Control device for vehicle

Abstract

To provide a control device for a vehicle that is able to realize stable control for automatic drive when torque distribution control and automatic drive control are executed in an overlapping manner.SOLUTION: When automatic drive control is being executed, torque distribution control is executed while correction of fixed torque distribution ratio by feedback control is restricted or not performed, as compared with that when manual drive control is being executed. As a result, interference of a change in torque distribution between front and rear wheels with optimal control for automatic operation is curbed or avoided during traveling when the automatic drive control is executed. Therefore, when the torque distribution control and the automatic drive control are executed in an overlapping manner, stable control for the automatic drive can be realized.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a vehicle control device capable of adjusting the torque distribution between the front and rear wheels.

Background Art

[0002] A vehicle control device that can adjust the torque distribution between the front and rear wheels and can select between a manual driving mode and an automatic driving mode is well known. For example, the vehicle driving control device described in Patent Document 1 is such a device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in the torque distribution control for performing the torque distribution between the front and rear wheels, the torque distribution ratio between the front and rear wheels is set based on the running state. On the other hand, in the automatic driving mode, as the optimal control for automatic driving, automatic driving control is performed to drive the vehicle by automatically performing steering and acceleration / deceleration. Therefore, if the torque distribution between the front and rear wheels is changed based on the running state during running when the automatic driving mode is selected, it may interfere with the optimal control (for example, acceleration / deceleration control) in that running state for automatic driving, and there is a possibility that stable control for automatic driving cannot be realized.

[0005] The present invention has been made based on the above circumstances, and an object thereof is to provide a vehicle control device capable of realizing stable control for automatic driving when the torque distribution control and the automatic driving control are executed overlappingly.

Means for Solving the Problems

[0006] The gist of the first invention is as follows: (a) a control device for a vehicle capable of adjusting the torque distribution between the front and rear wheels and selectable between a manual driving mode and an automatic driving mode, (b) setting a fixed torque distribution ratio of the front and rear wheels predetermined based on the driving state and correcting the fixed torque distribution ratio by feedback control so as to reduce the difference between the rotational speed of the front wheels and the rotational speed of the rear wheels, thereby executing a torque distribution control for performing the torque distribution between the front and rear wheels, (c) when the manual driving mode is selected, executing a manual driving control for driving the vehicle based on the driving operation of the driver, while when the automatic driving mode is selected, executing an automatic driving control for driving the vehicle by automatically performing steering and acceleration / deceleration, and (d) when the automatic driving control is being executed by the driving control unit, the drive control unit suppresses or does not perform the correction of the fixed torque distribution ratio by the feedback control as compared with the execution of the manual driving control, and executes the torque distribution control.

Effect of the Invention

[0007] According to the first invention, when the automatic driving control is being executed, the correction of the fixed torque distribution ratio by the feedback control is suppressed or not performed as compared with the execution of the manual driving control, and the torque distribution control is executed. Thereby, during traveling when the automatic driving control is being executed, it is suppressed or avoided that the change in the torque distribution between the front and rear wheels interferes with the optimal control for the automatic driving. Therefore, when the torque distribution control and the automatic driving control are executed overlappingly, stable control for the automatic driving can be realized.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment

[0010] FIG. 1 is a diagram for explaining the schematic configuration of a vehicle 10 to which the present invention is applied, and is also a diagram for explaining the main parts of the control functions and control systems for various controls in the vehicle 10. In FIG. 1, the vehicle 10 includes wheels WH including left and right front wheels 12 and left and right rear wheels 14, a front-wheel drive device 20 for driving the front wheels 12, and a rear-wheel drive device 30 for driving the rear wheels 14. Further, the vehicle 10 includes a battery 40 or the like which is a rechargeable DC power source. Note that the above “left and right” refers to the left and right with respect to the forward direction of the vehicle 10.

[0011] The vehicle 10 is a four-wheel drive vehicle capable of adjusting the torque distribution of the front wheels 12 and the rear wheels 14, that is, the front and rear wheels. All-wheel drive (=AWD) and four-wheel drive (=4WD) are synonymous.

[0012] The front-wheel drive device 20 includes an engine 22, a first electric motor MG1, a second electric motor MG2, a power split mechanism 24, a front-wheel transmission mechanism 26, a boost converter 28, a front-wheel inverter 29, and the like.

[0013] The engine 22 is a known internal combustion engine. The first electric motor MG1 and the second electric motor MG2 are each a known rotary electric machine, that is, a so-called motor generator. The engine 22 and the second electric motor MG2 function as power sources for traveling.

