Distributed electric truck torque distribution method

Abstract

The invention provides a distributed electric truck torque distribution method, and belongs to the technical field of new energy commercial vehicle control. The method specifically comprises the steps that according to the current vehicle speed, the accelerator pedal opening degree and the change rate of the accelerator pedal opening degree, if the vehicle speed is smaller than a threshold value or the accelerator pedal opening degree and the change rate of the accelerator pedal opening degree are larger than the threshold value, a dynamic torque distribution control method is adopted for adjusting output torque of a middle shaft and a rear shaft; otherwise, the output torque of the middle shaft and the output torque of the rear shaft are adjusted through an economical torque distribution control method. And finally, judging whether the motor rotating speed of the rear axle integrated gear-shifting electric drive axle is within the set gear-shifting point rotating speed range or not, if the motor rotating speed is not within the set gear-shifting point rotating speed range, keeping an original torque distribution control method, and if the motor rotating speed is within the set gear-shifting point rotating speed range, adopting a gear-shifting torque distribution control method, it is ensured that when the rotating speed of the motor of the integrated gear-shifting electric drive axle reaches the gear-shifting rotating speed point, the output torque of the rear axle is zero or the output torque of the middle axle reaches the maximum, the gear-shifting time is shortened, and no power interruption exists in the gear-shifting process.

Description

Technical Field

[0001] The present invention relates to the field of new energy commercial vehicle control technology, and more specifically to a distributed electric truck torque distribution method. Background Art

[0002] Under the background of the vigorous development of electrification innovation in the truck industry, major automakers have also begun to focus on the research and development of truck power control systems. With the continuous deepening of research on integrated shift electric drive axles and distributed drive related technologies for new energy trucks, the power system configuration combining integrated shift electric drive axles and distributed electric drive axles is gradually gaining attention.

[0003] At present, there are some torque distribution methods for dual electric drive axles, such as the Chinese patent application with publication number CN 118182101A, which discloses a torque distribution system and method for dual electric drive axles of a vehicle, wherein the torque distribution method includes obtaining the requested torque by the vehicle controller of the vehicle; and judging whether the requested torque should be distributed between the first electric drive axle and the second electric drive axle in the dual electric drive axle. This patent mainly increases the working efficiency of the dual electric drive axle vehicle and reduces energy consumption while reasonably allocating the use and deactivation stages between the two electric drive axles to increase the service life of the electric drive axle, but does not consider the shift torque distribution control during driving, and has little effect on improving vehicle performance.

[0004] The Chinese patent application with publication number CN 116587880A discloses a dual-bridge electric drive bridge collaborative control method, a dual-bridge electric drive bridge and a vehicle. The patent first determines the torque distribution scheme. If the dual-bridge drive mode is adopted, the optimal dual-bridge electric drive bridge torque distribution ratio is determined according to the correspondence between the vehicle speed and the driver's required driving torque and the optimal dual-bridge electric drive bridge torque distribution ratio coefficient. At the same time, a shifting strategy is designed. When the vehicle meets the shifting conditions, a certain bridge is shifted first, and the vehicle driving torque remains unchanged during the shifting process. After completion, the other bridge is switched. This patent is to reduce the torque first when the shift speed point is reached, and then shift when the torque is zero. The total shifting time of this shifting method is relatively long, and the improvement of vehicle power and smoothness is not enough. Summary of the invention

[0005] The present invention provides a distributed electric truck torque distribution method to solve the shortcomings of the existing dual electric drive axle gear shift torque distribution, such as a long total gear shift time and insufficient improvement in vehicle power and smoothness.

