Control device and control method for a vehicle

Abstract

This invention provides a vehicle control device and control method capable of suppressing the increase in computational load when setting a target steering angle in each calculation cycle and achieving a smooth driving trajectory. The control device includes a setting unit that sets a target steering angle based on the curvature of an arc passing through the current position of the vehicle in each predetermined cycle, and a control unit that controls the steering angle based on the target steering angle. The setting unit calculates the arc passing through the current position of the vehicle and tangent to the vehicle's direction of travel based on the sum of the shortest distances from each of a plurality of target points set on the target trajectory to the arc, and sets the target steering angle for the next cycle before the vehicle reaches the position corresponding to the farthest target point among the plurality of target points used to set the target steering angle in one cycle.

Description

Technical Field

[0001] This invention relates to a vehicle control device and control method. Background Technology

[0002] In recent years, there has been a push for the practical application of technologies related to autonomous driving, which enables vehicles to drive automatically regardless of the driver's actions. During autonomous driving, control is implemented to keep the vehicle following a target trajectory. As a technology related to such autonomous driving, for example, Patent Document 1 discloses a driving assistance device that provides a smooth steering feel and prevents the vehicle from deviating from its lane. Specifically, Patent Document 1 discloses a driving assistance device that repeatedly performs the following operations: calculating two or more correction values ​​to reduce the lateral deviation between a target location on the target trajectory and two or more predicted locations on the trajectory after the current time, and correcting the vehicle's steering state based on the calculated correction values.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-126077 Summary of the Invention

[0006] Technical issues

[0007] Here, the driving assistance device disclosed in Patent Document 1 determines a driving trajectory approximated by multiple arcs in each calculation cycle to reduce the lateral deviation between multiple target points and the actual driving trajectory in the vehicle width direction, and sets the target steering angle based on the foremost arc. However, when the driving trajectory is determined using multiple arcs, the difference in the radii of curvature of each arc may become large, causing the steering angle to change drastically. To suppress this drastic change in steering angle, it is necessary to evaluate the steering speed along with the lateral deviation, which may increase the computational load and the load on the control device.

[0008] The present invention was made in view of the above-mentioned problems. The object of the present invention is to provide a vehicle control device and control method that can suppress the increase of computational load when setting the target steering angle in each operation cycle and achieve a smooth driving trajectory.

[0009] To address the aforementioned issues, according to a certain aspect of the present invention, a vehicle control device is provided. This vehicle control device includes a setting unit that sets a target steering angle based on the radius of curvature of an arc passing through the current position of the vehicle in each predetermined cycle, and a control unit that controls the steering angle based on the target steering angle. The setting unit calculates the arc passing through the current position of the vehicle and tangent to the vehicle's direction of travel based on the sum of the shortest distances from each of a plurality of target points set on a target trajectory to the arc, and sets the target steering angle for the next cycle before the vehicle reaches a position corresponding to the farthest target point among the plurality of target points used to set the target steering angle in one cycle.

[0010] In the aforementioned vehicle control device, the setting unit can repeatedly set the target steering angle so that at least one of the multiple target points for setting the target steering angle in one cycle is included in the multiple target points for setting the target steering angle in the following cycle.

[0011] In the aforementioned vehicle control device, multiple target points can be set at equal intervals based on the vehicle's speed.

[0012] In the aforementioned vehicle control device, when the vehicle speed is lower than a predetermined threshold, the setting unit can fix the interval between multiple target points to a predetermined minimum value or higher.

[0013] In the aforementioned vehicle control device, the setting unit can calculate the minimum arc by summing the shortest distances from each of the multiple target points to the arc.

[0014] In the aforementioned vehicle control device, the setting unit can calculate the arc by weighting the shortest distance from each of multiple target points to the arc.

[0015] In addition, to solve the above-mentioned problems, according to another aspect of the present invention, a vehicle control method is provided, which includes the steps of setting a target steering angle based on the radius of curvature of an arc passing through the current position of the vehicle in each predetermined cycle, and the steps of controlling the steering angle based on the target steering angle. In the step of setting the target steering angle, the target steering angle is set based on the sum of the shortest distances from each of a plurality of target points set on a target trajectory to the arc, the arc passing through the current position of the vehicle and tangent to the direction of travel of the vehicle is obtained, and the target steering angle of the next cycle is set before the vehicle reaches the position corresponding to the farthest target point among the plurality of target points used to set the target steering angle in one cycle.

[0016] Technical effect

[0017] As explained above, according to the present invention, it is possible to suppress the increase in the amount of calculation when setting the target steering angle in each calculation cycle and to achieve a smooth driving trajectory. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating an example of the configuration of a vehicle equipped with a control device according to an embodiment of the present invention.

[0019] Figure 2 This is a block diagram illustrating an example of the configuration of the vehicle control device according to this embodiment.

[0020] Figure 3 This is an explanatory diagram showing the driving trajectory set according to the reference example.

[0021] Figure 4 This is an explanatory diagram showing the driving trajectory without considering steering speed in the reference example.

[0022] Figure 5 This is an explanatory diagram illustrating the method for calculating the arc implemented in this embodiment.

[0023] Figure 6 This is an explanatory diagram illustrating the calculation method for the shortest distance between the target point and the arc.

[0024] Figure 7 This is an explanatory diagram showing the arc set according to each operation cycle.

