Contact detection device

Abstract

To provide a contact detection device capable of performing a contact determination with high reliability.SOLUTION: An AC power supply 120 of a contact detection device 100 can apply a high-frequency AC voltage and an intermediate frequency AC voltage to an electrode 111. A contact detection part 130 acquires an output value on the basis of an output signal when applying the high-frequency AC voltage and the intermediate frequency AC voltage, and calculates a high-frequency difference value HD and an intermediate high-frequency difference value MD that indicates a difference between the output value and a reference value to be acquired. In addition, the contact detection part 130 performs a contact determination on the basis of the high-frequency difference value HD when a difference from a difference value ME after the intermediate high-frequency correction obtained by correcting and calculating the high-frequency difference value HD and the intermediate high-frequency AC voltage on the basis of a frequency of the high-frequency difference voltage and a frequency of the intermediate frequency AC voltage intermediate high-frequency correction is within a first allowable range.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The disclosed technology relates to a contact detection device including a contact detection unit that detects contact of a conductor with a contacted portion.

Background Art

[0002] For example, a contact detection device that detects contact of a human body is mounted on a steering wheel of an automobile or the like. As a contact detection device that detects contact of a conductor such as a human body, for example, Patent Document 1 describes a technique for determining the presence or absence of gripping of a steering wheel based on an alternating voltage applied to a sensor electrode and an output signal from the sensor electrode to which the alternating voltage is applied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, depending on the environment in which the contact detection device is used, for example, other electronic devices may also be mounted. In such a case, for example, the output signal from the sensor electrode may be affected by radio waves radiated from other electronic devices. And when noise is added to the output signal from the sensor electrode, there is a possibility that an accurate output signal cannot be detected. That is, there was a possibility that the presence or absence of contact of the conductor with the contacted portion could not be accurately determined.

[0005] The disclosed technology aims to provide a contact detection device capable of performing highly reliable contact determination.

Means for Solving the Problems

[0006] One aspect of the disclosed technology includes a contacted part including at least an electrode, an AC power supply that applies an AC voltage to the electrode, and a contact detection unit that detects contact of a conductor with the contacted part by performing a contact determination based on an output signal from the electrode that changes according to the contact state of the conductor with the contacted part. The AC power supply can apply a first AC voltage of a first frequency and a second AC voltage of a second frequency different from the first frequency to the electrode. The contact detection unit acquires an output value by performing a predetermined output value acquisition process based on the output signal from the electrode to which the AC voltage is applied. A first difference value is calculated, which indicates the difference between a first output value obtained by the output value acquisition process based on the output signal from the electrode to which the first AC voltage is applied and a first reference value that is a reference value for the first output value. A second difference value is calculated, which indicates the difference between a second output value obtained by the output value acquisition process based on the output signal from the electrode to which the second AC voltage is applied and a second reference value that is a reference value for the second output value. When the difference between the first difference value and a second corrected difference value calculated by correcting the calculated second difference value based on the first frequency and the second frequency is within a predetermined first allowable range, the contact determination is made based on the first difference value. This is a contact detection device.

[0007] The difference values will be different from each other according to the frequency of the AC voltage applied to the electrode, even if the degree of contact of the conductor with the contacted part is the same. The contact detection unit of the contact detection device according to the above aspect can check whether it is within the allowable range in a state where the difference between two difference values that become different values according to the frequency of the AC voltage applied to the electrode is eliminated by correction based on the frequency. Therefore, it is possible to accurately determine whether two difference values related to different frequencies are within the allowable range. Also, when performing a contact determination based on the difference value, the contact determination can be made in a state where an equivalent determination result is also confirmed by the corrected difference value related to a frequency different from that of the difference value. Therefore, the contact detection device according to the above aspect can perform a highly reliable contact determination.

Advantages of the Invention

[0008] According to the disclosed technology, there is provided a contact detection device capable of performing a highly reliable contact determination.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

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Figure 6

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Figure 9

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments embodying the disclosed technology will be described in detail with reference to the accompanying drawings. The contact detection device 100 according to this embodiment detects contact of a human body with the steering wheel 1. The steering wheel 1 is mounted on a vehicle and can, for example, be gripped by a driver's hand and perform an operation input regarding the traveling direction of the vehicle.

[0011] The contact detection device 100 has a contact portion 110 provided on the steering wheel 1. The contact detection device 100 detects the contact of a conductor with the contact portion 110 by means of a capacitance method. For this reason, the contact detection device 100 can detect the contact of the human body, which is a conductor, with the contact portion 110. Thereby, the contact detection device 100 can detect the state in which the driver is gripping the steering wheel 1.

[0012] FIG. 2 is a block diagram showing the configuration of the contact detection device 100. The contact detection device 100 includes a contact portion 110, an AC power source 120, and a contact detection unit 130. The contact portion 110 of this embodiment provided on the steering wheel 1 has an electrode 111 and an epidermis 112. The epidermis 112 constitutes the surface of the steering wheel 1. The electrode 111 is provided on the inner side rather than the epidermis 112.

[0013] The contact portion 110 is provided continuously for one round in the circumferential direction of the annular steering wheel 1. Note that the contact portion 110 may be provided on a part of the steering wheel 1. Also, for example, the contact portion 110 may be configured without the epidermis 112. Further, a plurality of regions may be provided in the circumferential direction of the steering wheel 1, and the contact portion 110 may be provided for each region.

[0014] The AC power source 120 is connected to the electrode 111. The AC power source 120 can apply an AC voltage to the electrode 111. The AC power source 120 can apply AC voltages of a plurality of different frequencies to the electrode 111. The AC power source 120 of this embodiment can apply AC voltages of three different frequencies to the electrode 111 at different periods, respectively.

[0015] That is, the AC power supply 120 can output a high-frequency AC voltage, an intermediate-frequency AC voltage with a frequency lower than that of the high-frequency AC voltage, and a low-frequency AC voltage with a frequency lower than that of the intermediate-frequency AC voltage. The high-frequency AC voltage can be set, for example, in the range of 100 to 150 kHz, the intermediate-frequency AC voltage can be set, for example, in the range of 50 to 100 kHz, and the low-frequency AC voltage can be set, for example, in the range of 5 to 50 kHz. Specifically, the AC power supply 120 of this embodiment can output a high-frequency AC voltage with a frequency of 150 kHz, an intermediate-frequency AC voltage with a frequency of 100 kHz, and a low-frequency AC voltage with a frequency of 50 kHz.

[0016] Also, the AC power supply 120 outputs a high-frequency AC voltage, an intermediate-frequency AC voltage, and a low-frequency AC voltage respectively for a predetermined high-frequency period, intermediate-frequency period, and low-frequency period. That is, the AC power supply 120 outputs a high-frequency AC voltage for the high-frequency period, an intermediate-frequency AC voltage for the intermediate-frequency period after the high-frequency period, and a low-frequency AC voltage for the low-frequency period after the intermediate-frequency period. Also, after the low-frequency period, a high-frequency period for outputting a high-frequency AC voltage is provided. For example, the high-frequency period, the intermediate-frequency period, and the low-frequency period can all be periods of the same length. Note that the order of the high-frequency period, the intermediate-frequency period, and the low-frequency period is not limited to this order.

