Rudder angle determination device

Abstract

To provide a rudder angle determination device that can improve the accuracy of determining the midpoint of operation and the midpoint of the rudder angle. [Solution] The steering angle determination device 10 includes an operation midpoint determination unit 102 that determines whether the center mark is located in an operation midpoint region that is pre-set to allow the vehicle to travel in a straight line within the operating range, based on an image of the center mark (image data DM) captured by a driver monitor camera, and a steering angle midpoint determination unit 104 that, when the operation midpoint determination unit 102 has determined that the center mark is located in the operation midpoint region, determines whether the steering wheel has been steered to a steering angle midpoint region that is pre-set to include the steering angle midpoint that allows the vehicle to travel in a straight line, based on images of the steering state (image data DR and image data DL) captured by a right-side camera and a left-side camera.

Description

Technical Field

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[0001] The present invention relates to a rudder angle determination device.

Background Art

[0002] [[ID=II]] Conventionally, for example, a parking assistance system disclosed in Patent Document 1 has been known. The conventional parking assistance system detects the turning angle of the front wheels based on the three-dimensional distance information of the front wheels measured by one of the infrared laser cameras provided on both sides of the vehicle, and corresponds the turning angle of the front wheels to the steering angle of the steering wheel to determine the midpoint of the steering wheel. Thus, although it is difficult to detect the midpoint of the steering wheel only by the steering angle of the steering wheel, by detecting the turning condition of the front wheels and detecting the midpoint of the steering wheel, the calculation of the planned travel trajectory can be accurately performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the conventional parking assistance system, the midpoint of the operation in the operation range of the steering wheel, that is, the steering wheel, is determined only based on the determination based on the three-dimensional distance information of the front wheels, that is, the steered wheels, imaged by the infrared laser camera. Usually, in the steering control of the steered wheels of the vehicle, it is necessary to accurately determine and decide the midpoint of the operation of the steering wheel and the midpoint of the steering angle of the steered wheels. In this regard, in the conventional parking assistance system, improvement for improving the accuracy of the determination of the midpoint of the operation and the midpoint of the steering angle is necessary. <000,026>

[0005] An object of the present invention is to provide a rudder angle determination device capable of improving the determination accuracy of the midpoint of the operation and the midpoint of the steering angle.

Means for Solving the Problems

[0006] The steering angle determination device of the present invention is applied to a vehicle equipped with a steering wheel on which a center mark indicating the midpoint of operation within the driver's operating range is provided, a first imaging device positioned to capture images of the steering wheel and capable of capturing images of the center mark, and a second imaging device capable of capturing images of the steering state of the steering wheels that are steered in response to the operation of the steering wheel, and comprises an operating midpoint determination unit that determines whether the center mark is located in an operating midpoint region that is pre-set to cause the vehicle to travel in a straight line within the operating range, based on an image of the center mark captured by the first imaging device, and a steering angle midpoint determination unit that, given that the operating midpoint determination unit has determined that the center mark is located in the operating midpoint region, determines whether the steering wheels are steered to a steering angle midpoint region that is pre-set to include the midpoint of the steering angle that causes the vehicle to travel in a straight line, based on an image of the steering state captured by the second imaging device. [Effects of the Invention]

[0007] According to the present invention, when the operation midpoint determination unit determines that the center mark is located in the operation midpoint region based on an image of the center mark captured by the first imaging device, the steering angle midpoint determination unit can determine that the steering wheel is located in the steering angle midpoint region based on an image of the steering state of the steering wheel captured by the second imaging device. Therefore, the steering angle determination device of the present invention can improve the accuracy of determining the operation midpoint and the steering angle midpoint. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram illustrating a vehicle to which the steering angle determination device of this embodiment is applied. [Figure 2] This is a schematic block diagram illustrating the configuration of the rudder angle determination device. [Figure 3] (A) and (B) are diagrams to explain the determination of the center mark. [Figure 4](A) and (B) are diagrams illustrating the determination of the steering state. [Figure 5] This is a flowchart of the steering angle determination program. [Modes for carrying out the invention]

[0009] Hereinafter, a steering angle determination device 10, which is an embodiment of the present invention, will be described in detail with reference to the drawings. In addition to the embodiments described below, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

[0010] 1. Configuration of the vehicle 1 to which the steering angle determination device 10 is applied In this embodiment, the steering angle determination device 10 is applied to the vehicle 1 shown in Figure 1. The vehicle 1 is equipped with wheels 2 consisting of a right front wheel 21, a left front wheel 22, a right rear wheel 23, and a left rear wheel 24. The vehicle 1 is also equipped with a steering device 3 that steers the right front wheel 21 and the left front wheel 22 as steering wheels when driving. In this embodiment, the steering device 3 is exemplified as a well-known electric power steering device. The configuration of the steering device 3, i.e., the electric power steering device, will be briefly described below.

