JPH11157464A - Automatic steering unit of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an automatic steering unit equipped with a power steering. SOLUTION: In a power steering control proces, at the time of ordinary travel that any autoamtic steering travel is not yet indicated, steering auxiliary force conformed to steering torque to be produced in a steering shaft 5 by an operation of a dry bar's steering wheel 4 is generated, facilitating a driver's steering operation, and in the case where the autoamtic steering travel is indicated, a steering auxiliary motor 7 is driven and controlled so as to generate a yet larger steering auxilairy force than in time of the ordinary travel in comparison. In brief, in time of the automatic steering travel, since steering force to drive the steering shaft 5 to be generated by an automatic steering motor 16, is generated by the steering auxiliary motor 7 of a power steering instead, the steering force to be generated by the autoamtic steering motor 16 is reduced as far as the portion concerned in consequence. Therefore, the automatic steering motor 16 is miniaturizable, whereby the miniaturization of an automatic steering mechanism is thus promotable as well.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic steering apparatus for automatically steering a vehicle in order to make the vehicle travel along a lane, and more particularly, to a power steering apparatus for assisting a steering force. It relates to an automatic steering device.

[0002]

2. Description of the Related Art An example of such a conventional automatic steering apparatus for a vehicle is disclosed in, for example, Japanese Patent Application Laid-Open No. 4-287206.

In the automatic steering apparatus for a vehicle described in the above publication, a line drawn on a traveling path is recognized from an image photographed by a photographing device such as a camera, and travel is performed based on a distance between the recognized line and the vehicle. By calculating the angle deviation of the vehicle body with respect to the road and adding the calculated angle deviation to the current steering angle and controlling the steering angle so as to match the target steering angle, the vehicle can be automatically moved along the traveling road. I try to run.
Also, for example, a magnetic force source such as a magnet called a magnetic nail is buried along the lane, and this is detected by a magnetic sensor attached to the vehicle to detect the lateral displacement of the vehicle. In some cases, the front wheels or the rear wheels are steered by an actuator so as to match the lateral displacement.

[0004]

Here, in power steering, in which a steering assist force is applied to a steering system in accordance with a steering torque acting on a steering shaft, in order to improve a steering feeling during high-speed running, The steering assist force is reduced as the vehicle speed increases.

When such a power steering is applied to the conventional automatic steering device for a vehicle, when the steering shaft is driven by the automatic steering device, the power steering is actuated in accordance therewith, and the steering assist force is reduced. Will be granted. At this time, since the steering assist force by the power steering decreases as the vehicle speed increases, the automatic steering device requires a larger steering force at a high speed than at a low speed. As a result, there is a problem that the capacity of the electric motor increases and the size of the automatic steering device increases.

Further, since the self-aligning torque fluctuates as the vehicle speed increases, there is a problem that the fluctuation of the self-aligning torque is applied as a disturbance to the steering servo system, and the lane following ability is deteriorated.

Therefore, the present invention has been made in view of the above-mentioned conventional problems, and aims to reduce the size of the automatic steering device without deteriorating the feeling of the steering force at the time of manual steering, and to reduce the speed at high speed. It is an object of the present invention to provide an automatic steering device for a vehicle, which can avoid a decrease in lane following performance of the automatic steering device.

[0008]

To achieve the above object, an automatic steering apparatus for a vehicle according to a first aspect of the present invention provides a steering assisting force corresponding to a steering torque generated in a steering system of the vehicle. A power steering provided to the system, calculating a target steering angle of a steered wheel for lane following, and controlling a steering actuator so that the target steering angle matches the actual steering angle of the steered wheel. In an automatic steering device for a vehicle that controls wheels, the power steering may provide a larger steering assist force during automatic steering in which the steering actuator controls the steered wheels as compared to non-automatic steering. It is characterized in that it is provided to the steering system.

According to the first aspect of the present invention, the steering shaft is driven by controlling the steering actuator so that the target steering angle of the steered wheel calculated for lane following coincides with the actual steering angle. As a result, the steered wheels are controlled to the target steering angle, whereby the lane following is performed.
Also, by the power steering, a steering assist force according to the steering torque generated in the steering system is given to the steering system,
Steering is easily performed.

At this time, during the automatic steering in which the steered wheels are controlled by the steering actuator, a larger steering assist force is generated by the power steering as compared with non-automatic steering, that is, when the steered wheels are manually steered. Is done. Therefore, since the steering force to be generated by the steering actuator can be reduced by that amount, the size of the steering actuator can be reduced, and the size of the entire automatic steering device can be reduced.

