DRIVING ASSISTANCE DEVICE

Abstract

Driving assistance device which features: a vehicle-integrated camera for recording an area in front of the vehicle in one direction of travel; a radar device for emitting test waves to an area in front of the vehicle in the direction of travel and for receiving reflection waves; a roadside detection unit for detecting a roadside as a side of a road on which the vehicle is driving, based on information from the reflection waves received by the radar device; a lane line detection unit for detecting left and right lane lines that define a lane, using an image captured by the vehicle's own camera; a determination unit for determining whether an estimated width, defined as the width between the road edge detected by the road edge detection unit and the lane line on the side of the road edge detected by the lane line detection unit, is less than a predetermined width; and a driving assistance unit for performing driving assistance for the own vehicle in order to maintain a lateral position of the own vehicle in a vehicle width direction at a predetermined position on an estimated lane as the lane estimated from the left and right lane lines detected by the lane line detection unit, wherein The driving assistance unit sets the predetermined position to a position that is further away from the lane line on the side of the road on the estimated lane when the determining unit determines that the estimated width is smaller than the predetermined width, than when the determining unit determines that the estimated width is not smaller than the predetermined width. the vehicle includes an electric power steering system (13) for controlling the direction of travel of the vehicle using an output torque of a motor (13a), The driving assistance is controlled by the electric power steering in such a way that the vehicle drives by maintaining the predetermined position, and also includes: a computing unit (10) for calculating a change torque quantity when a driver operates the electric power steering, so that a change torque is generated to change the direction of travel of the vehicle; and a driving assistance cancellation unit (10) for canceling the driving assistance provided by the driving assistance unit when the change moment magnitude calculated by the computing unit is greater than a first threshold, provided that the driving assistance is provided by the driving assistance unit and the estimated width is not less than the predetermined width; and The driving assistance cancellation unit cancels the driving assistance provided by the driving assistance unit when the change moment quantity calculated by the computing unit is greater than a second threshold that is smaller than the first threshold, provided that the driving assistance is provided by the driving assistance unit and the estimated width is smaller than the predetermined width.

Description

Technical field

[0001] The present invention relates to a driving assistance device mounted on a vehicle to detect lane lines that define lanes and causes the vehicle to perform driving assistance based on the detected lane lines. State of the art

[0002] The road shape recognition device described in JP 5 711 721 B2, for example, detects a white line of a lane in which the vehicle is traveling from image information captured by a camera. A lane is estimated based on white line information, and then a driving trajectory of the vehicle is estimated.

[0003] US Patent 2013 / 0274959A1 discloses a driver assistance device comprising: a vehicle-mounted camera for recording an area in front of the vehicle in a direction of travel; a radar device for transmitting test waves to an area in front of the vehicle in the direction of travel and for receiving reflection waves; a road edge detection unit for detecting a road edge as one side of a road on which the vehicle is traveling, based on information from the reflection waves received by the radar device; a lane line detection unit for detecting left and right lane lines that define a lane, based on an image captured by the vehicle-mounted camera; and a determination unit for determining whether an estimated width is the width between the road edge detected by the road edge detection unit and the lane line on the side of the road edge.which is detected by the lane line detection unit, is smaller than a predetermined width; and a driving assistance unit for performing driving assistance for the own vehicle to maintain a lateral position of the own vehicle in a vehicle width direction at a predetermined position on an estimated lane than the lane estimated from the left and right lane lines detected by the lane line detection unit, wherein the driving assistance unit sets the predetermined position to a position that is further away from the lane line on the side of the road on the estimated lane when the determination unit determines that the estimated width is smaller than the predetermined width, than when the determination unit determines that the estimated width is not smaller than the predetermined width.The vehicle includes an electric power steering system for controlling the vehicle's direction of travel using an output torque from a motor; the driving assistance provided by the electric power steering system is controlled in such a way that the vehicle travels by maintaining a predetermined position; and it also includes a processing unit for calculating a change torque quantity when a driver operates the electric power steering system, thus generating a change torque to alter the vehicle's direction of travel.

