Vehicle control method and vehicle control system

Abstract

This invention provides a vehicle control method that accurately detects the distance to the stopping position and performs braking control. [Solution] While the vehicle 100 is in motion, the camera 30 detects a stopping target at a location where the vehicle 100 should stop based on the image it acquires. Based on information acquired from the camera 30 and the travel distance sensor 25, the distance between the stopping target and the current position of the vehicle 100 is acquired. A braking map is used to stop the vehicle 100 based on the stopping target, and this braking map associates the distance between the stopping target and the current position of the vehicle 100 with the vehicle speed of the vehicle 100. When the acquired distance reaches a predetermined distance, the electric motor 20 is braked so that the vehicle speed corresponds to that distance.

Description

Technical Field

[0001] The present invention relates to a vehicle control method and a vehicle control system.

Background Art

[0002] Patent Document 1 discloses a vehicle that obtains the distance between a target position and the vehicle using information transmitted from a transmitter installed on a road, and performs braking control on the vehicle according to this distance.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of the Invention

[0004] The device described in Patent Document 1 requires a mechanism for receiving beacons transmitted by a transmitter, so there is a problem that braking control cannot be performed in a vehicle that does not have such a mechanism. Further, when detecting a stop position using a vehicle sensor such as a camera, there is a problem that the distance to the stop position may not be accurately detected due to the resolution of the camera, vibration of the vehicle, or the like.

[0005] The present invention has been made in view of such problems, and an object of the present invention is to provide a vehicle control method that accurately detects the distance to a stop position and executes braking control.

[0006] According to one aspect of the present invention, there is a vehicle control method comprising an electric motor, a camera that acquires an image of the direction of travel of the vehicle, a distance sensor capable of acquiring information on the distance traveled by the vehicle, and a controller that controls the driving of the electric motor. While the vehicle is traveling, the camera detects a stopping target at a location where the vehicle should stop based on the image it acquires, and the distance between the stopping target and the vehicle's current position is acquired based on the information acquired from the camera and the distance sensor. A braking map for stopping the vehicle based on the stopping target is used, and the electric motor is braked when the acquired distance reaches a predetermined distance so that the vehicle speed corresponds to that distance.

[0007] According to the present invention, the distance between the vehicle and the stopping target is obtained based on at least two sensors (a camera and a distance sensor). Therefore, even if the accuracy of the distance obtained from the camera is low, for example, the distance to the stopping position can be accurately detected, and the vehicle's braking control can be continuously performed based on this. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is an explanatory diagram of a vehicle according to an embodiment of the present invention. [Figure 2] Figure 2 is a block diagram of the controller configuration. [Figure 3] Figure 3 is a flowchart of the control performed by the controller. [Figure 4] Figure 4 is an explanatory diagram of the braking map. [Figure 5] Figure 5 is an explanatory diagram of the distance acquired by the controller. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings and other documents.

[0010] Figure 1 is an explanatory diagram of a vehicle 100 according to an embodiment of the present invention.

[0011] The vehicle 100 includes a controller 10, an electric motor 20, a camera 30, and a navigation system 40.

[0012] The controller 10 controls the driving state of the vehicle 100 by controlling the rotation of the electric motor 20. The electric motor 20 is powered by a battery (not shown). As will be described later, the controller 10 controls the rotation of the electric motor 20 to brake the vehicle 100 while it is in motion. Thus, the vehicle 100 is equipped with a vehicle control system in which the controller 10 controls the electric motor 20. The electric motor 20 is equipped with a resolver 25, which is a sensor for acquiring the rotation angle of the motor's rotation axis.

[0013] Camera 30 is equipped with a pair of horizontally aligned video sensors and acquires a stereo image of the area in front of the vehicle 100. Based on the image acquired by Camera 30, Controller 10 detects an object in front of the vehicle 100 and obtains the distance between the detected object and the vehicle 100.

[0014] The navigation system 40 receives signals from GPS satellites and obtains the current position of the vehicle 100 on the map from the stored map information.

[0015] Figure 2 is a block diagram of the controller 10 in this embodiment.

