Driving assistance systems

Abstract

The present invention provides a driver assistance device that can reduce driver discomfort by suppressing sudden acceleration of the vehicle when transitioning from a state in which the driver is accelerating the vehicle to a state in which the vehicle's speed is automatically adjusted by an automatic speed adjustment process. [Solution] When the ECU 10 is in a state where it is not executing the automatic speed adjustment process and is controlling the predetermined device so that the vehicle is accelerated at an acceleration corresponding to a manual driving operation that accelerates the vehicle, and transitions to a state in which the vehicle is accelerated by the automatic speed adjustment process, it obtains the current value of the vehicle's acceleration and executes an acceleration suppression process in which it assigns the obtained current value to the upper limit of the target acceleration in place of the first predetermined value.

Description

Technical Field

[0001] The present invention relates to a driving support device that supports a driving operation for adjusting the speed of a host vehicle.

Background Art

[0002] There has been proposed a driving support device that supports a driving operation for adjusting the speed of a host vehicle (see, for example, Patent Document 1 below). A processor of this driving support device (hereinafter referred to as "conventional device") can execute an automatic speed adjustment process (automatic acceleration process and automatic deceleration process) for controlling a device of the host vehicle (a driving device and a braking device (hereinafter referred to as "driving device etc.")) so that the speed (measured value) of the host vehicle matches a target speed (a value set by a driver or a value determined based on information about an object around the host vehicle).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] By the way, in a vehicle to which this type of driving support device is applied, a scene is assumed in which the driver of the host vehicle transitions from a state of mainly performing a driving operation of relatively gently accelerating the host vehicle to a state of entrusting the driving operation to the driving support device. Here, an upper limit value of the acceleration of the host vehicle when the driving support device executes an automatic acceleration process is determined in advance. When the driving support device starts to execute an automatic acceleration process, the upper limit value may be assigned to the target acceleration of the host vehicle. In this case, the acceleration of the host vehicle may increase rapidly, and the host vehicle may be suddenly accelerated. If the host vehicle is suddenly accelerated in this way, the driver may feel uncomfortable.

[0005] One of the objectives of the present invention is to provide a driver assistance device that can reduce driver discomfort by suppressing sudden acceleration of the vehicle when transitioning from a state in which the driver is accelerating the vehicle to a state in which the vehicle's speed is automatically adjusted by an automatic speed adjustment process.

[0006] To achieve the above objective, the driving assistance device (1) of the present invention is: An on-board sensor (20) for acquiring information about objects around the vehicle, information about the driving operation of the vehicle (V0), information about the speed of the vehicle, and information about the acceleration of the vehicle, A processor (10) is configured to determine the target speed (spt) and target acceleration (αt) of the vehicle based on information acquired from the vehicle-mounted sensors, and to perform an automatic speed adjustment process that controls predetermined devices (30, 40) of the vehicle so that the vehicle's speed changes at the target acceleration and the vehicle's speed (sp0) matches the target speed, and to assign a first predetermined value (αacc1) to the upper limit of the target acceleration (αtmax), It is equipped with. When the processor is in a state where it is not executing the automatic speed adjustment process and is controlling the predetermined device so that the vehicle is accelerated at an acceleration corresponding to a manual driving operation that accelerates the vehicle, and then transitions to a state in which the vehicle is accelerated by the automatic speed adjustment process, it obtains the current value of the vehicle's acceleration (αdrv) and executes an acceleration suppression process in which it assigns the obtained current value to the upper limit of the target acceleration in place of the first predetermined value.

[0007] The processor of the driver assistance system according to the present invention assigns the acceleration at the time the condition is met (i.e., the acceleration at the time the driver is actively performing an operation to accelerate the vehicle) as the upper limit of the target value of the vehicle's acceleration in the automatic speed adjustment process when a predetermined condition is met. Therefore, according to the driver assistance system according to the present invention, sudden acceleration of the vehicle is suppressed when transitioning from a state in which the driver is performing an operation to accelerate the vehicle to a state in which the vehicle's speed is automatically adjusted by the automatic speed adjustment process. This reduces driver discomfort.

