JP2652806B2 - Anti-skid control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to anti-skid control for vehicles, and more particularly to control of pressure applied to a rear wheel brake.

[Conventional technology]

In conventional anti-skid control, emphasis is placed on stability on a road surface having a different friction coefficient between the left and right wheels of the vehicle (referred to as a straddling road). Select low control for controlling the hydraulic pressure of the rear wheel brake (Japanese Patent Laid-Open No. 61-33 / 1986)
353).

[Problems to be Solved by the Invention] However, as in the conventional case, when the load applied to the left and right wheels is different from each other, the braking force is sufficiently applied to one of the rear wheels when the load on the left and right wheels is different only by the select-low control. Because it had never been before, there was a disadvantage that the braking distance was extended.

In addition, the four-wheel steering (hereinafter referred to as 4WS) system improves vehicle stability and allows more use of the braking force of the rear wheels. Due to problems such as poor stability at the time of sudden braking on the road, this braking force cannot be fully utilized.

Therefore, the present invention adds select-low control to the control of the rear wheels, independent control in which the hydraulic pressure is independently controlled by the locking tendency for each wheel, and control of the oil pressure of the wheels that do not exhibit the locking tendency by the wheels that exhibit an intermediate locking tendency. The purpose of the present invention is to improve the braking force and ensure stability by providing respective control devices for the independent limiting control and switching to the optimum control according to the driving situation.

[Means for solving the problem]

As is Anchisukitsudo control device of the present invention in order to solve the above problems is shown in FIG. 1, the left and right rear wheel speed detecting means M ₁ for detecting the speed of the rear wheels of the vehicle, on the basis of the wheel speeds of the left and right rear wheels a locking tendency determination means M ₂ separately determined locking tendency of the rear wheels, a running state detecting means M ₄ for detecting a running condition of the vehicle, the rear wheels based on the detection signal of the running state detecting means M ₄ (right rear wheel 5, the wheel control selection means M ₃ after selecting either of the select-low control and independently limit control and independent control of the control of the left rear wheel 7), rear wheel selected by the rear wheel control selection means M ₃ controlled by adjusting the locking tendency of the rear wheels based on (select-low control and independently limit control and independent control) and control means M ₅ for controlling the brake pressure.

[Action]

The select row control selected by the rear wheel control selecting means controls the locking tendency of the other rear wheel in accordance with the rear wheel having a large locking tendency, and the independent restriction control increases the other rear wheel by the rear wheel having a large locking tendency. Control is performed by limiting the pressure tendency, and independent control is performed independently in accordance with the locking tendency of each rear wheel. The braking force of the rear wheels by these controls is the largest in independent control, the smallest in select low control, the independent limiting control indicates an intermediate braking force, and the independent limiting control and the independent control are selected from select low control. When increasing the braking force on the rear wheels to improve the braking force, or returning from independent control or independent limiting control to select low control, reducing the braking force on the rear wheels to improve stability during braking May be secured.

〔Example〕

FIG. 2 shows a configuration of an anti-skid control device according to one embodiment of the present invention. The present embodiment is an example in which the present invention is applied to a front-wheel steering and rear-wheel drive four-wheeled vehicle.

Electromagnetic pickup-type or photoelectric conversion-type rotational speed sensors 9, 11, 13, 15 are arranged on the right front wheel 1, the left front wheel 3, the right rear wheel 5, and the left rear wheel 7, respectively. A pulse signal is output according to the rotation of 7. Further, hydraulic brake devices 17, 19, 21, and 23 are disposed on the wheels 1, 3, 5, and 7, respectively, and the brake pedal 25 or the pressure control actuators 27, 29, 31, and 3 are provided.
The hydraulic pressure is sent to or regulated by the hydraulic brake devices 17, 19, 21, and 23 via the hydraulic lines 35, 37, 39, and 41 by means of 3. Therefore, the braking force on the wheels 1, 3, 5, 7 can be adjusted by the actuators 27, 29, 31, 33 and the brake pedal 25. The depression state of the brake pedal 25 is detected by the stop switch 43, and an ON signal is output during braking and an OFF signal is output during non-braking.

Normally, depressing the bregie pedal 25 generates hydraulic pressure in the hydraulic cylinder 45, which can brake the wheels 1, 3, 5, and 7.However, as a hydraulic source for slip control, an engine drive or an electric motor There is also provided a hydraulic pump 47 for generating a hydraulic pressure by the drive of. The electronic control circuit 49 controls these actuators 27, 29, 31, 33 to adjust the hydraulic pressure from the hydraulic cylinder 45 or the hydraulic pump 47 and send it to the hydraulic brake devices 17, 19, 21, 23. The braking force can be adjusted for each of the wheels 1, 3, 5, and 7. The hydraulic brake devices 21 and 23 of the rear wheels 5 and 7 may be adjusted by one actuator. In that case, three hydraulic actuators are sufficient.

