Position detection device

Abstract

The present invention comprises: one reference electrode (103); two detection electrodes (101); a measurement unit (110) that measures the capacitance values (C) between the reference electrode (103) and each of the detection electrodes (101); and a position detection unit (120) that detects a human body position on the basis of the capacitance value (C) measured by the measurement unit (110) for each detection electrode (101). The relative relationship of the magnitudes of the capacitance values (C) differs depending on the direction in which the human body position is separated from the detection electrodes (101). Therefore, even when the human body is at a position separated from the detection electrodes (101), the human body position can be accurately detected.

Description

Position detection device CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2024-86539 filed in Japan on May 28, 2024, the contents of which are incorporated by reference in their entirety.

[0002] The present invention relates to a position detection device that detects the position of a human body.

[0003] The system disclosed in Patent Document 1 includes multiple capacitance sensors in the seat, and determines whether a person is seated on each sensor by comparing the capacitance values ​​detected by the multiple capacitance sensors with a threshold value. The contents of the prior art document are incorporated by reference as explanations of the technical elements in this specification.

[0004] JP 2022-87450 A

[0005] The method disclosed in Patent Document 1 simply compares the capacitance value with a threshold value to determine whether a person is seated on each capacitance sensor, and therefore cannot detect the position of a person when the person is not seated, i.e., when the person is located far from the capacitance sensor.

[0006] The present disclosure has been made based on this situation, and its purpose is to provide a position detection device that can detect the position of a human body even if the human body is located away from a detection electrode for detecting a capacitance value.

[0007] The above object is achieved by the combination of features recited in the independent claims, and the subclaims define further advantageous specific examples. The reference numerals in parentheses in the claims correspond to specific aspects described in the following embodiments as one aspect, and do not limit the technical scope of the disclosure.

[0008] One disclosure for achieving the above object is a position detection device comprising one reference electrode, two or more detection electrodes, a measurement unit that measures capacitance-related values, which are either the capacitance value between the reference electrode and each detection electrode or values ​​that change in relation to the capacitance value, and a position detection unit that detects the position of a human body based on the capacitance-related values ​​measured by the measurement unit for each detection electrode.

[0009] In this position detection device, a reference electrode is common to two or more detection electrodes, and the measurement unit measures the capacitance value between the reference electrode and each detection electrode or a capacitance-related value, which is a value that changes in relation to the capacitance value. The relative relationship of the magnitude of each capacitance-related value varies depending on the direction in which the human body position is separated from the detection electrode. Therefore, the human body position can be detected with high accuracy even if the human body is located far from the detection electrode used to detect the capacitance value.

[0010] 1 is a diagram for explaining the configuration of a position detection device according to a first embodiment; a diagram showing the arrangement of detection electrodes; a diagram showing the configuration of a measurement unit; a diagram for explaining the relationship between a capacitance ratio and a foot position; a diagram showing the relationship between a capacitance ratio and a foot position in the vehicle width direction; a diagram showing an example of position detection processing; a diagram showing the position detection processing executed by a position detection unit in a second embodiment; a diagram showing the relationship between the distance between a detection electrode and a foot, and a capacitance value; a diagram showing the configuration of a position detection device according to a fourth embodiment; a diagram for explaining a fifth embodiment; a diagram showing the configuration of a position detection device according to a sixth embodiment; a diagram showing the position detection processing in the sixth embodiment; a diagram for explaining detection electrodes in a seventh embodiment; a diagram showing the arrangement of detection electrodes in an eighth embodiment.

[0011] First Embodiment An embodiment will now be described with reference to the drawings. FIG. 1 is a diagram illustrating the configuration of a position detection device 100 according to this embodiment. The position detection device 100 is mounted on a vehicle 10. The position detection device 100 includes a detection electrode 101, a reference electrode 103, a measurement unit 110, and a position detection unit 120. In the first embodiment, the reference electrode 103 is the body of the vehicle 10. The body of the vehicle 10 exists in various locations on the vehicle 10, but if it can be considered to have the same potential, there is only one reference electrode 103.

[0012] As shown in FIG. 2 , the detection electrodes 101 are respectively disposed on the accelerator pedal 11a and the brake pedal 11b of the vehicle 10. The detection electrode 101 disposed on the accelerator pedal 11a is referred to as the detection electrode 101a, and the detection electrode 101 disposed on the brake pedal 11b is referred to as the detection electrode 101b. Both of the two detection electrodes 101a and 101b are flat. When there is no need to distinguish between the two detection electrodes 101a and 101b, they are referred to as the detection electrodes 101. When there is no need to distinguish between the accelerator pedal 11a and the brake pedal 11b, they are referred to as the pedals 11.

[0013] The measurement unit 110 can apply an AC voltage to the detection electrode 101. The measurement unit 110 measures the capacitance value C between the detection electrode 101a and the reference electrode 103, and between the detection electrode 101b and the reference electrode 103.

[0014] When an AC voltage is applied to the detection electrode 101, the reference electrode 103, which is the body of the vehicle 10, becomes GND, and an electric circuit is generated that includes the detection electrode 101, the occupant P, and metal parts inside the seat 12 of the vehicle 10. In this electric circuit, capacitance and resistance exist between the reference electrode 103 and the detection electrode 101, as indicated by symbols in Fig. 1. As shown in Fig. 2, the capacitance value C between the reference electrode 103 and the detection electrode 101a is defined as capacitance value Ca, and the capacitance value C between the reference electrode 103 and the detection electrode 101b is defined as capacitance value Cb.

