Grip detection device, failure determination method, and program

Abstract

A grip detection device according to one embodiment of the present invention is a grip detection device (1) for a steering wheel (2) that comprises a metal core (23), a shield electrode (22) that is provided outside the metal core (23) with an insulating body (In) therebetween, and a sensor electrode (21) that is provided outside the shield electrode (22) with an insulating body (In) therebetween. The grip detection device comprises a control unit (11) that acquires a capacitance value for the sensor electrode (21) when the shield electrode (22) and the metal core (23) have been short-circuited and determines whether a failure has occurred on the basis of the capacitance value.

Description

[Technical Field]

[0001] The present technology relates to a grip detection device, a failure determination method, and a program. [Background technology]

[0002] Conventionally, a steering wheel unit has been disclosed that can diagnose whether a capacitance sensor for detecting gripping of the steering wheel is malfunctioning (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-23011 A Summary of the Invention [Problem to be solved by the invention]

[0004] The steering wheel unit described in Patent Document 1 can diagnose a fault in the capacitance sensor only when the steering wheel is not gripped, and cannot diagnose a fault in the capacitance sensor when the steering wheel is gripped.

[0005] The present invention has been made in consideration of the above circumstances, and aims to provide a grip detection device etc. that can determine a malfunction whether the steering wheel is gripped or not gripped. [Means for solving the problem]

[0006] A grip detection device according to one embodiment of the present invention is a grip detection device (1) for a steering wheel (2) that includes a core (23), a shield electrode (22) that is provided outside the core (23) with an insulator (In) between them, and a sensor electrode (21) that is provided even further outside the shield electrode (22) with an insulator (In) between them, and includes a control unit (11) that acquires the capacitance value of the sensor electrode (21) when the shield electrode (22) and the core (23) are short-circuited, and determines whether or not there is a malfunction based on the capacitance value.

[0007] A grip detection device according to one embodiment of the present invention includes a first switch (13a) that is provided between the shield electrode (22) and the core wire (23) and that, when turned on, shorts the shield electrode (22) and the core wire (23). The control unit (11) determines whether or not a malfunction has occurred when the first switch (13a) is turned on.

[0008] In the grip detection device according to one embodiment of the present invention, the control unit (11) determines that a failure has occurred when the acquired capacitance value is less than a predetermined value.

[0009] The grip detection device according to one embodiment of the present invention includes an additional circuit (132) that is connected to the shield electrode (22), applies a voltage to the shield electrode (22), and measures the voltage value of the applied voltage. When the voltage value of the voltage applied by the additional circuit (132) is lower than a specified value, the control unit (11) determines that a fault state has occurred in which the shield electrode (22) and the core wire (23) are short-circuited.

[0010] A grip detection device according to one embodiment of the present invention includes a second switch (13b) that is provided between the shield electrode (22) and the additional circuit (132) and that, when turned on, allows electricity to flow between the shield electrode (22) and the additional circuit (132). When the second switch (13b) is turned on, the control unit (11) determines whether or not the shield electrode (22) and the core wire (23) are short-circuited.

[0011] In the grip detection device according to one embodiment of the present invention, the control unit (11) determines whether or not the steering wheel (2) is being gripped when the second switch (13b) is turned on.

[0012] A fault determination method according to one embodiment of the present invention is a fault determination method for a grip detection device (1) of a steering wheel (2) that includes a core (23), a shield electrode (22) that is provided outside the core (23) separated by an insulator (In), and a sensor electrode (21) that is provided further outside the shield electrode (22) separated by an insulator (In), in which the capacitance value of the sensor electrode (21) is obtained when the shield electrode (22) and the core (23) are short-circuited, and the presence or absence of a fault is determined based on the capacitance value.

