Vehicle driving assistance systems

Abstract

To prevent the hunting of a steering assisting control at a narrow road.SOLUTION: A controller of a vehicle drive assisting device includes: a boundary detecting unit 15a that detects right and left traffic road boundaries; a limit steering angle detecting unit 15b that detects the limit steering angle which is an amount of steering from a reference steering position So for a vehicle to run along a traffic lane and which is a steering angle to reach the traffic road boundary within a predefined time; an actual steering angle detecting unit 15c that detects the actual steering angle from the reference steering position; a comparing unit 15d that compares the actual steering angle with the limit steering angle; a steering assisting unit 15e that generates steering reaction force in a direction in which the actual steering angle that is caused by a steering operation when the actual steering angle exceeds the limit steering angle is decreased; a determining unit 15f that determines whether a predetermined condition like a narrow road is satisfied or not; and an assist adjusting unit 15g which virtually sets the right and left traffic road boundaries at the center of the traffic lane in the widthwise direction when it is determined that the condition is satisfied, obtains a right limit steering angle and a left limit steering angle based on the right and left traffic road boundaries that are virtually set, and causes the steering assisting unit to generate the steering reaction force.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a device that supports a driver's driving operation of a vehicle based on the driving environment or driving state of the vehicle, and particularly to a device that supports a steering operation so as to maintain a driving lane.

Background Art

[0002] When a vehicle travels on a road, it is necessary to avoid changing lanes unnecessarily or erratically, and it is required to maintain the lane. However, since the road is not always straight and the road surface may be inclined to either the left or the right due to its structure, the driver needs to steer according to those situations. In order to reduce the burden on the driver caused by steering due to such external factors, various driving support devices that automatically apply a steering force or a steering reaction force have been studied.

[0003] An example is described in Patent Document 1. The device described in Patent Document 1 detects the lane dividing lines on both the left and right sides of the host vehicle, and shifts from the support pause mode to the supportable mode when approaching the lane dividing lines by a predetermined distance. Further, when the lane dividing line is detected only on either the left or the right side, if the distance from the lane dividing line on that side is greater than or equal to a predetermined distance, it is configured to maintain the support pause mode. That is, in the device described in Patent Document 1, each time the vehicle approaches the lane dividing line, an auxiliary steering force acts in the direction of returning the vehicle to the center of the lane.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The assistance described in Patent Document 1 is a control system that applies an auxiliary steering force to the steering device (e.g., the steering wheel) to maintain the vehicle's position in the center of the lane when it is anticipated that the vehicle will deviate from the lane. In other words, when the vehicle moves away from the center of the lane and approaches the lane markings, an auxiliary steering force is applied to return the vehicle to the center. Therefore, on so-called wide roads where the lane width is somewhat wider than the vehicle width, the auxiliary steering force will not be applied if the vehicle only deviates slightly to the left or right from the center of the lane. However, on so-called narrow roads where the lane width is narrower than the vehicle width, as soon as the vehicle deviates slightly to either the left or right from the center of the lane, it is immediately determined that the vehicle is approaching the lane markings or that it is anticipated that the vehicle will deviate from the lane, and the auxiliary steering force is applied. Based on this, when the steering wheel (or steering device) is turned back to the other side, that is, when the vehicle returns to the center of the lane, the auxiliary steering force ceases to be applied. However, when the lane is narrow, the vehicle may slightly shift from the center of the lane to the other side, in which case the auxiliary steering force acts in the opposite direction to before. On narrow roads, this activation and deactivation of the auxiliary steering force, or the switching between support-enabled and support-disabled modes, occurs repeatedly. In other words, so-called hunting occurs, where steering and steering reaction force alternate in the left-right direction, which can feel unnatural.

[0006] This invention has been made in view of the above-mentioned technical problems, and aims to provide a driving assistance device that can avoid or suppress repeated execution and interruption of lane-keeping assistance, even when driving in a narrow lane. [Means for solving the problem]

[0007] To achieve the above objective, this invention provides a vehicle driving assistance device that assists steering to prevent a vehicle traveling within a predetermined lane from deviating from the lane, comprising a controller for adjusting the steering force, the controller comprising a boundary detection unit that detects the left and right lane boundary lines that demarcate the lane in which the vehicle is traveling, and a right limit steering unit that determines the steering angle at which the right lane boundary line will be reached if the vehicle travels for a predetermined time at the current vehicle speed. Corner and front The left limit rudder is the steering angle that reaches the left-hand track boundary line. At least one of the corners A limit steering angle detection unit to detect, and an actual steering angle detection unit that detects the actual steering angle, which is the amount of steering performed from the steering position that moves the vehicle straight, and When the limit steering angle detection unit detects the right limit steering angle, the left limit steering angle, or both, the actual Rudder angle and the aforementioned right limit rudder Corner or front The steering system is characterized by comprising: a comparison unit that compares the actual steering angle with the left limit steering angle; a steering support unit that, when the actual steering angle exceeds the right limit steering angle or the left limit steering angle, generates a steering reaction force in a direction that reduces the difference between the actual steering angle and the right limit steering angle or the left limit steering angle that the actual steering angle exceeds; a determination unit that determines whether predetermined conditions based on the width of the lane are met; and, when the determination unit determines that the predetermined conditions are met, a support adjustment unit that virtually sets the left and right road boundary lines of the lane to the center in the width direction of the lane, and determines the right limit steering angle and the left limit steering angle based on the virtually set left and right road boundary lines, and generates the steering reaction force using the steering support unit.

[0008] In this invention, the predetermined conditions may include either that the deviation between the right limit steering angle and the left limit steering angle is less than or equal to a predetermined threshold, or that the lane is a narrow road with a width narrower than a predetermined standard width.

[0009] In this invention, the vehicle is further provided with an operating unit that rotates or tilts to turn the vehicle, and the actual steering angle, the right limit steering angle, and the left limit steering angle may be measured by setting the operating amount of the operating unit that moves the vehicle straight as "0 degrees", the operating amount of the operating unit that turns the vehicle to the right or left as "positive", and the operating amount of the operating unit that turns the vehicle to the right or left as "negative".

[0010] In this invention, the steering support unit may be configured to generate a steering reaction force of a magnitude corresponding to the amount by which the actual steering angle exceeds the right limit steering angle, or the amount by which the actual steering angle exceeds the left limit steering angle.