[0006] The present invention adopts the following technical solution:

[0007] A distributed electric truck torque distribution method, wherein the second and third axles of the electric truck are both drive axles, namely a central axle distributed electric drive axle and a rear axle integrated shift electric drive axle, and the specific method is as follows:

[0008] S1. Determine the current speed of the electric truck, the accelerator pedal opening and its change rate. If the speed is less than a threshold or the accelerator pedal opening and its change rate are greater than a threshold, give priority to meeting the driver's power demand, and adopt a dynamic torque distribution control method to adjust the output torque of the central axle distributed electric drive axle and the rear axle integrated shift electric drive axle according to the driver's required torque and the maximum torque allowed to be output by the central axle and the rear axle;

[0009] S2. If the speed of the electric truck exceeds the threshold and the accelerator pedal opening and its change rate are less than the threshold, the economic torque distribution control method is adopted. According to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive axle, the distribution ratio coefficient MAP with the best driving efficiency is queried to obtain the optimal distribution ratio coefficient, and the output torque of the rear axle integrated shift electric drive axle and the central axle distributed electric drive axle is adjusted in real time;

[0010] S3. Determine whether the motor speed of the rear axle is within the shift point speed range. If the motor speed is not within the set shift point speed range, maintain the original torque distribution control method; if the motor speed is within the set shift point speed range, adopt the shift torque distribution control method to reduce the output torque of the rear axle integrated shift electric drive axle in advance, and superimpose the reduced output torque on the central axle distributed electric drive axle, so that the sum of the output torques of the dual electric drive axles is consistent with the total required torque.

[0011] The dynamic torque distribution control method in step S1 specifically includes:

[0012] S11. Calculate the maximum torque T allowed to be output by the central axle distributed electric drive axle according to the current vehicle speed. middle_high The maximum torque T that the integrated shift electric drive axle of the rear axle allows to output rear_high , and compare the maximum and minimum values ​​of the two, and then compare them with the total required driving torque T req By comparison, the required torque T of the middle shaft is obtained. middle_req and the required torque T of the rear axle rear_req ;

[0013] S12: If half of the total required driving torque exceeds the maximum of the two, that is, 0.5*T req >max(T middle_high , T rear_high ), the required torque of the middle axle and the required torque of the rear axle are: In the formula, ΔT middle_high is the maximum torque increase allowed by the central shaft distributed electric drive axle, ΔT rear_high is the maximum torque increase allowed by the rear axle integrated shift electric drive axle, T middle is the actual torque of the central axis distributed electric drive axle at the current moment, T rearis the actual torque of the rear axle integrated shift electric drive axle at the current moment;

[0014] S13. If half of the required driving torque is between the maximum and minimum values, that is, min(T middle_high , T rear_high )≤0.5*T req ≤max(T middle_high , T rear_high ), then compare the maximum torques allowed by the middle and rear axles at the current vehicle speed. If the maximum torque allowed by the distributed electric drive axle of the middle axle is less than the maximum torque allowed by the integrated shifting electric drive axle of the rear axle, that is, T middle_high ≤T rear_high , then the required torque of the middle axle and the required torque of the rear axle are:

[0015] S14. If the maximum torque allowed to be output by the central axle distributed electric drive axle is greater than the maximum torque allowed to be output by the rear axle integrated shift electric drive axle, that is, T middle_high >T rear_high , then the required torque of the middle axle and the required torque of the rear axle are:

[0016] S15. If half of the required driving torque is less than the minimum of the two, that is, 0.5*Teq<min(T middle_high , T rear_high ), the required torque of the middle axle and the required torque of the rear axle are:

[0017] The economic torque distribution control method in step S2 is as follows: according to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive bridge, the optimal distribution ratio coefficient k is obtained by querying the distribution ratio coefficient MAP based on the optimal driving efficiency. opt , and then the required torques of the middle and rear axles are obtained, which are:

[0018]

[0019] In the formula, ΔT increase is the calibrated increase in inter-axle torque, ΔT decrease is the calibrated shaft torque reduction, ΔT middle_low is the maximum torque reduction allowed by the central shaft distributed electric drive axle, ΔT rear_low The maximum torque reduction allowed by the rear axle integrated shift electric drive axle.

