JP2623565B2 - Anti-skid control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention controls a braking force of a braking device based on a vehicle body speed and a wheel rotation speed to prevent occurrence of a transient slip on wheels during vehicle braking. More specifically, the present invention relates to an anti-skid control device that performs control by estimating the vehicle speed from the vehicle acceleration.

[Prior Art] The anti-skid control device reduces safety due to wheel lock during vehicle braking, that is, the vehicle cannot be steered by locking the front wheels of the vehicle, or causes a swaying phenomenon (skid) due to locking of the rear wheels of the vehicle. In order to prevent this, the slip ratio SL of each wheel of the vehicle [(body speed-wheel rotation speed)
/ Vehicle speed] is controlled to around 20% to control the rotation speed of the wheel so that the friction coefficient between the tire and the road surface is maximized. Usually provided on the wheel based on the body speed and the rotation speed of the wheel It is configured to control the braking force of the control device (ie, the brake device).

Further, the detection of the vehicle body speed is performed, for example, in Japanese Unexamined Patent Publication No. 61-89.
As described in Japanese Patent Application Publication No. 156, a method is adopted in which an acceleration sensor is provided on a vehicle body and a vehicle speed is obtained by integrating the vehicle acceleration detected by the acceleration sensor. The acceleration sensor detects the acceleration acting on the sensor using the inertia of a pendulum or a magnetic fluid.

[Problems to be Solved by the Invention] However, when the vehicle speed is detected by using the acceleration sensor as described above, the acceleration sensor does not detect acceleration due to rolling, pitching, yawing, or the like acting on the vehicle body. It is necessary to mount the acceleration sensor near the center of gravity of the vehicle body, and it is troublesome to secure the mounting position and adjust the position. Also, some kind of vibration is always acting on the running vehicle, and the output of the acceleration sensor
Not only the vehicle acceleration but also the noise component of the vibration acceleration is included, and the output of the acceleration sensor cannot be said to indicate the accurate vehicle acceleration. A signal processing device or a signal processing program for removing such a noise component There was a problem that had to be provided.

Therefore, the present invention estimates the vehicle speed from the vehicle acceleration,
In an anti-skid control device for performing control, the object is to provide a vehicle body acceleration with a simple configuration without providing an acceleration sensor on the vehicle body.

[Means for Solving the Problems] That is, the present invention, which has been made to achieve the above object, provides a braking device M2 for braking the rotation of a wheel M1 supported on a vehicle body as shown in FIG. 1, for example.
Wheel speed detecting means M3 for detecting the rotation speed of the wheel M1
A vehicle speed estimating means M4 for estimating a vehicle speed, and at least the vehicle speed estimated by the vehicle speed estimating device M4 and the wheels detected by the wheel speed detecting device M3
A control means M5 for adjusting a braking force of the braking device 2 based on the rotation speed of M1 and controlling a slip generated between the wheel M1 and the vehicle M1 during braking of the vehicle. Means M4, a braking force detecting means M6 for detecting a braking force generated by a braking device M2 provided on each wheel of the vehicle, and a vehicle acceleration estimated from the braking force of each wheel of the vehicle detected by the braking force detecting means M6. And vehicle body acceleration estimating means M7 to perform the integration processing of the vehicle body acceleration estimated by the vehicle body acceleration estimating means M7 during slip control to calculate the vehicle body speed. M5, a target rotational speed calculating means for calculating a target rotational speed of the wheel M1 from the vehicle speed estimated by the vehicle speed estimating means M4.
M8 and the braking device based on an optimal feedback gain determined in advance according to a dynamic model of a system related to braking of the vehicle so that the rotation speed of the wheel M1 becomes the target rotation speed.
Command value calculation means M9 for calculating the braking force command value for M2
And an anti-skid control device characterized in that the braking force of the braking device M2 is adjusted to the braking force command value.

Here, as the brake device M2, a hydraulic brake device that presses a friction member against a member that rotates with the wheel by hydraulic pressure, an electromagnetic brake device that brakes a magnetic body that rotates with the wheel by an electromagnetic force, or the like can be used. The former braking force is a hydraulic pressure, and the latter is an electric quantity, for example, a pulse or a voltage.

The rotation speed detecting means M3 is for detecting the rotation speed of the wheel M1, and may be an electromagnetic pickup type sensor, an optical sensor, or the like which outputs a pulse having a period proportional to the rotation speed.