According to a second aspect of the present invention, there is provided an automatic steering apparatus for a vehicle which calculates a target steering angle of a steered wheel for following a lane so that the target steering angle coincides with an actual steering angle of the steered wheel. In an automatic steering apparatus for a vehicle that controls a steering actuator to control the steered wheels, a steering torque detecting unit that detects a steering torque generated in a steering system of the vehicle, and a steering assist force according to the steering torque. Power steering applied to the steering system with a predetermined steering assist force application characteristic, automatic steering state detection means for detecting whether the steering actuator is performing automatic steering for controlling the steered wheels, and the automatic steering state When the detecting means detects that non-automatic steering is being performed, the steering assist force applying characteristic is set to the first steering assist force applying characteristic, and when it is detected that automatic steering is being performed, the steering is performed. Characteristic switching means for setting the assisting force imparting characteristic to a second steering assisting force imparting characteristic for applying a steering assisting force larger than the steering assisting force based on the first steering assisting force imparting characteristic. .

According to the second aspect of the present invention, the steering actuator is controlled such that the target steering angle of the steered wheels calculated for lane following and the actual steering angle coincide with each other, and the actual steering angle becomes equal to the target steering angle. Thus, the steering shaft is driven so that the vehicle follows the lane. Further, by the power steering, a steering assisting force corresponding to the steering torque generated in the steering system of the vehicle is applied to the steering system, and the steering is easily performed.

At this time, in the power steering, if the steering torque is generated manually, that is, when the steering wheel is steered by the driver, the first torque is generated.
The steering assist force is generated based on the steering assist force applying characteristic of the automatic steering device. When the steering shaft is driven by the automatic steering device and the steering torque is generated, the steering assist force is generated based on the second steering assist force applying characteristic. generate. At this time, if the second steering assist force applying characteristic is set so as to apply a larger steering assist force than the first steering assist force applying characteristic, the steering force generated by the automatic steering device is reduced. Since it is possible to reduce the amount, the size of the automatic steering device can be reduced.

According to a third aspect of the present invention, in the automatic steering apparatus for a vehicle, the second steering assisting force application characteristic is set so that the steering assisting force increases as the vehicle speed increases. Vehicle speed detecting means for detecting a vehicle speed, wherein the steering assist force applying characteristic is changed to the second steering assist force applying characteristic according to the detected vehicle speed of the vehicle speed detecting means. .

According to the third aspect of the present invention, the second steering assist force applying characteristic is set so that the steering assist force increases as the vehicle speed increases. , The steering assisting force imparting characteristic becomes the second steering assisting force imparting characteristic, that is,
Control is performed so that the steering assist force increases as the vehicle speed increases. Therefore, the self-aligning torque increases as the vehicle speed increases, but since the steering assist force is set to increase according to the vehicle speed, the influence of the self-aligning torque acting as a disturbance on the steering servo system is accurately reduced. As a result, a decrease in the vehicle speed following ability is avoided.

According to a fourth aspect of the present invention, in the vehicle automatic steering system, the second steering assist force applying characteristic is a characteristic that applies the steering assist force according to a self-aligning torque. .

According to the fourth aspect of the present invention, since the second steering assisting force applying characteristic is a characteristic for applying a steering assisting force according to the self-aligning torque, the self-aligning torque is applied to the steering servo system as a disturbance. It is possible to appropriately suppress the influence of the action.

Further, the automatic steering apparatus for a vehicle according to a fifth aspect is characterized in that a lower limit is provided for the second steering assist force applying characteristic. According to the fifth aspect of the present invention, the second
Since the lower limit is provided in the steering assist force applying characteristic of the automatic steering device, even when steering is performed by an automatic steering device at a low vehicle speed, such as when the vehicle is swept, an accurate steering assist force can be obtained by power steering.

[0019]

As described above, according to the first aspect of the present invention,
The automatic steering device for a vehicle according to the present invention increases the steering assist force by power steering during automatic steering in which the steering shaft is driven by the steering actuator as compared to during non-automatic steering. The steering force to be generated can be reduced, and the size of the automatic steering device can be reduced.

In the automatic steering apparatus for a vehicle according to the present invention, during the automatic steering in which the steering shaft is driven by the steering actuator, compared with the first steering assist force applying characteristic during the non-automatic steering, Since the steering assist force is applied so as to have the second steering assist force applying characteristic for applying a large steering assist force, the assist force to be generated by the steering actuator can be reduced, and the size of the automatic steering device can be reduced. Can be achieved.

According to a third aspect of the present invention, in the automatic steering apparatus for a vehicle, the second steering assist force applying characteristic is set such that the steering assist force increases as the vehicle speed increases. Since the steering assist force is applied so as to have the second steering assist force applying characteristic in accordance with the vehicle speed detected in the above, the influence of the self-aligning torque acting as a disturbance on the steering servo system can be accurately reduced. Thus, it is possible to avoid a decrease in vehicle speed following ability.

