CN113232525B - Control method of four-wheel drive electric vehicle and computer readable storage medium - Google Patents

Control method of four-wheel drive electric vehicle and computer readable storage medium Download PDF

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Publication number
CN113232525B
CN113232525B CN202110649371.2A CN202110649371A CN113232525B CN 113232525 B CN113232525 B CN 113232525B CN 202110649371 A CN202110649371 A CN 202110649371A CN 113232525 B CN113232525 B CN 113232525B
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motor
vehicle
driving
mode
driving mode
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CN113232525A (en
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冯琳
于航飞
侯明月
刘绍辉
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Evergrande Hengchi New Energy Automobile Research Institute Shanghai Co Ltd
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Evergrande Hengchi New Energy Automobile Research Institute Shanghai Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L15/00—Methods, circuits, or devices for controlling the traction-motor speed of electrically-propelled vehicles
    • B60L15/32—Control or regulation of multiple-unit electrically-propelled vehicles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/10—Vehicle control parameters
    • B60L2240/12—Speed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/42—Drive Train control parameters related to electric machines
    • B60L2240/423—Torque
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2260/00—Operating Modes
    • B60L2260/20—Drive modes; Transition between modes
    • B60L2260/26—Transition between different drive modes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/72—Electric energy management in electromobility

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Electric Propulsion And Braking For Vehicles (AREA)

Abstract

The application discloses a control method of a four-wheel drive electric vehicle and a computer readable storage medium, and the scheme provided by the application comprises the following steps: determining a target required torque of the vehicle according to the running state of the vehicle and the opening degree of an accelerator pedal; determining a motor driving mode of the vehicle according to the target required torque and the current speed of the vehicle, wherein the motor driving mode comprises a double-motor driving mode and a single-motor driving mode; distributing target required torques for a front axle driving motor and a rear axle driving motor of the vehicle according to a motor driving mode of the vehicle; the front shaft driving motor and the rear shaft driving motor are permanent magnet synchronous motors. The control of the four-wheel drive electric vehicle of the embodiment of the application can reflect excellent dynamic property and simultaneously give consideration to economy.

Description

Control method of four-wheel drive electric vehicle and computer readable storage medium
Technical Field
The present application relates to the field of electric vehicle technologies, and in particular, to a control method for a four-wheel drive electric vehicle and a computer-readable storage medium.
Background
With the rapid development of the technology level, the control level of the new energy vehicle is higher and higher, the driving range is greatly increased while the energy consumption of the whole vehicle is optimized, and the range anxiety of a user is greatly relieved, so that the new energy pure electric vehicle is rapidly developed. With the popularization of electric vehicles, more and more users are pursuing the extreme acceleration, and four-wheel drive electric vehicles have better acceleration performance, but the efficiency of driving motors is reduced to a certain degree compared with that of two-wheel drive electric vehicles, so that the energy consumption is increased.
In order to reduce the energy consumption of the four-wheel drive electric automobile, the torques of the front and rear axle driving motors of the four-wheel drive electric automobile are distributed according to the load by adopting a dynamic proportion at present, but the average efficiency of the front and rear motors cannot be greatly improved by the distribution method.
How to effectively reduce the high energy consumption of the four-wheel drive electric automobile is a technical problem to be solved at present.
Disclosure of Invention
An embodiment of the present application provides a control method for a four-wheel drive electric vehicle and a computer readable storage medium, so as to solve the problem that an existing four-wheel drive electric vehicle is high in energy consumption.
In order to solve the above technical problem, the present specification is implemented as follows:
in a first aspect, a control method for a four-wheel drive electric vehicle is provided, including: determining a target required torque of the vehicle according to the running state of the vehicle and the opening degree of an accelerator pedal; determining a motor driving mode of the vehicle according to the target required torque and the current speed of the vehicle, wherein the motor driving mode comprises a double-motor driving mode and a single-motor driving mode; distributing target required torques for a front axle driving motor and a rear axle driving motor of the vehicle according to a motor driving mode of the vehicle; the front shaft driving motor and the rear shaft driving motor are permanent magnet synchronous motors.
Optionally, determining the driving modes corresponding to the front axle driving motor and the rear axle driving motor according to the target required torque and the current vehicle speed of the vehicle, including:
when the target required torque is less than a first threshold value and the current vehicle speed is less than a second threshold value, the driving mode of the vehicle is determined to be a single-motor driving mode.
