Steering wheel holding determination device

Abstract

To suppress occurrence of a holding / fixing state.SOLUTION: A steering wheel holding determination device is provided with: an electrostatic capacity sensor 11 that can detect, as a detected electrostatic capacity, an electrostatic capacity between an electrode and an object; a steering input value sensor 12 that can detect a steering input value which is an input value based on operation of a steering wheel by a driver in a vehicle; and a control unit 10 that is configured to renew a reference electrostatic capacity by the detected electrostatic capacity every time when a predetermined calculation time elapses and to perform holding-determination of whether the steering wheel is in a holding state where the steering wheel is held by the driver or not, on the basis of a result of whether the detected electrostatic capacity is over a holding determination threshold calculated based on the reference electrostatic capacity or not. The control unit stops renewal of the reference electrostatic capacity when the steering input value is equal to a predetermined steering input threshold or more when the detected electrostatic capacity is detected.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a steering wheel holding determination device that determines whether or not a steering wheel of a vehicle is being held by a driver. [Background technology]

[0002] A steering wheel holding determination device (hereinafter also simply referred to as a "holding determination device") that determines whether or not the steering wheel of a vehicle is being held by a driver (held state) has been known. This holding determination device includes a capacitance sensor built into the steering wheel. The capacitance sensor detects the capacitance between an electrode and an object (i.e., the steering wheel). The holding determination device performs the holding determination based on the detected capacitance (hereinafter also referred to as the "detected capacitance") every time a predetermined calculation time elapses during the period in which the capacitance is being detected (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-009470 Summary of the Invention

[0004] Specifically, the hold determination device updates the reference capacitance with the detected capacitance every time the calculation time elapses, and calculates the hold determination threshold based on the reference capacitance (for example, calculates the hold determination threshold by adding a predetermined capacitance to the reference capacitance). Then, when the detected capacitance exceeds the hold determination threshold, it determines that the steering wheel is in a held state, and when the detected capacitance is equal to or less than the hold determination threshold, it determines that the steering wheel is in a non-held state (a state in which the steering wheel is not held by the driver), thereby making the hold determination. However, this hold determination device is configured to stop updating the reference capacitance for a predetermined period when the detected capacitance is significantly larger or smaller than the reference capacitance. One example of this is when the driver holds the steering wheel. That is, when the driver holds the steering wheel, the detection value (detected capacitance) of the capacitance sensor increases significantly with respect to the reference capacitance. In such a case, the hold determination device stops updating the reference capacitance for a predetermined period. With this configuration, the hold determination can be appropriately performed based on the detected capacitance.

[0005] Incidentally, since the capacitance sensor is a relatively expensive part, there are steering wheels in which the capacitance sensor is not built in (installed) over the entire circumference, but is installed only in a part of the circumference (typically, the left and right parts that are generally held by the driver). Even with such a steering wheel, when the driver holds the left and / or right parts, the holding determination device can properly perform the holding determination as described above. However, when the driver holds the part of the steering wheel where the capacitance sensor is not installed (hereinafter also referred to as the "non-sensor installation part"), the detection value of the capacitance sensor does not increase (in other words, the detection value is detected to be equal to the detection value in the non-held state), so that the holding determination device erroneously determines that the steering wheel is in the non-held state and continues to update the reference capacitance unnecessarily, which may result in a holding fixation state. Here, the holding fixation state means "a state in which the holding determination is continuously determined to be in the held state regardless of whether the driver is holding the steering wheel or not (i.e., a state in which the determination result is fixed to the held state)."

[0006] The stuck-hold state occurs as follows. That is, in general, the detection value of a capacitance sensor is easily fluctuated by external influences. For example, the detected capacitance decreases when a vehicle passes directly under a power line or when a positively charged object is brought close. Therefore, when the driver is subjected to the above-mentioned external influence while driving the vehicle while holding the non-sensor portion of the steering wheel, the detected capacitance gradually decreases from a normal value. Then, the reference capacitance gradually decreases as it is updated based on the detected capacitance, and the hold determination threshold also gradually decreases. The longer the period of exposure to external influences, the greater the decrease in the hold determination threshold.

