Method and apparatus for steering wheel touch detection

Abstract

The present disclosure relates to a method for steering wheel touch detection. The method comprises: for each touch detection channel, setting a reference load for detection by the touch detection channel to a preset reference capacitance value and a reference resistance value; measuring, by the touch detection channel, a capacitance value and a resistance value of the reference load; determining whether the operation of the touch detection channel is normal based on the preset reference capacitance value and the reference resistance value, and the measured capacitance value and resistance value; and in the case where it is determined that the operation of the touch detection channel is normal, measuring, by the touch detection channel, a capacitance value and a resistance value of a corresponding touch detection sensor thereof, and performing touch detection of the steering wheel based on the measured capacitance value and resistance value of the touch detection sensor. By adding an additional reference load, the present disclosure simply, low-cost and reliably implements a check on whether the off-hand detection of the steering wheel is operating normally.

Description

Technical Field

[0001] This disclosure relates to the field of steering wheel hands-off detection, and more specifically, to a method and apparatus for steering wheel touch detection. Background Technology

[0002] In driving, drivers need to use the steering wheel to steer. Furthermore, with technological advancements, drivers can also use the steering wheel to control multimedia and adjust driver assistance settings. Therefore, to improve driving safety, it's necessary to monitor whether the driver's hands are correctly positioned on the steering wheel and controlling the vehicle. For example, the latest revised UN R79 regulation requires vehicles equipped with Lane Keeping Assist System (LKAS) to detect whether the driver is holding the steering wheel.

[0003] In today's ADAS (Advanced Driver Assistance Systems), at high levels of autonomous driving (such as L2-L4), the vehicle itself can automatically take control of the driving, and the driver can remove their hands from the steering wheel. However, in some situations, the driver is required to reclaim control, and there must be a clear distinction in time between the driver's control of the vehicle and the vehicle's autonomous driving.

[0004] Hand-off detection (HOD) technology can be applied to the steering wheel to detect whether the driver is holding it. There are many methods for implementing HOD, such as pressure sensing and capacitive sensing. In pressure sensing-based HOD, a pressure sensor is installed on the steering wheel to detect pressure changes. However, pressure-based HOD is affected by the driver's individual grip strength, leading to misjudgments and affecting accuracy. In the commonly used capacitive sensing method, the capacitive sensor is located on the outer rim of the steering wheel. When the driver places or removes their hand from the steering wheel, it causes a change in the capacitance of parasitic capacitors. The capacitive sensor measures this change and records whether the driver's hand is on the wheel. However, capacitive sensing HOD has drawbacks: sensitivity decreases when the driver is wearing gloves, and it is also susceptible to errors when other parts of the body accidentally touch the steering wheel, or when someone intentionally or unintentionally touches the steering wheel with a substitute that causes a capacitance change.

[0005] To achieve efficient and reliable HOD (Hyper-Loading) technology, ams Semiconductor offers the AS8579, a high-precision sensor based on IQ demodulation technology and driven by capacitance measurement. The AS8579 sensor generates a sine wave to drive the load via a transmitting module, while a receiving module detects the load current, converts it into voltage, and demodulates it into in-phase (I) and quadrature-phase (Q) signals. An external processor can then read the I and Q values ​​and calculate the corresponding resistance and reactance values. HOD solutions based on the AS8579 do not require special pressure on the steering wheel and, through high-resolution detection, prevent the impact of single-finger or knee movements.

[0006] To meet the ASIL C / D level requirements of ISO 26262 ASIL (Automotive Safety Integration Level) in the automotive industry, all components across the entire vehicle system must possess very high robustness or self-testing capabilities. However, for widely used HOD sensors, such as the AS8579 sensor, only ASIL B safety level can be guaranteed. Therefore, additionally checking the proper functioning of the HOD sensors themselves is crucial for improving the overall vehicle safety level. Summary of the Invention

[0007] To address the aforementioned issues, this disclosure provides a method for steering wheel touch detection. Based on the previously mentioned steering wheel touch detection method, this method adds an additional reference load, thus achieving a simple, low-cost, and reliable check of whether the steering wheel's HOD is functioning properly.

[0008] This disclosure provides a method for steering wheel touch detection, wherein the steering wheel is divided into at least one touch detection area, each touch detection area includes at least one touch detection sensor, and each touch detection sensor has its corresponding touch detection channel. The method includes: for each touch detection channel, setting a reference load for detection by the touch detection channel to a preset reference capacitance value and a reference resistance value; using the touch detection channel, measuring the capacitance value and resistance value of the reference load; determining whether the operation of the touch detection channel is normal based on the preset reference capacitance value and reference resistance value, and the measured capacitance value and resistance value; and if the operation of the touch detection channel is determined to be normal, using the touch detection channel to measure the capacitance value and resistance value of its corresponding touch detection sensor, and performing touch detection of the steering wheel based on the measured capacitance value and resistance value of the touch detection sensor.

[0009] According to an embodiment of this disclosure, for each touch detection channel, the corresponding preset reference capacitance value and reference resistance value are non-constant values.

[0010] According to an embodiment of this disclosure, determining whether the operation of the touch detection channel is normal based on the preset capacitance value and preset resistance value, as well as the measured capacitance value and resistance value, includes: determining that the touch detection channel is operating normally when the deviation of the measured capacitance value relative to the preset reference capacitance value is within a predetermined deviation range, and the deviation of the measured resistance value relative to the preset reference resistance value is within a predetermined deviation range; otherwise, determining that the touch detection channel has malfunctioned.

[0011] According to an embodiment of this disclosure, the reference load is connected to the touch detection channel via a switching device. The switching device is disconnected during the measurement of the touch detection sensor and connected during the measurement of the reference load.