Further, the braking force detecting means M6 is for detecting the braking force of the braking device M2. If the braking device M2 is a hydraulic braking device, it is a hydraulic sensor that detects the hydraulic pressure. A sensor or an electric circuit for detecting the amount of electricity to be performed, or a unit for storing a control amount output from the control unit M5.

Next, the vehicle body acceleration estimating means M7 detects the vehicle body acceleration based on the braking force of the braking device M2 detected by the braking force detecting means M6. Hereinafter, the reason why the vehicle body acceleration can be estimated from the braking force of the braking device M2 will be briefly described with reference to FIG.

First, the force F acting on the vehicle body during braking of the vehicle is the sum of the forces f applied from the wheels of the vehicle, and by dividing this by the inertial mass M of the vehicle body, the vehicle body acceleration Ma can be obtained.

Then, considering the force f of each wheel acting on the vehicle body,
This force f is given by the friction torque Tf acting by the friction between the wheels and the road surface. This friction torque Tf is
Based on the balance of the torque around the wheels, it is given by the braking torque Tb acting by the braking force of the braking device and the rotation torque Tb. Further, the rotational torque Tr is given based on a rotational acceleration Vwd obtained by time-differentiating the rotational speed Vw of the wheel.

Therefore, the vehicle body acceleration Ma can be obtained from the rotational speed Vw of the vehicle square wheels and the braking force of the braking device.

Here, considering the case where the rotational speed Vw of the wheel is appropriately controlled, the rotational acceleration Vwd is substantially constant. Therefore, in a vehicle in which the wheel rotational speed Vw is controlled by the anti-skid control within a range in which the wheels do not lock, the vehicle body acceleration Ma can be obtained only from the braking force of the braking device M2.

Therefore, the acceleration estimating means M7 includes the vehicle acceleration
The relationship between Ma and the braking force of the braking device M2 is experimentally obtained in advance,
Record the measurement result as a map or arithmetic expression,
When executing the control, the vehicle acceleration Ma may be designated using the map or the arithmetic expression.

Next, the vehicle speed estimation means M4 includes the braking force detection means M6 and the vehicle acceleration estimation means M7.
The vehicle speed V is estimated by integrating the vehicle acceleration Ma estimated in step (1).

Further, the control means M5 adjusts the braking force based on at least the vehicle speed estimated by the vehicle speed estimation means M4 and the rotation speed of the wheel M1 detected by the wheel speed detection means M3, and controls the slip of the wheel. In the present invention, the vehicle acceleration is estimated from the braking force of the braking device M2 by the vehicle acceleration estimating means M7, and thus the control system by the control means M5 is used. Must be improved so that the rotational acceleration of the wheel M1 can be controlled to be substantially constant when the control is executed.

Therefore, in the present invention, the control means M5 includes a vehicle speed estimation means.
A target rotational speed calculating means M8 for calculating a target rotational speed of the wheel M1 from the vehicle speed estimated in M4, and a dynamic model of a system relating to braking of the vehicle in advance so that the rotational speed of the wheel M1 becomes the target rotational speed. Command value calculating means M9 for calculating a braking force command value for the braking device M2 based on the optimal feedback gain determined according to the following formula, and the braking force of the braking device M2 is calculated by the command value calculating means M9. It is adjusted to the command value.

That is, to perform feedback control of the rotation speed of the wheel M1 to the target rotation speed, a so-called PID based on the conventional classical control is used.
(Proportional / Integral / Derivative) control can also be realized, but in this case, the rotational speed of the wheel M1 tends to hunt due to a response delay of the control system and the like, and the rotational acceleration of the wheel M1 may not be able to be controlled to a constant value. According to the present invention, the slip control (that is, the anti-skid control) by the control means 5 is based on modern control theory in which the rotational speed of the wheel M1 can be made to converge more quickly to the target rotational speed, and the rotational acceleration can be made substantially constant. This is achieved by optimal feedback control.

[Operation] In the anti-skid control device of the present invention configured as described above, the wheel speed detecting means M3 detects the rotation speed of the wheel M1, the vehicle speed estimating means M4 estimates the vehicle speed,
The control means M5 adjusts the braking force generated by the braking device M2 based on at least the rotation speed of the wheel M1 and the vehicle speed.

