Steering system

Abstract

To improve the robustness of steering wheel grip detection against environmental changes. [Solution] The steering device 50 includes sensor units 13L and 13R, which include sensors 13L1 to 13L6 and 13R1 to 13R6 that detect contact or proximity of a human body in a plurality of detection target areas provided on the steering wheel, and a grip determination unit 112 that compares the output values ​​of the sensor units 13L and 13R with a determination threshold to determine whether or not the steering wheel is being gripped. The electrodes SL1 to SL6 and SR1 to SR6 of the sensors 13L1 to 13L6 and 13R1 to 13R6 include a pair of electrodes that are arranged so that their detection target areas overlap and have different surface areas. The grip determination unit 112 calculates the moving average of the detection values ​​of each electrode in the pair, and further compares the sum of the moving averages of each electrode in the pair with the determination threshold as the output values ​​of the sensor units 13L and 13R.

Description

Technical Field

[0001] The present invention relates to a steering device having a function of detecting the grip of a steering wheel by an occupant.

Background Art

[0002] In recent years, efforts have been actively made to provide access to a sustainable transport system that takes into account people in vulnerable positions among traffic participants. Toward this realization, research and development have focused on further improving traffic safety and convenience through research and development of driving support technologies. Conventionally, there has been known a device that compares a detection value of a capacitance sensor provided on a steering wheel with a threshold value to determine whether a human body is in contact with the steering wheel (see, for example, Patent Document 1). In the device described in Patent Document 1, in order to suppress a decrease in detection accuracy due to deterioration of the capacitance sensor or the like, a correction value is calculated based on a moving average value of detection values for a predetermined number of most recent times including the current detection value, and the current detection value is corrected using the correction value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, simply correcting the detection value using a correction value as in the device described in Patent Document 1 may cause a decrease in detection accuracy when the environment (for example, humidity) changes.

Means for Solving the Problems

[0005] A steering device according to one aspect of the present invention includes a sensor unit including a plurality of sensors that detect contact or proximity of a human body in a plurality of detection target areas provided on the steering wheel, and a determination unit that compares the output value of the sensor unit with a determination threshold to determine whether or not the steering wheel is being gripped. The plurality of sensors have a plurality of electrodes. The plurality of electrodes include a pair of electrodes that are arranged so that their detection target areas overlap and have different surface areas. The determination unit calculates the moving average of the detection values ​​of each of the pair of electrodes according to a predetermined number of terms for each of the pair of electrodes, and further compares the sum of the moving averages of each of the pair of electrodes with the determination threshold as the output value of the sensor unit. [Effects of the Invention]

[0006] According to the present invention, the robustness of the steering wheel grip detection against environmental changes can be improved. [Brief explanation of the drawing]

[0007] [Figure 1A] A front view of a steering wheel to which a steering device according to an embodiment of the present invention is applied. [Figure 1B] Figure 1A shows an example of electrodes embedded in the spokes of the steering wheel. [Figure 2A] A diagram showing an example of an electrode unit including electrodes. [Figure 2B] A perspective view of the steering wheel hub in Figure 1A. [Figure 3] A block diagram showing the main components of a steering device according to an embodiment of the present invention. [Figure 4] Figure 1A shows what happens when a beverage is spilled on the steering wheel. [Figure 5] Figure 3 shows an example of the configuration of a driver assistance system equipped with a steering device. [Figure 6] A flowchart showing an example of the processing performed by the controller's CPU in Figure 3. [Modes for carrying out the invention]

[0008] The embodiments of the invention will now be described with reference to the drawings. Figure 1A is a front view of a steering wheel to which the steering device according to an embodiment of the present invention is applied. The steering device according to an embodiment of the present invention can be applied to a manually driven vehicle equipped with a driver assistance system such as ADAS (Advanced driver-assistance systems). The vehicle to which the steering device according to this embodiment is applied may be referred to as "the vehicle" to distinguish it from other vehicles. The steering wheel 2 in Figure 1A is operated by the driver in the driver's seat of the vehicle. In a front view (as seen from the driver's perspective), a steering shaft 3 that pivotally supports the steering wheel 2 is connected to the rear side of the steering wheel 2.

[0009] For convenience, the two orthogonal axis directions shown in the diagram are defined as the left-right direction and the up-down direction. Furthermore, the front side of the steering wheel 2 is defined as the front, and the rear side as the rear. The configuration of each part will be described below according to these definitions. The left-right direction corresponds to the left-right direction of the vehicle. The up-down direction corresponds to the up-down direction of the steering wheel 2 in a front view. Note that the up-down and up-down directions are not necessarily the same as the up-down and up-down and front-back directions of the vehicle.