[0008] In a driving support device according to one aspect of the present invention, If the current value of the acquired acceleration is equal to or greater than the first predetermined value, the processor maintains the state in which the first predetermined value is assigned to the upper limit.

[0009] According to this, the automatic speed adjustment process prevents excessive acceleration when the vehicle accelerates, thus maintaining a high level of vehicle safety.

[0010] In another aspect of the present invention, in a driving support device, The processor assigns the second predetermined value to the upper limit if the current value of the acquired acceleration is less than or equal to the second predetermined value (αacc2), which is smaller than the first predetermined value.

[0011] According to this, the automatic speed adjustment process prevents the acceleration of the vehicle from becoming too low (resulting in sluggish acceleration).

[0012] In another aspect of the present invention, in a driving support device, The processor assigns the first predetermined value to the upper limit when the vehicle accelerates and reaches the target speed or a threshold (spth) smaller than the target speed, while the upper limit has been assigned a value smaller than the first predetermined value due to the acceleration suppression process.

[0013] According to this, when the vehicle's speed increases and reaches the target speed (or threshold) while the acceleration suppression process has assigned the acquired acceleration to the upper limit (in a state where acceleration is suppressed), the automatic speed adjustment process is executed again and the vehicle accelerates, but the acceleration of the vehicle is not suppressed. Therefore, the vehicle's speed can reach the target speed relatively quickly.

[0014] Furthermore, in a driving support device according to another aspect of the present invention, The processor executes the acceleration suppression process when the driver activates the automatic speed adjustment function while pressing the accelerator pedal, and the vehicle's speed at that time is less than the target speed, while the automatic speed adjustment function is disabled.

[0015] Furthermore, in a driver assistance device according to another aspect of the present invention, the processor executes an override process to control the predetermined device so that the vehicle accelerates at the acceleration corresponding to the acceleration corresponding to the acceleration corresponding to the acceleration corresponding to the acceleration of the accelerator pedal when the accelerator pedal of the vehicle is pressed down while the automatic speed adjustment process is being executed, if the acceleration corresponding to the manner of pressing down is greater than the target acceleration determined in the automatic speed adjustment process (when the override condition is met). The processor executes the acceleration suppression process when the vehicle changes lanes while it is behind a preceding vehicle, in a state where the automatic speed adjustment process can be executed, and the vehicle is accelerating due to the override process, and the override condition is not met, and the speed of the vehicle at that time is less than the target speed.

[0016] Furthermore, in a driver assistance device according to another aspect of the present invention, the processor is in a state where it can perform automatic speed adjustment processing behind a preceding vehicle and is accelerating its own vehicle by override processing, and when the override condition becomes unmet due to the vehicle changing lanes, and the speed of the vehicle at that time is less than the target speed, the processor performs the acceleration suppression processing.

[0017] Furthermore, in a driving assistance device according to another aspect of the present invention, the processor controls the predetermined device so that the lateral acceleration of the vehicle is maintained to be below a threshold value on a curved road when the override condition is met, and the override condition becomes unmet when the vehicle enters a straight road from the curved road while the override process is being executed, and the speed of the vehicle at that time is less than the target speed, the processor executes the acceleration suppression process.

[0018] Further, in the driving support device according to another aspect of the present invention, when an operation for transitioning from a state where the automatic speed adjustment process cannot be executed to a state where the function can be executed is performed, the processor assigns the speed of the host vehicle at that time to the target speed and transitions to a state where the automatic speed adjustment process can be executed. When the host vehicle is traveling at the target speed by the automatic speed adjustment process, the override process is started. When an operation for increasing the target speed is performed during the override process, if the override condition becomes false and the speed of the host vehicle at that time is lower than the target speed (changed), an acceleration suppression process is executed.