[0012] According to an embodiment of this disclosure, the method further includes: in the event of an operational malfunction of the touch detection channel, adjusting the preset reference capacitance and reference resistance values ​​of the reference load, and using the touch detection channel to measure the adjusted capacitance and resistance values ​​of the reference load; and determining whether the operation of the touch detection channel is normal based on the preset reference capacitance and reference resistance values ​​and the measured capacitance and resistance values.

[0013] According to an embodiment of this disclosure, the touch detection channel is an IQ modulation / demodulation touch detection channel. Measuring the capacitance and resistance values ​​of the reference load using this touch detection channel includes: applying a first carrier signal to the reference load; modulating the first carrier signal using the capacitance and resistance values ​​of the reference load to obtain a first carrier modulation signal; and using the touch detection channel to perform IQ demodulation on the first carrier modulation signal to obtain the capacitance and resistance values ​​of the reference load.

[0014] According to an embodiment of this disclosure, measuring the capacitance and resistance values ​​of the corresponding touch detection sensor using the touch detection channel includes: applying a second carrier signal to the touch detection sensor; modulating the second carrier signal through the touch detection sensor to obtain a second carrier modulation signal; and using the touch detection channel to perform IQ demodulation on the second carrier modulation signal to obtain the capacitance and resistance values ​​of the touch detection sensor.

[0015] According to an embodiment of this disclosure, the first carrier signal and the second carrier signal have the same carrier waveform and carrier frequency.

[0016] According to an embodiment of this disclosure, the method further includes: in the event of an operational malfunction of the touch detection channel, adjusting the carrier waveform and / or carrier frequency of the first carrier signal, and applying the adjusted first carrier signal to the reference load; modulating the adjusted first carrier signal using the capacitance and resistance values ​​of the reference load to obtain an updated first carrier modulation signal; using the touch detection channel to perform IQ demodulation on the updated first carrier modulation signal to obtain the capacitance and resistance values ​​of the reference load; and determining whether the operation of the touch detection channel is normal based on the preset reference capacitance and resistance values ​​and the measured capacitance and resistance values.

[0017] According to an embodiment of this disclosure, when each touch detection area includes multiple touch detection sensors, a touch on the touch detection area is determined based on the measurement results of the multiple touch detection sensors on the touch detection area; the method further includes: when the steering wheel is divided into multiple touch detection areas, a touch operation on the steering wheel is determined based on the touch detection results of at least one of the multiple touch sensing areas.

[0018] This disclosure provides an apparatus for steering wheel touch detection, wherein the steering wheel is divided into at least one touch detection area, each touch detection area including at least one touch detection sensor. The apparatus includes: a plurality of touch detection channels, each touch detection channel having its corresponding touch detection sensor for measuring the capacitance and resistance values ​​of its corresponding touch detection sensor; and at least one reference load, wherein each touch detection channel has its corresponding reference load, the reference load being set to preset reference capacitance and reference resistance values, and each touch detection channel further measuring the capacitance and resistance values ​​of its corresponding reference load; and a processor unit configured to: for each touch detection channel, determine whether the operation of the touch detection channel is normal based on the preset reference capacitance and reference resistance values ​​of the reference load and the measured capacitance and resistance values ​​of the reference load, and, if the operation of the touch detection channel is determined to be normal, perform touch detection of the steering wheel based on the measured capacitance and resistance values ​​of the touch detection sensor.

[0019] According to an embodiment of this disclosure, the processor unit is configured to: determine that the touch detection channel is operating normally when the measured capacitance value deviates from the preset reference capacitance value within a predetermined deviation range, and the measured resistance value deviates from the preset reference resistance value within a predetermined deviation range; otherwise, determine that the touch detection channel has malfunctioned.

[0020] According to an embodiment of this disclosure, the device includes a switching device, the reference load is connected to the touch detection channel through the switching device, the switching device is disconnected during the measurement of the touch detection sensor, and the switching device is turned on during the measurement of the reference load.

[0021] According to an embodiment of this disclosure, the touch detection channel is an IQ modulation and demodulation touch detection channel, which is configured to: apply a first carrier signal to the reference load; and perform IQ demodulation on the first carrier modulation signal to obtain the capacitance and resistance values ​​of the reference load, wherein the first carrier modulation signal is obtained by modulating the first carrier signal with the capacitance and resistance values ​​of the reference load.

[0022] According to an embodiment of this disclosure, the touch detection channel is configured to: apply a second carrier signal to the touch detection sensor; and perform IQ demodulation on the second carrier modulation signal to obtain the capacitance and resistance values ​​of the touch detection sensor, wherein the second carrier modulation signal is obtained by modulating the second carrier signal through the touch detection sensor. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are merely some exemplary embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0024] Figure 1A and Figure 1B The implementation methods of the steering wheel are shown respectively;

[0025] Figure 2A A schematic diagram of the structure of a device for steering wheel touch detection according to the present disclosure is shown;

[0026] Figure 2B A schematic diagram of the structure of a device for steering wheel touch detection with an IQ modulation and demodulation touch detection channel is shown.

[0027] Figure 2C A schematic diagram of the structure of a device for steering wheel touch detection with multiple touch detection channels is shown.

[0028] Figures 3A to 3C A flowchart of a method for steering wheel touch detection according to this disclosure is shown. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this disclosure more apparent, exemplary embodiments according to this disclosure will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this disclosure, and not all embodiments of this disclosure. It should be understood that this disclosure is not limited to the exemplary embodiments described herein.

