JP2023180546A - Steering wheel holding determination device - Google Patents

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering wheel holding determination device that determines whether a vehicle's steering wheel is being held by a driver.

Conventionally, there has been known a steering wheel retention determination device (hereinafter also simply referred to as a "holding determination device") that determines whether or not the steering wheel of a vehicle is in a state where it is being held by a driver (holding state). There is. This retention determination device includes a capacitance sensor built into the steering handle. A capacitive sensor detects the capacitance between an electrode and an object (ie, a steering wheel). The retention determination device determines the retention based on the detected capacitance (hereinafter also referred to as "detected capacitance") every time a predetermined calculation time elapses during the period in which the capacitance is being detected. A determination is made (for example, see Patent Document 1).

JP2021-009470A

Specifically, the retention determination device updates the reference capacitance with the detected capacitance every time the calculation time elapses, and calculates the retention determination threshold based on the reference capacitance (for example, The retention determination threshold is calculated by adding a predetermined capacitance to the capacitance.) If the detected capacitance exceeds the holding judgment threshold, it is determined that the steering wheel is in the held state, and if the detected capacitance is below the holding judgment threshold, it is determined that the steering wheel is not held (the steering wheel is held by the driver). A retention determination is made by determining that the data is in a state in which the However, this retention determination device is configured to stop updating the reference capacitance for a predetermined period if the detected capacitance is significantly larger or smaller than the reference capacitance. An example of this is when the driver is holding the steering wheel. That is, when the driver holds the steering wheel, the detected value of the capacitance sensor (detected capacitance) increases significantly relative to the reference capacitance. In such a case, the retention determination device stops updating the reference capacitance for a predetermined period. According to this configuration, retention determination can be appropriately performed based on the detected capacitance.

By the way, the capacitance sensor is a relatively expensive component, so the capacitance sensor is not built in (installed) in the entire circumference of the steering wheel, but in a part of the circumference ( Typically, there are types that are built only into the left side and right side (which are commonly held by the driver). Even with such a steering wheel, if the driver is holding the left side and/or right side of the steering wheel, the holding determination device can appropriately perform the holding determination as described above. However, if the driver holds the part of the steering wheel where the capacitance sensor is not installed (hereinafter also referred to as the "sensor-free part"), the detection value of the capacitance sensor does not increase. (In other words, it detects a value equivalent to the value detected in the non-holding state). Therefore, the holding judgment device incorrectly determines that the steering wheel is in the non-holding state and continues updating the reference capacitance unnecessarily. As a result, there is a possibility that the device may become stuck. Here, the holding state is defined as a state in which the holding state is continuously determined in the holding judgment regardless of whether or not the driver is holding the steering wheel (i.e., the judgment result is that the steering wheel is stuck in the holding state). (a state of having done something).

The stuck holding state occurs as follows. That is, in general, the detected value of a capacitance sensor tends to fluctuate due to external influences. For example, when a vehicle passes directly under a power transmission line or when a positively charged object approaches, the detected capacitance decreases. Therefore, if the driver receives the external influence while driving the vehicle while holding the part of the steering wheel where the sensor is not installed, the detected capacitance gradually decreases from its normal value. Then, since the reference capacitance is updated based on the detected capacitance and gradually decreases, the holding determination threshold value also gradually decreases. The longer the period of external influence, the greater the retention determination threshold decreases.

Thereafter, when the vehicle is no longer subject to the above external influences, the detected capacitance returns to its normal value. At this time, since the holding judgment threshold is decreasing, the detected capacitance is likely to exceed the holding judgment threshold. It is determined that the steering wheel is in the holding state regardless of whether the steering wheel is in the holding state, and updating of the reference capacitance is stopped for a predetermined period. If the vehicle is not affected by external influences after the period has elapsed, the capacitance sensor will detect a normal value, so a situation in which the detected capacitance exceeds the holding judgment threshold will occur again, and as a result, The holding determination device again determines that the steering wheel is in the held state and stops updating the reference capacitance.

In this way, if the driver holds the part of the steering wheel where the sensor is not installed, it will be erroneously determined that the steering wheel is not in the holding state, and the reference capacitance will continue to be updated unnecessarily. The holding judgment threshold may decrease significantly, and in such cases, the detection capacitance returns to its normal value and once the relationship of "detection capacitance > holding judgment threshold" is established, it will not be in the holding state in the holding judgment. A situation occurs where it is continuously determined that there is. A stuck hold condition occurs in this way.

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 stuck holding state.

The steering wheel retention determination device according to the present invention (hereinafter referred to as the “device of the present invention”) includes:
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) that 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 detection capacitance (C) every time a predetermined calculation time elapses;
Whether or not the steering wheel is in a held state held by the driver based on whether the detected capacitance exceeds a holding determination threshold (Chth) calculated based on the reference capacitance. a control unit (10) configured to perform a retention determination to determine whether the
A steering wheel retention determination device comprising:
The control unit includes:
When the detection capacitance is detected and the steering input value is equal to or higher than a predetermined steering input threshold (Tsth), stopping updating of the reference capacitance;
It is configured as follows.