[0025] Figure 8 This is a flowchart illustrating the steering control process performed by the vehicle's control device according to this embodiment.

[0026] Symbol Explanation

[0027] 1…Vehicle; 11L, 11R…Wheels; 19…Drive shaft; 21…Electric 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…Storage unit Detailed Implementation

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in this specification and the accompanying drawings, constituent elements having substantially the same functional configuration are omitted from repeated description by using the same reference numerals.

[0029] <1. Example of vehicle composition>

[0030] First, one configuration of a vehicle equipped with the control device of the vehicle according to an embodiment of the present invention will be described.

[0031] Figure 1 This is a schematic diagram illustrating an example configuration of vehicle 1. Vehicle 1 includes wheels 11L and 11R, a power transmission system 17, a drive motor 35, an inverter 33, a battery 31, a braking 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, braking system 15, electric steering system 21, vehicle operation behavior sensor 41, vehicle position sensor 43, and navigation device 45 are each directly connected to the control device 50, or connected to the control device 50 via communication methods such as CAN (Controller Area Network) or LIN (Local Internet).

[0032] Figure 1 The vehicle 1 shown is an electric vehicle that uses only a drive motor 35 as its drive source and operates using the power output from the drive motor 35. The driving mode of vehicle 1 can be switched between manual driving mode and automatic driving mode. Manual driving mode controls the acceleration, deceleration, and steering angle of vehicle 1 based on the driver's driving operations. Automatic driving mode automatically controls the acceleration, deceleration, and steering angle of vehicle 1 regardless of the driver's driving operations.

[0033] It should be noted that the driving mode can be switched by the driver, or it can be switched from manual driving mode to automatic driving mode through the intervention of control device 50. Additionally, it can be switched from automatic driving mode to manual driving mode in automatic driving mode when the driver performs specific operations such as braking.

[0034] The drive motor 35 is a motor that outputs power to the wheels 11L and 11R of the vehicle 1. The drive motor 35 is, for example, a three-phase AC motor. The drive motor 35 is connected to the battery 31 via an inverter 33 and is driven by power supplied from the battery 23, thereby outputting power.

[0035] It should be noted that the drive motor 35 can also be a motor that is regeneratively driven when the vehicle 1 decelerates, and can generate electricity using the kinetic energy of the wheels 11L and 11R. In this case, the electricity generated by the drive motor 35 charges the battery 31 through the inverter 33.

[0036] The output shaft of the drive motor 35 is connected to the drive shaft 19, which is connected to the wheels 11L and 11R, 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.

[0037] It should be explained that Figure 1 The wheels 11L and 11R shown are front wheels whose steering angle is controlled by the electric 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 could also be rear wheels. Alternatively, the power output from the drive motor 35 could be transmitted to both the front and rear wheels via a drive shaft (not shown).

[0038] Inverter 33 is a power conversion device that performs bidirectional power conversion. For example, inverter 33 includes a three-phase bridge circuit. Inverter 33 converts the direct current supplied from battery 31 into alternating current and supplies it to drive motor 35. In addition, inverter 33 converts the alternating current generated by drive motor 35 into direct current and supplies it to battery 31. The drive of inverter 33 is controlled by control device 50.

[0039] The storage battery 31 is a battery capable of charging and discharging electricity. While batteries such as lithium-ion batteries, lithium-ion polymer batteries, nickel-metal hydride batteries, nickel-cadmium batteries, or lead-acid batteries may be used as the storage battery 31, other types of batteries may also be used. The storage battery 31 stores the electricity supplied to the drive motor 35.

[0040] The braking system 15 controls the hydraulic pressure supplied to braking devices 13L, 13R located on, for example, each wheel 11L, 11R, thereby controlling the braking force applied to each wheel 11L, 11R. The braking system 15 includes, for example, a master cylinder (not shown), a power assist device, and a hydraulic control unit. The master cylinder is connected to the brake pedal via the power assist device, which assists the driver's pedal force and transmits it to the master cylinder.

[0041] The master cylinder and braking devices 13L and 13R are connected via a hydraulic circuit located in the hydraulic control unit. The master cylinder supplies working oil to the hydraulic circuit according to the amount of brake pedal operation. The hydraulic control unit has a solenoid control valve and an electric pump, and controls the flow rate of working oil supplied to each braking device 13L and 13R.

[0042] The braking devices 13L and 13R installed on each wheel 11L and 11R include brake calipers, which include, for example, brake pads and wheel cylinders. A pair of brake pads are respectively disposed opposite each other on both sides of the brake disc, which rotates integrally with the wheels 11L and 11R. The wheel cylinder is a hydraulic chamber formed within the brake caliper, and each brake pad moves toward both sides of the brake disc as the pressure within the wheel cylinder increases. Thus, the brake disc is clamped by the pair of brake pads, and braking force is applied to the wheels 11L and 11R through friction.

[0043] The hydraulic control unit controls the flow rate of working oil supplied to each braking device 13L, 13R, thereby regulating the pressure in the wheel cylinders of each braking device 13L, 13R, and controlling the braking force applied to each wheel 11L, 11R. The drive of the braking system 15 is controlled by the control device 50.

