WO2023082854A1

WO2023082854A1 - Power system control method for four-wheel-drive all-electric vehicle, and power system

Info

Publication number: WO2023082854A1
Application number: PCT/CN2022/120447
Authority: WO
Inventors: 刘力源; 王燕; 刘建康
Original assignee: 中国第一汽车股份有限公司
Priority date: 2021-11-15
Filing date: 2022-09-22
Publication date: 2023-05-19
Also published as: CN113910922B; CN113910922A

Abstract

A power system control method for a four-wheel-drive all-electric vehicle, and a power system. The method comprises: acquiring a first required torque M11 for driving a vehicle to travel under a driving working condition, acquiring the sum of the maximum output torque of a first motor (1) and the maximum output torque of a second motor (2) as M21, and comparing magnitudes of M11 and M21; in response to determining that M11 > M21, controlling a clutch (5) to engage, and the first motor (1), the second motor (2) and a third motor (3) to simultaneously output a torque, the sum of the output torques being M11; and in response to determining that M11 ≤ M21, controlling the clutch (5) to disengage, and the first motor (1) and the second motor (2) to output a torque, the sum of the output torques being equal to M11, thereby reasonably allocating output torque of the multiple motors.

Description

Power system control method and power system of four-wheel drive pure electric vehicle

This application claims priority to a Chinese patent application with application number 202111345369.2 filed with the China Patent Office on November 15, 2021, the entire contents of which are incorporated herein by reference.

technical field

The present application relates to the technical field of vehicles, for example, to a power system control method and power system of a four-wheel drive pure electric vehicle.

Background technique

In order to pursue extreme braking performance, pure electric vehicles adopt a four-wheel drive configuration and are equipped with two, three, or even four motor systems; however, users do not blindly pursue power in the actual use process, and long cruising range is also one of the main needs of users , and how to use multiple motors to meet the long cruising range is the problem to be solved in this patent. In order to meet the user's demand for power and economy at the same time, the whole vehicle must be equipped with more motor systems, and different driving modes must be set, and a single or multiple motors can be used to drive the vehicle through clutches and other devices, which not only meets the power requirements Demand also meets long-mileage needs.

The power system of an electric vehicle and the electric vehicle with it are disclosed in the related art. The power system of the electric vehicle adopts two motors, and is equipped with a clutch and a planetary gear, etc.; the previous patent with the application number CN202010214247. A pure electric vehicle power drive system and a vehicle with a force separation device. The pure electric vehicle power drive system with a power separation device includes a main drive system, an auxiliary drive system, an active power separation device and an auxiliary power separation device, etc.; Four driving power system and electric vehicle, the four driving power system includes two sets of powertrains, each powertrain has a motor, motor controller, reducer, etc. However, no specific control strategy is given for how to distribute torque among multiple motors in the above-mentioned patents.

Therefore, there is an urgent need for a power system control method and a power system of a four-wheel drive pure electric vehicle to solve the above problems.

Contents of the invention

The present application provides a power system control method and a power system of a four-wheel drive pure electric vehicle, so as to rationally distribute output torques of multiple motors.

In one aspect, the present application provides a power system control method of a four-wheel drive pure electric vehicle. The power system of the vehicle includes a first motor, a second motor, a third motor, a power battery, and a clutch. The first motor and the second motor The two motors are respectively connected to the wheel ends, the third motor is selectively connected to the wheel ends through the clutch, and the power battery is set to supply power to the first motor, the second motor and the third motor. power supply, and the first motor, the second motor and the third motor can respectively generate electricity and charge the power battery; the method includes:

Obtain the current working condition of the vehicle;

performing drive torque distribution in response to determining that the current operating condition is a driving condition in which an accelerator pedal of the vehicle is depressed;

The execution of drive torque distribution includes:

Acquiring a first required torque M11 for driving the vehicle;

Obtaining the maximum output torques of the first motor, the second motor, and the third motor respectively, and the sum of the maximum output torque of the first motor and the maximum output torque of the second motor is M21;

Compare the size of M11 and M21;

In response to determining M11>M21, the clutch is controlled to engage, the first motor, the second motor and the third motor simultaneously output torque, and the actual output torque of the first motor, the second motor The sum of the actual output torque of and the actual output torque of the third motor is equal to M11;

In response to determining M11≤M21, the clutch is controlled to disengage, the first motor and the second motor output torque, and the sum of the actual output torque of the first motor and the actual output torque of the second motor is equal to M11.

On the other hand, the present application also provides a power system of a four-wheel-drive pure electric vehicle. The power system of the four-wheel-drive pure electric vehicle includes a first motor, a second motor, a third motor, a power battery, a clutch and a controller. The first motor and the second motor are respectively connected to the wheel end in transmission, the third motor is selectively connected to the wheel end through the clutch, and the power battery is set to supply power to the first motor, the second The second motor and the third motor supply power, and the first motor, the second motor and the third motor can respectively generate electricity and charge the power battery;

The controller is configured to implement the power system control method of a four-wheel-drive pure electric vehicle described in any of the above solutions.

