JP2003261053A - Automatic steering system for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively reduce uncomfortable feeling of a driver at a time of automatic steering, while preventing steering reaction from being too small at a time of normal steering. <P>SOLUTION: A correction turning torque Te for cancelling reaction torque of automatic steering by a turning angle variable device 30 so as to perform stable turning travel of a vehicle is calculated (S20-40), and assisting turning torque Tab of feedback controlled variables for lightening burden of steering of the driver is calculated (S130-150). Next, an electric power steering 16 is controlled based on a target assisting turning torque Ta that is sum of an assisting turning torque Tab and the correction turning torque Te (A160, 170), and the assisting turning torque Tab is calculated based on a map in which a ratio of magnitude of the assisting turning torque Tab to the magnitude of a steering torque Ts at the time of automatic steering is larger than that at a time of non-automatic steering (S130-150). <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering device for a vehicle such as an automobile, and more particularly to an automatic steering device for automatically steering steered wheels as necessary.

[0002]

2. Description of the Related Art As disclosed in, for example, Japanese Patent Application Laid-Open No. 11-78949, a steering wheel is steered by a driving torque of an electric motor of an electric power steering apparatus and steering assist is performed when a driver steers. Electric power steering devices have been known for some time.

[0003]

According to the electric power steering device described in the above publication, the steering wheel can be steered and the steering assist can be performed by one electric motor. However, the electric power steering device is It is difficult to prevent the reaction torque generated when the steered wheels are steered from being transmitted to the steer rig wheel and causing the driver to feel uncomfortable.

In order to solve this problem, for example, Japanese Unexamined Patent Publication No.
As described in Japanese Patent No. 777751, a transmission ratio variable device provided in a steering system between a steering wheel and a steered wheel and serving as a steering drive means for steering the steered wheel relative to the steering wheel ( Steering angle variable mechanism)
And a power steering device as a steering assist force generating means provided in the steering system, and the steering wheel is automatically steered by driving the steering wheel by a transmission ratio variable device,
2. Description of the Related Art An automatic steering device configured to cancel a reaction torque generated by a transmission ratio varying device during automatic steering by a steering assist force of a power steering device has been conventionally known.

In this type of automatic steering device, the sum of the feedback control amount based on the steering torque of the steering system and the feedforward control amount for canceling the reaction torque generated by the transmission ratio varying device during automatic steering. It is conceivable to reduce the reaction torque transmitted to the steering wheel during automatic steering by controlling the steering assist force generation means based on the above, but the feedback gain is high so that the reaction torque can be effectively reduced. If set, the steering reaction force during normal steering by the driver becomes too small and the steering wheel wobbles easily. Conversely, if the feedback gain is set low, the driver normally operates during steering. The problem is that the steering burden on the driver cannot be effectively reduced due to the reduction of the auxiliary steering torque. There is.

According to the present invention, an auxiliary steering means is provided in a steering system between a steering wheel and a steering wheel for auxiliary steering the steering wheel relative to the steering wheel, and a steering wheel provided in the steering system. The present invention is made in view of the above problems in a semi-steer-by-wire type automatic vehicle steering system having an auxiliary steering force generating means for generating an auxiliary steering force for assisting the rudder, and is a main feature of the present invention. The problem is to change the degree of contribution of the feedback control based on the steering torque of the steering system depending on whether or not the auxiliary steering means is driven and the automatic steering is performed, so that the driver can perform normal steering. It is to effectively reduce the discomfort felt by the driver during automatic steering while preventing the steering reaction force from becoming too small.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the main problems described above are provided in a steering system between a steering wheel and a steered wheel, and the steered wheel is assisted relative to the steering wheel. Auxiliary steering means for steering, auxiliary steering force generating means for generating an auxiliary steering force provided in the steering system for assisting steering of the steered wheels, the auxiliary steering means and the auxiliary steering force generation. A semi-steer-by-wire type vehicle automatic steering device having a control means for controlling the means, wherein the control means calculates a target auxiliary turning amount calculation means for calculating a target auxiliary turning amount of the auxiliary turning means, and Means for detecting the torque of the steering system, target auxiliary turning force calculation means for calculating the target auxiliary turning force based on the detected torque,
An auxiliary turning control means for controlling the auxiliary turning means based on the target auxiliary turning amount, and an auxiliary turning force control means for controlling the auxiliary turning force generating means based on the target auxiliary turning force. The target auxiliary turning force calculation means has means for determining a driving state of the auxiliary turning drive means, and when the auxiliary turning means is driven, when the auxiliary turning means is not driven. And a means for increasing the ratio of the target auxiliary turning force to the detected torque in comparison with the automatic steering apparatus for a vehicle (structure of claim 1), or a steering wheel and a steering wheel. And an auxiliary steering means that is provided in a steering system between the steering wheels and assists the steered wheels relative to the steering wheel, and an auxiliary steering force that is provided in the steering system and assists the steering of the steered wheels. Auxiliary steering force generation A semi-steer-by-wire type automatic steering apparatus for a vehicle, which has a step and a control means for controlling the auxiliary steering means and the auxiliary steering force generating means, wherein the control means is a target auxiliary steering means for the auxiliary steering means. Target auxiliary turning amount calculating means for calculating a steering amount; means for detecting a torque of the steering system; target auxiliary turning force calculating means for calculating a target auxiliary turning force based on the detected torque; The target steering force is a reaction force reduction steering force for reducing the torque that acts on the steering wheel due to the reaction force when the auxiliary steering means performs auxiliary steering of the steered wheels based on the target auxiliary steering amount. Reaction force reduction turning force calculation means for calculating based on the auxiliary turning amount, target auxiliary turning force correction means for correcting the target auxiliary turning force based on the reaction force reduction turning force, and the target auxiliary The auxiliary steering wheel based on the steering amount And an auxiliary turning force control means for controlling the auxiliary turning force generating means based on the target auxiliary turning force corrected by the reaction force reducing turning force. However, the target auxiliary steering force calculation means compares the means for determining the driving state of the auxiliary steering drive means with the means for determining the drive state of the auxiliary steering drive means when the auxiliary steering means is not driven. And a means for increasing the ratio of the target assisted steering force to the detected torque, the automatic steering apparatus for a vehicle (the structure of claim 2).

