Contact detection method and contact detection device

Abstract

Provided is a contact determination method for determining contact of a driver with a steering wheel, on the basis on an electric signal detected from a sheet-like electrode part that is formed by stacking a first electrode and a second electrode in layers with an insulator interposed therebetween, and is installed to cover an outer peripheral part of the steering wheel. This contact determination method comprises a detection step for detecting capacitance and impedance generated at the electrode part, and a determination step for determining, on the basis of the capacitance and impedance detected in the detection step, whether or not a hand of the driver has contacted the steering wheel, and whether or not the electrode part is abnormal. In the determination step, when the capacitance exceeds a first threshold, and the impedance is lower than a second threshold, the electrode part is determined to be abnormal.

Description

[Technical Field]

[0001] The present invention relates to a contact determination method and a contact determination device for determining whether a driver has contacted a steering wheel. [Background technology]

[0002] WO2021 / 095478 discloses a technology in which two electrodes are provided on the outer periphery of a steering wheel, stacked with an insulator between them, to determine whether the driver is touching the steering wheel.

[0003] Generally, steering wheels are often not flat but have complex surfaces. Therefore, when attaching the sheet-shaped electrodes and insulators to the steering wheel, it is necessary to use a jig or other tool to attach them according to the steering wheel's complex surface. However, if the electrodes are defective or damaged during the installation process, there is a risk that part of the electrode will be severed. In such a state, the electrodes will be in an abnormal state and proper contact detection will not be possible.

[0004] An object of the present invention is to more reliably determine an abnormal state of an electrode portion when determining whether the driver has come into contact with the steering wheel.

[0005] One aspect of the present invention is a contact determination method in which a sheet-like electrode unit, formed by stacking a first electrode and a second electrode with an insulator sandwiched between them, is provided to cover the outer periphery of a steering wheel, and a contact determination is made based on an electrical signal detected from the electrode unit. This contact determination method includes a detection step of detecting capacitance and impedance generated in the electrode unit, and a determination step of determining whether the driver's hand has touched the steering wheel and whether the electrode unit is abnormal, based on the capacitance and impedance detected in the detection step. In the determination step, if the capacitance exceeds a first threshold and the impedance is below a second threshold, it is determined that the electrode unit is abnormal. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a diagram showing a simplified configuration example of a collision determination device. [Figure 2] FIG. 2 is a diagram showing an example in which a part of the second electrode is cut off. [Figure 3] FIG. 3 is a diagram showing an example of contact determination as a comparative example. [Figure 4] FIG. 4 is a diagram illustrating an example of a determination process for determining contact based on the capacitance and impedance generated in the electrode portion. [Figure 5] FIG. 5 is a flowchart showing an example of a contact determination process in the contact determination device. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0008] [Configuration example of a contact detection device] 1 is a simplified diagram showing an example of the configuration of a contact determination device 1. The contact determination device 1 is a device installed in a vehicle, and determines whether or not the hands H1, H2 of a vehicle driver are in contact with a steering wheel 10. The steering wheel 10 is installed in front of a seat (driver's seat) in which the driver sits.

[0009] The contact determination device 1 includes a sheet-like electrode unit 20 installed on the steering wheel 10, and an ECU (Electronic Control Unit) 30. The electrode unit 20 functions as a so-called touch sensor, and is a sheet-like electrode unit configured by stacking a first electrode 21 and a second electrode 22 with an insulator 23 sandwiched therebetween. The first electrode 21 can also be called an active shield electrode, and the second electrode 22 can also be called a sensor electrode. The touch sensor realized by the electrode unit 20 is, for example, a capacitance-type touch sensor.

[0010] Here, the steering wheel 10 is an operating member that includes a metal core 11 that forms the framework of the steering wheel 10, and is used by a driver of a vehicle when steering the vehicle. The roughly annular grip portion of the steering wheel 10 is the portion that the driver grips with his or her hand, and the periphery of the core 11 is covered with a base. An insulating material is used as the base. For example, a resin material such as urethane is used as the base.

[0011] The first electrode 21 is a sheet-like electrode electrically connected to the ECU 30 via a signal line S1. The second electrode 22 is a sheet-like electrode electrically connected to the ECU 30 via a signal line S2. The insulator 23 is an elastic sheet-like insulator, for example, an insulating sheet.

