JP4069530B2 - Vehicle control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle control apparatus that performs automatic steering.
[0002]
[Prior art]
In recent vehicles, there has been proposed a vehicle that performs automatic steering along a traveling lane for driver assistance. Japanese Patent Application Laid-Open No. 9-142327 proposes an apparatus that performs automatic steering and performs a brake operation or a reduction in engine output in order to reduce the turning level when turning close to the vehicle performance limit.
[0003]
[Problems to be solved by the invention]
By the way, in the case of performing automatic steering, it is a precondition that the direction of the vehicle is changed, that is, the vehicle is turned as it is automatically steered (a control target value for automatic steering is realized). On the other hand, auto-steering is steered regardless of the driver's intention to steer. Therefore, in the case of auto-steering, safety is ensured more sufficiently than when the driver is manually steering. It is desirable. That is, as described in the above publication, it is not preferable in terms of safety to perform automatic steering near the motion performance limit level of the vehicle, particularly in automatic steering that intervenes to prevent the vehicle from entering an inappropriate state by manual steering. It will be a thing.
[0004]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a vehicle control apparatus that can perform automatic steering, in particular, automatic steering during turning more safely. .
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the following solution is adopted in the present invention. That is, as described in claim 1 in the claims,
In a vehicle control apparatus that performs automatic steering control with a steering control target value determined to travel along a traveling lane,
Driving force adjusting means for adjusting the driving force of the vehicle;
A target lateral force determining means for determining, as a target lateral force, a lateral force required to ensure the turning by the control of the automatic steering based on the driving state of the vehicle relating to the turning;
An actual lateral force determining means for determining a lateral force that can be actually secured based on the running state of the vehicle;
The driving force of the vehicle is controlled by controlling the driving force adjusting means so that the actual lateral force determined by the actual lateral force determining means is larger than a value obtained by adding a marginal lateral force to the target lateral force. Driving force control means for reducing the control,
It is supposed to be equipped with. A preferred mode based on the above solution is as described in claim 2 and the following claims.
[0006]
【The invention's effect】
According to claim 1, it is ensured that the actual lateral force is larger than the target lateral force required for turning based on automatic steering by a predetermined marginal lateral force, and the vehicle is turned with a margin by this marginal lateral force. This is extremely preferable for safety.
[0007]
According to the second aspect, the marginal lateral force is set to a more optimal value by correction, which is preferable in satisfying both safety ensuring and driving performance ensuring at a high level.
According to the third aspect, it becomes a throw-in / fast-out that is preferable in cornering, and while exiting the corner safely, exits the corner promptly and satisfies the acceleration performance near the end of the turn. be able to.
According to the fourth aspect of the present invention, the marginal lateral force (the basic value) is increased as the deviation amount from the travel lane where the degree of automatic steering becomes stronger is increased, which is extremely preferable for safety.
[0008]
According to claim 5, it is possible to satisfy both a quick turn and a safe turn at a high level in accordance with the visibility.
According to the sixth aspect, it is preferable to safely perform turning by automatic steering at night when visibility is poor.
According to the seventh aspect, it is preferable to safely perform turning by automatic steering in rainy weather where visibility is poor.
According to the eighth aspect, the marginal lateral force is corrected in accordance with the size of the lane width that indicates the margin of the lane departure, thereby satisfying both a quick turn and a safe turn at a high level. be able to.
According to claim 9, it is possible to satisfy the driver's aggressive acceleration request.
[0009]
According to the tenth aspect, it is possible to satisfy the driver's willingness to ensure safety.
According to the eleventh aspect, it is possible to satisfy both a quick turn and a safe turn at a high level in response to a change in the turning radius.
