CN113460006A - Vehicle brake control device and vehicle brake control method - Google Patents
Vehicle brake control device and vehicle brake control method Download PDFInfo
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- CN113460006A CN113460006A CN202010243852.9A CN202010243852A CN113460006A CN 113460006 A CN113460006 A CN 113460006A CN 202010243852 A CN202010243852 A CN 202010243852A CN 113460006 A CN113460006 A CN 113460006A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
- B60T8/00—Arrangements for adjusting wheel-braking force to meet varying vehicular or ground-surface conditions, e.g. limiting or varying distribution of braking force
- B60T8/17—Using electrical or electronic regulation means to control braking
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Abstract
The present invention relates to a vehicle brake control device and a vehicle brake control method. In a vehicle brake control device (10) and a vehicle brake control method, an external environment detection unit (66) acquires road surface information of a vehicle (12) in front in the traveling direction, a road surface state determination unit (40b) determines the state of the road surface in front in the traveling direction on the basis of the road surface information, and a threshold value change processing unit (40d) increases a slip ratio threshold value (Sth) on the basis of the state of the road surface. Accordingly, a decrease in fuel efficiency and a decrease in merchantability of the vehicle can be prevented.
Description
Technical Field
The present invention relates to a vehicle brake control device and a vehicle brake control method for switching from regenerative braking of a drive wheel to friction braking of the drive wheel and a driven wheel when a slip ratio (slip ratio) of the drive wheel of a vehicle exceeds a slip ratio threshold value.
Background
In the related art, when regenerative braking is performed on the drive wheels during deceleration traveling of the vehicle, if the slip ratio of the drive wheels exceeds a slip ratio threshold value, the regenerative braking is switched to friction braking on the drive wheels and the driven wheels, thereby stabilizing the behavior of the vehicle. In this case, it is necessary to use some mechanism to determine whether the slip ratio exceeds the slip ratio threshold value.
For example, japanese patent application laid-open No. 2004-144644, which is japanese laid-open publication, discloses recognizing a three-dimensional shape of a ground surface in front of a moving body in a traveling direction by using a stereo camera mounted on the moving body. Therefore, it is considered to determine the slip ratio from the three-dimensional shape of the recognized ground using this technique, and determine whether the determined slip ratio exceeds a slip ratio threshold.
Disclosure of Invention
However, when the vehicle passes through a step or a bump in the front in the traveling direction, the slip ratio temporarily increases, and the slip ratio may be larger than the slip ratio threshold value. Accordingly, it may be erroneously determined that the drive wheels are slipping and the regenerative braking may be switched to the friction braking. In this case, when the regenerative braking is switched to the friction braking, it takes time to return from the friction braking to the regenerative braking. As a result, regenerative energy by regenerative braking cannot be recovered, and the amount of regeneration (the amount of charge to the battery) is insufficient. Therefore, there is a possibility that the fuel efficiency of the vehicle is reduced, so that the merchantability of the vehicle is reduced.
The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a vehicle brake control device and a vehicle brake control method that prevent a decrease in fuel efficiency and a decrease in commercial value of a vehicle by avoiding an inadvertent switch from regenerative braking to friction braking.
An aspect of the present invention relates to a vehicle brake control device and a vehicle brake control method that are applied to a vehicle equipped with a regenerative brake device for performing regenerative braking on a drive wheel and a friction brake device that switches from regenerative braking to friction braking when a slip ratio of the drive wheel exceeds a slip ratio threshold value; the friction braking device is used for performing friction braking on the driving wheel and the driven wheel.
In this case, the vehicle brake control device further includes a road surface information acquisition unit that acquires road surface information ahead in the traveling direction of the vehicle, a road surface state determination unit, and a threshold value change processing unit; the road surface state determination section determining a state of the road surface ahead in the traveling direction based on the road surface information; the threshold value change processing unit increases the slip ratio threshold value according to the road surface state.
Further, the vehicle brake control method includes: a step of acquiring road surface information ahead of the vehicle in a traveling direction by a road surface information acquisition unit; determining, by a road surface state determination unit, a road surface state ahead in the traveling direction based on the road surface information; and a step of increasing the slip ratio threshold value by a threshold value change processing unit according to the road surface state.