[0011] In this invention, the determination unit determines when the vehicle is traveling in the center of the lane in a direction along the lane. The right rudder angle detection unit detected The limit steering angle is in the direction that causes the vehicle to turn to the left. The angle at which the steering reaction force is generated. It becomes a degree, and before The above, detected by the limit rudder angle detection unit The left limit steering angle is the direction that causes the vehicle to turn to the right. The angle at which the steering reaction force is generated. When the temperature reaches a certain level, it may be determined that the aforementioned predetermined conditions have been met. [Effects of the Invention]

[0012] In this invention, the limit steering angle is determined as the steering angle at which a vehicle traveling within a predetermined lane will reach the right or left lane boundary line in a predetermined time. When the vehicle is traveling in the center of the lane along the direction of the lane, the left and right limit steering angles are equal. If the vehicle is approaching either the left or right lane boundary line, the right or left limit steering angle closer to that boundary line will be smaller than the other limit steering angle. The actual steering angle is the amount of steering input from the position where the vehicle is moving straight, with "0 degrees" being the angle at which it moves straight. If this exceeds either the left or right limit steering angle, a steering reaction force acts in a direction that reduces the angle difference between the actual steering angle and the limit steering angle. Therefore, steering is assisted to prevent the vehicle from approaching the lane or deviating from the lane.

[0013] Furthermore, if the deviation between the right limit steering angle and the left limit steering angle falls below a predetermined threshold, or if predetermined conditions related to lane width, such as the lane being a narrow road, are met, a virtual left-right road boundary line is set as a single line in the center of the lane in the width direction. Based on this virtual road boundary line, the left and right limit steering angles are determined, and the steering response force is controlled by the steering support unit based on these limit steering angles and the actual steering angle. Therefore, when driving on a so-called narrow road along the virtual left-right road boundary line set in the center of the lane, the limit steering angle and the actual steering angle coincide, and so-called steering support that generates a steering response force is not performed. In contrast, if the vehicle's orientation deviates (shifts) relative to a virtually defined lane boundary line, the limit steering angle is calculated as a predetermined angle. However, since the vehicle's orientation is deviated relative to the lane boundary line and the actual steering angle already exceeds the limit steering angle, a steering reaction force is generated by the steering support unit, and steering support is performed to return the vehicle to the center of the lane (the position where the virtual lane boundary line is set). In other words, if the vehicle is slightly steered while driving near the center of the lane, or if the vehicle's orientation deviates relative to the virtual lane boundary line, a steering reaction force acts on the steering wheel and other steering components to move in the direction of driving toward the virtual lane boundary line. As a result, when the actual steering angle is about to deviate from the virtual lane boundary line, i.e., the center of the lane, a steering reaction force is generated in the direction of returning the vehicle to the center of the lane, thereby preventing or suppressing hunting in the vehicle's behavior and support control.

[0014] Furthermore, in this invention, by making the steering reaction force corresponding to the amount by which the actual steering angle exceeds the limit steering angle, the driver can know the degree to which the vehicle is approaching the road boundary line or the urgency of avoiding lane departure through the steering force, and avoidance maneuvers become easier. Moreover, since there is no difference in the left and right steering reaction force or steering force on narrow roads, it is possible to prevent or avoid any discomfort in steering. [Brief explanation of the drawing]

[0015] [Figure 1]This is a schematic diagram for explaining an example of an electric power steering apparatus that can be targeted by this invention. [Figure 2] This is a block diagram for explaining a control system of an embodiment of this invention that executes steering assist control. [Figure 3] This is an explanatory diagram for explaining a limit steering angle in an embodiment of this invention. [Figure 4] This is an explanatory diagram for explaining the implementation status of steering assist control on a wide road. [Figure 5] This is a block diagram for explaining the functional configuration of a controller. [Figure 6] This is a flowchart for explaining an example of steering assist control in an embodiment of this invention. [Figure 7] This is an explanatory diagram for explaining the execution status of steering assist control on a wide road and the reaction force map at that time. [Figure 8] This is an explanatory diagram for explaining the execution status of steering assist control on a narrow road and the reaction force map at that time. [Figure 9] (A), (B), and (C) are each explanatory diagrams for explaining the relationship between the actual steering angle and the limit steering angle when a virtual lane boundary line is set. [Figure 10] This is a diagram schematically showing the direction of steering assist, the limit steering angle, and the assist torque. (A) shows an example when the limit steering angle is adjusted, and (B) shows an example when the limit steering angle is not adjusted. [Figure 11] This is an explanatory diagram for explaining the assist torque when the left and right assist execution regions partially overlap. [Figure 12] This is an explanatory diagram for explaining the assist torque when the left and right assist execution regions partially overlap and the limit steering angle is adjusted. [Embodiments for Carrying Out the Invention]

[0016] Hereinafter, embodiments of this invention will be described while referring to the drawings. Note that the embodiments described below are merely examples when this invention is implemented, and do not limit this invention.

[0017] The vehicle driving assistance device as an embodiment of this invention is a device for assisting steering by changing the steering angle, and in particular, a device that controls the steering force (steering torque) to avoid or suppress the vehicle from deviating from its lane. Therefore, the steering device is configured to electrically control the steering torque, and one example of this is an electric power steering (EPS) device. Figure 1 schematically shows the basic configuration of EPS1.

[0018] The EPS1 is mounted on the vehicle 2 and is configured to steer the steering wheels 3, such as the front wheels, which change the direction (turn) of the vehicle 2. A steering wheel 4 is provided as the operating part for this operation. This steering wheel 4 is connected to a steering linkage 6 via a steering shaft 5 and is configured to steer the steering wheels 3 according to the rotation angle of the steering wheel 4. The steering linkage 6, as an example, has a rack 7 that moves back and forth in the width direction of the vehicle 2, a pinion 8 that meshes with the rack 7, and a tie rod 9 that connects the rack 7 and the steering wheels 3, and the steering shaft 5 is connected to the pinion 8. Therefore, when the steering wheel 4 is rotated to the right or left, the pinion 8 rotates and the rack 7 moves to the right or left, and the steering wheels 3 are steered accordingly. In the embodiment described here, the steering wheel 4 used to move the vehicle 2 straight is defined as a steering angle of "0 degrees". From this position, the steering amount measured to the left is defined as a "positive" steering angle, and the steering amount measured to the right is defined as a "negative" steering amount. Therefore, operating the steering wheel 4 to turn the vehicle 2 to the left increases the steering angle, and conversely, operating the steering wheel 4 to turn the vehicle 2 to the right decreases the steering angle.

[0019] A motor 10 is provided to adjust the steering force. The motor 10 only needs to be configured to adjust torque or longitudinal power to the steering wheel 4, steering shaft 5, or rack 7. In the example shown in Figure 1, the motor 10 is connected to the steering shaft 5 via a reduction gear 11. A torque sensor 12 for detecting steering torque and a steering angle sensor 13 for detecting steering angle are also provided. These sensors 12 and 13 input detection signals to an electronic control unit (EPS-ECU) 14 for the electric power steering system (EPS). The EPS-ECU 14 is mainly composed of a microcomputer, and in addition to the detection signals from the sensors 12 and 13 (steering torque, steering angle), it also receives vehicle speed signals and control command signals from a controller, which will be described later. The EPS-ECU 14 performs calculations using the input data and pre-stored data, and is configured to control the motor 10 in the forward or reverse direction based on the result of these calculations. In other words, the EPS-ECU14 is configured to perform control by applying steering torque in a direction that encourages steering, or conversely, applying steering torque (steering reaction force) in a direction that restricts steering.

