JP2004256076A - Automatic steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an automatic steering device capable of accurately detecting steering intervention by a driver and capable of smoothly shifting from automatic steering to manual steering. <P>SOLUTION: In a steering torque setting means 11, steering torque is set by adding assist torque in correspondence with steering torque of the driver detected by a torque sensor 14 and automatic steering torque set in an automatic steering ECU, and the set steering torque is applied to a steering shaft 24 by an electric motor 16. During automatic steering, gain of the assist torque with respect to steering torque input by the driver is set to be lower than at the time of manual steering. When steering intervention by the driver is detected by output of the torque sensor 14, the gain of the assist torque is gradually increased, and the gain of the automatic steering toque in correspondence with automatic steering torque input is gradually reduced. Thus, the steering is switched to manual steering. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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]
As a technique applied to parking assistance and an automatic traveling device, there is an automatic steering device that controls a steering angle without depending on a driver's steering. In such an automatic steering device, when the driver performs steering, switching to manual steering is generally performed. Patent Document 1 and Patent Document 2 describe such switching. .
[0003]
In the technique of Patent Literature 1, automatic steering torque and power steering assist torque are generated simultaneously, thereby facilitating a steering operation input by a driver during automatic steering. That is, it is described that the steering torque for winning the automatic steering torque is reduced by the assist torque of the power steering, and the burden is reduced when the driver tries to perform the steering operation during the automatic steering. It is also described that since the steering torque for winning out of the automatic steering torque is small, the change in the steering reaction force is less than that in the prior art, and smooth switching can be performed.
[0004]
Patent Document 2 discloses a technique for switching from automatic steering to manual steering when a steering operation is performed, and describes that the presence or absence of a steering operation is recognized based on a steering torque detection value detected by a steering torque sensor. ing.
[0005]
[Patent Document 1]
JP-A-4-205505 (pages 3-4, Fig. 1)
[0006]
[Patent Document 2]
JP-A-11-198839 (paragraphs 0027 to 0033, FIGS. 4 to 7)
[0007]
[Problems to be solved by the invention]
In the case of the automatic steering device disclosed in Patent Document 1 capable of simultaneously generating the automatic steering torque and the assist torque of the power steering, the driver operates the steering operation against the automatic steering with a small steering torque even during the automatic steering. However, since the steering torque by the driver does not increase, it is difficult to detect the presence or absence of the steering operation from the detected steering torque value. In order to recognize the steering operation even with a small steering torque, it is necessary to lower the threshold value of the detected steering torque value. In this case, the steering torque based on the driver's steering operation and the inertia torque of the steering wheel itself The steering operation input cannot be accurately detected.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic steering device that can accurately detect steering intervention by a driver and that enables a smooth transition from automatic steering to manual steering.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, an automatic steering apparatus according to the present invention is an automatic steering apparatus capable of performing both automatic steering and manual steering with an assist torque, steering detection means for detecting a steering torque input of a driver, Steering torque applying means for applying a set steering torque to the steering mechanism, and control means for setting the amount of steering torque applied by the steering torque applying means, and assisting in accordance with the steering torque input detected by the steering detecting means A steering torque setting means for calculating a torque and an automatic steering torque corresponding to an external automatic steering torque input and setting the set steering torque by adding both is provided. The assist torque gain for the driver's steering torque input is set lower during manual steering than during manual steering, and steering detection means during automatic steering Therefore, when the steering intervention of the driver is detected, the assist torque gain is gradually increased, and the automatic steering torque gain corresponding to the automatic steering torque input is gradually decreased to switch to manual steering. .
[0010]
During automatic steering, by reducing the assist torque gain compared to during manual steering, the steering torque associated with steering operation during automatic steering can be increased to some extent, and the steering torque for detecting steering operation input is increased. Even if the threshold value is set to a relatively large value, the detection becomes easy, and the steering wheel can be easily distinguished from the inertia torque. 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. In addition, the steering torque is gradually increased by steering intervention, while the steering torque gain for automatic steering is gradually decreased, thereby suppressing the discontinuous change of the steering torque and suppressing the generation of reaction force at the time of switching. Therefore, the transition from automatic steering to manual operation can be made smooth.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In order to facilitate the understanding of the description, the same reference numerals are given to the same components in the drawings as much as possible, and duplicate descriptions are omitted.
