Control method and device for electric vehicle

Abstract

This application provides a control method and apparatus for an electric vehicle. The electric vehicle includes a motor, a hydraulic braking system, a first front wheel, a second front wheel, a first rear wheel, a second rear wheel, and a rear axle. The method includes: when both the first and second rear wheels are on a high-friction coefficient road surface, controlling the motor to output a first torque and controlling the hydraulic braking system to apply a first hydraulic braking force to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel; when the first rear wheel enters a low-friction coefficient road surface and the second rear wheel is on a high-friction coefficient road surface, controlling the motor to output a second torque less than the first torque, and controlling the hydraulic braking system to apply a second hydraulic braking force to the first rear wheel based on the first torque; wherein the friction coefficient of the low-friction coefficient road surface is less than the friction coefficient of the high-friction coefficient road surface. This application can improve the driving stability of the electric vehicle.

Description

Technical Field

[0001] This application relates to the field of electric vehicle control technology, and in particular to a control method and device for an electric vehicle. Background Technology

[0002] In rear-axle driven electric vehicles, braking torque is provided by the rear axle motor. Regenerative braking is performed during braking to improve the vehicle's range. When a single rear axle wheel travels on a low-friction surface, the rear wheel is prone to locking up, disengaging regenerative braking. The rear axle fails to establish hydraulic braking force, while the front axle does. This can cause the driver to experience a lurching sensation forward, increasing the risk of accidents. Summary of the Invention

[0003] This application provides a control method and device for electric vehicles, which can make electric vehicles drive more stably.

[0004] This application provides a control method for an electric vehicle, the electric vehicle including a motor, a hydraulic braking system, a first front wheel, a second front wheel, a first rear wheel, a second rear wheel, and a rear axle connecting the first rear wheel and the second rear wheel, the motor being disposed on the rear axle, and the hydraulic braking system being connected to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel; the method includes:

[0005] When both the first rear wheel and the second rear wheel are on a road surface with a high coefficient of adhesion, the motor is controlled to output a first torque, and the hydraulic braking system is controlled to apply a first hydraulic braking force to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel.

[0006] When the first rear wheel enters a low-friction coefficient road surface and the second rear wheel is on a high-friction coefficient road surface, the motor is controlled to output a second torque that is less than the first torque, and the hydraulic braking system is controlled to apply a second hydraulic braking force to the first rear wheel according to the first torque; wherein the friction coefficient of the low-friction coefficient road surface is less than the friction coefficient of the high-friction coefficient road surface.

[0007] Optionally, controlling the hydraulic braking system to apply a second hydraulic braking force to the first rear wheel based on the first torque includes:

[0008] Based on the electric vehicle model and the first torque, the hydraulic braking system is controlled to apply a second hydraulic braking force to the first rear wheel.

[0009] Optionally, the method further includes:

[0010] When the first rear wheel enters a low-friction coefficient road surface and the second rear wheel is on a high-friction coefficient road surface, the hydraulic braking system is controlled to apply front axle hydraulic braking force to the first front wheel and the second front wheel based on the first hydraulic braking force and the second hydraulic braking force.

[0011] Optionally, the first front wheel and the first rear wheel are located on the same side of the electric vehicle, and the second front wheel and the second rear wheel are located on the same side of the electric vehicle; controlling the hydraulic braking system to apply front axle hydraulic braking force to the first front wheel and the second front wheel includes: controlling the hydraulic braking system to apply a first front axle hydraulic braking force to the first front wheel, and controlling the hydraulic braking system to apply a second front axle hydraulic braking force to the second front wheel; wherein, the first front axle hydraulic braking force is less than the second front axle hydraulic braking force.

[0012] Optionally, controlling the hydraulic braking system to apply a first front axle hydraulic braking force to the first front wheel and controlling the hydraulic braking system to apply a second front axle hydraulic braking force to the second front wheel includes:

[0013] Based on the functional relationship between the first front axle hydraulic braking force, the second front axle hydraulic braking force, the first hydraulic braking force, and the second hydraulic braking force, the hydraulic braking system is controlled to apply a first front axle hydraulic braking force to the first front wheel, and the hydraulic braking system is controlled to apply a second front axle hydraulic braking force to the second front wheel.

[0014] The sum of the first front axle hydraulic braking force and the second front axle hydraulic braking force is directly proportional to the first hydraulic braking force and inversely proportional to the second hydraulic braking force; the difference between the second front axle hydraulic braking force and the first front axle hydraulic braking force is directly proportional to the second hydraulic braking force.

