JP3951781B2 - Vehicle travel control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle travel control device having an inter-vehicle control function for causing an own vehicle to travel following a preceding vehicle.
[0002]
[Prior art]
Conventionally, as a technique for improving the driving safety of a car and reducing the operation burden on the driver, an inter-vehicle control function for automatically following the preceding vehicle at a vehicle speed within a predetermined vehicle speed range, Further, there is known a vehicle travel control device having a vehicle speed control function for traveling at a constant speed while maintaining a speed (set vehicle speed) set by a vehicle driver within a predetermined vehicle speed range.
[0003]
Such a vehicle travel control device generally detects the host vehicle speed and the inter-vehicle distance based on output signals from a vehicle speed sensor and a laser radar, sets a target acceleration according to the inter-vehicle distance and the host vehicle speed, and sets the target acceleration. Based on the above, the acceleration / deceleration of the vehicle was controlled. Further, when the detected vehicle speed is equal to or lower than a predetermined speed, the inter-vehicle distance control at the time of stopping or starting is performed more smoothly by changing the characteristic of the target acceleration.
[0004]
However, there is a problem that if the target acceleration is set based only on the own vehicle speed as described above, high-accuracy inter-vehicle distance control cannot be realized because the accuracy of the vehicle speed sensor is reduced in an extremely low speed range. .
Under such circumstances, for example, Japanese Patent Application Laid-Open No. 2000-219059 discloses a first braking / driving torque calculating means for calculating the first braking / driving torque based on the vehicle speed and a second braking / driving torque based on the inter-vehicle distance. There has been proposed a technique including second braking / driving torque calculating means. In this technique, the first braking / driving torque is set as the target braking / driving torque when the vehicle speed is equal to or higher than a predetermined value, and based on the first and second braking / driving torques when the vehicle speed is smaller than the predetermined value. Weighting is performed to calculate the target braking / driving torque, and control is performed so that the target braking / driving torque approaches the second braking / driving torque as the vehicle speed decreases.
[0005]
With this technology, it is possible to perform inter-vehicle control and vehicle speed control in an extremely low speed range with higher accuracy, and to smoothly switch braking / driving torque.
[0006]
[Problems to be solved by the invention]
However, all of the above conventional vehicle travel control devices calculate the target acceleration and the target braking / driving torque based on the vehicle speed and the inter-vehicle distance to perform the inter-vehicle control, and therefore grasp the acceleration / deceleration status of the preceding vehicle. I can't. For this reason, for example, if the preceding vehicle is accelerating and decelerating when the vehicle speed and the inter-vehicle distance are the same, it is not possible to immediately shift to the control that follows the preceding vehicle, and a sense of delay occurs in the inter-vehicle control. As a result, there is a problem that the driving behavior of the preceding vehicle cannot be quickly handled. In addition, for example, when the preceding vehicle suddenly brakes, the distance between the vehicles is abruptly shortened, but because the vehicle is controlled based on the distance between the vehicles, the vehicle is subjected to a sudden brake more than the preceding vehicle. There was also a problem of feeling a sense of delay or discomfort.
[0007]
The present invention has been made in view of such a problem, and an object of the present invention is to realize a vehicle travel control that can cope with the behavior of a preceding vehicle without causing a sense of delay in control and that does not cause a sense of incongruity to a passenger.
[0008]
[Means for Solving the Problems]
In view of the above problem, in the vehicle travel control apparatus according to claim 1, the inter-vehicle deviation calculating means calculates an inter-vehicle distance deviation that is a deviation between the inter-vehicle distance between the host vehicle and the preceding vehicle and a preset target inter-vehicle distance. The relative speed calculation means calculates the relative speed between the host vehicle and the preceding vehicle.
[0009]
Then, the target acceleration calculating means calculates the target acceleration required to make the host vehicle follow the preceding vehicle based on the inter-vehicle distance deviation calculated by the inter-vehicle deviation calculating means and the relative speed calculated by the relative speed calculating means. Then, the braking / driving force control means controls the driving force or braking force of the own vehicle according to the target acceleration calculated by the target acceleration calculating means, and controls the acceleration of the own vehicle to the target acceleration.
[0010]
Here, the target acceleration calculating means includes a plurality of calculation units for calculating the target acceleration corresponding to the acceleration / deceleration state of at least one of the own vehicle and the preceding vehicle, and the switching means includes at least the own vehicle and the preceding vehicle. Based on one of the accelerations, the target acceleration output by any of the calculation units is switched as the target acceleration used by the braking / driving control means.
[0011]
  That is, the target acceleration calculation means indicates the acceleration state, constant speed state, deceleration state or the degree of the own vehicle or the preceding vehicle, or the relative acceleration between the own vehicle and the preceding vehicle is positive, zero, negative, or the degree thereof. A plurality of calculation units for calculating different target accelerations according to the acceleration / deceleration state are provided. Which of the target accelerations calculated by each of these calculation units is selected in advance corresponding to the acceleration of at least one of the own vehicle and the preceding vehicle, and the switching means is based on the actual acceleration / deceleration state. To select the calculation unit and set the output value as the target acceleration.
