A control method and system for an electric drive system of an electric vehicle

Abstract

The application provides a control method and system for an electric drive system of an electric vehicle, the method comprising: continuously acquiring a motor speed and a motor torque of the electric vehicle; determining that the electric vehicle is in a first running stage if the current motor speed is greater than or equal to a first preset threshold, and determining that the electric vehicle is in a second running stage if the current motor speed is less than a second preset threshold; in the first running stage, judging whether to perform anti-slip control on the electric vehicle according to a change in the motor speed of the electric vehicle; in the second running stage, judging whether to perform anti-shake control on the electric vehicle according to the current motor torque, and if so, performing torque compensation on the electric vehicle according to a motor speed waveform of the electric vehicle to improve the stability of the electric vehicle during driving.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electric vehicle drive control, and particularly relates to a control method and system for an electric vehicle electric drive system. BACKGROUND

[0002] Compared with a fuel vehicle, an electric vehicle reduces shock absorbers such as clutches, gearboxes, hydraulic torque converters and other transmission systems, and the connection mode is relatively hard. In addition, the electric vehicle uses a motor to drive the vehicle to travel, and the typical characteristics of the motor are fast torque response and large torque at low speed, which also belong to hard characteristics. The superposition of the two makes the electric vehicle prone to vehicle shaking, abnormal noise, skidding and other problems in starting, climbing, bumpy road and other working conditions, which seriously affects the vehicle quality and the experience of the driver and passengers.

[0003] The existing methods for improving the stability of the vehicle running include improving the performance of the chassis shock-absorbing parts (such as suspensions, shock absorbers, suspensions and the like), increasing the air gap of the motor, adding a buffer rubber in the motor, and improving the purity of the input power of the motor controller (adding a filter circuit), which increases the cost of parts or materials and leads to an increase in the cost of the vehicle. SUMMARY

[0004] To solve the above technical problems, the present application provides a control method and system for an electric vehicle electric drive system, which improves the stability of the electric vehicle during driving and improves the riding experience of the user.

[0005] In a first aspect, the present application provides a control method for an electric vehicle electric drive system, comprising:

[0006] continuously obtaining the motor speed and the motor torque of the electric vehicle;

[0007] If the current motor speed is greater than or equal to a first preset threshold, it is determined that the electric vehicle is in a first running stage, and if the current motor speed is less than a second preset threshold, it is determined that the electric vehicle is in a second running stage;

[0008] When the electric vehicle is in the first running stage, it is judged whether to perform anti-skid control on the electric vehicle according to the change of the motor speed of the electric vehicle in the first running stage;

[0009] When the electric vehicle is in the second running stage, it is judged whether to perform anti-shaking control on the electric vehicle according to the current motor torque;

[0010] When the anti-shaking control is performed on the electric vehicle, torque compensation is performed on the electric vehicle according to the motor speed waveform of the electric vehicle.

[0011] The embodiment of the present application provides a control method for an electric drive system of an electric vehicle. First, the electric vehicle is determined to be in a first running stage or a second running stage according to the motor speed. When the electric vehicle is in the first running stage, it is determined that the electric vehicle is in a high-speed running state. Based on the characteristics of the motor drive of the electric vehicle, when the motor is in the high-speed running state and accelerates, there is a high risk of slipping. Therefore, whether to perform anti-slip control on the electric vehicle is determined according to the change of the motor speed. In addition, when the electric vehicle is in the second running stage, it is determined that the electric vehicle is in a low-speed running state. Due to the motor tooth slot torque, dead zone, current harmonic, vehicle mechanical resonance and other reasons, in the case of low-speed large torque, the vibration phenomenon is obvious, which affects the vehicle comfort and driving experience. At this time, whether to perform anti-vibration control is determined according to the current motor torque. In the anti-vibration control process, the torque of the electric vehicle is compensated according to the motor speed waveform diagram, the speed fluctuation of the electric vehicle in the low-speed running state is reduced, and the stability of the electric vehicle in the low-speed running state is improved. In summary, the embodiment of the present application can effectively improve the stability of the electric vehicle during running, and improve the riding experience of the user.

[0012] In a possible implementation, when the anti-slip control is performed on the electric vehicle, the execution torque of the electric vehicle is controlled according to a preset dynamic stability coefficient.

[0013] In the anti-slip control process, the execution torque of the electric vehicle is adjusted to perform anti-slip control, and the stability of the electric vehicle in the high-speed running state is improved.

[0014] Further, the execution torque of the electric vehicle is controlled according to the preset dynamic stability coefficient, including:

[0015] When the anti-slip control is started on the electric vehicle, the dynamic stability coefficient is initialized;

[0016] In the process of performing the anti-slip control on the electric vehicle, at each time, the requested torque of the electric vehicle at the current time is obtained, the dynamic stability coefficient at the current time is calculated according to the dynamic stability coefficient at the last time, then the dynamic stability coefficient at the current time is multiplied by the requested torque to calculate the execution torque at the current time, wherein the dynamic stability coefficient at the current time is less than the dynamic stability coefficient at the last time, and the dynamic stability coefficient does not change when the dynamic stability coefficient reaches a preset minimum value.

