Torque redistribution adjustment method and corresponding control unit and electric vehicle

Abstract

The invention discloses a method for readjusting the torque distribution of an electric vehicle (1), wherein the electric vehicle (1) comprises at least a first electric drive (17) for a front axle (11) and a second electric drive (18) for a rear axle (14), the method comprising at least the steps of determining whether the electric vehicle (1) is in a state in which a readjustment of the torque distribution is required, and if the electric vehicle (1) is determined to be in the state in which the readjustment of the torque distribution is required, adjusting the torque initially distributed to the front axle (11) and / or to the rear axle (14) or the torque initially distributed to the respective wheels by controlling the first electric drive (17) and / or the second electric drive (18). Furthermore, a corresponding control unit (19) for an electric vehicle (1), a corresponding computer-readable program carrier and a corresponding electric vehicle (1) are disclosed. A better torque distribution can be achieved for specific driving states.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for readjusting the redistribution of torque of an electric vehicle, a corresponding control unit for an electric vehicle, a corresponding computer readable program carrier and a corresponding electric vehicle. BACKGROUND

[0002] An electric vehicle refers to a vehicle that is at least partially powered by an on-board power source and can travel at least partially relying on electric motor to drive the wheels. At present, electric vehicles can be mainly divided into three categories: pure electric vehicles, hybrid electric vehicles and fuel cell vehicles.

[0003] An electric vehicle is usually equipped with corresponding drive motors on the front and rear axles to drive the wheels of the front and rear axles to rotate. When driving normally, the vehicle control unit calculates the total torque required by the vehicle according to some parameters and the degree of depression of the accelerator pedal, and then distributes the total torque to the drive motors of the front and rear axles in a 1:1 ratio in order to drive the vehicle to travel smoothly.

[0004] However, electric vehicles, especially electric trucks, often face some unconventional driving states and may put the electric vehicle in a situation that needs to be rescued. For example, if the total torque is still distributed to the drive motors of the front and rear axles in a 1:1 ratio when the truck is climbing a slope, in an extreme case, although the calculated total torque meets the requirements, it may make it difficult for the truck to complete the climb or make it very difficult to climb. There are other similar situations, such as the front wheels or rear wheels getting stuck in a mud pit, which can also cause this problem.

[0005] Therefore, it is necessary to improve the electric vehicle to further improve the adaptability of the electric vehicle to various driving states. SUMMARY

[0006] The object of the present application is to provide an improved method for readjusting the redistribution of torque of an electric vehicle, an improved control unit for an electric vehicle, an improved computer readable program carrier and an improved electric vehicle.

[0007] According to a first aspect of the present application, a method for readjusting the redistribution of torque of an electric vehicle is provided, wherein the electric vehicle comprises at least a first electric drive device for a front axle and a second electric drive device for a rear axle, the method comprising at least the following steps: determining whether the electric vehicle is in a driving state requiring redistribution of torque; and if it is determined that the electric vehicle is in the driving state requiring redistribution of torque, adjusting the torque initially distributed to the front axle and / or the rear axle or the torque initially distributed to the corresponding wheels by controlling the first electric drive device and / or the second electric drive device.

[0008] According to a second aspect of the present application, a control unit for an electric vehicle is provided, the control unit being configured to be adapted to the above-mentioned method.

[0009] According to a third aspect of the present application, a computer readable program carrier is provided, the computer readable program carrier storing program instructions, which, when executed by a processor, perform the above-mentioned method.

[0010] According to a fourth aspect of the present application, an electric vehicle is provided, the electric vehicle comprising the above-mentioned control unit and / or the above-mentioned computer readable program carrier.

[0011] With the electric vehicle according to the present application, a better torque distribution can be achieved for specific driving conditions. BRIEF DESCRIPTION OF DRAWINGS

[0012] The principles, features and advantages of the present application will be better understood by referring to the following detailed description in conjunction with the accompanying drawings, in which:

[0013] Figure 1 A basic schematic diagram of an electric vehicle according to an exemplary embodiment of the present application is shown.

[0014] Figure 2 A flow chart of a method for adjusting the torque distribution of an electric vehicle for a hill climbing condition according to an exemplary embodiment of the present application is shown.

[0015] Figure 3 A flow chart of a method for adjusting the torque distribution of an electric vehicle based on the slope of a hill according to a further exemplary embodiment of the present application is shown. DETAILED DESCRIPTION

[0016] In order to make the technical problems to be solved by the present application, the technical solutions and the beneficial technical effects more clearly understood, the present application will be further described in detail below in conjunction with the drawings and multiple exemplary embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the protection scope of the present application.

[0017] Figure 1 A basic schematic diagram of an electric vehicle according to an exemplary embodiment of the present application is shown.

