Steering system

Abstract

To promptly detect a steering operation by a driver and prevent steering operation feeling from deteriorating.SOLUTION: A steering device 1 is configured so as to be automatically perform a steering operation of a steering wheel 10. The steering device 1 determines, based on a steering angle of the steering wheel 10 and a target steering angle, during an operation mode in which at least the steering operation of the steering wheel 10 is performed automatically, that the steering operation of the steering wheel 10 is performed by the driver. When it is determined that the steering operation of the steering wheel 10 has been performed by the driver, the steering device is configured to change operation characteristics of the steering wheel 10 such that the steering force required for the driver to steer the steering wheel 10 before the determination reduces.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a steering device.

Background Art

[0002] Patent Document 1 discloses a conventional vehicle driving control system configured to switch the driving mode to a driving mode that requires a driver's steering operation when it is determined that the driver is trying to hold the steering during a driving mode that does not require a driver's steering operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] During a driving mode that does not require a driver's steering operation, the driver may perform a steering operation of the steering wheel to correct the steering angle. At this time, if the vehicle side cannot detect early enough that the driver has performed a steering operation, the vehicle side may determine the steering input by the driver's steering operation as a disturbance and try to cancel the steering input, which may deteriorate the operation feeling of the steering wheel.

[0005] The present invention has been made paying attention to such problems, and an object thereof is to detect a driver's steering operation early and suppress deterioration of the operation feeling of the steering wheel.

Means for Solving the Problems

[0006] To solve the above problems, a steering device according to one aspect of the present invention is configured to enable automatic steering of the steering wheel. The steering device is configured to determine, at least during a mode in which steering of the steering wheel is performed automatically, whether the steering of the steering wheel was performed by a driver based on the steering angle of the steering wheel and the target steering angle, and when it is determined that the steering of the steering wheel was performed by a driver, to change the operating characteristics of the steering wheel so that the steering force required by the driver to steer the wheel is reduced compared to before the determination. [Effects of the Invention]

[0007] According to this aspect of the present invention, the driver's steering operation can be determined early based on the steering angle of the steering wheel and the target steering angle, and the steering wheel's operating characteristics can be changed so that the steering force required by the driver to steer the wheel is reduced compared to before the determination. Therefore, deterioration of the steering wheel's operating feel can be suppressed. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of a steering device according to the first embodiment of the present invention. [Figure 2] This is a control block diagram illustrating steering control according to the first embodiment of the present invention. [Figure 3] This is a time chart illustrating the effects and benefits of steering control according to the first embodiment of the present invention. [Figure 4] This is a time chart illustrating the effects of steering control according to the second embodiment of the present invention. [Figure 5] Figure 5 is a time chart showing the case when the driver stops the rotation of the steering wheel by holding the steering wheel while in automatic steering driving mode. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following description, similar components will be given the same reference numerals.

[0010] (First Embodiment) Figure 1 is a schematic diagram of the steering device 1 according to the first embodiment of the present invention.

[0011] The steering device 1 according to this embodiment is a device for changing the direction of travel of a vehicle by steering the left and right wheels (hereinafter referred to as "steering wheels") 2 of the vehicle, and comprises a steering wheel 10, a steering shaft 20, a rack and pinion type gear mechanism 30 including a pinion shaft 31 and a rack shaft 32, a link mechanism 40 connecting the gear mechanism 30 and the steering wheels 2, a steering support mechanism 50, and an electronic control unit 60.

[0012] The steering wheel 10 is located in the driver's seat of the vehicle and is operated by the vehicle's driver. When the vehicle's driver operates the steering wheel 10 and rotates it, the steering angle of the steering wheels 2 changes via the steering shaft 20, gear mechanism 30, and linkage mechanism 40, thereby changing the direction of travel of the vehicle.

