JPH08324448A - Diagnostic device of vehicular electric steering device - Google Patents

Abstract

PURPOSE: To prevent the mis-diagnosis for the abnormality of electric source voltage by diagnosing the abnormality of the electric source voltage by compar ing the electric source voltage of an actuator for steering with a prescribed threshold value and changing the prescribed threshold value in response to a current controlled by a servo means for controlling the current supplied to the actuator at this time. CONSTITUTION: At the vehicle running time, the electric power source voltage VM of a motor is read in CPU26a. Then, it is judged whether rear wheel steering control is carried out after the ON control of a motor relay 52 and a motor command current IM* (current command value) is read in at YES time. It is judged whether such state as VM<VB-IM*.Zo-α is continued more than a prescribed time, at YES time, it is judged that a drive circuit 26b is short- circuited and the relay 52 is OFF controlled and also the order current IM* is held to zero. Here, VB is an ignition voltage, α is fixed value as a spare and Zo is a harness impedance between a battery 51 and the drive circuit 26b (servo means).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diagnostic device for a vehicle electric steering device, and more particularly to a device for diagnosing an abnormality in a power supply voltage of a steering actuator.

[0002]

2. Description of the Related Art Conventionally, there has been known a rear wheel steering control device for giving an auxiliary steering angle to a rear wheel based on information such as vehicle speed and steering steering angle in order to improve steering stability of a vehicle. A configuration is known in which a motor is used as an actuator and an auxiliary steering angle is given to the rear wheels according to the amount of rotation of the motor.

In such an electric auxiliary steering system, for example, the system configuration as shown in FIG. 12 is used to adjust the current supplied to the motor to give the auxiliary steering angle to the rear wheels. In FIG. 12, the rear wheel steering angle target value calculation means A
Calculates the target value θs of the rear wheel steering angle based on the detection signal such as the vehicle speed and the steering angle, and the rear wheel actual steering angle detection means B detects the actual rear wheel steering angle θ.

Then, the servo means C adjusts the current Iout supplied to the motor D via the motor relay E so that the actual steering angle θ coincides with the target value θs. Here, the abnormality determination means F is, for example, when the motor relay E is in the ON control state and the power supply voltage VM of the motor D is the predetermined value Vo.
When the voltage is (for example, 2 V) or less, it is determined that the motor power supply voltage VM has become abnormal due to a short circuit failure in the servo means C, the motor relay E is turned off, and the power supply to the motor D is cut off.

Thus, even if a short-circuit failure occurs in the servo means C, it is possible to avoid an excessive current being supplied to the motor D and an abnormal steering angle being given to the rear wheels.

[0006]

However, when the impedance Zo in the harness from the battery to the servo means C becomes so large that it cannot be ignored due to the length of the harness, the installation of the coil for noise removal, etc., the impedance Zo. The power supply voltage VM is lowered even in the normal state due to the voltage drop due to, and the voltage drop margin is increased in accordance with the increase of the current Iout.

Therefore, when the impedance Zo is large, it is necessary to reduce the predetermined value Vo in order to avoid erroneous diagnosis of a short-circuit failure (power supply voltage abnormality), but erroneous diagnosis is performed even when the maximum current is applied. If a low predetermined value Vo that is not set is set, it may not be possible to reliably diagnose the occurrence of a short circuit failure when the applied current is relatively small. If it is raised, a false diagnosis may occur at high current.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a diagnostic device for an electric vehicle steering system that can reliably and reliably diagnose an abnormality in a power supply voltage for an actuator without erroneous diagnosis. .

[0009]

Therefore, according to the first aspect of the invention, the actual steering angle of the wheels matches the target steering angle.
In a vehicular electric steering system including servo means for controlling a current supplied to a steering actuator, a diagnostic device for diagnosing an abnormality in a power supply voltage is configured as shown in FIG.

