JP3024664B2 - Electric motor driven four-wheel steering system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric motor-driven four-wheel steering apparatus 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 of 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. 1-29776.
No. 4 is known.

[0003] 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 becomes 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 direction between 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 is a value in the right steering direction of the rear wheel, a motor in which the actual current value is a value in the left steering direction. When the control current is abnormal, if the deviation of the absolute value of the output current value is equal to or less than the abnormality determination threshold value, the motor control current is erroneously detected as normal.

[0005] Particularly, in the case of an electric motor-driven four-wheel steering system, this erroneous detection is performed, for example, in order to aim at turning stability.
When trying to steer the rear wheels in phase, the rear wheels are allowed to be steered in the opposite phase, resulting in a sudden change in vehicle behavior due to control that is completely opposite to the intended control, ensuring safety. Again, this false detection must be avoided.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide a motor-controlled four-wheel steering system in which a rear wheel steering angle is controlled by an electric motor. On the other hand, when the motor control current is in the opposite direction, the motor control current is detected abnormally without erroneous detection, and sufficient time is required to prevent erroneous detection.
While maintaining the motor control current abnormality
The purpose is to prevent sudden changes in behavior .

[0007]

In order to solve the above-mentioned problems, in an electric motor-driven four-wheel steering system according to the present invention, when a motor control current command is issued, a motor control current not less than a set value is applied to the motor control current command. a state where the flows in the opposite direction, Mo
Even if the motor responds at the maximum speed, the rear wheel steering angle fluctuation tolerance
A motor control current monitoring means is provided for detecting that the motor control current is abnormal when a predetermined period of time, which is a time during which only the rear wheel steering angle fluctuation less than the allowable value , is allowed .

That is, as shown in the claim correspondence diagram of FIG. 1, an electric motor a for controlling a rear wheel steering angle by driving by applying a motor control current, and an electric motor a connected to the electric motor a for transmitting a motor control current command to an electric motor. A motor drive control circuit b for converting the motor drive current to the motor a, a motor control current command for the motor control current command and a motor control current command detecting means c for detecting the command direction, A motor control current detecting means d for detecting a motor control current flowing in the motor control current direction, and a state in which a motor control current exceeding a set value flows in a direction opposite to the motor control current command when a motor control current command is issued. , Motor is at maximum speed
Rear wheel steering angle less than the allowable rear wheel steering angle fluctuation value
When a predetermined time, which is a time that allows only fluctuation, continues for
A motor control current monitoring means e for detecting that the motor control current is abnormal.

[0009]

When the rear wheel steering angle is controlled, the motor control current monitor means e sets the motor control current command based on the detection by the motor control current detection means d when the motor control current command is output based on the detection by the motor control current command detection means c. When the motor control current that exceeds the value flows in the opposite direction to the motor control current command, even if the motor responds at the maximum speed, the rear wheel steering angle fluctuation
If the predetermined time, which is the time during which only the rear wheel steering angle variation less than the allowable value is allowed, continues, it is detected that the motor control current is abnormal.

Therefore, since the motor control current direction and the direction of the motor control current command are included in the criterion for judging the abnormality of the motor current, whether the motor control current is in the reverse direction to the motor control current command is included. In some cases, an abnormality in the motor control current can be detected. In addition, in this determination, the time condition that the motor control current that is equal to or greater than the set value flows in the opposite direction to the motor control current command is maintained for a predetermined period of time, so that the motor control current is normal. However, 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. can do.
The time condition for the motor control current abnormality determination is
Is less than the rear wheel steering angle fluctuation tolerance even if the vehicle responds at the maximum speed
Is a predetermined value that allows only the rear wheel steering angle variation
Therefore, while securing sufficient time to prevent false detection,
To prevent sudden changes in vehicle behavior due to delays in
Can be stopped.

[0011]

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

First, the configuration will be described.

FIG. 2 is an overall system diagram showing a vehicle to which the electric motor-driven four-wheel steering device according to the embodiment of the present invention is applied. FIG. 3 is an electric motor-driven four-wheel steering device according to the embodiment. FIG. 4 shows the mechanism, and FIG.
FIG. 2 is an electronic control system diagram centered on an 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.

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

The electric rear wheel steering mechanism 6 includes four
The rotational force of the high cas motor 15 (corresponding to the electric motor a) controlled by the motor output from the WS control unit 14 is transmitted to the worm 16 and the worm wheel 17.
And the rotational motion of the worm wheel 17 is converted into linear motion of the rack shaft 19 by meshing the gear portion of the pinion shaft 18 with the gear portion of the rack shaft 19, and the side rods 20, 21 and the knuckle arm are transferred from the rack shaft 19. Via the rear wheels 3,
4 to provide a steering angle.