[0012]
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. The automatic steering device includes an automatic steering ECU (Electrical Control Unit) 10, an EMPS (Electric Motor Steering Power Steering) ECU 12, a steering torque sensor 14, an electric motor 16, and gears 18a and 18b. And an EMPS actuator 20 in combination.
[0013]
The automatic steering ECU 10 and the EMPS / ECU 12 constitute a steering torque setting means 11 of the automatic steering device. The steering torque sensor (steering torque detection means) 14 is disposed on a steering shaft 24 directly connected to the steering wheel 22 and detects the amount and direction of 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 meshed with a gear 18 b fixed to the shaft of the electric motor (steering torque applying means) 16.
[0014]
The steering shaft 24 is spliced at a predetermined position by a universal joint 26, and the front end of the steering shaft 24 is connected to a side rod 30 connected to a steering wheel (not shown) by a gear box 28 such as a rack and pinion type steering gear box. Connected with.
[0015]
The steering torque setting means 11 calculates the torque amount to be applied by the actuator 20 and controls the operation of the actuator 20 so that the torque applied to the steering shaft 24 becomes the calculated torque amount.
[0016]
Next, the operation of this embodiment will be described with reference to the flowcharts shown in FIGS. FIG. 2 is a flowchart showing a steering torque application process, and FIG. 3 is a main flowchart of the steering control operation of the present embodiment. The steering torque application process shown in FIG. 2 is called from the process shown in FIG. 3 and is also executed as steering assist control during manual steering.
[0017]
2 will be described first. First, the automatic steering ECU 10 sets the automatic steering torque amount Tauto, and the EMPS / ECU 12 sets the target assist torque amount Tasst corresponding to the manual steering (step S1). This target assist torque amount Tasst is obtained by multiplying the steering torque input Tman detected by the steering torque sensor 14 by an assist torque gain Kasst0 in a narrow sense. That is, Tasst = Kasst0 × Tman. The narrow assist torque gain Kasst0 is set to 15, for example.
[0018]
Next, the EMPS • ECU 12 obtains a steering torque amount (hereinafter referred to as a target actuator torque amount) Tt to be applied to the steering shaft 24 by the actuator 20 (step S2). Tt is obtained by multiplying the target assist torque amount Tasst and the automatic steering torque amount Tato by coefficients Kasst and Kato, respectively. Then, the actuator 20 is controlled so as to obtain a torque amount that matches the calculated target actuator torque amount Tt (step S3).
[0019]
At the time of manual steering, that is, non-automatic steering, since the automatic steering torque amount Tato is 0, Tt = Kastst × Tast. At this time, since Kasst is set to 1 as will be described later, Tt = Tasst. Therefore, during non-automatic steering, the EMPS • ECU 12 determines the target assist torque amount Tast based on the steering torque input Tman detected by the steering torque sensor 14, and the assist torque Tt that matches the target assist torque amount Tast. The actuator 20 is controlled so as to generate
[0020]
At the time of automatic steering, the target assist torque amount Tast is obtained by multiplying the automatic steering torque input Tauto determined by the automatic steering ECU 10 by the coefficient Kauto (referred to as the gain of the automatic steering torque with respect to the automatic steering torque input). Is multiplied by the coefficient Kasst to obtain a target actuator torque amount Tt, and the EMPS • ECU 12 further controls the actuator 20 to generate a torque that matches the target actuator torque amount Tt. Hereinafter, when simply referred to as assist torque gain, it refers to Kasst × Kasst0 (referred to as assist torque gain in a broad sense when distinguished from Kasst0).
[0021]
During automatic steering, if the steering operation by the driver is not applied, the steering torque amount Tman detected by the steering torque sensor 14 is 0 except when automatic steering is started and ended, and the coefficient Kauto is 1 as described later. Therefore, the target actuator torque amount Tt = automatic steering torque input Tato.
