Protection control method for differential mechanism of pure electric vehicle

Abstract

The invention discloses a protection control method for a differential mechanism of a pure electric vehicle, which relates to the technical field of electric vehicle driving, and comprises the following steps: acquiring wheel speed signals of wheels on two sides of a vehicle driving shaft, and calculating the rotating speed difference of the wheels on two sides; according to the rotating speed difference, a protection torque upper limit value and a protection torque lower limit value under the current rotating speed are determined through a preset rotating speed and protection torque threshold value mapping table; judging whether the motor request torque exceeds the upper limit value or the lower limit value of the protection torque; if the time exceeds the preset activation delay time, activating the differential protection function; and in the state that the differential protection function is activated, the actual output torque is controlled to be between the protection torque upper limit value and the protection torque lower limit value. Abnormal abrasion or impact damage of internal elements of the differential mechanism caused by excessive slip of a single-side wheel can be effectively avoided, so that the service life of the differential mechanism is greatly prolonged, the maintenance cost is reduced, and intense driving control and power requirements are met.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle drive technology, and in particular to a protection and control method for a differential in a pure electric vehicle. Background Technology

[0002] Electric vehicle drive systems primarily employ a motor-reducer assembly paired with an open differential. Compared to traditional gasoline vehicles, they offer higher output torque and greater impact. However, in scenarios involving single-wheel slippage, such as high-speed cornering or off-road traction, the electric drive system is more prone to power loss due to the open differential's inability to control torque, leading to wheel spin and power loss, or even differential damage. Therefore, a torque protection and transfer strategy based on differential speed needs to be designed at the drive system level to meet the demands of aggressive driving and power while ensuring the normal lifespan of the open differential. Summary of the Invention

[0003] In view of the above, the present invention aims to provide a protection control method for the differential of a pure electric vehicle to solve the aforementioned technical problems.

[0004] The technical solution adopted in this invention is as follows:

[0005] This invention provides a protection control method for the differential of a pure electric vehicle, comprising:

[0006] Acquire the wheel speed signals of the wheels on both sides of the vehicle's drive axle and calculate the speed difference between the two wheels;

[0007] Based on the speed difference, the upper limit and lower limit of the protection torque at the current speed are determined by a preset speed-to-protection torque threshold mapping table.

[0008] Determine whether the motor's requested torque exceeds the upper or lower limit of the protected torque;

[0009] If the time exceeds the preset activation delay time, the differential protection function will be activated.

[0010] When the differential protection function is activated, the actual output torque is controlled to be between the upper limit and the lower limit of the protection torque.

[0011] Optionally, the speed-to-protection torque threshold mapping table is obtained through differential opening test calibration;

[0012] The upper limit value is a positive value mapping table, and the lower limit value is a negative value mapping table. The upper and lower limit curves are symmetrical about the zero point of the speed difference.

[0013] Optionally, the activation delay time is determined based on the on / off state of the traction control system:

[0014] When the traction control system is activated, the activation delay time is a first preset time;

[0015] When the traction control system is turned off or malfunctions, the activation delay time is a second preset time, and the second preset time is less than the first preset time.

[0016] Optionally, the first preset time is 500ms, and the second preset time is 10ms.

[0017] Optionally, when the differential protection function is activated, the actual output torque is controlled to be between the upper and lower limits of the protection torque, including:

[0018] When the motor requests a positive torque, the minimum value between the motor's requested torque and the upper limit of the protection torque is taken as the actual output torque.

[0019] When the requested torque of the motor is negative, the maximum value between the requested torque of the motor and the lower limit of the protection torque is taken as the actual output torque.

[0020] Optionally, when the speed difference is within the protection torque threshold range and the time does not exceed the limit for a preset exit delay time, the differential protection function is exited.

