TORQUE REDISTRIBUTION AND ADJUSTMENT METHOD, AND CORRESPONDING CONTROL UNIT AND ELECTRIC VEHICLE

Technical Field

The present invention relates to a method for redistributing and adjusting torque of an electric vehicle, a corresponding control unit for an electric vehicle, a corresponding computer-readable program medium and a corresponding electric vehicle.

Background Art

An electric vehicle is a vehicle that is powered at least partially by an electric power supply on board and can at least partially rely on an electric machine to drive its wheels. At present, electric vehicles can be divided mainly into three categories, i.e. battery electric vehicles, hybrid electric vehicles, and fuel cell vehicles.

Typically, the front and rear axles of an electric vehicle are equipped with respective driving motors to drive the rotation of wheels of the front and rear axles. During normal driving, a vehicle control unit calculates a total torque required by the vehicle according to some parameters and a depression degree of an accelerator pedal, and then distributes the total torque to the driving motors of the front and rear axles, respectively, at a ratio of 1 : 1, in order to drive the vehicle smoothly.

However, electric vehicles, especially electric trucks, often face some unusual driving conditions, which may put them in a situation where they need to get out of trouble. For example, if the total torque is still distributed to the driving motors of the front and rear axles at the ratio of 1 : 1 when a truck climbs a hill, in extreme cases, although the calculated total torque meets the requirements, it makes the truck unable to complete the climb or makes it very difficult to climb the hill. There are other similar situations, such as a front wheel or a rear wheel getting stuck in a mud pit.

Therefore, improvements need to be made to electric vehicles to further improve the adaptability of the electric vehicles to various driving conditions.

Summary of the Invention

It is an object of the present invention to provide an improved method for redistributing and adjusting torque of an electric vehicle, an improved control unit for an electric vehicle, an improved computer-readable program medium and an improved electric vehicle. According to a first aspect of the present invention, there is provided a method for redistributing and adjusting torque of an electric vehicle, wherein the electric vehicle at least comprises a first electric drive for a front axle and a second electric drive for a rear axle, the method comprising at least the steps of: determining whether the electric vehicle is in a driving state requiring redistribution of torque; and adjusting the torque initially distributed to the front axle and/or the rear axle or the torque initially distributed to the respective wheels by controlling the first electric drive and/or the second electric drive if it is determined that the electric vehicle is in the driving state requiring redistribution of torque.

According to a second aspect of the present invention, there is provided a control unit for an electric vehicle, which control unit is configured to perform the above method.

According to a third aspect of the present invention, there is provided a computer-readable program medium storing program instructions, which are executable by a processor to perform the above method.

According to a fourth aspect of the present invention, there is provided an electric vehicle comprising the control unit described above and/or the computer-readable program medium described above.

According to the electric vehicle provided by the present invention, better torque distribution can be made for specific driving states.

Brief Description of the Drawings

In the following, the principles, features and advantages of the present invention can be better understood by describing the present invention in more detail with reference to the accompanying drawings. In the drawings:

Fig. 1 schematically shows a basic schematic diagram of an electric vehicle according to an exemplary embodiment of the present invention;

Fig. 2 shows a flowchart of a method for adjusting torque distribution of an electric vehicle for a climbing state according to an exemplary embodiment of the present invention; and

Fig. 3 shows a flowchart of a method for adjusting torque distribution of an electric vehicle based on the slope of a hill according to a further exemplary embodiment of the present invention.

Detailed Description of Embodiments

In order to clarify the technical problems to be solved by the present invention, the technical solutions and the beneficial technical effects, the present invention will be described in further detail below with reference to the drawings and various exemplary embodiments. It should be understood that the specific embodiments described herein are only for the purpose of explaining the present invention and are not intended to limit the scope of protection of the present invention.

Fig. 1 schematically shows a basic schematic diagram of an electric vehicle according to an exemplary embodiment of the present invention.

As shown in Fig. 1, the exemplary electric vehicle 1 includes: a first front wheel 12 and a second front wheel 13 on a front axle 11; a first rear wheel 15 and a second rear wheel 16 on a rear axle 14; a first electric drive 17, such as a motor, for the front axle 11 for driving the first front wheel 12 and the second front wheel 13; a second electric drive 18, such as a motor, for the rear axle 14 for driving the first rear wheel 15 and the second rear wheel 16; and a control unit 19 for controlling the first electric drive 17 and the second electric drive 18. Here, the control unit 19 may be a vehicle control unit (VCU) of the electric vehicle.

According to the present invention, the control unit 19 is configured to be able to adjust the torque distribution of the electric vehicle 1 in real time, for example, by controlling the first electric drive 17 and/or the second electric drive 18 according to the driving state of the electric vehicle 1, for example, adjusting the distribution of the actual total torque output between the front axle 11 and the rear axle 14.

