JPH04191430A - Slip control device for vehicle - Google Patents

Abstract

PURPOSE:To prevent a vehicle from showing an excessive under-steering tendency and improve the operability or running stability by determining an actual turning radius on the basis of the wheel speed difference between left and right driven wheels, and starting slip control when this radius is larger than a turning radius corresponding to steering angle. CONSTITUTION:A vehicle has a slip control means 8 for controlling the drive of driving wheels 2FL, 2FR so as to conform the slip amount to road surface of the driving wheels 2FL, 2FR with a target value, and a trace means 11 for preventing the vehicle from showing an excessive understeering tendency in turning run by utilizing the control means 8. In this case, the trace means 11 operates the actual turning radius of the vehicle by a means 12 on the basis of the wheel speeds of driven wheels 2RL, 2RR detected by wheel speed sensors 9RL, 9RR. A turning radius corresponding to the steering angle of the vehicle is also operated by a means 73. Whether the slip control should be started is further judged on the basis of the actual turning radius and the turning radius corresponding to steering angle, and a slip control start signal is outputted from a means 14 to the control means 8.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a slip control device for a vehicle.

(Prior art) In order to prevent the drive wheels from slipping due to excessive drive torque and deteriorating acceleration performance when a vehicle is accelerating, the slip value of the drive wheels is detected and the target slip value of the drive wheels is determined. Traction control that controls the engine output and the application of braking force to the wheels (reducing the engine output or increasing the braking force) is generally known.

In addition, when performing the above-mentioned traction control, the vehicle speed and steering angle are detected, and at low vehicle speeds, the slip control target value is changed according to the steering angle, ensuring the lateral stability of the vehicle when the steering angle starts. A proposal to do so is known (see Japanese Unexamined Patent Publication No. 64-30869).

(Problem to be solved by the invention) Vehicles are generally manufactured in such a way that their steering characteristics tend to understeer, or the understeer characteristics change depending on the road surface conditions, etc., and when the understeer becomes excessive, the steering characteristics become difficult to control. becomes worse, making it impossible to obtain good maneuverability.

That is, an object of the present invention is to prevent a vehicle from exhibiting an excessive understeer tendency by traction control.

(Means for Solving the Problems) To solve such problems, the present invention compares the actual turning radius of the vehicle with the turning radius corresponding to the steering angle to detect an understeer tendency in advance. By starting traction control, the tendency to understeer is prevented from increasing and the maneuverability or running stability of the vehicle is ensured.

That is, a specific means for this purpose is to control the amount of slip between the left and right driven wheels in a slip control device for a vehicle that is equipped with a slip control means that controls the drive of the drive wheels so that the slip amount of the drive wheels with respect to the road surface reaches a target value. A driven wheel wheel speed detection means for detecting wheel speed; and an actual turning radius calculation means for calculating the actual turning radius R of the vehicle based on the difference in wheel speed of both driven wheels detected by the driven wheel speed detection means. a rudder angle detection means for detecting a rudder angle; and a rudder angle corresponding turning radius calculation for calculating a turning radius Ri of the vehicle, which is set in advance in correspondence with the rudder angle, based on the rudder angle detected by the rudder angle detection means. Based on the actual turning radius R calculated by the actual turning radius calculating means, and the turning radius R1 calculated by the steering angle corresponding turning radius calculating means,
A slip control device for a vehicle, comprising: slip control starting means for causing the slip control means to start slip control when the R becomes larger than Ri.

In this case, the slip control means may control the torque generated by the engine that drives the drive wheels.

(Function) In the above slip control device, the actual turning radius R of the vehicle
When the turning radius R1 becomes larger than the steering angle corresponding turning radius R1, it can be said that the vehicle has begun to exhibit a tendency to understeer. However, if slip control is started at this point, the drive torque of the drive wheels is reduced by this slip control, and the deceleration effect of the vehicle and the nature of understeering itself (as the vehicle speed decreases, the turning radius becomes smaller). This makes it possible to suppress the tendency to understeer. In particular, in the case of front-wheel drive vehicles, the change in moment around the center of gravity of the vehicle caused by the sudden change in direction of the forward force of the front wheels;
By recovering the cornering force that had been reduced by the driving force, the above-mentioned understeer tendency can be positively eliminated.

