JPH0649449B2 - Vehicle braking control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to braking control transmission of a vehicle, and more specifically, to a braking pressure during vehicle braking based on a dynamic model of a system relating to vehicle braking. The present invention relates to a braking control device for a vehicle that is optimally controlled.

[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 the 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 1
There is known a vehicle braking control device, which is a so-called anti-skid control device, which controls the rotational speed of wheels so as to maximize the frictional force between a tire and a road surface by controlling the friction force between 5 and 20% (for example, JP-A-57-57). 11149, etc.). In this type of anti-skid control device, the wheels are not locked during vehicle braking, and the frictional force between the tires and the road surface is maximized so that the vehicle can be stopped quickly. The speed determined from the rotational speed (hereinafter referred to as the rotational speed) is, for example, the reference speed V obtained from the following formula V = Vs (1-S) (where S is the slip ratio 0.15 to 0.2) based on the vehicle speed Vs. By controlling the brake oil pressure to increase / decrease, the wheel rotation speed is controlled to the reference speed. 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, the braking of the wheels is usually performed by controlling the brake fluid pressure to drive the wheel cylinders provided on the respective wheels and transmit the force to the braking members such as the brake shoes and the discs. Therefore, in a conventional braking control device such as an anti-skid device, for a hydraulic system from a master cylinder that generates hydraulic pressure in conjunction with a brake pedal to a wheel cylinder that directly controls a braking member,
A braking force is controlled by providing a hydraulic pressure adjusting device that reduces, pressurizes or holds the braking hydraulic pressure.

[Problems to be Solved by the Invention] However, in the above-described conventional vehicle braking control device, the following problems have been left unsolved, and improvements have been strongly desired.

(1) When it is determined that the wheels are locked, the control for reducing the brake hydraulic pressure is performed, and when the lock is released and the braking force is required, the control for increasing the brake hydraulic pressure is performed. However, response delay time ((Dead Time)
Is always present. Since the response delay of the hydraulic system cannot be detected at all, in the conventional vehicle braking control device, if the brake hydraulic pressure is feedback-controlled based on the slip ratio of the wheel to be controlled or its rotation angular velocity, There was a problem of causing control. That is, when the anti-skid control is performed, the brake fluid pressure repeats overshoot and undershoot, which is a factor that deteriorates the drive feeling.

(2) The problem of over-control can be avoided by slowing the control of the brake fluid pressure in order to ensure good operability and drive feeling, but in this case, the braking characteristics are sacrificed. There was a problem that had to be. That is, the slip ratio cannot be optimally controlled, and the braking distance becomes long.

The problems of (1) and (2) above are to reduce the brake fluid pressure.
In the case where the decompression piston provided in the hydraulic system is used for volumetric control, and the operation of the decompression piston is controlled by the opening / closing operation of a separately provided actuator such as a solenoid valve, The response delay time cannot be overlooked,
It was considered to be a particular problem.

(3) Further, in the braking control of the vehicle, the rotation state of the wheels is the control target, but in the conventional braking control device, the slip ratio may be calculated from the rotation state of the wheel that is the control target. Therefore, as a result, it may be considered that sufficient control cannot be performed.

Therefore, the present invention has been made to solve the above problems, and an object thereof is to provide a braking control device for a vehicle that performs braking at an optimum slip ratio without causing overcontrol due to a response delay of a pressure system that performs braking. .