[0021] The above-described solution of the present invention has at least the following beneficial effects:

[0022] The above-described solution of the present invention acquires the wheel speed signals of the wheels on both sides of the vehicle's drive axle and calculates the speed difference between the two wheels. Based on the speed difference, it determines the upper and lower limits of the protection torque at the current speed using a preset speed-to-protection torque threshold mapping table. It then determines whether the motor's requested torque exceeds the upper or lower limit of the protection torque. If it does, and the excess time reaches a preset activation delay time, the differential protection function is activated. While the differential protection function is activated, the actual output torque is controlled to be between the upper and lower limits of the protection torque. This allows for real-time monitoring of the speed difference between the wheels on both sides of the drive axle and dynamic limiting of the motor output torque based on a pre-calibrated protection torque threshold. This effectively avoids abnormal wear or impact damage to internal differential components caused by excessive slippage of one wheel, thereby significantly extending the differential's service life, reducing maintenance costs, and meeting the demands of aggressive driving and power. Attached Figure Description

[0023] 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:

[0024] Figure 1 A flowchart of a protection control method for a differential in a pure electric vehicle provided in an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the speed and protection torque threshold mapping table provided in an embodiment of the present invention. Detailed Implementation

[0026] 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.

[0027] This invention proposes an embodiment of a protection control method for the differential of a pure electric vehicle, specifically, as follows: Figure 1 As shown, it includes:

[0028] Step 11: Obtain the wheel speed signals of the wheels on both sides of the vehicle drive axle and calculate the speed difference between the two wheels;

[0029] Step 12: Based on the speed difference, determine the upper limit and lower limit of the protection torque at the current speed using a preset speed-to-protection torque threshold mapping table;

[0030] Step 13: Determine whether the requested torque of the motor exceeds the upper or lower limit of the protection torque;

[0031] Step 14: If the time exceeds the preset activation delay time, then the differential protection function will be activated.

[0032] Step 15: With the differential protection function activated, control the actual output torque to be between the upper limit and lower limit of the protection torque.

[0033] The protection and control method for the differential of pure electric vehicles in this embodiment is applicable to drive shafts equipped with open differentials, but not to drive shafts of distributed electric drives.

[0034] The following prerequisites must be met for the differential protection function to be activated:

[0035] The vehicle is in a drivable condition;

[0036] The vehicle is actually in D or R gear.

[0037] No torque output restriction fault;

[0038] Both the wheel speed signal valid bit and the wheel rolling direction valid bit are valid.

[0039] The motor speed and torque exceeded the limit for 500ms.

[0040] If any of the following preconditions are met, the main control unit (VCU) will not respond to the differential protection function:

[0041] The vehicle is not in a drivable condition.

[0042] The vehicle is actually in neutral (N) or park (P).

[0043] There is a fault that prevents torque output.

[0044] The valid bits of the wheel speed signal and the valid bits of the wheel rolling direction are invalid.

[0045] The motor speed and torque did not exceed the limit value map or the exceedance did not last for 500ms;

[0046] Differential protection function activation conditions:

[0047] If the requested torque of the motor exceeds the protection torque range at the current speed, the intervention request will be filtered, and the lower value will be selected by comparing the requested torque of the motor with the upper limit of the protection torque.

[0048] In a specific embodiment of the present invention, the relative speed difference between the wheels on both sides of the drive axle is first calculated based on the wheel speed signal and wheel rolling direction signal sent by the electronic stability control system of the chassis:

[0049] , These are signals indicating the direction of wheel rotation, representing reverse rotation, stationary rotation, and forward rotation, respectively.

[0050] This is the wheel speed signal. For the filter coefficients:

[0051] ;

[0052] like This indicates that the left and right wheels are rotating in the same direction. In this case, the wheel speed difference between the left and right wheels on both sides of the drive axle is calculated.

[0053] .

[0054] The differential protection function determines whether the motor speed has reached the intervention threshold based on the wheel speed difference. The speed threshold value is obtained from the differential durability test. A hysteresis range is set for intervention; if the motor speed and torque exceed the limit map and continuously exceed the anti-shake delay time, the differential protection function will intervene; otherwise, it will not intervene if the anti-shake delay time is not exceeded.

[0055] Furthermore, based on the wheel speed difference on both sides of the same drive shaft The upper and lower limits of the protection torque threshold are calculated in real time. This speed and the protection torque threshold map are obtained through differential opening tests. Figure 2 As shown, the upper limit of the map table is a positive value mapping table, and the lower limit is a negative value mapping table. The upper and lower limit curves are symmetrical about the zero point of the speed difference.

[0056] To address the risk of differential failure due to misuse of operating conditions caused by the long delay in differential protection activation and anti-shake mechanism activation in vehicle traction control systems, the differential activation time requirements are as follows:

[0057] a) When the vehicle's traction control system is activated, if the motor's requested torque continuously exceeds the protection range for a cumulative period of 500ms, the differential protection will be activated. If the requested torque exceeds the limit for a duration of 0-500ms, the differential protection strategy will not be activated.

