JP2907529B2 - Vehicle slip control device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vehicle slip control device.

(Prior Art) In order to prevent the drive wheels from slipping due to excessive driving torque and deteriorating the acceleration when the vehicle is accelerating, the slip amount of the drive wheels is detected, and the slip amount of the drive wheels is set to a target Traction control that controls the application of an engine output or a braking force to wheels so as to obtain a value (reduces the engine output or increases the braking force) is generally known.

Then, in performing the traction control, there is a proposal to obtain the slip amount in consideration of a wheel speed difference generated between the inside and outside drive wheels when the vehicle turns. That is, Japanese Patent Application Laid-Open No. 62-60937 discloses that, based on the wheel speeds of inner and outer driven wheels during turning of a vehicle,
It is disclosed that the wheel speed of each of the inner and outer drive wheels at a slip ratio of zero is determined, and the slip amount is calculated based on each wheel speed at the zero slip ratio and the actual wheel speed.

(Problem to be Solved by the Invention) A first problem of the present invention is to determine a slip amount of each drive wheel in slip control of a vehicle, which occurs between both inside and outside drive wheels when the vehicle turns. It is to obtain a desired slip control characteristic while taking the wheel speed difference into consideration.

A second object of the present invention is to prevent the vehicle from exhibiting an excessive understeer tendency while solving the first object.

(Means for Solving the Problems) The present invention provides a method for correcting the wheel speed or the slip amount of the drive wheels in consideration of the difference between the wheel speeds of the inner and outer drive wheels at the time of cornering. In addition, a correction value using the vehicle speed and the turning radius as factors as factors for this correction is stored in advance, and a desired slip control characteristic is determined by the method of setting the correction value. To be obtained.

A specific means for this is a vehicle slip control device that controls the driving of the driving wheels so that the slip amount of the driving wheels with respect to the road surface becomes a target value, and a vehicle speed detecting unit that detects a vehicle speed. Wheel speed detecting means for detecting the wheel speed of the driving wheel; turning radius detecting means for detecting the turning radius of the vehicle; vehicle body speed detected by the vehicle speed detecting means; and wheels detected by the wheel speed detecting means. An apparent slip amount calculating means for calculating an apparent slip amount of the drive wheel based on the speed; and a turning of the vehicle for correcting a slip amount based on a wheel speed difference between an inner wheel and an outer wheel during turning of the vehicle. Correction value storage means for storing a correction value set as a factor of a radius and a vehicle speed, a vehicle speed detected by the vehicle speed detection means, and a vehicle detected by the turning radius detection means Correction value calculation means for obtaining a correction value from the correction value storage means based on the turning radius; and a wheel speed detected by the wheel speed detection means based on the correction value obtained by the correction value calculation means. And a correcting means for correcting the apparent slip amount obtained by the apparent slip amount calculating means (hereinafter referred to as first means).

In order to solve the second problem, a turning radius corresponding to a steering angle is used as the turning radius of the vehicle in the above means.

Specifically, means for detecting a steering angle is provided, and the turning radius detecting means obtains the turning radius corresponding to the steering angle, and the correction value storage means is set so that the slip amount increases as the turning radius decreases. This correction value is stored (hereinafter referred to as a second means).

(Operation) The difference in wheel speed between the inner wheel and the outer wheel during turning of the vehicle changes according to the turning radius of the vehicle and the vehicle speed. In the first means, the turning radius and the vehicle diameter are determined. Since the wheel speed or the slip amount of the drive wheel is corrected based on the correction value set as the factor, the slip amount of the drive wheel finally obtained is not the apparent slip amount determined from the vehicle body speed and the wheel speed, but This is a substantial slip amount in consideration of the wheel speed difference. Therefore, by controlling the driving of the drive wheels using the slip amount obtained by this correction, the desired slip control can be performed.

Then, since the correction value is set and stored as a factor of the turning radius and the vehicle speed of the vehicle, this setting is corrected so that the slip amount is determined to be large, for example. It is possible to start the slip control at an early stage or to increase the slip control amount, that is, to tune the slip control characteristics to desired characteristics.

