An Anti-lock Braking System (ABS) Control Method and System for Electric Vehicles

Abstract

The present invention discloses an anti-slip control method and system for an electric vehicle, including: calculating the slip ratio of the vehicle under different operating states, determining whether the slip ratio is valid, and determining the effective slip ratio; based on the wheel speed difference of the vehicle and the effective slip ratio, determining whether the vehicle enters a slipping state; if entering the slipping state, determining the torque request value for exiting the slip according to the torque actually executed in the Nth cycle before the slip is triggered and the difference between the effective slip ratio and the set target slip ratio value; otherwise, performing gradient loading restriction on the driving torque of the vehicle according to the value of the effective slip ratio. The present invention adds the judgment of the effective slip ratio. When the wheel speed of a single wheel is too small, resulting in an excessive wheel speed difference, the slip ratio is judged to be invalid, reducing the phenomenon of false triggering of anti-slip caused by unilateral potholes or speed bumps.

Description

Technical Field

[0001] The present invention relates to the technical field of electric vehicles, and particularly to a driving anti-skid control method and system for an electric vehicle. Background Art

[0002] The statements in this part only provide background technical information related to the present invention and do not necessarily constitute prior art.

[0003] In the automotive industry, with the technological progress and development of pure electric vehicles, many new technologies have emerged to save costs. For example, for electric vehicles driven by a single motor, a VCU is used in cooperation with the power system to achieve driving anti-skid, replacing the original ESP / TCS, which can reduce costs. However, at the same time, due to the lack of verification in actual use scenarios for the new technologies, there are also some defects in different actual use scenarios.

[0004] Currently, for the case where a single-motor-driven electric vehicle is not equipped with a traction control system / electronic stability program (ESP / TCS), the main measure is to reduce the requested driving torque through the vehicle control unit (VCU) to relieve skidding when the vehicle skids. The specific process is as follows: The VCU calculates the slip ratio by calculating the wheel speed difference of the four wheels. If the calculated slip ratio is greater than the target slip ratio, it is determined that the vehicle has entered the skidding state; at this time, the vehicle requested torque is reduced to reduce the slip ratio and relieve skidding.

[0005] In the above process, since the slip ratio is calculated based on the wheel speed difference of the four wheels, in actual driving, for the case where the wheel speed difference is too large caused by a single-sided pothole, it will also be misjudged as vehicle skidding, resulting in mis-triggering of driving anti-skid; in addition, due to the characteristics of large motor torque and fast loading speed, when starting on a wet and slippery road surface, skidding occurs due to too fast torque loading. When the VCU detects vehicle skidding and quickly reduces the requested torque to make the slip ratio reach the target and then executes the throttle requested torque, there will be a process of vehicle torque unloading and reloading in a short time. Due to the excessive unloading and reloading of torque, it will cause discomfort to the driver and affect the driving experience. Summary of the Invention

[0006] In order to solve the above problems, the present invention proposes a driving anti-skid control method and system for an electric vehicle, which is applicable to a single-motor-driven electric vehicle. The vehicle control unit VCU calculates the slip ratio and the torque for exiting the skidding state of the vehicle according to the wheel speed and the actual executed torque of the motor, and at the same time increases the control of the torque loading gradient according to the slip ratio to improve the mis-triggering and easy-triggering phenomena of driving anti-skid.

[0007] According to the first aspect of the embodiments of the present invention, a driving anti-skid control method for an electric vehicle is provided, including:

[0008] Calculate the vehicle slip ratio under different operating conditions of the vehicle, determine whether the slip ratio is valid, and determine the effective slip ratio;

[0009] Based on the wheel speed difference of the vehicle and the effective slip ratio, determine whether the vehicle enters a skidding state;

[0010] If it enters the skidding state, determine the torque request value to exit the skidding according to the torque actually executed in the Nth cycle before triggering the skidding and the difference between the effective slip ratio and the set target slip ratio value; otherwise, perform gradient loading limit on the vehicle driving torque according to the value of the effective slip ratio.

[0011] According to the second aspect of the embodiments of the present invention, there is provided an electric vehicle drive anti-skid control system, including:

[0012] An effective slip ratio determination module, configured to calculate the vehicle slip ratio under different operating conditions of the vehicle, determine whether the slip ratio is valid, and determine the effective slip ratio;

[0013] A skidding state determination module, configured to determine whether the vehicle enters a skidding state based on the wheel speed difference of the vehicle and the effective slip ratio;

[0014] A torque management module, configured to, when entering the skidding state, determine the torque request value to exit the skidding according to the torque actually executed in the Nth cycle before triggering the skidding and the difference between the effective slip ratio and the set target slip ratio value; otherwise, perform gradient loading limit on the vehicle driving torque according to the value of the effective slip ratio.