  These calculation means and switching means are provided for each predetermined speed area of the own vehicle, and the target acceleration set in each speed area is switched based on the own vehicle speed.
[0012]
According to such a configuration, the target acceleration is switched based on the acceleration instead of the speed of the own vehicle or the preceding vehicle, so that control in accordance with the behavior of the own vehicle or the preceding vehicle can be performed. For this reason, it is possible to effectively prevent the driver from feeling uncomfortable or uncomfortable by causing the own vehicle to decelerate or accelerate more rapidly than the preceding vehicle. In addition, since control based on acceleration, which is a time derivative of speed, is performed, it is possible to perform control in consideration of changes in speed. For this reason, finer control than the control based on the vehicle speed can be realized.
[0013]
Specifically, as described in claim 2, for example, the switching means can switch the target acceleration based on the relative acceleration between the host vehicle and the preceding vehicle.
According to such a configuration, it is possible to perform control that quickly responds to the difference in behavior between the host vehicle and the preceding vehicle, and it is possible to realize control without a sense of delay in relation to the preceding vehicle.
[0014]
Further, as described in claim 3, the switching means may switch the target acceleration based on the absolute acceleration of the preceding vehicle.
According to such a configuration, it is possible to realize control that is more suitable for the feeling of the occupant of the own vehicle. That is, the occupant of the own vehicle does not usually feel the acceleration / deceleration of the preceding vehicle as a relative acceleration with the preceding vehicle. For example, the brake light of the preceding vehicle is lit or the rear of the preceding vehicle when the preceding vehicle accelerates or decelerates. Recognize and feel the movements (sinking and floating) Since the movement of the preceding vehicle is based on the absolute acceleration (acceleration with respect to the road surface) of the preceding vehicle, acceleration / deceleration that matches the occupant's feeling when the target acceleration is switched based on the absolute acceleration of the preceding vehicle. Can be created.
[0015]
In the target acceleration switching process, as described in claim 4, the switching means may perform a blending process in which the target acceleration before and after switching is continuously weighted and changed.
In other words, when switching between target accelerations, if the target acceleration before and after the switching is digitally switched, it is switched continuously (analog) in order to give the passenger discomfort due to shock accompanying sudden acceleration or sudden deceleration. This is to solve this problem.
[0016]
As a specific method for performing the “weighting”, for example, as described in claim 5, the switching unit calculates the target acceleration A * (target acceleration after mixing) in the calculation processing of the target acceleration. It is conceivable to calculate based on the following equation using the target acceleration A1 calculated by one of the above and the target acceleration A2 (A1 <A2) calculated by the other of the calculation unit.
[0017]
A * = αA1 + (1-α) A2
However, the coefficient α is a value determined as follows based on the acceleration Aa of the own vehicle or the preceding vehicle and predetermined thresholds ATH1 and ATH2 (ATH1 <ATH2).
Aa ≦ ATH1; α = 1
ATH1 <Aa <ATH2; 0 <α <1
ATH2 ≦ Aa; α = 0
Note that the target accelerations A1 and A2 here are not limited to the above-described two calculation units. That is, when there are two or more calculation units, it means each of the two target accelerations to be switched. Therefore, when there are three or more switching processes, the above equation can be used for each switching process.
[0018]
ATH1 and ATH2 are accelerations serving as a reference for starting or ending the switching process, and can be appropriately set depending on the operation of the switching process. For example, when the switching process is set based on the absolute acceleration of the preceding vehicle as will be described later in the embodiment, the target acceleration before and after the switching is completed until the absolute acceleration of the preceding vehicle exceeds ATH1 and reaches ATH2. Blending is performed at a ratio of α (or 1-α).
[0019]
Furthermore, the coefficient α may be changed linearly or may be changed in a curved line as long as it changes continuously until the target acceleration changes from A1 to A2. However, as will be described later in the embodiments, the linear change is simple as the control and can be easily realized.
[0020]
Further, as described in claim 6EachThe target acceleration set in the speed region may be switched based on the vehicle speed, and the target acceleration may be changed by continuously weighting as described above during the switching process.
[0021]
This is based on the assumption that the control system is divided into high-speed ACC control and low-speed ACC control, for example in inter-vehicle control (ACC), and further divided into extremely low-speed control and low-speed control in low-speed ACC. It is.
In such inter-vehicle control, a systematic system can be constructed by setting the target accelerations individually for each speed region with weighting and further weighting them based on the vehicle speed.
[0022]
In this case, as described in claim 7, it is preferable that a plurality of the plurality of calculation units be provided as the speed region is the low speed region.
As described in the description of the prior art, fine control is required in the low speed region, which is taken into consideration.
[0023]
With this configuration, highly accurate and smooth control can be realized.