[0014] The power split mechanism 24 is, for example, a known single pinion type planetary gear device. The power split mechanism 24 mechanically splits the power of the engine 22 input to the carrier, for example, into the sun gear (that is, the first motor MG1 connected to be able to transmit power to the sun gear) and the ring gear. By controlling the operating state of the first motor MG1, the differential state of the power split mechanism 24 is controlled, thereby constituting a known electric transmission mechanism.

[0015] The front-wheel transmission mechanism 26 includes, for example, a reduction gear mechanism including a differential gear, a drive shaft, etc., and transmits the power output from the power split mechanism 24 and the power output from the second motor MG2 to the front wheels 12.

[0016] The boost converter 28 is a buck-boost circuit having a function of boosting the voltage of the battery 40 and supplying it to the front-wheel inverter 29, and a function of stepping down the voltage converted to direct current by the front-wheel inverter 29 and supplying it to the battery 40. The front-wheel inverter 29 converts the direct current from the boost converter 28 into an alternating current for driving the first motor MG1 and the second motor MG2. The front-wheel inverter 29 converts the alternating current generated by the first motor MG1 by the power of the engine 22 and the alternating current generated by the second motor MG2 by the regenerative brake into a direct current.

[0017] The rear-wheel drive device 30 includes a rear-wheel motor MGR, a rear-wheel transmission mechanism 32, a rear-wheel inverter 34, etc. The rear-wheel motor MGR is a known rotary electric machine, which is a so-called motor generator. The rear-wheel motor MGR functions as a power source for traveling. The rear-wheel transmission mechanism 32 includes, for example, a reduction gear mechanism including a differential gear, a drive shaft, etc., and transmits the power output from the rear-wheel motor MGR to the rear wheels 14. The rear-wheel inverter 34 converts the direct current from the battery 40 into an alternating current for driving the rear-wheel motor MGR. The rear-wheel inverter 34 converts the alternating current generated by the rear-wheel motor MGR by the regenerative brake into a direct current and supplies it to the battery 40.

[0018] Vehicle 10 includes an electronic control unit 50 that contains a control device for the vehicle 10 related to various controls. The electronic control unit 50 is configured to include a so-called microcomputer equipped with, for example, a CPU, RAM, ROM, input / output interfaces, and the like.

[0019] Various signals (for example, engine rotational speed Ne, MG1 rotational speed Nmg1, MG2 rotational speed Nmg2, MGR rotational speed Nmgr, wheel speed Nw, accelerator opening θacc, throttle valve opening θth, brake-on signal Bon, brake operation amount Bra, longitudinal acceleration Gx, lateral acceleration Gy, yaw rate Ryaw, steering angle θsw, steering direction Dsw, vehicle surrounding information Iard, position information Ivp, navigation information Inavi, automatic driving setting signal Sad, etc.) based on detection values by various sensors (engine rotational speed sensor 60, MG1 rotational speed sensor 62, MG2 rotational speed sensor 64, MGR rotational speed sensor 66, wheel speed sensor 68, accelerator opening sensor 70, throttle valve opening sensor 72, brake pedal sensor 74, G sensor 76, yaw rate sensor 78, steering sensor 80, vehicle surrounding information sensor 82, vehicle position sensor 84, navigation system 86, automatic driving selection switch 88, etc.) provided in the vehicle 10 are respectively supplied to the electronic control unit 50. The wheel speed sensor 68 includes a left front wheel speed sensor 68fl, a right front wheel speed sensor 68fr, a left rear wheel speed sensor 68rl, and a right rear wheel speed sensor 68rr.

[0020] The wheel speed Nw is the rotational speed of the wheel WH, including the left front wheel speed Nwfl and the right front wheel speed Nwfr as the front wheel speed Nwf, which is the rotational speed of the front wheels 12, and the left rear wheel speed Nwrl and the right rear wheel speed Nwrr as the rear wheel speed Nwr, which is the rotational speed of the rear wheels 14. The accelerator opening θacc is a signal corresponding to the acceleration demand amount representing the magnitude of the driver's acceleration operation and is the accelerator operation amount by the driver. The brake operation amount Bra is a signal representing the magnitude of the brake operation by the driver. The steering wheel angle θsw is the steering angle of the steering wheel. The steering direction Dsw is the steering direction of the steering wheel. The automatic driving setting signal Sad is a signal indicating the setting by the driver in the automatic driving control CTad. The electronic control unit 50 acquires the vehicle speed V based on the wheel speed Nw.