Brief Description of the Drawings

[0019] [Figure 1] FIG. 1 is a block diagram of a driving support device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a time chart showing changes in the on / off state of the first switch, speed, acceleration, and accelerator opening. [Figure 3] FIG. 3 is a plan view showing a scene where the host vehicle changes lanes behind the preceding vehicle. [Figure 4] FIG. 4 is a plan view showing a scene where the preceding vehicle changes lanes in front of the host vehicle. [Figure 5] FIG. 5 is a plan view showing a scene where the host vehicle enters a straight road from a curved road. [Figure 6] FIG. 6 is a flowchart of a program executed by the CPU to realize a function of setting an upper limit value of the target acceleration according to the driving scene.

Mode for Carrying Out the Invention

[0020] (Schematic) The driving support device 1 according to an embodiment of the present invention is applied to, for example, a vehicle V0 (hereinafter referred to as "host vehicle") equipped with an automatic driving function. The driving support device 1 has an automatic speed adjustment function for assisting a driving operation to adjust the speed sp0 of the host vehicle. The automatic speed adjustment function includes a function (automatic acceleration function) for automatically accelerating the host vehicle. The driving support device 1 has a function of setting an upper limit value of a target acceleration when automatically accelerating the host vehicle by the automatic acceleration function according to the driving scene.

[0021] (Specific Configuration) As shown in FIG. 1, the driving support device 1 includes an ECU 10, an in-vehicle sensor 20, a driving device 30, and a braking device 40.

[0022] The ECU 10 includes a microcomputer having a CPU 10a, a ROM 10b, a RAM 10c, a timer 10d, etc. The ECU 10 is connected to other ECUs provided in the host vehicle via a CAN (Controller Area Network).

[0023] The in-vehicle sensor 20 includes a front sensor that acquires information on an object located in front of the host vehicle. Specifically, the in-vehicle sensor 20 includes a millimeter-wave radar 21, a sonar 22, and a front camera 23 as the front sensor.

[0024] The millimeter-wave radar 21 includes a transmission / reception unit and a signal processing unit (not shown). The transmission / reception unit radiates radio waves in the millimeter-wave band (hereinafter referred to as "millimeter waves") to the front area of the host vehicle and receives the millimeter waves (reflected waves) reflected by a three-dimensional object (preceding vehicle V1) located within the radiation range. The signal processing unit calculates the distance between the host vehicle and the three-dimensional object, the speed (relative speed) of the three-dimensional object, etc. based on the time from when the transmission / reception unit radiates the millimeter waves until the reflected waves are received, the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, etc., and provides the calculation result to the ECU 10.

[0025] The sonar 22 emits ultrasonic waves in the area in front of the vehicle and receives ultrasonic waves (reflected waves) reflected by three-dimensional objects. Based on the time from when the ultrasonic waves are transmitted until the reflected waves are received, the sonar 22 calculates the distance between the vehicle and the three-dimensional object, the position (direction) of the three-dimensional object relative to the vehicle, etc., and provides the calculation results to the ECU 10.

[0026] The front camera 23 is equipped with an imaging device and an image analysis device. The imaging device incorporates a lens and an image sensor such as a CCD (charge coupled device) or CIS (CMOS image sensor). The imaging device is positioned at the top of the front windshield glass and directed forward. The imaging device captures the foreground of the vehicle at a predetermined frame rate and acquires image data. The imaging device transmits the image data to the image analysis device. The image analysis device analyzes the acquired image data and obtains information about objects located in front of the vehicle from the image. For example, the image analysis device identifies (recognizes) the type of object located in front of the vehicle (e.g., another vehicle, lane mark, etc.) and provides the identification result to the ECU 10.

[0027] In addition, the on-board sensor 20 includes sensors that acquire information regarding the vehicle's behavior (speed and acceleration). Specifically, the on-board sensor 20 includes a speed sensor 24 and an acceleration sensor 25.

[0028] The speed sensor 24 detects the rotational speed (wheel speed) of each wheel and calculates the vehicle's speed sp0 (measured value) based on the wheel speed. The speed sensor 24 provides the calculation result to the ECU 10.

[0029] The acceleration sensor 25 detects the acceleration α0 of the vehicle in the longitudinal (front-rear) and lateral (side-to-side) directions. The acceleration sensor 25 provides the detection results to the ECU 10.

