阅读说明：本技术 一种适时四驱控制方法、车辆及存储介质 (Timely four-wheel drive control method, vehicle and storage medium ) 是由 崔金龙 周泽慧 赵洋 刘元治 吴爱彬 孙起春 于 2021-08-31 设计创作，主要内容包括：本发明公开了一种适时四驱控制方法、车辆及存储介质。适时四驱控制方法包括：A、工作模式：根据车辆状态识别和车辆模式选择,确定适时四驱系统工作模式；B、前馈控制：根据车辆工作模式和驾驶员操作信息确定不同四驱系统工作模式对应的前馈扭矩；C、反馈控制：包括横摆反馈控制和滑差反馈控制,根据车辆横摆率偏差和前后轴滑差实现闭环反馈控制,计算出满足车辆操稳和牵引需求的反馈扭矩；D、扭矩限制：根据适时四驱系统工作模式、车辆工作状态和ESP指令,计算适时四驱系统扭矩上限,确保适时四驱系统安全和车辆稳定。本发明能根据车辆行驶状态自动调节适时四驱系统,实现两驱/四驱工作模式,提升车辆牵引性、安全性、经济性和操稳性。(The invention discloses a timely four-wheel drive control method, a vehicle and a storage medium. The timely four-wheel drive control method comprises the following steps: A. the working mode is as follows: determining a working mode of the four-wheel drive system at proper time according to vehicle state identification and vehicle mode selection; B. feed-forward control: determining feedforward torques corresponding to different four-wheel drive system working modes according to the vehicle working mode and the driver operation information; C. feedback control: the method comprises yaw feedback control and slip feedback control, wherein closed-loop feedback control is realized according to the yaw rate deviation of the vehicle and the slip of a front shaft and a rear shaft, and feedback torque meeting the requirements of vehicle stability and traction is calculated; D. and (3) torque limitation: and calculating the torque upper limit of the timely four-wheel drive system according to the working mode of the timely four-wheel drive system, the working state of the vehicle and the ESP instruction, so as to ensure the safety of the timely four-wheel drive system and the stability of the vehicle. The invention can automatically adjust the timely four-wheel drive system according to the running state of the vehicle, realize the two-wheel drive/four-wheel drive working mode and improve the traction, safety, economy and operation stability of the vehicle.)

1. A timely four-wheel drive control method is characterized by comprising the following steps:

A. the working mode is as follows: determining a working mode of the four-wheel drive system at proper time according to vehicle state identification and vehicle mode selection; the vehicle state includes wet road running, slope running and rapid acceleration running; the vehicle mode includes an economy mode, a comfort mode, an automatic mode, a sport mode, an off-road mode, a sand mode, and a snow mode; the working modes of the timely four-wheel drive system comprise a high-efficiency four-wheel drive mode, a motion four-wheel drive mode and a forced four-wheel drive mode;

B. feed-forward control: determining feedforward torques corresponding to different timely four-wheel drive system working modes according to the vehicle working mode and the driver operation information;

C. feedback control: the method comprises yaw feedback control and slip feedback control, wherein closed-loop feedback control is realized according to the yaw rate deviation of the vehicle and the slip of a front shaft and a rear shaft, and feedback torque meeting the requirements of vehicle stability and traction is calculated;

D. and (3) torque limitation: and calculating the torque upper limit of the timely four-wheel drive system according to the working mode of the timely four-wheel drive system, the working state of the vehicle and the ESP instruction, so as to ensure the safety of the timely four-wheel drive system and the stability of the vehicle.

2. The timely four-wheel drive control method according to claim 1, wherein in the step a, the method for judging the vehicle state is as follows:

and (3) judging running on a wet and slippery road surface: when the TCS working flag bit of the vehicle is 1, the wheel is considered to be in a slip state; when the wheels rotate in a sliding mode, the ratio of the current acceleration measurement value to the gravity acceleration is used as a road adhesion coefficient, and when the wheels do not rotate in a sliding mode, the maximum value of the ratio of the current acceleration measurement value to the gravity acceleration and the road adhesion coefficient at the last moment is used as the road adhesion coefficient; when the road adhesion coefficient value is less than 0.3 or the wheels are in a slip state, the vehicle is considered to be in a wet-slippery road driving state;

and (3) judging the slope driving: estimating the running state of the vehicle according to the vehicle ramp signal, and when the absolute value of the ramp signal is more than 10%, determining that the vehicle runs on a ramp;

the rapid acceleration driving state: and judging whether the vehicle is in an acceleration state or not according to the opening degree of the accelerator, and when the development of the accelerator is more than 60%, determining that the vehicle is in a rapid acceleration driving state.

