VEHICLE DISTURBANCE HANDLING SYSTEM

Abstract

A vehicle disturbance handling system to handle a disturbance that is an external force that acts on a vehicle and causes deflection of the vehicle, including: a disturbance detecting portion configured to determine an occurrence of the disturbance and to estimate a degree of influence of the disturbance; and a disturbance handling portion configured to handle the disturbance based on the estimated degree, wherein, when it is determined that the disturbance is occurring, the handling portion controls a brake device and a steering device of the vehicle to handle the disturbance, and wherein the handling portion is configured to determine a disturbance-handling braking force, which is a braking force that should be applied to the vehicle by the brake device to reduce the influence of the disturbance, and to gradually decrease the disturbance-handling braking force with a lapse of time from a time point of the occurrence of the disturbance.

Claims

1. A disturbance handling system for a vehicle to handle a disturbance, the disturbance being an external force that acts on the vehicle and causes deflection of the vehicle, comprising: a disturbance detecting portion configured to determine an occurrence of the disturbance and to estimate a degree of influence of the disturbance; and a disturbance handling portion configured to handle the disturbance based on the estimated degree of influence of the disturbance, wherein, when it is determined that the disturbance is occurring, the disturbance handling portion controls a brake device and a steering device of the vehicle to handle the disturbance, and wherein the disturbance handling portion is configured to determine a disturbance-handling braking force and to gradually decrease the disturbance-handling braking force with a lapse of time from a time point of the occurrence of the disturbance, the disturbance-handling braking force being a braking force that should be applied to the vehicle by the brake device to reduce the influence of the disturbance.

2. The disturbance handling system according to claim 1, which is configured to handle the disturbance due to a crosswind.

3. The disturbance handling system according to claim 1, wherein the disturbance handling portion is configured to determine a disturbance-handling steering force and to gradually increase the disturbance-handling steering force with a lapse of time from the time point of the occurrence of the disturbance, the disturbance-handling steering force being a steering force that should be applied to the vehicle by the steering device to reduce the influence of the disturbance.

4. The disturbance handling system according to claim 3, wherein the disturbance handling portion is configured to gradually decrease the disturbance-handling braking force in accordance with a gradual increase of the disturbance-handling steering force.

5. The disturbance handling system according to claim 3, wherein a deviation of an actual yaw rate from a standard yaw rate is defined as a yaw rate deviation to indicate the degree of influence of the disturbance, the standard yaw rate being a yaw rate of the vehicle determined based on a steering operation, and wherein the disturbance handling portion is configured to determine the disturbance-handling braking force based on the yaw rate deviation and to determine the disturbance-handling steering force based on an integral value of the yaw rate deviation.

6. The disturbance handling system according to claim 5, wherein the disturbance handling portion is configured to control the steering device to generate the disturbance-handling steering force at a time point when the integral value of the yaw rate deviation exceeds a set value and to gradually increase the disturbance-handling steering force in accordance with an increase in the integral value of the yaw rate deviation starting from the time point.

7. The disturbance handling system according to claim 1, wherein the disturbance handling portion is configured to control the steering device to handle the disturbance such that the steering device performs automatic steering of the vehicle so as to attain a standard running state that is a running state to be attained if the disturbance is not occurring.

8. The disturbance handling system according to claim 7, wherein the disturbance handling portion is configured to control the steering device to perform the automatic steering of the vehicle so as to attain the standard running state, based on information obtained by a camera provided on the vehicle to monitor a view ahead of the vehicle.

9. The disturbance handling system according to claim 7, wherein the disturbance handling portion is configured to limit a change gradient of a steering amount to be not larger than a set gradient in the automatic steering of the vehicle performed by the steering device to attain the standard running state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The objects, features, advantages, and technical and industrial significance of the present disclosure will be better understood by reading the following detailed description of embodiments, when considered in connection with the accompanying drawings, in which:

[0057] FIG. 1 is a schematic view illustrating a structure of a vehicle on which is installed a vehicle disturbance handling system according to a first embodiment;

[0058] FIG. 2 is a block diagram illustrating functions of a disturbance detecting portion of a disturbance-handling electronic control unit of the disturbance handling system according to the first embodiment;

[0059] FIG. 3A is a view schematically illustrating a state in which the crosswind is acting on the vehicle running straightforward;

[0060] FIG. 3B is a graph showing a relationship between two standard yaw rates and an actual yaw rate in the state of FIG. 3A;

[0061] FIG. 4 is a block diagram illustrating functions of a crosswind determination portion of the disturbance detecting portion illustrated in FIG. 2;

[0062] FIG. 5A is a view schematically illustrating a state in which the vehicle is traveling on a cant road:

[0063] FIG. 5B is a graph showing a relationship between the two standard yaw rates and the actual yaw rate in the state of FIG. 5A;

[0064] FIG. 6 is a block diagram illustrating functions of a disturbance handling portion of the disturbance-handling electronic control unit of the disturbance handling system according to the first embodiment;

[0065] FIG. 7A is a graph showing a disturbance-handling braking force determined by the disturbance handling portion;

[0066] FIG. 7B is a graph showing a disturbance-handling steering force determined by the disturbance handling portion;

[0067] FIG. 7C is a graph showing an adjustment gain determined by the disturbance handling portion;

[0068] FIG. 7D is a graph showing temporal changes of the determined disturbance-handling braking force and the determined disturbance-handling steering force;

[0069] FIG. 8 is a flowchart indicating a disturbance handling program executed in the disturbance handling system according to the first embodiment;

[0070] FIG. 9 is a block diagram illustrating functions of a disturbance handling portion of a disturbance-handling electronic control unit of a vehicle disturbance handling system according to a second embodiment;

[0071] FIG. 10A is a view schematically illustrating a standard driving line identified as a standard running state and an actual driving line identified as an actual running state when a disturbance is handled by the disturbance handling system according to the second embodiment;

[0072] FIG. 10B is a graph showing an adjustment gain determined by a disturbance handling portion; and

[0073] FIG. 11 is a flowchart indicating a disturbance handling program relying on a standard running state executed in the disturbance handling system according to the second embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0074] Referring to the drawings, there will be explained below in detail a vehicle disturbance handling system (hereinafter simply referred to as disturbance handling system where appropriate) according to embodiments of the present disclosure. It is to be understood that the present disclosure is not limited to the details of the following embodiments but may be embodied based on the forms described in Various Forms and may be changed and modified based on the knowledge of those skilled in the art.

1. First Embodiment

[0075] A. Structure of Vehicle in Connection with Disturbance Handling

[0076] A vehicle disturbance handling system according to a first embodiment is for handling or coping with a crosswind that acts on a vehicle on which the present system is installed. In connection with handling of the crosswind, the vehicle has a structure schematically illustrated in FIG. 1. Referring to FIG. 1, the structure of the vehicle will be explained.

i) Steering Device

[0077] A vehicle on which the disturbance handling system is installed (hereinafter simply referred to as the vehicle or the present vehicle) has two front wheels 10F that are steerable wheels and two rear wheels 10R. The vehicle includes a steering device 12 for steering the two front wheels 10F. The front wheels 10F and/or the rear wheels 10R are drive wheels. The front wheels 10F and the rear wheels 10R will be collectively referred to as wheels 10 where it is not necessary to distinguish the front wheels 10F and the rear wheels 10R from each other.

[0078] The steering device 12 includes: a pair of steering knuckles 14 that rotatably hold the corresponding front wheels 10F; a steering rod 18 whose opposite ends are coupled to the respective steering knuckles 14 via respective tie rods 16; a steering wheel 20 as a steering operation member; a steering shaft 22 that rotates with the steering wheel 20; a motion converting mechanism 24 configured to convert the rotating motion of the steering shaft 22 into a linear movement of the steering rod 18 in the right-left direction; and a steering actuator 26 configured to apply, to the steering rod 18, a force for moving the steering rod 18 in the right-left direction (hereinafter referred to as moving force where appropriate) or configured to move the steering rod 18 in the right-left direction.