[0015] 3 shows the configuration of the measurement unit 110. The measurement unit 110 includes a current measurement unit 111, a detector 112, and a power supply 113. The measurement unit 110 can also be referred to as a measurement device or a measurement circuit. The current measurement unit 111 detects the amplitude and phase of the current flowing through the detection electrode 101, and may use a shunt resistor, for example. A current measurement unit 111 is provided for each of the multiple detection electrodes 101.

[0016] The detector 112 detects current information and voltage information of the current flowing through the current measuring unit 111. This current information and voltage information include amplitude and phase. The detector 112 then calculates impedance or admittance based on the detected current information and voltage information. Furthermore, the detector 112 calculates a capacitance component from the calculated impedance or admittance. The value of the capacitance component calculated based on the current information and voltage information of the current measuring unit 111 corresponding to the detection electrode 101a is the capacitance value Ca, and the value of the capacitance component calculated based on the current information and voltage information of the current measuring unit 111 corresponding to the detection electrode 101b is the capacitance value Cb.

[0017] The position detection unit 120 controls the measurement unit 110 to cause the measurement unit 110 to measure the capacitance values ​​Ca and Cb. The position detection unit 120 detects the human body position based on the capacitance values ​​Ca and Cb measured by the measurement unit 110. In the first embodiment, the human body position to be detected is the position of the feet PF of the occupant P, which is a part of the human body. The feet PF are parts below the ankles. The position detection unit 120 can be realized, for example, by a computer including a processor and a memory. Furthermore, the position detection unit 120 is not limited to a computer, and may be configured to include a hardware circuit that performs the following processes.

[0018] Specifically, the position detection unit 120 uses the two capacitance values ​​Ca and Cb by calculating the ratio between the two capacitance values ​​Ca and Cb. Hereinafter, the ratio between the capacitance values ​​Ca and Cb will be referred to as the capacitance ratio. Either the capacitance value Ca or Cb may be used as the denominator. In the following description, the capacitance ratio Ca / Cb is calculated using the capacitance value Cb as the denominator.

[0019] The relationship between the capacitance ratio Ca / Cb and the position of the foot PF will be explained using Figure 4. (A) shows a state in which the foot PF is located above and near the brake pedal 11b. (B) shows a state in which the foot PF is located above and near the accelerator pedal 11a. (C) shows a state in which the foot PF is located above the brake pedal 11b but away from it.

[0020] In the case of (A), the capacitance value Cb increases and the capacitance value Ca decreases, resulting in a small capacitance ratio Ca / Cb. In the case of (B), the capacitance value Cb decreases and the capacitance value Ca increases, resulting in a large capacitance ratio Ca / Cb. In the case of (C), both capacitance values ​​Cb and Ca are small, but the capacitance value Cb is larger than the capacitance value Ca. Therefore, the capacitance ratio Ca / Cb is small, although not as small as in the case of (A).

[0021] FIG. 5 shows the relationship between the capacitance ratio Ca / Cb and the position of the foot PF in the vehicle width direction. In FIG. 5, (A), (B), and (C) represent the states (A), (B), and (C) in FIG. 4, respectively. As shown in FIG. 5, the capacitance ratio Ca / Cb is significantly affected by the position of the foot PF in the vehicle width direction, i.e., the direction in which the detection electrodes 101 are arranged, and is hardly affected by the vertical position of the foot PF. The capacitance values ​​Ca and Cb are also affected by differences in the material of the sole. This is because the dielectric constant changes depending on the material of the sole. However, by making the ratio, differences in the material of the sole are canceled out.

[0022] 6 shows an example of the position detection process. This process is executed by the position detection unit 120. In S10, the measurement unit 110 measures the capacitance value Ca and acquires the value. In S20, the measurement unit 110 measures the capacitance value Cb and acquires the value. In S30, the capacitance values ​​Ca and Cb acquired in S10 and S20 are used to calculate the capacitance ratio Ca / Cb.

[0023] In S40, it is determined whether the capacitance values ​​Ca and Cb acquired in S10 and S20 are both equal to or less than a proximity threshold. The proximity threshold is a value for determining whether a human body is present near the detection electrode 101 corresponding to the capacitance values ​​Ca and Cb. In this embodiment, the proximity threshold is a fixed value determined in advance. If the capacitance values ​​Ca and Cb are both equal to or less than the proximity threshold, the process proceeds to S50. In S50, it is determined that the foot PF, which is the detection target, is not present near the detection electrode 101.

[0024] If the determination result in S40 is NO, the process proceeds to S60. In S60, the capacitance ratio Ca / Cb is compared with position determination thresholds TH1 and TH2. The position determination thresholds TH1 and TH2 are shown in FIG. 5. The position determination threshold TH1 is a threshold for determining whether the foot PF is near the detection electrode 101b, i.e., near the brake pedal 11b. The position determination threshold TH2 is a threshold for determining whether the foot PF is near the detection electrode 101a, i.e., near the accelerator pedal 11a. The specific values ​​of the position determination thresholds TH1 and TH2 are determined based on experiments, etc.

[0025] Since the position determination thresholds TH1 and TH2 are of such values, if the determination in S60 shows that the capacitance ratio Ca / Cb is equal to or less than the position determination threshold TH1, the process proceeds to S70, where it is determined that the foot PF is near the brake pedal 11b. If the determination in S60 shows that the capacitance ratio Ca / Cb is greater than the position determination threshold TH1 but less than the position determination threshold TH2, the process proceeds to S80, where it is determined that the foot PF is between the brake pedal 11b and the accelerator pedal 11a. If the determination in S60 shows that the capacitance ratio Ca / Cb is equal to or greater than the position determination threshold TH2, the process proceeds to S90, where it is determined that the foot PF is near the accelerator pedal 11a.