[0013] A program according to one embodiment of the present invention is a program for determining whether or not there is a fault in a grip detection device (1) of a steering wheel (2) that includes a core (23), a shield electrode (22) that is provided outside the core (23) separated by an insulator (In), and a sensor electrode (21) that is provided even further outside the shield electrode (22) separated by an insulator (In), and the program acquires the capacitance value of the sensor electrode (21) when the shield electrode (22) and the core (23) are short-circuited, and determines whether or not there is a fault based on the capacitance value. [Effects of the Invention]

[0014] The grip detection device according to one embodiment of the present invention can determine whether a malfunction has occurred whether the steering wheel is being gripped or not. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a block diagram showing an example of the configuration of a steering wheel device according to an embodiment of the present invention; [Figure 2] 1 is a front view of a steering wheel of a steering wheel device according to an embodiment of the present invention. FIG. [Figure 3] 3 is a cross-sectional view of the rim portion of the steering wheel taken along line III-III in FIG. 2. [Figure 4] FIG. 10 is an explanatory diagram showing a specific example of connections of a capacitance measuring circuit and the like. [Figure 5] 10 is a table illustrating capacitance values ​​acquired by the capacitance sensor in each failure mode when the first switch is turned on. [Figure 6] 10 is a flowchart illustrating an example of a processing procedure of a control unit. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] Fig. 1 is a block diagram showing an example of the configuration of a steering wheel device 100 according to this embodiment. The steering wheel device 100 includes a grip detection ECU (Electronic Control Unit) 1 and a steering wheel 2. The grip detection ECU 1 corresponds to the grip detection device. The grip detection ECU 1 is communicatively connected to in-vehicle devices such as a driving assistance ECU 6 via an in-vehicle network provided in the vehicle.

[0018] 2 is a front view of the steering wheel 2 of the steering wheel device 100 according to this embodiment. The steering wheel 2 comprises a circular rim portion 3 and a hub portion 4 located in the center of the rim portion 3. The hub portion 4 houses, for example, an airbag (not shown). The hub portion 4 is connected to the rim portion 3 by three spokes 5.

[0019] The rim portion 3 is covered with a covering layer 24 such as leather, and the hub portion 4 and spoke portions 5 are covered with, for example, a resin material. The rim portion 3 is not limited to a circular ring shape, and may be non-circular (for example, D-shaped or C-shaped).

[0020] A sensor electrode 21 is provided inside the rim portion 3 along the circumferential direction of the rim portion 3. The rim portion 3 is divided into three equal parts in the circumferential direction, and a sensor electrode 21 is provided inside each of these parts. The number of sensor electrodes 21 is not limited to three, and may be two or less, or four or more. The sensor electrode 21 forms a capacitor between itself and a shield electrode 22 (described later) and / or a human body that is in contact with the steering wheel 2, and a capacitance sensor 131 (described later) detects the magnitude of the capacitance (capacitance value), which changes depending on whether the human body is in contact with the steering wheel 2 or not.

[0021] 3 is a cross-sectional view of the rim portion 3 of the steering wheel 2 taken along line III-III in FIG. 2. A core metal 23 is provided in the center of the rim portion 3. A shield electrode 22 is provided around the core metal 23, with an insulator In between. A sensor electrode 21 is provided around the shield electrode 22, with an insulator In between. The outside of the sensor electrode 21 is covered with a covering layer 24 such as leather.

[0022] As shown in FIG. 1, the grip detection ECU 1 includes a control unit 11, a storage unit 12, a capacitance measurement circuit 13, and a communication unit .

[0023] The control unit 11 is, for example, a microcontroller equipped with a processor using one or more CPUs (Central Processing Units), GPUs (Graphics Processing Units), etc. The control unit 11 uses a built-in clock, counter, etc. to read and execute programs and data stored in the storage unit 12 or ROM (Read Only Memory), etc., thereby performing various control processes and arithmetic processes.

[0024] The storage unit 12 includes a nonvolatile memory element such as a flash memory or an EEPROM (Electrically Erasable Programmable Read Only Memory). The storage unit 12 stores various programs and data referenced by the control unit 11. In this embodiment, the storage unit 12 stores a program 121 for causing a computer to execute processes related to grip detection (grip determination) and fault state determination (fault determination). The storage unit 12 also stores predetermined values ​​and specified values ​​used for fault determination, as well as threshold values ​​related to grip determination. The predetermined values, specified values, and threshold values ​​will be described later.

[0025] The program (program product) stored in the storage unit 12 may be recorded on a computer-readable recording medium. The storage unit 12 stores a program read from the recording medium 1A by a reading device (not shown). The recording medium 1A is, for example, a magnetic disk, an optical disk, or a semiconductor memory. The program may also be downloaded from an external server connected to a communication network (not shown) and stored in the storage unit 12. The program 121 may be a single computer program or may be composed of multiple computer programs, and may be executed on a single computer or multiple computers interconnected by a network.

