Controlling system of vehicle

Abstract

To provide a controlling system of a vehicle which can perform automatic brake control as necessary in a case of collision possibility with an obstacle even when abnormality exists in an acceleration sensor.SOLUTION: A controlling system of a vehicle comprises: an obstacle detection device which detects an obstacle ahead of the vehicle; an acceleration detection device which detects longitudinal acceleration of the vehicle; a collision determination unit which determines collision possibility with the obstacle; a deceleration setting unit which sets a target deceleration to perform automatic brake control according to the collision possibility determined by the collision determination unit; a brake control unit which controls the deceleration of the vehicle based on the longitudinal acceleration detected by the acceleration detection device so as to generate brake force according to the target deceleration set by the deceleration setting unit; and an adjustment unit which changes, when an abnormality determination unit determines abnormality of the acceleration detection device, the target deceleration to a fixed value set in advance to adjust actuation of the brake control unit to generate the brake force according to the fixed value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle control system. [Background technology]

[0002] Vehicle control systems that automatically activate the brakes when a collision with an obstacle such as a preceding vehicle in front of the vehicle is predicted have been put into practical use. Systems that automatically activate the brakes after a collision with an obstacle are also known. For example, Patent Document 1 discloses a device that automatically activates the brakes when a vehicle collides, based on the pressure detected by a collision detection sensor and the acceleration measured by an acceleration sensor (G sensor). In the device of Patent Document 1, when a fault diagnosis of the acceleration sensor is being performed or a fault is confirmed, the braking force of the automatic brakes after the collision is changed to a braking force smaller than normal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6071987 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, even in a control system that activates an automatic brake to reduce damage caused by a collision when a collision with an obstacle is predicted, control may be performed using the vehicle's acceleration detected by an acceleration sensor. In such a system, if the braking force of the automatic brake is reduced when the acceleration sensor fails, as in Patent Document 1, the effect of reducing collision damage may be reduced more than usual.

[0005] The present invention has been made in consideration of the above-described circumstances, and its object is to provide a vehicle control system that can perform necessary automatic brake control when there is a possibility of a collision with an obstacle, even if there is an abnormality in the acceleration sensor. [Means for solving the problem]

[0006] According to one aspect of the present invention, a vehicle control system includes an obstacle detection device that detects an obstacle in front of the vehicle, an acceleration detection device that detects longitudinal acceleration of the vehicle, a collision determination unit that determines the possibility of a collision with the obstacle, a deceleration setting unit that sets a target deceleration for performing automatic brake control in accordance with the possibility of collision determined by the collision determination unit, a brake control unit that controls the deceleration of the vehicle based on the longitudinal acceleration detected by the acceleration detection device so as to generate a braking force in accordance with the target deceleration set by the deceleration setting unit, an abnormality determination unit that determines an abnormality in the acceleration detection device, and an adjustment unit that, when an abnormality in the acceleration detection device is determined by the abnormality determination unit, changes the target deceleration to a predetermined fixed value and adjusts the operation of the brake control unit so as to generate a braking force in accordance with the fixed value. Effect of the Invention

[0007] The vehicle control device according to the present invention can perform the necessary automatic brake control when there is a possibility of a collision with an obstacle, even if an abnormality occurs in the acceleration sensor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram showing a schematic configuration of a vehicle control system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flowchart showing a flow of automatic brake control in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle control system according to an embodiment of the present invention will now be described in detail with reference to the drawings. Fig. 1 is a block diagram showing a schematic configuration of the vehicle control system according to the present embodiment.

[0010] As shown in Fig. 1, the vehicle control system 1 includes, for example, an obstacle detection device 10 that detects an obstacle in front of the vehicle, an acceleration sensor 11 that detects the longitudinal acceleration of the vehicle, a control device 20 that performs control related to automatic brake control of the vehicle, and a brake device 30. The vehicle control system 1 according to this embodiment is configured to be mounted on a vehicle and to perform control related to automatic brake control of the vehicle. In addition, the control device 20 of the vehicle control system 1 is configured to be capable of transmitting and receiving signals to and from a driving stability control system 40 that controls the behavior of the vehicle and the like to support stable driving of the vehicle.

[0011] The obstacle detection device 10 is configured to detect an obstacle in front of the vehicle and measure the relative distance (inter-vehicle distance) between the vehicle and the obstacle. For example, a millimeter wave radar, a camera, a sonar sensor, a LiDAR (Light Detection and Ranging), etc. can be used as the obstacle detection device 10. The measurement of the relative distance by the obstacle detection device 10 is dynamically performed at a predetermined measurement period. The relative distance between the vehicle and the obstacle detected by the obstacle detection device 10 is input to the control device 20.

