CN113573941A

CN113573941A - Vehicle control device

Info

Publication number: CN113573941A
Application number: CN202080020282.5A
Authority: CN
Inventors: 宫本直树; 清水亮
Original assignee: Mitsubishi Motors Corp
Current assignee: Mitsubishi Motors Corp
Priority date: 2019-03-13
Filing date: 2020-03-10
Publication date: 2021-10-29
Anticipated expiration: 2040-03-10
Also published as: WO2020184537A1; CN113573941B; JP7127733B2; JPWO2020184537A1

Abstract

A vehicle control device is provided with a front motor (12) for a front wheel (11), a rear motor (14) for a rear wheel (13), an angular velocity calculation unit (15) for calculating the angular velocities of the motors before and after the motor rotation speed, an output calculation unit (17) for calculating a total output limit value that can be output from a battery (16) based on the state of the battery (16), and a torque calculation unit (18) for calculating the torque distribution to the front and rear motors (12, 14), when a difference in magnitude occurs between the axle speeds of the front and rear wheels (11, 13), the upper limit of the required torque is limited by a total torque limit value calculated based on the motor angular speed of the motor on the low rotation side, the torque of the motor on the low rotation side is maintained with respect to the torque request value after the torque distribution to the front and rear motors (12, 14), and limits the torque of the motor on the high rotation side based on the total torque limit value and the torque of the motor on the low rotation side.

Description

Vehicle control device

Technical Field

The present invention relates to a vehicle control device.

Background

In a four-wheel drive vehicle in which motors are provided for front wheels and rear wheels, such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle, a required torque is calculated based on an accelerator operation amount of a driver, and the required torque is distributed to front and rear motors. Electric power is supplied from the battery to the front and rear motors. The upper limit power of the supplied power from the battery is determined based on the battery state such as the battery temperature and the remaining battery level. When electric power is supplied from the battery to the front and rear motors, the torque distributed to the front and rear motors is limited so as not to exceed the upper limit electric power.

For example, in the control device of patent document 1, a required torque required by a driver is calculated based on an accelerator opening degree signal, a brake signal, a vehicle speed signal, an axis position signal, a signal corresponding to a behavior of a vehicle, and the like. Then, based on a prescribed torque distribution ratio, torques (command torques) that distribute the required torque to the front wheel side and the rear wheel side are calculated.

Here, torques that can be output from the front and rear rotating electrical machines (motors) are calculated. Then, a power distribution ratio, which is a distribution ratio of electric power from the battery to the rotating electric machine, is calculated based on the prescribed torque distribution ratio. Further, the power distribution ratio is corrected based on the outputable torques of the front and rear rotating electric machines, and electric power is distributed from the battery to the front and rear rotating electric machines based on the corrected power distribution ratio. In this way, the power supplied to the front and rear rotating electric machines is controlled so as not to exceed the upper limit power of the battery (see paragraphs 0036 to 0048 of patent document 1, fig. 3, and the like).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2015-53782

Technical problem to be solved by the invention

In the control device of patent document 1, when an angular velocity difference occurs between the angular velocities of the front and rear axles due to a slip or the like, the power balance between the front and rear motors may be lost. Here, a case where a slip occurs in the rear wheel and the angular velocity of the axle on the rear wheel side is greater than the angular velocity of the axle on the front wheel side will be described as an example. The relationship of P ═ T × ω among the output power P of the battery, the motor torque T, and the angular velocity ω is established, but with reference to the front wheel side (low ω) of low rotation, the apparent torque T of the above equation becomes large, exceeding the upper limit power of the battery, and there is a problem of accelerating the deterioration of the battery.

On the other hand, when the rear wheel side (high ω) of high rotation is used as a reference, the apparent torque T of the above equation has to be reduced, and there is a problem that the upper limit electric power of the battery cannot be used up and the power performance of the vehicle is impaired.

Disclosure of Invention

Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a four-wheel drive vehicle in which motors are provided to front wheels and rear wheels, respectively, and which can utilize the power supply capability of a battery in a small amount.