[0024]
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram schematically showing a system configuration of a vehicle travel control device 1 according to the present embodiment, and includes an inter-vehicle control electronic control device (hereinafter referred to as “inter-vehicle control ECU”) 2, an engine control electronic control device. (Hereinafter referred to as “engine ECU”) 6 and a brake electronic control device (hereinafter referred to as “brake ECU”) 4.
[0026]
The inter-vehicle control ECU 2 is an electronic circuit mainly composed of a microcomputer, and includes a current vehicle speed (Vn) signal, a steering angle (str-eng, S0) signal, a yaw rate signal, a target inter-vehicle time signal, wiper switch information, idle Control state signals for control and brake control are received from the engine ECU 6. Then, the inter-vehicle distance control ECU 2 estimates a curve curvature radius R or performs an inter-vehicle distance control calculation based on the received data.
[0027]
The laser radar sensor 3 is an electronic circuit mainly composed of a laser scanning range finder and a microcomputer. The angle and relative speed of the preceding vehicle detected by the scanning range finder and the inter-vehicle distance control ECU 2 Based on the received current vehicle speed (Vn) signal, curve curvature radius R, etc., the own lane probability of the preceding vehicle is calculated and transmitted to the inter-vehicle control ECU 2 as preceding vehicle information including information such as relative speed. Also, its own diagnosis signal is transmitted to the inter-vehicle distance control ECU 2.
[0028]
Further, the inter-vehicle distance control ECU 2 determines the preceding vehicle to be subjected to the inter-vehicle distance control based on the own lane probability included in the preceding vehicle information received from the laser radar sensor 3 as described above, and appropriately adjusts the inter-vehicle distance with the preceding vehicle. As a control command value, a target acceleration signal, a fuel cut request signal, an OD cut request signal, a third speed shift down request signal, and a brake request signal are transmitted to the engine ECU 6. In addition, the generation of an alarm is determined, and an alarm sound request signal or an alarm sound release request signal is transmitted. Further, a diagnosis signal, a display data signal, etc. are transmitted.
[0029]
The brake ECU 4 is an electronic circuit that is configured around a microcomputer, and detects a steering sensor 8 that detects the steering angle of the vehicle, a yaw rate sensor 10 that detects the yaw rate as a turning state of the vehicle, and detects the speed of each wheel. The steering angle and the yaw rate are obtained from the wheel speed sensor 12 that transmits the data, and these data are transmitted to the inter-vehicle control ECU 2 via the engine ECU 6. Further, the brake ECU 4 opens and closes the pressure increase control valve / pressure reduction control valve provided in the brake hydraulic circuit in order to control the brake force in response to a brake request based on the target acceleration or the like from the inter-vehicle control ECU 2 via the engine ECU 6. The alarm buzzer 14 is sounded in response to an alarm request signal from the inter-vehicle control ECU 2 via the engine ECU 6.
[0030]
The engine ECU 6 is an electronic circuit mainly composed of a microcomputer, and includes an accelerator pedal sensor 15 for detecting the depression amount of the accelerator pedal, a vehicle speed sensor 16 for detecting the vehicle speed, and a brake for detecting whether or not the foot brake is depressed. Detection signals from the switch 18, cruise control switch 20, cruise main switch 22, and other sensors and switches are received, and various signals from the brake ECU 4 and the inter-vehicle control ECU 2 are received.
[0031]
The engine ECU 6 then drives the actuator drive stage of the throttle actuator 24 and the transmission 26 for adjusting the throttle opening of the internal combustion engine (in this case, the gasoline engine) in accordance with the operating state determined from the received signal. Is output. With these actuators, it is possible to control the output, braking force or shift shift of the internal combustion engine.
[0032]
Next, the outline of the auto cruise control of the present embodiment will be described with reference to the state transition diagram of FIG.
The control starts from the “cruise OFF” state in step A, and transitions to the “cruise ready” state in step B by turning on the cruise main switch 22. Then, when the cruise set switch in the cruise control switch 20 is turned on in the state of step B, the transition to the cruise control of step C is made. If the foot brake is turned on during the cruise control in step C or if the predetermined effective vehicle speed range is exceeded, the cruise control in step C transitions to the cruise ready state in step B.
[0033]
In the cruise control of Step C, when there is no preceding vehicle below the set vehicle speed, the vehicle speed control (constant speed running) is performed at Step D, and when there is a preceding vehicle below the set vehicle speed, the inter-space control at Step E is performed. Perform (follow-up running). When the accelerator pedal is depressed during the cruise control including the vehicle speed control and the inter-vehicle distance control, a transition is made to the override state in step F when a predetermined condition is satisfied.
[0034]
Next, a method for calculating the target acceleration set by the inter-vehicle distance control ECU 2 in the vehicle speed control in step D or the inter-vehicle distance control in step E will be described with reference to FIG. FIG. 3 is a functional block diagram of vehicle travel control in this embodiment.