[0004] DE 10 2015 207 025 A1 discloses a driver assistance system in a motor vehicle that performs active lateral control interventions (in particular steering interventions), can be activated independently of the activation of a longitudinal control system, can be active both with and without longitudinal control, and includes both a traffic jam assist sub-function and a lane guidance assist sub-function, wherein the two sub-functions can be activated and deactivated together by a single on / off button (STA / ALC). Summary of the invention

[0005] Consider a scenario where a vehicle is traveling on a road with a shoulder on one side, where walls, embankments, or guardrails are located. If, in this scenario, a wall or guardrail is included in image information captured by a camera, a pattern on the wall or an uneven portion of the guardrail may be mistakenly identified as a white line (road edge line marking the edge of the road) of the lane. JP 5 711 721 B2 does not address the problem of mistakenly identifying a wall pattern or guardrail unevenness as a white line of a road, nor does it disclose or suggest any countermeasures regarding this problem.Accordingly, in the technology described in JP 5 711 721 B2, the lane position cannot be accurately estimated due to faulty white line information, and therefore appropriate driving assistance cannot be provided. In particular, there is concern that the vehicle will travel at a position closer to the road edge line than is appropriate.

[0006] The present invention solves the above problem, and its main objective is to provide a driving assistance device that can prevent the vehicle from driving at a position closer to an actual road edge than a suitable position, even when the road edge is mistakenly detected as a road edge, based on an image taken by a vehicle-mounted camera that detects lane lines of a lane in which the vehicle is traveling. This objective is achieved by a driving assistance device with the features of claim 1 and claim 2, respectively. The dependent claims are directed to advantageous embodiments of the invention.

[0007] The present invention relates to a driving assistance device comprising: a vehicle-integrated camera for recording an area in front of the vehicle in its direction of travel, a radar device for emitting test waves to an area in front of the vehicle in its direction of travel and for receiving reflection waves, a road edge detection unit for detecting a road edge as one side of a road on which the vehicle is traveling, based on information from the reflection waves received by the radar device, a lane line detection unit for detecting left and right lane lines defining a lane, based on an image captured by the vehicle-integrated camera, and a determination unit for determining whether an estimated width is the width of the road edge detected by the road edge detection unit and the lane line on the side of the road edge.the lane line detection unit detects is narrower than a predetermined width, and a driving assistance device for performing driving assistance for the own vehicle to maintain a lateral position of the own vehicle in a vehicle width direction at a predetermined position on an estimated lane than the lane estimated from the left and right lane lines detected by the lane line detection unit, wherein the driving assistance unit sets the predetermined position to a position further away from the lane line on the side of the road edge on the estimated lane when the determination unit determines that the estimated width is less than the predetermined width, than when the determination unit determines that the estimated width is not less than the predetermined width.

[0008] A lane line detection unit detects left and right lane lines that define traffic lanes using an image captured by a vehicle-mounted camera. It then provides lane guidance for the vehicle on the estimated lane, which is determined based on the detected left and right lane lines, thus maintaining the vehicle's lateral position at the predetermined location. If a wall or guardrail is present at the roadside of such a vehicle, the lane line detection unit is likely to mistakenly interpret the wall pattern or the guardrail's irregularity as a lane line.In particular, if the width between the road edge (the side of the road) and the lane line at the road edge (detected by the lane line detection unit) is less than the predetermined width, the lane line detection unit will likely mistakenly detect the road edge as the road edge. In this case, the estimated lane line will be based on faulty white line information, and therefore appropriate driving assistance cannot be provided. Specifically, the vehicle will likely be traveling in an unsuitable position within the lane. Note that the road edge (the side of the road) is located further out than the road edge.

[0009] In the present embodiment, the road edge detection unit detects a road edge based on information from reflection waves received by the radar device. If the determination unit determines that the estimated width—the width between the road edge detected by the road edge detection unit and the lane line at the road edge detected by the lane line detection unit—is less than the predetermined width, the lane line detection unit is likely to erroneously detect a road edge line as the road edge.

[0010] If the determination unit determines that the estimated width is smaller than the predetermined width, the predetermined position will accordingly be set to a position farther from the lane line at the edge of the road on the estimated lane than if the determination unit determines that the estimated width is not smaller than the predetermined width. If a road edge line is captured to define roads using the image taken by the vehicle's own camera, it is possible, even if the estimated lane is not correctly estimated as a road edge line due to an incorrect detection of the road edge, to prevent the vehicle from traveling at a position closer to the actual road edge line than the appropriate position. Brief description of the drawings

[0011] The above-described problem and further problems, features and advantages of the present invention will become clear with reference to the following description and the accompanying drawings. These show: Fig. 1 a schematic diagram of an advance vehicle tracking system according to the present embodiment; Fig. 2 a diagram showing a state in which a stationary object present at the edge of a road is mistakenly recorded as a road edge line; Fig. 3 a flowchart of the control carried out by a sensing ECU according to the present embodiment. Description of the embodiments

[0012] With reference to Fig. Section 1 describes the forward vehicle tracking system 100 used for a vehicle. The forward vehicle tracking system 100 includes a detection ECU 10, an imaging device (equivalent to a vehicle-integrated camera) 11, a radar device 12, and an electric power steering system 13.

