Contact detection device

Abstract

To provide a contact determination device that is capable of detecting a contact failure of disconnection or the like, without requiring an element for disconnection detection.SOLUTION: A contact determination device includes: a reference signal generation section for generating a first reference signal FA of a sinusoidal wave with a frequency and a phase equal to a detection signal outputted from a sensor section, and a second reference signal FB of a sinusoidal wave with a frequency equal to a detection signal and with a shifted phase; a demodulation circuit for generating first and second demodulation signals obtained by multiplying a detection signal by the first reference signal and the second reference signal; a low-pass filter for extracting first and second direct current signals that are direct current components of the first and second demodulation signals; a contact determination section for determining contact on the basis of the first direct current signal; and a contact determination section for determining a state of contact between the sensor section and a detection circuit on the basis of the first and second direct current signals. The contact determination section determines a connection state to be failing if change directions of the first and second direct current signals are the same, and determines the connection state to be normal if the change directions are reverse.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a contact determination device.

Background Art

[0002] There are automobiles that can be automatically driven only under conditions such as when driving on a highway or at low speed. Such automobiles need to detect the driver's state in order to safely switch between automatic driving and manual driving. As one of the devices for detecting the driver's state, there is a device that detects the state of the driver's grip on the steering wheel. In a contact determination device for detecting the state of the grip on the steering wheel, there is no space for providing a contact determination circuit at the position where the sensor is attached, and wiring for connecting the sensor and the contact determination circuit is required. Since the contact determination device for the steering wheel is an important device for ensuring safety, a function for detecting disconnection of the wiring is required. Conventionally, there has been a contact determination device that includes a sensor electrode and a disconnection detection electrode on the steering wheel to enable disconnection detection (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventional contact determination devices have provided a disconnection detection electrode and a signal line for disconnection detection connected to the disconnection detection electrode for disconnection detection, and components for disconnection detection are required.

[0005] Therefore, an object is to provide a contact determination device that can detect contact failures such as disconnection without requiring components for disconnection detection.

Means for Solving the Problems

[0006] The contact determination device of the embodiment of the present disclosure comprises a sensor unit that outputs a sinusoidal detection signal having an amplitude corresponding to the capacitance between a detection electrode provided at a contact portion that the object to be detected can touch and the object to be detected, and a detection circuit that determines whether the object to be detected is in contact with the contact portion based on the detection signal, wherein the detection circuit comprises a first reference signal generation unit that generates a sinusoidal first reference signal having the same frequency and phase as the detection signal, a second reference signal generation unit that generates a sinusoidal second reference signal having the same frequency as the detection signal and being out of phase with respect to the detection signal, and a first demodulated signal that generates a signal obtained by multiplying the detection signal output from the sensor unit by the first reference signal, and a signal obtained by multiplying the detection signal output from the sensor unit by the second reference signal The sensor includes a demodulation circuit that generates a signal as a second demodulated signal, a first low-pass filter that extracts a first DC signal which is the DC component of the first demodulated signal, a second low-pass filter that extracts a second DC signal which is the DC component of the second demodulated signal, and a contact determination unit that determines whether the object to be detected is in contact with the contact area based on the first DC signal. The contact determination unit determines that the connection between the sensor unit and the detection circuit is poor if the latest direction of change in the amount of change of the first DC signal that exceeds a first threshold is the same as the latest direction of change in the amount of change of the second DC signal that exceeds a second threshold, and determines that the connection between the sensor unit and the detection circuit is normal if the latest direction of change in the amount of change of the first DC signal that exceeds a first threshold is the same as the latest direction of change in the amount of change of the second DC signal that exceeds a second threshold is opposite. [Effects of the Invention]

[0007] This device provides a contact determination device that can detect contact problems such as wire breaks without requiring components for wire break detection. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows a steering wheel 10 with the contact detection device 100 of the embodiment installed. [Figure 2]This figure shows an example of the output sine wave of the electrostatic sensor 110. [Figure 3] This diagram illustrates the detection of contact using reference values. [Figure 4] This is a diagram of AFE120A. [Figure 5] This figure shows the reference signal generation unit 40 included in AFE120A. [Figure 6A] This diagram illustrates the problems with the contact detection device used for comparison. [Figure 6B] This diagram illustrates the problems with the contact detection device used for comparison. [Figure 7A] This figure shows the characteristics of the first DC signal CA and the second DC signal CB. [Figure 7B] This figure shows the characteristics of the first DC signal CA and the second DC signal CB. [Figure 8] This diagram shows the determination process performed by the MPU 120B of the contact detection device 100. [Figure 9] This flowchart shows an example of the initial setup process for sub-programs. [Figure 10] This flowchart shows an example of the process for determining the subconnection status. [Figure 11] This flowchart shows an example of the process for sub-contact detection. [Figure 12] This flowchart shows an example of the subbase calculation process. [Figure 13A] This diagram illustrates an example of the effect of the contact detection device 100. [Figure 13B] This diagram illustrates an example of the effect of the contact detection device 100. [Figure 14A] This diagram illustrates an example of the effect of the contact detection device 100. [Figure 14B] This diagram illustrates an example of the effect of the contact detection device 100. [Modes for carrying out the invention]

[0009] The following describes embodiments to which the contact detection device of this disclosure is applied.

[0010] <Embodiment> FIG. 1 is a diagram showing a steering wheel 10 equipped with a contact determination device 100 according to an embodiment. As shown in FIG. 1, the steering wheel 10 is mounted on a vehicle, and an electrostatic sensor 110 of the contact determination device 100 is mounted inside a grip 11. The electrostatic sensor 110 is an example of a sensor unit. The contact determination device 100 determines whether a 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 target. The grip 11 of the steering wheel 10 is an example of a contact part where the detection target can make contact.

[0011] Hereinafter, the driver of the vehicle is referred to as an operator of the contact determination device 100. A contact determination device 100 will be described which determines whether an operator's hand H as a detection target is in contact with an object provided with an electrostatic sensor 110. An operator touching an object provided with the electrostatic sensor 110 is referred to as an operation of the operator.

[0012] <Configuration of Contact Determination Device 100> The contact determination device 100 includes a connector 105, an electrostatic sensor 110, and a HOD_ECU (Hands Off Detection Electronic Control Unit) 120. The HOD_ECU 120 is an example of a detection circuit. The connector 105 is a connector having a signal terminal and a ground terminal of the HOD_ECU 120. The connector 105 is connected to a connector 15 having a signal terminal and a ground terminal of the steering wheel 10. The signal line connecting the plurality of signal terminals of the connector 105 and the plurality of signal terminals of the connector 15 includes the signal line 12 shown in FIG. 1. In FIG. 1, signal lines other than 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 column shaft 10A to which the steering wheel 10 is attached via a core metal provided around the grip 11 of the steering wheel 10. By connecting the connector 105 and the connector 15, the ground potential of the HOD_ECU 120 becomes equal to the ground potential of the steering wheel 10 and the column shaft 10A.