When the vehicle speed estimating unit M4 estimates the vehicle speed while the braking unit M5 is performing such slip control, the braking device M2 provided on each wheel of the vehicle is detected by the braking force detecting unit M6. The vehicle speed is calculated by detecting the generated braking force, estimating the vehicle acceleration from the detected braking force of each wheel of the vehicle by the vehicle acceleration estimating means M7, and integrating the estimated vehicle acceleration. I do.

On the other hand, when the control means M5 adjusts the braking force of the braking device M2 during vehicle braking, the target rotation speed calculation means M8 calculates the target rotation speed of the wheels M1 from the vehicle speed estimated by the vehicle speed estimation means M4. The command value calculation means M9 calculates the rotation speed of the wheel M1 based on the optimum feedback gain predetermined according to a dynamic model of the system related to the braking of the vehicle so that the rotation speed of the wheel M1 becomes the calculated target rotation speed. A braking force command value for the braking device M2 is calculated, and the braking force of the braking device M2 is adjusted to the calculated braking force command value.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. The following examples show one embodiment of the present invention, and the present invention includes other embodiments without departing from the gist.

FIG. 3 is a schematic configuration diagram showing the overall configuration of an anti-skid control device for a vehicle mounted on a four-wheeled vehicle as an embodiment of the present invention. FIG. It is a control system diagram shown with a figure.

First, an overall configuration and an outline of a hydraulic system and an electric system will be described.

As shown in the figure, a braking member M2 is provided on each wheel 1, 2, 3, 4 of the vehicle.
, And electromagnetic pickup type wheel speed sensors 15 and 16 for detecting the respective rotation speeds are attached to the right and left front wheels 1 and 2. The rotation speeds of the rear wheels 3, 4 that rotate by receiving the rotation of the output shaft 19 of the transmission 18 via the differential gear 21 are detected by a wheel speed sensor 22 for the rear wheels provided in the transmission 18.

Hydraulic brake devices 11 to 14 provided on each wheel are tandem type master cylinders etc.
The high oil pressure that generates 25 is used as the brake oil pressure for each wheel 1
The brake oil pressure is adjusted by actuators 31, 32, and 33 transmitted from the master cylinder 25 via the hydraulic system MPS. Actuator 31, 3
Numerals 2 and 33 independently adjust the brake hydraulic pressure of the right front wheel 1, left front wheel 2, left and right rear wheels 3 and 4, and are controlled by an electronic control unit (ECU) 40.

The hydraulic pressure of the hydraulic system RHS of the brake hydraulic pressure to the right front wheel 1 is controlled by a hydraulic sensor 51, the hydraulic pressure of the hydraulic system LHS of the left front wheel 2 is controlled by a hydraulic sensor 52, and the hydraulic pressure of the hydraulic system BHS of the rear wheels 3, 4 is controlled by a hydraulic sensor 53. , Respectively.

The ECU 40 includes a signal corresponding to the oil pressure from the oil pressure sensors 51, 52, 53, a wheel speed signal from the wheel speed sensors 15, 16, 22, and a brake switch 55 for detecting operation of the brake pedal 24. And controls the actuators 31, 32, and 33 (ie, controls the braking forces of the hydraulic brake devices 11 to 14) to control the rotational speeds of the wheels 1 to 4.

Since the control of the braking force of the right front wheel 1, the left front wheel 2, and the rear wheels 3 and 4 is performed independently, the right front wheel 1 will be described below. FIG. 4 is a configuration diagram mainly showing a system for controlling braking of the right front wheel 1. As shown in the figure, the ECU 40 includes a power supply unit 58 that receives a power supply voltage from a battery 57 via an ignition key 56 and supplies a constant voltage to the entire unit, and mainly includes a well-known CPU 61, a ROM 63, a RAM 65, and the like. The output port 67, the analog input port 69, the pulse input port 71, and the like are configured as a logical operation circuit in which they are mutually connected by a bus 72.

On the other hand, the actuator 31 includes a bypass valve 73 and a three-position valve 74.
Consists of The bypass valve 73 is provided in an oil path directly connecting the master cylinder 25 and the hydraulic brake device 11, and shuts off this oil path in response to a command from the ECU 40. The three-position valve 74 has a first position a for holding the hydraulic pressure of the hydraulic brake device 11, a second position b for increasing the hydraulic pressure of the hydraulic brake device 11, and a third position c for reducing the hydraulic pressure of the hydraulic brake device 11. And is normally biased to the second position b.

