JP2003320929A - Braking controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform proper anti-skid control. <P>SOLUTION: This controller calculates a target braking torque Tdcom (S105) based on a stroke Lb of an occupant, and distributes the target braking torque Tdcom to regenerative braking and hydraulic braking component (S108). When a driving wheel slip ratio Si is 3 5%, this controller distributes the target braking torque Tdcom to the regenerative braking and the hydraulic braking so that the smaller an estimated vehicle deceleration αv is when the slip ratio Si is 3 5%, the larger the ratio of ration to the hydraulic braking becomes (steps S107 and S110). When the wheel slip ratio Si is 3 15%, this controller performs the anti-skid control (S112 and S113). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a braking control device which is mounted on an electric vehicle or a hybrid vehicle having a regenerative braking device and a friction braking device and controls distribution of regenerative braking torque and friction braking torque.

[0002]

2. Description of the Related Art For example, Japanese Unexamined Patent Publication No. 9-215107 has a regenerative braking device and a hydraulic braking device, and calculates a required braking torque required by a driver based on a stepping amount of a brake pedal. A technique of operating the regenerative braking device and the hydraulic braking device according to the required braking torque is disclosed.

Further, for example, in Japanese Unexamined Patent Publication No. 3-92463, a target wheel speed is set based on the estimated vehicle body speed so as to obtain an ideal slip ratio with an emphasis on braking force, and the target wheel speed is followed. As described above, a technique for calculating and setting the braking fluid pressure and performing anti-skid control is disclosed.
The estimated vehicle body speed is obtained from the wheel speed of each wheel.

[0004]

By the way, when the above-mentioned conventional techniques are combined, the regenerative braking is prioritized over the hydraulic braking in consideration of the improvement in fuel consumption. However, for example, the regenerative braking control command value is filtered, the response speed of the regenerative braking torque is reduced due to the motor characteristics, and the inertial mass of the regenerative braking device including the motor, the drive system components, and the multiple wheels is used to perform the regenerative braking. It is considered that the response speed of the wheel speed due to is slower than the response speed of hydraulic braking, that is, friction braking. For this reason, when anti-skid control is performed in a state where the ratio of regenerative braking is large, the response speed of the wheel speed of the drive wheels is slow, so that the vehicle speed does not immediately return and braking is performed only by friction braking. It takes time to recover. In addition, when only the driving wheels enter the anti-skid control and the driven wheels do not reach the anti-skid intervention, it is difficult to recover the actual vehicle speed in this way. When the estimated vehicle body speed is calculated to be smaller than the actual vehicle body speed according to the wheel speeds of the accompanying wheels, the slip amount of each wheel is calculated to be smaller than the actual vehicle body speed based on the estimated vehicle body speed, and only a very short time However, there was a risk that proper anti-skid control could not be performed.

Therefore, the present invention has been made in view of the unsolved problems of the above-mentioned conventional techniques, and it is an object of the present invention to provide a braking control device capable of executing appropriate anti-skid control. To do.

[0006]

In order to solve the above-mentioned problems, a braking control device according to a first aspect of the present invention provides a regenerative braking means for applying an electric load to generate a braking torque and a frictional force. The friction braking means for acting to generate a braking torque, the target braking torque calculating means for calculating the target braking torque based on the braking operation of the occupant, and the target braking torque calculated by the target braking torque calculating means for the regenerative braking. Means and the target braking torque distributing means for distributing to the friction braking means, a slip state detecting means for detecting a slip rate of the wheel, and a slip rate detected by the slip state detecting means is equal to or more than a first threshold value. The target includes: a braking force control unit that performs anti-skid control at a certain time; and a friction braking torque detection unit that detects a braking torque generated by the friction braking unit. Dynamic torque distribution means when the detected slip ratio by the slip state detecting means is equal to or larger than the first threshold value is smaller than the second threshold value,
The target is set such that the smaller the braking torque generated by the friction braking means when the slip ratio is equal to or higher than the second threshold value, the larger the ratio of the distribution amount to the friction braking means. The target braking torque calculated by the braking torque calculating means is distributed to the regenerative braking means and the friction braking means.

