JP2003154947A - Automatic steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic steering device capable of easily detecting steering operation input. SOLUTION: In a steering control part 11, an actuator 20 is controlled to set generated torque of the actuator 20 as total of an automatic steering torque value for automatic steering and a target assist torque value for power steering. Assist torque gain in automatic steering is controlled to be set lower than assist torque gain in manual steering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic steering device applied when a vehicle is automatically parked without depending on a steering operation by a driver.

[0002]

2. Description of the Related Art As prior art relating to an automatic steering device,
There is one disclosed in Japanese Patent Laid-Open No. 4-205505. In this conventional technique, the automatic steering torque and the assist torque of the power steering are generated at the same time, so that the steering operation input by the driver during the automatic steering can be facilitated. That is, the assist torque of the power steering makes it possible to reduce the steering torque to overcome the automatic steering torque, and to reduce the load when the driver attempts to perform the steering operation during the automatic steering.

Further, when the driver performs steering control during automatic steering to stop automatic steering and switch to manual steering, the above-mentioned conventional technique enables smooth switching. In the automatic steering device prior to the above-mentioned prior art, since the assist torque of the power steering is not generated during automatic steering, the automatic steering torque suddenly disappears at the time of switching, and the assist torque in the opposite direction to the automatic steering torque also suddenly occurs. . Therefore, the steering reaction force changes abruptly. However, according to the above-mentioned conventional technique, since the steering torque for overcoming the automatic steering torque is small, the change in the steering reaction force is small and smooth switching can be performed.

A technique for switching from automatic steering to manual steering when a steering operation is performed is disclosed in Japanese Patent Laid-Open No. 11-
No. 198839, the presence or absence of steering operation is recognized based on the steering torque detection value detected by the steering torque sensor.

[0005]

In the case of the above-described conventional automatic steering device capable of simultaneously generating the automatic steering torque and the assist torque of the power steering, the driver can maintain a small steering torque even during the automatic steering. Although it has an advantage that steering operation can be performed against automatic steering, it is rather bad that the steering torque by the driver does not increase, and it is difficult to detect the presence or absence of steering operation from the steering torque detection value. Creates a problem. In other words, in order to recognize the steering operation, the threshold value of the steering torque detection value must be lowered, but if this is done, the steering torque based on the steering operation of the driver will be reduced by noise such as inertia torque of the steering wheel itself. Becomes difficult to identify,
The steering operation input cannot be detected accurately.

[0006]

The automatic steering system of the present invention has been made to solve such a problem, and in an automatic steering system capable of executing both automatic steering and manual steering, a driver The assist torque is generated with respect to the steering torque given by, and the assist torque is smaller during automatic steering than during manual steering. More specifically, in an automatic steering device that applies an automatic steering torque to a steering shaft of a steering mechanism in which wheels are steered in accordance with rotation of a steering shaft connected to a steering wheel, an automatic steering torque value and a target assist torque value And a steering control unit for generating a torque, which is an actuator controlled by the steering control unit, and which gives a torque to the steering shaft that is equal to the sum of the automatic steering torque value and the target assist torque value. The target assist torque value is generated by multiplying the steering torque given from the wheel to the steering shaft by the assist torque gain, and the assist torque gain during automatic steering is made smaller than that during non-automatic steering.

During automatic steering, the assist torque, more specifically, the assist torque gain, is being steered (during manual steering).
Since the value is smaller than that in (1), the steering torque associated with the steering operation during automatic steering is increased to some extent. Therefore, the steering torque threshold value for detecting the steering operation input can be set to a large value, and it can be easily distinguished from the inertia torque of the steering wheel. Therefore, the presence or absence of the steering operation can be recognized without error based on the detected steering torque, and the manual steering can be accurately switched based on the recognition result.

Although the steering torque during the automatic steering has increased to some extent, the steering operation during the automatic steering is easier than when the assist torque is not generated, and the automatic steering is switched to the manual steering based on the steering operation. The sudden decrease in steering torque that occurs when switching is also mitigated.

It is desirable that the actuator includes an electric motor as a means for applying a torque to the steering shaft, and the steering control unit controls the electric motor so that the torque matches the sum of the target assist torque value and the automatic steering torque value. .