Further, according to the present invention, in order to effectively achieve the above-mentioned main problem, in the structure according to claim 1 or 2, the control means has a large target auxiliary steering amount. It is configured to increase the ratio as much as possible (configuration of claim 3).

[0009]

According to the first and second aspects of the present invention, the driving state of the auxiliary turning drive means is determined, and the auxiliary turning means is not driven when the auxiliary turning means is being driven. Since the ratio of the target auxiliary turning force to the detected torque is increased compared to the above, the ratio of the target auxiliary turning force to the detected torque of the steering system during the normal steering by the driver must be too large. It is possible to prevent the steering reaction force from becoming too small due to this, and increase the ratio of the target assisted steering force to the detected torque of the steering system during automatic steering, thereby assisting during automatic steering. It is possible to effectively reduce the discomfort felt by the driver due to the reaction force when the steering means steer the steering wheels.

Particularly, according to the structure of the above-mentioned claim 2, the torque acting on the steering wheel due to the reaction force when the auxiliary turning means auxiliary turns the steered wheels based on the target auxiliary turning amount is reduced. The reaction force reduction turning force for calculating the target auxiliary turning force is calculated based on the target auxiliary turning amount, the target auxiliary turning force is corrected based on the reaction force reducing turning force, and the target corrected by the reaction force reducing turning force is calculated. Since the auxiliary turning force generating means is controlled based on the auxiliary turning force, it is possible to more effectively reduce the discomfort felt by the driver during automatic steering as compared with the case of the configuration of claim 1. it can.

According to the third aspect of the present invention, the larger the target auxiliary turning amount is, the larger the ratio is. Therefore, the target auxiliary turning amount is large and the steered wheels are steered. The larger the reaction force at the time is, the larger the target auxiliary turning force is. Therefore, compared with the case where the ratio when the auxiliary turning means is driven is constant, the strange feeling that the driver feels during automatic steering Can be appropriately reduced.

[0012]

According to a preferred embodiment of the present invention, in the structure of claim 1 or 2,
The means for determining the driving state of the auxiliary turning drive means is configured to determine the driving state of the auxiliary turning drive means based on the target auxiliary turning amount (preferred aspect 1).

According to another preferred aspect of the present invention, in the structure of claim 1 or 2, the auxiliary turning force generating means is provided in a steering system between the auxiliary turning means and the steered wheels. (Preferred embodiment 2).

According to another preferred embodiment of the present invention, in the structure of the preferred embodiment 2, the steering system includes a first steering shaft and a second steering shaft connected to the steering wheel, The steering means is an auxiliary steering electric motor having a housing connected to one of the first and second steering shafts and a rotor connected to the other of the first and second steering shafts and rotating relative to the housing. The second steering shaft is rotationally driven relative to the first steering shaft (preferred aspect 3).

According to another preferred aspect of the present invention, in the structure of claim 2, the reaction force reduction steering force calculation means is a reaction force torque acting on the steering wheel due to the reaction force. Is configured to calculate a reaction force reducing steering force for canceling the above-mentioned value based on the target auxiliary steering amount (preferred aspect 4).