The regenerative braking means may be any as long as it can apply an electric load to generate a braking torque. For example, when the regenerative braking means is applied to an electric vehicle, a hybrid vehicle or the like, a traveling motor is operated as a generator. The braking torque may be generated by a brake generator, or may be a generator provided separately from the traveling motor. Also,
The friction braking device may be any device that can generate a braking torque by using a frictional force, and may be, for example, a hydraulic brake that presses a friction material by a general hydraulic pressure to generate a braking torque, It may be a so-called electric brake that presses a friction material by the force of an electric motor to generate a braking torque.

The invention according to claim 2 is the braking control device according to claim 1, further comprising deceleration detecting means for detecting deceleration of the vehicle body, and the friction braking torque detecting means is When the slip ratio detected by the slip state detecting means is equal to or more than the second threshold value,
The braking torque generated by the friction braking unit is detected based on the deceleration detected by the deceleration detecting unit.

[0009]

Therefore, in the braking control device according to the present invention, the target braking torque is calculated based on the braking operation of the occupant, and the target braking torque is calculated by the regenerative braking means and the friction braking means. When the slip ratio of the wheels is equal to or more than the second threshold value, the friction braking means decreases as the braking torque of the friction braking means becomes equal to or more than the second threshold value. The target braking torque is distributed so that the ratio of the distribution amount to the ratio becomes large, and the anti-skid control is performed when the slip ratio is greater than or equal to the first threshold value that is greater than the second threshold value. The antiskid control is performed after the ratio of the distribution amount to the friction braking means is increased. For example, the filtering process of the regenerative braking control command value, the motor characteristic, the rotation Even if the response speed of the wheel speed due to regenerative braking is slow due to the size of the inertial mass of the braking device, etc., the overall response speed is improved by the friction braking, which has a high response speed. It is possible to quickly return to the vehicle body speed, reduce the time when the estimated vehicle body speed is calculated to be smaller than the actual value, and execute appropriate anti-skid control.

Further, in the braking control device according to the second aspect of the present invention, when the slip ratio of the wheels becomes equal to or more than the second threshold value, the friction braking means operates based on the deceleration of the vehicle body. Since the configuration is such that the braking torque that is being generated is detected, a special sensor for detecting the braking torque that is being generated by the friction braking means is not required, and the braking control device can be constructed at low cost.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic system configuration diagram showing an embodiment of the present invention, which comprises means for controlling a regenerative braking torque by an electric load of a motor and means for controlling a friction braking torque by a braking fluid pressure. The braking control device of the present invention is applied to a regenerative cooperative brake control system that cooperatively controls means to efficiently recover regenerative energy.

In FIG. 1, front wheels 1 of this vehicle are driven by an AC synchronous motor, a so-called motor generator 2. The motor generator 2 can drive the wheels 1 as an electric motor by the electric power supplied from the battery, and can store electricity in the battery as a generator by the road surface reaction torque from the wheels 1. At the time of collecting the electric power to the battery, the road surface reaction torque is consumed to rotate the motor generator 2, and as a result, the braking force is applied to the drive wheels.

The motor generator 2 is controlled by a command from the motor control unit 3. For example, when the vehicle starts, the motor generator 2 is operated as an electric motor to drive the front wheels 1, which are the driving wheels. Further, when the vehicle coasts or decelerates, the motor generator 2 is operated as a generator to apply a regenerative braking force. Therefore, the operating state and the battery state of the motor generator 2 are input to the motor control unit 3.
The motor control unit 3 controls the regenerative braking state of the motor generator 2 in accordance with the regenerative braking torque command value Tmcom calculated by the later-described arithmetic processing of the motor control unit 3.

On the other hand, in the wheel cylinder 4 of each wheel 1,
A braking fluid pressure actuator 5 for individually controlling the braking fluid pressure of each wheel cylinder 4 is connected. The braking fluid pressure actuator 5 supplies the output of a built-in fluid pressure pump to each wheel cylinder 4 to increase / decrease the pressure of each wheel cylinder 4 according to a control signal from the braking fluid pressure control unit 6. It is possible to control the fluid pressure individually.

