Vehicle control device

Abstract

To prevent a wheel speed of a drive wheel while traveling on an uneven road from significantly exceeding a rotation speed of an electric motor which inputs and outputs power into and from a drive shaft connected to the drive wheel.SOLUTION: A vehicle control device is mounted on an electric vehicle provided with an electric motor for traveling and a brake device. The vehicle control device predicts a wheel speed predicted value as a predicted value of a wheel speed of a drive wheel and a rotation speed predicted value obtained by being converted into a wheel speed of a predicted value of a rotation speed of the electric motor. When the wheel speed predicted value while traveling on an uneven road is larger than the rotation speed predicted value by a predetermined threshold or more, the vehicle control device controls the electric motor and the brake device so as to reduce a difference between the wheel speed of the drive wheel and the rotation speed of the electric motor.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a vehicle control device, and more particularly, to a vehicle control device mounted on an electric vehicle that includes an electric motor for driving capable of inputting and outputting power to a drive shaft connected to drive wheels, and a brake device capable of applying a braking force to the drive wheels. [Background technology]

[0002] Conventionally, a vehicle control device of this type has been proposed which, when a slip state of the drive wheels is detected based on the difference between the rotation speed of the motor and the rotation speed of the driven wheels, controls the motor to reduce the torque of the motor so as to converge to a target control wheel speed, and controls the rotation speed of the drive wheels using a braking device based on the rotation speed of the drive wheels and the rotation speed of the driven wheels (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-091388 A Summary of the Invention [Problem to be solved by the invention]

[0004] When traveling over a bump, the drive wheels tend to lift off the ground immediately after climbing over the bump, and the wheel speed of the drive wheels significantly exceeds the rotation speed of the motor that inputs and outputs power to the drive shaft. When the vehicle touches the ground after passing over the bump immediately after this state, a torque corresponding to the difference in rotation speed between the wheel speed of the drive wheels and the rotation speed of the motor acts on the drive shaft, and if the difference in rotation speed is large, there is a risk of damaging the drive shaft.

[0005] The main objective of the vehicle control device disclosed herein is to prevent the wheel speed of the drive wheels from significantly exceeding the rotation speed of an electric motor that inputs and outputs power to a drive shaft connected to the drive wheels when traveling over a stepped road. [Means for solving the problem]

[0006] The vehicle control device of the present disclosure employs the following means to achieve the above-mentioned main object.

[0007] The vehicle control device according to the present disclosure includes: A vehicle control device is mounted on an electric vehicle including an electric motor for driving capable of inputting and outputting power to a drive shaft connected to drive wheels, and a brake device capable of applying a braking force to the drive wheels, and controls the electric motor and the brake device, predicting a wheel speed prediction value as a prediction value of the wheel speed of the drive wheels and a rotation speed prediction value obtained by converting a prediction value of a rotation speed of the electric motor into a wheel speed; When the wheel speed prediction value becomes larger than the rotation speed prediction value by a predetermined threshold value or more when traveling on a stepped road, the electric motor and / or the brake device is controlled in a direction such that a difference between the wheel speed of the driving wheels and the rotation speed of the electric motor becomes smaller. It is characterized by:

[0008] The vehicle control device of the present disclosure is mounted on an electric vehicle equipped with a driving electric motor capable of inputting and outputting power to a drive shaft connected to a drive wheel, and a brake device capable of applying a braking force to the drive wheel, and controls the electric motor and the brake device. Then, a wheel speed prediction value as a prediction value of the wheel speed of the drive wheel and a rotation speed prediction value obtained by converting a predicted value of the rotation speed of the electric motor into a wheel speed are predicted, and when the wheel speed prediction value becomes larger than the rotation speed prediction value by a predetermined threshold or more when traveling on a step road, the electric motor and the brake device are controlled in a direction to reduce the difference between the wheel speed of the drive wheel and the rotation speed of the electric motor. This reduces the difference between the wheel speed of the drive wheel and the rotation speed of the electric motor, and when traveling on a step road, it is possible to prevent the wheel speed of the drive wheel from greatly exceeding the rotation speed of the electric motor that inputs and outputs power to the drive shaft connected to the drive wheel. As a result, it is possible to prevent excessive torque from acting on the drive shaft when the vehicle touches the ground immediately after running over a step. [Brief description of the drawings]

[0009] [Figure 1]1 is a diagram showing an outline of the configuration of an electric vehicle 20 equipped with a vehicle control device according to an embodiment of the present disclosure. [Diagram 2] 4 is a flowchart showing an example of a step road traveling process executed by an electronic control unit 40. [Diagram 3] 11 is an explanatory diagram showing an example of changes over time in drive shaft torque, wheel speed, and motor rotation speed when a step road traveling process is executed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Next, an embodiment of the present disclosure will be described. Fig. 1 is a schematic diagram showing the configuration of an electric vehicle 20 equipped with a vehicle control device according to an embodiment of the present disclosure. As shown in the figure, the electric vehicle 20 of the embodiment includes a motor 22, an inverter 24, a battery 30, a system main relay 34, an electronic control unit 40, and a brake device 60. The electronic control unit 40 corresponds to the vehicle control device of the embodiment.

