Driving assistance device

Abstract

The present invention provides a driving assistance device capable of suppressing rapid acceleration of a host vehicle when transitioning from a state in which a driver performs a driving operation for accelerating the host vehicle to a state in which the speed of the host vehicle is automatically adjusted by an automatic speed adjustment process, thereby reducing a feeling of discomfort of the driver. The ECU executes an acceleration suppression process when transitioning from a state in which the automatic speed adjustment process is not executed and a state in which the prescribed device is controlled at an acceleration corresponding to a manual driving operation for accelerating the own vehicle to a state in which the own vehicle is accelerated by the automatic speed adjustment process. The acceleration suppression process acquires a current value of an acceleration of the own vehicle and assigns the acquired current value to an upper limit value of the target acceleration instead of the first predetermined value.

Description

Driver assistance devices Technical Field

[0001] This invention relates to a driving assistance device that assists in adjusting the speed of one's own vehicle. Background Technology

[0002] A driving assistance device for assisting in adjusting the speed of one's own vehicle is proposed (for example, see Patent Document 1 below). The processor of this driving assistance device (hereinafter referred to as "the prior art") is capable of performing automatic speed adjustment processing (automatic acceleration processing and automatic deceleration processing), which controls the means of the vehicle (drive and braking devices (hereinafter referred to as "drive devices, etc.")) to make the speed of the vehicle (measured value) consistent with the target speed (a value set by the driver or a value determined based on information related to objects around the vehicle).

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-41839 Summary of the Invention

[0004] In vehicles equipped with this type of driver assistance system, a scenario can be envisioned where the driver actively performs driving operations to gradually accelerate the vehicle, transitioning to a state where this driving operation is delegated to the driver assistance system. Here, an upper limit for the vehicle's acceleration is predetermined when the driver assistance system performs automatic acceleration processing. When the driver assistance system begins automatic acceleration processing, this upper limit is sometimes allocated to the vehicle's target acceleration. In this case, the vehicle's acceleration may increase sharply, resulting in rapid acceleration. Thus, the driver may experience discomfort during rapid acceleration.

[0005] One of the objectives of this invention is to provide a driving assistance device that can suppress rapid acceleration of the vehicle when transitioning from a state in which the driver performs a driving operation to accelerate the vehicle to a state in which the vehicle's speed is automatically adjusted by an automatic speed adjustment process, thereby reducing the driver's discomfort.

[0006] To achieve the above objectives, the driving assistance device (1) of the present invention comprises: an on-board sensor (20) for acquiring information related to objects around the vehicle, information related to driving operations of the vehicle (V0), information related to the speed of the vehicle, and information related to the acceleration of the vehicle; and a processor (10) configured to perform an automatic speed adjustment process, wherein the automatic speed adjustment process determines a target speed (spt) and a target acceleration (αt) of the vehicle based on information acquired from the on-board sensor, and controls a predetermined device (30, 40) of the vehicle to change the speed of the vehicle by the target acceleration, thereby making the speed (sp0) of the vehicle consistent with the target speed; and assigns a first predetermined value (αacc1) to an upper limit value (αtmax) of the target acceleration.

[0007] When the processor transitions from a state where it does not perform the automatic speed adjustment process and accelerates the vehicle by controlling the prescribed device with acceleration in a manner corresponding to manual driving operations that accelerate the vehicle, to a state where it accelerates the vehicle by the automatic speed adjustment process, the processor performs an acceleration suppression process. The acceleration suppression process acquires the current value (αdrv) of the vehicle's acceleration and assigns the acquired current value to the upper limit of the target acceleration instead of the first prescribed value.

[0008] The processor of the driving assistance device according to the present invention, when a predetermined condition is met, allocates the acceleration at the time the condition is met (i.e., the acceleration at the moment the driver actively performs an operation to accelerate the vehicle) as an upper limit of the target value of the vehicle's acceleration during automatic speed adjustment processing. Therefore, according to the driving assistance device of the present invention, abrupt acceleration of the vehicle is suppressed when transitioning from a state where the driver performs a driving operation to accelerate the vehicle to a state where the vehicle's speed is automatically adjusted by the automatic speed adjustment processing. This reduces driver discomfort.

[0009] In a driving assistance device according to one aspect of the present invention,

[0010] If the current value of the obtained acceleration is above the first predetermined value, the processor maintains the state of assigning the first predetermined value to the upper limit value.