A brake stroke sensor 8 is provided on the brake pedal 7 operated by the driver. The brake stroke sensor 8 detects the stroke amount Lb of the brake pedal 7 and outputs the detection result to the motor control unit 3. Then, the motor control unit 3 determines, based on the stroke amount Lb input from the brake stroke sensor 8 and the wheel speed Vwi detected by the wheel speed sensor 9 of each wheel 1,
The deceleration that meets the driver's demand is obtained, and the fluid pressure braking torque command values PbcomF, PbcomR and the regenerative braking torque command value Tmc are normally high in the recovery efficiency of the vehicle kinetic energy.
Calculate om. Also, this fluid pressure braking torque command value Pbc
omF and PbcomR are output to the braking fluid pressure control unit 6, and a control signal corresponding to the regenerative braking torque command value Tmcom is generated based on the operating state and the battery state input from the motor generator 2 to generate the control signal. Output to. On the other hand, the braking fluid pressure control unit 6 creates a control signal corresponding to the fluid pressure braking torque command values PbcomF and PbcomR and outputs it to the braking fluid pressure actuator 5.

Next, the motor control unit 3
The calculation process for calculating the regenerative braking torque command value Tmcom and the fluid pressure braking torque command values PbcomF, PbcomR performed in the following will be described with reference to the flowchart of FIG. This calculation process is executed as a timer interrupt process for each predetermined time ΔT (for example, 10 msec.). It should be noted that in this flowchart, steps for communication are not particularly provided, but the information obtained by the calculation is stored at any time, and the stored information is read at any time as necessary.

In this calculation process, first, in step S101.
Then, the stroke amount Lb input from the brake stroke sensor 8 is read. Next, in step S102, the wheel speed Vwi of each wheel is read from the wheel sensor 9, and the largest of them is estimated vehicle speed Vr.
As a result, the estimated vehicle deceleration αv is calculated using the bandpass filter represented by the following equation (1).

Fbpf (s) = s / (s2 / ω2 + 2ζs / ω + 1) (1) Next, the process proceeds to step S103, and the maximum regeneration is performed based on the operating state and the battery state input from the motor generator 2. The braking torque Tmmax is calculated. Next, the process proceeds to step S104, and the stroke amount Lb read in step S101 is set to a constant K1 determined from vehicle specifications.
The target deceleration αdem is calculated by multiplying (<0).

Next, in step S105, the target deceleration αdem calculated in step S104 is calculated by using the filter C (s) represented by the following equation (2) to calculate the target braking torque Tdcom. C (s) = K2Fref (s) / αdem (s) = K2 (Tps + 1) / (Trs + 1) ... (2) However, K2 is a constant determined from vehicle specifications, and Fref
(S) = 1 / (Tr · s + 1) is a reference model, and αd
em (s) = 1 / (Tp · s + 1) is a controlled object model.

Next, at step S106, a value obtained by subtracting each wheel speed Vwi read from the wheel speed sensor 9 from the estimated vehicle body speed Vr set at step S102 is divided by the estimated vehicle body speed Vr to obtain each value. The slip ratio Si of the wheel is calculated. Next, the process proceeds to step S107, and the slip ratio Si of each wheel calculated in step S106 is calculated.
The minimum value of is, for example, "5%" or more,
If it is "5%" or more (Yes), step S11
0, otherwise (No) Step S
Move to 108.

In step S108, in order to prioritize energy recovery by regenerative braking, step S105 is performed.
In step S103, the regenerative braking torque command value Tmcom is generated so as to give priority to the front wheel motor generator 2 from the target braking torque Tdcom calculated in step 1, that is, to increase the ratio of regenerative braking in the total braking force of the front wheels. Calculated within a range that does not exceed the calculated maximum regenerative braking torque Tmmax,
Of the target braking torque Tdcom, the regenerative braking torque command value T
The amount that is insufficient by mcom alone is generated by generating braking fluid pressure in the wheel cylinders 4 of the front and rear wheels so that the relationship between the total braking torque of the front wheels and the braking torque of the rear wheels provides an ideal braking force distribution. Front wheel fluid pressure braking torque command value PbcomF and rear wheel fluid pressure braking torque command value Pb
Calculate comR and.

