JPH03112754A - Turn action control device for vehicle - Google Patents

Abstract

PURPOSE:To stably run a vehicle always in a grip region by respectively braking both wheels in the inner and outer of turn direction so as to decrease a car speed to a limited value in a mode, where a limit yaw rate is generated, when a detected car speed exceeds the tire grip limit car speed. CONSTITUTION:A steering amount of a wheel W in a vehicle is detected by a means A. While a car speed is detected by a means B. Further a tire limit car speed in every steering amount of the wheel W is detected by a means C. On the other hand, a limit yaw rate of the vehicle, which must be obtained by the steering amount of the wheel W and the tire grip limit car speed, is calculated by a means D. When the detected car speed exceeds the tire grip limit car speed, both the wheels W in the inner and outer of turning direction are respectively braked by an automatic brake means E so that the car speed is decreased to the limit car speed in a mode where the limit yaw rate is generated. Thus by running the vehicle always in a grip region, undesired turn action is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a device for suppressing undesirable behavior of a vehicle during turning by automatic braking.

(Prior Art) As a turning behavior control device for this type of vehicle, that is, automatic braking technology, there is a device that applies braking force only to the wheels on the inside of the turn during turning to assist the generation of the vehicle's yaw rate. This is proposed in Japanese Patent Application Laid-Open No. 63-279976.

(Problems to be Solved by the Invention) Although this device is intended to assist the vehicle in turning, it is not effective against lateral slip of the wheels. In other words, when the vehicle enters a corner at high speed and turns the steering wheel, or when the steering wheel is turned further while turning, etc.
Centrifugal force exceeding the grip limit of the wheels is generated, causing the wheels to slip laterally, making it impossible to prevent the vehicle from spinning or lifting out to the outside in the turning direction.

Since such undesirable turning behavior is based on excessive vehicle speed that cannot be suppressed by braking only the wheels on the inside of the turn, the present invention automatically brakes the wheels on the inside and outside of the turn to reduce the excess vehicle speed. In addition, when this automatic braking is applied, the inner and outer wheels of the turning are braked in such a manner that the yaw rate of the vehicle becomes the limit yaw rate that should be obtained in the vehicle speed suppression state. The purpose is to provide equipment.

(Means for Solving the Problems) For this purpose, the turning behavior control device of the present invention, as conceptually shown in FIG. a vehicle speed detection means for detecting vehicle speed; a limit vehicle speed detection means for determining a tire grip limit vehicle speed for each steering amount; and a limit yaw rate calculation for calculating a vehicle limit yaw rate to be obtained with the steering amount and tire grip limit vehicle speed. and automatic braking means for respectively braking the inner and outer wheels of the turn so as to reduce the vehicle speed to the limit vehicle speed in such a manner that the limit yaw rate occurs when the detected vehicle speed exceeds the tire grip limit vehicle speed. It is something.

(Operation) When the vehicle is turning with its wheels steered, the steering amount detection means detects the steering amount of the wheels, and the limit vehicle speed detection means determines the tire grip limit vehicle speed from this steering amount. When the vehicle speed detected by the vehicle speed detection means exceeds the tire grip limit vehicle speed, the automatic braking means brakes the inner and outer wheels of the turn to reduce the vehicle speed to the tire grip limit vehicle speed, and The inner and outer wheels of the turn are braked so that the limit yaw rate determined by the yaw rate calculation means is achieved.

Therefore, the vehicle speed will not exceed the grip limit speed of the tires under any amount of steering, and the vehicle will always run in the grip range, causing the vehicle to spin when turning,
It is possible to increase the vehicle's yaw rate to its limit and improve turning performance as much as possible while preventing drift-out.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the device of the present invention, in which IL and IR represent left and right front wheels, 2L and 2R represent left and right rear wheels, 3L, 3R represent front wheel cylinders, and 4L and 4R represent rear wheel cylinders, respectively. 5 is a brake pedal, and 6 is a master cylinder that simultaneously outputs the same hydraulic pressure to two systems 7 and 8 when the brake pedal is depressed.The master cylinder hydraulic pressure of system 7 is routed through branched systems 7L and 7R to wheel cylinder 3L.
, 3R, the front wheels IL and IR are braked, and the master cylinder hydraulic pressure of system 8 passes through the branched systems 8L and 8R, reaches wheel cylinders 4L and 4R, and is applied to the rear wheel 2L.

