A method and apparatus for composite braking distribution of a multi-axle commercial vehicle

Abstract

The application discloses a kind of composite brake distribution method and device of multi-axle commercial vehicle.The method, dynamics analysis is carried out, and the whole vehicle demand brake torque and single axle demand brake torque are determined.According to driving behavior data, the required braking mode is determined.In the case of hydraulic braking, according to the single axle demand brake torque, the brake torque supplied by the hydraulic system to each axle is distributed.In the case of composite braking, according to the distribution characteristics of motor mechanical efficiency and battery charging efficiency, the maximum regenerative braking torque that the motor can provide is determined.According to the relative relationship between the maximum regenerative braking torque and the whole vehicle demand brake torque, the compensation brake torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined in the case of required braking mode being composite braking.According to the single axle demand brake torque, regenerative braking torque and compensation brake torque, the brake torque supplied by the hydraulic system and the motor to each axle is distributed.The scheme guarantees the safety of braking and improves the braking effect.

Description

Technical Field

[0001] The embodiments of the present invention relate to automotive control technology, and more particularly to a composite braking distribution method and device for a multi-axle commercial vehicle. Background Technology

[0002] The electrification trend of multi-axle commercial vehicles is obvious at present. The good dynamic characteristics of motors enable them to have driving capabilities as well as reverse braking and energy recovery functions, realizing the secondary use of energy and improving the vehicle's range.

[0003] Unlike the braking torque distribution in two-axle vehicles, multi-axle commercial vehicles currently primarily employ two methods to distribute braking torque: the equivalent dual-axle method and the adhesion coefficient graphical method. However, the equivalent dual-axle method addresses static braking load distribution and does not consider dynamic axle load transfer. The adhesion coefficient graphical method relies on expert experience and requires repeated testing and adjustments. Therefore, the braking performance of both methods is not ideal. Summary of the Invention

[0004] This invention provides a composite braking distribution method and device for multi-axle commercial vehicles to ensure braking safety and improve braking performance.

[0005] In a first aspect, embodiments of the present invention provide a composite braking distribution method for a multi-axle commercial vehicle, the composite braking distribution method for a multi-axle commercial vehicle comprising:

[0006] A dynamic analysis was conducted on the multi-axle commercial vehicle to determine the required braking torque for the entire vehicle and the required braking torque for each axle.

[0007] Based on the driving behavior data of the multi-axle commercial vehicle, the required braking mode is determined, wherein the braking mode includes hydraulic braking and compound braking;

[0008] When the required braking mode is hydraulic braking, the hydraulic system supplies braking torque to each shaft according to the single-axis braking torque requirement.

[0009] When the braking mode is compound braking, the maximum regenerative braking torque that the motor can provide is determined based on the distribution characteristics of the motor mechanical efficiency and battery charging efficiency.

[0010] Based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined when the required braking mode is compound braking.

[0011] Based on the single-axis braking torque requirement, the regenerative braking torque, and the compensating braking torque, the braking torque supplied to each axis by the hydraulic system and the motor is allocated.

[0012] Optionally, after distributing the braking torque supplied to each shaft by the hydraulic system and the motor respectively, the method further includes:

[0013] Based on the braking torque error and slip ratio error of the multi-axle commercial vehicle, the braking torque output of the motor is dynamically adjusted.

[0014] Optionally, based on the braking torque error and slip ratio error of the multi-axle commercial vehicle, the braking torque output of the motor is dynamically adjusted, including:

[0015] Based on the braking torque error and the slip ratio error, the torque adjustment coefficient of the motor is determined;

[0016] The braking torque variation rate of the motor is adjusted in real time according to the torque adjustment coefficient.

[0017] Based on the actual braking torque of the motor and the adjusted rate of change of the braking torque, the braking torque that the motor needs to provide at the next moment is determined.

[0018] Optionally, the real-time adjustment includes PID control.

[0019] Optionally, the driving behavior data includes the rate of change of pedal travel, the amount of change of pedal travel, and the current vehicle speed;

[0020] Based on the driving behavior data of the multi-axle commercial vehicle, the required braking mode is determined, including:

[0021] The braking conditions of the multi-axle commercial vehicle are determined based on the pedal travel change rate and the pedal travel change amount. The braking conditions include normal braking, emergency braking and short-term braking.

[0022] When the braking condition is emergency braking, the required braking mode for the multi-axle commercial vehicle is determined to be hydraulic braking.

[0023] When the braking condition is normal braking, the required braking mode for the multi-axle commercial vehicle is determined to be the compound braking.

[0024] When the braking condition is short-term braking, the required braking mode is determined based on the relative relationship between the current speed of the multi-axle commercial vehicle and the preset speed range.

[0025] Optionally, the braking conditions of the multi-axle commercial vehicle are determined based on the driving behavior data of the multi-axle commercial vehicle, including:

[0026] Based on the relative relationship between the pedal travel change rate and the preset change rate, it is determined whether the braking condition of the multi-axle commercial vehicle is emergency braking.

[0027] When the braking condition of the multi-axle commercial vehicle is not emergency braking, the relative relationship between the change in pedal travel and the preset change is used to determine whether the braking condition of the multi-axle commercial vehicle is normal braking.

[0028] When the braking condition of the multi-axle commercial vehicle is neither emergency braking nor normal braking, the braking condition of the multi-axle commercial vehicle is determined to be short-term braking.

[0029] Optionally, the driving behavior data includes the amount of pedal travel variation;

[0030] A dynamic analysis was performed on the multi-axle commercial vehicle to determine the overall vehicle braking torque requirement and the single-axle braking torque requirement, including:

[0031] Based on the pedal travel variation and the maximum braking intensity limit of the multi-axle commercial vehicle, the required braking intensity of the multi-axle commercial vehicle under different pedal travel variations is determined.

[0032] The required braking torque of the multi-axle commercial vehicle is determined based on the required braking intensity of the entire vehicle, the weight of the multi-axle commercial vehicle, and the wheel radius.

[0033] A multi-axle braking balance matrix of the multi-axle commercial vehicle is established with any axle of the multi-axle commercial vehicle as the center.

[0034] Based on the multi-axle braking balance matrix, and combined with the suspension stress conditions and suspension deformation coordination equations, the single-axle braking torque requirement of each axle on the multi-axle commercial vehicle is solved.

