Vehicle control device

Abstract

To provide a control device of a vehicle that can reduce deviations between a target trajectory and an actual travelling trajectory and reduce vibrations of steering, when running on a curve.SOLUTION: A control device of a vehicle sets a first reference point in front of a flexion point on a target trajectory before the vehicle passes on the flexion point with curvature on the target trajectory; sets a target steering angle on the basis of curvature of a circular arc that is set so as to pass on a current position of the vehicle and the first reference point; sets a second reference point so that in comparison of a vehicle speed with at least either of acceleration / deceleration and a steering angle under the same travelling condition, a second distance which is a distance from the current position of the vehicle to the second reference position set on the target trajectory is larger than a first distance which is a distance from the current position of the vehicle at the time before the vehicle passes on the flexion point to the first reference point; and sets a target steering angle on the basis of the curvature of the circular arc set so as to pass on the current position of the vehicle and the second reference point.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In recent years, the practical application of technologies related to autonomous driving in which a vehicle is automatically driven without depending on a driving operation by a driver has been promoted. In autonomous driving, control is performed to drive the vehicle along a target trajectory. As a technology related to such autonomous driving, for example, Patent Document 1 discloses a technology in which a reference point with respect to the current position of a vehicle is set on the target trajectory of the vehicle, and the steering of the vehicle is controlled based on an arc that has a tangent along the traveling direction of the vehicle and passes through the reference point and the current position.

[0003] In the control device described in Patent Document 1, when the current position of the host vehicle deviates from the target trajectory, a reference point is set assuming that the host vehicle has traveled on the target trajectory for a predetermined time from a position on the target trajectory close to the host vehicle. Further, in the control device described in Patent Document 1, when the current position of the host vehicle does not deviate from the target trajectory, the reference point is set closer as the curvature of an arc passing through three certain points set on the target trajectory becomes larger, and is set farther as the curvature of the arc approaches zero.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, when controlling the steering of a vehicle based on an arc that has a tangent along the traveling direction of the vehicle and passes through a reference point and the current position, the actual traveling trajectory of the vehicle changes depending on the set position of the reference point. For example, if the reference point is too far when entering a curve, the traveling trajectory during the curve passage may deviate from the target trajectory toward the inside of the curve. Also, if the reference point is too close when shifting from a curve to straight-ahead driving, the curvature of the arc may become large with respect to the target trajectory, possibly causing steering vibration. However, since the control device described in Patent Document 1 does not consider that the problems that can occur during the period of entering a curve and the period of leaving a curve are different, there is a possibility that the above problems cannot be solved.

[0006] The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a vehicle control device and a control method capable of reducing the deviation between a target trajectory and an actual traveling trajectory and reducing steering vibration when traveling on a curve.

Means for Solving the Problems

[0007] To solve the above problems, according to an aspect of the present disclosure, there are provided one or more processors and one or more memories communicably connected to the one or more processors. Before the vehicle passes through an inflection point of the curvature of the target trajectory, the processor sets a first reference point in front of the inflection point on the target trajectory, sets a target steering angle based on the curvature of an arc set to pass through the current position of the vehicle and the first reference point, and after the vehicle passes through the inflection point of the curvature of the target trajectory, when at least one of the vehicle speed, acceleration or deceleration, or steering angle is compared under the same driving conditions, the second reference point is set so that a second distance, which is the distance from the current position of the vehicle to the second reference point set on the target trajectory, is greater than a first distance, which is the distance from the current position of the vehicle before passing through the inflection point to the first reference point, and a target steering angle is set based on the curvature of an arc set to pass through the current position of the vehicle and the second reference point, and a vehicle control device that executes a process including controlling the steering angle based on the target steering angle is provided.

Advantages of the Invention

[0008] As described above, according to the present disclosure, when traveling on a curve, it is possible to reduce the deviation between the target trajectory and the actual traveling trajectory and to reduce the vibration of steering.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0010] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description is omitted.

[0011] <1. Configuration Example of Vehicle> First, an example of the configuration of a vehicle equipped with a vehicle control device according to an embodiment of the present disclosure will be described.

[0012] FIG. 1 is a schematic diagram showing a configuration example of a vehicle 1. The vehicle 1 includes wheels 11L and 11R, a power transmission system 17, a drive motor 35, an inverter 33, a battery 31, a brake system 15, an electric steering system 21, a vehicle operation / behavior sensor 41, a vehicle position sensor 43, a navigation device 45, and a control device 50. The inverter 33, the brake system 15, the electric steering system 21, the vehicle operation / behavior sensor 41, the vehicle position sensor 43, and the navigation device 45 are each directly or connected to the control device 50 via communication means such as a CAN (Controller Area Network) or a LIN (Local Inter Net).

[0013] The vehicle 1 shown in FIG. 1 is an electric vehicle that includes only the drive motor 35 as a drive source and travels using the power output from the drive motor 35. The driving mode of the vehicle 1 can be switched between a manual driving mode and an automatic driving mode. The manual driving mode is a driving mode in which the acceleration / deceleration and steering angle of the vehicle 1 are controlled according to the driver's driving operation. The automatic driving mode is a driving mode in which the acceleration / deceleration and steering angle of the vehicle 1 are automatically controlled without depending on the driver's driving operation.

[0014] Note that the driving mode may be switchable by the driver, or may be switched to the automatic driving mode by the intervention of the control device 50 during the manual driving mode. Further, when a specific operation such as a brake operation is performed by the driver during the automatic driving mode, it may be possible to switch from the automatic driving mode to the manual driving mode.

[0015] The drive motor 35 is a motor that outputs power transmitted to the wheels 11L and 11R of the vehicle 1. As the drive motor 35, for example, a three-phase alternating current motor is used. The drive motor 35 is connected to the battery 31 via the inverter 33, is driven using the power supplied from the battery 23, and outputs power.

[0016] Note that the drive motor 35 may be a motor that can be regeneratively driven during deceleration of the vehicle 1 and generate electricity using the kinetic energy of the wheels 11L and 11R. In this case, the electric power generated by the drive motor 35 is charged to the battery 31 via the inverter 33.

