Proximity determination device and proximity determination method

Abstract

To provide a proximity determination device capable of appropriately updating a reference value in accordance with an increase or a decrease in temperature in order to correctly determine proximity of an indicator.SOLUTION: A proximity determination device includes: an electrostatic sensor electrode covered with a cover having an operation surface; a measurement circuit configured to measure a capacitance between the electrostatic sensor electrode and a pointer; a proximity determination part configured to determine whether the pointer is in a proximity state in which the pointer is in proximity to the electrostatic sensor electrode based on a difference value obtained by subtracting a reference value from the capacitance; and a correction part configured to correct the reference value. The correction part causes a storage part to store a cumulative input lower limit value based on the reference value before the proximity state, calculates a cumulative value of the variation of the capacitance in the proximity state, updates the reference value based on the cumulative input value having either the cumulative value or the cumulative input lower limit value, sets the cumulative input value to the cumulative value if the cumulative value is larger than the cumulative input lower limit value, and sets the cumulative input value to the cumulative input lower limit value if the cumulative value is smaller than the cumulative input lower limit value.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a proximity determination device and a proximity determination method. [Background technology]

[0002] Conventionally, there has been an input device that detects an operation including at least one of contact of a pointer (hand) and proximity of the operating object, the input device including: a measurement unit (electrostatic sensor electrode) that measures a physical quantity corresponding to the operation; a determination unit that determines an operation state including an operation-performed state and an operation-non-operation state based on at least a reference value and the physical quantity; and a reference value update unit that updates the reference value using the physical quantity when the magnitude of change in the physical quantity per predetermined time is within a predetermined range during an operation-performed period in which the operation state is the operation-performed state. Also, it has been disclosed that even while the pointer is in proximity to the input device, the reference value is changed in accordance with changes in the detection signal output from the measurement unit due to temperature changes (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-218506 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional input devices can erroneously determine whether a pointer is near or not if the temperature changes significantly while the pointer is near the input device. Also, these input devices are designed for personal computers and smartphones and do not have a fail-safe function.

[0005] Therefore, an object of the present invention is to provide a proximity determination device and a proximity determination method that can appropriately update a reference value in response to an increase or decrease in temperature so as to be able to correctly determine the proximity of a pointer. [Means for solving the problem]

[0006] A proximity determination device according to an embodiment of the present invention includes an electrostatic sensor electrode covered by a cover having an operating surface, a measurement circuit that measures the capacitance between the electrostatic sensor electrode and an indicator, a proximity determination unit that determines whether the indicator is in proximity to the electrostatic sensor electrode based on a difference value obtained by subtracting a reference value from the capacitance measured by the measurement circuit, a correction unit that corrects the reference value, and a memory unit, wherein the correction unit causes a cumulative input lower limit value based on the reference value before the indicator entered the proximity state to be stored in the memory unit, calculates a cumulative value of fluctuations in the capacitance in the proximity state, updates the reference value based on a cumulative input value that takes either the cumulative value or the cumulative input lower limit value, and if the cumulative value is greater than the cumulative input lower limit value, sets the cumulative input value to the cumulative value, and if the cumulative value is smaller than the cumulative input lower limit value, sets the cumulative input value to the cumulative input lower limit value. [Effects of the Invention]

[0007] In order to be able to correctly determine the proximity of a pointer, it is possible to provide a proximity determination device and a proximity determination method that can appropriately update a reference value in response to an increase or decrease in temperature. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a steering wheel on which a proximity determination device according to an embodiment is mounted; [Figure 2] 10 is a diagram illustrating an example of an output sine wave of an electrostatic sensor of the proximity determination device according to the embodiment. [Figure 3] FIG. 10 is a diagram illustrating contact determination using a reference value. [Figure 4] 10 is a flowchart illustrating a proximity determination process executed by an MPU of the proximity determination device according to the embodiment. [Figure 5] 10 is a flowchart illustrating a reference value correction process for a released state executed by an MPU of the proximity determination device according to the embodiment. [Figure 6]10 is a flowchart illustrating a touch state initialization process executed by an MPU of the proximity determination device according to the embodiment. [Figure 7] 10 is a flowchart illustrating a proximity determination process executed by an MPU of the proximity determination device according to the embodiment. [Figure 8A] 10 is a diagram illustrating an example of the operation of the proximity determination device of Comparative Example 1. FIG. [Figure 8B] 10 is a diagram illustrating an example of the operation of the proximity determination device of Comparative Example 2. FIG. [Figure 9] 10 is a diagram illustrating an example of the operation of the proximity determination device 100. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment to which the proximity determination device and proximity determination method of the present invention are applied will be described.

[0010] <Embodiment> Fig. 1 is a diagram showing a steering wheel 10 equipped with a proximity determination device 100 according to an embodiment. As shown in Fig. 1, the steering wheel 10 is mounted on a vehicle, for example, and an electrostatic sensor electrode 110 of the proximity determination device 100 is mounted inside a grip 11. The grip 11 is a cover for the rim of the steering wheel 10, and covers the electrostatic sensor electrode 110. The grip 11 is an example of a cover, and the surface of the grip 11 is an example of an operation surface.