[0007] After that, when the vehicle is no longer subject to the external influence, the detected capacitance returns to a normal value. At this time, since the hold determination threshold is decreased, the detected capacitance is likely to exceed the hold determination threshold, and in that case, the hold determination device determines that the steering wheel is in a held state regardless of whether the driver is holding the steering wheel (including the left and right parts) and stops updating the reference capacitance for a predetermined period. If the vehicle is not subject to external influences after the period has elapsed, the capacitance sensor detects a normal value, and the detected capacitance exceeds the hold determination threshold again, and as a result, the hold determination device again determines that the steering wheel is in a held state and stops updating the reference capacitance.

[0008] In this way, if the driver holds the non-sensor part of the steering wheel, the hold determination erroneously determines that the steering wheel is not held, and the reference capacitance continues to be updated unnecessarily, which may result in a large decrease in the hold determination threshold value. In such a case, once the detected capacitance returns to a normal value and the relationship "detected capacitance>hold determination threshold value" is established, the hold determination will continuously determine that the steering wheel is held. This is how the stuck hold state occurs.

[0009] The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to provide a steering wheel holding determination device that can suppress the occurrence of a holding stuck state.

[0010] The steering wheel holding determination device according to the present invention (hereinafter referred to as the "present invention device") is Mounted on the vehicle, a capacitance sensor (11) capable of detecting capacitance between an electrode and an object as a detection capacitance; a steering input value sensor (12) capable of detecting a steering input value (Ts) which is an input value based on an operation of a steering wheel (SW) by a driver of the vehicle; updating the reference capacitance (Cr) with the detected capacitance (C) every time a predetermined calculation time has elapsed; a control unit (10) configured to perform a hold determination for determining whether or not the steering wheel is in a held state, that is, held by the driver, based on whether or not the detected capacitance exceeds a hold determination threshold (Chth) calculated based on the reference capacitance; In a steering wheel holding determination device comprising: The control unit When the detected capacitance is detected and the steering input value is equal to or greater than a predetermined steering input threshold (Tsth), updating of the reference capacitance is stopped. It is structured as follows.

[0011] The device of the present invention includes a steering input value sensor capable of detecting a steering input value. The steering input value sensor is, for example, a steering torque sensor, a steering angle sensor, and / or a steering angle sensor. The device of the present invention is configured to stop updating the reference capacitance when the detected capacitance is detected and the steering input value is equal to or greater than a predetermined steering input value threshold. Here, "the steering input value is equal to or greater than the steering input value threshold" typically means that the driver is operating the steering wheel (hereinafter also referred to as "steering operation"). According to this configuration, when the driver is operating the steering wheel, the update of the reference capacitance is stopped. Therefore, even if the capacitance sensor is installed only on a part of the steering wheel in the circumferential direction, it is possible to suppress unnecessary continuation of updating the reference capacitance due to the driver holding the non-sensor-installed part of the steering wheel. As a result, it is possible to reduce the possibility that the holding determination threshold value is significantly reduced due to external influences, so that the detected capacitance is less likely to exceed the holding determination threshold value, and the holding determination is less likely to continuously determine that the steering wheel is in a held state, thereby suppressing the occurrence of a holding fixation state.

[0012] In the above description, in order to facilitate understanding of the invention, the symbols used in the embodiments are added in parentheses to the constituent elements of the invention corresponding to the embodiments, but each constituent element of the invention is not limited to the embodiment defined by the said symbols. [Brief description of the drawings]

[0013] [Figure 1] 1 is a schematic diagram of a steering wheel holding determination device (present embodiment device) according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the position where a capacitance sensor is built in (installed) on a steering wheel. [Diagram 3] 4 is a flowchart showing a routine executed by a CPU of a steering ECU provided in the embodiment of the present invention. [Figure 4] 10 is a time chart comparing the results of determination by the steering wheel holding determination device according to the present embodiment with those of a conventional steering wheel holding determination device when a non-sensor portion of the steering wheel is held. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] (Embodiment) Hereinafter, a steering wheel holding determination device according to this embodiment (hereinafter also referred to as "this embodiment device") will be described with reference to the drawings. As shown in FIG. 1, this embodiment device includes a steering ECU 10, and a capacitance sensor 11 and a steering torque sensor 12 connected thereto. The steering ECU 10 includes a microcomputer as a main part. ECU is an abbreviation for Electronic Control Unit. The microcomputer includes a CPU, storage devices such as ROM and RAM, and an interface (I / F), and the CPU realizes various functions by executing instructions (programs) stored in the ROM. Hereinafter, a vehicle equipped with this embodiment device will be referred to as "own vehicle".