Description of drawings

Fig. 1 is a structural schematic diagram 1 of a power system of a four-wheel drive pure electric vehicle in an embodiment of the present application;

Fig. 2 is the structural schematic diagram II of the four-wheel drive pure electric vehicle power system in the embodiment of the present application;

Fig. 3 is the structural schematic diagram 3 of the four-wheel drive pure electric vehicle power system in the embodiment of the present application;

FIG. 4 is a structural schematic diagram 4 of a power system of a four-wheel-drive pure electric vehicle in an embodiment of the present application.

In the picture:

1. The first motor; 2. The second motor; 3. The third motor; 4. Power battery; 5. Clutch;

61. First motor controller; 62. Second motor controller; 63. Third motor controller; 64. Battery controller; 65. Vehicle controller; 66. Electronic stability system;

7. Rear axle; 8. Rear reducer; 9. Front axle; 10. Front reducer.

Detailed ways

In the description of this application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the application and simplification of the description, rather than indicating or implying that the referred device or element must have a specific orientation, use a specific orientation construction and operation, therefore should not be construed as limiting the application. In addition, the terms "first" and "second" are used for descriptive purposes only, and should not be construed as indicating or implying relative importance. Wherein, the terms "first position" and "second position" are two different positions, and "above", "above" and "above" the first feature on the second feature include that the first feature is on the second feature. Directly above and obliquely above, or simply means that the first feature level is higher than the second feature. "Below", "beneath" and "under" the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

In the description of this application, it should be noted that unless otherwise specified and limited, the terms "installation", "connection", and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in this application in specific situations.

Embodiments of the present application are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary, are only for explaining the present application, and should not be construed as limiting the present application.

As shown in Figures 1 to 4, this embodiment provides a power system of a four-wheel drive pure electric vehicle, the power system of the four-wheel drive pure electric vehicle includes a first motor 1, a second motor 2, a third motor 3, a power battery 4. The controller and the clutch 5, the first motor 1 and the second motor 2 are connected to the wheel end drive, the third motor 3 is selectively connected to the wheel end drive through the clutch 5, and the power battery 4 is set to provide the first motor 1, The second motor 2 and the third motor 3 supply power, and the first motor 1 , the second motor 2 and the third motor 3 can generate electricity and charge the power battery 4 . By controlling the coupling or disengagement of the clutch 5, the third motor 3 can be connected or withdrawn from power transmission. Wherein, the power battery 4 includes one or more of a lithium-ion power battery, a flywheel energy storage battery system, and a fuel cell system. The models of the first motor 1 , the second motor 2 and the third motor 3 can be the same or different, and can be specifically selected according to needs.

As shown in FIGS. 1 and 2 , the first motor 1 is in transmission connection with the front axle 9 ; the second motor 2 is in transmission connection with the rear axle 7 , and the third motor 3 is selectively in transmission connection with the rear axle 7 through the clutch 5 . When the clutch 5 is combined, the third motor 3 can be connected to the transmission connection with the rear axle 7; when the clutch 5 is disengaged, the third motor 3 can be withdrawn from the transmission connection with the rear axle 7. For example, the power system law of a four-wheel drive pure electric vehicle also includes a rear reducer 8, which is connected to the rear axle 7 in transmission. As shown in Figure 1, along the left-right direction of the automobile, the third motor 3 is arranged on the left side, and the third motor 3 is selectively connected with the input gear of the rear speed reducer 8 through the clutch 5, and the second motor 2 is arranged on the right side , the second motor 2 is arranged coaxially with the third motor 3 , and the second motor 2 is connected to the input gear of the rear reducer 8 through transmission. As shown in Figure 2, along the left-right direction of the automobile, the third motor 3 can also be arranged on the right side, and the third motor 3 is selectively connected with the input gear of the rear speed reducer 8 through the clutch 5, and the second motor 2 is arranged on the On the left side, the second motor 2 and the third motor 3 are coaxially arranged, and the second motor 2 is connected to the input gear of the rear reducer 8 in transmission.

For example, as shown in FIG. 3 and FIG. 4 , both the first motor 1 and the second motor 2 are in drive connection with the rear axle 7 , and the third motor 3 is selectively in drive connection with the front axle 9 through the clutch 5 . When the clutch 5 is engaged, the transmission of the third motor 3 can be connected to the front axle 9; For example, the power system method of a four-wheel drive pure electric vehicle also includes a front speed reducer 10, wherein, as shown in Figure 3, the third motor 3 is selectively connected to the input gear of the front speed reducer 10 through the clutch 5, and the front speed reducer 10 The output gear is connected with front axle 9 transmissions. As shown in FIG. 4 , the third motor 3 is in drive connection with the input gear of the front reducer 10 , and the output gear of the front reducer 10 is selectively drive connected with the front axle 9 through the clutch 5 .