3. The timely four-wheel-drive control method according to claim 1, wherein in the step a, the corresponding relationship between the vehicle working mode and the timely four-wheel-drive system working mode is as follows:

when the vehicle mode is an economic mode, a comfortable mode and an automatic mode, the corresponding timely four-wheel drive system working mode is a high-efficiency four-wheel drive mode;

when the vehicle mode is the motion mode, the corresponding timely four-wheel drive system working mode is the motion four-wheel drive mode;

when the vehicle mode is a cross-country mode, a sand mode and a snow mode, the corresponding working mode of the timely four-wheel drive system is a forced four-wheel drive mode;

in the step A, when the vehicle is detected to be in the wet road running, the slope running and the rapid acceleration running, the working mode of the timely four-wheel drive system is switched to the forced four-wheel drive mode from the high-efficiency four-wheel drive mode or the motion four-wheel drive mode.

4. The timely four-wheel drive control method according to claim 1, wherein in the step B:

in the efficient four-wheel drive mode, the feedforward torque is zero, and the vehicle runs in two-wheel drive;

under the motion four-wheel drive mode, in a straight line driving state, the torque distribution of the front axle and the rear axle is distributed according to 50: 50; in a steering driving state, when the lateral acceleration of the vehicle is less than 0.4g and the steering wheel angle is more than 60 degrees, the torque distribution of the front axle and the rear axle is distributed according to the ratio of 0: 100; when the lateral acceleration of the vehicle is more than 0.4g or the steering wheel rotation angle is less than 60 degrees, distributing the torque of the front axle and the rear axle according to the ratio of 30: 70;

under the forced four-wheel drive mode, the four-wheel drive system is combined with the maximum capacity in due time under the low-speed running working condition that the speed of the vehicle is lower than 5 km/h; the vehicle speed is higher than 5km/h, and the front axle and the rear axle are distributed according to the ratio of 50: 50; under the steering working condition, when the steering wheel rotating angle is smaller than 90 degrees and larger than 30 degrees, the timely four-wheel drive system is arranged according to the following steps that: 70, distributing; when the steering wheel rotating angle is larger than 90 degrees, the timely four-wheel drive system is in accordance with the following 10: 90 are distributed.

5. The timely four-wheel drive control method according to claim 1, wherein in the step C,

the yaw feedback control includes:

calculating a target yaw rate according to the front wheel rotation angle and the vehicle speed of the vehicle

In the formula, gamma_targetIs the target yaw angular velocity, in units rad/s; v. of_xIs the speed of the vehicle in m/s; δ is the front wheel steering angle, in units rad; l is the wheelbase in m;

yaw feedback control torque of T_yaw＝k_P(γ_target-γ_real)；

In the formula, T_yawIs yaw feedback torque, in Nm; k is a radical of_PIs a calibration parameter; gamma ray_realIs the actual measured yaw rate in rad/s.

6. The timely four-wheel drive control method according to claim 1, wherein in the step C,

the slip feedback control comprises slip calculation and slip feedback torque calculation;

the actual slip of the front axle and the rear axle is calculated according to the vehicle speed, the corner of the front wheel and the target slip rate to obtain:

in the formula, v_diffActual slip of the front shaft and the rear shaft is in km/h; v. of_RLThe speed of the left rear wheel is km/h; v. of_RRThe speed of a right rear wheel is km/h; v. of_FLThe wheel speed of the left front wheel is km/h; v. of_FRThe speed of a right front wheel is km/h;

the front and rear axis target slip is calculated as:

in the formula, v_{diff_target}The target slip of the front and rear shafts is in km/h; t is_sumIn Nm for total drive torque; t is_disThe system is a timely four-wheel drive system for transmitting torque in Nm; d_xIs the tire longitudinal drive stiffness, in Nm;

the slip torque is calculated as:

T_vdiff＝k_P(v_diff-v_{diff_target})+k_I∫(v_diff-v_{diff_target})

in the formula, T_vdiffIs slip feedback torque, in Nm; k is a radical of_PAnd k_IThe proportional differential feedback control coefficient is a calibration value;

the target torque for the on-time four-wheel drive system is calculated as:

T_target＝T_mode+T_yaw+T_vdiff

in the formula, T_targetIs the target torque, T, of the four-wheel-drive system in time_modeFeed forward is the feed forward torque in step B.

7. The timely four-wheel drive control method according to claim 1, wherein in the step D, the torque limiting method comprises:

for efficient four-wheel drive, the upper limit of the feedforward torque is 0, and the upper limit of the yaw feedback control torque is 30% of the maximum capacity of the timely four-wheel drive system;

for the motion four-wheel drive mode, the upper limit of the feedforward control torque is 40% of the maximum capacity of the timely four-wheel drive system; the upper torque limit of the yaw feedback control is 60% of the maximum capacity of the timely four-wheel drive system;

for the forced four-wheel drive mode, the upper limit of the feedforward control torque is the maximum capacity of the timely four-wheel drive system, and the upper limit of the yaw feedback control torque is 30% of the maximum capacity of the timely four-wheel drive system.