[0011] As an example, the proximity determination device 100 determines whether the driver's hand H is in contact with the grip 11 of the steering wheel 10. Because the electrostatic sensor electrode 110 is covered by the grip 11, the hand H is in proximity to the electrostatic sensor electrode 110 when in contact with the grip 11. "In proximity" refers to a state in which an indicator such as the operator's hand is separated from the electrostatic sensor electrode 110 but comes very close, causing the capacitance between the electrostatic sensor electrode 110 and the indicator to increase to a measurable value.

[0012] For the sake of generalization, the driver of the vehicle will be referred to as the operator of the proximity determination device 100 below. The proximity determination device 100 is not limited to an application in which it is incorporated into a steering wheel 10 as shown in FIG. 1. The following describes a proximity determination device 100 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 electrode 110 is provided. The operator's touching of an object on which an electrostatic sensor electrode 110 is provided is referred to as an "operator's operation."

[0013] <Configuration of proximity determination device 100> The proximity determination device 100 includes an electrostatic sensor electrode 110 and a Hands Off Detection Electronic Control Unit (HODECU) 120.

[0014] The electrostatic sensor electrode 110 is provided around the entire circumference of the grip 11 of the steering wheel 10 and is made of, for example, a metal electrode. The electrostatic sensor electrode 110 is connected to the HODECU 120 via a signal line 12.

[0015] 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.

[0016] The AFE 120A is connected to the electrostatic sensor electrode 110, and inputs a sine wave (input sine wave) to the electrostatic sensor electrode 110 based on a command input from the MPU 120B, and acquires a sine wave (output sine wave) output from the electrostatic sensor electrode 110. The AFE 120A acquires the capacitance value of the electrostatic sensor electrode 110 from the input sine wave and output sine wave, converts it to a digital value, and performs noise removal using a low-pass filter, and outputs it to the MPU 120B as an AD value. The AD value is an example of a measurement value, and is a value proportional to the electrostatic capacitance of the electrostatic sensor electrode 110. The AD value is expressed as a unitless count value, for example. By the AFE 120A performing noise removal using a low-pass filter, the proximity determination device 100 can acquire an AD value from which noise above a predetermined frequency has been removed.

[0017] 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.

[0018] The MPU 120B has a main control unit 121, a correction unit 122, a proximity determination unit 123, and a memory 124. The main control unit 121, the correction unit 122, and the proximity determination unit 123 are functional blocks representing the functions of the programs executed by the MPU 120B. The memory 124 is a functional representation of the memory of the MPU 120B.

[0019] 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 correction unit 122 and the proximity determination unit 123.

[0020] The correction unit 122 corrects a reference value used by the proximity determination unit 123 for determination. The reference value is a reference value of the capacitance value of the electrostatic sensor electrode 110 used by the proximity determination unit 123 when determining whether the hand H is in contact with the grip 11 of the steering wheel 10. In other words, the reference value is the electrostatic capacitance when the hand H is not near the electrostatic sensor electrode 110. For example, when the hand H is in contact with the grip 11, the capacitance value of the electrostatic sensor electrode 110 fluctuates due to temperature changes, etc. The reference value of the capacitance value of the electrostatic sensor electrode 110 is used to eliminate fluctuations in the capacitance value of the electrostatic sensor electrode 110 due to such fluctuations and to detect fluctuations in the capacitance value due to the presence or absence of contact of the hand H. The correction unit 122 corrects the detection value in accordance with subtle changes in distance, temperature, etc. The method of correcting the detection value by the correction unit 122 will be described later with reference to FIGS. 4 to 7. The correction unit 122 has a timer used when executing the processes of FIGS. 6 and 7.

[0021] The proximity determination unit 123 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 electrode 110 exceeds a threshold value. The proximity determination unit 123 notifies the ECU 50 of data representing the determination result.

[0022] The memory 124 stores programs, data, etc. required for the main control unit 121, the correction unit 122, and the proximity determination unit 123 to perform processing. The memory 124 stores data representing the capacitance value of the electrostatic sensor electrode 110, data generated by the correction unit 122 and the proximity determination unit 123 during processing, etc.

[0023] <Output sine wave of electrostatic sensor electrode 110> Fig. 2 is a diagram showing an example of an output sine wave of the electrostatic sensor electrode 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 of the electrostatic sensor electrode 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, by determining in advance the timing at which the amplitude becomes zero at the time of release as the detection timing td and detecting the amplitude of the sine wave at the detection timing td, it is possible to obtain an AD value according to the degree of contact of the hand H. This is because the change in amplitude at the detection timing td corresponds to the AD value.

[0026] <Contact determination using reference values> Figure 3 is a diagram illustrating contact determination using a reference value. In Figure 3, the horizontal axis represents time and the vertical axis represents voltage. In Figure 3, the AD value is shown by a solid line, the reference value is shown by a dashed line, and the difference between the AD value and the reference value (AD value - reference value) is shown by a dashed line.

[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 AD value rises relative to the reference value. At this time, the difference (AD value - reference value) also rises and exceeds an ON threshold Th1 (160, for example), so the proximity determination unit 123 determines that the hand H has come into contact with (touched) the grip 11. Furthermore, when the hand H leaves the grip 11 at time t2, the AD value falls. At this time, the difference (AD value - reference value) also falls and becomes less than an OFF threshold Th2 (128, for example) that is lower than the ON threshold Th1, so the proximity determination unit 123 determines that the hand H has left (released) the grip 11.