The controller includes a first motor controller 61 , a second motor controller 62 and a third motor controller 63 . Wherein, the first motor controller 61 is connected with the first motor 1 and the power battery 4, and the first motor controller 61 is set to control the magnitude of the current output by the power battery 4 to the first motor 1, and then control the actual power of the first motor 1. Output torque; at the same time, it can also control the magnitude of the current input to the power battery 4 when the first motor 1 generates power, and then control the braking torque generated by the first motor 1 . The second motor controller 62 is connected to the second motor 2 and the power battery 4, and the second motor controller 62 is configured to control the current output from the power battery 4 to the second motor 2, thereby controlling the actual output torque of the second motor 2; At the same time, the magnitude of the current input to the power battery 4 when the second motor 2 generates power can also be controlled, thereby controlling the braking torque generated by the second motor 2 . The third motor controller 63 is connected to the third motor 3 and the power battery 4, and the third motor controller 63 is configured to control the output current of the power battery 4 to the third motor 3, thereby controlling the actual output torque of the third motor 3; At the same time, the magnitude of the current input to the power battery 4 when the third motor 3 generates power can also be controlled, thereby controlling the braking torque generated by the third motor 3 . By controlling the output torques of the three motors, the magnitude of the output torque for driving the vehicle can be adjusted; by controlling the braking torque of the three motors, the magnitude of the braking torque for braking the vehicle can be adjusted.

The controller also includes a battery controller 64, the battery controller 64 is connected to the power battery 4, and is set to be charged according to the state of charge (State of Charge, SOC) of the power battery 4, the voltage of the power battery 4 and the temperature of the power battery 4. Evaluate the maximum discharge power and maximum charge power of the power battery 4 . Wherein, the temperature of the power battery 4 can be collected by a temperature sensor connected to the battery controller 64, and the voltage of the power battery 4 can be collected by a voltage sensor connected to the power battery 4, and the acquisition of the SCO of the battery is a prior art, and will not be described here. Let me repeat. Wherein, the voltage of the power battery 4 is the output voltage or the input voltage of the power battery 4 .

The temperature of the power battery 4, the input voltage of the power battery 4, the charging correspondence diagram of the SCO of the power battery 4 and the maximum charging power of the power battery 4 can be obtained through a large number of tests, and then according to the obtained temperature of the power battery 4, the power battery 4 The input voltage of the power battery 4 and the SOC of the power battery 4 can be queried from the above charging correspondence diagram for the maximum charging power of the corresponding power battery 4; similarly, the temperature of the power battery 4, the output voltage of the power battery 4, and the SCO and the maximum discharge power discharge correspondence diagram of the power battery 4, and then query the corresponding power battery 4 from the above discharge correspondence diagram according to the acquired temperature of the power battery 4, the output voltage of the power battery 4, and the SOC of the power battery 4 amplified discharge power.

The maximum charging current of the power battery 4 can be calculated by the maximum charging power of the power battery 4 and the input voltage of the power battery 4 . The maximum discharge current of the power battery 4 can be calculated from the maximum discharge power of the power battery 4 and the output voltage of the power battery 4 . The maximum charging current can be allocated to the first motor 1, the second motor 2 and the third motor 3 according to the first setting ratio, and then the maximum charging current of the first motor 1, the maximum charging current of the second motor 2 and the third motor can be obtained. The maximum charging current of motor 3. The maximum discharge current can be allocated to the first motor 1, the second motor 2 and the third motor 3 according to the second setting ratio, and then the maximum supply current of the first motor 1, the maximum supply current of the second motor 2 and the third The maximum supply current of motor 3. Wherein, the first setting ratio and the second setting ratio can be set as required. Taking the second setting ratio as an example, the second setting ratio may be the ratio between the rated output power of the first motor 1 , the rated output power of the second motor 2 and the rated output power of the third motor 3 .

The first motor controller 61 is also configured to evaluate the maximum output torque of the first motor 1 . For example, the first motor controller 61 acquires the first temperature of the first motor 1, the first voltage at the input end of the first motor 1, and the maximum supply current of the first motor 1, and the first motor controller 61 obtains the first temperature, The first voltage, the maximum supply current of the first motor 1 Query the corresponding first motor 1 from the map1 between the first temperature, the first voltage, the maximum supply current of the first motor 1 and the maximum output torque of the first motor 1 the maximum output torque. Among them, map1 can be obtained through a large number of previous experiments. The first motor controller 61 can obtain the temperature of the first motor 1 through the temperature sensor connected with the first motor controller 61, and obtain the first voltage of the input terminal of the first motor 1 through the voltage sensor connected with the first motor controller 61 .

The second motor controller 62 is also configured to evaluate the maximum output torque of the second motor 2 . For example, the second motor controller 62 acquires the second temperature of the second motor 2, the second voltage at the input terminal of the second motor 2, and the maximum supply current of the second motor 2, and the second motor controller 62 obtains the second temperature, The second voltage, the maximum supply current of the second motor 2 query the corresponding second motor 2 from the map2 between the second temperature, the second voltage, the maximum supply current of the second motor 2 and the maximum output torque of the second motor 2 the maximum output torque. Among them, map2 can be obtained through a large number of experiments in the early stage. The second motor controller 62 can obtain the temperature of the second motor 2 through the temperature sensor connected with the second motor controller 62, and obtain the second voltage of the input terminal of the second motor 2 through the voltage sensor connected with the second motor controller 62 .

