Limp control method and system for single motor failure of electric four-wheel drive vehicle

Abstract

The present invention provides a limp home control method and system for a single motor failure in an electric four-wheel drive vehicle, wherein the method comprises the following steps: after the vehicle is started, a vehicle controller VCU detects whether a four-wheel drive power system has a fault; when a fault is detected in a single front motor or a single rear motor system, the vehicle speed is intelligently adjusted according to a slope condition to enter a limp home mode; after entering the limp home mode, a maximum rotation speed n1 allowed by the single front motor or the single rear motor is calculated and input into the vehicle controller; the vehicle controller VCU obtains the current vehicle driving information, calculates the maximum rotation speed allowed by a normal motor corresponding to a dynamic slope; calculates the rotation speed n2 corresponding to the faulty motor at the maximum rotation speed; compares n1 and n2 and takes the smaller one, and calculates the maximum vehicle speed V that the vehicle can support at this time; the vehicle controller VCU coordinates a driving system and a braking system to control the maximum vehicle speed to be V.

Description

Technical Field

[0001] The present invention relates to autonomous driving, and specifically, to a limp-home control method and system for a single-motor failure of an electric four-wheel drive vehicle model. Background Art

[0002] With the progress of new energy vehicle technology, four-wheel drive electric vehicles are increasingly favored by consumers. Such vehicle models usually are equipped with two sets of independent power systems for the front drive and the rear drive to provide stronger power and better handling performance. For example, the front drive part may be equipped with a permanent magnet synchronous motor, and the rear drive part may also use a similar motor configuration. The design purpose of the four-wheel drive system is to provide superior performance under various driving conditions, including harsh road conditions such as slippery, muddy or snowy roads. However, if one of the motor systems fails, that is, a certain motor cannot work properly, this will lead to an imbalance in the power distribution of the whole vehicle.

[0003] The existing solutions for dealing with such a failure are relatively simple. Usually, the controller of the failed motor is completely turned off, so that when a failure occurs, the vehicle can only be driven by the remaining motors. This processing method may cause the vehicle to be unable to continue driving, or show unstable performance during driving. In extreme cases, the vehicle may stop operating and need to be towed for rescue. This not only causes great inconvenience to users, but also may lead to customer dissatisfaction with the product and affect the brand image.

[0004] To address this problem, some existing technical solutions attempt to deal with partial failures of the power system through a control system. For example, some high-end vehicle models may be equipped with a failure detection and automatic adjustment function, which can automatically switch to a mode that only uses the normal system after detecting a failure of a certain power system. However, these solutions usually cannot effectively handle the optimization problem of vehicle speed under different road conditions. Therefore, when facing complex road conditions such as steep slopes and muddy roads, these vehicles may still have insufficient performance or excessive power system consumption. Summary of the Invention

[0005] Aiming at the defects in the prior art, the purpose of the present invention is to provide a limp-home control method and system for a single-motor failure of an electric four-wheel drive vehicle model. By identifying different slope road conditions and dynamically adjusting the vehicle speed limit in the limp-home mode, the mechanical power of the normal driving motor is effectively limited to avoid problems such as overheating, thereby protecting the normal driving system. At the same time, on the premise of ensuring driving safety, the availability and driving performance of the vehicle are improved as much as possible.

[0006] According to a first aspect of the present invention, there is provided a limp-home control method for a single-motor failure of an electric four-wheel drive vehicle model, including the following steps:

[0007] Step 1: After the vehicle is started, the vehicle control unit VCU detects whether there is a failure in the four-wheel drive power system;

[0008] Step 2: When a fault is detected in the front single-motor or rear single-motor system, the vehicle speed is intelligently adjusted according to the ramp condition, and the limp-home mode is entered.

[0009] Step 3: After entering the limp-home mode, calculate the maximum allowable speed n1 of the front single-motor or rear single-motor and input it to the vehicle controller.

[0010] Step 4: The vehicle controller VCU obtains the driving information of the current vehicle and calculates the maximum allowable speed of the normal motor corresponding to the dynamic gradient.

[0011] Step 5: Calculate the speed n2 of the faulty motor corresponding to the maximum speed.

[0012] Step 6: Compare the magnitudes of n1 and n2 and take the smaller value, and calculate the maximum vehicle speed V that the vehicle can support at this time.

[0013] Step 7: The vehicle controller VCU coordinates the drive system and the braking system to control the maximum vehicle speed to V.

[0014] Preferably, the driving information of the current vehicle obtained in Step 4 includes vehicle speed information, gradient information, and driving resistance information; the vehicle controller VCU obtains the current road condition gradient s, the full-load mass m of the vehicle, the driving resistance coefficients a, b, c, the rolling radius r, the drive motor speed ratio i, the vehicle speed v, and the continuous power P of the remaining normal drive motors. r .

[0015] Preferably, the road condition gradient s needs to satisfy the climbing torque as follows:

[0016] T = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * i .

[0017] Preferably, the climbing wheel-side power corresponding to the climbing torque is:

[0018] P = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * v / 3600 ;

[0019] where P ≤ Pr.