[0020] The above-mentioned distribution ratio coefficient MAP based on optimal driving efficiency is obtained by offline calculation based on the speed ratio of different gears of the rear axle integrated shift electric drive axle, the required torque, the vehicle speed, and the electric drive system efficiency curves of the rear axle integrated shift electric drive axle and the central axle distributed electric drive axle. The details are as follows: first, the same gear, speed ratio, required torque and vehicle speed are set, and then the total power of the electric drive system with different distribution ratio coefficients is calculated and compared. On the premise of meeting the required torque, the distribution ratio coefficient with the smallest total power of the electric drive system is selected and saved, and finally it is made into the distribution ratio coefficient MAP.

[0021] The shift torque distribution control method in step S3 specifically includes:

[0022] S31, calculating the shift speed point n of the rear axle integrated shift electric drive axle according to the accelerator pedal opening and the current vehicle speed gear , determine the motor speed n of the rear axle integrated shift electric drive bridge center Is it within the gear shift speed range? Calculate the difference between the current speed and the optimal gear shift speed point Δn=n gear -n center Whether it exceeds the threshold Δn thresold If it exceeds the threshold, the original torque distribution control method is maintained; if it is less than the threshold, the maximum torque allowed to be output by the central axis distributed electric drive axle is compared with the required torque;

[0023] S32, if the maximum torque allowed to be output by the central axis distributed electric drive axle exceeds the required torque, that is, T req ≤T middle_high , it is necessary to ensure that the output torque of the rear axle has dropped to zero when the rear axle motor speed reaches the shift speed point. Therefore, according to the required torque, speed difference, and the actual output torque of the rear axle integrated shift electric drive axle at the current moment, the torque change ΔT between the axes is calculated, which is expressed as: In the formula, ΔT rear is the torque change of the rear axle integrated shift electric drive axle, Δt0 is the calibrated inter-axle torque change adjustment time, and Δt is the inter-axle torque change adjustment time calculated according to the speed difference; the required torque of the middle axle and the required torque of the rear axle are:

[0024] S33, if the maximum torque allowed by the central axis distributed electric drive axle is less than the required torque, that is, T req >T middle_high , it is necessary to ensure that the output torque of the middle shaft has reached the maximum when the rear axle motor speed reaches the shift speed point. Therefore, according to the required torque, speed difference, the actual output torque of the middle shaft distributed electric drive axle at the current moment and the maximum torque allowed to be output by the middle shaft, the torque change between the shafts (ΔT) is calculated and expressed as: The required torque of the middle axle and the required torque of the rear axle are:

[0025] S34, when the motor speed of the rear axle integrated shift electric drive axle reaches the shift speed point, the rear axle integrated shift electric drive axle directly performs the gear shifting, speed adjustment and gear shifting operations. At this time, the required torques of the middle axle and the rear axle are respectively:

[0026] S35. When the rear axle integrated shift electric drive axle shift operation is completed, the optimal allocation ratio coefficient k is obtained by querying the allocation ratio coefficient MAP based on the optimal driving efficiency according to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive axle. opt , and then the required torques of the middle and rear axles are obtained, which are:

[0027] It can be seen from the above description of the present invention that, compared with the prior art, the present invention has the following advantages:

[0028] 1. The torque distribution control method of the present invention is aimed at the gear shifting process. By reducing the output torque of the rear axle integrated gear shifting electric drive bridge in advance and superimposing the reduced output torque on the middle axle distributed electric drive bridge, the sum of the output torques of the dual electric drive bridges is ensured to be consistent with the total required torque. At the same time, the torque control method based on the speed difference is combined to ensure that when the motor speed of the rear axle integrated gear shifting electric drive bridge reaches the gear shifting speed point, the rear axle output torque is zero or the middle axle output torque reaches the maximum, thereby shortening the gear shifting time and achieving no power interruption during the gear shifting process, thereby improving power and smoothness.

[0029] 2. The present invention fully considers the impact of the efficiency of each electric drive system on energy consumption and economy, and establishes the optimal allocation ratio coefficient MAP offline according to the vehicle speed, gear, total required torque and the efficiency curve of each electric drive system. The optimal allocation ratio coefficient is obtained by querying MAP. At the same time, the torque slope change is considered in the torque distribution process to improve smoothness and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a torque distribution control flow chart of the present invention.

