A distributed electric truck torque distribution method

Abstract

The present invention provides a distributed electric truck torque distribution method, which belongs to the field of new energy commercial vehicle control technology. Specifically, it includes: judging based on the current vehicle speed, accelerator pedal opening and its change rate, if the vehicle speed is less than a threshold value or the accelerator pedal opening and its change rate is greater than a threshold value, adopting a dynamic torque distribution control method to adjust the output torque of the middle shaft and the rear shaft; conversely, adopting an economic torque distribution control method to adjust the output torque of the middle shaft and the rear shaft. Finally, it is judged whether the motor speed of the rear axle integrated shift electric drive bridge is within the set shift point speed range. If the motor speed is not within the set shift point speed range, the original torque distribution control method is maintained. If the motor speed is within the set shift point speed range, the shift torque distribution control method is adopted to ensure that when the motor speed of the integrated shift electric drive bridge reaches the shift speed point, the rear axle output torque is zero or the middle shaft output torque reaches the maximum, thereby shortening the shift time and achieving a shift process without power interruption.

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] Amidst the booming electrification revolution in the truck industry, major automakers are also focusing on the research and development of truck powertrain control systems. As research into integrated shifting electric axles and distributed drive technologies for new energy trucks continues to deepen, powertrain configurations combining these two technologies are also gaining increasing attention.

[0003] Currently, several methods for distributing torque for dual electric axles have emerged, such as Chinese patent application CN 118182101A, which discloses a torque distribution system and method for dual electric axles in a vehicle. The method includes obtaining a requested torque from a vehicle controller and determining whether the requested torque should be distributed between a first electric axle and a second electric axle in the dual electric axle. This patent primarily addresses increasing the efficiency of dual electric axle vehicles and reducing energy consumption while rationally allocating the active and inactive phases between the two axles to extend their service life. However, it fails to consider shift torque distribution control during driving, resulting in limited improvements to vehicle performance.

[0004] The Chinese patent application with publication number CN 116587880A discloses a dual-bridge electric drive bridge cooperative control method, a dual-bridge electric drive bridge, and a vehicle. The patent first determines the torque distribution scheme. If a dual-bridge drive mode is adopted, the optimal dual-bridge electric drive bridge torque distribution ratio is determined based on 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. The patent first reduces the torque when the shift speed point is reached, and then shifts 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 insufficient. Summary of the Invention

[0005] The present invention provides a distributed electric truck torque distribution method to address 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 solutions:

[0007] A distributed torque distribution method for an electric truck, 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, is disclosed. The specific method is as follows:

[0008] S1. Determine the current speed of the electric truck, the accelerator pedal opening, and its rate of change. If the speed is less than a threshold or the accelerator pedal opening and its rate of change are greater than a threshold, prioritize 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 based on the driver's required torque and the maximum torque allowed to be output by the central axle and rear axle;

[0009] S2. If the speed of the electric truck exceeds a threshold and the accelerator pedal opening and its rate of change are less than a threshold, an economic torque distribution control method is used. Based on 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 axis distributed electric drive axle based on the current vehicle speed. middle_high The maximum torque T that the rear axle integrated shift electric drive bridge allows to output rear_high , and compare to get the maximum and minimum values ​​of the two, and then compare them with the total required driving torque T req Compare and then get the required torque T of the middle shaft 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: Where, ΔT middle_high is the maximum torque increase allowed by the central shaft distributed electric drive axle, ΔT rear_high T is the maximum torque increase allowed by the rear axle integrated shift electric drive axle. middle is the actual torque of the central axis distributed electric drive bridge 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 to be output by the middle and rear axles at the current vehicle speed. If the maximum torque allowed to be output by the distributed electric drive axle of the middle axle is less than the maximum torque allowed to be output 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 as follows:

[0018]