[0018] As Figure 1As shown, the exemplary electric vehicle 1 comprises a first front wheel 12 and a second front wheel 13 located on a front axle 11, a first rear wheel 15 and a second rear wheel 16 located on a rear axle 14, a first electric drive 17, e.g. an electric motor, for driving the first front wheel 12 and the second front wheel 13 for the front axle 11, a second electric drive 18, e.g. an electric motor, for driving the first rear wheel 15 and the second rear wheel 16 for the rear axle 14, and a control unit 19 for controlling the first electric drive 17 and the second electric drive 18. Here, the control unit 19 can be a vehicle control unit (VCU) of the electric vehicle.

[0019] According to the present application, the control unit 19 is configured to adjust the torque distribution of the electric vehicle 1, e.g. the distribution of the total torque actually outputted between the front axle 11 and the rear axle 14, in real time by controlling the first electric drive 17 and / or the second electric drive 18, e.g. depending on the driving state of the electric vehicle 1.

[0020] In the following, this will be described in more detail with respect to more specific exemplary embodiments.

[0021] For example, when the electric vehicle 1 is in a hill climbing driving state, more torque can be distributed to the rear axle 14 than to the front axle 11, which makes it easier for the electric vehicle 1 to climb a hill, especially for an electric truck.

[0022] To this end, according to one exemplary embodiment of the present application, as shown in Figure 2 the following operation steps can be performed: S1) obtaining the slope of the hill; S2) deciding whether to trigger a hill climbing mode; and S3) if the hill climbing mode is triggered, increasing the torque distributed to the rear axle 14 of the electric vehicle 1, which can be implemented by the control unit 15 controlling the first electric drive 17 and / or the second electric drive 18, for example. Preferably, when adjusting the torque distribution, the total torque is kept constant, so in this case, when the torque distributed to the rear axle 14 is increased, the torque distributed to the front axle 11 is correspondingly decreased. Of course, it is understood by those skilled in the art that in some cases, the total torque can even be changed, which is not limited by the present application.

[0023] The slope of the hill can be obtained in various ways, which are not limited by the present application, as long as the slope of the hill can be reliably obtained. For example, according to one exemplary embodiment of the present application, if the electric vehicle is equipped with a slope sensor, the slope can be directly measured by the slope sensor.

[0024] Those skilled in the art will understand that, assuming other potentially influencing parameters remain constant, the vehicle's acceleration is related to the actual total output torque. When a vehicle travels on a slope, it also experiences a downward force along the slope due to the slope's action; therefore, the acceleration is also related to the slope's gradient. Therefore, according to another exemplary embodiment of the present invention, the slope's gradient can be calculated based on the actual total output torque and the vehicle's acceleration.

[0025] Those skilled in the art will also understand that vehicle acceleration can be obtained through many different methods. For example, vehicle acceleration can be measured directly by an acceleration sensor, or it can be calculated indirectly based on some parameters. This invention does not limit this.

[0026] Figure 3 A flowchart is shown of a method for adjusting the torque distribution of an electric vehicle 1 based on the slope gradient according to a further exemplary embodiment of the present invention.

[0027] like Figure 3 As shown, in step S11, the slope s of the incline that the electric vehicle 1 is climbing is obtained. In step S12, the slope s is compared with a predetermined limit threshold s1 to determine whether the slope s is reasonable, for example, whether the slope s is less than or equal to the predetermined limit threshold s1 = 10%. If it exceeds the predetermined limit threshold s1, the slope s is considered unreasonable, and the process proceeds to step S15, maintaining the current torque distribution mode, or returns to step S11 to obtain a new slope s. If the slope s is less than or equal to the predetermined limit threshold s1, the slope s is considered reasonable, and the process proceeds to step S13. In step S13, it is determined whether an additional predetermined condition for realignment of torque is met. If the additional predetermined condition is met, the process proceeds to step S14. In step S14, the torque allocated to the rear axle 14 is increased, for example, the torque allocated to the rear axle 14 can be adjusted based on the magnitude of the slope s. If the additional predetermined condition is not met, the process can also proceed to step S15, maintaining the current torque distribution mode.

[0028] According to an exemplary embodiment of the present invention, in step S11, the obtained slope s is filtered, for example, by low-pass filtering, to obtain a more reliable slope s value, thereby reducing misjudgments.

[0029] As mentioned above, the slope s of the ramp can be calculated based on the actual total output torque T and the vehicle acceleration a. In this case, the relationship between the slope s of the ramp and the actual total output torque T and the vehicle acceleration a can be expressed by the following function (1):

[0030] s = f(T, a) (1)

[0031] According to an exemplary embodiment of the present application, the slope s of the slope can be determined directly from the total torque T actually output and the acceleration a of the vehicle by means of a look-up table, which can simplify the calculation process and save valuable computing resources. The look-up table can be pre-stored in a corresponding memory, for example, in the control unit 15.