[0011] The steering system 3 comprises a steering wheel 31, a steering shaft 32, a steering column 33, and a steering mechanism 34. The steering wheel 31 is an operating member operated by the driver. The steering shaft 32 is composed of a column shaft, intermediate shaft, pinion shaft, universal joint, etc., which is rotatably supported by the steering column 33. The steering column 33 is supported by an instrument panel reinforcement (not shown) provided in the vehicle 1.

[0012] The steering wheel 31 is connected to the upper end of the steering shaft 32, and the steering mechanism 34 is connected to the lower end of the steering shaft 32. In this way, in the steering device 3, the steering input given by the driver to the steering wheel 31 is transmitted to the steering mechanism 34 via the steering shaft 32.

[0013] The steering mechanism 34 has a rack and pinion mechanism consisting of a pinion gear (not shown) fixed to the pinion shaft that constitutes the steering shaft 32, and a rack bar 35 supported by a housing that is movable in the left-right direction and has rack teeth (not shown) that mesh with the pinion gear. The steering mechanism 34 also has an electric motor 36 that provides assist force to the rack bar 35 in response to the operation input transmitted from the steering wheel 31. The electric motor 36 is a so-called rack-parallel type electric motor, mounted on the rack bar 35 so that its axis of rotation is parallel to the central axis of the rack bar 35.

[0014] Although not shown in the diagram, the steering mechanism 34 is provided with, for example, a ball screw mechanism that converts the rotation of the electric motor 36 into the reciprocating motion of the rack bar 35 and reduces its speed. In this embodiment, the steering device 3 is exemplified as a rack-assist type electric power steering device in which an electric motor 36 is attached to the rack bar 35 to provide assist force. However, the steering device 3 may also be a pinion-assist type electric power steering device that provides assist force via a pinion shaft (pinion gear) constituting the steering shaft 32, or a rack-assist type electric power steering device that provides assist force via a column shaft constituting the steering shaft 32.

[0015] The steering mechanism 34 has a rack bar 35, the ends of which are connected to the left and right steering knuckles 38 via link rods 37. Therefore, the steering mechanism 34 steers the steering wheels, namely the right front wheel 21 and the left front wheel 22, in the left and right directions by reciprocating the rack bar 35 in the left and right directions in response to the operation of the steering wheel 31.

[0016] As a result, in this embodiment, the steering wheel 31 is connected to the right front wheel 21 and the left front wheel 22 via the steering shaft 32 and the steering mechanism 34, so that the movement in the direction of operation due to the operation of the steering wheel 31 corresponds to the movement in the left-right direction (steering direction) due to the steering of the right front wheel 21 and the left front wheel 22. In other words, in this embodiment, the operation of the steering wheel 31 and the steering state of the steering wheels (right front wheel 21 and left front wheel 22) steered by the steering mechanism 34, i.e., the steering state of the steering wheels (right front wheel 21 and left front wheel 22) corresponding to the operation of the steering wheel 31 have a predetermined relationship, for example, a one-to-one relationship.

[0017] Furthermore, the steering wheel 31 is marked with a center mark 4. The center mark 4 corresponds to the midpoint of the steering wheel 31's operation range by the driver, for example, the boundary position between a rightward rotation and a leftward rotation, which enables the vehicle 1 to travel straight, in other words, the neutral position of the steering wheel 31. In this embodiment, when the steering wheel 31 is operated to the neutral position, the center mark 4 is placed on the opposite side of the steering column 33 (towards the steering column 33) of the apex position of the steering wheel 31 (the position that is upward in the vertical direction) (see Figure 3).

[0018] The vehicle 1 also includes a driver monitor camera 5 as a first imaging device. The driver monitor camera 5 is mainly configured to be able to image the face of the driver sitting in the driver's seat. Therefore, the driver monitor camera 5 is arranged inside the vehicle cabin of the vehicle 1 at a position where the face of the seated driver can be imaged. In the present embodiment, an example is given where the driver monitor camera 5 is provided on the upper surface (upper face) in the vertical direction of the steering column 33. Note that the driver monitor camera 5 can also be arranged, for example, on the dashboard, the sun visor, or the like.

