Vehicle control method

Abstract

To provide a vehicle control method capable of mitigating impact acting on an occupant of a four wheel independent steering vehicle when the four wheel independent steering vehicle stops an ultra-pivotal turn.SOLUTION: In a vehicle control method, braking force Fb is reduced by providing time difference between a plurality of wheels after reducing rotation speed V to a threshold value V1 by applying braking force Fb1 to the plurality of wheels during an ultra-pivotal turn of a four wheel independent steering vehicle.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a vehicle control method.

Background Art

[0002] Conventionally, a vehicle travel control device that controls the travel of a vehicle in an independently steerable vehicle in which three or more tires can be independently steered is known (for example, Patent Document 1 below).

[0003] In the above vehicle travel control device, at the time of acceleration, the driving force of the pseudo front wheel portion is set to be larger than the driving force of the pseudo rear wheel portion, and at the time of braking, the braking force of the pseudo rear wheel portion is set to be larger than the braking force of the pseudo front wheel portion, so that a lift-up can be prevented.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the independently steerable vehicle in which three or more tires described in Patent Document 1 can be independently steered, it is difficult to adjust the rotation speed during a super-low-speed turn in which the vehicle turns on the spot, and the impact received by the vehicle occupants tends to increase when the super-low-speed turn stops.

[0006] The present disclosure provides a vehicle control method capable of reducing the impact received by the vehicle occupants when a four-wheel independently steered vehicle stops during a super-low-speed turn.

Means for Solving the Problems

[0007] One aspect of the present disclosure provides a vehicle control method in which, during a super-low-speed turn of a four-wheel independently steered vehicle, braking force is applied to a plurality of wheels to reduce the rotation speed to a threshold value, and then a time difference is provided between the plurality of wheels to reduce the braking force.

Advantages of the Invention

[0008] According to the above aspect of the present disclosure, it is possible to provide a vehicle control method capable of reducing the impact received by the vehicle occupants when the four-wheel independent steering vehicle stops during extremely low-speed turning.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0010] Hereinafter, modes for carrying out the invention will be described with reference to the drawings.

[0011] First, with reference to FIGS. 1 and 2, a four-wheel independent steering vehicle 100 as a control target in an embodiment of the vehicle control method according to the present disclosure will be described, and then, with reference to FIG. 3, an embodiment of the vehicle control method according to the present disclosure will be described.

[0012] FIG. 1 is a schematic diagram of a four-wheel independent steering vehicle 100 as a control target in an embodiment of the vehicle control method according to the present disclosure. FIG. 2 is a block diagram showing an example of the configuration of the four-wheel independent steering vehicle 100 in FIG. 1.

[0013] The four-wheel independently-steerable vehicle 100 has, for example, as shown in FIG. 1, a vehicle body 101 and four wheels 102. Further, the four-wheel independently-steerable vehicle 100 includes, for example, as shown in FIG. 2, a positioning device 103, a speed sensor 104, an acceleration sensor 105, an angular velocity sensor 106, and an operation device 107. Further, the four-wheel independently-steerable vehicle 100 includes, for example, a steering device 108, a driving device 109, a braking device 110, a user interface 111, and a control device 112. Further, the four-wheel independently-steerable vehicle 100 may include, for example, external sensors such as a camera and LiDAR.

[0014] The vehicle body 101 includes, for example, a platform which is a basic structure, and a body mounted on the platform to form a cabin. The vehicle body 101 has a generally rectangular shape having, for example, a front portion 101F, a rear portion 101R, a left side portion 101SL, and a right side portion 101SR. Note that the vehicle body 101 may have any shape without distinguishing the front portion 101F, the rear portion 101R, the left side portion 101SL, and the right side portion 101SR.

[0015] The four wheels 102 include, for example, a left front wheel 102FL, a right front wheel 102FR, a left rear wheel 102RL, and a right rear wheel 102RR. The left front wheel 102FL and the right front wheel 102FR are respectively attached to the corner on the left side portion 101SL side and the corner on the right side portion 101SR side of the front portion 101F. The left rear wheel 102RL and the right rear wheel 102RR are respectively attached to the corner on the left side portion 101SL side and the corner on the right side portion 101SR side of the rear portion 101R. Note that the four wheels 102 may not have the distinction of front, rear, left, and right.

[0016] The positioning device 103 is constituted by, for example, a receiver of a global navigation satellite system (GNSS) mounted on the vehicle body 101. The positioning device 103 acquires, for example, the position information of the four-wheel independently-steerable vehicle 100 and outputs it to the control device 112.

