Contact detection device

Abstract

To provide a contact detection device with which it is possible to accurately detect a conductor contacting a part which is the object to be contacted.SOLUTION: A contact detection unit 130 of a contact detection device 100 acquires a first output value and a second output value on the basis of an output signal from an electrode 111 in an output value acquisition process. In a difference value calculation process, a first difference value indicating the difference between the first output value and a first reference value and a second difference value indicating the difference between the second output value and a second reference value are calculated. In a contact determination process, it is determined that a driver is in contact with a part 110 which is the object to be contacted when the first difference value equals a temporary contact value within a first temporary contact range and the second difference value equals a temporary contact value within a second temporary contact range. Meanwhile, when the first difference value equals the temporary contact value and the second difference value does not equal the temporary contact value, a specific correction for correcting the first reference value pertaining to the first difference value to become close to the first output value is carried out in a reference value setting process.SELECTED DRAWING: Figure 7

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. 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 steering wheel gripping based on whether the difference between the capacitance and a reference value exceeds a threshold range for a plurality of detection regions. Further, Patent Document 1 discloses that when it is estimated that the change in capacitance in a plurality of detection regions is due to a change in the environment, the reference value is corrected.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for example, when there are a plurality of detection regions, the ambient temperatures of the respective detection regions are not necessarily the same. For example, in the steering wheel of an automobile, the degrees to which the respective detection regions are affected by temperature changes associated with air conditioner blowing or sunlight irradiation may be different. For this reason, in the above prior art, the reference value may not be accurately corrected. As a result, there is a possibility that contact of the conductor cannot be accurately detected.

[0005] The disclosed technology aims to provide a contact detection device that can accurately detect contact of a conductor with a contacted portion.

Means for Solving the Problems

[0006] One aspect of the disclosed technology includes a contacted part including at least an electrode, and a contact detection unit that detects contact of a conductor with the contacted part by performing 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 contact detection unit acquires a first output value and a second output value as output values based on the output signal from the electrode, calculates a first difference value as a difference value indicating a difference between the acquired first output value and a first reference value that is a reference value for the first output value, calculates a second difference value as a difference value indicating a difference between the acquired second output value and a second reference value that is a reference value for the second output value, and in the contact determination, when the first difference value is a tentative contact value within a predetermined first tentative contact range and the second difference value is a tentative contact value within a predetermined second tentative contact range, it is determined that the conductor is in contact with the contacted part. When one of the first difference value and the second difference value is a tentative contact value in the contact determination, it is a contact detection device that corrects the reference value related to the difference value that is the tentative contact value so as to approach the output value.

[0007] The output value acquired based on the output signal from the electrode may vary with changes in the environment of the contacted part. When two output values are acquired based on the output signal from the electrode, the degree of variation in accordance with changes in the environment of each of those two output values may differ for each output value. Specifically, for example, one output value may be affected by changes in the environmental temperature, while the other output value may hardly change even when the environmental temperature changes. And when one output value varies with changes in the environment, the reference value for that one output value may be an inappropriate value. In such a case, the contact detection device according to the above aspect can appropriately correct the inappropriate reference value so as to approach the output value. Therefore, the contact detection device according to the above aspect can accurately detect the contact of the conductor with the contacted part.

Effect of the Invention

[0008] According to the disclosed technology, there is provided a contact detection device that can accurately detect the contact of a conductor with a contacted part.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

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. Therefore, 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 supply 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 supply 120 is connected to the electrode 111. The AC power supply 120 can apply an AC voltage to the electrode 111.

[0015] The contact detection unit 130 has an output signal acquisition unit 140, a difference value calculation unit 150, a contact determination unit 160, a reference value setting unit 161, and a storage unit 170.

[0016] 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 has an output value acquisition unit 141 and a reference value acquisition unit 142.

[0017] The output value acquisition unit 141 performs an output value acquisition process of acquiring a first output value and a second output value based on the output signal from the electrode 111 to which an AC voltage is applied. In the output value acquisition unit 141 of this embodiment, in the output value acquisition process, the output signal from the electrode 111 is A / D converted and quadrature demodulated to obtain a quadrature phase component (Quadrature component) and an in-phase component (In-phase component) by the quadrature demodulation. Then, in the output value acquisition process, the output value acquisition unit 141 of this embodiment acquires the first output value based on the quadrature phase component. Also, in the output value acquisition process, the output value acquisition unit 141 of this embodiment acquires the second output value based on the in-phase component. That is, the output value acquisition unit 141 can acquire two output values based on the output signal from one electrode 111.

[0018] In the output value acquisition process of this embodiment, the first output value is calculated by an operation based on the quadrature phase component acquired this time and the past first output value, which is the first output value calculated before the timing when the quadrature phase component of this time was acquired. In this embodiment, the past first output value is the first output value calculated in the previous output value acquisition process. That is, in the output value acquisition process, the first output value of this time is calculated based on the quadrature phase component acquired this time and the previous first output value calculated in the previous output value acquisition process.

[0019] Specifically, in the output value acquisition process, the output value acquisition unit 141 of this embodiment calculates the first output value A1 of this time by the following formula (1). A1=(1 - e)·A1L+e·Q ···(1) A1L: The previous first output value Q: The quadrature phase component acquired this time e: A coefficient satisfying 0≦e≦1

[0020] In this embodiment, a value greater than 0.5 is adopted as the value of the coefficient e. That is, in the output value acquisition process of this embodiment, the first output value is calculated by an operation in which the influence degree of the quadrature phase component acquired this time on the previous first output value is high, using the quadrature phase component acquired this time and the previous first output value calculated in the previous output value acquisition process. For the first first output value acquired in a state where there is no past first output value, the value of the quadrature phase component acquired this time can be used as it is.

