Contact detection device

Abstract

This invention provides a contact determination device. The contact determination device includes: a reference signal generation unit that generates a first reference signal (FA) having a sine wave with the same frequency and phase as a detection signal output from a sensor unit, and a second reference signal (FB) having a sine wave with the same frequency but a different phase than the detection signal; a demodulation circuit that generates first and second demodulated signals obtained by multiplying the detection signal by the first and second reference signals; a low-pass filter that extracts the DC components of the first and second demodulated signals, i.e., the first and second DC signals; a contact determination unit that performs contact determination based on the first DC signal; and a contact determination unit that determines the connection state between the sensor unit and the detection circuit based on the first and second DC signals, wherein the contact determination unit determines a poor connection state when the changing directions of the first and second DC signals are the same, and a normal connection state when the changing directions are opposite.

Description

Technical Field

[0001] This disclosure relates to a contact determination device. Background Technology

[0002] There are cars capable of autonomous driving under conditions limited to highway driving and low-speed driving. To safely switch between autonomous and manual driving, such cars need to detect the driver's state. One device for detecting the driver's state is a device that detects the driver's steering wheel grip. In contact determination devices used to detect steering wheel grip, there is no space for a contact determination circuit at the sensor mounting location, requiring wiring to connect the sensor and the contact determination circuit. Since the contact determination device for the steering wheel is a crucial safety feature, it needs a function to detect wire breakage. Previously, there have been contact determination devices that incorporate sensor electrodes and wire breakage detection electrodes within the steering wheel to perform wire breakage detection (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: JP 2021-178527

[0006] Existing contact detection devices require components for wire breakage detection, such as wire breakage detection electrodes and signal lines connected to the wire breakage detection electrodes. Summary of the Invention

[0007] Therefore, the objective is to provide a contact determination device that can detect poor contact such as wire breakage without requiring components for wire breakage detection.

[0008] The contact determination device according to an embodiment of this disclosure includes: a sensor unit that outputs a detection signal having a sinusoidal wave with an amplitude corresponding to the electrostatic capacitance between a detection electrode disposed at a contact portion that can contact a detection object and the detection object; and a detection circuit that detects whether the detection object is in contact with the contact portion based on the detection signal, the detection circuit comprising: a first reference signal generation unit that generates a first reference signal having a sinusoidal wave with a frequency equal to and a phase equal to the detection signal; a second reference signal generation unit that generates a second reference signal having a sinusoidal wave with a frequency equal to the detection signal but a phase deviation relative to the detection signal; and a demodulation circuit that generates a signal obtained by multiplying the detection signal output from the sensor unit by the first reference signal as a first demodulated signal, and generates a signal obtained by multiplying the detection signal output from the sensor unit by the first reference signal. The signal obtained using the second reference signal is used as the second demodulated signal; a first low-pass filter extracts the DC component of the first demodulated signal, i.e., the first DC signal; a second low-pass filter extracts the DC component of the second demodulated signal, i.e., the second DC signal; and a contact determination unit determines whether the detected object is in contact with the contact part based on the first DC signal. If the latest change direction of the change amount of the first DC signal exceeding the first threshold is the same as the latest change direction of the change amount of the second DC signal exceeding the second threshold, the contact determination unit determines that the connection between the sensor unit and the detection circuit is poor. If the latest change direction of the change amount of the first DC signal exceeding the first threshold is opposite to the latest change direction of the change amount of the second DC signal exceeding the second threshold, the contact determination unit determines that the connection between the sensor unit and the detection circuit is normal.

[0009] The effects of the invention

[0010] It can provide a contact determination device that can detect poor contact such as wire breakage without the need for components used in wire breakage detection. Attached Figure Description

[0011] Figure 1 This is a diagram showing a steering wheel 10 with the contact determination device 100 of the embodiment installed.

[0012] Figure 2 This is a diagram showing an example of the output sine wave of the electrostatic sensor 110.

[0013] Figure 3 This diagram illustrates the determination of contact using a reference value.

[0014] Figure 4 This is a diagram representing AFE120A.

[0015] Figure 5This is a diagram showing the reference signal generation unit 40 contained in AFE120A.

[0016] Figure 6A This diagram illustrates the problem points in the contact determination device used for comparison.

[0017] Figure 6B This diagram illustrates the problem points in the contact determination device used for comparison.

[0018] Figure 7A This is a diagram showing the characteristics of the first DC signal CA and the second DC signal CB.

[0019] Figure 7B This is a diagram showing the characteristics of the first DC signal CA and the second DC signal CB.

[0020] Figure 8 This diagram illustrates the determination process performed by the MPU120B of the contact determination device 100.

[0021] Figure 9 This is a flowchart illustrating an example of the initial settings process for the sub.

[0022] Figure 10 This is a flowchart illustrating an example of the sub-connection state determination process.

[0023] Figure 11 This is a flowchart illustrating an example of the sub-contact determination process.

[0024] Figure 12 This is a flowchart illustrating an example of the subBase computation process.

[0025] Figure 13A This is a diagram illustrating an example of the effect of the contact determination device 100.

[0026] Figure 13B This is a diagram illustrating an example of the effect of the contact determination device 100.

[0027] Figure 14A This is a diagram illustrating an example of the effect of the contact determination device 100.

[0028] Figure 14B This is a diagram illustrating an example of the effect of the contact determination device 100.

[0029] Explanation of reference numerals in the attached figures

[0030] H-hand (an example of a test subject)

[0031] 10 steering wheels

[0032] 10A Steering Column

[0033] 11. A case study of a contact point that the test subject can reach.

[0034] 15 connectors

[0035] 22 Demodulation Circuit

[0036] 30 Sine Wave Generator

[0037] 35 Drive Signal Generation Unit

[0038] 40. Reference signal generation unit (an example of a first reference signal generation unit and an example of a second reference signal generation unit)

[0039] 100 Contact Detection Device

[0040] 105 connector

[0041] 110 Electrostatic Sensor (An Example from the Sensor Section)

[0042] 120HOD ECU (An example of a detection circuit)

[0043] 121 Main Control Unit

[0044] 122 Contact Detection Unit

[0045] 122A timer

[0046] 123A timer

[0047] 124 memory

[0048] 211A / D converter

[0049] 212 multiplication circuit

[0050] 213 Low-pass filter (an example of the first low-pass filter)

[0051] 222 Multiplication Circuit

[0052] 223 Low-pass filter (an example of the second low-pass filter) Detailed Implementation

[0053] The following describes an implementation of the contact determination device using the present disclosure.

[0054] <Implementation Method>

[0055] Figure 1 This is a diagram showing a steering wheel 10 with the contact determination device 100 of the embodiment installed. (See diagram below.) Figure 1As shown, the steering wheel 10 is mounted on a vehicle, and an electrostatic sensor 110 of the contact determination device 100 is installed inside the grip 11. The electrostatic sensor 110 is an example of a sensor unit. The contact determination device 100 determines whether the driver's hand H is in contact with the grip 11 of the steering wheel 10. The hand H is an example of a detection object. The grip 11 of the steering wheel 10 is an example of a contact area that the detection object can touch.

[0056] The driver of the vehicle will be referred to as the operator of the contact determination device 100. The contact determination device 100 will be described as a device that determines whether the operator's hand H, the object to be detected, is in contact with an object equipped with the electrostatic sensor 110. The situation where the operator comes into contact with an object equipped with the electrostatic sensor 110 is referred to as the operator's operation.