According to the present invention, the slip ratio threshold value is increased in advance in accordance with the road surface state ahead of the vehicle in the traveling direction. Accordingly, even when the vehicle passes over a step (a rough road surface) or an uneven road surface, it is possible to avoid the slip ratio temporarily exceeding the slip ratio threshold value and inadvertently switching from regenerative braking to friction braking. As a result, regenerative energy can be recovered while regenerative braking is maintained, and thus a decrease in fuel efficiency and a decrease in commercial value of the vehicle can be prevented.
The above objects, features and advantages should be readily understood from the following description of the embodiments with reference to the accompanying drawings.
Drawings
Fig. 1 is a schematic configuration diagram of a vehicle in which a control device according to the present embodiment is mounted.
Fig. 2 is a block diagram of a vehicle including the control device of fig. 1.
Fig. 3 is a flowchart showing an operation (vehicle braking control method) of the control device of fig. 1 and 2.
Detailed Description
A vehicle brake control device and a vehicle brake control method according to the present invention will be described below by way of examples of preferred embodiments with reference to the accompanying drawings.
[1. Structure of the present embodiment ]
Fig. 1 is a schematic configuration diagram showing a configuration of a vehicle 12 including a vehicle brake control device 10 according to an embodiment of the present invention (hereinafter also referred to as a control device 10 according to the present embodiment).
The vehicle 12 is a four-wheeled electric vehicle having left and right front wheels 14 and left and right rear wheels 16, and travels by rotationally driving the rear wheels 16 as drive wheels by an electric motor 18 as a drive source. That is, in the vehicle 12, the left and right rear wheels 16 are driving wheels, and the left and right front wheels 14 are driven wheels. In addition, the vehicle 12 includes: a regenerative braking device 20 that regeneratively brakes the left and right rear wheels 16; and a friction brake device 22 (hydraulic brake device) that performs friction braking on each front wheel 14 and each rear wheel 16. The control device 10 according to the present embodiment is mounted on such a vehicle 12.
The vehicle 12 may be an electric vehicle or a hybrid vehicle in which a drive wheel is rotationally driven by the electric motor 18. Therefore, the vehicle 12 is not limited to the four-wheel vehicle shown in fig. 1, and can be applied to various vehicles such as a single-wheel vehicle, a two-wheel vehicle, and a three-wheel vehicle. The vehicle 12 is not limited to a rear-wheel drive type vehicle, and may be applied to a front-wheel drive type vehicle or a four-wheel drive type vehicle. In the following description, as shown in fig. 1, a case where the control device 10 is applied to a vehicle 12 that is an electric vehicle of a rear-wheel drive type will be described.
In the vehicle 12, the electric motor 18 is electrically connected to a battery 24, and is coupled to a differential device 26 provided at the rear of the vehicle 12. The differential device 26 is connected to left and right axles 28 extending outward in the vehicle width direction. A rear wheel 16 is connected to the vehicle-widthwise outer end of each axle 28. On the other hand, an axle 30 extending in the vehicle width direction is disposed at the front portion of the vehicle 12. The left and right front wheels 14 are coupled to both ends of the axle 30 on the outer side in the vehicle width direction.
In this case, the electric motor 18 is rotated by electric power supplied from the battery 24, and the rotational driving force is transmitted to the differential device 26. The differential device 26 distributes the rotational driving force and transmits it to the left and right axles 28. Accordingly, the rear wheels 16 connected to the axles 28 are rotationally driven by the transmitted rotational driving force. As a result, the vehicle 12 travels at an arbitrary vehicle speed. On the other hand, when the vehicle 12 decelerates, the electric motor 18 functions as a generator, and charges (regenerates) the battery 24 with the generated electric power (regenerative energy).
In addition, the vehicle 12 is provided with an accelerator pedal 32 and a brake pedal 34 that are operated by the driver. An accelerator opening detection sensor 36 for detecting a depression amount (accelerator opening) of the accelerator pedal 32 by the driver is provided near the accelerator pedal 32. The brake pedal 34 is provided with a brake switch 38 for detecting whether the driver has stepped on (stepped on or off) the brake pedal 34. The detection results of the accelerator opening detection sensor 36 and the brake switch 38 are output to an ecu (electronic Control unit) 40.
