System for preventing instability of a vehicle caused by regenerative braking of rear wheels

Abstract

The present application provides a system for preventing instability of a vehicle caused by regenerative braking of rear wheels, which reduces the regenerative braking in advance to ensure stability of the vehicle according to braking conditions and update a regenerative braking map, which can include a first controller configured to distribute braking torque of front wheels and braking torque of rear wheels according to a basic regenerative braking distribution ratio on a regenerative braking map according to a deceleration level based on a required braking amount of a driver, and configured to reduce rear wheel regenerative braking torque of the rear wheels to a first reference value or less than the first reference value in an adjustment interval between a first deceleration and a second deceleration, and a second controller connected to the first controller and configured to further reduce the rear wheel regenerative braking torque to send it to the first controller if a wheel slip value is greater than a reference slip value according to vehicle travel information during braking of the vehicle.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to Korean Patent Application No. 10-2020-0074873, filed on June 19, 2020, the entire contents of which are incorporated herein for all purposes by this reference. TECHNICAL FIELD

[0003] The present invention relates to a system for preventing instability of a vehicle due to regenerative braking of rear wheels. More particularly, the present invention relates to a system and method for preventing instability of a vehicle due to regenerative braking of rear wheels of the vehicle, which reduces the amount of regenerative braking in advance before the rear wheels slip, thereby securing stability of the vehicle, and updates a regenerative braking map according to braking conditions. BACKGROUND

[0004] When a vehicle is braked, an environmentally-friendly vehicle such as an electric vehicle (EV) or a hybrid electric vehicle (HEV) driven by an electric motor, such as a fuel cell vehicle (FCV), performs regenerative braking.

[0005] A regenerative braking system of an environmentally-friendly vehicle converts kinetic energy of the vehicle into electric energy when the vehicle is braked, and stores the energy in a battery, and reuses the energy to drive the electric motor when the vehicle is running, thereby improving energy efficiency of the vehicle.

[0006] An environmentally-friendly vehicle is provided with a hydraulic braking system that generates braking force by hydraulic pressure. It can be difficult to obtain sufficient braking effect using only regenerative braking force. In addition, since regenerative braking force is generated only in a drive wheel connected to an electric motor, it can be difficult to achieve ideal control of vehicle behavior by braking only the drive wheel.

[0007] Therefore, in order to perform regenerative braking in a vehicle while satisfying the braking force required by a driver, it is necessary to appropriately distribute the regenerative braking force generated by the drive motor and the hydraulic braking force generated by the brake.

[0008] Meanwhile, the regenerative braking control of a vehicle in which regenerative braking is implemented in the rear wheels is different from that of a conventional vehicle in which regenerative braking is implemented only in the front wheels. An eco-friendly vehicle in which regenerative braking is implemented only in the front wheels has a drive motor in the front wheels. When the drive motor charges a battery to recover energy, a regenerative braking force is generated, and this braking force acts only on the front wheels. Even if the total braking force of the front wheels is large due to the regenerative braking force of the front wheels, the possibility of the vehicle spinning is small. Therefore, in order to recover energy as much as possible, the amount of generation of the regenerative braking force can be maximized. However, in the case of a vehicle in which regenerative braking is implemented in the rear wheels of the vehicle, when the regenerative braking force of the rear wheels is increased in order to recover more energy, the rear wheels can lock up before the front wheels, so that the vehicle can spin, and thus, there is a limit to increasing the regenerative braking force.

[0009] Meanwhile, in order to prevent the wheels from slipping according to road conditions when the vehicle is braked, various techniques for controlling a regenerative braking torque are disclosed. As a prior art, if wheel slip is detected while control is performed to generate a first slip torque in a motor that provides a driving force to the wheels, the motor is controlled to generate a second slip torque lower than the first slip torque.

[0010] However, if the braking system of the prior art and the control method thereof are applied to a regenerative braking vehicle in which the rear wheels are driven, since control is performed after the rear wheels slip, it is difficult to promptly cope with the slip of the rear wheels. In addition, as shown in FIG. 1, the rear wheels first reach the friction limit on a low-friction road, and thus, control is frequently performed, resulting in different braking feelings. Figure 1

[0011] In order to solve these problems, a method of reducing the amount of basic regenerative braking can be used, but this is disadvantageous in terms of energy efficiency of the vehicle.

[0012] The information included in this Background section of the present disclosure is only for increasing the understanding of the background of the present disclosure, and should not be considered as admitting that this information constitutes prior art that is already known in this field. SUMMARY

[0013] Various aspects of the present disclosure are directed to providing a new system in which a braking torque of the front wheels and a braking torque of the rear wheels are allocated according to a regenerative braking map, the regenerative braking torque of the rear wheels is previously reduced in a predetermined deceleration range, so that the rear wheels are prevented from slipping, and after the wheel slip occurs, the regenerative braking map is updated to be suitable for stability or energy efficiency of the vehicle, considering the intervening control of reducing the regenerative braking torque of the rear wheels.