Since the function of giving the automatic steering torque and the function of giving the assist torque to the steering shaft are realized by one electric motor, the structure of the actuator can be simplified.

[0011]

1 is a diagram showing an automatic steering apparatus according to an embodiment of the present invention and a steering mechanism (steering mechanism) applied to the automatic steering apparatus. This automatic steering system
Automatic steering ECU (Electrical Control Unit) 10 and E
MPS (electric power steering) / ECU 12,
Steering torque sensor 14, electric motor 16 and gear 1
EMPS actuator 2 by combination of 8a and 18b
It is configured with 0 and.

Automatic steering ECU 10 and EMPS / ECU 1
Reference numeral 2 constitutes a steering control unit 11 of this automatic steering device. The steering torque sensor 14 is the steering wheel 2
It is arranged on a steering shaft (steering shaft) 24 directly connected to 2, and detects the value of the steering torque applied from the steering wheel 22 to the steering shaft 24. Gear 18
A is fixed to the steering shaft 24 and is combined with a gear 18b fixed to the shaft of the electric motor 16.

The steering shaft 24 is a universal joint 2
6, the front end portion of the steering shaft 24 is connected to the side rod 30 by a gear box 28 such as a rack and pinion type steering gear box.

The steering control unit 11 calculates a target actuator torque value and controls the actuator 20 so that the actuator 20 gives a torque that matches the target actuator torque value to the steering shaft 24.

The target actuator torque value is the sum of the target assist torque value and the automatic steering torque value, and the target assist torque value is calculated by the EMPS / ECU 12 based on the steering torque detection value detected by the steering torque sensor 14. It

The automatic steering torque value is calculated by the automatic steering ECU 10 and given to the EMPS · ECU 12. EMP
The S-ECU 12 adds the automatic steering torque value from the automatic steering ECU 10 to the target assist torque value calculated by itself to obtain the target actuator torque value.

During manual steering, that is, during non-automatic steering, the automatic steering torque value becomes zero, so that target actuator torque value = target assist torque value. Therefore, E
During non-automatic steering, the MPS / ECU 12 determines the target assist torque value based on the steering torque detection value detected by the steering torque sensor 14 and generates an assist torque that matches the target assist torque value. The actuator 20 will be controlled. At this time, EMP
The target assist torque value calculated by the S-ECU 12 is obtained by multiplying the steering torque detection value detected by the steering torque sensor 14 by the assist torque gain.

During automatic steering, the EMPS-ECU 12 adds the target assist torque value to the automatic steering torque value determined by the automatic steering ECU 10 to obtain a target actuator torque value. Control to generate the matched torque.

During the automatic steering, unless the driver operates the steering wheel, the steering torque detection value detected by the steering torque sensor 14 is zero except when the automatic steering is started and ended. = Automatic steering torque value.

At the start and end of automatic steering, inertia torque is momentarily generated in the direction opposite to the force direction of automatic steering due to the weight of the steering wheel 22. Therefore, the inertia torque is detected by the steering torque sensor 14 as noise of the steering torque.

FIG. 2 is a timing chart for explaining the inertia torque, FIG. 2 (a) is a timing chart regarding the steering angle, and FIG. 2 (b) is a timing chart regarding the steering torque detection value. In this figure, automatic steering starts at time t1 and ends at time t2. That is, the automatic steering according to the automatic steering torque value is executed between the times t1 and t2. When such automatic steering is executed, as shown in FIG. 2B, an impulse-shaped steering torque detection value is detected at times t1 and t2. This is the inertia torque based on the weight of the steering wheel 22.

Next, the operation of the automatic steering apparatus of the present embodiment thus constructed will be described with reference to the flow chart shown in FIG.

First, in step S1, it is determined whether or not automatic steering is in progress. As a result, if the automatic steering is being performed, control for reducing the assist torque gain is performed in the EMPS / ECU 32 in step S2.

