JP2001334842A - Apparatus of follow-up control for vehicle running ahead - Google Patents

Abstract

PROBLEM TO BE SOLVED: To start control taking account into a coefficient of friction for the surface of a road on a running road surface in earlier step and to avoid to ensure a distance between two cars driving before and after over requirement. SOLUTION: A difference between velocities of a front and a rear wheel is integrated during slip being caused and then presumed value 1/k of the coefficient of friction on the surface of the road based on this is calculated. Characteristic of controlled response for the distance between the two cars driving before and behind, using while desired velocity V* based upon desired distance L* between the two cars driving before and behind is calculated, is varied in response to the calculated presumed value 1/k of coefficient of friction on the surface of the road and the smaller the calculated presumed value 1/k of coefficient of the friction on the surface of the road becomes, the lower the desired velocity V* is attempting to be set. Consequently, if so, that is, damping force will become to be generated earlier. Thus, the lower the coefficient of the friction on the surface of the road becomes, the earlier the damping force is generated so that the distance between two cars driving before and after does not have to be ensured sufficiently by taking account into the coefficient of the friction on the surface of the road.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preceding vehicle follow-up control device that recognizes a preceding vehicle and follows the preceding vehicle while maintaining a constant inter-vehicle distance.

[0002]

2. Description of the Related Art Conventionally, this type of preceding vehicle follow-up control device is based on a vehicle speed, an inter-vehicle distance to a preceding vehicle, a target inter-vehicle distance, a relative speed between the preceding vehicle and the own vehicle, and the like. A known vehicle speed is calculated such that the inter-vehicle distance keeps the target inter-vehicle distance, and a braking force or a driving force is generated to control the vehicle speed so as to reach the target vehicle speed.

In general, the running condition of a vehicle greatly varies depending on the state of the running road surface. Therefore, it is necessary to control the vehicle speed in consideration of the road surface friction coefficient μ of the running road surface. As described above, as a method of controlling the inter-vehicle distance in consideration of the road surface friction coefficient μ, for example, as described in JP-A-6-144169, the road surface friction coefficient of the road surface on which the vehicle is traveling is described. , A safe inter-vehicle distance is set based on the road surface friction coefficient and the traveling speed of the own vehicle, and brake control is performed based on the safe inter-vehicle distance.
As described in Japanese Patent Publication No. 346, when the inter-vehicle distance from the preceding vehicle becomes equal to or less than the first inter-vehicle distance, gentle braking is generated, and a road surface friction coefficient μ is calculated from the vehicle state at this time. There has been proposed a technique in which a second inter-vehicle distance is set based on the set value, and a full brake is activated when the inter-vehicle distance from the preceding vehicle becomes equal to or less than the second inter-vehicle distance.

[0004]

However, in the vehicle described in the above publication, the road surface friction coefficient μ is taken into consideration in the method of detecting the road surface friction coefficient of the traveling road surface and setting the safe inter-vehicle distance by taking this into account. Since the inter-vehicle safety distance is set and the brake is applied when the actual inter-vehicle distance becomes smaller than the inter-vehicle safety distance, the smaller the road surface friction coefficient μ, the longer the inter-vehicle safety distance. Also, in the method of calculating the road surface friction coefficient μ by generating a gentle brake, the road surface friction coefficient μ cannot be calculated unless the gentle brake is generated, that is, the road surface friction coefficient must be calculated after the gentle brake is generated. It is difficult to execute the control in consideration of the coefficient μ, and there is a problem that the timing of executing the control in consideration of the road surface friction coefficient μ is delayed.

Therefore, the present invention has been made in view of the above-mentioned unsolved problem in the prior art, and starts the control in consideration of the road surface friction coefficient μ at an earlier stage to secure the inter-vehicle distance more than necessary. It is an object of the present invention to provide a preceding vehicle following control device that is unnecessary.

[0006]

In order to achieve the above object, a preceding vehicle follow-up control device according to a first aspect of the present invention comprises a vehicle speed detecting means for detecting a traveling speed of the vehicle, An inter-vehicle distance detecting means for detecting an inter-vehicle distance; and an inter-vehicle distance calculating a target inter-vehicle distance with a preceding vehicle based on the own vehicle speed detected by the own vehicle speed detecting means and the actual inter-vehicle distance detected by the inter-vehicle distance detecting means. Distance target value calculation means, road surface friction coefficient detection means for detecting a road surface friction coefficient of a running road surface, based on the own vehicle speed and the actual inter-vehicle distance, the inter-vehicle distance with the preceding vehicle is the inter-vehicle distance target value Inter-vehicle distance control means for calculating a vehicle speed target value according to the road surface friction coefficient detected by the road surface friction coefficient detection means, and controlling braking / driving force such that the own vehicle speed matches the vehicle speed target value. It is characterized by having.

According to the first aspect of the present invention, the target distance between the vehicle and the preceding vehicle is set based on the own vehicle speed detected by the own vehicle speed detecting means and the actual inter-vehicle distance detected by the inter-vehicle distance detecting means. The vehicle speed target value is calculated based on the own vehicle speed and the actual inter-vehicle distance so that the actual inter-vehicle distance becomes the inter-vehicle distance target value, and the braking / driving force is controlled such that the own vehicle speed matches the vehicle speed target value. At this time, the setting of the vehicle speed target value is set in consideration of the road surface friction coefficient of the traveling road surface of the own vehicle detected by the road surface friction coefficient detection unit.

Therefore, the vehicle speed target value is set according to the traveling road surface. Therefore, for example, by setting the vehicle speed target value smaller as the road surface friction coefficient becomes lower, the timing of generation of braking / driving force is advanced. There is no need to secure the inter-vehicle distance in consideration of the road surface friction coefficient. Further, in the preceding vehicle following control device according to claim 2 of the present invention, in the preceding vehicle following control device according to claim 1, the inter-vehicle distance control means sets a response characteristic of an inter-vehicle distance to the preceding vehicle. It is set in accordance with the road surface friction coefficient detected by the road surface friction coefficient detecting means, and the vehicle speed target value is calculated based on the response characteristic.

In the invention according to claim 2, the inter-vehicle distance control means sets the response characteristic of the inter-vehicle distance between the host vehicle and the preceding vehicle in accordance with the road surface friction coefficient detected by the road surface friction coefficient detection means. . Then, a vehicle speed target value is calculated based on a response characteristic corresponding to the road surface friction coefficient. Therefore, by performing control such that the vehicle speed target value set based on the response characteristic corresponding to the road surface friction coefficient and the own vehicle speed match, it is possible to generate braking / driving force at an accurate timing. Become.

