Distribution control method of driving torque of front and rear shafts of four-wheel electric automobile

Abstract

The invention relates to the field of automobile power distribution, in particular to a distribution control method of driving torque of front and rear shafts of a four-wheel electric automobile. Themethod includes the following steps of 1, according to an accelerator pedal and an automobile speed value, calculating a driver total torque instruction Td; 2, on the basis of an optimal system efficiency principle, conducting initial torque distribution to obtain initial driving torque Tdf0 of the front shaft and initial driving torque Tdr0 of the rear shaft; 3, estimating an available pavement attachment coefficient to obtain an attachment coefficient mu; 4, according to the attachment coefficient mu, calculating a driving torque limit value Tufmax of the front shaft and a driving torque limit value Turmax of the rear shaft; 5, according to the driving torque limit value Tufmax of the front shaft and the driving torque limit value Turmax of the rear shaft, adjusting distribution of the initial torque of the front and rear shafts; 6, calculating a motor torque instruction Tmf of the front shaft and a motor torque instruction Tmr of the rear shaft separately, calculating the optimal driving power limit values of the front and rear shafts by identifying the pavement attachment coefficient in real time, and according to the instructions above, conducting shift distribution on the driving torque of the front and rear shafts. Therefore, the optimal power performance is achieved, and wheels can be prevented from sliding and rotating in an initiative mode.

Description

technical field [0001] The present invention relates to the field of automobile power distribution, and more particularly, relates to a method for controlling the distribution and control of front and rear axle driving torque of a four-wheel drive electric vehicle. Background technique [0002] At present, with the popularization of environmental protection knowledge, people pay more and more attention to environmental protection and energy saving, and some new energy equipment gradually replace traditional energy equipment. Among them, new energy electric vehicles are popular because of their advantages of energy saving and environmental protection. [0003] On the basis of energy saving and environmental protection, the four-wheel drive system can provide better power performance and handling performance. Therefore, more and more new energy electric vehicles also adopt the four-wheel drive power system. Among them, the more common The four-drive power system adopts indepen...

AI Technical Summary

Problems solved by technology

[0003] On the basis of energy saving and environmental protection, the four-wheel drive system can provide better power performance and handling performance. Therefore, more and more new energy electric vehicles also adopt the four-wheel drive power system. Among them, the more common The four-drive power system adopts independent motors for the front and rear axles, and transmits the power to the front and rear half-shafts through the front and rear differential subtraction assemblies for driving. However, unlike two-wheel drive electric vehicles, four-wheel drive electric vehicles need For torque distribution, an effective torque distribution control algorithm is required to give full play to the advantages of the four-drive system, which has certain control complexity

[0004] Four-wheel drive electric vehicles need to distribute the driving torque reasonably between the front and rear wheels in order to give full play to the advantages of the four-wheel drive system. When distributing, it is necessary to consider improving the operating efficiency of the system and make full use of the adhesion coefficient of the road surface. Realize control technologies such as drive anti-skid, but, from the current situation of this technical field, the public documents mostly consider the front and rear axle drive torque distribution from the perspective of improving system efficiency, and there are also control methods to improve vehicle passability by switching between two-wheel drive and four-wheel drive Method, there is a document on driving anti-skid in coordination with electronic stability control unit to realize driving anti-skid, but there is no document disclosing the distribution of front and rear axle torque from the perspective of improving the utilization rate of road surface adhesion coefficient. The present invention relates to four-wheel drive electric vehicles The front and rear axle torque distribution control method effectively distributes the driving torque of the front and rear axles from the perspective of fully utilizing the road surface adhesion coefficient, reduces invalid torque distribution, and avoids wheel slippage

[0005] In the existing Chinese patent literature, the announcement number is CN201710001686.X, which discloses a torque distribution control method for front and rear axles of a four-wheel drive electric vehicle based on the principle of optimal system efficiency. The optimal torque distribution table for system efficiency is obtained through offline calculation. According to The current vehicle speed and total torque demand table look-up calculates the best torque distribution coefficient. This method can achieve better economy, but does not take into account the power of the car. In the Chinese patent document with the publication number CN201610663212.7, A control method for switching four-wheel drive and rear drive modes in real time according to motor efficiency is disclosed, but it still does not take into account the power of the car

[0006] In the Chinese patent document with the announcement number CN201510446261.0, a control method for receiving electronic stability intervention signals and then adjusting the torque distribution of the front and rear axles is disclosed, which realizes the passive driving anti-skid function. Using the technology of the above documents can Optimizing the economy of four-wheel drive electric vehicles and realizing the passive anti-skid function, however, because the adhesion of the road surface is not considered, the torque of the front and rear axles cannot be limited and adjusted according to the limit values ​​of the driving force of the front and rear axles, and the optimum performance cannot be realized. The best power performance, also can not realize the active driving anti-skid function

[0007] In the prior art, the driving torque of the front and rear axles is distributed through the principle of optimal system efficiency. Although better economy can be achieved to a certain extent, it cannot guarantee the maximum dynamic performance of the vehicle, especially in low adhesion coefficients. On the road surface, the driving wheels may slip, and the technical solution of switching between two-wheel drive and four-wheel drive can only improve the passing performance of the vehicle in limited circumstances, and cannot achieve the best torque distribution control at any time. The technical solution of driving anti-slip control through electronic stability control unit coordination can only be carried out after the wheel slips, and the wheel slip cannot be avoided in advance

[0008] In short, because the existing technical solutions do not consider how to make full use of the road surface adhesion coefficient, the best dynamic performance cannot be obtained, and the vehicle may even slip, causing longitudinal acceleration performance and lateral stability to decline, and affecting vehicle safety. Therefore, It is necessary to propose a control method for front and rear axle drive torque distribution of four-wheel drive electric vehicles to solve the above problems

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