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, as shown in FIG. 1, the vehicle braking control device of the present invention sets a rotational angular velocity detecting means M5 for detecting the rotational angular velocity of each wheel M1 of the vehicle and a target rotational angular velocity of each wheel M1 of the vehicle. The target rotational angular velocity setting means M9, the brake pressure adjusting means M4 for adjusting the brake pressure transmitted to the braking member M2 of the wheel M1 according to the given drive signal, and the detected rotational angular velocity of each wheel M1 are A braking control device for a vehicle, comprising: a braking control means M7 for controlling the brake pressure adjusting means M4 so that the set target rotational angular velocity of each wheel M1 is achieved; Brake pressure detection means M10 for detecting is provided, and the braking control means M7 is set to a parameter preset based on a dynamic model of a system relating to braking of the vehicle. Used, the braking control means M7
A state observing section M8 for estimating a state variable amount representing a response delay in control of the system from the target brake pressure when controlling the brake pressure adjusting means M4 and the detected brake pressure, and for each wheel M1. An accumulator M11 for obtaining a deviation between the rotational angular velocity detected by the rotational angular velocity detecting means M5 and the target rotational angular velocity set by the target rotational angular velocity setting means M9, and calculating an integrated value of the deviation; A brake pressure determining unit M12 that determines a target brake pressure of the braking member M2 from the calculated brake pressure, the estimated state variable amount, the calculated integral value, and a preset optimum feedback gain; , And is configured as an additional integral type optimum regulator.

[Operation] The state observing unit M8 estimates the state variable amount representing the response delay in the control of the system, and the brake pressure determining unit M12 uses the state variable amount representing the estimated response delay to preset the optimum value. The target brake pressure of the braking member M2 is determined based on the feedback gain. Therefore, the target brake pressure is set in consideration of the response delay so that the delay can be covered even if the response delay exists.

Further, the brake pressure determination unit M12 also uses the integrated value of the deviation between the rotation angular velocity and the target rotation angular velocity calculated by the accumulation unit M11 in determining the target brake pressure. From this, a more accurate target brake pressure can be set.

[Embodiment] First, before describing an embodiment of a braking control device mounted on an actual vehicle, a schematic description of the present invention will be given.

As the braking member M2 for the wheel M1, 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 M1, and the wheel cylinders and the like are driven by transmitting the brake fluid pressure generated according to the operation of the vehicle driver, for example, the depression of the brake pedal. Has been done. A hydraulic system for transmitting brake hydraulic pressure, that is, a system M3 for braking this vehicle
Is configured to transmit force by gas such as air or liquid such as hydraulic pressure. 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 the system M3 so as to pressurize, depressurize or hold it, and has a predetermined volume effective for the system M3, for example. A configuration in which the force transmitted to the braking member M2 is reduced and the opposite control is performed at the time of pressurization, or a configuration in which a pump serving as a pressure source, a reservoir, and a switching valve are provided to directly increase / decrease or hold the pressure in the system M3 There are various possibilities.

The rotational angular velocity detection means M5 detects the rotational angular velocity of the wheel M1. The rotational angular velocity of the wheel M1 is
It may be detected from the number of rotations obtained by the number-of-rotations sensor provided in the vehicle, or may be obtained by various methods such as obtaining by integrating the rotational torque of the wheels M1 in consideration of the inertia of the wheels M1. You can

The rotational angular velocity detecting means M5 can be individually configured as a discrete circuit, but can also be configured as a logical operation circuit using a microcomputer or the like together with the braking control means M7 described later.

The braking control means M7 controls the brake pressure adjusting means M4 so that the rotational angular velocity of the wheel M1 becomes the target rotational angular velocity, and includes a state observing section M8, an accumulating section M11 and a brake pressure determining section M12. It is configured as an additional integral type optimum regulator.

The state observing unit M8 uses the preset parameters based on the dynamic model of the system relating to the braking of the vehicle, and the target brake pressure at the time of controlling the brake pressure adjusting unit M4 by the braking control unit M7 and the detected brake. From the pressure, the state variable quantity representing the control response delay of the system is estimated. The state variable amount that cannot be directly measured, for example, the response delay of the system is thus determined by the estimation, and it is possible to guarantee the sufficient certainty necessary for control.

The accumulating unit M11 obtains a deviation between the rotational angular velocity detected by the rotational angular velocity detecting means M5 and the target rotational angular velocity set by the target rotational angular velocity setting means M9, and calculates an integrated value of the deviation.

The brake pressure determination unit M12 is a brake pressure detection unit M1.
From the brake pressure detected at 0, the state variable amount estimated by the state observing unit M8, the integral value calculated by the accumulating unit M11, and the preset optimum feedback gain,
The target braking pressure of the braking member M2 is determined.