[0035] Optionally, the maximum regenerative braking torque that the motor can provide is determined based on the distribution characteristics of the motor's mechanical efficiency and the battery's charging efficiency, including:

[0036] Based on the external characteristic curve of the motor, the maximum torque of the motor is obtained according to the current speed of the motor;

[0037] Based on the distribution characteristics of the motor mechanical efficiency, determine the motor efficiency correction coefficient for the maximum torque;

[0038] Based on the distribution characteristics of the battery charging efficiency, determine the battery efficiency correction coefficient for the maximum torque;

[0039] The maximum regenerative braking torque that the motor can provide is calculated based on the product of the motor's maximum torque, the motor efficiency correction factor, and the battery efficiency correction factor.

[0040] Optionally, based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined when the required braking mode is compound braking, including:

[0041] If the required braking torque of the whole vehicle is less than or equal to the maximum regenerative braking torque, it is determined that the regenerative braking torque provided by the motor is equal to the required braking torque of the whole vehicle, and the compensating braking torque provided by the hydraulic system is equal to 0.

[0042] When the required braking torque of the vehicle is greater than the maximum regenerative braking torque, it is determined that the regenerative braking torque provided by the motor is equal to the maximum regenerative braking torque, and the compensating braking torque provided by the hydraulic system is equal to the difference between the required braking torque of the vehicle and the maximum regenerative braking torque.

[0043] Secondly, embodiments of the present invention also provide a composite braking distribution device for a multi-axle commercial vehicle, the composite braking distribution device for a multi-axle commercial vehicle including a braking mode determination module, a braking torque determination module, a maximum regenerative braking torque determination module, a dual braking torque determination module, and a dual braking torque distribution module;

[0044] The braking mode determination module is used to determine the required braking mode based on the driving behavior data of the multi-axle commercial vehicle, wherein the braking mode includes hydraulic braking and compound braking.

[0045] The braking torque determination module is used to perform dynamic analysis on the multi-axle commercial vehicle to determine the vehicle's overall braking torque requirement and the single-axle braking torque requirement.

[0046] The hydraulic braking torque distribution module is used to distribute the braking torque supplied by the hydraulic system to each shaft according to the single-shaft braking torque requirement when the required braking mode is hydraulic braking.

[0047] The maximum regenerative braking torque determination module is used to determine the maximum regenerative braking torque that the motor can provide based on the distribution characteristics of the motor mechanical efficiency and battery charging efficiency when the braking mode is compound braking.

[0048] The dual braking torque determination module is used to determine the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor when the required braking mode is compound braking, based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque.

[0049] The dual braking torque distribution module is used to distribute the braking torque supplied by the hydraulic system and the motor to each shaft according to the single-shaft braking torque requirement, the regenerative braking torque, and the compensating braking torque.

[0050] The present invention provides a composite braking distribution method and device for multi-axle commercial vehicles. Combining dynamic analysis, it determines the required braking torque for the entire vehicle and the required braking torque for each axle. Based on the driving behavior data of the multi-axle commercial vehicle, the required braking mode is determined. On one hand, when the required braking mode is hydraulic braking, the braking torque supplied to each axle by the hydraulic system is distributed according to the required braking torque for each axle. On the other hand, when the braking mode is composite braking, the maximum regenerative braking torque that the motor can provide is determined based on the distribution characteristics of the motor's mechanical efficiency and battery charging efficiency. Then, based on the relative relationship between the maximum regenerative braking torque and the required braking torque for the entire vehicle, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined. By distributing the braking torque supplied to each axle by the hydraulic system and the motor according to the required braking torque for each axle, based on the single-axle braking torque, the regenerative braking torque, and the compensating braking torque, the braking distribution of the multi-axle commercial vehicle is realized. Determining the braking mode according to driving behavior data allows the braking distribution to better meet user needs, ensuring braking safety and improving braking performance. In the combined braking mode, the braking torque provided by the motor is adjusted according to the distribution of motor mechanical efficiency and battery charging efficiency, so that the braking torque provided by the motor can ensure the power generation efficiency of the motor and the charging efficiency of the battery, thereby improving the energy recovery efficiency during braking. Attached Figure Description

[0051] Figure 1 A flowchart illustrating a composite braking distribution method for a multi-axle commercial vehicle provided in an embodiment of the present invention;

[0052] Figure 2 A schematic flowchart of another compound braking distribution method for a multi-axle commercial vehicle provided in an embodiment of the present invention;

[0053] Figure 3 A schematic flowchart of another compound braking distribution method for a multi-axle commercial vehicle provided in an embodiment of the present invention;

[0054] Figure 4 A schematic flowchart of a braking mode determination method provided in an embodiment of the present invention;

[0055] Figure 5 This is a schematic diagram illustrating the composition of a composite braking distribution device for a multi-axle commercial vehicle, as provided in an embodiment of the present invention. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0057] As described in the background section, multi-axle commercial vehicles currently primarily employ two methods for distributing braking torque: the equivalent dual-axle method and the adhesion coefficient graphical method. However, the equivalent dual-axle method addresses static braking load distribution and does not consider dynamic axle load transfer, leading to an unreasonable distribution of braking torque. The adhesion coefficient graphical method relies on expert experience, requires repeated testing and correction, and involves large amounts of data processing at a slow speed. Therefore, the braking performance of existing braking distribution methods is not ideal.

[0058] The inventors discovered that some existing technologies employ composite braking distribution schemes. For example, Chinese Patent Publication No. CN201410226728.6 proposes a composite braking system and method for electric vehicles. This method predicts future braking conditions using historical data. However, the uncertain composite braking model created by this method relies on prior data training and cannot be applied to complex and variable operating conditions, exhibiting poor generalization. Another example is Chinese Patent Publication No. CN201811349994.2, which proposes an electro-hydraulic composite braking system and its control method. This method employs a composite braking distribution strategy where the motor compensates for the torque of the hydraulic system. However, the calculation of vehicle braking torque lacks theoretical support, and braking torque may be canceled during braking, resulting in poor vehicle braking performance.

[0059] To address the shortcomings of the prior art, this invention provides a composite braking distribution method for multi-axle commercial vehicles. Figure 1 This is a flowchart illustrating a composite braking distribution method for a multi-axle commercial vehicle provided in an embodiment of the present invention, with reference to... Figure 1 The compound braking distribution methods for multi-axle commercial vehicles include:

[0060] S101. Perform dynamic analysis on multi-axle commercial vehicles to determine the required braking torque for the entire vehicle and the required braking torque for each axle.

[0061] Specifically, dynamic analysis refers to the structural dynamics analysis of a multi-axle commercial vehicle. It involves simultaneously analyzing the normal force balance equations, torque balance equations, and suspension force and deformation coordination equations of the entire vehicle, centered on a pre-defined axle. For example, the pre-defined axle can be the first axle closest to the front of the vehicle. Based on the dynamic analysis, the braking torque distribution coefficient can be obtained, and then combined with the overall vehicle braking torque requirement, the single-axle braking torque requirement can be determined. The overall vehicle braking torque requirement can be determined based on the brake pedal travel.

