A control method of an electric vehicle, a controller, and an electric vehicle

Abstract

This application provides a control method, controller, and electric vehicle for an electric vehicle. During the light braking phase (when the brake pedal opening is less than a first opening), the four wheels are controlled to primarily utilize regenerative braking force, supplemented by friction braking force. During the strong braking phase (when the brake pedal opening is greater than the first opening), the method further controls the two first wheels (whose brakes are not lightweighted) to primarily utilize friction braking force, supplemented by regenerative braking force, based on the different brakes on each wheel. Conversely, the two second wheels (whose brakes are lightweighted) are controlled to primarily utilize regenerative braking force, supplemented by friction braking force. This allows the two first wheels to bear the main friction braking load, preventing brake fade due to overheating of the two second wheels' brakes. This achieves a reasonable distribution of friction braking force and regenerative braking force among the four wheels, ensuring braking safety while also considering energy recovery efficiency. This reduces the unsprung mass of the vehicle and improves its overall energy efficiency.

Description

Technical Field

[0001] This application relates to the field of electric vehicles, and more particularly to a control method, controller, and electric vehicle for electric vehicles. Background Technology

[0002] Traditional vehicle braking systems are often designed for extreme load conditions such as long downhill slopes and high-speed emergency braking. To ensure braking performance, the braking system requires brake discs with larger outer diameters and thicker thicknesses, while the brake calipers and brackets also need to be strengthened. Although this type of braking system ensures the safety of the vehicle under extreme conditions, it also increases the unsprung mass of the vehicle, thereby reducing the overall energy efficiency of the vehicle.

[0003] Therefore, how to improve the overall energy efficiency of vehicles is an urgent problem to be solved. Summary of the Invention

[0004] This application provides a control method, controller, and electric vehicle for electric vehicles, which improves the overall energy efficiency of the vehicle by controlling the braking force of different wheels in stages.

[0005] To achieve the above objectives, this application adopts the following technical solution: Firstly, a control method for an electric vehicle is provided. This method coordinates the regenerative braking force output by the drive system to the four wheels and the friction braking force output by the braking system to the four wheels. The control method includes: During the braking process of an electric vehicle, after the brake pedal opening begins to increase but before it reaches the first opening degree, the total regenerative braking force output by the control drive system to the four wheels is greater than the total frictional braking force output by the braking system to the four wheels. During the braking process after the brake pedal opening reaches the first opening degree, the regenerative braking force output by the control drive system to the two first wheels is less than the regenerative braking force output to the two second wheels, and the frictional braking force output by the control braking system to the two first wheels is greater than the frictional braking force output to the two second wheels. Specifically, the brake mass of the two first wheels is greater than the brake mass of the two second wheels, or the friction area of ​​the two first wheels is greater than the friction area of ​​the two second wheels. The two first wheels can be either the two front wheels or the two rear wheels.

[0006] The control method provided in this embodiment controls braking force for electric vehicles with partially lightweight brakes based on different stages of brake pedal opening. During the light braking stage (brake pedal opening less than the first opening), the four wheels are controlled to primarily use regenerative braking force, supplemented by friction braking force. During the strong braking stage (brake pedal opening greater than the first opening), the two first wheels (with brakes not lightweighted) are further controlled to primarily use friction braking force, supplemented by regenerative braking force, based on the characteristics of each wheel's brakes. Conversely, the two second wheels (with lightweight brakes) are controlled to primarily use regenerative braking force, supplemented by friction braking force. This allows the two first wheels to bear the main friction braking load, preventing brake fade due to overheating of the two second wheels. This achieves a reasonable distribution of friction braking force and regenerative braking force among the four wheels, ensuring braking safety while also considering energy recovery efficiency. This reduces the unsprung mass of the vehicle and improves overall vehicle energy efficiency.

[0007] In one embodiment, the control method specifically includes: during the braking process after the brake pedal starts to increase but before the brake pedal opening increases to a first opening, controlling the rate of increase of the regenerative braking force output by the drive system to the two first wheels to be less than the rate of increase of the regenerative braking force output to the two second wheels.

[0008] In this embodiment, the two second wheels receive a larger share of the regenerative braking force distribution process, so that the regenerative braking force of the two second wheels replaces the friction braking force more in this stage, reducing the frictional heat generated by the brakes of the two second wheels in this stage and effectively reducing the temperature rise of the brakes of the two second wheels.

[0009] In one embodiment, the control method further includes: during the braking process after the brake pedal opening begins to increase and before the brake pedal opening increases to the first opening, controlling the total regenerative braking force output by the drive system to the four wheels to increase with the increase of the brake pedal opening, and controlling the total friction braking force output by the braking system to the four wheels to be zero.

[0010] This embodiment controls the total frictional braking force to zero, allowing the electric vehicle to rely entirely on regenerated braking force to meet braking requirements during this phase. This avoids heat generation in the brakes due to friction and reduces the temperature rise of the brakes. Simultaneously, since the frictional braking force is zero, all the kinetic energy of the electric vehicle is recovered and converted into electrical energy through the drive motor, improving energy recovery efficiency and avoiding energy loss caused by frictional braking, thereby improving the overall energy efficiency of the vehicle.

[0011] In one embodiment, the control method further includes: during braking after the brake pedal opening increases to a first opening, controlling the difference in regenerative braking force output by the drive system to the two first wheels and the two second wheels to increase with the increase in the driving speed of the electric vehicle, and controlling the difference in friction braking force output by the braking system to the two first wheels and the two second wheels to increase with the increase in the driving speed of the electric vehicle.

[0012] As the driving speed increases, the difference between the regenerative braking force output by the drive system to the two second wheels and the regenerative braking force output to the two first wheels further increases, allowing the two second wheels to bear more of the regenerative braking force. Simultaneously, the difference between the frictional braking force output by the braking system to the two first wheels and the two second wheels also further increases, allowing the two first wheels to bear more frictional braking force. Through this adjustment, the higher the driving speed, the greater the difference between the frictional braking forces of the two first wheels and the two second wheels, effectively reducing the frictional heat generated by the brakes of the two second wheels under high-speed braking conditions and preventing overheating and brake fade due to insufficient heat capacity during high-speed braking.

[0013] In one embodiment, the control method further includes: after the brake pedal opening increases to a first opening and before it increases to a second opening greater than the first opening, controlling the regenerative braking force output by the drive system to the two first wheels to stop increasing with the increase of the brake pedal opening, and controlling the regenerative braking force output by the drive system to the two second wheels to continue increasing with the increase of the brake pedal opening. After the brake pedal opening is increased to the second opening, the regenerative braking force output by the control drive system to the two first wheels and the two second wheels stops increasing with the increase of the brake pedal opening.