[0031] Figure 2 The figure is a flow chart of calculating the distribution ratio coefficient based on the optimal driving efficiency of the present invention.

[0032] Figure 3 This is a shift torque distribution control flow chart of the present invention. DETAILED DESCRIPTION

[0033] The specific implementation of the present invention is described below with reference to the accompanying drawings. In order to fully understand the present invention, many details are described below, but for those skilled in the art, the present invention can be implemented without these details. For well-known components, methods and processes, they are not described in detail below.

[0034] The embodiment provides a torque distribution method for a distributed drive electric truck, which is mainly for a 6x4 new energy electric truck, whose second and third axles are drive axles, namely a central axle distributed electric drive axle and a rear axle integrated shift electric drive axle. The specific method is as follows:

[0035] 1. Determine the current speed of the electric truck, the accelerator pedal opening and its change rate. If the speed is less than the threshold or the accelerator pedal opening and its change rate are greater than the threshold, the driver's power demand is met first, and a dynamic torque distribution control method is adopted to adjust the output torque of the central axle distributed electric drive axle and the rear axle integrated shift electric drive axle according to the driver's required torque and the maximum torque allowed to be output by the central axle and the rear axle.

[0036] The dynamic torque distribution control in the above step 1 is to meet the driver's power demand as the control target, and adjust the driving torque of the middle axle and the rear axle in real time. Specifically, it includes:

[0037] S11. Calculate the maximum torque T allowed to be output by the central axle distributed electric drive axle according to the current vehicle speed. middle_high The maximum torque T that the integrated shift electric drive axle of the rear axle allows to output rear_high , and compare the maximum and minimum values ​​of the two, and then compare them with the total required driving torque T req By comparison, the required torque T of the middle shaft is obtained. middle_req and the required torque T of the rear axle rear_req ;

[0038] S12: If half of the total required driving torque exceeds the maximum of the two, that is, 0.5*T req >max(T middle_high , T rear_high ), the required torque of the middle axle and the required torque of the rear axle are: In the formula, ΔT middle_high is the maximum torque increase allowed by the central shaft distributed electric drive axle, ΔT rear_high is the maximum torque increase allowed by the rear axle integrated shift electric drive axle, T middle is the actual torque of the central axis distributed electric drive axle at the current moment, T rear is the actual torque of the rear axle integrated shift electric drive axle at the current moment;

[0039] S13. If half of the required driving torque is between the maximum and minimum values, that is, min(T middle_high , Trear_high )≤0.5*T req ≤max(T middle_high , T rear_high ), then compare the maximum torques allowed by the middle and rear axles at the current vehicle speed. If the maximum torque allowed by the distributed electric drive axle of the middle axle is less than the maximum torque allowed by the integrated shifting electric drive axle of the rear axle, that is, T middle_high ≤T rear_high , then the required torque of the middle axle and the required torque of the rear axle are:

[0040] S14. If the maximum torque allowed to be output by the central axle distributed electric drive axle is greater than the maximum torque allowed to be output by the rear axle integrated shift electric drive axle, that is, T middle_high >T rear_high , then the required torque of the middle axle and the required torque of the rear axle are:

[0041] S15. If half of the required driving torque is less than the minimum of the two, that is, 0.5*Teq<min(T middle_high , T rear_high ), the required torque of the middle axle and the required torque of the rear axle are:

[0042] 2. If the speed of the electric truck exceeds the threshold and the accelerator pedal opening and its change rate are less than the threshold, the economic torque distribution control method is adopted. According to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive axle, the distribution ratio coefficient MAP with the best driving efficiency is queried to obtain the optimal distribution ratio coefficient, and the output torque of the rear axle integrated shift electric drive axle and the central axle distributed electric drive axle is adjusted in real time;

[0043] The economic torque distribution control in step 2 takes the optimal motor drive efficiency as the control target and adjusts the drive torque of the middle and rear axles in real time. Specifically, it includes: according to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive axle, the optimal distribution ratio coefficient k is obtained by querying the distribution ratio coefficient MAP based on the optimal drive efficiency. opt , and then the required torques of the middle and rear axles are obtained, which are:

[0044]

[0045] In the formula, ΔT increase is the calibrated increase in inter-axle torque, ΔT decrease is the calibrated shaft torque reduction, ΔT middle_low is the maximum torque reduction allowed by the central shaft distributed electric drive axle, ΔT rear_low The maximum torque reduction allowed by the rear axle integrated shift electric drive axle.

