JP2001106105A - Steering assist unit for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively assist the driver in his or her steering manipulation. SOLUTION: If an actual steering angle θ is substantially equal to a desired steering angle θt (S90), a pseudo-lock condition is held so that no steering assist force is effected (S150). Meanwhile, if the actual steering angle θ is substantially not equal to the desired steering angle θt and if the driver does not steer the vehicle in such a direction that the steering angle θ goes away from the desired steering angle θt (S100), an actual assist torque Tas in the same direction as a steering direction by the driver is exerted to a steering wheel 14 (S100 to S130), but if the actual steering angle θ is substantially not equal to the desired steering angle θt and if the driver steers the vehicle in such a direction that the steering angle θ goes away from the desired steering angle θ, a steering assist torque (counter-steering force) in a direction reverse to a steering direction by the driver is exerted to the steering wheel 14 S190 to S180).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steering assist device for a vehicle, and more particularly, to a steering assist device for assisting a driver's steering operation by generating a steering reaction force or a steering assist force.

[0002]

2. Description of the Related Art As one of steering assist devices for vehicles such as automobiles, for example, as described in Japanese Patent Application Laid-Open No. 10-268441, a parking position and a parking route of a vehicle are calculated, and the driver is steered by voice. A parking assist device has been conventionally known which is configured to stop the vehicle at a parking position and to lock the steering angle to the instructed steering angle.

According to such a parking assist device, a parking position and a parking route of a vehicle are calculated, and a driver is instructed to steer by voice. Therefore, the driver only has to perform steering according to the instruction, and the steering angle is instructed. When the steering angle is reached, the steering angle is locked at the instructed steering angle, so that the vehicle can be easily and reliably parked at a predetermined position without requiring subsequent steering by the driver.

[0004]

However, in a conventional steering assist device such as the above-mentioned parking assist device, the driver must perform a steering operation in accordance with a voice instruction until the steering angle matches the instructed steering angle. Therefore, it is difficult to quickly match the steering angle with the instructed steering angle, and therefore, there is a problem that the driver's steering operation cannot be effectively assisted. Such a problem is the same in the case of a steering assist device in which a driver is instructed to perform steering by an image or by voice and image.

The present invention has been made in view of the above-mentioned problems in a conventional steering assist device configured to instruct a driver to perform steering by voice or image, and a main problem of the present invention. Is to effectively assist a driver's steering operation by generating a steering reaction force or a steering assist force such that the steering angle quickly matches the target steering angle.

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a vehicle steering assist device for assisting a driver's steering operation, comprising: means for detecting a steering angle; And a means for generating a steering reaction force when the driver is performing steering in a direction away from the target steering angle (the configuration according to claim 1). Or a vehicle steering assist device for assisting a driver's steering operation, wherein a means for detecting a steering angle, a means for calculating a target steering angle, and a steering operation in a direction away from the target steering angle by the driver. Means for generating a steering assist force when not performed is achieved by a vehicle steering assist device (the configuration of claim 2).

According to the first aspect of the present invention, a steering reaction force is generated when the driver is performing steering in a direction away from the target steering angle, so that the driver can steer in a direction away from the target steering angle. In addition, the driver recognizes that the steering direction is the opposite direction to the preferred direction due to the steering reaction force, so that the driver can surely steer in the preferred direction without hesitation.

According to the second aspect of the present invention, a steering assist force is generated when the driver does not perform steering in a direction away from the target steering angle, so that the driver moves in a direction away from the target steering angle. Steering is suppressed, and the driver can easily and surely steer in a preferred direction by steering according to the steering assist force.

According to the present invention, in order to effectively achieve the above-mentioned main object, in the configuration of the first aspect, the means for generating the steering reaction force is an assist motor of an electric power steering device. It is configured as such (the configuration of claim 3).

According to the third aspect of the present invention, since the means for generating the steering reaction force is the assist motor of the electric power steering device, the steering reaction force is reliably utilized by effectively using the assist motor of the electric power steering device. Can be generated.

According to the present invention, in order to effectively achieve the above-mentioned main object, the means for generating the steering assist force is an assist motor of an electric power steering device. It is configured as such (the configuration of claim 4).

