JPH0659822B2 - Vehicle braking control device - Google Patents

Description

The present invention relates to a braking control device for a vehicle, and more particularly, to a vehicle braking system that automatically and optimally controls a braking pressure according to a driver's brake depression state. The present invention relates to a control device.

[Prior Art] Conventionally, there is a decrease in safety due to wheel locking during vehicle braking, that is, vehicle front wheel locking causes the vehicle to become uncontrollable,
In order to prevent the tail swing phenomenon (skid) from occurring due to locking of the rear wheels of the vehicle, the slip ratio S [(vehicle body speed-wheel rotational speed) / body speed] of each vehicle wheel is set to 20.
%, There is known a vehicle braking control device, which is a so-called anti-skid control device, which controls the rotational speed of the wheels so that the frictional force between the tire and the road surface is maximized by controlling the forward and backward directions (for example, JP-A-58-71246). Gazette). With this kind of anti-skid control device, wheel lock does not occur during vehicle braking,
Moreover, in order that the frictional force between the tire and the road surface becomes maximum and the vehicle can be stopped quickly, the rotation speed is usually detected for each wheel, and the speed determined from the rotation speed (hereinafter, referred to as rotation speed) is, for example, Based on the vehicle speed Vs, the following formula V = Vs (1-S) (where S is the slip ratio = 0.2) is used to increase / decrease the reference speed V by controlling the brake hydraulic pressure to increase / decrease. The rotation speed of the wheels is controlled so as to be the reference speed, that is, the predetermined slip ratio. That is, when the rotation speed of the wheel is lower than the reference speed, the brake pressure of the wheel is reduced, and when the rotation speed exceeds the reference speed, the brake pressure is increased. It is configured to approach the reference speed.

By the way, braking of a wheel is usually performed by controlling a brake pressure to drive a wheel cylinder provided on each wheel to transmit a force to a braking member such as a brake shoe or a disc. Therefore, in a conventional braking control device such as an anti-skid device, for a pressure transmission system from a master cylinder that generates pressure in conjunction with a brake pedal to a wheel cylinder that directly controls a braking member,
The braking force is controlled by providing a brake pressure adjusting device that reduces, pressurizes or holds the brake pressure.

[Problems to be Solved by the Invention] However, if it is considered to start the braking control only when the slip ratio reaches a predetermined value, the hydraulic pressure from the master cylinder side is cut and switched to the controlled hydraulic pressure. Since it takes time, the problem of locking the wheels during that time was considered.

On the other hand, considering this point and setting a predetermined value of the slip ratio which is low by a certain amount, there is sufficient room for the wheels to lock due to the increase in hydraulic pressure due to the depression of the brake pedal, so it is particularly difficult to perform on an asphalt road surface that is difficult to lock. It was a control, and there was a risk that the braking distance would be extended.

In addition, the driving feeling may be different depending on whether the brake pedal is stepped on or off. This is because with slow braking, the slip rate desired by the driver is low,
Since the slip ratio controlled by the brake pressure adjusting device is high, there are cases in which sudden braking is applied that is not desired by the driver.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a braking control device for a vehicle that performs braking at an optimum slip ratio without causing lock or overcontrol from the start of braking control. It was

Structure of the Invention [Means for Solving Problems] In order to achieve the above object, the present invention has the following structures as means for solving the problems. That is, the present invention is the first
As illustrated in the figure, the brake pressure generating means M1 for generating a brake pressure based on the operation of the vehicle driver, and the brake pressure generated by the brake pressure generating means M1 are adjusted to the braking member M3 of the wheel M2. Brake pressure adjusting means M4 for transmitting, vehicle body speed detecting means M5 for detecting the speed of the vehicle body, wheel speed detecting means M6 for detecting the rotational speed of the wheels M2.
Based on the behavior of the slip ratio represented by the vehicle speed detected by the vehicle speed detecting means M5 and the rotation speed detected by the wheel speed detecting means M6, the current slip ratio reaches the predetermined slip ratio. A time estimating means M7 for estimating a time, and after the time when the estimated time is within a predetermined time,
At least the state variable quantity representing the internal state of the system for braking the wheel M2, including at least the control response delay of the pressure transmission system in which the brake pressure is adjusted, is determined by estimating and / or detecting, and the wheel M2 is also determined. The brake pressure adjusting means M using the optimum feedback gain predetermined according to the dynamic model of the system for braking, the predetermined state variable amount, and the predetermined slip ratio.
And a braking control means M8 configured as an optimum regulator for performing the feedback control so that the slip ratio becomes close to a predetermined slip ratio, and a braking control device for a vehicle. Use as a summary.

Here, the brake pressure generating means M1 generates a pressure for operating the braking member M3 by a driver's operation, for example, a hydraulic pressure. For example, there is a combination of a brake pedal and a master cylinder.

As the braking member M3 for the wheel M2, a brake shoe for a drum brake and a disc and a friction pad for a disc brake are well known. The brake shoes and the like are driven by the wheel cylinders and the like provided on each wheel M2, and the wheel cylinders and the like are driven by transmitting the brake pressure generated in response to the operation of the vehicle driver, for example, the depression of the brake pedal. ing. The pressure transmission system of the brake pressure is configured to transmit pressure by a gas such as air or a liquid such as oil. Of course, a so-called power brake may be configured by using a booster or the like.

The brake pressure adjusting means M4 is for adjusting the pressure of this pressure transmission system so as to pressurize, depressurize or hold it.
For example, it has a predetermined volume effective for the pressure transmission system, expands this volume at the time of decompression, reduces the pressure transmitted to the braking member M3, and performs the reverse control at the time of pressurization, or a pressure source. It has a pump, a reservoir and a switching valve,
Various configurations are conceivable such as a configuration for increasing / decreasing or maintaining the pressure of the direct pressure transmission system.

The vehicle body speed detection means M5 is based on a speed obtained from the ground speed sensor utilizing the Doppler effect or the like, or the idle wheel rotation speed immediately before the start of braking, and the acceleration of the vehicle calculated by the acceleration sensor (deceleration during braking). ) Is sequentially integrated to detect the value.