[0021] The vehicle surrounding information sensor 82 includes at least one of, for example, a lidar, a radar, and an in-vehicle camera. The vehicle surrounding information sensor 82 detects an object in front of, on the side of, or behind the vehicle 10, respectively, and outputs object information regarding the detected object as the vehicle surrounding information Iard. The vehicle position sensor 84 includes a GPS (Global Positioning System) antenna and the like. The position information Ivp includes the own vehicle position information, which is information indicating the current position of the vehicle 10 on the ground surface or on a map based on a GPS signal (orbital signal) transmitted by a GPS satellite. The navigation system 86 is a known navigation system. The navigation information Inavi includes map information such as road information and facility information based on map data previously stored in the navigation system 86, for example. The automatic driving selection switch 88 is a switch operated by the driver when executing the automatic driving control CTad.

[0022] From the electronic control device 50, various command signals (such as engine control command signal Se, MG1 control command signal Smg1, MG2 control command signal Smg2, MGR control command signal Smgr, wheel brake control command signal Sbra, steering control command signal Sste for controlling the steering of the front wheels 12, information notification control command signal Sinf for notifying various information to the driver, etc.) are output to each device (such as the engine 22, front-wheel inverter 29, rear-wheel inverter 34, wheel brake device 90, steering device 92, display device 94, etc.) provided in the vehicle 10, respectively.

[0023] The wheel brake device 90 is a brake device that applies braking torque by the wheel brake to the wheel WH by the electronic control device 50. The wheel brake device 90 normally supplies the master cylinder hydraulic pressure corresponding to the brake operation amount Bra as the brake hydraulic pressure to the wheel cylinder. On the other hand, the wheel brake device 90 supplies the brake hydraulic pressure corresponding to the required braking torque to the wheel cylinder, for example, when the automatic driving control CTad is executed. The steering device 92 applies an assist torque corresponding to, for example, the vehicle speed V, steering wheel angle θsw, steering direction Dsw, yaw rate Ryaw, etc. to the steering system of the vehicle 10. The steering device 92 applies a torque for controlling the steering of the front wheels 12 to the steering system of the vehicle 10, for example, during the automatic driving control CTad. The display device 94 is a device such as a multi-information display that displays various information to the driver. The display device 94 displays, for example, the state of torque distribution to the front and rear wheels in the front-rear wheel torque distribution control CTdt.

[0024] The electronic control device 50 includes a drive control unit 52 and an operation control unit 54 to realize various controls in the vehicle 10.

[0025] The drive control unit 52 calculates the drive demand amount for the vehicle 10 by the driver, for example, by applying the accelerator opening θacc and the vehicle speed V to a predetermined drive demand amount map. This drive demand amount uses, for example, the required drive torque Twdem [Nm] as the required value of the drive torque Tw, which is the torque at the wheel WH, the required drive force Fwdem [N] as the required value of the drive force Fw, and the like. The required drive torque Twdem is the combined value of the required front wheel torque Twfdem as the required value of the front wheel torque Twf, which is the torque at the front wheels 12, and the required rear wheel torque Twrdem as the required value of the rear wheel torque Twr, which is the torque at the rear wheels 14. Note that when not particularly distinguished, torque and force (drive force) are synonymous.

[0026] The drive control unit 52 sets the torque distribution ratio between the front and rear wheels by applying a plurality of drive force-related values such as the accelerator opening θacc, the vehicle speed V, the longitudinal acceleration Gx, and the yaw rate Ryaw to a predetermined torque distribution ratio map, for example. This torque distribution ratio is the fixed torque distribution ratio γfr between the front and rear wheels predetermined based on the driving state. The drive control unit 52 calculates the required front wheel torque Twfdem and the required rear wheel torque Twrdem based on the required drive torque Twdem and the fixed torque distribution ratio γfr. The drive control unit 52 outputs an engine control command signal Se, an MG1 control command signal Smg1, and an MG2 control command signal Smg2 for controlling the front wheel drive device 20 so as to realize the required front wheel torque Twfdem. The drive control unit 52 outputs an MGR control command signal Smgr for controlling the rear wheel drive device 30, that is, the rear wheel motor MGR, so as to realize the required rear wheel torque Twrdem.