In FIG. 1, the abnormality diagnosing means compares the power supply voltage of the actuator with a predetermined threshold value to make an abnormality diagnosis of the power supply voltage. Here, the threshold changing means is
The predetermined threshold value is changed according to the current controlled by the servo means. In the diagnostic device for a vehicle electric steering device according to the invention of claim 2, the threshold value changing means increases the multiplication value of the current and the impedance between the actuator power supply and the servo means which is obtained in advance. Accordingly, the threshold value is changed to a lower value.

According to another aspect of the present invention, there is provided a diagnosis device for an electric vehicle steering system, wherein the threshold value changing means indirectly detects a current based on a current command value in the servo means, and the abnormality diagnosis is performed. The means determines that the power supply voltage is abnormal when the power supply voltage of the actuator is lower than the predetermined threshold value for a predetermined time or more.

On the other hand, according to the invention of claim 4, an electric vehicle type vehicle comprising servo means for controlling the current supplied to the steering actuator so that the actual steering angle of the wheels coincides with the target steering angle. In the steering system, a diagnostic device for diagnosing an abnormality in the power supply voltage is configured as shown in FIG. In FIG. 2, the abnormality diagnosing means compares the power supply voltage of the actuator with a predetermined threshold value to make an abnormality diagnosis of the power supply voltage.

Here, the diagnosis permission means permits the abnormality diagnosis by the abnormality diagnosis means only when the current controlled by the servo means is equal to or less than a predetermined value. In the diagnostic device for a vehicle electric steering system according to the invention of claim 5, the diagnosis permission means indirectly detects the current based on the current command value in the servo means, and corresponds to the current command value. When the state in which the applied current is less than or equal to the predetermined value continues for the predetermined time or more, the abnormality diagnosis by the abnormality diagnosis means is permitted.

According to a sixth aspect of the present invention, there is provided a diagnostic device for an electric vehicle steering system, comprising an energization interruption means for interrupting energization to the actuator when the abnormality diagnosis means determines an abnormality in the power supply voltage. And

[0015]

According to the diagnostic device for an electric vehicle steering system according to the invention of claim 1, it is determined whether or not the power supply voltage is abnormal by comparing the actual power supply voltage of the actuator with a predetermined threshold value. However, by changing the predetermined threshold value according to the current controlled by the servo means, the diagnosis is made based on the threshold value corresponding to the drop in the normal voltage due to the increase in the current.

According to the second aspect of the present invention, there is provided a diagnostic device for an electric vehicle steering system, wherein the impedance between the actuator power source and the servo means is determined in advance in the configuration in which the threshold value is changed according to the current. In addition, the threshold value is changed in accordance with the voltage drop due to the impedance, which increases as the current increases. Claim 3
According to the diagnostic device for a vehicle electric steering device according to the invention, in the configuration for indirectly detecting the current based on the current command value in the servo means, in consideration of the response delay of the actual current with respect to the current command value, The abnormality determination is performed on condition that the power supply voltage of the actuator is lower than the predetermined threshold value for a predetermined time or more.

According to the fourth aspect of the present invention, there is provided a diagnostic device for an electric vehicle steering system, which compares the actual power source voltage of the actuator with a predetermined threshold value to determine whether or not the power source voltage is abnormal. However, such discrimination is permitted only when the current controlled by the servo means is equal to or less than a predetermined value, that is, when the voltage drop margin (normal voltage drop) due to the impedance of the harness is sufficiently small.

According to a fifth aspect of the present invention, there is provided a diagnostic device for an electric vehicle steering system, wherein the current is indirectly detected based on the current command value in the servo means. In consideration of the response delay, the diagnosis is allowed under the condition that the current detected through the current command value is below a predetermined value for a predetermined time or more.

According to the diagnostic device for an electric vehicle steering system according to the invention of claim 6, when the abnormality of the power supply voltage is judged, the energization to the actuator is cut off and the excess current is supplied to the actuator. To avoid.