8. The timely four-wheel drive control method according to claim 1, wherein in the step D, the torque limiting method further comprises:

the upper torque limit of the slip feedback control is the maximum capacity of the timely four-wheel drive system in any mode;

for the sliding and braking working conditions, the torque upper limit of the timely four-wheel drive system is the maximum sliding deceleration torque of the vehicle;

when the rolling radii of the wheels of the vehicle are inconsistent due to tire replacement or tire pressure undervoltage, the upper limit of the feedforward control torque in any four-wheel drive working mode is set to be 0;

when the ESP sends a timely four-wheel drive system torque limiting or disconnection command, the ESP command is responded preferentially;

and when the four-wheel drive system gives an over-temperature alarm in due time, the four-wheel drive is timely disconnected.

9. A vehicle, characterized in that the vehicle comprises:

one or more processors;

a memory for storing one or more programs;

when executed by the one or more processors, cause the one or more processors to implement the timely four-drive control method of any of claims 1-8.

10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the method for timely four-wheel drive control according to any one of claims 1-8.

Technical Field

The invention relates to the technical field of automobiles, in particular to a timely four-wheel drive control method, a vehicle and a storage medium.

Background

The four-wheel drive system can be divided into time-sharing four-wheel drive, timely four-wheel drive and full-time four-wheel drive according to the working principle. The time-sharing four-wheel drive system needs a driver to manually select a four-wheel drive working mode, and the time-sharing four-wheel drive working mode is not suitable for a high-attachment road surface. The full-time four-wheel drive system defaults that the vehicle is always in a working state, and ensures the four-wheel drive performance of the vehicle under any road environment, but the four-wheel drive system has high cost, high oil consumption and heavy weight. The working mode can be selected according to the needs in due time and four-wheel drive, and is reasonable.

At present, a timely four-wheel drive control system basically adopts a control strategy of taking feedforward control as a main strategy and feedback control as an auxiliary strategy, the feedforward sets four-wheel drive transmission torque according to the driving torque of an engine and the steering wheel rotation angle of a driver, and the feedback carries out closed-loop control according to the rotating speed difference of a front shaft and a rear shaft so as to reduce the single-shaft slip phenomenon.

Therefore, it is desirable to provide a timely four-wheel drive control method, a vehicle and a storage medium to solve the above problems.

Disclosure of Invention

The invention provides a timely four-wheel drive control method, a vehicle and a storage medium, which can improve the traction, safety, economy and operation stability of the vehicle.

In order to realize the purpose, the following technical scheme is provided:

a timely four-wheel drive control method comprises the following steps:

A. the working mode is as follows: determining a working mode of the four-wheel drive system at proper time according to vehicle state identification and vehicle mode selection; the vehicle state includes wet road running, slope running and rapid acceleration running; the vehicle mode includes an economy mode, a comfort mode, an automatic mode, a sport mode, an off-road mode, a sand mode, and a snow mode; the working modes of the timely four-wheel drive system comprise a high-efficiency four-wheel drive mode, a motion four-wheel drive mode and a forced four-wheel drive mode;

B. feed-forward control: determining feedforward torques corresponding to different timely four-wheel drive system working modes according to the vehicle working mode and the driver operation information;

C. feedback control: the method comprises yaw feedback control and slip feedback control, wherein closed-loop feedback control is realized according to the yaw rate deviation of the vehicle and the slip of a front shaft and a rear shaft, and feedback torque meeting the requirements of vehicle stability and traction is calculated;

D. and (3) torque limitation: and calculating the torque upper limit of the timely four-wheel drive system according to the working mode of the timely four-wheel drive system, the working state of the vehicle and the ESP instruction, so as to ensure the safety of the timely four-wheel drive system and the stability of the vehicle.

As an alternative to the timely four-wheel drive control method, in step a, the method for determining the vehicle state is:

and (3) judging running on a wet and slippery road surface: when the TCS working flag bit of the vehicle is 1, the wheel is considered to be in a slip state; when the wheels rotate in a sliding mode, the ratio of the current acceleration measurement value to the gravity acceleration is used as a road adhesion coefficient, and when the wheels do not rotate in a sliding mode, the maximum value of the ratio of the current acceleration measurement value to the gravity acceleration and the road adhesion coefficient at the last moment is used as the road adhesion coefficient; when the road adhesion coefficient value is less than 0.3 or the wheels are in a slip state, the vehicle is considered to be in a wet-slippery road driving state;

and (3) judging the slope driving: estimating the running state of the vehicle according to the vehicle ramp signal, and when the absolute value of the ramp signal is more than 10%, determining that the vehicle runs on a ramp;

the rapid acceleration driving state: and judging whether the vehicle is in an acceleration state or not according to the opening degree of the accelerator, and when the development of the accelerator is more than 60%, determining that the vehicle is in a rapid acceleration driving state.