[0057] <Structure of Contact Detection Device 100>

[0058] The contact detection device 100 includes a connector 105, an electrostatic sensor 110, and a HOD_ECU (HandsOff Detection Electronic Control Unit) 120. The HOD_ECU 120 is an example of a detection circuit. The connector 105 is a connector having signal terminals and a ground terminal of the HOD_ECU 120. The connector 105 is connected to a connector 15 having signal terminals and a ground terminal of the steering wheel 10. The signal lines connecting the plurality of signal terminals of the connector 105 and the plurality of signal terminals of the connector 15 include... Figure 1 Signal line 12 is shown. In Figure 1 In this diagram, all signal lines except for the signal line 12 connected to the electrostatic sensor 110 are omitted. The ground terminal of the steering wheel 10 is electrically connected to the steering column 10A, on which the steering wheel 10 is mounted, via a core metal disposed around the circumference of the steering wheel cover 11. By connecting connectors 105 and 15, the ground potential of the HOD_ECU 120 becomes equal to the ground potential of the steering wheel 10 and the steering column 10A.

[0059] The electrostatic sensor 110 is disposed around the circumference of the steering wheel 10's grip 11, insulated from the central metal portion of the grip 11. It is made of, for example, metal electrodes. The electrostatic sensor 110 is connected to the HOD_ECU 120 via signal line 12. Multiple electrodes can be used for the electrostatic sensor 110. For example, if four electrostatic sensors 110 are disposed at 90 degrees on each side of the steering wheel 10's grip 11, it is possible to detect two hands H in contact with a position more than 90 degrees away.

[0060] HOD_ECU120 is located inside the dashboard as an example. HOD_ECU120 has an AFE (Analog Front End) 120A and an MPU (Micro Processor Unit) 120B.

[0061] AFE120A is connected to electrostatic sensor 110 and inputs a sine wave (input sine wave) to electrostatic sensor 110 based on instructions received from MPU120B, obtaining a sine wave (output sine wave) output from electrostatic sensor 110. AFE120A obtains the capacitance value (electrostatic capacitance) of electrostatic sensor 110 from the input and output sine waves, performs digital conversion, and performs noise removal based on a low-pass filter, outputting the amplitude AD value to MPU120B. Furthermore, the amplitude AD value does not necessarily have to be expressed in farads to represent the capacitance value of the electrostatic sensor. Preferably, the sensitivity (recognition limit) of the electrostatic sensor is approximately equal to one unit of the AD value. When the sensitivity of the electrostatic sensor and one unit of the AD value are equal, the capacitance value can be represented as an integer with the fewest possible digits without reducing resolution. By performing noise removal based on a low-pass filter, an amplitude AD value with noise removed above a given frequency can be obtained. The AFE120A generates a first DC signal CA and a second DC signal CB as amplitude AD values ​​and outputs them to the MPU120B. The first DC signal CA is the amplitude AD value, while the second DC signal CB differs from the first DC signal CA and is a DC signal generated based on the capacitance value (electrostatic capacitance) of the electrostatic sensor 110. Regarding the first DC signal CA and the second DC signal CB, [the following is used...] Figure 4 , Figure 7A as well as Figure 7B The following will be described.

[0062] The MPU120B is implemented as a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), input / output interfaces, and an internal bus. The MPU120B is connected to an ECU50 as an example. The ECU50 is a control device that controls the electronic equipment of the vehicle equipped with the steering wheel 10. This electronic equipment may be, for example, related to the vehicle's autonomous driving capabilities.

[0063] The MPU120B includes a main control unit 121, a contact determination unit 122, and a memory 124. The main control unit 121 and the contact determination unit 122 are structured to represent the functions of the program executed by the MPU120B as function blocks. Furthermore, the memory 124 functionally represents the memory of the MPU120B.

[0064] The main control unit 121 is a processing unit that integrates the control processing of MPU120B and performs processing other than that performed by the contact determination unit 122.

[0065] The contact determination unit 122 determines whether the hand H is in contact with the steering wheel cover 11 by judging whether the difference obtained by subtracting a reference value from the amplitude AD value (first DC signal CA) exceeds a threshold. This is the contact determination process performed by the contact determination unit 122. In addition, the contact determination unit 122 notifies the ECU 50 of data characterizing the determination result. Here, the reference value is the capacitance value of the electrostatic sensor 110 used by the contact determination unit 122 to determine whether the hand H is in contact with the steering wheel cover 11 of the steering wheel 10, and is the capacitance value of the electrostatic sensor 110 when the hand H is not in contact with the steering wheel cover 11.

[0066] Furthermore, the contact determination unit 122 includes a timer 122A used in the contact determination process. The contact determination process and the timer 122A will be described later.

[0067] The contact determination unit 122 determines whether the connection status between connector 105 and connector 15 is normal or whether there is poor contact based on the first DC signal CA and the second DC signal CB.

[0068] Furthermore, the contact determination unit 122 includes a timer 123A used in the connection state determination process. The connection state determination process and the timer 123A will be described later.

[0069] The memory 124 stores the programs and data required for processing by the main control unit 121 and the contact determination unit 122. The memory 124 stores data characterizing the capacitance value of the electrostatic sensor 110, data generated by the contact determination unit 122 during processing, and other data.

[0070] <Output sine wave of electrostatic sensor 110>

[0071] Figure 2 This is a diagram illustrating an example of the output sine wave of the electrostatic sensor 110. Figure 2 In the diagram, the solid line represents the output sine wave when the hand H is removed from the grip 11 (when the hand is released), and the dashed line represents the output sine wave when the hand H is gripping the grip 11 (when the hand is in contact).

[0072] The capacitance value measured in the electrostatic sensor 110 changes when the hand H contacts the grip 11 compared to when it is released. Therefore, the phase and amplitude of the sine wave during contact change compared to the sine wave when the hand is released. The phase and amplitude of the sine wave during contact change according to the degree of contact between the hand H and the grip 11. The degree of contact refers to, for example, whether the hand H lightly or firmly grips the grip 11, or whether the contact area between the hand H and the grip 11 is small or large.

[0073] For example, if the timing when the amplitude becomes zero when the hand is released is predetermined as the detection timing td, and the amplitude of the sine wave is detected at the detection timing td, the amplitude AD value (AD value) corresponding to the degree of contact between the hand and H can be determined. The amplitude AD value in the detection timing td can be regarded as the value corresponding to the degree of contact between the hand and H.

[0074] <Contact determination using reference values>

[0075] Figure 3 This diagram illustrates the contact determination using reference values. Figure 3 In the graph, the horizontal axis represents time, and the vertical axis represents the AD value. Figure 3 In the diagram, the solid line represents the amplitude AD value (first DC signal CA), the dashed line represents the reference value, and the dotted-dash line represents the difference ΔAD (AD value - reference value) between the amplitude AD value and the reference value. The amplitude AD value is the value output by AFE120A. The amplitude AD value represents the electrostatic capacitance between the electrostatic sensor 110 and the surrounding conductors. The reference value represents the electrostatic capacitance between the electrostatic sensor 110 and the surrounding conductors when there is no hand H nearby. The difference ΔAD is the difference between the electrostatic capacitance between the electrostatic sensor 110 and the surrounding conductors when the hand H is nearby and when the hand H is not nearby. That is, the difference ΔAD is the electrostatic capacitance between the electrostatic sensor 110 and the hand H.

