JPH03182861A - Turning behavior controller for vehicle - Google Patents

Abstract

PURPOSE:To ensure safe running of a vehicle by detecting a tire-slip-range, in which undesirable turning behavior of a vehicle takes place, based on a ratio of turning behavior variation to steering angle variation, and, when the vehicle is judged to be in the range, controlling automatic brakes of right and left wheels so as to avoid undesirable turning behavior of the vehicle. CONSTITUTION:A steering angle detecting means A, a vehicle speed detecting means B, and a turning behavior detecting means C, which detects at least a yawing rate as the behavior accompanying a turn of a vehicle, are provided. When a ratio of turning behavior variation is smaller than a pre-set value, it is judged by a wheel slip judging means D that the vehicle-tire is in a lateral slip condition. In addition, a tire-grip-limit-vehicle-speed corresponding to the steering angle is obtained by a limit-vehicle-speed detecting means E, and a target yawing rate, which corresponds to both this limit-vehicle-speed and the steering angle, is obtained by a target yawing rate setting means F. When the vehicle-tire is judged to be in a slip condition, the brake is put on both inner and outer wheels with respect to the turning direction separately by a breaking means G so that the detected vehicle speed is lowered to the limit-vehicle-speed in such a manner that the detected yawing rate approaches the target yawing rate.

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) This type of vehicle turning behavior control device, that is, automatic braking technology, is a device that applies braking force only to the vehicle on the inner side of the turning direction during turning, and assists the generation of the vehicle's yaw rate. This is proposed in Japanese Patent Application Laid-Open No. 63279976.

(Problems to be Solved by the Invention) However, this device is intended to promote the generation of the yaw rate of the vehicle during turning, and is not effective in suppressing 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, a centrifugal force that exceeds the grip limit of the wheels is generated on the vehicle, causing the vehicle to widen the vehicle. It is not possible to prevent the vehicle from slipping laterally, causing the vehicle to spin or drift out to the outside in the turning direction.

The present invention provides the following advantages: since such undesirable turning behavior can be determined from the rate of change in vehicle behavior with respect to changes in steering amount, and because undesirable turning behavior is based on excessive vehicle speed and excessive yaw rate, To provide a device which suppresses the excess vehicle speed at the time of the determination by automatic braking, and at this time individually brakes the inner and outer wheels in the turning direction so as to suppress the excessive yaw rate, thereby preventing undesirable turning behavior from occurring. The purpose is to

(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 turning behavior detection means for detecting at least a yaw rate as a behavior accompanying turning of the vehicle; A wheel slip determining means for determining a lateral slump state, a limit vehicle speed detecting means for determining a tire grip limit vehicle speed corresponding to the steering amount, and a target yaw rate for determining a target yaw rate corresponding to these steering amounts and tire grip limit vehicle speed. a setting means; and a braking means for individually braking the inner wheel and the outer wheel in the turning direction so that the detected vehicle speed decreases to the limit vehicle speed in such a manner that the detected yaw rate approaches the target yaw rate when determining the slip state. It is composed of

(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. The turning behavior detecting means detects at least a yaw rate as a behavior accompanying the turning of the vehicle, and the wheel slip determining means detects a lateral slip state of the wheels and tires when the rate of change in the turning behavior with respect to a change in the steering amount is less than a set value. It is determined that Further, the target yaw rate setting means determines the target yaw rate that should naturally be obtained from the steering amount and tire grip limit vehicle speed. When determining the slip state, the braking means individually controls the inner and outer wheels in the turning direction so that the vehicle speed detected by the vehicle speed detection means decreases to the tire grip limit vehicle speed in such a manner that the yaw rate determined by the turning behavior detection means approaches the target yaw rate. to brake.

This reduces the vehicle speed, and the wheels and tires are free from lateral slip under any steering conditions, allowing the vehicle to run in the grip range at all times, and the vehicle's yaw rate does not exceed the target yaw rate, causing the vehicle to It can prevent spinning or drifting out when turning.

(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 and 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 7.8 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, and reaches wheel cylinders 4L and 4R, where it brakes the rear wheels 2 and 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 65 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 I by the circuit 18.
LL, IIR, 12L, and 12R, and these cut valves respond to the accumulator internal pressure to open the corresponding system 7.
L.

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 the drain circuit 23 according to the solenoid drive currents i and -i4, and supply hydraulic pressure proportional to the corresponding solenoid drive current to the cylinders 19L, 19R, 2OL, and 2OR. do.

The solenoid drive current lI~14 is 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. Yaw rate sensor 3 detects signals from wheel rotation sensors 35 to 38 that detect wheel rotation speed ω3 and right rear wheel rotation speed ω4, respectively, and yaw rate Y of the vehicle.
Signal from 9, I detects the lateral acceleration G acting on the vehicle
The signal from the G sensor 40 is manually input. Note that the yaw rate Y and the lateral acceleration G are examples of behavior associated with turning of the vehicle.