[0014] ​According to an aspect of the present application, various aspects of the present application strive to provide a system including: a first controller configured to distribute brake torque of front wheels and brake torque of rear wheels for a deceleration level according to a base regenerative braking distribution ratio on a regenerative braking map based on a required braking amount of a driver, and configured to pre-reduce rear wheel regenerative braking torque of the rear wheels to a first reference value or less in an adjustment interval between a first deceleration and a second deceleration; and a second controller connected to the first controller and configured to further reduce the rear wheel regenerative braking torque to send the reduced torque to the first controller if a rear wheel slip value generated by the rear wheels is greater than a reference slip value according to vehicle travel information during braking of the vehicle. Here, the first controller can adjust the rear wheel regenerative braking torque or the rear wheel hydraulic braking torque of the adjustment interval according to the degree of intervention of the second controller, thereby updating the regenerative braking map.

[0015] According to various exemplary embodiments of the present application, the following effects are achieved.

[0016] First, by pre-reducing the rear wheel regenerative braking torque before the rear wheels slip, stability of the vehicle can be secured, and the base regenerative braking torque does not need to be reduced, thereby improving energy efficiency of the vehicle.

[0017] Second, the control of reducing the rear wheel regenerative braking torque does not frequently intervene, and thus different braking feeling and noise, vibration, harshness (NVH) can be minimized while driving.

[0018] Third, by monitoring in real time whether the rear wheels slip, the regenerative braking map can be updated considering intervention or frequency of intervention of controlling the reduction of the rear wheel regenerative braking torque, thereby further reducing different braking feeling according to braking situations.

[0019] The method and apparatus of the present application has other characteristics and advantages which will be apparent from or will be explained in the accompanying drawings and subsequent detailed description, which are incorporated herewith, and which together serve to explain the particular principles of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A braking map to show frequent intervention of the second controller.

[0021] Figure 2 A schematic view to schematically show a system configuration according to various exemplary embodiments of the present application.

[0022] Figure 3A And Figure 3BA brake map showing the state before and after applying the regenerative braking map.

[0023] Figure 4A A base regenerative braking map system according to various example embodiments of the present application, Figure 4B To update the regenerative braking map to a stability example mode, Figure 4A To update the regenerative braking map to a stability example mode, Figure 4C To update the regenerative braking map to a stability example mode, Figure 4A To update the regenerative braking map to an energy efficiency example mode.

[0024] Figure 5 A flowchart showing a control process of the first controller according to various example embodiments of the present application.

[0025] Figure 6 A flowchart showing a control process of the second controller according to various example embodiments of the present application.

[0026] Figure 7 A flowchart showing a process of updating the X deceleration according to various example embodiments of the present application.

[0027] Figure 8 A flowchart showing a process of updating the X deceleration according to various example embodiments of the present application.

[0028] It is to be understood that the figures are not necessarily to scale, and that certain features that are not essential to the understanding of the application are omitted from the drawings for the sake of clarity. Specific design features of the application disclosed herein (including, for example, specific dimensions, orientations, locations, and shapes) will be determined in part by the specific environment in which the application is applied and used.

[0029] In these figures, like reference numerals identify like parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0030] Reference will now be made in detail to various embodiments of the application, examples of which are illustrated in the accompanying drawings and described below. While the application will be described in conjunction with the example embodiments, it will be understood that the application is not limited to the example embodiments. On the contrary, the application is intended to cover alternatives, modifications, equivalents, and other embodiments, which can be included within the spirit and scope of the application as defined by the appended claims.

[0031] Hereinafter, exemplary embodiments of a system for preventing instability of a vehicle due to regenerative braking of rear wheels according to various aspects of the present application will be described in detail with reference to the accompanying drawings. Furthermore, the terms or words used in the specification and claims of the present application should not be construed as limited to the commonly or dictionary meanings and should be interpreted as concepts based on the principle of the present application along with the concept of the inventor to provide the most reasonable interpretation of the present application. Accordingly, the terms and words used in the specification and claims should be interpreted based on the meanings of the terms and words and the concept of the inventor to provide the most reasonable interpretation of the present application.

[0032] Figure 2 FIG. 1 is a schematic diagram for schematically showing a system configuration according to various exemplary embodiments of the present application, Figure 3A and Figure 3B FIG. 2 is a brake map for showing a state before and after applying a regenerative braking map.

[0033] Referring to Figure 2 , a system for preventing instability of a vehicle due to regenerative braking of rear wheels according to various exemplary embodiments of the present application includes a first controller 10 and a second controller 20.

[0034] The first controller 10 controls to perform braking according to a preset regenerative brake map (RBM). The regenerative brake map is a brake map that allocates brake torque (or braking force) of front wheels or rear wheels according to a deceleration level based on a required braking amount 30 of a driver, and is configured to adjust regenerative brake torque of rear wheels.

