JP7032967B2 - Vehicle steering support device - Google Patents

Description

The present invention relates to a vehicle steering support device that performs steering support control via a steering device on the premise that the driver holds the steering wheel.

Vehicles such as automobiles are equipped with a steering device such as an electric power steering device that can control the steering angle via an electric motor, and are provided via the steering device based on the external environment around the vehicle recognized by a camera, a radar device, or the like. Steering support control that supports the steering operation of the driver is known.

Such steering assist control is often executed on the premise that the driver holds the steering wheel, and when the driver releases the steering wheel, it is determined that the steering wheel has been released and a warning is given. It has become.

Therefore, it is necessary to accurately determine the state of letting go of the steering wheel. For example, in Patent Document 1, it is difficult to determine the state of letting go of the steering wheel when the straight path is detected, as compared with the case where the straight path is not detected. A technique for determining a determination threshold is disclosed.

Japanese Patent No. 580971

However, in the conventional steering wheel release determination as disclosed in Patent Document 1, sufficient determination accuracy may not be obtained depending on the shape of the curve of the traveling path, and the determination may be due to disturbances such as crosswinds and cross slopes of roads. On the other hand, it is difficult to secure the determination accuracy.

The present invention has been made in view of the above circumstances, and when the steering support control is executed on the premise that the driver holds the steering wheel, the influence of the shape of the traveling path and the disturbance is eliminated to ensure the accuracy of the steering wheel release determination. The purpose is to provide a steering support device for vehicles that can be used.

The vehicle steering support device according to one aspect of the present invention is a vehicle steering support device that performs steering support control via the steering device on the premise that the driver holds the steering wheel, and is used in the steering support control via the steering device. Based on the target output change rate calculation unit that calculates the change rate of the target output and the target output or the change rate of the target output, a threshold value for determining the handle release state in which the driver does not hold the handle is set. The steering wheel is provided with a hand-release determination threshold correction unit that corrects the steering wheel in a direction in which it is easy to determine that the steering wheel is in the state of being released.

According to the present invention, when the steering support control is executed on the premise that the driver holds the steering wheel, it is possible to eliminate the influence of the shape of the traveling path and the disturbance and ensure the accuracy of the steering wheel release determination.

Configuration diagram of vehicle steering system Block diagram showing the function of the steering control system Flowchart of handle release judgment process

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 indicates an electric power steering (EPS) device as a steering device capable of controlling a steering angle via an actuator independently of a steering operation by a driver. In this EPS device 1, the steering shaft 2 is rotatably supported by a vehicle body frame of a vehicle such as an automobile (not shown) via a steering column 3.

One end of the steering shaft 2 extends to the driver's seat side, and the other end extends to the engine room side. A steering wheel (steering wheel) 4 is fixedly attached to the driver's seat side end of the steering shaft 2, and a steering angle sensor 21 is arranged on the outer peripheral side of the steering shaft 2 to which the steering wheel 4 is connected.

The rudder angle sensor 21 is configured to include, for example, two sets of magnetoresistive elements that detect the rotation of a magnet built in a detection gear inside the steering angle sensor 21. The steering angle sensor 21 sets a reference rotation position of the handle 4 (for example, the rotation position of the upper part of the handle 4 in a straight-ahead state of the vehicle) in advance, and based on the magnetic change generated by the rotation of the detection gear, the steering angle sensor 21 is used. The rotation angle (steering angle) and rotation direction (steering direction) from a preset fixed reference position are detected.

Further, a torsion bar 2a is interposed in the middle of the steering shaft 2, and a pinion shaft 5 is continuously provided at an end extending toward the engine room side. A torque sensor 22 is arranged on the outer peripheral side of the torsion bar 2a. The torque sensor 22 detects the steering torque operated by the driver by detecting the displacement between the steering wheel 4 side and the pinion shaft 5 side generated around the axis of the steering shaft 2 due to the twist of the torsion bar 2a.