Further, in the automatic steering apparatus for a vehicle according to the fourth aspect, the second steering assist force applying characteristic is a characteristic of applying a steering assist force according to the self-aligning torque.
The effect of the self-aligning torque acting as a disturbance on the steering servo system can be accurately suppressed,
It is possible to avoid a decrease in lane following ability.

Further, in the automatic steering apparatus for a vehicle according to the present invention, since the second steering assist force applying characteristic has a lower limit, even when the automatic steering apparatus is steered at a low vehicle speed, the power steering is performed. Thus, an accurate steering assist force can be obtained.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. Here, an automatic steering device that steers only the front wheels will be described.

FIG. 1 is a schematic diagram showing an example of an automatic steering apparatus according to the present invention. In the figure, 1F indicates front left and right wheels, 1R indicates rear left and right wheels, and a very common rack and pinion type steering mechanism is added to the front left and right wheels 1F. This steering mechanism includes a rack 2 connected to a steering shaft (tie rod) of the front left and right wheels 1F, a pinion 3 meshing with the rack 2, a steering shaft 5 for rotating the pinion 3 by a steering torque given to a steering wheel 4. And a steering system is constituted by the rack 2, the pinion 3, the steering wheel 4 and the steering shaft 5.

A ring gear 6 constituting a speed reducer is coaxially fixed above the pinion 3 in the steering shaft 5, and a steering assist motor 7 is attached to the ring gear 6.
The ring gear 8 connected to the drive shaft is meshed, and the steering assist motor 7 is controlled to generate a steering assist force corresponding to the steering torque by a duty-controlled pulse current output from a control unit 10 described later. . The control unit 1 controls the ring gears 6 and 8, the steering assist motor 7, and the steering assist motor 7.
0 constitutes power steering.

A steering torque sensor (steering torque detecting means) 12 constituting a torque detecting mechanism is provided above the ring gear 6 in the steering shaft 5. The torque detecting mechanism includes a steering shaft 5
And a torsion bar (not shown) connecting the lower end of the pinion 3 and the upper end of the pinion 3 and the steering torque sensor 12 disposed on the outer periphery thereof. Then, the steering torque sensor 12 detects the steering torque from the amount of twist of the torsion bar, and outputs a voltage signal corresponding to the magnitude of the steering torque. The steering torque T which is a negative voltage signal at the left turn of the control unit 1
Supply 0.

Further, an automatic steering mechanism for automatically steering the front left and right wheels 1F is added above the steering torque sensor 12 in the steering shaft 5. The automatic steering mechanism includes a driven gear 14 mounted coaxially with the steering shaft 5, a drive gear 15 meshing with the driven gear 14, and an automatic steering motor 16 for driving the drive gear 15 to rotate. Note that a clutch mechanism 17 is interposed between the automatic steering motor 16 and the drive gear 15, and the clutch mechanism 17 is connected only during the automatic steering control. 16 is prevented from being input to the steering shaft 5. These mechanisms constitute a steering actuator, and an automatic steering mechanism including the automatic steering motor 16 is controlled by a control signal from the control unit 10.

Various sensors are mounted on the vehicle. Figure 21 is a steering angle sensor, and outputs to the control unit 10 by indexing the actual front wheel steering angle [delta] _F of left and right front wheels 1F from the rotation angle of the steering shaft 5. In the figure, reference numeral 22 denotes a vehicle speed sensor (vehicle speed detecting means).
The control unit 10 detects the moving speed (vehicle speed V) of the vehicle from the rotational speed of the output shaft of the transmission, for example.
Output to Reference numeral 23 in the figure denotes a lane curvature detection device that detects the curvature of the lane. For example, the lane curvature information wirelessly transmitted by a coaxial leaky cable or the like installed on the side of the road is obtained, and the lane curvature ρ is controlled by the control unit. Output to 10 Reference numeral 24 in the figure denotes an automatic steering switch (automatic steering state detection means) for instructing execution of automatic steering control by the automatic steering device. When the driver turns on the automatic steering switch 24, "H" is set. Is output to the control unit 10.

On the other hand, the magnetic force of a magnet (not shown) buried along the lane as a magnetic force source is detected by a magnetic sensor 25 attached to a lower front part of the vehicle. The magnetic sensor 25 decomposes not only the magnitude of the magnetic force of the magnet but also a magnetic force vector into a vertical component corresponding to the vehicle vertical direction and a horizontal component corresponding to the vehicle width direction. And size can be detected.