[0035] Herein, the expression "front wheel brake torque" indicates front wheel hydraulic brake torque, and the expression "rear wheel brake torque" indicates a sum of rear wheel regenerative brake torque and rear wheel hydraulic brake torque. Here, the rear wheel regenerative brake torque includes rear wheel coasting regenerative brake torque.

[0036] Figure 3A and Figure 3B The brake map of FIG. 1 shows a state of allocating front wheel brake torque (x-axis) and rear wheel brake torque (y-axis) according to a deceleration level. In the brake map of FIG. 1, Figure 3A and Figure 3B In the brake map of FIG. 1, a portion indicated by a diagonal line indicates uniform deceleration, and each allocation line that allocates brake torque of front wheels and brake torque of rear wheels is shown. Here, a basic regenerative brake allocation line indicates an allocation relationship between front wheel hydraulic brake torque and rear wheel brake torque, a basic hydraulic brake allocation line indicates an allocation relationship between front wheel hydraulic brake torque and rear wheel hydraulic brake torque, and a minimum regenerative brake allocation line indicates an allocation relationship between front wheel hydraulic brake torque, rear wheel coasting regenerative brake torque, and rear wheel hydraulic brake torque.

[0037] InFigure 3A and Figure 3B In the braking map of the first and second deceleration, the first deceleration and the second deceleration can be set. The first deceleration can be set as a deceleration when only the base regenerative braking torque is applied to the rear wheels before the hydraulic braking torque of (the front wheels and the rear wheels) is intervened. The base regenerative braking torque can be determined as a level at which excessive wheel slip does not occur when only the rear wheel regenerative braking torque is applied. In this regard, the expression "a level at which excessive wheel slip does not occur" can mean a level of about 15% or less with respect to the total wheel slip rate. The second deceleration can be determined as a level at which only a minimum reserved regenerative braking torque is maintained by reducing the rear wheel regenerative braking torque to a level at which the rear wheels do not lock before the front wheels on a high-friction road. In various exemplary embodiments of the present application, the reserved regenerative braking torque can be set as any value equal to the rear wheel coasting regenerative braking torque. Here, the rear wheel coasting regenerative braking torque is a regenerative torque according to the vehicle speed during coasting.

[0038] Referring to Figure 3A In a state in which the rear wheel regenerative braking map is not applied, the braking torque of the front wheels and the braking torque of the rear wheels are distributed along the base regenerative braking distribution line. In an interval from the initial braking deceleration to the first deceleration, the base regenerative braking torque is generated. In an interval from the first deceleration to the second deceleration, the front wheel hydraulic braking torque, the rear wheel regenerative braking torque, and the rear wheel hydraulic braking torque are generated. In order to secure the stability of the vehicle after the second deceleration, the braking torque of the front wheels and the braking torque of the rear wheels are distributed along the minimum regenerative braking distribution line. Here, a difference that occurs between the base hydraulic braking distribution line and the minimum regenerative braking distribution line corresponds to the reserved regenerative braking torque.

[0039] As Figure 3A indicated, unless the regenerative braking map is set, the rear wheels of the vehicle can generate excessive braking torque, so that wheel slip can occur due to the early lock of the rear wheels. In order to solve this problem, a method of reducing the base regenerative braking torque can be considered, but is disadvantageous in terms of the energy efficiency of the vehicle. Accordingly, in various exemplary embodiments of the present application, control of the regenerative braking map is performed, which reduces the rear wheel regenerative braking torque in advance in an interval between the first deceleration and the second deceleration (hereinafter, referred to as an "adjustment interval").

[0040] Referring to Figure 3BIn the adjustment interval, the X deceleration is set so that the first adjustment interval and the second adjustment interval appear. Since the rear wheel regenerative braking torque and the rear wheel hydraulic braking torque can be generated in the first adjustment interval, the rear wheel braking torque can be increased, but the rear wheel regenerative braking torque is formed to be equal to or less than a preset first reference value. In the second adjustment interval, the rear wheel regenerative braking torque is decreased, and the rear wheel hydraulic braking torque is increased. However, the rear wheel braking torque is formed to be equal to or less than a second reference value. The first reference value and the second reference value will be described below.

[0041] After the second adjustment interval, the braking torque of the front wheel and the braking torque of the rear wheel are distributed along the minimum regenerative braking distribution line.

[0042] Meanwhile, with reference to Figure 3B In the adjustment interval, the X deceleration can be moved along the basic regenerative braking distribution line. In other words, the lower limit value of the X deceleration is the first deceleration, and the upper limit value of the X deceleration is the second deceleration. The first distribution line to the third distribution line appear according to the position of the X deceleration. The regenerative braking map having the first distribution line is a braking map in which the rear wheel regenerative braking torque is decreased, and is formed considering the stability of the vehicle, and the regenerative braking map having the third distribution line is a braking map in which the rear wheel regenerative braking torque is increased, and is formed considering the energy efficiency of the vehicle.