Means for solving the problems

In order to solve the above-described problem, the present invention provides a vehicle control device including: a front motor driving a front wheel; a rear motor driving the rear wheel; an angular velocity calculation unit that calculates motor angular velocities before and after the motor rotation speed of the front motor and the motor rotation speed of the rear motor, respectively; an output calculation unit that calculates a total output limit value that can be output from a battery that supplies electric power to the front motor and the rear motor, based on a state of the battery; and a torque calculation unit that calculates torque distribution to the front motor and the rear motor, wherein when a difference in magnitude occurs between the axle speeds of the front wheel and the rear wheel calculated from the motor angular speed calculated by the angular speed calculation unit, an upper limit of a required torque calculated based on an accelerator operation amount of a driver is limited by a total torque limit value calculated based on a motor angular speed of a motor on a low rotation side of the front motor and the rear motor, and wherein a torque of the motor on the low rotation side is maintained for a torque required value after the torque distribution to the front motor and the rear motor, and a torque of the motor on a high rotation side is limited based on the total torque limit value and the torque of the motor on the low rotation side.

In the above-described configuration, when the rate of increase in the motor angular velocity of the front motor and the rear motor during traveling is smaller than a predetermined value set in advance, the motor angular velocity may be calculated based on the current value of the motor rotational speed at each time during traveling, and when the rate of increase in the motor angular velocity is equal to or greater than the predetermined value, the motor angular velocity may be calculated based on a predicted value of the motor rotational speed predicted from the current value of the motor rotational speed at the rate of increase.

In each of the above configurations, the corrected axle speed of the front wheel obtained by adding a predetermined speed correction value set in advance to the axle speed of the front wheel may be calculated, and the magnitude relationship between the corrected axle speed and the axle speed of the rear wheel may be determined.

In this configuration, the speed correction value applied at the time of turning, the time of acceleration, or the time of climbing may be configured to be increased with respect to the speed correction value applied at the time of straight-ahead traveling at a constant speed.

Effects of the invention

In the present invention, a vehicle control device is configured to include: a front motor driving a front wheel; a rear motor driving the rear wheel; an angular velocity calculation unit that calculates motor angular velocities before and after the motor rotation speed of the front motor and the motor rotation speed of the rear motor, respectively; an output calculation unit that calculates a total output limit value that can be output from a battery that supplies electric power to the front motor and the rear motor, based on a state of the battery; and a torque calculation unit that calculates torque distribution to the front motor and the rear motor, wherein when a difference in magnitude occurs between the axle speeds of the front wheel and the rear wheel calculated from the motor angular speed calculated by the angular speed calculation unit, an upper limit of a required torque calculated based on an accelerator operation amount of a driver is limited by a total torque limit value calculated based on a motor angular speed of a motor on a low rotation side of the front motor and the rear motor, and wherein a torque of the motor on the low rotation side is maintained for a torque required value after the torque distribution to the front motor and the rear motor, and a torque of the motor on a high rotation side is limited based on the total torque limit value and the torque of the motor on the low rotation side. According to this vehicle control device, in a four-wheel drive type vehicle in which the motors are provided in the front wheels and the rear wheels, respectively, the power supply capacity of the battery can be utilized as much as possible.

Drawings

Fig. 1 is a schematic diagram showing an example of a vehicle (four-wheel drive vehicle) on which a vehicle control device according to the present invention is mounted.

Fig. 2 is a flowchart showing a processing flow of the vehicle control device.

Fig. 3 is a control block diagram (based on output) of the vehicle control apparatus.

Fig. 4 is a control block diagram (based on torque) of the vehicle control device.

Fig. 5 is a timing chart of the vehicle control apparatus.

Fig. 6 is a diagram illustrating correction of the motor angular velocity.

Detailed Description

Fig. 1 shows an example of a vehicle 10 on which a vehicle control device according to the present invention is mounted. The vehicle 10 is a four-wheel drive vehicle in which

motors

12 and 14 are provided on front and

rear wheels

11 and 13, respectively.