[0028] <Correction of Reference Value by Correction Unit 122> The correction unit 122 changes the calculation method of the reference value between the time of release and the time of touch.

[0029] At the time of release, the correction unit 122 calculates the reference value using the following formula (1). M represents the weight in the weighted average. The reference value (10 ms ago) is the reference value calculated by the correction unit 122 10 ms ago. The correction unit 122 calculates the weighted average of the reference value (10 ms ago) and the AD value by multiplying the reference value (10 ms ago) by the weight M based on formula (1). Formula (1) is a formula that reflects the latest AD value in the reference value (10 ms ago) as a weighted average. The larger the value of M, the less the reference value calculated by formula (1) is affected by the AD value. In other words, the larger the value of M, the more gradually the reference value calculated by formula (1) changes. Conversely, the smaller the value of M, the more easily the reference value calculated by formula (1) is affected by the AD value. In other words, the larger the value of M, the more quickly the reference value calculated by formula (1) changes. The value of weight M can be set to an appropriate value depending on the characteristics, sensitivity, etc. of the electrostatic sensor electrode 110.

[0030]

number

[0031] Furthermore, when a touch is made, the correction unit 122 calculates the reference value using the following equation (2). M represents the weight in the weighted average. The weight M may be the same as the weight M in equation (1), or may be a different value. The correction unit 122 multiplies the reference value (1 s ago) by the weight M based on equation (2) to obtain a weighted average of the reference value (1 s ago) and the accumulated input value. In other words, the correction unit 122 corrects the reference value based on the accumulated input value.

[0032]

number

[0033] Here, the cumulative input value is a parameter that takes either the cumulative value or the cumulative input lower limit value. The cumulative value is the cumulative value obtained by accumulating the change ΔAD in the AD value at the time of contact of the hand H with the grip 11 to the reference value before the start of contact of the hand H with the grip 11. As an example, the change ΔAD in the AD value is the value obtained by subtracting the AD value 1 s before from the current AD value. When calculating (updating) the cumulative value, the correction unit 122 does not accumulate the change ΔAD in the AD value without limit, but limits it to a value within a certain range and adds it to the previously calculated cumulative value. The cumulative input lower limit value is the value obtained by subtracting a predetermined value from the reference value immediately before the hand H contacts the grip 11. The cumulative input lower limit value is provided to limit the lower limit of the cumulative input value when the cumulative value is too low. Details of this process will be described later using FIG. 7.

[0034] Equation (2) is an equation for reflecting the cumulative input value on the reference value (1 s before) by weighted average. The larger the value of M, the less the reference value calculated by Equation (2) is affected by the cumulative input value. That is, the larger the value of M, the more gently the reference value calculated by Equation (2) changes. Conversely, the smaller the value of M, the more easily the reference value calculated by Equation (2) is affected by the cumulative input value. That is, the larger the value of M, the faster the reference value calculated by Equation (2) changes. The value of the weight M may be set to an appropriate value according to the characteristics and sensitivity of the electrostatic sensor electrode 110. Also, as described above, the weight M in Equation (2) may be the same as or different from the weight M in Equation (1). Also, as described above, the frequency (temporal interval) of updating the reference value at the time of touch may be lower than or the same as the frequency of updating the reference value at the time of release.

[0035] The correction unit 122 corrects the reference value using Equation (1) at the time of release and corrects the reference value using Equation (2) at the time of touch. Since the capacitance value of the electrostatic sensor electrode 110 also varies due to changes in temperature during touch, etc., the correction unit 122 obtains the reference value according to Equation (2) using the cumulative input value so as not to cause misjudgment.

[0036] <Proximity determination process executed by MPU120B> 4 to 7 are flowcharts showing the proximity determination process executed by the MPU 120 B. The method realized by the processes shown in FIGS. 4 to 7 is the proximity determination method of the embodiment, and is executed by the proximity determination device 100.

[0037] When power is turned on, the proximity determination unit 123 starts processing and sets the initialization flag to TRUE (step S1).

[0038] The proximity determination unit 123 sets the reference value to MAX (step S2).

[0039] The proximity determiner 123 sets the contact state to Release (State=Release) (step S3).

[0040] The proximity determiner 123 acquires the AD value from the AFE 120A (step S4). The AD value is a measurement value proportional to the capacitance of the electrostatic sensor electrode 110.

[0041] The proximity determiner 123 determines whether the difference between the AD value and the reference value (AD value-reference value) is greater than the ON threshold value Th1 (step S5A).

[0042] If the proximity determination unit 123 determines that the difference (AD value - reference value) is not greater than the ON threshold Th1 (S5A: No), it determines whether the difference (AD value - reference value) between the AD value and the reference value is smaller than the OFF threshold Th2 (step S5B). The OFF threshold Th2 is a value smaller than the ON threshold Th1. As an example, the ON threshold Th1 is 160, and the OFF threshold Th2 is 128. The ON threshold Th1 and the OFF threshold Th2 are set to different values ​​to provide hysteresis between the contact state of touch (State = Touch) and release (State = Release). If the difference is between the ON threshold Th1 and the OFF threshold Th2, the proximity determination unit 123 does not update the contact state.