The third motor controller 63 is configured to evaluate the maximum output torque of the third motor 3 . For example, the third motor controller 63 acquires the third temperature of the third motor 3, the third voltage at the input end of the third motor 3, and the maximum supply current of the third motor 3, and the third motor controller 63 obtains the third temperature, The third voltage, the maximum supply current of the third motor 3 Query the corresponding third motor 3 from the map3 between the third temperature, the third voltage, the maximum supply current of the third motor 3 and the maximum output torque of the third motor 3 the maximum output torque. Among them, map3 can be obtained through a large number of experiments in the early stage. The third motor controller 63 can obtain the temperature of the third motor 3 through the temperature sensor connected with the third motor controller 63, and obtain the third voltage of the input terminal of the third motor 3 through the voltage sensor connected with the third motor controller 63 .

The first motor controller 61 is also arranged to evaluate the maximum braking torque of the first motor 1 . The first motor controller 61 acquires the first temperature of the first motor 1, the first charging voltage at the output end of the first motor 1, and the maximum charging current of the first motor 1, and the first motor controller 61 according to the first temperature, the first A charging voltage, the maximum charging current of the first motor 1 Query the corresponding first Maximum braking torque of motor 1. Among them, map11 can be obtained through a large number of previous experiments. The first motor controller 61 can acquire the first voltage of the output end of the first motor 1 through a voltage sensor connected to the first motor controller 61 .

The second electric machine controller 62 is also arranged to evaluate the maximum braking torque of the second electric machine 2 . The second motor controller 62 acquires the second temperature of the second motor 2, the second charging voltage at the output end of the second motor 2, and the maximum charging current of the second motor 2, and the second motor controller 62 obtains the second temperature according to the second temperature, the second Two charging voltage, the maximum charging current of the second motor 2 query the corresponding second Maximum braking torque of motor 2. Among them, map21 can be obtained through a large number of previous experiments. The second motor controller 62 can obtain the second voltage of the output terminal of the second motor 2 through a voltage sensor connected to the second motor controller 62 .

The third motor controller 63 is also configured to evaluate the maximum braking torque of the third motor 3 . The third motor controller 63 obtains the third temperature of the third motor 3, the third charging voltage of the output terminal of the third motor 3, and the maximum charging current of the third motor 3, and the third motor controller 63 according to the third temperature, the third Three charging voltages, the maximum charging current of the third motor 3 Query the corresponding third temperature from the map31 among the third temperature, the third charging voltage, the maximum charging current of the third motor 3 and the maximum braking torque of the third motor 3. Maximum braking torque of motor 3. Among them, map31 can be obtained through a large number of previous experiments. The third motor controller 63 can obtain the third voltage of the output terminal of the third motor 3 through a voltage sensor connected to the third motor controller 63 .

The controller also includes a vehicle controller 65 . The whole vehicle controller 65 is connected with the clutch 5 to control the coupling or disengagement of the clutch 5, and then control whether the third motor 3 is involved in the power transmission with the wheel end.

The whole vehicle controller 65 can also be set to judge the working condition of the current vehicle. When the brake pedal of the vehicle is stepped on, the whole vehicle controller 65 can judge that the current vehicle is in the braking condition; when the accelerator pedal of the vehicle is stepped on, The vehicle controller 65 can determine that the current vehicle is in a driving condition, that is, the vehicle is moving forward or reversing. For example, taking judging that the vehicle is in a braking condition as an example, a position sensor can be installed on the brake pedal, and the position information of the brake pedal can be obtained through the position sensor. The position information and the opening degree of the brake pedal can be set in advance in the vehicle controller 65. By querying the corresponding graph, the brake pedal opening corresponding to the position information can be obtained, and then analyzed whether the brake pedal is stepped on.

The whole vehicle controller 65 can also calculate the first wheel end demand torque of the vehicle according to the opening degree of the accelerator pedal, the vehicle speed and the rate of change of the opening degree of the accelerator pedal. Among them, the vehicle speed can be collected by the speed sensor. The change rate of the accelerator pedal opening is the change rate of the accelerator pedal position when the driver steps on the accelerator pedal, which corresponds to the target acceleration that the driver expects to accelerate to the target vehicle speed at the current moment. The ratio of the opening degree to the time when the accelerator pedal opening degree is generated is determined. The accelerator pedal opening, vehicle speed, and the rate of change of the accelerator pedal opening can be preset in the vehicle controller 65 in advance. The rate of change of the pedal opening obtains the corresponding first wheel end demand torque from the first relationship diagram. The first relationship diagram can be obtained through a large number of experiments in the early stage.

The controller also includes an electronic stability system 66. The electronic stability system 66 is connected to the vehicle controller 65. The electronic stability system 66 can calculate the maximum adhesion of multiple wheels of the vehicle according to the road surface adhesion parameters and wheel pressure parameters, and calculate the maximum adhesion according to the maximum adhesion. and the number of wheels of the vehicle to calculate the second wheel end demand torque for vehicle running. Among them, the adhesion parameter of the wheel can be characterized by the slip rate of the car, which is the degree of slippage of the car. The electronic stability system 66 can obtain the actual rotational speed of the wheel through the rotational speed sensor connected to it, and obtain the target vehicle speed of the vehicle in combination with the diameter of the wheel, then calculate the difference between the target vehicle speed and the actual vehicle speed, and then calculate the ratio of the difference to the actual vehicle speed Can be used as the slip ratio of the car. The wheel pressure parameter may be tire pressure, which can be obtained through a tire pressure sensor. In the electronic stability system 66, a relational table of road surface adhesion parameters, wheel pressure parameters and maximum adhesion can be preset in advance, and the corresponding maximum adhesion can be queried from the relational table. It should be noted that the calculation of the second wheel end required torque for vehicle running according to the maximum adhesion force and the number of vehicle wheels is a prior art, and will not be repeated here.