[0015] Optionally, the method further includes:

[0016] The maximum braking torque of the electric vehicle is obtained based on the road conditions of the low-adhesion coefficient road surface and the high-adhesion coefficient road surface.

[0017] If the braking torque of the electric vehicle is less than the maximum braking torque, the anti-lock braking system of the electric vehicle is activated. The maximum slip ratio of the front wheel of the electric vehicle is less than a first threshold, the maximum slip ratio of the first rear wheel and the second rear wheel is greater than a second threshold, and the difference between the slip ratio of the first rear wheel and the slip ratio of the second rear wheel is greater than a third threshold. It is determined that the first rear wheel has entered a low-friction coefficient road surface and the second rear wheel has entered a high-friction coefficient road surface.

[0018] Optionally, controlling the motor to output a second torque that is less than the first torque includes:

[0019] The second torque is determined based on the vehicle speed at the moment the first rear wheel enters the low-friction surface and the deceleration of the electric vehicle.

[0020] Optionally, after controlling the motor to output a second torque less than the first torque, and controlling the hydraulic braking system to apply a second hydraulic braking force to the first rear wheel based on the first torque, the method includes:

[0021] When the first rear wheel leaves the road surface with a low coefficient of adhesion, the hydraulic braking system is controlled to output the first hydraulic braking force, and the motor is controlled to output the first torque.

[0022] Optionally, the method further includes:

[0023] If the anti-lock braking system of the electric vehicle is not activated, the slip ratio of the first rear wheel and the second rear wheel is less than the fourth threshold, and the distance traveled by the electric vehicle from the moment the first rear wheel enters the low-friction coefficient road surface reaches the distance threshold, it is determined that the first rear wheel leaves the low-friction coefficient road surface.

[0024] Optionally, the distance threshold is determined based on the wheelbase of the electric vehicle.

[0025] This application provides a computer-readable storage medium including one or more processors for implementing the control method for an electric vehicle as described in any of the preceding claims.

[0026] This application provides a control device for an electric vehicle, including one or more processors for implementing the electric vehicle control method as described in any of the preceding claims.

[0027] This application also provides an electric vehicle, including: a motor, a hydraulic braking system, a first front wheel, a second front wheel, a first rear wheel, a second rear wheel, a rear axle connecting the first rear wheel and the second rear wheel, and a control device for the electric vehicle as described above.

[0028] The motor is mounted on the rear axle, and the hydraulic braking system is connected to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel. The control device is communicatively connected to the motor and the hydraulic braking system, and is used to control the output torque of the motor and to control the hydraulic braking system to apply hydraulic braking force to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel.

[0029] In some embodiments, the electric vehicle includes a motor, a hydraulic braking system, a first front wheel, a second front wheel, a first rear wheel, a second rear wheel, and a rear axle connecting the first and second rear wheels. The motor is located on the rear axle and can provide a reverse drag torque during braking. The hydraulic braking system is connected to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel and can provide hydraulic braking force during braking. When both the first and second rear wheels are on a road surface with a high coefficient of friction, the motor is controlled to output a first torque, and the hydraulic braking system is controlled to apply a first hydraulic braking force to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel to provide braking for the electric vehicle. When the first rear wheel enters a road surface with a low coefficient of friction and the second rear wheel is on a road surface with a high coefficient of friction, the first rear wheel is prone to lock up, and the braking torque of the rear axle decreases. The motor is controlled to output a second torque less than the first torque, and the hydraulic braking system is controlled to apply a second hydraulic braking force to the first rear wheel based on the first torque. This can improve the braking force of the second rear wheel, which helps to reduce the driving instability caused by the loss of braking deceleration of the electric vehicle and improve the safety of the electric vehicle.

[0030] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0031] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0032] Figure 1 The diagram shown is a structural schematic of one embodiment of the electric vehicle of this application.

[0033] Figure 2 The diagram shown is a flowchart of one embodiment of the electric vehicle control method of this application.

[0034] Figure 3 As shown Figure 1 The diagram shows a scenario where an electric vehicle is driving on a road.

[0035] Figure 4 As shown Figure 1 The diagram shows another working condition of an electric vehicle traveling on a road.

[0036] Figure 5 As shown Figure 1 The diagram shows another working condition of an electric vehicle traveling on a road.

[0037] Figure 6 As shown Figure 1 The diagram shows another working condition of an electric vehicle traveling on a road.