As shown in the figure, the inter-vehicle control ECU 2 includes a low-speed ACC control unit and a high-speed ACC control unit that are related to the inter-vehicle control, and a constant speed CC control unit that is related to the vehicle speed control. Acceleration is calculated respectively. In order to smoothly connect a plurality of target acceleration switching processes calculated in each control unit, or a target acceleration switching process between the control units, a so-called membership function described later is used for switching the target acceleration. Processing (weighting) is performed stepwise to calculate a target acceleration as a final set value and output it to the engine ECU 6.
[0035]
Specifically, as shown in the figure, in the inter-vehicle control when there is a preceding vehicle, the low speed ACC control unit calculates the target acceleration mainly when the host vehicle speed is less than 50 km / h, and the high speed ACC control. The unit calculates the target acceleration mainly when the host vehicle speed is 60 km / h or higher. In addition, in the vehicle speed control when there is no preceding vehicle, the constant speed CC control unit calculates a target acceleration for causing the host vehicle to travel at a constant speed.
[0036]
In addition, for the reason that fine control is required as in the case of low-speed traveling, the low-speed ACC control unit includes an extremely low-speed calculation unit that calculates the target acceleration mainly when the host vehicle speed is less than 20 km / h. A low speed calculation unit for calculating the target acceleration is provided mainly when the host vehicle speed is 30 km / h or higher, and finer control is possible particularly in the extremely low speed calculation unit.
[0037]
That is, in the extremely low speed calculation unit, the inter-vehicle control calculation unit (1) that calculates the target acceleration when the relative acceleration between the host vehicle and the preceding vehicle is negative, and the inter-vehicle distance that calculates the target acceleration when the relative acceleration is zero. A control calculation unit (2) and an inter-vehicle control calculation unit (3) when the relative acceleration is positive are provided. Each inter-vehicle distance control calculation unit calculates a target acceleration based on a pre-calculated inter-vehicle distance deviation and a relative speed, which are calculated later. The reason why the plurality of inter-vehicle distance control operation units are provided in the extremely low speed operation unit is that the target acceleration changes sensitively depending on the acceleration / deceleration state of the host vehicle. For example, even if the inter-vehicle distance deviation and the relative speed are both the same at a certain point in time, if the relative acceleration is negative, the target acceleration needs to be on the negative side (deceleration side) to prevent rear-end collision, The necessity is small when the vehicle is traveling at a relative acceleration of zero. Furthermore, considering that it is necessary to shift the target acceleration to the plus side when the relative acceleration is positive, a plurality of inter-vehicle control calculation units are provided, and an appropriate target acceleration is determined depending on the acceleration / deceleration state of the relative acceleration. It can be selected.
[0038]
In the low speed calculation unit, an inter-vehicle control calculation unit (4) for calculating a target acceleration when the relative acceleration between the host vehicle and the preceding vehicle is negative, and an inter-vehicle control calculation unit when the relative acceleration is positive or zero. (5) is provided. Similarly to the above, each inter-vehicle control calculation unit calculates the target acceleration using the inter-vehicle distance deviation and the relative speed calculated in advance with the preceding vehicle.
[0039]
As described above, the extremely low speed calculation unit is provided with more inter-vehicle distance control calculation units than the low speed calculation unit, because the very low speed calculation unit has a smaller target inter-vehicle distance, and therefore fine control for preventing rear-end collision is performed. Because it is needed.
In this embodiment, the high-speed ACC control unit is also provided with a calculation unit similar to the low-speed calculation unit, but the description thereof is omitted.
[0040]
When the target acceleration is calculated in each inter-vehicle control calculation unit as described above, first, based on the absolute acceleration of the preceding vehicle (hereinafter referred to as “preceding vehicle acceleration”) separately detected, The target acceleration is blended (weighted). The absolute acceleration of the preceding vehicle is calculated using the vehicle speed of the host vehicle obtained based on the output signals from the vehicle speed sensor 16 and the laser radar sensor 3 and the relative speed between the host vehicle and the preceding vehicle. That is, the absolute acceleration of the preceding vehicle is calculated by adding the relative acceleration between the own vehicle and the preceding vehicle obtained by the time differentiation of the relative speed to the absolute acceleration of the own vehicle obtained by the time differentiation of the vehicle speed.
[0041]
The blending process is performed using a preset membership function. That is, as shown in the figure, in the membership function of the extremely low speed calculation unit, the blending ratio of the calculation value of the inter-vehicle control calculation unit (1) indicates that the preceding vehicle acceleration is -0.5 (m / s²) Is less than 100% and −0.5 (m / s²) To 0 (m / s²) To decrease linearly. Further, the blending ratio of the calculation value of the inter-vehicle control calculation unit (2) is such that the preceding vehicle acceleration is 0 (m / s²) Is 100% and −0.5 (m / s²) To 0 (m / s²) Linearly increasing to 0 (m / s²) To 0.5 (m / s²) To decrease linearly. Further, the blending ratio of the calculation value of the inter-vehicle control calculation unit (3) is such that the preceding vehicle acceleration is 0.5 (m / s²) 100% in the above case, 0.5 (m / s)²) To 0 (m / s²) To decrease linearly.
