WO2018121601A1

WO2018121601A1 - Antislip drive control method and apparatus for four-wheel drive electric automobile

Info

Publication number: WO2018121601A1
Application number: PCT/CN2017/118967
Authority: WO
Inventors: 廉玉波; 凌和平; 陈昊; 田果; 魏新铭
Original assignee: 比亚迪股份有限公司
Priority date: 2016-12-29
Filing date: 2017-12-27
Publication date: 2018-07-05
Also published as: CN108248449B; CN108248449A

Abstract

An antislip drive control method for a four-wheel drive electric automobile, comprising the following steps: detecting the wheel speeds of four wheels of an electric automobile and the depth of an accelerator pedal of the electric automobile; estimating the vehicle speed of the electric automobile according to the wheel speeds of the four wheels, and determining a target difference value between the vehicle speed and the wheel speeds according to the vehicle speed; acquiring a required torque of the electric automobile according to the depth of the accelerator pedal; and performing antislip drive control on the wheels corresponding to the wheel speeds according to the wheel speeds, the vehicle speed, the target difference value and the required torque. Also disclosed is an antislip drive control apparatus for the four-wheel drive electric automobile. In practical use, the difference value between the wheel speeds and the vehicle speed may be stabilized in a corresponding target difference value range so as to maintain a suitable slip rate, wherein road surface identification is not required, thereby reducing error caused by road surface identification.

Description

Driving anti-skid control method and device for four-wheel drive electric vehicle

This application claims priority to Chinese Patent Application No. 201611248509.3, filed on Dec. 29, 2016, and entitled "Sliding Control Method and Apparatus for Driving of Four-wheel Drive Electric Vehicles", the entire contents of which are incorporated by reference. In this application.

Technical field

The present application relates to the field of electric vehicle technology, and in particular to a driving anti-skid control method for a four-wheel drive electric vehicle and a driving anti-skid control device for the four-wheel drive electric vehicle.

Background technique

In the related art, a four-wheel hub electric vehicle anti-skid control method is proposed. Specifically, the optimal slip ratio of the wheel is calculated in real time by the road surface recognition algorithm, and the desired rotational speed of the wheel is calculated from the optimal slip ratio of the wheel. Then, according to the state of the wheel, the compensation torque of the wheel is calculated; if the wheel is slipping, the desired wheel speed is taken as the control target, and the compensation torque is calculated by the PI controller of the wheel speed, if the wheel does not slip, the compensation turns The moment is zero; at the same time, the vehicle speed control takes the desired vehicle speed as the control target, and calculates the command torque of the motor according to the vehicle speed controller; finally, the previously added compensation torque and the command torque are added and input into the motor to realize the four-wheel hub. Electric vehicle anti-skid control.

However, the above technique requires road surface recognition first, then calculates the optimal slip ratio, and controls with the optimal slip rate as the target. However, in practical applications, the speed difference of the wheel speed increases with the increase of the vehicle speed during driving, which causes the vehicle to skid and the direction cannot be controlled, and the road surface identification itself also causes a certain error, so the optimal slip ratio It is not practical to control the target.

Summary of the invention

The present invention aims to solve at least one of the technical problems in the above-mentioned techniques to some extent.

To this end, a first object of the present invention is to provide a driving slip control method for a four-wheel drive electric vehicle. The control method can stabilize the difference between the wheel speed and the vehicle speed within the corresponding target difference range, so as to maintain a suitable slip ratio, without the need for road surface recognition, reducing the error caused by the road surface recognition, and being more practical. value.

A second object of the present invention is to provide a drive slip control device for a four-wheel drive electric vehicle.

In order to achieve the above object, a first aspect of the present invention provides a driving slip control method for a four-wheel drive electric vehicle, comprising the steps of: detecting a wheel speed of four wheels of the electric vehicle and a depth of an accelerator pedal; Estimating the vehicle speed of the electric vehicle according to the wheel speeds of the four wheels, determining a target difference between the vehicle speed and the wheel speed according to the vehicle speed, and acquiring a demand torque of the electric vehicle according to the depth of the accelerator pedal Driving the slip control corresponding to the wheel speed according to the wheel speed, the vehicle speed, the target difference value, and the demand torque.

The driving slip prevention method of the four-wheel drive electric vehicle according to the embodiment of the present invention estimates the vehicle speed of the electric vehicle according to the wheel speeds of the four wheels of the electric vehicle, and obtains the target difference between the vehicle speed and the wheel speed according to the vehicle speed, and according to the accelerator pedal The depth acquires the demand torque of the electric vehicle, and then drives the anti-skid control of the wheel corresponding to the wheel speed according to the wheel speed, the vehicle speed, the target difference, and the demand torque. Thereby, the difference between the wheel speed and the vehicle speed can be stabilized within the corresponding target difference range, the appropriate slip ratio can be maintained, and the road surface recognition is not required, the error caused by the road surface recognition is reduced, and the utility model has more practical value. .

In order to achieve the above object, a second aspect of the present invention provides a driving anti-skid control device for a four-wheel drive electric vehicle, comprising: a detecting module for detecting a wheel speed of the electric vehicle and a depth of an accelerator pedal; and an estimating module, Means for estimating a vehicle speed of the electric vehicle according to the wheel speed; determining a module, configured to determine a target difference between the vehicle speed and the wheel speed according to the vehicle speed; and acquiring a module for using the accelerator pedal a depth of the demand torque of the electric vehicle; a control module, the control module being respectively connected to the detection module, the estimation module, the determination module, and the acquisition module, for The vehicle speed, the target difference value, and the demand torque drive the slip control of the wheel corresponding to the wheel speed.