The ECU40 is an electronic control device configured by a microcomputer and generally controls the entire vehicle 12, and reads and executes a program stored in a memory, not shown, to implement various functions. Details of the function of the ECU40 are described later.
The friction brake device 22 is a hydraulic brake device that performs friction braking on each front wheel 14 and each rear wheel 16 using hydraulic pressure (hydraulic). Specifically, the friction brake device 22 includes a brake pedal 34, a brake actuator 44 including a master cylinder 42 and the like, a hydraulic pump 46, a hydraulic unit 48, friction brakes 50, and the like.
The brake actuator 44 includes: a brake booster (brake booster)52 connected to the brake pedal 34; and a master cylinder 42 connected to the brake booster 52. The master cylinder (master cylinder)42 is connected to the hydraulic unit 48 through a hydraulic pipe 54. The hydraulic pump 46 is connected to the hydraulic unit 48 through a hydraulic pipe 56.
Here, when the driver steps on the brake pedal 34, the master cylinder 42 generates a hydraulic pressure (hydraulic) having a magnitude corresponding to the stepping amount of the brake pedal 34. The hydraulic pressure in the master cylinder 42 is detected by a hydraulic pressure sensor 60. The detection result of the hydraulic pressure sensor 60 is output to the ECU 40. The generated hydraulic pressure is supplied to the brake pads 50b of the friction brakes 50 through the hydraulic piping 54, the hydraulic unit 48, and the hydraulic piping 58.
Accordingly, the brake pads 50b are clamped and pressed against the brake disc 50a by the supplied hydraulic pressure. As a result, frictional resistance (frictional braking force) is generated between each brake pad 50b and each brake disc 50a, and the front wheels 14 and the rear wheels 16 can be braked by the frictional resistance.
Even when the driver does not step on the brake pedal 34, the hydraulic pump 46 is driven under the control of the ECU40, and the pressurized hydraulic pressure can be supplied from the hydraulic pipe 56 to the friction brakes 50 via the hydraulic unit 48 and the hydraulic pipes 58. In this case, the brake pads 50b of the friction brakes 50 can also sandwich the brake disc 50a by the supplied hydraulic pressure to brake the front wheels 14 or the rear wheels 16.
The regenerative braking device 20 is a braking device that regeneratively brakes each rear wheel 16, and includes a battery 24, a motor 18, and the like. As described above, when the vehicle 12 decelerates, the electric motor 18 functions as a generator, and converts a part of the kinetic energy into electric power (regenerative energy) and recovers the electric power, thereby charging the battery 24. At this time, the electric motor 18 functions as a regenerative brake for braking each rear wheel 16.
The vehicle 12 further includes a rotation sensor 62, and the rotation sensor 62 detects the rotation speed of the electric motor 18. The detection result of the rotation sensor 62 is output to the ECU 40.
Fig. 2 is a block diagram of a vehicle 12 including the control device 10 according to the present embodiment. Note that fig. 2 illustrates only functional blocks related to the control device 10 among the components of the vehicle 12.
The vehicle 12 further has: 4 wheel speed sensors 64 provided near the respective front wheels 14 and the respective rear wheels 16 for detecting the wheel speeds of the respective front wheels 14 or the respective rear wheels 16; an external environment detection unit 66 (road surface information acquisition unit) that detects an external environment ahead of the vehicle 12 in the traveling direction; a DC/DC converter 68 that converts the direct-current voltage from the battery 24 into an arbitrary direct-current voltage; an inverter (inverter)70 that converts the DC voltage converted by the DC/DC converter 68 into an ac voltage and supplies the ac voltage to the motor. In this case, the regenerative braking device 20 is configured by the battery 24, the DC/DC converter 68, the inverter 70, and the motor 18.
The control device 10 according to the present embodiment includes various sensors shown on the left side of fig. 2 and an ECU40, and the ECU40 controls the regenerative braking device 20 and the friction braking device 22 based on the detection results of the sensors to brake the front wheels 14 and the rear wheels 16.
