Vehicle control method
The vehicle control method addresses the challenge of increased impact during pivot turns in four-wheel independently steered vehicles by reducing braking force and adjusting steering angles, enhancing safety and reliability during super-low-speed turns.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-01-11
- Publication Date
- 2026-07-07
AI Technical Summary
In four-wheel independently steered vehicles, it is difficult to adjust the rotation speed during a super-low-speed turn, leading to increased impact on occupants when the vehicle stops during a pivot turn.
A vehicle control method that reduces braking force applied to multiple wheels during a pivot turn, adjusts rotational speed to a threshold, and changes steering angles to mitigate impact.
Mitigates the impact on occupants by slowing down the rotational speed decrease and ensuring reliable stopping during pivot turns, reducing the need for excessive braking force adjustments.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a vehicle control method.
Background Art
[0002] Conventionally, a vehicle travel control device for controlling the travel of a vehicle in an independent steering 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 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 independent steering vehicle described in Patent Document 1 in which three or more tires 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 when the super-low-speed turn stops tends to increase.
[0006] The present disclosure provides a vehicle control method capable of reducing the impact received by the vehicle occupants when a super-low-speed turn of a four-wheel independently steered vehicle stops.
Means for Solving the Problems
[0007] One aspect of this disclosure provides a vehicle control method that reduces the braking force applied to multiple wheels during a four-wheel independent steering vehicle's pivot turn, causing the rotational speed to drop to a threshold, and also changes the steering angles of the multiple wheels from the steering angles at the time of the pivot turn. [Effects of the Invention]
[0008] According to the above aspects of this disclosure, it is possible to provide a vehicle control method that can mitigate the impact received by the occupants of a four-wheel independently steered vehicle when the vehicle comes to a stop during a pivot turn. [Brief explanation of the drawing]
[0009] [Figure 1] This is a schematic diagram of the controlled object in an embodiment of the vehicle control method relating to this disclosure. [Figure 2] Figure 1 is a block diagram showing an example configuration of a four-wheel independent steering vehicle as the control target. [Figure 3] This is a graph illustrating an embodiment of the vehicle control method relating to this disclosure. [Modes for carrying out the invention]
[0010] The following describes embodiments for carrying out the invention with reference to the drawings.
[0011] In the following, we will first describe the four-wheel independent steering vehicle 100 as the controlled object in an embodiment of the vehicle control method according to the present disclosure with reference to Figures 1 and 2, and then describe an embodiment of the vehicle control method according to the present disclosure with reference to Figure 3.
[0012] Figure 1 is a schematic diagram of a four-wheel independently steered vehicle 100 as the control target in an embodiment of the vehicle control method according to this disclosure. Figure 2 is a block diagram showing an example of the configuration of the four-wheel independently steered vehicle 100 in Figure 1.
[0013] The four-wheel independent steering vehicle 100 has, for example, a vehicle body 101 and four wheels 102, as shown in Figure 1. The four-wheel independent steering vehicle 100 also includes, for example, a positioning device 103, a speed sensor 104, an acceleration sensor 105, an angular velocity sensor 106, and an operating device 107, as shown in Figure 2. The four-wheel independent steering vehicle 100 also includes, for example, a steering device 108, a drive device 109, a braking device 110, a user interface 111, and a control device 112. The four-wheel independent steering vehicle 100 may also include, for example, external sensors such as a camera or LiDAR.
[0014] The vehicle body 101 includes, for example, a platform which is a basic structure, and a body which is mounted on the platform and forms the cabin. The vehicle body 101 has a generally rectangular shape, for example, having a front section 101F, a rear section 101R, a left side section 101SL, and a right side section 101SR. However, the vehicle body 101 may have any shape without distinction between the front section 101F, the rear section 101R, the left side section 101SL, and the right side section 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 mounted on the left side corner 101SL and the right side corner 101SR of the front section 101F, respectively. The left rear wheel 102RL and the right rear wheel 102RR are mounted on the left side corner 101SL and the right side corner 101SR of the rear section 101R, respectively. Note that the four wheels 102 do not necessarily have to have a distinction between front, rear, left, and right.
[0016] The positioning device 103 consists of, for example, a receiver of the 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 steered 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 sensor mounted on the vehicle body 101, and detects the acceleration of the four-wheel independent steering vehicle 100 in the longitudinal direction, lateral direction, and vertical 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 autonomous driving switching switch, and the like.
[0021] Also, 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] The normal driving mode of the four-wheel independently steerable vehicle 100 is, for example, similar to that of a normal automobile. In this mode, 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 move forward SF, move backward SB, and turn left and right.