The detection signal of the magnetic sensor 25 is output to a lateral displacement detecting device 26. This lateral displacement detecting device 26
Detects (calculates) the direction and magnitude of the lateral displacement of the vehicle (strictly speaking, the magnetic sensor 25) with respect to the lane (strictly speaking, the magnet) from the vertical and horizontal component ratio of the magnetic force vector detected based on the principle described later. The lateral displacement detecting device 26 is constituted by a discrete digital system such as a microcomputer (not shown). The lateral displacement y of the vehicle detected by the lateral displacement detecting device 26 is controlled by the control unit 10.
Is output to

The control unit 10 is constituted by a discretized digital system such as a microcomputer (not shown). This digital system, like an existing microcomputer, has an input interface circuit for reading detection signals from the sensors, a storage device such as a ROM and a RAM for storing necessary programs and calculation results, and an actual system. And an arithmetic processing device such as a microprocessor unit having a certain amount of buffer mechanism, and a control signal set by the arithmetic processing device is transmitted to the steering assist motor 7 of the power steering and the automatic steering mechanism of the automatic steering mechanism. Steering motor 1
6 is provided with an output interface circuit and the like for outputting the data to the control circuit 6. The control unit 10 drives the steering assist motor 7 based on the detection signals from the various sensors to generate a steering assist force corresponding to the steering torque generated on the steering shaft 5 and to control the automatic steering motor 16.
To automatically steer the vehicle so that the vehicle travels along the lane.

Next, the automatic steering control process executed in the control unit 10 will be described with reference to the flowchart of FIG. Although this flowchart does not particularly include a step for transmitting and receiving information, the information read by the arithmetic processing unit, the physical quantity, or the calculated operation result is updated and stored in the storage device as needed, and Necessary programs, maps, tables, and the like are read from the storage device to the buffer of the arithmetic processing device at any time.

This arithmetic processing is performed, for example, for 10 msec. Is executed as a timer interrupt process at every preset sampling time ΔT. First, the lateral displacement y from the lateral displacement detector 26 is read (step S1), and then the lane curvature ρ from the lane curvature detector 23 is read (step S2). Then, the vehicle speed V from the vehicle speed sensor 22 is read (step S3).

Next, the target front wheel steering angle δ for lane following
^* Is set (step S4). This target front wheel steering angle δ ^*
Is, as shown in FIG. 3, a feedforward term set by, for example, a lane curvature ρ and a steering gain Gρ,
It is given from the sum with the feedback term calculated based on the lateral displacement y.

Strictly speaking, the steering gain Gρ is
The gain depends on the vehicle speed V.
Steering in the vehicle speed region where automatic driving is frequently performed
The ring gain may be set as a representative value.
No. When using the vehicle speed dependent steering gain Gρ
Is the gain of the lateral acceleration with respect to the steering angle.
Then, the steering gain Gρ may be calculated. Also before
The feedback term is, for example, a PID system which is a classical control.
The proportional term K of the lateral displacement y₁p, integral term Ki ₁/
s, differential term Kd₁・ Gives the sum of s (s is the Laplace operator)
The proportional coefficient K ₁p, integral coefficient Ki₁, Derivative K
d₁Are determined from the viewpoints of stability, convergence, etc.
It is.

FIG. 4 shows a steering servo according to the present embodiment.
FIG. 3 is a block diagram showing a system, forming a closed loop;
I have. Then, the target front wheel steering angle δ^*And the actual front wheel steering angle δ_FWith
Based on the deviation, for example, the command voltage V^*
Is set, and this command voltage V ^*Is the command current I^*Converted to
And supplied to the automatic steering actuator. The figure
Medium, K_Twop, Ki_Two/ S, Kd_Two・ S is PID respectively
Represents the proportional, integral, and derivative terms in control, and the proportional coefficient
K_Twop, integral coefficient Ki_Two, Derivative Kd_TwoAre each cheap
Determined from the viewpoint of qualitative and convergence properties. Also, in FIG.
K_VIIs the command voltage V^*With the command current I^*Convert to amp
J is the inertia of the rotating part of the automatic steering mechanism.
It is.

Next, it is determined whether or not the switch information from the automatic steering switch 24 is "ON", that is, whether or not the automatic steering is instructed (step S5). Is output (step S6). Then, the actual front wheel steering angle, that is, the actual front wheel steering angle δ from the steering angle sensor 21
A control signal for matching _F to the target front wheel steering angle δ ^* set in step S4 is generated and output (step S7). Then, the process ends.

On the other hand, if the switch information from the automatic steering switch 24 is "OFF", that is, if the automatic steering is not instructed, a control signal for releasing the clutch mechanism 17 is output (step S8), and the process is terminated. I do.

