Braking control method and device for two-wheel drive electric vehicle

Abstract

The present application belongs to the technical field of electric vehicle braking, and specifically relates to a braking control method and device for a two-wheel drive electric vehicle; wherein the braking control method comprises the following steps: obtaining a brake pedal position signal, a current vehicle speed V, a current battery state of charge value SOC, and calculating a brake pedal stroke Ba; determining whether the current vehicle speed V, the current battery state of charge value SOC, and the brake pedal stroke Ba simultaneously satisfy a preset relationship; if so, determining whether the current vehicle speed V is equal to a preset maximum vehicle speed threshold value V. high , and selects one of the two parallel braking control methods for control according to the judgment result; if it is not satisfied, the friction braking torque of the drive shaft and the non-drive shaft is controlled accordingly. The braking control method and device of the present application, at a lower vehicle speed, reduces the proportion of the motor braking torque in the total braking torque to reduce the electrical cycle between the motor and the battery, while taking into account the energy recovery efficiency and improving the battery life.

Description

Technical Field

[0001] The present application belongs to the technical field of electric vehicle braking, and specifically relates to a braking control method and device for a two-wheel drive electric vehicle. Background Art

[0002] Braking energy recovery is one of the ways for electric vehicles to improve energy utilization. It can convert the kinetic energy of the vehicle during braking into electrical energy storage in the battery through the electric motor, and then use it for traction drive, avoiding the loss of energy into frictional heat energy, thereby improving energy utilization efficiency and increasing the driving range of electric vehicles.

[0003] The key component of electric vehicles is the battery. The amount of energy stored in the power battery is an important factor in determining the driving range of electric vehicles. However, battery technology is still a bottleneck in the development of electric vehicles. No breakthrough has been made, and the driving range of electric vehicles cannot meet the needs of users. If the kinetic energy during vehicle deceleration is converted into electrical energy and recycled into the battery instead of being wasted by friction, it is undoubtedly equivalent to increasing the capacity of the battery. Under existing technical conditions, doing so is of great significance in improving the driving range performance of electric vehicles.

[0004] The current energy recovery strategy of electric vehicles focuses more on improving energy recovery efficiency, striving to recover as much energy as possible during vehicle driving to significantly increase driving range. However, at lower vehicle speeds, the current that the generator can generate is relatively small, the battery charging efficiency is not ideal, and this low-power charging state will reduce the service life of the power system, especially the battery. Summary of the invention

[0005] In order to solve at least one technical problem existing in the prior art, the present application provides a braking control method and device for a two-wheel drive electric vehicle.

[0006] In a first aspect, the present application discloses a braking control method for a two-wheel drive electric vehicle, comprising the following steps:

[0007] Step S1, obtaining a brake pedal position signal, a current vehicle speed V, and a current battery state of charge value SOC when the electric vehicle brakes;

[0008] Step S2: according to a preset time interval t 1 The brake pedal position signal collected within the preset time interval t is calculated 1 The brake pedal stroke Ba is pressed down;

[0009] Step S3: determine whether the current vehicle speed V, the current battery state of charge SOC and the brake pedal travel Ba simultaneously satisfy the following relationship:

[0010] V>V low , SOC<SOC high , Ba<Be;

[0011] Among them, V low is the preset minimum vehicle speed threshold, SOC high is the preset maximum battery state of charge threshold, Be is the preset minimum brake pedal travel threshold;

[0012] If the conditions are met, proceed to step S4; otherwise, the friction braking torques of the drive shaft and the non-drive shaft are controlled according to a fixed distribution ratio;

[0013] Step S4: Determine the current vehicle speed V and the preset maximum vehicle speed threshold V high When V is greater than V high When V is less than V high When , proceed to step S6;

[0014] Step S5, controlling the braking sequence and torque magnitude of the drive shaft energy recovery, the drive shaft friction braking and the non-drive shaft friction braking according to the preset first braking mode and the first braking torque ratio distribution scheme, wherein the control priority of the drive shaft energy recovery is higher than that of the non-drive shaft friction braking, and the control priority of the non-drive shaft friction braking is higher than that of the drive shaft friction braking;

[0015] Step S6, according to the preset second braking mode and second braking torque ratio distribution scheme, the braking sequence and torque size of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled, wherein the control priority of the non-drive shaft friction braking is higher than that of the drive shaft energy recovery, and the control priority of the drive shaft energy recovery is higher than that of the drive shaft friction braking.

