JP5527124B2 - Vehicle travel control device - Google Patents

Vehicle travel control device Download PDF

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JP5527124B2
JP5527124B2 JP2010203437A JP2010203437A JP5527124B2 JP 5527124 B2 JP5527124 B2 JP 5527124B2 JP 2010203437 A JP2010203437 A JP 2010203437A JP 2010203437 A JP2010203437 A JP 2010203437A JP 5527124 B2 JP5527124 B2 JP 5527124B2
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steering
vehicle
target
control
trajectory
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JP2012056512A (en
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純郎 山本
武志 後藤
三幸 大内
修司 藤田
洋司 国弘
実栄 増田
恵太郎 仁木
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トヨタ自動車株式会社
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Description

  The present invention relates to a vehicle travel control device, and more particularly to a vehicle travel control device that corrects and controls a steering angle of a steered wheel so that the vehicle travels along a target locus (target travel line).

  Various vehicle travel control devices that control the trajectory of a vehicle so that the vehicle travels along a target trajectory have been proposed. For example, in Patent Document 1 below, a lane tracking is performed in which a target trajectory of a vehicle is set based on road lane information in front of the vehicle, and an automatic steering actuator is controlled so that a deviation between the target trajectory and the forward gaze point of the vehicle is reduced. An apparatus is described.

JP 2001-48035 A JP 2007-269180 A

[Problems to be Solved by the Invention]
According to the lane tracking device described in Patent Document 1, it is possible to prompt the driver to perform a steering operation or to correct the steering angle of the steered wheels by controlling the steering torque so that the vehicle travels along the target locus. it can.

  However, in the lane tracking device described in Patent Document 1, the lane information of the road ahead of the vehicle for setting the target locus of the vehicle and the information of the front gazing point of the vehicle corresponding to the actual locus of the vehicle are acquired. A vehicle information acquisition means such as a camera is essential. Further, since the target trajectory is basically determined based on the lane information, the target trajectory of the vehicle cannot always be set to a trajectory according to the driver's desire. Furthermore, in a situation where there is no lane information on the road ahead of the vehicle or in a situation where lane information cannot be obtained, the target locus cannot be set, and therefore the vehicle cannot travel along the target locus.

  In Patent Document 2, a steering control device that sets a target trajectory of a vehicle based on a steering angle and a vehicle speed and controls the steering transmission ratio variable device so as to reduce a deviation between the target trajectory and the actual trajectory of the vehicle is disclosed. Have been described. According to the steering control device described in Patent Document 2, the steering angle of the steered wheels can be controlled so that the vehicle travels along the target locus.

  However, the steering control device described in Patent Document 2 requires vehicle information acquisition means such as GPS for obtaining the actual locus of the vehicle. In addition, since the steering angle of the steered wheels is feedback controlled based on the deviation between the target locus and the actual locus, the steering angle cannot be controlled unless the actual locus is obtained. Thus, the vehicle cannot preferably travel along the target locus.

  In order to solve the above problem, for example, the target of the steered wheels for causing the vehicle to travel along the target locus necessary for the vehicle to reach the target arrival position in the target traveling direction based on the driver's steering operation amount and the vehicle speed. It is conceivable to calculate the rudder angle and control the rudder angle of the steered wheels based on the target rudder angle. According to the control of the steering angle of the steered wheels, the steered wheels are controlled so that the trajectory of the vehicle becomes a trajectory according to the driver's wishes without requiring acquisition of outside information for obtaining the target trajectory and actual trajectory of the vehicle. The rudder angle can be controlled without delay.

  In the control of the steering angle of the steered wheel, a device for controlling the steered angle of the steered wheel based on the target steered angle, that is, the steered angle of the steered wheel is set to the target steered angle without requiring the driver's steering operation. A device for turning the steered wheels is necessary. However, for example, a semi-steer-by-wire steering device provided with a steering gear ratio variable device (VGRS) that steers the steering wheel relative to the steering input means, or the steering input means and the front wheels are not mechanically connected. Steer-by-wire steering devices are expensive.

  Therefore, in order to drive the vehicle along the target trajectory by controlling the steering angle of the steering wheel, the steering wheel is steered without using an expensive steering device, and the steering angle of the steering wheel is controlled to the target steering angle. It is preferable to obtain.

The present invention has been made in view of the above-described problems in a conventional travel control device that controls the trajectory of a vehicle so that the vehicle travels along a target trajectory. The main problem of the present invention is that the steering wheel is steered using the steering assist force to drive the vehicle along the target trajectory without the need to acquire outside information for obtaining the target trajectory and actual trajectory of the vehicle. It is to let you.
[Means for Solving the Problems and Effects of the Invention]

Major problems described above is applied to a vehicle without a steering angle control means for changing the relationship between the steering angle of the steering wheel to the steering operation by a driver, a steering wheel by the steering assist force of the steering assist force generating means the cruise control apparatus modifiable vehicle steering angle of the steering wheel by turning, when it is determined that the starting condition or update condition is previously set for controlling the trajectory of vehicles is established, in that time A target steering angle of a steered wheel for driving the vehicle along a target locus necessary for the vehicle to reach the target arrival position in the target traveling direction based on the steering operation amount and the vehicle speed of the driver in the vehicle; in the travel control device for a vehicle steering angle of the steering wheel is Gosei power sale by becomes the target steering angle, the target traveling direction is determined based on the steering operation amount of at the driver to the point, the The target arrival position is The angle determined based on the amount of steering operation of the driver is a reference angle, and exists on a straight line drawn in a direction inclined by the reference angle with respect to the vehicle longitudinal direction from the vehicle position at the time point, and The steering wheel is steered by the steering assisting force of the steering assisting force generating means, and the steered angle of the steered wheel becomes the target steered angle by determining the position at a distance depending on the vehicle speed from the position of the vehicle at the time. This is achieved by a vehicle travel control device (structure of claim 1) characterized by controlling the steering assist force of the steering assist force generating means .

  As will be described in detail later, the amount of steering operation by the driver is related to the direction from the current position of the vehicle to the target arrival position with reference to the current traveling direction of the vehicle, and the vehicle speed is from the current position of the vehicle to the target arrival position. Is related to the distance. The driver's steering operation amount is also related to the target traveling direction when the vehicle reaches the target arrival position.

A time point at which it is determined that a preset start condition or update condition for the control of the vehicle trajectory is satisfied is referred to as a reference time point. According to the configuration of the first aspect, the vehicle travels along the target locus for the vehicle to reach the target arrival position in the target traveling direction based on the steering operation amount and the vehicle speed of the driver at the reference time. The target rudder angle of the steered wheel is calculated, and the rudder angle of the steered wheel is controlled based on the target rudder angle. In particular, the target traveling direction is determined based on the driver's steering operation amount at the reference time, and the target arrival position is determined based on the angle determined based on the driver's steering operation amount at the reference time. As a result, it is determined to be a position that lies on a straight line drawn in a direction inclined by a reference angle with respect to the front-rear direction of the vehicle from the position of the vehicle at the reference time point and is a distance depending on the vehicle speed from the vehicle position at the reference time point The

Accordingly, it is not necessary to obtain information on the outside of the vehicle for obtaining the target locus or actual locus of the vehicle, and it is also possible to obtain the actual locus based on the information on the outside of the vehicle based on the deviation between the target locus and the actual locus. It is not necessary to perform feedback control. Therefore, the steering angle of the steered wheels can be controlled without delay so that the vehicle trajectory becomes a trajectory in accordance with the driver's desire, and the vehicle can travel along the target trajectory desired by the driver.
In particular, the target arrival position can be determined based on the driver's steering operation amount and vehicle speed at the reference time, and the target traveling direction can be determined based on the driver's steering operation amount at the reference time. In addition, the angle determined based on the amount of steering operation of the driver at the reference time is set as the reference angle, and a straight line drawn in a direction inclined by the reference angle with respect to the vehicle longitudinal direction from the vehicle position at the reference time. The target arrival position can be determined as a position at a distance that depends on the vehicle speed from the position of the vehicle at the reference time point. Therefore, the target locus of the vehicle for the vehicle to reach the target arrival position in the target traveling direction can be obtained based on the driver's steering operation amount and the vehicle speed at the reference time.

According to the first aspect of the present invention, the travel control device of the present invention is applied to a vehicle that does not include a steering angle control means for changing the steering angle of the steering wheel with respect to the steering operation amount of the driver. The steering assist force of the steering assist force generating means is controlled so that the steering angle becomes the target rudder angle. Therefore, the steering angle of the steered wheels can be controlled to the target steering angle without requiring an expensive steering device such as a semi-steer-by-wire type steering device provided with a steering gear ratio variable device (VGRS).

According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 1, the first steering assist force control amount for reducing the driver's steering burden, The target steering assist force is summed with the second steering assist force control amount for turning the steered wheel to the target rudder angle by turning the steered wheel with the steering assist force of the steering assist force generating means. A control amount is calculated, and the steering assist force of the steering assist force generating means is controlled based on the target steering assist force control amount (configuration of claim 2).

According to the above configuration, the steering wheel is steered by turning the steering wheel with the first steering assist force control amount for reducing the driver's steering burden and the steering assist force of the steering assist force generating means. Is calculated as a target steering assist force control amount, and the steering assist of the steering assist force generating means is calculated based on the target steering assist force control amount. Force is controlled. Therefore, the steering angle of the steered wheels can be controlled to the target steering angle while reducing the driver's steering burden.

  According to the present invention, in order to effectively achieve the main problem described above, the driver's steering burden is detected, and the first steering assist force control amount is at least It is comprised so that it may calculate based on the detected driver | operator's steering burden (structure of Claim 3).

  According to the third aspect of the present invention, the first steering assist force control amount is calculated based on at least the detected driver's steering burden. Therefore, since the change in the driver's steering burden accompanying the control of the steering angle of the steering wheel is reflected in the first steering assist force control amount, the magnitude of the change in the steering transmission ratio is the magnitude of the change rate in the steering operation. Compared to the case where the setting is made regardless, the uncomfortable feeling felt by the driver due to the control of the steering angle of the steered wheels can be reduced.