[0015] The steering ECU 10 is configured to acquire signals transmitted by the sensors 11 and 12 at every predetermined calculation time, and perform a holding determination (described later) based on the acquired signals. Hereinafter, the steering ECU 10 is also simply referred to as "ECU 10."

[0016] Fig. 2 is a diagram showing a steering wheel SW of a vehicle (hereinafter, simply referred to as "steering wheel SW"). As shown in Fig. 2, the capacitance sensor 11 is installed (built-in) only on a part of the circumference of the steering wheel SW, and more specifically, on the left and right parts (see dashed lines) of the steering wheel SW. In other words, the capacitance sensor 11 is installed only on the part of the steering wheel SW that is generally held by the driver.

[0017] The capacitance sensor 11 detects the capacitance between the electrode and the target object (i.e., the steering wheel SW) as a detected capacitance C, and transmits a signal representing the detected capacitance C to the ECU 10. The detected capacitance C increases when the driver holds the left and / or right parts of the steering wheel SW, but when the driver holds the upper and / or lower parts of the steering wheel SW, it has the same value as when the driver is not holding the steering wheel SW. The upper and lower parts of the steering wheel SW are typically the parts surrounded by dashed lines A1 and A2 in FIG. 2, respectively. Hereinafter, these parts are referred to as the "sensor-free part A1" and the "sensor-free part A2".

[0018] Returning to Fig. 1, the explanation will be continued. The steering torque sensor 12 (steering input value sensor) detects the steering torque Ts of the steering wheel SW and transmits the detection signal to the ECU 10. The steering torque sensor 12 detects the steering torque Ts as a positive value when the steering wheel SW is operated to the right, and detects the steering torque Ts as a negative value when the steering wheel SW is operated to the left. The steering torque Ts is an example of "an input value based on the operation of the steering wheel SW (steering operation) by the driver".

[0019] When the ECU 10 acquires the detected capacitance C from the capacitance sensor 11, the ECU 10 performs a hold determination to determine whether or not the handle SW is in a held state every time a calculation time elapses. Specifically, the ECU 10 updates the reference capacitance Cr with the detected capacitance C. This is performed by setting the detected capacitance C acquired in the immediately preceding cycle as the reference capacitance Cr in the current cycle. Next, the ECU 10 calculates a hold determination threshold Chth based on the reference capacitance Cr. The hold determination threshold Chth in the current cycle is calculated by adding a predetermined capacitance C (in this embodiment, a positive constant) to the reference capacitance Cr in the same cycle. This hold determination threshold Chth is a threshold for determining whether or not the handle SW is in a held state, and can be determined by setting the capacitance C to an appropriate value based on an experiment or a simulation.

[0020] However, the ECU 10 is configured to stop updating the reference capacitance Cr for a predetermined period when the detected capacitance C in the immediately preceding cycle is significantly larger or smaller than the reference capacitance Cr in the same cycle. For example, when the driver holds the left and / or right parts of the steering wheel SW, the detected capacitance C becomes significantly larger than the reference capacitance Cr (typically exceeds the holding determination threshold Chth), so the ECU 10 stops updating the reference capacitance Cr for a predetermined period in such a case. Note that the case in which the detected capacitance C becomes significantly smaller than the reference capacitance Cr is not directly related to this embodiment, so a description thereof will be omitted.

[0021] The ECU 10 performs a holding determination by determining that the handle SW is in a held state when the detected capacitance C in the current cycle exceeds the holding determination threshold Chth in the same cycle, and determining that the handle SW is in a non-held state when the detected capacitance C is equal to or less than the holding determination threshold Chth.

