Control method and system for electric drive system of electric vehicle

Abstract

The invention provides a control method and system for an electric drive system of an electric vehicle. The method comprises the steps that the motor rotating speed and the motor torque of the electric vehicle are continuously obtained; if the current rotating speed of the motor is larger than or equal to a first preset threshold value, it is determined that the electric vehicle is in a first operation stage, and if the current rotating speed of the motor is smaller than a second preset threshold value, it is determined that the electric vehicle is in a second operation stage; in the first operation stage, whether anti-skid control is carried out on the electric automobile or not is judged according to the change of the rotating speed of a motor of the electric automobile; and in the second operation stage, whether anti-shake control is conducted on the electric automobile or not is judged according to the current motor torque, if yes, torque compensation is conducted on the electric automobile according to a motor rotating speed oscillogram of the electric automobile, and the stability of the electric automobile in the running process is improved.

Description

Technical Field

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

[0002] Compared with fuel vehicles, electric vehicles have fewer shock absorbers in the transmission system, such as clutches, gearboxes, and torque converters, and the connection method is relatively rigid. In addition, electric vehicles use electric motors to drive the vehicle, and the typical characteristics of motors are fast torque response and high torque at low speed, which are also relatively rigid characteristics. The combination of the two makes electric vehicles prone to vehicle shaking, abnormal noise, slipping, and other problems in working conditions such as starting, climbing, and bumpy roads, which seriously affects the quality of the vehicle and the experience of drivers and passengers.

[0003] Existing methods to improve the operating stability of automobiles include improving the performance of chassis shock-absorbing parts (such as suspension, shock absorbers, mounts, etc.), increasing the motor air gap, adding buffer glue to the motor, and improving the purity of the motor controller input power (adding filtering circuits). These methods require increasing the cost of parts or materials, resulting in an increase in the cost of the entire vehicle. Summary of the invention

[0004] In response to the above technical problems, the present application provides a control method and system for an electric drive system of an electric vehicle, which improves the stability of the electric vehicle during driving and enhances the user's riding experience.

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

[0006] Continuously obtain the motor speed and 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 operation stage; if the current motor speed is less than a second preset threshold, it is determined that the electric vehicle is in a second operation stage;

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

[0009] When the electric vehicle is in the second operation stage, judging whether to perform anti-shake control on the electric vehicle according to the current motor torque;

[0010] When anti-shake 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 judged to be in the first operation stage or the second operation stage by the motor speed. When the electric vehicle is in the first operation stage, 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 accelerates, 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 operation stage, it means that the electric vehicle is in a low-speed driving state. Due to the motor slot torque, dead zone, current harmonics, mechanical resonance of the whole vehicle and other reasons, the shaking phenomenon is obvious in the case of low speed and high torque on the whole vehicle, which affects the comfort and driving experience of the whole vehicle. At this time, it is judged whether to perform anti-shake control according to the current motor torque. In the process of anti-shake control, the electric vehicle is subjected to torque compensation 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 riding experience of the user.

[0012] In a possible implementation, when anti-skid 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-skid control process, the embodiment of the present application performs anti-skid control by adjusting the execution torque of the electric vehicle, thereby improving the stability of the electric vehicle under high-speed operation.

[0014] Further, the controlling the execution torque of the electric vehicle according to a preset dynamic stability coefficient includes:

[0015] When starting to perform anti-skid control on the electric vehicle, initializing the dynamic stability coefficient;

[0016] In the process of 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 of the current moment is calculated according to the dynamic stability coefficient of the previous moment, and then the dynamic stability coefficient of the current moment and the requested torque are multiplied to calculate the execution torque of the current moment, wherein the dynamic stability coefficient of the current moment is less than the dynamic stability coefficient of the previous moment, and when the dynamic stability coefficient reaches a preset minimum value, it will no longer change.

[0017] The embodiment of the present application provides an anti-skid control method. When the electric vehicle enters the anti-skid control stage, it means that the electric vehicle is traveling at high speed and in the acceleration stage. It is necessary to gradually reduce the execution torque based on the request torque to avoid slipping due to excessive torque. Therefore, the embodiment of the present application sets a dynamic stability coefficient, updates the dynamic stability coefficient at each moment, and then uses the dynamic stability coefficient to calculate the request torque. Through multiple moments, the execution torque is gradually reduced to a fixed multiple of the request torque, thereby improving the stability of the electric vehicle during driving.