[0012] An electrode unit 20 is attached to the outer periphery of a base constituting the grip portion of the steering wheel 10 so as to cover the base in the circumferential direction of the steering wheel 10. A first electrode 21 is arranged on the inner periphery of the steering wheel 10, and a second electrode 22 is arranged on the outer periphery of the steering wheel 10. While FIG. 1 shows an example in which the electrode unit 20 is provided on the entire circumferential portion of the steering wheel 10, the electrode unit 20 may be provided on only a portion of the circumferential direction of the steering wheel 10. An exterior portion is attached to the outer periphery of the electrode unit 20 as a contact portion that is gripped by the driver's hand. This exterior portion is preferably made of insulating leather, resin, or the like. In this way, the electrode unit 20 is arranged between the base and the exterior portion in the grip portion of the steering wheel 10. In other words, the electrode unit 20 is covered by the exterior portion.

[0013] The ECU 30 controls each part based on various programs stored in a storage unit (not shown), and includes a detection unit 31 and a determination unit 32. The ECU 30 is realized by, for example, a processing device such as a CPU (Central Processing Unit). The storage unit also stores various pieces of information (for example, control programs, various detected values) required for the ECU 30 to perform various processes. The storage unit may be, for example, a read-only memory (ROM), a random access memory (RAM), a hard disk drive (HDD), a solid state drive (SSD), or a combination thereof.

[0014] The detection unit 31 is connected to the first electrode 21 via signal line S1 and to the second electrode 22 via signal line S2. It detects the capacitance and impedance occurring across the first electrode 21 and the second electrode 22 and outputs the detection results to the determination unit 32. For example, the detection unit 31 supplies an AC signal to the electrode unit 20 and detects the capacitance and impedance occurring across the first electrode 21 and the second electrode 22 based on a response signal acquired in response to the AC current. Note that known measurement methods can be used to measure the capacitance and impedance. For example, an AC signal can be applied to the electrode unit 20, and impedance can be detected based on the signal ratio (current / voltage) acquired from the measurement results obtained by simultaneously measuring the voltage and current. For example, an absolute self-capacitance electrostatic IC can be used as the detection unit 31. This electrostatic IC can simultaneously measure sensor inputs from multiple zones and has a sinusoidal sensor drive waveform. This electrostatic IC drives the shield electrode (first electrode 21) and compares the drive waveform with the input waveform from the sensor electrode (second electrode 22). The electrostatic IC then digitally converts the compared differential waveform, demodulates it with the sine and cosine components of the drive frequency, and integrates it to calculate a detection value. Of these detection values, the impedance is calculated based on the calculation result of the sine component, and the capacitance is calculated based on the calculation result of the cosine component. In this way, the detection unit 31 outputs a sine wave to the electrode unit 20, and can detect the capacitance and impedance based on the difference in phase and amplitude between the sine wave and the response wave.

[0015] Furthermore, for example, when the driver's hand touches or approaches the steering wheel 10, the driver's hand approaches the second electrode 22, causing a change in the capacitance Crg of the second electrode 22. The capacitance Crg of the second electrode 22 can be detected by a capacitance method such as a self-capacitance method or a mutual capacitance method. That is, the detection unit 31 can detect the capacitance generated in the second electrode 22 in response to the driver's contact with the steering wheel 10 by a capacitance method such as a self-capacitance method or a mutual capacitance method.

[0016] [Example of electrode failure] 2A and 2B are diagrams showing an example in which a portion of the second electrode 22 is cut. Fig. 2A shows a simplified view of a position 25 in the steering wheel 10 where a portion of the second electrode 22 is cut. Note that Fig. 2A omits some of the components of the contact determination device 1 shown in Fig. 1. For ease of explanation, Fig. 2B schematically shows the relationship between the first electrode 21, the second electrode 22, and the ECU 30.

[0017] Here, the process of attaching the electrode unit 20 to the steering wheel 10 will be described. Here, an example is shown in which conductive cloth, which is a cloth woven into a mesh structure and metal-plated, is used as the sheet-like first electrode 21 and second electrode 22. This conductive cloth is flexible and extensible, but it is also possible that the metal plating may peel off or the mesh of the conductive cloth may easily widen.

[0018] For example, when installing the sheet-shaped electrode 20 on the steering wheel 10, it is necessary to wrap the sheet-shaped electrode 20 around the steering wheel 10 using a jig such as a punching rod. However, because the steering wheel 10 does not have a flat surface, the sheet-shaped electrode 20 must be wrapped around a complex surface. During this installation, it is possible that the conductive cloth may stretch, or that excessive pressure on the stretched conductive cloth with the punching rod may further damage the conductive cloth. It is also possible that the electrode on the conductive cloth may be defective, such as having a defect. If the electrode is defective or damaged during installation, a portion of the electrode may be severed. In this state, after the leather wrapping process of wrapping the exterior part around the sheet-shaped electrode 20, gripping the exterior part with a screwdriver may cause the conductive cloth to stretch and expand, further widening the cut portion of the electrode. If the cut portion of the electrode further widens, the resistance value of the cut portion will increase.