On the other hand, in the engine room, a steering gear box 6 extending in the vehicle width direction is arranged, and the rack shaft 7 is inserted and supported in the steering gear box 6 so as to be reciprocating. A rack (not shown) formed on the rack shaft 7 is meshed with a pinion formed on the pinion shaft 5, and a rack and pinion type steering mechanism is formed.

Further, the left and right ends of the rack shaft 7 are respectively projected from the end portions of the steering gear box 6, and front knuckles 9 are continuously provided at the end portions via the tie rods 8. The front knuckle 9 rotatably supports the left and right wheels 10L and 10R as steering wheels, and is rotatably supported by the vehicle body frame. When the steering wheel 4 is operated to rotate the steering shaft 2 and the pinion shaft 5, the rack shaft 7 moves in the left-right direction due to the rotation of the pinion shaft 5, and the front knuckle 9 moves the kingpin shaft (not shown) by the movement. Rotating to the center, the left and right wheels 10L and 10R are steered in the left-right direction.

Further, an electric power steering motor (EPS motor) 12 as an actuator that enables assist and automatic steering for the driver's steering operation is connected to the pinion shaft 5 via an assist transmission mechanism 11 including a reduction gear mechanism such as a worm gear. It is set up. The EPS motor 12 is, for example, an electric motor including a DC brushless motor having a stator fixed to a case and a rotor that rotates inside the stator, and the rotation of the rotor of the electric motor is a rack shaft via an assist transmission mechanism 11. It is converted into the axial movement of 7.

The EPS motor 12 is driven and controlled by the steering control device 50. The steering control device 50 is a control unit configured around a microcomputer, and drives and controls the EPS motor 12 via the motor drive unit 20. The steering control device 50 includes a steering angle sensor 21, a torque sensor 22, other sensors such as a vehicle speed sensor 24 for detecting vehicle speed, a rotation speed around the vertical axis of the vehicle, that is, a yaw rate sensor 25 for detecting yaw rate, and switches (not shown). A signal from the class is input.

Further, the steering control device 50 is connected to the communication bus 200 forming the in-vehicle network. The communication bus 200 includes an external environment recognition device 150 that recognizes the external environment of the vehicle and acquires driving environment information, and other controls such as an engine control device, a transmission control device, and a brake control device (not shown). The devices are connected, and each control device can exchange control information with each other via the communication bus 200.

The external environment recognition device 150 includes detection information of objects around the own vehicle by various devices such as a front recognition camera, a millimeter wave radar, a side camera for side recognition, and a side radar, road-to-vehicle communication, vehicle-to-vehicle communication, and the like. Traffic information acquired by infrastructure communication, positioning information of own vehicle position based on signals from GPS satellites, road shape data such as road curvature, lane width, road shoulder width, road azimuth angle, lane division line type, etc. The external environment around the own vehicle is recognized by high-definition map information including driving control data such as the number of lanes.

In the present embodiment, the external environment recognition device 150 mainly recognizes the front environment of the own vehicle by the in-vehicle camera and the image recognition device, and the front recognition camera captures the same object from different viewpoints. A stereo camera consisting of two cameras is used. The two cameras constituting this stereo camera are shutter-synchronized cameras having image pickup elements such as CCD and CMOS. For example, they are arranged in the vicinity of the rear-view mirror inside the front window in the upper part of the vehicle interior with a predetermined baseline length. There is.

The processing of the image data from the stereo camera is performed as follows, for example. First, a distance image having distance information is generated from a set of stereo image pairs in the traveling direction of the own vehicle captured by the stereo camera from the amount of deviation of the corresponding positions, and the distance information of this distance image is used to generate a white line. It recognizes lane markings such as, and recognizes three-dimensional objects such as preceding vehicles and oncoming vehicles.

