Methods, devices and media for determining motor drive torque

Abstract

This disclosure relates to a method for determining motor drive torque, a vehicle controller, and an automobile, belonging to the field of four-wheel drive pure electric vehicle technology. The method includes: acquiring the accelerometer pedal depth and vehicle speed; determining the required drive torque based on the accelerometer pedal depth and vehicle speed; determining the load ratio between the front and rear axles; determining the torque distribution ratio between the front and rear axles based on the load ratio, wherein the required drive torque is the sum of the front and rear axle torques; detecting the steering wheel angle to determine the vehicle's driving trajectory; compensating or not compensating the torque distribution ratio between the front and rear axles based on the vehicle's driving trajectory, the TCS trigger flag, and the VDC trigger flag to obtain the final torque distribution ratio; determining the motor drive torque based on the final torque distribution ratio; and calculating the final motor drive torque by taking the smaller of the motor drive torque and a motor drive torque threshold. The motor drive torque determined by this disclosure enables the vehicle to prevent slippage.

Description

Technical Field

[0001] This disclosure pertains to the field of four-wheel drive pure electric vehicle technology, and particularly relates to a method, device, and medium for determining motor drive torque. Background Technology

[0002] The dual-motor four-wheel drive system is an advanced powertrain method that uses two independent motors to drive the front and rear axles of the vehicle, thus achieving a full-time four-wheel drive effect. The main advantages of this system include: First, powerful driving force and climbing performance: the two independent motors can apply different torques to the front and rear axles according to road conditions and driving needs, greatly improving the vehicle's traction and climbing ability. Second, flexible torque distribution: the system can adjust the torque distribution ratio between the front and rear wheels in real time, thereby improving the vehicle's handling stability and passability.

[0003] When driving on surfaces with low traction, such as ice and snow, four-wheel drive is easier to control and provides better active safety compared to two-wheel drive. With the development of electric vehicle technology, users have placed higher demands on fuel economy, power, and driving stability. The introduction of four-wheel drive technology allows electric vehicles to start, climb hills, and accelerate better on low-traction and split-road surfaces. However, the instantaneous torque output characteristics of electric motors result in faster vehicle power response and greater initial driving force, making wheels prone to slippage on low-traction surfaces, leading to decreased vehicle stability. Therefore, improving vehicle anti-slip performance while maintaining power and stability is a crucial issue that urgently needs to be addressed. Summary of the Invention

[0004] This disclosure proposes a method for determining motor drive torque, a vehicle controller, and an automobile to solve the aforementioned technical problems.

[0005] According to a first aspect of this disclosure, a method for determining motor drive torque is provided. The method includes: acquiring accelerometer pedal depth and vehicle speed; determining drive demand torque based on the accelerometer pedal depth and vehicle speed; determining the load ratio between the front axle and the rear axle; determining the torque distribution ratio between the front axle and the rear axle based on the load ratio, wherein the drive demand torque is the sum of the front axle torque and the rear axle torque; detecting steering wheel angle to determine the vehicle's driving trajectory; detecting a TCS trigger flag and a VDC trigger flag; compensating or not compensating the torque distribution ratio between the front axle and the rear axle based on the vehicle's driving trajectory, the TCS trigger flag, and the VDC trigger flag to obtain a final torque distribution ratio; determining the motor drive torque based on the final torque distribution ratio; and calculating the final motor drive torque by taking the smaller value between the motor drive torque and a motor drive torque threshold.

[0006] In some embodiments, determining the load ratio of the front axle to the rear axle includes: according to the formula: Determine the load on the front axle. G represents the car's weight, g represents gravitational acceleration, b represents the distance from the rear axle to the car's center of gravity, and L represents the car's wheelbase. This indicates that the car has a high center of gravity. Indicates the acceleration of a car. The value represents air resistance, r represents the tire rolling radius, and f represents the road friction coefficient. Indicates the road slope angle;

[0007] According to the formula: Determine the load on the rear axle , This represents the distance from the front axle to the vehicle's center of gravity; the load ratio of the front axle to the rear axle is... : .