Brake 2R.

In contrast to such a normal front-rear split type two-system hydraulic brake system, in this example, cut valves 11L are provided in systems 7L, 7R, 8L, and 8R, respectively, to open these systems in the normal state.

Insert 11R, 12L, and 12R. An accumulator 13 is provided which functions as a hydraulic pressure source for automatic braking, and a pump 14 supplies brake fluid from a reservoir 45 to this accumulator 13 to accumulate hydraulic pressure for automatic braking. The drive motor 15 of the pump 14 is connected to a power source 17 via a pressure switch 16, which opens when the internal pressure of the accumulator 13 reaches a specified value, and the motor 15
(pump 14) shall be turned off. In this way, the above specified pressure is always stored in the accumulator 13.

The internal pressure of the accumulator 13 is controlled by the cut valve 1 by the circuit 18.
1L, IIR, 12L, and 12R, and these cut valves respond to the accumulator internal pressure to open the corresponding system 7.

7R, 8L, and 8R shall be cut off. The output chambers of cylinders 19L, 19R, 2OL, and 2OR are connected to these systems, respectively, and an electromagnetic proportional valve 21L is connected to the human power chamber of the cylinder.
, 21R.

Connect the output ports of 22L and 22R. These electromagnetic proportional valves connect their output ports to the accumulator pressure circuit 18 and drain circuit 23 according to the solenoid drive currents 11 to 14, and apply hydraulic pressure proportional to the corresponding solenoid drive current to the cylinders 19L, 19R, 2OL, and 2OR. supply

The solenoid drive currents 11 to i4 are controlled by a controller 31, which includes hydraulic pressure PF of systems 7 and 8,
Signals from the pressure sensors 32 and 33 that detect the PR, signals from the steering angle sensor 34 that detects the turning angle θ of the steering wheel (not shown), the left front wheel rotation speed ω1, the right front wheel rotation speed ω2, and the left rear wheel rotation speed ω1. Signals from wheel rotation sensors 35 to 38 that detect wheel rotation speed ω3 and right rear wheel rotation speed ω, signals from yaw rate sensor 39 that detects vehicle yaw rate ψ, and lateral acceleration Gy near the vehicle center of gravity are detected. signal from the lateral acceleration sensor 40, and further the wheel cylinder 3.
Brake fluid pressure Pw l to L, 3R, 4L, 4R
+ P W 21 P W 3 *The signals from the pressure sensors 41 to 44 that detect PW4 are manually generated.

The controller 31 executes the control program shown in FIG. 3 from this input information to perform normal wheel braking and wheel braking for turning behavior control, which will be described below. That is, first, in steps 50 to 53, the brake hydraulic pressure P□ of each wheel, the hydraulic pressure Pp of the brake systems 7 and 8, the PII wheel rotational speed ω, -ω4, the steering angle θ, the yaw rate ψ, and the lateral acceleration Gy are read. Of course, the pressures Pp and Pa are 0 unless the brake pedal 5 is depressed. In the next step 54, the wheel rotation speed ω, ~
ω.

The vehicle speed V is calculated from. In this calculation, during non-braking when the brake pedal 5 is not depressed, the rotation speed of the front wheel, which is a non-driving wheel, is ω1. Since ω2 almost matches the vehicle speed, when the front wheel radius is R and closed, V=R.

It is determined by the calculation of (ω, +ω2)/2. However, during braking, a pseudo vehicle speed is calculated from all wheel rotational speeds ω1 to ω4 using a method commonly used in anti-skid control.
Let this be the vehicle speed V.

In step 55, it is determined from the vehicle speed V and steering angle θ whether the vehicle is in the grip region or slip region as shown in FIG. In Figure 4, α indicates the tire grip limit vehicle speed,
Although it varies depending on the steering angle θ, if the vehicle speed V is below the limit vehicle speed, it is in the grip region, and if it exceeds the limit vehicle speed, it is in the slip region. In the slip area, the tires cannot resist the centrifugal force that accompanies cornering and slip, causing the vehicle to spin or drift out.

For example, while driving at point A in Figure 4 (vehicle speed Vo, steering angle θO), by increasing the steering angle θ to 01,
To explain the case where the vehicle shifts to running at a point, the vehicle enters the slip region from the grip region, causing the vehicle to spin or drift out. In this case, if the vehicle speed is below the limit vehicle speed V5 on the line α, the above-mentioned undesirable turning behavior will not occur.