[0032] Those skilled in the art can understand that the look-up table can change with changes in some influencing parameters, for example, the vehicle weight and / or the transmission system parameters will affect the determination of the slope s. For this purpose, according to an exemplary embodiment of the present application, a step of updating the function formula (1) or the look-up table according to the slope calculation influencing parameters can also be performed before step S11. For example, the current slope calculation influencing parameters of the vehicle can be obtained and the function formula (1) or the look-up table can be updated in real time to ensure that the calculation of the slope s is more accurate.

[0033] According to an exemplary embodiment of the present application, the additional predetermined condition can include a predetermined vehicle speed threshold and / or a predetermined minimum slope threshold.

[0034] For example, only when the speed of the vehicle is less than a predetermined vehicle speed threshold, for example, 80 km / h, the subsequent torque redistribution operation is continued. It can be understood that if the speed of the vehicle is greater than the predetermined vehicle speed threshold, on the one hand, it indicates that the slope s of the slope is generally relatively small, and it can not be necessary to adjust the current torque distribution mode, on the other hand, if the torque distribution is adjusted at this time, it can also make the vehicle travel unsafe.

[0035] If the slope s of the slope is less than or equal to the predetermined minimum slope threshold, it also indicates that the slope is small, and it is also unnecessary to adjust the current torque distribution mode.

[0036] According to an exemplary embodiment of the present application, the torque increase amount AT of the rear axle 14 of the electric vehicle 1 is determined based on the slope s, for example, which can be represented by the following function formula (2):

[0037] AT = f (s) (2)

[0038] According to an exemplary embodiment of the present application, the torque increase amount AT can be a percentage relative to the total torque T, or can be an actual torque value.

[0039] According to an exemplary embodiment of the present application, the torque increase amount AT can be represented by the following function formula (3):

[0040] AT = k1-s-T (3)

[0041] Wherein, k1 represents a predetermined coefficient.

[0042] Therefore, the torque T1 of the rear axle 14 of the redistributed electric vehicle 1 can be expressed by the following function (4):

[0043] T1 = T0 + △T (4)

[0044] Where T0 is the torque initially allocated to the rear axle 14.

[0045] The torque T0 initially allocated to the rear axle 14 can be expressed as a percentage of the total torque T, for example, by the following function (5):

[0046] T0 = ​​k2·T (5)

[0047] Where k2 is a predetermined coefficient, for example, k2 = 0.5.

[0048] The following describes another application scenario to better understand the technical concept of the present invention.

[0049] For example, when one of a vehicle's wheels gets stuck in mud, that wheel slips and cannot help the vehicle get out of trouble. Therefore, increasing the torque on the other axle can help get the vehicle out of trouble more effectively.

[0050] For this application scenario, according to an exemplary embodiment of the present invention, the following steps may be included: detecting the wheel slippage state; if the wheel is slipping, increasing the torque allocated to the other axle; otherwise, maintaining the current torque allocation mode unchanged.

[0051] According to an exemplary embodiment of the present invention, it is possible to determine whether a wheel is slipping based on the difference between the speed of the rear axle 14 and the speed of the front axle 11. For example, if the wheel of the rear axle 14 slips, the speed of the rear axle 14 will increase due to the decrease in resistance. Therefore, the speed difference between the front and rear axles will increase accordingly, and it can be determined that the wheel of the rear axle 14 is slipping, and vice versa.

[0052] The speed difference between the front and rear axles can be expressed by the following function (6):

[0053] △r= r1-r2 (6)

[0054] Where △r represents the speed difference between the front and rear axles, r1 represents the speed of the rear axle 14, and r2 represents the speed of the front axle 11.

[0055] To more reliably determine if a wheel is slipping, the absolute value of the speed difference Δr between the front and rear axles can be compared with a predetermined speed difference threshold r0. If Δr is greater than or equal to r0, the wheel is considered to be slipping; if Δr is less than r0, the wheel is not considered to be slipping or no torque distribution adjustment is needed.

[0056] Those skilled in the art can understand that the signal processing method described above in connection with the climbing scene can also be used to process the speed difference Δr of the front and rear axles to improve the reliability and accuracy of the judgment.

[0057] According to an exemplary embodiment of the present application, the torque increase amount of the other axle can be determined based on the speed difference Δr of the front and rear axles. Those skilled in the art can easily understand based on the foregoing description that the details are not described here.

[0058] The technical idea of the present application is described above in two specific application scenarios, but for those skilled in the art, the present application is obviously not limited to the above application scenarios. On the contrary, any driving state that needs to readjust the torque distribution can use the idea of the present application. Such a driving state can be referred to as a driving state that needs to readjust the torque distribution. For example, when the vehicle is reversing uphill, it can also be necessary to readjust the torque, for example, to increase the torque of the front axle.

