JPH06219288A - Electric motor-driven four-wheel steering device - Google Patents

Abstract

PURPOSE:To detect abnormality of a motor control current by providing a motor control current supervising means for detecting the motor control current in abnormality in the case that a condition of flowing the motor control current in a reverse direction to a motor control current command is continued for a predetermined time, when the motor control current command is output. CONSTITUTION:At the time of controlling a rear wheel steering angle, in a motor control current supervising means (e), at the time of generating a motor control current command based on detection by a motor control current command detecting means (c), in the case that a condition of flowing a motor control current of preset value or more in a reverse direction to the motor control current command, based on detection by a motor control current detecting means (d), is continued for a predetermined time, the motor control current is detected abnormal. Accordingly, by including whether the motor control current is in the reverse direction or not to the motor control current command in a reference of judging motor current abnormality, in the case that the motor control current is in the reverse direction relating to the motor control current command, abnormality of the motor control current can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor drive type four-wheel steering system for controlling a rear wheel steering angle by an electric motor, and more particularly to a technique for detecting an abnormality in a motor control current.

[0002]

2. Description of the Related Art Conventionally, as a technique for detecting an abnormality in a motor control current in a control system using an electric motor, for example,
Japanese Utility Model Laid-Open No. 62-16561 and Japanese Patent Laid-Open No. 1-22976.
The one described in Japanese Patent Publication No. 4 is known.

These conventional sources show a technique for detecting an abnormality in the motor control current when the deviation between the control command current value and the actual current value to the electric motor is abnormal by a predetermined value.

[0004]

However, in the above prior art, the abnormality of the motor control current is detected only by the deviation without judging the directions of the control command current value and the actual current value. For example, in an electric motor-driven four-wheel steering system, when the control command current value has a value in the direction of steering the rear wheels to the right, the actual current value has a value in the direction of steering to the left. In the case of an abnormal control current, if the deviation of the absolute value of the output current value is less than or equal to the abnormality determination threshold value, the motor control current is erroneously detected as normal.

Particularly, in the case of an electric motor-driven four-wheel steering system, this erroneous detection is aimed at, for example, turning stability.
When trying to steer the rear wheels in the same phase, the result is that the rear wheels are allowed to be steered in the opposite phase, and the control is completely opposite to the expected control, which causes a sudden change in vehicle behavior and ensures safety. Even above, this false positive must be avoided.

The present invention has been made in view of the above problems, and an object thereof is to provide a motor control current command in an electric motor drive type four-wheel steering system for controlling a rear wheel steering angle by an electric motor. On the other hand, when the motor control current is in the opposite direction, the abnormality of the motor control current is detected without erroneous detection.

[0007]

In order to solve the above-mentioned problems, in the electric motor drive type four-wheel steering system of the present invention, when a motor control current command is issued, a motor control current of a set value or more is applied to the motor control current command. The motor control current monitoring means is provided for detecting that the motor control current is abnormal when the current flowing in the opposite direction continues for a predetermined time.

That is, as shown in the claim correspondence diagram of FIG. 1, an electric motor a for controlling the rear wheel rudder angle by driving by applying a motor control current, and an electric motor a connected to the electric motor a to output a motor control current command. A motor drive control circuit b for converting into a motor control current flowing to the motor a, a motor control current command detecting means c for detecting a motor control current command of a motor control current command and its command direction, and the motor drive control circuit b are actually used. The motor control current detecting means d for detecting the motor control current flowing in the direction and its direction, and when the motor control current command is issued, the state in which the motor control current of the set value or more flows in the opposite direction to the motor control current command. The motor control current monitoring means e detects that the motor control current is abnormal when the motor control current continues for a predetermined time.

[0009]

When the rear wheel steering angle control is performed, when the motor control current monitor means e issues a motor control current command based on the detection by the motor control current command detection means c, it is set based on the detection by the motor control current detection means d. When the state in which the motor control current equal to or larger than the value is flowing in the direction opposite to the motor control current command continues for a predetermined time, the motor control current is detected to be abnormal.

Therefore, by including whether the direction of the motor control current and the direction of the motor control current command are opposite directions in the criterion for determining the motor current abnormality, the motor control current is in the opposite direction with respect to the motor control current command. In some cases, an abnormality in the motor control current can be detected. Moreover, in this judgment, the motor control current is normal because the condition that the motor control current of the set value or more flows in the opposite direction to the motor control current command is maintained for the predetermined time. Even if the current direction is reversed, the loop current due to the back electromotive force generated in the electric motor a may momentarily flow in the direction opposite to the motor control current command, but erroneous detection in such a case is prevented. can do.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

First, the structure will be described.

