JP2004210065A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device reducing the motor current not abruptly but gradually when a torque sensor detects abnormality to stop the motor current without giving an uncomfortable feeling to a driver. <P>SOLUTION: The electric power steering device drives an electric motor 5 based on a steering torque signal detected by a torque sensor 1 to supplement the steering force with the driving force of the electric motor 5. The electric power steering device has a detection means 7 for determining whether a detected steering torque signal is abnormal or not, and a filter means 9 for wave filtering of the steering torque signal. When the detection means 7 detects the abnormality of the steering torque signal, the electric power steering device stops the torque sensor 1 and drives the electric motor 5 based on the steering torque signal wave-filtered by the filter means 9, which gradually decreases due to the stop of the torque sensor 1. It is thereby possible to achieve the electric power steering device that reduces the motor current not abruptly but gradually when the torque sensor detects abnormality so as to stop the motor current without giving an uncomfortable feeling to a driver. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device that drives an electric motor based on a steering torque signal detected by a torque sensor and assists a steering force with a driving force of the electric motor.
[0002]
[Prior art]
In a conventional electric power steering device using an electric motor, a steering torque signal detected by a torque sensor is monitored, and when the steering torque signal exceeds a predetermined threshold as shown in FIG. Then, it is determined that the torque sensor is abnormal.
Therefore, when it is determined that the torque sensor is abnormal during steering, the steering torque signal has an abnormal value exceeding the threshold value, and to prevent the steering from rotating or locking, FIG. As shown in (b), the motor current is suddenly cut off.
As a result, the steering becomes suddenly heavy, and the driver feels uneasy or confused.
[0003]
[Patent Document 1]
Japanese Patent Publication No. 6-9973
[Problems to be solved by the invention]
In order to solve such a problem, even if a torque sensor abnormality occurs, the motor current is not cut off suddenly, but is gradually reduced, so that the driver does not feel uncomfortable. Should be stopped. However, the motor current is determined based on the value of the steering torque signal, and since the steering torque signal has an abnormal value, the motor current cannot be gradually reduced from the steering torque signal. There is a problem.
As a technique related to such a problem, Patent Document 1 discloses that when the deviation between the first and second displacements of the torque sensor and the electric signal becomes equal to or greater than a predetermined value, the control unit determines that the torque sensor is abnormal, and A "motor-driven power steering control device" for interrupting the current of the electromagnetic clutch and the voltage applied to the electromagnetic clutch is disclosed.
[0005]
The present invention has been made in view of the circumstances described above, and even when a torque sensor becomes abnormal, it is possible to gradually reduce the motor current without suddenly shutting off the motor current. It is an object of the present invention to provide an electric power steering device capable of stopping a motor current without causing a user to feel uncomfortable.
[0006]
[Means for Solving the Problems]
An electric power steering apparatus according to a first aspect of the present invention is an electric power steering apparatus that drives an electric motor based on a steering torque signal detected by a torque sensor and assists a steering force with a driving force of the electric motor. A determining unit that determines whether the detected steering torque signal is abnormal; anda filter unit that filters the steering torque signal.When the determining unit determines that the steering torque signal is abnormal, The torque sensor is stopped, and the electric motor is driven based on a steering torque signal filtered by the filter means, which gradually decreases when the torque sensor stops.
[0007]
An electric power steering device according to a second aspect of the present invention is an electric power steering device that drives an electric motor based on a steering torque signal detected by a torque sensor and assists a steering force with a driving force of the electric motor. Determining means for determining whether the detected steering torque signal is abnormal; filter means for filtering the steering torque signal; and the determining means, when determining that the steering torque signal is abnormal, Signal output means for outputting a signal that gradually reduces the steering torque signal filtered by the filter means as an initial value, and when the steering torque signal is abnormal, the electric motor is controlled based on the signal output by the signal output means. Is driven.
[0008]
In the first invention and the second invention, even when the torque sensor becomes abnormal, the motor current can be gradually reduced without suddenly shutting off the motor current, and the driver feels uncomfortable. Thus, an electric power steering device that can stop the motor current can be realized.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described with reference to the drawings showing the embodiments.
Embodiment 1 FIG.
FIG. 1 is a block diagram showing a main configuration of an electric power steering apparatus according to a first embodiment of the present invention. In this electric power steering device, a steering torque signal detected by a torque sensor 1 is given to a target motor current deriving unit 2, and the target motor current deriving unit 2 determines a relationship between a predetermined steering torque and a target motor current, Based on the given steering torque signal and a given steering torque signal, a target motor current is derived and given to the motor current controller 3.
