JP2004196128A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve steering feeling when abnormality occurs in a steering state detection means. <P>SOLUTION: When an abnormality determination part 22 determines occurrence of abnormality of a torque sensor 5 or a signal transmitting system thereof, a limit calculation part 25 executes limit calculation, for example calculation for calculating an absolute minimum value, an intermediate value or an average value, with respect to a steering torque value maintained in a steering torque storage part 23 before occurrence of the abnormality, and thereby an abnormal time steering torque value can be calculated. With the usage of the abnormal time steering torque value, life prolongation control is performed with respect to an electric motor M. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device configured to transmit driving force of an electric motor to a steering mechanism to assist steering.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electric power steering device that assists steering by transmitting a torque generated by an electric motor to a steering mechanism of a vehicle has been used. The drive of the electric motor is controlled based on a target current determined according to a steering torque applied to the steering wheel and a vehicle speed.
When an abnormality (torque sensor system failure) occurs in the torque sensor that detects the steering torque or its signal transmission system, the electric motor cannot be controlled appropriately, and the steering assist is hindered. Therefore, the electronic control unit for controlling the electric motor always performs abnormality detection processing for monitoring the occurrence of a failure in the torque sensor system, and executes fail-safe control when an abnormality is detected. .
[0003]
One of the fail-safe controls is a so-called life extension control. The life extension control is not to stop the steering assist immediately when the torque sensor fails, but to control the steering assist force based on the steering torque value held a predetermined time before the occurrence of the failure (Patent Reference 1). Thus, the steering behavior at the time of occurrence of a failure can be reduced.
[0004]
[Patent Document 1]
JP 2001-122143 A [0005]
[Problems to be solved by the invention]
However, if noise that may occur at the time of failure of the torque sensor system is erroneously held before abnormality detection, steering assistance corresponding to a steering torque value having a large absolute value may be performed at the beginning of life extension control. For example, when the held steering torque value is a value corresponding to the maximum target current value of the electric motor, there is a possibility that steering (so-called self-steering) or steering assist contrary to the driver's intention is performed. There is a possibility that a feeling of strange steering may occur when an abnormality occurs.
[0006]
Therefore, an object of the present invention is to provide an electric power steering device capable of appropriately performing control when an abnormality occurs in a steering state detecting unit, thereby improving a steering feeling when an abnormality occurs. It is to be.
[0007]
Means for Solving the Problems and Effects of the Invention
According to an embodiment of the present invention, there is provided an electric power steering apparatus for transmitting a driving force of an electric motor (M) to a steering mechanism (3) to assist in steering, and detects a steering state. A steering state detecting means (5) for outputting a steering state detection signal; an abnormality determining means (22) for determining whether or not the steering state detecting means is abnormal; and an abnormality determining means for determining whether the steering state detecting means is abnormal. Storage means (23) for storing the steering state detection signal output by the steering state detection means before it is determined that the steering state has occurred; and performing a predetermined limit operation on the steering state detection signal stored in the storage means. An abnormal steering state signal generating means (25) for generating an abnormal steering state signal used when an abnormality occurs, and the abnormality determining means determining that the steering state detecting means has no abnormality. Sets a drive target value for controlling the electric motor based on a steering state detection signal output by the steering state detection means, and determines that the abnormality has occurred in the steering state detection means. A driving target value setting means (21) for setting a driving target value for controlling the electric motor based on the abnormal steering state signal generated by the abnormal steering state signal generating means; An electric power steering device characterized by including:
[0008]
It should be noted that the alphanumeric characters in parentheses indicate corresponding components and the like in embodiments described later. Hereinafter, the same applies in this section.
The steering state detecting means may be a torque sensor that detects a steering torque applied to an operation member (for example, a steering wheel) for steering operation.
Further, it is preferable that the abnormality determination means determines whether there is an abnormality in the steering state detection means itself and whether there is an abnormality in a transmission system of an output signal of the steering state detection means.
[0009]
Further, the storage means may detect the steering state detected by the steering state detection means immediately before the abnormality determination means determines that an abnormality has occurred in the steering state detection means (for example, one or more immediately preceding control cycles). Preferably, it stores signals.