[0059] In addition, although the above embodiment in which one electric drive device is provided for each of the front and rear axles describes the technical idea of the present application, the present application is not limited thereto. For example, if each wheel is provided with a corresponding electric drive device, it is even possible to readjust the distribution of the total torque among the wheels by controlling the electric drive devices of the corresponding wheels based on the idea of the present application. For example, for the case where a certain wheel is slipping due to sinking into a mud pit, it is even possible to only reduce the torque allocated to the slipping wheel.

[0060] For those skilled in the art, in addition to adjusting the torque distribution, it is even possible to adjust the total torque, for example, to appropriately increase the total torque, when it is detected that the electric vehicle is in a driving state that needs to readjust the torque distribution.

[0061] In addition, those skilled in the art can understand that the technical idea of the present application is applicable to all types of electric vehicles, including hybrid electric vehicles.

[0062] Although specific embodiments of the present application are described in detail herein, they are given for the purpose of explanation only and should not be considered as limiting the scope of the present application. Various substitutions, changes and modifications can be conceived without departing from the spirit and scope of the present application.

[0063] List of reference signs

[0064] 1 electric vehicle

[0065] 11 front axle

[0066] 12 first front wheel

[0067] 13 second front wheel

[0068] 14 rear axle

[0069] 15 first rear wheel

[0070] 16 second rear wheel

[0071] 17 first electric drive

[0072] 18 second electric drive

[0073] 19 control unit

Claims

1. A method for redistributing torque in an electric vehicle (1), wherein, The electric vehicle (1) includes at least a first electric drive unit (17) for the front axle (11) and a second electric drive unit (18) for the rear axle (14), and the method includes at least the following steps: Determine whether the electric vehicle (1) is in a driving state requiring torque redistribution; and If it is determined that the electric vehicle (1) is in the driving state that requires torque redistribution, the torque initially allocated to the front axle (11) and / or the rear axle (14) or the torque initially allocated to the corresponding wheels is adjusted by controlling the first electric drive unit (17) and / or the second electric drive unit (18). In the case where the torque redistribution driving state is in the climbing state, the step of updating the function (1) or lookup table based on the slope to calculate the influence parameters is executed. Then, the slope of the slope that the electric vehicle (1) is climbing is compared with a predetermined limit threshold. If it exceeds the predetermined limit threshold, the slope is considered unreasonable and the current torque distribution mode remains unchanged. Otherwise, it is further determined whether the first additional predetermined condition that the torque redistribution adjustment is indeed met is met. If the first additional predetermined condition is met, the torque allocated to the rear axle or the front axle is increased. If the first additional predetermined condition is not met, the current torque distribution mode remains unchanged. s = f (T, a) (1) Where s is the slope of the incline, T is the actual total output torque T, and a is the vehicle's acceleration. In the case of wheel slippage, it is determined whether the electric vehicle (1) meets the second additional predetermined condition that torque redistribution adjustment is indeed necessary. Torque redistribution adjustment is only performed when the second additional predetermined condition is met. Among them, when an electric vehicle is detected to be in a driving state that requires torque redistribution, in addition to adjusting the torque distribution, the total torque can also be adjusted.

2. The method according to claim 1, wherein, When the driving state requiring torque redistribution is a wheel slippage state, the torque is redistributed and adjusted based on the speed difference between the front axle (11) and the rear axle (14).

3. The method according to claim 1, wherein, Determine whether an electric vehicle (1) is climbing a slope based on the slope gradient.

4. The method according to claim 2, wherein, Whether the electric vehicle (1) is in a state of wheel slippage is determined based on the speed of the front axle (11) and the speed of the rear axle (14).

5. The method according to any one of claims 1-4, wherein, For the climbing state, the first additional predetermined condition includes: the speed of the electric vehicle (1) is less than a predetermined vehicle speed threshold and / or the slope of the ramp is greater than a predetermined minimum slope threshold.

6. The method according to claim 2 or 4, wherein, For wheel slippage, the second additional predetermined condition includes: the absolute value of the difference between the speed of the front axle (11) and the speed of the rear axle (14) is greater than a predetermined speed difference threshold.

7. The method according to any one of claims 1-4, wherein, For climbing situations, torque is redistributed and adjusted based on the slope gradient.

8. The method according to any one of claims 1-4, wherein, For forward climbing, the torque distributed to the rear axle (14) is increased based on the slope gradient while maintaining the same total torque; and / or The slope is processed by low-pass filtering.

9. A control unit (19) for an electric vehicle (1), the control unit (19) being configured to perform the method according to any one of claims 1-8.

10. An electric vehicle (1) comprising a control unit (19) according to claim 9.

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