[0013] The steering shaft 20 is connected at one end to the steering wheel 10 and rotates together with the steering wheel 10, while its other end is connected to the pinion shaft 31 of the gear mechanism 30. The steering shaft 20 is divided into a steering input shaft 20a on the steering wheel 10 side and a steering output shaft 20b on the gear mechanism 30 side, and these are connected by a torsion bar 21 that twists according to the direction and magnitude of the torque ST (hereinafter referred to as "steering torque") applied to the steering shaft 20 from the steering wheel 10.

[0014] The gear mechanism 30 is configured to convert the rotational motion of the pinion shaft 31 into left-right linear motion along the axial direction of the rack shaft 32. One end of the pinion shaft 31 is connected to the steering output shaft 20b and rotates together with the steering shaft 20. A pinion gear is formed on the outer circumferential surface of the other end of the pinion shaft 31. The rack shaft 32 extends left and right approximately parallel to the vehicle width direction, and a rack gear that meshes with the pinion gear is formed on a part of its outer circumferential surface. As a result, when the pinion shaft 31 rotates, the rack shaft 32 moves left and right along the axial direction in accordance with the direction of rotation.

[0015] The link mechanism 40 includes tie rods 41 attached to both ends of the rack shaft 32, and knuckle arms (not shown) connected to each tie rod 41 to support each steering wheel 2, and is configured to transmit the left and right linear motion of the rack shaft 32 to the steering wheels 2, thereby changing their direction (steering angle).

[0016] The steering support mechanism 50 includes an electric motor 51 and a reduction gear 52 that transmits the output of the electric motor 51 to the steering output shaft 20b. The steering support mechanism 50 generates motor torque MT with the electric motor 51 and transmits the motor torque MT to the steering output shaft 20b via the reduction gear 52. The steering support mechanism 50 can reduce the steering force of the steering wheel 10 and automate the steering operation of the steering wheel 10.

[0017] The electronic control unit 60 is a microcomputer equipped with a central processing unit (CPU), memory such as read-only memory (ROM) and random access memory (RAM), input ports, and output ports, all interconnected by a bidirectional bus. The electronic control unit 60 executes various computer programs stored in memory and is configured to automatically perform steering operations of the steering wheel 10, at least in automatic steering driving modes (for example, during autonomous driving or driving assistance such as lane keeping control).

[0018] The electronic control unit 60 receives output signals from a steering angle sensor 61 for obtaining the rotation angle (hereinafter referred to as "steering angle") Θr of the steering wheel 10 during a steering operation, a steering torque sensor 62 for obtaining the steering torque ST, a vehicle speed sensor 63 for obtaining the vehicle speed, a surrounding sensor 64 for obtaining surrounding data representing the situation around the host vehicle, and the like. The surrounding sensor 64 is, for example, one or a plurality of external cameras for photographing the surroundings of the host vehicle. In the present embodiment, when the steering wheel 10 is in the neutral position, the steering angle Θr is set to 0°, the rotation angle in the right direction from the neutral position of the steering wheel 10 is represented by a positive value, and the rotation angle in the left direction from the neutral position of the steering wheel 10 is represented by a negative value.

[0019] The electronic control unit 60 functions as a steering assist unit 70 and a steering determination unit 80 as shown in FIG. 2 by executing processing according to a computer program, and operates as a functional unit (module) that realizes a predetermined function. In the following description, when explaining the processing with each functional unit as the subject, it indicates that the electronic control unit is executing a program that realizes the functional unit. Details of each functional unit 70, 80 will be described later.

[0020] Here, during the above-described automatic steering operation mode, the driver may perform a steering operation of the steering wheel 10 to correct the steering angle. At this time, if the steering device 1 cannot detect the driver's steering operation early, the steering device 1 may determine the steering input by the driver's steering operation as a disturbance and try to cancel the steering input, so that the operation feeling of the steering wheel 10 may deteriorate. Therefore, when detecting the driver's steering operation during the automatic steering operation mode, for example, by weakening the force to cancel the steering input by the driver's steering operation, it is desirable to change the operation characteristics of the steering wheel 10 so that the steering force required for the driver to steer the steering wheel 10 is reduced compared to before the detection of the steering operation.