The wheel speed detecting means M6 detects the rotation speed of the wheel M2. The rotation speed of the wheel M2 may be detected from the rotation angular velocity obtained by the rotation speed sensor provided on the wheel M2 and the radius of the wheel M2. Instead of the rotation angular velocity, the rotation speed of the wheel M2 may be detected. It can be detected by various methods such as obtaining by integrating by considering the inertia of the wheel M2. The rotation speed of the wheel M2 is the rotation speed on the ground contact surface, but a rotation angular velocity that is uniquely determined can also be used as the rotation speed.

The vehicle body speed detecting means M5 and the wheel speed detecting means M6 are
Although they can be individually configured as discrete circuits, they can also be configured as a logical operation circuit using a microcomputer or the like together with a time estimation means M7 and a braking control means M8 which will be described later.

The time estimating means M7 estimates the time from the present time to the predetermined slip ratio based on the behavior of the detected vehicle speed and wheel speed. For example, it is performed by extending the same change as the immediately preceding change in the slip ratio to obtain the time point at which the predetermined slip ratio should be reached.

When it is determined that the estimated time is within the predetermined time, the braking control means M8 determines the brake pressure adjusting means M.
4 is feedback-controlled.

This feedback control is performed as an optimum regulator, and is executed by detecting the state variable amount and obtaining the feedback amount using the optimum feedback gain.

The predetermined slip ratio is usually calculated as a slip ratio at which the wheel M2 exerts the maximum braking force. Instead of the predetermined slip ratio, the slip ratio SL may be converted into the target rotation speed ω ^* by using the rotation speed ωf of the vehicle M2 when the slip ratio is 0% in the following formula.

[omega] ^* = [omega] f * (1-SL) The predetermined slip ratio is usually set to a value that maximizes the braking force, but can be varied according to the vehicle operation. For example, there is a case where the predetermined slip ratio to be realized is changed according to the depression state of the brake pedal. Fig. 2 shows the relationship between slip ratio and frictional force.
As shown in the figure, when the slip ratio is around 20%, the frictional force becomes maximum, so that the wheel M2 exerts the maximum braking force.
Therefore, when the amount of depression of the brake pedal is large, it is determined that the driver is requesting a large braking force, and the predetermined slip ratio SL is set to about 20% so that the vehicle stops at the shortest distance, while the brake pedal When the depression amount is small, it is possible that the driver determines that the driver wants gentle deceleration and sets the predetermined slip ratio SL to a small value such as 5%. In this case, the predetermined slip ratio SL is set. The target rotation speed ω ^* is changed according to

The state variable amount detection processing in the braking control means M8 is determined by estimating and / or detecting the state variable amount representing the internal state of the system that controls the wheels M2, and at least the brake pressure is adjusted. State variable quantity corresponding to the response delay in the control of the pressure transmission system, which is sufficient to control the rotational speed of the wheel M2, such as the pressure of the pressure transmission system or the control force applied to the wheel M2. Is estimated and / or detected. It should be noted that of the state variable quantities that cannot be directly measured, for example, the response delay of the system is determined by estimation, but if estimated using an observer, etc., a sufficient certainty necessary for control must be guaranteed. You can The structure of the observer will be described later.

The braking control means M8 is usually realized by using a microcomputer including peripheral elements such as ROM and RAM and input / output circuits around a microprocessor. The braking control means M8 of the present invention utilizes not only the control circuit used for the conventional anti-skid control but also the optimum feedback gain determined in advance according to the dynamic model of the system for braking the vehicle. Based on the brake pressure, the brake pressure to be transmitted to the braking member M3 is known, and the brake pressure adjusting means M4 for adjusting to this brake pressure is provided.
Is calculated and a control signal corresponding to this is output. That is, the braking control means M8 is configured as an additional integral type optimum regulator that determines the optimum feedback amount from the detected state variable amount and the predetermined slip ratio.

The method of constructing this optimum integral type optimum regulator is described in, for example, Katsuhisa Furuta "Linear System Control Riwa" (1976).
It is described in detail in Shoshodo, etc., but here we give a general view of the actual construction method.

In the following explanation, Etc. show the vector quantity (matrix), The subscript ^{T such as} is the transpose of the matrix, Subscript -1 such as For subscripts such as, it is an estimate, Another system such as symbol ~ is generated by the conversion or the like from the system control object, wherein the state observer (hereinafter, referred to as an observer) that the amount covered in, y ^* of such symbols ^*
Indicates that each is a target value.

In the braking control of the controlled object, here the vehicle, the dynamic behavior of this controlled object is Is a state variable quantity that represents the internal state of the system related to vehicle braking, Is a control input amount for the controlled object, that is, here, the brake pressure, for example, the hydraulic pressure u, Are the control output quantities of the controlled object, here the rotation speed ω, the variable DLY corresponding to the response delay of the control system, the actual hydraulic pressure P, etc.
Then, It is described as. Equations (1) and (2) are described in a discrete system, and the subscript k indicates that the value at the present time is k + 1.
Indicates the values at the time of the next sampling.

State variable quantity that indicates the internal state of the vehicle braking system Shows information about the history of the system that is necessary and sufficient for predicting the future influence of the control system. Therefore, a dynamic model of the system for braking the wheel M2 becomes clear, and the vector of the equations (1) and (2) is obtained. If we can determine The vehicle control can be optimally controlled by using.
In actual control, it is necessary to expand the system, which will be described later.

By the way, a dynamic model of a complex controlled object such as vehicle braking control may not be a linear model in the entire control range. However, when the vehicle is brake-controlled under a predetermined condition, for example, a certain vehicle speed, it can be considered that a linear approximation is established in the vicinity of that state. Therefore, the model is calculated according to the state equations of equations (1) and (2). Can be built. Therefore, when the dynamic model is non-linear like the system related to vehicle braking, linear approximation can be performed by separating into a plurality of stationary conditions, and each dynamic model can be calculated. It can be set.