The main structural elements of the vehicle control device are: a front motor 12 for driving the front wheels 11, a rear motor 14 for driving the rear wheels 13, an angular velocity calculation unit 15 for calculating the angular velocities of the front and rear motors from the motor rotation speeds of the front and

rear motors

12, 14, respectively, an output calculation unit 17 for calculating a total output limit value that can be output from the battery 16 based on the state of the battery 16 for supplying electric power to the front and

rear motors

12, 14, and a torque calculation unit 18 for calculating the torque distribution to the front and

rear motors

12, 14. As shown in fig. 1, the angular velocity calculation unit 15, the output calculation unit 17, and the torque calculation unit 18 may be included in a part of the functions of the electronic control unit 19, but may be configured separately from the electronic control unit 19.

The axle speed of the front and

rear wheels

11, 13 can be calculated by multiplying a predetermined conversion factor by the motor angular speed calculated by the angular speed calculation unit 15. Specifically, the front axle speed is calculated by multiplying the motor angular speed of the front motor 12 by the front motor conversion factor, and the rear axle speed is calculated by multiplying the motor angular speed of the rear motor 14 by the rear motor conversion factor.

The depression amount of the accelerator pedal 20 by the driver is detected by the depression force sensor 21. Then, based on the detection value of the pedaling force sensor 21, the required torque of the driver is calculated by a required torque calculation unit 22 provided in the electronic control unit 19.

When the vehicle is running without slipping at both the front and

rear wheels

11, 13, the front axle speed and the rear axle speed match. On the other hand, if a slip occurs in at least one of the front and

rear wheels

11, 13, the axle speed of the front and

rear wheels

11, 13 may be deviated. For example, when the front axle speed is greater than the rear axle speed, it can be determined that a slip is generated in the front wheels 11. On the other hand, when the rear axle speed is higher than the front axle speed, it can be determined that a slip is generated at the rear wheels 13. This slip may occur not only on the front and

rear wheels

11, 13 but also on both the front and

rear wheels

11, 13.

The total output limit value of the battery 16 is calculated based on the battery state such as the battery temperature and the remaining battery level. Since the output of the battery 16 decreases as the battery temperature decreases and the remaining battery level decreases, the total output limit value is substantially suppressed to be small.

The torque distribution to the front and

rear motors

12 and 14 is basically a predetermined ratio (for example, 4: 6) set in advance, but the torque distribution to the front and

rear motors

12 and 14 is appropriately corrected by the torque calculation unit 18 in accordance with the axle speed difference between the front and

rear wheels

11 and 13 detected by the angular speed calculation unit 15.

Fig. 2 is a flowchart showing a processing flow of the vehicle control device. In this processing flow, first, the output arithmetic unit 17 calculates a total output limit value corresponding to the upper limit electric power of the battery 16 (step S1). Next, the angular velocity calculation unit 15 calculates the front motor angular velocity of the front motor 12 and the rear motor angular velocity of the rear motor 14, respectively (steps S2 and S3).

Further, the magnitudes of the front axle speed and the rear axle speed calculated by the angular speed calculation unit 15 are compared (step S4). When the front axle speed is less than the rear axle speed (yes in step S4), the driver required torque is limited by the torque value obtained by dividing the total output limit value of the battery 16 by the angular speed of the front motor (step S5). Then, the rear torque is limited by a torque value obtained by dividing the value obtained by subtracting the output of the front motor from the total output limit value by the angular velocity of the rear motor (step S6), and the series of processing procedures ends (step S7).

On the other hand, when the current axle speed is equal to or higher than the rear axle speed (no in step S4), the driver-requested torque is limited by a torque value obtained by dividing the total output limit value of the battery 16 by the rear motor angular speed (step S8). Then, the front torque is limited by a torque value obtained by dividing the value obtained by subtracting the output of the rear motor from the total output limit value by the angular velocity of the front motor (step S9), and the series of processing procedures is terminated (step S7).