[0021] Also, in the output value acquisition process, the output value acquisition unit 141 of this embodiment calculates the second output value by an operation based on the in-phase component acquired this time and the past second output value, which is the second output value calculated before the timing when the in-phase component of this time was acquired. In this embodiment, the past second output value is the second output value calculated in the previous output value acquisition process. That is, in the output value acquisition process, the output value acquisition unit 141 calculates the second output value of this time based on the in-phase component of this time and the previous second output value calculated in the previous output value acquisition process.

[0022] Specifically, in the output value acquisition process, the output value acquisition unit 141 of this embodiment calculates the second output value A2 of this time by the following formula (2). A2=(1-f)·A2L+f·I ···(2) A2L: The previous second output value I: The in-phase component acquired this time f: A coefficient satisfying 0≦f≦1

[0023] In this embodiment, a value greater than 0.5 is adopted as the value of the coefficient f. That is, in the output value acquisition process of this embodiment, the second output value is calculated by using the in-phase component obtained this time and the previous second output value calculated in the previous output value acquisition process, and by performing an operation with a high influence degree of the in-phase component obtained this time on the previous second output value. For the first second output value obtained in a state where there is no past second output value, the value of the in-phase component obtained this time can be directly used. Also, in this embodiment, the same value is used as the values of the coefficient e and the coefficient f that determine the influence degree of the previous output value on the output value calculated this time. Different values may be used as the values of the coefficient e and the coefficient f, respectively.

[0024] The reference value acquisition unit 142 performs a reference value acquisition process of acquiring reference values for the first output value and the second output value, respectively. The reference value is a value serving as a standard when the driver's hand is not in contact with the contacted portion 110, i.e., in a non-contact state. In this embodiment, the reference value may be corrected after being acquired as an initial reference value. The reference value acquisition unit 142 of this embodiment acquires a first initial reference value, which is an initial reference value for the first output value, and a second initial reference value, which is an initial reference value for the second output value, in the reference value acquisition process.

[0025] In the reference value acquisition process of this embodiment, the first initial reference value is acquired based on a plurality of orthogonal phase components acquired in the initial period. Specifically, for example, the average value of a plurality of orthogonal phase components acquired in the initial period can be used as the first initial reference value. Also, in the reference value acquisition process, the second initial reference value is acquired based on a plurality of in-phase components acquired in the initial period. Specifically, for example, the average value of a plurality of in-phase components acquired in the initial period can be used as the second initial reference value.

[0026] The initial period starts in response to the power supply of the contact detection device 100 being turned on from off, and ends when a predetermined end condition is satisfied from 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 satisfied, for example, in response to a certain period of time having elapsed after the power supply of the contact detection device 100 is turned on from off. Also, for example, the start condition of the initial period may start in response to the values of the quadrature phase component and 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 after the power supply of the contact detection device 100 is turned on from off.

[0027] The difference value calculation unit 150 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. That is, in the difference value calculation process, the difference value calculation unit 150 calculates a first difference value that is the difference value between the first output value and the first reference value, and a second difference value that is the difference value between the second output value and the second reference value. The difference value can be calculated, for example, by subtracting the output value from the reference value. The difference value may be any value that indicates the difference between the output value and the reference value for that output value, and instead of these subtractions, for example, it may be calculated by the ratio of the reference value to the output value.

[0028] The contact determination unit 160 performs a contact determination process based on the difference value calculated by the difference value calculation unit 150. In the contact determination process, for each of the first difference value and the second difference value, it is determined whether it is a value indicating the contact state. In the contact determination process, when both the first difference value and the second difference value are values indicating the contact state, it is determined that the driver's hand is in contact with the contacted portion 110.

[0029] Specifically, in the contact determination process, for each of the first difference value and the second difference value, it is determined whether they are within the provisional contact range indicating the contact state. If both the first difference value and the second difference value are provisional contact values within the provisional contact range, it is determined that the driver's hand is in contact with the contacted part 110. On the other hand, in the contact determination process, if at least one of the first difference value and the second difference value is not within the provisional contact range, it is determined that the driver's hand is not in contact with the contacted part 110, i.e., a non-contact state. Thereby, a contact determination is made as to whether the driver is in contact with the contacted part 110.

[0030] The reference value setting unit 161 may perform a reference value setting process of correcting the reference value so as to approach the output value. The output value may differ depending on external factors of the contacted part 110 even when the degree of contact of the driver's hand with the contacted part 110 is the same. Specifically, for example, the quadrature phase component may obtain different values when the temperature is different even if there is no conductor contact with the contacted part 110 at all.

[0031] Therefore, if the reference value is not changed from the initial reference value obtained in the initial period, even if the state where no conductor is in contact with the contacted part 110 continues, as the environment changes, a difference value indicating the contact state may be calculated. Such environmental dependence tends to be different between the quadrature phase component and the in-phase component. That is, as described above, the quadrature phase component tends to vary accordingly when a temperature change occurs in the contacted part 110. On the other hand, for the in-phase component, unlike the quadrature phase component, it tends not to vary in response to a temperature change in the contacted part 110.

[0032] Therefore, the reference value setting unit 161 may correct the value of the reference value so as to approach the corresponding output value in the reference value setting process. In the reference value setting process of this embodiment, when it is determined that at least one of the difference values is not within the provisional contact range in the contact determination process, the reference value is corrected so as to approach the corresponding output value.

[0033] In the reference value setting unit 161 of this embodiment, in the reference value setting process when at least one of the difference values is not within the provisional contact range, for each of the first reference value and the second reference value, standard correction and specific correction different from the standard correction can be performed. Both the standard correction and the specific correction are the same in that they correct the reference value so as to approach the corresponding output value.

[0034] In this embodiment, in the standard correction and the specific correction in the reference value setting process, a value calculated by an operation based on the first output value acquired this time and the past first reference value, which is the first reference value calculated before the timing when the current first output value was acquired, is set as the current first reference value. The past first reference value is, for example, the first initial reference value calculated by the reference value acquisition process in the first reference value setting process. Also, for example, the past first reference value is the first reference value set in the previous reference value setting process in the reference value setting process after the second time.