[0019] When the driver monitor camera 5 is arranged on the steering column 33, as shown in FIG. 1, the driver monitor camera 5 is arranged in front of the steering wheel 31 in the vehicle 1 and images the face of the driver sitting over the steering wheel 31. Thereby, the driver monitor camera 5 can image the center mark 4 provided at the apex position of the steering wheel 31. Here, when the driver monitor camera 5 is provided on the upper surface of the steering column 33, the driver monitor camera 5 can image the center mark 4 only when the steering wheel 31 is returned to the vicinity of the neutral position.

[0020] Furthermore, the vehicle 1 includes a surrounding camera 6 as a second imaging device. The surrounding camera 6 images the surrounding area of the vehicle 1 including a part of the vehicle 1, and includes a right-side camera 61 provided on the right side of the vehicle 1 to image the right-side periphery of the vehicle 1, and a left-side camera 62 provided on the left side of the vehicle 1 to image the left-side periphery of the vehicle 1. The right-side camera 61 is provided, for example, on the right outer mirror of the vehicle 1, and images a part including the right front wheel 21 as a part of the vehicle 1 (see FIG. 4). The left-side camera 62 is provided, for example, on the left outer mirror of the vehicle 1, and images a part including the left front wheel 22 as a part of the vehicle 1 (see FIG. 4). Incidentally, although not shown, the surrounding camera 6 may include a front camera provided in front of the vehicle 1 to image the front of the vehicle 1 and a rear camera provided behind the vehicle 1 to image the rear of the vehicle 1, and the front camera, the right-side camera 61, the left-side camera 62, and the rear camera can image the surrounding area of the vehicle 1.

[0021] Furthermore, the vehicle 1 includes a controller 7 configured to include a plurality of electronic control units (Electric Control Unit) having a microcomputer having a CPU, a ROM, a RAM, and various interfaces as a main part. In the present embodiment, the controller 7 includes an electronic control unit 71 (hereinafter referred to as "EPS-ECU71") that controls the operation of the steering device 3, and an electronic control unit 72 (hereinafter referred to as "DM-ECU72") that executes various driving support processes based on an image captured by the driver monitor camera 5, and an electronic control unit 73 (hereinafter referred to as "PVM-ECU73") that generates a surrounding image of the vehicle 1 using an image captured by the surrounding camera 6 and executes various driving support processes.

[0022] Furthermore, in this embodiment, the controller 7 includes an electronic control unit 74 (hereinafter referred to as "AB-ECU74") that controls the operation of an airbag system (not shown) mounted on the vehicle 1, an electronic control unit 75 (hereinafter referred to as "A-ECU75") that controls the operation of a driving force generating device (not shown), such as an internal combustion engine or a drive electric motor, mounted on the vehicle 1, and an electronic control unit 76 (hereinafter referred to as "B-ECU76") that controls the operation of a brake system (not shown) mounted on the vehicle 1. The EPS-ECU71, DM-ECU72, PVM-ECU73, AB-ECU74, A-ECU75, and B-ECU76 are connected to a communication line L (for example, CAN (Car Area Network or Controllable Area Network)) established in the vehicle 1, enabling them to communicate with each other.

[0023] The EPS-ECU71 is connected to the torque sensor 81 and motor rotation angle sensor 82, which constitute the sensor group 8. The torque sensor 81 detects and outputs torque T as an input from the driver, for example, based on the twist of a torsion bar provided on the upper steering shaft of the steering shaft 32. The torque sensor 81 can also be configured to be provided on the electric motor 36 to detect the torque generated by the electric motor 36. The motor rotation angle sensor 82 is provided on the electric motor 36 and detects and outputs the motor rotation angle θ of the electric motor 36 (corresponding to the steering angle of the steering wheels, the right front wheel 21 and the left front wheel 22). Based on the torque T output from the torque sensor 81 and the motor rotation angle θ output from the motor rotation angle sensor 82, the EPS-ECU71 controls the operation of the electric motor 36 to apply assist force in response to the driver's input to the steering wheel 31.

