JP2023074883A - Vehicle control method - Google Patents

Abstract

To perform appropriate steering control depending on a road feature and the presence or absence of a lane change.SOLUTION: A vehicle control method is applied to a vehicle capable of controlling steering of front and rear wheels independently. In the control method, information related to a feature of a travel road ahead is obtained. In a case where the travel road is straight, or the travel road is curved and the vehicle changes lanes outward relative to a turning direction of the travel road, the rear wheels are controlled in the same phase as the front wheels. In contrast, in a case where the travel road is curved and the vehicle changes lanes inward relative to the turning direction of the travel road, or in a case where the travel road is curved and the vehicle does not change lanes, steering of the rear wheels is inhibited.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to vehicle control methods.

Japanese Patent Application Laid-Open No. 2002-200002 describes a steering control device that independently controls the steering of the front wheels and the rear wheels of a vehicle. This steering control device controls the front wheels and the rear wheels according to a control law that establishes a proportional relationship between the vehicle body lateral acceleration and the steering wheel angle when the road ahead is a straight road or a road on which high-speed driving is possible.

JP 2006-315514 A

According to the steering control of Patent Document 1, the rear wheel steering angle is controlled according to different control rules depending on whether the road ahead is straight or curved. In particular, in Patent Document 1, when the road ahead is curved, the rear wheel steering angle is controlled so that the vehicle body slip angle becomes zero. At this time, the rear wheels are controlled in phase with the front wheels. become. When the rear wheels are controlled in phase with the front wheels, the vehicle body slip angle is smaller than when the rear wheels are not steered (that is, when the rear wheel steering angle is zero). For this reason, the driver may feel that the vehicle is headed out, and may feel uncomfortable that it is difficult to turn.

In addition, there are cases where the traveling road ahead of the course is curved and has a plurality of lanes, and has a road shape that may change lanes during the curve. In this regard, the steering control of Patent Document 1 depends only on recognition of whether the shape of the traveling road in front of the vehicle is straight or curved, and there is room for improvement.

The present invention has been made in view of the above problems, and provides an improved vehicle control method that performs appropriate rear wheel steering control according to the shape of the road and the presence or absence of a lane change.

A vehicle control method according to the present invention is a control method for a vehicle capable of independently steering control of front wheels and rear wheels of the vehicle. In this vehicle control method, information about the shape of the road ahead of the vehicle is acquired. Then, when the road is straight, or when the road is curved and the lane is changed to the outside with respect to the turning direction of the road, the rear wheels are controlled in phase with the front wheels. On the other hand, when the road is curved and the lane is to be changed inward with respect to the turning direction of the road, or when the road is curved and the lane is not to be changed, steering of the rear wheels is prohibited.

According to the above control, when the road is straight, or when the road is curved and the lane is changed to the outside with respect to the turning direction of the road, the rear wheels are steered in the same phase as the front wheels. Lane change stability can be improved. In addition, when the road is curved and the lane is changed inward with respect to the turning direction, or when the lane is not changed, the steering of the rear wheels is prohibited, thereby improving the turning performance.

FIG. 2 is a diagram for explaining an overview of steering control in Embodiment 1 of the present invention; FIG. 4 is a flowchart showing operations of steering control executed by the control device according to Embodiment 1 of the present invention; FIG. 5 is a diagram for explaining an overview of steering control in another example of the first embodiment of the present invention; FIG. FIG. 7 is a flowchart showing another example of steering control executed by the control device according to Embodiment 1 of the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the same reference numerals are given to the same or corresponding parts, and the description thereof will be simplified or omitted.

1. Embodiment 1
The vehicle according to the present embodiment includes a front wheel steering actuator that drives the front wheels and a rear wheel steering actuator that drives the rear wheels, and the front wheels and the rear wheels are controlled independently. The vehicle is equipped with forward traveling road recognition means. The forward travel path recognition means includes means capable of detecting at least the shape of the travel path ahead of the vehicle. The road ahead recognition means may include, for example, a preview camera and LiDAR (Laser Imaging Detection and Ranging).

