Pure Electric Vehicle Catapult Start Control Method, System, Device and Storage Medium

Abstract

The present invention discloses a control method, system, device and storage medium for the catapult start of a pure electric vehicle. The method includes: after receiving a signal for activating the catapult start function initiated by a user, prompting the user to deeply step on the accelerator to warm up the tires on a catapult road surface and obtaining the wheel slip ratio; determining the completion status of tire warming based on the wheel slip ratio; obtaining the wheel-ground adhesion coefficient based on the completion status of tire warming, and determining the motor locked-rotor torque corresponding to the catapult system according to the wheel-ground adhesion coefficient and the wheel slip ratio; and performing catapult start control on the pure electric vehicle according to the motor locked-rotor torque. Compared with the prior art in which a fixed motor locked-rotor torque needs to be set in advance and then the torque is limited through the intervention of the traction control system, the present invention can determine the current road surface condition according to the wheel-ground adhesion coefficient before the catapult start, and then set the optimal motor locked-rotor torque corresponding to the catapult system according to the wheel-ground adhesion coefficient and the wheel slip ratio, thereby improving the vehicle power performance and operation stability.

Description

Technical Field

[0001] The present invention relates to the technical field of launch control, and in particular to a method, system, device and storage medium for controlling the launch of a pure electric vehicle. Background Art

[0002] The principle of launch control is to use the transmission to adjust the engine speed to the output state of the maximum torque, so that the engine starts to output the maximum torque at the moment of starting, and then to achieve an acceleration technology with the best acceleration.

[0003] The implementation method of electric vehicles is similar to that of fuel vehicles, and the torque output changes from the engine to the drive motor. Among them, the implementation steps are: First, turn off the Electronic Stability Program (ESP) (if manual shutdown is required); Second, step on the brake pedal to the preset stroke; Third, step on the accelerator pedal to the preset stroke; Fourth, quickly release the brake when the rotational speed climbs to the optimal starting rotational speed.

[0004] In the prior art, the process of launch control is to set a fixed motor locked-rotor torque in advance. After the electronic parking brake system releases and the wheels slip violently, the traction control system intervenes to limit the torque. However, this method cannot ensure the vehicle's power performance and handling stability. Therefore, how to improve the vehicle's power performance and handling stability has become an urgent problem to be solved.

[0005] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is the prior art. Summary of the Invention

[0006] The main object of the present invention is to provide a method, system, device and storage medium for controlling the launch of a pure electric vehicle, aiming to solve the technical problem of how to improve the vehicle's power performance and handling stability.

[0007] To achieve the above object, the present invention provides a method for controlling the launch of a pure electric vehicle, the method for controlling the launch of a pure electric vehicle includes:

[0008] After receiving the activation signal of the launch control function initiated by the user, prompt the user to deeply step on the accelerator to warm up the tires on the launch road surface, and obtain the wheel slip ratio;

[0009] Determine the completion state of tire warming based on the wheel slip ratio;

[0010] Obtain the wheel-ground adhesion coefficient based on the completion state of tire warming, and determine the motor locked-rotor torque corresponding to the launch system according to the wheel-ground adhesion coefficient and the wheel slip ratio;

[0011] Perform catapult start control on the pure electric vehicle according to the locked-rotor torque of the motor.

[0012] Optionally, the step of, after receiving the activation signal of the catapult start function initiated by the user, prompting the user to deeply step on the accelerator to warm up the tires on the catapult road surface and obtaining the wheel slip ratio includes:

[0013] After receiving the activation signal of the catapult start function initiated by the user, prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtain the wheel rolling radius, the angular velocity of the wheel rotation, and the longitudinal speed of the wheel center;

[0014] Determine the wheel slip ratio according to the wheel rolling radius, the angular velocity of the wheel rotation, and the longitudinal speed of the wheel center.

[0015] Optionally, the step of determining the tire warming completion state according to the wheel slip ratio includes:

[0016] Judge whether the wheel slip ratio is within the preset slip threshold range;

[0017] If the wheel slip ratio is within the preset slip threshold range, determine the tire warming completion state according to the wheel slip ratio.

[0018] Optionally, after the step of judging whether the wheel slip ratio is within the preset slip threshold range, it further includes:

[0019] If the wheel slip ratio is not within the preset slip threshold range, return to the step of prompting the user to deeply step on the accelerator to warm up the tires on the catapult road surface and obtaining the wheel slip ratio.

[0020] Optionally, the step of obtaining the wheel-ground adhesion coefficient based on the tire warming completion state includes:

[0021] Obtain the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel based on the tire warming completion state;

[0022] Determine the wheel-ground adhesion coefficient according to the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel.

[0023] Optionally, the step of obtaining the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel based on the tire warming completion state includes:

[0024] Generate a relationship characteristic diagram of the coefficient and the slip ratio based on the tire warming completion state according to multiple wheel-ground adhesion coefficient samples and multiple wheel slip ratio samples;

[0025] Determine the maximum adhesion coefficient according to the relationship characteristic diagram of the coefficient and the slip ratio;

[0026] Determine the tangential adhesion of the ground to the wheel according to the maximum adhesion coefficient and the normal reaction force of the ground on the wheel.

[0027] Optionally, before the step of performing a catapult start control on a pure electric vehicle according to the motor stall torque, the method further includes:

[0028] Obtain the maximum torque capacity of the motor of the pure electric vehicle;

[0029] Determine whether the motor stall torque is greater than the maximum torque capacity of the motor;

[0030] If the motor stall torque is greater than the maximum torque capacity of the motor, then use the motor stall torque as the maximum torque capacity of the motor.