[0018] In a possible implementation, judging whether anti-skid control is required for the electric vehicle according to the change in the motor speed of the electric vehicle in the first operation stage includes:

[0019] According to the motor speed of the electric vehicle at each moment in the first operation stage, calculating the motor speed change rate of the electric vehicle at each moment in the first operation stage;

[0020] Subtract the motor speed change rate of the electric vehicle at a previous moment from the motor speed change rate at each moment in the first operation stage to calculate and obtain the motor speed change rate increment at each moment in the first operation stage of the electric vehicle;

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

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

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

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

[0025] In an embodiment of the present application, a first preset condition is set for exiting the current anti-skid control, which not only takes into account the influence of the motor speed change rate increment and the motor speed, but also takes into account the user's active operation behavior. When the brake signal is detected for M consecutive moments, it means that the user has actively decelerated. At this time, there is no need to additionally control the execution torque of the electric vehicle, and the anti-skid control can be exited to improve the user's driving experience.

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

[0027] When starting to perform torque recovery on the electric vehicle, initializing the dynamic adjustment coefficient;

[0028] In the process of performing torque recovery on the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and the dynamic adjustment coefficient of the current moment is calculated based on the dynamic adjustment coefficient of the previous moment, and then the requested torque is divided by the dynamic adjustment coefficient of the current moment to calculate the execution torque of the current moment, wherein the dynamic adjustment coefficient of the current moment is less than the dynamic adjustment coefficient of the previous moment, and when the dynamic adjustment coefficient reaches a preset minimum value, it will no longer change.

[0029] In an embodiment of the present application, a torque recovery function after exiting anti-skid control is further designed. When the electric vehicle exits the anti-skid control stage, there is still a large difference between the execution torque and the requested torque. The execution torque cannot be directly increased to the size of the requested torque. Instead, the dynamic adjustment coefficient is updated at each moment through a dynamic adjustment coefficient, and then the requested torque is calculated using the dynamic adjustment coefficient. Through multiple moments, the execution torque is gradually increased to a fixed multiple of the requested torque, thereby improving the stability of the electric vehicle during driving.

[0030] In a possible implementation, judging whether it is necessary to perform anti-shake control on the electric vehicle according to the current motor torque 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 anti-shake control needs to be performed on the electric vehicle.

[0032] Further, when 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, the torque compensation of the electric vehicle according to the motor speed waveform of the electric vehicle includes:

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

[0036] Extract the main harmonics in the transformation waveform diagram to construct a speed harmonic diagram;

[0037] In the process of performing torque compensation on the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and according to 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, the requested torque is torque compensated, and the execution torque at the current moment is calculated.

[0038] The embodiment of the present application provides an anti-shake control method, which extracts the main harmonics in the motor speed waveform through Fourier transform and constructs a speed harmonic graph. Then, according to the speed harmonic graph, a torque in the opposite direction can be applied to the speed fluctuation of the electric vehicle at each moment to improve the speed fluctuation, reduce the shake of the electric vehicle in the low-speed driving stage, effectively improve the stability of the electric vehicle during driving, and improve the user's riding experience.

[0039] Furthermore, the request torque of the electric vehicle at the current moment is obtained, and torque compensation is performed on the request torque according to 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, and the execution torque at the current moment is calculated. The specific formula is:

[0040] T MCU =T VCU -h×(N t -N t-1 )

[0041] Among them, T MCU is the execution torque at the current moment, T VCU is the requested torque at the current moment, h is the harmonic damping coefficient of the motor at low speed, N t is the speed value corresponding to the current moment in the speed harmonic diagram, N t-1 is the speed value corresponding to the previous moment in the speed harmonic diagram.