When the vehicle shows an understeer tendency, the actual turning radius of the vehicle becomes larger than the turning radius corresponding to the steering angle. And, as in the second means, when the turning radius corresponding to the steering angle is used as the turning radius of the vehicle, and the correction value is set so that the slip amount increases as the turning radius decreases, when the vehicle shows an understeer tendency, The turning radius used for calculating the correction value is smaller than the actual turning radius, so that the correction amount is larger and the slip amount is larger than when the actual turning radius is used as a reference. As a result, it is possible to prevent the vehicle from exhibiting an excessive understeer tendency by starting the slip control early, that is, by reducing the drive torque of the drive wheels early, or to reduce the slip control amount. Many more
The understeer tendency can be reliably suppressed.

(Effects of the Invention) Therefore, according to the first means, the wheel speed or the slip amount of the drive wheel is corrected based on the correction value previously set and stored as the turning radius and the vehicle speed of the vehicle as factors. Therefore, the slip control can be performed in consideration of the wheel speed difference between the outer wheel and the outer wheel during turning of the vehicle, and the maneuverability or running stability during turning can be improved, and A desired slip control characteristic can be obtained by setting the correction value.

According to the second means, since the turning radius corresponding to the steering angle is used as the turning radius of the vehicle, and the correction value is set so that the slip amount increases as the turning radius decreases, the vehicle exhibits an excessive understeer tendency. Can be prevented.

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

 FIG. 1 shows the overall configuration of the embodiment.

First, in the vehicle, the left and right front wheels 2FL, 2FR are set as drive wheels,
The left and right rear wheels 2RL, 2RR are driven wheels. That is,
A V-type 6-cylinder engine 1 is mounted at the front of the vehicle body. The generated torque of the engine 1 passes through an automatic transmission 3 and a differential device 4 and then to a left front wheel 2FL via a left drive shaft 5L and to a right drive shaft. 5R
Via the right front wheel 2FR.

The vehicle includes a slip control unit 8 that controls the driving of the drive wheels 2FL and 2FR so that the slip amount of the drive wheels 2FL and 2FR relative to the road surface becomes a target value.

The control means 8 includes a brake sensor 6 for detecting whether or not the four wheels 2FL, 2FR, 2RL, 2RR are braked,
The steering angle sensor 7 for detecting the steering angle of the steering wheel of the vehicle, the four wheels described above
Wheel speed sensors 9FL, 9 that detect the wheel speed of 2FL, 2FR, 2RL, 2RR
FR, 9RL, 9RR, and each signal from the engine speed sensor 28 for detecting the engine speed are input, signal processing is performed, and an ignition timing control signal and fuel injection for reducing the output torque to the engine 1 are performed. It outputs a limit signal.

For this purpose, the control means 8 includes an input interface for receiving signals from the sensors, a CPU and a ROM.
A microcomputer comprising a RAM, an output interface, and a drive circuit for driving the igniter and the fuel injection device are provided.The ROM is provided with a control program required for slip control, various maps or tables, and the RAM is provided with a RAM. Various memories necessary for executing the control are provided. The control means 8 includes a slip determination threshold value setting means 32, a slip amount calculation means 33, a slip determination means 34, a control target value setting means 35, a control level calculation means 36, and an engine output control means 37. It has.

[Slip Amount Calculation] First, the slip calculation means 33 will be described. This is based on the means 11 for calculating the apparent slip amount of the drive wheels 2FL and 2FR, and the wheel speed difference between the inner wheel and the outer wheel during turning of the vehicle. A storage means for storing a slip amount correction value; a correction value calculation means for calculating a slip amount correction value from the storage means; and a correction means for correcting the apparent slip amount. Based on the amount, the average slip amount is calculated by the average slip amount calculating means 15, and the maximum slip amount is calculated by the maximum slip amount calculating means 16.

