Vehicle steering assistance device, steering assistance method, and program thereof

Abstract

The present invention provides a vehicle steering assistance system that can perform steering guide assistance control even when driving on a circuit. [Solution] The steering support ECU (20) is applied to a vehicle (HV) equipped with a steering device (10) that provides a basic return torque, which is a torque that increases in magnitude as the steering angle increases and is in a direction that returns the steering wheel (11) to the neutral position. The steering support ECU (20) determines a target guide torque so that the steering angle (θact) is easily maintained within a predetermined target steering angle range that includes the target steering angle, and generates a torque in the electric motor (21) corresponding to the target guide torque. If the vehicle forward image acquired by the camera sensor (34) includes a curve boundary provided on the curved road portion of the circuit, the steering support ECU (20) determines the target driving line of the vehicle using the curve boundary and determines the target steering angle based on the determined target driving line.

Description

Technical Field

[0001] The present invention relates to a vehicle steering assist device, a steering assist method, and a program thereof for assisting a driver in steering a vehicle.

Background Art

[0002] One of the conventionally known vehicle steering assist devices determines a target travel line based on "the left and right lane lines (for example, white lines) of the road on which the vehicle is traveling" recognized by an in-vehicle camera, and applies a steering reaction force to the steering wheel so that the steering angle is within an appropriate range for causing the vehicle to travel along the target travel line. According to this, the driver can maintain the subjective feeling of steering and can easily drive the vehicle along the target travel line (see, for example, Patent Documents 1 to 3). Such steering assistance may be referred to as steering guide assistance control or PDA-SA (Proactive Driving Assist - Steering Assist).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0004] The above-described conventional device cannot perform steering guide assistance control when the left and right lane lines of the road cannot be recognized by the in-vehicle camera. Therefore, when the vehicle is traveling on a "road without lane lines (white lines)" such as a circuit, the steering guide assistance control cannot be executed.

[0005] This invention was made to address the above-mentioned problems. Specifically, one of the objectives of this invention is to provide a steering assistance device, a steering assistance method, and a program thereof for a vehicle that can perform steering guide assistance control even when driving on a circuit.

[0006] One embodiment of the vehicle steering assistance device of the present invention is: The system is applied to a vehicle (HV) equipped with a steering device (10) that applies a basic return torque (TR) to the steering wheel, which is a torque that increases in magnitude as the steering angle, which is the amount of movement of the steering wheel (11), increases, and is a torque that returns the steering wheel to the neutral position. The system includes a camera sensor (34) that acquires a vehicle front image by capturing the scene in front of the vehicle, an electric motor (21) that generates the torque to be applied to the steering wheel, and a controller (20) that controls the electric motor.

[0007] The controller is configured to determine a target guide torque (TGtgt) (S645) such that the steering angle (θact) is easily maintained within a predetermined target steering angle range (from θtgt-θc to θtgt+θc) that includes the target steering angle (θtgt), and to generate a torque in the electric motor corresponding to the target guide torque (S625).

[0008] Furthermore, the controller, If the steering angle is within the target steering angle range, the target guide torque is determined such that the ratio of the increase in torque applied to the steering wheel when the electric motor generates the target guide torque to the increase in the steering angle is greater than the ratio of the increase in torque applied to the steering wheel when the electric motor does not generate the target guide torque to the increase in the steering angle. If the vehicle forward image includes curved section boundaries (C1 to C4), which are road boundaries provided in the curved section of the circuit, the target driving line of the vehicle (T2, T4, T6, T8) is determined using the curved section boundaries included in the vehicle forward image, and the target steering angle (θtgt) is determined based on the determined target driving line.

[0009] According to this, when a vehicle is traveling on a circuit track without lane markings, a target driving line is determined based on the curve boundary, and a target steering angle is determined based on that target driving line, thus enabling steering guide support control.