[0035] Specifically, in the standard correction and the specific correction in the reference value setting process, the reference value setting unit 161 of this embodiment calculates the current first reference value B1 by the following formula (3). B1=(1 - g)·B1L+g·A1 ···(3) B1L: The previous first reference value A1: The first output value acquired this time g: A coefficient satisfying 0 < g < 1

[0036] When performing specific correction, the reference value setting unit 161 uses a larger value for the coefficient g than when performing standard correction. In this embodiment, regardless of whether specific correction or standard correction is performed, a value smaller than 0.5 is adopted as the value of the coefficient g. That is, in the standard correction and specific correction in the reference value setting process of this embodiment, the first reference value is calculated by an operation with a high influence degree of the past first reference value on the first output value obtained this time, using the first output value obtained this time and the past first reference value. And in specific correction, it is calculated by an operation with a high influence degree of the first output value obtained this time compared with standard correction. Thereby, in specific correction, the first reference value is corrected to be closer to the first output value compared with standard correction.

[0037] In this embodiment, in the standard correction and specific correction in the reference value setting process, the value calculated by an operation based on the second output value obtained this time and the past second reference value, which is the second reference value calculated before the timing when the second output value of this time was obtained, is set as the second reference value of this time. The past second reference value is, for example, the second initial reference value calculated in the reference value acquisition process in the first reference value setting process. Also, for example, the past second reference value is the second reference value set in the previous reference value setting process in the reference value setting process after the second time.

[0038] Specifically, in the standard correction and specific correction in the reference value setting process of this embodiment, the reference value setting unit 161 of this embodiment calculates the second reference value B2 of this time by the following formula (4). B2=(1 - h)·B2L+h·A2 ···(4) B2L: The previous second reference value A2: The second output value obtained this time h: A coefficient satisfying 0 < h < 1

[0039] When performing specific correction, the reference value setting unit 161 uses a larger value for the coefficient h than when performing standard correction. In this embodiment, regardless of whether specific correction or standard correction is performed, a value smaller than 0.5 is adopted as the value of the coefficient h. That is, in the standard correction and specific correction in the reference value setting process of this embodiment, the second reference value is calculated by an operation with a high influence degree of the past second reference value on the second output value obtained this time, using the second output value obtained this time and the past second reference value. And in specific correction, it is calculated by an operation with a high influence degree of the second output value obtained this time compared with standard correction. Thereby, in specific correction, compared with standard correction, the second reference value is corrected to be closer to the second output value.

[0040] In this embodiment, it is assumed that the same values are used for the coefficient g and the coefficient h that determine the influence degree of the current output value in the reference value calculated this time, respectively, when performing standard correction and when performing specific correction. That is, when performing standard correction, the same values are used for the coefficient g and the coefficient h. Also, when performing specific correction, the same values are used for the coefficient g and the coefficient h.

[0041] By performing standard correction or specific correction, when one of the first output value and the second output value fluctuates due to environmental changes, the reference value for the fluctuated output value can be corrected to an appropriate value. Also, in specific correction, compared with standard correction, the reference value can be corrected to be closer to the output value. For this reason, when performing specific correction, even when one of the first output value and the second output value fluctuates rapidly due to environmental changes, the reference value for the output value can be corrected to an appropriate value at an early stage.

[0042] The memory unit 170 stores various values necessary for the processes performed by the contact detection unit 130. For example, it has an area for storing past reference values, a provisional contact range to be referred to when performing contact determination processing, and the like. Furthermore, the memory unit 170 also has an area for storing each flag used in the processes performed by the contact detection unit 130. Also, if necessary, it may have an area for storing values acquired or calculated in the past.

[0043] 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 reference value acquisition process (S102), a difference value calculation process (S103), a contact determination process (S104), and further performs a reference value setting process (S106). In this embodiment, the reference value setting process (S106) is performed when the reference value correction flag is ON. Note that the initial values of the respective flags used in the contact detection process are OFF.

[0044] In the output value acquisition process (S101), an output value is acquired based on the output signal from the electrode 111 to which an AC voltage is applied. That is, based on the output signal from the electrode 111, the first output value A1 related to the quadrature phase component is acquired by the formula (1) described above. Also, based on the output signal from the electrode 111, the second output value A2 related to the in-phase component is acquired by the formula (2) described above.

[0045] In the reference value acquisition process (S102), a reference value is acquired based on the output signal from the electrode 111 to which an AC voltage is applied during the initial period. In this embodiment, a first initial reference value is calculated based on a plurality of quadrature phase components acquired during the initial period. The first initial reference value is the initial first reference value B1. Also, a second initial reference value is calculated based on a plurality of in-phase components acquired during the initial period. The second initial reference value is the initial second reference value B2.

[0046] Specifically, in the reference value acquisition process (S102), first, as shown in FIG. 4, it is determined whether the reference value correction flag is OFF (S111). The reference value correction flag is OFF when the power of the contact detection device 100 is turned on from OFF, and is turned on when the acquisition of the initial reference value is completed. In this embodiment, the period during which this reference value correction flag is OFF is the initial period for acquiring the initial reference value. If the reference value correction flag is not OFF (NO in S111), this process ends.

[0047] If the reference value correction flag is OFF (YES in S111), values for calculating the initial reference value are acquired (S112). That is, the quadrature phase component used for calculating the first initial reference value and the in-phase component used for calculating the second initial reference value are acquired and stored in the storage unit 170. Next, it is determined whether the acquisition of the values used for calculating the initial reference value is completed (S113). If the acquisition of the values used for calculating the initial reference value is not completed (NO in S113), this process ends. That is, also in the next reference value acquisition process (S102), the acquisition of the next value used for calculating the initial reference value is performed.

[0048] If the acquisition of the values used for calculating the initial reference value is completed (YES in S113), the initial reference value is calculated (S114). In this embodiment, the first initial reference value is calculated by averaging a plurality of quadrature phase components acquired during the initial period. Thereby, the initial first reference value B1 is acquired. Also, the second initial reference value is calculated by averaging a plurality of in-phase components acquired during the initial period. Thereby, the initial second reference value B2 is acquired. After calculating the initial reference value, the reference value correction flag is turned on (S115), and this process ends.