Next, in step S109, the front wheel fluid pressure braking torque command value PbcomF and the rear wheel fluid pressure braking torque command value PbcomR calculated in step S108 are transmitted to the braking fluid pressure control unit 6 and then this The arithmetic processing ends. On the other hand, in step S110,
In order to prioritize the improvement of wheel speed responsiveness during anti-skid control, the target braking torque Tdcom calculated in step S105 is set to a distribution ratio Rm (regenerative braking): Rp (friction) set in a distribution ratio changing process described later. Braking), regenerative braking torque command value Tmcom is calculated, and target braking torque Tdc is calculated.
Of the om, the amount which is insufficient only with the regenerative braking torque command value Tmcom is applied to the wheel cylinders 4 of the front and rear wheels so that the relationship between the total braking torque of the front wheels and the braking torque of the rear wheels is an ideal braking force distribution. Front wheel fluid pressure braking torque command value Pbcom so that the total braking torque of the vehicle is adjusted by
F and the rear wheel fluid pressure braking torque command value PbcomR are calculated.

Next, in step S111, the front wheel fluid pressure braking torque command value PbcomF and the rear wheel fluid pressure braking torque command value PbcomR calculated in step S110 are transmitted to the braking fluid pressure control unit 6. Next, the process proceeds to step S112, and the minimum value of the slip ratio Si of each wheel calculated in step S106 is, for example, "15%".
It is determined whether or not it is the above, and if it is "15%" or more (Yes), the process proceeds to step S113, and if not (No), this arithmetic processing is ended.

In the step S113, the step S11 is performed so that the ideal slip ratio with the emphasis on the braking force is obtained.
The regenerative braking torque command value Tmcom, the front wheel fluid pressure braking torque command value PbcomF, and the rear wheel fluid pressure braking torque command value PbcomR calculated by 0 are used as the basis for the anti-skid correction control, and the wheel cylinder 4 of each wheel and The motor generator 2 is controlled to instruct the anti-skid control processing to control the braking torque of each wheel, and then this arithmetic processing is ended.

Next, step S110 of the above arithmetic processing.
Then, the distribution ratio Rm: Rp used to calculate the regenerative braking torque command value Tmcom and the front wheel fluid pressure braking torque command value PbcomF.
Will be described with reference to FIG. As shown in FIG. 3, the smaller the estimated vehicle deceleration αv, the larger the ratio of the distribution amount of the front wheels to the wheel cylinders 4, so that the distribution amount of the target braking torque Tdcom to the motor generator 2 and the wheel cylinders of the front wheels are increased. The distribution ratio Rm: Rp to the distribution amount to 4 is determined. Specifically, paying attention to the fact that the wheel cylinder pressure of the front wheels fluctuates according to the estimated vehicle body deceleration αv calculated in step S102, referring to the map data as shown in FIG. Distribution ratio Rm: Rp of the calculated distribution amount of the target braking torque Tdcom to the motor generator 2 and the distribution amount of the front wheels to the wheel cylinder 4.
Is set. As described above, in the present embodiment, the ratio of the distribution amount of the front wheels to the wheel cylinders 4 is set based on the estimated vehicle body deceleration αv, so that a pressure sensor for detecting the wheel cylinder pressure of the front wheels is not required. The braking control device can be constructed at low cost. It goes without saying that the ratio may be set based on the output values of the front and rear G sensors instead of the estimated vehicle deceleration αv.

Next, the operation of this embodiment will be described in detail based on a specific situation. First, as shown in FIG. 4, it is assumed that when the occupant depresses the brake pedal 7 (time t0) in order to brake the vehicle (time t0), the motor control unit 3 executes the distribution ratio changing process. Then,
In the motor control unit 3, as shown in FIG. 2, first, the stroke amount Lb is read in step S101, the estimated vehicle deceleration αv is calculated in step S102, the maximum regenerative braking torque Tmmax is calculated in step S103, and step S104. The target deceleration αdem is calculated in step S105, the target braking torque Tdcom is calculated in step S105, and the slip ratio Si of each wheel is calculated in step S106.