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 steering input value is equal to or greater than a predetermined steering input value threshold when the detection capacitance is detected. Here, "the steering input value is greater than or equal to the steering input value threshold" typically means that the driver is operating the steering wheel (hereinafter also referred to as "steering operation"). do. According to this configuration, updating of the reference capacitance is stopped when the driver is performing a steering operation. For this reason, for example, even if the capacitance sensor is installed only on a part of the steering wheel in the circumferential direction, the standard may be lowered due to the driver holding the part of the steering wheel where the sensor is not installed. Unnecessary continuation of updating of capacitance can be suppressed. As a result, it is possible to reduce the possibility that the holding judgment threshold value will be significantly reduced due to external influences, making it difficult for the detection capacitance to exceed the holding judgment threshold value, so that the holding state is continuously determined in the holding judgment. This is less likely to occur, and the occurrence of a stuck state can be suppressed.

In the above description, in order to facilitate understanding of the invention, the reference numerals used in the embodiment are added to the constituent features of the invention corresponding to the embodiments in parentheses. The present invention is not limited to the embodiments defined by the following.

1 is a schematic configuration diagram of a steering wheel retention determination device (this embodiment device) according to an embodiment of the present invention. FIG. 3 is a diagram showing a position where a capacitance sensor is built in (installed) in a steering wheel. 2 is a flowchart showing a routine executed by the CPU of the steering ECU included in the present embodiment device. 12 is a time chart comparing the determination results of the holding determination when the sensor-uninstalled portion of the steering wheel is held, between the present embodiment device and the conventional steering wheel retention determining device.

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

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

FIG. 2 is a diagram showing the steering handle SW (hereinafter also simply referred to as "handle SW") of the own vehicle. As shown in FIG. 2, the capacitance sensor 11 is installed (built-in) only in a part of the handle SW in the circumferential direction, and more specifically, on the left side and right side of the handle SW (see the dashed line). It is installed in In other words, the capacitance sensor 11 is installed only in the portion of the steering wheel SW that is generally held by the driver.

The capacitance sensor 11 detects the capacitance between the electrode and the object (namely, the handle SW) as a detection capacitance C, and transmits a signal representing the detection capacitance C to the ECU 10. The detection capacitance C increases when the driver holds the left and/or right side of the handle SW, but when the driver holds the upper and/or lower part of the handle SW. The value is the same as when the handle SW is not held. Note that the upper part and the lower part of the handle SW are typically the parts surrounded by the broken line A1 and the broken line A2 in FIG. 2, respectively. Hereinafter, these parts will be referred to as "sensor non-installation part A1" and "sensor non-installation part A2."

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 handle SW is operated to the right, and detects the steering torque Ts as a negative value when the handle SW is operated to the left. do. The steering torque Ts is an example of "an input value based on the driver's operation of the steering wheel SW (steering operation)".

When the ECU 10 acquires the detected capacitance C from the capacitance sensor 11, it performs a retention determination to determine whether the handle SW is in the retention state every time the calculation time elapses. Specifically, the ECU 10 updates the reference capacitance Cr with the detected capacitance C. This is done by setting the detected capacitance C acquired in the immediately previous cycle to the reference capacitance Cr in the current cycle. Subsequently, the ECU 10 calculates a holding determination threshold Chth based on the reference capacitance Cr. The holding 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 holding determination threshold Chth is a threshold for determining whether or not the handle SW is in the holding state, and can be determined by setting the capacitance C to an appropriate value based on experiments or simulations.

However, if the detected capacitance C in the immediately previous cycle is significantly larger or smaller than the reference capacitance Cr in the same cycle, the ECU 10 stops updating the reference capacitance Cr for a predetermined period. It is configured as follows. For example, when the driver holds the left and/or right side of the handle SW, the detected capacitance C becomes significantly larger than the reference capacitance Cr (typically exceeds the holding determination threshold Chth). In such a case, the ECU 10 stops updating the reference capacitance Cr for a predetermined period. Note that the case in which the detected capacitance C is significantly smaller than the reference capacitance Cr is not directly relevant to this embodiment, and therefore its explanation will be omitted.

The ECU 10 determines that the handle SW is in the holding state when the detected capacitance C in the current cycle exceeds the holding judgment threshold Chth in the same cycle, and the ECU 10 determines that the steering wheel SW is in the holding state when the detected capacitance C is less than the holding judgment threshold Chth. A retention determination is made by determining that the SW is in a non-retention state.