[0011] The motor 22 is configured as a synchronous generator motor, and includes a rotor in which a permanent magnet is embedded and a stator around which a three-phase coil is wound. The rotor of the motor 22 is connected to a drive shaft 26 that is connected to drive wheels 28a, 28b via a differential gear 27.

[0012] The inverter 24 is connected to the motor 22 and also to the power line 32. The inverter 24 is configured as a well-known inverter circuit having six transistors and six diodes.

[0013] The battery 30 is configured as, for example, a lithium ion secondary battery or a nickel-hydrogen secondary battery, and is connected to a power line 32. A system main relay 34 is attached to the power line 32. Although not shown, the system main relay 34 has a positive relay provided on a positive bus bar of the power line 32, a negative relay provided on a negative bus bar of the power line 32, and a precharge circuit in which a precharge resistor and a precharge relay are connected in series to bypass the negative relay. A smoothing capacitor 36 and auxiliary equipment (not shown) are also connected to the power line 32.

[0014] The electronic control unit 40 is configured as a microprocessor centered around a CPU 42, and in addition to the CPU 42, includes a ROM 44 for storing processing programs, a RAM 46 for temporarily storing data, a flash memory (not shown), an input / output port (not shown), a communication port (not shown), etc.

[0015] Signals from various sensors are input to the electronic control unit 40 via input ports. Examples of signals input to the electronic control unit 40 include a rotational position θm from a rotational position detection sensor (e.g., resolver) 22a that detects the rotational position of the rotor of the motor 22, a voltage VB from a voltage sensor 31a attached between the terminals of the battery 30, and a current IB from a current sensor 31b attached to the output terminal of the battery 30. Also included is a voltage Vin of the capacitor 36 (power line 32) from a voltage sensor 37 attached between the terminals of the capacitor 36. Further examples include a start signal from a start switch 50, a shift position SP from a shift position sensor 52 that detects the operation position of the shift lever 51, an accelerator opening from an accelerator pedal position sensor 54 that detects the depression amount of an accelerator pedal 53, a brake pedal position from a brake pedal position sensor 56 that detects the depression amount of a brake pedal 55, and a vehicle speed V from a vehicle speed sensor.

[0016] Various control signals are output via an output port from the electronic control unit 70. Examples of signals output from the electronic control unit 70 include a switching control signal to the transistor of the inverter 24, a drive control signal to the system main relay 34, and the like.

[0017] The brake device 60 includes a brake actuator 62 and a brake electronic control unit (hereinafter referred to as brake ECU) 64. The brake actuator 62 is configured to adjust the hydraulic pressure of the pistons of the disc brakes 66a to 66d so that a braking force corresponding to a brake share in the braking force acting on the vehicle according to the pressure (brake pressure) of the brake master cylinder 61 generated in response to depression of the brake pedal and the vehicle speed V acts on the driven wheels 29a, 29b and the driving wheels 28a, 28b, and to adjust the hydraulic pressure of the pistons of the disc brakes 66a to 66d so that a braking force acts on the driven wheels 29a, 29b and the driving wheels 28a, 28b regardless of depression of the brake pedal 55. Hereinafter, the braking force acting on the driven wheels 29a, 29b and the driving wheels 28a, 28b by the operation of the brake actuator 62 may be referred to as a hydraulic brake. The brake actuator 62 is controlled by the brake ECU 64. The brake ECU 64 communicates with the electronic control unit 40, drives and controls the brake actuator 62 according to control signals from the electronic control unit 40, and outputs data relating to the state of the brake actuator 62 to the electronic control unit 40 as necessary.

[0018] The brake ECU 64 receives signals such as wheel speeds Vdr, Vdl, Vnr, and Vnl from wheel speed sensors 68a to 68d attached to the drive wheels 28a, 28b and driven wheels 29a, 29b, and steering angles from a steering angle sensor (not shown), and calculates braking torques to be applied to the drive wheels 28a, 28b and driven wheels 29a, 29b when the driver depresses the brake pedal 55. The brake ECU 64 then divides the braking torque to be applied to the drive wheels 28a, 28b into braking torques by the disc brakes 66a, 66b and braking torques by regenerative control of the motor 22. The brake actuator 62 is driven and controlled so that the braking torques to be applied from the disc brakes 66a to 66d are applied. The braking torque due to the regenerative control of the motor 22 is transmitted to the electronic control unit 40, and the electronic control unit 40 receives this and controls the switching of the switching elements of the inverter 24 so that the braking torque that should be output to the motor 22 is output.