[0022]
Next, details of the processing during automatic steering will be described with reference to FIG. This process is executed at the start of automatic steering, and the automatic steering is canceled when it is finished.
[0023]
First, various coefficients and flag settings are set to the initial values of the automatic steering word (step S21). Specifically, the coefficient Kato is set to 1, the coefficient Kasst is set to α, the transition control flag SFflag is set to 0 indicating that the transition is not being performed, and the end flag XFlag is set to 0 indicating that the transition is not in the end state. Here, α is a positive number smaller than 1, and is set to 0.2, for example. Thus, in the automatic steering state, the assist torque gain (Kasst × Kasst0) in a broad sense takes a numerical value that is α times smaller than that during manual steering.
[0024]
Next, the steering torque input Tman detected by the steering torque sensor 14 is read (step S22). Then, the presence or absence of steering intervention by the driver is determined based on the read steering torque input Tman and the change over time (step S23). The determination of the presence or absence of this steering intervention is made based on whether or not the time during which the steering torque detection value Tman exceeds the threshold value Th has exceeded a predetermined duration S. 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.
[0025]
As an example, a plurality of combinations relating to the setting of the threshold value Th of the steering torque input and the predetermined duration S are shown. For example, three types of threshold values Th1, Th2, Th3 (Th1 <Th2 <Th3) are prepared, and three types of predetermined durations S1, S2, S3 (S1>S2> S3) are prepared, 1) When steering torque input is Th1 or more and continues for S1 or more 2) When steering torque input is Th2 or more and continues for S2 or more 3) When steering torque input is Th3 or more and continues for S3 or more It is determined that there is a steering intervention when the condition is satisfied.
[0026]
If the judgment criterion of the steering intervention is set in this way, the automatic steering can be stopped in a short time when the driver gives a large steering torque. When a small steering torque is given, the automatic steering is performed after a certain long margin time has passed. Can be canceled. For this reason, when the driver is merely touching the steering wheel (in such a case, a small steering torque is detected for a relatively long time), it is erroneously determined as steering intervention. Therefore, accurate detection of steering intervention is possible.
[0027]
When the steering torque is suddenly changed, such as 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 may be detected as noise of the steering torque by the steering torque sensor 14. However, erroneous determination can be prevented by taking a time sufficiently longer than the duration of the inertia torque as the predetermined duration S.
[0028]
In step S24, the determination result is examined. Only when it is determined that there is an intervention, the process proceeds to step S25 before the process proceeds to step S26, and the transition control flag SFlag is set to 1 indicating that the transition control for shifting from automatic steering to manual steering is being performed. Thereby, it shifts from automatic steering control to transition control.
[0029]
In step S26, the value of the transition control flag SFlag is checked. If SFlag is 1, i.e., when in transition control, the process proceeds to step S27, the value of Kauto reduced from the previous time step by the predetermined value _{K 1,} whereas, the last value of Kasst increase from time step by a predetermined value K _2. Here, both K ₁ and K ₂ are numerical values much smaller than 1. Next, a process of resetting to 0 when Kato falls below 0 and resetting to 1 when Kasst exceeds 1 is performed by this calculation (step S28). As a result, Kato is gradually decreased from 1 to 0 with a predetermined gradient, and Kasst is gradually increased from α to 1 with a predetermined gradient (see FIG. 4). The time until Kato reaches 1 to 0 and the time until Kasst reaches 1 from α may be the same, or one may be longer than the other.
[0030]
Next, it is determined whether Kato has reached 0 and Kasst has reached 1. Only when both of the conditions are satisfied, the transition control flag SFflag is set to 0 indicating that the transition is not being performed via step S30, and the end flag XFlag is set to 1 indicating the end state to end the transition control. To do. Thereafter, the process proceeds to step S31, where the steering torque applying process described above is performed, and the process returns to step S22.
[0031]
If it is determined in step S26 that the transition control is not being performed, the process proceeds to step S32 to check the value of the end control flag XFlag. If XFlag is not 0, that is, if it is determined that the flag is not in an end state, the process proceeds to step S31. On the other hand, when XFlag is 1, that is, when it is determined as the end state, this control process is ended and the process shifts to manual steering.
