JP3693048B2 - Automatic steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an automatic steering apparatus that is applied to a case where a vehicle is parked automatically regardless of a driver's steering operation.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 4-205505 discloses a conventional technique related to an automatic steering device. In this prior art, it is possible to facilitate the steering operation input by the driver during the automatic steering by simultaneously generating the automatic steering torque and the assist torque of the power steering. That is, the steering torque for winning the automatic steering torque is reduced by the assist torque of the power steering, and the burden can be reduced when the driver tries to perform the steering operation during the automatic steering.
[0003]
In addition, when the driver performs a steering operation by the driver during the automatic steering, when the control is performed such that the automatic steering is stopped and switched to the manual steering, the switching can be smoothly performed according to the related art. The automatic steering device before the above prior art does not generate the assist torque of the power steering during the automatic steering, so the automatic steering torque disappears suddenly at the time of switching and the assist torque in the direction opposite to the automatic steering torque suddenly occurs. . Therefore, the steering reaction force changes abruptly. However, according to the above prior art, since the steering torque for winning out of the automatic steering torque is small, the change in the steering reaction force is small and smooth switching can be performed.
[0004]
A technique of switching from automatic steering to manual steering when there is a steering operation is disclosed in Japanese Patent Laid-Open No. 11-198839, and the presence or absence of a steering operation is recognized based on a detected steering torque value detected by a steering torque sensor. To do.
[0005]
[Problems to be solved by the invention]
In the case of the above-described conventional automatic steering device capable of generating the automatic steering torque and the assist torque of the power steering at the same time, the driver performs the steering operation against the automatic steering with a small steering torque even during the automatic steering. However, the fact that the steering torque by the driver does not increase causes a problem that it is difficult to detect the presence or absence of the steering operation from the detected steering torque value. 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 driver's steering operation is reduced to noise such as the inertia torque of the steering wheel itself. And the steering operation input cannot be detected accurately.
[0006]
[Means for Solving the Problems]
The automatic steering apparatus according to the present invention is made to solve such a problem. In an automatic steering apparatus capable of performing both automatic steering and manual steering, a steering torque applied by a driver during automatic steering is provided. When the value is equal to or greater than a predetermined value, it is determined that the driver has input steering operation, and switching to manual steering is performed. Assist torque is generated in response to the steering torque given by the driver. It is characterized by making it smaller.
More specifically, an automatic steering torque value and a target assist torque value in an automatic steering device that applies an automatic steering torque to a steering shaft of a steering mechanism that turns a wheel in response to rotation of a steering shaft connected to a steering wheel. And an actuator that is controlled by the steering control unit and that applies a torque to the steering shaft that matches the sum of the automatic steering torque value and the target assist torque value. A target assist torque value is generated by multiplying the steering torque applied from the wheel to the steering shaft by an assist torque gain, and the assist torque gain during automatic steering is made smaller than during non-automatic steering.
[0007]
During automatic steering, the assist torque becomes smaller than that during steering (manual steering), more specifically, the steering torque accompanying steering operation during automatic steering increases to some extent. Therefore, the steering torque threshold value for detecting the steering operation input can be set to a large value, and the distinction from the inertia torque of the steering wheel becomes easy. Therefore, the presence or absence of steering operation can be recognized without error based on the detected steering torque value, and switching to manual steering can be performed accurately based on the recognition result.
[0008]
Although the steering torque during automatic steering has increased to some extent, the steering operation during automatic steering is easier than when no assist torque is generated, and when automatic steering is switched to manual steering based on the steering operation. The sudden decrease in the steering torque that occurs in the vehicle is also alleviated.
[0009]
The actuator preferably includes an electric motor as means for applying torque to the steering shaft, and the steering control unit preferably controls the electric motor so that the torque matches the sum of the target assist torque value and the automatic steering torque value.
[0010]
Since the function of giving the automatic steering torque to the steering shaft and the function of giving the assist torque are realized by one electric motor, the configuration of the actuator can be simplified.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram illustrating an automatic steering apparatus according to an embodiment of the present invention and a steering mechanism (steering mechanism) applied thereto. This automatic steering device includes an automatic steering ECU (Electrical Control Unit) 10, an EMPS (Electric Power Steering) ECU 12, a steering torque sensor 14, an EMPS actuator 20 by a combination of an electric motor 16 and gears 18a and 18b. It is prepared for.
[0012]
The automatic steering ECU 10 and the EMPS / ECU 12 constitute a steering control unit 11 of the automatic steering device. The steering torque sensor 14 is disposed on a steering shaft (steering shaft) 24 directly connected to the steering wheel 22, and detects the value of the steering torque applied from the steering wheel 22 to the steering shaft 24. The gear 18 a is fixed to the steering shaft 24 and combined with a gear 18 b fixed to the shaft of the electric motor 16.
[0013]
The steering shaft 24 is spliced at a predetermined location by a universal joint 26, and the distal 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.