[0017] The contact detection unit 130 includes an output signal acquisition unit 140, an output value calculation unit 150, a provisional contact determination unit 160, a difference value correction unit 161, a difference value comparison unit 162, a contact determination decision unit 163, and a storage unit 170.

[0018] The input side of the output signal acquisition unit 140 is connected to the electrode 111. Thereby, the output signal acquisition unit 140 acquires the output signal output from the electrode 111 to which the AC voltage is applied. The output signal acquisition unit 140 includes a provisional output value acquisition unit 141 and a reference value acquisition unit 142.

[0019] The provisional output value acquisition unit 141 performs a provisional output value acquisition process of A / D converting and quadrature demodulating an output signal from the electrode 111 to which an AC voltage is applied, and acquiring a quadrature phase component (Quadrature component) or an in-phase component (In-phase component) as a provisional output value by the quadrature demodulation. The provisional output value acquisition process may acquire the quadrature phase component as the provisional output value, or may acquire the in-phase component as the provisional output value. The provisional output value acquisition unit 141 uses, as the provisional output value, a value that may be corrected later. Therefore, the provisional output value and the provisional output value acquisition process are respectively the pre-correction output value and the pre-correction output value acquisition process.

[0020] The provisional output value acquisition unit 141 acquires a provisional output value for each frequency. That is, during the high-frequency period, the provisional output value acquisition unit 141 acquires a provisional output value related to the high frequency from the output signal from the electrode 111 to which the high-frequency AC voltage is applied. During the intermediate-frequency period, the provisional output value acquisition unit 141 acquires a provisional output value related to the intermediate frequency from the output signal from the electrode 111 to which the intermediate-frequency AC voltage is applied. During the low-frequency period, the provisional output value acquisition unit 141 acquires a provisional output value related to the low frequency from the output signal from the electrode 111 to which the low-frequency AC voltage is applied.

[0021] The reference value acquisition unit 142 performs a reference value acquisition process of acquiring, as a reference value, the value of the quadrature phase component or the in-phase component when the hand of the driver is not in contact with the contacted part 110, i.e., in a non-contact state. Naturally, in the reference value acquisition process in the case of performing the provisional output value acquisition process of acquiring the quadrature phase component as the provisional output value, the reference value is acquired based on the quadrature phase component. Also, in the reference value acquisition process in the case of performing the provisional output value acquisition process of acquiring the in-phase component as the provisional output value, the reference value is acquired based on the in-phase component.

[0022] The reference value acquisition unit 142 can use, for example, the value of the quadrature phase component or the in-phase component acquired during the non-contact period in the non-contact state as the reference value. Also, for example, a value calculated based on a plurality of values of the quadrature phase component or the in-phase component acquired during the non-contact period in the non-contact state may be used as the reference value. Specifically, for example, the average value of a plurality of quadrature phase components acquired during the non-contact period in the non-contact state can be used as the reference value.

[0023] The non-contact period can be, for example, an initial period that starts in response to the power supply of the contact detection device 100 being turned on from OFF and ends when a certain period of time has elapsed since the start. The initial period can also start, for example, when a predetermined condition is satisfied after the power supply of the contact detection device 100 is turned on from OFF. The start condition of the initial period can be, for example, one that is satisfied in response to a certain period of time having elapsed since the power supply of the contact detection device 100 was turned on from OFF. Also, for example, the start condition of the initial period may start in response to the value of the quadrature phase component or the in-phase component within a certain range where it can be determined that the driver is not in contact with the contacted portion 110 being detected after the power supply of the contact detection device 100 is turned on from OFF. Also, for example, the reference value may be appropriately updated by the value of the quadrature phase component or the in-phase component acquired during the non-contact period set in response to a predetermined condition being satisfied after the elapse of the initial period.

[0024] The reference value acquisition unit 142 acquires a reference value for each frequency. That is, the reference value acquisition unit 142 acquires the reference value related to the high frequency based on the provisional output value acquired during the high frequency period in the non-contact period. The reference value related to the intermediate frequency is acquired based on the provisional output value acquired during the intermediate frequency period in the non-contact period. The reference value related to the low frequency is acquired based on the provisional output value acquired during the low frequency period in the non-contact period.

[0025] The input side of the output value calculation unit 150 is connected to the output signal acquisition unit 140. Thereby, the output value calculation unit 150 acquires each value acquired by the output signal acquisition unit 140. The output value calculation unit 150 includes an output value correction unit 151 and a difference value calculation unit 152.

[0026] The output value correction unit 151 performs an output value correction process for correcting some provisional output values. The quadrature phase component and the in-phase component obtained from the electrode 111 to which an AC voltage is applied are values that change in different ranges according to the frequency of the AC voltage applied to the electrode 111. That is, the provisional output value and the reference value are different from each other according to the frequency of the applied AC voltage.

[0027] Therefore, in the output value correction process, the output value correction unit 151 corrects the provisional output value obtained for each frequency according to the difference between the respective reference values. Specifically, in the output value correction process, among a plurality of high frequencies, intermediate frequencies, and low frequencies, the provisional output value related to a specific frequency is not corrected, and the provisional output value related to a non-specific frequency other than the specific frequency is corrected. The correction amount of the provisional output value related to the non-specific frequency is the difference between the reference value related to the non-specific frequency and the reference value related to the specific frequency.

[0028] In the output value correction process, the provisional output value related to the specific frequency is adopted as the output value as it is. On the other hand, for the provisional output value related to the non-specific frequency, a value corrected so as to approach the provisional output value related to the specific frequency by the reference difference, which is the difference between the reference value related to the non-specific frequency and the reference value related to the specific frequency, is adopted as the output value.

[0029] In this embodiment, the high frequency (150 kHz) is defined as the specific frequency. That is, in this embodiment, the intermediate frequency (100 kH) and the low frequency (50 kHz) are non-specific frequencies. Note that the specific frequency can be, for example, the intermediate frequency or the low frequency.

[0030] The difference value calculation unit 152 performs a difference value calculation process for calculating a difference value that indicates the difference between the output value and the reference value for that output value. The difference value can be calculated, for example, by subtracting the output value from the reference value. The difference value only needs to indicate the difference between the output value and the reference value for that output value. Instead of these subtractions, for example, it may be calculated by the ratio of the reference value to the output value. Further, when calculating the difference value using the output value after the output value correction process, for the output value related to each frequency, using each reference value preset for each frequency or each reference value calculated using the output value related to each frequency, the difference value can also be calculated. Further, when calculating the difference value using the output value after the output value correction process, the same reference value can be used for the output value related to any frequency. Specifically, when calculating the difference value using the output value after the output value correction process, for the output value related to any frequency, a value indicating the difference from the reference value related to a specific frequency can be calculated.