[0026] The capacitance measuring circuit 13 is connected to the sensor electrode 21 and the shield electrode 22 of the steering wheel 2, and is an electric circuit for measuring the capacitance of the sensor electrode 21. The control unit 11 acquires the capacitance value measured by the capacitance measuring circuit 13 and performs grip detection based on the acquired capacitance value. Specifically, the control unit 11 compares the capacitance value with a predetermined threshold value to determine whether the steering wheel 2 is in a gripped state or an ungripped state (grip determination). Here, the gripped state means a state in which the driver is gripping the steering wheel 2, and the ungripped state means a state in which the driver is not gripping the steering wheel 2 and has his hands off it.

[0027] The communication unit 14 is a communication interface for transmitting and receiving information to and from other in-vehicle devices via an in-vehicle network. The communication unit 14 is connected to a communication line (LAN) provided in the vehicle, and transmits and receives information to and from the driving assistance ECU 6, etc. The communication unit 14 transmits the result of the grip determination by the control unit 11 to the driving assistance ECU 6.

[0028] The driving assistance ECU 6 is an ECU that executes processing related to the advanced driving assistance system. The driving assistance ECU 6 receives a signal indicating the result of the grip determination by the control unit 11 via the communication unit 14, and executes predetermined processing related to the advanced driving assistance system according to the result of the grip determination. For example, during autonomous driving, if the driving assistance ECU 6 receives a grip determination result from the control unit 11 indicating that the steering wheel 2 is in an ungripped state, the driving assistance ECU 6 terminates the autonomous driving. Note that the processing of the driving assistance ECU 6 is not limited to autonomous driving, and may be, for example, lane keep assist, parking assist, etc.

[0029] FIG. 4 is an explanatory diagram showing a specific connection example of the capacitance measurement circuit 13 and other components. The capacitance measurement circuit 13 includes a connector 130, a capacitance sensor 131, an additional circuit 132, a first switch 13a, and a second switch 13b. The connector 130 includes a sensor connector 130a connected to the sensor electrode 21 and a shield connector 130b connected to the shield electrode 22. The capacitance sensor 131 includes a resistor Ra connected to the sensor connector 130a, a resistor Rb connected to the shield connector 130b, an ammeter A connected to the resistor Ra, an AC power source Sa connected to the ammeter A, and an AC power source Sb connected to the resistor Rb. The AC power sources Sa and Sb apply equivalent voltages to the sensor electrode 21 and the shield electrode 22. The ammeter A measures the amount of current flowing from the AC power source Sa to the sensor electrode 21, and the capacitance sensor 131 obtains the capacitance value of the sensor electrode 21 based on the amount of current measured by the ammeter A. It should be noted that the larger the amount of current measured by ammeter A, the larger the capacitance value acquired by capacitance sensor 131 becomes.

[0030] The shield electrode 22 is connected to a core 23, which has the same potential (GND potential) as the ground (GND), via a first switch 13a. When the first switch 13a is turned on, the shield electrode 22 and the core 23 are shorted and electrically conductive. The shield electrode 22 is also connected to an additional circuit 132 via a second switch 13b. When the second switch 13b is turned on, the shield electrode 22 and the additional circuit 132 are electrically conductive.

[0031] The additional circuit 132 includes a voltage application circuit 132a, a resistor Rc, and a voltmeter V. When the second switch 13b is turned on, the voltage application circuit 132a applies a voltage to the shield electrode 22. The voltmeter V acquires the value of the voltage applied to the shield electrode 22 by the voltage application circuit 132a.

[0032] The control unit 11 can acquire a capacitance value from the capacitance sensor 131 and a voltage value from the voltmeter V. The first switch 13a and the second switch 13b are switched on or off under the control of the control unit 11. The control unit 11 turns on only one of the first switch 13a and the second switch 13b, and does not turn on both switches at the same time. In addition, the control unit 11 can control the application of a voltage to the shield electrode 22 by the voltage application circuit 132a.