The apparent slip amount calculating means 11 includes a vehicle speed Vr obtained by the vehicle speed detecting means 21 and wheel speed sensors 9FL and 9FR.
Based on the wheel speeds VFL, VFR of the drive wheels (front wheels) obtained by the above, the apparent slip amounts SFL, SFR of the drive wheels are obtained by the following equation (1).

SFL = VFL-Vr SFR = VFR-Vr In this case, the vehicle speed detecting means 21 is provided by the wheel speed sensors 9RL and 9R.
Wheel speeds VRL, VR of left and right driven wheels (rear wheels) obtained by R
The higher wheel speed of R is detected as the vehicle speed Vr.

The correction value storage means 12 stores a turning radius R (unit;
m) and the vehicle speed Vr (unit: km / h) as factors, each slip amount correction value for the driving inner wheel and the driving outer wheel
k1 and k2 are stored. The set slip amount correction values k1 and k2 are shown in the following k1 table and k2 table.

Note that the difference between the correction terms of the left and right wheels is different from k1 and k2, as the vehicle speed Vr, without using the average value of the wheel speeds VRL and VRR of the left and right rear wheels, and using the higher wheel speed as the vehicle speed Vr Because it is.

When the vehicle is turning, based on the steering angle θH obtained by the steering angle sensor 7, the correction value calculating means 13 calculates the vehicle speed Vr detected by the vehicle speed detecting means 21 and the turning radius calculating means 22. The slip amount correction values k1 and k2 are obtained by three-dimensional interpolation from the correction value storage means 12 (the above-described k1 table and k2 table) based on the turning radius of the vehicle calculated by the above. In this case, the turning radius calculating means 22
Is based on the absolute value of the steering angle θH detected by the steering angle sensor 7, and the next R which is set in advance to correspond to the steering angle in a unified manner.
From the table, a steering angle-corresponding turning radius R (substantially corresponding to the turning radius in neutral steering) is obtained by linear interpolation.

The slip amount correction means 14 calculates the slip amount correction value obtained by the correction value calculation means 13 based on the steering angle θH obtained by the steering angle sensor 7 if the vehicle is turning.
The apparent slip amounts SFL and SFR obtained by the apparent slip amount calculating means 11 are corrected based on k1 and k2 (see the following equations (2) and (3)).

SFL ← SFL + k1 SFR ← SFR−k2 SFL ← SFL−k2 SFR ← SFL + k1 SFL ← SFL + k1 SFR ← SFL + k1 SFR ← SFL−k2 SFR ← SFR + k1 Based on the steering angle θH detected by the sensor 7, the average slip amount SAv is calculated based on the apparent slip amounts SFL and SFR when the vehicle is not turning, and the corrected slip amounts SFL and SFR are calculated when the vehicle is turning. Based on this, the average slip amount SAv is calculated.

The maximum slip amount calculating means 16 determines the higher one of the apparent slip amounts SFL and SFR as the maximum slip amount when the vehicle is not turning, based on the steering angle θH detected by the steering angle sensor 7. The slip amount is obtained as the maximum slip amount SHi, and the higher slip amount of the corrected slip amounts SFL and SFR is obtained as the maximum slip amount SHi during turning.

FIG. 2 shows the flow of the slip amount correction control.

That is, while the vehicle is running, each wheel speed VFL, VFR, V
Data about RL, VRR and the steering angle θH are input, and the apparent slip amounts SFL, SFR are calculated (steps S1, S2).
If it is determined that the vehicle is turning based on the steering angle θH, the correction value calculating means 13 and the slip amount correcting means 14 correct the slip amount, and the slip amount (SFL or SFR) ), The slip correction amount k1 is added, and the slip correction amount k2 is subtracted from the driving outer wheel slip (SFL or SFR) (steps S3, S4).

In the above example, the apparent slip amounts SFL, SFR are corrected, but the wheel speeds VFL, VFR of the drive wheels may be corrected as shown in the following equations (4) and (5). .