As an alternative of the timely four-wheel drive control method, in step a, the corresponding relationship between the vehicle operating mode and the timely four-wheel drive system operating mode is as follows:

when the vehicle mode is an economic mode, a comfortable mode and an automatic mode, the corresponding timely four-wheel drive system working mode is a high-efficiency four-wheel drive mode;

when the vehicle mode is the motion mode, the corresponding timely four-wheel drive system working mode is the motion four-wheel drive mode;

when the vehicle mode is a cross-country mode, a sand mode and a snow mode, the corresponding working mode of the timely four-wheel drive system is a forced four-wheel drive mode;

in the step A, when the vehicle is detected to be in the wet road running, the slope running and the rapid acceleration running, the working mode of the timely four-wheel drive system is switched to the forced four-wheel drive mode from the high-efficiency four-wheel drive mode or the motion four-wheel drive mode.

As an alternative to the timely four-wheel drive control method, in the step B:

in the efficient four-wheel drive mode, the feedforward torque is zero, and the vehicle runs in two-wheel drive;

under the motion four-wheel drive mode, in a straight line driving state, the torque distribution of the front axle and the rear axle is distributed according to 50: 50; in a steering driving state, when the lateral acceleration of the vehicle is less than 0.4g and the steering wheel angle is more than 60 degrees, the torque distribution of the front axle and the rear axle is distributed according to the ratio of 0: 100; when the lateral acceleration of the vehicle is more than 0.4g or the steering wheel rotation angle is less than 60 degrees, distributing the torque of the front axle and the rear axle according to the ratio of 30: 70;

under the forced four-wheel drive mode, the four-wheel drive system is combined with the maximum capacity in due time under the low-speed running working condition that the speed of the vehicle is lower than 5 km/h; the vehicle speed is higher than 5km/h, and the front axle and the rear axle are distributed according to the ratio of 50: 50; under the steering working condition, when the steering wheel rotating angle is smaller than 90 degrees and larger than 30 degrees, the timely four-wheel drive system is arranged according to the following steps that: 70, distributing; when the steering wheel rotating angle is larger than 90 degrees, the timely four-wheel drive system is in accordance with the following 10: 90 are distributed.

As an alternative to the timely four-wheel drive control method described above, in step C,

the yaw feedback control includes:

calculating a target yaw rate according to the front wheel rotation angle and the vehicle speed of the vehicle

In the formula, gamma_targetIs the target yaw angular velocity, in units rad/s; v. of_xIs the speed of the vehicle in m/s; δ is the front wheel steering angle, in units rad; l is the wheelbase in m;

yaw feedback control torque of T_yaw＝k_P(γ_target-γ_real)；

In the formula, T_yawIs yaw feedback torque, in Nm; k is a radical of_PIs a calibration parameter; gamma ray_realIs the actual measured yaw rate in rad/s.

As an alternative to the timely four-wheel drive control method described above, in step C,

the slip feedback control comprises slip calculation and slip feedback torque calculation;

the actual slip of the front axle and the rear axle is calculated according to the vehicle speed, the corner of the front wheel and the target slip rate to obtain:

in the formula, v_diffActual slip of the front shaft and the rear shaft is in km/h; v. of_RLThe speed of the left rear wheel is km/h; v. of_RRThe speed of a right rear wheel is km/h; v. of_FLThe wheel speed of the left front wheel is km/h; v. of_FRThe speed of a right front wheel is km/h;

the front and rear axis target slip is calculated as:

in the formula, v_{diff_target}The target slip of the front and rear shafts is in km/h; t is_sumIn Nm for total drive torque; t is_disIs a timely four-wheel drive systemTransmission torque, in Nm; d_xIs the tire longitudinal drive stiffness, in Nm;

the slip torque is calculated as:

T_vdiff＝k_P(v_diff-v_{diff_target})+k_I∫(v_diff-v_{diff_target})

in the formula, T_vdiffIs slip feedback torque, in Nm; k is a radical of_PAnd k_IThe proportional differential feedback control coefficient is a calibration value;

the target torque for the on-time four-wheel drive system is calculated as:

T_target＝T_mode+T_yaw+T_vdiff

in the formula, T_targetIs the target torque, T, of the four-wheel-drive system in time_modeFeed forward is the feed forward torque in step B.