The hydraulic pressure generating device 43 pressurizes the brake oil of the reservoir 43a by the pump 43b and supplies it to the three-position valve 74 via the accumulator 43c. The high oil pressure from the oil pressure generator 43 is supplied to the hydraulic brake device 11 at the second position b of the three-position valve 74.
At the third position c of the three-position valve 74, the hydraulic pressure of the hydraulic brake device 11 is released to the reservoir 43a.

In the hydraulic brake device 11, the piston 75 is pushed out by the supplied hydraulic pressure, and the brake pad 76 is brought into contact with the disk plate 77 which rotates together with the wheel 1, thereby braking these rotations. In the drawing, reference numerals 80a, 80b, 80c denote orifices, and 81a, 81b, 81c, 81d, 81e denote check valves.

 Here, the outline of the operation of the control system shown in FIG. 4 will be described.

When the driver depresses the brake pedal 24, hydraulic pressure is generated in the master cylinder 25, and this hydraulic pressure is transmitted to the hydraulic brake device 11 via the bypass valve 73, and the wheels 1 are braked.

When the braking force is strong and the wheel 1 becomes close to locking and the slip ratio exceeds a predetermined value, the ECU 40 detects this and starts anti-skid control.

First, the pump 43b is driven, but this pump may be always operable to keep the pressure of the accumulator 43c constant. By driving the bypass valve 73 to the second position b, the direct connection between the master cylinder 25 and the hydraulic brake device 11 is cut off. Thereby, the master cylinder 25 and the hydraulic brake device 11 communicate with each other via the three-position valve 74 and the orifices 80a and 80b.

Thereafter, while the brake pedal 24 is being depressed, the ECU 40 sets the target rotation speed Vw ^* at which the vehicle can be braked at the shortest distance ^.
The three-position valve 74 is driven by calculating a command oil pressure that makes the rotation speed Vw of the wheel 1 coincide with the target rotation speed Vw ^* . The control of the three-position valve 74 includes the first position a, the second position b, and the third position b.
The control is performed by switching the position c and the hydraulic pressure of the hydraulic brake device 11 is maintained, increased, and reduced to control the brake hydraulic pressure to the command hydraulic pressure.

In the present embodiment, the braking device M2 is the hydraulic braking device 11
The braking force is substituted by the hydraulic pressure of the hydraulic brake device 11.

Next, the control by the ECU 40 will be described in more detail.

First, the braking system of the vehicle will be described with reference to FIGS. FIG. 2 shows the force acting between the vehicle body and the wheels as described above, and FIG. 5 is a block diagram modeling the braking system. In the following description of the block diagram, the operation 1 / S represents time integration, and the operation S represents time differentiation.

When a hydraulic pressure of prs is instructed by the ECU 42, a hydraulic pressure of pro is supplied to the hydraulic brake device by a hydraulic servo.

The hydraulic brake device generates a braking torque Tb for braking the wheels. The braking torque Tb is determined by the coefficient Kt determined by the structure and characteristics of the hydraulic brake device and the hydraulic pressure pro.

On the other hand, the wheels are rotating at the speed Vw,
Exercise in.

The value obtained by dividing the difference between the rotation speed Vw and the vehicle speed V by the vehicle speed V is the slip ratio SL, and the friction coefficient μ between the road surface and the wheels is determined by the nonlinear operation.

From the friction coefficient μ, the vehicle body mass m of one wheel, the gravitational acceleration G, and the effective radius r of the wheel, the friction torque Tf that the wheel receives from the road surface is determined.

The difference between the friction torque Tf and the braking torque Tb is the rotation torque Tr acting on the wheels.

The rotational acceleration Vwd of the wheel is determined from the rotational torque Tr, the effective radius r of the wheel, and the rotational inertia moment I of the wheel, and the rotational speed Vw is obtained by integrating the rotational acceleration Vwd.

On the other hand, f acting on the axle is determined from the friction coefficient μ, the vehicle body mass m of one wheel, and the gravitational acceleration G.