[0020]

Embodiments of the present invention will be described below. FIG.
1 is a system diagram showing a four-wheel steering vehicle to which an electric vehicle steering system according to the present invention is applied for rear wheel steering. In FIG. 3, steering of the front wheels 1 and 2 is performed by a steering handle 3 and a mechanical link type steering mechanism 4. This is composed of, for example, a steering gear, a pitman arm, a relay rod, side rods 5, 6 and knuckle arms 7, 8.

On the other hand, steering of the rear wheels 9 and 10 is performed by an electric steering device 11. The rear wheels 9 and 10 are connected by a rack shaft 12, side rods 13 and 14, and knuckle arms 15 and 16, and a rack tube 17 in which the rack shaft 12 is inserted has a reduction mechanism 18 and a steering actuator. A motor 19 and a motor speed sensor are provided.
Drive control is performed by a controller 26 (servo means) that inputs signals from the front wheel steering angle sensor 22, the front wheel steering angle sensor 22, the rear wheel steering angle main sensor 23, the rear wheel steering angle sub sensor 24, the yaw rate sensor 25, and the like.

FIG. 4 is a sectional view showing a concrete structure of the electric steering device 11. In FIG. 4, the rack shaft
The rack tube 17 into which 12 is inserted is fixed to the vehicle body via a bracket (not shown). Rack shaft 12
The side rods 13 and 14 are connected to both end portions of the side via ball joints. The reduction mechanism 18 is provided in a housing 34 formed integrally with the rack tube 17, and a motor 19 fixed to the housing 34 with a bolt 47.
One end is connected to the motor shaft and the other end is a ball bearing
A pinion gear 32 (driving gear) rotatably supported by a housing 34 by a 44, a ring gear 33 (driven gear) meshing with the pinion gear 32, a ring gear 33 rotatably provided on the rack shaft 12 The rack pin 35 to be fitted together. The rack pin 35 is provided eccentrically with respect to the rotation shaft of the ring gear 33,
When the ring gear 33 rotates, the rack pin 35 can move left and right in the figure.

Therefore, when the motor shaft of the motor 19 rotates, the rotation is transmitted from the pinion gear 32 to the ring gear 33, and the rack pin 35 moves left and right in the figure as the ring gear 33 rotates, so that the rack pin 35 is fitted. The rack shaft 12 being moved moves in the axial direction to steer the rear wheels 9 and 10. The steering amount (auxiliary steering angle) of the rear wheels 9 and 10 corresponds to the axial movement amount of the rack shaft 12, that is, the rotation amount of the motor shaft.

The ring gear 33 is provided with a potentiometer-type rear wheel steering angle main sensor 23 for detecting the rear wheel steering angle based on the amount of rotation thereof, and further, according to the amount of axial movement of the rack shaft 12. A potentiometer-type rear wheel steering angle sub-sensor 24 for detecting the wheel steering angle is provided. The ring gear 33 has a bevel gear formed around an axis on a plane orthogonal to the axis thereof, and the pinion gear 32 with respect to the ring gear 33 is about an axis on a plane orthogonal to the axis of the ring gear 33. It has a worm gear that is formed and meshes with the bevel gear (see FIG. 5).

In this embodiment, the power from the pinion gear 32 is transmitted to the ring gear 33 side. However, even if the ring gear 33 tries to rotate, the pinion gear is set by the angle setting of the teeth.
The configuration is such that 32 does not rotate and has an irreversible characteristic. Here, a spring (elastic member) 45 for urging the flange portion 33a of the ring gear 33 toward the pinion gear 32 side along the axial direction of the ring gear 33 is provided, and the urging force of the spring 45 causes the ring gear 33 to move. By pressing the pinion gear 32 side, the ring gear 33 and the pinion gear
It is designed to minimize the clearance between the tooth flanks between 32 and 32.

FIG. 6 is a block diagram showing an electronic control system of the electric steering system 11 centered on the controller 26. In FIG. 6, 21 is a vehicle speed sensor, 22 is a front wheel steering angle sensor (steering angle sensor), 23 is a rear wheel steering angle main sensor,
24 is a rear wheel steering angle sub sensor, 25 is a yaw rate sensor, 26 is a controller, 26a is a CPU, 26b is a motor drive circuit,
26c is a fail-safe circuit.