In addition, in slip control, if braking force is applied to the drive wheels, cornering force will be reduced,
The vehicle may no longer have sufficient lateral grip, or
If the torque generated by the engine is controlled, the above problem will not occur.

(Effect of the Invention) Therefore, according to the present invention, the actual turning radius R is determined based on the wheel speed difference between the left and right driven wheels, and the slip control is performed when the actual turning radius R becomes larger than the turning radius Ri corresponding to the steering angle. By starting the vehicle, it is possible to prevent the vehicle from exhibiting an excessive tendency to understeer, thereby improving maneuverability or driving stability.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows the overall configuration of the embodiment.

First, the left and right front wheels 2PL and 2PR of the vehicle are driving wheels, and the left and right rear wheels 2RL and 2RR are driven wheels. In other words, a V-type 6-cylinder engine 1 is installed at the front of the vehicle.
The torque generated by the engine 1 passes through the automatic transmission 3 and the differential gear 4, and then is transmitted to the left front wheel 2PL via the left drive shaft 5L. The power is transmitted to the right front wheel 2PR via the right drive shaft 5R.

The vehicle then operates the drive wheels 2FL and 2PR so that the amount of slip on the road surface becomes a target value.
Slip control means 8 for controlling the drive of PL and 2PH
and a tracing means 11 that utilizes the control means 8 to prevent the vehicle from exhibiting an excessive tendency to understeer during cornering.

The control means 8 controls the four wheels 2PL, 2PR, 2RL,
A brake sensor 6 detects whether the brake is applied to the 2RR, a steering angle sensor 7 detects the steering angle of the vehicle, the four wheels 2PL, 2PR, 2RL,
A wheel speed sensor 9PL that detects the wheel speed of 2RR,
9FR.

Signals from 9RL, 9RR1 and an engine rotational speed sensor 28 that detects the engine rotational speed are input, and the signals are processed to generate an ignition timing control signal and a fuel injection restriction signal for causing the engine 1 to reduce its output torque. This is what is output.

The tracing means 11 causes the control means 8 to start slip control when the actual turning radius R of the vehicle becomes larger than the (ideal, so to speak) turning radius Ri that corresponds uniformly to the steering angle, so that the vehicle This prevents excessive understeer from occurring.

Hereinafter, the tracing means 11 and the control means 8 will be specifically explained in this order.

<Tracing means> The tracing means 11 includes an actual turning radius calculating means 12 for calculating the actual turning radius R of the vehicle, a steering angle corresponding turning radius calculating means 13 for calculating the turning radius Ri corresponding to the steering angle of the vehicle, and the above-mentioned actual turning radius calculating means 13 for calculating the turning radius Ri corresponding to the steering angle of the vehicle. The slip control starting means 14 determines whether or not slip control should be started based on the turning radius R and the turning radius Ri corresponding to the steering angle, and outputs a slip control starting signal to the control means 8.

First, the actual turning radius calculation means 12 is a wheel speed sensor 9RL.
, driven wheels 2RL and 2R detected by 9RR
The actual turning radius R is calculated based on the wheel speeds VRL and VRR of R according to the following equation (1).

-(1) Formula- R-Min (VRL, VRR) X T + l
VRL - VRRl 11/2XT In this case, Min (VRL, VRR) means the smaller wheel speed of both driven wheels, VRL and VRR. Also, l VRL-VRRl is both wheel speed VRL
, is the absolute value of the difference in VRR, and T is the tread of the vehicle (eg 1.7 m).

On the other hand, the steering angle corresponding turning radius calculating means 13 includes the steering angle sensor 7.
Based on the absolute value of the steering angle θH' detected by , the turning radius Ri corresponding to the steering angle approximately corresponds to the turning radius in neutral steering from the following Ri table, which is set in advance to correspond to the steering angle in an integrated manner. ) is obtained by linear interpolation.

Ri table Then, the slip control starting means 14 compares the actual turning radius R calculated by the actual turning radius calculating means 12 and the turning radius Ri calculated by the steering angle corresponding turning radius calculating means 13, and calculates the following. When the condition shown in equation (2) is satisfied, (
When the actual turning radius R becomes larger than the steering angle corresponding turning radius Ri), a slip control start signal (slip flag 5FL) is activated.
-1 signal) is output to the control means 8.

-Equation (2)- Actual turning radius R> Turning radius corresponding to steering angle Ri FIG. 2 shows the flow of control in the tracing means 11.