[0030] In this specification and accompanying drawings, substantially the same or similar steps and elements are indicated by the same or similar reference numerals, and repeated descriptions of these steps and elements will be omitted. Furthermore, in the description of this disclosure, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance or order.

[0031] In this specification and accompanying drawings, elements are described in singular or plural forms according to embodiments. However, the singular and plural forms have been suitably chosen for the presented cases merely for ease of explanation and are not intended to limit this disclosure. Thus, a singular form may include a plural form, and a plural form may include a singular form, unless the context clearly indicates otherwise.

[0032] Figure 1A A steering wheel is shown. This steering wheel, as a steering wheel, has a central area 102 consisting of spoke portions 1021, 1022, and 1023, and a rim portion 101. With the increasing prevalence of vehicle multimedia and ADAS (Advanced Driver Assistance Systems), more and more control functions are integrated into the central area 102 for controlling multimedia and ADAS. These control functions can be achieved by the driver operating controllers located in the central area. These controllers are typically positioned in the central area, easily accessible to the thumbs of both hands when the driver holds the steering wheel correctly. These controllers are typically designed in the form of buttons, scroll wheels, joysticks, paddle shifters, etc., meaning that the structure or operation of these controllers is designed so that the driver's thumbs can easily operate them when holding the steering wheel correctly.

[0033] In common multi-functional steering wheel layouts on the market, for example, a scroll wheel for selecting multimedia menus and buttons for making and receiving Bluetooth calls are arranged on the left spoke 1021.

[0034] On the right-hand wheel spoke 1022, there are rollers for monitoring vehicle status and controllers related to ADAS functions. ADAS functions commonly used in vehicles on the market include Intelligent Speed ​​Adaptive (ISA), Vehicular Communication Systems, Adaptive Cruise Control (ACC), Lane Departure Warning System (LDWS), Lane Keep Assist System (LKAS), Collision Avoidance or Precrash System, Night Vision System, Adaptive Light Control, Pedestrian Protection System, Automatic Parking, Traffic Sign Recognition, Blind Spot Detection, Driver Drowsiness Detection, Hill Descent Control, and Electric Vehicle Warning Sounds. Most of these systems or functions will automatically activate when the vehicle is started, but some of them need to be manually activated by the driver according to their driving needs. Therefore, on the right-hand spoke 1022, there is a MAIN button for activating some ADAS functions (such as adaptive cruise control ACC and lane keeping assist system LKAS) and a CANCEL button for deactivating them, as well as a corresponding joystick for increasing or decreasing cruise speed.

[0035] The rim portion 101 of the steering wheel is designed for comfortable grip by the driver. For the HOD (Hands-on-Demand) function, the outer surface of the rim portion 101 serves as the touch detection area 104, where a touch detection sensor 103 is arranged. The touch detection sensor 103 is typically a strip-shaped flexible capacitive sensor. This sensor can be smoothly integrated into the rim portion of the steering wheel without being limited by the shape of the rim's outer surface, such as... Figure 1AThe touch detection sensor 103 shown surrounds the entire rim portion 101 of the steering wheel. When the driver's hand touches or grips the steering wheel, it causes a change in the impedance value, i.e., the capacitance and resistance value, of the touch detection sensor 103.

[0036] In another implementation, multiple touch detection areas can be divided on the rim of the steering wheel. For example... Figure 1B As shown, the steering wheel rim is divided into three touch detection areas: the front of the rim is divided into a left touch detection area 106 and a right touch detection area 107, while the back of the rim is divided into a separate touch detection area 108. This finer division of the touch detection areas allows for more accurate detection of the driver's steering wheel control. With the aforementioned three touch detection areas, the three touch sensors can identify whether the driver is driving with their left hand, their right hand, and whether their hands are resting on the steering wheel.

[0037] In embodiments according to this disclosure, such as Figure 1A As shown, a reference load 105 is provided independently of the steering wheel. The touch detection channel used to measure the touch detection sensor 103 is also used to measure this reference load 105. The reference load 105 may have preset reference capacitance and reference resistance values. (See below for reference...) Figure 2A To explain in more detail the role of the reference load and the principle of the device for touch detection according to this disclosure.

[0038] Figure 2A A schematic diagram of a device for steering wheel touch detection according to the present disclosure is shown. In this embodiment, only one touch detection sensor and one reference load are illustrated by way of example; however, the design can be redundantly implemented in the same manner when multiple touch detection sensors and reference loads are present.

[0039] The device for steering wheel touch detection has a touch detection channel 202, which is used to measure the reactance value of the touch detection sensor 103, namely the capacitance value Csen and the resistance value Rsen, and also to measure the capacitance value Cref.m and the resistance value Rref.m of the reference load 105.

[0040] The device also includes a processor unit 201, which determines whether the operation of the touch detection channel is normal based on the preset reference capacitance value Cref.s and reference resistance value Rref.s of the reference load 105, and the measured capacitance value Cref.m and resistance value Rref.m of the reference load 105. If the operation of the touch detection channel is determined to be normal, the device performs touch detection of the steering wheel based on the measured capacitance value Csen and resistance value Rsen of the touch detection sensor.

[0041] In a specific implementation, the touch detection sensor 103 has a capacitive element. However, this capacitive element cannot be an ideal capacitor in practice; that is, it cannot only have a capacitance value, but must also have a resistance value. Therefore, in order to more accurately detect changes occurring in the touch detection sensor 103 or its capacitive element, both the capacitance value Csen and the resistance value Rsen must be considered. Thus, the impedance value of the touch detection sensor 103 depends on the capacitance value Cref.m and the resistance value Rref.m of its capacitive element, as well as the frequency of the voltage applied to the capacitive element.