[0013] The electrostatic sensor 110 is provided over one circumference of the grip 11 of the steering wheel 10 in a state insulated from the core metal provided over one circumference of the grip 11 of the steering wheel 10, and is composed of, for example, electrodes made of metal. The electrostatic sensor 110 is connected to the HOD_ECU 120 via the signal line 12. The electrostatic sensor 110 may use a plurality of electrodes. For example, if four electrostatic sensors 110 are provided at 90-degree intervals on the grip 11 of the steering wheel 10, it is possible to detect that two hands H are in contact at positions separated by 90 degrees or more.

[0014] The HOD_ECU 120 is provided inside the instrument panel as an example. The HOD_ECU 120 has an AFE (Analog Front End) 120A and an MPU (Micro Processor Unit) 120B.

[0015] The AFE120A is connected to the electrostatic sensor 110 and inputs a sine wave (input sine wave) to the electrostatic sensor 110 based on commands received from the MPU120B, and acquires the sine wave (output sine wave) output from the electrostatic sensor 110. The AFE120A acquires the capacitance value of the electrostatic sensor 110 from the input sine wave and output sine wave, digitally converts it, and performs noise removal using a low-pass filter, etc., before outputting it to the MPU120B as an amplitude AD value. The amplitude AD value is expressed as a unitless count value, for example. By performing noise removal using a low-pass filter, it is possible to obtain an amplitude AD value from which noise above a predetermined frequency has been removed. 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, and the second DC signal CB is a DC signal generated separately from the first DC signal CA based on the capacitance value of the electrostatic sensor 110. The first DC signal CA and the second DC signal CB will be described later using Figures 4, 7A, and 7B.

[0016] The MPU120B is implemented by a computer that includes a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), input / output interfaces, and an internal bus. An ECU50 is connected to the MPU120B as an example. The ECU50 is a control device that controls the electronic equipment of the vehicle on which the steering wheel 10 is mounted. The electronic equipment may be, for example, electronic equipment related to the autonomous driving of the vehicle.

[0017] The MPU120B comprises a main control unit 121, a contact detection unit 122, and a memory 124. The main control unit 121 and the contact detection unit 122 represent the functions of the program executed by the MPU120B as functional blocks. The memory 124 functionally represents the memory of the MPU120B.

[0018] The main control unit 121 is a processing unit that oversees the control processing of the MPU 120B and executes processes other than those performed by the contact determination unit 122.

[0019] The contact determination unit 122 determines whether the hand H is in contact with the grip 11 by determining whether the difference obtained by subtracting a reference value from the amplitude AD value (first DC signal CA) exceeds a threshold. This is the contact determination process performed by the contact determination unit 122. The contact determination unit 122 also notifies the ECU 50 of data representing the determination result. Here, the reference value is the reference value of the capacitance value of the electrostatic sensor 110 used by the contact determination unit 122 when determining whether the hand H is in contact with the grip 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 grip 11.

[0020] Furthermore, the contact detection unit 122 has a timer 122A used for contact detection processing. The contact detection processing and timer 122A will be described later.

[0021] The contact determination unit 122 determines whether the connection between connector 105 and connector 15 is normal or has a poor connection based on the first DC signal CA and the second DC signal CB.

[0022] Furthermore, the contact detection unit 122 has a timer 123A used for determining the connection status. The connection status determination process and the timer 123A will be described later.

[0023] Memory 124 stores programs and data necessary for the main control unit 121 and the contact determination unit 122 to perform processing. Memory 124 stores data representing the capacitance value of the electrostatic sensor 110, and data generated by the contact determination unit 122 during the processing process.

[0024] <Sine wave output from electrostatic sensor 110> Figure 2 shows an example of the output sine wave of the electrostatic sensor 110. In Figure 2, the output sine wave when hand H is released from the grip 11 is shown by a solid line, and the output sine wave when hand H is gripping the grip 11 is shown by a dashed line.

[0025] The capacitance value measured by 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 at contact change compared to the sine wave at release. The phase and amplitude of the sine wave at contact change depending on the degree of contact between the hand H and the grip 11. The degree of contact refers to, for example, whether the hand H is lightly gripping or tightly gripping the grip 11, or whether the area of ​​contact between the hand H and the grip 11 is small or large.

[0026] For example, by pre-determining the timing at which the amplitude becomes zero during release as the detection timing td, and detecting the amplitude of the sine wave at detection timing td, it is possible to measure the amplitude AD value (AD value) corresponding to the degree of contact of the hand H. The amplitude AD value at detection timing td can be considered a value corresponding to the degree of contact of the hand H.

[0027] <Contact detection using reference values> Figure 3 illustrates the determination of contact using a reference value. In Figure 3, the horizontal axis represents time, and the vertical axis represents the AD value. In Figure 3, the amplitude AD value (first DC signal CA) is shown by a solid line, the reference value is shown by a dashed line, and the difference ΔAD (AD value - reference value) between the amplitude AD value and the reference value is shown by a dashed line. The amplitude AD value is the value output by AFE120A. The amplitude AD value represents the capacitance between the electrostatic sensor 110 and the surrounding conductor. The reference value represents the capacitance between the electrostatic sensor 110 and the surrounding conductor measured when a hand H is not nearby. The difference ΔAD is the difference between the capacitance between the electrostatic sensor 110 and the surrounding conductor when a hand H is nearby and the capacitance between the electrostatic sensor 110 and the surrounding conductor when a hand H is not nearby. That is, the difference ΔAD is the capacitance between the electrostatic sensor 110 and the hand H.

[0028] In Figure 3, before time t1, hand H is not in contact with grip 11. When hand H makes contact with grip 11 at time t1, the amplitude AD value rises relative to the reference value. At this time, the difference (AD value - reference value) also rises and becomes greater than or equal to the on threshold Th1, causing the contact determination unit 122 to determine that hand H has made contact with grip 11. The on threshold Th1 is an example of a first contact threshold. When hand H moves away from grip 11 at time t2, the amplitude AD value falls. At this time, the difference (AD value - reference value) also falls and becomes less than or equal to the off threshold Th2, which is lower than the on threshold Th1, causing the contact determination unit 122 to determine that hand H has moved away from grip 11. The off threshold Th2 is an example of a second contact threshold.

[0029] Figure 4 shows the AFE120A. Figure 4 also shows the electrostatic sensor 110 and the MPU120B. In Figure 4, the commands input from the MPU120B to the AFE120A are omitted. Figure 5 shows the reference signal generation unit 40 included in the AFE120A.