[0020] Preferably, when P = Pr, the maximum speed n2 of the faulty motor corresponding to the vehicle speed v is:

[0021] n 2 = v * i / 0.377 / r .

[0022] Preferably, the calculation formula for the maximum vehicle speed V is:

[0023] V = 0.377 * (min(n1 , n 2 )) * r / i 。

[0024] Preferably, in step 4, the vehicle control unit (VCU) obtains the driving information of the current vehicle through a ramp sensor or an acceleration sensor.

[0025] According to a second aspect of the present invention, there is provided a limp-home control system for a single-motor failure of an electric four-wheel drive vehicle model, which is used to implement the limp-home control method for a single-motor failure of the electric four-wheel drive vehicle model described above. The system is characterized in that it includes a vehicle control unit (VCU), a gradient sensor, an acceleration sensor, a drive motor, and a braking system;

[0026] The vehicle control unit (VCU) adjusts the vehicle limp-home speed in real time according to the ramp gradient of the current road condition, and coordinates the braking system to maintain the limp-home state with the vehicle speed v below the maximum vehicle speed V.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The limp-home control method and system for a single-motor failure of an electric four-wheel drive vehicle model provided by the present invention can quickly identify and handle motor failures through the failure motor detection and response mechanism, avoiding potential equipment damage and safety risks.

[0029] 2. The limp-home control method and system for a single-motor failure of an electric four-wheel drive vehicle model provided by the present invention ensure the safe operation of the vehicle in case of failure through the calculation method of the maximum limp-home speed, optimizing the overall performance of the vehicle.

[0030] 3. The limp-home control method and system for a single-motor failure of an electric four-wheel drive vehicle model provided by the present invention ensure the stability and consistency in different failure cases through system integration protection, improving the overall reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] By reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings, other features, objects, and advantages of the present invention will become more apparent:

[0032] Figure 1 It is a flowchart of the limp-home control method for a single-motor failure of an electric four-wheel drive vehicle model in the first embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and illustrated herein can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0035] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, all directional indications (such as up, down, left, right, front, back, bottom, etc.) in the present invention are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly. Further, the descriptions involving "first", "second", etc. in the invention are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features.

[0036] First Embodiment

[0037] As Figure 1 shown, a limp-home control method for a single-motor failure of an electric four-wheel drive vehicle model provided in this embodiment includes:

[0038] Step 1: After the vehicle starts, the vehicle control unit (VCU) detects whether there is a failure in the four-wheel drive power system.

[0039] Step 2: When the vehicle control unit detects no failure in the power system, normal driving is performed; when the vehicle control unit detects that both the single front motor and single rear motor systems fail and cannot work, the vehicle is prohibited from driving; when the vehicle control unit detects a failure in the single front motor or single rear motor system, the vehicle speed is intelligently adjusted according to the ramp condition and the limp-home mode is entered.

[0040] Step 3: After entering the limp home mode, the faulty motor needs to stop working immediately, and the motor controller performs the switching tube operation. The faulty motor may have too high a back electromotive force due to excessive speed. At this time, if the motor controller maintains the switching tube state, current backflow is likely to occur, causing damage to the power battery. Therefore, at this time, the motor controller needs to perform the active short-circuit motor operation, and the vehicle controller needs to control the cooling system to operate at high power; if the motor controller performs the active short-circuit motor operation, and the motor maintains the active short-circuit state for a long time at this time, it is likely to overheat and cause further damage to the faulty motor. Therefore, it is necessary to control the maximum speed of the faulty motor, and this maximum speed can keep the motor controller in the switching tube state. At this time, calculate the maximum allowable speed n1 of the single front motor or single rear motor and input it to the vehicle controller.

[0041] Step 4: The vehicle controller VCU obtains the driving information of the current vehicle through the ramp sensor or acceleration sensor, including vehicle speed information, slope information, and driving resistance information, specifically including the current road condition slope s, the full-load mass m of the vehicle, the driving resistance coefficients a, b, c, the rolling radius r, the drive motor speed ratio i, and the vehicle speed v. Considering that the remaining normal motors need to undertake the subsequent driving tasks of the whole vehicle, and the vehicle conditions may encounter working conditions such as long-time climbing, in order to avoid problems such as overheating and failure, the power of the remaining normal motors needs to be limited within the continuous power. Therefore, it is also necessary to obtain the continuous power P of the remaining normal drive motors. r 。

[0042] The climbing vehicle speed corresponding to the current slope s needs to satisfy the climbing torque as follows:

[0043] T = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * i 。

[0044] The climbing wheel-side power corresponding to the climbing torque is:

[0045] P = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * v / 3600 ;

[0046] To limit the power of the remaining normal motors within the continuous power, it is necessary to keep P ≤ Pr. At this time, calculate the maximum allowable speed of the normal motors corresponding to the dynamic slope;

[0047] Step 5: When P = Pr, the speed n2 of the faulty motor corresponding to the maximum speed is:

[0048] n 2 = v * i / 0.377 / r 。

[0049] Step 6: Compare the magnitudes of n1 and n2 and take the smaller one, and calculate the maximum vehicle speed V that the whole vehicle can support at this time:

[0050] V = 0.377 * (min(n 1 , n 2 )) * r / i 。

[0051] Step Seven: The vehicle control unit (VCU) coordinates the drive system and the braking system to control the maximum vehicle speed at V. After calculating the maximum allowable vehicle speed, the VCU needs to intelligently adjust the vehicle's limp-home speed in real time according to the slope of the current road condition. If the vehicle speed exceeds the maximum speed at this time, the VCU needs to coordinate the braking system or the remaining normal drive system to reduce the speed below the maximum speed to maintain limp-home driving.