[0012] The acceleration sensor 11 is installed near the center of gravity of the vehicle and configured to detect the acceleration of the vehicle. The acceleration sensor 11 is an acceleration detection device that measures at least the acceleration in the front-rear direction of the vehicle (longitudinal acceleration). The acceleration sensor 11 may be configured to measure the acceleration in the left-right direction of the vehicle (lateral acceleration) in addition to the front-rear acceleration. In this case, the acceleration sensor 11 can be configured as a two-axis acceleration sensor that detects the acceleration in the front-rear direction and the lateral direction of the vehicle. The acceleration of the vehicle detected by the acceleration sensor 11 is input to the control device 20.

[0013] The control device 20 is configured by a computer including, for example, a ROM storing programs and data, a CPU performing arithmetic processing, a RAM storing dynamic data and arithmetic processing results, an input / output interface, etc. The control device 20 is configured to execute the functions of an AEB control unit 21, an abnormality determination unit 22, a friction coefficient calculation unit 23, a straight running determination unit 24, an adjustment unit 25, etc., and to control the entire vehicle control system 1. Note that the vehicle control system 1 may implement the AEB control unit 21 as a controller separate from the control device 20.

[0014] The AEB control unit 21 is configured to execute automatic brake control that activates an automatic brake, so-called autonomous emergency braking (AEB), by the brake device 30 depending on the possibility of collision between the vehicle and an obstacle. The AEB control unit 21 has, for example, a collision determination unit 21a, a deceleration setting unit 21b, and a brake control unit 21c. The automatic brake control executed by the AEB control unit 21 in this embodiment includes a first brake control that generates a weak brake force to prompt the driver to brake when it is determined that there is a high possibility of collision with an obstacle, and a second brake control that generates a strong brake force equivalent to a maximum deceleration when it is determined that a collision with an obstacle cannot be avoided.

[0015] The collision determination unit 21a is configured to determine the possibility of a collision between the vehicle and the obstacle based on the relative distance to the obstacle input from the obstacle detection device 10. The collision determination unit 21a can calculate, for example, a collision prediction time TTC (Time-To-Collision) required for the vehicle to approach and come into contact with the obstacle as the collision possibility. Specifically, the collision determination unit 21a calculates the relative speed between the vehicle and the obstacle, which represents the change in relative distance per unit time, from the relative distance to the obstacle, and calculates the collision prediction time TTC as a value obtained by dividing the relative distance by the relative speed.

[0016] The deceleration setting unit 21b is configured to set a target deceleration for performing automatic brake control according to the collision possibility determined by the collision determination unit 21a. For example, when the vehicle approaches an obstacle and the collision prediction time TTC becomes equal to or less than a first threshold TTC1 set in advance, the deceleration setting unit 21b sets a first deceleration for performing the first brake control as a target deceleration (required deceleration). The first deceleration is designed to activate a warning brake for notifying the driver that the vehicle is approaching an obstacle by generating a weak braking force, and can be set to, for example, about 0.4 G.

[0017] When the vehicle and the obstacle get closer and the collision prediction time TTC becomes equal to or less than a preset second threshold TTC2, the deceleration setting unit 21b sets a second deceleration for executing the second brake control as a target deceleration. The second threshold TTC2 is a threshold for determining that a collision between the vehicle and the obstacle is unavoidable, and is set to a value smaller than the first threshold TTC1. The second deceleration is designed to activate an emergency brake to avoid a collision with the obstacle or to reduce damage in the event of a collision, and can be set to a value larger than the first deceleration, for example, about 1 G.

[0018] The brake control unit 21c is configured to control the brake device 30 so as to generate a braking force corresponding to the target deceleration set by the deceleration setting unit 21b. Here, the brake control unit 21c performs feedback control so that the actual longitudinal acceleration coincides with the target deceleration based on the longitudinal acceleration of the vehicle detected by the acceleration sensor 11. This is because even if the brake hydraulic pressure of the brake device 30 is set so as to generate a braking force corresponding to the target deceleration, the deceleration actually generated in the vehicle may change due to the influence of various factors of the vehicle or the surroundings of the vehicle, such as the loading state of the vehicle, the road gradient, or the road surface friction coefficient (road surface μ).

[0019] The braking device 30 includes a brake (e.g., a disc brake, a drum brake, etc.) provided on the wheel, a brake actuator connected to the brake via hydraulic piping, and a brake controller, and is configured to control the hydraulic pressure in accordance with a deceleration command from the control device 20 and control the braking force of the brake.