[0030] The AFE120A includes a capacitance detection circuit 102, a demodulation circuit 22, a sine wave generation unit 30, a drive signal generation unit 35, and a reference signal generation unit 40. In the following description, it is assumed that there is a capacitor Cx between the hand H and the electrode of the electrostatic sensor 110. The reference signal generation unit 40 is an example of both a first reference signal generation unit and a second reference signal generation unit.

[0031] [Capacitance detection circuit 102] The capacitance detection circuit 102 generates a detection signal S corresponding to the capacitance of capacitor Cx based on the charge transmitted to capacitor Cx via the electrostatic sensor 110. The capacitance detection circuit 102 applies a drive signal Vd to capacitor Cx via the electrostatic sensor 110 and generates a detection signal S corresponding to the charge transmitted to capacitor Cx in response to the application of the drive signal Vd. The detection signal S has an amplitude corresponding to the capacitance of capacitor Cx.

[0032] The capacitance detection circuit 102 includes an operational amplifier 102A and a capacitor Cf1, as shown in Figure 4, for example. Capacitor Cf1 is connected between the inverting input terminal and the output terminal of the operational amplifier 102A. A sinusoidal drive voltage Vd is supplied to the 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 drive voltage Vd is, for example, a sinusoidal AC voltage. 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 equal, so that an AC voltage approximately the same as the drive voltage Vd is generated in capacitor Cx. When an AC voltage is generated in capacitor Cx, a change in charge proportional to this AC voltage and the capacitance of capacitor Cx occurs. The change in charge in capacitor Cx is approximately equal to the change in charge in capacitor Cf1. As a result, the AC voltage generated in capacitor Cf1 has an amplitude roughly proportional to the capacitance of capacitor Cx. The detection signal S is the voltage generated between the output terminal and the non-inverting input terminal of the operational amplifier 102A, and is approximately equal to the AC voltage generated across capacitor Cf1. Therefore, the detection signal S has an amplitude that is roughly proportional to the capacitance of capacitor Cx.

[0033] [Sine wave generation unit 30] The sine wave generator 30 generates a sine wave signal W, which is the basis for the drive signal Vd, in accordance with the control of the main control unit 121 of the MPU 120B. The sine wave generator 30 is a digital circuit that operates in synchronization with, for example, the clock of the MPU 120B, and the sine wave signal W is a digital signal set to the drive frequency fd.

[0034] [Drive signal generation unit 35] The drive signal generation unit 35 generates a sinusoidal drive signal Vd, which is an analog signal, based on the sinusoidal signal W generated in the sinusoidal wave generation unit 30. In one example, the drive signal Vd is a sinusoidal AC voltage, but in other examples, the drive signal Vd may be a non-sinusoidal (e.g., square wave) AC voltage. By making the drive signal Vd a sinusoidal AC voltage, harmonic noise emitted from the electrostatic sensor 110 can be reduced.

[0035] [Reference signal generation unit 40] 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. As shown in Figure 5, 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 the sinusoidal signal W as input and outputs the first reference signal FA. The detection signal S has a phase shift of φ1 relative to the drive signal Vd. The phase adjustment unit 44 adjusts the phase of the first reference signal FA so that the phase of the detection signal S and the first reference signal FA match. The first reference signal FA is output as one output of the reference signal generation unit 40 and is also input to the phase adjustment unit 45. The phase adjustment unit 45 outputs a signal with a phase shift of 1 / 4 period relative to the first reference signal FA as the second reference signal FB.

[0036] The first reference signal FA is a sinusoidal reference signal having the same frequency as the sinusoidal detection signal S and the same phase as the sinusoidal detection signal S. The reference signal generation unit 40 generates the first reference signal FA having the same frequency as the drive frequency fd of the drive signal Vd input from the drive signal generation unit 35 and having a predetermined phase φ1 with respect to the drive signal Vd.

[0037] Furthermore, the reference signal generation unit 40 generates a second reference signal FB which is a sinusoidal wave and has the same frequency as the sinusoidal detection signal S, but whose phase is shifted by one-quarter of a period relative to the sinusoidal detection signal S. The reference signal generation unit 40 generates a second reference signal FB which has the same frequency as the drive frequency fd, but whose phase relative to the drive signal Vd is shifted by one-quarter of a period compared to the first reference signal FA. Since the phase of the first reference signal FA is almost the same as that of the detection signal S, the second reference signal is a signal whose phase is shifted by one-quarter of a period relative to the detection signal S.

[0038] [Demodulation circuit 22] The demodulation circuit 22 includes an A / D converter 211 that converts an analog detection signal S into a digital signal, a multiplier circuit 212, a low-pass filter 213, a multiplier circuit 222 that multiplies the output signal of the A / D converter 211 (the digitized signal of the detection signal S) with a second reference signal FB, and a low-pass filter 223 that extracts the DC component from the multiplication result of the multiplier circuit 222. The low-pass filter 213 is an example of a first low-pass filter. The low-pass filter 223 is an example of a second low-pass filter.

[0039] 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 also 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 MPU 120B.

[0040] The A / D converter 211 includes a differential amplifier that, for example, amplifies the difference between the output signal of the 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 (a signal corresponding to the AC voltage of capacitor Cf1) into a digital signal. The multiplier circuit 212 multiplies the detection signal S, which has been converted into a digital signal in the A / D converter 211, with the first reference signal FA.

[0041] The multiplier circuit 222 multiplies the detection signal S, which has been converted into a digital signal by the A / D converter 211, with the second reference signal FB. The low-pass filter 213 removes the high-frequency components contained in the first demodulated signal, which is the result of the multiplication by the multiplier circuit 212, and extracts the DC component. The DC component extracted by the low-pass filter 213 is output to the MPU 120B as the first DC signal CA. The low-pass filter 223 removes the high-frequency components contained in the second demodulated signal, which is the result of the multiplication by the multiplier circuit 222, and extracts the DC component. The DC component extracted by the low-pass filter 223 is output to the MPU 120B as the second DC signal CB.

[0042] The first DC signal CA is a signal corresponding to the DC component contained in the signal obtained by multiplying the detection signal S and the first reference signal FA. The angular frequencies ω of the detection signal S and the first reference signal FA are "2πfd". When the detection signal S is "As·sin(ωt-φ1)" and the first reference signal FA is "Af·sin(ωt-φ1)", the signal Y1 obtained by multiplying the detection signal S and the first reference signal FA is expressed by the following equation (1).

[0043] Y1 = As·sin(ωt-φ1)×Af·sin(ωt-φ1) = - K·cos(2ωt-2φ1)+K … (1) However, K = As·Af / 2

[0044] The first DC signal CA is a signal corresponding to the DC component of signal Y1 shown in equation (1), and has a magnitude proportional to "K". Af is a predetermined constant value of magnitude. The magnitude of As is proportional to the capacitance of capacitor Cx. Therefore, the first DC signal CA generated by the demodulation circuit 22 is a signal whose magnitude is proportional to the capacitance of capacitor Cx. Note that the phase of the detection signal S changes as the capacitance of capacitor Cx changes, so the phase of the detection signal S and the phase of the first reference signal FA do not necessarily perfectly coincide. However, the difference between the phase of the detection signal S and the phase of the first reference signal FA is negligibly small.

