JP2000052804A - Vehicle speed control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a vehicle speed so as to suppress slips as much as possible even on a low μ road. SOLUTION: A first target vehicle speed VSET1 is set according to a driving condition by a first target vehicle speed setting part 101 and responding to this, a braking/ driving force control parts 109, 110 controls a braking/driving force, thus controlling a vehicle speed so that the vehicle speed matches the first target vehicle speed VSET1. In such a vehicle speed control, a wheel speed of a driven wheel Vw2 is detected by a driven wheel speed detecting part 102-2, a wheel speed of a driving wheel Vw1 is detected by a driving wheel speed detecting part 102-1, and also, a vehicle body speed Vr1 is estimated by a vehicle body speed estimating part 103, a slip ratio SLIP is estimated by a slip ratio estimating part 104, and based on the slip ratio SLIP, a change rate limit value setting part 105 sets a vehicle speed change rate limit value LIM. Thus, a second target vehicle speed VSET2 is set by a second target vehicle speed setting part 106 so that the vehicle body speed follows the first target speed VSET1 within the range of the vehicle speed change rate limit value LIM, and the braking/driving force control parts 109, 110 controls the braking/driving force of the vehicle so as to match the vehicle speed with the second target vehicle speed VSET2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a vehicle speed control device.

[0002]

2. Description of the Related Art Conventionally, braking / driving force control means such as a throttle opening and a brake are set so that a target vehicle speed is set according to a distance between the vehicle and a preceding vehicle, and the speed of the own vehicle is made equal to the target vehicle speed. 2. Description of the Related Art There is known a vehicle speed control device that operates to control the braking / driving force of a vehicle.

[0003]

However, in the conventional vehicle speed control device, the target vehicle speed is set on the assumption that the driving wheels hardly slip, and the braking / driving force control means is adjusted to match the target vehicle speed. There are the following problems due to the operation of That is, the tire grip limit is low on a low μ road such as a snow-covered road or a frozen road, and when a large braking / driving force (braking force or engine torque) is generated, the tire slips, and a desired braking / driving force is obtained. And the actual vehicle speed cannot be matched with the target vehicle speed.

[0004] FIG. 17 shows the vehicle speed when the vehicle speed is increased from 40 km / h to 60 km / h by 0.06 G at a timing of 20 to 30 sec when the friction coefficient μ of the road surface is 0.1 in the prior art. Shows the change characteristics. As can be seen from FIG. 17, the wheel speeds of the drive wheels are almost equal to the target vehicle speed, but the driving force of the vehicle is reduced due to the slip of the drive wheels, and the actual vehicle speed (vehicle speed) ) Cannot follow the target vehicle speed, and conversely decreases.

The present invention has been made in view of such a conventional problem, and has as its object to provide a vehicle speed control device capable of effectively controlling the vehicle speed even on a low μ road.

[0006]

According to a first aspect of the present invention, there is provided a vehicle speed control apparatus comprising: first target vehicle speed setting means for setting a first target vehicle speed according to driving conditions; Non-driving wheel speed detecting means for detecting, driving wheel speed detecting means for detecting wheel speed of driving wheels, vehicle speed estimating means for estimating vehicle speed, slip rate estimating means for estimating slip rate, Change rate limit value setting means for setting a vehicle speed change rate limit value based on the slip rate; and a second target so that the vehicle body speed follows the first target vehicle speed within a range of the vehicle speed change rate limit value. The vehicle includes second target vehicle speed setting means for setting the vehicle speed, and braking / driving force control means for controlling the braking / driving force of the vehicle such that the vehicle body speed matches the second target vehicle speed.

In the vehicle speed control device according to the first aspect of the present invention,
The first target vehicle speed setting means sets the first target vehicle speed according to the driving situation.
In response to this, the braking / driving force control means controls the braking / driving force, and controls the vehicle speed so that the vehicle speed coincides therewith.