[0020] The running stability control system 40 is a system for controlling the vehicle to run stably, and includes, for example, an anti-skid control device 41 and a traction control device 42. The anti-skid control device 41 is configured to control the brake device 30 and the drive device 50 and adjust the braking force, driving force, etc. of the vehicle to prevent the vehicle from skidding and run stably. The traction control device 42 is configured to control the brake device 30 and the drive device 50 so as to adjust the braking force, driving force, etc. of the vehicle to prevent tire slippage (slip) when the vehicle starts and accelerates. Since the anti-skid control and the traction control are known vehicle controls, detailed description will be omitted. Note that the running stability control system 40 is an optional component of the vehicle control system 1 in this embodiment, and is not an essential component.

[0021] As described above, in the vehicle control system 1 according to this embodiment, when the AEB control unit 21 performs automatic brake control in response to the possibility of a collision between the vehicle and an obstacle, feedback control is performed so that the actual longitudinal acceleration coincides with the target deceleration based on the longitudinal acceleration of the vehicle detected by the acceleration sensor 11. If an abnormality occurs in the acceleration sensor 11 and an accurate actual longitudinal acceleration cannot be obtained, feedback control cannot be performed and detailed control of the deceleration occurring in the vehicle cannot be performed.

[0022] When the acceleration sensor 11 is configured as a two-axis acceleration sensor and its output signal is used not only by the AEB control unit 21 but also by the driving stability control system 40 that performs skid prevention control and traction control, the driving stability control system 40 is generally configured to stop functioning because accurate longitudinal acceleration and lateral acceleration of the vehicle cannot be obtained when an abnormality occurs in the acceleration sensor 11. In a situation where the function of stable driving control (behavior control) of the vehicle by skid prevention control or traction control has stopped, the behavior of the vehicle may become unstable when the automatic brake control by the AEB control unit 21 is activated.

[0023] Therefore, it is conceivable that the vehicle control system 1 also prohibits the AEB control unit 21 from executing automatic brake control when an abnormality occurs in the acceleration sensor 11. However, when there is a possibility of a collision with an obstacle, it is desirable to execute the necessary automatic brake control even if feedback control cannot be performed.

[0024] Therefore, the vehicle control system 1 according to this embodiment is configured to be able to perform the necessary automatic brake control when there is a possibility of collision with an obstacle, even if an abnormality occurs in the acceleration sensor 11 and feedback control of the deceleration cannot be performed. For this reason, the vehicle control system 1 further includes a steering angle sensor 12 and a road shape acquisition device 13. The control device 20 is configured to execute the functions of an abnormality determination unit 22, a friction coefficient calculation unit 23, a straight running determination unit 24, an adjustment unit 25, etc. in addition to the AEB control unit 21.

[0025] The steering angle sensor 12 is configured to detect the steering angle (front wheel steering angle) of the vehicle. The steering angle detected by the steering angle sensor 12 is input to the control device 20.

[0026] The road shape acquisition device 13 is configured to acquire information about the shape of the road ahead in the traveling direction of the vehicle. For example, the road shape acquisition device 13 can be configured as a camera that captures an image of the area ahead of the vehicle, or a map information database that has information about the road shape. As the road shape acquisition device 13, a LiDAR that acquires the shape of the road ahead as point cloud data, or other range sensors, etc. can also be used. The information about the road shape acquired by the road shape acquisition device 13 is input to the control device 20.

[0027] The abnormality determination unit 22 is configured to determine an abnormality in the acceleration sensor 11. The abnormality determination unit 22 can determine that the acceleration sensor 11 is abnormal, for example, when the output data of the acceleration sensor 11 is outside a normal range, when the data is fixed at a substantially constant value and does not fluctuate, when a CPU in the sensor fails and data is not output, etc. Alternatively, when the acceleration sensor 11 is also used in another vehicle control system (for example, a driving stability control system 40) and the driving stability control system 40 is configured to perform an abnormality determination of the acceleration sensor 11, the abnormality determination unit 22 may determine that the acceleration sensor 11 is abnormal when an abnormality determination signal is input from the driving stability control system 40.

[0028] The friction coefficient calculation unit 23 is configured to calculate the friction coefficient of the road surface on which the vehicle travels. The friction coefficient can be obtained by various methods, but in this embodiment, it is preferable that the friction coefficient calculation unit 23 estimates the road surface friction coefficient without using the measured value of the longitudinal acceleration of the vehicle by the acceleration sensor 11. For example, the road surface friction coefficient can be estimated from the relationship between the estimated value of the brake torque applied to the wheels and the estimated value of the vehicle body deceleration based on the output signal of the wheel speed sensor. Note that the friction coefficient calculation unit 23 may be configured to estimate whether or not the friction coefficient of the road surface corresponds to a so-called low μ road, instead of calculating the value of the friction coefficient of the road surface.