[0010] In the above description, to aid in understanding the present invention, the names and / or reference numerals used in the embodiments described later are indicated in parentheses for the components of the invention corresponding to those embodiments. However, the components of the present invention are not limited to the embodiments defined by the above names and / or reference numerals. The present invention also extends to vehicle steering assistance methods and programs thereof. [Brief explanation of the drawing]

[0011] [Figure 1] A schematic diagram of a steering assistance device for a vehicle according to an embodiment of the present invention. [Figure 2] (A) is a graph showing the relationship between steering angle and basic return torque, and (B) is a graph showing the relationship between steering angle and target assist torque. [Figure 3] (A) is a graph showing the relationship between steering angle and target guide torque, and (B) is a graph showing the relationship between steering angle and post-control return torque. [Figure 4]A diagram illustrating how to determine the target racing line on a circuit. [Figure 5] A diagram illustrating how to determine the target racing line on a circuit. [Figure 6] The routine executed by the CPU of the steering assistance ECU shown in Figure 1. [Modes for carrying out the invention]

[0012] The steering assist device for a vehicle according to an embodiment of the present invention (hereinafter referred to as "device DS") has the components shown in Figure 1 and is applied to (mounted on) a vehicle HV. The vehicle HV may be any of the following: a vehicle powered by an internal combustion engine, an electric vehicle, or a hybrid vehicle.

[0013] The steering system 10 of the hybrid vehicle is a device for steering the steering wheels, namely the left front wheel FLW and the right front wheel FRW, and comprises a steering wheel 11, a steering shaft 12 connected to the steering wheel 11, a universal joint 13 with one end connected to the steering shaft 12, and a pinion shaft 14 with the other end of the universal joint 13 connected.

[0014] Furthermore, the steering device 10 includes a rack bar 15 that meshes with a pinion gear provided at the tip of the pinion shaft 14, a tie rod 16L connected to the left end of the rack bar 15 and the knuckle arm of the left front wheel FLW, and a tie rod 16R connected to the right end of the rack bar 15 and the knuckle arm of the right front wheel FRW.

[0015] The rotational torque (steering input) input to the steering wheel 11 is converted into a force that moves the rack bar 15 in the vehicle width direction, and by this force, the left front wheel FLW and the right front wheel FRW are steered. That is, the steering wheel 11 and the left and right front wheels are connected so as to be able to transmit torque. Therefore, the self-aligning torque acting on the left and right front wheels during turning of the vehicle HV is transmitted to the steering wheel 11. That is, a "basic return torque TR in the direction of returning the steering wheel 11 to the neutral position" shown by the broken line in FIG. 2(A) acts on the steering wheel 11.

[0016] The device DS includes a steering assist ECU 20. The steering assist ECU 20 includes a microcomputer (not shown) including a CPU (processor), ROM, RAM, and an interface, etc. Note that "ECU" means an electronic control device and is also referred to as a controller or a computer.

[0017] The steering assist ECU 20 executes steering assist control that generates a steering reaction force on the steering wheel 11 to make it easier for the steering angle based on the turning operation (i.e., steering) of the driver's steering wheel 11 to be within the "appropriate range for the vehicle to travel within the lane". This steering assist control is also referred to as "steering guide assist control" and will be described in detail later.

[0018] The steering assist ECU 20 is connected to an electric motor 21 and controls the electric motor 21. The torque generated by the electric motor 21 is converted into a force that moves the rack bar 15 in the vehicle width direction via a torque conversion mechanism (not shown). Therefore, the steering reaction force can be adjusted by changing the torque generated by the electric motor 21.

[0019] The steering assist ECU 20 is connected to the sensors, switches, and devices described below and receives their detection signals, output signals, or information.

[0020] Steering Angle Sensor 31: The steering angle sensor 31 detects the steering angle θ, which is the rotation angle of the steering wheel 11. The steering angle θ becomes a positive value when the steering wheel 11 is rotated clockwise from the neutral position, and a negative value when the steering wheel 11 is rotated counterclockwise from the neutral position. Note that the actual steering angle θ detected by the steering angle sensor 31 may be denoted as "θact". Steering Torque Sensor 32: The steering torque sensor 32 detects the steering torque Ts. Vehicle Speed Sensor 33: The vehicle speed sensor 33 detects the speed (vehicle speed) V of the vehicle HV.