The driving anti-skid control device for the four-wheel drive electric vehicle according to the embodiment of the present invention estimates the vehicle speed of the electric vehicle according to the wheel speed of the four wheels of the electric vehicle through the estimating module, and determines the target difference between the vehicle speed and the wheel speed according to the vehicle speed by the determining module. The value, and the acquisition module acquires the required torque of the electric vehicle according to the depth of the accelerator pedal, and then controls the anti-skid control of the wheel corresponding to the wheel speed according to the wheel speed, the vehicle speed, the target difference and the demand torque through the control module. Thereby, the difference between the wheel speed and the vehicle speed can be stabilized within the corresponding target difference range, the appropriate slip ratio can be maintained, and the road surface recognition is not required, the error caused by the road surface recognition is reduced, and the utility model has more practical value. .

DRAWINGS

The above and/or additional aspects and advantages of the present invention will become apparent and readily understood from

1 is a flow chart of a method for driving slip prevention of a four-wheel drive electric vehicle according to an embodiment of the present invention;

2 is a specific flowchart of step S3 in the method for driving slip prevention of a four-wheel drive electric vehicle according to an embodiment of the present invention;

3 is a schematic diagram showing the principle of a driving slip control method for a four-wheel drive electric vehicle according to an embodiment of the present invention;

4a and 4b are respectively a graph of joint simulation of Carsim and Simulink when the anti-skid function is not activated and the anti-skid function is activated according to an embodiment of the present invention;

5 is a graph of a real vehicle matching test for driving slip control of a four-wheel drive electric vehicle according to an embodiment of the present invention;

6 is a flow chart of a method for driving slip prevention of a four-wheel drive electric vehicle according to another embodiment of the present invention;

7a-7g are schematic views respectively showing road conditions in which an electric vehicle is in accordance with another embodiment of the present invention;

8 is a graph showing actual vehicle test data of an electric vehicle from a low attached road surface to a high attached road surface according to another embodiment of the present invention;

9 is a graph showing actual vehicle test data of an electric vehicle from a high attached road surface to a low attached road surface according to another embodiment of the present invention;

10 is a graph showing actual vehicle test data of an electric vehicle on a facing road surface according to another embodiment of the present invention;

11 is a block diagram showing the structure of a driving slip control device for a four-wheel drive electric vehicle according to an embodiment of the present invention.

detailed description

The embodiments of the present invention are described in detail below, and the examples of the embodiments are illustrated in the drawings, wherein the same or similar reference numerals are used to refer to the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the drawings are intended to be illustrative of the invention and are not to be construed as limiting.

A driving slip control method for a four-wheel drive electric vehicle and a driving anti-skid control device for a four-wheel drive electric vehicle according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

1 is a flow chart of a method for driving slip prevention of a four-wheel drive electric vehicle according to an embodiment of the present invention. As shown in FIG. 1, the driving slip prevention method of the four-wheel drive electric vehicle includes the following steps:

S1, detecting the wheel speed of the four wheels of the electric vehicle and the depth of the accelerator pedal.

In the embodiment of the present invention, the wheel speed of each wheel of the electric vehicle can be detected by a wheel speed sensor mounted on each wheel of the electric vehicle, and the depth of the accelerator pedal can be detected by a displacement sensor mounted on the accelerator pedal. The wheel speed sensor may be, but not limited to, a magnetoelectric wheel speed sensor, a Hall type wheel speed sensor, or the like.

S2, estimating the vehicle speed of the electric vehicle according to the wheel speed of the four wheels, determining the target difference between the vehicle speed and the wheel speed according to the vehicle speed, and obtaining the demand torque of the electric vehicle according to the depth of the accelerator pedal.

Specifically, when estimating the vehicle speed of the electric vehicle based on the wheel speed, (1) the minimum wheel speed method can be employed. When the electric vehicle drives the anti-skid control during driving, since the wheel slips and the wheel speed is greater than the vehicle speed, the minimum wheel speed of the four wheels can be taken as the vehicle speed; (2) the slope method. Through the analysis and processing of a large number of experimental data, the average acceleration that the electric vehicle can achieve on various road surfaces is determined. Based on this, in the process of driving the anti-skid control, the initial vehicle speed entering the driving anti-skid control is determined, and the road surface condition and the driving anti-skid are performed. After the working condition is identified, the acceleration of the electric vehicle is determined, and the speed value is calculated in real time according to the speed formula as the reference vehicle speed; (3) the determination method based on the vehicle system dynamics model. The method is based on the model of the whole vehicle and the tire, and can correct the reference vehicle speed in real time, and can better simulate the actual vehicle speed. It can be understood that the method for estimating the vehicle speed in the embodiment of the present invention is not limited to the above three types.

Further, in the embodiment of the present invention, there is a correspondence relationship between the vehicle speed and the target difference, and when the vehicle speed is greater than 10 km/h, the corresponding target difference ranges from 1.5 km/h to 2 km/h. If the vehicle speed is 15km/h, the corresponding target difference is 2km/h.

Specifically, the target difference value Dv_aim is not fixed and varies with the change of the vehicle speed. When the vehicle speed is low, the target difference value Dv_aim is large, and when the vehicle speed is high, the target difference value Dv_aim is small.

