Motor driving torque determination method and device and medium

Abstract

The invention relates to a motor driving torque determination method, a vehicle control unit and a vehicle, and belongs to the technical field of four-wheel-drive pure electric vehicles. The method comprises the steps that the acceleration pedal depth and the vehicle speed are obtained; determining a driving demand torque based on the acceleration pedal depth and the vehicle speed; determining the load ratio of the front axle to the rear axle; according to the load ratio of the front axle and the rear axle, the torque distribution proportion of the front axle and the rear axle is determined, and the driving demand torque is the sum of the front axle torque and the rear axle torque; detecting a steering wheel angle and determining a vehicle driving track; according to the vehicle driving track, the TCS trigger flag bit and the VDC trigger flag bit, the torque distribution proportion of a front axle and a rear axle is compensated or not compensated, and the final torque distribution proportion is obtained; determining a motor driving torque based on the final torque distribution proportion; and performing minimum calculation on the motor driving torque and the motor driving torque threshold value to obtain the final motor driving torque. Through the motor driving torque determined by the invention, an automobile can be prevented from slipping.

Description

Technical Field

[0001] The present invention belongs to the technical field of four-wheel drive pure electric vehicles, and in particular relates to a method, device and medium for determining motor drive torque. Background Art

[0002] The dual-motor four-wheel drive system is an advanced power transmission method that uses two independent motors to drive the front and rear axles of the vehicle, thereby achieving the effect of full-time four-wheel drive. The main advantages of this system include: First, strong 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 of the front and rear wheels in real time, thereby improving the vehicle's handling stability and passability.

[0003] When a car is driving on a road with a poor adhesion coefficient such as ice and snow, four-wheel drive is easier to master and has active safety performance compared to two-wheel drive. With the development of electric vehicle technology, users have put forward higher requirements for the fuel economy, power and driving stability of the car. The introduction of four-wheel drive technology enables electric vehicles to start, climb and accelerate better in poor driving conditions such as low-adhesion roads and separated roads. Due to the instantaneous torque output characteristics of the electric motor, the vehicle's power response is faster, resulting in a large instantaneous driving force when the electric vehicle starts. The wheels are prone to slipping on low-adhesion roads, resulting in poor vehicle stability. Therefore, how to improve the anti-skid performance of the vehicle while maintaining power and stability is an important issue that needs to be solved urgently. Summary of the invention

[0004] The present disclosure proposes a motor drive torque determination method, a vehicle controller, and a vehicle to solve the above technical problems.

[0005] According to a first aspect of the present disclosure, a method for determining a motor drive torque is provided, the method comprising: obtaining an accelerator pedal depth and a vehicle speed; determining a drive demand torque based on the accelerator pedal depth and the vehicle speed; determining a load ratio between a front axle and a rear axle; determining a torque distribution ratio between the front axle and the rear axle based on the load ratio between the front axle and the rear axle, the drive demand torque being the sum of the front axle torque and the rear axle torque; detecting a steering wheel angle to determine a vehicle 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 driving trajectory, the TCS trigger flag and the VDC trigger flag to obtain a final torque distribution ratio; determining a motor drive torque based on the final torque distribution ratio; and calculating the smaller of the motor drive torque and a motor drive torque threshold to obtain a final motor drive torque.

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

[0007] According to the formula: , determine the load on the rear axle , represents the distance from the front axle to the center of mass of the vehicle; the load ratio between the front axle and the rear axle is : .

[0008] In some embodiments, the torque distribution ratio of the front axle to the rear axle is determined according to the load ratio of the front axle to the rear axle, including: the torque distribution ratio of the front axle is , the torque distribution ratio of the rear axle is .