[0033] The sensor electrode 21 and the shield electrode 22 constitute a capacitor Cs with an insulator In provided therebetween. In a state where no fault occurs (normal state), the same voltage is applied to the sensor electrode 21 and the shield electrode 22, so no current can flow between the sensor electrode 21 and the shield electrode 22 (capacitor Cs). However, in a state where a fault occurs (fault state), if a potential difference occurs between the sensor electrode 21 and the shield electrode 22, the capacitor Cs can conduct current.

[0034] The dashed lines in Figure 4 indicate the circuit when the driver is gripping the steering wheel 2. When the driver grips the steering wheel 2, the sensor electrode 21 is electrically connected to the chassis 7 via the driver's body and the vehicle seat or the air inside the vehicle. The chassis 7 is connected to GND and is at GND potential. Because the driver's body forms a capacitor Cb and has resistance, even in the gripping state, if there is another circuit with a low resistance connecting the sensor electrode 21 to GND, the capacitor Cb will not conduct electricity.

[0035] FIG. 5 is a table illustrating capacitance values ​​acquired by the capacitance sensor 131 in each failure mode when the first switch 13a is turned on. In this embodiment, the failure state includes five failure modes. The sensor open mode is a state in which the sensor electrode 21 and the sensor connector 130a are disconnected, preventing current from passing through. The shield open mode is a state in which the shield electrode 22 and the shield connector 130b are disconnected, preventing current from passing through. The sensor ground short mode is a state in which the sensor electrode 21 is short-circuited to the core metal 23, which is at GND potential. The shield ground short mode is a state in which the shield electrode 22 is short-circuited to the core metal 23, which is at GND potential. The sensor shield short mode is a state in which the sensor electrode 21 and the shield electrode 22 are short-circuited.

[0036] When the sensor is in the non-gripping state and no fault has occurred, turning on first switch 13a and shorting shield electrode 22 and core 23 sets the potential of shield electrode 22 to the GND potential, generating a potential difference between sensor electrode 21 and shield electrode 22. This allows current to flow through capacitor Cs, causing a current to flow through ammeter A. Furthermore, when the sensor is in the gripping state and no fault has occurred, capacitor Cb can be conducted, causing a current to flow through ammeter A. Therefore, when the sensor is in the non-gripping state and gripping state, the capacitance value is large.

[0037] In the non-gripping state in the sensor open mode, the sensor electrode 21 is disconnected from the sensor connector 130a, so no current flows through ammeter A. Similarly, in the gripping state in the sensor open mode, no current flows through ammeter A. Therefore, in the sensor open mode, the capacitance value is small in both the non-gripping state and the gripping state.

[0038] In the non-gripping state in the shield open mode, turning on first switch 13a to short-circuit shield electrode 22 and core 23 causes shield electrode 22 to be at GND potential, but no current flows to ammeter A because the capacitance between sensor electrode 21 and GND is smaller than the capacitance between sensor electrode 21 and shield electrode 22. Also, in the gripping state in the shield open mode, capacitor Cb becomes conductive, so current flows to ammeter A. Therefore, in the shield open mode, the capacitance value is small in the non-gripping state and large in the gripping state.

[0039] In the sensor ground short mode, when first switch 13a is turned on to short-circuit shield electrode 22 and core 23, sensor electrode 21 is at GND potential, reducing the potential difference across AC power supply Sa. As a result, no current flows through ammeter A in either the gripped or non-gripped state, and the capacitance value is small in both the gripped and non-gripped states.

[0040] In the shield ground short mode, when the first switch 13a is turned on, the connection state is the same as when the first switch 13a is turned on and the shield electrode 22 and the core wire 23 are shorted when no fault has occurred, so the capacitance value is large in both the non-gripping state and the gripping state.

[0041] In the sensor shield short mode, when first switch 13a is turned on to short-circuit shield electrode 22 and core 23, sensor electrode 21 is at GND potential, reducing the potential difference across AC power supply Sa. As a result, no current flows through ammeter A in either the gripped or non-gripped state, and the capacitance value is small in both the gripped and non-gripped states.