Optionally, distributing the target required torque for the front axle driving motor and the rear axle driving motor of the vehicle according to the motor driving mode of the vehicle, including:
acquiring the current speed of the vehicle, wherein the current rotating speed corresponds to the rotating speed of a first motor driven in a front shaft driving motor and a rear shaft driving motor;
when the current speed of the vehicle is not greater than a third threshold value, distributing all proportions of target required torque for the first motor, and distributing zero torque for a non-driven second motor in the front axle driving motor and the rear axle driving motor, wherein the third threshold value is smaller than the second threshold value.
Optionally, distributing the target required torque for the front axle driving motor and the rear axle driving motor of the vehicle according to the motor driving mode of the vehicle, including:
acquiring the current speed of the vehicle, wherein the current rotating speed corresponds to the rotating speed of a first motor driven in a front axle driving motor and a rear axle driving motor;
when the current speed of the vehicle is greater than a third threshold value, distributing all proportions of target required torque for the first motor, and enabling a non-driven second motor in the front axle driving motor and the rear axle driving motor to be in a free dragging state mechanically dragged by the first motor, wherein the third threshold value is smaller than the second threshold value.
Optionally, when the second motor is in a free-drag state, the method further includes:
acquiring counter electromotive force corresponding to the rotating speed when the second motor is in a free dragging state;
acquiring the voltage of a battery connected with a second motor;
and when the counter electromotive force is not greater than the battery voltage, keeping the second motor in a free dragging state.
Optionally, the method further includes:
when the counter electromotive force is greater than the battery voltage, the motor drive mode is switched from the single motor drive mode to the dual motor drive mode.
Optionally, after determining that the driving mode of the vehicle is the single-motor driving mode, the method further includes:
respectively determining system efficiency corresponding to a front shaft driving motor and a rear shaft driving motor according to basic characteristic parameters of the motors;
and selecting a motor with high system efficiency as the first motor.
Optionally, determining a motor driving mode of the vehicle according to the target required torque and the current vehicle speed of the vehicle, includes:
and when the target required torque is not less than the first threshold value or the current vehicle speed is not less than the second threshold value, determining that the motor driving mode of the vehicle is a double-motor driving mode.
Optionally, allocating target required torques for the front axle driving motor and the rear axle driving motor according to a motor driving mode of the vehicle, includes:
respectively determining the system efficiency of a front axle driving motor and a rear axle driving motor according to a plurality of preset torque distribution proportion combinations corresponding to the target required torque;
and distributing the torque to the front axle driving motor and the rear axle driving motor according to the torque distribution proportion combination with the highest system efficiency.
In a second aspect, a computer-readable storage medium is provided, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to the first aspect.
In the embodiment of the application, the target required torque of the vehicle is determined according to the running state of the vehicle and the opening degree of an accelerator pedal, the motor driving mode of the vehicle is determined to be a single-motor driving mode or a double-motor driving mode according to the target required torque and the current speed of the vehicle, and the target required torque is distributed to the front-axle driving motor and the rear-axle driving motor of the vehicle according to the motor driving mode of the vehicle, so that the reasonable motor driving mode of the vehicle can be determined according to different requests of a driver, corresponding motor torque distribution is carried out, the purpose of executing the two-motor simultaneous driving mode in a staged and time-sharing mode of the four-wheel drive electric vehicle is achieved, compared with the mode that the two-motor simultaneous driving mode is executed in any stage and all time in the prior art, the control of the four-wheel drive electric vehicle in the embodiment of the application can embody excellent power performance and simultaneously take the economy into account, so that the high energy consumption of the four-wheel drive electric vehicle can be effectively reduced on the whole, and the performance of the four-wheel drive electric vehicle can be improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 is a flowchart illustrating a control method of a four-wheel drive electric vehicle according to an embodiment of the present application.
FIG. 2 is a schematic diagram of an overall architecture of a torque distribution mode of a vehicle motor according to an embodiment of the present application.
Fig. 3 is a schematic flow chart of the vehicle motor torque distribution according to the first embodiment of the present application.
FIG. 4 is a schematic flow chart of vehicle motor torque distribution according to a second embodiment of the present application.