[0021] Camera Sensor 34: The camera sensor 34 includes a "camera and image ECU" (not shown). The camera captures a scene included in the front shooting area of the vehicle HV at a predetermined angle of view every time a predetermined time elapses to obtain a vehicle front image. The image ECU generates "camera information including camera target information and lane information, etc." based on the vehicle front image. The lane information includes information on lane lines (e.g., white lines) drawn on the road and "those indicating the road boundary (hereinafter simply referred to as the 'road boundary')" existing in front of the vehicle.

[0022] Steering Assist Switch 35: The steering assist switch 35 generates an on signal for allowing steering guide assist control and an off signal for stopping the same according to the driver's operation.

[0023] The navigation device 40 is connected to a "GPS receiver, a map information storage device storing map information, and a display" (not shown). The navigation device 40 acquires the current position of the vehicle HV based on the GPS signal received by the GPS receiver and performs well-known route guidance. The map information stores information for indicating in which area a specific position is located. Therefore, the navigation device 40 can provide the steering assist ECU 20 with information indicating whether the vehicle HV is located within the circuit.

[0024] (Operation) <Target Assist Torque TAtgt> As mentioned above, when the vehicle HV is turning, a basic return torque TR due to the self-aligning torque acts on the steering wheel 11 (see the dashed line in Figure 2(A)). The magnitude of the basic return torque TR increases as the steering angle θ increases. The basic return torque TR acts counterclockwise with respect to a clockwise steering angle θ. Therefore, by reducing the magnitude of the basic return torque TR, the driver can easily steer.

[0025] The device DS determines the target assist torque TAtgt, which changes as shown in Figure 2(B). The absolute value of the target assist torque TAtgt increases as the steering angle θ increases, and it acts clockwise with respect to a clockwise steering angle θ. That is, the direction of the target assist torque TAtgt with respect to the steering angle θ is opposite to that of the basic return torque TR. The device DS generates a torque in the electric motor 21 corresponding to the target assist torque TAtgt.

[0026] As a result, the final recovery torque is the "recovery torque TRb corrected by the target assist torque TAtgt," as shown by the solid line in Figure 2(A). A torque corresponding to the target assist torque TAtgt is always applied.

[0027] <Target guide torque TGtgt> The device DS determines the target steering angle θtgt based on a predetermined method which will be described in detail later. The target steering angle θtgt is the steering angle θ required for the vehicle HV to travel along the target driving line TL. Generally, when the left and right lane markings (white lines) are detected by the camera sensor 34, the target driving line TL is set to the center line of the left and right lane markings.

[0028] The device DS determines a target guide torque TGtgt by adjusting the steering reaction force, thereby making it easier for the driver to maintain the steering angle θ near the target steering angle θtgt.

[0029] More specifically, as shown in Figure 3(A), the target guide torque TGtgt is a counterclockwise torque when the actual steering angle θact is within the range of "θtgt" to "θtgt+θc" (i.e., when the steering angle deviation Δθ (=θact-θtgt) is within the range of "0" to "θc"), and its magnitude gradually increases as the magnitude of the steering angle θact increases. The target guide torque TGtgt is a clockwise torque when the actual steering angle θact is within the range of "θtgt" to "θtgt-θc" (i.e., when the steering angle deviation Δθ (=θact-θtgt) is within the range of "0" to "-θc"), and its magnitude gradually increases as the magnitude of the steering angle θact increases.