Here, the dynamic model of the system relating to braking can be constructed by a mechanical model of the pressure transmission system based on a law of motion or the like, or can be determined by performing system identification. For the response delay of the control system, an approximate model can be constructed by the transient response method.

Once the dynamic model is established, the amount of state variables And the rotational speed ω (k) of each wheel M1 and its target rotational speed ω
^{* The} amount of feedback is determined from (k) and the amount of control of the brake pressure adjusting means M4 that controls the brake pressure of each wheel M2 Is theoretically optimally determined. In the control system for normal vehicle braking, various quantities directly related to vehicle braking include, for example, load applied to each wheel M2, acceleration, moving speed of oil or gas transmitted to the braking member M3, dynamic behavior of the control member M3, Moreover, the response delay of the pressure transmission system, etc. However, it is extremely difficult to directly observe most of these quantities. Therefore, in such a case, a means called a state observer is formed in the braking control means M8, and the state variable amount of the vehicle is adjusted. You can estimate what you need. This is the so-called observer in modern control theory, and various observers and their design methods are known. These are, for example, "Mechanical system control" by Katsuhisa Furuta et al.
, Etc.) and the applicable control target,
Here, it may be designed as a minimum-dimensional observer or a finite settling observer according to the mode of the vehicle and its braking control device.

The braking control means M8 uses the state variable amount detected by observation or the state variable amount estimated by the above observer. In addition to the above, the cumulative value obtained by accumulating the deviation between the target rotational speed of each wheel M2 calculated from the vehicle speed and the rotational speed detected by the wheel speed detecting means M6 and the value obtained by accumulating the cumulative value are enlarged. In the above system, an optimum feedback amount may be determined from both of them and a predetermined optimum feedback gain to control the brake pressure adjusting means M4. The cumulative value and the cumulative value of the cumulative value are necessary amounts because the calculated target rotation speed decreases in a ramp function in accordance with the vehicle body speed. That is, generally, in the control of the servo system, it is necessary to perform control so as to eliminate the steady-state deviation between the target value and the actual control value, which is required to include 1 / S ^l (integral of order ¹ ) in the transfer function. It Further, in the case of a control system such as a digital control in which the control amount can be determined only with finite accuracy, it is desirable to include the above integral amount from the viewpoint of control stability and noise stability. For this reason, this cumulative value is used. Therefore, the amount of state variables The system is expanded by adding this cumulative value to When the feedback amount is determined by and, the control amount for the controlled object, that is, the control amount of the brake pressure of each wheel M2 is determined as the additional integral type optimum regulator.

Next, the optimum feedback gain will be described. In the optimum regulator to which the integral amount is added as described above, it has been clarified how to obtain the control input (here, various amounts of the brake pressure control of each braking member M3) that minimizes the evaluation function J, and the optimum feedback is obtained. The gain of the solution of the Riccati equation and the state equation (1) and the output equation (2) It is known that it can be obtained from the matrix and the weight parameter matrix used for the evaluation function (supra, etc.). Where the weight parameter Is initially given arbitrarily, and changes the weight that restricts the behavior of the brake pressure of the system in which the evaluation function J controls the braking of the vehicle. It is possible to determine an optimum value by giving a weighting parameter arbitrarily and performing simulation by a large computer, changing the weighting parameter by a predetermined amount from the obtained behavior of the brake pressure and repeating the simulation. As a result, the optimum feedback gain Is also defined.

Therefore, the braking control means M8 of the braking control device of the present invention is
In addition to those based on classical control, it can be configured as an additional integral optimal regulator using a predetermined dynamic model of the system related to vehicle braking, and observer parameters and optimal feedback gain inside it can be configured. All can be determined in advance by simulation.

In the above explanation, the state variable amount Has been described as a quantity that represents the internal state of the vehicle, but this need not be a variable quantity that corresponds to an actual physical quantity, but can be designed as a vector quantity of an appropriate order that represents the state of the vehicle.

[Operation] When the driver steps on the brake pedal, a brake pressure is generated in the brake pressure generating means M1, and the braking member M3 starts braking the wheel M2.

The time estimating means M7 observes the rotation speed of the wheel M2 detected by the wheel speed detecting means M6 and the speed of the vehicle body detected by the vehicle body speed detecting means M5, and a predetermined slip ratio is calculated from the current slip ratio. Estimate time to.

The braking control means M8 executes the following processing as an optimum regulator after the time when the estimated time is within the predetermined time.

That is, the braking control means M8 estimates and / or detects the amount of state variables representing the internal state of the system for braking the wheels, including at least the control response delay of the pressure transmission system in which the brake pressure is adjusted. In addition, the control amount of the brake pressure adjusting means is determined by using the optimum feedback gain previously determined according to the dynamic model of the system for braking the wheel, the predetermined state variable amount, and the predetermined slip ratio. Then, the feedback control is performed so that the slip ratio becomes close to the predetermined slip ratio.

The state variable amount represents the internal state in consideration of the response delay in control of the pressure transmission system. Therefore, when feedback control is performed based on the optimum feedback gain using the above-mentioned state variable amount, each control mechanism is started in anticipation of a response delay and before a certain amount of time so as not to cause a response delay. In the conventional classical PID control, each control mechanism does not start to move unless the predetermined slip ratio is reached.

As described above, in the braking control device of the present invention, each control mechanism starts to move in advance in anticipation of a response delay. From this, when the control of the present invention is started, compared with the classical control, it is possible to further maximize the advantages of the control of the present invention by performing the control before the time when the predetermined slip ratio is reached. It will be. Therefore, the above-mentioned predetermined time is provided.

Therefore, the slip control can be appropriately performed without delay in the control response from the start of the control.

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings. The following examples show one aspect of the present invention, and the present invention includes other aspects without departing from the gist.

FIG. 3 is a schematic configuration diagram showing an overall configuration of a braking control device mounted on a four-wheel vehicle as an embodiment, and FIG. 4 is a control system diagram showing a control system for the right front wheel together with a block diagram of an electronic control unit. is there. First, the overall configuration and hydraulic system
The outline of the electric system will be described.