FIG. 2 is an overall system diagram showing a vehicle to which the electric motor-driven four-wheel steering system of the embodiment of the present invention is applied, and FIG. 3 is an electric rear-wheel steering system of the electric-motor-driven four-wheel steering system of the embodiment. FIG. 4 is a view showing the mechanism, and FIG. 4 is a 4 W of the embodiment device.
It is an electronic control system system diagram centering on the S control unit.

In FIG. 2, 1 and 2 are front wheels, 3 and 4 are rear wheels, 5 is a mechanical front wheel steering mechanism, and 6 is an electric rear wheel steering mechanism.

In the mechanical front wheel steering mechanism 5, the steering force input from the steering wheel 7 steered by the driver via the steering shaft 8 is increased by the power steering (not shown), and the increased steering force is increased by the rack shaft 9. Is transmitted via the side rods 10 and 11 and the knuckle arms 12 and 13 to give a steering angle to the front wheels 1 and 2.

The electric rear wheel steering mechanism 6 has four
The rotational force of the high-cass motor 15 (corresponding to the electric motor a) controlled by the motor output from the WS control unit 14 is applied to the worm 16 and the worm wheel 17.
The rotational movement of the worm wheel 17 is converted into a linear movement of the rack shaft 19 by the engagement of the gear portion of the pinion shaft 18 and the gear portion of the rack shaft 19, and the rack shaft 19 is converted into a linear movement. Transmission via 22 and 23, rear wheel 3,
4 is used as a mechanism for giving a steering angle.

The 4WS control unit 14 is
As shown in FIG. 4, the power supply circuit 14a and the sensor power supply circuit 1
4b, input interface 14c, CPU1, CPU
2, monitoring circuit 14d, D / A conversion 14e, 14f, 14
g, 14h, 14i, a CPU output monitoring circuit 14j, a relay output driver 14k, a motor output driver 14m (corresponding to the motor drive control circuit b), and a power steering solenoid output driver 14n.

The power supply circuit 14a includes a battery power source directly from the battery 24 and an ignition switch 25.
Ignition power from is input.

The input interface 14c includes sensor signals from the rear steering angle main sensor 26 and the rear steering angle sub-sensor 27, a sensor signal from the steering sensor 28, a sensor signal from the vehicle speed sensor 29, and a stop lamp. Switch signals from the switch 30, the brake switch 31, and the inhibit switch 32 are input. Here, the rear steering angle main sensor 26 is a sensor that detects the rotation amount of the pinion shaft 18, and the rear steering angle sub-sensor 27 is a sensor that detects the stroke amount of the rack shaft 19.

The relay output driver 14k receives the monitoring output from the monitoring circuit 14d and the warning valve output from the warning valve 33, and receives the high-casing relay 34.
The high-cass relay output is sent to.

The motor output driver 14m is driven by a motor power source via a high-casing relay 34, and C
A rear wheel steering angle command is input from the PU 1 via the D / A conversions 14g and 14h, and a motor output is sent to the high-cass motor 15.

The power steering solenoid output driver 14
n receives a power steering command from the CPU 1 via the D / A conversion 14i, and sends a power steering solenoid output to the power steering solenoid 35.

Next, the operation will be described.

[Motor control current monitoring operation] FIG.
Each step will be described below (corresponding to the motor control current monitoring means e) in the flowchart showing the flow of the motor control current monitoring operation performed by the monitoring circuit 14d of the control unit 14.

In step 50, the motor output driver 14m passes through the D / A converters 14g and 14h from the CPU 1.
The motor control current command I ^* and its direction I ^* D input to are read (corresponding to the motor control current command detection means c).

In step 51, the motor output driver 1
The motor control current I and its direction ID are read by measuring the current actually flowing through 4 m (corresponding to the motor control current detection means d).

In step 52, the rear rudder angle main sensor 26 detects the current rear rudder angle δr and the rear rudder angle δr- 5 msec before.
1 is read. .

In step 53, the rear steering angles δr and δr-1
The rear rudder angle direction ΔrD is calculated from the sign of the difference.

In step 54, the control current difference Δ, which is the absolute value of the difference between the motor control current I and the motor control current command I ^*.
I is calculated.