[0026] After executing any one of S50, S60, S80, and S90, the process proceeds to S100, where the determination result is notified to the outside, for example, by displaying the determination result on a predetermined display unit.

[0027] (Summary of First Embodiment) The position detection device 100 of the first embodiment described above includes two detection electrodes 101 and a common reference electrode 103, and the measurement unit 110 measures the capacitance values ​​Ca and Cb between the reference electrode 103 and each detection electrode 101 (S10, S20). As described with reference to Fig. 4, the relative relationship between the magnitudes of the capacitance values ​​Ca and Cb varies depending on the direction in which the foot PF is separated from the detection electrode 101. Therefore, the position detection device 100 can accurately detect the position of the foot PF even if the foot PF is separated from the detection electrode 101.

[0028] In the first embodiment, the body of the vehicle 10 serves as the reference electrode 103. Therefore, when the position detection device 100 is installed in the vehicle 10, it is not necessary to prepare a separate reference electrode 103.

[0029] In the first embodiment, the position detector 120 detects the position of the foot PF based on the capacitance ratio Ca / Cb (S60, S70, S80, S90). The capacitance ratio Ca / Cb is less affected by the vertical position of the foot PF and the material of the sole. Therefore, the position of the foot PF in the vehicle width direction can be detected with high accuracy.

[0030] In the first embodiment, the position detection unit 120 determines whether the foot PF is near the detection electrode 101 based on the capacitance values ​​Ca and Cb used to calculate the capacitance ratio Ca / Cb (S40, S50). This improves the accuracy of detecting the position of the foot PF.

[0031] In the first embodiment, the two detection electrodes 101 a and 101 b are provided on the accelerator pedal 11 a and the brake pedal 11 b. Therefore, when S50 in Fig. 6 is executed, it can be determined that the foot PF is neither near the accelerator pedal 11 a nor near the brake pedal 11 b.

[0032] Second Embodiment Next, a second embodiment will be described. In the following description of the second embodiment, elements having the same reference numerals as those used previously are the same as those in the previous embodiments unless otherwise specified. Furthermore, when only a portion of the configuration is described, the previously described embodiment can be applied to the other portions of the configuration.

[0033] 7 shows the position detection process executed by the position detection unit 120 in the second embodiment. Although not shown, steps S10, S20, S30, and S40 are the same as those in FIG. 6. Also, steps S50, S60, S70, S80, and S90 shown in the figure are the same as those in FIG. 6.

[0034] If it is determined in S70 that the foot PF is near the brake pedal 11b, the process proceeds to S71. In S71, a differential value of the capacitance value Cb is calculated. In the following S72, the pedal operation state is determined based on the differential value calculated in S71. There are four pedal operation states: The first state is when the depression amount of the brake pedal 11b is increasing; the second state is when the depression state of the brake pedal 11b is maintained; and the third state is when the depression amount of the brake pedal 11b is decreasing. These first to third states are when the detection electrode 101b and the brake pedal 11b are pressed down. The final fourth state is when the foot PF is not in contact with the brake pedal 11b.

[0035] 8 shows the relationship between the distance D between the detection electrode 101b and the foot PF and the capacitance value Cb when the detection electrode 101b is installed on the brake pedal 11b. The distance D is to the right of 0 on the horizontal axis, and distance D = 0 indicates a state in which the foot PF is in contact with the brake pedal 11b. The scale to the left of 0 on the horizontal axis indicates a state in which the foot PF is pressing down on the brake pedal 11b. The scale to the left of 0 on the horizontal axis indicates the amount of operation of the brake pedal 11b.

[0036] As shown in FIG. 8 , the capacitance value Cb changes more significantly as the distance D approaches zero from a large distance D. The change in capacitance Cb then becomes even greater as the brake pedal 11b is depressed. When the occupant P operates the brake pedal 11b, there is a correlation between the distance D or the depression amount of the brake pedal 11b and time. Therefore, in the first state, i.e., when the depression amount of the brake pedal 11b is increasing, the absolute value of the derivative of the capacitance value Cb increases. Similarly, in the third state, i.e., when the depression amount of the brake pedal 11b is decreasing, the absolute value of the derivative of the capacitance value Cb also increases. To determine the absolute value of the derivative that determines whether the depression amount of the brake pedal 11b is increasing or decreasing, a pedal depression threshold is set based on experiments or the like, and the absolute value of the derivative exceeds the pedal depression threshold.

[0037] If the absolute value of the differential value exceeds the pedal depression threshold value for the first time after determining that the foot PF is near the brake pedal 11b, it can be determined that the first state has been reached. Subsequently, as the change in the amount of depression of the brake pedal 11b decreases, such as when the brake pedal 11b is fully depressed, the change in the capacitance value Cb also decreases. Therefore, when the process of FIG. 7 is repeatedly executed and S70 is continuously executed, if the differential value of the capacitance value Cb falls below the pedal depression threshold value after determining that the first state has been reached, it can be determined that the second state has been reached, i.e., the brake pedal 11b is still being depressed. Furthermore, if the differential value has the opposite sign to that when the first state was determined, but the absolute value exceeds the pedal depression threshold value, it can be determined that the third state has been reached, i.e., the amount of depression of the brake pedal 11b is decreasing. If the differential value subsequently falls below the pedal depression threshold value, it can be determined that the fourth state has been reached, i.e., the foot PF is not in contact with the brake pedal 11b.

