JP2581982B2 - Vehicle drive wheel slip control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention (1) Industrial application field The present invention relates to a reference value setting means for setting a reference value of a slip state of a drive wheel, and a reference value setting means for determining a slip state of the drive wheel. A driving wheel slip control device for a vehicle, comprising: a driving wheel torque reducing means for reducing the torque of the driving wheel when the value exceeds the value.

(2) Prior Art Conventionally, as a drive wheel slip control device for a vehicle, one that changes a reference value for obtaining an appropriate slip ratio of a drive wheel based on a friction coefficient of a road surface estimated from longitudinal acceleration of the vehicle has been proposed. (See, for example, Japanese Patent Publication No. 58-20051). A method of correcting the yaw motion by detecting that the yaw motion of the vehicle deviates from the steering characteristic required by the driver of the vehicle has been proposed by the present applicant (JP-A-63-2198).
No. 28).

(3) Problems to be solved by the invention By the way, in the above-mentioned conventional drive wheel slip control device,
Simply estimate the friction coefficient of the road surface from the longitudinal acceleration of the vehicle,
Since the reference speed is changed by the estimated friction coefficient, for example, if the vehicle accelerates during cornering near the limit lateral force of the tire on a high grip road, the longitudinal acceleration cannot be obtained greatly, and it is erroneously judged as a low grip road and a low reference value is obtained. May be selected. Further, when the road surface grip force is low, the limit lateral force of the tire is originally low, and particularly in a rear-wheel drive vehicle, a small driving force change (increase) easily causes a rearward swinging state. Therefore, the reference slip value at the time of starting acceleration of the vehicle is It is better to keep it low, but if it is determined that the grip is high, unless the reference value is raised quickly, the acceleration performance will be deteriorated.

Further, in the above method proposed by the present applicant, the reference speed under a specific road surface-tire condition obtained experimentally by a deviation of the actual yaw rate from the reference yaw rate during cornering of a vehicle required to maintain the lateral force of the tire is calculated. In the condition of high grip, the slip of the drive wheels is rather suppressed and the acceleration performance is deteriorated, the drifting is hindered by the power-on, and the drive after passing the corner is performed. There were inconveniences such as a delay in the rise of force, and as a result, there were cases where sporty running became difficult and cases where original acceleration could not be obtained.

A first object of the present invention is to estimate a grip state of a road surface and a tire as a total grip force and change a reference value of a slip of a driving wheel, thereby accurately detecting a change in a road surface and a tire to obtain a high grip state. The object of the present invention is to effectively suppress the hip swing in a low grip state without sacrificing the acceleration of the vehicle.

A second object of the present invention is to estimate a grip state between a road surface and a tire as a total grip force, and pay attention to the fact that a control delay between a slip state of a drive wheel and a reference value thereof is different, so that control suitable for the total grip force is performed. In providing responsiveness.

B. Configuration of the Invention (1) Means for Solving the Problems In order to achieve the above object, the present invention provides a drive wheel slip which can obtain an appropriate slip state as shown in FIG. A drive wheel slip of a vehicle comprising: a reference value setting means for setting a reference value; and a drive wheel torque reducing means for reducing a torque of the drive wheel when a slip state of the drive wheel exceeds the reference value. In the control device, a grip force calculating means for estimating a total grip force of the driving wheels corresponding to a total acceleration obtained based on the longitudinal acceleration and the lateral acceleration;
The first feature is that reference value correcting means 8 that corrects the reference value in accordance with the total grip force output by the controller is provided.

As shown in FIG. 1 as a claim correspondence diagram, the present invention provides a reference value setting means 7 for setting a reference value of a drive wheel slip which can obtain an appropriate slip state, A driving wheel slip control device for a vehicle, comprising: a driving wheel torque reducing unit 10 for reducing the torque of the driving wheel when the driving wheel slip exceeds the driving wheel torque. Grip force calculation means 13 for estimating total grip force
And a driving wheel torque reduction characteristic changing unit 19 that changes the relationship of the driving wheel torque reduction amount of the driving wheel torque reduction unit 10 with respect to the slip state according to the total grip force output by the gripping force calculation unit 13. The second feature is to provide.