According to a third aspect of the present invention, there is provided a preceding vehicle follow-up control device according to the first or second aspect, wherein the inter-vehicle distance control means is adapted to a preset vehicle reference model. The vehicle speed target value is calculated based on a relative value between the preceding vehicle and the own vehicle with respect to the inter-vehicle distance target value and an actual relative value between the preceding vehicle and the own vehicle. .

In the invention according to claim 3, the inter-vehicle distance control means has a preset reference model of the vehicle, and the preceding vehicle and the own vehicle with respect to the target inter-vehicle distance obtained based on the reference model are obtained. And the relative relationship value such as relative vehicle speed or inter-vehicle distance, and the actual relative relationship value, that is,
The vehicle speed target value is calculated based on the actual relative vehicle speed or the actual inter-vehicle distance obtained by differentiating the actual inter-vehicle distance obtained by the inter-vehicle distance detection means. Therefore, the inter-vehicle distance target value is filtered by the reference model, and the vehicle speed target value is set based on this, so that a sudden change in vehicle behavior is avoided.

According to a fourth aspect of the present invention, there is provided a preceding vehicle following control apparatus according to any one of the first to third aspects, wherein the slip amount detecting means detects a slip amount of a driving wheel. Means, wherein the road surface friction coefficient detecting means estimates the road surface friction coefficient based on the integrated value of the slip amount during the occurrence of slip, and the road surface friction coefficient decreases as the integrated value of the slip amount increases. Is determined.

In the invention according to claim 4, the detection of the road surface friction coefficient by the road surface friction coefficient detecting means is performed as follows. In other words, the slip amount of the driving wheel is detected by the slip amount detecting means, and the slip amount detecting means detects the slip amount based on, for example, a wheel speed difference between the driving wheel and the driven wheel. For example, while it is determined that a slip has occurred based on the slip amount detected by the slip amount detecting means, the slip amount detected by the slip amount detecting means is integrated. As the integrated value increases, the road surface friction increases. Assuming that the coefficient is low, the road surface friction coefficient is estimated.

According to a fifth aspect of the present invention, there is provided a preceding vehicle follow-up control device according to any one of the first to third aspects, wherein the inter-vehicle distance control means is configured to control the vehicle speed. A target acceleration for matching the vehicle speed target value is calculated, the braking / driving force is controlled based on the target acceleration, and the road surface friction coefficient detecting means includes an acceleration detecting means for detecting an actual acceleration of the own vehicle. And estimating the road surface friction coefficient based on the actual acceleration when there is a difference between the target acceleration and the actual acceleration, and determining that the road surface friction coefficient is lower as the actual acceleration becomes smaller. It is characterized by.

According to the fifth aspect of the present invention, the inter-vehicle distance control means calculates a target acceleration for matching the own vehicle speed with the target vehicle speed, and controls the braking / driving force based on the target acceleration. . In the road surface friction coefficient detecting means, the actual acceleration of the vehicle is detected by the acceleration detecting means. When a difference is generated between the actual acceleration and the target acceleration, that is, the actual acceleration when the slip occurs. The road surface friction coefficient is estimated on the basis of the above, and it is estimated that the road surface friction coefficient is lower as the actual acceleration is smaller, that is, the acceleration is not obtained.

According to a sixth aspect of the present invention, there is provided a preceding vehicle follow-up control device according to any one of the first to third aspects, wherein the road surface friction coefficient detecting means includes a road surface friction coefficient. A road surface information receiving unit capable of receiving the road surface friction coefficient information from a road surface information transmitting unit that transmits information, wherein the road surface friction coefficient is estimated based on the road surface friction coefficient information received by the road surface information receiving unit. It is characterized by being.

In the invention according to claim 6, the road surface friction coefficient detecting means is, for example, an AHS (Advanced Cruise Assisut).
Highway Systems) Road surface information receiving means capable of receiving road surface friction coefficient information transmitted by road surface information transmitting means for transmitting information by wireless communication, such as an information communication infrastructure facility in a driving support road system, is provided. Then, the road surface friction coefficient is estimated based on the road surface friction coefficient information received by the road surface information receiving means, and when the road surface friction coefficient itself is received, this is used as an estimated value of the road surface friction coefficient.

[0018]

According to the preceding vehicle following control apparatus of the present invention, the road surface friction coefficient of the traveling road surface is detected and the vehicle speed target value is set in accordance with the detected coefficient. The vehicle speed target value can be set, and the braking / driving force can be generated at the right timing.Therefore, it is not necessary to secure the inter-vehicle distance in consideration of the road surface friction coefficient, and it is necessary to secure it according to the road surface friction coefficient. It is possible to prevent the required inter-vehicle distance from becoming long.

Further, according to the preceding vehicle following control device of the present invention, the response characteristic of the inter-vehicle distance between the host vehicle and the preceding vehicle is set in accordance with the road surface friction coefficient, and based on this, Since the vehicle speed target value is set, the vehicle speed target value according to the road surface friction coefficient can be easily and accurately set. According to the preceding vehicle following control device of the third aspect of the present invention, since the vehicle speed target value is calculated based on the preset vehicle reference model, it is possible to avoid a sudden change in vehicle behavior. .

Further, according to the preceding vehicle following control device of the present invention, the integrated value of the slip amount of the drive wheel, the actual acceleration when there is a difference between the target acceleration and the actual acceleration, or Since the road surface friction coefficient is estimated based on the road surface friction coefficient information from the road surface information transmitting means, the road surface friction coefficient can be easily detected.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention, in which 1FL and 1FR are left and right front wheels as driven wheels, and 1RL and 1RR are left and right rear wheels as driving wheels. The rear wheels 1RL and 1R are driven by the engine 2 with the automatic transmission 3, the propeller shaft 4,
It is transmitted through the final reduction gear 5 and the axle 6 and is driven to rotate.

Front wheels 1FL, 1FR and rear wheels 1RL, 1R
R has a disc brake 7 for generating a braking force.
The braking oil pressure of these disk brakes 7 is controlled by a braking control device 8. This braking control device 8
Generates a braking oil pressure in accordance with the depression of a brake pedal (not shown) and generates a braking oil pressure corresponding to the magnitude of the braking pressure command value P _B ^* supplied from the follow-up control controller 20 to the disc brake 7. It is configured to supply.

The engine 2 is provided with an engine output control device 9 for controlling the output. The engine output control device 9 includes, for example, a throttle valve 11
The engine speed is controlled by adjusting the opening of the engine. Further, the automatic transmission 3 is provided with a transmission control device 10 for controlling the shift position.