[0038] If it is determined in S90 that the foot PF is near the accelerator pedal 11a, the process proceeds to S91. In S91, a differential value of the capacitance value Ca is calculated. In the following S92, the pedal operation state is determined based on the differential value calculated in S91. The pedal operation state is the four states determined in S72, but with the accelerator pedal 11a replaced, and there are four states as follows: The first state is when the depression amount of the accelerator pedal 11a is increasing. The second state is when the depression state of the accelerator pedal 11a is maintained. The third state is when the depression amount of the accelerator pedal 11a is decreasing. The fourth state is when the foot PF is not in contact with the accelerator pedal 11a.

[0039] If the pedal depression threshold is exceeded for the first time after determining that the foot PF is near the accelerator pedal 11a, it can be determined that the first state is being reached, i.e., the amount of depression of the accelerator pedal 11a is increasing. The pedal depression threshold is determined based on experiments, etc. The pedal depression threshold may be the same as or different from that in S72.

[0040] Subsequently, as the change in the depression amount of the accelerator pedal 11a decreases, the change in the capacitance value Ca also decreases. Therefore, when the process of FIG. 7 is repeatedly executed and S70 is continuously executed, if the differential value of the capacitance value Ca falls below the pedal depression threshold after determining that the first state is present, it can be determined that the second state is present, i.e., the accelerator pedal 11a is still depressed. Furthermore, if the differential value has the opposite sign to that when the first state was determined, but the absolute value of the differential value exceeds the pedal depression threshold, it can be determined that the third state is present, i.e., the depression amount of the accelerator pedal 11a is decreasing. If the differential value then falls below the pedal depression threshold, it can be determined that the fourth state is present, i.e., the foot PF is not in contact with the accelerator pedal 11a.

[0041] In S110, the result of the determination in S50, S72, or S92 is notified.

[0042] In the second embodiment, it is possible to determine whether the foot PF is in the vicinity of the detection electrode 101 (S70, S90), and also to determine whether the detection electrodes 101b, 101a are being pressed down based on the differential values ​​of the capacitance values ​​Ca, Cb.

[0043] Third Embodiment In the second embodiment, the pedal operation state is determined based on the capacitance values ​​Cb and Ca. In the third embodiment, the pedal operation state is determined based on the capacitance ratio Ca / Cb. When it is determined that the foot PF is near the brake pedal 11b (S70), the change in the capacitance value Ca is not large regardless of the first to fourth states determined in S72. Therefore, when it is determined that the foot PF is near the brake pedal 11b, the capacitance value Cb and the capacitance ratio Ca / Cb are correlated.

[0044] Therefore, in S71, the differential value of the capacitance ratio Ca / Cb is calculated instead of the differential value of the capacitance value Cb, and in S72, the pedal operation state can be determined based on the differential value of the capacitance ratio Ca / Cb.

[0045] Similarly, when it is determined that the foot PF is near the accelerator pedal 11a (S90), the change in the capacitance value Cb is not large regardless of the state determined in S92 from states 1 to 4. Therefore, when it is determined that the foot PF is near the accelerator pedal 11a, the capacitance value Ca and the capacitance ratio Ca / Cb are correlated.

[0046] Therefore, in S91, the differential value of the capacitance ratio Ca / Cb is calculated instead of the differential value of the capacitance value Ca, and in S92, the pedal operation state can be determined based on the differential value of the capacitance ratio Ca / Cb.

[0047] 9 shows the configuration of a position detection device 400 according to a fourth embodiment. In the position detection device 400, a reference electrode 403 is disposed in the base portion 12a of the seat 12. The other configuration is the same as that of the position detection device 100.

[0048] When the reference electrode 103 is the body of the vehicle 10 as in the first embodiment, the distance between the occupant P and the reference electrode 103 changes when the occupant P approaches the door of the vehicle 10, for example. Therefore, in the first embodiment, the capacitance values ​​Ca and Cb are easily affected by the posture of the occupant P.

[0049] In contrast, in the fourth embodiment, the reference electrode 403 is disposed in the seat portion 12a of the seat 12, so the distance between the occupant P and the reference electrode 403 is stable regardless of the posture of the occupant P. This increases the correlation between the capacitance values ​​Ca and Cb and the position of the foot PF. This improves the accuracy of detecting the position of the foot PF based on the capacitance values ​​Ca and Cb.

[0050] Fifth Embodiment The fifth embodiment can be combined with the first to fourth embodiments. It can also be combined with the embodiments described below. However, for convenience of explanation, a case where it is combined with the first embodiment will be described. FIG. 10 is a diagram illustrating the fifth embodiment. As shown in FIG. 10, the fifth embodiment includes a guard electrode 502 near the detection electrode 101. In addition, the guard electrode 502 includes a voltage follower circuit 504 for applying the same potential as the detection electrode 101 to the guard electrode 502.

[0051] The guard electrode 502 is provided for the purpose of preventing electric field lines from spreading to unnecessary areas so that the capacitance values ​​Ca and Cb measured by the measurement unit 110 become the capacitance value C of the portion where the occupant P is present between the detection electrode 101 and the reference electrode 103. For this purpose, the guard electrode 502 is provided in a direction from the detection electrode 101 toward the reference electrode 103 without passing through the occupant P. Although two guard electrodes 502 are provided in FIG. 10 , the number of guard electrodes 502 can be adjusted as appropriate for the above purpose. The number of guard electrodes 502 may be one, or three or more.