During the vehicle speed control, the wheel speed of the non-driving wheel is detected by the non-driving wheel speed detecting means, the wheel speed of the driving wheel is detected by the driving wheel speed detecting means, and the vehicle speed is detected by the vehicle speed estimating means. Is estimated by the slip rate estimating means, and the change rate limit value setting means sets the vehicle speed change rate limit value based on the slip rate.

Then, the second target vehicle speed is set by the second target vehicle speed setting means so that the vehicle speed follows the first target vehicle speed within the range of the vehicle speed change rate limit value, and the braking / driving force control means sets the second target vehicle speed. The braking / driving force of the vehicle is controlled so that the vehicle speed matches the second target vehicle speed.

In this way, the first target vehicle speed setting means is used when the inter-vehicle distance with the preceding vehicle is increased and acceleration is required, or when the inter-vehicle distance with the preceding vehicle is reduced and deceleration is required. As described above, the first target vehicle speed is set in accordance with the driving situation. However, since the rate of change of the first target vehicle speed is large, the braking / driving force control means tries to follow this and suddenly accelerates or decelerates. When there is a possibility that a slip may occur in the driving wheels, a second target vehicle speed having a change rate that does not cause such a slip is set, and the vehicle speed control is performed so as to follow this. Vehicle speed control that suppresses the occurrence of slip and consequently effectively follows the first target vehicle speed is performed.

According to a second aspect of the present invention, in the vehicle speed control apparatus according to the first aspect, the vehicle speed estimating means sets the wheel speed of the non-driving wheels to the vehicle speed, and the slip rate estimating means sets the non-driving speed. The slip rate is estimated based on the difference between the wheel speed of the wheel and the wheel speed of the drive wheel. Since the non-drive wheel does not slip during acceleration, the wheel speed of the non-drive wheel is determined by the vehicle speed. By estimating the slip ratio from the difference between the vehicle speed and the wheel speed of the drive wheels, it is possible to accurately estimate the actually occurring slip ratio, and to effectively suppress such slip. Vehicle speed control.

According to a third aspect of the present invention, in the vehicle speed control apparatus according to the first or second aspect, the second target vehicle speed setting means determines a wheel speed of the non-driving wheel when the slip ratio is equal to or more than a predetermined value. Is set to the second target vehicle speed. In a situation where the vehicle speed to be matched is originally too high and the slip ratio becomes large even if the change rate of the control vehicle speed is restricted, By setting the wheel speeds of the wheels to the second target vehicle speed, the slip amount of the drive wheels is prevented from increasing, and as a result, vehicle speed control that effectively follows the first target vehicle speed is performed.

According to a fourth aspect of the present invention, in the vehicle speed control apparatus according to the third aspect, the second target vehicle speed setting means is configured to control the slip when the vehicle brake is automatically operated by the braking / driving force control means. The second target vehicle speed set immediately before the rate becomes equal to or more than a predetermined value is maintained. Particularly, in a situation where the non-driving wheels are locked by a sudden braking operation on a low μ road, locking is performed. By maintaining the wheel speed of the non-driving wheel immediately before falling below the predetermined value as the second target vehicle speed instead of setting the wheel speed of the non-driving wheel that is zero to the second target vehicle speed,
The target vehicle speed does not drop sharply, and the non-driven wheels do not come to a state close to the lock due to the braking / driving force control that attempts to follow the target vehicle speed, and stable vehicle speed control can be performed.

[0014]

As described above, according to the first aspect of the present invention,
The first target vehicle speed setting means determines the driving situation such as when the inter-vehicle distance with the preceding vehicle is increased and acceleration is required, or conversely, when the inter-vehicle distance with the preceding vehicle is reduced and deceleration is required. The first target vehicle speed is set in response to this. However, since the rate of change of the first target vehicle speed is large, the braking / driving force control means suddenly accelerates or decelerates in an attempt to follow the first target vehicle speed. If there is a possibility that the slip will occur, the second
The target vehicle speed is set, and the vehicle speed is controlled so as to follow the target speed.
Vehicle speed control that effectively follows the target vehicle speed of the vehicle.