As shown, the wheels 1, 2, 3, 4 of the vehicle are equipped with hydraulic brake devices 11, 12, 13, which correspond to the braking member M3.
14 are provided, and the right and left front wheels 1 and 2 are respectively provided with electromagnetic pickup type rotational angular velocity sensors 15 and 16 as wheel velocity detecting means M6 for detecting the rotational angular velocity thereof. The rotational angular velocities of the rear wheels 3 and 4 that receive the rotation of the main shaft 19 of the transmission 18 via the differential gear 21 and rotate are the wheel speed detecting means M6 for the rear wheels provided in the transmission 18.
Is detected by the rotational angular velocity sensor 22.

Hydraulic brake devices 11 to 14 provided on each wheel
Uses the high hydraulic pressure generated by a tandem type master cylinder 25 as the brake pressure generating means M1 which is interlocked with the brake pedal 24 as the brake hydraulic pressure to brake the rotation of each wheel 1 to 4. This brake hydraulic pressure transmitted via the hydraulic system MPS is adjusted by actuators 31, 32 and 33. The actuators 31, 32, and 33 independently control the brake hydraulic pressures of the right front wheel 1, the left front wheel 2, the left and right rear wheels 3 and 4, and are controlled by an electronic control unit (ECU) 40. The configurations of the actuators 31 to 33 will be described in detail later, but the hydraulic pressure transmitted from the hydraulic pressure generating device 43 for power steering via the hydraulic system (power steering hydraulic system PPS) is used to drive the wheels 1 to 4 respectively. It functions as a brake pressure adjusting means M4 for adjusting the brake pressure.

The hydraulic system RHS of the brake hydraulic pressure to the right front wheel 1 uses the hydraulic pressure sensor 51, the hydraulic pressure of the hydraulic system LHS of the left front wheel 2 uses the hydraulic pressure sensor 52, and the hydraulic system B of the rear wheels 3 and 4
The hydraulic pressure of HS is detected by the hydraulic pressure sensor 53.

The ECU 40 receives signals from the hydraulic pressure sensors 51, 52, 53 according to the hydraulic pressures, and also outputs the rotational angular velocity sensors 15, 1
6 and 22, rotational angular velocity signals, further, a signal from an acceleration sensor 54 that detects the acceleration (including deceleration) of the vehicle, a signal from a brake sensor 55 that detects the operation of the brake pedal 24, etc. are input, Actuators 31, 3
2 and 33 are controlled to control the rotational angular velocity ω of each wheel 1 to 4.

Since the control of the braking force of the right front wheel 1, the left front wheel 2, the rear wheels 3 and 4 is independently performed, the control of the right front wheel 1 will be described below. FIG. 4 is a block diagram mainly showing the system for controlling the braking of the right front wheel 1. As shown, EC
U40 is connected to the battery 5 via the ignition key 56.
7, a power supply unit 58 for supplying a constant voltage to the entire unit upon receiving the supply of the power supply voltage, and a well-known CPU 61, ROM
63, the RAM 65 and the like, the output port 67, the analog input port 69, the pulse input port 71, the level input port 72 and the like are connected to each other by a bus 73, and are configured as a logical operation circuit. When the predetermined condition is satisfied, the ECU 40 determines the main relay 74 and the actuator 31 of the main relay 74.
By driving the main solenoid valve 75 and the sub solenoid valve 76 therein, the brake hydraulic pressure transmitted from the master cylinder 25 to the hydraulic brake device 11 via the pressure reducing cylinder 78 and the bypass cylinder 80 is controlled. When the brake oil pressure rises, the hydraulic brake device 11 presses the friction pad 83 against the disk 82 that rotates with the wheel 1 to cause the wheel 1 to rotate.
Works to stop the rotation of. That is, the ECU 40 corresponds to the braking control means M8 and the time estimation means M7.

The power steering hydraulic pump 90 and the power steering hydraulic pressure from the power steering hydraulic pressure generator 43 including a reservoir (not shown) are transmitted to the actuator 31, but the power steering hydraulic system PPS is provided in a state where the brake hydraulic pressure is not particularly controlled. In the oil, oil is supplied from the hydraulic pump 90 to the regulator 91 in the actuator 31 and the power steering gearbox 92.
It circulates through and. The regulator piston 91a of the regulator 91 receives the brake hydraulic pressure on the end surface 91b, and when the brake hydraulic pressure becomes high, it operates so as to reduce the flow passage cross-sectional area of the power steering hydraulic system PPS. It works to increase hydraulic pressure (hereinafter referred to as steering hydraulic pressure).

The decompression cylinder 78 includes a spring 78a and a ball 78b.
The cut valve 78c and the decompression piston 78d are composed as essential parts. The pressure reducing piston 78d operates by the balance between the force received by the brake hydraulic pressure and the force received by the steering hydraulic pressure. Normally, the main solenoid valve 75 and the sub solenoid valve 76 are both in the off state, and the steering hydraulic pressure is directly applied to the end of the pressure reducing piston 78d. Since it is received by the pressure receiving portion formed in the above, the pressure reducing piston 78d is pushed to the position shown in FIG.
Is open.

Similarly, the bypass cylinder 80, which mainly includes a switching valve 80c including a spring 80a and a ball 80b and a bypass piston 80d, is also normally pushed to the position shown in FIG. Therefore, when the brake pedal 24 is depressed in this state and the brake hydraulic pressure is increased by the master cylinder 25, the brake hydraulic pressure is generated by the passage I-II-III-IV-V shown in FIG. 4 in the brake hydraulic pressure system MPS. It is guided to the hydraulic brake device 11.

On the other hand, the ECU 40 is operating normally, the main relay 74 is driven via the output port 67, and its contact point 74
When the control of the slip ratio is executed with a closed, the brake fluid pressure is controlled as follows.