[0011] This prevents excessive acceleration when the vehicle accelerates through automatic speed adjustment, thus maintaining a high level of vehicle safety.

[0012] In another aspect of the invention, a driving assistance device,

[0013] If the current value of the obtained acceleration is below a second predetermined value (αacc2), the processor assigns the second predetermined value to the upper limit value, which is less than the first predetermined value.

[0014] This prevents the vehicle from accelerating too slowly when the automatic speed adjustment process accelerates the vehicle (resulting in the vehicle accelerating more slowly).

[0015] In another aspect of the invention, a driving assistance device,

[0016] When the processor assigns the first predetermined value to the upper limit value while the vehicle accelerates to the target speed or a threshold (spth) smaller than the target speed through the acceleration suppression process, the processor assigns the first predetermined value to the upper limit value.

[0017] Therefore, in the state where the acquired acceleration is allocated to the upper limit value through acceleration suppression processing (acceleration suppressed state), after the vehicle's speed increases to reach the target speed (or threshold), the automatic speed adjustment processing is executed again so that the vehicle's acceleration is not suppressed. Thus, the vehicle's speed can reach the target speed relatively quickly.

[0018] Furthermore, in another aspect of the driving assistance device according to the present invention,

[0019] When the automatic speed adjustment function is disabled, and the driver is pressing the accelerator pedal while performing an operation to enable the automatic speed adjustment function, and the vehicle's speed at that moment is less than the target speed, the processor performs the acceleration suppression process.

[0020] Furthermore, in another aspect of the driving assistance device according to the present invention,

[0021] When the accelerator pedal of the vehicle is depressed during the automatic speed adjustment process, if the acceleration corresponding to the depressing operation is greater than the target acceleration determined in the automatic speed adjustment process (if the override condition is met), the processor performs override processing. The override processing controls the specified device to cause the vehicle to accelerate at the acceleration corresponding to the depressing operation of the accelerator pedal.

[0022] Furthermore, in another aspect of the driving assistance device according to the present invention,

[0023] When a vehicle is behind a preceding vehicle and can perform automatic speed adjustment processing and accelerates through overtaking processing, if the overtaking condition is not met when the vehicle changes lanes, and the vehicle's speed at that moment is less than the target speed, the processor performs the acceleration suppression processing.

[0024] Furthermore, in another aspect of the driving assistance device according to the present invention,

[0025] On a curved road segment, when the override condition is met while the specified device is controlled in a manner that maintains the lateral acceleration of the vehicle below a threshold, if the override condition is not met when the vehicle enters a straight road segment from the curved road segment during the override process, and if the speed of the vehicle at that moment is less than the target speed, the processor executes the acceleration suppression process.

[0026] Furthermore, in another aspect of the driving assistance device according to the present invention,

[0027] If the process transitions from a state where automatic speed adjustment processing cannot be performed to a state where the function can be performed, the processor assigns the vehicle's current speed to the target speed and transitions to a state where automatic speed adjustment processing can be performed. In the state where the vehicle is traveling at the target speed through automatic speed adjustment processing, overdrive processing is started. If the overdrive processing performs an operation to increase the target speed but the overdrive condition is not met, and if the vehicle's current speed is less than the target speed (which has been changed), the processor performs acceleration suppression processing. Attached Figure Description

[0028] Figure 1 is a block diagram of a driving assistance device according to an embodiment of the present invention.

[0029] Figure 2 is a timing diagram showing the changes in the on / off state of the first switch, speed, acceleration, and throttle opening.

[0030] Figure 3 is a top view showing a scenario where a vehicle changes lanes behind a vehicle that is ahead.

[0031] Figure 4 is a top view showing a scenario where a vehicle ahead of another vehicle changes lanes.

[0032] Figure 5 is a top view showing the scene of a vehicle entering a straight section from a curved section of road.

[0033] Figure 6 is a flowchart of the program executed by the CPU to implement the function of setting the upper limit of the target acceleration according to the driving scenario. Detailed Implementation

[0034] (roughly)

[0035] One embodiment of the present invention relates to a driving assistance device 1, which is applied, for example, to a vehicle V0 (hereinafter referred to as "the vehicle itself") equipped with an autonomous driving function. The driving assistance device 1 has an automatic speed adjustment function that supports driving operations that adjust the speed sp0 of the vehicle itself. The automatic speed adjustment function includes a function that automatically accelerates the vehicle itself (automatic acceleration function). The driving assistance device 1 has a function that sets an upper limit value of the target acceleration when the vehicle itself is automatically accelerated by the automatic acceleration function, based on the driving scenario.