As an alternative to the timely four-wheel drive control method, in step D, the method for limiting the torque includes:

for efficient four-wheel drive, the upper limit of the feedforward torque is 0, and the upper limit of the yaw feedback control torque is 30% of the maximum capacity of the timely four-wheel drive system;

for the motion four-wheel drive mode, the upper limit of the feedforward control torque is 40% of the maximum capacity of the timely four-wheel drive system; the upper torque limit of the yaw feedback control is 60% of the maximum capacity of the timely four-wheel drive system;

for the forced four-wheel drive mode, the upper limit of the feedforward control torque is the maximum capacity of the timely four-wheel drive system, and the upper limit of the yaw feedback control torque is 30% of the maximum capacity of the timely four-wheel drive system.

As an alternative to the timely four-wheel drive control method, in step D, the method for limiting the torque further includes:

the upper torque limit of the slip feedback control is the maximum capacity of the timely four-wheel drive system in any mode;

for the sliding and braking working conditions, the torque upper limit of the timely four-wheel drive system is the maximum sliding deceleration torque of the vehicle;

when the rolling radii of the wheels of the vehicle are inconsistent due to tire replacement or tire pressure undervoltage, the upper limit of the feedforward control torque in any four-wheel drive working mode is set to be 0;

when the ESP sends a timely four-wheel drive system torque limiting or disconnection command, the ESP command is responded preferentially;

and when the four-wheel drive system gives an over-temperature alarm in due time, the four-wheel drive is timely disconnected.

A vehicle, the vehicle comprising:

one or more processors;

a memory for storing one or more programs;

when executed by the one or more processors, cause the one or more processors to implement any of the timely four-drive control methods described above.

A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements any of the above described timely four-wheel-drive control methods.

Compared with the prior art, the invention has the beneficial effects that: the working mode estimates the states of vehicle speed, front and rear axle slip, wheel slip state, road adhesion coefficient and the like according to the information of the vehicle sensor, so as to determine the optimal working mode of the vehicle four-wheel drive system; the feedforward control determines the magnitude of the transmission torque according to the timely four-wheel drive working mode, and the expected four-wheel drive performance of a driver is ensured; the feedback control comprises yaw feedback control and slip feedback control, wherein the yaw feedback control automatically adjusts the four-wheel drive transmission torque of the vehicle according to the insufficient/excessive steering state of the vehicle, and the slip control automatically adjusts the four-wheel drive transmission torque according to the slip states of the front and rear axles; the torque limiting module limits four-wheel drive transmission torque according to vehicle states and external control intervention commands such as an Electronic Stability Program (ESP) and the like, and guarantees vehicle Stability and safety. By utilizing the timely four-wheel drive control method, the vehicle traction, safety, economy and operation stability are obviously improved.

Drawings

FIG. 1 is a simplified flow diagram of a method for controlling a four-wheel-drive system in an embodiment of the present invention;

FIG. 2 is a block flow diagram of a method for controlling a four-wheel drive in due course according to an embodiment of the present invention;

fig. 3 is a table showing the correspondence between the vehicle mode and the timely four-wheel drive system operating mode according to the embodiment of the present invention.

Detailed Description

The following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

The embodiment discloses a timely four-wheel drive control method. Referring to fig. 1 and 2, the timely four-wheel-drive control method includes four major steps, namely, working mode selection, feed-forward control, feedback control and torque limitation. Specifically, the timely four-wheel drive control method comprises the following steps:

s100, working mode: determining a working mode of the four-wheel drive system at proper time according to vehicle state identification and vehicle mode selection; the vehicle state includes wet road running, slope running and rapid acceleration running; the vehicle mode includes an economy mode, a comfort mode, an automatic mode, a sport mode, an off-road mode, a sand mode, and a snow mode; the working modes of the timely four-wheel drive system comprise a high-efficiency four-wheel drive mode, a motion four-wheel drive mode and a forced four-wheel drive mode.

In step S100, the method for determining the vehicle state includes:

and (3) judging running on a wet and slippery road surface: when the working flag bit of a vehicle TCS (Traction Control System) is 1, the wheel is considered to be in a slip state; when the wheels rotate in a sliding mode, the ratio of the current acceleration measurement value to the gravity acceleration is used as a road adhesion coefficient, and when the wheels do not rotate in a sliding mode, the maximum value of the ratio of the current acceleration measurement value to the gravity acceleration and the road adhesion coefficient at the last moment is used as the road adhesion coefficient; when the road adhesion coefficient value is less than 0.3 or the wheels are in a slip state, the vehicle is considered to be in a wet road running state, otherwise, the vehicle is considered to be in a normal state.