According to the fourth aspect of the present invention, since the means for generating the steering assist force is the assist motor of the electric power steering device, the steering assist force is reliably utilized by effectively utilizing the assist motor of the electric power steering device. Can be generated.

[0013]

According to a preferred aspect of the present invention, in the configuration of the first aspect, the means for generating a steering reaction force has a large deviation between a target steering angle and an actual steering angle. Is smaller than the reference value, a steering reaction force is not generated (preferred mode 1).

According to another preferred embodiment of the present invention, in the configuration according to the second aspect, the means for generating the steering assist force is such that the magnitude of the deviation between the target steering angle and the actual steering angle is large. When the value is equal to or less than the reference value, the steering assist force is not generated (preferred mode 2).

According to another preferred aspect of the present invention, in the configuration of the first aspect, the steering assist device includes a means for detecting a steering torque, and the means for generating a steering reaction force includes: When the driver is performing steering in a direction away from the target steering angle and the steering torque exceeds a reference value, no steering reaction force is generated (preferred mode 3).

According to another preferred embodiment of the present invention, in the configuration of the first aspect, the means for generating the steering reaction force has a deviation between the target steering angle and the actual steering angle. It is configured to generate a higher steering reaction force as the value is larger (preferred mode 4).

According to another preferred embodiment of the present invention, in the configuration according to the second aspect, the means for generating the steering assist force has a magnitude of a deviation between the target steering angle and the actual steering angle. It is configured to generate a higher steering assist force as the value is larger (preferred mode 5).

According to another preferred embodiment of the present invention, in the configuration of the first aspect, the means for generating the steering reaction force includes a change rate of a deviation between a target steering angle and an actual steering angle. The larger the magnitude, the higher the steering reaction force is generated (preferred mode 6).

According to another preferred embodiment of the present invention, in the configuration according to the second aspect, the means for generating a steering assist force includes a rate of change of a deviation between a target steering angle and an actual steering angle. The larger the magnitude is, the lower the steering assist force is generated (preferred mode 7).

According to another preferred aspect of the present invention, in the configuration of the first aspect, when the deviation between the target steering angle and the actual steering angle increases, the driver can set the target steering angle. It is configured that it is determined that steering in a direction away from the steering angle is being performed (preferred mode 8).

According to still another preferred aspect of the present invention, in the configuration of the second aspect, when the magnitude of the deviation between the target steering angle and the actual steering angle does not decrease, the driver sets the target steering angle. It is configured that it is determined that steering in a direction away from the steering angle is not performed (preferred mode 9).

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a preferred embodiment of a vehicle steering assist device according to the present invention.

In FIG. 1, 10FL and 10FR denote left and right front wheels of the vehicle 12, respectively, and 10RL and 10RR denote left and right rear wheels which are driving wheels of the vehicle, respectively. The left and right front wheels 10FL and 10FR, which are both driven wheels and steering wheels, are driven by a rack and pinion type electric power steering device 16 which is driven in response to steering of a steering wheel 14 by a driver. Steered via 20L and 20R.

The steering wheel 14 is connected to a steering gear box 24 by a steering shaft 22, and a power unit 28 is drivingly connected to the steering shaft 22 by a gear reduction mechanism 26. The power unit 28 has a motor 30 and an electromagnetic clutch 32 for selectively drivingly connecting the gear reduction mechanism 26 and the motor 30.

In the illustrated embodiment, the steering shaft 22 is provided with a steering angle sensor 34 for detecting the steering angle θ and a torque sensor 36 for detecting the steering torque T. The outputs of these sensors are electronically controlled. It is supplied to the control device 38. Further, a signal indicating the vehicle speed V detected by the vehicle speed sensor 40 and a signal indicating whether or not the switch is in an on state are input from the steering assist switch (SW) 42 to the electronic control unit 38. .

Although not shown in detail in FIG. 1, the electronic control unit 38 includes a central processing unit (CPU), a read only memory (ROM), and a random access memory (RA).
M) and an input / output port device, which may comprise a microcomputer and a drive circuit connected to each other by a bidirectional common bus. Further, the steering angle sensor 34 and the torque sensor 36 detect the steering angle θ and the steering torque T, respectively, assuming that the steering in the left turning direction of the vehicle is positive.

