Motor torque control method, system and device and automobile

Abstract

The invention discloses a motor torque control method which is applied to an electric vehicle, and the electric vehicle is a double-motor four-wheel-drive electric vehicle. The method comprises the steps that front and rear motors are controlled to apply torque to front and rear shafts to make wheels rotate; front axle differential protection limiting torque is determined according to the rotating speed difference of left and right front wheels; determining a rear axle differential protection limiting torque according to the rotating speed difference of the left and right rear wheels; judging whether the front axle and the rear axle slip or not according to the front axle differential protection limiting torque and the rear axle differential protection limiting torque; when one of the front axle and the rear axle slips and the other one does not slips, the differential protection limiting torque corresponding to the slipped axle is subtracted from the request torque applied to the slipped axle; adding differential protection limiting torque corresponding to the shaft which slips into the request torque applied to the shaft which does not slips; and the left front wheel, the right front wheel, the left rear wheel and the right rear wheel are driven to rotate through the adjusted request torque.

Description

Technical Field

[0001] The present application relates to the technical field of electric vehicles, and in particular to a motor torque control method, system, device and vehicle. Background Art

[0002] With the rapid development of the pure electric vehicle industry, various manufacturers have conducted more in-depth explorations in the field of pure electric vehicles, and the requirements for automobile driving safety and driving experience have gradually increased. Compared with traditional fuel vehicles, electric vehicles have faster torque loading rates and greater torque outputs. Their transmission components will be subjected to instantaneous strong impact loads, causing the instantaneous wheel speed difference between the left and right to exceed the set standard under conditions such as single-axle wheel slippage and suspension. At this time, the lubricating oil film between the cross shaft and other components in the differential will be destroyed, causing the cross shaft to wear and the differential to be damaged. When the differential protection function fails, the vehicle will be at a major safety risk, endangering the lives and property of passengers, so the differential protection function is of great significance.

[0003] The existing technology is to equip the vehicle with a dynamic stability system, which is controlled by a brake control module. During driving, the dynamic stability system monitors the differential speed and slippage of the left and right wheels, and intervenes in control when the speed difference between the left and right wheels reaches a certain threshold; or by limiting the output torque of the slip shaft motor, the speed difference between the two wheels is reduced to a controllable range. The existing technology usually provides users with a button to turn off the active intervention of the ESP system, but if the ESP system is turned off, the vehicle cannot cope well with severe differential conditions; although the speed difference can be reduced by limiting the output torque of the slipping shaft motor in the existing technology, the vehicle power will be instantly reduced or lost, reducing the vehicle's dynamic driving experience, which is unacceptable for models aimed at smooth dynamic driving; when there is a speed difference, the ESP system may intervene too late. If it intervenes when the speed is too high, the torque output will be large and the speed difference will be difficult to control, which will make it difficult to play an effective protective role; or the speed limit purpose can be achieved by quickly limiting the torque to a lower value, which will make the vehicle power output feel strong and the driving experience not smooth; the existing technology also controls the wheel speed based on the wheel speed sensor. This method is affected by the communication delay of the wheel speed signal transmission. If the speed difference is set to exceed a large value before control, the control will lag, resulting in poor control effect. Summary of the invention

[0004] In order to solve the above problems, the present invention proposes a motor torque control method, which can effectively alleviate the above problems of control lag and strong sense of frustration during control, while improving driving safety and ensuring comfort.

[0005] In a first aspect, the present invention provides a motor torque control method, which is applied to an electric vehicle, wherein the electric vehicle is a dual-motor four-wheel drive electric vehicle, including a front motor, a rear motor, a left front wheel and a right front wheel drivingly connected to the front motor via a front axle and a front axle differential, and a left rear wheel and a right rear wheel drivingly connected to the rear motor via a rear axle and a rear axle differential; the method comprises the following steps: controlling the front motor to apply a preset front motor request torque to the front axle to drive the left front wheel and the right front wheel to rotate; controlling the rear motor to apply a preset rear motor request torque to the rear axle to drive the left rear wheel and the right rear wheel to rotate; determining the front axle differential speed of the front axle according to the speed difference between the left front wheel and the right front wheel the rear axle differential protection limiting torque of the rear axle is determined according to the speed difference between the left rear wheel and the right rear wheel; whether the front axle and the rear axle are slipping is determined according to the front axle differential protection limiting torque and the rear axle differential protection limiting torque; when one of the front axle and the rear axle is slipping and the other is not slipping, the differential protection limiting torque corresponding to the slipping axle is subtracted from the request torque applied to the slipping axle, and the differential protection limiting torque corresponding to the slipping axle is added to the request torque applied to the non-slipping axle; the left front wheel, the right front wheel, the left rear wheel and the right rear wheel are driven to rotate by the adjusted request torque.