[0019] For example, as shown in Fig. 2(A), assume that a portion of the second electrode 22 is cut at position 25 on the steering wheel 10. For ease of explanation, Fig. 2(B) schematically shows a case in which the sheet-like first electrode 21 and second electrode 22 are parallel to each other. Such a cut portion is sometimes referred to as a plating crack.

[0020] For example, even if a portion of the second electrode 22 is cut at position 25 shown in FIG. 2A, the electrodes are electrically connected if they are in contact with each other at the cut portion. This connected state can also be called pseudo-contact. In this way, when the cut portion at position 25 is electrically connected, both the capacitance and resistance between the first electrode 21 and the second electrode 22 often have normal values.

[0021] However, when the driver grips the cut portions of the steering wheel 10 via the exterior, the load causes slight deformation, causing the cut portions to separate slightly. In this case, the electrical resistance between the cut portions increases, making it difficult for current to flow, and the resistance of the cut portions of the second electrode 22 increases abnormally.

[0022] Furthermore, if the distance between the cut portions becomes too great, the cut portions will also be completely disconnected electrically, resulting in a loss of area of second electrode 22 beyond the cut portion indicated by position 25, and therefore a decrease in capacitance in accordance with the decrease in area. Note that in FIG. 2(B), the range of area of second electrode 22 beyond the cut portion indicated by position 25 is indicated by R1. In this way, if the cut portion of second electrode 22 also becomes disconnected electrically, the resistance value at the cut portion will increase, but the capacitance will decrease.

[0023] [Example of collision detection as a comparative example] 3 is a diagram showing a comparative example of contact determination, specifically showing an example of the relationship between the capacitance generated in the electrode unit 20 and the determination value ΔAD used to determine whether the driver has contacted the steering wheel 10.

[0024] Fig. 3(A) shows an example where the electrode unit 20 is in a normal state, i.e., where there is no abnormality in the electrode unit 20, and Fig. 3(B) shows an example where the electrode unit 20 is in a disconnected state, i.e., where there is an abnormality in the electrode unit 20. Note that Fig. 3(B) shows an example where position 25 is the disconnected portion, similar to the example shown in Fig. 2(B).

[0025] In this embodiment, the state in which the second electrode 22 is disconnected is referred to as an abnormal state, but this can also be applied to cases in which the first electrode 21 is disconnected or an abnormal state occurs for other reasons.

[0026] Furthermore, in this embodiment, the explanation is given in terms of a case where the electrode unit 20 becomes abnormal, but this is not limited to this, and a case where the electrode unit 20 becomes abnormal may also be referred to as a case where the electrode unit 20 becomes defective, a case where the electrode unit 20 becomes broken, etc.

[0027] First, the judgment value ΔAD used in the comparative example will be described. The judgment value ΔAD can be calculated using the following formula 1. Crg is the capacitance generated between the driver's hand and the second electrode 22 when the driver's hand approaches the second electrode 22. Crs is the capacitance between the first electrode 21 and the second electrode 22. In other words, Crs means the capacitance originally held by the electrode unit 20. Instead of the judgment value ΔAD, the difference value of ΔAD shown in formula 1 may be used as the judgment value. ΔAD=Crg / (Crs+Crg) ...Equation 1

[0028] The capacitance Crs between the first electrode 21 and the second electrode 22 can be calculated by the following equation 2. Here, εrs is the dielectric constant between the first electrode 21 and the second electrode 22. Furthermore, drs is the distance between the first electrode 21 and the second electrode 22. Furthermore, Srs is the area of the second electrode 22. Crs=εrs(Srs / drs) …Equation 2

[0029] In the electrode portion 20, a capacitance Crgl between the metal core 11 and the second electrode 22 and a capacitance Csg between the metal core 11 and the first electrode 21 also occur, but a description thereof will be omitted here.

[0030] The capacitance Crs between the first electrode 21 and the second electrode 22 is normally fixed. In contrast, the capacitance Crg changes in value depending on the driver's contact state with the steering wheel 10. Specifically, when the driver's hands are not touching the steering wheel 10, the capacitance Crg is 0 or close to 0. On the other hand, when the driver's hands are touching the steering wheel 10, the capacitance Crg increases in value depending on the degree of contact. That is, when the driver grips the steering wheel 10, the capacitance Crg is increased, and the judgment value ΔAD increases. Furthermore, when the driver continues to grip the steering wheel 10, the judgment value ΔAD remains high. On the other hand, when the driver releases the steering wheel 10, the judgment value ΔAD decreases rapidly.