[0031] In addition, to achieve the above object, the present invention also provides a catapult start control system for a pure electric vehicle, the catapult start control system for a pure electric vehicle includes:

[0032] A processing module, configured to, after receiving a signal for activating the catapult start function initiated by a user, prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtain the wheel slip ratio;

[0033] A determination module, configured to determine the warm-up completion state according to the wheel slip ratio;

[0034] A calculation module, configured to obtain the wheel-ground adhesion coefficient based on the warm-up completion state, and determine the motor stall torque corresponding to the catapult system according to the wheel-ground adhesion coefficient and the wheel slip ratio;

[0035] A control module, configured to perform a catapult start control on the pure electric vehicle according to the motor stall torque.

[0036] In addition, to achieve the above object, the present invention also provides a catapult start control device for a pure electric vehicle, the device includes: a memory, a processor, and a pure electric vehicle catapult start control program stored on the memory and executable on the processor, the pure electric vehicle catapult start control program is configured to implement the steps of the pure electric vehicle catapult start control method as described above.

[0037] In addition, to achieve the above object, the present invention also provides a storage medium, on which a pure electric vehicle catapult start control program is stored, and when the pure electric vehicle catapult start control program is executed by a processor, it implements the steps of the pure electric vehicle catapult start control method as described above.

[0038] After receiving the signal for activating the launch control function initiated by the user, the present invention first prompts the user to deeply step on the accelerator to warm up the tires on the launch road surface, and obtains the wheel slip ratio. Then, it determines the tire warming completion state based on the wheel slip ratio, obtains the wheel-ground adhesion coefficient based on the tire warming completion state, and determines the motor locked-rotor torque corresponding to the launch system according to the wheel-ground adhesion coefficient and the wheel slip ratio. After that, it performs launch control on the pure electric vehicle according to the motor locked-rotor torque. Compared with the prior art where a fixed motor locked-rotor torque is set in advance and the traction control system intervenes to limit the torque after the wheels slip violently when the electronic parking brake system is released, this method cannot ensure the vehicle's power performance and handling stability. However, the present invention can determine the current road surface condition based on the wheel-ground adhesion coefficient before the launch, then set the optimal motor locked-rotor torque corresponding to the launch system according to the wheel-ground adhesion coefficient and the wheel slip ratio, and perform launch control on the pure electric vehicle according to the motor locked-rotor torque, thereby improving the vehicle's power performance and operating stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic structural diagram of a pure electric vehicle launch control device for the hardware operating environment involved in the embodiment solution of the present invention;

[0040] Figure 2 is a schematic flowchart of the first embodiment of the pure electric vehicle launch control method of the present invention;

[0041] Figure 3 is a characteristic diagram of the relationship between the coefficient and the slip ratio of the first embodiment of the pure electric vehicle launch control method of the present invention;

[0042] Figure 4 is a launch flowchart of the first embodiment of the pure electric vehicle launch control method of the present invention;

[0043] Figure 5 is a diagram of the relationship between time, rotational speed, and torque of the first embodiment of the pure electric vehicle launch control method of the present invention;

[0044] Figure 6 is a schematic flowchart of the second embodiment of the pure electric vehicle launch control method of the present invention;

[0045] Figure 7 is a structural block diagram of the first embodiment of the pure electric vehicle launch control system of the present invention.

[0046] The realization, functional features, and advantages of the object of the present invention will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0048] Reference Figure 1 , Figure 1 is a schematic structural diagram of an electric vehicle catapult start control device for the hardware operating environment involved in the solution of the embodiment of the present invention.

[0049] As Figure 1 shown, the electric vehicle catapult start control device may include: a processor 1001, such as a central processing unit (CPU), a communication bus 1002, a user interface 1003, a network interface 1004, and a memory 1005. Among them, the communication bus 1002 is used to realize the connection and communication between these components. The user interface 1003 may include a display screen (Display), an input unit such as a keyboard (Keyboard), and optionally the user interface 1003 may further include a standard wired interface and a wireless interface. The network interface 1004 may optionally include a standard wired interface and a wireless interface (such as a wireless-fidelity (Wi-Fi) interface). The memory 1005 may be a high-speed random access memory (Random Access Memory, RAM), or a stable non-volatile memory (Non-Volatile Memory, NVM), such as a disk memory. Optionally, the memory 1005 may also be a storage system independent of the aforementioned processor 1001.

[0050] Those skilled in the art can understand that Figure 1 the structure shown in

[0051] does not constitute a limitation on the electric vehicle catapult start control device, and may include more or fewer components than shown in the figure, or combine certain components, or have different component arrangements. Figure 1 As

[0052] shown, in the memory 1005 as a storage medium, there may be included an operating system, a network communication module, a user interface module, and an electric vehicle catapult start control program. Figure 1 In the electric vehicle catapult start control device shown in

[0053] An embodiment of the present invention provides a method for controlling the catapult start of a pure electric vehicle. Refer to Figure 2 , Figure 2 which is a schematic flowchart of the first embodiment of the method for controlling the catapult start of the pure electric vehicle of the present invention.

[0054] In this embodiment, the method for controlling the catapult start of the pure electric vehicle includes the following steps:

[0055] Step S10: After receiving the signal for activating the catapult start function initiated by the user, prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtain the wheel slip ratio.

[0056] It is easy to understand that the execution subject of this embodiment can be a control device for the catapult start of a pure electric vehicle with functions such as data processing, network communication, and program operation, or other computer devices with similar functions. This embodiment does not impose any restrictions.

[0057] In this embodiment, after receiving the signal for activating the catapult start function initiated by the user, the method of prompting the user to deeply step on the accelerator to warm up the tires on the catapult road surface and obtaining the wheel slip ratio is: after receiving the signal for activating the catapult start function initiated by the user, prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtain the wheel rolling radius, the wheel rotational angular velocity, and the longitudinal speed of the wheel center. Then, determine the wheel slip ratio according to the wheel rolling radius, the wheel rotational angular velocity, and the longitudinal speed of the wheel center.

[0058] In specific implementation, after the user activates the catapult start function on the screen, the system will prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface. At this time, the output torque of the motor controller microcontroller unit (MCU) will gradually increase from 0 Nm, and the vehicle will record the wheel-ground adhesion coefficient and the wheel slip ratio in real time.