According to the second aspect of the present invention, the wheel speed of the non-driven wheels is set to the vehicle speed, and the slip ratio is estimated from the vehicle speed and the wheel speed of the driven wheels. The slip rate can be accurately estimated, and vehicle speed control that effectively suppresses such slip can be performed.

According to the third aspect of the present invention, in a situation where the vehicle speed itself to be matched even if the change rate of the target vehicle speed is restricted is too high and the slip ratio becomes large, the non-driving wheel is increased. By setting the wheel speed at the second target vehicle speed, it is possible to prevent the slip amount of the drive wheels from increasing, and as a result, to perform vehicle speed control that effectively follows the first target vehicle speed.

According to the fourth aspect of the present invention, in particular, in a situation where the non-driving wheels are locked by a sudden braking operation on a low μ road, the wheel speed of the non-driving wheels that are locked and become zero is set to the first speed. By maintaining the wheel speed of the non-driving wheels before decreasing to a predetermined value or less as the second target vehicle speed instead of setting the target vehicle speed to 2, the second target vehicle speed drops sharply and attempts to follow it. The non-drive wheels do not become close to the lock by the braking / driving force control,
Stable vehicle speed control is possible.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows the configuration of the first embodiment of the present invention. The vehicle speed control device according to the first embodiment includes a first target vehicle speed setting unit 101 that sets a target vehicle speed from an environment such as an inter-vehicle distance to a preceding vehicle, a driving wheel that detects a wheel speed of a driving wheel of the vehicle. Speed detecting unit 102-1, non-driving wheel speed detecting unit 102-that detects a wheel speed of a non-driving wheel
2. A vehicle speed estimating unit 10 for estimating the vehicle speed from the non-driving wheel speed detected by the non-driving wheel speed detecting unit 102-2.
3. A slip ratio estimating unit 104 for estimating a slip ratio based on the driving wheel speed detected by the driving wheel speed detecting unit 102-1 and the vehicle speed estimated by the vehicle speed estimating unit 103 is provided.

The vehicle speed control device further includes a change rate limit value setting section 105 for setting a change rate limit value of the target vehicle speed based on the slip rate estimated by the slip rate estimation section 104;
A second target indicating a change rate that minimizes slipping based on the first target vehicle speed set by the target vehicle speed setting section 101 and the change rate limit value set by the change rate limit value setting section 105 as much as possible. The vehicle includes a second target vehicle speed setting unit 106 for setting the vehicle speed.

The vehicle speed control unit further includes a target braking / driving force setting unit for setting a target braking / driving force required to match the second target vehicle speed set by the second target vehicle speed setting unit 106 with the vehicle speed. 107, the target braking / driving force setting unit 10
7, a braking / driving force command value setting unit 108 for distributing the target braking / driving force set by the internal combustion engine operation amount and the brake operation amount, and an internal combustion engine operation amount command value set by the braking / driving force command value setting unit 108. Internal combustion engine operation unit 10 for operating the engine
9, and a brake operation unit 110 that operates the brake according to the brake operation amount command value.

Each of the driving wheel speed detecting section 102-1 and the non-driving wheel speed detecting section 102-2 has a tire based on a rotational angular velocity obtained from a Hall IC type rotation sensor attached to the rotating shaft of the wheel. The wheel speed of is detected. Since the instantaneous values of the outputs of the wheel speed detection units 102-1 and 102-2 have large fluctuations, signals after averaging processing and filtering processing can be used.

The target braking / driving force setting section 107 can use a PID controller. Further, as the internal combustion engine operation unit 109 for operating the driving force of the vehicle, for example, one that operates the throttle opening degree can be adopted. Further, as the brake operation unit 110 for operating the braking force of the vehicle, for example, a unit that operates the pressure of the brake master cylinder can be adopted.