[0031] The provisional contact determination unit 160 performs a provisional contact determination process based on the difference value for each frequency calculated by the difference value calculation unit 152. In the provisional contact determination process, when the difference value is within a preset provisional contact range, it is determined that the provisional contact state exists. Note that when the difference value is not within the provisional contact range, it is determined that the provisional non-contact state exists. In the provisional contact determination process, the provisional contact determination unit 160 determines whether each difference value for each frequency is in the provisional contact state.

[0032] The difference value correction unit 161 performs a difference value correction process for correcting some difference values. Even if the degree of contact of the driver's hand with the contacted portion 110 is the same, the difference values will be different from each other according to the frequency of the alternating voltage applied to the electrode 111.

[0033] Therefore, in the differential value correction unit 161 of this embodiment, in the differential value correction process, among the differential values for each frequency calculated by the differential value calculation unit 152, the differential value related to the non-specific frequency may be corrected. Also, in the differential value correction process of this embodiment, for the differential value related to the non-specific frequency, when it is determined to be in the tentative contact state in the tentative contact determination process, correction is performed based on the non-specific frequency and the specific frequency. In the differential value correction process, for the differential value related to the non-specific frequency, if it is not determined to be in the tentative contact state in the tentative contact determination process, the value as it is is used without correction. Note that hereinafter, for the differential value related to the non-specific frequency, the differential value when not corrected by the differential value correction process and the corrected differential value when corrected by the differential value correction process may be collectively referred to simply as the differential value.

[0034] In the differential value correction process of this embodiment, specifically, when correcting the differential value related to the intermediate frequency, a value obtained by multiplying the ratio (150 / 100) of the value of the high frequency (150) to the value of the intermediate frequency (100) is calculated as the corrected differential value related to the intermediate frequency. Also, in the differential value correction process of this embodiment, when correcting the differential value related to the low frequency, a value obtained by multiplying the ratio (150 / 50) of the value of the high frequency (150) to the value of the low frequency (50) is calculated as the corrected differential value related to the intermediate frequency. Note that in the differential value correction process, it is only necessary to cancel the difference between the differential values related to two different frequencies based on those two different frequencies, and it is not limited to the above calculation.

[0035] The difference value comparison unit 162 compares a plurality of values among the difference values related to the specific frequency and the difference values related to the non-specific frequency. When the difference value related to the non-specific frequency is corrected by the difference value correction process, the corrected difference value is used as the value of the difference value related to the non-specific frequency. Then, it is determined whether the compared values indicate the same state in either the contact state or the non-contact state. Specifically, it is determined whether the difference between the compared difference values is within a predetermined allowable range. When the difference between the compared difference values is within the allowable range, it is determined that they match in terms of indicating the same state. On the other hand, when the difference between the compared values is not within the allowable range, it is determined that they indicate different states.

[0036] The contact determination decision unit 163 performs a contact determination decision process for finally determining whether the driver's hand is in a contact state of contacting the contacted portion 110 or a non-contact state of not contacting. The difference value correction process by the difference value correction unit 161 and the comparison of a plurality of difference values (corrected difference values) by the difference value comparison unit 162 may be performed in the contact determination decision process.

[0037] In the contact determination decision process, the contact determination decision unit 163 simply performs a majority vote based on the difference value related to the specific frequency and the difference value related to the non-specific frequency. Specifically, among the difference values related to the specific frequency and the difference values related to the non-specific frequency, the final contact determination is made using any one of the difference values that account for a majority as the value indicating either the contact state or the non-contact state. As a result, the contact determination decision unit 163 of this embodiment can use a highly reliable difference value for the final contact determination. Also, the contact determination decision unit 163 of this embodiment uses the difference value related to the highest frequency among the difference values that account for a highly reliable majority in the final contact determination.

[0038] The storage unit 170 stores various values necessary for the processes performed by the contact detection unit 130. For example, it has an area for storing a provisional contact range to be referred to when performing provisional contact determination, a contact range to be referred to when performing final contact determination, an allowable range for allowing that the calculated two values indicate the same state, and the like. Also, as necessary, it has an area for storing values acquired or calculated in the past. Further, the storage unit 170 also has an area for storing each flag used in the processes performed by the contact detection unit 130.

[0039] Next, the contact detection process performed by the contact detection unit 130 will be described with reference to FIGS. 3 to 6. As shown in FIG. 3, in the contact detection process, the contact detection unit 130 performs an output value acquisition process (S101), a difference value calculation process (S102), a provisional contact determination process (S103), and a contact determination decision process (S104). Note that the initial values of each flag used in the contact detection process are OFF.

[0040] In the output value acquisition process (S101), an output value is acquired based on the output signal from the electrode 111 to which an alternating voltage is applied. The output value is acquired as a value corresponding to the frequency applied to the electrode 111. In the output value acquisition process (S101), as shown in FIG. 4, a provisional output value acquisition process (S111), a reference value acquisition process (S112), and an output value correction process (S113) are performed.

[0041] In the provisional output value acquisition process (S111), a provisional output value is acquired based on the output signal from the electrode 111 to which an alternating voltage is applied. In this embodiment, in the provisional output value acquisition process (S111) during the high-frequency period, a high-frequency provisional output value HA is acquired as the provisional output value. In the provisional output value acquisition process (S111) during the intermediate-frequency period, an intermediate-frequency provisional output value MA is acquired as the provisional output value. In the provisional output value acquisition process (S111) during the low-frequency period, a low-frequency provisional output value LA is acquired as the provisional output value.

[0042] In the reference value acquisition process (S112), a reference value is acquired based on the output signal from the electrode 111 to which an alternating voltage is applied during the non-contact period. In this embodiment, in the reference value acquisition process (S112) during the high-frequency period in the non-contact period, a high-frequency reference value HB is acquired as the reference value. In the reference value acquisition process (S112) during the intermediate-frequency period in the non-contact period, an intermediate-frequency reference value MB is acquired as the reference value. In the reference value acquisition process (S112) during the low-frequency period in the non-contact period, a low-frequency reference value LB is acquired as the reference value.

[0043] In the output value correction process (S113), a provisional output value related to an unspecified frequency is corrected so as to approach the provisional output value related to a specific frequency by an amount equal to the reference difference, which is the difference between the reference value related to the unspecified frequency and the reference value related to the specific frequency, and an output value related to the unspecified frequency is acquired. In the output value correction process (S113) of this embodiment, the intermediate-frequency provisional output value MA acquired during the intermediate-frequency period is corrected so as to approach the high-frequency provisional output value HA by an amount equal to the difference between the high-frequency reference value HB and the intermediate-frequency reference value MB, and an intermediate-frequency output value MC is acquired. Also, in the output value correction process (S113), the low-frequency provisional output value LA acquired during the low-frequency period is corrected so as to approach the high-frequency provisional output value HA by an amount equal to the difference between the high-frequency reference value HB and the low-frequency reference value LB, and a low-frequency output value LC is acquired. In the output value correction process (S113) of this embodiment, for the high-frequency provisional output value HA acquired during the high-frequency period, that value is adopted as the high-frequency output value HC.