[0059] It should also be noted that at the moment of catapult start, the large torque in the locked-rotor state is instantaneously released through the drive wheels, and after being applied to the tires, it causes a certain elastic deformation, resulting in the wheels being in a state of both rolling and sliding. The sliding part will cause the ground to exert a reaction force on the wheels, which is the traction force required to drive the vehicle. Usually, the wheel slip ratio is used as a parameter to characterize the sliding degree of the drive wheels. The slip ratio formula is s = (rw - v) / (rw), where s is the wheel slip ratio, r is the wheel rolling radius (in meters), w is the wheel rotational angular velocity (in rad / s), and v is the longitudinal speed of the wheel center (in m / s).

[0060] It should be understood that the wheel rolling radius r is a fixed parameter of the vehicle, and the wheel rotational angular velocity w and the longitudinal speed v of the wheel center can be obtained from the vehicle body sensors. Therefore, the wheel slip ratio s can be calculated in real time during the driving process.

[0061] According to different changes in the slip ratio, the driving state of the vehicle can also be divided into three states: First, the pure rolling state (s = 0), where the relative speed between the wheel and the road surface is 0, usually when the vehicle is in a gliding state; Second, a state where gliding and rolling coexist (0 < s < 1), which is the most common tire slip situation. That is, when the vehicle accelerates, there is a relative speed between the tire and the ground, causing the tire to deform and thus driving the vehicle; Third, the pure sliding state (s = 1), at this time the vehicle speed is 0 and the wheel is in a state of spinning in place. From the above three states, it can be seen that when the vehicle is moving forward, it is most often in a state where rolling and sliding coexist (0 < s < 1), and the larger the wheel slip ratio, the greater the degree of wheel sliding.

[0062] Step S20: Determine the warm-up completion state according to the wheel slip ratio.

[0063] In this embodiment, the method of determining the warm-up completion state according to the wheel slip ratio can be to judge whether the wheel slip ratio is within a preset slip threshold range. If the wheel slip ratio is within the preset slip threshold range, the warm-up completion state is determined according to the wheel slip ratio; if the wheel slip ratio is not within the preset slip threshold range, a prompt is returned to the user to deeply step on the accelerator pedal for warm-up on the catapult road surface, and the operation of obtaining the wheel slip ratio is performed.

[0064] It should be noted that the preset slip threshold range can be user-defined, such as 0.35 - 0.42, etc.

[0065] In specific implementation, when deeply stepping on the accelerator pedal for warm-up on the catapult road surface, the output torque of the motor controller micro-control unit will gradually increase from 0 Nm, and the vehicle records the wheel slip ratio in real time. If the wheel slip ratio is 0.4 and the preset slip threshold range is 0.35 - 0.42, the user is prompted that the warm-up is completed.

[0066] Step S30: Obtain the wheel-ground adhesion coefficient based on the warm-up completion state, and determine the motor locked-rotor torque corresponding to the catapult system according to the wheel-ground adhesion coefficient and the wheel slip ratio.

[0067] From the above three driving states of the vehicle, it can be seen that when the wheel slip ratio exceeds a certain limit, it will exceed the maximum adhesion of the road surface, and the wheel will have excessive sliding. At this time, not only the original power performance will be affected, but even the vehicle will swing laterally and lose stability, being in a dangerous state. Therefore, to control the wheel slip ratio within a reasonable range, it is necessary to ensure that the vehicle driving force is less than the maximum tangential adhesion force Fxmax that the road surface can provide to the wheel at this time, and the wheel-ground adhesion coefficient is used to characterize the relationship between the tangential adhesion force of the ground to the wheel and the normal reaction force of the ground to the wheel. Among them, the tangential adhesion force indicates the degree of adhesion that the road surface can provide, and the tangential driving force is a force actively provided by the vehicle.

[0068] In this embodiment, after the tire warm-up is completed, the method for obtaining the wheel-ground adhesion coefficient is to obtain the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel, and then calculate the wheel-ground adhesion coefficient according to the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel through a preset coefficient formula. The preset coefficient formula is u = Fx / Fz, where u is the wheel-ground adhesion coefficient, Fx is the tangential adhesion force of the ground on the wheel, and Fz is the normal reaction force of the ground on the wheel.

[0069] It should also be noted that during a launch control start, since the drive motor has been in a high-torque stall state before, the vehicle driving force will be loaded on the wheels at the moment when the electronic parking brake system (EPB) is released. If the stall torque set by the previous launch control system is unreasonable, it is very likely that the vehicle driving force at this time is much greater than the maximum tangential adhesion force Fxmax that the road surface can provide at this time. In the case of severe wheel slip, not only the advantage of shortening the acceleration time of the launch control start function cannot be reflected, but also the power performance and stability will deteriorate, and there is a risk of the vehicle swinging out of control. Therefore, in order to obtain the optimal launch control start torque and make the starting state stable, it is necessary to master the relationship between the wheel-road adhesion coefficient and the slip ratio at this time, and calculate the maximum tangential adhesion force of the ground on the wheel under the condition of the optimal slip ratio.

[0070] In this embodiment, the method for obtaining the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel based on the completed tire warm-up state is to generate a coefficient-slip ratio relationship characteristic diagram according to multiple wheel-ground adhesion coefficient samples and multiple wheel slip ratio samples, and determine the maximum adhesion coefficient according to the coefficient-slip ratio relationship characteristic diagram. Then, the tangential adhesion force of the ground on the wheel is determined according to the maximum adhesion coefficient and the normal reaction force of the ground on the wheel. The multiple wheel-ground adhesion coefficient samples and multiple wheel slip ratio samples are multiple wheel-ground adhesion coefficients and multiple wheel slip ratios collected in real time by the vehicle on the current road surface, etc.