If the grip area does not cause this undesirable turning behavior,
Step 56: front wheel cylinder 3L.

Target brake fluid pressure P1 to 3R. Set Pa to the same as the hydraulic pressure P of the corresponding system 7, and press the rear wheel cylinder 4L.
, Set the target brake hydraulic pressures Ps and Pa to 4R to be the same as the hydraulic pressure PR of the corresponding system 8. and step 57
Then, in order to obtain these target brake fluid pressures, set the electromagnetic proportional valves 21L and 21R from the table data corresponding to Fig. 5.
, 22L, and 22R are looked up, and in step 58 these are output to the corresponding electromagnetic proportional valves.

By the way, if the automatic brake fluid pressure sources 13 to 17 are normal and pressure is stored in the accumulator 13, in response to this, the cut valves 11L, 11R, 12L, and 12R will open the corresponding systems 7L, 7R, 8L, and 8R. It's blocked.

For this reason, the electromagnetic proportional valves 21L, 21R, 22L, 2
2R is supplied with drive currents 11 to I4, and pressures proportional to these are applied to the corresponding cylinders 19L, 19R, 2OL,
When feeding the 2OR, these cylinders can supply brake fluid pressure to the corresponding wheel cylinders.

Incidentally, since the electromagnetic proportional valve drive currents 11 to 14 are determined as described above so that these brake fluid pressures are the same as the fluid pressures PF and PR from the master cylinder 6, each wheel is braked as usual.

If it is determined in step 55 that it is a slip area, step 5
At step 9, the tire grip limit vehicle speed Vs (see FIG. 4) corresponding to the current steering angle θ is looked up. Next, in step 60, the limit yaw rate ψ that should naturally be obtained at the current steering angle θ and the tire grip limit vehicle speed Vs is determined using the following equation.

ψS = "G-/V-" Here, 07% is the lateral acceleration limit value of the vehicle, which is determined for each vehicle, and is, for example, about 0.8g.In addition, in this example, the vehicle speed is Since V is controlled so as not to exceed the limit tonne speed Vs, the limit yaw rate ψ,
may be determined by ψs ''G, , /V instead of the above formula.

In the next step 61, the deviation E9 between the vehicle speed V and the limit vehicle speed Vs, and the deviation Eφ between the yaw rate ψ and the limit yaw rate ψ are determined, and in steps 62 to 67, the deviation E9 is calculated.
Target brake fluid pressure PI- to bring v, Eφ close to 0
P4 is determined as follows.

That is, first, in steps 62 and 63, the target longitudinal deceleration GX% and target yaw angular acceleration ψS of the vehicle in order to bring Ev and Eφ closer to O at predetermined speeds are calculated using the following equations.

G,,=mI E.

ψ5=nEψ (m−n is a coefficient related to the above-mentioned planned speed) Instead of these equations, the following equation may be used.

Gxs=m+ ・Ev+rrh# Evψs = n
I @Ei +n 2@Ep(mI+ m2 +n
l+β2 is a coefficient related to the planned speed) Then step 6
4, the yawing torque T generated by the braking force from the current brake fluid pressure PWI~PW4 is expressed as TB = at 'Pwl+82''Pw2+a3
・Pw++a4”PVA (aI+ a2+ a3+ β
4 is a constant for each vehicle). In the next step 65, the yawing torque TB% due to the above braking force, the yaw angular acceleration ψ (calculated by the differentiation of the detected yaw rate ψ)
, and yaw inertia I, calculate the yawing torque T generated by a force other than the braking force by calculating T=I・ψ−TB, and in the next step 66 set E, , = 0 (achieve ψ). Therefore, the target yawing torque TBS to be generated by the braking force is TBS=I−ψs
Find it by T.

In step 67, the target brake fluid pressure PI-P4 for each wheel is determined as follows to set Ev to 0 (to achieve G, , ) and to set E to Q (to achieve ψS). , the equation of motion of the vehicle in the longitudinal direction is G, , -W=αr * P , +α2・P2+α3”P
3+α4”P4(W...vehicle weight, β1.β2.β3
．． α, . . . a constant determined by the vehicle), the equation of motion of the vehicle in one direction is T8.
=β1・P1+β2・P2+β3・P3+β4・P4(
β1. β2. β3. β, ... constant determined by the vehicle)
The target brake fluid pressures P1 to P4 are determined so as to satisfy both of these equations. For example, the brake fluid pressure ratio between the front and rear wheels and between the left and right wheels is h.