The CPU 26a includes a feedforward target value calculation unit 261, an estimated yaw rate calculation unit 262, a feedback target value calculation unit 263, a rear wheel steering angle target value calculation unit 264,
It has a steering angle servo calculation unit 265. The motor drive circuit 26
b is the motor drive current I to the motor 19 which is the motor command current IM ^* (current command value) from the steering angle servo calculator 265.
Convert to M.

The fail-safe circuit 26c is provided, for example, between the rear wheel steering angle main sensor 23 and the rear wheel steering angle sub sensor 24.
When the detection deviation of the rear wheel steering angle amount occurs, the output of the motor drive current IM is forcibly stopped, and the rear wheels are maintained in the fail-safe operating state. FIG. 7 is a flowchart showing a flow of rear wheel steering control performed by the CPU 26a of the controller 26.

First, at step 40, the vehicle speed V, the steering angle θ, the actual yaw rate Ψ's, and the rear wheel steering angle main sensor.
The output values δrs and 23 are read. Here, the actual yaw rate Ψ's is calculated from the yaw rate sensor value VΨ 'from the yaw rate sensor 25 and the latest yaw rate zero correction memory value VΨ'om obtained by the detected yaw rate correction processing for removing the influence of the temperature drift.

In step 41, the rear wheel steering angle feedforward target value δ RFF is calculated by the following equation based on the phase inversion delay control method using the vehicle speed V and the steering steering angle θ.
^* (Hereinafter, * represents a target value.) Is calculated. δ RFF ^* = Kθ + τθ + τ′θ The calculation process in step 41 is performed by the feedforward (F / F) target value calculation unit 261.

In step 42, the rear wheel steering angle actuator (motor) is the amount by which the rear wheel steering angle actuator (motor) actually steers the rear wheels when the rear wheel steering angle feedforward target value δ RFF ^* is given using the actuator model. An estimated angle value Δ RFF ^# (hereinafter, # means an estimated value) is calculated. This actuator model is given by the transfer characteristic of the actual rear wheel steering angle obtained by driving the actual actuator with respect to the rear wheel steering angle command value.

In step 43, the vehicle model is used to calculate the yaw rate estimated value Ψ '^# when the vehicle is assumed to travel with the vehicle speed V, the steering steering angle θ, and the rear wheel steering angle estimated value δ RFF ^# . A linear two-degree-of-freedom plane vehicle model is used as this vehicle model. In step 44, the estimated yaw rate Ψ's ^# is calculated from the estimated yaw rate Ψ '^# using the yaw rate sensor model. This yaw rate sensor model is given by a transfer function based on experimental results of sensor dynamic characteristics such as frequency response of the sensor.

The calculation processing of steps 42 to 44 is performed by the estimated yaw rate calculation unit 262. In step 45,
The yaw rate deviation Ψ'e is calculated from the difference between the actual yaw rate Ψ's and the estimated yaw rate Ψ's ^# . In step 46, the feedback compensator-1 that constitutes the first-order lag filter is
Thus, the yaw rate deviation Ψ'e is input, and an output signal Ψ'ecl from which high frequency noise included in the output of the yaw rate sensor 25 is removed is obtained.

In step 47, the feedback compensator-2 forming a first-order / first-order filter receives the output signal Ψ'ec1 and the vehicle speed C as an input, and an output signal Ψ whose transient response of the vehicle to disturbance is adjusted. Get'ec2. In step 48, the feedback proportional gain Kp is used to input Ψ'ec2 and the vehicle speed V, and the feedback rear wheel steering angle command value δRFBO
^* Is calculated.