[0045] On the other hand, if the second reference signal FB, which is phase-shifted by one-quarter period (π / 2 radians) with respect to the detected signal S, is defined as "Af·sin(ωt-φ1-π / 2)", then the signal Y2 obtained by multiplying the detected signal S and the second reference signal FB is expressed by the following equation (2).

[0046] Y2 = As·sin(ωt-φ1)×Af·sin(ωt-φ1-π / 2) = - K·cos(2ωt-2φ1−π / 2)+K·cos(π / 2) … (2)

[0047] The second DC signal CB is a signal corresponding to the DC component of signal Y2 shown in equation (2). "cos(π / 2)" is zero. Therefore, if there is no noise component superimposed on the detection signal S, the DC component of signal Y2 becomes zero, and thus the second DC signal CB also becomes zero (or a reference value equivalent to zero). Conversely, the second DC signal CB has the same frequency as the drive frequency fd and has a magnitude corresponding to a noise component with a different phase than the detection signal S. Therefore, the second DC signal CB generated by the demodulation circuit 22 is a signal with a magnitude corresponding to a noise component with the same frequency as the drive frequency fd superimposed on the detection signal S. Note that because the phase of the detection signal S changes as the capacitance of capacitor Cx changes, the difference between the phase of the detection signal S and the phase of the second reference signal FA is not necessarily exactly π / 2. However, the difference between the phase of the detection signal S and the phase of the first reference signal FA is negligibly small. Therefore, the difference between the phase of the detection signal S and the phase of the second reference signal FA can be considered to be π / 2.

[0048] <Problems with the comparative contact detection device> Figures 6A and 6B illustrate the problems in the comparative contact detection device. The comparative contact detection device has a configuration similar to the AFE120A shown in Figure 4, but without the multiplication circuit 222 and the low-pass filter 223. It outputs only the first DC signal CA and does not output the second DC signal CB. The MPU of the comparative contact detection device determines whether a hand H is placed on the grip 11 (hands-on) based on the first DC signal CA.

[0049] In Figures 6A and 6B, the horizontal axis represents time, and the vertical axis shows the first DC signal CA output by the comparison AFE, the capacitance of the reference value Base, and the judgment value as count values. The judgment value is the reference value Base plus a threshold value for contact detection (on threshold Th1 or off threshold Th2). The values ​​of the on threshold Th1 and the off threshold Th2 are different as shown in Figure 3, but for the sake of simplicity, the judgment value is shown as a single value here.

[0050] If the connection between connector 105 and connector 15 is faulty, the signal level of the first DC signal CA may fluctuate. A faulty connection between connector 105 and connector 15 occurs when the mating of connector 105 and connector 15 (see Figure 1) is insufficient, or when there is damage such as a break in the wiring connected to connector 105 or connector 15. An insufficient mating of connector 105 and connector 15 occurs, for example, when connector 105 is loose relative to connector 15, or when connector 105 is not properly fitted into connector 15.

[0051] As a prerequisite, the contact detection device 100 is configured to determine whether a hand H is resting on the steering wheel 10 in accordance with the request of the HOD_ECU 120 when the vehicle's ignition is switched from off to on. However, if the vehicle's ignition is switched from off to on while a hand H is resting on the steering wheel 10, the reference value Base, which is calculated when a hand H is not resting on the steering wheel 10, cannot be calculated correctly. Therefore, it is necessary to remove the hand H from the steering wheel 10, wait for the correct reference value Base to be calculated, and then place the hand H on the steering wheel 10 again.

[0052] First, using Figure 6A, we will explain the operation when the connection between connector 105 and connector 15 is normal. In Figure 6A, at approximately 22 seconds, with hand H resting on grip 11, the vehicle's ignition switches from off to on, and hand H is removed from grip 11. When the first DC signal CA decreases after approximately 22 seconds, the MPU of the contact detection device for comparison decreases the reference value Base and resets. The reference value Base for the state when hand H is not resting on grip 11 is calculated, and the reference value Base is reset to the calculated value.

[0053] As the reference value Base decreases, the judgment value also decreases. At approximately 23 seconds, when hand H is placed on grip 11 again, the first DC signal CA increases. When it exceeds the judgment value, the MPU of the comparison contact detection device determines that hand H is on grip 11 (hands-on). Subsequently, at approximately 24 seconds, when hand H is removed from grip 11 again, the first DC signal CA decreases. When it falls below the judgment value, the MPU of the comparison contact detection device determines that hand H has left grip 11. As mentioned above, the judgment value is the reference value Base plus a threshold for contact detection (on threshold Th1 or off threshold Th2).

[0054] Next, using Figure 6B, we will explain the operation when the connection between connector 105 and connector 15 is faulty. Figure 6B shows the behavior when hand H is not resting on grip 11. When the connection is faulty, the electrical connection between connector 105 and connector 15 may or may not be maintained. This will be explained in detail below.

[0055] In Figure 6B, when the first DC signal CA decreases after approximately 13 seconds, the MPU of the contact detection device used for comparison resets the reference value Base to a lower value. The reference value Base is calculated for the state where hand H is not resting on grip 11, and the reference value Base is reset to the calculated value. The detection value also decreases in accordance with the decrease in the reference value Base.

[0056] Subsequently, even though hand H is not resting on grip 11, if the first DC signal CA fluctuates like noise between approximately 24 seconds and 30 seconds, 53 seconds and 56 seconds, 58 seconds and 62 seconds, 68 seconds and 73 seconds, 85 seconds and 86 seconds, 87 seconds and 91 seconds, and 96 seconds and 100 seconds, the system incorrectly determines that hand H is resting on grip 11 (i.e., hands-on). In other words, a hands-on misjudgment occurs.

[0057] Such misjudgments in hands-on testing occur because the electrical connection between connector 105 and connector 15 is not maintained, causing fluctuations in the ground potential and thus fluctuations in the first DC signal CA. Furthermore, the poor connection between connector 105 and connector 15 causes heavy components that are held at ground potential, such as the column shaft, to vibrate, increasing the fluctuations in the first DC signal CA and making misjudgments in hands-on testing more likely.

[0058] As described above, the poor connection between connector 105 and connector 15 causes the first DC signal CA to fluctuate like noise, leading to a false detection that a hand H is placed on the grip 11 (hands-on).