[0016] The controller 10 is configured to include a processor and a memory device, and the following components are realized when the processor executes a program stored in the memory device.

[0017] The controller 10 includes a stopping target detection unit 110, a distance acquisition unit 120, a braking control unit 130, and a distance completion unit 140.

[0018] The stopping target detection unit 110 detects the location and stopping target where the vehicle 100 should stop, based on information acquired by the camera 30 and the navigation system 40. The distance acquisition unit 120 acquires the distance between the vehicle 100's current position and the stopping target based on information acquired from the camera 30. The braking control unit 130 uses a braking map that associates the distance between the vehicle 100's current position and the stopping target with the vehicle speed of the vehicle 100 to control the electric motor 20 so that the vehicle speed corresponds to the acquired distance, thereby braking the vehicle 100. The distance completion unit 140 completes the distance acquired by the camera 30 based on information acquired from the resolver 25.

[0019] When the stopping target detection unit 110 detects, based on information from the navigation system 40, that the vehicle 100 has reached a predetermined distance from the place where it should stop (e.g., an intersection), the braking control unit 130 performs braking control to brake the vehicle 100 from its current position to the stopping target (e.g., a stop line) at the stopping location, either in place of or assisting the driver's operation. In this braking control, the electric motor 20 is controlled according to a pre-stored braking map so that the vehicle speed corresponds to the distance between the vehicle 100's current position and the stopping target.

[0020] Furthermore, it is preferable to use a braking map that reflects the driver's preferences. As shown in Figure 4, the braking map is a map that stores the starting position P1 for initiating braking, the starting vehicle speed V1 for initiating braking, a profile showing how the vehicle speed should change in relation to the distance from the starting position P1 to the stopping position P2, the distance from the stopping target P3 to the stopping position P2, and so on.

[0021] Since the starting position P1, starting vehicle speed V1, profile, and stopping position P2 differ depending on the driver's preferences, a braking map is set for each driver. The set braking map is pre-stored in the memory of the controller 10. Alternatively, when the driver operates the vehicle 100, the controller 10 may learn the braking map by recording the driver's actions each time the driver applies the brakes and updating the braking map.

[0022] The controller 10 determines the braking force from the electric motor 20 based on this braking map, the distance between the vehicle 100 and the stopping target, and performs braking control on the electric motor 20. Thereby, the vehicle 100 is braked in accordance with the braking map shown in FIG. 4 until the vehicle 100 reaches the stopping target.

[0023] Here, in a vehicle that calculates the distance using camera images, the distance to the stopping target may not be accurately acquired depending on the driving environment of the vehicle. Specifically, when the distance between the vehicle and the stopping target is too large, there is a risk that a distance with sufficient accuracy cannot be acquired depending on the resolution of the camera. Further, if another vehicle enters between the vehicle and the stopping target and the camera can no longer detect the stopping target, the distance to the stopping target cannot be acquired. Furthermore, the same applies when the image captured by the camera becomes unclear due to vehicle vibration, rain, fog, sunlight, or the like, resulting in low distance accuracy or the inability to acquire the distance.

[0024] When the distance to the stopping target cannot be accurately acquired in this manner, it becomes difficult to brake the vehicle 100 to the stopping target in accordance with the braking map.

[0025] Therefore, in the present embodiment, the following control is configured to enable more appropriate braking control even when the distance cannot be accurately detected from the image captured by the camera 30.

[0026] FIG. 3 is a flowchart of the braking process executed by the controller 10 of the present embodiment.

[0027] First, in step S10, the stopping target detection unit 110 determines whether the vehicle 100 is traveling based on position information from the navigation system 40 or a detection value from a vehicle speed sensor mounted on the vehicle 100. If it is determined that the vehicle 100 is traveling, the process proceeds to step S20. If the vehicle is not traveling, this process is repeated.

[0028] In step S20, the stopping target detection unit 110 determines whether the distance from the vehicle 100's current position on the map detected by the navigation system 40 to the intersection (the place where the vehicle should stop) is a predetermined distance. If it determines that the distance between the vehicle 100 and the intersection is less than or equal to the predetermined distance (for example, 150m), the process proceeds to step S30. If it is not the predetermined distance, this process is repeated.