[0017] The output shaft of the drive motor 35 is connected to the drive shaft 19 to which the wheels 11L and 11R are connected via the power transmission system 17. Therefore, the power output from the drive motor 35 is transmitted to the wheels 11L and 11R via the power transmission system 17 and the drive shaft 19.

[0018] Note that the wheels 11L and 11R shown in FIG. 1 are front wheels whose steering angles are controlled by the electric power steering system 21, and the power output from the drive motor 35 is transmitted to at least the front wheels. However, the wheels 11L and 11R to which the power output from the drive motor 35 is transmitted may be rear wheels. Further, the power output from the drive motor 35 may be transmitted to both the front wheels and the rear wheels via a propeller shaft (not shown).

[0019] The inverter 33 is a power conversion device that performs bidirectional power conversion. For example, the inverter 33 includes a three-phase bridge circuit. The inverter 33 converts the DC power supplied from the battery 31 into AC power and supplies it to the drive motor 35. Further, the inverter 33 converts the AC power generated by the drive motor 35 into DC power and supplies it to the battery 31. The drive of the inverter 33 is controlled by the control device 50.

[0020] The battery 31 is a battery that can charge and discharge electric power. As the battery 31, for example, a lithium ion battery, a lithium ion polymer battery, a nickel hydrogen battery, a nickel cadmium battery, or a lead storage battery is used, but other batteries may be used. The battery 31 stores the electric power supplied to the drive motor 35.

[0021] The brake system 15 controls the braking force applied to each of the wheels 11L, 11R by controlling the hydraulic pressure supplied to the brake devices 13L, 13R provided on each of the wheels 11L, 11R, for example. The brake system 15 includes, for example, a master cylinder, a booster, and a hydraulic control unit (not shown). The master cylinder is connected to the brake pedal via the booster, and the booster multiplies the depressing force of the brake pedal by the driver and transmits it to the master cylinder.

[0022] The master cylinder and the brake devices 13L, 13R are connected via a hydraulic circuit provided in the hydraulic control unit. The master cylinder supplies hydraulic oil to the hydraulic circuit according to the operation amount of the brake pedal. The hydraulic control unit includes an electromagnetic control valve and an electric pump, and controls the flow rate of the hydraulic oil supplied to each of the brake devices 31L, 31R.

[0023] The brake devices 13L, 13R provided on each of the wheels 11L, 11R include, for example, a caliper including brake pads and wheel cylinders. A pair of brake pads are provided to face each other on both sides of a brake disk that rotates integrally with the wheels 11L, 11R. The wheel cylinder is a hydraulic chamber formed in the brake caliper, and as the pressure in the wheel cylinder increases, each brake pad moves toward both sides of the brake disk. As a result, the brake disk is sandwiched between the pair of brake pads, and a braking force is applied to the wheels 11L, 11R by the frictional force.

[0024] By controlling the flow rate of the hydraulic oil supplied by the hydraulic control unit to each of the brake devices 31L, 31R, the pressure in the wheel cylinder of each of the brake devices 31L, 31R is adjusted, and the braking force applied to each of the wheels 11L, 11R is controlled. The drive of the brake system 15 is controlled by the control device 50.

[0025] The electric power steering system 21 assists the steering operation using the driver's steering wheel. For example, the electric power steering system 21 includes a rotation sensor that detects the rotation angle of the steering wheel (not shown), and an electric motor that controls the steering angles of the wheels 11L and 11R according to the rotation angle of the steering wheel detected by the rotation sensor. The electric power steering system 21 may further include an electric motor capable of outputting power to rotate the steering wheel. The drive of the electric power steering system 21 is controlled by the control device 50.

[0026] In the autonomous driving mode, the steering angles of the wheels 11L and 11R are controlled using the electric power steering system 21.

[0027] The vehicle operation / behavior sensor 41 consists of at least one sensor that detects the operation state and behavior of the vehicle. The vehicle operation / behavior sensor 41 includes, for example, at least one of a vehicle speed sensor, an acceleration sensor, and an angular velocity sensor, and detects information on the behavior of the vehicle such as vehicle speed, longitudinal acceleration, lateral acceleration, and yaw rate. Further, the vehicle operation / behavior sensor 41 includes, for example, at least one of an accelerator position sensor, a brake stroke sensor, a brake pressure sensor, a steering angle sensor, and an engine speed sensor, and detects information on the operation state of the vehicle such as the steering angle of the steering wheel or the steering wheels, the accelerator opening, and the brake operation amount. The vehicle operation / behavior sensor 41 transmits a sensor signal including the detected information to the control device 50.

[0028] The vehicle position sensor 43 detects the position of the vehicle 1 and outputs the detection result to the control device 50. For example, the vehicle position sensor 43 may be a GPS (Global Positioning System) sensor that receives satellite signals from GPS satellites. The GPS sensor transmits the position information of the vehicle on the map data included in the received satellite signals to the navigation device 45 and the control device 50. Note that instead of the GPS antenna, an antenna that receives satellite signals from another satellite system for specifying the position of the vehicle may be provided.

[0029] In addition, the vehicle position sensor 43 may further include a measuring device capable of detecting the position of the host vehicle in the road, such as an external camera, LiDAR (Light Detection and Ranging or Laser Imaging Detection and Ranging), or a radar sensor.

[0030] The navigation device 45 is a device that guides a driving route from the current position of the vehicle 1 to a set destination. Map data is stored in the navigation device 45 in advance. The map data includes data of a target trajectory, which is a driving trajectory serving as a reference when the vehicle 1 in the automatic driving mode travels on each road. The data of the target trajectory can be configured as data of a target point group. The navigation device 45 acquires information on the current position of the vehicle 1 output from the vehicle position sensor 43, and sets a driving route from the current position to the set destination. The navigation device 45 outputs information indicating the driving route and the target trajectory to the control device 50.

[0031] In addition, the navigation device 45 has a function of visually displaying information, and displays various pieces of information related to route guidance, such as the current position of the vehicle 1, the driving route, the position of the destination, the distance to the destination, and the predicted arrival time, on the map data.