[0059] <Characteristics of the first DC signal CA and the second DC signal CB> Figures 7A and 7B show the characteristics of the first DC signal CA and the second DC signal CB. In Figures 7A and 7B, the horizontal axis represents time, the left vertical axis represents the first DC signal CA (count value), and the right vertical axis represents the second DC signal CB (count value). The right and left vertical axes have different scales because the maximum and minimum values ​​of the first DC signal CA and the second DC signal CB have different ranges. However, Figures 7A and 7B show the movement of the first DC signal CA and the second DC signal CB within their possible ranges.

[0060] Figure 7A shows the characteristics of the first DC signal CA and the second DC signal CB when the connection between connector 105 and connector 15 is normal. When the connection is normal, and the hand H is resting on the 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. When the hand H is removed from the grip 11 after 22 seconds, the first DC signal CA decreases toward approximately its minimum value, while the second DC signal CB increases toward approximately its maximum value, changing in the opposite direction to the first DC signal CA. Thus, when the connection is normal, the first DC signal CA and the second DC signal CB change in opposite directions (the direction of change is reversed).

[0061] Figure 7B illustrates the operation when the connection between connector 105 and connector 15 is faulty. Figure 7B shows the experimental result of making the connection between the ground terminal of connector 105 and the ground terminal of connector 15 unstable. In Figure 7B, the ground terminals of connector 105 and connector 15 alternate between being connected and not connected from 0 to 110 seconds.

[0062] At 10 seconds, both the first DC signal CA and the second DC signal CB are at approximately their maximum values. Subsequently, at approximately 12 seconds, as the first DC signal CA decreases toward approximately its minimum value, the second DC signal CB also changes simultaneously and decreases toward approximately its minimum value. Furthermore, at approximately 24 seconds, as the first DC signal CA increases toward approximately its maximum value, the second DC signal CB also changes simultaneously and increases toward approximately its maximum value. Similarly thereafter, the first DC signal CA and the second DC signal CB change at the same timing and in the same direction (the direction of change is the same).

[0063] 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 time.

[0064] The contact detection device 100 of this embodiment utilizes the characteristics of the direction of change of the first DC signal CA and the second DC signal CB to determine whether the connection state of the ground terminal of connector 105 and the ground terminal of connector 15 is normal or abnormal. If the connection state of connector 105 and connector 15 is abnormal, all terminals will be in an abnormal state, so the connection state of the entire connector can be determined by the connection state of the ground terminal. Furthermore, if only the signal line 12 is broken, the contact state will remain in a "Hands Off" state regardless of the actual contact state between hand H and grip 11, so the break can be determined. In addition, the magnitude of noise components can also be measured using the first DC signal CA and the second DC signal CB. In other words, it is possible to measure the magnitude of noise components and determine whether the connection state of connector 105 and connector 15 is normal or abnormal using the same circuit. For this reason, an increase in circuit size can be suppressed. The determination method will be described below.

[0065] <Judgment method> Figure 8 shows the determination process performed by the MPU 120B of the contact detection device 100.

[0066] The contact detection unit 122 calls the subroutine "subinitial settings" to perform initial settings (step S1). Initial settings perform subroutine processing to initialize various values ​​to be used in subsequent processing. Details will be described later with reference to Figure 9.

[0067] The contact determination unit 122 acquires the first DC signal CA and the second DC signal CB (step S2). This process acquires the latest first DC signal CA and second DC signal CB in order to determine the connection status.

[0068] The contact determination unit 122 calls the subroutine "subconnection status determination" and performs a process to determine the connection status between connector 105 and connector 15 (step S3). Details will be described later with reference to Figure 10.

[0069] The contact detection unit 122 calls the subroutine "sub-contact detection" to perform contact detection (step S4). Details will be described later with reference to Figure 11.

[0070] When MPU120B finishes the process of step S4, it returns the flow to step S2 and repeatedly executes the processes from step S2 to S4 at a cycle of 10 ms as an example.

[0071] Next, with reference to FIG. 9, the initial setting process performed based on the subroutine "sub Initial setting" of step S1 in FIG. 8 will be described. FIG. 9 is a flowchart showing an example of the process of sub Initial setting.

[0072] When 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 a process of acquiring the latest first DC signal CA and second DC signal CB for the initial setting process.

[0073] The contact determination unit 122 sets the reference value 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) may be any value that can be the reference value Base under normal conditions. For example, a value measured at room temperature (20°C) during design may be used. The contact determination unit 122 sets the values of the first DC signal CA and the second DC signal CB one cycle before (CA_old, CB_old) to the first DC signal CA and the second DC signal CB at the initial setting (CA_old = CA, CB_old = CB). Also, 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 representing the change directions of the first DC signal CA and the second DC signal CB. "Plus" indicates that the change direction is an increase (+). Also, the variables Decision_A and Decision_B may take the value "Minus". "Minus" indicates that the change direction is a decrease (-). Since the variables Decision_A and Decision_B take two types of values, "Plus" and "Minus", a Boolean (logical) type variable may be used.

[0074] The contact determination unit 122 resets the timer 123A to zero (Timer = 0) and sets the contact state to hands-off (contact state = HandOff) (step S13). The contact state indicates whether the hand H is in contact with the grip 11 of the steering wheel 10. The contact state takes the values of hands-off or hands-on. Since the contact state as a variable takes two types of values, "HandOff" and "HandOn", a Boolean (logical) type variable may be used.

[0075] With the above, the contact determination unit 122 finishes the initial setting process.

[0076] Next, using Figure 10, we will explain the connection status determination process performed based on the subroutine "sub-connection status determination" in step S3 of Figure 8.

[0077] Figure 10 is a flowchart showing an example of the sub-connection state determination process. When the contact determination unit 122 starts the sub-connection state determination process, it uses the first DC signal CA and the second DC signal CB acquired in step S2 to calculate the changes ΔCA and ΔCB of the first DC signal CA and the second DC signal CB (step S31). The change ΔCA of the first DC signal CA is CA - CA_old, which is the change from the value one cycle ago. The change ΔCB of the second DC signal CB is CB - CB_old, which is the change from the value one cycle ago. CA_old immediately after startup is the CA at the time of initial setup (see step S12). CB_old immediately after startup is the CB at the time of initial setup (see step S12). ΔCA and ΔCB immediately after startup are the changes from the time of initial setup. CA_old other than immediately after startup is the CA from one cycle ago (see step S38). CB_old other than immediately after startup is the CB from one cycle ago (see step S38). ΔCA and ΔCB, except immediately after startup, represent the changes from the previous cycle.

[0078] The contact determination unit 122 determines whether the change in the first DC signal CA ΔCA is greater than the threshold TH_CA_P (step S32). The threshold TH_CA_P is a threshold used to determine whether the change in ΔCA is increasing. The threshold TH_CA_P is an example of a first threshold when the change in ΔCA is increasing.