[0044] In the difference value calculation process (S102), a difference value is calculated that indicates the difference between the output value and the reference value for that output value. In the difference value calculation process (S102) of this embodiment, the high-frequency output value HC related to the high-frequency period is subtracted from the high-frequency reference value HB by an arithmetic operation to calculate a high-frequency difference value HD. Also, in the difference value calculation process (S102), the intermediate-frequency output value MC related to the intermediate-frequency period is subtracted from the high-frequency reference value HB by an arithmetic operation to calculate an intermediate-frequency difference value MD. Also, in the difference value calculation process (S102), the low-frequency output value LC related to the low-frequency period is subtracted from the high-frequency reference value HB by an arithmetic operation to calculate a low-frequency difference value LD.

[0045] In the provisional contact determination process (S103), for each of the difference values corresponding to the respective frequencies calculated immediately before, it is determined whether it is in a provisional contact state. In this embodiment, the larger the area of the driver's hand in contact with the contacted portion 110, the higher the difference value. Then, when the difference value is within the provisional contact range, which is the range estimated to be in the contact state, it can be determined that it is in the provisional contact state.

[0046] In the provisional contact determination process (S103) of this embodiment, as shown in FIG. 5, first, it is determined whether the high-frequency difference value HD is within the provisional contact range (S121). When the high-frequency difference value HD is within the provisional contact range (YES in S121), the high-frequency provisional contact flag is turned on (S122). That is, it is determined that it is in the provisional contact state based on the high-frequency difference value HD. Next, it is determined whether the intermediate-frequency difference value MD is within the provisional contact range (S123). When the intermediate-frequency difference value MD is within the provisional contact range (YES in S123), the intermediate-frequency provisional contact flag is turned on (S124). That is, it is determined that it is in the provisional contact state based on the intermediate-frequency difference value MD. Next, it is determined whether the low-frequency difference value LD is within the provisional contact range (S125). When the low-frequency difference value LD is within the provisional contact range (YES in S125), the low-frequency provisional contact flag is turned on (S126). That is, it is determined that it is in the provisional contact state based on the low-frequency difference value LD.

[0047] As described above, even if the degree of contact of the driver's hand with the contacted portion 110 is the same, the difference values are different from each other according to the frequency of the alternating voltage applied to the electrode 111. For this reason, for each of the high-frequency difference value HD, the intermediate-frequency difference value MD, and the low-frequency difference value LD, different value ranges are predetermined as the provisional contact range.

[0048] In the contact determination decision process (S104), a final determination is made as to whether the driver's hand is in a contact state where it is in contact with the contact portion 110 or a non-contact state where it is not in contact, based on a plurality of difference values with different frequencies. The final determination as to whether it is in a contact state or not in the contact determination decision process (S104) is made based on the difference value corresponding to the highest frequency among the difference values determined to be highly reliable.

[0049] In the contact determination decision process (S104) of this embodiment, as shown in FIG. 6, first, it is determined whether the intermediate frequency provisional contact flag is ON (S131). When the intermediate frequency provisional contact flag is ON (YES in S131), a difference value correction process is performed on the intermediate frequency difference value MD (S132). That is, the intermediate frequency difference value MD is corrected based on the high frequency and the intermediate frequency, and the intermediate frequency corrected difference value ME is calculated. In this embodiment, when the intermediate frequency provisional contact flag is OFF (NO in S131), the difference value correction process is not performed on the intermediate frequency difference value MD.

[0050] Next, it is determined whether the difference between the high frequency difference value HD and the intermediate frequency difference value is within a predetermined first allowable range (S133). In step S133, when the intermediate frequency provisional contact flag is ON, it is determined whether the difference between the high frequency difference value HD and the intermediate frequency corrected difference value ME is within the first allowable range. That is, when the difference value correction process (S132) has been performed on the intermediate frequency difference value MD, it is determined whether the difference between the high frequency difference value HD and the intermediate frequency corrected difference value ME, which is the corrected intermediate frequency difference value, is within the first allowable range. On the other hand, when the intermediate frequency provisional contact flag is OFF, it is determined whether the difference between the high frequency difference value HD and the intermediate frequency difference value MD is within the first allowable range. That is, when the difference value correction process (S132) has not been performed on the intermediate frequency difference value MD, it is determined whether the difference between the high frequency difference value HD and the intermediate frequency difference value MD is within the first allowable range.

[0051] When the difference between the high-frequency difference value HD and the intermediate-frequency difference value is within the first allowable range (YES in S133), contact determination is performed based on the high-frequency difference value HD (S134). Also, in step S134, the high-frequency tentative contact flag, the intermediate-frequency tentative contact flag, and the low-frequency tentative contact flag are all set to OFF.

[0052] When the difference between the high-frequency difference value HD and the intermediate-frequency difference value is not within the first allowable range (NO in S133), it is determined whether the low-frequency tentative contact flag is ON (S135). When the low-frequency tentative contact flag is ON (YES in S135), differential value correction processing is performed on the low-frequency difference value LD (S136). That is, the low-frequency difference value LD is corrected based on the high frequency and the low frequency, and the low-frequency corrected differential value LE is calculated. In this embodiment, when the low-frequency tentative contact flag is OFF (NO in S135), differential value correction processing is not performed on the low-frequency difference value LD.

[0053] Next, it is determined whether the difference between the high-frequency difference value HD and the low-frequency difference value is within a predetermined second allowable range (S137). In step S137, when the low-frequency tentative contact flag is ON, it is determined whether the difference between the high-frequency difference value HD and the low-frequency corrected differential value LE is within the second allowable range. That is, when differential value correction processing (S136) has been performed on the low-frequency difference value LD, it is determined whether the difference between the high-frequency difference value HD and the low-frequency corrected differential value LE, which is the corrected low-frequency difference value, is within the second allowable range. On the other hand, when the low-frequency tentative contact flag is OFF, it is determined whether the difference between the high-frequency difference value HD and the low-frequency difference value LD is within the second allowable range. That is, when differential value correction processing (S136) has not been performed on the low-frequency difference value LD, it is determined whether the difference between the high-frequency difference value HD and the low-frequency difference value LD is within the second allowable range.

[0054] When the difference between the high-frequency difference value HD and the low-frequency difference value is within the second allowable range (YES in S137), contact determination is performed based on the high-frequency difference value HD (S134). Also, in step S134, as described above, the high-frequency provisional contact flag, the intermediate-frequency provisional contact flag, and the low-frequency provisional contact flag are all set to OFF.

[0055] When the difference between the high-frequency difference value HD and the low-frequency difference value is not within the second allowable range (NO in S137), it is determined whether the difference between the intermediate-frequency difference value and the low-frequency difference value is within the third allowable range (S138). In step S138, when both the intermediate-frequency provisional contact flag and the low-frequency provisional contact flag are ON, it is determined whether the difference between the intermediate-frequency corrected difference value ME and the low-frequency corrected difference value LE is within the third allowable range. That is, when the difference value correction process has been performed for both the intermediate-frequency difference value MD and the low-frequency difference value LD, it is determined whether the difference between the corrected intermediate-frequency corrected difference value ME and the low-frequency corrected difference value LE is within the third allowable range. On the other hand, when both the intermediate-frequency provisional contact flag and the low-frequency provisional contact flag are OFF, it is determined whether the difference between the intermediate-frequency difference value MD and the low-frequency difference value LD is within the third allowable range. That is, when the difference value correction process has not been performed for both the intermediate-frequency difference value MD and the low-frequency difference value LD, it is determined whether the difference between the intermediate-frequency difference value MD and the low-frequency difference value LD is within the third allowable range.