[0049] In the difference value calculation process (S103), a difference value that indicates the difference between the output value and the reference value for that output value is calculated. In the difference value calculation process (S103) of this embodiment, the first difference value C1 is calculated by subtracting the first output value A1 from the first reference value B1. Also, the second difference value C2 is calculated by subtracting the second output value A2 from the second reference value B2.

[0050] In the contact determination process (S104), based on the first difference value C1 and the second difference value C2, it is determined whether the driver's hand is in a contact state of contacting the contacted portion 110 or a non-contact state of not contacting. Specifically, in the contact determination process (S104), first, as shown in FIG. 5, it is determined whether the first difference value C1 is within the first tentative contact range, which is a range estimated to be in the contact state (S121). When the first difference value C1 is within the first tentative contact range (YES in S121), next, it is determined whether the second difference value C2 is within the second tentative contact range, which is a range estimated to be in the contact state (S122).

[0051] When the first difference value C1 is within the first tentative contact range (YES in S121) and the second difference value C2 is within the second tentative contact range (YES in S122), it is determined that it is in the contact state (SS123). Further, it is determined whether the reference value fixed flag is OFF (S124). If the reference value fixed flag is OFF (YES in S124), the reference value fixed flag is turned ON (S125), and this process ends. The reference value fixed flag is a flag that determines whether to maintain the reference value at a constant value. During the period when the reference value fixed flag is ON, the first reference value B1 and the second reference value B2 are maintained at constant values.

[0052] When the first difference value C1 is within the first tentative contact range (YES in S121) and the second difference value C2 is not within the second tentative contact range (NO in S122), the first reference value specific correction flag is turned ON (S126). The first reference value specific correction flag is a flag that determines whether to perform specific correction on the first reference value B1 in the reference value setting process. When the first reference value specific correction flag is ON, specific correction is performed on the first reference value B1 in the reference value setting process. Further, it is determined that it is in the non-contact state (S127), and the process proceeds to step S130.

[0053] When the first difference value C1 is not within the first provisional contact range (NO in S121) and the second difference value C2 is within the second provisional contact range (YES in S128), the second reference value specific correction flag is turned ON (S129). The second reference value specific correction flag is a flag that determines whether to perform specific correction on the second reference value B2 in the reference value setting process. When the second reference value specific correction flag is ON, specific correction is performed on the second reference value B2 in the reference value setting process. Further, it is determined that the non-contact state exists (S127), and the process proceeds to step S130.

[0054] When the first difference value C1 is not within the first provisional contact range (NO in S121) and the second difference value C2 is not within the second provisional contact range (NO in S128), it is determined that the non-contact state exists (S127), and the process proceeds to step S130. When the first difference value C1 is not within the first provisional contact range (NO in S121) and the second difference value C2 is not within the second provisional contact range (NO in S128), neither the first reference value specific correction flag nor the second reference value specific correction flag is turned ON.

[0055] In step S130, it is determined whether the reference value fixed flag is ON. If the reference value fixed flag is ON (YES in S130), the reference value fixed flag is turned OFF (S131), and this process ends.

[0056] In this embodiment, the reference value fixed flag is turned ON when it is determined that the contact state exists in the contact determination process. On the other hand, the reference value fixed flag is turned OFF when it is determined that the non-contact state exists.

[0057] Also, in this embodiment, when both the first difference value C1 and the second difference value C2 are tentative contact values within their respective tentative contact ranges, it is determined that the contact state exists. On the other hand, when at least one of the first difference value C1 and the second difference value C2 is not a tentative contact value, it is determined that the non-contact state exists. In the contact determination process (S104), the contact determination is performed based on the first difference value C1 and the second difference value C2 in this way. And in the contact determination process, when one of the first difference value C1 and the second difference value C2 is a tentative contact value, the specific correction flag for the reference value related to the difference value that is the tentative contact value is turned ON.

[0058] The reference value setting process (S106) is a process that may correct the reference value, and as shown in FIG. 3, it is performed when the reference value correction flag is ON. That is, the first reference value B1 and the second reference value B2 are acquired with initial values in the initial period, and after the initial period, their values are corrected as appropriate.

[0059] In the reference value setting process (S106), as shown in FIG. 6, first, it is determined whether the first reference value specific correction flag is ON (S141). When the first reference value specific correction flag is ON (YES in S141), specific correction is performed on the first reference value B1 (S142), and standard correction (S142) is performed on the second reference value B2. Further, the first reference value specific correction flag is turned OFF (S144), and this process ends.

[0060] When the first reference value specific correction flag is not ON (NO in S141), it is determined whether the second reference value specific correction flag is ON (S145). When the second reference value specific correction flag is ON (YES in S145), standard correction is performed on the first reference value B1 (S146), and specific correction (S147) is performed on the second reference value B2. Further, the second reference value specific correction flag is turned OFF (S148), and this process ends.

[0061] When the second reference value specific correction flag is not ON (NO in S145), it is determined whether the reference value fixed flag is OFF (S149). When the reference value fixed flag is OFF (YES in S149), standard correction is performed on the first reference value B1 (S150), and standard correction (S151) is performed on the second reference value B2. That is, standard correction is performed on both the first reference value B1 and the second reference value B2, and this process ends.

[0062] When the reference value fixed flag is not OFF (NO in S149), the previous first reference value B1L is set for the first reference value B1 (S152), and the previous second reference value B2L is set for the second reference value B2 (S153), and this process ends.