[0017] The embodiment of the present application provides a kind of anti-skid control method, when electric vehicle enters anti-skid control stage, it indicates that electric vehicle is high-speed running and is in acceleration stage at this time, needs to be gradually reduced based on request torque execution torque, avoid slip due to excessive torque.It is therefore provided with dynamic stability coefficient in the embodiment of the present application, first update dynamic stability coefficient at each time, then using dynamic stability coefficient to calculate request torque, through multiple time, execution torque is gradually reduced to the fixed multiple of request torque, improve the stability of electric vehicle in the process of driving.

[0018] In a possible implementation manner, the determining whether the anti-skid control needs to be performed on the electric vehicle according to the change of the motor speed of the electric vehicle in the first running stage includes:

[0019] The motor speed change rate of the electric vehicle at each time in the first running stage is calculated according to the motor speed of the electric vehicle at each time in the first running stage.

[0020] The motor speed change rate increment of the electric vehicle at each time in the first running stage is calculated by subtracting the motor speed change rate at the previous time from the motor speed change rate of the electric vehicle at each time in the first running stage.

[0021] When the motor speed change rate increment is greater than a third preset threshold value for N consecutive times, it is determined that the anti-skid control needs to be performed on the electric vehicle, where N is a preset value.

[0022] The embodiment of the present application provides a judgment method of whether to perform anti-skid control, by calculating the motor speed change rate increment at each time, the real acceleration condition of the electric vehicle can be reflected, and by setting the third preset threshold value as a reference value, the motor speed change rate increment is compared with the third preset threshold value to determine whether to perform anti-skid control.In addition, the embodiment of the present application sets the judgment of N consecutive times in the judgment condition, only when the motor speed change rate increment is greater than the third preset threshold value for N consecutive times, the anti-skid control is entered, and such setting avoids the misdirection of anti-skid judgment due to user misoperation, and improves the judgment accuracy.

[0023] Further, when the anti-skid control is performed on the electric vehicle, if the electric vehicle satisfies a first preset condition, the anti-skid control is stopped, including:

[0024] If the motor speed change rate increment is less than a fourth preset threshold value for M consecutive times, or the motor speed is less than the first preset threshold value for M consecutive times, or the brake signal is detected for M consecutive times, the anti-skid control is stopped.

[0025] In the embodiment of the present application, the first preset condition is set for exiting the current anti-slip control, not only considering the influence of the motor speed change rate increment and the motor speed, but also considering the active operation behavior of the user. When the brake signal is detected in the continuous M time, it is indicated that the user performs the active deceleration operation. At this time, it is not necessary to additionally control the execution torque of the electric vehicle, and the anti-slip control can be exited to improve the driving experience of the user.

[0026] Further, when stopping the anti-slip control, the torque recovery of the electric vehicle is performed according to a preset dynamic adjustment coefficient, including:

[0027] When starting the torque recovery of the electric vehicle, the dynamic adjustment coefficient is initialized;

[0028] In the process of the torque recovery of the electric vehicle, at each time, the requested torque of the electric vehicle at the current time is obtained, the dynamic adjustment coefficient at the current time is calculated according to the dynamic adjustment coefficient at the last time, and then the requested torque is divided by the dynamic adjustment coefficient at the current time to calculate the execution torque at the current time. Wherein, the dynamic adjustment coefficient at the current time is less than the dynamic adjustment coefficient at the last time, and when the dynamic adjustment coefficient reaches a preset minimum value, it is no longer changed.

[0029] In the embodiment of the present application, the torque recovery function after exiting the anti-slip control is further designed. When the electric vehicle exits the anti-slip control stage, there is still a large difference between the execution torque and the requested torque, and the execution torque cannot be directly increased to the size of the requested torque. Instead, the dynamic adjustment coefficient is updated at each time, and then the requested torque is calculated using the dynamic adjustment coefficient. Through multiple times, the execution torque is gradually increased to a fixed multiple of the requested torque, and the stability of the electric vehicle in the driving process is improved.

[0030] In a possible implementation manner, the method further includes:

[0031] If the absolute value of the current motor torque is greater than or equal to a fifth preset threshold, it is determined that the anti-shake control needs to be performed on the electric vehicle.

[0032] Further, when the anti-shake control is performed on the electric vehicle, if the electric vehicle meets a second preset condition, the anti-shake control is stopped, including:

[0033] If the absolute value of the current motor torque is less than the fifth preset threshold, or the current motor speed is greater than or equal to the second preset threshold, the anti-shake control is stopped.

[0034] In a possible implementation manner, the torque compensation on the electric vehicle according to the motor speed waveform of the electric vehicle comprises:

[0035] performing Fourier transform on the motor speed waveform of the electric vehicle to obtain a transformed waveform;

[0036] extracting main harmonics in the transformed waveform to construct a speed harmonic diagram;

[0037] In the process of performing torque compensation on the electric vehicle, at each time, the requested torque of the electric vehicle at the current time is obtained, the requested torque is compensated according to the difference between the speed value corresponding to the current time and the speed value corresponding to the previous time in the speed harmonic diagram, and the executed torque at the current time is calculated.