And (3) judging the slope driving: and estimating the driving state of the vehicle according to the vehicle ramp signal, and when the absolute value (including an ascending slope and a descending slope) of the ramp signal is more than 10%, considering that the vehicle is in the ramp driving, and otherwise, considering that the vehicle is in the normal state.

The rapid acceleration driving state: and judging whether the vehicle is in an acceleration state or not according to the opening degree of the accelerator, and when the development of the accelerator is more than 60%, considering that the vehicle is in a rapid acceleration running state, otherwise, considering that the vehicle is in a normal state.

The vehicle itself has a plurality of modes that can be selected by the driver, as shown in fig. 3, the corresponding relationship between the vehicle mode and the timely four-wheel drive system working mode is as follows:

when the vehicle mode is an economic mode, a comfortable mode and an automatic mode, the corresponding timely four-wheel drive system working mode is a high-efficiency four-wheel drive mode;

when the vehicle mode is the motion mode, the corresponding timely four-wheel drive system working mode is the motion four-wheel drive mode;

when the vehicle mode is a cross-country mode, a sand mode and a snow mode, the corresponding timely four-wheel drive system working mode is a forced four-wheel drive mode.

In step S100, when it is detected that the vehicle is running on a wet road, running on a slope, and running with rapid acceleration, the timely four-wheel drive system operating mode is switched from the high-efficiency four-wheel drive or motion four-wheel drive mode to the forced four-wheel drive mode.

As shown in fig. 2, the timely four-wheel drive control method further includes the steps of:

s200, feedforward control: and determining the feedforward torques corresponding to the working modes of the four-wheel drive system at different proper times according to the working mode of the vehicle and the operation information of the driver.

In step S200:

in the efficient four-wheel drive mode, the feedforward torque is zero, and the vehicle runs in two-wheel drive;

under the motion four-wheel drive mode, the torque distribution of the front axle and the rear axle is distributed according to 50:50 under the straight-line running state, so that the straight-line acceleration four-wheel drive performance of the vehicle is ensured; in a steering driving state, when the lateral acceleration of the vehicle is less than 0.4g and the steering wheel angle is more than 60 degrees, the torque distribution of the front shaft and the rear shaft is distributed according to the ratio of 0:100 so as to reduce the steering interference of the vehicle; when the lateral acceleration of the vehicle is greater than 0.4g or the steering wheel angle is less than 60 degrees, the torque distribution of the front shaft and the rear shaft is distributed according to the ratio of 30:70, the superior performance of four-wheel drive acceleration of a curve is ensured, and the operation stability of the vehicle is improved;

under the forced four-wheel drive mode, the low-speed running working condition that the speed is lower than 5km/h, and the four-wheel drive system is combined with the maximum capacity in due time to realize the strongest four-wheel drive capacity; the vehicle speed is higher than 5km/h, and the front and rear shafts are distributed according to the ratio of 50:50, so that the linear acceleration four-wheel drive performance of the vehicle is ensured; under the steering working condition, when the steering wheel rotating angle is smaller than 90 degrees and larger than 30 degrees, the timely four-wheel drive system is arranged according to the following steps that: 70, distributing; when the steering wheel rotating angle is larger than 90 degrees, the timely four-wheel drive system is in accordance with the following 10: 90 distribution, certain four-wheel drive traction performance under the steering working condition is ensured, and the steering interference braking phenomenon is reduced.

T for feedforward torque_modeExpressed in Nm, represents the feedforward control torque in the different modes.

As shown in fig. 2, the timely four-wheel drive control method further includes the steps of:

s300, feedback control: the method comprises yaw feedback control and slip feedback control, wherein closed-loop feedback control is realized according to the yaw rate deviation of the vehicle and the slip of a front axle and a rear axle, and feedback torque meeting the requirements of vehicle stability and traction is calculated.

Yaw feedback control is mainly used for under/over steering control of the vehicle under steering conditions. When the vehicle is under-steered, the torque is transferred to the rear axle, and when the vehicle is over-steered, the torque is transferred to the front axle, so that the phenomenon of under-steering/over-steering of the vehicle is improved, and the stability of the vehicle is improved.

The calculation method of the yaw feedback control comprises the following steps:

calculating a target yaw rate according to the front wheel rotation angle and the vehicle speed of the vehicle

In the formula, gamma_targetIs the target yaw angular velocity, in units rad/s; v. of_xIs the speed of the vehicle in m/s; δ is the front wheel steering angle, in units rad; l is the wheelbase in m;

yaw feedback control knobMoment of T_yaw＝k_P(γ_target-γ_real)；

In the formula, T_yawIs yaw feedback torque, in Nm; k is a radical of_PIs a calibration parameter; gamma ray_realIs the actual measured yaw rate in rad/s.