[0014]
The steering control unit 11 calculates a target actuator torque value, and controls the actuator 20 so that the actuator 20 applies a torque that matches the target actuator torque value to the steering shaft 24.
[0015]
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.
[0016]
The automatic steering torque value is calculated by the automatic steering ECU 10 and given to the EMPS / ECU 12. The EMPS • 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.
[0017]
At the time of manual steering, that is, non-automatic steering, the automatic steering torque value becomes zero, so that target actuator torque value = target assist torque value. Accordingly, the EMPS / ECU 12 determines the target assist torque value based on the detected steering torque value detected by the steering torque sensor 14 during non-automatic steering, and generates assist torque that matches the target assist torque value. Thus, the actuator 20 is controlled. At this time, the target assist torque value calculated by the EMPS / ECU 12 is obtained by multiplying the steering torque detection value detected by the steering torque sensor 14 by the assist torque gain.
[0018]
At the time of automatic steering, the EMPS • ECU 12 adds a target assist torque value to the automatic steering torque value determined by the automatic steering ECU 10 to obtain a target actuator torque value. The EMPS • ECU 12 further increases the torque at which the actuator 20 matches the target actuator torque value. Control to generate.
[0019]
During automatic steering, if the steering operation by the driver is not applied, the steering torque detection value detected by the steering torque sensor 14 is zero except when the automatic steering starts and ends, so that the target actuator torque value = automatic steering Torque value.
[0020]
At the start and end of automatic steering, inertia torque is instantaneously generated in the direction opposite to the direction of automatic steering due to the weight of the steering wheel 22. Therefore, this inertia torque is detected as noise of the steering torque by the steering torque sensor 14.
[0021]
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 detected steering torque value. In this figure, automatic steering starts at time t1, and automatic steering ends at time t2. That is, automatic steering according to the automatic steering torque value is executed between times t1 and t2. When such automatic steering is executed, an impulse-like steering torque detection value is detected at times t1 and t2, as shown in FIG. 2 (b). This is the inertia torque based on the weight of the steering wheel 22.
[0022]
Next, the operation of the automatic steering apparatus of this embodiment configured as described above will be described with reference to the flowchart shown in FIG.
[0023]
First, in step S1, it is determined whether automatic steering is in progress. As a result, if automatic steering is being performed, control to lower the assist torque gain is performed in the EMPS / ECU 32 in step S2.
[0024]
In this control, the assist torque gain during automatic steering is made lower than the assist torque gain during manual steering. For example, if the assist torque gain at the time of manual steering is set so that the ratio of the steering torque to the assist torque is 1:15, the ratio of the steering torque to the assist torque is 1: 3 at the time of automatic steering. The gain value is reduced to such an assist torque gain.
[0025]
Next, in step S3, the automatic steering ECU 10 calculates an automatic steering torque value. Thereafter, the steering torque is detected by the steering torque sensor 14 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.
[0026]
If it is determined in step S1 that automatic steering is not being performed, the processes in steps S2 and S3 are skipped, and the process proceeds to step S4.
[0027]
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 the target actuator torque value, and the torque output from the actuator 20 is the target actuator torque value. The actuator 20 is controlled so as to coincide with.
[0028]
After this control, it is determined again in step S7 whether automatic steering is in progress. As a result, if automatic steering is in progress, the process proceeds to step S8, and a steering operation input, that is, a manual steering input is determined from the detected torque value of the steering torque sensor 14. If the result of determination in step S7 is non-automatic steering (manual steering), manual steering input determination in step S8 is not performed.
[0029]
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 relating to the steering angle, and FIGS. 4B to 4D are timing charts relating to the detected steering torque values. In this timing chart, automatic steering starts at time t1, manual steering input (steering operation by the driver) occurs at time t2, manual steering input disappears at time t3, and automatic steering ends at time t4. That is, automatic steering according to the automatic steering torque value is executed from time t1 to t4, and during time t2 to t3 in the middle, steering by manual steering is performed so that the steering angle does not change against automatic steering. Torque is applied by the driver.
[0030]
FIG. 4 (b) shows the time change of the steering torque detection value in the conventional apparatus that does not use the power assist function during automatic steering. FIG. 4 (c) also shows the state during automatic steering as in this embodiment. FIG. 6 shows the change over time in the detected steering torque value in another conventional apparatus in which the power assist function is activated but the assist torque gain at that time is the same as that during non-automatic steering. FIG. 4D shows the change over time of the detected steering torque value in the automatic steering apparatus of the present embodiment.
[0031]
If power assist is not performed when automatic steering as shown in FIG. 4A and steering operation by the driver in the middle are performed, as shown by the torque value T1 in FIG. Therefore, a large steering torque must be given by steering operation.
[0032]
On the other hand, according to another conventional device that exhibits the power assist function with the same assist torque gain as in manual steering, as shown by the torque value T2 in FIG. The steering angle can be maintained against automatic steering. At this time, the assist torque covers the difference from the torque value T1. According to this conventional apparatus, 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. Yes.
