A Distributed Traction Control Method for Pure Electric Vehicles

Abstract

This invention discloses a distributed traction control method for pure electric vehicles, comprising: acquiring wheel speed signals, steering wheel angle signals, yaw rate signals, and longitudinal acceleration signals; calculating a target slip ratio based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value; determining the driver-requested torque based on the steering wheel angle signal; determining the target motor speed based on the target slip ratio and non-drive wheel speeds; determining whether wheel slippage has occurred based on the motor speed and motor speed acceleration; if slippage is detected, performing PID control with the target motor speed as the target, and outputting the control system-requested torque; and performing torque arbitration based on the driver-requested torque, the control system-requested torque, and the motor torque limit, and outputting the target torque. This method constructs an integrated "perception-decision-execution" control link, resulting in a short signal transmission path and fast torque response, effectively solving problems such as long transmission paths and untimely slippage suppression.

Description

Technical Field

[0001] This invention relates to the field of vehicle drive anti-skid control technology, and in particular to a distributed traction control method for pure electric vehicles. Background Technology

[0002] Traction control system (TCS) is one of the core safety features of automobiles. It was developed in the era of gasoline-powered vehicles and can effectively prevent the drive wheels from slipping and fishtailing when the vehicle accelerates on roads with low coefficient of friction, thereby improving driving stability.

[0003] In the era of electric vehicles, TCS (Traction Control System) functions are typically integrated into the Wheel Control System (WCBS). The WCBS calculates the slip ratio based on the drive wheel speed and the reference vehicle speed, controls the target slip ratio in a closed loop, and sends a torque request to the Vehicle Controller Unit (VCU). The VCU arbitrates the torque request from the driver's pedal and the torque request from the WCBS, and then sends the torque command to the Motor Controller Unit (PCU). Finally, the PCU controls the motor to output torque, keeping the slip ratio close to the target value.

[0004] However, the aforementioned control chain is relatively long, involving multiple signal interactions between the three controllers WCBS, VCU, and PCU. This results in significant control delays and excessively long torque adjustment times, making it unsuitable for matching the characteristics of the drive motor, which requires high torque at low speeds and rapid loading rates. On roads with low coefficient of friction, vehicles are prone to slippage, fishtailing, and other unstable phenomena. The TCS function suffers from lag in torque response, untimely slippage suppression, and communication delays between multiple modules, leading to low control efficiency.

[0005] In existing technologies, the TCS enabling module only considers the rate of change of motor speed to determine whether slippage has occurred, without taking into account the road surface adhesion coefficient, reference vehicle speed, and changes in the adhesion coefficient under cornering conditions. This fails to fully utilize the road surface adhesion coefficient, affecting acceleration performance. Furthermore, slippage is not coordinated with braking force control, resulting in insufficient power and a risk of rolling backwards on ramps. Additionally, when calculating the drive shaft speed under transient conditions, only wheel speed and steering wheel angle are considered, which is incomplete and also fails to fully utilize the road surface adhesion coefficient to improve acceleration performance. Moreover, the lack of coordinated braking force control on ramps further contributes to the risk of rolling backwards. Summary of the Invention

[0006] In view of the above, the present invention aims to provide a distributed traction control method for pure electric vehicles to solve the aforementioned technical problems.

[0007] The technical solution adopted in this invention is as follows:

[0008] This invention provides a distributed traction control method for a pure electric vehicle, comprising:

[0009] Collect wheel speed signals, steering wheel angle signals, yaw rate signals, and longitudinal acceleration signals;

[0010] The target slip ratio is calculated based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value.

[0011] Determine the driver's requested torque based on the steering wheel angle signal;

[0012] The target motor speed is determined based on the target slip ratio and the speed of the non-driving wheels;

[0013] Determine whether wheel slippage has occurred based on motor speed and motor acceleration.

[0014] If slippage is detected, PID control is performed with the target motor speed as the target, and the output is the torque requested by the control system.