S3, driving the anti-skid control on the wheel corresponding to the wheel speed according to the wheel speed, the vehicle speed, the target difference and the demand torque.

Specifically, for each wheel, as shown in FIG. 2, step S3 further includes the following steps:

S31. Determine whether the difference between the wheel speed and the vehicle speed is greater than the target difference. If yes, go to S32, if no, go to S37.

S32. Control a wheel corresponding to the wheel speed to start the anti-skid function. That is, if the difference between the wheel speed and the vehicle speed is greater than the target difference, the wheel corresponding to the wheel speed is controlled to drive the anti-skid function.

S33. Correct the PI controller corresponding to the driving slip control of the wheel motor according to the wheel speed, the vehicle speed and the target difference, so as to output the corresponding driving anti-skid torque through the corrected PI controller.

In the embodiment of the present invention, the PI controller for driving the slip control corresponding to the wheel motor is based on the conventional classical PI control, and the feedback amount (Dvx-Dv_aim) is introduced to correct the proportional coefficient P and the integral coefficient I. Where Dvx is the difference between the wheel speed and the vehicle speed, and Dv_aim is the target difference corresponding to the current vehicle speed.

Specifically, the integral coefficient I of the PI controller is corrected according to the difference Dvx between the wheel speed and the vehicle speed and the target difference value Dv_aim, and the proportional coefficient of the PI controller is kept unchanged; and further, the difference value Dvx and the target difference value Dv_aim are used. The difference between the two is used as the feedback value of the PI controller, and the corresponding driving anti-skid torque T_value is output.

Among them, the proportional coefficient P can be obtained by simulation and real vehicle debugging, and the integral value of the modified PI controller is proportional to the absolute value of (Dvx–Dv_aim). That is, the larger the absolute value, the larger the integral coefficient; the smaller the absolute value, the smaller the integral coefficient; when the absolute value is 0, the integral coefficient is zero.

Specifically, with (Dvx–Dv_aim) as feedback, multiply by the proportional coefficient to obtain the proportional term P_value; at the same time, integrate the product of (Dvx–Dv_aim) and the integral coefficient to obtain the integral term I_value; then the proportional term and the integral The items are added together to obtain the driving anti-skid torque T_value. If the calculated T_value is less than 0, it is limited to 0, that is, the driving anti-skid process does not give the wheel motor a negative driving torque.

At S34, it is judged whether the driving anti-skid torque is less than the required torque, and if so, the process proceeds to S35, and if not, the process proceeds to S36.

S35. Determine a driving torque of the wheel motor to drive the anti-skid torque. That is, if the driving anti-skid torque is less than the required torque, it is determined that the driving torque of the wheel motor is the driving anti-skid torque.

S36, determining that the driving torque of the wheel motor is the required torque, and controlling the wheel to exit the driving anti-skid function. That is, if the driving anti-skid torque is greater than or equal to the required torque, it is determined that the driving torque of the wheel motor is the required torque, and the wheel is controlled to drive the anti-skid function.

S37, the wheel does not start to drive the anti-skid control function. It can be understood that if the difference between the wheel speed and the vehicle speed is less than or equal to the target difference, the wheel does not start to drive the anti-skid control function, and the driving torque of the wheel motor is the demand torque.

In order to facilitate understanding of the driving slip control method of the four-wheel drive electric vehicle of the above embodiment, it can be illustrated by FIG. 3, FIG. 4a, FIG. 4b, and FIG.

As shown in FIG. 3, the accelerator signal is input through the accelerator pedal of the electric vehicle, and the required torque of the electric vehicle is obtained based on the throttle signal. The wheel speeds of the four wheels of the electric vehicle are detected by the wheel speed sensor, and the vehicle speed of the electric vehicle can be estimated based on the four wheel speeds. Further, the target difference value Dv_aim between the vehicle speed and the wheel speed is obtained based on the vehicle speed, and for each wheel, the difference Dvx between the wheel speed and the vehicle speed can be calculated. When the Dvx is greater than Dv_aim, the wheel is controlled to drive the anti-skid function.

Further, the difference between the difference value Dvx and the target difference value Dv_aim (ie, Dvx-Dv_aim) is calculated, and the proportional coefficient P and the integral coefficient I of the PI controller for driving the slip control corresponding to the wheel motor are corrected according to the difference. . Among them, the proportional coefficient P can be kept constant by simulation and real vehicle debugging, and the integral coefficient I is proportional to the absolute value of (Dvx-Dv_aim), that is, the larger the absolute value, the larger the modified integral coefficient is, absolutely The smaller the value, the smaller the integral coefficient. When the absolute value is 0, the integral coefficient is zero. Further, according to the modified PI controller output driving anti-skid torque, when the driving anti-skid torque is less than the demand torque, the driving torque of the wheel motor is the driving anti-skid torque, and when the driving anti-skid torque is greater than or equal to the required torque, the driving torque of the wheel motor is taken as Demand torque and control the electric car to exit the drive anti-skid function. Thereby, the wheel of the electric vehicle can be stabilized under the driving anti-skid function, the proper slip ratio is maintained, and the ground driving force of the wheel is increased.

As shown in Fig. 4a, when the driver on the low-impedance road slams on the accelerator and the wheel does not start to drive the anti-skid function, the wheel speed of the skid wheel will rise rapidly to the maximum speed of the wheel motor, which cannot be stabilized; as shown in Fig. 4b, After starting the anti-skid function, the wheel can be controlled by the PI controller with a slight slip, so that the wheel speed is gradually stabilized.