[0044] The electric steering system 21 assists the driver in steering operations using the steering wheel. For example, the electric steering system 21 includes a rotation sensor (not shown) that detects the rotation angle of the steering wheel, and an electric motor that controls the steering angle of the wheels 11L and 11R based on the rotation angle of the steering wheel detected by the rotation sensor. The electric steering system 21 may also include an electric motor capable of outputting power to rotate the steering wheel. The drive of the electric steering system 21 is controlled by the control unit 50.

[0045] It should be noted that in the automatic driving mode, the electric steering system 21 is used to control the steering angle of the wheels 11L and 11R.

[0046] The vehicle operation behavior sensor 41 includes at least one sensor for detecting the vehicle's operating state and behavior. The vehicle operation behavior sensor 41 includes at least one of, for example, a vehicle speed sensor, an acceleration sensor, and an angular velocity sensor, and detects information about the vehicle's behavior such as vehicle speed, longitudinal acceleration, lateral acceleration, and yaw rate. Additionally, the vehicle operation behavior sensor 41 includes at least one of, for example, an accelerator position sensor, a brake travel sensor, a brake pressure sensor, a steering angle sensor, and an engine speed sensor, and detects information about the vehicle's operating state such as the steering angle of the steering wheel or steering wheel, accelerator opening, and brake input. The vehicle operation behavior sensor 41 sends sensor signals including the detected information to the control device 50.

[0047] Vehicle position sensor 43 detects the position of vehicle 1 and outputs the detection result to control device 50. For example, vehicle position sensor 43 can be a GPS sensor that receives satellite signals from GPS (Global Positioning System) satellites. The GPS sensor sends the vehicle's position information on the map data contained in the received satellite signals to navigation device 45 and control device 50. It should be noted that an antenna that receives satellite signals from other satellite systems used to determine the vehicle's position can also be used instead of a GPS antenna.

[0048] In addition, the vehicle position sensor 43 may also include external cameras and / or LiDAR (Light Detection and Ranging or Laser Imaging Detection and Ranging), radar sensors, and other measuring devices capable of detecting the vehicle's position on the road.

[0049] The navigation device 45 guides vehicle 1 along a route from its current location to a set destination. Map data is pre-stored in the navigation device 45. This map data includes data on the target trajectory, which serves as a reference for vehicle 1's movement on various roads in autonomous driving mode. The target trajectory data includes, for example, data on the centerline of the driving lane in the vehicle width direction, and can be configured as a group of target points. The navigation device 45 acquires information about the current position of vehicle 1 output from the vehicle position sensor 43 and sets a route from the current location to the set destination. The navigation device 45 outputs information representing the route and target trajectory to the control device 50.

[0050] In addition, the navigation device 45 has the function of visually displaying information, and displays various information related to route guidance on the map data, such as the current location and / or driving route of the vehicle 1, the location of the destination, the distance from the destination and / or the estimated arrival time.

[0051] In the autonomous driving mode of vehicle 1, control device 50 performs autonomous driving control, which controls inverter 33, braking system 15 and electric steering system 21, so that vehicle 1 automatically travels along the driving route set by navigation device 45. Control device 50 sets at least the target steering angle of wheels 11L and 11R, and controls the steering angle of wheels 11L and 11R based on the target steering angle.

[0052] <2. Control Device>

[0053] Next, the vehicle control device 50 of this embodiment will be described in detail.

[0054] (2-1. Example of composition)

[0055] The control device 50 is configured to include at least a CPU (Central Processing Unit) or MPU (Micro Processing Unit) and a storage unit for storing various data. It should be noted that part or all of the control device 50 may be composed of updatable devices such as firmware, or it may be a program module executed according to instructions from the CPU or the like.

[0056] Figure 2 This is a block diagram illustrating 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. It should be noted that the functions of the control device 50 in this embodiment can be implemented by a single control device, or by multiple control devices that can communicate with each other via a communication method such as CAN.

[0057] (2-1-1. Storage Department)

[0058] Storage unit 61 includes storage elements such as ROM (Read Only Memory) for storing programs executed by the arithmetic processing unit and / or various arithmetic parameters used for arithmetic processing, and RAM (Random Access Memory) for storing various detection data and arithmetic results acquired by the arithmetic processing unit. Storage unit 61 may also include HDD (Hard Disk Drive) and / or CD (Compact Disc), DVD (Digital Versatile Disc), SSD (Solar Surface Mount Device), etc. i Storage media include solid-state drives (SSDs), USB (Universal Serial Bus) flash memory, and other storage devices.

[0059] (2-1-2. Setting Department)

[0060] In the autonomous driving mode of vehicle 1, the setting unit 51 sets the target steering angle θt of wheels 11L and 11R to enable vehicle 1 to travel along the target trajectory Ttgt on the driving route obtained from navigation device 45. In this embodiment, the setting unit 51 sets a predetermined arc At based on the current position Pa of vehicle 1 output from vehicle position sensor 43 and multiple target points P1 to P5 set on the target trajectory Ttgt obtained from navigation device 45, and sets the target steering angle θt based on the radius of curvature r of the arc At. The setting unit 51 sets the target steering angle θt according to, for example, the processing speed of the processing unit at each predetermined preset processing cycle.

[0061] In addition to obtaining target trajectory Ttgt data from navigation device 45, setting unit 51 can also calculate the center line of driving lane as target trajectory Ttgt based on data output from cameras outside the vehicle and / or sensors that detect the vehicle's surrounding environment.