(1) When it is determined that the brake fluid pressure is increasing, the wheel 1 approaches the over-braking, and it is within a predetermined time when slip occurs, the ECU 40 operates as an optimum regulator and considers the response delay of the brake hydraulic system. The main electromagnetic valve 75 of the actuator 31 is turned on at the optimal timing. At this time, the valve body 75a of the main solenoid valve 75 is pulled upward in FIG. 4, so that the steering hydraulic pressure supplied to the pressure reducing cylinder 78 is shut off. As a result,
The oil in the left chamber 78L of the decompression cylinder 78 is slowly discharged to the reservoir (not shown) of the steering hydraulic system PPS via the orifices B and C. Therefore, the pressure reducing piston 78d is pulled out, and the cut valve 78c
Closes. As the pressure reducing piston 78d is pulled out, the volume of the brake hydraulic system RHS gradually increases, so the brake hydraulic pressure gradually decreases.

(2) When the sub electromagnetic valve 76 is turned on in the same state, the bypass passage 76b that bypasses the orifice B is formed, so that the oil in the left chamber 78L of the depressurizing cylinder 78 is rapidly discharged only through the orifice C. As a result, the brake oil pressure also drops sharply.

(3) On the other hand, when the main solenoid valve 75 is turned off, the discharge of oil via the orifice C is stopped, and the oil rapidly flows from the steering hydraulic system PPS through the orifice A and the bypass path 76b, and the depressurizing cylinder 78 is discharged. Left chamber 7
The pressure of 8L also increases. As a result, the pressure reducing piston 78d is pushed in rapidly, and the brake hydraulic pressure also rises sharply.

(4) When the sub solenoid valve 76 is further turned off in this state, the bypass passage 76 is closed, so that the steering oil pressure P
The inflow of oil from PS is performed via the orifices A and B, and the pressure in the left chamber 78L rises gently. As a result, the brake fluid pressure also rises slowly.

Since the response delay is taken into consideration in the decrease / increase of the hydraulic pressure in the above (1) to (4), it is appropriate with almost no response delay with respect to the timing when the slip ratio becomes too large or too small. It is done at the right timing.
Moreover, at the start of the control, the brake pressure control is performed before the slip occurs, so that the control without the response delay is performed from the beginning.

The relationship between the states of these solenoid valves 75 and 76 and the brake oil pressure is illustrated in the timing chart of FIG. As shown in the figure, the hydraulic pressure of the hydraulic brake device 11 is controlled by the solenoid valves 75, 76.
Depending on the state, the pressure is reduced or increased based on the hydraulic pressure Pm generated in the master cylinder 25 by the driver's operation.
Therefore, as shown in FIG. 6, it is necessary to control the opening / closing time of the solenoid valves 75 and 76 in order to realize the required hydraulic pressure Po. That is, assuming that the current hydraulic pressure is Pa, the time t
Supposing that the hydraulic pressure required after 2 is Po, in this hydraulic system, from the four control patterns, the rapid pressure increase a, the slow pressure increase b, the slow pressure decrease c, and the rapid pressure decrease d, the pressure increase time from time 0 to t1 is rapidly increased. Then, it is necessary to control the brake hydraulic pressure by selecting a control pattern such that the pressure is gradually increased until t2.

Next, the outline of signal processing and system control in this embodiment will be described with reference to FIG. Such signal processing is realized by executing a control program, which will be described later, according to the flowchart of FIG. 8 in the hardware configuration shown in FIG. Therefore, FIG. 7 does not show the hardware configuration, but conceptually shows the flow of signal processing.

In the present embodiment, what is finally controlled is the rotational angular velocity ω of the wheel, and control is performed to match this with the target rotational angular velocity ω ^* . The directly detected physical quantity is the hydraulic pressure P of the hydraulic brake devices 11 to 14 of the wheels 1 to 4.
m, which are the respective rotational angular velocities Nfr detected by the wheel rotational angular velocity sensors 15, 16, 22 and the vehicle acceleration G detected by the acceleration sensor 54.
Therefore, inside the ECU 40, a coefficient K2, which has been experimentally obtained in advance, for the hydraulic pressure Pm of the wheel is first performed by the operation indicated by K2.
The braking torque Tb for the wheel is calculated by multiplying by. On the other hand, if the friction coefficient μ between the wheel and the road surface is used, it is possible to know the rotational torque Tf received from the road surface in the direction in which the wheel is to be rotated using the predetermined coefficient K1 by the operation indicated by K1. Here, the coefficient K1 is a value determined from the load W applied to the wheel, the wheel radius r, and a constant. Friction coefficient μ
Is calculated from the hydraulic pressure Pm and the rotational angular velocity Nfr for each wheel by the operation indicated by k6.

Using the actual torque Tr (= Tf-Tb) after subtracting the braking torque Tb applied to the wheel 1 from the hydraulic brake device 11 and the rotational torque Tf applied to the wheel 1 from the road surface, then K3 / S The rotational angular velocity ω of the wheel 1 is obtained by the operation shown. Here, the actual torque Tr is integrated (1 /
S), and the rotational angular velocity ω is obtained by multiplying by the coefficient K3 in consideration of the inertia I of the wheel 1.

On the other hand, the vehicle speed V is calculated by the vehicle speed Vo obtained from the rotational angular speed Nfr of the wheel 1 immediately before the start of braking and the value obtained by integrating the acceleration G detected by the acceleration sensor 54 once (1 / S). (If it is shown by a general formula, V = V
o + Gt, t is the elapsed time from the start of braking). This is shown by K4 / S in FIG. With respect to the vehicle speed V thus obtained, the target rotational angular velocity ω ^* is obtained from the following equation in consideration of the operation shown by K5 in FIG. 7, that is, the slip ratio SL, the radius r of the wheel 1, the coefficient K5, and the like. To be That is, ω ^* = K5 · V · (1-SL) / r. Here, the slip ratio SL may be a fixed value or may be variable according to control.

The deviation Δω is obtained from the target rotation angular velocity ω ^* and the above-described actual rotation angular velocity ω of the wheel 1, and this deviation is integrated (1 / S) to obtain the primary cumulative value INTω. Further, this is further integrated to obtain a secondary cumulative value WINTω for following the vehicle speed (wheel rotational angular speed) that decreases as a ramp function during deceleration.