Next, the operation of the vehicle speed control device having the above configuration will be described. First, the speed control principle of the vehicle speed control device according to the first embodiment will be described. As shown in FIG. 2, when operating the internal combustion engine and the brake so that the actual vehicle speed Vrl matches the first target vehicle speed VSET1, the first target vehicle speed VSET1, which is the final target vehicle speed, Separately, a second target vehicle speed VSET2 is set, and control is performed so that the vehicle body speed Vrl matches the second target vehicle speed VSET2. Further, the slip rate slip of the drive wheel is estimated, and the change rate α of the second target vehicle speed VSET2 is limited according to the slip rate slip.

Thus, the first target vehicle speed, i.e., the first
The target vehicle speed VSET1 has a large change rate, and the driving force is increased to rapidly follow the target vehicle speed VSET1 and the vehicle is rapidly accelerated, so that the slip amount of the drive wheels increases, and the actual vehicle speed Vrl cannot be matched with the target vehicle speed. The occurrence of the situation is suppressed, and the vehicle speed is controlled to follow the second target vehicle speed that changes more gradually as indicated by β, so that the vehicle speed finally matches the target vehicle speed VSET1.

In order to realize this vehicle speed control principle, first,
The vehicle speed control device of the embodiment operates as follows. As shown in the flowchart of FIG. 3, the vehicle speed control program by the vehicle speed control device is canceled when the driver performs a brake operation or an accelerator operation (step S101), but is continued without the driver's intervention operation. Is performed (step S102).

The vehicle speed control routine is executed according to the flowchart shown in FIG. When the first target vehicle speed VSET1 is set by the first target vehicle speed setting unit 101 (step S2).
01), the drive wheel speed detector 102-1 detects the wheel speed Vw1 of the drive wheel, and the non-drive wheel speed detector 102-2 detects the wheel speed Vw2 of the non-drive wheel (steps S202, S202).
203). Then, the vehicle speed estimating unit 103 considers that no slip has occurred in the non-driving wheels, and determines the non-driving wheel speed V.
w2 is estimated as the vehicle speed Vrl (step S204).

Subsequently, the slip ratio estimating unit 104 executes a slip ratio estimating routine to estimate the slip ratio slip (step S205). This slip ratio estimating routine has the contents shown in the flowchart of FIG. 5. The drive wheel speed Vw1 is read from the drive wheel speed detector 102-1 (step S51), and the non-drive wheel speed detector 1-2 is executed.
-2 is read from the non-drive wheel speed Vw2 (step S5).
2) Return after calculating the slip ratio slip by the calculation of the following equation (step S53).

[0028]

(Equation 1) Subsequently, the change rate limit value setting unit 105 executes a change rate limit value setting routine of step S206 in the flowchart of FIG. 4 to set a change rate limit value LIM for the second target vehicle speed VSET2. The change rate limit value setting routine has the contents shown in the flowchart of FIG. 6, reads the slip rate slip calculated by the slip rate estimating unit 104 (step S61), and changes the change rate limit value LIM according to the estimated slip rate slip. And return (step S
62). For example, with reference to the table data TB1 shown in FIG. 7, the change rate limit change amount γ corresponding to the value of the read estimated slip rate slip is multiplied by the previous change rate limit value LIM to obtain a new change rate limit value LIM. Ask for.

[0029]

[Expression 2] LIM ← LIM * γ Thus, the rate-of-change limit value for the second target vehicle speed VSET2
When the LIM is obtained, next, the second target vehicle speed setting unit 106 executes a second target vehicle speed setting routine (step S20).
7). This second target vehicle speed setting routine has the contents shown in the flowchart of FIG. First, the first target vehicle speed VSET1 set by the first target vehicle speed setting unit 101 is read (step S71), and the change rate limit value setting unit 105 is set.
The rate-of-change limit value LIM set in (1) is read (step S
72). Then, the second target vehicle speed VSET2 is set so as to follow the first target vehicle speed VSET1, and the process returns (step S73).