[0038] Figure 7 The diagram shown is a schematic representation of some parameters of the electric vehicle control method of this application.

[0039] Figure 8 The diagram shown is a structural block diagram of the control device for an electric vehicle provided in an embodiment of this application. Detailed Implementation

[0040] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0041] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit the application. Unless otherwise defined, the technical or scientific terms used in this application should be understood in their ordinary sense by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in this application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "a" or "one," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. "A plurality" or "several" indicates two or more. Unless otherwise indicated, the terms "front," "rear," "lower," and / or "upper," etc., are for ease of description only and are not limited to a location or spatial orientation. The terms "comprising" or "including," etc., mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including" and their equivalents, and do not exclude other elements or objects. The terms "connected," "linked," etc., are not limited to physical or mechanical connections and can include electrical connections, whether direct or indirect.

[0042] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0043] The electric vehicle of this application embodiment includes a motor, a hydraulic braking system, a first front wheel, a second front wheel, a first rear wheel, a second rear wheel, and a rear axle. The method includes: when both the first and second rear wheels are on a high-friction coefficient road surface, controlling the motor to output a first torque and controlling the hydraulic braking system to apply a first hydraulic braking force to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel; when the first rear wheel enters a low-friction coefficient road surface and the second rear wheel is on a high-friction coefficient road surface, controlling the motor to output a second torque less than the first torque, and controlling the hydraulic braking system to apply a second hydraulic braking force to the first rear wheel according to the first torque; wherein the friction coefficient of the low-friction coefficient road surface is less than the friction coefficient of the high-friction coefficient road surface. This application can improve the driving stability of the electric vehicle.

[0044] This application provides a control method and apparatus for an electric vehicle. The control method and apparatus for an electric vehicle of this application will be described in detail below with reference to the accompanying drawings. Unless otherwise specified, the features in the following embodiments and implementations can be combined with each other.

[0045] Figure 1 The diagram shown is a structural schematic of one embodiment of the electric vehicle 10 of this application. Figure 1 As shown, the electric vehicle 10 includes: a motor 15, a hydraulic braking system 16, a first front wheel 11, a second front wheel 12, a first rear wheel 13, a second rear wheel 14, a rear axle 18 connecting the first rear wheel 13 and the second rear wheel 14, and a control device 19 for the electric vehicle.

[0046] The electric vehicle 10 also includes a front axle 17, with a first front wheel 11 and a second front wheel 12 connected via the front axle 17 and located on both sides of the electric vehicle 10. A first rear wheel 13 and a second rear wheel 14 are located on both sides of the electric vehicle 10. Specifically, the first front wheel 11 and the first rear wheel 13 are located on the same side of the electric vehicle 10, and the second front wheel 12 and the second rear wheel 14 are located on the same side of the electric vehicle 10.

[0047] The motor 15 is mounted on the rear axle 18. When the electric vehicle 10 brakes, the motor 15 provides a reverse drag torque to provide braking force to the electric vehicle 10, and can also charge the battery of the electric vehicle 10 to recover braking energy.

[0048] The hydraulic braking system 16 is connected to the first front wheel 11, the second front wheel 12, the first rear wheel 13, and the second rear wheel 14. When the electric vehicle 10 brakes, the hydraulic braking system 16 can apply the same or different hydraulic braking forces to the first front wheel 11, the second front wheel 12, the first rear wheel 13, and the second rear wheel 14.

[0049] The control device 19 is communicatively connected to the motor 15 and the hydraulic braking system 16, and is used to control the output torque of the motor 15 and to control the hydraulic braking system 16 to apply hydraulic braking force to the first rear wheel 13 and the second rear wheel 14. The control device 19 is also used to control the hydraulic braking system 16 to apply hydraulic braking force to the first front wheel 11 and the second front wheel 12. The control device 19 controls the output torque of the motor 15 and the hydraulic braking system 16 to apply hydraulic braking force to the wheels based on the wheel cylinder pressure, wheel speed signal, anti-lock braking system activation signal, brake pedal travel, accelerator pedal signal, motor regenerative torque, motor maximum regenerative capacity, and vehicle acceleration of the electric vehicle 10.

[0050] Figure 2 The diagram shown is a flowchart of one embodiment of the electric vehicle control method 20 of this application.

