Motor torque control method for dual-motor electric automobile

Abstract

The invention belongs to the technical field of electric vehicles, and particularly relates to a motor torque control method for a dual-motor electric vehicle, which comprises the following steps of: acquiring a motor end demand torque, determining a main drive motor and an auxiliary drive motor, performing torque distribution on the main drive motor and the auxiliary drive motor, and performing torque control on the main drive motor and the auxiliary drive motor. The motor aging factors caused by the actual capacity, the motor temperature and the load rate of the two motors are considered, the main / auxiliary drive switching principle is provided, the dynamic property of the whole vehicle is effectively improved, the service life of the motors is effectively prolonged, on the premise that the dynamic property of the whole vehicle is met, the situation that the motors work in a low economic area is effectively avoided, and the economical efficiency of the whole vehicle is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of electric vehicles, and in particular relates to a motor torque control method for a dual-motor electric vehicle. Background Art

[0002] At present, most pure electric vehicle power systems use a single motor, which includes a drive motor, a transmission, and a power battery pack. In order to improve the power of the whole vehicle, dual-motor electric vehicles came into being. Compared with a single-motor drive system, a dual-motor drive system has a more flexible torque distribution method, and its economy and power are greatly improved.

[0003] In current dual-motor electric vehicles, during normal driving, the dual motors mostly use an average torque distribution method. However, in the actual driving process, the torque demand of the entire vehicle changes continuously with the complex driving conditions. If the average distribution method is used for torque distribution, it will not be possible to distribute the required torque to the two motors according to the principle of optimal economy, and it will not be possible to ensure the lowest energy consumption of the entire vehicle, that is, it will not be possible to ensure the economy of the entire vehicle. In addition, when the capacity of a single motor is limited, the use of average distribution will result in a "barrel effect", and the full capacity of the other motor cannot be brought into play, that is, it is impossible to achieve the optimal power of the entire vehicle. Therefore, the existing dual-motor torque average distribution method cannot meet the user's requirements for the economy and power of dual-motor electric vehicles. Summary of the invention

[0004] The present invention provides a motor torque control method for a dual-motor electric vehicle, which takes into account the actual capacity of the two motors, the motor temperature and the motor aging factor caused by the load rate, and proposes a main / auxiliary drive switching principle, which effectively improves the power of the whole vehicle and extends the service life of the motor. On the premise of meeting the power of the whole vehicle, it effectively avoids the motor from working in a low economic zone, thereby improving the economy of the whole vehicle.

[0005] To achieve the above object, the present invention provides a motor torque control method for a dual-motor electric vehicle, comprising the following steps:

[0006] S100: Obtaining the required torque at the motor end;

[0007] S200: Determine the main drive motor and the auxiliary drive motor;

[0008] S300: Distributing the torque between the main drive motor and the auxiliary drive motor;

[0009] S400: Perform torque control on the main drive motor and the auxiliary drive motor.

[0010] The present invention comprehensively considers the actual capacity of the two motors, the motor temperature and the motor aging factor caused by the load rate of the dual-motor power system, performs main / auxiliary drive switching, effectively improves the power of the whole vehicle and prolongs the service life of the motor;

[0011] Specifically, the method for obtaining the required torque at the motor end in step S100 of the present invention includes:

[0012] Step S110: querying MAP according to the vehicle speed and the accelerator pedal opening to obtain the required torque at the wheel end;

[0013] Step S120: considering the battery allowable discharge power, accessory consumption and other vehicle energy management to obtain the required wheel-end torque after restrictions;

[0014] Step S130: Calculate the motor end torque requirement based on the limited wheel end torque and in combination with the current gearbox speed ratio and rear axle speed ratio.