[0019] Where, ΔT increase is the calibrated increase in inter-axle torque, ΔT decrease is the calibrated inter-axis 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 set the same gear, speed ratio, required torque and vehicle speed, and then calculate the total power of the electric drive system with different distribution ratio coefficients and compare them. On the premise of meeting the required torque, select the distribution ratio coefficient with the smallest total power of the electric drive system and save it, and finally make it 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 bridge 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, based on the required torque, the 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 axles is calculated and expressed as: Where, ΔT rear is the torque variation of the rear axle integrated shift electric drive axle, Δt0 is the calibrated inter-axle torque variation adjustment time, and Δt is the inter-axle torque variation adjustment time calculated based on the speed difference; the required torques of the middle axle and the rear axle are:

[0024] S33, if the maximum torque allowed to be output by the central axis distributed electric drive bridge 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 its maximum when the rear axle motor speed reaches the shift speed point. Therefore, based on the required torque, the 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 variation between the axes (ΔT) is calculated and expressed as: The required torques of the middle axle and 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 shifting, speed adjustment and shifting operations. At this time, the required torques of the center axle and the rear axle are:

[0026] S35. When the rear axle integrated shift electric drive axle shift operation is completed, the optimal distribution ratio coefficient k is obtained by querying the distribution 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 as follows:

[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 present invention provides a torque distribution control method for the gear shifting process. By reducing the output torque of the rear axle integrated gear-shifting electric drive axle in advance and superimposing the reduced output torque on the central axle distributed electric drive axle, the sum of the output torques of the dual electric drive axles is ensured to be consistent with the total required torque. At the same time, combined with a torque control method based on speed difference, the rear axle output torque is ensured to be zero or the central axle output torque is maximized when the motor speed of the rear axle integrated gear-shifting electric drive axle reaches the gear shifting speed point, thereby shortening the gear shifting time and achieving no power interruption during the gear shifting process, thereby improving power performance and smoothness.

[0029] 2. The present invention fully considers the impact of the efficiency of each electric drive system on energy consumption and economy. The optimal distribution ratio coefficient MAP is established offline based on vehicle speed, gear position, total required torque, and the efficiency curves of each electric drive system. The optimal distribution ratio coefficient is obtained by querying the 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 This is a flow chart of the calculation of the distribution ratio coefficient based on the optimal driving efficiency of the present invention.

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

[0033] The following describes specific embodiments of the present invention with reference to the accompanying drawings. Numerous details are provided below to provide a comprehensive understanding of the present invention, but those skilled in the art will appreciate that the present invention can be practiced without these details. Well-known components, methods, and processes are not described in detail below.

[0034] This embodiment provides a distributed drive electric truck torque distribution method, which is mainly for 6x4 new energy electric trucks, whose second and third axles are drive axles, namely the central axle distributed electric drive axle and the 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 rate of change. If the speed is less than a threshold or the accelerator pedal opening and its rate of change 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 based on the driver's required torque and the maximum torque allowed to be output by the central axle and rear axle.

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

[0037] S11. Calculate the maximum torque T allowed to be output by the central axis distributed electric drive axle based on the current vehicle speed. middle_high The maximum torque T that the rear axle integrated shift electric drive bridge allows to output rear_high , and compare to get the maximum and minimum values ​​of the two, and then compare them with the total required driving torque T req Compare and then get the required torque T of the middle shaft 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: Where, ΔT middle_high is the maximum torque increase allowed by the central shaft distributed electric drive axle, ΔT rear_high T is the maximum torque increase allowed by the rear axle integrated shift electric drive axle. middle is the actual torque of the central axis distributed electric drive bridge 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 to be output by the middle and rear axles at the current vehicle speed. If the maximum torque allowed to be output by the distributed electric drive axle of the middle axle is less than the maximum torque allowed to be output 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] Second, if the speed of the electric truck exceeds a threshold and the accelerator pedal opening and its rate of change are less than a threshold, an economic torque distribution control method is used. Based on 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 center and rear axles in real time. Specifically, it includes: according to the current gear position of the rear axle integrated shift electric drive axle, vehicle speed and required torque, 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 as follows:

[0044]

[0045] Where, ΔT increase is the calibrated increase in inter-axle torque, ΔT decrease is the calibrated inter-axis 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 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, the electric drive system efficiency curve 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 under 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 and rear axles; select the torque distribution ratio coefficients of the middle and rear axles from (0-100%), and calculate the total input power of the middle and rear axle electric drive systems according to the efficiency of the middle and rear axle electric drive systems and the distribution ratio coefficients; 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 and rear axle electric drive systems.