On the other hand, by constructing an observer, the hydraulic pressure P as a control input
From o and the actually detected oil pressure Pm, a variable DLY corresponding to the response delay in control is obtained as a state variable. Although a configuration example of the observer will be described later, the element of the response delay time handled in the present embodiment can be represented as e ^−LS on the S plane, and thus can be treated as the state variable amount DLY by approximation of the ^putter. . In the present embodiment, a quadratic approximation is considered as the Pattie approximation.

Deviation Δ of rotational angular velocity obtained by the above signal processing
ω, cumulative values INTω, WINTω, variable DLY, and torque Tr are set to predetermined optimum feedback gains. Is multiplied by to obtain the control amount Po of the hydraulic pressure of the hydraulic system for control. Here, Po is a calculated value of the brake hydraulic pressure (target hydraulic pressure) required to maintain the wheel 1 at the predetermined slip ratio. The hydraulic pressure is actually the main solenoid valve 75 and the sub solenoid valve 76.
Since it is controlled by the opening / closing valve operation, the control amount setting unit obtains the actual control amount of the hydraulic pressure and outputs it to the control system.

However, the control amount setting unit is configured to start output when receiving a permission signal from the start time point estimation unit, which is a feature of this embodiment.

When the brake sensor 55 is in the ON state, the start point estimation unit
It is estimated whether or not the actual rotation angular velocity ω reaches the target rotation angular velocity ω ^* of the wheel 1 calculated based on the vehicle speed V and its acceleration G within a predetermined time or less, here, for example, 25 msec or less.

This estimation calculation is performed, for example, by extrapolating from each change amount and error per a predetermined time immediately before. In the present embodiment, the predetermined time of 25 msec is the time from the start of the braking control until the cut valve 78C of the pressure reducing cylinder 78 is completely closed.

Judging the immediately preceding time by such a predetermined time is
This is because even if the brake hydraulic system is in a state where the maximum response delay occurs at the start of control, the control side can take measures so as not to substantially delay the response.

Returning the above description to the state equation (1) and the output equation (2), in this embodiment, the state variable amount of the expanded system is obtained. Control output to control target Controlled output As Will be treated as

Next, the control that the ECU 40 actually performs will be described with reference to the flowcharts of FIGS.

FIG. 8A is a flow chart showing the main routine of control. This process is started by turning on the key switch of the engine. First, in step 100, R
Initial values of various variables are set in the AM65. Next, at step 110, the flag F is reset. The flag F determines to actually start the braking control.

Next, at step 120, it is judged if the flag F = 1. Since F = 0 in the initial stage, it is determined to be "NO", and after the diagnosis process and the like performed at the time of brake off in step 130, the process returns to step 120 again. Thus, as long as F = 0, the above process is repeated.

The process for setting the flag F = 1 is performed by the process shown in FIG. If F = 1 in this process, it is determined to be "YES" in step 120, and the braking control process of step 140 is executed. The braking control process will be described later.

Next, the start determination interrupt routine executed in FIG. 8B will be described. This routine is F = every 5 msec.
This is an interrupt routine that is executed only when 0.
In the following description, the amount handled in the actual process is added with the subscript (j), the amount handled in the next process performed after the sample time T is added with the subscript (j + 1), and the estimation is performed 25 msec ahead. The value will be expressed with a subscript (j + 5).

First, in step 200, a process of reading the acceleration of the vehicle from the acceleration sensor 54 (which is a negative value because the vehicle is decelerating here) is performed. 2 in the following step 210
A process of calculating the vehicle speed V (j + 5) after 5 msec (the time required to completely close the cut valve 78C) is performed.
The vehicle speed V (j + 5) is obtained by setting T25 = 25 msec and V (j + 5) = V (j) + G · T25 (6).
The initial value V (0) of (k) is obtained from the rotational angular velocity Nfr of the right front wheel 1 and the radius r of the wheel 1 which were rotating as idler wheels at a rotational angular velocity corresponding to the vehicle speed immediately before braking.

In step 220, 25 ms is calculated based on the vehicle speed V (j + 5).
The calculation process for obtaining the target rotational angular velocity ω ^* (j + 5) of the wheel 1 after ec, ω ^* (j + 5) = K5 · V (j + 5) · (1-SL) / r ... (7) is performed.

Next, at step 230, the oil pressure Pm (j) of the hydraulic system for braking the right front wheel 1 is read by the oil pressure sensor 51, and at step 240, the oil pressure increment D (j) per time (5 msec) is obtained. Next, at step 250, the effective hydraulic pressure Pa (j) is calculated by the following equation.

Pa (j) = [5 · Pm (j) + (25 · 10 ⁻³ / 2) · D (j)] / 5 This effective hydraulic pressure is the hydraulic pressure between (j) and (j + 5) at the time of sampling. It is the average hydraulic pressure that allows for the change.

Next, at step 260, an estimation calculation of μ is performed by the following equation.

β5 = [μ (j) · k1-Pm (j) · k2] · k3 · T5 μerr (j) = ω (j) −ω (j−1) −β5 μ (j) = μ (j) + k10 · μerr (j) Next, in step 280, an estimated value ω (j + 5) of the wheel rotation angular velocity after 25 msec is calculated by the following equation.

β = [μ (j) · K1-Pa (j) · K2] · K3 · T25 ω (j + 5) = ω (j) + β Next, at step 310, the estimated value ω (j + 5) is the target value ω.
^{* It} is determined whether or not the value is (k + 5) or less. If ω (j + 5) still exceeds ω ^* (j + 5), it is determined to be “NO”, and at step 320, the counter j
After is incremented, the process ends once. If "YES", then in step 330, flag F is set. If the flag F is set, it is determined to be "YES" in step 120 of the above-mentioned main routine, and the braking control process of step 140 is started.

That is, the timing determined as “YES” in this step 120 is the timing before a predetermined time that can be started without causing a response delay even if the braking control process by the brake hydraulic pressure control is started.