[0052] By providing the guard electrode 502 to which the same potential as that of the detection electrode 101 is applied, the correlation between the capacitance values ​​Ca and Cb and the capacitance of the occupant P becomes high, so that changes in the position of the feet PF, which are part of the occupant P, are more likely to affect the capacitance values ​​Ca and Cb. This improves the accuracy of detecting the position of the feet PF based on the capacitance values ​​Ca and Cb.

[0053] 11 shows the configuration of a position detection device 600 according to a sixth embodiment. The position detection device 600 includes the measurement unit 110, the detection electrode 101, and the reference electrode 403 described in the previous embodiments. The position detection device 600 also includes a press detection unit 610, a position detection unit 620, and an occupant identification unit 630.

[0054] The depression detection unit 610 detects that the occupant P has pressed down the pedal 11 on which the detection electrode 101 is arranged. Because the detection electrode 101 is arranged on the accelerator pedal 11a and the brake pedal 11b, the depression detection unit 610 detects that the accelerator pedal 11a and the brake pedal 11b have been pressed down, respectively. The depression detection unit 610 detects that the pedal 11 has been pressed down based on a characteristic value different from the capacitance values ​​Ca and Cb. The depression of the accelerator pedal 11a can be determined based on a signal from an accelerator position sensor, for example. The depression of the brake pedal 11b can be determined based on a signal from a brake switch.

[0055] The position detection unit 620 detects the position of the foot PF through the process shown in FIG. 12 . In S230 of FIG. 12 , proximity thresholds THa and THb are used. The position detection unit 620 adjusts the proximity thresholds THa and THb based on the capacitance values ​​Ca and Cb measured by the measurement unit 110 when the depression detection unit 610 detects that the accelerator pedal 11a or the brake pedal 11b has been depressed. Specifically, for example, the proximity threshold THa is set to a value obtained by multiplying the capacitance value Ca measured by the measurement unit 110 when the depression detection unit 610 detects that the accelerator pedal 11a has been depressed by a predetermined coefficient smaller than 1. Similarly, the proximity threshold THb is set to a value obtained by multiplying the capacitance value Cb measured by the measurement unit 110 when the depression detection unit 610 detects that the brake pedal 11b has been depressed by a predetermined coefficient smaller than 1.

[0056] Next, Fig. 12 will be described. Steps S210 and S220 are the same as steps S10 and S20 in Fig. 6, and the position detection unit 620 causes the measurement unit 110 to measure the capacitance values ​​Ca and Cb, and acquires the values.

[0057] In S230, it is determined whether the capacitance value Ca acquired in S210 is equal to or less than the proximity threshold value THa and whether the capacitance value Cb acquired in S220 is equal to or less than the proximity threshold value THb. If the determination result in S230 is YES, the process proceeds to S240. In S240, it is determined that there is no foot PF near the detection electrode 101.

[0058] If the determination result in S230 is NO, the process proceeds to S250. In S250, it is determined whether the magnitude of the capacitance value Ca acquired in S210 is greater than the proximity threshold value THa. If the determination result in S250 is YES, the process proceeds to S260. In S260, it is determined that the foot PF is near the accelerator pedal 11a.

[0059] If the determination result in S250 is NO, the process proceeds to S270. In S270, it is determined whether the magnitude of the capacitance value Cb acquired in S220 is greater than the proximity threshold value THb. If the determination result in S270 is YES, the process proceeds to S280. In S280, it is determined that the foot PF is near the brake pedal 11b.

[0060] In S300, the result of the determination made in any one of S240, S260, S280, and S290 is notified to the outside.

[0061] 11 , the occupant identification unit 630 identifies the occupant P based on the capacitance values ​​Ca and Cb measured by the measurement unit 110 while the depression detection unit 610 detects that the pedal 11 is depressed. The occupant P is identified based on the correlation between the capacitance values ​​Ca and Cb and the physique of the occupant P.

[0062] When it can be determined that the state of the foot PF with respect to the pedal 11 is in a certain state, such as when the depression detection unit 610 detects that the pedal 11 is depressed, the difference in the capacitance values ​​Ca and Cb is largely influenced by the difference in the physique of the occupant P. In particular, in this embodiment, because the reference electrode 403 is provided in the bottom portion 12a of the seat 12, there is little change in the capacitance values ​​Ca and Cb due to changes in the posture of the occupant P. Therefore, when it can be determined by the depression detection unit 610 that the state of the foot PF with respect to the pedal 11 is in a certain state, it can be estimated based on the capacitance values ​​Ca and Cb measured by the measurement unit 110 whether the occupant P is one or more persons whose capacitance values ​​Ca and Cb have been detected in the past, or whether the occupant P is a person whose capacitance values ​​Ca and Cb have never been detected in the past.

[0063] The state of the foot PF relative to the pedal 11 may be, for example, a state in which the foot PF of the occupant P starts to press the pedal 11 or a state in which the foot PF of the occupant P has fully depressed the pedal 11. Furthermore, if a sensor is provided to detect the amount of depression of the accelerator pedal 11a and the brake pedal 11b, the state of the foot PF relative to the pedal 11 may be a state in which the pedal 11 has been depressed by a preset amount.

[0064] In the sixth embodiment, the capacitance values ​​Ca and Cb corresponding to the detection electrodes 101a and 101b are obtained (S210, S220), and the position of the foot PF is detected based on the capacitance values ​​Ca and Cb for each of the detection electrodes 101a and 101b (S230 to S290). As in this embodiment, the position of the foot PF can also be detected based on the capacitance values ​​Ca and Cb, rather than the capacitance ratio Ca / Cb.