As shown in this series of processing flows, the required torque required by the driver is limited based on the angular velocity of the motor on the side of the front and

rear wheels

11, 13 where the axle velocity is low, and therefore the power supply capability of the battery 16 can be fully utilized without a margin. Further, the surplus torque of the required torque distributed to the wheel side at the low axle speed is distributed to the side (the side at which the slip occurs) of the front and

rear wheels

11, 13 at which the axle speed is high (the side at which the torque at the high axle speed is limited), and therefore, the limited torque can suppress an excessive increase in the axle speed due to the slip, and realize stable running.

Fig. 3 and 4 show control block diagrams of the vehicle control device. Fig. 3 is a diagram showing the calculation of the motor torques of the front and

rear wheels

11, 13 based on the total output limit value (based on the output) of the battery 16, and fig. 4 is a diagram showing the calculation of the motor torques of the front and

rear wheels

11, 13 based on the total torque limit values (based on the torques) of the front and

rear motors

12, 14, respectively.

In the control block diagram shown in fig. 3, a total output limit value (block B2) corresponding to the upper limit electric power of the battery 16 (block B1) is calculated. Here, a total torque limit value is calculated (block B5) based on the total output limit value (block B2), the front motor angular velocity (block B3), and the rear motor angular velocity (block B4). The total torque limit value can be calculated by the following equation a.

Total torque limit value ═ total output limit value ÷ motor angular velocity (a type)

Note that, the total torque limit value may be calculated as needed using equation a, or a map calculated in advance may be provided in the vehicle 10, and a value determined from the map may be selected to shorten the control time.

Here, the motor angular velocity is selected from the angular velocities of the motors on the low rotation side of the front and

rear motors

12 and 14. In the formula a, by selecting one of the angular velocities of the front and

rear motors

12 and 14 calculated by the angular velocity calculation unit 15, the formula a can be applied to the control at all times regardless of the magnitude of the angular velocity of the front and

rear motors

12 and 14. Therefore, a delay associated with switching of the control type can be eliminated, and a trouble such as a torque loss during driving operation can be prevented.

Further, the total torque limit value (block B5) is set as an upper limit, and the limit of the total torque is applied to the required torque (block B6) requested by the driver (block B7). Then, based on the total torque limit, torque distribution to the front and

rear motors

12, 14 is calculated (block B8), and outputs to the front and

rear motors

12, 14 are distributed according to the torque distribution.

Here, when the motor angular velocity of the front motor 12 is smaller than the motor angular velocity of the rear motor 14, the rear torque limit value is calculated (block B9) based on the output split from the front motor 12, the total output limit value (block B2), and the rear motor angular velocity (block B4). The rear torque limit value can be calculated by the following equation B.

Rear torque limit (total output limit-front motor output)/rear motor angular velocity (B type)

Note that, instead of calculating the rear torque limit value as needed using equation B, the vehicle 10 may have a map calculated in advance, and a value determined from the map may be selected to shorten the control time.

Further, the rear motor torque is determined (block B11) by limiting the rear torque (block B10) by comparing the torque distribution to the rear motor 14 (block B8) and the rear torque limit value (block B9).

In addition, when the motor angular velocity of the rear motor 14 is smaller than the motor angular velocity of the front motor 12, the front torque limit value is calculated (block B12) based on the output split from the rear motor 14, the total output limit value (block B2), and the front motor angular velocity (block B3). The front torque limit value can be calculated by the following equation C.

Front torque limit (total output limit-rear motor output) ÷ front motor angular velocity (C type)

Note that, in addition to the calculation of the rear torque limit value as needed using the above-described formula C, the vehicle 10 may be provided with a map calculated in advance, and a value determined from the map may be selected to shorten the control time.

Further, the front motor torque is determined (block B14) by limiting the front torque (block B13) by comparing the torque distribution to the front motor 12 (block B8) and the front torque limit value (block B12).

The basic configuration of the control block diagram shown in fig. 4 is common to the control block diagram shown in fig. 3 (blocks B1 to B14). On the other hand, the calculation of the front torque limit value (block B12) and the calculation of the rear torque limit value (block B9) differ in that the total torque limit value (block B5) is used instead of the total output limit value (block B2), the front-rear motor torque (block B8) is used instead of the front-rear motor output, and the angular velocity ratio (block B15) is used instead of the angular velocities of the front-rear motors 12, 14 (blocks B3, B4), respectively.

