JP2018177128A - Path following control system - Google Patents

Abstract

An object of the present invention is to accurately set a steering angle midpoint when path following control is started.
A path tracking control system includes a steering device, a steering angle sensor that acquires a steering angle of a wheel based on a steering angle midpoint as a sensor steering angle, and a control device that performs path tracking control. . The control device calculates a target path, calculates a target steering angle necessary for the vehicle to follow the target path according to the turning radius of the target path, and turns the steering device so that the sensor steering angle becomes the target steering angle. Control. The sensor steering angle at the start of the path following control is the driver steering angle. At the start of the path following control, the control device acquires the driver's steering angle and the target steering angle, and sets the steering angle midpoint based on the difference between the driver's steering angle and the target steering angle.
[Selected figure] Figure 4

Description

  The present invention relates to a path following control system that controls the travel of a vehicle so that the vehicle follows a target path.

  A steering angle sensor is known which calculates the steering angle of the wheels of a vehicle. The steering angle calculated by the steering angle sensor is hereinafter referred to as "sensor steering angle". When a relative angle sensor is used as a steering angle sensor, a "steering angle middle point" as a reference of the sensor steering angle is required. The steering angle midpoint is a sensor steering angle when the vehicle is in a straight traveling state, and is also referred to as a "straight steering angle" or a "neutral steering angle". The steering angle midpoint is stored in the storage device and is used to calculate a sensor steering angle by the steering angle sensor. Also in the absolute angle sensor, since the neutral position steering angle of the sensor and the straight steering angle sometimes do not match, it is necessary to separately store the straight steering angle.

  However, the steering angle midpoint may change with the passage of time. For example, the steering angle midpoint changes due to aging of a steering angle sensor or a vehicle component (suspension, etc.), temperature change, or maintenance of a vehicle. As a result, the steering angle midpoint currently in use may be deviated from the accurate steering angle midpoint. Since such a deviation of the steering angle midpoint causes a reduction in the accuracy of vehicle control, it is important to grasp the steering angle midpoint with high accuracy.

  Patent Document 1 discloses a follow-up control device that performs control of causing a vehicle to follow a preceding vehicle. When the vehicle is traveling straight, the follow-up control device acquires the steering angle of the preceding vehicle through inter-vehicle communication, and calculates the steering angle of the own vehicle by the steering angle sensor. Then, the follow-up control device sets the difference between the steering angle of the preceding vehicle and the steering angle of the host vehicle as the steering angle midpoint.

  Patent Document 2 discloses an electric power steering apparatus. The electric power steering apparatus includes straight traveling state determination means and steering angle midpoint calculation means. The straight traveling state determination unit determines whether the vehicle is in a straight traveling state. When the vehicle is traveling straight, the steering angle midpoint computing means calculates an average value of a plurality of detected angles detected by the steering angle sensor within a predetermined time, and computes the steering angle midpoint using the average value Do.

  Patent Document 3 discloses an automatic driving system. The automatic driving system includes a peripheral information detection unit that detects peripheral information of the vehicle, a travel plan generation unit that generates a travel plan of the vehicle based on the detected peripheral information and map information, and the vehicle according to the generated travel plan And a traveling control unit that automatically controls traveling of the vehicle.

JP, 2013-107571, A Unexamined-Japanese-Patent No. 2006-103390 JP, 2016-099713, A

  As a type of automatic driving control or driving support control in a vehicle, "path-following control" is known. In the path following control, the traveling of the vehicle is automatically controlled such that the vehicle follows the target path. More specifically, a target steering angle necessary for the vehicle to follow the target path is calculated. Then, steering control of the vehicle is performed such that the sensor steering angle calculated by the steering angle sensor becomes the target steering angle.

  Here, as described above, the steering angle midpoint currently in use is not necessarily accurate. That is, the steering angle midpoint currently in use may be deviated from the actual straight ahead state. Such a deviation of the steering angle midpoint causes a decrease in the accuracy of the path following control, that is, a decrease in the performance of following the target path. Therefore, when carrying out the path following control, it is desirable to grasp the steering angle midpoint with high accuracy.

