Vehicle speed limiting function starting control method based on double-motor electric drive axle

Abstract

The invention discloses a vehicle speed limiting function starting control method based on a double-motor electric drive axle, which mainly comprises the following steps: continuously calculating a transmission shaft rotating speed value according to double-motor rotating speed, and obtaining a transmission shaft rotating speed limit value according to a preset vehicle speed limit value and a transmission shaft rotating speed set limit value; the difference value between the transmission shaft rotating speed value and the transmission shaft rotating speed limit value is obtained based on the processing; then fusing the accelerator pedal request torque and the dual-motor torque, and dynamically obtaining a pre-calibrated corresponding starting threshold value in combination with the current gear; and finally, deciding whether to start a vehicle speed limiting function or not by utilizing the difference value and a starting threshold value. According to the method, a vehicle speed limiting mode only under simple dimension consideration is abandoned, the continuous driving shaft rotating speed difference trend and the whole vehicle working condition are comprehensively considered, the problem of a double-motor electric drive axle system in the aspect of torque distribution is effectively solved, the whole performance of a new energy vehicle is improved, and the whole vehicle safety is ensured; and the phenomena of shaking and power interruption when the whole vehicle advances are effectively reduced.

Description

Technical Field

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

[0002] With the rapid development of new energy vehicle technology, the vehicle control unit (VCU), as the core control unit of the vehicle, undertakes key tasks such as multi-system coordination, energy management and safety control. As an important part of the VCU, the speed limit function has a direct impact on the safety, economy and user experience of the vehicle. Traditional speed limit strategies mainly rely on fixed threshold control, such as limiting the speed to no more than 20km / h in R gear, limiting the speed to 15km / h in limp mode, or reducing power output through driving modes (such as ECO mode) to achieve speed limit. However, such methods have the problem of insufficient dynamic adaptability under complex working conditions. For example, when the driver makes a mistake, the road slope changes, or the battery status fluctuates, it is easy to cause the vehicle speed to overshoot or control failure, causing safety risks.

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

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

[0005] Existing VCUs adjust torque response characteristics based on preset driving modes (such as ECO, NORMAL, and SPORT). For example, ECO mode reduces energy consumption by limiting motor power output and the vehicle's upper speed limit (typically 100-120 km / h), while SPORT mode allows higher speeds to improve power performance. This approach relies on a static map, making it difficult to adapt to real-time road conditions and battery status, and also creates conflicts between energy recovery and power output.

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

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

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

[0009] Existing technology proposes a speed limit strategy that integrates navigation destination mileage. When the remaining battery charge is insufficient to reach the destination based on current driving habits, the VCU dynamically adjusts the maximum speed limit (for example, to below 60 km / h) by consulting the per-kilometer minimum power consumption map and forcibly shuts off high-voltage accessories like the air conditioner to reduce energy consumption. This approach integrates navigation data with real-time power consumption analysis to achieve coordinated control of energy optimization and speed limit.

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

[0011] Existing technologies require that the speed limit function of a VCU comply with the ISO 26262 functional safety standard, with its ASIL level determined through a hazard analysis and risk assessment (HARA) process. For example, in the gear shift function, the VCU ensures safety degradation in the event of a failure through redundant signal monitoring and safe state transition logic (such as vehicle speed detection when shifting into P gear). This approach assigns ASIL levels to each subsystem through a hierarchical control strategy, 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 startup control method based on a dual-motor electric drive axle to solve the above-mentioned technical problems.

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

[0014] The present invention provides a method for starting and controlling a vehicle speed limit function based on a dual-motor electric drive axle, which includes:

[0015] Continuously calculating the transmission shaft speed value according to the speed of the first motor and the speed of the second motor in the dual motors;

[0016] Obtaining a transmission shaft speed limit value according to a preset vehicle speed limit value and a transmission shaft speed setting limit value;

[0017] Calculating a difference between the transmission shaft speed value and the transmission shaft speed limit;

[0018] The accelerator pedal request torque and dual motor torque are integrated, and the pre-calibrated function activation threshold is dynamically obtained in combination with the current gear;

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

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

[0021] determining whether the rotational 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 calculation results of the transmission shaft speeds of the different motors;

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

[0024] In at least one possible implementation, calculating the transmission shaft speed value further includes:

[0025] When the calculation results of the two motors differ greatly, determining whether the motor speed corresponding to the larger transmission shaft speed calculation result exceeds the preset maximum speed of the motor;

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

[0027] If it is determined that it does not exceed, the smaller calculated result of the two motors is selected as the transmission shaft speed value.