The environment Detection unit 66 is a distance measurement device such as a stereo camera and LiDAR (Light Detection and Ranging) provided in the vehicle 12. The stereo camera stereoscopically photographs the road surface ahead of the vehicle 12 in the traveling direction. The distance measuring device detects a distance to a target, a shape of the target, and the like, wherein the target is a step or a bump existing on a road surface in front of the vehicle 12 in the traveling direction. The image captured by the stereo camera and the detection result (information of the target) by the distance measuring device are output to the ECU40 as road surface information. Each wheel speed sensor 64 detects the wheel speed of each front wheel 14 or each rear wheel 16, and outputs the detection result to the ECU 40.
The ECU40 realizes the functions of the external world identification unit 40a, the road surface condition determination unit 40b, the slip ratio calculation unit 40c, the threshold value change processing unit 40d, the switching determination unit 40e, and the brake control processing unit 40f by executing the programs, not shown, as described above. The functions of the respective parts in the ECU40 will be described later. In addition, the ECU40 controls the DC/DC converter 68, the inverter 70, and the hydraulic pump 46 according to the detection results of the respective sensors and the like.
[2. operation of the control device 10 ]
The vehicle 12 including the control device 10 in the present embodiment is configured as described above. Next, the operation of the brake control of the vehicle 12 by the control device 10 (vehicle brake control method) will be described with reference to the flowchart of fig. 3. Here, an operation in a case where there is a step or a bump on a road surface ahead in the traveling direction when the vehicle 12 mounted with the control device 10 travels at a reduced speed on the road surface will be described. In describing this operation, the description will be given with reference to fig. 1 and 2 as necessary.
During the deceleration running of the vehicle 12, the electric motor 18 functions as a generator, and charges (regenerates) the battery 24 with electric power generated by the generation. At this time, the electric motor 18 functions as a regenerative brake that brakes each rear wheel 16.
In step S1 of fig. 3, the stereo camera constituting the environment detection unit 66 (see fig. 2) captures an image of the road surface ahead of the vehicle 12 (see fig. 1 and 2) in the traveling direction, and generates a stereo image of the road surface. The distance measuring device detects a distance, a shape, and the like of an object, which is a step or a projection or a depression existing on a road surface, and acquires information on the detected object. The information on these images and the target is output to the ECU40 as road surface information.
In step S1, each wheel speed sensor 64 detects the wheel speed of each front wheel 14 or each rear wheel 16, and outputs the detection result to the ECU 40. The accelerator opening detection sensor 36 detects the accelerator opening and outputs the detection result to the ECU 40. The brake switch 38 detects the presence or absence of depression of the brake pedal 34, and outputs the detection result to the ECU 40. The rotation sensor 62 detects the rotation speed of the motor 18, and outputs the detection result to the ECU 40. The hydraulic pressure sensor 60 detects the hydraulic pressure of the master cylinder 42, and outputs the detection result thereof to the ECU 40.
Then, in step S2, the external world identification unit 40a identifies whether there is a step or an irregularity on the road surface ahead in the traveling direction of the vehicle 12, based on the road surface information from the external world detection unit 66.
Then, in steps S3 and S4, the road surface condition determination unit 40b determines the road surface condition ahead of the vehicle 12 in the traveling direction based on the recognition result of the external world recognition unit 40a in step S2.
Specifically, in step S3, the road surface condition determination unit 40b estimates the friction coefficient μ of the road surface from the stereo image captured by the stereo camera and the information of the target detected by the distance measuring device. For example, the undulation (step or irregularity) of the road surface in front in the traveling direction is recognized from the stereoscopic image and the information of the target, and the friction coefficient μ is estimated from the height of the recognized undulation.
Next, the road surface condition determination unit 40b determines whether or not the friction coefficient μ exceeds a friction coefficient threshold value μ th. Here, the friction coefficient threshold value μ th is a value of the friction coefficient corresponding to the default value Sth0 of the slip ratio threshold value Sth. The slip ratio threshold value Sth is a determination threshold value of the slip ratio S when the braking of the front wheels 14 or the rear wheels 16 of the vehicle 12 is switched from the regenerative braking to the friction braking. That is, if the slip ratio S is equal to or less than the slip ratio threshold value Sth (S ≦ Sth), it is determined that the vehicle 12 can be appropriately braked only by regenerative braking of each rear wheel 16. On the other hand, if the slip ratio S exceeds the slip ratio threshold value Sth (S > Sth), it is difficult to appropriately brake the vehicle 12 only by regenerative braking, and therefore it is determined that it is appropriate to switch to friction braking for the front wheels 14 and the rear wheels 16. As will be described later, the slip ratio S is calculated by the slip ratio calculating unit 40c based on the wheel speeds of the front wheels 14 and the rear wheels 16 detected by the wheel speed sensors 64.