The 4WS control unit 14 includes:
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 conversions 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 has a battery power supply directly from the battery 24 and an ignition switch 25.
The ignition power from is input.

The input interface 14c includes a sensor signal from a rear steering angle main sensor 26 and a rear steering angle sub sensor 27 by a potentiometer, a sensor signal from a steering sensor 28, a sensor signal from a 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
Sends a high cas relay output to

The motor output driver 14m is driven by a motor power supply via a high cas relay 34,
A rear wheel steering angle command is input from PU1 via D / A converters 14g and 14h, and a motor output is sent to the high cas motor 15.

The power steering solenoid output driver 14
n inputs a power steering command from the CPU 1 via the D / A converter 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 with reference to a flowchart showing the flow of the motor control current monitoring operation performed by the monitoring circuit 14d of the control unit 14 (corresponding to the motor control current monitoring means e).

In step 50, the motor output driver 14m passes the D / A conversions 14g and 14h from the CPU 1.
The motor control current command I ^* and its direction I ^* D 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 detecting means d).

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

In step 53, the rear steering angles δr and δr-1
The rear steering 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 a 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 equal to or greater than the first set current value I1.

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

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

In step 58, it is determined whether the first timer value T1 is equal to or greater than the set timer value T0.

Here, the set timer value T0 is a 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 permitted even if the high cas motor 15 responds at the maximum speed. 15 ± 5 msec.

In step 59, when the time condition in 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 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, it is determined that the motor control current command has not been issued, the motor control current I is not less than the first set current value I1. It is determined whether or not.

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

In step 58, it is determined whether 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 = ID in step 62
If it is determined that 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 whether the control current difference ΔI is equal to or greater than the second set current value I2.

Here, the second set current value I2 is set to 10 ± 1A so that it can be determined that an abnormality occurs when an excessive current continues to flow through 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.

In step 58, it is determined whether the third timer value T3 is equal to or greater than the set timer value T0.

In step 65, when the conditions in steps 60, 62 and 63 are not satisfied, a process for resetting each of the timer values T1, T2 and T3 to zero is performed.

In step 66, the high cas motor 15
Is determined to be in a normal state.
Based on this determination, normal rear wheel steering angle control is performed.

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

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

That is, the condition that the motor control current command in step 55 is issued, the motor control current command direction I ^* D and the motor control current direction ID in step 56 are opposite to each other, and Is the first set current value I1
The state that satisfies the above condition is satisfied in step 58
If the set timer value T0 (= 15 ± 5 msec) or more has been continued for a while, it is determined in step 59 that the motor control current is abnormal.

As a specific example, as shown in FIG. 6, the motor control current command I ^* is stepped in the direction in which the rear wheels are steered to the right ^.
Is given, the motor control current I increases in the direction in which the rear wheels are steered to the left, at time t ₀ , the 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 judgment condition of the motor control current abnormality will be established at t _2.

Also, as shown in FIG. 7, when the rear steering angle exceeds the target value, the motor control current I is reversed in order to change the rear wheels from right steering to left steering even though the motor control current command is reversed. If Yuku as it increases in the direction of rightward steering the rear wheels, at time t _3, a motor control current command direction I ^* D and the motor control current direction ID and the reverse, and, a motor control current I is first 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.

Therefore, when the motor control current command is issued and the motor control current command direction I ^* D is opposite to the motor control current direction ID, the motor control current I may be output abnormally. In addition, when the motor control current I normally outputs, the abnormality of the motor control current can be detected.

[No. No. 3 abnormality detection] Among the motor control current abnormalities, No. 3 in the above table. The abnormality detection of No. 3 is performed in the flowchart of FIG. 5 by referring to steps 50 to 55 → step 60 → step 61 → step 58 → step 59.
Is determined by the flow.

That is, the condition satisfying the condition that the motor control current command is not issued in step 55 and the condition that the motor control current I is greater than or equal to the first set current value I1 in step 60 are set in step 58. Timer value T0
(= 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, even though the motor control current command has shifted from a command to steer the rear wheel to the right to a command to keep the rear wheel in the neutral position (I ^* = 0). when the motor control current I which continues to be output directly in the direction of rightward steering the rear wheels, at time t _5, satisfy the condition that the motor control current I is first set current value I1 or more, the time t judgment condition of the motor control current abnormality will be established at the time t _{6 to 5} from 15 ± 5 msec elapsed.

Therefore, when the motor control current I is not output 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. No. 4 abnormality detection] Among the motor control current abnormalities, No. 4 in the above table. The abnormality detection of No. 4 is performed in steps 50 to 56 → step 62 → step 63 → step 64 → step 58 in the flowchart of FIG.
→ It is determined by the flow of step 59.