[0065] The position detection unit 620 adjusts the proximity thresholds THa and THb based on the capacitance values ​​Ca and Cb when it detects that the accelerator pedal 11 a or the brake pedal 11 b is pressed down. This improves the accuracy of the determinations in S230, S250, and S270, thereby improving the accuracy of detecting the position of the foot PF.

[0066] The sixth embodiment includes an occupant identification unit 630 that identifies the occupant P based on the capacitance values ​​Ca and Cb measured by the measurement unit 110 while the pedal 11 is pressed down. Therefore, in addition to detecting the position of the foot PF of the occupant P, the occupant P can also be identified.

[0067] 13 , two detection electrodes 701, i.e., a detection electrode 701a arranged on the accelerator pedal 11a and a detection electrode 701b arranged on the brake pedal 11b, have different areas. Note that these detection electrodes 701a and 701b may be applied to the previous embodiments. Furthermore, the detection electrodes 101a and 101b of the previous embodiments may have the same area.

[0068] When the areas of the detection electrodes 701a and 701b are different, as will be described below, the capacitance value C ｂｏ As shown in equation (1), the capacitance value Ca can be calculated by ｆａ and C ｂｏ It can be expressed as follows: C ｆａ is the capacitance value C between the foot PF and the detection electrode 101a arranged on the accelerator pedal 11a, and C ｂｏ is the capacitance value C between the body of the occupant P and the reference electrode 103. As shown in equation (2), the capacitance value Cb is ｆｂ and C ｂｏ It can be expressed as follows: C ｆｂ is the capacitance value C between the foot PF and the detection electrode 101b arranged on the brake pedal 11b. ｆａ , C ｆｂ can also be expressed by equations (3) and (4), respectively. In equations (3) and (4), ε is the dielectric constant determined by the material of the shoe sole, d is the thickness of the shoe sole, and Sａ is the area of ​​the detection electrode 101a, S ｂ is the area of ​​the detection electrode 101b.

[0069] From equations (3) and (4), equation (5) is obtained. Substituting equation (5) into equation (1) gives equation (6). Looking at equations (6) and (2), we can see that the unknown is C ｆｂ and C ｂｏ Therefore, from the two equations (6) and (2), C ｆｂ and C ｂｏ The two unknowns can be found.

[0070] As in the seventh embodiment, by making the areas of the detection electrodes 101a and 101b different, C ｆｂ C does not contain ｂｏ can be obtained. ｂｏ By using the above, the accuracy of identifying the occupant P is improved.

[0071] 14 shows the arrangement of detection electrodes 801 in an eighth embodiment. In the eighth embodiment, the detection electrodes 801 include detection electrodes 801a1, 801a2, 801b1, 801b2, and 801b3. The detection electrodes 801a1 and 801a2 are arranged on the accelerator pedal 11a. The detection electrodes 801b1, 801b2, and 801b3 are arranged on the brake pedal 11b.

[0072] In the eighth embodiment, to detect the position of the foot PF of the occupant P, the sum of the capacitance value C between the detection electrode 801a1 and the reference electrode 103 and the capacitance value C between the detection electrode 801a2 and the reference electrode 103 is used as the capacitance value Ca. Also, the sum of the capacitance values ​​C between the detection electrodes 801b1, 801b2, and 801b3 and the reference electrode 103 is used as the capacitance value Cb. Then, by the processing described in the previous embodiments, it is determined whether the foot PF is near the accelerator pedal 11a or the brake pedal 11b.

[0073] When it is determined that the foot PF is near the accelerator pedal 11a, the detection electrode 801a1 or 801a2 that the foot PF is stepping on is determined using the magnitude or ratio of two capacitance values ​​C between the detection electrode 801a1, the detection electrode 801a2 and the reference electrode 103. When the magnitude of the capacitance value C is used, it can be determined that the foot PF is more likely to be stepping on the detection electrode 801a1 or 801a2 with the larger capacitance value C. When the ratio of the capacitance values ​​C is used, it can be determined that the larger the ratio, the more likely the foot PF is stepping on the detection electrode 801a1 or 801a2 that corresponds to the capacitance value C used as the numerator.

[0074] When it is determined that the foot PF is near the brake pedal 11b, the detection electrodes 801b1, 801b2, and 801b3 that the foot PF is stepping on are determined using the magnitude or ratio of the three capacitance values ​​C between the detection electrodes 801b1, 801b2, and 801b3 and the reference electrode 103. When using ratios, three ratios are calculated. Two of the three ratios have the capacitance value C corresponding to one of the three detection electrodes 801b1, 801b2, and 801b3 as the denominator. For example, the capacitance value C corresponding to the detection electrode 801b1 is used as the denominator. The remaining one of the two ratios is the ratio of the capacitance values ​​C corresponding to the detection electrodes 801b2 and 801b3, which were not used as the denominators in the previous two ratios.

[0075] In the eighth embodiment, the accelerator pedal 11a and the brake pedal 11b are each provided with a plurality of detection electrodes 801a1, 801a2, 801b1, 801b2, and 801b3. Then, the capacitance value C between each of the detection electrodes 801a1, 801a2, 801b1, 801b2, and 801b3 and the reference electrode 103 is calculated. In this way, it is possible to determine where on the pedal 11 the foot PF is pressing, or how the pedal 11 is being pressed.