According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 3, the target auxiliary turning amount calculation means is the target relative rotation angle of the second steering shaft with respect to the first steering shaft. Is configured to calculate the target auxiliary turning amount of the auxiliary turning means (preferred aspect 5).

According to another preferred aspect of the present invention, in the configuration of the preferred aspect 5, the reaction force reducing steering force calculating means is the target relative rotation of the second steering shaft with respect to the first steering shaft. It is configured to calculate a reaction force reduction turning torque for canceling a torque acting on the steering wheel due to a reaction force torque when the steering wheel is auxiliary steered based on the angle based on the target auxiliary turning amount. (Preferred embodiment 6).

According to another preferred aspect of the present invention, in the structure of the above-mentioned claim 1, the control means includes a reaction force and an auxiliary rotation caused by auxiliary steering of the steered wheels by the auxiliary steering means. Timing control for controlling the control timing of the auxiliary turning control means and the auxiliary turning force control means so that the auxiliary turning forces generated by the rudder force generating means based on the reaction force reducing turning force are generated in synchronization with each other. It is configured to have means (preferred aspect 7).

According to another preferred aspect of the present invention, in the structure of the above-mentioned claim 2, the control means includes a reaction force and an auxiliary steering force caused by the steering wheel being assisted by the auxiliary steering means. Auxiliary steering control means and auxiliary steering force control so that the auxiliary steering forces generated based on the target auxiliary steering force corrected by the reaction force reduction steering force by the force generating means are generated in synchronization with each other. It is configured to have timing control means for controlling the control timing of the means (preferred aspect 8).

According to another preferred embodiment of the present invention, in the configuration of the preferred embodiment 7 or 8, the timing control means is the auxiliary steering control means and the output timing of the control command to the auxiliary steering force control means. By controlling the control timing of the auxiliary steering control means and the auxiliary steering force control means (preferred aspect 9).

According to another preferred aspect of the present invention, in the structure of claim 2, the target auxiliary turning force calculation means is provided in the auxiliary turning force control means, and the auxiliary turning force control means is provided. Control the auxiliary turning force generating means based on the sum of the target auxiliary turning force and the reaction force reducing turning force, and the timing control means outputs the control command to the auxiliary turning control means based on the target auxiliary turning amount. The control timing of the auxiliary turning control means and the auxiliary turning force control means is controlled by controlling the output timing of the control command to the auxiliary turning force control means based on the timing and the reaction force reduction turning force ( Preferred embodiment 10).

According to another preferred aspect of the present invention, in the structure of claim 1 or 2, the auxiliary steering force generating means is configured to be an electric power steering device (preferred aspect 11). ).

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram showing one embodiment of an automatic steering apparatus for a vehicle according to the present invention, which is applied to a semi-steer-by-wire type vehicle equipped with a steering angle varying device and an electric power steering device. .

In FIG. 1, 10FL and 10FR respectively indicate the left and right front wheels of the vehicle 12, and 10RL and 10RR respectively indicate the left and right rear wheels of the vehicle. The left and right front wheels 10FL and 10FR, which are steered wheels, are driven by a rack-and-pinion type electric power steering device 16 driven in response to a driver's operation of the steering wheel 14, via a rack bar 18 and tie rods 20L and 20R. Be steered.

In the illustrated embodiment, the electric power steering device 16 is a rack coaxial type electric power steering device. The electric motor 22 and the rotational torque of the electric motor 22 are reciprocating force of the rack bar 18. And a conversion mechanism 24 of, for example, a ball screw type, and generates an auxiliary steering force that drives the rack bar 18 relative to the housing 26, thereby reducing the steering burden on the driver. Functions as a force generating means. The auxiliary turning force generating means may have any configuration known in the art, and may be provided on the left and right front wheels side of the turning angle varying device 30 described later.

The steering wheel 14 is the upper steering shaft 2 as the first steering shaft.
8A, a turning angle varying device 30, a lower steering shaft 28B as a second steering shaft, and a joint 32 are drivingly connected to a pinion shaft 34 of the electric power steering device 16. In the illustrated embodiment, the turning angle varying device 30 includes a housing 36.
The auxiliary steering drive electric motor 36 is connected to the lower end of the upper steering shaft 28A on the A side and to the upper end of the lower steering shaft 28B on the rotor 36B side.

Thus, the steered angle varying device 30 rotates the second steering shaft relative to the first steering shaft, so that the left and right front wheels 10FL and 10FR, which are the steered wheels, are relatively moved with respect to the steering wheel 14. It functions as an auxiliary steering means for driving the auxiliary steering.

