Contact determination device

Abstract

To provide a contact determination device capable of determining a contact with high precision even under a noise changing environment.SOLUTION: A contact determination device includes an electrostatic sensor mounted on an object and a contact determination section which determines whether or not the hand is in contact with the object on the basis of an electrostatic capacitance measured by the electrostatic sensor. The contact determination section, when the electrostatic capacitance is at least a first contact threshold value, determines that the hand is contact with the object and continues a state where a correction value is added to the first contact threshold value during a second prescribed time after a variation at a first prescribed time of the electrostatic capacitance has become at least a noise threshold value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a collision detection device. [Background technology]

[0002] Conventionally, there has been a management device that includes a receiving unit that receives capacitance change data detected by a touch panel from a display device equipped with a capacitive touch panel, and a determining unit that determines one of a plurality of operating modes with different thresholds for identifying whether or not a touch has occurred based on the change data, and transmits the determined operating mode to the display device (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-071020 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method of determining one of a plurality of operation modes according to the change amount data, it is difficult to detect a touch with high accuracy in an environment where there is noise in the capacitance and the noise changes over time.

[0005] Therefore, an object of the present invention is to provide a contact determination device that can determine contact with high accuracy even in an environment where noise changes. [Means for solving the problem]

[0006] A contact determination device according to an embodiment of the present invention includes an electrostatic sensor provided on an object, and a contact determination unit that determines whether a hand is in contact with the object based on the capacitance measured by the electrostatic sensor. The contact determination unit determines that a hand has contacted the object when the capacitance is equal to or greater than a first contact threshold, and continues to add a correction value to the first contact threshold for a second predetermined time after the amount of change in the capacitance over a first predetermined time period becomes equal to or greater than a noise threshold. [Effects of the Invention]

[0007] It is possible to provide a contact determination device that can determine contact with high accuracy even in an environment where noise changes. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing a steering wheel 10 equipped with a contact determination device 100 according to an embodiment. [Figure 2] 10 is a diagram showing an example of an output sine wave of the electrostatic sensor 110. FIG. [Figure 3] FIG. 10 is a diagram illustrating contact determination using a reference value. [Figure 4] FIG. 10 is a flowchart showing a contact determination process executed by a contact determination unit 122. [Figure 5] FIG. 10 is a flowchart showing a contact determination process executed by a contact determination unit 122. [Figure 6] FIG. 10 is a flowchart showing a contact determination process executed by a contact determination unit 122. [Figure 7] FIG. 10 is a flowchart showing a contact determination process executed by a contact determination unit 122. [Figure 8] 3A to 3C are diagrams illustrating the operation of the contact determination device 100 according to the embodiment. [Figure 9] 3A to 3C are diagrams illustrating the operation of the contact determination device 100 according to the embodiment. [Figure 10] 3A to 3C are diagrams illustrating the operation of the contact determination device 100 according to the embodiment. [Figure 11] 3A to 3C are diagrams illustrating the operation of the contact determination device 100 according to the embodiment. [Figure 12] 10A and 10B are diagrams illustrating the operation of a comparative contact determination device. [Figure 13] 10A and 10B are diagrams illustrating the operation of a comparative contact determination device. [Figure 14] 10A and 10B are diagrams illustrating the operation of a comparative contact determination device. [Figure 15] 10A and 10B are diagrams illustrating the operation of a comparative contact determination device. [Figure 16] FIG. 10 is a flowchart showing the processing of a subroutine "sub initial setting" according to a modified example. [Figure 17] FIG. 10 is a flowchart showing the processing of a subroutine "sub on threshold Th1 correction" according to a modified example. [Figure 18] 10A and 10B are diagrams illustrating the operation of a contact determination device according to a modified example of the embodiment. [Figure 19] 10A and 10B are diagrams illustrating the operation of a contact determination device according to a modified example of the embodiment. [Figure 20] 10A and 10B are diagrams illustrating the operation of a contact determination device according to a modified example of the embodiment. [Figure 21] 10A and 10B are diagrams illustrating the operation of a contact determination device according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment to which the contact determination device of the present invention is applied will be described.

[0010] <Embodiment> FIG. 1 is a diagram showing a steering wheel 10 equipped with a contact determination device 100 according to an embodiment. As shown in FIG. 1, the steering wheel 10 is mounted on a vehicle, and an electrostatic sensor 110 of the contact determination device 100 is mounted inside a grip 11. The grip 11 is an example of an object. The contact determination device 100 determines whether a driver's hand H is in contact with the grip 11 of the steering wheel 10.

[0011] Hereinafter, the driver of the vehicle will be referred to as the operator of the contact determination device 100. The contact determination device 100 will be described as a device that can determine whether an operator's hand H, which serves as a detection object, is in contact with an object on which an electrostatic sensor 110 is provided. The operator's touching the object on which the electrostatic sensor 110 is provided will be referred to as the operator's operation.

[0012] <Configuration of the Contact Determination Device 100> The contact determination device 100 includes an electrostatic sensor 110 and a Hands-Off Detection Electronic Control Unit (HODECU) 120.

[0013] The electrostatic sensor 110 is provided around the grip 11 of the steering wheel 10 and is configured with, for example, a metal electrode. The electrostatic sensor 110 is connected to the HODECU 120 via a signal line 12.

[0014] As an example, the HODECU 120 is provided inside the steering wheel 10. Fig. 1 shows an enlarged view of the HODECU 120. The HODECU 120 includes an AFE (Analog Front End) 120A and an MPU (Micro Processor Unit) 120B.

[0015] The AFE 120A is connected to the electrostatic sensor 110, and inputs a sine wave (input sine wave) to the electrostatic sensor 110 based on a command input from the MPU 120B, and acquires a sine wave (output sine wave) output from the electrostatic sensor 110. The AFE 120A acquires the capacitance value (electrostatic capacitance) of the electrostatic sensor 110 from the input sine wave and output sine wave, converts it to digital, and performs noise removal using a low-pass filter, and outputs it to the MPU 120B as an AD value. The AD value is expressed as a count value without a unit, for example. By performing noise removal using a low-pass filter, it is possible to acquire an AD value from which noise above a predetermined frequency has been removed.

[0016] The MPU 120B is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, etc. As an example, the MPU 120B is connected to an ECU 50. The ECU 50 is a control device that controls electronic devices of a vehicle in which the steering wheel 10 is mounted. The electronic devices may be, for example, electronic devices related to automatic driving of the vehicle.

[0017] The MPU 120B has a main control unit 121, a contact determination unit 122, and a memory 123. The main control unit 121 and the contact determination unit 122 are functional blocks that represent the functions of the programs executed by the MPU 120B. The memory 123 is a functional representation of the memory of the MPU 120B.

[0018] The main control unit 121 is a processing unit that supervises the control processing of the MPU 120B, and executes processing other than the processing performed by the contact determination unit 122.

