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

Abstract

The invention provides an electric four-wheel drive type single motor fault limp control method and system, and the method comprises the following steps: after a vehicle is started, a vehicle control unit (VCU) detects whether a four-wheel drive power system has a fault or not; when it is detected that a single front motor system or a single rear motor system breaks down, the vehicle speed is intelligently adjusted according to the ramp working condition, and a limp mode is started; after the limping mode is entered, the allowable maximum rotating speed n1 of the single front motor or the single rear motor is calculated and input to a vehicle control unit; the vehicle control unit VCU obtains driving information of the current vehicle and calculates the maximum rotating speed allowed by a normal motor corresponding to the dynamic gradient; calculating the rotating speed n2 of the corresponding fault motor under the maximum rotating speed; n1 and n2 are compared and smaller, and the maximum vehicle speed V of the whole vehicle capable of supporting driving at the moment is calculated; and the vehicle control unit VCU coordinates the driving system and the braking system to control the maximum vehicle speed to be V.

Description

Technical Field

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

[0002] With the advancement of new energy vehicle technology, four-wheel drive electric vehicles are becoming more and more popular among consumers. Such models are usually equipped with two independent power systems, front-wheel drive and rear-wheel drive, to provide stronger power and better handling. For example, the front-wheel drive part may be equipped with a permanent magnet synchronous motor, and the rear-wheel drive part may also use a similar motor configuration. The original intention of the four-wheel drive system is to provide superior performance in various driving conditions, including bad road conditions such as wet, muddy or snowy roads. However, if one of the motor systems fails, that is, a motor cannot work properly, this will cause an imbalance in the power distribution of the entire vehicle.

[0003] Existing solutions for this kind of fault are relatively simple, usually completely shutting down the controller of the faulty motor, so that the vehicle can only rely on the remaining motor to drive when the fault occurs. This treatment method may cause the vehicle to be unable to continue driving, or exhibit unstable performance during driving. In extreme cases, the vehicle may be shut down and require a tow truck for rescue. This not only causes great inconvenience to users, but may also lead to customer dissatisfaction with the product and affect the brand image.

[0004] In order to deal with this problem, some existing technical solutions try to deal with partial failures of the power system through the control system. For example, some high-end models may be equipped with fault detection and automatic adjustment functions, which can automatically switch to a mode that only uses the normal system after detecting a power system failure. However, these solutions are usually unable to effectively deal with the problem of optimizing vehicle speed under different road conditions. Therefore, when faced with complex road conditions such as steep slopes and muddy roads, these vehicles may still experience insufficient performance or excessive loss of the power system. Summary of the invention

[0005] In view of 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 in an electric four-wheel drive vehicle. By identifying different slope road conditions, the speed limit in the limp home mode is dynamically adjusted to effectively limit the mechanical power of the normal drive motor and avoid problems such as overheating, thereby protecting the normal drive system. At the same time, under the premise of ensuring driving safety, the vehicle's availability and driving performance are improved as much as possible.

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

[0007] Step 1: After the vehicle is started, the vehicle controller VCU detects whether there is any fault in the four-wheel drive power system;

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

[0009] 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;

[0010] Step 4: The vehicle controller VCU obtains the current vehicle driving information and calculates the maximum speed allowed by the normal motor corresponding to the dynamic slope;

[0011] Step 5: Calculate the speed n2 of the corresponding faulty motor at the maximum speed;

[0012] 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;

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

[0014] Preferably, the current vehicle driving information obtained in step 4 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 .

[0015] Preferably, the road condition slope s needs to satisfy the climbing torque of:

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

[0017] Preferably, the climbing wheel 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] n2 = v * I / 0.377 / r.

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

[0023] V = 0.377 * (min(n1, n2)) * r / i.

[0024] Preferably, in step 4, the vehicle controller VCU obtains the current vehicle driving information through a slope sensor or an acceleration sensor.

[0025] According to a second aspect of the present invention, a limp home control system for a single motor failure of an electric four-wheel drive vehicle is provided, which is used to implement any of the above-mentioned limp home control methods for a single motor failure of an electric four-wheel drive vehicle, characterized in that the system comprises a vehicle controller VCU, a slope sensor, an acceleration sensor, a drive motor and a braking system;

[0026] 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.

[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 provided by the present invention, and the faulty motor detection and response mechanism can quickly identify and handle motor failures, thereby avoiding potential equipment damage and safety risks.

[0029] 2. The limp home control method and system for a single motor failure in an electric four-wheel drive vehicle provided by the present invention ensures that the vehicle can run safely in the event of a failure through a calculation method for the maximum limp home speed, thereby 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 provided by the present invention ensures stability and consistency under different failure conditions through system integrated protection, thereby improving the overall reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. In addition, all directional indications in the present invention (such as up, down, left, right, front, back, bottom...) are only used to explain the relative position relationship, movement, etc. between the components in a certain specific posture (as shown in the drawings). If the specific posture changes, the directional indication 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 suggesting their relative importance or implicitly indicating the number of technical features indicated.