Next, the steering assist control in the illustrated embodiment will be described with reference to the flowchart 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 θ is read. At the start of the control, a control signal is output to the electromagnetic clutch 32 prior to step 10 to connect the clutch.

In step 20, it is determined whether or not the steering assist switch 42 is on, that is, whether or not the driver desires steering assist. The process proceeds to step 70, and proceeds to step 30 when a negative determination is made.

In step 30, the basic assist amount Tab is calculated from the map corresponding to the graph shown in FIG. 5 based on the steering torque T. In step 40, the basic assist amount Tab is calculated based on the vehicle speed V as shown in FIG. The vehicle speed coefficient Kv is calculated from the map corresponding to the graph, the assist torque Ta is calculated as the product of the vehicle speed coefficient Kv and the basic assist amount Tab in step 50, and the assist torque Ta is calculated in step 60. A control signal is output to the motor 30, whereby power assist for reducing the steering force required for the driver is executed.

In step 70, for example, Japanese Patent Application No. 10-293159 before the publication of the application of the present applicant.
The target steering angle θt is calculated as in the parking assist system described in the specification and the drawings, and in step 80, the deviation between the target steering angle θt and the actual steering angle θ is calculated according to the following equation 1. Δθ is calculated. Δθ = θt−θ (1)

In step 90, it is determined whether or not the absolute value of the steering angle deviation Δθ is smaller than a reference value θo (positive constant), that is, the actual steering angle θ is substantially the same as the target steering angle θt. Is determined, the process proceeds to step 150 when the determination is affirmative, and proceeds to step 100 when the determination is negative.

In step 100, the steering angle deviation Δθ
Is determined, that is, whether the driver is performing steering in the direction in which the actual steering angle θ is away from the target steering angle θt, and an affirmative determination is made. If so, the process proceeds to step 140, and if a negative determination is made, the process proceeds to step 110.

In step 110, the steering angle deviation Δθ
The coefficient Ksn is calculated from a map corresponding to the graph shown by the solid line in FIG. 3 based on the absolute value of the steering angle deviation. In step 120, the time differential value Δθd of the steering angle deviation Δθ is calculated, and the time differential value is calculated. The steering assist torque Tan is calculated from a map corresponding to the graph shown by the solid line in FIG. 4 based on the absolute value of Δθd.

In step 130, the steering assist torque Tas in the forward direction, that is, the same direction as the steering direction by the driver, is calculated as the product of the coefficient Ksn and the steering assist torque Tan according to the following equation (2). Is output to the motor 30, whereby steering assist for assisting the driver's steering operation is executed, and thereafter, the process returns to step 10. Tas = KsnTan (2)

In step 140, it is determined whether or not the absolute value of the steering torque T exceeds a reference value To (positive constant), that is, whether or not the driver is performing steering with a relatively large steering torque. When a negative determination is made, the process proceeds to step 160, and when an affirmative determination is made, the driver is actively trying to steer the actual steering angle θ away from the target steering angle θt. Therefore, in step 150, the application of the forward or reverse steering assist torque for the steering assist is stopped or the state where the application of the steering assist torque is not performed is maintained (a pseudo lock state). Step 10
Return to

In step 160, the steering angle deviation Δθ
The coefficient Ksr is calculated from the map corresponding to the graph shown by the broken line in FIG. 3 based on the absolute value of the steering angle deviation. In step 170, the time differential value Δθd of the steering angle deviation Δθ is calculated and the time differential value is calculated. The steering assist torque Tar is calculated from the map corresponding to the graph shown by the broken line in FIG. 4 based on the absolute value of Δθd.

In step 180, the steering assist torque (steering reaction torque) Tas in the opposite direction, that is, the direction opposite to the steering direction by the driver, is calculated as the product of the coefficient Ksr and the steering assist torque Tar according to the following equation (3). The calculated control signal corresponding to the steering assist torque Tas is output to the motor 30, whereby the steering assist for prompting the driver to perform the steering in the reverse direction is executed, and thereafter, the process returns to step 10. Tas = Ksrtar (3)

Thus, according to the illustrated embodiment, when the steering assist switch 42 is in the ON state in step 20 and it is determined that the driver desires steering assist, in step 70, the target The steering angle θt is calculated, and in step 80, the deviation Δθ between the target steering angle θt and the actual steering angle θ is calculated.