It can be understood that, when the vehicle is driving on a slippery road, the driver performs a vehicle acceleration operation, and wheel slippage may occur. That is to say, at this moment, the required torque of the first wheel end is greater than the required torque of the second wheel end. If there is a slipping situation, the vehicle controller 65 distributes the required torque at the first wheel end of the automobile calculated according to the opening degree of the accelerator pedal, the vehicle speed and the rate of change of the opening degree of the accelerator pedal to multiple motors, and makes the output of the multiple motors match with it Torque will result in a waste of energy. At the same time, this also shows that the driver's driving expectations are too high for the vehicle speed, and there are safety risks, and the driver's driving expectations need to be adjusted to a safe range. Therefore, when controlling the torque output by the motor, not only the required torque of the first wheel end but also the required torque of the second wheel end should be considered. In this embodiment, the vehicle controller 65 acquires the second wheel end demand torque through the electronic stability system 66, and the vehicle controller 65 compares the first wheel end demand torque with the second wheel end demand torque, and uses the first wheel end demand torque The smaller value of the required torque and the second wheel end required torque is used as the first required torque. This can ensure driving safety and reduce the waste of electric energy of the power battery 4 . For example, when the vehicle controller 65 determines that the required torque at the first wheel end is greater than the required torque at the second wheel end, the vehicle controller 65 controls the alarm device to issue an alarm to remind the driver to pay attention to driving safety.

The vehicle controller 65 is also respectively connected with the first motor controller 61, the second motor controller 62 and the third motor controller 63, so that the vehicle controller 65 can obtain the maximum output torque of the first motor 1, the second motor 2 and the maximum output torque of the third motor 3. The first required torque is M11, the vehicle controller 65 calculates the sum of the maximum output torque of the first motor 1 and the maximum output torque of the second motor 2, and the maximum output torque of the first motor 1 and the maximum output torque of the second motor 2 The sum is M21, the vehicle controller 65 compares the magnitudes of M11 and M21; in response to determining M11>M21, it indicates that the first demand torque is relatively large, and the output torque provided by only the first motor 1 and the second motor 2 is not enough to meet The driving expectation of the driver, so the vehicle controller 65 needs to control the clutch 5 to be engaged, so that the three motors output torque simultaneously. In response to the determination of M11≤M21, indicating that the output torque provided by the first motor 1 and the second motor 2 can meet the driver's expectation at this time, the clutch 5 is controlled to be disengaged, and only the first motor 1 and the second motor 2 provide output torque. In this way, under the premise of ensuring the power performance of the whole vehicle, the number of motors used is reduced to reduce the load on the third motor 3 and improve the service life of the third motor 3; at the same time, due to the limitation of the energy conversion efficiency of the motor itself, it cannot 100% conversion of electric energy into kinetic energy, as long as it is used, there is energy waste, so not using the third motor 3 at this time can avoid energy waste and prolong the mileage of the car.

It should be noted that the sum of the maximum output torque of the first motor 1 , the maximum output torque of the second motor 2 and the maximum output torque of the third motor 3 is greater than the first required torque.

The vehicle controller 65 can also calculate the second required torque of the vehicle according to the opening of the brake pedal, the vehicle speed and the rate of change of the opening of the brake pedal. Among them, the rate of change of the brake pedal opening is the rate of change of the brake pedal position when the driver steps on the brake pedal, which corresponds to the target deceleration that the driver expects to decelerate to the target vehicle speed at the current moment, which can be determined by the brake pedal opening The ratio of the time to produce the brake pedal opening is determined. The brake pedal opening, vehicle speed, and the second relational diagram of the rate of change of the brake pedal opening and the second demand torque can be preset in the vehicle controller 65 in advance, and can be obtained according to the obtained brake pedal opening, vehicle speed and The rate of change of the opening of the brake pedal obtains the corresponding second required torque from the second relational graph. The second relationship diagram can be obtained through a large number of experiments in the early stage.