[0010]
The motor current control unit 3 controls the driving of the motor drive circuit 4 based on the motor current of the electric motor 5 detected by the motor current detector 6 and the target motor current. The motor drive circuit 4 drives the electric motor 5 by supplying a current to the electric motor 5 according to the drive control of the motor current control unit 3. By driving the electric motor 5, a steering assist force is applied to a steering mechanism (not shown).
[0011]
On the other hand, the steering torque signal detected by the torque sensor 1 is also provided to the abnormality determination unit 7 (determination unit) and the filter 9 (filter unit).
The filter 9 has such a time constant that the filtered steering torque signal does not change significantly during the abnormality determination time from when the steering torque signal becomes abnormal to when the torque sensor is determined to be abnormal. In addition, the means for filtering the filter 9 is not limited to a normal filter, but may be a means for limiting the rate of change of the steering torque signal.
The abnormality determination unit 7 determines that the torque sensor 1 is abnormal when the applied torque signal exceeds a threshold for abnormality determination, or when the torque signal exceeds a threshold for abnormality determination a predetermined number of times within a predetermined time. Is notified to the abnormality determination processing unit 8 and the detection operation of the torque sensor 1 is stopped.
[0012]
When the abnormality determination unit 7 is notified from the abnormality determination unit 7 that the torque sensor 1 is abnormal, the abnormality determination processing unit 8 starts giving the steering torque signal filtered by the filter 9 to the target motor current deriving unit 2. The target motor current deriving unit 2 derives a target motor current based on a predetermined relationship between the steering torque and the target motor current and a steering torque signal filtered by the filter 9 and supplies the target motor current to the motor current control unit 3.
The above-described motor current derivation unit 2, motor current control unit 3, abnormality determination unit 7, and abnormality determination processing unit 8 are realized by software using a microcomputer 10, for example. Further, the filter 9 may be realized by software using the microcomputer 10.
[0013]
Hereinafter, the operation of deriving the target motor current of the electric power steering apparatus having such a configuration will be described with reference to the flowchart of FIG.
When deriving the target motor current, the electric power steering device first determines whether or not the torque sensor 1 is stopped (S2). If not, the electric power steering device outputs a steering torque signal detected by the torque sensor. Read (S4).
Next, in the electric power steering device, the abnormality determination unit 7 determines whether the read steering torque signal is abnormal (S6), and if not, determines that the torque sensor 1 is normal. Then, the target motor current deriving unit 2 derives a target motor current based on the steering torque signal (S16), gives the derived target motor current to the motor current control unit 3 (S14), and returns.
[0014]
In this electric power steering device, when the abnormality determination unit 7 determines that the steering torque signal is abnormal (S6), the torque sensor 1 determines that the torque sensor 1 is abnormal and stops the torque sensor 1 (S8). . Next, the abnormality determination processing unit 8 reads the filter signal, which is the steering torque signal filtered by the filter 9, and provides the filter signal to the target motor current deriving unit 2 (S10).
It is needless to say that when the torque sensor 1 stops, the steering torque signal filtered by the filter 9 gradually decreases in accordance with the time constant.
[0015]
The target motor current deriving unit 2 derives a target motor current based on the provided filter signal (S12), provides the derived target motor current to the motor current control unit 3 (S14), and returns.
At this time, since the detection operation of the torque sensor 1 is stopped (S8), the steering torque signal (filter signal) filtered by the filter 9 is changed according to the time constant of the filter 9 as shown in FIG. Accordingly, the target motor current correspondingly gradually decreases as shown in FIG. 3B.
In this electric power steering apparatus, when the torque sensor 1 is stopped (S2), the abnormality determination processing unit 8 reads a filter signal, which is a steering torque signal filtered by the filter 9, and gives the filter signal to the target motor current deriving unit 2. (S10).
[0016]
Embodiment 2 FIG.