This control makes the assist torque gain during automatic steering lower than the assist torque gain during manual steering. As an example, if the assist torque gain during manual steering is set so that the ratio of steering torque to assist torque is 1:15, the ratio of steering torque to assist torque is 1: 3 during automatic steering.
The assist torque gain is set so that the gain value is reduced.

Next, in step S3, the automatic steering ECU 10
At, the automatic steering torque value is calculated. Then, the steering torque sensor 14 detects the steering torque in step S4, and the target assist torque value is calculated by the EMPS / ECU 12 in step S5 in accordance with the detected steering torque value.

If it is determined in step S1 that the automatic steering is not being performed, the processes of steps S2 and S3 are skipped and the process proceeds to step S4.

Next, in step S6, the target assist torque value calculated in step S5 and the automatic steering torque value calculated in step S3 are added to obtain a target actuator torque value, and the torque output by the actuator 20 is the target. The actuator 20 is controlled so as to match the actuator torque value.

After this control, it is judged again in step S7 whether or not the automatic steering is in progress. As a result, if the automatic steering is in progress, the process proceeds to step S8, and the steering operation input, that is, the manual steering input is determined from the torque value detected by the steering torque sensor 14. As a result of the judgment in step S7,
If it is during non-automatic steering (during manual steering), the manual steering input determination in step S8 is not performed.

Next, the manual steering input determination in step S8 will be described with reference to the timing chart shown in FIG. FIG. 4A is a timing chart regarding the steering angle, and FIGS. 4B to 4D are timing charts regarding the steering torque detection value. In this timing chart, automatic steering starts at time t1, there is a manual steering input (steering operation by the driver) at time t2, the manual steering input disappears at time t3, and the automatic steering ends at time t4. That is, automatic steering according to the automatic steering torque value is performed between times t1 and t4, and during times t2 and t3 in the middle, steering by manual steering is performed so that the steering angle does not change against automatic steering. Torque is added by the driver.

FIG. 4B shows a change over time of the steering torque detection value in the conventional device in which the power assist function is not activated during the automatic steering, and FIG. 4C shows the automatic steering like the present embodiment. The power assist function is also operated during the operation, but the assist torque gain at that time is shown to be the same as that at the time of non-automatic steering. FIG. 4D shows the change over time of the steering torque detection value in the automatic steering device of the present embodiment.

If the power assist is not performed when the automatic steering as shown in FIG. 4 (a) and the steering operation by the driver during the automatic steering are performed, as shown by the torque value T1 in FIG. 4 (b). A large steering torque must be applied to the negative side by steering operation.

On the other hand, according to another conventional device that exhibits the power assist function with the same assist torque gain as during manual steering, as shown by the torque value T2 in FIG. 4 (c),
The steering angle can be maintained against automatic steering simply by applying a small steering torque to the negative side. At this time, the difference from the torque value T1 is covered by the assist torque. According to this conventional device, there is an advantage that the steering operation during the automatic steering becomes easy. However, since the steering torque is small, it is difficult to detect the manual steering input based on the detection value of the steering torque sensor. There is.

According to the automatic steering apparatus of this embodiment, the assist torque gain during automatic steering is made smaller than that during non-automatic steering, so the steering torque detection value based on the steering operation during automatic steering is as shown in FIG. ), The waveform has a certain width and a certain magnitude, which is clearly different from the impulse-shaped steering torque detection value caused by the inertia torque. Therefore, the change in the steering torque detection value based on the steering operation can be discriminated from the change in the steering torque detection value due to the inertia torque based on the width and size of the waveform.

As described above, according to the automatic steering apparatus of this embodiment, the power assist is performed even during the automatic steering, so that the steering operation can be easily performed, and
The manual steering input can be accurately detected.

In the operation example of FIG. 4, the automatic steering is maintained after the steering operation is completed for the sake of simplicity. However, in reality, the steering operation (manual steering input) during the automatic steering is performed. When detected, control is performed so that automatic steering is stopped and switched to manual steering. That is, the automatic steering torque is set to zero when the steering operation is detected.

At this time, as shown in the example of FIG. 4B, if the power assist is not working during the automatic steering, the steering torque is large, so that the steering torque reaction force becomes zero when the automatic steering torque becomes zero. It sharply decreases and gives a driver discomfort regarding steering.