[0076] Although the embodiments have been described above, the disclosed technology is not limited to the above-described embodiments, and the following modifications are also included in the scope of the disclosure. Furthermore, various modifications other than those described below can be made without departing from the spirit of the invention.

[0077] <Modification 1> In the embodiments described above, the reference electrodes 103, 403 are provided on the body of the vehicle 10 or the seat portion 12a of the seat 12. However, the reference electrodes may be provided on the floor surface of the vehicle 10. For example, the reference electrode 403 may be arranged near the feet of the driver's seat of the vehicle 10 so as to include an area where the left foot of the occupant P is placed. As an example of a reference electrode provided on the floor surface, the reference electrode 403 may be provided on a footrest. When the reference electrode 403 is provided on the floor surface of the vehicle 10, the capacitance values ​​Ca, Cb are less likely to be affected by the upper body posture of the occupant P.

[0078] <Modification 2> In the fourth embodiment, the reference electrode 403 is provided in the seat portion 12a of the seat 12. However, the reference electrode 403 may be provided in the backrest portion of the seat 12 instead of or in addition to the seat portion 12a of the seat 12. When the reference electrodes 403 are provided in the seat portion 12a and the backrest portion of the seat 12, the reference electrode 403 provided in the seat portion 12a and the reference electrode 403 provided in the backrest portion are electrically connected to form a single reference electrode 403.

[0079] <Modification 3> In the embodiment, the position of the human body is detected based on the capacitance value C. However, the position of the human body may be detected using the impedance Z instead of the capacitance value C. This is because the impedance Z is a capacitance-related value that changes in relation to the capacitance value C, and the impedance Z and the capacitance value C have a relationship of Z=-1 / jωC.

[0080] <Modification 4> In the embodiment, the detection electrodes 101, 701, 801 are arranged on the pedal 11. However, the detection electrodes 101, 701, 801 may be arranged on one or both of the steering wheel of the vehicle 10 and the operation panel surface of the vehicle 10. When the detection electrodes 101, 701, 801 are provided on the steering wheel of the vehicle 10 and the operation panel surface of the vehicle 10, the positions of the hands of the occupant P are to be detected.

[0081] <Modification 5> In the eighth embodiment, multiple detection electrodes 801 are arranged on each of the accelerator pedal 11a and the brake pedal 11b. However, multiple detection electrodes 801 may be arranged on a component other than the accelerator pedal 11a or the brake pedal 11b. Also, multiple detection electrodes 801 may be arranged on only one of the accelerator pedal 11a or the brake pedal 11b. Furthermore, the number of detection electrodes 801 arranged on one component can be adjusted as appropriate based on the size, shape, etc. of the component.

[0082] (Disclosure of Technical Ideas) This specification discloses multiple technical ideas described in the following multiple clauses. Some clauses may be described in a multiple dependent form, with the subsequent clause alternatively referring to the preceding clause. Furthermore, some clauses may be described in a multiple dependent form, with the subsequent clause referring to another multiple dependent clause. These multiple dependent clauses define multiple technical ideas.

[0083] (Technical Idea 1) A position detection device comprising: one reference electrode (103, 403); two or more detection electrodes (101, 701, 801); a measurement unit (110) that measures a capacitance-related value, which is either a capacitance value between the reference electrode and each detection electrode or a value that changes in relation to the capacitance value; and a position detection unit (120) that detects a human body position based on the capacitance-related value measured by the measurement unit for each detection electrode.

[0084] (Technical Idea 2) The position detection device according to Technical Idea 1, wherein the reference electrode (103) is the body of the vehicle (10). (Technical Idea 3) The position detection device according to Technical Idea 1, wherein the reference electrode (403) is provided on one or both of the seat portion (12a) and the backrest portion of the seat (12) of the vehicle (10). (Technical Idea 4) The position detection device according to Technical Idea 1, wherein the reference electrode is provided on the floor of the vehicle. (Technical Idea 5) The position detection device according to any one of Technical Ideas 1 to 4, comprising a guard electrode (502) to which the same potential as that of the detection electrode is applied. (Technical Idea 6) The position detection device according to any one of Technical Ideas 1 to 5, wherein the position detection unit detects the human body position based on the magnitude of the capacitance-related value for each detection electrode. (Technical Idea 7) The position detection device according to any one of Technical Ideas 1 to 5, wherein the position detection unit detects the human body position based on the ratio of the capacitance-related values. (Technical Idea 8) The position detection device according to Technical Idea 7, wherein the position detection unit determines whether a human body is located near the detection electrode corresponding to the capacitance-related value based on the magnitude of the capacitance-related value used in calculating the ratio of the capacitance-related values. (Technical Idea 9) The position detection device according to Technical Idea 7, wherein the detection electrode is arranged on a pedal (11) of a vehicle, and the position detection unit determines whether a human body is located near the detection electrode arranged on the pedal based on the magnitude of the capacitance-related value used in calculating the ratio of the capacitance-related values. (Technical Idea 10) The position detection device according to any one of Technical Ideas 1 to 9, wherein the position detection unit determines whether a human body is pressing down on the detection electrode corresponding to the capacitance-related value based on a differential value of the capacitance-related value. (Technical Idea 11) The position detection device according to Technical Idea 7 or 8, wherein the position detection unit determines whether or not a human body is pressing down on the detection electrode corresponding to the capacitance-related value used to calculate the ratio of the capacitance-related values, based on a differential value of the ratio of the capacitance-related values.(Technical Idea 12) The position detection device according to any one of Technical Ideas 1 to 8 and 11, wherein the detection electrode is arranged on a pedal (11) of a vehicle. (Technical Idea 13) The position detection device according to Technical Idea 12, further comprising a press detection unit (610) that detects that the pedal has been pressed down based on a characteristic value different from the capacitance-related value, and adjusts a threshold value for determining the position of the human body based on the capacitance-related value measured by the measurement unit when the press detection unit detects that the pedal has been pressed down. (Technical Idea 14) The position detection device according to any one of Technical Ideas 1 to 9, wherein the detection electrode is arranged on at least one of a steering wheel of a vehicle and an operation panel surface of the vehicle. (Technical Idea 15) The position detection device according to any one of Technical Ideas 1 to 14, wherein a plurality of the detection electrodes (801) are arranged on a single member that determines whether a human body is in contact with the member. (Technical Idea 16) The position detection device according to any one of Technical Ideas 9, 12, and 13, further comprising an occupant identification unit (630) that identifies an occupant based on the capacitance-related value measured by the measurement unit when the pedal is pressed down. (Technical Idea 17) The position detection device according to Technical Idea 1, further comprising an occupant identification unit (630) that identifies an occupant based on the capacitance-related value measured by the measurement unit when the pedal is pressed down, wherein the reference electrode (403) is provided on a seat cushion (12a) of a vehicle seat, and the detection electrode is provided on a pedal (11) of the vehicle, further comprising an occupant identification unit (630) that identifies an occupant based on the capacitance-related value measured by the measurement unit when the pedal is pressed down. (Technical Idea 18) The position detection device according to Technical Idea 16 or 17, further comprising a plurality of detection electrodes that are provided on a plurality of pedals of the vehicle, respectively, and the areas of the plurality of detection electrodes are different from one another, and the occupant identification unit identifies the occupant based on the capacitance-related value measured by the measurement unit when the plurality of pedals is pressed down.