[0015] Specifically, the method for determining the main drive motor and the auxiliary drive motor in step S200 of the present invention, that is, the main / auxiliary drive switching principle of the present invention, includes the following steps: the power system of the present invention includes a first motor and a second motor, and after the vehicle is powered on, the first motor is the main drive motor by default, and the second auxiliary drive motor is the auxiliary motor by default. If any of the following conditions is met, the main drive motor and the auxiliary drive motor are switched, and if not, the first motor is kept as the main drive motor and the second motor is kept as the auxiliary drive motor; the specific conditions are as follows:

[0016] (1) The time integral value of the actual torque of the first motor minus the time integral value of the actual torque of the second motor is greater than or equal to A;

[0017] (2) The actual temperature of the first motor minus the actual temperature of the second motor is greater than or equal to t1;

[0018] (3) The actual temperature of the first motor controller minus the actual temperature of the second motor controller is greater than or equal to t2;

[0019] (4) The maximum available torque of the second motor minus the maximum available torque of the first motor is greater than or equal to T1;

[0020] (5) The minimum available torque of the first motor minus the minimum available torque of the second motor is greater than or equal to T2.

[0021] Specifically, in step S200 of the present invention, it is stipulated that the whole vehicle is powered on and off as a driving cycle, and the main drive motor and the auxiliary drive motor are set when the whole vehicle is powered on, and the main drive motor and the auxiliary drive motor are not switched within the driving cycle.

[0022] Specifically, in step S200 of the present invention, A=638400 N·min, t1=60° C., t2=50° C., T1=500 Nm, T2=500 Nm.

[0023] Specifically, the torque distribution of the main drive motor and the auxiliary drive motor in step S300 of the present invention includes the following steps:

[0024] Step S310: The motor-side required torque is preferentially allocated to the main drive motor. When the main drive motor allocated torque reaches a set limit, the remaining torque is allocated to the auxiliary drive motor.

[0025] Step S320: setting 0 torque, the economic lower limit of the main drive motor torque, the economic upper limit of the main drive motor torque and the maximum torque of the main drive motor for the main drive motor; setting 0 torque, the economic lower limit of the auxiliary drive motor torque, the economic upper limit of the auxiliary drive motor torque and the maximum torque of the auxiliary drive motor for the auxiliary drive motor.

[0026] Step S330: Torque loading, first loading the main drive motor with torque, then loading the auxiliary drive motor, and alternately loading the torque in sequence until the main drive motor is loaded to the maximum torque of the main drive motor and the auxiliary drive motor is loaded to the maximum torque of the auxiliary drive motor, and the torque loading is completed;

[0027] Step S340: Torque unloading, first unloading the torque of the auxiliary drive motor, then unloading the torque of the main drive motor, and unloading the torque alternately in sequence until both the main drive motor and the auxiliary drive motor are unloaded to 0 torque, and the torque unloading is completed.

[0028] Specifically, the torque loading in step S330 of the present invention, that is, the main / auxiliary drive torque loading strategy, has the following steps: S331, loading the main drive motor torque until the main drive motor torque is loaded to the economic upper limit of the main drive motor torque; S332, when the main drive motor torque is loaded to the economic upper limit of the main drive motor torque, switching the auxiliary drive motor loading torque; S333, when the auxiliary drive motor torque is loaded to the economic upper limit of the auxiliary drive motor torque, switching the main drive motor loading torque; S334, when the main drive motor loading torque reaches the maximum torque of the main drive motor, switching the auxiliary drive motor loading torque; S335, loading the torque alternately in sequence until the main drive motor is loaded to the maximum torque of the main drive motor and the auxiliary drive motor is loaded to the maximum torque of the auxiliary drive motor, and the torque loading is completed.

[0029] Specifically, the torque unloading in step S340 of the present invention, that is, the main / auxiliary drive torque unloading strategy, has the following steps: S341, unloading the auxiliary drive motor torque until the auxiliary drive motor torque is unloaded to the auxiliary drive motor torque economic upper limit; S342, when the auxiliary drive motor torque is unloaded to the torque economic upper limit, switching the main drive motor unloading torque; S343, when the main drive motor torque is unloaded to the main drive motor torque economic upper limit, switching the auxiliary drive motor unloading torque; S344, when the auxiliary drive motor unloading torque is to the auxiliary drive motor torque economic lower limit, switching the main drive motor unloading torque; S345, when the main drive motor unloading torque is to the main drive motor torque economic lower limit, switching the auxiliary drive motor unloading torque; S346, when the auxiliary drive motor unloading torque is to 0 torque, switching the main drive motor unloading torque; S347, unloading the torque alternately in sequence until both the main drive motor and the auxiliary drive motor are unloaded to 0 torque, and the torque unloading is completed.