  However, according to the method of setting the steering angle midpoint disclosed in Patent Document 1, information on the steering angle of the preceding vehicle is required. Therefore, when there is no preceding vehicle, the steering angle midpoint can not be set. Moreover, in patent document 1 and patent document 2, when setting a steering angle middle point, it is necessary for the vehicle to travel straight. Therefore, when the vehicle is not traveling straight, the steering angle midpoint can not be set.

  When starting the path following control, the preceding vehicle may not be conveniently present. In addition, when the path following control is started, the vehicle is not always traveling straight. If the steering angle midpoint can not be set with high accuracy when starting the path following control, the accuracy of the subsequent path following control decreases and the tracking performance for the target path decreases.

  An object of the present invention is to provide a technique capable of setting a steering angle midpoint with high accuracy when starting path following control for controlling the traveling of a vehicle so as to follow a target path.

In one aspect of the present invention, a path following control system mounted on a vehicle is provided.
Path tracking control system
A steering device for steering the wheels of the vehicle;
A steering angle sensor that acquires a steering angle of the wheel based on a steering angle middle point as a sensor steering angle;
And a control device for performing path following control to automatically control traveling of the vehicle such that the vehicle follows a target path.
The controller is
A process of calculating the target path;
A process of calculating a target steering angle necessary for the vehicle to follow the target path according to a turning radius of the target path;
And controlling the steering device such that the sensor steering angle becomes the target steering angle.
The sensor steering angle at the start of the path following control is a driver steering angle.
At the start of the path following control, the control device acquires the driver steering angle and the target steering angle, and sets the steering angle midpoint based on the difference between the driver steering angle and the target steering angle.

  The path following control system according to the present invention can set the steering angle midpoint at the start of the path following control. The setting of the steering angle midpoint is based on the following findings.

  That is, when traveling on a lane of the same shape (turning radius), the driver of the vehicle and the path following control system are considered to steer the wheels by the same amount. The turning amount by the driver is reflected on the driver steering angle which is a sensor steering angle at the start of the path following control. On the other hand, the turning amount by the path following control system is reflected on the target steering angle according to the turning radius. If the steering angle midpoint currently in use matches the exact steering angle midpoint, it is considered that there is no difference between the driver's steering angle and the target steering angle. On the other hand, when the steering angle midpoint currently in use deviates from the accurate steering angle midpoint, the deviation amount appears as a difference between the driver's steering angle and the target steering angle.

  Therefore, the path following control system according to the present invention acquires the driver steering angle and the target steering angle at the start of the path following control, and sets the steering angle midpoint based on the difference between the driver steering angle and the target steering angle Update. As a result, the accuracy of the subsequent path tracking control is improved, and the tracking performance for the target path is improved.

  Further, according to the present invention, the vehicle may go straight or turn as long as the driver's steering angle and the target steering angle can be acquired. Since information on the leading vehicle is also unnecessary, it is not necessary for the leading vehicle to be present. Compared to Patent Document 1 and Patent Document 2, it can be said that the present invention has fewer restrictions. Therefore, it becomes easy to set the steering angle midpoint, and as a result, it becomes easy to start high-accuracy path tracking control.

It is a conceptual diagram for demonstrating the path following control by the path following control system concerning an embodiment of the invention. It is a conceptual diagram for demonstrating "deviation" of the steering angle middle point of the steering angle sensor in embodiment of this invention. It is a conceptual diagram for demonstrating the setting method of the steering angle midpoint which concerns on embodiment of this invention. It is a conceptual diagram for demonstrating the setting method of the steering angle midpoint which concerns on embodiment of this invention. FIG. 1 is a block diagram showing a configuration example of a path tracking control system according to an embodiment of the present invention. It is a block diagram showing functional composition of a control device of a path following control system concerning an embodiment of the invention. It is a flowchart which shows the setting method of the steering angle midpoint in the path | pass tracking control system which concerns on embodiment of this invention.

  Embodiments of the present invention will be described with reference to the attached drawings.

1. Overview FIG. 1 is a conceptual diagram for explaining path following control by a path following control system according to the present embodiment. The path tracking control system is mounted on the vehicle 1 and automatically controls the traveling of the vehicle 1 so that the vehicle 1 follows the target path TP. Such path following control is a type of automatic driving control or driving support control. That is, the path following control system is part of an automatic driving system or a driving support system.