[0036] First embodiment

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

[0038] Step 1: After the vehicle is started, the vehicle controller detects whether there is any fault in the four-wheel drive power system.

[0039] Step 2: When the vehicle controller detects that there is no power system fault, it drives normally; when the vehicle controller detects that both the single front motor and the single rear motor system are faulty and cannot work, the vehicle is prohibited from driving; when the vehicle controller detects that there is a fault in the single front motor or the single rear motor system, it intelligently adjusts the vehicle speed according to the slope conditions and enters the limp mode.

[0040] Step 3: After entering the limp home mode, the faulty motor must stop working immediately and the motor controller performs the shut-down operation. The faulty motor will cause the back electromotive force to be too high due to the excessively high speed. If the motor controller is maintained in the shut-down state at this time, it is easy for current to flow back and cause damage to the power battery. Therefore, the motor controller needs to perform active short-circuit motor operation at this time, and the vehicle controller needs to control the cooling system to operate at high power; if the motor controller performs active short-circuit motor operation, if the motor is maintained in the active short-circuit state for a long time, it is easy to overheat and cause further damage to the faulty motor. Therefore, it is necessary to control the maximum speed of the faulty motor, which can keep the motor controller in the shut-down state. At this time, the maximum speed n1 allowed by the single front motor or the single rear motor is calculated and input into the vehicle controller.

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

[0042] The current slope s corresponds to the climbing speed, and the climbing torque required is:

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

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

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

[0046] In order to limit the power of the remaining normal motor to the continuous power, P ≤ Pr needs to be maintained. At this time, the dynamic slope is calculated to correspond to the maximum speed allowed by the normal motor;

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

[0048] n2 = v * I / 0.377 / r.

[0049] 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:

[0050] V = 0.377 * (min(n1, n2)) * r / i.

[0051] Step 7: The vehicle controller coordinates the drive system and the brake system to control the maximum speed to V. After calculating the maximum allowable speed, the vehicle controller needs to intelligently adjust the vehicle's limp speed in real time according to the current road condition and slope. If the vehicle speed exceeds the maximum speed at this time, the vehicle controller needs to coordinate the brake system or the remaining normal drive system to slow down to below the maximum speed to maintain limp speed.

[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 use efficiency of the remaining normal motors by introducing a limp home mode when a single motor fails. After detecting the faulty motor, the system will dynamically adjust the vehicle speed through an intelligent control strategy to prevent the normal motor from failing due to overload and overheating. The vehicle can maintain driving performance and handling stability in the event of a failure, thereby alleviating the performance degradation problem caused by motor failure. On the other hand, the present invention improves driving safety in limp home mode through real-time road condition recognition and dynamic adjustment of the speed limit. For different ramps and road conditions, the system can adjust the speed limit in real time to ensure that the vehicle maintains an appropriate speed during driving, avoiding safety hazards caused by excessive or slow speeds, and the vehicle can maintain a relatively safe driving state under a variety of road conditions even in the event of a single motor failure.

[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 controller, a slope sensor, an acceleration sensor, a drive motor and a braking system. The vehicle controller adjusts the limp home speed of the vehicle 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 home.

[0055] The above describes the specific embodiments of the present invention. Based on the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present 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, the vehicle speed is adjusted according to the slope condition and the vehicle 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 and calculates the maximum speed allowed by the normal motor corresponding to the dynamic slope; Step 5: Calculate the speed n2 of the corresponding faulty motor at the maximum speed; 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 current vehicle driving information obtained in step 4 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 .

3. The limp home control method for a single motor failure of an electric four-wheel drive vehicle according to claim 2, characterized in that: The road condition slope s needs to satisfy the climbing torque of: T = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * i。 4. The limp home control method for a single motor failure of an electric four-wheel drive vehicle according to claim 3, characterized in that: The climbing wheel power corresponding to the climbing torque is: P = (a + bv + cv 2 + 9.8 * m * sin(ATAN(s))) * v / 3600; Where P ≤ P r .

5. The limp home control method for a single motor failure of an electric four-wheel drive vehicle according to claim 4, characterized in that: When P= Pr, the maximum speed n2 of the faulty motor corresponding to the vehicle speed v is: n2 = v * I / 0.377 / r.

6. The limp home control method for a single motor failure of an electric four-wheel drive vehicle according to claim 5, characterized in that: The calculation formula of the maximum vehicle speed V is: V = 0.377 * (min(n1, n2)) * r / i.

7. 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.

8. 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 7, 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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