[0079] Though illustration of an internal structure of the motion converting mechanism 24 is omitted, the motion converting mechanism 24 includes an input shaft 30 coupled to the steering shaft 22. A rack is formed on the steering rod 18, and a pinion is provided on the input shaft 30 so as to be held in engagement with the rack and so as to rotate with the input shaft 30. That is, the motion converting mechanism 24 is a rack-and-pinion mechanism. Though not illustrated, a thread groove is formed at a part of the steering rod 18, which part is located in a housing 28 of the steering actuator 26. A nut is disposed in the housing 28 so as to be threadedly engaged with the thread groove via bearing balls. A steering motor 32, which is an electric motor (brushless DC motor), is provided on the housing 28, and a timing belt 34 is looped over the nut and a motor shaft of the steering motor 32. When an electric current is supplied to the steering motor 32, the steering actuator 26 applies, to the steering rod 18, the moving force in the right-left direction that corresponds to the supplied current or the steering actuator 26 moves the steering rod 18 in the right-left direction.

[0080] The steering device 12 is provided with an operation angle sensor 36 for detecting a steering operation angle that is an operation amount of the steering wheel 20. The steering operation angle will be hereinafter simply referred to as operation angle where appropriate. The steering shaft 22 and the input shaft 30 of the motion converting mechanism 24 are coupled to each other via a torsion bar 38. The steering device 12 is provided with an operation force sensor 40 for detecting an amount of torsion of the torsion bar 38 caused by the steering operation by the driver, namely, for detecting an operation torque Tq as an operation force applied to the steering wheel 20 by the driver. This operation force will be hereinafter referred to as steering operation force where appropriate.

[0081] The steering device 12, namely, the steering motor 32 of the steering actuator 26, is controlled by a steering electronic control unit 42 constituted by a computer and an inverter as a driver of the steering motor 32. The steering electronic control unit 42 will be hereinafter referred to as steering ECU 42. The present steering device 12 is a power steering device. Normally, a supply current to the steering motor 32 is controlled such that the steering actuator 26 applies the moving force to the steering rod 18 as a steering assist force, based on the operation torque Tq detected by the operation force sensor 40. The steering assist force is a force for assisting steering of the front wheels 10F.

[0082] As later explained in detail, control of the steering device 12 is executed in the present vehicle as driving assist for assisting the driver to prevent driving lane departure of the vehicle contrary to a driver's intention. This control is automatic steering control that may be referred to as lane keeping assist. Instead of the normal control described above, this automatic steering control is executed such that the moving force is applied to the steering rod 18 by the steering actuator 26 in a direction to prevent the vehicle from departing from the driving lane or such that steering of the front wheels 10F is performed so as to attain the steering amount determined to prevent the driving lane departure. In this respect, the steering amount means a steering angle of the front wheels 10F and is estimated based on a motor rotation angle detected by a motor rotation angle sensor 44 (such as a resolver) provided for the steering motor 32 for phase switching in electric current supply to the steering motor 32.

ii) Brake Device

[0083] A brake device 50 of the present vehicle is an ordinary hydraulic brake device. The brake device 50 includes: a brake pedal 52 as a brake operation member; a master cylinder 56 to which a reservoir 54 is attached and which is connected to the brake pedal 52; a brake actuator 58 connected to the master cylinder 56; and wheel brakes 60 provided for the respective wheels 10 and operable by a working fluid supplied from the brake actuator 58. Though illustration of an internal structure of the brake actuator 58 is omitted, the brake actuator 58 is constituted by a pump operable by a pump motor (that is an electric motor) and configured to pressurize the working fluid, an accumulator for storing the working fluid pressurized by the pump, electromagnetic valves for controlling the pressure of the working fluid supplied to the wheel brakes 60 of the respective wheels 10, etc. Each wheel brake 60 includes: a disc rotor that rotates with the corresponding wheel 10; and a brake caliper 62 including a wheel cylinder configured such that brake pads as friction members are pushed onto the disc rotor by the working fluid supplied thereto.

[0084] The present brake device 50 is a brake-by-wire brake device. In a normal condition, a master-cut valve 64 prohibits a flow of the working fluid between the master cylinder 56 and the brake actuator 58. In this state, the pump motor and the electromagnetic valves of the brake actuator 58 are controlled, so that a braking force desired by the driver is applied to the wheels 10.

[0085] The brake device 50 is controlled by a brake electronic control unit 66 constituted by a computer, drivers of the pump motor and the electromagnetic valves of the brake actuator 58, etc. The brake electronic control unit 66 will be hereinafter referred to as brake ECU 66 where appropriate. The brake pedal 52 is provided with a stroke sensor 68 for detecting a pedal stroke E. The stroke sensor 68, which is an operation amount sensor, detects the pedal stroke E as a brake operation amount. The brake ECU 66 determines, based on the pedal stroke E detected by the stroke sensor 68, a target braking force that is the braking force desired by the driver, and controls the electromagnetic valves of the brake actuator 58 based on the target braking force, so as to control the braking force to be applied to each wheel 10 by the corresponding wheel brake 60.

[0086] The brake ECU 66 controls the brake device 50 such that the braking forces to be applied to the respective four wheels 10 can be controlled independently of each other. It is thus possible to make a difference between the braking force to be applied to the right wheels 10 and the braking force to be applied to the left wheels 10. Further, in a case where any of the wheels 10 lock, control is executable in which the braking force applied to the locked wheel/wheels 10 is canceled so as to cancel the locking, namely, anti-skid control (ABS control) is executable. In this respect, each wheel 10 is provided with a wheel speed sensor 70 for detecting a wheel rotational speed Vw of the corresponding wheel 10 for the purpose of detecting a running speed of the vehicle and determining whether the corresponding wheel 10 is locking. The wheel speed sensors 70 are connected to the brake ECU 66.

[0087] The present vehicle is equipped with a controllable area network or car area network (CAN) 80. The brake ECU 66 and the steering ECU 42 are both connected to the CAN 80 so as to communicable with each other. Other electronic control units that will be later explained are also connected to the CAN 80, and the electronic control units connected to the CAN 80 are communicable with each other.

iii) Steering Assist Device

[0088] The present vehicle is equipped with a steering assist device 90 configured to execute control for assisting driving by the driver, namely, automatic steering control that may be referred to as the lane keeping assist explained above. The control will be hereinafter referred to as LKA control where appropriate. For executing control processing of the LKA control, the steering assist device 90 includes: a steering assist electronic control unit 92 (hereinafter referred to as steering assist ECU 92 where appropriate) that includes a computer as a main constituent element; a camera 94 for monitoring a view ahead of the vehicle; and a notifying device 96 configured to notify the driver that the own vehicle is departing from or is about to depart from the driving lane in which the own vehicle is traveling, by means of a speaker and an indicator.

[0089] The LKA control is known ordinary control, and its detailed explanation is dispensed with. In the LKA control, the steering assist ECU 92 identifies two lane markers that demarcate the driving lane in which the own vehicle is traveling, based on front-view image information obtained by the camera 94. When the steering assist ECU 92 judges that a possibility that the own vehicle will cross any of the two lane markers becomes high or judges that the vehicle has crossed any of the two lane markers, based on the front-view image information, the steering assist ECU 92 determines the moving force to be applied to the steering rod 18 by the steering actuator 26 or determines the steering amount of the front wheels 10F to be attained by the steering device 12, so as to steer the vehicle toward the middle of the driving lane.

[0090] The notifying device 96 is disposed in an instrument panel. The steering assist ECU 92 controls the notifying device 96 to notify the driver that the own vehicle is departing from or is about to depart from the driving lane. Further, the steering assist ECU 92 transmits information about the determined moving force or the determined steering amount to the steering ECU 42 via the CAN 80. When received the information, the steering ECU 42 controls, based on the information, the steering device 12, i.e., the steering actuator 26 of the steering device 12, so as to prevent the vehicle from departing from the driving lane.