[0032] During the automatic driving mode of the vehicle 1, the control device 50 controls the inverter 33, the brake system 15, and the electric steering system 21 to perform automatic driving control for automatically driving the vehicle 1 along the driving route set by the navigation device 45. The control device 50 sets at least the target steering angles of the wheels 11L and 11R, and controls the steering angles of the wheels 11L and 11R based on the target steering angles.

[0033] <2. Control Device> Subsequently, the control device 50 of the vehicle according to the present embodiment will be specifically described.

[0034] (2-1. Configuration Example) The control device 50 is configured to include at least one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and one or more memories that are communicably connected to the processor and store various data. Note that part or all of the control device 50 may be configured with updatable components such as firmware, or may be program modules or the like executed according to instructions from a CPU or the like.

[0035] FIG. 2 is a block diagram showing an example of the functional configuration of the control device 50. The control device 50 includes a setting unit 51, a control unit 53, and a storage unit 61. Note that the functions of the control device 50 according to the present embodiment may be realized by a single control device, or may be realized by a plurality of control devices that can communicate with each other via communication means such as CAN.

[0036] (2-1-1. Storage Unit) The storage unit 61 includes memories such as a ROM (Read Only Memory) that stores programs executed by the processor and various arithmetic parameters used for arithmetic processing, and a RAM (Random Access Memory) that stores various detection data and arithmetic results obtained by the processor. The storage unit 61 may include storage media such as an HDD (Hard Disk Drive), a CD (Compact Disc), a DVD (Digital Versatile Disk), an SSD (Solid State Drive), a USB (Universal Serial Bus) flash drive, and a storage device.

[0037] (2-1-2. Setting Unit) During the automatic driving mode of the vehicle 1, the setting unit 51 sets the target steering angle θt of the wheels 11L and 11R in order to make the vehicle 1 travel along the target trajectory Ttgt on the driving route acquired from the navigation device 45. In the present embodiment, the setting unit 51 sets a predetermined arc At based on the current position of the vehicle 1 output from the vehicle position sensor 43 (the current position Pa1 and the current position Pa2: collectively referred to as the current position Pa when no particular distinction is required) and the reference points (the first reference point Pt1 and the second reference point Pt2: collectively referred to as the reference point Pt when no particular distinction is required) set on the target trajectory Ttgt acquired from the navigation device 45, and sets the target steering angle θt based on the curvature c of the arc At. The setting unit 51 sets the target steering angle θt at predetermined calculation cycles set in advance according to, for example, the processing speed of the processor.

[0038] (2-1-3. Control Unit) The control unit 53 includes one or more processors, executes various arithmetic processes by executing the programs stored in the storage unit 61, and controls the operations of the respective devices of the vehicle 1. In the present embodiment, the control unit 53 includes a motor control unit 55, a brake control unit 57, and a steering control unit 59.

[0039] The motor control unit 55 controls the operation of the drive motor 35. Specifically, the motor control unit 55 controls the supply of electric power from the battery 31 to the drive motor 35 and the charging of the generated electric power by the drive motor 35 to the battery 31 by controlling the operation of the switching elements of the inverter 33. Thereby, the motor control unit 55 can control the output of power by the drive motor 35 and the charging of the battery 31.

[0040] The brake control unit 57 controls the operation of the brake system 15. Specifically, the brake control unit 57 controls the pressure in the wheel cylinders of the respective brake devices 13L and 13R provided on the respective wheels 11L and 11R by controlling the operation of the hydraulic control unit. Thereby, the brake control unit 57 can control the braking force applied to the vehicle 1.

[0041] The steering control unit 59 controls the operation of the electric steering system 21. Specifically, the steering control unit 59 can control the steering angle θ of the wheels 11L and 11R by controlling the output of the electric motor of the electric steering system 21. The steering control unit 59 only needs to be configured to be able to control at least the steering angle θ of the wheels 11L and 11R, but may also control the rotation angle of the steering wheel in correspondence with the steering angle θ of the wheels 11L and 11R.

[0042] As described above, the driving mode of the vehicle 1 can be switched between the manual driving mode and the automatic driving mode. The control unit 53 controls the acceleration and deceleration and the steering angle of the vehicle 1 according to the driving mode.

[0043] For example, in the manual driving mode, the control unit 53 controls each device so that the acceleration and deceleration of the vehicle 1 become the acceleration and deceleration corresponding to the accelerator operation and the brake operation by the driver. Specifically, the control unit 53 controls the operation of the drive motor 35 so that the driving force applied to the vehicle 1 becomes the driving force corresponding to the accelerator opening. Thereby, the acceleration of the vehicle 1 can be controlled according to the accelerator operation by the driver. In addition, the control unit 53 controls the operation of the brake system 15 so that the braking force applied to the vehicle 1 becomes the braking force corresponding to the brake operation amount. Thereby, the deceleration of the vehicle 1 can be controlled according to the brake operation by the driver. Further, when the driver performs a steering operation, the control unit 53 controls the operation of the electric motor so that the steering angle θ of the wheels 11L and 11R becomes the cut angle corresponding to the rotation angle of the steering wheel. Thereby, the steering angle θ of the wheels 11L and 11R can be controlled according to the steering operation of the driver.

[0044] In the automatic driving mode, the control unit 53 controls each device so that the vehicle 1 automatically travels along the driving route set by the navigation device 45. Specifically, the control unit 53 controls each device so that the vehicle 1 automatically travels along the target trajectory Ttgt on the driving route acquired from the navigation device 45. The control unit 53 controls the operation of the electric steering system 21 so that the steering angles θ of the wheels 11L and 11R become the target steering angle θt set by the setting unit 51. Further, the control unit 53 controls the acceleration and deceleration of the vehicle 1 so that, for example, the vehicle speed V of the vehicle 1 is maintained at the set speed. The control unit 53 sets the control target of each device, for example, at the same calculation cycle as the setting unit 51.

[0045] In addition, when there is a preceding vehicle in front of the vehicle 1 or there are pedestrians, obstacles, etc. around the vehicle 1, the control unit 55 adjusts the driving trajectory or vehicle speed of the vehicle 1 so as to avoid a collision between the preceding vehicle, pedestrians, etc. and the vehicle 1. However, hereinafter, for the sake of easy understanding of the technology of the present disclosure, it will be described assuming that there are no preceding vehicles, pedestrians, etc.