When the friction coefficient μ exceeds the friction coefficient threshold value μ th (μ > μ th, step S3: YES), the road surface condition determination unit 40b proceeds to step S4 to determine whether the cause of the friction coefficient μ exceeding the friction coefficient threshold value μ th is a step or an irregularity.
When the friction coefficient μ exceeds the friction coefficient threshold value μ th due to the presence of the step or the irregularity (yes in step S4), the road surface condition determination unit 40b determines that the slip ratio S may exceed the default value Sth0 of the slip ratio threshold value Sth when the vehicle 12 passes through the step or the irregularity present forward in the traveling direction, and therefore, needs to increase the slip ratio threshold value Sth in advance.
In the next step S5, the threshold value change processing unit 40d changes (increases) the slip ratio threshold value Sth from the default value Sth0 to an arbitrary value Sth1 larger than the default value Sth0 (Sth1 > Sth 0). The amount of increase in the slip ratio threshold Sth (Sth1-Sth0) may be such that the slip ratio S due to the step or the unevenness does not exceed the increased slip ratio threshold Sth (Sth 1).
On the other hand, if the determination results in the negative in steps S3 and S4 (steps S3 and S4: no), that is, if there is no step or unevenness, the friction coefficient μ is low (step S3: no), or if there is no step or unevenness although the friction coefficient μ is high (step S4: no), the road surface condition determination unit 40b determines that the slip ratio S may not exceed the default Sth0 even if the slip ratio threshold Sth is maintained at the default Sth0(S ≦ Sth 0). As a result, the process of step S5 is skipped, and the slip ratio threshold Sth is not increased.
In step S6, the slip ratio calculator 40c calculates the slip ratio S of each rear wheel 16 based on the wheel speeds of each front wheel 14 and each rear wheel 16 detected by each wheel speed sensor 64 in step S1. Next, the switching determination unit 40e determines whether the calculated slip ratio S is equal to or less than the slip ratio threshold Sth.
When the slip ratio S is equal to or less than the slip ratio threshold Sth (yes in step S6), the switching determination unit 40e determines that the regenerative braking is not required to be switched to the friction braking in the next step S7, and determines to hold the regenerative braking.
On the other hand, when the slip ratio S exceeds the slip ratio threshold value Sth (S > Sth, no in step S6), the switching determination unit 40e determines that switching from regenerative braking to friction braking is necessary in the next step S8.
In the next step S9, the brake control processing unit 40f executes control processing for the regenerative brake device 20 or the friction brake device 22 based on the determination result in step S7 or S8.
Specifically, when the switching determination unit 40e performs the determination process of step S7, the brake control processing unit 40f controls the DC/DC converter 68 and the inverter 70 of the regenerative brake device 20 to continue the braking operation of each rear wheel 16 by the regenerative braking.
On the other hand, when the switching determination unit 40e performs the determination process of step S8, the brake control processing unit 40f stops the control of the DC/DC converter 68 and the inverter 70 of the regenerative brake device 20, drives the hydraulic pump 46 of the friction brake device 22, and starts the supply of the hydraulic pressure from the hydraulic pump 46 to each friction brake 50 via the hydraulic unit 48. Accordingly, switching from regenerative braking to friction braking is performed, and braking operation is performed on each front wheel 14 and each rear wheel 16 by friction braking.
In the next step S10, the road surface condition determination unit 40b determines whether or not the increased slip ratio threshold Sth (Sth1) needs to be returned to the default Sth 0. When it is determined from the road surface information acquired in step S1 that the vehicle 12 has passed through a step or an irregularity, the road surface condition determination unit 40b determines to return the slip ratio threshold value Sth to the default value Sth0 (step S10: yes). Accordingly, in the next step S11, the threshold change processing unit 40d returns the slip ratio threshold Sth from the increased value Sth1 to the default value Sth 0.