[0062] (2-1-3. Control Department)

[0063] The control unit 53 performs various arithmetic operations by executing programs stored in the storage unit 61, and controls the operation of various devices in the vehicle 1. In this embodiment, the control unit 53 includes a motor control unit 55, a brake control unit 57, and a steering control unit 59.

[0064] The motor control unit 55 controls the operation of the drive motor 35. Specifically, the motor control unit 55 controls the power supply from the battery 31 to the drive motor 35 and the charging of the battery 31 by the generated power from the drive motor 35 by controlling the operation of the switching elements of the inverter 33. Thus, the motor control unit 55 can control the power output used by the drive motor 35 and the charging of the battery 31.

[0065] 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 brake devices 13L and 13R installed on each wheel 11L and 11R by controlling the operation of the hydraulic control unit. As a result, the brake control unit 57 can control the braking force applied to the vehicle 1.

[0066] 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. Although the steering control unit 59 only needs to be configured to control at least the steering angle θ of the wheels 11L and 11R, the steering control unit 59 can also control the rotation angle of the steering wheel in correspondence with the steering angle θ of the wheels 11L and 11R.

[0067] As described above, the driving mode of vehicle 1 can be switched between manual driving mode and automatic driving mode. The control unit 53 controls the acceleration, deceleration and steering angle of vehicle 1 according to the driving mode.

[0068] For example, in manual driving mode, the control unit 53 controls each device so that the acceleration and deceleration of the vehicle 1 correspond to the acceleration and braking operations performed 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 corresponds to the accelerator opening. Thus, the acceleration of the vehicle 1 can be controlled according to the acceleration operation performed by the driver. Furthermore, the control unit 53 controls the operation of the braking system 15 so that the braking force applied to the vehicle 1 corresponds to the braking force of the braking operation. Thus, the deceleration of the vehicle 1 can be controlled according to the braking operation performed by the driver. Additionally, 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 a cutting angle corresponding to the rotation angle of the steering wheel. Thus, the steering angle θ of the wheels 11L and 11R can be controlled according to the driver's steering operation.

[0069] In autonomous driving mode, the control unit 53 controls each device to make the vehicle 1 automatically travel along the driving route set by the navigation device 45. Specifically, the control unit 53 controls each device to make the vehicle 1 automatically travel along the target trajectory Ttgt on the driving route obtained from the navigation device 45. The control unit 53 controls the operation of the electric steering system 21 so that the steering angle θ of the wheels 11L and 11R becomes the target steering angle θt set by the setting unit 51. In addition, 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 a set speed. The control unit 53 sets the control target of each device in each calculation cycle, in the same manner as, for example, the setting unit 51.

[0070] It should be noted that when there is a vehicle ahead of vehicle 1, or when there are pedestrians and / or obstacles around vehicle 1, the control unit 55 adjusts the driving trajectory or speed of vehicle 1 to avoid collisions between vehicle 1 and the vehicle ahead or pedestrians. However, for the sake of easy understanding of the present invention, the following description assumes that there are no vehicles ahead or pedestrians.

[0071] (2-2. Example of control device operation)

[0072] Next, an example of the control device 50's processing of the steering angle θ of the wheels 11L and 11R will be described as an example of the operation of the control device 50 of the vehicle in this embodiment.

[0073] (2-2-1. Reference Example)

[0074] First, before explaining the method for setting the target steering angle θt implemented in this embodiment, refer to... Figure 3 and Figure 4 An example is given where the vehicle drives in an autonomous driving mode based on a target steering angle set by the reference example.

[0075] Figure 3 and Figure 4 This is an example of repeatedly executing the following process in a time sequence: using multiple (in) methods that can reflect and be set on the target trajectory. Figure 3 and Figure 4 In the example, the evaluation function for the lateral deviations dL1 to dL3 between each of the three target points P1 to P3 is used to set the target steering angle based on the approximate vehicle trajectory of multiple arcs A1 to A3 set for each target point P1 to P3. The so-called lateral deviation dL... i This refers to the error in the width direction between each target point and the vehicle's trajectory. In this case, the reference for determining the vehicle's position can be arbitrarily set, such as the position of the vehicle's center of gravity or the vehicle's center position.

[0076] Figure 3 This illustrates an example of using an evaluation function to set the vehicle's trajectory. This function is configured to reflect both the driver's steering speed and the lateral deviations dL1 to dL3 between the vehicle and each target point P1 to P3. Figure 3 In the example shown, at the vehicle's current position Pa, the target steering angle is calculated by approximating the minimum driving trajectory of the evaluation function with multiple arcs A1 to A3 corresponding to each target point P1 to P3, and the target steering angle is set based on the foremost arc A1.

[0077] The evaluation function can be expressed as follows:

[0078] Evaluation function = Sum of lateral deviations X × coefficient α + Sum of steering speeds Ω × coefficient β.

[0079] Figure 4 Indicates in Figure 3 The example shown demonstrates setting the driving trajectory without considering steering speed. For example... Figure 4 As shown, when using an evaluation function that only reflects the lateral deviations dL1 to dL3 between each target point P1 to P3 without considering steering speed, the difference in curvature of the obtained arcs A1 to A3 may become large, resulting in a sharp change in steering speed. Therefore, when setting the target steering angle by approximating the vehicle's trajectory with multiple arcs in a way that reduces the lateral deviations dL1 to dL3 between each target point P1 to P3, it is necessary to... Figure 3 As illustrated in the example, an evaluation function is used that reflects not only the lateral deviations dL1 to dL3 between the target points P1 to P3, but also the steering speed. Therefore, the computational load may increase in each operation cycle, leading to a greater load on the control unit.