In recognition of lane markings such as white lines, based on the feature that the lane markings are brighter than the road surface, the change in brightness in the width direction of the road is evaluated, and the left and right lane markings on the image plane are evaluated. Specify the position on the image plane. The position (x, y, z) of this lane marking line in real space is based on the position (i, j) on the image plane and the parallax calculated for this position, that is, based on the distance information. It is calculated from a well-known coordinate conversion formula.

The recognition result of the external environment by the external environment recognition device 150 is transmitted to the steering control device 50 and other control devices. The steering control device 50 executes steering support control that supports automatic driving of the own vehicle and steering operation of the driver. The steering support control includes lane keeping control that keeps the own vehicle in the center position of the lane, following vehicle following control that follows the preceding vehicle, and lane departure prevention control that prevents the own vehicle from deviating from the lane. be.

The target route may be set by another control device such as the external environment recognition device 150 instead of the steering control device 50.

Such steering support control is executed on the premise that the driver holds the steering wheel 4 and applies a predetermined steering holding force (steering wheel holding state). If the driver releases the steering wheel 4 while the steering support control is being executed and the steering holding force becomes small, it is determined that the steering wheel is released and the steering assist control is released.

The magnitude of the steering holding force is determined by comparing the torque value (torque sensor value) detected by the torque sensor 22 with the threshold value. When the torque sensor value of the torque sensor 22 is equal to or greater than the threshold value, it is determined to be in the "handle holding state", and when the torque sensor value is less than the threshold value for a certain period of time or longer, it is determined to be in the "handle release state".

In this case, since the steering support control is executed under various driving environments, the target output described later may suddenly change or be larger than a predetermined value due to the curvature of the road or disturbance (crosswind, cross slope of the road, etc.). May be output. In such a case, the torsion bar 2a is twisted by an external force transmitted from the road surface side, and even if the driver does not grip the handle 4, the torque sensor value fluctuates and exceeds the threshold value, and the handle is released. May not be determined correctly.

Therefore, as shown in FIG. 2, the steering control device 50 correctly determines the steering wheel release state by eliminating the influence of the external force from the road surface side on the steering support control unit 51 that executes the steering support control. As functional units of the above, a target output change rate calculation unit 52, a release determination threshold value correction unit 53, and a handle release determination unit 54 are provided.

The steering support control unit 51 performs lane keeping control, preceding vehicle follow-up control, based on information from the external environment recognition device 150 and detection information from each sensor (rudder angle sensor 21, vehicle speed sensor 24, yaw rate sensor 25). Executes steering support control such as lane deviation prevention control. This steering support control is executed when the driver grips the steering wheel 4 and the torque sensor value of the torque sensor 22 is determined to be a "handle state" equal to or higher than the threshold value, and the torque sensor value is less than the threshold value "handle release state". If it is determined, it will be canceled.

In the steering support control by the steering support control unit 51, the lane keeping control and the preceding vehicle tracking control are basically the same control, and the target route is taken from the locus of the target point to be followed based on the recognition result of the external environment. Is set, and it is executed as a control to follow this target path. For example, in lane keeping control, the target point to be followed is set at the center position of the left and right white lines as lane marking lines in the road width direction, and in preceding vehicle follow-up control, it is set at the center position in the vehicle width direction of the preceding vehicle. Then, the locus of such a target point is calculated and used as a target route.

The steering support control unit 51 calculates a target steering angle for following the target path, and outputs an instruction torque corresponding to the target steering angle to the EPS device 1. The EPS device 1 controls the drive current of the EPS motor 12 via the motor drive unit 20 so that a steering torque corresponding to the indicated torque can be obtained. As a result, the actual steering angle of the own vehicle is controlled to converge to the target steering angle, and steering support control for following the target path is realized.

Further, in the lane departure prevention control, the steering support control unit 51 estimates and estimates the time until the own vehicle crosses the lane in the deviation direction with respect to the lane in which the traveling direction of the own vehicle is facing the deviation direction. If the set time is less than or equal to the set value, the lane departure prevention control is executed. Specifically, the steering support control unit 51 calculates a target yaw rate, which is a target turning amount for preventing deviation from the lane, and outputs a target steering torque corresponding to this target yaw rate as an instruction torque for the EPS device 1. do.