[0030] Furthermore, the on-board sensor 20 includes an accelerator pedal sensor 26 and a switch 27 as operation sensors. The accelerator pedal sensor 26 detects the depression depth AD (accelerator opening) of the accelerator pedal AP and provides the detection result to the ECU 10. The switch 27 is, for example, a lever-type device and includes a lever that can be tilted upward and downward from a neutral position, as well as a first switch and a second switch. When the lever is tilted upward from the neutral position, the first switch transitions from the off state to the on state, and when the lever is tilted downward from the neutral position, the second switch transitions from the off state to the on state. The switch 27 is used to activate the automatic speed adjustment function (transition the operating mode from the first operating mode to the second operating mode), which will be described later. That is, when the lever of switch 27 is tilted upward from the neutral position while the function is disabled (first operating mode), the automatic speed adjustment function is activated (second operating mode). Furthermore, switch 27 is used to input (set) the upper limit value spmax of the vehicle's speed sp0 when the automatic speed adjustment function automatically adjusts the vehicle's speed sp0. For example, when the automatic speed adjustment function is enabled, if the lever of switch 27 is moved upward from the neutral position, the upper limit value spmax is increased. On the other hand, if the lever is moved downward from the neutral position, the upper limit value spmax is decreased. The upper limit value spmax is stored in ROM 10b. When the automatic speed adjustment function is disabled and then re-enabled, the upper limit value spmax (the previous setting) is read from ROM 10b.

[0031] The drive unit 30 applies driving force to the drive wheels. The drive unit 30 includes an engine ECU, an internal combustion engine, a transmission, and a driving force transmission mechanism that transmits driving force to the wheels. The engine ECU obtains information (target value) representing the target driving force from another ECU (ECU 10). The engine ECU drives the throttle valve of the internal combustion engine to match the driving force applied to the drive wheels to the target value.

[0032] Furthermore, if the vehicle to which the driver assistance system 1 is applied is a hybrid electric vehicle (HEV), the engine ECU can adjust the output (driving force) of either the internal combustion engine or the electric motor, or both, as the vehicle's power source. Also, if the vehicle to which the driver assistance system 1 is applied is an electric electric vehicle (BEV), an electric motor ECU that adjusts the output (driving force) of the electric motor, which is the vehicle's power source, is used instead of the engine ECU.

[0033] The braking system 40 applies braking force to the wheels (brake discs). The braking system 40 includes a brake ECU, brake calipers, etc. The brake calipers include actuators that press brake pads against the brake discs. The brake ECU obtains information (target value) representing the target braking force from other ECUs. The brake ECU drives the actuators of the brake calipers to match the braking force applied to the wheels (brake discs) to the target value.

[0034] (Operation) When the ECU 10 detects that the first switch of switch 27 has transitioned from the off state to the on state, it determines whether or not there is a preceding vehicle V1, and based on the determination result, executes an automatic speed adjustment process to control the drive system, etc. (drive system 30 and / or brake system 40). This function (automatic speed adjustment function) is also called adaptive cruise control (ACC). This function includes a constant speed driving function and a distance keeping function. In the normal state (a state in which condition A described later is not met), the ECU 10 assigns a predetermined value αacc1 (>0) to the upper limit αtmax of the target value (target acceleration αt) of the vehicle's acceleration α0 when accelerating the vehicle by the automatic speed adjustment process. On the other hand, in the normal state, the ECU 10 assigns a predetermined value αdec1 (<0) to the lower limit of the target value (maximum value of the target value of backward acceleration) of the vehicle's acceleration (deceleration) α0 when decelerating the vehicle by the automatic speed adjustment process. The above predetermined values ​​αacc1 and αdec1 are determined at the vehicle design stage. The predetermined value αacc1 corresponds to the first predetermined value of the present invention. As will be described in detail later, when the predetermined conditions are met, the ECU10 assigns a value smaller than the predetermined value αacc1 to the upper limit value αtmax.