[0029] In step S30, the stopping target detection unit 110 determines whether or not it has detected a stop line (stopping target) at the intersection based on the image acquired by the camera 30. If a stop line is detected, the process proceeds to step S50. If a stop line is not detected, the process proceeds to step S40.

[0030] In step S40, the stopping target detection unit 110 determines, based on the image acquired by the camera 30, whether or not it has detected an indicator other than a stop line, such as a traffic light (red light) or a road sign (stop sign), that should cause the vehicle 100 to stop. If such indicators are detected, the process proceeds to step S50. If not detected, the process in step S30 is executed.

[0031] In step S50, the braking control unit 130 sets the stop line, signal, or road sign detected by the stopping target detection unit 110 as the stopping target. Then, in step S60, the braking control unit 130 starts braking control based on the distance to the stopping target acquired by the distance acquisition unit 120 and the braking map. Specifically, the braking control unit 130 uses the braking map to control the electric motor 20 so that the vehicle speed corresponds to the acquired distance, thereby braking the vehicle 100. At this time, even if the driver makes an action (for example, pressing the brake pedal or accelerator pedal), the electric motor 20 is controlled in accordance with the braking map. However, if the amount the brake pedal is pressed is large, the electric motor 20 and brakes may be controlled to perform emergency braking without following the braking map.

[0032] Next, in step S70, the braking control unit 130 determines whether the detection accuracy of the distance to the stopping target acquired by the distance acquisition unit 120 is low. More specifically, the braking control unit 130 determines that the distance detection accuracy is low if, based on the image information acquired from the camera 30, the acquired image quality is poor, the stopping target cannot be detected, the image is unclear, etc. If it is determined that the distance detection accuracy is low, the process proceeds to step S80. If the distance detection accuracy is sufficient, the process from step S80 to S110 is skipped and the process proceeds to step S120.

[0033] In step S80, the distance interpolation unit 140 detects the rotation angle of the electric motor 20 from the resolver 25 of the electric motor 20 and calculates the distance traveled by the vehicle 100 per predetermined time based on the detected rotation angle. This distance traveled may be calculated based on the detected rotation angle, the reduction ratio of the reduction gear, the wheel diameter, etc.

[0034] Then, in step S90, the distance interpolation unit 140 interpolates the distance obtained by the stopping target detection unit 110 using the camera 30 in the previous processing using the calculated travel distance. In other words, the distance interpolation unit 140 calculates the distance between the current vehicle 100 and the stopping target by subtracting the travel distance calculated using the detection signal of the resolver 25 from the distance calculated using the camera 30 before it was determined that the accuracy was low.

[0035] Thus, if the distance accuracy is low, the braking control unit 130 continues braking control to the stopping target based on the compensated distance.

[0036] Next, in step S100, the braking control unit 130 determines whether the video signal from the camera 30 acquired by the stopping target detection unit 110, or the rotation angle signal from the resolver 25 acquired by the distance interpolation unit 140, is abnormal and whether a malfunction has occurred in either of them. If both the camera 30 and the resolver 25 are determined to be normal, the process in step S120 is executed. If at least one of the signals is determined to be abnormal and a malfunction has occurred, the process in step S110 is executed.

[0037] A malfunction can be detected, for example, by detecting that the signals sent from the camera 30 or resolver 25 are either nonexistent or exceed the normal range. Malfunctions include not only failures of the camera 30 or resolver 25, but also failures of the harness connecting them to the controller 10.

[0038] In step S110, the braking control unit 130 performs a process to weaken the braking control. Specifically, if a sensor or the like malfunctions, the distance between the vehicle 100 and the stopping target cannot be accurately detected. Therefore, in this embodiment, for example, the braking control in S60 that brakes the vehicle toward the stopping target is canceled, and the braking force of the electric motor 20 is suppressed more than the braking control performed in step S60, so that the braking force of the electric motor 20 becomes smaller without following the braking map. For example, the electric motor 20 is controlled so that the deceleration of the current vehicle 100 remains constant. After the processing in step S110, the processing according to this flowchart is terminated.