Fig. 5 is a flowchart of an overall example of a control method of the four-wheel drive electric vehicle of the embodiment of the present application.
Fig. 6 is a block diagram showing the configuration of a control device for a four-wheel drive electric vehicle according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some, but not all, embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. The reference numbers in the present application are only used for distinguishing the steps in the scheme and are not used for limiting the execution sequence of the steps, and the specific execution sequence is described in the specification.
In order to solve the problems in the prior art, an embodiment of the present application provides a control method for a four-wheel drive electric vehicle, and fig. 1 is a schematic flow chart of the control method for the four-wheel drive electric vehicle according to the embodiment of the present application.
As shown in fig. 1, the method comprises the following steps:
step 102, determining a target required torque of the vehicle according to the running state of the vehicle and the opening degree of an accelerator pedal;
104, determining a motor driving mode of the vehicle according to the target required torque and the current speed of the vehicle, wherein the motor driving mode comprises a double-motor driving mode and a single-motor driving mode;
106, distributing target required torques for a front axle driving motor and a rear axle driving motor of the vehicle according to the motor driving mode of the vehicle;
the front shaft driving motor and the rear shaft driving motor are permanent magnet synchronous motors.
In step 102, the operating state of the vehicle includes an acceleration when the driver is currently depressing the accelerator pedal, and the magnitude of the accelerator pedal opening indicates how fast the driver is currently requiring the vehicle to accelerate.
According to the stepping-on acceleration of the accelerator pedal of the vehicle and the stepping-on opening degree of the accelerator pedal, whether the current vehicle needs to be accelerated to the expected speed or accelerated to the expected speed slowly can be judged. The target required torque of the vehicle is determined by the accelerator pedal opening to achieve the driver's desired vehicle speed.
In an embodiment of the present application, a four-wheel drive electric vehicle includes a front axle drive motor and a rear axle drive motor.
In step 104, the motor driving modes of the vehicle include a dual motor mode in which the front axle driving motor and the rear axle driving motor are simultaneously driven, and a single motor mode in which only one of the two motors is driven. The dual-motor mode can provide higher dynamic performance for the vehicle, and the single-motor mode can obviously reduce the energy consumption of the vehicle and provide higher economy for the vehicle.
Different motor driving modes can be switched for the vehicle according to different conditions of the current speed of the vehicle and the target required torque determined by the current driver stepping on the accelerator pedal.
In the embodiment of the application, the motor driving mode of the vehicle is determined according to the target required torque and the current vehicle speed of the vehicle, and the following conditions are mainly included:
the 1 st: when the target required torque is not less than the first threshold value, the motor drive mode of the vehicle is determined to be a two-motor drive mode.
The 2 nd: and when the current vehicle speed of the vehicle is not less than the second threshold value, determining that the motor driving mode of the vehicle is a double-motor driving mode.
And (3) type: when the target required torque is smaller than a first threshold value and the current vehicle speed of the vehicle is smaller than a second threshold value, the driving mode of the vehicle is determined to be a single-motor driving mode.
The first threshold value is, for example, in the range of 2000-3000rpm for different vehicle types, and for the case 1, if the target required torque of the vehicle is not less than the first threshold value, it can be judged that the driver's current demand intention is to pursue the dynamic property of the vehicle, and it is necessary to realize the high-speed running of the vehicle. At this time, it is determined that the vehicle needs to be operated in the dual motor drive mode. That is, the dual motor drive mode corresponds to the driver's power demand mode.
For different vehicle types, the second threshold value is located in the range of 120-130km/h, for example, for the 2 nd case, if the current vehicle speed of the vehicle is not less than the second threshold value and the accelerator pedal of the vehicle is still pressed by the driver, it can be judged that the current demand intention of the driver is still pursuing the dynamic property of the vehicle, and the high-speed running of the vehicle needs to be realized. At this point, it is determined that the vehicle still needs to operate in the dual motor drive mode.
For the case 3, if the target required torque is smaller than the first threshold value and the current vehicle speed of the vehicle is smaller than the second threshold value, it may be determined that the driver's current demand intends to pursue the economy of the vehicle, that is, to reduce the energy consumption of the vehicle. At this time, it is determined that the vehicle needs to be operated in the single motor drive mode. That is, the single motor drive mode corresponds to the economy demand mode of the driver.