[0030] When the steering assist switch 35 is on, the device DS generates a torque in the electric motor 21 corresponding to the torque obtained by adding the target assist torque TGtgt to the target guide torque TGtgt (TAtg + TGtgt). As a result, the "return torque TRb corrected only by the target assist torque TAtgt" shown by the solid line in Figure 3(B) is corrected to the post-control return torque TRc shown by the dashed line. Note that Figure 3(B) shows the relationship between the steering angle θ and torque only when the steering angle θ is a positive value (clockwise value).

[0031] As a result, when the driver attempts to increase the steering angle θ by turning the steering wheel 11 beyond the target steering angle θtgt, the steering reaction force suddenly increases. Therefore, such further turning by the driver is suppressed. Conversely, when the driver attempts to decrease the steering angle θ by rotating the steering wheel 11 from the target steering angle θtgt to the neutral position, the steering reaction force decreases suddenly at a large rate, and then the rate of decrease becomes smaller. Therefore, such counter-turning by the driver is suppressed. The magnitude of the target guide torque TGtgt is approximately one-tenth the magnitude of the corrected return torque TRb.

[0032] The target guide torque TGtgt remains approximately constant as long as the actual steering angle θact is greater than the value obtained by adding the value θc to the target steering angle θtgt (θtgt+θc), and gradually decreases as the actual steering angle θact increases further. The target guide torque TGtgt remains approximately constant as long as the actual steering angle θact is smaller than the value obtained by subtracting the value θc from the target steering angle θtgt (θtgt-θc). As the actual steering angle θact becomes even smaller, its magnitude gradually decreases.

[0033] <Method for determining the target steering angle θtgt> 1. When the vehicle is traveling on a normal road. When a vehicle HV is traveling on a normal road where the left and right lane markings can be recognized by the camera sensor 34, the device DS determines the center line of the left and right lane markings as the target driving line TL. The device DS calculates the curvature ρp of the target driving line TL at a look-ahead distance D ahead of the vehicle HV. The look-ahead distance D is the product of a constant look-ahead time Δt and the vehicle speed V.

[0034] The device DS calculates the target steering angle θtgt according to the following equation (1). In the following equation (1), R is the steering gear ratio, A is the stability factor of the vehicle HV (see, for example, Japanese Patent Publication No. 2013-129316, Japanese Patent Publication No. 2013-132938, and Japanese Patent Publication No. 2005-8066, etc.), and Lw is the wheelbase of the vehicle HV. θtgt=R·(1+A·V 2 )·ρp·Lw …(1)

[0035] 2. When the vehicle is running on a circuit. Unlike ordinary roads, the circuit track does not have lane markings on either side. However, as shown in Figures 4 and 5, the circuit track CR has "road boundaries (C1 to C4) provided in the curved sections of the circuit." These road boundaries provided in the curved sections of the circuit may hereafter be simply referred to as "curved section boundaries." The device DS uses these curved section boundaries to determine the target driving line TL, as described below.

[0036] For example, when the vehicle HV is traveling at position P1 shown in Figure 4, the camera sensor 34 recognizes the curve boundary C1. In Figure 4, the area indicated by the dashed line Cap represents the area captured by the camera sensor 34.

[0037] The curve boundary indicating a right curve curves to the right as it moves away from the vehicle HV. The curve boundary indicating a left curve curves to the left as it moves away from the vehicle HV. The curve boundary at the exit of a curve has a straight section. Based on these characteristics of the curve boundary, the device DS determines whether the curve boundary C1 indicates a right curve, a left curve, or the exit of a curve.

[0038] In the example shown in Figure 4, the device DS determines that "the curve boundary C1 indicates a right curve." Therefore, the device DS uses the extension line L1 on the right side of the vehicle HV as the reference line. Such an extension line is in the same direction as the vehicle HV's direction of travel.

[0039] Furthermore, if the device DS determines that the curve boundary indicates a left curve, it uses the extension of the left side of the vehicle HV as the reference line (see straight line L7 in Figure 5). If the device DS determines that the curve boundary indicates the curve exit, it uses the extension of the side of the vehicle HV on the outside of the turn at the current point as the reference line (see straight line L3 in Figure 4).