[0046] The above distribution ratio coefficient MAP based on the optimal driving efficiency is calculated offline based on the speed ratio of different gears of the rear axle integrated shift electric drive axle, the required torque, the vehicle speed, and the electric drive system efficiency curves of the rear axle integrated shift electric drive axle and the central axle distributed electric drive axle. Specifically, it includes: first setting the same gear, speed ratio, required torque and vehicle speed, then calculating the total power of the electric drive system with different distribution ratio coefficients and comparing them, and on the premise of meeting the required torque, selecting the distribution ratio coefficient with the smallest total power of the electric drive system and saving it, and finally making it into the distribution ratio coefficient MAP. Figure 2 The specific calculation process of the distribution ratio coefficient MAP based on the optimal driving efficiency is as follows: determine the required torque, vehicle speed, gear position and speed ratio of the middle axle and rear axle; select the torque distribution ratio coefficient of the middle axle and rear axle from (0-100%), and calculate the total input power of the middle axle and rear axle electric drive system according to the efficiency of the middle axle and rear axle electric drive system and the distribution ratio coefficient; compare the total input power with the original value, if it is less than the original value, update the original value and record the distribution ratio system; if it is greater than the original value, keep the original value and do not record the distribution ratio coefficient; after all the distribution ratio coefficients are compared, save the distribution ratio system with the smallest total input power of the middle axle and rear axle electric drive system.

[0047] 3. Determine whether the motor speed of the rear axle is within the shift point speed range. If the motor speed is not within the set shift point speed range, maintain the original torque distribution control method; if the motor speed is within the set shift point speed range, adopt the shift torque distribution control method to reduce the output torque of the rear axle integrated shift electric drive axle in advance, and superimpose the reduced output torque on the central axle distributed electric drive axle, so that the sum of the output torques of the dual electric drive axles is consistent with the total required torque.

[0048] The shift torque distribution control method in step 3 above specifically includes:

[0049] S31, calculating the shift speed point n of the rear axle integrated shift electric drive axle according to the accelerator pedal opening and the current vehicle speed gear , determine the motor speed n of the rear axle integrated shift electric drive bridge center Is it within the gear shift speed range? Calculate the difference between the current speed and the optimal gear shift speed point Δn=n gear -n center Whether it exceeds the threshold Δn thresold If it exceeds the threshold, the original torque distribution control method is maintained; if it is less than the threshold, the maximum torque allowed to be output by the central axis distributed electric drive axle is compared with the required torque;

[0050] S32, if the maximum torque allowed to be output by the central axis distributed electric drive axle exceeds the required torque, that is, T req ≤T middle_high, it is necessary to ensure that the output torque of the rear axle has dropped to zero when the rear axle motor speed reaches the shift speed point. Therefore, according to the required torque, speed difference, and the actual output torque of the rear axle integrated shift electric drive axle at the current moment, the torque change ΔT between the axes is calculated, which is expressed as: In the formula, ΔT rear is the torque change of the rear axle integrated shift electric drive axle, Δt0 is the calibrated inter-axle torque change adjustment time, and Δt is the inter-axle torque change adjustment time calculated according to the speed difference; the required torque of the middle axle and the required torque of the rear axle are:

[0051] S33, if the maximum torque allowed by the central axis distributed electric drive axle is less than the required torque, that is, T req >T middle_high , it is necessary to ensure that the output torque of the middle shaft has reached the maximum when the rear axle motor speed reaches the shift speed point. Therefore, according to the required torque, speed difference, the actual output torque of the middle shaft distributed electric drive axle at the current moment and the maximum torque allowed to be output by the middle shaft, the torque change between the shafts (ΔT) is calculated and expressed as: The required torque of the middle axle and the required torque of the rear axle are:

[0052] S34, when the motor speed of the rear axle integrated shift electric drive axle reaches the shift speed point, the rear axle integrated shift electric drive axle directly performs the gear shifting, speed adjustment and gear shifting operations. At this time, the required torques of the middle axle and the rear axle are respectively:

[0053] S35. When the rear axle integrated shift electric drive axle shift operation is completed, the optimal allocation ratio coefficient k is obtained by querying the allocation ratio coefficient MAP based on the optimal driving efficiency according to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive axle. opt , and then the required torques of the middle and rear axles are obtained, which are:

[0054] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A distributed electric truck torque distribution method, wherein the second and third axles of the electric truck are both drive axles, namely the central axle distributed electric drive axle and the rear axle integrated shift electric drive axle, characterized in that: The specific method is as follows: S1. Determine the current speed of the electric truck, the accelerator pedal opening and its change rate. If the speed is less than a threshold or the accelerator pedal opening and its change rate are greater than a threshold, give priority to meeting the driver's power demand, and adopt a dynamic torque distribution control method to adjust the output torque of the central axle distributed electric drive axle and the rear axle integrated shift electric drive axle according to the driver's required torque and the maximum torque allowed to be output by the central axle and the rear axle; S2. If the speed of the electric truck exceeds the threshold and the accelerator pedal opening and its change rate are less than the threshold, the economic torque distribution control method is adopted. According to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive axle, the distribution ratio coefficient MAP with the best driving efficiency is queried to obtain the optimal distribution ratio coefficient, and the output torque of the rear axle integrated shift electric drive axle and the central axle distributed electric drive axle is adjusted in real time; S3. Determine whether the motor speed of the rear axle is within the shift point speed range. If the motor speed is not within the set shift point speed range, maintain the original torque distribution control method; if the motor speed is within the set shift point speed range, adopt the shift torque distribution control method to reduce the output torque of the rear axle integrated shift electric drive axle in advance, and superimpose the reduced output torque on the central axle distributed electric drive axle, so that the sum of the output torques of the dual electric drive axles is consistent with the total required torque.

2. A distributed electric truck torque distribution method as claimed in claim 1, characterized in that: The dynamic torque distribution control method in step S1 specifically includes: S11. Calculate the maximum torque T allowed to be output by the central axle distributed electric drive axle according to the current vehicle speed. middle_high The maximum torque T that the integrated shift electric drive axle of the rear axle allows to output rear_high , and compare the maximum and minimum values ​​of the two, and then compare them with the total required driving torque T req By comparison, the required torque T of the middle shaft is obtained. middle_req and the required torque T of the rear axle rear_req ; S12: If half of the total required driving torque exceeds the maximum of the two, that is, 0.5*T req >max(T middle_high , T rear_high ), the required torque of the middle axle and the required torque of the rear axle are: In the formula, ΔT middle_high is the maximum torque increase allowed by the central shaft distributed electric drive axle, ΔT rear_high is the maximum torque increase allowed by the rear axle integrated shift electric drive axle, T middle is the actual torque of the central axis distributed electric drive axle at the current moment, T rear is the actual torque of the rear axle integrated shift electric drive axle at the current moment; S13. If half of the required driving torque is between the maximum and minimum values, that is, min(T middle_high , T rear_high )≤0.5*T req ≤max(T middle_high , T rear_high ), then compare the maximum torques allowed by the middle and rear axles at the current vehicle speed. If the maximum torque allowed by the distributed electric drive axle of the middle axle is less than the maximum torque allowed by the integrated shifting electric drive axle of the rear axle, that is, T middle_high ≤T rear_high , then the required torque of the middle axle and the required torque of the rear axle are: S14. If the maximum torque allowed to be output by the central axle distributed electric drive axle is greater than the maximum torque allowed to be output by the rear axle integrated shift electric drive axle, that is, T middle_high ≥T rear_high , then the required torque of the middle axle and the required torque of the rear axle are: S15. If half of the required driving torque is less than the minimum of the two, that is, 0.5*Teq<min(T middle_high , T rear_high ), the required torque of the middle axle and the required torque of the rear axle are:

3. A distributed electric truck torque distribution method as claimed in claim 2, characterized in that: The economic torque distribution control method in step S2 is specifically as follows: according to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive bridge, the optimal distribution ratio coefficient k is obtained by querying the distribution ratio coefficient MAP based on the optimal driving efficiency. opt , and then the required torques of the middle and rear axles are obtained, which are: In the formula, ΔT increase is the calibrated increase in inter-axle torque, ΔT decrease is the calibrated shaft torque reduction, ΔT middle_low is the maximum torque reduction allowed by the central shaft distributed electric drive axle, ΔT rear_low The maximum torque reduction allowed by the rear axle integrated shift electric drive axle.

4. A distributed electric truck torque distribution method as claimed in claim 3, characterized in that: The distribution ratio coefficient MAP based on optimal driving efficiency is obtained by offline calculation based on the speed ratio of different gears of the rear axle integrated shift electric drive axle, the required torque, the vehicle speed, and the electric drive system efficiency curves of the rear axle integrated shift electric drive axle and the central axle distributed electric drive axle. The details are as follows: first, the same gear, speed ratio, required torque and vehicle speed are set, and then the total power of the electric drive system with different distribution ratio coefficients is calculated and compared. On the premise of meeting the required torque, the distribution ratio coefficient with the smallest total power of the electric drive system is selected and saved, and finally the distribution ratio coefficient MAP is made.

5. A distributed electric truck torque distribution method as claimed in claim 3, characterized in that: The shift torque distribution control method in step S3 specifically includes: S31, calculating the shift speed point n of the rear axle integrated shift electric drive axle according to the accelerator pedal opening and the current vehicle speed gear , determine the motor speed n of the rear axle integrated shift electric drive bridge center Is it within the gear shift speed range? Calculate the difference between the current speed and the optimal gear shift speed point Δn=n gear -n center Whether it exceeds the threshold Δn thresold If it exceeds the threshold, the original torque distribution control method is maintained; if it is less than the threshold, the maximum torque allowed to be output by the central axis distributed electric drive axle is compared with the required torque; S32, if the maximum torque allowed to be output by the central axis distributed electric drive axle exceeds the required torque, that is, T req ≤T middle_high , it is necessary to ensure that the output torque of the rear axle has dropped to zero when the rear axle motor speed reaches the shift speed point. Therefore, according to the required torque, speed difference, and the actual output torque of the rear axle integrated shift electric drive axle at the current moment, the torque change ΔT between the axes is calculated, which is expressed as: In the formula, ΔT rear is the torque change of the rear axle integrated shift electric drive axle, Δt0 is the calibrated inter-axle torque change adjustment time, and Δt is the inter-axle torque change adjustment time calculated according to the speed difference; the required torque of the middle axle and the required torque of the rear axle are: S33, if the maximum torque allowed by the central axis distributed electric drive axle is less than the required torque, that is, T req >T middle_high , it is necessary to ensure that the output torque of the middle shaft has reached the maximum when the rear axle motor speed reaches the shift speed point. Therefore, according to the required torque, speed difference, the actual output torque of the middle shaft distributed electric drive axle at the current moment and the maximum torque allowed to be output by the middle shaft, the torque change between the shafts (ΔT) is calculated and expressed as: The required torque of the middle axle and the required torque of the rear axle are: S34, when the motor speed of the rear axle integrated shift electric drive axle reaches the shift speed point, the rear axle integrated shift electric drive axle directly performs the gear shifting, speed adjustment and gear shifting operations. At this time, the required torques of the middle axle and the rear axle are respectively: S35. When the rear axle integrated shift electric drive axle shift operation is completed, the optimal allocation ratio coefficient k is obtained by querying the allocation ratio coefficient MAP based on the optimal driving efficiency according to the current gear position, vehicle speed and required torque of the rear axle integrated shift electric drive axle. opt , and then the required torques of the middle and rear axles are obtained, which are:

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