Next, the power steering control processing executed in the control unit 10 will be described with reference to the flowchart of FIG. Although this flowchart does not particularly include a step for exchanging information, the information read by the arithmetic processing unit, the physical quantity, or the calculated operation result is updated and stored in the storage device at any time. Necessary programs, maps, tables, and the like are read from the storage device to the buffer of the arithmetic processing device at any time.

This arithmetic processing is performed, for example, for 10 msec. Is executed as a timer interrupt process at every preset sampling time ΔT. First, step S11
Reads the vehicle speed V from the vehicle speed sensor 22, and then reads the steering torque T from the steering torque sensor 12 (step S12). Next, based on the vehicle speed V and the steering torque T, for example, the vehicle speed and the steering torque are set such that the steering assist force increases as the steering torque increases, and the steering assist force decreases as the vehicle speed increases. And the target drive current value i ^*
A target drive current value i ^* to the steering assist motor 7 is determined with reference to a previously set control map (not shown) that represents the correspondence with (step S13).

Next, the switch information from the automatic steering switch 24 is read. If the switch information from the automatic steering switch 24 is "ON", that is, if the driver instructs automatic steering (step S14), step S14 is executed. The process proceeds to S15, and assist characteristics during normal running (first
The steering assist force difference corresponding to the vehicle speed V from the vehicle speed sensor 22 is obtained from the control map of FIG. 6 showing the steering assist force imparting characteristic of the vehicle and the assist characteristic during automatic steering traveling (second steering assist force imparting characteristic). That is, at the vehicle speed V, the difference between the steering assist force during normal running and the steering assist force during automatic steering running is detected,
A correction value Δi that can realize the steering assist force of the difference is detected.

As shown in FIG. 6, the control map representing the assist characteristic shows the correspondence between the vehicle speed V and the steering assist force to be generated when the steering torque T is constant. At the time of steering traveling, it is set so as to generate a larger steering assist force as compared with the time of normal traveling.

Then, the process proceeds to step S16, where the correction value Δi detected in step S15 is added to the target drive current value i ^* set in step S13, and this is set as a new target drive current value i ^* . Then, control goes to a step S17.

On the other hand, in step S14, if the switch information from the automatic steering switch 24 is "OFF", that is, if the driver has not instructed the automatic steering traveling, the process directly proceeds to step S17.

In step S17, for example, whether the vehicle is in a right-turn state or a left-turn state is detected based on the steering torque T, and the actual drive current i of the steering assist motor 7 is detected and calculated. Duty control is performed so that the target drive current value i ^* coincides with the target drive current value i ^*, and a control signal capable of realizing this is generated and output to the steering assist motor 7.

Here, the processing of steps S14 to S17 corresponds to the characteristic switching means. Next, the operation of the present embodiment will be described. Here, when a magnet is used as a magnetic force source, the principle of detecting the lateral displacement of the vehicle with respect to the lane based on the magnetic force from the magnet will be briefly described. When the line of magnetic force from the magnet is generated as shown in FIG. 7, the level (height) of the magnetic sensor is constant. Therefore, if the ratio of the vertical and horizontal components of the detected magnetic force vector is known, the magnetic sensor, that is, the vehicle Indicates how far the vehicle is deviated from the magnet, that is, the lane. In other words, if the magnetic sensor is directly above the magnet, the ratio of the vertical and horizontal components of the detected magnetic force vector becomes 1: 0, and the more it is shifted in the horizontal direction, the more the horizontal component of the detected magnetic force vector is shifted. Becomes large, and the vertical component becomes small. Further, it can be determined from the direction in which the lateral component of the magnetic force vector is generated, which direction the magnetic sensor, that is, the vehicle is deviated from the magnet, that is, the lane.

Next, the timing for detecting the lateral displacement of the vehicle with respect to the lane using this principle will be briefly described. Now, assuming that the magnetic sensor mounted on the vehicle is not displaced in the lateral direction with respect to the magnet as described in FIG. 7 (even if it is displaced, if the lateral displacement is the same, the result is the same). Assuming that the distance between the magnetic sensor and the magnet is D, the relationship between the distance D and the magnetic force is as shown in FIG. 8B. That is, when the magnetic sensor is closest to the magnet, the detected magnetic force also becomes maximum. Therefore, when the detected magnetic force is maximized, the lateral displacement of the vehicle can be accurately detected from the ratio of the vertical and horizontal component of the magnetic force vector.