[0062] S102. Determine the required braking mode based on the driving behavior data of the multi-axle commercial vehicle.

[0063] Specifically, driving behavior data refers to measurement or sensor data about the vehicle's driving status and the driver's driving behavior, which may include driver operation data and vehicle driving data. Braking mode refers to the braking method used by the vehicle, including hydraulic braking and combined braking. Hydraulic braking refers to a braking method that uses only the hydraulic system to provide braking torque to the vehicle. Combined braking refers to a braking method that uses both hydraulic and electric motor systems to provide braking torque to the vehicle. In combined braking, the electric motor's braking torque has higher priority than the hydraulic system, with the hydraulic system playing an auxiliary braking role. Driving behavior data can reflect the vehicle's driving status and the driver's driving behavior, based on which the current braking needs of the multi-axle commercial vehicle can be analyzed, and the corresponding braking mode can be selected according to the braking needs. It should be noted that the implementation order of steps S101 and S102 can be interchanged; no restriction is placed here.

[0064] For example, if the rate of change of brake pedal travel in the driving behavior data is greater than or equal to a preset rate of change, the current braking demand of the multi-axle commercial vehicle can be determined to be emergency braking. Since high braking strength and responsiveness are required during emergency braking, the required braking mode can be determined to be hydraulic braking, which offers high braking strength and good braking responsiveness. In hydraulic braking mode, the vehicle is braked solely by the hydraulic system. If the rate of change of brake pedal travel in the driving behavior data is less than a preset rate of change, but the amount of change in brake pedal travel is greater than or equal to a preset amount, the current braking demand of the multi-axle commercial vehicle can be determined to be normal braking. Since low braking strength and responsiveness are required during normal braking, the required braking mode can be determined to be composite braking. In composite braking mode, braking torque is provided to the vehicle by prioritizing electric motor braking and supplementing it with hydraulic system braking.

[0065] S103. When the required braking mode is hydraulic braking, the braking torque supplied by the hydraulic system to each shaft is distributed according to the braking torque required for a single shaft.

[0066] Specifically, if the required braking mode is hydraulic braking, it means that during this braking process, only the hydraulic system provides braking torque to the multi-axle commercial vehicle. Therefore, when the required braking mode is hydraulic braking, the hydraulic system can distribute the braking torque supplied to each axle according to the single-axle braking torque requirement determined in step S102.

[0067] S104. When the braking mode is compound braking, determine the maximum regenerative braking torque that the motor can provide based on the distribution characteristics of the motor mechanical efficiency and battery charging efficiency.

[0068] Specifically, the required braking mode is compound braking, meaning that during this braking process, both the electric motor and the hydraulic system jointly provide braking torque for the multi-axle commercial vehicle. Since electric motor braking is regenerative braking, the motor can recover the energy generated during reverse braking, achieving secondary energy utilization. Therefore, in compound braking mode, the priority of the electric motor providing braking torque is set higher than that of the hydraulic system. That is, the regenerative braking capability of the electric motor is maximized first; if the braking torque provided by the electric motor is insufficient, the hydraulic system is used to compensate for the remaining required braking torque. In this case, it is necessary to determine the maximum regenerative braking torque that the electric motor can provide. The maximum torque of the electric motor can be determined based on its rotational speed. Based on the maximum torque of the electric motor, on the one hand, to consider the electric motor's power generation efficiency during braking, the distribution characteristics of the electric motor's power generation efficiency can be considered, and the electric motor torque can be adjusted once according to the distribution of the electric motor's power generation efficiency to ensure that the braking torque provided by the electric motor guarantees the electric motor's power generation efficiency. On the other hand, to consider the battery's charging efficiency during braking, the distribution characteristics of the battery's charging efficiency can be considered, and the electric motor torque can be adjusted again according to the distribution of the battery's charging efficiency to ensure that the braking torque provided by the electric motor guarantees the battery's charging efficiency. The electric motor torque after these two adjustments is the maximum regenerative braking torque that the electric motor can provide. Maximum regenerative braking torque can represent the maximum braking torque that the motor can provide.

[0069] For example, the maximum torque of the motor can be determined based on the current speed of the motor. Based on the maximum torque of the motor, a correction coefficient can be determined according to the distribution characteristics of the motor's power generation efficiency, and another correction coefficient can be determined according to the distribution characteristics of the battery's charging efficiency. Then, the maximum torque of the motor is corrected twice using the two correction coefficients to determine the maximum regenerative braking torque that the motor can provide. This maximum regenerative braking torque is the maximum braking torque that the motor can provide under the premise that the motor's power generation efficiency and battery charging efficiency are appropriate.

[0070] S105. Based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, determine the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor when the required braking mode is compound braking.

[0071] Specifically, in the combined braking mode, priority is given to the recovery of regenerative braking energy by the electric motor, while the hydraulic system compensates for the remaining braking torque. Therefore, based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, it can be determined whether the hydraulic system needs to compensate for the remaining braking torque and the specific compensation torque. Regenerative braking torque refers to the braking torque provided by the electric motor in the combined braking mode; the regenerative braking energy generated by this torque can be recovered by the motor to generate electricity and recharge the energy storage battery. Compensating braking torque refers to the braking torque provided by the hydraulic system in the combined braking mode; this portion of braking torque is not equal to zero only when the vehicle's required braking torque exceeds the maximum regenerative braking torque.

[0072] S106. Based on the single-axis braking torque requirement, regenerative braking torque, and compensating braking torque, distribute the braking torque supplied to each axis by the hydraulic system and the motor respectively.

[0073] Specifically, based on the braking torque required for each single shaft, the braking torque required for each single shaft can be obtained. Based on the regenerative braking torque and compensating braking torque determined in step S105, the braking torque required by the motor and hydraulic system can be obtained respectively. Furthermore, by combining the braking torque required by each single shaft, the specific distribution of the braking torque provided by the hydraulic system and motor to each shaft can be achieved. The braking torque supplied by the hydraulic system and motor to each shaft respectively refers to the target value of the braking torque that the hydraulic system and motor should supply to each shaft respectively under the combined braking mode.

