Speed ​​Limit Function Activation Control Method Based on Dual-Motor Electric Drive Axle

Abstract

This invention discloses a vehicle speed limiting function activation control method based on a dual-motor electric drive axle. It primarily calculates the driveshaft speed value continuously based on the dual motor speeds, and obtains the driveshaft speed limit value according to a preset vehicle speed limit value and a set limit value for the driveshaft speed. Based on the aforementioned processing, the difference between the driveshaft speed value and the driveshaft speed limit value is calculated. Then, the accelerator pedal requested torque and the dual motor torque are integrated, and a pre-calibrated corresponding activation threshold is dynamically obtained in conjunction with the current gear position. Finally, the difference and the activation threshold are used to decide whether to activate the vehicle speed limiting function. This invention abandons the vehicle speed limiting mode that only considers a simple dimension, but instead comprehensively considers the continuous trend of driveshaft speed difference and the overall vehicle operating conditions, effectively solving the torque distribution problem of the dual-motor electric drive axle system. While improving the overall performance of new energy vehicles and ensuring vehicle safety, it effectively reduces vehicle vibration and power interruption phenomena during driving.

Description

Technical Field

[0001] This invention relates to the field of new energy vehicle control technology, and in particular to a method for starting the vehicle speed limit function based on a dual-motor electric drive axle. Background Technology

[0002] With the rapid development of new energy vehicle technology, the Vehicle Control Unit (VCU), as the core control unit of a vehicle, undertakes key tasks such as multi-system coordination, energy management, and safety control. The speed limiting function, as an important component of the VCU, directly impacts vehicle safety, fuel economy, and user experience. Traditional speed limiting strategies mainly rely on fixed threshold control, such as limiting the speed to no more than 20 km / h in reverse gear, limiting the speed to 15 km / h in limp mode, or reducing power output through driving modes (such as ECO mode) to achieve speed limiting. However, such methods suffer from insufficient dynamic adaptability under complex operating conditions. For example, driver error, changes in road gradient, or fluctuations in battery status can easily lead to speed overshoot or control failure, posing safety risks.

[0003] Furthermore, the energy recovery mechanism of new energy vehicles is closely related to the vehicle speed limiting function. When the vehicle enters braking or deceleration mode, the VCU needs to coordinate the motor to switch to generator mode, converting kinetic energy into electrical energy stored in the battery. During this process, the accuracy of the speed limit directly affects the energy recovery efficiency and braking comfort. In existing technologies, some models use the CAN bus to monitor the accelerator pedal (APS) and brake pedal (BPS) signals in real time, employing a braking priority strategy to ensure safety, but this does not fully consider the nonlinear characteristics under dynamic operating conditions. A more detailed analysis follows:

[0004] 1. Speed ​​limit based on mode switching:

[0005] In existing technologies, the VCU adjusts torque response characteristics through preset driving modes (such as ECO, NORMAL, and SPORT). For example, in ECO mode, energy consumption is reduced by limiting motor power output and vehicle speed limit (usually 100-120 km / h), while SPORT mode allows higher speeds to improve power performance. This method relies on static MAP (Motor Mapping) data, making it difficult to adapt to real-time road conditions and battery status changes, and there is a conflict between coordinating energy recovery and power output.

[0006] 2. Proportional-integral control and dynamic torque limiting:

[0007] A patent proposes a vehicle speed limiting method based on proportional-integral (PI) control. This method dynamically adjusts the integral term torque to suppress overshoot by comparing the current vehicle speed with the target speed limit in real time. Specifically, when the vehicle speed exceeds the target value, the VCU activates the speed limiting function, clears the integral term torque of the PI control to zero, and determines the requested torque based on the minimum value between the accelerator pedal travel and the limit torque. This method monitors the relationship between the pedal torque and the limit torque, dynamically adjusting the integral term to avoid control delay caused by integral saturation, thus significantly improving speed limiting accuracy.

[0008] 3. Power limitations based on navigation information:

[0009] Existing technology proposes a speed limit strategy that combines navigation destination mileage. When the remaining battery power is insufficient to support the current driving habits to reach the destination, the Vehicle Control Unit (VCU) dynamically adjusts the maximum speed limit (e.g., limiting it to below 60 km / h) by looking up the minimum energy consumption per kilometer MAP table, and forcibly shuts down high-voltage accessories such as air conditioning to reduce energy consumption. This method achieves coordinated control of energy optimization and speed limit by integrating navigation data with real-time energy consumption analysis.