[0014] When the brake pedal opening continues to increase from the initial opening, it indicates that the driver's braking demand is further increasing, and at this stage, the regenerative braking force output capacity of the drive system may not be able to simultaneously meet the regenerative braking force requirements of both the first and second wheels. In this case, this embodiment first controls the regenerative braking force output by the drive system to stop increasing, so that the remaining distributable regenerative braking force of the drive motor is used to meet the needs of the two second wheels, thereby delaying the moment when the regenerative braking force reaches its upper limit as much as possible and reducing the risk of overheating of the brakes of the two second wheels.

[0015] In one embodiment, the control method further includes: after the brake pedal opening increases to a first opening and before the brake pedal opening increases to a second opening greater than the first opening, controlling the regenerative braking force output by the drive system to the two first wheels to stop increasing with the increase of the brake pedal opening, and controlling the regenerative braking force output by the drive system to the two first wheels to decrease with the increase of the brake pedal opening.

[0016] When the regenerative braking force of the two first wheels is actively reduced, the reduced regenerative braking force of the two first wheels can be redistributed to the two second wheels, so that the regenerative braking force of the two second wheels can continue to increase with the increase of the brake pedal opening, further reducing the participation of the friction braking force of the two second wheels, thereby avoiding increasing the thermal load of the two second wheels.

[0017] In one embodiment, the control method specifically includes: controlling the regenerative braking force output by the drive system to the two first wheels to decrease to zero when the brake pedal opening increases to a second opening.

[0018] This embodiment uses this control method to completely cancel the regenerative braking force of the two first wheels when the brake pedal opening increases to the second opening, so that the entire available share of the total regenerative braking force is distributed to the two second wheels. This ensures that the regenerative braking force of the two second wheels reaches its maximum value at the second opening, maximally replacing the friction braking force of the two second wheels and preventing the brakes of the two second wheels from overheating during strong braking.

[0019] In one embodiment, the control method further includes: controlling the rate of decrease of the regenerative braking force output by the drive system to the two first wheels to increase as the temperature of the friction pads of the two second wheels increases.

[0020] When the friction pads of the two second wheels are at a low temperature, it indicates that the thermal load on the two second wheels is relatively small. At this time, the regenerative braking force of the two first wheels can decrease at a slower rate, transferring to the two second wheels more gradually. When the friction pads of the two second wheels rise to a higher level, it indicates that the two second wheels are at risk of overheating. If the two first wheels continue to transfer the regenerative braking force to the two second wheels at a slower rate, the friction braking force of the two second wheels will engage in braking, causing the friction pad temperature of the two second wheels to increase further. Therefore, this embodiment controls the regenerative braking force of the two first wheels to decrease at a faster rate when the friction pad temperature of the two second wheels increases, accelerating the rate of transfer to the two second wheels, thereby reducing the participation of the friction braking force of the two second wheels and preventing the friction pad temperature of the two second wheels from rising further.

[0021] In one embodiment, the control method further includes: after the brake pedal opening increases to a first opening and before it increases to a level greater than a second opening, controlling the regenerative braking force output by the drive system to the two first wheels to remain constant for a preset time after it stops increasing with the increase of the brake pedal opening, and then starting to decrease with the increase of the brake pedal opening after the preset time.

[0022] By setting a preset holding period after the regenerative braking force increases, the regenerative braking force of the two first wheels remains constant within this preset period, providing time for the two second wheels to utilize the remaining allocable regenerative braking force. During this preset period, the two second wheels can gradually increase their regenerative braking force, utilizing the remaining allocable force to meet their increasing braking demands. When the preset period ends, the two second wheels have completed utilizing the remaining allocable regenerative braking force, raising their regenerative braking force to a higher level. At this point, the regenerative braking force of the two first wheels begins to decrease and is transferred to the two second wheels, avoiding energy waste caused by premature transfer of regenerative braking force from the two first wheels and improving the energy utilization efficiency of the electric vehicle.

[0023] In one embodiment, the control method further includes: controlling a preset duration inversely proportional to the driving speed of the electric vehicle.

[0024] When the driving speed is high, the preset duration is short, causing the regenerative braking force of the two first wheels to remain constant for a short period before decreasing. This allows the two second wheels to quickly utilize the regenerative braking force transferred from the first wheels, meeting the rapid braking response requirements of electric vehicles during high-speed braking. When the driving speed is low, the preset duration is long, causing the regenerative braking force of the two first wheels to remain constant for a longer period. This delays the transfer of regenerative braking force from the two first wheels when the utilization rate of the two second wheels is slower, avoiding energy waste caused by premature transfer of regenerative braking force from the two first wheels.

[0025] In one embodiment, the control method further includes: controlling the second braking torque output by the braking system to the two first wheels to increase at a first rate within a preset time period, and to increase at a second rate greater than the first rate after the preset time period.

[0026] Within a preset time period during which the regenerative braking force of the two first wheels remains constant, their frictional braking force is gradually increased at a small first rate to smoothly compensate for the braking force gap caused by the cessation of regenerative braking force increase, thus avoiding sudden changes in braking force. After a preset time period during which the regenerative braking force of the two first wheels begins to decrease, their frictional braking force increases rapidly at a larger second rate, which not only meets the ever-increasing braking demand but also compensates for the braking force lost by the two first wheels due to the decrease in regenerative braking force.

[0027] In one embodiment, the control method further includes controlling the difference between the first opening degree and the second opening degree to be inversely proportional to the remaining power charge of the electric vehicle's power battery.

[0028] When the remaining charge of the power battery is high, the difference between the first and second opening degrees is small; when the remaining charge of the power battery is low, the difference between the first and second opening degrees is large. Through this control, the difference between the first and second opening degrees is dynamically adjusted according to the remaining charge of the power battery, so that the output range of the regenerative braking force matches the charging acceptance capacity of the power battery. This protects the power battery from the risk of overcharging while maximizing the utilization of regenerative braking force, thereby improving the energy recovery efficiency of the entire vehicle.

[0029] Secondly, this application provides a controller for an electric vehicle, which is used to: during braking, after the brake pedal opening of the electric vehicle begins to increase but before the brake pedal opening increases to a first opening, control the total regenerative braking force output by the drive system to the four wheels to be greater than the total frictional braking force output by the braking system to the four wheels. During braking after the brake pedal opening increases to the first opening, control the regenerative braking force output by the drive system to the two first wheels to be less than the regenerative braking force output to the two second wheels, and control the frictional braking force output by the braking system to the two first wheels to be greater than the frictional braking force output to the two second wheels. Wherein, the brake mass of the two first wheels is greater than the brake mass of the two second wheels, or the friction area of ​​the two first wheels is greater than the friction area of ​​the two second wheels, and the two first wheels are either two front wheels or two rear wheels.

[0030] In one embodiment, the controller is further configured to: during braking after the brake pedal opening increases to a first opening, control the difference in regenerative braking force output by the drive system to the two first wheels and the two second wheels to increase as the driving speed of the electric vehicle increases, and control the difference in friction braking force output by the braking system to the two first wheels and the two second wheels to increase as the driving speed of the electric vehicle increases.