[0024] Furthermore, the DM-ECU72 acquires image data DM representing an image that may include the center mark 4 captured by the driver monitor camera 5, performs various driving support processes, and outputs the image data DM to the EPS-ECU71, or more specifically, the steering angle determination device 10, which will be described in detail later, via the communication line L. Furthermore, the PVM-ECU73 acquires image data DR representing an image including the steering state of the right front wheel 21 captured by the right side camera 61, and image data DL representing an image including the steering state of the left front wheel 22 captured by the left side camera 62, performs processing to generate an image of the area around the vehicle 1, and outputs the image data DR and image data DL to the EPS-ECU71, or more specifically, the steering angle determination device 10, which will be described in detail later, via the communication line L.

[0025] Furthermore, the AB-ECU74 is connected to the yaw rate sensor 83 and acceleration sensor 84, which are mounted on the vehicle 1 and constitute the sensor group 8. The yaw rate sensor 83 detects and outputs the yaw rate γ around the center of gravity generated in the vehicle 1. The acceleration sensor 84 detects and outputs the acceleration G generated in the vehicle 1. As a result, the AB-ECU74 controls the operation of the airbag system (not shown) based on the yaw rate γ output from the yaw rate sensor 83 and the acceleration G output from the acceleration sensor 84, and also outputs the yaw rate γ and acceleration G to the EPS-ECU71, or more specifically, the steering angle determination device 10, which will be described in detail later, via the communication line L.

[0026] Furthermore, the A-ECU75 is mounted on the vehicle 1 and connected to the accelerator sensor 85, which is part of the sensor group 8. The accelerator sensor 85 detects and outputs the amount A of operation of the accelerator operating member (accelerator pedal, etc.) operated by the driver. Based on the amount A output from the accelerator sensor 85, the A-ECU75 controls the operation of the drive force generating device (not shown).

[0027] Furthermore, the B-ECU76 is connected to the brake sensor 86 and wheel speed sensor 87, which are mounted on the vehicle 1 and constitute the sensor group 8. The brake sensor 86 detects and outputs the amount B of operation of the brake operating member (brake pedal, etc.) operated by the driver. The wheel speed sensor 87 detects and outputs the wheel speed Wv of the right front wheel 21, left front wheel 22, right rear wheel 23, and left rear wheel 24. As a result, the B-ECU76 controls the operation of the braking system (not shown) based on the amount B of operation output from the brake sensor 86 and the wheel speed Wv output from each wheel speed sensor 87, and outputs the wheel speed Wv to the EPS-ECU71, or more specifically, the steering angle determination device 10 which will be described in detail later, via the communication line L.

[0028] 2. Configuration of the rudder angle determination device 10 Furthermore, as shown in Figures 1 and 2, the vehicle 1 is equipped with a steering angle determination device 10 that determines the midpoint of the steering angle, which is the reference steering angle when steering the right front wheel 21 and the left front wheel 22, which are the steering wheels. In this embodiment, the case in which the steering angle determination device 10 is provided in the EPS-ECU 71 is illustrated. The steering angle determination device 10 can be provided in other ECUs, including the aforementioned ECUs, that are different from the EPS-ECU 71, or it can be provided independently of the ECU.

[0029] The rudder angle determination device 10 also includes a microcomputer with a CPU, ROM, RAM, and various interfaces as its main components. As shown in Figure 2, the rudder angle determination device 10 is composed of an acquisition unit 101, an operation midpoint determination unit 102, a rudder angle storage unit 103, a rudder angle midpoint determination unit 104, a rudder angle midpoint correction unit 105, and an output unit 106.

[0030] The acquisition unit 101 is connected to the communication line L. Through this connection, the acquisition unit 101 acquires image data DM output via DM-ECU72, image data DR and image data DL output via PVM-ECU73, yaw rate γ and acceleration G output via AB-ECU74, and wheel speed Wv output via B-ECU76. The acquisition unit 101 also acquires the motor rotation angle θ output from the motor rotation angle sensor 82. The acquisition unit 101 then outputs the acquired image data DM to the steering midpoint determination unit 102, the acquired motor rotation angle θ to the steering angle storage unit 103, the acquired image data DR and image data DL to the steering angle midpoint determination unit 104, and the acquired yaw rate γ, acceleration G, and wheel speed Wv to the steering angle midpoint correction unit 105.

[0031] The operation midpoint determination unit 102 determines whether the center mark 4 is located in the operation midpoint region Ro, which is pre-set within the operating range of the steering wheel 31 to allow the vehicle 1 to travel in a straight line, based on the image of the center mark 4 represented by the image data DM. Specifically, the operation midpoint determination unit 102 determines, based on the image data DM representing the image captured by the driver monitor camera 5, that the center mark 4 is located in the pre-set operation midpoint region Ro, as shown in Figure 3(A), when the steering wheel 31 is operated to near the neutral position (or maintains a stopped state near the midpoint position), that is, when the center mark 4 is visible in the image represented by the image data DM.