B. Disturbance Handling System

i) Outline of Disturbance Handling System

[0091] The crosswind that acts on the vehicle is a disturbance that causes deflection of the vehicle. Thus, the driving stability of the vehicle can be enhanced by detecting the deflection due to the crosswind and reducing the deflection. To this end, the present vehicle includes a disturbance handling system 100 for handling or coping with the crosswind that acts on the vehicle.

[0092] The disturbance handling system 100 includes, as its main element, a disturbance-handling electronic control unit 102 (hereinafter referred to as disturbance handling ECU 102 where appropriate) including a computer as a main constituent element. The disturbance handling ECU 102 is configured such that the computer executes a disturbance handling program at a short time pitch. The disturbance handling ECU 102 includes a disturbance detecting portion 104 and a disturbance handling portion 106 each as a functional portion that work by execution of the program. The disturbance detecting portion 104 determines an occurrence of the crosswind as the disturbance and estimates a degree of influence of the crosswind. The disturbance handling portion 106 executes processing for handling the crosswind based on the estimated degree of influence of the crosswind.

[0093] There will be hereinafter explained in detail functions of the disturbance handling ECU 102, i.e., functions of the disturbance detecting portion 104 and the disturbance handling portion 106 while explaining a detecting process for detecting the crosswind and a handling process for handling the crosswind that are executed by the disturbance handling system 100. For handling the crosswind, the vehicle is equipped with: a yaw rate sensor 108 for detecting a yaw rate Yr when the vehicle is turning or being deflected; and a lateral acceleration sensor 110 for detecting lateral acceleration Gy of the vehicle that is being generated due to an inertial force in the lateral direction of the vehicle. It is noted that turning of the vehicle and deflection of the vehicle are the same phenomenon in behavior of the vehicle though there is a difference therebetween in terms of (i) the presence or absence of the driver's intension and (ii) a change rate of the orientation of the vehicle, for instance. Thus, in a case where the following explanation refers to one of turning of the vehicle and deflection of the vehicle, the other of turning of the vehicle and deflection of the vehicle can be included.

ii) Detection of Crosswind

[0094] When the vehicle is deflected by the crosswind that acts thereon, an actual yaw rate Yr.sub.SEN that is a yaw rate Yr actually detected by the yaw rate sensor 108 differs from a standard yaw rate Yr.sub.STD that is a yaw rate Yr theoretically determined based on the steering operation angle , a vehicle running speed V, and so on. The disturbance handling system 100 determines, based on this phenomenon, whether the vehicle is being deflected due to the crosswind and estimates, as a degree of influence of the crosswind, a yaw rate deviation Yr that is a deviation of the actual yaw rate Yr.sub.SEN from the standard yaw rate Yr.sub.STD. The disturbance detecting portion 104 for detecting the crosswind includes functional portions schematically illustrated in the block diagram of FIG. 2. Referring to FIG. 2, the process for detecting the crosswind will be explained.

[0095] In the following explanation, the steering operation angle is defined to be 0 when the steering wheel 20 is located at the neutral position (at which the steering wheel 20 is operated in neither right nor left). Further, the steering operation angle is defined to take a positive value when a steering operation to turn the vehicle to the left is being performed and is defined to take a negative value when a steering operation to turn the vehicle to the right is being performed. Similarly, the yaw rate Yr is defined to take a positive value when the vehicle is turning to the left (or when the vehicle is being deflected in the left direction) and is defined to take a negative value when the vehicle is turning to the right. Similarly, lateral acceleration Gy is defined to take a positive value when the inertial force in the right direction is acting on the vehicle body, namely, when the vehicle is turning to the left, and is defined to take a negative value when the inertial force in the left direction is acting on the vehicle body, namely, when the vehicle is turning to the right. Here, the inertial force is regarded as centrifugal force that acts on the vehicle body arising from the turning (deflection) of the vehicle.

[0096] As later explained in detail, the disturbance handling system 100 utilizes a first standard yaw rate Yr.sub.STD1 and a second standard yaw rate Yr.sub.STD2 each as the standard yaw rate Yr.sub.STD in order to exclude, from a target to be handled, deflection of the vehicle that arises from a road inclined in the right-left direction (hereinafter referred to as cant road where appropriate). The disturbance detecting portion 104 includes a first-standard-yaw-rate determination portion 120 for determining the first standard yaw rate Yr.sub.STD1 and a second-standard-yaw-rate determination portion 122 for determining the second standard yaw rate Yr.sub.STD2.

[0097] The first-standard-yaw-rate determination portion 120 determines the first standard yaw rate Yr.sub.STD1 according to the following equation based on: the steering operation angle detected by the operation angle sensor 36; the lateral acceleration Gy detected by the lateral acceleration sensor 110; the vehicle running speed V that is determined by the brake ECU 66 based on the wheel rotational speeds Vw of the respective wheels 10 detected by the respective wheel speed sensors 70 and that is transmitted via the CAN 80; and a stability factor Kh, an overall steering gear ratio n, and a wheel base L that are stored in the disturbance handling ECU 102 as vehicle specifications of the present vehicle:

[00001] $\begin{matrix} {Yr}_{STD .Math. .Math. 1} = \frac{V .Math.}{n .Math. L} - Gy .Math. V .Math. Kh & (1) \end{matrix}$

[0098] The second-standard-yaw-rate determination portion 122 determines the second standard yaw rate Yr.sub.STD2 based on the steering operation angle and the vehicle running speed V according to the following equation:

[00002] $\begin{matrix} {Yr}_{STD .Math. .Math. 2} = \frac{V .Math.}{n .Math. L} .Math. \frac{1}{1 + Kh .Math. V^{2}} & (2) \end{matrix}$

[0099] As apparent from the above two equations, the first standard yaw rate Yr.sub.STD1 is determined in consideration of the detected lateral acceleration Gy whereas the second standard yaw rate Yr.sub.STD2 is determined without considering the lateral acceleration Gy.

[0100] The filter processing portion 124 performs a low-pass filter processing on each of the determined first standard yaw rate Yr.sub.STD1 and the second standard yaw rate Yr.sub.STD2. The low-pass filter processing is a processing for compensating for a delay in time required for the steering operation to be reflected in the change of the actual yaw rate Yr. That is, the low-pass filter processing is a delay compensation processing that takes account of a delay of a vehicle behavior.

[0101] Here, the interrelationship among the first standard yaw rate Yr.sub.STD1, the second standard yaw rate Yr.sub.STD2, and the actual yaw rate Yr.sub.SEN will be explained. When the crosswind acts on the vehicle in a situation in which the vehicle is traveling straight without the steering wheel 20 being operated by the driver from the neutral position as illustrated in FIG. 3A, the first standard yaw rate Yr.sub.STD1, the second standard yaw rate Yr.sub.STD2, and the actual yaw rate Yr.sub.SEN change as indicated in a graph of FIG. 3B. Specifically, the second standard yaw rate Yr.sub.STD2 remains 0 whereas the first standard yaw rate Yr.sub.STD1 and the actual yaw rate Yr.sub.SEN take respective values opposite in sign because of the lateral acceleration Gy generated based on the inertial force (centrifugal force) F.sub.INA that arises from the deflection of the vehicle. In this respect, in a case where the steering wheel 20 is being operated, the second standard yaw rate Yr.sub.STD2 is not 0 but takes a value corresponding to the steering operation angle , and the first standard yaw rate Yr.sub.STD1 and the actual yaw rate Yr.sub.SEN take respective values that interpose the second standard yaw rate Yr.sub.STD2 therebetween.