On the other hand, an inter-vehicle distance sensor 12 for detecting an inter-vehicle distance L with respect to a preceding vehicle is provided below the vehicle body on the front side of the vehicle.
The inter-vehicle distance sensor 12 measures the inter-vehicle distance L between the preceding vehicle and the own vehicle by emitting, for example, infrared light and receiving reflected light from the preceding vehicle. The inter-vehicle distance sensor 12 is set so as to capture a preceding vehicle ahead.

The following distance sensor 12 includes:
For example, a laser radar device that measures the distance between vehicles by using laser light, a laser device that measures by using millimeter waves or ultrasonic waves, and the like can be applied. Further, the vehicle, by detecting the rotational speed of the propeller shaft 4, a vehicle speed sensor 13 for detecting a vehicle speed Vs is disposed, further, detects the rotational speed Vw _FL ~Vw _RR of each wheel 1FL~1RR Wheel speed sensors 14FL to 14RR are provided.
Furthermore, a throttle opening sensor 15 for detecting the degree of opening of the throttle valve 11, an engine rotational speed sensor 16 for detecting the engine rotational speed N _E, a torque converter output rotation speed sensor 17 for detecting an output rotational speed N _T of the torque converter Are arranged.

The output signals of the following distance sensor 12, the vehicle speed sensor 13, the wheel speed sensors 14FL to 14RR, the throttle opening sensor 15, the engine speed sensor 16, and the torque converter output speed sensor 17 are output to the tracking control controller 20. The following control controller 20 inputs the following distance L detected by the following distance sensor 12, the own vehicle speed Vs detected by the vehicle speed sensor 13, and the wheel speed Vw _FL detected by the wheel speed sensors 14FL to 14RR.
～Vw _RR, the throttle opening θ detected by the throttle opening sensor 15, engine rotational speed detected by the engine rotational speed sensor 16 N _E, a torque converter output rotation speed detected by the torque converter output rotation speed sensor 17 N _T
Based on the brake control device 8, the engine output control device 9
In addition, by controlling the transmission control device 10, the following traveling control is performed to follow the vehicle while maintaining an appropriate inter-vehicle distance with the preceding vehicle. At this time, the road surface friction coefficient is estimated, and the following running control is performed according to the estimated road surface friction coefficient.

The tracking control controller 20 includes, for example, a microcomputer and peripheral devices such as a storage device. And, as shown in the block diagram of FIG.
The detection signals of _{FL to} 14RR are input to a signal input processing unit 21. The signal input processing unit 21 converts the detection signals of the own vehicle speed Vs and the wheel speeds Vw _{FL to} Vw _RR composed of pulse signals into the own vehicle speed Vs and the wheel speed of digital signals. Vw _{FL to} Vw _RR are detected. The inter-vehicle distance L detected by the inter-vehicle distance sensor 12 is input to the signal input processing unit 22.

Then, the wheel speed sensors 14FL to 14RR
Wheel speed Vw from_FL~ Vw_RRIs output to the friction coefficient estimation unit 23.
In the friction coefficient estimating unit 23, for example, the vehicle on the front wheel side
Road surface friction coefficient estimated value 1 from the difference between wheel speed and wheel speed on the rear wheel side
/ K is calculated. And the calculated road friction coefficient estimation value 1
/ K is output to the following distance control section 25. Meanwhile, the signal input
The headway from the headway distance sensor 12 input to the processing unit 22
The distance L is input to a target inter-vehicle distance calculation unit 24, and the target L
The inter-vehicle distance calculating section 24 receives the signal from the signal input processing section 21.
Target inter-vehicle distance L based on vehicle speed Vs and inter-vehicle distance L^* Act
This is output to the following distance control unit 25.

The inter-vehicle control unit 25 is connected to the friction coefficient estimating unit 23.
Road friction coefficient estimation value 1 / k and target inter-vehicle distance calculation unit
Based on the target inter-vehicle distance calculated in 24, a constant inter-vehicle distance
Target vehicle speed V for following the vehicle while maintaining^*Is calculated
This is output to the vehicle speed control unit 26. Vehicle speed control unit 26
Then, the target vehicle speed V from the inter-vehicle control unit 25^*And actual vehicle speed Vs
And the target acceleration G^*And calculate this
Output to the dynamic torque calculator 27. This target braking / driving torque
The calculation unit 27 calculates the target acceleration G from the vehicle speed control unit 26.^*
Calculates the drive shaft torque based on the
28 and the engine output calculator 30.

The braking hydraulic pressure calculating section 28 calculates a target braking pressure P _B ^* based on the drive shaft torque calculated by the target braking / driving torque calculating section 27, and uses this as a braking pressure command value. Output to Further, the engine output calculating section 30 calculates a target throttle opening θ ^* based on the drive shaft torque calculated by the target braking / driving torque calculating section 27, and
In step 1, this is output to the engine output control device 9 as a throttle opening command value.

Here, the vehicle speed sensor 13 corresponds to the own vehicle speed detecting means, the inter-vehicle distance sensor 12 corresponds to the inter-vehicle distance detecting means, and the processing of step S4 in FIG. 3 corresponds to the inter-vehicle distance target value calculating means. 2 corresponds to road surface friction coefficient detecting means, the processing of steps S5 to S7 in FIG. 2 corresponds to inter-vehicle distance control means, and calculates a wheel speed difference between front wheels and rear wheels in step S14 in FIG. The processing to be performed corresponds to the slip amount detecting means.

Next, the operation of the first embodiment will be described with reference to the flowchart of FIG. 3 showing a control processing procedure executed by the follow-up control controller 20. The follow-up control controller 20 executes the follow-up traveling control process shown in FIG. 3 as a timer interrupt process, for example, every 10 msec. In the following traveling control process, first, in step S1
Then, the detection signals of the inter-vehicle distance sensor 12, the vehicle speed sensor 13, and the wheel speed sensors 14FL to 14RR are read, and based on the detection signals of the vehicle speed sensor 13, the wheel speed sensors 14FL to 14RR, the own vehicle speed Vs and the wheel speeds Vw _{FL to} Vw. Calculate _RR .

Next, the process proceeds to step S2, where it is determined whether a preceding vehicle has been detected. This determination is made, for example, when the inter-vehicle distance L read in step S1
It is determined by determining whether or not the distance is within the detection limit value. When the inter-vehicle distance L is within the detection limit value, it is determined that there is a preceding vehicle, and the process proceeds to step S3. On the other hand, when the inter-vehicle distance L is larger than the detection limit value, it is determined that there is no preceding vehicle, and the process proceeds to step S10 described later.