[0015] Torque arbitration is performed based on the driver's requested torque, the control system's requested torque, and the motor's torque limit to output the target torque.

[0016] Optionally, the target slip ratio is calculated based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value, including:

[0017] The basic target slip ratio is calibrated based on vehicle speed and road surface adhesion coefficient;

[0018] The cornering correction coefficient is determined based on the yaw rate, and the basic target slip ratio is corrected accordingly.

[0019] When braking torque compensation is present, a fixed correction slip ratio is superimposed to obtain the target slip ratio.

[0020] Optionally, the target motor speed is calculated based on the target slip ratio and the speed of the non-driving wheels, including:

[0021] ;

[0022] in, The target speed of the motor. The target wheel speed, i is the speed ratio output by the speed ratio self-learning module, and R is the rolling radius of the tire.

[0023] Optionally, the condition for determining wheel slippage is:

[0024] The motor speed is greater than the target motor speed, which is greater than the first threshold, or the motor speed acceleration is greater than the second threshold.

[0025] Optionally, when a wheel slips, braking force is applied to the wheel based on the difference in the amount of slip of the drive wheel to obtain a braking torque compensation value.

[0026] Optionally, torque arbitration is performed based on the driver's requested torque, the control system's requested torque, and the motor's torque limit to output a target torque, including:

[0027] Compare the driver's requested torque with the control system's requested torque, and use the smaller value between the driver's requested torque and the control system's requested torque as the arbitration basis torque;

[0028] The arbitration base torque is limited by the maximum and minimum output torques of the motor to output the target torque.

[0029] Optionally, the arbitration base torque is limited by the maximum and minimum output torques of the motor to output the target torque, including:

[0030] When the arbitration base torque is greater than the maximum output torque, the target torque is the maximum output torque of the motor;

[0031] When the arbitration base torque is less than the minimum output torque, the target torque is the minimum output torque of the motor;

[0032] When the arbitration basis torque Maximum output torque or the arbitration base torque At minimum output torque, the target torque is the arbitration base torque.

[0033] The above-described solution of the present invention has at least the following beneficial effects:

[0034] The above-described solution of the present invention collects wheel speed signals, steering wheel angle signals, yaw rate signals, and longitudinal acceleration signals; calculates the target slip ratio based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value; determines the driver's requested torque based on the steering wheel angle signal; determines the target motor speed based on the target slip ratio and non-drive wheel speeds; determines whether wheel slippage has occurred based on the motor speed and motor speed acceleration; if slippage is detected, performs PID control with the target motor speed as the target, outputting the control system's requested torque; and performs torque arbitration based on the driver's requested torque, the control system's requested torque, and the motor torque limit, outputting the target torque. By constructing an integrated "perception-decision-execution" control link, the signal transmission path is short and the torque response is fast, effectively solving problems such as long transmission paths and untimely slippage suppression. Attached Figure Description

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings, wherein:

[0036] Figure 1 A flowchart of a distributed traction control method for pure electric vehicles provided in an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of a distributed traction control system for a pure electric vehicle provided in an embodiment of the present invention. Detailed Implementation

[0038] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0039] This invention proposes an embodiment of a distributed traction control method for pure electric vehicles, specifically, as follows: Figure 1 As shown, it includes:

[0040] Step 11: Collect wheel speed signal, steering wheel angle signal, yaw rate signal, and longitudinal acceleration signal;

[0041] Step 12: Calculate the target slip ratio based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value;

[0042] Step 13: Determine the driver's requested torque based on the steering wheel angle signal;

[0043] Step 14: Determine the target motor speed based on the target slip ratio and the speed of the non-driving wheels;

[0044] Step 15: Determine whether wheel slippage has occurred based on motor speed and motor speed acceleration;

[0045] Step 16: If slippage is detected, PID control is performed with the target motor speed as the target, and the requested torque is output to the control system.

[0046] Step 17: Perform torque arbitration based on the driver's requested torque, the control system's requested torque, and the motor's torque limit, and output the target torque.