[0031] In this comparative example, when the judgment value ΔAD exceeds the contact threshold TH1, it is determined that contact has occurred. For example, as shown by the curve L1 in the lower graph of FIG. 3(A), when the judgment value ΔAD exceeds the contact threshold TH1, it is determined that contact has occurred.

[0032] Here, the capacitance and resistance between the first electrode 21 and the second electrode 22 when the electrode unit 20 is in a normal state (see FIG. 3(A)) and when the electrode unit 20 is in a disconnected state (see FIG. 3(B)) will be described.

[0033] Comparing the case where the electrode unit 20 is in a normal state (see FIG. 3(A)) with the case where the electrode unit 20 is in a disconnected state (see FIG. 3(B)), when the electrode unit 20 is in a disconnected state, the area of the second electrode 22 following the disconnected portion indicated by position 25 is lost. This makes it difficult for electricity to flow between the first electrode 21 and the second electrode 22, and the resistance value Rs2 between the first electrode 21 and the second electrode 22 when the electrode unit 20 is in a disconnected state is greater than the resistance value Rs1 between the first electrode 21 and the second electrode 22 when the electrode unit 20 is in a normal state.

[0034] Furthermore, since the area of the second electrode 22 is lost, the capacitance Crs2 between the first electrode 21 and the second electrode 22 when the electrode portion 20 is in a disconnected state is lower than the capacitance Crs1 between the first electrode 21 and the second electrode 22 when the electrode portion 20 is in a normal state.

[0035] As described above, when the area of the second electrode 22 decreases, the capacitance Crs2 between the first electrode 21 and the second electrode 22 decreases, and the denominator of Equation 1 also increases, resulting in a larger value for the determination value ΔAD. Furthermore, if the electrode unit 20 remains disconnected after the driver releases his / her hand from the steering wheel 10, the determination value ΔAD may remain large and exceed the contact threshold TH1. For example, as shown by curve L2 in the lower graph of FIG. 3B, the determination value ΔAD may remain above the contact threshold TH1 even after the driver releases his / her hand from the steering wheel 10. In this case, the contact determination device 1 may make an erroneous determination. Therefore, this embodiment illustrates an example in which contact determination is performed using a decrease in capacitance and an increase in resistance when the electrode unit 20 is disconnected. This allows, for example, implementation of logic that does not determine contact when a decrease in capacitance and an increase in resistance are clearly due to electrode disconnection.

[0036] [Example of contact detection based on capacitance and impedance] Fig. 4 is a diagram showing an example of a determination process for determining contact based on the capacitance ΔCa and impedance ΔZb generated in the electrode unit 20. The horizontal axis shown in Fig. 4 represents the capacitance ΔCa, and the vertical axis shown in Fig. 4 represents the impedance ΔZb. Impedance refers to the resistance when an alternating current flows, and is also called AC resistance.

[0037] 4 indicates the capacitance generated in the second electrode 22 in response to the driver's contact with the steering wheel 10. Furthermore, the impedance ΔZb indicates the impedance between the first electrode 21 and the second electrode 22.

[0038] Here, when the electrode unit 20 is in a normal state, when the driver grips the steering wheel 10, the capacitance Crg increases in accordance with the driver's contact with the steering wheel 10. However, the resistance between the first electrode 21 and the second electrode 22 does not change due to the driver's contact, and therefore the fluctuation in impedance ΔZb is small. Therefore, when the electrode unit 20 is in a normal state, even when the driver grips the steering wheel 10, the gradient (ΔZb / ΔCa) of the capacitance ΔCa and the impedance ΔZb is low, for example, about 1 / 8 to 1 / 15. In other words, when the electrode unit 20 is in a normal state, even when the driver grips the steering wheel 10, the gradient (ΔZb / ΔCa) of the capacitance ΔCa and the impedance ΔZb is small.

[0039] On the other hand, when the electrode unit 20 is in an abnormal state, for example, when the second electrode 22 is in a disconnected state, the capacitance Crg increases depending on the driver's contact state with the steering wheel 10 when the driver grips the steering wheel 10. Furthermore, when the second electrode 22 is disconnected due to the driver's contact, the resistance between the first electrode 21 and the second electrode 22 changes depending on the driver's contact, as shown in FIGS. 2 and 3 . That is, when the second electrode 22 is disconnected due to the driver's contact, the resistance value changes to a smaller value depending on the driver's contact state. Therefore, the fluctuation of the impedance ΔZb becomes larger. That is, the impedance ΔZb decreases significantly depending on the driver's contact state, and therefore the fluctuation also becomes larger.