[0021] As a method of steering determination for determining that a driver's steering operation has been performed during the automatic steering operation mode, for example, there is a method of detecting whether or not the steering torque ST generated by the driver's steering operation has become equal to or greater than a predetermined threshold value. However, there is a time delay between when the driver performs the steering operation and when the steering torque ST is detected. Therefore, in this method, when the driver quickly turns the steering wheel 10, that is, when the driver performs a quick steering (hereinafter referred to as "early steering"), the time from when the steering operation is performed until the steering torque ST reaches the predetermined threshold value tends to be long.

[0022] Therefore, when the driver performs early steering, the time required from when the steering operation is performed until the steering determination tends to be long, and as a result, there is a possibility that the period during which the operation feeling of the steering wheel 10 deteriorates becomes long.

[0023] Therefore, in the present embodiment, even when the driver performs early steering, it is possible to perform the steering determination at an early stage. Hereinafter, the steering control according to the present embodiment will be described with reference to FIG. 2.

[0024] FIG. 2 is a control block diagram for explaining the steering control according to the present embodiment, and is a diagram for explaining the contents of the above-described steering support unit 70 and steering determination unit 80.

[0025] The steering support unit 70 includes an input parameter calculation unit 71, a target steering angle calculation unit 72, a target steering torque calculation unit 73, a steering reaction force coefficient calculation unit 74, an assist torque calculation unit 75, a target motor torque calculation unit 76, and a motor control unit 77.

[0026] The input parameter calculation unit 71 acquires the surrounding data of the host vehicle acquired by the surrounding sensor 64.

[0027] The input parameter calculation unit 71 recognizes the driving lane the vehicle is traveling in based on surrounding data of the vehicle, and calculates input parameters for calculating the target steering angle based on the recognition result. In this embodiment, the input parameter calculation unit 71 calculates the radius of curvature of the driving lane, the amount of lateral displacement of the vehicle's center position from the center line of the driving lane (hereinafter referred to as "the vehicle's offset amount"), and the vehicle's yaw angle with respect to the target driving line (the rotation angle of the vehicle around its vertical axis) as input parameters for calculating the target steering angle. There are no particular limitations on how the target driving line is set; for example, in this embodiment, the center line of the driving lane is set as the target driving line, but the driving trajectory of a preceding vehicle recognized based on surrounding data of the vehicle may also be set as the target driving line.

[0028] The target steering angle calculation unit 72 acquires the input parameters for calculating the target steering angle, the steering judgment result output from the steering judgment result output unit 83 (described later) indicating whether or not steering operations are being performed by the driver (hereinafter referred to as the "steering judgment result"), and the vehicle speed V detected by the vehicle speed sensor 63.

[0029] The target steering angle calculation unit 72 first calculates two types of target steering angles (first target steering angle Θt1 and second target steering angle Θt2) corresponding to the vehicle speed V, based on the input parameters for calculating the target steering angle, in order to drive the vehicle along the target driving line. The first target steering angle Θt1 and second target steering angle Θt2 calculated by the target steering angle calculation unit 72 are such that if the vehicle's driving line deviates from the target driving line, the absolute value of the first target steering angle Θt1 is larger than the absolute value of the second target steering angle Θt2.

[0030] The target steering angle calculation unit 72 then sets either the first target steering angle Θt1 or the second target steering angle Θt2 as the target steering angle Θt based on the steering determination result. Specifically, if the steering determination result is a "no steering determination" indicating that no steering operation has been performed by the driver, the target steering angle calculation unit 72 sets the first target steering angle Θt1 as the target steering angle Θt. On the other hand, if the steering determination result is a "steering determination" indicating that steering operation has been performed by the driver, the target steering angle calculation unit 72 sets the second target steering angle Θt2 as the target steering angle Θt.

[0031] The target steering torque calculation unit 73 obtains the steering angle Θr detected by the steering angle sensor 61 and the target steering angle Θt. Based on the steering angle Θr and the target steering angle Θt, the target steering torque STt is calculated to make the steering angle Θr follow the target steering angle Θt with a desired response.