[0038] The embodiment of the present application provides a kind of anti-shake control method, main harmonic in motor speed waveform is extracted by Fourier transform, speed harmonic diagram is constructed, then according to speed harmonic diagram, a torque in opposite direction is applied to electric vehicle speed fluctuation at each time to improve speed fluctuation, reduce the jitter of electric vehicle in low-speed travel stage, effectively improve the stability of electric vehicle in the process of driving, improve the user's ride experience.

[0039] Further, the requested torque of the electric vehicle at the current time is obtained, the requested torque is compensated according to the difference between the speed value corresponding to the current time and the speed value corresponding to the previous time in the speed harmonic diagram, and the executed torque at the current time is calculated, and the specific formula is:

[0040] T MCU = T VCU -h×(N t -N t-1 )

[0041] Wherein, T MCU is the executed torque at the current time, T VCU is the requested torque at the current time, h is the harmonic damping coefficient of motor low-speed operation, N t is the speed value corresponding to the current time in the speed harmonic diagram, and N t-1 is the speed value corresponding to the previous time in the speed harmonic diagram.

[0042] Secondly, the present application provides a kind of control system for electric vehicle electric drive system, including acquisition module, running stage judging module, anti-skid judging module, anti-shake judging module and anti-shake module;

[0043] Wherein, the acquisition module is used to continuously acquire the motor speed and motor torque of electric vehicle;

[0044] The running stage judging module is configured to determine that the electric vehicle is in a first running stage if the current motor speed is greater than or equal to a first preset threshold, and determine that the electric vehicle is in a second running stage if the current motor speed is less than a second preset threshold.

[0045] The anti-slip judging module is configured to judge whether to perform anti-slip control on the electric vehicle according to the change of the motor speed of the electric vehicle in the first running stage when the electric vehicle is in the first running stage.

[0046] The anti-shake judging module is configured to judge whether to perform anti-shake control on the electric vehicle according to the current motor torque when the electric vehicle is in the second running stage.

[0047] The anti-shake module is configured to perform torque compensation on the electric vehicle according to the motor speed waveform of the electric vehicle when the anti-shake control is performed on the electric vehicle. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 FIG. 1 is a flow diagram of a control method for an electric drive system of an electric vehicle according to an embodiment of the present application.

[0049] Figure 2 FIG. 5 is a comparison diagram of real speed fluctuation and ideal compensation torque in a control method for an electric drive system of an electric vehicle according to an embodiment of the present application.

[0050] Figure 3 FIG. 7 is a structural diagram of a control system for an electric drive system of an electric vehicle according to an embodiment of the present application. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0052] It should be noted that the step numbers in the text are only for the convenience of explaining the specific embodiments, and do not limit the execution sequence of the steps. In the description of the present application, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first" and "second" can explicitly or implicitly include one or more of the features.

[0053] Embodiment one:

[0054] As Figure 1 shown, embodiment one provides a control method for an electric vehicle electric drive system, comprising steps S1-S5:

[0055] Step S1, continuously acquiring the motor speed and motor torque of the electric vehicle;

[0056] Step S2, if the current motor speed is greater than or equal to a first preset threshold, it is determined that the electric vehicle is in a first running phase, and if the current motor speed is less than a second preset threshold, it is determined that the electric vehicle is in a second running phase;

[0057] Step S3, when the electric vehicle is in the first running phase, according to the change of the motor speed of the electric vehicle in the first running phase, it is judged whether to perform anti-skid control on the electric vehicle;

[0058] Step S4, when the electric vehicle is in the second running phase, according to the current motor torque, it is judged whether to perform anti-shake control on the electric vehicle;

[0059] Step S5, when the electric vehicle is subjected to anti-shake control, torque compensation is performed on the electric vehicle according to the motor speed waveform diagram of the electric vehicle.

[0060] The embodiment of the present application provides a control method for an electric vehicle electric drive system. First, the motor speed is used to determine whether the electric vehicle is in a first running phase or a second running phase. When the electric vehicle is in the first running phase, it means that the electric vehicle is in a high-speed driving state. Based on the characteristics of the electric vehicle motor drive, when the motor is in a high-speed driving state and is accelerating, there is a high risk of slipping, so it is necessary to further judge whether to perform anti-skid control on the electric vehicle according to the change of the motor speed. In addition, when the electric vehicle is in the second running phase, it means that the electric vehicle is in a low-speed driving state. Due to reasons such as motor tooth slot torque, dead zone, current harmonic, vehicle mechanical resonance, etc. on the whole vehicle, in the case of low-speed large torque, the shaking phenomenon is obvious, which affects the vehicle comfort and driving experience. At this time, according to the current motor torque, it is judged whether to perform anti-shake control, and in the anti-shake control process, torque compensation is performed on the electric vehicle in combination with the motor speed waveform diagram, so as to reduce the speed fluctuation of the electric vehicle in the low-speed driving state and improve the stability of the electric vehicle in the low-speed running state. In summary, the embodiment of the present application can effectively improve the stability of the electric vehicle during driving and improve the user's riding experience.

[0061] In a preferred embodiment, in step S1, the motor speed, motor torque and other power parameters of the electric vehicle are detected in real time by the vehicle control unit (VCU), in step S2, the first preset threshold and the second preset threshold are obtained by combining experience and experiments, and according to experience, the first preset threshold is usually above 1000 rpm, and the second preset threshold is usually between 100-300 rpm. Specifically, relevant experiments need to be carried out on a sample vehicle on a real road, and according to the collected speed and NVH (noise and vibration), the specific first preset threshold and second preset threshold can be obtained.