[0013] The imaging device 11 is, for example, a CCD camera, a CMOS image sensor, a near-infrared camera, or similar device. The imaging device 11 is mounted at a predetermined vertical position on the vehicle, which is its transverse center, to capture a bird's-eye view of an area extending within a predetermined angular range in front of the vehicle and outputs the captured image information to the sensing ECU 10. The imaging device 11 can be a single-lens camera or a stereo camera.

[0014] The radar device 12, for example, is a known millimeter-wave radar that uses a high-frequency signal in the millimeter-wave band as transmit waves and is mounted on a front end of the vehicle. In the radar device 12, an area within a predetermined detection angle is defined as a detection range capable of detecting a target, and the position of a target within the detection range (referred to as the radar detection target) is detected. In particular, the radar device 12 transmits test waves in a predetermined cycle to receive reflected waves using multiple antennas. The radar device 12 calculates the distance to the radar detection target based on the transmission time of the test waves and the reception time of the reflected waves.Furthermore, a relative velocity is calculated using the frequency of the waves reflected by the radar target, the frequency of which changes due to the Doppler effect. Additionally, the radar device 12 calculates the direction of a radar target based on the phase difference between the reflected waves received by the antennas. If the distance and direction of a radar target can be calculated, the relative position of the radar target with respect to the vehicle can be determined. The radar device 12 cyclically transmits test waves, receives reflected waves, calculates the relative position and velocity, and then transmits the calculated relative position and velocity to the detection ECU 10.

[0015] The detection ECU 10 is connected to the imaging device 11 and the radar device 12. The detection ECU 10 is a computer containing a CPU, RAM, ROM, I / O, and similar components. The CPU executes programs installed in the ROM to perform various functions. Therefore, the detection ECU 10 functions as a roadside detection unit, a lane line detection unit, a determination unit, a computing unit, and a driver assistance cancellation unit.

[0016] In the present embodiment, several programs are installed in the ROM. The installed programs include, in particular, a white line detection program, a lane keeping assist control program (LKA control program), a change moment calculation program, and an LKA cancellation program.

[0017] In the white line detection program, the detection ECU 10 uses image information acquired by the imaging device 11 to detect a white line as a lane line that defines a lane (hereinafter referred to as the own lane) on which the own vehicle is traveling.

[0018] In particular, the imaging device 11 extracts change points in contrast (edge ​​intensity) between a white line defining a lane and a road surface as edge candidate points based on the luminance or brightness of the image captured by the imaging device 11. A candidate boundary line is then extracted from the sequence of extracted edge candidate points. More precisely, image information obtained by the imaging device 11 is continuously processed at a predetermined sampling period, and multiple points whose luminance changes rapidly in the horizontal direction of the image are extracted as edge candidate points.Then a Hough transform is applied to the sequence of extracted edge candidate points to obtain a sequence of edge candidate points, and several candidate lines that have a sequence of obtained edge candidate points are extracted as left and right contours.

[0019] Then, for each of the candidate lines, the degree to which the feature is present as a boundary line (white line) for defining a lane is calculated at each candidate edge point. Among these candidate lines, the line with the highest feature degree is identified as a white line for defining a lane. Among the identified white lines, the left and right white lines that approach the vehicle and are positioned such that they contain the vehicle between them are recognized as white lines for defining lines (hereinafter referred to as the vehicle's own lane) on which the vehicle is traveling.

[0020] In the LKA control program, the detection ECU 10 performs LKA control. LKA control is a steering control for controlling the direction of travel of the vehicle such that the lateral position of the vehicle, in the direction of its width, is maintained at the predetermined position on its own lane, which is estimated based on the detected white lines (hereinafter referred to as the estimated own lane). In the present embodiment, the predetermined position is set to a lateral position that indicates the center of the estimated own lane. Note that the predetermined position is not limited to the lateral position that indicates the center of the estimated own lane, but can be set to another lateral position on the estimated own lane.

[0021] The vehicle includes an electric power steering system 13 as a safety device, which is driven by a steering command. The detection ECU 10 and the electric power steering system 13 together form a driver assistance unit.