[0010] 4. Functional safety-oriented hierarchical control:

[0011] In existing technologies, the vehicle speed limiting function of the VCU must meet the ISO 26262 functional safety standard, and the ASIL level is determined through Hazard Analysis and Risk Assessment (HARA). For example, in the gear shifting function, the VCU ensures safety degradation in failure scenarios through redundant signal monitoring and safe state transition logic (such as vehicle speed detection when shifting to P gear). This type of approach uses a hierarchical control strategy to allocate ASIL levels to each subsystem, reducing system complexity and development costs. Summary of the Invention

[0012] In view of the above, the present invention aims to provide a vehicle speed limit function start control method based on a dual-motor electric drive axle to solve the aforementioned technical problems.

[0013] The technical solution adopted in this invention is as follows:

[0014] This invention provides a vehicle speed limit function start control method based on a dual-motor electric drive axle, including:

[0015] Based on the speeds of the first and second motors in the dual-motor system, the drive shaft speed is continuously calculated.

[0016] The transmission shaft speed limit is obtained by setting the limit based on the preset vehicle speed limit and the transmission shaft speed limit.

[0017] Calculate the difference between the drive shaft speed value and the drive shaft speed limit value;

[0018] It integrates the torque requested by the accelerator pedal and the torque of the dual motors, and dynamically obtains the pre-calibrated function activation threshold based on the current gear position;

[0019] Based on the difference and the function activation threshold, a decision is made on whether to enable the vehicle speed limit function.

[0020] In at least one possible implementation, calculating the drive shaft speed value includes:

[0021] Determine if the speed of the first motor is correct;

[0022] After confirming that the speed of the first motor is normal, the speed of the first motor and the speed of the second motor are divided by the corresponding speed ratio to obtain the calculated speed of the transmission shaft of different motors.

[0023] When the calculation results of the two motors are close, the transmission shaft speed calculated based on the speed of the first motor is selected as the transmission shaft speed value.

[0024] In at least one possible implementation, the calculation of the drive shaft speed value further includes:

[0025] When the calculation results of the two motors differ significantly, determine whether the motor speed corresponding to the larger calculated transmission shaft speed exceeds the preset maximum speed of that motor.

[0026] If it is determined to be excessive, the calculated result of the drive shaft speed corresponding to the motor is selected as the drive shaft speed value;

[0027] If it is determined that the value is not exceeded, the smaller calculated value between the two motors is selected as the transmission shaft speed value.

[0028] In at least one possible implementation, obtaining the drive shaft speed limit includes:

[0029] Select the minimum speed limit value among the preset normal vehicle speed limit value and the fault speed limit value corresponding to different fault levels, and calculate the corresponding drive shaft speed limit value.

[0030] Then, the smaller value between the calculated limit of the drive shaft speed and the set limit of the drive shaft speed is selected as the limit of the drive shaft speed.

[0031] In at least one of the possible implementations, the decision on whether to enable the vehicle speed limit function includes: based on the sum of the requested torque corresponding to the average accelerator pedal opening per unit time and the torque of the two motors, using a pre-calibrated mapping table related to the gear position, finding the predetermined rate of change of transmission speed difference corresponding to the current gear position.

[0032] In at least one of the possible implementations, the difference is equal to the drive shaft speed value minus the drive shaft speed limit, and when the difference is determined to be positive, the step of dynamically obtaining the start-up threshold is performed.