[0027] FIG. 2 is a diagram for explaining an example of the fixed torque distribution ratio γfr between the front and rear wheels using the torque distribution to the rear wheel 14. In FIG. 2, for example, at the start on a slippery road surface, torque distribution to the rear wheel 14 is performed, and the torque distribution to the rear wheel 14 is decreased as the vehicle speed V increases. Also, for example, during steady driving with a constant vehicle speed V, a fixed torque distribution ratio γfr in which the torque distribution to the rear wheel 14 becomes 0 [%] is set. Also, for example, when driving on rough ground or sandy ground, a fixed torque distribution ratio γfr of 50 [%] on the front wheel 12 side and 50 [%] on the rear wheel 14 side is set. Also, for example, during braking in the 4WD state, the torque distribution to the rear wheel 14 is decreased and the 4WD state is released.

[0028] Returning to FIG. 1, when the drive control unit 52 determines that slip has occurred in either the front wheel 12 or the rear wheel 14, the drive control unit 52 corrects the fixed torque distribution ratio γfr so as to increase the torque distribution to the wheel WH where no slip has occurred. That is, the drive control unit 52 executes a slip suppression control CTslp that corrects the fixed torque distribution ratio γfr by feedback control (= FB control) so as to reduce the difference between the front wheel speed Nwf and the rear wheel speed Nwr. For example, in the slip suppression control CTslp, the greater the slip, the greater the torque distribution to the wheel where no slip has occurred. In this way, the drive control unit 52 sets the fixed torque distribution ratio γfr based on the driving state and corrects the fixed torque distribution ratio γfr by the slip suppression control CTslp, thereby executing a torque distribution control CTdt that distributes torque between the front and rear wheels.

[0029] The operation control unit 54 executes a manual operation control CTmd and an automatic operation control CTad as the operation control of the vehicle 10. The manual operation control CTmd is an operation control for operating the vehicle 10 based on the driver's operation. The automatic operation control CTad is an operation control for operating the vehicle 10 by automatically performing steering and acceleration / deceleration regardless of the driver's operation. Note that acceleration / deceleration includes braking.

[0030] When the automatic driving selection switch 88 is turned off, that is, when the manual driving mode is selected, the driving control unit 54 establishes the manual driving mode and executes the manual driving control CTmd. The driving control unit 54 executes the manual driving control CTmd by outputting commands for controlling the front-wheel drive device 20 and the rear-wheel drive device 30 respectively according to, for example, the driver's operation. Note that the driving demand amount based on the accelerator opening θacc and vehicle speed V described above is the driving demand amount on the vehicle 10 by the driver during the manual driving control CTmd.

[0031] When the automatic driving selection switch 88 is turned on, that is, when the automatic driving mode is selected, the driving control unit 54 establishes the automatic driving mode and executes the automatic driving control CTad. During the automatic driving control CTad, the driving control unit 54 calculates the driving demand amount for the vehicle 10 required by the automatic driving control CTad. The driving control unit 54 automatically sets the target driving state based on, for example, the destination, the vehicle position information based on the position information Ivp, the map information based on the navigation information Inavi, and various information on the driving route based on the vehicle surrounding information Iard. The driving control unit 54 outputs commands for controlling the front-wheel drive device 20, the rear-wheel drive device 30, the wheel brake device 90, the steering device 92, etc. respectively so as to automatically perform acceleration / deceleration and steering based on the set target driving state, thereby performing the automatic driving control CTad.

[0032] In this way, the vehicle 10 can select between the manual driving mode and the automatic driving mode. Note that the automatic driving (mode) which is driving in the automatic driving control CTad includes manned driving and unmanned driving. The manned driving in the automatic driving control CTad is the manned automatic driving (mode), and the unmanned driving in the automatic driving control CTad is the unmanned automatic driving (mode).

[0033] Incidentally, in the slip suppression control CTslp by FB control in the drive control unit 52, the fixed torque distribution ratio γfr is corrected while realizing the required drive torque Twdem. On the other hand, when it is determined that slip has occurred during running in the automatic driving control CTad in the operation control unit 54, for example, the drive demand amount (required drive torque Twdem) for the vehicle 10 is reduced so that the slip is suppressed. Therefore, there is a possibility that the slip suppression control CTslp and the automatic driving control CTad interfere with each other, and it may not be possible to set an optimal operation (steering operation, acceleration / deceleration operation) that does not become unstable for the automatic driving control CTad. For example, problems are likely to occur in scenarios such as driving in a limit area such as an automatic driving rally or driving on a slippery road surface.