[0009] In some embodiments, the vehicle driving trajectory is a straight line; the TCS trigger flag indicates that a single-axis TCS function is triggered; and according to the vehicle driving trajectory and the TCS trigger flag, the torque distribution ratio between the front axle and the rear axle is compensated, including: obtaining a road adhesion coefficient, a front slip rate, and a rear slip rate; according to the road adhesion coefficient, the front slip rate, and the rear slip rate, the driving torque of the slipping axle is transferred to the non-slipping axle.

[0010] In some embodiments, the vehicle driving trajectory is a straight line; the TCS trigger flag indicates that the dual-axis TCS function is triggered simultaneously; the corresponding strategy is executed based on the vehicle driving trajectory and the TCS trigger flag, and the torque distribution ratio between the front axle and the rear axle is not compensated, including: obtaining the road adhesion coefficient, the front slip rate, and the rear slip rate; according to the road adhesion coefficient, the front slip rate, and the rear slip rate, the maximum driving torque of the front axle and the maximum driving torque of the rear axle are actively limited.

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

[0012] In some embodiments, the vehicle driving trajectory is a curve; the VDC trigger flag indicates that a VDC function is triggered; and according to the vehicle driving trajectory and the VDC trigger flag, the torque distribution ratio between the front axle and the rear axle is compensated, including: obtaining an actual yaw angular velocity, a target yaw angular velocity, a front axle slip rate, and a rear periphery slip rate; and adjusting the torque distribution ratio between the front axle and the rear axle according to the front axle slip rate, the rear periphery slip rate, and the difference between the actual yaw angular velocity and the target yaw angular velocity.

[0013] In some embodiments, the motor drive torque is determined based on the final torque distribution ratio, including: 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 driving demand torque; the rear axle motor driving torque is .

[0014] According to a second aspect of the present disclosure, a vehicle controller is provided, comprising: a memory; and a processor coupled to the memory, wherein the processor is 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 the present disclosure, a car is provided, comprising the above-mentioned vehicle controller.

[0016] The beneficial effects of the present disclosure are as follows: the motor driving torque determined by the present disclosure can prevent a car from slipping when driving on a low-adhesion road, improve the power performance of the car, ensure the stability of the car, and further prevent traffic accidents caused by slipping. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0018] Figure 1 Flow chart of a method for determining motor drive torque.

[0019] Figure 2 Schematic diagram of the forces acting on a car accelerating uphill.

[0020] Figure 3 A block diagram of a device for determining a motor drive torque. DETAILED DESCRIPTION

[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 the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure unless otherwise specifically stated.

[0022] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0023] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the specification.

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

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

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

[0027] According to the formula: , determine the load on the rear axle , represents the distance from the front axle to the center of mass of the vehicle; the load ratio between the front axle and the rear axle is : .

[0028] In some embodiments, the torque distribution ratio of the front axle to the rear axle is determined according to the load ratio of the front axle to the rear axle, including: the torque distribution ratio of the front axle is , the torque distribution ratio of the rear axle is .

[0029] In some embodiments, the vehicle driving trajectory is a straight line; the TCS trigger flag indicates that a single-axis TCS function is triggered; and according to the vehicle driving trajectory and the TCS trigger flag, the torque distribution ratio between the front axle and the rear axle is compensated, including: obtaining a road adhesion coefficient, a front slip rate, and a rear slip rate; according to the road adhesion coefficient, the front slip rate, and the rear slip rate, the driving torque of the slipping axle is transferred to the non-slipping axle.

[0030] In some embodiments, the vehicle driving trajectory is a straight line; the TCS trigger flag indicates that the dual-axis TCS function is triggered simultaneously; the corresponding strategy is executed based on the vehicle driving trajectory and the TCS trigger flag, and the torque distribution ratio between the front axle and the rear axle is not compensated, including: obtaining the road adhesion coefficient, the front slip rate, and the rear slip rate; according to the road adhesion coefficient, the front slip rate, and the rear slip rate, the maximum driving torque of the front axle and the maximum driving torque of the rear axle are actively limited.