[0042] Accordingly, the reference load 103 must also have capacitance and resistance values. The processor unit 201 can preset these as reference capacitance value Cref.s and reference resistance value Rref.s to detect whether the touch detection channel 202 is operating normally. Furthermore, the processor unit 201 can also adjust the reference capacitance value Cref.s and reference resistance value Rref.s of the reference load 105. To ensure the correctness and reliability of the verification, and to eliminate the influence of environmental and circuit faults on the reference load, the reference capacitance value Cref.s and reference resistance value Rref.s of the reference load need to be non-constant, i.e., variable. This is because for a fixed reference load, the reference capacitance and reference resistance values ​​of the reference load 103 will gradually change due to temperature and aging as the environment changes. Furthermore, if the processor unit 201 still compares with the previously recorded reference capacitance / resistance values, an incorrect judgment will inevitably occur. In a specific implementation, the reference capacitance value Cref.s and the reference resistance value Rref.s of the reference load can be changed before each measurement of the impedance value of the touch detection sensor 103, or they can be randomly set within a specified range.

[0043] According to embodiments of this disclosure, the touch detection channel 202 is an IQ modulation / demodulation touch detection channel, such as... Figure 2B As shown, processor unit 201 applies a first carrier signal, such as a sinusoidal signal, to reference load 105 via transceiver 2011 and touch detection channel 202; the capacitance value Cref.m and resistance value Rref.m of reference load 105 modulate the first carrier signal to obtain a first carrier modulated signal; the transceiver receives the first carrier modulated signal and forwards it to IQ demodulator 2012. By demodulating the received first carrier modulated signal, the I and Q components, i.e., the capacitance value Cref.m and resistance value Rref.m of reference load 105, can be obtained, and then transmitted to another device or processor via output interface 2013 to determine whether the operation of the touch detection channel is normal.

[0044] Similarly, processor unit 201 applies a second carrier signal, such as a sinusoidal signal, to touch detection sensor 103 via transceiver 2011 through touch detection channel 202; due to the driver's hand touching or gripping the steering wheel, the current capacitance value of touch detection sensor 103 is Csen and the resistance value is Rsen. The capacitance value Csen and resistance value Rsen of touch detection sensor 103 modulate the second carrier signal to obtain a second carrier modulated signal; the transceiver receives this second carrier modulated signal and forwards it to IQ demodulator 2012. By demodulating the received second carrier modulated signal, the I and Q components, the capacitance value Csen and resistance value Rsen of touch detection sensor 103 can be obtained, and then transmitted through output interface 2013 to another device or processor to determine whether the driver is gripping the steering wheel.

[0045] Since the measurement results of the touch detection channel 202 depend not only on the capacitance and resistance values ​​of the touch detection sensor 103 or the reference load 105, but also on the frequency of the first or second carrier signal, and the carrier signal may be interfered with by other electromagnetic waves in the environment, in order to more reliably detect whether the touch detection channel 202 is operating normally, especially whether it can work properly when actually detecting the touch detection sensor 103, preferably, the first carrier signal and the second carrier signal are the same, that is, they have the same carrier waveform and carrier frequency. Therefore, the capacitance value Cref.m and resistance value Rref.m of the reference load 105 and the capacitance value Csen and resistance value Rsen of the touch detection sensor 103 modulate the same carrier signal. Thus, the process of detecting the touch detection sensor 103 using the touch detection channel 202 is completely simulated during the detection of the reference load 105, thereby further ensuring the reliability of verifying the normal operation of the device through the reference load.

[0046] In a specific implementation, in the AS8579 processor chip mentioned above, the processor's transmitter provides a sinusoidal voltage signal as a carrier signal to the reference load 105 or the touch detection sensor 103. The capacitance value Cref.m and resistance value Rref.m of the reference load 105 directly cause changes in the sinusoidal voltage signal, i.e., the capacitance value Cref.m and resistance value Rref.m modulate the sinusoidal voltage signal. Additionally, for the touch detection sensor 103, when a person's hand approaches or applies pressure to the touch detection sensor 103, the impedance value of the touch detection sensor 103 itself changes, i.e., new capacitance values ​​Csen and resistance values ​​Rsen are generated. These new capacitance values ​​Csen and resistance values ​​Rsen also modulate the sinusoidal voltage signal. The voltage signal is converted into a current signal through the capacitance and resistance. This current signal is received by the receiver of the processor unit and demodulated into in-phase (I) and quadrature (Q) components. After filtering and offset compensation of the I / Q signals, the measured value is converted into a digital value by the processor for further processing.

[0047] During the measurement of the reference load 105 and the touch detection sensor 103 using the touch detection channel 202, the touch detection channel 202 needs to switch between these two measurement processes. In one embodiment, the touch detection channel 202 can be connected to the reference load 105 and the touch detection sensor 103 via a switching device. When measuring the reference load 105, the switching device turns on the reference load and disconnects the touch detection sensor 103; when measuring the touch detection sensor 103, the switching device turns on the touch detection sensor 103 and disconnects the reference load 105. In another embodiment, the processor unit 201 can simultaneously apply the same carrier signal to the reference load 105 and the touch detection sensor 103 and receive the modulated signal using the touch detection channel 202 in a time-division multiplexing or frequency-division multiplexing manner. The processor unit can then process the signal from the reference load 105 and the signal from the touch detection sensor 103 separately.