Based on this input information, the controller 31 repeatedly executes the control program shown in FIG. 3 at fixed time intervals/it to perform normal wheel braking and wheel braking for turning behavior control, which will be described below. That is, first, in steps 41 to 43, system 7,
Read the hydraulic pressure PF, PR, wheel rotation speed ω1 to ω1, yaw rate) Y, lateral acceleration G1, and steering angle θ of 8. pressure PF,
Of course, PR is 0 unless the brake pedal 5 is depressed. In the next step 44, the current turning behavior read value Y (or G) and steering angle θ and the turning behavior Y (OLD) [or G (0], D)] and θ (01, D) and the difference AYC or AG) and Aθ are calculated. Next, in step 45, the ratio AY/Aθ (or A
G/Aθ> is calculated. In the next step 46, the vehicle speed V is calculated from the wheel rotational speeds ω1 to ω4. 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 Ra, V=R, (ω1+
It is obtained by calculating ω2)/2. However, during braking, a pseudo vehicle speed is determined from all wheel rotational speeds ω1 to ω4 using a method normally used in anti-skid control, and this is calculated as the vehicle speed V.
shall be.

In step 47, the vehicle speed V is determined from the table data of FIG.
Turning behavior change rate AY with respect to steering amount change corresponding to
/Aθ (AG/Aθ) setting value β is looked up.

Figure 4 shows the boundary between whether the wheels and tires are gripping the road surface or slipping, expressed as a rate of change in turning behavior relative to a change in the amount of steering, which can be determined in advance through experiments as a function of vehicle speed V for each vehicle. . Therefore, the area above the boundary line in FIG. 4 indicates the grip area, and the area below the boundary line indicates the slip area. For example, the vehicle speed is V. If the vehicle is running at point A (in the slip region), this means that the tires are slipping laterally because they cannot resist the centrifugal force that accompanies cornering, causing the vehicle to spin or drift out. The set value β is the turning behavior ratio on the boundary line corresponding to the current vehicle speed in FIG. 4 (β in FIG. 4 is the vehicle speed V). ) and the vehicle speed V. If the turning behavior ratio AY/Aθ (or /IG/Aθ) is greater than or equal to the set value β, it indicates that the wheels and tires are gripping the road surface, but if it is less than the set value β, the wheels and tires slip laterally. Show what you are doing.

In step 48, it is determined from this whether the grip region is a grip region where AY/Aθ≧β (or /IG/Aθ≧β) or not (slip region). If the grip is within the grip range, undesirable turning behavior such as vehicle spin or drift-out will not occur, so the control proceeds to steps 49 to 51 and the brake pedal depression force is used as shown below. I do. That is, in step 49, the target brake fluid pressure P1. to the front wheel cylinders 3L, 3R is determined. P2 is set to be the same as the hydraulic pressure Pp of the corresponding system 7, and the target brake hydraulic pressure P3 to the rear wheel cylinders 4L and 4R is set. P, is set equal to the hydraulic pressure P, of the corresponding system 8. Then, in step 50, the electromagnetic proportional valves 21L, 21R, 22L are determined from the table data corresponding to FIG. 6 so that these target brake fluid pressures can be obtained.

22R drive currents 11 to 14 are looked up, and in step 51 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, the cut valves 11L, IIR, 12L, and 12R will respond to the corresponding systems 7L, 7R, 8L, and 8R. It's blocked. For this reason, solenoid proportional valves 2LL, 21R, 22L,
22R is supplied with drive currents 11 to 1, and pressures proportional to these are applied to the corresponding cylinders 19L, 19R, 2OL.
, 2OR, these cylinders can supply brake fluid pressure to the corresponding wheel cylinders. By the way, these brake fluid pressures are applied to the master cylinder 6.
In order to determine the electromagnetic proportional valve drive current +1'□+1 as described above so that it is the same as the hydraulic pressure PFI F'11 from PFI F'11, each wheel is braked normally according to the brake pedal depression force.

In addition, in the final step 52, the current read value Y (or G)
and θ are set to Y (OLD) C or G (01, D)] and θ (OLD) in preparation for the next step 44.

If the slip area is determined in step 48, step 5
The control proceeds to step 3, and the automatic brake for turning behavior control is applied as follows. That is, in step 53, the tire grip limit vehicle speed V corresponding to the current steering angle θ is determined from the table data corresponding to FIG.

Look up. In FIG. 5, α indicates the tire grip limit vehicle speed, which varies depending on the steering angle θ, but if the vehicle speed V is less than 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, as described above with reference to FIG. 4, the tires cannot resist the centrifugal force that accompanies cornering and slip laterally, causing the vehicle to spin or drift out. For example, while driving at point B in Figure 5 (vehicle speed V, steering angle θ), by increasing the steering angle θ to θ1, driving at point A (same as point A in Figure 4). To explain the case where the transition is from the grip area to the slip area,
This causes the vehicle to spin or drift out. In this case, the vehicle speed is the limit vehicle speed V on the line α.