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

[0032] In some embodiments, the vehicle driving trajectory is a curve; the VDC trigger flag indicates that a VDC function is triggered; and according to the vehicle driving trajectory and the VDC trigger flag, the torque distribution ratio between the front axle and the rear axle is compensated, including: obtaining an actual yaw angular velocity, a target yaw angular velocity, a front axle slip rate, and a rear periphery slip rate; and adjusting the torque distribution ratio between the front axle and the rear axle according to the front axle slip rate, the rear periphery slip rate, and the difference between the actual yaw angular velocity and the target yaw angular velocity.

[0033] In some embodiments, the motor drive torque is determined based on the final torque distribution ratio, including: 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 driving demand torque; the rear axle motor driving torque is .

[0034] Vehicle stability is usually controlled by ESP (electronic stability system), straight-line driving conditions are usually controlled by the TCS (traction control unit) module, and cornering driving conditions are controlled by the VDC (vehicle dynamic control) module. ESP reduces wheel slip or improves vehicle steering performance by reducing driving torque or increasing braking pressure, but it will sacrifice power.

[0035] The present invention enhances the dynamic performance under low-adhesion and harsh road conditions such as snow and ice, improves vehicle stability, and reduces the occurrence of skidding accidents through the dynamic distribution of front and rear axle torque by the VCU (vehicle control unit) and the coordination of the ESP system.

[0036] The present invention uses VCU to coordinate with ESP system (electronic stability program). When ESP is not triggered, it dynamically distributes the front and rear axle torques according to the front and rear axle load ratio. When ESP is triggered, it compensates the front and rear axle torque distribution ratio. Through multiple torque dynamic distributions, it coordinates with ESP to solve the problems of a single TCS module being unable to completely prevent driving problems such as excessive wheel slip and vehicle jerking due to TCS, as well as problems such as understeering or easy tailspin when driving on a curve. It not only improves the vehicle stability on low-attachment roads, but also improves the vehicle's power and drivability.

[0037] 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 rate, target yaw rate, actual yaw rate, road adhesion coefficient, etc. through CAN bus technology, and perform collaborative control through shared information.

[0038] like Figure 2 As shown in FIG. 1 , the VCU distributes the front and rear axle torque ratios according to the front and rear axle load ratios as the basic distribution ratio. The front and rear axle loads of the vehicle are obtained by simplified calculation based on the vehicle dynamics equation.

[0039] In the figure, G is the gravity of the car. is the vehicle speed, is the vehicle acceleration, α is the road slope angle, The car has a high center of mass. is the air resistance, = (C is the drag coefficient, A is the windward area, obtained from wind tunnel tests), is the ground reaction force acting on the front and rear wheels, that is, the front and rear axle loads. L is the wheelbase of the car, , b is the distance from the center of mass of the car to the front and rear axles, is the tire rolling radius, is the road friction coefficient, , is the rolling resistance acting on the front and rear wheels, If the forces acting on the car are taken as the distance between the center of the contact surface between the front and rear wheels and the road, the equation of motion can be obtained:

[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, 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. , Therefore, distributing the torque according to the load ratio of the front and rear axles can make full use of the road adhesion.

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

[0043] Based on the information on CAN, the VCU determines whether the TCS functions of the front and rear axles are triggered and executes the corresponding strategies.

[0044] Strategy 1: The vehicle's driving trajectory is straight and the single-axis TCS function is triggered, and the front and rear axle torque distribution ratio compensation control is performed. The torque distribution ratio is based on the road adhesion coefficient and the front and rear slip rates. 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 value is shown in Table 1:

[0046] Table 1

[0047]

[0048] A1 to A10 do not disclose specific values ​​for confidentiality reasons. Based on this table, the following rules are disclosed: the greater the front axle slip rate, the smaller the front axle torque distribution ratio, and the greater the rear axle torque distribution ratio. The greater the road adhesion coefficient, the greater the proportion that can be distributed.