The main relay 51 switches the connection between the electromagnetic solenoids of the actuators 27, 29, 31, and 33 and the power supply according to the output of the electronic control circuit 49. The indicator lamp 53 is provided with a wheel rotation speed sensor 9, 11, 13, 15
If a failure occurs in the anti-skid control device, such as disconnection of the electromagnetic solenoids of the actuators 27, 29, 31, 33, or disconnection of the stop switch 43, an error occurs in the system by the driver with the output of the electronic control circuit 49. Notify that

The electronic control circuit 49 is supplied with electric power when the ignition switch 50 is turned on, and the vehicle speed sensors 9.1
1, 13 and 15, and the signals from the stop switch 43 and the load sensors 95 and 97. In the case of 4WS, for the slip control, information from the 4WS control electronic control circuit (hereinafter referred to as 4WSECU) 99 is added. To generate an output for controlling the actuators 27, 29, 31, 33, the main relay 51 and the indicator lamp 53 as described above.

The electronic control circuit 49 has a circuit configuration as shown in FIG. Here, the waveform shaping amplifier circuits 60, 62, 64, and 66 convert the signals of the vehicle speed sensors 9, 11, 13, and 15 into pulse signals of a form suitable for processing by the microcomputer 68, and the buffer circuit 70 outputs the signal from the stop switch 43. The power supply circuit 72 temporarily holds signals, supplies a constant voltage to the microcomputer 68 and the like when the ignition switch 50 is turned on, and the microcomputer 68 includes a CPU 76, a ROM 78, a RAM 80, an I / O circuit 82, and the like. Thus, a control signal is output to each drive circuit based on the input data.

The drive circuits 84, 86, 88, 90, 92, and 94 output signals corresponding to control signals from the microcomputer 68, and among them, the actuator drive circuits 84, 86, 88, 90
Drives the electromagnetic solenoids of the actuators 27, 29, 31, and 33, and the main relay drive circuit 92 energizes the coin 98 of the main relay 51 having the normally open contact 96 to turn on the normally open contact 96. The indicator lamp drive circuit 94 turns on the indicator lamp 53.

Next, the processing and operation of the anti-skid control device thus configured will be described.

When the ignition switch 50 is turned on, the power supply circuit
The constant voltage from 72 is applied to the microcomputer 68 and the like, and the CPU 76 of the microcomputer 68 starts executing the arithmetic processing according to the program stored in the ROM 78 in advance.

This anti-skid control processing will be described with reference to the control flow shown in FIG.

In step 100, the CPU is initialized when the ignition key is ON. In step 200, signals from the vehicle speed sensors 9, 11, 13, 15 are received, and the pulse input time is stored. Step 30
At 0, the speed / acceleration of each wheel and the estimated vehicle speed are obtained based on the time at step 200. At step 400, the tendency of the wheels to lock is determined from the speed and acceleration at step 300, and the mode is switched to the pressure increasing mode, the holding mode, or the pressure reducing mode. Pressure increase, holding, and pressure reduction are collectively referred to as a locking tendency, and the locking tendency increases as the pressure decreases. In step 500, the respective modes determined in step 400 are branched into select low, independent restriction, and independent control processes for each rear wheel control condition. Step
At 600, processing for driving the actuator in the mode determined at steps 400 and 500 is performed.

The method of the rear wheel control processing in step 500 will be described. In step 510, it is determined whether or not the control target is the rear wheel. If the control target is not the rear wheel, the process proceeds to step 600, and the process proceeds to step 600.
Then, the actuator is driven in accordance with the mode determined in steps 400 and 500. If the control object is the rear wheel, the process proceeds to step 520.In step 520, the control condition of the rear wheel is determined.If the control target is the select low control, the process proceeds to step 530 to change the mode of the wheel having a tendency to lock to the mode of the wheel having no rock tendency. Replace with Step for independent limit control
Proceed to 540 to restrict the mode of non-locking wheels with rocking wheels. In the case of independent control, the process proceeds to step 550, and the mode determined for each wheel is kept as it is.

Here, the operation mode (pressure increase mode,
The details of switching to the holding mode and the pressure reducing mode will be described with reference to the control flow of FIG.

At step 410, it is determined whether or not the slip ratio of the wheel is large. If it is, the process proceeds to step 420, where it is determined whether or not the wheel acceleration is positive. When the wheel acceleration is positive, the process proceeds to step 430 to select the holding mode, and when the wheel acceleration is negative, the process proceeds to step 440 to select the decompression mode. When the slip ratio is small in step 410, the pressure increasing mode of step 450 is selected. The flow of steps 410 to 450 proceeds to step 500 after calculating the order of all the wheels, for example, front right wheel → front left wheel → rear right wheel → rear left wheel.

Next, the processes of select row control, independent limit control, and independent control will be described with reference to a control flow.

 FIG. 6 shows a control flow of the select row control.