[0015] According to the third aspect of the embodiments of the present invention, there is provided a terminal device, which includes a processor and a memory. The processor is used to implement each instruction; the memory is used to store multiple instructions, and the instructions are suitable for being loaded and executed by the processor to perform the above-mentioned electric vehicle drive anti-skid control method.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] (1) The present invention adds the judgment of the effective slip ratio. When the single wheel speed is too small and causes the wheel speed difference to be too large, the slip ratio is judged to be invalid, reducing the false triggering phenomenon of drive anti-skid caused by unilateral potholes or speed bumps.

[0018] (2) In the process of vehicle torque control, the present invention uses the effective slip ratio as a limiting condition. When entering the skidding state, according to the torque actually executed in the Nth cycle before triggering the skidding and the difference between the effective slip ratio and the set target slip ratio value, comprehensively determine the torque request value to exit the skidding; avoiding the bad driving experience brought to the driver by the rapid decrease of the vehicle torque;

[0019] When not in the skidding state, the vehicle drive torque is limited by gradient loading according to the value of the effective slip ratio; realizing the gradient management of the vehicle torque, effectively controlling the vehicle torque gradually before the vehicle skids, and avoiding the vehicle entering the skidding trigger state.

[0020] Advantages of additional aspects of the present invention will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of an anti-skid control method for an electric vehicle drive in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units need not be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0024] In the case of no conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0025] Embodiment 1

[0026] In one or more embodiments, an anti-skid control method for an electric vehicle drive is disclosed. Combining Figure 1 , the specific process is as follows:

[0027] S101: Calculate the vehicle slip ratio of the vehicle in different operating states, determine whether the slip ratio is valid, and determine the effective slip ratio;

[0028] The slip ratio refers to the proportion of the slip component in the longitudinal movement of the wheel during the braking process. In this embodiment, according to the ratio of the difference between the rotational speed of the right drive wheel and the rotational speed of the right driven wheel in the driving state to the rotational speed of the right drive wheel, the first slip ratio is obtained;

[0029] The second slip ratio is obtained according to the ratio of the difference between the rotational speed of the right driving wheel and the rotational speed of the right driven wheel in the recovery state to the rotational speed of the right driven wheel;

[0030] The third slip ratio is obtained according to the ratio of the difference between the rotational speed of the left driving wheel and the rotational speed of the left driven wheel in the driving state to the rotational speed of the left driving wheel;

[0031] The fourth slip ratio is obtained according to the ratio of the difference between the rotational speed of the left driven wheel and the rotational speed of the left driving wheel in the recovery state to the rotational speed of the left driven wheel.

[0032] Among them, the recovery state refers to the state where the motor generates electricity to charge the battery, and the driving state refers to the state where the battery outputs;

[0033] In this embodiment, the slip ratios under different working conditions are calculated respectively, which can more accurately determine whether the vehicle enters the skidding state.

[0034] In this embodiment, the method for judging whether the slip ratio is valid is as follows:

[0035] Remove the wheel with the lowest wheel speed among the four wheels, and take the difference between the wheel speeds of the remaining three wheels pairwise. If the obtained differences are all within the set range, it is possible that the vehicle is passing over a speed bump or a pit on one side at this time, and it is judged that the calculated slip ratio of the vehicle is invalid; if the differences are outside the set range, it is determined that the calculated slip ratio is valid; select the largest one of the first slip ratio, the second slip ratio, the third slip ratio and the fourth slip ratio as the valid slip ratio.

[0036] Among them, the wheel speed difference between the inner wheel and the outer wheel when the vehicle turns is used as the upper limit of the above-mentioned set range.

[0037] In this embodiment, by determining the valid slip ratio, it is possible to avoid false triggering of vehicle skidding caused by the vehicle passing over a pit or a speed bump on one side.

[0038] S102: Based on the wheel speed difference and the valid slip ratio of the vehicle, determine whether the vehicle enters the skidding state;

[0039] In this embodiment, when the slip ratio is valid, if any of the following conditions is met, it is determined that the vehicle enters the skidding state:

[0040] ① |Front wheel speed difference| > the first set value;

[0041] ② |Rear wheel speed difference| > the second set value;

[0042] ③ |Average front wheel speed - rear wheel speed difference| > the third set value;

[0043] ④ Valid slip ratio > the fourth set value;

[0044] The values of the above first set value, second set value, third set value, and fourth set value are selected according to actual needs and vehicle control requirements.