[0032] On the other hand, the operation midpoint determination unit 102 determines, based on the image data DM representing the image captured by the driver monitor camera 5, that the center mark 4 is not in the operation midpoint region Ro if, as shown in Figure 3(B), the steering wheel 31 is operated to a position away from the neutral position (or maintains a stopped state at a position away from the midpoint position), that is, if the center mark 4 is not visible in the image represented by the image data DM. The operation midpoint determination unit 102 then outputs a determination result H1 indicating that the center mark 4 is in the operation midpoint region Ro to the steering angle storage unit 103.

[0033] Based on the determination result H1 obtained from the operation midpoint determination unit 102, the steering angle memory unit 103 stores the steering angles of the right front wheel 21 and the left front wheel 22 at the time of determination as the temporary steering angle midpoint θt, if the center mark 4 is in the operation midpoint region Ro. That is, the steering angle memory unit 103 obtains the motor rotation angle θ corresponding to the steering angle of the steering wheels, the right front wheel 21 and the left front wheel 22, from the acquisition unit 101. The steering angle memory unit 103 then stores the motor rotation angle θ obtained when the determination result H1 was obtained, i.e., when the operation midpoint determination unit 102 made the determination, as the temporary steering angle midpoint θt. The steering angle memory unit 103 then outputs the temporary steering angle midpoint θt to the steering angle midpoint determination unit 104.

[0034] The steering angle midpoint determination unit 104 determines, based on the steering state of the right front wheel 21 represented by image data DR and the steering state of the left front wheel 22 represented by image data DL, whether the steering wheels, the right front wheel 21 and the left front wheel 22, are steered to a predetermined steering angle midpoint region Rs that includes the steering angle midpoint θf that causes the vehicle 1 to travel in a straight line, when the operating midpoint determination unit 102 has determined that the center mark 4 is in the operating midpoint region Ro. Here, the steering angle midpoint region Rs and the operating midpoint region Ro have a corresponding relationship with each other.

[0035] Specifically, the steering angle midpoint determination unit 104 determines, based on the image data DR representing the image captured by the right-side camera 61 and the image data DL representing the image captured by the left-side camera 62, that, as shown in Figure 4(A), for example, if the side Mt extending in the longitudinal direction of the vehicle 1 at the right front wheel 21 and the left front wheel 22 is approximately parallel to the side Mc of the vehicle body 1, then the provisional steering angle midpoint θt is located in the steering angle midpoint region Rs. In other words, in this case, the right front wheel 21 and the left front wheel 22 are located near the so-called center. Here, the angle of the side Mt with respect to the side Mc corresponds to the steering angle of the steering wheels, the right front wheel 21 and the left front wheel 22.

[0036] On the other hand, the steering angle midpoint determination unit 104 determines, based on the image data DR representing the image captured by the right-side camera 61 and the image data DL representing the image captured by the left-side camera 62, that, as shown in Figure 4(B), if, for example, the side Mt of the right front wheel 21 and the left front wheel 22 is not parallel to the side Mc of the vehicle 1, the provisional steering angle midpoint θt is not located in the steering angle midpoint region Rs. In other words, in this case, the right front wheel 21 and the left front wheel 22 are not located near the center. The steering angle midpoint determination unit 104 then outputs a determination result H2 to the steering angle midpoint correction unit 105, indicating that the provisional steering angle midpoint θt is located in the steering angle midpoint region Rs, that is, that the right front wheel 21 and the left front wheel 22 are located near the center. Furthermore, if the temporary steering angle midpoint determination unit 104 is located in the steering angle midpoint region Rs, it determines the temporary steering angle midpoint θt as the initial steering angle midpoint θc and outputs the initial steering angle midpoint θc to the steering angle midpoint correction unit 105.