On the other hand, when it is determined in step S10 that the vehicle 12 will pass a step or a bump next based on the road surface information acquired in step S1, the road surface condition determination unit 40b determines that the increased slip ratio threshold Sth (Sth1) is maintained (step S10: no). Accordingly, the process of step S11 is skipped. In step S10, when the slip ratio threshold Sth is the default value Sth0, the process of step S11 is also skipped.
In step S12, the switching determination unit 40e determines whether or not to return from the friction braking to the regenerative braking. When the friction braking is returned to the regenerative braking (yes in step S12), the switching determination unit 40e stops the driving of the hydraulic pump 46, restarts the control of the DC/DC converter 68 and the inverter 70, and restarts the regenerative braking in step S13. On the other hand, in the case where the friction braking is maintained in step S12 (step S12: NO), the process of step S13 is skipped.
In step S14, the ECU40 determines whether or not to repeat the processing of steps S1 to S13. For example, when the vehicle 12 is decelerating (step S13: YES), the ECU40 returns to step S1 and repeatedly executes the processes of steps S1 to S13. Therefore, the processing of steps S1 to S13 is repeated until the vehicle 12 stops (step S14: NO).
[3. modification ]
In the above description, the case where the vehicle 12 travels on a road surface having steps or irregularities is described. The present embodiment can also be applied to a case where the vehicle 12 travels on a road surface such as an icy or snowy road, a gravel road, or an uneven road.
[4. effect of the present embodiment ]
As described above, the present embodiment relates to a control device 10 (vehicle brake control device) and a control method (vehicle brake control method) applied to a vehicle 12 having a regenerative brake device 20 and a friction brake device 22 mounted thereon, the regenerative brake device 20 being for regenerative braking each rear wheel 16 (drive wheel) and switching from regenerative braking to friction braking when a slip ratio S of each rear wheel 16 exceeds a slip ratio threshold value Sth (S > Sth); the friction brake device 22 is used to perform friction braking on each front wheel 14 (driven wheel) and each rear wheel 16.
In this case, the control device 10 further includes an external environment detection unit 66 (road surface information acquisition unit) that acquires road surface information ahead of the vehicle 12 in the traveling direction, a road surface state determination unit 40b, and a threshold value change processing unit 40 d; the road surface condition determination unit 40b determines the road surface condition ahead in the traveling direction based on the road surface information; the threshold value change processing unit 40d increases the slip ratio threshold value Sth according to the road surface state.
In addition, the control method comprises the following steps: a step (step S1 in fig. 3) in which the external world detection unit 66 acquires road surface information ahead of the vehicle 12 in the direction of travel; a step (steps S3, S4) in which the road surface condition determination unit 40b determines the condition of the road surface ahead in the traveling direction based on the road surface information; and a step of increasing the slip ratio threshold value Sth by the threshold value change processing unit 40d in accordance with the road surface state (step S5).
In this way, the slip ratio threshold value Sth is increased in advance in accordance with the road surface state ahead of the vehicle 12 in the traveling direction. Accordingly, even when the vehicle 12 passes through a step or a bump, it is possible to avoid the slip ratio S temporarily exceeding the slip ratio threshold value Sth and inadvertently switching from regenerative braking to friction braking. As a result, regenerative energy can be recovered while maintaining regenerative braking, and a decrease in fuel efficiency and a decrease in commercial value of the vehicle 12 can be prevented.
In this case, the environment detection unit 66 is a distance measurement device such as a stereo camera (camera) or LiDAR provided in the vehicle 12. The road surface condition determination section 40b determines the road surface condition based on the image of the road surface ahead in the traveling direction captured by the stereo camera or information of the object present on the road surface ahead in the traveling direction detected by the distance measuring device. Accordingly, the road surface condition determination unit 40b can accurately perform the determination process of the road surface condition using the image and the information of the target.
When the road surface condition determination unit 40b determines that there is a step or an irregularity on the road surface ahead in the traveling direction based on the information of the image or the target, the threshold value change processing unit 40d increases the slip ratio threshold Sth, the step or the irregularity serving as the target corresponding to the slip ratio S exceeding the slip ratio threshold Sth (yes at steps S3 and S4). Accordingly, it is possible to reliably prevent the inadvertent switching from the regenerative braking to the friction braking when the vehicle 12 passes over a step or a bump, and to reliably recover the regenerative energy.