In step S3, an estimated road surface friction coefficient 1 / k is calculated. That is, as shown in the flowchart of FIG. 4, first, in step S11, it is determined whether or not the vehicle is slipping. For this determination, for example, the average value of the front wheel side and rear wheel side wheel speeds is calculated based on the detection signals of the respective wheel speed sensors 14FL to 14RR to calculate the front wheel speed Vf and the rear wheel speed Vr. It is determined that a slip has occurred when these differences exceed a preset threshold value.

When it is determined that the vehicle is slipping, the flow shifts to step S12, where it is determined whether or not the flag F is F = 1.
13, the integral value k is set to k = 0, and the flag F is set to F
After setting = 1, the process proceeds to step S14. on the other hand,
If the flag is F = 1 in step S12, the process directly proceeds to step S14.

In step S14, the front wheel speed Vf and the rear wheel speed Vr are calculated according to the following equation (1).
And the road surface friction conversion coefficient C set in advance,
An integral value k is calculated, and the reciprocal 1 / k is calculated as an estimated road surface friction coefficient. Then, the process returns to the flowchart of FIG. Note that s in the expression is a Laplace operator. C (Vr−Vf) · (1 / s) = k (1) On the other hand, when the own vehicle is not slipping in step S11, the process proceeds to step S15, and it is determined whether or not the flag F is F = 1. , F = 1, the flow shifts to step S16 to set the flag F to F = 0, and then returns to the flowchart of FIG. On the other hand, in step S15, the flag F is set to F
If it is not = 1, the process proceeds to step S17, and it is determined whether or not the own vehicle is accelerating based on, for example, an acceleration obtained by differentiating the own vehicle speed Vs. Then, the road friction coefficient estimation value 1 / k is set to, for example, “1” as an initial value, and
Return to the flowchart of FIG. On the other hand, when it is determined that the vehicle is not accelerating, the process returns to the flowchart of FIG.

That is, as shown in FIG. 5, the difference between the wheel speed Vr of the rear wheel and the wheel speed Vf of the front wheel, that is, the integrated amount of the slip amount is obtained, and the road surface friction coefficient estimation value 1 is obtained based on the maximum value.
/ K is calculated. The relationship between the estimated value 1 / k of the road surface friction coefficient and the actual road surface friction coefficient μ is managed proportionally as shown in FIG. Next, the process proceeds to step S4 to calculate a target inter-vehicle distance L ^* . That is, as shown in the following equation (2),
The time T ₀ (inter-vehicle time constant value) until the vehicle reaches the position L ₀ [m] behind the current preceding vehicle, the vehicle speed Vs,
It is calculated from the inter-vehicle distance L.

L^*= T₀× (Vs + L × d / dt) (2) Next, the process proceeds to step S5, and as shown in FIG.
Target inter-vehicle distance L calculated in step S4^*Based on the
Feedforward phase compensator G_FF(S), feedback
Compensator G_FB(S) and target inter-vehicle distance L^*Filter
Preset reference model to prevent sudden changes
Target vehicle speed V based on^*Is calculated. In other words, the target headway
Distance L^*Include, for example, a second-order phase advance element for the second order
Feedforward phase compensator G represented by transfer function_FF
Phase compensation value VSP obtained through (s)_FFCalculate
You. Also, the target inter-vehicle distance L^*Through the reference model
From the inter-vehicle distance and the relative vehicle speed, the actual inter-vehicle distance L and
Actual relative vehicle speed ΔV obtained by differentiating this inter-vehicle distance L
Is subtracted, and this is subtracted, for example, from the
Feedback compensator G_FBFeed obtained through (s)
Back compensation value VSP_FB Is calculated. And complement these positions
Reward VSP_FFAnd feedback compensation value VSP_FBAdd
Then, this added value is calculated as the actual relative vehicle speed ΔV and the own vehicle speed Vs.
Is subtracted from the added value of the target vehicle speed V.^*And

The transfer function G _FF (s) of the feedforward phase compensator is represented by an inter-vehicle distance control response characteristic ω ² / (s ²
+ 2ζωs + ω ² ) and the inverse of the transfer function from the vehicle speed to the inter-vehicle distance L. Here, the natural angular frequency ω of the inter-vehicle distance control response characteristic is set in the step S3.
Is multiplied by the estimated value of the road surface friction coefficient 1 / k calculated in step (1), and the inter-vehicle distance control response characteristic in consideration of the road surface friction coefficient is used. The transfer function from the vehicle speed to the inter-vehicle distance L is represented by the product of the transfer characteristic ω _V / (s + ω _V ) of the vehicle speed control system and an integrator for integrating the relative speed to obtain the actual vehicle speed. From
ω _V / [s (s + ω _V )]. Therefore, the transfer function G _FF (s) of the feedforward phase compensator is
It is expressed by the following equation (3).

G _FF (s) = [(1 / k) ω] ² · s (s + ω _V ) / ｛ω _V (s ² + 2ζ [(1 / k) ω] s + [(1 / k) ω] ² … (3) Also, the transfer function G _FB (s) of the feedback compensator
Is represented by the following equation (4). Incidentally, f _V in the formula is a gain related to the velocity components, is f _d is a gain related to the distance component.

G _FB (s) = f _V · s + f _d (4) Next, the process proceeds to step S6, and the target acceleration / deceleration G ^* is calculated by differentiating the target vehicle speed V ^* calculated in step S5 ^.
(G ^* = dV ^* / dt) is calculated. Next, the process proceeds to step S7, where the target acceleration / deceleration G calculated in step S6 is calculated.
^* Control the distance between vehicles based on ^* .

That is, the target wheel torque τ _W ^* is calculated based on the target acceleration / deceleration G ^* , the vehicle weight m and the wheel radius r. Then, based on the engine rotation speed N _E (rpm) detected by the engine rotation speed sensor 16 and the torque converter output rotation speed _NT (rpm) detected by the torque converter output rotation speed sensor 17, the following equation (5) is calculated. Then, the speed ratio e is calculated.

E = N _T / N _E (5) Next, based on the speed ratio e, a torque ratio η _T is calculated by referring to a torque ratio calculation map stored in advance in a storage device such as a ROM. . For example, as shown in FIG. 8, this torque ratio calculation map takes the maximum torque ratio when the speed ratio e is “0”, and the torque ratio η _T changes linearly as the speed ratio e increases from this state. It is set to decrease gradually.