[0008] In some embodiments, determining the torque distribution ratio between the front axle and the rear axle based on the load ratio between the front axle and the rear axle includes: the torque distribution ratio of the front axle is... The torque distribution ratio of the rear axle is .

[0009] In some embodiments, the vehicle's driving trajectory is a straight line; the TCS trigger flag indicates that the single-axis TCS function is triggered; the compensation of the torque distribution ratio between the front axle and the rear axle based on the vehicle's driving trajectory and the TCS trigger flag includes: obtaining the road adhesion coefficient, the front slip ratio, and the rear slip ratio; and transferring the driving torque of the slipping axle to the non-slipping axle based on the road adhesion coefficient, the front slip ratio, and the rear slip ratio.

[0010] In some embodiments, the vehicle's driving trajectory is a straight line; the TCS trigger flag indicates that the dual-axle TCS function is triggered simultaneously; the step of executing a corresponding strategy based on the vehicle's driving trajectory and the TCS trigger flag, without compensating for the torque distribution ratio between the front axle and the rear axle, includes: obtaining the road adhesion coefficient, front slip ratio, and rear slip ratio; and actively limiting the maximum driving torque of the front axle and the maximum driving torque of the rear axle based on the road adhesion coefficient, front slip ratio, and rear slip ratio.

[0011] In some embodiments, the vehicle's driving trajectory is a curve; the VDC trigger flag indicates that the VDC function has not been triggered; the torque distribution ratio between the front axle and the rear axle is compensated according to the vehicle's driving trajectory and the VDC trigger flag, including: obtaining the actual yaw rate and the target yaw rate; and adjusting the torque distribution ratio between the front axle and the rear axle based on the difference between the actual yaw rate and the target yaw rate.

[0012] In some embodiments, the vehicle's driving trajectory is a curve; the VDC trigger flag indicates that the VDC function is triggered; compensation is made for the torque distribution ratio between the front axle and the rear axle based on the vehicle's driving trajectory and the VDC trigger flag, including: obtaining the actual yaw rate, the target yaw rate, the front axle slip ratio, and the rear circumferential slip ratio; and adjusting the torque distribution ratio between the front axle and the rear axle based on the front axle slip ratio, the rear circumferential slip ratio, and the difference between the actual yaw rate and the target yaw rate.

[0013] In some embodiments, determining the motor drive torque based on the final torque distribution ratio includes: the motor drive torque of the front axle is... Where K represents the compensated front axle distribution ratio, T represents the compensated rear axle distribution ratio, and E represents the required drive torque; the motor drive torque of the rear axle is... .

[0014] According to a second aspect of this disclosure, a vehicle controller is provided, comprising: a memory; and a processor coupled to the memory, the processor being configured to execute the motor drive torque determination method as described above based on instructions stored in the memory.

[0015] According to a third aspect of this disclosure, an automobile is provided, including the aforementioned vehicle controller.

[0016] The beneficial effects of this disclosure are: the motor drive torque determined by this disclosure can prevent the vehicle from slipping when driving on low-friction roads, improve the vehicle's power performance, ensure the vehicle's stability, and further prevent traffic accidents caused by slippage. Attached Figure Description

[0017] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the present disclosure and, together with their description, serve to explain the principles of the present disclosure.

[0018] Figure 1 A flowchart for the method of determining the motor drive torque.

[0019] Figure 2 This is a diagram illustrating the forces acting on a car accelerating uphill.

[0020] Figure 3 Block diagram of a device for determining motor drive torque. Detailed Implementation

[0021] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present disclosure.

[0022] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this disclosure or its application or use.