[0047] The method in this embodiment is applied to a distributed traction control system (dTCS) for pure electric vehicles. This system includes a linear control braking system (WCBS) and a motor controller (PCU). The linear control braking system and the motor controller are directly connected by electrical signals, eliminating the intermediate link of the traditional vehicle controller (VCU). The torque control module (TCS) is located in the motor controller, while the braking force control module remains in the linear control braking system, forming an integrated "perception-decision-execution" control chain.

[0048] like Figure 2As shown, in the dTCS architecture, WCBS is responsible for collecting sensor signals such as wheel speed, steering wheel angle, yaw rate, and longitudinal acceleration, and calculating the target motor speed and braking torque compensation value based on these signals. The TCS torque control module in the PCU is responsible for slippage detection, target speed closed-loop control, and dTCS requested torque calculation.

[0049] Specifically, in step 11, signals from four wheel speed sensors, steering wheel angle, yaw rate, and longitudinal acceleration are first acquired. These signals are used for subsequent calculations of target slip ratio, motor reference speed, motor target speed, braking torque compensation, and speed ratio self-learning.

[0050] In step 12, the driver's requested torque is determined based on the steering wheel angle signal and the accelerator pedal signal. In this embodiment, the steering wheel angle signal serves as the primary representation of the driver's intention.

[0051] In step 13, the target slip ratio is calculated based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value.

[0052] First, determine the basic target slip ratio based on vehicle speed and road surface adhesion coefficient. Specifically, a three-dimensional table of basic target slip ratio, vehicle speed, and road surface adhesion coefficient is obtained in advance through actual vehicle calibration. The calibration principle is: no slippage, fast acceleration, and no fishtailing.

[0053] Secondly, the cornering correction factor K is determined based on the yaw rate. A one-dimensional table of K values ​​corresponding to different yaw rates is obtained through actual vehicle calibration. The calibration principle is: no understeer, no sideslip, and the longitudinal slip ratio should not be too large in corners. The larger the yaw rate, the smaller K is. The range of K values ​​is as follows: Then calculate the target slip ratio after cornering correction: .

[0054] Finally, when braking torque compensation is present, to avoid conflict and oscillation between motor torque and braking torque, a fixed correction value is superimposed on the target slip ratio in the curve. This value is determined through actual vehicle calibration, with the goal of eliminating impacts and vibrations. The final target slip ratio is:

[0055] ;

[0056] Furthermore, in step 14, the target motor speed is calculated based on the target slip ratio and the speed of the non-driving wheels.

[0057] First calculate the reference speed The average wheel speed of the left and right non-drive wheels is used:

[0058] ;

[0059] in, , These are the wheel speeds of the left and right rear wheels, respectively.

[0060] Calculate the target wheel speed:

[0061] ;

[0062] Calculate the target speed of the motor:

[0063] ;

[0064] in This is the speed ratio output by the speed ratio self-learning module. This refers to the tire rolling radius. The speed ratio self-learning module is used to compensate for manufacturing deviations in different motor reducers and speed ratio deviations caused by long-term wear, thereby improving the accuracy of the motor target speed calculation.

[0065] In step 15, it is determined whether wheel slippage has occurred based on the current motor speed and motor acceleration. The determination criteria are: the motor speed is greater than the target motor speed and exceeds a first threshold (e.g., exceeding the target speed by 5%), or the motor acceleration is greater than a second threshold (e.g., the acceleration exceeds a preset acceleration threshold). If either condition is met, wheel slippage is determined.

[0066] In step 16, if slippage is detected, the speed control mode is entered, and the motor speed is set to the target speed. To achieve the target speed, PID control is applied to the actual motor speed. The parameters of the PID controller are obtained through a lookup table; different vehicle speeds correspond to different PID parameters. The parameter table is calibrated based on the actual operating conditions of the entire vehicle. The output of the PID controller is the torque requested by the control system.

[0067] In step 17, torque arbitration is performed based on the driver's requested torque, the control system's requested torque, and the motor's torque limit to output the final target torque.