[0031] In one embodiment, the controller is further configured to: after the brake pedal opening increases to a first opening and before it increases to a second opening greater than the first opening, control the regenerative braking force output by the drive system to the two first wheels to stop increasing with the increase of the brake pedal opening, and control the regenerative braking force output by the drive system to the two second wheels to continue increasing with the increase of the brake pedal opening. After the brake pedal opening is increased to the second opening, the regenerative braking force output by the control drive system to the two first wheels and the two second wheels stops increasing with the increase of the brake pedal opening.

[0032] In one embodiment, the controller is further configured to: control the difference between the first opening degree and the second opening degree to be inversely proportional to the remaining power of the electric vehicle's power battery.

[0033] In one embodiment, the controller is further configured to: after the brake pedal opening increases to a first opening and before the brake pedal opening increases to a second opening greater than the first opening, control the regenerative braking force output by the drive system to the two first wheels to stop increasing with the increase of the brake pedal opening, and control the regenerative braking force output by the drive system to the two first wheels to decrease with the increase of the brake pedal opening.

[0034] In one embodiment, the controller is specifically configured to: control the regenerative braking force output by the drive system to the two first wheels to decrease to zero when the brake pedal opening increases to a second opening.

[0035] In one embodiment, the controller is further configured to: control the rate of decrease of the regenerative braking force output by the drive system to the two first wheels to increase as the temperature of the friction pads of the two second wheels increases.

[0036] In one embodiment, the controller is further configured to: after the brake pedal opening increases to a first opening and before it increases to a level greater than a second opening, control the regenerative braking force output by the drive system to the two first wheels to remain constant for a preset time after it stops increasing with the increase of the brake pedal opening, and then begin to decrease with the increase of the brake pedal opening after the preset time.

[0037] In one embodiment, the controller is further configured to: control a preset duration inversely proportional to the driving speed of the electric vehicle.

[0038] In one embodiment, the controller is further configured to: control the second braking torque output by the braking system to the two first wheels to increase at a first rate within a preset time period, and to increase at a second rate greater than the first rate after the preset time period.

[0039] In one embodiment, the controller is specifically configured to: during braking, after the brake pedal begins to increase but before the brake pedal opening increases to a first opening, control the rate of increase of the regenerative braking force output by the drive system to the two first wheels to be less than the rate of increase of the regenerative braking force output to the two second wheels.

[0040] In one embodiment, the controller is further configured to: during braking, after the brake pedal opening begins to increase but before the brake pedal opening increases to a first opening, control the total regenerative braking force output by the drive system to the four wheels to increase with the increase of the brake pedal opening, and control the total friction braking force output by the braking system to the four wheels to be zero.

[0041] Thirdly, this application provides an electric vehicle, which includes a braking system, a drive system, and a controller. The drive system is used to output regenerative braking force to four wheels, the braking system is used to output friction braking force to four wheels, and the controller is used to execute the control methods as described in the first aspect and various embodiments of the first aspect.

[0042] For details on other beneficial effects, please refer to the beneficial effects described in the first aspect, which will not be repeated here. Attached Figure Description

[0043] Figure 1 A schematic diagram of a vehicle architecture provided for an embodiment of this application; Figure 2 A schematic diagram of the structure of a drive system provided in an embodiment of this application; Figure 3 This is a schematic diagram of a braking system provided in an embodiment of this application; Figure 4 This is a schematic diagram of operating parameters during vehicle braking, provided as an embodiment of this application. Detailed Implementation

[0044] The technical solutions in this application will now be described in conjunction with the accompanying drawings. The detailed descriptions and drawings of the following embodiments are used to exemplarily illustrate the principles of this application, but should not be used to limit the scope of this application; that is, this application is not limited to the described embodiments.

[0045] It should be noted that, in this application, the terms "exemplary" or "for example" are used to indicate that something is being described as an example, illustration, or illustration. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design solutions. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0046] Traditional vehicle braking systems are often designed for extreme load conditions such as long downhill slopes and high-speed emergency braking. To ensure braking performance, the braking system requires brake discs with larger outer diameters and thicker thicknesses, while the brake calipers and brackets also need to be strengthened. Although this type of braking system ensures the safety of the vehicle under extreme conditions, it also increases the unsprung mass of the vehicle, thereby reducing the overall energy efficiency of the vehicle.

[0047] In one embodiment, brake discs and calipers made of lightweight materials such as carbon fiber or aluminum alloy can be used to reduce the overall weight of the braking system. However, the manufacturing process of such a lightweight braking system is relatively complex, which is not conducive to reducing the manufacturing cost of the vehicle.

[0048] To address the aforementioned issues, this application provides a control method, controller, and electric vehicle for an electric vehicle. This electric vehicle features lightweight brakes on two second wheels, reducing their mass or friction area to less than that of two first wheels. Furthermore, it controls the braking force of each of the four wheels based on different stages of brake pedal opening. During light braking (when the brake pedal opening is less than the first opening), the four wheels are controlled to primarily utilize regenerative braking, supplemented by friction braking. During strong braking (when the brake pedal opening is greater than the first opening), the two first wheels with unlightened brakes are controlled to primarily utilize friction braking, supplemented by regenerative braking, while the two second wheels with lightweight brakes are controlled to primarily utilize regenerative braking, supplemented by friction braking. This allows the two first wheels to bear the primary friction braking load, preventing brake fade due to overheating of the two second wheels. This achieves a reasonable distribution of friction braking and regenerative braking among the four wheels, ensuring braking safety while also considering energy recovery efficiency, thereby reducing the unsprung mass of the vehicle and improving its overall energy efficiency.

[0049] The following section will introduce the vehicle architecture and system architecture on which this application is based.

[0050] See Figure 1 , Figure 1 This is a schematic diagram of a vehicle architecture provided in an embodiment of this application. Vehicle 10 may be an electric vehicle. Figure 1 As shown, vehicle 10 includes a drive system 110, a braking system 150, and a vehicle controller 140 connected to the drive system 110 and the braking system 150, respectively. The drive system 110 drives vehicle 10. The braking system 150 outputs braking force to the four wheels of vehicle 10. The vehicle controller 140 controls the torque output by the drive system 110 to the four wheels of vehicle 10 and the friction braking force output by the braking system 150 to the four wheels of vehicle 10.

[0051] The four wheels of vehicle 10 can be divided into two front wheels 120 and two rear wheels 130 according to their position on the axle. The two front wheels 120 are located on the front axle of vehicle 10, and the two rear wheels 130 are located on the rear axle of vehicle 10. For two wheels located on the same axle, according to their position relative to the vehicle body, the two front wheels 120 can be further divided into left front wheels and right front wheels, and the two rear wheels can be divided into left rear wheels and right rear wheels. That is to say, vehicle 10 has two front wheels 120 (left front wheel and right front wheel) and two rear wheels 130 (left rear wheel and right rear wheel).