[0042] In the second aspect, accordingly, the embodiment of the present application provides a control system for an electric drive system of an electric vehicle, including an acquisition module, an operation stage judgment module, an anti-skid judgment module, an anti-shake judgment module, and an anti-shake module;

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

[0044] The operation stage judgment module is used to determine that the electric vehicle is in the first operation stage 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 stage if the current motor speed is less than a second preset threshold;

[0045] The anti-skid judgment module is used to judge 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 operating stage when the electric vehicle is in the first operating stage;

[0046] The anti-shake judgment module is used 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 operation stage;

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

[0048] Figure 1 : A flow chart of a control method for an electric drive system of an electric vehicle provided in an embodiment of the present application.

[0049] Figure 2 : A schematic diagram comparing actual speed fluctuation and ideal compensation torque in a control method for an electric drive system of an electric vehicle provided in an embodiment of the present application.

[0050] Figure 3 : A structural schematic diagram of a control system for an electric vehicle electric drive system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0052] It should be noted that the step numbers in the text are only for the convenience of explanation of the specific embodiments and do not serve to limit the order in which the steps are executed. In the description of this application, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0053] Embodiment 1:

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

[0055] Step S1, continuously obtaining 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 operation stage; if the current motor speed is less than a second preset threshold, it is determined that the electric vehicle is in a second operation stage;

[0057] Step S3: when the electric vehicle is in the first operation stage, judging 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 operation stage;

[0058] Step S4: when the electric vehicle is in the second operation stage, judging whether to perform anti-shake control on the electric vehicle according to the current motor torque;

[0059] Step S5: When anti-shake 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.

[0060] The embodiment of the present application provides a control method for an electric drive system of an electric vehicle. First, the electric vehicle is judged to be in the first operation stage or the second operation stage by the motor speed. When the electric vehicle is in the first operation stage, 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 accelerates, 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 operation stage, it means that the electric vehicle is in a low-speed driving state. Due to the motor slot torque, dead zone, current harmonics, mechanical resonance of the whole vehicle and other reasons, the shaking phenomenon is obvious in the case of low speed and high torque on the whole vehicle, which affects the comfort and driving experience of the whole vehicle. At this time, it is judged whether to perform anti-shake control according to the current motor torque. In the process of anti-shake control, the electric vehicle is subjected to torque compensation 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 riding experience of the user.

[0061] In a preferred embodiment, in step S1, the motor speed, motor torque and other dynamic parameters of the electric vehicle are detected in real time by the vehicle controller (VCU). In step S2, the first preset threshold and the second preset threshold are obtained by combining experience and experiments. According to experience, the first preset threshold is usually above 1000rpm, and the second preset threshold is usually between 100-300rpm. Specifically, it is necessary to conduct relevant experiments on real roads with a prototype vehicle, and the specific first preset threshold and the second preset threshold can be obtained according to the speed and NVH (noise vibration, etc.) collected in the experiment.

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

[0063] Further, the controlling the execution torque of the electric vehicle according to a preset dynamic stability coefficient includes:

[0064] When starting to perform anti-skid control on the electric vehicle, initializing the dynamic stability coefficient;

[0065] In the process of 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 of the current moment is calculated according to the dynamic stability coefficient of the previous moment, and then the dynamic stability coefficient of the current moment and the requested torque are multiplied to calculate the execution torque of the current moment, wherein the dynamic stability coefficient of the current moment is less than the dynamic stability coefficient of the previous moment, and when the dynamic stability coefficient reaches a preset minimum value, it will no longer change.

[0066] The embodiment of the present application provides an anti-skid control method. When the electric vehicle enters the anti-skid control stage, it means that the electric vehicle is traveling at high speed and in the acceleration stage. It is necessary to gradually reduce the execution torque based on the request torque to avoid slipping due to excessive torque. Therefore, the embodiment of the present application sets a dynamic stability coefficient, updates the dynamic stability coefficient at each moment, and then uses the dynamic stability coefficient to calculate the request torque. Through multiple moments, the execution torque is gradually reduced to a fixed multiple of the request 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 during the anti-slip control process is:

[0068] T MCU =T VCU ×S

[0069] S i =S (i-1) ×η 2

[0070] Among them, S is the dynamic stability coefficient, S (i-1) is the dynamic stability coefficient of the previous moment, S i is the dynamic stability coefficient at the current moment, η 2 is a custom constant, the initial value of S is 1, 0.5≤S≤1, 0.5≤η 2 ≤1.

