JP4667893B2 - Automatic vehicle steering system - Google Patents

Description

  The present invention relates to an automatic steering apparatus for a vehicle.

Conventionally, data on the correlation between the movement trajectory and the target turning angle is previously stored for each predetermined movement state of the vehicle, and when the vehicle moves from the current position to an appropriate target position, for example, during parking, etc. Of the vehicle that automatically steers the steered wheels so that the steered wheel turning angle is equal to the target steered angle corresponding to the memorized or computed travel trajectory. An automatic steering device is known (see, for example, Patent Document 1).
JP 11-321687 A

By the way, in the vehicle automatic steering apparatus according to the above-described prior art, the steering wheel is only automatically steered based on the data of the correlation between the preset movement locus and the target turning angle. In some cases, it may be difficult to control the actual movement state with the same accuracy as the predetermined movement state. In other words, the steering torque required to realize the target turning angle corresponding to a predetermined movement state varies depending on, for example, the grounding load of each steered wheel, the speed of the vehicle, the friction characteristics between the tire and the road surface, and the like. For this reason, it is difficult to accurately realize a predetermined movement state only by turning the steered wheels according to the movement locus of the vehicle.
The present invention has been made in view of the above circumstances, and an object thereof is to provide an automatic steering device for a vehicle capable of appropriately executing control for automatically turning a steered wheel.

In order to solve the above-described problems and achieve the object, the vehicle automatic steering apparatus according to the first aspect of the present invention is a driving means for driving a steering mechanism capable of steering a steering wheel of the vehicle (for example, implementation) An automatic steering device for a vehicle comprising an EPS actuator 14) in the form and a control means (for example, an automatic steering control unit 24 in the embodiment) for automatically turning the steered wheels by the driving means. Steering angle detection means for detecting the direction and magnitude of the steering angle, which is the rotation angle of the steering wheel, and before the execution of automatic steering by the control means and in a state where the vehicle has stopped running, A stationary means (for example, the stationary control unit 21 in the embodiment) for turning by the stationary means of the driving means, and at least the vehicle state or the road surface state when the steering by the stationary means is executed. And detecting means for detecting (e.g., steering state quantity detecting section 22 in the embodiment, the friction state quantity detecting unit 23), said detection means during execution of the turning by the static steering unit, the steering A midpoint angle of a corner is detected, and the control means automatically steers the steered wheel based on the vehicle state or the road surface condition detected by the detection means after the steering by the stationary means. It is characterized by.

According to the above-described vehicle automatic steering device, at least the vehicle state (for example, the maximum steering angle in the right direction) at the time of executing the steering by the stationary stop that is executed before the automatic steering is performed and the vehicle is stopped. By detecting θR, leftward maximum steering angle θL, etc.) or road surface condition (for example, road surface friction coefficient μ, etc.), control for automatically turning the steered wheels based on these detection results is appropriately executed. be able to.

Furthermore, in the automatic steering device for a vehicle according to the second aspect of the present invention, when the steering is executed, the stationary means has a predetermined limit for turning the steering wheel in one of the left and right directions with a predetermined steering torque. After turning to an angle, the steering is turned to a predetermined limit angle with respect to turning in the other direction, and the detection means is configured to turn the predetermined steering torque and the steering angle when the steering in the other direction is executed by the stationary means. The road surface state is detected based on the angular velocity of the vehicle, and the midpoint angle of the steering angle is detected based on the limit angle for the one direction and the limit angle for the steering in the other direction .

According to the above-described automatic steering device for a vehicle, the midpoint angle of the steering angle is detected with high accuracy at the time of executing the steering by the stationary stop executed before the automatic steering is performed and the vehicle is stopped. be able to.

As described above, according to the automatic steering device for a vehicle of the present invention described in claim 1, at least the vehicle state (for example, the rightward maximum steering angle θR, the leftward maximum steering angle θL, etc.) or the road surface state (for example, Based on the detection result of the road surface friction coefficient μ and the like, it is possible to appropriately execute control for automatically turning the steered wheels.
Furthermore, according to the automatic steering device for a vehicle according to the second aspect of the present invention, it is possible to accurately detect the midpoint angle of the steering angle when executing the turning by the stationary stop .