[0079] If the contact determination unit 122 determines that the change in the first DC signal CA, ΔCA, is greater than the threshold TH_CA_P (S32: Yes), it sets (updates) the variable Decision_A to Plus (Decision_A="Plus") (step S33A). After completing the processing in step S33A, the contact determination unit 122 proceeds to step S34.

[0080] In step S32, if the contact determination unit 122 determines that the change in the first DC signal CA ΔCA is not greater than the threshold TH_CA_P (S32: No), it determines whether the change in the first DC signal CA ΔCA is less 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 decreasing. The threshold TH_CA_M is an example of a first threshold when the change in ΔCA is decreasing.

[0081] If the contact determination unit 122 determines that the change in the first DC signal CA ΔCA is smaller than the threshold TH_CA_M (S33B: Yes), it sets (updates) the variable Decision_A to Minus (Decision_A="Minus") (step S33C). After completing the processing in step S33C, the contact determination unit 122 proceeds to step S34.

[0082] Furthermore, if the contact determination unit 122 determines in step S33B that the change in the first DC signal CA ΔCA is not smaller than the threshold TH_CA_M (S33B: No), the flow proceeds to step S34. In this case, the variable Decision_A is not updated, so the value before the update is used.

[0083] 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 increasing. The threshold TH_CB_P is an example of a second threshold when the change in ΔCB is increasing.

[0084] If the contact determination unit 122 determines that the change in the second DC signal CB ΔCB is greater than the threshold TH_CB_P (S34: Yes), it sets (updates) the variable Decision_B to Plus (Decision_B="Plus") (step S35A). After completing the processing in step S35A, the contact determination unit 122 proceeds to step S36.

[0085] In step S34, if the contact determination unit 122 determines that the change in the second DC signal CB ΔCB is not greater than the threshold TH_CB_P (S34: No), it determines whether the change in the second DC signal CB ΔCB is less 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 decreasing. The threshold TH_CB_M is an example of a second threshold when the change in ΔCB is decreasing.

[0086] If the contact determination unit 122 determines that the change in the second DC signal CB ΔCB is smaller than the threshold TH_CB_M (S35B: Yes), it sets (updates) the variable Decision_B to Minus (Decision_B="Minus") (step S35C). After completing the process in step S35C, the contact determination unit 122 proceeds to step S36.

[0087] Furthermore, if the contact determination unit 122 determines in step S35B that the change in the second DC signal CB ΔCB is not smaller than the threshold TH_CB_M (S35B: No), the flow proceeds to step S36. In this case, the variable Decision_B is not updated, so the value before the update is used.

[0088] The contact determination unit 122 determines whether the changes in 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".

[0089] 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 state to True (step S37A). A connection state of True means that the connection state between connector 105 and connector 15 is normal. After completing the processing in step S37A, the contact determination unit 122 proceeds to step S38.

[0090] In step S36, the contact detection unit 122 determines that the connection is poor if it determines that the changes in the first DC signal CA and the second DC signal CB are not in opposite directions (S36: No), and sets the connection state to False (step S37B). If the contact detection unit 122 determines that the connection is poor, it outputs a connection failure signal indicating that the connection is poor. The connection failure signal is output from the MPU 120B to the ECU 50. As a result, the ECU 50 recognizes that the connection is poor.

[0091] The contact detection unit 122 sets the contact state to hands-off (contact state = HandOff) (step S37C). After completing the process in step S37C, the contact detection unit 122 proceeds to step S38. The contact detection unit 122 also notifies the ECU 50 that the contact state is hands-off. As a result, the ECU 50 recognizes that the contact state is hands-off. The reason for notifying the ECU 50 that the contact state is hands-off is that even if the capacitance has not changed since startup, the process will follow step 37C, and therefore, following step S37C does not necessarily mean that the connection is faulty. Furthermore, if the hands-off state continues even when the hand H touches the grip 11, a faulty connection can be easily detected during a test run before shipment. Also, even if a faulty connection occurs after shipment, it can be easily identified as a malfunction through the display of a hands-off warning, etc. In other words, the fail-safe function is activated by step S37C.

[0092] The contact determination unit 122 sets the values ​​of the first DC signal CA and the second DC signal CB from one cycle prior (CA_old, CB_old) to the latest (current cycle) first DC signal CA and second DC signal CB (CA_old=CA, CB_old=CB) (step S38). CA_old and CB_old are used as the values ​​from one cycle prior when the subroutine "sub-contact state determination" is executed again.

[0093] This completes the connection status determination process.

[0094] Next, using FIG. 11, the contact determination process performed based on the subroutine "Sub contact determination" in step S4 of FIG. 8 will be described. FIG. 11 is a flowchart showing an example of the process of sub contact determination.

[0095] 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 ago.

[0096] When the previous state is not contact (HandsOn) (S41: No), the contact determination unit 122 determines whether the difference (CA - Base) obtained by subtracting the reference value Base from the first DC signal CA is equal to or greater than the on - threshold Th1 (step S42). The on - threshold Th1 is used to determine whether there is contact. The reference value Base indicates the capacitance of the electrostatic sensor 110 when the hand H is not in contact with the grip 11. The difference (CA - Base) indicates the capacitance between the electrostatic sensor 110 and the hand H.

[0097] When the contact determination unit 122 determines that the difference ΔAD is equal to or greater than the on - threshold Th1 (S42: Yes), it determines whether the connection state is normal (True) (step S43).

[0098] When the contact determination unit 122 determines that the connection state is normal (True) (S43: Yes), it increments the count time TimerS of the timer 122A (step S44A). That is, TimerS = TimerS + 1.

[0099] The contact detection unit 122 determines whether the count time TimerS of the timer 122A is greater than or equal to the time threshold THT (step S44C). The time threshold THT may be a predetermined value. This is because, rather than determining that the hand H is in contact with the grip 11 of the steering wheel 10 immediately when the difference (CA-Base) exceeds the on threshold Th1, contact is determined only when the difference (CA-Base) exceeds the on threshold Th1 for a certain period of time (time threshold THT). For this reason, if the contact detection unit 122 determines that the count time TimerS is not greater than or equal to the time threshold THT (S44C: No), it terminates the flow (end). When the subroutine for sub-contact detection is completed, the program returns to step S2.

[0100] When the contact detection unit 122 determines that the count time TimerS is greater than or equal to the time threshold THT (S44C: Yes), it sets the contact state to contact (HandsOn) (step S44D). After completing the processing in step S44D, the contact detection unit 122 terminates the flow (end). When the subroutine for sub-contact detection finishes, it returns to step S2.

[0101] Furthermore, if the contact detection unit 122 determines in step S43 that the connection state is not normal (S43: No), it resets the count time TimerS of the timer 122A to zero (step S44B). After completing the processing in step S44B, the contact detection unit 122 terminates the flow (end). When the sub-contact detection subroutine finishes, it returns to step S2.