[0040] Therefore, when the electrode unit 20 is in an abnormal state, the absolute value of the gradient (ΔZb / ΔCa) of the capacitance ΔCa and the impedance ΔZb becomes high, for example, 1 to 2 or more, when the driver grips the steering wheel 10. That is, when the electrode unit 20 is in an abnormal state, the gradient (ΔZb / ΔCa) of the capacitance ΔCa and the impedance ΔZb becomes large when the driver grips the steering wheel 10. That is, the amount of change in impedance ΔZb fluctuates greatly with respect to the amount of change in capacitance ΔCa.

[0041] When second electrode 22 is in a disconnected state regardless of whether the driver is in contact or not, the resistance between first electrode 21 and second electrode 22 does not change due to driver contact, but the resistance value is small. Therefore, when second electrode 22 is in a disconnected state regardless of whether the driver is in contact or not, the value of impedance ΔZb is small.

[0042] Therefore, in this embodiment, contact determination is performed using the relationship between the capacitance ΔCa and the impedance ΔZb. Specifically, if the capacitance ΔCa is equal to or less than the contact threshold TH11 indicated by the line SL2, it is determined that there is no contact. In other words, if the intersection of the capacitance ΔCa and the impedance ΔZb is in the non-contact area NCA1, it is determined that there is no contact.

[0043] On the other hand, if the capacitance ΔCa exceeds the contact threshold TH11 indicated by the line SL2, it is determined that contact has occurred. However, even if the capacitance ΔCa exceeds the contact threshold TH11 (line SL2), if the impedance ΔZb is equal to or less than the stepped broken line SL1, it is assumed that the electrode unit 20 is in an abnormal state, for example, that the second electrode 22 is in a disconnected state, and therefore it is determined that an abnormality has occurred. In other words, if the intersection of the capacitance ΔCa and the impedance ΔZb is in the contact area CA1, it is determined that contact has occurred, but if the intersection of the capacitance ΔCa and the impedance ΔZb is in the abnormal area AA1, it is determined that an abnormality has occurred.

[0044] Here, the contact threshold TH11 is a contact determination threshold used when determining whether the driver has contacted the steering wheel 10. The contact threshold TH11 can be set appropriately based on experimental data, etc. The contact threshold TH11 may be a fixed value or may be variable depending on the driver, the internal environment of the vehicle, and the environment around the vehicle, such as temperature and humidity.

[0045] The stepped broken line SL1 represents the abnormality determination threshold used when determining whether or not there is an abnormality in the electrode unit 20. For example, when the capacitance ΔCa is greater than the contact threshold TH11 and falls within a range equal to or less than TH12, the abnormality determination threshold is set to TH21. When the capacitance ΔCa is greater than TH12 and falls within a range equal to or less than TH13, the abnormality determination threshold is set to TH22. Similarly, the abnormality determination thresholds TH23 to TH25 are set according to the range of the capacitance ΔCa (TH13 to TH15). In this way, values TH21 to TH25 that decrease as the capacitance ΔCa increases can be set as the abnormality determination thresholds.

[0046] 4 shows an example in which the abnormality determination thresholds TH21 to TH25 are set to decrease stepwise, but other thresholds that decrease in accordance with an increase in the capacitance ΔCa may also be set as the abnormality determination thresholds. For example, the value TH shown in the following equation 3 may be set as the abnormality determination threshold. Note that DC1 and α1 are diagnostic coefficients and can be set appropriately based on experimental data, etc. TH=ΔCa×DC1+α1…Equation 3

[0047] That is, if the capacitance ΔCa is greater than the contact threshold TH11 and the impedance ΔZb satisfies the following formula 4, it is determined that contact has occurred. On the other hand, if the capacitance ΔCa is greater than the contact threshold TH11 but the impedance ΔZb does not satisfy the following formula 4, it is determined that an abnormality has occurred. ΔZb>ΔCa×DC1+α1…Formula 4

[0048] For ease of explanation, Figure 4 shows an example of contact determination using the relationship between the most recent capacitance ΔCa and impedance ΔZb. However, since it is expected that abnormal values may be detected due to variations or radio noise, it is preferable to use multiple detection results to eliminate such abnormal values and improve reliability. An example of this is shown in Figure 5.

[0049] [Example of contact detection device operation] 5 is a flowchart showing an example of the contact determination process in the contact determination device 1. The contact determination process is executed by the ECU 30 based on a program stored in a storage unit (not shown). The contact determination process is constantly executed for each control cycle. The determination unit 32 holds the capacitance and impedance detected by the detection unit 31 a predetermined number of times. The predetermined number of times is a value equal to or greater than N. Here, N is a value that is appropriately set based on experimental data, etc.

[0050] In step S501, the detection unit 31 detects the capacitance ΔCa and impedance ΔZb of the electrode unit 20.