Formula (4) (when turning right)-VFL ← VFL + k1 VFR ← VFR-k2-Formula (5) (when turning left)-VFL ← VFL-k2 VFR ← VFR + k1 [Setting of slip judgment threshold] This slip judgment The threshold value is for determining whether or not the slip control is required. For setting the threshold value, as shown in FIG. 3, the vehicle body acceleration calculating means 41, the road surface friction coefficient calculating means 42, and A threshold calculating means 43 for obtaining a threshold is provided.

The vehicle acceleration calculation means 41 and the friction coefficient calculation means 42 will be described. To calculate the vehicle acceleration VG, a timer A (1
00 msec count) and timer B (500 msec count). That is, the vehicle body acceleration VG is the vehicle body speed Vr for 100 msec every 100 msec from the start of the slip control until the lapse of 500 msec (the vehicle acceleration is not sufficiently large). Based on the change in the faster one of the two wheel speeds), the following formula (6) is used.
After 0msec (body acceleration is fully developed), every 100msec
It is obtained from the following equation (7) based on the change in the vehicle speed Vr for 500 msec.

-Equation (6)-VG = Gk1 x {Vr (k)-Vr (k-100)}-Equation (7)-VG = Gk2 x {Vr (k)-Vr (k-500)} The above Gk1 and Gk2 Is a coefficient. Vr (k) is at the present time, Vr (k−100) is 100 ms before, Vr (k−500) is 500 ms
It is each vehicle speed before ec.

Then, the road surface friction coefficient μ is obtained by three-dimensional interpolation using the following μ table from the vehicle body acceleration VG and the vehicle body speed Vr calculated as described above.

When the slip control is not being performed, the road surface friction coefficient μ is set to 3.0.

Then, the threshold value calculating means 43 obtains a threshold value from the vehicle speed Vr and the road surface friction coefficient μ. That is, the threshold is calculated from the following threshold tables 1 and 2 by three-dimensional interpolation.

The threshold table 1 is for determining whether to start the slip control, and the threshold table 2 is for continuing the slip control.

[Slip Determination] The slip determination means 34 determines that the slip control is necessary when the following equation (8) is satisfied, and sets the slip flag SFL to 1, based on the maximum slip amount SHi and the slip determination threshold value. -(8)-SHi≥Slip determination threshold In this case, the slip determination threshold is determined by the slip control determination means 67 described later in a non-control state (CFL = 0).
Is determined, the threshold based on the threshold table 1 (for start) described above is used, and when slip control is determined (CFL = 1), the threshold based on the threshold table 2 (for continuation) is used. Is used.

[Setting of Control Target Value] The control target value T is a target value as the slip amount of the front wheels 2FL and 2FR. The control target value calculating means 35 calculates the following based on the vehicle speed Vr and the road surface friction coefficient μ. Is calculated by three-dimensionally interpolating the control target value from the control target value table.

[Control Level Calculation] The control level FC is determined on the basis of the deviation EN of the average slip amount SAv from the control target amount T and the rate of change DEN of this deviation. The feedback correction and the initial value correction are added and set in the range of 0 to 15. For this purpose, as shown in FIG. 4, a deviation calculation means 60, a deviation change rate calculation means 61, a basic control level calculation means 62, a feedback correction means 63, an initial correction amount calculation means 64, a final control level Calculation means 65 are provided.

The deviation calculating means 60 calculates the deviation EN by subtracting the control target value T from the average slip amount SAv.

The deviation change rate calculating means 61 calculates the average slip amount change rate DSAv based on the following equation (9), and sets this as the deviation change rate DEN.

DSAv = SAv (K) -SAv (K-1) The basic control level calculation means 62 converts the basic control level FCB to the next basic control level based on the deviation EN and the deviation change rate DEN. This is calculated using a table.

The feedback correction means 63 determines that the current control level FC
The control level FC (K-1) of the previous operation is added to (K).

The initial correction amount calculating means 64 forcibly increases the control level from when the slip of the front wheels is determined for the first time until the first slip determination disappears. For this purpose, the slip control shown in FIG. A determining means 66 and an initial slip control determining means 67 shown in FIG. 6 are provided.