During the process of setting the second target vehicle speed VSET2, the rate of change is limited as follows. For example, the difference ΔV between the previous second target vehicle speed VSET2_old and the newly set first target vehicle speed VSET1_new (= | VSET1_new-V
If SET2_old |) is within the range of the change rate limit value LIM, (Δ
V ≦ LIM), and substitutes the newly set first target vehicle speed VSET1_new as the second target vehicle speed VSET2_new (VSET2_n)
ew ← VSET1_new) If it exceeds the range of the change rate limit value LIM (ΔV> LIM), a value obtained by adding the change rate limit value LIM to the previous second target vehicle speed VSET2_old as the second target vehicle speed VSET2 is newly added. Is set as the second target vehicle speed VSET2_new (VSET2_new ← VSET2_old + LIM).

[0031]

(Equation 3) By setting the second target vehicle speed VSET2 (VSET2_new in the above calculation routine) in this way, the second target vehicle speed VSET2 is set to the final target vehicle speed, and the target braking / driving force setting unit 107 sets the PID. The required target braking / driving force is set by the control calculation (step S208). In response thereto, the braking / driving force command value setting unit 108 sets the driving force command value for the internal combustion engine operation unit 109 and the braking force command value for the brake operation unit 110. Is distributed (step S209), and when the brake operating unit 110 receives the braking force command value, the braking force is operated accordingly to decelerate the vehicle (step S210), or the internal combustion engine operating unit 109 changes the driving force command value. When it is received, the vehicle is accelerated by controlling the driving force accordingly (step S2).
11). Hereinafter, by repeating the above-described series of braking / driving force control, the vehicle speed is controlled so as to finally match the first target vehicle speed VSET1.

As a result, in the vehicle speed control device of the first embodiment, as shown in the time chart of FIG. 2, when the rate of change of the set value of the first target vehicle speed is large and slip occurs, The second target vehicle speed VSET2, which is the final target vehicle speed, is switched to control to gradually accelerate the vehicle so that the rate of change from the previous target vehicle speed is within the limit value LIM so as to reduce the slip ratio. Control is performed to follow the target vehicle speed while suppressing the occurrence of slip as much as possible even on a low μ road.

Next, a vehicle speed control device according to a second embodiment of the present invention will be described. In the vehicle speed control device according to the second embodiment, the second target vehicle speed setting unit 106 '
1 is characterized in that the arithmetic processing shown in the flowchart of FIG. 1 is executed, and the configuration of the other parts is the same as that of the first embodiment shown in FIG.

Next, the operation of the vehicle speed control device according to the second embodiment will be described. First, the operating principle is shown in FIG.
Description will be made based on a time chart of 0. During the vehicle speed control operation of the first embodiment shown in FIG. 2, a limit value LIM is set for the rate of change of the second target vehicle speed VSET2, which is the final target vehicle speed, and the previous target vehicle speed VSET2_old and the new target vehicle speed VSE
Although a limit value LIM is provided for the rate of change between T1_new and the target vehicle speed at which rapid acceleration is set, control is performed so as to follow gently, but in the vehicle speed control according to the second embodiment,
As shown in the time chart of FIG. 10, when the slip ratio exceeds the predetermined value slip_o even by the vehicle speed control of the first embodiment, the second target vehicle speed VSET2 is further restricted to generate a slip. It suppresses.

The operation of the vehicle speed control device according to the second embodiment is similar to that of the first embodiment shown in FIGS.
Based on the flowchart of FIG. However, the second target vehicle speed setting routine of step S207 executed by the second target vehicle speed setting unit 106 'is changed to a second target vehicle speed setting routine S207' shown in FIG.

The second target vehicle speed setting routine S207 'in the second embodiment will be described. As in the case of the first embodiment, first, the first target vehicle speed setting unit 101
The first target vehicle speed VSET1 set in step S7 is read (step S71), and the change rate limit value LIM set by the change rate limit value setting unit 105 is read (step S7).
2). Subsequently, the slip ratio slip estimated by the slip ratio setting unit 104 is read (step S73-1), and the non-driving wheel speed Vw2 detected by the non-driving wheel speed detector 102-2 is read (step S73-2). ). Then, based on these data, the second target vehicle speed VSET2 is set based on the judgment of the following equation (4), and the process returns (step S73-3).