The drive target value setting means is responsive to the abnormality determination means determining that an abnormality has occurred in the steering state detection means, and the abnormal state steering state signal generation means generates the abnormal state steering state signal generation means. It is preferable to include means for changing the drive target value over time so that the absolute value of the drive target value is gradually reduced with the drive target value corresponding to the initial value as the initial value. Thus, when an abnormality occurs, it is possible to perform life extension control for gradually reducing the steering assist force and leading the electric motor to a stop state.
[0010]
According to the first aspect of the present invention, an abnormal-time steering state signal is generated by performing a predetermined limit operation on the steering-state detection signal stored in the storage unit before the occurrence of the abnormality. The drive target value is set based on the state signal. Therefore, when a failure occurs in the steering state detection means or its signal transmission system, noise is generated, and even if this noise is erroneously held in the storage means as the steering state detection signal, excessive steering assist from the electric motor is generated. No force is applied to the steering mechanism, and steering or steering assist contrary to the driver's intention can be avoided. Thereby, the steering feeling at the time of occurrence of an abnormality can be improved.
[0011]
According to a second aspect of the present invention, the storage unit outputs a steering state detection signal output at a plurality of different times by the steering state detection unit before the abnormality determination unit determines that an abnormality has occurred in the steering state detection unit. The abnormal state steering state signal generating means obtains an abnormal state steering state signal by performing a predetermined limit operation on the plurality of steering state detection signals stored in the storage means. The electric power steering apparatus according to claim 1, wherein
[0012]
According to the present invention, the steering state detection signals at a plurality of times before the occurrence of the abnormality are stored in the storage means, and the steering state signal for an abnormal state is obtained by performing a predetermined limit operation on the plurality of steering state detection signals. . This makes it possible to reliably eliminate the influence of noise and the like and determine an appropriate abnormal-state steering state signal.
Specifically, as in the third aspect, the abnormal-state steering state signal generating means includes, as the limit operation, a minimum absolute value of the plurality of steering state detection signals stored in the storage means. It may include absolute value minimum value calculating means (B2, E2) for performing absolute value minimum value calculation to determine the absolute value steering condition signal.
[0013]
Further, as in the fourth aspect, the abnormal-state steering state signal generating means may include, as the limit operation, a signal having an intermediate value among a plurality of steering state detection signals stored in the storage means. It may include an intermediate value calculation means (B2, E2) for performing an intermediate value calculation defined as the abnormal state steering state signal.
Further, as described in claim 5, the abnormal state steering state signal generating means obtains an average value of the plurality of steering state detection signals stored in the storage means as the limit calculation, and calculates the average value. It may include an average value calculating means (B2, E2) for performing an average value calculation defined as the abnormal state steering state signal.
[0014]
According to a sixth aspect of the present invention, the abnormal state steering state signal generating means compares the absolute value of the steering state detection signal stored in the storage means with a predetermined upper limit value as the limit calculation. If the absolute value of the state detection signal is equal to or less than the upper limit, the steering state detection signal is determined as the abnormal state steering state signal. If the absolute value of the steering state detection signal exceeds the upper limit, the upper limit is set. 2. The electric power steering apparatus according to claim 1, further comprising means (C2 to C6) for assigning the same sign as the sign of the steering state detection signal to the value to determine the value as the abnormal state steering state signal.
[0015]
According to the present invention, it is determined whether or not the absolute value of the steering state detection signal stored in the storage means exceeds a predetermined upper limit value. By determining the signal, a so-called life extension control is performed. On the other hand, when the absolute value of the steering state detection signal exceeds the upper limit, the upper limit is given the same sign as that of the steering state detection signal, and the abnormal state steering state signal is obtained. Accordingly, since the absolute value of the abnormal state steering state signal does not exceed the upper limit value, it is possible to prevent undesired steering or steering assist from being performed when an abnormality occurs.