[0016] According to at least one embodiment of the present application, in step S5, the first braking mode includes the following parallel sub-modes:

[0017] Submode A1: When T reg >T r When , only the drive shaft energy recovery is performed, where T reg is the maximum braking torque that can be generated by the drive shaft energy recovery, T r It is the total braking torque calculated based on the current vehicle speed V;

[0018] Submode A2: When α·T r <T reg <T r, performing energy recovery of the drive shaft and friction braking of the non-drive shaft simultaneously, wherein α is the friction braking torque coefficient allocated to the drive shaft in the fixed allocation ratio of the friction braking torque of the drive shaft and the non-drive shaft in step S3;

[0019] Submode A3: When T reg <α·T r , and T r <T reg +T nf When the drive shaft energy recovery and non-drive shaft friction braking are performed simultaneously, T nf is the maximum value of the friction braking torque of the non-driving shaft;

[0020] Submode A4: When T reg <α·T r , and T reg +T nf <T r <T reg +T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T df is the maximum value of the friction braking torque of the drive shaft;

[0021] Submode A5: When T r >T reg +T nf +T df When braking, drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously.

[0022] According to at least one embodiment of the present application, in step S5, the first braking torque ratio distribution scheme corresponds to each sub-mode of the first braking mode, wherein:

[0023] For sub-mode A1, the energy recovery torque of the drive shaft is controlled to be T r ;

[0024] For sub-mode A2, the energy recovery torque of the drive shaft is controlled to be α·T r , the friction braking torque of the non-driving shaft is (1-α)·T r ;

[0025] For sub-mode A3, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the non-driving shaft is T nf =T r -T reg ;

[0026] For sub-mode A4, the energy recovery torque of the drive shaft is controlled to be T reg, the friction braking torque of the drive shaft is T r -T nf -T reg , the friction braking torque of the non-driving shaft is T nf ;

[0027] For sub-mode A5, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T nf .

[0028] According to at least one embodiment of the present application, in step S6, the second braking mode includes the following parallel sub-modes:

[0029] Submode B1: When T reg >α·T r When the drive shaft energy recovery and non-drive shaft friction braking are performed simultaneously, T reg is the maximum braking torque that can be generated by the drive shaft energy recovery, T r is the total braking torque calculated according to the current vehicle speed V, α is the friction braking torque coefficient allocated to the driving shaft in the fixed allocation ratio of the friction braking torque of the driving shaft and the non-driving shaft in step S3;

[0030] Submode B2: When T reg <α·T r <T reg +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T df is the maximum value of the friction braking torque of the drive shaft;

[0031] Submode B3: When α·T r >T reg +T df , and T r <T reg +T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T nf is the maximum value of the friction braking torque of the non-driving shaft;

[0032] Submode B4: When T r >T reg +T nf +T df When braking, drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously.

[0033] According to at least one embodiment of the present application, in step S5, the first braking torque ratio distribution scheme corresponds to each sub-mode of the first braking mode, wherein:

[0034] For sub-mode B1, the energy recovery torque of the drive shaft is controlled to be α·T r , the friction braking torque of the non-driving shaft is (1-α)·T r ;

[0035] For sub-mode B2, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is α·T r -T reg , the friction braking torque of the non-driving shaft is (1-α)·T r ;

[0036] For sub-mode B3, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T r -T reg -T df ;

[0037] For sub-mode B4, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T nf .

[0038] According to at least one embodiment of the present application, in the fixed distribution ratio of the friction braking torque of the drive shaft and the non-drive shaft in step S3, the value of the friction braking torque coefficient α distributed to the drive shaft is greater than 0.5.