In step 106, according to the vehicle motor driving mode determined in step 104, it is further required to allocate the target required torque to the vehicle front axle driving motor and the vehicle rear axle driving motor in the single motor driving mode or the dual motor driving mode, so that each motor operates according to the allocation result, thereby enabling the vehicle to reach the target required torque expected by the driver.
Hereinafter, the above-described different cases will be separately explained with reference to the drawings.
Fig. 2 is a schematic diagram of a general architecture of a vehicle motor torque distribution manner according to an embodiment of the present application, and fig. 2 shows a corresponding vehicle motor torque distribution situation in different vehicle speed intervals.
As shown, the vehicle speed is divided into three different phases 1, 2, 3, where phase 1 is a low speed section, phase 2 is a medium speed section, and phase 3 is a high speed drive. The low speed and the medium speed correspond to a low-medium speed conversion point, and the speed of the conversion point is within the range of 20-30km/h for different vehicle types; the medium and high speeds correspond to a medium-high speed transition point, which is located, for example, in the range of 120-130km/h, i.e. the second threshold value mentioned above, for different vehicle models.
As described above, if the current vehicle speed is not less than the second threshold or the target required torque is not less than the first threshold, the vehicle motor needs to be operated in the dual motor drive mode; if the target requested torque is less than the first threshold and the current vehicle speed is less than the second threshold, the vehicle electric machines may be operated in the single-motor drive mode.
However, in the case where the vehicle is operated in the single-motor drive mode, it is also necessary to perform different target required torque distribution manners in conjunction with the current vehicle speed of the vehicle.
Referring to fig. 3, fig. 3 is a schematic flow chart of the vehicle motor torque distribution of the first embodiment of the present application.
As shown in fig. 3, allocating target required torques to a front axle drive motor and a rear axle drive motor of a vehicle according to a motor drive mode of the vehicle specifically includes the steps of:
step 202, acquiring the current speed of the vehicle, wherein the current rotating speed corresponds to the rotating speed of a first motor driven in a front axle driving motor and a rear axle driving motor;
and 204, when the current vehicle speed of the vehicle is not greater than a third threshold value, distributing all proportions of target required torque to the first motor, and distributing zero torque to a non-driven second motor in the front axle driving motor and the rear axle driving motor, wherein the third threshold value is smaller than the second threshold value.
Referring to fig. 4, fig. 4 is a schematic flow chart of a vehicle motor torque distribution of a second embodiment of the present application.
As shown in fig. 4, allocating target required torques to a front axle drive motor and a rear axle drive motor of a vehicle according to a motor drive mode of the vehicle specifically includes the steps of:
step 302, acquiring the current speed of the vehicle, wherein the current rotating speed corresponds to the rotating speed of a first motor driven in a front axle driving motor and a rear axle driving motor;
and 304, when the current speed of the vehicle is greater than a third threshold value, distributing all proportions of target required torque for the first motor, and enabling a non-driven second motor in the front axle driving motor and the rear axle driving motor to be in a free dragging state mechanically dragged by the first motor, wherein the third threshold value is smaller than the second threshold value.
The current speed of a four-wheel Drive Electric vehicle is achieved by controlling the rotation speed of an electronically controlled Drive Unit (EDU) to Drive a motor integrated with a vehicle motor to rotate. In the single motor mode, only one of the front axle drive motor and the rear axle drive motor is driven, i.e., the current vehicle speed is provided by the currently driven first motor. The other non-driven electric machine, i.e. the electric machine which does not provide any power to the vehicle, is referred to as non-driven electric machine, i.e. the above second electric machine.
As mentioned above, the second threshold is the medium-high speed transition point, which is 120-130km/h. The third threshold corresponds to the low and medium speed transition point of fig. 2 and is 20-30km/h.
As shown in fig. 2 and 4, in the single-motor drive mode, when the vehicle speed is in the middle speed interval of stage 2, which corresponds to the middle speed and low torque, the full proportion of the target required torque is allocated to the first motor of the drive motors, and the torque allocated to the second motor, which is not the drive motor, is such that the second motor is in a free-drag state, i.e., no electric signal is supplied to the second motor. At this time, the first motor outputting torque to provide vehicle power drives the second motor to rotate through the transmission shaft, that is, the second motor is in a mechanical reverse-dragging state.