[0035] (Constant Speed ​​Driving Function) The ECU 10 determines the presence or absence of a preceding vehicle V1 based on information acquired from the forward sensors (millimeter-wave radar 21, sonar 22, and forward camera 23). If no preceding vehicle V1 exists, the ECU 10 executes constant speed driving processing. Specifically, the ECU 10 assigns an upper limit spmax set by the driver to the target value of the vehicle's speed sp0 (target speed spt). The ECU 10 then controls the drive system, etc., so that the speed sp0 matches the target speed spt. For example, if the vehicle's speed sp0 is lower than the target speed spt, the ECU 10 controls the drive system, etc., so that the vehicle's acceleration α0 matches the target acceleration αt (≤αacc1) determined based on various conditions. Hereinafter, this process will be referred to as "automatic acceleration processing". As a result, the vehicle's speed sp0 approaches the target speed spt (=spmax). Furthermore, even if a preceding vehicle V1 exists, if its speed sp1 is greater than the upper limit spmax, the ECU10 will execute constant speed driving control.

[0036] [Distance Maintaining Control] On the other hand, if the ECU 10 determines that a preceding vehicle V1 exists and the speed sp1 of the preceding vehicle V1 is less than the upper limit spmax, it executes distance maintaining processing. Specifically, the ECU 10 obtains the distance D between the preceding vehicle V1 and the own vehicle based on the information obtained from the on-board sensor 20. Based on the speed sp0 of the own vehicle and the speed sp1 of the preceding vehicle V1, the ECU 10 determines a target value Dt for the distance D.

[0037] If the speed sp1 of the preceding vehicle V1 relative to the speed sp0 of the own vehicle (relative speed spr = sp1 - sp0) is greater than "0", the distance between vehicles D increases. When the distance between vehicles D is greater than the target value Dt, the ECU 10 determines the target acceleration αt (≤ αacc1) so that the speed sp0 of the own vehicle is greater than the speed sp1 of the preceding vehicle V1. The ECU 10 then controls the drive system etc. so that the acceleration α0 of the own vehicle matches the target acceleration αt (automatic acceleration processing). As a result, the distance between vehicles D decreases and approaches the target value Dt. From the point when the distance between vehicles D matches the target value Dt, the ECU 10 controls the drive system etc. so that the own vehicle travels at the same speed as the preceding vehicle V1.

[0038] On the other hand, when the relative velocity spr is less than "0", the distance between vehicles D decreases. When the distance between vehicles D is less than the target value Dt, the ECU 10 determines the target acceleration αt (≧αdec1) so that the speed sp0 of the vehicle itself is less than the speed sp1 of the preceding vehicle V1. The ECU 10 then controls the drive system and other components so that the acceleration α0 (measured value) of the vehicle itself matches the target acceleration αt (automatic deceleration process). As a result, the distance between vehicles D increases and approaches the target value Dt. From the point when the distance between vehicles D matches the target value Dt, the ECU 10 controls the drive system and other components so that the vehicle itself travels at the same speed as the preceding vehicle V1.

[0039] The target value Dt is related to the speed sp0 of the vehicle itself and the speed sp1 of the preceding vehicle V1. For example, the target value Dta when speeds sp0 and sp1 are relatively small is smaller than the target value Dtb when speeds sp0 and sp1 are relatively large. A database (table) representing the relationship between speeds sp0, sp1 and the target value Dt, or a calculation formula for determining the target value Dt, is stored in the ROM 10b. The ECU 10 determines the target value Dt based on the above database or calculation formula.

[0040] Furthermore, when the vehicle is traveling on a curved road, the ECU 10 sets a target speed spt and / or target acceleration αt so that the lateral acceleration acting on the vehicle remains below a threshold.

[0041] The ECU10 gradually reduces the target acceleration αt from a little before the point in time when the vehicle's speed sp0 reaches the target speed spt (times t3 and t5 in Figure 2), so that the vehicle's acceleration α0 becomes "0" at that point in time. This prevents the speed sp0 from exceeding the target speed spt (overshoot). Hereafter, this process will be referred to as the "overshoot suppression process".