[0102] In view of the relationship described above, the crosswind determination portion 126 determines whether the crosswind that should be handled is acting on the vehicle based on: the first standard yaw rate Yr.sub.STD1 and the second standard yaw rate Yr.sub.STD2 that have been subjected to the delay compensation processing described above; and the actual yaw rate Yr.sub.SEN. For convenience sake, this determination will be hereinafter referred to as crosswind determination where appropriate. The crosswind determination portion 126 has a functional configuration illustrated in a block diagram of FIG. 4. Specifically, it is needed to satisfy all of four conditions explained below to determine that the vehicle is receiving the crosswind that should be handled. The crosswind determination portion 126 includes four condition satisfaction determination portions 128-134 corresponding to the four conditions.

[0103] The first-condition satisfaction determination portion 128 determines whether a first condition represented by the following inequality is satisfied:

Yr.sub.STD 1Yr.sub.STD 2|>Yr.sub.TH 1(3)

In a case where this condition is satisfied, it is estimated that the vehicle is receiving the force in the lateral direction. Specifically, when the crosswind acts on the vehicle in the situation in which the vehicle is traveling straight without the steering wheel 20 being operated by the driver, the second standard yaw rate Yr.sub.STD2 is equal to 0 whereas the first standard yaw rate Yr.sub.STD1 is not equal to 0. Thus, the fact that a difference between the first standard yaw rate Yr.sub.STD1 and the second standard yaw rate Yr.sub.STD2 is greater than a set first threshold Yr.sub.TH1 is set as a necessary condition to determine that the crosswind that should be handled is occurring.

[0104] The second-condition satisfaction determination portion 130 determines whether a second condition represented by the following inequality is satisfied:

|Yr.sub.SENYr.sub.STD 2>Yr.sub.TH 2(4)

Also in a case where this condition is satisfied, it is estimated that the vehicle is receiving the force in the lateral direction. Specifically, when the crosswind acts on the vehicle in the situation in which the vehicle is traveling straight without the steering wheel 20 being operated by the driver, the second standard yaw rate Yr.sub.STD2 is equal to 0 whereas the actual yaw rate Yr.sub.SEN somewhat deviates from the second standard yaw rate Yr.sub.STD2. Thus, the fact that the deviation is greater than a set second threshold Yr.sub.TH2 is set as a necessary condition to determine that the crosswind that should be handled is occurring.

[0105] The third-condition satisfaction determination portion 132 determines whether a third condition represented by the following inequality is satisfied:

|Yr.sub.SENYr.sub.STD1|=|Yr|>Yr.sub.TH 3+A(5)

This condition is a main condition in the crosswind determination. Here, a deviation of the actual yaw rate Yr.sub.SEN from the first standard yaw rate Yr.sub.STD1 is defined as a main yaw rate deviation Yr for the crosswind determination. In this case, the yaw rate deviation Yr is regarded as a degree of influence of the disturbance, namely, a degree to which the vehicle is deflected due to the crosswind. The crosswind determination portion 126 determines that the third condition is satisfied in principle when the yaw rate deviation Yr, that is, an absolute value of the yaw rate deviation Yr in a strict sense, is greater than a set third threshold Yr.sub.TH3.

[0106] As mentioned above, the crosswind determination portion 126 determines that the third condition is satisfied in principle when the yaw rate deviation Yr is greater than the set third threshold Yr.sub.TH3. In determining whether the third condition is satisfied, the threshold used for the determination is sometimes increased by adding, to the set third threshold Yr.sub.TH3, an adjustment value A that is a positive value. Specifically, when the automatic steering is performed in a situation in which the LKA control is being executed, for instance, the steering device 12 receives a large steering operation force if the driver applies a force to the steering wheel 20 for maintaining a current operation angle of the steering wheel 20. That is, the torsion bar 38 is twisted by an amount corresponding to the operation torque Tq. As understood from the above equation, the first standard yaw rate Yr.sub.STD1 is determined based on the steering operation angle . If the torsion bar 38 is twisted to a certain extent, there is generated a difference between the first standard yaw rate Yr.sub.STD1 and the actual yaw rate Yr.sub.SEN as indicated in the graph of FIG. 3B, causing an increase in the yaw rate deviation Yr. This difference is referred to as apparent deviation Yr. In consideration of the apparent deviation Yr, the adjustment value A, which is determined to be equal to 0 when the LKA control, namely, the automatic steering control, is not being executed, is changed to a value except for 0 when the automatic steering control is being executed. That is, a dead zone in the determination is enlarged in the situation in which the automatic steering control is being executed, in order to avoid erroneous determination that there is an influence of the crosswind though in fact there is no influence of the crosswind, due to the phenomenon described above. In this respect, the adjustment value A is considered as a change amount of the set third threshold Yr.sub.TH3.

[0107] The adjustment value A is determined by an adjustment value determination portion 136. Two determination processes, i.e., a first determination process and a second determination process, are set for determining the adjustment value A. The driver may select one of the two determination processes. Alternatively, one of the two determination processes may be set in advance by the manufacturer of the vehicle. Regardless of which one of the two processes is employed, the adjustment value determination portion 136 determines the adjustment value A to be equal to 0 in the situation in which the LKA control is not being executed, based on information as to whether the LKA control is being executed or not (ON/OFF), the information being sent from the steering assist ECU 92 via the CAN 80.

[0108] When the first determination process is employed in the situation in which the LKA control is being executed, the adjustment value determination portion 136 determines a torsion-dependent operation angle that is the operation angle of the steering wheel 20 corresponding to the torsion amount of the torsion bar 38. The torsion-dependent operation angle is determined based on the operation torque Tq detected by the operation force sensor 40 and pre-stored torsional stiffness of the torsion bar 38, according to the following equation. Here, the torsion-dependent operation angle is considered as a variation amount of the steering operation that arises from the operation torque Tq as the steering operation force. The adjustment value determination portion 136 estimates the torsion-dependent operation angle .

.Math.Tq(6)

Based on the determined torsion-dependent operation angle , the apparent deviation Yr is determined according to the following equation. The apparent deviation Yr is considered as a variation amount of the yaw rate Yr that arises from the variation amount of the steering operation, namely, the apparent deviation Yr is considered as the yaw rate variation amount. The adjustment value determination portion 136 estimates the yaw rate variation amount.

[00003] $\begin{matrix} .Math. .Math. {Yr}^{} = \frac{V .Math.^{}}{n .Math. L} . \frac{1}{1 + Kh .Math. V^{2}} + \frac{V .Math.^{}}{n .Math. L} .Math. \frac{1}{1 + Kh .Math. V^{2}} .Math. (Kh .Math. V^{2}) & (7) \end{matrix}$

The first term in the above equation corresponds to a difference between the actual yaw rate Yr.sub.SEN and the second standard yaw rate Yr.sub.STD2 indicated in the graph of FIG. 3B. The second term in the above equation corresponds to a difference between the first standard yaw rate Yr.sub.STD1 and the second standard yaw rate Yr.sub.STD2 indicated in the graph of FIG. 3B.

[0109] When the first determination process is employed, the adjustment value A is made equal to a value of the apparent deviation Yr determined as described above. That is, the adjustment value determination portion 136 determines a change amount of the set third threshold Yr.sub.TH3 that is the set threshold, based on the apparent deviation Yr that is the yaw rate variation amount.

A=Yr(8)

[0110] When the second determination process is employed, on the other hand, the adjustment value A is made equal to an expectable maximum deviation Yr.sub.MAX set as a fixed value, irrespective of the value of the apparent deviation Yr.

A=Yr.sub.MAX(9)

The expectable maximum deviation Yr.sub.MAX is an apparent deviation Yr estimated based on a maximum operation torque Tq that is anticipated to be detected in the LKA control. By employing the second determination process, the dead zone in the crosswind determination can be easily and reliably enlarged.

[0111] The fourth-condition satisfaction determination portion 134 determines whether the fourth condition represented by the following inequality is satisfied.