[0046] (2-2. Operation example of the control device) Next, as an operation example of the vehicle control device 50 according to the present embodiment, an example of a process of controlling the steering angle θ of the wheels 11L and 11R by the control device 50 will be described.

[0047] (2-2-1. Outline of the method for setting the target steering angle) First, with reference to FIG. 3, an outline of the method for setting the target steering angle θt, which is the basis when the setting unit 51 sets the target steering angle θt, will be described. FIG. 3 is an explanatory diagram showing the basic concept of the setting process of the target steering angle θt.

[0048] The setting unit 51 acquires information on the current position Pa of the vehicle 1 transmitted from the vehicle position sensor 43, and also acquires information on the target trajectory Ttgt on the travel route output from the navigation device 45. The setting unit 51 sets a reference point Pt on the forward target trajectory Ttgt according to a predetermined standard, uses the current traveling direction of the vehicle 1 as a tangent line, and calculates an arc At that passes through both the current position Pa of the vehicle 1 and the reference point Pt. Then, the setting unit 51 sets the target steering angles θt of the wheels 11L and 11R so that the traveling trajectory has the curvature c of the obtained arc At.

[0049] Here, in the control device 50 according to the present embodiment, the setting unit 51 obtains an inflection point Pc of the curvature c of the target trajectory Ttgt, and sets the reference point Pt according to different standards before and after the vehicle 1 passes through the inflection point Pc. Specifically, before the vehicle 1 passes through the inflection point Pc on the target trajectory Ttgt, the setting unit 51 sets the first reference point Pt1 in front of the inflection point Pc. Also, when comparing under the same driving conditions, the setting unit 51 sets the first reference point Pt1 and the second reference point Pt2 such that the second distance L2, which is the distance from the current position Pa of the vehicle 1 after the vehicle 1 passes through the inflection point Pc to the second reference point Pt2, is greater than the first distance L1, which is the distance from the current position Pa of the vehicle 1 before the vehicle 1 passes through the inflection point Pc to the first reference point Pt1. The same driving conditions refer to the condition that at least one or all of the vehicle speed, acceleration / deceleration, and steering angle are the same.

[0050] FIGS. 4 and 5 are explanatory diagrams showing an example of a method for specifying the inflection point Pc of the curvature c of the target trajectory Ttgt. The setting unit 51 selects an arbitrary plurality of target points from the group of target points constituting the target trajectory Ttgt acquired from the navigation device 45. In the examples of FIGS. 4 and 5, five target points P1 to P5 are selected. For the five selected target points P1 to P5, the setting unit 51 determines the coordinates (x i , y i ) in the two-dimensional space and the curvature c i of the target trajectory Ttgt.

[0051] The two-dimensional space used at this time may be, for example, a two-dimensional space with the current position Pa of the vehicle 1 as the origin and the traveling direction of the vehicle 1 as the y-axis. Also, the curvature c of the target trajectory Ttgt at each of the target points P1 to P5 i may be included in the data of the target trajectory Ttgt acquired from the navigation device 45, or may be calculated by the setting unit 51 based on the data of the coordinates of each target point on the two-dimensional space that constitutes the acquired target trajectory Ttgt. However, the method for calculating the curvature c i is not particularly limited.

[0052] The setting unit 51 sets the target point with the largest value among the obtained curvatures c1 to c5 among the target points P1 to P5 as the inflection point Pc. In the examples of FIGS. 4 and 5, the curvatures c1 to c3 increase from the target points P1 to P3 (that is, the curvature radii r1 to r3 decrease), and after the target point P3, the curvatures c3 to c5 decrease. For this reason, the setting unit 51 sets the target point P3 as the inflection point Pc.

[0053] At this time, the setting unit 51 may set the target point as the inflection point Pc when the curvature c of the target point with the largest value of the curvature c exceeds a predetermined value set in advance. When traveling on a gentle curve, the curvature of the arc At to be set is in a small state, and the degree of deviation of the target trajectory Ttgt in the inner direction of the curve is less likely to increase, and the vibration of the steering is also less likely to increase. For this reason, the opportunity to execute the process of changing the reference for the setting position of the reference point Pt is limited, and the load on the control device 50 can be reduced.

[0054] The number of target points to be selected is not limited to five. The larger the number of target points to be selected, the more accurately the inflection point Pc of the curvature c can be specified. However, if the number of target points to be selected is too large, the time required for the arithmetic processing becomes long. Therefore, it is preferable to set the number of target points in consideration of these factors.

[0055] Also, the positions of the respective target points P1 to P5 may be arbitrarily selected, but it is preferable that the positions of the target points P1 to P5 are selected at equal intervals. By selecting the plurality of target points P1 to P5 at equal intervals, it is possible to reduce the risk that the position of the required inflection point Pc deviates significantly from the actual inflection point. For example, the setting unit 51 selects the foremost target point (first target point) P1 at a position at a predetermined distance from the current position Pa of the vehicle 1, and selects the subsequent target points P2 to P5 at equal intervals. When the current position Pa of the vehicle 1 is not on the target trajectory Ttgt, the setting unit 51 uses the point on the target trajectory Ttgt closest to the current position Pa of the vehicle 1 as a starting point (starting points Pb1 and Pb2: collectively referred to as starting point Pb when no particular distinction is required), and selects the target point (first target point) P1 at a position at a predetermined distance from the starting point Pb instead of the current position Pa, and selects the subsequent target points P2 to P5 at equal intervals.

[0056] In this case, the distance from the starting point Pb to the first target point P1 may be arbitrarily selected, or may be set according to the current vehicle speed V of the vehicle 1. Similarly, when the intervals between the target points P1 to P5 are selected at equal intervals, the intervals between the respective target points P1 to P5 may be set according to the current vehicle speed V of the vehicle 1. Specifically, it is preferable that the distance from the starting point Pb to the first target point P1 and the intervals between the target points P1 to P5 are set to increase as the current vehicle speed V of the vehicle 1 increases. By setting the distance from the starting point Pb to the first target point P1 and the intervals between the target points P1 to P5 in proportion to the vehicle speed V of the vehicle 1, the range of the target trajectory Ttgt for obtaining the position of the inflection point Pc according to the reachable distance of the vehicle 1 is set, and the process of varying the criteria for setting the reference point Pt before and after passing through the inflection point Pc can be surely executed.