  In the example shown in FIG. 1, the shape of the target path TP is defined by the turning radius Rp. Once the shape of the target path TP (that is, the turning radius Rp), the relative position between the target path TP and the vehicle 1, and the vehicle speed Vx are determined, the vehicle state quantity required for the vehicle 1 to follow the target path TP can be determined. it can. Such vehicle state quantities include the yaw rate Yr, the lateral acceleration Gy, and the yaw angle offset θyo. Here, the yaw angle offset θyo is an angle between the traveling direction of the vehicle 1 and the tangent of the target path TP at a position closest to the vehicle 1.

  Furthermore, the path following control system calculates a vehicle control amount necessary for the vehicle 1 to follow the target path TP from the above-described vehicle state amount. Then, the path following control system controls the traveling of the vehicle 1 in accordance with the calculated vehicle control amount. Typically, the vehicle control amount includes the target steering angle of the wheels of the vehicle 1. The path following control system performs steering control to automatically steer the wheels such that the steering angle of the wheels becomes the target steering angle.

  In this steering control, the steering angle of the wheel is acquired by a steering angle sensor. The steering angle acquired by the steering angle sensor is hereinafter referred to as "sensor steering angle". When a relative angle sensor is used as the steering angle sensor, a “steering angle midpoint θn” as a reference of the sensor steering angle is required. The steering angle midpoint θn is a sensor steering angle when the vehicle 1 is in a straight traveling state, and is also referred to as a “straight steering angle” or a “neutral steering angle”. The steering angle midpoint θn is stored in the storage device and used for calculation of a sensor steering angle by the steering angle sensor.

  However, the steering angle midpoint θ n may change with the passage of time. For example, the steering angle midpoint θ n changes due to aging of a steering angle sensor or a vehicle component (suspension or the like), temperature change, or maintenance of the vehicle 1. As a result, there is a possibility that the steering angle midpoint θn currently in use deviates from the accurate steering angle midpoint θn.

  FIG. 2 is a conceptual diagram for explaining the “deviation” of the steering angle midpoint θn of the steering angle sensor. The horizontal axis indicates the sensor steering angle, and the vertical axis indicates the actual steering angle. As described above, the steering angle midpoint θ n is a sensor steering angle when the vehicle 1 is in a straight ahead state, and is a sensor steering angle when the actual steering angle is zero. In FIG. 2, the steering angle midpoint θn currently in use is offset from the accurate steering angle midpoint θn. The amount of deviation between the exact steering angle midpoint θn and the steering angle midpoint θn currently in use is represented by the offset δoff.

  Such a deviation of the steering angle midpoint θn causes a decrease in the accuracy of the path tracking control, that is, a decrease in the tracking performance for the target path TP. In particular, if the steering angle midpoint θn can not be set with high accuracy when starting the path following control, the accuracy of the subsequent path following control is reduced, and the tracking performance for the target path TP is reduced. Therefore, when starting the path following control, it is desirable to set the steering angle midpoint θn with high accuracy.

  FIG.3 and FIG.4 is a conceptual diagram for demonstrating the setting method of steering angle middle point (theta) n which concerns on this Embodiment. According to the present embodiment, the steering angle midpoint θn is set (updated) at the start of the path following control.

  For example, as shown in FIG. 3, it is assumed that the path following control is started when the vehicle 1 is turning. Before the start of the path following control, the driver of the vehicle 1 performs steering using the steering wheel, and after the start of the path following control, the path following control system performs the steering control. When turning a curve of the same curvature (turning radius Rp), it is conceivable that both the driver and the path following control system steer the wheels by approximately the same amount.

  This will be described in more detail with reference to FIG. Column (a) in FIG. 4 indicates the amount of turning by the driver immediately before the start of the path following control. The horizontal axis indicates the actual steering angle, and the vertical axis indicates the curvature of the traveling lane. Just before the start of the path following control, the driver steers the steering wheel so that the vehicle 1 travels along the traveling lane. The turning amount (actual steering angle) at this time changes in accordance with the curvature of the traveling lane, and as the curvature increases, the actual steering angle also increases. When the curvature is a certain value C, it is assumed that the turning amount by the driver is δc.