[0020] A controller 15 is provided to assist in steering the vehicle 2 to prevent it from deviating from its lane. The controller 15 is an electronic control unit mainly composed of a microcomputer consisting of memory elements (RAM, ROM), processing elements (CPU), and input / output interfaces. As shown in Figure 2, it is configured to perform calculations using input data and pre-stored data, and to output the result of these calculations as a control command signal to the EPS-ECU 14. Examples of input data include image data from a camera 16 that photographs the front and surroundings of the vehicle 2, position data from a navigation system (NAVI) 17, vehicle speed data from a vehicle speed sensor 18 mounted on the vehicle 2, and data on the actual steering angle detected by the steering angle sensor 13 mentioned above.

[0021] Here, the image data obtained by camera 16 includes the road boundary lines that demarcate the lane in which vehicle 2 is currently traveling, and the relative position of vehicle 2 and the road boundary lines is determined based on this image data. If the road boundary lines are not immediately clear from the image data, AI (artificial intelligence) can be used to determine the road boundary lines. Furthermore, by combining the position information obtained by NAVI 17 with the map data described later, the current position of vehicle 2 and its relative position to the road boundary lines on both its left and right sides can be determined.

[0022] On the other hand, examples of data that are stored in advance include map data 19 that associates road and other facility information with the coordinate locations used by NAVI17, limit steering angle data for the left and right sides 20, predetermined value data 21 which is a reference value for determining the width of the distance between the left and right support start positions determined by the limit steering angles for the left and right sides, and a reaction force map 22 which defines the magnitude of the steering reaction force according to the deviation between the actual steering angle and the limit steering angle.

[0023] In this embodiment of the invention, the limit steering angle is the steering angle required for the vehicle 2 to reach the road boundary line at its current speed after traveling for a predetermined time (hereinafter sometimes referred to as the look-ahead time). For example, by turning the steering wheel 4 to change the actual steering angle in either the left or right direction, the vehicle 2 travels along a curve with a turning radius (or curvature) corresponding to that actual steering angle. As shown in Figure 3, the position after a predetermined look-ahead time t from the start of the turn is represented by x representing the longitudinal direction of the vehicle 2, v representing the longitudinal velocity component, y representing the width (lateral direction) of the vehicle 2, and u representing the lateral velocity component. x=v·t, y=u·t Therefore, the steering angle at which the lateral distance y is the distance between the vehicle 2 and the road boundary line at that time is the limit steering angle δmax, and considering that the vehicle speed is relatively high and therefore the steering angle that is actually expected to be operated is small, this is approximately δmax = sin -1 (y / x) This is expressed as follows. In addition to the above calculation, it is also possible to determine the limit steering angle by calculating the curvature from the above relationship between x and y, assuming that the relationship between the curvature of the road surface and the steering angle is known, as in the equation of motion for a vehicle in a steady-state circular turn. In the embodiment described here, similar to the actual steering angle described above, the angle to the left is considered "positive," the angle to the right is considered "negative," and the center is considered "0 degrees."

[0024] The limit steering angle determined in this way is an angle corresponding to the vehicle speed, and the shorter the distance from the road boundary line to vehicle 2, the smaller the angle. This can be predetermined and stored in accordance with the vehicle speed, or it can be calculated using the detected vehicle speed and lane width. Furthermore, since road boundary lines exist on both the left and right sides of vehicle 2, the limit steering angle is determined in each direction. Therefore, for example, if vehicle 2 is traveling in the direction of the lane in the center of the lane, the limit steering angles on the left and right sides will be equal. Also, even if vehicle 2 is traveling in the direction of the lane, if vehicle 2 moves away from the center of the lane and approaches either the left or right road boundary line, the limit steering angle on the side of the road boundary line that vehicle 2 is approaching will be smaller than the limit steering angle on the opposite side. Moreover, even if vehicle 2 is in the center of the lane, if the direction of the vehicle is deflected to either the left or right, the limit steering angle on the road boundary line in the direction of the deflection will be smaller than the limit steering angle on the opposite side.

[0025] The steering reaction force to prevent vehicle 2 from approaching the road boundary line or deviating from the lane is generated when the actual steering angle exceeds the limit steering angle δmax. Therefore, if the distance between the position of vehicle 2 and the road boundary line after a predetermined look-ahead time t is greater than the lateral distance y that defines the limit steering angle, the actual steering angle at that time does not exceed the limit steering angle δmax, and no steering reaction force is generated. On the other hand, if vehicle 2 is approaching the road boundary line or is deflecting toward the road boundary line, vehicle 2 will reach the road boundary line in a shorter time than the aforementioned look-ahead time t. In this case, the actual steering angle at that time exceeds the limit steering angle δmax, and a steering reaction force is generated according to the magnitude of the actual steering angle (or the difference between the limit steering angle δmax and the actual steering angle δ). The position at which the control to generate this steering reaction force is started is determined by the distance from the road boundary line, which is shown by a dashed line in Figure 4. In Figure 4, reference numeral 23 indicates a lane, reference numeral 24 indicates the road boundary line on the shoulder side (left side), reference numeral 25 indicates the road boundary line on the center line side (right side) (not shown), reference numeral 26 indicates the left support start position, and reference numeral 27 indicates the right support start position. Therefore, in the region between the left and right support start positions 26 and 27, no steering reaction force for steering support is generated, so this region becomes the support ineffective region 28. In the region between the respective left and right support start positions 26 and 27 and the left and right road boundary lines 24 and 25, steering reaction force for steering support is generated, so these regions become the support execution regions 29 and 30.

[0026] Furthermore, regarding the steering reaction force, it is the torque that steers the vehicle 2 in a direction that avoids or prevents it from approaching the road boundary lines 24, 25 or deviating from the lane. This steering reaction force can be a predetermined constant value, but in the embodiment described here, the steering reaction force is configured to be larger as the actual steering angle exceeds the limit steering angle and the difference between the two is large. Note that the difference between the actual steering angle and the limit steering angle can increase as the actual steering angle increases or as the limit steering angle decreases. An example of the former is when the vehicle is approaching the road boundary lines 24, 25 and is further steered in the direction of approaching. An example of the latter is when the limit steering angle δmax decreases as the vehicle 2 approaches the road boundary lines 24, 25 (as the lateral distance y mentioned above decreases), and the difference between the actual steering angle and the limit steering angle increases even if the actual steering angle does not change. Therefore, the reaction force map 22 can be represented as a two-dimensional map, as shown in Figure 4, with the horizontal axis representing the deviation of the rudder angle (= limit rudder angle - actual rudder angle) Δδ and the vertical axis representing the steering reaction force (support torque) τ. The support torque τ, which increases in proportion to the deviation of the rudder angle Δδ, is configured to increase. Although only the right-side reaction force map 22 is shown in Figure 4, reaction force maps 22 are provided similarly on both the left and right sides.