[0051] In step S502, the determination unit 32 acquires N capacitances from the capacitances detected by the detection unit 31. Here, the N capacitances are N values from the most recently acquired capacitance to the capacitances acquired up to the Nth time before.

[0052] In step S503, the determination unit 32 calculates a moving average value ΔCa1 of the capacitances acquired N times in step S501. Here, the moving average value ΔCa1 means the average value of the capacitances acquired N times. Note that, although an example using the moving average value ΔCa1 is shown in FIG. 5, as described above, a single capacitance may be used, or another value calculated using one or more capacitances may be used.

[0053] In step S504, the determination unit 32 determines whether the moving average value ΔCa1 calculated in step S502 is greater than the contact threshold value TH11 (see FIG. 4). If the moving average value ΔCa1 is equal to or less than the contact threshold value TH11, the process proceeds to step S505. On the other hand, if the moving average value ΔCa1 is greater than the contact threshold value TH11, the process proceeds to step S506.

[0054] In step S505, the determination unit 32 determines that the driver's hands are not in contact with the steering wheel 10. That is, since the moving average value ΔCa1 is in the non-contact area NCA1 (see FIG. 4), it is determined that there is no contact.

[0055] In step S506, the determination unit 32 acquires N impedances from the impedances detected by the detection unit 31. Here, the N impedances are N values from the last acquired impedance to the impedances acquired up to the Nth time before.

[0056] In step S507, the determination unit 32 calculates a moving average value ΔZb1 of the impedances acquired N times in step S505. Here, the moving average value ΔZb1 means the average value of the impedances acquired N times. Note that, although an example using the moving average value ΔZb1 is shown in FIG. 5, as described above, a single impedance may be used, or another value calculated using one or more impedances may be used.

[0057] In step S508, the determination unit 32 determines whether the moving average value ΔZb1 calculated in step S506 satisfies the above-mentioned formula 4. If the moving average value ΔZb1 satisfies the above-mentioned formula 4, the process proceeds to step S509. On the other hand, if the moving average value ΔZb1 does not satisfy the above-mentioned formula 4, the process proceeds to step S510.

[0058] In step S509, the determination unit 32 determines that the driver's hands are in contact with the steering wheel 10. That is, since the intersection of the moving average value ΔZb1 and the moving average value ΔCa1 exists in the contact area CA1 (see FIG. 4), it is determined that the driver's hands are in contact with the steering wheel 10.

[0059] In step S510, the determination unit 32 determines that there is an abnormality in the contact determination device 1. That is, since the intersection of the moving average value ΔZb1 and the moving average value ΔCa1 exists in the abnormal area AA1 (see FIG. 4), it is determined that there is an abnormality.

[0060] The determination unit 32 also outputs the determination result for use in autonomous driving and outputting a warning. For example, if it is determined that a driver is driving a vehicle with their hands off the wheel at a predetermined autonomous driving level, a warning is output. Also, for example, a warning may be output when an abnormality in the electrode unit 20 is determined.

[0061] 5 shows an example in which the electrode unit 20 is determined to be abnormal even when the moving average value ΔCa1 exceeds the contact threshold value TH11 and the moving average value ΔZb1 is equal to or less than the abnormality determination threshold value (the abnormality determination threshold value TH shown in Equation 4) only once. However, the electrode unit 20 may be determined to be abnormal when the moving average value ΔCa1 exceeds the contact threshold value TH11 and the moving average value ΔZb1 is equal to or less than the abnormality determination threshold value (the abnormality determination threshold value TH shown in Equation 4) only once. In this way, even when an abnormal value is detected due to variations, radio wave noise, or the like, the abnormal value can be eliminated, thereby improving the accuracy of the contact determination.

[0062] As described above, in this embodiment, when determining whether the driver has contacted the steering wheel 10, the capacitance ΔCa and impedance ΔZb of the electrode unit 20 can be used to more reliably determine an abnormal state of the electrode unit 20. This makes it possible to prevent, for example, an electrode failure from preventing appropriate contact determination. Furthermore, simply by changing the software logic, the accuracy of contact determination can be improved, and robustness can be improved.