In step 55, the motor control current command I
^It is determined whether ^* is I ^* ≠ 0, that is, whether the motor control current command is issued.

In step 56, I ^{* in} step 55
When the condition of ≠ 0 is satisfied, the motor control current command direction I ^* D
And the motor control current direction ID are opposite directions, and it is determined whether the motor control current I is the first set current value I1 or more.

Here, the first set current value I1 is 2 ± 0. So that the dark current of the high-cass motor 15 is 3 A so that it can be detected before the high-cass motor 15 starts moving.
It is set to 5A.

In step 57, when the condition of step 56 is satisfied, the first timer value T1 is set to T1 = T1 + 1.

At step 58, it is judged if the first timer value T1 is equal to or greater than the set timer value T0.

Here, the set timer value T0 is the time during which only the rear wheel steering angle fluctuation of 0.15 °, which is less than the rear wheel steering angle fluctuation allowable value of 0.2 °, is allowed even if the high-cass motor 15 responds at the maximum speed. Is set to 15 ± 5 msec.

In step 59, when the time condition of step 58 is satisfied, it is determined that the motor control current is abnormal.
Based on this abnormality determination, a fail-safe process of prohibiting the rear wheel steering angle control and turning on the warning valve 33 is performed.

In step 60, when it is determined in step 55 that the motor control current command I ^* is I ^* = 0, that is, when the motor control current command is not issued, the motor control current I is the first set current value I1. It will be judged.

In step 61, when the condition of step 60 is satisfied, the second timer value T2 is set to T2 = T2 + 1.

At step 58, it is judged if the second timer value T2 is equal to or greater than the set timer value T0.

In step 62, when it is determined that the current reverse direction condition in step 56 is not satisfied, it is determined whether the motor control current direction ID and the rear steering angle direction δrD are the same.

In step 63, ID =
When it is determined to be δrD, it is determined whether the motor control current command direction I ^* D and the motor control current direction ID are in the same direction, and the control current difference ΔI is the second set current value I2 or more.

Here, the second set current value I2 is set to 10 ± 1 A so that it can be judged as abnormal if an excessive current continues to flow in the high-cass motor 15.

In step 64, when the condition of step 63 is satisfied, the third timer value T3 is set to T3 = T3 + 1.

At step 58, it is judged if the third timer value T3 is not less than the set timer value T0.

In step 65, when the conditions in steps 60, 62 and 63 are not satisfied, the timer values T1, T2 and T3 are reset to zero.

In step 66, the high-cass motor 15
It is determined that the motor control current to is in a normal state.
Based on this determination, normal rear wheel steering angle control is performed.

[Pattern of Abnormal Motor Control Current] The abnormal motor control current has the patterns shown in the following table.

[0048] [No. 1 and No. Abnormality detection of No. 2] Of the motor control current abnormalities, No. 1 in the above table. 1 and No. 2 abnormality detection,
In the flowchart of FIG. 5, the determination is made according to the flow of steps 50 to 59.

That is, the condition that the motor control current command is issued in step 55 is opposite to the motor control current command direction I ^* D and the motor control current direction ID in step 56, and the motor control current I Is the first set current value I1
The state satisfying the above condition is step 58.
When it continues for the set timer value T0 (= 15 ± 5 msec) or more in step 59, it is determined in step 59 that the motor control current is abnormal.

As a concrete example, as shown in FIG. 6, the motor control current command I ^* is stepwise in the direction to steer the rear wheels to the right ^.
Despite is given, if the motor control current I which slide into increased in the direction of left steering the rear wheels, at time t _0, and a motor control current command direction I ^* D and the motor control current direction ID time reverse a satisfies the condition that it is, the timer counts from the time t ₁ which satisfies the condition that the motor control current I is first set current value I1 or so, and 15 ± 5 msec elapsed from the time t ₁ At t ₂ , the motor control current abnormality determination condition is satisfied.

Further, as shown in FIG. 7, when the rear steering angle exceeds the target value, the motor control current I is reversed even if the motor control current command is reversed so as to change the rear wheels from right steering to left steering. Is increasing in the direction for steering the rear wheels to the right, the motor control current command direction I ^* D is opposite to the motor control current direction ID at the time point t ₃ , and the motor control current I is satisfies the condition that is 1 set current value I1 or more, the determination condition of the motor control current abnormality will be established at the time t ₄ when the 15 ± 5 msec elapses from the time point t _3.