[0030] Specifically, the present invention also includes a method for handling abnormal situations: if the maximum allowable torque of the motor is limited due to a motor failure, and the maximum allowable torque of the motor is less than a preset upper limit or lower limit of the motor torque, if the maximum allowable torque of the motor is limited before the motor torque is loaded, then the process goes to step S510; if the maximum allowable torque of the motor is limited after the motor torque is loaded, then the process goes to step S520; if the maximum allowable torque of the limited motor is restored, then the process goes to step S530;

[0031] Step S510: according to the alternating loading sequence of step S330, after loading the restricted motor to the maximum allowable torque, stop loading the restricted motor and switch to another motor for loading until the maximum allowable torque of the restricted motor is reached, and the torque loading is terminated;

[0032] Step S520: Adjust the torque of the limited motor to the maximum allowable torque after limitation, and load the reduced torque to another motor. The torque loaded on the other motor will not exceed the capacity of the limited motor, that is, the maximum allowable torque of the limited motor.

[0033] Step S530: Carry out the loading sequence according to step S330.

[0034] Specifically, in step S320 of the present invention, the economic lower limit of the main drive motor torque is 500Nm, and the economic upper limit of the main drive motor torque is 1000Nm; the economic lower limit of the auxiliary drive motor torque is 500Nm, and the economic upper limit of the auxiliary drive motor torque is 1000Nm.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. Taking into account the actual capacity of the two motors, the motor temperature and the motor aging factors caused by the load rate, the main / auxiliary drive switching principle is proposed to avoid overloading or overheating of a single motor, effectively improve the power of the whole vehicle and extend the service life of the motor;

[0037] 2. A main / auxiliary drive torque loading and unloading strategy is proposed. Under the premise of meeting the vehicle's power performance, dual motors are used to coordinate torque output so that the motors can operate within the torque economy lower limit and torque economy upper limit range, effectively avoiding the motors from operating in the low-economic zone and improving the vehicle's economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of the steps of a motor torque control method for a dual-motor electric vehicle described in the present invention.

[0039] Figure 2 It is a schematic diagram of the loading and unloading process of the first case in a specific implementation manner of the present invention.

[0040] Figure 3 Schematic diagram of the loading and unloading process of the second case in the specific implementation mode of the present invention

[0041] Figure 4 Schematic diagram of the loading and unloading process of the third case in the specific implementation mode of the present invention

[0042] Figure 5 Schematic diagram of the loading and unloading process of the fourth case in the specific implementation mode of the present invention DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0044] To achieve the above object, the present invention provides a motor torque control method for a dual-motor electric vehicle, comprising the following steps:

[0045] S100: Obtaining the required torque at the motor end;

[0046] S200: Determine the main drive motor and the auxiliary drive motor;

[0047] S300: Distributing the torque between the main drive motor and the auxiliary drive motor;

[0048] S400: Perform torque control on the main drive motor and the auxiliary drive motor.

[0049] The method for obtaining the required torque at the motor end in step S100 of this embodiment includes:

[0050] Step S110: querying MAP according to the vehicle speed and the accelerator pedal opening to obtain the required torque at the wheel end;

[0051] Step S120: considering the battery allowable discharge power, accessory consumption and other vehicle energy management to obtain the required wheel-end torque after restrictions;

[0052] Step S130: Calculate the motor end torque requirement based on the limited wheel end torque and in combination with the current gearbox speed ratio and rear axle speed ratio.