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

[0072] In a possible implementation, in step S3, judging whether anti-skid control is required for the electric vehicle according to the change in the motor speed of the electric vehicle in the first operation stage includes:

[0073] According to the motor speed of the electric vehicle at each moment in the first operation stage, calculating the motor speed change rate of the electric vehicle at each moment in the first operation stage;

[0074] Subtract the motor speed change rate of the electric vehicle at a previous moment from the motor speed change rate at each moment in the first operation stage to calculate and obtain the motor speed change rate increment at each moment in the first operation stage of the electric vehicle;

[0075] When the motor speed change rate increment is greater than a third preset threshold value for N consecutive moments, it is determined that anti-skid control is required for the electric vehicle, where N is a preset value.

[0076] The embodiment of the present application provides a method for determining whether to perform anti-skid control. By calculating the increment of the motor speed change rate at each moment, the actual acceleration of the electric vehicle can be reflected. The third preset threshold is set as a reference value, and the increment of the motor speed change rate is compared with the third preset threshold to determine whether to perform anti-skid control. In addition, the embodiment of the present application sets a judgment for N consecutive moments in the judgment condition. Anti-skid control is entered only when the increment of the motor speed change rate is greater than the third preset threshold for N consecutive moments. Such a setting avoids misleading the anti-skid judgment due to user misoperation and improves the accuracy of the judgment.

[0077] In a preferred embodiment, the above N is set to 3, and the sampling interval of the electric vehicle motor speed is set to 10ms. When the motor speed is greater than the first preset threshold, the motor speed change rate increment is judged, and the motor speed change rate increment within the 10ms is detected once every 10ms. If the motor speed change rate increment is detected to be greater than the third preset threshold in three consecutive 10ms operation cycles, the anti-skid flag is set, and the anti-skid flag is used to indicate whether the anti-skid control stage is performed. When the anti-skid flag is set, it indicates that the electric vehicle needs to be anti-skid controlled; when the anti-skid flag is reset, it indicates that the electric vehicle exits the anti-skid control stage.

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

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

[0080] In an embodiment of the present application, a first preset condition is set for exiting the current anti-skid control, which not only takes into account the influence of the motor speed change rate increment and the motor speed, but also takes into account the user's active operation behavior. When the brake signal is detected for M consecutive moments, it means that the user has actively decelerated. At this time, there is no need to additionally control the execution torque of the electric vehicle, and the anti-skid control can be exited to improve the user's driving experience.

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

[0082] Further, when the anti-skid control is stopped, torque recovery is performed on the electric vehicle according to a preset dynamic adjustment coefficient, including:

[0083] When starting to perform torque recovery on the electric vehicle, initializing the dynamic adjustment coefficient;

[0084] In the process of performing torque recovery on the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and the dynamic adjustment coefficient of the current moment is calculated based on the dynamic adjustment coefficient of the previous moment, and then the requested torque is divided by the dynamic adjustment coefficient of the current moment to calculate the execution torque of the current moment, wherein the dynamic adjustment coefficient of the current moment is less than the dynamic adjustment coefficient of the previous moment, and when the dynamic adjustment coefficient reaches a preset minimum value, it will no longer change.

[0085] In an embodiment of the present application, a torque recovery function after exiting anti-skid control is further designed. When the electric vehicle exits the anti-skid control stage, there is still a large difference between the execution torque and the requested torque. The execution torque cannot be directly increased to the size of the requested torque. Instead, the dynamic adjustment coefficient is updated at each moment through a dynamic adjustment coefficient, and then the requested torque is calculated using the dynamic adjustment coefficient. Through multiple moments, the execution torque is gradually increased to a fixed multiple of the requested torque, thereby improving the stability of the electric vehicle during driving.

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

[0087] T MCU =T VCU / K

[0088] K i =K (i-1) ×η 1

[0089] Among them, 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 of the previous moment, K i is the dynamic adjustment coefficient at the current moment, the initial value of K is 2, η 1 is a custom constant, 1≤K≤2, 0.1≤η1≤1. The vehicle controller can obtain the current requested torque by looking up the table according to the current accelerator pedal opening, motor speed, current high-voltage electrical power consumption, current power available from the power battery, etc.