  Column (b) in FIG. 4 indicates the turning amount by the path following control system after the start of the path following control. The horizontal axis indicates the sensor steering angle, and the vertical axis indicates the curvature of the target path TP. After the start of the path tracking control, the path tracking control system sets a target path TP along the traveling lane, and performs steering control so that the vehicle 1 follows the target path TP. The target steering angle in this turning control is mainly calculated according to the curvature of the target path TP, that is, the turning radius Rp (see FIG. 1) of the target path TP. The target steering angle component calculated according to the turning radius Rp of the target path TP is hereinafter referred to as “target steering angle θrp”. That is, the target steering angle θrp is expressed as a function of the turning radius Rp, as in the following equation (1).

Formula (1):
θrp = f (Rp)

  When traveling on a lane of the same shape (curvature C, turning radius Rp), both the driver and the path following control system are considered to steer the wheels by approximately the same amount. That is, it is considered that the target steering angle θrp according to the turning radius Rp is substantially equal to the steering amount δc by the driver shown in the (a) column in FIG.

Formula (2):
θrp = f (Rp) ≒ δc

  Column (c) in FIG. 4 shows the superposition of columns (a) and (b). The horizontal axis indicates the sensor steering angle, and the vertical axis indicates the curvature. As in the case of FIG. 2 already described, the steering angle midpoint θn currently in use is offset from the correct steering angle midpoint θn. The amount of deviation between the exact steering angle midpoint θn and the steering angle midpoint θn currently in use is the offset δoff. Determining the offset δoff is equivalent to determining the accurate steering angle midpoint θn.

  The driver is steering until just before the start of the path following control. Therefore, the sensor steering angle at the start of the path following control becomes a value reflecting the turning amount δc by the driver. The sensor steering angle at the start of such path following control is hereinafter referred to as “driver steering angle θstr”. As can be seen from FIG. 4, the driver's steering angle θstr is represented by the sum of the turning amount δc and the offset δoff. That is, the driver's steering angle θstr is expressed by the following equation (3).

Formula (3):
θstr = δc + δoff

  From the equations (1) to (3), the offset δoff, that is, the accurate steering angle midpoint θn is expressed by the following equation (4).

Formula (4):
θ n = δ off
Θ θstr-θrp
= Θ str-f (R p)

  That is, the accurate steering angle midpoint θn at the start of the path following control is given by the difference between the driver steering angle θstr and the target steering angle θrp. The path following control system according to the present embodiment acquires the driver's steering angle θstr and the target steering angle θrp at the start of the path following, and sets (updates) the steering angle midpoint θn according to the equation (4). As a result, the accuracy of the subsequent path tracking control is improved, and the tracking performance for the target path TP is improved.

  Further, as can be seen from FIG. 4, even if the curvature C is zero, that is, even if the vehicle 1 is traveling straight, the equation (4) holds. As long as the driver steering angle θstr and the target steering angle θrp can be acquired, the vehicle 1 may go straight or turn. In addition, information on the leading vehicle is unnecessary, and the leading vehicle does not have to be present. That is, in comparison with the method disclosed in Patent Document 1 or Patent Document 2 described above, it can be said that the method of setting the steering angle midpoint θn according to the present embodiment is less restrictive. Accordingly, it becomes easy to set the steering angle midpoint θn, and as a result, it becomes easy to start the high-accuracy path tracking control.

  Hereinafter, the path tracking control system according to the present embodiment will be described in more detail.

2. Path Following Control System FIG. 5 is a block diagram showing a configuration example of the path following control system 10 according to the present embodiment. The path tracking control system 10 is a part of an automatic driving system or a driving support system mounted on the vehicle 1 and performs path tracking control. More specifically, the path tracking control system 10 includes a GPS (Global Positioning System) receiver 20, a map database 30, a sensor group 40, an HMI (Human Machine Interface) unit 50, a traveling device 60, and a control device 100. There is.

  The GPS receiver 20 receives signals transmitted from a plurality of GPS satellites, and calculates the position and orientation of the vehicle 1 based on the received signals. The GPS receiver 20 sends the calculated information to the control device 100.

  In the map database 30, information indicating the boundary position of each lane on the map is recorded in advance. The boundary position of each lane is represented by a point group or line group. The map database 30 is stored in a predetermined storage device.

