阅读说明：本技术 车辆驱动轴间输出力矩调整方法及其系统、控制设备 (Method and system for adjusting output torque between vehicle driving shafts and control equipment ) 是由 张进 梅兴泰 周伟 于 2020-04-17 设计创作，主要内容包括：本发明涉及车辆驱动轴间输出力矩调整方法及其系统、控制设备,所述方法包括：周期性地根据车辆的车速和纵向加速度获得车辆的驾驶风格,所述驾驶风格采用数值表示；周期性地根据预设车辆模型、车辆启用四驱驱动控制时前轴轮胎纵向力和后轴轮胎纵向力关系计算车辆当前周期的前、后轴轮胎力,并根据所述前、后轴轮胎力确定的前、后轴轮胎力的安全边界；根据当前周期的驾驶风格确定对应的安全边界阈值,并将当前周期的前、后轴轮胎安全边界分别与所述安全边界阈值进行比较,并根据比较结果确定是否启用四驱控制系统进行驱动控制,以对驱动轴间输出力矩调整。实施本发明,能够实现根据驾驶员的驾驶风格对驱动轴间输出力矩进行调整。(The invention relates to a method for adjusting output torque between driving shafts of a vehicle, a system and a control device thereof, wherein the method comprises the following steps: periodically obtaining the driving style of the vehicle according to the speed and the longitudinal acceleration of the vehicle, wherein the driving style is represented by numerical values; periodically calculating the tire force of a front axle and a rear axle of the vehicle in the current period according to a preset vehicle model and the relationship between the longitudinal force of the tire of the front axle and the longitudinal force of the tire of the rear axle when the four-wheel drive control is started by the vehicle, and determining the safety boundary of the tire force of the front axle and the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle; and determining corresponding safety boundary thresholds according to the driving style of the current period, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period with the safety boundary thresholds respectively, and determining whether a four-wheel drive control system is started to carry out drive control according to a comparison result so as to adjust the output torque between the driving axles. By implementing the invention, the output torque between the driving shafts can be adjusted according to the driving style of the driver.)

1. A method of adjusting output torque between drive shafts of a vehicle, the method comprising:

periodically obtaining the driving style of the vehicle according to the speed and the longitudinal acceleration of the vehicle, wherein the driving style is represented by numerical values;

periodically calculating the tire force of a front axle and a rear axle of the vehicle in the current period according to a preset vehicle model and the relationship between the longitudinal force of the tire of the front axle and the longitudinal force of the tire of the rear axle when the four-wheel drive control is started, and determining the safety boundary of the tire force of the front axle and the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle;

and determining corresponding safety boundary thresholds according to the driving style of the current period, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period with the safety boundary thresholds respectively, and determining whether a four-wheel drive control system is started to carry out drive control according to a comparison result so as to adjust the output torque between the driving axles.

2. The method for adjusting the output torque between the drive shafts of the vehicle according to claim 1, wherein the driving style of the vehicle is periodically obtained according to the vehicle speed and the longitudinal acceleration of the vehicle, and specifically comprises:

acquiring the speed and the longitudinal acceleration of the vehicle at preset time intervals, and acquiring the dispersion of the acceleration change of the current time period according to all the speeds and the longitudinal accelerations acquired in the current time period; the current time period is a time period from the end to the current acquisition time, and the length of the time period is preset;

respectively comparing the dispersion of the acceleration change in the current time period with a plurality of preset threshold values, and taking the threshold value corresponding to the minimum comparison deviation as the driving style identification result at the current acquisition moment;

and acquiring the driving style recognition results of all the acquisition moments in the current time period, and acquiring the current driving style according to the driving style recognition results of all the acquisition moments in the current time period.

3. The method for adjusting the output torque between the drive shafts of the vehicle according to claim 2, wherein the obtaining of the current driving style according to the driving style recognition results at all the acquisition times in the current time period specifically includes:

obtaining a transient driving style recognition result and a steady-state driving style recognition result of the current time period according to the driving style recognition results of all the collected moments in the current time period;

determining the current driving style m according to the comparison result of the absolute value of the deviation between the steady-state driving style recognition result and the transient driving style recognition result of the current time period and a preset threshold value_driver(ii) a Wherein m is_driverExpressed by a numerical value, m_driverThe larger the driving style, the more aggressive m_driverThe smaller, the more robust the driving style.

4. The method of adjusting output torque between drive shafts of a vehicle according to claim 3, characterized in thatThe identification result of the transient driving style comprises the average value m of the transient driving style₀The steady-state driving style recognition result comprises a steady-state driving style average value m₁；

Wherein:

setting the current time period as the kth time period, calculating the average value and the standard deviation of the driving style identification results of all the acquisition moments in the current time period, and taking the average value as the average value m of the transient driving style of the current time period_1(k)；

Average value m of transient driving style according to current time period_1(k)Calculating a steady-state driving style accumulated value m for a current time period_0(k)；

Wherein m is_0(k)＝α₀×m_1(k)+(1-α₀)×m_0(k-1)，m₀₍₀₎＝0，α₀Is a weight coefficient, 0<α₀<1。

5. The method according to claim 4, wherein the current driving style m is determined based on a comparison result between an absolute value of a deviation between the steady-state driving style recognition result and the transient driving style recognition result for the current time period and a preset threshold value_driverThe method specifically comprises the following steps:

if the steady-state driving style accumulated value m of the current time period₀And the average value m of the transient driving style₁Is less than a set threshold m_th1Then the current driving style m_driverIs m₀；

If the steady-state driving style accumulated value m of the current time period₀And the average value m of the transient driving style₁Is greater than a set threshold m_th1And is less than a set threshold value m_th2Then the current driving style m_driverIs (m)₁+m₀)/2；

If the steady-state driving style accumulated value m of the current time period₀And the average value m of the transient driving style₁Is greater than a set threshold m_th2Then the current driving style m_driverIs m₁。

6. The method of adjusting vehicle inter-drive-axle output torque according to claim 4, characterized in that the transient driving style recognition result further includes a transient driving style standard deviation v₁The steady-state driving style recognition result further comprises a steady-state driving style standard deviation v₀；

Wherein:

setting the current time period as the kth time period, calculating the standard deviation of the driving style recognition results at all the acquisition moments in the current time period, and taking the standard deviation as the transient driving style standard deviation v of the current time period_1(k)；

According to the current time period and the top n₀The accumulated value of the steady-state driving style of each time period forms a value matrix [ m ]_0(k)，m_0(k-1)，…,m_0(k-n0)]And obtaining the standard deviation of the numerical matrix as the standard deviation v of the steady-state driving style of the current time period_0(k)；

The obtaining of the current driving style according to the driving style recognition results of all the collection moments in the current time period specifically further includes:

if the transient driving style and the steady-state driving style in the current time period simultaneously meet the following conditions (1) - (3), determining the current driving style m according to the comparison result of the absolute value of the deviation between the steady-state driving style recognition result and the transient driving style recognition result in the current time period and the preset threshold value_driverA step (2);

condition (1): the number of times that the identified transient or steady-state driving style meets the preset typical working condition is accumulated to be more than or equal to n_t1；

Condition (2): n is continuous_m1N corresponding to each time period_m1Accumulated value m of steady driving style₀The standard deviation of the formed vector is less than or equal to m_t1；

Condition (1): n is continuous_v1N corresponding to each time period_v1Standard deviation v of steady-state driving style₀V is less than or equal to 80% of the value of the formed vector_t1；

Wherein n is_t1、n_m1、m_t1、n_v1、v_t1Are all preset values.