[0056] When the difference between the intermediate-frequency difference value and the low-frequency difference value is within the third allowable range (YES in S138), contact determination is performed based on the intermediate-frequency difference value (S139). In step S139, when the intermediate-frequency provisional contact flag is ON and the difference value correction process has been performed for the intermediate-frequency difference value MD, contact determination is performed based on the intermediate-frequency corrected difference value ME. On the other hand, when the intermediate-frequency provisional contact flag is OFF and the difference value correction process has not been performed for the intermediate-frequency difference value MD, contact determination is performed based on the intermediate-frequency difference value MD. Also, in step S139, the high-frequency provisional contact flag, the intermediate-frequency provisional contact flag, and the low-frequency provisional contact flag are all set to OFF.

[0057] When the difference between the intermediate frequency difference value and the low frequency difference value is not within the third allowable range (NO in S138), contact determination is performed based on the difference value used for contact determination in the previous contact determination process (S104) (S140). That is, contact determination is performed based on either the high frequency difference value HD used in the most recent step S134, the corrected intermediate frequency difference value ME used in step S139, or the intermediate frequency difference value MD. Therefore, when proceeding to step S140, the determination result of the previous time is adopted as it is also in the current contact determination process (S104). Also, in step S140, the high frequency tentative contact flag, the intermediate frequency tentative contact flag, and the low frequency tentative contact flag are all set to OFF.

[0058] Note that when one of the intermediate frequency tentative contact flag and the low frequency tentative contact flag is ON and the other is OFF, basically, the difference between the intermediate frequency difference value and the low frequency difference value will not be within the third allowable range. This is because the difference value correction process is performed for one side and not for the other side. Also, when one of the intermediate frequency tentative contact flag and the low frequency tentative contact flag is ON and the other is OFF, the result in the tentative contact determination differs depending on whether it is in the tentative contact state or not. That is, when one of the intermediate frequency tentative contact flag and the low frequency tentative contact flag is ON and the other is OFF, it is difficult to determine which of the intermediate frequency difference value and the low frequency difference value is a reliable value. Therefore, in this embodiment, when one of the intermediate frequency tentative contact flag and the low frequency tentative contact flag is ON and the other is OFF, in step S138, the determination result is the same as when the difference between the intermediate frequency difference value and the low frequency difference value is not within the third allowable range. Note that in step S138 when one of the intermediate frequency tentative contact flag and the low frequency tentative contact flag is ON and the other is OFF, it may also be determined whether the difference between the intermediate frequency difference value and the low frequency difference value is within the third allowable range.

[0059] In the contact determination decision process (S104), the results of the contact determinations performed in step S134, step S139, and step S140 are determined as the final contact determination result. That is, in the contact determination based on the difference value or the corrected difference value, if the value is within a predetermined contact range, it is determined that the contact state exists. On the other hand, if it is not determined that the contact state exists, it is determined that the non-contact state exists. That is, in the contact determination based on the difference value or the corrected difference value, if the value is not within the predetermined contact range, it is determined that the non-contact state exists. Thereby, the contact detection unit 130 detects that the driver is in contact with the contacted part 110.

[0060] Note that in the contact determination (S134) based on the high-frequency difference value HD, the value of the high-frequency provisional contact flag may be referred to and the result of the provisional contact determination may be adopted. Also, in the contact determination (S134) based on the high-frequency difference value HD, the contact determination based on the high-frequency difference value HD may be performed again. In any case, in step S134, the final contact determination is still made based on the high-frequency difference value HD. Also, the first allowable range, the second allowable range, and the third allowable range used when comparing a plurality of difference values related to different frequencies can all be the same value range. Note that the first allowable range, the second allowable range, and the third allowable range can also be different value ranges respectively.

[0061] Next, the transitions of each value used when the contact detection process is performed will be described with reference to FIGS. 7 to 9. FIG. 7 is a graph showing the transition of a provisional output value obtained from the output signal from the electrode 111 to which an alternating voltage is applied. In FIG. 7, the output value shown on the vertical axis is the provisional output value. FIG. 8 is a graph showing the transition of the output value after performing output value correction on the provisional output value. In FIG. 8, the output value is shown on the vertical axis. FIG. 9 is a graph showing the transition of the output value after differential value correction performed on the output value. In FIG. 9, the output value after differential value correction is shown on the vertical axis. Also, in FIGS. 7, 8, and 9, the elapsed time is shown on the horizontal axis. Note that the transitions of each value shown in FIGS. 7, 8, and 9 show similar tendencies whether the quadrature phase component or the in-phase component is used as the output value.

[0062] FIG. 7 shows the high-frequency provisional output value HA, the intermediate-frequency provisional output value MA, and the low-frequency provisional output value LA. As shown in FIG. 7, the provisional output value generally tends to be lower as the frequency of the alternating voltage applied to the electrode 111 is higher.

[0063] FIG. 7 shows the contact period T which is a contact state where the driver is in contact with the contacted portion 110. The period other than the contact period T is a non-contact period where the driver is not in contact with the contacted portion 110. FIG. 7 shows the first contact period T1, the second contact period T2, the third contact period T3, and the fourth contact period T4 as the contact period T. As shown in FIG. 7, the provisional output value tends to be lower in the contact state than in the non-contact state. That is, when the driver contacts the contacted portion 110, the provisional output value tends to decrease.

[0064] The first contact period T1, the second contact period T2, the third contact period T3, and the fourth contact period T4 are, in this order, periods during which the area of the driver's hand in contact with the contacted portion 110 is large. That is, for example, the fourth contact period T4 is a period during which the driver is more surely gripping the steering wheel 1 than the first contact period T1. And the provisional output value tends to show a lower value as the area of the driver's hand in contact with the contacted portion 110 is larger. That is, the provisional output value tends to decrease as the driver more surely grips the contacted portion 110.

[0065] As shown in FIG. 7, for each of the contact periods T, the provisional output value tends to show a lower value as the frequency of the alternating voltage applied to the electrode 111 is higher, as compared with the non-contact period. That is, for example, in the fourth contact period T4, the decrease amount of the high-frequency provisional output value HA from the non-contact period is larger than that of the low-frequency provisional output value LA.

[0066] FIG. 7 shows a high-frequency reference value HB, an intermediate-frequency reference value MB, and a low-frequency reference value LB. As shown in FIG. 7, the high-frequency reference value HB is a value comparable to the high-frequency provisional output value HA in the non-contact period. The intermediate-frequency reference value MB is a value comparable to the intermediate-frequency provisional output value MA in the non-contact period. The low-frequency reference value LB is a value comparable to the low-frequency provisional output value LA in the non-contact period.