[0052] refer to Figure 2The diagram illustrates the structure of a drive system. The drive system 110 can be referred to as a powertrain. This application does not limit the specific type of the drive system 110. The drive system 110 includes a drive motor 111 and a drive controller 112 connected to the drive motor 111. There may be two drive motors 111, each connected to two front wheels 120 and two rear wheels 130, respectively, for outputting torque to the two front wheels 120 and the two rear wheels 130. The drive controller 112 controls the drive motors 111 to output torque to the two front wheels 120 and the two rear wheels 130.

[0053] The torque output by the drive motor 111 during vehicle 10 operation can be converted into a driving force that causes the two front wheels 120 and the two rear wheels 130 to rotate, and also into a regenerative braking force that resists the rotation of the two front wheels 120 and the two rear wheels 130. Specifically, the drive motor 111 is an electric generator that simultaneously functions as a motor and a generator. When the drive motor 111 is in motor mode, it outputs positive torque. This positive torque is transmitted to the two front wheels 120 and the two rear wheels 130 via the transmission and drive shaft, forming a driving force that propels the vehicle forward, causing the two front wheels 120 and the two rear wheels 130 to roll forward against road friction and air resistance. When the vehicle 10 decelerates or brakes, the drive motor 111 switches to generator mode. At this time, the two front wheels 120 and the two rear wheels 130 will continue to rotate due to inertia, dragging the rotor of the drive motor 111 in the opposite direction. The rotating rotor cuts magnetic field lines in the magnetic field generated by the stator windings, thereby generating induced electromotive force and current, and also producing a reverse torque opposite to the direction of rotor rotation. This reverse torque acts in the opposite direction to the two front wheels 120 and the two rear wheels 130 through the drive shaft, thus forming a regenerative braking force that opposes the rotation of the two front wheels 120 and the two rear wheels 130.

[0054] refer to Figure 3 The diagram illustrates the structure of a braking system 150. The braking system 150 includes four brakes 151 and a brake controller 152 connected to each of the four brakes 151. The four brakes 151 are respectively connected to two front wheels 120 and two rear wheels 130, and are used to output friction braking forces to the two front wheels 120 and two rear wheels 130 respectively. The brake controller 152 controls the four brakes 151 to output friction braking forces to the two front wheels 120 and two rear wheels 130 respectively.

[0055] Brake 151 can be either a shoe brake or a caliper brake. The following description uses a caliper brake as an example. Brake 151 can include a brake caliper and a brake disc. The brake disc is connected to the wheel and rotates with the wheel during wheel rotation. The brake caliper is mounted on the axle and remains relatively stationary to the vehicle body while the vehicle 10 is in motion. When the vehicle 10 brakes, the brake caliper tightens to clamp the brake disc, using the frictional braking force generated by clamping the brake disc to brake the vehicle 10. The contact area between the brake caliper and the brake disc when clamping is called the friction area. Similarly, for a shoe brake, the friction area can refer to the contact area between the friction lining on the brake shoe and the brake drum when the brake 151 outputs frictional braking force.

[0056] For the braking system 150, the brakes of the two first wheels can be reinforced brakes, and the brakes of the two second wheels can be lightweight brakes, thereby reducing the unsprung mass of the vehicle 10. Specifically, the mass of the brakes of the two first wheels is greater than the mass of the brakes of the two second wheels, or the friction area of ​​the two first wheels is greater than the friction area of ​​the two second wheels. The two first wheels can be two front wheels 120, and the two second wheels can be two rear wheels 130, or the two first wheels can be two rear wheels 130, and the two second wheels can be two front wheels 120.

[0057] The following combination Figures 1 to 3 The vehicle architecture shown in this application details the control method for the electric vehicle provided in this application. The control method provided in this application can be controlled collaboratively by the vehicle controller 140, the drive controller 112, and the brake controller 152, or it can be controlled independently by a single controller that integrates the control functions of the vehicle controller 140, the drive controller 112, and the brake controller 152.

[0058] The following description uses a vehicle 10 with two front wheels 120 as the first wheels and two rear wheels 130 as the second wheels as the third wheels. In actual control, the control method mentioned below can also be applied to the vehicle 10 with two rear wheels 130 as the first wheels and two front wheels 120 as the second wheels. The specific control method when applied to this vehicle 10 can be found below, and will not be repeated here.

[0059] refer to Figure 4The diagram illustrates the operating parameters during vehicle braking. Before time t1, the driver has not pressed the brake pedal, and the brake pedal opening of vehicle 10 is zero. At time t1, the driver begins to press the brake pedal, causing the brake pedal opening to increase from time t1. At time t2, after time t1, the brake pedal opening increases to a first opening. At time t3, after time t2, the brake pedal opening increases to a second opening greater than the first opening. Time t4 is the time between time t2 and time t3, with a preset time interval from time t2. The first and second openings are preset different pedal opening thresholds used to distinguish different braking stages.

[0060] Before time t1, the driver has not pressed the brake pedal, the brake pedal opening is zero, and vehicle 10 is in a non-braking state. When the driver begins to press the brake pedal, the brake pedal opening starts to increase at time t1, and vehicle 10 enters a braking state. During the braking process after time t1 and before time t2, that is, after the brake pedal opening begins to increase but before it reaches the first opening, the brake pedal opening is relatively small, the driver's braking demand is small, and it can be basically met by the regenerative braking force output by the drive system.

[0061] Therefore, between time t1 and time t2, the vehicle controller 140 can send control commands to the drive controller 112 and the brake controller 152 respectively. This causes the drive controller 112 to control the total regenerative braking force output by the drive motor 111 to the four wheels to be greater than the total frictional braking force output by the brake 151 to the four wheels, and the brake controller 152 to control the total frictional braking force output by the brake 151 to the four wheels to be less than the total regenerative braking force output by the drive motor 111 to the four wheels. Through this control method, the regenerative braking force can dominate during this stage, while the frictional braking force participates less, reducing the heat generated by the brake 151 during this stage. This helps to lower the temperature of the brake 151 and reserves heat capacity for potentially more intense braking in the future.

[0062] As the driver continues to depress the brake pedal, the brake pedal opening increases to its initial position at time t2. During the braking process after time t2 (including the time interval from t2 to t3 and beyond), the brake pedal opening is relatively large, indicating a strong braking demand from the driver. Therefore, to meet this strong braking demand, it is necessary to increase the total frictional braking force to increase the overall braking force of the electric vehicle.

[0063] Furthermore, because the brakes 151 of the two rear wheels 130 are lightweight, the brakes of the two front wheels 120 have a greater mass than the brakes of the two rear wheels 130, or the friction area of ​​the two front wheels 120 is greater than that of the two rear wheels 130. Therefore, the heat capacity of the two front wheels 120 is greater than that of the two rear wheels 130. This makes the brakes 151 of the two rear wheels 130 more prone to thermal fade due to excessive heat. Considering this, in one embodiment, the vehicle controller 140 can send control commands to the drive controller 112 and the brake controller 152 respectively, so that the drive controller 112 controls the drive motor 111 to output a less regenerative braking force to the two front wheels 120 than to the two rear wheels 130, and the brake controller 152 controls the brakes 151 to output a greater frictional braking force to the two front wheels 120 than to the two rear wheels 130.