[0010] As shown in Figure 1A, the steering handle 2 is an irregularly shaped handle and comprises a hub portion 21, a rim portion (grip portion) 22, and spoke portions 23 connecting the hub portion 21 and the rim portion 22. The rim portion 22 includes a pair of left and right rim portions (vertical portions) 22L, 22R extending substantially vertically to the left and right of the hub portion 21, and a horizontal portion 22H extending substantially horizontally below the hub portion 21 and connecting the rim portions (vertical portions) 22L, 22R. The spoke portion 23 includes horizontal portions 23L, 23R connecting the hub portion 21 and the rim portions (vertical portions) 22L, 22R, and a vertical portion 23V connecting the hub portion 21 and the horizontal portion 22H. The rim portion (vertical portion) 22L is provided such that its end portion 24L protrudes above the connection portion 25L between the spoke portion (horizontal portion) 23L and the rim portion (vertical portion) 22L. Similarly, the rim portion (vertical portion) 22R is provided such that its end portion 24R protrudes above the connection portion 25R between the spoke portion (horizontal portion) 23R and the rim portion (vertical portion) 22R.

[0011] As shown in Figure 1A, the spoke sections 23L and 23R are each provided with operation console units (hereinafter also referred to as function switch units) 5L and 5R, respectively, for the driver to operate vehicle auxiliary equipment (navigation system, audio system, air conditioning system, etc.) and ADAS functions (not shown). The driver can operate the vehicle auxiliary equipment, etc., by operating the multiple switches provided on the operation console units 5L and 5R with their fingers.

[0012] Figure 1B shows an example of electrodes for a capacitance sensor built into the spoke. For clarity of the drawing, the operation console units 5L and 5R are omitted in Figure 1B. The hub section 21 incorporates conductive, plate-shaped electrodes SL1 to SL6 and SR1 to SR6. Electrodes SL1 to SL6 are located near the recommended gripping area HL for the left hand, defined for the rim section 22 of the steering handle 2. As shown in Figure 1B, electrodes SL1 and SL4 are located along the upper left side wall of the hub section 21. Electrodes SL2 and SL5 are located along the left side wall of the hub section 21. Electrodes SL3 and SL6 are located along the lower left side wall of the hub section 21. Region RL1 represents the detection area for electrodes SL1 and SL4. Region RL2 represents the detection area for electrodes SL2 and SL5. Region RL3 represents the detection area for electrodes SL3 and SL6. As shown in Figure 1B, electrodes SL1 to SL6 are positioned so that the detection target areas RL1 to RL3 cover the entire recommended gripping area HL.

[0013] Electrodes SR1 to SR6 are positioned near the recommended gripping area HR for the right hand, defined for the rim portion 22 of the steering handle 2. As shown in Figure 1B, electrodes SR1 and SR4 are positioned along the upper right side wall of the hub portion 21. Electrodes SR2 and SR5 are positioned along the right side wall of the hub portion 21. Electrodes SR3 and SR6 are positioned along the lower right side wall of the hub portion 21. Region RR1 represents the detection target area for electrodes SR1 and SR4. Region RR2 represents the detection target area for electrodes SR2 and SR5. Region RR3 represents the detection target area for electrodes SR3 and SR6. As shown in Figure 1B, electrodes SR1 to SR6 are positioned such that detection target areas RR1 to RR3 cover the entire recommended gripping area HR.

[0014] Electrodes SL1-SL6 and SR1-SR626 are connected via signal lines (not shown) to the gripping sensors 13L1-13L6 and 13R1-13R6 of the sensor units 13L and 13R shown in Figure 3, which will be described later. (These sensors may be simply referred to as sensors below.)

[0015] Here, electrodes SL1-SL6 and SR1-SR6 will be explained in detail using Figures 2A and 2B. Figure 2A shows an example of an electrode unit RU including electrodes SR1-SR6. In Figure 2A, the shaded area is the joint between electrode SR1 and electrode SR2, and also functions as a mounting part for fixing the electrode unit RU to the hub 21. Note that the electrode unit LU (not shown), which includes electrodes SL1-SL6, is the same as the electrode unit RU in Figure 2A, so only the configuration of the electrode unit RU will be explained below. Figure 2B is a perspective view of the hub 21 of the steering wheel 2. In Figure 2B, the electrode unit RU built into the hub 21 is shown by a dashed line. Note that for the sake of readability, the operation console units 5L and 5R are omitted in Figure 2B. Also, in Figure 2B, the electrode unit LU built into the left side of the hub 21 is omitted.

[0016] Electrodes SR4, SR5, and SR6 are positioned such that their detection ranges (detection target areas) are approximately the same as those of electrodes SR1, SR2, and SR3. Specifically, as shown in Figures 2A and 2B, electrodes SR4, SR5, and SR6 are positioned adjacent to electrodes SR1, SR2, and SR3 such that, when built into the hub portion 21, their distance from the rim portion 22 of the steering handle 2 is approximately the same as that of electrodes SR1, SR2, and SR3. Hereafter, the positional relationship between electrodes SR1, SR2, and SR3 and electrodes SR4, SR5, and SR6 as shown in Figure 2A will be referred to as a paired arrangement.