Since this force f is the force that the vehicle body receives from one wheel, the force F acting on the vehicle body is the sum of the forces received from all the wheels, and the force F acting on the vehicle body is determined.

By dividing the force F acting on the vehicle body by the vehicle body mass M,
The vehicle acceleration Ma is determined, and the vehicle speed V is determined by integrating the vehicle acceleration Ma.

Therefore, as described above, the vehicle body acceleration Ma is determined by the rotation speed Vw of each wheel detected by the wheel speed sensors 15, 16, and 22,
It can be estimated from the brake hydraulic pressure pro of each hydraulic brake device detected by the hydraulic sensors 51, 52, 53. That is, the friction torque Tf that each wheel receives from the road surface is expressed by the following equation (1): Tf = pro + Kt + Vwd + (I / r) (1) The force f that the vehicle body receives from these wheels is expressed by the following equation (2). F = Tf / r (2) In the case of a four-wheeled vehicle as in the present embodiment, the force F received by all the wheels from the vehicle body is as shown in the following equation (3). F = fFR + fFL + fRR + fRL (3) The vehicle acceleration Ma can be obtained by the following equation (4).

Ma = F / M (4) where fFR is the front right wheel, fFL is the front left wheel, fRR is the rear right wheel, fRL
Indicates the force of the left rear wheel.

In the present embodiment, the rotational speed Vw of each wheel is appropriately controlled by anti-skid control described later so that the wheel does not lock, so that the rotational acceleration Vwd of each wheel is almost constant. Therefore, assuming that Vwd in the above equation (1) is constant, the above equation (4) finally becomes Ma = (PFR + PFL + PRR + PRL) + K1 + K2 (4) '. Here, PFR indicates the right front wheel, PFL indicates the left front wheel, PRR indicates the right rear wheel, PRL indicates the brake oil for the left rear wheel, and K1 and K2 indicate constants.

Then, the vehicle was actually run, and the vehicle acceleration Ma when braking was applied to the wheels while gradually applying hydraulic pressure to each hydraulic brake device was measured. As a result, data as shown in FIG. 6 was obtained. Therefore, by using this measurement data as a map and using the oil pressure data obtained by the oil pressure sensor at high speed, the vehicle body acceleration Ma can be estimated with almost no error. In FIG. 6, Pall indicates the total hydraulic pressure of each hydraulic brake device.

 Next, a control system by the ECU 40 will be described.

In the present embodiment, state feedback is performed by an optimal regulator based on modern control theory.

Therefore, the method of the optimal feedback of the present embodiment will be briefly described. Regarding modern control theory, for example, Katsuhisa Furuta, “Linear System Control Theory” (Showa 51, Shoshodo) and Katsuhisa Furuta, “Mechanical System Control” (Showa
(59, Ohmsha), etc., so I will not explain the derivation of equations or other methods in detail. In the following description, And so on represent vector quantities (matrix), Respectively represent the inverse matrices.

In this embodiment, the control system includes the ECU 40,
This is a sample value system that performs sampling at predetermined time intervals. In such a sample value system, the state variable quantity representing the internal state of the control Control input quantities for the controlled object Control output amount for the controlled object Then, these relationships are expressed by the following equations (5) and (6).

Note that the subscript k indicates the sampling time, and k +
1 indicates the next sampling time.

Here, the dynamic model of the controlled object becomes clear, and the vector If we can clarify And control output Asked, Control input for controlling Can be obtained, and the control target can be optimally controlled.

The control object of this embodiment, that is, the dynamic model of the control system is as shown in FIG. 5 from the equation of motion and the like.
Further, in this embodiment, since control is required to eliminate the steady-state deviation between the target value of the control output and the actual control output value, the integral value of the difference between the target value and the output value is determined by the state variable quantity. In addition to expanding the system. Therefore, in this embodiment, the state variable quantity Control input Is sucked as shown in the following equations (7), (8) and (9).

Next, the optimal feedback gain Will be described. In this embodiment, the optimum feedback gain Is obtained from the following equation (10).

Note that Is the solution of the Ricarich equation of the following equation (11).

here Is a parameter meter selected as an optimum value by a computer simulation in which the evaluation function J in the following equation (12) is minimized.

In this embodiment, the parameters of the evaluation function J Is changed and computer simulation is repeated, the optimal parameters are determined from the behavior of the braking system obtained by the simulation, and the optimal feedback gain is determined. It was determined.