[0033] Compared with existing technologies, the main design concept of this invention lies in continuously calculating the drive shaft speed value based on the dual motor speeds, obtaining the drive shaft speed limit value based on the preset vehicle speed limit value and the drive shaft speed setting limit value, and calculating the difference between the drive shaft speed value and the drive shaft speed limit value based on the aforementioned processing; then, integrating the accelerator pedal requested torque and the dual motor torque, and dynamically obtaining the pre-calibrated corresponding start threshold value in conjunction with the current gear; finally, using the difference value and the start threshold value to decide whether to activate the vehicle speed limit function. This invention effectively solves the problem of torque distribution in dual-motor electric drive axle systems, improving the overall performance of new energy vehicles (especially heavy truck models) while avoiding frequent activation of the vehicle speed limit due to fault modes and controlling torque fluctuations at critical points during the vehicle speed limit process. This invention abandons the vehicle speed limit mode that only considers a simple dimension, but instead comprehensively considers the continuous drive shaft speed difference trend and the overall vehicle operating conditions, effectively avoiding vehicle vibration and power interruption while ensuring the safety of the entire vehicle. Attached Figure Description

[0034] 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:

[0035] Figure 1 This is a schematic diagram of a vehicle speed limit function start-up control method based on a dual-motor electric drive axle provided in an embodiment of the present invention. Detailed Implementation

[0036] 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.

[0037] This invention proposes an embodiment of a vehicle speed limiting function start control method based on a dual-motor electric drive axle. Specifically, as follows: Figure 1 As shown, it includes:

[0038] Step S1: Continuously calculate the transmission shaft speed value based on the speed of the first motor and the speed of the second motor in the dual motors;

[0039] In practice, you can first determine whether the speed of the first motor is correct (for example, by combining the calibrated threshold or other vehicle operating parameters); then, divide the speed of the first motor and the speed of the second motor by their respective speed ratios to obtain the calculated results of the drive shaft speeds of different motors; when the calculated results of the two are close (the preset deviation threshold between the two can be used as a criterion), select the drive shaft speed calculated based on the speed of the first motor as the final result.

[0040] Based on this concept, it can be further pointed out that when the speed difference between the aforementioned calculation results of the two motors is large (which can also be judged by a preset deviation threshold), it is determined whether the motor speed corresponding to the larger transmission shaft speed calculation result exceeds the preset maximum speed of the motor; if it is determined to exceed, the transmission shaft speed calculation result corresponding to the motor is selected as the final result (that is, the larger of the two calculated values ​​is selected as the transmission shaft speed value to be obtained in this step); otherwise, if it is determined not to exceed, the smaller of the two calculated values ​​is selected as the transmission shaft speed value to be obtained in this step.

[0041] Step S2: Obtain the drive shaft speed limit value by setting the limit value according to the preset vehicle speed limit value and the drive shaft speed setting value;

[0042] Specifically, the minimum speed limit is selected from the preset normal vehicle speed limit (e.g., 255 km / h for a certain model) and the corresponding fault speed limit for different fault levels (e.g., three different fault speed limits for a certain model). (For example, if the fault is not activated, the selected speed limit is 255 km / h). This minimum speed limit is used to calculate the corresponding driveshaft speed limit (here is a calculation method: driveshaft speed limit = speed limit / wheel radius / 3.6 * 2 * pi / 60). This value is then compared with the set driveshaft speed limit, and the smaller value is selected as the target result obtained in this step, i.e., the driveshaft speed limit.

[0043] Step S3: Calculate the difference between the transmission shaft speed value and the transmission shaft speed limit value;

[0044] Understandably, each time the difference is calculated, the following formula applies: drive shaft speed value - drive shaft speed limit. Furthermore, the next step can be performed only after determining that the difference is positive, i.e., drive shaft speed value - drive shaft speed limit > 0.

[0045] Step S4: Combine the accelerator pedal requested torque and the dual motor torque, and dynamically obtain the pre-calibrated function activation threshold based on the current gear position;

[0046] For example, in some preferred embodiments of the present invention, based on the sum of the requested torque corresponding to the average accelerator pedal opening per unit time (e.g., 1 second) and the torque of the two motors, a pre-calibrated MAP table related to the gear position is used to find the rate of change of the predetermined transmission speed difference corresponding to the current gear position.

[0047] Step S5: Based on the difference and the function activation threshold, decide whether to enable the vehicle speed limit function.

[0048] Unlike typical processing logic, this invention proposes first obtaining the rate of increase based on the continuously calculated difference, and then determining whether the rate of increase exceeds the function activation threshold, in which case the vehicle speed limiting function is activated. Understandably, the aforementioned function activation threshold can be pre-defined in specific units based on different processing logics, such as the aforementioned axle speed change rate, or it can be the axle speed itself.