Particularly, in the turning angle varying device 30, the holding current for preventing the relative rotation of the housing 36A and the rotor 36B during normal operation is applied to the electric motor 36, whereby the relative rotation of the lower steering shaft 22B with respect to the upper steering shaft 22A. The angle (simply referred to as a relative rotation angle) is maintained at 0, but during automatic steering, the electric motor 36 positively rotates the lower steering shaft 22B relatively to the upper steering shaft 22A, thereby depending on the steering operation of the driver. Left and right front wheels 10
Automatically steers FL and 10FR.

In the illustrated embodiment, the upper steering shaft 22A has a steering angle sensor 4 for detecting a rotation angle of the upper steering shaft as a steering angle θs.
A torque sensor 42 for detecting 0 and steering torque Ts is provided, and a steering angle sensor 44 for detecting the rotation angle of the lower steering shaft 22B as the actual steering angle θa of the left and right front wheels is provided on the lower steering shaft 22B. The outputs of these sensors are supplied to the steering control device 46. A signal indicating the vehicle speed V detected by the vehicle speed sensor 48 and a signal indicating the vehicle yaw rate γ detected by the yaw rate sensor 50 are also input to the steering control device 46.

The signal indicating the steering angle θa and the signal indicating the vehicle speed V are also input from the steering control device 46 to the steering angle variable control device 52 for controlling the steering angle variable device 30, and the signal indicating the steering torque Ts and The signal indicating the vehicle speed V is the steering control device 4
6 is also input to the electric power steering (electric PS) control device 54 for controlling the electric power steering device 16. Also, the signal indicating the steering angle θa detected by the steering angle sensor 44 is the left and right front wheels 10FL after the completion of automatic steering.
And 10FR to align the straight position with the neutral position of the steering wheel 14.

As will be described later, the steering control device 46 calculates the target yaw rate γt of the vehicle and, at the same time, calculates the target yaw rate γt.
And a steering angle varying device 3 for reducing a deviation Δγ between the vehicle yaw rate γ detected by the yaw rate sensor 50 and the vehicle yaw rate γ.
A target relative rotation angle θr of the lower steering shaft 22B with respect to the upper steering shaft 22A is calculated as a target auxiliary steering amount of 0, and a command signal indicating the target relative rotation angle θr is output to the steering angle variable control device 52.

Further, the steering control device 46 is a turning angle changing device 3.
Steering wheel 1 by automatic steering by 0 operation
The correction steering torque Te for canceling the reaction torque transmitted to the motor 4 is calculated based on the target relative rotation angle θr, and a command signal indicating the correction steering torque Te is output to the electric power steering controller 54.

The steering angle variable control device 52 maintains the relative rotation angle of the steering angle variable device 30 at 0 during the normal steering by the driver, and the steering control device 46 inputs a signal indicating the target relative rotation angle θr. At this time, the electric motor 36 of the steering angle varying device 30 is controlled based on the target relative rotation angle θr so that the lower steering shaft 22B rotates relative to the upper steering shaft 22A by the target relative rotation angle θr. And 10FR are automatically steered to reduce the yaw rate deviation Δγ of the vehicle to improve the running stability of the vehicle when turning.

The electric power steering control device 54 calculates an auxiliary turning torque Tab for reducing the steering load on the driver according to the steering torque Ts and the vehicle speed V, and inputs the auxiliary turning torque Tab from the steering control device 46. Calculated as the target auxiliary steering torque Ta by adding the corrected steering torque Te
By controlling the electric motor 22 of the electric power steering device 16 based on the target auxiliary turning torque Ta, the steering assist is performed and the reaction torque generated by the operation of the turning angle varying device 30 during automatic steering is offset. .

In the illustrated embodiment, in particular, the electric power steering control device 54 is used when the target relative rotation angle θr is not 0 and automatic steering is performed by the steering angle varying device 30, and when automatic steering is not performed. The auxiliary steering torque Tab is calculated so that the ratio of the magnitude of the auxiliary steering torque Tab to the magnitude of the steering torque Ts becomes larger than that of the steering torque Ts, and the steering torque Ts becomes larger as the target relative rotation angle θr becomes larger. The auxiliary turning torque Tab is calculated so that the ratio of the size of the auxiliary turning torque Tab to the size thereof becomes large.

Further, in the illustrated embodiment, the steering control device 46 corrects the reaction torque generated by the operation of the turning angle varying device 30 and the correction generated by the electric power steering device 16 to cancel the reaction torque. The torque corresponding to the steered torque Te is generated in synchronization with each other, so that the reaction torque generated by the operation of the steered angle varying device 30 is reliably and appropriately controlled by the torque corresponding to the corrected steered torque Te. The output timing of the command signal to the electric power steering controller 54 is controlled so as to cancel each other.