[0022] In the conventional steering wheel SW (a steering wheel SW in which a capacitance sensor is installed only on a part of its circumference), when the driver holds the non-sensor-installed parts A1 and A2 of the steering wheel SW, the detected capacitance C is equal to or smaller than the hold determination threshold Chth, and the hold determination device erroneously determines that the steering wheel SW is not in a hold state, and continues to update the reference capacitance Cr unnecessarily. If the hold determination threshold Chth is significantly decreased due to an external influence such as the vehicle passing directly under a power line or a positively charged body being brought close to the steering wheel SW during this period, the relationship "detected capacitance C>hold determination threshold Chth" is established when the external influence is no longer present. Once this relationship is established, a situation may occur in which the hold determination is continuously determined to be in a hold state, resulting in a stuck hold state.

[0023] Therefore, in this embodiment, the ECU 10 is configured to stop updating the reference capacitance Cr when it is clear that the driver is performing a steering operation based on the steering torque Ts acquired from the steering torque sensor 12, thereby suppressing the occurrence of the holding fixation state. Furthermore, the ECU 10 is configured to stop updating the reference capacitance Cr for a predetermined time T even when there is a possibility that the driver has changed the operating direction of the steering wheel SW, thereby more reliably suppressing the occurrence of the holding fixation state. Hereinafter, a specific description will be given with reference to FIG. 3.

[0024] The CPU of the ECU 10 is configured to repeatedly execute the routine shown in the flowchart of FIG. 3 every time a calculation time elapses while the ignition switch is in the ON state.

[0025] At a predetermined timing, the CPU starts processing from step 300 and proceeds to step 310 to determine whether or not the capacitance C has been detected (i.e., whether or not the detected capacitance C has been acquired from the capacitance sensor 11). If the detected capacitance C has not been acquired (step 310: No), the CPU proceeds to step 395 and temporarily ends this routine. On the other hand, if the detected capacitance C has been acquired (step 310: Yes), the CPU proceeds to step 320.

[0026] In step 320, the CPU determines whether or not the absolute value of the steering torque Ts acquired from the steering torque sensor 12 is equal to or greater than a predetermined steering torque threshold value Tsth. The steering torque threshold value Tsth is a threshold value for determining whether or not the driver is performing a steering operation, and can be set in advance by experiment or simulation. If the absolute value of the steering torque Ts is equal to or greater than the steering torque threshold value Tsth (step 320: Yes), the CPU determines that the driver is performing a steering operation (is in an operating state), and proceeds to step 330 to set the value of the steering operation flag Fs to "1."

[0027] Next, the CPU advances the process to step 340, where it stops updating the reference capacitance Cr. After that, the CPU advances the process to step 395, where it temporarily ends this routine.

[0028] On the other hand, if the absolute value of the steering torque Ts is less than the steering torque threshold value Tsth in step 320 (step 320: No), the CPU determines that no steering operation is being performed (no operation state) and proceeds to step 350 to determine whether the value of the steering operation flag Fs is "1" (i.e., whether a steering operation has been performed in the past). If the value of the steering operation flag Fs is "1" (step 350: Yes), the CPU determines that a steering operation has been performed in the past and proceeds to step 360. Note that the value of the steering operation flag Fs is set to "0" when the ignition switch is turned on.

[0029] In step 360, the CPU determines whether or not a predetermined time T has elapsed since the steering torque Ts < the steering torque threshold Tsth was established (more specifically, since the relationship |Ts| ≧ Tsth changed to the relationship |Ts| < Tsth). The time T is a value for determining whether or not the driver is likely to have stopped the steering operation, and can be preset in advance through experiments or simulations. If the time T has not yet elapsed since |Ts| < Tsth was established (step 360: No), the CPU determines that it cannot be said with certainty that the driver has stopped the steering operation (i.e., there is a possibility that the driver has switched the operation direction of the steering wheel SW), and proceeds with the processing to step 340. The processing of step 340 is as described above.