[0037] The steering angle midpoint correction unit 105 corrects the initial steering angle midpoint θc determined by the steering angle midpoint determination unit 104 by performing steering angle midpoint learning while the vehicle 1 is traveling in a straight line, thereby determining a more accurate steering angle midpoint θf. Specifically, the steering angle midpoint correction unit 105 acquires the yaw rate γ, acceleration G, and wheel speed Wv from the acquisition unit 101, as well as the motor rotation angle θ, and executes a well-known steering angle midpoint learning process while traveling. Here, an example of a well-known steering angle midpoint learning process while traveling is a learning process that determines whether the vehicle 1 is traveling in a straight line using at least one of the state variables among the yaw rate γ, acceleration G, and wheel speed Wv (more specifically, the wheel speed pulse), and learns the relationship between the state variable and the motor rotation angle θ when the vehicle 1 is traveling in a straight line. Then, the steering angle midpoint correction unit 105 determines the steering angle midpoint θf by correcting the initial steering angle midpoint θc using, for example, a value related to the steering angle that can be calculated based on the state variables of the vehicle 1 while it is in motion, based on the results of the steering angle midpoint learning process during driving.

[0038] The steering angle midpoint correction unit 105 then outputs the determined steering angle midpoint θf to the output unit 106. The steering angle midpoint correction unit 105 also outputs the determined steering angle midpoint θf to the steering angle memory unit 103. As a result, the EPS-ECU 71 can use the steering angle midpoint θf stored in the steering angle memory unit 103 as the reference steering angle to control the operation of the electric motor 36 of the steering device 3.

[0039] The output unit 106 outputs the steering angle midpoint θf, which has been corrected and determined by the steering angle midpoint correction unit 105, via the communication line L. This allows, for example, ECUs other than the EPS-ECU 71 that make up the controller 7, and ECUs other than the controller 7, to use a highly accurate steering angle midpoint θf as needed in their own control.

[0040] 3. Operation of the rudder angle determination device 10 Next, the operation of the steering angle determination device 10 in this embodiment will be explained using Figure 5. Based on various information supplied from A-ECU75 and B-ECU76, the CPU of the steering angle determination device 10 (or the CPU of EPS-ECU71) starts executing the steering angle determination program shown in Figure 5 in step S10, for example, when the vehicle 1 starts moving from a state where it is parked in a parking lot or the like.

[0041] Then, in the following step S11, the steering angle determination unit 102 of the steering angle determination device 10 determines whether the center mark 4 is in the steering midpoint region Ro, for example, when the vehicle 1 is stationary. That is, based on the image data DM acquired from the driver monitor camera 5, the steering midpoint determination unit 102 determines "Yes" if the center mark 4 has been captured, i.e., the center mark 4 is in the steering midpoint region Ro, and the steering angle determination device 10 executes the step processing of step S12. In this case, the steering midpoint determination unit 102 outputs a determination result H1 indicating that the center mark 4 is in the steering midpoint region Ro to the steering angle storage unit 103. On the other hand, based on the image data DM, the steering midpoint determination unit 102 determines "No" if the center mark 4 has not been captured, i.e., the center mark 4 is not in the steering midpoint region Ro, and repeatedly executes the step processing of step S11 until the center mark 4 is in the steering midpoint region Ro.

[0042] In step S12, the steering angle storage unit 103 of the steering angle determination device 10 performs provisional steering angle midpoint learning when the center mark 4 is in the operating midpoint region Ro, based on the determination result H1 obtained from the operating midpoint determination unit 102. That is, when the steering angle storage unit 103 determines that the center mark 4 is in the operating midpoint region Ro, it obtains the motor rotation angle θ detected by the motor rotation angle sensor 82 via the acquisition unit 101. The steering angle storage unit 103 then learns and stores the acquired motor rotation angle θ as the provisional steering angle midpoint θt for the steering wheels, the right front wheel 21 and the left front wheel 22, and outputs the provisional steering angle midpoint θt to the steering angle midpoint determination unit 104. The steering angle determination device 10 then performs the step processing of step S13.

[0043] In step S13, the steering angle midpoint determination unit 104 of the steering angle determination device 10 determines, for example, whether the right front wheel 21 and the left front wheel 22, which are the steering wheels, are near the center when the vehicle 1 is stationary, that is, whether the provisional steering angle midpoint θt supplied from the steering angle memory unit 103 in step S12 is located in the steering angle midpoint region Rs. Specifically, the steering angle midpoint determination unit 104 determines "Yes" based on the image data DR and image data DL acquired from the surrounding cameras 6 (right-side camera 61 and left-side camera 62), because if the side Mt is approximately parallel to the side Mc, the right front wheel 21 and the left front wheel 22 are located near the center. In other words, the steering angle midpoint determination unit 104 determines that the provisional steering angle midpoint θt is located in the steering angle midpoint region Rs. Then, the steering angle midpoint determination unit 104 executes the step processing of step S14.