The target rotational angular velocity is usually calculated as a rotational angular velocity that realizes a slip ratio such that the wheel M1 exerts the maximum braking force. That is, the target rotational angular velocity ω ^* is calculated as ω ^* ωf × (1-SL) with respect to the rotational angular velocity ωf of the wheel M1 converted from the vehicle speed. Here, SL means the slip ratio.

The slip ratio is usually set to a value that exerts the maximum braking force, but it may be variable according to the operation of the vehicle. For example, there is a case where the slip ratio to be realized is changed according to the depression state of the brake pedal. FIG. 2 shows the relationship between the slip ratio SL and the frictional force M. As shown in the figure, the frictional force M becomes maximum when the slip ratio SL is 10 to 20%, so that the wheel M1 exerts the maximum braking force. Demonstrate. 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 slip ratio is set to 10 to 20% so that the vehicle stops at the shortest distance, while the depression of the brake pedal is performed. When the amount is small,
It is also conceivable that the driver determines that the driver wants gentle deceleration and sets the slip ratio to a small value such as 5%. In this case, the target rotational angular velocity ω ^* is set according to the slip ratio SL. It will be changed.

The braking control means M7 is usually realized by using a microcomputer mainly composed of a microprocessor, peripheral devices such as ROM and RAM, and input / output circuits. Unlike the conventional control circuit used for anti-skid control, the braking control means M7 of the present invention includes a state observing section M8, an accumulating section M11, and a brake pressure determining section M12 so that the system related to vehicle braking can be operated in advance. Optimal feedback gain determined according to a conventional model The brake pressure to be transmitted to each braking member M2 is known based on the above, the feedback control amount of the brake pressure adjusting means M4 for adjusting to this brake pressure is obtained, and a control signal corresponding to this is output. That is, the braking control means M7 is configured as an additional integral type optimum regulator that determines the optimum feedback amount from the detected state variable amount and slip ratio.

The method of constructing the optimum integral-type regulator is described in, for example, Katsuhisa Furuta, "Linear System Control Theory" (Showa 51).
The details are given in Shoshodou et al., 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} Subscript such as That it is an estimate, Symbol such as The control target of another system generated by the conversion or the like from the system, wherein the state monitoring section (hereinafter, referred to as observer) is that the amount covered in, y ^* of such symbol ^* is the target value This is shown respectively.

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, Control input quantities for the controlled object, that is, the hydraulic pressure u, Are the control output quantities of the controlled object, here the rotational angular velocity ω, the variable DLY corresponding to the response delay of the control system, and the actual hydraulic pressure P.
And so on, It is described as. Equations (1) and (2) are described in a discrete system, and the subscript k indicates that it is a value at the present time, k-1
Indicates that the value is the value at the time of sampling one time before.

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 M1 is clarified, and the vector of the equations (1) and (2) is obtained. If we can determine Thus, the braking of the vehicle 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 from the law of motion by setting a mechanical model of the hydraulic system, 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 The feedback amount is determined from the rotational angular velocity ω (k) of each wheel M1 and its target rotational angular velocity ω ^* (k).
Amount of brake pressure adjusting means M2 for controlling the brake pressure of Is theoretically optimally determined. In a normal vehicle braking control system, various amounts directly related to vehicle braking include, for example, load applied to each wheel M1, acceleration, moving speed of oil or gas transmitted to the braking member M2, dynamic behavior of the control member M2, In addition, the response delay of the system M3, etc. However, it is extremely difficult to directly observe most of these quantities. Therefore, in such a case, a means called a state observing section (observer) is configured in the braking control means M to measure the state variable amount of the vehicle. 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, Katsuhisa Furuta "Mechanical System Control" (Showa 59).
Year), which is explained in detail by Ohmsha Co., Ltd.
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 M7 determines the state variable amount estimated by the above observer. In addition to the above, in the system expanded by using the cumulative value obtained by accumulating the deviation between the target rotational angular velocity of each wheel M1 calculated from the vehicle speed and the rotational angular velocity detected by the rotational angular velocity detecting means M5, An optimal feedback amount is determined from the determined optimal feedback gain and the brake pressure adjusting means M4 is controlled. The cumulative value is an amount necessary because the calculated target rotation angular velocity decreases in a ramp function according to the vehicle body speed. That is, generally, in the control of the servo system, it is necessary to eliminate the steady-state deviation between the target value and the actual control value, and this needs to include 1 / S ^l (integral of order ¹ ) in the transfer function. To be done. 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 as the integral quantity. Therefore, the amount of state variables The system is expanded by adding this cumulative value to If the feedback amount is determined by and, the control amount to the controlled object, that is, the control amount of the brake pressure of each wheel M1 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 quantities of the brake pressure control of each braking member M2) 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 the optimum value by giving a weighting parameter arbitrarily and performing a 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 M7 of the braking control device of the present invention is
It is configured as an additional integral type optimal regulator using a predetermined dynamic model of the system related to vehicle braking, and observer parameters and optimal feedback gain inside the regulator are added. Are all 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.