[0039] As a result, the driver will need to apply the brakes to bring the vehicle 100 to a stop at the target location. The braking control unit 130 may also notify the driver that the braking control has been reduced by displaying a message on the instrument panel or the like. In response, the driver will be able to recognize that braking is required.

[0040] In step S120, the braking control unit 130 determines whether the vehicle speed of the vehicle 100 has become 0 and the vehicle has come to a stop. If it is determined that the vehicle 100 has come to a stop, the process according to this flowchart is terminated. Otherwise, the process in step S70 is executed.

[0041] With the control described above, if the distance to the stopping target can no longer be accurately detected by the image acquired by the camera 30, the braking control can be continued by compensating for the distance to the stopping target based on the signal from the resolver 25 of the electric motor 20.

[0042] Figure 5 is an explanatory diagram illustrating braking control by the controller 10.

[0043] Braking control is initiated at time t0 as shown in Figure 5. Here, between timing t0 and timing t1, the distance to the stopping target is large, and the accuracy of the distance acquired by camera 30 is low, resulting in a sparse distance being acquired. In this case, the distance interpolation unit 140 interpolates the distance after the distance acquired by camera 30 at timing t0 based on the signal acquired from resolver 25, so that the distance during this period is acquired as shown by the dotted line.

[0044] Furthermore, between timing t1 and timing t2, the camera 30 is unable to correctly recognize the stopping target and therefore cannot accurately detect the distance. In this case, the distance interpolation unit 140 interpolates the distance after the distance acquired by the camera 30 at timing t1 based on the signal acquired from the resolver 25, so that the distance during this period is obtained as shown by the dotted line.

[0045] Furthermore, since the distance accuracy is low between timing t2 and timing t3, similar to the distance between timing t0 and timing t1, the distance is interpolated using the signal obtained from resolver 25. Additionally, since the distance cannot be obtained between timing t3 and timing t4, similar to the distance between timing t1 and timing t2, the distance is interpolated using the signal obtained from resolver 25. In this way, the distance is obtained as shown by the dotted line.

[0046] From timing t4 onward, since the distance detection accuracy acquired by camera 30 is sufficient, braking control of vehicle 100 towards the stopping target is performed using this distance.

[0047] As described above, this embodiment is a vehicle control system comprising an electric motor 20, a camera 30 that acquires an image of the direction of travel of the vehicle 100, a resolver 25 as a distance sensor capable of acquiring information on the distance traveled by the vehicle 100, and a controller 10 that controls the driving of the electric motor 20. The controller 10 detects a stopping target at a location where the vehicle 100 should stop, based on the image acquired by the camera 30 while the vehicle 100 is traveling. Based on the information acquired from the camera 30 and the resolver 25, the controller 10 acquires the distance between the stopping target and the current position of the vehicle 100. Using a braking map for stopping the vehicle 100 based on the stopping target, which associates the distance between the stopping target and the current position of the vehicle 100 with the vehicle speed of the vehicle 100, the controller 10 brakes the electric motor 20 so that the vehicle speed becomes corresponding to the distance when the acquired distance reaches a predetermined distance.

[0048] In this configuration, the distance between the vehicle 100 and the stopping target is obtained based on at least two sensors (camera 30 and resolver 25). Therefore, even if the accuracy of the distance obtained from camera 30 is low, for example, the distance to the stopping position can be accurately detected, and braking control of the vehicle 100 can be continued based on this.

[0049] Furthermore, since the braking map of this embodiment reflects the driver's personal preferences regarding braking, the vehicle 100 can be braked according to the driver's preferences.

[0050] In this embodiment, the camera 30 is an image sensor capable of detecting the distance to the stopping target from the acquired image, and the travel distance sensor is a resolver 25 capable of detecting the travel distance of the vehicle 100 per unit time by acquiring the rotation angle of the electric motor 20. Based on the information detected by the camera 30, the distance is acquired, and if the accuracy of the acquired distance is low, the distance acquired by the camera 30 is supplemented based on the travel distance of the vehicle 100 produced using the rotation angle detected by the resolver 25.

[0051] In this configuration, even if the accuracy of the distance acquired from the camera 30 is low, the distance to the stopping position can be accurately detected based on the signal from the resolver 25.