First, in step 531, it is determined whether the control mode of one of the rear wheels is the pressure reduction mode and the other is the pressure increase mode. In the single wheel pressure reduction mode and the single wheel pressure increase mode, the process proceeds to step 532, where the control mode of the wheel on the pressure increase mode side is adjusted to the pressure reduction mode. If it is not the one-wheel pressure reduction mode or the one-wheel pressure increase mode, the process proceeds to step 533.In step 533, it is determined whether or not one wheel is in the hold mode and the other one is in the pressure increase mode. Time is a step
Proceeding to 534, the control mode on the pressure increasing mode side is switched to the holding mode in step 534.

As described above, the select row control is a mode in which the rear wheels are controlled in the pressure reduction mode.

The control flow of the independent control is as shown in FIG.
At 551 each rear wheel remains in the mode selected in step 400.

 FIG. 8 shows a control flow of the independent restriction control.

In step 541, the output mode determined in step 400 for both wheels is checked, and it is determined whether one wheel is in the pressure reducing mode and the other wheel is in the pressure increasing mode. In the case of the one-wheel pressure reduction mode or the one-wheel pressure increase mode, the process proceeds to step 542, and the output mode of the wheel whose pressure increase mode is selected in step 542 is adjusted to the hold mode.

Here, the characteristics of the rear wheel control by the select row control, the independent limit control, and the independent control will be seen in an image graph of the rear wheel control in FIG. This graph shows changes in the brake oil pressure applied to the left and right rear wheels and changes in the rear wheel speed when the road surface friction coefficients of the left and right rear wheels are different.

When the wheel speed (left rear wheel speed V _WRL , right rear wheel speed V _WRR ) is in a high speed range, select low control indicated by a solid line is performed, and pressurization / release of the brake oil pressure for both the left and right wheel oil pressures P _RR and P _RL is repeated. When the hydraulic pressure is applied, the rear left wheel speed V _WRL gradually decreases, and when the hydraulic pressure is released, the rear left wheel speed V _WRL increases. Right rear wheel speed
V _WRR gradually reduces the speed while repeatedly adding and releasing hydraulic pressure. Then, the vehicle speed or vehicle estimated speed (wheel speed V _WRR, V _WRL) is or time t ₁ is determined to slow, the oil pressure of the according to the right rear wheel in the case of converting the control method from the time t ₁ from the start of control Watch the change. Select-row control is indicated by a solid line, independent control is indicated by a broken line, and independent control is indicated by a chain line. According to this, in the select low control, the addition and release of the brake oil pressure is continued at a fixed cycle, and in the independent control, the brake oil pressure is rapidly increased,
In the independent limit control, the brake oil pressure takes a control form that continues to increase at a slow speed, and in the independent limit control, the rear wheels are controlled with a brake oil pressure that is almost intermediate between the oil pressure in the select low control and the oil pressure in the independent control. You can see that.

As described above, the independent limit control is a control in which, when there is a difference in the locking tendency between the left and right rear wheels, the wheel having a large locking tendency restricts the pressure increasing tendency of the other rear wheel. Instead, the brake hydraulic pressure is intermediate between select-low control and independent control.

Next, details of the determination of the rear wheel control at step 520 will be described with reference to a control flow.

The method of branching (switching) to select low, independent restriction, and independent control in step 520 includes the following methods based on signals from the wheel speed detecting means M ₁ and the traveling state detecting means M ₄ . As the running state detecting means M _4, a load detecting means for detecting a load of the left and right rear wheels, Fueiru detecting means 4WS controller, vehicle speed detecting means for detecting a vehicle speed of the vehicle, detects an actual steering angle of the vehicle Steering angle detecting means, lateral acceleration (lateral G) detecting means for detecting the lateral acceleration of the vehicle, running road surface detecting means for detecting the running road surface of the vehicle, yaw rate detecting means for detecting the yaw rate of the vehicle, side slip angle of the vehicle Is included.

(1) Method based on vehicle speed This method switches the control of the rear wheels according to the vehicle speed or the estimated vehicle speed. In other words, select-low control is used in the high-speed range, stability is ensured, and the braking force is emphasized by switching to the independent limit control and the independent control as the vehicle speed decreases.
Further, the control of the rear wheels is switched according to the time from the start of control or the number of control cycles. That is, select low control is performed in the initial stage of control to ensure stability, and thereafter, switching is made to independent limit control and independent control to emphasize braking force.

(2) Method using 4WS fail signal In this method, if independent or independent limiting control is performed by the 4WS fail signal, the control is switched to select low control to ensure stability during braking during 4WS fail.

(3) Method to cope with the occurrence of the braking force difference between the left and right rear wheels in advance This method is independent control or independent limitation when the left and right rear wheel left and right load difference is large, based on the rear wheel left and right load or the signal from the active suspension. Emphasis is placed on braking force as control, and when the load difference is small, select-low control is used to ensure stability.