[0027] In the case of a wide road, where the width of lane 23 is sufficiently wide relative to the width of vehicle 2, the width of the support invalidation area 28 described above is wider than the width of vehicle 2, and when driving in the center of lane 23, areas where steering assistance is not provided are created on both the left and right sides of vehicle 2. In contrast, on a so-called narrow road, the width of the support invalidation area 28 becomes close to the width of vehicle 2, or even narrower than the width of vehicle 2, and in some cases the left and right support execution areas 29 and 30 overlap, eliminating the support invalidation area 28. A narrow road is a road where the width of lane 23 is such that the distance between the left and right support execution areas 29 and 30 (the distance between support start positions 26 and 27, or the width of the support invalidation area 28) is less than or equal to a predetermined value. When vehicle 2 is driving on such a narrow road, if it steers slightly to the right or left, steering assistance is initiated when it exceeds either the left or right support start position 26 (27). That is, a steering reaction force (assistance torque) is generated in the direction of turning the steering wheel 4 back. Such steering assistance occurs in both the rightward and leftward directions, causing the steering wheel 4 to be turned back in the direction of the steering reaction force, resulting in a steering angle in the opposite direction to before. Therefore, on a narrow road, the actual steering angle exceeds the limit steering angle δmax, generating a steering reaction force (assistance torque) in the opposite direction to before. The controller 15 described above is configured to adjust the limit steering angle δmax in order to avoid this so-called control hunting. Specifically, when the vehicle is driving near the center of lane 23, the deviation (sum of absolute values ​​if there is a positive or negative sign) of the left and right limit steering angles δmax becomes small enough to fall below a threshold, or when predetermined conditions are met, such as the width of lane 23 being narrower than a predetermined width, the controller 15 virtually sets the left and right road boundary lines as a single line in the center of lane 23 in the width direction, and calculates the left and right limit steering angles δmax based on this virtual road boundary line (hereinafter referred to as the virtual road boundary line).

[0028] The controller 15 is equipped with the functional means (functional configuration) shown in Figure 5 to perform steering assistance control, including the control of the steering reaction force and adjustment of the limit steering angle δmax as described above. In Figure 5, the controller 15 is equipped with a boundary detection unit 15a that detects the right-hand lane boundary line 25 and the left-hand lane boundary line 24 that demarcate the lane 23 in which the vehicle 2 is traveling. These lane boundary lines 24 and 25 can be detected using image data obtained by the camera 16 described above. The positions of each lane boundary line 24 and 25 can be determined as a coordinate system with the vehicle 2 as the origin, or as a map position based on information from NAVI 17 and map data.

[0029] The system includes a limit steering angle detection unit 15b that detects the aforementioned limit steering angle δmax. As described above, the limit steering angle δmax is the steering angle required for the vehicle 2 to reach the track boundary lines 24, 25, or the steering angle required for the vehicle 2 to be on the track boundary lines 24, 25, assuming the vehicle 2 travels at the current vehicle speed for a predetermined look-ahead time t. Similar to the actual steering angle, this is expressed, for example, as the amount of steering of the steering wheel 4, with the angle at which the vehicle 2 does not turn to the left or right being defined as "0 degrees" (or the neutral position or reference steering position So), and is expressed as the angle from this point. As described above, in the embodiment described here, the left direction is defined as "positive" and the right direction as "negative," and the limit steering angle is larger to the left from the reference steering position So, and smaller to the right. Furthermore, the relative position between the vehicle 2 and the left and right road boundary lines 24 and 25 can be detected by information from NAVI 17 and detection data from the boundary detection unit 15a, and the vehicle speed is detected by the vehicle speed sensor 18. In addition, a predetermined look-ahead time t is set in advance, so the limit steering angle δmax is given by the aforementioned formula (δmax = sin -1This can be determined using (y / x) or the turning curvature from the vehicle's equation of motion for steady-state circular turns. Note that both the left limit steering angle Lδmax (when vehicle 2 is moving to the left) and the right limit steering angle Rδmax (when vehicle 2 is moving to the right) can be determined as limit steering angles δmax. Furthermore, to represent the direction of these limit steering angles Lδmax and Rδmax, for example, the left limit steering angle Lδmax is set to a positive angle, and the right limit steering angle Rδmax is set to a negative angle.

[0030] The system includes an actual steering angle detection unit 15c. The actual steering angle δ is the amount of rotation from the aforementioned reference steering position So when the steering wheel 4 is rotated, and can be detected based on the detection data from the steering angle sensor 13. In the embodiment described here, the actual steering angle δ is detected as a positive steering angle when the vehicle 2 is turned to the left, and as a negative steering angle when the vehicle 2 is turned to the right.

[0031] The system includes a comparison unit 15d that compares the actual steering angle δ with the limit steering angle δmax, and a steering support unit 15e that generates a steering reaction force based on the result of the comparison. The comparison unit 15d detects whether the actual steering angle δ when steering to the left exceeds the left limit steering angle Lδmax, whether the actual steering angle δ when steering to the right exceeds the right limit steering angle Rδmax, and the difference between the two angles. The steering support unit 15e generates a steering reaction force (support torque) in the direction that reduces the steering angle in the operated direction when the actual steering angle δ exceeds the limit steering angle δmax. In other words, it generates a steering reaction force (support torque) in the direction that reduces the angle difference between the actual steering angle δ and the limit steering angle δmax. For example, if steering to the left causes the actual steering angle δ to exceed the left limit steering angle Lδmax, a steering reaction force is generated in the rightward direction to turn the steering wheel 4 back to the right. Conversely, if steering to the right causes the actual steering angle δ to exceed the right limit steering angle Rδmax, a leftward steering reaction force is generated to turn the steering wheel 4 back to the left. This steering reaction force may be a predetermined constant value, or it may be a steering reaction force (support torque) τ of a magnitude corresponding to the deviation Δδ of the steering angle. For example, if the left support torque is Lτ and the right support torque is Rτ, Lτ=K(Lδmax-δ), Rτ=K(Rδmax-δ) Generate the torque represented by [the formula]. Here, K is a predetermined coefficient, which may be a constant, or may be a variable determined according to the vehicle speed or the like.

