JP2007112231A - Travel control device - Google Patents

Abstract

[PROBLEMS] To eliminate a sense of crisis and anxiety due to a rear-end collision or an unnecessarily strong braking force by setting an appropriate target deceleration in deceleration traveling control.
A deceleration setting unit 63, a target deceleration alpha _a ', to ensure a predetermined vehicle distance l according to the vehicle speed V _a, lowering the vehicle speed V _a to the preceding vehicle speed V _f, and The own vehicle and the preceding vehicle are derived from a relational expression configured to satisfy the condition that both stop at the same time when the current deceleration is maintained. This relational expression is the correspondence between the own vehicle speed V _a , the inter-vehicle distance L, the target inter-vehicle distance l, the preceding vehicle speed V _f and the preceding vehicle deceleration α _f, and the own vehicle deceleration α _a ′. Show the relationship. Based on the target deceleration rate α _a ′, the braking instruction unit 65 sends an instruction to the brake driving unit 3b and the throttle valve 1a, thereby controlling deceleration.
[Selection] Figure 2

Description

  The present invention relates to a traveling control device mounted on a vehicle, and more particularly, to deceleration control for a preceding vehicle in a traveling vehicle.

Conventionally, a traveling control device that automatically decelerates the host vehicle in accordance with the deceleration of the preceding vehicle is known. The rear-end collision prevention device disclosed in Patent Document 1 calculates a target deceleration from the relative speed and the inter-vehicle distance of a preceding vehicle that has interrupted the train, and controls the brake based on the target deceleration. In addition, the travel control device disclosed in Patent Document 2 sets the target deceleration so as not to exceed a predetermined value during deceleration in the travel control.
Japanese Patent No. 2979707 JP 11-11273 A

  In the conventional traveling control apparatus as described above, a predetermined condition is set and the target deceleration is calculated. However, an appropriate value is not necessarily calculated. As a result, drivers and passengers may have a sense of crisis and anxiety due to rear-end collisions and unnecessarily strong braking force.

  The present invention has been made in view of such circumstances, and an object of the present invention is to eliminate an occupant's sense of crisis and the like by setting an appropriate target deceleration in the deceleration traveling control.

  In order to solve such a problem, the present invention provides a travel control device that is mounted on a vehicle and controls deceleration of the vehicle according to a target deceleration. The travel control device includes a vehicle speed sensor, a preview sensor, a preceding vehicle information generation unit, and a deceleration setting unit. The vehicle speed sensor detects the speed of the host vehicle, and the preview sensor detects the inter-vehicle distance from the preceding vehicle. The preceding vehicle information generation unit specifies the speed of the preceding vehicle based on the speed of the host vehicle and the inter-vehicle distance. When the host vehicle is faster than the preceding vehicle, the deceleration setting unit sets the deceleration of the host vehicle as an output in a predetermined correspondence relationship based on the host vehicle speed, the inter-vehicle distance, the predetermined target inter-vehicle distance, and the preceding vehicle speed. Get. The deceleration setting unit sets the obtained deceleration as the target deceleration. The predetermined correspondence relationship is to secure a predetermined target inter-vehicle distance, to reduce the speed of the own vehicle to the speed of the preceding vehicle, and to stop simultaneously when the own vehicle and the preceding vehicle maintain the current deceleration. It is configured so as to satisfy this condition.

  In this invention, it is preferable to further have a target inter-vehicle distance update part. That is, the target inter-vehicle distance update unit decreases the predetermined target inter-vehicle distance used for setting the target deceleration according to the detected decrease in the speed of the own vehicle.

  According to the present invention, in deceleration (braking) control, the speed of the own vehicle is reduced to the speed of the preceding vehicle while securing a predetermined target inter-vehicle distance, and both the own vehicle and the preceding vehicle temporarily reduce the current deceleration. Since the target deceleration is set so that it stops simultaneously when maintained, it eliminates the occupant's sense of crisis about rear-end collision that may have occurred in the past, and arises from unnecessarily strong braking force that has occurred in the past Anxiety can be resolved.