(3) I: Switching method based on steering wheel angle and vehicle speed (3) II: Method for estimating and switching the amount of lateral load movement using an acceleration sensor (4) Estimating the coefficient of friction (hereinafter referred to as μ) with the road surface Independently on high μ roads and rough roads, at least one wheel is switched to select low control when on low μ roads. (5) 4WS fail signal, yaw rate, steering wheel angle, vehicle speed (6) Active suspension There are methods such as switching based on the signal of the failure, yaw rate, lateral acceleration, steering wheel angle, and vehicle speed.

 FIG. 10 shows a control flow according to the method (1).

In step 5201, the vehicle speed is set to the preset speed V ₁
Determine if it is faster. Vehicle speed if faster than the speed V ₁ to the select-low control proceeds to step 530.
If the vehicle speed is slower than the speed V ₁ proceeds to step 5202,
Vehicle speed determined whether faster than the speed V ₂ which is set in advance in step 5202. Here, the vehicle speed V ₁ > the vehicle speed V ₂ . When than the speed V ₂ the vehicle speed is fast advances to step 540, performs independent restriction control in step 540. If the vehicle speed is slower than the speed V ₂ proceeds to step 550, and independent control at step 550.

 FIG. 11 shows a control flow according to the method (2).

At step 5203, read the 4WS file signal and execute step 5.
At 204, the 4WS control ECU detects a failure in the operation of the sensor and CPU,
It is determined whether a fail signal has been generated. 4WS
If there is Fueiru signal proceeds to step 530, select-low control at step 530, in the case of no normal Fueiru signal determines whether the vehicle speed at step 5205 proceeds to step 5205 is faster than the speed V _3. If the vehicle speed is faster than the speed V _3, the process proceeds to step 540, performs an independent restriction control in step 540, if slower than the speed V ₃ performs the independent control at step 550 the process proceeds to step 550.

In the method (3), the following can generally be said.

Absolute value α of lateral acceleration related to lateral load movement amount
Is the vehicle speed (hereinafter referred to as the vehicle speed) as V, and the absolute value δ of the actual steering angle generated by operating the steering wheel is roughly in the linear region in the steady state, α = δV ² / L… <1> (where L is Wheelbase). Therefore, when a contour line with α constant is drawn, the relationship between the vehicle speed V and the actual steering angle δ is approximately as shown in the graph of FIG. Here, the line K ₁ has a small value α, and the line K ₂ has a value α.
In, a line K ₃ shows a case where the value α large. The line K ₄ shows a case where the absolute value of the acceleration alpha is the maximum value of the road surface μ and the vehicle speed V, the absolute value of the absolute value by connexion determined acceleration δ of actual steering angle alpha. Area beyond the Supporting connexion K ₄ is a region in which characteristics of the vehicle deviates from the linear region (drift state), the the present invention linear K ₁ ~K ₄ to control switching reference.

A method for switching the control of the above (3) I will be described with reference to the control flow of FIG.

First, the vehicle speed V in step 5206, calculates the absolute value δ of the actual steering angle obtained from Matsupu corresponding to the graph shown in Figure 13 that the control switching reference K ₁ ~K ₄ has been stored in the ROM corresponding to the lateral acceleration . Step the actual steering angle δ and the reference K ₁ ~K ₄ with the following step
5207, step 5208, step 5209, sequentially comparing and determining the order of step 5210, [delta] <to select-low control in step 530 in K ₁ and _{δ ≧ K 4, K 1 ≦} δ <K 2 and K ₃ ≦ δ <K ₄ Step 54
The control is switched to the independent limit control of 0, and to the independent control of step 550 when K ₂ ≦ δ <K ₃ . In this method, a road surface μ estimating process (to be described later) is also used, and appropriate control switching criteria K _{1 to} K ₄ are stored in the ROM according to the road surface condition (bad road, high μ, low μ). Alternatively, the rear wheel control may be switched according to the road surface condition. According to this method, the performance in the turning state can be improved with a relatively small increase in cost by simply adding a handle angle sensor and a processing circuit to the basic configuration of the conventionally used anti-skid control device. That is, in the vehicle linear (stable) region not exceeding the limit, the steering stability and the braking efficiency are simultaneously improved by switching the rear wheels to the independent control side in accordance with the increase of the lateral acceleration (transfer of the left and right loads). On the other hand, in the vehicle non-linear (unstable) region exceeding the limit, the spin is prevented by switching to the select low control side in accordance with the increase in the turning amount of the steering angle, so that a braking state emphasizing stability can be exhibited.

Since the first equation holds in a steady state, it does not hold immediately after a sudden steering operation. Therefore, more reliable and stable control is possible by switching the control under the condition that there is no sudden change in the steering angle for a predetermined time or more.

The switching by the method (2) of (3) will be described based on the control flow of FIG.