[0076] exist Figure 3 In the state prior to time t1, hand H is not in contact with handlebar 11. If hand H contacts handlebar 11 at time t1, the amplitude AD value increases relative to the reference value. At this time, the difference (AD value - reference value) also increases, and the contact determination unit 122 determines that hand H is in contact with handlebar 11 by becoming above the activation (ON) threshold Th1. The activation threshold Th1 is an example of the first contact threshold. Furthermore, if hand H leaves handlebar 11 at time t2, the amplitude AD value decreases. At this time, the difference (AD value - reference value) also decreases, and the contact determination unit 122 determines that hand H has left handlebar 11 by becoming below the failure threshold Th2, which is lower than the activation threshold Th1. The failure (OFF) threshold Th2 is an example of the second contact threshold.

[0077] Figure 4This is a diagram representing AFE120A. In Figure 4 The image also shows electrostatic sensor 110 and MPU120B. Furthermore, in... Figure 4 The instructions for inputting from MPU120B to AFE120A are omitted. Figure 5 This is a diagram showing the reference signal generation unit 40 contained in AFE120A.

[0078] The AFE120A includes a capacitance detection circuit 102, a demodulation circuit 22, a sine wave generator 30, a drive signal generator 35, and a reference signal generator 40. The following description addresses the case where a capacitor Cx exists between the hand H and the electrodes of the electrostatic sensor 110. The reference signal generator 40 is an example of both a first and a second reference signal generator.

[0079] [Electrostatic Capacitance Detection Circuit 102]

[0080] The electrostatic capacitance detection circuit 102 generates a detection signal S corresponding to the electrostatic capacitance of capacitor Cx based on the charge transferred to capacitor Cx via electrostatic sensor 110. The electrostatic capacitance detection circuit 102 applies a drive signal Vd to capacitor Cx via electrostatic sensor 110, generating a detection signal S corresponding to the charge transferred to capacitor Cx with the application of drive signal Vd. The detection signal S has an amplitude corresponding to the electrostatic capacitance of capacitor Cx.

[0081] For example, Figure 4 As shown, the electrostatic capacitance detection circuit 102 includes an operational amplifier 102A and a capacitor Cf1. The capacitor Cf1 is connected between the inverting input terminal and the output terminal of the operational amplifier 102A. A sinusoidal driving voltage Vd is supplied to the non-inverting (non-inverting) input terminal of the operational amplifier 102A by the drive signal generation unit 35. The electrostatic sensor 110 is connected to the inverting input terminal of the operational amplifier 102A. The driving voltage Vd is, for example, a sinusoidal AC voltage. Because the operational amplifier 102A controls the output voltage so that the voltage at the inverting input terminal and the voltage at the non-inverting input terminal are approximately the same, an AC voltage approximately the same as the driving voltage Vd is generated in the capacitor Cx. When an AC voltage is generated in the capacitor Cx, a change in charge proportional to this AC voltage and the electrostatic capacitance of the capacitor Cx is generated. The change in charge in the capacitor Cx is approximately equal to the change in charge in the capacitor Cf1. As a result, the AC voltage generated in the capacitor Cf1 has an amplitude approximately proportional to the electrostatic capacitance of the capacitor Cx. The detection signal S is the voltage generated between the output terminal and the non-inverting input terminal of operational amplifier 102A, which is approximately equal to the AC voltage generated in capacitor Cfl. Therefore, the detection signal S has an amplitude that is approximately proportional to the electrostatic capacitance of capacitor Cx.

[0082] [Sine wave generation section 30]

[0083] The sine wave generation unit 30 generates a sine wave signal W, which forms the basis of the drive signal Vd, under the control of the main control unit 121 of the MPU120B. The sine wave generation unit 30 is, for example, a digital circuit that operates synchronously with the clock of the MPU120B, and the sine wave signal W is a digital signal set to the drive frequency fd.

[0084] [Drive signal generation unit 35]

[0085] The drive signal generation unit 35 generates a sinusoidal drive signal Vd as an analog signal based on the sinusoidal signal W generated in the sinusoidal signal generation unit 30. In one example, the drive signal Vd is a sinusoidal AC voltage, but in other examples, the drive signal Vd may also be a non-sinusoidal AC voltage (e.g., a square wave). By setting the drive signal Vd to a sinusoidal AC voltage, harmonic noise emitted from the electrostatic sensor 110 can be reduced.

[0086] [Reference signal generation unit 40]

[0087] The reference signal generation unit 40 simultaneously generates a first reference signal FA and a second reference signal FB based on a sinusoidal signal W. For example... Figure 5 As shown, the reference signal generation unit 40 includes a phase adjustment unit 44 and a phase adjustment unit 45. The phase adjustment unit 45 is connected to the output side of the phase adjustment unit 44. The phase adjustment unit 44 receives a sinusoidal signal W as input and outputs a first reference signal FA. The detection signal S deviates from the driving signal Vd. The phase adjustment unit 44 adjusts the phase of the first reference signal FA so that the phases of the detection signal S and the first reference signal FA are synchronized. The first reference signal FA is output as one of the outputs of the reference signal generation unit 40 and input to the phase adjustment unit 45. The phase adjustment unit 45 outputs a signal whose phase deviates from that of the first reference signal FA by a quarter period as the second reference signal FB.

[0088] The first reference signal FA is a sine wave reference signal having the same frequency and phase as the sine wave detection signal S. The reference signal generation unit 40 generates a reference signal having the same frequency fd as the drive frequency of the drive signal Vd input from the drive signal generation unit 35 and a given phase relative to the drive signal Vd. The first reference signal FA.

[0089] Furthermore, the reference signal generation unit 40 generates a second reference signal FB0, which has the same frequency as the sinusoidal detection signal S and whose phase is offset from the sinusoidal detection signal S by a quarter period. The reference signal generation unit 40 also generates a second reference signal FB0, which has the same frequency as the driving frequency fd and whose phase is offset from the first reference signal FA by a quarter period compared to the driving signal Vd. Since the phase of the first reference signal FA is approximately the same as the detection signal S, the second reference signal becomes a signal whose phase is offset from the detection signal S by a quarter period.

[0090] [Demodulation Circuit 22]

[0091] The demodulation circuit 22 includes: an A / D converter 211 that converts the analog detection signal S into a digital signal; a multiplication circuit 212; a low-pass filter 213; a multiplication circuit 222 that performs a multiplication operation on the output signal of the A / D converter 211 (the signal that digitizes the detection signal S) and a second reference signal FB; and a low-pass filter 223 that extracts the DC component from the multiplication result of the multiplication circuit 222. Low-pass filter 213 is an example of a first low-pass filter. Low-pass filter 223 is an example of a second low-pass filter.

[0092] The demodulation circuit 22 generates a first DC signal CA by multiplying the detection signal S output from the capacitance detection circuit 102 by the first reference signal FA, and generates a second DC signal CB by multiplying the detection signal S output from the capacitance detection circuit 102 by the second reference signal FB. The demodulation circuit 22 outputs the first DC signal CA and the second DC signal CB to the MPU120B.

[0093] The A / D converter 211 includes, for example, a differential amplifier that amplifies the difference between the output signal of operational amplifier 102A and the drive signal Vd, and also functions as a low-pass filter to prevent aliasing. The A / D converter 211 converts the output signal of this differential amplifier (equivalent to the AC voltage signal of capacitor Cf1) into a digital signal. The multiplication circuit 212 multiplies the detection signal S, converted into a digital signal in the A / D converter 211, with the first reference signal FA.