Then, the target wheel torque τ_W ^*, Torque ratio
η_T, And gear ratio η_GThe following equation (6) is calculated based on
Is the target engine torque τ_E ^*Is calculated. τ_E ^*= Τ_W ^*/ (Η_T・ Η_G) (6) Next, the calculated target engine torque τ_E ^*And the engine
Rotation speed N_EIn advance in a storage device such as a ROM based on
Refer to the throttle opening calculation map
Rottle opening θ^*Is calculated. This throttle opening calculation
The map is, for example, as shown in FIG.
Rolling speed N_EAnd the vertical axis represents the target engine torque τ_E ^*To
The target throttle opening θ^*Is set as a parameter.
And the target throttle opening θ^*But about 40%
When the engine speed N_E Almost straight as the increase
Target throttle opening θ^*Is 60% to 100
%, As the increase increases,
The curvature is set to be convex so that the target throttle
Opening θ^*Decreases to 20% to 0%,
It is set in a concave shape where the curvature rate increases as it becomes
I have. Then, the target throttle opening θ^*Is less than 20%
The engine speed N_EIncreases when the target
Gin torque τ_E ^*Is negative and the engine brakes
Live.

Next, the actual throttle opening θ, engine
Rotation speed N_E, Target acceleration / deceleration G^* Target system based on
Dynamic pressure P_B ^*And outputs this to the braking control device 8
Terminates the timer interrupt processing from
Return to Ram. The target braking pressure P_B ^*First, the slot
Actual throttle opening detected by the throttle opening sensor 15
θ and the engine speed detected by the engine speed sensor 16.
Rolling speed N_EFrom the above, the throttle opening calculation
And the engine torque τ_EIs calculated.

Then, by calculating the following equation (7) based on the calculated engine torque τ _E and the above-mentioned torque ratio τ _T and gear ratio η _G , an estimated wheel torque value τ _{W is obtained.}
Is calculated. τ _W = τ _E η _T η _G (7) Next, the acceleration / deceleration estimated value is calculated by performing the calculation of the following equation (8) based on the estimated wheel torque value τ _W , the vehicle weight m and the wheel radius r. Calculate G.

G = τ _W / (r · m) (8) Next, the following equation (9) is calculated based on the target acceleration / deceleration G ^* and the estimated acceleration / deceleration G calculated in step S 6. The acceleration / deceleration deviation ΔG is calculated. ΔG = G ^* −G (9) Then, wheel radius r, vehicle weight m, and acceleration / deceleration deviation ΔG
The target braking torque τ _B ^* is calculated by performing the calculation of the following equation (10) based on

Τ _B ^* = r · m · ΔG / 2 (10) Based on the target braking torque τ _B ^* and the control gain g, the following equation (11) is used to calculate the target braking pressure P _B ^*. Is calculated. P _B ^* = − g · τ _B ^* (11) Then, the target throttle opening θ ^* is output to the engine output control device 9, and the target brake pressure P _B ^* is output to the brake control device 8.

In response to this, in the engine output control device 9, the throttle opening deviation between the target throttle opening θ ^* input from the follow-up control controller 20 and the actual throttle opening θ detected by the throttle opening sensor 15. Δθ is calculated, and based on the throttle opening deviation Δθ, for example, P
Performs the ID control, etc., it calculates a throttle actuator command value theta _T, controls the throttle opening theta and outputs it to the throttle valve 11.

The braking control device 10 calculates a braking pressure deviation ΔB between the target braking pressure P _B ^* input from the follow-up control controller 20 and the actual braking pressure P _B, and calculates the braking pressure deviation ΔP _B based braking pressure command value P _BT is calculated by performing with eg a PID control, and supplies the braking pressure P in accordance with the braking pressure command value P _BT to the disc brakes 7. On the other hand, in step S10, since it is determined that there is no preceding vehicle, the driver performs a vehicle speed control process for matching the own vehicle speed Vs with a preset target vehicle speed V ^* , and then terminates the timer interrupt process and performs a predetermined process. Return to the main program.

That is, first, the driver calculates the target acceleration / deceleration G _V ^* so that the actual vehicle speed Vs matches the target vehicle speed V ^* set in advance by the driver. This target acceleration / deceleration G _V ^*
The vehicle speed deviation ΔVs is obtained by subtracting the own vehicle speed Vs from the target vehicle speed V ^*.
(= V ^* −Vs), and is calculated by performing, for example, PID control based on the vehicle speed deviation ΔVs. Then, based on the target acceleration / deceleration G _V ^* , the above (4)-
(6) is calculated, the torque ratio η _T is calculated with reference to the torque ratio calculation map of FIG. 8, and the target throttle opening θ ^* is calculated with reference to the throttle opening calculation map of FIG. After calculating and outputting this to the engine output control device 10, the timer interrupt process is terminated and the process returns to the predetermined main program.

Therefore, when the vehicle is in the following control state with the driver setting the target vehicle speed V ^* and the preceding vehicle is not captured by the inter-vehicle distance sensor 13, the following processing is performed in the following traveling control process of FIG. proceeds from step S2 to step S10, and calculates the vehicle speed control target acceleration G _V ^* based on the vehicle speed deviation ΔV between the target vehicle speed V ^* and the current vehicle speed Vs set by the driver in advance, for the vehicle speed control Target acceleration / deceleration G
By calculating the target throttle opening θ ^* based on _V ^* and outputting the target throttle opening θ ^* to the engine output control device 9, the vehicle speed Vs is controlled only by controlling the throttle opening without exerting the braking force with the disk brake 7. The vehicle speed control is performed such that the vehicle speed coincides with a preset target vehicle speed V ^* .

From this vehicle speed control state, the following distance sensor 1
When the vehicle is in a state of capturing the preceding vehicle in Step 2, the process proceeds from Step S2 to Step S3, and the wheel speed sensors 11FL to 11R
The front wheel-side wheel speed Vf and the rear wheel-side wheel speed Vr are calculated based on the R detection signal, and the difference between them is integrated according to the above equation (1) to calculate the road surface friction coefficient estimated value 1 / k. .

That is, while the slip occurs, the integral value k increases as the slip amount increases, and the estimated friction coefficient 1 / k decreases accordingly. When the vehicle is accelerating on a high road surface, since the slip amount is small, the integral value k is a relatively small value and the road surface friction coefficient estimated value 1 / k is a value relatively close to "1". Conversely, when the vehicle is accelerating on a road surface having a low coefficient of road surface friction, a slip occurs between the front and rear wheels, and the amount of slip increases. Therefore, the integral value k becomes a relatively large value and the road surface coefficient of friction estimation is performed. The value 1 / k is a relatively small value.

Subsequently, in the processing of step S4, a predetermined time T ₀ (inter-vehicle time) until the vehicle reaches the position L ₀ [m] behind the current preceding vehicle, and the detection of the vehicle speed sensor 13 When the target inter-vehicle distance L ^* is calculated according to the equation (2) based on the own vehicle speed Vs based on the signal and the inter-vehicle distance L from the inter-vehicle distance sensor 12, the target inter-vehicle distance L ^* becomes
The value increases as the vehicle speed Vs increases, and increases as the inter-vehicle distance L increases.