The slip feedback control is mainly used for increasing four-wheel drive transmission torque when a vehicle slips on a single shaft under an acceleration working condition so as to reduce the phenomenon of single shaft slip and improve the four-wheel drive performance of the vehicle.

The slip feedback control includes a slip calculation and a slip feedback torque calculation.

The actual slip of the front axle and the rear axle is calculated according to the vehicle speed, the corner of the front wheel and the target slip rate to obtain:

in the formula, v_diffActual slip of the front shaft and the rear shaft is in km/h; v. of_RLThe speed of the left rear wheel is km/h; v. of_RRThe speed of a right rear wheel is km/h; v. of_FLThe wheel speed of the left front wheel is km/h; v. of_FRThe speed of a right front wheel is km/h;

the front and rear axis target slip is calculated as:

in the formula, v_{diff_target}The target slip of the front and rear shafts is in km/h; t is_sumIn Nm for total drive torque; t is_disThe system is a timely four-wheel drive system for transmitting torque in Nm; d_xIs the tire longitudinal drive stiffness, in Nm;

the slip torque is calculated as:

T_vdiff＝k_P(v_diff-v_{diff_target})+k_I∫(v_diff-v_{diff_target})

in the formula, T_vdiffIs slip feedback torque, in Nm; k is a radical of_PAnd k_IThe proportional differential feedback control coefficient is a calibration value;

the target torque for the on-time four-wheel drive system is calculated as:

T_target＝T_mode+T_yaw+T_vdiff

in the formula, T_targetIs the target torque, T, of the four-wheel-drive system in time_modeThe feedforward is a feedforward torque in step S200.

As shown in fig. 2, the timely four-wheel drive control method further includes the steps of:

s400, torque limitation: and calculating the torque upper limit of the timely four-wheel drive system according to the working mode of the timely four-wheel drive system, the working state of the vehicle and the ESP instruction, so as to ensure the safety of the timely four-wheel drive system and the stability of the vehicle.

The target torque of the timely four-wheel drive system also needs to be limited according to the timely four-wheel drive system working mode, the vehicle working state, ESP and other external requests, so that the safety of the vehicle and the four-wheel drive system is ensured.

For efficient four-wheel drive, the upper limit of the feedforward torque is 0, and the upper limit of the yaw feedback control torque is 30 percent (specifically calibratable) of the maximum capacity of the timely four-wheel drive system, so that the NVH problem under the high-speed steering working condition is reduced;

for the motion four-wheel drive mode, the upper limit of the feedforward control torque is 40 percent (specifically calibratable) of the maximum capacity of the timely four-wheel drive system; the upper torque limit of the yaw feedback control is 60 percent (specifically calibratable) of the maximum capacity of the timely four-wheel drive system so as to ensure the optimal vehicle operation stability and the better four-wheel drive traction performance;

for the forced four-wheel drive mode, the upper limit of the feedforward control torque is the maximum capacity of the timely four-wheel drive system, and the upper limit of the yaw feedback control torque is 30% of the maximum capacity of the timely four-wheel drive system, so that the four-wheel drive traction performance of the vehicle is highlighted.

The upper torque limit of the slip feedback control is the maximum capacity of the timely four-wheel drive system in any mode.

And for the sliding and braking working conditions, the torque upper limit of the timely four-wheel drive system is the maximum sliding deceleration torque of the vehicle.

When the rolling radii of the wheels of the vehicle are inconsistent due to tire replacement or tire pressure undervoltage, the upper limit of the feedforward control torque in any four-wheel drive working mode is set to be 0.

When the ESP sends a timely four-wheel drive system torque limiting or disconnection command, the ESP command should be responded preferentially to ensure the safety and stability of the vehicle.

When the timely four-wheel drive system gives an over-temperature alarm, the four-wheel drive system is timely disconnected, and the safety of a vehicle power system is ensured.

According to the invention, the timely four-wheel drive system can be automatically adjusted according to the running state of the vehicle, a two-wheel drive/four-wheel drive working mode is realized, the two-wheel drive mode is adopted under the normal running working condition to improve the economy of the vehicle, and the four-wheel drive mode is automatically switched under the working conditions of low adhesion, climbing, acceleration, cross country and the like to improve the traction and the operation stability of the vehicle.

According to the invention, the working mode estimates the states of vehicle speed, front and rear axle slip, wheel slip state, road adhesion coefficient and the like according to the information of a vehicle sensor, so that the optimal working mode of the vehicle four-wheel drive system is determined; the feedforward control determines the magnitude of the transmission torque according to the timely four-wheel drive working mode, and the expected four-wheel drive performance of a driver is ensured; the feedback control comprises yaw feedback control and slip feedback control, wherein the yaw feedback control automatically adjusts the four-wheel drive transmission torque of the vehicle according to the insufficient/excessive steering state of the vehicle, and the slip control automatically adjusts the four-wheel drive transmission torque according to the slip states of the front and rear axles; the torque limiting module limits four-wheel drive transmission torque according to vehicle states and external control intervention commands such as an Electronic Stability Program (ESP) and the like, and guarantees vehicle Stability and safety.