In this case, the following formula B 'is used instead of the above formula B for calculating the rear torque limit value, and the following formula C' is used instead of the above formula C for calculating the front torque limit value. The angular velocity ratio is defined by the following formula D.

Rear torque limit value (total torque limit value-front motor torque) x angular velocity ratio (B' type)

Front torque limit value ═ (total torque limit value-rear motor torque) ÷ angular velocity ratio (C' type)

Angular velocity ratio of front motor angular velocity ÷ rear motor angular velocity (D type)

Note that, instead of calculating the rear torque limit value as needed using the above-described B ', C ', and D ' equations, a map obtained by calculation in advance may be provided in the vehicle 10, and a value determined from the map may be selected to shorten the control time.

The control block diagram shown in fig. 3 and the control block diagram shown in fig. 4 are different only in the calculation of the motor torque before and after the output-based or torque-based control, and the contents of these controls are common.

The processing flow (fig. 2) based on the flowchart described above and the control (fig. 3 and 4) based on the control block are continuously performed while the vehicle 10 is traveling. This control is a control for limiting the front-rear torque based on the front-rear axle speed, and can be combined with other controls such as traction control for suppressing a slip.

Fig. 5 is a timing chart showing the operation of the vehicle 10 when the control is performed based on the above-described control. The time chart shows, in order from the upper stage to the lower stage, "vehicle speed", "axle torque" (the sum of front and rear torques), "front axle motor torque", "rear axle motor torque", and "vehicle drive power and battery power".

As indicated by the "vehicle speed" section, the vehicle 10 is accelerated by the depression amount of the accelerator pedal 20 by the driver. Here, the vehicle body speed is an ideal vehicle speed (based on the depression amount of the accelerator pedal 20) expected by the driver. In this vehicle speed example, the front axle speed and the rear axle speed are both large relative to the vehicle body speed, and the rear axle speed is greater than the front axle speed. This means that the front and

rear wheels

11, 13 both slip with acceleration, and particularly the amount of slip on the rear wheel 13 side is large.

As indicated by the segment "vehicle drive power and battery power", the vehicle drive power accompanies the slave parking state (time t)₀) The acceleration started is increased and at time t₁To the upper limit of the power of the battery. If continuing to move forwards and backwardsWhen the

motors

12 and 14 supply electric power, the vehicle driving electric power exceeds the upper limit electric power of the battery 16 (time t)₁Later), the charge capacity of the battery 16 may decrease.

Then, when the vehicle driving power reaches the upper limit power of the battery 16 (time t)₁) As indicated by the "rear axle motor torque" section, the motor torque of the rear axle having a relatively high axle speed is limited. As a result, the vehicle drive power can be suppressed to the upper limit power of the battery, and the rear axle speed can be brought close to the front axle speed as indicated by the "vehicle speed" range, thereby achieving stable running of the vehicle 10.

When the difference between the front axle speed and the rear axle speed is small, the vehicle drive power may not be limited to the upper limit power of the battery 16 even if only the motor torque on the high-speed rear axle side is limited. In this case, as shown in the "front axle motor torque" section, the low-speed front axle motor torque is also limited (time t)₂Later), thereby suppressing the vehicle driving power.

Next, the correction of the motor angular velocity will be described with reference to fig. 6. As described above, the motor angular velocity is calculated by the angular velocity calculation unit 15 based on the motor rotation speed. At this time, the current value (actual value) at that time is used as the motor rotation speed. However, the current value is transmitted within the control system with a slight communication delay, and when the rate of increase in the motor angular velocity is large, such as when the vehicle 10 suddenly slips during normal running, a delay in the control may occur due to the communication delay (see the control value in fig. 6 (before correction)).

Then, at a time (time t) when the rate of increase of the angular velocity of the motor becomes greater than a predetermined value (switching threshold value) set in advance₁) The motor angular velocity is corrected based on a predicted value of the motor rotational velocity corresponding to the rate of increase thereof, instead of the current value of the motor rotational velocity. By performing the correction in this way, the control value of the motor angular velocity can be made close to the actual value (see the control value in fig. 6 (after correction)), and the motor angular velocity can be controlled with high accuracy. In order to improve the accuracy of the control value, the correction is preferably made larger as the rate of increase in the angular velocity of the motor increases.