In step 49, the steering angle limiter returns the feedback rear wheel steering angle command value δRFBO ^* according to the vehicle speed V.
The feedback rear-wheel steering angle limit command value ΔRFBL ^* is calculated by smoothly limiting the maximum value of. In step 50, the minute change absorber is used to input δRFBL ^* and the rear wheel steering angle feedback target value δRFB ^* , and the feedback rear wheel steering angle limit command value δRFBL ^* is provided with hysteresis to eliminate minute yaw rate vibrations due to feedback. The feedback rear wheel steering angle limit command value ΔRFBH ^* is calculated.

In step 51, the actuator phase compensator forming the secondary / secondary filter is used to input the feedback rear wheel steering angle limit command value δRFBH ^* , and the transfer characteristic set in the actuator control system is desired. Rear wheel steering angle feedback target value ΔRFB ^*
Is calculated. The calculation processing of steps 45 to 51 is performed by the feedback (F / B) target value calculation unit 263.

At step 52, the rear wheel steering angle feedforward target value δRFF ^* and the rear wheel steering angle feedback target value δ
The rear wheel steering angle target value ΔR ^* is calculated by the sum with RFB ^* . The calculation processing in this step is performed by the rear wheel steering angle target value calculation unit 264. In step 53, using the rear wheel steering angle main sensor value δrs and the robust model matching method,
Motor command current rear wheel steering angle target value δR ^* can be obtained IM ^*
Is output to the motor drive circuit 26b. Then, the motor drive circuit 26b outputs the motor drive current IM to the motor 19 as an actuator of the electric steering apparatus 11.

Here, the drive current I for the motor 19 is
The M supply circuit is specifically configured as shown in FIG. 8, in the motor drive circuit 26b, the battery 51 is turned on / off by the CPU 26a as a power source.
It is connected via the controlled motor relay 52, and controls the drive current IM of the motor 19 according to the motor command current IM ^* based on the power supply.

Further, the power supply voltage VM of the motor 19 and the ignition voltage V via the ignition switch 53
B (battery voltage) is monitored by the CPU 26a. Then, as will be described later, the CPU 26a diagnoses an abnormality in the power supply voltage VM, and when an abnormality occurs, forcibly turns off the motor relay 52 as an energization interrupting means to interrupt the current supply to the motor 19. It is designed to hold the wheel in its failsafe operating condition.

The flowchart of FIG. 9 shows the CPU 26a.
3 shows a first embodiment of the power supply voltage abnormality diagnosis by the above. In S61, the motor power supply voltage VM is read. S62
Then, the motor relay 52 is ON-controlled to determine whether or not the rear-wheel steering control is being executed.

If the motor relay 52 is being turned off, the process proceeds to S63, in which the read motor power supply voltage VM is read.
Is above a preset first threshold voltage (for example, 2 V). Then, the motor power supply voltage VM
Is above the first threshold voltage, the motor relay 52 remains in the ON state without actually being switched to the OFF state despite the OFF control (relay O
N failure), the process proceeds to S64, the motor command current IM ^* thereafter is held at zero, and
A warning light provided in the passenger compartment is turned on and the driver is relayed.
Warning of occurrence of N failure (failure of electric steering device).

On the other hand, in S62, the motor relay 52 is ON-controlled.
It is determined that the rear wheel steering control is being executed.
Sometimes, the process proceeds to S65, where the motor command current IM^*(Current finger
Read the command value). In the next S66, VM <VB-IM^*
・ Zo-α state is for a predetermined time Δt (for example, 100 ms) or more.
Determine whether it is continuing above. In this S66
(VB-IM ^*・ Zo-α) is a threshold change
It corresponds to the means.

Here, VB is the ignition voltage VB,
IM ^* is a motor command current (current command value), α is a fixed value (for example, 2 V) preset as a margin, and Zo is a harness impedance between the battery 51 and the motor drive circuit 26b (servo means). It has been actually measured and stored in advance. Here, (VB-IM ^*
When the state where the actual motor power supply voltage VM is lower than the second threshold voltage given as Zo-α) continues for a predetermined time Δt or more, the process proceeds to S67 and the drive circuit 26b.
It is determined that the short circuit failure has occurred, and in the next S68, the motor relay 52 is forcibly turned off (energization interruption means), and the subsequent motor command current IM ^* is held at zero, and further, the vehicle interior A warning light provided on the vehicle is turned on to warn the driver of the occurrence of a short circuit failure (a failure of the electric steering device).