  The sensor group 40 detects the situation around the vehicle 1 and the traveling state of the vehicle 1. The sensor group 40 sends the detected information to the control device 100.

  For example, the sensor group 40 includes a steering angle sensor 45. The steering angle sensor 45 acquires (calculates or estimates) the steering angle of the wheels of the vehicle 1. For example, the steering angle sensor 45 is a relative angle sensor, and acquires a steering angle based on the steering angle midpoint θn. The steering angle obtained by the steering angle sensor 45 is a sensor steering angle. Further, the steering angle midpoint θn is stored in a predetermined storage device, and can be updated as needed.

  The sensor group 40 further includes a rider (LIDAR: Laser Imaging Detection and Ranging), a radar, a camera, a vehicle speed sensor, a yaw rate sensor, a lateral acceleration sensor, and the like. The rider uses the light to detect targets around the vehicle 1. The radar detects targets around the vehicle 1 using radio waves. The camera captures the situation around the vehicle 1. The vehicle speed sensor detects the speed of the vehicle 1. The yaw rate sensor detects the yaw rate of the vehicle 1. The lateral acceleration sensor detects a lateral acceleration acting on the vehicle 1.

  The HMI unit 50 is an interface for providing information to the driver of the vehicle 1 and for receiving information from the driver. For example, the HMI unit 50 includes an input device, a display device, a speaker, and a microphone. Examples of the input device include a touch panel, a keyboard, a switch, and a button. The driver can input information to the HMI unit 50 using an input device. For example, the driver can use an input device to instruct the start of path tracking control. The HMI unit 50 sends the information input from the driver to the control device 100.

  The traveling device 60 includes an actuator for controlling the traveling of the vehicle 1. More specifically, the traveling device 60, the drive device, the braking device, and the steering device 65 are included. The driving device is a power source that generates a driving force. An engine and an electric motor are illustrated as a drive device. The braking device generates a braking force.

  The steering device 65 steers the wheels of the vehicle 1. For example, the steering device 65 includes a power steering (EPS) device. The wheels can be steered by controlling the drive of the motor of the power steering device. The steering angle sensor 45 may be incorporated in the power steering apparatus.

  The control device 100 performs path following control of the vehicle 1. Typically, the control device 100 is a microcomputer provided with a processor, a storage device, and an input / output interface. Control device 100 is also called an ECU (Electronic Control Unit). The control device 100 receives various information through the input / output interface. Then, the control device 100 performs path tracking control based on the received information.

  FIG. 6 is a block diagram showing a functional configuration of control device 100 according to the present embodiment. The control device 100 includes, as functional blocks, an information acquisition unit 110, a target path calculation unit 120, a vehicle travel control unit 130, and a steering angle midpoint setting unit 140. These functional blocks are realized by the processor of the control device 100 executing the control program stored in the storage device. The control program may be stored in a computer readable recording medium.

  The information acquisition unit 110 acquires various types of information. Specifically, the information acquisition unit 110 acquires, from the GPS receiver 20, position orientation information indicating the current position and orientation of the vehicle 1.

  The information acquisition unit 110 also reads out information on lanes from the map database 30 and generates lane information. The lane information includes the arrangement (position, shape, inclination) of each lane on the map. The information acquisition unit 110 can calculate the lane curvature, the lane width, and the like based on the lane information. Also, the information acquisition unit 110 can grasp merging, branching, crossing, and the like of lanes based on the lane information.

  Furthermore, the information acquisition unit 110 generates vehicle state information and surrounding state information based on the information acquired by the sensor group 40. The vehicle state information includes a sensor steering angle obtained by the steering angle sensor 45. Besides, the vehicle state information includes the speed of the vehicle 1, the yaw rate, the lateral acceleration and the like. The surrounding condition information includes target information on targets around the vehicle 1. As a target, a white line, a roadside thing, a surrounding vehicle, etc. are illustrated.

  Furthermore, the information acquisition unit 110 receives input information from the driver through the HMI unit 50. The input information from the driver includes, for example, an instruction to start path tracking control.