  FIG. 1 is a diagram showing a schematic configuration of a vehicle on which a travel control device 6 according to the present embodiment is mounted. This vehicle is a four-wheel drive vehicle, and drives all four wheels, front, rear, left and right. The vehicle can control deceleration by the brake device 3 and the travel control device 6 so as to follow the preceding vehicle. The travel control device 6 has a feature in setting a target deceleration at this time.

  The engine 1 as a drive source is provided with a throttle valve 1a for adjusting the intake air amount, and this throttle valve 1a has a predetermined actuator. A control signal corresponding to the amount of depression of the accelerator pedal by the driver is generated by the travel control device 6, and the opening of the throttle valve 1a is adjusted by operating the actuator according to this control signal. Then, air containing fuel corresponding to the opening is sucked into the engine 1. The power from the engine 1 is transmitted to the front wheel side and rear wheel side axles (drive shafts) via a differential mechanism (not shown). The power transmitted to each axle generates a driving torque on each wheel 2, and thereby a driving force is applied to each wheel 2.

  The brake device 3 mainly includes a brake mechanism 3a, a brake drive unit 3b, and a brake control unit 3c. The brake mechanism 3a is provided for each wheel 2 and is, for example, a known hydraulic brake mechanism including a master cylinder, a wheel cylinder, a disk rotor, a caliper, a brake pad, and the like. Each brake mechanism 3a presses the brake pad against the disc rotor, thereby applying a brake torque corresponding to the friction force to the wheel 2 to generate a braking force. That is, when the brake pedal connected to the master cylinder is depressed by the driver, the brake fluid is pressed from the master cylinder to each wheel cylinder via the brake drive unit 3b. Due to the fluid pressure supplied to the wheel cylinder, the caliper presses the brake pad against the disc rotor, and brake torque is generated in the wheel 2.

  The brake drive unit 3b is generally called a hydraulic control unit, and includes a motor, a solenoid valve, a reservoir, and the like. The brake drive unit 3b is connected to a wheel cylinder and a master cylinder of each brake mechanism 3a through a fluid passage. The brake drive unit 3b can automatically operate the brake mechanism 3a based on a control signal from the travel control device 6 regardless of the depression amount of the brake pedal.

The brake control unit 3c determines whether or not to perform antilock braking when the brake mechanism 3a operates. The brake control unit 3c, a vehicle speed sensor 4 for detecting the speed V _a of the vehicle in response to the wheel speed of each wheel 2 is connected, for determining whether or not performing anti-lock brakes, a vehicle speed sensor 4 A detection signal is input from. The brake control unit 3c selects one of the hydraulic pressure modes among pressure increasing, holding, and pressure reducing when performing anti-lock braking. A control signal corresponding to the selected mode is output to the brake drive unit 3b. On the other hand, when the antilock brake is not performed, a control signal corresponding to the normal brake mode is output to the brake drive unit 3b. In the normal brake mode, the brake drive unit 3b operates according to the amount of depression of the brake pedal or a control signal from the travel control device 6 described later.

  The preview sensor 5 is a sensor that detects an inter-vehicle distance L between the preceding vehicle and the host vehicle. Here, the preview sensor 5 is a known stereo image processing device configured by a pair of CCD cameras and an image processing system. This stereo image processing apparatus calculates distance data based on a pair of image data obtained from each CCD camera. In the distance data, the position on the two-dimensional area defined by the image data is associated with the distance (or parallax) to the object projected at this position, and the distance to the object in front of the vehicle is Distribution is represented. The preview sensor 5 detects the inter-vehicle distance L after recognizing the position of the preceding vehicle in the three-dimensional space based on the distance data. A function equivalent to the preview sensor 5 can be realized by using a monocular camera, a laser radar, a millimeter wave radar, or the like alone or in combination.