[0017] Figure 3 is a block diagram showing the main components of the steering device according to this embodiment. As shown in Figure 3, the steering device 50 includes a controller 10, sensor units 13L and 13R, a steering torque sensor (hereinafter simply referred to as a torque sensor) 14, a communication unit 15, and an output device 16. The communication unit 15 connects the steering device 50 to a communication network such as CAN (Controller Area Network). The steering device 50 can communicate with in-vehicle devices (not shown) via CAN communication or the like through the communication unit 15. The steering device 50 may also be able to communicate with in-vehicle devices or external devices (not shown) via a wireless communication network.

[0018] The sensor unit 13L has gripping sensors 13L1 to 13L6 respectively connected to the electrodes SL1 to SL6 in FIG. 1B via signal lines not shown. The sensor unit 13R has gripping sensors 13R1 to 13R6 respectively connected to the electrodes SR1 to SR6 in FIG. 1B via signal lines not shown. The gripping sensors 13L1 to 13L6 and 13R1 to 13R6 respectively detect the electrical characteristics (for example, the capacitance between the electrode and the ground (for example, the vehicle body)) of the electrodes SL1 to SL6 and SR1 to SR6.

[0019] The torque sensor 14 detects the torque around the rotation axis of the steering handle 2 input by the driver, that is, the steering torque.

[0020] The output device 16 is a general term for devices that output information to the driver. The output device 16 includes a display that provides information to the driver via a display image, a speaker that provides information to the driver by voice, and the like.

[0021] By the way, capacitance sensors such as the gripping sensors 13L1 to 13L6 and 13R1 to 13R6 have the characteristic that their detection sensitivity increases due to water or moisture. FIG. 4 is a diagram showing a state when a beverage spills on the steering handle 2. FIG. 4 shows a state where the beverage WR spills from the container (can) CA to the end portion 24R. Hereinafter, as shown in FIG. 4, the situation where the steering handle 2 gets wet when a liquid such as water splashes on it is expressed as the steering handle 2 being wetted.

[0022] When the steering wheel 2 is submerged in water, the electrodes corresponding to the submerged area will have increased detection sensitivity due to the above-mentioned characteristics. In the example shown in Figure 4, the electrodes SR1 and SR4 corresponding to the submerged area RR1 will have increased detection sensitivity. Therefore, when determining whether the steering wheel 2 is being gripped based on the magnitude of the output value (electrode capacitance) of the capacitance sensor, if the steering wheel 2 is submerged in water, there is a risk that it may be incorrectly determined that the steering wheel 2 is being gripped even though it is not. Furthermore, if the electrodes of the capacitance sensor themselves are submerged in water, a normal output value cannot be obtained from the capacitance sensor, and it becomes impossible to perform a grip determination on the steering wheel 2. To address these problems, in this embodiment, the controller 10 of the steering device 50 is configured as follows.

[0023] The controller 10 includes a processing unit 11 such as a CPU (microprocessor) and a storage unit 12. The processing unit 11 has a functional configuration that includes a water exposure detection unit 111, a gripping detection unit 112, and a notification unit 113. The storage unit 12 stores information such as programs for various controls and thresholds used in the programs.

[0024] The water exposure detection unit 111 determines whether or not water has been exposed to electrodes SL1 to SL6 and SR1 to SR6 based on the output values ​​of the gripping sensors of sensor units 13L and 13R.

[0025] In a capacitance sensor, the smaller the electrode area (surface area of ​​the electrode), the larger the ratio of electrode area to moisture content. Therefore, electrodes with smaller surface areas are more susceptible to water exposure. The water exposure detection unit 111 monitors the capacitance of electrodes SL4, SL5, and SL6, which have small surface areas, to determine whether or not water has entered the electrode unit LU.

[0026] Specifically, the water exposure detection unit 111 determines that the electrode corresponding to a gripping sensor has been exposed to water when the output value of any of the gripping sensors 13L4 to 13L6 included in the output value of the sensor unit 13L is greater than or equal to a predetermined value PC. The predetermined value PC may be set to a value indicating an abnormality (detection error) of the gripping sensor, or it may be set to any other value.

[0027] Furthermore, the water exposure detection unit 111 monitors the capacitance of electrodes SR4, SR5, and SR6, which have small surface areas, to determine whether or not the electrode unit RU is exposed to water. The determination of whether or not the electrode unit RU is exposed to water is the same as the determination of whether or not the electrode unit LU is exposed to water.

[0028] Furthermore, if electrodes SL4, SL5, and SL6 are exposed to water, it is assumed that electrodes SL1, SL2, and SL3, which are positioned opposite them, are also exposed to water. Similarly, if electrodes SR4, SR5, and SR6 are exposed to water, it is assumed that electrodes SR1, SR2, and SR3, which are positioned opposite them, are also exposed to water. Therefore, the water exposure determination unit 111 determines that if the output value of any of the gripping sensors 13L4~13L6 and 13R4~13R6 is greater than or equal to a predetermined value PC, then both the electrode corresponding to that gripping sensor and the electrode positioned opposite it are exposed to water.