[0052] Furthermore, in this embodiment, if at least one of the camera 30 and the resolver 25 fails, the braking control of the electric motor 20 is suppressed.

[0053] In this configuration, if at least one of the camera 30 and the resolver 25 is not functioning correctly, the braking force can be suppressed, allowing the driver to brake the vehicle 100.

[0054] Furthermore, if a malfunction occurs and the braking force of the electric motor 20 is suppressed, the driver is notified of this, so the driver can understand that the vehicle 100 will not automatically brake.

[0055] Furthermore, in this embodiment, the stopping targets are stop lines, traffic lights, and stop signs at intersections, so the vehicle 100 can be reliably stopped at the designated stopping location.

[0056] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

[0057] In this embodiment, the distance to the stopping target is obtained from the stereo image acquired by the camera 30, but this is not limited to this. For example, if the accuracy of the position information acquired by the navigation system 40 is high, the distance to the stopping target may be obtained using this information, or the distance to the stopping target may be obtained using other sensors (e.g., ultrasonic sensors). Furthermore, the acquisition of the travel distance by the distance interpolation unit 140 may be performed not by the resolver 25, but by a rotation sensor provided in the reduction gear or axle, etc. [Explanation of Symbols]

[0058] 10: Controller, 20: Electric motor, 25: Resolver, 30: Camera, 40: Navigation system, 100: Vehicle, 110: Stop target detection unit, 120: Distance acquisition unit, 130: Braking control unit, 140: Distance completion unit

Claims

1. A vehicle control method comprising an electric motor, a camera for acquiring images of the vehicle's direction of travel, a distance sensor capable of acquiring information regarding the vehicle's travel distance, and a controller for controlling the operation of the electric motor, While the vehicle is in motion, the camera detects a stopping target at a location where the vehicle should stop, Based on the information obtained from the camera and the distance sensor, the distance between the stopping target and the current position of the vehicle is obtained. A braking map for stopping the vehicle based on the aforementioned stopping target, wherein the braking map associates the distance between the stopping target and the vehicle's current position with the vehicle's speed, and the electric motor is braked so that the vehicle speed becomes corresponding to the distance when the acquired distance reaches a predetermined distance. A method for controlling a vehicle.

2. A vehicle control method according to claim 1, The aforementioned braking map is a map that reflects the driver's personal preferences regarding braking. A method for controlling a vehicle.

3. A vehicle control method according to claim 1 or 2, The camera is an image sensor capable of detecting the distance to the stopping target from the acquired image, The aforementioned distance sensor is a resolver that acquires the rotation angle of the electric motor, Based on the information acquired by the video sensor, the distance is acquired, If the accuracy of the acquired distance is low, the distance acquired by the video sensor is supplemented based on the vehicle's travel distance calculated using the rotation angle acquired by the travel distance sensor. A method for controlling a vehicle.

4. A vehicle control method according to claim 2, If it is determined that at least one of the camera and the distance sensor is malfunctioning, The braking power of the aforementioned electric motor is suppressed. A method for controlling a vehicle.

5. A vehicle control method according to claim 4, When the braking force of the electric motor is suppressed, the driver is notified accordingly. A method for controlling a vehicle.

6. A vehicle control method according to claim 1, The aforementioned stopping targets are stop lines, traffic lights, and stop signs at intersections. A method for controlling a vehicle.

7. A vehicle control system comprising an electric motor, a camera that acquires an image of the vehicle's direction of travel, a distance sensor capable of acquiring information regarding the vehicle's travel distance, and a controller that controls the operation of the electric motor, The aforementioned controller, While the vehicle is in motion, the camera detects a stopping target at a location where the vehicle should stop, Based on the information obtained from the camera and the distance sensor, the distance between the stopping target and the current position of the vehicle is obtained. A braking map for stopping the vehicle based on the aforementioned stopping target, wherein the braking map associates the distance between the stopping target and the vehicle's current position with the vehicle's speed, and the electric motor is braked so that the vehicle speed becomes corresponding to the distance when the acquired distance reaches a predetermined distance. Vehicle control system.

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