[0019] The brake ECU 64 also performs vehicle behavior stability control such as anti-lock brake system (ABS) control to prevent either the driven wheels 29a, 29b or the driving wheels 28a, 28b from locking and slipping when the driver depresses the brake pedal 55, traction control (TRC) to prevent either the driven wheels 29a, 29b or the driving wheels 28a, 28b from slipping due to spinning when the driver depresses the accelerator pedal, and vehicle stance maintenance control (VSC) to maintain the vehicle stance when the vehicle is turning.

[0020] Further, the electronic control unit 70 predicts a wheel speed prediction value Vest, which is the future wheel speed of the drive wheels 28a, 28b, and a rotation speed prediction value Nest, which is a wheel speed conversion value of the future rotation speed of the motor 22. In the embodiment, the wheel speed prediction value Vest and the rotation speed prediction value Nest are obtained using a trained model obtained by machine learning using the vehicle speed V, the wheel speeds Vdr, Vdl, Vnr, Vnl, the pressure of the brake master cylinder 61, the vehicle height, the torque Tm of the motor 22, the rotation speed Nm of the motor 22, and the like as input data, and the wheel speeds Vdr, Vdl of the drive wheels 28a, 28b 5 msec later, 10 msec later, 15 msec later, and 20 msec later as teacher data.

[0021] Next, the operation of the electric vehicle 20 of this embodiment configured as described above, in particular the operation when traveling over a stepped road, will be described. FIG 2 is a flow chart showing an example of a process for traveling over a stepped road executed by the electronic control unit 40.

[0022] When the step road traveling process is executed, the electronic control unit 40 first determines whether or not the slip prevention control is being executed (step S100). The slip prevention control is executed when slippage is occurring or when there is a possibility of slippage, so this process, which targets slippage immediately after going over a step road, is executed only when the slip prevention control is being executed. As the slip prevention control, for example, a process of imposing a limit on the torque Tm of the motor 22 is executed. When it is determined in step S100 that the slip prevention control is not being executed, it is determined that this process is not applicable, and this process is terminated.

[0023] When it is determined in step S100 that slip suppression control is being executed, the wheel speed prediction value Vest and the rotation speed prediction value Nest are input (step S110). As described above, the wheel speed prediction value Vest and the rotation speed prediction value Nest are the wheel speeds of the driving wheels 28a, 28b and the rotation speed of the motor 22 for a predetermined time (5 msec, 10 msec, 15 msec, 20 msec, etc.) in the future, and can be obtained by applying the vehicle speed V, the wheel speeds Vdr, Vdl, Vnr, Vnl, the pressure of the brake master cylinder 61, the vehicle height, the torque Tm of the motor 22, the rotation speed Nm of the motor 22, etc. to the trained model obtained by the above-mentioned machine learning.

[0024] Then, it is determined whether the value obtained by subtracting the predicted rotation speed value Nest from the predicted wheel speed value Vest is greater than the threshold value Vref or more, in other words, whether the predicted wheel speed value Vest is greater than the predicted rotation speed value Nest by the threshold value Vref or more (step S120). If it is determined that the value obtained by subtracting the predicted rotation speed value Nest from the predicted wheel speed value Vest is less than the threshold value Vref, it is determined that no excessive torque is acting on the drive shaft 26, and this process is terminated.

[0025] When it is determined in step S120 that the value obtained by subtracting the rotation speed predicted value Nest from the wheel speed predicted value Vest is greater than or equal to the threshold value Vref, it is determined that there is a possibility that excessive torque is acting on the drive shaft 26, and the motor 22 and the brake device 60 are controlled so that the difference between the wheel speeds Vdr, Vdl of the drive wheels 28a, 28b and the rotation speed Nm of the motor 22 becomes smaller (step S130), and this process ends. Specifically, this control is performed by reducing the output torque of the motor 22 and applying a braking force to the drive wheels 28a, 28b by the brake actuator 62 of the brake device 60.