Because the free dragging of the second motor is a pure mechanical action, the mechanical loss is less than the electric energy loss, so the vehicle has no electric energy consumption, and the single motor driving mode corresponding to the stage 2 is the most electricity-saving economic mode.
In addition, the counter-dragging effect of the free-drag of the second motor increases the load on the first motor for driving the motor, which increases the system efficiency of the first motor at the same vehicle speed.
Although the energy consumption of the vehicle can be greatly reduced and the system efficiency of the first motor can be increased when the second motor is in the free-towing state, if the current vehicle speed is not greater than the third threshold value, for example, a speed of not greater than 20-30km/h, the free-towing state of the second motor will affect the smoothness of the vehicle at a lower vehicle speed, resulting in a significant shock of the vehicle. Thereby causing a poor driving experience for the driver or other personnel in the vehicle cabin.
To avoid the above problem, as shown in fig. 2 and 3, in the single motor driving mode, when the vehicle speed is in the low speed section of stage 1, which corresponds to the low speed low torque, the target required torque of the whole proportion is still distributed to the first motor of the driving motor, and the torque distributed to the second motor which is not the driving motor is 0, that is, the vehicle outputs an electric signal to control the torque of the second motor to be 0. At this point, the output electrical signal consumes electrical power compared to the embodiment of fig. 4, but distributes 0 torque to the second electric machine so that the second electric machine does not power the vehicle but is not back-towed by the first electric machine. At the moment, the vehicle can be driven stably, and the shock is avoided.
In addition, when the second motor is in the free-tow state, as described above, the first motor rotates the second motor such that the second motor is in the mechanical anti-tow state. At this time, the second motor drives the corresponding wheel to rotate, so that the torque generated by the second motor is negative, and thus, counter electromotive force is generated. The second motor is connected with a bus of a vehicle battery, the high-voltage safety requirement does not allow the situation that the counter electromotive force of the motor is higher than the voltage of the battery,
therefore, in order to avoid the free-drag state of the second motor from affecting the high voltage safety, in one embodiment, when the second motor is in the free-drag state, the method further includes: acquiring counter electromotive force corresponding to the rotating speed when the second motor is in a free dragging state; acquiring the voltage of a battery connected with a second motor; and when the counter electromotive force is not greater than the battery voltage, keeping the second motor in a free dragging state.
Through comparing battery voltage and back electromotive force voltage in real time, can in time detect the second motor and freely draw the back electromotive force that the state produced whether can influence high-pressure safety. If not, the present vehicle may continue to maintain the second electric machine in free-tow condition to reduce vehicle energy consumption to a greater extent, providing vehicle economy.
When the counter electromotive force is greater than the battery voltage, the motor drive mode is switched from the single motor drive mode to the dual motor drive mode. That is, vehicle safety is the most important, and in this case, it is necessary to switch from the vehicle economy demand mode to the power demand mode, and to avoid the influence of the counter electromotive force generated by the second motor on the high-voltage safety of the vehicle.
And distributing torque for the front axle driving motor and the rear axle driving motor according to the current target required torque under the condition of switching to the dual-motor driving mode. Specifically, the system efficiency of a front axle driving motor and the system efficiency of a rear axle driving motor are respectively determined according to a plurality of preset torque distribution proportion combinations corresponding to the target required torque; and distributing the torque to the front axle driving motor and the rear axle driving motor according to the torque distribution proportion combination with the highest system efficiency.
For the determination of the driving motor and the non-driving motor in the single motor mode, any one of the front axle driving motor and the rear axle driving motor may be randomly selected as the driving motor, and the remaining one is the non-driving motor.
Further, which of the drive motors is determined may be determined based on the system efficiency corresponding to the front axle drive motor and the rear axle drive motor.
Therefore, in one embodiment, after determining that the driving mode of the vehicle is the single-motor driving mode, the method further includes: respectively determining system efficiency corresponding to a front shaft driving motor and a rear shaft driving motor according to basic characteristic parameters of the motors; and selecting a motor with high system efficiency as the first motor.
The basic characteristic parameters of the motor can be obtained from the Map of the corresponding motor, and corresponding simulation calculation is carried out to evaluate the system efficiency of each motor. The motor with high energy consumption circulation efficiency is used as the first motor driven in full time, and the system corresponding to the motor with high energy consumption circulation efficiency is high in efficiency. Meanwhile, the motor with low energy consumption cycle efficiency is used as a second motor driven in non-full time.
