Control method for electric vehicle and electric vehicle

Abstract

The invention discloses a control method for an electric vehicle and the electric vehicle, and relates to the technical field of new energy automobiles. The control method is used for controlling a driving system and a braking system to achieve safe braking of the electric vehicle after braking of two wheels of the electric vehicle fails, and comprises the steps that in the running process of the electric vehicle, before the electric vehicle is braked, the driving torque output by the driving system is controlled to change along with the change of the opening degree of an accelerator pedal; the direction of the driving torque is the same as the rotating speed direction of wheels of the electric vehicle. In the braking process that braking of the left front wheel and the right rear wheel of the electric vehicle fails, the driving system is controlled to output reverse torque to the two front wheels and the two rear wheels of the electric vehicle, and the direction of the reverse torque is opposite to the rotating speed direction of the two front wheels. According to the scheme, effective braking can be achieved, no obvious yawing exists, and the braking safety and stability of the electric vehicle are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electric vehicles, and more particularly, to a control method for an electric vehicle and an electric vehicle. BACKGROUND

[0002] An electronic mechanical brake (EMB) system completely replaces the hydraulic transmission medium in a traditional hydraulic or pneumatic brake system with an electric control brake. The electronic mechanical brake system combines electronic technology and mechanical brake principles, controls the action of the brake through an electronic control unit, and realizes the braking function of the vehicle. When the wheel end brake device of two wheels fails or the wheel speed sensor fails, resulting in brake failure, the brake failure wheel loses braking force and can only rely on the normally braking wheels to brake, which affects the braking force and makes the electronic mechanical brake system unable to meet the braking demand of the driver. During braking, when two wheels fail to brake, the imbalance of braking torque on both sides of the vehicle will cause the vehicle to yaw or run off and spin, and even cause the vehicle to lose stability, causing serious driving safety problems.

[0003] Therefore, how to realize safe braking when two wheels of an electric vehicle fail to brake is a problem to be solved. SUMMARY

[0004] The present application provides a control method for an electric vehicle and an electric vehicle. When two wheels of the electric vehicle fail to brake, reverse torque is output by the drive system to brake, which can effectively brake without obvious yaw, and improves the safety and stability of the electric vehicle braking.

[0005] In a first aspect, the present application provides a control method for an electric vehicle. The control method is used to control the drive system and the brake system to realize safe braking of the electric vehicle after two wheels of the electric vehicle fail to brake. The control method includes, during driving of the electric vehicle, before braking of the electric vehicle, controlling the drive torque output by the drive system to change with the opening of the accelerator pedal, and the direction of the drive torque is the same as the direction of the wheel speed of the electric vehicle. During braking of the left front wheel and the right rear wheel of the electric vehicle, the drive system outputs reverse torque to the two front wheels and the two rear wheels of the electric vehicle, respectively, and the direction of the reverse torque is opposite to the direction of the wheel speed of the two front wheels.

[0006] The wheel brake failure in the present application refers to the wheel end brake device for braking the wheel in the brake system cannot normally output brake force to the wheel. The brake system includes four wheel end brake devices, and each wheel end brake device is used to output brake force to the wheel of the electric vehicle. The four wheel end brake devices correspond to the four wheels one by one, and the four wheel end brake devices are used to output brake force respectively. In the normal state, the four wheel end brake devices are used to output the brake force indicated by the opening degree of the brake pedal. When the wheel brake fails, the wheel end brake device for braking the wheel cannot output brake force. The causes of wheel brake failure include actuator failure, brake motor failure, controller failure, and wheel speed sensor failure. When the wheel brake fails, the brake system cannot output brake force to the wheel, which will reduce the total brake force that the brake system can generate, affecting the braking safety and stability of the electric vehicle. The brake failure of two wheels includes the brake failure of two coaxial wheels, the brake failure of two wheels on the same side, and the brake failure of two diagonal wheels. The two front wheels or the two rear wheels of the electric vehicle are coaxial wheels, the two left wheels or the two right wheels of the electric vehicle are wheels on the same side, and the left front wheel and the right rear wheel of the electric vehicle are diagonal wheels or the right front wheel and the left rear wheel are diagonal wheels.

[0007] During the driving of the electric vehicle, before starting braking, the brake failure of two wheels basically does not cause any impact, and the drive system outputs the drive torque indicated by the opening degree of the accelerator pedal, which is used to drive the wheels. The direction of the drive torque is the same as the direction of the speed of the wheels of the electric vehicle. The brake failure of two wheels of the electric vehicle occurs before or after starting braking, and the brake system detects the failure and controls the drive system. During the braking process of the left front wheel and the right rear wheel of the electric vehicle, the drive system outputs reverse torque to the two front wheels and the two rear wheels of the electric vehicle respectively, and the direction of the reverse torque is opposite to the direction of the speed of the wheels.

[0008] The size of the reverse torque in this application is the absolute value of the output torque of the drive system, increasing the output of the reverse torque is equal to increasing the absolute value of the output torque. In the process of forward driving of the electric vehicle, the positive torque is used to drive the vehicle, and the negative torque is used to brake the vehicle, at this time the driving torque is positive torque and the reverse torque is negative torque. The drive system changes the phase of the three-phase current output by the motor controller to the drive motor to make the rotor cut the magnetic field generated by the stator winding, and the kinetic energy of the rotor becomes electric energy input into the power battery, at this time the drive motor outputs negative torque. The motor controller changes the size of the three-phase current output to the motor, which can increase or decrease the positive or negative torque output by the drive. It should be understood that in the process of reversing the electric vehicle, the positive torque is used to brake the vehicle, and the negative torque is used to drive the vehicle. In this application, the forward driving of the electric vehicle is taken as an example for description, and the similar description can be referred to in the scenario of reversing the electric vehicle, the direction of the torque output by the drive motor can be modified accordingly, and the function of the torque should remain consistent.

[0009] The accelerator pedal in this application is also called the electric gate pedal or the throttle pedal. The opening degree of the accelerator pedal indicates the size of the driving force required by the driver, and the greater the opening degree of the accelerator pedal, the greater the demand of the driver for driving, and the greater the torque required by the drive motor. The drive system controls the current output to the drive motor according to the opening degree of the accelerator pedal to make the drive motor output the torque indicated by the opening degree of the throttle pedal, and the greater the opening degree of the accelerator pedal, the greater the current and the greater the torque output by the drive motor, and the smaller the opening degree of the accelerator pedal, the smaller the current and the smaller the torque output by the drive motor. The driving torque output by the drive system changes with the change of the opening degree of the throttle pedal.

[0010] When the left front wheel and the right rear wheel brake failure, the drive system outputs reverse torque to the two front wheels and the two rear wheels respectively in the process of braking of the left front wheel and the right rear wheel brake failure.

[0011] It should be understood that because it is necessary to control the drive system to output reverse torque to the two front wheels and the two rear wheels, at least two drive motors are included in the drive system, the two front wheels are driven by at least one drive motor, and the two rear wheels are driven by at least one drive motor. When the two coaxial wheels are driven by two drive motors respectively, the two drive motors are controlled to output reverse torque at the same time to brake the two coaxial wheels.

[0012] In another embodiment, when the right front wheel and the left rear wheel brake failure, the drive system outputs reverse torque to the two front wheels and the two rear wheels respectively in the process of braking of the right front wheel and the left rear wheel brake failure.

[0013] According to the scheme of the application, when diagonal wheel braking fails, reverse torques are output to the two front wheels and the two rear wheels by controlling the driving system to compensate for the failure of the braking force, the output of a larger braking force is achieved, the braking distance is shortened, and the safety and stability of the braking of the electric vehicle are improved.

[0014] In combination with the first aspect, in some implementations of the first aspect, the control method further includes, in the braking process in which the left front wheel and the right rear wheel fail to brake, first controlling the driving system to output reverse torques to the two front wheels and the two rear wheels, respectively, and then controlling the braking system to output braking forces to the right front wheel and the left rear wheel of the electric vehicle.

[0015] In the braking process in which the left front wheel and the right rear wheel fail to brake, the driving system outputs reverse torques to the two front wheels and the two rear wheels, but the maximum braking capacity that can be generated by the reverse torques is smaller than the maximum braking effect of the braking forces output by the braking system. Therefore, when the braking force demand is large, the reverse torques output by the driving system to the two front wheels and the two rear wheels are not enough to generate sufficient braking effect, at which time the braking system is controlled to output braking forces to the two wheels that are normally braked, thereby effectively improving the braking capacity by diagonal braking.

[0016] Specifically, when the left front wheel and the right rear wheel fail to brake, in the braking process in which the left front wheel and the right rear wheel fail to brake, first controlling the driving system to output reverse torques to the two front wheels and the two rear wheels, respectively, and then controlling the braking system to output braking forces to the right front wheel and the left rear wheel of the electric vehicle.

[0017] In another embodiment, when the right front wheel and the left rear wheel fail to brake, in the braking process in which the right front wheel and the left rear wheel fail to brake, first controlling the driving system to output reverse torques to the two front wheels and the two rear wheels, respectively, and then controlling the braking system to output braking forces to the left front wheel and the right rear wheel of the electric vehicle.

[0018] According to the scheme of the application, when diagonal wheel braking fails, reverse torques are output to the two front wheels and the two rear wheels by controlling the driving system to compensate for the failure of the braking force, the output of a larger braking force is achieved, the braking distance is shortened, and the safety and stability of the braking of the electric vehicle are improved.

[0019] In combination with the first aspect, in some implementations of the first aspect, the control method specifically includes, in the braking process in which the left front wheel and the right rear wheel fail to brake, when the opening degree of the brake pedal of the electric vehicle is less than a preset opening degree, controlling the braking system to output a braking force of zero. When the opening degree of the brake pedal is increased to be greater than or equal to the preset opening degree, the braking system is controlled to output braking forces to the right front wheel and the left rear wheel of the electric vehicle.

[0020] The opening degree of the brake pedal is used to determine whether the driver needs emergency braking. When the opening degree of the brake pedal is less than a preset opening degree, the driver does not need emergency braking. At this time, the control system controls the driving system to output reverse torques to the two front wheels and the two rear wheels of the electric vehicle. At this time, the braking force required by the electric vehicle can be compensated by the reverse torques output by the driving system, and the brake system does not output braking force to the two normally braked wheels.

[0021] When the opening degree of the brake pedal is greater than or equal to the preset opening degree, it is determined that the driver needs emergency braking. At this time, the braking force required by the electric vehicle cannot be completely compensated by the reverse torques output by the driving system, and therefore the control system controls the brake system to output braking force to the two normally braked wheels. The diagonal wheels are further braked to improve the braking force and effectively realize emergency braking. The preset opening degree is pre-calibrated according to real vehicle experiments and / or model calculations, or is pre-set by comprehensively considering the vehicle requirements and vehicle performance.

[0022] According to the scheme of the present application, whether the electric vehicle needs emergency braking is determined according to the opening degree of the brake pedal, so as to control whether the brake system outputs braking force to the diagonally braked wheels. The braking ability is further improved, and the safety and stability of the electric vehicle braking are improved.

[0023] In combination with the first aspect, in some implementations of the first aspect, the control method specifically includes, in the braking process of the left front wheel and the right rear wheel brake failure, before the reverse torque output by the driving system to the two front wheels and the two rear wheels increases to a preset torque, controlling the brake system to output zero braking force. After the reverse torque output by the driving system to the two front wheels and the two rear wheels increases to the preset torque, the control system controls the brake system to output braking force to the right front wheel and the left rear wheel of the electric vehicle.

[0024] During the process of outputting reverse torques to the two front wheels and the two rear wheels by the driving system, the braking forces received by the two sides of the electric vehicle are equal, and there is no yawing during braking, which is more stable. When the reverse torque output by the driving system to the left front wheel and the right rear wheel brake failure is less than the preset torque, the braking force can be improved by increasing the reverse torque output, without the need to control the brake system to output braking force to the two normally braked wheels. When the reverse torque output by the driving system to the left front wheel and the right rear wheel brake failure increases to the preset torque, the braking force cannot be improved by increasing the reverse torque output, and therefore the control system controls the brake system to output braking force to the diagonally braked wheels to further improve the braking ability. The preset torque is pre-calibrated according to real vehicle experiments and / or model calculations, or is pre-set by comprehensively considering the vehicle requirements and vehicle performance.

[0025] According to the scheme of the application, whether the braking system outputs braking force to the two normal braking wheels is controlled according to whether the output torque of the driving system reaches the maximum braking effect, thereby improving the safety and stability of braking of the electric vehicle.

[0026] With reference to the first aspect, in some implementations of the first aspect, during the process in which the reverse torque output by the driving system to the two front wheels and the two rear wheels increases to the preset torque, the control method further comprises controlling the reverse torque output by the driving system to the two front wheels to change with the average slip ratio of the two front wheels, and controlling the reverse torque output by the driving system to the two rear wheels to change with the average slip ratio of the two rear wheels.