Then, based on the target inter-vehicle distance L ^* calculated in step S4, the phase compensation value VSP is obtained from the above equation (3).
_FF is calculated, and a feedback compensation value VSP _FB is calculated from the equation (4). Then, these added values are
Relative vehicle speed ΔV and own vehicle speed V obtained by differentiating inter-vehicle distance L
The target vehicle speed V ^* is calculated by subtracting from the value added to s. At this time, the transfer function G _FF of the feedforward phase compensator
(S) changes according to the road surface friction coefficient estimated value 1 / k as shown in the above equation (3), and the road surface friction coefficient estimated value 1 / k
Is smaller so that the natural frequency of the inter-vehicle distance control response characteristic becomes smaller, and based on this, the phase compensation value VSP _FF
Is calculated.

In other words, the frequency characteristic of the inter-vehicle distance control response characteristic is, as shown in FIG.
Is smaller, the stable frequency range is higher. Therefore, a sufficient gain can be obtained even in a high frequency range, and a sufficient gain can be obtained even if the frequency characteristic of the input signal changes with a change in the road surface friction coefficient. Therefore, the phase compensation value VSP calculated based on the inter-vehicle distance control response characteristic set in this way.
_FF is a value that is not affected by a decrease in the road surface friction coefficient.

The road surface friction coefficient estimated value 1
/ K and on the basis of the phase compensation value VSP _FF calculated in consideration to calculate the target vehicle speed V ^*, on the basis of the target vehicle speed V ^*, calculates the target deceleration G ^* (step S6), and the target acceleration The target throttle opening θ ^* and the target braking pressure P _B ^* that can realize the speed G ^* are calculated (step S7), and when these are output to the engine output control device 9 and the brake control device 8, respectively, Since the engine output control device 9 or the brake control device 8 operates to adjust the opening of the throttle valve 11 and control the braking pressure to the disk brake 7, a driving force or a braking force is generated and the target acceleration / deceleration G Control will be performed to generate ^* .

When the vehicle changes from a state in which the vehicle is accelerating to a state in which the vehicle is traveling at a constant speed, the flow proceeds from step S11 to step S11.
15 and the flag F is F = 1, so that step S
The process proceeds to step S16, and the flag F is updated to F = 0. If the vehicle is not accelerating, the process of step S17 is repeated through steps S11 and S15. Control is performed based on the road surface friction coefficient estimated value 1 / k calculated in the processing.

Then, from this state, the vehicle enters an acceleration state. At this time, when the vehicle is running on a road surface having a relatively large road surface friction coefficient, no slip occurs.
The process moves from step 1 to step S17 via step S15,
At this time, since the vehicle is accelerating, the process proceeds to step S18, where the road friction coefficient correction value 1 / k is set to "1", and thereafter, control is performed based on the road friction coefficient correction value 1 / k. .

As described above, the road surface friction coefficient is estimated, the response characteristic of the following distance control is changed in accordance with the estimated value 1 / k, and the target vehicle speed V ^* is determined and maintained based on the response characteristic. Therefore, the following distance control can be performed according to the road surface friction coefficient of the traveling road surface of the own vehicle. That is, FIG.
As shown in FIG. 0, since the inter-vehicle distance control response characteristic is changed with a decrease in the road surface friction coefficient so that a sufficient gain can be obtained even when the road surface friction coefficient decreases, with the decrease in the road surface friction coefficient, The phase compensation value VSP _FF is set to be relatively large, and as a result, the target vehicle speed V ^* tends to decrease, that is, the timing at which the braking force is generated is advanced, and the phase compensation value VSP _FF is accurately determined according to the road surface condition. The braking force can be generated at an appropriate timing. Therefore, the braking force is generated earlier as the road surface friction coefficient decreases, so that it is not necessary to secure a safe distance more than necessary, and the inter-vehicle distance can be maintained safely.

At this time, the integral of the slip amount of the vehicle is calculated.
The road surface friction coefficient estimated value 1 / k is calculated based on the
It is easy to estimate the road surface friction coefficient
it can. In addition, the road surface friction coefficient is estimated from the running state of the vehicle.
And the target vehicle speed V^* Is set to
From the time when the road friction coefficient was estimated from
Can be controlled in accordance with

Note that in the first embodiment,
The case where the present invention is applied to a rear-wheel drive vehicle has been described. However, the present invention is not limited to this, and the present invention can be applied to a front-wheel drive vehicle or a four-wheel drive vehicle. In this case, the calculation of the road surface friction coefficient estimated value 1 / k is performed in the case of a front wheel drive vehicle.
It may be performed based on the following equation (12), and in the case of a four-wheel drive vehicle, may be performed based on the following equation (13). It should be noted that Vi in the equation (13) is obtained, for example, by a select low that selects the lowest value among the wheel speeds of the four wheels,
Alternatively, as described in JP-A-11-189063, the vehicle speed is calculated by a method of selecting a third largest value among the wheel speeds Vw _{FL to} Vw _RR , and the like.
Vfr is an average of the wheel speeds of the four wheels calculated based on, for example, Vfr = (Vf + Vr) / 2.

C (Vf−Vr) · (1 / s) = k (12) C (Vi−Vfr) · (1 / s) = k (13) Next, the second embodiment of the present invention will be described. An embodiment will be described. This second
The second embodiment is the same as the first embodiment except that the method of calculating the estimated value of the road surface friction coefficient 1 / k is different. Omitted.

That is, in the second embodiment, the estimation of the estimated value 1 / k of the road surface friction coefficient shown in FIG. 3 is performed by utilizing the fact that there is a correspondence between the road surface friction coefficient μ and the vehicle acceleration α. In the processing, a road surface friction coefficient estimated value 1 / k is calculated based on the target acceleration / deceleration G ^* and the actual acceleration / deceleration. That is,
The relationship F = mα holds between the weight m and acceleration α of the vehicle and the engine output F. Further, the load acting on the road surface in the drive wheels (drag) is N, the maximum output of the engine which can be transmitted to the road surface without slipping drive wheel when the F _MAX, between these, F _MAX = [mu] N The relationship holds. This means that the engine output that can be transmitted to the road surface is limited according to the road surface condition, that is, μ. That, F greater engine power than the maximum output F _MAX is not transmitted to the road surface, the drive wheel to try to convey will slip.

Here, while the drive wheel is slipping,
Since the engine output above F _MAX is not transmitted to the road surface,
The relationship _MAX ≒ F holds, that is, mα ≒ μN holds. Since the vehicle weight m and the load N are constants determined for each vehicle, μ ≒ mα / N, and the road surface friction coefficient μ
Is proportional to the acceleration α.