Here, the full-time driving means that the motor is driven to operate in any one of the stages corresponding to the single-motor driving mode and the dual-motor driving mode, and the non-full-time driving means that the motor is driven to operate only in the stage corresponding to the dual-motor driving mode, and is not driven to operate in the stage corresponding to the single-motor driving mode.
As described above, for the above cases 1 and 2, that is, the current vehicle speed is not less than the second threshold or the target required torque is not less than the first threshold, the vehicle motor needs to be operated in the dual motor drive mode. Then according to the motor drive mode of vehicle, for front axle driving motor and rear axle driving motor distribution target demand torque, specifically include:
respectively determining the system efficiency of a front axle driving motor and a rear axle driving motor according to a plurality of preset torque distribution proportion combinations corresponding to the target required torque;
and distributing the torque to the front axle driving motor and the rear axle driving motor according to the torque distribution proportion combination with the highest system efficiency.
And under a dynamic demand mode entering a dual-motor driving mode, calculating the optimal distribution torque of the front and rear axle driving motors according to the system efficiency corresponding to the front and rear axle driving motors.
Fig. 5 is a flowchart of an overall example of a control method of the four-wheel drive electric vehicle according to the embodiment of the present application, as shown in fig. 5, including the steps of:
step 402, acquiring a torque demand of a driver according to the running state of the vehicle and the opening degree of an accelerator pedal;
step 404, judging whether the torque demand of the driver corresponds to a power mode of a double-motor driving mode or an economic mode of a single-motor driving mode according to the torque demand mode;
step 406, if the power mode is judged, calculating the torque distribution of the vehicle motor;
step 408, if the economic mode is judged, judging based on the state of the non-driving motor; acquiring corresponding back electromotive force V2 according to the current rotating speed of the non-driving motor, comparing the back electromotive force with the voltage V1 of the battery, and judging whether the back electromotive force corresponding to the current rotating speed of the non-driving motor can influence the high-voltage safety of the vehicle;
step 410, if V2< K X V1, K is a safety coefficient, requesting to enter a free dragging state;
step 412, determining a corresponding motor torque distribution mode based on the current vehicle speed judgment;
step 414, determining that the vehicle speed is not greater than the low and medium speed switching point;
step 416, distributing target required torques of all proportions by the driving motor, and distributing 0 torque by the non-driving motor;
418, driving a motor to achieve the target torque required by the driver according to the distributed torque;
step 420, the vehicle speed is greater than the low-medium speed switching point;
step 422, the driving motor distributes all proportional torques, the non-driving motor drags freely, and the step 408 can be returned to in the process of dragging freely of the non-driving motor to detect whether the non-driving motor can be kept in a free dragging state;
step 424, if V2> = K × V1, request entry into power mode;
at 426, a vehicle motor torque distribution is calculated.
According to the control method and the control device, the target required torque of the vehicle is determined according to the running state of the vehicle and the opening degree of the accelerator pedal, whether the motor driving mode of the vehicle is the single-motor driving mode or the double-motor driving mode is determined according to the target required torque and the current speed of the vehicle, and the target required torque is distributed to the front shaft driving motor and the rear shaft driving motor of the vehicle according to the motor driving mode of the vehicle, so that the reasonable motor driving mode of the vehicle can be determined according to different requests of a driver, corresponding motor torque distribution is carried out, the two-motor simultaneous driving mode of the four-wheel drive electric vehicle is executed in a staged and time-sharing mode, compared with the mode that the two-motor simultaneous driving mode is executed at any stage and at all times in the prior art, the control method and the four-wheel drive electric vehicle can embody excellent power performance and give consideration to economy, and therefore the high energy consumption of the four-wheel drive electric vehicle can be effectively reduced on the whole.
Optionally, an embodiment of the present application further provides a control device for a four-wheel drive electric vehicle, and fig. 6 is a block diagram of a structure of the control device for a four-wheel drive electric vehicle according to the embodiment of the present application.
As shown in fig. 6, the control device 2000 includes a memory 2200 and a processor 2400 electrically connected to the memory 2200, where the memory 2200 stores a computer program that can be executed by the processor 2400, and when the computer program is executed by the processor, the control device implements each process of any one of the embodiments of the control method for a four-wheel drive electric vehicle, and can achieve the same technical effect, and therefore, for avoiding repetition, the description is not repeated here.