[0043] If the proximity determiner 123 determines that the difference (AD value-reference value) is smaller than the OFF threshold value Th2 (S5B: Yes), it determines that the contact state is released (State=Release) (step S6).

[0044] The proximity determination unit 123 sets the initialization flag to TRUE (step S7). The initialization flag is used to determine whether the contact state has just changed to a touch state or whether the contact state continues to be a touch state. This will be described in detail later (see steps S11 to S13).

[0045] The proximity determination unit 123 executes a process of causing the correction unit 122 to correct the reference value in the released state (step S8). The process of correcting the reference value by the correction unit 122 is a process of updating the reference value. Details of the process of step S8 will be described later with reference to FIG. 5.

[0046] After completing the process of step S8, the proximity determination unit 123 determines whether or not to end the series of processes (step S9). The series of processes ends when, for example, the power is turned off.

[0047] If the proximity determination unit 123 determines not to end the series of processes (continue the processes) (S9: No), it returns the flow to step S4. This is to acquire the AD value and repeat the processes. Also, if the proximity determination unit 123 determines to end the series of processes (S9: Yes), it ends the series of processes (end).

[0048] If the proximity determiner 123 determines in step S5B that the difference (AD value - reference value) is not smaller than the threshold value Th2 (S5B: No), it determines whether to end the series of processes without updating the contact state (State) (step S9). The difference (AD value - reference value) is a value between the two threshold values ​​(Th1, Th2), and the contact state is considered to be continuing in the previous state.

[0049] If the proximity determiner 123 determines in step S5A that the difference (AD value-reference value) is greater than the ON threshold Th1 (S5A: Yes), it determines that the contact state is touch (State=Touch) (step S10).

[0050] The proximity determination unit 123 determines whether the initialization flag is TRUE (step S11). The initialization flag becomes TRUE in the released state (step S7), and becomes FALSE when touch state initialization (step S13) is completed. Therefore, the proximity determination unit 123 can determine whether touch state initialization processing (S13) is necessary by checking both the contact state and the initialization flag.

[0051] The proximity determination unit 123 causes the correction unit 122 to execute processing to initialize the touch state (step S12). Details of the processing of step S12 will be described later with reference to FIG. 6. After completing the processing of step S12, the proximity determination unit 123 sets the initialization flag to FALSE (step S13). After completing the processing of step S13, the proximity determination unit 123 advances the flow to step S9.

[0052] If the proximity determination unit 123 determines in step S11 that the initialization flag is not TRUE (S11: No), it causes the correction unit 122 to execute processing to correct the reference value of the touch state (step S14). The processing by the correction unit 122 to correct the reference value is processing to update the reference value. Details of the processing of step S14 will be described later with reference to FIG. 7. After completing the processing of step S14, the proximity determination unit 123 causes the flow to proceed to step S9.

[0053] <Processing of Correcting Reference Value of Release State by Correction Unit 122 (FIG. 5)> The details of the process of step S8 are shown in FIG. 5. When the correction unit 122 starts the process of correcting the reference value for the released state shown in FIG. 5, it performs the process of correcting the reference value for the released state according to equation (1) (step S8A). Based on equation (1), the correction unit 122 multiplies the reference value (10 ms ago) by a weight M to obtain a weighted average of the reference value (10 ms ago) and the AD value. In this way, the correction unit 122 updates the reference value for the released state. In preparation for performing the process of S8A again, the correction unit 122 substitutes the reference value for the reference value (10 ms ago) (step S8B). This completes the process of correcting the reference value for the released state by the correction unit 122 (END). When the process of correcting the reference value is completed, the process proceeds to step S9 in FIG. 4. Note that the time required to perform the processes from step S4 to step S9 is approximately 10 ms. Therefore, the reference value (10 ms ago) indicates the reference value calculated approximately 10 ms ago. However, there may be variation in the time for performing the processes from step S4 to step S9; in other words, the reference value (10 ms ago) may be a value calculated more than 10 ms ago, or a value calculated 1 ms to 10 ms ago.

[0054] <Processing by the correction unit 122 to initialize the touch state (FIG. 6)> Details of the process in step S12 are shown in Fig. 6. The correction unit 122 executes the process of initializing the touch state only when the initialization flag shown in Fig. 6 is TRUE.

[0055] When the correction unit 122 starts the process of initializing the touch state shown in FIG. 6, it sets a timer to 0 seconds (step S12A).

[0056] Correction unit 122 sets the cumulative value to the reference value 1 s ago (1 s ago), sets the cumulative input value to the reference value 1 s ago (1 s ago), and sets the cumulative input lower limit value to a value obtained by subtracting a predetermined value (320, for example) from the reference value 1 s ago (1 s ago) (step S12B). The value obtained by subtracting the predetermined value (320, for example) from the reference value 1 s ago (1 s ago) is an example of a value obtained by subtracting a predetermined value from the reference value immediately before the proximity state was reached.