Thus the optimal feedback gain Is determined, the control input Is represented by the following equation (13).

However, due to the response delay of the control system, Cannot be used directly. Therefore, by substituting the right side of equation (5), the control input Is obtained from the following equation (14).

here, Then, the above (14) becomes the following equation (15).

If it is set, the control input, that is, the command hydraulic pressure prs to the hydraulic brake device can be obtained.

Can be obtained in advance according to the vehicle speed, and these can be switched according to the vehicle speed. For example, the above parameters can be set so that the convergence speed of the system decreases as the vehicle speed decreases.

Next, FIG. 7 shows a control system block diagram of the present embodiment configured as described above.

As shown in the figure, a hydraulic pressure is supplied to the control system from a hydraulic servo, and a supplied hydraulic pressure pro and a rotation speed Vw are detected from a hydraulic pressure sensor and a wheel speed sensor, respectively. Then, the output value Vw from the wheel speed sensor is converted into a rotational acceleration Vwd by performing time differentiation.

Further, the output value pro of the hydraulic pressure sensor is added together with the output value pro from another hydraulic pressure sensor, and is converted into a vehicle body acceleration Ma based on a map representing the relationship between the brake hydraulic pressure and the vehicle body acceleration as shown in FIG. The vehicle speed V is obtained by integrating the vehicle acceleration Ma.

From the determined vehicle speed V, a target rotational speed Vw ^* is determined with a slip ratio at which the vehicle is most efficiently braked at 20%, and the target rotational speed Vw ^* and the detected value Vw of the wheel speed sensor are calculated. INT ΔVw by integrating the difference ΔVw
Is required.

Further, the output value from the wheel speed sensor (that is, the rotational speed of the wheel) Vw obtained as described above, the acceleration Vw
d and the integral value INTΔVw of the difference between the target rotation speed Vw ^* and the previous command oil pressure prs, the optimum feedback gain , The command hydraulic pressure prs is obtained.

On the other hand, the detection value Vw of the wheel speed sensor is converted into a wheel acceleration Vwd by a differential operation, and is converted into a wheel rotation torque Tr from the effective radius r of the wheel and the rotational moment of inertia I,
The detection value pro of the hydraulic pressure sensor is converted into a braking torque Tb acting on the wheels from a coefficient Kt determined from the structure and characteristics of the hydraulic brake device. Then, based on the rotation torque Tr and the braking torque Tb, the start hydraulic pressure calculation unit calculates the command hydraulic pressure prs at the beginning of the anti-skid control start.

Next, a flowchart of the ECU 40 that implements the above-described control system will be described.

The flowchart in FIG. 8 shows the anti-skid control by the ECU 40. In addition to the anti-skid control shown in FIG. 7, the ECU 40 also executes a process of self-diagnosing a failure of each sensor, the ECU 40, and the like, and starts an operation upon turning on a power supply by an ignition key provided in the vehicle.

When the process is started, step 100 is first executed to initialize a memory area used for the anti-skid control and to set initial values of each memory.

In step 110, it is determined whether or not control has been started. In this embodiment, the control is determined to be started when the slip ratio becomes 8% or more, and the process branches to yes. Here, the condition that the slip ratio is 8% means that the control target is 20%,
This is determined in view of the response delay of the hydraulic servo from the start of the control, that the anti-skid control should not be started on a high μ road unless the braking is very abrupt, but that it is desired to start as soon as possible on a low μ road.

In step 120, the initial command oil pressure prs immediately after the control is started is calculated, and the routine proceeds to step 130 where the initial command oil pressure prs is calculated.
Command the valve position to supply.

In step 140, the rotation speed Vw of each wheel is input from the wheel speed sensors 15, 16, 22.

In step 150, the rotational acceleration Vwd of each wheel is calculated from the rotational speed Vw of each wheel by the following equation (16).

Vwd (k + 1) = (Vw (k + 1) -Vw (k)) / T ... (1
6) Here, T is a sample period of the rotation speed Vw,
This is the time until the process of 0 is executed again. In the following description, T represents this time.