[0064] In this embodiment, after time t2, the two front wheels 120 rely more on friction braking force, and the two rear wheels 130 rely more on regenerative braking force. This allows the brakes 151 of the two front wheels 120, which have a larger heat capacity, to bear the main friction braking load, thus preventing the brakes 151 of the two rear wheels 130 from generating too much heat and causing thermal fade, thereby ensuring the driving safety of the vehicle 10.

[0065] In summary, the control method provided in this embodiment adopts different braking control measures for the vehicle 10 with partially lightweight brakes 151 according to different stages of brake pedal opening. Specifically, during the slight braking stage when the brake pedal opening is less than the first opening, the four wheels are controlled to primarily use regenerative braking force, supplemented by friction braking force. During the strong braking stage when the brake pedal opening is greater than the first opening, the two front wheels 120 with non-lightweight brakes 151 are further controlled to primarily use friction braking force, supplemented by regenerative braking force, based on the characteristics of each wheel's brake 151. The two rear wheels 130 with lightweight brakes 151 are controlled to primarily use regenerative braking force, supplemented by friction braking force. This allows the two front wheels 120 to bear the main friction braking load to avoid overheating and brake fade of the two rear wheels 130's brakes 151, achieving a reasonable distribution of friction braking force and regenerative braking force among the four wheels. This ensures braking safety while also considering energy recovery efficiency, thereby reducing the unsprung mass of the vehicle and improving the overall energy efficiency.

[0066] Based on the above control method, this application can be further improved to enhance the driving performance of vehicle 10 in all aspects, as detailed below.

[0067] The two front wheels 120 and the two rear wheels 130 have different heat capacities due to differences in brake mass or friction area. The brakes 151 of the two front wheels 120 have a greater heat capacity difference compared to the brakes 151 of the two rear wheels 130 because they have a larger brake mass or friction area. Therefore, during the slight braking phase after time t1 and before time t2, the brakes 151 of the two rear wheels 130 are more prone to overheating due to their smaller heat capacity.

[0068] Considering this issue, in this embodiment, between time t1 and time t2, the rate of increase of the regenerative braking force output by the drive motor 111 to the two front wheels 120 is less than the rate of increase of the regenerative braking force output to the two rear wheels 130, so that the two rear wheels 130 receive a larger share in the process of regenerative braking force distribution, and the regenerative braking force of the two rear wheels 130 replaces the friction braking force more in this stage, reducing the frictional heat generated by the brakes 151 of the two rear wheels 130 in this stage, and effectively reducing the temperature rise of the brakes 151 of the two rear wheels 130.

[0069] Furthermore, the brake pedal opening is relatively small between time t1 and time t2, indicating a mild braking demand from the driver. During this phase, when vehicle 10 relies on frictional braking force to meet the braking demand, brake 151 generates heat due to friction, causing its temperature to rise. Moreover, given the relatively low braking demand during this phase, the participation of frictional braking force causes some kinetic energy to be converted into heat energy through friction, resulting in some energy not being effectively utilized.

[0070] To address this issue, in this embodiment, during the braking process between time t1 and time t2, the vehicle controller 140 outputs control commands to the drive controller 112 and the brake controller 152 respectively. This causes the drive controller 112 to control the drive motor 111 to increase the total regenerative braking force output to the four wheels as the brake pedal opening increases, while the brake controller 152 controls the brake 151 to output zero total frictional braking force to the four wheels. By controlling the total frictional braking force to zero, the vehicle 10 relies entirely on regenerative braking force to meet braking requirements during this phase, avoiding heat generation from friction in the brake 151 and reducing its temperature rise. Simultaneously, since the frictional braking force is zero, all the kinetic energy of the vehicle 10 is recovered and converted into electrical energy through the drive motor 111, improving energy recovery efficiency, avoiding energy loss due to frictional braking, and thus improving the overall vehicle energy efficiency.

[0071] In one embodiment, when the driver depresses the brake pedal, it can first determine whether the current braking is emergency braking. If the brake pedal opening is greater than a preset opening and the rate of increase of the brake pedal opening is greater than a preset rate, then it is determined to be emergency braking; otherwise, it is non-emergency braking. In the event of emergency braking, between time t1 and t2, the vehicle controller 140 can ensure that the total regenerative braking force output by the drive motor 111 to the four wheels is greater than the total frictional braking force output by the brake 151 to the four wheels, and that the brake controller 152 ensures that the total frictional braking force output by the brake 151 to the four wheels is less than the total regenerative braking force output by the drive motor 111 to the four wheels. Furthermore, in the event of emergency braking, the drive controller 112 ensures that the regenerative braking force output by the drive motor 111 to the two front wheels 120 is less than the regenerative braking force output to the two rear wheels 130, and the brake controller 152 ensures that the frictional braking force output by the brake 151 to the two front wheels 120 is greater than the frictional braking force output to the two rear wheels 130.

[0072] During actual driving, the braking intensity and thermal load conditions of vehicle 10 vary significantly when it undergoes high-intensity braking at different speeds. When vehicle 10 brakes at higher speeds, its kinetic energy is greater, and the brakes 151 generate more heat, thus increasing the thermal load on the brakes 151 of both front wheels 120 and rear wheels 130. However, because the brakes of the two front wheels 120 have a greater mass than those of the two rear wheels 130, or because the friction area of ​​the two front wheels 120 is greater than that of the two rear wheels 130, under the same braking intensity, the temperature rise rate of the brakes 151 of the two rear wheels 130 is faster than that of the brakes 151 of the two front wheels 120, and their risk of thermal fade is also higher.

[0073] This embodiment takes this problem into consideration. During the braking process after time t2, the vehicle controller 140 sends control commands to the drive controller 112 and the brake controller 152 respectively. This causes the difference in regenerative braking force output by the drive motor 111 controlled by the drive controller 112 to the two front wheels 120 and the two rear wheels 130 to increase as the vehicle speed of 10 increases. It also causes the brake controller 152 to control the difference in friction braking force output by the brake 151 to the two front wheels 120 and the two rear wheels 130 to increase as the vehicle speed of 10 increases.

[0074] As the driving speed increases, the difference between the regenerative braking force output by the drive motor 111 to the two rear wheels 130 and the regenerative braking force output to the two front wheels 120 further increases, allowing the two rear wheels 130 to bear more of the regenerative braking force. Simultaneously, the difference between the frictional braking force output by the brake 151 to the two front wheels 120 and the frictional braking force output to the two rear wheels 130 also further increases, allowing the two front wheels 120 to bear more of the frictional braking force. Through this adjustment, the greater the difference between the frictional braking forces of the two front wheels 120 and the two rear wheels 130 at higher speeds, the less frictional heat is generated by the brakes 151 of the two rear wheels 130, thus preventing overheating and brake fade during high-speed braking due to insufficient heat capacity.