[0019] The contact determination unit 122 determines whether the hand H is in contact with the grip 11 by determining whether the difference obtained by subtracting a reference value from the capacitance value of the electrostatic sensor 110 exceeds a threshold value. This is the contact determination process executed by the contact determination unit 122. The contact determination unit 122 also notifies the ECU 50 of data representing the determination result. Here, the reference value is a reference value of the capacitance value of the electrostatic sensor 110 that is used when the contact determination unit 122 determines whether the hand H is in contact with the grip 11 of the steering wheel 10.

[0020] The contact determination unit 122 also has a first timer 122A and a second timer 122B used in the contact determination process. The contact determination process, the first timer 122A, and the second timer 122B will be described later.

[0021] Radio waves from a smartphone or the like may be present inside the vehicle. These radio waves become noise for the contact determination device 100. The contact determination unit 122 controls the threshold value to suppress the influence of such noise. The control of the threshold value will be described in detail later.

[0022] The memory 123 stores programs and data necessary for the main control unit 121 and the contact determination unit 122 to perform processing. The memory 123 stores data representing the capacitance value of the electrostatic sensor 110, data generated by the contact determination unit 122 during processing, and the like.

[0023] <Output sine wave of electrostatic sensor 110> Fig. 2 is a diagram showing an example of an output sine wave of the electrostatic sensor 110. In Fig. 2, the output sine wave when the hand H is released from the grip 11 (at release) is shown by a solid line, and the output sine wave when the hand H is gripping the grip 11 (at touch) is shown by a dashed line.

[0024] The capacitance value measured by the electrostatic sensor 110 changes when the hand H touches the grip 11 compared to when it is released, and therefore the phase and amplitude of the sine wave at the time of touch change compared to the sine wave at the time of release. The phase and amplitude of the sine wave at the time of touch change depending on the degree of contact of the hand H with the grip 11. The degree of contact refers to, for example, whether the hand H is lightly or firmly gripping the grip 11, or whether the area of ​​the hand H touching the grip 11 is small or large.

[0025] For example, if the timing at which the amplitude becomes zero upon release is determined in advance as the detection timing td and the amplitude of the sine wave is detected at the detection timing td, it is possible to measure an amplitude AD value corresponding to the degree of contact of the hand H. The amplitude AD value at the detection timing td can be considered to be a value corresponding to the degree of contact of the hand H. However, the detection timing td at which the amplitude becomes zero upon release changes due to changes in temperature, etc. Furthermore, the contact determination device 100 cannot determine whether the hand H is sufficiently separated from the electrostatic sensor 110. For this reason, the detection timing td is fixed, and a correction value is used instead of using the amplitude AD value as is.

[0026] <Contact determination using reference values> FIG. 3 is a diagram illustrating contact determination using a reference value. In FIG. 3, the horizontal axis represents time, and the vertical axis represents voltage. In FIG. 3, the amplitude AD value is indicated by a solid line, the reference value is indicated by a dashed line, and the difference ΔAD between the amplitude AD value and the reference value (AD value - reference value) is indicated by a dashed line. The amplitude AD value is a value output by the AFE 120A. The amplitude AD value indicates the capacitance between the electrostatic sensor 110 and the surrounding conductor. The reference value indicates the capacitance between the electrostatic sensor 110 and the surrounding conductor measured when no hand H is present near the electrostatic sensor 110. The difference ΔAD is the difference between the capacitance between the electrostatic sensor 110 and the surrounding conductor and the capacitance between the electrostatic sensor 110 and the surrounding conductor when no hand H is present nearby. In other words, the difference ΔAD is the capacitance between the electrostatic sensor 110 and the hand H.

[0027] Before time t1, the hand H is not in contact with the grip 11. When the hand H comes into contact with the grip 11 at time t1, the amplitude AD value rises relative to the reference value. At this time, the difference (AD value - reference value) also rises and becomes equal to or greater than the on threshold Th1, so that the contact determination unit 122 determines that the hand H has come into contact with the grip 11. The on threshold Th1 is an example of a first contact threshold. Furthermore, when the hand H leaves the grip 11 at time t2, the amplitude AD value falls. At this time, the difference (AD value - reference value) also falls and becomes equal to or less than the off threshold Th2, which is lower than the on threshold Th1, so that the contact determination unit 122 determines that the hand H has left the grip 11. The off threshold Th2 is an example of a second contact threshold.

[0028] <Contact Determination Process Executed by the Contact Determination Unit 122> 4 to 7 are diagrams showing flowcharts illustrating the contact determination process executed by the contact determination unit 122. This process is executed by the contact determination unit 122. FIG. 4 shows a main flow, and FIGS. 5 to 7 show the subroutine process flows of steps S1, S5, and S6 in FIG. 4, respectively. The main flow in FIG. 4 is repeatedly executed every 10 ms control period, for example. The contact state (State) is notified to the ECU 50 from the MPU 120B every 10 ms.

[0029] When the contact determination unit 122 starts processing, it calls a subroutine "subinitial setting" and performs initial setting (step S1). In the initial setting, it performs subroutine processing to initialize various values ​​to be used in subsequent processing. Details will be described later with reference to FIG. 5.

[0030] The contact determination unit 122 acquires the amplitude AD value 1 from the AFE 120A (step S2).

[0031] The contact determination unit 122 acquires an amplitude AD value 2 from the AFE 120A when time T1 has elapsed since acquiring the amplitude AD value 1 (step S3). Time T1 is an example of a first predetermined time, and is, for example, a time (period) of approximately 400 μs to 500 μs. Over a short time period of approximately 400 μs to 500 μs, changes in the amplitude AD value due to human movement are small. For this reason, if the amplitude AD value 1 and the amplitude AD value 2 are acquired with a short interval of approximately 400 μs to 500 μs between them, it is considered that most of the change is due to noise. In other words, the difference (amount of change) between the amplitude AD value 1 acquired in the first measurement and the amplitude AD value 2 acquired in the second measurement after time T1 is regarded as the noise level.

[0032] The contact determination unit 122 calculates the absolute value of the difference between the amplitude AD value 1 and the amplitude AD value 2 (step S4). The absolute value of the difference between the amplitude AD value 1 and the amplitude AD value 2 is |AD value 1 - AD value 2|, and is calculated as an amount representing noise. Hereinafter, the noise amount Noise = |AD value 1 - AD value 2|.

[0033] The contact determination unit 122 calls a subroutine "sub ON threshold Th1 correction" and corrects the ON threshold Th1 (step S5). The contact determination unit 122 performs subroutine processing to correct the ON threshold Th1 using the noise amount Noise calculated in step S4. Details will be described later with reference to FIG. 6.

[0034] The contact determination unit 122 calls the subroutine "sub contact determination" and performs contact determination (step S6). The contact determination unit 122 executes the subroutine process for performing contact determination using the on threshold value Th1 corrected in step S5. Details will be described later with reference to FIG. 7. After completing the process of step S6, the contact determination unit 122 returns to step S2 and repeats the series of processes.

[0035] <Subroutine "sub initial setting"> Next, the initial setting process performed based on the subroutine "sub initial setting" of step S1 in FIG. 4 will be described with reference to FIG.