(Y.sub.STD1Yr.sub.STD2).Math.(Y.sub.SENYr.sub.STD2)<0(10)

The fourth condition is a condition for excluding, from the disturbance to be handled, the deflection of the vehicle caused when the vehicle is traveling on the cant road.

[0112] In a situation in which the vehicle is traveling on the cant road as illustrated in FIG. 5A, inertial force F.sub.INA based on the gravity acts on the vehicle, so that the vehicle is deflected. This phenomenon is a natural phenomenon, and such deflection is a disturbance different in type from the crosswind to be handled. The fourth condition is set in consideration of this fact. When the vehicle enters the cant road without the steering wheel 20 being operated from the neutral position, the first standard yaw rate Yr.sub.STD1, the second standard yaw rate Yr.sub.STD2, and the actual yaw rate Yr.sub.SEN change as indicated in the graph of FIG. 5B. As apparent from comparison between FIG. 3A, FIG. 3B and FIGS. 5A, 5B, because of a difference in the direction in which the inertial force F.sub.INA acts, the first standard yaw rate Yr.sub.STD1 in the graph of FIG. 5B is opposite in sign to the first standard yaw rate Yr.sub.STD1 in the graph of FIG. 3B. That is, in this case, unlike the case in which the vehicle is deflected due to the crosswind, a deviation of the first standard yaw rate Yr.sub.STD1 from the second standard yaw rate Yr.sub.STD2 is equal in sign to a deviation of the actual yaw rate Yr.sub.SEN from the second standard yaw rate Yr.sub.STD2. In consideration of this fact, the fourth-condition satisfaction determination portion 134 determines that the fourth condition is satisfied when those deviations are opposite in sigh to each other.

[0113] The crosswind determination portion 126 includes a final determination portion 138 as illustrated in the block diagram of FIG. 4. The final determination portion 138 receives, from the first-through fourth-condition satisfaction determination portions 128-134, signals as to whether or not the first through fourth conditions are satisfied (Yes/No). The final determination portion 138 determines whether the vehicle is receiving the crosswind necessary to be handled, namely, determines the presence or absence of the crosswind (ON/OFF), based on whether all of the first through fourth conditions are satisfied, and outputs the determination result. In the present crosswind detecting process, it is determined that the disturbance due to the crosswind is not occurring when the fourth condition is not satisfied even if the third condition, as a main condition, is satisfied. That is, it is determined that the disturbance due to the crosswind is not occurring when the deviation of the actual yaw rate Yr.sub.SEN from the first standard yaw rate Yr.sub.STD1 is equal in sign to the deviation of the actual yaw rate Yr.sub.SEN from the second standard yaw rate Yr.sub.STD2, irrespective of the degree of the deviation of the actual yaw rate Yr.sub.SEN from the first standard yaw rate Yr.sub.STD1.

[0114] The determination result as to the presence or absence of the crosswind made by the crosswind determination portion 126 is sent to a yaw rate deviation output portion 140 illustrated in FIG. 2. When the vehicle is receiving the crosswind necessary to be handled, the yaw rate deviation output portion 140 outputs, as the degree of influence of the crosswind, the yaw rate deviation Yr according to the following equation:

Yr=Yr.sub.SENYr.sub.STD 1(11)

When the vehicle is not receiving the crosswind necessary to be handled, on the other hand, the yaw rate deviation output portion 140 outputs the yaw rate deviation Yr that is determined to be 0 according to the following equation:

Yr=0(12)

[0115] As explained above, in the present process for detecting the crosswind disturbance, it is determined that the disturbance due to the crosswind is occurring when the yaw rate deviation Yr (the deviation of the actual yaw rate Yr.sub.SEN from the first standard yaw rate Yr.sub.STD1 as the standard yaw rate Yr.sub.STD1 that is the yaw rate Yr of the vehicle determined based on the steering operation) is greater than the set threshold (i.e., the set third threshold Yr.sub.TH3). Further, the set threshold is increased in the situation in which the vehicle is being automatically steered. Thus, in the case where the driver performs the steering operation that counters or opposes the automatic steering, the present process obviates a possibility that the behavior of the vehicle resulting from such steering operation is determined to be due to the disturbance. In other words, the present process eliminates a possibility of erroneous determination as to the occurrence of the disturbance.

iii) Process for Handling Crosswind

[0116] The deflection of the vehicle due to the crosswind adversely influences driving stability and driving comfortability of the vehicle, for instance. It is thus desirable that the deflection due to the crosswind be reduced. In the disturbance handling system 100, the deflection of the vehicle due to the crosswind is handled by both the brake device 50 and the steering device 12. The crosswind is handled by the disturbance handling portion 106 of the disturbance handling ECU 102 illustrated in FIG. 1. The disturbance handling portion 106 includes functional portions schematically shown in a block diagram of FIG. 6. Referring to FIG. 6, a process for handling the crosswind will be explained.

[0117] The disturbance handling portion 106 includes a brake moment determination portion 150, an integral processing portion 152, and a steering moment determination portion 154. The yaw rate deviation Yr transmitted as the degree of influence of the crosswind from the disturbance detecting portion 104 is input to the brake moment determination portion 150 and the integral processing portion 152. The integral processing portion 152 executes an integral processing of the yaw rate deviation Yr from a time point of the occurrence of the crosswind to be handled, namely, from a time point when the yaw rate deviation Yr transmitted from the disturbance detecting portion 104 is no longer equal to 0. Here, a value obtained by the integral processing is represented as a yaw rate deviation integral value Yrdt. The integral processing portion 152 outputs the yaw rate deviation integral value Yrdt to the steering moment determination portion 154. In this respect, the integral processing portion 152 resets the yaw rate deviation integral value Yrdt to 0 at a time point when the yaw rate deviation Yr transmitted from the disturbance detecting portion 104 becomes equal to0.

[0118] The brake moment determination portion 150 determines, based on the yaw rate deviation Yr, a brake counter moment Mb that is a counter yaw moment M that should be applied to the vehicle by the braking force of the brake device 50 to decrease the yaw rate deviation Yr, in other words, to counter the crosswind. The disturbance handling ECU 102 stores map data shown in a graph of FIG. 7A. Specifically, the disturbance handling ECU 102 stores data of the brake counter moment Mb with respect to the yaw rate deviation Yr. Referring to the stored map data, the brake moment determination portion 150 determines the brake counter moment Mb as follows. The brake counter moment Mb is applied to the vehicle when the yaw rate deviation Yr, i.e., the absolute value of the yaw rate deviation Yr in a strict sense, increases to a certain extent. The brake counter moment Mb increases with an increase in the yaw rate deviation Yr. When the yaw rate deviation Yr further increases to a certain extent, the brake counter moment Mb kept at a constant level is applied. The brake counter moment Mb is considered as a disturbance-handling braking force that is a braking force to be applied to the vehicle by the brake device 50 to reduce the influence of the disturbance.

[0119] The steering moment determination portion 154 determines, based on the yaw rate deviation integral value Yrdt, a steering counter moment Ms that is a counter yaw moment M that should be applied to the vehicle in dependence on steering of the front wheels 10F by the steering device 12 to decrease the yaw rate deviation Yr, in other words, to counter the crosswind. The disturbance handling ECU 102 stores map data shown in a graph of FIG. 7B. Specifically, the disturbance handling ECU 102 stores data of the steering counter moment Ms with respect to the yaw rate deviation integral value Yrdt. Referring to the stored map data, the steering moment determination portion 154 determines the steering counter moment Ms as follows. The steering counter moment Ms is applied to the vehicle when the yaw rate deviation integral value Yrdt, i.e., the absolute value of the yaw rate deviation integral value Yrdt in a strict sense, increases to a certain extent. The steering counter moment Ms increases with an increase in the yaw rate deviation integral value Yrdt. When the yaw rate deviation integral value Yrdt further increases to a certain extent, the steering counter moment Ms kept at a constant level is applied. The steering counter moment Ms is considered as a disturbance-handling steering force that is a steering force to be applied to the vehicle by the steering device 12 to reduce the influence of the disturbance.