[0057] Figures 6 and 7 are explanatory diagrams showing the setting range of the first reference point Pt1 before passing through the inflection point Pc and the setting range of the second reference point Pt2 after passing through the inflection point Pc, respectively. In Figures 6 and 7, with respect to the current positions Pa1, Pa2 of the vehicle 1, the first reference point Pt1 and the second reference point Pt2 are set on any target trajectory Ttgt within a set range α. The range α may be set, for example, as a range including a predetermined number of target points or as a range of a predetermined distance, but is not limited to these examples. In the examples shown in Figures 6 and 7, the range α is a range including three target points.

[0058] As shown in Figure 6, before the vehicle 1 passes through the inflection point Pc, the range α for setting the first reference point Pt1 for obtaining the arc At is set in front of the inflection point Pc. As a result, until the vehicle 1 approaches the inflection point Pc, the possibility of setting the first reference point Pt1 across the position where the curvature c of the target trajectory Ttgt is maximized in front of the vehicle 1 is reduced, and the degree to which the actual travel trajectory of the vehicle 1 deviates in the inner direction of the target trajectory Ttgt can be reduced.

[0059] Further, as shown in FIGS. 6 and 7, the distance from the current position Pa2 (or the starting point Pb2) after the vehicle 1 has passed through the inflection point Pc to the setting range α of the second reference point Pt2 is made larger than the distance from the current position Pa1 (or the starting point Pb1) before passing through the inflection point Pc to the setting range α of the first reference point Pt1. In the present embodiment, regardless of the vehicle speed V of the vehicle 1, even when compared under the same driving conditions, the distance (second distance) D2 from the current position Pa2 (or the starting point Pb2) after the vehicle 1 has passed through the inflection point Pc to the second reference point Pt2 is made larger than the distance (first distance) D1 from the current position Pa1 (or the starting point Pb1) before passing through the inflection point Pc to the first reference point Pt1, and the first reference point Pt1 and the second reference point Pt2 are respectively set. Thereby, when the vehicle 1 passes through the inflection point Pc and the curvature c of the target trajectory Ttgt becomes small, the second reference point Pt2 is set farther away, and the curvature of the required arc At becomes small. For this reason, when the steering angles θ of the wheels 11L and 11R are controlled based on the target steering angle θt set for each calculation cycle, steering vibration can be reduced.

[0060] (2-2-2. Specific Example of Method for Setting Reference Point) Subsequently, a specific example of a method for setting the first reference point Pt1 and the second reference point Pt2 so that the second distance D2 is larger than the first distance D1 when compared under the same driving conditions will be described.

[0061] (First Example) In the first example, the setting unit 51 sets the reference point Pt at the position of the vehicle 1 on the target trajectory Ttgt that is assumed to be reached after a predetermined unit time. At this time, the setting unit 51 makes the value of the second unit time T2 used after the vehicle 1 has passed through the inflection point Pc larger than the value of the first unit time T1 used before passing through the inflection point Pc. Thereby, when compared under the same driving conditions, the first reference point Pt1 and the second reference point Pt2 are respectively set so that the second distance D2 is larger than the first distance D1.

[0062] When setting the reference point Pt based on the position of the vehicle 1 on the target trajectory Ttgt that is assumed to be reached after a specified unit time, the distance from the current position Pa (or the starting point Pb) to the reference point Pt becomes larger as the vehicle speed V is higher and smaller as the vehicle speed V is lower. At this time, the first unit time T1 used before the vehicle 1 passes through the inflection point Pc is set such that the position of the vehicle 1 on the target trajectory Ttgt that is assumed to be reached after the first unit time T1 in the state of the current vehicle speed V is in front of the inflection point Pc. However, the first unit time T1 is set to be longer than the interval of the calculation cycle of the setting unit 51. For example, when the interval of the calculation cycle of the setting unit 51 is 0.1 second, the first unit time T1 is set to 0.2 to 1.0 seconds.

[0063] Before the vehicle 1 passes through the inflection point Pc, the setting unit 51 may adjust the position of the first reference point Pt1 based on the curvature c of the inflection point Pc. Specifically, when comparing under the same driving conditions, the setting unit 51 adjusts the position of the first reference point Pt1 such that the larger the curvature c of the inflection point Pc, the smaller the first distance D1, and the smaller the curvature c of the inflection point Pc, the larger the first distance D1. For example, as shown in FIG. 8, the first unit time T1 may be adjusted such that the larger the curvature c of the inflection point Pc, the shorter the first unit time T1. Alternatively, a coefficient may be set such that it becomes smaller as the curvature c of the inflection point becomes larger, and the coefficient may be multiplied by the first distance D1 to the first reference point Pt1 obtained according to the vehicle speed V as described above. Thereby, when the curvature of the inflection point Pc is large, that is, when the curve is sharp, the first reference point Pt1 is set closer, and the deviation degree of the driving trajectory to the inside of the curve of the target trajectory Ttgt can be reduced.

[0064] Also, in the first example, the second unit time T2 used after the vehicle 1 passes through the inflection point Pc is set to a value larger than the first unit time T1. Thereby, after passing through the inflection point Pc, in a state where the curvature c of the target trajectory Ttgt becomes large, the second reference point Pt2 is set farther, and the curvature of the arc At used for calculating the target steering angle θt can be increased. Therefore, the vibration of the steering can be reduced.

[0065] In addition, when the setting unit 51 detects the existence of the next inflection point beyond a certain inflection point, the setting unit 51 switches the unit time used for setting the reference point Pt from the second unit time T2 to the first unit time T1 with an appropriate position between the two inflection points as the boundary. For example, before reaching the midpoint between the two inflection points, the setting unit 51 may use the second unit time T2 as the state after the passage of the previous inflection point, and after reaching the midpoint, the setting unit 51 may use the first unit time T1 as the state before the passage of the next inflection point.