[0036] (Specific structure)

[0037] As shown in Figure 1, the driving assistance device 1 includes an ECU 10, an on-board sensor 20, a drive unit 30, and a braking device 40.

[0038] ECU10 includes a microcomputer with CPU10a, ROM10b, RAM10c, timer10d, etc. ECU10 is connected to other ECUs in the vehicle via Controller Area Network (CAN).

[0039] The vehicle-mounted sensor 20 includes a front sensor that acquires information about a target located in front of the vehicle. Specifically, the vehicle-mounted sensor 20 includes a millimeter-wave radar 21, a sonar 22, and a front camera 23, which serve as front sensors.

[0040] The millimeter-wave radar 21 includes a transceiver unit and a signal processing unit (not shown). The transceiver unit radiates radio waves in the millimeter-wave band (hereinafter referred to as "millimeter waves") toward the area in front of its own vehicle and receives millimeter waves (reflected waves) reflected by a three-dimensional object (the preceding vehicle V1) located within the radiation range. The signal processing unit calculates the distance between its own vehicle and the three-dimensional object, the speed of the three-dimensional object (relative speed), etc., based on the time from the time the transceiver unit radiates the millimeter waves to the time it receives the reflected waves, the phase difference between the transmitted millimeter waves and the received reflected waves, and the attenuation level of the reflected waves, and provides the calculation results to the ECU 10.

[0041] Sonar 22 radiates ultrasonic waves toward the area in front of its own vehicle and receives ultrasonic waves reflected by three-dimensional objects (reflected waves). Sonar 22 calculates the distance between its own vehicle and the three-dimensional object, the position (direction) of the three-dimensional object relative to its own vehicle, etc., based on the time from sending ultrasonic waves to receiving reflected waves, and provides the calculation results to ECU 10.

[0042] The forward-facing camera 23 includes a camera and an image analysis unit. The camera incorporates a lens and an image sensor element of either a charge-coupled device (CCD) or a CMOS image sensor (CIS). The camera faces forward and is located at the top of the windshield. The camera captures image data of the foreground of its own vehicle at a predetermined frame rate. The camera then sends the image data to the image analysis unit. The image analysis unit analyzes the acquired image data to extract information related to objects located in front of the vehicle. For example, the image analysis unit identifies the type of target object in front of the vehicle (e.g., other vehicles, lane markings, etc.) and provides this identification result to the ECU 10.

[0043] Furthermore, the vehicle-mounted sensor 20 includes sensors that acquire information related to the dynamics (speed and acceleration) of the vehicle itself. Specifically, the vehicle-mounted sensor 20 includes a speed sensor 24 and an acceleration sensor 25.

[0044] 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 speeds. Speed ​​sensor 24 then provides this calculation result to ECU 10.

[0045] Accelerometer 25 detects the longitudinal and lateral acceleration α0 of the vehicle. Accelerometer 25 provides the detection results to ECU 10.

[0046] Furthermore, the on-board sensor 20 includes a throttle pedal sensor 26 and a switch 27, which function as operation sensors. The throttle pedal sensor 26 detects the throttle pedal AP's depressance AD ​​(throttle opening) and provides this detection result to the ECU 10. The switch 27 is, for example, a lever-type device, including a lever that can tilt upwards and downwards from a neutral position, a first switch, and a second switch. When the lever is tilted upwards from the neutral position, the first switch transitions from a closed state to an open state; when the lever is tilted downwards from the neutral position, the second switch transitions from a closed state to an open state. The switch 27 is used to activate the automatic speed adjustment function (which will be described later) (transitioning the operating mode from a first operating mode to a second operating mode). That is, when the function is deactivated (first operating mode), tilting the lever of the switch 27 upwards from the neutral position activates the automatic speed adjustment function (second operating mode). Furthermore, switch 27 is used to input (change) 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 tilted upward from the neutral position, the upper limit value spmax increases. On the other hand, if the lever is tilted downward from the neutral position, the upper limit value spmax decreases. The upper limit value spmax is stored in ROM 10b. When the automatic speed adjustment function is enabled again after being temporarily disabled, the upper limit value spmax (the previously set value) is read from ROM 10b.

