CN109080442B - Range-extended electric vehicle four-wheel drive system and control method thereof - Google Patents

Range-extended electric vehicle four-wheel drive system and control method thereof Download PDF

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CN109080442B
CN109080442B CN201810936692.9A CN201810936692A CN109080442B CN 109080442 B CN109080442 B CN 109080442B CN 201810936692 A CN201810936692 A CN 201810936692A CN 109080442 B CN109080442 B CN 109080442B
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controller
vehicle
generator
power battery
electric
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CN109080442A (en
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杨世春
陈昱伊
陈飞
闫啸宇
华旸
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Beihang University
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Beihang University
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K6/00—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00
    • B60K6/20—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs
    • B60K6/42—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs characterised by the architecture of the hybrid electric vehicle
    • B60K6/44—Series-parallel type
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K6/00—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00
    • B60K6/20—Arrangement or mounting of plural diverse prime-movers for mutual or common propulsion, e.g. hybrid propulsion systems comprising electric motors and internal combustion engines ; Control systems therefor, i.e. systems controlling two or more prime movers, or controlling one of these prime movers and any of the transmission, drive or drive units Informative references: mechanical gearings with secondary electric drive F16H3/72; arrangements for handling mechanical energy structurally associated with the dynamo-electric machine H02K7/00; machines comprising structurally interrelated motor and generator parts H02K51/00; dynamo-electric machines not otherwise provided for in H02K see H02K99/00 the prime-movers consisting of electric motors and internal combustion engines, e.g. HEVs
    • B60K6/50—Architecture of the driveline characterised by arrangement or kind of transmission units
    • B60K6/52—Driving a plurality of drive axles, e.g. four-wheel drive
    • 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
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Abstract

The invention relates to a range-extended electric vehicle four-wheel drive system and a control method thereof, the system is specifically provided with a range extender system, an external clutch and a rear motor controller, the range extender system is connected with a front speed reducer through the external clutch, the rear motor controller is sequentially connected with a rear driving motor and the rear speed reducer, the range extender system comprises a generator, a generator controller, an engine controller, an internal clutch and a range extender controller, wherein the generator is connected with the front speed reducer through the external clutch, the engine is connected with the generator through the internal clutch, the range extender controller is respectively connected with the engine controller and the generator controller while the range extender controller is connected with and receives the control of the whole vehicle controller, the rear motor controller is connected with the whole vehicle controller, a power battery is respectively connected with the generator controller and the rear motor controller, the system improves the power performance and the energy utilization rate of the electric vehicle and increases the driving range.

Description

Range-extended electric vehicle four-wheel drive system and control method thereof
Technical Field
The invention relates to the technical field of electric vehicles, in particular to a range-extended electric vehicle four-wheel drive system and a control method thereof.
Background
The pure electric vehicle drives wheels by supplying electric energy stored in the power battery to the driving motor, has the advantages of excellent power performance, zero emission and no pollution, and is developed on a large scale at present. However, the driving range of the pure electric vehicle is obviously limited due to the problems that the power battery is easy to age, the capacity of the power battery is easy to attenuate at low temperature and the like, so that the electric vehicle (namely, the range-extended electric vehicle) with the auxiliary power unit has the advantages of simple structure and strong power, and overcomes the defect of insufficient driving range of the pure electric vehicle to a certain extent, and the range-extended electric vehicle becomes one of important research directions in the field of new energy vehicles.
Although mode switching can be realized by referring to main parameters including the residual capacity (SOC) of a power battery, torque, required power, vehicle speed, oil consumption and the like, the driving control system and the control strategy of the extended-range electric vehicle commonly used at the present stage neglect attention to the driving performance of the electric vehicle while realizing extension of the driving range, reduction of the oil consumption and improvement of driving comfort, and the driving range can be greatly reduced even when the acceleration mode or the ultra-strong acceleration mode is started, so that the power performance of the extended-range electric vehicle has a great improvement space, the layout of the four-wheel drive system of the extended-range electric vehicle is still to be improved, the control strategy is not complete enough, and further research and improvement are urgently needed.
Disclosure of Invention
The invention provides a range-extended electric vehicle four-wheel drive system aiming at the defects of poor power performance of an electric vehicle, greatly reduced driving range when an acceleration mode is started, incomplete system control strategy and the like in the prior art, the system is characterized in that a range extender system with a specific structure is respectively connected with a front speed reducer and a rear motor controller for controlling a rear driving motor by reasonably setting a system layout structure, the range extender system is effectively utilized to provide necessary power output for the whole vehicle, the whole vehicle controller is utilized to reasonably control the range extender system and other systems to quickly and efficiently switch working modes, the structure is simple, the configuration is innovative, the control is convenient and fast, the power performance and the energy utilization rate of the electric vehicle are greatly improved, and the driving range is increased. The invention further provides a control method of the four-wheel drive system of the extended range electric vehicle.
The technical scheme of the invention is as follows:
a range-extended electric vehicle four-wheel drive system comprises a vehicle control unit, a power battery, a battery management system, a rear driving motor, a front speed reducer and a rear speed reducer, wherein the battery management system is respectively connected with the power battery and the vehicle control unit, the system further comprises a range extender system, an external clutch and a rear motor controller, the range extender system is arranged at a position close to a front axle and is connected with the front speed reducer through the external clutch and provides power for the front speed reducer, the rear motor controller is sequentially connected with the rear driving motor and the rear speed reducer and further provides power for the rear speed reducer, the range extender system comprises a generator, a generator controller, an engine controller, an internal clutch and a range extender controller, the generator is connected with the front speed reducer through the external clutch, the engine is connected with the generator through the internal clutch, the range extender controller is respectively connected with an engine controller for controlling the engine and a generator controller for controlling the generator, further respectively controls the working states of the engine and the generator, is connected with the whole vehicle controller and receives the control of the whole vehicle controller, the rear motor controller is connected with the whole vehicle controller and receives the control of the whole vehicle controller, and the power battery is respectively connected with the generator controller and the rear motor controller.
The extended range electric vehicle four-wheel drive system further comprises a plurality of data sensors for acquiring corresponding working condition parameters, each data sensor is connected with the vehicle control unit, and the vehicle control unit controls the data sensors to acquire and analyze a plurality of working condition parameters and then controls the whole system to switch working modes and make corresponding power distribution strategies according to requirements of different working conditions through mode switching control strategies.
The working condition parameters collected and analyzed by the data sensor include but are not limited to the current speed of the electric vehicle, the current residual capacity of the power battery, the opening degree of an accelerator pedal, a brake pedal signal and the slip rate of the vehicle, and the whole system is controlled to switch the working modes according to the requirements of different working conditions after the working condition parameters are jointly matched.