If the minimum value of the slip ratio Si of each wheel is calculated to be smaller than "5%", then step S
The determination of 107 is “No”, and in step S108,
Regenerative braking torque command value Tmcom to be generated preferentially to the front wheel motor generator 2 and front wheel fluid pressure braking torque command to be generated in the front and rear wheel cylinders 4 so that the braking torque of the front and rear wheels approaches the ideal braking force distribution. Value PbcomF
And the rear wheel fluid pressure braking torque command value PbcomR are calculated,
In step S109, the front wheel fluid pressure braking torque command value Pbc
The omF and the rear wheel fluid pressure braking torque command value PbcomR are transmitted to the braking fluid pressure control unit 6.

While the above flow is repeated, it is assumed that the slip ratio Si of the driving wheel becomes "5%" or more at time t1 as indicated by the solid line showing the driving wheel speed in FIG. Then, as shown in FIG. 2, through steps S101 to S106, the determination in step S107 becomes “Yes”,
In step S110, the distribution ratio R set in FIG.
m: According to Rp, the regenerative braking torque command value Tmcom, the front wheel fluid pressure braking torque command value PbcomF, and the rear wheel fluid pressure braking torque command value Pbcom are calculated so that the target braking torque Tdcom is obtained. Pressure braking torque command value PbcomF and rear wheel fluid pressure braking torque command value Pbco
mR is transmitted to the braking fluid pressure control unit 6.

While the above flow is repeated, time t2
Further, it is assumed that the slip ratio Si of the driving wheels calculated in step S106 of the arithmetic processing becomes "15%" or more. Then, as shown in FIG. 2, the steps S107 to S1 are performed.
After step 11, the determination in step S112 becomes “Yes”, and in step S113, the anti-skid control process for controlling the braking torque of each wheel is executed.

Therefore, up to the point where the dotted line indicating the driven wheel speed and the solid line indicating the driving wheel speed intersect, the driven wheel speed smaller than the actual vehicle speed is selected high with a slight slip ratio with respect to the vehicle speed. After passing the crossing point, the driving wheel speed is selected high, and the calculated estimated vehicle body speed Vr is smaller than the actual vehicle body speed, but the area becomes smaller because the response speed of the driving wheel speed becomes faster.

As described above, in the present embodiment, the smaller the estimated vehicle body deceleration αv when the slip ratio Si is "5%" or more, that is, the smaller the wheel cylinder pressure, the smaller the front wheel wheel cylinder 4 is. Since the anti-skid control is started after setting the distribution ratio Rm: Rp so that the ratio of the distribution amount to the vehicle becomes large, the control of the braking torque of the driving wheels is mainly performed by the hydraulic braking. For example, even if the response speed of the wheel speed due to regenerative braking is slow due to the large inertial mass of the motor generator 2 or the like, the response speed of the wheel speed is high. Response speed is increased, the wheel speed of the driving wheels can be quickly returned to the vehicle body speed, and the estimated vehicle body speed Vr calculated by the select high of each wheel speed is
The time required to be calculated to be smaller than the actual vehicle speed is reduced, and appropriate anti-skid control can be executed.

Incidentally, in the conventional method in which the anti-skid control is started by performing the regenerative braking with priority over the hydraulic braking even after the slip ratio Si becomes "5%" or more, the conventional method shown in FIG. As indicated by the alternate long and short dash line, the control of the braking torque of the driving wheels is mainly performed by the regenerative braking. For example, if the response speed of the regenerative braking torque is slow due to the large inertial mass of the motor generator 2 etc. 1
The wheel speed of the vehicle does not return to the vehicle speed immediately and it takes time. Further, since the estimated vehicle body speed Vr is calculated to be small in accordance with the wheel speed Vwi of the front wheels 1 that does not accelerate as described above, the slip ratio Si is set to a small value based on the estimated vehicle body speed Vr and appropriate anti-skid control is performed. Can not be executed.

In the above embodiment, the motor generator 2 and the motor control unit 3 correspond to regenerative braking means, the wheel cylinder 4 and the braking fluid pressure control unit 6 correspond to friction braking means, and step S104 and S105 corresponds to the target braking torque calculation means, steps S108 to S111 correspond to the target braking torque distribution means, step S106 corresponds to the slip state detection means, and steps S112 and S113 correspond to the braking force control means.