[0027] The driving system comprises a resolver sensor, and the rotational speed of the driving motor can be obtained through a resolver signal of the resolver sensor. The angular speed of the wheels can be calculated through the rotational speed of the driving motor and the transmission ratio of the electric vehicle, and further combined with the wheel radius and the speed of the electric vehicle to obtain the slip ratio of each wheel. The slip ratio of the wheels affects the braking effect of the wheels, and when the slip ratio of the wheels is too large, the wheels slip, and at this time the wheels cannot generate effective braking force. Since the slip ratio of the wheels directly affects the braking effect of the wheels, the driving system controls the size of the reverse torque output to regulate the slip ratio of the wheels. Specifically, when the average slip ratio of the two wheels is less than a preset slip ratio, the driving system is controlled to increase the reverse torque output to the two wheels, and when the average slip ratio of the two wheels is greater than the preset slip ratio, the driving system is controlled to decrease the reverse torque output to the two wheels. Thus, the reverse torque output by the driving system can generate effective braking effect.

[0028] The preset slip ratio is pre-calibrated according to real vehicle experiments and / or model calculation, or is pre-set by comprehensively considering the whole vehicle demand and vehicle performance.

[0029] According to the scheme of the application, the size of the reverse torque output by the driving system is adjusted according to the average slip ratio of the two wheels, so that the slip ratio of the two wheels is within a suitable range, the reverse torque output by the driving system can generate better braking effect, and the safety and stability of braking of the electric vehicle are improved.

[0030] With reference to the first aspect, in some implementations of the first aspect, the control method specifically comprises, in the braking process in which the left front wheel and the right rear wheel are out of order, controlling the reverse torque output by the driving system to the two front wheels and the two rear wheels to change with the opening of the brake pedal, and controlling the reverse torque output by the driving system to change with the opening of the brake pedal.

[0031] The brake pedal in the present application is also called as the brake or the brake pedal. The opening degree of the brake pedal indicates the size of the brake force required by the driver. The greater the opening degree of the brake pedal, the greater the requirement of the driver for the brake, and the greater the brake force required to be output by the brake system. When the electric vehicle is in normal driving, the brake system controls the wheel end brake device according to the opening degree of the brake pedal, so as to output the brake force indicated by the opening degree of the brake pedal. The greater the opening degree of the brake pedal, the greater the brake force output by the wheel end brake device. The smaller the opening degree of the brake pedal, the smaller the brake force output by the wheel end brake device. The brake force output by the brake system changes with the change of the opening degree of the brake pedal.

[0032] In the braking process of the left front wheel and the right rear wheel brake failure, the reverse torque output by the driving system changes with the change of the opening degree of the brake pedal. In the driving process of the electric vehicle, before braking, the driving torque output by the driving system changes with the change of the opening degree of the accelerator pedal. After starting braking and both wheels brake failure, the driving system outputs the reverse torque, and the size of the reverse torque is determined according to the opening degree of the brake pedal. The size of the reverse torque changes with the change of the opening degree of the brake pedal.

[0033] According to the scheme of the present application, in the braking process of the diagonal wheel brake failure, the reverse torque output by the driving system changes with the change of the opening degree of the brake pedal. The adjustment of the reverse torque is made according to the indication of the driver, which improves the operability of the electric vehicle and maintains the responsiveness and effectiveness of the braking.

[0034] In combination with the first aspect, in some implementations of the first aspect, the control method specifically comprises, in the braking process of the left front wheel and the right rear wheel brake failure, controlling the reverse torque output by the driving system to the two front wheels to be always greater than the reverse torque output to the two rear wheels, and then controlling the brake force output by the brake system to the right front wheel to be always greater than the brake force output to the left rear wheel.

[0035] When the electric vehicle brakes, the center of gravity of the electric vehicle moves forward, resulting in that the two front wheels obtain greater downforce, the load of the front wheels increases, so as to provide greater grip and brake force. The downforce of the rear wheels decreases, and the load of the rear wheels decreases. If the same or greater brake force as the two front wheels is allocated to the two rear wheels, the rear wheels will be locked before the front wheels due to insufficient normal force. Once the rear wheels are locked, the electric vehicle will lose lateral grip, and is easy to spin or slide to cause the vehicle to lose control. The front wheels are steering wheels, and even if locking occurs, it will only cause steering failure, and the electric vehicle slides along a straight line, which is relatively easy to control. Therefore, in the process of controlling the reverse torque output by the driving system or the brake force output by the brake system, the reverse torque output by the driving system to the front wheels is greater than the reverse torque output to the rear wheels, and the brake force output by the brake system to the front wheels is greater than the brake force output to the rear wheels, so that the brake force received by the two front wheels is greater than the brake force received by the two rear wheels.

[0036] According to the scheme of the application, the control method controls the driving system to output a reverse torque to the front wheels greater than a reverse torque output to the rear wheels, and controls the braking system to output a braking force to the front wheels greater than a braking force output to the rear wheels, and the distribution of the reverse torque and the braking force enables the electric vehicle to obtain greater grip and braking effect, improving the safety and stability of braking of the electric vehicle.

[0037] In combination with the first aspect, in some implementations of the first aspect, the control method further comprises, in a braking process in which the left front wheel and the left rear wheel of the electric vehicle are braking failure, or in a braking process in which the right front wheel and the right rear wheel of the electric vehicle are braking failure, controlling the driving system to output a reverse torque to the two front wheels and the two rear wheels.

[0038] When the two wheels on the same side are failure, if the braking system outputs a braking force, it will cause the braking forces received by the two sides of the electric vehicle to be unequal and generate a yawing torque, affecting the stability of the vehicle, so the braking system cannot output a braking force to the wheels of the electric vehicle. At this time, the driving system is controlled to output a reverse torque to the two front wheels and the two rear wheels.

[0039] According to the scheme of the application, when the two wheels on the same side are braking failure, the driving system is controlled to output a reverse torque to make up for the lack of braking force, realizing the output of the braking force, effectively braking, and improving the safety and stability of braking of the electric vehicle.

[0040] In combination with the first aspect, in some implementations of the first aspect, the control method specifically comprises, in a braking process in which the left front wheel and the left rear wheel of the electric vehicle are braking failure, or in a braking process in which the right front wheel and the right rear wheel of the electric vehicle are braking failure, controlling the reverse torque output by the driving system to change with the opening of the brake pedal.

[0041] In the braking process in which the left front wheel and the left rear wheel are braking failure, or in the braking process in which the right front wheel and the right rear wheel are braking failure, the reverse torque output by the driving system changes with the opening of the brake pedal. Before braking during the driving of the electric vehicle, the driving torque output by the driving system changes with the opening of the accelerator pedal, and after the start of braking and the two wheels on the same side are braking failure, the driving system outputs a reverse torque, and the size of the reverse torque is determined according to the opening of the brake pedal, and the size of the reverse torque changes with the opening of the brake pedal.

[0042] According to the scheme of the application, in the braking process in which the two wheels on the same side are braking failure, the reverse torque output by the driving system changes with the opening of the brake pedal, and the adjustment of the reverse torque is made according to the indication of the driver, improving the operability of the electric vehicle and maintaining the responsiveness and effectiveness of braking.

[0043] With reference to the first aspect, in some implementations of the first aspect, during the controlling of the driving system to output the reverse torques to the two front wheels and the two rear wheels, the control method further includes that the sum of the reverse torques output by the driving system to the two front wheels is always greater than the sum of the reverse torques output to the two rear wheels.

[0044] When the electric vehicle brakes, the center of gravity of the electric vehicle moves forward, resulting in that the two front wheels obtain greater downward pressure, the load of the front wheels increases, and thus the front wheels can provide greater grip and braking force. The downward pressure of the rear wheels decreases, and the load of the rear wheels decreases. If the two rear wheels are allocated the same or greater braking force as the two front wheels, the rear wheels will lock up before the front wheels due to insufficient normal pressure, and once the rear wheels lock up, the electric vehicle will lose lateral grip and be prone to spin or slide, causing the vehicle to lose control. The front wheels are steering wheels, and even if they lock up, they will only cause steering failure, and the electric vehicle will slide along a straight line, which is relatively easier to control. Therefore, during the controlling of the driving system to output the reverse torques, the sum of the reverse torques output by the driving system to the two front wheels is greater than the sum of the reverse torques output to the two rear wheels, so that the braking force received by the two front wheels is greater than the braking force received by the two rear wheels.

[0045] According to the scheme of the present application, the sum of the reverse torques output by the driving system to the two front wheels is greater than the sum of the reverse torques output to the two rear wheels, and the distribution of the reverse torques enables the electric vehicle to obtain greater grip and braking effect, thereby improving the safety and stability of the braking of the electric vehicle.

[0046] With reference to the first aspect, in some implementations of the first aspect, the control method further includes, during the braking process in which the two front wheels of the electric vehicle fail to brake, controlling the braking system to output braking force to the two rear wheels of the electric vehicle, and controlling the driving system to output reverse torque to the two front wheels.

[0047] When the two wheels on the same shaft fail to brake, the driving system is controlled to output reverse torque to the two wheels on the braking-failed shaft, and the braking system is controlled to output braking force to the two wheels on the normally-braking shaft, so as to brake.

[0048] In another embodiment, during the braking process in which the two rear wheels of the electric vehicle fail to brake, the braking system is controlled to output braking force to the two front wheels of the electric vehicle, and the driving system is controlled to output reverse torque to the two rear wheels.

[0049] According to the scheme, the driving system is controlled to output reverse torques to the two wheels of the wheel shaft where the brake failure occurs to compensate for the failure of the braking force, and the braking system is controlled to output braking forces to the two wheels of the normal shaft, so that the yaw of the electric vehicle caused by unilateral wheel braking is avoided, a large braking force is output, the braking distance is shortened, and the safety and stability of the braking of the electric vehicle are improved.

[0050] In combination with the first aspect, in some implementations of the first aspect, the control method specifically includes, in the braking process where the two front wheels fail to brake, controlling the braking force output by the braking system to the two rear wheels to change with the opening of the brake pedal, and controlling the reverse torque output by the driving system to change with the opening of the brake pedal.

[0051] In the braking process where the two front wheels fail to brake, the reverse torque output by the driving system is controlled to change with the opening of the brake pedal. Before braking, the driving torque output by the driving system is controlled to change with the opening of the accelerator pedal during the driving of the electric vehicle, after the braking is started and the two wheels on the same shaft fail to brake, the driving system is controlled to output a reverse torque, and the size of the reverse torque is determined according to the opening of the brake pedal, and the size of the reverse torque changes with the opening of the brake pedal.

[0052] In another embodiment, in the braking process where the two rear wheels fail to brake, the braking force output by the braking system to the two front wheels is controlled to change with the opening of the brake pedal, and the reverse torque output by the driving system is controlled to change with the opening of the brake pedal.

[0053] According to the scheme, in the braking process where the two wheels on the same shaft fail to brake, the reverse torque output by the driving system is controlled to change with the opening of the brake pedal, and the adjustment of the reverse torque is performed according to the indication of the driver, so that the operability of the electric vehicle is improved, and the responsiveness and effectiveness of the braking are maintained.

[0054] In combination with the first aspect, in some implementations of the first aspect, in the process of controlling the driving system to output the reverse torque to the two front wheels, the control method further includes controlling the reverse torque output by the driving system to the two front wheels to change with the average slip ratio of the two front wheels.

[0055] The slip ratio of the wheel affects the braking effect of the wheel. When the slip ratio of the wheel is too large, the wheel slips, and the wheel cannot generate an effective braking force. Since the slip ratio of the wheel directly affects the braking effect of the wheel, the driving system adjusts the slip ratio of the wheel by controlling the size of the reverse torque output.

[0056] In another embodiment, during the braking process of two rear wheel brake failures, the control brake system changes the brake force output to the two front wheels with the change of the opening degree of the brake pedal, and the control drive system changes the reverse torque output to the two rear wheels with the change of the average slip ratio of the two rear wheels.

[0057] According to the scheme of the present application, the size of the reverse torque output by the drive system is adjusted according to the average slip ratio of the wheels, so that the slip ratio of the wheels is within a suitable range, the reverse torque output by the drive system can produce better braking effect, and the safety and stability of the braking of the electric vehicle are improved.

[0058] In a second aspect, the present application provides an electric vehicle, the electric vehicle comprising a brake pedal, an accelerator pedal, a brake system, a drive system and four wheels, the opening degree of the brake pedal being used to instruct the brake system to output a brake force, the accelerator pedal being used to instruct the drive system to output a drive torque, and the brake system and the drive system being used to perform the control method as described in the first aspect and various implementation manners thereof.