[0063] For the specific correction and standard correction of the first reference value B1, the operation using the formula (3) described above is performed, and the value calculated by the operation is set as the first reference value B1. That is, for the specific correction and standard correction of the first reference value B1, the current first reference value is calculated by an operation using the currently acquired first output value A1 and the past first reference value B1L. The currently acquired first output value A1 is, that is, the first output value A1 acquired in the current output value acquisition process (S101). The past first reference value B1L is, that is, the first reference value B1 set in the previous reference value setting process (S106). By performing such correction on the first reference value B1, even when a change in the environment has occurred, the first reference value B1 can be corrected to follow the first output value A1.

[0064] Furthermore, in the specific correction for the first reference value B1, it is calculated by an operation with a higher influence degree of the first output value A1 obtained this time compared to the standard correction for the first reference value B1. Thereby, in the specific correction for the first reference value B1, the value of the first reference value B1 can be corrected so as to be closer to the first output value A1 compared to the standard correction for the first reference value B1. When the obtained first output value A1 varies greatly with changes in the environment, the first difference value C1 may become larger than the second difference value C2. In such a case, in the contact determination process (S104), the first reference value specific correction flag is set to ON. Then, in the reference value setting process (S106) when the first reference value specific correction flag is ON, by performing specific correction on the first reference value B1, the first reference value B1 can be corrected to an appropriate value earlier compared to the standard correction. The same applies to the second reference value B2.

[0065] Next, the transition of each value in the contact detection process of this embodiment and the contact determination based thereon will be described with reference to FIGS. 7 and 8. FIG. 7 is a graph showing the first output value A1 based on the quadrature phase component. FIG. 8 is a graph showing the second output value A2 based on the in-phase component. Both FIGS. 7 and 8 show examples of the transition of values obtained during the same period in the same contact detection device 100. In FIGS. 7 and 8, the output value is shown on the vertical axis and the elapsed time is shown on the horizontal axis.

[0066] In the examples shown in FIGS. 7 and 8, the period from time T0 to time T3 is a non-contact period in which the driver is not in contact with the contacted portion 110, and the period after time T3 is a contact period in which the driver is in contact with the contacted portion 110. Further, in FIG. 7, the first reference value B1 and the first difference value C1 are shown together with the first output value A1. In FIG. 8, the second reference value B2 and the second difference value C2 are shown together with the second output value A2. Also, in FIG. 7, the first tentative contact lower limit value D1, which is the lower limit value of the first tentative contact range for the first difference value C1, is also shown. In FIG. 8, the second tentative contact lower limit value D2, which is the lower limit value of the second tentative contact range for the second difference value C2, is also shown.

[0067] As shown in FIGS. 7 and 8, the first output value A1 and the second output value A2 are significantly lower at time T3 than before. This decrease in the output value is due to the driver's contact with the contacted portion 110. Also, at time T3, with the driver's contact with the contacted portion 110, both the first difference value C1 and the second difference value C2 have increased compared to before.

[0068] After time T3, the first difference value C1 becomes a tentative contact value equal to or greater than the first tentative contact lower limit value D1. Also, with the first difference value C1 becoming a tentative contact value, as shown in the upper part of FIG. 7, the first difference value C1 indicates a contact state. Further, after time T3, with the second difference value C2 becoming a tentative contact value equal to or greater than the second tentative contact lower limit value D2, as shown in the upper part of FIG. 8, the second difference value C2 indicates a contact state. Note that the detection of the contact state based on each of these two difference values becoming a tentative contact value alone is tentative. And in the contact detection process of this embodiment, when both the tentative contact state based on the first difference value C1 and the tentative contact state based on the second difference value C2 are detected, it is determined that there is a contact state with the contacted portion 110.

[0069] Here, regarding the second output value A2 based on the in-phase component shown in FIG. 8, it has changed stably at about the same level as the second reference value B2 from time T0 to time T3, which is a non-contact period. On the other hand, regarding the first output value A1 based on the quadrature phase component shown in FIG. 7, it has a tendency to gradually decrease from time T0 to time T3. This is associated with the increase in the temperature of the contacted portion 110. That is, the temperature of the contacted portion 110 has been gradually increasing from time T0 to time T3. As a result, a decrease in the first output value A1 based on the quadrature phase component, which is easily affected by temperature changes, has occurred.

[0070] As shown in FIG. 7, the variation of the first output value A1 in response to the temperature change tends to deviate from the first reference value B1. Therefore, it can be seen that the first difference value C1 increases during the non-contact period even though the driver is not in contact with the contacted part 110. Specifically, the first difference value C1 increases from time T0 and becomes a tentative contact value equal to or greater than the first tentative contact lower limit value D1 at time T1. Therefore, at time T1, the first difference value C1 is a value indicating the contact state. At this time T1, as shown in FIG. 8, the second difference value C2 related to the in-phase component does not become a value indicating the contact state. This is because the second output value A2 based on the in-phase component is less affected by the temperature change.

[0071] Therefore, after time T1, in the contact detection process of this embodiment, specific correction is performed on the first reference value B1 related to the first difference value C1, which is the tentative contact value. That is, the value of the first reference value B1 is corrected to approach the first output value A1. FIG. 7 shows the first initial reference value B11. The first initial reference value B11 is a constant value that does not change with the passage of time. And the first reference value B1 transitions to a value closer to the first output value A1 than the first initial reference value B11 during the non-contact period. That is, the first reference value B1 transitions so as to follow the first output value A1.

[0072] As a result, in FIG. 7, the situation where only the first difference value C1 is the tentative contact value is eliminated at time T2. And at the subsequent time T3, in response to both the first difference value C1 and the second difference value C2 becoming the tentative contact values, the contact of the driver with the contacted part 110 can be accurately detected. That is, in the contact detection device 100 according to this embodiment, even when environmental changes occur, the first reference value B1 can be appropriately corrected, so that the contact of the driver with the contacted part 110 can be accurately detected.

[0073] FIG. 9 shows an example in which, unlike the present embodiment, correction of the reference value related to the quadrature phase component is not performed. That is, it is a case where the first initial reference value B11 is used as the first reference value. The first output value A1 shown in FIG. 9 is the same as that in FIG. 7. Further, FIG. 9 shows a first difference value C11 calculated using the first initial reference value B11.