[0090] In a preferred embodiment, after the anti-skid flag is reset, let the variable Coeff = 1 / K to represent the multiple relationship between the requested torque and the executed torque, and accordingly, 1 / 2≤Coeff≤1. The actual executed torque of the motor controller is Coeff times the requested torque issued by the vehicle controller. After the anti-skid flag is reset, Coeff gradually increases to 1.0 in an exponential form, and the increase formula is Coeff(i) = Coeff(i-1)*1.025. The limit value is 1.0. When Coeff is restored 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, judging whether it is necessary to perform anti-shake control 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 anti-shake control needs to be performed on the electric vehicle.

[0093] Further, when 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:

[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 the second preset threshold, the anti-shake control is stopped.

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

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

[0097] Extract the main harmonics in the transformation waveform diagram to construct a speed harmonic diagram;

[0098] In the process of performing torque compensation on the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and according to 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, the requested torque is torque compensated, and the execution torque at the current moment is calculated.

[0099] The embodiment of the present application provides an anti-shake control method, which extracts the main harmonics in the motor speed waveform through Fourier transform and constructs a speed harmonic graph. Then, according to the speed harmonic graph, a torque in the opposite direction can be applied to the speed fluctuation of the electric vehicle at each moment to improve the speed fluctuation, reduce the shake of the electric vehicle in the low-speed driving stage, effectively improve the stability of the electric vehicle during driving, and improve the user's riding experience.

[0100] Furthermore, the request torque of the electric vehicle at the current moment is obtained, and torque compensation is performed on the request torque according to 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, and the execution torque at the current moment is calculated. The specific formula is:

[0101] T MCU =T VCU -h×(N t -N t-1 )

[0102] Among them, T MCU is the execution torque at the current moment, T VCU is the requested torque at the current moment, h is the harmonic damping coefficient of the motor at low speed, N t is the speed value corresponding to the current moment in the speed harmonic diagram, N t-1 is the speed value corresponding to the previous moment in the speed harmonic diagram.

[0103] In a preferred embodiment, the parameters are set as follows: 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. This parameter is used to limit the jitter suppression compensation torque to avoid excessive torque suppression.

[0104] In a preferred embodiment, the comparison diagram between the actual speed fluctuation and the ideal compensation torque is as follows: Figure 2 As shown, during the anti-shake 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. The superimposed torque is used to reduce or increase the speed to improve the speed fluctuation and realize anti-shake control of the electric vehicle.

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

[0106] Embodiment 2:

[0107] like Figure 3 As shown, accordingly, embodiment 2 provides a control system for an electric drive system of an electric vehicle, including an acquisition module 10, an operation stage judgment module 20, an anti-skid judgment module 30, an anti-shake judgment module 40 and an anti-shake module 50;

[0108] Wherein, the acquisition module 10 is used to continuously acquire the motor speed and motor torque of the electric vehicle;

[0109] The operation stage judgment module 20 is used to determine that the electric vehicle is in the first operation stage 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 stage if the current motor speed is less than a second preset threshold;

[0110] The anti-skid judgment module 30 is used to judge 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 operating stage when the electric vehicle is in the first operating stage;

[0111] The anti-shake judgment module 40 is used 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 operation stage;

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

[0113] In a possible implementation, the control system further includes an anti-skid module, and the anti-skid module is used to control the execution torque of the electric vehicle according to a preset dynamic stability coefficient when performing anti-skid control on the electric vehicle.

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

[0115] When starting to perform anti-skid control on the electric vehicle, initializing the dynamic stability coefficient;

[0116] In the process of 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 of the current moment is calculated according to the dynamic stability coefficient of the previous moment, and then the dynamic stability coefficient of the current moment and the requested torque are multiplied to calculate the execution torque of the current moment, wherein the dynamic stability coefficient of the current moment is less than the dynamic stability coefficient of the previous moment, and when the dynamic stability coefficient reaches a preset minimum value, it will no longer change.