[0048] Figure 2C A schematic diagram of a device for steering wheel touch detection with multiple touch detection channels is shown. When the steering wheel is divided into multiple touch detection zones, a touch operation on the steering wheel can be determined based on the touch detection result of at least one of the multiple touch sensing zones, for example, as... Figure 1B As shown, the steering wheel is divided into three touch detection zones. For each touch detection zone, the following steps are implemented: Figure 2AThe touch detection channels shown are touch detection channels 2021, 2022, and 2023. Each touch detection channel is equipped with a touch detection sensor 103 and a reference load 105, with each reference load set to preset reference capacitance and resistance values. Each touch detection channel is used to measure both the capacitance and resistance values ​​of its corresponding touch detection sensor and its corresponding reference load. For each touch detection channel 2021, 2022, and 2023, the processor unit 201 can determine whether the operation of the corresponding touch detection channel is normal based on the preset reference capacitance and resistance values ​​of the corresponding reference load, as well as the measured capacitance and resistance values ​​of the reference load. If the operation of the corresponding touch detection channel is determined to be normal, touch detection of the steering wheel is performed based on the measured capacitance and resistance values ​​of the touch detection sensor. This allows for the determination of whether the driver's hand is located in the corresponding touch detection area, thus enabling a more accurate assessment of the driver's posture relative to the steering wheel.

[0049] Figure 3A A flowchart of a method for steering wheel touch detection according to this disclosure is shown. For each touch detection channel, as already referred to... Figure 2A To explain, processor unit 201 first executes method step S100, which sets the reference load 105 to a preset reference capacitance value Cref.s and a reference resistance value Rref.s. As mentioned earlier, the required reference capacitance value Cref.s and reference resistance value Rref.s of the reference load are non-constant values. Therefore, for example, each time method step S100 is executed, the reference capacitance value Cref.s and reference resistance value Rref.s can be preset to be different from the previously set reference capacitance value Cref.s and reference resistance value Rref.s. Alternatively, the reference capacitance value Cref.s and reference resistance value Rref.s can be preset randomly within a specified range of variation. The specified range of variation depends on the impedance detection range obtained by processor unit 201 in cooperation with touch detection sensor 103, which is also the typical impedance change range caused by the driver's hand on touch detection sensor 103. Taking processor unit AS8579 as an example, it can sense a capacitance value variation range of 20-2000pF. In this case, the reference capacitance value Cref.s can be set to any value within the range of 20-2000pF.

[0050] After the preset is completed, method step S200 is executed, in which the touch detection channel 202 measures the reference load 105 to obtain the capacitance value Cref.m and the resistance value Rref.m. Specifically, the processor unit 201 transmits a sinusoidal voltage as a carrier signal to the reference load 105. The capacitance value Cref.m and the resistance value Rref.m of the reference load 105 directly cause changes in the sinusoidal voltage signal to generate a current signal, that is, the sinusoidal voltage signal is modulated. The current signal is received by the receiver of the processor unit and demodulated into in-phase (I) and quadrature (Q) components. After filtering and offset compensation of the I / Q signal, the processor unit obtains the capacitance value Cref.m and the resistance value Rref.m at the current time point.

[0051] Then, the processor unit 201 executes method step S300, determining whether the operation of the touch detection channel 202 is normal based on the preset reference capacitance value Cref.s and reference resistance value Rref.s, and the measured capacitance value Cref.m and resistance value Rref.m. In one embodiment, the preset reference capacitance value Cref.s / reference resistance value Rref.s can be subtracted from the measured capacitance value Cref.m / resistance value Rref.m respectively. If the difference is zero or within a predetermined deviation range, the reference capacitance value Cref.s / reference resistance value Rref.s is considered equal to the measured capacitance value Cref.m / resistance value Rref.m, thereby determining that the touch detection channel is working normally. Conversely, if one of the differences exceeds the predetermined deviation range, a fault is determined to exist in the entire touch detection channel. Alternatively, the percentage change of the measured capacitance value Cref.m / resistance value Rref.m relative to the preset reference capacitance value Cref.s / resistance value Rref.s can be calculated separately, i.e., (Cref.m-Cref.s) / Cref.s and (Rref.m-Rref.s) / Rref.s. In another embodiment, the ratio of the preset reference capacitance value Cref.s / reference resistance value Rref.s to the measured capacitance value Cref.m / resistance value Rref.m can also be calculated. If the ratio is equal to or within a predetermined deviation range, the reference capacitance value Cref.s / reference resistance value Rref.s is considered equal to the measured capacitance value Cref.m / resistance value Rref.m, thereby determining that the touch detection channel is working normally. Conversely, if either of the ratios exceeds the predetermined deviation range, a fault is determined to exist in the entire touch detection channel.

[0052] If the touch detection channel is working normally, i.e., the judgment result is "yes", the measurement of the touch detection sensor is performed, i.e., step S400. At this time, similar to step S200, the transmitter of the processor unit 201 transmits a sinusoidal voltage as a carrier signal to the touch detection sensor 103. The current capacitance and resistance values ​​on the touch sensor cause changes in the sinusoidal voltage signal and generate a current signal, i.e., the sinusoidal voltage signal is modulated. This current signal is also received by the receiver of the processor unit and demodulated into in-phase (I) and quadrature (Q) components. After filtering and offset compensation of the I / Q signal, the processor unit obtains the capacitance value Csen and resistance value Rsen of the touch detection sensor at the current time point.