[0062] In a possible implementation manner, in step S3, when the anti-slip control is performed on the electric vehicle, the execution torque of the electric vehicle is controlled according to the preset dynamic stability coefficient.

[0063] Further, the execution torque of the electric vehicle is controlled according to the preset dynamic stability coefficient, including:

[0064] When the anti-slip control is started on the electric vehicle, the dynamic stability coefficient is initialized;

[0065] In the process of performing the anti-slip control on the electric vehicle, at each time, the requested torque of the electric vehicle at the current time is obtained, the dynamic stability coefficient at the current time is calculated according to the dynamic stability coefficient at the last time, and then the dynamic stability coefficient at the current time is multiplied by the requested torque to calculate the execution torque at the current time, wherein the dynamic stability coefficient at the current time is less than the dynamic stability coefficient at the last time, and when the dynamic stability coefficient reaches a preset minimum value, the dynamic stability coefficient is no longer changed.

[0066] The embodiment of the application provides an anti-slip control method, when the electric vehicle enters the anti-slip control stage, it indicates that the electric vehicle is currently driving at high speed and is in an acceleration stage, and the execution torque needs to be gradually reduced based on the requested torque to avoid slipping due to too large torque. Therefore, the embodiment of the application sets a dynamic stability coefficient, which is updated at each time, and then the requested torque is calculated using the dynamic stability coefficient, and through multiple times, the execution torque is gradually reduced to a fixed multiple of the requested torque, thereby improving the stability of the electric vehicle during driving.

[0067] In a preferred embodiment, the calculation formula of the execution torque and the dynamic stability coefficient in the anti-slip control process is:

[0068] T MCU =T VCU ×S

[0069] S i =S (i-1) ×η2

[0070] Wherein, S is a dynamic stability coefficient, S (i-1) S is a dynamic stability coefficient of the previous time, S i S is a dynamic stability coefficient of the current time, η2 is a self-defined constant, the initial value of S is 1, 0.5≤S≤1, 0.5≤η2≤1.

[0071] In a preferred embodiment, whether to perform the anti-slip control on the electric vehicle is determined by setting the setting and resetting of the anti-slip flag, when the anti-slip flag is set, the variable Coeff is equal to 1 / K to represent the multiple relationship between the requested torque and the executed torque, and correspondingly, 1 / 2≤Coeff≤1. The actual executed torque of the motor controller is the Coeff times of the requested torque issued by the vehicle controller. After the anti-slip flag is set, the Coeff decreases exponentially from 1.0, Coeff(i)=0.97*Coeff(i-1), and the execution period is 10 ms. The minimum value of Coeff(K) is 0.5, that is, after entering the anti-slip, the minimum executed torque of the MCU is 0.5 times of the torque issued by the VCU.

[0072] In a possible implementation manner, in step S3, the determining whether to perform the anti-slip control on the electric vehicle according to the change of the motor speed of the electric vehicle in the first running phase comprises:

[0073] According to the motor speed of the electric vehicle at each time in the first running phase, the motor speed change rate of the electric vehicle at each time in the first running phase is calculated and obtained;

[0074] The motor speed change rate of the electric vehicle at each time in the first running phase is subtracted by the motor speed change rate of the previous time, and the motor speed change rate increment of the electric vehicle at each time in the first running phase is calculated and obtained;

[0075] When the motor speed change rate increment is greater than a third preset threshold value for N continuous times, it is determined that the anti-slip control needs to be performed on the electric vehicle, wherein N is a preset value.

[0076] The embodiment of the present application provides a judgment method of whether to perform the anti-slip control, by calculating the motor speed change rate increment at each time, the real acceleration of the electric vehicle can be reflected, and by setting the third preset threshold value as a reference value, the motor speed change rate increment is compared with the third preset threshold value to judge whether to perform the anti-slip control. In addition, the embodiment of the present application sets the judgment of N continuous times in the judgment condition, only when the motor speed change rate increment is greater than the third preset threshold value for N continuous times, the anti-slip control is entered, and such setting avoids the misdirection of the anti-slip judgment due to the user's misoperation, and improves the judgment accuracy.

[0077] In a preferred embodiment, the N is set to 3, and the sampling interval of the motor speed of the electric vehicle is set to 10 ms. When the motor speed is greater than a first preset threshold, the motor speed change rate increment is determined. The motor speed change rate increment in 10 ms is detected every 10 ms. If the motor speed change rate increment is greater than a third preset threshold in the continuous 3 10 ms operation periods, the anti-slip flag is set. The anti-slip flag is used to indicate whether the anti-slip control stage is performed. When the anti-slip flag is set, it indicates that the anti-slip control of the electric vehicle is needed. When the anti-slip flag is reset, it indicates that the electric vehicle exits the anti-slip control stage.