[0045] S103: If entering the skidding state, determine the torque request value for exiting the skidding according to the torque actually executed in the Nth cycle before triggering the skidding and the difference between the effective slip ratio and the set target slip ratio value;

[0046] S104: Otherwise, perform a gradient loading limit on the vehicle driving torque according to the value of the effective slip ratio.

[0047] In this embodiment, if it is determined that the vehicle enters the skidding state, the torque request value for exiting the skidding is determined according to the following process:

[0048] ① Select the torque actually executed in the Nth cycle before triggering the skidding as the torque request value T1;

[0049] ② Subtract the actual effective slip ratio from the set slip ratio threshold, and determine the torque value that needs to be reduced according to the difference; thereby obtaining the torque request value T2 for exiting the skidding;

[0050] Among them, the set target slip ratio value refers to the slip ratio value when the vehicle triggers skidding. Table 1 in this embodiment gives the corresponding relationship between the slip ratio difference and the torque that needs to be reduced.

[0051] Table 1

[0052] Slip ratio difference 0 5 10 20 30 50 80 Estimated reduced torque 0 10 30 50 60 80 120

[0053] Take the minimum value of the torque request values T1 and T2 as the torque request value T for exiting the skidding.

[0054] In this embodiment, the actual execution torque of the motor is feedback-regulated according to the difference between the actual execution torque Ta of the motor and the torque request value T for exiting the skidding. Table 2 gives the relationship between the difference between the actual execution torque and the target torque and the loading torque. The greater the difference, the greater the torque value that can be loaded.

[0055] Table 2

[0056]

[0057]

[0058] If it is determined that the vehicle has not entered the skidding state, the driving torque of the vehicle is limited by gradient loading according to the value of the effective slip ratio; in this embodiment, when the value of the slip ratio is between 4% and 8% (usually the vehicle starts to skid when the slip ratio is 10%), when the vehicle has a tendency to skid, the limitation coefficient of the driving torque of the vehicle is determined according to the value of the effective slip ratio; the larger the value of the effective slip ratio, the smaller the limitation coefficient of the driving torque of the vehicle. Table 3 shows the relationship between the effective slip ratio and the torque coefficient.

[0059] Table 3

[0060] Effective slip ratio 4％ 5％ 6％ 7％ 8％ Torque coefficient 0.5 0.4 0.3 0.2 0.1

[0061] Among them, the actually loaded torque is the product of the torque value applied by the accelerator pedal and the torque coefficient.

[0062] According to the magnitude of the effective slip ratio, the torque value is controlled step by step in advance to avoid a sudden decrease in torque when the vehicle triggers the skid control, and improve the driving experience.

[0063] Embodiment 2

[0064] In one or more embodiments, an anti-skid control system for an electric vehicle drive is disclosed, including:

[0065] An effective slip ratio determination module, configured to calculate the slip ratio of the vehicle in different operating states, determine whether the slip ratio is effective, and determine the effective slip ratio;

[0066] A skidding state determination module, configured to determine whether the vehicle has entered a skidding state based on the wheel speed difference and the effective slip ratio of the vehicle;

[0067] A torque management module, configured to, when entering the skidding state, determine the torque request value for exiting the skidding according to the torque actually executed in the Nth cycle before triggering the skidding and the difference between the effective slip ratio and the set target slip ratio value; otherwise, limit the driving torque of the vehicle by gradient loading according to the value of the effective slip ratio.

[0068] It should be noted that the specific implementation manners of the above modules have been described in Embodiment 1, and will not be elaborated here.

[0069] Embodiment 3

[0070] In one or more embodiments, a terminal device is disclosed, including a server, where the server includes a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the program, it implements the anti-skid control method for an electric vehicle drive in Embodiment 1. For the sake of brevity, it will not be elaborated here.

[0071] Those skilled in the art should understand that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0072] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to generate a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one or more of the processes Figure 1 or a plurality of processes and / or blocks

[0073] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one or more of the processes Figure 1 or a plurality of processes and / or blocks

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the processes Figure 1 or a plurality of processes and / or blocks

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific embodiments of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered by the protection scope of the claims of the present invention.