[0120] The disturbance handling portion 106 utilizes an adjustment gain B for the brake counter moment Mb to decrease the brake counter moment Mb with an increase in the steering counter moment Ms. To this end, the disturbance handling portion 106 includes an adjustment gain determination portion 156 for determining the adjustment gain B. The disturbance handling ECU 102 stores map data relating to the adjustment gain B for gradually decreasing the brake counter moment Mb. Specifically, the disturbance handling ECU 102 stores data shown in a graph of FIG. 7C for determining the adjustment gain B such that the adjustment gain B decreases from 1 in accordance with an increase in the steering counter moment Ms and such that the adjustment gain B becomes equal to 0 when the steering counter moment Ms increases to a certain extent or more. Referring to the map data, the adjustment gain determination portion 156 determines the adjustment gain B.

[0121] The brake counter moment Mb determined by the brake moment determination portion 150 is adjusted by an adjusting portion 158 in accordance with the adjustment gain B determined by the adjustment gain determination portion 156. That is, the brake counter moment Mb is multiplied by the adjustment gain B.

[0122] The thus adjusted brake counter moment Mb is transmitted to a crosswind-handling wheel braking force determination portion 160. The crosswind-handling wheel braking force determination portion 160 determines, based on the brake counter moment Mb, the braking forces to be applied by the brake device 50 to the right and left wheels 10 for reducing the deflection of the vehicle due to the crosswind. Specifically, to suppress the deflection of the vehicle due to the crosswind, the crosswind-handling wheel braking force determination portion 160 determines a crosswind-handling left wheel braking force Fb.sub.L that is the braking force to be applied to the left wheels 10 or a crosswind-handling right wheel braking force Fb.sub.R that is the braking force to be applied to the right wheels 10. The process for determining those braking forces is known in the art, and its explanation is dispensed with. Information on the crosswind-handling left wheel braking force Fb.sub.L or the crosswind-handling right wheel braking force Fb.sub.R determined as described above is transmitted to the brake ECU 66 of the brake device 50 via the CAN 80. The brake ECU 66 controls the brake device 50 based on the crosswind-handling left wheel braking force Fb.sub.L or the crosswind-handling right wheel braking force Fb.sub.R. As a result, the braking force based on the braking force Fb.sub.L is applied to the left wheels 10 or the braking force based on the braking force Fb.sub.R is applied to the right wheels 10. Alternatively, in a situation in which the braking force based on the brake operation of the driver is already being applied to the wheels 10 at this point in time, the braking force Fb.sub.L is added to the left wheels 10 or the braking force Fb.sub.R is added to the right wheels 10.

[0123] The steering counter moment Ms determined by the steering moment determination portion 154 is transmitted to a crosswind-handling steering amount determination portion 162. The crosswind-handling steering amount determination portion 162 determines, based on the steering counter moment Ms, a steering amount of the front wheels 10F to be steered by the steering device 12, namely, a crosswind-handling steering amount , for reducing the deflection of the vehicle due to the crosswind. The process for determining the crosswind-handling steering amount is known in the art, and its explanation is dispensed with. Information on the determined crosswind-handling steering amount is transmitted to the steering ECU 42 of the steering device 12 via the CAN 80. The steering ECU 42 controls the steering device 12 based on the crosswind-handling steering amount . As a result, the front wheels 10F are steered by the steering amount corresponding to the crosswind-handling steering amount . Alternatively, in a situation in which the front wheels 10F are already being steered, the steering amount of the front wheels 10F is changed in accordance with the crosswind-handling steering amount . In this respect, the crosswind-handling steering amount is determined to be a positive value for causing deflection of the vehicle in the left direction while the crosswind-handling steering amount is determined to be a negative value for causing deflection of the vehicle in the right direction.

[0124] In the present process for handling the crosswind, the brake counter moment Mb as the disturbance-handling braking force and the steering counter moment Ms as the disturbance-handling steering force change with a time t that elapses from the time point of the occurrence of the crosswind to be handled, as schematically shown in a graph of FIG. 7D. Specifically, a relatively large value of the brake counter moment Mb is applied from immediately after the time point of the occurrence of the crosswind disturbance. Thereafter, the brake counter moment Mb is gradually decreased and finally made equal to 0. In contrast, the steering counter moment Ms is made equal to 0 immediately after the time point of the occurrence of the crosswind disturbance and gradually increased thereafter. Finally, a relatively large value of the steering counter moment Ms is applied. In the present process, therefore, the brake counter moment Mb is gradually decreased, so that the vehicle is prevented from greatly decelerating when the crosswind disturbance is handled. Further, the steering counter moment Ms, which is not yet generated at the time point of the occurrence of the crosswind disturbance, is gradually increased thereafter. This obviates a phenomenon in which the steering wheel 20 moves abruptly, thus reducing or avoiding an unnatural feeling felt by the driver.

[0125] As apparent from the graph of FIG. 7D, the brake counter moment Mb is gradually decreased in accordance with the gradual increase of the steering counter moment Ms. Accordingly, this configuration enables the handling of the crosswind disturbance to be smoothly shifted from handling by the braking force to handling by the steering force, in other words, to be smoothly shifted from handling by the brake device 50 to handling by the steering device 12. Specifically, the steering counter moment Ms is generated at a time point when the yaw rate deviation integral value Yrdt exceeds a set valueYrdt.sub.0 as shown in the graph of FIG. 7B.

iv) Flow of Processes

[0126] The computer of the disturbance handling ECU 102 executes a disturbance handling program at a short time pitch, e.g., about several to several tens of milliseconds (msec), so that the detecting process for detecting the crosswind disturbance and the handling process for handling the crosswind disturbance are executed. The disturbance handling program is indicated by a flowchart of FIG. 8. Referring to the flowchart, the detecting process and the handling process will be briefly explained.

[0127] In the disturbance handling program, the first standard yaw rate Yr.sub.STD1 is determined at Step 1 according to the technique explained above. (Hereinafter, Step 1 is abbreviated as S1, and other steps are similarly abbreviated.) At S2, the second standard yaw rate Yr.sub.STD2 is determined according to the technique explained above. At S3, the filter processing of the first standard yaw rate Yr.sub.STD1 and the second standard yaw rate Yr.sub.STD2 is executed as described above.

[0128] In the disturbance handling system 100, the adjustment value A is used in determining whether the third condition for the crosswind determination is satisfied, in consideration of the situation in which the automatic steering control is already being performed. In this case, it is needed to select, as the adjustment value A, one of the apparent deviation Yr that depends on the operation torque Tq and the expectable maximum deviation Yr.sub.MAX that is a fixed value. For this selection, an adjustment value selection flag FA is used. The flag value of the adjustment value selection flag FA is set to 1 when the apparent deviation Yr is selected by the driver or the manufacturer of the vehicle while the flag value is set to 0 when the expectable maximum deviation Yr.sub.MAX is selected by the driver or the manufacturer. At S4, the flag value of the adjustment value selection flag FA is judged. When the flag value is 1, the control flow goes to S5 at which the apparent deviation Yr is calculated according to the process described above and the adjustment value A is determined to be equal to the apparent deviation Yr. When the flag value is 0, the control flow goes to S6 at which the adjustment value A is determined to be equal to the expectable maximum deviation Yr.sub.MAX.

[0129] At S7, it is determined whether the first through fourth conditions for the crosswind determination are satisfied. In the situation in which the LKA control is being executed, the adjustment value A determined as described above is used in determining whether the third condition is satisfied. When all of the first through fourth conditions are satisfied, it is determined at S8 that the crosswind that should be handled is occurring.