[0078] Further, when the anti-slip control of the electric vehicle is performed, if the electric vehicle meets a first preset condition, the anti-slip control is stopped, including:

[0079] If the motor speed change rate increment is less than a fourth preset threshold for continuous M times, or the motor speed is less than the first preset threshold for continuous M times, or the brake signal is detected for continuous M times, the anti-slip control is stopped.

[0080] In the embodiments of the present application, the first preset condition is set to exit the current anti-slip control. Not only the influence of the motor speed change rate increment and the motor speed is considered, but also the active operation behavior of the user is considered. When the brake signal is detected for continuous M times, it indicates that the user performs the active deceleration operation. At this time, it is not necessary to additionally control the execution torque of the electric vehicle, and the anti-slip control can be exited to improve the driving experience of the user.

[0081] In a preferred embodiment, the M is set to 3. In the anti-slip control stage, if the motor speed is less than the first preset threshold for continuous 3 sampling periods, or the motor speed change rate increment detected for continuous 3 sampling periods is less than the fourth preset threshold, or the brake signal is detected for continuous 3 sampling periods, the anti-slip flag is reset, and the anti-slip control is stopped.

[0082] Further, when the anti-slip control is stopped, the torque of the electric vehicle is recovered according to a preset dynamic adjustment coefficient, including:

[0083] When the torque recovery of the electric vehicle is started, the dynamic adjustment coefficient is initialized.

[0084] In the process of torque recovery of the electric vehicle, at each time, the requested torque of the electric vehicle at the current time is obtained, the dynamic adjustment coefficient at the current time is calculated according to the dynamic adjustment coefficient at the last time, then the requested torque is divided by the dynamic adjustment coefficient at the current time to calculate the execution torque at the current time, wherein the dynamic adjustment coefficient at the current time is less than the dynamic adjustment coefficient at the last time, and the dynamic adjustment coefficient does not change when the dynamic adjustment coefficient reaches a preset minimum value.

[0085] In the embodiment of the application, a torque recovery function after exiting the anti-slip control is further designed. When the electric vehicle exits the anti-slip control stage, there is still a large difference between the execution torque and the requested torque, and the execution torque cannot be directly increased to the size of the requested torque, but the dynamic adjustment coefficient is updated at each time, then the requested torque is calculated using the dynamic adjustment coefficient, and through multiple times, the execution torque is gradually increased to a fixed multiple of the requested torque, thereby improving the stability of the electric vehicle in the driving process.

[0086] In a preferred embodiment, the calculation formula of the execution torque and the dynamic adjustment coefficient in the torque recovery process is:

[0087] T MCU = T VCU / K

[0088] K i = K (i-1) × η1

[0089] Wherein, T MCU is the execution torque of the motor controller (MCU), T VCU is the requested torque of the vehicle controller (VCU), K is the dynamic adjustment coefficient, K (i-1) is the dynamic adjustment coefficient at the last time, K i is the dynamic adjustment coefficient at the current time, the initial value of K is 2, η1 is a self-defined constant, 1≤K≤2, 0.1≤η1≤1. Wherein, the vehicle controller can obtain the requested torque at the current time by table lookup method according to the opening degree of the current accelerator pedal, the motor speed, the current high-voltage electrical power, the current power supply power of the power battery, etc.

[0090] In a preferred embodiment, when the anti-skid flag is reset, a variable Coeff is set to 1 / K to represent the multiple relationship between the requested torque and the executed torque, and correspondingly, 1 / 2≤Coeff≤1. The actual executed torque of the motor controller is the Coeff times of the requested torque issued by the vehicle controller. After the anti-skid flag is reset, the Coeff gradually increases to 1.0 in an exponential form, and the increasing formula is Coeff(i) = Coeff(i-1)*1.025. The limiting value is 1.0, and when the Coeff returns to 1.0, the executed torque is equal to the requested torque, and the torque recovery is completed.

[0091] In a possible implementation, in step S4, the determining whether the anti-shake control needs to be performed on the electric vehicle according to the current motor torque includes:

[0092] If the absolute value of the current motor torque is greater than or equal to a fifth preset threshold, it is determined that the anti-shake control needs to be performed on the electric vehicle.

[0093] Further, when the anti-shake control is performed on the electric vehicle, if the electric vehicle satisfies a second preset condition, the anti-shake control is stopped, including:

[0094] If the absolute value of the current motor torque is less than the fifth preset threshold, or the current motor speed is greater than or equal to a second preset threshold, the anti-shake control is stopped.

[0095] In a possible implementation, in step S5, the torque compensation is performed on the electric vehicle according to the motor speed waveform of the electric vehicle, including:

[0096] Performing Fourier transform on the motor speed waveform of the electric vehicle to obtain a transformed waveform;

[0097] Extracting main harmonics in the transformed waveform to construct a speed harmonic diagram;

[0098] In the process of performing the torque compensation on the electric vehicle, at each time, the requested torque of the electric vehicle at the current time is obtained, the requested torque is compensated according to the difference between the speed value corresponding to the current time and the speed value corresponding to the previous time in the speed harmonic diagram, and the executed torque at the current time is calculated.

[0099] The anti-shake control method provided in the embodiments of the present application extracts main harmonics in the motor speed waveform by Fourier transform, constructs a speed harmonic diagram, and then can exert a torque in the opposite direction on the speed fluctuation of the electric vehicle at each time according to the speed harmonic diagram, so as to improve the speed fluctuation, reduce the shaking of the electric vehicle in the low-speed driving stage, effectively improve the stability of the electric vehicle in the driving process, and improve the riding experience of the user.