The mode switching control strategy is as follows: the vehicle control unit controls the engine controller and the generator controller through the range extender controller so as to control the working states of the engine and the generator, and simultaneously controls the working state of the power battery through the battery management system and the working state of the rear driving motor through the rear motor controller so as to control the whole system to switch the working modes and make a corresponding power distribution strategy.
The working modes include, but are not limited to, a parking charging mode, a strongest acceleration mode, a pure electric four-wheel drive mode, a pure electric front drive mode, a pure electric rear drive mode, an extended range drive mode, a cruise drive mode and an energy recovery mode.
A control method for controlling the four-wheel drive system of the extended range electric vehicle comprises the following steps:
step A, firstly judging the current residual capacity value of the power battery, cutting off power output when the current residual capacity value is smaller than a charging limit value, entering a parking charging mode, sending a control signal to the interior of a range extender system by a vehicle control unit, sending the control signal to an engine controller and a generator controller by the range extender controller, controlling a generator to enter a power generation mode after receiving the control signal by the generator controller, controlling the engine to start after receiving the control signal by the engine controller, and converting the generated kinetic energy into electric energy through the generator to charge the power battery; b, when the current residual capacity value of the power battery is larger than the charging limit value and larger than the electric energy sufficiency limit value, executing the step B; when the current residual capacity value of the power battery is larger than the charging limit value and smaller than the electric energy sufficiency limit value, executing the step C;
step B, judging the opening value of the accelerator pedal, switching to or keeping in a strongest acceleration mode when the opening value of the accelerator pedal is larger than a pure electric four-wheel drive limit value, wherein the range extender system and the power battery provide power, the engine controller controls the kinetic energy generated by the engine to be transmitted to the generator through the internal clutch after receiving a control signal transmitted by the range extender controller, the electric energy output by the power battery under the control of the battery management system respectively controls the generator and the rear drive motor to enter a working state through the generator controller and the rear motor controller, the electric energy flowing through the generator is converted into the kinetic energy, then the kinetic energy is combined with the kinetic energy provided by the engine in the range extender system and transmitted to a front wheel through the front speed reducer, and the other part of electric energy drives the rear drive motor to transmit the converted kinetic energy to a rear wheel through the rear speed reducer; when the opening value of the accelerator pedal is smaller than the pure electric four-wheel drive limit value, switching to or keeping in a pure electric four-wheel drive mode, wherein the power of the vehicle is completely provided by a power battery, and the electric energy output by the power battery under the control of a battery management system respectively controls a generator and a rear driving motor through a generator controller and a rear motor controller to transmit the converted kinetic energy to the front wheel through a front speed reducer and to the rear wheel through a rear speed reducer;
step C, judging the opening degree value of the accelerator pedal, and when the opening degree value is larger than a front-rear driving limit value, switching to or keeping in a pure electric rear-driving mode, wherein the vehicle power is completely provided by a power battery, and the electric energy output by the power battery under the control of a battery management system is controlled by a rear motor controller to control a rear driving motor to transmit the converted kinetic energy to a rear wheel through a rear speed reducer; when the opening value of the accelerator pedal is smaller than the front-rear driving limit value, the electric vehicle is switched to or kept in the pure electric-drive mode, at the moment, the power of the vehicle is completely provided by the power battery, and the electric energy output by the power battery under the control of the battery management system controls the generator to transmit the converted kinetic energy to the front wheel through the front speed reducer through the generator controller.
In the step C of the control method, the current residual capacity value of the power battery can be judged, when the current residual capacity value of the power battery is larger than the range-increasing limit value, the opening value of the accelerator pedal is judged, and the pure electric rear-drive mode or the pure electric front-drive mode is executed; the range-extended limit value is between the charging limit value and the electric energy sufficient limit value, when the current residual capacity value of the power battery is smaller than the range-extended limit value, the range-extended driving mode is switched to, at the moment, the power is provided by the engine and the electric energy is supplemented to the power battery, the battery management system transmits a signal that the electric quantity of the power battery is insufficient to the whole vehicle controller, the whole vehicle controller feeds back a discharge stopping instruction, the range-extended controller simultaneously controls the generator controller and the engine controller after receiving a working instruction sent by the whole vehicle controller, the generator and the engine are respectively started, the kinetic energy generated by the engine is converted into electric energy through the generator, one part of the electric energy flows to the power battery to charge the power battery, and the other part of the electric energy flows to the rear motor controller to further control the rear driving motor to start and then transmit the kinetic energy to the rear wheel through the rear speed reducer to realize driving.
In the step C of the control method, after the pure electric front driving mode is switched to or kept in, the vehicle slip rate is judged, when the vehicle slip rate is larger than the slip rate limit value, the vehicle slip rate is firstly switched to the pure electric rear driving mode, and if the vehicle slip rate is still larger than the slip rate limit value on the basis, the vehicle slip rate is further switched to the pure electric four-wheel driving mode; and after the vehicle is switched to or kept in the pure electric rear-drive mode and the range-extended drive mode, judging the slip rate of the vehicle, and when the slip rate is greater than the slip rate limit value, further switching to the pure electric four-wheel drive mode.
The control method can also comprise a step D of judging the current speed of the electric vehicle, switching to or keeping a cruise drive mode when the current speed is larger than or equal to a speed limit value, providing power by an engine of the range extender system and converting energy into a power battery for charging by using a generator, enabling the engine and the generator to enter a working state after receiving signals of corresponding controllers respectively, transmitting kinetic energy generated by the engine to the generator through an internal clutch, converting the kinetic energy into electric energy to charge the power battery on one hand, and transmitting the electric energy to front wheels through mechanical transmission to realize driving on the other hand.
In the step D of the control method, when the current speed of the electric vehicle is less than the speed limit value and is more than or equal to the energy recovery limit value, the step E is executed;
step E, switching to or keeping an energy recovery mode, wherein at the moment, the vehicle control unit sends corresponding working instructions to the range extender controller and the rear motor controller, so that an engine controller in the range extender system controls the engine to be in a closed state, the generator controller controls the generator to enter a power generation mode, and the kinetic energy of the front wheels is transmitted to the generator through the front speed reducer and the external clutch so as to be converted into electric energy which is supplemented into the power battery through the generator controller; the kinetic energy of the rear wheel is converted into electric energy through the rear driving motor by the rear speed reducer and then is supplemented into the power battery by the rear motor controller to charge the power battery.