[0074] As shown in FIG. 9, the first difference value C11 rises from time T0 as the temperature changes, and becomes a tentative contact value equal to or higher than the first tentative contact lower limit value D1 after time T11. Further, as the first difference value C11 becomes a tentative contact value, as shown in the upper part of FIG. 9, the first difference value C11 is a value indicating the contact state. In the example of FIG. 9 where the correction of the first initial reference value B11 is not performed, the situation where only the first difference value C11 is a tentative contact value is not resolved even at times T2 and T3 after time T11.

[0075] From this, it can be seen that when contact determination is performed using only the quadrature phase component, the contact state may be erroneously detected in response to a change in temperature even though it is actually in a non-contact state. Further, even if the first difference value related to the quadrature phase component and the second difference value related to the in-phase component are obtained, if the reference value is not appropriately corrected in response to one of them being a tentative contact value, the situation where only that one is a tentative contact value is not resolved. That is, when an environmental change occurs, the first difference value and the second difference value may become tentative contact values at different timings. In such a case, it may not be possible to appropriately and accurately determine which of the first difference value and the second difference value should be used as the basis for contact determination. On the other hand, the contact detection device 100 according to the present embodiment can appropriately correct the first reference value even when the temperature changes and the first output value fluctuates, so that the contact state can be accurately detected in response to both the first difference value and the second difference value becoming tentative contact values.

[0076] Further, in the specific correction of the reference value setting process, the reference value setting unit 161 of this embodiment sets the value calculated by the operation based on the currently acquired first output value A1 and the past first reference value B1L as the current first reference value B1. Thereby, the first reference value B1 can be appropriately corrected so as to approach the first output value A1 that has varied according to the change in the environment.

[0077] Further, in the reference value setting process when the first difference value C1 is the provisional contact value and the second difference value C2 is not the provisional contact value, the reference value setting unit 161 of this embodiment performs specific correction on the first reference value B1. In the specific correction for the first reference value B1, the current first reference value B1 is calculated by an operation with a high influence degree of the past first reference value B1L on the currently acquired first output value A1. Thereby, the first reference value B1, which has become an inappropriate value as a reference value due to the change in the environment, can be appropriately corrected so as to approach the first output value A1. The same applies to the second reference value B2.

[0078] Note that, in the specific correction for the first reference value B1, the current first reference value B1 may be calculated by an operation with a high influence degree of the currently acquired first output value A1 on the past first reference value B1L. In such specific correction, the first reference value B1, which has become an inappropriate value as a reference value due to the change in the environment, can be corrected so as to approach the first output value A1 earlier. The same applies to the second reference value B2.

[0079] Further, in the reference value setting process where both the first difference value C1 and the second difference value C2 are provisional contact values, the reference value setting unit 161 of this embodiment sets the first reference value B1 to the same value as the past first reference value B1L. That is, as the reference value setting process, the value of the first reference value B1L set in the past is also set as the first reference value B1 this time. Thereby, after changing from the non-contact state to the contact state, for example, it is possible to suppress the value of the first reference value B1 from greatly fluctuating due to the influence of noise or the like. That is, it is possible to suppress the calculation of the first difference value C1, which is a value indicating the non-contact state, due to the influence of noise or the like even though the driver is continuously in contact with the contacted portion 110. Therefore, after changing from the non-contact state to the contact state, it is possible to suppress the first difference value C1 from becoming unstable due to the influence of noise or the like. The same applies to the second reference value B2.

[0080] Further, in the reference value setting process where both the first difference value C1 and the second difference value C2 are not provisional contact values, the reference value setting unit 161 of this embodiment performs standard correction on the first reference value B1. In the standard correction for the first reference value B1, the current first reference value B1 is calculated by an operation with a high influence degree of the past first reference value B1L on the currently acquired first output value A1. Thereby, during the non-contact period, the first reference value B1 can always be corrected to approach the first output value A1. That is, during the non-contact period, it is possible to suppress the first reference value B1 from gradually deviating from an appropriate value as a reference value due to environmental changes. The same applies to the second reference value B2.

[0081] Note that the specific calculation details of the standard correction and specific correction in the reference value setting process are not, of course, limited to the above formulas (3) and (4). For example, in the standard correction and specific correction in the reference value setting process related to the first reference value, it may be possible to set, as the first reference value, a value calculated by an operation based on a group of acquired quadrature phase components (acquired quadrature phase component group) that were acquired before the timing at which the current first output value was obtained. The same applies to the standard correction and specific correction for the second reference value related to the in-phase component. That is, in the standard correction and specific correction in the reference value setting process, it may be possible to set, as the reference value, a value calculated by an operation based on a group of one-phase components (one-phase component group) that is one of the quadrature phase components and the in-phase component. The one-phase component group is a plurality of one-phase components that were acquired before the timing at which the current output value was obtained.

[0082] Also, in this case, as the specific correction, it is possible to perform a correction in which the reference value related to the one-phase component is corrected by an operation that increases the influence degree as the older one-phase component in the one-phase component group. Thereby, it is possible to appropriately correct a reference value that has become an inappropriate value as a reference value due to environmental changes so as to approach the output value. Further, as the specific correction, it is also possible to perform a correction in which the reference value related to the one-phase component is corrected by an operation that increases the influence degree as the newer one-phase component in the one-phase component group. By doing so, it is possible to correct, at an earlier stage, a reference value that has become an inappropriate value due to environmental changes so as to approach the first output value.

[0083] Also, for the standard correction, it is possible to perform a correction in which the reference value related to the one-phase component is corrected by an operation that increases the influence degree as the older one-phase component in the one-phase component group. Thereby, during the non-contact period, it is possible to always appropriately correct the reference value so as to approach the output value. That is, during the non-contact period, it is possible to suppress the reference value from gradually deviating from an appropriate value.