[0068] Specifically, the driver's requested torque is first compared with the control system's requested torque, and the smaller of the two is taken as the arbitration basis torque:

[0069] ;

[0070] Then the arbitration base torque With the motor's current maximum allowable output torque and minimum output torque Amplitude limiting is applied:

[0071] like Then the target torque ;

[0072] like Then the target torque ;

[0073] otherwise, .

[0074] Ultimately, PCU based on Control the output torque of the motor.

[0075] Furthermore, in situations where there is a significant difference in the coefficient of friction between the left and right drive wheels, this embodiment also includes a braking force compensation mechanism. When a wheel slips, the braking force control module in the WCBS applies braking force to the wheel on the side with the lower coefficient of friction based on the difference in slippage between the left and right drive wheels. Simultaneously, based on the magnitude of the applied braking force, a corresponding drive torque compensation value is superimposed on the torque requested by the dTCS to compensate for the power loss caused by the braking force, improve vehicle acceleration performance, and prevent the vehicle from rolling backwards. This braking torque compensation value is fed back to the target slip ratio calculation in step 3, forming a closed-loop coordinated control.

[0076] Furthermore, this embodiment also includes a dTCS exit strategy under fault conditions:

[0077] Condition 1: If WCBS malfunctions but PCU is not malfunctioning, the dTCS requested torque will slowly increase at a preset slope until the driver requests torque, and then the dTCS function will be deactivated.

[0078] Condition 2: If the PCU fails (regardless of whether the WCBS fails), the dTCS requested torque will be directly restored to the driver's requested torque, and the dTCS function will be immediately deactivated.

[0079] When the motor speed is less than the exit threshold, the dTCS requests the torque to be restored to the torque requested by the driver, and exits the speed control mode normally.

[0080] The distributed traction control method for pure electric vehicles in this embodiment effectively solves the problems of long transmission paths and untimely slippage suppression in the prior art by constructing an integrated control link of "perception-decision-execution". The signal transmission path is short and the torque response is fast.

[0081] WCBS transmits signals directly to PCU, eliminating the VCU transmission link. The signal transmission path is short, which can effectively reduce wheel slippage, shorten stabilization time, reduce steering wheel correction angle and yaw rate, and improve vehicle driving stability and acceleration performance.

[0082] Taking into account factors such as vehicle speed, road surface adhesion coefficient, yaw rate, and braking force, the target slip ratio is accurately calculated through cornering correction and braking torque compensation to ensure that the vehicle is always in the best adhesion state.

[0083] The motor target speed calculation speed ratio uses a self-learning value, which can avoid speed ratio deviations caused by the manufacturing and use of the motor reducer and improve the accuracy of motor speed calculation; the motor speed and motor speed acceleration are used to comprehensively judge whether the wheel is slipping, and the slipping judgment response is fast, which can quickly judge and suppress slipping when the vehicle is about to slip.

[0084] An embodiment of the present invention also provides a computing device, including: a processor and a memory storing a computer program, wherein the computer program, when executed by the processor, performs the method described in the above embodiments. All implementations in the above method embodiments are applicable to this embodiment and can achieve the same technical effect.

[0085] In this embodiment of the invention, a computer-readable storage medium is also provided, storing instructions that, when executed on a computer, cause the computer to perform the method described in the above embodiments. All implementations of the methods described in the above embodiments are applicable to this embodiment and can achieve the same technical effect.

[0086] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0087] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0088] In the embodiments provided by this invention, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0089] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0090] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0091] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0092] Furthermore, it should be noted that in the apparatus and method of the present invention, it is obvious that the components or steps can be decomposed and / or recombined. These decompositions and / or recombinations should be considered equivalent solutions of the present invention. Moreover, the steps performing the above series of processes can naturally be executed in the order described, but are not necessarily required to be executed in chronological order; some steps can be executed in parallel or independently of each other. Those skilled in the art will understand that all or any step or component of the method and apparatus of the present invention can be implemented in any computing device (including processors, storage media, etc.) or network of computing devices, in hardware, firmware, software, or a combination thereof. This is something that those skilled in the art can achieve by using their basic programming skills after reading the description of the present invention.