The invention has the following technical effects:
the invention relates to a range-extended electric vehicle four-wheel drive system, which is characterized in that a range-extended device system which comprises a generator, a generator controller, an engine controller, an internal clutch and a range-extended device controller and is connected with each component by adopting a specific structure is respectively connected with a front speed reducer and a rear motor controller for controlling a rear driving motor, a system layout structure is reasonably and innovatively arranged, the range-extended device system is effectively utilized to provide necessary power output for a whole vehicle, in addition, in the range-extended device system, the generator is connected with the front speed reducer by an external clutch to form a necessary channel for the range-extended device system to transmit power and energy with external components, on one hand, the range-extended device controller respectively controls the working states of the engine and the generator by the engine controller and the generator controller, on the other hand, the range-extended device controller also receives the control of the whole vehicle controller, therefore, multilayer effective control is formed, the power battery is respectively connected with the generator controller and the rear motor controller to transmit electric energy to the front axle and the rear axle respectively so as to form a front energy flow channel and a rear energy flow channel respectively, the front energy flow channel and the rear energy flow channel are matched to work, the reasonable control and the coordination of the whole vehicle controller on the range extender controller, the battery management system and the rear motor controller can quickly and efficiently realize the switching of working modes required under different working conditions, the structure is simple, the configuration is innovative, the control is convenient and fast, the power performance and the energy utilization rate of the electric vehicle are greatly improved, and the driving range is greatly increased.
Furthermore, the extended range electric vehicle four-wheel drive system also comprises a plurality of data sensors for acquiring corresponding working condition parameters, each data sensor is connected with the whole vehicle controller, so that the whole vehicle controller controls each data sensor to acquire and analyze a plurality of working condition parameters and then controls the whole system to switch working modes and make corresponding power distribution strategies according to the requirements of different working conditions through mode switching control strategies, namely, the whole vehicle controller is used for integrating, coordinating and optimally controlling the power distribution of the extended range system, the power battery and other systems, the power performance of the electric vehicle is optimized to a greater extent, even the electric vehicle can work at the optimal power performance, the service life of the electric vehicle can be prolonged and the driving experience of a driver can be improved through optimizing the power performance; and the working condition parameters acquired and analyzed by the data sensor preferably comprise a plurality of parameters such as the current speed of the electric vehicle, the current residual capacity of the power battery, the opening degree of an accelerator pedal, a brake pedal signal, the vehicle slip rate and the like, particularly, the vehicle slip rate parameters are newly introduced, and the whole system is controlled to switch the working modes according to the requirements of different working conditions after the joint matching of the working condition parameters, so that the switching is more accurate and more efficient.
Furthermore, the working modes of the system include, but are not limited to, a parking charging mode, a strongest acceleration mode, a pure electric four-wheel drive mode, a pure electric front drive mode, a pure electric rear drive mode, a range extending drive mode, a cruise drive mode and an energy recovery mode, and all the working modes are matched with corresponding power distribution strategies, so that better power output performance corresponding to the current working condition can be provided for the electric vehicle, and the overall working efficiency and the energy utilization rate of the electric vehicle are effectively improved.
The invention also relates to a control method for controlling the range-extended electric vehicle four-wheel drive system, which is characterized in that the current residual capacity value of a power battery is respectively compared with a charging limit value and an electric energy sufficient limit value to realize switching into a parking charging mode or judging again, then the opening value of an accelerator pedal is further compared with a pure electric four-wheel drive limit value to realize switching into a strongest acceleration mode or a pure electric four-wheel drive mode, then the opening value of the accelerator pedal is further compared with a front-rear drive limit value to realize switching into a pure electric rear-drive mode or a pure electric front-drive mode, and the switching control of various working modes can be realized according to the comparison result of the current value of a specific parameter and the corresponding limit value The power battery and the rear driving motor respectively enter different working states to control the whole four-wheel drive system to switch the corresponding working modes, and under the condition that the range of the electric vehicle is extended, the control of the working mode switching is more efficient and convenient, and meanwhile, the power performance of the electric vehicle is greatly improved.
Further, the situation that the ground adhesion force is smaller than the driving force may occur under working conditions such as uphill slope and acceleration during the driving process of the electric vehicle, so that the wheel slip phenomenon may occur, and the driving performance of the vehicle is limited. In all the working modes, the driving performance of the four-wheel drive mode of the vehicle is strongest, and the driving performance of the rear-wheel drive mode of the vehicle is stronger than that of the front-wheel drive mode, so that after a four-wheel drive system (or called a driving system) enters a certain working mode (such as a pure electric drive mode is switched or kept), the slip rate of the vehicle can be judged, the electric vehicle is controlled to switch modes by judging and comparing the slip rate of the vehicle and the slip rate limit value, the working mode meeting the requirement of an actual working condition is further switched, and the working mode is switched timely to provide an adhesion coefficient more beneficial to keeping the driving stability of the vehicle.
Furthermore, the judgment and comparison of the current vehicle speed and the vehicle speed limit value can be carried out in the judgment and comparison process of the current vehicle speed and the vehicle speed limit value, so that the driving system can enter an energy recovery mode, the power battery can be charged at the moment, the power performance of the driving system can be improved, meanwhile, the energy can be recovered, and the energy can be recycled for subsequent reuse in other working modes, and the energy utilization rate is greatly improved.
Drawings
FIG. 1: the invention relates to a preferable structure diagram of a four-wheel drive system of an extended range electric vehicle.
FIG. 2: the invention relates to a preferred flow chart of a control method for controlling a four-wheel drive system of an extended range electric vehicle.
FIG. 3: power distribution diagram in the parking charging mode.
FIG. 4: control strategy diagram in parking charging mode.
FIG. 5: power split map for the strongest acceleration mode.
FIG. 6: control strategy diagram in the strongest acceleration mode.
FIG. 7: and (4) power distribution diagram in the pure electric four-wheel drive mode.
FIG. 8: and a control strategy diagram in the pure electric four-wheel drive mode.
FIG. 9: and (4) power distribution diagram in the pure electric rear-drive mode.
FIG. 10: control strategy diagram in the pure electric rear-drive mode.
FIG. 11: and (4) power distribution diagram in the pure electric driving mode.
FIG. 12: control strategy diagram in pure electric forerunner mode.
FIG. 13: a power split map in the extended range drive mode.
FIG. 14: control strategy diagram in extended range drive mode.
FIG. 15: power split map in cruise drive mode.
FIG. 16: control strategy diagram in cruise drive mode.
FIG. 17: power split map in energy recovery mode.
FIG. 18: control strategy diagram in energy recovery mode.
The various reference numbers in the figures are listed below:
1-a range extender system; 2-external clutch; 3, a front speed reducer; 4-a power battery; 5-a battery management system; 6-vehicle control unit; 7-rear motor controller; 8-rear drive motor; 9-rear reducer;
11-a generator; 12-a generator controller; 13-an engine; 14-an engine controller; 15-an internal clutch; 16-range extender controller.
