can also be provided analogously as the reference impedances of the transmission channels between the functional module 6 and the functional group 7.

[0088] Reference Figure 2, an example of the specific operation of device 2 can be described in more detail, which can be controlled for reliable hand contact detection. In this regard, Figure 2 An exemplary schematic method flow chart V is shown. Each step here, also referred to as a program, is shown according to time t1.

[0089] As Figure 2 shown in the example in, the device 2 is operated by means of the control electronic device 4 to detect hand contact and to heat the steering wheel 3 in a time-division multiplexing method TDM. The heating routine H, the test routine P, and the measurement routine M are continuously executed alternately at a predetermined, for example, respectively specified time interval, that is, executed in a temporarily separated manner from each other. For example, a delay D, that is, a predetermined time delay, is executed before the cycle of the heating routine H, the test routine P, and the measurement routine M is executed again. In the heating routine H, as described above, the steering wheel 3 is heated. The test routine then checks whether the sensor element 8 is affected by an interference signal N. For this purpose, the test routine checks whether the test signal provided by the sensor element 8 during the test routine P exceeds a predetermined limit value or threshold value. The limit value represents the limit at which the test signal distorts the measurement signal S in such a way that an incorrect hand contact detection occurs.

[0090] If the limit value is exceeded, the test signal is interpreted or marked as an interference signal N. Otherwise, the test signal is recognized as harmless. If the interference signal N exceeds the limit value, a predetermined measure is executed for the measurement routine M immediately following in the time-division multiplexing method TDM. For this purpose, the test module 5 can control the measurement module with a trip signal. For example, according to the trip signal, another protocol for executing the measurement routine M is then selected in the measurement routine M.

[0091] Figure 2 An example shows that there is a corresponding interference signal N for the second cycle. As Figure 2 shown, the measure can now include, for example, changing the measurement module or the sensor element 8 for hand detection to a safe state. In this safe state, the measurement routine M is suspended, that is, not executed in the relevant cycle. The hand contact detection is thus skipped once. This preferably only applies to the measurement routine M that is immediately pending or upcoming in the cycle of the time-division multiplexing method. Figure 2 An example shows that instead of the measurement routine M, the delay D is then directly executed, and then a new cycle of the time-division multiplexing method TDM is started with the heating routine H.

[0092] With Figure 2The comparison of different measures can include compensating for the interference signal N. Here, the signal characteristics of the interference signal, such as frequency or amplitude or edge steepness, can be determined with the aid of the test module 5. Depending thereon, the corresponding signal characteristics of the reference signal R can then be adjusted for performing the measurement routine. This means that, for example, the frequency, amplitude, and / or baseline (i.e., the zero line) of the reference signal can be adjusted based on the signal characteristics of the interference signal N.

[0093] Additionally or alternatively, compensation can subsequently be performed, especially after the measurement of the sensor element 8 has been carried out. Here, for example, a filter can be used to filter out the known signal characteristics of the interference signal N from the measurement signal S. Filtering the measurement signal S enables the bandwidth of the measurement signal S to be restricted or reduced, such that noise frequencies are blocked or excluded from the spectrum of the measurement signal S.

[0094] Another option is to adjust the sampling rate based on the signal characteristics of the interference signal N, at which the measurement signal S is sampled or digitized when captured by the measurement module.

[0095] Overall, the noise can thus be removed or filtered before the data is processed for hand contact detection. This can improve the processing time of hand contact detection, since no time is spent evaluating distorted data. Additionally, for example, the measurement frequency or filter frequency can thus be optimally adapted to the respective requirements.

[0096] The functions of the steering wheel system 1 described according to the exemplary embodiment can be summarized as follows. As Figure 1 shown, for example, before performing hand contact detection and processing, the state of the functional group 7 can be checked in a simple manner using the analog and measurement interfaces of the microcontroller. The idea is generally to check for the presence of electromagnetic interference, such as due to heating elements or, for example, the power supply lines of the control electronics. For this purpose, one or more analog inputs or connections can be used, or, for example, so-called GPIO connections with ADC capabilities. Such electromagnetic interference can generate feedback for hand contact detection, since the functional group 9 (i.e., the line) acts like an antenna. The feedback allows a strong electric field to induce a voltage in the functional group, which can be observed via the input of the microcontroller.