  Hereinafter, an automatic steering device for a vehicle according to an embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, for example, an automatic steering device 10 for a vehicle according to the present embodiment includes a steering angle sensor 11, a speed sensor 12, an electronic control unit (ECU) 13, and an electric power steering (EPS) actuator 14. And an input operation unit 15 that is input by an operator.
The steering angle sensor 11 detects the direction and magnitude of the steering wheel angle (steering angle), which is the rotation angle of the steering wheel.
The speed sensor 12 detects the speed of the vehicle (vehicle speed).

The electronic control unit (ECU) 13 includes a stationary control unit 21, a turning state amount detection unit 22, a friction state amount detection unit 23, and an automatic steering control unit 24.
The stationary control unit 21 stationaryly steers the steered wheels in a state where automatic steering is stopped by an automatic steering control unit 24, which will be described later, and the vehicle is stopped based on a detection signal from the speed sensor 12. To output a steering torque command for turning left and right to drive the EPS actuator 14. Here, the stationary control unit 21 detects a change in time of the steering angle detected based on a detection signal of the steering state amount detected by the steering state amount detection unit 22, for example, a detection signal of the steering angle sensor 11. When a signal is input and the time change of the steering angle becomes less than or equal to a predetermined value when steering is performed by a stationary operation in a predetermined direction, it is determined that the maximum steering state in the predetermined direction has been reached, and The output of the steering torque command for turning by turning is stopped.

The steered state amount detection unit 22 is steered based on a detection signal of the steering angle sensor 11 in a state where the steered wheel is steered in one of the left and right steered directions by the stationary control under the control of the stationary control unit 21. A time change of the corner is detected, and it is determined whether or not the time change is a predetermined value or less. When it is determined that the time change of the steering angle is equal to or less than the predetermined value, the detected steering angle value θ detected at this time is set to the maximum steering angle, that is, the maximum steering angle θL with respect to the left and right turning directions, Store as θR. Based on the maximum steering angles θL and θR, a reference point (for example, a midpoint) of the steering angle is calculated and output to the automatic steering control unit 24.
The friction state quantity detection unit 23 controls the steering angle based on the detection signal of the steering angle sensor 11 in a state in which the steered wheel is steered in any of the left and right steering directions by the control of the stationary control unit 21. The friction coefficient (road surface friction coefficient) μ between the tire of the steered wheel and the road surface is calculated based on this angular speed and a predetermined steering state quantity such as the ground load of the steered wheel and the steering gear ratio, for example. Detect and output to the automatic steering control unit 24.
The automatic steering control unit 24 performs automatic steering based on the reference point of the steering angle detected by the steering state amount detection unit 22 and the road surface friction coefficient μ detected by the friction state amount detection unit 23. To do.

The vehicle automatic steering apparatus 10 according to the present embodiment has the above-described configuration. Next, the operation of the vehicle automatic steering apparatus 10 will be described.
For example, the following series of processing is executed when the operator operates the input operation unit 15 to instruct execution of automatic turning of the vehicle.

First, for example, in step S01 shown in FIG. 2, it is determined based on the detection signal of the speed sensor 12 whether or not the vehicle is in a travel stop state.
When the determination result is “NO”, the series of processes is terminated.
On the other hand, if this determination is “YES”, the flow proceeds to step S 02.
In step S02, first, the steered state of the steered wheels at this time is set as a reference state at the time of start. For example, as shown in FIG. ) Set θ to the starting reference point, ie zero. As a result, when the vehicle is steered rightward from this reference state, a negative value (−θ) is output from the steering angle sensor 11 as the steering angle detection value, and when the vehicle is steered leftward from this reference state. The steering angle sensor 11 outputs a positive value (θ) as the detected steering angle value. Then, the EPS actuator 14 is driven so that a predetermined steering torque is output, and the steered wheels are steered to the right by stationary.
FIG. 3 shows a state in which the starting reference point is shifted to the right from a predetermined midpoint.

In step S03, based on the detection signal of the steering angle sensor 11, it is determined whether or not the steering angle change amount (steering angle change amount) in a predetermined time width is, for example, equal to or less than a predetermined value near zero. .
If the determination result of step S03 is “NO”, the process returns to step S02 described above.
On the other hand, if the determination result in step S03 is “YES”, it is determined that a predetermined limit state for rightward turning (for example, right full turning shown in FIG. 3) has been reached, and the process proceeds to step S04.
In step S04, the detected value (steering angle detected value = −θ) of the steering angle sensor 11 at this time is set as the maximum steering angle θR in the right direction (θR = −θ), and the stationary in the right direction is performed. The elapsed time t from the start time to this time is set as the right direction time tR.