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

[0050] Table 2

[0051]

[0052] Strategy 2: The vehicle's driving trajectory is straight and the dual-axis TCS is triggered simultaneously. No front and rear axle torque distribution ratio compensation control is performed. The maximum driving torque of the front and rear axles is actively limited based on the road adhesion coefficient and the front and rear axle slip rate.

[0053] The dual-axis TCS function is triggered, and the maximum torque limit value of the front axle is shown in Table 3:

[0054] Table 3

[0055]

[0056] The dual-axis TCS function is triggered simultaneously, limiting the maximum torque according to the front axle slip rate and road adhesion coefficient. The greater the slip rate, the greater the torque limit, and the greater the road adhesion coefficient, the less the torque limit.

[0057] The dual-axis TCS function is triggered, and the maximum torque limit value of the rear axle is shown in Table 4:

[0058] Table 4

[0059]

[0060] Strategy 3: When the vehicle's driving trajectory is straight and both axle TCSs are triggered, no front and rear axle torque distribution ratio compensation control is performed, and all vehicle anti-skid control is handed over to TCS.

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

[0062] Strategy 1: When the vehicle is traveling on a curve and VDC is not triggered, the front and rear axle torque distribution ratio compensation control is performed. Based on the difference between the actual yaw rate and the target yaw rate, the front and rear axle torque distribution is redistributed. Please note that the greater the difference between the actual yaw rate and the target yaw rate, the more compensation is paid to the front axle. The greater the slip rate of the front axle, the smaller the compensation ratio.

[0063] The VDC function is not triggered, and the front axle torque distribution ratio compensation value is 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 of the front axle, and the smaller the torque distribution ratio of the rear axle.

[0067] The VDC function is not triggered, and the rear axle torque distribution ratio compensation value is shown in Table 6:

[0068] Table 6

[0069]

[0070] Strategy 2: When the vehicle is traveling on a curve and the VDC function is triggered, the front and rear axle torque distribution ratio compensation control is performed. Based on the difference between the actual yaw rate and the target yaw rate and the front and rear axle slip rate, the front and rear axle torque distribution ratio compensation is performed. At this time, if the VCU front and rear axle torque distribution is too fast, it is easy to interfere with the VDC control. Therefore, the front and rear axle torque distribution ratio compensation is too small in this working condition.

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

[0072] Table 7

[0073]

[0074] Because this working condition is easily controlled by VDC, the allocation ratio of this working condition is relatively small compared with Table 5.

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

[0076] Table 8

[0077]

[0078] S5: The final torque distribution ratio of the front and rear axles is composed of the basic distribution ratio and the compensation distribution ratio. The final output torque of the front and rear axle motors is: The motor driving 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 driving demand torque; the rear axle motor driving torque is .

[0079] Since the motor torque capacity is limited, it is necessary to take the smaller of the front and rear axle motor drive torque calculated based on the final distribution ratio and the motor capacity to output the final front and rear axle motor drive torque.

[0080] The present invention improves the anti-skid performance and dynamic performance of a vehicle when driving on low-adhesion roads, enhances the vehicle's stability when driving on low-adhesion roads, and can prevent traffic accidents caused by wheel slippage in rainy and snowy weather.

[0081] The present disclosure also provides a vehicle controller, comprising: a memory; and a processor coupled to the memory, wherein the processor is configured to execute the motor drive torque determination method as described above based on instructions stored in the memory.

[0082] The present disclosure also provides a car, comprising the above-mentioned vehicle controller.

[0083] Although some specific embodiments of the present disclosure have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A method for determining a motor driving torque, characterized in that: The method comprises: Get the accelerator pedal depth and vehicle speed; determining a driving demand torque based on the accelerator pedal depth and the vehicle speed; Determine the load ratio between the front and rear axles; Determine the torque distribution ratio of the front axle and the rear axle according to the load ratio of the front axle and the rear axle, the driving demand torque being the sum of the front axle torque and the rear axle torque; Detect the steering wheel angle to determine the vehicle's driving trajectory; Detect TCS trigger flag and VDC trigger flag; According to the vehicle driving trajectory, the TCS trigger flag, and the VDC trigger flag, the torque distribution ratio between the front axle and the rear axle is compensated or not compensated to obtain a final torque distribution ratio; Determining the motor driving torque based on the final torque distribution ratio; The motor drive torque and the motor drive torque threshold are calculated to obtain the final motor drive torque.