[0042]
Specifically, the target acceleration obtained by this blending process is obtained as follows. That is, when the target acceleration A * obtained by the blending process is expressed as a target acceleration A1 calculated by one of the calculation units and a target acceleration A2 (A1 <A2) calculated by the other of the calculation units, the following equation (1) It becomes like this.
A * = αA1 + (1-α) A2 (1)
However, the coefficient α is a value determined as follows based on the preceding vehicle acceleration Aa and predetermined threshold values ATH1 and ATH2 (ATH1 <ATH2).
[0043]
Aa ≦ ATH1; α = 1
ATH1 <Aa <ATH2; 0 <α <1
ATH2 ≦ Aa; α = 0
That is, the above example shown in the extremely low speed calculation unit in FIG. 3 will be described with reference to the above equation (1) as shown in FIG.
[0044]
That is, in the above example, the target acceleration is set to three stages using the output values respectively obtained from the inter-vehicle distance control calculation units (1) to (3), but the calculation of the blending process is performed to two stages before and after. It is done separately. That is, the blending process of the target acceleration calculated by the inter-vehicle control calculation unit (1) and the target acceleration calculated by the inter-vehicle control calculation unit (2) is ATH1 = −0 as shown in the upper right part of FIG. .5 (m / s²), ATH2 = 0 (m / s²) Will be set. The coefficient α is set so that each of the target acceleration of the inter-vehicle control calculation unit (1) and the target acceleration of the inter-vehicle control calculation unit (2) changes linearly. Further, the blending process of the target acceleration calculated by the inter-vehicle control calculation unit (2) and the target acceleration calculated by the inter-vehicle control calculation unit (3) is ATH1 = 0 ( m / s²), ATH2 = 0.5 (m / s²) Will be set. The coefficient α is set so that the target acceleration of the inter-vehicle control calculation unit (2) and the target acceleration of the inter-vehicle control calculation unit (3) change linearly. Then, when the upper right stage and the lower right stage in FIG. 10A are combined, the result becomes the left stage in FIG.
[0045]
Therefore, in FIG. 3, for example, the preceding vehicle acceleration is -0.25 (m / s²), The calculated value of the inter-vehicle control calculation unit (1) and the calculated value of the inter-vehicle control calculation unit (2) are blended at a ratio of 50%, for example, the preceding vehicle acceleration is 0.25 (m / s)²), The calculated value of the inter-vehicle control calculation unit (2) and the calculated value of the inter-vehicle control calculation unit (3) are mixed at a ratio of 50%.
[0046]
In addition, in the membership function of the low speed calculation unit, the blend ratio of the calculation value of the inter-vehicle control calculation unit (4) is such that the preceding vehicle acceleration is -2.0 (m / s²) Is less than 100% and −2.0 (m / s²) To -0.5 (m / s²) To decrease linearly. In addition, the blending ratio of the calculation value of the inter-vehicle control calculation unit (5) indicates that the preceding vehicle acceleration is -0.5 (m / s²) 100% in the above case, -0.5 (m / s²) To -2.0 (m / s²) To decrease linearly.
[0047]
The target acceleration obtained by this blending process is also calculated by the above formula (1). This will be described with reference to the above equation (1) as shown in FIG.
That is, in this case, as shown in FIG. 5B, ATH1 = −2.0 (m / s²), ATH2 = −0.5 (m / s)²) Will be set. The coefficient α is set so that each of the target acceleration of the inter-vehicle control calculation unit (4) and the target acceleration of the inter-vehicle control calculation unit (5) changes linearly.
[0048]
For this reason, in FIG. 3, for example, the preceding vehicle acceleration is -1.25 (m / s²), The calculated value of the inter-vehicle control calculation unit (4) and the calculated value of the inter-vehicle control calculation unit (5) are mixed at a ratio of 50%.
Each target acceleration weighted in this way by the very low speed calculation unit and the low speed calculation unit is further weighted by a membership function based on the vehicle speed.
[0049]
Specifically, the blending ratio of the calculation values of the extremely low speed calculation unit is 100% when the vehicle speed is less than 20 (km / h), and from 20 (km / h) to 30 (km / h) ) To decrease linearly. In addition, the blending ratio of the calculation values of the low-speed calculation unit is 100% when the vehicle speed is 30 (km / h) or more, and is linear from 30 (km / h) to 20 (km / h). Is set to decrease.
[0050]
The target acceleration obtained by this blending process is obtained by the following formula (2) according to the above formula (1). That is, when the target acceleration A ** obtained by the blending process is expressed as the target acceleration A3 calculated by the extremely low speed calculation unit and the target acceleration A4 calculated by the low speed calculation unit, the following equation (2) is obtained.
A ** = α′A3 + (1−α ′) A4 (2)
However, the coefficient α ′ is a value determined as follows based on the vehicle speed Va and predetermined threshold values VTH1 and VTH2 (VTH1 <VTH2).