FIG. 8C is a flowchart showing the details of the braking control process of step 140. When the process is started, first in step 400, a process for obtaining a hydraulic pressure control pattern is performed based on the control output Po (k) obtained in the previous step 530. That is, as already described with reference to FIG. 6, the oil pressure Po is reduced within the sampling time T.
The opening / closing time of the main solenoid valve 75 and the sub solenoid valve 76 is determined so as to reach (k).

In step 410, a process of appropriately controlling the main solenoid valve 75 and the sub solenoid valve 76 according to the control pattern obtained in step 400 is performed.

Next, at step 420, a process of reading the acceleration of the vehicle from the acceleration sensor 54 (which is a negative value because the vehicle is decelerating here) is performed. In the following step 430, a process of calculating the vehicle speed V (k + 1) used in the next process is performed. The vehicle speed V (k + 1) is calculated as V (k + 1) = V (k) + G · T, where T is the time required to process this control routine once.
The initial value V (0) of (k) is obtained from the rotational angular velocity Nfr of the right front wheel 1 and the radius r of the wheel 1 which were idle wheels immediately before braking and were rotating at a rotational angular velocity corresponding to the vehicle speed.

In step 440, a calculation process for obtaining the target rotational angular velocity ω ^* (k + 1) of the wheel 1 from the vehicle speed V (k + 1), ω ^* (k + 1) = K5 · V (k + 1) · (1-SL) / r, is performed.

In the next step 450, a process of reading the hydraulic pressure Pm (k) of the hydraulic system for braking the right front wheel 1 by the hydraulic sensor 51 is performed.

Next, at step 470, the friction coefficient μ between the road surface and the wheel 1
Is calculated. [mu] is calculated from the hydraulic pressure Pm (k) and the rotational angular velocity Nfr (k) of the wheel 1 measured by the rotational angular velocity sensor 15 by the following equation.

μerr (k) = ω (k) −ω (k−1) − [μ (k) · k1-Pm (k) · k2] k3 · T25 μ (k + 1) = μ (k) + k10 · μerr (k) In the following step 490, the target rotational angular velocity ω ^* (k) calculated in step 440 and the actual rotational angular velocity ω (k)
A process of obtaining a deviation Δω (k) from and is performed.

In step 500 following step 490, a process for obtaining the control output Po (k + 1) is performed. The control output Po (k + 1) is the optimum feedback gain. And state variable quantity From However, due to the response delay of the braking system, Cannot be used. From the state equation (1), Therefore, Has already been sought as Can be approximated using. Therefore, However, the state variable amount from the equation (I) of step 530 described later, which was previously performed Is the observer estimate Can be replaced with. That is, As a result, the control output Po (k + 1) can be calculated. Where the optimal feedback gain Is Is required as. In the above formula Is Riccati equation, Is the solution of Is the evaluation function, Is a parameter that is used as a minimum value and is selected as an optimum value. Therefore Is predetermined, and in the present embodiment, for example, the optimum feedback gain Is Met. So, in advance, Can be asked for.

The parameter Can be switched according to the vehicle speed. For example, these parameters can be set in advance so that the convergence speed of the system becomes slower as the vehicle speed becomes lower.

In this example, Are both 1 × 1 matrices, that is, scalar quantities.

In step 500 this Using, Is calculated and the hydraulic pressure Po (k +
1) The required processing is performed. The above equation can be expressed by the following equation when expressed by more specific parameters.

In subsequent steps 510 and 520, a process of integrating this is performed. That is, in step 510, INTω (k + 1) = INTω (k) + T · Δω (k) is used as the first-order integration, and in step 520, WINTω (k + 1) = WINTω (k) + T · Each INTω (k) is calculated. In this way, the cumulative value INTω, W obtained by integrating the deviation amount Δω (k) between the target rotation angular velocity ω ^* (k) and the actual rotation angular velocity ω (k) of the wheel 1.
INTω (k) is obtained.

In the following step 530, predetermined parameters are set. Is used to calculate the variable Z (k) in the observer. The observer is designed as a minimum-dimensional observer, and estimates the variable DLY corresponding to the response delay by the two-dimensional approximation of the pattern, but if the internal variable is set to Z (k), As the state variable quantity Is estimated. Where the parameters Is a dynamic model of a predetermined control system More required, Is.

Note that the output of the observer here includes the variable DLY corresponding to the response delay and the state variable amount other than the hydraulic pressure PF (Pm), which is merely formal, and the step 4
90, 510, 520 (Δω, INTω,
WINTω) is just output as it is.

Next, in step 540, a process of incrementing k indicating the number of samplings by 1 is performed.

In the following step 550, the state of the brake sensor 55 read through the level input port 72 is checked to determine whether it is “on”, that is, whether or not braking is being performed, and the brake pedal 2 is depressed for a while. If the braking is continued, the process returns to step 400 to repeat the above-described processes, steps 400 to 550. On the other hand, if the braking has been released, the flag F is reset in step 560, the process goes to NEXT, and this control routine ends.

According to the present embodiment configured as described above, the response delay time of the system that controls the brake hydraulic pressure of the hydraulic brake device 11 is approximated / estimated by the observer, so that the wheel does not cause overcontrol due to the response delay. Rotational angular velocity of 1 ω
Can be controlled to a target rotational angular velocity ω ^* that is optimally determined from the vehicle speed. Moreover, the control is started by estimating the optimum timing from the change of the brake oil pressure Pm so that the control can be performed from the start of the control with the slip ratio optimum for the braking, so that stable braking is realized from the initial stage. Therefore,
It is possible to stop the vehicle at the shortest braking distance while maintaining the same and good drive feeling, regardless of how quickly the brake pedal is depressed.

FIG. 9A shows the brake oil pressure Pm, the vehicle body speed, and the wheel rotation speed according to this embodiment at the initial stage of brake depression,
That is, it shows a timing chart with the rotation speed of the wheel on the ground contact surface.