[0080] (2-2-2. Method for setting the target steering angle implemented in this embodiment)

[0081] Next, an outline of the method for setting the target steering angle θt implemented by the setting unit 51 of the control device 50 in this embodiment will be described.

[0082] In the control device 50 of this embodiment, the setting unit 51 acquires information about the current position Pa of the vehicle 1 sent from the vehicle position sensor 43, and acquires information about the target trajectory Ttgt on the driving route output from the navigation device 45. The setting unit 51 sets an arc At that takes the current driving direction of the vehicle 1 as a tangent and passes through the current position Pa of the vehicle 1. Furthermore, the setting unit 51 sets the target steering angle θt of the wheels 11L and 11R so that the vehicle 1 travels along the obtained arc At. For example, the setting unit 51 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 faster the vehicle speed V, the greater the centrifugal force, when the vehicle 1 travels on the same arc At, the faster the vehicle speed V, the larger the target steering angle θt is set to.

[0083] Here, in the control device 50 of this embodiment, the setting unit 51 sets a plurality of target points Pi on the target trajectory Ttgt, and calculates an arc At for setting the target steering angle θt based on the sum of the shortest distances from each of these target points Pi to the arc At. The smaller the sum of the shortest distances from each of the target points Pi to the arc At, the closer the calculated arc At will be to the target trajectory Ttgt within the calculation range of the currently set target points Pi, and the closer the actual driving trajectory will be to the target trajectory Ttgt. Therefore, the setting unit 51 preferably calculates an arc At with the smallest sum of the shortest distances from each of these target points Pi to the arc At. By setting the arc At with the smallest sum of shortest distances, the arc At that is closest to the target trajectory Ttgt within the current calculation range can be set, and the driving trajectory of the vehicle 1 can be made close to the target trajectory Ttgt.

[0084] At this time, if it is desired that vehicle 1 travels near one or more of the multiple target points Pi, or if it is desired that vehicle 1 travels at a distance from a specific target point Pi, the setting unit 51 can set the shortest distance dL for each target point Pi. i Weighted. Thus, it is possible to set an arc At that passes through the vicinity or distance of a specific target point Pi and approaches the target trajectory Ttgt within the calculation range of multiple set target points Pi, and to set the target steering angle θt based on this arc At.

[0085] Furthermore, before vehicle 1 reaches the position corresponding to the target point farthest from the current position Pa among the multiple target points Pi used to set the target steering angle θt in one cycle, the setting unit 51 repeatedly sets the target steering angle θt for the next cycle. This suppresses the situation where the difference in curvature of the arc At obtained in each calculation cycle increases. Therefore, when obtaining the arc At used to set the target steering angle θt, the driving trajectory can be smooth without considering steering speed, and the computational load on the control device 50 can be reduced, thus lessening the load on the control device 50.

[0086] Figure 5 This is an explanatory diagram showing the method for setting multiple target points Pi.

[0087] The setting unit 51 sets any number of target points Pi on the target trajectory Ttgt obtained from the navigation device 45. Figure 5 In the example shown, five target points P1 to P5 are set on the target trajectory Ttgt. The number of target points Pi is not limited to five; it can be four or fewer, or even six or more. However, the more target points Pi there are, the closer the calculated arc At will be to the target trajectory Ttgt. On the other hand, since the processing time increases if too many target points Pi are selected, it is preferable to set the number of target points accordingly.

[0088] Furthermore, among the five target points P1 to P5, the target point P1 closest to the current position Pa is preferably set at a position that is at least closer to the position that vehicle 1 will reach before the next calculation cycle. Therefore, since the trajectory traveled by vehicle 1 before the next calculation cycle reflects the target steering angle θt calculated in the current calculation cycle, it is possible to suppress the situation where vehicle 1 deviates significantly from the target trajectory Ttgt. In this case, if the current position Pa of vehicle 1 is not on the target trajectory Ttgt, the starting point Pb can be set at the position closest to the current position Pa on the target trajectory Ttgt to replace the current position Pa. Additionally, if the position that vehicle 1 will reach before the next calculation cycle is not on the target trajectory Ttgt, the position closest to that destination on the target trajectory Ttgt can be used to replace the destination position.

[0089] Furthermore, the setting unit 51 can set the distance from the current position Pa (or the starting point Pb) to the target point P1 to be increased proportionally to the current vehicle speed V of the vehicle 1. By setting the distance from the current position Pa (or the starting point Pb) to the target point P1 proportionally to the vehicle speed V, multiple target points Pi can be set according to the reachable distance of the vehicle 1, and the vehicle 1 can be driven without deviating significantly from the target trajectory Ttgt based on the target steering angle θt set based on the calculated arc At.