In this case, it is intended to further improve the performance at the time of turning by using a sensor (hereinafter, referred to as a lateral G sensor) for detecting the acceleration in the left-right direction in combination with the switching method I in the above (3). . First, in step 5211, the vehicle speed V, the actual steering angle δ, and the actual measured value α of the lateral acceleration obtained from the lateral G sensor are calculated. In the following step 5212, the value of the lateral acceleration to be naturally generated is obtained from the vehicle speed V and the actual steering angle δ if the motion characteristic of the vehicle obtained by the above-mentioned equation (1) is in the linear region. Since this is used as a comparison determination reference value for switching the rear wheel control, this value is hereinafter referred to as a lateral acceleration reference value, and the first reference value is K ₁ G,
Let the second reference value be K ₂ G.

Here, K ₁ G is a value obtained by multiplying a value obtained from the first equation by a predetermined proportional constant (for example, 0.6), and similarly, K ₂ G is a value obtained by multiplying the value by a proportional constant (for example, 0.2).

In the following step 5212, the actual measured value α of the lateral acceleration and the first lateral acceleration obtained under the same conditions of the vehicle speed V and the actual steering angle δ are compared with the reference K ₁ G. If α <K ₁ G, the step 530 is executed. Proceed to
Perform select row control. Next, in step 5214, the above α is compared with the _second reference K ₂ G, and if α <K ₂ G, step 540
To perform independent limit control, and if α ≧ K ₂ G, step 5
Proceed to 50 to perform independent control.

As described above, according to this switching method, based on the vehicle speed V and the actual steering angle δ, depending on the level of the measured value of the lateral acceleration with respect to the reference value of the lateral acceleration to be generated in the vehicle motion characteristics. ,
If it is close to the reference value, it is regarded as a high μ road or a vehicle stable area in which tires are gripped, and rear wheel independent control is performed to improve braking efficiency.On the other hand, if it is far from the reference value, in other words, if it is significantly below the reference value, it will be low μ. Assuming that the vehicle is in an unstable region where the road or the tire is slipped, the rear wheel select low control is performed and the control with emphasis on the steering stability is performed.

As described above, the addition of the lateral G sensor enables the vehicle state and the tire grip state to be reliably determined, and the control of the rear wheels is appropriately switched according to the determination result. And improvement in braking efficiency can be realized.

 FIG. 15 shows a control flow according to the method (4).

In step 5215, the road surface μ is estimated (details will be described later), and if it is determined in step 5216 that the road is a rough road or a high μ road, step 550 is performed.
Proceed to step 550 to perform independent control in step 550, and
If one wheel is low μ, proceed to step 530 and proceed to step 530.
To select low control, otherwise step 540
Proceeding to step 540, the independent limit control is performed.

Here, the road surface μ estimation is for judging a bad road, a high μ road, and a single-wheel low μ road.

First, bad road determination is a determination made by focusing on abnormally oscillating wheel speeds during braking, such as a wheel vibrating up and down like a wavy road or a stepped road. If a large wheel acceleration / deceleration occurs more than a predetermined number of times, it is determined that the road is bad.

Next, the high-μ road determination is performed when all four wheels satisfy the following conditions, focusing on the tendency of the wheels to fall and the tendency to recover during braking. In other words, referring to the conceptual diagram of the one-wheel low-μ road determination shown in FIG. 16, the wheel speed (slip rate) reference KV ₁ , which is one reference for pressure reduction, and the wheel speed, which is the first determination reference for low-μ road determination With respect to the reference KV ₂ , the wheel drop time Td (the time from when the wheel speed falls below the reference KV _{1 to the} time when the wheel speed falls again to the reference KV ₁ again), which is the second reference for the low μ road determination, The condition is that the wheel speed is always KV ₂ or more and the wheel drop time Td satisfies the condition within a predetermined time for determining a high μ road. Note that, as the wheel drop time Td, a decompression equivalent time may be used in addition to the above method.

Next, the one wheel low μ determination condition is that at least one wheel among the four wheels satisfies the wheel speed reference KV ₁ or less, or the wheel drop time Td satisfies a condition that is equal to or longer than a predetermined time for low μ road determination. It is. As described above, by making a determination based on at least one of the four wheels, particularly in a general vehicle such as a front-wheel-drive vehicle, the front wheel falls first, so that a low μ determination can be made before the rear wheel falls, which enables quick and reliable determination. The rear wheels can be switched to the select low control, and the stability of the vehicle can be improved.

Further, according to the above method, one of the left and right sides is a low μ road, and the other is a high-medium μ road, so-called “crossover road”. Can be improved.

 FIG. 17 shows a control flow according to the method (5).

This branch relates to anti-skid control of vehicles equipped with a 4WS system, and aims to improve maneuverability and stability braking efficiency by switching the rear wheel control method using the yaw rate sensor signal used in the 4WS system. .

First, in step 5218, a fail signal of the 4WS control ECU is read, and in step 5219, a fail determination is made.If the result is a fail, the process proceeds to step 530 to switch to rear wheel select low control, thereby reducing the vehicle stability during the 4WS fail. The compensation is made by moving the anti-skid control to the stable side.