[0043] The first controller 10 sets any one of the regenerative braking maps having the first distribution line to the third distribution line as a basic regenerative braking map, and controls to distribute the braking torque of the front wheel and the braking torque of the rear wheel according to the basic regenerative braking map. In this case, since the basic regenerative braking torque does not need to be decreased in the regenerative braking map, this is advantageous in terms of the energy efficiency of the vehicle.

[0044] The first controller 10 controls to update the regenerative braking maps having the first distribution line to the third distribution line. For example, if the regenerative braking map having the second distribution line is the basic regenerative braking map, the first controller 10 controls to change the position of the X deceleration considering the braking situation, and updates the regenerative braking map of the vehicle stability mode or the regenerative braking map of the vehicle energy efficiency mode. Here, the updated regenerative braking map is applied to the next braking operation after the braking is completed.

[0045] Figure 4A For the basic regenerative braking map system according to each exemplary embodiment of the present application, Figure 4B For the regenerative braking map to be updated Figure 4A to the stability exemplary mode, Figure 4C For the regenerative braking map to be updated Figure 4A to the energy efficiency exemplary mode.

[0046] Meanwhile, Figure 4A the regenerative braking map corresponding to the second distribution line having Figure 3B , Figure 4B the regenerative braking map corresponding to the first distribution line having Figure 3B , Figure 4C the regenerative braking map corresponding to the third distribution line having Figure 3B .

[0047] Figure 4A , Figure 4B and Figure 4C the braking map shows a state in which the front wheel braking torque and the rear wheel braking torque are distributed according to the deceleration level in the total braking torque to satisfy the driver required braking torque 30.

[0048] Figure 4A is a basic regenerative braking map set for the X deceleration located in the adjustment interval. As shown in Figure 4A , in the interval from the initial braking deceleration to the first deceleration, only the rear wheel regenerative braking torque is generated. Here, the rear wheel regenerative braking torque of the first deceleration is defined as the basic regenerative braking torque. In the first adjustment interval, the rear wheel hydraulic braking torque is generated, and the rear wheel regenerative braking torque is formed to be equal to or less than the first reference value. Figure 4A An example is shown in which the first reference value is equal to the basic regenerative braking torque, and the rear wheel regenerative braking torque is maintained as the first reference value in the first adjustment interval. In the second adjustment interval, the rear wheel regenerative braking torque is reduced while the rear wheel hydraulic braking torque is increased, but the rear wheel braking torque is formed to be equal to or less than the second reference value. The second reference value can be set to be equal to or greater than the first reference value. Figure 4A An example is shown in which the rear wheel braking torque is maintained as the second reference value in the second adjustment interval. In the second adjustment interval, the rear wheel regenerative braking torque is reduced to the point where it becomes the remaining regenerative braking torque.

[0049] Figure 4B is a regenerative braking map showing a state in which the X deceleration becomes the first deceleration. The interval from the initial braking deceleration to the first deceleration is the same as the operation process of Figure 4A . However, since the X deceleration is the same as the first deceleration, the operation process of the first adjustment interval such as Figure 4B is not shown in Figure 4A , and the operation process of the second adjustment interval such as Figure 4Athe operation process of the second adjustment interval. In this case, the first reference value and the second reference value are equal to each other, the rear wheel regenerative braking torque formed at the first deceleration is reduced, and the rear wheel hydraulic braking torque is increased, but the rear wheel braking torque is formed to be equal to or less than the second reference value. Here, in the adjustment interval, the rear wheel braking torque is distributed at least along the minimum regenerative braking distribution line. In other words, as shown in Figure 4B the rear wheel braking torque formed in the adjustment interval is distributed along the minimum regenerative braking distribution line to be equal to or less than the second reference value from the M deceleration. Figure 4B It can be a braking map in which the stability of the vehicle is prioritized because the rear wheel regenerative braking torque is reduced and the rear wheel hydraulic braking torque is increased in the adjustment interval.

[0050] Figure 4C is a regenerative braking map showing a state in which the X deceleration becomes the second deceleration. The interval from the initial braking deceleration to the first deceleration is the same as that of Figure 4A the operation process of the second adjustment interval. However, since the X deceleration is the same as the second deceleration, the operation process of the second adjustment process such as Figure 4A is not shown, and the operation process such as the first adjustment process is shown. Therefore, the rear wheel regenerative braking torque in the adjustment interval is formed to be equal to or less than the first reference value, and the rear wheel hydraulic braking torque is increased along the basic regenerative braking distribution line to the limit. Figure 4C It can be a braking map in which the energy efficiency of the vehicle is prioritized because the rear wheel hydraulic braking torque is reduced and the rear wheel regenerative braking torque is increased in the adjustment interval.