[0029] The grip determination unit 112 detects whether or not a human body is in contact with the detection target areas RL1~RL3 and RR1~RR3 based on whether or not the output values ​​of the sensor units 13L and 13R are equal to or greater than the determination threshold C_Th. If the grip determination unit 112 detects human body contact with any of the detection target areas RL1~RL3 and RR1~RR3, it determines that the steering wheel 2 is being gripped by the driver.

[0030] Capacitive sensors can store more capacitance the larger their electrode area, and therefore, the larger the electrode area, the greater the fluctuation in output values ​​in response to changes in humidity and moisture. Such fluctuations in output values ​​may reduce the accuracy of the gripping determination by the gripping determination unit 112. Therefore, the gripping determination unit 112 calculates the output values ​​of the sensor units 13L and 13R, which are used for comparison with the determination threshold C_Th, as follows.

[0031] First, the gripping determination unit 112 calculates the moving averages ma_l1 and ma_l4 of the output values ​​of a pair of electrodes SL1 and SL4, respectively, according to a predetermined number of terms for each electrode. The number of terms in the moving average is determined based on the electrode area. Specifically, electrodes with larger surface areas have a larger number of terms in the moving average. Similarly, the gripping determination unit 112 calculates the moving averages ma_l2 and ma_l5 of the output values ​​of a pair of electrodes SL2 and SL5, and the moving averages ma_l3 and ma_l6 of the output values ​​of a pair of electrodes SL3 and SL6.

[0032] Next, the gripping determination unit 112 calculates the sum of moving averages ma_l1 and ma_l4, sm_l1, the sum of moving averages ma_l2 and ma_l5, and sm_l3, respectively. The gripping determination unit 112 acquires the sums sm_l1, sm_l2, and sm_l3 as output values ​​for the sensor unit 13L.

[0033] The gripping determination unit 112 compares the output value of the sensor unit 13L obtained in this manner with the determination threshold C_Th to detect whether or not there is human body contact with the detection target areas RL1 to RL3, i.e., human body contact with the recommended gripping area HL. When the total value sm_l1 is equal to or greater than the determination threshold C_Th, human body contact with the detection target area RL1 is detected. Similarly, when the total value sm_l2 is equal to or greater than the determination threshold C_Th, human body contact with the detection target area RL2 is detected, and when the total value m_l3 is equal to or greater than the determination threshold C_Th, human body contact with the detection target area RL3 is detected.

[0034] The grip determination unit 112 similarly detects whether or not there is contact of a human body with the detection target areas RR1 to RR3, that is, with the recommended grip area HR. If the grip determination unit 112 detects contact of a human body with either the recommended grip area HL or HR, it determines that the steering wheel 2 is being gripped by the driver.

[0035] Furthermore, if proximity of a human body to the recommended gripping areas HL and HR (approaching motion within a predetermined distance) is detected, it can be determined that the driver is in a state where they can immediately grip the steering wheel 2. Therefore, the gripping determination unit 112 may also determine that the steering wheel 2 is being gripped by the driver if proximity of a human body to either of the recommended gripping areas HL or HR is detected. In other words, the gripping determination unit 112 may determine that the steering wheel 2 is being gripped by the driver if it detects contact or proximity of a human body to either of the recommended gripping areas HL or HR. When contact or proximity to the recommended gripping areas HL and HR is detected, the determination threshold C_Th is set to a smaller value than when only contact to the recommended gripping areas HL and HR is detected.

[0036] The notification unit 113 generates information indicating the gripping state (hereinafter referred to as gripping state information) based on the determination results of the water exposure determination unit 111 and the gripping determination unit 112. When the gripping determination unit 112 determines that the steering handle 2 is being gripped, the notification unit 113 generates gripping state information indicating "Grip (Normal)" as the gripping state. When the gripping determination unit 112 determines that the steering handle 2 is not being gripped, the notification unit 113 generates gripping state information indicating "Not Gripped" as the gripping state. Furthermore, when the water exposure determination unit 111 determines that the electrode of any of the gripping sensors 13L4~13L6, 13R4~13R6 has been exposed to water, the notification unit 113 generates gripping state information indicating "Grip Determination Impossible" as the gripping state. The notification unit 113 outputs the generated gripping state information to the output device 16 mounted on the vehicle.

[0037] Furthermore, when the notification unit 113 generates gripping status information indicating "not gripping," it may include warning information in the gripping status information prompting the driver to grip the steering wheel 2. The warning information may include display information and audio information output to a display or speaker, as well as signals to illuminate or flash warning lights provided on or around the steering wheel 2 (instrument panel, etc.). The notification unit 113 may also output the gripping status information to an in-vehicle device or an external device via the communication unit 15.

[0038] Figure 5 shows an example of the configuration of a driver assistance system 1 equipped with a steering device 50 according to this embodiment. As shown in Figure 5, the driver assistance system 1 comprises a steering device 50 and a driver assistance device 70, which is one of the in-vehicle devices. The steering device 50 is connected to the driver assistance device 70 via a CAN bus 60 so as to be able to communicate.