In order to immediately respond to the start of automatic operation, the control unit 10 starts automatic steering control processing from the time when the ignition switch is turned on, and sets the lateral displacement y from the lateral displacement detection device 26, the lane The target front wheel steering angle δ ^* is always calculated based on the lane curvature ρ from the curvature detector 23 and the vehicle speed V from the vehicle speed sensor 22. When the driver turns on the automatic steering switch 24, the driver outputs a control signal for connecting the clutch mechanism 17 so that the rotational force of the automatic steering motor 16 can be input to the steering shaft 5. the target front wheel steering angle [delta] ^* that, on the basis of the actual front wheel steering angle [delta] _F from the steering angle sensor 21, and outputs it to generate a control signal for synchronizing them to automatic steering motor 16.

As a result, the torque of the automatic steering motor 16 is input to the steering shaft 5, and the actual front wheel steering angle δ _F is controlled so as to coincide with the target front wheel steering angle δ ^* .
The vehicle enters an automatic steering running state.

On the other hand, when the ignition switch is turned on and the control unit 10 is activated, the power steering control process is also executed at a predetermined sampling cycle, and the vehicle speed V from the vehicle speed sensor 22 and the steering from the steering torque sensor 12 are controlled. Based on the torque T, a target drive current value i ^* to the steering assist motor 7 is obtained from a control map based on the torque T.
Is determined. Then, when the automatic steering switch 24 is off, that is, when the driver does not instruct the automatic steering traveling, the target drive current value i ^* and the actual actual drive current i of the steering assist motor 7 match. The steering assist motor 7 in the steering direction detected from the steering torque T.
Is performed, and as a result, a steering assist force corresponding to the steering torque T and the vehicle speed V is applied to the steering shaft according to the steering of the driver.

At this time, the steering assist force is controlled to increase as the steering torque T increases, and the steering assist motor 7 is controlled such that the steering assist force decreases as the vehicle speed increases. From, the driver
During high-speed running, a good steering feeling can be obtained, and an appropriate steering assist force can be obtained according to the steering torque acting on the steering wheel.

On the other hand, when the automatic steering switch 24 is turned on,
That is, when the driver is instructed to perform automatic steering, the steering torque T from the steering torque sensor 12 is used.
The target drive current value i ^* is determined from the control map based on the vehicle speed V from the vehicle speed sensor 22 and the assist characteristics during normal running and the assist characteristics during automatic steering running in FIG. From the control map, a steering assist force difference corresponding to the vehicle speed V is detected, and a correction value Δi that can realize this is detected.

[0054] Then, the sum of the correction value Δi and the target drive current value i ^* is set as a new target drive current value i ^*, and the actual current i of the target drive current value i ^* a steering assist motor 7 Control is performed so that they match. As a result, a steering assist force corresponding to the steering torque T generated on the steering shaft 5 by driving the automatic steering motor 16 by the automatic steering control process is applied to the steering shaft 5, and the steering at the front wheel steering angle is assisted. .

At this time, in the power steering control processing, the target drive current value i ^* is corrected to a larger value according to the control map of FIG. 6 during the automatic steering operation. A larger steering assist force than during traveling is generated.

Therefore, even when the same steering torque T is generated on the steering shaft 5, a larger steering assist force can be obtained during automatic steering traveling than during normal traveling. The steering assisting force of the steering assisting motor 7 bears the force of the steering assisting motor 7 to rotate the steering shaft 5 to be generated.

Therefore, since the steering assist motor 7 bears the steering force to be generated by the automatic steering motor 16, the capacity of the automatic steering motor 16 can be reduced accordingly, and the size of the automatic steering motor 16 can be reduced. Becomes possible.

At this time, only during automatic steering operation,
Since the steering assist force is strengthened, the steering feeling given to the driver during manual steering does not deteriorate.

In the above-described embodiment, according to the control map shown in FIG. 6, a larger steering assist force is generated during automatic steering traveling than during normal traveling, and the steering assist force increases as the vehicle speed increases. Although the case where the force is reduced has been described, for example, the steering assist force may be uniformly increased during automatic steering traveling. Further, the power assisting force may be increased as the vehicle speed increases.

That is, as shown in the block diagram of the steering servo system in FIG. 9, in the PID control in the automatic steering control process, when there is no integral element, that is, Ki ₂ / s, the torque is proportional to the torque applied to the steering shaft 5. A steady deviation (here, a steady front wheel steering angle deviation) occurs. this is,
It is a desirable structure as a steering servo for automatic steering,
For example, during automatic steering, the driver
Steering the increases with the target front wheel steering angle [delta] _M, if the deviation and the actual front wheel steering angle [delta] _F is generated, if you had if integral element Ki ₂ / s, the feedback term, over time, The steering shaft 5 is returned to the original position. Therefore, it is preferable that the deviation remains in the sense of allowing the driver's intervention.