[0059] The beneficial effects of other aspects can refer to the beneficial effects described in the first aspect, which will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 is a schematic diagram of an electric vehicle provided by an embodiment of the present application;

[0061] Figure 2 is a schematic diagram of a brake system architecture provided by an embodiment of the present application;

[0062] Figure 3 is a schematic diagram of an electric vehicle architecture provided by an embodiment of the present application;

[0063] Figure 4 is a schematic diagram of a drive system and brake system control during a single wheel brake failure braking process provided by an embodiment of the present application;

[0064] Figure 5 is a schematic diagram of a single wheel brake failure braking process scenario provided by an embodiment of the present application;

[0065] Figure 6 is a schematic diagram of a drive system and brake system control during another single wheel brake failure braking process provided by an embodiment of the present application;

[0066] Figure 7 is a schematic diagram of another single wheel brake failure braking process scenario provided by an embodiment of the present application;

[0067] Figure 8 is a schematic diagram of a brake system control during a single wheel brake failure braking process provided by an embodiment of the present application;

[0068] Figure 9 is another single-wheel brake failure braking process scene schematic diagram provided by an embodiment of the application;

[0069] Figure 10 is another single-wheel brake failure braking process braking system control schematic diagram provided by an embodiment of the application;

[0070] Figure 11 is a single-wheel brake failure braking process scene schematic diagram provided by an embodiment of the application;

[0071] Figure 12 is a double-wheel brake failure braking process driving system and braking system control schematic diagram provided by an embodiment of the application;

[0072] Figure 13 is a double-wheel brake failure braking process scene schematic diagram provided by an embodiment of the application;

[0073] Figure 14 is another double-wheel brake failure braking process driving system control schematic diagram provided by an embodiment of the application;

[0074] Figure 15 is another double-wheel brake failure braking process scene schematic diagram provided by an embodiment of the application;

[0075] Figure 16 is another double-wheel brake failure braking process driving system and braking system control schematic diagram provided by an embodiment of the application;

[0076] Figure 17 is another double-wheel brake failure braking process scene schematic diagram provided by an embodiment of the application;

[0077] Figure 18 is a double-wheel brake failure braking control flow schematic diagram provided by an embodiment of the application;

[0078] Figure 19 is a multi-wheel brake failure braking process driving system control schematic diagram provided by an embodiment of the application;

[0079] Figure 20 is another multi-wheel brake failure braking process driving system control schematic diagram provided by an embodiment of the application;

[0080] Figure 21 is another multi-wheel brake failure braking process driving system control schematic diagram provided by an embodiment of the application;

[0081] Figure 22 is a multi-wheel brake failure braking process scene schematic diagram provided by an embodiment of the application;

[0082] Figure 23is another multi-wheel brake failure braking process scenario schematic diagram provided by an embodiment of the present application.

[0083] Figure 24 is a multi-wheel brake failure braking control flow schematic diagram provided by an embodiment of the present application. DETAILED DESCRIPTION

[0084] The technical solutions in the present application will be described below with reference to the drawings. The detailed description of the following embodiments and the drawings are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0085] The braking capability of an electric vehicle is an important capability that affects the safety of the electric vehicle. An electronic mechanical brake system usually brakes four wheels of the electric vehicle respectively to realize the braking function. When wheel end brake devices of the wheels fail or wheel speed sensors fail, resulting in brake failure, the wheels with brake failure lose braking force and can only rely on the wheels with normal braking to brake, which affects the braking force and makes the electronic mechanical brake system unable to meet the braking demand of the driver. During braking, when some wheels brake fail, the vehicle being braked will yaw or deviate and spin out due to the imbalance of braking torques on both sides of the vehicle, and even can lose stability, causing serious driving safety problems.

[0086] Based on the above problems, the embodiments of the present application provide a control method for an electric vehicle and the electric vehicle. When two wheels brake fail, reverse torque is output by a driving system to brake, which can effectively brake without obvious yaw, and improves the safety and stability of the electric vehicle braking.

[0087] Figures 1-3 is a schematic diagram of an electric vehicle 10 architecture provided by an embodiment of the present application.

[0088] As shown in Figure 1 , the electric vehicle 10 includes a vehicle controller 20, a driving system 50 and a brake system 60. The driving system 50 includes a motor controller 40 and a driving motor 30. The motor controller 40 is used to output current to the driving motor 30 to control the driving motor 30 to output torque to drive the electric vehicle 10. The brake system 60 is used to output braking force to brake four wheels of the electric vehicle 10.

[0089] As shown in Figure 2 , the brake system 60 includes a brake pedal and four wheel end brake devices. During driving of the electric vehicle 10, when the electric vehicle 10 needs to brake, the driver steps on the brake pedal, and the brake system 60 controls the four wheel end brakes to output braking force to brake the electric vehicle 10.

[0090] The brake pedal in this application is also called as the brake or the brake pedal. The opening degree of the brake pedal indicates the size of the brake force required by the driver. The greater the opening degree of the brake pedal, the greater the demand of the driver for braking, and the greater the brake force required by the brake system 60 to output. When the electric vehicle 10 is in normal driving process, the brake system 60 controls the wheel end brake device according to the opening degree of the brake pedal, so as to output the brake force indicated by the opening degree of the brake pedal. The greater the opening degree of the brake pedal, the greater the brake force output by the wheel end brake device. The smaller the opening degree of the brake pedal, the smaller the brake force output by the wheel end brake device. The brake force output by the brake system 60 changes with the change of the opening degree of the brake pedal.

[0091] Exemplarily, the brake system includes four wheel end brake devices, which include wheel end brake device 61, wheel end brake device 62, wheel end brake device 63 and wheel end brake device 64. The wheel end brake device 61 is used to brake the wheel 51, the wheel end brake device 62 is used to brake the wheel 52, the wheel end brake device 63 is used to brake the wheel 53, and the wheel end brake device 64 is used to brake the wheel 54.

[0092] In an embodiment, the electric vehicle 10 is a distributed four-drive motor driving architecture, and the drive motors are arranged on the driven wheel side and controlled by separate motor controllers 40. In an embodiment, the electric vehicle 10 is also a centralized drive motor driving architecture, and the drive motors for driving two front wheels or two rear wheels are arranged together. The motor controller 40 is one or more. The motor controller 40 is one-to-one corresponding to the drive motor, or one motor controller 40 corresponds to multiple drive motors. The motor controller 40 is used to control one or more drive motors to output torque to drive the electric vehicle 10.

[0093] In an embodiment, as shown in (a) of FIG. 1, Figure 3 the electric vehicle 10 is a distributed four-drive motor driving architecture, and the drive motors are arranged on the driven wheel side and controlled by separate motor controllers. The electric vehicle 10 is also a centralized four-drive motor driving architecture as shown in (b) of FIG. 1, Figure 3 two drive motors for driving two front wheels or two rear wheels are arranged together.

[0094] Exemplarily, the electric vehicle 10 includes four motor controllers, which include motor controller 41, motor controller 42, motor controller 43 and motor controller 44. The four motors include drive motor 31, drive motor 31, drive motor 33 and drive motor 34. The motor controller 41 controls the drive motor 31 to drive the wheel 51, the motor controller 42 controls the drive motor 32 to drive the wheel 52, the motor controller 43 controls the drive motor 33 to drive the wheel 53, and the motor controller 44 controls the drive motor 34 to drive the wheel 54.

[0095] In one embodiment, the electric vehicle 10 is also a centralized drive motor architecture as shown in (c) in Figure 3 In one embodiment, the electric vehicle 10 is also a centralized drive motor architecture as shown in (c) in

[0096] In one embodiment, the electric vehicle 10 is also a centralized drive motor architecture as shown in (c) in

[0097] The electric vehicle 10 also includes an accelerator pedal and a steering wheel. The accelerator pedal is used to indicate the driving system to output driving torque to the wheels of the electric vehicle 10. The steering angle of the steering wheel is used to indicate the steering angle of the two front wheels.

[0098] The accelerator pedal in this application is also called a throttle pedal or a gas pedal. The opening of the accelerator pedal indicates the driving force required by the driver. The larger the opening of the accelerator pedal, the greater the driver's demand for driving, and the greater the torque required by the drive motor to output. The driving system controls the current output to the drive motor according to the opening of the accelerator pedal to make the drive motor output the torque indicated by the opening of the accelerator pedal. The larger the opening of the accelerator pedal, the greater the current and the greater the torque output by the drive motor. The smaller the opening of the accelerator pedal, the smaller the current and the smaller the torque output by the drive motor. The driving torque output by the driving system changes with the change of the opening of the accelerator pedal.

[0099] In one embodiment, each motor controller 40 is directly connected to the accelerator pedal and controls the torque output by the corresponding drive motor according to the torque signal output by the accelerator pedal.

[0100] In one embodiment, each motor controller 40 is connected to a resolver sensor for detecting the speed of the drive motor 30 controlled by the motor controller 40, and the motor controller 40 is used to receive signals from the resolver sensor. The resolver sensor can accurately detect the position, direction and speed of the motor rotor, is responsible for monitoring and extracting the rotational speed of the drive motor, has a high sampling rate, and is directly connected to the motor controller 40 with a short signal transmission time and higher stability.

[0101] In one embodiment, the motor controller 40 also obtains the vehicle speed, yaw rate and center side deflection angle of the electric vehicle 10 through the signal interface from the vehicle controller 20 or other sensors of the electric vehicle 10.

[0102] The failure of the braking system 60 includes various cases, such as single-wheel braking failure, double-wheel braking failure, three-wheel braking failure and four-wheel braking failure.

[0103] Different control methods for the electric vehicle 10 are provided below in different failure scenarios.

[0104] The control method for the electric vehicle 10, the braking system 60, and the electric vehicle 10 are described below in combination with Figures 4-7 the single-wheel braking failure of the electric vehicle provided by the embodiments of the present application. Figure 4 and Figure 6 a signal timing diagram of the electric vehicle 10 during driving, Figure 4 and Figure 6 the relationship between the driving system 50, the braking system 60, and the brake pedal opening during the process of controlling the driving system 50 and the braking system 60 to achieve safe braking of the electric vehicle 10 after the braking failure of one wheel of the electric vehicle 10. Figure 5 and Figure 7 a scenario diagram of the electric vehicle 10 during braking.

[0105] The control method provided by the present application is used to control the driving system 50 and the braking system 60 to achieve safe braking of the electric vehicle 10 after the braking failure of one wheel of the electric vehicle 10. When the braking of one wheel fails, the driving system 50 outputs reverse torque for braking, and at the same time, the two wheels of the normal axle output braking force, which can effectively brake without obvious yaw and improve the safety and stability of the braking of the electric vehicle 10.

[0106] As shown in Figure 4 and Figure 6 , the control method includes controlling the driving torque output by the driving system 50 to change with the opening of the accelerator pedal during the driving of the electric vehicle 10 before the braking of the electric vehicle 10, and the direction of the driving torque is the same as the direction of the wheel speed of the electric vehicle 10. During the braking process of the electric vehicle 10 with the braking failure of one front wheel, the braking system 60 is controlled to output braking force to the two rear wheels of the electric vehicle 10, and the driving system 50 is controlled to output reverse torque to the two front wheels, and the direction of the reverse torque is opposite to the direction of the speed of the two front wheels.

[0107] In the driving process of the electric vehicle 10, before starting braking, the brake failure of one wheel basically does not cause impact, the driving system 50 is controlled to output the driving torque of the opening degree indication of the accelerator pedal, the driving torque is used to drive the wheel, the direction of the driving torque is the same as the direction of the rotation speed of the wheel of the electric vehicle 10. When the brake failure of one wheel of the electric vehicle 10 occurs before starting braking or after starting braking, the brake system 60 detects the failure and controls the driving system 50. In the braking process of the brake failure of one wheel of the electric vehicle 10, the brake system 60 is controlled to output the braking force to the same side wheel of the one wheel and the diagonal wheel of the one wheel, and the driving system 50 is controlled to output the reverse torque to the one wheel and the coaxial wheel of the one wheel, the direction of the reverse torque is opposite to the direction of the rotation speed of the wheel. The front left wheel and the rear right wheel of the electric vehicle 10 are the diagonal wheels, or the front right wheel and the rear left wheel are the diagonal wheels, the two left wheels or the two right wheels of the electric vehicle 10 are the same side wheels, and the two front wheels or the two rear wheels of the electric vehicle 10 are the coaxial wheels.

[0108] The brake system 60 includes four wheel end brake devices, each of which is used to output the braking force to the wheel of the electric vehicle 10. The four wheel end brake devices correspond to the four wheels one by one, and are used to output the braking force respectively. In the normal state, the four wheel end brake devices are used to output the braking force indicated by the opening degree of the brake pedal. When one wheel fails, the wheel end brake device used to brake the one wheel cannot output the braking force, at this time, the brake system 60 is controlled to output the braking force to the same side wheel of the one wheel and the diagonal wheel of the one wheel.