[0075] The total regenerative braking force output capacity of the drive motor 111 is limited. Once the brake pedal opening increases to the initial opening, as the driver continues to depress the brake pedal, the braking demand will further increase, and the actual total regenerative braking force output by the drive motor 111 will gradually approach its output limit. In this situation, if the brake pedal opening continues to increase, the risk of overheating of the brakes 151 on the two rear wheels 130 will rise sharply due to their relatively small heat capacity and the limited regenerative braking force reaching their limit.

[0076] This embodiment takes this problem into consideration. Between time t2 and time t3, the vehicle controller 140 sends control commands to the drive controller 112, causing the drive controller 112 to control the regenerative braking force output by the drive motor 111 to the two front wheels 120 to stop increasing with the increase of the brake pedal opening, while controlling the regenerative braking force output by the drive motor 111 to the two rear wheels 130 to continue increasing with the increase of the brake pedal opening. After time t3, the drive controller 112 further controls the regenerative braking force output by the drive motor 111 to both the two front wheels 120 and the two rear wheels 130 to stop increasing with the increase of the brake pedal opening.

[0077] When the brake pedal opening continues to increase from the initial opening, it indicates that the driver's braking demand is further increasing, and at this stage, the regenerative braking force output capability of the drive motor 111 may not be able to simultaneously meet the regenerative braking force requirements of the two front wheels 120 and the two rear wheels 130. In this case, this embodiment first controls the drive system to stop increasing the regenerative braking force output to the two front wheels 120, so that the remaining distributable regenerative braking force of the drive motor 111 is used to meet the needs of the two rear wheels 130, thereby delaying the moment when the regenerative braking force reaches its upper limit as much as possible and reducing the risk of overheating of the brakes 151 of the two rear wheels 130.

[0078] Furthermore, between time t2 and time t3, after the regenerative braking force output by the drive motor 111 to the two front wheels 120 stops increasing with the increase of the brake pedal opening, the frictional braking force output by the brakes 151 of the two front wheels 120 can be controlled to begin increasing with the increase of the brake pedal opening, thereby meeting the driver's braking needs through the increased frictional braking force. Similarly, after time t3, when the regenerative braking force output by the drive motor 111 to both front wheels 120 and both rear wheels 130 stops increasing with the increase of the brake pedal opening, the frictional force output by the brakes 151 of the two rear wheels 130 can also be controlled to begin increasing with the increase of the brake pedal opening.

[0079] After time t2, as time t3 approaches, the total regenerative braking force output by the drive motor 111 gradually approaches its upper limit. At this point, if the regenerative braking force of the two front wheels 120 stops increasing and remains constant, then even with the total regenerative braking force approaching its upper limit, the regenerative braking force available to the two rear wheels 130 will still be limited and insufficient to fully meet their needs. The two rear wheels 130 will then have to increase the participation of friction braking force, leading to an increase in the thermal load on the brakes 151 of the two rear wheels 130.

[0080] To address this issue, in this embodiment, between time t2 and t3, the drive controller 112 controls the drive motor 111 to stop increasing the regenerative braking force output to the two front wheels 120 as the brake pedal opening increases, and controls the drive motor 111 to decrease the regenerative braking force output to the two front wheels 120 as the brake pedal opening increases. When the regenerative braking force of the two front wheels 120 actively decreases, the reduced regenerative braking force can be redistributed to the two rear wheels 130, allowing the regenerative braking force of the two rear wheels 130 to continue increasing as the brake pedal opening increases, further reducing the participation of friction braking force in the two rear wheels 130, thereby avoiding increasing the thermal load on the two rear wheels 130.

[0081] Between time t2 and t3, the regenerative braking force of the two front wheels 120 will gradually decrease as the brake pedal opening increases. After time t3, the regenerative braking force of the two rear wheels 130 will stop increasing. If, at time t3, when the pedal opening increases to the second opening, the regenerative braking force of the two front wheels 120 still maintains a value greater than zero, then this portion of the regenerative braking force still occupies a limited share of the total regenerative braking force, preventing the two rear wheels 130 from obtaining the maximum possible regenerative braking force and thus failing to minimize the risk of overheating.

[0082] This embodiment takes this problem into consideration. The drive controller 112 controls the drive motor 111 to reduce the regenerative braking force output to the two front wheels 120 to zero when the brake pedal opening increases to the second opening degree. Through this control method, the regenerative braking force of the two front wheels 120 is completely canceled when the brake pedal opening increases to the second opening degree, so that the entire available share of the total regenerative braking force is distributed equally to the two rear wheels 130. This ensures that the regenerative braking force of the two rear wheels 130 reaches its maximum value at the second opening degree, maximally replacing the friction braking force of the two rear wheels 130 and preventing overheating of the brakes 151 of the two rear wheels 130 during strong braking.

[0083] Furthermore, since the brakes 151 of the two front wheels 120 have a larger heat capacity, even if the two front wheels 120 rely entirely on their friction braking force to provide braking force, they can withstand the heat load brought by the friction braking force without heat fade. Thus, under the premise of fully ensuring the braking safety of the two front wheels 120, the brakes 151 of the two rear wheels 130 are prevented from overheating.

[0084] Between time t2 and t3, the regenerative braking force of the two front wheels 120 gradually decreases as the brake pedal opening increases. The braking force lost by the two front wheels 120 due to the decrease in regenerative braking force is compensated by the friction braking force output by the brake 151. During this process, the two rear wheels 130 mainly rely on regenerative braking force to achieve braking, with less participation from friction braking force. However, since the total regenerative braking force output capacity of the drive motor 111 is limited, when the braking demand increases rapidly, the regenerative braking force released by the two front wheels 120 may not be able to meet the regenerative braking force demand of the two rear wheels 130. The two rear wheels 130 will then have to brake through friction braking force, resulting in a significant increase in the temperature of the friction pads of the two rear wheels 130.

[0085] Considering this issue, in this embodiment, the rate at which the regenerative braking force output by the drive controller 112 to the two front wheels 120 decreases increases as the temperature of the friction pads of the two rear wheels 130 increases. When the temperature of the friction pads of the two rear wheels 130 is low, it indicates that the thermal load on the two rear wheels 130 is small. At this time, the regenerative braking force of the two front wheels 120 can decrease at a small rate and be transferred to the two rear wheels 130 at a relatively gentle speed. When the temperature of the friction pads of the two rear wheels 130 rises to a high level, it indicates that the two rear wheels 130 are at risk of overheating. If the two front wheels 120 continue to transfer the regenerative braking force to the two rear wheels 130 at a small rate, the friction braking force of the two rear wheels 130 will intervene in the braking of the two rear wheels 130, causing the temperature of the friction pads of the two rear wheels 130 to increase further. Therefore, in this embodiment, the regenerative braking force of the two front wheels 120 is controlled to decrease at a relatively large rate when the temperature of the friction plates of the two rear wheels 130 increases, thereby accelerating the rate at which it is transferred to the two rear wheels 130, thus reducing the participation of the friction braking force of the two rear wheels 130 and preventing the temperature of the friction plates of the two rear wheels 130 from rising further.