[0032] The lane 23 on which the vehicle 2 is traveling is usually defined by the left and right road boundary lines 24 and 25. Therefore, the left and right limit steering angles Lδmax and Rδmax are constantly detected as described above. On the other hand, since the steering reaction force is applied when the actual steering angle δ exceeds the limit steering angle δmax, when the following relationship holds between the actual steering angle δ and the left and right limit steering angles Lδmax and Rδmax, the above-described left and right assist torques Lτ and Rτ are calculated. That is, when steering to the left and the actual steering angle δ is greater than the left limit steering angle Lδmax (Lδmax < δ), an assist torque Lτ (= K(Lδmax - δ)) in the direction of reducing the angle difference is calculated. Similarly, when steering to the right and the actual steering angle δ is less than the right limit steering angle Rδmax (δ < Rδmax), an assist torque Rτ (= K(Rδmax - δ)) in the direction of reducing the angle difference is calculated. When the actual steering angle δ is less than or equal to the left limit steering angle Lδmax and greater than or equal to the right limit steering angle Rδmax (Rδmax ≤ δ ≤ Lδmax), the vehicle 2 is in the assist invalid region 28, so the assist torques Lτ and Rτ are not generated (Lτ, Rτ = 0). Here, "greater," "less," and "greater than or equal to" are expressions based on setting the operation amount to the left from the above-described reference steering position So of the steering wheel 4 as "positive" and the operation amount to the opposite right direction as "negative."

[0033] Note that the actual steering angle δ changes by steering, and the left and right limit steering angles Lδmax and Rδmax change as the distance between the vehicle 2 and the road boundary lines 24 and 25 changes, as described above. Therefore, due to these changes, the steering angle deviation Δδ and the left and right assist torques Lτ and Rτ based on it change.

[0034] The limit steering angle δmax becomes larger as the distance between the vehicle 2 and the road boundary lines 24 and 25 (the distance y measured in the width direction of lane 23 as described above) increases. Therefore, even if the actual steering angle δ while driving in the center of lane 23 does not exceed the limit steering angle δmax at that time, if the vehicle continues to drive at that actual steering angle δ and approaches either of the road boundary lines 24 or 25, the limit steering angle δmax will decrease. As a result, even without changing the actual steering angle δ, the actual steering angle δ will exceed the limit steering angle δmax, and consequently, a support torque τ will be generated to provide steering assistance. In other words, the position where the assistance starts is one that is a distance y from the road boundary lines 24 and 25 based on the lateral movement amount y described above, which is determined by the limit steering angle δmax.

[0035] The controller 15 includes a determination unit 15f that determines whether predetermined conditions related to the width of lane 23 are met, such as whether the vehicle 2 is traveling near the center of lane 23, or whether lane 23 is a narrow road. This determination can be made by calculating the deviation of the sequentially calculated left and right limit steering angles Lδmax and Rδmax, and comparing that deviation with a predetermined threshold. Alternatively, it can be made by calculating the distance between the left and right road boundary lines 24 and 25 from the data on those road boundary lines 24 and 25, and comparing that distance with a predetermined value. Furthermore, it can be made by comparing the distance between the aforementioned support start positions 26 and 27 with a predetermined value. The predetermined value that serves as the basis for this determination can be predetermined based on the width of the vehicle 2, etc.

[0036] A lane determined to be a narrow road may be either a lane where the aforementioned support invalidation area 28 exists but is narrow, or a lane where the left and right support execution areas 29 and 30 partially overlap and the support invalidation area 28 does not exist. In either of these cases, a slight change in the actual steering angle δ may trigger steering assistance that generates the aforementioned steering reaction force, potentially increasing its frequency and repetition count. To avoid or suppress this so-called control hunting, a support adjustment unit 15g is provided to adjust the limit steering angle δmax. This support adjustment unit 15g is configured to calculate and set the left and right limit steering angles Lδmax and Rδmax based on the left and right road boundary lines, which are virtually set as a single line in the center of the lane 23, as will be described later. Therefore, in this case, the left and right limit steering angles Lδmax and Rδmax will be the same angle. Also, in this case, the left and right support start positions 26 and 27 will coincide with the center of the lane 23. Therefore, if the steering wheel 4 is rotated even slightly to the right or left from the aforementioned reference steering position So, the actual steering angle δ will exceed the limit steering angle δmax, resulting in a steering reaction force in the opposite direction to the rotation operation. As a result, the steering angle or steering position is maintained at the reference steering position So, and so-called control hunting, which involves repeated steering to the left and right and then reversing that direction, is eliminated or suppressed.

[0037] Next, an example of steering assistance control performed by the controller 15 described above will be explained with reference to the flowchart shown in Figure 6. First, various data are read in step S1. As previously mentioned, this data includes image data of the area around the vehicle 2 including the road boundary lines 24 and 25, data on vehicle speed, position data of the vehicle 2, data on steering angle, and a reaction force map. Based on this data, the left and right road boundary lines 24 and 25 are detected (step S2). In step S2, the positions of the left and right road boundary lines 24 and 25 on the map or their relative positions to the vehicle 2 are detected. Furthermore, based on this data on the left and right road boundary lines 24 and 25, and the vehicle speed and a predetermined time (look-ahead time) t, the left and right limit steering angles Lδmax and Rδmax are detected (step S3).

[0038] Next, it is determined whether predetermined conditions are met in the current driving situation of vehicle 2 (step S4). Here, predetermined conditions are conditions for adjusting the left and right limit steering angles Lδmax, Rδmax obtained as described above, and are conditions that the determination unit 15f determines to be met. That is, the deviation of the left and right limit steering angles Lδmax, Rδmax (the sum of the absolute values ​​of the left and right limit steering angles Lδmax, Rδmax) is less than or equal to a predetermined threshold, or the width of lane 23 is less than or equal to a predetermined width, and other conditions predetermined with the width of lane 23 as a factor. Therefore, the determination in step S4 can be made based on the calculated left and right limit steering angles Lδmax, Rδmax, the detected width of lane 23, etc. Alternatively, since the left and right road boundary lines 24, 25 and the left and right limit steering angles Lδmax, Rδmax have been determined, the left and right support start positions 26, 27 can be determined based on this data, and the distance between these left and right support start positions 26, 27 can be compared with a predetermined value stored in advance as a judgment criterion to make the determination in step S4.

[0039] If a positive result is obtained in step S4, the left and right limit steering angles Lδmax and Rδmax are adjusted (step S5). Specifically, as described above, a virtual road boundary line is set in the center of the width direction of lane 23, and the left and right limit steering angles Lδmax and Rδmax are calculated based on this virtual road boundary line. Therefore, these limit steering angles Lδmax and Rδmax will be the same angle. Also, the left and right support start positions 26 and 27 will be set to the same position, such as in the center of lane 23. As a result, the aforementioned support invalidation area 28 is eliminated, and the left and right sides from the center of lane 23 are set as the support execution areas 29 and 30.