[0052] The limp-home control method for a single-motor failure of an electric four-wheel drive vehicle provided by the present invention optimizes the utilization efficiency of the remaining normal motors by introducing a limp-home mode when a single-motor failure occurs. After detecting the faulty motor, the system will dynamically adjust the vehicle speed through an intelligent control strategy to prevent the normal motor from overloading and overheating and failing. The vehicle can maintain its driving performance and handling stability under fault conditions, thereby reducing the performance degradation problem caused by motor failure. On the other hand, the present invention improves the driving safety in the limp-home mode through real-time road condition recognition and dynamic adjustment of speed limits. For different ramp and road conditions, the system can dynamically adjust the speed limit in real time to ensure that the vehicle maintains an appropriate speed during driving and avoid potential safety hazards caused by excessive or too slow speed. Even when a single-motor failure occurs, the vehicle can maintain a relatively safe driving state under various road conditions.

[0053] Second Embodiment

[0054] This embodiment provides a limp-home control system for a single-motor failure of an electric four-wheel drive vehicle, which is used to implement the limp-home control method for a single-motor failure of an electric four-wheel drive vehicle provided in the above embodiment. The system includes a vehicle control unit (VCU), a slope sensor, an acceleration sensor, a drive motor, and a braking system. The VCU adjusts the vehicle's limp-home speed in real time according to the slope of the current road condition and coordinates the braking system to keep the vehicle speed v below the maximum speed V to maintain limp-home driving.

[0055] The specific embodiments of the present invention have been described above. Through the above description, relevant staff can make various changes and modifications within the scope not deviating from the technical idea of this invention.

Claims

1. A limp home control method for a single motor failure of an electric four-wheel drive vehicle, characterized in that: The method comprises the following steps: Step 1: After the vehicle is started, the vehicle controller VCU detects whether there is any fault in the four-wheel drive power system; Step 2: When the vehicle controller VCU detects a fault in the single front motor or single rear motor system, it intelligently adjusts the vehicle speed according to the slope condition and enters the limp home mode; Step 3: After entering the limp home mode, the maximum speed n1 allowed by the single front motor or the single rear motor is calculated and input to the vehicle controller VCU; Step 4: The vehicle controller VCU obtains the current vehicle driving information, which includes vehicle speed information, slope information and driving resistance information; the vehicle controller VCU obtains the current road slope s, the vehicle full load mass m, driving resistance coefficients a, b, c, rolling radius r, drive motor speed ratio i, vehicle speed v and the remaining normal drive motor continuous power P r ; Keep P ≤ P r , limit the power of the remaining normal motor to the continuous power, and calculate the maximum speed allowed by the normal motor corresponding to the dynamic slope; The road slope s needs to satisfy the climbing torque of: T = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * i; The climbing wheel power corresponding to the climbing torque is: P = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * v / 3600; Step 5: When P = P r When the dynamic slope corresponds to the maximum speed allowed by the normal motor, the speed n2 of the faulty motor is calculated. The maximum speed n2 of the faulty motor corresponding to the vehicle speed v is: n 2 = v * i / 0.377 / r; Step 6: Compare n1 and n2 and take the smaller one, and calculate the maximum speed V that the vehicle can support at this time; Step 7: The vehicle controller VCU coordinates the drive system and the brake system to control the maximum vehicle speed to V.

2. The limp home control method for a single motor failure of an electric four-wheel drive vehicle according to claim 1, characterized in that: The calculation formula of the maximum vehicle speed V is: V = 0.377 * (min(n 1 , n 2 )) * r / i 。 3. The limp home control method for a single motor failure of an electric four-wheel drive vehicle according to claim 1, characterized in that: In the step 4, the vehicle controller VCU obtains the current vehicle driving information through a slope sensor or an acceleration sensor.

4. A limp home control system for a single motor failure of an electric four-wheel drive vehicle, used to implement the limp home control method for a single motor failure of an electric four-wheel drive vehicle as claimed in any one of claims 1 to 3, characterized in that: The system includes a vehicle controller VCU, a slope sensor, an acceleration sensor, a drive motor and a braking system; The vehicle controller VCU adjusts the vehicle limp speed in real time according to the current road condition and slope, and coordinates the braking system to keep the vehicle speed v below the maximum vehicle speed V to maintain limp speed.

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