In addition to these forward traveling road recognizing means, the vehicle is provided with various vehicle sensors for acquiring information regarding the motion state of the vehicle. Vehicle sensors include, for example, a yaw rate sensor, a steering angle (steering wheel angle) sensor, a rear wheel steering angle sensor, and vehicle speed detection means. The steering angle (steering wheel angle) sensor measures the front wheel steering angle (steering wheel angle). The rear wheel steering angle sensor detects the steering angle of the rear wheels. The yaw rate sensor measures the turning angular velocity of the vehicle. The vehicle speed detection means may include, for example, a speed sensor that measures the running speed of the vehicle from the rotational speed of the wheels, an acceleration sensor that measures the acceleration acting on the vehicle, and the like.

The vehicle is equipped with a control device. The control device is an ECU (Electronic Control Unit) having at least one memory, at least one processor, and an input/output interface. The input/output interface takes in information from various sensors attached to the vehicle and outputs operation signals to various actuators of the vehicle. The various sensors and the like mentioned here include the above-mentioned forward traveling road recognition means, yaw rate sensor, steering angle (steering wheel angle) sensor, rear wheel steering angle sensor, speed detection means, etc. Various actuators include, for example, Included are the rear wheel steering actuators mentioned above and the like.

A processor of the control device performs various calculations based on output signals from various sensors and the like for vehicle control. The storage device stores various control programs for controlling various actuators. The processor reads the control program from the storage device and executes it. As a result, various types of vehicle control (for example, vehicle stability control (VSC)) processing is realized. The control device also processes an image of the road ahead of the vehicle captured by the preview camera. Note that the control device may be a plurality of ECUs. That is, for example, the control device may separately include an image processing ECU that performs image processing and a VSC-ECU that performs VSC control.

The control device according to the present embodiment performs steering control of the rear wheels and the front wheels by switching between a rear wheel in-phase mode in which the rear wheels are controlled in phase with the front wheels and a rear wheel steering prohibition mode in which rear wheel steering is prohibited. Execute the vehicle control method. Specifically, when the road ahead of the vehicle is straight, or when the road is curved and the lane is changed to the outside with respect to the turning direction of the road, the rear wheels are in the rear wheel in-phase mode, It is controlled by the rear wheel steering actuator. On the other hand, when the road ahead of the vehicle is curved and the lane change is not performed, or when the lane change is performed inward with respect to the turning direction, steering control is performed in the rear wheel steering prohibition mode. In either case, the front wheels are controlled according to the steering angle (steering wheel angle) obtained according to the steering angle sensor.

FIG. 1 is a diagram for explaining an example of steering control executed by a control device according to the present embodiment. A vehicle 1 is equipped with a camera 10 for photographing the front. In the example of FIG. 1, based on the image information from the camera 10 at point A, it is detected that the traveling road ahead is curved. At this time, the rear wheel steering prohibition mode is set. After that, at point B, it is determined whether or not there is a lane change.

When there is a lane change and the direction of the lane change is a turn in the C direction, which is a lane change to the outside with respect to the turning direction of the traveling road, the rear wheel steering inhibition mode is switched to the rear wheel common mode mode. As a result, the rear wheels are controlled in phase with the front wheels during a lane change on a curved road. Here, the lane change is to the outside of the turning direction, so even if the slip angle of the vehicle body is small, the driver will not feel the head out. can.

On the other hand, if there is no lane change, or if the vehicle is turning in the D direction, which is a lane change to the inside of the turn, steering control is performed in the rear wheel steering prohibition mode. As a result, it is possible to improve the turning performance during turning and improve the turning performance.

FIG. 2 is a flowchart showing a steering control routine executed by the control device according to the present embodiment. The steering control routine shown in FIG. 2 is repeatedly executed while the vehicle is running. In the routine shown in FIG. 2, first, in step S102, information such as image information of the traveling road ahead is obtained by the camera and the LiDAR. Next, in step S104, it is determined whether or not the road ahead is straight. If it is determined in step S104 that the road is not straight, it is considered that the road is curved.