That is, while the vehicle is running, the driven wheel speed VRL,
Data regarding VRR and steering angle θH are input,
The actual turning radius R and the turning radius Ri corresponding to the steering angle can be calculated (
Steps 81-S3). Then, when the actual turning radius R becomes larger than the steering angle corresponding turning radius Ri, a slip control start signal is output (steps S4 and S5).

Control means> The control means 8 includes an input interface for receiving signals from each of the sensors, a microcomputer consisting of a CPU, ROM, and RAM, an output interface, and a drive for driving the igniter and fuel injection device. The ROM is provided with control programs and various maps or tables necessary for slip control, and the RA
M is provided with various memories necessary for executing control. As shown in FIG. 3, this control means 8 includes a slip determination threshold setting means 32, a slip amount calculation means 33, a slip determination means 34, a control target value setting means 35, and a control level calculation means. 36 and engine output control means 37.

[Slip Judgment Threshold Setting] This slip judgment threshold is used to judge whether or not slip control is required. In order to set this threshold, as shown in Fig. 4, the vehicle acceleration A calculating means 41, a road surface friction coefficient calculating means 42, and a threshold calculating means 43 for calculating the above threshold value are provided.

To explain the vehicle body acceleration calculation means 41 and the friction coefficient calculation means 42, a timer A is used to calculate the vehicle body acceleration VC.
(100Illsec count) and timer B (50
0a+sec count). In other words, the vehicle body acceleration VC is 100 m5 from the start of slip control until 500 m5 elapses (vehicle body acceleration is not large enough).
For each ec, the following ( 3) After 500111Sec has elapsed (vehicle body acceleration has sufficiently developed), the following (4
) is calculated using the formula.

-Equation (3)- VC-GklX iV r (k) -V r (k
-100) 1-(4) Formula - VC=Gk2X iV r(k) -V r(k-5
00) 1 The above Gkl and Gk2 are coefficients. Also,
V r (k) is the current time, V r (k-100) is 1
Before 00m5ec, VR (k-500) is 500m5e
It is each vehicle body speed before c.

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

Note that when slip control is not in progress, the road surface friction coefficient μ
Set to 3.0.

Then, the threshold calculation means 43 calculates a threshold value from the vehicle speed Vr and the road surface friction coefficient μ. That is, the threshold value is calculated by three-dimensional interpolation from the following threshold value table 1.2.

Threshold table 1 (for starting) Threshold table 2 (for continuation) The above threshold table 1 is for determining whether to start slip control, and threshold table 2 is for continuing slip control. It is.

[Slip Amount Calculation] As shown in FIG. 5, the slip calculation means 33 includes an actual slip amount calculation means 45, an average slip amount calculation means 48, and a maximum slip amount calculation means 49.

The actual slip amount calculating means 45 is for the left and right front wheels 2 PL.

The vehicle body speed Vr is subtracted from the wheel speeds VFL and VFR of 2PR to find the slips of these two wheels jlsL and SR. Further, the average slip amount calculation means 48 calculates the slip amount SL.
, SR based on the average slip amount SAV, and the maximum slip amount calculation means 49 calculates both the above-mentioned slip amounts SL,
The higher slip amount of SR is the maximum slip amount SH
It is obtained as i.

[Slip Judgment] The slip judgment means 34 determines the maximum slip amount "SHi".
Based on the slip determination threshold and the slip determination threshold, when the following equation (5) holds true, it is determined that slip control is necessary, and the slip flag S is set.
Assuming that FL is 1 - Equation (5) - 3Hi≧Slip determination threshold In this case, the slip determination threshold is determined by the slip control determination means 67 to be described later. ! (C.F.L.
-0), the threshold based on the aforementioned threshold table 1 (for start) is used, and when it is determined that slip control is in progress (CFL-1), threshold table 2 (for continuation) is used. A threshold based on is used.

[Setting of control target value] This control target value T is
This is the target value for the knob amount, and the control target value calculation means 35 calculates the control target value by three-dimensional interpolation from the following control target value table based on the vehicle speed Vr and the road surface friction coefficient μ. be.

Control target value table [Control level calculation] For the control level FC, the deviation EN of the average slip ■SAv from the control target amount T and the rate of change of this deviation DEN
The feedback correction of the previous value F C (K-1) and the initial value correction are added to this, and the value is set in the range of 0 to 15.