An embodiment of the present invention will be described below with reference to the drawings. Third
FIG. 4 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. First, the overall configuration and the outline of the hydraulic system / electric system will be described.

As shown in the figure, each of the wheels 1, 2, 3, 4 of the vehicle has a hydraulic brake device 11, 12, 13, 14 corresponding to a braking member.
The left and right front wheels 1 and 2 are each provided with an electromagnetic pickup type rotation speed sensor 1 for detecting the rotation speed thereof.
5, 16 are attached. Further, the rotation of the main shaft 19 of the transmission 18 is controlled by the differential gear 21.
The rotation speeds of the rear wheels 3 and 4 which are received and rotated via the are detected by a rotation speed sensor 22 for the rear wheels provided in the transmission 18.

Hydraulic brake devices 11 to 14 provided on each wheel
Uses the high hydraulic pressure generated by the master cylinder 25 such as a tandem type in conjunction with the brake pedal 21 as a brake hydraulic pressure to brake the rotation of each of the wheels 1 to 4, but is transmitted from the master cylinder 25 via a hydraulic system MPS. This brake hydraulic pressure 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 hydraulic pressure adjusting means for adjusting the brake hydraulic 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 pressure, and also rotates speed sensors 15, 16,
The rotational speed signal from the actuator 22, the signal from the acceleration sensor 54 that detects the acceleration (including deceleration) of the vehicle, the signal from the brake sensor 55 that detects the operation of the brake pedal 24, etc. are input to the actuator 31. , 32, 33
To control the rotational angular velocity ω of each of the wheels 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 to form a logical operation circuit. The ECU 40 drives the main relay 74 and the main solenoid valve 75 and the sub solenoid valve 76 in the actuator 31, thereby transmitting from the master cylinder 25 to the hydraulic brake device 11 via the pressure reducing cylinder 78 and the bypass cylinder 80. Controls brake hydraulic pressure. When the brake hydraulic pressure rises, the hydraulic brake device 11 presses the friction pad 83 against the disc 82 rotating with the wheel 1 to stop the rotation of the wheel 1.

The power steering hydraulic pump 90 and the power steering hydraulic pressure from the power steering hydraulic pressure generation device 43 including a reservoir (not shown) are transmitted to the actuator 31. In a state where the brake hydraulic pressure is not particularly controlled, the power steering hydraulic system PPS is used. Oil circulates from the hydraulic pump 90 via a regulator 91 in the actuator 31 and a power steering gearbox 92. 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 too high and the wheel 1 is over-braked and slippage occurs (for example, S >> 0.2), the ECU 40 causes the actuator 31 to operate.
The main solenoid valve 75 is operated in the ON state. 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 left chamber 78 of the decompression cylinder 78
The oil in L is gently discharged to the reservoir (not shown) of the steering hydraulic system PPS through the orifices B and C. Therefore, the decompression piston 78d is pulled out, and the cut valve 78c is closed. Decompression piston 78
As d is pulled out, the volume of the brake hydraulic system PHS 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 oil discharge through the orifice C is stopped, the oil rapidly flows from the steering hydraulic system PPS through the orifice A and the bypass passage 76b, and the decompression cylinder 78. The pressure in the left chamber 78L also increases. As a result, the decompression piston 78d
Is pushed in rapidly and the brake oil pressure 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.