When defining k (h>O, k>[]), P+=P+ P2 = k” P+ P,=h−P.

P, = to -h P.

Then, the target brake fluid pressure P, ~P, for each wheel is determined.

Next, the control proceeds to steps 57 and 58, where the electromagnetic proportional valve drive currents lI to 14 for obtaining the target brake fluid pressures P1 to P4 obtained as described above are looked up, and these are applied to the corresponding electromagnetic proportional valves. By outputting this output, the vehicle speed is brought to the limit vehicle speed by automatic braking without having to press the brake pedal.

Therefore, when the vehicle enters the slip region, the vehicle speed is reduced to the limit vehicle speed and returned to the grip region, making it possible to prevent the vehicle from spinning or drifting out. Also, when reducing the vehicle speed in this way, the target brake fluid pressure P, -
As mentioned above for P4, the yaw rate ψ is the limit yaw rate ψ5
Since it is determined to match the yaw rate, it is possible to increase the yaw rate to the limit and improve the turning performance as much as possible.

In addition, if the above-mentioned braking operation becomes impossible due to a failure in the hydraulic pressures 13 to 17, the pressure in the accumulator pressure circuit 18 disappears, so the cut valves 11L, IIR, 12L, and 12R are connected to the corresponding systems 7L, 7R, 8L, and 8R. to open. Therefore, when the brake pedal 5 is depressed, the master cylinder hydraulic pressure output from the master cylinder 6 to the systems 7 and 8 is directly applied to the wheel cylinders 3L, 3R, and 4L.

Heading to 4R, you can brake each wheel directly without becoming unable to brake.

By the way, the configuration of the illustrated example allows the controller 31 to easily execute a well-known anti-skid control program or traction control program to prevent wheel braking slip or acceleration slip, and these controls and the automatic brake control described above can easily prevent wheel braking slip or acceleration slip. By combining these, it is also possible to eliminate the instability of vehicle behavior when applying braking or driving force that exceeds the capacity of the wheels and tires.

(Effects of the Invention) Thus, as described above, the device of the present invention suppresses the excessive vehicle speed that causes undesirable turning behavior of the vehicle by automatically braking the wheels on the inside and outside of the turn, and at this time, the yaw rate increases to the limit. Since the system is configured to automatically determine the braking force for each wheel, the vehicle can always run in the grip range, preventing undesirable turning behavior such as vehicle spins and drift-outs, which greatly improves safety. In addition, it is possible to improve the turning performance of the vehicle as much as possible.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of the turning behavior control device of the present invention, Fig. 2 is a system diagram showing an embodiment of the device of the present invention, Fig. 3 is a flowchart showing the control program of the controller on the same side, Fig. 4 is a diagram illustrating the tire grip limit vehicle speed, and FIG. 5 is a diagram illustrating the relationship between the electromagnetic proportional valve drive current and the target brake fluid pressure. IL, IR...Front wheel 2L, 2R...
・Rear wheels 3L, 3R, 4L, 4R...Wheel cylinder 5...Brake pedal 6...Master cylinder 11L, IIR, 12L, 12R...
Cut valve 13...Accumulator 14...Pump 19L, 19R, 2OL, 2OR...Cylinder 2LL, 21R, 22L, 22R...Solenoid proportional valve 31...Controller 32, 33.41-44. ...Pressure sensor 34...Rudder angle sensor 35-38...Wheel rotation sensor 39...Yaw rate sensor 40...Lateral acceleration sensor Fig. 1 Fig. 3 Fig. 4

Claims (1)

[Claims] 1. In a vehicle that is turned by steering the wheels, a steering amount detection means for detecting the steering amount of the wheels, a vehicle speed detection means for detecting the vehicle speed, a limit vehicle speed detection means for determining a tire grip limit vehicle speed for each steering amount, and this steering limit yaw rate calculation means for calculating a limit yaw rate of the vehicle to be obtained based on the tire grip limit vehicle speed and tire grip limit vehicle speed; 1. A turning behavior control device for a vehicle, comprising automatic braking means for braking inner and outer wheels, respectively.