Detailed Description
The invention relates to a range-extended electric vehicle four-wheel drive system, which comprises a vehicle control unit, a power battery, a battery management system, a rear drive motor, a front speed reducer and a rear speed reducer, wherein the battery management system is respectively connected with the power battery and the vehicle control unit, the range-extended electric vehicle four-wheel drive system further comprises a range extender system, an external clutch and a rear motor controller, the range extender system specifically comprises a generator, a generator controller, an engine controller, an internal clutch and a range extender controller The system layout structure is innovatively arranged, the range extender system is effectively utilized to provide necessary power output for the whole vehicle, the vehicle controller is utilized to reasonably control the range extender system and other systems to quickly and efficiently switch the working modes, the structure is simple, the configuration is innovative, the control is convenient and fast, the power performance and the energy utilization rate of the electric vehicle can be effectively improved, and meanwhile, the driving range is greatly increased.
The present invention will be described in detail with reference to the accompanying drawings.
The invention relates to a range-extended electric vehicle four-wheel drive system, which has a preferable structure as shown in figure 1, and specifically comprises a range extender system 1, an external clutch 2 and a rear motor controller 7 besides a front speed reducer 3, a power battery 4, a vehicle control unit 6, a battery management system 5 for connecting the power battery 4 and the vehicle control unit 6, a rear driving motor 8 and a rear speed reducer 9, wherein the range extender system 1 is constructed based on a thermal engine type power source and is arranged at a position close to a front axle, is connected with the front speed reducer 3 through the external clutch 2 and provides power for the front speed reducer 3, the rear motor controller 7 is sequentially connected with the rear driving motor 8 and the rear speed reducer 9 and provides power for the rear speed reducer 9, and the range extender system 1 further comprises a generator 11, a generator controller 12, an engine 13 and an engine controller 14, The power generator 11 is connected with the front speed reducer 3 through the external clutch 2 to form a passage which is necessary for the range extender system 1 to transmit power and energy with an external component, the engine 13 is connected with the power generator 11 through the internal clutch 15, the range extender controller 16 is respectively connected with an engine controller 14 for controlling the engine 13 and a power generator controller 12 for controlling the power generator 11 to further respectively control the working states of the engine 13 and the power generator 11, meanwhile, the range extender controller 16 is outwards connected with the whole vehicle controller 6 and controlled by the whole vehicle controller 6, the rear motor controller 7 is connected with the whole vehicle controller 6 and controlled by the whole vehicle controller 6, and specifically, the whole vehicle controller 6 is respectively connected with the range extender controller 16, the power generator 11 and the front speed reducer 3 through control signal lines (shown in the figure) and controlled by the whole vehicle controller 6, The battery management system 5 for controlling the power battery 4 and the rear motor controller 7 for controlling the rear driving motor 8 are used for respectively controlling each component, the battery management system 5 is also used for collecting, controlling and managing the state information of the power battery 4 through a control signal line, the power battery 4 is respectively connected with the generator controller 12 and the rear motor controller 7, and the concrete expression is that the power battery 4 is connected to the generator controller 12 in the range extender system 1 through a power line (shown as a thick solid line) and then is connected to the generator 11, and the other line is connected to the rear driving motor 8 through the rear motor controller 7 so as to respectively transmit electric energy to the front axle and the rear axle to respectively form a front energy flow channel and a rear energy flow channel, and the front energy flow channel and the rear energy flow channel are matched to work, the invention respectively connects the range extender system 1 with a specific structure with the front speed reducer 3 and connects the rear motor controller 7 for controlling the rear driving motor 8, reasonably, innovatively and optimally sets the layout structure and the connection mode of the driving system, the range extender system 1 can be effectively utilized to provide necessary power output for the whole vehicle, in the range extender system 1, the range extender controller 16 respectively controls the working states of the engine 13 and the generator 11 through the engine controller 14 and the generator controller 12 on one hand, and on the other hand, the range extender controller 16 is also controlled by the whole vehicle controller 6 on the other hand, thus forming multilayer effective control, and the reasonable control and coordination of the range extender controller 16, the battery management system 5 and the rear motor controller 7 by the whole vehicle controller 6 can quickly and efficiently realize the switching of the required working modes under different working conditions, the system has the advantages of simple structure, innovative configuration and convenient control, greatly improves the power performance and the energy utilization rate of the electric vehicle, and greatly increases the driving range.
Furthermore, the extended range electric vehicle four-wheel drive system further includes a plurality of data sensors (not shown in the figure) for acquiring corresponding working condition parameters, each data sensor is connected with the vehicle control unit 6, the vehicle control unit 6 controls each data sensor to acquire and analyze a plurality of working condition parameters, and then controls the whole system to switch the working modes and make corresponding power distribution strategies according to actual requirements of different working conditions on power performance, that is, the vehicle control unit 6 is used to integrate, coordinate and optimally control the power distribution of the extended range unit system 1, the power battery 4 and other systems, that is, to execute the mode switching control strategies, and the mode switching control strategies are combined with the attached drawing 1, that is, the vehicle control unit 6 is used to control the engine controller 14 and the generator controller 12 through the extended range unit controller 16 so as to control the engine 13 and the generator 11 to enter different working states, the working state of a power battery 4 is controlled by a vehicle control unit 6 through a battery management system 5, the working state of a rear driving motor 8 is controlled by the vehicle control unit 6 through a rear motor controller 7, so that the whole system is controlled to switch working modes and make a corresponding power distribution strategy, the power performance of the electric vehicle can be optimized to a greater extent, even the electric vehicle can work at the best power performance, and the good effects of prolonging the service life of the electric vehicle and improving the driving experience of a driver can be achieved by optimizing the power performance; the plurality of working condition parameters collected and analyzed by the data sensor can specifically comprise a plurality of parameters such as the current speed of the electric vehicle, the current residual capacity of the power battery, the opening degree of an accelerator pedal, a brake pedal signal and the slip ratio of the vehicle, wherein, in order to obtain the maximum longitudinal adhesion coefficient of the tire and simultaneously keep a larger transverse adhesion coefficient, the vehicle slip ratio needs to be controlled near the slip ratio corresponding to the peak adhesion coefficient, and particularly compared with the traditional control strategy, the invention newly introduces the vehicle slip ratio parameter to optimize the working mode switching control strategy, so that the basis of control switching is more accurate and reliable, the driving performance is more improved, in addition, the working mode switching of the whole system is controlled according to actual requirements of different working conditions after the combined matching of all working condition parameters, so that the switching result is more accurate and efficient.
Furthermore, the working modes of the system include, but are not limited to, a parking charging mode, a strongest acceleration mode, a pure electric four-wheel drive mode, a pure electric front drive mode, a pure electric rear drive mode, a range extending drive mode, a cruise drive mode and an energy recovery mode, and all the working modes are matched with corresponding power distribution strategies, so that better power output performance corresponding to the current working condition can be provided for the electric vehicle, and the overall working efficiency and the energy utilization rate of the electric vehicle are effectively improved.