  The target path calculation unit 120 calculates the target path TP based on the information acquired by the information acquisition unit 110. For example, the target path TP is calculated based on the position and orientation information, the lane information, and the surrounding condition information. Thereby, the information acquisition unit 110 can calculate the target path TP along the lane shape.

  The vehicle travel control unit 130 performs vehicle travel control for controlling the travel of the vehicle 1 so as to follow the target path TP. Specifically, the vehicle travel control unit 130 recognizes the relative position between the target path TP and the vehicle 1 based on the information on the target path TP, the position and orientation information, and the vehicle state information, and the vehicle 1 A vehicle control amount necessary to follow is calculated. Then, the vehicle travel control unit 130 operates the travel device 60 according to the calculated vehicle control amount.

  For example, the vehicle travel control unit 130 calculates a target steering angle necessary for the vehicle 1 to follow the target path TP. Further, the vehicle travel control unit 130 acquires a sensor steering angle obtained by the steering angle sensor 45 from the vehicle state information. Then, the vehicle travel control unit 130 controls the operation of the steering device 65 so that the sensor steering angle becomes the target steering angle. Specifically, vehicle travel control unit 130 calculates a motor current command value according to the difference between the sensor steering angle and the target steering angle, and drives the motor of the power steering apparatus according to the motor current command value. Thus, vehicle travel control is realized.

  The steering angle midpoint setting unit 140 sets (updates) the steering angle midpoint θn of the steering angle sensor 45. More specifically, the steering angle midpoint setting unit 140 sets (updates) the steering angle midpoint θ n based on the principle shown in FIG. 4 at the start of the path following control.

  Hereinafter, the method of setting the steering angle midpoint θn according to the present embodiment will be described in more detail.

3. Method of Setting Steering Angle Midpoint FIG. 7 is a flowchart showing a method of setting the steering angle midpoint θn according to the present embodiment.

Step S10:
The driver can use the input device of the HMI unit 50 to input an instruction to start path tracking control. The steering angle midpoint setting unit 140 determines whether a path following control start instruction has been input. If the path tracking control start instruction is input, the process proceeds to step S20.

Step S20:
The steering angle midpoint setting unit 140 acquires the driver steering angle θstr. As shown in FIG. 4, the driver steering angle θstr is a sensor steering angle at the start of the path following control. Thereafter, the process proceeds to step S30.

Step S30:
The target path calculation unit 120 calculates the first target path TP after the start of the path follow-up control. Thereafter, the process proceeds to step S40.

Step S40:
The vehicle travel control unit 130 obtains a vehicle state amount necessary for the vehicle 1 to follow the target path TP. The vehicle state quantities include a yaw rate Yr, a lateral acceleration Gy, and a yaw angle offset θyo (see FIG. 1). Furthermore, the vehicle travel control unit 130 calculates a vehicle control amount necessary for the vehicle 1 to follow the target path TP from the vehicle state amount. The vehicle control amount includes the target steering angle. In particular, the vehicle travel control unit 130 calculates the target steering angle θrp according to the turning radius Rp of the target path TP according to the above equation (1). Thereafter, the process proceeds to step S50.

Step S50:
The steering angle midpoint setting unit 140 determines whether a predetermined condition is satisfied. The predetermined condition here is that each of the yaw angle offset θyo, the yaw rate Yr, and the lateral acceleration Gy is within a predetermined value.

  If the predetermined condition is not satisfied (step S50; No), it means that the current travel route of the vehicle 1 is too far from the target path TP. In that case, the principle shown in FIG. 4 does not necessarily hold. Therefore, the steering angle midpoint setting unit 140 ends the process without updating the steering angle midpoint θn. On the other hand, when the predetermined condition is satisfied (step S50; Yes), the process proceeds to step S60.

Step S60:
The steering angle midpoint setting unit 140 calculates and updates the steering angle midpoint θn in accordance with the above equation (4). That is, the steering angle midpoint setting unit 140 sets the difference between the driver's steering angle θstr and the target steering angle θrp to the latest steering angle midpoint θn. As a result, the accuracy of the subsequent path tracking control is improved, and the tracking performance for the target path TP is improved.

  Note that after the steering angle midpoint θn is set at the start of the path following control, the steering angle midpoint θn may be further updated through learning or the like. The method of updating the steering angle midpoint θ n through learning is well known.