[0040] Next, it is determined whether the actual steering angle δ on either the left or right side is greater than the left limit steering angle Lδmax, or less than the right limit steering angle Rδmax (step S6). In terms of the absolute value of each angle, this determination is whether the actual steering angle exceeds the limit steering angle on either side. If the determination in step S4 above is negative, the process proceeds immediately to step S6.

[0041] If the actual steering angle δ exceeds the limit steering angle δmax and this is determined positively in step S6, the steering reaction force (support torque) is calculated (step S7). If the actual steering angle δ exceeds the left limit steering angle Lδmax in the leftward direction, the steering reaction force Lτ is calculated by multiplying the deviation by a predetermined coefficient K. This steering reaction force Lτ is a torque that reduces the angular difference between the actual steering angle δ and the left limit steering angle Lδmax, and acts to rotate the steering wheel 4 to the right. Similarly, if the actual steering angle δ exceeds the right limit steering angle Rδmax in the rightward direction, the rightward steering reaction force (rightward support torque) Rτ is calculated by multiplying the deviation by a predetermined coefficient K. This rightward steering reaction force Rτ is a torque that reduces the angular difference between the actual steering angle δ and the right limit steering angle Rδmax, and acts to rotate the steering wheel 4 to the left.

[0042] If the actual steering angle δ exceeds either the left or right limit steering angle Lδmax or Rδmax (as an absolute value), the steering reaction forces Lτ and Rτ are calculated as described above, and a control command signal is output to the EPS-ECU14 to apply these steering reaction forces Lτ and Rτ to the EPS1 or steering wheel 4 (step S8). Then, the system returns.

[0043] Furthermore, if a negative result is obtained in step S6 as described above, that is, if the actual steering angle δ does not exceed the limit steering angles Lδmax,Rδmax, then the system returns immediately.

[0044] The behavior of vehicle 2 and the generation of steering reaction force when the steering assist control described above is performed will be explained. Figure 7 is a schematic diagram to explain the situation when driving on a so-called wide road, and because the width of lane 23 is sufficiently wide compared to the width of vehicle 2, the assist invalidation area 28 is wide, and therefore the left and right limit steering angles Lδmax and Rδmax are large angles (angles from the neutral position where the steering angle determined by the mechanism is zero). Therefore, even if the steering wheel 4 of vehicle 2 driving in the assist invalidation area 28 is rotated and its actual steering angle δ changes, the direction of travel of vehicle 2 changes to the right or left, and the limit steering angle δmax changes due to the change in the orientation of vehicle 2, vehicle 2 remains in the assist invalidation area 28. Therefore, in this state, no steering reaction force is generated. The driver of vehicle 2 usually tries to drive along lane 23, such as in the center of lane 23, so when vehicle 2 moves to the right or left of lane 23, the driver steers to correct the deviation from the center of lane 23. In other words, vehicle 2 travels within the assist-disabled region 28, as shown by the gentle wavy line in Figure 7, and no steering reaction force acts upon it. To put it another way, vehicle 2 travels according to the steering intended by the driver.

[0045] Figure 8 is a schematic diagram illustrating the situation when driving on a so-called narrow road. Due to the narrow width of lane 23, the distance between the left and right support start positions 26 and 27 (width of the support inactive area 28), which is determined according to the left and right limit steering angles Lδmax and Rδmax obtained from the vehicle speed and the aforementioned look-forward time, is narrowed to approximately the width of vehicle 2. Therefore, if the left and right limit steering angles Lδmax and Rδmax, as explained with reference to step S5 in Figure 6, are not adjusted, vehicle 2 will cross the support start positions 26 and 27 each time it deviates slightly to the left or right from the center of lane 23, generating steering reaction force. To avoid this, on a narrow road, a virtual road boundary line is set at the center of lane 23, and the limit steering angle δmax is adjusted. As a result, the left and right limit steering angles Lδmax and Rδmax become the same angle, and the left and right support start positions 26 and 27 are set to the same position, such as the center of lane 23. In other words, if the center of lane 23 is considered the normal driving position, the aforementioned support ineffective area 28 is eliminated, and the areas to the left and right of the center of lane 23 become the support execution areas 29 and 30.

[0046] FIG. 8 shows the left and right reaction force maps 22 side by side, and the greater the deviation from the center of the lane 23, the greater the steering reaction force τ will act. Specifically, the symbol "Lc" in FIG. 8 indicates the virtual travel boundary line. Assuming that the vehicle 2 is traveling while being somewhat deflected to the right with respect to the direction of the lane 23 (the direction of the virtual travel boundary line Lc) from the center of the lane 23, the limit steering angle δmax is obtained based on the virtual travel boundary line Lc. Since the virtual travel boundary line Lc is set at the center of the lane 23, the vehicle 2 shown in FIG. 8 has already crossed the travel boundary line, and the actual steering angle δ exceeds the right limit steering angle Rδmax. Therefore, an assist torque corresponding to the difference between the actual steering angle δ and the right limit steering angle Rδmax obtained based on the virtual travel boundary line Lc acts in the direction of returning the vehicle 2 to the center of the lane 23. That is, in this case, since the actual steering angle δ is smaller than the right limit steering angle Rδmax (δ < Rδmax, large in the negative direction), the above-described assist torque Rτ (= K(Rδmax - δ)) is calculated. In that case, since the relationship (Lδmax < δ) described above does not hold between the actual steering angle δ and the left limit steering angle Lδmax, the other assist torque Lτ (= K(Lδmax - δ)) is not calculated. The same situation applies when the vehicle 2 is deflected to the left with respect to the virtual travel boundary line Lc. Note that FIG. 8 shows the left and right assist start positions 26, 27 in terms of the rotation angle of the steering wheel 4, and the regions on both sides of the neutral position where the steering angle determined by the mechanism is zero are the assist execution regions 29, 30.

[0047] Therefore, when trying to steer to either the left or right, the steering reaction force immediately acts, and as a result, the steering reaction force acts so that the vehicle 2 does not deviate from the center of the lane 23. Eventually, since the steering reaction force acts from both the left and right directions to hold the steering wheel 4 at the above neutral position, even if the vehicle 2 temporarily travels as shown by the wavy line in FIG. 8, the steering wheel 4 is held at the neutral position, and the vehicle 2 travels along the center of the lane 23 (the virtual travel boundary line Lc). That is, so-called control hunting in which the steering reaction force alternately occurs and acts on the left and right is avoided or suppressed.