7. The method for adjusting the output torque between the driving axles of the vehicle according to claim 1, wherein the method for periodically calculating the tire force of the front axle and the tire force of the rear axle in the current period of the vehicle according to the preset vehicle model and the relationship between the tire force of the front axle and the tire force of the rear axle when the four-wheel drive control of the vehicle is started, and determining the safety boundary of the tire force of the front axle and the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle specifically comprises:

periodically sampling and acquiring the corner, longitudinal acceleration, lateral acceleration and yaw angular acceleration of a front wheel of the vehicle;

calculating the longitudinal force and the lateral force of the front axle tire and the rear axle tire by calculating the front axle tire and the rear axle tire according to the corner, the longitudinal acceleration, the lateral acceleration, the yaw angular acceleration, the linear three-degree-of-freedom vehicle motion differential equation and the relationship between the longitudinal force of the front axle tire and the longitudinal force of the rear axle tire of the vehicle;

calculating the vertical force of the front axle tire and the rear axle tire according to the longitudinal force and the lateral force of the front axle tire and the rear axle tire;

and calculating the safety boundary of the tire force of the front axle and the rear axle according to the vertical force of the tire of the front axle and the rear axle.

8. The method according to claim 7, wherein the linear three-degree-of-freedom differential equation of vehicle motion is expressed by the following expression:

wherein, F_{x_f}、F_{x_r}、F_{y_f}、F_{y_r}Respectively the longitudinal force of the front axle tire, the longitudinal force of the rear axle tire, the lateral force of the front axle tire and the lateral force of the rear axle tire, l_fAnd l_rThe distance from the vehicle mass center to the front axle and the distance from the vehicle mass center to the rear axle respectivelyDistance, theta is the front wheel angle, a_xAcceleration along the x-axis of the vehicle at the center of mass of the vehicle, a_yAs the acceleration along the y-axis of the vehicle at the center of mass of the vehicle,yaw angular acceleration of the vehicle, m vehicle mass, I_zIs the moment of inertia of the vehicle about the z-axis;

the relation between the longitudinal force of the vehicle front axle tire and the longitudinal force of the vehicle rear axle tire is shown as the following expression:

F_{x_f}·i_{d_r}-F_{x_r}·i_{d_f}＝0

wherein i_{d_f}And i_{d_r}The percentage of front and rear axle drive torque to total drive torque, respectively.

9. The method of adjusting an output torque between drive shafts of a vehicle according to claim 7, wherein vertical forces of the front and rear tires are calculated from longitudinal and lateral forces of the front and rear tires as expressed by the following expressions:

wherein the content of the first and second substances,vertical force of front axle tire, F_{x_f}Longitudinal force of the front and rear axle tires, F_{y_f}Is the lateral force of the rear axle tire,vertical force of rear axle tire, F_{x_r}Longitudinal force of rear axle tires, F_{y_r}A and b are preset constants for the lateral force of the rear axle tire.

10. The method of adjusting an output torque between drive shafts of a vehicle according to claim 7, wherein said calculating a safety margin of the tire force of the front and rear shafts based on the vertical force of the tire of the front and rear shafts includes:

calculating the utilization coefficient of the tire force of the front axle and the rear axle according to the following expression:

wherein the content of the first and second substances,is the vertical force of the front axle tire,is the vertical force, eta, of the rear axle tire_fCoefficient of utilization of front axle tire force, η_rThe utilization coefficient of the tire force of the rear axle;

and obtaining the safety boundary of the tire force of the front axle and the rear axle according to the calculated utilization coefficient of the tire force of the front axle and the rear axle.

11. The method for adjusting the output torque between the driving shafts of the vehicle according to claim 1, wherein a corresponding safety boundary threshold is determined according to the driving style of the current period, the safety boundaries of the tires of the front and rear shafts of the current period are respectively compared with the safety boundary threshold, and whether a four-wheel drive control system is used for driving control is determined according to the comparison result so as to adjust the output torque between the driving shafts, and specifically comprises the following steps:

determining a safety boundary threshold corresponding to the driving style according to the driving style of the current period;

comparing the safety boundaries of the front axle tire and the rear axle tire in the current period and the safety boundaries of the front axle tire and the rear axle tire in the previous period with the safety boundary threshold respectively, and determining a state value Af _ flag of the safety boundaries of the front axle tire and a state value Ar _ flag of the safety boundaries of the rear axle tire according to the comparison result; the state values Af _ flag and Ar _ flag are 0 or 1, when the state values Af _ flag and Ar _ flag are 1, the corresponding safety boundary is low, and when the state values Af _ flag and Ar _ flag are 0, the corresponding safety boundary is high;

and determining a corresponding torque adjustment strategy according to the state values Af _ flag and Ar _ flag, and adjusting the output torque between the driving shafts according to the torque adjustment strategy.

12. The vehicle inter-drive-axle output torque adjustment method according to claim 11, characterized in that the safety margin threshold includes Af_th1、Af_th2、Ar_th1、Ar_th2，Af_th1<0<Af_th2，Ar_th1<0<Ar_th2；

The determining of the state value Af _ flag of the safety boundary of the front axle tire and the state value Ar _ flag of the safety boundary of the rear axle tire according to the comparison result specifically comprises the following steps:

the initial value of Af _ flag is 0; if the safety margin eta of the front axle tyre of the previous period_{t_f}Less than a threshold Af_th2And safety margin eta of front axle tires of the current cycle_{t_f}Greater than a threshold value Af_th2If yes, setting Af _ flag to 0; if the safety margin eta of the front axle tyre of the previous period_{t_f}Greater than a threshold value Af_th1And safety margin eta of front axle tires of the current cycle_{t_f}Less than a threshold Af_th1If yes, setting Af _ flag to be 1; otherwise, the Af _ flag keeps the value of the previous period unchanged;

the initial value of Ar _ flag is 0; if the front axle tire safety boundary eta of the previous period_{t_r}Less than a threshold Ar_th2And front axle tire safety margin η of the current cycle_{t_r}Greater than a threshold value Ar_th2If the value is equal to the value Ar _ flag, Ar _ flag is set to 0; if the front axle tire safety boundary eta of the previous period_{t_r}Greater than a threshold value Ar_th1And front axle tire safety margin η of the current cycle_{t_r}Less than a threshold Ar_th1If the value of Ar _ flag is 1; otherwise, Ar _ flag keeps the value of the last period unchanged.