[0039] In a second aspect, the present application further discloses a brake control device for a two-wheel drive electric vehicle, comprising:

[0040] A signal acquisition unit is used to collect the brake pedal position signal, the current vehicle speed V and the current battery state of charge value SOC when the electric vehicle brakes;

[0041] Control unit for:

[0042] According to a preset time interval t 1 The brake pedal position signal collected within the preset time interval t is calculated 1 The brake pedal stroke Ba is pressed down;

[0043] When V>V low 、SOC<SOC highWhen any of the three conditions, Ba<Be, is not met, the friction braking torque of the driving shaft and the non-driving shaft is controlled according to a fixed distribution ratio, where V low is the preset minimum vehicle speed threshold, SOC high is the preset maximum battery state of charge threshold, Be is the preset minimum brake pedal travel threshold;

[0044] When V>V high 、SOC<SOC high When the three conditions of Ba<Be are met, the braking sequence and torque size of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled according to the preset first braking mode and the first braking torque ratio distribution scheme, wherein the control priority of the drive shaft energy recovery is higher than that of the non-drive shaft friction braking, and the control priority of the non-drive shaft friction braking is higher than that of the drive shaft friction braking, V high is the preset maximum vehicle speed threshold V high ;

[0045] When judging V low <V<V high 、SOC<SOC high When the three conditions of Ba<Be are met, the braking sequence and torque size of drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled according to the preset second braking mode and second braking torque ratio distribution scheme, among which the control priority of non-drive shaft friction braking is higher than that of drive shaft energy recovery, and the control priority of drive shaft energy recovery is higher than that of drive shaft friction braking.

[0046] According to at least one embodiment of the present application, the signal acquisition unit includes:

[0047] The accelerator pedal sensor is used to detect the brake pedal position signal;

[0048] The vehicle speed sensor is used to detect the current vehicle speed V when the electric vehicle brakes;

[0049] The SOC signal collector is used to collect the single cell voltage of the electric vehicle battery pack and calculate the current battery state of charge value SOC of the battery pack according to the single cell voltage.

[0050] According to at least one embodiment of the present application, the control unit includes:

[0051] A signal receiving unit, used to receive all signals collected by the signal collecting unit;

[0052] A preset storage unit is used to preset and store the minimum vehicle speed threshold V low , Maximum speed threshold V low, maximum battery state of charge threshold SOC high and a minimum brake pedal travel threshold value Ba;

[0053] A comparing unit, used for comparing the signal received by the signal receiving unit with a corresponding preset value in the preset unit;

[0054] A control instruction generating unit, configured to generate corresponding control instructions for controlling the braking sequence and torque value of the drive shaft energy recovery, the drive shaft friction braking and the non-drive shaft friction braking after the comparison result in the comparing unit meets a predetermined condition;

[0055] The instruction output unit is used to send the control instruction generated by the control instruction generating unit to the corresponding control object.

[0056] According to at least one embodiment of the present application, the control instruction generating unit includes:

[0057] A first instruction generation module, used to generate corresponding braking sequence control instructions according to conditions;

[0058] The second instruction generation module is used to generate corresponding torque magnitude value control instructions according to conditions.

[0059] This application has at least the following beneficial technical effects:

[0060] 1) In the braking control method and device for a two-wheel drive electric vehicle of the present application, the current vehicle speed, emergency braking state (judged by comparing the brake pedal stroke), and SOC state are integrated to automatically control the braking sequence and braking torque of the drive shaft energy recovery, drive shaft friction braking, and non-drive shaft friction braking. At lower vehicle speeds, the proportion of the motor torque in the total braking torque is reduced to reduce the electrical cycle between the motor and the battery, thereby improving the battery life while taking into account the energy recovery efficiency;

[0061] 2) In the braking control method and device for a two-wheel drive electric vehicle of the present application, when the current battery state of charge value SOC and the brake pedal travel Ba both meet the judgment conditions, the current vehicle speed V is V>V high and V low <V<V high The judgment conditions further subdivide the control method of the braking sequence and the braking torque to achieve more precise braking control that takes energy recovery into consideration and better improve battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 is a flowchart of a braking control method for a two-wheel drive electric vehicle of the present application;

[0063] Figure 2 It is an execution logic flow chart of one of the braking modes of the braking control method for a two-wheel drive electric vehicle of the present application;

[0064] Figure 3 is with Figure 2 The braking torque distribution strategy diagram corresponding to the braking mode;

[0065] Figure 4 It is an execution logic flow chart of another braking mode of the braking control method for a two-wheel drive electric vehicle of the present application;

[0066] Figure 5 is with Figure 4 The braking torque distribution strategy diagram corresponding to the braking mode;

[0067] Figure 6 is a structural block diagram of a brake control device for a two-wheel drive electric vehicle of the present application;

[0068] Figure 7 This is a structural block diagram of a signal acquisition unit in a brake control device for a two-wheel drive electric vehicle of the present application;