Therefore, in order to keep the steady-state deviation within a certain range, the aforementioned torque may be set within a certain range. If a self-aligning torque is given as a disturbance applied to the steering system, the power assisting force of the power steering may be varied so that the influence of the self-aligning torque falls within a certain range on the steering shaft 5. That is, since the self-aligning torque increases as the vehicle speed increases, the steering assist force may be increased as the self-aligning torque increases, that is, as the vehicle speed increases.

Specifically, the steering assist force may be generated as follows. That is, the self-aligning torque is Ts, the caster rail is ξ, the cornering power per front wheel is Kf, the center-of-gravity point side slip angle is β, the distance between the center-of-gravity point front wheel shafts is Lf, the yaw rate is r, and the front wheel steering angle is δ. Assuming that the vehicle speed is V, the self-aligning torque Ts is given by the following equation (1). The yaw rate r and the center-of-gravity point side slip angle β during steady turning are given by the following equations (2) and (3). In the equation, m represents the vehicle mass, L represents the distance between the front and rear wheel shafts, Kr represents the cornering power of one rear wheel, and Lr represents the distance between the center of gravity and the rear wheel shaft. These equations (1) to (3) are known and described in, for example, "Motion and Control of Automobiles" (P. 69, P. 131 by Masato Abe, Sankaido).

[0063] By substituting the equations (2) and (3) into the equation (1), the following equation (4) can be obtained.

Ts = 2 · ξ · Kf · δ · (m / 2L ² ) · (Lr / Kf) / C (4) C = 1 / V ² − (m / 2L ² ) · ((Lf · Kf−Lr · Kr) / (Kf · Kr)) Here, since a general vehicle is set to understeer, Lf · Kf <Lr · Kr, and the self-aligning torque Ts is calculated from the equation (4). Always positive. Therefore, the self-aligning torque Ts becomes a monotonically increasing function with respect to the vehicle speed V. The steering assist force P is set, for example, as shown in the following equation (5) in order to act to cancel this effect. Note that K in the equation is a proportional coefficient.

P = K / C (5) FIG. 10 shows an assist characteristic representing the correspondence between the steering assist force applied according to the equation (5) and the vehicle speed.

By applying the steering assist force in accordance with the above equation (5), the steering assist force increases as the vehicle speed increases, and the steering assist force is set so as to cancel the disturbance due to the self-aligning torque. Therefore, the influence of the self-aligning torque can be accurately reduced, and a decrease in vehicle speed following ability can be avoided.

When the steering assist force P is set according to the above (5), the steering assist force P converges to zero as the vehicle speed approaches zero. In this case, it becomes impossible to obtain the steering assist force P when performing automatic steering at a low vehicle speed, such as in a corner. Therefore, if a lower limit value is set for the steering assist force P and a certain amount of the steering assist force P is applied even at a low vehicle speed, a sufficient steering assist force by power steering can be obtained even when the vehicle is swirling. And steering can be easily performed.

In a method of increasing the steering assist force as the vehicle speed increases, for example, a torque sensor is provided between the steering wheel and the force application point of the automatic steering mechanism on the steering shaft, and the automatic steering mechanism is operated during the automatic steering. It is also effective when applied to a mechanism or the like in which automatic steering is canceled when the value detected by the torque sensor exceeds a predetermined value when the driver performs a steering operation (for example, this is performed mechanically. Japanese Patent Application Laid-Open No. 4-38266.
And others described in Japanese Patent Publication No. ).

In such a mechanism, when the steering assist force is increased during the automatic steering operation, the predetermined value for canceling the automatic steering must be set low in order to cancel the automatic steering operation as in the normal operation. . Here, since it is necessary to prevent erroneous automatic steering from being canceled due to noise or the like applied to the torque sensor, it is difficult to set the predetermined value too low.

However, when a larger steering assist force is applied at the time of automatic steering as compared with the time of normal steering traveling,
By controlling the steering assist force to decrease as the vehicle speed decreases, it is possible to more accurately set the predetermined value for canceling the automatic steering as compared to a case where the steering assist force is uniformly increased. As a result, the automatic steering can be released more accurately.

In the above embodiment, the lane curvature ρ
Is read only as information from the outside, the lane curvature ρ is calculated based on the lateral displacement y, the yaw rate,
Since it is well known that the equation of motion such as yaw angle and vehicle speed is expressed, it is also possible to estimate using these.

Further, in the above-described embodiment, a case has been described in which the present invention is applied to a front wheel steering vehicle in which front wheels are steered by a power steering and an automatic steering device. However, a rear wheel steering vehicle in which rear wheels are steered by a power steering and an automatic steering device is described. It is also possible to apply to.