[0071] In specific implementation, refer to Figure 3 , Figure 3This is the characteristic diagram of the relationship between the coefficient and the slip ratio of the first embodiment of the pure electric vehicle catapult start control method of the present invention. It can be seen from the figure that as the wheel slip ratio increases, the wheel-ground adhesion coefficient will first increase. After it reaches the maximum value, the wheel-ground adhesion coefficient begins to gradually decrease, that is, the maximum tangential adhesion force Fxmax provided by the ground will gradually decrease, and the power performance of the vehicle decreases. To obtain the maximum tangential adhesion force Fxmax, the derivative can be taken of the curve of the wheel-ground adhesion coefficient u and the wheel slip ratio s: du / ds = 0. The point where the slope is 0 corresponds to the maximum wheel-ground adhesion coefficient. The maximum wheel-ground adhesion coefficient multiplied by the road surface normal reaction force at this time gives the maximum tangential adhesion force Fxmax. Finally, before the catapult start, the relationship between the adhesion coefficient μ and the slip ratio S is obtained, and the optimal adhesion coefficient is obtained through derivation, so as to calculate the motor locked-rotor torque Ts max set by the system.

[0072] It should also be understood that the tangential adhesion force Fx of the ground on the wheel is a variable quantity, and the maximum tangential adhesion force Fxmax is the maximum value of this variable quantity.

[0073] Step S40: Perform catapult start control on the pure electric vehicle according to the motor locked-rotor torque.

[0074] Before performing catapult start control on the electric vehicle according to the motor locked-rotor torque, it is also necessary to obtain the maximum torque capacity of the motor of the pure electric vehicle, and then judge whether the motor locked-rotor torque is greater than the maximum torque capacity of the motor. If the motor locked-rotor torque is greater than the maximum torque capacity of the motor, the motor locked-rotor torque is taken as the maximum torque capacity of the motor.

[0075] In specific implementation, the maximum driving force of the wheel during catapult start needs to satisfy the maximum tangential driving force Fmax < the maximum tangential adhesion force Fxmax, so as to inversely deduce the motor locked-rotor torque Tsmax set by the catapult system (if Tsmax > Tmax, then Tsmax = Tmax, and Tmax is the maximum torque capacity of the motor), to ensure a reasonable slip ratio at the moment of catapult start.

[0076] Reference Figure 4 and Figure 5 , Figure 4 This is the catapult start flow chart of the first embodiment of the pure electric vehicle catapult start control method of the present invention. Figure 5This is the time, rotational speed, and torque relationship diagram of the first embodiment of the pure electric vehicle's catapult start control method of the present invention. The steps of the catapult start process in the figure are as follows: First, meet the preconditions for catapult start: The vehicle driving preference selects the Sport mode and the gear position is in D gear. Second, the Human Machine Interface (HMI) enables the catapult start function: The vehicle HMI develops a "catapult start mode" button. When the driver actively clicks it, the catapult start Enable status bit should be notified to the core electronic control unit VCU, motor controller, etc. that implement vehicle control decisions (Note: The catapult start function can also be enabled through a combination of the accelerator and / or brake). Third, the HMI prompts the user to deeply step on the accelerator to warm up the tires: The torque output by the motor controller gradually increases. After the wheel slides to the preset slip ratio, the torque decreases. Fourth, the HMI prompts the user that the tire warming is completed: At this time, after the user stops the vehicle, subsequent operations can be entered. Fifth, deeply step on the brake pedal: It is considered to meet the condition only when it is greater than the fixed stroke (calibrated during the development stage). Sixth, deeply step on the accelerator pedal, and the catapult start mode is activated: It is considered to meet the condition only when it is greater than the fixed stroke (calibrated during the development stage). At this time, the catapult start mode is activated, the motor remains stationary but the torque Tsmax has been pre-loaded, that is, it enters the locked-rotor state. Seventh, release the brake pedal: It is considered to meet the condition only when it is less than the fixed stroke (calibrated during the development stage). Eighth, judge the time from activating the catapult start to releasing the brake: After activating the catapult start, the HMI will prompt "Please completely release the brake pedal within n seconds". When the driver releases the pedal, the VCU calculates the interval time from activation to release. If it is greater than n seconds (calibrated during the development stage), the catapult start fails, and the VCU requests the motor controller to output 0 Nm; if it is less than n seconds, the catapult start is successful, and the vehicle accelerates forward. Ninth, judge the catapult start exit condition: Set the exit logic according to the vehicle speed, accelerator pedal, acceleration time, etc. If the preset conditions are met, the catapult start mode is exited, and the catapult start status bit is reset to Disable, and the entire process ends.

[0077] It should also be noted that compared with the existing fuel vehicle catapult start scheme, the present invention describes the catapult start process of electric vehicles in detail and clarifies the control logic of the catapult start function. The maximum locked-rotor time and locked-rotor torque allowed by the motor controller before catapult start are defined as boundaries, avoiding excessive temperature rise of the electric drive caused by long-term locked-rotor, which may lead to hardware damage. After catapult start, the torque loading and rotational speed response of the motor controller are described. Compared with the traditional fixed locked-rotor torque for catapult start, the present invention obtains the optimal tangential driving force through pre-warming the tires, thereby obtaining the optimal catapult start locked-rotor torque. This locked-rotor torque is not fixed but is calculated in real time according to the current road conditions. Therefore, it can ensure the optimal slip ratio at the moment of starting, greatly improving the power performance and handling stability of the vehicle during catapult start and optimizing the user experience of the electric vehicle catapult start function.