According to the twelfth aspect, while ensuring sufficient safety at the beginning of the turn when the behavior change in the unstable direction of the vehicle becomes large, a quick turn in the middle of the turn and sufficient acceleration from the latter part of the turn Can be satisfied at a high level.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In FIG. 1, reference numeral 1 denotes a vehicle (automobile), which is an FF vehicle in the embodiment. The traveling lane is indicated by reference numeral 2, the left boundary line (white line) thereof is indicated by reference numeral 2L, and the right boundary line is indicated by reference numeral 2R. Although not displayed in the actual travel lane 2, the center line of the travel lane 2 is indicated by a one-dot chain line and denoted by reference numeral 2C. The vehicle 1 is automatically steered with the center line 2C as a target locus. In FIG. 1, the vehicle 1 is slightly deflected to the right with respect to the center line 2C, and the front of the vehicle body is slightly inclined to the right. Is shown. In the state of FIG. 1, during automatic steering, a steering force is applied so that the left and right front wheels 3 as steering wheels are directed to the left, and a steering reaction force corresponding to left steering is applied to the steering handle 4 as a steering unit. (The direction of the reaction force applied to the handle 4 is the right direction opposite to the left direction in which the steered wheels 3 are steered).
[0011]
A steering system and a control system of the vehicle 1 are shown in FIG. In FIG. 2, left and right front wheels 3 as steering wheels are mechanically connected to each other via a pair of left and right knuckle arms 11, a pair of left and right tie rods 12, and a drive mechanism (reduction gear mechanism) 13 that connects the left and right tie rods 12. Are linked together. Each of the constituent elements 11, 12, and 13 constitutes a steering mechanism as a steering section, and the drive mechanism 13 is provided with a motor (actuator) 14 as a steering force applying means. The handle 4 is configured separately and independently from the steering mechanisms 11 to 13, and a motor 15 is provided as a steering reaction force applying means for a steering shaft 4 a attached to the handle 4.
[0012]
During automatic steering, as will be described in detail later, a steering torque (steering force) is applied to the left and right front wheels 3 by the motor 14, while a steering reaction force is applied to the handle 4 by the motor 15. Note that, during normal manual steering that is not automatic steering, that is, during steering that the driver manually operates the handle 4, the motor 14 is driven in accordance with the steering amount or steering torque of the handle 4 to operate the handle 4. The front wheel 3 is steered and a steering reaction force corresponding to the steering amount or the steering torque is given by the motor 15.
[0013]
Each of the motors 14 and 15 is controlled by a controller U configured using a microcomputer. As shown in FIG. 3, the controller U receives signals from various sensors, switches, and the like, and detects (or calculates) the following various states. Various states to be detected (or calculated) are as follows. First, the position of the center line 2C of the travel lane 2 as the target locus is detected as yc using a camera mounted on the vehicle 1, for example. Further, the current lateral deviation between the center line 2C in the front-rear direction and the center line 2C of the vehicle 1 is detected as yo using the camera, for example. The current vehicle speed is detected as v by the vehicle speed sensor. The yaw angle of the vehicle 1 is detected as yw using the camera, for example. The steering amount (actual steering amount of the front wheels 3) is detected as θ by the steering angle sensor. The curvature of the traveling lane 2 uses the above-mentioned camera or navigation system, a beacon that receives a signal from a road information transmitting device attached along the road surface, and a magnetic nail that indicates road information embedded in the road surface. Detected. A signal indicating the current gear position of the automatic transmission EAT) 22 of the vehicle, a signal indicating the operating state of the brake switch, a signal indicating the operating state of the headlight switch, and a signal indicating the lane width (using the above camera) are input. The It should be noted that conventionally known appropriate methods can be adopted as the above-described various state detection methods.
[0014]
Since the automatic steering is performed so as to travel along the center line 2C as the target locus, the future lateral deviation amount y1 after T seconds is determined. This future lateral deviation amount y1 is calculated from the center line position yc after T seconds, where T is the vehicle head time, which is the time predicted for the vehicle 1 to reach the forward gaze point P (see FIG. 1). Based on the current lateral deviation amount yo, the vehicle head time T, the vehicle speed v, and the yaw angle yw, the following equation 1 is used.
[0015]
y1 = yc− (yo + T × v × yw) (1)
[0016]
During automatic steering, the steering torque T2 as the first control target value for determining the steering force and the steering torque T1 as the second control target value for determining the steering reaction force are respectively based on the future lateral deviation amount y1, It is determined as shown in FIG. The steering torque T2 is always larger than the steering torque T1, but the deviation is set so as to increase as the steering torque T2 increases. Each torque T1, T2 is set so as to increase as the future lateral deviation amount y1 increases, but an upper limit value is also set.