The invention also relates to a control method for controlling the four-wheel drive system of the extended range electric vehicle, which comprises mode switching control strategies corresponding to each working mode and corresponding power distribution strategies formulated for each working mode, namely, a whole vehicle controller is used for controlling an engine controller and a generator controller through a range extender controller so as to control the working states of an engine and a generator, and meanwhile, the whole vehicle controller is used for controlling the working state of a power battery through a battery management system and controlling the working state of a rear drive motor through a rear motor controller so as to control the whole system to switch the working modes and formulate the corresponding power distribution strategies, so that a corresponding power distribution diagram (which can be understood as an energy flow route diagram) and a control outline diagram are corresponding to each working mode, and fig. 2 is a corresponding excellent control method for controlling the four-wheel drive system of the extended range electric vehicle, which is disclosed by the invention Selecting a flow chart, and combining with the attached figure 2, the method specifically comprises the following steps on the basis of collecting the current speed of the electric vehicle, the current residual capacity SOC of the power battery, the opening degree of an accelerator pedal, a brake pedal signal and the vehicle slip rate:
step A, firstly, judging the current residual capacity SOC value of the power battery, when the current residual capacity SOC value is less than the charging limit value, specifically, when the current SOC value of the power battery is less than the charging limit S1(S1 is the minimum SOC limit corresponding to the parking charging mode), it indicates that the current SOC of the power battery is insufficient and needs to be charged, the power output is cut off, the parking charging mode is entered, and in combination with the corresponding power distribution diagram shown in fig. 3 and the control strategy diagram shown in fig. 4, the vehicle control unit 6 sends a control signal to the inside of the range extender system 1, the control signal is sent to the engine controller 14 and the generator controller 12 through the range extender controller 16, the generator controller 12 receives the control signal and then controls the generator 11 to enter a power generation mode, meanwhile, the engine controller 14 receives the control signal and then controls the engine 13 to start, and the generated kinetic energy is converted into electric energy through the generator 11 to charge the power battery 4; when the current remaining capacity SOC value of the power battery is larger than the charging limit value S1 and is larger than the electric energy sufficiency limit value S2 (the electric energy sufficiency limit value S2 is larger than the charging limit value S1), indicating that the electric energy available for providing driving by the power battery is sufficient at the moment, and executing the step B; when the current residual capacity SOC value of the power battery is larger than the charging limit value S1 and smaller than the electric energy sufficiency limit value S2 (the electric energy sufficiency limit value S2 is larger than the charging limit value S1), executing the step C;
step B, judging the opening degree value of the accelerator pedal, when the opening degree value is larger than a pure electric four-wheel drive limit value K1 (when an accelerator signal exists), the acceleration requirement of the vehicle is high, because the acceleration performance of the strongest acceleration mode in the plurality of working modes is strongest, and then the pure electric four-wheel drive mode is adopted, the vehicle is switched to or kept in the strongest acceleration mode at the moment, the corresponding power distribution diagram shown in the attached figure 5 and the control strategy diagram shown in the figure 6 are combined, the range extender system 1 and the power battery 4 provide power at the moment, specifically, the engine 13 in the range extender system 1 enters the working state to provide power together with the power battery 4, the whole vehicle controller 6 communicates with the battery management system 5, the range extender system 1 and the rear motor controller 7 and sends corresponding working instructions, and the range extender system 1 provides a power part: the range extender controller 16 in the range extender system 1 receives the information and then sends a working instruction to the engine controller 14 and the generator controller 12 at the same time, at this time, the engine controller 14 controls the engine 13 to enter a working mode after receiving a control signal transmitted by the range extender controller 16, and the kinetic energy generated by the engine 13 is transmitted to the generator 11 through the internal clutch 15; the power battery 4 provides a power part: the electric energy output by the power battery 4 under the control of the battery management system 5 is transmitted to the generator 11 through the generator controller 12 and the rear motor controller 7, the generator 11 and the rear drive motor 8 are respectively controlled to enter a working state through the rear drive motor 8, the electric energy flowing through the generator 11 is converted into kinetic energy, the kinetic energy is combined with the kinetic energy provided by the engine 13 in the range extender system 1 and transmitted to the front wheel through the front speed reducer 3, the other part of the electric energy drives the rear drive motor 8 to transmit the converted kinetic energy to the rear wheel through the rear speed reducer 9, four-wheel drive is realized, and the engine is added on the basis of the four-wheel drive as a power source, so that the strongest acceleration mode that the output power reaches the maximum is realized. When the opening value of the accelerator pedal is smaller than the pure electric four-wheel drive limit value K1 (when an accelerator signal exists), the operation mode is switched to or kept in the pure electric four-wheel drive mode, and when the opening value of the accelerator pedal is combined with a corresponding power distribution diagram as shown in fig. 7 and a control strategy diagram as shown in fig. 8, at this time, the vehicle power is completely provided by the power battery 4 and the engine 13 inside the range extender system 1 does not provide power, the vehicle control unit 6 communicates with the battery management system 5, the range extender system 1 and the rear motor controller 7 and sends corresponding operation instructions, the electric energy output by the power battery 4 under the control of the battery management system 5 respectively controls the generator 11 and the rear drive motor 8 through the front speed reducer 3 and transmits the converted kinetic energy to the front wheels through the rear speed reducer 9, and can be understood as that the power battery transmits power to the front and rear motor controllers (the generator controller 12 and the rear motor controller 7), the generator 11 and the rear drive motor 8 are driven respectively to transmit power to the front and rear wheel wheels (front axle and rear axle) simultaneously;
step C, judging the opening degree value of the accelerator pedal, and when the opening degree value is larger than a front-rear driving limit value K2(K2 is smaller than K1, and when an accelerator signal exists), switching to or keeping in a pure electric rear driving mode, combining a corresponding power distribution diagram shown in the figure 9 and a control strategy diagram shown in the figure 10, wherein at the moment, the power of the vehicle is completely provided by a power battery 4, an engine 13 in the range extender system 1 does not provide power, the vehicle controller 6 is communicated with the battery management system 5 on one hand, so that the power is output by the power battery 4, and is communicated with a rear motor controller 7 on the other hand, the electric energy output by the power battery 4 under the control of the battery management system 5 is controlled by the rear motor controller 7, and the converted kinetic energy is transmitted to a rear wheel through the rear reducer 9 to realize driving; when the opening value of the accelerator pedal is smaller than the front-rear driving limit value K2(K2 is smaller than K1, when there is an accelerator signal), switching to or maintaining the pure electric drive mode, combining the corresponding power distribution diagram shown in fig. 11 and the control strategy diagram shown in fig. 12, at this time, the vehicle power is completely provided by the power battery 4, the engine in the range extender system 1 does not provide power, the vehicle control unit 6 communicates with the battery management system 5 to send a working instruction to control the power output of the power battery 4, on the other hand, because the configuration of the present invention is characterized in that when the front wheel provides driving force, the power must pass through the generator controller 12 in the range extender system 1 to drive the generator 11 to be combined with the external clutch 2 to be transmitted to the front axle, so the vehicle control unit 6 communicates with the range extender controller 16 at this time to further control the generator controller 12 to work, the electric energy output by the battery 4 under the control of the battery management system 5 controls the generator to be converted by the generator controller The converted kinetic energy is transmitted to the front wheels through the front speed reducer, and the power provided by the pure electric front driving mode is smaller than the power provided by the pure electric rear driving mode.