In this case, the process then proceeds to step S106 to determine whether or not there is a lane change. If it is determined in step S106 that there is a lane change, the process proceeds to step S108. In step S108, it is determined whether or not the lane change is an inward lane change in the turning direction.

If it is determined in step S104 that the road is going straight, or if it is determined in step S108 that the lane is not changing to the inside in the turning direction, the process proceeds to step S110, and steering control is performed in the rear wheel in-phase mode. done.

On the other hand, if it is determined that there is no lane change in step S106, or if it is determined that the vehicle is turning inward in the turning direction in step S108, the process proceeds to step S112, and steering control is performed in the rear wheel steering prohibition mode. .

As described above, according to the control of the present embodiment, it is possible to perform appropriate steering control according to whether the road ahead of the vehicle is straight or curved, and whether or not there is a lane change. . That is, when the road is straight or curved and the lane is changed to the outside in the turning direction, the stability of the vehicle can be improved by controlling the rear wheels in the same phase as the front wheels. If the road is curved and the lane is not changed, or if the lane is changed inward in the turning direction, the rear wheel steering is prohibited, thereby improving the turning performance.

2. Other Examples For example, even if a camera or the like is mounted, it may not be possible to recognize from the camera image whether the road ahead of the vehicle is a straight line or a curved line. Also, even when changing lanes, it may not be possible to determine whether the vehicle is traveling on the curved side or on the straight side. In such a case, the lane change direction may be determined from the past travel history of the location where the vehicle is currently traveling. For example, the example of FIG. 3 shows a traveling road shape in which a lane change to either the curved side or the straight side is expected ahead of the straight traveling road. In this example, the running shape ahead of the course cannot be recognized, but from the past running history, it is expected that the lane will be changed to the curved side (arrow E side in FIG. 3). In this case, a lane change is made in the turning direction of a curve, so steering control is performed in the rear wheel steering prohibition mode with emphasis on turning performance.

FIG. 4 is a flowchart showing a steering control routine when the road shape is unknown. The routine of FIG. 4 is executed instead of the routine of FIG. The routine in FIG. 4 is the same as the routine in FIG. 2 except that it has steps S200, S202 and S204.

Specifically, when it is determined in step S104 that the traveling road ahead is not straight, it is further determined in step S200 whether or not the traveling road is curved. If it is determined in step S200 that the road is curved, the process proceeds to step S106. On the other hand, if it is determined in step S200 that the road is not curved, the controller cannot determine whether the road ahead is straight or curved. In this case, the process proceeds to step 202 and it is determined whether or not there is a past travel history.

If it is determined in step S202 that there is a past travel history, then in step S204 it is determined whether or not the frequency of travel on the straight side is higher than the frequency of travel on the curve side based on the travel history. If it is determined in step S204 that the frequency of traveling on the straight side is high, the process proceeds to step S110, and steering control in the rear wheel common mode mode is executed.

On the other hand, if it is determined in step S202 that there is no past running history, or if it is determined in step S204 that the frequency of running on the straight side is not high, the process proceeds to step S112, and steering is performed in the rear wheel steering prohibition mode. control is performed.

With the above control, it is possible to appropriately select the steering control mode for the rear wheels even when the shape of the road ahead cannot be determined.

Claims (1)

Applied to a vehicle in which the front and rear wheels of the vehicle can be independently steered and controlled,
Acquiring information about the shape of the running path ahead of the vehicle,
controlling the rear wheels to be in phase with the front wheels when the travel path is straight or when the travel path is curved and lane changes are made to the outside with respect to the turning direction of the travel path;
The steering of the rear wheels is prohibited when the road is curved and a lane change is to be made inward with respect to the turning direction of the road, or when the road is curved and the lane is not changed. vehicle control method.

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