[0042] When the capacitance value acquired from the capacitance sensor 131 is less than a threshold, the control unit 11 determines that the capacitance value is small, and when the capacitance value is equal to or greater than the threshold, the control unit 11 determines that the capacitance value is large. As shown in FIG. 5, a small capacitance value indicates one of the failure modes, so the control unit 11 can determine that a failure state exists when the capacitance value is small. Note that the capacitance value is large when in the gripped state in the shield open mode, but is small when in the non-grip state, so the control unit 11 can determine that a failure due to the shield open mode exists when in the non-grip state. Since it is possible to determine a failure due to the shield open mode by performing a failure determination when the driver is not gripping the steering wheel 2, there is no problem with determining a failure due to the shield open mode.

[0043] Furthermore, with the second switch 13b turned on, the control unit 11 determines whether the device is in the shield ground short mode. Specifically, with the second switch 13b turned on and the first switch 13a turned off, the control unit 11 causes the voltage application circuit 132a to apply a voltage to the shield electrode 22. The control unit 11 acquires the voltage value of the voltage applied to the shield electrode 22 from the voltmeter V. If the shield electrode 22 is shorted to the core metal 23, the potential difference between both ends of the additional circuit 132 becomes small, and the voltage value measured by the voltmeter V becomes small. If the voltage value is smaller than a specified value, the control unit 11 determines that the device is in a fault state due to the shield ground short mode.

[0044] With second switch 13b turned on, control unit 11 determines whether the fault state is due to the shield ground short mode based on the voltage value acquired from voltmeter V, and if the fault state is not due to the shield ground short mode, turns on first switch 13a and determines whether the fault state is due to a fault mode other than the shield ground short mode. This allows control unit 11 to determine fault states due to all fault modes without omission.

[0045] 6 is a flowchart showing an example of a processing procedure of the control unit 11. The processing in each of the following flowcharts may be executed by the control unit 11 in accordance with a program 121 stored in the storage unit 12 of the grip detection ECU 1, or may be realized by a dedicated hardware circuit (for example, an FPGA or an ASIC) provided in the control unit 11, or may be realized by a combination thereof. After detecting activation of the sensor electrode 21, for example, the control unit 11 of the grip detection ECU 1 repeatedly executes the following processing at predetermined or appropriate time intervals.

[0046] The control unit 11 turns on the second switch 13b (S1) and causes the voltage application circuit 132a to apply a voltage to the shield electrode 22 (S2). The control unit 11 acquires the voltage value applied to the shield electrode 22 by the voltage application circuit 132a from the voltmeter V (S3). The control unit 11 determines whether the acquired voltage value is equal to or greater than a specified value (S4). If the voltage value is less than the specified value (S4: NO), the control unit 11 determines that a fault state has occurred in which the shield electrode 22 and the core metal 23 are shorted (S5), and transmits the determination result to, for example, the driving assistance ECU 6 (S6), thereby ending the process.

[0047] If the voltage value is equal to or greater than the specified value (S4: YES), the control unit 11 turns on the first switch 13a (S7) and acquires from the capacitance sensor 131 the capacitance value (first capacitance value) in a state in which the shield electrode 22 and the core metal 23 are short-circuited (S8). The control unit 11 also turns on the second switch 13b (S9) and acquires the second capacitance value from the capacitance sensor 131 (S10). The control unit 11 determines whether the first capacitance value is equal to or greater than a predetermined value (S11). If the first capacitance value is less than the predetermined value (S11: NO), the control unit 11 determines that a fault has occurred (S12), transmits the determination result to, for example, the driving assistance ECU 6 (S13), and ends the process.

[0048] If the first capacitance value is equal to or greater than a predetermined value (S11: YES), the control unit 11 determines whether the second capacitance value is equal to or greater than a threshold value related to grip determination (S14). If the second capacitance value is equal to or greater than the threshold value (S14: YES), the control unit 11 determines that the steering wheel 2 is in a gripped state (S15). If the second capacitance value is less than the threshold value (S14: NO), the control unit 11 determines that the steering wheel 2 is in an ungripped state (S16). The control unit 11 transmits the determination result in S15 or S16 to, for example, the driving assistance ECU 6 (S17), and returns the process to S2.