  Further, according to the present invention, in order to effectively achieve the main problem described above, in the configuration according to any one of claims 1 to 3, the target trajectory is a straight line indicating the target traveling direction. Of the exponential function with the elapsed time from the time point as an index variable in virtual orthogonal coordinates with the perpendicular line drawn from the vehicle position at the time point to the time coordinate axis as the distance coordinate axis. It is comprised so that it may be a curve (structure of Claim 4).

  According to the configuration of the fourth aspect, in a virtual orthogonal coordinate system, a straight line indicating the target traveling direction is a time coordinate axis, and a perpendicular line drawn from the vehicle position at the reference time point to the time coordinate axis is a distance coordinate axis. Thus, the target trajectory can be obtained as an exponential function curve using the elapsed time from the reference time as an exponent variable.

  According to the present invention, in order to effectively achieve the above-described main problems, in the configuration according to any one of claims 1 to 3, the target locus is located at a vehicle position at the time point. In this case, it is configured to be an arcuate curve that is in contact with a straight line indicating the front-rear direction of the vehicle at the time point and in contact with a straight line indicating the target traveling direction at the target arrival position. .

  According to the fifth aspect of the present invention, the vehicle position at the reference time point is in contact with the straight line indicating the front-rear direction of the vehicle at the reference time point, and is in contact with the straight line indicating the target traveling direction at the target arrival position. The target locus can be obtained as an arcuate curve.

Further, according to the present invention, in order to effectively achieve the main problems described above, in the configuration according to any one of claims 1 to 5, the position of the vehicle at the time point and the target arrival position DOO as the direction of the reference line a straight line connecting the configuration of the target traveling direction is configured to be determined in a direction the reference angle inclined with respect to the reference line of the direction at the target position (claim 6 ).

According to the configuration of the sixth aspect , a direction that is inclined by a reference angle with respect to the reference line of the direction at the target arrival position, with the straight line connecting the position of the vehicle and the target arrival position at the reference time point as the reference line of direction. Can be determined in the target traveling direction.

Further, according to the present invention, in order to effectively achieve the above main problem, in the situation where the trajectory is not controlled in the configuration according to any one of claims 1 to 6 , the operation is performed. The change rate of the driver's steering operation amount is greater than the first reference value for determining the start condition, and the change rate of the driver's steering operation amount is used to determine the start condition. When it becomes smaller than the second reference value, it is determined that a start condition for controlling the trajectory is satisfied (configuration of claim 7 ).

  Generally, when the driver changes the course of the vehicle, the steering operation amount is first changed relatively quickly, and then the change in the steering operation amount is moderated. Therefore, it is possible to determine the necessity of starting or updating the control of the vehicle trajectory based on the transition of the change rate of the steering operation amount of the driver.

According to the configuration of the seventh aspect, in the situation where the trajectory control is not performed, the magnitude of the change rate of the steering operation amount of the driver is larger than the first reference value for the control start determination. When it becomes smaller than the second reference value of the control start determination later, it can be determined that the start condition of the trajectory control is satisfied .

According to the present invention, in order to effectively achieve the main problems described above, in the situation where the trajectory is controlled in the configuration according to any one of claims 1 to 6 , the operation is performed. 's steering magnitude of the operation amount of the change rate of the steering operation amount of the rate of change of the driver after becoming larger than the first reference value for determining the updated conditions magnitude for determining the update condition When it becomes smaller than the 2nd standard value, it is constituted so that it may judge with the renewal conditions of the control of the above-mentioned locus being satisfied (the composition of Claim 8 ).

According to the configuration of claim 8, in the situation where the trajectory is controlled, the magnitude of the change rate of the steering operation amount of the driver is larger than the first reference value for the control update determination. When it becomes smaller than the second reference value for the control update determination later, it can be determined that the update control conditions for the trajectory are satisfied .

According to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 4, the distance from the vehicle to the coordinate axis of the time at the time point is used as the reference distance. A target distance is obtained as a product of a reference distance and a natural exponential function having an elapsed time from the time point as an index variable, and the target locus is obtained as a line connecting the position of the target distance from the coordinate axis of the time. (Structure of claim 9 ).

According to the configuration of claim 9, the target distance is obtained as a product of the reference distance and a natural exponential function having an elapsed time from the reference time as an index variable, and the target distance is obtained as a line connecting the position of the target distance from the time coordinate axis The trajectory can be obtained.

Further, according to the present invention, in order to effectively achieve the above main problem, in the configuration of claim 9 described above, the human visual information outside the vehicle related to the necessity of the steering operation has occurred. Is a general time required to perceive the change of the visual information is ΔT, a Weber ratio is −k, an elapsed time from the time is t, and the natural exponential function is − (k / ΔT) configured to be the t (structure of claim 1 0).

According to this configuration 1 0, the exponent of the natural exponential function - because it is (k / ΔT) t, it obtains a target distance of the vehicle to suit the perception characteristics of the human, thereby matching the perceptual characteristics of the human The target trajectory of the vehicle can be obtained.
[Preferred embodiment of problem solving means]

According to one preferred embodiment of the present invention, in the any one of the foregoing aspect 1 1 0, the steering assist force generation means is a steering assist torque generating apparatus, rolling the steered wheels by the steering assist torque It is comprised so that it may steer (the preferable aspect 1).

According to the aspect of the present invention, in the any one of the foregoing aspect 3 to 1 0, the steering assist force generation means is a steering assist torque generating apparatus, the steering load of the driver It is comprised so that it may be a steering torque (Preferable aspect 2).

According to another preferred embodiment of the present invention, in the configuration according to any one of the first to fifth aspects, the travel control device includes a driver's steering operation amount and vehicle speed and a target steering angle of the steered wheel. stores the relationship, configured to calculate a target steering angle of the steering wheel from the relationship on the basis of the steering operation amount and vehicle speed at a driver when the conditions for starting the control of the trajectory of the vehicle is determined to have satisfied (Preferred embodiment 3).

According to the aspect of the present invention, in the configuration of the fourth aspect, the traveling control unit steering the elapsed time and the driver from the time of determination start condition of the control of the trajectory of the vehicle is satisfied operation amount and the vehicle speed and stores the relationship between the target steering angle of the steering wheel, the conditions for starting the elapsed time and control the path of the vehicle from the time when the conditions for starting the control of the trajectory of the vehicle is determined to have satisfied satisfied configured to calculate a target steering angle of the steering wheel from the relationship on the basis of the time of the determination were as on the steering operation amount and vehicle speed at a driver (preferred embodiment 4).

According to another preferred aspect of the present invention, in the configuration of claim 5, the travel control device stores the relationship between the driver's steering operation amount and the vehicle speed and the target steering angle of the steered wheels. , the steering operation amount and vehicle speed at a driver when the start condition of the control is judged to be satisfied in the path of the vehicle regardless of the elapsed time from when the start condition is determined to have satisfied the control of the trajectory of the vehicle Based on the above relationship, the target steering angle of the steered wheels is calculated (preferred aspect 5).

1 is a schematic configuration diagram showing a first embodiment of a travel control device for a vehicle according to the present invention applied to a vehicle equipped with an electric power steering device. It is a flowchart which shows the main routine of the traveling control in 1st embodiment. It is a flowchart which shows the establishment determination routine of the start condition of locus | trajectory control in 1st embodiment. It is a flowchart which shows the establishment determination routine of the update conditions of locus | trajectory control in 1st embodiment. It is a flowchart which shows the routine of steering burden reduction control and locus | trajectory control in 1st embodiment. It is a graph which shows the relationship between steering torque Thd and basic assist torque Tpab. It is a graph which shows the relationship between the vehicle speed V and the vehicle speed coefficient Kv. It is a graph which shows the relationship among steering torque Thd, vehicle speed V, and target assist torque Tat. It is a flowchart which shows the main routine of the traveling control in 2nd embodiment. It is a flowchart which shows the routine of steering burden reduction control and locus | trajectory control in 2nd embodiment. It is a flowchart which shows the main routine of the traveling control in 3rd embodiment. It is a flowchart which shows the target steering angle calculation routine of the front wheel in 3rd embodiment. It is a flowchart which shows the routine of steering burden reduction control and locus | trajectory control in 3rd embodiment. It is a flowchart which shows the main routine of the traveling control in 4th embodiment. It is a flowchart which shows the routine of steering burden reduction control and locus | trajectory control in 4th embodiment. It is explanatory drawing which shows the case where the vehicle of a two-wheel model changes a course. It is explanatory drawing which shows the case where a vehicle carries out a regular circle | round | yen and draws an arc-shaped locus | trajectory. It is explanatory drawing which shows the circular-arc-shaped locus | trajectory of the vehicle by steady circle turning about the case where the rudder angle of a front wheel is a rudder angle corrected based on the rudder angle and guide rod model corresponding to a driver | operator's steering operation amount. Explanatory diagram showing a minimum amount Δx ″ that allows a person to perceive a change in the horizontal acceleration x ″ and a minimum time ΔT required for a person to perceive a change in the minimum amount minimum amount Δx ″ in a situation where the horizontal acceleration x ″ changes. It is. It is explanatory drawing which shows the case where a vehicle travels by drawing the locus | trajectory of an exponential function from the reference position of a guide rod to the front-end | tip position of a guide rod. FIG. 5 is an explanatory diagram showing a situation in which the vehicle moves to a position between the reference position of the guide rod and the tip position of the guide rod when the vehicle travels while drawing an exponential function locus. It is explanatory drawing which shows decomposition | disassembly of the vehicle speed into the component parallel to the coordinate axis regarding distance, and the coordinate axis regarding time about the condition shown by FIG.