2. The method for determining the motor driving torque according to claim 1, characterized in that: Determining the load ratio between the front axle and the rear axle includes: According to the formula: , determine the load on the front axle , G represents the gravity of the car, g represents the acceleration of gravity, b represents the distance from the rear axle to the center of mass of the car, L represents the wheelbase of the car, Indicates that the car has a high center of mass. represents the car acceleration, represents air resistance, r represents tire rolling radius, and f represents road friction coefficient. Indicates the road slope angle; According to the formula: , determine the load on the rear axle , Indicates the distance from the front axle to the center of mass of the vehicle; The load ratio between the front axle and the rear axle is : .

3. The method for determining the motor driving torque according to claim 2, characterized in that: Determining the torque distribution ratio between the front axle and the rear axle according to 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 .

4. The method for determining the motor driving torque according to claim 1, characterized in that: The vehicle's driving trajectory is a straight line; The TCS trigger flag bit represents the triggering of a single-axis TCS function; The compensating the torque distribution ratio between the front axle and the rear axle according to the vehicle driving trajectory and the TCS trigger flag includes: Obtain road adhesion coefficient, front slip rate, and rear slip rate; The driving torque of the slipping axle is transferred to the non-slipping axle according to the road adhesion coefficient, front slip ratio, and rear slip ratio.

5. The method for determining the motor driving torque according to claim 1, characterized in that: The vehicle's driving trajectory is a straight line; The TCS trigger flag indicates that the dual-axis TCS function is triggered simultaneously; The executing a corresponding strategy according to the vehicle driving trajectory and the TCS trigger flag, and not compensating the torque distribution ratio between the front axle and the rear axle, includes: Obtain road adhesion coefficient, front slip rate, and rear slip rate; According to the road adhesion coefficient, front slip rate and rear slip rate, the maximum driving torque of the front axle and the maximum driving torque of the rear axle are actively limited.

6. The method for determining the motor driving torque according to claim 1, characterized in that: The vehicle driving trajectory is a curve; The VDC trigger flag indicates that the VDC function is not triggered; According to the vehicle driving trajectory and the VDC trigger flag, the torque distribution ratio between the front axle and the rear axle is compensated, including: Obtain actual yaw angular velocity and target yaw angular velocity; Based on the difference between the actual yaw rate and the target yaw rate, the torque distribution ratio between the front axle and the rear axle is adjusted.

7. The method for determining the motor driving torque according to claim 1, characterized in that: The vehicle driving trajectory is a curve; The VDC trigger flag indicates that the VDC function is triggered; According to the vehicle driving trajectory and the VDC trigger flag, the torque distribution ratio between the front axle and the rear axle is compensated, including: Obtain actual yaw rate, target yaw rate, front axle slip rate, and rear axle slip rate; The torque distribution ratio between the front axle and the rear axle is adjusted according to the front axle slip rate, the rear axle slip rate, and the difference between the actual yaw rate and the target yaw rate.

8. The method for determining the motor driving torque according to claim 3, characterized in that: The determining the motor driving torque based on the final torque distribution ratio includes: The motor driving 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 driving demand torque; The motor driving torque of the rear axle is .

9. A vehicle controller, characterized in that: include: Memory; as well as A processor coupled to the memory, wherein the processor is configured to execute the motor driving torque determination method according to any one of claims 1 to 8 based on instructions stored in the memory.

10. An automobile, characterized in that: Including the vehicle controller as described in claim 9.

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