Claims

1. An anti - slip control method for an electric vehicle drive, characterized in that, it includes: Calculating the vehicle slip ratio under different operating states of the vehicle, determining whether the slip ratio is valid, and determining the effective slip ratio; Based on the wheel speed difference of the vehicle and the effective slip ratio, determining whether the vehicle enters a skidding state; If it enters a skidding state, according to the torque actually executed in the Nth cycle before triggering skidding and the difference between the effective slip ratio and the set target slip ratio value, determining the torque request value for exiting the skidding state; Otherwise, according to the value of the effective slip ratio, performing gradient loading restriction on the vehicle drive torque; If it enters a skidding state, according to the torque actually executed in the Nth cycle before triggering skidding and the difference between the effective slip ratio and the set target slip ratio value, determining the torque request value for exiting the skidding state; specifically including: If it enters a skidding state, selecting the torque actually executed in the Nth cycle before triggering skidding as the torque request value T1; Subtracting the effective slip ratio from the set target slip ratio value, determining the torque request to be reduced according to the size of the difference, and then obtaining the torque request value T2; Selecting the minimum value between the torque request value T1 and the torque request value T2 as the torque request value for exiting the skidding state; The performing gradient loading restriction on the vehicle drive torque according to the value of the effective slip ratio specifically includes: When the value of the effective slip ratio satisfies the set range before reaching the set target slip ratio value, determining the restriction coefficient for the vehicle drive torque according to the value of the effective slip ratio; the larger the value of the effective slip ratio, the smaller the restriction coefficient for the vehicle drive torque.

2. An anti - slip control method for an electric vehicle drive according to claim 1, characterized in that, Calculating the vehicle slip ratio under different operating states of the vehicle specifically includes: Obtaining the first slip ratio according to the ratio of the difference between the rotational speed of the right front wheel and the rotational speed of the right rear wheel to the rotational speed of the right front wheel in the driving state; Obtaining the second slip ratio according to the ratio of the difference between the rotational speed of the right front wheel and the rotational speed of the right rear wheel to the rotational speed of the right rear wheel in the recovery state; Obtaining the third slip ratio according to the ratio of the difference between the rotational speed of the left front wheel and the rotational speed of the left rear wheel to the rotational speed of the left front wheel in the driving state; Obtaining the fourth slip ratio according to the ratio of the difference between the rotational speed of the left front wheel and the rotational speed of the left rear wheel to the rotational speed of the left rear wheel in the recovery state.

3. An anti - slip control method for an electric vehicle drive according to claim 1, characterized in that, The determining whether the slip ratio is valid is specifically: Removing the wheel with the lowest rotational speed among the four wheels, taking the difference between the rotational speeds of the remaining three wheels pairwise. If the obtained differences are all within the set range, it is determined that the vehicle slip ratio is invalid; otherwise, the slip ratio is valid.

4. An anti - slip control method for an electric vehicle drive according to claim 1, characterized in that, The determining the effective slip ratio is specifically: taking the maximum slip ratio value among the calculated vehicle slip ratios under different operating states of the vehicle as the effective slip ratio.

5. An anti - slip control method for an electric vehicle drive according to claim 1, characterized in that, Based on the wheel speed difference of the vehicle and the effective slip ratio, determining whether the vehicle enters a skidding state; specifically including: Meeting any of the following conditions, it is determined that the vehicle is skidding: |Front wheel speed difference| > the first set value; |Rear wheel speed difference| > Second set value; |Average front wheel speed - Rear wheel speed difference| > Third set value; Effective slip ratio > Fourth set value.

6. A driving anti-slip control method for an electric vehicle according to claim 1, characterized in that, further comprising: According to the difference between the torque request value for exiting the slip and the actual executed torque, feedback-adjust the value of the actual executed torque.

7. A driving anti-slip control system for an electric vehicle, adopting a driving anti-slip control method for an electric vehicle according to any one of claims 1-6, characterized in that, comprising: An effective slip ratio determination module, configured to calculate the vehicle slip ratio of the vehicle under different operating states, determine whether the slip ratio is effective, and determine the effective slip ratio; A slip state determination module, configured to determine whether the vehicle enters a slip state based on the wheel speed difference and the effective slip ratio of the vehicle; A torque management module, configured to, when entering the slip state, determine the torque request value for exiting the slip according to the torque actually executed in the Nth cycle before triggering the slip and the difference between the effective slip ratio and the set target slip ratio value; Otherwise, according to the value of the effective slip ratio, perform gradient loading restriction on the vehicle driving torque.

8. A terminal device, comprising a processor and a memory, the processor is used to implement each instruction; the memory is used to store multiple instructions, characterized in that, The instructions are adapted to be loaded and executed by the processor to perform the driving anti-slip control method for an electric vehicle according to any one of claims 1-6.

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