The above-mentioned steps S66 to S68 correspond to abnormality diagnosing means. The short circuit failure is caused by the ignition voltage VB.
On the other hand, it is possible to make a diagnosis based on the fact that the power supply voltage VM drops by a predetermined value or more. However, when the harness impedance Zo becomes so large that it cannot be ignored due to the installation of a noise removal coil, etc. However, the larger the drive current IM is, the larger the drive current IM is, and even in the normal state, when the drive current IM is large, the power supply voltage VM greatly drops.

Therefore, in the present embodiment, the second threshold voltage to be compared with the power supply voltage VM is set to the drive current IM (in response to the increase in the voltage drop due to the harness impedance Zo as the drive current IM increases. Motor command current IM ^*
And the impedance Zo) are increased (see FIG. 10).
While avoiding erroneous diagnosis of a voltage drop due to occurrence of a short-circuit failure, when a short-circuit failure actually occurs, this can be reliably diagnosed.

Further, in this embodiment, the motor command current IM
^The drive current IM is indirectly detected based on the ^* (current command value), but there is a response delay until the actual drive current IM is generated corresponding to the motor command current IM ^* , so VM
<VB-IM ^* · Zo-α correlation may occur due to the response delay. Therefore, the abnormality is diagnosed only when the correlation continues for a predetermined time Δt corresponding to the response delay time, so that the false diagnosis due to the response delay is prevented.

By the way, in the power supply voltage diagnosis shown in the flow chart of FIG. 9, the motor command current IM ^* has a configuration in which the threshold value is changed so as to decrease as the motor command current IM ^* increases in order to cope with the voltage drop due to the impedance Zo. Since a large current is not output as IM ^* (driving current IM) infrequently, it is fixed to the driving current change only when the motor command current IM ^* is relatively small and the voltage drop due to the impedance Zo is sufficiently small. The threshold value and the power supply voltage VM may be compared to perform a power supply voltage abnormality diagnosis.

When the impedance Zo is large, the power supply voltage VM in the normal state becomes lower as the motor command current IM ^* (driving current IM) becomes larger, and when the power supply voltage VM in the normal state becomes lower, the power supply voltage at the time of the short-circuit failure becomes normal. The power supply voltage at that time is close. Therefore, if the threshold value is fixed, in a region where the motor command current IM ^* (driving current IM) is large, it is not possible to have a predetermined margin or more from the power supply voltage at the time of the short circuit failure and the power supply voltage at the normal time,
In a region where the drive current IM is relatively small, in which the difference between the power supply voltage at the time of short-circuit failure and the power supply voltage at the time of normal operation is sufficiently wide,
Even with a fixed threshold value, it is possible to secure a margin of a predetermined value or more from the power supply voltage at the time of a short circuit failure and the power supply voltage at the normal time. However, as described above, since the frequency of large current output is low, even if the diagnostic region is limited to a region where the driving current is relatively small, the reliability of diagnostic control does not significantly decrease.

Therefore, in the second embodiment of the power supply voltage diagnosis shown in the flowchart of FIG. 11, it is possible to set fixed thresholds capable of ensuring a predetermined margin or more from the power supply voltage at the time of short-circuit failure and the power supply voltage at the normal time. By making the diagnosis only in the small drive current region, it is possible to surely diagnose the occurrence of the short-circuit failure while avoiding the erroneous diagnosis of the short-circuit failure.

In the flowchart of FIG. 11, first, S
At 71, the motor power supply voltage VM is read. In S72, the ON / OFF control state of the motor relay 52 is discriminated and turned OFF.
When in the control state, the process proceeds to S73, and it is determined whether or not the read motor power supply voltage VM exceeds a preset first threshold voltage (for example, 2V).