[0053] The method for determining the main drive motor and the auxiliary drive motor in step S200 of the present embodiment, i.e., the main / auxiliary drive switching principle of the present invention, comprises the following steps: the power system of the present invention comprises a first motor and a second motor, after the vehicle is powered on, the first motor is the main drive motor by default, and the second auxiliary drive motor is the auxiliary motor by default, if any of the following conditions is met, the main drive motor and the auxiliary drive motor are switched, if not met, the first motor is kept as the main drive motor and the second motor is kept as the auxiliary drive motor; the specific conditions are as follows:

[0054] (1) The time integral value of the actual torque of the first motor minus the time integral value of the actual torque of the second motor is greater than or equal to A;

[0055] (2) The actual temperature of the first motor minus the actual temperature of the second motor is greater than or equal to t1;

[0056] (3) The actual temperature of the first motor controller minus the actual temperature of the second motor controller is greater than or equal to t2;

[0057] (4) The maximum available torque of the second motor minus the maximum available torque of the first motor is greater than or equal to T1;

[0058] (5) The minimum available torque of the first motor minus the minimum available torque of the second motor is greater than or equal to T2.

[0059] In step S200 of this embodiment, it is stipulated that the whole vehicle is powered on and off as a driving cycle, and the main drive motor and the auxiliary drive motor are set when the whole vehicle is powered on, and the main drive motor and the auxiliary drive motor are not switched within the driving cycle.

[0060] In step S200 of this embodiment, A=638400 N·min, t1=60°C, t2=50°C,

[0061] T1=500Nm,T2=500Nm.

[0062] In step S300 of this embodiment, the torque distribution between the main drive motor and the auxiliary drive motor includes the following steps:

[0063] Step S310: The motor-side required torque is preferentially allocated to the main drive motor. When the main drive motor allocated torque reaches a set limit, the remaining torque is allocated to the auxiliary drive motor.

[0064] Step S320: setting 0 torque, the economic lower limit of the main drive motor torque, the economic upper limit of the main drive motor torque and the maximum torque of the main drive motor for the main drive motor; setting 0 torque, the economic lower limit of the auxiliary drive motor torque, the economic upper limit of the auxiliary drive motor torque and the maximum torque of the auxiliary drive motor for the auxiliary drive motor.

[0065] Step S330: Torque loading, first loading the main drive motor with torque, then loading the auxiliary drive motor, and alternately loading the torque in sequence until the main drive motor is loaded to the maximum torque of the main drive motor and the auxiliary drive motor is loaded to the maximum torque of the auxiliary drive motor, and the torque loading is completed;

[0066] Step S340: Torque unloading, first unloading the torque of the auxiliary drive motor, then unloading the torque of the main drive motor, and unloading the torque alternately in sequence until both the main drive motor and the auxiliary drive motor are unloaded to 0 torque, and the torque unloading is completed.

[0067] The torque loading in step S330 of the present embodiment, i.e., the main / auxiliary drive torque loading strategy, comprises the following steps: S331, loading the main drive motor with torque until the main drive motor torque is loaded to the economic upper limit of the main drive motor torque; S332, when the main drive motor torque is loaded to the economic upper limit of the main drive motor torque, switching the auxiliary drive motor loading torque; S333, when the auxiliary drive motor torque is loaded to the economic upper limit of the auxiliary drive motor torque, switching the main drive motor loading torque; S334, when the main drive motor loading torque reaches the maximum torque of the main drive motor, switching the auxiliary drive motor loading torque; S335, loading the torque alternately in sequence until the main drive motor is loaded to the maximum torque of the main drive motor and the auxiliary drive motor is loaded to the maximum torque of the auxiliary drive motor, and the torque loading ends.

[0068] The torque unloading in step S340 of the present embodiment, i.e., the main / auxiliary drive torque unloading strategy, comprises the following steps: S341, unloading the auxiliary drive motor torque until the auxiliary drive motor torque is unloaded to the auxiliary drive motor torque economic upper limit; S342, when the auxiliary drive motor torque is unloaded to the torque economic upper limit, switching to the main drive motor unloading torque; S343, when the main drive motor torque is unloaded to the main drive motor torque economic upper limit, switching to the auxiliary drive motor unloading torque; S344, when the auxiliary drive motor unloading torque is to the auxiliary drive motor torque economic lower limit, switching to the main drive motor unloading torque; S345, when the main drive motor unloading torque is to the main drive motor torque economic lower limit, switching to the auxiliary drive motor unloading torque; S346, when the auxiliary drive motor unloading torque is to 0 torque, switching to the main drive motor unloading torque; S347, unloading the torque alternately in sequence until both the main drive motor and the auxiliary drive motor are unloaded to 0 torque, and the torque unloading is completed.