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

[0029] Selecting the minimum speed limit value among the preset normal vehicle speed limit value and the fault speed limit values ​​corresponding to different fault levels, and calculating the corresponding transmission shaft speed calculation limit value;

[0030] The smaller value between the transmission shaft speed calculation limit and the transmission shaft speed setting limit is then selected as the transmission shaft speed limit.

[0031] In at least one possible implementation, the decision of whether to turn on the speed limit function includes: based on the sum of the requested torque corresponding to the average accelerator pedal opening per unit time and the dual-motor torque, using a pre-calibrated mapping table related to the gear position, looking up the corresponding established transmission speed difference change rate under the current gear position.

[0032] In at least one possible implementation manner, the difference=the transmission shaft speed value-the transmission shaft speed limit value, and when it is determined that the difference is positive, the step of dynamically acquiring the start threshold is performed.

[0033] Compared to the prior art, the present invention's key design concept lies in continuously calculating the driveshaft speed based on the dual-motor speeds. The driveshaft speed limit is then determined based on a preset vehicle speed limit and a set driveshaft speed limit. Based on this processing, the difference between the driveshaft speed value and the driveshaft speed limit is calculated. The accelerator pedal torque request and the dual-motor torque are then integrated, and a pre-calibrated activation threshold is dynamically determined based on the current gear position. Finally, the difference and the activation threshold are used to determine whether to activate the speed limit function. This invention effectively addresses torque distribution issues in dual-motor electric drive axle systems, improving the overall performance of new energy vehicles (especially heavy-duty trucks) while avoiding frequent speed limit activation due to fault modes and controlling torque fluctuations at critical points during speed limiting. This invention eschews simplistic speed limit models and instead comprehensively considers the continuous driveshaft speed difference trend and overall vehicle operating conditions, effectively preventing vehicle vibration and power interruption while ensuring vehicle safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described below with reference to the accompanying drawings, in which:

[0035] Figure 1 A schematic diagram of a method for starting and controlling a vehicle speed limit function based on a dual-motor electric drive axle according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0037] The present invention proposes an embodiment of a vehicle speed limit function start control method based on a dual-motor electric drive bridge. Specifically, Figure 1 shown, including:

[0038] Step S1, continuously calculating the transmission shaft speed value according to the speed of the first motor and the speed of the second motor in the dual motors;

[0039] In actual operation, it is possible to first determine whether the speed of the first motor is correct (for example, in combination with a calibrated threshold or other vehicle operating parameters); then, the speed of the first motor and the speed of the second motor are divided by their corresponding speed ratios respectively 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 measurement standard), the drive shaft speed calculated based on the speed of the first motor is selected as the final result.

[0040] Based on this conception, 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 calculated value of the two is selected as the transmission shaft speed value to be obtained in this step); conversely, if it is determined that it does not exceed, the smaller calculated value of the two is selected as the transmission shaft speed value to be obtained in this step.

[0041] Step S2: obtaining a transmission shaft speed limit value according to a preset vehicle speed limit value and a transmission shaft speed setting limit value;

[0042] Specifically, from the preset normal vehicle speed limit value (such as 255km / h for a certain vehicle model) and the fault speed limit values ​​corresponding to different fault levels (such as three different fault speed limit values ​​corresponding to three fault levels set for a certain vehicle model), the minimum speed limit value is selected (combined with the example, if the fault is not activated, the selected speed limit value is 255km / h) to obtain the corresponding drive shaft speed calculation limit value (here is a calculation method: drive shaft speed calculation limit value = speed limit value / wheel radius / 3.6*2*pi / 60), and compared with the drive shaft speed setting limit value, and then the smaller value after comparison is selected as the target result obtained in this step, that is, the drive shaft speed limit value.

[0043] Step S3, calculating the difference between the transmission shaft speed value and the transmission shaft speed limit;

[0044] It is understood that each time the difference is calculated, the following formula is used: transmission shaft speed value - transmission shaft speed limit. Furthermore, the next step may be performed after determining that the difference is positive, that is, transmission shaft speed value - transmission shaft speed limit > 0.

[0045] Step S4: integrating the accelerator pedal request torque and the dual-motor torque, and dynamically obtaining a pre-calibrated function activation threshold in combination with the current gear;

[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 (such as 1s) and the dual-motor torque, a pre-calibrated MAP table related to the gear position is used to find the corresponding established transmission speed difference change rate under the current gear position.