4. As described above, the path following control system 10 according to the present embodiment can set the steering angle midpoint θn at the start of the path following control. The setting of the steering angle midpoint θn is based on the following findings.

  That is, when traveling on a lane of the same shape (turning radius Rp), the driver of the vehicle 1 and the path following control system 10 are considered to steer the wheels by approximately the same amount. The turning amount by the driver is reflected on a driver steering angle θstr which is a sensor steering angle at the start of the path following control. On the other hand, the turning amount by the path following control system 10 is reflected in the target steering angle θrp according to the turning radius Rp. If the steering angle midpoint θn currently in use coincides with the accurate steering angle midpoint θn, it is considered that there is no difference between the driver's steering angle θstr and the target steering angle θrp. On the other hand, when the steering angle midpoint θn currently in use deviates from the accurate steering angle midpoint θn, the deviation amount appears as a difference between the driver steering angle θstr and the target steering angle θrp.

  Therefore, the path tracking control system 10 according to the present embodiment acquires the driver steering angle θstr and the target steering angle θrp at the start of the path tracking control, and based on the difference between the driver steering angle θstr and the target steering angle θrp. The steering angle midpoint θn is set (updated). As a result, the accuracy of the subsequent path tracking control is improved, and the tracking performance for the target path TP is improved.

  Further, according to the present embodiment, as long as the driver steering angle θstr and the target steering angle θrp can be acquired, the vehicle 1 may go straight or turn. Since information on the leading vehicle is also unnecessary, it is not necessary for the leading vehicle to be present. Thus, it can be said that the method of setting the steering angle midpoint θn according to the present embodiment has few restrictions. Accordingly, it becomes easy to set the steering angle midpoint θn, and as a result, it becomes easy to start the high-accuracy path tracking control.

5. Modified Example Next, a modified example of the method of setting the steering angle midpoint θn according to the present embodiment will be described. The modification is the same as the above except for step S60. In step S60 according to the modification, the steering angle midpoint setting unit 140 takes into consideration vehicle state quantities such as the yaw angle offset θyo, the yaw rate Yr, and the lateral acceleration Gy. The correction amount Δ corresponding to the yaw angle offset θyo, the yaw rate Yr, and the lateral acceleration Gy is expressed by the following equation (5).

Formula (5):
Δ = g (θyo, Yr, Gy)

  For example, a correction amount map defining the relationship between the vehicle state amount (θyo, Yr, Gy) and the correction amount Δ is created in advance and stored in the storage device of the control device 100. The steering angle midpoint setting unit 140 can calculate the correction amount Δ based on the correction amount map and the vehicle state amounts (θyo, Yr, Gy). Then, the steering angle midpoint setting unit 140 calculates and updates the steering angle midpoint θn according to the following equation (6).

Formula (6):
θ n θ θ str-θ rp-Δ
= Θstr-f (Rp)-g (θyo, Yr, Gy)

  Thus, the accuracy of the steering angle midpoint θn is further improved by considering the yaw angle offset θyo, the yaw rate Yr, and the correction amount Δ according to the lateral acceleration Gy.

Reference Signs List 1 vehicle 10 path tracking control system 20 GPS receiver 30 map database 40 sensor group 45 steering angle sensor 50 HMI unit 60 traveling device 65 steering device 100 control device 110 information acquisition unit 120 target path calculation unit 130 vehicle travel control unit 140 steering Corner midpoint setting unit TP target path

Claims (1)

A path following control system mounted on a vehicle,
A steering device for steering the wheels of the vehicle;
A steering angle sensor that acquires a steering angle of the wheel based on a steering angle middle point as a sensor steering angle;
A control device for performing path following control to automatically control traveling of the vehicle so that the vehicle follows a target path;
The controller is
A process of calculating the target path;
A process of calculating a target steering angle necessary for the vehicle to follow the target path according to a turning radius of the target path;
Controlling the steering device so that the sensor steering angle becomes the target steering angle;
The sensor steering angle at the start of the path following control is a driver steering angle,
At the start of the path follow-up control, the control device acquires the driver's steering angle and the target steering angle, and sets the steering angle midpoint based on the difference between the driver's steering angle and the target steering angle. Tracking control system.

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