As shown in Fig. 5, in the actual vehicle test, the test condition is that the low-impedance full throttle starts, taking into consideration the comfort of the driver and the passenger. It can be seen from Fig. 5 that the driving anti-skid control of the invention has better control effect and the real vehicle experience is good.

The driving anti-skid control method for the four-wheel drive electric vehicle according to the embodiment of the present invention adjusts the driving torque of the wheel motor by the difference between the wheel speed and the vehicle speed as a control target, if the difference between the wheel speed and the vehicle speed does not exceed the target difference For the value, the drive slip control is not performed. If the difference between the wheel speed and the vehicle speed exceeds the target difference, the drive slip control is performed, and the parameters of the PI controller that drives the slip control are corrected, and the corrected PI control is performed. The drive calculates the slip resistance torque, and the drive torque of the control wheel motor takes the smaller of the drive slip torque and the demand torque. Thereby, the difference between the wheel speed and the vehicle speed can be stabilized within the corresponding target difference range, the appropriate slip ratio can be maintained, and the road surface recognition is not required, the error caused by the road surface recognition is reduced, and the utility model has more practical value. .

Based on the above embodiment, in order to better ensure the stability of the electric vehicle and improve the ability of the electric vehicle to escape from the vehicle, it is necessary to consider the road condition of the electric vehicle when driving the electric vehicle.

In an embodiment of the present invention, as shown in FIG. 6, the step S2 further includes determining the road condition of the electric vehicle according to the wheel speed of the four wheels and the vehicle speed of the electric vehicle, and the step S3 further includes: according to the road condition and the demand torque. The four wheels are driven to drive slip control.

In an embodiment of the invention, the road conditions include a low-attached road surface, a docking road surface, and a facing road surface.

Specifically, determining the road condition of the electric vehicle according to the wheel speed and the vehicle speed of the four wheels, including: determining whether the wheel speed of the four wheels is greater than the vehicle speed; if the wheel speeds of the four wheels are both greater than the vehicle speed, determining that the road condition is low If the wheel speed of the front wheel of the electric vehicle is equal to the vehicle speed, and the wheel speed of the rear wheel is greater than the vehicle speed, it is determined that the road condition is the docking road surface, and the electric vehicle enters the high road surface from the low attached road surface; if the front wheel wheel If the speed is greater than the vehicle speed, and the wheel speed of the rear wheel is equal to the vehicle speed, the road condition is determined to be the docking road surface, and the electric vehicle enters the low road surface from the high-attached road surface; if only one wheel has a wheel speed greater than the vehicle speed, and the other three wheels If the wheel speed is equal to the vehicle speed, it is determined that the road condition is a split road surface, and a single wheel is on a low attached road surface; if the wheel speed of one side wheel is greater than the vehicle speed, and the wheel speed of the other side wheel is equal to the vehicle speed, the road condition is determined to be a split road surface. And the same side wheel is on the low attached road surface; if the wheel speed of the one-corner wheel is greater than the vehicle speed, and the wheel speed of the other diagonal wheel is equal to the vehicle speed, it is determined that the road condition is off Surface, and a pair of corner wheels attached in a low road surface; three wheels if the wheel speed is greater than the vehicle speed, the wheel and the other wheel speed is equal to vehicle speed, it is determined that the road is a split road surface, and three wheels are attached to a low road surface.

Further, in one example of the present invention, if the road condition is a low-attached road surface, the four wheels of the electric vehicle are controlled to drive the anti-slip function, and each wheel is individually controlled by the corresponding motor.

Specifically, as shown in FIG. 7a, if the wheel speeds of the four wheels of the electric vehicle are both greater than the vehicle speed, the four wheels simultaneously slip, that is, the electric vehicle is on the low-attach road surface. At this time, all four wheels are controlled to start the anti-skid function, and each wheel is individually controlled by the corresponding motor, and does not affect each other.

In another example of the present invention, as shown in FIG. 7b, if the electric vehicle enters the high-attached road surface from the low-attached road surface, the integral coefficient in the PI controller corresponding to the front wheel motor is respectively increased to increase the front wheel. The anti-skid torque is driven, and when the driving anti-skid torque of the front wheel is greater than or equal to the required torque, the front wheel is controlled to exit the driving anti-skid function.

Specifically, as shown in FIG. 8 , when the electric vehicle is on the low attached road surface, the four wheels start to drive the anti-skid function, the wheel speed is greater than the vehicle speed, and the front wheel enters the high-attached road surface, and the wheel speed is equal to the vehicle speed. At this time, respectively, the integral coefficient I in the PI controller corresponding to the front wheel motor is increased, and the corresponding driving anti-skid torque will rise rapidly. When the driving anti-skid torque is equal to the demand torque, the front wheel is controlled to exit the driving anti-skid function.

It can be understood that there will be a short time before the front wheel enters the high attached road surface, and the rear wheel is still in the low attached road condition. At this time, the front wheel is processed according to the above strategy, and the rear wheel is still in the driving anti-skid function starting state, after waiting After the wheel enters the high-attached road surface, it is also treated according to the above strategy, wherein the front and rear wheels are carried out separately and do not affect each other.

Correspondingly, as shown in FIG. 7c, if the electric vehicle enters the low-attached road surface from the high-attached road surface, the front wheel is controlled to drive the anti-skid function, and the front wheel motor is down-twisted to prevent the front wheel from flying.