[0029] The straight-line determination unit 24 is configured to determine whether or not the vehicle is moving straight. For example, the straight-line determination unit 24 can determine whether or not the vehicle is moving straight based on the steering angle (front wheel steering angle) of the vehicle input from the steering angle sensor 12. Alternatively, the straight-line determination unit 24 may determine whether or not the road on which the vehicle is traveling is a straight road based on information on the road shape (image data, point cloud data, map information, etc.) input from the road shape acquisition device 13. If the road is a straight road, it can be estimated that the vehicle is moving straight. In this case, the straight-line determination unit 24 can function as a straight road determination unit.

[0030] The adjustment unit 25 is configured to adjust the operation of the automatic brake control executed by the AEB control unit 21. Specifically, when the abnormality determination unit 22 determines that the acceleration sensor 11 is abnormal, the adjustment unit 25 changes the target deceleration to a preset fixed value and adjusts the operation of the brake control unit 21c so as to generate a brake force corresponding to the fixed value without performing feedback control. Here, the fixed value of the deceleration can be set to the maximum deceleration in the automatic brake control. When the maximum deceleration=the second deceleration, the adjustment unit 25 prohibits the execution of the first brake control that generates a weak brake force corresponding to the first deceleration when the acceleration sensor 11 is abnormal, and allows only the execution of the second brake control that generates a strong brake force corresponding to the second deceleration (maximum deceleration). By setting the target deceleration to the maximum deceleration, it is possible to generate a desired deceleration, i.e., a brake force, without performing detailed control of the deceleration.

[0031] As described above, considering that the function of stable vehicle driving control (behavior control) by anti-skid control or traction control is stopped when the acceleration sensor 11 is abnormal, the automatic brake control may be executed only in a situation where unstable vehicle behavior such as skid is unlikely to occur even if the automatic brake control is executed. In other words, in a situation where unstable vehicle behavior is expected to occur, the execution of the automatic brake control may be prohibited.

[0032] Therefore, the adjustment unit 25 adjusts the operation of the automatic brake control based on the road friction coefficient of the vehicle calculated by the friction coefficient calculation unit 23. Specifically, the adjustment unit 25 prohibits the execution of the automatic brake control when an abnormality is determined in the acceleration sensor 11 and the road friction coefficient is less than a predetermined value. Here, the predetermined value of the road friction coefficient can be set, for example, to a value (for example, μ=about 0.3) for determining whether the road surface is a so-called low μ road.

[0033] Furthermore, the adjustment unit 25 adjusts the operation of the automatic brake control depending on whether the vehicle is traveling straight or not. Specifically, when an abnormality is determined in the acceleration sensor 11 and the straight traveling determination unit 24 determines that the vehicle is not traveling straight or the road on which the vehicle is traveling is not a straight road, the adjustment unit 25 prohibits the execution of the automatic brake control.

[0034] Meanwhile, the vehicle control system 1 is usually configured to enable override by the driver's operation intervention during operation of the automatic brake control. Override is a function that stops the control in operation and transfers authority to the driver when the driver's operation intervention exceeds an override threshold during operation of the automatic brake control. If the driver performs steering or the like on an instantaneous basis during operation of the automatic brake control and overrides the automatic brake control, the automatic brake control stops and transitions to a manual driving mode. For example, in a situation where the function of stable driving control (behavior control) of the vehicle by anti-skid control or traction control has stopped due to an abnormality in the acceleration sensor 11, if the automatic brake control is overridden by a sudden driving operation such as sudden steering by the driver, the behavior of the vehicle may become unstable, resulting in a risk.

[0035] Therefore, when an abnormality is determined in the acceleration sensor 11, the adjustment unit 25 sets the override threshold for the automatic brake control to a value OR2 (OR1>OR2) that is smaller than the override threshold OR1 when an abnormality is not determined in the acceleration sensor 11. By making the override threshold smaller, the automatic brake control is more likely to be overridden by the driver's operation intervention compared to when an abnormality in the acceleration sensor 11 is not determined.

[0036] The override of the automatic brake control may include an acceleration override caused by the driver's acceleration operation intervention, a deceleration override caused by the driver's deceleration operation intervention, and a steering override caused by the driver's steering intervention. The adjustment unit 25 changes an override threshold value for determining the presence or absence of a steering override caused by the driver's steering intervention. The automatic brake control is overridden when the steering torque (or steering angle, steering angle speed) caused by the driver's manual steering is equal to or greater than the override threshold value. By reducing the override threshold value, the automatic brake control is more likely to be overridden by the driver's manual steering compared to when an abnormality in the acceleration sensor 11 is not determined. As a result, when an abnormality occurs in the acceleration sensor 11, the automatic brake control is quickly terminated by the driver's operation intervention, and driving operation according to the driver's intention can be realized.