[0086] Between time t2 and t3, the regenerative braking force of the two front wheels 120 will first stop increasing with the increase of the brake pedal opening, and then begin to decrease. When the regenerative braking force of the two front wheels 120 stops increasing, the total regenerative braking force output by the drive motor 111 to the four wheels has not yet reached its upper limit, and there is still residual regenerative braking force that can be distributed to the two rear wheels 130. At this time, if the regenerative braking force of the two front wheels 120 begins to decrease immediately after it stops increasing, the regenerative braking force transferred from the two front wheels 120 will not be utilized effectively.

[0087] To address this issue, in this embodiment, the drive controller 112 first maintains a constant regenerative braking force output by the drive motor 111 to the two front wheels 120 between timest2 and t4. Then, between timest4 and t3, it controls the regenerative braking force output by the drive motor 111 to the two front wheels 120 to decrease as the brake pedal opening increases. By setting a preset holding period after the increase stops, the regenerative braking force of the two front wheels 120 remains constant within this preset period, providing time for the two rear wheels 130 to utilize the remaining allocable regenerative braking force. Within this preset period, the two rear wheels 130 can gradually increase their regenerative braking force, utilizing the remaining allocable regenerative braking force to meet their increasing braking demands. When the preset period ends, the two rear wheels 130 have completed utilizing the remaining allocable regenerative braking force, raising their regenerative braking force to a higher level. At this time, the regenerative braking force of the two front wheels 120 begins to decrease and is transferred to the two rear wheels 130, avoiding the energy waste caused by the premature transfer of the regenerative braking force of the two front wheels 120, and improving the energy utilization efficiency of the vehicle 10.

[0088] The regenerative braking force of the two front wheels 120 remains constant for a preset time after it stops increasing, while the two rear wheels 130 gradually increase their regenerative braking force during this preset time to utilize the remaining distributable regenerative braking force. During the process of the two rear wheels 130 utilizing the remaining distributable regenerative braking force, the utilization rate of the two rear wheels 130 is affected by the vehicle speed 10; a higher speed results in a faster utilization rate, and a lower speed results in a slower utilization rate.

[0089] To address this issue, in this embodiment, the drive controller 112 controls the preset duration of the interval between time t2 and time t4 to be inversely proportional to the vehicle 10's speed. When the speed is high, the preset duration is short, causing the regenerative braking force of the two front wheels 120 to remain constant for a short period before decreasing. This allows the two rear wheels 130 to quickly utilize the regenerative braking force transferred from the two front wheels 120, meeting the vehicle 10's need for rapid braking response during high-speed braking. When the speed is low, the preset duration is long, causing the regenerative braking force of the two front wheels 120 to remain constant for a longer period. This delays the transfer of regenerative braking force from the two front wheels 120 when the utilization rate of the two rear wheels 130 is slower, avoiding energy waste caused by premature transfer of regenerative braking force from the two front wheels 120.

[0090] Therefore, it can be seen that the preset duration of control in this embodiment is inversely proportional to the driving speed of the vehicle 10. By adaptively adjusting the preset duration according to the driving speed, the timing of the release of regenerative braking force by the two front wheels 120 can be matched with the actual utilization of the two rear wheels 130, thereby ensuring that the regenerative braking force output by the drive motor 111 can be fully utilized at all stages of the vehicle 10's driving, thereby improving the energy efficiency of the vehicle 10.

[0091] The regenerative braking force output by the drive motor 111 to the two front wheels 120 will remain constant for a preset time after it stops increasing, and will begin to decrease as the brake pedal opening increases after the preset time. However, regardless of whether it is within or after the preset time, the braking demand of the vehicle 10 on the two front wheels 120 will increase as the brake pedal opening increases. Therefore, the regenerative braking force of the two front wheels 120 will stop increasing with the brake pedal opening after time t2, and may even decrease with the brake pedal opening, making it impossible for the two front wheels 120 to meet the braking demand of the vehicle 10 after time t2.

[0092] This embodiment takes this problem into consideration. The brake controller 152 controls the brake 151 to increase the frictional braking force output to the two front wheels 120 at a first rate between time t2 and t4, and at a second rate greater than the first rate between time t4 and t3. Between time t2 and t4, when the regenerative braking force of the two front wheels 120 remains constant, the frictional braking force is controlled to gradually increase at a smaller first rate to smoothly compensate for the braking force gap caused by the cessation of regenerative braking force increase, avoiding sudden changes in braking force. Between time t4 and t3, when the regenerative braking force of the two front wheels 120 begins to decrease, the frictional braking force increases rapidly at a larger second rate, satisfying the continuously increasing braking demand and compensating for the braking force lost by the two front wheels 120 due to the decrease in regenerative braking force.

[0093] Through the above control, the rate of increase of the friction braking force of the two front wheels 120 increases slowly at a small rate when the regenerative braking force of the two front wheels 120 remains constant, and increases rapidly at a larger rate when the regenerative braking force of the two front wheels 120 decreases. This makes the growth rhythm of the friction braking force of the two front wheels 120 match the change law of the regenerative braking force of the two front wheels 120, thus ensuring the smoothness and effectiveness of braking.

[0094] The total regenerative braking force output by the drive motor 111 varies with the remaining charge of the power battery. When the remaining charge of the power battery is high, the acceptable charging power of the power battery is limited, thus the upper limit of the total regenerative braking force output by the drive motor 111 is low. Conversely, when the remaining charge of the power battery is low, the acceptable charging power of the power battery is high, thus the upper limit of the total regenerative braking force output by the drive motor 111 is high. Therefore, if the first opening degree and the second opening degree remain unchanged during the driving of the vehicle 10, the regenerative braking force output capability of the drive motor 111 may not be fully utilized.

[0095] To address this issue, this embodiment controls the difference between the first and second opening degrees to be inversely proportional to the remaining charge of the power battery. When the remaining charge of the power battery is high, the difference between the first and second opening degrees is smaller; when the remaining charge of the power battery is low, the difference between the first and second opening degrees is larger. Through this control, the difference between the first and second opening degrees is dynamically adjusted according to the remaining charge of the power battery, matching the output range of the regenerative braking force with the charging acceptance capacity of the power battery. This protects the power battery from the risk of overcharging while maximizing the utilization of regenerative braking force, thereby improving the energy recovery efficiency of the entire vehicle.

[0096] In this embodiment of the application, a controller for an electric vehicle is also provided, and the control method executed by the controller is the same as described above. Figures 1-4The control functions implemented by the relevant control methods correspond to the control functions.