[0016]
According to a seventh aspect of the present invention, the abnormal state steering state signal generating means compares the absolute value of the steering state detection signal stored in the storage means with a predetermined upper limit value as the limit calculation. If the absolute value of the state detection signal is equal to or less than the upper limit, the steering state detection signal is determined as the abnormal state steering state signal.If the absolute value of the steering state detection signal exceeds the upper limit, the steering state is determined. 2. The electric power steering apparatus according to claim 1, further comprising means (D2 to D4) for multiplying the detection signal by 1 / n (where n is a number greater than 1) and determining the detection signal as an abnormal-time steering state signal. is there.
[0017]
According to the present invention, when the absolute value of the steering state detection signal stored in the storage means exceeds the predetermined upper limit, the steering state detection signal for abnormal time is obtained by multiplying the steering state detection signal by 1 / n. . This can prevent undesired steering or steering assist from being performed against the driver's intention when an abnormality occurs.
The invention according to any one of claims 1 to 7, further comprising the step of: when the abnormality determining means determines that the steering state detecting means is abnormal, the abnormal state steering state signal generating means generates the abnormal state steering state signal generating means. A stop control means (24) for stopping the electric motor on condition that the steering direction corresponding to the steering state signal for use does not match the steering direction detected by the steering direction detection means (steering angle sensor 6). You may go out. Accordingly, steering or steering assist in a direction contrary to the driver's intention is not performed, and the steering feeling when an abnormality occurs can be further improved.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a block diagram showing an electric configuration of an electric power steering apparatus according to one embodiment of the present invention. A steering torque applied to a steering wheel 1 as an operation member is mechanically transmitted to a steering mechanism 3 via a steering shaft 2. A steering assist force is transmitted from the electric motor M to the steering mechanism 3.
[0019]
The steering shaft 2 is divided into an input shaft 2A connected to the steering wheel 1 and an output shaft 2B connected to the steering mechanism 3. The input shaft 2A and the output shaft 2B are connected to a torsion bar 4. Are connected to each other. The torsion bar 4 generates a twist in accordance with the steering torque, and the direction and amount of the twist are detected by a torque sensor 5.
[0020]
The torque sensor 5 is, for example, a magnetic sensor that detects a magnetic resistance that changes in accordance with a change in the positional relationship between the input shaft 2A and the output shaft 2B in the rotation direction. The output signal of the torque sensor 5 is input to a controller 10 (ECU: electronic control unit).
The controller 10 further receives input signals from a steering angle sensor 6 for detecting a steering angle of the steering wheel 1 and a vehicle speed sensor 7 for detecting a vehicle speed of a vehicle equipped with the electric power steering device. Has become.
[0021]
The controller 10 determines a target current value of the electric motor M according to the steering torque detected by the torque sensor 5 and the vehicle speed detected by the vehicle speed sensor 7, and applies a steering assist force corresponding to the steering torque to the steering mechanism 3. Drive control of the electric motor M so that
The controller 10 includes a microcomputer 20 and a motor driver 30 that drives the electric motor M based on a control signal from the microcomputer 20.
[0022]
The microcomputer 20 substantially has a plurality of function processing units realized by executing the program processing. Specifically, the microcomputer 20 captures the output of the torque sensor 5 and the target current value setting unit 21 that sets the target current value of the electric motor M based on the outputs of the torque sensor 5 and the vehicle speed sensor 7. An abnormality determining unit 22 that determines whether there is an abnormality in the torque sensor 5 or its signal transmission path, and a plurality of steering torque values output by the torque sensor 5 when the abnormality determining unit 22 determines that there is no abnormality in a time series. A steering torque storage unit 23 (memory) for storing the electric motor M and a stop control unit 24 for stopping the electric motor M by forcibly setting the target current value set by the target current value setting unit 21 to zero. When the abnormality determination unit 22 determines that an abnormality has occurred, the stop control unit 24 determines a steering direction corresponding to the steering torque storage value that is the steering torque value stored in the steering torque storage unit 23 and a steering angle sensor. 6 compares the detected steering direction, and operates so that the target current value is forcibly set to zero on condition that the two steering directions do not match.