(2) Operation According to the first feature of the present invention described above, the total grip force of the tire is estimated by the grip force calculating means during the running of the vehicle, and the reference is determined according to the estimated total grip force. The value correcting means can increase the reference value of the slip state of the drive wheel calculated by the reference value setting means. As a result, the reference value is increased as the total grip force of the tire is increased, so that a power drift running on a dry road surface and a quick rise of a driving force after passing a corner can be achieved. In addition, even when tires having different gripping forces are mounted, a reference value adapted to the tire can be obtained, so that optimal control of driving wheel slip can always be performed.

According to the second feature of the present invention, the total grip force of the tire is estimated by the grip force calculating means during running of the vehicle,
Since the control response speed of the driving wheel torque can be changed according to the estimated magnitude of the total grip force, the optimum driving wheel slip control characteristic can be obtained even when the road surface condition or the tire changes.

(3) Example Hereinafter, an example of the present invention will be described with reference to the drawings.

In FIG. 2, left and right driving wheel speeds of a vehicle, for example, left and right rear wheel speeds Wrl and Wrr of a rear wheel driving vehicle are detected by a rear wheel speed detector 1 and left and right front wheel speeds Wfl and Wfr as driven wheel speeds. Are respectively detected by the front wheel speed detector 2. The left and right rear wheel speeds Wrl, Wrr detected by the rear wheel speed detector 1 are input to the drive wheel speed calculation means 3, where the drive wheel speed Vw is changed to the left and right rear wheel speeds Wrl, Wrl.
It is calculated as the average value of Wrr. On the other hand, the left and right front wheel speeds Wfl, Wfr detected by the front wheel speed detector 2 are input to the vehicle speed calculating means 4, where the vehicle speed Vv is calculated as an average value of the left and right front wheel speeds Wfl, Wfr.

The left and right front wheel speeds Wfl and Wfr detected by the front wheel speed detector 2 are input to the wheel speed difference calculation means 5, where the left and right wheel speed differences Wfl-Wfr are calculated. In the actual yaw rate calculating means 6, the wheel speed difference Wfl-Wfr passes through a low-pass filter to remove the influence of the resonance component of the vibration of the suspension on the front wheel speeds Wfl and Wfr, and is used in a low frequency region used for controlling the vehicle motion. (Eg 10 Hz or less) filtered to leave the actual yaw rate Y
Is calculated.

The vehicle speed Vv calculated by the vehicle speed calculating means 4 is a reference value setting means 7 representing a reference value of the slip state of the drive wheels.
Is input to The reference value setting means 7 calculates the first reference speed VR1, the target reference speed VRP, the second reference speed VRP of the driving wheel speed from the following formulas, formulas, and formulas according to the input vehicle speed Vv.
The reference speed VR2 is calculated.

_{VR1 = K 1 * Vv ...... VRP} = K P * Vv ...... VR2 = K 2 * Vv ...... _{where, K 1, K P, K} 2 is K ₁ <K _P <K ₂ becomes constant, thus VR1 <VRP <VR2.

In the above formulas, the first reference speed VR1 indicates a reference speed at which the slip control of the drive wheels is started by means such as decreasing the output of the engine when the speed of the drive wheels exceeds the value, and the target reference speed. VRP indicates a driving wheel speed at which a proper slip ratio of the driving wheel is obtained, and a second reference speed VR2
Indicates the reference speed at which the slip rate of the drive wheel becomes excessive when the speed of the drive wheel reaches that value, for example, the engine is controlled to the minimum output. At this time, the condition of the road surface is detected at the same time, and the control is performed such that the proportional constants K ₁ , K _P , and K ₂ become larger in the case of a rough road where the slip of the drive wheels is unlikely to occur than in the case of the normal road. It is also possible.