[0036] The contact determination unit 122 sets the initial value of the count time TimerN of the first timer 122A to T2 and the initial value of the count time TimerS of the second timer 122B to zero (step S11). That is, TimerN=T2, TimerS=0. The time T2 is an example of a second predetermined time, and is stored in the memory 123.

[0037] The contact determination unit 122 sets the initial value of the contact state State to non-contact (HandsOff) (step S12). That is, State=HandsOff. The contact state State in the initial state is a state in which the hand H is not in contact with the grip 11 of the steering wheel 10.

[0038] The contact determination unit 122 sets the initial value of the reference value Base to the maximum value MAX (step S13). That is, Base=MAX. As an example, in the initial state, the reference value Base is set to the maximum value MAX. The maximum value MAX is stored in the memory 123.

[0039] The contact determination unit 122 sets InitialTh1 to a predetermined value and also sets OFF threshold Th2 to a predetermined value (step S14). InitialTh1 is the initial value of the ON threshold Th1. The ON threshold Th1 may be corrected to be greater than InitialTh1, but the OFF threshold Th2 is a fixed value (constant value). InitialTh1 is stored in the memory 123.

[0040] The contact determination unit 122 sets a correction value CorrectionTh1 of the on threshold Th1 to a predetermined value (step S15). The value of the correction value CorrectionTh1 may be determined in advance through, for example, simulation or experiment, so as to suppress the occurrence of erroneous determination due to noise.

[0041] The contact determination unit 122 sets the noise threshold NoiseTh to a predetermined value (step S16). The value of the noise threshold NoiseTh may be determined in advance, for example, through simulation or experiment, in order to make noise distinguishable. By the above processing of steps S11 to S16, the processing of the subroutine "sub initial setting" is completed (END).

[0042] <Subroutine "sub on threshold Th1 correction"> Next, the correction process of the ON threshold Th1 performed based on the subroutine "sub ON threshold Th1 correction" in step S5 of FIG. 4 will be described with reference to FIG.

[0043] The contact determination unit 122 determines whether the noise amount Noise is greater than the noise threshold NoiseTh (step S51) in order to determine whether or not there is noise.

[0044] When the contact determination unit 122 determines that the noise amount Noise is greater than the noise threshold NoiseTh (S51: Yes), the contact determination unit 122 resets the first timer 122A (step S52). That is, the count time TimerN of the first timer 122A is set to 0. As a result, TimerN=0, and the counting of the first timer 122A is restarted.

[0045] The contact determination unit 122 corrects the on threshold value Th1 (step S53). Specifically, the contact determination unit 122 adds the correction value CorrectionTh1 to the initial value InitialTh1 of the on threshold value Th1. That is, Th1=InitialTh1+CorrectionTh1.

[0046] Furthermore, if the contact determination unit 122 determines in step S51 that the noise amount Noise is not greater than the noise threshold NoiseTh (S51: No), it increments the count time TimerN of the first timer 122A (step S54). That is, TimerN=TimerN+1.

[0047] The contact determination unit 122 determines whether the count time TimerN of the first timer 122A exceeds T2 (step S55). If the contact determination unit 122 determines that the count time TimerN has not exceeded T2 (S55: No), the flow proceeds to step S53. If noise occurs and a determination of Yes is made in step S51, and then the noise disappears and a process of determining No in step S51 is repeated, the state in which the correction value CorrectionTh1 is added to the on threshold value Th1 in step S53 continues until the count time TimerN of the first timer 122A exceeds T2. This is to enable contact to be determined with high accuracy even in an environment where noise changes.

[0048] If the contact determination unit 122 determines in step S55 that the count time TimerN exceeds T2 (S55: Yes), it resets the count time TimerN of the first timer 122A to T2 (step S56). If the noise-free state continues, the count time TimerN continues to be incremented in step S54. For this reason, resetting the count time TimerN to T2 prevents overflow.

[0049] If the period of low noise continues for T2 or more, the contact determination unit 122 sets the on threshold Th1 to the initial value InitialTh1 (step S57). Returning the on threshold Th1 to the initial value InitialTh1 means stopping the addition of the correction value CorrectionTh1 to the on threshold Th1. The above steps S51 to S57 complete the process of "sub on threshold Th1 correction" (END).

[0050] <Subroutine "sub contact detection"> Next, the contact determination process performed based on the subroutine "sub contact determination" in step S6 of FIG. 4 will be described with reference to FIG.

[0051] The contact determination unit 122 determines whether the contact state State in the immediately previous control cycle is contact (hands on) (step S61). Since the control cycle is 10 ms, the contact state State in the immediately previous control cycle is the determination result from 10 ms ago.

[0052] If the previous state was not "Hands On" (S61: No), the contact determination unit 122 determines whether the difference ΔAD obtained by subtracting the reference value Base from the amplitude AD value 1 is equal to or greater than the on threshold value Th1 (step S62). The on threshold value Th1 is used to determine whether there is contact. The amplitude AD value 1 indicates the capacitance between the electrostatic sensor 110 and the surrounding conductors. The reference value Base indicates the capacitance between the electrostatic sensor 110 and the surrounding conductors when the hand H is not present. The difference ΔAD indicates the capacitance between the electrostatic sensor 110 and the hand H.

[0053] When the contact determination unit 122 determines that the difference ΔAD is equal to or greater than the ON threshold Th1 (S62: Yes), it increments the count time TimerS of the second timer 122B (step S63). That is, TimerS=TimerS+1.

[0054] The contact determination unit 122 determines whether the count time TimerS of the second timer 122B has exceeded T3 (step S64). T3 is an example of a third predetermined time. This is because the hand H is not determined to be in contact with the grip 11 of the steering wheel 10 immediately (instantly) when the difference ΔAD has exceeded the on threshold Th1, but is determined to be in contact when the difference ΔAD has exceeded the on threshold Th1 for a certain period of time T3. For this reason, when the contact determination unit 122 determines that the count time TimerS has not exceeded T3 (S64: No), it ends the flow (END). When the subroutine for sub-contact determination ends, the process returns to step S2.

[0055] The reason for determining that contact exists when the difference ΔAD exceeds the on threshold Th1 for a certain period of time T3 is to ensure stability when switching the contact state from non-contact to contact. If a large noise component is added to the difference ΔAD, the difference ΔAD may exceed the on threshold Th1 even when the hand H is not in contact with the grip 11 of the steering wheel 10. However, because noise changes, it is rare for large noise components to be added to the difference ΔAD repeatedly. Also, if similarly large noise components are added to the amplitude AD value 1 and the amplitude AD value 2 after time T1, the noise level may be erroneously determined to be low. In this case, if the on threshold Th1 is set too low, the difference ΔAD may exceed the on threshold Th1 even when the hand H is not in contact with the grip 11 of the steering wheel 10. However, because noise changes, it is rare for similarly large noise components to be added to the amplitude AD value 1 and the amplitude AD value 2 after time T1. Therefore, by determining that contact exists when the difference ΔAD exceeds the on threshold Th1 for a certain period of time T3, erroneous determination can be prevented.