Specifically, as shown in FIG. 9, when the wheel enters the low-attached road surface from the high-attached road surface, if the driver's accelerator pedal is deep and the road surface adhesion coefficient is small, the front wheel may suddenly slip. At this time, the front wheel is controlled to immediately start the anti-skid function to reduce the driving torque of the front wheel motor, so that the front wheel does not fly or briefly fly, and the rear wheel does not process when it enters the low road surface, and waits until the rear wheel After entering the low attached road surface, the drive anti-skid function is activated.

In still another example of the present invention, as shown in FIG. 7d, if only one wheel is on the low road surface, it is determined whether the vehicle speed is less than the preset vehicle speed; if the vehicle speed is less than the preset vehicle speed, controlling the wheel starting drive on the low road surface Anti-skid function; if the vehicle speed is greater than or equal to the preset speed, the wheel motor on the high-attachment road coaxial with the wheel on the low-attachment road is limited to prevent the electric vehicle from being deflected, wherein, The driving torque of the wheel motor on the high-attachment road with the wheel coaxial = the driving torque of the wheel motor at the low attached road surface + the preset torque limit value.

In an embodiment of the invention, the preset torque limit difference can be derived by simulation and real vehicle matching.

Specifically, if the vehicle speed is low, it can be regarded as the electric vehicle getting out of the trap or driving at a low speed. At this time, only the wheels on the low road surface are controlled to start the anti-skid function, and the other wheels are not processed, that is, the driving torque of the other wheel motors is required. Torque; if the vehicle speed is high, it is necessary to properly limit the wheel motor on the high-attachment road that is coaxial with the skid wheel (ie, the wheel on the low road surface), so that the electric vehicle does not have side deflection. The torque limiting method is: the driving torque of the wheel motor on the high road surface coaxial with the slipping wheel = the driving torque of the wheel motor on the low attached road surface + the preset limit torque difference value.

In the fourth example of the present invention, as shown in FIG. 7e, if the ipsilateral wheel is on the low road surface, the wheel on the low side road is controlled to start the anti-skid function, and the wheel on the high road surface is limited. In order to prevent the electric vehicle from being deflected, the driving torque of the wheel motor on the high-attached road surface=the corresponding motor torque of the wheel on the low-attached road surface + the preset limit torque difference value.

In the fifth example of the present invention, as shown in FIG. 7f, if the diagonal wheel is on the low road surface, the diagonal wheel that controls the low road surface is activated to drive the anti-skid function, and the diagonal wheel motor is on the low road surface. Make a twist.

Specifically, if the pair of angle wheels are on the low road surface, the diagonal wheel on the low road surface is controlled to start the anti-skid function, so that the motor is down-twisted, and the diagonal wheel on the high road surface does not start to drive the anti-skid function. The corresponding motor does not need to limit the torque and directly respond to the demand torque. It can be understood that there is no side bias in the electric car at this time.

In the sixth example of the present invention, as shown in FIG. 7g, if three wheels are on the low road surface, the three wheels that are controlled on the low road surface are activated to drive the anti-skid function, and determine whether the vehicle speed is less than the preset vehicle speed; If the vehicle speed is less than the preset vehicle speed, the driving torque of the wheel motor that controls the high-attach road surface is the demand torque; if the vehicle speed is greater than or equal to the preset vehicle speed, the wheel motor on the high-attach road surface is limited to prevent the electric vehicle from being deflected. Wherein, the driving torque of the wheel motor on the high road surface = the driving torque of the wheel motor that is on the low road surface and coaxial with the wheel on the high road surface + the preset torque limit difference.

Specifically, if three wheels are on the low road surface, the three wheels are controlled to drive the anti-slip function. If the vehicle speed is low, it can be regarded as electric vehicle running at low speed or vehicle getting out of trouble, and the motor with high attached road surface responds to demand torque; if the vehicle speed is high, in order to prevent the electric vehicle from deflecting, the wheel motor with high attached road surface can be appropriately limited. The torque limiting method is: the driving torque of the wheel motor on the high attached road surface = the driving torque of the wheel motor on the low attached road surface and coaxial with the wheel on the high attached road surface + the preset limit torque difference value.

Specifically, as shown in FIG. 10, when the road condition of the electric vehicle is the off-road surface, the driving torque of the wheel motor with the high road surface and the driving torque of the wheel motor with the low road surface maintain an appropriate torque difference, so that the vehicle does not occur. Sideways.

It should be noted that, for the wheels on the low road surface in the above various examples, in order to maintain a suitable slip ratio, the driving slip control method for a single wheel in the above embodiment can be used between the wheel speed and the vehicle speed. When the difference exceeds the target difference, the driving torque of the wheel motor is PI adjusted according to the difference between the wheel speed and the vehicle speed, and the driving torque control of the wheel is combined with the required torque.

In summary, the driving anti-skid control method of the four-wheel drive electric vehicle determines the road condition of the electric vehicle according to the wheel speed and the vehicle speed of the four wheels of the electric vehicle, and adopts a corresponding control strategy to drive the electric vehicle according to the road condition. Control, and for the wheel that starts the anti-skid control function, when the difference between the wheel speed and the vehicle speed exceeds the target difference, the driving torque of the wheel motor is PI adjusted with the difference between the wheel speed and the vehicle speed as the control target. Therefore, it can be ensured that the wheel does not fly after the electric vehicle starts to drive the anti-skid function, the electric vehicle does not have side deflection, the yaw rate is within a certain range, and the ground adhesion can be utilized to the maximum extent, so that the difference between the wheel speed and the vehicle speed is obtained. Stabilizing within the corresponding target difference range to maintain a suitable slip ratio helps to improve the ability of the electric vehicle to escape.