The configuration of the main part of the electric power steering apparatus according to the second embodiment of the present invention is the same as the block diagram showing the main part configuration of the first embodiment shown in FIG. However, when the abnormality determination unit 7 is notified from the abnormality determination unit 7 that the torque sensor 1 is abnormal, the abnormality determination processing unit 8 (the signal output unit) outputs the steering torque signal (filter signal) filtered by the filter 9 at that time. A signal that gradually decreases as an initial value is created and output, and is given to the target motor current deriving unit 2. The target motor current deriving unit 2 determines the target motor current based on the relationship between the predetermined steering torque and the target motor current and the gradually decreasing signal output by the abnormality determination processing unit 8, and considers the gradually decreasing signal as the steering torque signal. The motor current is derived and given to the motor current controller 3. The other configuration is the same as that of the first embodiment, and the description is omitted.
[0017]
Hereinafter, the operation of deriving the target motor current of the electric power steering device having such a configuration will be described with reference to the flowchart of FIG.
When deriving the target motor current, the electric power steering device first determines whether or not the torque sensor 1 is stopped (S20), and if not stopped, outputs the steering torque signal detected by the torque sensor. Read (S22).
Next, in the electric power steering device, the abnormality determination unit 7 determines whether the read steering torque signal is abnormal (S24), and if not, determines that the torque sensor 1 is normal. Then, the target motor current deriving unit 2 derives a target motor current based on the steering torque signal (S36), gives the derived target motor current to the motor current control unit 3 (S34), and returns.
[0018]
In this electric power steering device, when the abnormality determination unit 7 determines that the steering torque signal is abnormal (S24), the torque sensor 1 determines that the torque sensor 1 is abnormal and stops the torque sensor 1 (S26). . Next, the abnormality determination processing unit 8 reads a filter signal, which is a steering torque signal filtered by the filter 9 (S28), and creates and outputs a signal that gradually decreases using the read filter signal as an initial value (S30).
It is needless to say that when the torque sensor 1 stops, the steering torque signal filtered by the filter 9 gradually decreases in accordance with the time constant.
[0019]
The target motor current deriving unit 2 derives a target motor current based on the gradually decreasing signal output from the abnormality determination processing unit 8 (S32), gives the derived target motor current to the motor current control unit 3 (S34), and returns. .
At this time, the gradually decreasing signal output by the abnormality determination processing unit 8 gradually decreases similarly to the steering torque signal (filter signal) filtered by the filter 9 shown in FIG. 3A, and the target motor current also changes accordingly. Thus, as in the case of FIG.
In the electric power steering device, when the torque sensor 1 is stopped (S20), the abnormality determination processing unit 8 creates and outputs a signal that gradually decreases with the filter signal as an initial value (S30). The target motor current deriving unit 2 derives a target motor current based on the gradually decreasing signal output from the abnormality determination processing unit 8 (S32).
[0020]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the electric power steering apparatus which concerns on this invention, even if a torque sensor becomes abnormal, it can reduce a motor current gradually, without suddenly interrupting a motor current, and makes a driver feel uncomfortable. Thus, an electric power steering device that can stop the motor current can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a main configuration of an electric power steering apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing an example of the operation of the electric power steering device according to the present invention.
FIG. 3 is a graph for explaining the operation of the electric power steering device according to the present invention.
FIG. 4 is a flowchart showing an example of the operation of the electric power steering device according to the present invention.
FIG. 5 is a graph for explaining the operation of a conventional electric power steering device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Torque sensor 2 Target motor current derivation part 3 Motor current control part 4 Motor drive circuit 5 Electric motor 6 Motor current detector 7 Abnormality judgment part (judgment means)
8 Abnormality judgment processing unit (signal output means)
9 Filter (filter means)
10. Microcomputer

Claims (2)

An electric power steering apparatus that drives an electric motor based on a steering torque signal detected by a torque sensor and assists the steering force with the driving force of the electric motor.
A determining unit that determines whether the detected steering torque signal is abnormal; anda filter unit that filters the steering torque signal.When the determining unit determines that the steering torque signal is abnormal, An electric power steering apparatus for driving the electric motor based on a steering torque signal filtered by the filter means, the torque sensor being stopped, and gradually decreasing when the torque sensor is stopped. . An electric power steering apparatus that drives an electric motor based on a steering torque signal detected by a torque sensor and assists the steering force with the driving force of the electric motor.
Determining means for determining whether the detected steering torque signal is abnormal; filter means for filtering the steering torque signal; and the determining means, when determining that the steering torque signal is abnormal, Signal output means for outputting a signal that gradually reduces the steering torque signal filtered by the filter means as an initial value, wherein when the steering torque signal is abnormal, the electric motor An electric power steering device characterized in that the electric power steering device is driven.

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