Therefore, as shown in FIG. 11, the target acceleration when the difference between the target acceleration and the actual acceleration when control is performed on the target acceleration is maximum is a value proportional to the road surface friction coefficient μ. For example, a road friction coefficient estimation value K is calculated by multiplying a road friction conversion coefficient C ′ set in advance. That is, as shown in FIG. 12, first, in step S21, the wheel speed Vr (n) of the driven wheel is calculated based on the detection signals of the wheel speed sensors 14RF and 14RR, and Vr ( The acceleration / deceleration estimated value Gα is calculated from the difference from (n-1) (acceleration detecting means). Then, the absolute value of the difference between the estimated acceleration / deceleration Gα and the target acceleration / deceleration G ^* (n−1) calculated and stored in the previous control cycle is obtained, and this is calculated as the acceleration / deceleration deviation ΔG (n) (= ｜ G
^* (N-1) -Gα |).

Next, the process proceeds to step S22, where it is determined whether or not the vehicle is slipping based on, for example, whether or not the acceleration / deceleration deviation ΔG (n) exceeds a preset threshold value. If determined, step S
Moves to 23, acceleration deviation .DELTA.G calculated in step S21 (n) determines whether exceeds the maximum acceleration deviation .DELTA.G _MAX. If not ΔG (n)> ΔG _MAX, the program returns to the main program as it is, and ΔG (n)> ΔG
_If it is _MAX , the process moves to step S24. In addition,
The maximum acceleration / deceleration deviation ΔG _MAX is set to an initial value G ₀ at startup.
Is set to

In step S24, ΔG (n)> Δ
Considers deceleration estimated value Gα used for calculating the acceleration speed deviation .DELTA.G (n) when a G _MAX a value corresponding to the road surface friction coefficient, road surface friction transform coefficient C ₁ that is preset in the deceleration estimated value Gα Is multiplied by the road surface friction coefficient estimated value K.
(= C ₁ × Gα). Also updates sets the acceleration deviation .DELTA.G (n) of this time as the maximum acceleration deviation .DELTA.G _MAX. Then, the process returns to the main program.

On the other hand, if it is determined in step S22 that the vehicle has not slipped, the flow shifts to step S25.
For example, it is determined whether acceleration / deceleration is being performed based on whether the estimated acceleration / deceleration value Gα exceeds a preset threshold value, and when acceleration / deceleration is not being performed, the process directly returns to the main program. On the other hand, when it is determined that acceleration / deceleration is being performed,
The process proceeds to step S26, in which the road surface friction coefficient is considered to be high because acceleration / deceleration is occurring but no slip occurs, and a relatively high predetermined value (for example, “1”) is set as the road surface friction coefficient estimated value K. Also, the maximum acceleration / deceleration deviation ΔG _MAX
Is set to the initial value G ₀ . Then, the process returns to the main program.

Accordingly, in a state where the vehicle is accelerating on a road surface having a relatively high coefficient of road surface friction, no slip occurs when the vehicle is accelerated. Therefore, the process proceeds from step S22 to step S26 via step S25, and proceeds to step S26. For example, “1” is set as the estimated friction coefficient K. And
From this state, when the vehicle enters a road surface having a relatively low road surface friction coefficient and a slip occurs, the process proceeds from step S22 to step S23. And the previous target acceleration / deceleration G
^{* The} acceleration deviation ΔG (n), which is the difference between (n−1) and the acceleration / deceleration estimated value Gα calculated this time, is the maximum acceleration deviation ΔG _MAX
As long as the acceleration / deceleration deviation ΔG (n) exceeds the maximum acceleration / deceleration deviation ΔG _MAX , the process returns from step S23 to step S24, and according to the acceleration estimated value Gα at this time. The value is set as the road surface friction coefficient estimated value K, and the acceleration / deceleration deviation ΔG (n) at this time is set as the maximum acceleration / deceleration deviation ΔG _MAX .

Accordingly, the road surface friction coefficient estimation value K is set according to the acceleration estimation value Gα when the acceleration / deceleration deviation ΔG during the slip is maximized. Then, when the vehicle shifts to the constant speed running from this state, when the process shifts from step S22 to step S25, the process proceeds to step S25.
Since the flow returns to step S21 from step S25, the road surface friction coefficient estimated value K set at the time of slip is maintained, and from this state, when the vehicle enters the road surface having a relatively high road surface friction coefficient and performs acceleration traveling, steps S22 to S25 are performed. Then, the process proceeds to step S26, where the road surface friction coefficient estimated value K is updated to "1".

Then, the control process is performed in the same manner as in the first embodiment, assuming that the estimated value of the road surface friction coefficient K is 1 / k in the equation (3). Therefore, also in this case, the same operation and effect as those of the first embodiment can be obtained. Next, a third embodiment of the present invention will be described.

In the third embodiment, the AHS (Advance
d cruise assisut Highway Systems) This is for acquiring road surface friction coefficient information from an information and communication infrastructure facility in a driving support road system or the like. Since the configuration is the same as that of the embodiment, the same portions are denoted by the same reference numerals, and detailed description thereof will be omitted.

That is, the third embodiment is different from FIG.
As shown in FIG. 3, in the schematic configuration diagram in the first embodiment shown in FIG. 1, an infrastructure information receiver 18 as road surface information receiving means is added. The infrastructure information receiver 18 receives, for example, information from a transmitter (not shown) as road surface information transmitting means provided on a road, and the transmitter includes at least a road surface friction near a position where the transmitter is provided. It is configured to be able to transmit infrastructure information including coefficient information. And the infrastructure information receiver 18 receives the infrastructure information from the transmitter,
This is output to the tracking control controller 20.

In the tracking control controller 20, as shown in FIG. 14, a signal input processing unit 32 is newly provided in place of the friction coefficient estimating unit 23 in the block diagram of the first embodiment shown in FIG. Is provided. The signal input processing unit 32 inputs the infrastructure information received by the infrastructure information receiver 18, extracts road surface friction coefficient information from the information, and outputs the information to the inter-vehicle control unit 25.

The inter-vehicle control unit 25 sets the road friction coefficient μ specified by the road friction coefficient information to the estimated road friction coefficient 1 / k, and thereafter sets the target vehicle speed V ^* in the same manner as in the first embodiment ^. Is calculated. Therefore, also in this case, the same operation and effect as those of the first embodiment can be obtained.