[0051]
Va ≦ VTH1; α ′ = 1
VTH1 <Va <VTH2; 0 <α '<1
VTH2 ≦ Va; α ′ = 0
The above example of FIG. 3 will be described with reference to the above equation (2) as shown in FIG.
[0052]
That is, in the above example, the blending process of the target acceleration calculated by the extremely low speed calculation unit and the target acceleration calculated by the low speed calculation unit is VTH1 = 20 (km / h), VTH2 as shown in FIG. = 30 (km / h). The coefficient α ′ is set so that each of the target acceleration of the extremely low speed calculation unit and the target acceleration of the low speed calculation unit changes linearly.
[0053]
For this reason, in FIG. 3, for example, when the host vehicle speed is 25 (km / h), the calculation value of the extremely low speed calculation unit and the calculation value of the low speed calculation unit are respectively blended at a ratio of 50%. Yes.
In the high-speed ACC control unit as well, a blending process related to a calculation value in a not-shown inter-vehicle distance control calculation unit is performed, and a target acceleration is set.
[0054]
And each target acceleration set in each of the low speed ACC control part and the high speed ACC control part in this way is further weighted with the membership function based on the own vehicle speed.
Specifically, the blending ratio of the calculation value of the low speed ACC control unit is 100% when the vehicle speed is less than 50 (km / h), and from 50 (km / h) to 60 (km / h) ) To decrease linearly. Moreover, the blending ratio of the calculation value of the high-speed ACC control unit is 100% when the own vehicle speed is 60 (km / h) or more, and is linear from 60 (km / h) to 50 (km / h). Is set to decrease.
[0055]
The target acceleration obtained by this blending process is also calculated by the above equation (2). This will be described with reference to the above equation (2) as shown in FIG.
That is, in this case, the blending process of the target acceleration calculated by the low-speed ACC control unit and the target acceleration calculated by the high-speed ACC control unit is VTH1 = 50 (km / h), VTH2 = It will be set to 60 (km / h). The coefficient α ′ is set such that each of the target acceleration of the low speed ACC control unit and the target acceleration of the high speed ACC control unit changes linearly.
[0056]
Therefore, in FIG. 3, for example, when the preceding vehicle acceleration is 55 (km / h), the calculated value of the low speed ACC control unit and the calculated value of the high speed ACC control unit are blended at a ratio of 50%. ing.
As described above, the target acceleration in the inter-vehicle control when the preceding vehicle exists is determined.
[0057]
On the other hand, the constant speed CC control unit selects a predetermined set vehicle speed according to the vehicle speed according to the current host vehicle speed, and sets an appropriate acceleration as a target acceleration to control from the current vehicle speed to the set vehicle speed. To do.
Then, on condition that the cruise set switch in the cruise control switch 20 is ON, the target acceleration or constant speed CC set by the ACC control unit described above depending on whether the current cruise control is inter-vehicle control or constant speed control. Any one of the target accelerations set in step S5 is output to the engine ECU 6.
[0058]
Next, details of the vehicle travel control process executed by the inter-vehicle control ECU 2 will be described with reference to FIGS. 4 and 5.
FIG. 4 is a flowchart showing a main process in the inter-vehicle distance control ECU 2. First, state transition flag processing is performed in the first step S110. In this state transition flag processing, the main switch flag processing for setting the main switch flag to ON or OFF according to the ON / OFF state of the cruise main switch 22 and the ON / OFF state of the cruise set switch in the cruise control switch 20 are performed. In-cruise control flag processing for setting the cruise control flag to ON or OFF in response, inter-vehicle cruise control flag processing to set the inter-vehicle cruise control flag to ON or OFF depending on whether the inter-vehicle control is being performed, and Overriding flag processing for setting the overriding flag to ON or OFF is sequentially performed depending on whether or not the override is in progress.
[0059]
Subsequently, a set vehicle speed calculation is performed (S120). Here, based on a signal from the cruise control switch 20 or the like, a process of calculating a set vehicle speed in response to the own vehicle speed when switching from the inter-vehicle control to the constant speed control in the cruise control is performed.
[0060]
Subsequently, the curve radius is estimated (S130). Here, based on the steering angle detected by the steering sensor 8, a process of calculating the curve radius of the own lane ahead of the own vehicle is performed.
Subsequently, a preceding vehicle is selected (S140). Here, a preceding vehicle candidate group is extracted based on the target data received from the laser radar sensor 3, and if there is a preceding vehicle candidate, processing for selecting a target with the smallest inter-vehicle distance as the preceding vehicle is performed.
[0061]
Then, an inter-vehicle cruise target acceleration calculation process is performed. Here, the target acceleration used for the inter-vehicle control and the vehicle speed control is calculated based on the acceleration of the preceding vehicle. Hereinafter, the target acceleration calculation process will be described in detail with reference to FIG.