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 P ^* . That is, assuming that the current hydraulic pressure is Po and the required hydraulic pressure P ^* after the time t2, in this hydraulic system, four control patterns, rapid pressure increase a, rapid pressure decrease b, slow pressure decrease c, and rapid pressure decrease d are provided. It is necessary to control the brake hydraulic pressure by selecting a control pattern from among these such that the pressure is rapidly increased from time 0 to t1 and then gradually increased until t2.

Next, the outline of signal processing and system control in this embodiment will be described with reference to FIG. This kind of signal processing is the fourth
In the hardware configuration shown in the figure, it is realized by executing a control program described later according to the flowchart of 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, which is controlled to match it with the target rotational angular velocity ω ^* . However, the directly detected physical quantity is the hydraulic pressure P of the hydraulic brake devices 11 to 14 of the wheels 1 to 4, and the rotational speeds Nfr, Nfl, Nr and acceleration sensors detected by the rotational speed sensors 15, 16, 22 of the wheels. The acceleration G of the vehicle detected by 54. Therefore, inside the ECU 40, first, the wheel hydraulic pressure P is multiplied by a coefficient K2 that is experimentally obtained in advance to obtain the braking torque Tb for the wheel. 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. Here, the coefficient K1 is a value determined from the load W applied to the wheel, the turning radius r of the wheel, and a constant. In this embodiment, the friction coefficient μ between the wheel and the road surface is
Is not actually measured, so that this control system can respond sufficiently to the change, that is, it is sufficient even if the friction coefficient μ changes within the range of values that can actually be taken (for example, 0.7 ± 0.4 range). The system is configured to control the slip ratio. Such a system configuration is achieved by designing the optimum feedback gain so that the output is not sensitive to a certain range of .mu. Changes. For example, when obtaining the optimum feedback gain, evaluation functions and parameters are used as will be described later, but by adjusting the weighting of these evaluation functions and parameters, it is possible to make them insensitive to μ change in a certain range. Of course, there is no problem in measuring and using this with a μ sensor or the like.

Next, 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, the rotation of the wheel 1 is performed next. The angular velocity ω is obtained. Here, the actual velocity Tr is integrated (1 / S) and multiplied by a coefficient K3 considering the inertia I of the wheel 1 to obtain the angular velocity ω.
Is required.

On the other hand, the vehicle speed V is calculated by once integrating (1 / S) the vehicle speed Vo obtained from the rotation speed Nfr of the wheel 1 immediately before the start of braking and the acceleration G detected by the acceleration sensor 54 thereafter (( If expressed by a general formula, V = Vo + G
t and t indicate the elapsed time from the start of braking). This is the seventh
It is shown by K4 / S in the figure. With respect to the vehicle speed V thus obtained, the operation indicated by K5 in FIG. 7, that is, the slip ratio S
The target rotational angular velocity ω ^* is obtained from the following equation in consideration of L, the radius r of the wheel 1, the constant K5 ′, and the like. 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 WINω for following the vehicle speed (wheel rotational angular speed) that decreases as a ramp function during deceleration.

On the other hand, an observer is built to control the hydraulic pressure u as a control output.
From the oil pressure P actually detected, the variable DLY corresponding to the response delay in control and the oil pressure PF are obtained as state variables. 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 INSω, WINω, variable DLY, and hydraulic pressure PF are set to predetermined optimum feedback gains. Is multiplied by to obtain the hydraulic pressure control amount u of the hydraulic system for control. 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.

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 flowchart of FIG. In the following description, the amount handled in actual processing is added with a subscript (k),
The quantity handled in the previous processing performed before the sample time T will be represented by the subscript (k-1).

When the vehicle driver gives a braking instruction by stepping on the brake 24 while the vehicle is traveling, the CPU 61 performs the eighth operation.
The braking control process shown in the drawing is started, and this process is repeated until the brake pedal 24 is no longer depressed.