[0017]
In FIG. 4, the future lateral deviation amount y1 is mapped as a parameter, and torques T1 and T2 are created and stored in advance. However, based on y1 using a control constant (control gain), FIG. Torques T1 and T2 can also be calculated. That is, for example, it can be calculated as T1 = k1 × y1 and T2 = k2 × y1 (k1 and k2 are control constants, and k1 <k2). The output of the steering torque T2 to the motor 14 is preferably delayed by a predetermined amount t with respect to the output of the steering reaction force T1 to the motor 15, and the degree of delay (delay time) t is determined according to the running state. It can also be changed.
[0018]
The controller U controls the driving force so that the direction of the vehicle is changed according to the automatic steering and the automatic steering is performed safely in addition to controlling the automatic steering so as to travel along the traveling lane. (Control of torque applied to the drive wheels) is performed, and for this reason, the throttle actuator 21 that opens and closes the throttle valve of the engine is also controlled. In order to prevent the vehicle from entering the curve at an overspeed, the shift control of the automatic transmission is also performed.
[0019]
The basic control contents of the controller U are as follows. That is, the target lateral force Ff required for realizing the automatic steering, the lateral force Ft that can be actually secured, and the marginal lateral force α are determined (estimated), and the relationship of Ft> Ff + α is satisfied. The throttle actuator 21 is controlled (when Ft ≦ Ff + α is established, control for recommending the throttle opening is performed). The lateral force indicates the lateral grip force of the tire, but any value related to the lateral grip force can be appropriately used as the lateral force. The marginal lateral force α is appropriately corrected so that both safe turning by automatic steering and quick turning are satisfied at a high level.
[0020]
As shown in FIG. 3, the above-described target lateral force Ft is determined based on the target locus (target turning locus) and the vehicle speed. The side slip angle of the vehicle is estimated based on the vehicle speed and the rudder angle, and the actual driving force is calculated from the engine speed, the throttle opening, and the current gear position, and from this side slip angle and the actual driving force, The actual lateral force (maximum lateral force that can be secured) Ft is calculated (using a friction circle indicating the relationship between the longitudinal grip force and the lateral grip force of the tire).
[0021]
The marginal lateral force α described above is basically determined based on the above-described future deviation amount y1, and α is set to be larger as y1 is larger. Then, the basic marginal lateral force α determined based on y1 is corrected in accordance with the presence / absence of brake operation, the presence / absence of lighting of the headlight, the size of the lane width, the change in curvature of the target locus, and the like.
[0022]
As control before the curve, in order to prevent the curve from entering at a dangerous speed, two threshold values F1 and F2 indicating lateral force are set (F1 <F2). That is, when the target lateral force Ff is greater than the first threshold value F1 before the first predetermined time t1 seconds before entering the curve, the throttle valve is fully closed. Further, when the target lateral force Ff is larger than the second threshold value F2 before the second predetermined time t2 seconds before entering the curve (t1> t2), the automatic transmission is shifted down by one stage. Such a throttle valve fully-closed control and shift-down control prevent the vehicle from entering a curve at a dangerous speed.
[0023]
Next, the control contents of the controller U will be described in detail with reference to the flowcharts of FIGS. 5 to 7. In the following description, Q indicates a step. First, after the various data shown in FIG. 3 are input (calculated) in Q1 of FIG. 5, the future lateral deviation amount y1 is calculated as described above in Q2. In Q3, the steering torque T2 (steering reaction force T1) is determined from the map shown in FIG. 4 based on the future lateral deviation amount y1. In Q4, the marginal lateral force α is determined based on the future lateral deviation amount y1.
[0024]
In Q5, the marginal lateral force α is corrected according to the formula shown here, with the lane width W and d indicating whether or not the headlight is turned on as parameters. That is, α is corrected so as to decrease as the lane width W increases, d is set to a predetermined positive value when the headlight is turned on, and d is set to 0 when the headlight is not turned on (when the headlight is turned on). The marginal lateral force α is increased compared to when the lamp is not lit).