[0078] In this embodiment, after receiving the signal for activating the launch control function initiated by the user, the user is first prompted to deeply step on the accelerator to warm up the tires on the launch road surface, and the wheel slip ratio is obtained. Then, the tire warming completion state is determined based on the wheel slip ratio, the wheel-ground adhesion coefficient is obtained based on the tire warming completion state, and the locked-rotor torque of the motor corresponding to the launch system is determined according to the wheel-ground adhesion coefficient and the wheel slip ratio. After that, the launch start control of the pure electric vehicle is performed according to the locked-rotor torque of the motor. Compared with the existing launch start scheme of fuel vehicles and the traditional fixed locked-rotor torque for launch start, when the electronic parking brake system releases and the wheels slip violently, the traction control system intervenes to limit the torque. However, this method cannot ensure the vehicle's power performance and handling stability. In this embodiment, before the launch start, the current road surface condition can be determined according to the wheel-ground adhesion coefficient, and then the optimal locked-rotor torque of the motor corresponding to the launch system is set according to the wheel-ground adhesion coefficient and the wheel slip ratio, and the launch start control of the pure electric vehicle is performed according to the locked-rotor torque of the motor, thereby improving the vehicle's power performance and operation stability.

[0079] Reference Figure 6 , Figure 6 is a schematic flow chart of the second embodiment of the launch start control method for the pure electric vehicle of the present invention.

[0080] Based on the above first embodiment, in this embodiment, the step S10 further includes:

[0081] Step S101: After receiving the signal for activating the launch control function initiated by the user, the user is prompted to deeply step on the accelerator to warm up the tires on the launch road surface, and the wheel rolling radius, the wheel angular velocity, and the longitudinal speed of the wheel center are obtained.

[0082] In this embodiment, in a specific implementation, after the user activates the launch control function on the screen, the system will prompt the user to deeply step on the accelerator to warm up the tires. At this time, the output torque of the motor controller micro control unit will gradually increase from 0 Nm, and then the wheel rolling radius, the wheel angular velocity, and the longitudinal speed of the wheel center are obtained.

[0083] Step S102: Determine the wheel slip ratio according to the wheel rolling radius, the wheel angular velocity, and the longitudinal speed of the wheel center.

[0084] The vehicle records in real time the wheel slip ratio calculated according to the wheel rolling radius, the wheel angular velocity, and the longitudinal speed of the wheel center.

[0085] It should also be noted that at the moment of catapult start, the large torque in the locked-rotor state is instantaneously released through the driving wheels and applied to the tires, resulting in a certain elastic deformation, causing the wheels to be in a state of both rolling and sliding. The sliding part causes the ground to exert a reaction force on the wheels, which is the traction force required to drive the vehicle. Usually, the wheel slip ratio is used to characterize the sliding degree of the driving wheels. The slip ratio formula is s = (rw - v) / (rw), where s is the wheel slip ratio, r is the rolling radius of the wheel (in meters), w is the angular velocity of the wheel rotation (in rad / s), and v is the longitudinal velocity of the wheel center (in m / s).

[0086] It should be understood that the rolling radius r of the wheel is a fixed parameter of the vehicle. The angular velocity w of the wheel rotation and the longitudinal velocity v of the wheel center can be obtained from the vehicle body sensors. Therefore, the wheel slip ratio s can be calculated in real time during the driving process.

[0087] According to different changes in the slip ratio, the driving state of the vehicle can also be divided into three states: First, the pure rolling state (s = 0), where the relative speed between the wheel and the road surface is 0, usually when the vehicle is in a coasting state; Second, the coexistence of coasting and rolling (0 < s < 1), which is the most common tire slip situation. That is, when the vehicle accelerates, there is a relative speed between the tire and the ground, resulting in tire deformation, thereby driving the vehicle; Third, the pure sliding state (s = 1), at this time the vehicle speed is 0, and the wheel is in a state of rotating in place. From the above three states, it can be seen that when the vehicle is moving, it is most often in a state of coexistence of rolling and sliding (0 < s < 1), and the larger the wheel slip ratio, the greater the sliding degree of the wheel. When the wheel slip ratio exceeds a certain limit value, it will exceed the maximum adhesion of the road surface, and the wheel will have excessive sliding. At this time, not only the original power performance will be affected, but even the vehicle will swing laterally and lose stability, being in a dangerous state.

[0088] In this embodiment, after receiving the signal for activating the catapult start function initiated by the user, the user is prompted to deeply step on the accelerator to warm up the tires on the catapult road surface, and the rolling radius of the wheel, the angular velocity of the wheel rotation, and the longitudinal velocity of the wheel center are obtained. Then, the wheel slip ratio is determined according to the rolling radius of the wheel, the angular velocity of the wheel rotation, and the longitudinal velocity of the wheel center. Compared with the prior art where the process of warming up the tires is not involved, in this embodiment, after receiving the signal for activating the catapult start function initiated by the user, the user is prompted to deeply step on the accelerator to warm up the tires on the catapult road surface, and at the same time, the wheel slip ratio is recorded in real time according to the rolling radius of the wheel, the angular velocity of the wheel rotation, and the longitudinal velocity of the wheel center, thereby avoiding the lateral swing of the vehicle and further ensuring the vehicle stability.

[0089] Refer to Figure 7 , Figure 7 which is the structural block diagram of the first embodiment of the catapult start control system for the pure electric vehicle of the present invention.

[0090] As Figure 7As shown in the figure, the electric vehicle launch control system proposed in the embodiment of the present invention includes:

[0091] A processing module 7001, configured to, after receiving a signal for activating the launch function initiated by a user, prompt the user to deeply step on the accelerator to warm up the tires on the launch road surface, and obtain the wheel slip ratio.

[0092] In this embodiment, after receiving the signal for activating the launch function initiated by the user, the manner of prompting the user to deeply step on the accelerator to warm up the tires on the launch road surface and obtaining the wheel slip ratio is that after receiving the signal for activating the launch function initiated by the user, the user is prompted to deeply step on the accelerator to warm up the tires on the launch road surface, and the wheel rolling radius, the wheel rotational angular velocity, and the longitudinal speed of the wheel center are obtained, and then the wheel slip ratio is determined according to the wheel rolling radius, the wheel rotational angular velocity, and the longitudinal speed of the wheel center.