[0094] Multiplication circuit 222 multiplies the detection signal S, converted into a digital signal by A / D converter 211, with the second reference signal FB. Low-pass filter 213 removes the high-frequency components from the first demodulated signal of the multiplication result from multiplication circuit 212, extracting the DC component. The DC component extracted by low-pass filter 213 is output as the first DC signal CA to MPU120B. Low-pass filter 223 removes the high-frequency components from the second demodulated signal of the multiplication result from multiplication circuit 222, extracting the DC component. The DC component extracted by low-pass filter 223 is output as the second DC signal CB to MPU120B.

[0095] The first DC signal CA is the signal corresponding to the DC component contained in the result of the multiplication of the detection signal S and the first reference signal FA. The angular frequency ω of the detection signal S and the first reference signal FA is "2πfd". Let the detection signal S be set to "As·sin Set the first reference signal FA to "Af·sin In the case of “”, the signal Y1 obtained by multiplying the detection signal S and the first reference signal FA is characterized by the following equation (1).

[0096]

[0097] Where K = As·Af / 2

[0098] The first DC signal CA is the signal corresponding to the DC component of the signal Y1 shown in equation (1), and has a magnitude proportional to "K". Af is a fixed value whose magnitude is known in advance. The magnitude of As is the magnitude corresponding to the static capacitance of capacitor Cx. Therefore, the first DC signal CA generated by demodulation circuit 22 becomes a signal with a magnitude corresponding to the static capacitance of capacitor Cx. In addition, since the phase change of signal S is detected by the change in the static capacitance of capacitor Cx, the phase of the detected signal S and the phase of the first reference signal FA are not necessarily completely consistent. However, the difference between the phase of the detected signal S and the phase of the first reference signal FA is so small as to be negligible.

[0099] On the other hand, the second reference signal FB, whose phase deviates from the detection signal S by a quarter period (πr / 2 radians), is set as "Af·sin In the case of “”, the signal Y2 obtained by multiplying the detection signal S and the second reference signal FB can be characterized by equation (2).

[0100]

[0101] The second DC signal CB is the signal corresponding to the DC component of signal Y2 as shown in equation (2). “cos(π / 2)” is zero. Therefore, in the case where there are no overlapping noise components in the detection signal S, since the DC component of signal Y2 becomes zero, the second DC signal CB also becomes zero (or equivalent to a zero reference value). Conversely, the second DC signal CB has the same frequency as the driving frequency fd and has a magnitude corresponding to a noise component with a different phase from the detection signal S. Therefore, the second DC signal CB generated by the demodulation circuit 22 becomes a signal with a magnitude corresponding to a noise component with the same frequency as the driving frequency fd that overlaps with the detection signal S. In addition, since the phase of the detection signal S changes due to the change in the electrostatic capacitance of capacitor Cx, the difference between the phase of the detection signal S and the phase of the second reference signal FA is not necessarily π / 2. However, the difference between the phase of the detection signal S and the phase of the first reference signal FA is so small as to be negligible. Therefore, the difference between the phase of the detection signal S and the phase of the second reference signal FA can be considered as π / 2.

[0102] <Problems in the contact determination device used for comparison>

[0103] Figure 6A as well as Figure 6B This diagram illustrates the problem points in the contact determination device used for comparison. The contact determination device used for comparison has... Figure 4 The AFE120A shown omits the multiplication circuit 222 and the low-pass filter 223, outputting only the first DC signal CA and not the second DC signal CB. The MPU of the contact determination device used for comparison determines whether the hand H is attached to the grip 11 (gripping) based on the first DC signal CA.

[0104] exist Figure 6A as well as Figure 6B In the diagram, the horizontal axis represents time, and the vertical axis represents the first DC signal CA output by the AFE used for comparison, the electrostatic capacitance of the reference value Base, and the decision value. The decision value is the reference value Base plus the value of the threshold used for contact determination (effective threshold Th1 or failure threshold Th2). The values ​​of effective threshold Th1 and failure threshold Th2 are as follows: Figure 3 The result is different from what is shown, but for the sake of simplicity, the decision value is represented as a single value here.

[0105] In cases of poor connection between connectors 105 and 15, fluctuations may occur in the signal level of the first DC signal CA. A poor connection between connectors 105 and 15 refers to a situation where connectors 105 and 15 (refer to...) are not properly connected. Figure 1This includes situations where the connector 105 and connector 15 are not properly fitted, or where there is breakage or damage to the wiring connected to connector 105 or connector 15. Insufficient fitting of connector 105 and connector 15 can be caused by, for example, connector 105 being loose relative to connector 15, or connector 105 not being properly inserted into connector 15.

[0106] As a prerequisite, the contact determination device 100 is configured such that if the vehicle's ignition switches from off to on, it determines whether the hand H is currently attached to the steering wheel 10 according to the request of the HOD_ECU 120. If the vehicle's ignition switches from off to on while the hand H is attached to the steering wheel 10, the reference value Base for the state where the hand H is not attached to the steering wheel 10 cannot be correctly calculated. Therefore, the hand H must be removed from the steering wheel 10, and the correct reference value Base must be calculated before the hand H is reattached to the steering wheel 10.

[0107] First, use Figure 6A This describes the operation under the condition that the connection between connector 105 and connector 15 is normal. Figure 6A At approximately 22 seconds, with hand H attached to grip 11, the vehicle's ignition switches from off to on, and hand H leaves grip 11. If the first DC signal CA decreases after approximately 22 seconds, the MPU of the contact determination device used for comparison lowers the reference value Base for reset. The reference value Base is calculated when hand H is not attached to grip 11, and the reference value Base is reset to the calculated value.

[0108] As the reference value Base decreases, the determination value also decreases. When hand H is reattached to the grip 11 at approximately 23 seconds, the first DC signal CA increases. If this increases to above the determination value, the MPU of the comparison contact determination device determines that hand H is attached to the grip 11 (handon). Then, at approximately 24 seconds, hand H is removed from the grip 11 again. The first DC signal CA decreases. If this decreases to below the determination value, the MPU of the comparison contact determination device determines that hand H has been removed from the grip 11. As described above, the determination value is the reference value Base plus the value of the contact determination threshold (effective threshold Th1 or ineffective threshold Th2).

[0109] Next, use Figure 6B This describes the action taken to explain the poor connection between connector 105 and connector 15. Figure 6B This refers to the behavior when the hand H is not attached to the grip sleeve 11. In cases of poor connection, there will be instances where the electrical connection between connector 105 and connector 15 is maintained, and instances where the electrical connection between connector 105 and connector 15 is not maintained. These will be described in detail below.

[0110] exist Figure 6BIf the first DC signal CA decreases after approximately 13 seconds, the MPU of the contact determination device used for comparison resets the reference value Base to a low value. The reference value Base is calculated when the hand H is not attached to the handle sleeve 11, and the reference value Base is reset to the calculated value. The determination value decreases as the reference value Base decreases.

[0111] Subsequently, if, although hand H is not attached to grip 11, the first DC signal CA fluctuates like noise during approximately 24 to approximately 30 seconds, approximately 53 to approximately 56 seconds, approximately 58 to approximately 62 seconds, approximately 68 to approximately 73 seconds, approximately 85 to approximately 86 seconds, approximately 87 to approximately 91 seconds, and approximately 96 to approximately 100 seconds, it will be incorrectly determined that hand H is attached to grip 11 (becoming a hand grip). That is, a misjudgment of hand grip occurs.