In step 160, based on the output signals from the oil pressure sensors 51, 52, 53, the hydraulic brake devices 11, 12, 13 and
Hydraulic pressure pro supplied to 14 (specifically Pfr, Pfl, Prr)
Enter

In step 170, the hydraulic pressure pro supplied to each of the read hydraulic brake devices 11 to 14 is added, and the vehicle acceleration Ma is calculated from the map shown in FIG.

That is, the oil pressure sensors 51 and 5 read in the above step 160
2, each hydraulic brake device 1 based on the output signal from 53
The total hydraulic pressure Pall supplied to 1, 12, 13, and 14 is calculated by the following equation (17), and the vehicle acceleration Ma is calculated from a preset map based on the calculation result.

Pall = Pfr + Pfl + 2 + Prr (17) In step 180, the vehicle speed V is calculated from the vehicle acceleration Ma calculated in step 170 by the following equation (18).

V (k + 1) = V (k) + Ma (k) + T (18) In step 190, the target rotational speed Vw ^{* at} which the vehicle is most efficiently braked is calculated from the following equation (19).

Vw ^* = V + (1−SL) (19) where SL is the slip ratio, and braking is most efficiently performed if the slip ratio at which the frictional force is maximized (20% in this embodiment). Further, the slip ratio SL may be variable according to the vehicle speed at the start of braking.

In step 200, the integral value INTΔVw of the rotation speed Vw of each wheel is calculated by the following equation (20).

INTΔVw (k + 1) = INTΔVw (k) + ΔVw (k) + T (20) In step 210, the command hydraulic pressure prs of each wheel is calculated. Since the command hydraulic pressure prs corresponds to the control input, the above equation (1
From 5), it is obtained by the following equation (21).

In step 220, based on the command hydraulic pressure prs of each wheel,
In order to control the brake hydraulic pressure of each wheel, a control pattern of the three-position valve corresponding to the right front wheel, the left front wheel, and the rear wheel is selected, and a command is issued to the three-position valve. Incidentally, the actual step 22
In the case of 0, since a command is issued at the next sampling (time before step 140) based on the command oil pressure obtained this time, the actual response delay of the control system can be considered.

That is, the three-position valve is driven such that the brake oil pressure of each wheel becomes the command oil pressure prs (k + 1) of each wheel during the sampling time T.

In step 230, k indicating the sampling time is incremented by one.

In step 240, it is determined whether to continue the anti-skid control. For example, it is determined whether or not the brake pedal is depressed or whether or not the vehicle has stopped. If the process is to be continued, the process returns to step 140.
Move to 0.

As described above, in the present embodiment, the hydraulic pressure of the hydraulic brake device is detected, the vehicle acceleration is estimated from the detection result, and the vehicle speed is obtained. Therefore, the vehicle speed can be detected without providing an acceleration sensor on the vehicle body, and can be realized with a simple circuit configuration without providing a processing circuit for processing an output signal from the acceleration sensor as in the related art. If the road surface suddenly changes during control,
For example, if the vehicle jumps from asphalt to a frozen road surface, the control hydraulic pressure becomes too large and the wheels may lock up.
Since 0 is instantaneously output as rs and the actual control oil pressure immediately becomes a small value, the vehicle body acceleration Ma can be estimated from the oil pressure of the hydraulic brake device without causing a large error that may cause a problem in control.

In the above embodiment, the present invention is applied to a rear-wheel drive vehicle. However, the present invention is applied to a front-wheel drive or four-wheel drive vehicle or a one-wheel drive vehicle.
Naturally, it can also be applied to wheels and three-wheeled vehicles.

In the above embodiment, the front two wheels are controlled independently and the rear two wheels are controlled collectively. However, all the wheels may be controlled independently.

Further, in the above embodiment, the vehicle acceleration is calculated as the sum of the forces applied by the wheels to the vehicle body, and the total hydraulic pressure of each hydraulic brake device is calculated.
Although it was configured to obtain from Pall, the force that each wheel applied to the vehicle body was obtained for each wheel from the hydraulic pressure of each hydraulic brake device, the acceleration applied to the vehicle body was calculated for each wheel, and this was synthesized with the vehicle center of gravity Thus, the vehicle acceleration can be well estimated. In such a configuration, the direction of the vehicle body acceleration can also be obtained.