[0057] The correction unit 122 sets the AD value from one second ago (1(s) ago) as the current AD value (step S12C). The correction unit 122 performs the process of step S12C to be used when correcting (updating) the reference value of the touch state one second later. This completes the process of the correction unit 122 initializing the touch state (END). When the process of initializing the touch state is completed, the process proceeds to step S9 in FIG. 4.

[0058] <Processing of Correcting Reference Value of Touch State by Correction Unit 122 (FIG. 7)> Details of the process of step S14 are shown in Fig. 7. When the correction unit 122 starts the process of correcting the reference value of the touch state shown in Fig. 7, it determines whether the timer has reached one second or more (step S20). This is because the cumulative value is updated every second.

[0059] If the correction unit 122 determines that the timer is not at least 1 second (S20: No), it adds 0.01 seconds (10 ms) to the timer (step S21). In this embodiment, the AD value is acquired every 0.01 seconds, and the touch state reference value correction process is performed every second. After completing the process of step S21, the correction unit 122 ends the series of processes (END). After completing the series of processes, the process proceeds to step S9 in FIG. 4.

[0060] If the correction unit 122 determines in step S20 that the timer is at least one second long (S20: Yes), it determines whether the change in the AD value obtained by subtracting the AD value from one second ago (1 (s) ago) from the current AD value is greater than C2 and less than C1 (step S23A). Temperature fluctuations cause slight changes in capacitance. On the other hand, moving the hand H causes significant changes in capacitance. Rather than accumulating the AD value change indefinitely, the change in AD value is limited to a certain range and added to the previously calculated cumulative value, thereby accumulating the change in capacitance due to temperature. The value within the certain range is an example of a value within a predetermined range, and is defined by a lower limit C2 and an upper limit C1. The lower limit C2 and upper limit C1 may be set to appropriate values ​​depending on the maximum magnitude of the change in sensitivity of the electrostatic sensor electrode 110 due to a temperature change over one second. For example, C2 = −50 and C1 = 50. The AD value from a certain number of seconds ago to be subtracted from the current AD value is not limited to one second ago, and may be set to any appropriate value.

[0061] The HODECU 120 measures the AD value every 10 ms. On the other hand, during touch, the correction unit 122 updates the reference value every second, so the determination in step S20 is Yes when the count time of the timer reaches 1 second.

[0062] If the correction unit 122 determines that the fluctuation in the AD value is greater than C2 and smaller than C1 (S23A: Yes), it sets the fluctuation in the AD value ΔAD to the fluctuation in the AD value obtained by subtracting the AD value from one second ago (1(s) ago) from the current AD value (step S24A). After completing the process of step S24A, the correction unit 122 causes the flow to proceed to step S25. Here, the fluctuation in the AD value is the fluctuation (difference) in the AD value obtained by subtracting the AD value from one second ago (1(s) ago) from the current AD value, and is a value used in calculating the cumulative value.

[0063] If the correction unit 122 determines in step S23A that the variation in the AD value is not greater than C2 or not smaller than C1 (S23A: No), it determines whether the variation in the AD value is equal to or smaller than C2 (step S23B).

[0064] If the correction unit 122 determines that the fluctuation in the AD value is equal to or smaller than C2 (S23B: Yes), it sets the fluctuation in the AD value ΔAD to C2 (step S24B). In this case, it sets the fluctuation in the AD value ΔAD to a lower limit value C2 for limiting the fluctuation in the AD value ΔAD to a value within a certain range. After completing the process of step S24B, the correction unit 122 causes the flow to proceed to step S25.

[0065] Furthermore, if the correction unit 122 determines in step S23B that the fluctuation in the AD values ​​is not equal to or less than C2 (S23B: No), it sets the fluctuation in the AD values ​​ΔAD to C1 (step S24C). In this case, the fluctuation in the AD values ​​is equal to or greater than C1, so the fluctuation in the AD values ​​ΔAD is set to the upper limit C1 for limiting the fluctuation in the AD values ​​to a value within a certain range. After completing the process of step S24C, the correction unit 122 causes the flow to proceed to step S25.

[0066] The correction unit 122 updates the accumulated value by adding the fluctuation amount ΔAD of the AD value to the accumulated value at the current time (step S25). That is, accumulated value (updated value) = accumulated value (current value before update) + ΔAD.

[0067] The correction unit 122 determines whether the current cumulative input lower limit value is smaller than the cumulative value updated in step S25 (step S26), in order to determine whether the cumulative value has decreased too much.

[0068] If the correction unit 122 determines that the cumulative value updated in step S25 is greater than the cumulative input lower limit value (S26: Yes), it updates the cumulative input value to the cumulative value updated in step S25 (step S27A). That is, the cumulative input value=the cumulative value.

[0069] The correction unit 122 resets the timer to 0 seconds (step S28) in order to count the next second.

[0070] The correction unit 122 sets the AD value from one second ago (1(s) ago) as the current AD value (step S29). That is, the AD value (1(s) ago) = the AD value. This is because the current AD value is used as the AD value one second from now (1(s) ago) in preparation for processing one second from now. Note that the AD value from how many seconds ago (1(s) ago) is set as the current AD value is not limited to one second ago, and may be set to any appropriate value.