Figure 11 is a block diagram showing the structure of a driving anti-skid control device for a four-wheel drive electric vehicle according to an embodiment of the present invention. As shown in FIG. 11, the apparatus includes: a detection module 10, an estimation module 20, an acquisition module 30, and a control module 40.

The detection module 10 is configured to detect the wheel speeds of the four wheels of the electric vehicle and the depth of the accelerator pedal. The estimation module 20 is for estimating the vehicle speed of the electric vehicle based on the four wheel speeds. The determining module 30 is configured to determine a target difference between the vehicle speed and the wheel speed according to the vehicle speed. The acquisition module 40 is configured to acquire the required torque of the electric vehicle according to the depth of the accelerator pedal. The control module 50 is respectively connected to the detecting module 10, the estimating module 20, the determining module 30 and the obtaining module 40, and the control module 50 is configured to drive the anti-skid control of the wheel corresponding to the wheel speed according to the wheel speed, the vehicle speed, the target difference value and the demand torque. .

In the embodiment of the present invention, there is a corresponding relationship between the vehicle speed and the target difference, and when the vehicle speed is greater than 10 km/h, the corresponding target difference value ranges from 1.5 km/h to 2 km/h, if the vehicle speed is At 15 km/h, the corresponding target difference is 2 km/h.

In an embodiment of the present invention, the control module 50 is specifically configured to determine whether the difference between the wheel speed and the vehicle speed is greater than a target difference; and when the difference between the wheel speed and the vehicle speed is greater than the target difference, the wheel is controlled. The speed-corresponding wheel starts to drive the anti-skid function, and the PI controller for correcting the driving anti-skid control of the wheel motor according to the wheel speed, the vehicle speed and the target difference is used to output the corresponding driving anti-skid torque through the corrected PI controller; Whether the torque is less than the required torque; determining that the driving torque of the wheel motor is the driving anti-skid torque when the driving anti-skid torque is less than the required torque; and determining the driving torque of the wheel motor as the demanding torque when the driving anti-skid torque is greater than or equal to the required torque, and controlling the wheel Exit the drive slip function.

It can be understood that when the difference between the wheel speed and the vehicle speed is less than or equal to the target difference, the wheel corresponding to the wheel speed does not start to drive the anti-skid function, and the driving torque of the wheel motor is the demand torque.

In one embodiment of the present invention, the PI controller introduces a feedback amount to correct the proportional coefficient P and the integral coefficient I on the basis of the conventional classical PI control.

Specifically, the control module 50 corrects the PI controller for driving the slip control corresponding to the wheel motor according to the wheel speed, the vehicle speed, and the target difference, so as to output the corresponding driving anti-skid torque through the modified PI controller, specifically for using the wheel speed. The difference value Dvx between the vehicle speed and the target difference value Dv_aim corrects the integral coefficient of the PI controller and keeps the proportional coefficient of the PI controller unchanged. And the difference between the difference value Dvx and the target difference value Dv_aim is used as the feedback value of the PI controller, and the corresponding driving anti-skid torque T_value is output.

It should be noted that the specific implementation manner of the driving anti-skid control device for the four-wheel drive electric vehicle according to the embodiment of the present invention can be referred to the specific implementation manner of the driving anti-skid control method for the four-wheel drive electric vehicle according to the above embodiment of the present invention, in order to reduce redundancy. I will not repeat them here.

The driving anti-skid control device for the four-wheel drive electric vehicle according to the embodiment of the present invention performs PI adjustment on the driving torque of the wheel motor with the difference between the wheel speed and the vehicle speed as a control target, if the difference between the wheel speed and the vehicle speed does not exceed the target difference For the value, the drive slip control is not performed. If the difference between the wheel speed and the vehicle speed exceeds the target difference, the drive slip control is performed, and the parameters of the PI controller that drives the slip control are corrected, and the corrected PI control is performed. The drive calculates the slip resistance torque, and the drive torque of the control wheel motor takes the smaller of the drive slip torque and the demand torque. Thereby, the difference between the wheel speed and the vehicle speed can be stabilized within the corresponding target difference range, the appropriate slip ratio can be maintained, and the road surface recognition is not required, the error caused by the road surface recognition is reduced, and the utility model has more practical value. .

Specifically, the determining module 30 is further configured to determine the road condition of the electric vehicle according to the wheel speed and the vehicle speed of the four wheels, wherein the road condition includes a low-attached road surface, a docking road surface, and a facing road surface. The control module 50 is configured to drive the anti-skid control of the four wheels according to the road condition and the demand torque.