Accordingly, when the motor control current command is issued and the motor control current command direction I ^* D and the motor control current direction ID are in opposite directions, even when the motor control current I is abnormally output. Also, the abnormality of the motor control current can be detected even when the motor control current I is normally output.

[No. Abnormality detection of No. 3] No. in the above table among the motor control current abnormalities. In the flowchart of FIG. 5, the abnormality detection of No. 3 is step 50 to step 55 → step 60 → step 61 → step 58 → step 59.
It is judged by the flow of.

That is, the condition in which the motor control current command in step 55 is not issued and the condition in which the motor control current I in step 60 is equal to or larger than the first set current value I1 are set in step 58. Timer value T0
When it continues for (= 15 ± 5 msec) or more, it is determined in step 59 that the motor control current is abnormal.

As a specific example, as shown in FIG. 8, although the motor control current command shifts from the command for steering the rear wheels to the right to the command for maintaining the rear wheels in the neutral position (I ^* = 0). If the motor control current I continues to be output as it is in the direction of steering the rear wheels to the right, at time t ₅ , the condition that the motor control current I is the first set current value I1 or more is satisfied, and at this time t At a time point t ₆ when 15 ± ₅ msec has elapsed from ₅ , the motor control current abnormality determination condition is satisfied.

Therefore, when the motor control current command is not issued and the motor control current I is abnormally output, the abnormality of the motor control current can be detected by the above detection processing.

[No. Abnormality detection of No. 4] Among the motor control current abnormalities, No. 4 in the above table. In the flowchart of FIG. 5, the abnormality detection of No. 4 is step 50 to step 56 → step 62 → step 63 → step 64 → step 58.
→ Judgment is made according to the flow of step 59.

That is, the condition that the motor control current command in step 55 is issued, the condition that the motor control current direction ID in step 62 and the rear steering angle direction δrD are the same, and the motor control current command direction in step 63 I ^* D and the motor control current direction ID are in the same direction, and the condition that the control current difference ΔI is the second set current value I2 or more is satisfied, and the set timer value T0 in step 58 is satisfied.
When it continues for (= 15 ± 5 msec) or more, it is determined in step 59 that the motor control current is abnormal.

As a specific example, as shown in FIG. 9, a command for steering the rear wheels to the right is issued as the motor control current command I ^* , and the motor control current I is output in the same direction. ^{When the} motor control current I is excessive with respect to ^* , at time t ₇ , the motor control current command I ^* and the motor control current I are output in the same direction, but the motor control current I is the second set current value. The timer count is started from time t ₈ when the condition of being I2 or more is satisfied, and time t ₈
At the time t ₉ when 15 ± 5 msec has elapsed from then, the judgment condition of the motor control current abnormality is satisfied.

Here, the reason why the condition that the motor control current direction ID and the rear steering angle direction δrD are the same is included will be described.

In the case of a four-wheel steering system, the motor control current command characteristic shown in FIG. 10 is used because, for example, the phase inversion control is performed to shift the rear wheels from the reverse phase to obtain the turning property to the same phase to obtain the stability. As shown, the motor control current command I ^*
May reverse between the right steering direction and the left steering direction. At this time, the loop current due to the back electromotive force generated in the high-cass motor 15 may momentarily flow in the same direction as the motor control current command I ^* . In this case, as shown in the motor control current characteristic of FIG. A situation is realized in which the abnormality determination condition that the control current I is excessive is satisfied.
Therefore, if the condition that the motor control current direction ID and the rear steering angle direction δrD are the same is weighted, as shown in the condition for seeing failure in FIG. 10, when a loop current is generated, it is excluded from the abnormality determination. False detection can be prevented.

[0062] Therefore, when the motor control current command I ^* is out, when it motor control current I is the same direction as the motor control current command I ^* becomes excessive output to the motor control current command I ^* is By the above abnormality detection processing, it is possible to detect an abnormality in the motor control current while preventing erroneous detection at the time of command reversal.

Next, the effect will be described.

(1) In an electric motor drive type four-wheel steering system in which the rear wheel steering angle is controlled by the high-cass motor 15,
When the motor control current command I ^* is issued, the motor control current I of the first set current value I1 or more is the motor control current command I ^*.
Since the device for monitoring the motor control current detects that the motor control current is abnormal when the current flowing in the opposite direction continues for a predetermined time, the motor control current I is opposite to the motor control current command I ^* . In the case of the direction, the abnormality of the motor control current I can be detected without misdetection by including the direction determination.