Hereinafter, this will be described in more detail with reference to more specific exemplary embodiments.

For example, when the electric vehicle 1 is in a 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.

To this end, according to an exemplary embodiment of the present invention, as shown in Fig. 2, the following operation steps may be performed: SI) acquiring a slope of a hill; S2) determining whether to trigger a climbing mode; and S3) if the climbing mode is triggered, increasing the torque distributed to the rear axle 14 of the electric vehicle 1, which can be implemented by controlling the first electric drive 17 and/or the second electric drive 18 via the control unit 15, for example. Preferably, the total torque is fixed while the torque distribution is adjusted, so in this case, when the torque distributed to the rear axle 14 increases, the torque distributed to the front axle 11 decreases accordingly. Of course, those skilled in the art can understand that even the total torque can be changed in some cases, and the present invention does not impose restrictions on this.

The slope of a hill can be obtained in various approaches, which is not limited by the present invention, no matter which approach is used, it is feasible as long as the slope of the hill can be obtained reliably. For example, according to an exemplary embodiment of the present invention, if an electric vehicle is equipped with a slope sensor, the slope can be directly measured by using the slope sensor.

It can be understood by those skilled in the art that, under the condition that other possible influencing parameters are unchanged, the acceleration of a vehicle during driving is related to the actual total torque output; however, when the vehicle is driving on a hill, the vehicle will also be affected by a force downward along the hill due to the effect of the hill, so the acceleration will also be related to the slope of the hill. Therefore, according to another exemplary embodiment of the present invention, the slope of the hill can be calculated based on the actual total torque output and the acceleration of the vehicle.

Those skilled in the art can also understand that the acceleration of the vehicle can be obtained by many different methods. For example, the acceleration of the vehicle can be directly measured by an acceleration sensor or indirectly obtained by calculation based on some parameters. The present invention does not impose restrictions on this.

Fig. 3 shows a flowchart of a method for adjusting torque distribution of the electric vehicle 1 based on the slope of a hill according to a further exemplary embodiment of the present invention.

As shown in Fig. 3, at step Sll, the slope s of the hill which the electric vehicle 1 is climbing is acquired. At step S12, the slope s of the hill is compared with a predetermined limit threshold si to determine whether the slope s is reasonable, for example, whether the slope s is less than or equal to the predetermined limit threshold sl=10%. If it exceeds the predetermined limit threshold si, it can be considered that the slope s is unreasonable, and the method can proceed to step S15 in which the current torque distribution mode is maintained unchanged or return to step Sll in which a new slope s is acquired again. If the slope s is less than or equal to the predetermined limit threshold si, the slope s is considered reasonable, and therefore, the method can proceed to step S13. At step S13, it is determined whether an additional predetermined condition for necessary torque redistribution and adjustment is met. If the additional predetermined condition is met, the method proceeds to step S14. At step S14, the torque distributed to the rear axle 14 is increased. For example, the torque distributed to the rear axle 14 may be adjusted based on the magnitude of the slope s. If the additional predetermined condition is not met, the method can also proceed to step S15 in which the current torque distribution mode is maintained unchanged.

According to an exemplary embodiment of the present invention, in step Sll, the obtained slope s is subjected to filtering processing, such as low-pass filtering processing, so as to obtain a more reliable value of the slope s, thereby reducing incorrect determination. As described above, the slope s of the hill can be calculated based on the actual total torque output T and the acceleration a of the vehicle. In this case, the relationship between the slope s of the hill, the actual total torque output T and the acceleration a of the vehicle can be expressed in the following function expression (1):

S = f (T, a) (1)

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

Those skilled in the art can understand that the look-up table may vary as some influencing parameters change, for example, the vehicle weight and/or parameters of the transmission system will both affect the determination of the slope s. Therefore, according to an exemplary embodiment of the present invention, a step of updating the function expression (1) or the look-up table according to influencing parameters for slope calculation may be performed additionally before step Sll. For example, the current influencing parameters for slope calculation of the vehicle can be obtained and the function expression (1) or the look-up table can be updated in real time to ensure that the calculation of the slope s is more accurate.

According to an exemplary embodiment of the present invention, the additional predetermined condition may include a predetermined vehicle speed threshold and/or a predetermined minimum slope threshold.

For example, only when the speed of the vehicle is less than the predetermined vehicle speed threshold, such as 80 km/h, the method will continue with subsequent torque redistribution operation. It can be understood that if the speed of the vehicle is greater than the predetermined vehicle speed threshold, on the one hand, it means that the slope s of the hill is usually small, and it may not be necessary to adjust the current torque distribution mode; on the other hand, if the torque distribution is adjusted in this case, the driving of the vehicle may become unsafe.