[0102] Furthermore, if the contact determination unit 122 determines in step S42 that the difference (CA-Base) is not equal to or greater than the on threshold Th1 (S42: No), it calls the subroutine "subBase calculation" and performs the process of calculating the reference value Base (step S45). Details will be described later with reference to Figure 12.

[0103] The contact determination unit 122 resets the count 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 flow (end). When the subroutine of sub contact determination ends, it returns to step S2.

[0104] Also, in step S41, when the previous determination was contact (HandsOn) (S41: Yes), the contact determination unit 122 determines whether the difference (CA - Base) obtained by subtracting the reference value Base from the first DC signal CA is less than or equal to the off threshold Th2 (step S47).

[0105] When the contact determination unit 122 determines in step S47 that the difference (CA - Base) is less than or equal to the off threshold Th2 (S47: Yes), it determines that the contact state is non - contact (HandsOff) (step S48). That is, the contact state = HandsOff.

[0106] The contact determination unit 122 resets the count 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 flow (end). When the subroutine of sub contact determination ends, it returns to step S2.

[0107] Note that when the contact determination unit 122 determines in step S47 that the difference (CA - Base) is not less than or equal to the off threshold Th2 (S47: No), it advances the flow to step S49.

[0108] <subBase calculation> Next, using FIG. 12, the calculation process of the reference value Base performed based on the subroutine "subBase calculation" of step S45 in FIG. 11 will be described. FIG. 12 is a flowchart showing an example of the process of subBase calculation.

[0109] The contact determination unit 122 determines whether the connection status is normal (True) (step S51).

[0110] If the contact determination unit 122 determines that the connection status is normal (True) (S51:Yes), it sets (updates) the difference to (CA-Base) (step S52). In other words, the difference with the reference value Base is updated using the latest first DC signal CA.

[0111] The contact determination unit 122 determines whether the difference is smaller than the drop threshold DropTH (step S53). The drop threshold DropTH is a threshold used to determine whether the first DC signal CA is dropping sharply, for example, after 22 seconds in Figure 7A.

[0112] If the contact detection unit 122 determines that the difference is smaller than the drop threshold DropTH (S53: Yes), it increments the count value Timer of the timer 123A (step S54A). That is, Timer = Timer + 1. After completing the processing in step S54A, the contact detection unit 122 proceeds to step S55.

[0113] On the other hand, if the contact detection unit 122 determines in step S53 that the difference is not smaller than the drop threshold DropTH (S53: No), it resets the timer 123A (step S54B). That is, Timer = 0. After completing the processing in step S54B, the contact detection unit 122 proceeds to step S55.

[0114] The contact detection unit 122 determines whether the count value (Timer) of the timer 123A has exceeded the drop time (Step S55).

[0115] When the contact detection unit 122 determines that the count value (Timer) of the timer 123A has exceeded the drop time (S55: Yes), it sets the reference value Base to the first DC signal CA (step S56A). After completing the process in step S56B, the contact detection unit 122 finishes the subBase calculation process.

[0116] If the contact determination unit 122 determines that the count value (Timer) of the timer 123A does not exceed the drop time (S55: No), it calculates the reference value Base based on the following formula (3) (step S56B).

[0117]

number

[0118] The contact detection unit 122 calculates the reference value Base as the weighted average of the reference value (10ms ago) and the first DC signal CA by multiplying the reference value Base (10ms ago) by a weight M based on equation (3). After completing the processing in step S56B, the contact detection unit 122 completes the subBase calculation process.

[0119] Furthermore, if the contact determination unit 122 determines in step S51 that the connection state is not normal (S51: No), it terminates the subBase calculation process without calculating the reference value Base. In other words, the contact determination unit 122 terminates the subBase calculation process without resetting the reference value Base.

[0120] When the subroutine for subBase calculation is completed, the contact determination unit 122 proceeds to step S46 in Figure 11.

[0121] <Effects> Figures 13A and 13B illustrate an example of the effect of the contact detection device 100. Figures 13A and 13B show the operation when the connection status of connector 105 and connector 15 is normal.

[0122] In Figure 13A, the horizontal axis represents time, and the vertical axis shows the first DC signal CA, the capacitance of the reference value Base, and the judgment value as count values. The judgment value is the reference value Base plus a threshold value for contact detection (on threshold Th1 or off threshold Th2). The values ​​of the on threshold Th1 and the off threshold Th2 are different as shown in Figure 3, but here, for the sake of simplicity, the judgment value is shown as a single value. In Figure 13B, the horizontal axis represents time, the left vertical axis shows the first DC signal CA as count values, and the right vertical axis shows the second DC signal CB as count values.

[0123] In Figure 13A, at approximately 22 seconds, with hand H resting on grip 11, the vehicle's ignition switches from off to on, and hand H is removed from grip 11. When the first DC signal CA decreases after approximately 22 seconds, the MPU 120B of the contact detection device 100 decreases the reference value Base and resets. The reference value Base for the state where hand H is not resting on grip 11 is calculated, and the reference value Base is reset to the calculated value. This operation is the same as that of the comparative contact detection device shown in Figure 6A.

[0124] Furthermore, as shown in Figure 13B, 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.

[0125] Figures 14A and 14B illustrate an example of the effect of the contact detection device 100. Figures 14A and 14B show the operation when the connection between connector 105 and connector 15 is faulty.

[0126] In Figure 14A, even if the first DC signal CA drops sharply, as in the case shown in Figure 6B, the connection state is set to False because the connection state between connector 105 and connector 15 is poor. Therefore, in step S51 of Figure 12, it is determined to be No, and the reference value Base is not reset but remains at a high value. Since the reference value Base maintains a high value, the judgment value also becomes high, so even if the first DC signal CA changes, it will not fall below the judgment value, and no misjudgment occurs during hands-on testing.

[0127] Furthermore, as shown in Figure 14B, 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.