First, as shown in FIG. 6A, it is determined whether or not a preceding vehicle is being recognized (S310). If the preceding vehicle is not being recognized at this time (S310: NO), the calculation result in the constant speed CC control unit described above, that is, the acceleration for controlling the set vehicle speed when the preceding vehicle is unrecognized is set as the target acceleration. Setting is made (S370).
[0062]
On the other hand, if the preceding vehicle is being recognized in S310 (S310: YES), the process proceeds to S320 to calculate the inter-vehicle distance deviation. This inter-vehicle distance deviation (m) is a value obtained by subtracting a preset target inter-vehicle distance from the current inter-vehicle distance. Note that the target inter-vehicle distance can be made variable according to the vehicle speed, so that it can more closely match the driver's feeling.
[0063]
Further, in the subsequent S330, the relative speed is calculated. In calculating the relative speed, the relative speed detected a plurality of times is smoothed in order to reduce the influence of noise and the like.
Then, based on the inter-vehicle distance deviation and the relative speed obtained in this way, the target acceleration is calculated in the inter-vehicle control calculation units of the low speed ACC control unit and the high speed ACC control unit described above (S340).
[0064]
Each inter-vehicle control calculation unit is provided with a control map for determining a target acceleration according to the inter-vehicle distance deviation and the relative speed as shown in FIG. 5 (b). Select acceleration. In the figure, an example of a control map provided in the inter-vehicle distance control calculation unit (1) is shown. This control map has seven values of -15, -10, -5, 0, 5, 10, 15 as inter-vehicle distance deviation (m), and 16, 8, 0, -8, as relative speed (km / h). The target accelerations for the six values of −16 and −24 are shown, but for the values not shown as map values, values calculated by linear interpolation are adopted in the map, and values at the map end outside the map. Is adopted. In addition, when using the values in the map, it may be possible to apply predetermined upper and lower limit guards. Such a control map is provided for each of the inter-vehicle control calculation units with different relationships between the inter-vehicle distance deviation and the relative speed, and the target acceleration is set in each inter-vehicle control calculation unit.
[0065]
When the calculation of the target acceleration is completed in all the inter-vehicle distance control calculation units (S350: YES), the above-described blending process for smoothly setting the target acceleration is performed (S360).
That is, the blending process is first performed in each of the low speed ACC control unit and the high speed ACC control unit. At this time, as described above, the low speed ACC control unit first performs a blending process based on the preceding vehicle acceleration in each of the extremely low speed calculation unit and the low speed calculation unit, and then, for each target acceleration set thereby, the own vehicle A blending process based on the speed is performed. As a result, the target acceleration set in the present processing is set by performing a blending process based on the vehicle speed for the target acceleration set by the low speed ACC control unit and the target acceleration set by the high speed ACC control unit. Is done.
[0066]
Returning to FIG. 4, when each target acceleration in the inter-vehicle control and the vehicle speed control is set in this way, a process for determining whether to output any target acceleration to the engine ECU 6 is performed.
That is, it is first determined whether or not the cruise control flag is ON. If the cruise control flag is OFF (S160: NO), this process is terminated. On the other hand, if the cruise control flag is ON (S160: YES), it is then determined whether the overriding flag is ON (S170). If the overriding flag is ON (S170: YES). Then, this process is finished as it is.
[0067]
On the other hand, if the overriding flag is OFF (S170: NO), it is then determined whether or not the inter-vehicle cruise control flag is ON (S180). If the inter-vehicle cruise control flag is ON (S180: YES), the inter-vehicle control target acceleration calculated in S150 is set as the control target acceleration, and if the inter-vehicle cruise control flag is OFF (S180: NO), the target acceleration for vehicle speed control calculated in S150 is set as the control target acceleration.
[0068]
The control target acceleration set in this way is output to the engine ECU 6 as a control command value. The engine ECU 6 executes engine control for realizing the control target acceleration.
As described above, in the vehicle travel control device 1 of this embodiment, the inter-vehicle control ECU 2 includes a plurality of inter-vehicle control calculation units that calculate the target accelerations corresponding to the relative acceleration states of the host vehicle and the preceding vehicle, respectively. The target acceleration calculated by the plurality of inter-vehicle control calculation units is blended based on the preceding vehicle acceleration, and further blended and set based on the own vehicle speed. Then, the target acceleration set in this way is output to the engine ECU 6.
[0069]
That is, since the target acceleration is set based on the absolute acceleration of the preceding vehicle, it is possible to perform control in accordance with the behavior of the preceding vehicle. For this reason, it is possible to suppress sudden deceleration or rapid acceleration of the host vehicle accompanying the behavior of the preceding vehicle during control, and to effectively prevent the passenger from feeling uncomfortable or uncomfortable. In addition, since control based on acceleration, which is a time derivative of speed, is performed, it is possible to perform control in consideration of changes in speed. For this reason, finer control than the control based on the vehicle speed can be realized.
[0070]
Further, since the target acceleration is set based on the absolute acceleration of the preceding vehicle, it is possible to realize control that matches the feeling of the passenger of the own vehicle.