[0051] In each of the exemplary embodiments of the present application, since the first controller 10 distributes the braking torque according to the regenerative braking map in which the rear wheel regenerative braking torque is reduced in advance, the rear wheel slip can be prevented. The control of the regenerative braking map can be referred to as feedforward control.

[0052] The first controller 10 can distribute the braking torque according to the regenerative braking map in which the rear wheel regenerative braking torque is reduced in advance, and the rear wheel hydraulic braking torque is increased in the adjustment interval. Figure 4A , Figure 4B and Figure 4CThe brake map of any one of the first to third embodiments is set as a basic regenerative brake map. The first controller 10 performs control according to the basic regenerative brake map, and if a brake condition is changed, the brake map is updated in consideration of the stability of the vehicle or the energy efficiency of the vehicle, and control is performed according to the updated brake map. The brake condition indicates a condition in which the rear wheels are likely to slip depending on the road surface condition and the inclination during braking of the vehicle. Since the possibility of the rear wheels slipping is high when braking on a low-friction road or on a slope, the brake map needs to be updated to a brake map in which the stability of the vehicle is prioritized. Since the possibility of the rear wheels slipping is low when braking on a high-friction road, the brake map needs to be updated to a brake map in which the energy efficiency of the vehicle is prioritized.

[0053] Figure 5 A flowchart showing the control process of the first controller according to each of the example embodiments of the present application is shown. Figure 5 Only the control process of the rear wheel brake torque is shown.

[0054] Reference Figure 5 The first controller 10 compares the driver-requested deceleration DMD with the first deceleration (step S10). If DMD is smaller than the first deceleration, the first controller 10 performs control to generate the rear wheel regenerative brake torque (including the reserve regenerative brake torque) by setting the basic regenerative brake torque to the limit (step S12). If DMD is larger than the first deceleration, the first controller 10 compares DMD with the brake torque of the X deceleration (step S20). If DMD is smaller than the X deceleration, the first controller 10 performs control to generate the rear wheel regenerative brake torque (including the reserve regenerative brake torque) and the rear wheel hydraulic brake torque by setting the first reference value to the limit (step S22). If DMD is larger than the X deceleration and smaller than the second deceleration, the first controller 10 performs control so that the sum of the rear wheel hydraulic brake torque and the rear wheel regenerative brake torque (including the reserve regenerative brake torque) is equal to or smaller than the second reference value (step S32). If DMD is larger than the second deceleration, control is performed to generate the rear wheel hydraulic brake torque and the reserve regenerative brake torque (step S34).

[0055] Returning to Figure 2 If the brake force of the rear wheels is large during braking according to the regenerative brake map, so that wheel slip occurs, the second controller 20 further reduces the rear wheel regenerative brake torque to ensure the stability of the vehicle. In other words, with reference to Figure 4A If control of the first controller 10 is performed according to the rear wheel regenerative brake torque that is reduced in advance in the basic regenerative brake map, and wheel slip occurs during braking of the vehicle, the second controller 20 further reduces the rear wheel regenerative brake torque.

[0056] According to the vehicle running information 40, if the rear wheel slip value is greater than a predetermined reference slip value, the second controller 20 reduces the rear wheel regenerative braking torque.

[0057] The second controller 20 performs regenerative braking torque reduction control (WBR) based on wheel slip monitoring. After the second controller 20 receives the vehicle running information 40 and detects in real time whether the wheels are slipping, the operation is performed after the wheel slip occurs. Therefore, the control of the second controller 20 can be feedback control.

[0058] Unless the control is performed according to the regenerative braking map, a larger rear wheel braking torque will be allocated. Therefore, the second controller 20 will frequently intervene to prevent wheel slip, resulting in a different braking feeling. However, in the various exemplary embodiments of the present application, since the control is performed according to the rear wheel braking allocation map in which the rear wheel braking torque is reduced in advance, the likelihood of the second controller 20 frequently intervening is low.

[0059] Meanwhile, if the stability of the vehicle is ensured after the rear wheel regenerative braking torque is further reduced, the second controller 20 increases the rear wheel regenerative braking torque according to the controlled regenerative braking map.

[0060] Figure 6 A flowchart showing the control process of the second controller according to the various exemplary embodiments of the present application is shown.

[0061] Reference Figure 6 The second controller 20 compares the rear wheel slip value with a reference slip value (step S40). If the rear wheel slip value is greater than the reference slip value, the second controller 20 transmits a control signal for reducing the rear wheel regenerative braking torque to the first controller 10 (step S42), and determines whether the braking has returned to a stable state (step S50). Subsequently, if it is determined that the braking has returned to a stable state, the second controller 20 transmits a control signal for restoring the rear wheel regenerative braking torque on the regenerative braking map to the first controller 10 (step S52). In contrast, if it is determined that the braking is unstable, the second controller 20 reduces or maintains the rear wheel regenerative braking torque until the braking returns to a stable state.