[0023] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0024] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0025] like Figure 1 As shown, the method for determining motor drive torque includes: acquiring the accelerometer pedal depth and vehicle speed; determining the required drive torque based on the accelerometer pedal depth and vehicle speed; determining the load ratio between the front axle and the rear axle; determining the torque distribution ratio between the front axle and the rear axle according to the load ratio, wherein the required drive torque is the sum of the front axle torque and the rear axle torque; detecting the steering wheel angle to determine the vehicle's driving trajectory; detecting the TCS trigger flag and the VDC trigger flag; compensating or not compensating the torque distribution ratio between the front axle and the rear axle according to the vehicle's driving trajectory, the TCS trigger flag, and the VDC trigger flag to obtain the final torque distribution ratio; determining the motor drive torque based on the final torque distribution ratio; and calculating the final motor drive torque by taking the smaller value between the motor drive torque and a motor drive torque threshold.

[0026] In some embodiments, determining the load ratio of the front axle to the rear axle includes: according to the formula: Determine the load on the front axle. G represents the car's weight, g represents gravitational acceleration, b represents the distance from the rear axle to the car's center of gravity, and L represents the car's wheelbase. This indicates that the car has a high center of gravity. Indicates the acceleration of a car. The value represents air resistance, r represents the tire rolling radius, and f represents the road friction coefficient. Indicates the road slope angle;

[0027] According to the formula: Determine the load on the rear axle , This represents the distance from the front axle to the vehicle's center of gravity; the load ratio of the front axle to the rear axle is... : .

[0028] In some embodiments, determining the torque distribution ratio between the front axle and the rear axle based on the load ratio between the front axle and the rear axle includes: the torque distribution ratio of the front axle is... The torque distribution ratio of the rear axle is .

[0029] In some embodiments, the vehicle's driving trajectory is a straight line; the TCS trigger flag indicates that the single-axis TCS function is triggered; the compensation of the torque distribution ratio between the front axle and the rear axle based on the vehicle's driving trajectory and the TCS trigger flag includes: obtaining the road adhesion coefficient, the front slip ratio, and the rear slip ratio; and transferring the driving torque of the slipping axle to the non-slipping axle based on the road adhesion coefficient, the front slip ratio, and the rear slip ratio.

[0030] In some embodiments, the vehicle's driving trajectory is a straight line; the TCS trigger flag indicates that the dual-axle TCS function is triggered simultaneously; the step of executing a corresponding strategy based on the vehicle's driving trajectory and the TCS trigger flag, without compensating for the torque distribution ratio between the front axle and the rear axle, includes: obtaining the road adhesion coefficient, front slip ratio, and rear slip ratio; and actively limiting the maximum driving torque of the front axle and the maximum driving torque of the rear axle based on the road adhesion coefficient, front slip ratio, and rear slip ratio.

[0031] In some embodiments, the vehicle's driving trajectory is a curve; the VDC trigger flag indicates that the VDC function has not been triggered; the torque distribution ratio between the front axle and the rear axle is compensated according to the vehicle's driving trajectory and the VDC trigger flag, including: obtaining the actual yaw rate and the target yaw rate; and adjusting the torque distribution ratio between the front axle and the rear axle based on the difference between the actual yaw rate and the target yaw rate.

[0032] In some embodiments, the vehicle's driving trajectory is a curve; the VDC trigger flag indicates that the VDC function is triggered; compensation is made for the torque distribution ratio between the front axle and the rear axle based on the vehicle's driving trajectory and the VDC trigger flag, including: obtaining the actual yaw rate, the target yaw rate, the front axle slip ratio, and the rear circumferential slip ratio; and adjusting the torque distribution ratio between the front axle and the rear axle based on the front axle slip ratio, the rear circumferential slip ratio, and the difference between the actual yaw rate and the target yaw rate.

[0033] In some embodiments, determining the motor drive torque based on the final torque distribution ratio includes: the motor drive torque of the front axle is... Where K represents the compensated front axle distribution ratio, T represents the compensated rear axle distribution ratio, and E represents the required drive torque; the motor drive torque of the rear axle is... .