General Description of Embodiments Prior to the description of specific embodiments, technical matters common to the embodiments will be described generally.
1) Guide rod model

  Since the driver's intention regarding the vehicle trajectory is considered to be reflected in the driver's steering operation amount, the direction of the front wheel that is the steering wheel, that is, the steering angle of the front wheel is considered to be the driver's forward gaze direction. May be. Therefore, a virtual vehicle having a virtual guide rod installed on the front wheel is defined, and it is assumed that the driver is driving the vehicle so that the tip of the guide rod moves along a desired locus. In that case, it is considered that the forward gaze distance, that is, the distance from the vehicle to the position where the driver gazes corresponds to the length of the guide rod and changes according to the vehicle speed.

  In the present specification, a vehicle model provided with the above-described virtual guide rod is referred to as a “guide rod model”. According to the guide rod model, a preferable target trajectory of the vehicle can be set as a trajectory passing through the tip of the guide rod based on the driver's steering operation amount and vehicle speed when the driver tries to change the course of the vehicle. it can.

  Therefore, by controlling the rudder angle of the front wheels so that the vehicle travels along the set target trajectory, the vehicle surrounding information is not required to be acquired by photographing or communicating from outside the vehicle. Can be driven along a preferable target locus.

  In order to facilitate understanding of the vehicle trajectory control based on the guide rod model, it is assumed that the vehicle is a two-wheel model vehicle 104 including a front wheel 100 and a rear wheel 102 as shown in FIG. Consider a case where the vehicle 104 changes its course to a target course 108 that is inclined by an angle φ with respect to a line 106 indicating the front-rear direction. The unit of angle is rad.

  As shown in the figure, it is assumed that a virtual guide rod 110 protrudes from the center O of the front wheel 100 to a point P on the target course 108 along the front-rear direction of the front wheel in the front-rear direction of the vehicle. Let the inclination angle be β. The length of the guide rod 110, that is, the length of the line segment OP is A, and the angle formed by the target course 108 and the guide rod 110 is α. The distance from the center O of the front wheel 100 to the target course 108 is x, and the steering angle of the front wheel 100 is δ (δ = β). Further, the wheel base of the vehicle 104 is WB, and the vehicle speed is V. The unit of length is m, and the unit of time is sec.

  When the minute time dt elapses without the steering angle δ and the vehicle speed V changing, the vehicle 104 moves from the position indicated by the solid line to the position indicated by the broken line, and the accompanying angle φ and distance x The following formulas 1 to 4 are established, where dφ and distance dx are respectively changed. Since the minute time dt is very small, it is considered that the front wheel 100 moves to a point on the guide rod 110 and the rear wheel 102 moves to a point on the line 106 indicating the front-rear direction of the vehicle before movement as shown in the figure. Good.

β = φ-α (1)
x = A * sinα (2)
-WBdφ = Vdt * sinβ (3)
-Dx = Vdt * sinα (4)

Differentiating Equation 2 by α yields Equation 5 below, so dx is expressed by Equation 6 below.
dx / dα = A * cosα (5)
dx = A * cosα * dα (6)

By substituting Equation 6 into Equation 4 above, the following Equation 7 is obtained, so that the length A of the guide rod is expressed by Equation 8 below.
-A * cosα * dα = Vdt * sinα (7)
A =-(Vdt * sinα) / (cosα * dα)
=-(Vdt * tanα) / dα
= −Vdt * {1 / (cosα) 2 } (8)

Further, when Equation 3 is solved for Vdt, the following Equation 9 is obtained, and when Equation 9 is substituted into Equation 8, the following Equation 10 is obtained.
Vdt = (− WBdφ) / sinβ (9)
A = − (− WBdφ) / sinβ * {1 / (cosα) 2 } (10)

Non-straight running of the vehicle such as turning can be considered as a combination of steady circular running, and when the locus is an arc, the angles α and β are the same. Β is the same as the steering angle δ of the front wheels. Therefore, the length A of the guide rod can be expressed by Equation 11 by rewriting the angles α and β in Equation 10 to the steering angle δ.
A = (WBdφ) / sinδ * {1 / (cosδ) 2 } (11)

In equation 11, dφ is the yaw rate YR of the vehicle, and the yaw rate YR is expressed by equation 12 below.
YR = V / WB * δ (12)

Therefore, the length A of the guide rod can be expressed by Expression 13 by substituting Expression 12 into dφ of Expression 11.
A = WB (V / WB * δ) / sinδ * {1 / (cosδ) 2 }
= (V * δ) / sinδ * {1 / (cosδ) 2 } (13)

  If the sign of the steering angle δ differs depending on whether the turning direction of the vehicle is a left turn or a right turn, if the sign of the steering angle δ is reversed by reversing the turning direction of the vehicle, the sign of sin δ is also the same. Therefore, the length A of the guide rod is always a positive value.

  In the above description, the guide rod model has been described on the assumption that the guide rod 110 has the center O of the front wheel 100 as a reference position and protrudes forward from the reference position along the front-rear direction of the front wheel. However, since it is preferable to consider the vehicle trajectory as the trajectory of the center of gravity of the vehicle, in the following description, the guide rod has the center of gravity of the vehicle as a reference position and the front of the vehicle along the front-rear direction of the front wheel from the reference position. Suppose that

2) Arc-shaped locus As shown in FIG. 19, the steering angle δ and the vehicle speed V of the front wheels are set to constant values, and the vehicle 104 turns in a steady circle, and the arc shape extends from the position P0 to the position P1. Let us consider a case where the vehicle travels while drawing its trajectory Tc. In this case, the line segment corresponding to the guide rod when the center of gravity of the vehicle 104 is at the position P0 extends from the reference point P0 to the tip P1.

Since the motion of the vehicle 104 is a steady circular turning motion, the yaw rate YR of the vehicle is expressed by the above formula 12, and the lateral acceleration LA of the vehicle is expressed by the following formula 14.
LA = YR * V (14)

Therefore, the radius R of the arcuate trajectory Tc is expressed by the following Expression 15.
R = V 2 / LA
= V 2 / (YR * V)
= V / YR
= V / (V / WB * δ)
= WB / δ (15)

  Further, as shown in FIG. 19, a line 106 indicating the front-rear direction of the vehicle 104 and a line 108 indicating the target course are tangent lines that touch the arcuate trajectory Tc at positions P0 and P1, respectively. Let Q1 be the intersection of the lines 106 and 108, and let Q2 be the foot of the perpendicular line that descends from the center Oc of the arc-shaped locus Tc to the guide rod 110. Since the triangle P0OcP1 is an isosceles triangle having the center Oc as a vertex, the angle P0OcQ2 and the angle P1OcQ2 are equal to each other, and these are γ. Also, the angle OcP0Q2 and the angle OcP1Q2 are equal to each other, and these are λ.

As understood from FIG. 19, the following equations 16 and 17 hold. Thus, the angle γ is the same as the angles α and δ.
α + λ = δ + λ = π / 2 (16)
γ + λ = π / 2 (17)

As can be seen from FIG. 19, the length A0 of the line segment corresponding to the guide rod is twice the line segment P0Q2, and the length of the line segment P0Q2 is R * sinγ = R * sinδ. Therefore, the length A0 of the line segment corresponding to the guide rod is expressed by Equation 18.
A0 = 2R * sinδ
= 2 (WB / δ) * sinδ (18)

  The length A0 of the line segment corresponding to the guide rod expressed by Equation 18 does not include the vehicle speed V and does not depend on the vehicle speed V. From the comparison between the length A0 of this line segment and the length A of the guide rod represented by Equation 13, if the rudder angle δ of the front wheel is not corrected, it follows an arcuate path passing through the tip of the guide rod 110. It can be seen that the vehicle cannot be driven. In other words, in order to set the length A0 of the line segment to the same value as the length A of the guide rod represented by Expression 13, the steering angle determined by the driver's steering operation amount and the steering gear ratio (“originally The steering angle of the front wheels must be corrected to a value different from δ).

  As shown in FIG. 20, when the rudder angle of the front wheels is modified from the original rudder angle δ to the modified rudder angle δ ′, the vehicle 104 has an arcuate trajectory Tc passing through the tip P1 ′ of the guide rod 110. Suppose that it can drive along '. Further, it is assumed that the center and radius of the arc-shaped locus Tc ′ are Oc ′ and R ′, respectively.

The radius R ′ is expressed by the following equation 19 corresponding to the above equation 15.
R ′ = WB / δ ′ (19)

Since the triangle P0P1Oc and the triangle P0P1'Oc 'are similar, the following equation 20 holds.
R / R '= A0 / A (20)

Substituting the above equation 13 and the above equations 15, 18, and 19 in which δ is rewritten into δ ′ into this equation 20, the following equation 21 is obtained.
δ ′ / δ = 2WB * sinδ ′ * sinδ * (cosδ ′) 2 / (V * δ ′ * δ)
(21)

When the steering angle δ of the front wheel and the corrected steering angle δ ′ are small values, sin δ and sin δ ′ may be regarded as δ and δ ′, respectively, and cos δ ′ is regarded as 1. Good. Therefore, the rudder angle δ ′ after correction is expressed by the following formula 22 obtained by modifying the above formula 21.
δ ′ = (2WB / V) * δ (22)

Assuming that the steering angle as the amount of steering operation of the driver is θ and the steering gear ratio is N, the original steering angle δ of the front wheels is expressed by the following Expression 23.
δ = θ / N (23)

Therefore, the corrected steering angle δ ′ is expressed by the following Expression 24.
δ ′ = (2WB / V) * θ / N (24)

Further, Ta is the time required for the vehicle to travel along the arcuate trajectory Tc 'from the position P0 to the position P1' in a state where the steering angle and the vehicle speed of the front wheels are maintained at constant δ 'and V, respectively. The time Ta is a time required for the circular motion at the yaw rate YR expressed by the equation 25 along the fan-shaped circular arc having the central angle 2γ = 2δ and the radius R ′. Therefore, the time Ta is 1 [sec] as represented by the equation 26, and does not depend on the vehicle speed V.
YR = V / WB * δ ′ (25)
Ta = 2δ / YR
= 2WB * δ / (V * δ ′)
= 2WB * δ / {V * (2WB / V) * δ}
= 1 (26)

  Therefore, in a situation where the original steering angle of the front wheels is δ, by controlling the steering angle of the front wheels by maintaining the vehicle speed V at a constant value and setting the target steering angle δat to the corrected steering angle δ ′. The vehicle can travel along an arcuate trajectory Tc ′ passing through the tip P1 ′ of the guide rod 110. Regardless of the value of the vehicle speed V, the vehicle passes the position P1 'when the time Ta = 1 [sec] has elapsed.