If the slope s of the hill is less than or equal to the predetermined minimum slope threshold, it also means that the slope is small and it is not necessary to adjust the current torque distribution mode.

According to an exemplary embodiment of the present invention, the torque increase AT of the rear axle 14 of the electric vehicle 1 is determined based on the slope s, which, for example, can be expressed by the following function expression (2):

AT = f (s) (2) According to an exemplary embodiment of the present invention, the torque increase AT may be a percentage relative to the total torque T, or may be an exact value by which the torque increases.

According to an exemplary embodiment of the present invention, the torque increase AT can be expressed by the following function expression (3):

AT = kl · s · T (3) where kl represents a predetermined coefficient.

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

T1 = T0 + AT (4) where TO is the torque initially distributed to the rear axle 14.

The torque TO initially distributed to the rear axle 14 can be expressed as a percentage of the total torque T, for example, by the following function expression (5):

TO = k2 · T (5) where k2 is a predetermined coefficient, for example, k2 = 0.5.

Next, another application scenario will be described in order to better understand the technical concept of the present invention.

For example, when a wheel of a vehicle is stuck in a mud pit, the wheel cannot help the vehicle get out of the pit because it slips, so increasing the torque of another axle can better help the vehicle to get out of the pit.

For this application scenario, according to an exemplary embodiment of the present invention, the following steps may be included: detecting the slip state of a wheel, and if the wheel is in a slip state, increasing the torque distributed to the other axle, otherwise, maintaining the current torque distribution mode unchanged.

According to an exemplary embodiment of the present invention, whether a wheel is in a slip state may be determined based on the difference between the speed of the rear axle 14 and the speed of the front axle 11. For example, if a wheel of the rear axle 14 slips, the speed of the rear axle 14 will increase as the resistance becomes smaller, so the difference between the speeds of the front and rear axles will correspondingly increase, and thus it can be determined that the wheel of the rear axle 14 slips, and vice versa.

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

Ar = rl-r2 (6) where Ar represents the speed difference between the front and rear axles, rl represents the speed of the rear axle 14, and r2 represents the speed of the front axle 11. In order to more reliably determine whether a wheel is in a slip state, the absolute value of the speed difference Ar between the front and rear axles can be compared with a predetermined speed difference threshold rO. If Ar is greater than or equal to rO, the wheel is considered to be in a slip state; and if Ar is less than rO, the wheel is not considered to be in a slip state or a torque distribution adjustment is unnecessary.

Those skilled in the art can understand that the signal processing method described above in combination with the climbing scenario can also be used to process the speed difference Ar between the front and rear axles, so as to improve the reliability and accuracy of the determination.

According to an exemplary embodiment of the present invention, the torque increase amount of the other axle can be determined based on the speed difference Ar between the front and rear axles. For those skilled in the art, it can be easily understood based on the foregoing description and will not be repeated here.

The above describes the technical concept of the present invention with two specific application scenarios, but for those skilled in the art, it is obvious that the present invention is not limited to the above application scenarios. On the contrary, the concept of the present invention can be used in any driving state requiring readjustment of torque distribution. This kind of driving state can be called a driving state requiring redistribution of torque. For example, when the vehicle climbs a hill while backing up, it may also be necessary to redistribute the torque, for example, by increasing the torque of the front axle.

In addition, although the concept of the present invention has been described in the above embodiments in which the front and rear axles are each provided with an electric drive, the present invention is not limited thereto. For example, if each wheel is equipped with a corresponding electric drive, it is even possible to readjust the distribution of total torque between the individual wheels by controlling the electric drive of the corresponding wheel based on the concept of the present invention. For example, when a certain wheel slips because it is stuck in a mud pit, it is even possible to only reduce the torque distributed to the slipping wheel.

For those skilled in the art, it can be understood that when it is detected that the electric vehicle is in a driving state requiring redistribution of torque, in addition to adjusting the torque distribution, even the total torque can be adjusted, for example, by increasing the total torque appropriately.

In addition, those skilled in the art can understand that the technical concept of the present invention is applicable to all types of electric vehicles, including hybrid electric vehicles. Although specific embodiments of the present invention have been 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 invention. Various substitutions, alterations and modifications may be devised without departing from the spirit and scope of the present invention.

List of Reference Numerals

1 Electric vehicle

11 Front axle

12 First front wheel

13 Second front wheel

14 Rear axle

15 First rear wheel

16 Second rear wheel

17 First electric drive

18 Second electric drive

19 Control unit