[0093] In a specific implementation, after the user activates the launch function on the screen, the system will prompt the user to deeply step on the accelerator to warm up the tires on the launch road surface. At this time, the output torque of the motor controller microcontroller unit (MCU) will gradually increase from 0 Nm, and the vehicle will record the wheel-ground adhesion coefficient and the wheel slip ratio in real time.

[0094] It should also be noted that at the moment of launch, the large torque in the locked-rotor state is instantaneously released through the drive wheels and applied to the tire, resulting in a certain elastic deformation of the tire, causing the wheel to be in a state of both rolling and sliding. The sliding part will cause the ground to exert a reaction force on the wheel, that is, the traction force required to drive the vehicle. Usually, this parameter of the wheel slip ratio is used to characterize the sliding degree of the drive wheel. The slip ratio formula is s = (rw - v) / (rw), where s is the wheel slip ratio, r is the wheel rolling radius (in meters), w is the wheel rotational angular velocity (in rad / s), and v is the longitudinal speed of the wheel center (in m / s).

[0095] It should be understood that the wheel rolling radius r is a fixed parameter of the vehicle, and the wheel rotational angular velocity w and the longitudinal speed v of the wheel center can be obtained from the vehicle body sensors. Therefore, the wheel slip ratio s can be calculated in real time during the driving process.

[0096] According to different changes in the slip ratio, the driving state of the vehicle can also be divided into three states: First, the pure rolling state (s = 0), where the relative speed between the wheel and the road surface is 0, usually when the vehicle is in a gliding state; Second, the coexistence of gliding and rolling (0 < s < 1), which is the most common tire slip situation. That is, when the vehicle accelerates, there is a relative speed between the tire and the ground, causing the tire to deform, thereby driving the vehicle; Third, the pure sliding state (s = 1), at this time the vehicle speed is 0, and the wheel is in a state of rotating in place. From the above three states, it can be seen that when the vehicle is moving forward, it is most often in a state where rolling and sliding coexist (0 < s < 1), and the larger the wheel slip ratio, the greater the degree of wheel sliding.

[0097] The determination module 7002 is used to determine the completion state of tire warming according to the wheel slip ratio.

[0098] In this embodiment, the processing method for determining the completion state of tire warming according to the wheel slip ratio can be to judge whether the wheel slip ratio is within a preset slip threshold range. If the wheel slip ratio is within the preset slip threshold range, the completion state of tire warming is determined according to the wheel slip ratio; if the wheel slip ratio is not within the preset slip threshold range, a prompt is returned to the user to deeply step on the accelerator pedal on the catapult road surface to warm the tire, and the operation of obtaining the wheel slip ratio is performed.

[0099] It should be noted that the preset slip threshold range can be user-defined, such as 0.35 - 0.42, etc.

[0100] In specific implementation, when deeply stepping on the accelerator pedal to warm the tire on the catapult road surface, the output torque of the motor controller micro-control unit will gradually increase from 0 Nm, and the vehicle records the wheel slip ratio in real time. If the wheel slip ratio is 0.4 and the preset slip threshold range is 0.35 - 0.42, the user is prompted that the tire warming is completed.

[0101] The calculation module 7003 is used to obtain the wheel-ground adhesion coefficient based on the completion state of tire warming, and determine the motor locked-rotor torque corresponding to the catapult system according to the wheel-ground adhesion coefficient and the wheel slip ratio.

[0102] From the above three driving states of the vehicle, it can be seen that when the wheel slip ratio exceeds a certain limit, it will exceed the maximum adhesion of the road surface, and the wheel will have excessive sliding. At this time, not only the original power performance will be affected, but even the vehicle will swing laterally and lose stability, being in a dangerous state. Therefore, to control the wheel slip ratio within a reasonable range, it is necessary to ensure that the driving force of the vehicle is less than the maximum tangential adhesion force Fxmax that the road surface can provide to the wheel at this time, and the wheel-ground adhesion coefficient is used to characterize the relationship between the tangential adhesion force of the road surface to the wheel and the normal reaction force of the road surface to the wheel. Among them, the tangential adhesion force indicates the degree of adhesion that the road surface can provide, and the tangential driving force is a force actively provided by the vehicle.

[0103] In this embodiment, after the tire warm-up is completed, the method for obtaining the wheel-ground adhesion coefficient is to obtain the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel, and then calculate the wheel-ground adhesion coefficient according to the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel through a preset coefficient formula. The preset coefficient formula is u = Fx / Fz, where u is the wheel-ground adhesion coefficient, Fx is the tangential adhesion force of the ground on the wheel, and Fz is the normal reaction force of the ground on the wheel.

[0104] It should also be noted that during a launch control start, since the drive motor has been in a high-torque stall state, the vehicle driving force will be loaded on the wheels at the moment when the electronic parking brake system (EPB) is released. If the previously set stall torque of the launch control system is unreasonable, it is very likely that the vehicle driving force at this time is much greater than the maximum tangential adhesion force Fxmax that the road surface can provide at this time. In the case of severe wheel slippage, not only the advantage of shortening the acceleration time of the launch control start function cannot be reflected, but also the power performance and stability will deteriorate, and the vehicle will have the risk of swaying out of control. Therefore, in order to obtain the optimal launch control start torque and make the starting state stable, it is necessary to master the relationship between the wheel-road adhesion coefficient and the slip ratio at this time, and calculate the maximum tangential adhesion force of the ground on the wheel under the condition of the optimal slip ratio.

[0105] In this embodiment, the method for obtaining the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel based on the completion state of the tire warm-up is to generate a coefficient-slip ratio relationship characteristic diagram according to multiple wheel-ground adhesion coefficient samples and multiple wheel slip ratio samples, and determine the maximum adhesion coefficient according to the coefficient-slip ratio relationship characteristic diagram. Then, the tangential adhesion force of the ground on the wheel is determined according to the maximum adhesion coefficient and the normal reaction force of the ground on the wheel. The multiple wheel-ground adhesion coefficient samples and multiple wheel slip ratio samples are multiple wheel-ground adhesion coefficients and multiple wheel slip ratios collected in real time by the vehicle on the current road surface, etc.