[0032] The steering reaction coefficient calculation unit 74 acquires the vehicle speed V detected by the vehicle speed sensor 63 and the steering judgment result.

[0033] The steering reaction coefficient calculation unit 74 first calculates two types of steering reaction coefficients (first steering reaction coefficient α1 and second steering reaction coefficient α2) according to the vehicle speed V. The first steering reaction coefficient α1 is set to be smaller than the second steering reaction coefficient α2.

[0034] The steering reaction coefficient calculation unit 74 then sets the first steering reaction coefficient α1 and the second steering reaction coefficient α2 as the steering reaction coefficient α based on the steering determination result. Specifically, if the steering determination result is "no steering determination", the steering reaction coefficient calculation unit 74 sets the first steering reaction coefficient α1 as the steering reaction coefficient α. On the other hand, if the steering determination result is "steering determination", the steering reaction coefficient calculation unit 74 sets the second steering reaction coefficient α2 as the steering reaction coefficient α.

[0035] The assist torque calculation unit 75 obtains the steering torque ST detected by the steering torque sensor 62 and the steering reaction force coefficient α. The assist torque calculation unit 75 calculates the assist torque AT by multiplying the steering reaction force torque corresponding to the steering torque ST by the steering reaction force coefficient α.

[0036] The target motor torque calculation unit 76 obtains the target steering torque STt and the assist torque AT. The target motor torque calculation unit 76 calculates the target motor torque MTt by adding the assist torque AT to the target steering torque STt.

[0037] The motor control unit 77 acquires the target motor torque MTt. The motor control unit 77 controls the motor 51 so that its torque (motor torque) becomes the target motor torque MTt. As a result, the steering angle Θr is automatically changed so that the vehicle travels along the target driving line.

[0038] The steering determination unit 80 includes a normal steering determination unit 81, a rapid steering determination unit 82, and a steering determination result output unit 83.

[0039] The normal steering determination unit 81 acquires the steering torque ST detected by the steering torque sensor 62. If the steering torque ST is equal to or greater than a predetermined normal determination threshold STTH, the normal steering determination unit 81 determines that steering operations are being performed by the driver and outputs a normal steering determination. Otherwise, it outputs a non-steering determination.

[0040] The early steering determination unit 82 acquires the steering angle Θr detected by the steering angle sensor 61 and the target steering angle Θt calculated by the target steering torque calculation unit 73.

[0041] The premature steering determination unit 82 calculates the deviation Θd (=Θr-Θt) between the steering angle Θr and the target steering angle Θt. If the steering deviation Θd is greater than or equal to a predetermined positive premature steering determination threshold PTH, or if the steering deviation Θd is less than or equal to a predetermined negative premature steering determination threshold NTH, it determines that steering operations have been performed by the driver and outputs a premature steering determination. Otherwise, it outputs a non-steering determination. The reason for providing a positive threshold PTH and a negative threshold NTH is that the steering angle Θr when the steering wheel 10 is in the neutral position is set to 0°, the rotation angle to the right from the neutral position of the steering wheel 10 is represented by a positive value, and the rotation angle to the left from the neutral position of the steering wheel 10 is represented by a negative value.

[0042] The steering judgment result output unit 83 obtains the judgment result from the normal steering judgment unit 81 and the judgment result from the fast steering judgment unit 82.

[0043] The steering determination result output unit 83 outputs "steering determination" as the steering determination result if a normal steering determination is output from the normal steering determination unit 81 or if an early steering determination is output from the early steering determination unit 82. On the other hand, if a non-steering determination is output from both the normal steering determination unit 81 and the early steering determination unit 82, the steering determination result output unit 83 outputs "non-steering determination" as the steering determination result.

[0044] As mentioned above, when the vehicle's driving line deviates from the target driving line, the absolute value of the first target steering angle Θt1 is greater than the absolute value of the second target steering angle Θt2. Therefore, in this embodiment, the target steering torque STt is smaller when the steering judgment result is a steering judgment (when the target steering angle Θt is set to the second target steering angle Θt2) than when the steering judgment result is a non-steering judgment (when the target steering angle Θt is set to the first target steering angle Θt1). In other words, in this embodiment, the force attempting to counteract the steering input due to the driver's steering operation is weaker when the steering judgment result is a steering judgment than when the steering judgment result is a non-steering judgment.