The first reference speed VR1, the target reference speed VRP, and the second reference speed VR2 set by the reference value setting means 7 are inputted to the reference value correcting means 8, and as will be described later in detail, the grip state of the tire and the steering of the vehicle will be described. Corrected according to the state. Modified first reference speed VR corrected by reference value correcting means 8
1 'and the drive wheel speed Vw calculated by the drive wheel speed calculation means 3 are input to the control start / end determination means 9, and when the drive wheel speed Vw exceeds the modified first reference speed VR1', the drive torque reduction means 10 is operated. Command the start of the slip control of the drive wheels.
In addition to the output signal of the control start / end determining means 9, the driving wheel torque reducing means 10 further includes a corrected target reference speed VRP 'and a corrected second reference speed VR2' from the reference value correcting means 8, and a driving wheel speed calculating means. 3 is input, and the driving wheel torque is adjusted so that the driving wheel speed Vw converges to the corrected target reference speed VRP '.
Feedback control is performed by PID control obtained by multiplying the integrated value of the deviation and the drive wheel acceleration ΔVw by the control gains Kp, Ki, and Kd, respectively. The drive wheel torque reducing means 10 includes a means for controlling the output torque of the engine or a means for controlling the braking force of the vehicle. And the latter is executed by decreasing the brake oil pressure.

Next, the first reference speed VR based on the grip state of the tire
1. The correction of the target reference speed VRP and the second reference speed VR2 will be described.

The vehicle speed Vv output from the vehicle speed calculating means 4 is input to the longitudinal acceleration calculating means 11, where the longitudinal acceleration Fg of the vehicle is calculated based on the history of the differential value of the vehicle speed Vv and the history of the vehicle speed Vv. Is calculated from

(K) = σ1 * (k−1) + σ2 * (k−2) + σ3 *
(K-3) + τ0 * Vv (k) + τ1 * Vv (k-1) + τ2 * Vv (k−
2) + τ3 * Vv (k -3) ... Fg = K 3 * (k) ... here, σ1, σ2, σ3, τ0 , τ1, τ2, τ3, K 3 is a constant, subscript (k, k- 1, k−2, k−3) indicate the current value, the previous value, the value before the previous time, and the value before the previous time, respectively.

On the other hand, the vehicle speed calculated by the vehicle speed calculating means 4
Vv and the actual yaw rate Y calculated by the actual yaw rate calculating means 6 are input to the lateral acceleration calculating means 12, where the lateral acceleration Lg of the vehicle body is calculated from the following equation.

Lg = K ₄ * Vv * Y Here, K ₄ is a constant.

The longitudinal acceleration Fg and the lateral acceleration Lg of the vehicle body calculated as described above are input to the tire grip force calculating means 13,
Based on the following equation, a total grip force Tg in terms of driving wheel acceleration is calculated as a total acceleration which is a root mean square of the longitudinal acceleration Fg and the lateral acceleration Lg.

Subsequently, in the reference value correction amount determining means 14, the first reference speed VR1, the target reference speed VRP,
The correction amount of the second reference speed VR2 is determined. That is, as shown in FIG. 3, the correction amount VRPg of the target reference speed VRP is zero when the total grip force Tg is smaller than the lower limit value TgL, and when the total grip force Tg is larger than the upper limit value TgH. Constant value (for example, 5km / h), lower limit TgL and upper limit
Although it is set to increase linearly during TgH for easy calculation, it may be a non-linear function according to the characteristics of the tire and the like. Correction amount VR1g of first reference speed VR1
The correction amount VR2g of the second reference speed VR2 is also the same as the correction amount VRPg of the target reference speed VRP, that is, is set in the range of 0 to 5 km / h.
VR1g, VRPg, and VR2g can be individually set.