[0074] The composite braking distribution method for multi-axle commercial vehicles provided in this invention combines dynamic analysis to determine the required braking torque for the entire vehicle and the required braking torque for each axle. Based on the driving behavior data of the multi-axle commercial vehicle, the required braking mode is determined. On one hand, when the required braking mode is hydraulic braking, the braking torque supplied by the hydraulic system to each axle is distributed according to the required braking torque for each axle. On the other hand, when the braking mode is composite braking, the maximum regenerative braking torque that the motor can provide is determined based on the distribution characteristics of the motor's mechanical efficiency and battery charging efficiency. Then, based on the relative relationship between the maximum regenerative braking torque and the required braking torque for the entire vehicle, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined. By distributing the braking torque supplied by the hydraulic system and the motor to each axle according to the required braking torque for each axle, regenerative braking torque, and compensating braking torque, the braking distribution for multi-axle commercial vehicles is realized. Determining the braking mode based on driving behavior data allows the braking distribution to better meet user needs, ensuring braking safety and improving braking performance. In the combined braking mode, the braking torque provided by the motor is adjusted according to the distribution of motor mechanical efficiency and battery charging efficiency, so that the braking torque provided by the motor can ensure the power generation efficiency of the motor and the charging efficiency of the battery, thereby improving the energy recovery efficiency during braking.

[0075] Based on the aforementioned embodiments, the inventors discovered that during vehicle braking, both regenerative braking by the electric motor and conventional braking by the hydraulic system need to be considered. During the switching period from hydraulic braking mode to composite braking mode, the initial stage of entering composite braking mode, and the exit stage, due to the response differences between the two braking modes, if braking is directly applied according to the braking force distribution, it will cause abnormal fluctuations in the vehicle's braking force, thereby affecting the driving experience and even reducing the overall vehicle safety performance.

[0076] Based on this, this invention proposes another compound braking distribution method for multi-axle commercial vehicles. This method, based on the aforementioned compound braking distribution method for multi-axle commercial vehicles, adds a step of dynamically adjusting the braking torque output of the motor after the braking torque distribution in the compound braking mode, in order to reduce abnormal fluctuations in the vehicle's braking force in the compound braking mode.

[0077] Figure 2 A flowchart illustrating another compound braking distribution method for a multi-axle commercial vehicle provided in an embodiment of the present invention is shown below. Figure 2 The compound braking distribution methods for multi-axle commercial vehicles include:

[0078] S201. Perform dynamic analysis on multi-axle commercial vehicles to determine the vehicle-wide braking torque requirement and the single-axle braking torque requirement.

[0079] S202. Determine the required braking mode based on the driving behavior data of the multi-axle commercial vehicle.

[0080] S203. When the required braking mode is hydraulic braking, the braking torque supplied by the hydraulic system to each shaft is distributed according to the braking torque required for a single shaft.

[0081] S204. When the braking mode is compound braking, determine the maximum regenerative braking torque that the motor can provide based on the distribution characteristics of the motor mechanical efficiency and battery charging efficiency.

[0082] S205. Based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, determine the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor when the required braking mode is compound braking.

[0083] S206. Based on the single-axis braking torque requirement, regenerative braking torque, and compensating braking torque, the hydraulic system and motor supply braking torque to each axis respectively.

[0084] Steps S201, S202, S203, S204, S205, and S206 correspond one-to-one with steps S101, S102, S103, S104, S105, and S106 in the aforementioned embodiments, and will not be repeated here.

[0085] S207: Based on the braking torque error and slip ratio error of multi-axle commercial vehicles, dynamically adjust the braking torque output of the motor.

[0086] Specifically, to achieve a rapid response to the vehicle's required braking torque and reduce the impact of hydraulic system hysteresis on braking performance, in a compound braking mode, the rapid response of the electric motor can be utilized to quickly and safely bring the vehicle's actual braking torque close to the required braking torque. During braking, the braking torque supply cannot immediately reach the target value. This is because hydraulic systems exhibit braking hysteresis, meaning the output braking torque does not immediately reach the compensating braking torque. Furthermore, if the braking torque provided by the electric motor instantaneously reaches a very high level, such as regenerative braking torque, wheel lock-up can easily occur, affecting the braking safety of multi-axle commercial vehicles. Therefore, the increase in braking torque requires a responsive process; that is, the increase in the braking torque output by the electric motor needs corresponding control.

[0087] During the response process, the braking torque output of the motor can be dynamically adjusted based on the braking torque error and slip ratio error of the multi-axle commercial vehicle. The braking torque error refers to the difference between the required braking torque of the vehicle and the actual braking torque of the vehicle; this error indicates the amount of additional braking torque needed at that moment. The slip ratio error refers to the difference between the actual slip ratio of the multi-axle commercial vehicle and the optimal slip ratio; this error indicates the magnitude of the slip ratio that needs to be adjusted by adjusting the braking torque. The actual slip ratio can be calculated based on the actual vehicle speed and wheel speed of the multi-axle commercial vehicle. The optimal slip ratio refers to the preset slip ratio that optimizes the coefficient of friction between the wheels and the road surface, and can be determined through slip ratio experiments. To reduce the braking torque error and slip ratio error of the multi-axle commercial vehicle, the braking torque output of the motor can be adjusted. For example, adjusting the braking torque output of the motor can be achieved by adjusting the rate of change of the braking torque output of the motor.

[0088] For example, the torque adjustment coefficient of the motor can be determined based on the braking torque error and the slip ratio error. For instance, the braking torque error is determined based on the difference between the required braking torque of the multi-axle commercial vehicle and the actual braking torque; the slip ratio error is determined based on the difference between the actual slip ratio and the optimal slip ratio; and the torque adjustment coefficient of the motor can be determined by combining the braking torque error and the slip ratio error.

[0089] The braking torque change rate of the motor is adjusted in real time based on the torque adjustment coefficient. This real-time adjustment can be PID control, where the input parameter is the motor's torque adjustment coefficient, and the output parameter is the motor's torque change rate. Based on the motor's actual braking torque and the adjusted braking torque change rate, the braking torque required by the motor at the next moment is determined. For example, the braking torque required by the motor at the next moment can be equal to the sum of the motor's actual braking torque at this moment and the motor's torque change rate (i.e., the change in motor torque per unit time).

[0090] The compound braking distribution method for multi-axle commercial vehicles provided in this embodiment, based on the aforementioned compound braking distribution method for multi-axle commercial vehicles, adds a step of dynamically adjusting the braking torque output of the motor after the braking torque distribution in the compound braking mode. This realizes the dynamic adjustment of the braking torque output of the motor during the braking response process, optimizes the braking response efficiency and vehicle slip ratio, reduces abnormal fluctuations in vehicle braking force in the compound braking mode, and further improves the safety of the braking distribution method.

[0091] Figure 3 A flowchart illustrating another compound braking distribution method for a multi-axle commercial vehicle provided in this embodiment of the invention is shown below. Figure 3 The compound braking distribution methods for multi-axle commercial vehicles include:

[0092] S301. Based on the change in pedal travel and the maximum braking intensity limit of the multi-axle commercial vehicle, determine the required braking intensity of the multi-axle commercial vehicle under different pedal travel changes.