[0045] On the other hand, the first steering reaction coefficient α1 is set to be smaller than the second steering reaction coefficient α2. Therefore, in this embodiment, the assist torque AT is greater when the steering judgment result is steering (when the steering reaction coefficient α is set to the second steering reaction coefficient α2) than when the steering judgment result is non-steering (when the steering reaction coefficient α is set to the first steering reaction coefficient α1). In other words, in this embodiment, the force assisting the driver's steering is stronger when the steering judgment result is steering than when the steering judgment result is non-steering.

[0046] In this embodiment, when the driver performs a steering operation during automatic steering driving mode and the steering judgment result switches from non-steering to steering, the force attempting to cancel out the steering input from the driver's steering operation weakens, and the assist torque AT (force assisting the driver's steering) increases. Therefore, in this embodiment, when the steering judgment result switches from non-steering to steering during automatic steering driving mode, the operating feel of the steering wheel 10 improves compared to before the switch.

[0047] Figure 3 is a time chart illustrating the effects of steering control according to this embodiment.

[0048] As shown in Figure 3, for example, when the vehicle is moving straight in automatic steering driving mode (i.e., when the steering angle Θr and target steering angle Θt are both zero), if the driver performs a premature steering operation at time t1 and the steering wheel 10 is quickly rotated clockwise from the neutral position, the steering angle Θr increases in response to the premature steering operation, and the steering torque ST increases at time t4, delayed by the premature steering operation. Therefore, the steering torque ST becomes equal to or greater than the normal judgment threshold STTH and a normal steering judgment is output, which occurs at time t5, further delayed from time t4.

[0049] When the driver performs a premature steering maneuver, the target steering angle Θt is changed at time t3, after a delay from the premature steering maneuver, by the electronic control unit 60, which has determined the premature steering maneuver by the driver to be a disturbance, in the opposite direction to the change in the steering angle Θr. However, the steering deviation Θd between the steering angle Θr and the target steering angle Θt increases from time t1 without delay from the premature steering maneuver.

[0050] Therefore, according to this embodiment, at time t2 when the steering deviation Θd is equal to or greater than the early steering determination threshold PTH, the steering determination result output unit 83 can output "steering determination". In other words, according to this embodiment, at time t2 earlier than time t5 when the steering torque ST is equal to or greater than the normal determination threshold STTH, the operating characteristics of the steering wheel 10 in automatic steering driving mode can be switched. As a result, the second target steering angle Θt2 can be set to the target steering angle Θt from time t3 onwards, thereby suppressing deterioration of the operating feel of the steering wheel 10.

[0051] The steering device 1 according to this embodiment, as described above, is configured to automatically perform steering operations on the steering wheel 10. At least during the automatic steering driving mode in which steering operations on the steering wheel 10 are performed automatically, the device determines whether the steering operation on the steering wheel 10 was performed by a driver based on the steering angle Θr and the target steering angle Θt of the steering wheel 10. When it is determined that the steering operation on the steering wheel 10 was performed by a driver, the device is configured to change the operating characteristics of the steering wheel 10 so that the steering force required by the driver to steer the steering wheel 10 is reduced compared to before the determination.

[0052] More specifically, the steering device 1 is configured to determine whether a steering operation of the steering wheel 10 has been performed by the driver based on the steering deviation Θd between the steering angle Θr and the target steering angle Θt. By making a steering determination based on the steering deviation Θd in this way, it is possible to detect whether or not a steering operation has been performed by the driver earlier than by making a steering determination based on the steering torque ST, and to change the operating characteristics of the steering wheel 10, thereby suppressing deterioration of the operating feel of the steering wheel 10. (Second Embodiment) Next, a second embodiment of the present invention will be described. This embodiment differs from the first embodiment in the contents of the early steering determination unit 82. The following will focus on explaining these differences.