[0006] In some embodiments, the front wheel speed difference differential change rate is calculated based on the speed difference between the left front wheel and the right front wheel, and the front axle differential protection differential torque limit coefficient is determined according to the front wheel speed difference change rate; the front axle differential protection proportional torque limit coefficient is determined based on the speed difference between the left front wheel and the right front wheel; the front axle differential protection limit torque is calculated based on the front motor request torque, the front axle differential protection differential torque limit coefficient, and the front axle differential protection proportional torque limit coefficient.

[0007] In some embodiments, the front axle differential protection limit torque = (front axle differential protection proportional torque limit coefficient + front axle differential protection differential torque limit to coefficient) * front motor requested torque; wherein, the value of (front axle differential protection proportional torque limit coefficient + front axle differential protection differential torque limit to coefficient) does not exceed 1.

[0008] In some embodiments, the rear wheel speed difference differential change rate is calculated based on the speed difference between the left rear wheel and the right rear wheel, and the rear axle differential protection differential torque limit coefficient is determined according to the rear wheel speed difference differential change rate; the rear axle differential protection proportional torque limit coefficient is obtained based on the speed difference between the left rear wheel and the right rear wheel; the rear axle differential protection limit torque is calculated based on the rear motor request torque, the rear axle differential protection differential torque limit coefficient, and the rear axle differential protection proportional torque limit coefficient.

[0009] In some embodiments, the rear axle differential protection limit torque = (rear axle differential protection proportional torque limit coefficient + rear axle differential protection differential torque limit coefficient) * rear motor requested torque; wherein, the value of the rear axle differential protection proportional torque limit coefficient + the rear axle differential protection differential torque limit coefficient does not exceed 1.

[0010] In some embodiments, if the front axle slips and the rear axle does not slip, the front axle differential protection limit torque is subtracted from the front motor request torque, and the front axle differential protection limit torque is added to the rear motor request torque; the front motor is controlled to apply the adjusted front motor request torque to the front axle to drive the left front wheel and the right front wheel to rotate; the rear motor is controlled to apply the adjusted rear motor request torque to the rear axle to drive the left rear wheel and the right rear wheel to rotate.

[0011] In some embodiments, if the rear axle slips and the front axle does not slip, the rear axle differential protection limit torque is subtracted from the rear motor request torque, and the rear axle differential protection limit torque is added to the front motor request torque; the rear motor is controlled to apply the adjusted rear motor request torque to the rear axle to drive the left rear wheel and the right rear wheel to rotate; the front motor is controlled to apply the adjusted rear motor request torque to the front axle to drive the left front wheel and the right front wheel to rotate.

[0012] In some embodiments, when slip occurs on both the front axle and the rear axle at the same time, the front motor request torque and the rear motor request torque are reduced at the same time.

[0013] In a second aspect, an embodiment of the present invention provides a motor torque control system, the system comprising a vehicle controller, a front axle, a rear axle, a front axle differential, a rear axle differential, a front axle drive motor and a rear axle drive motor; the front axle comprises a left front axle and a right front axle, the rear axle comprises a left rear axle and a right rear axle; the left front axle and the right front axle are connected via the front axle differential, and the front axle drive motor is connected to the front axle via the front axle differential; the left rear axle and the right rear axle are connected via the rear axle differential, and the rear axle drive motor is connected to the rear axle via the rear axle differential; the vehicle controller adjusts the torque of the front axle drive motor and the rear axle drive motor by acquiring signals from the front axle differential and the rear axle differential.

[0014] In a third aspect, an embodiment of the present invention provides a dual-motor four-wheel drive electric vehicle, including the motor torque control system described above.