(2) Even if the high-cass motor 15 responds at the maximum speed, the time condition for the motor control current abnormality determination is 0.15 ° which is less than the rear wheel steering angle variation allowable value of 0.2 °. Set timer value T0, which is the time allowed only
Since (= 15 ± 5 msec) is set, it is possible to prevent a sudden change in vehicle behavior due to a delay in the motor control current abnormality determination while ensuring a sufficient time for preventing erroneous detection.

(3) The first set current value I1, which is the current value condition for determining the motor control current abnormality, is set to the high-cass motor 15
Since it is set to 2 ± 0.5A, which is lower than the dark current of 3A, the abnormal motor control current can be detected before the high-cass motor 15 starts to move and the rear wheel steering angle fluctuates when the motor control current is abnormal. .

[0067] (4) when the motor control current command I ^* is out, but the motor control current I is the same direction as the motor control current command I ^* becomes excessive output to the motor control current command I ^* Sometimes, the condition that the motor control current command is issued, the condition that the motor control current direction ID and the rear steering angle direction δrD are the same, and that the motor control current command direction I ^* D
And the motor control current direction ID are in the same direction, and when the condition that the control current difference ΔI is the second preset current value I2 or more is satisfied and the preset timer value T0 or more continues, it is detected as an abnormality. Therefore, it is possible to detect an abnormality in the motor control current while preventing erroneous detection at the time of command reversal.

Although the embodiments have been described above with reference to the drawings, the specific structure is not limited to the embodiments, and modifications and additions within the scope of the present invention are included in the present invention. Be done.

For example, the first set current value I1 (2 ± 0.5
A), the second set current value I2 (10 ± 1 A), and the set timer value T0 (15 ± 5 msec) are not limited to the values in the embodiment, and are appropriately set by the control system or the vehicle in which the system is mounted. be able to.

[0070]

As described above, according to the present invention, in the electric motor drive type four-wheel steering system in which the rear wheel steering angle is controlled by the electric motor, the set value is set when the motor control current command is issued. When the above motor control current is flowing in the opposite direction to the motor control current command for a predetermined period of time, the motor control current monitoring means is provided to detect that the motor control current is abnormal. As a result, when the motor control current is in the opposite direction, it is possible to detect an abnormality in the motor control current without erroneous detection.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to claims showing an electric motor driven four-wheel steering system according to the present invention.

FIG. 2 is an overall system diagram showing a vehicle to which an electric motor drive type four-wheel steering system according to an embodiment of the present invention is applied.

FIG. 3 is a diagram showing an electric rear wheel steering mechanism of the electric motor driven four-wheel steering system according to the embodiment.

FIG. 4 is a system diagram of an electronic control system centering on a 4WS control unit of the embodiment apparatus.

FIG. 5 is a flowchart showing a flow of motor control current monitoring operation performed by a monitoring circuit of the 4WS control unit of the embodiment apparatus.

FIG. 6 is a time chart of an abnormality determining operation when the motor control current is abnormal (No. 1 pattern).

7 is a time chart of an abnormality determination operation when the motor control current is abnormal (No. 2 pattern).

FIG. 8 is a time chart of an abnormality determination operation when the motor control current is abnormal (No. 3 pattern).

FIG. 9 is a time chart of an abnormality determination operation when the motor control current is abnormal (No. 4 pattern).

FIG. 10 is a time chart of an abnormality determination operation when the motor control current is normal and the motor control current command fluctuates.

[Explanation of symbols]

 a electric motor b motor drive control circuit c motor control current command detection means d motor control current detection means e motor control current monitoring means

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Claims (1)

[Claims] 1. An electric motor for controlling a rear wheel steering angle by driving by applying a motor control current, and a motor drive control circuit connected to the electric motor for converting a motor control current command into a motor control current to flow to the electric motor. A motor control current command of the motor control current command and a motor control current command detecting means for detecting the command direction thereof; and a motor control current detecting means for detecting a motor control current actually flowing in the motor drive control circuit and the direction thereof. , When the motor control current command is issued, if the motor control current above the set value is flowing in the opposite direction to the motor control current command for a predetermined time, it is detected that the motor control current is abnormal. An electric motor drive type four-wheel steering device comprising: a current monitoring unit.