[0090] Furthermore, although the positions of each target point P1 to P5 can be arbitrarily selected, it is preferable to set the positions of target points P1 to P5 at equal intervals. In this case, the interval is set to be shorter than the distance that vehicle 1 is assumed to travel within the interval of the calculation cycle. By setting multiple target points P1 to P5 at equal intervals, the calculated arc At can be made to more closely approximate the target trajectory Ttgt. When setting the interval of target points P1 to P5 at equal intervals, the interval of target points P1 to P5 can be set to increase proportionally to the current speed V of vehicle 1. Specifically, it can be set such that the faster the current speed V of vehicle 1, the larger the interval of target points P1 to P5. By setting the interval of target points P1 to P5 proportionally to the speed V, multiple target points Pi can be set according to the reachable distance of vehicle 1, and vehicle 1 can travel without deviating significantly from the target trajectory Ttgt according to the target steering angle θt set based on the calculated arc At.

[0091] At this time, when the vehicle speed V of vehicle 1 is lower than a predetermined threshold, the setting unit 51 can calculate the arc At by fixing the interval between multiple target points Pi to a predetermined minimum value or higher, and set the target steering angle θt. Therefore, when the vehicle speed V is low, it can suppress the situation where the range for calculating the arc At becomes too small, causing the difference in curvature of the arc At calculated in each calculation cycle to increase. Thus, it can suppress abrupt changes in steering speed. Furthermore, when a lateral deviation dL occurs between the target trajectory Ttgt and the actual driving trajectory, it is necessary to set the target points Pi to a distance that can eliminate the lateral deviation dL. Therefore, by setting the interval between multiple target points Pi to a value above a lower limit such that the distance up to the farthest target point among the multiple target points Pi is a predetermined distance or higher, it can prevent the situation where the lateral deviation dL cannot be corrected when it occurs.

[0092] For example, a threshold value for vehicle speed V can be set such that the interval between target points Pi becomes a lower limit. Within a range where the vehicle speed V of vehicle 1 is above this threshold, the interval between target points Pi is set to increase proportionally to the vehicle speed V. Furthermore, if the vehicle speed V falls below the threshold, the setting unit 51 maintains the interval set during the calculation cycle when the vehicle speed V is about to fall below the threshold. Alternatively, the interval set when the vehicle speed V falls below the threshold can be predetermined as a fixed value.

[0093] In addition, such as Figure 5 As shown, the setting unit 51 is based on the shortest distance dL from each of the multiple target points Pi set on the target trajectory Ttgt to the arc At. iThe sum of these sums is used to find the arc At that passes through the current position Pa of vehicle 1 and is tangent to the direction of travel of vehicle 1. At this point, it is possible to form the shortest distance dL from each of the multiple target points Pi to the arc At. i The sum of these becomes the smallest arc At, forming the arc At that most closely approximates the target trajectory Ttgt within the calculation range of the set target point Pi.

[0094] In this embodiment, the setting unit 51 uses the least squares method to find the shortest distance dL from each of the plurality of target points Pi to the arc At. i The sum of these values ​​constitutes the radius of curvature r of the smallest arc At. For example, the setting unit 51 calculates the coordinates (x, y, y) of the five selected target points P1 to P5 in two-dimensional space. i y i The two-dimensional space used here can be, for example, a two-dimensional space with the current position Pa of vehicle 1 as the origin and the direction of travel of vehicle 1 as the y-axis. Therefore, it is easy to calculate the shortest distance dL from each of the multiple target points Pi to the arc At. i The sum of these elements forms the smallest arc At.

[0095] Specifically, such as Figure 6 As shown, if the coordinates of the center C of the imaginary arc are set to (x... a y a Let the radius of curvature of the arc At be r. Then, the following equation (1) expresses the curvature of the arc from the center C(x) of the imaginary arc. a y a ) to the target point Pi(x) i y i The difference S between the power of the distance to be reached and the power of the radius of curvature r. i .

[0096] Formula 1

[0097] S i =[(x i -x a ) 2 +(y i -y a ) 2 -r 2 …(1)

[0098] Here, when using a two-dimensional space with the current position Pa of vehicle 1 as the origin and the direction of travel of vehicle 1 as the y-axis, since the coordinates of the center C of the imaginary arc are (r, 0), the aforementioned difference S i It can be expressed as the following formula (2).

[0099] Formula 2

[0100] S i =[(x i -r) 2 +y i 2 ]-r 2 …(2)

[0101] Therefore, the difference S for all target points Pi i The sum of powers of is expressed by the following formula (3).

[0102]

Formula 3

[0103]

[0104] Furthermore, as shown in equations (4) and (5) below, differentiating equation (3) above makes the difference S i The radius of curvature r that makes the sum of powers of 0 is the difference S. i The radius of curvature r of the smallest circular arc At.

[0105]

Formula 4

[0106]

[0107]

Formula 5

[0108]

[0109] The setting unit 51 calculates the target steering angle θt that enables the vehicle 1 to travel on the arc At with a curvature radius r based on the radius of curvature r obtained by equation (5) above and the current vehicle speed V of the vehicle 1 in each calculation cycle. Since the target steering angle θt is set in this way, the arc At obtained in each calculation cycle is only one and only the lateral deviation dL between it and each target point Pi can be evaluated, so the amount of calculation can be reduced, thereby reducing the load on the control device 50.

[0110] Furthermore, before the vehicle 1 reaches the position corresponding to the farthest target point P5 among the multiple target points P1 to P5 used to set the target steering angle θt in one calculation cycle, the setting unit 51 repeatedly sets the target steering angle θt for the next calculation cycle. In other words, at least the farthest target point P5 among the multiple target points P1 to P5 is set at a position farther than the foremost target point used when setting the target steering angle θt at the position that the vehicle 1 will reach before the next calculation cycle.