[0047] 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 drive force transmission mechanism that transmits driving force to the wheels. The engine ECU obtains information (target value) representing the target driving force from other ECUs (ECU 10). The engine ECU drives the throttle valve of the internal combustion engine to ensure that the driving force applied to the drive wheels matches the target value.

[0048] Furthermore, when the vehicle using driver assistance device 1 is a hybrid electric vehicle (HEV), the engine ECU can adjust the output (driving force) of any one or both of the "internal combustion engine and electric motor" that serve as the vehicle's drive source. And, when the vehicle using driver assistance device 1 is a battery electric vehicle (BEV), instead of the engine ECU, an electric motor ECU is used to adjust the output (driving force) of the "electric motor" that serves as the vehicle's drive source.

[0049] Braking device 40 applies braking force to the wheels (brake discs). Braking device 40 includes a brake ECU, brake calipers, etc. The brake calipers include actuators that press the brake pads onto 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 make the braking force applied to the wheels (brake discs) match the target value.

[0050] (Work)

[0051] When the first switch of switch 27 is detected to transition from the closed state to the open state, ECU 10 determines whether the preceding vehicle V1 is present and executes automatic speed adjustment processing to control the drive unit (drive unit 30 and / or braking unit 40) according to the determination result. This function (automatic speed adjustment function) is also called adaptive cruise control (ACC). This function includes constant speed driving function and vehicle distance keeping function. In the normal state (the state where condition A described later is not met), ECU 10 assigns a predetermined value αacc1 (>0) to the upper limit value αtmax of the target value (target acceleration αt) of the acceleration α0 of its own vehicle when accelerating through the automatic speed adjustment processing. On the other hand, in the normal state, ECU 10 assigns a predetermined value αdec1 (<0) to the lower limit value (maximum value of the target value of backward acceleration) of the acceleration (deceleration) α0 of its own vehicle when decelerating through the automatic speed adjustment processing. The aforementioned predetermined values ​​αacc1 and αdec1 are determined during the vehicle design stage. In addition, the predetermined value αacc1 is equivalent to the first predetermined value of the present invention. As will be described in detail later, under specified conditions, ECU10 will assign a value smaller than the specified value αacc1 to the upper limit value αtmax.

[0052] (Cruise control function)

[0053] The ECU 10 determines the presence of a preceding vehicle V1 based on information obtained from front sensors (millimeter-wave radar 21, sonar 22, and front camera 23). If the preceding vehicle V1 is not present, the ECU 10 performs constant speed control. Specifically, the ECU 10 assigns a target value (target speed spt) to its own vehicle's speed sp0, set by the driver as an upper limit value spmax. Furthermore, the ECU 10 controls the drive system to ensure 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 to ensure that the vehicle's acceleration α0 matches the target acceleration αt (≤ αacc1) determined based on various conditions. This process will be referred to as "automatic acceleration processing." Thus, the vehicle's speed sp0 approaches the target speed spt (= spmax). Additionally, even if the preceding vehicle V1 is present, if its speed sp1 is greater than the upper limit value spmax, the ECU 10 performs constant speed control.

[0054] [Vehicle Distance Maintenance Control]

[0055] On the other hand, when ECU 10 determines that there is a preceding vehicle V1 and the speed sp1 of the preceding vehicle V1 is less than the upper limit value spmax, it performs vehicle spacing maintenance processing. Specifically, ECU 10 obtains the vehicle spacing D between the preceding vehicle V1 and its own vehicle based on information obtained from the on-board sensor 20. ECU 10 determines the target value Dt of the vehicle spacing D based on the speed sp0 of its own vehicle and the speed sp1 of the preceding vehicle V1.

[0056] When the speed sp1 (relative speed spr = sp1 - sp0) of the preceding vehicle V1 is greater than 0 relative to the speed sp0 of the preceding vehicle, the vehicle spacing D increases. When the vehicle spacing D is greater than the target value Dt, the ECU 10 determines a target acceleration αt (≤ αacc1) to make the speed sp0 of the preceding vehicle V1 greater than the speed sp1 of the preceding vehicle V1. Furthermore, the ECU 10 controls the drive system, etc., to make the acceleration α0 of the preceding vehicle match the target acceleration αt (automatic acceleration processing). As a result, the vehicle spacing D decreases and approaches the target value Dt. The ECU 10 controls the drive system, etc., to make the preceding vehicle travel at the same speed as the preceding vehicle V1 from the moment the vehicle spacing D matches the target value Dt.