[0051] Figures 3-6 As shown Figure 1 The diagram shows different operating conditions of the electric vehicle 10 traveling on the road surface. The road surface includes a high-coefficient road surface 31 and a low-coefficient road surface 30, wherein the coefficient of friction of the low-coefficient road surface 30 is less than that of the high-coefficient road surface 31. When the electric vehicle 10 travels on the low-coefficient road surface 30, the friction force provided by the road surface to the wheels is relatively small.

[0052] The control method 20 for electric vehicles includes steps 21 and 22.

[0053] Step 21: When both the first rear wheel 13 and the second rear wheel 14 are on the road surface 31 with a high coefficient of adhesion, control the motor 15 to output the first torque and control the hydraulic braking system 16 to apply the first hydraulic braking force to the first front wheel 11, the second front wheel 12, the first rear wheel 13, and the second rear wheel 14.

[0054] like Figure 3 As shown, the rear axle 18 of the electric vehicle 10 is not on the low-friction surface 30, and the electric vehicle 10 is in regenerative braking mode. The braking torque output by the motor 15 and the hydraulic braking force applied to the wheels by the hydraulic braking system 16 together provide braking force for the electric vehicle 10. In some embodiments, the hydraulic braking system 16 applies the same first hydraulic braking force to the first front wheel 11, the second front wheel 12, the first rear wheel 13, and the second rear wheel 14. In other embodiments, the hydraulic braking system 16 applies slightly different first hydraulic braking forces to the first front wheel 11, the second front wheel 12, the first rear wheel 13, and the second rear wheel 14.

[0055] Step 22: When the first rear wheel 13 enters the low-friction coefficient road surface 30 and the second rear wheel 14 is on the high-friction coefficient road surface 31, the control motor 15 outputs a second torque that is less than the first torque, and according to the first torque, the control hydraulic braking system 16 applies a second hydraulic braking force to the first rear wheel 13.

[0056] like Figure 4 As shown, when the first rear wheel 13 enters the low-friction coefficient surface 30 and the second rear wheel 14 is on the high-friction coefficient surface 31, the friction force provided by the road surface to the first rear wheel 13 decreases, the anti-lock braking system of the electric vehicle 10 is activated, and the electric vehicle 10 exits the regenerative braking mode. The motor 15 needs to output a second torque less than the first torque. Due to the presence of the differential of the electric vehicle 10, the torques of the first rear wheel 13 and the second rear wheel 14 are both the second torque. The hydraulic braking system 16 applies a second hydraulic braking force to the first rear wheel 13, and the second hydraulic braking force is obtained based on the first torque. In this way, even when the torque output by the motor 15 decreases, the torque capability of the second rear wheel 14 can be increased, allowing the electric vehicle 10 to maintain the braking force it had when the first rear wheel 13 did not enter the low-friction coefficient surface 30, reducing the loss of braking deceleration.

[0057] like Figure 5 As shown, after the first rear wheel 13 enters the low-adhesion road surface 30, the second torque output by the control motor 15 gradually decreases to zero.

[0058] In some embodiments, step 22, “controlling the motor 15 to output a second torque less than the first torque”, includes: determining the second torque based on the vehicle speed at the moment the first rear wheel 13 enters the low-adhesion road surface 30 and the deceleration of the electric vehicle.

[0059] In some embodiments, step 22 further includes: controlling the torque output by the motor 15 to gradually decrease to a second torque. The rate of decrease of the torque output by the motor 15 is determined based on the vehicle speed and braking deceleration of the electric vehicle 10. In some embodiments, to maintain vehicle stability, the rate of decrease is proportional to the vehicle speed and braking deceleration. In some embodiments, the rate of decrease is determined based on the hydraulic build-up rate of the hydraulic braking system 16 and the overall vehicle NVH performance.

[0060] In some embodiments, step 22, “controlling the hydraulic braking system 16 to apply a second hydraulic braking force to the first rear wheel 13 according to the first torque”, includes: controlling the hydraulic braking system 16 to apply a second hydraulic braking force to the first rear wheel 13 according to the model of the electric vehicle 10 and the first torque.

[0061] The second hydraulic braking force can be calculated using the following formula:

[0062] Mb_Act=Motor_CurrentBrkTrq+(pModel_FL+pModel_FR)*Cp_FA+(pModel_RL+pModel_RR)*Cp_RA formula (1)

[0063] pTarRA_LowMu=Motor_CurrentBrkTrq*CalCRegnTrqComp / (Cp_RA*2) formula (2)

[0064] Mb_Act represents the total braking torque of the electric vehicle 10, Motor_CurrentBrkTrq represents the first torque, pModel_FL represents the cylinder pressure of the first front wheel 11, pModel_FR represents the cylinder pressure of the second front wheel 12, pModel_RL represents the cylinder pressure of the first rear wheel 13, pModel_RR represents the cylinder pressure of the second rear wheel 14, Cp_FA represents the Cp value of the front axle 17, and Cp_RA represents the Cp value of the rear axle 18. The Cp value is used to represent the relationship between braking force and braking torque, and is obtained from the mechanical parameters of the electric vehicle 10.