[0063] [Configuration and Effects of This Embodiment] The contact determination method according to this embodiment is a contact determination method in which a sheet-like electrode unit 20, which is formed by stacking a first electrode 21 and a second electrode 22 with an insulator 23 sandwiched therebetween, is provided to cover the outer periphery of a steering wheel 10, and determines whether the driver has contacted the steering wheel 10 based on an electrical signal detected from the electrode unit 20. This contact determination method includes a detection step (step S501) of detecting capacitance ΔCa and impedance ΔZb generated in the electrode unit 20, and a determination step (steps S502 to S510) of determining whether the driver's hand has contacted the steering wheel 10 and whether an abnormality exists in the electrode unit 20, based on the capacitance ΔCa and impedance ΔZb detected in the detection step. In the judgment steps (steps S504, S508, S510), if the capacitance ΔCa exceeds the contact threshold TH11 (an example of the first threshold) and the impedance ΔZb falls below the abnormality judgment threshold (the broken line SL1 (see FIG. 4), the abnormality judgment threshold TH (an example of the second threshold) shown in Equation 4), it is judged that the electrode unit 20 is abnormal.

[0064] According to this configuration, when determining whether the driver has contacted the steering wheel 10, the capacitance ΔCa and impedance ΔZb of the electrode unit 20 can be used to more reliably determine whether the electrode unit 20 is in an abnormal state.

[0065] Furthermore, in the contact determination method according to this embodiment, a fixed value is set as the contact threshold TH11 (an example of a first threshold), and a variable value that decreases in accordance with an increase in capacitance is set as the abnormality determination threshold (the broken line SL1 (see FIG. 4), the abnormality determination threshold TH (an example of a second threshold) shown in Equation 4).

[0066] According to this configuration, an appropriate threshold value can be set, and an abnormal state of the electrode unit 20 can be determined more reliably.

[0067] Furthermore, in the contact determination method according to this embodiment, the abnormality determination threshold TH (an example of a second threshold) shown in Equation 4 is a value (ΔCa×DC1+α1) calculated based on the capacitance ΔCa and predetermined coefficients (DC1, α1).

[0068] According to this configuration, the abnormal state of the electrode unit 20 can be determined more reliably by setting the threshold value using specific parameters.

[0069] Furthermore, in the contact determination method according to this embodiment, in the determination steps (steps S504, S508, S510), if the moving average value ΔCa1 of a predetermined number of capacitances detected within a predetermined time exceeds a contact threshold value TH11 (an example of a first threshold value) and the moving average value ΔZb1 of a predetermined number of impedances detected within a predetermined time falls below an abnormality determination threshold value (broken line SL1 (see FIG. 4), abnormality determination threshold value TH (an example of a second threshold value) shown in Equation 4) the number of times that falls is equal to or greater than a predetermined number.

[0070] According to this configuration, even if an abnormal value is detected due to variations, radio noise, or the like, the abnormal value can be eliminated, thereby improving the accuracy of determining an abnormal state.

[0071] In the contact determination method according to the present embodiment, in the determination step, if the moving average value ΔCa1 of a predetermined number of capacitances detected within a predetermined time is equal to or less than a contact threshold value TH11 (an example of a first threshold value) in steps S504 and S505, it is determined that the driver's hand is not in contact with the steering wheel 10. In addition, in steps S504, S508, and S509, if the moving average value ΔCa1 of the capacitance is greater than the contact threshold value TH11 and the moving average value ΔZb1 of a predetermined number of impedances detected within a predetermined time is greater than an abnormality determination threshold value (broken line SL1 (see FIG. 4), abnormality determination threshold value TH (an example of a second threshold value) shown in Equation 4), it is determined that the driver's hand is in contact with the steering wheel 10. In addition, in steps S504, S508, and S510, if the moving average value ΔCa1 of the capacitance is greater than the contact threshold value TH11 and the moving average value ΔZb1 of the impedance is equal to or less than the abnormality determination threshold value, it is determined that the electrode unit 20 is abnormal.

[0072] According to this configuration, it is possible to more reliably determine whether the steering wheel 10 has been contacted and whether the electrode unit 20 is in an abnormal state, using a specific control logic.

[0073] Furthermore, in the contact determination method according to this embodiment, the electrode unit 20 is configured so that the second electrode 22 is disposed on the outer side of the steering wheel 10 and the first electrode 21 is disposed on the inner side of the steering wheel 10. In the detection step (step S501), the capacitance ΔCa generated in the second electrode 22 and the impedance ΔZb generated between the first electrode 21 and the second electrode 22 are detected based on the difference between the AC signal and a response signal acquired in response to the AC signal input to the electrode unit 20.

[0074] According to this configuration, the capacitance ΔCa and impedance ΔZb can be detected appropriately, and the abnormal state of the electrode unit 20 can be determined more reliably.