[0071] The correction unit 122 calculates the reference value at the time of touch using equation (2) (step S30). Based on equation (2), the correction unit 122 multiplies the reference value (1 s ago) by a weight M to obtain a weighted average of the reference value (1 s ago) and the cumulative input value. That is, the correction unit 122 adds a correction value based on the cumulative input value to the reference value at the time when the hand H starts to contact the grip 11 of the steering wheel 10. This allows the proximity determination device 100 to improve the accuracy of correction of the reference value.

[0072] The correction unit 122 substitutes the reference value for the reference value (1 second before) (step S31). The correction unit 122 performs the process of step S31 to use the reference value when correcting (updating) the reference value of the touch state one second later.

[0073] If the correction unit 122 determines in step S26 that the current cumulative input lower limit value is not smaller than the cumulative value updated in step S25 (S26: No), it sets the cumulative input value to the cumulative input lower limit value (step S27B). After completing the process of step S27B, the correction unit 122 causes the flow to proceed to step S27C. The correction unit 122 outputs a signal indicating a decrease in accuracy (accuracy decrease signal) (step S27C). After completing the process of step S27C, the correction unit 122 causes the flow to proceed to step S28. In particular, in HoD, for fail-safe purposes, it is preferable to make it easier to determine a release if the accuracy of the reference value decreases. If the cumulative value becomes smaller than the cumulative input lower limit value, there is a possibility that the accuracy of the reference value has decreased. For this reason, the reference value is not made lower, making it easier to determine a release. Furthermore, even if the grip strength of the user's hand H on the grip 11 of the steering wheel 10 gradually weakens, the cumulative input value does not decrease too much, so the touch state can be correctly determined even if the grip strength gradually weakens.

[0074] <Explanation of the Operation of the Proximity Determination Device 100> Here, before describing the operation of the proximity determination device 100, the operation of the proximity determination devices of Comparative Examples 1 and 2 will be described. FIGS. 8A and 8B are diagrams showing an example of the operation of the proximity determination devices of Comparative Examples 1 and 2. The proximity determination devices of Comparative Examples 1 and 2 are proximity determination devices for comparison, rather than the proximity determination device 100 of the embodiment. The proximity determination device of Comparative Example 1 is a proximity determination device that always uses an accumulated value as the accumulated input value of the proximity determination device 100 of the embodiment. Moreover, the proximity determination device of Comparative Example 2 is a proximity determination device that uses a maximum accumulated value instead of the accumulated input value of the proximity determination device 100 of the embodiment.

[0075] The maximum cumulative value is the maximum value of the cumulative values, and more specifically, is the maximum value when the direction in which the AD value changes in response to an increase in the degree of contact (the direction in which the AD value increases) is taken as positive.

[0076] In Figures 8A and 8B, the horizontal axis represents time. Figure 8A shows the AD value, reference value, cumulative value, and contact state. The AD value, reference value, and cumulative value are represented as capacitance count values. Figure 8B shows the AD value, reference value, cumulative maximum value, and contact state. The AD value, reference value, and cumulative maximum value are represented as capacitance count values. The AD value is a measured value. The contact state represents the determination result of the proximity determination devices of Comparative Examples 1 and 2, either a released state (0) or a touched state (1).

[0077] 8A and 8B, at time 0, the temperature of the electrostatic sensor electrode 110 is -20°C, and as time passes, the temperature rises to 50°C at time 50, and then drops from time 50 to -20°C at time 100. The user's hand H is in contact with the grip 11 of the steering wheel 10 from time 0 to time 115. In the experiments, a human body phantom was used as the user's hand H.

[0078] In Comparative Example 1 shown in Fig. 8A, the reference value changes as the AD value increases or decreases from time 0 to time 120. However, errors in the cumulative value accumulate, and the cumulative value becomes too small, so the touch state (1) continues even after time 115. This is a state in which the touch state (1) is determined even after the hand H is released from the grip 11 of the steering wheel 10.

[0079] In Comparative Example 2 shown in FIG. 8B, from time 0 to around time 50, the reference value increases as the AD value increases. However, after around time 50 when the temperature drops, the AD value decreases while the reference value becomes a constant value. Due to an incorrect calculation of the reference value, the contact state changes to the released state (0) around time 100. This is a state in which the hand H is in contact with the grip 11 of the steering wheel 10, but is determined to be in the released state (0). In Comparative Example 2, when the hand H is released from the grip 11 of the steering wheel 10, the proximity determination device 100 almost certainly determines that the state is in the released state (0), thereby achieving a fail-safe.

[0080] In this way, with the comparative proximity determination device, when the hand H is in contact with the grip 11 of the steering wheel 10 and the temperature of the electrostatic sensor electrode 110 changes drastically, it may not be possible to correctly determine the contact state.

[0081] FIG. 9 is a diagram illustrating an example of the operation of the proximity determination device 100 according to the embodiment. In FIG. 9, the horizontal axis represents time (seconds). In FIG. 9, the AD value, reference value, cumulative input value, and contact state are represented by capacitance count values. The contact state represents the determination result of the proximity determination device 100, i.e., the released state (0) or the touched state (1). The proximity determination device 100 according to the embodiment shown in FIG. 9 changes temperature under the same conditions and moves the user's hand H for the same period of time as the proximity determination device according to Comparative Example 1 shown in FIG. 8A and the proximity determination device according to Comparative Example 2 shown in FIG. 9B. That is, in the proximity determination device 100 according to the embodiment shown in FIG. 9, the temperature of the electrostatic sensor electrode 110 is −20°C at time 0, and increases over time to 50°C at time 50. From time 50, the temperature decreases and reaches −20°C at time 100. The user's hand H is in contact with the grip 11 of the steering wheel 10 from time 0 to time 115.