[0057] On the other hand, when the relative speed spr is less than 0, the vehicle spacing D decreases. When the vehicle spacing D is less than the target value Dt, the ECU 10 determines a target acceleration αt (≥αdec1) to make its own vehicle's speed sp0 less than the speed sp1 of the preceding vehicle V1. Furthermore, the ECU 10 controls the drive system, etc., to make its own vehicle's acceleration α0 (measured value) match the target acceleration αt (automatic deceleration). As a result, the vehicle spacing D increases and approaches the target value Dt. Moreover, the drive system, etc., is controlled to make its own vehicle travel at the same speed as the preceding vehicle V1 from the moment the vehicle spacing D matches the target value Dt.

[0058] Furthermore, 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 is smaller when speeds sp0 and sp1 are 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 formula for calculating the target value Dt, is stored in ROM 10b. ECU 10 determines the target value Dt based on the aforementioned database or formula.

[0059] Furthermore, when the vehicle is traveling on a curved road, the ECU10 sets a target speed spt and / or a target acceleration αt to maintain the lateral acceleration acting on the vehicle below a threshold.

[0060] Starting slightly earlier than this time (the moment when the speed sp0 is slightly lower than the threshold spth of the target speed sppt (times t2 and t4 in Figure 2)), ECU10 gradually reduces the target acceleration αt so that when the vehicle's speed sp0 reaches the target speed sppt (times t3 and t5 in Figure 2), the vehicle's acceleration α0 becomes "0". This suppresses the situation where the speed sp0 exceeds the target speed sppt (overshoot). This process will be referred to as "overshoot suppression processing" below.

[0061] Furthermore, when performing automatic speed adjustment processing (automatic acceleration processing and automatic deceleration processing), the ECU10 calculates the acceleration αap (target value) corresponding to the accelerator pedal operation method (e.g., pedal depth AD) when the accelerator pedal AP is depressed. If the calculated result is greater than the target acceleration αt determined based on various information during the automatic speed adjustment processing, an override condition is determined to be met. In this case, the ECU10 controls the drive unit, etc., to accelerate the vehicle at acceleration αap (override processing). That is, in this case, the driver's manual driving operation is prioritized. In addition, in this case, the automatic speed adjustment function remains in an active state, and the automatic speed adjustment processing restarts when the override condition is not met (αap < αt).

[0062] For example, in a situation where the automatic speed adjustment function is disabled, it is conceivable that while the driver is pressing the accelerator pedal (AP), an operation is performed to request the activation of the automatic speed adjustment function (by tilting the lever of switch 27 upwards). If the override condition is not met at the time of this switch operation (αap < αt), the vehicle's speed sp0 is automatically adjusted by the automatic speed adjustment function. Conversely, if the override condition is met at the time of this switch operation, ECU 10 performs override processing. That is, the automatic speed adjustment function is activated at the time of this switch operation, but the speed sp0 is not automatically adjusted. Then, at the time when the override condition is not met (αap < αt), the speed sp0 is automatically adjusted.

[0063] In a scenario where automatic acceleration begins from the moment the aforementioned switch operation is performed (sp0 < spt), assuming a predetermined value αacc1 is assigned to the upper limit αtmax of the target acceleration αt, the vehicle's own acceleration α0 (measured value) may increase dramatically (the vehicle may accelerate rapidly). For example, in a scenario where there is no preceding vehicle V1 at time t0, the target acceleration αt is set to the upper limit αtmax (= αacc1). If the vehicle's own acceleration α0 (= αap) is relatively small at or before time t0, the difference between this acceleration α0 and the target acceleration αt is large. Therefore, through automatic speed adjustment (automatic acceleration), the vehicle accelerates rapidly (refer to the example shown by the solid line in Figure 2). Thus, the driver may feel uncomfortable with the rapid acceleration of the vehicle.

[0064] Therefore, when condition A (acceleration suppression condition) is met, ECU10 assigns the vehicle's own acceleration α0 (acceleration under manual driving operation) 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 will be referred to as "acceleration αdrv".