[0069] Figure 8 This is a structural block diagram of a control unit in a brake control device for a two-wheel drive electric vehicle in the present application;

[0070] in:

[0071] Signal acquisition unit-101;

[0072] Accelerator pedal sensor-1011; Vehicle speed sensor-1012; SOC signal collector-1013;

[0073] Control unit-102;

[0074] Signal receiving unit-1021; preset storage unit-1022; comparison unit-1023; control instruction generating unit-1024; instruction output unit-1025. DETAILED DESCRIPTION

[0075] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0076] In the following description, specific details such as specific system structures, technologies, etc. are proposed for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from hindering the description of the present application.

[0077] It should be noted that most two-wheel drive pure electric vehicles are front-wheel drive. During the application process, the braking control strategy (method and device) described in this application only needs to distinguish between the drive shaft and the non-drive shaft, and has nothing to do with whether the vehicle adopts front-wheel drive or rear-wheel drive. Therefore, the braking control strategy described in this application is applicable to both front-wheel drive and rear-wheel drive pure electric vehicles.

[0078] In a first aspect, the present application discloses a braking control method for a two-wheel drive electric vehicle, referring to Figure 1 As shown, the braking control method comprises the following steps:

[0079] Step S1, obtaining a brake pedal position signal, a current vehicle speed V, and a current battery state of charge value SOC when the electric vehicle brakes.

[0080] Step S2: according to a preset time interval t 1 The brake pedal position signal collected within the preset time interval t is calculated 1 The brake pedal travel is Ba.

[0081] The preset time interval t 1 The calculation starts from the moment the driver steps on the brake pedal. It is mainly used to determine the brake pedal travel within the time interval, so as to determine whether the vehicle taking the braking action is in an emergency braking state (for example, when Ba<Be, it is determined to be a non-emergency braking state, and when Ba>Be, it is determined to be an emergency braking state). Therefore, the preset time interval t 1 The value can be set appropriately according to the specific operation needs.

[0082] Step S3: determine whether the current vehicle speed V, the current battery state of charge SOC and the brake pedal travel Ba simultaneously satisfy the following relationship:

[0083] V>V low , SOC<SOC high , Ba<Be;

[0084] Among them, V low is the preset minimum vehicle speed threshold, SOC high is the preset maximum battery state of charge threshold, Be is the preset minimum brake pedal travel threshold;

[0085] If the above relationship is satisfied, the subsequent step S4 is performed; if the above relationship is not satisfied, the friction braking torque of the drive shaft and the non-drive shaft are controlled according to the fixed distribution ratio. The fixed distribution ratio is usually appropriately set according to the front and rear braking performance of the vehicle, the front and rear weight distribution ratio, the driving comfort performance, etc. In this embodiment, it is preferred that the fixed distribution ratio of the friction braking torque of the drive shaft and the non-drive shaft is such that the value of the friction braking torque coefficient α allocated to the drive shaft is greater than 0.5.

[0086] Step S4: Determine the current vehicle speed V and the preset maximum vehicle speed threshold V high When V is greater than V high When V is less than V high When (because V>V low , so this is equivalent to V low <V<V high ), proceed to step S6.

[0087] Step S5, according to the preset first braking mode and the first braking torque ratio distribution scheme, the braking sequence and torque size of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled, wherein the control priority of the drive shaft energy recovery is higher than that of the non-drive shaft friction braking, and the control priority of the non-drive shaft friction braking is higher than that of the drive shaft friction braking.

[0088] Step S6, according to the preset second braking mode and second braking torque ratio distribution scheme, the braking sequence and torque size of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled, wherein the control priority of the non-drive shaft friction braking is higher than that of the drive shaft energy recovery, and the control priority of the drive shaft energy recovery is higher than that of the drive shaft friction braking.

[0089] It should be noted that the above steps S5 and S6 are equivalent to the following conditions: when the current battery state of charge value SOC and the brake pedal travel Ba both meet the judgment conditions, according to V>V high and V low <V<V high The judgment conditions divide the control of the braking sequence and the braking torque size (collectively referred to as braking control here) into two parallel braking control methods, which will be described in detail below.