  The travel control device 6 is mainly composed of a microcomputer, and includes a CPU, a ROM, a RAM, an input / output interface, and the like. The travel control device 6 performs an operation related to travel control according to the travel control program stored in the ROM so that the inter-vehicle distance between the host vehicle and the preceding vehicle becomes the target inter-vehicle distance. Driving is performed. In order to perform such calculation, detection values from the vehicle speed sensor 4 and the preview sensor 5 are input, and a control signal corresponding to the calculation result is output to the throttle valve 1a or the brake drive unit 3b.

FIG. 2 is a block diagram showing a main configuration related to the deceleration control of the traveling control device 6 in particular. As described above, the traveling control device 6 is composed of a microcomputer. The program relating to the deceleration control executed here mainly includes a target inter-vehicle distance update unit 61, a preceding vehicle information generation unit 62, a deceleration setting unit 63, a brake torque correspondence map 64, and a braking instruction unit 65. Have The target inter-vehicle distance update unit 61 sets the target inter-vehicle distance l based on the speed V _{a of the} own vehicle detected by the vehicle speed sensor 4 (an average for four wheels, etc.). The function l (V _a ) is _a monotonically increasing function of the host vehicle speed V _a (Equation 1), that is, the target inter-vehicle distance l decreases (increases) as the host vehicle speed V _a decreases (increases). The form of this function l (V _a ) can be determined based on data obtained by a traffic flow survey or the like.

Preceding vehicle information generation unit 62, based on the inter-vehicle distance L detected by the vehicle speed V _a and preview sensor 5 detected by the vehicle speed sensor 4, and calculates the relative velocity V _fa of the preceding vehicle relative to the vehicle. That is, the relative speed V _fa is obtained as a change in the inter-vehicle distance per unit time (= ΔL / Δt) from the inter-vehicle distance L at time t and the inter-vehicle distance (L + ΔL) at time (t + Δt). Is possible. When the relative speed V _fa is positive, it means that the own vehicle is moving away from the preceding vehicle, and when V _fa is negative, it means that the own vehicle approaches the preceding vehicle. The deceleration setting unit 63 calculates the target deceleration α _a ′ of the own vehicle by substituting the own vehicle speed V _a , the relative speed V _fa , the inter-vehicle distance L, and the target inter-vehicle distance l into the following Expression 2.

That is, as shown in the equation, the target deceleration rate α _a ′ of the host vehicle is doubled by multiplying the product of the _host vehicle speed V _a and the relative speed V _fa by subtracting the target inter-vehicle distance l from the inter-vehicle distance L. It is calculated by dividing by the thing and adding this to the minus. The brake torque correspondence map 64 is a map in which the correspondence relationship between the target deceleration rate α _a ′ and the brake torque is described in advance, and this correspondence relationship is set through experiments and simulations. The braking instruction unit 65 refers to the map 64, specifies the brake torque corresponding to the calculated target deceleration rate α _a ′, and outputs a control signal for instructing the brake torque to the brake driving unit 3b. . Similarly, the braking instruction unit 65 instructs the opening degree of the throttle valve 1a.

  FIG. 3 is a flowchart showing the procedure of travel control including these deceleration controls. The traveling control device 6 calls and executes this traveling control program at predetermined intervals. In particular, steps 3 to 9 relate to deceleration control. First, in step 1, it is determined whether or not it is the preceding vehicle following mode, that is, which value is the mode flag corresponding to 0 for the normal mode and 1 for the preceding vehicle following mode. Unlike the normal mode in which the vehicle speed is adjusted by the driver's own operation, the preceding vehicle following mode is a mode in which the vehicle speed is automatically adjusted following the preceding vehicle. These two modes are appropriately selected by the driver using a predetermined operation switch. If a negative determination is made in step 1, that is, if the normal mode is selected, the process proceeds to step 2. On the other hand, when the preceding vehicle follow-up mode is selected by the driver, an affirmative determination is made in step 1 until the mode is canceled, that is, until the next normal mode is selected, and the process proceeds to step 3.