[0042] Furthermore, if the accelerator pedal AP is pressed while the automatic speed adjustment process (automatic acceleration process and automatic deceleration process) is being performed, the ECU 10 calculates an acceleration αap (target value) corresponding to the manner of accelerator pedal operation (e.g., depression depth AD). If the result of this calculation is greater than the target acceleration αt determined based on various information in the automatic speed adjustment process, the ECU 10 determines that the override condition has been met. In this case, the ECU 10 controls the drive system etc. so that the vehicle accelerates at acceleration αap (override process). In other words, in this case, manual driving operation by the driver takes precedence. In this case, the automatic speed adjustment function remains enabled, and the automatic speed adjustment process is resumed when the override condition is no longer met (αap < αt).

[0043] Incidentally, for example, a scene is assumed in which, under a situation where the automatic speed adjustment function is disabled, the driver performs an operation (an operation of tilting the lever of switch 27 upward) to request activation of the automatic speed adjustment function while depressing the accelerator pedal AP. When the override condition is not satisfied (αap < αt) at the time when the switch operation is executed, the speed sp0 of the host vehicle is automatically adjusted by the automatic speed adjustment function. Incidentally, when the override condition is satisfied at the time when the switch operation is executed, the ECU 10 executes override processing. That is, the automatic speed adjustment function is activated at the time when the switch operation is executed, but the speed sp0 is not automatically adjusted. Thereafter, when the override condition becomes not satisfied (αap < αt), the speed sp0 is automatically adjusted.

[0044] In a scene (sp0 < spt) where automatic acceleration processing is started from the time when the above switch operation is executed, if a predetermined value αacc1 is assigned to the upper limit value αtmax of the target acceleration αt, there is a possibility that the acceleration α0 (measured value) of the host vehicle suddenly increases (there is a possibility that the host vehicle is suddenly accelerated). For example, in a scene where there is no preceding vehicle V1 at time t0, the target acceleration αt is set to the upper limit value αtmax (= αacc1). When the acceleration α0 (= αap) of the host vehicle at time t0 or immediately before that is relatively large, the difference between the acceleration α0 and the target acceleration αt is relatively large. Therefore, the host vehicle is suddenly accelerated by the automatic speed adjustment process (automatic acceleration process) (see the example shown by the solid line in FIG. ). There is a possibility that the driver feels uncomfortable in a state where the host vehicle is suddenly accelerated in this way.

[0045] Therefore, when the following condition A (acceleration suppression condition) is satisfied, the ECU 10 assigns the acceleration α0 (acceleration in a state where manual driving operation is being performed) of the host vehicle at time t0 to the upper limit value αtmax of the target acceleration αt instead of the predetermined value αacc1. Hereinafter, the acceleration α0 (measured value) at time t0 is referred to as "acceleration αdrv". (Condition A) The vehicle transitioned from a state where it was accelerating according to manual driving operations to a state where it was accelerating due to automatic acceleration processing.

[0046] For example, if the automatic speed control function is disabled and the driver activates it by pressing the accelerator pedal AP, and the speed sp0 at that time is less than the target speed spt, then condition A is met.

[0047] Furthermore, for example, if the automatic speed adjustment function is enabled behind the preceding vehicle V1, and the vehicle is accelerating due to the override process, and the vehicle changes lanes, causing the override condition to be invalidated, then condition A is valid if the speed sp0 at that time (when the override condition is invalidated) is smaller than the target speed spt (see Figure 3).

[0048] Furthermore, for example, if the automatic speed adjustment function is enabled behind the preceding vehicle V1, and the vehicle is accelerating due to override processing, and the override condition is not met when the preceding vehicle changes lanes, and the speed sp0 at that time is less than the target speed spt, then condition A is met (see Figure 4).

[0049] Furthermore, for example, if the override condition is met when the drive system, etc., is controlled to maintain a state where the lateral acceleration of the vehicle is below a threshold on a curved road, and the override process is being executed, and the vehicle enters a straight road from the curved road, causing the override condition to become unmet, and the speed sp0 at that time is smaller than the target speed spt, then condition A is met (see Figure 5).