For this purpose, as shown in FIG. A calculation means 65 is provided.

The deviation calculation means 60 subtracts the control target value T from the average slip Ji SAv to obtain the deviation EN.

The deviation change rate calculation means 61 calculates the average slip amount change rate DSAv based on the following equation (6), and calculates this as the deviation change rate D.
EN.

-Equation (6)- D S A v = S A v (K) - S A
v (K-1) The basic control level calculation means 62 calculates the basic control level FCB based on the deviation EN and the deviation change rate DEN using the following basic control level table.

The basic control level table feedback correction means 63 calculates the current control level FC.
The control level F C (K-1) of the previous calculation is added to (K).

The initial correction amount calculation means 64 is for forcibly increasing the control level from when it is determined for the first time that the front wheels are slipping until the initial slip determination is eliminated, and for this purpose, the slip control shown in FIG. determining means 66;
Initial slip control determining means 67 shown in the figure is also provided.

In FIG. 7, 68 is an AND circuit that outputs a set signal to flip-flop 69 when slip flag 5FL=1 and in a non-braking state, and 70 is an AND circuit that outputs a set signal to flip-flop 69 when FC≦3 and -) DSAV≦0, 3g. AND whose output is 1
The circuit 71 outputs the slip flag 5F via the counter 72.
Receive L=0 signal continuously for 1000 m5ec,
Alternatively, when the output signal 1 is continuously received from the AND circuit 70 for 500 m5ec via the counter 73, the OR circuit outputs a reset signal to the flip-flop 69. When the flip-flop 69 receives the set signal, it outputs a signal indicating control flag CFL=1 (slip control in progress).

In addition, in FIG. 8, 74 is the current control flag CFL.
(K)-1 and previous control flag CFL(K-1)=
0, an AND circuit outputs a set signal to the flip-flop 75, 76 is the current slip flag 5FL (K
)=0 and the previous slip flag 5FL (K-1>-
This is an AND circuit that sends eight reset signals to the flip-flop 75 when the signal is 1. Then, the flip-flop 75 receives the set signal and operates the first flag 5TFL-1 (
Outputs the signal (during initial control).

The initial correction amount calculation means 64 inputs the initial flag 5TFL signal and the average slip amount change rate DSAv, and calculates the 5TF
When L-1 and DSAv≧0, the initial correction amount (+5) is calculated and output, and when 5TFL-1 and DSAv<Q, the initial correction amount (+2) is calculated and output.

The final control level calculation means 65 adds the above-mentioned initial correction amount to the feedback-corrected control level FC.

[Output control, trolley control, ignition timing control] Regarding the ignition timing, as shown in FIG. 9, the amount of retard is determined and outputted according to the above control level. In this case, as shown in FIG. 10, 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 (the higher the level, the higher the pattern is selected). In this case, as shown in FIG. 11, a fuel cut prohibition condition is attached to each control level so that fuel cut is restricted in a region where the engine speed is low. Note that X in the above table means fuel injection cut.

FIG. 12 shows the flow of the slip control described above.

In other words, the threshold value for determining the start of slip control for transition from a non-control state to slip control is determined by calculating a basic value using a starting basic value table, and setting the threshold value to a relatively high threshold value (
(corresponding to sh in FIG. 12). Therefore, due to disturbance etc., the wheel speed of the driving wheels becomes high (maximum slip f; k
Even if SHi becomes large), the slip flag SFL is set and control is not started unless it exceeds the threshold sh. When the driving wheel speed exceeds the threshold value sh, the slip flag SFL is set, and if the brake is not in operation, the control flag CFL and the initial flag 5TFL are set. This will start slip control.

Furthermore, even if the driving wheel speed does not exceed the threshold value sh, if the actual turning radius R becomes larger than the steering angle corresponding turning radius Ri during turning of the vehicle, the slip flag SFL
is established, and slip control is started in the same way as in the above case.

In slip control, it is calculated based on the average slip amount SAv, front wheel speed VFL, VFR, and vehicle speed Vr, and on the other hand, it is set based on the control target value T or vehicle speed V' and the road surface friction coefficient μ. Then, the basic control level is set based on the deviation EN of the average slip m S A v from the control target value T and the rate of change DEN of this deviation, and an initial correction is applied to this to obtain the control level FC. is determined, and ignition timing control and fuel injection restriction control are performed according to this control level FC.