The EPS device 1 controls the drive current of the EPS motor 12 so that the steering torque becomes the target steering torque, and controls so that the yaw rate of the own vehicle becomes the target yaw rate. As a result, turning behavior corresponding to the target yaw rate is generated in the own vehicle, and lane departure prevention control for preventing deviation from the lane is realized.

The target output change rate calculation unit 52 reads the target output TGT of the steering support control by the steering support control unit 51, calculates the change rate (target output change rate) ΔTGT of the target output TGT per predetermined time, and releases the target output threshold value. Send to the correction unit 53. As the target output TGT for steering support control, at least one of the above-mentioned target steering angle, target yaw rate, and instruction torque to the EPS device 1 is used.

The release determination threshold value correction unit 53 determines the steering wheel release state during steering support control based on the target output TGT of the steering support control unit 51 or the target output change rate ΔTGT calculated by the target output change rate calculation unit 52. The threshold Dth of is corrected. Specifically, the threshold Dth for determining the steering wheel release in normal driving is set in advance as a fixed value, and the target output TGT and the output threshold TGTth are compared, and the target output change rate ΔTGT and the change rate threshold ΔTGTth are compared. Correct the normal threshold Dth.

In this case, the output threshold TGTth is set as a torque having a predetermined magnification with respect to the reference value, for example, when the target output TGT is the indicated torque to the EPS device 1, the indicated torque when traveling on a normal straight road is used as a reference. Torque. The magnification with respect to the reference torque is a factor of the magnitude of the external force from the road surface side that causes the torsion bar 2a in which the torque sensor 22 is arranged to be twisted, for example, the magnitude of the curvature of the traveling road, the crosswind and the road. It is set according to the vehicle weight, tire size, and characteristics of the steering mechanism in consideration of the required steering holding force for the magnitude of disturbance such as a cross slope.

Further, the rate of change threshold ΔTGTth is predetermined with respect to the reference value, for example, when the target output TGT is set as the target steering angle for following the target path, the change speed of the steering angle when traveling on a normal straight road is used as a reference. It is set as the rate of change of magnification. The magnification with respect to the reference change speed is the change speed of the external force from the road surface side that causes the torsion bar 2a in which the torque sensor 22 is arranged to be twisted, for example, the change in the curvature of the traveling road, the crosswind, the cross slope of the road, and the like. It is set according to the vehicle weight, tire size, and steering mechanism characteristics in consideration of the required steering holding force for the changing speed of disturbance.

When the target output TGT is less than the output threshold TGTth and the target output change rate ΔTGT is less than the change rate threshold ΔTGTth, the threshold Dth of a normal value is sent to the handle release determination unit 54. On the other hand, when the target output TGT is larger than the output threshold TGTth, or when the target output change rate ΔTGT is larger than the change rate threshold ΔTGTth, the threshold Dth is made larger than the normal value and it is easy to determine that the “handle is released”. Correct in the direction of.

The correction for the threshold value Dth may be a correction in which a preset constant value is made larger than a normal value, or may be a correction according to the curvature of the traveling path, the cross slope, and the estimated crosswind strength. For example, the larger the curvature of the travel path obtained from the external environment recognition device 150 or the map information, the larger the threshold Dth for the handle release determination than the normal value, and the larger the crossing gradient, the normal value the threshold Dth. Make it larger than. Further, the strength of the crosswind is estimated from, for example, the magnitude of the local change in the target output, and the stronger the crosswind, the larger the threshold Dth than the normal value.

The handle release determination unit 54 compares the torque sensor value Tsen from the torque sensor 22 with the threshold value Tth from the release determination threshold value correction unit 53, and the gripping state of the handle 4 by the driver is either the “handle holding state” or the “handle release state”. ". When the torque sensor value Tsen is equal to or greater than the threshold value Tth, it is determined to be in the "handle holding state", and when the torque sensor value Tsen is less than the threshold value Tth for a certain period of time or longer, it is determined to be in the "handle release state".