[0106] In a specific implementation, refer to Figure 3 , Figure 3It is the characteristic diagram of the relationship between the coefficient and the slip ratio in the first embodiment of the pure electric vehicle catapult start control method of the present invention. It can be seen from the figure that as the wheel slip ratio increases, the wheel-ground adhesion coefficient will first increase. After it reaches the maximum value, the wheel-ground adhesion coefficient begins to gradually decrease, that is, the maximum tangential adhesion force Fxmax provided by the ground will gradually decrease, and the power performance of the vehicle decreases. To obtain the maximum tangential adhesion force Fxmax, the derivative can be taken of the curve of the wheel-ground adhesion coefficient u and the wheel slip ratio s: du / ds = 0. The point where the slope is 0 corresponds to the maximum wheel-ground adhesion coefficient. The maximum wheel-ground adhesion coefficient is multiplied by the normal reaction force of the road surface at this time to obtain the maximum tangential adhesion force Fxmax. Finally, before the catapult start, the relationship between the adhesion coefficient μ and the slip ratio S is obtained, and the optimal adhesion coefficient is obtained through derivation, so as to calculate the motor locked-rotor torque Ts max set by the system.

[0107] It should also be understood that the tangential adhesion force Fx of the ground on the wheel is a variable quantity, and the maximum tangential adhesion force Fxmax is the maximum value in this variable quantity.

[0108] The control module 7004 is used to perform catapult start control on the pure electric vehicle according to the motor locked-rotor torque.

[0109] Before performing catapult start control on the electric vehicle according to the motor locked-rotor torque, it is also necessary to obtain the maximum torque capacity of the motor of the pure electric vehicle, and then judge whether the motor locked-rotor torque is greater than the maximum torque capacity of the motor. If the motor locked-rotor torque is greater than the maximum torque capacity of the motor, the motor locked-rotor torque is used as the maximum torque capacity of the motor.

[0110] In a specific implementation, the maximum driving force of the wheel during catapult start needs to satisfy the maximum tangential driving force Fmax < the maximum tangential adhesion force Fxmax, so as to inversely deduce the motor locked-rotor torque Tsmax set by the catapult system (if Tsmax > Tmax, then Tsmax = Tmax, and Tmax is the maximum torque capacity of the motor), ensuring a reasonable slip ratio at the moment of catapult start.

[0111] Reference Figure 4 and Figure 5 , Figure 4 is the catapult start flowchart of the first embodiment of the pure electric vehicle catapult start control method of the present invention, Figure 5This is the time, rotational speed, and torque relationship diagram of the first embodiment of the pure electric vehicle's catapult start control method of the present invention. The steps of the catapult start process in the diagram are as follows: 1. Meet the preconditions for catapult start: The vehicle driving preference selects the Sport mode and the gear position is in D gear. 2. The Human Machine Interface (HMI) enables the catapult start function: The vehicle HMI develops a "catapult start mode" button. When the driver actively clicks it, the catapult start Enable status bit should be notified to the core electronic control unit VCU, motor controller, etc. that implement vehicle control decisions (Note: The catapult start function can also be enabled through a combination of the accelerator and / or brake). 3. The HMI prompts the user to deeply step on the accelerator to warm up the tires: The torque output by the motor controller gradually increases. After the wheels slide to the preset slip ratio, the torque decreases. 4. The HMI prompts the user that the tire warming is completed: At this time, after the user stops the vehicle, subsequent operations can be entered. 5. Deeply step on the brake pedal: It is considered to meet the condition only when it is greater than a fixed stroke (calibrated during the development stage). 6. Deeply step on the accelerator pedal, and the catapult start mode is activated: It is considered to meet the condition only when it is greater than a fixed stroke (calibrated during the development stage). At this time, the catapult start mode is activated, the motor remains stationary but the torque Tsmax has been pre-loaded, that is, it enters the locked-rotor state. 7. Release the brake pedal: It is considered to meet the condition only when it is less than a fixed stroke (calibrated during the development stage). 8. Judge the time from activating the catapult start to releasing the brake: After activating the catapult start, the HMI will prompt "Please completely release the brake pedal within n seconds". When the driver releases the pedal, the VCU calculates the interval time from activation to release. If it is greater than n seconds (calibrated during the development stage), the catapult start fails, and the VCU requests the motor controller to output 0 Nm; if it is less than n seconds, the catapult start is successful, and the vehicle accelerates forward. 9. Judge the catapult start exit condition: Set the exit logic according to vehicle speed, accelerator pedal, acceleration time, etc. If the preset conditions are met, the catapult start mode is exited, and the catapult start status bit is reset to Disable, and the entire process ends.

[0112] It should also be noted that compared with the existing fuel vehicle catapult start scheme, the present invention describes the catapult start process of electric vehicles in detail and clarifies the control logic of the catapult start function. It defines the boundaries of the maximum locked-rotor time and locked-rotor torque allowed by the motor controller before catapult start, avoiding excessive temperature rise of the electric drive caused by long-term locked-rotor, which may lead to hardware damage. It also describes the torque loading and speed response of the motor controller after catapult start. Compared with the traditional fixed locked-rotor torque of catapult start, the present invention obtains the best tangential driving force through pre-warming of the tires, thus obtaining the optimal catapult start locked-rotor torque. This locked-rotor torque is not fixed but is calculated in real time according to the current road surface conditions. Therefore, it can ensure the optimal slip ratio at the moment of starting, greatly improving the power performance and handling stability of the vehicle during catapult start and optimizing the user experience of the electric vehicle catapult start function.