[0049] In summary, this invention continuously calculates the driveshaft speed based on the dual motor speeds, and obtains the driveshaft speed limit based on the preset vehicle speed limit and driveshaft speed setting limit. The difference between the driveshaft speed value and the driveshaft speed limit is then calculated based on the aforementioned processing. Next, the accelerator pedal requested torque and the dual motor torque are integrated, and the corresponding pre-calibrated start threshold is dynamically obtained based on the current gear position. Finally, the difference and start threshold are used to determine whether to activate the vehicle speed limit function. This invention effectively solves the torque distribution problem in dual-motor electric drive axle systems, improving the overall performance of new energy vehicles (especially heavy-duty trucks) while avoiding frequent activation of the speed limit due to fault modes and controlling torque fluctuations at critical points during speed limiting. This invention abandons the speed limit mode that only considers a simple dimension, but instead comprehensively considers the continuous trend of driveshaft speed differences and the overall vehicle operating conditions, effectively avoiding vehicle vibration and power interruption while ensuring vehicle safety.

[0050] In this invention, when directional terms are mentioned, they are relative concepts based on the embodiments. Furthermore, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0051] The above description of the structure, features, and effects of the present invention is based on the embodiments shown in the figures. However, the above are only preferred embodiments of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred methods can be reasonably combined and matched by those skilled in the art to form a variety of equivalent solutions without departing from or changing the design concept and technical effects of the present invention. Therefore, the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method for starting a vehicle speed limiting function based on a dual-motor electric drive axle, characterized in that, include: Based on the speeds of the first and second motors in the dual-motor system, the drive shaft speed is continuously calculated. The transmission shaft speed limit is obtained by setting the limit based on the preset vehicle speed limit and the transmission shaft speed limit. Calculate the difference between the drive shaft speed value and the drive shaft speed limit value; It integrates the torque requested by the accelerator pedal and the torque of the dual motors, and dynamically obtains the pre-calibrated function activation threshold based on the current gear position; Based on the difference and the function activation threshold, a decision is made on whether to enable the vehicle speed limit function, including: based on the sum of the requested torque corresponding to the average accelerator pedal opening per unit time and the torque of the two motors, using a pre-calibrated mapping table related to the gear position, finding the predetermined transmission speed difference change rate of the motor drive shaft corresponding to the current gear.

2. The vehicle speed limiting function start control method based on a dual-motor electric drive axle according to claim 1, characterized in that, The calculation of the drive shaft speed value includes: Determine if the speed of the first motor is correct; After confirming that the speed of the first motor is normal, the speed of the first motor and the speed of the second motor are divided by the corresponding speed ratio to obtain the calculated speed of the transmission shaft of different motors. When the difference between the calculation results of the two motors is small, the transmission shaft speed calculated based on the speed of the first motor is selected as the transmission shaft speed value.

3. The vehicle speed limiting function start control method based on a dual-motor electric drive axle according to claim 2, characterized in that, The calculation of the drive shaft speed value also includes: When the calculation results of the two motors differ significantly, determine whether the motor speed corresponding to the larger calculated transmission shaft speed exceeds the preset maximum speed of that motor. If it is determined to be excessive, the calculated result of the drive shaft speed corresponding to the motor is selected as the drive shaft speed value; If it is determined that the value is not exceeded, the smaller calculated value between the two motors is selected as the transmission shaft speed value.

4. The vehicle speed limiting function start control method based on a dual-motor electric drive axle according to claim 1, characterized in that, The obtained drive shaft speed limit includes: Select the minimum speed limit value among the preset normal vehicle speed limit value and the fault speed limit value corresponding to different fault levels, and calculate the corresponding drive shaft speed limit value. Then, the smaller value between the calculated limit of the drive shaft speed and the set limit of the drive shaft speed is selected as the limit of the drive shaft speed.

5. The vehicle speed limiting function start control method based on a dual-motor electric drive axle according to any one of claims 1 to 4, characterized in that, The difference is equal to the drive shaft speed value minus the drive shaft speed limit. When the difference is determined to be positive, the step of dynamically obtaining the start-up threshold is executed.

Images