On the other hand, if it is not the 4WS file, the vehicle speed is set at step 5220.
An actual measurement value τ of the yaw rate obtained from V, the actual steering angle δ, and the yaw rate sensor signal is calculated.

In the following step 5221, the yaw rate reference value K _{1 is} calculated from the vehicle speed V and the actual steering angle δ based on the following relational expression based on the vehicle motion characteristics.
To calculate the Y~K ₃ Y.

KiY = ki.δ.V / L (i = 1 to 3) ... <2> Here, ki is a proportional constant of k ₁ = 1.2, k ₂ = 0.6, and k ₃ = 0.2.

In the next step 5222, the actual measured value τ of the yaw rate is compared with the _first yaw rate reference value K ₁ Y obtained under the same condition (V, δ). If τ ≧ K ₁ Y, the process proceeds to step 530 to select low. Perform control. On the other hand, if τ <K ₁ Y, step 5223
Is compared with the _second yaw rate reference value K ₂ Y. If τ ≧ K ₂ Y, the process proceeds to step 550 to perform independent control.

On the other hand, if τ <K ₂ Y, τ is compared with the _third yaw rate reference K ₃ Y in step 5224, and if τ ≧ K ₃ Y,
Proceed to 540 to perform independent limit control.

On the other hand, if τ <K ₃ Y, the flow advances to step 530 to perform select low control.

As described above, according to this method, on the basis of the vehicle speed V and the actual steering angle δ, on the basis of the motion characteristics of the vehicle, the level of the actually measured value of the yaw rate with respect to the reference value of the yaw rate to be originally generated , The rear wheel independent control is performed near the first reference value and if the reference value is not exceeded and the braking efficiency is improved, while the second reference value K ₂ Y which is smaller than the first reference is equal to or less than and If the third reference value K ₃ Y is larger than the third reference value K ₃ Y, intermediate independent limit control is performed, and the value is smaller than the minimum reference value K ₃ Y (including the minus direction) or larger than the reference value K ₁ Y. In such a case, it is considered that the vehicle is in an unstable state (spin, drift, large tire slip, etc.) and rear-wheel select-low control is performed to perform control emphasizing stability (steerability). By using the yaw rate sensor as described above, it is possible to reliably determine the vehicle state, and to appropriately switch the control according to the determination result, and to cope with the anti-skid control in a stable direction during 4WS failure, which is preferable. The steering stability and braking efficiency can be compatible at a high level.

 FIG. 18 shows a control flow according to the method (6).

This is an active suspension (having a hydraulic or pneumatic source, etc., and variably controlling the pressure of a cylinder attached to a plurality of suspensions to change the dynamic characteristics of the suspension and to adapt the vehicle's attitude and motion characteristics to the running conditions. Change)
This is related to anti-skid control of vehicles equipped with the system, and aims to improve steering stability and braking efficiency by switching the rear wheel control method using a lateral G sensor and a yaw rate sensor often used in this system. It is.

First, a fail signal from the active suspension control ECU is read in step 5225, and if the result of the determination in step 5226 is a fail, the process proceeds to step 540 to switch to the independent restriction control.

On the other hand, if the result of the determination at step 5226 is not a fail, at step 5227 the vehicle speed V, its differential value, the actual steering angle δ obtained from the steering wheel angle sensor, the lateral acceleration α obtained from the lateral G sensor, and the yaw rate obtained from the yaw rate sensor Calculate τ. Next, at step 5228, it is determined whether or not all the sensors are normal.

When the vehicle speed V and the actual steering angle δ are almost constant and the vehicle is in a steady state, the vehicle is almost neutrally steered (the stability actor is zero)
Assuming that the sideslip angle β of the center of gravity of the vehicle can be regarded as zero, the turning curvature ρ (the reciprocal of the turning radius) can be calculated by using the coaxial right and left wheel speed difference ΔVw and the tread W obtained based on the wheel sensor signal as follows: ΔVw / (WV)... <3>

When the turning curvature ρ is expressed using the actual steering angle δ and the wheel base L obtained based on the steering wheel angle sensor signal, the following equation is obtained.

ρ = δ / L ... <4> Also, the lateral acceleration α obtained based on the lateral G sensor signal,
When expressed using the vehicle speed V, the following expression is obtained.

^{ρ = α / V 2 ...... <} 5> Further, the following equation and the yaw rate τ obtained based on the yaw rate sensor signal, when expressed using the vehicle speed V.

ρ = τ / V... <6> Therefore, as the failure judgment of the sensors, first, the vehicle speed V,
The actual steering angle δ is read, and it is determined whether or not the change amount is small for a predetermined period of time. If an affirmative determination is made, first, it is assumed that the vehicle is in a steady state, and then the wheel speed sensor signal is obtained based on the third equation. The value of ρ is calculated using ΔVw, V obtained from the above and stored in a predetermined storage area (RO1) in both areas of the RAM. Where ΔV
w is calculated from the idle left and right axes if all four wheel speed sensors are normal, while w is calculated based on the signals of the left and right wheel speed sensors of the normal axle if any of them is abnormal. I do.