Here, in a conventional steering wheel SW (a steering wheel SW in which a capacitance sensor is installed only in a part of the circumferential direction), the driver holds the sensor-free portions A1 and A2 of the steering wheel SW. In this case, since the detected capacitance C is less than or equal to the holding determination threshold Chth, the holding determining device erroneously determines that the handle SW is in the non-holding state and continues updating the reference capacitance Cr unnecessarily. During that time, if the holding determination threshold Chth decreases significantly due to external influences such as the vehicle passing directly under a power transmission line or a positively charged object being brought close to the steering wheel SW, then When the capacitance is gone, the relationship "detection capacitance C>holding determination threshold Chth" is established. Once this relationship is established, a situation may occur in which the holding state is continuously determined in the holding determination, resulting in a stuck holding state.

Therefore, in this embodiment, the ECU 10 stops updating the reference capacitance Cr when it is clear that the driver is performing a steering operation based on the steering torque Ts obtained from the steering torque sensor 12. This structure suppresses the occurrence of a stuck state. Furthermore, the ECU 10 is configured to stop updating the reference capacitance Cr for a predetermined time T even if the driver may have changed the operating direction of the steering wheel SW. It is now possible to more reliably suppress the occurrence of A detailed explanation will be given below with reference to FIG. 3.

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

At a predetermined timing, the CPU starts the process from step 300 and proceeds to step 310 to check whether the capacitance C has been detected (that is, to obtain the detected capacitance C from the capacitance sensor 11). (whether or not). If the detected capacitance C has not been acquired (step 310: No), the CPU advances the process to step 395 and temporarily ends this routine. On the other hand, if the detected capacitance C is obtained (step 310: Yes), the CPU advances the process to step 320.

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

Subsequently, the CPU advances the process to step 340 and stops updating the reference capacitance Cr. Thereafter, the CPU advances the process to step 395 and temporarily ends this routine.

On the other hand, if the absolute value of the steering torque Ts is less than the steering torque threshold Tsth at step 320 (step 320: No), the CPU determines that the steering operation is not being performed (no operation state), The process proceeds to step 350, where it is determined whether the value of the steering operation flag Fs is "1" (that is, whether a steering operation was 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 advances the process to step 360. Note that the value of the steering operation flag Fs is set to "0" when the ignition switch is turned on.

In step 360, the CPU performs a predetermined process after |steering torque Ts|<steering torque threshold Tsth (more specifically, after the relationship |Ts|≧Tsth changes to |Ts|<Tsth). It is determined whether the time T has elapsed. The time T is a value for determining whether there is a high possibility that the driver has stopped the steering operation, and can be set in advance by experiment or simulation. If the time T has not yet elapsed since |Ts| , the driver may have switched the operating direction of the steering wheel SW), and the process proceeds to step 340. The processing at step 340 is as described above.

On the other hand, if the time T has elapsed since |Ts| . In step 370, the CPU resumes updating 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.

On the other hand, if the value of the steering operation flag Fs is "0" at step 350 (step 350: No), the CPU determines that no steering operation has been performed since the ignition switch was turned on, or that no steering operation has been performed in the past. It is determined that time T has elapsed since the steering operation was stopped although the steering operation was being performed, and the process proceeds 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.

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 Tsth, updating of the reference capacitance Cr is stopped. That is, when the driver holds the non-sensor installed portions A1 and A2 of the steering wheel SW and performs a steering operation, updating of the reference capacitance Cr is stopped. Therefore, it is possible to prevent the reference capacitance Cr from being updated unnecessarily even though the driver is holding the handle SW. As a result, it is possible to reduce the possibility that the retention determination threshold Chth will be significantly reduced due to external influences, making it difficult for the detection capacitance C to exceed the retention determination threshold Chth, and suppressing the occurrence of a retention stuck state. .

In particular, in this embodiment, updating of the reference capacitance Cr is also stopped when the time T has not yet elapsed since the relationship |Ts|≧Tsth changed to the relationship |Ts|<Tsth. When the driver changes the operating direction of the steering wheel SW during steering operation, the absolute value of the steering torque Ts decreases temporarily, but by setting the time T to an appropriate value, the operating direction of the steering wheel SW can be changed. When switching the reference capacitance Cr, unnecessary updating of the reference capacitance Cr can be suppressed. As a result, the occurrence of a stuck holding state can be more reliably suppressed.

FIG. 4 shows a time chart comparing the determination result of the holding determination of the present embodiment device with that of a conventional steering wheel retention determination device (hereinafter also simply referred to as "conventional device"). In the example of FIG. 4, it is assumed that the driver is holding the sensor-free portions A1 and A2 of the steering wheel SW. In FIG. 4, from top to bottom, the absolute value of the steering torque Ts, the steering operation determination (see step 320 in FIG. 3), the detection capacitance C, the reference capacitance Crp of the conventional device, the retention determination result of the conventional device, and the main The reference capacitance Cr of the implementation device and the holding determination result of the implementation device are shown in time charts based on capacitance and steering torque (both will be described later), respectively.