[0053] In this embodiment as well, the early steering determination unit 82 acquires the steering angle Θr detected by the steering angle sensor 61 and the target steering angle Θt calculated by the target steering torque calculation unit 73, similar to the first embodiment, and calculates the steering deviation Θd (=Θr-Θt).

[0054] In this embodiment, the early steering determination unit 82 further calculates the rate of change of steering deviation Θd (hereinafter referred to as "deviation speed") Θd' and the rate of change of steering angle Θr (hereinafter referred to as "steering speed") Θr'. The early steering determination unit 82 then determines that steering operations are being performed by the driver and outputs an early steering determination if the deviation speed Θd' is greater than or equal to a predetermined first positive early steering determination threshold PTH1 and the steering speed Θr' is greater than or equal to a predetermined second positive early steering determination threshold PTH2, or if the deviation speed Θd' is less than or equal to a predetermined first negative early steering determination threshold NTH1 and the steering speed Θr' is less than or equal to a predetermined second negative early steering determination threshold NTH2. In all other cases, it outputs a non-steering determination.

[0055] Figure 4 is a time chart illustrating the effects of steering control according to this embodiment.

[0056] Similar to the first embodiment, when the driver performs a rapid steering operation at time t1, causing the steering wheel 10 to rotate quickly clockwise from the neutral position, the steering angle Θr increases in response to the rapid steering operation, and the steering torque ST increases at time t4 with a delay following the rapid steering operation. At time t5, the steering torque ST becomes equal to or greater than the normal judgment threshold STTH, and a normal steering judgment is output.

[0057] In contrast, the deviation velocity Θd' and steering velocity Θr' increase from time t1 without delay to the early steering operation, and their rate of change becomes particularly fast when an early steering operation is performed. Therefore, almost simultaneously with the early steering operation, the deviation velocity Θd' becomes equal to or greater than the first early steering judgment threshold PTH1 and the steering velocity Θr' becomes equal to or greater than the second early steering judgment threshold PTH2, allowing the steering judgment result output unit 83 to output "steering judgment" at an even earlier stage than in the first embodiment. The values ​​of the first early steering judgment threshold PTH1 and the second early steering judgment threshold PTH2 may be the same or different. The same applies to the first negative early steering judgment threshold NTH1 and the second negative early steering judgment threshold NTH2.

[0058] Furthermore, as in this embodiment, by determining that premature steering has occurred only when both the deviation speed Θd' and the steering speed Θr' are greater than or equal to the positive thresholds PTH1 and PTH2, or less than or equal to the negative thresholds NTH1 and NTH2, it is possible to suppress the misinterpretation of a driver holding the steering wheel 10 (steering control) as a steering operation during automatic steering driving mode.

[0059] Figure 5 is a time chart showing the case where, during automatic steering driving mode, the target driving line is changed, the target steering angle Θt is changed from time t1, and while the steering wheel 10 is being automatically steered so that the steering angle Θr follows the target steering angle Θt, the driver stops the rotation of the steering wheel 10 by holding it at time t2.

[0060] When the driver steers the steering wheel 10, as described above with reference to Figure 3, the direction of change of the steering angle Θr and the direction of change of the target steering angle Θt are opposite. On the other hand, when the driver holds the steering wheel 10, as shown in Figure 5, the direction of change of the steering angle Θr and the direction of change of the target steering angle Θt are the same.

[0061] In this case, if, as in the first embodiment, it is determined that steering operation has been performed by the driver when the steering deviation Θd is greater than or equal to a positive threshold PTH, or less than or equal to a negative threshold NTH, then it will be determined that steering operation has been performed even though a holding operation has been performed.

[0062] In contrast, if a holding operation is performed, as shown in Figure 5, the direction of change of the deviation velocity Θd' and the direction of change of the steering velocity Θr' become opposite. Therefore, by determining that premature steering has occurred only when both the deviation velocity Θd' and the steering velocity Θr' are above the positive thresholds PTH1 and PTH2, or below the negative thresholds NTH1 and NTH2, it is possible to suppress the misinterpretation of a driver's holding operation as a steering operation.