[0056] When the contact determination unit 122 determines that the count time TimerS has exceeded T3 (S64: Yes), it sets the contact state State to contact (HandsOn) (step S65). When the contact determination unit 122 completes the process of step S65, it ends the flow (end). When the subroutine for subcontact determination ends, it returns to step S2.

[0057] If the contact determination unit 122 determines in step S62 that the difference ΔAD is not equal to or greater than the on threshold Th1 (S62: No), it updates the reference value Base (step S63A). Specifically, the reference value Base is updated by calculating a weighted average using the amplitude AD value 1 at that time. If the difference ΔAD is less than the on threshold Th1, there is no hand H near the electrostatic sensor 110. The reference value Base changes depending on temperature, etc. The weighted average value of the amplitude AD1 value when there is no hand H near the electrostatic sensor 110 is set as the reference value Base. Here, as an example, the following equation is used to calculate a weighted average when the weight is 9: Base = (9 × Base + AD1) / 10

[0058] The contact determination unit 122 resets the count time TimerS of the second timer 122B (step S64A). That is, TimerS=0, and the counting of the second timer 122B restarts. When the contact determination unit 122 completes the processing of step S64A, it ends the flow (END). When the subroutine for sub-contact determination ends, the process returns to step S2.

[0059] Furthermore, in step S61, if the previous determination was contact (HandsOn) (S61: Yes), the contact determination unit 122 determines whether the difference ΔAD obtained by subtracting the reference value Base from the amplitude AD value 1 is equal to or less than the off threshold Th2 (step S66).

[0060] If the contact determination unit 122 determines that the difference ΔAD is not equal to or less than the OFF threshold value Th2 (S66: No), the flow ends (END). When the subroutine for sub-contact determination ends, the process returns to step S2. In this case, the state in which it is determined that contact exists continues.

[0061] If the contact determination unit 122 determines in step S66 that the difference ΔAD is equal to or smaller than the OFF threshold Th2 (S66: Yes), it determines that the contact state State is non-contact (HandsOff) (step S67). That is, State=HandsOff.

[0062] When switching the contact state State from non-contact to contact, the process waits until the count time TimerS of the second timer 122B exceeds T3 in the contact state (see S64), but the switch from contact to non-contact is performed immediately because, for safety reasons, if the hand H leaves the grip 11 of the steering wheel 10, it is necessary to notify the ECU 50 immediately.

[0063] The contact determination unit 122 resets the count time TimerS of the second timer 122B (step S68). That is, TimerS=0, and the counting of the second timer 122B restarts. When the contact determination unit 122 completes the processing of step 69, it ends the flow (end). When the sub-contact determination subroutine ends, the process returns to step S62.

[0064] <Operation of the Contact Determination Device 100 of the Embodiment> 8 to 11 are diagrams showing the operation of the contact determination device 100 according to the embodiment. In Fig. 8 to Fig. 11, the horizontal axis represents time (no unit).

[0065] FIG. 8 shows amplitude AD value 1, amplitude AD value 2, noise, noise threshold NoiseTh, on threshold Th1, off threshold Th2, and contact state State. FIG. 9 shows amplitude AD value 1, amplitude AD value 2, and noise. FIG. 10 shows noise, noise threshold NoiseTh, and on threshold Th1. FIG. 11 shows amplitude AD value 1, on threshold Th1, off threshold Th2, and contact state State. However, the noise in FIG. 8 does not represent actual noise components. The noise in FIG. 8 is a value calculated by |amplitude AD value 1-amplitude AD value 2|.

[0066] The solid double-headed arrows and dashed arrows shown at the top of Figures 8 to 11 indicate the actual movement of hand H. The time period indicated by the solid double-headed arrows is when hand H is gripping grip 11. The time period indicated by the dashed arrows before the time period indicated by the solid double-headed arrows is when hand H is beginning to grip grip 11. The time period indicated by the dashed arrows after the time period indicated by the solid double-headed arrows is when hand H is beginning to release grip 11.

[0067] The actual movement of the hand H is initially in a non-contact state where it is not in contact with the grip 11, then comes into contact with the grip 11, and then the hand H is released from the grip 11 and goes back into a non-contact state. Then, after noise is generated, the hand H comes into contact with the grip 11, and then the hand H is released from the grip 11 and goes back into a non-contact state. We will now explain whether or not such actual movement of the hand H matches the contact state determination result by the contact determination device 100.

[0068] During the period from time 1 to time 51, noise is small. During the period from time 1 to time 51, the measured noise (=|AD value 1 - AD value 2|) is sufficiently small. While the measured noise remains small, the on threshold Th1 is set to InitialTh1. At time 11, the hand H begins to grasp the grip. Accordingly, the amplitude AD value 1 increases. At time 17, the amplitude AD value 1 becomes equal to or greater than the on threshold Th1. In this example, the reference value Base is set to 0. That is, the capacitance ΔAD between the electrostatic sensor 110 and the hand H, calculated by subtracting the reference value Base from the amplitude AD value 1, is equal to the amplitude AD value 1. Then, at time 21, the contact state State changes to contact. Here, the time (5) from time 17, when the amplitude AD value 1 (difference ΔAD) becomes equal to or greater than the on threshold Th1, to time 21, when the contact state State changes to contact, corresponds to time T3.

[0069] At time 30, the hand H begins to leave the grip 11. As a result, the amplitude AD value 1 begins to decrease. At time 35, the AD value 1 (=difference ΔAD) becomes equal to or less than the OFF threshold value Th2. At this time, the contact state State immediately switches to non-contact.

[0070] At time 51, when the noise increases and exceeds the noise threshold NoiseTh, the on-threshold Th1 is corrected and a correction value CorrectionTh1 is added. The on-threshold Th1 increases to InitialTh1+CorrectionTh1. After time 51, the increased noise is added to the amplitude AD.

[0071] At times 58 and 63, the AD value 1 exceeds InitialTh1, but since the ON threshold Th1 has been increased by the correction, the contact state State does not change to contact at this time.

[0072] The amplitude AD value 1 exceeds the ON threshold Th1 at time 65. At time 70, when a time T3(5) has elapsed from this point in time, the contact state State switches to contact.

[0073] At time 80, the hand begins to leave the grip 11. As a result, the amplitude AD value 1 begins to decrease. At time 87, the amplitude AD value 1 becomes equal to or less than the off threshold Th2. At this time, the contact state State immediately switches to non-contact.

[0074] In reality, large noise occurs between time 51 and time 114. However, there is a point in time when the measured noise falls below the noise threshold NoiseTh due to noise of the same level being added to amplitude AD value 1 and AD value 2. However, when large noise is added, it is rare for noise of the same level to be added repeatedly in succession to amplitude AD value 1 and AD value 2, so the on threshold Th1 continues to have a correction value added to it.