[0065] pTarRA_LowMu is the second hydraulic braking force. CalCRegnTrqComp is an adjustment parameter that is adjusted according to the model of the electric vehicle 10 or the driver's driving experience.

[0066] In some embodiments, the electric vehicle 10 includes a motor 15, a hydraulic braking system 16, a first front wheel 11, a second front wheel 12, a first rear wheel 13, a second rear wheel 14, and a rear axle 18 connecting the first rear wheel 13 and the second rear wheel 14. The motor 15 is disposed on the rear axle 18 and can provide a reverse drag torque during braking. The hydraulic braking system 16 is connected to the first front wheel 11, the second front wheel 12, the first rear wheel 13, and the second rear wheel 14 and can provide hydraulic braking force during braking. When both the first rear wheel 13 and the second rear wheel 14 are on a high-friction coefficient road surface 31, the motor 15 is controlled to output a first torque, and the hydraulic braking system 16 is controlled to apply pressure to the first front wheel. 11. The second front wheel 12, the first rear wheel 13, and the second rear wheel 14 apply a first hydraulic braking force to provide braking for the electric vehicle 10. When the first rear wheel 13 enters the low-friction coefficient road surface 30 and the second rear wheel 14 is on the high-friction coefficient road surface 31, the first rear wheel 13 is prone to lock up, the braking torque of the rear axle 18 decreases, the control motor 15 outputs a second torque less than the first torque, and according to the first torque, the control hydraulic braking system 16 applies a second hydraulic braking force to the first rear wheel 13. This can improve the braking force of the second rear wheel 14, which helps to reduce the driving instability caused by the loss of braking deceleration of the electric vehicle 10 and improve the safety of the electric vehicle 10.

[0067] In some embodiments, the control method 20 for an electric vehicle further includes:

[0068] Based on the road conditions of low-adhesion-coefficient road surface 30 and high-adhesion-coefficient road surface 31, the maximum braking torque of electric vehicle 10 is obtained.

[0069] If the braking torque of electric vehicle 10 is less than the maximum braking torque, the anti-lock braking system of electric vehicle 10 is activated. The maximum slip ratio of the front wheel of electric vehicle 10 is less than the first threshold, the maximum slip ratio of the first rear wheel 13 and the second rear wheel 14 is greater than the second threshold, and the difference between the slip ratio of the first rear wheel 13 and the slip ratio of the second rear wheel 14 is greater than the third threshold. It is determined that the first rear wheel 13 has entered the low-adhesion coefficient road surface 30 and the second rear wheel 14 has entered the high-adhesion coefficient road surface 31.

[0070] The control device 19 acquires the wheel slip ratio of the electric vehicle 10 and, within the range of the maximum braking torque of the electric vehicle 10, determines whether the first rear wheel 13 has entered the low-friction surface 30 based on the wheel slip ratio and whether the anti-lock braking system is activated. In some embodiments, the first threshold is 1%, the second threshold is 5%, and the third threshold is 4.5%.

[0071] In some embodiments, the control method 20 for an electric vehicle further includes:

[0072] When the first rear wheel 13 enters the low-friction coefficient road surface 30 and the second rear wheel 14 is on the high-friction coefficient road surface 31, the hydraulic braking system 16 is controlled to apply front axle hydraulic braking force to the first front wheel 11 and the second front wheel 12 according to the first hydraulic braking force and the second hydraulic braking force.

[0073] After the second torque output by the motor 15 drops to zero, the braking force of the electric vehicle 10 is entirely provided by the front axle hydraulic braking force.