The initial correction is (+5) until the rate of change of the average slip amount DSAv becomes zero for the first time, and then the initial flag 5
The time it takes for TFL to reach O is (+2). By this initial correction, the control amount is forcibly increased, and the slip can be brought to an early conclusion.

The first time flag 5TFL becomes 0 when the maximum slip amount S Hi due to the wheel speed of the higher driving wheel becomes less than the threshold for determining whether to continue slip control, and at this point slip control is temporarily discontinued. . This threshold value for continuation determination (corresponding to Sl in FIG. 12) is calculated from the basic value or the continuation basic value table, and is set to a relatively low threshold value. Therefore, the slip can be reliably stopped.

As described above, even if the driving wheel speed does not exceed the threshold value Sh, if the actual turning radius R becomes larger than the steering angle corresponding turning radius Ri, slip control is started.
Since the drive torque of the drive wheels (front wheels) is reduced, it is possible to prevent the vehicle from exhibiting an excessive tendency to understeer. In other words, a tuck-in phenomenon occurs due to the decrease in the drive torque of the drive wheels, which is caused by a change in the moment around the center of gravity of the vehicle caused by the sudden change in direction of the forward force of the front wheels, and a decrease due to the drive force. By recovering the cornering force, it is possible to prevent the above-mentioned understeer tendency from becoming excessive.

Then, even if the wheel speed of the higher driving wheel becomes equal to or less than the continuation determination threshold value 51, the control flag CFL remains set unless the condition continues for more than one second. Then, as the slip control is discontinued, the driving wheel speed increases again and exceeds the continuation determination threshold Sl, the slip flag SFL is set again and the slip control is restarted. In this case, the initial flag 5TFL is not set, and there is no initial correction of the control level FC. Therefore, the control level FC is initially set to the deviation E
Only the basic control level is set based on N and the deviation change rate DEN, and thereafter, the basic control level plus the previous value by feedback correction is set as the control level FC.

As described above, when the slip converges and the slip flag SFL remains low for more than one second, the control flag CFL becomes O, and this series of slip control ends.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is an overall configuration diagram of a slip control device for a vehicle, FIG. 2 is a flow diagram of starting slip control based on the turning radius of a vehicle, and FIG. 3 is a configuration of a slip control means. 4 is a block diagram of the slip control threshold setting means, FIG. 5 is a block diagram of the slip amount calculating means, FIG. 6 is a block diagram of the control level calculating means, and FIG. 7 is a block diagram of the slip control determining means. , FIG. 8 is a configuration diagram of the initial slip control determination means, FIG. 9 is a characteristic diagram showing the relationship between the control level and the ignition timing retard amount, and FIG. 10 is a characteristic diagram showing the restriction of the ignition timing retard amount depending on the engine rotation speed. Figure 11 is a characteristic diagram showing the fuel cut restriction area depending on the engine speed.
FIG. 2 is a time chart of slip control. 1...Engine 2FL, 2PR...Front wheel (drive wheel) 2RL
, 2RR... Rear wheel (driven wheel) 7...
- Rudder angle sensor 8... Control means 9FL to 9RR... Wheel speed sensor 11...
... Trace means 12 ... Actual turning radius calculation means 13 ... Rudder angle corresponding turning radius calculation means 14 ...
...Slip control starting means Fig. 2 and Fig. 3

Claims (2)

[Claims] (1) In a slip control device for a vehicle equipped with a slip control means that controls the drive of the drive wheels so that the amount of slip of the drive wheels with respect to the road surface becomes a target value, a driven wheel that detects the wheel speed of the left and right driven wheels. wheel speed detection means; actual turning radius calculation means for calculating an actual turning radius R of the vehicle based on the difference in wheel speed of both driven wheels detected by the driven wheel wheel speed detection means; and detection of a steering angle. rudder angle detection means; rudder angle corresponding turning radius calculation means for calculating a turning radius Ri of the vehicle, which is preset in correspondence with the rudder angle, based on the rudder angle detected by the rudder angle detection means; and the actual turning radius. Actual turning radius R determined by calculation means
and slip control starting means for causing the slip control means to start slip control when the turning radius Ri obtained by the steering angle corresponding turning radius calculation means is larger than Ri. A slip control device for a vehicle, characterized in that: (2) The slip control device for a vehicle according to claim (1), wherein the slip control means controls the torque generated by the engine that drives the drive wheels.