[0044] On the other hand, the steering angle midpoint determination unit 104 determines "No" based on image data DR and image data DL acquired from the surrounding cameras 6 (right-side camera 61 and left-side camera 62), because if side Mt is not parallel to side Mc, the right front wheel 21 and left front wheel 22 are not near the center. In other words, the steering angle midpoint determination unit 104 determines that the provisional steering angle midpoint θt is not in the steering angle midpoint region Rs. In this case, the steering angle determination device 10 repeatedly executes each step process from step S11 onwards until the steering angle midpoint determination unit 104 determines that the right front wheel 21 and left front wheel 22 are near the center, that is, that the provisional steering angle midpoint θt is in the steering angle midpoint region Rs.

[0045] In step S14, the steering angle midpoint determination unit 104 determines the provisional steering angle midpoint θt located in the steering angle midpoint region Rs as the initial steering angle midpoint θc, and outputs the initial steering angle midpoint θc to the steering angle midpoint correction unit 105 of the steering angle determination device 10, along with the determination result H2 indicating that the right front wheel 21 and the left front wheel 22 are located near the center. As a result, the steering angle midpoint correction unit 105 executes the step processing of step S15.

[0046] In step S15, the steering angle midpoint correction unit 105 of the steering angle determination device 10 performs steering angle midpoint learning during driving. Based on the results of the steering angle midpoint learning during driving, the steering angle midpoint correction unit 105 corrects the initial steering angle midpoint θc and determines the steering angle midpoint θf. Then, in step S16, the steering angle determination device 10 terminates the execution of the steering angle determination program.

[0047] As can be understood from the above explanation, the steering angle determination device 10 is applied to a vehicle 1 which is equipped with a steering wheel 31 on which a center mark 4 is provided to indicate the midpoint of operation within the driver's operating range, a driver monitor camera 5 as a first imaging device that is positioned to capture images of the steering wheel 31 and is capable of capturing images of the center mark 4, and a right-side camera 61 and a left-side camera 62 (peripheral camera 6) as a second imaging device that is capable of capturing images of the steering state of the right front wheel 21 and the left front wheel 22, which are steering wheels that are turned in response to the operation of the steering wheel 31, and the center mark 4 is used to determine if the vehicle 1 is traveling in a straight line within the operating range. The system includes: an operation midpoint determination unit 102 that determines whether the center mark 4 is in a pre-set operation midpoint region Ro based on an image (image data DM) of the center mark 4 captured by the driver monitor camera 5; and a steering angle midpoint determination unit 104 that, when the operation midpoint determination unit 102 determines that the center mark 4 is in the operation midpoint region Ro, determines whether the right front wheel 21 and the left front wheel 22 are steered to a pre-set steering angle midpoint region Rs that includes the steering angle midpoint that causes the vehicle 1 to travel straight, based on images (image data DR and image data DL) of the steering state captured by the right side camera 61 and the left side camera 62.

[0048] In this case, the steering angle determination device 10 may have a steering angle storage unit 103 that stores the steering angles of the right front wheel 21 and the left front wheel 22 as the temporary steering angle midpoint θt when the operating midpoint determination unit 102 determines that the center mark 4 is in the operating midpoint region Ro.

[0049] In this case, the steering angle midpoint determination unit 104 can determine the provisional steering angle midpoint θt as the initial steering angle midpoint θc when it determines that the right front wheel 21 and the left front wheel 22 are in the steering angle midpoint region Rs.

[0050] In this case, the steering angle determination device 10 may have a steering angle midpoint correction unit 105 that corrects the initial steering angle midpoint θc when the vehicle 1 is traveling in a straight line.

[0051] According to the steering angle determination device 10, when the operation midpoint determination unit 102 determines that the center mark 4 is in the operation midpoint region Ro based on the image data DM of the center mark 4 captured by the driver monitor camera 5, the steering angle midpoint determination unit 104 can determine that the right front wheel 21 and the left front wheel 22, i.e., the provisional steering angle midpoint θt, are in the steering angle midpoint region Rs based on the steering state image data DR and image data DL of the steering state of the right front wheel 21 and the left front wheel 22 captured by the right side camera 61 and the left side camera 62. Therefore, the steering angle determination device 10 can improve the accuracy of determining the operation midpoint and the steering angle midpoint.

[0052] In implementing the present invention, it is possible to carry it out with various modifications, without being limited to the embodiments described above.