[0109] Specifically, as shown in Figure 4 and Figure 5 , when the brake of the front left wheel fails, in the braking process of the brake failure of the front left wheel, the brake system 60 is controlled to output the braking force to the two rear wheels, and the driving system 50 is controlled to output the reverse torque to the two front wheels, the direction of the reverse torque is opposite to the direction of the rotation speed of the two front wheels. When the brake of the front right wheel fails, in the braking process of the brake failure of the front right wheel, the brake system 60 is controlled to output the braking force to the two rear wheels, and the driving system 50 is controlled to output the reverse torque to the two front wheels, the direction of the reverse torque is opposite to the direction of the rotation speed of the two front wheels.

[0110] It should be understood that because it is necessary to control the driving system 50 to output the reverse torque to the two front wheels, at least one driving motor 30 is included in the driving system 50 to drive the two front wheels. When the two front wheels are driven by two driving motors 30 respectively, the two driving motors 30 are controlled to output the reverse torque simultaneously to brake the two front wheels.

[0111] In another embodiment, as shown in Figure 6 and Figure 7As shown, the wheel whose brake fails is a rear wheel. During the braking process when a rear wheel of the electric vehicle 10 fails, the control brake system 60 outputs brake force to the two front wheels of the electric vehicle 10, and the control drive system 50 outputs reverse torque to the two rear wheels, the direction of the reverse torque being opposite to the direction of the rotation speed of the two rear wheels.

[0112] Specifically, when the brake of the left rear wheel fails, during the braking process when the brake of the left rear wheel fails, the control brake system 60 outputs brake force to the two front wheels, and the control drive system 50 outputs reverse torque to the two rear wheels, the direction of the reverse torque being opposite to the direction of the rotation speed of the two rear wheels. When the brake of the right rear wheel fails, during the braking process when the brake of the right rear wheel fails, the control brake system 60 outputs brake force to the two front wheels, and the control drive system 50 outputs reverse torque to the two rear wheels, the direction of the reverse torque being opposite to the direction of the rotation speed of the two rear wheels.

[0113] It should be understood that, because it is necessary to control the drive system 50 to output reverse torque to the two rear wheels, at least one drive motor 30 is included in the drive system 50 for driving the two rear wheels. When the two rear wheels are driven by two drive motors 30 respectively, the two drive motors 30 are controlled to output reverse torque simultaneously to brake the two rear wheels.

[0114] According to the scheme of the present application, by controlling the drive system 50 to output reverse torque to the two wheels of the wheel shaft whose brake fails to make up for the failure of brake force, and cooperating with the control brake system 60 to output brake force to the two wheels of the normal shaft, the yaw of the electric vehicle 10 caused by unilateral wheel braking is avoided, a larger brake force is output, the braking distance is shortened, and the safety and stability of the braking of the electric vehicle 10 are improved.

[0115] In an embodiment, the control method specifically includes, during the braking process when a front wheel fails, controlling the brake system 60 to output brake force to the two rear wheels of the electric vehicle 10 to change with the opening of the brake pedal, and controlling the drive system 50 to output reverse torque to change with the opening of the brake pedal.

[0116] In a braking process of one front wheel brake failure, the control method controls the braking force outputted by the braking system 60 to the two rear wheels of the electric vehicle 10 to vary with the opening of the brake pedal, and controls the reverse torque outputted by the driving system 50 to vary with the opening of the brake pedal. In a driving process of the electric vehicle 10, before braking, the control method controls the driving torque outputted by the driving system 50 to vary with the opening of the accelerator pedal, and after starting braking and one front wheel brake failure, the control method controls the driving system 50 to output a reverse torque to the one front wheel and the coaxial wheel of the one front wheel, and the magnitude of the reverse torque is determined according to the opening of the brake pedal, and the magnitude of the reverse torque varies with the opening of the brake pedal. The braking force outputted by the braking system 60 to the two coaxial wheels with normal braking varies with the opening of the brake pedal.

[0117] In an embodiment, the control method specifically comprises, in a braking process of one front wheel brake failure, controlling the braking system 60 to output the braking force to the two rear wheels of the electric vehicle 10 to be equal.

[0118] In order to avoid the braking force generated on both sides of the electric vehicle 10 being unequal to generate a yawing torque to make the electric vehicle 10 have a yawing tendency, the braking system 60 should be controlled to output the braking force to the two coaxial wheels to be equal, so as to not generate a yawing torque.

[0119] In an embodiment, the control method further comprises, in a braking process of one front wheel brake failure, first controlling the braking system 60 to output the braking force to the two rear wheels of the electric vehicle 10, and controlling the driving system 50 to output a reverse torque to the two front wheels, and then controlling the braking system 60 to output the braking force to the other front wheel.

[0120] In a braking process of one wheel brake failure, the reverse torque outputted by the driving system 50 to the one wheel and the coaxial wheel of the one wheel can brake the one wheel and the coaxial wheel of the one wheel, but the maximum braking capacity that can be generated by the reverse torque is smaller than the maximum braking effect of the braking force outputted by the braking system 60. Therefore, when the braking force demand is large, the reverse torque outputted by the driving system 50 to the one wheel and the coaxial wheel of the one wheel is not enough to generate sufficient braking effect, at this time, the braking system 60 outputs the braking force to the third wheel with normal braking, thereby effectively improving the braking capacity.

[0121] Specifically, when the braking of the left rear wheel fails, the braking system 60 is controlled to output braking force to the two rear wheels of the electric vehicle 10 during the braking process of the braking failure of the left front wheel, and the driving system 50 is controlled to output reverse torque to the two front wheels, and then the braking system 60 is controlled to output braking force to the right front wheel. When the braking of the right front wheel fails, the braking system 60 is controlled to output braking force to the two rear wheels of the electric vehicle 10 during the braking process of the braking failure of the right front wheel, and the driving system 50 is controlled to output reverse torque to the two front wheels, and then the braking system 60 is controlled to output braking force to the left front wheel.

[0122] In another embodiment, the one wheel with braking failure is a rear wheel. During the braking process of the braking failure of one rear wheel, the braking system 60 is controlled to output braking force to the two front wheels of the electric vehicle 10, and the driving system 50 is controlled to output reverse torque to the two rear wheels, and then the braking system 60 is controlled to output braking force to the other rear wheel.

[0123] Specifically, when the braking of the left rear wheel fails, the braking system 60 is controlled to output braking force to the two front wheels of the electric vehicle 10 during the braking process of the braking failure of the left rear wheel, and the driving system 50 is controlled to output reverse torque to the two rear wheels, and then the braking system 60 is controlled to output braking force to the right rear wheel. When the braking of the right rear wheel fails, the braking system 60 is controlled to output braking force to the two front wheels of the electric vehicle 10 during the braking process of the braking failure of the right rear wheel, and the driving system 50 is controlled to output reverse torque to the two rear wheels, and then the braking system 60 is controlled to output braking force to the left rear wheel.

[0124] In one embodiment, the control method specifically comprises that, during the braking process of the braking failure of one front wheel, the braking force output by the braking system 60 to the other front wheel is always less than the braking force output to any one of the two rear wheels.

[0125] After the braking system 60 outputs braking force to the third wheel with normal braking, the total braking force received by the third wheel is greater than the braking force received by the one wheel with braking failure on the same shaft, and the braking forces generated on the two sides of the electric vehicle 10 are not equal, which generates yawing torque and makes the electric vehicle 10 have a yawing tendency. The greater the braking force output by the braking system 60 to the third wheel with normal braking, the greater the yawing torque generated by the electric vehicle 10, and thus the size of the braking force output by the braking system 60 to the third wheel with normal braking needs to be limited.

[0126] Specifically, during the braking process of the braking failure of one front wheel, the braking force output by the braking system 60 to the other front wheel is always less than the braking force output to any one of the two rear wheels. During the braking process of the braking failure of one rear wheel, the braking force output by the braking system 60 to the other rear wheel is always less than the braking force output to any one of the two front wheels.

[0127] In one embodiment, the control method specifically comprises, during the braking process of one front wheel brake failure, when the opening degree of the brake pedal is less than a preset opening degree, controlling the brake system 60 to output zero brake force to the other front wheel. When the opening degree of the brake pedal is increased to be greater than or equal to the preset opening degree, controlling the brake system 60 to output brake force greater than zero to the other front wheel.

[0128] After the brake system 60 outputs brake force to the third wheel which is the wheel coaxial with the brake failure wheel, the third wheel will be subjected to the reverse torque output by the brake system 60 and the brake force output by the brake system 60, which will cause the total brake force on the third wheel to be greater than the brake force on the coaxial brake failure wheel, and the brake forces generated on both sides of the electric vehicle 10 will be unequal, which will generate yaw torque and cause the electric vehicle 10 to have a yaw tendency. However, in the case of emergency braking, the demand for brake force is more urgent, and therefore, in order to safely brake the electric vehicle 10, it is permissible to generate a controllable range of yaw torque.

[0129] The opening degree of the brake pedal is used to determine whether the driver needs emergency braking. When the opening degree of the brake pedal is less than a preset opening degree, the driver does not need emergency braking, at which time the brake system 60 is controlled to output brake force to the two rear wheels of the electric vehicle 10, and the drive system 50 is controlled to output reverse torque to the two front wheels. At this time, the brake force required by the electric vehicle 10 can be compensated by the reverse torque output by the drive system 50, at which time the brake system 60 does not output brake force to the third wheel which is the wheel that brakes normally. The output of brake force by the brake system 60 to the two rear wheels and the output of reverse torque by the drive system 50 to the two front wheels are symmetrical, and the electric vehicle 10 will not yaw, which can achieve sufficient braking capability while maintaining the stability of the body of the electric vehicle 10 during braking. When the opening degree of the brake pedal is increased to be greater than or equal to the preset opening degree, it is determined that the driver needs emergency braking, at which time the brake force required by the electric vehicle 10 cannot be completely compensated by the reverse torque output by the drive system 50, and therefore the brake system 60 is controlled to output brake force to the third wheel which is the wheel that brakes normally, thereby further increasing the brake force and effectively achieving emergency braking.

[0130] In one possible implementation, the preset opening degree is 80%.

[0131] In one embodiment, the control method specifically comprises, during the braking process of the left front wheel brake failure, before the reverse torque output by the drive system 50 to the two front wheels is increased to a preset torque, controlling the brake system 60 to output zero brake force to the right front wheel. After the reverse torque output by the drive system 50 to the two front wheels is increased to the preset torque, controlling the brake system 60 to output brake force greater than zero to the right front wheel.

[0132] When the control braking system 60 outputs the braking force to the third wheel which is normally braked, the total braking force on the third wheel will be greater than the braking force on the coaxial wheel which is not braked, and the braking forces generated on the two sides of the electric vehicle 10 will be unequal, which will generate a yawing torque and make the electric vehicle 10 have a yawing tendency. Therefore, the emergency braking should be realized by the symmetrical control mode as far as possible. When the reverse torque output by the drive system 50 to the wheel which is not braked and the coaxial wheel of the wheel which is not braked is less than the preset torque, the braking force can be increased by increasing the reverse torque output, without the need of the control braking system 60 outputting the braking force to the third wheel which is normally braked. When the reverse torque output by the drive system 50 to the wheel which is not braked and the coaxial wheel of the wheel which is not braked is increased to the preset torque, the braking force cannot be increased by increasing the reverse torque output, and thus the control braking system 60 outputs the braking force to the third wheel which is normally braked to further increase the braking ability.

[0133] In an embodiment, the control method specifically comprises, in the braking process of the wheel which is not braked, before the reverse torque output by the drive system 50 to the two front wheels is increased to the preset torque, controlling the control braking system 60 to output the braking force to the other front wheel as zero. After the reverse torque output by the drive system 50 to the two front wheels is increased to the preset torque, when the average slip ratio of the two front wheels is less than the preset value, controlling the control braking system 60 to output the braking force to the other front wheel as greater than zero.

[0134] The drive system 50 comprises a resolver sensor, and the rotation speed of the drive motor 30 can be obtained through the resolver signal of the resolver sensor. The angular speed of the wheel can be calculated through the rotation speed of the drive motor 30 and the transmission ratio of the electric vehicle, and the slip ratio of each wheel can be obtained by further combining the wheel radius and the speed of the electric vehicle 10. The slip ratio of the wheel affects the braking effect of the wheel, and when the slip ratio of the wheel is too large, the wheel slips, and the wheel cannot generate effective braking force.

[0135] Therefore, when the average slip ratio of the two wheels is greater than the preset value, the control braking system 60 cannot further improve the braking effect by outputting the braking force to the third wheel which is normally braked. After the reverse torque output by the drive system 50 to the two front wheels is increased to the preset torque, and when the average slip ratio of the two front wheels is less than the preset value, the control braking system 60 is controlled to output the braking force to the other front wheel as greater than zero.