[0130] When the vehicle is receiving the crosswind that should be handled, the yaw rate deviation Yr as a parameter indicative of the degree of influence of the crosswind is identified at S9 according to the technique described above. At S10, the integral processing is performed on the identified yaw rate deviation Yr. At S11, the brake counter moment Mb as the disturbance-handling braking force is determined referring to the map data shown in FIG. 7A based on the yaw rate deviation Yr. At S12, the steering counter moment Ms as the disturbance-handling steering force is determined referring to the map data shown in FIG. 7B based on the yaw rate deviation integral value Yrdt obtained by the integral processing of the yaw rate deviation Yr.

[0131] After the brake counter moment Mb and the steering counter moment Ms are determined, the control flow goes to S13 at which the adjustment gain B used for gradually decreasing the brake counter moment Mb is determined referring to the map data shown in FIG. 7C based on the yaw rate deviation integral value Yrdt. At S14, the brake counter moment Mb is adjusted based on the determined adjustment gain B. At S15, based on the adjusted brake counter moment Mb, the crosswind-handling left wheel braking force Fb.sub.L or the crosswind-handling right wheel braking force Fb.sub.R is determined. The crosswind-handling left wheel braking force Fb.sub.L or the crosswind-handling right wheel braking force Fb.sub.R determined at S15 is sent to the brake ECU 66. At S16, the crosswind-handling steering amount is determined based on the steering counter moment Ms. The determined crosswind-handling steering amount w is sent to the steering ECU 42.

[0132] One execution of the disturbance handling program ends after execution of a series of processing described above. In this respect, when it is determined at S8 that the crosswind to be handled is not occurring, namely, when at least one of the first through fourth conditions is not satisfied, one execution of the disturbance handling program ends without S9 and steps thereafter being implemented

[0133] As explained above, the disturbance handling ECU 102 is configured such that the computer executes a series of processing described above by executing the disturbance handling program. The disturbance handling system 100, i.e., the disturbance handling ECU 102, may include a dedicated circuit for executing a part of or an entirety of a series of processing described above, in place of the computer.

Second Embodiment

[0134] A vehicle disturbance handling system (hereinafter simply referred to as disturbance handling system where appropriate) according to a second embodiment differs from the disturbance handling system 100 according to the first embodiment only in the process for handling the crosswind disturbance. Accordingly, the disturbance handling system of the second embodiment and a disturbance handling ECU in the system of the second embodiment will be respectively referred to as a disturbance handling system 100 and a disturbance handling ECU 102 as shown bracketed in FIG. 1. Further, a disturbance handling portion of the present disturbance handling system will be referred to as a disturbance handling portion 106 as shown bracketed in FIG. 1. The disturbance handling system 100 of the second embodiment will be explained focusing only on the disturbance handling portion 106. Reference numerals as used for the functional portions of the disturbance handling portion 106 are used to identify functional portions of the disturbance handling portion 106 having the same functions. Further, the functional portions of the disturbance handling portion 106 that are similar in function to those of the disturbance handling portion 106 are indicated by attaching a prime symbol () to reference numerals indicating the functional portions of the disturbance handling portion 106.

[0135] The difference between the disturbance handling portion 106 of the second embodiment and the disturbance handling portion 106 of the first embodiment is as follows. In the disturbance handling system 100 of the first embodiment, the crosswind-handling steering amount as the steering amount of the front wheels 10F for handling the crosswind disturbance is determined based on the yaw rate deviation Yr as the parameter indicative of the degree of influence of the crosswind disturbance, namely, based on the yaw rate deviation integral value Yrdt that is an integral value of the yaw rate deviation Yr. Further, the steering device 12 is controlled based on the crosswind-handling steering amount , so that the crosswind disturbance is handled by the steering device 12. In the disturbance handling system 100 of the second embodiment, in contrast, the vehicle is automatically steered by the steering device 12 to attain a standard running state that is a running state of the vehicle that should be attained unless the disturbance occurs, in other words, unless the vehicle is receiving the crosswind. Specifically, a driving line on which the vehicle should drive is identified as an index of the standard running state. This driving line will be referred to as standard driving line where appropriate. When the crosswind that should be handled is occurring, the vehicle is automatically steered so as to drive on the standard driving line, so that the crosswind disturbance is handled by the steering device 12. Referring to a block diagram of FIG. 9, there will be explained in detail the functional portions of the disturbance handling portion 106 and a process for handling the crosswind.

[0136] Unlike the disturbance handling portion 106, the disturbance handling portion 106 does not include the integral processing portion 152 and the steering moment determination portion 154. A crosswind-handling steering amount determination portion 162 for determining the crosswind-handling steering amount greatly differs in function from the crosswind-handling steering amount determination portion 162 of the disturbance handling portion 106. To the crosswind-handling steering amount determination portion 162, front-view image information obtained by the camera 94 is sent from the steering assist ECU 92. When the crosswind that should be handled is occurring, namely, when the yaw rate deviation Yr sent from the disturbance detecting portion 104 is not 0, the crosswind-handling steering amount determination portion 162 identifies a standard driving line L.sub.STD of the vehicle and an actual driving line L.sub.REAL on which the vehicle is anticipated to actually drive, as schematically shown in FIG. 10A, based on the front-view image information, information on the vehicle running speed V sent from the brake ECU 66, information on the steering operation angle sent from the steering ECU 42, information on the actual yaw rate Yr.sub.SEN from the yaw rate sensor 108, information on the lateral acceleration Gy from the lateral acceleration sensor 110, etc. The actual driving line L.sub.REAL is an index of a state in which the vehicle will be placed when the vehicle will actually run, i.e., an index of an actual running state. In FIG. 10A, the standard driving line L.sub.STD is defined by a virtual line set in the middle of the driving lane in which the vehicle is driving and which is demarcated by a pair of lane markers L.sub.DIF. Further, FIG. 10A illustrates a state in which the vehicle is deflected by the crosswind acting thereon and the actual driving line L.sub.REAL is shifted in the right direction from the standard driving line L.sub.STD curved in the left direction.

[0137] The crosswind-handling steering amount determination portion 162 determines, as the crosswind-handling steering amount , the steering amount of the front wheels 10F required for canceling a deviation of the actual driving line L.sub.REAL from the standard driving line L.sub.STD. The deviation is an amount of shift of the actual driving line L.sub.REAL from the standard driving line L.sub.STD. The process for determining the crosswind-handling steering amount is known in the art, and explanation thereof is dispensed with. In this respect, the deviation of the actual driving line L.sub.REAL from the standard driving line L.sub.STD can be considered as the degree of influence of the disturbance.

[0138] Like the disturbance handling portion 106, the disturbance handling portion 106 includes the brake moment determination portion 150, the adjusting portion 158, and the crosswind-handling wheel braking force determination portion 160. Functions of those portions 150, 158, 160 are the same as those of the disturbance handling portion 106, and explanation thereof is dispensed with. It is noted, however, that the adjustment gain determination portion 156 configured to determine the adjustment gain B used for gradually decreasing the brake counter moment Mb differs in the process for determining the adjustment gain B from the adjustment gain determination portion 156 of the disturbance handling portion 106. The adjustment gain determination portion 156 determines the adjustment gain B referring to map data shown in a graph of FIG. 10B, not based on the yaw rate deviation integral value Yrdt, but based on a lapse of the time t from the time point of the occurrence of the crosswind, namely, from the time point when the yaw rate deviation Yr sent from the disturbance detecting portion 104 is no longer equal to 0. Specifically, the adjustment gain B is determined to be 1 at the time point of the occurrence of the crosswind, and thereafter gradually decreases to 0 with a lapse of the time t. By thus determining the adjustment gain B, the brake counter moment Mb is gradually decreased in the disturbance handling system 100 of the second embodiment as shown in FIG. 7D, as in the disturbance handling system 100 of the first embodiment.