[0034] Vehicle stability is typically controlled by ESP (Electronic Stability Program), straight-line driving conditions are usually controlled by TCS (Traction Control System) module, and cornering driving conditions are controlled by VDC (Vehicle Dynamics Control) module. ESP reduces wheel slippage or improves vehicle steering performance by reducing drive torque or increasing braking pressure, but it sacrifices power.

[0035] This disclosure enhances vehicle performance under low-traction and harsh road conditions such as snow and ice by dynamically distributing torque between the front and rear axles through the VCU (Vehicle Control Unit) and coordinating with the ESP system, thereby improving vehicle stability and reducing the occurrence of skidding accidents.

[0036] This disclosure utilizes the VCU in conjunction with the ESP (Electronic Stability Program) system to dynamically distribute torque between the front and rear axles by adjusting the load ratio when ESP is not triggered. When ESP is triggered, it compensates for the torque distribution ratio between the front and rear axles. Through multiple dynamic torque distributions, it works in conjunction with ESP to address driving issues such as excessive wheel slippage and vehicle jerking caused by TCS activation, which cannot be completely prevented by a single TCS module, as well as understeer or fishtailing when the vehicle is cornering. This not only improves vehicle stability on low-friction roads but also enhances vehicle power and drivability.

[0037] The VCU and ESP share information such as TCS trigger flag, VDC trigger flag, wheel speed, steering wheel angle, vehicle speed, front and rear axle slip ratio, target yaw rate, actual yaw rate, and road adhesion coefficient through CAN bus technology, and perform coordinated control by sharing information.

[0038] like Figure 2 As shown, the VCU distributes the torque ratio between the front and rear axles based on the front and rear axle load ratio, which serves as the basic distribution ratio. The front and rear axle loads of the entire vehicle are obtained through simplified calculations using the vehicle dynamics equations.

[0039] In the diagram, G represents the weight of the car. For vehicle speed, Let α be the vehicle acceleration and α be the road slope angle. Because the car has a high center of gravity, For air resistance, = (C is the drag coefficient, and A is the frontal area, obtained from wind tunnel tests). This refers to the ground reaction force acting on the front and rear wheels, i.e., the front and rear axle loads. L is the vehicle wheelbase. b represents the distance from the car's center of gravity to the front and rear axles, respectively. The tire's rolling radius, The coefficient of friction of the road. , The rolling resistance couple acting on the front and rear wheels. If we take the moment of force acting on the car about the center of the contact surface between the front and rear wheels and the road, we can obtain the equation of motion:

[0040] , .

[0041] The degree of tire slippage is related to the tangential reaction force of the ground on the tire. When the tangential reaction force of the ground on the tire is greater than the ground adhesion force, the tire will slip. The tangential reaction force of the ground on the tire is related to the front axle load and the rear axle load. , The torque is proportional to the front and rear axle loads, so the torque distribution can make full use of the road surface adhesion.

[0042] The front axle torque distribution ratio is: The rear axle torque distribution ratio is: .

[0043] The VCU determines whether the front and rear axle TCS functions are triggered based on the information from the CAN bus and executes the corresponding strategies.

[0044] Strategy 1: When the vehicle travels in a straight line and the single-axle TCS function is triggered, front and rear axle torque distribution ratio compensation control is performed. The torque distribution ratio is based on the road adhesion coefficient and front and rear slip ratios, and the torque of the slipping axle is transferred to the non-slipping axle.

[0045] When the single-axis TSC function is triggered, the front axle torque distribution ratio compensation values ​​are shown in Table 1:

[0046] Table 1

[0047]

[0048] Due to confidentiality reasons, specific values ​​for A1 to A10 are not disclosed. Based on this table, the following patterns are revealed: the larger the front axle slip ratio, the smaller the front axle torque distribution ratio, and the larger the rear axle torque distribution ratio. The larger the road adhesion coefficient, the larger the distributable ratio.