[0074] In some embodiments, the control method 20 for an electric vehicle further includes: controlling the hydraulic braking system 16 to apply a first front axle hydraulic braking force to the first front wheel 11, and controlling the hydraulic braking system 16 to apply a second front axle hydraulic braking force to the second front wheel 12; wherein the first front axle hydraulic braking force is less than the second front axle hydraulic braking force. Since the first rear wheel 13 travels on a low-friction coefficient road surface 30, the first rear wheel 13 locks up, and the unilateral torque of the second rear wheel 14 easily causes the electric vehicle 10 to yaw. Controlling the hydraulic braking system 16 to apply a first front axle hydraulic braking force to the first front wheel 11 less than the second front axle hydraulic braking force to the second front wheel 12 can reduce the yaw moment of the electric vehicle 10 and improve its driving stability. By setting the difference between the first front axle hydraulic braking force and the second front axle hydraulic braking force, the yaw moment of the electric vehicle 10 can be offset, thus further improving the driving stability of the electric vehicle 10.

[0075] In some embodiments, the control method 20 for an electric vehicle further includes:

[0076] Based on the functional relationship between the first front axle hydraulic braking force, the second front axle hydraulic braking force, the first hydraulic braking force, and the second hydraulic braking force, the hydraulic braking system 16 is controlled to apply the first front axle hydraulic braking force to the first front wheel 11 and to apply the second front axle hydraulic braking force to the second front wheel 12; wherein, the sum of the first front axle hydraulic braking force and the second front axle hydraulic braking force is directly proportional to the first hydraulic braking force and inversely proportional to the second hydraulic braking force; the difference between the second front axle hydraulic braking force and the first front axle hydraulic braking force is directly proportional to the second hydraulic braking force.

[0077] The first and second front axle hydraulic braking forces can be obtained using the following formulas:

[0078] pTarFA_Inc=(Mb_Act-pTarRA_LowMu*Cp_RA) / (Cp_FA*2)=

[0079] Formula (3) for pTarFA_H+pTarFA_L

[0080] delta_pFA=pTarFA_H-pTarFA_L=pTarRA_LowMu*Cp_RA / Cp_FA Formula (4)

[0081] pTarFA_Inc is the front axle hydraulic braking force, pTarFA_H is the second front axle hydraulic braking force, pTarFA_L is the first front axle hydraulic braking force, and delta_pFA is the difference between the second front axle hydraulic braking force and the first front axle hydraulic braking force.

[0082] In some embodiments, after step 22, the electric vehicle control method 20 further includes:

[0083] When the first rear wheel 13 leaves the low-adhesion road surface 30, the hydraulic braking system 16 is controlled to output the first hydraulic braking force, and the motor 15 is controlled to output the first torque.

[0084] like Figure 6 As shown, when the first rear wheel 13 leaves the low-friction coefficient surface 30, the braking force of the electric vehicle 10 returns to the level before the first rear wheel 13 entered the low-friction coefficient surface 30, and the electric vehicle 10 performs normal braking. In some embodiments, after the first rear wheel 13 leaves the low-friction coefficient surface 30, the hydraulic braking system 16 is controlled to gradually reduce the output hydraulic braking force, and the motor 15 is controlled to gradually increase the output torque. In this way, the braking force of the electric vehicle 10 is provided by the motor 15 as much as possible, which can generate more electricity for the battery of the electric vehicle 10 and increase the driving range of the electric vehicle 10.

[0085] In some embodiments, the control method 20 for an electric vehicle further includes:

[0086] If the anti-lock braking system of the electric vehicle 10 is not activated, the slip ratio of the first rear wheel 13 and the second rear wheel 14 is less than the fourth threshold, and the electric vehicle 10 has traveled a distance threshold from the moment the first rear wheel 13 enters the low-adhesion coefficient road surface 30, it is determined that the first rear wheel 13 has left the low-adhesion coefficient road surface 30.

[0087] In some embodiments, the fourth threshold is 1%.

[0088] In some embodiments, the distance threshold is determined based on the wheelbase of the electric vehicle 10.

[0089] Figure 7 The diagram shown is a partial parameter diagram of the electric vehicle control method 20 of this application. The horizontal axis represents time; between point A and point B, the electric vehicle 10 is on a high-adhesion road surface 31, corresponding to… Figure 3 Between points B and D, electric vehicle 10 is on a road surface with a low coefficient of adhesion 30; between points B and C, the corresponding... Figure 4 Point C to point D corresponds to Figure 5 Between point D and point E, electric vehicle 10 is on a high-adhesion road surface 31, corresponding to... Figure 6 .

[0090] Line a represents the torque output by motor 15. Between point A and point B, motor 15 outputs the first torque. Between point B and point D, motor 15 outputs the second torque. The second torque gradually decreases between point B and point C, and drops to zero between point C and point D. Between point D and point E, the torque output by the motor gradually increases until it reaches the first torque.