13. The method for adjusting the output torque between the drive shafts of the vehicle according to claim 12, wherein determining the safety margin threshold corresponding to the driving style according to the driving style of the current cycle specifically comprises:

Af_th1＝-x1×m_driver–x2

Ar_th1＝-x1×m_driver–x2

wherein m is_driverFor driving style, x1, x2, Af_th2、Ar_th2Are all preset constant values.

14. The method for adjusting the output torque between the drive shafts of the vehicle according to claim 12, wherein a corresponding torque adjustment strategy is determined according to the state values Af _ flag and Ar _ flag, and the output torque between the drive shafts is adjusted according to the torque adjustment strategy, specifically comprising:

if Af _ flag is equal to 0 and Ar _ flag is equal to 0, detecting the yaw rate and the steering wheel angle speed of the vehicle in real time, and when the ratio of the yaw rate to the steering wheel angle is lower than a threshold value kappa at a certain speed_th1Starting the four-wheel drive control system to intervene and continuously control until the proportion of the yaw angular velocity of the vehicle to the steering wheel angle is higher than a threshold value kappa at a certain vehicle speed_th2When the system is in use, the four-wheel drive control system exits;

if Af _ flag is equal to 1 and Ar _ flag is equal to 0, the four-wheel drive control system continuously controls to adjust the driving torque of the front and rear shafts until Af _ flag is equal to 0 or Ar _ flag is equal to 1, and the four-wheel drive control system exits;

if Af _ flag is equal to 0 and Ar _ flag is equal to 1, immediately closing the four-wheel drive control system and stopping adjusting the driving torque of the front shaft and the rear shaft;

and if Af _ flag is equal to 1 and Ar _ flag is equal to 1, keeping the control strategy of the four-wheel drive control system in the previous period unchanged.

15. The method according to claim 14, wherein a corresponding torque adjustment strategy is determined according to the state values Af _ flag and Ar _ flag, and the inter-drive-shaft output torque is adjusted according to the torque adjustment strategy, and specifically further comprising:

determining a corresponding threshold value kappa according to the driving style of the current period_th1And kappa_th2(ii) a Wherein the more aggressive the driving style the threshold k is_th1And kappa_th2The lower the value of (k), the more robust the driving style is_th1And kappa_th2The higher the value of (c).

16. A vehicle inter-drive-shaft output torque adjustment system for implementing the vehicle inter-drive-shaft output torque adjustment method according to any one of claims 1 to 15, characterized by comprising:

the driving style determining unit is used for periodically obtaining the driving style of the vehicle according to the vehicle speed and the longitudinal acceleration of the vehicle, and the driving style is represented by numerical values;

the safety boundary calculation unit is used for periodically calculating the tire force of the front axle and the tire force of the rear axle in the current period of the vehicle according to a preset vehicle model and the relationship between the longitudinal force of the front axle tire and the longitudinal force of the rear axle tire when the four-wheel drive control is started by the vehicle, and determining the safety boundary of the tire force of the front axle and the safety boundary of the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle; and

and the driving torque adjusting unit is used for determining a corresponding safety boundary threshold according to the driving style of the current period, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period with the safety boundary threshold respectively, and determining whether a four-wheel drive control system is started to carry out driving control according to the comparison result so as to adjust the output torque between the driving shafts.

17. A control apparatus characterized by the vehicle inter-drive shaft output torque adjustment system according to claim 16; or a memory and a processor, the memory having stored therein computer readable instructions which, when executed by the processor, cause the processor to perform the steps of the vehicle inter-drive axle output torque adjustment method according to any one of claims 1-15.

Technical Field

The invention relates to the technical field of vehicle engine control, in particular to a method, a system and control equipment for adjusting output torque between vehicle driving shafts.

Background

The existing non-full-time four-wheel drive control system has certain limitations, which are mainly embodied in that the control mode is single (for example, a fixed inter-axle torque distribution is adopted) or the manual adjustment is required by a driver (for example, multiple driving modes correspond to multiple inter-axle torque distributions, but the manual adjustment is required by setting the driving modes by the driver).

Different drivers have different requirements on insufficient or excessive steering characteristics of the vehicle under different working conditions, and a fixed or multiple steering characteristic adjusting mode which needs manual selection is difficult to meet the use requirements under different road conditions. Although a professional driver can adjust the center of mass through acceleration and deceleration control, change the vertical load of each driving wheel to adjust the lateral rigidity of each wheel, and further adjust the steering characteristic of the vehicle, the driver needs to be familiar with the dynamic characteristic of the vehicle and have enough experience and operation skill, and the steering characteristic of the vehicle is not strict for a general driver.

The four-wheel drive control system of the vehicle adjusts the output torque between the driving shafts, and the steering characteristic of the vehicle and the adjustment of the lateral safety boundary of the vehicle are almost generated simultaneously, but the existing four-wheel drive control system of the vehicle is usually calibrated to meet the requirement of the lateral safety boundary of the vehicle. Therefore, the lateral boundary of the vehicle is met, and when the vehicle has the steering characteristic adjustment requirement, the vehicle four-wheel drive control system cannot intervene, so that the control requirement of a driver on driving at a curve cannot be fully met; further, the steering characteristic adjustment of the vehicle is not adjusted in accordance with the change in the style of the driver, thereby reducing the driving pleasure and increasing the operation load.

Disclosure of Invention

The invention aims to provide a method and a system for adjusting output torque between driving shafts of a vehicle, control equipment and the vehicle, so as to adjust the output torque between the driving shafts according to the driving style of a driver.

An embodiment of the invention provides a method for adjusting output torque between vehicle driving shafts, which comprises the following steps:

periodically obtaining the driving style of the vehicle according to the speed and the longitudinal acceleration of the vehicle, wherein the driving style is represented by numerical values;

periodically calculating the tire force of a front axle and a rear axle of the vehicle in the current period according to a preset vehicle model and the relationship between the longitudinal force of the tire of the front axle and the longitudinal force of the tire of the rear axle when the four-wheel drive control is started by the vehicle, and determining the safety boundary of the tire force of the front axle and the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle;

and determining corresponding safety boundary thresholds according to the driving style of the current period, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period with the safety boundary thresholds respectively, and determining whether a four-wheel drive control system is started to carry out drive control according to a comparison result so as to adjust the output torque between the driving axles.