If the motor power supply voltage VM exceeds the first threshold voltage, the motor relay 52 remains in the ON state without being switched to the OFF state despite the OFF control ( It is determined that the relay ON failure) has occurred, the process proceeds to S74, and the subsequent motor command current I
While keeping M ^* at zero, the warning light provided in the vehicle compartment is turned on to warn the driver of the occurrence of relay ON failure (failure of the electric steering device).

On the other hand, when the motor relay 52 is in the ON control state,
In step S75, the motor command current IM ^*After loading
Motor command current read in S76 (diagnosis permission means)
IM ^*Is equal to or less than the predetermined value Io for a predetermined time Δt
It is determined whether (for example, 100 ms) or more is continued. Before
The predetermined value Io is the power supply voltage at the time of short circuit failure and the
It is possible to secure more than a specified margin from the power supply voltage.
To the maximum current value in the drive current area where a fixed threshold can be set.
Corresponding.

Therefore, when the motor command current IM ^* is less than or equal to the predetermined value Io, the impedance Zo
Even if there is a voltage drop due to, the power supply voltage VM can be accurately diagnosed by comparison with a fixed threshold value. On the other hand, when the motor command current IM ^* exceeds the predetermined value Io, the voltage drop due to the impedance Zo is large,
Since it becomes impossible to set a fixed threshold value that can secure a sufficient margin with respect to a change in the motor command current IM ^* , the power supply voltage is not diagnosed in this embodiment. However,
Since the frequency of the large current output exceeding the predetermined value Io is sufficiently low, the reliability of diagnosis is not significantly deteriorated.

The condition is that the predetermined time Δt is continued.
Is the motor command current IM as described above. ^*Driving power for
This is to cope with the response delay of the flow IM. In S76,
Command current IM^*Is below a predetermined value Io at a predetermined time
If it is determined that the period has continued for Δt or more, go to S77.
move on. In S77, the motor command current IM^*Against changes in
The motor power supply voltage VM is higher than the fixed third threshold voltage Vo.
The low state continues for a predetermined time t (for example, 2 seconds) or more
Or not. The third threshold voltage Vo is
Can be set as ignition voltage VB-fixed voltage
preferable.

If the motor power supply voltage VM is lower than the third threshold voltage Vo for a predetermined time t or longer, the process proceeds to S78, and it is determined that the short circuit failure of the drive circuit 26b has occurred. Then, in the next S79, the motor relay
52 is forcibly turned off (energization interruption means),
After that, the motor command current IM ^* is held at zero, and a warning light provided in the vehicle compartment is turned on to warn the driver of the occurrence of a short-circuit failure (a failure of the electric steering device).

The above steps S77 to S79 correspond to the abnormality diagnosing means.

[0057]

As described above, according to the diagnostic device for an electric vehicle steering system according to the invention of claim 1, the threshold value is changed according to the drive current of the actuator to perform the abnormality diagnosis of the power supply voltage. Since the configuration is adopted, the abnormality diagnosis can be performed based on the threshold value corresponding to the drop of the normal voltage due to the increase of the drive current, and the abnormal state can be surely diagnosed without erroneous diagnosis regardless of the change of the drive current.

According to the second aspect of the present invention, there is provided a diagnostic device for an electric vehicle steering system, which detects abnormalities in the power supply voltage based on a threshold value corresponding to a normal voltage drop due to impedance between the actuator power supply and the servo means. It has the effect of being able to diagnose. According to the diagnostic device for a vehicle electric steering device according to the invention of claim 3, there is an effect that the drive current can be accurately detected from the current command value, and the threshold value corresponding to the actual drive current can be set. .

According to the fourth aspect of the present invention, there is provided a diagnostic device for an electric vehicle steering system, wherein when the drive current is below a predetermined value, the actual power supply voltage of the actuator is compared with a predetermined threshold value to determine the power supply voltage. Since the abnormality diagnosis is performed, there is an effect that it is possible to perform the abnormality diagnosis with high precision without changing the threshold value according to the drive current.