[0136] In an embodiment, in the process of controlling the drive system 50 to increase the reverse torque output to the two front wheels to the preset torque, the control method further comprises controlling the reverse torque output by the drive system 50 to the two front wheels to change with the average slip ratio of the two front wheels.

[0137] Since the slip ratio of the wheels directly affects the braking effect of the wheels, the driving system 50 adjusts the slip ratio of the wheels by controlling the size of the reverse torque output. Specifically, when the average slip ratio of the two wheels is less than the preset slip ratio, the driving system 50 is controlled to increase the reverse torque output to the two wheels, and when the average slip ratio of the two wheels is greater than the preset slip ratio, the driving system 50 is controlled to decrease the reverse torque output to the two wheels. Thus, the reverse torque output by the driving system 50 can produce an effective braking effect.

[0138] In an embodiment, the control method further includes, after controlling the braking system 60 to output the braking force to the other front wheel greater than zero, controlling the braking force output by the braking system 60 to the other front wheel to change with the change of the yaw angle of the electric vehicle 10.

[0139] Controlling the braking system 60 to output the braking force to the normally-braking third wheel causes the total braking force received by the third wheel to be greater than the braking force received by the coaxial wheel with braking failure, and the braking forces generated on both sides of the electric vehicle 10 are not equal, which generates a yawing torque to cause the electric vehicle 10 to have a yawing trend. Adjusting the size of the braking force output by the braking system 60 to the normally-braking third wheel according to the yaw angle of the electric vehicle 10 can avoid the yaw angle of the electric vehicle 10 being too large to cause the electric vehicle 10 to lose control.

[0140] In an embodiment, the control method further includes, after controlling the braking system 60 to output the braking force to the other front wheel greater than zero, controlling the braking force output by the braking system 60 to the other front wheel to change with the change of the steering wheel angle of the electric vehicle 10.

[0141] Controlling the braking system 60 to output the braking force to the normally-braking third wheel causes the total braking force received by the third wheel to be greater than the braking force received by the coaxial wheel with braking failure, and the braking forces generated on both sides of the electric vehicle 10 are not equal, which generates a yawing torque to cause the electric vehicle 10 to have a yawing trend. At this time, the driver can adjust the steering wheel angle due to the change in the body posture of the electric vehicle 10, and when the steering wheel angle changes, the steering system of the electric vehicle 10 adjusts the orientation of the wheels, which can offset the yawing torque generated by the electric vehicle 10 to a certain extent. At this time, increasing the braking force output by the braking system 60 to the normally-braking third wheel can obtain a greater braking force.

[0142] The braking system 60 provided by the embodiments of the present application is used to implement the action of the braking system 60 in the control method described above.

[0143] When the driving system 50 only includes one driving motor 30, and the driving motor 30 is used to drive the wheel with braking failure, the safe braking control can be performed only by the braking system 60.

[0144] The following will be described in combination withFigures 8-11 Another brake system 60 control method provided by the embodiments of the application is described. Figure 8 and Figure 10 A signal timing diagram of the electric vehicle 10 during driving, Figure 8 and Figure 10 The relationship between the brake system 60 and the brake pedal opening during the process of adjusting the brake force output by the brake system 60 to achieve safe braking of the electric vehicle 10 after brake failure of one wheel of the electric vehicle 10. Figure 9 and Figure 11 A scene diagram of the electric vehicle 10 during braking.

[0145] The brake system 60 is used to control the brake system 60 to output the brake force indicated by the opening of the brake pedal to the four wheels of the electric vehicle 10 before braking of the electric vehicle 10 during driving of the electric vehicle 10. During braking with brake failure of the left front wheel of the electric vehicle 10, the brake system 60 is controlled to output brake force to the right front wheel and the left rear wheel of the electric vehicle 10, and the brake force output by the brake system 60 to the left rear wheel is controlled to change with the change of the yaw angle of the electric vehicle 10.

[0146] When brake failure occurs in one front wheel of the electric vehicle 10, the brake system 60 is controlled to output brake force to the same side wheel of the one wheel and the same axle wheel of the one wheel to achieve diagonal braking. At the same time, the difference between the brake forces of the two rear wheels is controlled to adjust the yaw angle of the electric vehicle 10.

[0147] Specifically, as shown in Figure 8 and Figure 9 During braking with brake failure of the left front wheel of the electric vehicle 10, the brake system 60 is controlled to output brake force to the right front wheel and the left rear wheel of the electric vehicle 10, and when the yaw angle of the electric vehicle 10 becomes larger to the left, the brake system 60 is controlled to reduce the brake force output to the left rear wheel, and when the yaw angle of the electric vehicle 10 becomes larger to the right, the brake system 60 is controlled to increase the brake force output to the left rear wheel.

[0148] Specifically, during braking with brake failure of the right front wheel of the electric vehicle 10, the brake system 60 is controlled to output brake force to the left front wheel and the right rear wheel of the electric vehicle 10, and when the yaw angle of the electric vehicle 10 becomes larger to the left, the brake system 60 is controlled to increase the brake force output to the right rear wheel, and when the yaw angle of the electric vehicle 10 becomes larger to the right, the brake system 60 is controlled to reduce the brake force output to the right rear wheel.

[0149] In an embodiment, the brake system 60 is further configured to, during the braking process after the brake failure of the left front wheel, control the brake system 60 to output zero brake force to the right rear wheel of the electric vehicle 10 when the brake pedal opening increases and the brake pedal opening is less than a preset opening. When the brake pedal opening increases to be greater than or equal to the preset opening, control the brake system 60 to output brake force greater than zero to the right rear wheel, and control the drive system 50 to output brake force greater than the brake force output to the right rear wheel to the left rear wheel.

[0150] The driver's demand for emergency braking is determined by the brake pedal opening. When the brake pedal opening is less than the preset opening, the driver does not need emergency braking. At this time, the brake system 60 is controlled to output zero brake force to the diagonal wheel of the wheel with brake failure. When the brake pedal opening increases to be greater than or equal to the preset opening, it is determined that the driver needs emergency braking. At this time, the brake system 60 is controlled to output brake force to the diagonal wheel of the wheel with brake failure, thereby further increasing the brake force and effectively achieving emergency braking.

[0151] In an embodiment, as shown in Figure 10 and Figure 11 , the brake system 60 is further configured to, during the braking process after the brake failure of the left rear wheel of the electric vehicle 10, first control the brake system 60 to output brake force to the two front wheels of the electric vehicle 10, and then control the brake system 60 to output brake force to the right rear wheel of the electric vehicle 10.

[0152] In an embodiment, the brake system 60 is specifically configured to, during the braking process after the brake failure of the left rear wheel of the electric vehicle 10, control the brake system 60 to output brake force to the two front wheels of the electric vehicle 10 when the brake pedal opening increases and the brake pedal opening is less than a preset opening. When the brake pedal opening increases to be greater than or equal to the preset opening, control the brake system 60 to output brake force to the right rear wheel of the electric vehicle 10, and control the brake system 60 to output brake force to the right rear wheel that changes with the yaw angle of the electric vehicle 10.

[0153] The driver's demand for emergency braking is determined by the brake pedal opening. When the brake pedal opening is less than the preset opening, the driver does not need emergency braking. When the brake of one rear wheel of the electric vehicle 10 fails, the brake system 60 is controlled to output brake force to the two front wheels to achieve front axle braking. When the brake pedal opening increases to be greater than or equal to the preset opening, it is determined that the driver needs emergency braking. At this time, the brake system 60 is controlled to output brake force to the other rear wheel, thereby further increasing the brake force and effectively achieving emergency braking. At the same time, the difference between the brake forces of the two rear wheels is controlled to adjust the yaw angle of the electric vehicle 10.

[0154] Specifically, in the braking process of the left rear wheel brake failure of the electric vehicle 10, the control brake system 60 outputs brake force to the two front wheels of the electric vehicle 10, and when the yaw angle of the electric vehicle 10 becomes larger to the left, the control brake system 60 increases the brake force output to the right rear wheel, and when the yaw angle of the electric vehicle 10 becomes larger to the right, the control brake system 60 reduces the brake force output to the right rear wheel.

[0155] Specifically, in the braking process of the right rear wheel brake failure of the electric vehicle 10, the control brake system 60 outputs brake force to the two front wheels of the electric vehicle 10, and when the yaw angle of the electric vehicle 10 becomes larger to the left, the control brake system 60 reduces the brake force output to the left rear wheel, and when the yaw angle of the electric vehicle 10 becomes larger to the right, the control brake system 60 increases the brake force output to the left rear wheel.

[0156] According to the above-mentioned scheme of the present application, when one wheel of the front axle fails, the brake system 60 performs yaw torque control by outputting brake force to the diagonal wheels and adjusting the brake force output to the two wheels of the rear axle according to the yaw angle and acceleration; when one wheel of the rear axle fails, the brake system 60 performs yaw torque control by outputting brake force to the two wheels of the front axle and adjusting the brake force output to the wheels of the rear axle according to the yaw angle and acceleration, which can effectively improve the braking ability.

[0157] The following will be described in combination with Figures 12-17 The control method for the electric vehicle 10 and the electric vehicle 10 provided by the embodiments of the present application will be described when two wheels of the electric vehicle 10 fail. Figure 12 、 Figure 14 and Figure 16 are signal timing diagrams of the electric vehicle 10 during driving, Figure 12 、 Figure 14 and Figure 16 include the relationship between the drive system 50, the brake system 60 and the brake pedal opening in the process of controlling the drive system 50 and the brake system 60 to achieve safe braking of the electric vehicle 10 after the brake failure of the two wheels of the electric vehicle 10. Figure 13 、 Figure 15 and Figure 17 are scene schematic diagrams of the electric vehicle 10 during braking.

[0158] The brake failure of the two wheels includes the brake failure of the two coaxial wheels, the brake failure of the two wheels on the same side, and the brake failure of the two diagonal wheels. The two front wheels or the two rear wheels of the electric vehicle 10 are coaxial wheels, the two left wheels or the two right wheels of the electric vehicle 10 are wheels on the same side, and the left front wheel and the right rear wheel of the electric vehicle 10 are diagonal wheels or the right front wheel and the left rear wheel are diagonal wheels.

[0159] As Figure 12 andFigure 13 As shown, the control method comprises, during the driving of the electric vehicle 10, before the braking of the electric vehicle 10, controlling the driving torque output by the driving system 50 to vary with the opening degree of the accelerator pedal, the direction of the driving torque being the same as the direction of the rotation speed of the wheels of the electric vehicle 10. During the braking of the left front wheel and the right rear wheel of the electric vehicle 10, the driving system 50 outputs reverse torques to the two front wheels and the two rear wheels of the electric vehicle 10 respectively, the direction of the reverse torque being opposite to the direction of the rotation speed of the two front wheels.

[0160] During the driving of the electric vehicle 10, before the braking is started, the braking failure of the two wheels does not cause much influence, the driving system 50 outputs the driving torque indicated by the opening degree of the accelerator pedal, the driving torque being used to drive the wheels, the direction of the driving torque being the same as the direction of the rotation speed of the wheels of the electric vehicle 10. When the braking failure of the two wheels of the electric vehicle 10 occurs before the braking is started or after the braking is started, the braking system 60 detects the failure and controls the driving system 50. During the braking of the left front wheel and the right rear wheel of the electric vehicle 10, the driving system 50 outputs reverse torques to the two front wheels and the two rear wheels of the electric vehicle 10 respectively, the direction of the reverse torque being opposite to the direction of the rotation speed of the wheels.

[0161] When the braking failure of the left front wheel and the right rear wheel, during the braking of the left front wheel and the right rear wheel, the driving system 50 outputs reverse torques to the two front wheels and the two rear wheels respectively.

[0162] It should be understood that, because the driving system 50 needs to output reverse torques to the two front wheels and the two rear wheels, the driving system 50 comprises at least two driving motors 30, the two front wheels being driven by at least one driving motor 30, the two rear wheels being driven by at least one driving motor 30. When the two coaxial wheels are driven by two driving motors 30 respectively, the two driving motors 30 are controlled to output reverse torques simultaneously to brake the two coaxial wheels.

[0163] In another embodiment, when the braking failure of the right front wheel and the left rear wheel, during the braking of the right front wheel and the left rear wheel, the driving system 50 outputs reverse torques to the two front wheels and the two rear wheels respectively.

[0164] According to the scheme of the present application, when the diagonal wheels brake fail, the driving system 50 is controlled to output reverse torques to the two front wheels and the two rear wheels to compensate for the failure of the braking force, the output of the larger braking force is realized, the braking distance is shortened, and the safety and stability of the braking of the electric vehicle 10 are improved.

[0165] In one embodiment, the control method further comprises, during the braking process when the braking of the left front wheel and the right rear wheel fails, firstly controlling the driving system 50 to output reverse torques to the two front wheels and the two rear wheels respectively, and then controlling the braking system 60 to output braking forces to the right front wheel and the left rear wheel of the electric vehicle 10.