In summary, the control method for controlling the four-wheel drive system of the extended range electric vehicle including the step A, B, C mainly performs switching control of multiple working modes according to the comparison result between the current value of the specific parameter and the corresponding limit value, and reasonably optimizes the control method so that the control method is more suitable for specific situations and has stronger pertinence to different working conditions, thereby really controlling the generator and the engine, the power battery and the rear-mounted driving motor in the extended range device system to enter different working states respectively according to actual requirements of different working conditions to control the whole four-wheel drive system to perform corresponding working mode switching, so that the control switching is more efficient and convenient, and meanwhile, the power performance of the electric vehicle is greatly improved.
When the current remaining capacity SOC of the power battery does not reach the electric energy sufficiency limit value S2, the magnitude of the driving force provided by the electric energy of the power battery 4 is not as large as that of the two modes (the strongest acceleration mode and the pure electric four-wheel drive mode), and then the pure electric front-drive mode or the pure electric rear-drive mode is selected, wherein the driving force provided by the pure electric rear-drive mode is larger than that of the pure electric front-drive mode. At this time, the determination of the current remaining capacity SOC of the power battery is continued, that is, it is further preferable, preferably, in step C, as shown in the embodiment of fig. 2, the determination of the current remaining capacity SOC value of the power battery may also be performed first, when the current SOC value of the power battery is larger than the range-extending limit value S3 (the range-extending limit value S3 is between the charging limit value S1 and the electric energy sufficiency limit value S2, namely the electric energy sufficiency limit value S2 is larger than the range-extending limit value S3 is larger than the charging limit value S1), the opening value of the accelerator pedal is judged, the pure electric rear-drive mode or the pure electric front-drive mode is executed, namely when the opening value of the accelerator pedal is larger than the front-rear driving limit value K2(K2 < K1 when an accelerator signal exists), the electric vehicle is switched to or kept in the pure electric rear driving mode, when the opening value of the accelerator pedal is smaller than a front-rear driving limit value K2(K2 is smaller than K1, when an accelerator signal exists), switching to or keeping in a pure electric driving mode; when the current SOC of the power battery is smaller than the range-extended limit S3 (the sufficient power limit S2 is greater than the range-extended limit S3 is greater than the charging limit S1), it is difficult to provide a desired working effect only through the power battery, so at this time, the range-extended driving mode needs to be switched to or maintained, in combination with the corresponding power distribution diagram shown in fig. 13 and the control strategy diagram shown in fig. 14, at this time, the power battery 4 is supplied with power through the engine 13 while the power battery 13 is supplied with power through the engine 13, the battery management system 5 transmits a power battery power shortage signal to the vehicle controller 6, the vehicle controller 6 feeds back a stop discharge command, the power battery 4 is about to enter a charging state, the range-extended controller 16 receives a working command from the vehicle controller 6, and simultaneously controls the generator controller 12 and the engine controller 14, respectively starts the generator 11 (makes the generator enter a generating mode) and the engine 13, the kinetic energy generated by the engine 13 is converted into electric energy through the generator 11, one part of the electric energy flows to the power battery 4 to charge the power battery 4, and the other part of the electric energy flows to the rear motor controller 7 to control the rear driving motor 8 to start and then transfer the kinetic energy to the rear wheel through the rear speed reducer 9 to realize driving.
The condition that the ground adhesion force is smaller than the driving force may occur under the working conditions of uphill, acceleration and the like in the driving process of the electric vehicle, so that the wheel slip phenomenon may occur, and the driving performance of the vehicle is limited. In all the working modes, the driving performance of the vehicle four-wheel drive mode is strongest, and the driving performance of the vehicle rear drive mode is stronger than that of the vehicle front drive mode, so that after the four-wheel drive system (or called driving system) enters a certain working mode (for example, after the four-wheel drive system is switched or kept in the pure electric front drive mode), the slip rate of the vehicle can be judged, as further preferable in the method shown in fig. 2, in the step C, after the four-wheel drive system is switched or kept in the pure electric front drive mode, the slip rate of the vehicle is judged, when the slip rate is greater than a slip rate limit value W, the longitudinal adhesion coefficient and the lateral adhesion coefficient deviate from an ideal range, so that the four-wheel drive mode is switched to the pure electric rear drive mode, and if the slip rate of the vehicle is still greater than the slip rate limit value W on the basis, the four-wheel drive mode is further switched to the pure electric four-wheel drive mode; similarly, after the pure electric rear drive mode and the extended range drive mode are switched or kept, the vehicle slip rate is judged, when the vehicle slip rate is larger than the slip rate limit value W, the pure electric four-wheel drive mode is further switched, and by innovatively introducing the vehicle slip rate parameter and the adhesion coefficient, more accurate comparison and judgment can be further realized, so that more effective and accurate control basis is provided for the working mode switching control.
The method shown in fig. 2 preferably further includes step D of determining the current vehicle speed of the electric vehicle, and when the current vehicle speed is greater than or equal to the vehicle speed limit U1, switching to or maintaining the cruise driving mode, and combining the corresponding power distribution diagram shown in fig. 15 and the control strategy diagram shown in fig. 16, where the engine 13 of the range extender system 1 provides power, and the generator 11 can be used to convert energy into the power battery 4 for charging, the engine 13 and the generator 11 enter the operating state after receiving signals from the corresponding controllers, respectively, kinetic energy generated by the engine 13 is transmitted to the generator 11 through the internal clutch 15, and is converted into electric energy to charge the power battery 4 on the one hand, and is transmitted to the front wheels through mechanical transmission to realize driving on the other hand, where the electric vehicle maintains a large driving speed and the operating efficiency of the engine is relatively high, and the engine supplies power to the generator, and then the operation of charging the power battery after energy conversion can greatly improve the overall energy utilization rate, and the practicability is extremely strong.