[0093] Specifically, the change in pedal travel reflects the driver's demand for braking force. Generally, a larger change in travel indicates a greater demand for braking force. Furthermore, considering the physical strength of multi-axle commercial vehicles, they may not be able to withstand excessively high braking forces. Therefore, it is necessary to consider the maximum braking force limit of multi-axle commercial vehicles. For example, the maximum braking force limit of multi-axle commercial vehicles can be obtained through experimental testing.

[0094] For example, based on the change in brake pedal travel and considering the vehicle's maximum braking intensity limit, the required braking intensity of the vehicle under different pedal travel variations is determined according to a first calculation formula. The first calculation formula is as follows: Where z represents the required braking intensity of the entire vehicle, and l brk The pedal travel is a variable, while the maximum braking force of the vehicle is limited to 0.83.

[0095] S302. Determine the required braking torque of the multi-axle commercial vehicle based on the overall vehicle braking intensity requirements, the weight of the multi-axle commercial vehicle, and the wheel radius.

[0096] Specifically, by substituting the required braking intensity of the entire vehicle, the weight of the multi-axle commercial vehicle, and the wheel radius into the second calculation formula, the required braking torque of the multi-axle commercial vehicle can be determined. The second calculation formula is T. req_b =mgzr, where, T req_b Let r be the braking torque required for the multi-axle commercial vehicle, m be the wheel radius of the multi-axle commercial vehicle, g be the mass of the multi-axle commercial vehicle, and g be the acceleration due to gravity.

[0097] S303. Establish a multi-axle braking balance matrix for a multi-axle commercial vehicle, with any axle of the multi-axle commercial vehicle as the center.

[0098] Specifically, any axle can be selected as the first axle closest to the front of the vehicle in a multi-axle commercial vehicle. First, with the first axle of the vehicle as the center, establish the normal force balance equation and torque balance equation for the entire vehicle, i.e., the third calculation formula. and the fourth calculation formula Where i is the axle number, F zi Let l be the normal force acting on the i-th axle of a multi-axle commercial vehicle. i Let l be the distance from the i-th axle to the first axle of a multi-axle commercial vehicle. c The distance from the center of gravity of a multi-axle commercial vehicle to the first axle. For the braking deceleration of multi-axle commercial vehicles, h c The height of the center of gravity of the multi-axle commercial vehicle. By combining the third and fourth calculation formulas into a system of equations and then matrixing them, the multi-axle braking balance matrix can be obtained, i.e., the first matrixed equation TF. z =M, where T=[e n L], e n =[1 1 … 1] 1*n L = [l1 l2 … l n ], F z =[F z1 F z2 … F zn ] T , n represents the total number of axles in a multi-axle commercial vehicle.

[0099] S304. Based on the multi-axle braking balance matrix, and combined with the suspension stress and suspension deformation coordination equation, solve for the single-axle braking torque required by each axle in the multi-axle commercial vehicle.

[0100] Specifically, the normal force of a multi-axle commercial vehicle can also be solved based on the suspension forces, forming the fifth calculation equation F. zi =K i Δx i K i For suspension stiffness, Δx iLet F be the deformation of the suspension on the i-th axle of a multi-axle commercial vehicle. The second matrix-based equation F can be obtained by matrixing the fifth calculation equation. z =KΔx, where K = diag[K1 K2 … K n ], △x=[△x1 △x2 … △x n ] T The suspension coordination equation for multi-axle commercial vehicles is the sixth calculation equation. Furthermore, by transforming the sixth calculation equation, we can obtain the seventh calculation equation AΔx=[b pq ] (n-2)×n Δx = 0, where, p = 1, 2, ..., n-2; q = 1, 2, ..., n. By combining the second matrix equation and the sixth computational equation, the third matrix equation AK can be obtained. -1 F z =0, substituting the third matrix equation into the first matrix equation yields the fourth matrix equation. make Then the fourth matrix equation can be expanded to obtain the expanded fourth matrix equation. This leads to the eighth computational equation F. zi =P i1 mg+P i2 mgl c -P i2 mh c in, Let ξ d =-P i2 mh c C t =P i1 mg+P i2 mgl i Then the eighth calculation equation can be simplified to the ninth calculation equation. The braking force distribution coefficients for each axle can be determined according to the tenth calculation equation, which is: Where k is the correction coefficient for the required torque, which can be determined based on experimental data. Finally, the eleventh calculation equation T is used. req_bi =mgzrβ i To calculate the required braking torque for each axle.

[0101] S305. Based on the pedal travel variation rate and pedal travel variation of the multi-axle commercial vehicle, determine the braking conditions of the multi-axle commercial vehicle.

[0102] Specifically, driving behavior data includes the rate of change of pedal travel, the amount of change of pedal travel, and the current vehicle speed. Braking conditions include normal braking, emergency braking, and short-term braking. Based on the rate of change of pedal travel and the amount of change of pedal travel, the braking condition can be determined.

[0103] For example, Figure 4 This is a flowchart illustrating a braking mode determination method provided in an embodiment of the present invention, in conjunction with... Figure 4 According to the rate of change of pedal travel Compared with the preset rate of change The relative relationship between the values ​​indicates whether the braking condition of a multi-axle commercial vehicle is emergency braking. For example, if the rate of change of pedal travel is greater than or equal to the preset rate of change, it indicates that the driver applied the brakes very quickly, and the braking condition of the multi-axle commercial vehicle can be determined as emergency braking.

[0104] In non-emergency braking conditions of a multi-axle commercial vehicle, the change in pedal travel I is compared with the preset change I. thre The relative relationship can determine whether the braking condition of a multi-axle commercial vehicle is normal braking. For example, if the pedal travel change I is greater than or equal to the preset change I... thre If the driver applies the brakes deeply, it indicates that the braking condition of the multi-axle commercial vehicle is normal.

[0105] If the braking condition of a multi-axle commercial vehicle is neither emergency braking nor normal braking, it indicates that the driver's braking was not urgent and was relatively shallow, thus confirming that the braking condition is short-term braking. Short-term braking refers to a braking method with a short duration and shallow braking degree; under short-term braking, the speed change of the multi-axle commercial vehicle is also relatively small.

[0106] S306. Under emergency braking conditions, the required braking mode for multi-axle commercial vehicles shall be hydraulic braking.

[0107] Specifically, continue to combine Figure 4 When the braking condition is emergency braking, it indicates that the driver intends to reduce the speed of the multi-axle commercial vehicle by a large range in a short period of time. Under this condition, the braking strength and response accuracy of the braking mode are required to be high. To ensure vehicle safety, the traditional hydraulic braking mode can be selected to use the hydraulic system to brake the multi-axle commercial vehicle individually, thereby achieving a rapid and stable reduction in vehicle speed.