[0093] Therefore, the object of the present invention can also be achieved by running a program or a set of programs on any computing device. The computing device can be a known general-purpose device. Therefore, the object of the present invention can also be achieved simply by providing a program product containing program code implementing the method or apparatus. That is, such a program product also constitutes the present invention, and the storage medium storing such a program product also constitutes the present invention. Obviously, the storage medium can be any known storage medium or any storage medium developed in the future. It should also be noted that in the apparatus and method of the present invention, it is obvious that the components or steps can be decomposed and / or recombined. These decompositions and / or recombinations should be considered equivalent to the present invention. Furthermore, the steps performing the above series of processes can naturally be performed in the order described, but are not necessarily required to be performed in chronological order. Some steps can be performed in parallel or independently of each other.

[0094] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A distributed traction control method for a pure electric vehicle, characterized in that, A distributed traction control system for pure electric vehicles, comprising a linear control braking system, a motor controller electrically connected to the linear control braking system, and a torque control module disposed within the motor controller, the method comprising: Collect wheel speed signals, steering wheel angle signals, yaw rate signals, and longitudinal acceleration signals; The target slip ratio is calculated based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value. Determine the driver's requested torque based on the steering wheel angle signal; The target motor speed is determined based on the target slip ratio and the speed of the non-driving wheels; Determine whether wheel slippage has occurred based on motor speed and motor acceleration. If slippage is detected, PID control is performed with the target motor speed as the target, and the output is the torque requested by the control system. Torque arbitration is performed based on the driver's requested torque, the control system's requested torque, and the motor's torque limit to output the target torque.

2. The distributed traction control method for pure electric vehicles according to claim 1, characterized in that, The target slip ratio is calculated based on vehicle speed, road surface adhesion coefficient, yaw rate, and braking torque compensation value, including: The basic target slip ratio is calibrated based on vehicle speed and road surface adhesion coefficient; The cornering correction coefficient is determined based on the yaw rate, and the basic target slip ratio is corrected accordingly. When braking torque compensation is present, a fixed correction slip ratio is superimposed to obtain the target slip ratio.

3. The distributed traction control method for pure electric vehicles according to claim 1, characterized in that, The target motor speed is calculated based on the target slip ratio and the speed of the non-driving wheels, including: ； in, The target speed of the motor. The target wheel speed, i is the speed ratio output by the speed ratio self-learning module, and R is the rolling radius of the tire.

4. The distributed traction control method for pure electric vehicles according to claim 1, characterized in that, The criteria for determining wheel slippage are as follows: The motor speed is greater than the target motor speed, which is greater than the first threshold, or the motor speed acceleration is greater than the second threshold.

5. The distributed traction control method for pure electric vehicles according to claim 1, characterized in that, When a wheel slips, braking force is applied to the wheel based on the difference in slippage between the drive wheels to obtain the braking torque compensation value.

6. The distributed traction control method for pure electric vehicles according to claim 1, characterized in that, Torque arbitration is performed based on the driver's requested torque, the control system's requested torque, and the motor's torque limit to output the target torque, including: Compare the driver's requested torque with the control system's requested torque, and use the smaller value between the driver's requested torque and the control system's requested torque as the arbitration basis torque; The arbitration base torque is limited by the maximum and minimum output torques of the motor to output the target torque.

7. The distributed traction control method for pure electric vehicles according to claim 6, characterized in that, The arbitration base torque is limited by the maximum and minimum output torques of the motor to output the target torque, including: When the arbitration base torque is greater than the maximum output torque, the target torque is the maximum output torque of the motor; When the arbitration base torque is less than the minimum output torque, the target torque is the minimum output torque of the motor; When the arbitration basis torque Maximum output torque or the arbitration base torque At minimum output torque, the target torque is the arbitration base torque.

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