[0034] Therefore, when the automatic driving control CTad is being executed by the operation control unit 54, the drive control unit 52 suppresses or does not perform the correction of the fixed torque distribution ratio γfr in the slip suppression control CTslp in the torque distribution control CTdt, that is, the correction by FB control, as compared with when the manual driving control CTmd is executed, and executes the torque distribution control CTdt. Suppressing the correction of the fixed torque distribution ratio γfr as compared with when the manual driving control CTmd is executed means, for example, making the value of the FB gain in the FB control smaller than when the manual driving control CTmd is executed. Not performing the correction of the fixed torque distribution ratio γfr means, for example, deleting the FB term in the torque distribution control CTdt and using only the fixed torque distribution ratio γfr (feedforward term) set from the torque distribution ratio map.

[0035] FIG. 3 is a flowchart for explaining the main part of the control operation of the electronic control device 50, and is a flowchart for explaining the control operation for realizing stable control for automatic driving when the torque distribution control CTdt and the automatic driving control CTad are executed overlappingly, and is repeatedly executed, for example.

[0036] In FIG. 3, first, in step S10 corresponding to the function of the driving control unit 54 (hereinafter, steps are omitted), it is determined whether the automatic driving mode is selected. If the determination in S10 is affirmative, then in S20 corresponding to the function of the driving control unit 54, it is determined whether unmanned automatic driving is selected. If the determination in S20 is affirmative, then in S30 corresponding to the function of the drive control unit 52, it is determined that the unmanned automatic driving mode is being executed. Next, in S40 corresponding to the function of the drive control unit 52, torque distribution tuning for unmanned automatic driving is performed. For example, the FB term in the torque distribution control CTdt is deleted. If the determination in S20 is negative, then in S50 corresponding to the function of the drive control unit 52, it is determined that the manned automatic driving mode is being executed. Next, in S60 corresponding to the function of the drive control unit 52, torque distribution tuning for manned automatic driving is performed. For example, the value of the FB gain of the FB control in the torque distribution control CTdt is made smaller compared to when the manual driving control CTmd is executed. If the determination in S10 is negative, then in S70 corresponding to the function of the drive control unit 52, normal control, that is, the manual driving control CTmd is executed. Next, in S80 corresponding to the function of the drive control unit 52, torque distribution tuning for manual driving is performed. For example, the FB control in the torque distribution control CTdt is performed without being restricted.

[0037] As described above, according to this embodiment, when the automatic driving control CTad is being executed, the correction of the fixed torque distribution ratio γfr by the FB control is suppressed or not performed compared to when the manual driving control CTmd is executed, and the torque distribution control CTdt is executed. Thereby, during traveling when the automatic driving control CTad is being executed, the change in the torque distribution between the front and rear wheels is suppressed or avoided from interfering with the optimal control for automatic driving. Therefore, when the torque distribution control CTdt and the automatic driving control CTad are executed overlappingly, stable control for automatic driving can be realized.

[0038] As described above, the embodiments of the present invention have been described in detail based on the drawings, but the present invention is also applicable in other aspects.

[0039] For example, in the above-described embodiment, the front-wheel drive device 20 may also be a drive device driven by an electric motor, similar to the rear-wheel drive device 30. Further, the vehicle may not be a four-wheel independent drive type, but may be a vehicle in which torque is distributed to the front and rear wheels by, for example, a transfer. In short, the present invention can be applied to any vehicle that can adjust the torque distribution between the front and rear wheels and can select between a manual driving mode and an automatic driving mode.

[0040] Note that the above is merely one embodiment, and the present invention can be implemented in various modified and improved forms based on the knowledge of those skilled in the art.

Explanation of Reference Numerals

[0041] 10: Vehicle 12: Front wheel 14: Rear wheel 50: Electronic control device (control device) 52: Drive control unit 54: Driving control unit

Claims

[Claim 1] A control device for a vehicle capable of adjusting torque distribution between front and rear wheels and selecting a manual driving mode and an automatic driving mode, a drive control unit that executes torque distribution control to distribute torque between the front and rear wheels by setting a fixed torque distribution ratio between the front and rear wheels that is determined in advance based on a running state and correcting the fixed torque distribution ratio by feedback control so as to reduce a difference between a rotation speed of the front wheels and a rotation speed of the rear wheels; a driving control unit that, when the manual driving mode is selected, executes manual driving control to drive the vehicle based on a driving operation by a driver, and, when the automatic driving mode is selected, executes automatic driving control to drive the vehicle by automatically performing steering and acceleration / deceleration; and A vehicle control device characterized in that, when the automatic driving control is being executed by the driving control unit, the drive control unit executes the torque distribution control by suppressing or not correcting the fixed torque distribution ratio by the feedback control compared to when the manual driving control is being executed.

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