[0030] On the other hand, if the time T has elapsed since |Ts| < Tsth was established (step 360: Yes), the CPU determines that the driver is likely to have stopped the steering operation, and proceeds with the processing to step 370. In step 370, the CPU resumes the update of the reference capacitance Cr and sets (resets) the value of the steering operation flag Fs to "0". Thereafter, the CPU proceeds to step 395 and temporarily ends this routine.

[0031] In contrast, if the value of the steering operation flag Fs is "0" in step 350 (step 350: No), the CPU determines that no steering operation has been performed since the ignition switch was turned on, or that the time T has elapsed since the steering operation, which was performed in the past, was stopped, and proceeds with the processing to step 380. In step 380, the CPU updates the reference capacitance Cr. Thereafter, the CPU proceeds to step 395 and temporarily ends this routine.

[0032] According to this configuration, when the detected capacitance C is acquired and the absolute value of the steering torque Ts is greater than or equal to the steering torque threshold value Tsth, the update of the reference capacitance Cr is stopped. That is, when the driver holds the non-sensor parts A1 and A2 of the steering wheel SW and performs a steering operation, the update of the reference capacitance Cr is stopped. For this reason, it is possible to suppress the unnecessary continuation of the update of the reference capacitance Cr even though the driver is holding the steering wheel SW. As a result, it is possible to reduce the possibility that the holding determination threshold value Chth greatly decreases due to external influences, so that it becomes difficult for the detected capacitance C to exceed the holding determination threshold value Chth, and the occurrence of a holding stuck state can be suppressed.

[0033] In particular, in the present embodiment, even when the time T has not elapsed since the relationship |Ts| < Tsth changed from the relationship |Ts| ≧ Tsth, the update of the reference capacitance Cr is stopped. When the driver switches the operation direction of the steering wheel SW during the steering operation, the absolute value of the steering torque Ts temporarily decreases. However, by setting the time T to an appropriate value, it is possible to suppress the unnecessary update of the reference capacitance Cr when switching the operation direction of the steering wheel SW. As a result, the occurrence of a holding stuck state can be more reliably suppressed.

[0034] FIG. 4 shows a time chart comparing the determination result by the holding determination of the present embodiment apparatus with that of a conventional steering wheel holding determination apparatus (hereinafter, also simply referred to as "conventional apparatus"). In the example of FIG. 4, it is assumed that the driver is holding the non-sensor parts A1 and A2 of the steering wheel SW. In FIG. 4, in order from the top, the absolute value of the steering torque Ts, the steering operation determination (see step 320 in FIG. 3), the detected capacitance C, the reference capacitance Crp of the conventional apparatus, the holding determination result of the conventional apparatus, the reference capacitance Cr of the present embodiment apparatus, and the holding determination result of the present embodiment apparatus are shown as time charts based on capacitance and steering torque (both will be described later), respectively.

[0035] In this example, the driver continues the steering operation until time t3 and stops the steering operation at time t3. Therefore, in the first time chart (|steering torque Ts|), at time t3, |Ts| (see solid line) changes from |Ts| ≥ Tsth to |Ts| < Tsth. As a result, in the second time chart (steering operation determination), at time t3, the determination result of the steering operation changes from the operating state to the non-operating state.

[0036] Also, in this example, from time t1 to time t2, the host vehicle passes under the power transmission line and is affected by external influences. Therefore, in the third time chart (detected capacitance C), the detected capacitance C remains constant until time t1, gradually decreases from time t1 to time t2, and increases after time t2. In this example, since the driver holds the non-sensor parts A1 and A2 of the steering wheel SW, in the fourth time chart (reference capacitance Crp of the conventional device), the value of the reference capacitance Crp gradually decreases due to the update of the reference capacitance Crp even during the period of being affected by external influences. Accordingly, the holding determination threshold value Chpth of the conventional device (see the third time chart) also gradually decreases. Then, when the detected capacitance C exceeds the holding determination threshold value Chpth at time t2, the conventional device stops updating the reference capacitance Crp for a predetermined period (a period shorter than the period from time t2 to time t3). As a result, the holding determination threshold value Chpth maintains a constant value for a predetermined period (see the third time chart). Also, according to the third time chart, since at time t2, it changes from C ≤ Chpth to C > Chpth, in the fifth time chart (holding determination result of the conventional device), it is determined that the steering wheel SW is in the non-held state until time t2, and it is determined that the steering wheel SW is in the held state for a predetermined period from time t2.