[0082] As shown in FIG. 9 , in the proximity determination device 100 of the embodiment, the reference value changes as the AD value increases or decreases from time 0 to around time 100. From time 0 to around time 100, the cumulative input value is used as the cumulative input value. The reference value is a weighted average of the cumulative input value and changes smoothly. From around time 100 to around time 115, the cumulative input lower limit value is used as the cumulative input value. The reference value becomes a value close to the cumulative input lower limit value. After around time 115, the user's hand H leaves the grip 11. Therefore, around time 115, the AD value suddenly decreases. As the AD value decreases, the grip determination changes to the released state (0). In this example, the proximity determination device 100 can correctly determine the touch state even when the temperature of the electrostatic sensor electrode 110 changes. Note that the cumulative value also decreases if the user's hand H gradually weakens its grip on the grip 11 of the steering wheel 10. However, because the cumulative input value does not fall below the cumulative input lower limit, the touch state can be accurately determined even if the grip force changes gradually. Although not shown, if the temperature of the electrostatic sensor electrode 110 further drops, the accuracy of the cumulative input value deteriorates, and it becomes impossible to accurately determine whether the hand H is in contact with the grip, the released state (0) is more likely to be determined. In HoD, for fail-safe purposes, it is preferable to determine the released state (0) when a determination cannot be made. In this embodiment, when a touch state continues, a lower limit is set for the cumulative input value used to calculate the reference value, so that when a determination cannot be made, the released state (0) is determined. The proximity determination device 100 of the embodiment is similar to the proximity determination device of Comparative Example 2 in that it has a fail-safe function. The proximity determination device 100 of the embodiment achieves a fail-safe in a different way from the proximity determination device of Comparative Example 2, thereby almost reliably detecting the released state (0) and improving determination accuracy compared to the proximity determination device of Comparative Example 2.

[0083] Although the above describes a form in which the proximity determination device 100 is used to determine HoD, the use of the proximity determination device 100 is not limited to determining HoD. If an object on which the electrostatic sensor electrode 110 is arranged is touched for a relatively long time with a part of a living body such as a hand H, the proximity determination device 100 can similarly determine the contact state. Furthermore, even for products other than HoD, if a similar fail-safe function is required, the same effect as HoD can be achieved.

[0084] <Effects> The proximity determination device 100 includes an electrostatic sensor electrode 110 covered with a cover (grip 11) having an operation surface, a measurement circuit (AFE120A) that measures the capacitance between the electrostatic sensor electrode 110 and the indicator, a proximity determination unit 123 that determines whether the indicator is in proximity to the electrostatic sensor electrode 110 based on a difference obtained by subtracting a reference value from the capacitance (AD value) measured by the measurement circuit (AFE120A), a correction unit 122 that corrects the reference value, and a storage unit (memory 124).The correction unit 122 stores a cumulative input lower limit value based on the reference value before the indicator is in proximity in the storage unit (memory 124), calculates a cumulative value of the variation in capacitance in the proximity state, updates the reference value based on the cumulative input value that takes either the cumulative value or the cumulative input lower limit value, and sets the cumulative input value to the cumulative value if the cumulative value is greater than the cumulative input lower limit value, or sets the cumulative input value to the cumulative input lower limit value if the cumulative value is smaller than the cumulative input lower limit value. Therefore, even if the temperature of the electrostatic sensor electrode 110 rises or falls, the reference value can be appropriately updated by changing the cumulative input value based on the cumulative value. If the temperature of the electrostatic sensor electrode 110 rises, the reference value can be increased, and if the temperature of the electrostatic sensor electrode 110 falls, the reference value can be decreased. Furthermore, because the reference value does not fall too much, the release state can be determined almost reliably.

[0085] Therefore, it is possible to provide the proximity determination device 100 that can appropriately update the reference value in response to an increase or decrease in temperature so as to be able to correctly determine the proximity of the pointer.

[0086] The cumulative input lower limit value may be a value obtained by subtracting a predetermined value from the reference value before the proximity state is reached. By using the cumulative input lower limit value obtained by subtracting a predetermined value from the reference value before the proximity state is reached, the reference value can be appropriately updated in response to an increase or decrease in the temperature of the electrostatic sensor electrode 110.

[0087] The correction unit 122 may also set upper and lower limit values ​​for the amount of change in capacitance (AD value) per unit time, and if the amount of change is smaller than the lower limit value, set the amount of change to the lower limit value, and if the amount of change is larger than the upper limit value, set the amount of change to the upper limit value. By setting appropriate upper and lower limit values ​​for the amount of change in capacitance (AD value) per unit time, it is possible to limit the amount of change in the AD value to a value within a certain range and add it to the previously calculated cumulative value, rather than accumulating it indefinitely. Furthermore, by limiting the amount of change to a value within a certain range, it is possible to appropriately update the reference value.