[0067] FIG. 7 shows a first reference difference G1 which is the difference between the high-frequency reference value HB and the intermediate-frequency reference value MB. Also shown is a second reference difference G2 which is the difference between the high-frequency reference value HB and the low-frequency reference value LB. In a state where such a first reference difference G1 and second reference difference G2 exist, it is difficult to simply compare the high-frequency provisional output value HA, the intermediate-frequency provisional output value MA, and the low-frequency provisional output value LA. This is because the high-frequency provisional output value HA, the intermediate-frequency provisional output value MA, and the low-frequency provisional output value LA always change within different ranges by the differences between the high-frequency reference value HB, the intermediate-frequency reference value MB, and the low-frequency reference value LB. Therefore, in this embodiment, output value correction is performed.

[0068] The output values related to each frequency shown in FIG. 8 have the values during the non-contact period being similar due to performing the output value correction process. Specifically, the high-frequency output value HC, the intermediate-frequency output value MC, and the low-frequency output value LC during the non-contact period are all of similar values. Also, the high-frequency output value HC, the intermediate-frequency output value MC, and the low-frequency output value LC during the non-contact period are all of values similar to the high-frequency reference value HB. Thereby, the comparison of the high-frequency output value HC, the intermediate-frequency output value MC, and the low-frequency output value LC is easier than the comparison of the high-frequency provisional output value HA, the intermediate-frequency provisional output value MA, and the low-frequency provisional output value LA before the output value correction process.

[0069] FIG. 8 shows the high-frequency difference value HD, the intermediate-frequency difference value MD, and the low-frequency difference value LD during the fourth contact period T4. As shown in FIG. 8, it can be seen that the values of the high-frequency difference value HD, the intermediate-frequency difference value MD, and the low-frequency difference value LD are all different. Specifically, the difference value tends to be higher as the frequency of the alternating voltage applied to the electrode 111 is higher even when the contact state to the contacted part 110 is the same. For this reason, it is difficult to simply compare the high-frequency difference value HD, the intermediate-frequency difference value MD, and the low-frequency difference value LD during the fourth contact period T4. The same applies to the first contact period T1, the second contact period T2, and the third contact period T3 other than the fourth contact period T4.

[0070] The difference between the difference values related to such two different frequencies can be eliminated by performing correction based on those two different frequencies. Specifically, for example, the difference between the high-frequency difference value HD and the intermediate-frequency difference value MD can be eliminated by multiplying the intermediate-frequency difference value MD by the ratio of the high-frequency value to the intermediate-frequency value. Also, the difference between the high-frequency difference value HD and the low-frequency difference value LD can be eliminated by multiplying the low-frequency difference value LD by the ratio of the high-frequency value to the low-frequency value.

[0071] Therefore, as shown in FIG. 9, for the output values related to each frequency, the transitions of the output values related to each frequency after differential value correction with differential value correction performed respectively are also of the same level during the contact period T. In FIG. 9, based on the high-frequency output value HC, the intermediate-frequency output value and the low-frequency output value during the contact period T are corrected respectively. That is, the differential-corrected intermediate-frequency output value MF shown in FIG. 9 is the value obtained by performing differential value correction on the intermediate-frequency output value MC during the contact period T. The differential-corrected low-frequency output value LF is the value obtained by performing differential value correction on the low-frequency output value LC during the contact period T.

[0072] As shown in FIG. 9, in all of the non-contact period and the contact period T, the high-frequency output value HC, the differential-corrected intermediate-frequency output value MF, and the differential-corrected low-frequency output value LF are all of the same level. And the difference between the differential-corrected intermediate-frequency output value MF and the high-frequency reference value HB during the contact period T is the intermediate-frequency corrected differential value ME. Also, the difference between the differential-corrected low-frequency output value LF and the high-frequency reference value HB during the contact period T is the low-frequency corrected differential value LE.

[0073] That is, in the contact determination decision process of this embodiment, in the state shown in FIG. 9 where the difference in differential values caused by the difference in the frequencies applied to the electrode 111 is eliminated, it is determined whether those differences are within the allowable range. Thereby, in the contact determination decision process of this embodiment, it can be simply determined whether the differences in differential values related to each frequency are within the allowable range. That is, it is possible to simply and accurately determine whether the high-frequency differential value HD, the intermediate-frequency differential value (intermediate-frequency differential value MD, intermediate-frequency corrected differential value ME), and the low-frequency differential value (low-frequency differential value LD, low-frequency corrected differential value LE) are of the same level within a predetermined allowable range.

[0074] Here, depending on the environment in which the contact detection device 100 is used, noise may be superimposed on the alternating voltage applied from the AC power supply 120 to the electrode 111. Also, noise may be superimposed on the output signal from the electrode 111 to which the alternating voltage is applied. That is, the acquired output value may be affected by noise. And if the contact or non-contact is determined based only on the output value affected by such noise, of course, there is a possibility of misjudgment.

[0075] On the other hand, when the difference between the difference values related to at least two output values obtained by applying alternating voltages of different frequencies to the electrode 111 is within the allowable range, the contact detection device 100 makes a final contact determination in the contact determination process based on one of the difference values.

[0076] On the other hand, when the difference between the difference values related to the two output values is not within the allowable range, the final contact determination is not made using those difference values as they are. That is, when two highly reliable difference values can be obtained from the two output values not affected by noise, the contact determination can be made using one of the difference values. Thereby, for example, even when the output value related to the frequency of 150 kHz is affected by noise, it is possible to avoid making the final contact determination based on the difference value obtained from the output value related to the frequency of 150 kHz. That is, the contact detection device 100 according to this embodiment can make a highly reliable contact determination even in an environment susceptible to noise.

[0077] Also, as described above, for the final contact determination in the contact determination process, the contact determination determination unit 163 of this embodiment uses the value related to the highest frequency among the two difference values or corrected difference values indicating within the allowable range. Specifically, when the difference between the high-frequency difference value HD and the intermediate-frequency corrected difference value ME is within a predetermined first allowable range, the contact determination unit 163 performs a contact determination based on the high-frequency difference value HD. When the difference between the high-frequency difference value HD and the low-frequency corrected difference value LE is within a second allowable range, the contact determination unit 163 performs a contact determination based on the high-frequency difference value HD. When the difference between the intermediate-frequency corrected difference value ME and the low-frequency corrected difference value LE is within a third allowable range, the contact determination unit 163 performs a contact determination based on the intermediate-frequency corrected difference value ME.

[0078] As shown in FIGS. 7 and 8, the higher the frequency of the AC voltage applied to the electrode 111, the more likely the difference between the non-contact state and the contact state is to be clearly shown in the output value. For this reason, the more the output value when an AC voltage of a high frequency is applied is used for the final contact determination in the contact determination process, the more likely it is to accurately determine whether the driver is in contact with the contact portion 110.

[0079] In addition, the output value correction unit 151 of this embodiment performs an output value correction process of correcting the provisional output values obtained for each frequency according to the difference between the respective reference values. Thereby, the output values related to a plurality of different frequencies can be more easily and accurately compared etc. based on a common reference value.