Although not shown in detail in FIG. 1, the steering control device 46, the turning angle variable control device 52, and the electric power steering control device 54 respectively include a CPU, a ROM, and an R.
It may include an AM and an input / output port device, which are composed of a microcomputer and a driving circuit which are connected to each other by a bidirectional common bus. Further, steering angle sensors 40 and 44, torque sensor 42, yaw rate sensor 5
0 indicates that the steering angles θs and θa, the steering torque Ts, and the yaw rate γ are positive when the steering of the vehicle to the left turning direction is positive.

The target auxiliary turning amount calculation and timing control routine achieved by the steering control device 46 in the illustrated embodiment will now be described with reference to the flow chart shown in FIG. The control according to the flowchart shown in FIG. 2 is started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, in step 10, a signal indicating the steering angle θs is read, and in step 20, the actual steering angle δ of the front wheels is calculated based on the steering angle θs, and H is set to the wheel base of the vehicle. And the target yaw rate γt of the vehicle according to the following equation 1 with Kh as a stability factor.
Is calculated, and the deviation Δγ (= γt−γ) between the target yaw rate γt and the detected yaw rate γ is calculated. γt = V ・ δ / (1 + Kh ・ V ² ) H (1)

In step 30, the yaw rate deviation Δ
A target auxiliary turning amount of the turning angle varying device 30, that is, a target relative rotation angle θr of the lower steering shaft 22B with respect to the upper steering shaft 22A is calculated from a map corresponding to the graph shown in FIG. 3 based on γ.

In step 40, I is the moment of inertia of the electric motor 36 of the steering angle varying device 30, C is the viscosity coefficient of the steering angle varying device 30, etc., and α is the turning of the electric power steering device 16. A steering angle is used as the steering angle, and θrd and θrtd are used as differential values and second-order differential values of the target relative rotation angle θr, respectively, and a feed for canceling the reaction torque generated by the automatic steering by the turning angle varying device 30 according to the following formula 2. A corrected steering torque Te, which is a forward control amount, is calculated. Te = Iθrtd + Cθrd−αTs (2)

In step 50, a command signal indicating the target relative rotation angle θr is transmitted to the variable steering angle control device 52, the count value T of the timer is incremented by 1 in step 60, and in step 70. Is to determine whether or not the count value T of the timer is greater than or equal to the reference value Tc (a positive constant), that is, is it the timing to output the command signal indicating the corrected turning torque Te to the electric power steering control device 54. If it is determined whether or not the determination is negative, the process returns to step 60 when the determination is negative, and the process proceeds to step 80 when the determination is positive, the command signal indicating the corrected turning torque Te is transmitted to the electric power steering controller 54. To be done.

As shown in FIG. 7, the steering control device 4
6, the time from the time t1 when the target relative rotation angle θr is calculated to the time t3 when the command signal indicating the target relative rotation angle θr is transmitted is Tv1, and the steering angle variable control device 52 sets the target from the time t3. Tv2 is the time until the time t7 at which the command signal indicating the relative rotation angle θr is received and the electric motor 36 of the turning angle varying device 30 operates to generate the torque for automatic steering. Further, in the steering control device 46, the corrected steering torque Te
The time from the time t2 when T is calculated to the time t4 when the command signal indicating the corrected turning torque Te is transmitted is set to Te1, and the electric power steering control device 54 receives the command signal indicating the corrected turning torque Te from the time t4. Then, the time until the time point t8 at which the electric motor 22 of the electric power steering device 16 operates to generate steering assist torque is Te2.

Reference value T in the determination of step 70
c corresponds to the reaction torque generated by the automatic steering by the steering angle varying device 30 and the corrected steering torque Te generated by the electric power steering device 16 when the time t8 becomes the same as the time t7. The value corresponding to the time ΔT from time t3 to time t4 is set so that the torques are generated in synchronization with each other.

Although not shown in the figure, the steered angle variable control device 52 controls the target relative rotation angle θ by the steering control device 46.
When the command signal indicating r is received, the electric motor 36 is controlled to rotate the lower steering shaft 22B relative to the upper steering shaft 22A by a target relative rotation angle θr, whereby the left and right front wheels 10FL and 1FL are rotated.
Automatically steer 0FR.

Next, the auxiliary turning force control routine achieved by the electric power steering control unit 54 in the illustrated embodiment will be described with reference to the flowchart shown in FIG. The control according to the flow chart shown in FIG. 4 is also started by closing an ignition switch (not shown) and is repeatedly executed at predetermined time intervals.

First, in step 110, a signal or the like indicating the steering torque Ts detected by the torque sensor 42 is read, and in step 120, the corrected turning torque Te input from the steering control device 46 is read. The indicated signal is read.