In the embodiment of the present invention, the determining module 30 is specifically configured to: determine whether the wheel speed of the four wheels is greater than the vehicle speed of the electric vehicle; and determine that the road condition is a low-attached road surface when the wheel speeds of the four wheels are both greater than the vehicle speed; When the wheel speed of the front wheel of the electric vehicle is equal to the vehicle speed, and the wheel speed of the rear wheel is greater than the vehicle speed, it is determined that the road condition is the docking road surface, and the electric vehicle enters the high attached road surface from the low attached road surface; the wheel speed of the front wheel is greater than the vehicle speed. When the wheel speed of the rear wheel is equal to the vehicle speed, the road condition is determined as the docking road surface, and the electric vehicle enters the low road surface from the high-attached road surface; the wheel speed of only one wheel is greater than the vehicle speed, and the wheel speeds of the other three wheels are equal to When the vehicle speed is determined, the road condition is determined to be the off road surface, and the single wheel is on the low road surface; when the wheel speed of the same side wheel is greater than the vehicle speed, and the wheel speed of the other side wheel is equal to the vehicle speed, the road condition is determined as the off road surface, and the same side The wheel is on the low attached road surface; when the wheel speed of the one-corner wheel is greater than the vehicle speed, and the wheel speed of the other diagonal wheel is equal to the vehicle speed, the road condition is determined to be the off-road surface, and the pair of angle wheels are at Attached pavement; three wheels in the wheel speed is greater than the vehicle speed, the wheel and the other wheel when the vehicle speed is equal to the speed determined for the split road surface, and three wheels are attached to a low road surface.

Further, in an example of the present invention, as shown in FIG. 7a, the control module 50 is specifically configured to control the four wheels of the electric vehicle to start the driving anti-skid function when the road condition is a low-attached road surface, and each wheel is driven by The corresponding motor is controlled separately.

In another example of the present invention, as shown in FIG. 7b, the control module 50 is specifically configured to increase the integral coefficient in the PI controller corresponding to the front wheel motor when the electric vehicle enters the high-attached road surface from the low-attach road surface. In order to increase the corresponding driving anti-skid torque, and control the front wheel to exit the driving anti-skid function when the driving anti-skid torque is greater than or equal to the required torque. As shown in FIG. 7c, when the electric vehicle enters the low-attached road surface from the high-attached road surface, the front wheel is controlled to drive the anti-skid function, and the driving torque of the front wheel motor is respectively reduced to prevent the front wheel from flying.

In still another example of the present invention, as shown in FIG. 7d, the control module 50 is further configured to: determine whether the vehicle speed is less than a preset vehicle speed when only one wheel is on a low road surface; and control when the vehicle speed is less than the preset vehicle speed; The wheel on the low attached road starts to drive the anti-skid function; when the vehicle speed is greater than or equal to the preset speed, the wheel motor on the high-attachment road coaxial with the wheel on the low-attached road is limited to prevent the electric vehicle from being deflected. Among them, the driving torque of the wheel motor on the high side road surface coaxial with the wheel on the low side road surface = the driving torque of the wheel motor on the low side road surface + the preset limit torque difference value.

In an example of the present invention, as shown in FIG. 7e, the control module 50 is further configured to: when the same side wheel is on the low road surface, control the wheel on the low side road to start the driving anti-skid function, and The wheel motor of the road surface is torque-limited to prevent side deflection of the electric vehicle. Among them, the driving torque of the wheel motor on the high-attached road surface=the driving torque of the wheel motor corresponding to the coaxial low-surface road + the preset torque difference value .

In the fifth example of the present invention, as shown in FIG. 7f, the control module 50 is further configured to: when the diagonal wheel is on the low road surface, control the diagonal wheel on the low road surface to start the driving anti-skid function, The diagonal wheel motor with low road surface is down-twisted.

In the sixth example of the present invention, the control module 50 is further configured to: when three wheels are on the low road surface, control the three wheels on the low road surface to start the driving anti-skid function, and determine whether the vehicle speed is less than the preset speed. When the vehicle speed is less than the preset vehicle speed, the driving torque of the wheel motor that controls the high-attached road surface is the demand torque; when the vehicle speed is greater than or equal to the preset vehicle speed, the wheel motor on the high-attached road surface is torque-limited to prevent the electric vehicle from appearing. Side deflection, wherein the driving torque of the wheel motor on the high-attachment road surface = the driving torque of the wheel motor that is on the low road surface and coaxial with the wheel on the high-attachment road + the preset torque limit difference.

It should be noted that the specific implementation manner of the driving anti-skid control device for the four-wheel drive electric vehicle of the embodiment can be referred to the specific implementation manner of the driving anti-skid control method for the four-wheel drive electric vehicle according to the above embodiment of the present invention, in order to reduce redundancy, Do not repeat it.

In summary, the driving anti-skid control device of the four-wheel drive electric vehicle determines the road condition of the electric vehicle according to the wheel speed and the vehicle speed of the four wheels of the electric vehicle through the determining module, and adopts a corresponding control strategy according to the road condition by the control module. Driving the anti-skid control of the electric vehicle, and for the wheel that starts the anti-skid control function, when the difference between the wheel speed and the vehicle speed exceeds the target difference through the control module, the difference between the wheel speed and the vehicle speed is used as the control target to the wheel The motor's drive torque is PI adjusted. Therefore, it can be ensured that the wheel does not fly after the electric vehicle starts to drive the anti-skid function, the electric vehicle does not have side deflection, the yaw rate is within a certain range, and the ground adhesion can be utilized to the maximum extent, so that the difference between the wheel speed and the vehicle speed is obtained. Stabilizing within the corresponding target difference range to maintain a suitable slip ratio helps to improve the ability of the electric vehicle to escape.

The above description is only a preferred embodiment of the invention and is not intended to limit the invention in any way. While the invention has been described above in the preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention by using the methods and technical contents disclosed above, or modify the equivalents of equivalent changes without departing from the scope of the technical solutions of the present invention. Example. Therefore, any simple modifications, equivalent changes, and modifications of the above embodiments may be made without departing from the spirit and scope of the invention.