[0050] Furthermore, for example, if the automatic speed adjustment function is disabled and an operation is performed to enable the automatic speed adjustment function, the speed sp0 at that time is assigned to the target speed spt and the automatic speed adjustment function is enabled, and the override process is started while the vehicle is traveling at the target speed spt due to the automatic speed adjustment function, and an operation to increase the target speed spt is performed during the override process, causing the override condition to be not met, and if the speed sp0 at that time is smaller than the target speed spt (changed), then condition A is met.

[0051] Here, at time t0 when condition A is met, an upper limit value αtmax may be assigned to the target acceleration αt. For example, if there is no preceding vehicle V1 at time t0, an upper limit value αtmax is assigned to the target acceleration αt. In this case, the upper limit value αtmax is assigned to the acceleration αdrv (acceleration intended by the driver) that would have been achieved when the speed sp0 was being adjusted according to manual driving operations, so the vehicle's acceleration α0 (measured value) does not change when the automatic acceleration process starts. In other words, the vehicle's sudden acceleration is suppressed (see the changes in speed and acceleration shown by the dashed lines in Figure 2).

[0052] Incidentally, if the acceleration αdrv acquired at time t0 is excessive, there is a risk that the safety of the vehicle may be reduced during the subsequent automatic acceleration process. Therefore, if the acceleration αdrv is greater than a predetermined value αacc1, the ECU 10 maintains the state in which the predetermined value αacc1 is assigned to the upper limit value αtmax of the target acceleration αt. On the other hand, if the acceleration αdrv acquired at time t0 is insufficient, the acceleration of the vehicle will be sluggish during the subsequent automatic acceleration process. Therefore, if the acceleration αdrv is less than a predetermined value αacc2, which is less than the predetermined value αacc1, the ECU 10 assigns the predetermined value αacc2 (the second predetermined value of the present invention) to the upper limit value αtmax of the target acceleration αt instead of the acceleration αdrv.

[0053] When the vehicle's speed sp0 increases and reaches a threshold spth that is slightly lower than the target speed spt (time t4 in the example in Figure 2), the ECU 10 resets the upper limit value αtmax to its original value, while the acquired acceleration αdrv is assigned to the upper limit value αtmax. That is, the ECU 10 assigns a predetermined value αacc1 to the upper limit value αtmax. In the example shown in Figure 2, the ECU 10 starts the overshoot suppression process from time t4 when the speed sp0 increases and reaches the threshold spth, but the overshoot suppression process (the process of gradually reducing the target acceleration αt) may also be started from a predetermined time before (or after) the speed sp0 reaches the threshold spth.

[0054] It should be noted that this invention applies to scenarios where the driver assistance device 1 accelerates the vehicle, and does not apply to scenarios where the vehicle decelerates. In other words, the ECU 10 always assigns a predetermined value αdec1 to the lower limit of the target acceleration αt (the maximum value of the target acceleration αt for the backward acceleration α0) when executing the automatic deceleration process.

[0055] Next, we will explain the program PR1 executed by the CPU 10a (hereinafter simply referred to as "CPU") in order to realize the function of the above-mentioned driver assistance device 1 (a function that suppresses sudden acceleration of the vehicle when condition A is met). The ECU 10 executes program PR1 at predetermined intervals.

[0056] (Program PR1) The CPU starts executing program PR1 from step 100 and proceeds to step 101.

[0057] In step 101, the CPU determines whether condition A is met. If the CPU determines that condition A is met (101: Yes), it proceeds to step 102. On the other hand, if the CPU does not determine that condition A is met (101: No), it proceeds to step 106.

[0058] In step 102, the CPU obtains acceleration α0 (acceleration αdrv) from the acceleration sensor 25 and determines whether the acceleration αdrv is less than a predetermined value αacc1. If the CPU determines that acceleration αdrv is less than the predetermined value αacc1 (102: Yes), it proceeds to step 103. On the other hand, if the CPU does not determine that acceleration αdrv is less than the predetermined value αacc1 (102: No), it proceeds to step 106.