Under braking conditions, the vehicle controller 65 can also obtain the maximum braking torque of the first motor 1 and the maximum braking torque of the second motor 1 from the first motor controller 61, the second motor controller 62 and the third motor controller 63 respectively. 2 and the maximum braking torque of the third motor 3. The second required torque is M12, the vehicle controller 65 calculates the sum of the maximum braking torque of the first motor 1 and the maximum braking torque of the second motor 2, and calculates the maximum braking torque of the first motor 1, the maximum braking torque of the second motor The sum of the maximum braking torque of 2 and the maximum braking torque of the third motor 3. The sum of the maximum braking torque of the first motor 1 and the maximum braking torque of the second motor 2 is M22, the maximum braking torque of the first motor 1, the maximum braking torque of the second motor 2 and the maximum braking torque of the third motor 3 The sum of the braking torques is M23. The vehicle controller 65 compares the sizes of M12 and M22. In response to the determination of M12>M22, it indicates that the first required torque is relatively large, and the braking torque provided by only the first motor 1 and the second motor 2 is not enough to meet the driver's driving desire. At this time, the vehicle controller 65 can control the clutch 5 combined so that the three motors provide braking torque simultaneously. The vehicle controller 65 further compares the sizes of M12 and M23. When M12>M23, it means that even if the three motors provide braking torque at the same time, the driving expectation of the driver cannot be met, and the hydraulic brake mechanism is activated to brake the wheel ends. . For example, the brake torque provided by the hydraulic brake mechanism is equal to the difference between M12 and M23. In response to the determination of M12≤M22, it means that the output torque provided by the first motor 1 and the second motor 2 can meet the driver's expectation at this time, and the clutch 5 is controlled to disengage, and only the first motor 1 and the second motor 2 provide braking torque . In this way, on the premise of ensuring the normal braking of the whole vehicle, the use of the third motor 3 is avoided to reduce the load on the third motor 3 and improve the service life of the third motor 3. At the same time, due to the energy conversion of the third motor 3 Due to the limited efficiency, 100% kinetic energy cannot be converted into electric energy. As long as it is used, there is energy waste. Therefore, not using the third motor 3 can improve the recovery efficiency of electric energy and extend the mileage of the car.

This embodiment also provides a control method for the power system of the four-wheel-drive pure electric vehicle implemented by the power system of the above-mentioned four-wheel-drive pure electric vehicle. A power system control method for a four-wheel-drive pure electric vehicle includes the following steps.

S10: Obtain the current working condition of the vehicle;

In response to determining that the current working condition is a driving working condition, execute S20; in response to determining that the current working condition is a braking working condition, execute S30.

S20: Execute drive torque distribution.

S30: Execute braking torque distribution.

Perform drive torque distribution including:

S21: Obtain the first required torque M11 for driving the vehicle.

The method of obtaining the first required torque for driving the vehicle includes:

Calculate the required torque at the first wheel end of the car according to the accelerator pedal opening, vehicle speed and the rate of change of the accelerator pedal opening;

Calculate the maximum adhesion force of multiple wheels of the car according to the road surface adhesion parameters and wheel pressure parameters, and calculate the second wheel end demand torque for vehicle driving according to the maximum adhesion force and the number of car wheels;

The smaller value of the first wheel-end required torque and the second wheel-end required torque is used as the first required torque.

S22: Obtain the maximum output torques of the first motor 1, the second motor 2, and the third motor 3 respectively, and the sum of the maximum output torque of the first motor 1 and the maximum output torque of the second motor 2 is M21.

For example, the method for obtaining the maximum output torque of the first motor 1 includes: obtaining the first temperature of the first motor 1, the first voltage of the input terminal of the first motor 1, and the maximum supply current of the first motor 1, according to the first temperature , the first voltage, the maximum supply current of the first motor 1, and query the corresponding maximum output torque.

The method for obtaining the maximum output torque of the second motor 2 includes: obtaining the second temperature of the second motor 2, the second voltage of the input terminal of the second motor 2, and the maximum supply current of the second motor 2, according to the second temperature, the second The second voltage, the maximum supply current of the second motor 2 query the corresponding maximum output torque of the second motor 2 from the map2 between the second temperature, the second voltage, the second maximum supply current and the maximum output torque of the second motor 2 ;

The method for obtaining the maximum output torque of the third motor 3 includes: obtaining the third temperature of the third motor 3, the third voltage of the input terminal of the third motor 3, and the maximum supply current of the third motor 3, according to the third temperature, the first Three voltages, the maximum power supply current of the third motor 3 Query the corresponding maximum output torque of the third motor 3 from the map3 between the third temperature, the third voltage, the third maximum power supply current and the maximum output torque of the third motor 3 .

S23: Compare the sizes of M11 and M21.

In response to determination of M11>M21, S24 is performed; in response to determination of M11≦M21, S25 is performed.

S24: Control the clutch 5 to engage, the first motor 1, the second motor 2 and the third motor 3 output torque at the same time, and the actual output torque of the first motor 1, the actual output torque of the second motor 2, and the third motor 3 The sum of the actual output torque is equal to M11.

M11>M21, indicating that the first required torque is relatively large, and the output torque provided by only the first motor 1 and the second motor 2 is not enough to meet the driver's driving expectations. Therefore, the vehicle controller 65 needs to control the clutch 5 to engage, so that The three motors output torque simultaneously.

S25: Control the clutch 5 to disengage, only the first motor 1 and the second motor 2 output torque, and the sum of the actual output torque of the first motor 1 and the actual output torque of the second motor 2 is equal to M11.

M11≤M21, it means that the output torque provided by the first motor 1 and the second motor 2 can meet the driver's expectation at this time, the clutch 5 is controlled to disengage, and only the first motor 1 and the second motor 2 provide output torque.

Brake torque distribution includes:

S31: Obtain the second required torque M12 for vehicle braking.