[0037]

(Equation 4) That is, if the estimated slip rate slip is equal to or less than the slip rate threshold slip_o, the second target vehicle speed VSET2 (here, VSET2_new) is set in the same manner as in the determination processing of Expression 3, and the slip rate slip exceeds the threshold slip_o. In this case, the second target vehicle speed VSET2 is set to the wheel speed Vw2 of the non-driven wheels. The wheel speed Vw2 of the non-driven wheels matches the estimated vehicle speed Vrl.

When the second target vehicle speed VSET2 (VSET2_new in the above calculation routine) is set in this way, the second target vehicle speed VSET2 is set to the target vehicle speed, and the same as in the first embodiment, FIG. Steps S208 to S2 in 4
By the processing in step 11, the control for controlling the braking / driving force of the vehicle to match the vehicle speed Vrl (that is, the vehicle speed) to the second target vehicle speed VSET2 is repeated, so that the vehicle speed Vrl finally matches the first target vehicle speed VSET1. Control the vehicle speed.

Thus, in the vehicle speed control device of the second embodiment, as shown in the time chart of FIG. 10, when the rate of change of the set value of the first target vehicle speed is large and slip occurs, In order to reduce the slip ratio, the vehicle speed is controlled by the second target vehicle speed VSET2 which changes within a range where the vehicle speed change rate does not exceed the limit value LIM.
If the value of ip exceeds the predetermined threshold value slip_o, the second target vehicle speed VSET2 is set to a lower value to match the wheel speed Vw2 of the non-driving wheel, thereby preventing the slip ratio of the driving wheel from increasing. The control that follows the target vehicle speed is performed while preventing this.

Next, a vehicle speed control device according to a third embodiment of the present invention will be described. The vehicle speed control device according to the third embodiment is a device obtained by further improving the vehicle speed control device according to the second embodiment, and as shown in FIG. 12, a second target in the second embodiment. Vehicle speed setting unit 106 '
Is provided with a second target vehicle speed setting unit 106 ″, and the second target vehicle speed setting unit 106 ″
It is characterized in that the arithmetic processing of the flowchart of FIG. The other components are common to the first embodiment shown in FIG. 1 and the second embodiment shown in FIG.

Next, the operation of the vehicle speed control device according to the third embodiment will be described. First, the operating principle is shown in FIG.
3 and a time chart of FIG. At the time of the vehicle speed control operation of the second embodiment, assuming a vehicle in which the braking force by the brake acts on four wheels, the wheels of the non-driving wheels may slip significantly during the brake operation on a low μ road. is there. Then, as shown in FIG. 13, if the braking force is large, the non-driven wheels are locked, and the wheel speed Vw2 of the non-driven wheels may become zero. In this case, since the vehicle speed estimating unit 103 sets the wheel speed Vw2 of the non-driven wheels as the vehicle speed Vrl, the estimated vehicle speed Vrl also becomes zero.

In the case of the second embodiment, the slip ratio slip
Exceeds the threshold value slip_o, the second target vehicle speed VSET2 is set to the wheel speed Vw2 of the non-driven wheels, which is the estimated vehicle speed Vrl, as the second target vehicle speed VSET2. May be awkward.

Therefore, in order to improve this, the control is changed to the control shown in FIG. In other words, the brake operation is not performed by the driver's brake operation, but by the brake operation unit 11 by the device.
When a large braking is applied by the automatic braking operation of 0 and the slip ratio slip exceeds a predetermined threshold value slip_o, the wheel speed Vw2 of the non-driving wheel is 0 (this wheel speed Vw2 is estimated to be the estimated vehicle speed Vrl).
Therefore, if the vehicle speed Vrl also becomes 0), the second period immediately before the wheel speed Vw2 = 0 becomes the period indicated by the box A.
By maintaining the target vehicle speed VSET2, the second target vehicle speed is prevented from dropping sharply, the brake operation is released, the non-driven wheels are quickly released from the lock, and the stable vehicle speed control can be continued. You do it.