[0022] The electric power steering system 13 includes a steering mechanism 13b for actuating a steering angle of the steering wheel 20, which is located in the vehicle, and a steering motor (equivalent to a motor) 13a. The steering motor 13a generates a steering force (torque) to assist the operating force of the steering wheel 13b. The greater the torque, the greater the steering angle of the steering wheel 20. The steering motor 13a generates a steering force (torque) to actuate the steering mechanism 13b when the LKA control is performed.

[0023] In the change moment calculation program, the acquisition ECU 10 calculates the change moment quantity, which is described later and is generated in the output shaft of the steering motor 13a.

[0024] In the LKA override program, the sensing ECU 10 overrides the LKA control if the steering 13b is actuated by the driver during LKA control to generate a torque for changing the direction of travel of their own vehicle (hereinafter referred to as change torque), which is generated in the steering motor 13a. Specifically, if the change torque magnitude generated at the output shaft of the steering motor 13a is greater than a first threshold value, the LKA control is overridden by the LKA control program. The change torque magnitude is calculated by the sensing ECU 10 when the change torque magnitude calculation program is executed.

[0025] It is assumed that the acquisition ECU 10 performs the LKA control of the vehicle while the vehicle is traveling on a road where a wall or guardrail is present on the side of the road on which the vehicle can travel. If, in this case, a wall or guardrail is included in the image information acquired by the imaging device 11, a pattern of the wall or an irregular portion of the guardrail may be erroneously detected as the white line (road edge line) of the road. Fig. Figure 2 shows an example of a case where a wall pattern is mistakenly detected as a road edge line. Based on the mistakenly detected road edge line and the other white line, it is evident that the vehicle's lane is not being correctly estimated. Because, in this case, the lane control is based on the incorrectly estimated lane, the vehicle is likely driving on the shoulder of the road instead of in the center of its actual lane. Note that the side of the roadway, as the side of the road, is located further out than the road edge line.

[0026] In the present embodiment, the ROM also includes a roadside detection program, a width calculation program, and a determination program.

[0027] In the roadside information acquisition program, the detection ECU 10 obtains position information about a stationary object (e.g., guardrails, walls, etc.) that is present at the roadside along the lane on which the vehicle is traveling, based on information from a reflection wave received by the radar device 12.

[0028] In the width calculation program, the acquisition ECU 10 calculates an estimated width from the road edge to the road edge line using the obtained position information about a stationary object present at a road edge and position information of a white line of the road edge (hereinafter referred to as the road edge line) which is acquired by executing the white line acquisition program.

[0029] In the determination program, the detection ECU 10 determines, based on the width from the existing road edge line to the road edge, whether the estimated width from the road edge to the road edge line calculated by the width calculation program is less than a predetermined width that is less than a minimum width.

[0030] If the calculated estimated width from the road edge to the road edge line is less than the predetermined width, the detection ECU 10 has likely mistakenly detected a stationary object present at the road edge as the road edge line. If the LKA control system estimates that the estimated width from the road edge to the road edge line is less than the predetermined width, the detection ECU 10 accordingly sets the predetermined position to a position that is further from the road edge line than the center of its estimated lane, by the amount of the detected white line.

[0031] A case is assumed in which there is a large discrepancy between the position information of the detected road edge line and the position of the actual road edge line when the detection ECU 10 determines that the calculated estimated width from the road edge to the road edge line is smaller than the predetermined width (when a stationary object present at the road edge is recognized as a road edge line). Even if the predetermined position is set to a position on the estimated own lane that is further than the center from the road edge line, in this case the own vehicle is likely to travel while maintaining its lateral position in the vehicle width direction on the side of the road edge line instead of in the center of its actual own lane.Conversely, in a situation where the calculated estimated width from the road edge to the road edge line is smaller than the predetermined width, the difference between the position information of the detected road edge line and the actual position of the road edge line is assumed to be minute. If, in this case, the predetermined position is set to a position further from the road edge line than the center of the estimated lane, the vehicle will likely travel while maintaining its lateral position (in the vehicle width direction) at a position further from the outer line than the center of its actual lane.