[0066] Alternatively, when the inflection point Pc of the curvature c of the target trajectory Ttgt is specified, the setting unit 51 may execute a process of varying the reference for the setting position of the reference point Pt for specific sections before and after passing through the inflection point Pc. Thereby, the process of varying the reference for the setting position of the reference point Pt is executed only in a scene where it is easy to obtain an effect of reducing the deviation of the traveling trajectory to the inside of the curve of the target trajectory Ttgt or reducing the vibration of the steering, and the load on the control device 50 can be reduced.

[0067] (Second example) In the second example, the setting unit 51 sets the first reference point Pt1 and the second reference point Pt2 respectively using a coefficient set such that the second distance D2 is greater than the first distance D1 when compared under the same driving conditions at least one of before or after the vehicle 1 passes through the inflection point Pc. For example, the setting unit 51 calculates the predicted arrival distance of the vehicle 1 after the elapse of the unit time using the same unit time regardless of whether it is before or after passing through the inflection point Pc. Then, the setting unit 51 multiplies the predicted arrival distance by a coefficient set such that the second distance D2 is greater than the first distance D1 when compared under the same driving conditions, and sets the first reference point Pt1 or the second reference point Pt2 at the position corresponding to the calculated predicted arrival distance.

[0068] For example, when multiplying a coefficient only for the predicted distance before passing through the inflection point Pc, the coefficient is set to an appropriate value less than 1. Also, when multiplying a coefficient only for the predicted distance after passing through the inflection point Pc, the coefficient is set to an appropriate value greater than 1. Alternatively, when multiplying coefficients for the predicted distance before passing through the inflection point Pc and the predicted distance after passing through the inflection point Pc respectively, the second coefficient used after passing through the inflection point Pc is set to a value larger than the first coefficient used before passing through the inflection point Pc. Thereby, when comparing under the same driving conditions, the first reference point Pt1 and the second reference point Pt2 are set respectively so that the second distance D2 becomes larger than the first distance D1. After passing through the inflection point Pc, in a state where the curvature c of the target trajectory Ttgt increases, the second reference point Pt2 is set farther away. Therefore, the curvature of the arc At used for calculating the target steering angle θt can be increased, and the vibration of the steering can be reduced.

[0069] In addition, in the second example, instead of using a predetermined coefficient, the setting unit 51 may add or subtract a predetermined distance. For example, the setting unit 51 may subtract a predetermined distance from the predicted distance before passing through the inflection point Pc, or may add a predetermined distance to the predicted distance before passing through the inflection point Pc. Alternatively, a predetermined distance may be added or subtracted from the predicted distances before and after passing through the inflection point Pc respectively. In this case, the predetermined distance (positive or negative value) added or subtracted from the predicted distance after passing through the inflection point Pc is set to a value larger than the predetermined distance (positive or negative value) added or subtracted from the predicted distance before passing through the inflection point Pc. Also by the method of adding or subtracting a predetermined distance, the reference point Pt can be set so that the second distance becomes larger than the first distance when comparing under the same driving conditions.

[0070] Also, in the second example, instead of the predicted distance after a unit time, a constant distance independent of the vehicle speed V may be used as the distance before multiplying the coefficient or before adding or subtracting the predetermined distance. Also in this case, when comparing under the same driving conditions, the first reference point Pt1 and the second reference point Pt2 can be set respectively so that the second distance D2 becomes larger than the first distance D1.

[0071] Also, also in the second example, the setting unit 51 may adjust the position of the first reference point Pt1 based on the curvature c of the inflection point Pc before the vehicle 1 passes through the inflection point Pc. Further, when the setting unit 51 detects the presence of the next inflection point beyond a certain inflection point, the setting unit 51 may switch the unit time used for setting the reference point Pt from the second unit time T2 to the first unit time T1 with an appropriate position between the two inflection points as a boundary. Furthermore, when the inflection point Pc of the curvature c of the target trajectory Ttgt is specified, the setting unit 51 may execute a process of making the reference for the setting position of the reference point Pt different for a specific section before and after passing through the inflection point Pc.

[0072] (Third example) In the third example, the setting unit 51 sets the reference point Pt at a position on the target trajectory Ttgt at a predetermined distance ahead from the current position Pa (or the starting point Pb) of the vehicle 1, which is a constant independent of the vehicle speed. At this time, the setting unit 51 makes the value of the second distance D2 used after the vehicle 1 passes through the inflection point Pc larger than the value of the first distance D1 used before passing through the inflection point Pc. Thereby, without multiplying by a coefficient or adding or subtracting a distance, the first reference point Pt1 and the second reference point Pt2 can be set so that the second distance D2 is larger than the first distance D1.

[0073] However, also in the third example, the setting unit 51 may adjust the position of the first reference point Pt1 based on the curvature c of the inflection point Pc before the vehicle 1 passes through the inflection point Pc. Further, when the setting unit 51 detects the presence of the next inflection point beyond a certain inflection point, the setting unit 51 may switch the distance used for setting the reference point Pt from the second distance D2 to the first distance D1 with an appropriate position between the two inflection points as a boundary. Furthermore, when the inflection point Pc of the curvature c of the target trajectory Ttgt is specified, the setting unit 51 may execute a process of making the reference for the setting position of the reference point Pt different for a specific section before and after passing through the inflection point Pc.

[0074] (2-3. Steering control process) Next, an example of the steering control process by the control device 50 of the vehicle 1 will be described according to the flowchart of FIG. 9.

[0075] First, the setting unit 51 acquires data on the current position Pa of the vehicle 1 and data on the target trajectory Ttgt from the vehicle position sensor 43 and the navigation device 45 (step S11). Next, the setting unit 51 determines whether there is a target point group that constitutes the target trajectory Ttgt in the traveling direction of the vehicle 1 (step S13). Here, it is determined whether the vehicle 1 is set to the automatic driving mode and is automatically driving along the driving route in a state before reaching the destination. If the target point group does not exist (S13 / No), the setting unit 51 ends this routine.