The correction amounts VR1g, VRPg, VR2g determined by the reference value correction amount determining means 14 are input to the reference value correcting means 8, and the first reference speed VR1 is set in accordance with the increase in the total grip force Tg of the tire. , The target reference speed VRP and the second reference speed VR2 are corrected. In this way, since the initial reference speed is set according to the low grip force, the hip swing is suppressed at the start acceleration under the low grip state, and when it is determined that the grip force is high, the reference speed is immediately changed to the high reference speed. Therefore, good acceleration can be secured.

Further, the total grip force is calculated by the grip force calculating means 13.
When Tg is obtained, the output thereof sends the feedback gains Kp, Ki, Kd for giving the control speed suitable for the grip force at that time by the drive wheel torque reduction characteristic changing means 19 to the drive wheel torque reduction means. Thus, when the grip force is low, a small gain is supplied because the delay from the reduction of the drive wheel torque to the elimination of the inertia of the wheel is large, and when the grip force is high, a large gain is supplied.

Next, the correction of the first reference speed VR1, the target reference speed VRP, and the second reference speed VR2 based on the steering state will be described.

The turning angle δ output from the turning angle detector 15 attached to the steering wheel is input to the reference yaw rate calculating means 16 together with the vehicle speed Vv output from the vehicle speed calculating means 4. The reference yaw rate W output from the reference yaw rate calculation means 16 and the actual yaw rate Y output from the actual yaw rate calculation means 6 are input to the US / OS determination means 17.
Based on the difference between W and Y, whether the vehicle is in the understeer state or the oversteer state, and the degree of deviation of the actual yaw rate Y from the reference yaw rate W are calculated. continue,
The reference value correction amount determining means 18 corrects the first reference speed VR1, the target reference speed VRP, and the second reference speed VR2 according to the steering state of the vehicle, and corrects three target reference speeds VR1s, VRPs, VR2s is determined. Correction amount VR1s, V above
The values of RPs and VR2s are, for example, to increase the drive wheel torque when a tendency of understeer occurs during steering in a rear-wheel drive vehicle, and to decrease the drive wheel torque when a tendency of oversteer occurs, This is determined to prevent the vehicle from turning in an undesirable direction.

Next, the operation of the embodiment of the present invention having the above-described configuration will be described.

Based on the vehicle speed Vv output from the vehicle speed calculating means 4,
The reference value setting means 7 includes a first reference speed VR1 at which the slip control of the drive wheels is started when the drive wheel speed Vw exceeds the value, a target reference speed VRP indicating the drive wheel speed Vw at which an appropriate slip ratio is obtained, and When the drive wheel speed Vw reaches that value, it is determined that the slip ratio of the drive wheels has become excessive, and the second reference speed VR2 that is controlled to minimize the drive wheel torque is determined. In the reference value correcting means 8, the first reference speed
VR1, target reference speed VRP, and second reference speed VR2 are correction amounts VR1g, VRPg, determined based on the total grip force Fg of the driving wheels.
The following correction is performed by VR2g and correction amounts VR1s, VRPs, and VR2s determined according to the understeer state or the oversteer state of the vehicle.

VR1 '= VR1 + VR1g + VR1s VRP' = VRP + VRPg + VRPs VR2 '= VR2 + VR2g + VR2s When the driving wheel speed Vw exceeds the corrected first reference speed VR1' corrected by the reference value correcting means 8, the control wheel start / end determining means 9 instructs the driving wheels. The torque reduction means 10 starts the slip control of the drive wheels, and the engine speed is adjusted so that the drive wheel speed Vw converges to the corrected target reference speed VRP 'between the corrected first reference speed VR1' and the corrected second reference speed VR2 '. The drive wheel torque is controlled by means such as increase or decrease of the output torque or increase or decrease of the braking force, whereby an appropriate slip ratio is maintained while preventing excessive slip of the drive wheel.