For example, the vehicle's second wheel end demand torque is calculated according to the rate of change of the accelerator pedal opening, vehicle speed and brake pedal opening.

S32: Obtain the maximum braking torques of the first motor 1, the second motor 2, and the third motor 3 respectively, and the sum of the maximum braking torque of the first motor 1 and the maximum braking torque of the second motor 2 is M22.

Wherein, obtaining the maximum braking torque of the first motor 1 includes: obtaining a first temperature of the first motor 1 , a first charging voltage at an output terminal of the first motor 1 , and a maximum charging current of the first motor 1 . According to the first temperature, the first charging voltage, the maximum charging current of the first motor 1 from the map11 between the first temperature, the first charging voltage, the maximum charging current of the first motor 1 and the maximum braking torque of the first motor 1 Query the corresponding maximum charging torque of the first motor 1 in .

Obtaining the maximum braking torque of the second electric machine 2 includes: obtaining a second temperature of the second electric machine 2 , a second charging voltage at the output terminal of the second electric machine 2 , and a maximum charging current of the second electric machine 2 . From the map21 between the second temperature, the second charging voltage, the maximum charging current of the second motor 2 and the maximum braking torque of the second motor 2 according to the second temperature, the second charging voltage, and the maximum charging current of the second motor 2 Query the corresponding maximum charging torque of the second motor 2 in .

Obtaining the maximum braking torque of the third motor 3 includes: obtaining a third temperature of the third motor 3 , a third charging voltage at an output terminal of the third motor 3 , and a maximum charging current of the third motor 3 . From the map31 between the third temperature, the third charging voltage, the maximum charging current of the third motor 3 and the maximum braking torque of the third motor 3 according to the third temperature, the third charging voltage, and the maximum charging current of the third motor 3 Query the corresponding maximum charging torque of the third motor 3 in .

S33: Compare the sizes of M12 and M22.

In response to determination of M12≦M22, S34 is performed; in response to determination of M12>M22, S35 is performed.

S34: Control the clutch 5 to disengage, and only the first motor 1 and the second motor 2 generate power at the same time to output braking torque.

M12≤M22, it means that the output torque provided by the first motor 1 and the second motor 2 can meet the driver's expectation at this time, the clutch 5 is controlled to disengage, and only the first motor 1 and the second motor 2 provide braking torque.

S35: Control the engagement of the clutch 5, the first motor 1, the second motor 2 and the third motor 3 simultaneously generate power to output braking torque.

M12>M22, indicating that the first required torque is relatively large, and the braking torque provided by only the first motor 1 and the second motor 2 is not enough to meet the driver's driving expectations. At this time, the vehicle controller 65 can control the clutch 5 to engage, In order to make the three motors provide braking torque at the same time.

S36: Calculate the sum of the maximum braking torque of the first motor 1, the maximum braking torque of the second motor 2, and the maximum braking torque of the third motor 3 as M23.

S37: Compare the sizes of M12 and M23; in response to determining M12>M23; execute S38; in response to determining M12≦M23, execute S10.

S38: Start the hydraulic braking mechanism to brake the wheel ends.

M12>M23, indicating that even if the three motors provide braking torque at the same time, the driver's driving expectations cannot be met, and the hydraulic braking mechanism is activated to brake the wheel ends.

In the power system control method of the four-wheel drive pure electric vehicle, when only the first motor 1 and the second motor 2 are put into use to meet the driving needs, the third motor 3 can be turned off, thereby reducing the use time of the third motor 3 , prolong the service life of the third motor 3, and at the same time avoid the waste of energy caused by the limitation of the energy conversion efficiency of the third motor 3, thereby prolonging the cruising range.

The present application provides a power system control method and a power system of a four-wheel drive pure electric vehicle. The power system control method of the four drive pure electric vehicle includes: when the current working condition is a driving working condition, executing drive torque distribution. Executing the drive torque distribution includes obtaining the first required torque M11 for driving the vehicle, respectively obtaining the maximum output torques of the first motor, the second motor and the third motor, and the maximum output torque of the first motor and the maximum output torque of the second motor The sum of the maximum output torque is M21, compare the magnitudes of M11 and M21, and respond to the determination of M11>M21, control the clutch engagement, the first motor, the second motor and the third motor output torque at the same time, and the actual output torque of the first motor, The sum of the actual output torque of the second motor and the actual output torque of the third motor is equal to M11; in response to determining M11≤M21, the clutch is controlled to disengage, only the first motor and the second motor output torque, and the actual output of the first motor The sum of the torque and the actual output torque of the second motor is equal to M11. At this time, the use of the third motor can be avoided and the driving expectation of the driver can be met, thereby reducing the energy consumption caused by the fact that the conversion efficiency of the third motor itself cannot reach 100%. waste, thereby extending the cruising range of the car.