[0097] If such interference occurs during hand contact detection, the heating function is typically disabled. However, the parasitic capacitance, especially the series capacitance, present between the power supply lines (i.e., the channels) can be charged during heating. Depending on the capacitance of the parasitic capacitance, a pure DC voltage can be separated there, and any noise in the power supply lines can cause voltage fluctuations in these capacitances, which can then be monitored again via the input of the microcontroller. If, for example, the measurement results output by the ADC converter of the microcontroller increase and / or there are fluctuations in the channels used for hand contact detection, this noise can be detected or recognized as the interference signal N.

[0098] If these variations or fluctuations exceed a predefined threshold, this is detected as noise, i.e., interference signal N. Then, the system should, for example, change to a safe state where hand contact detection is no longer performed, or the noise should be filtered from the original measurement data of the hand contact detection.

[0099] An improvement can be to use two connections of a control electronic device or a microcontroller, for example having ADC capabilities, to measure both ends of functional group 7. Any interference signal is visible at both inputs. This enables the interference signals on the two lines to be compared, thus allowing the characteristics of interference signal N to be inferred more precisely and easily.

[0100] If two inputs are used to check for noise, they can also be used to implement the two - hand detection concept. Here, for example, the test module can be used as an additional measurement module. For example, the known impedances Z1, Z2, Z11, Z12, Z21, and Z22 can be used in the Figure 1 example to determine the variable impedance Zx of the steering wheel with or without hands, for example by using the above - mentioned charge / discharge method. Alternatively, a resistive voltage divider can be used instead of a capacitive voltage divider to determine hand contact. This means that hand contact detection is implemented redundantly, which means higher safety requirements in line with the ASIL standard, especially higher than ASIL C.

[0101] As Figure 1 shown, the test module 5 can be designed as an independent component of the functional module, that is, for example, a second microcontroller. For example, this can be used as a noise scanner to determine for the functional module which frequencies are less noisy and thus less affected by noise for hand contact detection. Such a noise scanner can be implemented, for example, by using a dedicated frequency - selective RF power detector IC. This can, for example, directly measure the amplitude of each frequency in the relevant range in the transmission channel of functional group 7 and thus be able to determine the intensity and frequency of interference signal N. This allows the implementation of a frequency - selective detector. In this way, a more precise method can be implemented to determine the spectrum and intensity of the interference signal while reducing the data - processing load for hand contact detection.

[0102] Preferably, for example, the analog - to - digital converter of the microcontroller used to evaluate interference signal N can be designed for oversampling. This means that a higher sampling rate can be achieved, thus simplifying and improving the resolution of the interference signal and thus simplifying and improving the determination of the signal characteristics.

[0103] Another option is to use the average value of the interference signal. If interference signal N follows a deterministic structure or pattern, second - order filtering may be sufficient, for example, to apply or superimpose the inverted interference signal on the measurement signal in order to improve the hand contact detection quality. Similar processes are known in image processing, for example, from so - called dithering, also known as error diffusion.

[0104] Further improvements may include, for example, performing a test routine during a heating routine.

[0105] The above solution can be applied to all interference signals N coupled to the steering wheel system, for example, due to electromagnetic interference. Such interference may be generated, for example, by the environment, such as when making a phone call, or due to noise in the system. In addition, the system can also be used for humidity measurement. This is based on the resistive component of the impedance Zx. When the humidity on the steering wheel (i.e., on the functional group) increases, the resistive component of the impedance Zx will decrease. This is visible in the change in the system impedance at the measurement connection of the measurement module. By adjusting the values of the impedances Z1, Z2, Z11, Z12, Z21, and Z22, noise detection can be made more refined, and the measurement can be performed more robustly and accurately.

[0106] Overall, the exemplary embodiments show how to implement noise detection in a measurement for detecting hand contact on a steering wheel.

Claims

1. A device (2) for detecting hand contact and for heating a steering wheel (3) of a motor vehicle, characterized in that - a heating element (9) for heating the steering wheel (3), - a sensor element (8) for detecting hand contact on the steering wheel (3), wherein the heating element (9) and the sensor element (8) are assigned to a common functional group (7) for integration in the steering wheel (3), and - a control electronics (4) which is designed to alternately control the heating element (9) in a heating routine (H) for heating the steering wheel (3) and to control the sensor element (8) in a measurement routine (M) for detecting hand contact on the steering wheel (3) by means of a time-division multiplexing method (TDM), wherein the control electronics (4) is also designed to check in a test routine (P) whether the sensor signal (8) is affected by an interference signal (N) before executing the respective measurement routine (M), and the control electronics (4) is designed to execute a predetermined measure for adjusting the measurement routine (M) only for the subsequent measurement routine (M) in the time-division multiplexing method (TDM) when the interference signal (N) exceeds a predetermined limit value, such that the influence of the interference signal (N) on the hand contact detection is at least reduced.