Since ΔVw is easily affected by road surface disturbance, a predetermined filter is used. When the variation of ΔVw is large, such as when driving on a rough road, the fail determination is not performed.

Next, the value of ρ is calculated using the actual steering angle δ obtained from the steering wheel angle sensor signal based on the fourth equation, and is similarly stored in another storage area (RO2).

Further, the value of ρ is calculated using the lateral acceleration α obtained from the lateral G sensor signal based on the fifth equation, and is similarly stored in another storage area (RO3).

Next, the value of ρ is calculated using the yaw rate τ obtained from the yaw rate sensor signal based on the sixth equation, and is similarly stored in another storage area (RO4).

The RAM value (RO1) of the value of ρ obtained as described above and (RO2
4) are compared with each other. If the relative error is greater than a predetermined value continuously for a predetermined time or more, it is determined that a sensor signal related to the RAM value is abnormal (for example, a steering wheel angle sensor for RO2, a horizontal sensor for RO3). If the G sensor or RO4, the yaw rate sensor is abnormal.)

As described above, the same physical quantity obtained from a plurality of sensors (in this case, the turning curvature, but also other simple deformations, such as the actual steering angle, lateral acceleration, yaw rate, etc.) is used as a common comparison criterion. After performing the fail determination process for the sensors, if any of the sensor signals is abnormal, the process proceeds to step 5229 and the following steps. If all the sensor signals are normal, the process proceeds to step 5230.

In this step, the yaw rate reference values K ₁ Y and K ₃ Y are calculated from V and δ based on the following relational expression based on the motion characteristics of the vehicle.

KiY = ki.δ.V / L (i = 1,3) (2 ′) Here, ki is a proportional constant of k ₁ = 1.2, k ₃ = 0.2.

Next, in step 5231, the vehicle side slip angle β is calculated using the following equation.

DBETA = τ−α / V + (/ V) · BETA (n−1)... <7> BETA (n) = BETA (n−1) + DBETA. The differential value of β (DBET calculated from the definition equation of the vehicle center-of-gravity skid angle β
A) is an approximation expression of Expression (8), Expression 8 is an integral expression of β using DBETA, and BETA (n) is a current value of ECU calculation, BETA (n−
1) is the previous value. Further, in order to reduce the integration error of the BETA, when the absolute value of the measured value τ of the yaw rate and the measured value α of the lateral acceleration are both equal to or less than a predetermined value close to zero and continue for a predetermined time, or the left and right wheel speed difference ΔVw The BETA value shall be cleared when a similar condition close to zero is satisfied.

Next, in step 5232, the actual measured value τ of the yaw rate is compared with the _first yaw rate reference K ₁ Y obtained under the same condition (V, δ). If τ ≧ K ₁ Y, the flow proceeds to step 530 to select low. Perform control.

On the other hand, if τ ≦ K ₁ Y, the value of τ is compared with the reference K ₃ Y in step 5233. If τ ≦ K ₃ Y, the process proceeds to step 530 to perform select-low control, while τ> K _{If 3} Y, proceed to step 5234. In the same step,
The side slip angle BETA calculated by the first side slip angle reference K ₁ β
(= 5deg). If BETA> K ₁ β, step 53
The process proceeds to 0, and if BETA ≦ K ₁ β, the process proceeds to step 5235. In this step, BETA is set to the second side slip angle reference K ₂ β (= 3de
In comparison with g), if BETA> K ₂ β, the process proceeds to step 540 to perform independent restriction control. If BETA ≦ K ₂ β, the process proceeds to step 550 to perform independent control.

On the other hand, if any one of the sensors is abnormal in step 5228, it is first determined in step 5229 whether only the steering wheel angle sensor is abnormal. Perform determination processing. On the other hand, if a negative determination is made, the process proceeds to step 5236, where it is determined whether only the yaw rate sensor is abnormal.
Proceeding to a step 5237, a rear wheel control switching process based on the vehicle speed V, the steering wheel angle δ, and the acceleration α similar to the method (II) of the above (3) is performed. On the other hand, if a negative determination is made, the process proceeds to step 5238 to determine whether only the lateral acceleration sensor is abnormal. If an affirmative determination is made, the process proceeds to step 5239, and the vehicle speed V, the steering wheel angle δ, and the yaw rate are the same as in the method (5). The rear wheel switching process is performed based on the measured value τ of the rear wheel.

On the other hand, if a negative determination is made, the process proceeds to step 5240, where the vehicle speed V,
It is determined whether or not the actual measured value δ of the actual steering angle obtained from the steering wheel angle sensor signal is normal. If the determination is affirmative, the process proceeds to step 5241 to determine the vehicle speed V and the absolute value of the actual steering angle in the same manner as in the method (3) I. A rear wheel switching process based on the value δ is performed. On the other hand, if a negative determination is made, the process proceeds to step 540 to perform independent restriction control.