[0076] On the other hand, if the target point group exists (S13 / Yes), the setting unit 51 selects a plurality of target points P1 to P5 from the target point group that constitutes the target trajectory Ttgt, and the coordinates (x i , y i ) and the curvature c in the two-dimensional space of each of the target points P1 to P5 are obtained (step S15). As described above, the more the number of target points to be selected, the more accurately the inflection point Pc of the curvature c can be specified. However, if the number of target points to be selected is too large, the time required for the arithmetic processing becomes long. Therefore, it is preferable to set the number of target points in consideration of these factors. Also, the curvature c of each of the target points P1 to P5 may be included in the data of the target trajectory Ttgt, or may be calculated based on the coordinates in the two-dimensional space of each target point that constitutes the target trajectory Ttgt.

[0077] Next, the setting unit 51 sets the target point with the largest curvature c among the selected target points P1 to P5 as the inflection point Pc (step S17). At this time, as described above, the setting unit 51 may set the target point with the largest curvature c as the inflection point Pc when the curvature c of the target point with the largest curvature c exceeds a predetermined value set in advance. Thereby, the opportunity to execute the process of changing the reference for the setting position of the reference point Pt is limited, and the load on the control device 50 can be reduced. Although not shown, if there is no corresponding inflection point Pc, the setting unit 51 sets the reference point Pt according to the reference set in advance regardless of before and after the passage of the inflection point Pc, and proceeds to step S25.

[0078] When the inflection point Pc is specified in step S17, the setting unit 51 determines whether the current position Pa of the vehicle 1 is in front of the inflection point Pc (step S19). If the current position Pa is in front of the inflection point Pc (S19 / Yes), the setting unit 51 sets the first reference point Pt1 in front of the inflection point Pc (step S21). On the other hand, if the current position Pa exceeds the inflection point Pc (S19 / No), the setting unit 51 sets the second reference point Pt2 so that the second distance D2 from the current position Pa to the reference point Pt (second reference point Pt2) is larger than the first distance D1 to the first reference point Pt1 set before the passage of the inflection point Pc when compared under the same driving conditions (step S23).

[0079] For example, in the above first example, before the passage of the inflection point Pc, the setting unit 51 sets the first reference point Pt1 at a position on the target trajectory Ttgt that is assumed to be reached after the first unit time T1, which is longer than the interval of the calculation cycle, in the state where the vehicle 1 has the current vehicle speed V and is in front of the inflection point Pc (step S21). Also, after the passage of the inflection point Pc, the setting unit 51 sets the second reference point Pt2 at a position on the target trajectory Ttgt that is assumed to be reached after the second unit time T2, which is longer than the first unit time T1, in the state where the vehicle 1 has the current vehicle speed V (step S23).

[0080] Also, in the above-described second example, before the vehicle passes through the inflection point Pc, the setting unit 51 sets the first reference point Pt1 at a position on the target trajectory Ttgt that the vehicle 1 is assumed to reach after a unit time longer than the interval of the calculation cycle in the state of the current vehicle speed V, and at a position in front of the inflection point Pc (step S21). Further, after the vehicle passes through the inflection point Pc, the setting unit 51 calculates the expected arrival distance that the vehicle 1 is assumed to reach after the same unit time in the state of the current vehicle speed V, and sets the second reference point Pt2 at a position corresponding to the expected arrival distance obtained by multiplying the expected arrival distance by a coefficient set to a value greater than 1 (step S23). After the vehicle passes through the inflection point Pc, based on the expected arrival distance that is assumed to be reached after the same unit time, in step S21, before the vehicle passes through the inflection point Pc, the expected arrival distance that is assumed to be reached after the same unit time may be calculated, and the expected arrival distance may be multiplied by a coefficient set to a value less than 1. Alternatively, in each of step S21 and step S23, the expected arrival distance may be obtained by multiplying by a coefficient to set the first reference point Pt1 and the second reference point Pt2, respectively. In this case, the coefficient used in step S23 is set to a value larger than the coefficient used in step S21. Alternatively, in step S21 and step S23, instead of multiplying by a coefficient, a predetermined distance may be added or subtracted.

[0081] Also, in the above-described third example, before the vehicle passes through the inflection point Pc, the setting unit 51 sets the first reference point Pt1 at a position on the target trajectory Ttgt that is located at a first distance D1, which is a constant independent of the vehicle speed, from the current position Pa1 (or the starting point Pb1) of the vehicle 1, and at a position in front of the inflection point Pc (step S21). Further, after the vehicle passes through the inflection point Pc, the setting unit 51 sets the second reference point Pt2 at a position on the target trajectory Ttgt that is located at a second distance D2, which is larger than the first distance D1 and is a constant independent of the vehicle speed, from the current position Pa2 (or the starting point Pb2) of the vehicle 1 (step S23).

[0082] In any of the first to third examples, in step S21, the setting unit 51 may adjust the position of the first reference point Pt1 based on the curvature c of the inflection point Pc before the vehicle 1 passes through the inflection point Pc.

[0083] After the first reference point Pt1 or the second reference point Pt2 is set in steps S21 and S23, the setting unit 51 uses the current traveling direction of the vehicle 1 as a tangent line, and calculates an arc At passing through the current position Pa1 of the vehicle 1 and the first reference point Pt1 or an arc At passing through the current position Pa2 of the vehicle 1 and the second reference point Pt2 (step S25).

[0084] Next, the setting unit 51 sets the target steering angle θt of the wheels 11L and 11R so that the traveling trajectory of the calculated curvature of the arc At is realized (step S27). Specifically, the setting unit 51 calculates the steering angle when the vehicle 1 travels on the calculated arc At, and sets the steering angle as the target steering angle θt. For example, the setting unit 52 refers to a steering angle map that defines the target steering angle θt set according to the radius of curvature r of the arc At and the vehicle speed V, and sets the target steering angle θt based on the calculated radius of curvature r of the arc At and the current vehicle speed V of the vehicle 1. Since the centrifugal force increases as the vehicle speed V increases, when the vehicle 1 travels on the same arc At, the target steering angle θt is set to a larger value as the vehicle speed V increases.

[0085] Next, the steering control unit 59 of the control unit 53 controls the electric steering system 21 so that the steering angles of the wheels 11L and 11R become the target steering angle θt (step S29). Thereafter, the process returns to step S11, and the processes of each step described so far are repeatedly executed.