[0090] like Figure 2 and Figure 3 As shown, the first braking mode in step S5 includes parallel sub-modes and the first braking torque ratio distribution scheme corresponding to each sub-mode is as follows:

[0091] Submode A1: When Treg >T r When , only the drive shaft energy recovery is performed, where T reg is the maximum braking torque that can be generated by the drive shaft energy recovery, T r is the total braking torque calculated based on the current vehicle speed V; at this time, the energy recovery torque of the drive shaft is controlled to be T r .

[0092] Submode A2: When α·T r <T reg <T r When the drive shaft energy recovery and non-drive shaft friction braking are performed simultaneously, α is the friction braking torque coefficient allocated to the drive shaft in the fixed allocation ratio of the drive shaft and non-drive shaft friction braking torque in step S3; at this time, the drive shaft energy recovery torque is controlled to be α·T r , the friction braking torque of the non-driving shaft is (1-α)·T r .

[0093] Submode A3: When T reg <α·T r , and T r <T reg +T nf When the drive shaft energy recovery and non-drive shaft friction braking are performed simultaneously, T nf is the maximum value of the friction braking torque of the non-driving shaft; at this time, the energy recovery torque of the driving shaft is controlled to be T reg , the friction braking torque of the non-driving shaft is T nf =T r -T reg .

[0094] Submode A4: When T reg <α·T r , and T reg +T nf <T r <T reg +T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T df is the maximum value of the friction braking torque of the drive shaft; at this time, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T r -T nf -T reg , the friction braking torque of the non-driving shaft is T nf .

[0095] Submode A5: When T r >T reg+T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously; at this time, the drive shaft energy recovery torque is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T nf .

[0096] Further, such as Figure 4 and Figure 5 As shown, the second braking mode in step S5 includes parallel sub-modes and the second braking torque ratio distribution scheme corresponding to each sub-mode is as follows:

[0097] Submode B1: When T reg >α·T r When the drive shaft energy recovery and non-drive shaft friction braking are performed simultaneously, T reg is the maximum braking torque that can be generated by the drive shaft energy recovery, T r is the total braking torque calculated according to the current vehicle speed V, α is the friction braking torque coefficient allocated to the drive shaft in the fixed distribution ratio of the friction braking torque of the drive shaft and the non-drive shaft in step S3; at this time, the energy recovery torque of the drive shaft is controlled to be α·T r , the friction braking torque of the non-driving shaft is (1-α)·T r .

[0098] Submode B2: When T reg <α·T r <T reg +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T df is the maximum value of the friction braking torque of the drive shaft; at this time, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is α·T r -T reg , the friction braking torque of the non-driving shaft is (1-α)·T r .

[0099] Submode B3: When α·T r >T reg +T df , and T r <T reg +T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T nfis the maximum value of the friction braking torque of the non-driving shaft; at this time, the energy recovery torque of the driving shaft is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T r -T reg -T df .

[0100] It should be noted here that the braking torque coefficient α allocated to the drive shaft is usually large. r <T reg +T nf +T df When there is no non-drive shaft braking torque (1-α)·T r >T nf situation.

[0101] Submode B4: When T r >T reg +T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously; at this time, the drive shaft energy recovery torque is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T nf .

[0102] In summary, the braking control method for a two-wheel drive electric vehicle of the present application combines the current vehicle speed, emergency braking status (determined by comparing the brake pedal stroke), and SOC status to automatically control the braking sequence and braking torque of the drive shaft energy recovery, drive shaft friction braking, and non-drive shaft friction braking. At lower vehicle speeds, the proportion of the electric motor braking torque in the total braking torque is reduced to reduce the electrical circulation between the motor and the battery, thereby improving the battery life while taking into account the energy recovery efficiency.

[0103] Furthermore, according to V>V high and V low <V<V high The judgment conditions divide the control of the braking sequence and the braking torque into two more detailed parallel braking control methods, so as to achieve more precise braking control that takes energy recovery into consideration and better improve battery life.

[0104] Among them, for the first braking control mode (which includes the energy recovery strategy), the driving shaft braking recovery torque is used first; when the driving shaft braking recovery torque cannot meet the braking demand, the non-driving shaft friction braking torque is used to supplement the braking torque; when the sum of the driving shaft braking recovery torque and the non-driving shaft friction braking torque still cannot meet the braking demand, the driving shaft friction braking torque is used to supplement the braking torque.