[0084] As described in detail above, the contact detection device 100 according to the present embodiment includes a contacted portion 110 and a contact detection portion 130. The contacted portion 110 includes at least an electrode 111. The contact detection portion 130 may perform an output value acquisition process, a difference value calculation process, a contact determination process, and a reference value setting process. In the output value acquisition process, a first output value A1 and a second output value A2 are acquired as output values based on an output signal from the electrode 111. In the difference value calculation process, a first difference value C1 that indicates the difference between the first output value A1 and the first reference value B1 is calculated. Further, in the difference value calculation process, a second difference value C2 that indicates the difference between the second output value A2 and the second reference value B2 is calculated. In the contact determination process, when the first difference value C1 is a tentative contact value within the first tentative contact range and the second difference value C2 is a tentative contact value within the second tentative contact range, it is determined that the driver is in contact with the contacted portion 110. Then, in the contact determination process, when the first difference value C1 is a tentative contact value and the second difference value C2 is not a tentative contact value, in the reference value setting process, a specific correction is performed to correct the first reference value B1 related to the first difference value C1 so as to approach the first output value A1. In the contact determination process, when the second difference value C2 is a tentative contact value and the first difference value C1 is not a tentative contact value, in the reference value setting process, a specific correction is performed to correct the second reference value B2 related to the second difference value C2 so as to approach the second output value A2. That is, when one of the first difference value C1 and the second difference value C2 is a tentative contact value, the reference value related to the difference value that is the tentative contact value is corrected so as to approach the output value. Thereby, an inappropriate reference value can be appropriately corrected so as to approach the output value. Therefore, a contact detection device capable of performing highly reliable contact determination is realized.

[0085] Each of the above embodiments is merely an example and does not limit the disclosed technology in any way. Therefore, the disclosed technology can naturally be variously improved and modified without departing from the gist thereof.

[0086] For example, in the above embodiment, it has been described that the first output value is calculated based on the quadrature phase component acquired this time and the previous first output value. However, the first output value may be, for example, the value of the quadrature phase component acquired this time. Also, for example, the first output value may be calculated based on a predetermined number of quadrature phase components acquired most recently among the plurality of quadrature phase components acquired so far. Specifically, the first output value can be calculated based on the average value of a predetermined number of quadrature phase components acquired most recently. Regarding the second output value related to the in-phase component, similar to the first output value related to the quadrature phase component, it can be calculated by a method different from the method described in the above embodiment.

[0087] Also, in the above embodiment, in the reference value setting process, it has been described that when at least one of the difference values is not the provisional contact value, specific correction is performed on the reference value related to the difference value that is the provisional contact value, and standard correction is performed on the reference value related to the difference value that is not the provisional contact value. That is, it has been described that for the reference value, standard correction is performed on those determined to be appropriate values, and specific correction is performed on those determined to deviate from the appropriate value. However, for example, in the reference value setting process, it may be sufficient to perform only specific correction without performing standard correction. This is because the reference value that has deviated from the appropriate value can be appropriately corrected.

[0088] Also, in the above embodiment, it has been described that in the reference value setting process, specific correction can be executed for both the first reference value and the second reference value. However, for example, in the reference value setting process, it may be sufficient to perform specific correction only for the first reference value. That is, for the second reference value, for example, a fixed value may be used without correction.

[0089] In the above-described embodiment, it has been described that the initial reference value is calculated in the initial period. However, for example, as the initial reference value, it is possible to use a predetermined fixed value. Note that the values of the quadrature phase component or the in-phase component acquired in the initial period may vary depending on the ambient temperature and the like in which the contact detection device is used. For this reason, it is preferable that the reference value is calculated based on the value of the quadrature phase component or the in-phase component acquired during the non-contact period by the reference value acquisition process. For example, it is possible to store the value of the quadrature phase component or the in-phase component acquired during the non-contact period in the storage unit and use the value stored in the storage unit as the initial reference value.

[0090] In the above-described embodiment, it has been described that the first output value, the first reference value, and the first difference value are calculated based on the quadrature phase component, and the second output value, the second reference value, and the second difference value are calculated based on the in-phase component. However, it is also possible to calculate the first reference value and the first difference value based on the in-phase component, and calculate the second output value, the second reference value, and the second difference value based on the quadrature phase component. That is, the contact detection unit may be such that it quadrature demodulates the output signal from the electrode to obtain the quadrature phase component and the in-phase component, obtains the first output value based on one of the quadrature phase component and the in-phase component, and obtains the second output value based on the other phase component different from the one phase component.

[0091] In the above-described embodiment, the contact detection device for detecting contact with the steering wheel has been described. However, the contact detection device is not limited to the steering wheel, and of course, it can also be used for other applications. Further, for example, the contact detection device is not limited to detecting contact of a human body with the contacted portion, and may be any device that detects contact of a conductor.

[0092] The above-disclosed technology also includes the following means 1 to means 10. [Means 1] The contact detection device according to claim 1, comprising an AC power source for applying an AC voltage to the electrode, wherein the contact detection unit Quadrature demodulate the output signal from the electrode to which an AC voltage is applied to obtain a quadrature phase component and a in-phase component, Obtain the first output value based on one phase component of the quadrature phase component and the in-phase component, A contact detection device that obtains the second output value based on the other phase component different from the one phase component.

[0093] [Means 2] The contact detection device according to Means 1, The contact detection unit, A contact detection device that may perform a reference value setting process of setting, as the current first reference value, a value calculated by an operation based on the current first output value and the past first reference value, which is the first reference value calculated before the timing of obtaining the current first output value.

[0094] [Means 3] The contact detection device according to Means 2, The contact detection unit, When the first difference value is the provisional contact value and the second difference value is not the provisional contact value, as the reference value setting process, a contact detection device that calculates the current first reference value by an operation with a high influence degree of the past first reference value on the current first output value obtained this time.

[0095] [Means 4] The contact detection device according to Means 2, The contact detection unit, When the first difference value is the provisional contact value and the second difference value is not the provisional contact value, as the reference value setting process, a contact detection device that calculates the current first reference value by an operation with a high influence degree of the current first output value obtained this time on the past first reference value.