[0039] The driver assistance system 70 is comprised of an electronic control unit (ECU). The driver assistance system 70 includes a calculation unit 71 such as a CPU (microprocessor) and a storage unit 72. Functionally, the calculation unit 71 has a driving control unit 711. The storage unit 72 stores information such as programs for various controls and thresholds used in the programs. The driving control unit 711 controls driving actuators (not shown) based on information obtained from on-board sensors (such as camera images). Driving actuators include a throttle actuator that adjusts the opening degree of the engine's throttle valve (throttle opening), a brake actuator that operates the vehicle's braking system, and a steering actuator that drives the steering system.

[0040] The driver assistance system 70 has various driver assistance functions such as LKAS and ACC (Adaptive Cruise Control). When LKAS is enabled, the driving control unit 711 recognizes the lane markings that define the vehicle's lane based on information obtained from on-board sensors and controls the steering actuator so that the vehicle travels near the center of its lane.

[0041] At this time, the driving control unit 711 acquires grip state information output from the notification unit 113 of the steering device 50 via the CAN bus 60, and recognizes the grip state of the steering wheel 2 based on the grip state information. When the driving control unit 711 recognizes that the driver is not gripping the steering wheel 2, it temporarily stops the driving assistance (steering assistance) by LKAS. If the driver is not gripping the steering wheel 2 for a predetermined time, the driving control unit 711 cancels the steering assistance. If the driver is recognized to be gripping the steering wheel 2 before the predetermined time has passed, the temporarily stopped steering assistance is restarted. In this way, the grip state information output from the steering device 50 is used to control the driving assistance functions of the driving assistance device 70, such as temporarily stopping, restarting, and canceling them.

[0042] Figure 6 is a flowchart showing an example of a process executed by the CPU of the controller 10 in Figure 3 according to a predetermined program. The process shown in this flowchart is executed at predetermined intervals, for example, when the vehicle is in motion.

[0043] First, in step S1, the controller 10 acquires the output values ​​of the gripping sensors 13L1 to 13L6 and 13R1 to 13R6. The acquired output values ​​are stored in the memory unit 12 for a certain period of time.

[0044] In step S2, the controller 10 selects the sensor unit to be processed (hereinafter referred to as the target sensor unit). Once the target sensor unit is selected, in step S3, the controller 10 determines whether or not the electrodes of the gripping sensor included in the target sensor unit have been exposed to water.

[0045] If sensor unit 13L is selected as the target sensor unit, the controller 10 compares the output values ​​of gripping sensors 13L4 to 13L6 with a predetermined value PC. If the output value of any of the gripping sensors 13L4 to 13L6 is greater than or equal to the predetermined value PC, the controller 10 determines that the electrode corresponding to that gripping sensor and the electrode positioned opposite it have been exposed to water. For example, if the output value of gripping sensor 13L5 is greater than or equal to the predetermined value PC, it is determined that electrodes SL2 and SL5 have been exposed to water.

[0046] On the other hand, if sensor unit 13R is selected as the target sensor unit, the controller 10 compares the output values ​​of gripping sensors 13R4 to 13R6 with a predetermined value PC. If the output value of any of the gripping sensors 13R4 to 13R6 is greater than or equal to the predetermined value PC, the controller 10 determines that the electrode corresponding to that gripping sensor and the electrode positioned opposite it have been exposed to water. For example, if the output value of gripping sensor 13R4 is greater than or equal to the predetermined value PC, it is determined that electrodes SR1 and SR4 have been exposed to water.

[0047] If the result in step S3 is positive, that is, if it is determined that the electrodes of the gripping sensor included in the target sensor unit have been exposed to water, in step S4 the controller 10 generates gripping status information indicating "Gripping not possible".

[0048] On the other hand, if the process is rejected in step S3, in step S5, the controller 10 selects a pair of sensors to be processed (hereinafter referred to as the target sensors) from among the gripping sensors included in the target sensor unit.

[0049] In step S6, the controller 10 calculates the moving average of the output values of a pair of sensors selected as the target sensors, and determines whether the total value thereof is equal to or greater than the determination threshold value C_Th. For example, when the gripping sensors 13L1 and 13L4 of the sensor unit 13L are selected as the target sensors, the controller 10 calculates the moving averages ma_l1 and ma_l4 of the output values of the gripping sensors 13L1 and 13L4. The moving average ma_l1 is the average of the output values for the most recent n times including the current output value of the gripping sensor 13L1. The moving average ma_l4 is the average of the output values for the most recent m (<n) times including the current output value of the gripping sensor 13L4. As described above, the number of terms n is determined based on the size of the surface area of the electrode SL1 of the gripping sensor 13L1. The number of terms m is determined based on the size of the surface area of the electrode SL4 of the gripping sensor 13L4. When the moving averages ma_l1 and ma_l4 are calculated, the controller 10 determines whether the total value sm_l2 thereof is equal to or greater than the determination threshold value C_Th.