[0032] Under these circumstances, the vehicle can move while its lateral position, in the direction of its width, is held at an unsuitable position within its lane. It is therefore assumed that the driver, dissatisfied with the situation, will operate the steering wheel 13b in the direction that would allow the vehicle to move towards the center of its actual lane. In this case, the steering wheel 13b is actuated by the driver, generating a change torque greater than a first threshold in the output shaft of the steering motor 13a. Specifically, if the current LKA control is performed in a situation where the calculated estimated width from the edge of the road to the road edge line is less than the predetermined width, the LKA control will very likely be overridden by the LKA cancellation program.Thus, if the detection ECU 10 determines that the calculated estimated width from the road edge to the road edge line is less than the predetermined width, and if the change moment magnitude is greater than a second threshold that is less than the first threshold, the detection ECU 10 cancels the LKA control by executing the LKA cancellation program. Accordingly, the LKA control can be easily canceled if the detection ECU 10 is likely to mistakenly detect a road edge as a road edge line in the white line detection program.

[0033] In the present embodiment, the LKA control is in Fig. 3, which will be described later, is carried out by the acquisition ECU 10. The acquisition ECU 10 executes the deviation avoidance control, which is described in Fig. 3 is shown, cyclically through, while the power supply to the detection ECU 10 is switched on.

[0034] First, in step S100, the position information of a white line defining the vehicle's lane is obtained based on image information acquired by the imaging device 11. In step S110, the radar device 12 obtains position information of a stationary object located at the roadside.

[0035] In step S120, using the position information of the white line obtained in step S100, it is determined whether the estimated width from the white line (corresponding to the road edge line) to the stationary object located at the road edge (obtained in step S110) is less than a predetermined width. If the result in step S120 is yes, the controller proceeds to step S130.

[0036] In step S130, the predetermined position is set to a position that is further from the road edge line than the center of the estimated own lane, which is estimated based on the white line recorded in step S100. The target torque value (control variable) to be generated in the steering motor 13a is calculated such that the own vehicle travels while maintaining the predetermined position to which the lateral position of the own vehicle in the vehicle width direction is set.

[0037] In step S140, a cancellation threshold, used to determine whether the LKA control should be deactivated, is set as a second threshold. In step S150, the steering motor 13a is caused to generate a target torque value, calculated in step S130 or in step S180 described later, in order to execute the LKA control.

[0038] In step S160, the change torque magnitude generated in the steering motor 13a is calculated. In step S170, it is determined whether the change torque magnitude calculated in step S160 is greater than the cancellation threshold set in step S140 or in step S190, described later. If the result in step S170 is "No," the control process terminates. If the result in step S170 is "Yes," the control process proceeds to step S200, the LKA control is stopped, and then the control process terminates.

[0039] If the result in step S120 is "No", the control system proceeds to step S180. In step S180, the predetermined position in the lateral direction is set, which indicates the center of the estimated own lane, estimated using a white line obtained in step S100. Then, the target torque to be generated in the steering motor 13a is calculated so that the own vehicle travels while maintaining the predetermined position, to which the lateral position of the own vehicle in the vehicle width direction is set. In step S190, the cancellation threshold is set as the first threshold, and then the system proceeds to step S150.

[0040] The present embodiment with the above configuration achieves the following advantageous effects.

[0041] The detection ECU 10 acquires position information of a stationary object located at the roadside, as received by the radar device 12. If it is determined that the estimated width from the roadside to the road edge is less than the predetermined width, it can be recognized that the stationary object located at the roadside is being erroneously detected as the road edge.

[0042] Accordingly, the predetermined position is set to a position located further from the road edge than the center of the estimated lane, which is determined using the detected white line, when it is determined that the calculated estimated width from the road edge to the road edge is not less than the predetermined width. This prevents the vehicle from driving in a position close to the road edge.

[0043] The above embodiment can be modified and implemented as follows.

[0044] In the embodiment described above, the LKA cancellation program is installed in the ROM located in the acquisition ECU 10. The acquisition ECU 10 can also contain a ROM without an LKA cancellation program installed. Since LKA control can still be performed in this case, similar operations and effects are achieved as in the embodiment described above.

[0045] In the embodiment described above, if the determination program determines during the lane-control operation that the estimated width from the road edge to the lane edge line calculated by the width calculation program is less than the predetermined width, the lane-control program sets the predetermined position to a position further from the lane edge line than the center of the estimated lane. If, in this regard, the determination program determines that the estimated width from the road edge to the lane edge line calculated by the width calculation program is less than the predetermined width, the lane-control program can set the predetermined position to a position close to the white line located on the estimated lane opposite the lane edge line. Accordingly, this configuration achieves the same advantageous effects as the embodiment described above.