[0053] For example, in the embodiment described above, an example was given in which the center mark 4 is placed at the top of the steering wheel 31 so that it can be captured by the driver monitor camera 5 located on the steering column 33. However, it goes without saying that the center mark 4 can be placed at a position other than the top when the steering wheel 31 is in the neutral position, as long as it can be captured by the first imaging device located inside the vehicle, including the driver monitor camera 5.

[0054] Furthermore, in the above-described embodiment, an example was given in which the steering angle midpoint determination unit 104 determines whether the steering state of the right front wheel 21 and the left front wheel 22, i.e., whether the provisional steering angle midpoint θt is in the steering angle midpoint region Rs, based on both the image data DR from the right-side camera 61 and the image data DL from the left-side camera 62. Incidentally, in the vehicle 1 of the above-described embodiment, the steering wheels, the right front wheel 21 and the left front wheel 22, are connected to each other by a rack bar 35 and steer similarly. For this reason, the steering angle midpoint determination unit 104 can also make a determination using the steering state of either the right front wheel 21 or the left front wheel 22, instead of using the steering state of both the right front wheel 21 and the left front wheel 22 for the determination.

[0055] Furthermore, in the above-described embodiment, an example was given in which the steering angle determination device 10 (or EPS-ECU 71) executes the steering angle determination program when the vehicle 1 is about to start moving quickly from a stationary state. However, the steering angle determination program can also be executed when the vehicle 1 is moving. Also, if the vehicle 1 remains stationary, the steering angle determination device 10 (or EPS-ECU 71) can execute the process up to step S14, that is, until the initial steering angle midpoint θc is determined, and then, when the vehicle 1 starts moving, it can execute the steps from step S15 onwards.

[0056] Furthermore, in the embodiments described above, an example was given in which an electric power steering system was used as the steering system 3. Alternatively, the steering system 3 could be a so-called steer-by-wire system in which the mechanical connection between the steering wheel 31 and the steering mechanism 34 is released. In this case as well, the operating midpoint and the steering angle midpoint can be accurately determined, similar to the embodiments described above. [Explanation of Symbols]

[0057] 1...Vehicle, 2...Wheel, 21...Right front wheel (steering wheel), 22...Left front wheel 22 (steering wheel), 3...Steering device, 31...Steering wheel, 33...Steering column, 4...Center mark, 5...Driver monitor camera (first imaging device), 6...Surrounding camera (second imaging device), 61...Right side camera (second imaging device), 62...Left side camera (second imaging device), 7...Controller, 71...EPS-ECU 71, 10...Steering angle determination device, 101...Acquisition unit, 102...Operation midpoint determination unit, 103...Steering angle memory unit, 104...Steering angle midpoint determination unit, 105...Steering angle midpoint correction unit, 106...Output unit, Ro...Operation midpoint area, Rs...Steering angle midpoint area

Claims

1. A steering wheel with a center mark indicating the midpoint of operation within the driver's operating range, A first imaging device positioned to capture the steering wheel and enabling imaging of the center mark, This is applied to a vehicle equipped with a second imaging device capable of imaging the steering state of the steering wheels that are steered in response to the operation of the steering wheel, An operation midpoint determination unit determines whether the center mark is located within the operation midpoint region of the operation range that is pre-set to allow the vehicle to travel in a straight line, based on an image of the center mark captured by the first imaging device. When the operation midpoint determination unit determines that the center mark is located in the operation midpoint region, the steering angle midpoint determination unit determines, based on the image of the steering state captured by the second imaging device, whether the steering wheel is steered to a steering angle midpoint region that is set in advance to include the steering angle midpoint that causes the vehicle to travel in a straight line, A rudder angle determination device equipped with the following features.

2. The steering angle determination device according to claim 1, further comprising a steering angle storage unit that stores the steering angle of the steering wheel as a provisional steering angle midpoint when the operation midpoint determination unit determines that the center mark is located in the operation midpoint region.

3. The steering angle determination device according to claim 2, wherein the steering angle midpoint determination unit determines that the steering wheel is in the steering angle midpoint region and sets the provisional steering angle midpoint as the initial steering angle midpoint.

4. The steering angle determination device according to claim 3, further comprising a steering angle midpoint correction unit for correcting the initial steering angle midpoint when the vehicle is traveling in a straight line.

5. The steering angle determination device according to any one of claims 1 to 4, wherein the first imaging device is a driver monitor camera installed inside the vehicle's cabin and positioned to capture images of at least the driver's face and also capture images of the center mark.

Images