[0062] Returning to Figure 2 The first controller 10 and the second controller 20 are connected to the drive system 50 (rear wheel regenerative braking torque generation system) and the braking system 60 (hydraulic braking torque generation system), and generate control signals to allocate braking torque to the front and rear wheels.

[0063] Figure 7 A flowchart showing the process of updating the X deceleration according to the various exemplary embodiments of the present application is shown, Figure 8To show the flowchart of the process of updating the X-deceleration according to each exemplary embodiment of the present application. Meanwhile, in Figure 7 and Figure 8 , the X-deceleration before the update is denoted as X-deceleration 当前 , and the X-deceleration after the update is denoted as X-deceleration 更新 .

[0064] As described above, the case of updating the regenerative braking map is the case where the braking situation changes during the braking of the vehicle. This can be determined according to the degree of intervention of the second controller 20. For example, if the degree of intervention of the second controller 20 is large, the map needs to be updated to a regenerative braking map suitable for the stability of the vehicle (see Figure 4B ). If there is no intervention of the second controller 20, the map needs to be updated to a regenerative braking map suitable for improving the energy efficiency of the vehicle (see Figure 4C ). The regenerative braking map is updated while changing the position of the X-deceleration in the adjustment range.

[0065] Here, unless the rear wheels slip when braking at the X-deceleration or more, there is no problem with the stability of the vehicle, and thus the X-deceleration needs to be increased to improve the energy efficiency of the vehicle. In contrast, if the rear wheels slip, the X-deceleration needs to be decreased to ensure the stability of the vehicle.

[0066] Referring to Figure 7 , the first controller 10 first determines whether the braking of the vehicle is being performed (step S100). When the braking is being performed, if the rear wheels slip in the case where the driver-required deceleration is equal to or greater than the X-deceleration 当前 (which can be determined by the intervention of the second controller 20), the first controller 10 decreases the X-deceleration 当前 by a deceleration a1, and then updates it to the X-deceleration 更新 (step S112). However, the X-deceleration 更新 cannot be updated to be less than the first deceleration. In contrast, if the rear wheels do not slip in the case where the driver-required deceleration is equal to or greater than the X-deceleration 当前 , the first controller 10 increases the X-deceleration 当前 by a deceleration a2 to update it to the X-deceleration 更新 (step S114). However, the X-deceleration 更新 cannot be updated to be greater than the second deceleration.

[0067] When the braking is not performed, it is determined whether there is information about updating the X-deceleration in the previous braking operation (step S120). When there is information about updating the X-deceleration, the first controller 10 updates the X-deceleration 当前Updated to X-deceleration_ 更新 (Step S122). Of course, X-deceleration... 当前 It exists between the first deceleration and the second deceleration.

[0068] According to various exemplary embodiments of the present invention, the second controller 20 monitors in real time whether the rear wheel slips, and the first controller 10 updates the X deceleration according to the degree of intervention of the second controller 20, and then applies it to the regenerative braking map in subsequent braking operations.

[0069] As described above, in various exemplary embodiments of the present invention, the second controller 20 monitors rear wheel slippage in real time and then sends it to the first controller 10, which updates the X deceleration during subsequent braking operations. However, according to various exemplary embodiments of the present invention, when braking is performed, the first controller 10 updates the X deceleration after a predetermined time period has elapsed since the intervention level of the second controller 20 has been verified over a predetermined time period (cumulative braking time).

[0070] refer to Figure 8 First, the first controller 10 determines whether vehicle braking is being performed (step S200). When braking is being performed, the first controller 10 determines whether the accumulated braking time after the previous X-deceleration update is greater than a predetermined reference time (step S210). If the accumulated braking time is less than the reference time, it is determined that insufficient braking time for updating X-deceleration has been accumulated, thus further obtaining braking time. Conversely, if the accumulated braking time is greater than the reference time, the first controller 10 determines whether the intervention frequency of the second controller 20 is greater than a predetermined reference frequency (step S220). If the intervention frequency of the second controller 20 is greater than the predetermined reference frequency, the first controller 10 will adjust the X-deceleration... 当前 Decrease the deceleration a1' to update it to X deceleration_ 更新 (Step S222). However, X deceleration_ 更新 It cannot be updated to a value less than the first deceleration. If the intervention frequency of the second controller 20 is less than the reference frequency, the first controller 10 will adjust the X deceleration. 当前 Increase the deceleration a2' to update it to X-deceleration_ 更新 (Step S224). However, X deceleration_ 更新 It cannot be updated to be greater than the second deceleration. Here, the intervention frequency of the second controller 20 can be determined by the intervention time of the second controller 20 relative to the braking time, and a reference frequency, deceleration a1', and deceleration a2' are preset so that there is no different braking sensation.

[0071] At the same time, due to Figure 8the case where no brake operation is performed in step S230 and step S232 of the case Figure 7 will be omitted herein.