[0017] The speed sensor 104 is composed of, for example, wheel speed sensors mounted on each wheel 102, and detects the speed of the four-wheel independent steering vehicle 100 based on the rotational speed of each wheel 102. The speed sensor 104 outputs the detected speed of the four-wheel independent steering vehicle 100 to the control device 112.

[0018] The acceleration sensor 105 is, for example, a piezoelectric or capacitance-type sensor mounted on the vehicle body 101, and detects the acceleration of the four-wheel independent steering vehicle 100 in the front-rear direction, left-right direction, and up-down direction by converting inertial force into an electrical signal. The acceleration sensor 105 outputs the detected acceleration of the four-wheel independent steering vehicle 100 to the control device 112.

[0019] The angular velocity sensor 106 is composed of, for example, an inertial sensor mounted on the vehicle body 101. The angular velocity sensor 106 detects, for example, the angular velocity around each axis of the roll axis, pitch axis, and yaw axis of the four-wheel independent steering vehicle 100. The angular velocity sensor 106 outputs the detected angular velocity of the four-wheel independent steering vehicle 100 to the control device 112.

[0020] The operation device 107 is operated by the driver of the four-wheel independent steering vehicle 100 during manual driving, for example, and detects the operation amount by the driver. The operation device 107 includes, for example, an accelerator pedal, a brake pedal, a steering wheel, a driving mode switching switch, an automatic driving switching switch, and the like.

[0021] Further, the operation device 107 includes, for example, an accelerator pedal sensor that detects the operation amount of the accelerator pedal, a brake pedal sensor that detects the operation amount of the brake pedal, a steering angle sensor that detects the rotation angle of the steering wheel, and the like. The operation device 107 outputs the detected operation amount to the control device 112.

[0022] The driving mode switching switch of the operation device 107 is configured to be able to switch the driving mode of the four-wheel independent steering vehicle 100, for example. The driving mode of the four-wheel independent steering vehicle 100 includes, for example, a normal driving mode, a parallel driving mode, a front-rear reverse steering mode, a super-low-speed turning mode, and the like.

[0023] In the normal driving mode of the four-wheel independently steerable vehicle 100, for example, similar to a normal automobile, the left rear wheel 102RL and the right rear wheel 102RR are fixed in the longitudinal direction of the four-wheel independently steerable vehicle 100, and the left front wheel 102FL and the right front wheel 102FR are steered to perform forward movement SF, reverse movement SB, and left and right turns.

[0024]

[0023] The straight-line driving mode of the four-wheel independently steerable vehicle 100 is a driving mode in which, for example, by steering the four wheels 102 in the same direction, the vehicle can move straight in all 360° directions. Specifically, in the straight-line driving mode, the four-wheel independently steerable vehicle 100 can, for example, perform forward movement SF, reverse movement SB, left straight movement LT, right straight movement RT, left diagonal forward movement LF, right diagonal forward movement RF, left diagonal reverse movement LB, right diagonal reverse movement RB, etc.

[0025] In the front-rear reverse steering mode of the four-wheel independently steerable vehicle 100, for example, the left front wheel 102FL and the right front wheel 102FR, and the left rear wheel 102RL and the right rear wheel 102RR are steered in opposite directions to perform right turns and left turns.

[0026]

[0026] In the ultra-low-radius turning mode of the four-wheel independently steerable vehicle 100, for example, as shown in FIG. 1, the four wheels 102 are steered so as to face the tangential direction of the turning circle centered on the vehicle body 101 and rotated in the same direction, and left turns TL or right turns TR are performed on the spot.

[0027] The automatic driving switch of the operation device 107, for example, when turned on, starts the automatic driving of the four-wheel independently steerable vehicle 100 by the control device 112, and when turned off, enables manual driving by the driver of the four-wheel independently steerable vehicle 100. When the automatic driving of the four-wheel independently steerable vehicle 100 is started, the control device 112 autonomously drives the four-wheel independently steerable vehicle 100 from the current location to a preset destination while appropriately switching the driving mode of the four-wheel independently steerable vehicle 100.

[0028] The steering device 108 is composed of, for example, one or more steering motors and a steering mechanism driven by the steering motor to independently change the steering angle θ of each wheel 102. The steering device 108 adjusts the steering angle θ of each wheel 102 to an arbitrary independent steering angle based on, for example, the steering command of each wheel 102 input from the control device 112.