[0091] Line b represents the front axle hydraulic braking force applied by the hydraulic braking system 16 to the first front wheel 11 and the second front wheel 12. Between point B and point C, the front axle hydraulic braking force gradually increases; between point C and point D, the front axle hydraulic braking force remains at a stable level; and between point D and point E, the front axle hydraulic braking force gradually returns to the level between point A and point B.

[0092] Line c represents the hydraulic braking force applied by the hydraulic braking system 16 to the first rear wheel 13. Between points B and C, the hydraulic braking force applied by the hydraulic braking system 16 to the first rear wheel 13 gradually increases to the second hydraulic braking force. Between points C and D, the hydraulic braking force remains at a stable level. Between points D and E, the hydraulic braking force gradually returns to the level between points A and B, i.e., the first hydraulic braking force.

[0093] Line d represents the braking deceleration of electric vehicle 10. From the moment the first rear wheel 13 enters the low-friction coefficient road surface 30 until the first rear wheel 13 leaves the low-friction coefficient road surface 30, the braking deceleration remains stable.

[0094] Line e represents the maximum slip ratio of the front wheel of the electric vehicle 10. From the moment the first rear wheel 13 enters the low-friction coefficient road surface 30 until the first rear wheel 13 leaves the low-friction coefficient road surface 30, the maximum slip ratio of the front wheel remains stable.

[0095] Line f represents the maximum slip ratio of the rear wheel of electric vehicle 10. Between points B and C, the maximum slip ratio of the rear wheel increases, and between points C and D, the maximum slip ratio of the rear wheel returns to a stable level.

[0096] The g-line is the marker position of the anti-lock braking system. After the first rear wheel 13 enters the low-friction coefficient road surface 30, the anti-lock braking system is activated. After the control hydraulic braking system 16 applies a second hydraulic braking force to the first rear wheel 13, the anti-lock braking system is deactivated.

[0097] Figure 8 The diagram shown is a structural block diagram of the control device 19 for an electric vehicle provided in an embodiment of this application.

[0098] like Figure 8 As shown, the electric vehicle control device 19 includes one or more processors 41 for implementing the electric vehicle control method 20 as described above.

[0099] In some embodiments, the control device 19 of the electric vehicle may include a computer-readable storage medium 42, which may store a program that can be invoked by a processor 41, and may include a non-volatile storage medium. In some embodiments, the control device 19 of the electric vehicle may include memory 43 and an interface 44. In some embodiments, the control device 19 of the electric vehicle may also include other hardware depending on the actual application.

[0100] The computer-readable storage medium 42 of this application embodiment stores a program that, when executed by the processor 41, is used to implement the electric vehicle control method 20 described above.

[0101] This application may take the form of a computer program product implemented on one or more computer-readable storage media 42 (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing program code. The computer-readable storage media 42 includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented using any method or technology. The information may be computer-readable instructions, data structures, program modules, or other data. Examples of computer-readable storage media 42 include, but are not limited to: phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device.

[0102] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0103] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A control method for an electric vehicle, the electric vehicle comprising a motor, a hydraulic braking system, a first front wheel, a second front wheel, a first rear wheel, a second rear wheel, and a rear axle connecting the first rear wheel and the second rear wheel, wherein the motor is disposed on the rear axle, and the hydraulic braking system is connected to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel; characterized in that, The method includes: When both the first rear wheel and the second rear wheel are on a road surface with a high coefficient of adhesion, the motor is controlled to output a first torque, and the hydraulic braking system is controlled to apply a first hydraulic braking force to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel. When the first rear wheel enters a low-friction coefficient road surface and the second rear wheel is on a high-friction coefficient road surface, the motor is controlled to output a second torque that is less than the first torque, and the hydraulic braking system is controlled to apply a second hydraulic braking force to the first rear wheel according to the first torque; wherein the friction coefficient of the low-friction coefficient road surface is less than the friction coefficient of the high-friction coefficient road surface.

2. The control method for an electric vehicle according to claim 1, characterized in that, The step of controlling the hydraulic braking system to apply a second hydraulic braking force to the first rear wheel based on the first torque includes: Based on the electric vehicle model and the first torque, the hydraulic braking system is controlled to apply a second hydraulic braking force to the first rear wheel.

3. The control method for an electric vehicle according to claim 1, characterized in that, The method further includes: When the first rear wheel enters a low-friction coefficient road surface and the second rear wheel is on a high-friction coefficient road surface, the hydraulic braking system is controlled to apply front axle hydraulic braking force to the first front wheel and the second front wheel based on the first hydraulic braking force and the second hydraulic braking force.