The determination result of the steering wheel release determination unit 54 is sent to the steering support control unit 51. When it is determined that the steering wheel has been released, the steering support control unit 51 cancels the steering support control and warns the driver with a display, an alarm sound, or the like to ensure that the steering wheel 4 is held.

Next, the steering wheel release determination process in the steering control device 50 will be described with reference to the flowchart of FIG.

In the first step S1, the steering control device 50 acquires the target output TGT in the steering support control. Next, the process proceeds to step S2, and the rate of change per control cycle (processing cycle) of the target output TGT is calculated as the target output change rate ΔTGT.

After that, the process proceeds to step S3, and the target output TGT and the output threshold value TGTth are compared to check whether or not the target output TGT has become larger than the threshold value. When the target output TGT becomes equal to or higher than the output threshold value TGTth, the process proceeds from step S3 to step S5, the threshold value Dth of the steering wheel release determination is made larger than the normal value, and the process proceeds to step S6.

On the other hand, if the target output TGT is less than the output threshold TGTth in step S3, the process proceeds from step S3 to step S4, and the target output change rate ΔTGT and the change rate threshold ΔTGTth are compared. As a result, when the target output change rate ΔTGT becomes the change rate threshold value ΔTGTth or more, the process proceeds from step S4 to step S6 through the above-mentioned step S5, and when the target output change rate ΔTGT is less than the change rate threshold value ΔTGTth, the handle. The process proceeds to step S6 with the threshold Dth of the release determination as a normal value.

In step S6, the torque (torque sensor value) Tsen detected by the torque sensor 22 is compared with the threshold value Tth, and the handle release determination is performed. When the torque sensor value Tsen is equal to or higher than the threshold value Tth, it is determined as "steering wheel holding state" and the execution of steering support control is permitted. It determines that the steering wheel has been released, and warns the driver to hold the steering wheel securely.

As described above, in the present embodiment, when it is determined that the disturbance such as the curvature of the traveling path, the crosswind, and the cross slope of the road is large, the threshold value Tth of the steering wheel release determination is made larger than the normal value. Even if the torsion bar 2a is twisted due to an external force from the road surface side, it is possible to prevent erroneous determination and accurately determine the handle release state.

1 Electric power steering (EPS) device 2a Torsion bar 4 Handle 12 EPS motor 15 Steering support control device 20 Motor drive unit 21 Steering angle sensor 22 Torque sensor 24 Vehicle speed sensor 25 Yaw rate sensor 50 Steering control device 51 Steering support control unit 52 Target output Change rate calculation unit 53 Release judgment threshold correction unit 54 Handle release judgment unit 150 External environment recognition device

Claims (4)

It is a steering support device for a vehicle that performs steering support control via a steering device on the premise that the driver holds the steering wheel.
A target output change rate calculation unit that calculates a change rate of the target output in the steering support control via the steering device, and a target output change rate calculation unit.
Based on the target output or the rate of change of the target output, the threshold for determining the handle release state in which the driver does not hold the handle is corrected in a direction that makes it easier to determine the handle release state. A vehicle steering support device characterized by having a correction section. In the release determination threshold value correction unit, when the target output is larger than the threshold value set in consideration of the magnitude of the external force transmitted from the road surface side to the steering device, or the rate of change of the target output is from the road surface side. When it is larger than the threshold value set in consideration of the change speed of the external force transmitted to the steering device, the threshold value for determining the handle release state is set to be larger than the value during normal driving. The vehicle steering support device according to claim 1. The vehicle steering support device according to claim 1 or 2, wherein the target output is a target steering angle for following a target path on which the own vehicle travels. The vehicle steering support device according to claim 1 or 2, wherein the target output is an instruction torque with respect to the steering torque of the steering device.

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