[0065] (Condition A) The state of accelerating the vehicle based on manual driving operation is transitioned to the state of accelerating the vehicle based on automatic acceleration through automatic acceleration processing.

[0066] For example, if the automatic speed adjustment function is disabled, and the driver performs the operation of pressing the accelerator pedal AP to enable the automatic speed adjustment function, and the speed sp0 at that moment is less than the target speed spt, then condition A is met.

[0067] Furthermore, for example, if the automatic speed adjustment function is activated behind the leading vehicle V1 and the vehicle accelerates through overdrive processing, and the vehicle changes lanes but the overdrive condition is not met, and the speed sp0 at that moment (the moment the overdrive condition is not met) is less than the target speed spt, then condition A is met (see Figure 3).

[0068] Furthermore, for example, if the automatic speed adjustment function is activated and the vehicle accelerates through overdrive processing behind the preceding vehicle V1, and the preceding vehicle changes lanes but the overdrive condition is not met, and the speed sp0 at that moment is less than the target speed spt, then condition A is met (see Figure 4).

[0069] Furthermore, for example, on a curved road segment, in a state where the drive unit is controlled to maintain the lateral acceleration of the vehicle below a threshold, if the override condition is met and the vehicle enters a straight road segment from the curved road segment while the override condition is not met, and the speed sp0 at that moment is less than the target speed spt, then condition A is met (see Figure 5).

[0070] Furthermore, for example, if an operation to enable the automatic speed adjustment function is performed while the automatic speed adjustment function is disabled, the speed sp0 at that moment is assigned to the target speed spt, and the automatic speed adjustment function is enabled. Override processing begins while the vehicle is traveling at the target speed spt through the automatic speed adjustment function. If an operation to increase the target speed spt is performed but the override condition is not met, and the speed sp0 at that moment is less than the target speed spt (which has been changed), then condition A is met.

[0071] Here, at time t0 when condition A is met, sometimes the upper limit value αtmax is assigned to the target acceleration αt. For example, if there is no preceding vehicle V1 at time t0, the upper limit value αtmax is assigned to the target acceleration αt. In this case, since the acceleration αdrv (the acceleration intended by the driver) under the state of adjusting speed sp0 according to manual driving operation is assigned to the upper limit value αtmax, the vehicle's own acceleration α0 (measured value) will not change when automatic acceleration processing begins. That is, rapid acceleration of the vehicle itself is suppressed (refer to the speed and acceleration changes shown by the dashed lines in Figure 2).

[0072] If the acceleration αdrv acquired at time t0 is too large, the safety of the vehicle may decrease during subsequent automatic acceleration processing. Therefore, when the acceleration αdrv is greater than the predetermined value αacc1, the ECU 10 maintains the state of allocating the predetermined value αacc1 to the upper limit value αtmax of the target acceleration αt. On the other hand, if the acceleration αdrv acquired at time t0 is too small, the acceleration of the vehicle will be slower during subsequent automatic acceleration processing. Therefore, when the acceleration αdrv is less than the predetermined value αacc1 and less than the predetermined value αacc2, the ECU 10 allocates 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.

[0073] When ECU 10 assigns the acquired acceleration αdrv to the upper limit value αtmax, at the moment when its own vehicle speed sp0 rises to a threshold spth slightly below the target speed sppt (time t4 in the example of Figure 2), the upper limit value αtmax is restored to its original value. That is, ECU 10 assigns a predetermined value αacc1 to the upper limit value αtmax. Furthermore, in the example shown in Figure 2, ECU 10 starts overshoot suppression processing from the moment t4 when speed sp0 rises to reach the threshold spth, but it can also start overshoot suppression processing (gradually reducing the target acceleration αt) from a predetermined moment before (or after) when speed sp0 reaches the threshold spth.

[0074] Furthermore, this invention focuses on scenarios where the driver assistance device 1 accelerates the vehicle itself, not scenarios where it decelerates the vehicle. That is, 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 performing automatic deceleration processing.

[0075] Next, the program PR1 executed by the CPU 10a (hereinafter referred to as "CPU") to achieve the function of the aforementioned driving assistance device 1 (the function of suppressing the rapid acceleration of the vehicle when condition A is met) will be described. The ECU 10 executes program PR1 at a predetermined cycle.

[0076] (Program PR1)

[0077] The CPU starts executing program PR1 from step 100 and proceeds to step 101.