[0049] When the single-axis TSC function is triggered, the rear axle torque distribution ratio compensation values ​​are shown in Table 2:

[0050] Table 2

[0051]

[0052] Strategy 2: When the vehicle travels in a straight line and both axles TCS are triggered simultaneously, no front and rear axle torque distribution ratio compensation control is performed. Instead, the maximum driving torque of the front and rear axles is actively limited by looking up the road adhesion coefficient and the front and rear axle slip ratios in a table.

[0053] When the dual-axis TCS function is triggered, the maximum torque limit for the front axle is shown in Table 3:

[0054] Table 3

[0055]

[0056] When both axles of the TCS function are triggered simultaneously, the maximum torque is limited based on the front axle slip ratio and the road adhesion coefficient. The greater the slip ratio, the more torque is limited, and the greater the road adhesion coefficient, the less torque is limited.

[0057] When the dual-axis TCS function is triggered, the maximum torque limit for the rear axle is shown in Table 4:

[0058] Table 4

[0059]

[0060] Strategy 3: When the vehicle travels in a straight line and both axle TCSs are triggered, no front and rear axle torque distribution ratio compensation control is performed, and the vehicle anti-skid control is entirely handled by the TCS.

[0061] S4: The VCU determines whether the VDC function is triggered based on the information on the CAN bus and executes the corresponding strategy.

[0062] Strategy 1: If the vehicle's trajectory is a curve and VDC is not triggered, perform front and rear axle torque distribution compensation control. Based on the difference between the actual yaw rate and the target yaw rate, readjust the front and rear axle torque distribution. Note that the larger the difference between the actual and target yaw rates, the more compensation is given to the front axle. The higher the front axle slip ratio, the smaller the compensation ratio.

[0063] The VDC function was not triggered, and the front axle torque distribution ratio compensation values ​​are shown in Table 5.

[0064] Table 5

[0065]

[0066] The greater the difference between the actual yaw rate and the target yaw rate, the greater the torque distribution ratio to the front axle and the smaller the torque distribution ratio to the rear axle.

[0067] The VDC function was not triggered, and the rear axle torque distribution ratio compensation values ​​are shown in Table 6.

[0068] Table 6

[0069]

[0070] Strategy 2: When the vehicle's trajectory is a curve and the VDC function is triggered, front and rear axle torque distribution ratio compensation control is performed. This compensation is based on the difference between the actual and target yaw rates and the front and rear axle slip ratios. However, if the VCU distributes the front and rear axle torque too quickly, it can easily interfere with VDC control; therefore, the front and rear axle torque distribution ratio compensation is relatively low under this condition.

[0071] When the VDC function is triggered, the front axle torque distribution ratio compensation values ​​are shown in Table 7:

[0072] Table 7

[0073]

[0074] Because this operating condition is easily controlled by VDC, the allocation ratio for this operating condition is relatively lower than that in Table 5.

[0075] When the VDC function is triggered, the rear axle torque distribution ratio compensation values ​​are shown in Table 8:

[0076] Table 8

[0077]

[0078] S5: The final torque distribution ratio between the front and rear axles is composed of a base distribution ratio and a compensation distribution ratio. The final output torque of the front and rear axle motors is: the drive torque of the front axle motor is... Where K represents the compensated front axle distribution ratio, T represents the compensated rear axle distribution ratio, and E represents the required drive torque; the motor drive torque of the rear axle is... .

[0079] Due to the limited torque capacity of the motors, the front and rear axle motor drive torques calculated based on the final distribution ratio need to be reduced by the motor capacity before the final front and rear axle motor drive torques are output.

[0080] This disclosure improves the anti-skid performance and power performance of vehicles on low-friction roads, enhances vehicle stability when driving on low-friction roads, and can prevent traffic accidents caused by wheel slippage in rainy or snowy weather.

[0081] This disclosure also provides a vehicle controller, including: a memory; and a processor coupled to the memory, the processor being configured to execute the motor drive torque determination method described above based on instructions stored in the memory.

[0082] This disclosure also provides an automobile, including the aforementioned vehicle controller.