4. The control method for an electric vehicle according to claim 3, characterized in that, The first front wheel and the first rear wheel are located on the same side of the electric vehicle, and the second front wheel and the second rear wheel are located on the same side of the electric vehicle; controlling the hydraulic braking system to apply front axle hydraulic braking force to the first front wheel and the second front wheel includes: controlling the hydraulic braking system to apply a first front axle hydraulic braking force to the first front wheel, and controlling the hydraulic braking system to apply a second front axle hydraulic braking force to the second front wheel; wherein, the first front axle hydraulic braking force is less than the second front axle hydraulic braking force.

5. The control method for an electric vehicle according to claim 4, characterized in that, The control of the hydraulic braking system to apply a first front axle hydraulic braking force to the first front wheel and to apply a second front axle hydraulic braking force to the second front wheel includes: Based on the functional relationship between the first front axle hydraulic braking force, the second front axle hydraulic braking force, the first hydraulic braking force, and the second hydraulic braking force, the hydraulic braking system is controlled to apply a first front axle hydraulic braking force to the first front wheel, and the hydraulic braking system is controlled to apply a second front axle hydraulic braking force to the second front wheel. The sum of the first front axle hydraulic braking force and the second front axle hydraulic braking force is directly proportional to the first hydraulic braking force and inversely proportional to the second hydraulic braking force; the difference between the second front axle hydraulic braking force and the first front axle hydraulic braking force is directly proportional to the second hydraulic braking force.

6. The control method for an electric vehicle according to claim 1, characterized in that, The method further includes: The maximum braking torque of the electric vehicle is obtained based on the road conditions of the low-adhesion coefficient road surface and the high-adhesion coefficient road surface. If the braking torque of the electric vehicle is less than the maximum braking torque, the anti-lock braking system of the electric vehicle is activated. The maximum slip ratio of the front wheel of the electric vehicle is less than a first threshold, the maximum slip ratio of the first rear wheel and the second rear wheel is greater than a second threshold, and the difference between the slip ratio of the first rear wheel and the slip ratio of the second rear wheel is greater than a third threshold. It is determined that the first rear wheel has entered a low-friction coefficient road surface and the second rear wheel has entered a high-friction coefficient road surface.

7. The control method for an electric vehicle according to claim 1, characterized in that, The control of the motor to output a second torque less than the first torque includes: The second torque is determined based on the vehicle speed at the moment the first rear wheel enters the low-friction surface and the deceleration of the electric vehicle.

8. The control method for an electric vehicle according to claim 1, characterized in that, After controlling the motor to output a second torque less than the first torque, and controlling the hydraulic braking system to apply a second hydraulic braking force to the first rear wheel based on the first torque, the method includes: When the first rear wheel leaves the road surface with a low coefficient of adhesion, the hydraulic braking system is controlled to output the first hydraulic braking force, and the motor is controlled to output the first torque.

9. The control method for an electric vehicle according to claim 8, characterized in that, The method further includes: If the anti-lock braking system of the electric vehicle is not activated, the slip ratio of the first rear wheel and the second rear wheel is less than the fourth threshold, and the distance traveled by the electric vehicle from the moment the first rear wheel enters the low-friction coefficient road surface reaches the distance threshold, it is determined that the first rear wheel leaves the low-friction coefficient road surface.

10. The control method for an electric vehicle according to claim 9, characterized in that, The distance threshold is determined based on the wheelbase of the electric vehicle.

11. A computer-readable storage medium, characterized in that, It stores a program that, when executed by a processor, implements the control method for an electric vehicle as described in any one of claims 1-10.

12. A control device for an electric vehicle, characterized in that, It includes one or more processors for implementing the control method for an electric vehicle according to any one of claims 1-10.

13. An electric vehicle, characterized in that, include: The electric motor, hydraulic braking system, first front wheel, second front wheel, first rear wheel, second rear wheel, rear axle connecting the first rear wheel and the second rear wheel, and control device for an electric vehicle as claimed in claim 12; The motor is mounted on the rear axle, and the hydraulic braking system is connected to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel. The control device is communicatively connected to the motor and the hydraulic braking system, and is used to control the output torque of the motor and to control the hydraulic braking system to apply hydraulic braking force to the first front wheel, the second front wheel, the first rear wheel, and the second rear wheel.

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