[0078] In step 101, the CPU determines whether condition A is true or false. If the CPU determines that condition A is true (101: Yes), it proceeds to step 102. On the other hand, if the CPU does not determine that condition A is true (101: No), it proceeds to step 106.

[0079] In step 102, the CPU acquires acceleration α0 (acceleration αdrv) from the accelerometer 25 and determines whether the acceleration αdrv is less than a predetermined value αacc1. If the CPU determines that the 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 the acceleration αdrv is less than the predetermined value αacc1 (102: No), it proceeds to step 106.

[0080] In step 103, the CPU determines whether the acceleration αdrv exceeds the 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.

[0081] In step 104, the CPU assigns the acceleration αdrv to the upper limit value αtmax. Then, the CPU proceeds to step 107. In step 105, the CPU assigns the predetermined value αacc2 to the upper limit value αtmax. Then, the CPU proceeds to step 107. In step 106, the CPU assigns the predetermined value αacc1 to the upper limit value αtmax. Then, the CPU proceeds to step 109.

[0082] In step 107, the CPU determines whether the speed sp0 of its own vehicle 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.

[0083] In step 108, the CPU assigns the specified value αacc1 to the upper limit value αtmax. Then, the CPU proceeds to step 109. In step 109, the CPU terminates the execution of program PR1.

[0084] (Effect)

[0085] When condition A (acceleration suppression condition) is met, the ECU 10 of the driver assistance device 1 allocates the acceleration α0 at the time t0 when condition A is met (i.e., the acceleration αdrv at the time when the driver actively performs the operation to accelerate the vehicle) to the upper limit value αtmax of the target acceleration αt in the automatic speed adjustment process. Therefore, according to the driver assistance device 1 of this embodiment, the rapid acceleration of the vehicle is suppressed when transitioning from a state in which the driver performs a driving operation to accelerate the vehicle to a state in which the speed of the vehicle is automatically adjusted by the automatic speed adjustment process. As a result, driver discomfort can be reduced.

[0086] (Variation example)

[0087] In the above implementation, the threshold spth is less than the target speed spt, but the threshold spth can be the same value as the target speed spt. Furthermore, when condition A is met, the value assigned to the upper limit αtmax can be either the instantaneous value at the same moment as the current value of the vehicle's acceleration α0 at time t0, or the average value of the acceleration α0 over a specified period prior to that moment.

[0088] Symbol Explanation

[0089] 1-Driver assistance device, 10-ECU, 20-Vehicle sensor, 30-Drive device, 40-Brake device.

Claims

1. A driving assistance device comprising: an onboard sensor for acquiring information related to objects around the vehicle, information related to driving operations of the vehicle, information related to the speed of the vehicle, and information related to the acceleration of the vehicle; and a processor configured to perform an automatic speed adjustment process, wherein the automatic speed adjustment process determines a target speed and a target acceleration of the vehicle based on information acquired from the onboard sensor, and controls a predetermined device of the vehicle to change the speed of the vehicle by the target acceleration, thereby making the speed of the vehicle consistent with the target speed; and assigns a first predetermined value to an upper limit of the target acceleration, the driving assistance device being characterized in that: when transitioning from a state in which the automatic speed adjustment process is not performed and the vehicle is accelerated by controlling the predetermined device with acceleration corresponding to a manual driving operation that accelerates the vehicle to a state in which the vehicle is accelerated by the automatic speed adjustment process, the processor performs an acceleration suppression process, wherein the acceleration suppression process acquires a current value of the vehicle's acceleration and assigns the acquired current value to the upper limit of the target acceleration instead of the first predetermined value.

2. The driving assistance device according to claim 1, characterized in that, The configuration is such that, when the current value of the acquired acceleration is above the first predetermined value, the processor maintains the state of assigning the first predetermined value to the upper limit value.

3. The driving assistance device according to claim 1, characterized in that, The configuration is such that, when the current value of the obtained acceleration is below a second predetermined value, the processor assigns the second predetermined value to the upper limit value, the second predetermined value being less than the first predetermined value.

4. The driving assistance device according to any one of claims 1 to 3, characterized in that, The configuration is as follows: when the upper limit value is assigned a value smaller than the first predetermined value through the acceleration suppression process, and the vehicle accelerates to reach the target speed or a threshold value smaller than the target speed, the processor assigns the first predetermined value to the upper limit value.

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