First, at step 100, 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 110, processing for calculating the current vehicle speed V (k) is performed.
The vehicle speed V (k) is calculated as V (k) = V (k−1) + G · T (6), where T is the time required to process this control routine once. )
The initial value V (O) is calculated from the rotational speed Nfr of the right front wheel 1 that was rotating as an idler wheel at a rotational speed according to the vehicle speed immediately before braking. The above steps 100 and 110 function as vehicle speed detection means.

In step 120, a calculation process for obtaining the target rotational angular velocity ω ^* (k) of the wheel 1 from the vehicle speed V (k), ω ^* (k) = k5 ′ · V (k) · (1-SL) / r ... (7 ) Is performed.

In the next step 130, a process of reading the hydraulic pressure P (k) of the hydraulic system for braking the right front wheel 1 by the hydraulic sensor 51 is performed. In the following step 140, processing for obtaining the rotational angular velocity ω (k) of the wheel 1 is performed. Rotational angular velocity ω
(K) is the hydraulic pressure P (k) as described above with reference to FIG.
Is determined by the coefficients K1, K2, K3 and one integration. The above steps 130 and 140 function as a rotational angular velocity detecting means.

In the following step 150, a process of obtaining a deviation Δω (k) between the target rotational angular velocity ω ^* (k) calculated in step 120 and the actual rotational angular velocity ω (k) determined in step 140 is performed, and the subsequent step In 160 and 170, a process of integrating this is performed. That is, in step 160, INTω (k) = INTω (k-1) + T · Δω (k) is used as the first-order integration, and in step 170, WINω (k) = WINω (k- 1) + T · INTω (k) is calculated respectively. In this way, the cumulative value INTω, WI obtained by integration from the deviation amount Δω (k) between the target rotational angular velocity ω ^* (k) and the actual rotational angular velocity ω (k) of the wheel 1.
Nω (k) was determined.

In the following step 180, 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.

It should be noted that, here, the output of the observer includes the variable DLY corresponding to the response delay and the state variable amount other than the hydraulic pressure PF, which is merely formal, and each amount obtained in steps 150 to 170. (Δω, INTω, WINω)
Is just output as is.

In step 190 following step 180, a process for obtaining the control output u (k) is performed. Control output u
(K) is the optimal 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 equation (9) Is the observer estimate Can be replaced. That is, As a result, the control output u (k) can be calculated. Where the optimal feedback gain Is Is required as. In equation (13) Is Riccati equation, Is the solution of Is the evaluation function, Is the parameter used in the simulation that minimizes and is selected as the 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 190 make use of, Is performed to obtain the hydraulic pressure u (k) as the control output.

In the following step 200, processing for obtaining the hydraulic pressure control pattern is performed based on the control output u (k) obtained in step 190. That is, as already described with reference to FIG. 6, the opening / closing time of the main solenoid valve 75 and the sub solenoid valve 76 is determined so that the hydraulic pressure u (k) is reached within the sampling time T.

At step 210, the main solenoid valve 75 and the sub solenoid valve 76 are appropriately controlled according to the control pattern obtained at step 190, and then at step 220, K indicating the number of samplings is indicated.
Is incremented by 1.

In the following step 230, the state of the brake sensor 55 read via the level input port 72 is checked to determine whether or not the braking is being performed, and the brake pedal 24 is depressed, and the braking is continued. For example, the process returns to step 100 to repeat the above process, steps 100 to 230. On the other hand, if the braking has been released, the control is exited to NEXT and this control routine is ended.

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. Therefore, the vehicle can be stopped at the shortest braking distance while maintaining a good drive feeling.