That is, the condition that the motor control current command is issued in step 55, the condition that the motor control current direction ID is the same as the rear steering angle direction δrD in step 62, and the condition that the motor control current command The state where the condition that I ^* D and the motor control current direction ID are the same direction and the control current difference ΔI is equal to or more than the second set current value I2 is satisfied is the set timer value T0 in step 58.
(= 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 to steer the rear wheels to the right is issued as the motor control current command I ^* , and the motor control current I is issued in the same direction. If the motor control current I is too large with respect to ^*, at time t _7, but the motor control current command I ^* in the same direction as the motor control current I is out, the motor control current I is the second set current value from the time t ₈ satisfying the condition that is I2 or greater than the timer count is started, the time t ₈
Judgment condition of the motor control current abnormality will be established at 15 ± 5 msec elapsed time t ₉ from.

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

In the case of a four-wheel steering system, for example, because the phase inversion control for shifting the rear wheel from the reverse phase for turning to the same phase for stability is performed, the motor control current command characteristic shown in FIG. As shown, the motor control current command I ^*
May be reversed in the right steering direction and the left steering direction. At this time, a 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 where the abnormality determination condition that the control current I is excessive is satisfied is realized.
Therefore, when 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 of seeing the failure in FIG. 10, when a loop current occurs, the condition 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 According to the 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 effects will be described.

(1) In an electric motor-driven 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 equal to or more than the first set current value I1 is applied to the motor control current command I ^*.
And if the state of flow in the direction opposite to the direction continues for a predetermined time, since the motor control current is a device for performing the motor control current monitoring to detect that there is an abnormality, the motor control current I to the motor control current command I ^* is reversed In the case of the direction, the abnormality of the motor control current I can be detected without erroneous detection by including the direction determination.

(2) Regarding the time condition of the motor control current abnormality determination, even if the high cas motor 15 responds at the maximum speed, the rear wheel steering angle fluctuation less than the allowable rear wheel steering angle fluctuation value 0.2 ° of 0.15 °. Timer value T0, which is a time that allows only
(= 15 ± 5 msec), it is possible to prevent a sudden change in vehicle behavior due to a delay in the determination of a motor control current abnormality while securing a sufficient time for preventing erroneous detection.

(3) The first set current value I1, which is a current value condition for judging a motor control current abnormality, is
Is set to 2 ± 0.5 A, which is lower than the dark current 3 A, so that when the motor control current is abnormal, the motor control current abnormality can be detected before the high cas motor 15 starts to move and changes the rear wheel steering angle. .

[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 the condition that the motor control current command direction I ^* D
And the motor control current direction ID is the same direction, and the state that satisfies the condition that the control current difference ΔI is equal to or more than the second set current value I2 is detected as abnormal when the set timer value T0 or more is continued. With this configuration, it is possible to detect an abnormality in the motor control current while preventing erroneous detection at the time of command reversal.

Although the embodiment has been described with reference to the drawings, the specific configuration is not limited to the embodiment, and even if there are changes and additions without departing from the gist of the invention, the invention is included in the invention. It is.

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 of 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-driven four-wheel steering system in which the rear wheel steering angle is controlled by the electric motor, when the motor control current command is issued, the set value is set. If a state in which the motor control current is flowing in the opposite direction to the motor control current command continues for a predetermined time, the motor control current monitoring means for detecting that the motor control current is abnormal is provided. co to be able to detect the abnormality of the motor control current without erroneous detection when the motor control current are opposite Te
In addition, while securing sufficient time to prevent false detections,
Of sudden changes in vehicle behavior due to delays in data control current abnormality judgment
Effect that can be.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to a claim showing an electric motor-driven four-wheel steering device of the present invention.

FIG. 2 is an overall system diagram showing a vehicle to which the electric motor-driven four-wheel steering device according to the 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 device of the embodiment.

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

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

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

FIG. 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 detecting means d motor control current detecting means e motor control current monitoring means

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI B62D 113: 00 (58) Field surveyed (Int.Cl. ⁷ , DB name) B62D 5/04 B62D 6/00 B62D 7/14

Claims (1)

(57) [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 and converting a motor control current command into a motor control current flowing to the electric motor. A motor control current command of a motor control current command and a motor control current command detecting means for detecting a command direction thereof; a motor control current actually flowing through the motor drive control circuit and a motor control current detecting means for detecting a direction thereof. When the motor control current command is issued, the motor control current that is equal to or greater than the set value is flowing in the opposite direction to the motor control current command even if the motor responds at the maximum speed.
And a motor control current monitoring means for detecting that the motor control current is abnormal when the predetermined time has elapsed, which is a time in which only the rear wheel steering angle variation less than the allowable motion value is allowed. Electric motor driven four-wheel steering device.