In step 130, it is determined whether the absolute value of the corrected steering torque Te is positive, that is, whether the steering angle varying device 30 is performing automatic steering. When a positive determination is made, the routine proceeds to step 150, and when a negative determination is made, at step 140, the driver's steering burden is calculated from the map corresponding to the graph shown in FIG. 5 based on the steering torque Ts and the vehicle speed V. Auxiliary steering torque T, which is a feedback control amount for reducing
ab is calculated. In this case, as can be seen from FIG. 5, the magnitude of the auxiliary turning torque Tab increases as the magnitude of the steering torque Ts increases, and decreases as the vehicle speed V increases for the same steering torque Ts.

In step 150, as shown in FIG. 6, a map for calculating the auxiliary steering torque Tab is selected according to the absolute value of the corrected steering torque Te, and the map is selected from the selected map. The auxiliary steering torque Tab is calculated. In this case, as can be seen from FIG. 6, the corrected steering torque Te
The map is selected such that the larger the absolute value of A, in other words, the larger the control amount of automatic steering, the larger the ratio of the magnitude of the auxiliary turning torque Tab to the magnitude of the steering torque Ts.

In step 160, the target auxiliary turning torque Ta of the electric power steering device 16 is calculated as the sum of the auxiliary turning torque Tab and the corrected turning torque Te, and in step 170 the target auxiliary turning torque Ta is calculated. Rudder torque Ta
2 of the electric power steering device 16 based on
The target drive current for 2 is calculated, and the electric motor 22 is controlled based on the target drive current.

Thus, according to the illustrated embodiment, the yaw rate γ of the vehicle is set to the target yaw rate γt in steps 20 and 30 and is set as the target control amount for automatically steering the left and right front wheels in order to stably turn the vehicle. The target auxiliary turning amount of the turning angle varying device 30, that is, the lower steering shaft 22 with respect to the upper steering shaft 22A.
The target relative rotation angle θr of B is calculated, and in step 40, the corrected turning torque Te for canceling the reaction torque generated by the automatic steering by the turning angle varying device 30 is calculated.

Then, in steps 130 to 150, the auxiliary steering torque Tab, which is the feedback control amount for reducing the steering load on the driver, is calculated, and step 160
In step 170, the target auxiliary turning torque Ta of the electric power steering device 16 is calculated as the sum of the auxiliary turning torque Tab and the corrected turning torque Te, and in step 170, the target auxiliary turning torque Ta is electrically operated based on the target auxiliary turning torque Ta. The electric motor 22 of the power steering device 16 is controlled.

In this case, the auxiliary turning torque Tab is calculated from a map in which the magnitude ratio of the auxiliary turning torque Tab to the magnitude of the steering torque Ts is larger during automatic steering than during non-automatic steering, and as a result, the steering torque Ts is calculated. Since the gain of the feedback control based on is increased, the auxiliary steering torque Tab is prevented from becoming too large during the non-automatic steering and the steering reaction force during the normal steering by the driver is prevented from becoming too small, and the automatic steering is performed. At times, the torque acting on the steering wheel due to the reaction force due to the automatic steering can be effectively reduced, and thereby the discomfort felt by the driver during the automatic steering can be effectively reduced.

In particular, according to the illustrated embodiment, the larger the absolute value of the corrected steering torque Te, in other words, the larger the control amount of the automatic steering, the larger the magnitude of the auxiliary steering torque Tab with respect to the magnitude of the steering torque Ts. Since the map with the larger ratio is selected, the larger the control amount of the automatic steering is and the higher the reaction force by the automatic steering is, the higher the gain of the feedback control based on the steering torque Ts is. Therefore, regardless of the control amount of the automatic steering, Compared with the case where the auxiliary turning torque Tab is calculated from one map, the torque acting on the steering wheel due to the reaction force due to the automatic steering during the automatic steering is effectively and appropriately reduced. It is possible to effectively and appropriately reduce the discomfort felt by the driver during steering.

Also according to the illustrated embodiment, step 5
At 0, the command signal indicating the target relative rotation angle θr is output to the variable steering angle control device 52, and the reaction torque generated by the automatic steering by the variable steering angle device 30 and the electric power steering device 16 are generated. In steps 60 to 80, the target relative rotation angle θr is generated so that torques corresponding to the corrected steering torque Te are generated in synchronization with each other.
The timing at which the command signal indicating the target auxiliary turning torque Ta is transmitted to the electric power steering control device 54 is controlled with reference to the timing at which the command signal indicating the is transmitted to the variable steering angle control device 52.

Then, in steps 120 to 160, the target auxiliary turning torque Ta of the electric power steering device 16 is calculated as the sum of the auxiliary turning torque Tab and the corrected turning torque Te, and in step 170 the target auxiliary turning torque Ta is calculated. The electric power steering device 16 is controlled based on the turning torque Ta.