[0050] If it is affirmed in step S6, in step S7, the controller 10 determines that the steering wheel 2 is being gripped by the driver, and generates gripping state information indicating "gripping (normal)". On the other hand, if it is negated in step S6, in step S8, the controller 10 determines whether or not the process (the process in step S6) has been performed on all the sensors (a pair of sensors) included in the target sensor unit.

[0051] If it is affirmed in step S8, in step S9, the controller 10 determines whether or not the process (gripping determination) has been performed on all the sensor units. On the other hand, if it is negated in step S8, that is, when there is an unprocessed sensor among the gripping sensors included in the target sensor unit, the controller 10 returns to the process in step S5, selects a pair of sensors to be processed from among the unprocessed sensors, and repeats the process in step S6.

[0052] If step S9 is rejected, that is, if there are unprocessed sensor units, the process returns to step S2, a sensor unit to be processed is selected from the unprocessed sensor units, and steps S3 to S8 are repeated.

[0053] On the other hand, if the result in step S9 is positive, in step S10 the controller 10 determines that the steering wheel 2 is not being held by the driver and generates gripping status information indicating "not held". Finally, in step S11 the controller 10 outputs the gripping status information generated in step S4, S7, or S10 to the output device 16 and terminates the process.

[0054] In step S2, the controller 10 selects the target sensor units in the order of sensor unit 13L, then sensor unit 13R. However, the selection order of the target sensor units is not limited to this.

[0055] Furthermore, if sensor unit 13L is selected as the target sensor unit, the controller 10 selects the target sensors in step S5 in the order of gripping sensors 13L1, 13L4, gripping sensors 13L2, 13L4, and gripping sensors 13L3, 13L6. On the other hand, if sensor unit 13R is selected as the target sensor unit, the controller 10 selects the target sensors in step S5 in the order of gripping sensors 13R1, 13R4, gripping sensors 13R2, 13R4, and gripping sensors 13R3, 13R6. However, the selection order of the target sensors is not limited to this.

[0056] According to the embodiments described above, the following effects and advantages can be obtained. (1) The steering device 50 includes sensor units 13L and 13R that include grip sensors 13L1 to 13L6 and 13R1 to 13R6 for detecting contact or proximity of a human body in a plurality of detection target regions RL1 to RL3 and RR1 to RR3 provided on the steering handle 2, and a grip determination unit 112 that compares the output values of the sensor units 13L and 13R with a determination threshold value C_Th to determine whether the steering handle 2 is being gripped. The grip sensors 13L1 to 13L6 and 13R1 to 13R6 have electrodes SL1 to SL6 and SR1 to SR6. The electrodes SL1 to SL6 and SR1 to SR6 are arranged such that the detection target regions thereof overlap each other, and include a pair of electrodes (for example, electrode SL1 and electrode SL4) having different surface areas from each other. The grip determination unit 112 calculates the moving average (for example, moving average ma_l1 and moving average ma_l4) of the detection values (capacitance) of each of the pair of electrodes according to a predetermined number of terms (for example, number of terms n and number of terms m (<n)) for each of the pair of electrodes, and further compares the total value of the moving averages of each of the pair of electrodes (for example, total value sm_l1 (= ma_l1 + ma_l4)) with the determination threshold value C_Th as the output value of the sensor units 13L and 13R. Note that the electrodes SL1 to SL6 and SR1 to SR6 include a plurality of pairs of electrodes with different detection target regions from each other, and the grip determination unit 112 calculates the total value of the moving average for each pair of electrodes, and determines that the steering handle 2 is being gripped when the total value of the moving average of any one of the plurality of pairs of electrodes is equal to or greater than the determination threshold value C_Th.

[0057] In this way, by configuring the sensor electrodes corresponding to each of the plurality of detection target regions arranged on the steering handle 2 with a pair of electrodes having different surface areas from each other, robust grip determination against changes in the environment such as humidity becomes possible. Further, by smoothing the output value of the sensor by moving average, false determination caused by environmental changes can be suppressed, and the robustness against environmental changes can be further improved.

[0058] (2) The gripping determination unit 112 calculates the moving average of the detected values ​​of each electrode in a pair, according to a predetermined number of terms based on the surface area of ​​each electrode in the pair. More specifically, the gripping determination unit 112 determines the number of terms in the moving average of each electrode in a pair, such that the number of terms in the moving average increases as the surface area of ​​the electrode increases. The fluctuation of the output value in response to environmental changes increases as the surface area of ​​the electrode increases, but by determining the number of terms (number of samples) in the moving average according to the surface area of ​​the electrode as described above, gripping can be determined accurately regardless of the size of the surface area of ​​the electrode. On the other hand, the number of samples for electrodes with small surface areas that are less affected by environmental changes can be reduced, thereby reducing the computational load.