Claims

1. A position detection device comprising: one reference electrode (103, 403); two or more detection electrodes (101, 701, 801); a measurement unit (110) that measures a capacitance-related value, which is either a capacitance value between the reference electrode and each detection electrode or a value that changes in relation to the capacitance value; and a position detection unit (120) that detects a human body position based on the capacitance-related value measured by the measurement unit for each detection electrode.

2. The position detection device according to claim 1, wherein the reference electrode (103) is the body of the vehicle (10).

3. The position detection device according to claim 1, wherein the reference electrode (403) is provided on one or both of a seat portion (12a) and a backrest portion of a seat (12) of a vehicle (10).

4. The position detection device according to claim 1, wherein the reference electrode is provided on the floor of the vehicle.

5. The position detection device according to claim 1, further comprising a guard electrode (502) to which the same potential as that of the detection electrode is applied.

6. The position detection device according to claim 1, wherein the position detection unit detects the position of the human body based on the magnitude of the capacitance-related value for each of the detection electrodes.

7. The position detection device according to claim 1, wherein the position detection unit detects the position of the human body based on a ratio of the capacitance-related values.

8. The position detection device according to claim 7, wherein the position detection unit determines whether or not a human body is located near the detection electrode corresponding to the capacitance-related value based on the magnitude of the capacitance-related value used in calculating the ratio of the capacitance-related values.

9. A position detection device according to claim 7, wherein the detection electrode is arranged on a pedal (11) of a vehicle, and the position detection unit determines whether or not a human body is located near the detection electrode arranged on the pedal based on the magnitude of the capacitance-related value used to calculate the ratio of the capacitance-related values.

10. The position detection device according to claim 1, wherein the position detection unit determines whether or not the human body is pressing down on the detection electrode corresponding to the capacitance-related value based on the differential value of the capacitance-related value.

11. A position detection device as described in claim 7 or 8, wherein the position detection unit determines whether or not a human body is pressing down on the detection electrode corresponding to the capacitance-related value used to calculate the ratio of the capacitance-related values, based on the differential value of the ratio of the capacitance-related values.

12. A position detection device according to any one of claims 1 to 8 and 10, wherein the detection electrode is arranged on a pedal (11) of a vehicle.

13. A position detection device as described in claim 12, further comprising a press detection unit (610) that detects that the pedal has been pressed down based on a characteristic value different from the capacitance-related value, and wherein, while the press detection unit detects that the pedal has been pressed down, the threshold value for determining the human body position is adjusted based on the capacitance-related value measured by the measurement unit.

14. The position detection device according to claim 1, wherein the detection electrode is disposed on at least one of a steering wheel of a vehicle and an operation panel surface of the vehicle.

15. The position detection device according to claim 1, wherein a plurality of the detection electrodes (801) are arranged on a single member that determines whether or not the member is in contact with a human body.

16. The position detection device according to claim 13, further comprising an occupant identification unit (630) that identifies an occupant based on the capacitance-related value measured by the measurement unit when the pedal is pressed down.

17. A position detection device as described in claim 1, wherein the reference electrode (403) is provided on a seat portion (12a) of a vehicle seat, the detection electrode is provided on a pedal (11) of the vehicle, and the device further comprises an occupant identification unit (630) that identifies an occupant based on the capacitance-related value measured by the measurement unit when the pedal is pressed down.

18. A position detection device as described in claim 17, wherein a plurality of the detection electrodes are provided on a plurality of pedals of the vehicle, and the areas of the plurality of detection electrodes are different from one another, and the occupant identification unit identifies the occupant based on the capacitance-related values ​​measured by the measurement unit when each of the plurality of pedals is pressed down.

Images