  If the normal mode is selected in step 1, normal control is performed in step 2. The travel control device 6 sets the opening degree of the throttle valve 1a based on the operation amount of the accelerator pedal of the driver, and outputs a control signal corresponding to the set amount toward the throttle valve 1a. The brake device 3 applies brake torque to each wheel 2 in accordance with the amount of operation of the driver's brake pedal. After this, the routine is exited.

When the follow-up mode is selected, first, in step 3, the detected value of the inter-vehicle distance L by the preview sensor 5 is read. In step 4, the relative speed is calculated as the time derivative of the inter-vehicle distance L as described above. V _fa is calculated. Specifically, the relative speed _Vfa is calculated from the inter-vehicle distance (L-ΔL) read before Δt seconds, which is the previous execution time of this process, and the inter-vehicle distance L read this time. In step 5, the detected value of the vehicular velocity V _a is read by the vehicle speed sensor 4, in step 6, the target following distance l is calculated on the basis of the vehicle speed V _a (the numerical formula 1). In step 7, it is determined whether or not to perform deceleration. Specifically, whether or not the vehicle is approaching the preceding vehicle, that is, whether or not the relative speed V _fa is negative, and whether or not the inter-vehicle distance L is appropriate for the target inter-vehicle distance l It is judged. If an affirmative determination is made in step 7 and deceleration is necessary, the process proceeds to step 8. If a negative determination is made in step 7 and deceleration is not necessary, the process proceeds to step 10.

In the case where the vehicle is decelerated based on the determination in step 7, in step 8, the inter-vehicle distance L read in step 3, the relative speed V _fa calculated in step 4, and the own vehicle speed read in step 5. V _a and the target inter-vehicle distance l calculated in step 6 are substituted into the above equation 2 to calculate the target deceleration α _a ′ of the host vehicle. The deceleration α _a ′ will be described in detail later. If the host vehicle catches up at a point before the target vehicle distance l from the preceding vehicle, the speed corresponding to the preceding vehicle speed V _f (≈V _a ) Is set. In step 9, deceleration control is performed so that a braking force according to the calculated deceleration rate α _a ′ is applied. Specifically, a control signal for instructing a brake torque corresponding to the deceleration α _a ′ is output to the brake drive unit 3b, and a predetermined control signal is also output to the throttle valve 1a. As a result, the throttle valve 1a is closed and the output of the engine 1 is reduced, while the brake drive unit 3b operates the brake mechanism 3a to apply a predetermined brake torque to the wheels 2. After this, the routine is exited.

  If the vehicle is not decelerated based on the determination in step 7, the vehicle is accelerated in step 10 by controlling the throttle valve 1a. That is, the opening degree of the throttle valve 1a is adjusted so that the inter-vehicle distance L approaches the target inter-vehicle distance l. Thereafter, the routine is exited.

The travel control device 6 is particularly characterized by Formula 2 used for calculating the target deceleration rate α _a ′ and conditions assumed when the formula is derived. By this α _a ′, it is possible to eliminate a sense of danger with respect to the rear-end collision and to suppress an unnecessarily strong braking force in the initial stage of the deceleration control.

Hereinafter, the derivation principle of the target deceleration rate α _a ′ and the grounds for the above effect will be described in detail. FIG. 4 is a diagram illustrating a situation in which the host vehicle decelerates with the preceding vehicle approaching. Subject vehicle deceleration alpha _a (a positive value, negative acceleration) of the vehicle speed V _a when decelerating, the velocity V _a and the position x _a of the vehicle is after t seconds, following relation equations 3 and 4 Meet.

Similarly, when the preceding vehicle having the vehicle speed V _f decelerates at the deceleration α _f , the speed V _f and the position x _f of the preceding vehicle after t seconds satisfy the following expressions 5 and 6.