[0108] S307. Under normal braking conditions, the required braking mode for multi-axle commercial vehicles is determined to be compound braking.

[0109] Specifically, continue to combine Figure 4If the braking condition is normal braking, it indicates that the driver does not intend to brake in an emergency and requires a large braking torque. In this case, a compound braking mode is selected, which uses both hydraulic and electric motor systems for braking. This can recover some braking energy and improve the vehicle's range.

[0110] S308. When the braking condition is short-term braking, the required braking mode is determined based on the relative relationship between the current speed of the multi-axle commercial vehicle and the preset speed range.

[0111] Specifically, continue to combine Figure 4 If the current speed of a multi-axle commercial vehicle is greater than or equal to the upper edge of the preset speed range, it indicates that the vehicle is traveling at a relatively high speed. During short-term braking, a more stable braking torque output is required to ensure higher safety. Therefore, when the current speed V of the multi-axle commercial vehicle is greater than or equal to the upper edge of the preset speed range, it indicates that the vehicle is traveling at a relatively high speed. max In this case, the required automatic mode can be determined to be hydraulic braking. If the current speed V of the multi-axle commercial vehicle is less than or equal to the lower edge value V of the preset speed range... min This indicates that the multi-axle commercial vehicle's speed is relatively slow. During short-term braking, the electric motor's braking efficiency is low. Therefore, when the current speed V of the multi-axle commercial vehicle is less than or equal to the lower edge value V of the preset speed range... min In such cases, the desired automatic mode can be determined to be hydraulic braking. Furthermore, if the current speed V of the multi-axle commercial vehicle is within the preset speed range V... min To V max The inner speed indicates that the multi-axle commercial vehicle has a moderate speed, which can adapt to the reverse power generation of the motor and has a high power generation efficiency. The vehicle's operation safety is also guaranteed to a certain extent during braking, and a compound braking mode can be selected.

[0112] S309. When the required braking mode is hydraulic braking, the braking torque supplied by the hydraulic system to each shaft is distributed according to the braking torque required for a single shaft.

[0113] Step S309 is identical to step S103 in the aforementioned embodiment, and will not be repeated here.

[0114] S310. When the braking mode is compound braking, the maximum torque of the motor is obtained based on the motor's external characteristic curve and the motor's current speed.

[0115] Specifically, the external characteristic curve of a motor refers to the curve showing the change in power or torque with speed when the motor is running at full load, which can be obtained through preliminary experiments. Based on the external characteristic curve, the relationship between the motor's speed and torque can be obtained, and the twelfth formula for calculating the motor's torque can be determined. Furthermore, by substituting the current speed of the motor into the twelfth formula, the maximum torque of the motor can be calculated. The twelfth formula is as follows: T rate ω is the rated torque of the motor. rate P is the rated speed of the motor. rate This refers to the rated power of the motor.

[0116] S311. Based on the distribution characteristics of the motor's mechanical efficiency, determine the motor efficiency correction coefficient for the maximum torque.

[0117] Specifically, to balance the motor's power generation efficiency, and considering the lower efficiency of the motor in the low-speed, high-torque and high-speed, low-torque ranges, a motor efficiency correction coefficient can be introduced to correct the motor's torque. The formula for calculating the motor efficiency correction coefficient is Formula Thirteen. γ bat This is the motor efficiency correction factor. This represents the actual efficiency of the motor. This represents the maximum power generation efficiency of the motor. This represents the lowest power generation efficiency of the motor.

[0118] S312. Based on the distribution characteristics of battery charging efficiency, determine the battery efficiency correction coefficient for the maximum torque.

[0119] Specifically, as the recipient of regenerative braking energy recovery, the battery's state parameters affect its charging efficiency, thus limiting the motor's regenerative braking capability. Therefore, to avoid wasting the motor's braking power, a battery efficiency correction coefficient can be introduced to further correct the braking torque provided by the motor. The formula for calculating the battery efficiency correction coefficient is the fourteenth formula. Where, γ bat This is the battery efficiency correction factor. This is for the battery's maximum charging efficiency. The lowest charging efficiency for the battery. This refers to the actual charging efficiency of the battery.

[0120] S313. Calculate the maximum regenerative braking torque that the motor can provide based on the product of the motor's maximum torque, the motor efficiency correction coefficient, and the battery efficiency correction coefficient.

[0121] Specifically, based on the motor's maximum torque, motor efficiency correction coefficient, and battery efficiency correction coefficient, the maximum regenerative braking torque that the motor can provide can be obtained by substituting these factors into the fifteenth calculation formula. The fifteenth calculation formula is T. mot_max =γ mot γ bat T mot , among which, T mot_max The maximum regenerative braking torque that the motor can provide.

[0122] S314. When the required braking torque of the whole vehicle is less than or equal to the maximum regenerative braking torque, the regenerative braking torque provided by the motor is determined to be equal to the required braking torque of the whole vehicle, and the compensating braking torque provided by the hydraulic system is equal to 0.

[0123] Specifically, if the required braking torque of the entire vehicle is less than or equal to the maximum available braking force of the motor, i.e., T req_b ≤T mot_max , among which, T req_b To meet the braking torque requirements of the entire vehicle, in the compound braking mode, the regenerative braking torque provided by the electric motor and the compensating braking torque provided by the hydraulic system satisfy the following conditions: Among them, T mot_brkreq The regenerative braking torque T provided to the motor hy d _ brkreq provides compensating braking torque for hydraulic systems.

[0124] S315. When the required braking torque of the vehicle is greater than the maximum regenerative braking torque, the regenerative braking torque provided by the motor is determined to be equal to the maximum regenerative braking torque, and the compensating braking torque provided by the hydraulic system is equal to the difference between the required braking torque of the vehicle and the maximum regenerative braking torque.

[0125] Specifically, if the required braking torque of the entire vehicle is greater than the maximum available braking force of the motor, i.e., T req_b >T mot_max In the combined braking mode, the regenerative braking torque provided by the motor and the compensating braking torque provided by the hydraulic system satisfy the requirements.

[0126] S316. Based on the single-axis braking torque requirement, regenerative braking torque, and compensating braking torque, the hydraulic system and motor supply braking torque to each axis respectively.

[0127] Step S316 is the same as step S106 in the previous embodiment, and will not be described again here.

[0128] S317. Determine the motor torque adjustment coefficient based on braking torque error and slip ratio error.