[0083] While specific embodiments of this disclosure have been described in detail by way of example, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A method of determining a motor drive torque, characterized by, The method comprises: obtaining acceleration pedal depth and vehicle speed; determining driving demand torque based on the acceleration pedal depth and the vehicle speed; determining a load ratio of front and rear axles; determining a torque distribution ratio of the front and rear axles according to the load ratio of the front and rear axles, the driving demand torque being a sum of front axle torque and rear axle torque; detecting steering wheel angle to determine vehicle travel trajectory; detecting TCS trigger flag and VDC trigger flag; compensating or not compensating the torque distribution ratio of the front and rear axles according to the vehicle travel trajectory, the TCS trigger flag and the VDC trigger flag to obtain a final torque distribution ratio, specifically including one of the following four: the vehicle travel trajectory is a straight line; the TCS trigger flag represents single-axis TCS function triggering; the torque distribution ratio of the front and rear axles is compensated according to the vehicle travel trajectory and the TCS trigger flag, including: according to the obtained road adhesion coefficient, front slip rate and rear slip rate; the driving torque of the slipping axle is transferred to the non-slip axle; the vehicle travel trajectory is a straight line; the TCS trigger flag represents double-axis TCS function triggering; the torque distribution ratio of the front and rear axles is not compensated according to the vehicle travel trajectory and the TCS trigger flag, including: according to the obtained road adhesion coefficient, front slip rate and rear slip rate, the front axle maximum driving torque and the rear axle maximum driving torque are actively limited; the vehicle travel trajectory is a curve; the VDC trigger flag represents that the VDC function is not triggered; the torque distribution ratio of the front and rear axles is compensated according to the vehicle travel trajectory and the VDC trigger flag, including: based on the difference between the actual yaw rate and the target yaw rate, the torque distribution ratio of the front and rear axles is adjusted; the vehicle travel trajectory is a curve; the VDC trigger flag represents that the VDC function is triggered; the torque distribution ratio of the front and rear axles is compensated according to the vehicle travel trajectory and the VDC trigger flag, including: the actual yaw rate, the target yaw rate, the front slip rate and the rear slip rate are obtained; according to the front slip rate, the rear slip rate and the difference between the actual yaw rate and the target yaw rate, the torque distribution ratio of the front and rear axles is adjusted; determining motor driving torque based on the final torque distribution ratio; performing minimum calculation between the motor driving torque and a motor driving torque threshold to obtain the final motor driving torque.

2. The motor drive torque determination method according to claim 1, characterized by, The determination of the load ratio of the front and rear axles comprises: The load on the front axle is determined according to the formula: G represents the weight of the vehicle, g represents the acceleration of gravity, b represents the distance from the rear axle to the center of gravity of the vehicle, L represents the wheelbase of the vehicle, h represents the height of the center of gravity of the vehicle, a represents the acceleration of the vehicle, r represents the rolling radius of the tire, and f represents the road friction coefficient, θ represents the road slope angle;​ The load on the rear axle is determined according to the formula: denotes the distance of the front axle to the center of mass of the vehicle.​​ The load ratio of the front axle to the rear axle is: .

3. The motor drive torque determination method according to claim 2, characterized by, The determination of the torque distribution ratio of the front and rear axles according to the load ratio of the front and rear axles comprises: The torque distribution ratio of the front axle is , and the torque distribution ratio of the rear axle is .

4. The motor drive torque determination method according to claim 3, characterized by, The determination of the motor driving torque based on the final torque distribution ratio comprises: The motor drive torque of the front axle is wherein K represents a compensated front axle distribution ratio, T represents a compensated rear axle distribution ratio, and E represents a drive demand torque. The motor drive torque of the rear axle is .

5. A vehicle control unit characterized by comprising: comprises: a memory; and a processor coupled to the memory, the processor being configured to execute the motor driving torque determination method according to any one of claims 1 to 4 based on instructions stored in the memory.

6. An automobile characterized by comprising: The vehicle controller according to claim 5.

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