[0080] In addition, the AC power supply 120 of this embodiment can apply AC voltages of three different frequencies to the electrode 111. When the contact determination unit 163 can determine that a plurality of difference values related to different frequencies are values indicating the same state, the final contact determination is performed using one of the difference values indicating the same state. Therefore, for example, even in an environment where the output value related to one of the three different frequencies is affected by noise, the output values related to the other two frequencies can be accurately obtained. Thus, for example, even when the output value related to the frequency of 150 kHz is affected by noise, the final contact determination can be performed based on the difference value obtained from the output value related to the frequency of 100 kHz. That is, even if the output values related to some frequencies are affected by noise, a highly reliable contact determination can be performed based on the difference values obtained from the output values related to other frequencies not affected by noise. As a result, the contact detection device 100 according to this embodiment has high resistance to noise.

[0081] As described in detail above, the contact detection device 100 according to the present embodiment includes a contacted portion 110, an AC power supply 120, and a contact detection unit 130. The contacted portion 110 includes at least an electrode 111. The AC power supply 120 can apply a plurality of types of AC voltages having different frequencies to the electrode 111. The AC power supply 120 of the present embodiment can apply a high-frequency AC voltage that is a first AC voltage of a first frequency and an intermediate-frequency AC voltage that is a second AC voltage of a second frequency different from the high-frequency AC voltage. Note that the AC power supply 120 can also apply a low-frequency AC voltage that is a third AC voltage of a third frequency different from the intermediate-frequency AC voltage. The contact detection unit 130 acquires output values related to each frequency by performing an output value acquisition process based on an output signal from the electrode 111 to which the AC voltage is applied. Further, the contact detection unit 130 calculates a high-frequency difference value HD that indicates the difference between a high-frequency output value HC acquired by the output value acquisition process based on the output signal from the electrode 111 to which the high-frequency AC voltage is applied and a high-frequency reference value HB that is a reference value thereof. Furthermore, an intermediate-frequency difference value MD that indicates the difference between an intermediate-frequency output value MC acquired by the output value acquisition process based on the output signal from the electrode 111 to which the intermediate-frequency AC voltage is applied and the high-frequency reference value HB is calculated. In addition, the intermediate-frequency difference value MD is corrected based on the frequency related to the high-frequency AC voltage and the frequency related to the intermediate-frequency AC voltage to calculate an intermediate-frequency corrected difference value ME. Then, when the difference between the high-frequency difference value HD and the intermediate-frequency corrected difference value ME is within a predetermined first allowable range, the contact detection unit 130 of the contact detection device 100 performs a contact determination based on the high-frequency difference value HD. Thereby, the contact detection unit 130 of the contact detection device 100 can confirm whether it is within the allowable range in a state where the difference between two difference values that become different values according to the frequency of the AC voltage applied to the electrode 111 is eliminated by correction based on the frequency. For this reason, it is possible to accurately determine whether two difference values related to different frequencies are within the allowable range. Also, when performing a contact determination based on the difference value, the contact determination can be performed in a state where an equivalent determination result is confirmed by a corrected difference value related to a frequency different from the difference value. Therefore, a contact detection device capable of performing a highly reliable contact determination is realized.

[0082] All of the above embodiments are merely illustrative and do not limit the disclosed technology in any way. Therefore, the disclosed technology can naturally be improved and modified in various ways without departing from its gist.

[0083] For example, in the above embodiment, the AC power supply has been described as applying AC voltages related to three different frequencies to the electrodes at different periods. However, the AC power supply only needs to be able to apply AC voltages related to at least two different frequencies to the electrodes. Also, the AC power supply can be configured to apply AC voltages related to four or more different frequencies to the electrodes. For another example, the AC power supply may be able to apply AC voltages related to three different frequencies during the same period. Specifically, the AC power supply may, for example, include a first AC voltage application unit that applies a first AC voltage, a second AC voltage application unit that applies a second AC voltage, and a third AC voltage application unit that applies a third AC voltage. In this case, as the electrode, an electrode having electrode portions to which the first AC voltage, the second AC voltage, and the third AC voltage are respectively applied can be used.

[0084] Also, in the above embodiment, it has been described that when the intermediate frequency difference value and the low frequency difference value are determined to be in a provisional contact state by the provisional contact determination process, the difference value correction process is performed. However, the difference value correction process may also be performed when the intermediate frequency difference value and the low frequency difference value are not determined to be in a provisional contact state. In the non-contact state, the difference value is originally a small value. Therefore, if correcting the intermediate frequency difference value and the low frequency difference value in the non-contact state by the difference value correction process does not affect the result of the final contact determination, the difference value correction process may be performed regardless of whether it is a provisional contact state or not. Also, in this case, the provisional contact determination process may not be performed. On the other hand, if correcting the intermediate frequency difference value and the low frequency difference value in the non-contact state by the difference value correction process affects the result of the final contact determination, it is preferable to follow the above embodiment.

[0085] Also, in the above-described embodiment, the contact detection unit has been described as obtaining the reference values (high-frequency reference value, intermediate-frequency reference value, low-frequency reference value) for each frequency by a reference value acquisition process that calculates based on the values of the quadrature phase components or the in-phase components acquired during the non-contact period. However, for the reference values for each frequency, for example, it is possible to use predetermined fixed values. Note that the values of the quadrature phase components or the in-phase components acquired during the non-contact period may vary depending on the environmental temperature and the like in which the contact detection device is used. For this reason, it is preferable that the reference values be calculated based on the values of the quadrature phase components or the in-phase components acquired during the non-contact period by the reference value acquisition process.

[0086] Also, for example, the non-contact period related to the reference value acquisition process is preferably a period during which no conductor is in contact with the contacted portion at all. However, the smaller the degree of contact of the conductor with the contacted portion, the more likely it is that the quadrature phase components or the in-phase components similar to those in the case where no conductor is in contact with the contacted portion at all are acquired. That is, if it is a period during which quadrature phase components or in-phase components similar to those in the period when no conductor is in contact with the contacted portion at all can be acquired, even if it is a period during which the conductor is in contact with the contacted portion, it may be possible to perform the reference value acquisition process using that period as the non-contact period. That is, the non-contact period is a period that is not the contact period, and does not only refer to the period during which no conductor is in contact with the contacted portion at all. And, depending on the degree of contact detected by the contact detection device, if it is a period in which the difference from the contact period can be clearly observed, it can be set as the non-contact period.

[0087] Also, for example, it is preferable that the difference value calculation process be performed in a state where the reference difference, which is the difference between the reference value for a specific frequency and the reference value for a non-specific frequency, is eliminated by the output value correction process. This is because the difference values can be calculated using a common reference value for the output values for any frequency. However, a difference value equivalent to that can also be calculated based on the difference between each provisional output value (output value before correction) for each frequency and its reference value. That is, it is not always necessary to perform the output value correction process.

[0088] In the above-described embodiment, a contact detection device for detecting contact with a steering wheel has been described. However, the contact detection device is not limited to the steering wheel and can naturally be used for other applications. For example, the contact detection device may detect contact not only with a human body but also with a conductor as long as it can detect contact with the object to be contacted.