The road surface condition determination unit 40b acquires the friction coefficient μ of the road surface ahead in the traveling direction from the image or the target information, and determines that the step or the irregularity is a step or an irregularity corresponding to the slip ratio S exceeding the slip ratio threshold Sth when the friction coefficient μ exceeds the friction coefficient threshold μ th (μ > μ th) and the friction coefficient μ is caused by the step or the irregularity. Accordingly, when there is a step or a projection and recess in the forward direction of travel, the slip ratio threshold value Sth can be reliably increased, and the occurrence of switching from regenerative braking to friction braking can be avoided.
When the vehicle 12 has passed through the steps or the unevenness, the threshold change processing unit 40d returns the increased slip ratio threshold Sth (Sth1) to the default Sth0 (initial value). Accordingly, the slip ratio threshold Sth can be temporarily increased only when the vehicle 12 passes through a step or a bump. As a result, the fuel efficiency and the reduction in the merchantability of the vehicle 12 can be minimized.
The present invention is not limited to the above-described embodiments, and it is needless to say that various configurations can be adopted according to the contents described in the present specification.
Claims (6)
1. A vehicle brake control device (10) is applied to a vehicle (12) equipped with a regenerative brake device (20) and a friction brake device (22), and switches from regenerative braking to friction braking when a slip ratio (S) of a drive wheel exceeds a slip ratio threshold value (Sth), wherein the regenerative brake device (20) performs the regenerative braking on the drive wheel (16); the friction braking device (22) is used for performing friction braking on the driving wheel and the driven wheel (14),
the vehicle brake control device (10) is characterized in that,
further comprises a road surface information acquisition unit (66), a road surface condition determination unit (40b), and a threshold value change processing unit (40d),
the road surface information acquisition unit (66) acquires road surface information ahead of the vehicle in the direction of travel;
the road surface condition determination unit (40b) determines the road surface condition ahead in the traveling direction based on the road surface information;
the threshold value change processing unit (40d) increases the slip ratio threshold value according to the road surface condition.
2. The vehicle brake control apparatus according to claim 1,
the road surface information acquiring unit is a camera or a distance measuring device disposed on the vehicle,
the road surface condition determination unit determines the road surface condition based on an image of the road surface ahead in the traveling direction captured by the camera or information of an object present on the road surface ahead in the traveling direction detected by the distance measurement device.
3. The vehicle brake control apparatus according to claim 2,
when the road surface condition determination unit determines that there is a step or an irregularity on the road surface ahead in the traveling direction based on the image or the information of the target, the threshold value change processing unit increases the slip ratio threshold value, the step or the irregularity being the target corresponding to the slip ratio exceeding the slip ratio threshold value.
4. The vehicle brake control apparatus according to claim 3,
the road surface condition determination unit acquires a friction coefficient (μ) of a road surface ahead in the traveling direction from the image or the information of the target, and determines that the step or the irregularity is a step or an irregularity corresponding to a slip ratio exceeding a slip ratio threshold when the friction coefficient exceeds a friction coefficient threshold (μ th) and the friction coefficient is caused by the step or the irregularity.
5. The vehicle brake control apparatus according to claim 3 or 4,
the threshold value change processing unit returns the increased slip ratio threshold value to an initial value (Sth0) when the vehicle has passed the step or the unevenness.
6. A vehicle brake control method applied to a vehicle equipped with a regenerative brake device for applying regenerative braking to a drive wheel and a friction brake device for switching from the regenerative braking to the friction braking when a slip ratio of the drive wheel exceeds a slip ratio threshold value; the friction braking device is used for performing friction braking on the driving wheel and the driven wheel,
the vehicle brake control method is characterized in that,
comprising:
a step of acquiring road surface information ahead of the vehicle in a traveling direction by a road surface information acquisition unit;
determining, by a road surface state determination unit, a road surface state ahead in the traveling direction based on the road surface information; and
and a step of increasing the slip ratio threshold value by a threshold value change processing unit according to the road surface state.
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| CN202010243852.9A CN113460006A (en) | 2020-03-31 | 2020-03-31 | Vehicle brake control device and vehicle brake control method |
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| CN202010243852.9A CN113460006A (en) | 2020-03-31 | 2020-03-31 | Vehicle brake control device and vehicle brake control method |
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2020
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