[0069] This embodiment also includes a method for handling abnormal situations: if the maximum allowable torque of the motor is limited due to a motor fault, and the maximum allowable torque of the motor is less than a preset upper limit or lower limit of the motor torque, if the maximum allowable torque of the motor is limited before the motor torque is loaded, then the process goes to step S510; if the maximum allowable torque of the motor is limited after the motor torque is loaded, then the process goes to step S520; if the maximum allowable torque of the limited motor is restored, then the process goes to step S530;

[0070] Step S510: according to the alternating loading sequence of step S330, after loading the restricted motor to the maximum allowable torque, stop loading the restricted motor and switch to another motor for loading until the maximum allowable torque of the restricted motor is reached, and the torque loading is terminated;

[0071] Step S520: Adjust the torque of the limited motor to the maximum allowable torque after limitation, and load the reduced torque to another motor. The torque loaded on the other motor will not exceed the capacity of the limited motor, that is, the maximum allowable torque of the limited motor.

[0072] Step S530: Carry out the loading sequence according to step S330.

[0073] In step S320 of this embodiment, the economic lower limit of the main drive motor torque is 500 Nm, and the economic upper limit of the main drive motor torque is 1000 Nm; the economic lower limit of the auxiliary drive motor torque is 500 Nm, and the economic upper limit of the auxiliary drive motor torque is 1000 Nm.

[0074] The motor torque loading / unloading strategy is described in detail below:

[0075] The economic lower limit of the main drive motor torque is set to 500Nm, and the economic upper limit of the main drive motor torque is set to 1000Nm; the economic lower limit of the auxiliary drive motor torque is set to 500Nm, and the economic upper limit of the auxiliary drive motor torque is set to 1000Nm.

[0076] The first case: when 0Nm≤required motor total torque≤main drive motor torque economic upper limit 1000Nm; if the above conditions are met, such as Figure 2 As shown, the vehicle controller VCU only loads and unloads the main drive motor. Figure 2 The process of loading the torque of the main drive motor is shown from left to right in sequence. In this process, the main drive motor is loaded with torque first until the main drive motor torque is loaded to the economic upper limit of the main drive motor torque of 1000Nm; Figure 2 The order from right to left is the order of the uninstallation process.

[0077] The second case: the economic upper limit of the main drive motor torque is 1000Nm < the total torque of the required motor < the economic upper limit of the main drive motor torque is 1000Nm + the economic lower limit of the auxiliary drive motor torque is 500Nm; if the above conditions are met, such as Figure 3 As shown, torque loading (the order from left to right is the loading route): the vehicle controller VCU preferentially loads the main drive motor to the main drive motor torque upper limit of 1000Nm, and then loads the remaining required torque to the auxiliary drive motor, and the auxiliary drive motor is loaded to the auxiliary drive motor torque economic lower limit of 500Nm; torque unloading (the order from right to left is the unloading route): the vehicle controller VCU preferentially unloads the auxiliary drive motor torque, and then unloads the main drive motor torque.

[0078] The third case: the economic upper limit of the main drive motor torque is 1000Nm + the economic lower limit of the auxiliary drive motor torque is 500Nm ≤ the total torque of the required motor ≤ the economic upper limit of the main drive motor torque is 1000Nm + the economic upper limit of the auxiliary drive motor torque is 1000Nm. If the above conditions are met, then Figure 4As shown, torque loading: the vehicle controller VCU preferentially loads the main drive motor to the main drive motor torque economic upper limit of 1000Nm, and then loads the remaining required torque to the auxiliary drive motor, and the auxiliary drive motor is loaded to the auxiliary drive motor torque economic upper limit of 1000Nm; torque unloading: the vehicle controller VCU preferentially performs auxiliary drive motor torque unloading, and when the auxiliary drive motor torque is unloaded to the auxiliary drive motor torque economic lower limit of 500Nm, it switches to main drive motor torque unloading; when the main drive motor torque is unloaded to the main drive motor torque economic lower limit of 500Nm, it switches to auxiliary drive motor torque unloading; when the auxiliary drive motor torque is unloaded to 0Nm, it switches to main drive torque unloading until the main drive torque is also unloaded to 0Nm.