If the brake pedal is depressed at time T0 while the vehicle is traveling, the rotational speed of the wheels decreases more than the decrease of the vehicle speed, and gradually departs from the vehicle speed. During this period, ω ^* (j + 5) is constantly calculated in the above-described start determination interrupt routine, but the actual hydraulic pressure Pm (j), the friction coefficient μ (j), and the wheel rotation angular velocity ω (j) at that time are calculated. Based on the value and the rate of increase, the rotational angular velocity ω (j +
5) is not estimated to reach the target rotational angular velocity ω ^* (j + 5), the control of the brake hydraulic pressure is not started.

When it is determined that the time point T1 is reached and ω ^* (j + 5) is reached within 25 msec, the braking control routine shown in FIG. 8C is started for the first time, taking into account the response delay of the brake hydraulic system. As soon as possible, change the wheel speed to 20% slip rate,
That is, it tries to control the speed around 80% of the vehicle speed. By the time T2, the cut valve 78C is completely closed, and hydraulic control can be actually performed. At time T2, the slip ratio is just the predetermined value, so that the braking control can be stably performed without any shock. 25 up to target angular velocity
If it is not estimated that it is before msec, overshoot and undershoot occur as shown by the dotted line, and instability may occur especially at the initial stage.

Thereafter, as shown in FIG. 9B, the braking control is performed until the vehicle stops. Of course, if the driver releases the depression of the brake, the braking control is stopped. FIG. 9B is a graph showing the rotational angular velocity of the wheel 1 until the vehicle stops. Until the vehicle stops, the target rotational angular velocity ω ^* (dashed line) decreases as a ramp function. On the other hand, in the braking control device of the present embodiment, the actual rotational velocity ω (solid line) of the wheel 1 is , Immediately follow this. If it is not estimated 25 msec before, overshoot and undershoot occur as shown by the dotted line in the initial stage of control.

As is clear from FIGS. 9 (a) and 9 (b), in the present embodiment, extremely excellent responsiveness and stability are obtained from the initial stage of control. Further, in the present embodiment, μ is constantly calculated even if the friction coefficient of the road surface changes in a wide range (μ = 0.7 ± 0.4 range), so the braking of the wheel 1 is controlled in a sufficiently stable manner. Because it is possible, even on a road surface where the friction coefficient of the road surface changes abruptly or on a straddle road where the left and right wheels have different friction coefficients,
It is possible to stably control the slip ratio and maintain high braking characteristics of the vehicle.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment. For example, the target rotational angular velocity ω ^* is made variable by the depression amount of the brake pedal, or the vehicle speed V is directly detected by the ground vehicle speed sensor, or the target rotational angular velocity ω ^* is changed stepwise to obtain the secondary integration amount. It is needless to say that the present invention can be implemented in various modes without departing from the scope of the present invention, such as a configuration not used.

As described above in detail, the vehicle braking control device of the present invention is
Since the braking control is started by estimating and judging whether or not it is within the predetermined time until the predetermined slip ratio that requires the braking control is reached, the actual brake pressure such as the switching time in the brake pressure adjusting means is started. The control considering the control start delay can be performed, and smooth and stable braking control can be performed from the initial stage. Further, regardless of whether the brake pedal is stepped on or off, it is not necessary to start the braking control until just before the state where the braking control is required, so that the driving feeling becomes extremely excellent. Therefore, according to the braking control device for a vehicle of the present invention, while maintaining a good drive feeling,
The vehicle can be stopped at the shortest braking distance.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of the present invention, FIG. 2 is a graph showing the relationship between slip ratio and frictional force, FIG. 3 is a schematic configuration diagram of one embodiment of the present invention, and FIG. 4 is a hydraulic pressure for the right front wheel. 5, a configuration diagram showing the system together with the configuration of an electronic control unit (ECU),
FIG. 7 is a timing chart showing an example of brake hydraulic pressure control by the operation of a solenoid valve, FIG. 6 is a graph explaining a hydraulic pressure control pattern, and FIG. 7 is a signal explaining an outline of signal processing and system control in this embodiment. 8 is a flowchart of a main routine showing a processing procedure in the embodiment, FIG. 8 (b) is a flowchart of a start determination interrupt routine, and FIG. 8 (c) is a flowchart of a braking control routine. FIG. 9A is a timing chart of brake hydraulic pressure, vehicle body speed, and wheel rotation speed at the initial stage of control in the embodiment, and FIG. 9B is a timing chart of wheel rotation angular speed. 1, 2, 3, 4 ... Wheels 11, 12, 13, 14 ... Hydraulic brakes 15, 16, 22 ... Rotational angular velocity sensor 18 ... Transmission 25 ... Master cylinder 31, 32, 33 ... Actuator 40 ... ... ECU 43 ... hydraulic pressure generator 51, 52, 53 ... hydraulic pressure sensor 54 ... acceleration sensor 61 ... CPU

Claims (3)

[Claims] 1. A brake pressure generating means for generating a brake pressure based on an operation of a vehicle driver, and a brake pressure adjusting means for adjusting and transmitting the brake pressure generated by the brake pressure generating means to a braking member of a wheel. A vehicle speed detecting means for detecting the speed of the vehicle body, a wheel speed detecting means for detecting the rotational speed of the wheels, a vehicle speed detected by the vehicle speed detecting means and a wheel speed detecting means. Based on the behavior of the slip ratio represented by the rotation speed and the time estimation means for estimating the time from the current slip ratio to the predetermined slip ratio, and after the time when the estimated time is within the predetermined time,
At least the state variable amount representing the internal state of the system for braking the wheel including the response delay in control of the pressure transmission system in which the brake pressure is adjusted is determined by estimating and / or detecting, and the wheel braking is performed. A predetermined control variable of the brake pressure adjusting means is determined by using an optimum feedback gain predetermined according to a dynamic model of the system, the predetermined state variable amount and the predetermined slip ratio, and the slip ratio is a predetermined slip. A braking control device for a vehicle, comprising: a braking control unit configured as an optimum regulator for performing the above feedback control so that the ratio becomes close to a ratio. 2. The braking control device for a vehicle according to claim 1, wherein the predetermined time is an initial adjustment time for adjusting the brake pressure by the brake pressure adjusting means. 3. The braking control device for a vehicle according to claim 1, wherein the slip ratio is converted into the rotational speed of the wheel.