As described above, the sensor failure determination is performed by comparing the plurality of sensors with each other, and if the specific sensor does not stop the switching determination even if the failure occurs, the switching determination is changed from time to time to the switching determination considered to be the best with a normal sensor, The reliability and control performance for the file can be improved.

Further, when all the sensors are normal, the rear wheel control is switched by combining the yaw rate τ and the estimated value BETA of the sideslip angle, so that highly accurate and reliable processing can be performed.

Further, at the time of active suspension failure, the anti-skid control is made compatible in a direction to achieve both stability and braking efficiency, so that the vehicle braking performance can be maintained at a high level even during failure.

In the above-described embodiment, the pressure increasing, holding, and pressure decreasing modes have been described. However, in addition to the above, a mode of gradual pressure increasing and gradual pressure decreasing may be added. However, the pressure increase may be gradually increased to limit the pressure increase tendency.

〔The invention's effect〕

The anti-skid control device of the present invention controls the rear wheels by independent limiting control or independent control when emphasizing braking force, and switches to select low control when emphasizing running stability, depending on driving conditions. Optimal rear wheel control can be performed in accordance with the driving state, and the improvement of braking force and the securing of running stability are achieved.

[Brief description of the drawings]

1 is an explanatory diagram of the configuration of an anti-skid control device, FIG. 2 is a configuration diagram of an anti-skid control device, FIG. 3 is a configuration diagram of an electronic control circuit, FIG. 4 is a flow chart of an anti-skid control process, and FIG. FIG. 6 is a flowchart of the select row control process, FIG. 7 is a flowchart of the independent control process, FIG. 8 is a flowchart of the independent limit control process, and FIG. 9 is the wheel speed and each control. Graph showing changes in brake oil pressure due to vehicle speed, Fig. 10 is a flowchart for rear wheel control processing based on vehicle speed, Fig. 11 is a flowchart for rear wheel control processing based on 4WS failure signals, and Fig. 12 is a rear chart based on steering wheel angle and vehicle speed. FIG. 13 is a flowchart of a wheel control process, FIG. 13 is a control switching reference map, and FIG. 14 is a flowchart of a rear wheel control process based on a steering wheel angle, a vehicle speed, and a lateral acceleration. Figure 15 is flow chart of the rear wheel control processing by the estimation of the friction coefficient of the road surface, Figure 16 is a conceptual explanatory diagram of determination one wheel low mu, Figure 17 is 4WS Fueiru signal, the yaw rate, steering wheel angle,
FIG. 18 is a flowchart of the rear wheel control processing based on the vehicle speed, and FIG. 18 is a flowchart illustrating the rear wheel control processing based on the active suspension fail signal, the yaw rate, the lateral acceleration, the steering wheel angle, and the vehicle speed. 1 ... Right front wheel, 3 ... Left front wheel, 5 ... Right rear wheel, 7 ... Left rear wheel, 9,11,13,15 ... Rotation speed sensor, 17,19,21,23 ... Hydraulic brake Equipment, 27,29,31,33 …… Actuator, 49 …… Electronic control circuit, 95,97… Load sensor, 99… 4WS control ECU, M ₁ …… wheel speed detection means, M ₂ … lock Trend determination means, M ₃ … rear wheel control selection means, M ₄ … running state detection means, M ₅ … brake pressure control means.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akira Fukushima 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-63-87356 (JP, A) JP-A-63-63 49577 (JP, A) JP-A-1-156176 (JP, A) JP-A-1-182156 (JP, A)

Claims (2)

(57) [Claims] 1. Wheel speed detecting means for detecting the speeds of left and right rear wheels of a vehicle; rocking tendency judging means for separately judging the locking tendency of the left and right rear wheels based on the wheel speeds of the left and right rear wheels; A running state detecting means for detecting the running state of the vehicle, and selecting the control of the rear wheel based on the detection signal of the running state detecting means in accordance with the rear wheel having a large rocking tendency to control the locking tendency of the other rear wheel. Rear wheel control that selects low control, independent limit control that limits the pressure increase tendency of the other rear wheel by the rear wheel that tends to lock, or independent control that controls independently according to the lock tendency of each rear wheel An anti-skid control device comprising: a selection unit; and a control unit that controls a brake pressure by adjusting a locking tendency of the left and right rear wheels based on the selected rear wheel control. 2. The vehicle according to claim 1, wherein said traveling state detecting means includes a load detecting means for detecting a load on the left and right rear wheels, a fail detecting means for a four-wheel steering control device, a vehicle speed detecting means for detecting a vehicle speed of the vehicle, Steering angle detecting means for detecting the actual steering angle, lateral G detecting means for detecting the lateral acceleration of the vehicle, running road surface detecting means for detecting the running road surface of the vehicle, yaw rate detecting means for detecting the yaw rate of the vehicle, and determining the side slip angle of the vehicle. 2. The anti-skid control device according to claim 1, comprising at least one of slip angle detecting means for detecting.