[0100] Further, the request torque of the electric vehicle at the current time is obtained, the request torque is compensated according to the difference between the speed value corresponding to the current time and the speed value corresponding to the previous time in the speed harmonic diagram, and the execution torque at the current time is calculated, and the specific formula is:

[0101] T MCU = T VCU -h×(N t -N t-1 )

[0102] Wherein, T MCU is the execution torque at the current time, T VCU is the request torque at the current time, h is the harmonic damping coefficient of low-speed operation of the motor, N t is the speed value corresponding to the current time in the speed harmonic diagram, and N t-1 is the speed value corresponding to the previous time in the speed harmonic diagram.

[0103] In a preferred embodiment, a parameter is set: the maximum value of the jitter suppression output, that is, h×(N t -N t-1 ) must be less than or equal to the maximum value of the jitter suppression output, and the jitter suppression compensation torque is limited by the parameter to avoid excessive suppression of the torque.

[0104] In a preferred embodiment, the real speed fluctuation and ideal compensation torque comparison diagram is as shown in Figure 2 During the anti-jitter control process, a small negative torque is superimposed on the output torque when the speed fluctuates upward, and a small positive torque is superimposed on the output torque when the speed fluctuates downward, and the speed is reduced or increased through the superimposed torque to improve the speed fluctuation, thereby realizing the anti-jitter control of the electric vehicle.

[0105] Further, if the current motor speed is less than a first preset threshold and greater than or equal to a second preset threshold, the actual execution torque of the motor controller is the request torque issued by the vehicle controller. If the current motor speed is less than the second preset threshold and the absolute value of the current motor torque is less than a fifth preset threshold, the actual execution torque of the motor controller is the request torque issued by the vehicle controller.

[0106] Embodiment two:

[0107] As Figure 3 shown, accordingly, embodiment two provides a control system for an electric vehicle electric drive system, comprising an acquisition module 10, a running stage judgment module 20, an anti-slip judgment module 30, an anti-jitter judgment module 40 and an anti-jitter module 50.

[0108] The acquisition module 10 is configured to continuously acquire the motor speed and the motor torque of the electric vehicle.

[0109] The running stage judgment module 20 is configured to determine that the electric vehicle is in a first running stage if the current motor speed is greater than or equal to a first preset threshold, and determine that the electric vehicle is in a second running stage if the current motor speed is less than a second preset threshold.

[0110] The anti-slip judgment module 30 is configured to judge whether to perform anti-slip control on the electric vehicle according to the change of the motor speed of the electric vehicle in the first running stage when the electric vehicle is in the first running stage.

[0111] The anti-shake judgment module 40 is configured to judge whether to perform anti-shake control on the electric vehicle according to the current motor torque when the electric vehicle is in the second running stage.

[0112] The anti-shake module 50 is configured to perform torque compensation on the electric vehicle according to the motor speed waveform of the electric vehicle when the anti-shake control is performed on the electric vehicle.

[0113] In a possible implementation, the control system further comprises an anti-slip module, which is configured to control the execution torque of the electric vehicle according to a preset dynamic stability coefficient when the anti-slip control is performed on the electric vehicle.

[0114] Further, the anti-slip module controls the execution torque of the electric vehicle according to the preset dynamic stability coefficient, including:

[0115] initializing the dynamic stability coefficient when the anti-slip control is started on the electric vehicle;

[0116] In the process of performing the anti-slip control on the electric vehicle, at each time, the requested torque of the electric vehicle at the current time is acquired, the dynamic stability coefficient at the current time is calculated according to the dynamic stability coefficient at the last time, then the dynamic stability coefficient at the current time is multiplied by the requested torque to calculate the execution torque at the current time, wherein the dynamic stability coefficient at the current time is less than the dynamic stability coefficient at the last time, and the dynamic stability coefficient stops changing when the dynamic stability coefficient reaches a preset minimum value.

[0117] In a possible implementation, the anti-slip judgment module 30 judges whether to perform anti-slip control on the electric vehicle according to the change of the motor speed of the electric vehicle in the first running stage, including:

[0118] According to the motor speed of the electric vehicle at each moment in the first running phase, the motor speed variation rate of the electric vehicle at each moment in the first running phase is calculated;

[0119] The motor speed variation rate of the electric vehicle at each moment in the first running phase is subtracted from the motor speed variation rate at the previous moment, and the motor speed variation rate increment of the electric vehicle at each moment in the first running phase is calculated;

[0120] When the motor speed variation rate increment is greater than a third preset threshold value for N consecutive moments, it is determined that the anti-slip control of the electric vehicle is required, wherein N is a preset value.

[0121] Further, when the anti-slip control of the electric vehicle is performed, if the electric vehicle meets a first preset condition, the anti-slip control is stopped, including:

[0122] If the motor speed variation rate increment is less than a fourth preset threshold value for M consecutive moments, or the motor speed is less than a first preset threshold value for M consecutive moments, or the brake signal is detected for M consecutive moments, the anti-slip control is stopped.