[0128] As described above, the contact detection device 100 includes an electrostatic sensor 110 that outputs a sinusoidal detection signal S having an amplitude corresponding to the capacitance between the detection electrode provided on the grip 11 of the steering wheel 10 that the hand H can contact and the hand H. The contact detection device 100 also includes a first reference signal generation unit (multiplier circuit 212 of the demodulation circuit 22, sinusoidal wave generation unit 30, and reference signal generation unit 40) that generates a sinusoidal first reference signal FA having the same frequency and phase as the detection signal S, and a second reference signal generation unit (multiplier circuit 222 of the demodulation circuit 22, sinusoidal wave generation unit 30, and reference signal generation unit 40) that generates a sinusoidal second reference signal FB having the same frequency as the detection signal S but with a phase shift relative to the detection signal S. Furthermore, the contact determination device 100 includes a demodulation circuit 22 that generates a first demodulated signal by multiplying the detection signal S output from the electrostatic sensor 110 by a first reference signal, and generates a second demodulated signal by multiplying the detection signal S output from the electrostatic sensor 110 by a second reference signal, a low-pass filter 213 that extracts a first DC signal CA, which is the DC component of the first demodulated signal, and a low-pass filter 223 that extracts a second DC signal CB, which is the DC component of the second demodulated signal. The contact determination device 100 also includes a contact determination unit 122 that determines whether a hand H is in contact with the grip 11 of the steering wheel 10 based on the first DC signal CA. The contact determination unit 122 determines that the connection between the sensor unit and the detection circuit is poor if the latest direction of change in the amount of change of the first DC signal CA exceeding the first threshold (TH_CA_P, TH_CA_M) is the same as the latest direction of change in the amount of change of the second DC signal CB exceeding the second threshold (TH_CB_P, TH_CB_M). The connection between the sensor unit and the detection circuit is normal if the latest direction of change in the amount of change of the first DC signal CA exceeding the first threshold (TH_CA_P, TH_CA_M) is the same as the latest direction of change in the amount of change of the second DC signal CB exceeding the second threshold (TH_CB_P, TH_CB_M).

[0129] In other words, the contact determination unit 122 determines that the connection is poor if the direction of change of the first DC signal CA and the second DC signal CB is the same, and determines that the connection is normal if the directions are opposite.

[0130] Therefore, a contact determination device 100 capable of detecting contact problems such as wire breaks can be provided without requiring a dedicated physical configuration for wire break detection.

[0131] Furthermore, if the contact detection unit 122 determines in step S37B that the connection is poor, it outputs a connection failure signal indicating that the connection is poor. This allows the ECU 50 to be notified that the connection between connector 105 and connector 15 is poor. When installing the contact detection device 100 in the vehicle, the connection failure between connector 105 and connector 15 can be checked on the inspection monitor connected to the ECU 50 without having to touch the grip 11 with the hand H. Also, if the connection is poor, the contact status is notified to the ECU 50 as "Hands Off". If there is a connection failure, even if the driver grips the grip 11 with their hand H, "Hands Off" will be displayed, so the driver can recognize the connection failure even without an inspection monitor.

[0132] Furthermore, in step S56A, the contact determination unit 122 updates the first DC signal CA, which is the value of the reference value Base when the hand H is not in contact with the grip 11 of the steering wheel 10. Also, if the contact determination unit 122 determines in step S37B that the connection state is poor, it does not update the reference value Base (see step S51: No). Therefore, the connection state can be determined using a determination value based on the reference value Base, which has a large value in the normal state before the update, and erroneous determinations can be effectively suppressed. In addition, by setting the initial value of the reference value Base to a default value at startup, the connection state can be determined using a determination value based on the reference value Base, which has a large value in the normal state, and erroneous determinations can be effectively suppressed.

[0133] The contact determination unit 122 has a timer 122A that counts the duration of the state in which the difference between the first DC signal CA and the reference value Base is greater than or equal to a threshold Th1. When the duration counted by the timer 122A reaches a predetermined time THT or longer, it is determined that the hand H has made contact with the grip 11 of the steering wheel 10 (see step S44D). Furthermore, if the contact determination unit 122 determines that the connection state is poor, it resets the duration counted by the timer 122A (see step S44B). Therefore, if the state in which the difference between the first DC signal CA and the reference value Base is greater than or equal to a threshold Th1 continues for a predetermined time THT or longer, it is possible to reliably determine that the hand H has made contact with the grip 11 of the steering wheel 10. In addition, since the duration counted by the timer 122A is reset when the contact determination unit 122 determines that the connection state is poor, it is possible to suppress the determination that the hand H has made contact with the grip 11 of the steering wheel 10 when the connection state is poor.

[0134] Although an exemplary embodiment of the contact detection device described herein has been explained above, this disclosure is not limited to the specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims. [Explanation of symbols]

[0135] H Hand (Example of a detected object) 10 Steering Wheel 10A Column Shaft 11. Grip (An example of a contact area that the detection target can touch) 15 connectors 22 Demodulation Circuit 30 Sine wave generation section 35 Drive signal generation unit 40. Reference signal generation unit (Example of first reference signal generation unit, example of second reference signal generation unit) 100 Contact determination device 105 Connector 110 Electrostatic Sensor (Example of Sensor Unit) 120 HOD_ECU (Example of a detection circuit) 121 Main Control Unit 122 Contact determination section 122A Timer 123A Timer 124 memory 211 A / D Converter 212 Multiplication Circuits 213 Low-pass filter (an example of a first low-pass filter) 222 Multiplication Circuit 223 Low-pass filter (an example of a second low-pass filter)

Claims

1. A sensor unit that outputs a sinusoidal detection signal having an amplitude corresponding to the capacitance between a detection electrode provided at a contact area that the object to be detected can touch and the object to be detected, The system includes a detection circuit that determines whether the object to be detected is in contact with the contact area based on the detection signal, The detection circuit is A first reference signal generation unit generates a sinusoidal first reference signal having the same frequency and phase as the detection signal, A second reference signal generation unit generates a second reference signal which is a sinusoidal wave having the same frequency as the detection signal and being out of phase with respect to the detection signal. A demodulation circuit generates a first demodulated signal by multiplying the detection signal output from the sensor unit by the first reference signal, and generates a second demodulated signal by multiplying the detection signal output from the sensor unit by the second reference signal, A first low-pass filter extracts a first DC signal, which is the DC component of the first demodulated signal, A second low-pass filter extracts a second DC signal, which is the DC component of the second demodulated signal, A contact determination unit that determines whether the object to be detected is in contact with the contact area based on the first DC signal, Includes, The contact determination unit is If the latest direction of change in the amount of change of the first DC signal that exceeds the first threshold is the same as the latest direction of change in the amount of change of the second DC signal that exceeds the second threshold, then it is determined that the connection state between the sensor unit and the detection circuit is poor. A contact determination device that determines that the connection state between the sensor unit and the detection circuit is normal when the latest direction of change in the amount of change of the first DC signal that exceeds a first threshold is opposite to the latest direction of change in the amount of change of the second DC signal that exceeds a second threshold.

2. The contact determination device according to claim 1, wherein the contact determination unit determines that the connection state is poor, and deems the contact state to be non-contact.

3. The contact determination unit updates the first DC signal as a reference value when the object being detected is not in contact with the contact area. The contact determination device according to claim 1 or 2, wherein the contact determination unit does not update the reference value when it determines that the connection state is poor.

4. The contact determination unit has a timer that counts the duration of the state in which the difference between the first DC signal and the reference value is greater than or equal to the first contact threshold. When the duration counted by the timer exceeds a predetermined time, it is determined that the object being detected has come into contact with the contact area. The contact detection device according to claim 3, wherein if it is determined that the connection state is poor, the device resets the duration counted by the timer.

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