[0089] The above-described disclosed technology includes the following means 1 to means 8. [Means 1] The contact detection device according to claim 1, wherein the first frequency is higher than the second frequency.

[0090] [Means 2] The contact detection device according to claim 1 or means 1, wherein the contact detection unit in the output value acquisition process, after performing a pre-correction output value acquisition process of acquiring a pre-correction output value based on an output signal from the electrode to which an alternating voltage is applied, an output value correction process of correcting the acquired pre-correction output value may be performed to acquire the output value. In the pre-correction output value acquisition process when a plurality of alternating voltages having different frequencies are applied to the electrode of the object to be contacted, as the pre-correction output value, a specific pre-correction output value corresponding to a predetermined specific frequency and a non-specific pre-correction output value corresponding to a frequency different from the specific pre-correction output value and having a predetermined reference difference from the specific pre-correction output value are acquired. In the output value correction process, the specific pre-correction output value is adopted as the output value, and for the non-specific pre-correction output value, a value corrected to approach the specific pre-correction output value by the amount of the reference difference is adopted as the output value.

[0091] [Means 3] The contact detection device according to any one of claim 1, means 1, and means 2, wherein the AC power supply The third AC voltage of a third frequency different from both the first frequency and the second frequency can be applied to the electrode. The contact detection unit calculates a third difference value that indicates the difference between a third output value obtained by the output value acquisition process based on the output signal from the electrode to which the third AC voltage is applied and a third reference value that is a reference value for the third output value. A contact detection device that performs the contact determination based on the first difference value when the difference between the first difference value and the second corrected difference value is not within the first allowable range, and the difference between the first difference value and the third corrected difference value calculated by correcting the calculated third difference value based on the first frequency and the third frequency is within a predetermined second allowable range.

[0092] [Means 4] The contact detection device according to Means 3, wherein the contact detection unit performs the contact determination based on the second corrected difference value when the difference between the first difference value and the third corrected difference value is not within the second allowable range, and the difference between the second corrected difference value and the third corrected difference value is within a predetermined third allowable range.

[0093] [Means 5] The contact detection device according to Means 4, wherein the contact detection unit when the difference between the first difference value and the third corrected difference value is not within the second allowable range and the difference between the second corrected difference value and the third corrected difference value is not within the third allowable range, adopts, as the result of the contact determination, the result determined based on an alternative value different from the first difference value, the second corrected difference value, and the third corrected difference value.

[0094] [Means 6] The contact detection device according to any one of Means 3 to 5, wherein the second frequency is higher than the third frequency.

[0095] [Means 7] The contact detection device according to any one of claims 1 and Means 1 to Means 6, wherein the output value is a value based on an in-phase component obtained by quadrature demodulating an output signal from the electrode to which an alternating voltage is applied.

[0096] [Means 8] The contact detection device according to any one of claims 1 and Means 1 to Means 6, wherein the output value is a value based on a quadrature phase component obtained by quadrature demodulating an output signal from the electrode to which an alternating voltage is applied.

Description of Reference Numerals

[0097] 100: Contact detection device 110: Contacted part 111: Electrode 120: AC power supply 130: Contact detection unit 141: Temporary output value acquisition unit 142: Reference value acquisition unit 151: Output value correction unit 152: Difference value calculation unit 161: Difference value correction unit 162: Difference value comparison unit 163: Contact determination decision unit

Claims

1. A contacted part including at least an electrode, An AC power supply for applying an AC voltage to the electrode, A contact detection unit that detects contact of a conductor with the contacted part by performing a contact determination based on an output signal from the electrode that changes according to the contact state of the conductor with the contacted part, The AC power supply, Can apply a first AC voltage of a first frequency and a second AC voltage of a second frequency different from the first frequency to the electrode, The contact detection unit, Obtains an output value by performing a predetermined output value acquisition process based on an output signal from the electrode to which the AC voltage is applied, Calculates a first difference value that indicates the difference between a first output value obtained by the output value acquisition process based on the output signal from the electrode to which the first AC voltage is applied and a first reference value that is a reference value for the first output value, Calculates a second difference value that indicates the difference between a second output value obtained by the output value acquisition process based on the output signal from the electrode to which the second AC voltage is applied and a second reference value that is a reference value for the second output value, A contact detection device that performs the contact determination based on the first difference value when the difference between the first difference value and the second corrected difference value calculated by correcting the calculated second difference value based on the first frequency and the second frequency is within a predetermined first allowable range.

2. The contact detection device according to claim 1, The first frequency is higher than the second frequency.

3. The contact detection device according to claim 1, The contact detection unit, In the output value acquisition process, after performing a pre-correction output value acquisition process of obtaining a pre-correction output value based on an output signal from the electrode to which the AC voltage is applied, the output value is obtained by performing an output value correction process of correcting the obtained pre-correction output value. In the pre-correction output value acquisition process where a plurality of AC voltages with different frequencies are applied to the electrode of the contacted portion, as the pre-correction output value, a specific pre-correction output value corresponding to a predetermined specific frequency and a non-specific pre-correction output value corresponding to a frequency different from the specific pre-correction output value and having a predetermined reference difference from the specific pre-correction output value are acquired. In the output value correction process, the specific pre-correction output value is adopted as the output value, and for the non-specific pre-correction output value, a value corrected to approach the specific pre-correction output value by the amount of the reference difference is adopted as the output value. A contact detection device.

4. The contact detection device according to any one of Claims 1 to 3, wherein the AC power supply can apply a third AC voltage of a third frequency different from both the first frequency and the second frequency to the electrode, the contact detection unit calculates a third difference value that indicates the difference between the third output value acquired in the output value acquisition process based on the output signal from the electrode to which the third AC voltage is applied and a third reference value that is a reference value for the third output value, When the difference between the first difference value and the second corrected difference value is not within the first allowable range, and when the difference between the first difference value and the third corrected difference value calculated by correcting the calculated third difference value based on the first frequency and the third frequency is within a predetermined second allowable range, the contact determination is made based on the first difference value. A contact detection device.

5. The contact detection device according to Claim 4, wherein the contact detection unit When the difference between the first difference value and the third corrected difference value is not within the second allowable range, and when the difference between the second corrected difference value and the third corrected difference value is within a predetermined third allowable range, the contact determination is made based on the second corrected difference value. A contact detection device.

6. The contact detection device according to claim 5, wherein the contact detection unit when the difference between the first difference value and the third corrected difference value is not within the second allowable range and the difference between the second corrected difference value and the third corrected difference value is not within the third allowable range, as a result of the contact determination, a result determined based on an alternative value different from the first difference value, the second corrected difference value, and the third corrected difference value is adopted. **Claim 7** The contact detection device according to claim 4, wherein the second frequency is higher than the third frequency. **Claim 8** The contact detection device according to any one of claims 1 to 3, wherein the output value is a value based on an in-phase component obtained by quadrature demodulating an output signal from the electrode to which an AC voltage is applied. **Claim 9** The contact detection device according to any one of claims 1 to 3, wherein the output value is a value based on a quadrature phase component obtained by quadrature demodulating an output signal from the electrode to which an AC voltage is applied.

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