Further, in the above embodiment, the hydraulic pressure-torque conversion coefficient Kt of the hydraulic brake device has been described as a fixed value.However, since this coefficient Kt changes depending on the state of the friction member and the weather environment, the ECU is configured to calculate it empirically. You may. For example, the configuration may be such that the correction gain K of the map is calculated from the hydraulic pressure and the rotational acceleration when slow braking in which the slip ratio does not increase so much, that is, when the anti-skid control is not executed and the CPU has a calculation surplus. In this case, the arithmetic expression in step 173 is Ma = K + f (Pall).

The braking device is not limited to the hydraulic braking device, but may be a device that adjusts the magnitude of the frictional force by using an electromagnetic force.

[Effects of the Invention] As described above in detail, in the anti-skid control device of the present invention, during the execution of the slip control, the vehicle body acceleration is estimated from the braking force generated by the braking device provided on each wheel of the vehicle. The vehicle speed is obtained by integrating the estimated vehicle acceleration. For this reason, the vehicle body acceleration, and hence the vehicle speed, can be obtained without providing an acceleration sensor on the vehicle body as in the prior art, and the circuit configuration for detecting the vehicle body acceleration is simplified.

As described above, in order to accurately estimate the vehicle body acceleration from the braking force generated by the braking device, the rotational acceleration of the wheels needs to be constant. However, in the present invention, anti-skid control is performed based on the estimated vehicle body speed. Find the target rotation speed of the wheel,
A braking force command value is calculated based on an optimum feedback gain determined in advance according to a dynamic model of a system related to vehicle braking so that the rotation speed of the wheel becomes the target rotation speed, and the braking force of the braking device is calculated. Adjust to the braking force command value,
Since the control is performed by the optimal feedback control based on the modern control theory, the anti-skid control can be performed with extremely high accuracy, and the rotational acceleration of the wheel can be controlled to be substantially constant.

Therefore, the vehicle body acceleration, and hence the vehicle body speed can be accurately estimated, and the control accuracy does not decrease due to the estimation error of the vehicle body speed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is an explanatory diagram showing forces acting on wheels and a vehicle body during braking of a vehicle, and FIG. 3 is a configuration showing an entire configuration of an anti-skid control device according to an embodiment. FIG. 4, FIG. 4 is a configuration diagram showing the configuration of the right front wheel in detail, FIG. 5 is a block diagram showing a dynamic model of a braking system of the embodiment, and FIG. FIG. 7 is a block diagram showing a braking system of the embodiment, and FIG. 8 is a flowchart showing an anti-skid control process executed by the ECU 40. M1,1,2,3,4 ... wheel M2 ... braking device (11,12,13,14 ... hydraulic brake device) M3 ... wheel speed detecting means (15,16,22 ... wheel speed sensor) M4 ... body speed estimation means, M5 ... control means M6 ... braking force detection means M7 ... body acceleration estimation means M8 ... target rotation speed calculation means M9 ... command value calculation means 40 ... electronic control unit

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Katsuhiro Oba 1-1-1 Showa-cho, Kariya-shi Nippon Denso Co., Ltd. (56) References JP-A-61-238557 (JP, A) JP-A-62-85752 (JP, A) JP-A-49-56094 (JP, A) JP-A-61-275050 (JP, A)

Claims (1)

(57) [Claims] 1. A braking device for braking the rotation of a wheel pivotally supported by a vehicle body, a wheel speed detecting means for detecting a rotational speed of the wheel, a vehicle speed estimating means for estimating a vehicle speed, and at least the vehicle speed The braking force of the braking device is adjusted based on the vehicle speed estimated by the estimating unit and the rotational speed of the wheel detected by the wheel speed detecting unit, and a slip generated between the wheel and the road surface during vehicle braking is controlled. An anti-skid control device comprising: a braking force detecting means for detecting a braking force generated by a braking device provided on each wheel of the vehicle; And a vehicle acceleration estimating means for estimating the vehicle acceleration from the detected braking force of each vehicle. During the slip control, the vehicle acceleration estimated by the vehicle acceleration estimating means is provided. A target rotation speed calculating means for calculating a target rotation speed of the wheels from the vehicle speed estimated by the vehicle body side degree estimating means; A command value calculation for calculating a braking force command value for the braking device based on an optimum feedback gain previously determined according to a dynamic model of a system relating to braking of the vehicle so that the rotation speed of the wheel becomes the target rotation speed. Means for adjusting the braking force of the braking device to the braking force command value.