[0053] In one embodiment, the processor unit 201 can determine whether the driver is holding the steering wheel based on the capacitance value Csen and resistance value Rsen of the touch detection sensor measured at different times. For example, when a person's hand is close to or grips the steering wheel, the parasitic capacitance of the human body will couple to the capacitive element of the touch detection sensor, causing the capacitance value of the capacitive element of the touch detection sensor to increase, that is, the impedance value of the touch detection sensor 103 changes. This new capacitance value Csen and resistance value Rsen causes a change in the sinusoidal voltage signal and generates a current signal, i.e., the sinusoidal voltage signal is modulated. This current signal is also received by the receiver of the processor unit and demodulated into in-phase (I) and quadrature (Q) components. After filtering and offset compensation of the I / Q signals, the processor unit obtains the capacitance value Csen and resistance value Rsen of the touch detection sensor at the current time point. In this case, for example, the capacitance value of the touch detection sensor measured at time t1 is Csen1 and the resistance value is Rsen1, while the capacitance value measured at a slightly later time t2 is Csen2 and the resistance value is Rsen2. Typically, the change in resistance value is small. When the capacitance value Csen2 at time t2 is greater than Csen1, it is determined that the driver's hand has changed from being off the steering wheel to being on the steering wheel. Conversely, if the capacitance value Csen2 is less than Csen1, it is determined that the driver's hand has left the steering wheel.

[0054] In another embodiment, the processor unit 201 can determine whether the driver is holding the steering wheel based on the capacitance value Csen and resistance value Rsen of the touch detection sensor measured multiple times over a period of time. For example, after the measured capacitance value first increases, the touch detection sensor can be measured multiple times at a specific frequency over a period of 5s, 10s, 30s, or longer. If the measured capacitance value is substantially the same each time, it is determined that the driver's hand is indeed holding the steering wheel. This avoids the processor incorrectly determining that the driver is holding the steering wheel due to the driver's intentional or unintentional touches on the steering wheel.

[0055] If, according to step S300 described above, it is determined that the touch detection channel 202 is not working properly, then Figure 3A The process then proceeds to step S500. Step S500 can be referred to as the fault handling step. In the simplest implementation, step S500 can directly issue a fault indication, such as prompting the driver via a warning light or in-vehicle screen, to remind the driver that the touch detection channel 202 needs to be inspected or repaired.

[0056] However, while the touch detection channel 202 itself may function normally, due to certain special reasons, the measured capacitance value Cref.m or resistance value Rref.m determined in step S300 may deviate significantly from the preset capacitance value Cref.s or resistance value Rref.s. To further ensure the reliability of the inspection of the touch detection channel 202, the inspection process needs to be adjusted to minimize the interference from these special reasons.

[0057] In one scenario, the impedance of the reference load 105 may suddenly change due to environmental influences, causing a deviation from the reference capacitance and resistance values ​​preset by the processor unit 201. When the deviation exceeds a predetermined range, a malfunction of the touch detection channel 202 is determined in step S300. In another scenario, when the processor unit 201 presets the reference capacitance and resistance values ​​of the reference load 105, the preset process fails due to a short circuit or open circuit in the peripheral circuitry of the reference load 105, resulting in the reference capacitance and resistance values ​​of the reference load 105 remaining at the previously set values. In this case, the subsequently measured reference capacitance and resistance values ​​will also deviate from the preset reference capacitance and resistance values ​​beyond a predetermined range.

[0058] In an advantageous embodiment of the method according to this disclosure, for the two possible scenarios described above, in Figure 3A The flowchart for the method of steering wheel touch detection shown has an additional step S501 added, such as... Figure 3BAs shown. When a malfunction is detected in the touch detection channel 202 in method step S300, the preset reference capacitance and reference resistance values ​​of the reference load 105 are adjusted in method step S501, i.e., their values ​​are changed. The new reference capacitance and reference resistance values ​​can be randomly selected within the detection range obtained by the processor unit 201 in cooperation with the touch detection sensor 103. After completing method step S501, method step S200 is re-executed, i.e., the adjusted capacitance and resistance values ​​of the reference load are measured using the touch detection channel 202. In method step S300, the processor unit 201, based on the adjusted preset reference capacitance and reference resistance values ​​and the measured capacitance and resistance values, re-determines whether the operation of the touch detection channel is normal.

[0059] If it is determined in step S300 that the touch detection channel 202 is working normally, i.e., the interference caused by the special reasons mentioned above has been eliminated, then step S400 can be continued to measure the impedance of the touch detection sensor 103. If it is still determined in step S300 that the touch detection channel 202 is faulty, then the touch detection channel is confirmed to be faulty, and a fault indication can be issued in step S502, for example, by prompting the driver through a warning light or vehicle screen to remind the driver to check or repair the touch detection channel 202.

[0060] In another implementation, step S501 can be repeated multiple times, with a condition for exiting the loop added. By redundantly performing step S501, interference from the aforementioned special reasons on determining whether the touch detection channel 202 is operating normally can be eliminated to the greatest extent. Advantageously, the exit condition can be the number of times step S501 has been executed, i. For example, when i equals 3, 5, or 10, step S501 is no longer executed, the loop is exited, and a fault indication is issued in S502.

[0061] Besides unexpected changes in the reference capacitance and resistance values ​​of the reference load 105 itself causing malfunctions in the touch detection channel 202, interference with the carrier signal can also lead to such malfunctions. As mentioned earlier, steering wheels now integrate more and more control functions for multimedia and ADAS control. To implement these control functions, a large number of chips and corresponding circuits are installed on the steering wheel, and data is transmitted between these chips. In addition, electric vehicles also have electric drive systems, and the high voltage and high current transients during the switching of high-power semiconductor switching devices can cause strong electromagnetic interference. This makes the electromagnetic environment in the steering wheel complex, so the carrier signal sent by the processor unit 201 through the touch detection channel 202 and the received carrier modulation signal may also be affected by electromagnetic interference, resulting in distortion of the carrier signal or carrier modulation signal, ultimately causing changes in the capacitance and resistance values ​​demodulated by IQ. When the touch detection channel 202 detects the reference load 105, electromagnetic interference can cause the demodulated capacitance and resistance values ​​of the reference load 105 to deviate from a predetermined range relative to the capacitance value preset by the processor unit 201. In this case, the touch detection channel 202 may be incorrectly determined to be faulty in method step S300.