[0049] According to the above configuration and processing, it is possible to determine a fault in the steering wheel 2 whether the steering wheel is being gripped by the driver or not. Furthermore, since the fault determination is based on the capacitance value at the time of measurement and there is no need to obtain the fluctuation range of the capacitance value over time, it is possible to determine the fault in a short time. Furthermore, by switching between the first switch 13a and the second switch 13b, it is possible to perform the grip determination and the fault determination using a single circuit configuration, which eliminates the need to provide a separate circuit or system for the fault determination, thereby reducing the cost of producing the grip detection device. Additionally, since the grip determination and the fault determination are repeatedly performed, it is possible to prevent erroneous grip determination due to a fault.

[0050] In addition, when symbols are used in the claims, the symbols are merely used for reference purposes in correspondence with the symbols used in the embodiments in order to facilitate understanding of the claims, and do not limit the scope of the claims.

[0051] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The technical features described in each embodiment may be combined with one another, and the scope of the present invention is intended to include all modifications within the scope of the claims and equivalents thereto. Furthermore, independent and dependent claims described in the claims may be combined with one another in any and all combinations, regardless of the reference format. Furthermore, while the claims use a format in which a claim references two or more other claims (multiple claim format), this is not limiting. Multiple claims (multiple multiple claims) that reference at least one other claim may also be used. [Explanation of symbols]

[0052] 1. Grasp detection ECU (grasp detection device) 11 Control section 13 Capacitance measurement circuit 13a First Switch 13b Second switch 131 Capacitive Sensor 132 Additional circuit 2 steering wheels 21 Sensor electrode 22 Shield electrode 23 Core Insulator

Claims

1. A grip detection device (1) for a steering wheel (2) including a core metal (23), a shield electrode (22) provided outside the core metal (23) with an insulator (In) between them, and a sensor electrode (21) provided further outside the shield electrode (22) with an insulator (In) between them, A control unit (11) that acquires the capacitance value of the sensor electrode (21) when the shield electrode (22) and the core metal (23) are short-circuited, and determines whether or not there is a malfunction based on the capacitance value. A grip detection device (1) comprising:

2. a first switch (13a) provided between the shield electrode (22) and the core metal (23) and short-circuiting the shield electrode (22) and the core metal (23) when turned on; The control unit (11) determines whether or not there is a malfunction when the first switch (13a) is turned on. The grip detection device (1) according to claim 1.

3. The control unit (11) determines that a fault has occurred when the acquired capacitance value is less than a predetermined value. A grip detection device (1) according to claim 1 or 2.

4. an additional circuit (132) connected to the shield electrode (22), applying a voltage to the shield electrode (22) and measuring the voltage value of the applied voltage; When the voltage value of the voltage applied by the additional circuit (132) is lower than a specified value, the control unit (11) determines that a fault state has occurred in which the shield electrode (22) and the core metal (23) are short-circuited. A grip detection device (1) according to claim 1 or 2.

5. a second switch (13b) provided between the shield electrode (22) and the additional circuit (132), which, when turned on, allows current to flow between the shield electrode (22) and the additional circuit (132); The control unit (11) determines whether or not the shield electrode (22) and the core metal (23) are short-circuited when the second switch (13b) is turned on. The grip detection device (1) according to claim 4.

6. The control unit (11) determines whether the steering wheel (2) is being gripped while the second switch (13b) is turned on. The grip detection device (1) according to claim 5.

7. A method for determining a fault in a grip detection device (1) of a steering wheel (2) including a core metal (23), a shield electrode (22) provided outside the core metal (23) with an insulator (In) between them, and a sensor electrode (21) provided further outside the shield electrode (22) with an insulator (In) between them, the method comprising: The capacitance value of the sensor electrode (21) is acquired in a state where the shield electrode (22) and the core metal (23) are short-circuited, and the presence or absence of a fault is determined based on the capacitance value. Failure determination method.

8. A program for determining a fault in a grip detection device (1) of a steering wheel (2) including a core (23), a shield electrode (22) provided outside the core (23) with an insulator (In) between them, and a sensor electrode (21) provided further outside the shield electrode (22) with an insulator (In) between them, The capacitance value of the sensor electrode (21) is acquired in a state where the shield electrode (22) and the core metal (23) are short-circuited, and the presence or absence of a fault is determined based on the capacitance value. A program that causes a computer to perform a process.

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