[0029] The drive device 109 includes, for example, one or more driving motors and a power transmission mechanism that transmits the driving force of the driving motor to rotate each wheel 102. More specifically, the drive device 109 includes, for example, an in-wheel motor provided on at least one of the left rear wheel 102RL and the right rear wheel 102RR. Further, the drive device 109 may include an in-wheel motor provided on at least one of the right front wheel 102FR and the right rear wheel 102RR. The drive device 109 adjusts the rotation direction and rotation speed of each wheel 102 based on, for example, the drive command of the rotation direction and rotation speed of each wheel 102 input from the control device 112.

[0030] The braking device 110 is composed of, for example, an electric brake actuator and a friction brake, and brakes each wheel 102 independently. The braking device 110 adjusts the braking force applied to each wheel 102 based on, for example, the braking command input from the control device 112. That is, brake-by-wire is adopted for the braking device 110.

[0031] The user interface 111 includes, for example, an output device and an input device. The output device includes, for example, a display, a speaker, an indicator lamp, a buzzer, etc. The input device includes, for example, a touch panel, an operation switch, an operation dial, an operation button, a keyboard, etc.

[0032] The user interface 111 causes, for example, an image to be displayed on a display and outputs sound or a warning sound from a speaker or a buzzer based on a control command input from the control device 112. Further, the user interface 111 receives, for example, the operation and voice of the occupant of the four-wheel independent steering vehicle 100 by an input device such as a touch panel or a microphone, and outputs a signal related to the operation and voice to the control device 112.

[0033] The control device 112 is constituted by, for example, one or more electronic control units (ECUs) including one or more microcontrollers. The control device 112 realizes various controls of the four-wheel independent steering vehicle 100 including the vehicle control method of the present embodiment described below by executing a program stored in a storage device such as a RAM or a ROM by a central processing unit (CPU).

[0034] In the four-wheel independent steering vehicle 100, for example, the difficulty of adjusting the rotation speed in the above-described super-creditable turning mode is higher than the speed adjustment in other driving modes such as the above-described normal driving mode and the straight-ahead mode. Therefore, for example, when the four-wheel independent steering vehicle 100 is manually driven, the driver tends to increase the rotation speed of the super-creditable turn more than necessary, and in order to decrease the rotation speed from that state, the driver tends to operate the brake pedal and the steering wheel more than necessary. As a result, the impact received by the occupant of the four-wheel independent steering vehicle 100 when the super-creditable turn stops also tends to increase.

[0035] Hereinafter, the vehicle control method of the present embodiment that can mitigate the impact received by the occupant of the vehicle when the super-creditable turn of the four-wheel independent steering vehicle 100 as described above stops will be described with reference to FIG. 3.

[0036] FIG. 3 is a graph for explaining an embodiment of the vehicle control method according to the present disclosure. Specifically, the upper graph in FIG. 3 shows the temporal change of the braking force Fb applied to each wheel 102 by the braking device 110 of the four-wheel independent steering vehicle 100, and the lower graph in FIG. 3 shows the temporal change of the rotational speed V during the ultra-low-radius turning of the four-wheel independent steering vehicle 100. In the upper graph of FIG. 3, the solid line L1, the one-dot chain line L2, the two-dot chain line L3, and the broken line L4 show the temporal change of the braking force Fb of different wheels 102.

[0037] When the ultra-low-radius turning mode is selected during manual driving or automatic driving and the four-wheel independent steering vehicle 100 starts ultra-low-radius turning, the control device 112 of the four-wheel independent steering vehicle 100 starts the vehicle control method of the present embodiment.

[0038] When starting the vehicle control method of the present embodiment, the control device 112 acquires the rotational speed of the four-wheel independent steering vehicle 100 based on the detection results of, for example, the speed sensor 104 or the angular velocity sensor 106. In addition, the control device 112 acquires the braking force Fb applied to each wheel 102, for example. Here, the control device 112 may calculate the braking force Fb based on the detection value of the brake pedal sensor included in the operation device 107, or may calculate the braking force Fb based on the output of the brake actuator of the braking device 110.

[0039] In the example shown in FIG. 3, the driver or the control device 112 of the four-wheel independent steering vehicle 100 performing ultra-low-radius turning at a predetermined rotational speed V0 operates the braking device 110 at time t0 to stop the ultra-low-radius turning. As a result, the braking force Fb applied to each of the four wheels 102 gradually increases from time t0, and when the braking force Fb reaches a predetermined braking force Fb1 at time t1, the rotational speed V0 of the four-wheel independent steering vehicle 100 gradually decreases and drops to a predetermined threshold value V1 at time t2.