However, according to the automatic steering apparatus of the present embodiment, as shown in FIG. 4 (d), since the power assist works during the automatic steering, it is possible to reduce the steering torque and switch to the manual steering. It is possible to mitigate the sudden decrease in the steering torque reaction force at the time.

As described above, the steering operation input is determined based on whether or not the detected steering torque value exceeds the threshold value, and whether or not the time during which the steering torque value exceeds the threshold value exceeds a predetermined duration. The threshold value Th of the steering torque detection value and the predetermined duration S may be set in one way, or a plurality of combinations may be prepared.

Here, the threshold value Th of the steering torque detection value
And an example of a plurality of combinations relating to the setting of the predetermined duration S. For example, as the threshold Th, Th1, Th
2 and Th3 (Th1 <Th2 <Th3) are prepared, and S1, S2, S3 (S1> S) are set as the predetermined duration S.
2>S3>), and when the steering torque detection value is Th1 or more and continues for S1 or more, or when the steering torque detection value is Th2 or more and continues for S2 or more, or the steering torque detection value is Th3. As described above, when S3 or more is continued, and when either of the following is satisfied, it is determined that the steering operation input has been made.

When the criterion for the steering operation input is set in this way, the automatic steering can be stopped in a short time when the driver gives a large steering torque, and a small margin time elapses when a small steering torque is given. After that, the automatic steering can be stopped.

In this embodiment, the actuator 2
0 is a single value, and the torque output by the actuator 20 is controlled so as to match the sum of the target assist torque value and the automatic steering torque value. However, an actuator for automatic steering and an actuator for power assist may be separately provided, and the output of the former may be controlled to match the automatic steering torque value, and the latter may be controlled to match the target actuator torque value. However, if the function of the actuator that gives the automatic steering torque and the function of the actuator that gives the assist torque are realized by one electric motor as in the present embodiment, the steering mechanism can be simplified.

[0042]

As described above, according to the automatic steering apparatus of the present invention, the assist torque during the automatic steering, more specifically, the assist torque gain during the non-automatic steering (during the manual steering).
Since it is smaller than the above, the steering torque when the steering operation is performed by the driver during the automatic steering becomes large to some extent. Therefore, the steering torque can be clearly distinguished from the inertia torque of the steering wheel, and the presence or absence of the steering operation can be accurately recognized based on the detected value of the steering torque. Therefore, it is possible to accurately switch to the manual steering based on the recognition result.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an automatic steering device according to an embodiment of the present invention.

FIG. 2 is a timing chart for explaining inertial torque.

FIG. 3 is a flowchart showing the operation of this embodiment.

FIG. 4 is a timing chart for explaining a steering operation input determination during automatic steering.

[Explanation of symbols]

10 ... Automatic steering ECU, 11 ... Steering control unit, 12 ... EM
PS / ECU, 14 ... Steering torque sensor, 16 ... Electric motor, 18a, 18b ... Gear, 20 ... Actuator.

Claims (3)

[Claims] 1. An automatic steering device capable of performing both automatic steering and manual steering, wherein an assist torque is generated with respect to a steering torque given by a driver, and the assist torque is generated during automatic steering more than during manual steering. An automatic steering device characterized by being made smaller. 2. An automatic steering device that applies automatic steering torque to the steering shaft of a steering mechanism in which wheels are steered in accordance with rotation of a steering shaft connected to a steering wheel. A steering control unit that generates a steering control unit, and an actuator that is controlled by the steering control unit, and that provides the steering shaft with a torque that matches a sum of the automatic steering torque value and the target assist torque value, The steering control unit generates the target assist torque value by multiplying the assist torque gain by the steering torque applied from the steering wheel to the steering shaft by the driver, and determines the assist torque gain during automatic steering during non-automatic steering. An automatic steering device characterized by being made smaller than the above. 3. The actuator includes an electric motor as means for applying a torque to the steering shaft, and the steering control unit determines that the torque applied to the steering shaft is the sum of the target assist torque value and the automatic steering torque value. The automatic steering apparatus according to claim 2, wherein the electric motors are controlled so that they coincide with each other.