[0075] The contact determination device 1 is a contact determination device in which a sheet-like electrode unit 20, which is formed by stacking a first electrode 21 and a second electrode 22 with an insulator 23 sandwiched therebetween, is provided to cover the outer periphery of the steering wheel 10, and determines whether the driver has contacted the steering wheel 10 based on an electrical signal detected from the electrode unit 20. The contact determination device 1 includes a detection unit 31 that detects a capacitance ΔCa and an impedance ΔZb generated in the electrode unit 20, and a determination unit 32 that determines whether the driver's hand has contacted the steering wheel 10 and whether the electrode unit 20 is abnormal, based on the capacitance ΔCa and impedance ΔZb detected by the detection unit 31. The determination unit 32 determines that the electrode unit 20 is abnormal when the capacitance ΔCa exceeds a contact threshold TH11 (an example of a first threshold) and the impedance ΔZb is below an abnormality determination threshold (broken line SL1 (see FIG. 4), an abnormality determination threshold TH (an example of a second threshold) shown in Equation 4).

[0076] According to this configuration, when determining whether the driver has contacted the steering wheel 10, the capacitance ΔCa and impedance ΔZb of the electrode unit 20 can be used to more reliably determine whether the electrode unit 20 is in an abnormal state.

[0077] Note that each processing procedure shown in this embodiment is an example for realizing this embodiment, and the order of some of the processing procedures may be changed within the scope that makes it possible to realize this embodiment, and some of the processing procedures may be omitted or other processing procedures may be added.

[0078] Note that each process described in this embodiment is executed based on a program that causes a computer to execute each processing procedure. Therefore, this embodiment can also be understood as an embodiment of a program that realizes the function of executing each process and a recording medium that stores the program. For example, an update process for adding a new function to the contact determination device can store the program in the storage device of the contact determination device. This makes it possible to cause the updated contact determination device to perform each process described in this embodiment.

[0079] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. A contact determination method comprising: a sheet-like electrode unit configured by stacking a first electrode and a second electrode with an insulator sandwiched between them, the sheet-like electrode unit being provided to cover an outer periphery of a steering wheel; and determining whether a driver has contacted the steering wheel based on an electrical signal detected from the electrode unit, a detection step of detecting capacitance and impedance generated in the electrode portion; a determining step of determining whether or not a driver's hand has touched the steering wheel and whether or not the electrode unit is abnormal, based on the capacitance and the impedance detected in the detecting step, In the determining step, when the capacitance exceeds a first threshold value and the impedance falls below a second threshold value, it is determined that the electrode unit is abnormal. Contact determination method.

2. The contact determination method according to claim 1 , a fixed value is set as the first threshold value, and a variable value that decreases in accordance with an increase in the capacitance is set as the second threshold value; Contact determination method.

3. 3. The contact determination method according to claim 1, further comprising: The second threshold value is a value calculated based on the capacitance and a predetermined coefficient. Contact determination method.

4. 4. The contact determination method according to claim 1, further comprising: In the determination step, it is determined that the electrode unit is abnormal when a moving average value of a predetermined number of the capacitances detected within a predetermined time exceeds the first threshold value and the number of times that a moving average value of a predetermined number of the impedances detected within the predetermined time falls below the second threshold value is equal to or greater than a predetermined number. Contact determination method.

5. 4. The contact determination method according to claim 1, further comprising: In the determination step, if a moving average value of a predetermined number of the capacitances detected within a predetermined time is equal to or less than the first threshold value, it is determined that the driver's hands are not in contact with the steering wheel; if the moving average value of the capacitances is greater than the first threshold value and the moving average value of a predetermined number of the impedances detected within the predetermined time is greater than the second threshold value, it is determined that the driver's hands are in contact with the steering wheel; and if the moving average value of the capacitances is greater than the first threshold value and the moving average value of the impedances is equal to or less than the second threshold value, it is determined that the electrode unit is abnormal. Contact determination method.

6. 6. A contact determination method according to claim 1, further comprising: the electrode unit is configured such that the second electrode is disposed on an outer side of the steering wheel and the first electrode is disposed on an inner side of the steering wheel, In the detecting step, the capacitance occurring in the second electrode and the impedance occurring between the first electrode and the second electrode are detected based on a difference between a response signal acquired in response to the AC signal input to the electrode unit and the AC signal. Contact determination method.

7. A contact determination device comprising: a sheet-like electrode portion configured by stacking a first electrode and a second electrode with an insulator sandwiched therebetween, the sheet-like electrode portion being provided so as to cover an outer periphery of a steering wheel; and the device determining whether a driver has contacted the steering wheel based on an electrical signal detected from the electrode portion, a detection unit that detects the capacitance and impedance generated in the electrode unit; a determination unit that determines whether a driver's hand has touched the steering wheel and whether the electrode unit is abnormal, based on the capacitance and the impedance detected by the detection unit, The determination unit determines that the electrode unit is abnormal when the capacitance exceeds a first threshold value and the impedance falls below a second threshold value. Contact determination device.

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