3) Exponential function locus From the above equation 2, the following equation 27 holds. However, from Equation 1, α = φ−β.
x ′ = − V * sin α (27)

From the above equations 2 and 27, the following equation 28 is established, and the equation 28 indicates that the distance x is a variable that changes according to the Weber rule.
x '=-(V / A) x (28)

Solving Equation 28 yields Equation 29. Therefore, by controlling the distance x so as to change according to the equation 29, the distance x can be controlled according to the Weber rule. X 0 is the value of the distance x when the time t is 0.
x = x 0 * exp {-(V / A) * t} (29)

Next, let us consider adapting the control of the distance x based on the above equation 29 to human perceptual characteristics. As shown in FIG. 21, when the horizontal acceleration x ″ of the vehicle, which is a differential value of the distance x twice, increases, the minimum amount that a person can perceive the change in the horizontal acceleration x ″ is Δx ″. The minimum time required for a person to perceive the change Δx ″ of the horizontal acceleration x ″ is ΔT. The minimum amount Δx ″ is expressed by the following equation 30 where the rate of change of the horizontal acceleration x ″ is x ″ ′.
Δx ″ = x ″ ′ * ΔT (30)

As can be seen from FIG. 21, the rate of change x ″ ′ of the horizontal acceleration x ″ is expressed by the following equation 31.
x ″ ′ = {(x ″ + Δx ″) − x ″} / {(T + ΔT) −T}
= Δx ″ / ΔT (31)

Since the following equation 32 is obtained by differentiating the equation 28 twice, the following equation 33 is established.
x ″ ′ = − (V / A) * x ″ (32)
x ″ ′ / x ″ = − (V / A) (33)

By substituting the equation 31 into the equation 33 and modifying it, the following equation 34 is obtained.
Δx ″ / x ″ = − (V / A) * ΔT (34)

Since the above equation 34 is an equation forming the Weber ratio, the above equation 34 can be rewritten as the following equation 35 with the Weber ratio being −k. However, k is a positive value represented by Expression 36.
Δx ″ / x ″ = − k (35)
k = (V / A) * ΔT (36)

  The minimum time ΔT is a value with individual differences, but the minimum time ΔT is an average constant value, and the Weber ratio −k is also a constant value.

The above equation 35 is modified as shown in the following equation 37, and the equation 37 is substituted into the above equation 30 and modified to obtain the following equation 38. Then, by solving the following equation 38, the following equation 39 is obtained.
Δx ″ = − k * x ″ (37)
x ″ ′ * ΔT = −k * x ″ (38)
x = x 0 * exp {− (k / ΔT) * t} (39)

  The above equations 29 and 39 both indicate that the distance x is an exponential function of the time t. According to the equation 39, the Weber ratio that does not depend on the vehicle speed V for the distance x, and hence the trajectory of the preferred exponential function of the vehicle. k and the minimum time ΔT.

Therefore, by controlling the vehicle trajectory using the above equation 39, the following advantages can be obtained as compared with the case where the vehicle locus is controlled using the above equation 29 depending on the vehicle speed V.
(1) Since the above equation 39 does not include the vehicle speed V, the amount of calculation can be reduced and the control can be simplified.
(2) The trajectory of the vehicle can be controlled to a preferable exponential function trajectory adapted to human perceptual characteristics.

  As can be understood from the above description, by controlling the vehicle trajectory by controlling the distance x according to Equation 39, the trajectory of the vehicle can be made an exponential function trajectory that is more favorable for human perception characteristics than an arc-shaped trajectory. it can.

  However, even if the trajectory of the vehicle is set as an exponential trajectory according to the above equation 39, if the time Tb required for the vehicle to reach the position P1 ′ is the same as the time Ta when the trajectory of the vehicle is an arc-shaped trajectory. Is not limited.

Therefore, the above equation 39 is rewritten as the following equation 40, where D is a correction coefficient for setting the time Tb to the same value as the time Ta.
x = x 0 * exp {− (k / ΔT) D * t} (40)

In order to set the time Tb required for the vehicle to reach the position P1 'as the time Ta, the distance x can be changed to xb when the time t is Ta in Equation 40, with xb being a positive constant close to 0. Therefore, the following equation 41 should be satisfied. Since Ta is 1 [sec], when equation 41 is solved for correction coefficient D, equation 42 is obtained.
xb = x 0 * exp {- (k / ΔT) D * Ta} ...... (41)
D = − (log e xb−log e x 0 ) * ΔT / (k * Ta)
=-(Log e xb-log e x 0 ) * ΔT / k (42)

  As shown in FIG. 22, by controlling the steering angle δ of the front wheels so that the distance x changes in accordance with the above equation 40, an index from the reference position P0 of the guide rod to the tip position P1 ′ of the guide rod is an index. Consider a case where the vehicle travels while drawing a function locus Te.

  Assume that the perpendicular foot drawn from the reference position P0 of the guide rod to the line 108 indicating the target course is the intersection point Q3. The exponential function represented by the above equation 40 is an orthogonal function in which the line 108 indicating the target course is a coordinate axis related to time, the line 106 indicating the longitudinal direction of the vehicle 104 is the coordinate axis related to the distance x, and the intersection Q3 is the origin. It is a function.

Assuming that the distance between the position P1 and the intersection point Q3 and the distance between the position P0 and the position intersection point Q3 are B and C, respectively, the distances B and C are expressed by the following equations 43 and 44, respectively.
B = A * cosδ (43)
C = A * sinδ
= 2R '* sinδ * sinδ
= 2 (WB / δ ′) * (sinδ) 2 (44)

When the steering angle δ is small, it may be considered that sin δ is equal to δ. Therefore, the distance C is expressed by the following equation 45 by substituting the equation 22 into the equation 44 and setting sin δ = δ. The distance C is a value x 0 of the distance x when the time t is 0, is a positive value. Thus, it is possible to obtain the distance x 0 by Equation 46 below corresponding to formula 45.
C = (V / δ) * δ 2
= V * δ (45)
x 0 = V * | δ | (46)

Thus calculated correction coefficient D and the distance x 0 by the respective formulas 42 and 46, by controlling the distance x according to equation 40, the time Ta = 1 arrives at the vehicle substantially located P1 'when [sec] has elapsed Thus, the vehicle can travel along the locus Te of the exponential function.

  Next, the control of the steering angle of the front wheels for controlling the vehicle trajectory to a preferable exponential trajectory Te by changing the distance x according to the above equations 40, 42 and 46 will be described.

First, the steering angle δ and the vehicle speed V of the front wheel are set to a constant δ ′ and a constant value, respectively, and the vehicle draws an arc-shaped trajectory Tc ′ from the guide rod reference position P0 to the guide rod tip position P1 ′. Consider the lateral acceleration LAa of the vehicle when traveling. If the slip angle of the vehicle is 0, the lateral acceleration LAa of the vehicle is equal to the product of the yaw rate YR and the vehicle speed V expressed by Equation 25, and is a value obtained by Equation 47 below.
LAa = YR * V
= V / WB * δ '* V
= V 2 / WB * δ ′
= V 2 / WB * (2WB / V) * θ / N
= 2V * θ / N (47)

  Further, when the vehicle speed V is set to a constant value and the steering angle δ of the front wheels is variably controlled to δb, the vehicle is expressed by the above equation 40 from the reference position P0 of the guide rod to the tip position P1 ′ of the guide rod. Consider the lateral acceleration LAb of the vehicle when traveling along an exponential function locus Te.

As shown in FIGS. 23 and 24, in the situation where the vehicle has moved to the position P3 between the reference position P0 and the tip position P1 ′, the vehicle speed V is converted into the component Vx parallel to the coordinate axis related to the distance x and the coordinate axis related to time. 48, the following equation 48 is established.
V = (Vx 2 + Vy 2 ) 1/2 (48)

Since the component Vx parallel to the coordinate axis with respect to the distance x is equal to the change rate of the distance expressed by the equation 40, the component Vx can be obtained by the following equation 49.
Vx = dx / dt
= | D [x 0 * exp {-(k / ΔT) D * t}] / dt
= | -V * δ * (k / ΔT * D) * exp {-(k / ΔT) D * t} | (49)

From Expression 48 and Expression 49, it can be seen that a component Vy parallel to the coordinate axis with respect to time can be obtained by Expression 50 below.
Vy = (V 2 −Vx 2 ) 1/2 (50)

As shown in FIG. 24, the angle formed by the line 106 indicating the longitudinal direction of the vehicle with respect to the line 112 parallel to the coordinate axis related to the distance x, that is, the angle formed by the component Vx parallel to the coordinate axis related to the distance x with respect to the vehicle speed V. It is assumed that σ. If the slip angle of the vehicle is 0, the following equation 51 is established. Therefore, the angle σ is expressed by the following formula 52.
tanσ = Vy / Vx (51)
σ = tan −1 (Vy / Vx) (52)

The vehicle lateral component of the component Vx parallel to the coordinate axis with respect to the distance x is defined as Vxx, and the vehicle lateral component of the component Vy parallel to the coordinate axis with respect to time is defined as Vyx. The components Vxx and Vyx in the lateral direction of the vehicle are expressed by equations 53 and 54, respectively.
Vxx = Vx * sinσ (53)
Vyx = Vy * cosσ (54)