Example two

Based on the timely four-wheel drive control method provided by the first embodiment, the invention also provides a timely four-wheel drive control system, which comprises four modules, wherein the four modules are respectively a working mode module, a feedforward control module, a feedback control module and a torque limiting module. The function of each module is as follows:

the working mode module is used for determining the working mode of the four-wheel drive system at the right time according to the vehicle state identification and the vehicle mode selection.

The feedforward control module is used for determining feedforward torques corresponding to different modes according to the working modes of the vehicle and the operation information of the driver.

The feedback control module is used for realizing closed-loop feedback control according to the yaw rate deviation of the vehicle and the slip of the front shaft and the rear shaft, and calculating feedback torque meeting the requirements of vehicle stability and traction.

The torque limiting module is used for calculating the torque upper limit of the timely four-wheel drive system according to the working mode of the vehicle, an ESP (electronic stability program) instruction and the clutch temperature protection control, and ensuring the safety of the timely four-wheel drive system and the stability of the vehicle.

Since the timely four-wheel-drive control system of this embodiment is used to implement the timely four-wheel-drive control method described in the first embodiment, the timely four-wheel-drive control system of this embodiment at least has the beneficial effects of the timely four-wheel-drive control method described in the first embodiment, and details thereof are not repeated here.

EXAMPLE III

The third embodiment of the present invention further provides a vehicle, and the components of the vehicle may include but are not limited to: the vehicle body, one or more processors, memory, and a bus connecting the various system components (including the memory and the processors).

The memory is used as a computer readable storage medium for storing software programs, computer executable programs, and modules, such as program instructions corresponding to the timely four-wheel drive control method in the embodiment of the present invention. The processor executes various functional applications and data processing of the vehicle by running software programs, instructions and modules stored in the memory, namely, the timely four-wheel drive control method is realized.

The memory can mainly comprise a program storage area and a data storage area, wherein the program storage area can store an operating system and an application program required by at least one function; the storage data area may store data created according to the use of the terminal, and the like. Further, the memory may include high speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid state storage device. In some examples, the memory may further include memory remotely located from the processor, and these remote memories may be connected to the vehicle over a network. Examples of such networks include, but are not limited to, the internet, intranets, local area networks, mobile communication networks, and combinations thereof.

Example four

The fourth embodiment of the present invention further provides a computer-readable storage medium, in which a computer program is stored, and when the computer program is executed by a processor, the timely four-drive control method is implemented, where the timely four-drive control method includes the following steps:

s100, working mode: determining a working mode of the four-wheel drive system at proper time according to vehicle state identification and vehicle mode selection; the vehicle state includes wet road running, slope running and rapid acceleration running; the vehicle mode includes an economy mode, a comfort mode, an automatic mode, a sport mode, an off-road mode, a sand mode, and a snow mode; the working modes of the timely four-wheel drive system comprise a high-efficiency four-wheel drive mode, a motion four-wheel drive mode and a forced four-wheel drive mode;

s200, feedforward control: determining feedforward torques corresponding to different timely four-wheel drive system working modes according to the vehicle working mode and the driver operation information;

s300, feedback control: the method comprises yaw feedback control and slip feedback control, wherein closed-loop feedback control is realized according to the yaw rate deviation of the vehicle and the slip of a front shaft and a rear shaft, and feedback torque meeting the requirements of vehicle stability and traction is calculated;

s400, torque limitation: and calculating the torque upper limit of the timely four-wheel drive system according to the working mode of the timely four-wheel drive system, the working state of the vehicle and the ESP instruction, so as to ensure the safety of the timely four-wheel drive system and the stability of the vehicle.

Of course, the computer-readable storage medium provided by the embodiments of the present invention has computer-executable instructions that are not limited to the method operations described above, and may also perform related operations in the timely four-wheel-drive control method provided by any embodiments of the present invention.

From the above description of the embodiments, it is obvious for those skilled in the art that the present invention can be implemented by software and necessary general hardware, and certainly, can also be implemented by hardware, but the former is a better embodiment in many cases. Based on such understanding, the technical solutions of the present invention may be embodied in the form of a software product, which can be stored in a computer-readable storage medium, such as a floppy disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a FLASH Memory (FLASH), a hard disk or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the methods according to the embodiments of the present invention.

In the above embodiment, each included unit and module is only divided according to functional logic, but is not limited to the above division as long as the corresponding function can be realized; in addition, specific names of the functional units are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present invention.

It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.