[0037] The flow of the automatic brake control in this embodiment will be described in detail below with reference to the flowchart of Fig. 2. The process shown in Fig. 2 is mainly executed by the control device 20 periodically.

[0038] First, in step S101, the collision determination unit 21a calculates a predicted collision time TTC between the vehicle and an obstacle based on the relative distance input from the obstacle detection device 10.

[0039] In step S102, abnormality determination unit 22 determines whether or not there is an abnormality in acceleration sensor 11. If there is an abnormality in acceleration sensor 11, the process proceeds to step S121 to adjust the operation of automatic brake control. On the other hand, if there is no abnormality in acceleration sensor 11, the process proceeds to step S111 to execute normal automatic brake control. First, the flow of normal automatic brake control will be described.

[0040] In step S111, it is determined whether the collision prediction time TTC calculated in step 101 is equal to or less than a preset second threshold TTC2. If the collision prediction time TTC is greater than the second threshold TTC2, the process proceeds to step S112, where it is determined whether the collision prediction time TTC is equal to or less than a preset first threshold TTC1. If the collision prediction time TTC is equal to or less than the first threshold TTC1, the process proceeds to step S113, where the deceleration setting unit 21b sets a first deceleration for executing the first brake control as the target deceleration. If the collision prediction time TTC is greater than the first threshold TTC1, this process ends.

[0041] On the other hand, if it is determined in step S111 that the collision prediction time TTC is equal to or less than the second threshold TTC2, the process proceeds to step S114, where the deceleration setting unit 21b sets a second deceleration (maximum deceleration) for executing the second brake control as the target deceleration.

[0042] In step S115, the brake control unit 21c performs feedback control based on the longitudinal acceleration of the vehicle detected by the acceleration sensor 11, and controls the brake device 30 so as to generate a braking force according to the target deceleration set in step S113 or step S114.

[0043] If it is determined in step S102 that there is an abnormality in the acceleration sensor 11, in step S121, the adjustment unit 25 sends a command to the driving stability control system 40 to prohibit the operation of the anti-skid control, which suppresses skidding of the vehicle, and the traction control, which suppresses over-rotation of the wheels.

[0044] In step S122, it is determined whether the collision prediction time TTC is equal to or less than the second threshold TTC2. If it is determined that the collision prediction time TTC is equal to or less than the second threshold TTC2, the process proceeds to step S123, where the deceleration setting unit 21b sets the maximum deceleration as the target deceleration. If the collision prediction time TTC is greater than the second threshold TTC2, this process is terminated.

[0045] In step S124, adjustment unit 25 determines whether the road friction coefficient of the vehicle calculated by friction coefficient calculation unit 23 is less than a predetermined value. If the road friction coefficient is equal to or greater than the predetermined value, the process proceeds to step S125. If the road friction coefficient is less than a predetermined value corresponding to, for example, a low μ road, the process proceeds to step S128, where execution of automatic brake control is prohibited, and the process ends.

[0046] In step S125, the straight-line determination unit 24 determines whether the vehicle is traveling straight or not, or whether the road on which the vehicle is traveling is a straight road, based on the information input from the road shape acquisition device 13. If it is determined that the vehicle is traveling straight or the road on which the vehicle is traveling is a straight road, the process proceeds to step S126. If it is determined that the vehicle is not traveling straight or the road on which the vehicle is traveling is not a straight road, the process proceeds to step S128, where the adjustment unit 25 prohibits the execution of automatic brake control, and the process ends.

[0047] In step S126, the adjustment unit 25 changes the override threshold for determining whether or not there is a steering override of the automatic brake control due to steering intervention to a value OR2 that is smaller than a normal override threshold OR1 at which an abnormality in the acceleration sensor 11 is not determined.

[0048] In step S127, the brake control unit 21c controls the brake device 30 without performing feedback control of the deceleration so as to generate a brake force corresponding to the target deceleration (maximum deceleration) set in step S123. At this time, if the driver performs a steering operation equal to or greater than the changed override threshold OR2, the automatic brake control is overridden. This ends the process. After the process ends, the override threshold OR2 is reset to the normal override threshold OR1.

[0049] The vehicle control system 1 according to the present embodiment described above can provide the following advantageous effects.