Therefore, the lateral speed Vz of the vehicle when the vehicle travels along an exponential function locus Te is expressed by the following equation 55, and the lateral acceleration LAb of the vehicle is expressed by the following equation 56.
Vz = Vyx-Vxx
= Vy * cosσ-Vx * sinσ (55)
LAb = d (Vz) / dt (56)

A deviation ΔLA between the lateral acceleration LAb of the vehicle when the vehicle travels along an exponential locus Te and the lateral acceleration LAa of the vehicle when the vehicle travels along an arcuate locus Tc is expressed by Expression 57. .
ΔLA = LAb−LAa (57)

The yaw rate YR of the vehicle is a value obtained by replacing δ ′ in Equation 25 with δb, and is a value obtained by dividing the lateral acceleration LAb of the vehicle by the vehicle speed V, so Equation 58 is established.
V / WB * δb = LAb / V (58)

Therefore, the steering angle δb of the front wheel for driving the vehicle so as to draw the locus Te of the exponential function is obtained by the following equation 59.
δb = (LAb / V) / (V / WB)
= (WB / V 2 ) * LAb (59)

Necessary for driving the vehicle to draw an exponential function locus Te on the basis of the steering angle δa of the front wheels (target steering angle δat = δ ′) for running the vehicle so as to draw an arc-shaped locus Tc ′. Let Δδb be the amount of correction of the steering angle of the front wheels. The correction amount Δδb of the front wheel rudder angle is obtained by the following equation 60 when turning left, and is obtained by equation 61 below when turning left.
Δδb = (WB / V 2 ) * ΔLA (60)
Δδb = − (WB / V 2 ) * ΔLA (61)

The steering angle δa of the front wheels for driving the vehicle so as to draw an arcuate trajectory Tc ′ is the corrected steering angle δ ′ represented by Expression 24. Therefore, the target rudder angle δbt of the front wheels for driving the vehicle so as to draw the locus Te of the exponential function is obtained by the following equation 62 when turning left and by the following equation 63 when turning right.
δbt = δ ′ + Δδb
= (2WB / V) * θ / N + (WB / V 2 ) * ΔLA (62)
δbt = δ ′ + Δδb
= (2WB / V) * θ / N- (WB / V 2 ) * ΔLA (63)

4) Control method of front wheel rudder angle As will be understood from the above description, by controlling the rudder angle δ ′ of the front wheel with the rudder angle δ ′ represented by Expression 24 as the target rudder angle δat, the arcuate locus Tc ′ is obtained. The vehicle can be driven to draw. In addition, by controlling the rudder angle δ of the front wheels so that the target rudder angle δbt obtained by the equation 62 or 63 is obtained, the vehicle can be driven to draw an exponential function locus Te.

  In both cases where the front wheel target rudder angle is δat and δbt, as a method of controlling the front wheel rudder angle δ to the target rudder angle, both feedforward control and feedback control are possible, Each has its advantages.

  The feedforward control calculates the target rudder angle when it is determined that the trajectory control should be started (at the start of control), and the rudder angle of the front wheels may be largely changed by the driver's steering operation after the control is started. On the assumption that there is no such thing, the steering angle of the front wheels is controlled to the target steering angle.

  In the case of feedforward control, the vehicle trajectory can be made the target trajectory without the driver performing a steering operation, so this control is more proficient in vehicle driving than a driver with a high level of vehicle driving proficiency. This control is suitable for low-level drivers.

  On the other hand, the feedback control calculates the target rudder angle at the start of control and assumes that the rudder angle of the front wheels may be changed by the steering operation of the driver after the start of control. The steering angle of the front wheels is controlled to the target steering angle by reducing the deviation from the angle.

  In the case of feedback control, the vehicle trajectory can be made the target trajectory even if the driver performs a steering operation, so this control has a vehicle driving proficiency level that is lower than that of a driver who has a low level of vehicle driving proficiency. This control is suitable for high drivers.

  It should be noted that the target trajectory is updated when a preset trajectory control update condition is satisfied, regardless of whether feed-forward control or feedback control is used to control the steering angle δ of the front wheels to the target rudder angle. Thus, the trajectory control is updated.

5) Front wheel rudder angle control device In order to control the trajectory of the vehicle to the target trajectory, a rudder angle control device that can control the rudder angle of the front wheel to the target rudder angle by turning the front wheel is required. It is.

  As such a steering angle control device, a steering input means such as a steering wheel and a front wheel are mechanically connected, a mechanical steering angle control device that steers the steering wheel relative to the steering input means, a steering input means, and a front wheel And a non-mechanical steering angle control device that is not mechanically connected to each other. The former includes, for example, a semi-steer-by-wire type steering device including a steering gear ratio variable device (VGRS), and the latter includes, for example, a steer-by-wire type steering device.

  However, any of the above steering angle control devices has a more complicated structure or control than a general mechanical steering angle control device in which the steered wheels are not steered relative to the steering input means, and avoids cost increase. I can't. Therefore, in the present invention, in a vehicle equipped with a general mechanical rudder angle control device, the front wheels, which are steered wheels, are steered using a steering assist force (assist torque), and the rudder angle is Controlled to the target rudder angle.

6) Classification of trajectory control and embodiments As will be understood from the above description, whether the trajectory is an arc or an exponential function, and whether the rudder angle control is feedforward (FF) control or feedback (FB) The trajectory control according to the present invention can be classified into controls 1 to 4 depending on whether it is a control.

  The following first to fourth embodiments are classified as shown in Table 1 below according to the classification items.

  In any of the first to fourth embodiments described later, the trajectory control is not started when the traveling control of another vehicle such as the anti-skid control is being executed. Further, when the start condition of the travel control of other vehicles such as the anti-skid control is satisfied in the situation where the trajectory control is being executed, the trajectory control is ended and the travel control of the other vehicle is started.

7) Control of assist torque
7-1) Relationship with Power Assist In general, in a vehicle such as an automobile, steering torque is reduced by power assist in order to reduce a driver's steering burden. The target value of the steering torque that is reduced by the power assist, that is, the target assist torque is Tat, and the target driving torque for turning the front wheels and controlling the steering angle to the target steering angle is Tst. The final target assist torque Tast is set to the sum of Tat and Tst.

7-2) Target driving torque When the target steering angle (δat or δbt) of the front wheels is δt and the target curvature of the trajectory for making the vehicle trajectory a target trajectory is ρt, the target curvature ρt of the trajectory is expressed by the following equation 64: It is represented by
ρt = δt / WB (64)

If the sum of the front wheel caster rail and the pneumatic trail is Lt [m] and the cornering power of the front wheel is Kf [Nm / rad], the kingpin shaft of the front wheel when the rudder angle is the target rudder angle δt [rad] The surrounding torque Tk is expressed by the following Expression 65.
Tk = -2Lt * Kf * δt (65)

The torque required for the steering wheel as the steering input means for generating the torque Tk, that is, the target drive torque Tst is expressed by the following equation 66 using the steering gear ratio N.
Tst = Tk / N
= -2Lt * Kf * δt / N (66)

7-3) When the target trajectory of the feedforward controlled vehicle is an arc-shaped trajectory, the target rudder angle δt is set to δat. When the target trajectory of the vehicle is an exponential function trajectory, the target rudder angle δt becomes δbt. Is set. Further, the change amount Δδt of the target rudder angle Δt for each cycle is calculated as a deviation between the target rudder angle Δt for the current cycle and the target rudder angle Δt for the previous cycle. Then, the target drive torque correction amount ΔTst is calculated according to the following equation 67 corresponding to equation 66.
ΔTst = −2Lt * Kf * Δδt / N (67)

  The final target assist torque Tast is set to the sum of the target assist torque Tat for reducing the driver's steering burden and the target drive torque correction amount ΔTst, and the assist torque becomes the final target assist torque Tast. Feedback controlled.

7-4) When the target locus of the feedback controlled vehicle is an arc-like locus, the target rudder angle δt is set to δat, and a deviation Δδat between the target rudder angle δat and the estimated rudder angle δ of the front wheels is calculated. . Then, a target drive torque correction amount ΔTst is calculated according to the following equation 68 corresponding to equation 66.
ΔTst = −2Lt * Kf * Δδat / N (68)

When the target locus of the vehicle is an exponential locus, the target steering angle δt is set to δbt, and a deviation Δδbt between the target steering angle δbt and the estimated steering angle δ of the front wheels is calculated. Then, a target drive torque correction amount ΔTst is calculated according to the following equation 69 corresponding to equation 66.
ΔTst = −2Lt * Kf * Δδbt / N (69)

  Regardless of the target locus, the final target assist torque Tast is set to the sum of the target assist torque Tat for reducing the driver's steering burden and the target drive torque correction amount ΔTst. Further, feedback control is performed so that the assist torque becomes the final target assist torque Tast.

  When the front wheels are steered by controlling the assist torque to be the final target assist torque Tast so as to control the rudder angle of the front wheels to the target rudder angle, the steering torque is caused by the steering of the front wheels. Fluctuates. However, since the change in the steering torque is reflected in the target assist torque Tat, the driver does not feel a large change in the steering torque due to the correction of the steering angle of the front wheels by the control of the assist torque.

  Next, the first to fourth embodiments of the present invention will be sequentially described with reference to the accompanying drawings.

First Embodiment As shown in Table 1 above, the target locus of this first embodiment is an arcuate locus, and the steering angle control is feedforward control.

  FIG. 1 is a schematic configuration diagram showing a first embodiment of a vehicle travel control device according to the present invention applied to a vehicle equipped with an electric power steering device.

  In FIG. 1, the code | symbol 10 has shown the whole traveling control apparatus of 1st embodiment of this invention. The travel control device 10 is mounted on a vehicle 12 and includes a rack and pinion type electric power steering device 14 and an electronic control device 16 for controlling the power steering device 14. In FIG. 1, 18FL and 18FR indicate the left and right front wheels of the vehicle 12, respectively, and 18RL and 18RR indicate the left and right rear wheels, respectively. The left and right front wheels 18FL and 18FR are steered wheels, and are steered via a rack bar 24 and tie rods 26L and 26R by a power steering device 14 driven in response to a steering operation of the steering wheel 20 by a driver.