Therefore, by automatically steering the yaw rate γ of the vehicle to the target yaw rate γt, the vehicle can be stably turned and the reaction torque generated by the operation of the turning angle varying device 30. Can be canceled reliably and appropriately by the torque corresponding to the corrected steering torque Te, thereby preventing the driver from feeling uncomfortable more reliably and appropriately than when the timing control is not performed. can do.

For example, the reaction torque when the automatic steering is performed without being steered by the driver is the turning angle varying device 3
If the relative rotation angle of 0 is changed as indicated by the chain double-dashed line in FIG. 8, the steering torque is reduced by the auxiliary turning torque Tab, and the torque felt by the driver is shown in FIG. And the reaction torque due to the automatic steering is reduced by the correction steering torque T.
The torque felt by the driver is canceled out by
In this case, as shown by the solid line, the torque is greatly reduced, and the fluctuation of the torque when the direction of the automatic steering is reversed is also significantly reduced. Note that, in FIG. 8, the alternate long and short dash line is calculated from the map shown in FIG. 5 in the same manner as in the case of the non-automatic steering when the auxiliary steering torque Tab is calculated during the automatic steering, and the electric power steering device 16 is operated by the auxiliary steering torque Tab. Shows the torque that the driver feels when is controlled as the target auxiliary turning torque Ta.

According to the illustrated embodiment, the output timing is controlled only for the signal indicating the corrected turning torque Te, and the output of the signal indicating the auxiliary turning torque Tab is not delayed, so that the auxiliary turning torque Tab is changed. It is possible to reliably prevent the driver from feeling an unnatural steering feeling due to the delay in the generation of the corresponding auxiliary turning torque.

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

For example, in the above embodiment, the larger the absolute value of the corrected steering torque Te, in other words, the larger the control amount of the automatic steering, the larger the auxiliary steering torque Tab with respect to the steering torque Ts. The map is selected such that the ratio of the steering torque Ts to the steering torque Ts is larger than that of the non-automatic steering during the automatic steering. As long as the rudder torque Tab is calculated, only one type of map may be used during automatic steering.

Further, in the above embodiment, the command signal indicating the target relative rotation angle θr is the steering angle variable control device 52.
A command signal indicating the target auxiliary turning torque Ta is output to the electric power steering control device 54. However, the command signal output to the steering angle variable control device 52 is a target relative rotation angle. Electric motor 36 corresponding to θr
For the electric power steering control device 54, or the target drive current for the electric motor 22 corresponding to the target auxiliary turning torque Ta.

Further, in the above-described embodiment, the corrected turning torque Te for canceling the reaction force torque generated by the automatic steering by the turning angle varying device 30 is calculated according to the above equation 2. However, the corrected steering torque Te
May be calculated in any manner known in the art, and in particular, the command signal output to the variable steering angle control device 52 is the target drive current for the electric motor 36 corresponding to the target relative rotation angle θr. In this case, the corrected turning torque Te may be modified so as to be calculated based on the target drive current for the electric motor 36.

Further, in the above embodiment, the electric power steering device 16 as the auxiliary turning force generating means is used.
Is provided on the steered wheel side with respect to the steered angle varying device 30 as the auxiliary steered means, but the auxiliary steered force generation means may be provided on the steering wheel side with respect to the auxiliary steered means.

Further, in the above-described embodiment, the corrected steering torque Te, which is the feedforward control amount for canceling the reaction torque generated by the automatic steering by the steering angle varying device 30, is calculated. , The steering torque Ts and the vehicle speed V, the auxiliary steering torque Tab which is a feedback control amount for reducing the steering burden on the driver is calculated, and the target auxiliary steering torque T of the electric power steering device 16 is calculated.
Although a is calculated as the sum of the auxiliary turning torque Tab and the corrected turning torque Te, the feedforward control amount may be omitted.

Further, in the above-described embodiment, the steered angle varying control device 52 maintains the relative rotation angle of the steerable angle varying device 30 at 0 during normal steering by the driver. The rudder angle varying device 30 adjusts according to the running condition of the vehicle such that the ratio of the rotation angle of the lower steering shaft 22B to the rotation angle of the upper steering shaft 22A becomes smaller as the vehicle speed V becomes higher during normal steering without automatic steering. It may be used as a gear ratio variable device.

In the above embodiment, the target turning amount of the steered wheels is the target turning amount for reducing the deviation between the actual yaw rate of the vehicle and the target yaw rate of the vehicle. As described in Japanese Patent Laid-Open No. 11-73597, a target steering amount for causing the vehicle to travel along the traveling lane, or, for example, as disclosed in Japanese Patent Laid-Open No. 10-31799, a laser radar or the like is used. When an obstacle ahead is detected, it may be a target steering amount for avoiding an obstacle ahead of the vehicle, and may be an arbitrary target steering amount other than these.