[0024] The parallel driving mode of the four-wheel independently steerable vehicle 100 is, for example, a driving mode in which all four wheels 102 can move forward in all 360° directions by steering the four wheels 102 in the same direction. Specifically, in the parallel driving mode, the four-wheel independently steerable vehicle 100 can, for example, move forward SF, move backward SB, move left LT, move right RT, move diagonally left forward LF, move diagonally right forward RF, move diagonally left backward LB, move diagonally right backward RB, etc.
[0025] The forward-backward reverse steering mode of the four-wheel independently steerable vehicle 100 is, for example, a driving mode in which 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 turn right and turn left.
[0026] The ultra-short turning mode of the four-wheel independently steerable vehicle 100 is, for example, as shown in FIG. 1, a driving mode in which 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 a left turn TL or a right turn TR is 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 those steering motors 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 independent arbitrary steering angle based on steering commands for each wheel 102 input from the control device 112.
[0029] The drive unit 109 includes, for example, one or more drive motors and a power transmission mechanism that transmits the driving force of the drive motors to rotate each wheel 102. More specifically, the drive unit 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. The drive unit 109 may also include an in-wheel motor provided on at least one of the right front wheel 102FR and the right rear wheel 102RR. The drive unit 109 adjusts the rotation direction and rotation speed of each wheel 102 based on, for example, drive commands for the rotation direction and rotation speed of each wheel 102 input from the control device 112.
[0030] The braking system 110 consists of, for example, an electric brake actuator and a friction brake, and independently brakes each wheel 102. The braking system 110 adjusts the braking force applied to each wheel 102 based on a braking command input from, for example, the control device 112. In other words, the braking system 110 employs a brake-by-wire system.
[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, for example, displays images on a display and outputs voices and warning sounds from speakers and buzzers based on control commands input from the control device 112. The user interface 111 also receives input devices such as a touch panel and microphone from the occupants of the four-wheel independent steering vehicle 100, for example, and outputs signals related to those operations and voices to the control device 112.
[0033] The control device 112 is composed of one or more electronic control units (ECUs), including, for example, one or more microcontrollers. The control device 112 implements various controls of the four-wheel independent steering vehicle 100, including the vehicle control method of this embodiment described below, by executing a program stored in a storage device such as RAM or ROM using a central processing unit (CPU).
[0034] For the four-wheel independent steering vehicle 100, adjusting the rotational speed in the aforementioned pivot turning mode is more difficult compared to adjusting the speed in other driving modes, such as the aforementioned normal driving mode or parallel driving mode. Therefore, for example, when manually driving the four-wheel independent steering vehicle 100, the driver tends to increase the rotational speed during a pivot turn more than necessary, and then excessively operate the brake pedal or steering wheel to reduce the rotational speed from that state. As a result, the impact experienced by the occupants of the four-wheel independent steering vehicle 100 when stopping during a pivot turn tends to be greater.
[0035] The following describes the vehicle control method of this embodiment, which can mitigate the impact received by the occupants of the four-wheel independent steering vehicle 100 when it comes to a stop during a pivot turn, with reference to Figure 3.
[0036] Figure 3 is a graph illustrating an embodiment of the vehicle control method according to this disclosure. The upper graph of Figure 3 shows the temporal change in rotational speed V during a four-wheel independently steered vehicle 100 when making a pivot turn. The middle graph of Figure 3 shows the temporal change in braking force Fb applied to each wheel 102 by the braking device 110 of the four-wheel independently steered vehicle 100.
[0037] The lower graph in Figure 3 shows the temporal change in the steering angle θ of each wheel 102 of the four-wheel independently steered vehicle 100 shown in Figure 1. In this graph, the solid lines represent the temporal change in the steering angle θ of the left front wheel 102FL and the right rear wheel 102RR, while the dotted lines represent the temporal change in the steering angle θ of the right front wheel 102FR and the left rear wheel 102RL.
[0038] The control device 112 of the four-wheel independent steering vehicle 100 starts the vehicle control method of this embodiment when, for example, the super-tight turning mode is selected during manual or automatic driving, and the four-wheel independent steering vehicle 100 starts super-tight turning.
[0039] When the vehicle control method of this embodiment is started, the control device 112 acquires the rotational speed V of the four-wheel independently steered vehicle 100 based on the detection result of the speed sensor 104 or the angular velocity sensor 106, for example. The control device 112 also acquires the braking force Fb applied to each wheel 102, for example. Furthermore, the control device 112 acquires the steering angle θ of each wheel 102 from the steering device 108, 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 operating device 107, or it may calculate the braking force Fb based on the output of the brake actuator of the braking device 110.