Further preferably, in step D, when the current vehicle speed of the electric vehicle is less than the vehicle speed limit U1 and greater than or equal to the energy recovery limit U2 (energy recovery limit U2 < vehicle speed limit U1), step E may also be executed;
step E, switching to or maintaining the energy recovery mode, and combining the corresponding power distribution diagram shown in fig. 17 and the control strategy diagram shown in fig. 18, at this time, the vehicle control unit 6 sends a corresponding working instruction to the range extender controller 16 and the rear motor controller 7, so that the engine controller 14 in the range extender system 1 controls the engine 13 to be in a closed state, the generator controller 12 controls the generator 11 to enter a power generation mode, and the kinetic energy of the front wheels is transmitted to the generator 11 through the front speed reducer 3 and the external clutch 2, and is converted into electric energy, and the electric energy is supplemented into the power battery 4 through the generator controller 12; the kinetic energy of the rear wheel also flows through a rear driving motor 8 through a rear speed reducer 9 (the rear motor controller 7 controls the rear driving motor to be switched from a driving mode to a power generation mode), the kinetic energy is converted into electric energy, the electric energy is supplemented into the power battery 4 through the rear motor controller 7, the power battery 4 is charged, the kinetic energy of a driving system can be promoted, meanwhile, the energy can be recovered, so that the energy can be recycled when other working modes are carried out subsequently, and the energy utilization rate is greatly improved.
Under the brake working condition, the wheel locking condition is easy to occur, the slip rate exceeds the limit value, and the wheel adhesion coefficient deviates from the ideal area, so that the brake stability is influenced. Therefore, it is also preferable to perform the slip ratio determination during braking. As shown in fig. 2, when the current vehicle speed of the electric vehicle is determined, it is determined whether the current vehicle speed is equal to or greater than a vehicle speed limit value U1, and when the determination is yes, the cruise drive mode is switched to or maintained, that is, step D is performed, and when the determination is no, a brake signal (or brake pedal signal) is determined, and also after the cruise drive mode, the brake signal is determined. When a braking signal is judged to exist, comparing the current speed of the electric vehicle with an energy recovery limit value U2, namely judging whether to execute the step E to switch to or keep the energy recovery mode, when the step E is not judged to be executed, judging the slip rate of the vehicle, preferably judging the slip rate of the vehicle again in the energy recovery mode of the step E, when the slip rate is larger than a slip rate limit value W, judging the current residual capacity SOC value of the power battery, when the current residual capacity SOC value of the power battery is larger than a range-increasing limit value S3 (the electric energy sufficient limit value S2 is larger than the range-increasing limit value S3 is larger than a charging limit value S1), firstly switching to a pure electric rear-drive mode, and if the slip rate of the vehicle is still larger than the slip rate limit value W on the basis, further switching to the pure electric four-drive mode; when the current residual capacity SOC value of the power battery is smaller than or equal to the range-extending limit value S3, the power battery is switched to or kept in the range-extending driving mode, the vehicle slip rate can be judged after the range-extending driving mode is started, and when the current residual capacity SOC value of the power battery is still larger than the slip rate limit value W, the power battery is further switched to the pure electric four-wheel drive mode.
Further, when in step D, when the electric vehicle current vehicle speed is less than the vehicle speed limit U1 and less than the energy recovery limit U2 (energy recovery limit U2 < vehicle speed limit U1), there is a brake signal but the energy recovery mode is not triggered, the following steps may also be performed: when the vehicle slip rate is greater than the slip rate limit value W, further judging the working mode, if the current working mode is the pure electric front driving mode, switching to the pure electric rear driving mode, entering the pure electric rear driving mode, further judging the vehicle slip rate, and when the vehicle slip rate is still greater than the slip rate limit value W, further switching to the pure electric four-wheel driving mode; if the current working mode is not the pure electric front-driving mode, the current working mode is further judged, and if the current working mode is further judged to be the pure electric rear-driving mode or the range-extending driving mode, the pure electric four-driving mode is switched.
If the current speed of the electric vehicle, the current residual capacity SOC of the power battery, the opening degree of an accelerator pedal, a brake pedal signal and the vehicle slip rate are not met, the current speed of the electric vehicle, the current residual capacity SOC of the power battery, the opening degree of the accelerator pedal, the brake pedal signal and the vehicle slip rate are collected and obtained again, and then the corresponding judgment process is carried out.
It should be noted that the above-mentioned embodiments enable a person skilled in the art to more fully understand the invention, without restricting it in any way. Therefore, although the present invention has been described in detail with reference to the drawings and examples, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention.

Claims (10)

1. A range-extended electric vehicle four-wheel drive system comprises a vehicle control unit, a power battery, a battery management system, a rear drive motor, a front speed reducer and a rear speed reducer, wherein the battery management system is respectively connected with the power battery and the vehicle control unit, and is characterized by further comprising a range extender system, an external clutch and a rear motor controller, the range extender system is arranged at a position close to a front axle and is connected with the front speed reducer through the external clutch and provides power for the front speed reducer, the range extender system is also connected with the rear motor controller for controlling the rear drive motor, the rear motor controller is sequentially connected with the rear drive motor and the rear speed reducer and provides power for the rear speed reducer, the range extender system comprises a generator, a generator controller, an engine controller, an internal clutch and a range extender controller, the generator is connected with the front speed reducer through an external clutch, the engine is connected with the generator through an internal clutch, the range extender controller is respectively connected with an engine controller for controlling the engine and a generator controller for controlling the generator so as to respectively control the working states of the engine and the generator, the range extender controller is connected with the whole vehicle controller outwards and is controlled by the whole vehicle controller to form multilayer effective control, the rear motor controller is connected with the whole vehicle controller and is controlled by the whole vehicle controller, the power battery is respectively connected with the generator controller and the rear motor controller so as to respectively transmit electric energy to the front axle and the rear axle to respectively form a front energy flow channel and a rear energy flow channel, the front energy flow channel and the rear energy flow channel are matched to work, and the whole vehicle controller is utilized to connect the range extender controller, The battery management system and the rear motor controller are controlled and coordinated, and the generator, the engine, the power battery and the rear driving motor in the range extender system are controlled to respectively enter different working states according to actual requirements of different working conditions, so that the whole four-wheel drive system is controlled to switch corresponding working modes, and a corresponding power distribution strategy is formulated.
2. The extended range electric vehicle four-wheel drive system of claim 1, further comprising a plurality of data sensors for acquiring corresponding working condition parameters, wherein each data sensor is connected with the vehicle control unit, and the vehicle control unit controls the whole system to switch working modes and make corresponding power distribution strategies according to the requirements of different working conditions through mode switching control strategies after each data sensor acquires and analyzes a plurality of working condition parameters.
3. The extended range electric vehicle four-wheel drive system of claim 2, wherein the operating condition parameters collected and analyzed by the data sensor include, but are not limited to, the current vehicle speed of the electric vehicle, the current remaining capacity of the power battery, the opening degree of an accelerator pedal, a brake pedal signal and a vehicle slip rate, and the whole system is controlled to switch the operating modes according to the requirements of different operating conditions after the operating condition parameters are matched in a combined manner.