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

[0048] Unlike conventional processing logic, the present invention first calculates the rate of increase based on the continuously calculated difference, then determines if the rate of increase exceeds the function activation threshold, thereby activating the speed limit function. It is understood that the aforementioned function activation threshold can be pre-calibrated to specific units based on different processing logic, such as the aforementioned shaft speed change rate, or the shaft speed itself.

[0049] In summary, the driveshaft speed is continuously calculated based on the dual-motor speeds. The driveshaft speed limit is then determined based on a preset vehicle speed limit and a set driveshaft speed limit. The difference between the driveshaft speed and the driveshaft speed limit is then calculated based on the aforementioned process. The accelerator pedal torque request and the dual-motor torque are then integrated, and a pre-calibrated activation threshold is dynamically determined based on the current gear position. Finally, the difference and the activation threshold are used to determine whether to activate the speed limit function. This invention effectively addresses torque distribution issues in dual-motor electric drive axle systems, improving the overall performance of new energy vehicles (especially heavy-duty trucks) while avoiding frequent speed limit activation due to fault conditions and controlling torque fluctuations at critical points during speed limiting. This invention avoids simplistic speed limit models and instead comprehensively considers the continuous driveshaft speed difference trend and the overall vehicle operating conditions, effectively preventing vehicle vibration and power interruption while ensuring vehicle safety.

[0050] If the expressions expressing directions are mentioned in the embodiments of the present invention, they are relative concepts based on the embodiments. In addition, "at least one" refers to one or more, and "more" refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in 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, b and c, where a, b, c can be single or multiple.

[0051] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings, but the above is only a preferred embodiment of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred modes can be reasonably combined and matched into a variety of equivalent schemes by those skilled in the art without departing from or changing the design ideas and technical effects of the present invention; therefore, the scope of implementation of the present invention is not limited to what is shown in the drawings. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the scope of protection of the present invention.

Claims

1. A method for starting and controlling a vehicle speed limit function based on a dual-motor electric drive axle, characterized in that: include: Continuously calculating the transmission shaft speed value according to the speed of the first motor and the speed of the second motor in the dual motors; Obtaining a transmission shaft speed limit value according to a preset vehicle speed limit value and a transmission shaft speed setting limit value; Calculating a difference between the transmission shaft speed value and the transmission shaft speed limit; The accelerator pedal request torque and dual motor torque are integrated, and the pre-calibrated function activation threshold is dynamically obtained in combination with the current gear; Based on the difference and the function activation threshold, a decision is made as to whether to activate the vehicle speed limit function.

2. The vehicle speed limit function startup control method based on a dual-motor electric drive axle according to claim 1 is characterized in that: Calculating the transmission shaft speed value includes: determining whether the rotational 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 calculation results of the transmission shaft speeds of the 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 limit function startup control method based on the dual-motor electric drive axle according to claim 2 is characterized in that: The calculation of the transmission shaft speed value further includes: When the calculation results of the two motors differ greatly, determining 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 be exceeded, the calculated result of the transmission shaft speed corresponding to the motor is selected as the transmission shaft speed value; If it is determined that it does not exceed, the smaller calculated result of the two motors is selected as the transmission shaft speed value.

4. The vehicle speed limit function startup control method based on a dual-motor electric drive axle according to claim 1 is characterized in that: Obtaining the transmission shaft speed limit includes: Selecting the minimum speed limit value among the preset normal vehicle speed limit value and the fault speed limit values ​​corresponding to different fault levels, and calculating the corresponding transmission shaft speed calculation limit value; The smaller value between the transmission shaft speed calculation limit and the transmission shaft speed setting limit is then selected as the transmission shaft speed limit.

5. The vehicle speed limit function startup control method based on a dual-motor electric drive axle according to claim 1 is characterized in that: The decision of whether to activate the speed limit function includes: searching for a predetermined transmission speed difference change rate corresponding to the current gear using a pre-calibrated mapping table related to the gear position based on the sum of the requested torque corresponding to the average accelerator pedal opening per unit time and the dual-motor torque.

6. The method for starting and controlling a vehicle speed limit function based on a dual-motor electric drive axle according to any one of claims 1 to 5, characterized in that: The difference=the transmission shaft speed value-the transmission shaft speed limit value, and when it is determined that the difference is positive, the step of dynamically obtaining the start threshold is executed.

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