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|), the torque changes from |Ts| (see solid line)≧Tsth to |Ts|<Tsth at time t3. As a result, in the second time chart (steering operation determination), the steering operation determination result changes from the operated state to the non-operated state at time t3.

Further, in this example, the own vehicle passes directly under the power transmission line from time t1 to time t2, and is therefore affected by external influences. Therefore, in the third time chart (detected capacitance C), the detected capacitance C remains flat until time t1, gradually decreases from time t1 to time t2, and after time t2 is increasing. In this example, the driver holds the sensor-free parts A1 and A2 of the steering wheel SW, so in the fourth time chart (reference capacitance Crp of the conventional device), during the period under external influence, As the reference capacitance Crp is updated, its value gradually decreases. Along with this, the retention determination threshold Chpth (see the third time chart) of the conventional device is also gradually decreasing. Then, when the detected capacitance C exceeds the holding determination threshold 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 Chpth maintains a constant value for a predetermined period (see the third time chart). In addition, according to the third time chart, at time t2, C≦Chpth changes to C>Chpth, so in the fifth time chart (results of holding judgment of the conventional device), until time t2, the handle SW is is determined to be in the non-holding state, and it is determined that the handle SW is in the held state for a predetermined period from time t2.

In the conventional device, when a predetermined period has elapsed from time t2, updating of the reference capacitance Crp is restarted. According to the third time chart, since there is no particular external influence at the time of restarting the update, the detected capacitance C exceeds the retention determination threshold Chpth. Therefore, the conventional device once again determines that the handle SW is in the holding state (see the fifth time chart) and stops updating the reference capacitance Crp for a predetermined period (the fourth time chart). (see chart). Thereafter, as this situation occurs continuously, the conventional device is stuck in a holding state (see the fifth time chart).

On the other hand, in the sixth time chart (reference capacitance Cr of the present device), the present device does not operate until time t3 based on the determination result of the steering operation (see the second time chart). Stop updating the reference capacitance Cr. This prevents the reference capacitance Cr from being updated unnecessarily during a period under external influence. Further, at time t3, updating of the reference capacitance Cr is stopped for a time T (a value larger than the time from time t3 to the end point of the time chart). Accordingly, the retention 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, the detected capacitance C remains below the holding judgment threshold Chth, so in the seventh time chart (the holding judgment result based on the capacitance of this device), the handle SW is is determined to be in a non-retention state. This suppresses the occurrence of a stuck holding state. Note that since this retention determination is based on the detected capacitance C, it will also be referred to as "capacitance-based retention determination" below.

In this embodiment, in addition to the capacitance-based retention determination, as shown in the eighth time chart, the steering torque-based retention determination is also performed. In this retention determination, if it is determined that the steering wheel SW is being operated based on the second time chart (i.e., the steering operation determination in step 320 in FIG. 3), it is determined that the steering wheel SW is in the retention state. If it is determined that the steering wheel SW is not being steered, it is determined that the steering wheel SW is not held. The present embodiment makes a final determination that the handle SW is in the held state when it is determined that the handle SW is in the held state in at least one of the capacitance-based holding determination and the steering torque-based holding determination. According to this configuration, in addition to being able to suppress the occurrence of a stuck holding state, when the driver is holding the non-sensor installed portions A1 and A2 of the steering wheel SW, it is incorrectly determined that the steering wheel SW is in the non-holding state. It can also be suppressed.

Although the steering wheel holding determination device according to the embodiment has been described above, the present invention is not limited to the above embodiment, and various changes can be made without departing from the purpose of the present invention.

For example, the process of stopping the update of the reference capacitance Cr for the time T after the relationship of |Ts|≧Tsth changes to the relationship of |Ts|<Tsth (the process of steps 350 to 370 in FIG. 3) is not performed. You don't have to. That is, if the determination in step 320 is "No", the process in step 380 may be performed directly. Generally, the time required to switch the operating direction of the handle SW is short, so there is a low possibility that it will be affected by an external influence during the relevant period, and even if it is affected by an external influence, the holding judgment threshold Chth will not change during the relevant period. It is unlikely that there will be a significant decline during this period. Therefore, this configuration can also provide the same effects as the embodiment.

10: Steering ECU 10, 11: Capacitance sensor, 12: Steering torque sensor

Claims (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 that 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 elapses;
Determining whether the steering wheel is in a holding state held by the driver based on whether the detected capacitance exceeds a holding judgment threshold calculated based on the reference capacitance. a control unit configured to make a retention determination;
A steering wheel retention determination device comprising:
The control unit includes:
If the detection capacitance is detected and the steering input value is equal to or greater than a predetermined steering input threshold, stopping updating of the reference capacitance;
configured as,
Steering handle retention determination device.

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