[0040] In the example shown in Figure 3, the driver or control device 112 of a four-wheel independently steered vehicle 100 performing a pivot turn at a predetermined rotational speed V0 activates the braking device 110 at time t1 to stop the pivot turn. As a result, the braking force Fb applied to each wheel 102 gradually increases from time t1, and when the braking force Fb reaches a predetermined braking force Fb1 at time t2, the rotational speed V0 of the four-wheel independently steered vehicle 100 gradually decreases and drops to a predetermined threshold V1 at time t3.
[0041] Then, for example, at time t3, the control device 112 gradually reduces the braking force Fb applied to each wheel 102, regardless of the braking force Fb based on the driver's brake pedal operation shown by the dashed line in the middle graph of Figure 3. Subsequently, at time t4, when the rotational speed V of the four-wheel independently steered vehicle 100 decreases to a predetermined threshold V2, the control device 112 outputs a steering command to the steering device 108, changing the steering angle θ of each wheel 102 from the steering angles θ1, -θ1 during a pivot turn.
[0042] Specifically, as shown in Figure 3, the control device 112 reduces the steering angle θ of the left front wheel 102FL and the right rear wheel 102RR from steering angle θ1 to steering angle θ2, while increasing the steering angle θ of the right front wheel 102FR and the left rear wheel 102RL from steering angle -θ1 to steering angle -θ2. As a result, the directions of the left front wheel 102FL and the right rear wheel 102RR, as shown in Figure 1, and the directions of the left rear wheel 102RL and the right rear wheel 102RR approach the longitudinal direction of the four-wheel independent steering vehicle 100, and a force that hinders pivot turning acts on each wheel 102.
[0043] As a result, the rate at which the rotational speed V of the four-wheel independently steered vehicle 100 decreases is slowed down, mitigating the impact when stopping, while also enabling the four-wheel independently steered vehicle 100 to stop more reliably during a pivot turn. Subsequently, if the pivot turn mode is maintained and the braking force Fb becomes zero, the control device 112 returns the steering angle θ of each wheel 102 to the steering angles θ1,-θ1 used during the pivot turn between time t5 and time t6.
[0044] As described above, the vehicle control method of this embodiment reduces the braking force Fb when a braking force Fb is applied to multiple wheels 102 during a four-wheel independently steered vehicle 100, causing the rotational speed V to drop to a threshold V1, and also changes the steering angle θ of the multiple wheels 102 from the steering angles θ1, -θ1 during the pivot turn.
[0045] With this configuration, the vehicle control method of this embodiment can slow down the rate of decrease in rotational speed V when a four-wheel independently steered vehicle 100 stops during a pivot turn, thereby mitigating the impact on the vehicle occupants when stopping during a pivot turn compared to conventional vehicle control methods. In addition, by changing the steering angle θ from the steering angles θ1, -θ1 during a pivot turn, the pivot turn can be stopped more reliably. Specifically, in conventional vehicle control methods, for example, as shown by the dashed line in the middle graph of Figure 3, the braking force Fb was gradually reduced and then increased again just before it became zero.
[0046] However, according to the vehicle control method of this embodiment, it is possible to reduce the impact on the occupants when stopping during a pivot turn more easily and reliably than with conventional vehicle control methods, and it is also possible to eliminate the need to increase the braking force Fb again or to suppress the amount of increase in the braking force Fb. As described above, according to this embodiment, it is possible to provide a vehicle control method that can reduce the impact received by the occupants of a four-wheel independent steering vehicle 100 when stopping during a pivot turn.
[0047] Preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the embodiments described above. Various modifications or substitutions can be applied to the embodiments described above without departing from the scope of the present invention.
[0048] For example, in the example shown in Figure 3, the braking force Fb is reduced when the rotational speed V drops to a threshold V1, and the steering angle θ is changed when the rotational speed V further drops to a threshold V2. However, the timing of reducing the braking force Fb and the timing of changing the steering angle θ can be simultaneous.
[0049] Furthermore, in the example shown in Figure 3, the steering angle θ was changed to move closer to the longitudinal direction of the four-wheel independently steered vehicle 100, but it may also be changed to move closer to the lateral direction of the four-wheel independently steered vehicle 100. In this case as well, each wheel 102 can act to apply a force that hinders a pivot turn. [Explanation of Symbols]
[0050] 100: Four-wheel independent steering vehicle, 102: Wheel, Fb: Braking force, V: Rotational speed, V1, V2: threshold, θ: rudder angle, θ1, -θ1: rudder angle during super-tight turning.
Claims
[Claim 1] A vehicle control method for a four-wheel independently steered vehicle, in which, when braking force is applied to multiple wheels during a pivot turn and the rotational speed drops to a threshold, the braking force is reduced and the steering angles of the multiple wheels are changed from the steering angles at the time of the pivot turn.