[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 three 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 bridge 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, based on the required torque, the 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 axles is calculated and expressed as: Where, ΔT rear is the torque variation of the rear axle integrated shift electric drive axle, Δt0 is the calibrated inter-axle torque variation adjustment time, and Δt is the inter-axle torque variation adjustment time calculated based on the speed difference; the required torques of the middle axle and the rear axle are:

[0051] S33, if the maximum torque allowed to be output by the central axis distributed electric drive bridge 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 its maximum when the rear axle motor speed reaches the shift speed point. Therefore, based on the required torque, the 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 variation between the axes (ΔT) is calculated and expressed as: The required torques of the middle axle and 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 shifting, speed adjustment and shifting operations. At this time, the required torques of the center axle and the rear axle are:

[0053] S35. When the rear axle integrated shift electric drive axle shift operation is completed, the optimal distribution ratio coefficient k is obtained by querying the distribution 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 as follows:

[0054] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited to this. 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: Step S1: Determine the current speed of the electric truck, the accelerator pedal opening, and its rate of change. If the speed is less than a threshold or the accelerator pedal opening and its rate of change are greater than a threshold, prioritize 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 based on the driver's required torque and the maximum torque allowed to be output by the central axle and rear axle; Step S2: If the speed of the electric truck exceeds the threshold and the accelerator pedal opening and its rate of change are less than the threshold, an economic torque distribution control method is used. 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; Step 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 bridge in advance, and superimpose the reduced output torque on the central axle distributed electric drive bridge, so that the sum of the output torques of the dual electric drive bridges is consistent with the total required torque.

2. A distributed electric truck torque distribution method according to 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 axis distributed electric drive axle based on the current vehicle speed. middle_high The maximum torque T that the rear axle integrated shift electric drive bridge allows to output rear_high , and compare to get the maximum and minimum values ​​of the two, and then compare them with the total required driving torque T req Compare and then get the required torque T of the middle shaft 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: Where, ΔT middle_high is the maximum torque increase allowed by the central shaft distributed electric drive axle, ΔT rear_high T is the maximum torque increase allowed by the rear axle integrated shift electric drive axle. middle is the actual torque of the central axis distributed electric drive bridge 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 to be output by the middle and rear axles at the current vehicle speed. If the maximum torque allowed to be output by the distributed electric drive axle of the middle axle is less than the maximum torque allowed to be output 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 according to claim 2, characterized in that: 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 as follows: Where, ΔT increase is the calibrated increase in inter-axle torque, ΔT decrease is the calibrated inter-axis 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. The distributed electric truck torque distribution method according to 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 specific 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 according to 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 bridge 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, based on the required torque, the 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 axles is calculated and expressed as: Where, ΔT rear is the torque variation of the rear axle integrated shift electric drive axle, Δt0 is the calibrated inter-axle torque variation adjustment time, and Δt is the inter-axle torque variation adjustment time calculated based on the speed difference; the required torques of the middle axle and the rear axle are: S33, if the maximum torque allowed to be output by the central axis distributed electric drive bridge 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 its maximum when the rear axle motor speed reaches the shift speed point. Therefore, based on the required torque, the 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 variation between the axes (ΔT) is calculated and expressed as: The required torques of the middle axle and 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 shifting, speed adjustment and shifting operations. At this time, the required torques of the center axle and the rear axle are: S35. When the rear axle integrated shift electric drive axle shift operation is completed, the optimal distribution ratio coefficient k is obtained by querying the distribution 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 as follows:

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