Next, in step S05, the EPS actuator 14 is driven so that a predetermined steering torque is output, and the steered wheels are steered to the left by stationary.
In step S06, based on the detection signal of the steering angle sensor 11, it is determined whether or not the amount of change in the steering angle (steering angle change amount) in a predetermined time width is equal to or less than a predetermined value near zero, for example. .
If the determination result of step S06 is “NO”, the process returns to step S05 described above.
On the other hand, if the determination result in step S06 is “YES”, it is determined that a predetermined limit state for leftward turning (for example, left full turning shown in FIG. 3) has been reached, and the process proceeds to step S07.
In step S07, the detected value (steering angle detected value = θ) of the steering angle sensor 11 at this time is set as the leftward maximum steering angle θL (θL = θ), and the left-side stationary is started. The elapsed time t from the time to this point is set as the left direction time tL.

In step S08, the change amount Δθ (= θL−θR) of the steering angle from the right full turning state to the left full turning state is greater than or equal to a predetermined upper limit value # θ (for example, 1000 °). It is determined whether or not there is.
When the determination result is “NO”, the process proceeds to step S09. In step S09, for example, the steering wheel is steered by an obstacle, or the tire pressure of the steering wheel is excessive. It is determined that there is an abnormal state, such as a state in which the EPS actuator 14 or the steering angle sensor 11 is abnormal, or the series of processing ends.
On the other hand, if the determination is “YES”, the flow proceeds to step S10.

In step S10, based on the amount of change Δθ (= θL−θR) of the steering angle and the time required until the amount of change Δθ of the steering angle is generated, that is, the time tL in the left direction, The angular velocity ω (= Δθ / tL) of the steering angle at is calculated.
In step S11, a road surface friction coefficient μ is calculated based on the angular velocity ω and a predetermined steering state quantity such as a grounding load and a steering gear ratio of the steered wheel, and an automatic operation is performed based on the road surface friction coefficient μ. The initial value of the control gain that is required when steering is executed is set.
In step S12, a steering angle correction value θC (= θL− (Δθ / 2)), which is an angle difference between the starting reference point and a predetermined midpoint, is calculated.
And in step S13, based on steering angle correction value (theta) C, a stationary run is performed from the state of left full turning to a middle point.
That is, when the steering angle correction value θC (= θL− (Δθ / 2)) is positive (θC ≧ 0 °), for example, as shown in FIG. 3, the starting reference point is on the right side of the predetermined middle point. In this case, the positive value (θ) as the steering angle detection value output from the steering angle sensor 11 is the steering angle correction value θC (= θL− (Δθ / 2)). Make a right turn until it becomes equal to.
On the other hand, when the steering angle correction value θC (= θL− (Δθ / 2)) is negative (θC <0 °), the starting reference point is shifted leftward from a predetermined midpoint. In this case, the negative value (−θ) as the steering angle detection value output from the steering angle sensor 11 is in the right direction until it becomes equal to the steering angle correction value θC (= θL− (Δθ / 2)). Make a deferral.
Then, this midpoint is newly set as a reference point for the detected value (steering angle detected value) θ of the steering angle sensor 11, and when the vehicle is steered rightward from this midpoint, a negative steering angle detected value is set. A value (−θ) is output from the steering angle sensor 11, and a positive value (θ) is output from the steering angle sensor 11 as a steering angle detection value when the vehicle is steered leftward from this midpoint. Set.
In step S14, automatic steering control is executed according to the detected steering angle value output from the steering angle sensor 11 and the initial value of the control gain calculated based on the detected road surface friction coefficient μ. Then, a series of processing is completed.