2. The device (2) according to claim 1, wherein, The control electronics (4) is designed according to the measure to adjust at least one relevant signal characteristic of a reference signal (R) based on at least one determined signal characteristic of the interference signal (N), the reference signal (R) being able to be supplied to the sensor element (8) for executing the measurement routine (M).

3. The device (2) according to any one of the preceding claims, wherein, The control electronics (4) is designed according to the measure to filter a measurement signal (S) which can be provided by the sensor element (8) based on at least one determined signal characteristic of the interference signal (N) during execution of the measurement routine (M), and / or to adjust the sampling rate by which the measurement signal (S) can be sampled during execution of the measurement routine (M).

4. The device (2) according to any one of the preceding claims, wherein, The control electronics (4) is designed according to the measure to skip the subsequent measurement routine (M) in the time-division multiplexing method (TDM) when the interference signal (N) exceeds the predetermined limit value.

5. The device (2) according to any one of the preceding claims, wherein, The control electronics (4) is redundantly designed and has at least two separate measurement modules for executing the measurement routine (M).

6. The device (2) according to any one of the preceding claims, wherein, The control electronics (4) has at least one measurement module for executing the measurement routine (M) and / or the heating routine (H) and at least one test module (5) separate from the measurement module for executing the test routine (P).

7. The device (2) according to any one of the preceding claims, wherein, The control electronics (4) has at least one measurement module for executing the measurement routine (M) and at least one heating module separate from the measurement module for executing the heating routine (H).

8. The device (2) according to claim 7, wherein, The control electronics (4) is designed to execute the test routine (P) at least partly during the heating routine (H).

9. The device (2) according to any one of the preceding claims, wherein, The control electronic device (4) has at least two test connections (5a, 5b) for performing the test routine, wherein a first test connection (5a) is coupled to an input connection (7a) of the sensor element (8), and a second test connection (5b) is coupled to an output connection (7b) of the sensor element (8).

10. The device (2) according to any one of the preceding claims, wherein, The control electronic device (4) is designed to determine the interference signal (N) and / or hand contact detection based on the capacitance value and / or impedance value of the sensor element (8).

11. The device (2) according to any one of the preceding claims, wherein, To determine the interference signal (N) and / or hand contact detection, the control electronic device (4) is designed to perform a humidity measurement and, in the process, determine at least the interference signal (N) based on the resistance value of the sensor element (8).

12. The device (2) according to any one of the preceding claims, wherein, The heating element (9) and / or the sensor element (8) are provided by at least one wire or wire mesh that can extend around the steering wheel rim (3a) of the steering wheel (3) in an integrated state.

13. The device (2) according to any one of the preceding claims, wherein, The heating element (9) and the sensor element (8) form a common component.

14. A steering wheel system (1) for a motor vehicle, having a steering wheel (3) and a device (2) as claimed in any one of the preceding claims, wherein a functional group (7) including a sensor element (8) and a heating element (9) is integrated in the steering wheel (3).

15. A method for detecting hand contact and for heating the steering wheel (3) of a motor vehicle characterized in that a heating element (9) for heating the steering wheel (3) and a sensor element (8) for detecting hand contact on the steering wheel (3) are alternately controlled in a heating routine (H) and a measurement routine (M) using a control electronic device (4) in a time-division multiplexing method (TDM), wherein the heating element (9) and the sensor element (8) are assigned to a common functional group (7) integrated in the steering wheel (3), and before performing the corresponding measurement routine (M), it is checked by the control electronic device (4) in a test routine (P) whether the sensor element (8) is affected by an interference signal (N), and a predetermined measure for adjusting the measurement routine (M) is performed only for the measurement routine (M) immediately following in the time-division multiplexing method (TDM) when the interference signal (N) exceeds a predetermined limit value, such that the influence of the interference signal (N) on hand contact detection is at least reduced.

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