When the actual steering angle θ is substantially the same as the target steering angle θt, an affirmative determination is made in step 90, and in step 150, the application of the steering assist torque is stopped, or the steering assist is stopped. Since the pseudo-lock state in which no torque is applied is maintained, and therefore the driver feels a relatively high steering reaction force in steering in any direction, the actual steering angle θ is substantially equal to the target steering angle θt. It can be determined that they are the same and are in an appropriate steering state.

If the actual steering angle θ is not substantially the same as the target steering angle θt, a negative determination is made in step 90, and in step 100, the driver sets the actual steering angle θ to the target steering angle θt. It is determined whether or not steering in a direction away from the angle θt is being performed. If a negative determination is made in this step, step 110
Since the steering assist torque Tas in the same direction as the steering direction by the driver is applied to the steering wheel 14 in steps 130 to 130, the driver is required to perform the steering operation so that the actual steering angle θ approaches the target steering angle θt. Can be encouraged.

Further, when the actual steering angle θ is not substantially the same as the target steering angle θt, and the driver is performing steering in a direction in which the actual steering angle θ deviates from the target steering angle θt, the routine proceeds to step 100. A positive determination is made, and in steps 160 to 180, a steering assist torque (steering reaction force torque) Tas in a direction opposite to the steering direction by the driver is applied to the steering wheel 14, so that the driver's steering direction is Can be recognized in a direction opposite to the preferred direction, and the driver can be prompted to perform a steering operation in a direction in which the actual steering angle θ approaches the target steering angle θt.

Therefore, according to the illustrated embodiment, the driver determines whether the steering state is appropriate based on the reaction force when the steering wheel 14 is steered, and determines the appropriate steering direction based on the ease of steering. Therefore, the driver can easily and surely perform a proper steering operation as compared with a case where the steering is instructed by a voice or a voice and an image, and quickly set a proper steering angle. Can be steered.

Further, according to the illustrated embodiment, the driver is more reliably instructed to steer to an angle other than the full turning angle as compared with the case where the steering is instructed by voice or voice and image. Therefore, even when the illustrated embodiment is applied to, for example, a parking assist device for a vehicle, the instruction steering angle for the driver is not limited to the full turning angle, and accordingly, the parking position and the vehicle before parking are not limited. Conditions such as the relationship with the stop position and the recommended route to the parking position are relaxed, whereby the margin of the parking support control and the driving operation of the driver can be expanded.

In particular, according to the illustrated embodiment, the steering assist torque Tas increases as the magnitude of the steering angle deviation Δθ increases, and therefore, as the magnitude of the steering angle deviation Δθ increases, the steering assist force or the steering assist force applied to the steering wheel 14 increases. Since the steering reaction force is high, the driver can surely steer in an appropriate direction even when the deviation between the actual steering angle θ and the target steering angle θt is large.

According to the illustrated embodiment, the steering assist torque Tas in a region where the absolute value of the steering angle deviation Δθ is slightly larger than the reference value θo increases sharply as the absolute value of the steering angle deviation Δθ increases. Therefore, in a situation where the absolute value of the steering angle deviation Δθ is equal to or smaller than the reference value θo, it is possible to effectively prevent the driver from performing steering such that the absolute value of the steering angle deviation Δθ becomes larger than the reference value θo. Can be.

According to the illustrated embodiment, the steering assist torque Tan when the driver steers relatively quickly in an appropriate direction is lower as the rate of change of the steering angle deviation Δθ is larger. When the driver steers relatively slowly, it is possible to give a reliable steering instruction to the driver,
Further, when the driver steers relatively quickly in an appropriate direction, a relatively gentle steering assist torque is applied to prevent the steering assist torque from becoming excessive, thereby reducing the actual steering angle θ to the target steering angle. Steering exceeding θt can be effectively prevented.