[0037] In the conventional device, when a predetermined period of time has elapsed from time t2, the update of the reference capacitance Crp is resumed. According to the third time chart, since there is no particular external influence at the time when the update is resumed, the detected capacitance C exceeds the hold determination threshold Chpth. Therefore, the conventional device again determines that the handle SW is in the held state (see the fifth time chart) and stops updating the reference capacitance Crp for a predetermined period of time (see the fourth time chart). After that, this situation occurs continuously, and the conventional device experiences a fixed hold state (see the fifth time chart).

[0038] On the other hand, in the sixth time chart (reference capacitance Cr of the present embodiment device), the present embodiment device stops updating the reference capacitance Cr until time t3 based on the steering operation determination result (see the second time chart). This prevents unnecessary continuation of the update of the reference capacitance Cr during the period when the device is subject to external influence. In addition, at time t3, the update of the reference capacitance Cr is stopped for a time T (a value greater than the time from time t3 to the end point of the time chart). Accordingly, the holding determination threshold Chth (see the third time chart) of the present embodiment device maintains a constant value from the start point to the end point of the time chart. As a result, since the detected capacitance C remains below the holding determination threshold Chth, in the seventh time chart (holding determination result based on capacitance of the present embodiment device), it is determined that the steering wheel SW is in a non-holding state from the start point to the end point of the time chart. This prevents the occurrence of a holding fixation state. Since this holding determination is based on the detected capacitance C, it is also referred to as a "holding determination based on capacitance" below.

[0039] In this embodiment, in addition to the holding determination based on capacitance, as shown in the eighth time chart, the holding determination based on the steering torque is further performed. In this holding determination, based on the second time chart (i.e., the steering operation determination in step 320 of FIG. 3), when it is determined that the steering wheel SW is being steered, it is determined that the steering wheel SW is in the held state, and when it is determined that the steering wheel SW is not being steered, it is determined that the steering wheel SW is in the non-held state. When it is determined that the steering wheel SW is in the held state in at least one of the holding determination based on capacitance and the holding determination based on the steering torque, the present apparatus finally determines that the steering wheel SW is in the held state. According to this configuration, in addition to suppressing the occurrence of the holding fixation state, it is also possible to suppress the erroneous determination that the steering wheel SW is in the non-held state when the driver holds the non-sensor parts A1 and A2 of the steering wheel SW.

[0040] As described above, the steering wheel holding determination device according to the embodiment has been described. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention.

[0041] For example, the process of stopping the update of the reference capacitance Cr for a time T after the relationship changes from |Ts|≥Tsth to |Ts|<Tsth (the processes in steps 350 to 370 of FIG. 3) may not be performed. That is, when it is determined "No" in step 320, the process of step 380 may be directly performed. Generally, since the time required to switch the operation direction of the steering wheel SW is short, the possibility of being affected by external influences during this period is low. Also, even if it is affected by external influences, the possibility that the holding determination threshold Chth significantly decreases during this period is low. Therefore, this configuration can also achieve the same operational effects as the embodiment.

Explanation of Reference Numerals

[0042] 10: Steering ECU 10, 11: Capacitance sensor, 12: Steering torque sensor

Claims

[Claim 1] Mounted on the vehicle, a capacitance sensor capable of detecting capacitance between an electrode and an object as a detection capacitance; a steering input value sensor capable of detecting a steering input value which is an input value based on an operation of a steering wheel by a driver of the vehicle; updating the reference capacitance with the detected capacitance every time a predetermined calculation time has elapsed; a control unit configured to perform a hold determination to determine whether or not the steering wheel is in a held state, based on whether or not the detected capacitance exceeds a hold determination threshold calculated based on the reference capacitance; and In a steering wheel holding determination device comprising: The control unit when the detected capacitance is detected and the steering input value is equal to or greater than a predetermined steering input threshold value, updating of the reference capacitance is stopped. It was configured as follows: Steering wheel holding determination device.

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