If it is below, the above-mentioned undesirable turning behavior will not occur.

In step 54, the target yaw rate Y8 of the vehicle, that is, the target yaw rate that should naturally be obtained from the current steering amount θ and the tire grip limit vehicle speed Vs is determined from Ys=GJvs. Here, 65 is the limit lateral acceleration at the tire grip limit of the vehicle body, which varies depending on the vehicle, for example 0.8
It is about G. In the next step 55, the deviation lEv between the detected vehicle speed V and the limit vehicle speed V is determined, and the deviation between the detected yaw rate Y and the target yaw rate Y5 is determined. Next, in step 56, the outer wheels in the turning direction are used to reduce the vehicle speed deviation By and the yaw rate deviation EY, that is, to bring the vehicle speed V closer to the limit vehicle speed V in such a manner that yawlay (Y) approaches the target yawlay (Ys). 3-Target brake fluid pressure P for. U, and the target brake fluid pressure P for the inner wheel in the turning direction, Pout=K, -E, +, ε.

P,l,-ni,・B,-ni,・snake.

Find it by Here, is the proportionality constant for vehicle speed deviation, K
, are proportional constants for the yaw rate deviation, and these make Ev
-0, Snake, and the speed up to -0 is determined. Also, if the vehicle is turning right, the target brake fluid pressure P for the left front and rear wheels IL, 2L is the target brake fluid pressure P for the wheels on the outside in the turning direction.
. Corresponding to ut, the target brake fluid pressure P2 for the right front and rear wheels IR, 2H. P4 corresponds to the target brake fluid pressure Pl for the inner wheel in the turning direction, and the opposite is true if the vehicle is turning left.

Next, the control proceeds to step 50.51, where the electromagnetic proportional valve drive current h~14 is used to obtain the target brake fluid pressure P1~P.
By finding this and outputting it to the corresponding solenoid proportional valve,
Individual automatic braking of the left and right wheels brings the yaw rate closer to the target yaw rate while bringing the vehicle speed to the limit vehicle speed. Therefore, when entering the slip region, the vehicle speed is reduced to the limit vehicle speed and returned to the grip region = 14, and the yaw rate of the vehicle is prevented from exceeding the target yaw rate, preventing the vehicle from spinning or drifting out. can do.

In addition, if the above-mentioned braking operation becomes impossible due to a failure of the hydraulic pressure sources 13 to 17, the pressure in the accumulator pressure circuit 18 disappears, so the cut valves 11L, IIR, 12L, 12R
opens the corresponding systems 7L, 7R, 811, and 8R.

Therefore, when the brake pedal 5 is depressed, the master cylinder hydraulic pressure output from the master cylinder 6 to the systems 7, 8 is directly applied to the wheel cylinders 3L, 3R, 4L,
Heading to 4R, you can brake each wheel directly without becoming unable to brake.

<Effects of the Invention> Thus, as described above, the device of the present invention can detect the tire slip region where undesirable turning behavior of the vehicle occurs, depending on the ratio of turning behavior change (yaw rate change/IY or lateral acceleration change 71G, etc.) to steering amount change Aθ. The system is configured to automatically brake the left and right wheels to suppress excessive vehicle speed and excessive yaw rate that would cause undesirable turning behavior of the vehicle at the time of this determination.
This allows the vehicle to run in the grip range at all times and prevents the yaw rate from exceeding the target yaw rate.
This makes it possible to prevent undesirable turning behavior such as vehicle spin and drift-out, greatly contributing to safety.

[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, and Fig. 4 is the main A slip area-grip area determination diagram used in the invention, FIG. 5 is a diagram illustrating tire grip limit vehicle speed, and FIG. 6 is a relationship diagram between electromagnetic proportional valve drive current and target brake fluid pressure. IL, IR...Front wheel 2L, 2R...Rear wheel 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 21L, 21R, 22L, 22R... Solenoid proportional valve 31... Controller 32.33... Pressure sensor 34... Rudder angle sensor 35-38... Wheel rotation sensor 39... Yaw rate sensor 40...
Lateral G sensor 7 Figure 5

Claims (1)

[Scope of Claims] 1. In a vehicle that is turned by wheel steering, a steering amount detection means for detecting the amount of wheel steering, a vehicle speed detection means for detecting vehicle speed, and at least a yaw rate as a behavior accompanying turning of the vehicle. a turning behavior detection means for detecting a turning behavior; a wheel slip determination means for determining that a wheel tire is in a lateral slip state when a change rate of the behavior with respect to a change in a steering amount is less than a set value; and a tire grip limit vehicle speed corresponding to the steering amount. limit vehicle speed detection means for determining a target yaw rate corresponding to the steering amount and tire grip limit vehicle speed; and target yaw rate setting means for determining a target yaw rate corresponding to the steering amount and the tire grip limit vehicle speed; A turning behavior control device for a vehicle, comprising: braking means for individually braking an inner wheel and an outer wheel in a turning direction so as to reduce the vehicle speed to the limit vehicle speed.