[0072] Furthermore, the term "controller" or "control unit" means a hardware device that includes a memory and a processor configured to perform one or more steps interpreted as an algorithmic structure. The memory stores the algorithmic steps, and the processor executes the algorithmic steps to perform one or more processes of the method according to various exemplary embodiments of the present application. The controller according to exemplary embodiments of the present application can be implemented by a non-volatile memory configured to store data for controlling operations of various components of a vehicle or software commands for executing the algorithm, and a processor configured to perform the above operations using the data stored in the memory. The memory and the processor can be separate chips. Alternatively, the memory and the processor can be integrated in a single chip. The processor can be implemented as one or more processors.

[0073] The controller or control unit can be at least one microprocessor operated by a predetermined program, which can include a series of commands for performing the method according to various exemplary embodiments of the present application.

[0074] The above-described application can also be implemented as computer-readable code on a computer-readable recording medium. The computer-readable recording medium is any data storage device that can store data that can be subsequently read by a computer system. Examples of the computer-readable recording medium include a hard disk drive (HDD), a solid state drive (SSD), a silicon disk drive (SDD), a read-only memory (ROM), a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and is implemented as a carrier wave (for example, transmission over the Internet).

[0075] For the convenience of explanation and precise definition of the appended claims, the terms "upper", "lower", "inner", "outer", "top", "bottom", "upward", "downward", "front", "rear", "back", "inward", "outward", "interior", "exterior", "internal", "external", "forward", "rearward" are used to describe features of the exemplary embodiments with reference to the positions of these features shown in the drawings. It should be further understood that the term "connected" or its derivatives means both direct and indirect connections.

[0076] The foregoing presentation of the specific exemplary embodiments of the present application is for illustrative purposes only. The foregoing description is not intended to be exhaustively exhaustive or to limit the application to the precise form disclosed. Obviously, many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the application be defined by the claims appended hereto and their equivalents.

Claims

1. A system for preventing instability of a vehicle due to regenerative braking of rear wheels of the vehicle, the system comprising: a first controller configured to distribute brake torque of front wheels and brake torque of rear wheels of the vehicle according to a base regenerative braking distribution on a regenerative braking map based on a required braking amount of a driver for a deceleration level, and to pre-reduce rear wheel regenerative brake torque of the rear wheels to a first reference value or less in an adjustment interval between a first deceleration and a second deceleration; and a second controller connected to the first controller and configured to further reduce the rear wheel regenerative brake torque to send a control signal for reducing the rear wheel regenerative brake torque to the first controller when it is determined that a rear wheel slip value generated by the rear wheels is greater than a reference slip value based on vehicle travel information during braking of the vehicle, wherein the first controller is configured to adjust the rear wheel regenerative brake torque or rear wheel hydraulic brake torque of the adjustment interval according to an intervention degree of the second controller to update the regenerative braking map, wherein an X deceleration is set between the adjustment intervals to divide the adjustment intervals into a first adjustment interval and a second adjustment interval, the X deceleration is moved along a base regenerative braking distribution line, and a lower limit value of the X deceleration is the first deceleration and an upper limit value of the X deceleration is the second deceleration, wherein the base regenerative braking distribution line indicates a distribution relationship between front wheel hydraulic brake torque and rear wheel brake torque, wherein the first controller is configured to control to increase the rear wheel hydraulic brake torque in the first adjustment interval between the first deceleration and the X deceleration in the adjustment interval. The first deceleration is set in consideration of regenerative brake torque distributed to the rear wheels before intervention of the rear wheel hydraulic brake torque.

2. The system for preventing instability of a vehicle due to regenerative braking of a rear wheel of the vehicle according to claim 1, wherein The second deceleration is set in consideration of a situation in which the rear wheel regenerative brake torque is removed except for a predetermined reserved regenerative brake torque to prevent the rear wheels from being locked first.

3. The system for preventing instability of a vehicle due to regenerative braking of a rear wheel of the vehicle according to claim 1, wherein The first controller is configured to reduce the rear wheel regenerative brake torque, increase the rear wheel hydraulic brake torque, and control so that the rear wheel brake torque is equal to or less than a second reference value in the second adjustment interval between the X deceleration and the second deceleration.

4. The system for preventing instability of a vehicle due to regenerative braking of a rear wheel of the vehicle according to claim 1, wherein The first controller is configured to monitor whether the second controller intervenes in real time to adjust the X deceleration.

5. The system for preventing instability of a vehicle due to regenerative braking of a rear wheel of the vehicle according to claim 4, wherein 6.The system for preventing instability of a vehicle due to regenerative braking of rear wheels of the vehicle according to claim 4, wherein the first controller is configured to adjust the X deceleration in consideration of an intervention frequency of the second controller collected within a predetermined braking time. The first controller is configured to control so that the rear wheel brake torque after the adjustment interval is distributed according to a minimum regenerative braking distribution on the regenerative braking map.