[0112] Because the connection between connectors 105 and 15 is poor and electrical connection is not maintained, the ground potential fluctuates, causing the first DC signal CA to change, resulting in a false hand-on detection. Furthermore, due to the poor connection between connectors 105 and 15, heavy components such as the steering column, which are maintained at ground potential, may sway, increasing the fluctuation of the first DC signal CA and making false hand-on detections more likely.

[0113] As described above, due to the poor connection between connector 105 and connector 15, the first DC signal CA fluctuates like noise, which may lead to a false judgment that the hand H is attached to the grip 11 (becoming a hand grip).

[0114] <Characteristics of the first DC signal CA and the second DC signal CB>

[0115] Figure 7A as well as Figure 7B This is a graph representing the characteristics of the first DC signal CA and the second DC signal CB. Figure 7A as well as Figure 7B In the diagram, the horizontal axis represents time, the left vertical axis represents the first DC signal CA, and the right vertical axis represents the second DC signal CB. Because the maximum and minimum values ​​of the first DC signal CA and the second DC signal CB can take different ranges, the scales of the right and left vertical axes are different. Figure 7A as well as Figure 7B Characterizes the range of activities that can be achieved by the first DC signal CA and the second DC signal CB.

[0116] Figure 7AThe characteristics of the first DC signal CA and the second DC signal CB, indicating the normal connection state between connectors 105 and 15, are described below. Under normal connection conditions, with hand H attached to grip 11 at approximately 22 seconds, the first DC signal CA is at approximately its maximum value, and the second DC signal CB is at approximately its minimum value. If hand H is removed from grip 11 after 22 seconds, the first DC signal CA decreases towards its minimum value, and the second DC signal CB increases towards its maximum value, changing in the opposite direction to the first DC signal CA. Thus, under normal connection conditions, the first DC signal CA and the second DC signal CB change in opposite directions.

[0117] Figure 7B This describes the action taken when the connection between connector 105 and connector 15 is faulty. Figure 7B The results show that the connection between the grounding terminal of connector 105 and the grounding terminal of connector 15 is unstable. Figure 7B In the process, the grounding terminals of connector 105 and connector 15 repeatedly switch between connected and unconnected states from 0 seconds to 110 seconds.

[0118] At the 10-second mark, both the first DC signal CA and the second DC signal CB are approximately at their maximum values. Then, at approximately the 12-second mark, as the first DC signal CA decreases towards its approximately minimum value, the second DC signal CB also changes and decreases towards its approximately minimum value. Furthermore, at approximately the 24-second mark, as the first DC signal CA increases towards its approximately maximum value, the second DC signal CB also changes and increases towards its approximately maximum value. Thereafter, similarly, the first DC signal CA and the second DC signal CB change in the same direction at the same timing (the direction of change is the same).

[0119] Thus, when the connection between connector 105 and connector 15 is normal, the first DC signal CA and the second DC signal CB change in opposite directions. On the other hand, when the connection between the ground terminal of connector 105 and the ground terminal of connector 15 is poor, the first DC signal CA and the second DC signal CB change in the same direction at the same timing.

[0120] The contact determination device 100 of the embodiment uses the characteristics of the change directions of such a first DC signal CA and a second DC signal CB to determine whether the connection state of the ground terminal of the connector 105 and the ground terminal of the connector 15 is normal or defective. When the connection state of the connector 105 and the connector 15 is defective, since the connection of all terminals becomes defective, the connection state of the entire connector can be judged based on the connection state of the ground terminal. In addition, when only the signal line 12 is broken, since the contact state continues to be in the "hands off" state regardless of the actual contact state between the hand H and the grip 11, the breakage can be judged. Furthermore, the magnitude of the noise component can also be measured by using the first DC signal CA and the second DC signal CB. That is, the measurement of the magnitude of the noise component and the determination of whether the connection state of the connector 105 and the connector 15 is normal or defective can be performed in the same circuit. Therefore, an increase in the circuit scale can be suppressed. The determination method will be described below.

[0121] <Determination Method>

[0122] Figure 8 This is a diagram showing the determination process executed by the MPU 120B of the contact determination device 100.

[0123] The contact determination unit 122 calls the subroutine "sub Initial Setting" to perform initial setting (step S1). In the initial setting, subroutine processing for initializing various values used in subsequent processing is performed. Details will be described later. Figure 9 It will be described later.

[0124] The contact determination unit 122 acquires the first DC signal CA and the second DC signal CB (step S2). This is a process of acquiring the latest first DC signal CA and second DC signal CB for determining the connection state.

[0125] The contact determination unit 122 calls the subroutine "sub Connection State Determination" to perform the process of determining the connection state of the connector 105 and the connector 15 (step S3). Details will be described later. [[ID=​​​​​​​​​​​​​​Next, use Figure 9 To explain based on Figure 8 The initial setting process is performed by the subroutine "subinitial setting" in step S1. Figure 9 This is a flowchart illustrating an example of the initial settings process for the sub.

[0130] If the contact determination unit 122 starts the initial setting process, it acquires the first DC signal CA and the second DC signal CB (step S11). This is the process of acquiring the latest first DC signal CA and second DC signal CB for the initial setting process.

[0131] The contact determination unit 122 sets reference values ​​Base, CA_old, CB_old, Decision_A, and Decision_B (step S12). Specifically, the contact determination unit 122 sets the reference value Base to the initial value (CA_ini) (Base = CA_ini). The initial value (CA_ini) can be any value that can become the reference value Base when it is normal. For example, the value measured at room temperature (20°C) during the design can also be used. As the values ​​(CA_old, CB_old) of the first DC signal CA and the second DC signal CB one cycle ago, the contact determination unit 122 sets the first DC signal CA and the second DC signal CB at the initial setting (CA_old = CA, CB_old = CB). In addition, the contact determination unit 122 sets the variables Decision_A and Decision_B to Plus (Decision_A = "Plus", Decision_B = "Plus"). The variables Decision_A and Decision_B are variables that characterize the direction of change of the first DC signal CA and the second DC signal CB. "Plus" indicates that the direction of change is increasing (+). In addition, variables Decision_A and Decision_B sometimes also take the value "Minus". "Minus" indicates that the direction of change is decreasing (-). Since variables Decision_A and Decision_B can take values ​​of both "Plus" and "Minus", they can be used as Boolean (logical) variables.

[0132] The contact determination unit 122 resets the timer 123A to zero (Timer = 0) and sets the contact state to "hand off" (contact state = HandOff) (step S13). The contact state indicates whether hand H is in contact with the grip 11 of the steering wheel 10. The contact state takes the value of "hand off" or "hand on". Since the contact state variable takes two values, "HandOff" and "HandOn", a Boolean (logical) variable can be used.

[0133] Above, the contact determination unit 122 finishes the process of initial setting.

[0134]

[0135] Next, use Figure 10 to explain the connection state determination process performed based on Figure 8 the subroutine "sub connection state determination" of step S3.

[0136] Figure 10 FIG. is a flowchart showing an example of the process of sub connection state determination. When the contact determination unit 122 starts the process of sub connection state determination, it calculates the change amounts ΔCA and ΔCB of the first DC signal CA and the second DC signal CB using the first DC signal CA and the second DC signal CB obtained in step S2 (step S31). The change amount ΔCA of the first DC signal CA is CA - CA_old, which is the change amount relative to the value one cycle ago. The change amount ΔCB of the second DC signal CB is CB - CB_old, which is the change amount relative to the value one cycle ago. CA_old just after startup is CA at the time of initial setting (refer to step S12). CB_old just after startup is CB at the time of initial setting (refer to step S12). ΔCA and ΔCB just after startup are the change amounts relative to the initial setting. CA_old other than just after startup is CA one cycle ago (refer to step S38). CB_old other than just after startup is CB one cycle ago (refer to step S38). ΔCA and ΔCB other than just after startup are the change amounts relative to one cycle ago.