[0105] For the second braking control method (which also includes an energy recovery strategy), when the vehicle speed is lower than a set threshold, the braking torque demand is proportionally distributed to the drive shaft and the non-drive shaft; among which, the non-drive shaft braking torque is the non-drive shaft friction braking torque, and the drive shaft braking torque gives priority to the drive shaft braking recovery torque, and when it is insufficient, the drive shaft friction braking torque is used.

[0106] In a second aspect, the present application also discloses a brake control device for a two-wheel drive electric vehicle, such as Figure 6 As shown, the brake control device may include a signal acquisition unit 101 and a control unit 102 .

[0107] Specifically, the signal acquisition unit 101 is used to collect the brake pedal position signal, the current vehicle speed V, and the current battery state of charge value SOC when the electric vehicle brakes.

[0108] It is understandable that, in order to realize the acquisition of the above-mentioned specific signal, the signal acquisition unit 101 can adopt a variety of known suitable devices. In the embodiment provided in this application, for example Figure 7 As shown, the signal acquisition unit 101 at least includes an accelerator pedal sensor 1011 , a vehicle speed sensor 1012 and an SOC signal collector 1013 .

[0109] Among them, the accelerator pedal sensor 1011 is used to detect the brake pedal position signal; the vehicle speed sensor 1012 is used to detect the current vehicle speed V when the electric vehicle brakes; the SOC signal collector 1013 is used to collect the single cell voltage of the electric vehicle battery pack and calculate the current battery state of charge value SOC of the battery pack based on the single cell voltage.

[0110] As a main functional component, the control unit 102 can at least realize the following functions:

[0111] 1) According to a preset time interval t 1 The brake pedal position signal collected within the preset time interval t is calculated 1 The brake pedal stroke Ba is pressed down;

[0112] 2) When V>V low 、SOC<SOC highWhen any of the three conditions, Ba<Be, is not met, the friction braking torque of the driving shaft and the non-driving shaft is controlled according to a fixed distribution ratio, where V low is the preset minimum vehicle speed threshold, SOC high is the preset maximum battery state of charge threshold, Be is the preset minimum brake pedal travel threshold;

[0113] 3) When V>V high 、SOC<SOC high When the three conditions of Ba<Be are met, the braking sequence and torque size of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled according to the preset first braking mode and the first braking torque ratio distribution scheme, wherein the control priority of the drive shaft energy recovery is higher than that of the non-drive shaft friction braking, and the control priority of the non-drive shaft friction braking is higher than that of the drive shaft friction braking, V high is the preset maximum vehicle speed threshold V high ;

[0114] 4) When judging V low <V<V high 、SOC<SOC high When the three conditions of Ba<Be are met, the braking sequence and torque size of drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled according to the preset second braking mode and second braking torque ratio distribution scheme, among which the control priority of non-drive shaft friction braking is higher than that of drive shaft energy recovery, and the control priority of drive shaft energy recovery is higher than that of drive shaft friction braking.

[0115] It is understandable that the specific structure of the control unit 102 to achieve the above functions can be appropriately configured as needed. In the embodiments provided in this application, Figure 8 As shown, the control unit 102 at least includes a signal receiving unit 1021 , a preset storage unit 1022 , a comparing unit 1023 , a control instruction generating unit 1024 and an instruction output unit 1025 .

[0116] Specifically, the signal receiving unit 1021 is used to receive all signals collected by the signal collecting unit; the preset storage unit 1022 is used to preset and store the minimum vehicle speed threshold V low , Maximum speed threshold V low , maximum battery state of charge threshold SOC high And the minimum brake pedal travel threshold value Ba; the comparison unit 1023 is used to compare the signal received by the signal receiving unit with the corresponding preset value in the preset unit.

[0117] The control instruction generation unit 1024 is used to generate corresponding control instructions for controlling the braking sequence and torque value of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking after the comparison result in the comparison unit meets the predetermined condition. In this embodiment, the control instruction generation unit 1024 can further include a first instruction generation module and a second instruction generation module, wherein the first instruction generation module is used to generate the corresponding braking sequence control instruction according to the condition, and the second instruction generation module is used to generate the corresponding torque value control instruction according to the condition.

[0118] The instruction output unit 1025 is used to send the control instruction generated by the control instruction generating unit to the corresponding control object.