[0079] The fourth case: the economic upper limit of the main drive motor torque is 1000Nm + the economic upper limit of the auxiliary drive motor torque is 1000Nm < the total torque of the required motor ≤ the maximum allowable torque of the main drive motor + the maximum allowable torque of the auxiliary drive motor, such as Figure 4 As shown, torque loading: first, the vehicle controller VCU loads the main drive motor to the main drive motor torque economic upper limit of 1000Nm, and then loads the auxiliary drive motor to the auxiliary drive motor torque economic upper limit of 1000Nm; the vehicle controller VCU loads the main drive motor to the maximum allowable torque of the main drive motor, and then loads the remaining required torque to the auxiliary drive motor; torque unloading: the vehicle controller VCU prioritizes auxiliary drive motor torque unloading, and when the auxiliary drive motor torque is unloaded to the auxiliary drive motor torque upper limit of 1000Nm, it switches to main drive motor torque unloading; when the main drive motor torque is unloaded to the main drive motor torque economic upper limit of 1000Nm, it switches to auxiliary drive motor torque unloading; when the auxiliary drive motor torque is unloaded to the auxiliary drive motor torque economic lower limit of 500Nm, it switches to main drive motor torque unloading; when the main drive motor torque is unloaded to the main drive motor torque economic lower limit of 500Nm, it switches to auxiliary drive motor torque unloading; when the auxiliary drive motor torque is unloaded to 0Nm, it switches to main drive torque unloading until the main drive torque is also unloaded to 0Nm.

Claims

1. A motor torque control method for a dual-motor electric vehicle, characterized in that The steps include: S100: Obtaining the required torque at the motor end; S200: Determine the main drive motor and the auxiliary drive motor; S300: Distributing the torque between the main drive motor and the auxiliary drive motor; S400: Perform torque control on the main drive motor and the auxiliary drive motor.

2. The motor torque control method of a dual-motor electric vehicle according to claim 1, characterized in that The method for determining the main drive motor and the auxiliary drive motor in step S200 includes the following steps: including a first motor and a second motor, after the vehicle is powered on, the first motor is the main drive motor by default, and the second auxiliary drive motor is the auxiliary motor by default, if any of the following conditions are met, the main drive motor and the auxiliary drive motor are switched, if not met, the first motor is kept as the main drive motor and the second motor is kept as the auxiliary drive motor; (1) The time integral value of the actual torque of the first motor minus the time integral value of the actual torque of the second motor is greater than or equal to A; (2) The actual temperature of the first motor minus the actual temperature of the second motor is greater than or equal to t1; (3) The actual temperature of the first motor controller minus the actual temperature of the second motor controller is greater than or equal to t2; (4) The maximum available torque of the second motor minus the maximum available torque of the first motor is greater than or equal to T1; (5) The minimum available torque of the first motor minus the minimum available torque of the second motor is greater than or equal to T2.

3. The motor torque control method of a dual-motor electric vehicle according to claim 2, characterized in that In step S200, it is stipulated that the whole vehicle is powered on and off as a driving cycle, and the main drive motor and the auxiliary drive motor are set when the whole vehicle is powered on, and the main drive motor and the auxiliary drive motor are not switched within the driving cycle.

4. The motor torque control method of a dual-motor electric vehicle according to claim 2 is characterized in that: A=638400N·min, t1=60℃, t2=50℃, T1=500Nm, T2=500Nm.