[0166] During the braking process when the braking of the left front wheel and the right rear wheel fails, the driving system 50 outputs reverse torques to the two front wheels and the two rear wheels, but the maximum braking capacity that can be generated by the reverse torques is less than the maximum braking effect of the braking forces output by the braking system 60. Therefore, when the braking force demand is large, the reverse torques output by the driving system 50 to the two front wheels and the two rear wheels are not enough to generate sufficient braking effect, at which time the braking system 60 is controlled to output braking forces to the two wheels that are normally braked, thereby effectively improving the braking capacity by adding diagonal braking.

[0167] Specifically, when the braking of the left front wheel and the right rear wheel fails, during the braking process when the braking of the left front wheel and the right rear wheel fails, firstly the driving system 50 is controlled to output reverse torques to the two front wheels and the two rear wheels respectively, and then the braking system 60 is controlled to output braking forces to the right front wheel and the left rear wheel of the electric vehicle 10.

[0168] In another embodiment, when the braking of the right front wheel and the left rear wheel fails, during the braking process when the braking of the right front wheel and the left rear wheel fails, firstly the driving system 50 is controlled to output reverse torques to the two front wheels and the two rear wheels respectively, and then the braking system 60 is controlled to output braking forces to the left front wheel and the right rear wheel of the electric vehicle 10.

[0169] In one embodiment, the control method specifically comprises, during the braking process when the braking of the left front wheel and the right rear wheel fails, when the opening of the brake pedal of the electric vehicle 10 is less than a preset opening, controlling the braking system 60 to output zero braking force. When the opening of the brake pedal is increased to be greater than or equal to the preset opening, the braking system 60 is controlled to output braking forces to the right front wheel and the left rear wheel of the electric vehicle 10.

[0170] Whether the driver needs emergency braking is determined by the opening of the brake pedal. When the opening of the brake pedal is less than the preset opening, the driver does not need emergency braking, at which time the driving system 50 is controlled to output reverse torques to the two front wheels and the two rear wheels of the electric vehicle 10, at which time the braking force demand of the electric vehicle 10 can be compensated by the driving system 50 outputting reverse torques, at which time the braking system 60 does not output braking forces to the two wheels that are normally braked.

[0171] When the opening of the brake pedal is increased to be greater than or equal to the preset opening, it is determined that the driver needs emergency braking, at this time the braking force required by the electric vehicle 10 cannot be completely compensated by the reverse torque output by the drive system 50, therefore the control system controls the brake system 60 to output braking force to the two normally-braking wheels, and further improves the braking force by braking the diagonal wheels, effectively realizing emergency braking. The preset opening is pre-calibrated according to real vehicle experiments and / or model calculations, or is pre-set by comprehensively considering the vehicle demand and vehicle performance.

[0172] In an embodiment, the control method specifically includes, during the braking process of the left front wheel and the right rear wheel brake failure, controlling the brake system 60 to output zero braking force before the reverse torque output by the drive system 50 to the two front wheels and the two rear wheels is increased to the preset torque. After the reverse torque output by the drive system 50 to the two front wheels and the two rear wheels is increased to the preset torque, the control system controls the brake system 60 to output braking force to the right front wheel and the left rear wheel of the electric vehicle 10.

[0173] During the process of outputting reverse torque by the drive system 50 to the two front wheels and the two rear wheels, the braking forces received by the two sides of the electric vehicle 10 are equal, and there is no yawing during braking, which is more stable. Before the reverse torque output by the drive system 50 to the brake-failed left front wheel and right rear wheel is less than the preset torque, the braking force can be improved by increasing the reverse torque output, without the need to control the brake system 60 to output braking force to the two normally-braking wheels. When the reverse torque output by the drive system 50 to the brake-failed left front wheel and right rear wheel is increased to the preset torque, the braking force cannot be improved by increasing the reverse torque output at this time, therefore the control system controls the brake system 60 to output braking force to the two diagonally-braking wheels to further improve the braking ability. The preset torque is pre-calibrated according to real vehicle experiments and / or model calculations, or is pre-set by comprehensively considering the vehicle demand and vehicle performance.

[0174] In an embodiment, during the process of increasing the reverse torque output by the drive system 50 to the two front wheels and the two rear wheels to the preset torque, the control method further includes controlling the reverse torque output by the drive system 50 to the two front wheels to change with the average slip ratio of the two front wheels, and controlling the reverse torque output by the drive system 50 to the two rear wheels to change with the average slip ratio of the two rear wheels.

[0175] The resolver sensor in the drive system 50 can obtain the rotational speed of the drive motor 30 through the resolver signal of the resolver sensor. The angular speed of the wheels can be calculated through the rotational speed of the drive motor 30 and the transmission ratio of the electric vehicle. Further, the slip ratio of each wheel can be obtained by combining the wheel radius with the speed of the electric vehicle 10. The slip ratio of the wheels affects the braking effect of the wheels. When the slip ratio of the wheels is too large, the wheels slip, and the wheels cannot generate effective braking force. Since the slip ratio of the wheels directly affects the braking effect of the wheels, the drive system 50 adjusts the slip ratio of the wheels by controlling the size of the reverse torque output by the drive system 50. Specifically, when the average slip ratio of the two wheels is less than a preset slip ratio, the drive system 50 is controlled to increase the reverse torque output to the two wheels. When the average slip ratio of the two wheels is greater than the preset slip ratio, the drive system 50 is controlled to decrease the reverse torque output to the two wheels. Thus, the reverse torque output by the drive system 50 can generate effective braking effect.

[0176] In an embodiment, the control method specifically includes, during the braking process in which the left front wheel and the right rear wheel fail to brake, controlling the drive system 50 to output the reverse torque to the two front wheels and the two rear wheels to change with the opening degree of the brake pedal, and controlling the reverse torque output by the drive system 50 to change with the opening degree of the brake pedal.

[0177] During the braking process in which the left front wheel and the right rear wheel fail to brake, the reverse torque output by the drive system 50 changes with the opening degree of the brake pedal. During the driving process of the electric vehicle 10, before braking, the drive torque output by the drive system 50 changes with the opening degree of the accelerator pedal. After the braking starts and the two wheels fail to brake, the drive system 50 outputs the reverse torque, and the size of the reverse torque is determined according to the opening degree of the brake pedal. The size of the reverse torque changes with the opening degree of the brake pedal.

[0178] In an embodiment, the control method specifically includes, during the braking process in which the left front wheel and the right rear wheel fail to brake, controlling the drive system 50 to output the reverse torque to the two front wheels to be always greater than the reverse torque output to the two rear wheels, and further controlling the brake system 60 to output the braking force to the right front wheel to be always greater than the braking force output to the left rear wheel.

[0179] When the electric vehicle 10 brakes, its center of gravity shifts forward, resulting in greater downforce on the two front wheels and increased load on the front wheels, thus providing greater grip and braking force. Conversely, the downforce on the rear wheels decreases, and the load on the rear wheels also decreases. If the two rear wheels are given the same or greater braking force as the two front wheels, the rear wheels will lock up before the front wheels due to insufficient positive pressure. Once the rear wheels lock up, the electric vehicle 10 will lose lateral grip, making it prone to fishtailing or skidding and loss of control. Since the front wheels are steering wheels, even if they lock up, it will only lead to steering failure, and the electric vehicle 10 will slide in a straight line, making it relatively easier to control. Therefore, in controlling the output of reverse torque by the drive system 50 or the output of braking force by the braking system 60, the reverse torque output by the drive system 50 to the front wheels is greater than the reverse torque output to the rear wheels, and the braking force output by the braking system 60 to the front wheels is greater than the braking force output to the rear wheels, resulting in a greater braking force on the two front wheels than on the two rear wheels.

[0180] like Figure 14 and Figure 15 As shown, the control method also includes controlling the drive system 50 to output reverse torque to the two front wheels and the two rear wheels during the braking process when the left front wheel and left rear wheel of the electric vehicle 10 fail to brake, or during the braking process when the right front wheel and right rear wheel of the electric vehicle 10 fail to brake.

[0181] When two wheels on the same side fail, if the braking system 60 outputs braking force, it will cause unequal braking forces on both sides of the electric vehicle 10, resulting in yaw torque and affecting the vehicle's stability. Therefore, the braking system 60 cannot output braking force to the wheels of the electric vehicle 10. At this time, the drive system 50 is controlled to output reverse torque to the two front wheels and the two rear wheels.

[0182] In one embodiment, the control method specifically includes controlling the reverse torque output by the drive system 50 to change with the opening of the brake pedal during the braking process when the left front wheel and left rear wheel of the electric vehicle 10 fail to brake, or during the braking process when the right front wheel and right rear wheel of the electric vehicle 10 fail to brake.

[0183] During braking when the left front and left rear wheels fail to brake, or during braking when the right front and right rear wheels fail to brake, the reverse torque output by the control drive system 50 varies with the opening of the brake pedal. During the operation of the electric vehicle 10, before braking, the drive torque output by the control drive system 50 varies with the opening of the accelerator pedal. After braking begins and the brakes on both wheels on the same side fail, the control drive system 50 outputs a reverse torque, the magnitude of which is determined by the opening of the brake pedal and varies with the opening of the brake pedal.

[0184] In one embodiment, during the process of controlling the driving system 50 to output reverse torques to the two front wheels and the two rear wheels, the control method further comprises that the sum of the reverse torques output by the driving system 50 to the two front wheels is always greater than the sum of the reverse torques output to the two rear wheels.

[0185] As shown in Figure 16 and Figure 17 , the control method further comprises that during the braking process of the two front wheels of the electric vehicle 10 failing to brake, the braking system 60 is controlled to output braking force to the two rear wheels of the electric vehicle 10, and the driving system 50 is controlled to output reverse torque to the two front wheels.

[0186] When the two wheels on the same shaft fail to brake, the driving system 50 is controlled to output reverse torque to the two wheels on the braking failure axle, and the braking system 60 is controlled to output braking force to the two wheels on the normal axle, so as to brake.

[0187] In another embodiment, during the braking process of the two rear wheels of the electric vehicle 10 failing to brake, the braking system 60 is controlled to output braking force to the two front wheels of the electric vehicle 10, and the driving system 50 is controlled to output reverse torque to the two rear wheels.

[0188] According to the scheme of the present application, by controlling the driving system 50 to output reverse torque to the two wheels on the axle where braking failure occurs to compensate for the failure of braking force, and cooperating with the braking system 60 to output braking force to the two wheels on the normal axle, the yaw of the electric vehicle 10 caused by single-side wheel braking is avoided, a larger braking force is output, the braking distance is shortened, and the safety and stability of the braking of the electric vehicle 10 are improved.

[0189] In one embodiment, the control method specifically comprises that during the braking process of the two front wheels failing to brake, the braking force output by the braking system 60 to the two rear wheels changes with the change of the opening degree of the brake pedal, and the reverse torque output by the driving system 50 changes with the change of the opening degree of the brake pedal.

[0190] During the braking process of the two front wheels failing to brake, the reverse torque output by the driving system 50 changes with the change of the opening degree of the brake pedal. During the driving process of the electric vehicle 10, before braking, the driving torque output by the driving system 50 changes with the change of the opening degree of the accelerator pedal, after the braking starts and the two wheels on the same shaft fail to brake, the driving system 50 outputs reverse torque, and the size of the reverse torque is determined according to the opening degree of the brake pedal, and the size of the reverse torque changes with the change of the opening degree of the brake pedal.

[0191] In another embodiment, during the braking process in which two rear wheels fail to brake, the control system controls the braking force output by the braking system 60 to the two front wheels to vary with the opening of the brake pedal, and controls the reverse torque output by the driving system 50 to vary with the opening of the brake pedal.

[0192] In an embodiment, during the control of the driving system 50 to output the reverse torque to the two front wheels, the control method further comprises controlling the reverse torque output by the driving system 50 to the two front wheels to vary with the average slip ratio of the two front wheels.

[0193] The slip ratio of the wheels affects the braking effect of the wheels. When the slip ratio of the wheels is too large, the wheels slip, and at this time the wheels cannot generate effective braking force. Since the slip ratio of the wheels directly affects the braking effect of the wheels, the driving system 50 adjusts the slip ratio of the wheels by controlling the size of the reverse torque output.

[0194] In another embodiment, during the braking process in which two rear wheels fail to brake, the control system controls the braking force output by the braking system 60 to the two front wheels to vary with the opening of the brake pedal, and controls the reverse torque output by the driving system 50 to the two rear wheels to vary with the average slip ratio of the two rear wheels.

[0195] Figure 18 The flowchart of the control method provided by the present application is shown.