[0111] Figure 7 This diagram illustrates the target points used to set the target steering angle θt in each calculation cycle. With vehicle 1 at its current position Pa1, the shortest distance dL from each of the five target points P1 to P5 (shown as white circles) is calculated.i The sum of these becomes the smallest arc At. In the next calculation cycle, vehicle 1 is at its current position Pa2, and the shortest distance dL from each of the five target points P4 to P8 (shown as black circles) is calculated. i The sum of these becomes the smallest arc At. In the next calculation cycle, vehicle 1 is at its current position Pa3, and the shortest distance dL from each of the five target points P7 to P11, indicated by a triangle, is calculated. i The sum of these elements forms the smallest arc At.

[0112] The setting unit 51 repeatedly calculates the arc At and sets the target steering angle θt in each calculation cycle. As a result, the ranges of the arc At calculated in consecutive calculation cycles can overlap, thereby suppressing abrupt changes in the curvature of the arc At and also suppressing abrupt changes in the target steering angle θt. Therefore, it is unnecessary to evaluate the steering speed, thus reducing the computational load.

[0113] For example, assuming a vehicle speed V of 20 km / h, and entering a curve with a radius of curvature of 20 m from a straight line, if the target steering angle θt is calculated by setting four target points P1 to P4 every second before reaching the position four seconds ahead, then the vehicle can travel on the arc At at a steering speed of less than 90 degrees per second. This steering speed is equal to the steering speed of a person performing a steering operation, and stable driving can be achieved even without evaluating the steering speed.

[0114] (2-3. Steering control processing)

[0115] Next, according to Figure 8 The flowchart illustrates an example of steering control processing performed by the control device 50 of vehicle 1.

[0116] First, the setting unit 51 obtains data on the current position Pa of vehicle 1 and the target trajectory Ttgt from vehicle position sensor 43 and navigation device 45 (step S11). Next, the setting unit 51 determines whether a group of target points constituting the target trajectory Ttgt exists in the direction of travel of vehicle 1 (step S13). Here, vehicle 1 is set to automatic driving mode, and before vehicle 1 reaches its destination, it determines whether vehicle 1 will automatically drive along the driving route. If no group of target points exists ("No" in S13), the setting unit 51 terminates the procedure.

[0117] On the other hand, if a target point group exists ("Yes" in S13), the setting unit 51 selects multiple target points P1 to P5 from the target point group constituting the target trajectory Ttgt, and calculates the coordinates (x, y) of each target point P1 to P5 in two-dimensional space. iy i (Step S15). As mentioned above, the more target points selected, the closer the arc At can be to the target trajectory Ttgt within the set range of target points P1 to P5. However, since the processing time required increases if too many target points are selected, it is preferable to set the number of target points accordingly.

[0118] Furthermore, the setting unit 51 preferably sets the distance from the current position Pa (or the starting point Pb) to the nearest target point P1 and the interval between multiple target points Pi based on the current vehicle speed V of the vehicle 1. Thus, the arc At is set within an appropriate calculation range corresponding to the reachable distance of the vehicle 1. At this time, the setting unit 51 preferably fixes the interval between target points Pi to a predetermined minimum value or higher when the vehicle speed V is below a predetermined threshold. This suppresses the increase in the difference in curvature of the arc At set in each calculation cycle. It should be noted that the target trajectory Ttgt can also be calculated by the control device 50. For example, the control device 50 can use data sent from an external camera or sensors detecting the surrounding environment of the vehicle 1 as the target trajectory Ttgt, obtained by connecting the center line of the driving lane ahead in the direction of travel.

[0119] Next, the setting unit 51 calculates the arc At (step S17) with the current direction of travel of the vehicle 1 as the tangent and passing through the current position Pa of the vehicle 1, based on the sum of the shortest distances dL1 to dL5 from each of the selected target points P1 to P5. For example, the setting unit 51 uses the above formula (5) to calculate the arc At with a radius of curvature r obtained by the least squares method. At this time, if it is desired to make the vehicle 1 travel near a specific target point Pi, or if it is desired to make the vehicle 1 travel far from a specific target point Pi, the shortest distance dL1 to dL5 from each target point Pi can be calculated. i Weighted.

[0120] Next, the setting unit 51 sets the target steering angle θt for wheels 11L and 11R to achieve a driving trajectory with the curvature of the calculated arc At (step S19). Specifically, the setting unit 51 calculates the steering angle for driving vehicle 1 on the calculated arc At, and sets this steering angle as the target steering angle θt. For example, the setting unit 51 refers to a steering angle mapping determined based on the radius of curvature r of arc At and vehicle speed V, and sets the target steering angle θt based on the obtained radius of curvature r of arc At and the current vehicle speed V of vehicle 1. Since the faster the vehicle speed V, the greater the centrifugal force, the faster the vehicle speed V, the larger the target steering angle θt is set when driving vehicle 1 on the same arc At.

[0121] Next, the steering control unit 59 of the control unit 53 controls the electric steering system 21 so that the steering angle of the wheels 11L and 11R becomes the target steering angle θt (step S21). After that, the process returns to step S11 and repeats the steps described above.