[0040] Next, the device DS sets a predetermined position on the trackside edge of the curve boundary C1 as the target point TGT1. For example, the target point TGT1 is set at a position where the distance along the trackside edge from the vehicle HV side end of the curve boundary C1 is a set distance DST1.

[0041] Next, the device DS determines the tangent line L2 at the target point TGT1 on the side edge of the track. The device DS calculates the arc T1 that is tangent to the extension line L1, which is the reference line, and the tangent line L2. Then, the device DS determines the curve T2, which is a concentric arc with arc T1 and passes through the center of the front end of the vehicle HV, as the target driving line TL, and calculates the curvature ρp of the target driving line TL at a forward distance D from the vehicle HV, and determines the target steering angle θtgt using equation (1) above.

[0042] As the vehicle HV reaches position P2 within a predetermined approach distance threshold from target point TGT1, the device DS newly recognizes the curve boundary C2. In this case, since the newly recognized curve boundary C2 has a straight section, it is determined to indicate the curve exit. Therefore, the device DS determines the extension line L3 of the left side of the vehicle HV, which is currently on the outside of the turn, as the reference line.

[0043] Next, the device DS sets a predetermined position on the trackside edge of the curve boundary C2 as the target point TGT2. For example, the target point TGT2 is set at a position where the distance along the trackside edge from the vehicle HV side end of the curve boundary C2 is a set distance DST2.

[0044] Next, the device DS determines the tangent line L4 at the target point TGT2 on the side edge of the track. The device DS calculates the arc T3 that is tangent to the extension line L3, which is the reference line, and the tangent line L4. Then, the device DS determines the curve T4, which is a concentric arc of arc T3 and passes through the center of the front end of the vehicle HV, as the target driving line TL, and calculates the curvature ρp of the target driving line TL at a forward distance D from the vehicle HV, and determines the target steering angle θtgt using equation (1) above.

[0045] In the example shown in Figure 5, the device DS sets the target travel line TL as described above. That is, when the vehicle HV is traveling at position P4 shown in Figure 5, the device DS recognizes the curve boundary C3 and determines, based on the shape of the curve boundary C3, that "the curve boundary C3 indicates a right curve." Therefore, the device DS determines the extension line L5 of the right side of the vehicle HV as the reference line.

[0046] Next, the device DS sets a predetermined position on the trackside edge of the curve boundary C3 as the target point TGT3. The target point TGT3 is determined based on the same criteria as the target point TGT1. The device DS finds the tangent line L6 at the trackside edge of the target point TGT3. The device DS calculates the arc T5 that is tangent to the extension line L5, which is the reference line, and the tangent line L6. Then, the device DS determines the curve T6, which is a concentric arc of the arc T5 and passes through the center of the front end of the vehicle HV, as the target driving line TL, finds the curvature ρp of the target driving line TL at a forward distance D from the vehicle HV, and determines the target steering angle θtgt using equation (1) above.

[0047] When the vehicle HV approaches position P5 shown in Figure 5, the device DS recognizes the curve boundary C4. Based on the shape of the curve boundary C4, the device DS determines that "the curve boundary C3 indicates a left curve" and uses the extension line L7 of the left side of the vehicle HV as the reference line.

[0048] Next, the device DS sets a predetermined position on the trackside edge of the curve boundary C4 as the target point TGT4. The target point TGT4 is determined based on the same criteria as the target point TGT1. The device DS finds the tangent line L8 at the trackside edge of the target point TGT4. The device DS calculates the arc T7 that is tangent to the extension line L7, which is the reference line, and the tangent line L8. Then, the device DS determines the curve T8, which is a concentric arc of the arc T7 and passes through the center of the front end of the vehicle HV, as the target driving line TL. In this case, the left front end of the vehicle HV traveling at position P5 and the "point of contact SP between arc T7 and extension line L7" are connected by a straight section St. Therefore, the target driving line TL, including curve T8, also has a straight section corresponding to this straight section St. The device DS finds the curvature ρp of the target driving line TL at a forward distance D from the vehicle HV and determines the target steering angle θtgt using equation (1) above.