Here, ignoring the deceleration α _f of the preceding vehicle, the condition that the own vehicle and the preceding vehicle are at the same speed at the point before the target inter-vehicle distance l from the preceding vehicle, that is, the following expressions 7 and 8 are satisfied. The deceleration α ₁ to be calculated is calculated by Equation 9. For example, Japanese Patent No. 2979707 discloses a mathematical expression similar to Expression 9, although the target inter-vehicle distance l is not taken into consideration.

When the deceleration control is performed based on the deceleration α ₁ according to the formula, it is possible to suppress the rear-end collision with the preceding vehicle. However, according to this deceleration control, the deceleration increases after the start of the deceleration control, that is, the deceleration in the latter half tends to increase with the delay of the deceleration due to the control or the delay of the hydraulic system. For this reason, the driver may feel anxiety about the rear-end collision.

For example, Japanese Patent Laid-Open No. 11-11273 discloses a calculation formula (Formula 10) for the deceleration α ₂ in consideration of deceleration of the preceding vehicle. First, the distance traveled to stop when the preceding vehicle maintains the current deceleration is calculated, and this is added to the current inter-vehicle distance L. Deceleration for stopping the vehicle is alpha ₂ in this preceding vehicle minus the target inter-vehicle distance l from the stop position the position. That is, Expression 10 is obtained by deleting t from Expressions 11 and 12 and making subscripts correspond.

In particular, the target inter-vehicle distance l Here, similar to the driving control unit 6, is variably set according to the vehicle speed V _a. When deceleration control is performed with the target deceleration rate α ₂ , the deceleration rate is large in the initial stage and gradually decreases after deceleration starts. According to this target deceleration rate α ₂ , it is possible to eliminate the inconvenience associated with the deceleration control according to Equation 9 described above, but there is a possibility of a rear-end collision with a preceding vehicle. That is, in Equation 4, 6 described above, the position x _a of the vehicle, when the difference between the preceding vehicle position x _f is 0 is present. For example, this is a case in which deceleration is started at a vehicle speed of 100 km / h and an inter-vehicle distance of 50 m with respect to a preceding vehicle that decelerates from a vehicle speed of 20 km / h to 0.01 G and then stops.

As described above, the target deceleration rate α _a shown in the following equation 13 is set because there is a possibility of a rear-end collision in both the target deceleration rates α ₁ and α ₂ . In the derivation of α _a , the deceleration α _f of the preceding vehicle is taken into account in addition to the conditions according to equations 7 and 8. In the deceleration control based on the target deceleration rate α _a, it is possible to decelerate the host vehicle speed V _a to the preceding vehicle speed V _f at _a point before the target inter-vehicle distance l from the preceding vehicle. Since the target inter-vehicle distance l is updated as appropriate according to the deceleration control speed V _a, and the deceleration α _f of the preceding vehicle is added, the target deceleration α ₁ according to Equation 9 is The occupant's anxiety about the rear-end collision can be resolved.

Further, the target deceleration rate α _a ′ that does not cause a rear-end collision is set while suppressing excessive deceleration in the initial stage. The condition shown in Equation 14 below is that the time when the preceding vehicle stops when the deceleration α _f is maintained is equal to the time when the host vehicle stops when the deceleration α _a is maintained. Add to. In other words, when Equation 14 is solved for α _f and this is substituted into Equation 13, the target deceleration rate α _a ′ of Equation 2 is obtained.

FIG. 5 is a diagram illustrating a result of simulating deceleration control using α _a ′ according to Formula 2. FIG. 4A shows the change over time in deceleration, FIG. 4B shows the change over time in vehicle speed, and FIG. 4C shows the change over time in the inter-vehicle distance. Here, it is assumed that the vehicle starts to decelerate from a preceding vehicle that decelerates at a speed of 0.1 G from a vehicle speed of 20 km / h and starts at a vehicle speed of 40 km / h and an inter-vehicle distance of 50 m. In the figure, the result of the target deceleration rate α _a ′ (Equation 2 above) is shown by a solid line, and for comparison, the result of the target deceleration rate α ₁ (Equation 9) is shown by a broken line with A, and the target deceleration rate is shown. The result of the speed α ₂ (Equation 10) is indicated by a broken line with B. In particular, as shown in FIG. 6A, the target deceleration rate α _a ′ in the deceleration control of the present embodiment is initially set to a value smaller than the target deceleration rate α ₂ . In addition, as shown in FIGS. 7B and 7C, the vehicle speed and the inter-vehicle distance due to the deceleration α _a ′ are gradually smoother than those due to the deceleration α ₁ to 0 km / h and 5 m, respectively. It has changed.