[0059] (3) The pair of electrodes includes a first electrode and a second electrode having a smaller surface area than the first electrode. The first and second electrodes are positioned adjacent to each other so that they are approximately the same distance from the rim portion 22 of the steering handle 2. The steering device 50 further includes a water exposure detection unit 111 that determines that the second electrode or the pair of electrodes has been exposed to water when the detection value of the second electrode, which has a smaller surface area, is greater than or equal to a predetermined value PC. This allows for the detection of environmental changes (such as changes in humidity) with the first electrode, which has a larger surface area, while simultaneously enabling early detection of water ingress or condensation on the pair of electrodes with the second electrode, which has a smaller surface area. In this way, by utilizing the characteristics of each electrode with different surface areas, a more appropriate grip determination becomes possible.

[0060] (4) The steering device 50 further includes an output device 16 that outputs information, and a notification unit 113 that notifies the driver via the output device 16 of the information generated based on the determination results of the water exposure determination unit 111 and the grip determination unit 112. This allows the driver to recognize the result of the grip determination. Furthermore, the result of the grip determination can be used for driver assistance functions such as LKAS. As a result, safety during steering can be improved.

[0061] (5) The steering handle 2 includes a hub portion 21, a rim portion (gripping portion) 22 having a pair of left and right vertical portions 22L, 22R extending substantially vertically to the left and right of the hub portion 21, and a horizontal portion 22H extending substantially horizontally below the hub portion 21 and connecting the pair of left and right vertical portions 22L, 22R, and spoke portions 23L, 23R connecting the pair of left and right vertical portions 22L, 22R to the hub portion 21. Sensor units 13L, 13R (more specifically, electrodes of the gripping sensors included in the sensor units 13L, 13R) are arranged in close proximity to function switch portions 5L, 5R for operating vehicle information or driving assistance functions, which are arranged on the left and right sides of the hub portion 21, respectively. By providing sensor units to the function switch portions arranged symmetrically on the hub portion 21 in this way, contact or proximity of the human body to the recommended gripping area arranged symmetrically on the rim portion 22 can be appropriately detected.

[0062] The above embodiment can be modified into various forms. Modifications will be described below. In the above embodiment, the notification unit 113 generates gripping state information that indicates the determination results of the water-exposed determination unit 111 and the gripping determination unit 112, which act as determination units. However, the notification unit may include information other than the above determination results in the gripping state information. For example, when generating gripping state information indicating "not possible to grip" in step S4, the notification unit may include information that can identify the electrode that has been exposed to water in the gripping state information. In addition, the gripping state information may include instruction information (display information, voice information, etc.) that instructs the occupant to wipe the water-exposed area. Furthermore, in the above embodiment, when the driving control unit 711 recognizes that the driver is not gripping the steering wheel 2, it temporarily stops the driving assistance (steering assistance, etc.), and cancels the driving assistance if the non-grip state continues for a predetermined time. However, the driving control unit may temporarily suspend or cancel the driving assistance based on the gripping state information output (transmitted) from the notification unit. For example, when the driving control unit recognizes water exposure to the electrodes based on the gripping state information, it may temporarily suspend or cancel the driving assistance depending on the size of the water-exposed area and the duration of the water-exposed state.

[0063] Furthermore, in the above embodiment, the gripping determination unit 112, acting as a determination unit, calculates a moving average of the detected values ​​(capacitance) of each of the pair of electrodes, compares the sum of these values ​​with a determination threshold C_Th, and determines whether or not the steering handle 2 is being gripped. However, the determination unit may perform the moving average only when the fluctuation (amount of change over a predetermined time) of any of the detected values ​​of electrodes SL1~SL6 and SR1~SR6 exceeds a predetermined level. That is, when the fluctuations of the detected values ​​of electrodes SL1~SL6 and SR1~SR6 are all below a predetermined level, the determination unit may not perform the moving average (set the number of terms in the moving average to 1). The determination unit may also perform the determination of whether or not to perform the moving average as described above using only electrodes SL1~SL3 and SR1~SR3, which have a large surface area and whose detected values ​​are easily affected by environmental changes. This allows for appropriate switching between performing and stopping the moving average. In addition, the determination unit may change the number of terms in the moving average according to the magnitude of the fluctuation when the fluctuation of any of the detected values ​​of electrodes SL1~SL6 and SR1~SR6 exceeds a predetermined level. Specifically, the greater the fluctuation in the detected values, the larger the number of terms in the moving average may be.

[0064] Furthermore, in the above embodiment, when it is determined that the electrode of any of the gripping sensors 13L4~13L6, 13R4~13R6 has been exposed to water, that is, when the result is confirmed in step S3 of Figure 6, the gripping determination is not performed, and gripping status information indicating "Gripping determination not possible" is generated. However, when the result is confirmed in step S3 of Figure 6, the determination unit may determine whether or not the steering handle 2 is being gripped based on the detected value of the torque sensor 14. The notification unit may then generate gripping status information indicating the result of that determination. In this case, the notification unit may include in the gripping status information that the electrode has been exposed to water and information that can identify the electrode that has been exposed to water.