[0113] In this embodiment, after receiving the activation signal of the launch control function initiated by the user, the system first prompts the user to deeply step on the accelerator to warm up the tires on the launch road surface and obtains the wheel slip ratio. Then, it determines the tire warming completion status based on the wheel slip ratio, obtains the wheel-ground adhesion coefficient based on the tire warming completion status, and determines the motor locked-rotor torque corresponding to the launch system according to the wheel-ground adhesion coefficient and the wheel slip ratio. After that, it performs launch control on the pure electric vehicle according to the motor locked-rotor torque. Compared with the existing launch control solutions for fuel vehicles and the traditional fixed locked-rotor torque for launch control, when the electronic parking brake system releases and the wheels slip violently, the traction control system intervenes to limit the torque. However, this method cannot ensure the vehicle's power performance and handling stability. In this embodiment, before the launch, the current road surface conditions can be determined according to the wheel-ground adhesion coefficient, and then the optimal motor locked-rotor torque corresponding to the launch system is set according to the wheel-ground adhesion coefficient and the wheel slip ratio, and launch control is performed on the pure electric vehicle according to the motor locked-rotor torque, thereby improving the vehicle's power performance and handling stability.

[0114] For other embodiments or specific implementation manners of the launch control system for the pure electric vehicle of the present invention, reference may be made to the above method embodiments, which will not be elaborated here.

[0115] It should be noted that in this article, the terms "including", "comprising" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or system including a series of elements not only includes those elements but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or system. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or system including that element.

[0116] The serial numbers of the above embodiments of the present invention are only for description and do not represent the superiority or inferiority of the embodiments.

[0117] Through the description of the above embodiments, those skilled in the art can clearly understand that the above method embodiments can be implemented by means of software plus a necessary general hardware platform. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation manner. Based on this understanding, the technical solution of the present invention, in essence, or the part that makes a contribution to the prior art, can be embodied in the form of a software product. The computer software product is stored in a storage medium (such as a read-only memory / random access memory, magnetic disk, optical disc), and includes several instructions for causing a terminal device (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0118] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A control method for the catapult start of a pure electric vehicle, characterized in that, The pure electric vehicle catapult start control method includes the following steps: After receiving the activation signal of the catapult start function initiated by the user, prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtain the wheel slip ratio; Determine the tire warming completion state according to the wheel slip ratio; Based on the tire warming completion state, obtain the wheel-ground adhesion coefficient, and determine the motor locked-rotor torque corresponding to the catapult system according to the wheel-ground adhesion coefficient and the wheel slip ratio; Perform catapult start control on the pure electric vehicle according to the motor locked-rotor torque.

2. The method according to claim 1, characterized in that, The step of, after receiving the activation signal of the catapult start function initiated by the user, prompting the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtaining the wheel slip ratio includes: After receiving the activation signal of the catapult start function initiated by the user, prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtain the wheel rolling radius, the wheel angular velocity, and the longitudinal speed of the wheel center; Determine the wheel slip ratio according to the wheel rolling radius, the wheel angular velocity, and the longitudinal speed of the wheel center.

3. The method according to claim 1 or 2, characterized in that, The step of determining the tire warming completion state according to the wheel slip ratio includes: Judge whether the wheel slip ratio is within a preset slip threshold range; If the wheel slip ratio is within the preset slip threshold range, determine the tire warming completion state according to the wheel slip ratio.

4. The method according to claim 3, characterized in that, After the step of judging whether the wheel slip ratio is within the preset slip threshold range, it further includes: If the wheel slip ratio is not within the preset slip threshold range, return to the step of prompting the user to deeply step on the accelerator to warm up the tires on the catapult road surface and obtaining the wheel slip ratio.

5. The method according to claim 3, characterized in that The step of obtaining the wheel-ground adhesion coefficient based on the tire warming completion state includes: Based on the tire warming completion state, obtain the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel; Determine the wheel-ground adhesion coefficient according to the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel.

6. The method according to claim 5, wherein The step of obtaining the tangential adhesion force of the ground on the wheel and the normal reaction force of the ground on the wheel based on the tire warming completion state includes: Based on the tire warming completion state, generate a coefficient-slip ratio relationship characteristic diagram according to multiple wheel-ground adhesion coefficient samples and multiple wheel slip ratio samples; Determine the maximum adhesion coefficient according to the coefficient-slip ratio relationship characteristic diagram; Determine the tangential adhesion force of the ground on the wheel according to the maximum adhesion coefficient and the normal reaction force of the ground on the wheel.

7. The method according to claim 6, characterized in that, Before the step of performing catapult start control on the pure electric vehicle according to the motor locked-rotor torque, it further includes: Obtain the maximum torque capacity of the motor of the pure electric vehicle; Judge whether the motor locked-rotor torque is greater than the maximum torque capacity of the motor; If the motor locked-rotor torque is greater than the maximum torque capacity of the motor, use the motor locked-rotor torque as the maximum torque capacity of the motor.

8. A pure electric vehicle catapult start control system, characterized in that, The pure electric vehicle catapult start control system includes: A processing module, configured to, after receiving the activation signal of the catapult start function initiated by the user, prompt the user to deeply step on the accelerator to warm up the tires on the catapult road surface, and obtain the wheel slip ratio; A determination module, configured to determine the tire warming completion state according to the wheel slip ratio; A calculation module, configured to obtain a wheel-ground adhesion coefficient based on the warm-up completion state, and determine a motor locked-rotor torque corresponding to the catapult system according to the wheel-ground adhesion coefficient and the wheel slip ratio; A control module, configured to perform catapult start control on the pure electric vehicle according to the motor locked-rotor torque.

9. An electric vehicle catapult start control device, characterized in that The device includes: a memory, a processor, and a pure electric vehicle catapult start control program stored on the memory and executable on the processor, and the pure electric vehicle catapult start control program is configured to implement the steps of the pure electric vehicle catapult start control method according to any one of claims 1 to 7.

10. A storage medium, characterized in that, A pure electric vehicle catapult start control program is stored on the storage medium, and when the pure electric vehicle catapult start control program is executed by a processor, the steps of the pure electric vehicle catapult start control method according to any one of claims 1 to 7 are implemented.

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