  The steering wheel 20 functions as a steering input means, and is drivingly connected to the pinion shaft 34 of the power steering apparatus 14 via the steering shaft 28 and the universal joint 32.

  In the illustrated embodiment, the electric power steering device 14 is a rack coaxial type electric power steering device, and converts the electric motor 38 and the rotational torque of the electric motor 38 into a force in the reciprocating direction of the rack bar 24. For example, a ball screw type conversion mechanism 40 is included. The electric power steering device 14 is controlled by an electronic control device 16. The electric power steering device 14 functions as an auxiliary steering force generator that reduces the driver's steering burden by driving the rack bar 24 relative to the housing 42, and also rotates the left and right front wheels 18FL and 18FR. It functions as a steering device that steers. The power steering device may be of any configuration known in the art as long as it can function as an auxiliary steering force generator and a steering device.

  In the illustrated embodiment, the steering shaft 28 is provided with a steering angle sensor 50 that detects the rotation angle of the steering shaft as the steering angle θ and a steering torque sensor 52 that detects the steering torque Thd. Signals indicating θ and steering torque Thd are input to the electronic control unit 16. A signal indicating the vehicle speed V detected by the vehicle speed sensor 56 is also input to the electronic control unit 16.

  The electronic control device 16 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus. Further, the steering angle sensor 50 and the steering torque sensor 52 detect the steering angle θ and the steering torque Thd, respectively, when the steering or turning in the left turn direction of the vehicle is positive.

  As will be described in detail later, the electronic control device 16 controls the electric power steering device 14 according to the flowcharts shown in FIGS. In particular, the electronic control unit 16 determines the necessity of vehicle trajectory control based on the steering angle θ and the vehicle speed V. When it is determined that the trajectory control is unnecessary, the electronic control unit 16 does not control the steering angle of the front wheels but performs power assist control that reduces the steering burden on the driver based on the steering torque Thd.

  On the other hand, when the electronic control unit 16 determines that the trajectory control is necessary, the target steering angle of the front wheels for causing the vehicle to travel along the arc-shaped target trajectory based on the steering angle θ and the vehicle speed V at that time. δat = δ ′ is calculated according to Equation 24 above. The electronic control device 16 controls the power assist, and controls the electric power steering device 14 in a feed-forward manner so that the steering angle of the left and right front wheels becomes the target steering angle δat. Drive along the trajectory.

  Note that the assist torque control itself when the trajectory control is unnecessary does not form the gist of the present invention, and this control may be executed in any manner known in the art. The same applies to other embodiments described later.

  Next, the vehicle travel control in the first embodiment will be described with reference to the flowcharts shown in FIGS. The travel control according to the flowchart shown in FIG. 2 is started by closing an ignition switch not shown in the figure, and is repeatedly executed every predetermined time.

  First, in step 50, whether or not the trajectory control is being executed is determined by determining whether or not the flag Fc indicating whether or not the trajectory control of the vehicle is being executed is 1. When it is determined that the trajectory control is not executed, the control proceeds to step 200, and when it is determined that the trajectory control is executed, the control proceeds to step 100. The flag Fc and a flag Fs described later are reset to 0 prior to the start of the travel control according to the flowchart shown in FIG.

  In step 100, it is determined whether or not the end condition of the trajectory control is satisfied in the travel control of the vehicle. When an affirmative determination is made, the control proceeds to step 150, and when a negative determination is made, the control proceeds to step 300. In this case, when any of the following (1) to (4) is satisfied, it may be determined that the end condition of the trajectory control is satisfied.

(1) A time Ta = 1 [sec] or more required for the vehicle to reach the target arrival point has elapsed since the time when the start condition or update condition (which will be described later) of the trajectory control is satisfied.
(2) The absolute value of the deviation ΔV between the vehicle speed V and the current vehicle speed V when the start condition or the update condition is satisfied is larger than the reference value Ve (positive value).
(3) The absolute value of the deviation Δθ between the steering angle θ and the current steering angle θ when the start condition or the update condition is satisfied is larger than the reference value θe (positive value).
(4) The absolute value of the steering angular velocity, that is, the absolute value of the rate of change θd of the steering angle θ is larger than the reference value θde (positive value).

  The reference values θe and θde may be constants, but may be variably set according to the vehicle speed V, for example, so as to decrease as the vehicle speed V at the time when the start condition or update condition is satisfied.

  In step 150, the trajectory control is ended when the control of changing the steering angle of the left and right front wheels to the target steering angle δat by the steering angle varying device 14 is completed. Further, the flag Fc indicating whether or not the trajectory control is being executed is reset to 0, and then the control proceeds to Step 800.

  In step 200, it is determined whether or not the start condition of the trajectory control is satisfied according to the flowchart shown in FIG. When an affirmative determination is made, control proceeds to step 400, and when a negative determination is made, control proceeds to step 800.

  In step 300, it is determined whether or not the update condition for the trajectory control is satisfied according to the flowchart shown in FIG. When an affirmative determination is made, control proceeds to step 400, and when a negative determination is made, control proceeds to step 500.

  In step 400, the target steering angle δat (= δ ′) of the front wheels for causing the vehicle to travel along the arc-shaped target locus is calculated according to the above equation 24 based on the current steering angle θ and vehicle speed V.

  In step 500, the basic assist torque Tpab is calculated from the map corresponding to the graph shown in FIG. 6 based on the steering torque Thd, and the vehicle speed coefficient Kv is calculated from the map corresponding to the graph shown in FIG. Is calculated. Further, the target assist torque Tat is calculated as a product of the vehicle speed coefficient Kv and the basic assist torque Tpab.

  In step 600, the electric power steering device 14 is controlled so that the assist torque becomes the target assist torque Tat according to the flowchart shown in FIG. As a result, both the steering burden reduction control for reducing the driver's steering burden and the trajectory control for controlling the steering angle of the front wheels to the target steering angle δat and causing the vehicle to travel along the arc-shaped target locus are executed. .

  In step 800, the target assist torque Tat is calculated in the same manner as in step 500 described above, and in step 900, the electric power steering apparatus 14 controls the assist torque to be the target assist torque Tat. Is done. Therefore, control of the steering angle of the front wheels for trajectory control is not performed, but the driver's steering burden is reduced.

  Instead of calculating the target assist torque Tat in step 500 or 800, the target assist torque Tat may be calculated from a map corresponding to the graph shown in FIG. 8 based on the steering torque Thd and the vehicle speed V.

  Next, with reference to the flowchart shown in FIG. 3, a routine for determining the establishment of the start condition of the trajectory control executed in step 200 will be described in detail.

  First, in step 205, the steering angle θlf after low-pass filtering is calculated by subjecting the steering angle θ to low-pass filtering. Then, it is determined whether or not the absolute value of the steering angle θlf after the low-pass filter processing is larger than a reference value θs0 (positive value) for control start determination. When a negative determination is made, the control proceeds to step 240, and when an affirmative determination is made, the control proceeds to step 210.

  In step 210, the steering angular velocity θd is calculated as a differential value of the steering angle θ, and the steering angular velocity θdlf after the low-pass filter processing is calculated by subjecting the steering angular velocity θd to low-pass filtering.

  In step 215, it is determined whether or not the absolute value of the steering angular velocity θdlf after the low-pass filter process is larger than the first reference value θds1 (positive value) for control start determination. When a negative determination is made, the control proceeds to step 225. When an affirmative determination is made, the flag Fs is set to 1 in step 220 to indicate that the start condition is being determined, and then the control is step 225. Proceed to

  In step 225, it is determined whether or not the flag Fs is 1, that is, whether or not the start condition is being determined. When a negative determination is made, the control proceeds to step 240, and when an affirmative determination is made, the control proceeds to step 230.

  In step 230, it is determined whether or not the absolute value of the steering angular velocity θdlf after the low-pass filter processing is smaller than the second reference value θds2 (positive value less than θds1) for control start determination. When a negative determination is made, the control proceeds to step 240, and when an affirmative determination is made, the control proceeds to step 235.

  In step 235, the flag Fs is reset to 0 to indicate that the start condition has not been determined, and the flag Fc is set to 1 to indicate that the trajectory control is being executed. Control continues to step 400.

  In step 240, the flag Fs is reset to 0 to indicate that the start condition has not been determined, and the flag Fc is reset to 0 to indicate that the trajectory control is not being performed. Control continues to step 800.

  The reference values θs0, θds1, and θds2 may be constants, but these reference values may also be variably set according to the vehicle speed V, for example, so as to decrease as the vehicle speed V increases.

  Steps 305 to 340 of the satisfaction determination routine of the locus control update condition shown in FIG. 4 are basically executed in the same manner as steps 205 to 240 of the satisfaction determination routine of the locus control start condition described above.

  However, the reference value for determination in step 305 is the reference value θr0 (positive value) for control update determination. The reference value for determination in step 315 is the first reference value θdr1 (positive value) for control update determination, and the reference value for determination in step 330 is the second reference value θdr2 (θdr1 for control update determination). The following positive value). The reference values θr0, θdr1, and θdr2 may be constants, but these reference values may be variably set according to the vehicle speed V, for example, so that the reference values θr0, θdr1, and θdr2 become smaller as the vehicle speed V increases.

  In Steps 320, 325, 335, and 340, the flag Fs is replaced with a flag Fr that indicates whether or not an update determination has been made. Further, when step 335 is completed, control proceeds to step 500, and when step 340 is completed, control proceeds to step 400.

  Next, with reference to the flowchart shown in FIG. 6, the routine of the steering burden reduction control and the front wheel steering angle control executed in step 600 will be described in detail.