[0075] At time 98, the measured noise becomes less than the noise threshold NoiseTh, and at time 107, which is after time T2, the on threshold Th1 is returned to InitialTh1. From time 107 to time 109, the on threshold Th1 is set to InitialTh1. In reality, large noise occurs from time 51 to time 114. In other words, during the period from time 107 to time 109, the on threshold Th1 is set low compared to the actual noise level.

[0076] As described above, from time 107 to time 109, the on-threshold Th1 is set low relative to the actual noise level. Furthermore, at time 108, the noise causes the amplitude AD value 1 to exceed the on-threshold Th1. However, this state in which the noise causes the amplitude AD value 1 to exceed the on-threshold Th1 does not continue for time T3, so the contact state State is maintained as non-contact. Because noise has a random magnitude, it is common for the measured noise |AD value 1 - AD value 2| to be measured as smaller than the actual noise. Because noise has a random magnitude, it is rare for the measured noise |AD value 1 - AD value 2| to be measured as smaller than the actual noise. As described above, large noise occurs from time 51 to time 114. During this period, the measured noise decreases several times. However, the period in which the measured noise remains small is limited to the period from time 98 to time 109. If the measured noise remains small 10 times in a row, the on-threshold Th1 is set low. For this reason, the period during which the on-threshold Th1 was set low relative to the actual noise level was limited to the period from time 107 to time 109. During the period from time 107 to time 109, the only time that the amplitude AD value 1 exceeded the on-threshold Th1 due to noise was time 108. If the amplitude AD value 1 exceeded the on-threshold Th1 five consecutive times, it was determined that hand H was gripping the grip. Therefore, hand H was not erroneously determined to be gripping the grip 11 when it was not gripping the grip 11. When hand H is not gripping the grip 11, even if large noise occurs continuously, it is rare for the noise to be observed as small and for the amplitude AD value 1 to be observed as large. In other words, even when the noise is large, it is extremely rare for the noise components of amplitude AD value 1 and amplitude AD value 2 to be similar and remain large for a long period of time. Therefore, the possibility of a false determination of contact due to noise when hand H is not gripping the grip 11 is extremely low. It takes time for the hand H to be determined to have made contact after gripping the grip 11. It is acceptable for the hand contact determination device to take a little time to detect that the steering wheel has been gripped by the hand.

[0077] Thereafter, when the noise exceeds the noise threshold Noise at time 110, the on-threshold Th1 is increased again. When the noise becomes equal to or less than the noise threshold Noise at time 112 and time T2 is exceeded, the on-threshold Th1 is returned to the initial value InitialTh1 at time 121. Note that the noise actually becomes smaller at time 115.

[0078] As described above, when noise is measured, erroneous determination is suppressed by adding the correction value CorrectionTh1 to the on threshold value Th1. Furthermore, erroneous determination is suppressed by continuing to add the correction value CorrectionTh1 to the on threshold value Th1 for a certain period after noise is measured. Furthermore, erroneous determination is suppressed by determining that contact has occurred after the amplitude AD value 1 (= capacitance ΔAD) has remained equal to or greater than the on threshold value Th1 for a certain period of time. In other words, it is possible to accurately determine whether the hand H is in contact with or not in contact with the grip 11 of the steering wheel 10.

[0079] When the change in the AD value (Noise) over time T1 exceeds the noise threshold NoiseTh, the contact determination unit 122 adds a correction value CorrectionTh1 to the ON threshold Th1 and starts counting the first timer 122A. When the change in the AD value (Noise) over time T1 remains below the noise threshold NoiseTh and the count time TimerN of the first timer 122A exceeds time T2, the contact determination unit 122 stops adding the correction value CorrectionTh1 to the ON threshold Th1. Therefore, from the time when the change in the AD value (Noise) over time T1 exceeds the noise threshold NoiseTh until the state of being below the noise threshold NoiseTh continues for time T2, the correction value CorrectionTh1 is added to the ON threshold Th1, thereby suppressing erroneous determination due to noise. Noise cannot be measured directly. In the present invention, the difference between two amplitude AD values ​​measured at short intervals, namely, amplitude AD value 1 and amplitude AD value 2, is considered to be the noise level. For this reason, if the two amplitude AD values ​​1 and 2 contain noise components of the same degree, the noise level will be measured as lower than it actually is. However, if the noise is large, it is unlikely that the same degree of noise will be continuously added to the two amplitude AD values ​​1 and 2. For this reason, the present invention can suppress erroneous determinations due to noise.

[0080] Furthermore, if the amount of change (Noise) in the AD value over time T1 becomes equal to or greater than the noise threshold NoiseTh before the count time TimerN of the first timer 122A exceeds time T2, the contact determination unit 122 resets the first timer 122A and restarts counting. This corresponds to the case in Fig. 6 where the flow passes through steps S51: No, S54, S55: No, and S53, returns to the main routine, and then returns to step S51, and then steps S51: Yes and S52. In this way, if the amount of change (Noise) in the AD value over time T1 becomes equal to or greater than the noise threshold NoiseTh before the count time TimerN exceeds time T2, the count time TimerN of the first timer 122A is reset, and therefore, from that point onward over time T2, the correction value CorrectionTh1 is added to the on threshold Th1, thereby suppressing erroneous determination due to noise.

[0081] Furthermore, the contact determination unit 122 determines that the hand H is in contact with the grip 11 when the capacitance ΔAD (AD value 1 - reference value) is equal to or greater than the on threshold Th1 for a period of time T3. This ensures stability when switching the contact state from non-contact to contact, and enables a stable determination that the hand H is in contact with the grip 11. In a noisy environment, the capacitance ΔAD may be measured as large even when the hand H is not in contact with the grip 11. However, because noise fluctuates, it is rare for a large noise component to be continuously added to the capacitance ΔAD. This makes it possible to suppress erroneous determinations due to noise.

[0082] Furthermore, when ΔAD (AD value 1-reference value) becomes equal to or less than the off threshold value Th2, the contact determination unit 122 immediately determines that the hand H is not in contact with the grip 11, and therefore, when the hand H leaves the grip 11 of the steering wheel 10, it can immediately notify the ECU 50 in consideration of safety. This ensures safety when the vehicle is traveling.

[0083] Furthermore, since the on threshold value Th1 is greater than the off threshold value Th2, a hysteresis characteristic can be provided when the contact state State is switched from non-contact to contact and when the contact state State is switched from contact to non-contact, and the contact state State can be determined stably.

[0084] <Operation of the comparative contact detection device> 12 to 15 are diagrams illustrating the operation of a comparative contact determination device. In FIGS. 12 to 15, the horizontal axis represents time (unitless). The comparative contact determination device differs from the contact determination device 100 of the embodiment in that the on-threshold value Th1 is not corrected but maintained at a constant value, and the contact state State immediately switches to contact when the amplitude AD value 1 becomes equal to or greater than the on-threshold value Th1. In addition, the amplitude AD value 2 for noise measurement is not measured, and there is no AD value 2. The actual movement of the hand H is the same as the movement in FIGS. 8 to 11.