[0026] FIG. 3 is an explanatory diagram showing an example of the change over time of the drive shaft torque, the wheel speed, and the motor rotation speed when the step road traveling process is executed. In the figure, the solid line in the drive shaft torque indicates the change over time of the drive shaft torque when the step road traveling process is not executed, and the thick dashed line indicates the change over time of the drive shaft torque when the step road traveling process is executed. The solid lines in the wheel speed and the motor rotation speed indicate the change over time of the wheel speed of the drive wheel when the step road traveling process is not executed, the dashed line indicates the change over time of the motor rotation speed when the step road traveling process is not executed, and the thick dashed line indicates the change over time of the wheel speed when the step road traveling process is executed. If it is determined that the wheel speed (wheel speed predicted value Vest) predicted at time T1 and time T2 is larger than the rotation speed (rotation speed predicted value Nest) of the motor 22 predicted in the same manner by more than the threshold value Vref, the difference between the wheel speed and the motor rotation speed is controlled to be small, and the wheel speed becomes small as shown by the thick dashed line. For this reason, the drive shaft torque becomes small as indicated by the thick dashed line, and it is possible to prevent excessive torque from acting on the drive shaft when the vehicle comes into contact with the ground immediately after going over the step (time T3).

[0027] In the electric vehicle 20 according to the embodiment described above, when the wheel speed prediction value Vest becomes greater than the rotation speed prediction value Nest by at least the threshold value Vref while traveling over a stepped road, the motor 22 is controlled in a direction to reduce the difference between the wheel speeds Vdr, Vdl of the driving wheels 28a, 28b and the rotation speed Nm of the motor 22, and the brake device 60 is also controlled. This makes it possible to prevent the wheel speeds Vdr, Vdl of the driving wheels 28a, 28b from significantly exceeding the rotation speed Nm of the motor 22 that inputs and outputs power to the driving shaft 26 connected to the driving wheels 28a, 28b while traveling over a stepped road, and as a result, makes it possible to prevent excessive torque from acting on the driving shaft 26 when the vehicle touches the ground immediately after going over a step.

[0028] In the embodiment, the electric vehicle 20 is configured to include a motor 22. However, the electric vehicle may be configured as an electric vehicle having various configurations, such as a fuel cell vehicle, as long as the electric vehicle is equipped with a motor and a brake device.

[0029] The correspondence between the main elements of the embodiment and the main elements of the invention described in the section on means for solving the problem will be described below. In the embodiment, the motor 22 corresponds to the "electric motor", the brake device 60 corresponds to the "brake device", and the electronic control unit 40 corresponds to the "vehicle control device".

[0030] Note that the correspondence between the main elements of the embodiment and the main elements of the invention described in the Means for Solving the Problem column does not limit the elements of the invention described in the Means for Solving the Problem column, since the embodiment is an example for specifically explaining the form for implementing the invention described in the Means for Solving the Problem column. In other words, the interpretation of the invention described in the Means for Solving the Problem column should be made based on the description in that column, and the embodiment is merely a specific example of the invention described in the Means for Solving the Problem column.

[0031] Although the embodiments of the present disclosure have been described above, the present disclosure is in no way limited to these embodiments, and it goes without saying that the present disclosure can be embodied in various forms without departing from the gist of the present disclosure. [Industrial Applicability]

[0032] The present disclosure can be used in the vehicle control device manufacturing industry and the like. [Explanation of symbols]

[0033] 20 electric vehicle, 22 motor, 22a rotational position detection sensor, 24 inverter, 26 drive shaft, 27 differential gear, 28a, 28b drive wheels, 29a, 29b driven wheels, 30 battery, 31a voltage sensor, 31b current sensor, 32 power line, 34 system main relay, 36 capacitor, 37 voltage sensor, 38 auxiliary equipment, 40 electronic control unit, 42 CPU, 44 ROM, 46 RAM, 50 start switch, 51 shift lever, 52 shift lever position sensor, 53 accelerator pedal, 54 accelerator pedal position sensor, 55 brake pedal, 56 brake pedal position sensor, 58 vehicle speed sensor, 60 brake device, 62 brake master cylinder, 62 brake actuator, 64 brake electronic control unit, 66a to 66d disc brake, 68a to 68d wheel speed sensor.

Claims

[Claim 1] A vehicle control device is mounted on an electric vehicle including an electric motor for driving capable of inputting and outputting power to a drive shaft connected to drive wheels, and a brake device capable of applying a braking force to the drive wheels, and controls the electric motor and the brake device, predicting a wheel speed prediction value as a prediction value of the wheel speed of the drive wheels and a rotation speed prediction value obtained by converting a prediction value of a rotation speed of the electric motor into a wheel speed; When the wheel speed prediction value becomes larger than the rotation speed prediction value by a predetermined threshold value or more when traveling on a stepped road, the electric motor and / or the brake device is controlled in a direction such that a difference between the wheel speed of the driving wheels and the rotation speed of the electric motor becomes smaller. A vehicle control device comprising:

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