[0129] Specifically, braking torque error refers to the difference between the vehicle's required braking torque and its actual braking torque. This braking torque error indicates the amount of additional braking torque needed at that moment. The braking torque error can be calculated using the sixteenth formula, which is ΔT. brk_err =T req_b -T brk_act , where △T brk-err For braking torque error; T brk_act The actual braking torque for a multi-axle commercial vehicle can be determined based on the actual output data of the motor and hydraulic system. The slip ratio error refers to the difference between the actual slip ratio and the optimal slip ratio of the multi-axle commercial vehicle. The slip ratio error indicates the magnitude of the slip ratio that needs to be adjusted by adjusting the braking torque at that moment. The slip ratio error can be calculated using the seventeenth formula, δ. err =δ act -δ opt , where △δ err For slip ratio error, δ act δ represents the actual slip ratio of a multi-axle commercial vehicle. opt For multi-axle commercial vehicles, the optimal slip ratio can be determined, for example, based on experimental data, when the slip ratio is between 15% and 20%, the wheel-to-road adhesion coefficient is optimal. Therefore, the optimal slip ratio can be any value between 15% and 20% as needed; for example, the optimal slip ratio could be 17%. Combining the braking torque error and the slip ratio error, the motor torque adjustment coefficient can be determined by substituting them into the eighteenth calculation formula. The eighteenth calculation formula is ΔErr = κΔT brk_err +μδ err , △E rr κ is the torque adjustment coefficient of the motor, κ is the distribution coefficient of braking torque error and κ∈[0 1], and μ is the distribution coefficient of slip ratio error and μ∈[0 1]; the values ​​of κ and μ can be determined based on experimental data of vehicle braking. The torque adjustment coefficient serves as the input parameter for motor torque adjustment.

[0130] S318. Adjust the rate of change of the motor's braking torque in real time according to the torque adjustment coefficient.

[0131] Specifically, to achieve optimal braking response and best slip ratio, the motor torque change rate is adjusted in real time using a torque adjustment coefficient. The motor torque change rate is T. △Err =PID(△E) rr ), where T △Err T represents the motor torque change rate. PID() is the PID control algorithm, which adjusts the motor torque according to the input torque adjustment coefficient and outputs the motor torque change rate. △Err It needs to be less than or equal to T τmax , among which, T τmaxThe maximum torque change rate is taken into account for motor characteristics.

[0132] S319. Based on the actual braking torque of the motor and the adjusted rate of change of braking torque, determine the braking torque that the motor needs to provide at the next moment.

[0133] Specifically, the current actual braking torque of the motor and the rate of change of motor torque determined in step S318 are substituted into the nineteenth calculation formula to obtain the braking torque provided by the motor at the next moment, so that the motor torque is adjusted towards the required torque. The nineteenth calculation formula is T. mot_brkactnext =T mot_brk_act +T △Err , among which, T mot_brkactnext T is the braking torque provided by the motor in the next moment. mot_brk_act T represents the actual braking torque of the current motor. mot_brkactnext ∈[T mot_brkreq ,0].

[0134] The compound braking distribution method for multi-axle commercial vehicles provided in this embodiment, based on the aforementioned compound braking distribution method for multi-axle commercial vehicles, adds a step of dynamically adjusting the braking torque output of the motor after the braking torque distribution in the compound braking mode. This realizes the dynamic adjustment of the braking torque output of the motor during the braking response process, optimizes the braking response efficiency and vehicle slip ratio, reduces abnormal fluctuations in vehicle braking force in the compound braking mode, and further improves the safety of the braking distribution method.

[0135] This invention also provides a composite braking distribution device for multi-axle commercial vehicles. Figure 5 This is a schematic diagram of the composition of a composite brake distribution device for a multi-axle commercial vehicle provided in an embodiment of the present invention, with reference to... Figure 5A composite braking distribution device for a multi-axle commercial vehicle includes: a braking mode determination module 501, a braking torque determination module 502, a hydraulic braking torque distribution module 503, a maximum regenerative braking torque determination module 504, a dual braking torque determination module 505, and a dual braking torque distribution module 506. The braking mode determination module 501 determines the required braking mode based on driving behavior data of the multi-axle commercial vehicle, where the braking mode includes hydraulic braking and composite braking. The braking torque determination module 502 performs dynamic analysis on the multi-axle commercial vehicle to determine the overall vehicle braking torque requirement and the single-axle braking torque requirement. The hydraulic braking torque distribution module 503, when the required braking mode is hydraulic braking, distributes the braking torque supplied by the hydraulic system to each axle according to the single-axle braking torque requirement. The maximum regenerative braking torque determination module 504, when the braking mode is composite braking, determines the maximum regenerative braking torque that the motor can provide based on the distribution characteristics of motor mechanical efficiency and battery charging efficiency. The dual braking torque determination module 505 is used to determine the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor when the required braking mode is compound braking, based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque. The dual braking torque distribution module 506 is used to distribute the braking torque supplied by the hydraulic system and the motor to each axle based on the single axle's required braking torque, maximum regenerative braking torque, and compensating braking torque.

[0136] Optionally, continue to refer to Figure 5 Based on the aforementioned embodiments, the composite braking distribution device for multi-axle commercial vehicles further includes a dynamic adjustment module 601, which is used to dynamically adjust the braking torque output by the motor based on the braking torque error and slip ratio error of the multi-axle commercial vehicle.

[0137] This invention provides a composite braking distribution method and device for multi-axle commercial vehicles. Combining dynamic analysis, it determines the required braking torque for the entire vehicle and the required braking torque for each axle. Based on driving behavior data of the multi-axle commercial vehicle, the required braking mode is determined. On one hand, when the required braking mode is hydraulic braking, the braking torque supplied by the hydraulic system to each axle is distributed according to the required braking torque of each axle. On the other hand, when the braking mode is composite braking, the maximum regenerative braking torque that the motor can provide is determined based on the distribution characteristics of motor mechanical efficiency and battery charging efficiency. Then, based on the relative relationship between the maximum regenerative braking torque and the required braking torque for the entire vehicle, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined. By distributing the braking torque supplied by the hydraulic system and the motor to each axle according to the required braking torque of each axle, regenerative braking torque, and compensating braking torque, the braking distribution for multi-axle commercial vehicles is realized. Determining the braking mode according to driving behavior data allows the braking distribution to better meet user needs, ensuring braking safety and improving braking performance. In the combined braking mode, the braking torque provided by the motor is adjusted according to the distribution of motor mechanical efficiency and battery charging efficiency, so that the braking torque provided by the motor can ensure the power generation efficiency of the motor and the charging efficiency of the battery, thereby improving the energy recovery efficiency during braking.

[0138] The above-described products can perform the methods provided in any embodiment of the present invention, and have the corresponding functional modules and beneficial effects for performing the methods.