Claims

[1] Driving assistance device comprising: a vehicle-integrated camera for recording an area in front of the vehicle in one direction of travel; a radar device for emitting test waves to an area in front of the vehicle in the direction of travel and for receiving reflection waves; a roadside detection unit for detecting a roadside as a side of a road on which the vehicle is driving, based on information from the reflection waves received by the radar device; a lane line detection unit for detecting left and right lane lines that define a lane, using an image captured by the vehicle's own camera; a determination unit for determining whether an estimated width, defined as the width between the road edge detected by the road edge detection unit and the lane line on the side of the road edge detected by the lane line detection unit, is less than a predetermined width; and a driving assistance unit for performing driving assistance for the own vehicle in order to maintain a lateral position of the own vehicle in a vehicle width direction at a predetermined position on an estimated lane as the lane estimated from the left and right lane lines detected by the lane line detection unit, wherein The driving assistance unit sets the predetermined position to a position that is further away from the lane line on the side of the road on the estimated lane when the determining unit determines that the estimated width is smaller than the predetermined width, than when the determining unit determines that the estimated width is not smaller than the predetermined width. the vehicle includes an electric power steering system (13) for controlling the direction of travel of the vehicle using an output torque of a motor (13a), The driving assistance is controlled by the electric power steering in such a way that the vehicle drives by maintaining the predetermined position, and also includes: a computing unit (10) for calculating a change torque quantity when a driver operates the electric power steering, so that a change torque is generated to change the direction of travel of the vehicle; and a driving assistance cancellation unit (10) for canceling the driving assistance provided by the driving assistance unit when the change moment magnitude calculated by the computing unit is greater than a first threshold, provided that the driving assistance is provided by the driving assistance unit and the estimated width is not less than the predetermined width; and The driving assistance cancellation unit cancels the driving assistance provided by the driving assistance unit when the change moment quantity calculated by the computing unit is greater than a second threshold that is smaller than the first threshold, provided that the driving assistance is provided by the driving assistance unit and the estimated width is smaller than the predetermined width. [2] Driving assistance device comprising: a vehicle-integrated camera for recording an area in front of the vehicle in one direction of travel; a radar device for emitting test waves to an area in front of the vehicle in the direction of travel and for receiving reflection waves; a roadside detection unit for detecting a roadside as one side of a road on which the vehicle is driving, based on information from the reflection waves received by the radar device; a lane line detection unit for detecting left and right lane lines that define a lane, using an image captured by the vehicle's own camera; a determination unit for determining whether an estimated width, defined as the width between the road edge detected by the road edge detection unit and the lane line on the side of the road edge detected by the lane line detection unit, is less than a predetermined width; and a driving assistance unit for preventing driving assistance for the own vehicle in order to maintain a lateral position of the own vehicle in a vehicle width direction at a predetermined position on an estimated lane as the lane estimated from the left and right lane lines detected by the lane line detection unit, wherein The driving assistance unit sets the predetermined position to a position closer to the lane line located on the estimated lane opposite the lane line on the side of the road, when the determining unit determines that the estimated width is smaller than the predetermined width, than when the determining unit determines that the estimated width is not smaller than the predetermined width. the vehicle includes an electric power steering system (13) for controlling the direction of travel of the vehicle using an output torque of a motor (13a), The driving assistance is controlled by the electric power steering in such a way that the vehicle drives by maintaining the predetermined position, and also includes: a computing unit (10) for calculating a change torque quantity when a driver operates the electric power steering, so that a change torque is generated to change the direction of travel of the vehicle; and a driving assistance cancellation unit (10) for canceling the driving assistance provided by the driving assistance unit when the change moment magnitude calculated by the computing unit is greater than a first threshold, provided that the driving assistance is provided by the driving assistance unit and the estimated width is not less than the predetermined width; and The driving assistance cancellation unit cancels the driving assistance provided by the driving assistance unit when the change moment quantity calculated by the computing unit is greater than a second threshold that is smaller than the first threshold, provided that the driving assistance is provided by the driving assistance unit and the estimated width is smaller than the predetermined width. [3] Driving assistance device according to claim 1, wherein the predetermined position is the transverse position which indicates a center on the estimated lane when the determining unit determines that the estimated width is not less than the predetermined width. [4] Driving assistance device according to claim 2, wherein the predetermined position is the transverse position which indicates a center on the estimated lane when the determining unit determines that the estimated width is not less than the predetermined width.

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