[0123] Further, when the anti-slip control is stopped, the torque recovery of the electric vehicle is performed according to a preset dynamic adjustment coefficient, including:

[0124] When the torque recovery of the electric vehicle is started, the dynamic adjustment coefficient is initialized;

[0125] During the torque recovery of the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, the dynamic adjustment coefficient at the current moment is calculated according to the dynamic adjustment coefficient at the previous moment, and then the requested torque is divided by the dynamic adjustment coefficient at the current moment to calculate the execution torque at the current moment, wherein the dynamic adjustment coefficient at the current moment is less than the dynamic adjustment coefficient at the previous moment, and when the dynamic adjustment coefficient reaches a preset minimum value, it no longer changes.

[0126] In a possible implementation manner, the anti-shake judgment module 40 judges whether the anti-shake control of the electric vehicle is required according to the current motor torque, including:

[0127] If the absolute value of the current motor torque is greater than or equal to a fifth preset threshold value, it is determined that the anti-shake control of the electric vehicle is required.

[0128] Further, when the anti-shake control of the electric vehicle is performed, if the electric vehicle meets a second preset condition, the anti-shake control is stopped, including:

[0129] If an absolute value of the current motor torque is less than a fifth preset threshold value, or the current motor speed is greater than or equal to the second preset threshold value, the anti-shake control is stopped.

[0130] In a possible implementation, the anti-shake module 50 compensates the torque of the electric vehicle according to a motor speed waveform of the electric vehicle, and the compensation includes:

[0131] The motor speed waveform of the electric vehicle is subjected to Fourier transform to obtain a transformed waveform;

[0132] Main harmonics in the transformed waveform are extracted to construct a speed harmonic diagram;

[0133] In the process of compensating the torque of the electric vehicle, at each time, a requested torque of the electric vehicle at a current time is obtained, the requested torque is compensated according to a difference between a speed value corresponding to the current time and a speed value corresponding to a previous time in the speed harmonic diagram, and an executed torque at the current time is calculated.

[0134] The embodiment of the present application provides a control system for an electric vehicle electric drive system. First, the motor speed is used to determine whether the electric vehicle is in a first running phase or a second running phase. When the electric vehicle is in the first running phase, it is in a high-speed running state. Based on the characteristics of the electric vehicle motor drive, when the motor is in a high-speed running state and is accelerating, there is a high risk of slipping, and therefore it is necessary to further determine whether to perform anti-slip control on the electric vehicle according to the change of the motor speed. In the process of anti-slip control, the executed torque of the electric vehicle is adjusted to perform anti-slip control, thereby improving the stability of the electric vehicle in a high-speed running state. In addition, when the electric vehicle is in the second running phase, it is in a low-speed running state. Due to the motor tooth slot torque, dead zone, current harmonic, vehicle mechanical resonance and other reasons, in the case of low-speed and large torque, the shaking phenomenon is obvious, which affects the vehicle comfort and driving experience. At this time, it is determined whether to perform anti-shake control according to the current motor torque, and in the process of anti-shake control, the torque of the electric vehicle is compensated according to the motor speed waveform, thereby reducing the speed fluctuation of the electric vehicle in a low-speed running state and improving the stability of the electric vehicle in a low-speed running state. In summary, the embodiment of the present application can effectively improve the stability of the electric vehicle during running and improve the user's riding experience.

[0135] The more detailed working principle and step flow of the embodiment can be but not limited to the related description of the first embodiment.

[0136] The above-described specific embodiments, purposes, technical solutions and beneficial effects of the present application are further described in detail, and it should be understood that the above-described is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. It is particularly pointed out that for those skilled in the art, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for an electric drive system of an electric vehicle, characterized in that, include: Continuously acquire the motor speed and motor torque of electric vehicles; If the current motor speed is greater than or equal to a first preset threshold, the electric vehicle is determined to be in a first operating stage; if the current motor speed is less than a second preset threshold, the electric vehicle is determined to be in a second operating stage. When the electric vehicle is in the first operating phase, the system determines whether to implement anti-skid control based on the change in motor speed during the first operating phase. This includes: calculating the rate of change of motor speed at each moment during the first operating phase based on the motor speed at each moment; subtracting the rate of change of motor speed from the previous moment from each rate of change of motor speed at each moment during the first operating phase to calculate the increment of the rate of change of motor speed at each moment during the first operating phase; and determining that anti-skid control is required for the electric vehicle if the increment of the rate of change of motor speed is greater than a third preset threshold for N consecutive moments, where N is a preset value. When the electric vehicle is in the second operating stage, it is determined whether to perform anti-shake control on the electric vehicle based on the current motor torque, including: if the absolute value of the current motor torque is greater than or equal to a fifth preset threshold, it is determined that anti-shake control is needed for the electric vehicle; When performing anti-shake control on the electric vehicle, torque compensation is performed on the electric vehicle based on the motor speed waveform. This includes: performing a Fourier transform on the motor speed waveform to obtain a transformed waveform; extracting the main harmonics from the transformed waveform to construct a speed harmonic diagram; during the torque compensation process, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and torque compensation is performed on the requested torque based on the difference between the speed value corresponding to the current moment and the speed value corresponding to the previous moment in the speed harmonic diagram, thus calculating the executed torque at the current moment.