[0049] (Specific operation) The CPU of the steering assist ECU20 (hereinafter simply referred to as "CPU") executes the routine shown in the flowchart in Figure 6 at predetermined intervals. In the following, "step" will be denoted as "S".

[0050] When the predetermined timing arrives, the CPU starts processing from S600 in Figure 6 and proceeds to S605, where it determines whether or not the steering assist switch 35 is generating an ON signal.

[0051] If the steering assist switch 35 does not generate an ON signal, the CPU proceeds from S605 to S610 and sets the target guide torque TGtgt to "0". In other words, the CPU does not perform steering guide assist control. After that, the CPU sequentially performs the processes described below in "S615 to S625" and proceeds to S695 to terminate this routine.

[0052] S615: The CPU obtains the target assist torque TAtgt by applying the actual steering angle θact to the lookup table MapTAtgt(θact) shown in Figure 2(B).

[0053] S620: The CPU sets the value of the control steering torque TS to the sum of the target assist torque TAtgt and the target guide torque TGtgt (TAtgt + TGtgt).

[0054] S625: The CPU controls the electric motor 21 so that torque corresponding to the controlled steering torque TS is applied to the steering wheel.

[0055] In this case, since the target guide torque TGtgt is set to "0" in S610, only the torque corresponding to the target assist torque TAtgt is applied from the electric motor 21 to the steering wheel 11. Therefore, the steering reaction force is as shown by the solid line in Figure 2(A).

[0056] On the other hand, if the steering assist switch 35 generates an ON signal, the CPU proceeds from S605 to S630 and determines whether the road information (or the image in front of the vehicle) acquired by the camera sensor 34 includes the left and right lane markings up to a predetermined distance in front of the vehicle HV.

[0057] If the left and right lane markings can be recognized up to a predetermined distance ahead, the CPU proceeds from S630 to S635 and determines the center line of the left and right lane markings as the target driving line TL. Next, the CPU proceeds to S640 and calculates the target steering angle θtgt according to equation (1) above.

[0058] Next, the CPU proceeds to S645, where it applies the value obtained by subtracting the target steering angle θtgt from the actual steering angle θact (θact-θtgt) to the lookup table MapTAGtgt(θact-θtgt) shown in Figure 3(A) to determine the target guide torque TGtgt.

[0059] Subsequently, the CPU executes the processes described in S615 to S625 and proceeds to S695. In this case, a torque corresponding to the sum of the target assist torque TAtgt and the target guide torque TGtgt is applied from the electric motor 21 to the steering wheel 11. Therefore, the driver can easily maintain the actual steering angle θact near the "target steering angle θtgt for driving the vehicle HV along the target driving line TL, which is the center line of the left and right lane markings." In other words, steering guide support control is performed.

[0060] In response to this, if the steering assist switch 35 generates an ON signal, but the left and right lane markings cannot be recognized up to a predetermined distance ahead, the CPU proceeds to S650 via S605 and S630. At S650, the CPU queries the navigation device 40 to determine whether or not the vehicle HV is currently located within the circuit.

[0061] If the vehicle HV is not currently located within the circuit, the CPU proceeds from S650 to S610. In this case, the target guide torque TGtgt is set to "0", so steering guide assistance control is not performed.

[0062] In contrast, if the vehicle HV is currently located within the circuit, the CPU proceeds from S650 to S655. Note that the processing in S650 may be omitted. In this case, if the CPU determines "No" in S630, it proceeds directly from S630 to S655.

[0063] The CPU, in S655, determines whether the track information acquired by the camera sensor 34 includes "road boundaries established in the curved sections of the circuit (i.e., curve boundaries)".