[0015] Compared with the prior art, the present invention is based on the proportional differential control of the left and right wheel speed difference, and actively performs torque limitation when the speed difference tends to increase rapidly to avoid control lag; by transferring the required torque generated by torque limitation on the slipping axle to the non-slipping axle, the overall required torque of the vehicle will not be reduced due to wheel slip on a single axle, thereby ensuring that the vehicle can maintain the power of the vehicle when the wheels slip. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of a motor torque control method in one embodiment of the present invention;

[0017] Figure 2 A schematic diagram of the connection between a vehicle control system and a CAN network in one embodiment of the present invention;

[0018] Figure 3 FIG. 4 is a schematic diagram of a motor torque control system of a vehicle in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings. Through the description of the specific implementation methods, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the drawings are only for reference and explanation purposes and are not used to limit the present invention.

[0020] Embodiment 1

[0021] See also Figure 1 The present invention provides a motor torque control method, which is applied to an electric vehicle, wherein the electric vehicle is a dual-motor four-wheel drive electric vehicle, including a front motor, a rear motor, a left front wheel and a right front wheel connected to the front motor through a front axle and a front axle differential, and a left rear wheel and a right rear wheel connected to the rear motor through a rear axle and a rear axle differential. The method comprises the following steps:

[0022] Step S0, controlling the front motor to apply a preset front motor request torque to the front axle to drive the left front wheel and the right front wheel to rotate; controlling the rear motor to apply a preset rear motor request torque to the rear axle to drive the left rear wheel and the right rear wheel to rotate.

[0023] Step S1, determining the front axle differential protection limit torque of the front axle according to the speed difference between the left front wheel and the right front wheel; determining the rear axle differential protection limit torque of the rear axle according to the speed difference between the left rear wheel and the right rear wheel.

[0024] Please refer to Figure 2 , Figure 3The vehicle control system includes a vehicle controller 110, a brake control module 111, a front motor drive module 112, and a rear motor drive module 113; the vehicle controller is connected to a high-speed CAN network. The brake control module is connected to the left front wheel speed sensor 2, the right front wheel speed sensor 5, the left rear wheel speed sensor 11, and the right rear wheel speed sensor 14 of the vehicle, and the brake control module is used to collect wheel speed signals of the four wheels and send the collected wheel speed signals to the CAN network; the vehicle controller obtains the wheel speed sensor signals of the left front wheel, the right front wheel, the left rear wheel, and the right rear wheel through the CAN network and performs real-time calculation to form a message containing the front motor request torque and the rear motor request torque, and sends the message to the CAN network with a period of 5-10ms.

[0025] In this embodiment, the differential change rate of the front wheel speed difference is calculated by the wheel speed difference between the left front wheel and the right front wheel; the front axle differential protection differential torque limit coefficient is determined according to the wheel speed difference differential change rate, and the front axle differential protection proportional torque limit coefficient is determined based on the left and right wheel speed difference; the front axle differential protection limit torque is calculated according to the front motor request torque, the front axle differential protection differential torque limit coefficient, and the front axle differential protection proportional torque limit coefficient.

[0026] Specifically, the calculation process of the front axle differential protection limiting torque is: front axle differential protection limiting torque = (front axle differential protection proportional torque limiting coefficient + front axle differential protection differential torque limited to coefficient) * front motor requested torque; wherein, the value of (front axle differential protection proportional torque limiting coefficient + front axle differential protection differential torque limited to coefficient) does not exceed 1.

[0027] In this embodiment, the rear wheel speed difference differential change rate is calculated by the speed difference between the left rear wheel and the right rear wheel, and the rear axle differential protection differential torque limit coefficient is determined according to the rear wheel speed difference differential change rate; the rear axle differential protection proportional torque limit coefficient is obtained based on the speed difference between the left rear wheel and the right rear wheel; the rear axle differential protection limit torque is calculated according to the rear motor request torque, the rear axle differential protection differential torque limit coefficient, and the rear axle differential protection proportional torque limit coefficient.

[0028] Specifically, the calculation process of the rear axle differential protection limiting torque is: rear axle differential protection limiting torque = (rear axle differential protection proportional torque limiting coefficient + rear axle differential protection differential torque limiting coefficient) * rear motor requested torque; wherein, the value of the rear axle differential protection proportional torque limiting coefficient + rear axle differential protection differential torque limiting coefficient does not exceed 1.

[0029] Step S2: judging whether the front axle and the rear axle are slipping according to the front axle differential protection limit torque and the rear axle differential protection limit torque.

[0030] Specifically, whether the front axle or rear axle is slipping is determined by determining whether the protection limit torque of the front axle or rear axle differential is greater than 0. If the protection limit torque of the front axle differential is greater than 0, the front axle is slipping; if the protection limit torque of the rear axle differential is greater than 0, the rear axle is slipping.