[0065] Furthermore, in the above embodiment, the sensor units 13L and 13R are configured to detect contact or proximity of a human body to the rim portion 22. However, the sensor units may also detect the gripping force applied to the rim portion 22. In this case, a pressure sensor is built into the rim portion 22, and the sensor unit detects the gripping force applied to the steering handle 2 based on the sensor value obtained from the pressure sensor via a signal line (not shown). The determination unit may determine whether or not the steering handle 2 is being gripped based on the magnitude of the gripping force detected by the pressure sensor, along with the output values ​​of the sensor units 13L and 13R, or instead of the output values ​​of the sensor units 13L and 13R. Note that sensors other than pressure sensors may be used to detect the gripping force applied to the steering handle 2.

[0066] Furthermore, in the above embodiment, the example given was that the controller 10 performs the process shown in Figure 6 while the vehicle is in motion. However, the controller 10 may start the process shown in Figure 6 when it receives a notification from the driver assistance device 70 indicating that a driver assistance function such as LKAS has been activated. Also, the controller 10 may refrain from performing the process shown in Figure 6 when the vehicle's speed is below a predetermined speed. Moreover, the controller 10 may refrain from performing the process shown in Figure 6 when a driver assistance function that does not require the driver to hold the steering wheel 2, such as an automatic parking function (parking assist system), is activated.

[0067] Furthermore, although an irregularly shaped steering wheel was exemplified as the steering wheel 2 in the above embodiment, the present invention can also be applied when using a steering wheel of other shapes (such as an annular shape). In addition, although the steering device 50 was applied to a manually driven vehicle equipped with ADAS in the above embodiment, the steering device 50 can also be applied to an autonomous vehicle.

[0068] The above description is merely an example, and the present invention is not limited by the embodiments and modifications described above, as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and to combine modifications with each other. [Explanation of symbols]

[0069] 1 Driving assistance system, 2 Steering wheel, 10 Controller, 11 Calculation unit, 12 Memory unit, 13L, 13R Sensor unit, 13L1~13L6, 13R1~13R6 Gripping sensors, 14 Torque sensor, 15 Communication unit, 16 Output device, SL1~SL6, SR1~SR6 Electrodes, 70 Driving assistance device, 111 Water exposure detection unit, 112 Gripping detection unit, 113 Notification unit

Claims

1. A sensor unit including multiple sensors that detect human contact or proximity in multiple detection target areas provided on the steering wheel, The system includes a determination unit that compares the output value of the sensor unit with a determination threshold to determine whether or not the steering handle is being held, The aforementioned plurality of sensors have a plurality of electrodes, The plurality of electrodes include a pair of electrodes that are arranged so that their detection target regions overlap and have different surface areas. The steering device is characterized in that the determination unit calculates a moving average of the detected values ​​of each of the pair of electrodes according to a predetermined number of terms for each of the pair of electrodes, and further compares the sum of the moving averages of each of the pair of electrodes with the determination threshold as the output value of the sensor unit.

2. In the steering device according to claim 1, The steering device is characterized in that the determination unit calculates the moving average of the detected values ​​of each of the pair of electrodes according to a predetermined number of terms based on the surface area of ​​each of the pair of electrodes.

3. In the steering device according to claim 2, The steering device is characterized in that the determination unit determines the number of terms in the moving average of each of the pair of electrodes such that the number of terms in the moving average increases as the surface area increases.

4. In the steering device according to claim 1, The plurality of electrodes include a plurality of pairs of electrodes, each having a different detection target area. The steering device is characterized in that the determination unit calculates the sum of the moving averages for each pair of electrodes, and determines that the steering handle is being held when the sum of the moving averages for any pair of electrodes among the plurality of pairs of electrodes is equal to or greater than the determination threshold.

5. In the steering device according to claim 1, The steering device is characterized in that the pair of electrodes includes a first electrode and a second electrode having a smaller surface area than the first electrode, and the first electrode and the second electrode are arranged adjacent to each other such that they are at substantially the same distance from the gripping portion of the steering handle.

6. In the steering device according to claim 5, The steering device is characterized in that the determination unit determines that the second electrode or the pair of electrodes has been exposed to water when the detected value of the second electrode, which has a smaller surface area than the pair of electrodes, is equal to or greater than a predetermined value.

7. In the steering device according to any one of claims 1 to 6, An output device that outputs information, A steering device further comprising a notification unit that notifies the driver of information generated based on the determination result by the determination unit via the output device.

8. In the steering device according to claim 1, Including a plurality of the aforementioned sensor units, The steering handle has a hub portion, a gripping portion having a pair of left and right vertical portions extending substantially vertically to the left and right of the hub portion and a horizontal portion extending substantially horizontally below the hub portion and connecting the pair of left and right vertical portions, and spoke portions connecting the pair of left and right vertical portions and the hub portion. A steering device characterized in that the multiple sensor units are arranged in close proximity to function switch sections for operating vehicle information or driving assistance functions, which are respectively located on the left and right sides of the hub.

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