[0058] b) If the vehicle's traction control system is turned off or the vehicle's traction control system malfunctions, and the motor's requested torque continuously exceeds the protection range for a cumulative period of 10ms, the differential torque limiting protection will be activated immediately to reduce the risk of differential failure.

[0059] After the differential protection function is activated, the main control unit (VCU) will reduce the absolute value of the protection torque threshold and the requested torque, and increase the absolute value of the threshold and the motor recovery request torque, thereby keeping the speed difference between the two drive wheels within a safe upper and lower limit; ensuring that the motor-end requested torque is within the threshold range when the differential protection function is activated.

[0060] Specifically, during the differential protection control process, the main control unit (VCU) determines the lifting torque based on the wheel speed signal sent by the brake control unit and the difference in slip speed between the wheels on both sides of a single drive shaft.

[0061] When the speed difference and actual torque exceed the protection torque range, the differential protection function is activated. When the motor request torque is positive, the minimum value between the motor request torque and the upper limit of the protection torque is used as the actual output torque; when the motor request torque is negative, the maximum value between the motor request torque and the lower limit of the protection torque is used as the actual output torque.

[0062] When the speed difference and actual torque are determined to be within the protection range, the differential protection function is deactivated and the corresponding requested torque is restored. When the electronic stability control system triggers the vehicle dynamic control system (VDC), traction control system (TCS), or dynamic traction control system (DTC) stability control functions, the differential protection function is not activated.

[0063] The protection and control method for the differential of a pure electric vehicle in this embodiment monitors the speed difference between the wheels on both sides of the drive shaft in real time and dynamically limits the output torque of the motor according to a pre-calibrated protection torque threshold. This can effectively prevent abnormal wear or impact damage to the internal components of the differential caused by excessive slippage of one wheel, thereby significantly extending the service life of the differential, reducing maintenance costs, and meeting the demands of aggressive driving and power.

[0064] It should be noted that this device is the same as the method described above. All implementations in the above method embodiments are applicable to the embodiments of this device and can achieve the same technical effect.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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 protection control method for a differential in a pure electric vehicle, characterized in that, include: Acquire the wheel speed signals of the wheels on both sides of the vehicle's drive axle and calculate the speed difference between the two wheels; Based on the speed difference, the upper limit and lower limit of the protection torque at the current speed are determined by a preset speed-to-protection torque threshold mapping table. Determine whether the motor's requested torque exceeds the upper or lower limit of the protected torque; If the time exceeds the preset activation delay time, the differential protection function will be activated. When the differential protection function is activated, the actual output torque is controlled to be between the upper limit and the lower limit of the protection torque.

2. The protection and control method for the differential of a pure electric vehicle according to claim 1, characterized in that, The speed-to-protection torque threshold mapping table was obtained through differential opening test calibration. The upper limit value is a positive value mapping table, and the lower limit value is a negative value mapping table. The upper and lower limit curves are symmetrical about the zero point of the speed difference.

3. The protection and control method for the differential of a pure electric vehicle according to claim 1, characterized in that, The activation delay time is determined based on the on / off state of the traction control system: When the traction control system is activated, the activation delay time is a first preset time; When the traction control system is turned off or malfunctions, the activation delay time is a second preset time, and the second preset time is less than the first preset time.

4. The protection and control method for the differential of a pure electric vehicle according to claim 3, characterized in that, The first preset time is 500ms, and the second preset time is 10ms.

5. The protection and control method for the differential of a pure electric vehicle according to claim 1, characterized in that, When the differential protection function is activated, the actual output torque is controlled to be between the upper and lower limits of the protection torque, including: When the motor requests a positive torque, the minimum value between the motor's requested torque and the upper limit of the protection torque is taken as the actual output torque. When the requested torque of the motor is negative, the maximum value between the requested torque of the motor and the lower limit of the protection torque is taken as the actual output torque.

6. The protection and control method for the differential of a pure electric vehicle according to claim 1, characterized in that, When the speed difference is within the protection torque threshold range and the time does not exceed the limit for a preset exit delay time, the differential protection function is deactivated.

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