In order to realize this vehicle speed control, in the vehicle speed control device of the third embodiment, the second target vehicle speed setting unit 106 ″ sets the second target vehicle speed setting in step S 207 in the flowchart of FIG. Instead of the routine, FIG.
A second target vehicle speed setting routine S207 ″ shown in the flowchart of FIG. 5 is executed.

A second target vehicle speed setting routine S207 ″ in the third embodiment will be described. As in the second embodiment, first, the first target vehicle speed setting section 1
01 is read (step S71), and the change rate limit value LIM set by the change rate limit value setting unit 105 is read (step S7).
2). Subsequently, the slip ratio slip estimated by the slip ratio setting unit 104 is read (step S73-1), and the non-driving wheel speed Vw2 detected by the non-driving wheel speed detector 102-2 is read (step S73-2). ). In the third embodiment, subsequently, the brake operating unit 1
10 brake operation amount Tbrake is read (step S
73-31).

Then, based on these data, the second target vehicle speed VSET2 is set based on the following equation (5), and the process returns (step S73-32).

[0047]

(Equation 5) That is, the brake operation amount Tbrak of the brake operation unit 110
If e exceeds the predetermined value and the non-driven wheels are locked, the second target vehicle speed VSET2_new is set to the previous value VSE
Keep T2_old. However, the brake operation amount Tbr
If ake is equal to or less than the predetermined value, no locking of the non-driven wheels has not occurred, so the slip ratio sl is similar to the second embodiment.
Make settings according to the size of ip. That is, if the estimated slip rate slip is equal to or less than the slip rate threshold slip_o, the second target vehicle speed VSET2 (here, VSET2_new) is set in the same manner as in the determination processing of Expression 3, and the slip rate slip is set to the threshold slip.
If it exceeds _o, the second target vehicle speed VSET2 is set to the wheel speed Vw2 of the non-driven wheels.

When the second target vehicle speed VSET2 (VSET2_new in the above calculation routine) is set in this way, the second target vehicle speed VSET2 is set to the target vehicle speed, and the same as in the first embodiment, FIG. Steps S208 to S2 in 4
By the processing in step 11, the control for controlling the braking / driving force of the vehicle to match the vehicle speed Vrl (that is, the vehicle speed) to the second target vehicle speed VSET2 is repeated, so that the vehicle speed Vrl finally matches the first target vehicle speed VSET1. Control the vehicle speed.

Thus, in the vehicle speed control device according to the third embodiment, in addition to the same operation and effect as the second embodiment, as shown in the time charts of FIGS. When a large brake is applied by the automatic brake operation of the brake operation unit 110 by the present device side, not by the brake operation of the present device, by maintaining the second target vehicle speed VSET2 before the brake operation is performed, It is possible to prevent the second target vehicle speed from dropping abruptly, release the large brake operation, release the non-driven wheels quickly from the lock, and continue stable vehicle speed control.

FIG. 16 shows a graph of a simulation result according to the third embodiment. As is clear from the simulation results, the frequency of occurrence of slip is remarkably reduced, the frequency of brake control and throttle control is also reduced as compared with the simulation result of the conventional example shown in FIG. It can be seen that the following control is realized.

[Brief description of the drawings]

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

FIG. 2 is a time chart illustrating a control principle executed by the embodiment.

FIG. 3 is a flowchart of a main routine of vehicle speed control according to the embodiment.

FIG. 4 is a flowchart of a vehicle speed control routine according to the embodiment.

FIG. 5 is a flowchart of a slip ratio setting routine according to the embodiment.

FIG. 6 is a flowchart of a change rate limit value setting routine according to the embodiment.