[0119] It should also be noted that the first and second braking modes and the first and second braking torque ratio distribution schemes mentioned in the braking control device for a two-wheel drive electric vehicle in the present application are the same as those in the braking control method of the first aspect mentioned above (and can be implemented by the control unit 102), so they will not be repeated here; in addition, the braking control device for a two-wheel drive electric vehicle in the present application can achieve the same technical effect as the above-mentioned braking control method, which will not be repeated here.

[0120] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A braking control method for a two-wheel drive electric vehicle, characterized in that: The steps include: Step S1, obtaining a brake pedal position signal, a current vehicle speed V, and a current battery state of charge value SOC when the electric vehicle brakes; Step S2, calculating the brake pedal travel Ba depressed within a preset time interval t1 according to the brake pedal position signal collected within the preset time interval t1; Step S3: determine whether the current vehicle speed V, the current battery state of charge SOC and the brake pedal travel Ba simultaneously satisfy the following relationship: V>V low ,SOC<SOC high ,Ba<Be; Among them, V low is the preset minimum vehicle speed threshold, SOC high is the preset maximum battery state of charge threshold, Be is the preset minimum brake pedal travel threshold; If the conditions are met, proceed to step S4; otherwise, the friction braking torques of the drive shaft and the non-drive shaft are controlled according to a fixed distribution ratio; Step S4: Determine the current vehicle speed V and the preset maximum vehicle speed threshold V high When V is greater than V high When V is less than V high When , proceed to step S6; Step S5, controlling the braking sequence and torque magnitude of the drive shaft energy recovery, the drive shaft friction braking and the non-drive shaft friction braking according to the preset first braking mode and the first braking torque ratio distribution scheme, wherein the control priority of the drive shaft energy recovery is higher than that of the non-drive shaft friction braking, and the control priority of the non-drive shaft friction braking is higher than that of the drive shaft friction braking; Step S6, according to the preset second braking mode and second braking torque ratio distribution scheme, the braking sequence and torque size of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled, wherein the control priority of the non-drive shaft friction braking is higher than that of the drive shaft energy recovery, and the control priority of the drive shaft energy recovery is higher than that of the drive shaft friction braking.

2. The braking control method according to claim 1, characterized in that: In step S5, the first braking mode includes the following parallel sub-modes: Submode A1: When T reg >T r When , only the drive shaft energy recovery is performed, where T reg is the maximum braking torque that can be generated by the drive shaft energy recovery, T r It is the total braking torque calculated based on the current vehicle speed V; Submode A2: When α·T r <T reg <T r , performing energy recovery of the drive shaft and friction braking of the non-drive shaft simultaneously, wherein α is the friction braking torque coefficient allocated to the drive shaft in the fixed allocation ratio of the friction braking torque of the drive shaft and the non-drive shaft in step S3; Submode A3: When T reg <α·T r , and T r <T reg +T nf When the drive shaft energy recovery and non-drive shaft friction braking are performed simultaneously, T nf is the maximum value of the friction braking torque of the non-driving shaft; Submode A4: When T reg <α·T r , and T reg +T nf <T r <T reg +T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T df is the maximum value of the friction braking torque of the drive shaft; Submode A5: When T r >T reg +T nf +T df When braking, drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously.

3. The braking control method according to claim 2, characterized in that: In step S5, the first braking torque ratio distribution scheme corresponds to each sub-mode of the first braking mode, wherein: For sub-mode A1, the energy recovery torque of the drive shaft is controlled to be T r ; For sub-mode A2, the energy recovery torque of the drive shaft is controlled to be α·T r , the friction braking torque of the non-driving shaft is (1-α)·T r ; For sub-mode A3, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the non-driving shaft is T n =T r -T reg ; For sub-mode A4, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T r -T nf -T reg , the friction braking torque of the non-driving shaft is T nf ; For sub-mode A5, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T nf .

4. The braking control method according to claim 1, characterized in that: In step S6, the second braking mode includes the following parallel sub-modes: Submode B1: When T reg >α·T r When the drive shaft energy recovery and non-drive shaft friction braking are performed simultaneously, T reg is the maximum braking torque that can be generated by the drive shaft energy recovery, T r is the total braking torque calculated according to the current vehicle speed V, α is the friction braking torque coefficient allocated to the driving shaft in the fixed allocation ratio of the friction braking torque of the driving shaft and the non-driving shaft in step S3; Submode B2: When T reg <α·T r <T reg +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T df is the maximum value of the friction braking torque of the drive shaft; Submode B3: When α·T r >T reg +T df , and T r <T reg +T nf +T df When the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously, wherein T nf is the maximum value of the friction braking torque of the non-driving shaft; Submode B4: When T r >T reg +T nf +T df When braking, drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are performed simultaneously.