[0050] (1) The vehicle control system 1 includes an obstacle detection device 10 that detects an obstacle in front of the vehicle, an acceleration sensor 11 that detects longitudinal acceleration of the vehicle, a collision determination unit 21a that determines the possibility of a collision with the obstacle, a deceleration setting unit 21b that sets a target deceleration for performing automatic brake control in accordance with the possibility of a collision determined by the collision determination unit 21a, a brake control unit 21c that controls the brake device 30 by performing feedback control of the deceleration of the vehicle based on the longitudinal acceleration detected by the acceleration sensor 11 so as to generate a braking force in accordance with the target deceleration set by the deceleration setting unit 21b, an abnormality determination unit 22 that determines an abnormality in the acceleration sensor 11, and an adjustment unit 25 that, when an abnormality in the acceleration sensor 11 is determined by the abnormality determination unit 22, changes the target deceleration to a predetermined fixed value and adjusts the operation of the brake control unit 21c so as to generate a braking force in accordance with the fixed value without performing feedback control.

[0051] When performing automatic brake control, the brake control unit 21c is usually configured to control the brake device 30 by performing feedback control of the deceleration of the vehicle based on the longitudinal acceleration detected by the acceleration sensor 11. However, when the acceleration sensor 11 is abnormal, accurate longitudinal acceleration cannot be obtained, and feedback control cannot be performed. However, if the execution of the automatic brake control is prohibited only based on the occurrence of an abnormality in the acceleration sensor 11, it becomes impossible to reduce collision damage by the automatic brake control when there is a high possibility of collision between the vehicle and an obstacle. Therefore, in the vehicle control system 1 according to this embodiment, when an abnormality in the acceleration sensor 11 is determined, the operation of the brake control unit 21c is adjusted so that a brake force according to a fixed value is generated without performing feedback control, so that automatic brake control required when there is a high possibility of collision with an obstacle can be performed even in a state where detailed deceleration control by feedback control cannot be performed.

[0052] (2) The adjustment unit 25 sets the maximum deceleration in the automatic brake control as a fixed value of the target deceleration. By executing the automatic brake control based on the maximum deceleration, it becomes possible to realize a desired deceleration without performing detailed control of the deceleration by feedback control.

[0053] (3) The automatic brake control includes a first brake control that generates a brake force corresponding to a first deceleration smaller than the maximum deceleration when the collision determination unit 21a determines that there is a high possibility of a collision with an obstacle, thereby encouraging the driver to apply the brakes, and a second brake control that generates a brake force corresponding to the maximum deceleration when the collision determination unit 21a determines that a collision with an obstacle cannot be avoided. When the abnormality determination unit 22 determines that the acceleration sensor 11 is abnormal, the adjustment unit 25 prohibits the execution of the first brake control. That is, when the acceleration sensor 11 is abnormal, the first brake control is not executed even if the collision prediction time TTC becomes equal to or less than a first threshold TTC set in advance, and when the collision prediction time TTC becomes equal to or less than a second threshold TTC2 set in advance, the second brake control that generates a brake force corresponding to the maximum deceleration is executed. This allows an emergency brake to be activated to avoid a collision or reduce damage during a collision in a situation where there is a very high risk that a collision with an obstacle cannot be avoided. Even if the collision prediction time TTC falls below the first threshold TTC when the acceleration sensor 11 is abnormal, automatic brake control is not performed to prompt the driver to apply the brakes. Therefore, when the situation is not one in which there is an extremely high risk of a collision with an obstacle being unavoidable, the first brake control is performed to generate a deceleration rate according to the distance to the obstacle, thereby preventing the driver from feeling uncomfortable or uneasy.

[0054] (4) The vehicle control system 1 further includes a friction coefficient calculation unit 23 that calculates the friction coefficient of the road surface on which the vehicle travels. When the abnormality determination unit 22 determines that the acceleration sensor 11 is abnormal and the friction coefficient calculated by the friction coefficient calculation unit 23 is less than a predetermined value, the adjustment unit 25 prohibits the execution of automatic brake control. On roads with a low friction coefficient of the road surface, such as so-called low μ roads, the vehicle is more likely to behave unstablely. In particular, when the acceleration sensor 11 is abnormal and the operation of the driving stability control system 40, such as the skid prevention control device 41 and the traction control device 42, is stopped, the vehicle's behavior may become unstable if the automatic brake control is activated. Therefore, the automatic brake control can be safely executed by prohibiting the execution of the automatic brake control on low μ roads with a low friction coefficient and permitting the execution of the automatic brake control only on high μ roads.

[0055] (5) The vehicle control system 1 further includes a straight road determination unit (straight road determination unit) 24 that determines whether the road on which the vehicle is traveling is a straight road. When the abnormality determination unit 22 determines that the acceleration sensor 11 is abnormal and the straight road determination unit 24 determines that the road on which the vehicle is traveling is not a straight road, the adjustment unit 25 prohibits the execution of automatic brake control. For example, on roads that are not straight, such as curved roads, the vehicle tends to behave unstablely due to driving operations such as manual steering by the driver. In particular, when the acceleration sensor 11 is abnormal and the operation of the driving stability control system 40, such as the skid prevention control device 41 and the traction control device 42, is stopped, the behavior of the vehicle may become unstable if the automatic brake control is activated on a curved road. Therefore, when the road on which the vehicle is traveling is not a straight road, the execution of the automatic brake control is prohibited, and the execution of the automatic brake control is permitted only when the road is a straight road, so that the automatic brake control can be safely executed.