[0088] Furthermore, the correction unit 122 may correct the reference value by calculating a weighted average of the reference value and the cumulative input value in the proximity state, or may correct the reference value by calculating a weighted average of the reference value and the capacitance (AD value) in the non-proximity state where the indicator is not in proximity to the electrostatic sensor electrode 110. In the proximity state and the non-proximity state, an appropriate reference value can be obtained by calculating a weighted average of the reference value and the cumulative input value, and the proximity determination device 100 can be provided that can appropriately update the reference value in response to increases and decreases in temperature.

[0089] The proximity determination method includes a proximity determination device 100 including an electrostatic sensor electrode 110 covered with a cover (grip 11) having an operation surface, a measurement circuit (AFE120A) that measures the capacitance between the electrostatic sensor electrode 110 and an indicator, a proximity determination unit 123 that determines whether the indicator is in proximity to the electrostatic sensor electrode 110 based on a difference obtained by subtracting a reference value from the capacitance measured by the measurement circuit (AFE120A), a correction unit 122 that corrects the reference value, and a storage unit (memory 124), in which the correction unit 122 stores a cumulative input lower limit value based on the reference value before the indicator is in proximity in the storage unit (memory 124), calculates a cumulative value of the variation in capacitance in the proximity state, updates the reference value based on the cumulative input value that takes either the cumulative value or the cumulative input lower limit value, and if the cumulative value is greater than the cumulative input lower limit value, sets the cumulative input value to the cumulative value, and if the cumulative value is smaller than the cumulative input lower limit value, sets the cumulative input value to the cumulative input lower limit value. Therefore, even if the temperature of the electrostatic sensor electrode 110 rises or falls, the reference value can be appropriately changed by changing the cumulative input value based on the cumulative value. If the temperature of the electrostatic sensor electrode 110 rises, the reference value can be increased, and if the temperature of the electrostatic sensor electrode 110 falls, the reference value can be decreased.

[0090] Therefore, it is possible to provide a proximity determination method that can appropriately update the reference value in response to an increase or decrease in temperature so as to be able to correctly determine the proximity of the pointer.

[0091] The above describes the proximity determination device and proximity determination method according to exemplary embodiments of the present invention. However, the present invention is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims. [Explanation of symbols]

[0092] 10. Steering wheel 11 Grip 12 Signal line 50 ECU 100 Proximity determination device 110 Electrostatic sensor electrode 120 HODECU 120A AFE 120B MPU 121 Main control unit 122 Correction unit 123 Proximity detection unit 124 memory

Claims

1. an electrostatic sensor electrode covered with a cover having an operation surface; a measurement circuit for measuring the capacitance between the electrostatic sensor electrode and a pointer; a proximity determination unit that determines whether the indicator is in a proximity state where it is close to the electrostatic sensor electrode, based on a difference obtained by subtracting a reference value from the electrostatic capacitance measured by the measurement circuit; a correction unit that corrects the reference value; Memory section and Including, The correction unit storing a cumulative input lower limit value based on the reference value before the proximity state is reached in the storage unit; calculating a cumulative value of the capacitance fluctuation in the proximity state; updating the reference value based on an accumulated input value that takes a value of either the accumulated value or the accumulated input lower limit value; If the cumulative value is greater than the cumulative input lower limit value, set the cumulative input value to the cumulative value; If the cumulative value is smaller than the cumulative input lower limit value, the proximity determination device sets the cumulative input value to the cumulative input lower limit value.

2. The proximity determination device according to claim 1 , wherein the cumulative input lower limit value is a value obtained by subtracting a predetermined value from the reference value before the proximity state is established.

3. The correction unit setting an upper limit value and a lower limit value for the fluctuation amount of the capacitance per unit time; If the fluctuation amount is smaller than the lower limit value, the fluctuation amount is set to the lower limit value; The proximity determination device according to claim 1 , wherein, when the amount of variation is greater than the upper limit, the amount of variation is set to the upper limit.

4. 4. The proximity determination device according to claim 1, wherein the correction unit corrects the reference value by calculating a weighted average of the reference value and the cumulative input value in the proximity state, or corrects the reference value by calculating a weighted average of the reference value and the capacitance in the non-proximity state in which the indicator is not in proximity to the electrostatic sensor electrode.

5. an electrostatic sensor electrode covered with a cover having an operation surface; a measurement circuit for measuring the capacitance between the electrostatic sensor electrode and a pointer; a proximity determination unit that determines whether the indicator is in a proximity state where it is close to the electrostatic sensor electrode, based on a difference obtained by subtracting a reference value from the electrostatic capacitance measured by the measurement circuit; a correction unit that corrects the reference value; Memory section and In a proximity determination device including: The correction unit: storing a cumulative input lower limit value based on the reference value before the proximity state is reached in the storage unit; calculating a cumulative value of the capacitance fluctuation in the proximity state; updating the reference value based on an accumulated input value that takes a value of either the accumulated value or the accumulated input lower limit value; If the cumulative value is greater than the cumulative input lower limit value, set the cumulative input value to the cumulative value; If the cumulative value is smaller than the cumulative input lower limit value, the cumulative input value is set to the cumulative input lower limit value.

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