[0048] Here, we will explain the relationship between the actual steering angle δ and the limit steering angle δmax when vehicle 2 is located on a virtual road boundary line Lc set in the center of lane 23 and is deviating to either the left or right with respect to the direction of lane 23. Figure 9(A) shows vehicle 2 located on the virtual road boundary line Lc and traveling along the direction of lane 23. In this case, since vehicle 2 is on and coincides with the virtual road boundary line Lc in terms of position and orientation, the limit steering angle δmax is "0 degrees", and the actual steering angle δ is also "0 degrees" as if traveling in a straight line. Therefore, since there is no angular difference between the actual steering angle δ and the limit steering angle δmax, the support torque τ is not calculated, and no steering reaction force is generated.

[0049] Figure 9(B) shows a state where vehicle 2 is on the virtual road boundary line Lc and is traveling with a predetermined angle of deflection to the left relative to the direction of lane 23. In this case, even if vehicle 2 is on the virtual road boundary line Lc and the actual steering angle δ is "0 degrees", the limit steering angle δmax is calculated because the vehicle body is deflected to the left. That is, if the vehicle continues to travel with such a deflection, it will deviate from the virtual road boundary line Lc, so the steering angle required to reach (return to) the virtual road boundary line Lc within a predetermined look-ahead time t is calculated as the limit steering angle δmax. In the example shown in Figure 9(B), the limit steering angle δmax is the angle at the position where the steering is turned to the right from the steering reference position So. Therefore, since the actual steering angle δ is larger than the limit steering angle δmax, the support torque Lτ (=K(Lδmax-δ)) is calculated according to the angle difference and steering support is performed.

[0050] Figure 9(C), contrary to the example shown in Figure 9(B) above, shows a state where vehicle 2 is on the virtual road boundary line Lc and is traveling with a predetermined angle of deflection to the right relative to the direction of lane 23. In this case, even if vehicle 2 is on the virtual road boundary line Lc and the actual steering angle δ is "0 degrees", the limit steering angle δmax is calculated because the vehicle body is deflected to the right. That is, if the vehicle continues to travel with such a deflection, it will deviate from the virtual road boundary line Lc, so the steering angle required to reach (return to) the virtual road boundary line Lc within a predetermined look-ahead time t is calculated as the limit steering angle δmax. In the example shown in Figure 9(C), the limit steering angle δmax is the angle at the position where the steering is turned to the left from the steering reference position So. Therefore, since the actual steering angle δ is smaller than the limit steering angle δmax, the support torque Rτ (=K(Rδmax-δ)) is calculated according to the angle difference and steering support is performed.

[0051] Figure 10(A) shows the direction of steering assistance, the deviation Δδ of the limit steering angle δmax and the actual steering angle δ from the limit steering angle δmax, and the way the steering reaction force (assistance torque) τ acts when the limit steering angle δmax is adjusted on a so-called narrow road. That is, in the case of a straight road, the limit steering angle δmax is zero degrees because the support start positions 26 and 27 are mechanically determined neutral positions, and the direction of assistance is in both left and right directions at the zero-degree position. Furthermore, the left and right limit steering angles δmax are determined based on the aforementioned virtual road boundary line Lc. That is, the limit steering angle δmax is determined as the steering angle at which the steering reaches (returns to) the virtual road boundary line Lc in a predetermined look-ahead time. As explained with reference to Figures 9(A), 9(B), and 9(C) above, the limit steering angle δmax is "0 degrees" when the vehicle 2 is on the virtual road boundary line Lc and traveling in a direction along lane 23 (virtual road boundary line Lc), and otherwise the limit steering angle δmax is calculated to a predetermined angle. Therefore, if the vehicle 2 is moving away from the center of lane 23, or is attempting to move away from the center of lane 23, a steering reaction force is generated according to the angle difference between the actual steering angle δ and the limit steering angle δmax, and steering assistance is performed to return the vehicle 2 to the center of lane 23 or to maintain it there. In other words, the deviation Δδ between the actual steering angle δ and the limit steering angle δmax gradually decreases and eventually becomes zero, and similarly the assistance torque τ also converges to zero.

[0052] For comparison, Figure 10(B) shows the direction of steering assistance, the deviation Δδ of the limit steering angle δmax and the actual steering angle δ from the limit steering angle δmax, and how the steering reaction force (assistance torque) acts when the limit steering angle δmax is not adjusted. In this case, the left and right support start positions 26 and 27 are separated by the support invalidation area 28, and limit steering angles Lδmax and Rδmax are set for the left and right sides respectively. Therefore, the direction of assistance is to the right when the vehicle is positioned closer to the left of lane 23, and to the left when the vehicle is positioned closer to the right of lane 23. Furthermore, when the vehicle is steered left or right to correct a deviation from the center of lane 23, and as a result the above deviation Δδ occurs, steering assistance is performed, and an assistance torque τ is generated while the deviation Δδ is present. Consequently, the vehicle 2 returns to the center of lane 23, and if a steering angle is still present at that time, a deviation Δδ in the opposite direction occurs, and steering assistance is performed by the assistance torque τ. Thus, on narrow roads, steering assistance is provided by a small actual steering angle δ and the resulting deviation Δδ, resulting in repeated reversals of steering wheel 4 and steering reaction forces. In other words, control hunting occurs.

[0053] The above example concerns a narrow road where a support invalidation area 28 occurs. However, in this embodiment of the invention, even when driving on a narrow road where the left and right support execution areas 29 and 30 partially overlap and no support invalidation area 28 occurs, the same limit steering angle adjustment as in the above example can be performed. To illustrate this example, Figure 11 shows an example on a narrow road where the left support start position 26 is located to the right of the center of lane 23, and the right support start position 27 is located to the left of the center of lane 23, with the left and right support execution areas 29 and 30 partially overlapping. In this state, even when vehicle 2 is driving in the center of lane 23, the vehicle is within the left and right support execution areas 29 and 30, so steering reaction forces are acting on the left and right. Since the directions of these steering reaction forces are opposite to each other, ultimately, the difference between the left and right steering reaction forces acts on the vehicle. Figure 11 shows the steering reaction forces (support torques) Lτ and Rτ on the left and right sides, and their difference Δτ, as diagrams.

[0054] As can be seen from this diagram, when vehicle 2 is located in the center of lane 23 and the actual steering angle δ is zero, even if steering reaction forces Lτ and Rτ act from both the left and right, their magnitudes are the same and their directions are opposite, so the steering reaction forces cancel each other out and become zero. When the steering wheel 4 is operated from that state and an actual steering angle δ is generated, the difference Δτ between the support torques Lτ and Rτ acts as the steering reaction force. Therefore, the steering reaction force that actually acts is the difference Δτ, and the change gradient of the difference Δτ (the amount of change relative to the amount of change in the steering angle deviation Δδ) is larger in the region where the support execution areas 29 and 30 overlap than in the other support execution areas 29 and 30. Thus, when the support execution areas 29 and 30 overlap on a narrow road, a step occurs in the change of the support torque τ, and the position or timing of this step differs depending on the driving conditions such as the lane width and vehicle speed, so the driver may feel uncomfortable with the steering assistance control.