An embodiment of the present invention further provides a system for adjusting an output torque between vehicle drive shafts, including:

the driving style determining unit is used for periodically obtaining the driving style of the vehicle according to the vehicle speed and the longitudinal acceleration of the vehicle, and the driving style is represented by numerical values;

the safety boundary calculation unit is used for periodically calculating the tire force of the front axle and the tire force of the rear axle in the current period of the vehicle according to a preset vehicle model and the relationship between the longitudinal force of the front axle tire and the longitudinal force of the rear axle tire when the four-wheel drive control is started by the vehicle, and determining the safety boundary of the tire force of the front axle and the safety boundary of the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle; and

and the driving torque adjusting unit is used for determining a corresponding safety boundary threshold according to the driving style of the current period, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period with the safety boundary threshold respectively, and determining whether a four-wheel drive control system is started to carry out driving control according to the comparison result so as to adjust the output torque between the driving shafts.

An embodiment of the present invention also provides a control apparatus, the vehicle inter-drive-shaft output torque adjustment system according to the above embodiment; or a memory and a processor, wherein the memory stores computer readable instructions, and the computer readable instructions, when executed by the processor, cause the processor to execute the steps of the vehicle driving inter-axle output torque adjusting method according to the above embodiment.

The above embodiment scheme has the following beneficial effects:

aiming at the limitation of a torque distribution adjustment mode between driving shafts of the existing vehicle four-wheel drive control system, an adjustment technical scheme of output torque between the driving shafts of the vehicle based on driving style identification is provided, and according to the driving style of an identified driver periodically, and in combination with a safety boundary of tire force of a front shaft and a rear shaft calculated according to a preset vehicle model and the relationship between the longitudinal force of a front shaft tire and the longitudinal force of a rear shaft tire when the vehicle starts four-wheel drive control, a driving shaft torque adjustment strategy corresponding to the driving style is adopted, so that drivers of different types can obtain better driving experience under respective styles, the vehicle can be kept in a stable state range, the requirements of the drivers of different types can be further met, the driving pleasure of driving of the vehicles is improved, and the operation load of a curve is reduced.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by the practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of a method for adjusting an output torque between driving axles of a vehicle according to an embodiment of the present invention.

FIG. 2 is a block diagram of a system for adjusting the output torque between the drive axles of a vehicle according to another embodiment of the present invention.

Detailed Description

Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers can indicate functionally identical or similar elements. While the various aspects of the embodiments are presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

In addition, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some instances, well known means have not been described in detail so as not to obscure the present invention.

An embodiment of the invention provides a method for adjusting output torque between vehicle driving shafts, which is suitable for an incomplete-time four-wheel-drive vehicle, wherein the incomplete-time four-wheel-drive vehicle refers to a vehicle which is driven by a front shaft (a main driving shaft is the front shaft) in general and driven by the front shaft and a rear shaft simultaneously (a secondary driving shaft is the rear shaft) when a four-wheel-drive control system needs to intervene when road surface trafficability is poor or vehicle stability changes.

Referring to fig. 1, the method includes the following steps S101 to S103:

s101, periodically obtaining the driving style of the vehicle according to the speed and the longitudinal acceleration of the vehicle, wherein the driving style is represented by numerical values;

specifically, real-time recognition of the driving style is a precondition for adjusting the vehicle dynamic response, and there are many methods for acquiring the driving style in real time at present. Generally, the more robust the style of driver, the more consistent the dynamics of the vehicle it controls. For example, when the vehicle is driven in a straight line, the vehicle speed controlled by a steady driver changes slowly, the acceleration changes slightly, and the vehicle body posture shake caused by the change is also small. And the more aggressive the style of driver, the more discrete the dynamics of the vehicle it controls. For example, when driving straight, the speed controlled by a driver with an aggressive style changes rapidly, and usually the driver drives at a high speed, but the driver is limited by road conditions, such as speed limit, other traffic participants, and the like, and often needs to accelerate and decelerate frequently, so that the acceleration change is large, and the posture of the vehicle body shakes greatly. Therefore, the acceleration change can be obtained according to the vehicle speed and the longitudinal acceleration during the running process of the vehicle, and whether the current driving style is biased or stable is judged according to the acceleration change.

It should be noted that any driving style method can be adopted for recognition in the present embodiment, and therefore, the driving style recognition means is not specifically limited in the present embodiment.

It can be understood that the driving style identification step is performed periodically, that is, the driving style is continuously updated according to the driving condition of the driver during the whole driving process, so as to reflect the driving style of the driver more truly and accurately.

Step S102, periodically calculating the tire force of a front axle and a rear axle of the vehicle in the current period according to a preset vehicle model and the relationship between the longitudinal force of the tire of the front axle and the longitudinal force of the tire of the rear axle when the four-wheel drive control is started, and determining the safety boundary of the tire force of the front axle and the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle;

specifically, a corresponding vehicle motion differential equation can be determined according to a preset vehicle model, wherein the vehicle motion differential equation represents the relationship between parameters such as the front axle tire force, the rear axle tire force, the front wheel corner, the vehicle acceleration, the yaw angular acceleration, the vehicle mass, the vehicle rotational inertia and the like of the vehicle, therefore, the front axle tire force and the rear axle tire force of the vehicle can be calculated by acquiring other dynamic parameters such as the front wheel corner and the like of the vehicle in real time based on the relationship between the front axle tire longitudinal force and the rear axle tire longitudinal force when the four-wheel drive control is started by the vehicle, and further, the safety boundary of the corresponding front axle tire force and the corresponding rear axle tire force can be determined according to the front axle tire force and the rear axle tire force.

Step S103, determining corresponding safety boundary threshold values according to the driving style of the current period, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period with the safety boundary threshold values respectively, and determining whether a four-wheel drive control system is started to carry out drive control according to the comparison result so as to adjust the output torque between the driving axles.

Specifically, the safety margin threshold corresponds to a driving style, and may be calibrated in advance through a real vehicle test.

The embodiment method provides an adjustment technical scheme of the output torque between the driving shafts of the vehicle based on the driving style identification aiming at the limitation of the torque distribution adjustment mode between the driving shafts of the existing vehicle four-wheel drive control system, and can periodically combine the safety boundary of the tire force of the front shaft and the tire force of the rear shaft obtained by calculating the relationship between the longitudinal force of the tire of the front shaft and the longitudinal force of the tire of the rear shaft when the vehicle starts the four-wheel drive control according to the driving style of the identified driver and the preset vehicle model, and adopt the torque adjustment strategy between the driving shafts corresponding to the driving style, so that the drivers of different types can obtain better driving experience under the respective styles, the vehicle can be kept in a stable state range, the requirements of the drivers of different types can be further met, the driving pleasure of the driving in curves is improved, and the operation load is reduced

In a specific embodiment, the step S101 specifically includes:

step S201, collecting the speed and the longitudinal acceleration of the vehicle once every preset time, and obtaining the dispersion of the acceleration change of the current time period according to all the speeds and the longitudinal accelerations collected in the current time period; the current time period is a time period from the end to the current acquisition time, and the length delta of the time period is preset;

specifically, the time period length δ for identifying the driving style is taken as a statistical sliding window length, and the statistical sliding window slides forward on the time axis, which is equivalent to sliding the sliding window forward every preset time t₀The vehicle speed and the longitudinal acceleration of the vehicle are collected once, and the acceleration change of the vehicle can be determined according to the vehicle speed and the longitudinal acceleration, so that the acceleration change of the vehicle in the statistical sliding window is counted, and the dispersion of the acceleration change of the current time period can be obtained by calculating the dispersion.