FIG. 7 is a table of table data used for a change rate limit value setting process according to the embodiment.

FIG. 8 is a flowchart of a second target vehicle speed setting routine according to the embodiment.

FIG. 9 is a block diagram showing a configuration of a second embodiment of the present invention.

FIG. 10 is a time chart for explaining a control principle executed by the embodiment.

FIG. 11 is a flowchart of a second target vehicle speed setting routine according to the embodiment.

FIG. 12 is a block diagram showing a configuration according to a third embodiment of the present invention.

FIG. 13 is a first time chart illustrating a control principle executed by the embodiment.

FIG. 14 is a second time chart illustrating a control principle executed by the embodiment.

FIG. 15 is a flowchart of a second target vehicle speed setting routine according to the embodiment.

FIG. 16 is a graph showing a simulation result of vehicle speed control according to the embodiment.

FIG. 17 is a graph showing a simulation result of vehicle speed control according to a conventional example.

[Explanation of symbols]

 Reference Signs List 101 First target vehicle speed setting unit 102-1 Driving wheel speed detecting unit 102-2 Non-driving wheel speed detecting unit 103 Body speed estimating unit 104 Slip rate estimating unit 105 Change rate limit value setting unit 106, 106 ', 106 ″ Second target vehicle speed setting unit 107 Target braking / driving force setting unit 108 braking / driving force command value setting unit 109 Internal combustion engine operation unit 110 Brake operation unit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 29/02 311 F02D 29/02 311A 3G301 41/14 320 41/14 320D G01P 15/00 G01P 15/00 BF term (reference) 3D037 FA23 FA25 FB00 FB03 3D041 AA48 AB01 AC04 AC26 AD10 AD41 AD51 AE04 AE41 AF01 AF09 3D044 AA45 AB01 AC01 AC15 AC24 AC26 AD04 AD21 AE04 AE14 AE21 3D046 BB23 EE01 GG02 H03 H01 H23H01 H03H01 GG02 H03 H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01H23H01) CB14 DB03 DB04 DB05 DB15 DB17 DB18 EA09 EB04 FA07 FA08 FB02 FB03 3G301 JA38 KB00 KB02 LA01 NA08 NA09 ND02 NE06 NE18 PF01Z PF03Z PF05Z

Claims (4)

[Claims] 1. A first target vehicle speed setting means for setting a first target vehicle speed according to a driving situation; a non-driving wheel speed detecting means for detecting a wheel speed of a non-driving wheel; and a wheel speed of a driving wheel. Wheel speed detecting means for detecting vehicle speed, vehicle speed estimating means for estimating vehicle speed, slip rate estimating means for estimating slip rate, and change rate limiting for setting a vehicle speed change rate limit value based on the slip rate. Value setting means; second target vehicle speed setting means for setting a second target vehicle speed such that the vehicle body speed follows the first target vehicle speed within a range of the vehicle speed change rate limit value; And a braking / driving force control means for controlling the braking / driving force of the vehicle such that the vehicle speed matches the target vehicle speed. 2. The vehicle speed control device according to claim 1, wherein the vehicle speed estimating means sets a wheel speed of the non-driving wheel to the vehicle speed, and the slip ratio estimating means sets a wheel speed of the non-driving wheel to the vehicle speed. A vehicle speed control device for estimating the slip ratio based on a difference between the driving wheel speed and the wheel speed. 3. The vehicle speed control device according to claim 1, wherein said second target vehicle speed setting means sets a wheel speed of said non-driving wheel to said second speed when said slip ratio is equal to or greater than a predetermined value. A vehicle speed control device for setting a target vehicle speed. 4. The vehicle speed control device according to claim 3, wherein the second target vehicle speed setting means is configured to set the slip ratio to a predetermined value or more when the vehicle brake is automatically operated by the braking / driving force control means. A vehicle speed control device for maintaining the second target vehicle speed set immediately before the vehicle speed control.