[0040] Then, for example, at time t2, the control device 112 gradually reduces the braking force Fb of the first wheel 102 indicated by the solid line L1 in the upper graph of FIG. 3 among the four wheels 102. After that, at time t3, the control device 112 gradually reduces the braking force Fb of the second wheel 102 indicated by the dashed-dotted line L2. Further thereafter, at time t4, the control device 112 gradually reduces the braking force Fb of the third wheel 102 indicated by the chain double-dashed line L3. Finally, at time t5, the control device 112 gradually reduces the braking force Fb of the fourth wheel 102 indicated by the broken line L4.

[0041] Here, the control device 112 sequentially reduces the braking force Fb of the four wheels 102, for example, in the direction opposite to the turning direction of the oversteering turn. Specifically, for example, when the four-wheel independent steering vehicle 100 shown in FIG. 1 is performing a right turn TR in an oversteering turn, the braking force Fb is first reduced with the right front wheel 102FR as the pseudo front wheel and the first wheel 102. Thereafter, from the first wheel 102 (right front wheel 102FR) in the counterclockwise direction opposite to the turning direction of the right turn TR, the braking force Fb is reduced in the order of the second wheel 102 (left front wheel 102FL), the third wheel 102 (left rear wheel 102RL), and the fourth wheel 102 (right rear wheel 102RR).

[0042] Also, for example, when the four-wheel independent steering vehicle 100 shown in FIG. 1 is performing a left turn TL in an oversteering turn, the braking force Fb is first reduced with the right rear wheel 102RR as the pseudo front wheel and the first wheel 102. Thereafter, from the first wheel 102 (right rear wheel 102RR) in the clockwise direction opposite to the turning direction of the left turn TL, the braking force Fb is reduced in the order of the second wheel 102 (left rear wheel 102RL), the third wheel 102 (left front wheel 102FL), and the fourth wheel 102 (right front wheel 102FR).

[0043] As described above, the vehicle control method of the present embodiment applies a braking force Fb to a plurality of wheels 102 during an oversteering turn of the four-wheel independent steering vehicle 100 to reduce the rotational speed V to the threshold value V1, and then provides a time difference among the plurality of wheels 102 to reduce the braking force Fb.

[0044] With such a configuration, according to the vehicle control method of this embodiment, the braking force Fb applied to the four wheels 102 can be made close to zero immediately before the stop of the oversteer turning of the four-wheel independent steering vehicle 100. As a result, the impact received by the occupants of the four-wheel independent steering vehicle 100 at the time of stopping the oversteer turning can be mitigated.

[0045] As described above, the preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments. Various modifications or substitutions etc. can be applied to the above-described embodiments without departing from the scope of the present invention.

[0046] For example, the order and combination of reducing the braking force Fb of the four wheels 102 are not particularly limited. Specifically, the left front wheel 102FL and the right front wheel 102FR, and the left rear wheel 102RL and the right rear wheel 102RR can be braked simultaneously, and it is assumed that an in-wheel motor is mounted on the right rear wheel 102RR. In this case, the braking force Fb of the left rear wheel 102RL and the right rear wheel 102RR may be reduced simultaneously, and then the braking force Fb of the left front wheel 102FL and the right front wheel 102FR may be reduced simultaneously. Also, among the four wheels 102, the braking force Fb of two wheels 102 located diagonally may be reduced simultaneously, and then the braking force Fb of the remaining wheels 102 may be reduced simultaneously.

[0047] Also, according to the center of gravity characteristics or the position of the drive wheels of the four-wheel independent steering vehicle 100, when the oversteer turning of the four-wheel independent steering vehicle 100 is a right turn TR, the braking force Fb of the four wheels 102 may be sequentially reduced in the clockwise direction, which is the same rotation direction as the right turn TR. Similarly, according to the center of gravity characteristics or the position of the drive wheels of the four-wheel independent steering vehicle 100, when the oversteer turning of the four-wheel independent steering vehicle 100 is a left turn TL, the braking force Fb of the four wheels 102 may be sequentially reduced in the counterclockwise direction, which is the same rotation direction as the left turn TL.

Explanation of Reference Numerals

[0048] 100: Four-wheel independent steering vehicle, 102: Wheel, Fb, Fb1: Braking force, V: Rotation speed, V1: Threshold value.

Claims

【Claim 1】 A vehicle control method in which, during super-low-speed turning of a four-wheel independently-steerable vehicle, braking force is applied to a plurality of wheels to reduce the rotational speed to a threshold value, and then a time difference is provided among the plurality of wheels to reduce the braking force.

Images