5. The braking control method according to claim 4, characterized in that: In step S5, the first braking torque ratio distribution scheme corresponds to each sub-mode of the first braking mode, wherein: For sub-mode B1, the energy recovery torque of the drive shaft is controlled to be α·T r , the friction braking torque of the non-driving shaft is (1-α)·T r ; For sub-mode B2, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is α·T r -T reg , the friction braking torque of the non-driving shaft is (1-α)·T r ; For sub-mode B3, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T r -T reg -T df ; For sub-mode B4, the energy recovery torque of the drive shaft is controlled to be T reg , the friction braking torque of the drive shaft is T df , the friction braking torque of the non-driving shaft is T nf .

6. The braking control method according to any one of claims 1 to 5, characterized in that: In the fixed distribution ratio of the friction braking torque of the driving shaft and the non-driving shaft in step S3, the value of the friction braking torque coefficient α distributed to the driving shaft is greater than 0.

5.

7. A brake control device for a two-wheel drive electric vehicle, characterized in that: include: A signal acquisition unit is used to collect the brake pedal position signal, the current vehicle speed V and the current battery state of charge value SOC when the electric vehicle brakes; Control unit for: Calculate the brake pedal travel Ba depressed within a preset time interval t1 according to the brake pedal position signal collected within the preset time interval t1; When V>V low 、SOC<SOC high When any of the three conditions, Ba<Be, is not met, the friction braking torque of the driving shaft and the non-driving shaft is controlled according to a fixed distribution ratio, where V low is the preset minimum vehicle speed threshold, SOC high is the preset maximum battery state of charge threshold, Be is the preset minimum brake pedal travel threshold; When V>V high 、SOC<SOC high When the three conditions of Ba<Be are met, the braking sequence and torque size of the drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled according to the preset first braking mode and the first braking torque ratio distribution scheme, wherein the control priority of the drive shaft energy recovery is higher than that of the non-drive shaft friction braking, and the control priority of the non-drive shaft friction braking is higher than that of the drive shaft friction braking, V high is the preset maximum vehicle speed threshold; When judging V low <V<V high 、SOC<SOC high When the three conditions of Ba<Be are met, the braking sequence and torque size of drive shaft energy recovery, drive shaft friction braking and non-drive shaft friction braking are controlled according to the preset second braking mode and second braking torque ratio distribution scheme, among which the control priority of non-drive shaft friction braking is higher than that of drive shaft energy recovery, and the control priority of drive shaft energy recovery is higher than that of drive shaft friction braking.

8. The brake control device according to claim 7, characterized in that: The signal acquisition unit comprises: The accelerator pedal sensor is used to detect the brake pedal position signal; The vehicle speed sensor is used to detect the current vehicle speed V when the electric vehicle brakes; The SOC signal collector is used to collect the single cell voltage of the electric vehicle battery pack and calculate the current battery state of charge value SOC of the battery pack according to the single cell voltage.

9. The brake control device according to claim 8, characterized in that: The control unit comprises: A signal receiving unit, used to receive all signals collected by the signal collecting unit; A preset storage unit is used to preset and store the minimum vehicle speed threshold V low , Maximum speed threshold V high , maximum battery state of charge threshold SOC high and a minimum brake pedal travel threshold value Be; A comparing unit, used for comparing the signal received by the signal receiving unit with a corresponding preset value in the preset unit; A control instruction generating unit, configured to generate corresponding control instructions for controlling the braking sequence and torque value of the drive shaft energy recovery, the drive shaft friction braking and the non-drive shaft friction braking after the comparison result in the comparing unit meets a predetermined condition; The instruction output unit is used to send the control instruction generated by the control instruction generating unit to the corresponding control object.

10. The brake control device according to claim 9, characterized in that: The control instruction generating unit comprises: A first instruction generation module, used to generate corresponding braking sequence control instructions according to conditions; The second instruction generation module is used to generate corresponding torque magnitude value control instructions according to conditions.

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