[0085] Fig. 12 shows the AD value 1, the ON threshold Th1, the OFF threshold Th2, and the contact state State. Fig. 13 shows the AD value 1. Fig. 14 shows the ON threshold Th1. Fig. 15 shows the AD value 1, the ON threshold Th1, the OFF threshold Th2, and the contact state State.

[0086] At time 11, hand H begins to grasp grip 11. As a result, amplitude AD value 1 increases. At time 17, amplitude AD value 1 becomes equal to or greater than on threshold Th1. At this point, the contact state State immediately switches to contact.

[0087] At time 30, the hand H begins to release the grip 11. As a result, the amplitude AD value 1 decreases. At time 35, the AD value 1 becomes equal to or less than the off threshold Th2. At this time, the contact state State immediately switches to non-contact.

[0088] The noise is large from time 51 to time 114. During this period, there are frequent moments when the noise component added to the amplitude AD value 1 is large. At times 58 and 63, AD value 1 exceeds the on threshold Th1, so the contact state State switches to contact. At these times, hand H is not actually gripping grip 11, resulting in an erroneous determination.

[0089] At time 61, the hand H begins to grasp the grip 11. At time 66, the amplitude AD value 1 exceeds the on threshold Th1. At this point, the contact state State immediately switches to contact.

[0090] At time 80, the hand H begins to release the grip 11. As a result, the AD value 1 begins to decrease. At time 87, the AD value 1 becomes equal to or less than the OFF threshold value Th2. At this time, the contact state State immediately switches to non-contact.

[0091] At time 92, from about time 95 to time 100, and from time 108, the AD value 1 exceeds the on threshold Th1, so the contact state State switches to contact. At this time, the hand H is not actually gripping the grip 11, and this is an erroneous determination.

[0092] As described above, when noise occurs in the comparative contact determination device, erroneous determination occurs and it is not possible to accurately determine the actual movement of the hand H. In contrast, as shown in Figures 8 to 11, when noise occurs, the contact determination device 100 of the embodiment adds the correction value CorrectionTh1 to the on threshold value Th1 to suppress erroneous determination and is able to accurately determine the actual movement of the hand H.

[0093] <Modification> The modified contact determination device 100 has a plurality of noise thresholds and correction values ​​for the on threshold Th1. Here, a modified example of the subroutine "sub initial setting" and a modified example of the subroutine "sub on threshold Th1 correction" will be described with reference to FIGS.

[0094] <Modification of the subroutine "sub initial setting"> Fig. 16 is a flowchart showing the processing of the subroutine "sub initial setting" of a modified example. The processing shown in Fig. 16 can be executed as the processing of step S1 in the main flow shown in Fig. 4, instead of the processing of the subroutine "sub initial setting" of Fig. 5.

[0095] The contact determination unit 122 sets the count times TimerN1 and TimerN2 of the first timer 122A to T2 (step S11A). That is, TimerN1=T2 and TimerN2=T2. The time T2 is an example of a second predetermined time, and is stored in the memory 123. In a modified example, the first timer 122A counts two count times TimerN1 and TimerN2.

[0096] The processing in steps S12 to S14 is the same as the processing in steps S12 to S14 shown in FIG. 5, and therefore a description thereof will be omitted here.

[0097] The contact determination unit 122 sets correction values ​​CorrectionTh1 and CorrectionTh2 for the on threshold Th1 (step S15A). The correction value CorrectionTh1 is larger than the correction value CorrectionTh2, and the correction value CorrectionTh2 is a correction value used when medium noise occurs. The correction value CorrectionTh1 is an example of a first correction value, and the correction value CorrectionTh2 is an example of a second correction value. The correction values ​​CorrectionTh1 and CorrectionTh2 are stored in the memory 123. The correction values ​​CorrectionTh1 and CorrectionTh2 may be determined in advance, for example, through simulation or experiment, so that the effects of large noise and medium noise can be suppressed.

[0098] The contact determination unit 122 sets noise thresholds NoiseTh1 and NoiseTh2 (step S16A). The noise threshold NoiseTh1 is larger than NoiseTh2. The noise threshold NoiseTh1 is an example of a first noise threshold, and the noise threshold NoiseTh2 is an example of a second noise threshold. The noise threshold NoiseTh1 is used to determine the occurrence of large noise, and the noise threshold NoiseTh2 is used to determine the occurrence of medium noise. The noise thresholds NoiseTh1 and NoiseTh2 are stored in the memory 123. The values ​​of the noise thresholds NoiseTh1 and NoiseTh2 may be determined in advance, for example, through simulation or experiment, so as to enable discrimination between large noise and medium noise. With the processing of steps S11A to S16A described above, the processing of the subroutine "sub initial setting" is completed (END).

[0099] <Modification of the subroutine "sub on threshold Th1 correction"> Fig. 17 is a flowchart showing the processing of the subroutine "sub on threshold Th1 correction" according to a modified example. The processing shown in Fig. 17 can be executed as the processing of step S5 in the main flow shown in Fig. 4, instead of the processing of the subroutine "sub on threshold Th1 correction" in Fig. 6.

[0100] The contact determination unit 122 determines whether the noise amount Noise is greater than the noise threshold NoiseTh1 (step S51A) in order to determine whether or not there is large noise.

[0101] When the contact determination unit 122 determines that the noise amount Noise is greater than the noise threshold NoiseTh1 (S51A: Yes), it resets the count times TimerN1 and TimerN2 of the first timer 122A (step S52A). That is, it sets the count times TimerN1 and TimerN2 of the first timer 122A to 0. As a result, TimerN1=0 and TimerN2=0, and the counting of the two count times TimerN1 and TimerN2 of the first timer 122A is restarted.

[0102] The contact determination unit 122 corrects the on threshold value Th1 (step S53A). Specifically, the contact determination unit 122 adds a correction value CorrectionTh1 to the initial value InitialTh1 of the on threshold value Th1. That is, Th1=InitialTh1+CorrectionTh1. The correction value CorrectionTh1 is added to deal with large noise.

[0103] Furthermore, if the contact determination unit 122 determines in step S51A that the noise amount Noise is not greater than the noise threshold NoiseTh1 (S51A: No), it increments the count time TimerN1 of the first timer 122A (step S54B). That is, TimerN1=TimerN1+1.

[0104] The contact determination unit 122 determines whether the noise amount Noise is greater than the noise threshold NoiseTh2 (step S51B). This is because there is no large noise, and therefore it is determined whether there is medium noise.

[0105] If the contact determination unit 122 determines that the noise amount Noise is greater than the noise threshold NoiseTh2 (S51B: Yes), it resets the count time TimerN2 of the first timer 122A (step S52B). That is, it sets the count time TimerN2 of the first timer 122A to 0. As a result, TimerN2=0, and the counting of one of the count times TimerN2 of the first timer 122A is restarted.