[0117] In a possible implementation, the anti-skid judging module 30 judges whether anti-skid control is required for the electric vehicle according to the change of the motor speed of the electric vehicle in the first operation stage, including:

[0118] According to the motor speed of the electric vehicle at each moment in the first operation stage, calculating the motor speed change rate of the electric vehicle at each moment in the first operation stage;

[0119] Subtract the motor speed change rate of the electric vehicle at a previous moment from the motor speed change rate at each moment in the first operation stage to calculate and obtain the motor speed change rate increment at each moment in the first operation stage of the electric vehicle;

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

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

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

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

[0124] When starting to perform torque recovery on the electric vehicle, initializing the dynamic adjustment coefficient;

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

[0126] In a possible implementation, the anti-shake determination module 40 determines whether anti-shake control is required for the electric vehicle 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, it is determined that anti-shake control needs to be performed on the electric vehicle.

[0128] Further, when 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:

[0129] 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.

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

[0131] Performing Fourier transformation on the motor speed waveform of the electric vehicle to obtain a transformed waveform;

[0132] Extract the main harmonics in the transformation waveform diagram to construct a speed harmonic diagram;

[0133] In the process of performing torque compensation on the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and according to 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, the requested torque is torque compensated, and the execution torque at the current moment is calculated.

[0134] The embodiment of the present application provides a control system for an electric drive system of an electric vehicle. First, the electric vehicle is judged to be in the first operation stage or the second operation stage by the motor speed. When the electric vehicle is in the first operation stage, 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 accelerates, there is a high risk of slipping. Therefore, 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 the anti-skid control process, the anti-skid control is performed by adjusting the execution torque of the electric vehicle to improve the stability of the electric vehicle in a high-speed running state. In addition, when the electric vehicle is in the second operation stage, it means that the electric vehicle is in a low-speed driving state. Due to the reasons such as the motor cogging torque, dead zone, current harmonics, and mechanical resonance of the whole vehicle, the shaking phenomenon is obvious in the case of low speed and high torque, which affects the comfort and driving experience of the whole vehicle. At this time, it is judged whether to perform anti-shake control according to the current motor torque. In the anti-shake control process, the electric vehicle is subjected to torque compensation in combination with the motor speed waveform diagram, and the speed fluctuation of the electric vehicle in a low-speed driving state is reduced, and the stability of the electric vehicle in a low-speed running state is improved. In summary, the embodiment of the present application can effectively improve the stability of the electric vehicle during driving and improve the riding experience of the user.

[0135] The more detailed working principle and step flow of this embodiment can refer to, but are not limited to, the relevant records of Embodiment 1.

[0136] The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present application in detail. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the scope of protection 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 should be included in the scope of protection of the present application.

Claims

1. A control method for an electric drive system of an electric vehicle, characterized in that: include: Continuously obtain the motor speed and motor torque of the electric vehicle; 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 operation stage; if the current motor speed is less than a second preset threshold, it is determined that the electric vehicle is in a second operation stage; When the electric vehicle is in the first operation stage, judging whether to perform anti-skid control on the electric vehicle according to a change in the motor speed of the electric vehicle in the first operation stage; When the electric vehicle is in the second operation stage, judging whether to perform anti-shake control on the electric vehicle according to the current motor torque; When anti-shake 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.

2. A control method for an electric vehicle electric drive system as claimed in claim 1, characterized in that: When anti-skid control is performed on the electric vehicle, the execution torque of the electric vehicle is controlled according to a preset dynamic stability coefficient.

3. A control method for an electric vehicle electric drive system as claimed in claim 2, characterized in that: The controlling the execution torque of the electric vehicle according to the preset dynamic stability coefficient includes: When starting to perform anti-skid control on the electric vehicle, initializing the dynamic stability coefficient; In the process of 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 of the current moment is calculated according to the dynamic stability coefficient of the previous moment, and then the dynamic stability coefficient of the current moment and the requested torque are multiplied to calculate the execution torque of the current moment, wherein the dynamic stability coefficient of the current moment is less than the dynamic stability coefficient of the previous moment, and when the dynamic stability coefficient reaches a preset minimum value, it will no longer change.