[0196] As shown in Figure 18 During driving, signals of the electric vehicle 10 such as the opening of the brake pedal, the power of the power battery, the yaw rate of the electric vehicle 10, the acceleration, etc. are collected. When the braking system 60 detects that two wheels fail to brake, the positions of the two wheels that fail to brake are determined. When the two wheels of the front axle fail to brake, the driving system 50 is controlled to output the reverse torque to the two wheels of the front axle, and the braking system 60 is controlled to output the braking force to the two wheels of the rear axle; when the two wheels of the rear axle fail to brake, the driving system 50 is controlled to output the reverse torque to the two wheels of the rear axle, and the braking system 60 is controlled to output the braking force to the two wheels of the front axle; when the two wheels at opposite angles fail to brake, the driving system 50 is controlled to output the reverse torque to the two wheels of the front axle and the two wheels of the rear axle, and when emergency braking is needed, the braking system 60 is controlled to output the braking force to the wheels that brake normally; when the two wheels at the same side fail to brake, the driving system 50 is controlled to output the reverse torque to the two wheels of the front axle and the two wheels of the rear axle.

[0197] According to the above scheme of the application, when two wheels of the electric vehicle 10 fail to brake, the drive system 50 outputs a reverse torque to generate an effective braking effect without obvious yaw, and the scenario of diagonal wheel brake failure superimposes the braking of the normal diagonal wheel brake during emergency braking to provide additional braking force, which can effectively improve the safety and braking stability of the electric vehicle 10.

[0198] The following will be described in combination with Figures 19-23 The control method for the electric vehicle 10, the drive system 50 and the electric vehicle 10 provided by the embodiments of the application are described when multiple wheels (for example, three wheels or four wheels) of the electric vehicle brake fail. Figures 19-21 The signal timing diagram of the electric vehicle 10 during driving, Figure 19 The electric vehicle 10 in the above includes four drive motors 30, each of which is used to drive one wheel; Figure 20 The electric vehicle 10 in the above includes three drive motors 30, two of which are used to drive two rear wheels respectively, and one of which is used to drive two front wheels; Figure 21 The electric vehicle 10 in the above includes two drive motors 30, one of which is used to drive two front wheels, and the other of which is used to drive two rear wheels. Figures 19-21 The relationship between the drive torque output by the drive system 50, the reverse torque, the speed of the electric vehicle 10 and the opening degree of the brake pedal is included in the above. Figure 22 and Figure 23 The scenario diagram of the electric vehicle 10 during braking is included in the above.

[0199] As Figures 19-23 shown, the control method includes, during driving when the accelerator pedal of the electric vehicle 10 is depressed and the brake pedal is not depressed, controlling the drive system 50 to output a drive torque and controlling the drive torque output by the drive system 50 to change with the opening degree of the accelerator pedal, the direction of the drive torque being the same as the direction of the speed of the wheels of the electric vehicle 10. After the accelerator pedal is released and the brake pedal is depressed, the drive system 50 is controlled to stop outputting the drive torque and the drive system 50 is controlled to output a reverse torque and the reverse torque is controlled to change with the opening degree of the brake pedal, the direction of the reverse torque being opposite to the direction of the speed of the wheels.

[0200] The driving system 50 is capable of achieving the driving function and the braking function of the electric vehicle 10 by outputting driving torque or reverse torque to the four wheels. In the driving process in which the accelerator pedal of the electric vehicle 10 is depressed and the brake pedal is not depressed, i.e. in the driving process in which the opening degree of the accelerator pedal is greater than zero and the opening degree of the brake pedal is equal to zero, the driving system 50 is controlled to output driving torque, and the driving torque output by the driving system 50 changes with the change of the opening degree of the accelerator pedal. After the accelerator pedal is released and the brake pedal is depressed, i.e. after the opening degree of the accelerator pedal is equal to zero and the opening degree of the brake pedal is greater than zero, the driving system 50 is controlled to stop outputting driving torque and output reverse torque, and the reverse torque output by the driving system 50 changes with the change of the opening degree of the brake pedal. The driving system 50 achieves the driving function when being controlled in response to the opening degree of the accelerator pedal, and achieves the braking function when being controlled in response to the opening degree of the brake pedal.

[0201] According to the scheme of the present application, the driving system 50 is capable of achieving the braking function of the electric vehicle 10 in place of the braking system 60, adjusting the torque output in response to the change of the opening degree of the brake pedal to brake, achieving backup of the braking function at low cost, and improving the safety and stability of the electric vehicle 10.

[0202] In an embodiment, the control method is used to achieve braking by controlling the driving system 50 when the braking system 60 of the electric vehicle 10 fails, and the control method specifically comprises, after the accelerator pedal is released and the brake pedal is depressed, when the braking system 60 of the electric vehicle 10 fails, controlling the driving system 50 to stop outputting driving torque and controlling the driving system 50 to output reverse torque and controlling the reverse torque to change with the change of the opening degree of the brake pedal.

[0203] The braking system 60 detects that failure occurs, and the failure of the braking system 60 means that multiple wheel end brake devices among the four wheel end brake devices for braking the four wheels in the braking system 60 cannot normally output braking force to the corresponding wheels. The failure of the braking system 60 includes three-wheel braking failure or four-wheel braking failure. The reasons for braking failure include actuator failure, brake motor failure, controller failure, and wheel speed sensor failure. When the braking of multiple wheels fails, the braking system 60 cannot output braking force to the multiple wheels, which will cause the total braking force that the braking system 60 can generate to decrease, affecting the braking safety and stability of the electric vehicle 10.

[0204] When the electric vehicle 10 is in normal driving, the braking system 60 controls the wheel end brake device according to the opening degree of the brake pedal, so as to output the braking force indicated by the opening degree of the brake pedal. The greater the opening degree of the brake pedal, the greater the braking force output by the wheel end brake device. The smaller the opening degree of the brake pedal, the smaller the braking force output by the wheel end brake device. The braking force output by the braking system 60 changes with the change of the opening degree of the brake pedal.

[0205] In the driving process of the electric vehicle 10, before starting braking, the failure of the braking system 60 basically does not cause any impact, the control system controls the driving system 50 to output the opening degree indication of the accelerator pedal, and the driving system 50 drives the wheels with the driving torque whose direction is the same as the rotation direction of the wheels of the electric vehicle 10. When the failure of the braking system 60 of the electric vehicle 10 occurs before starting braking or after starting braking, after the failure of the braking system 60 is detected, the control system controls the driving system 50 to stop outputting the driving torque and controls the driving system 50 to output the reverse torque which changes with the opening degree of the brake pedal, so as to realize braking.

[0206] In an embodiment, the control method is also used to control the driving system 50 to output the driving torque which changes with the vehicle speed of the electric vehicle 10 when the failure of the braking system 60 of the electric vehicle 10 occurs in the driving process in which the accelerator pedal of the electric vehicle 10 is stepped on and the brake pedal is not stepped on.

[0207] In the driving process of the electric vehicle 10, before starting braking, the failure of the braking system 60 basically does not cause any impact, the control system controls the driving system 50 to output the opening degree indication of the accelerator pedal, and the driving system 50 drives the wheels with the driving torque whose direction is the same as the rotation direction of the wheels of the electric vehicle 10. When the failure of the braking system 60 of the electric vehicle 10 occurs before starting braking or after starting braking, after the failure of the braking system 60 is detected, the control system controls the driving system 50 to stop outputting the driving torque and controls the driving system 50 to output the reverse torque which changes with the opening degree of the brake pedal, so as to realize braking.

[0208] When the failure of the braking system 60 is detected, the vehicle speed is immediately limited. Since the failure of the braking system 60 will reduce the braking ability of the electric vehicle 10, in order to ensure the safety of the passengers, the speed of the electric vehicle 10 should be limited to avoid too fast speed from causing loss of control or failure to stop in time. Therefore, when the failure of the braking system 60 of the electric vehicle 10 occurs, the control system controls the driving system 50 to output the driving torque which changes with the vehicle speed of the electric vehicle 10, so as to limit the speed and acceleration of the electric vehicle 10.

[0209] In an embodiment, the control method is specifically used to control the driving system 50 to increase the driving torque which increases with the opening degree of the accelerator pedal when the vehicle speed of the electric vehicle 10 is less than a preset vehicle speed in the driving process in which the accelerator pedal of the electric vehicle 10 is stepped on and the brake pedal is not stepped on. When the vehicle speed is greater than the preset vehicle speed, the control system controls the driving system 50 to reduce the output driving torque.

[0210] When the vehicle speed of the electric vehicle 10 is less than the preset vehicle speed after the braking system 60 of the electric vehicle 10 fails, the control increases the driving torque output by the driving system 50 as the opening of the accelerator pedal increases, ensuring a certain acceleration and driving capability of the electric vehicle 10. After the time t1, when the vehicle speed of the electric vehicle 10 is greater than the preset vehicle speed, the vehicle speed exceeds the speed limit, and at this time the control reduces the driving torque output by the driving system 50, so that the vehicle speed of the electric vehicle 10 no longer increases.

[0211] In an embodiment, the control method specifically includes that, in the process of controlling the driving system 50 to output the reverse torque, the sum of the reverse torques output by the driving system 50 to the two front wheels is greater than the sum of the reverse torques output to the two rear wheels.

[0212] When the electric vehicle 10 brakes, the center of gravity of the electric vehicle 10 moves forward, causing the two front wheels to obtain greater downward pressure, the load of the front wheels increases, thereby being able to provide greater grip and braking force. The downward pressure of the rear wheels decreases, and the load of the rear wheels decreases. If the two rear wheels are allocated the same or greater braking force as the two front wheels, the rear wheels will lock up before the front wheels due to insufficient normal pressure, and once the rear wheels lock up, the electric vehicle 10 will lose lateral grip, and is prone to spin or slide to cause the vehicle to lose control. The front wheels are steering wheels, and even if they lock up, they will only cause the steering to fail, and the electric vehicle 10 will slide along a straight line, which is relatively easier to control. Therefore, in the process of controlling the driving system 50 to output the reverse torque, the sum of the reverse torques output by the driving system 50 to the two front wheels is greater than the sum of the reverse torques output to the two rear wheels, so that the braking force received by the two front wheels is greater than the braking force received by the two rear wheels.

[0213] In an embodiment, the control method further includes, after the accelerator pedal is released and the brake pedal is depressed, increasing the reverse torque output by the driving system 50 to the preset torque and then maintaining the preset torque.

[0214] The driving system 50 is affected by the driving motor 30, the power battery, and the wheel grip, and the reverse torque output by the driving system 50 has a certain limit. After the driver depresses the brake pedal, the reverse torque output by the driving system 50 is first controlled to change linearly with the opening of the brake pedal, and the greater the opening of the brake pedal, the greater the reverse torque output by the driving system 50. When the reverse torque output by the driving system 50 increases to the preset torque, the reverse torque that the driving system 50 can output reaches the limit, at which time the maximum reverse torque that the driving system 50 can output or the maximum reverse torque that can produce a braking effect is reached, and then the driving system 50 is controlled to maintain the preset torque.

[0215] In one embodiment, the control method specifically includes, in the process of controlling the driving system 50 to output the reverse torque, controlling the reverse torque output by the driving system 50 to the two front wheels to change with the average slip ratio of the two front wheels, and controlling the reverse torque output by the driving system 50 to the two rear wheels to change with the average slip ratio of the two rear wheels.

[0216] The driving system 50 includes a resolver sensor, and the rotational speed of the driving motor 30 can be obtained through the resolver signal of the resolver sensor. The angular speed of the wheel can be calculated through the rotational speed of the driving motor 30 and the transmission ratio of the electric vehicle, and further combined with the wheel radius and the speed of the electric vehicle 10 to obtain the slip ratio of each wheel. The slip ratio of the wheel affects the braking effect of the wheel, and when the slip ratio of the wheel is too large, the wheel slips, and at this time the wheel cannot generate effective braking force. Since the slip ratio of the wheel directly affects the braking effect of the wheel, the driving system 50 adjusts the slip ratio of the wheel by controlling the size of the reverse torque output.

[0217] The average slip ratio of the two front wheels refers to the average of the slip ratio of the left front wheel and the slip ratio of the right front wheel, and the average slip ratio of the two rear wheels refers to the average of the slip ratio of the left rear wheel and the slip ratio of the right rear wheel.

[0218] It should be understood that for the driving system 50 including four driving motors 30 as shown in FIG. 1, the driving system 50 controls the reverse torque output according to the slip ratio of each wheel. For the driving system 50 including three driving motors 30 as shown in FIG. 2, the driving system 50 controls the reverse torque output to the two front wheels according to the average slip ratio of the two front wheels, and controls the reverse torque output to the left rear wheel and the right rear wheel according to the slip ratio of the two rear wheels, respectively. For the driving system 50 including two driving motors 30 as shown in FIG. 3, the driving system 50 controls the reverse torque output to the two front wheels according to the average slip ratio of the two front wheels, and controls the reverse torque output to the two rear wheels according to the average slip ratio of the two rear wheels. Figure 4 Figure 5 Figure 6

[0219] In one embodiment, the control method specifically includes, in the process of controlling the driving system 50 to output the reverse torque, controlling the driving system 50 to adjust the reverse torque output to the four wheels so that the average slip ratio of the two front wheels is greater than the average slip ratio of the two rear wheels.