Step S202, comparing the dispersion of the acceleration change in the current time period with a plurality of preset threshold values respectively, and taking the threshold value corresponding to the minimum comparison deviation as the driving style recognition result at the current acquisition moment;

specifically, the output value of the driving style recognition result in the step is a numerical value in the range of [ -1,1], and the closer the numerical value is to 1, the more aggressive the recognized driver style is; the closer the value is to-1, the more robust the identified driver style is. In the embodiment, a plurality of thresholds are preset, for example: the-1, -0.9, -0.8 … … are always increased to 1 by 0.1 increment, namely, 21 thresholds are provided, and when the dispersion of the identified acceleration change is 0.71, the deviation of the comparison with the threshold 0.7 is minimum, so that the driving style identification result output is 0.7.

Step S203, acquiring the driving style recognition results of all the acquisition moments in the current time period, and acquiring the current driving style according to the driving style recognition results of all the acquisition moments in the current time period.

Specifically, as can be seen from steps S201 to S202, the predetermined time t is set to each other₀If the output value of the driving style recognition result is updated once, and the current driving style of the driver is continuously recognized and updated, the number of the output values of the driving style recognition result in the time period of delta is n₁，n₁＝δ/t₀(ii) a That is, step S203 is performed according to n within the current time period₁The current driving style can be obtained by carrying out statistical analysis on the driving style identification result.

In an embodiment, the step S203 specifically includes:

step S301, obtaining a transient driving style recognition result and a steady driving style recognition result of the current time period according to the driving style recognition results of all the acquisition moments in the current time period;

specifically, the transient driving style recognition result is used for indicating the transient driving style of the driver in a short time, and mainly reflecting the change of the current driving condition or scene; the steady-state driving style recognition result is used to indicate the individual long-term driving style of the driver, i.e. the inherent driving tendency.

Step S302, determining the current driving style m according to the comparison result of the absolute value of the deviation between the steady-state driving style recognition result and the transient driving style recognition result of the current time period and a preset threshold value_driver(ii) a Wherein m is_driverExpressed by a numerical value, m_driverThe larger the driving style, the more aggressive m_driverThe smaller, the more robust the driving style.

In a specific embodiment, the transient driving style identification result comprises a transient driving style average value m₀The steady-state driving style recognition result comprises a steady-state driving style average value m₁；

Wherein the average value m of the transient driving style₀The calculation steps are as follows:

setting the current time period as the kth time period, calculating the average value of the driving style identification results of all the acquisition moments in the current time period, and taking the average value as the average value m of the transient driving style of the current time period_1(k)；

Wherein the average value m of the steady-state driving style₀The calculation steps are as follows:

average value m of transient driving style according to current time period_1(k)Calculating a steady-state driving style accumulated value m for a current time period_0(k)(ii) a Wherein m is_0(k)＝α₀×m_1(k)+(1-α₀)×m_0(k-1)，m₀₍₀₎＝m₀₍₁₎＝0，α₀Is a weight coefficient, 0<α₀<1。

Specifically, the weight coefficient α₀Setting according to the characteristics of the vehicle type and the target driving group, and if the vehicle type has a biased motion style, determining alpha₀Larger than the others; if the vehicle type itself is biased to business style, then alpha₀Smaller, usually a₀＝0.5。

In a specific embodiment, the current driving style m is determined according to the comparison result of the absolute value of the deviation between the steady-state driving style recognition result and the transient-state driving style recognition result of the current time period and a preset threshold value_driverThe method specifically comprises the following steps:

if the steady-state driving style accumulated value m of the current time period₀And the average value m of the transient driving style₁Is less than a set threshold m_th1Then the current driving style m_driverIs m₀；

If the steady-state driving style accumulated value m of the current time period₀And the average value m of the transient driving style₁Deviation of (2)Absolute value greater than set threshold m_th1And is less than a set threshold value m_th2Then the current driving style m_driverIs (m)₁+m₀)/2；

If the steady-state driving style accumulated value m of the current time period₀And the average value m of the transient driving style₁Is greater than a set threshold m_th2Then the current driving style m_driverIs m₁。

In a specific embodiment, the transient driving style recognition result further includes a standard deviation v of the transient driving style₁The steady-state driving style recognition result further comprises a steady-state driving style standard deviation v₀；

Wherein the standard deviation v of the transient driving style₁The calculation steps are as follows:

setting the current time period as the kth time period, calculating the standard deviation of the driving style recognition results at all the acquisition moments in the current time period, and taking the standard deviation as the transient driving style standard deviation v of the current time period_1(k)；

Wherein the steady state driving style standard deviation v₀The calculation steps are as follows:

according to the current time period and the top n₀The accumulated value of the steady-state driving style of each time period forms a value matrix [ m ]_0(k),m_0(k-1),…,m_0(k-n0)]And obtaining the standard deviation of the numerical matrix as the standard deviation v of the steady-state driving style of the current time period_0(k)；

The step S302 further includes:

determining whether the vehicle simultaneously satisfies the following conditions (1) - (3) according to the transient driving style and the steady driving style in the current time period;

if the conditions (1) - (3) are met, determining the current driving style m according to the comparison result of the absolute value of the deviation between the steady-state driving style recognition result and the transient driving style recognition result of the current time period and a preset threshold value_driverA step (2);

if the conditions (1) to (3) are not satisfied simultaneously, the operation according to the current time period is not performedDetermining the current driving style m according to the comparison result of the absolute value of the deviation between the steady-state driving style recognition result and the transient driving style recognition result and a preset threshold value_driverA step (2);

wherein, the conditions (1) to (3) are specifically as follows:

condition (1): the number of times that the identified transient or steady-state driving style meets the preset typical working condition is accumulated to be more than or equal to n_t1；

Condition (2): n is continuous_m1N corresponding to each time period_m1Accumulated value m of steady driving style₀The standard deviation of the formed vector is less than or equal to m_t1；

Condition (1): n is continuous_v1N corresponding to each time period_v1Standard deviation v of steady-state driving style₀V is less than or equal to 80% of the value of the formed vector_t1；

Wherein n is_t1、n_m1、m_t1、n_v1、v_t1Are all preset values.