In FIG. 5, reference numeral 68 denotes an AND circuit that outputs a set signal to the flip-flop 69 when the slip flag SFL = 1 and the brake is not applied, and 70 denotes FC ≦ 3 and DSAv ≦ 0.3.
The AND circuit 71 whose output becomes 1 at the time of g, receives the signal of the slip flag SFL = 0 through the counter 72 continuously for 1000 msec, or the AND circuit 70 through the counter 73.
This is an OR circuit that outputs a reset signal to the flip-flop 69 when the output signal 1 is continuously received for 500 msec. When receiving the set signal, the flip-flop 69 outputs a signal of the control flag CFL = 1 (during slip control).

In FIG. 6, reference numeral 74 denotes the current control flag FCL.
(K) = 1 and previous control flag CFL (K−1) = 0
Outputs a set signal to flip-flop 75 when
The D circuit 76 is an AND circuit that outputs a reset signal to the flip-flop 75 when the current slip flag SFL (K) = 0 and the previous slip flag SFL (K−1) = 1. Upon receiving the set signal, the flip-flop 75 outputs a signal of the initial flag STEL = 1 (during initial control).

The first correction amount calculating means 64 receives the first flag STFL signal and the average slip amount change rate DSAv, and sets STFL = 1 and
When DSAv ≧ 0, the first correction amount (+5) is calculated and output, and STEL
= 1 and DSAv <0, the first correction amount (+2) is calculated and output.

The final control level calculation means 65 adds the first correction amount to the feedback corrected control level FC.

[Output Control] -Ignition Timing Control- Regarding the ignition timing, as shown in FIG. 7, the retard amount is determined according to the above control level and output. In this case, as shown in FIG. 8, the maximum retard amount is limited in a region where the engine speed is high.

-Restriction of fuel injection (fuel cut)-Restriction of fuel injection is performed by selecting patterns 0 to 12 of the next fuel cut table based on the above control level (selecting a pattern with a higher value as the level increases). In this case, as shown in FIG. 9, a fuel cut prohibition condition is set for each control level so that the fuel cut is restricted in a region where the engine speed is low. Note that the symbol x in the above table means fuel injection cut.

FIG. 10 shows the flow of the slip control.

That is, the threshold value for the slip control start determination for shifting from the non-control state to the slip control is calculated based on the basic value table for the start, and a relatively high threshold value (corresponding to Sh in FIG. 10). ). Therefore, even if the wheel speed of the driving wheel becomes high (the maximum slip amount SHi becomes large) due to disturbance or the like, the slip flag SFL does not rise and control is not started unless the threshold Sh is exceeded. When the drive wheel speed exceeds the threshold value Sh, the slip flag SF
If L is on and the brake is in non-differential state, the control flag C
FL and initial flag STFL are set. Thereby, the slip control is started.

In this case, in the straight running of the vehicle, the maximum slip amount SHi is obtained from the apparent slip amounts SFL and SFR. On the other hand, during turning of the vehicle, the wheel speed of the outer wheel is higher than that of the inner wheel. Accordingly, when the apparent slip amount of the outer wheel is based on the maximum slip amount SHi may exceed the threshold value Sh, in the case of the present invention, the slip correction amount k2 is subtracted from the apparent slip amount of the outer wheel. Is used. Therefore, it is possible to prevent the slip control from being started although the actual slip amount is not large.

In the slip control, on the basis of the apparent slip amounts SFL and SFR in the straight running of the vehicle, and on the basis of the slip amounts corrected by the apparent slip amounts SFL and SFR by the correction values k1 and k2 in the turning travel, respectively. The slip amount SAv is calculated, and the control target value T is set based on the vehicle speed Vr and the road surface friction coefficient μ. The basic control level is set based on the deviation EN of the average slip amount SAv from the control target value T and the rate of change DEN of the deviation, and the control level FC is obtained by performing initial correction on the basic control level. Then, the ignition timing control and the fuel injection restriction control according to the control level FC are performed.