[0025]
In Q6 to Q10, the side slip angle is estimated, the actual driving force is estimated, the actual lateral force is estimated, the road curvature R is estimated, and the target lateral force Ff is estimated. After Q10, the process proceeds to Q21 in FIG. In Q21, it is determined whether the vehicle is currently traveling at the entrance of the curve or is in steady turning. If YES in Q21, it is determined in Q22 whether or not the rate of change of the reciprocal of the curvature R (curvature radius) is greater than or equal to 0, that is, whether or not the degree of road curvature is severe. . If the determination in Q23 is YES, the process proceeds to Q23.
[0026]
If NO in Q21 or NO in Q22, the process proceeds to Q24 to determine whether the vehicle is in a dangerous driving state. Specifically, in Q24, it is determined whether or not the brake is being turned on. If YES in Q24, the process proceeds to Q23, and if NO in Q24, the marginal lateral force α is corrected to a small value in Q25. The correction of Q25 is performed based on the ratio between the maximum curvature Rmax in the curve and the curvature R of the currently running curve portion (correction in the direction of decreasing α). After Q25, the process proceeds to Q23.
[0027]
In Q23, the driving force reduction amount (throttle opening reduction amount ΔTH) is calculated based on the equation shown here. In the equation, k is a control constant (control gain), and Ftmax is the maximum value of the actual lateral force Ft (in practice, the actual lateral force Ft set in Q8 is the maximum value that can be taken. Ft = Ftmax). As is apparent from this equation, the driving force reduction amount ΔTH is calculated so as to increase as the deviation obtained by subtracting “Ff + α” from Ftmax increases. After Q23, in Q24, it is determined whether or not the reduction amount ΔTH is smaller than zero. If YES in Q26, the current throttle opening TH is calculated by adding the reduction amount ΔTH to the current throttle opening TH (reduction of the throttle opening) in Q27.
[0028]
After Q27, or when NO is determined in Q26, it is determined in Q28 whether or not the accelerator opening degree AC is equal to or greater than a predetermined value a. If YES in Q28, it is determined in Q29 whether or not the change rate ΔAC of the accelerator opening obtained by differentiating the accelerator opening AC is equal to or greater than a predetermined value b. If YES in Q29, it is assumed that the driver has requested acceleration. In Q30, the throttle opening increase correction amount ΔTH1 is calculated according to the equation shown here. Thereafter, at Q31, the current throttle opening TH is calculated by adding the increase correction amount ΔTH1 to the throttle opening TH.
[0029]
If NO in Q28 or NO in Q29, the process returns without passing through Q30 and Q31. Note that the throttle opening (target throttle opening) TH set in Q27 or Q31 can be realized, for example, at a timing before the return after Q31, or by interruption processing every predetermined time. (The same applies to the realization of the steering torque set in Q5).
[0030]
The flow chart of FIG. 7 shows the contents of control for preventing a situation where the vehicle enters the curve at an overspeed, and is for performing throttle full-close control and shift-down control. That is, in Q41, it is determined whether it is t1 seconds before the curve. If YES in Q41, it is determined in Q42 whether the target lateral force Ff is greater than the threshold value F1. Determined. If YES in Q42, the throttle valve is fully closed in Q43. After Q43, or when NO is determined in Q41, and further when NO is determined in Q42, it is determined in Q44 whether or not it is t2 seconds before the curve, and YES in Q44 If it is, in Q45, it is determined whether or not the target lateral force Ff is larger than the threshold value F2. If the determination at Q45 is YES, a downshift is performed at Q46. When NO is determined in Q44 or NO in Q45, the process is returned.
[0031]
Although the embodiment has been described above, the present invention is not limited to this, and includes the following cases, for example. The automatic steering for tracking the target trajectory includes a case where automatic steering is performed so that the target trajectory is restored only when the target trajectory is deviated by a predetermined amount or more. In addition, the automatic steering is not limited to the case where the steered wheels 3 are actually steered, but includes the case where only the steering reaction force is applied to urge the driver to steer.
[0032]
The actual lateral force Ft can be determined using the road surface μ (road surface friction coefficient) as a parameter. Further, the marginal lateral force α can be corrected by the road surface μ (α is set to be larger as the road surface μ is smaller). The route from Q21 to Q25 corresponds to the control for correcting the marginal lateral force α in the latter half of the turn to be small. For example, the navigation system is used to detect that the vehicle is located in the latter half of the curve. Further, it is possible to perform correction for reducing the marginal lateral force α. Further, the marginal lateral force α can be gradually reduced (continuously variable or stepwise) in accordance with the elapsed time from the time when the vehicle entered the curve.