4. The extended range electric vehicle four wheel drive system of claim 3, wherein the mode switching control strategy is: the vehicle control unit controls the engine controller and the generator controller through the range extender controller so as to control the working states of the engine and the generator, and simultaneously controls the working state of the power battery through the battery management system and the working state of the rear driving motor through the rear motor controller so as to control the whole system to switch the working modes and make a corresponding power distribution strategy.
5. The extended range electric vehicle four-wheel drive system according to one of claims 2 to 4, wherein the operation modes include, but are not limited to, a parking charge mode, a maximum acceleration mode, an electric four-wheel drive mode, an electric front drive mode, an electric rear drive mode, an extended range drive mode, a cruise drive mode, and an energy recovery mode.
6. A control method for controlling the extended range electric vehicle four-wheel drive system according to one of claims 1 to 5, characterized by comprising the steps of:
step A, firstly judging the current residual capacity value of the power battery, cutting off power output when the current residual capacity value is smaller than a charging limit value, entering a parking charging mode, sending a control signal to the interior of a range extender system by a vehicle controller, sending the control signal to an engine controller and a generator controller by the range extender controller, controlling a generator to enter a power generation mode after the generator controller receives the control signal, controlling the engine to start after the engine controller receives the control signal, and converting generated kinetic energy into electric energy to charge the power battery by the generator; b, when the current residual capacity value of the power battery is larger than the charging limit value and larger than the electric energy sufficiency limit value, executing the step B; c, when the current residual capacity value of the power battery is larger than the charging limit value and smaller than the electric energy sufficiency limit value, executing the step C;
step B, judging the opening value of the accelerator pedal, switching to or keeping in a strongest acceleration mode when the opening value of the accelerator pedal is larger than a pure electric four-wheel drive limit value, wherein the range extender system and the power battery provide power, the engine controller controls the kinetic energy generated by the engine to be transmitted to the generator through the internal clutch after receiving a control signal transmitted by the range extender controller, the electric energy output by the power battery under the control of the battery management system respectively controls the generator and the rear drive motor to enter a working state through the generator controller and the rear motor controller, the electric energy flowing through the generator is converted into the kinetic energy, then the kinetic energy is combined with the kinetic energy provided by the engine in the range extender system and transmitted to a front wheel through the front speed reducer, and the other part of electric energy drives the rear drive motor to transmit the converted kinetic energy to a rear wheel through the rear speed reducer; when the opening value of the accelerator pedal is smaller than the pure electric four-wheel drive limit value, switching to or keeping in a pure electric four-wheel drive mode, wherein the power of the vehicle is completely provided by a power battery, and the electric energy output by the power battery under the control of a battery management system respectively controls a generator and a rear driving motor through a generator controller and a rear motor controller to transmit the converted kinetic energy to the front wheel through a front speed reducer and to the rear wheel through a rear speed reducer;
step C, judging the opening degree value of the accelerator pedal, and when the opening degree value is larger than a front-rear driving limit value, switching to or keeping in a pure electric rear driving mode, wherein the power of the vehicle is completely provided by a power battery, and the electric energy output by the power battery under the control of a battery management system is controlled by a rear motor controller to transmit the converted kinetic energy to a rear wheel through a rear speed reducer; when the opening value of the accelerator pedal is smaller than the front-rear driving limit value, the electric vehicle is switched to or kept in the pure electric-drive mode, at the moment, the power of the vehicle is completely provided by the power battery, and the electric energy output by the power battery under the control of the battery management system controls the generator to transmit the converted kinetic energy to the front wheel through the front speed reducer through the generator controller.
7. The control method according to claim 6, wherein in step C, the current remaining capacity value of the power battery is judged, and when the current remaining capacity value of the power battery is greater than the range-extending limit value, the opening value of the accelerator pedal is judged, and the pure electric rear-drive mode or the pure electric front-drive mode is executed; the range-extended limit value is between the charging limit value and the electric energy sufficient limit value, when the current residual capacity value of the power battery is smaller than the range-extended limit value, the range-extended driving mode is switched to, at the moment, the power is provided by the engine and the electric energy is supplemented to the power battery, the battery management system transmits a signal that the electric quantity of the power battery is insufficient to the whole vehicle controller, the whole vehicle controller feeds back a discharge stopping instruction, the range-extended controller simultaneously controls the generator controller and the engine controller after receiving a working instruction sent by the whole vehicle controller, the generator and the engine are respectively started, the kinetic energy generated by the engine is converted into electric energy through the generator, one part of the electric energy flows to the power battery to charge the power battery, and the other part of the electric energy flows to the rear motor controller to further control the rear driving motor to start and then transmit the kinetic energy to the rear wheel through the rear speed reducer to realize driving.
8. The control method according to claim 7, wherein in step C, after the pure electric forward driving mode is switched to or kept in, the vehicle slip rate is also determined, and when the vehicle slip rate is greater than the slip rate limit value, the vehicle slip rate is switched to the pure electric backward driving mode, and if the vehicle slip rate is still greater than the slip rate limit value on the basis, the vehicle slip rate is further switched to the pure electric four-wheel driving mode; and after the vehicle is switched to or kept in the pure electric rear-drive mode and the range-extended drive mode, judging the slip rate of the vehicle, and when the slip rate is greater than a slip rate limit value, further switching to the pure electric four-wheel drive mode.
9. The control method according to one of claims 6 to 8, further comprising a step D of judging the current speed of the electric vehicle, and when the current speed is greater than or equal to the speed limit value, switching to or keeping a cruise driving mode, wherein the engine of the range extender system provides power and the generator is used for converting energy into a power battery for charging, the engine and the generator respectively enter a working state after receiving signals of the corresponding controllers, kinetic energy generated by the engine is transmitted to the generator through the internal clutch, and is converted into electric energy to charge the power battery on one hand, and is transmitted to a front wheel through mechanical transmission to realize driving on the other hand.
10. The control method according to claim 9, wherein in step D, when the current vehicle speed of the electric vehicle is less than the vehicle speed limit value and equal to or greater than the energy recovery limit value, step E is executed;
step E, switching to or keeping an energy recovery mode, wherein at the moment, the vehicle control unit sends corresponding working instructions to the range extender controller and the rear motor controller, so that an engine controller in the range extender system controls the engine to be in a closed state, the generator controller controls the generator to enter a power generation mode, and the kinetic energy of the front wheels is transmitted to the generator through the front speed reducer and the external clutch so as to be converted into electric energy which is supplemented into the power battery through the generator controller; the kinetic energy of the rear wheel is converted into electric energy through the rear driving motor by the rear speed reducer and then is supplemented into the power battery by the rear motor controller to charge the power battery.
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