[0139] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A composite braking distribution method for a multi-axle commercial vehicle, characterized in that, include: A dynamic analysis was conducted on the multi-axle commercial vehicle to determine the required braking torque for the entire vehicle and the required braking torque for each axle. Based on the driving behavior data of the multi-axle commercial vehicle, the required braking mode is determined, wherein the braking mode includes hydraulic braking and compound braking; When the required braking mode is hydraulic braking, the hydraulic system supplies braking torque to each shaft according to the single-axis braking torque requirement. When the braking mode is compound braking, the maximum regenerative braking torque that the motor can provide is determined based on the distribution characteristics of the motor mechanical efficiency and battery charging efficiency. Based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined when the required braking mode is compound braking. Based on the single-axis braking torque requirement, the regenerative braking torque, and the compensating braking torque, the braking torque supplied by the hydraulic system and the motor to each axis is allocated. Based on the braking torque error and slip ratio error of the multi-axle commercial vehicle, the braking torque output of the motor is dynamically adjusted. Specifically, this includes: determining the torque adjustment coefficient of the motor based on the braking torque error and the slip ratio error; adjusting the braking torque change rate of the motor in real time according to the torque adjustment coefficient; and determining the braking torque that the motor needs to provide at the next moment based on the actual braking torque of the motor and the adjusted braking torque change rate.

2. The composite braking distribution method for multi-axle commercial vehicles according to claim 1, characterized in that, The real-time adjustment includes PID control.

3. The composite braking distribution method for multi-axle commercial vehicles according to claim 1, characterized in that, The driving behavior data includes the rate of change of pedal travel, the amount of change of pedal travel, and the current vehicle speed; Based on the driving behavior data of the multi-axle commercial vehicle, the required braking mode is determined, including: The braking conditions of the multi-axle commercial vehicle are determined based on the pedal travel change rate and the pedal travel change amount. The braking conditions include normal braking, emergency braking and short-term braking. When the braking condition is emergency braking, the required braking mode for the multi-axle commercial vehicle is determined to be hydraulic braking. When the braking condition is normal braking, the required braking mode for the multi-axle commercial vehicle is determined to be the compound braking. When the braking condition is short-term braking, the required braking mode is determined based on the relative relationship between the current speed of the multi-axle commercial vehicle and the preset speed range.

4. The composite braking distribution method for multi-axle commercial vehicles according to claim 3, characterized in that, Based on the driving behavior data of the multi-axle commercial vehicle, the braking conditions of the multi-axle commercial vehicle are determined, including: Based on the relative relationship between the pedal travel change rate and the preset change rate, it is determined whether the braking condition of the multi-axle commercial vehicle is emergency braking. When the braking condition of the multi-axle commercial vehicle is not emergency braking, the relative relationship between the change in pedal travel and the preset change is used to determine whether the braking condition of the multi-axle commercial vehicle is normal braking. When the braking condition of the multi-axle commercial vehicle is neither emergency braking nor normal braking, the braking condition of the multi-axle commercial vehicle is determined to be short-term braking.

5. The composite braking distribution method for multi-axle commercial vehicles according to claim 1, characterized in that, The driving behavior data includes the change in pedal travel; A dynamic analysis was performed on the multi-axle commercial vehicle to determine the overall vehicle braking torque requirement and the single-axle braking torque requirement, including: Based on the pedal travel variation and the maximum braking intensity limit of the multi-axle commercial vehicle, the required braking intensity of the multi-axle commercial vehicle under different pedal travel variations is determined. The required braking torque of the multi-axle commercial vehicle is determined based on the required braking intensity of the entire vehicle, the weight of the multi-axle commercial vehicle, and the wheel radius. A multi-axle braking balance matrix of the multi-axle commercial vehicle is established with any axle of the multi-axle commercial vehicle as the center. Based on the multi-axle braking balance matrix, and combined with the suspension stress conditions and suspension deformation coordination equations, the single-axle braking torque requirement of each axle on the multi-axle commercial vehicle is solved.

6. The composite braking distribution method for multi-axle commercial vehicles according to claim 1, characterized in that, Based on the distribution characteristics of motor mechanical efficiency and battery charging efficiency, the maximum regenerative braking torque that the motor can provide is determined, including: Based on the external characteristic curve of the motor, the maximum torque of the motor is obtained according to the current speed of the motor; Based on the distribution characteristics of the motor mechanical efficiency, determine the motor efficiency correction coefficient for the maximum torque; Based on the distribution characteristics of the battery charging efficiency, determine the battery efficiency correction coefficient for the maximum torque; The maximum regenerative braking torque that the motor can provide is calculated based on the product of the motor's maximum torque, the motor efficiency correction factor, and the battery efficiency correction factor.

7. The composite braking distribution method for multi-axle commercial vehicles according to claim 1, characterized in that, Based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor are determined when the required braking mode is compound braking, including: If the required braking torque of the whole vehicle is less than or equal to the maximum regenerative braking torque, it is determined that the regenerative braking torque provided by the motor is equal to the required braking torque of the whole vehicle, and the compensating braking torque provided by the hydraulic system is equal to 0. When the required braking torque of the vehicle is greater than the maximum regenerative braking torque, it is determined that the regenerative braking torque provided by the motor is equal to the maximum regenerative braking torque, and the compensating braking torque provided by the hydraulic system is equal to the difference between the required braking torque of the vehicle and the maximum regenerative braking torque.

8. A composite brake distribution device for a multi-axle commercial vehicle, characterized in that, include: The braking mode determination module is used to determine the required braking mode based on the driving behavior data of the multi-axle commercial vehicle, wherein the braking mode includes hydraulic braking and compound braking. The braking torque determination module is used to perform dynamic analysis on the multi-axle commercial vehicle to determine the vehicle's overall braking torque requirement and the single-axle braking torque requirement. A hydraulic braking torque distribution module is used to distribute the braking torque supplied by the hydraulic system to each shaft according to the single shaft's required braking torque when the required braking mode is hydraulic braking. The maximum regenerative braking torque determination module is used to determine the maximum regenerative braking torque that the motor can provide based on the distribution characteristics of the motor mechanical efficiency and battery charging efficiency when the braking mode is compound braking. A dual braking torque determination module is used to determine, based on the relative relationship between the maximum regenerative braking torque and the vehicle's required braking torque, the compensating braking torque provided by the hydraulic system and the regenerative braking torque provided by the motor when the required braking mode is compound braking. A dual braking torque distribution module is used to distribute the braking torque supplied by the hydraulic system and the motor to each shaft according to the single-shaft required braking torque, the regenerative braking torque, and the compensating braking torque.

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