[0137] The contact determination unit 122 determines whether the change amount ΔCA of the first DC signal CA is greater than the threshold TH_CA_P (step S32). The threshold TH_CA_P is a threshold for determining whether the change amount ΔCA is in an increasing trend. The threshold TH_CA_P is an example of the first threshold when the change amount ΔCA is in an increasing trend.

[0138] If the contact determination unit 122 determines that the change amount ΔCA of the first DC signal CA is greater than the threshold TH_CA_P (S32: Yes), it sets (updates) the variable Decision_A to Plus (Decision_A = "Plus") (step S33A). When the contact determination unit 122 finishes the process of step S33A, it advances the flow to step S34.

[0139] If the contact determination unit 122 determines in step S32 that the change in the first DC signal CA, ΔCA, is not greater than the threshold TH_CA_P (S32: No), then it determines whether the change in the first DC signal CA, ΔCA, is smaller than the threshold TH_CA_M (step S33B). The threshold TH_CA_M is a threshold used to determine whether the change in ΔCA is in a decreasing trend. The threshold TH_CA_M is an example of the first threshold when the change in ΔCA is in a decreasing trend.

[0140] If the contact determination unit 122 determines that the change ΔCA of the first DC signal CA is smaller than the threshold TH_CA_M (S33B: Yes), it sets (updates) the variable Decision_A to Minus (Decision_A = "Minus") (step S33C). If the contact determination unit 122 finishes the processing in step S33C, it advances the process to step S34.

[0141] Furthermore, if the contact determination unit 122 determines in step S33B that the change in the first DC signal CA, ΔCA, is not less than the threshold TH_CA_M (S33B: No), the process proceeds to step S34. In this case, since the variable Decision_A is not updated, the value before the update is used.

[0142] The contact determination unit 122 determines whether the change in the second DC signal CB, ΔCB, is greater than the threshold TH_CB_P (step S34). The threshold TH_CB_P is a threshold used to determine whether the change in ΔCB is trending upwards. The threshold TH_CB_P is an example of a second threshold when the change in ΔCB is trending upwards.

[0143] If the contact determination unit 122 determines that the change ΔCB of the second DC signal CB is greater than the threshold TH_CB_P (S34: Yes), it sets (updates) the variable Decision_B to Plus (Decision_B = "Plus") (step S35A). If the contact determination unit 122 finishes the processing in step S35A, it advances the process to step S36.

[0144] If the contact determination unit 122 determines in step S34 that the change in the second DC signal CB, ΔCB, is not greater than the threshold TH_CB_P (S34: No), then it determines whether the change in the second DC signal CB, ΔCB, is smaller than the threshold TH_CB_M (step S35B). The threshold TH_CB_M is a threshold used to determine whether the change in ΔCB is in a decreasing trend. The threshold TH_CB_M is an example of a second threshold for cases where the change in ΔCB is in a decreasing trend.

[0145] If the contact determination unit 122 determines that the change ΔCB of the second DC signal CB is smaller than the threshold TH_CB_M (S35B: Yes), it sets (updates) the variable Decision_B to Minus (Decision_B = "Minus") (step S35C). If the contact determination unit 122 finishes processing in step S35C, it proceeds to step S36.

[0146] Furthermore, if the contact determination unit 122 determines in step S35B that the change ΔCB of the second DC signal CB is not smaller than the threshold TH_CB_M (S35B: No), the process proceeds to step S36. In this case, since the variable Decision_B is not updated, the value before the update is used.

[0147] The contact determination unit 122 determines whether the changes of the first DC signal CA and the second DC signal CB are in opposite directions (step S36). More specifically, the contact determination unit 122 determines whether Decision_A = "Plus" and Decision_B = "Minus", or whether Decision_A = "Minus" and Decision_B = "Plus".

[0148] If the contact determination unit 122 determines that the changes in the first DC signal CA and the second DC signal CB are in opposite directions (S36: Yes), it sets the connection status to True (step S37A). A connection status of True means that the connection between connector 105 and connector 15 is normal. If the contact determination unit 122 finishes processing step S37A, it proceeds to step S38.

[0149] If the contact determination unit 122 determines in step S36 that the changes in the first DC signal CA and the second DC signal CB are not in opposite directions (S36: No), it determines that the connection status is poor and sets the connection status to False (step S37B). Furthermore, if the contact determination unit 122 determines that the connection status is poor, it outputs a connection failure signal indicating a poor connection status. The connection failure signal is output from MPU120B to ECU50. As a result, ECU50 identifies a poor connection status.

[0150] The contact determination unit 122 sets the contact state to hand-off (contact state = HandOff) (step S37C). When the contact determination unit 122 finishes the processing of step S37C, it advances the process to step S38. In addition, the contact determination unit 122 notifies the ECU 50 that the contact state is hand-off. As a result, the ECU 50 recognizes that the contact state is hand-off. The reason for notifying the ECU 50 that the contact state is hand-off is that even when the capacitance does not change after startup, step 37C is still passed through, and passing through step S37C does not necessarily mean a poor connection state. In addition, this is because if the state of hand-off continues even when the hand H is in contact with the grip 11, it is easy to detect a poor connection state during the test drive before shipment. In addition, this is because even if a poor connection state occurs after shipment, it is easy to recognize it as a failure through the display of a hand-off warning or the like. That is, through step S37C, the fail-safe function operates.

[0151] The contact determination unit 122 sets the values (CA old, Cb old) of the first DC signal CA and the second DC signal CB one cycle before as the latest (current cycle) first DC signal CA and second DC signal CB (CA old = CA, Cb old = CB) (step S38). When the subroutine "sub contact state determination" is executed again, CA old and Cb old are used as the values one cycle before.

[0152] Above, the determination process of the connection state ends.

[0153]

[0154] Next, use Figure 11 to explain Figure 8 the contact determination process performed by the subroutine "sub contact determination" of step S4. Figure 11 is a flowchart showing an example of the process of sub contact determination.

[0155] The contact determination unit 122 determines whether the contact state in the previous control cycle is contact (HandsOn) (step S41). Since the control cycle is 10 ms, the contact state in the previous control cycle is the determination result 10 ms before.

[0156] If the previous state was not a contact (HandsOn) (S41: No), the contact determination unit 122 determines whether the difference (CA-Base) between the first DC signal CA and the reference value Base is greater than or equal to the activation threshold Th1 (step S42). The activation threshold Th1 is used to determine whether there is contact. The reference value Base represents the electrostatic capacitance of the electrostatic sensor 110 when the hand H is not in contact with the handle 11. The difference (CA-Base) represents the electrostatic capacitance between the electrostatic sensor 110 and the hand H.

[0157] If the contact determination unit 122 determines that the differential ΔAD is above the effective threshold Th1 (S42: Yes), then it determines that the connection status is normal (True) (step S43).

[0158] If the contact determination unit 122 determines that the connection status is normal (True) (S43: Yes), it increments the counting time TimerS of the timer 122A (step S44A). That is, TimerS = TimerS + 1.