The initial correction is (+5) until the rate of change DSAv of the average slip amount becomes zero for the first time.
Is (+2) until is becomes zero. By this initial correction, the control amount is forcibly increased, and early convergence of the slip can be achieved.

The initial flag STFL becomes 0 when the maximum slip amount SHi due to the higher drive wheel speed becomes equal to or less than the threshold value for determining whether to continue the slip control, and the slip control is temporarily stopped at this time. The continuation determination threshold value (corresponding to S1 in FIG. 10) is set to a relatively low threshold value by calculating its basic value from the continuation basic value table. Therefore, the slip can be surely converged.

Then, even if the higher driving wheel speed becomes equal to or less than the continuation determination threshold S1, the control flag CFL remains set if the state does not continue for one second or more. Then, with the suspension of the slip control, the drive wheel speed increases again and exceeds the continuation determination threshold S1, and the slip flag
SFL is activated and slip control is resumed. in this case,
The initial flag STFL is not set, and there is no initial correction of the control level FC. Therefore, the control level FC is initially set only at the basic control level based on the deviation EN and the deviation change rate DEN, and thereafter, a value obtained by adding the previous value to the basic control level by feedback correction is set as the control level FC. Go.

As described above, when the slip converges and the state where the slip flag SFL does not stand for 1 second or more continues, the control flag CFL becomes 0, and this series of slip control ends.

[Brief description of the drawings]

1 shows an embodiment of the present invention, FIG. 1 is an overall configuration diagram of a vehicle slip control device, FIG. 2 is a flowchart of a slip amount correction control, FIG. 3 is a configuration diagram of a slip control threshold value setting means, FIG. 4 is a block diagram of the control level calculating means, FIG. 5 is a block diagram of the slip control determining means, FIG. 6 is a block diagram of the initial slip control determining means, and FIG. 7 is a relation between the control level and the ignition timing retard amount. FIG. 8 is a characteristic diagram showing the restriction of the ignition timing retard amount by the engine speed, and FIG.
FIG. 10 is a characteristic diagram showing a fuel cut restriction region depending on the engine speed, and FIG. 10 is a time chart of the slip control. 1 Engine 2FL, 2FR Front wheel (drive wheel) 2RL, 2RR Rear wheel (driven wheel) 7 Steering angle sensor 8 Control means 9FL-9RR Wheel speed sensor 11 Apparent slip Amount calculation means 12 ... Correction value storage means 13 ... Correction value calculation means 14 ... Slip amount correction means 21 ... Vehicle speed detection means 22 ... Turning radius calculation means

Claims (2)

(57) [Claims] 1. A vehicle slip control device for controlling driving of a drive wheel such that a slip amount of the drive wheel with respect to a road surface becomes a target value, a vehicle speed detection means for detecting a vehicle speed, and a wheel speed of the drive wheel. Wheel speed detecting means for detecting a turning radius of the vehicle, a turning radius detecting means for detecting a turning radius of the vehicle, a vehicle speed detected by the vehicle speed detecting means, and a wheel speed detected by the wheel speed detecting means. An apparent slip amount calculating means for calculating an apparent slip amount of the drive wheels; and a turning radius of the vehicle and a vehicle speed for correcting a slip amount based on a wheel speed difference between an inner wheel and an outer wheel during turning of the vehicle. Correction value storage means for storing a correction value set as a factor, a vehicle speed detected by the vehicle speed detection means, and a turning radius of the vehicle detected by the turning radius detection means. There are, a correction value calculating means for calculating a correction value from the correction value storing means, based on the correction value determined by the correction value calculating means,
And a correcting means for correcting the wheel speed detected by the wheel speed detecting means or the apparent slip amount obtained by the apparent slip amount calculating means. 2. A steering angle detecting means for detecting a steering angle, wherein the turning radius detecting means detects a turning radius set in advance corresponding to the steering angle based on the steering angle detected by the steering angle detecting means. The vehicle slip control means according to claim 1, wherein the correction value stored in the correction value storage means is set such that the slip amount increases as the turning radius decreases.