[0063] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0064] For example, in each of the above embodiments, the early steering determination unit 82 outputs an early steering determination result based on the steering angle Θr and the target steering angle Θt. In the first embodiment, the early steering determination result is output using the steering deviation Θd calculated based on the steering angle Θr and the target steering angle Θt. In the second embodiment, the early steering determination result is output using the deviation speed Θd', which is the rate of change of the steering deviation Θd, and the steering speed Θr', which is the rate of change of the steering angle Θr.

[0065] However, the system is not limited to these methods. For example, the system may output an early steering determination result using the steering angle Θr and the steering deviation Θd. Specifically, the system may output an early steering determination if the steering angle Θr is greater than or equal to a predetermined first positive early steering determination threshold PTH1 and the steering deviation Θd is greater than or equal to a predetermined second positive early steering determination threshold PTH2, or if the steering angle Θr is less than or equal to a predetermined first negative early steering determination threshold NTH1 and the steering deviation Θd is less than or equal to a predetermined second negative early steering determination threshold NTH2. In all other cases, the system may output a non-steering determination.

[0066] Alternatively, for example, the system may output the early steering determination result using the deviation velocity Θd'. Specifically, if the deviation velocity Θd' is greater than or equal to a predetermined positive early steering determination threshold PTH, or if the deviation velocity Θd' is less than or equal to a predetermined negative early steering determination threshold NTH, an early steering determination may be output, and otherwise, a non-steering determination may be output.

[0067] Furthermore, in each of the above embodiments, the early steering determination unit 82 outputted an early steering determination result based on the steering angle Θr and the target steering angle Θt. However, for example, the steering angle Θr and the target steering angle Θt can be replaced with parameters correlated with them. For example, a parameter correlated with the steering angle Θr is the amount of offset of the vehicle (the amount of lateral displacement of the center position of the vehicle from the center line of the driving lane). For example, a parameter correlated with the target steering angle Θt is the amount of target offset of the vehicle (the amount of lateral displacement between the center line of the driving lane and the target driving line). This is because if the steering angle Θr is controlled to be equal to the target steering angle Θt, the amount of offset of the vehicle will be controlled to be equal to the target offset.

[0068] Furthermore, in each of the above embodiments, when the steering judgment result output unit 83 outputs "steering judgment," in order to reflect the driver's operation in the vehicle behavior, in addition to reducing the steering force, various driving assistance functions may be reduced, such as VLO (Vehicle Lateral Offset) which automatically adjusts the distance between vehicles in adjacent lanes, automatic lane changes, and emergency braking, so as to prevent them from being activated. Also, in order to inform the driver that a "steering judgment" has been made, a so-called "hands-on" display may be shown, for example, on a display positioned where the driver can see it.

[0069] Furthermore, in each of the above embodiments, the computer program executed in the electronic control unit 60 may be provided in the form of a computer-readable portable recording medium, such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. [Explanation of Symbols]

[0070] 1. Steering system 10 Steering Wheel

Claims

[Claim 1] A steering system configured to automatically perform steering operations on the steering wheel, At least during a driving mode in which steering operations of the steering wheel are performed automatically, it is determined that the steering operation of the steering wheel was performed by the driver based on the steering angle of the steering wheel and the target steering angle. When it is determined that the steering operation of the steering wheel was performed by the driver, the steering wheel's operating characteristics are configured to change so that the steering force required by the driver to steer the steering wheel is reduced compared to before the determination. The system is configured to determine that the steering wheel was operated by the driver if the rate of change of the steering deviation between the steering angle and the target steering angle is greater than or equal to a predetermined first positive early steering determination threshold, and the rate of change of the steering angle is greater than or equal to a predetermined second positive early steering determination threshold, or if the rate of change of the steering deviation is less than or equal to a predetermined first negative early steering determination threshold, and the rate of change of the steering angle is less than or equal to a predetermined second negative early steering determination threshold. Steering system.

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