[0139] The disturbance handling portion 106 includes a time counter portion 170 for measuring a lapse of the time t from the time point of the occurrence of the crosswind. The time counter portion 170 measures the time t from the time point when the yaw rate deviation Yr sent from the disturbance detecting portion 104 is no longer equal to 0 and resets the measured time t when the vehicle no longer receives the crosswind to be handled, namely, resets the measured time t when the yaw rate deviation Yr sent from the disturbance detecting portion 104 becomes equal to 0.

[0140] In a case where the steering device 12 steers the front wheels 10F based on the crosswind-handling steering amount determined by the crosswind-handling steering amount determination portion 162, there is a possibility that the front wheels 10F may be abruptly steered. The disturbance handling portion 106 includes a crosswind-handling steering amount limiting portion 172 for limiting the value of the crosswind-handling steering amount so as not to be excessively large. Specifically, when the crosswind-handling steering amount determined by the crosswind-handling steering amount determination portion 162 is larger than a set steering amount .sub.0 that is set at a relatively small value, the crosswind-handling steering amount limiting portion 172 determines the crosswind-handling steering amount to be equal to the set steering amount .sub.0. Though not explained in detail, the crosswind-handling steering amount takes both a positive value and a negative value depending upon the direction of steering. In a strict sense, two values, i.e., a positive value and a negative value, are prepared for the set steering amount .sub.0 in accordance with the positive value and the negative value of the crosswind-handling steering amount . An absolute value of each of the positive value and the negative value of the set steering amount .sub.0 is set at a relatively small value.

[0141] The crosswind-handling steering amount is sent to the steering ECU 42, and the steering device 12 steers the front wheels 10F based on the crosswind-handling steering amount . Owing to provision of the crosswind-handling steering amount limiting portion 172 configured as described above, the front wheels 10F are relatively gently steered for reducing the deflection of the vehicle due to the crosswind. In other words, the automatic steering of the vehicle to handle the crosswind is performed not abruptly but gradually. The steering amount of the wheels 10F is considered as the steering amount that is an amount by which the orientation of the vehicle changes. The disturbance handling portion 106 is configured to limit a change gradient of the steering amount to be not larger than a set gradient. By thus limiting the steering amount and by gradually decreasing the brake counter moment Mb as described above, this configuration enables the handling of the crosswind disturbance to be smoothly shifted from handling by the brake device to handling by the steering device.

[0142] In the crosswind handling by the steering device 12 described above, the standard driving line L.sub.STD is used as an index of the standard running state, and the automatic steering is performed such that the actual driving line L.sub.REAL coincides with the standard driving line L.sub.STD. The crosswind handling by the steering device 12 may be performed otherwise. For instance, a state in which the vehicle does not run off a lane within which the vehicle is to travel may be used as the standard running state, and the automatic steering may be performed by the steering device 12 such that the vehicle does not cross the right-side and left-side lane markers L.sub.DIF. That is, automatic steering similar to that by the LKA control described above may be performed. Because the two sorts of the automatic steering are similar to or the same as the LKA control, the crosswind handling by the steering device 12 may be performed by the steering assist device 90. In this instance, the steering assist ECU 92 constitutes a part of the disturbance handling system 100. Further, the handling of the crosswind by the steering device 12 in the situation in which the LKA control is being executed by the steering assist device 90 may be executed by the LKA control. In other words, there is no need to execute any special control with respect to the crosswind. In this instance, it is desirable that the steering amount be limited, namely, the change gradient of the steering amount be limited, in the LKA control.

[0143] In the disturbance handling system 100, the disturbance handling ECU 102 repeatedly executes a disturbance handling program relying on the standard running state at a short time pitch, e.g., about several to several tens of milliseconds (msec), so that the detecting process for detecting the crosswind and the handling process for handling the crosswind are executed. This program differs from the disturbance handling program (indicated by the flowchart of FIG. 8) executed in the disturbance handling system 100 of the first embodiment in that the program has different steps in place of S10-S16 of the disturbance handling program of the flow chart of FIG. 8. Accordingly, the disturbance handling program relying on the standard running state will be explained focusing on the different steps by referring to a flowchart of FIG. 11 that mainly indicates the different steps of the program.

[0144] In the disturbance handling program relying on the standard running state indicated by the flow chart of FIG. 11, processing similar to the processing of S1-S7 of the disturbance handling program indicated by the flow chart of FIG. 8 is executed. That is, preliminary processing for crosswind detection at S21-S27 is executed. It is subsequently determined at S28 whether the crosswind that should be handled is occurring. When it is determined that the crosswind is occurring, the yaw rate deviation Yr as the parameter indicative of the degree of influence of the crosswind is identified at S29, and S30 and subsequent steps are implemented. On the other hand, when it is determined that the crosswind that should be handled is not occurring, one execution of the program ends without implementing S29 and subsequent steps.

[0145] When the crosswind that should be handled is occurring, it is determined at S30 whether the crosswind occurs for the first time in current execution of the program. In other words, it is determined whether the crosswind has been detected in previous execution of the program. When it is determined that the crosswind occurs for the first time in current execution of the program, a time counter t for indicating a lapse of time from the time point of the occurrence of the crosswind is reset at S31. At S32, the time counter t is incremented by a count-up value t. On the other hand, when it is determined that the crosswind does not occur for the first time in current execution of the program, namely, when it is determined that the crosswind has already occurred in previous execution of the program, the time counter t is not reset but is incremented by the count-up value t at S32. At S33, the adjustment gain B is determined referring to map data shown in FIG. 10B based on the count value of the time counter t. Processing at S34-S36 is similar to the processing of S11, S14, S15 in the disturbance handling program. Thus, a detailed explanation thereof is dispensed with.

[0146] At S37, the actual driving line L.sub.REAL and the standard driving line L.sub.STD as the index of the standard running state are identified based on the front-view image information, the vehicle running speed V, the steering operation angle , the actual yaw rate Yr.sub.SEN, the lateral acceleration Gy, etc., and the crosswind-handling steering amount is determined based on the deviation of the actual driving line L.sub.REAL from the standard driving line L.sub.STD. At S38, it is determined whether the determined crosswind-handling steering amount is larger than the set steering amount .sub.0, namely, whether the absolute value of the determined crosswind-handling steering amount is larger than the set steering amount .sub.0. When the crosswind-handling steering amount is not larger than the set steering amount .sub.0, the crosswind-handling steering amount is output as it is. When the crosswind-handling steering amount is larger than the set steering amount .sub.0, on the other hand, the crosswind-handling steering amount is limited to the set steering amount .sub.0 at S39, and the limited crosswind-handling steering amount is output.

VEHICLE DISTURBANCE HANDLING SYSTEM

Assignee

Inventors

Cpc classification

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B62D6/003

PERFORMING OPERATIONS; TRANSPORTING

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B62D6/04

PERFORMING OPERATIONS; TRANSPORTING

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B60W2510/18

PERFORMING OPERATIONS; TRANSPORTING

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B60T2260/024

PERFORMING OPERATIONS; TRANSPORTING

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B60W2520/14

PERFORMING OPERATIONS; TRANSPORTING

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B60W30/12

PERFORMING OPERATIONS; TRANSPORTING

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B60T2210/22

PERFORMING OPERATIONS; TRANSPORTING

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B60W2555/20

PERFORMING OPERATIONS; TRANSPORTING

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B60T8/17557

PERFORMING OPERATIONS; TRANSPORTING

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B60T2201/089

PERFORMING OPERATIONS; TRANSPORTING

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B60T2201/083

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60W2510/20

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60T2201/087

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60W2420/42

PERFORMING OPERATIONS; TRANSPORTING

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B60W30/08

PERFORMING OPERATIONS; TRANSPORTING

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B60W30/02

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60T2220/03

PERFORMING OPERATIONS; TRANSPORTING

International classification

Classification Explorer

B60W30/02

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B60W30/08

PERFORMING OPERATIONS; TRANSPORTING

Abstract

Claims

Description