[0033]
As a situation where the visibility becomes worse, there is rainy weather, and it is possible to perform correction to increase the marginal lateral force α during rainy weather. Further, when it is detected that the driver performs a deceleration operation, for example, an operation for fully closing the accelerator opening or a brake operation, the marginal lateral force α can be corrected to a large value. Further, the marginal lateral force α can be corrected every time the curvature R of the curve changes (can be limited to the case where there is a change amount of the curvature R greater than or equal to a predetermined value). Various members such as each step or sensor shown in the flowchart can be expressed by adding the name of the means to the high-level expression of the function. Further, the object of the present invention is not limited to what is explicitly stated, but also implicitly includes providing what is substantially preferred or expressed as an advantage. Furthermore, the present invention can also be expressed as a control method.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining automatic steering for tracking a target locus.
FIG. 2 is a diagram showing an example of a steering system and a control system used for automatic steering.
FIG. 3 is a block diagram showing the control system of FIG. 2;
FIG. 4 is a diagram showing a setting example of steering torque and steering torque.
FIG. 5 is a flowchart showing a control example of the present invention.
FIG. 6 is a flowchart showing a control example of the present invention.
FIG. 7 is a flowchart showing a control example of the present invention.
[Explanation of symbols]
1: Vehicle 2: Traveling lane 2C: Center line (target locus yc)
3: Front wheel (steering wheel)
4: Steering handle (steering part)
14: Motor (for steering torque generation)
15: Motor (for steering reaction force generation)
U: Controller y1: Future lateral deviation amount T1: Steering torque (steering reaction force)
T2: Steering torque (steering force)
Ff: target lateral force Ft: actual lateral force α: marginal lateral force

Claims (12)

In a vehicle control apparatus that performs automatic steering control with a steering control target value determined to travel along a traveling lane,
Driving force adjusting means for adjusting the driving force of the vehicle;
A target lateral force determining means for determining, as a target lateral force, a lateral force required to ensure the turning by the control of the automatic steering based on the driving state of the vehicle relating to the turning;
An actual lateral force determining means for determining a lateral force that can be actually secured based on the running state of the vehicle;
The driving force of the vehicle is controlled by controlling the driving force adjusting means so that the actual lateral force determined by the actual lateral force determining means is larger than a value obtained by adding a marginal lateral force to the target lateral force. Driving force control means for reducing the control,
The vehicle control apparatus characterized by the above-mentioned. In claim 1,
A vehicle control apparatus comprising: a correction unit that corrects the magnitude of the marginal lateral force. In claim 2,
The vehicle control apparatus according to claim 1, wherein the correction means is set to make the marginal lateral force smaller in the latter half of the turn than in the early turn. In claim 2,
The steering control target value is determined based on a predicted lateral deviation amount that is a laterally predicted lateral amount from the currently traveling lane,
The marginal lateral force is determined to be larger when the predicted lateral deviation amount is larger than when the predicted lateral deviation amount is smaller;
A control apparatus for a vehicle. In any one of Claims 2 thru | or 4,
The vehicle control apparatus according to claim 1, wherein the correction unit is set to correct the marginal lateral force according to a traveling environment related to a field of view. In claim 5,
The vehicle control apparatus according to claim 1, wherein the correction unit corrects the marginal lateral force to increase during night driving. In claim 5,
The vehicle control apparatus according to claim 1, wherein the correction unit corrects the marginal lateral force so as to increase during a rainy run. In any one of Claims 2 thru | or 4,
The vehicle control apparatus according to claim 1, wherein the correction means corrects the marginal lateral force to be larger when the width of the travel lane is small than when the width is large. In claim 2,
The vehicle control apparatus according to claim 1, wherein the correction means corrects the marginal lateral force to be small when the driver requests acceleration. In claim 2,
The vehicle control apparatus according to claim 1, wherein the correction unit corrects the marginal lateral force to increase when a driver requests deceleration. In claim 2,
The vehicle control apparatus, wherein the correction means corrects the marginal lateral force according to a change in a turning radius. In claim 2,
The correction means corrects the marginal lateral force so that it decreases with time.

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