FIG. 9 is a graph comparing the control of the rotational angular velocity of the wheel 1 between the start of braking and the stop of the vehicle between the present embodiment and the conventional example. Target rotational angular velocity ω until the vehicle stops
^* (Dashed-dotted line) decreases as a ramp function, whereas in the braking control device of the present embodiment, the actual wheel 1
The rotational angular velocity ω (solid line) is a slight overshoot,
Immediately follows the undershoot after it occurs. On the other hand, in the conventional example, hunting occurs due to the delay of the hydraulic system such as the operation delay of the solenoid valve, and the rotational angular velocity pa
(Dashed line) does not match the target rotational angular velocity for a long period of time. Moreover, in the conventional control, if the rotational angular velocity of the wheel is stably controlled, it becomes difficult to estimate the vehicle speed, and thus the control disturbance as shown by the range I in FIG. 9 may occur. However, these problems have been solved in a hurry. Further, in the conventional example shown in FIG. 9, since the drive feeling is emphasized rather than the braking characteristic, the braking distance and time are longer than those in the present embodiment. As is clear from FIG. 9, in this embodiment, extremely excellent responsiveness and stability were obtained. Further, in the present embodiment, the braking of the wheel 1 can be controlled sufficiently stably even if the friction coefficient of the road surface changes in a wide range (μ = 0.7 ± 0.4 range) by the adjustment at the time of setting the optimum feedback gain. 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, the slip ratio can be stably controlled to maintain a high braking characteristic of the vehicle.

Further, as the vehicle speed decreases, if parameters such as an observer are changed to slow down the convergence of control, stable control can be achieved even at low speed.

Although one embodiment of the present invention has been described above, the present invention is not limited to this embodiment, and the target rotational angular velocity ω ^* can be changed by the depression amount of the brake pedal, and the vehicle speed V can be a ground vehicle speed sensor. Configuration to detect directly by
Alternatively, it is needless to say that the target rotation angular velocity ω ^* can be changed in a stepwise manner so that the secondary integration amount is not used, and the present invention can be implemented in various modes without departing from the scope of the present invention.

As described above in detail, the vehicle braking control device of the present invention is
The state observation unit estimates the state variable amount representing the response delay in the control of the system, and the brake pressure determination unit uses the estimated state variable amount representing the response delay based on the preset optimum feedback gain. , The target braking pressure of the braking member is determined. Therefore, the target brake pressure is set in consideration of the response delay so that the delay can be covered even if the response delay exists. Further, the brake pressure determination unit also uses the integrated value of the deviation between the rotational angular velocity and the target rotational angular velocity calculated by the accumulating unit in the determination of the target brake pressure.
From this, a more accurate target brake pressure can be set. Therefore, while maintaining high responsiveness and stability,
It has an excellent effect that the braking control of the wheels can be optimally performed. Therefore, according to the vehicle braking control device of the present invention,
The vehicle can be stopped at the shortest braking distance while maintaining a good drive feeling.

[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. A flow chart, FIG. 8 is a flow chart showing the processing procedure in the embodiment, and FIG. 9 is a graph comparing the control characteristics in the embodiment with those of the conventional example. 1, 2, 3, 4 ... Wheels 11, 12, 13, 14 ... Hydraulic brakes 15, 16, 22 ... Rotation speed 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 (1)

[Claims] 1. A rotational angular velocity detecting means for detecting a rotational angular velocity of each wheel of a vehicle, a target rotational angular velocity setting means for setting a target rotational angular velocity of each wheel of the vehicle, and a drive signal of each wheel according to a given drive signal. Brake pressure adjusting means for adjusting the brake pressure transmitted to the braking member, and controlling the brake pressure adjusting means so that the detected rotational angular velocity of each wheel becomes the set target rotational angular velocity of each wheel. A braking control device for a vehicle, comprising: a braking control means; and a braking pressure detection means for detecting a braking pressure of each wheel, wherein the braking control means is a dynamic model of a system relating to braking of the vehicle. Based on the parameters set in advance, the target brake pressure when controlling the brake pressure adjusting means by the braking control means and the detected brake A state observing unit for estimating a state variable amount representing a response delay in control of the system from the brake pressure, a rotation angular velocity detected by the rotation angular velocity detecting means, and a target rotation angular velocity setting for each wheel. A deviation from the target rotational angular velocity set by the means, and an accumulator that calculates an integral value of the deviation, the detected brake pressure, the estimated state variable amount, and the calculated integral value. A braking control device for a vehicle, comprising: a brake pressure determining unit that determines a target brake pressure of the braking member based on a preset optimum feedback gain; .