Specifically, the step S101 is divided into two stages, where the first stage includes a transient-state obtained driving style recognition result and a steady-state driving style recognition result, and the ending condition of the first stage is that the above-mentioned 3 conditions are simultaneously satisfied. When the above 3 conditions are simultaneously satisfied, the corresponding current vehicle mileage is the mileage threshold L₁When the vehicle driving mileage L is larger than the driving mileage threshold value L₁Entering the second stage of step S101, namely determining the current driving style m according to the comparison result of the absolute value of the deviation between the steady-state driving style recognition result and the transient driving style recognition result of the current time period and the preset threshold value_driver。

More specifically, the first stage of the step S101 is mainly configured to consider that, within a short driving distance, the judgment event trigger of the driving style recognition is less, the sample of the driving style recognition cannot form a stable and significant statistical characteristic, and more accidental factors may cause more jumps in the steady-state driving style recognition result, and at this time, if the vehicle acceleration is directly adjusted according to the steady-state driving style recognition result, the vehicle steering characteristic may be caused by the jump of the accelerationAnd frequent fluctuations in stability, causing discomfort to the occupant. So that the driving style recognition sample is sufficiently stable and then enters the second stage of step S101. The condition (1) is used for judging whether the number of samples meets the requirement of statistical calculation; the condition (2) is used for judging whether the statistical result is stable; the condition (3) is used for judging the reliability requirement of the statistical result. Wherein, in the first stage of step S101, the current driving style m_driverIs 0.

The style of the driver has already stabilized in the second stage of step S101, e.g., m₀The larger the indication that the driver is a driver with an inherent bias to aggressive driving style, e.g. m₀The smaller, the more likely the driver is to be an inherently driver biased toward a robust driving style; average value m of driving style recognition results if transient state at that time₁Accumulated value m of driving style recognition result with steady state₀The deviation is large, which indicates that the driver deviates from the past relatively stable driving style, and may be that the driver desires to temporarily change the driving style, such as accidental aggressive driving or overtaking acceleration, or may be that the driver needs to temporarily change the driving style due to the working condition, such as having to steadily drive in a congestion state, and after the deviation is greater than the threshold, the weight of the transient driving style identification result is increased to correspond to the temporary driving style change condition of the driver.

In an embodiment, the step S102 specifically includes:

step S401, periodically sampling and acquiring the corner, longitudinal acceleration, lateral acceleration and yaw angular acceleration of the front wheel of the vehicle;

step S402, calculating front axle tires and rear axle tires to obtain longitudinal force and lateral force of the front axle tires and the rear axle tires according to the front wheel corner, longitudinal acceleration, lateral acceleration, yaw angular acceleration, linear three-degree-of-freedom vehicle motion differential equation and the relationship between the longitudinal force of the front axle tires and the longitudinal force of the rear axle tires of the vehicle;

specifically, a linear three-degree-of-freedom vehicle model is used to estimate the front and rear axle tire forces of the vehicle, taking into account the fineness and complexity of the vehicle tire force estimation. The three degrees of freedom are longitudinal movement of the vehicle along the x-axis of the vehicle, lateral movement along the y-axis of the vehicle, and yaw movement about the z-axis of the vehicle.

Step S403, calculating vertical forces of the front axle tire and the rear axle tire according to the longitudinal force and the lateral force of the front axle tire and the rear axle tire;

and S404, calculating safety boundaries of the tire forces of the front axle and the rear axle according to the vertical forces of the tires of the front axle and the rear axle.

Through the above steps S401 to S404, the safety margin of the corresponding front and rear axle tire force can be obtained in each cycle.

In a specific embodiment, the linear three-degree-of-freedom vehicle motion differential equation is shown by the following expression:

wherein, F_{x_f}、F_{x_r}、F_{y_f}、F_{y_r}Respectively the longitudinal force of the front axle tire, the longitudinal force of the rear axle tire, the lateral force of the front axle tire and the lateral force of the rear axle tire, l_fAnd l_rRespectively the distance from the center of mass of the vehicle to the front axle and the distance from the center of mass of the vehicle to the rear axle, theta is the corner of the front wheel, a_xAcceleration along the x-axis of the vehicle at the center of mass of the vehicle, a_yAs the acceleration along the y-axis of the vehicle at the center of mass of the vehicle,yaw angular acceleration of the vehicle, m vehicle mass, I_zIs the moment of inertia of the vehicle about the z-axis;

the relation between the longitudinal force of the vehicle front axle tire and the longitudinal force of the vehicle rear axle tire is shown as the following expression:

F_{x_f}·i_{d_r}-F_{x_r}·i_{d_f}＝0 (2)

wherein i_{d_f}And i_{d_r}The percentage of the front shaft driving torque and the rear shaft driving torque in the total driving torque is respectively; for example, when the front-rear drive torque distribution of the vehicle is 70:30, i_{d_f}＝70％、i_{d_r}＝30％。

In a specific embodiment, the calculation process of step S403 is specifically shown by the following expression:

wherein the content of the first and second substances,vertical force of front axle tire, F_{x_f}Longitudinal force of the front and rear axle tires, F_{y_f}Is the lateral force of the rear axle tire,vertical force of rear axle tire, F_{x_r}Longitudinal force of rear axle tires, F_{y_r}A and b are preset constants for the lateral force of the rear axle tire.

Specifically, from equations (1) and (2), the following system of equations can be obtained:

AX＝Y (4)

wherein the content of the first and second substances,

the longitudinal force and the lateral force of the tire on the front and rear axes can be solved and calculated by the equation set (3).

According to the longitudinal vehicle front and rear wheel grounding point moment balance, an equation set can be obtained:

wherein, F_{z_f}And F_{z_r}The vertical loads of the tires of the front axle and the rear axle are respectively, and h is the height of the mass center of the vehicle.

The tire vertical forces of the front axle and the rear axle of the vehicle can be calculated by the equation set (4).

From the equation set (3) and the equation set (4), the longitudinal force, the lateral force and the vertical force of the front and rear axle tires can be calculated.

According to the theory of the tire force friction ellipse, the maximum longitudinal force F which can be provided by the vehicle tire_{x_max}And maximum lateral force F_{y_max}The following relationship is established with the current vertical force of the tire within a certain range:

in the formula, a and b are the proportionality coefficients of the tire force friction ellipse, and are obtained by testing and calibrating according to different tire types, patterns, inflation pressure and the like.

Respectively utilizing the longitudinal force and the lateral force of the front axle and the longitudinal force and the lateral force of the rear axle to calculate the vertical force utilized by the front axle and the rear axle tires at the current momentEquation set (3) can be obtained.

In a specific embodiment, the step S404 includes:

calculating the utilization coefficient of the tire force of the front axle and the rear axle according to the following expression:

wherein the content of the first and second substances,is the vertical force of the front axle tire,is the vertical force, eta, of the rear axle tire_fCoefficient of utilization of front axle tire force, η_rThe utilization coefficient of the tire force of the rear axle;

and obtaining the safety boundary of the tire force of the front axle and the rear axle according to the calculated utilization coefficient of the tire force of the front axle and the rear axle.