According to the diagnostic device for an electric vehicle steering system according to the fifth aspect of the present invention, it is possible to reliably detect the state in which the drive current is equal to or less than a predetermined value from the current command value. According to the diagnostic device for an electric vehicle steering system according to the sixth aspect of the present invention, since the energization to the actuator is cut off when the power supply voltage is abnormal, it is possible to prevent an abnormal steering angle from being given.

[Brief description of drawings]

FIG. 1 is a basic configuration block diagram of a diagnostic device according to a first aspect of the invention.

FIG. 2 is a basic configuration block diagram of a diagnostic device according to a fourth aspect of the invention.

FIG. 3 is a system diagram showing a four-wheel steering vehicle to which the electric steering system according to the embodiment is applied.

FIG. 4 is a sectional view of an electric steering system according to an embodiment.

FIG. 5 is a diagram showing a pinion gear and a ring gear in the embodiment.

FIG. 6 is a block diagram showing an electronic control system of the steering device in the embodiment.

FIG. 7 is a flowchart showing rear wheel steering control in the embodiment.

FIG. 8 is a circuit block diagram showing a motor current supply circuit in the embodiment.

FIG. 9 is a flowchart showing a first embodiment of power supply voltage diagnosis.

FIG. 10 is a diagram showing threshold characteristics in the first embodiment.

FIG. 11 is a flowchart showing a second embodiment of power supply voltage diagnosis.

FIG. 12 is a block diagram showing a conventional power supply voltage abnormality diagnosis system.

[Explanation of symbols]

 9, 10 Rear wheels 11 Electric steering device 12 Rack shaft 12a Rack gear 13, 14 Side rod 15, 16 Knuckle arm 17 Rack tube 18 Reduction mechanism 19 Motor 26 Controller 26a CPU 26b Motor drive circuit 51 Battery 52 Motor relay 53 Ignition switch

Claims (6)

[Claims] 1. An electric steering system for a vehicle comprising servo means for controlling a current supplied to a steering actuator so that an actual steering angle of a wheel coincides with a target steering angle. An abnormality diagnosing means for comparing the power supply voltage with a predetermined threshold to perform abnormality diagnosis of the power supply voltage; and a threshold changing means for changing the predetermined threshold according to a current controlled by the servo means. A diagnostic device for a vehicle electric steering device, comprising: 2. The threshold value changing means changes the threshold value to a lower value in accordance with an increase in a product value of the current and the impedance between the actuator power source and the servo means which is obtained in advance. The diagnostic device for a vehicle electric steering device according to claim 1. 3. The threshold value changing means indirectly detects a current based on a current command value in the servo means, and the abnormality diagnosis means has a power supply voltage of the actuator lower than the predetermined threshold value. 3. The diagnostic device for an electric vehicle steering system according to claim 1, wherein the abnormality determination of the power supply voltage is performed when the state continues for a predetermined time or more. 4. A vehicle electric steering system comprising servo means for controlling a current supplied to a steering actuator so that an actual steering angle of a wheel matches a target steering angle. An abnormality diagnosis means for performing abnormality diagnosis of the power supply voltage by comparing a power supply voltage with a predetermined threshold, and an abnormality diagnosis by the abnormality diagnosis means only when the current controlled by the servo means is a predetermined value or less. A diagnostic device for a vehicle electric steering device, which is configured to include a diagnostic permission unit for permitting. 5. The diagnosis permitting means indirectly detects the current based on the current command value in the servo means, and the current corresponding to the current command value is below a predetermined value for a predetermined time or longer. 5. The diagnostic device for a vehicle electric steering system according to claim 4, wherein the abnormality diagnosis by the abnormality diagnosing means is permitted when continued. 6. An energization interruption means for interrupting energization to the actuator when the abnormality diagnosis means judges an abnormality in the power supply voltage, according to any one of claims 1 to 5. A diagnostic device for an electric steering device for a vehicle as described above.