[0055] In contrast, in the embodiment of this invention, when the conditions shown in Figure 11 are met, that is, when the vehicle is traveling along the lane in the center of the lane, and the right limit steering angle is an angle that turns the vehicle to the left, and the left limit steering angle is an angle that turns the vehicle to the right, the aforementioned virtual road boundary line Lc is set and the limit steering angle δmax is adjusted, and in that case the support torque τ becomes as shown in Figure 12. That is, in the example of Figure 12, the support start positions 26 and 27, which were separated on the left and right, are set to the same position in the center of lane 23, making the left and right limit steering angles Lδmax and Rδmax the same. By doing so, one support execution area 29 is set to the left of the center of lane 23, and the other support execution area 30 is set to the right. In other words, the overlap of support execution areas 29 and 30 is eliminated. This is the same as the state shown in Figure 8 above, and therefore hunting in support control can be eliminated, and steps in support torque can also be eliminated.

[0056] It should be noted that this invention is not limited to the embodiments described above, and can be applied and implemented in the same manner as the embodiments described above when driving on curved roads (revolving roads) in addition to when driving on straight roads. In the case of curved roads (revolving roads), the steering angle position at which the vehicle travels in the center of the lane according to the curvature of the lane is set as the reference steering position, and limit steering angles are set to the left and right of this reference steering position. In addition, in this invention, the operating unit for steering may be a steering stick (steering stick or joystick) instead of the steering wheel described above. In that case, since the steering stick is tilted left and right without rotating, the actual steering angle in the embodiments described above can be treated as the actual tilt angle, and the limit steering angle can be treated as the limit tilt angle. Therefore, the steering angle in this invention includes the angle of tilt. Furthermore, in the embodiments described above, the steering angle to the left was described as a "positive" angle, and the steering angle to the right was described as a "negative" angle, but these "positive" and "negative" may be the opposite of those in the embodiments described above, and absolute values ​​may be used without distinguishing between "positive" and "negative". [Explanation of Symbols]

[0057] 1. Electric Power Steering System (EPS) 2 vehicles 3 Steering Wheel 4 Steering Wheel 5. Steering shaft 6. Steering Linkage 7 racks 8 pinion 9 Tie rods 10 motors 11 Reducer 12 Torque Sensor 13. Steering angle sensor 14 Electronic control unit (EPS-ECU) 15 Controllers 15a Boundary detection unit 15b Limit rudder angle detection unit 15c Actual rudder angle detection unit 15d Comparison section 15e Steering Support Unit 15f Judgment section 15g Support Coordination Department 16 cameras 17. Navigation System (NAVI) 18. Vehicle speed sensor 19 Map data 20 Limit rudder angle data 21 Predetermined Value Data 22 Reaction Force Map 23 lanes 24,25 Runway boundary line 26,27 Support start position 28 Support Disabled Area 29,30 Support Implementation Areas Δδ (deviation between actual rudder angle and limit rudder angle) Δτ (difference of support torque) δ Actual steering angle δmax limit rudder angle τ Steering reaction force (support torque) Lc Virtual Road Boundary Lδmax Left limit rudder angle Lτ Left steering reaction force (support torque) Rδmax Right limit rudder angle Rτ Right steering reaction force (right support torque) So reference steering position

Claims

1. A vehicle driving assistance device that assists steering to prevent a vehicle traveling within a designated lane from deviating from the lane, Equipped with a controller to adjust the steering force, The aforementioned controller, A boundary detection unit that detects the right-hand and left-hand lane boundary lines that demarcate the lane in which the vehicle is traveling, A limit steering angle detection unit detects at least one of the right limit steering angle, which is the steering angle at which the vehicle reaches the right-hand road boundary line, and the left limit steering angle, which is the steering angle at which the vehicle reaches the left-hand road boundary line, assuming the vehicle is driven for a predetermined time at the current speed. A steering angle detection unit detects the actual steering angle, which is the amount of steering input performed from the steering position that allows the vehicle to move straight. When the limit steering angle detection unit detects the right limit steering angle, the left limit steering angle, or both, a comparison unit compares the actual steering angle with the right limit steering angle or the left limit steering angle. A steering support unit that, when the actual steering angle exceeds the right limit steering angle or the left limit steering angle, generates a steering reaction force in a direction that reduces the difference between the right limit steering angle or the left limit steering angle that the actual steering angle exceeds and the actual steering angle, A determination unit that determines whether predetermined conditions related to the width of the lane are met, If the determination unit determines that the predetermined conditions are met, the steering support adjustment unit virtually sets the left and right lane boundary lines to the center in the width direction of the lane, and based on the virtually set left and right lane boundary lines, determines the right limit steering angle and the left limit steering angle and generates the steering reaction force using the steering support unit. It has A vehicle driving assistance device characterized by the following features.

2. A vehicle driving assistance device according to claim 1, The aforementioned predetermined conditions include either that the deviation between the right limit steering angle and the left limit steering angle is less than or equal to a predetermined threshold, or that the lane is a narrow road with a width narrower than a predetermined standard width. A vehicle driving assistance device characterized by the following features.

3. A vehicle driving assistance device according to claim 1 or 2, The vehicle is further equipped with an operating unit for rotating or tilting in order to turn the vehicle around. The actual steering angle, the right limit steering angle, and the left limit steering angle are measured by setting the amount of operation of the control unit that moves the vehicle straight as "0 degrees," the amount of operation of the control unit that turns the vehicle to the right or left as "positive," and the amount of operation of the control unit that turns the vehicle to the right or left as "negative." A vehicle driving assistance device characterized by the following features.

4. A vehicle driving assistance device according to claim 1 or 2, The steering support unit generates a steering reaction force of a magnitude corresponding to the amount by which the actual steering angle exceeds the right limit steering angle, or the amount by which the actual steering angle exceeds the left limit steering angle. A vehicle driving assistance device characterized by the following features.

5. A vehicle driving assistance device according to claim 1 or 2, The determination unit determines that the predetermined conditions are met when, while the vehicle is traveling in the center of the lane in a direction along the lane, the right limit steering angle detected by the limit steering angle detection unit is at an angle that generates the steering reaction force in the direction that turns the vehicle to the left, and the left limit steering angle detected by the limit steering angle detection unit is at an angle that generates the steering reaction force in the direction that turns the vehicle to the right. A vehicle driving assistance device characterized by the following features.

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