The embodiment of the present application further provides a computer-readable storage medium, where a computer program is stored on the computer-readable storage medium, and when the computer program is executed by a processor, the computer program implements each process of any one of the above embodiments of the control method for a four-wheel drive electric vehicle, and can achieve the same technical effect, and in order to avoid repetition, the details are not repeated here. The computer-readable storage medium may be a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising a … …" does not exclude the presence of another identical element in a process, method, article, or apparatus that comprises the element.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solutions of the present application may be embodied in the form of a software product, which is stored in a storage medium (such as ROM/RAM, magnetic disk, optical disk) and includes instructions for enabling a terminal (such as a mobile phone, a computer, a server, an air conditioner, or a network device) to execute the method according to the embodiments of the present application.
While the present embodiments have been described with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiments described above, which are meant to be illustrative and not restrictive, and that various changes may be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (9)

1. A control method of a four-wheel-drive electric vehicle, characterized by comprising:
determining a target required torque of a vehicle according to the running state of the vehicle and the opening degree of an accelerator pedal;
determining a motor driving mode of the vehicle according to the target required torque and the current speed of the vehicle, wherein the motor driving mode comprises a double-motor driving mode and a single-motor driving mode;
according to the motor driving mode of the vehicle, distributing the target required torque for a front axle driving motor and a rear axle driving motor of the vehicle specifically comprises: acquiring the current speed of the vehicle, wherein the current speed corresponds to the rotating speed of a first motor driven in the front shaft driving motor and the rear shaft driving motor; when the current speed of the vehicle is greater than a third threshold value, distributing all proportions of the target required torque to the first motor, and enabling a non-driven second motor in the front axle driving motor and the rear axle driving motor to be in a free dragging state in which the non-driven second motor is mechanically dragged by the first motor;
the front shaft driving motor and the rear shaft driving motor are permanent magnet synchronous motors.
2. The method of claim 1, wherein determining the driving modes corresponding to the front axle driving motor and the rear axle driving motor according to the target required torque and the current vehicle speed of the vehicle comprises:
and when the target required torque is smaller than a first threshold value and the current vehicle speed is smaller than a second threshold value, determining that the driving mode of the vehicle is a single-motor driving mode.
3. The method according to claim 2, wherein the target required torque is allocated to a front axle drive motor and a rear axle drive motor of the vehicle according to a motor drive mode of the vehicle, further comprising:
when the current speed of the vehicle is not greater than the third threshold value, distributing all the proportion of the target required torque to the first motor, and distributing zero torque to a non-driven second motor in the front axle driving motor and the rear axle driving motor, wherein the third threshold value is smaller than the second threshold value.
4. The method of claim 1, further comprising, while the second motor is in a free-tow condition:
acquiring counter electromotive force corresponding to the rotating speed when the second motor is in a free dragging state;
acquiring the voltage of a battery connected with the second motor;
maintaining the second motor in a free-tow condition when the back EMF is not greater than the battery voltage.
5. The method of claim 4, further comprising:
switching the motor driving mode from a single motor driving mode to a dual motor driving mode when the counter electromotive force is greater than the battery voltage.
6. The method according to any one of claims 3 to 5, further comprising, after determining that the driving mode of the vehicle is the single-motor driving mode:
respectively determining system efficiency corresponding to the front shaft driving motor and the rear shaft driving motor according to the motor characteristic parameters;
and selecting a motor with high system efficiency as the first motor.
7. The method of claim 1, wherein determining a motor drive mode of the vehicle based on the target required torque and a current vehicle speed of the vehicle comprises:
and when the target required torque is not less than a first threshold value or the current vehicle speed is not less than a second threshold value, determining that the motor driving mode of the vehicle is a double-motor driving mode.
8. The method according to claim 7, wherein distributing the target required torques for the front axle drive motor and the rear axle drive motor according to a motor drive mode of the vehicle includes:
respectively determining the system efficiency of the front axle driving motor and the rear axle driving motor according to a plurality of preset torque distribution proportion combinations corresponding to the target required torque;
and distributing the torque to the front axle driving motor and the rear axle driving motor according to the torque distribution proportion combination with the highest system efficiency.
9. A computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, which computer program, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 8.
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