[0220] ​​​When the average slip ratio of the two front wheels is greater than the first slip ratio, the control system 50 reduces the reverse torque output to the two front wheels, and when the average slip ratio of the two front wheels is less than the first slip ratio, the control system 50 increases the reverse torque output to the two front wheels. When the average slip ratio of the two rear wheels is greater than the second slip ratio, the control system 50 reduces the reverse torque output to the two rear wheels, and when the average slip ratio of the two rear wheels is less than the second slip ratio, the control system 50 increases the reverse torque output to the two rear wheels.

[0221] The target slip ratio of the two front wheels, i.e. the first slip ratio, and the target slip ratio of the two rear wheels, i.e. the second slip ratio, are set respectively, and the target slip ratio of the front wheels is always greater than the target slip ratio of the rear wheels. During the output of the reverse torque, the control system 50 controls the size of the reverse torque output to the two front wheels and the size of the reverse torque output to the two rear wheels according to the average slip ratio of the two front wheels and the average slip ratio of the two rear wheels respectively, so that the slip ratios of the four wheels are within a suitable range, and thus the reverse torque output by the control system 50 can produce an effective braking effect. The first slip ratio and the second slip ratio are pre-calibrated according to real vehicle experiments and / or model calculations, or are pre-set by comprehensively considering the whole vehicle demand and vehicle performance.

[0222] In an embodiment, the control method further comprises, during the output of the reverse torque by the control system 50, when the yaw angle of the electric vehicle 10 is greater than zero, controlling the control system 50 to output a reverse torque to the left side wheels that is not equal to a reverse torque output to the right side wheels, and controlling the control system 50 to change the difference between the reverse torque output to the left side wheels and the reverse torque output to the right side wheels with the change of the yaw angle.

[0223] During braking, the electric vehicle 10 can yaw, and the electric vehicle 10 can deviate to one side. If the two coaxial wheels are respectively driven by the two drive motors 30, the reverse torque output by the left and right drive motors 30 is controlled according to the yaw angle of the electric vehicle 10, and the yaw of the electric vehicle 10 is suppressed by using the torque difference of the two drive motors 30. When the yaw angle of the electric vehicle 10 is greater than zero, it indicates that the electric vehicle 10 has yawed, at this time, the control system 50 controls the reverse torque output to the left side wheels to be not equal to the reverse torque output to the right side wheels, and controls the difference between the reverse torque output to the left side wheels and the reverse torque output to the right side wheels to change with the change of the yaw angle. The greater the yaw angle, the greater the difference between the reverse torque output to the left side wheels and the reverse torque output to the right side wheels.

[0224] In one embodiment, the control method further comprises, during the process of controlling the drive system 50 to output the reverse torque, when the steering wheel angle of the electric vehicle 10 does not change and the driving route of the electric vehicle 10 deviates to the left, controlling the drive system 50 to decrease the reverse torque output to one left wheel and increase the reverse torque output to one right wheel coaxial with the one left wheel.

[0225] During braking, the electric vehicle 10 can yaw when the steering wheel angle of the electric vehicle 10 does not change and the driving route of the electric vehicle 10 deviates to the left. At this time, the drive system 50 decreases the reverse torque output to one left wheel and increases the reverse torque output to one right wheel coaxial with the one left wheel, so that the reverse torque received by the two sides of the electric vehicle 10 is not equal, a yawing torque is generated, and the yawing of the electric vehicle 10 to the left is inhibited.

[0226] For example, as shown in FIG. 6, when the steering wheel angle of the electric vehicle 10 does not change and the driving route of the electric vehicle 10 deviates to the left, the drive system 50 decreases the reverse torque output to the left rear wheel and increases the reverse torque output to the right rear wheel. Figure 8

[0227] When the steering wheel angle of the electric vehicle 10 does not change and the driving route of the electric vehicle 10 deviates to the right, the drive system 50 decreases the reverse torque output to one right wheel and increases the reverse torque output to one left wheel coaxial with the one right wheel, so that the reverse torque received by the two sides of the electric vehicle 10 is not equal, a yawing torque is generated, and the yawing of the electric vehicle 10 to the right is inhibited.

[0228] For example, when the steering wheel angle of the electric vehicle 10 does not change and the driving route of the electric vehicle 10 deviates to the right, the drive system 50 decreases the reverse torque output to the right rear wheel and increases the reverse torque output to the left rear wheel.

[0229] In one embodiment, the control method specifically comprises, after the accelerator pedal is released and the brake pedal is depressed, controlling the preset torque output by the drive system 50 to change with the change of the power battery of the electric vehicle 10.

[0230] When the drive system 50 outputs the reverse torque, the drive system 50 outputs current to the power battery, thereby charging the power battery. Therefore, the amount of power of the power battery directly affects the preset torque that the drive system 50 can output, and when the amount of power of the power battery is high, the preset torque that the drive system 50 can output decreases.

[0231] ​In one embodiment, the control method is specifically used when the power battery of the electric vehicle 10 has an amount of electricity less than a preset value, the higher the amount of electricity of the power battery, the smaller the preset torque output by the drive system 50. When the amount of electricity of the power battery is greater than the preset value, the drive system 50 stops outputting the reverse torque.

[0232] When the remaining amount of electricity of the power battery is low, the battery management system allows the drive system 50 to output the reverse torque at the maximum power, at this time, the preset torque that can be output is large. When the remaining amount of electricity of the power battery is high, in order to protect the power battery from overcharging, the battery management system strictly limits or even prohibits the current input to the power battery, and the electric energy generated by the drive motor 30 cannot be effectively received by the power battery, so the drive system 50 must reduce the power generation, at this time, the preset torque that can be output by the drive system 50 is small.

[0233] When the amount of electricity of the power battery is less than the preset value, the preset torque that can be output by the drive system 50 decreases as the amount of electricity of the power battery increases. When the amount of electricity of the power battery is greater than the preset value, at this time, in order to protect the power battery from overcharging, the battery management system stops charging the power battery, and controls the drive system 50 to no longer output the reverse torque.

[0234] Figure 9 The flowchart of the control method provided by the present application is shown.

[0235] As shown in Figure 9 During driving, signals of the electric vehicle 10 such as the opening degree of the brake pedal, the amount of electricity of the power battery, the yaw angular velocity of the electric vehicle 10, the acceleration, etc. are collected. When the brake system 60 detects that failure occurs, it is determined whether the drive system 50 can output the reverse torque according to the amount of electricity of the power battery, and the size of the reverse torque that can be output is determined. After the brake system 60 fails, the drive system 50 is controlled to output the reverse torque to replace the brake system 60 to brake, before the reverse torque output by the drive system 50 reaches the preset torque, the reverse torque output by the drive system 50 has a linear relationship with the opening degree of the brake pedal, and the acceleration of the whole vehicle is limited. If the average slip ratio of the two wheels is greater than the target slip ratio, the size of the reverse torque output by the drive system 50 to the two wheels is adjusted.

[0236] For coaxial two wheels such as the left front wheel and the right front wheel or the left rear wheel and the right rear wheel, if there are two drive motors 30 to drive respectively, the drive system 50 controls the size of the reverse torque output by the left and right drive motors 30 according to the yaw angle and the acceleration of the electric vehicle 10, and uses the difference between the reverse torques output by the left and right drive motors 30 to suppress yaw.

[0237] According to the scheme of the application, when the brake system 60 fails, the acceleration of the whole vehicle is limited, and the drive system 50 is used to replace the brake system 60 to realize deceleration or stop. When the wheel slip rate becomes larger, the wheel slip rate is controlled by using the drive system 50, which can equivalently realize the anti-lock braking (ABS) function.

[0238] The above merely illustrates the specific embodiments of the application, but the protection scope of the application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A control method for electric vehicles, characterized in that, The control method is used to control the drive system and braking system to achieve safe braking of the electric vehicle after the braking of two wheels of the electric vehicle fails. The control method includes: During the operation of the electric vehicle, before the electric vehicle brakes, the drive torque output by the drive system is controlled to change with the opening of the accelerator pedal, and the direction of the drive torque is the same as the rotational speed direction of the wheels of the electric vehicle. During the braking process when the left front wheel and right rear wheel of the electric vehicle fail to brake, the drive system is controlled to output reverse torque to the two front wheels and two rear wheels of the electric vehicle respectively. The direction of the reverse torque is opposite to the rotational speed direction of the two front wheels.

2. The control method according to claim 1, characterized in that, The control method further includes: During the braking process when the left front wheel and right rear wheel brakes fail, the drive system is first controlled to output reverse torque to the two front wheels and the two rear wheels respectively, and then the braking system is controlled to output braking force to the right front wheel and left rear wheel of the electric vehicle.

3. The control method according to claim 1 or 2, characterized in that, The control method specifically includes: During the braking process when the left front wheel and right rear wheel brakes fail, if the opening of the brake pedal of the electric vehicle is less than the preset opening, the braking force output by the braking system is controlled to be zero. When the opening of the brake pedal increases to a value greater than or equal to the preset opening, the braking system is controlled to output braking force to the right front wheel and left rear wheel of the electric vehicle.

4. The control method according to claim 2 or 3, characterized in that, The control method specifically includes: During the braking process when the left front wheel and right rear wheel brakes fail, before the reverse torque output by the drive system to the two front wheels and the two rear wheels increases to a preset torque, the braking force output by the braking system is controlled to be zero. After the reverse torque output by the drive system to the two front wheels and the two rear wheels increases to the preset torque, the braking system is controlled to output braking force to the right front wheel and the left rear wheel of the electric vehicle.

5. The control method according to claim 4, characterized in that, During the process of the reverse torque output by the drive system to the two front wheels and the two rear wheels increasing to a preset torque, the control method further includes: The reverse torque output by the drive system to the two front wheels varies with the average slip ratio of the two front wheels, and the reverse torque output by the drive system to the two rear wheels varies with the average slip ratio of the two rear wheels.

6. The control method according to any one of claims 2-5, characterized in that, The control method specifically includes: During the braking process when the left front wheel and right rear wheel brakes fail, the drive system is controlled to output a reverse torque to the two front wheels and the two rear wheels that varies with the opening of the brake pedal, and the reverse torque output by the drive system is controlled to vary with the opening of the brake pedal.

7. The control method according to any one of claims 2-6, characterized in that, The control method specifically includes: During the braking process when the left front wheel and right rear wheel brakes fail, the reverse torque output by the drive system to the two front wheels is always greater than the reverse torque output to the two rear wheels, and the braking force output by the braking system to the right front wheel is always greater than the braking force output to the left rear wheel.

8. The control method according to any one of claims 1-7, characterized in that, The control method further includes: During the braking process when the left front wheel and left rear wheel of the electric vehicle fail to brake, or during the braking process when the right front wheel and right rear wheel of the electric vehicle fail to brake, the drive system is controlled to output reverse torque to the two front wheels and the two rear wheels.

9. The control method according to claim 8, characterized in that, The control method specifically includes: During the braking process when the left front wheel and left rear wheel of the electric vehicle fail to brake, or during the braking process when the right front wheel and right rear wheel of the electric vehicle fail to brake, the reverse torque output by the drive system changes with the opening of the brake pedal.

10. The control method according to claim 8 or 9, characterized in that, In the process of controlling the drive system to output reverse torque to the two front wheels and the two rear wheels, the control method further includes: The sum of the reverse torques output by the drive system to the two front wheels is always greater than the sum of the reverse torques output to the two rear wheels.

11. The control method according to any one of claims 1-10, characterized in that, The control method further includes: During the braking process when the brakes of the two front wheels of the electric vehicle fail, the braking system is controlled to output braking force to the two rear wheels of the electric vehicle, and the drive system is controlled to output reverse torque to the two front wheels.

12. The control method according to claim 11, characterized in that, The control method specifically includes: During the braking process when the two front wheels fail to brake, the braking force output by the braking system to the two rear wheels varies with the opening of the brake pedal, and the reverse torque output by the drive system varies with the opening of the brake pedal.

13. The control method according to claim 11 or 12, characterized in that, In the process of controlling the drive system to output reverse torque to the two front wheels, the control method further includes: The reverse torque output by the drive system to the two front wheels varies with the average slip ratio of the two front wheels.

14. An electric vehicle, characterized in that, The electric vehicle includes a brake pedal, an accelerator pedal, a braking system, a drive system, and four wheels. The opening of the brake pedal is used to indicate that the braking system outputs braking force, and the accelerator pedal is used to indicate that the drive system outputs drive torque. The braking system and the drive system are used to perform the control method as described in any one of claims 1-13.

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