According to the illustrated embodiment, the steering assist torque Tar when the driver steers in a direction opposite to the proper direction increases as the rate of change of the steering angle deviation Δθ increases. The degree of increase in the coefficient Ksr with the increase in the magnitude of the steering angle deviation Δθ when the driver steers in a direction opposite to the proper direction is determined when the driver steers in the proper direction. Is larger than the degree of increase of the coefficient Ksn, the driver may erroneously take an appropriate value due to a lack of a steering reaction force in a case where the driver operates relatively quickly in the direction opposite to the appropriate direction. Steering relatively quickly in the direction opposite to the direction can be reliably prevented.

According to the illustrated embodiment, for example, when the driver performs steering with a relatively large steering torque in a direction in which the actual steering angle θ is away from the target steering angle θt, such as during emergency avoidance steering, Since the affirmative determination is made in step 140 and the steering assist torque is not applied, the driver can steer in the direction desired by the driver if necessary even during the steering assist control.

Further, according to the illustrated embodiment, the application of the steering assist torque is achieved by the electric power steering device 16 which performs the power assist for reducing the driver's steering load during the normal running of the vehicle. The steering assist can be realized by effectively using the power steering device 16.

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

For example, in the above-described embodiment, the steering assist torque Tar when the driver steers in the direction opposite to the proper direction increases as the rate of change of the steering angle deviation Δθ increases. However, the steering assist torque Tar may be constant, or may be set to decrease slightly as the rate of change of the steering angle deviation Δθ increases.

In the above-described embodiment, the steering assist torque Tas is increased or decreased in accordance with the absolute value of the rate of change Δθd of the steering angle deviation Δθ. And the steering assist torque Tas when the driver steers in a direction opposite to the proper direction is corrected to be calculated from a map similar to the graph shown by the solid line and the broken line in FIG. 3, for example. Alternatively, the steering assist torque Tas may be modified so as to be variably set according to the vehicle speed so as to decrease as the vehicle speed V increases.

In the above-described embodiment, the steering such as the driver's emergency avoidance steering is determined in step 140. However, the determination in step 140 may be omitted. In addition to the determination of the absolute value of the change rate Δθd of the steering angle deviation Δθ,
A determination may be made as to whether or not (positive constant) is exceeded, and the process may be modified to proceed to step 150 when a positive determination is made.

[0056]

As is apparent from the above description, according to the present invention, the driver can determine whether the steering direction is appropriate based on the ease of steering, or can determine the steering angle based on the steering reaction force. Since it is possible to determine whether or not the steering angle is appropriate, the driver can easily and reliably perform the appropriate steering operation and promptly as compared with the case where the steering is instructed by voice or voice and image. Steering can be performed at an appropriate steering angle.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one preferred embodiment of a vehicle steering assist device according to the present invention.

FIG. 2 is a flowchart illustrating a steering assist control routine in the illustrated embodiment.

FIG. 3 is a graph showing a relationship between an absolute value of a steering angle deviation Δθ and coefficients Ksn and Ksr.

FIG. 4 is a graph showing a relationship between an absolute value of a time derivative Δθd of the steering angle deviation Δθ and steering assist torques Tan and Tar.

FIG. 5 is a graph showing a relationship between a steering torque T and a basic assist amount Tab.

FIG. 6 is a graph showing a relationship between a vehicle speed V and a vehicle speed coefficient Kv.

[Explanation of symbols]

 10FR to 10RL Wheels 16 Electric power steering device 28 Power unit 34 Steering angle sensor 36 Torque sensor 38 Electronic control device 40 Vehicle speed sensor 42 Steering assist switch

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D032 CC08 DA03 DA15 DA23 DA99 DB11 DC03 DD01 DD02 EA01 EB11 EB12 EC22 GG01 3D033 CA11 CA13 CA16 CA17 CA21 CA27

Claims (4)

[Claims] In a vehicle steering assist device for assisting a driver's steering operation, means for detecting a steering angle; means for calculating a target steering angle; Means for generating a steering reaction force when steering is being performed. 2. A vehicle steering assist device for assisting a driver's steering operation, comprising: means for detecting a steering angle; means for calculating a target steering angle; Means for generating a steering assist force when steering is not being performed. 3. The vehicle steering assist device according to claim 1, wherein the means for generating the steering reaction force is an assist motor of an electric power steering device. 4. The vehicle steering assist device according to claim 2, wherein the means for generating the steering assist force is an assist motor of an electric power steering device.