[0062] In order to minimize the impact of electromagnetic interference, Figure 3A The flowchart for the method of steering wheel touch detection shown is based on the previous one, with the addition of an additional step S503. The improved method flowchart is as follows: Figure 3C As shown. If an operational malfunction of the touch detection channel 202 is determined in method step S300, in method step S503, the carrier waveform and / or carrier frequency of the first carrier signal are adjusted. The carrier signal typically used can be a sine wave, a rectangular wave, or a sawtooth wave. In method step S503, for example, the carrier signal can be transformed from a sine wave to a rectangular wave or a sawtooth wave. Furthermore, in method step S503, the frequency of the first carrier signal can be changed within the operating frequency range of the transmitter and receiver of the processor unit 201, for example, from 45 to 125 kHz. Preferably, in method step S503, both the waveform and frequency of the first carrier signal can be changed, thereby minimizing the impact of current electromagnetic interference.

[0063] Then, method step S200 is performed again, whereby the touch detection channel 202 applies an adjusted first carrier signal to the reference load. The capacitance and resistance values ​​of the reference load are used to modulate the adjusted first carrier signal to obtain an updated first carrier modulation signal. Then, the processor unit 201 performs IQ demodulation on the updated first carrier modulation signal to finally obtain the capacitance and resistance values ​​of the reference load. Then, in method step S300, the processor unit 201 determines whether the operation of the touch detection channel is normal based on preset reference capacitance and resistance values ​​and the measured capacitance and resistance values. If the determination result indicates that the operation is normal, step S400 can be continued to measure the impedance of the touch detection sensor 103. If it is still determined in method step S300 that the touch detection channel 202 is faulty, then a fault indication can be issued in step S504, for example, by prompting the driver through a warning light or vehicle screen to remind the driver to check or repair the touch detection channel 202.

[0064] In another implementation, similar to step S501, step S503 can be repeated multiple times, with a condition for exiting the loop added. Redundantly performing step S503 minimizes interference that might be caused by electromagnetic interference affecting the determination of whether the touch detection channel 202 is operating normally. The condition for exiting the loop can be the number of times the first carrier signal is changed. If only the carrier waveform is changed, the condition can be changing the first carrier signal 1, 2, or 3 times. If the carrier frequency is changed, or both are changed simultaneously, the condition can be changing the first carrier signal 4 or more times. When the condition for exiting the loop is met, step S503 is no longer executed, the loop is exited, and a fault indication is issued in S504.

[0065] In a preferred embodiment, method steps S501 and S503 can be implemented in parallel. Specifically, for example, method step S501 is executed one or more times first, that is, the preset reference capacitance and reference resistance values ​​of the reference load 105 are adjusted one or more times. If, after one or more executions of method step S501, it is consistently determined in method step S300 that the touch detection channel 202 is faulty, then after the corresponding loop exit condition is met, method step S503 is executed, that is, the carrier waveform and / or carrier frequency of the first carrier signal is adjusted. If, after one or more executions of step S503, it is consistently determined in method step S300 that the touch detection channel 202 is faulty, then after the corresponding loop exit condition is met, a fault indication is issued. Conversely, if, in any of the above loops, it is determined in method step S300 that the touch detection channel 202 is operating normally, then method step S400 can continue to be executed, that is, the touch detection sensor 103 is measured.

[0066] Alternatively, method steps S501 and S503 can be implemented sequentially. In one loop, both the preset reference capacitance and reference resistance values ​​of the reference load 105 are adjusted, as are the carrier waveform and / or carrier frequency of the first carrier signal. If a fault is determined in method step S300 in the touch detection channel 202, the loop is repeated until the corresponding loop exit condition is met, and then a fault indication is issued.

[0067] In an advantageous embodiment, multiple touch detection sensors can be provided in the touch detection area. This allows for the setting of a corresponding reference load for each touch detection sensor, and the execution of functions such as... can be performed for each reference load. Figures 3A-3C The method steps S100 to S300, and possible method steps S501 and S502, are shown to check whether the corresponding touch detection channel is operating normally. When at least one of the multiple touch detection channels is determined to be operating normally, the touch detection sensor of the corresponding touch detection channel can be detected to determine whether the driver's hand is located in the touch detection area. By setting multiple touch detection sensors in the touch detection area, even if individual touch detection sensors or their corresponding touch detection channels fail, the remaining touch detection sensors can still detect whether the driver's hand is located in the touch detection area, thereby further improving the reliability of the HOD.

[0068] The exemplary embodiments of this disclosure described in detail above are merely illustrative and not restrictive. Those skilled in the art will understand that various modifications and combinations of these embodiments or their features can be made without departing from the principles and spirit of this disclosure, and such modifications should fall within the scope of this disclosure.

Claims

1. A method for steering wheel touch detection, wherein the steering wheel is divided into at least one touch detection area, each touch detection area includes at least one touch detection sensor, and each touch detection sensor has its corresponding touch detection channel, said touch detection channel being an IQ modulation / demodulation touch detection channel, the method comprising: For each of the touch detection channels Set the reference load used for detection by the touch detection channel to a preset reference capacitance and reference resistance value; Using this touch detection channel, the capacitance and resistance values ​​of the reference load are measured; Based on the preset reference capacitance and resistance values, as well as the measured capacitance and resistance values, determine whether the operation of the touch detection channel is normal; as well as If the touch detection channel is confirmed to be operating normally, the capacitance and resistance values ​​of the corresponding touch detection sensor are measured using the touch detection channel, and the touch detection of the steering wheel is performed based on the measured capacitance and resistance values ​​of the touch detection sensor.