[0064] The road boundaries on the curved sections of the circuit are marked with a special pattern (e.g., hatching), have a special color (e.g., red, yellow, and white), and are slightly higher than the track surface (i.e., they are raised above the track surface). The AI ​​(artificial intelligence) built into the image ECU of the camera sensor 34 has learned this information through machine learning. The camera sensor 34 provides the AI ​​with the vehicle-front image acquired by the camera, and outputs a signal indicating whether or not the track information includes the "road boundaries on the curved sections of the circuit." The CPU reads this output signal and makes the determination for S655.

[0065] If the track information does not include road boundaries on the curved sections of the circuit, the CPU proceeds from S655 to S610. In this case, the target guide torque TGtgt is set to "0", so steering guide assistance control is not performed.

[0066] In contrast, if the track information includes road boundaries (curve boundaries) established in the curved sections of the circuit, the CPU proceeds from S655 to S660 and determines the target point based on the method described above.

[0067] Next, the CPU proceeds to S665, where it determines the target driving line TL based on the position and direction of travel of the vehicle HV and the target point, etc., using the method described above. After that, the CPU proceeds to S640 to determine the target steering angle θtgt, and in S645 it determines the target guide torque TGtgt. Then the CPU performs the processing described in S615 to S625.

[0068] In this case, a torque corresponding to the sum of the target assist torque TAtgt and the target guide torque TGtgt is applied from the electric motor 21 to the steering wheel 11. Therefore, the driver can easily match the actual steering angle θact to the vicinity of the "target steering angle θtgt for driving the vehicle HV along the target driving line TL, which is determined based on the current position of the vehicle HV, a target point on the road boundary set up in the curved section of the circuit, etc." In other words, steering guide support control is performed.

[0069] According to the device DS described above, if the vehicle forward image acquired by the camera sensor (34) includes the curved section boundary (C1 to C4), which is the road boundary provided in the curved section of the circuit, the target driving line of the vehicle is determined using the curved section boundary, and the target steering angle (θtgt) is determined based on the determined target driving line. Then, the target guide torque TGtgt is determined based on the target steering angle. Therefore, the device DS can perform steering guide support control even on circuits where left and right lane lines are not drawn.

[0070] The present invention is not limited to the above embodiments, and various modifications can be adopted within the scope of the present invention. For example, the device DS determines the target driving line based on an arc tangent to a reference line, which is an extension of the side of the vehicle HV, and a tangent line passing through a target point on the side edge of the road on the boundary of the curved section. However, the target driving line may be determined not only by an arc, but also by a reference line, which is an extension of the side of the vehicle HV, a tangent line passing through a target point on the side edge of the road on the boundary of the curved section, and an n-th degree function such as a quadratic function. Furthermore, the device DS may provide the reference line, the tangent line passing through the target point, the position and direction of travel of the vehicle HV to an AI that has been pre-trained, and the AI ​​may determine the target driving line. Furthermore, the device DS may sequentially move the target point on the side edge of the road on the boundary of the curved section forward as the vehicle HV moves, and recalculate the target driving line based on a well-known two-wheel model each time the target point moves. The device DS is applicable to vehicles in an autonomous driving vehicle that have transitioned from autonomous driving to driver-operated driving mode. [Explanation of symbols]

[0071] 10... Steering system, 20... Steering assist ECU, 21... Electric motor, 34... Camera sensor.