[0056] (6) The vehicle control system 1 further includes a straight-line running determination unit 24 that determines whether the vehicle is running straight. When the abnormality determination unit 22 determines that there is an abnormality in the acceleration sensor 11 and the straight-line running determination unit 24 determines that the vehicle is not running straight, the adjustment unit 25 prohibits the execution of the automatic brake control. As a result, similar to (5) above, the execution of the automatic brake control is prohibited when the vehicle is not running straight, and the execution of the automatic brake control is permitted only when the vehicle is running straight, making it possible to safely execute the automatic brake control.

[0057] (7) The automatic brake control has an override function that stops the automatic brake control and transfers authority to the driver when the driver performs steering intervention equal to or greater than the override threshold while the automatic brake control is being executed. When the abnormality determination unit 22 determines that there is an abnormality in the acceleration sensor 11, the adjustment unit 25 makes the override threshold smaller than when there is no abnormality in the acceleration sensor 11. As a result, when there is an abnormality in the acceleration sensor 11, the automatic brake control is quickly terminated by the driver's intervention, and driving operations according to the driver's intentions can be realized.

[0058] (8) The acceleration sensor 11 is configured as a two-axis acceleration sensor capable of detecting the lateral acceleration of the vehicle in addition to the longitudinal acceleration of the vehicle. When the abnormality determination unit 22 determines that the acceleration sensor 11 has an abnormality, the adjustment unit 25 prohibits the operation of at least one of the anti-skid control device 41 that uses the detection signal from the acceleration sensor 11 to reduce the torque of the drive device 50 of the vehicle and / or activate the brake device 30 to suppress the vehicle from skidding, and the traction control device 42 that uses the detection signal from the acceleration sensor 11 to reduce the torque of the drive device 50 of the vehicle and / or activate the brake device 30 to suppress overspinning of the wheels.

[0059] -Variations- (1) In the above-described embodiment, the control device 20 includes the friction coefficient calculation unit 23, and is configured to prohibit the execution of automatic brake control when the friction coefficient of the road surface on which the vehicle is traveling is less than a predetermined value. However, the present invention is not limited to this, and the control device 20 may be configured to omit the friction coefficient calculation unit 23 and permit or prohibit the execution of automatic brake control regardless of the friction coefficient of the road surface.

[0060] (2) In the above-described embodiment, the control device 20 includes the straight-line determination unit 24, and is configured to prohibit the execution of automatic brake control when the vehicle is not traveling straight or the road on which the vehicle is traveling is not a straight road. However, the present invention is not limited to this, and the control device 20 may be configured to permit or prohibit the execution of automatic brake control regardless of whether the vehicle is traveling straight or not, or whether the road on which the vehicle is traveling is a straight road or not. In this case, the road shape acquisition device 13 and the straight-line determination unit 24 can be omitted.

[0061] (3) In the above-described embodiment, when an abnormality occurs in the acceleration sensor 11, the override threshold for the automatic brake control is changed to a value OR2 that is smaller than the normal override threshold OR1 at which no abnormality is determined in the acceleration sensor 11. However, this is not limited to this, and when an abnormality occurs in the acceleration sensor 11, the normal override threshold OR1 may be used as is.

[0062] (4) In the above-described embodiment, when an abnormality in the acceleration sensor 11 is determined, the target deceleration is fixed to the maximum deceleration of the automatic brake control, which is the second deceleration for executing the second brake control. However, the maximum deceleration is not limited to being equal to the second deceleration. An appropriate target deceleration other than the maximum deceleration may be set as the second deceleration for executing the second brake control.

[0063] (5) In the above embodiment, the acceleration sensor 11 may be configured as a two-axis acceleration sensor. However, the present invention is not limited to this. The acceleration sensor 11 may be configured as a three-axis acceleration sensor.

[0064] (6) In the above-described embodiment, the automatic brake control is configured to include a first brake control that generates a weak brake force to encourage the driver to apply the brakes when it is determined that the possibility of a collision with an obstacle is high, and a second brake control that generates a strong brake force equivalent to a maximum deceleration when it is determined that a collision with an obstacle cannot be avoided. However, the present invention is not limited to this, and the automatic brake control can be configured to include at least the second brake control.