[0159] The contact determination unit 122 determines whether the counting time TimerS of the timer 122A is greater than or equal to the time threshold THT (step S44C). The time threshold THT can be a predetermined value. This is because the contact between the hand H and the steering wheel 10's grip 11 is not immediately determined when the difference (CA-Base) exceeds the effective threshold Th1, but rather when the difference (CA-Base) exceeds the effective threshold Th1 after a certain period of time (time threshold THT). Therefore, if the contact determination unit 122 determines that the counting time TimerS is not greater than or equal to the time threshold THT (S44C: No), the process ends (ends). If the sub-contact determination subroutine ends, it returns to step S2.

[0160] If the contact determination unit 122 determines that the counting time TimerS is above the time threshold THT (S44C: Yes), it sets the contact state to contact (HandsOn) (step S44D). If the contact determination unit 122 finishes processing in step S44D, it ends the process (end). If the sub-contact determination subroutine ends, it returns to step S2.

[0161] Furthermore, if the contact determination unit 122 determines in step S43 that the connection state is abnormal (S43: No), it resets the counting time TimerS of timer 122A to zero (step S44B). If the contact determination unit 122 finishes processing in step S44B, it ends the process (end). If the sub-contact determination subroutine ends, it returns to step S2.

[0162] In addition, if the contact determination unit 122 determines in step S42 that the difference (CA - Base) is not equal to or greater than the effective threshold Th1 (S42: No), it calls the subroutine "subBase calculation" to perform the process of calculating the reference value Base (step S45). Details will be described Figure 12 later.

[0163] The contact determination unit 122 resets the counting time TimerS of the timer 122A (step S46). That is, TimerS = 0, and the counting of the timer 122A restarts. When the contact determination unit 122 finishes the process of step 46, it ends the process (ends). If the subroutine of sub - contact determination ends, it returns to step S2.

[0164] In addition, when the previous determination in step S41 by the contact determination unit 122 is contact (HandsOn) (S41: Yes), it determines whether the difference (CA - Base) obtained by subtracting the reference value Base from the first DC signal CA is equal to or less than the invalidation threshold Th2 (step S47).

[0165] If the contact determination unit 122 determines in step S47 that the difference (CA - Base) is equal to or less than the invalidation threshold Th2 (S47: Yes), it determines that the contact state is non - contact (HandsOff) (step S48). That is, the contact state = HandsOff.

[0166] The contact determination unit 122 resets the counting time TimerS of the timer 122A (step S49). That is, TimerS = 0, and the counting of the timer 122A restarts. When the contact determination unit 122 finishes the process of step S49, it ends the process (ends). If the subroutine of sub - contact determination ends, it returns to step S2.

[0167] In addition, if the contact determination unit 122 determines in step S47 that the difference (CA - Base) is not equal to or less than the invalidation threshold Th2 (S47: No), it advances the process to step S49.

[0168] <subBase calculation>

[0169] Next, use Figure 12 to illustrate the calculation process of the reference value Base performed by the subroutine "subBase calculation" in step S45 based on Figure 11 . Figure 12 is a flowchart showing an example of the process of subBase calculation.

[0170] The contact determination unit 122 determines whether the connection state is normal (True) (step S51).

[0171] If the contact determination unit 122 determines that the connection status is normal (True) (S51: Yes), it sets (updates) the differential to (CA-Base) (step S52). That is, the latest first DC signal CA is used to update the differential with the reference value Base.

[0172] The contact determination unit 122 determines whether the differential is smaller than the drop threshold DropTH (step S53). The drop threshold DropTH is used to determine whether the first DC signal CA exceeds, for example, the drop threshold DropTH. Figure 7A The threshold drops sharply in 22 seconds.

[0173] If the contact determination unit 122 determines that the difference is smaller than the drop threshold DropTH (S53: Yes), it increments the count value Timer of timer 123A (step S54A). That is, Timer = Timer + 1. If the contact determination unit 122 finishes processing in step S54A, it advances the process to step S55.

[0174] On the other hand, if the contact determination unit 122 determines in step S53 that the difference is not less than the drop threshold DropTH (S53: No), it resets the timer 123A (step S54B). That is, Timer = 0. If the contact determination unit 122 finishes the processing in step S54B, it advances the process to step S55.

[0175] The contact determination unit 122 determines whether the count value (Timer) of the timer 123A exceeds the drop time (Step S55).

[0176] If the contact determination unit 122 determines that the count value (Timer) of the timer 123A exceeds the drop time (S55: Yes), it sets the base value Base to the first DC signal CA (step S56A). If the contact determination unit 122 finishes the processing in step S56B, it ends the subBase calculation process.

[0177] If the contact determination unit 122 determines that the count value (Timer) of the timer 123A has not exceeded the drop time (S55: No), it calculates the base value Base based on the formula (3) (step S56B).

[0178]

Mathematical Formula 1

[0179]

[0180] The contact determination unit 122 calculates the weighted average of the reference value (10ms ago) and the first DC signal CA based on equation (3) by multiplying the reference value Base (10ms ago) by the weight M, and uses this average as the reference value Base. If the contact determination unit 122 finishes the processing of step S56B, it ends the subBase calculation process.

[0181] Furthermore, if the contact determination unit 122 determines in step S51 that the connection state is abnormal (S51: No), it will not calculate the base value Base and will end the subBase calculation process. That is, the contact determination unit 122 will end the subBase calculation process without resetting the base value Base.

[0182] If the contact determination unit 122 terminates the sub-routine of subBase calculation, it advances the process to... Figure 11 Step S46.

[0183] <Effect>

[0184] Figure 13A as well as Figure 13B This diagram illustrates an example of the effect of the contact detection device 100. Figure 13A as well as Figure 13B The diagram shows the operation when the connection between connector 105 and connector 15 is normal.

[0185] exist Figure 13A In the diagram, the horizontal axis represents time, and the vertical axis represents the first DC signal CA, the electrostatic capacitance of the reference value Base, and the judgment value. The judgment value is the reference value Base plus the threshold value used for contact determination (effective threshold Th1 or failure threshold Th2). The values ​​of the effective threshold Th1 and the failure threshold Th2 are as follows: Figure 3 The results are different from those shown, but for simplicity, the decision value will be presented as a single value here. Figure 13B In the diagram, the horizontal axis represents time, the vertical axis on the left represents the first DC signal CA, and the vertical axis on the right represents the second DC signal CB.

[0186] exist Figure 13A At approximately 22 seconds, while the hand H is attached to the steering wheel cover 11, the vehicle's ignition switches from off to on, and the hand H leaves the steering wheel cover 11. If the first DC signal CA decreases after approximately 22 seconds, the MPU120B of the contact determination device 100 lowers the reference value Base and resets it. The reference value Base is calculated when the hand H is not attached to the steering wheel cover 11, and the reference value Base is reset to the calculated value. This action is related to... Figure 6A The operation of the contact determination device used for comparison shown is the same.

[0187] In addition, such as Figure 13BAs shown, it can be confirmed that when the first DC signal CA changes, the second DC signal CB changes in the opposite direction to the first DC signal CA.

[0188] Figure 14A as well as Figure 14B This diagram illustrates an example of the effect of the contact detection device 100. Figure 14A as well as Figure 14B The diagram shows the operation when the connection between connector 105 and connector 15 is faulty.

[0189] exist Figure 14A In the middle, because even with Figure 6B Similarly, as shown, the first DC signal CA drops sharply, and the connection between connector 105 and connector 15 is also poor. Therefore, since the connection status is set to False, [the connection is lost / damaged]. Figure 12 In step S51, the determination is "No", so the reference value Base is not reset and becomes a high value. Since the reference value Base remains high, the determination value also becomes high. Therefore, even if the first DC signal CA changes, it will not fall below the determination value, and no false determination of hand grip will occur.