2. The method according to claim 1, wherein, For each touch detection channel, the corresponding preset reference capacitance value and reference resistance value are non-constant values.

3. The method according to claim 1, wherein, Using this touch detection channel, the capacitance and resistance values ​​of the reference load are measured, including: A first carrier signal is applied to the reference load; The first carrier signal is modulated using the capacitance and resistance values ​​of the reference load to obtain a first carrier modulated signal; and Using this touch detection channel, the first carrier modulation signal is IQ demodulated to obtain the capacitance and resistance values ​​of the reference load.

4. The method according to claim 3, wherein, The capacitance and resistance values ​​of the corresponding touch detection sensor are measured using this touch detection channel, including: A second carrier signal is applied to the touch detection sensor; The touch detection sensor modulates the second carrier signal to obtain a second carrier modulated signal; and Using this touch detection channel, the second carrier modulation signal is IQ demodulated to obtain the capacitance and resistance values ​​of the touch detection sensor.

5. The method according to claim 3, wherein, Based on the preset capacitance and resistance values, as well as the measured capacitance and resistance values, it is determined whether the operation of the touch detection channel is normal, including: when the measured capacitance value deviates from the preset reference capacitance value within a predetermined deviation range, and the measured resistance value deviates from the preset reference resistance value within a predetermined deviation range, the touch detection channel is determined to be operating normally; otherwise, the touch detection channel is determined to be faulty.

6. The method according to claim 4, wherein, The first carrier signal and the second carrier signal have the same carrier waveform and carrier frequency.

7. The method according to claim 5, further comprising: If a malfunction is determined in the touch detection channel, the preset reference capacitance and reference resistance values ​​of the reference load are adjusted. Using this touch detection channel, the capacitance and resistance values ​​of the adjusted reference load are measured; as well as Based on the preset reference capacitance and resistance values, as well as the measured capacitance and resistance values, it is determined whether the operation of the touch detection channel is normal.

8. The method according to claim 5 or 7, further comprising: If an operational malfunction is determined in the touch detection channel, the carrier waveform and / or carrier frequency of the first carrier signal are adjusted. An adjusted first carrier signal is applied to the reference load; The adjusted first carrier signal is modulated using the capacitance and resistance values ​​of the reference load to obtain an updated first carrier modulated signal. Using this touch detection channel, the updated first carrier modulation signal is IQ demodulated to obtain the capacitance and resistance values ​​of the reference load; as well as Based on the preset reference capacitance and resistance values, as well as the measured capacitance and resistance values, it is determined whether the operation of the touch detection channel is normal.

9. The method according to claim 4, wherein, The reference load is connected to the touch detection channel via a switching device. The switching device is disconnected during the measurement of the touch detection sensor and connected during the measurement of the reference load.

10. The method according to claim 1, wherein, In cases where each touch detection area includes multiple touch detection sensors, the touch on the touch detection area is determined based on the measurement results of the multiple touch detection sensors on that touch detection area; The method further includes: When the steering wheel is divided into multiple touch detection zones, a touch operation on the steering wheel is determined based on the touch detection result of at least one of the multiple touch detection zones.

11. An apparatus for steering wheel touch detection, wherein the steering wheel is divided into at least one touch detection area, each touch detection area including at least one touch detection sensor, the apparatus comprising: Multiple touch detection channels, each with its corresponding touch detection sensor, are used to measure the capacitance and resistance values ​​of the corresponding touch detection sensor. The touch detection channel is an IQ modulation and demodulation touch detection channel. as well as At least one reference load, wherein, Each touch detection channel has its corresponding reference load, which is set to a preset reference capacitance value and reference resistance value, and each touch detection channel is also used to measure the capacitance value and resistance value of its corresponding reference load. The processor unit is configured as follows: For each touch detection channel, based on the preset reference capacitance and resistance values ​​of the reference load, and the measured capacitance and resistance values ​​of the reference load, it is determined whether the operation of the touch detection channel is normal. If the touch detection channel is confirmed to be operating normally, touch detection of the steering wheel is performed based on the measured capacitance and resistance values ​​of the touch detection sensor.

12. The apparatus according to claim 11, wherein, The touch detection channel is configured to: apply a first carrier signal to the reference load; and perform IQ demodulation on the first carrier modulation signal to obtain the capacitance and resistance values ​​of the reference load, wherein the first carrier modulation signal is obtained by modulating the first carrier signal with the capacitance and resistance values ​​of the reference load.

13. The apparatus according to claim 12, wherein, The touch detection channel is configured to: apply a second carrier signal to the touch detection sensor; and perform IQ demodulation on the second carrier modulation signal to obtain the capacitance and resistance values ​​of the touch detection sensor, wherein the second carrier modulation signal is obtained by the touch detection sensor modulating the second carrier signal.

14. The apparatus according to claim 12, wherein, The processor unit is configured to determine that the touch detection channel is operating normally when the measured capacitance value deviates from the preset reference capacitance value within a predetermined deviation range and the measured resistance value deviates from the preset reference resistance value within a predetermined deviation range; otherwise, it is determined that the touch detection channel has malfunctioned.

15. The apparatus according to claim 11, wherein, The device has a switching device, and the reference load is connected to the touch detection channel through the switching device. The switching device is disconnected during the measurement of the touch detection sensor and connected during the measurement of the reference load.

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