[0031] Step S3, when one of the front axle and the rear axle slips and the other does not slip, the differential protection limit torque corresponding to the axle with slip is subtracted from the requested torque applied to the axle with slip, and the differential protection limit torque corresponding to the axle with slip is added to the requested torque applied to the axle without slip; the left front wheel, right front wheel, left rear wheel and right rear wheel are driven to rotate by the adjusted requested torque.

[0032] Specifically, when the front axle slips and the rear axle does not slip, that is, the front axle differential protection limit torque is greater than 0, the front axle differential protection limit torque is subtracted from the front motor request torque and the front axle differential protection limit torque is added to the rear motor request torque; the front motor is controlled to apply the adjusted front motor request torque to the front axle to drive the left and right front wheels to rotate; the rear motor is controlled to apply the adjusted rear motor request torque to the rear axle to drive the left and right rear wheels to rotate.

[0033] According to the torque adjustment of the front motor and the rear motor when the front axle slips but the rear axle does not slip, it can be known that when the front axle slips but the rear axle does not slip, the front motor output torque = front motor request torque - front axle differential protection limit torque; to ensure that the total output torque does not change significantly, the front axle differential protection limit torque is transferred to the rear axle output, and at this time the rear motor output torque = rear motor request torque + front axle differential protection limit torque.

[0034] If the front axle slip is eliminated, that is, the front axle is no longer in a slipping state, the front axle differential protection limit torque is equal to 0. In order to ensure that the overall output torque is within a stable range of variation, the rear axle differential protection limit torque is transferred to the front axle output. In this case, the front motor output torque = front motor request torque + rear axle differential protection limit torque.

[0035] Similarly, when the rear axle slips and the front axle does not slip, that is, the rear axle differential protection limit torque is greater than 0, the rear motor request torque is subtracted from the rear axle differential protection limit torque, and the front motor request torque is added to the rear axle differential protection limit torque; the rear motor is controlled to apply the adjusted rear motor request torque to the rear axle to drive the left and right rear wheels to rotate; at the same time, the front motor is controlled to apply the adjusted rear motor request torque to the front axle to drive the left and right front wheels to rotate.

[0036] According to the torque adjustment when the rear axle slips but the front axle does not slip as described above, it can be known that when the rear axle slips but the front axle does not slip, the rear motor output torque = rear motor request torque - rear axle differential protection limit torque; similarly, in order to prevent a significant change in the overall output torque, the rear axle differential protection limit torque is transferred to the front axle output, and the front motor output torque at this time = front motor request torque + rear axle differential protection limit torque.

[0037] When the rear axle slip is eliminated, the rear axle is no longer in a slipping state, that is, the rear axle differential protection limit torque is equal to 0. In order to ensure that the overall output torque is in a stable range of change, the front axle differential protection limit torque is transferred to the rear axle output. In this case, the rear motor output torque = rear motor request torque + front axle differential protection limit torque.

[0038] When one of the front axle or the rear axle slips, the vehicle controller transfers the rear axle differential protection limit torque to the front axle output. In this case, under the regulation of the front motor output torque = front motor request torque + rear axle differential protection limit torque, the motor of the slipping axle refuses to receive torque from the other non-slipping axle.

[0039] Other implementations further include step S4, when the front axle and the rear axle slip at the same time, the front motor request torque and the rear motor request torque are reduced at the same time.

[0040] When the front and rear axles slip at the same time, the torques of the front and rear motors are both greater than 0. In this case, neither the front nor the rear axle can receive torque from the other axle. Therefore, the slip situation is improved by reducing the requested torque of the front and rear motors.

[0041] Embodiment 2, the present invention provides a motor torque control system, see Figure 3 .

[0042] Figure 3Schematic diagram of the motor torque control system, including a left front wheel 1, a left front wheel speed sensor 2, a left front wheel hydraulic brake unit 3, a right front wheel 4, a right front wheel speed sensor 5, a right front wheel hydraulic brake unit 6, a front axle drive motor 7, a front axle reduction mechanism 8, a front axle differential 9, a left rear wheel 10, a left rear wheel speed sensor 11, a left rear wheel hydraulic brake unit 12, a right rear wheel 13, a right rear wheel speed sensor 14, a right rear wheel hydraulic brake unit 15, a rear axle drive motor 16, a rear axle reduction mechanism 17, and a rear axle differential 18.