5. The motor torque control method of a dual-motor electric vehicle according to claim 1, characterized in that The torque distribution of the main drive motor and the auxiliary drive motor in step S300 includes the following steps: Step S310: The motor-side required torque is preferentially allocated to the main drive motor. When the main drive motor allocated torque reaches a set limit, the remaining torque is allocated to the auxiliary drive motor. Step S320: setting 0 torque, the economic lower limit of the main drive motor torque, the economic upper limit of the main drive motor torque and the maximum torque of the main drive motor for the main drive motor; setting 0 torque, the economic lower limit of the auxiliary drive motor torque, the economic upper limit of the auxiliary drive motor torque and the maximum torque of the auxiliary drive motor for the auxiliary drive motor; Step S330: Torque loading, first loading the main drive motor with torque, then loading the auxiliary drive motor, and alternately loading the torque in sequence until the main drive motor is loaded to the maximum torque of the main drive motor and the auxiliary drive motor is loaded to the maximum torque of the auxiliary drive motor, and the torque loading is completed; Step S340: Torque unloading, first unloading the torque of the auxiliary drive motor, then unloading the torque of the main drive motor, and unloading the torque alternately in sequence until both the main drive motor and the auxiliary drive motor are unloaded to 0 torque, and the torque unloading is completed.

6. The motor torque control method of a dual-motor electric vehicle according to claim 5, characterized in that The torque loading steps in step S330 are as follows: S331, load the main drive motor torque until the main drive motor torque is loaded to the economic upper limit of the main drive motor torque; S332, when the main drive motor torque is loaded to the economic upper limit of the main drive motor torque, switch the auxiliary drive motor loading torque; S333, when the auxiliary drive motor torque is loaded to the economic upper limit of the auxiliary drive motor torque, switch the main drive motor loading torque; S334, when the main drive motor loading torque reaches the maximum torque of the main drive motor, switch the auxiliary drive motor loading torque; S335, alternately load the torque in sequence until the main drive motor is loaded to the maximum torque of the main drive motor and the auxiliary drive motor is loaded to the maximum torque of the auxiliary drive motor, and the torque loading is completed.

7. The motor torque control method of a dual-motor electric vehicle according to claim 5, characterized in that The torque unloading steps in step S340 are as follows: S341, unloading the torque of the auxiliary drive motor until the torque of the auxiliary drive motor is unloaded to the economic upper limit of the torque of the auxiliary drive motor; S342, when the torque of the auxiliary drive motor is unloaded to the torque economic upper limit, switching to the unloading torque of the main drive motor; S343, when the torque of the main drive motor is unloaded to the economic upper limit of the torque of the main drive motor, switching to the unloading torque of the auxiliary drive motor; S344, when the unloading torque of the auxiliary drive motor is to the economic lower limit of the torque of the auxiliary drive motor, switching to the unloading torque of the main drive motor; S345, when the unloading torque of the main drive motor is to the economic lower limit of the torque of the main drive motor, switching to the unloading torque of the auxiliary drive motor; S346, when the unloading torque of the auxiliary drive motor is to 0 torque, switching to the unloading torque of the main drive motor; S347, unloading the torque alternately in sequence until both the main drive motor and the auxiliary drive motor are unloaded to 0 torque, and the torque unloading is completed.

8. The motor torque control method of a dual-motor electric vehicle according to claim 1, characterized in that It also includes a method for handling abnormal situations: if the maximum allowable torque of the motor is limited due to a motor failure, and the maximum allowable torque of the motor is less than a preset upper limit or lower limit of the motor torque, if the maximum allowable torque of the motor is limited before the motor torque is loaded, then the process goes to step S510; if the maximum allowable torque of the motor is limited after the motor torque is loaded, then the process goes to step S520; if the maximum allowable torque of the limited motor is restored, then the process goes to step S530; Step S510: according to the alternating loading sequence of step S330, after loading the restricted motor to the maximum allowable torque, stop loading the restricted motor and switch to another motor for loading until the maximum allowable torque of the restricted motor is reached, and the torque loading is terminated; Step S520: adjusting the torque of the limited motor to the maximum allowable torque after limitation, and loading the reduced torque to another motor, so that the torque loaded on the other motor does not exceed the capacity of the limited motor; Step S530: Carry out the loading sequence according to step S330.

9. The motor torque control method of a dual-motor electric vehicle according to claim 5, characterized in that Step S320: the economic lower limit of the main drive motor torque is 500Nm, and the economic upper limit of the main drive motor torque is 1000Nm; the economic lower limit of the auxiliary drive motor torque is 500Nm, and the economic upper limit of the auxiliary drive motor torque is 1000Nm.

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