In the flowchart of fig. 2, the magnitude is directly compared between the front axle speed and the rear axle speed, but the magnitude may be compared between the rear axle speed and a value obtained by adding a predetermined speed correction value to the front axle speed, as shown in the following equation E.

Front axle speed + speed correction value < rear axle speed (E type)

When the vehicle 10 is accelerated, a driving torque larger than that of the front wheels 11 may be applied to the rear wheels 13, and a maximum traction force may be obtained when the rear wheels 13 tend to slightly slip. In this case, as shown in equation E, the speed correction value is added to the front axle speed to allow the rear wheels 13 to slightly slip, thereby ensuring higher running performance. The speed correction value can be appropriately changed in consideration of the running state of the vehicle 10, and for example, it is preferable that the speed correction value in a running state requiring a large traction force such as during turning, acceleration, and climbing is made larger than the speed correction value in a straight-ahead running at a constant speed.

The configuration of the vehicle control device, the flowchart, the control block, the timing chart, and the correction of the motor angular velocity described above are merely simple examples for describing the present invention, and in the four-wheel drive vehicle 10 in which the

motors

12 and 14 are provided for the front wheels 11 and the rear wheels 13, respectively, appropriate changes can be made to the above-described components, the processing flow, and the like as long as the technical problem of the present invention can be solved, that is, the power supply capability of the battery 16 is not used much or little.

The vehicle control device can be widely applied to a vehicle 10 in which front and

rear wheels

11 and 13 are provided with

motors

12 and 14, respectively, such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle.

Description of the symbols

10 vehicle

11 front wheel

12 front motor

13 rear wheel

14 rear motor

15 angular velocity calculating part

16 cell

17 output calculation unit

18 torque calculation unit

19 electronic control unit

20 accelerator pedal

21 stepping force sensor

22 requested torque calculation unit

Claims

1. A vehicle control device is characterized by comprising:

a front motor driving a front wheel;

a rear motor driving the rear wheel;

an angular velocity calculation unit that calculates motor angular velocities before and after the motor rotation speed of the front motor and the motor rotation speed of the rear motor, respectively;

an output calculation unit that calculates a total output limit value that can be output from a battery that supplies electric power to the front motor and the rear motor, based on a state of the battery; and

a torque calculation section that calculates a torque distribution to the front motor and the rear motor,

when a difference in magnitude occurs between the axle speeds of the front and rear wheels calculated from the motor angular speed calculated by the angular speed calculation unit, the upper limit of the required torque calculated from the accelerator operation amount of the driver is limited by a total torque limit value calculated from the total output limit value based on the motor angular speed of the motor on the low rotation side of the front and rear motors, and the torque of the motor on the high rotation side is limited based on the total torque limit value and the torque of the motor on the low rotation side while maintaining the torque of the motor on the low rotation side with respect to the torque required value after the torque distribution to the front and rear motors.

2. The vehicle control apparatus according to claim 1,

when the rate of increase of the motor angular velocity of the front motor and the rear motor during traveling is smaller than a predetermined value set in advance, the motor angular velocity is calculated based on the current value of the motor rotational speed at each time during traveling, and when the rate of increase of the motor angular velocity is equal to or larger than the predetermined value, the motor angular velocity is calculated based on a predicted value of the motor rotational speed predicted from the current value of the motor rotational speed at the rate of increase.

3. The vehicle control apparatus according to claim 1 or 2,

a corrected axle speed of the front wheel is calculated by adding a predetermined speed correction value set in advance to the axle speed of the front wheel, and the magnitude relationship between the corrected axle speed and the axle speed of the rear wheel is determined.

4. The vehicle control apparatus according to claim 3,

the speed correction value applied at the time of turning, at the time of acceleration, or at the time of climbing is increased relative to the speed correction value applied at the time of straight-ahead travel at a constant speed.