2. The control method for an electric vehicle drive system as described in claim 1, characterized in that, When the electric vehicle is subjected to anti-slip control, the execution torque of the electric vehicle is controlled according to a preset dynamic stability coefficient.

3. The control method for an electric vehicle drive system as described in claim 2, characterized in that, The step of controlling the execution torque of the electric vehicle according to a preset dynamic stability coefficient includes: When anti-skid control is initiated on the electric vehicle, the dynamic stability coefficient is initialized; During the anti-skid control of the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, the dynamic stability coefficient at the current moment is calculated based on the dynamic stability coefficient at the previous moment, and then the dynamic stability coefficient at the current moment is multiplied by the requested torque to calculate the executed torque at the current moment. The dynamic stability coefficient at the current moment is less than the dynamic stability coefficient at the previous moment, and it no longer changes when the dynamic stability coefficient reaches a preset minimum value.

4. The control method for an electric vehicle drive system as described in claim 1, characterized in that, When anti-skid control is applied to the electric vehicle, if the electric vehicle meets a first preset condition, the anti-skid control is stopped, including: If the increase in the rate of change of motor speed is less than the fourth preset threshold for M consecutive time periods, or the motor speed is less than the first preset threshold for M consecutive time periods, or a braking signal is detected for M consecutive time periods, then the anti-slip control is stopped.

5. The control method for an electric vehicle drive system as described in claim 4, characterized in that, When the anti-slip control is stopped, torque recovery of the electric vehicle is performed according to a preset dynamic adjustment coefficient, including: When torque recovery of the electric vehicle begins, the dynamic adjustment coefficient is initialized; During the torque recovery process of the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, the dynamic adjustment coefficient at the current moment is calculated based on the dynamic adjustment coefficient at the previous moment, and then the requested torque is divided by the dynamic adjustment coefficient at the current moment to calculate the executed torque at the current moment. The dynamic adjustment coefficient at the current moment is less than the dynamic adjustment coefficient at the previous moment, and it no longer changes when the dynamic adjustment coefficient reaches a preset minimum value.

6. The control method for an electric vehicle drive system as described in claim 1, characterized in that, When the electric vehicle is subjected to anti-shake control, if the electric vehicle meets a second preset condition, the anti-shake control is stopped, including: If the absolute value of the current motor torque is less than the fifth preset threshold, or the current motor speed is greater than or equal to the second preset threshold, then the anti-shake control is stopped.

7. The control method for an electric vehicle drive system as described in claim 1, characterized in that, The process involves obtaining the requested torque of the electric vehicle at the current moment, and then performing torque compensation on the requested torque based on the difference between the speed value at the current moment and the speed value at the previous moment in the speed harmonic diagram. The specific formula for calculating the execution torque at the current moment is as follows: T MCU = T VCU - h×(N t - N t-1 ) Among them, T MCU T represents the current torque being executed. VCU The torque is the requested torque at the current moment, and h is the harmonic damping coefficient for low-speed motor operation, N. t N represents the rotational speed value at the current moment in the rotational speed harmonic diagram. t-1 The value is the rotational speed at the previous moment in the rotational speed harmonic diagram.

8. A control system for an electric drive system of an electric vehicle, characterized in that, This includes an acquisition module, a running phase judgment module, an anti-slip judgment module, an anti-shake judgment module, and an anti-shake module; The acquisition module is used to continuously acquire the motor speed and motor torque of the electric vehicle; The operation phase determination module is used to determine that the electric vehicle is in the first operation phase if the current motor speed is greater than or equal to a first preset threshold, and to determine that the electric vehicle is in the second operation phase if the current motor speed is less than a second preset threshold. The anti-slip judgment module is used to determine whether to implement anti-slip control for the electric vehicle based on the change in motor speed during the first operating phase when the electric vehicle is in the first operating phase. This includes: calculating the rate of change of motor speed at each moment during the first operating phase based on the motor speed at each moment; subtracting the rate of change of motor speed from the previous moment from each rate of change of motor speed at each moment during the first operating phase to calculate the increment of the rate of change of motor speed at each moment during the first operating phase; and determining that anti-slip control is required for the electric vehicle if the increment of the rate of change of motor speed is greater than a third preset threshold for N consecutive moments, where N is a preset value. The anti-shake judgment module is used to determine whether to perform anti-shake control on the electric vehicle based on the current motor torque when the electric vehicle is in the second operating stage, including: if the absolute value of the current motor torque is greater than or equal to a fifth preset threshold, then it is determined that anti-shake control needs to be performed on the electric vehicle. The anti-shake module is used to perform torque compensation on the electric vehicle based on the motor speed waveform when performing anti-shake control on the electric vehicle. This includes: performing a Fourier transform on the motor speed waveform to obtain a transformed waveform; extracting the main harmonics from the transformed waveform to construct a speed harmonic diagram; and during the torque compensation process, at each moment, obtaining the requested torque of the electric vehicle at the current moment, and performing torque compensation on the requested torque based on the difference between the speed value corresponding to the current moment and the speed value corresponding to the previous moment in the speed harmonic diagram, thus calculating the executed torque at the current moment.

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