In the above embodiment, the turning angle varying device 30 is controlled by the turning angle varying control device 52,
The electric power steering device 16 is controlled by the electric power steering control device 54, and the steered angle variable control device 52 and the electric power steering control device 54 are controlled by the steering control device 46. Two controllers may be integrated into one controller.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a vehicle automatic steering apparatus according to the present invention, which is applied to a semi-steer-by-wire type vehicle including a turning angle varying device and an electric power steering device.

FIG. 2 is a flowchart showing target auxiliary turning amount calculation and timing control achieved by the steering control device according to the embodiment.

FIG. 3 is a graph showing a relationship between a yaw rate deviation Δγ and a target relative rotation angle θr.

FIG. 4 is a flowchart showing an auxiliary steering force control routine achieved by the electric power steering controller in the embodiment.

FIG. 5: Vehicle speed V and steering torque T during non-automatic steering
It is a graph which shows the relationship between s and target turning torque Tab.

FIG. 6 is a vehicle speed V and a steering torque Ts during automatic steering.
It is a graph which shows the relationship between and the target steering torque Tab.

FIG. 7 is an explanatory diagram showing the timing of each control achieved by the steering control device, the variable steering angle control device, and the electric power steering control device in the embodiment.

FIG. 8 is a schematic graph showing that reaction torque is reduced by the embodiment when automatic steering is performed without being steered by a driver.

[Explanation of symbols]

10FR-10RL ... Wheels 16 ... Electric power steering device 28A ... Upper steering shaft 28B ... Lower steering shaft 30 ... Steering angle variable device 40, 44 ... Steering angle sensor 42 ... Torque sensor 46 ... Steering control device 48 ... Vehicle speed sensor 50 ... Yaw rate sensor 52 ... Steering angle variable control device 54 ... Electric power steering (electric PS) control device

Claims (3)

[Claims] 1. An auxiliary steering means provided in a steering system between a steering wheel and a steered wheel for assisting the steered wheel relative to the steering wheel, and the steered wheel provided in the steering system. A semi-steer-by-wire vehicle automatic system having auxiliary steering force generating means for generating an auxiliary steering force for assisting steering of the vehicle and control means for controlling the auxiliary steering means and the auxiliary steering force generating means. As a steering device,
The control means calculates target auxiliary turning amount calculation means for calculating the target auxiliary turning amount of the auxiliary turning means, means for detecting torque of the steering system, and target auxiliary turning force based on the detected torque. Target auxiliary turning force calculation means, auxiliary turning control means for controlling the auxiliary turning means based on the target auxiliary turning amount, and auxiliary turning force generation based on the target auxiliary turning force An auxiliary steering force control means for controlling the means, wherein the target auxiliary steering force calculation means determines the driving state of the auxiliary steering drive means, and when the auxiliary steering means is driven. And a means for increasing the ratio of the target auxiliary turning force to the detected torque as compared with when the auxiliary turning means is not driven. 2. A steering system provided between a steering wheel and a steered wheel, the auxiliary steering means for assisting the steered wheel relative to the steering wheel, and the steered wheel provided in the steering system. A semi-steer-by-wire vehicle automatic system having auxiliary steering force generating means for generating an auxiliary steering force for assisting steering of the vehicle and control means for controlling the auxiliary steering means and the auxiliary steering force generating means. As a steering device,
The control means calculates target auxiliary turning amount calculation means for calculating the target auxiliary turning amount of the auxiliary turning means, means for detecting torque of the steering system, and target auxiliary turning force based on the detected torque. And a torque that acts on the steering wheel due to a reaction force when the auxiliary turning means auxiliary turns the steered wheels based on the target auxiliary turning amount. Reaction force reduction turning force calculation means for calculating a reaction force reduction turning force for reduction based on the target auxiliary turning amount, and correction of the target auxiliary turning force based on the reaction force reduction turning force Target auxiliary turning force correction means, auxiliary turning control means for controlling the auxiliary turning means based on the target auxiliary turning amount, and the target auxiliary turning corrected by the reaction force reducing turning force. Auxiliary for controlling the auxiliary steering force generation means based on force Steering assist control means, the target auxiliary steering force calculation means determines the drive state of the auxiliary steering drive means, and the auxiliary steering means when the auxiliary steering means is driven. And a means for increasing the ratio of the target auxiliary turning force to the detected torque as compared with when not being driven. 3. The automatic vehicle steering system according to claim 1, wherein the control unit increases the ratio as the target auxiliary steering amount increases.