[0190] In addition, such as Figure 14B As shown, it can be confirmed that when the first DC signal CA changes, the second DC signal CB changes in the same direction as the first DC signal CA.

[0191] As described above, the contact determination device 100 includes an electrostatic sensor 110, which outputs a detection signal S of a sine wave with an amplitude corresponding to the electrostatic capacitance between the detection electrode of the steering wheel 10 cover 11, which is in contact with the hand H, and the hand H. Furthermore, the contact determination device 100 includes: a first reference signal generation unit (multiplication operation circuit 212 of demodulation circuit 22, sine wave generation unit 30, and reference signal generation unit 40), which generates a first reference signal FA of a sine wave having the same frequency and phase as the detection signal S; and a second reference signal generation unit (multiplication operation circuit 222 of demodulation circuit 22, sine wave generation unit 30, and reference signal generation unit 40), which generates a second reference signal FB of a sine wave having the same frequency as the detection signal S but with a phase deviation relative to the detection signal S. Furthermore, the contact determination device 100 includes: a demodulation circuit 22 that generates a signal obtained by multiplying the detection signal S output from the electrostatic sensor 110 by a first reference signal as a first demodulated signal, and generates a signal obtained by multiplying the detection signal S output from the electrostatic sensor 110 by a second reference signal as a second demodulated signal; a low-pass filter 213 that extracts the DC component of the first demodulated signal, i.e., a first DC signal CA; and a low-pass filter 223 that extracts the DC component of the second demodulated signal, i.e., a second DC signal CB. Additionally, the contact determination device 100 includes: a contact determination unit 122 that determines whether the hand H is in contact with the steering wheel 10's grip 11 based on the first DC signal CA. If the latest change direction of the change in the first DC signal CA exceeding the first threshold (TH_CA_P, TH_CA_M) is the same as the latest change direction of the change in the second DC signal CB exceeding the second threshold (TH_CB_P, TH_CB_M), the contact determination unit 122 determines that the connection between the sensor unit and the detection circuit is poor. If the latest change direction of the change in the first DC signal CA exceeding the first threshold (TH_CA_P, TH_CA_M) is opposite to the latest change direction of the change in the second DC signal CB exceeding the second threshold (TH_CB_P, TH_CB_M), the contact determination unit 122 determines that the connection between the sensor unit and the detection circuit is normal.

[0192] That is, if the first DC signal CA and the second DC signal CB change in the same direction, the contact determination unit 122 determines that the connection is faulty; if they change in opposite directions, the connection is normal.

[0193] Therefore, a contact determination device 100 capable of detecting poor contact such as broken wires can be provided without the need for a dedicated physical structure for wire breakage detection.

[0194] Furthermore, if the contact determination unit 122 determines that the connection is faulty in step S37B, it outputs a connection failure signal indicating a faulty connection. Therefore, the ECU 50 can be notified of a faulty connection between connectors 105 and 15. When the contact determination device 100 is installed in the vehicle, even without touching the steering wheel cover 11 with the hand H, a faulty connection between connectors 105 and 15 can be confirmed on the inspection monitor connected to the ECU 50. Furthermore, in the case of a faulty connection, the contact state is set to "Hands Off," and the ECU 50 is notified. If there is a faulty connection, even if the driver holds the steering wheel cover 11 with their hand H, "Hands Off" is displayed; therefore, the driver can identify a faulty connection even without an inspection monitor.

[0195] Furthermore, in step S56A, the contact determination unit 122 updates the first DC signal CA to the reference value Base when the hand H is not in contact with the steering wheel 10's grip 11. Additionally, if the contact determination unit 122 determines that the connection status is poor in step S37B, it does not update the reference value Base (see step S51: No). Therefore, the connection status can be determined based on a determination value of Base, which has a large value in the normal state before the update, effectively suppressing false determinations. Furthermore, by setting the initial value of the reference value Base to a predetermined value at startup, the connection status can be determined based on a determination value of Base, which has a large value in the normal state, effectively suppressing false determinations.

[0196] The contact determination unit 122 includes a timer 122A that counts the duration of a state where the difference between the first DC signal CA and the reference value Base is a threshold Th1 or higher. If the duration counted by the timer 122A is a given time THT or higher, it is determined that the hand H is in contact with the steering wheel 10's grip 11 (see step S44D). Furthermore, if the contact determination unit 122 determines that the connection is faulty, it resets the duration counted by the timer 122A (see step S44B). Therefore, when the state where the difference between the first DC signal CA and the reference value Base is a threshold Th1 or higher continues for a given time THT or higher, it is possible to reliably determine that the hand H is in contact with the steering wheel 10's grip 11. In addition, since the contact determination unit 122 resets the duration counted by the timer 122A if it determines that the connection is faulty, it is possible to suppress the determination that the hand H is in contact with the steering wheel 10's grip 11 when the connection is faulty.

[0197] The above describes the contact determination device of the exemplary embodiments of the present disclosure, but the present disclosure is not limited to the specific embodiments disclosed, and various modifications and alterations can be made without departing from the claims.

Claims

1. A contact determination device, characterized in that, have: The sensor unit outputs a detection signal having a sinusoidal wave amplitude corresponding to the electrostatic capacitance between the detection electrode located at a contact point accessible to the detection object and the detection object; and The detection circuit uses the detection signal to detect whether the object being detected is in contact with the contact area. The detection circuit includes: The first reference signal generation unit generates a first reference signal having a sine wave with the same frequency and phase as the detection signal. The second reference signal generation unit generates a second reference signal having a frequency equal to the detection signal but with a phase deviation relative to the detection signal. The demodulation circuit generates a signal obtained by multiplying the detection signal output from the sensor unit by the first reference signal, as a first demodulated signal, and generates a signal obtained by multiplying the detection signal output from the sensor unit by the second reference signal, as a second demodulated signal. The first low-pass filter extracts the DC component of the first demodulated signal, i.e., the first DC signal. The second low-pass filter extracts the DC component of the second demodulated signal, i.e., the second DC signal; and The contact determination unit determines whether the detected object is in contact with the contact area based on the first DC signal. If the contact determination unit determines that the connection between the sensor unit and the detection circuit is faulty when the latest direction of the change in the first DC signal exceeding the first threshold is the same as the latest direction of the change in the second DC signal exceeding the second threshold, then the connection between the sensor unit and the detection circuit is faulty. If the latest direction of the change in the first DC signal exceeding the first threshold is opposite to the latest direction of the change in the second DC signal exceeding the second threshold, it is determined that the connection between the sensor unit and the detection circuit is normal.

2. The contact determination device according to claim 1, characterized in that, If the contact determination unit determines that the connection is faulty, it will treat the contact state as non-contact.

3. The contact determination device according to claim 1 or 2, characterized in that, The contact determination unit updates the first DC signal to a reference value when the detected object is not in contact with the contact part. If the contact determination unit determines that the connection status is poor, it will not update the reference value.

4. The contact determination device according to claim 3, characterized in that, The contact determination unit includes a timer that counts the duration of a state where the difference between the first DC signal and the reference value is greater than or equal to a first contact threshold. If the duration counted by the timer exceeds a given time, it is determined that the detected object is in contact with the contact area. If the connection is determined to be faulty, the duration counted by the timer is reset.

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