In each of the above embodiments, a case has been described in which the road surface friction coefficient is detected based on the road speed difference information notified as front and rear wheel speed difference, vehicle acceleration / deceleration or infrastructure information. However, the present invention is not limited to this, and it is only necessary that the road surface friction coefficient can be detected. For example, the road surface friction coefficient may be estimated from the outside temperature, that is, a new outside temperature sensor is provided, the outside temperature is measured by the outside temperature sensor, and the outside temperature and the road surface friction coefficient are set in advance. May be calculated from a control map representing the relationship. For example, when the outside temperature is below the freezing point, the control map determines that there is a frozen road surface and sets the road surface friction coefficient to a small value.When the temperature is higher than zero degrees, the road surface friction coefficient increases as the temperature increases while the temperature is relatively low. And a relatively large value when the temperature is equal to or higher than the predetermined temperature.

Further, in each of the above-described embodiments, the description has been made of the case where the following control controller 20 performs the arithmetic processing by software. However, the present invention is not limited to this. The function generator, the comparator, the arithmetic unit May be applied to hardware constituted by an electronic circuit configured by combining the above. Further, the case where the disk brake 7 is applied as the brake actuator has been described. However, the present invention is not limited to this, and other actuators such as a drum brake can be applied. In this case, a command value such as a target current is calculated in place of the target braking pressure P _B ^* ,
This may be output to the braking control device 8 that controls the brake actuator based on the command value.

The case where the engine 2 is applied as the rotary drive source has been described. However, the present invention is not limited to this, and an electric motor can be applied.
The present invention can also be applied to a hybrid vehicle using an engine and an electric motor.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a functional configuration of a tracking control controller.

FIG. 3 is a flowchart illustrating an example of a processing procedure of a following travel control process in a following control controller.

FIG. 4 is a flowchart illustrating an example of a processing procedure for calculating a friction coefficient estimated value in FIG. 3;

FIG. 5 is an explanatory diagram illustrating a method of calculating a friction coefficient estimated value.

FIG. 6 is a characteristic diagram showing a correspondence between a road friction coefficient estimated value 1 / k and an actual road friction coefficient μ.

FIG. 7 is a diagram illustrating a method of calculating a target vehicle speed V ^* .

FIG. 8 is a characteristic diagram showing a torque ratio calculation map representing a relationship between a speed ratio and a torque ratio.

FIG. 9 is a characteristic diagram showing a throttle opening calculation map showing a relationship between an engine rotation speed and an engine torque as a throttle opening parameter.

FIG. 10 is a frequency characteristic of the inter-vehicle distance control response characteristic G (s).

FIG. 11 is an explanatory diagram illustrating a method of calculating a road surface friction coefficient according to the second embodiment.

FIG. 12 is a flowchart illustrating an example of a processing procedure for calculating a friction coefficient estimated value according to the second embodiment.

FIG. 13 is a schematic configuration diagram showing a third embodiment.

FIG. 14 is a block diagram illustrating a functional configuration of a tracking control controller according to a third embodiment.

[Explanation of symbols]

 2 Engine 7 Disc brake 8 Brake control device 9 Engine output control device 11 Throttle valve 12 Inter-vehicle distance sensor 13 Vehicle speed sensor 14FL-14RR Wheel speed sensor 18 Infrastructure information receiver 20 Tracking control controller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ken Kimura 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Inside Nissan Motor Co., Ltd. (72) Inventor Taku Takahama 2 Takaracho, Kanagawa-ku, Yokohama City, Kanagawa Prefecture Terms (reference) 3D044 AA01 AA25 AA45 AB01 AC01 AC03 AC05 AC19 AC26 AC59 AD02 AD16 AD21 AE01 AE04 AE14 AE19 AE22 AE27 3D046 BB18 BB23 GG02 HH00 HH20 HH23 HH26 HH36 HH42 HH46 DB03 BA03 DB03 BA08 DB03 BA09 DB08 DB17 EA01 EB03 EB04 EC01 EC04 FA05 FA06 FA07 FA10 FB01 FB03 5H180 AA01 CC03 LL01 LL04 LL09

Claims (6)

[Claims] A vehicle speed detecting means for detecting a running speed of the vehicle; an inter-vehicle distance detecting means for detecting an inter-vehicle distance from a preceding vehicle; an own vehicle speed detected by the own vehicle speed detecting means and the inter-vehicle distance detecting means. An inter-vehicle distance target value calculating means for calculating an inter-vehicle distance target value with respect to the preceding vehicle based on the actual inter-vehicle distance detected in Step 1, a road surface friction coefficient detecting means for detecting a road surface friction coefficient of a running road surface, Based on the actual inter-vehicle distance, a vehicle speed target value is calculated in accordance with the road surface friction coefficient detected by the road surface friction coefficient detection means so that the inter-vehicle distance with the preceding vehicle becomes the inter-vehicle distance target value, A vehicle distance control means for controlling braking / driving force so that the vehicle speed coincides with the vehicle speed target value. 2. The inter-vehicle distance control means sets a response characteristic of an inter-vehicle distance with the preceding vehicle in accordance with a road surface friction coefficient detected by the road surface friction coefficient detection means, and sets the vehicle speed target value based on the response characteristic. The preceding vehicle following control device according to claim 1, wherein the following formula is calculated. 3. The inter-vehicle distance control means includes a relative value between the preceding vehicle and the own vehicle and an actual relative value between the preceding vehicle and the own vehicle with respect to the inter-vehicle distance target value obtained based on a preset vehicle reference model. 3. The preceding vehicle following control device according to claim 1, wherein the target vehicle speed value is calculated based on the following. 4. A road surface friction coefficient detecting unit for detecting a slip amount of a driving wheel, wherein the road surface friction coefficient detecting unit estimates the road surface friction coefficient based on an integrated value of the slip amount during a slip. The preceding vehicle follow-up control device according to any one of claims 1 to 3, wherein it is determined that the larger the integral value of the slip amount, the lower the road surface friction coefficient. 5. The inter-vehicle distance control means calculates a target acceleration for matching the own vehicle speed with the target vehicle speed, controls the braking / driving force based on the target acceleration, and detects the road surface friction coefficient. The means includes acceleration detection means for detecting an actual acceleration of the own vehicle, and estimates the road surface friction coefficient based on the actual acceleration when a difference occurs between the target acceleration and the actual acceleration. The preceding vehicle following control device according to any one of claims 1 to 3, wherein it is determined that the road surface friction coefficient is as low as possible. 6. The road surface friction coefficient detecting unit includes a road surface information receiving unit capable of receiving the road surface friction coefficient information from a road surface information transmitting unit that transmits the road surface friction coefficient information, and the road surface information receiving unit receives the road surface friction coefficient information. The preceding vehicle following control device according to any one of claims 1 to 3, wherein the road surface friction coefficient is estimated based on the road surface friction coefficient information.