[0097] In this embodiment of the application, an electric vehicle is also provided, including a braking system, a drive system, and a controller. The drive system is used to output regenerative braking force to the four wheels, the braking system is used to output friction braking force to the four wheels, and the control method executed by the controller is the same as described above. Figures 1-4 The control functions implemented by the relevant control methods correspond to the control functions.

[0098] For more detailed information on controllers and electric vehicles, please refer to the previous text. Figures 1-4 An introduction to the control methods of electric vehicles.

[0099] In the embodiments of this application, the words "exemplary," "for example," etc., are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design that is described as "exemplary" in this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of the term "exemplary" is intended to present the concept in a concrete manner.

[0100] It should be understood that the term "embodiment" used throughout this specification means that a specific feature, structure, or characteristic related to an embodiment is included in at least one embodiment of this application. Therefore, various embodiments throughout this specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0101] It should also be understood that in this application, "when," "if," "in the circumstances of," and "if" all refer to a situation where a corresponding action will be taken under certain objective circumstances, and are not time-limited. They do not require the device to perform a judgment action, nor do they imply any other limitations. Furthermore, in this application, the descriptions of conditions such as "when," "if," "in the circumstances of," and "if" can be understood as necessary conditions, without limiting whether the condition is a sufficient condition or a necessary and sufficient condition. For example, "in the case of A, execute B" can be understood as "if at least A is satisfied, execute B."

[0102] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A control method for an electric vehicle, characterized in that, The control method is used to coordinate the regenerative braking force output by the drive system of the electric vehicle to the four wheels and the friction braking force output by the braking system to the four wheels. The control method includes: During the braking process after the brake pedal opening of the electric vehicle begins to increase but before the brake pedal opening increases to the first opening, the total regenerative braking force output by the drive system to the four wheels is greater than the total friction braking force output by the braking system to the four wheels. During the braking process after the brake pedal opening is increased to the first opening, the regenerative braking force output by the drive system to the two first wheels is controlled to be less than the regenerative braking force output to the two second wheels, and the friction braking force output by the braking system to the two first wheels is controlled to be greater than the friction braking force output to the two second wheels. Wherein, the brake mass of the two first wheels is greater than the brake mass of the two second wheels, or the friction area of ​​the two first wheels is greater than the friction area of ​​the two second wheels, and the two first wheels are two front wheels or two rear wheels.

2. The control method according to claim 1, characterized in that, The control method further includes: During the braking process after the brake pedal opening increases to the first opening, the difference in regenerative braking force output by the drive system to the two first wheels and the two second wheels increases with the increase in the driving speed of the electric vehicle, and the difference in friction braking force output by the braking system to the two first wheels and the two second wheels increases with the increase in the driving speed of the electric vehicle.

3. The control method according to claim 1 or 2, characterized in that, The control method further includes: After the brake pedal opening increases to the first opening and before it increases to a second opening greater than the first opening, the regenerative braking force output by the drive system to the two first wheels is controlled to stop increasing with the increase of the brake pedal opening, and the regenerative braking force output by the drive system to the two second wheels continues to increase with the increase of the brake pedal opening. After the brake pedal opening is increased to the second opening, the regenerative braking force output by the drive system to the two first wheels and the two second wheels stops increasing with the increase of the brake pedal opening.

4. The control method according to claim 3, characterized in that, The control method further includes: The difference between the first opening degree and the second opening degree is controlled to be inversely proportional to the remaining power of the electric vehicle's power battery.

5. The control method according to claim 3 or 4, characterized in that, The control method further includes: After the brake pedal opening increases to the first opening and before the brake pedal opening increases to a second opening greater than the first opening, the regenerative braking force output by the drive system to the two first wheels is controlled to stop increasing with the increase of the brake pedal opening, and the regenerative braking force output by the drive system to the two first wheels is controlled to decrease with the increase of the brake pedal opening.

6. The control method according to claim 5, characterized in that, The control method specifically includes: The regenerative braking force output by the drive system to the two first wheels decreases to zero when the brake pedal opening increases to the second opening.

7. The control method according to claim 5 or 6, characterized in that, The control method further includes: The rate of decrease in the regenerative braking force output by the drive system to the two first wheels increases as the temperature of the friction pads of the two second wheels increases.

8. The control method according to any one of claims 5-7, characterized in that, The control method further includes: After the brake pedal opening increases to the first opening and before it increases to a level greater than the second opening, the regenerative braking force output by the drive system to the two first wheels remains constant for a preset time after it stops increasing with the increase of the brake pedal opening, and then begins to decrease with the increase of the brake pedal opening after the preset time.

9. The control method according to claim 8, characterized in that, The control method further includes: The preset duration is controlled to be inversely proportional to the driving speed of the electric vehicle.

10. The control method according to claim 8 or 9, characterized in that, The control method further includes: The braking system controls the second braking torque output to the two first wheels to increase at a first rate within a preset time period, and then increases at a second rate greater than the first rate after the preset time period.

11. The control method according to any one of claims 3-10, characterized in that, The control method specifically includes: During the braking process after the brake pedal starts to increase but before the brake pedal opening increases to the first opening, the rate of increase of the regenerative braking force output by the drive system to the two first wheels is less than the rate of increase of the regenerative braking force output to the two second wheels.

12. The control method according to any one of claims 1-11, characterized in that, The control method further includes: During the braking process after the brake pedal opening begins to increase but before the brake pedal opening increases to the first opening, the total regenerative braking force output by the drive system to the four wheels increases with the increase of the brake pedal opening, and the total friction braking force output by the braking system to the four wheels is controlled to be zero.

13. A controller for an electric vehicle, characterized in that, The controller is used for: During the braking process after the brake pedal opening of the electric vehicle begins to increase but before the brake pedal opening increases to the first opening, the total regenerative braking force output by the drive system to the four wheels is greater than the total friction braking force output by the braking system to the four wheels. During the braking process after the brake pedal opening is increased to the first opening, the regenerative braking force output by the drive system to the two first wheels is controlled to be less than the regenerative braking force output to the two second wheels, and the friction braking force output by the braking system to the two first wheels is controlled to be greater than the friction braking force output to the two second wheels. Wherein, the brake mass of the two first wheels is greater than the brake mass of the two second wheels, or the friction area of ​​the two first wheels is greater than the friction area of ​​the two second wheels, and the two first wheels are two front wheels or two rear wheels.

14. The controller for an electric vehicle according to claim 13, characterized in that, The controller is also used for: During the braking process after the brake pedal opening increases to the first opening, the difference in regenerative braking force output by the drive system to the two first wheels and the two second wheels increases with the increase in the driving speed of the electric vehicle, and the difference in friction braking force output by the braking system to the two first wheels and the two second wheels increases with the increase in the driving speed of the electric vehicle.

15. An electric vehicle, characterized in that, The electric vehicle includes a braking system, a drive system, and a controller. The drive system is used to output regenerative braking force to the four wheels, the braking system is used to output friction braking force to the four wheels, and the controller is used to execute the control method of the electric vehicle as described in any one of claims 1-12.

Images