[0122] <3. Effects of the control device in this embodiment>

[0123] As explained above, in the control device 50 of this embodiment, the setting unit 51 calculates an arc At that has a tangent along the travel direction of the vehicle 1 and passes through the current position Pa of the vehicle 1 based on the sum of the shortest distances between multiple target points Pi set on the target trajectory Ttgt and the arc At, and sets the target steering angle θt. Therefore, in each calculation cycle, it is not necessary to calculate multiple arcs corresponding to each target point Pi, and it is not necessary to consider the steering speed, thereby reducing the amount of calculation and lessening the load on the control device 50.

[0124] Furthermore, before vehicle 1 reaches the position corresponding to the farthest target point among the multiple target points Pi used to set the target steering angle θt in one cycle, the setting unit 51 repeatedly performs the process of setting the target steering angle θt for the next cycle. As a result, it is possible to set the target steering angle to coincide with a portion of the arc At calculated in each calculation cycle, and to suppress abrupt changes in the target steering angle θt to form a smooth driving trajectory.

[0125] Furthermore, the setting unit 51 calculates the arc At that minimizes the sum of the shortest distances between multiple target points Pi set on the target trajectory Ttgt, and sets the target steering angle θt. Therefore, within the calculation range of the target point Pi in each calculation cycle, the arc At can pass through the position closest to the target trajectory Ttgt, and the actual driving trajectory can be made close to the target trajectory Ttgt.

[0126] Furthermore, the setting unit 51 sets multiple target points Pi at equal intervals based on the current vehicle speed V of the vehicle 1. This allows the arc At to be set within a calculation range corresponding to the reachable distance of the vehicle 1, and suppresses situations where the vehicle 1's trajectory deviates significantly from the target trajectory Ttgt. At this time, if the vehicle speed V is below a predetermined threshold, the setting unit 51 fixes the interval between the multiple target points Pi to a predetermined minimum value or higher. This suppresses situations where the calculation range for the arc At is too small, resulting in a large difference in the curvature of the arc At calculated per calculation cycle, and also suppresses abrupt changes in steering speed.

[0127] Furthermore, the setting unit 51 can also calculate the arc At by weighting the shortest distance from each of the multiple target points Pi to the arc At. Therefore, the target steering angle θt can be set based on the arc At that is close to or far from a specific target point Pi. Thus, automated driving that takes into account the surrounding environment of the vehicle 1 and / or the driver's driving characteristics can be realized.

[0128] While preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It should be understood that those skilled in the art will readily conceive of various variations or modifications within the scope of the technical concept described in the claims, and these variations naturally fall within the technical scope of the present invention.

[0129] For example, in the above embodiment, although the least squares method is used to calculate the arc At that minimizes the sum of the shortest distances from each of the multiple target points Pi to the arc At, the present invention is not limited to this example. The method for calculating the arc At that minimizes the sum of the shortest distances from each of the multiple target points Pi to the arc At is not limited to the least squares method, and other suitable methods may also be used.

Claims

1. A control device of a vehicle characterized by comprising: It includes one or more processors and one or more memories communicatively connected to the one or more processors. The processor, The target steering angle is set for each predetermined cycle based on the radius of curvature of the arc tangent to the vehicle's current position and the direction of travel of the vehicle. The steering angle is controlled based on the target steering angle. The target steering angle is set based on the sum of the shortest distances from multiple target points equally spaced on the target trajectory to the arc, the arc whose sum of shortest distances is minimized, and the radius of curvature of the arc. Before the vehicle reaches the position corresponding to the farthest target point among the plurality of target points used to set the target steering angle in the first cycle, the target steering angle is set for the second cycle following the first cycle. The intervals between the multiple target points are shorter than the distance traveled by the vehicle in the first cycle. The target point closest to the current position among the plurality of target points is set at a position closer to the position the vehicle will reach in the first cycle.

2. The vehicle control device according to claim 1, characterized in that, The processor repeatedly sets the target steering angle such that at least one of the plurality of target points used to set the target steering angle in one cycle is included in the plurality of target points used to set the target steering angle in a subsequent cycle.

3. The vehicle control device according to claim 1 or 2, characterized in that, The multiple target points are set at equal intervals based on the vehicle's speed.

4. The vehicle control device according to claim 3, characterized in that, If the vehicle speed is lower than a predetermined threshold, the processor fixes the interval between the plurality of target points to a predetermined minimum value or higher.

5. The vehicle control device according to claim 1, characterized in that, The processor calculates the arc by weighting the shortest distances from each of the plurality of target points to the arc.

6. A control method of a vehicle characterized by comprising: include: The step of setting the target steering angle based on the radius of curvature of an arc tangent to the vehicle's current position and the direction of travel of the vehicle at each predetermined cycle; as well as The steps of controlling the steering angle based on the target steering angle. In the step of setting the target steering angle The target steering angle is set based on the sum of the shortest distances from multiple target points equally spaced on the target trajectory to the arc, the arc whose sum of shortest distances is minimized, and the radius of curvature of the arc. Before the vehicle reaches the position corresponding to the farthest target point among the plurality of target points used to set the target steering angle in one cycle, the target steering angle for the next cycle is set. The interval between the multiple target points is shorter than the distance the vehicle travels in one cycle. The target point closest to the current position among the plurality of target points is set at a position that is closer to the position that the vehicle will reach in one cycle.

Images