[0106] The contact determination unit 122 determines whether the count time TimerN1 of the first timer 122A exceeds T2 (step S55B). The count time TimerN1 indicates the time from the last occurrence of noise exceeding NoiseTh1 to the present. If the contact determination unit 122 determines that the count time TimerN1 of the first timer 122A has not exceeded T2 (S55B: No), the flow proceeds to step S53A. A process in which a large noise occurs and a determination of Yes is made in step S51A, and then the large noise disappears and a determination of No is made in step S51A is repeated. As a result, the state in which the correction value CorrectionTh1 is added to the on-threshold value Th1 in step S53A continues until the count time TimerN1 of the first timer 122A exceeds T2.

[0107] If the contact determination unit 122 determines in step S55B that the count time TimerN1 has exceeded T2 (S55B: Yes), the process proceeds to the next step (step S56B).

[0108] To prevent the count time TimerN1 from overflowing, the contact determination unit 122 resets the count time TimerN1 of the first timer 122A to T2 (step S56B).

[0109] The contact determination unit 122 corrects the on threshold Th1 (step S53B). Specifically, the contact determination unit 122 adds a correction value CorrectionTh2 to the initial value InitialTh1 of the on threshold Th1. That is, Th1=InitialTh1+CorrectionThB. To deal with a state where there is a medium level of noise, a correction value CorrectionTh2 smaller than CorrectionTh1 is added.

[0110] Furthermore, if the contact determination unit 122 determines in step S51B that the noise amount Noise is not greater than the noise threshold NoiseTh2 (S51B: No), it increments the count time TimerN2 of the first timer 122A (step S54C). That is, TimerN2=TimerN2+1. This is to count the time after the moderate noise has disappeared.

[0111] The contact determination unit 122 determines whether the count time TimerN2 of the first timer 122A exceeds T2 (step S55C). The count time TimerN2 indicates the time from the last occurrence of noise exceeding NoiseTh2 to the present. If the contact determination unit 122 determines that the count time TimerN2 has not exceeded T2 (S55C: No), the flow proceeds to step S56B. For a certain period of time since the last measurement of moderate noise, the state in which the correction value CorrectionTh2 for dealing with moderate noise is added to the on threshold Th1 in step S53B continues.

[0112] If the contact determination unit 122 determines in step S55C that the count time TimerN2 has exceeded T2 (S55C: Yes), the process proceeds to the next step (step S56C).

[0113] The contact determination unit 122 resets the count time TimerN2 of the first timer 122A to T2 to prevent overflow of TimerN2. Similarly, the contact determination unit 122 resets the count time TimerN1 of the first timer 122A to T2 to prevent overflow of TimerN1 (step S56C).

[0114] The contact determination unit 122 sets the on threshold Th1 to an initial value InitialTh1 (step S57). If the state in which the noise level is below the medium level continues, the on threshold Th1 is set to the initial value InitialTh1. The above steps S51A to S57 complete the processing of the "sub on threshold Th1 correction" of the modified example (END).

[0115] <Operation of the Contact Determination Device According to the Modification of the Embodiment> 18 to 21 are diagrams showing the operation of a collision determination device according to a modified example of the embodiment, in which the horizontal axis represents time (no unit).

[0116] Fig. 18 shows AD value 1, AD value 2, noise, noise threshold NoiseTh2, on threshold Th1, off threshold Th2, and contact state State. Fig. 19 shows AD value 1, AD value 2, and noise. Fig. 20 shows noise, noise thresholds NoiseTh1, NoiseTh2, and on threshold Th1. Fig. 21 shows AD value 1, on threshold Th1, off threshold Th2, and contact state State.

[0117] In Fig. 18, Th1(+C1) represents the ON threshold Th1 obtained by adding a correction value CorrectionTh1 for large noise countermeasures to the initial value InitialTh1. Th1(+C2) represents the ON threshold Th1 obtained by adding a correction value CorrectionTh2 for medium noise countermeasures to the initial value InitialTh1. Th1 represents the initial value InitialTh1.

[0118] 18 to 21, the time periods when medium noise and large noise are occurring are indicated by double-headed arrows. Medium noise, for example, indicates that a person is making a call on a smartphone in the back seat of a vehicle and medium-level noise is being applied to the steering wheel 10. Large noise, for example, indicates that a person is making a call on a smartphone in the passenger seat of a vehicle and large noise is being applied to the steering wheel 10.

[0119] Initially, the hand H is in a non-contact state where it is not in contact with the grip 11, then the hand H comes into contact with the grip 11, and then the hand H is released from the grip 11 and goes into a non-contact state again. Then, after noise is generated, the hand H comes into contact with the grip 11, and then the hand H is released from the grip 11 and goes into a non-contact state again. While noise is being generated, the hand H is released from the grip 11 and goes into a non-contact state, and after the hand H comes into contact with the grip 11 again, the hand H is released from the grip 11 and goes into a non-contact state again. That is, from a state where the hand H has released the grip 11, the hand grips the grip 11 three times, and finally the hand H is released from the grip 11. We will now explain whether such a movement of the hand H matches the contact state determination result made by the contact determination device of the modified example.

[0120] As shown in FIGS. 18 to 21, at time 6, hand H begins to grip grip 11. As a result, AD value 1 rises. At this time, the noise |AD value 1 - AD value 2| is sufficiently small, so on threshold Th1 is set to its minimum value, InitialTh1. At time 11, AD value 1 becomes equal to or greater than on threshold Th1. Then, at time 15, the contact state State switches to contact. Here, the time (5) from time 11, when AD value 1 becomes equal to or greater than on threshold Th1, to time 15, when the contact state State switches to contact, corresponds to time T3.

[0121] At time 25, the hand H begins to leave the grip 11. As a result, the AD value 1 begins to decrease. At time 30, the AD value 1 becomes equal to or less than the off threshold Th2. At this time, the contact state State immediately switches to non-contact.

[0122] A call is made in the back seat from time 41 to time 140, and the noise increases. When the noise exceeds the noise threshold NoiseTh2 at time 44, the on threshold Th1 is corrected and a correction value CorrectionTh2 is added. The on threshold Th1 increases to InitialTh1+CorrectionTh2.

[0123] Also, at time 46, hand H begins to grasp grip 11. Accordingly, AD value 1 begins to increase again. At time 48, AD value 1 exceeds InitialTh1, but because on threshold Th1 has been increased by correction, the contact state State does not switch to contact at this point. In other words, no erroneous determination occurs.

[0124] At time 49, the measured noise falls below the noise threshold NoiseTh2 and exceeds time T2, causing the on threshold Th1 to be set to the initial value InitialTh1 from time 58 to time 62. During this period, the noise is actually medium, but by chance, the same level of noise was added to AD value 1 and AD value 2. It can be seen that although there are time periods during which the on threshold Th1 is set to the initial value InitialTh1 despite the presence of medium-level noise, these are limited to short periods.

[0125] At time 51, the AD value 1 becomes equal to or greater than the on threshold Th1. Then, the contact state State changes to contact at time 55. Here, the time (5) from time 51, when the AD value 1 becomes equal to or greater than the on threshold Th1, to time 55, when the contact state State changes to contact, corresponds to time T3.