[0032]
Thus, when a steering intervention, the automatic steering amount of torque coefficient Kauto a predetermined transition time t1 (here, 1 / K ₁ time step), as shown in FIG. 4 over gradually from 1 to 0 with decreasing, sales of coefficients Kasst predetermined transition time t2 assist torque amount (in this case, 1 / K ₂ time steps) transition from performing over migration control gradually increases from α 1 to manual control. As a result, the sudden change in the control torque amount (target actuator torque amount Tt) is suppressed when the automatic control is released, so that the generation of reaction force due to this sudden change can also be suppressed. The effect of improving the drivability can be obtained by reducing the uncomfortable feeling at the time. In addition, since the assist torque gain is set to α × Kasst0 that is not 0 at the time of steering intervention, detection of the steering operation is facilitated.
[0033]
In the above description, an example in which Kasst and Kato are linearly increased or decreased has been described. However, as shown by the broken line in FIG. 5, the initial change amount of the transition time is increased or the initial value is indicated by the one-dot chain line. The change amount may be set small, the change amount in the latter period may be set large, or the change amount in the intermediate period may be set large as indicated by the thick line, and the change amount in the initial stage and the latter period may be set small. Further, the method of changing Kasst and Kato is not the same, and different combinations can be used. The way of changing Kasst and Kato during these transition periods is set according to the required vehicle characteristics, the structure of the steering system, and the like.
[0034]
Here, an example has been described in which the assist torque is set by applying a coefficient to the assist torque gain at the time of manual steering. However, the assist torque gain in a narrow sense may be changed without using the coefficient Kasst. The method of the change is the same as the change of the coefficient Kasst.
[0035]
In the present embodiment, the actuator 20 is single. However, an automatic steering actuator and a power assist actuator may be provided separately, and each may be controlled individually. However, if the actuator is composed of one electric motor as in this embodiment, the steering mechanism can be simplified.
[0036]
【The invention's effect】
As described above, according to the present invention, the assist torque gain during automatic steering is made smaller than that during manual steering, so that the steering torque associated with steering operation during automatic steering is increased to some extent to detect steering intervention. Making it easy. In addition, the steering torque is gradually increased by steering intervention, while the steering torque gain of automatic steering is gradually decreased, thereby suppressing the discontinuous change of the steering torque and suppressing the generation of reaction force at the time of switching. Therefore, the transition from automatic steering to manual operation can be made smooth.
[Brief description of the drawings]
FIG. 1 is a diagram showing an automatic steering apparatus according to an embodiment of the present invention and a steering mechanism (steering mechanism) applied thereto.
FIG. 2 is a main flowchart of the steering control operation of the apparatus of FIG.
FIG. 3 is a flowchart showing a steering torque application process in FIG. 2;
FIG. 4 is a graph showing changes over time in gain of automatic steering torque and gain of assist torque.
FIG. 5 is a graph showing a modification of the gain change in FIG. 4;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Automatic steering ECU, 11 ... Steering torque setting means, 12 ... EMPS * ECU, 14 ... Steering torque sensor (steering detection means), 16 ... Electric motor (steering torque provision means), 18a, 18b ... Gear, 20 ... Actuator .

Claims (1)

In an automatic steering device that can perform both automatic steering and manual steering with assist torque,
Steering torque detection means for detecting the steering torque input of the driver;
Steering torque applying means for applying a set steering torque to the steering mechanism;
A means for setting a steering torque amount to be applied by the steering torque applying means, wherein an assist torque corresponding to the steering torque input detected by the steering detecting means and an automatic steering torque corresponding to the automatic steering torque input from the outside are provided. A steering torque setting means for calculating and setting the set steering torque by adding both;
The steering torque setting means sets the assist torque gain with respect to the steering torque input of the driver to be lower than that at the time of manual steering during automatic steering, and when the steering intervention of the driver is detected by the steering detection means during automatic steering. An automatic steering device characterized by gradually increasing the gain of the assist torque and gradually decreasing the gain of the automatic steering torque corresponding to the automatic steering torque input to switch to manual steering.

Images