[0043] The left front wheel 1 is connected to the right front wheel 4 through the front axle transmission, the front axle includes a left front axle and a right front axle, the left front axle and the right front axle are connected through the front axle differential 9, and the front axle drive motor 7 is connected to the front axle through the front axle differential 9. The left rear wheel 10 and the right rear wheel 13 are connected through the rear axle, the rear axle includes a left rear axle and a right rear axle, the left rear axle and the right rear axle are connected through the rear axle differential 18, and the rear axle drive motor 16 is connected to the rear axle through the rear axle differential 18; the vehicle controller adjusts the torque of the front axle drive motor and the rear axle drive motor by obtaining signals from the front axle differential 9 and the rear axle differential 18.

[0044] The front motor 7 and the rear motor 16 are controlled to apply the motor request torque to the front and rear axles, driving the left front wheel 1, the right front wheel 4, the left rear wheel 10, and the right rear wheel 13 to rotate; the vehicle controller 110 obtains the wheel speed signal of each wheel through the left front wheel speed sensor 2, the right front wheel speed sensor 5, the left rear wheel speed sensor 11, and the right rear wheel speed sensor 14 to determine the front and rear axle differential protection limit torque, so it can be determined whether the front axle or the rear axle is slipping or has a tendency to slip; if slipping occurs, the front and rear axle torques are regulated by the vehicle control system to improve the slipping situation or prevent slipping.

[0045] Embodiment 3, the present invention provides a dual-motor four-drive electric vehicle, including the motor torque control system described in Embodiment 2.

[0046] Under some driving conditions, the vehicle is in a full-throttle cornering condition. Due to the large yaw angular velocity of the vehicle, the vehicle posture is cambered outward, which weakens the grip of the inner wheel of the front axle. At this time, it is easy to slip when driving with a large throttle. For conventional differential protection control algorithms, control is generally intervened only when the speed difference of the wheels is large. The motor torque control method provided by the present invention intervenes in control as soon as the wheel speed difference increases, thereby avoiding control lags. Experiments have shown that compared with conventional control algorithms, the control algorithm provided by the present invention intervenes in control significantly earlier, and when the control is intervened, the speed difference between the left and right wheels is still at a difference that is easy to control and adjust.

[0047] The present invention limits the differential protection torque, so that the differential torque limit can reach 0-1000Nm.

[0048] The advantage of the present invention over the prior art is that it intervenes and limits when it is identified that the speed difference between the left and right wheels has an increasing trend, which can avoid the uncontrollable situation caused by the further increase of the wheel speed difference, and when the wheel speed difference is not too large, it limits the wheel speed through torque transfer, which can reduce the sense of frustration during the adjustment process, thereby improving the comfort of the driver and passengers; in addition, the present invention can avoid the output torque from the slipping shaft to the non-slipping shaft output without a large loss in a short time, and ensure that the whole vehicle can maintain sufficient power when slipping. Through the above-mentioned motor torque control method and motor torque control system, the present invention effectively solves the problem of poor differential control effect caused by the late intervention of the vehicle controller system and the poor driving experience caused by the strong sense of frustration of the vehicle power output.

[0049] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes through the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A motor torque control method, applied to an electric vehicle, wherein the electric vehicle is a dual-motor four-wheel drive electric vehicle, comprising a front motor, a rear motor, a left front wheel and a right front wheel connected to the front motor via a front axle and a front axle differential, and a left rear wheel and a right rear wheel connected to the rear motor via a rear axle and a rear axle differential; characterized in that: The method comprises the following steps: S0, controlling the front motor to apply a preset front motor request torque to the front axle to drive the left front wheel and the right front wheel to rotate; controlling the rear motor to apply a preset rear motor request torque to the rear axle to drive the left rear wheel and the right rear wheel to rotate; S1, determining a front axle differential protection limit torque of the front axle according to a speed difference between the left front wheel and the right front wheel; determining a rear axle differential protection limit torque of the rear axle according to a speed difference between the left rear wheel and the right rear wheel; S2, judging whether the front axle and the rear axle are slipping according to the front axle differential protection limit torque and the rear axle differential protection limit torque; S3, when one of the front axle and the rear axle slips and the other does not slip, the differential protection limit torque corresponding to the axle with slip is subtracted from the requested torque applied to the axle with slip, and the differential protection limit torque corresponding to the axle with slip is added to the requested torque applied to the axle without slip; the left front wheel, right front wheel, left rear wheel and right rear wheel are driven to rotate by the adjusted requested torque.