7. The system for preventing instability of a vehicle due to regenerative braking of a rear wheel of the vehicle according to claim 1, wherein The second controller is configured to control to restore the regenerative brake torque of the rear wheels according to the base regenerative braking distribution when it is determined that vehicle stability is ensured after further reducing the rear wheel regenerative brake torque.

8. The system for preventing instability of a vehicle due to regenerative braking of a rear wheel of the vehicle according to claim 1, wherein ​ 9. A method of controlling a system for preventing instability of a vehicle due to regenerative braking of rear wheels of the vehicle, the system having a first controller and a second controller connected to the first controller, the method comprising: allocating, by the first controller, brake torque of front wheels and brake torque of rear wheels of the vehicle for a deceleration level based on a driver required braking amount according to a base regenerative braking distribution map, pre-reducing rear wheel regenerative brake torque of the rear wheels to a first reference value or less than the first reference value in an adjustment interval between a first deceleration and a second deceleration; further reducing, by the second controller, the rear wheel regenerative brake torque to reduce the rear wheel regenerative brake torque, when it is determined that a rear wheel slip value generated by the rear wheels is greater than a reference slip value according to vehicle travel information during braking of the vehicle, and transmitting a control signal for reducing the rear wheel regenerative brake torque to the first controller; wherein an X deceleration is set between the adjustment intervals, thereby dividing the adjustment intervals into a first adjustment interval and a second adjustment interval, the X deceleration is moved along the base regenerative braking distribution line, and a lower limit value of the X deceleration is the first deceleration and an upper limit value of the X deceleration is the second deceleration; wherein the base regenerative braking distribution line indicates a distribution relationship between front wheel hydraulic brake torque and rear wheel brake torque; wherein the first controller controls to increase the rear wheel hydraulic brake torque in a first interval between the first deceleration and the X deceleration in the adjustment interval.

10. The method of claim 9, further comprising: comparing, by the first controller, the driver required braking amount with the first deceleration; generating, by the first controller, the rear wheel regenerative brake torque by establishing the base regenerative brake torque as a limit when the driver required braking amount is less than the first deceleration.

11. The method of claim 10, wherein, comparing, by the first controller, the driver required braking amount with brake torque of the X deceleration when the driver required braking amount is greater than the first deceleration; generating, by the first controller, the rear wheel regenerative brake torque and the rear wheel hydraulic brake torque by establishing the first reference value as a limit when the driver required braking amount is less than the X deceleration.

12. The method of claim 11, wherein, controlling, by the first controller, a sum of the rear wheel hydraulic brake torque and the rear wheel regenerative brake torque to be equal to or less than a second reference value when the driver required braking amount is greater than the X deceleration and less than the second deceleration; generating, by the first controller, the rear wheel hydraulic brake torque and a remaining regenerative brake torque when the driver required braking amount is greater than the second deceleration.

13. The method of claim 9, further comprising: comparing, by the second controller, the rear wheel slip value with the reference slip value; transmitting, by the second controller, the control signal for reducing the rear wheel regenerative brake torque to the first controller when the rear wheel slip value is greater than the reference slip value, and determining whether braking has returned to a stable state; When the second controller determines that the braking has returned to a steady state, a control signal for restoring the rear wheel regenerative braking torque on the regenerative braking map is sent by the second controller to the first controller.

14. The method of claim 13, wherein, When the second controller determines that the braking is unstable, the rear wheel regenerative braking torque is reduced or maintained by the second controller until the braking returns to a steady state.

15. The method of claim 9, further comprising: determining, by the first controller, whether braking of the vehicle is being performed; when the braking is being performed and the rear wheel slips in a case where the amount of braking required by the driver is equal to or greater than the X deceleration, reducing the X deceleration by a predetermined deceleration and then updating the X deceleration to be equal to or greater than the first deceleration, by the first controller.

16. The method of claim 15, wherein, if the rear wheel does not slip in a case where the amount of braking required by the driver is equal to or greater than the X deceleration, increasing the X deceleration by a predetermined deceleration to update the X deceleration to be equal to or less than the second deceleration, by the first controller.

17. The method of claim 9, further comprising: determining, by the first controller, whether braking of the vehicle is being performed; when the braking is being performed, determining, by the first controller, whether the accumulated braking time is greater than a predetermined reference time; when the accumulated braking time is greater than the predetermined reference time, determining, by the first controller, whether the intervention frequency of the second controller is greater than a predetermined reference frequency; when the intervention frequency of the second controller is greater than the predetermined reference frequency, reducing the X deceleration by a predetermined deceleration to update the X deceleration to be equal to or greater than the first deceleration, by the first controller.

18. The method of claim 17, wherein, when the intervention frequency of the second controller is less than the predetermined reference frequency, the first controller is configured to increase the X deceleration by a predetermined deceleration to update the X deceleration to be equal to or less than the second deceleration.

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