Claims

A power system control method of a four-wheel drive pure electric vehicle, the power system of the vehicle includes a first motor, a second motor, a third motor, a power battery and a clutch, the first motor and the second motor are respectively connected to the wheel end transmission connection, the third motor is selectively connected to the wheel end through the clutch, the power battery is configured to supply power to the first motor, the second motor and the third motor, and the The first motor, the second motor and the third motor can respectively generate electricity and charge the power battery; the method includes:

Obtain the current working condition of the vehicle;

performing drive torque distribution in response to determining that the current operating condition is a driving condition in which an accelerator pedal of the vehicle is depressed;

The execution of drive torque distribution includes:

Acquiring a first required torque M11 for driving the vehicle;

Obtaining the maximum output torques of the first motor, the second motor, and the third motor respectively, and the sum of the maximum output torque of the first motor and the maximum output torque of the second motor is M21;

Compare the size of M11 and M21;

In response to determining M11>M21, the clutch is controlled to engage, the first motor, the second motor and the third motor simultaneously output torque, and the actual output torque of the first motor, the second motor The sum of the actual output torque of and the actual output torque of the third motor is equal to M11;

In response to determining M11≤M21, the clutch is controlled to disengage, the first motor and the second motor output torque, and the sum of the actual output torque of the first motor and the actual output torque of the second motor is equal to M11.
The method according to claim 1, wherein said acquiring the first required torque M11 for driving the vehicle comprises:

calculating the required torque at the first wheel end of the vehicle according to the opening degree of the accelerator pedal, the vehicle speed and the rate of change of the opening degree of the accelerator pedal;

Calculate the maximum adhesion of multiple wheels of the vehicle according to the road surface adhesion parameters and wheel pressure parameters, and calculate the second wheel end required torque for driving the vehicle according to the maximum adhesion and the number of wheels of the vehicle ;

The smaller value of the first wheel-side required torque and the second wheel-side required torque is used as the first required torque.
The method according to claim 1, wherein,

Obtaining the maximum output torques of the first motor, the second motor and the third motor respectively includes:

Obtain the first temperature of the first motor, the first voltage of the input terminal of the first motor, and the maximum supply current of the first motor, according to the first temperature, the first voltage, the first The maximum power supply current of a motor is queried from the map1 between the first temperature, the first voltage, the first maximum power supply current and the maximum output torque of the first motor for the corresponding maximum output torque of the first motor;

Obtain the second temperature of the second motor, the second voltage of the input end of the second motor, and the maximum supply current of the second motor according to the second temperature, the second voltage, the second The maximum power supply current of the motor queries the corresponding maximum output torque of the second motor from the map2 between the second temperature, the second voltage, the second maximum power supply current and the maximum output torque of the second motor;

Obtain a third temperature of the third motor, a third voltage at the input terminal of the third motor, and a maximum supply current of the third motor, according to the third temperature, the third voltage, the first The maximum supply current of the three motors is searched for the corresponding maximum output torque of the third motor from map3 among the third temperature, the third voltage, the third maximum supply current and the maximum output torque of the third motor.
The method according to claim 1, further comprising:

performing braking torque distribution in response to determining that the current operating condition is a braking operating condition, wherein a brake pedal of the vehicle is depressed during the braking operating condition;

The braking torque distribution includes:

Acquiring a second required torque M12 for braking the vehicle;

Obtain the maximum braking torque of the first motor, the second motor and the third motor respectively, and the sum of the maximum braking torque of the first motor and the maximum braking torque of the second motor is M22;

Compare the size of M12 and M22;

In response to determining M12>M22, controlling the clutch engagement, the first motor, the second motor and the third motor simultaneously generate power to output braking torque;

In response to determining M12≦M22, the clutch is controlled to disengage, and the first motor and the second motor simultaneously generate power to output braking torque.
The method according to claim 4, wherein, after said controlling said clutch to be engaged, said first motor, said second motor and said third motor simultaneously generate power to output braking torque, further comprising:

Calculate the sum of the maximum braking torque of the first motor, the maximum braking torque of the second motor and the maximum braking torque of the third motor as M23;

Compare the size of M12 and M23;

In response to determining M12>M23, the hydraulic brake mechanism is activated to brake the wheel end.
A power system of a four-wheel-drive pure electric vehicle, comprising a first motor, a second motor, a third motor, a power battery, a clutch and a controller, the first motor and the second motor are respectively connected to the wheel end drive, The third motor is selectively connected to the wheel end through the clutch, the power battery is configured to supply power to the first motor, the second motor and the third motor, and the first The motor, the second motor and the third motor can respectively generate electricity and charge the power battery;

The controller is configured to implement the power system control method of the four-wheel drive pure electric vehicle described in any one of claims 1-5.
The system according to claim 6, wherein the power battery comprises at least one of a lithium ion power battery, a flywheel energy storage battery system, and a fuel cell system.
The system according to claim 6, wherein the first motor and the second motor are respectively connected to the rear axle in transmission, and the third motor is selectively connected to the front axle through the clutch.
The system of claim 8, further comprising: a front retarder;

The clutch is arranged between the third motor and the front reducer; the front reducer is connected to the front axle in transmission; or,

The third motor is in transmission connection with the front reducer, and the clutch is arranged between the front reducer and the front axle.
The system according to claim 6, wherein the first electric motor is in transmission connection with the front axle; the second electric motor is in transmission connection with the rear axle, and the third electric motor is selectively in transmission connection with the rear axle through the clutch.