[0126] When a medium level of noise is measured again at time 63 and exceeds the noise threshold NoiseTh2, the ON threshold Th1 is corrected and a correction value CorrectionTh2 is added to the ON threshold Th1, increasing to InitialTh1+CorrectionTh2.

[0127] At time 65, the hand H begins to leave the grip 11. As a result, the AD value 1 begins to decrease. At time 72, the AD value 1 becomes equal to or less than the OFF threshold value Th2. At this time, the contact state State immediately switches to non-contact.

[0128] At time 69, the noise falls below the noise threshold NoiseTh and exceeds time T2, causing the on-threshold Th1 to return to the initial value InitialTh1 at time 78. During this period, a moderate level of noise is actually being added, but by chance, a state in which the same level of noise is being added to AD value 1 and AD value 2 continues. It can be seen that although there are time periods during which the on-threshold Th1 is set to the initial value InitialTh1 despite the presence of a moderate level of noise, these are limited to short periods of time.

[0129] A call is made on the smartphone in the passenger seat from time 81 to time 130, and the noise increases and exceeds the noise threshold NoiseTh1 as shown in Figure 20. The on threshold Th1 is corrected and a correction value CorrectionTh1 is added. The on threshold Th1 increases to InitialTh1+CorrectionTh1.

[0130] At time 92, the AD value 1 becomes equal to or greater than the on threshold Th1. Then, the contact state State changes to contact at time 96. Here, the time (5) from time 92, when the AD value 1 becomes equal to or greater than the on threshold Th1, to time 96, when the contact state State changes to contact, corresponds to time T3.

[0131] At time 105, the hand H begins to leave the grip 11. As a result, the AD value 1 begins to decrease. At time 113, the AD value 1 becomes equal to or less than the OFF threshold Th2. At this time, the contact state State immediately switches to non-contact.

[0132] At time 131, the smartphone call in the passenger seat ends, leaving only the call in the back seat. In this example, the measured noise becomes low while the smartphone call is in progress in the passenger seat. At time 118, the noise becomes less than the noise threshold NoiseTh1 but greater than NoiseTh2. As a result of exceeding time T2, at time 127, the on-threshold Th1 switches from a state in which the correction value CorrectionTh1 is added to a state in which the correction value CorrectionTh2 is added. In other words, the on-threshold Th1 decreases. From time 118 to time 130, large noise is actually applied to the electrostatic sensor 110. However, from time 118 to time 130, the difference between the noise components of AD value 1 and AD value 2 is small. In other words, the measured noise |AD value 1 - AD value 2| remains small compared to the actual noise. Therefore, at time 127, when the noise is actually large, the on-threshold Th1 switches to a state in which the correction value CorrectionTh2 for medium noise components is added. Although the actual noise was large, the time period in which the correction value CorrectionTh2 for a medium noise component was used was from time 127 to time 130. It can be seen that although there were time periods in which the correction value CorrectionTh2 for a medium noise component was used despite the presence of large noise, these were limited to short periods.

[0133] As described above, from time 127 to time 130, even though the actual noise was high, the on threshold Th1 was set to a value for a medium noise component. Therefore, due to the influence of noise, the AD value 1 momentarily exceeded the on threshold Th1 from time 127 to time 128. However, this state did not continue for time T3, so the contact state State remained non-contact. The present invention uses an on threshold appropriate for the noise level and determines contact only after the capacitance value exceeds the on threshold for a certain period of time. By combining these two methods, accurate contact determination can be made even in noisy environments. Furthermore, because the noise level is determined by whether a state below the noise threshold continues for a certain period of time, there is little chance of underestimating the noise.

[0134] The call in the back seat ends at time 141. In this example, the noise becomes less than the noise threshold NoiseTh2 from time 138 before the call ends and exceeds time T2, so that at time 147 the on threshold Th1 is returned to the initial value InitialTh1.

[0135] As described above, the on-threshold value Th1 is corrected in two stages using two correction values ​​CorrectionTh1 and CorrectionTh2 corresponding to the two noise threshold values ​​NoiseTh1 and NoiseTh2, so that it is possible to respond to large noise and medium noise in stages.

[0136] The above describes a contact determination device according to an exemplary embodiment of the present invention. However, the present invention is not limited to the specifically disclosed embodiment, and various modifications and changes are possible without departing from the scope of the claims. [Explanation of symbols]

[0137] 10. Steering wheel 11 Grip 12 Signal line 50 ECU 100 Contact determination device 110 Electrostatic Sensor 120 HODECU 120A AFE 120B MPU 121 Main control unit 122 Contact determination section 122A First Timer 122B Second timer 123 memory

Claims

1. an electrostatic sensor provided on the object; a contact determination unit that determines whether a hand is in contact with the object based on the capacitance measured by the electrostatic sensor; Equipped with The contact determination unit When the capacitance is equal to or greater than a first contact threshold, it is determined that a hand has contacted the object; a state in which the correction value is added to the first contact threshold is continued for a second predetermined time after the amount of change in the capacitance during a first predetermined time period has become equal to or greater than a noise threshold; determining that a hand has touched the object when the capacitance is equal to or greater than the first touch threshold for a third predetermined time period, and immediately determining that a hand is not touching the object when the capacitance is equal to or less than a second touch threshold; The second predetermined time is longer than the first predetermined time.

2. A contact detection device as described in claim 1, wherein the third predetermined time is longer than the first predetermined time.

3. The contact determination device according to claim 1 , wherein the first contact threshold is greater than the second contact threshold.

4. The contact determination unit When the change in the capacitance during the first predetermined time period is equal to or greater than the noise threshold, a first timer starts counting; 4. The contact determination device according to claim 1, wherein when the change in the capacitance over the first predetermined time period becomes less than the noise threshold and the count time of the first timer exceeds the second predetermined time period, the addition of the correction value to the first contact threshold value is stopped.

5. 5. The contact determination device according to claim 4, wherein the contact determination unit resets the first timer and restarts counting when the amount of change in the capacitance over the first predetermined time period becomes equal to or greater than the noise threshold before the count time of the first timer exceeds the second predetermined time period.

6. a plurality of the noise threshold values ​​and the correction values; The contact determination device according to claim 1 , wherein the contact determination unit uses a larger correction value among the plurality of correction values ​​when a larger noise threshold value among the plurality of noise threshold values ​​is used.

7. The contact determination unit When the change amount of the capacitance in the first predetermined time period becomes equal to or greater than a first noise threshold value among the plurality of noise threshold values, a first timer and a second timer start counting; When the change amount of the capacitance in the first predetermined time period exceeds a second noise threshold value that is smaller than the first noise threshold value among the plurality of noise threshold values, the second timer starts counting; before the first timer exceeds the second predetermined time, adding a first correction value to the first contact threshold; 7. The contact determination device according to claim 6, wherein, after the first timer exceeds the second predetermined time but before the second timer exceeds the second predetermined time, the state in which a second correction value smaller than the first correction value is added to the first contact threshold is continued.

8. The contact determination device according to claim 1 , wherein the electrostatic sensor is mounted inside a grip of a steering wheel of a vehicle.

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