Further, the above-mentioned embodiment shows an example of the braking control device of the present invention, and does not limit the configuration of the device. For example, in the above embodiment, an example in which the wheel cylinder 4 is operated to generate the braking torque has been shown, but the invention is not limited to the above embodiment, and an electric brake may be used, for example.

Further, the example in which the brake stroke sensor 8 detects the stroke amount Lb of the brake pedal 7 is shown, but the present invention is not limited to the above embodiment, and for example, a sensor for detecting a brake pedal force is provided, and the sensor output thereof is provided. Based on this, the braking torque required by the occupant may be detected. Furthermore, an example has been shown in which the motor control unit 3 performs arithmetic processing for calculating the regenerative braking torque command value Tmcom and the fluid pressure braking torque command values PbcomF and PbcomR, but the invention is not limited to the above-described embodiment, and for example, braking Alternatively, the fluid pressure control unit 6 may be used.

The braking fluid pressure control unit 6
Although the example in which the control signal to be output to the braking fluid pressure actuator 5 is generated and the control signal to be output to the motor generator 2 is generated by the motor control unit 2 has been shown, Alternatively, those control signals may be generated in one control unit.

Furthermore, as shown in FIG. 3, an example is shown in which the distribution ratio Rm: Rp is set such that the smaller the estimated vehicle deceleration αv, the larger the ratio of the distribution amount of the front wheels to the wheel cylinders 4. However, the present invention is not limited to this. For example, a pressure sensor for detecting the wheel cylinder pressure of the wheel cylinder 4 of the front wheel is provided, and the smaller the wheel cylinder pressure detected by the pressure sensor, the smaller the wheel cylinder 4 of the front wheel.
It is also possible to increase the ratio of the distribution amount to the.

If an electric brake is used instead of the hydraulic brake, the control current value or the like to the electric brake actuator is read, and the smaller the control current value, the ratio of the distribution amount of friction braking of the front wheels. May be increased. Further, the regenerative braking means may act on only one of the front and rear wheels, or may act on both the front and rear wheels.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a braking control device of the present invention.

FIG. 2 is a flowchart showing a calculation process executed in the motor control unit of FIG.

FIG. 3 is a control map showing a relationship between a distribution amount of front wheels to a wheel cylinder and an estimated vehicle body deceleration.

FIG. 4 is a graph for explaining the operation of the braking control device of the present invention.

[Explanation of symbols]

1 is a wheel 2 is a motor generator 3 is a motor control unit 4 is a wheel cylinder 5 is a braking fluid pressure actuator 6 is a braking fluid pressure control unit 7 is a brake pedal 8 is a brake stroke sensor 9 is a wheel speed sensor

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Claims (2)

[Claims] 1. A regenerative braking means for applying an electric load to generate a braking torque, a friction braking means for applying a frictional force to generate a braking torque, and a target braking torque calculated based on an occupant's braking operation. Target braking torque calculating means for
Target braking torque distributing means for distributing the target braking torque calculated by the target braking torque calculating means to the regenerative braking means and the friction braking means, a slip state detecting means for detecting a slip ratio of wheels, and the slip state Braking force control means for performing anti-skid control when the slip ratio detected by the detection means is equal to or greater than a first threshold value, and friction braking torque detection means for detecting the braking torque generated by the friction braking means. And a target braking torque distribution means, when the slip ratio detected by the slip state detection means is equal to or more than a second threshold value smaller than the first threshold value, the slip ratio is The smaller the braking torque generated by the friction braking means when the second threshold value is exceeded, the larger the distribution amount ratio to the friction braking means becomes. As described above, the target braking torque calculated by the target braking torque calculation means is distributed to the regenerative braking means and the friction braking means. 2. A deceleration detecting means for detecting a deceleration of a vehicle body, wherein the friction braking torque detecting means has a slip ratio detected by the slip state detecting means equal to or more than the second threshold value. The braking control device according to claim 1, wherein the braking torque generated by the friction braking unit is detected based on the deceleration detected by the deceleration detecting unit.