For example, as shown in FIG. 4 (a), when the automatic steering control is executed at the time of executing the garage entry operation, first, in the state a in which the vehicle is laid on the garage with the left side of the vehicle facing the entrance position of the garage. It is instructed whether or not to start automatic steering by an input operation of the operator. As a result, the processing from step S01 to step S13 described above is executed, and the steering wheel is suspended to a predetermined midpoint based on the steering angle correction value θC, and this midpoint is newly set in the steering angle sensor 11. It is set as a reference point for the detected value (steering angle detected value) θ and the control command value related to the steering angle (that is, the midpoint at which each value becomes zero), and further, the initial value of the control gain for the automatic steering control in step S14 Is calculated based on the road surface friction coefficient μ detected when the stationary operation is performed.
In the automatic steering control in step S14 described above, the automatic steering control unit 24 makes the steered state of the steered wheels equal to the target steered state (for example, the steered wheel steered angle in FIG. Control is performed so as to be equivalent to the reference turning angle θref shown in b) and so that the initial value of the control gain is equivalent to the initial value of the control gain calculated based on the road surface friction coefficient μ. For example, when the vehicle is moved forward by a predetermined forward movement distance Xb from the state a placed in the garage, the reference turning angle θref, which is a control command value related to the steering angle, gradually increases to a predetermined value in the right direction. Then, after the reference turning angle θref has reached a predetermined value and moved forward by a predetermined distance, the reference turning angle θref is gradually reduced to the middle point, that is, zero. Then, when the vehicle travels backward by a predetermined reverse movement distance Xc from the state b in which the forward movement is stopped by the movement distance reaching the forward movement distance Xb, the reference turning angle θref gradually increases to a predetermined value in the left direction. Then, after the reference turning angle θref has reached a predetermined value and moved backward by a predetermined distance, the reference turning angle θref is gradually reduced to the middle point, that is, zero. Then, in the state c in which the reverse movement is stopped when the movement distance reaches the reverse movement distance Xc, the garage entry operation ends.

  As described above, according to the vehicle automatic steering device 10 according to the present embodiment, the midpoint and the road surface friction coefficient μ, which are the reference points of the steering angle, can be detected with high accuracy when steering is performed by stationary driving. Thus, based on the detected steering angle reference point and the road surface friction coefficient μ, it is possible to appropriately execute control for automatically turning the steered wheels.

  In the above-described embodiment, the steering wheel is stationary to a predetermined midpoint based on the steering angle correction value θC before executing the control for automatically turning the steered wheel. Is newly set as a reference point for the detection value (steering angle detection value) θ of the steering angle sensor 11, but is not limited to this, for example, a reference for the detection value (steering angle detection value) θ of the steering angle sensor 11. When the automatic steering control is executed without setting a new point and holding the starting reference point, the detection value (steering angle detection value) θ of the steering angle sensor 11 and an appropriate control command value related to the steering angle are always obtained. May be corrected by the steering angle correction value θC.

1 is a functional block diagram showing a configuration of a vehicle automatic steering apparatus according to an embodiment of the present invention. It is a flowchart which shows operation | movement of the automatic steering device of the vehicle shown in FIG. It is a figure which shows an example in the state which the reference point at the time of start with respect to a steering angle has shifted | deviated to the right side rather than the predetermined | prescribed middle point. FIG. 4A is a diagram showing each movement state when the vehicle is moved into a predetermined parking section by automatic steering control, and FIG. 4B is related to a steering angle set when automatic steering control is executed. It is a graph which shows an example of the relationship between the standard turning angle (theta) ref which is a control command value, and the movement distance X. FIG.

Explanation of symbols

10. Vehicle automatic steering device 14. EPS actuator (drive means)
21 Stationary control unit (stationary means)
22 Steering state quantity detection part (detection means)
23 Friction state quantity detection unit (detection means)
24 Automatic steering control unit (control means)

Claims (2)

An automatic steering apparatus for a vehicle, comprising: a driving unit that drives a steering mechanism that can steer a steering wheel of the vehicle; and a control unit that automatically steers the steering wheel by the driving unit,
Steering angle detection means for detecting the direction and magnitude of the steering angle, which is the rotation angle of the steering wheel;
In automatic before execution of the steering and the state of the travel stop of the vehicle by the control means, and means outright laid to steer the steering wheel by the stationary steering of said drive unit,
Detecting means for detecting at least a vehicle state or a road surface state at the time of execution of steering by the stationary means,
The detecting means detects a midpoint angle of the steering angle at the time of execution of turning by the stationary means,
The control means automatically steers the steered wheel based on a vehicle state or a road surface state detected by the detection means after the steering by the stationary means is performed. . The steering means steers the steered wheel to a predetermined limit angle for steering in one of the left and right directions with a predetermined steering torque, and then to a predetermined limit angle for steering in the other direction when steering is performed. Steer,
The detecting means detects the road surface state based on the predetermined steering torque and an angular velocity of the steering angle when the stationary means performs the steering in the other direction, and detects the limit angle with respect to the one direction and the other The automatic steering apparatus for a vehicle according to claim 1, wherein a midpoint angle of the steering angle is detected based on a limit angle with respect to turning of the direction .

Images