[0096] [Means 5] The contact detection device according to Means 1, The contact detection unit, A contact detection device that performs a reference value setting process of setting, as the first reference value, a value calculated by an operation based on a group of the one-phase components acquired before the timing of acquiring the current first output value.

[0097] [Means 6] The contact detection device according to Means 5, wherein the contact detection unit when the first difference value is the provisional contact value and the second difference value is not the provisional contact value, as the reference value setting process, the first reference value is corrected by an operation in which the older the one-phase component in the one-phase component group has a higher influence degree. A contact detection device that performs such a process.

[0098] [Means 7] The contact detection device according to Means 5, wherein the contact detection unit when the first difference value is the provisional contact value and the second difference value is not the provisional contact value, as the reference value setting process, the first reference value is corrected by an operation in which the newer the one-phase component in the one-phase component group has a higher influence degree. A contact detection device that performs such a process.

[0099] [Means 8] The contact detection device according to any one of Means 2 to 4, wherein the contact detection unit when neither the first difference value nor the second difference value is the provisional contact value, as the reference value setting process, the current first reference value is calculated by an operation in which the influence degree of the past first reference value is high with respect to the currently acquired first output value. A contact detection device that performs such a process.

[0100] [Means 9] The contact detection device according to any one of Means 5 to 7, wherein the contact detection unit When neither the first difference value nor the second difference value is the provisional contact value, as the reference value setting process, a contact detection device that corrects the first reference value by an operation that increases the influence degree of the older one-phase component in the one-phase component group.

[0101] [Means 10] A contact detection device according to any one of Means 2 to Means 9, wherein the contact detection unit When both the first difference value and the second difference value are the provisional contact values, as the reference value setting process, a contact detection device that sets the value set as the first reference value in the past also as the first reference value this time.

Explanation of Signs

[0102] 100: Contact detection device 110: Contacted part 111: Electrode 120: AC power supply 130: Contact detection unit 141: Output value acquisition unit 150: Difference value calculation unit 160: Contact determination unit 161: Reference value setting unit

Claims

1. A contacted part including at least an electrode, and a contact detection unit that detects contact of a conductor with the contacted part by performing contact determination based on an output signal from the electrode that changes according to the contact state of the conductor with the contacted part, wherein the contact detection unit acquires a first output value and a second output value as output values based on the output signal from the electrode, calculates a first difference value as a difference value indicating a difference between the acquired first output value and a first reference value that is a reference value for the first output value, calculates a second difference value as a difference value indicating a difference between the acquired second output value and a second reference value that is a reference value for the second output value, in the contact determination, when the first difference value is a tentative contact value within a predetermined first tentative contact range and the second difference value is a tentative contact value within a predetermined second tentative contact range, it is determined that a conductor is in contact with the contacted part, and when one of the first difference value and the second difference value is the tentative contact value in the contact determination, a contact detection device that corrects the reference value related to the difference value that is the tentative contact value so as to approach the output value.

2. The contact detection device according to claim 1, comprising an AC power source that applies an AC voltage to the electrode, wherein the contact detection unit performs quadrature demodulation on an output signal from the electrode to which the AC voltage is applied to acquire a quadrature phase component and a in-phase component, acquires the first output value based on one phase component of the quadrature phase component and the in-phase component, and acquires the second output value based on the other phase component different from the one phase component.

3. The contact detection device according to claim 2, wherein the contact detection unit performs a reference value setting process in which a value calculated by an operation based on the currently acquired first output value and a past first reference value that is the first reference value calculated before the timing of acquiring the current first output value may be set as the current first reference value.

4. The contact detection device according to claim 3, wherein the contact detection unit when the first difference value is the tentative contact value and the second difference value is not the tentative contact value, as the reference value setting process, calculates the current first reference value by an operation with a high influence degree of the past first reference value on the currently acquired first output value.

5. The contact detection device according to claim 3, wherein the contact detection unit when the first difference value is the provisional contact value and the second difference value is not the provisional contact value, as the reference value setting process, the current first reference value is calculated by an operation with a high influence degree of the currently acquired first output value on the past first reference value. A contact detection device that performs such a calculation.

6. The contact detection device according to claim 2, wherein the contact detection unit A reference value setting process may be performed in which a value calculated by an operation based on a group of one-phase components, which is a group of a plurality of the one-phase components acquired before the timing of acquiring the current first output value, is set as the first reference value. Contact detection device.

7. The contact detection device according to claim 6, wherein the contact detection unit when the first difference value is the provisional contact value and the second difference value is not the provisional contact value, as the reference value setting process, the first reference value is corrected by an operation that increases the influence degree of the older one-phase components in the one-phase component group. A contact detection device that performs such a correction.

8. The contact detection device according to claim 6, wherein the contact detection unit when the first difference value is the provisional contact value and the second difference value is not the provisional contact value, as the reference value setting process, the first reference value is corrected by an operation that increases the influence degree of the newer one-phase components in the one-phase component group. A contact detection device that performs such a correction.

9. The contact detection device according to any one of claims 3 to 8, wherein the contact detection unit when both the first difference value and the second difference value are the provisional contact values, as the reference value setting process, a value set as the first reference value in the past is also set as the first reference value this time. A contact detection device that performs such a setting.

10. The contact detection device according to any one of claims 3 to 5, wherein the contact detection unit when both the first difference value and the second difference value are not the provisional contact values, as the reference value setting process, the current first reference value is calculated by an operation with a high influence degree of the past first reference value on the currently acquired first output value. A contact detection device that performs such a calculation.

11. The contact detection device according to any one of claims 6 to 8, wherein the contact detection unit When neither the first difference value nor the second difference value is the provisional contact value, as the reference value setting process, a contact detection device that corrects the first reference value by an operation that increases the influence degree of the older one-phase component in the one-phase component group is performed.

Images