2. The motor torque control method according to claim 1, characterized in that: The step S1 comprises: Calculating a front wheel speed difference differential change rate based on the speed difference between the left front wheel and the right front wheel, and determining a front axle differential protection differential torque limit coefficient according to the front wheel speed difference change rate; determining a front axle differential protection proportional torque limit coefficient based on the speed difference between the left front wheel and the right front wheel; The front axle differential protection limit torque is calculated according to the front motor request torque, the front axle differential protection differential torque limit coefficient, and the front axle differential protection proportional torque limit coefficient.

3. The motor torque control method according to claim 2, characterized in that: The calculating of the front axle differential protection limit torque according to the front motor request torque, the front axle differential protection differential torque limit coefficient, and the front axle differential protection proportional torque limit coefficient comprises: Front axle differential protection limit torque = (front axle differential protection proportional torque limit coefficient + front axle differential protection differential torque limit coefficient) * front motor request torque; Among them, the value of (front axle differential protection proportional torque limit coefficient + front axle differential protection differential torque limit coefficient) does not exceed 1.

4. The motor torque control method according to claim 1, characterized in that: The step S1 further comprises: Calculating a rear wheel speed difference differential change rate based on the speed difference between the left rear wheel and the right rear wheel, and determining a rear axle differential protection differential torque limit coefficient according to the rear wheel speed difference differential change rate; acquiring the rear axle differential protection proportional torque limit coefficient based on the speed difference between the left rear wheel and the right rear wheel; The rear axle differential protection limit torque is calculated according to the rear motor request torque, the rear axle differential protection differential torque limit coefficient, and the rear axle differential protection proportional torque limit coefficient.

5. The motor torque control method according to claim 4, characterized in that: The calculating of the rear axle differential protection limit torque according to the rear motor request torque, the rear axle differential protection differential torque limit coefficient, and the rear axle differential protection proportional torque limit coefficient comprises: Rear axle differential protection limit torque = (rear axle differential protection proportional torque limit coefficient + rear axle differential protection differential torque limit coefficient) * rear motor request torque; Among them, the rear axle differential protection proportional torque limit coefficient + the rear axle differential protection differential torque limit coefficient value does not exceed 1.

6. The motor torque control method according to claim 1, characterized in that: The step S3 comprises: If the front axle slips and the rear axle does not slip, the front axle differential protection limit torque is subtracted from the front motor request torque, and the front axle differential protection limit torque is added to the rear motor request torque; the front motor is controlled to apply the adjusted front motor request torque to the front axle to drive the left front wheel and the right front wheel to rotate; the rear motor is controlled to apply the adjusted rear motor request torque to the rear axle to drive the left rear wheel and the right rear wheel to rotate.

7. The motor torque control method according to claim 1, characterized in that: The step S3 further comprises: If the rear axle slips and the front axle does not slip, the rear axle differential protection limit torque is subtracted from the rear motor request torque, and the rear axle differential protection limit torque is added to the front motor request torque; the rear motor is controlled to apply the adjusted rear motor request torque to the rear axle to drive the left and right rear wheels to rotate; the front motor is controlled to apply the adjusted rear motor request torque to the front axle to drive the left and right front wheels to rotate.

8. The motor torque control method according to claim 1, characterized in that: The following steps are also included: S4: When the front axle and the rear axle slip at the same time, the front motor request torque and the rear motor request torque are reduced at the same time.

9. A motor torque control system, characterized in that: The system includes a vehicle controller, a front axle, a rear axle, a front axle differential, a rear axle differential, a front axle drive motor and a rear axle drive motor; the front axle includes a left front axle and a right front axle, and the rear axle includes a left rear axle and a right rear axle; the left front axle and the right front axle are connected via the front axle differential, and the front axle drive motor is connected to the front axle via the front axle differential; the left rear axle and the right rear axle are connected via the rear axle differential, and the rear axle drive motor is connected to the rear axle via the rear axle differential; the vehicle controller adjusts the torque of the front axle drive motor and the rear axle drive motor by acquiring signals from the front axle differential and the rear axle differential.

10. A dual-motor four-wheel drive electric vehicle, characterized in that: Includes the motor torque control system as described in claim 9.

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