  First, in step 605, it is determined whether or not the steering angle control is the initial steering angle control for the trajectory control, that is, whether or not the steering angle control is immediately after the trajectory control is started or updated. When a negative determination is made, control proceeds to step 620, and when an affirmative determination is made, control proceeds to step 610.

  In step 610, the steering angle δ of the front wheels is obtained based on the steering angle θ and the steering gear ratio N when the trajectory control is started or updated, and the deviation between the target steering angle δat and the steering angle δ of the front wheels is obtained. A deviation Δδat of the steering angle of the front wheels is calculated.

  In step 615, it is assumed that the steering operation is not performed by the driver, and for each cycle necessary to change the rudder angle of the front wheels to the target rudder angle δat at a change rate equal to or less than a preset limit value. A steering angle control amount Δδatc is calculated. For example, if the steering angle of the front wheels is changed to the target steering angle δat over Nc cycles, the steering angle control amount Δδatc is Δδat / Nc.

  In step 620, for example, whether the number of cycles since the start or update of the trajectory control is Nall, and whether or not the steering angle control of the front wheels for the trajectory control is completed by determining whether or not Nall is Nc. A determination of whether or not is made. When an affirmative determination is made, control proceeds to step 625, and when a negative determination is made, control proceeds to step 630.

  In step 625, the change amount Δδt of the target steering angle of the front wheels is set to the steering angle control amount Δδatc for each cycle, and in step 630, the change amount Δδt of the target steering angle of the front wheels is set to zero.

  In step 635, the target drive torque correction amount ΔTst is calculated according to the above equation 67 using the steering gear ratio N when the trajectory control is started or updated.

  In step 650, the final target drive torque Tatt is calculated as the sum of the target assist torque Tat calculated in step 500 and the target drive torque correction amount ΔTst calculated in step 635.

  In step 655, the electric power steering device 14 is feedback-controlled so that the assist torque becomes the target assist torque Tat. Therefore, power assist control for reducing the driver's steering burden is performed, and trajectory control for causing the vehicle to travel along the arc-shaped target trajectory is performed.

  In the first embodiment, when the start condition of the trajectory control is satisfied in a situation where the trajectory control is not executed, a negative determination is made in step 50 and an affirmative determination is made in step 200. Is called. In step 400, the target rudder angle δat of the front wheels for causing the vehicle to travel along the arc-shaped target locus is calculated. In step 600, the rudder angle of the front wheels is set to the feed-forward type by controlling the assist torque. The steering angle δat is controlled.

  Further, when the update condition of the trajectory control is satisfied in the situation where the trajectory control is being executed, an affirmative determination is made in steps 50 and 300. Steps 400 and 600 are then executed.

  Therefore, according to the first embodiment, in a situation where the trajectory control is to be executed, the rudder angle of the front wheels is controlled to the target rudder angle δat, so that the vehicle can be rotated without requiring a driver's steering operation. The traveling locus of the vehicle can be controlled to travel along the arc-shaped target locus.

  In particular, according to the first embodiment, the control of the steering angle of the front wheels is feedforward control performed based on the steering angle θ and the vehicle speed V when the trajectory control is started or updated. Further, once the front wheel rudder angle is controlled to the target rudder angle δat, the front wheel rudder angle is not controlled until the trajectory control is completed or updated. Therefore, as in the case of the second embodiment described later, the trajectory control with the arc-shaped trajectory as the target trajectory can be simply executed as compared with the case where the control of the steering angle of the front wheels is the feedback control.

Second Embodiment As shown in Table 1 above, the target locus of this second embodiment is also an arc-shaped locus, but the control of the steering angle is feedback control.

  The vehicle travel control in the second embodiment is basically executed in the same manner as in the first embodiment described above, but the steering angle control in step 600 is performed according to the flowchart shown in FIG. The steering angle of the front wheels is feedback controlled.

  As can be seen from a comparison between FIG. 10 and FIG. 5, steps 605 to 620 and steps 650 and 655 are executed in the same manner as in the first embodiment.

If a negative determination is made in step 620, the steering angle δ of the front wheel when the trajectory control is started or updated in step 625 is set to δ0 (= θ0 / N), and the front wheel The current target rudder angle δtp is calculated.
δtp = δ0 + (n−1) * Δδatc
= (N-1) * Δδatc + θ0 / N (70)

  If a negative determination is made in step 620, the current target rudder angle δtp of the front wheels is set to the target rudder angle δat of the front wheels in step 630.

  In step 640, the current steering angle δ of the front wheels is estimated, and a deviation Δδat between the current target steering angle δtp of the front wheels and the current steering angle δ is calculated.

  In step 645, the target drive torque correction amount ΔTst is calculated according to the above equation 68 based on the steering angle deviation Δδat of the front wheels.

  Therefore, according to the second embodiment, as in the case of the first embodiment described above, in the situation where the trajectory control is to be executed, the rudder angle of the front wheels is controlled to the target rudder angle δat. Thus, the traveling locus of the vehicle can be controlled so that the vehicle travels along the arc-shaped target locus.

  In particular, according to the second embodiment, the deviation Δδat of the front wheel steering angle is calculated as the deviation between the current target steering angle δtp of the front wheels and the current steering angle δ. Therefore, even if the driver performs a steering operation after the start or update of the trajectory control, the steering angle of the front wheels can be reliably controlled to the target steering angle δat. Further, when the driver performs a steering operation so that the steering angle is suitable for traveling the vehicle along the arc-shaped target locus, the feedback control amount is reduced. Therefore, when the driver is skilled in driving operation, the control amount of the electric power steering device 14 can be reduced and the load can be reduced as compared with the case of the first embodiment described above.

Third Embodiment As shown in Table 1 above, the target locus of this third embodiment is an exponential locus, and the steering angle control is feedforward control.

  As shown in FIG. 11, the traveling control of the vehicle in the third embodiment is basically executed in the same manner as in the first embodiment. In FIG. 11, steps corresponding to the steps shown in FIG. 2 are given the same step numbers as the step numbers given in FIG.

  However, if an affirmative determination is made in step 200 or 300, the target rudder angle δbt of the front wheels for driving the vehicle along the target locus of the exponential function is calculated in step 450 according to the flowchart shown in FIG. Is done.

As shown in FIG. 12, in step 455, the steering angle δ of the front wheel is obtained based on the steering angle θ and the steering gear ratio N, and based on the steering angle δ of the front wheel and the vehicle speed V, according to the above equation 46. distance x 0 is calculated. In step 455, the correction coefficient D is calculated in accordance with the above equation 42, with the minimum time ΔT and the Webber ratio k set to positive constants preset for general drivers.

  In step 460, the lateral acceleration LAa of the vehicle when the vehicle travels in an arc-shaped locus according to the above equation 47 is calculated based on the steering angle θ and the vehicle speed V when the locus control is started or updated. Is done.

  In step 465, a component Vx parallel to the coordinate axis related to the distance x is calculated as one of the components of the vehicle speed V according to the above equation 49 based on the steering angle δ of the front wheel and the vehicle speed V when the trajectory control is started or updated. Is done.

  In step 470, a component Vy parallel to the coordinate axis related to time is calculated as one of the components of the vehicle speed V according to the above equation 50, and an angle σ formed by the component Vx with respect to the vehicle speed V is calculated according to the above equation 52. .

  In step 475, the lateral components Vxx and Vyx of the vehicle are calculated according to the equations 53 and 54, respectively, and the lateral acceleration LAb of the vehicle is calculated according to the equations 55 and 56.

  In step 480, the deviation ΔLA between the lateral acceleration LAb of the vehicle when the vehicle travels along an exponential locus and the lateral acceleration LAa when the vehicle travels along an arcuate locus is expressed by the above equation. The operation is performed according to 57.

  In step 485, based on the steering angle θ, the vehicle speed V, and the lateral acceleration deviation ΔLA when the trajectory control is started or updated, the target steering angle of the front wheels for driving the vehicle to draw the trajectory of the exponential function δbt is calculated. In this case, the target rudder angle δbt is calculated according to the above equation 62 when turning left and according to the above equation 63 when turning right.

  In the third embodiment, the electric power steering device 14 is controlled in accordance with the flowchart shown in FIG. 13 in step 700 executed after step 500.

  As shown in FIG. 13, in step 710, the amount of change Δδt in the target rudder angle of the front wheel is calculated as a deviation between the target rudder angle δbt of the front wheel in the current cycle and the target rudder angle δbt of the front wheel in the previous cycle. The

  In step 720, the target drive torque correction amount ΔTst is calculated according to the above equation 67 using the steering gear ratio N when the trajectory control is started or updated.

  In step 730, the final target drive torque Tatt is calculated as the sum of the target assist torque Tat calculated in step 500 and the target drive torque correction amount ΔTst calculated in step 720.

  In step 740, the electric power steering device 14 is feedback-controlled so that the assist torque becomes the target assist torque Tat. Therefore, power assist control for reducing the driver's steering burden is performed, and trajectory control for causing the vehicle to travel along the target trajectory of the exponential function is performed.

Therefore, according to the third embodiment, in a situation where the trajectory control is to be executed, the steering angle of the front wheels is controlled to the target steering angle δbt, so that the vehicle can be indexed without requiring the driver's steering operation. The traveling locus of the vehicle can be controlled so as to travel along the target locus of the function.

  In particular, according to the third embodiment, the control of the steering angle of the front wheels is performed based on the steering angle θ and the vehicle speed V when the trajectory control is started or updated as in the first embodiment described above. Control. Therefore, as in the case of the fourth embodiment described later, the trajectory control with the trajectory of the exponential function as the target trajectory can be simply executed as compared with the case where the control of the steering angle of the front wheels is feedback control.

Fourth Embodiment As shown in Table 1 above, the target locus of the fourth embodiment is an exponential locus, and the steering angle control is feedback control.

  The vehicle travel control in the fourth embodiment is basically executed in the same manner as in the third embodiment described above. However, in step 750 executed after step 500, the electric power is controlled. The steering device 14 is controlled according to the flowchart shown in FIG.