[0059] In step 103, the CPU determines whether the acceleration αdrv exceeds a predetermined value αacc2. If the CPU determines that the acceleration αdrv exceeds the predetermined value αacc2 (103: Yes), it proceeds to step 104. On the other hand, if the CPU does not determine that the acceleration αdrv exceeds the predetermined value αacc2 (103: No), it proceeds to step 105.

[0060] In step 104, the CPU assigns the acceleration αdrv to the upper limit value αtmax. Then the CPU proceeds to step 107. Also, in step 105, the CPU assigns a predetermined value αacc2 to the upper limit value αtmax. Then the CPU proceeds to step 107. Also, in step 106, the CPU assigns a predetermined value αacc1 to the upper limit value αtmax. Then the CPU proceeds to step 109.

[0061] In step 107, the CPU determines whether the vehicle's speed sp0 exceeds the threshold spth. If the CPU determines that the speed sp0 exceeds the threshold spth (107: Yes), it proceeds to step 108. On the other hand, if the CPU does not determine that the speed sp0 exceeds the threshold spth (107: No), it executes step 107 again.

[0062] In step 108, the CPU assigns a predetermined value αacc1 to the upper limit value αtmax. Next, the CPU proceeds to step 109. In step 109, the CPU terminates the execution of program PR1.

[0063] (effect) When condition A (acceleration suppression condition) is met, the ECU 10 of the driver assistance device 1 assigns the acceleration α0 at time t0 when condition A is met (i.e., the acceleration αdrv at the time when the driver is actively performing an operation to accelerate the vehicle) as the upper limit αtmax of the target acceleration αt in the automatic speed adjustment process. Therefore, according to the driver assistance device 1 of this embodiment, the sudden acceleration of the vehicle is suppressed when transitioning from a state in which the driver is performing an operation to accelerate the vehicle to a state in which the vehicle's speed is automatically adjusted by the automatic speed adjustment process. This reduces driver discomfort.

[0064] (modified version) In the above embodiment, the threshold spth is smaller than the target speed spt, but the threshold spth may be the same value as the target speed spt. Also, the value assigned to the upper limit αtmax when condition A is met may be the current value of the vehicle's acceleration α0 at time t0, and may be the instantaneous value at that time, or it may be the average value of the acceleration α0 over a predetermined period prior to that time. [Explanation of Symbols]

[0065] 1…Driving assistance system, 10…ECU, 20…On-board sensor, 30…Drive system, 40…Braking system

Claims

1. An on-board sensor for acquiring information about objects around the vehicle, information about the vehicle's driving operations, information about the vehicle's speed, and information about the vehicle's acceleration, A processor configured to determine the target speed and target acceleration of the vehicle based on information acquired from the vehicle-mounted sensors, and to perform an automatic speed adjustment process that controls predetermined devices of the vehicle so that the vehicle's speed changes at the target acceleration and matches the target speed, and to assign a first predetermined value to the upper limit of the target acceleration, A driver assistance device equipped with, The driver assistance device is configured such that, when the processor is not performing the automatic speed adjustment process and transitions from a state in which the predetermined device is controlled so that the vehicle is accelerated at an acceleration corresponding to a mode of manual driving operation that accelerates the vehicle, to a state in which the vehicle is accelerated by the automatic speed adjustment process, it obtains the current value of the vehicle's acceleration and performs an acceleration suppression process in which it assigns the obtained current value to the upper limit of the target acceleration in place of the first predetermined value.

2. In the driving support device according to claim 1, The processor is configured to maintain a state in which the first predetermined value is assigned to the upper limit when the current value of the acquired acceleration is equal to or greater than the first predetermined value.

3. In the driving support device according to claim 1, The processor is configured to assign the second predetermined value to the upper limit when the current value of the acquired acceleration is less than or equal to a second predetermined value which is less than the first predetermined value.

4. In the driving support device according to any one of claims 1 to 3, The aforementioned processor is a driver assistance device configured to assign the first predetermined value to the upper limit when the vehicle accelerates and reaches the target speed or a threshold smaller than the target speed while the upper limit is assigned a value smaller than the first predetermined value due to the acceleration suppression process.

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