[0033]
According to the automatic steering device of the present embodiment, the assist torque gain during automatic steering is made smaller than during non-automatic steering, so the steering torque detection value based on the steering operation during automatic steering is the torque shown in FIG. As indicated by the value T3, the waveform has a certain width and a certain magnitude that is clearly different from the impulse-like steering torque detection value caused by the inertia torque. Therefore, it is possible to distinguish and pick up the change in the detected steering torque value based on the steering operation from the change in the detected steering torque value caused by the inertia torque based on the width and size of the waveform.
[0034]
As described above, according to the automatic steering apparatus of the present 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.
[0035]
In the operation example of FIG. 4, for easy explanation, automatic steering is maintained even after the steering operation is finished, but in reality, a steering operation (manual steering input) during automatic steering is detected. Then, control is performed so as to stop automatic steering and switch to manual steering. That is, the automatic steering torque is set to zero when the steering operation is detected.
[0036]
At this time, as in the example of FIG. 4B, if the power assist is not working during the automatic steering, the steering torque is large, so when the automatic steering torque becomes zero, the steering torque reaction force rapidly decreases, The driver feels uncomfortable steering.
[0037]
However, according to the automatic steering apparatus of the present embodiment, as shown in FIG. 4D, the power assist works during automatic steering, so that the steering torque can be reduced, and the steering at the time of switching to manual steering is possible. A sudden decrease in torque reaction force can be mitigated.
[0038]
As described above, the steering operation input is determined based on whether or not the detected steering torque value exceeds a threshold value and whether or not the time exceeding the threshold value exceeds a predetermined duration. The setting of the threshold value Th of the steering torque detection value and the predetermined duration S may be one way, or a plurality of combinations may be prepared.
[0039]
Here, an example of a plurality of combinations relating to the setting of the threshold value Th of the steering torque detection value and the predetermined duration S will be shown. For example, three types of threshold values Th1, Th1, Th2, and Th3 (Th1 <Th2 <Th3) are prepared, and three types of thresholds Th, S2, S3 (S1>S2>S3>) are prepared. ,
(1) When the detected steering torque value is Th1 or more and continues for S1 or more, or
(2) When the detected steering torque value is Th2 or more and continues for S2 or more, or
(3) When the steering torque detection value is Th3 or more and continues for S3 or more,
It is determined that there is a steering operation input when either of the above is satisfied.
[0040]
If the judgment criteria for steering operation input are set in this way, automatic steering can be stopped in a short time when the driver gives a large steering torque. Steering can be stopped.
[0041]
In the present embodiment, the actuator 20 is single, and the torque output from the actuator 20 is controlled to match the sum of the target assist torque value and the automatic steering torque value. However, an automatic steering actuator and a power assist actuator may be provided separately, and the former output may be controlled to match the automatic steering torque value, and the latter may be controlled to match the target actuator torque value. However, the steering mechanism can be simplified 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 a single electric motor as in this embodiment.
[0042]
【The invention's effect】
As described above, according to the automatic steering device of the present invention, the assist torque is reduced during automatic steering, more specifically, the assist torque gain is smaller than that during non-automatic steering (during manual steering). The steering torque when the steering operation is performed by the driver is increased 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, switching to manual steering can be accurately performed based on the recognition result.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an automatic steering apparatus according to an embodiment of the present invention.
FIG. 2 is a timing chart for explaining inertia torque.
FIG. 3 is a flowchart showing the operation of the embodiment.
FIG. 4 is a timing chart for explaining a steering operation input determination during automatic steering.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Automatic steering ECU, 11 ... Steering control part, 12 ... EMPS * ECU, 14 ... Steering torque sensor, 16 ... Electric motor, 18a, 18b ... Gear, 20 ... Actuator.

Claims (3)

In an automatic steering device that can perform both automatic steering and manual steering,
When the steering torque given by the driver during automatic steering is greater than or equal to a predetermined value, it is determined that the steering operation input by the driver has been made, and switching to manual steering is performed.
An automatic steering device characterized in that an assist torque is generated with respect to a steering torque applied by a driver, and the assist torque is made smaller during automatic steering than during manual steering. In an automatic steering device for applying an automatic steering torque to the steering shaft of a steering mechanism in which a wheel turns in response to rotation of a steering shaft connected to a steering wheel,
A steering control unit for generating an automatic steering torque value and a target assist torque value;
An actuator controlled by the steering control unit, and an actuator that applies a torque that matches a sum of the automatic steering torque value and the target assist torque value to the steering shaft,
The steering control unit generates the target assist torque value by multiplying a steering torque applied from the steering wheel to the steering shaft by a driver by an assist torque gain, and sets the assist torque gain at the time of automatic steering to a value at the time of non-automatic steering. Automatic steering device characterized by being made smaller.   The actuator includes an electric motor as means for applying torque to the steering shaft, and the steering control unit in the previous period is configured so that the torque applied to the steering shaft matches 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 motor is controlled.

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