In order to ensure that a certain tire force allowance is met in emergency working conditions, the tire force utilization coefficient facing common consumers is smaller than a set safety threshold eta_tSafety threshold η at the present moment_tCoefficient of utilization of tire force with front and rear axles eta_f、η_rDifference of [ ] n_{t_f}、η_{t_r}This is the safe boundary for the front and rear axle tire forces at the current vehicle state.

The safety boundary is a positive value, the vehicle state tends to be stable under the condition that the safety boundary is larger, and the tire force has enough allowance to deal with the operation under the emergency working condition; if the safety margin value is negative and smaller, the vehicle state tends to be unstable, and if an emergency situation occurs, the tire force has no margin for coping with the situation. The four-wheel drive control system of the vehicle can control the longitudinal force of the tires of the front and rear shafts by controlling the driving torque of the front and rear shafts, further adjust the vertical force utilized by the tires of the front and rear shafts, further adjust the utilization coefficient of the tire force, and further adjust the safety boundary of the tires of the front and rear shafts.

In addition, during wheel driving, the tire side force at the same side deflection angle will decrease as the tire driving force increases. Thus, as the front wheel drive force increases, the slip angle of the front wheels will necessarily increase, which will cause the vehicle to have a tendency to increase understeer, in order to provide the required lateral force; as the rear wheel driving force increases, the slip angle of the rear wheels inevitably increases in order to provide the required slip force, and the increase in slip angle of the rear wheels tends to increase the tendency of the vehicle to oversteer.

Thus, the steering characteristics of the vehicle and the vehicle lateral safety margin can be adjusted by controlling the drive torque ratio of the front and rear drive shafts (adjusting the vehicle four-wheel drive control system). Wherein the safety threshold η_tAnd the adjustment amount of the vehicle steering characteristic, can be adjusted according to different driving styles.

In an embodiment, the step S103 specifically includes:

step S501, determining a safety boundary threshold corresponding to a driving style according to the driving style of a current period;

step S502, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period and the safety boundaries of the front axle tire and the rear axle tire of the previous period with the safety boundary threshold respectively, and determining a state value Af _ flag of the safety boundaries of the front axle tire and a state value Ar _ flag of the safety boundaries of the rear axle tire according to the comparison result; the state values Af _ flag and Ar _ flag are 0 or 1, when the state values Af _ flag and Ar _ flag are 1, the corresponding safety boundary is low, and when the state values Af _ flag and Ar _ flag are 0, the corresponding safety boundary is high;

step S503, determining a corresponding torque adjustment strategy according to the state values Af _ flag and Ar _ flag, and adjusting the output torque between the driving shafts according to the torque adjustment strategy.

In a specific embodiment, the safety margin threshold comprises Af_th1、Af_th2、Ar_th1、Ar_th2，Af_th1<0<Af_th2，Ar_th1<0<Ar_th2；

In this embodiment, the step S502 specifically includes:

the initial value of Af _ flag is 0; if the safety margin eta of the front axle tyre of the previous period_{t_f}Less than a threshold Af_th2And safety margin eta of front axle tires of the current cycle_{t_f}Greater than a threshold value Af_th2If yes, setting Af _ flag to 0; if the safety margin eta of the front axle tyre of the previous period_{t_f}Greater than a threshold value Af_th1And safety margin eta of front axle tires of the current cycle_{t_f}Less than a threshold Af_th1If yes, setting Af _ flag to be 1; otherwise, the Af _ flag keeps the value of the previous period unchanged;

the initial value of Ar _ flag is 0; if the front axle tire safety boundary eta of the previous period_{t_r}Less than a threshold Ar_th2And front axle tire safety margin η of the current cycle_{t_r}Greater than a threshold value Ar_th2If the value is equal to the value Ar _ flag, Ar _ flag is set to 0; if the front axle tire safety boundary eta of the previous period_{t_r}Greater than a threshold value Ar_th1And front axle tire safety margin η of the current cycle_{t_r}Less than a threshold Ar_th1If the value of Ar _ flag is 1; otherwise, Ar _ flag remainsThe value of the previous cycle is unchanged.

In a specific embodiment, the step S501 specifically includes:

Af_th1＝-x1×m_driver–x2

Ar_th1＝-x1×m_driver–x2

wherein m is_driverFor driving style, x1, x2, Af_th2、Ar_th2Are all preset constant values.

Specifically, Af_th2The value of (A) can be scaled to 5%, Af_th1The numerical values of the air pressure and the air pressure are respectively calibrated according to different driving styles, and under the normal condition, the driving style is more aggressive, the numerical value of Afth1 is smaller, and the potential of fully squeezing the adhesive force of the tire is allowed to be aggressive; the more robust the driving style, Af_th1The larger the numerical value of the four-wheel drive control system is, the four-wheel drive control system can be involved to ensure the stability of the vehicle as soon as possible.

Taking a certain model as an example, the safety threshold eta of the front axle tire force utilization coefficient_tSet to 60%, and output m according to the recognition result of the driving style_driverX1, x2 are preferably but not limited to 0.1, calculated as Af_th1The following formula:

Af_th1＝-0.1m_driver-0.1 (8)

recognition result output m such as driving style_driver＝1，Af_th1-20% (coefficient of utilization η of tire force corresponding to front axle)_f80%); recognition result output m such as driving style_driver＝-1，Af_th10 (coefficient of utilization η of tire force corresponding to front axle)_f＝60％)。

Ar_th2The value of (A) can be scaled to 5%, Ar_th1Are respectively calibrated according to different driving styles, and Af_th1Similar to the calibration method, x1 and x2 are preferably but not limited to 0.1, and are not described in detail.

In an embodiment, the step S503 specifically includes:

if Af _ flag is equal to 0 and Ar _ flag is equal to 0, the safety boundary of the front and rear axle tires is high, and the control purpose of the four-wheel drive control system is mainly changed at the momentThe steering characteristic of the vehicle is changed, so that the vehicle meets the driving requirements of drivers with different styles. Since the transfer of the drive torque from the front wheels to the rear wheels increases the tendency of the vehicle to oversteer, in this case a first adjustment strategy is used, namely: detecting the yaw rate and the steering wheel angle of the vehicle in real time, and when the proportion of the yaw rate to the steering wheel angle is detected, the proportion is lower than a threshold value kappa under a certain vehicle speed_th1When the vehicle is in a normal state, the four-wheel drive control system is started to intervene and continuously control, and the excessive steering tendency of the vehicle is increased (namely the proportion of the yaw rate to the steering wheel angle of the vehicle is improved) until the proportion of the yaw rate to the steering wheel angle of the vehicle is higher than a threshold value kappa at a certain vehicle speed_th2When the system is in use, the four-wheel drive control system exits; or when the values of the Af _ flag and the Ar _ flag are changed, adjusting according to the strategy corresponding to the change of the values of the Af _ flag and the Ar _ flag.