Claims

1. This applies to a vehicle equipped with a steering system that applies a basic return torque to the steering wheel, which is a torque that increases in magnitude as the steering angle (the amount of steering wheel operation) increases, and is a torque that returns the steering wheel to the neutral position. A camera sensor that acquires an image of the area in front of the vehicle by capturing the scene in front of the vehicle, An electric motor that generates torque to be applied to the steering wheel, A controller for controlling the aforementioned electric motor, Equipped with, The aforementioned controller, A target guide torque is determined to make it easier to maintain the steering angle within a predetermined target steering angle range that includes the target steering angle. The electric motor generates a torque corresponding to the target guide torque. In a steering assist system for a vehicle configured as follows, The aforementioned controller, When the steering angle is within the target steering angle range, the target guide torque is determined such that the ratio of the increase in torque applied to the steering wheel when the electric motor generates the target guide torque to the increase in the magnitude of the steering angle is greater than the ratio of the increase in torque applied to the steering wheel when the electric motor does not generate the target guide torque to the increase in the magnitude of the steering angle. The controller further, If the vehicle forward image includes a curved section boundary, which is a road boundary provided in the curved section of the circuit, the target driving line of the vehicle is determined using the curved section boundary included in the vehicle forward image, and the target steering angle is determined based on the determined target driving line. It is configured in such a way. Steering assist device.

2. In the vehicle steering assist device according to claim 1, The aforementioned controller, A predetermined position on the side edge of the track at the boundary of the curved section is set as the target point, and the target driving line is determined based on the position of the vehicle, the direction of travel of the vehicle, and the target point. It is configured in such a way. Steering assist device.

3. A steering assistance method for a vehicle, applicable to a vehicle equipped with a steering system that applies a basic return torque to the steering wheel, which is a torque that increases in magnitude as the steering angle (the amount of steering wheel operation) increases, and is a torque that returns the steering wheel to the neutral position, wherein the torque ultimately applied to the steering wheel is adjusted by controlling an electric motor, A first step is to determine a target guide torque that makes it easier to maintain the steering angle within a predetermined target steering angle range that includes the target steering angle, A second step involves generating a torque in the electric motor corresponding to the target guide torque, Includes, The first step is, The step of determining the target guide torque is such that, when the steering angle is within the target steering angle range, the ratio of the increase in the magnitude of the torque applied to the steering wheel when the electric motor generates the target guide torque to the increase in the magnitude of the steering angle is greater than the ratio of the increase in the magnitude of the torque applied to the steering wheel when the electric motor does not generate the target guide torque to the increase in the magnitude of the steering angle. Furthermore, The first step is, If the forward-facing image of the vehicle acquired by a camera mounted on the vehicle includes a curved section boundary, which is a road boundary provided in the curved section of the circuit, the vehicle's target driving line is determined using the curved section boundary included in the forward-facing image of the vehicle, and the target steering angle is determined based on the determined target driving line. Steering assistance method.

4. In the vehicle steering assistance method described in claim 4, The first step is, The step involves setting a predetermined position on the side edge of the road boundary of the aforementioned line section as a target point, and determining the target driving line based on the position of the vehicle, the direction of travel of the vehicle, and the target point. Steering assistance method.

5. This program is applied to a vehicle equipped with a steering system that applies a basic return torque to the steering wheel, which is a torque that increases in magnitude as the steering angle (the amount of steering wheel operation) increases, and is a torque that returns the steering wheel to the neutral position, and causes a computer mounted on the vehicle to execute a step to adjust the torque ultimately applied to the steering wheel by controlling an electric motor. The program is sent to the computer, A first step is to determine a target guide torque that makes it easier to maintain the steering angle within a predetermined target steering angle range that includes the target steering angle, A second step involves generating a torque in the electric motor corresponding to the target guide torque, It is a program that executes, The first step is, The step of determining the target guide torque is such that, when the steering angle is within the target steering angle range, the ratio of the increase in the magnitude of the torque applied to the steering wheel when the electric motor generates the target guide torque to the increase in the magnitude of the steering angle is greater than the ratio of the increase in the magnitude of the torque applied to the steering wheel when the electric motor does not generate the target guide torque to the increase in the magnitude of the steering angle. Furthermore, The first step is, If the forward-facing image of the vehicle acquired by a camera mounted on the vehicle includes a curved section boundary, which is a road boundary provided in the curved section of the circuit, the vehicle's target driving line is determined using the curved section boundary included in the forward-facing image of the vehicle, and the target steering angle is determined based on the determined target driving line. program.

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