[0065] (7) In the above-described embodiment, when the abnormality determination unit 22 determines that there is an abnormality in the acceleration sensor 11, the adjustment unit 25 is configured to prohibit operation of at least one of the anti-skid control device 41 and the traction control device 42. However, this is not limited to this, and the control device 20 may be configured to receive, from the driving stability control system 40, an abnormality determination signal indicating an abnormality in the acceleration sensor 11, as well as a signal indicating that operation of the anti-skid control device 41 and the traction control device 42 is prohibited.

[0066] Although several embodiments of the present invention have been described above, it should be noted that the present invention is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the present invention. [Explanation of symbols]

[0067] 1 Vehicle control system 10 Obstacle detection device 11 Acceleration sensor (acceleration detection device) 21a collision determination unit, 21b deceleration setting unit, 21c brake control unit 22 Abnormality determination section 23 Friction coefficient calculation unit 24 Straight road judgment unit (straight road judgment unit) 25 Adjustment section 30 Brake device 41 Anti-skid control device, 42 Traction control device 50 Drive unit

Claims

1. An obstacle detection device that detects an obstacle in front of the vehicle; An acceleration detection device that detects longitudinal acceleration of a vehicle; a collision determination unit that determines a possibility of a collision with the obstacle; a deceleration setting unit that sets a target deceleration for performing automatic brake control in accordance with the collision possibility determined by the collision determination unit; a brake control unit that controls the deceleration of the vehicle based on the longitudinal acceleration detected by the acceleration detection device so as to generate a brake force corresponding to the target deceleration set by the deceleration setting unit; an abnormality determination unit that determines an abnormality in the acceleration detection device; an adjustment unit that changes the target deceleration to a preset fixed value when the abnormality determination unit determines that an abnormality has occurred in the acceleration detection device, and adjusts the operation of the brake control unit so as to generate a braking force corresponding to the preset fixed value; A vehicle control system comprising:

2. The vehicle control system according to claim 1 , wherein the adjustment unit sets a maximum deceleration in the automatic brake control as the fixed value.

3. The automatic brake control includes: a first brake control that generates a brake force corresponding to a first deceleration that is smaller than the maximum deceleration when the collision determination unit determines that there is a high possibility of a collision with the obstacle, to encourage a driver to perform a brake operation; a second brake control that generates a braking force according to the maximum deceleration when the collision determination unit determines that a collision with the obstacle cannot be avoided; Including, The vehicle control system according to claim 2 , wherein when the abnormality determination unit determines that an abnormality has occurred in the acceleration detection device, the adjustment unit prohibits execution of the first brake control.

4. A friction coefficient calculation unit that estimates a friction coefficient of a road surface on which the vehicle runs, 2. The vehicle control system of claim 1, wherein when the abnormality determination unit determines that an abnormality exists in the acceleration detection device and the friction coefficient calculation unit estimates that the friction coefficient is less than a predetermined value, the adjustment unit prohibits execution of the automatic brake control.

5. A straight road determination unit is further provided for determining whether or not the road on which the vehicle is traveling is a straight road, 2. The vehicle control system of claim 1, wherein when the abnormality determination unit determines that there is an abnormality in the acceleration detection device and the straight road determination unit determines that the road on which the vehicle is traveling is not a straight road, the adjustment unit prohibits execution of the automatic brake control.

6. A straight-line determination unit is further provided to determine whether the vehicle is traveling straight, 2. The vehicle control system of claim 1, wherein when the abnormality determination unit determines that there is an abnormality in the acceleration detection device and the straight-line driving determination unit determines that the vehicle is not driving straight, the adjustment unit prohibits execution of the automatic brake control.

7. The automatic brake control has an override function that stops the automatic brake control and transfers authority to the driver when a steering intervention by a driver is greater than or equal to an override threshold during execution of the automatic brake control, The vehicle control system according to claim 1 , wherein when the abnormality determination unit determines that an abnormality exists in the acceleration detection device, the adjustment unit reduces the override threshold value compared to when no abnormality is determined in the acceleration detection device.

8. the acceleration detection device is configured as a two-axis acceleration sensor capable of detecting a lateral acceleration of the vehicle in addition to a longitudinal acceleration of the vehicle, When the abnormality determination unit determines that an abnormality has occurred in the acceleration detection device, the adjustment unit a skid prevention control device that uses a detection signal from the acceleration detection device to reduce torque of a drive device of the vehicle and / or activates the brake device to suppress skid of the vehicle; A traction control device that uses a detection signal from the acceleration detection device to reduce torque of a drive device of the vehicle and / or activates the brake device to suppress overspinning of the wheels. The vehicle control system according to claim 4 , further comprising: a control unit for controlling a vehicle according to claim 5 , which inhibits operation of at least one of the above.

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