If Af _ flag is equal to 1 and Ar _ flag is equal to 0, the safety boundary of the front axle tire is low and the safety boundary of the rear axle tire is high, at this time, the control purpose of the four-wheel drive control system is mainly to change the safety boundaries of the front and rear axles of the vehicle and transfer the driving torque of the front axle to the rear axle according to a fixed ratio so as to reduce the longitudinal force of the front axle tire and further reduce the tire utilization coefficient of the front axle. In the driving torque regulation of the four-wheel-drive control system under the condition, the intervention of a vehicle dynamic control system such as ESC is carried out forcibly without considering the change of the steering characteristic of the vehicle, such as the change of the steering characteristic of the vehicle to an abnormal condition. Therefore, in this case, a second adjustment strategy is adopted, namely: the four-wheel drive control system continues to control to adjust the driving torque of the front and rear shafts until the four-wheel drive control system exits with Af _ flag equal to 0 or Ar _ flag equal to 1.

If Af _ flag is equal to 0 and Ar _ flag is equal to 1, the safety margin of the front axle tire is higher and the safety margin of the rear axle tire is lower, which generally occurs in dangerous working conditions such as tail flicking of the vehicle, the four-wheel drive control system should be immediately turned off, and the driving torque of the rear axle is also given to the front axle to improve the tire force safety margin of the rear axle, in which case, a third adjustment strategy is adopted, that is: and immediately closing the four-wheel drive control system and stopping adjusting the driving torque of the front shaft and the rear shaft.

If Af _ flag is 1 and Ar _ flag is 1, the safety margin for both front and rear axle tires is low, which is typically the case when the vehicle moves sideways on low-adhesion roads, in which case a fourth adjustment strategy is used, namely: and keeping the control strategy of the four-wheel drive control system of the last sampling period unchanged, and avoiding the vehicle from being out of control due to the sudden change of the tire force. For example, if the four-wheel drive control system is already involved at the last moment, the four-wheel drive control system is kept involved until Af _ flag is 0, namely the front wheels have enough safety boundaries to move back to the four-wheel drive control; and if the four-wheel drive control system in the previous sampling period is not involved, keeping the four-wheel drive control system not involved until the values of the Af _ flag and the Ar _ flag are changed, and adjusting according to the strategy corresponding to the change of the values of the Af _ flag and the Ar _ flag.

In particular, the method of the embodiment is suitable for the situation that when the vehicle moves laterally, the intervention of a four-wheel drive system is needed to change the steering characteristic or stability of the vehicle. The four-wheel drive vehicle is characterized in that the ratio of the driving torque output to a rear shaft by a four-wheel drive control system to the driving torque of a front shaft is fixed, and the four-wheel drive vehicle is combined or disconnected through a clutch, so that when the rear shaft is required to be driven, part of the driving torque is output to the rear shaft from the front shaft through the combination of the clutch; when rear axle drive is not required, the clutch is disengaged so that the rear axle becomes the non-driving axle. The driving torque proportion of a four-wheel drive control system to a rear shaft and a front shaft is variable, the driving torque proportion is adjusted through the slip ratio of a clutch, the clutch temperature of the four-wheel drive control system is rapidly increased due to the adjustment mode to cause overheating protection, and more clutches are combined and disconnected to output torque. Therefore, the present embodiment adjusts the duration of the output torque of the four-wheel drive control system by controlling the clutch engagement duration, specifically, as in step S503 above.

In a specific embodiment, the step S503 further includes:

determining a corresponding threshold value kappa according to the driving style of the current period_th1And kappa_th2(ii) a Wherein the more aggressive the driving style, the threshold k_th1And kappa_th2The lower the value of (k), the more robust the driving style, the threshold k_th1And kappa_th2The higher the value of (c).

As shown in fig. 2, an embodiment of the present invention further provides a vehicle inter-drive-shaft output torque adjustment system for performing the steps of the method of the above embodiment, the system comprising:

a driving style determination unit 1 for periodically obtaining a driving style of a vehicle from a vehicle speed and a longitudinal acceleration of the vehicle, the driving style being represented by numerical values;

the safety boundary calculation unit 2 is used for periodically calculating the tire force of the front axle and the tire force of the rear axle in the current period of the vehicle according to a preset vehicle model and the relationship between the longitudinal force of the front axle tire and the longitudinal force of the rear axle tire when the four-wheel drive control is started by the vehicle, and determining the safety boundary of the tire force of the front axle and the tire force of the rear axle according to the tire force of the front axle and the tire force of the rear axle; and

and the driving torque adjusting unit 3 is used for determining a corresponding safety boundary threshold according to the driving style of the current period, comparing the safety boundaries of the front axle tire and the rear axle tire of the current period with the safety boundary threshold respectively, and determining whether a four-wheel drive control system is started to perform driving control according to the comparison result so as to adjust the output torque between the driving shafts.

The above-described system embodiments are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.

It should be noted that the system described in the foregoing embodiment corresponds to the method described in the foregoing embodiment, and therefore, portions of the system described in the foregoing embodiment that are not described in detail can be obtained by referring to the content of the method described in the foregoing embodiment, and details are not described here. It is understood that the contents of the steps of the method described in the above embodiments are the functions of the system of the present embodiment.

Further, the adjustment system for output torque between drive shafts of a vehicle according to the above-described embodiment may be stored in a computer-readable storage medium if it is implemented in the form of a software functional unit and sold or used as a separate product.

A control apparatus according to still another embodiment of the present invention, the vehicle inter-drive-shaft output torque adjustment system according to the above embodiment; or a memory and a processor, wherein the memory stores computer readable instructions, and the computer readable instructions, when executed by the processor, cause the processor to execute the steps of the vehicle driving inter-axle output torque adjusting method according to the above embodiment.

Of course, the control device may also have components such as a wired or wireless network interface, a keyboard, and an input/output interface, so as to perform input/output, and the control device may also include other components for implementing the functions of the device, which are not described herein again.

Illustratively, the computer program may be divided into one or more units, which are stored in the memory and executed by the processor to accomplish the present invention. The one or more units may be a series of computer program instruction segments capable of performing specific functions, which are used to describe the execution of the computer program in the control device.

The Processor may be a Central Processing Unit (CPU), other general purpose Processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf Programmable Gate Array (FPGA) or other Programmable logic device, discrete Gate or transistor logic, discrete hardware components, etc. The general purpose processor may be a microprocessor or the processor may be any conventional processor or the like, the processor being the control center for the control device, with various interfaces and lines connecting the various parts of the overall control device.

The memory may be used for storing the computer program and/or unit, and the processor may implement various functions of the control device by executing or executing the computer program and/or unit stored in the memory and calling data stored in the memory. In addition, the memory may include high speed random access memory, and may also include non-volatile memory, such as a hard disk, a memory, a plug-in hard disk, a Smart Media Card (SMC), a Secure Digital (SD) Card, a Flash memory Card (Flash Card), at least one magnetic disk storage device, a Flash memory device, or other volatile solid state storage device.

Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.