In this way, when the total grip force Tg of the tire changes according to the running state of the vehicle or the type of the tire, the control is performed so that the reference value of the slip state of the drive wheel increases according to the increase in the total grip force Tg. Therefore, sporty traveling can be performed without impairing the slip control function of the drive wheels.

As described above, the embodiments of the present invention have been described in detail. However, the present invention is not limited to the above embodiments, and various small design changes can be made without departing from the present invention described in the claims. It is possible to do.

For example, control for correcting the first reference speed VR1, the target reference speed VRP, and the second reference speed VR2 in accordance with a steering state such as understeer or oversteer is not essential, and can be omitted as necessary. Further, in the present embodiment, the drive wheel reference speed is used as the reference value of the drive wheel slip. However, the present invention is not limited thereto, and any one of the drive wheel slip ratio and the reference slip ratio value, the drive wheel acceleration and the reference acceleration value, or It is good also as those combinations. Further, in the present embodiment, the reference value is corrected depending on the total grip force, but after the reference value reaches a maximum value in a series of correction operations, the reference value is returned to the original value by a time function. Is also good.

C. Effects of the Invention As described above, according to the first aspect of the present invention, the total grip force of the tire is calculated by the grip force calculating means, and the reference value correcting means is driven according to the magnitude of the total grip force. Since the reference value of the wheel slip state is corrected, the reference value can be increased as the overall grip force of the tire increases. As a result, for example, not only power drift running on dry roads and quick rise from corners are possible, but also summer tires,
When the tires are changed to snow tires, spike tires, or the like, a slip ratio corresponding to each tire is obtained, and optimal control of the drive wheel slip can always be performed.

According to the second feature of the present invention, the drive wheel torque reduction characteristic changing means changes the control response speed of the drive wheel torque reduction means according to the total grip force estimated by the grip force calculation means. The control response speed increases as the value increases, and good control performance can be obtained.

[Brief description of the drawings]

1 is a diagram corresponding to claims of the present invention, FIGS. 2 and 3 show an embodiment of the present invention, FIG. 2 is a block diagram thereof, and FIG. 3 is a total grip force Tg and a target reference speed. 9 is a graph showing the relationship between VRP correction amounts VRPg. 7: Reference value setting means, 8: Reference value correction means, 10: Driving wheel torque reduction means, 13: Grip force calculation means, 19: Driving wheel torque reduction characteristic changing means, Fg: longitudinal acceleration, Lg: lateral acceleration, Tg … Overall acceleration

Continuation of front page (72) Inventor Yoshiyasu Akuta 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda R & D Co., Ltd. (56) References JP-A-63-31859 (JP, A) JP-A-63- 31863 (JP, A) JP-A-63-149236 (JP, A)

Claims (2)

(57) [Claims] A reference value setting means (7) for setting a reference value of a drive wheel slip capable of obtaining an appropriate slip state, and a torque of the drive wheel when the slip state of the drive wheel exceeds the reference value. To reduce drive wheel torque (10)
A driving force slip calculating device for estimating a total grip force (Tg) of the driving wheel corresponding to a total acceleration obtained based on a longitudinal acceleration (Fg) and a lateral acceleration (Lg). (13) and a reference value correcting means (8) for correcting the reference value according to the total grip force (Tg) output from the grip force calculating means (13). Drive wheel slip control device. 2. A reference value setting means (7) for setting a reference value of a drive wheel slip capable of obtaining an appropriate slip state, and a torque of the drive wheel when the slip state of the drive wheel exceeds the reference value. To reduce drive wheel torque (10)
A driving force slip calculating device for estimating a total grip force (Tg) of the driving wheel corresponding to a total acceleration obtained based on a longitudinal acceleration (Fg) and a lateral acceleration (Lg). (13) and a relationship between the slip state and the drive wheel torque reduction amount of the drive wheel torque reduction unit (10) is changed according to the total grip force (Tg) output by the grip force calculation unit (13). A drive wheel slip control device for a vehicle, comprising: a drive wheel torque reduction characteristic changing means (19).