Claims

A driving anti-skid control method for a four-wheel drive electric vehicle, comprising the steps of:

Detecting a wheel speed of the four wheels of the electric vehicle and a depth of the accelerator pedal;

Estimating the vehicle speed of the electric vehicle according to the wheel speeds of the four wheels, determining a target difference between the vehicle speed and the wheel speed according to the vehicle speed, and acquiring the electric vehicle according to the depth of the accelerator pedal Demand torque

Driving the slip control corresponding to the wheel speed according to the wheel speed, the vehicle speed, the target difference value, and the demand torque.
A driving slip control method for a four-wheel drive electric vehicle according to claim 1, wherein said pair of said wheel speed, said vehicle speed, said target difference value, and said demand torque pair correspond to said wheel speed The wheels are driven to drive slip control, including:

Determining whether a difference between the wheel speed and the vehicle speed is greater than the target difference;

If the difference between the wheel speed and the vehicle speed is greater than the target difference, controlling a wheel corresponding to the wheel speed to start driving the anti-skid function;

Correcting a PI controller for driving the slip control corresponding to the wheel motor according to the wheel speed, the vehicle speed, and the target difference, so as to output a corresponding driving anti-skid torque through the corrected PI controller;

Determining whether the driving anti-skid torque is less than the required torque;

Determining, if the driving anti-skid torque is less than the required torque, determining a driving torque of the wheel motor as the driving anti-skid torque;

If the driving anti-skid torque is greater than or equal to the required torque, determining that the driving torque of the wheel motor is the required torque, and controlling the wheel to exit the driving anti-slip function.
The driving slip prevention control method for a four-wheel drive electric vehicle according to claim 1 or 2, wherein said correcting said driving slip control corresponding to said wheel motor based on said wheel speed, said vehicle speed and said target difference The PI controller outputs the corresponding driving anti-skid torque through the corrected PI controller, including:

Correcting an integral coefficient of the PI controller according to a difference Dvx between the wheel speed and the vehicle speed and the target difference value Dv_aim, and maintaining a proportional coefficient of the PI controller;

A difference value between the difference value Dvx and the target difference value Dv_aim is used as a feedback value of the PI controller, and a corresponding driving anti-skid torque T_value is output.
The driving slip prevention control method for a four-wheel drive electric vehicle according to claim 3, wherein the integral coefficient of the modified PI controller is proportional to the absolute value of (Dvx - Dv_aim).
The driving slip prevention control method for a four-wheel drive electric vehicle according to any one of claims 1 to 4, wherein a relationship between the vehicle speed and the target difference is present, and when the vehicle speed is greater than 10 km For /h, the corresponding target difference ranges from 1.5km/h to 2km/h.
A driving anti-skid control device for a four-wheel drive electric vehicle, comprising:

a detecting module, configured to detect a wheel speed of the four wheels of the electric vehicle and a depth of the accelerator pedal;

An estimating module, configured to estimate a vehicle speed of the electric vehicle according to a wheel speed of the four wheels;

a determining module, configured to determine a target difference between the vehicle speed and the wheel speed according to the vehicle speed;

Obtaining a module, configured to acquire a required torque of the electric vehicle according to a depth of the accelerator pedal;

a control module, the control module being respectively connected to the detecting module, the estimating module, the determining module, and the acquiring module, configured to perform, according to the wheel speed, the vehicle speed, the target difference, and the The demand torque drives the slip control of the wheel corresponding to the wheel speed.
The driving anti-skid control device for a four-wheel drive electric vehicle according to claim 6, wherein the control module is specifically configured to:

Determining whether a difference between the wheel speed and the vehicle speed is greater than the target difference;

Controlling, by the wheel, driving the anti-skid function when the difference between the wheel speed and the vehicle speed is greater than the target difference, and correcting the vehicle according to the wheel speed, the vehicle speed, and the target difference a PI controller for driving the anti-skid control corresponding to the wheel motor to output a corresponding driving anti-skid torque through the corrected PI controller;

Determining whether the driving anti-skid torque is less than the required torque;

Determining, when the driving anti-skid torque is less than the required torque, determining a driving torque of the wheel motor as the driving anti-skid torque;

When the driving anti-skid torque is greater than or equal to the required torque, it is determined that the driving torque of the wheel motor is the required torque, and the wheel is controlled to exit the driving anti-slip function.
A driving anti-skid control device for a four-wheel drive electric vehicle according to claim 6 or 7, wherein said control module corrects a drive corresponding to said wheel motor based on said wheel speed, said vehicle speed and said target difference The anti-skid controlled PI controller is used to output the corresponding driving anti-skid torque through the modified PI controller, specifically for:

Correcting an integral coefficient of the PI controller according to a difference Dvx between the wheel speed and the vehicle speed and the target difference value Dv_aim, and maintaining a proportional coefficient of the PI controller; and

A difference value between the difference value Dvx and the target difference value Dv_aim is used as a feedback value of the PI controller, and a corresponding driving anti-skid torque T_value is output.
The driving anti-skid control device for a four-wheel drive electric vehicle according to claim 8, wherein the integral coefficient of the modified PI controller is proportional to the absolute value of (Dvx - Dv_aim).
The driving anti-skid control device for a four-wheel drive electric vehicle according to any one of claims 6-9, wherein there is a correspondence between the vehicle speed and the target difference, and when the vehicle speed is greater than 10 km For /h, the corresponding target difference ranges from 1.5km/h to 2km/h.