As described above, the target deceleration rate α _a ′ used in the deceleration control of the present embodiment secures a predetermined target inter-vehicle distance l that is updated according to the vehicle speed V _a (Equation 8), and the own vehicle speed V _a Formula 2 configured to satisfy the condition that the vehicle speed is reduced to the preceding vehicle speed V _f (Equation 7), and the own vehicle and the preceding vehicle both stop simultaneously when the current deceleration is maintained (Equation 14). Is calculated from By setting the deceleration α _a ′ like this, it is possible to prevent rear-end collisions with the preceding vehicle, and to eliminate the sense of crisis that passengers have due to deceleration delay, etc. Thus, it is possible to eliminate the anxiety caused by excessive deceleration at the beginning of deceleration as in the prior art. Furthermore, in this deceleration control, the deceleration in the second half is set to be smaller than the first half, so it can be said that it is close to smooth braking by the driver's operation.

In the above embodiment, the preceding vehicle information generation unit 62 calculates the relative speed V _{fa and the} like of the preceding vehicle based on the inter-vehicle distance L detected by the preview sensor 5, and the deceleration setting unit 63 uses the V _fa Was used to calculate the target deceleration rate α _a ′. Instead of the relative speed V _fa , the target deceleration α _a ′ may be calculated using the speed V _{f of the} preceding vehicle. In each unit, the speed of the preceding vehicle, the target deceleration, etc. were calculated using mathematical expressions indicating the correspondence between the variables, but the speed of the preceding vehicle and the target vehicle were calculated using a table in which the calculation results were stored in advance. It is possible to specify (set) the target deceleration.

Schematic configuration diagram of a vehicle equipped with a travel control device 6 according to the present embodiment The block diagram which shows the main structures of the traveling control apparatus 6 Flow chart showing the procedure of travel control The figure which shows the deceleration situation of the own vehicle which brought the preceding vehicle close The figure which shows the simulation result of this deceleration control

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 1a Throttle valve 2 Wheel 3 Brake device 3a Brake mechanism 3b Brake drive part 3c Brake control part 4 Vehicle speed sensor 5 Preview sensor 6 Traveling control apparatus 61 Target inter-vehicle distance update part 62 Leading vehicle information generation part 63 Deceleration setting part 64 Brake Torque map 65 Braking instruction section

Claims (2)

In a travel control device that is mounted on a vehicle and controls deceleration of the vehicle according to a target deceleration,
A vehicle speed sensor that detects the speed of the vehicle;
A preview sensor that detects the distance between the vehicle and the preceding vehicle;
A preceding vehicle information generation unit that identifies the speed of the preceding vehicle based on the speed of the host vehicle and the inter-vehicle distance;
When the own vehicle is faster than the preceding vehicle, the reduction of the own vehicle as an output in a predetermined correspondence relationship based on the speed of the own vehicle, the inter-vehicle distance, the predetermined target inter-vehicle distance, and the speed of the preceding vehicle. A deceleration setting unit that obtains a speed and sets the deceleration as the target deceleration;
The predetermined correspondence relationship is to secure the predetermined target inter-vehicle distance, to reduce the speed of the own vehicle to the speed of the preceding vehicle, and the own vehicle and the preceding vehicle have a current deceleration. A travel control device configured to satisfy the condition of stopping simultaneously when maintained.   2. The target inter-vehicle distance update unit further configured to reduce the predetermined target inter-vehicle distance used for setting the target deceleration according to the detected decrease in the speed of the host vehicle. Travel control device.

Images