  As shown in FIG. 15, in step 760, the current steering angle δ of the front wheels is estimated, and a deviation Δδbt between the target steering angle δbt of the front wheels in the current cycle and the current steering angle δ is calculated. The

  In step 770, the target drive torque correction amount ΔTst is calculated according to the above equation 69 using the steering gear ratio N when the trajectory control is started or updated.

  In step 780, the final target drive torque Tatt is calculated as the sum of the target assist torque Tat calculated in step 500 and the target drive torque correction amount ΔTst calculated in step 770.

  In step 790, the electric power steering device 14 is feedback-controlled so that the assist torque becomes the target assist torque Tat. Therefore, power assist control for reducing the driver's steering burden is performed, and trajectory control for causing the vehicle to travel along the target trajectory of the exponential function is performed.

Therefore, according to the fourth embodiment, in a situation where the trajectory control is to be executed, the rudder angle of the front wheels is controlled to the target rudder angle δbt, so that the vehicle can be operated regardless of the presence or absence of the driver's steering operation. The traveling locus of the vehicle can be controlled to travel along the target locus of the exponential function.

  In particular, according to the fourth embodiment, the deviation Δδbt of the steering angle δ of the front wheels is calculated as the deviation between the target steering angle δbt and the current steering angle δ of the front wheels. Therefore, even if the driver performs a steering operation after the start or update of the trajectory control, the steering angle of the front wheels can be reliably controlled to the target steering angle δbt. In addition, when the driver performs a steering operation so that the steering angle is suitable for running the vehicle along the target locus of the exponential function, the feedback control amount becomes small. Therefore, when the driver is skilled in driving operation, the control amount of the electric power steering device 14 can be reduced and the load can be reduced as compared with the case of the third embodiment described above.

  According to the first to fourth embodiments, the target assist torque Tat for reducing the driver's steering burden is calculated in step 500, and the steering angle of the front wheels is controlled to the target steering angle. Assist torque for steering angle control is calculated. The sum of the target assist torque Tat and the steering angle control assist torque is calculated as the final target assist torque Tat, and the assist torque is controlled to be the final target assist torque Tat.

  When the front wheels are steered by the assist torque so that the steering angle of the front wheels becomes the target steering angle, the steering torque varies. However, the target assist torque Tat for reducing the driver's steering burden is increased or decreased in accordance with the change in the steering torque, and the change in the steering torque felt by the driver is reduced.

  Therefore, not only can the vehicle be driven along the target trajectory while reducing the driver's steering burden, but also fluctuations in steering torque due to control of the steering angle of the front wheels by trajectory control are reduced, resulting in trajectory control. Thus, the possibility that the driver feels uncomfortable with the steering torque can be reduced.

  Further, according to the first to fourth embodiments described above, the front wheels are controlled to be the target rudder angle by turning the front wheels with the assist torque. Therefore, for example, a semi-steer-by-wire steering device equipped with a steering gear ratio variable device (VGRS) that steers the steering wheel relative to the steering input means, or the steering input means and the front wheels are not mechanically connected. A steer-by-wire steering device is not required. Therefore, compared with the case where these steering devices are used, the structure of the travel control device can be simplified and the cost can be reduced.

  Further, according to the first and second embodiments described above, since the target locus is an arc-like locus, the required amount of calculation is reduced compared with the case where the target locus is an exponential locus, and the vehicle Can be easily controlled.

  Further, according to the third and fourth embodiments described above, since the target locus is an exponential locus, the vehicle locus is further improved for the vehicle occupant compared to the case where the target locus is an arcuate locus. It can be controlled to a preferable trajectory. In particular, according to these embodiments, the target locus of the exponential function is set so that the distance x changes according to the above equation 40. Therefore, a trajectory preferable for human perception characteristics can be achieved as compared with a case where the target trajectory is an arc-shaped trajectory.

  Although the present invention has been described in detail with respect to specific embodiments, the present invention is not limited to the above-described embodiments, and various other embodiments are possible within the scope of the present invention. It will be apparent to those skilled in the art.

  For example, the guide bar extends along the front-rear direction of the front wheel. However, as long as the inclination angle of the guide bar with respect to the front-rear direction of the vehicle is set based on the amount of steering operation by the driver, the front-rear direction of the front wheel The direction may be different from the direction along. For example, the inclination angle of the guide rod may be set to the product of the steering angle δ of the front wheels and the direction correction coefficient Kd.

  In each embodiment, the means for generating the steering assist force is an electric power steering device. However, the steering wheel is reduced so that the steering burden of the driver is reduced and the steering angle of the steering wheel becomes the target steering angle. Any configuration may be used as long as a steering assist force for turning can be generated.

  In each embodiment, the steering assist torque control for reducing the driver's steering burden is controlled by the second method described above, but may be executed in any manner. For example, it may be modified to be controlled by the first method.

  In each embodiment, the steering assist torque is controlled in a feedback manner based on the final target drive torque Tatt, but may be modified so as to be controlled in a feed forward manner.

  Further, in the first and second embodiments described above, the control amount of the steering angle for each cycle is set to the same value, but the control amount of the steering angle is a value that differs for each cycle. May be modified to be set to

  DESCRIPTION OF SYMBOLS 10 ... Driving control device, 14 ... Electric power steering device, 20 ... Steering wheel, 50 ... Steering angle sensor, 52 ... Steering torque sensor, 56 ... Vehicle speed sensor, 100 ... Front wheel, 102 ... Rear wheel, 104 ... Vehicle, 108 ... Target course, 110 ... Guide bar

Claims (10)

  1. The present invention is applied to a vehicle that does not include a steering angle control means that changes the relationship of the steering angle of the steering wheel with respect to the steering operation amount of the driver, and the steering wheel is steered by turning the steering wheel with the steering auxiliary force of the steering auxiliary force generating means. of a travel control device for modifiable vehicle steering angle, when the pre-set start condition or update condition for control of the trajectory of vehicles is judged to be satisfied, the steering operation of at driver that point Based on the amount and the vehicle speed, the target rudder angle of the steered wheels for driving the vehicle along the target trajectory necessary for the vehicle to reach the target arrival position in the target traveling direction is calculated. in the travel control device of the vehicle by cormorants control becomes the target steering angle,
    The target traveling direction is determined based on a driver's steering operation amount at the time point,
    The target arrival position is a direction inclined by the reference angle with respect to the front-rear direction of the vehicle from the position of the vehicle at the time, with an angle determined based on the steering operation amount of the driver at the time being the reference angle. Is located on a straight line drawn to the distance from the position of the vehicle at the time point, depending on the vehicle speed,
    The steering assist force of the steering assist force generating means is controlled by turning the steered wheels with the steering assist force of the steering assist force generating means so that the steering angle of the steered wheels becomes the target steering angle. A vehicle travel control apparatus characterized by the above.
  2. The steered wheel is turned to the target rudder angle by turning the steered wheel with the first steering assist force control amount for reducing the driver's steering burden and the steering assist force of the steering assist force generating means. And calculating a sum of the second steering assist force control amount as a target steering assist force control amount, and controlling the steering assist force of the steering assist force generating means based on the target steering assist force control amount. The vehicle travel control apparatus according to claim 1, wherein
  3.   3. The vehicle travel control apparatus according to claim 2, wherein a driver's steering burden is detected, and the first steering assist force control amount is calculated based on at least the detected driver's steering burden. .
  4.   The target trajectory is a virtual orthogonal coordinate in which a straight line indicating the target traveling direction is a time coordinate axis, and a perpendicular drawn from the vehicle position at the time point to the time coordinate axis is a distance coordinate axis. 4. The vehicle travel control apparatus according to claim 1, wherein the vehicle travel control apparatus is an exponential function curve in which an elapsed time from a time point is an index variable.
  5.   The target trajectory is in an arc shape in contact with a straight line indicating the front-rear direction of the vehicle at the time point at the vehicle position at the time point and in contact with a straight line indicating the target traveling direction at the target arrival position. The vehicle travel control apparatus according to any one of claims 1 to 3, wherein the vehicle travel control apparatus is a curve.
  6. A straight line connecting the vehicle position at the time point and the target arrival position is used as a reference line for the direction, and the target traveling direction is in a direction inclined at the reference angle with respect to the reference line of the direction at the target arrival position. The travel control device for a vehicle according to any one of claims 1 to 5, wherein the travel control device is determined.
  7. In a situation where the trajectory is not controlled, the driver's steering operation amount after the magnitude of the change rate of the driver's steering operation amount becomes larger than the first reference value for determining the start condition. the rate of change for the magnitude to determine a start condition for the second of claims 1 to 6 starting condition of control of the trajectory when it becomes smaller than the reference value and judging that the established The vehicle travel control device according to any one of the above.
  8. In the situation where the trajectory is controlled, the driver's steering operation amount after the change rate of the driver's steering operation amount becomes larger than the first reference value for determining the update condition. the magnitude of the change rate of claims 1 to 6, wherein the update condition of control of the trajectory to be determined to be satisfied when it becomes smaller than the second reference value for determining the update condition The vehicle travel control device according to any one of the above.
  9.   A target distance is obtained as a product of the reference distance and a natural exponential function with an elapsed time from the time as an index variable, with a distance from the vehicle to the coordinate axis of the time at the time as a reference distance, 5. The vehicle travel control apparatus according to claim 4, wherein the trajectory is obtained as a line connecting the position of the target distance from the coordinate axis of the time.
  10. ΔT is a general time required for a person to perceive the change in the visual information after the change in the visual information outside the vehicle related to the necessity of the steering operation, and the Weber ratio is −k. The vehicle travel control apparatus according to claim 9 , wherein an elapsed time of t is t and an exponent of the natural exponential function is − (k / ΔT) t.
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JP3777275B2 (en) * 1998-09-11 2006-05-24 本田技研工業株式会社 Vehicle steering control device
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