In the above-described embodiment, in the power steering control processing, the target drive current value i ^* corresponding to the steering torque T and the vehicle speed V is detected during the automatic steering operation, and the automatic steering operation and the normal operation are performed. detecting a correction value Δi which can achieve a steering assist force difference when, by adding the correction value Δi to the target drive current value i ^*, if you choose to set the target drive current value i ^* of the automatic steering travel However, for example, for each of the normal traveling and the automatic steering traveling, a control map representing the correspondence between the steering torque T and the target driving current value i ^* according to the vehicle speed V is set and stored, A target drive current value i ^* may be set by selecting a control map based on whether or not the vehicle is in automatic steering travel. Also, regardless of the control map, the steering torque T
And a function for the vehicle speed V, and it is also possible to set a target drive current value i ^* by performing a function operation based on the steering torque T and the vehicle speed V. Target drive current value i for vehicle speed V
Any method can be used as long as ^* can be set uniquely.

Further, in the above embodiment, the case where the electric power steering provided with the steering assist motor 7 is applied as the power steering has been described. However, the present invention can be applied to a hydraulic power steering.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing an example of an automatic steering device for a vehicle according to the present invention, where (a) is a side view and (b) is a plan view.

FIG. 2 is a flowchart illustrating an example of an automatic steering control process.

FIG. 3 is a block diagram illustrating a method of calculating a target front wheel steering angle δ ^* .

FIG. 4 is a block diagram illustrating an example of a steering servo system.

FIG. 5 is a flowchart illustrating an example of a power steering control process.

FIG. 6 is a control map showing assist characteristics during normal driving and automatic steering driving.

FIG. 7 is an explanatory diagram of a magnetic force vector from a magnet embedded in a lane.

FIG. 8 is an explanatory diagram for detecting a magnetic force of a magnet with a magnetic sensor attached to a vehicle.

FIG. 9 is an explanatory diagram serving to explain other assist characteristics of the present embodiment.

FIG. 10 is a control map showing an example of other assist characteristics according to the present embodiment.

[Explanation of symbols]

 1F, 1R wheels 5 steering shaft 7 steering assist motor 10 control unit 12 steering torque sensor 16 automatic steering motor 17 clutch mechanism 21 steering angle sensor 22 vehicle speed sensor 23 lane curvature detecting device 24 automatic steering switch 25 magnetic sensor 26 lateral displacement detecting device

Claims (5)

[Claims] 1. A vehicle comprising a power steering for applying a steering assist force to a steering system according to a steering torque generated in a steering system of a vehicle, calculating a target steering angle of a steered wheel for lane following, and calculating the target steering angle. An automatic steering apparatus for a vehicle that controls a steering actuator by controlling a steering actuator such that an actual steering angle of the steering wheel matches an actual steering angle of the steering wheel. An automatic steering apparatus for a vehicle, wherein a larger steering assist force is applied to the steering system during the automatic steering to be controlled as compared to during the non-automatic steering. 2. A method for calculating a target steering angle of a steered wheel for lane following, and controlling the steered wheel by controlling a steering actuator such that the target steered angle matches the actual steering angle of the steered wheel. In such an automatic steering device for a vehicle, a steering torque detecting means for detecting a steering torque generated in a steering system of the vehicle, and a steering assist force corresponding to the steering torque to the steering system with a predetermined steering assist force applying characteristic. Power steering to be applied, automatic steering state detecting means for detecting whether the steering actuator is performing automatic steering for controlling the steered wheels, and detecting that non-automatic steering is being performed by the automatic steering state detecting means. The steering assist force applying characteristic is set to the first steering assist force applying characteristic, and when the automatic steering is detected, the steering assist force applying characteristic is set to the first steering assist force applying characteristic. Automatic steering apparatus for a vehicle, characterized in that it comprises a characteristic switching means than the steering assist force based on the sex is set to the second steering assist force applying characteristic that imparts a large steering assist force, the. 3. The second steering assist force applying characteristic is set such that the steering assist force increases as the vehicle speed increases, and the power steering includes a vehicle speed detecting unit that detects a vehicle speed. 3. An automatic steering apparatus for a vehicle according to claim 2, wherein said steering assist force applying characteristic is changed to said second steering assist force applying characteristic according to a vehicle speed detected by a vehicle speed detecting means. 4. The automatic steering apparatus for a vehicle according to claim 3, wherein the second steering assist force applying characteristic is a characteristic that applies the steering assist force according to a self-aligning torque. 5. The automatic steering apparatus according to claim 2, wherein a lower limit is provided for the second steering assist force applying characteristic.