4. A control method for an electric vehicle electric drive system as claimed in claim 1, characterized in that: The step of judging whether anti-skid control is required for the electric vehicle according to the change in the motor speed of the electric vehicle in the first operation stage includes: According to the motor speed of the electric vehicle at each moment in the first operation stage, calculating the motor speed change rate of the electric vehicle at each moment in the first operation stage; Subtracting the motor speed change rate of the electric vehicle at a previous moment from the motor speed change rate at each moment in the first operation stage, and calculating the motor speed change rate increment of the electric vehicle at each moment in the first operation stage; When the motor speed change rate increment is greater than a third preset threshold value for N consecutive moments, it is determined that anti-skid control is required for the electric vehicle, where N is a preset value.

5. A control method for an electric vehicle electric drive system as claimed in claim 4, characterized in that: When anti-skid control is performed on the electric vehicle, if the electric vehicle meets a first preset condition, the anti-skid control is stopped, including: If the motor speed change rate increment is less than the fourth preset threshold for M consecutive moments, or the motor speed is less than the first preset threshold for M consecutive moments, or a brake signal is detected for M consecutive moments, the anti-skid control is stopped.

6. A control method for an electric vehicle electric drive system as claimed in claim 5, characterized in that: When the anti-skid control is stopped, the electric vehicle is subjected to torque recovery according to a preset dynamic adjustment coefficient, including: When starting to perform torque recovery on the electric vehicle, initializing the dynamic adjustment coefficient; In the process of performing torque recovery on the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and the dynamic adjustment coefficient of the current moment is calculated based on the dynamic adjustment coefficient of the previous moment, and then the requested torque is divided by the dynamic adjustment coefficient of the current moment to calculate the execution torque of the current moment, wherein the dynamic adjustment coefficient of the current moment is less than the dynamic adjustment coefficient of the previous moment, and when the dynamic adjustment coefficient reaches a preset minimum value, it will no longer change.

7. A control method for an electric vehicle electric drive system as claimed in claim 1, characterized in that: The step of judging whether it is necessary to perform anti-shake control on the electric vehicle according to the current motor torque includes: 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 needs to be performed on the electric vehicle.

8. A control method for an electric vehicle electric drive system as claimed in claim 7, characterized in that: 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: 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.

9. A control method for an electric vehicle electric drive system as claimed in claim 1, characterized in that: The method of performing torque compensation on the electric vehicle according to the motor speed waveform of the electric vehicle comprises: Performing Fourier transformation on the motor speed waveform of the electric vehicle to obtain a transformed waveform; Extract the main harmonics in the transformation waveform diagram to construct a speed harmonic diagram; In the process of performing torque compensation on the electric vehicle, at each moment, the requested torque of the electric vehicle at the current moment is obtained, and according to 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, the requested torque is torque compensated, and the execution torque at the current moment is calculated.

10. A control method for an electric vehicle electric drive system as claimed in claim 9, characterized in that: The request torque of the electric vehicle at the current moment is obtained, and torque compensation is performed on the request torque according to 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, and the execution torque at the current moment is calculated. The specific formula is: T MCU =T VCU -h×(N t -N t-1 ) Among them, T MCU is the execution torque at the current moment, T VCU is the requested torque at the current moment, h is the harmonic damping coefficient of the motor at low speed, N t is the speed value corresponding to the current moment in the speed harmonic diagram, N t-1 is the speed value corresponding to the previous moment in the speed harmonic diagram.

11. A control system for an electric vehicle electric drive system, characterized in that: It includes an acquisition module, an operation stage judgment module, an anti-skid judgment module, an anti-shake judgment module and an anti-shake module; Wherein, the acquisition module is used to continuously acquire the motor speed and motor torque of the electric vehicle; The operation stage judgment module is used to determine that the electric vehicle is in the first operation stage 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 stage if the current motor speed is less than a second preset threshold; The anti-skid judgment module is used to judge 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 operating stage when the electric vehicle is in the first operating stage; The anti-shake judgment module is used 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 operation stage; The anti-shake module is used to perform torque compensation on the electric vehicle according to the motor speed waveform of the electric vehicle when performing anti-shake control on the electric vehicle.

Images