Furthermore, the blending process is performed during the target acceleration switching process, and the target acceleration is continuously weighted and changed, so that a shock to the occupant due to sudden acceleration or sudden deceleration accompanying the switching process can be suppressed or avoided. The switching process can be performed smoothly.
[0071]
In the present embodiment, the inter-vehicle control ECU 2 corresponds to the inter-vehicle deviation calculation means, the relative speed calculation means, the target acceleration calculation means, and the switching means, and the engine ECU 6 corresponds to the braking / driving force control means.
As mentioned above, although the Example of this invention was described, it cannot be overemphasized that embodiment of this invention can take various forms, as long as it belongs to the technical scope of this invention, without being limited to the said Example at all. Nor.
[0072]
For example, in the above-described embodiment, three examples of the inter-vehicle control calculation unit are provided in the extremely low-speed calculation unit of the low-speed ACC control unit, and two inter-vehicle control calculation units are provided in the low-speed calculation unit. The number can be changed as appropriate depending on how precisely the control is performed. In addition, although an example in which the extremely low speed calculation unit and the low speed calculation unit are separately performed and the blending process is performed has been shown, these may be collectively used as a low speed calculation unit, and more rough calculation processing may be performed. The same applies to the high-speed ACC control unit.
[Brief description of the drawings]
FIG. 1 is a system block diagram of a vehicle travel control apparatus according to an embodiment.
FIG. 2 is a state transition diagram illustrating an outline of auto-cruise control according to the embodiment.
FIG. 3 is an explanatory diagram showing a target acceleration setting method executed by an inter-vehicle control ECU.
FIG. 4 is a flowchart showing a main process executed by an inter-vehicle distance control ECU.
FIG. 5 is a flowchart showing a target acceleration calculation process executed during the main process.
FIG. 6 is an explanatory diagram illustrating a target acceleration blending process executed by an inter-vehicle control ECU.
FIG. 7 is an explanatory diagram showing a target acceleration blending process executed by an inter-vehicle control ECU.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vehicle travel control apparatus, 2 ... Distance control ECU,
3 ... Laser radar sensor, 4 ... Brake ECU,
6 ... Engine ECU, 16 ... Vehicle speed sensor

Claims (7)

An inter-vehicle deviation calculating means for calculating an inter-vehicle distance deviation which is a deviation between an inter-vehicle distance between the own vehicle and a preceding vehicle and a preset target inter-vehicle distance;
A relative speed calculating means for calculating a relative speed between the host vehicle and the preceding vehicle;
Target acceleration calculation means for calculating a target acceleration required to cause the host vehicle to follow the preceding vehicle based on the inter-vehicle distance deviation calculated by the inter-vehicle deviation calculation means and the relative speed calculated by the relative speed calculation means; ,
Braking / driving force control means for controlling the driving force or braking force of the own vehicle according to the target acceleration calculated by the target acceleration calculating means to control the acceleration of the own vehicle to the target acceleration;
In a vehicle travel control device comprising:
The target acceleration calculating means includes
A plurality of calculation units for calculating the target acceleration corresponding to the acceleration / deceleration state of at least one of the host vehicle and the preceding vehicle ,
as well as,
Switching means for switching the target acceleration output by any of the calculation units as the target acceleration used by the braking / driving control means based on the acceleration of at least one of the host vehicle and the preceding vehicle ,
Prepare for each speed range of your own vehicle,
A vehicle travel control device, wherein the target acceleration set in each speed region is switched based on the vehicle speed .   The vehicle travel control device according to claim 1, wherein the switching means switches the target acceleration based on a relative acceleration between the host vehicle and a preceding vehicle.   The vehicle travel control device according to claim 1, wherein the switching means switches the target acceleration based on an absolute acceleration of a preceding vehicle.   The vehicle according to any one of claims 1 to 3, wherein the switching means performs a blending process of continuously weighting and changing the target acceleration before and after the switching in the target acceleration switching process. Travel control device. The switching means uses the target acceleration A * calculated by one of the calculation units, the target acceleration A2 calculated by one of the calculation units, and the target acceleration A2 calculated by the other of the calculation units (A1 <A2) during the target acceleration blending process. The vehicle travel control apparatus according to claim 4, wherein the vehicle travel control apparatus is calculated based on the following equation.
A * = αA1 + (1-α) A2
However, the coefficient α is a value determined as follows based on the acceleration Aa of the vehicle or the preceding vehicle and predetermined thresholds ATH1 and ATH2 (ATH1 <ATH2).
Aa ≦ ATH1; α = 1
ATH1 <Aa <ATH2; 0 <α <1
ATH2 ≦ Aa; α = 0 The target acceleration calculating means includes
6. The target acceleration is changed by continuously weighting the target acceleration set in each speed region in the switching process for switching based on the own vehicle speed. Vehicle travel control device.   The vehicle travel control device according to claim 6, wherein the plurality of calculation units are provided in such a manner that the speed region is a low speed region.

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