[0086] <3. Effects of the control device according to the present embodiment> As described above, according to the control device 50 according to the present embodiment, the setting unit 51 calculates an arc At that has a tangent line along the traveling direction of the vehicle 1 and passes through the current position Pa of the vehicle 1 and the reference point Pt set on the target trajectory Ttgt. Further, the setting unit 51 sets the target steering angle θt based on the steering angle when the vehicle 1 travels on the arc At. At this time, the setting unit 51 specifies the inflection point Pc of the curvature c of the target trajectory Ttgt, and sets a first reference point Pt1 in front of the inflection point Pc before the vehicle 1 passes through the inflection point Pc of the curvature c of the target trajectory Ttgt. As a result, the possibility of setting the first reference point Pt1 across the inflection point Pc of the curvature c of the target trajectory Ttgt is reduced, and when the vehicle 1 passes through a curve, the degree of deviation of the traveling trajectory to the inside of the curve of the target trajectory Ttgt can be reduced.

[0087] Further, the setting unit 51 sets the second reference point Pt2 so that the second distance D2 from the current position Pa2 of the vehicle 1 to the reference point Pt (second reference point Pt2) after the vehicle 1 passes through the inflection point Pc is larger than the first distance D1 from the current position Pa1 of the vehicle 1 to the first reference point Pt1 before the vehicle 1 passes through the inflection point Pc when compared under the same driving conditions. For this reason, in a state where the vehicle 1 passes through the inflection point Pc and the curvature c of the target trajectory Ttgt becomes small, the second reference point Pt2 is set farther away, and the curvature of the required arc At becomes small. Therefore, when the steering angles θ of the wheels 11L and 11R are controlled based on the target steering angle θt set for each calculation cycle, steering vibration can be reduced.

[0088] Further, it is preferable that the setting unit 51 adjusts the position of the first reference point Pt1 based on the curvature c at the inflection point Pc before the vehicle 1 passes through the inflection point Pc. As a result, when the curvature of the inflection point Pc is large, that is, when the curve is sharp, the first reference point Pt1 is set closer, and the degree of deviation of the traveling trajectory to the inside of the curve of the target trajectory Ttgt can be reduced.

[0089] Further, the setting unit 51 preferably sets a reference point Pt at the position of the vehicle 1 on the target trajectory Ttgt assumed to be reached after a predetermined unit time. Thereby, the higher the vehicle speed V is, the farther the reference point Pt is set, and it is possible to reduce the steering vibration caused by the increase in the curvature of the arc At.

[0090] As described above, the preferred embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, but the present disclosure is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present disclosure pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and it is naturally understood that these also belong to the technical scope of the present disclosure.

[0091] For example, in the above embodiment, one reference point Pt is set and one arc At is obtained to set the target steering angle θt, but the technology of the present disclosure is not limited to such an example. For example, two reference points (reference point A and reference point B) may be set, arcs may be formed for each reference point, and an instruction value of the target steering angle may be set based on the target steering angles obtained respectively. Also in this case, when comparing the reference point A set before and after passing through the inflection point Pc under the same driving conditions, the second distance D2 after passing through the inflection point Pc is set to be larger than the first distance D1 before passing through the inflection point Pc. Similarly, when comparing the reference point B set before and after passing through the inflection point Pc under the same driving conditions, the second distance D2 after passing through the inflection point Pc is set to be larger than the first distance D1 before passing through the inflection point Pc.

[0092] This reduces the likelihood of setting the reference points A and B across the inflection point Pc of the curvature c of the target trajectory Ttgt, and when the vehicle 1 passes through a curve, the degree of deviation of the travel trajectory inside the curve of the target trajectory Ttgt can be reduced. Also, when the vehicle 1 passes through the inflection point Pc and the curvature c of the target trajectory Ttgt becomes small, the reference points A and B will be set farther apart, and the required curvature of the arc At will become small. Therefore, when controlling the steering angles θ of the wheels 11L and 11R based on the target steering angle θt set for each calculation cycle, steering vibration can be reduced.

Explanation of Signs

[0093] 1…Vehicle, 11L, 11R…Wheels, 19…Drive shaft, 21…Electric power steering system, 41…Vehicle operation / behavior sensor, 43…Vehicle position sensor, 45…Navigation device, 50…Control device, 51…Setting unit, 53…Control unit, 55…Motor control unit, 57…Brake control unit, 59…Steering control unit, 61…Memory unit

Claims

1. One or more processors and one or more memories communicatively connected to the one or more processors, wherein the one or more processors before the vehicle passes through an inflection point of the curvature of the target trajectory, set a first reference point in front of the inflection point on the target trajectory, and set a target steering angle based on the curvature of an arc set to pass through the current position of the vehicle and the first reference point; after the vehicle passes through the inflection point of the curvature of the target trajectory, when at least one of vehicle speed, acceleration / deceleration or steering angle is compared under the same driving conditions, set the second reference point on the target trajectory from the current position of the vehicle so that a second distance, which is the distance to the second reference point, is greater than a first distance, which is the distance from the current position of the vehicle before passing through the inflection point to the first reference point, and set a target steering angle based on the curvature of an arc set to pass through the current position of the vehicle and the second reference point; and control the steering angle based on the target steering angle, and execute a process including this, a control device for a vehicle.

2. The one or more processors set the first reference point and the second reference point at the position of the vehicle on the target trajectory assumed to be reached after a predetermined unit time, The control device for a vehicle according to claim 1, wherein a value of a second unit time used after the vehicle passes through the inflection point is made larger than a value of a first unit time used before passing through the inflection point.

3. The one or more processors in at least one of before or after the vehicle passes through the inflection point, set the first reference point or the second reference point using a coefficient set so that the second distance is greater than the first distance when compared under the same driving conditions. The control device for a vehicle according to claim 1.

4. The one or more processors in at least one of before or after the vehicle passes through the inflection point, add or subtract a predetermined distance set so that the second distance is greater than the first distance when compared under the same driving conditions, and set the first reference point or the second reference point. The control device for a vehicle according to claim 1.

5. The one or more processors The vehicle control device according to claim 2 or 3, wherein the first reference point or the second reference point is set based on a position of the vehicle on the target trajectory that is assumed to be reached after a predetermined unit time.

Images