[0023]
The microcomputer 20 further includes a limit calculation unit 25. The limit calculation unit 25 stores a plurality of steering torque storage values stored in the steering torque storage unit 23 in chronological order (a plurality of temporally consecutive steering torque detection values immediately before an abnormality of the torque sensor system is detected). Based on the above, a predetermined limit calculation is performed to determine an abnormal-time steering torque value, and the abnormal-time steering torque value is given to the target current value setting unit 21.
[0024]
FIG. 2 is a diagram for explaining the operation of the target current value setting unit 21, and shows a relationship (assist characteristic) between the steering torque and the target current value. As the steering torque, for example, the torque for steering in the right direction has a positive value, and the torque for steering in the left direction has a negative value. The target current value is a positive value when the electric motor M is to generate a steering assist force for rightward steering, and is negative when the electric motor M is to generate a steering assist force for leftward steering. Value.
[0025]
The target current value has a positive value for a positive value of the steering torque, and has a negative value for a negative value of the steering torque. When the steering torque is a small value in the range (dead zone) of -T1 to T1, the target current value is set to zero. The absolute value of the target current value is set to decrease as the vehicle speed detected by the vehicle speed sensor 7 increases. As a result, a large steering assist force can be generated during low-speed running, and the steering assist force can be reduced during high-speed running.
[0026]
FIG. 3 is a flowchart for explaining the contents of processing repeatedly executed by the microcomputer 20 in each predetermined control cycle. The microcomputer 20 captures the steering torque signal output by the torque sensor 5 and the vehicle speed signal output by the vehicle speed sensor 7 (steps S1 and S2), and the abnormality determination unit 22 performs an abnormality determination process based on the detected steering torque. Is executed (step S3). As a result of the abnormality determination processing, if it is determined that there is no abnormality (NO in step S4), the abnormality occurrence flag is turned off (step S5), and the steering torque detection value at that time is stored in the steering torque storage unit 23 ( Step S6), a target current value is set based on the detected steering torque and the vehicle speed taken in steps S1 and S2 (step S7). Thereafter, by controlling the motor driver 30 according to the set target current value, a steering assist force corresponding to the target current value is transmitted from the electric motor M to the steering mechanism 3 (step S8).
[0027]
On the other hand, as a result of the abnormality determination process (step S3), when it is determined that the torque sensor system is abnormal (YES in step S4), it is checked whether the abnormality occurrence flag is on (step S9), and the abnormality is determined. If the occurrence flag is in the OFF state (NO in step S9), a process of calculating an abnormal-time steering torque value serving as a basis for setting the target current value is performed (step S10). Then, the abnormality occurrence flag is switched to the ON state (step S11), and a target current value is set in accordance with the characteristics of FIG. 2 based on the abnormality-time steering torque value obtained in step S10 (step S7). The drive control of the electric motor M is executed based on the set target current value (step S8).
[0028]
When it is determined in step S9 that the abnormality occurrence flag is in the ON state, that is, when the abnormality state continues from the previous control cycle, the gain for determining the target current value based on the abnormality-time steering torque value Is reduced by, for example, a fixed value (step S12). Accordingly, the target current value setting unit 21 obtains the target current value by multiplying the abnormal steering torque value by the reduced gain, and applying the multiplied value to the assist characteristic shown in FIG. Therefore, when the abnormal state of the torque sensor system continues, the gain decreases in each control cycle, and the target current value is led to zero. In this way, when an abnormality occurs in the torque sensor system, the life extension control is performed in which the absolute value of the target current value is gradually reduced to zero and the electric motor M is stopped.
[0029]
FIG. 4 is a flowchart for explaining the content of the abnormal-time steering torque value calculation processing. The limit calculation unit 25 reads a plurality of steering torque detection values (for example, 5 milliseconds before, 10 milliseconds before, and 15 milliseconds before) immediately before the abnormality determination unit 22 determines that there is an abnormality from the steering torque storage unit 23. The stored steering torque value corresponding to the detected steering torque value is read (step B1). Then, the limit calculating unit 25 calculates an absolute minimum value calculation for finding the absolute value of the plurality of read steering torque storage values having the smallest absolute value, and an intermediate value among the read steering torque storage values. Either an intermediate value calculation process for obtaining a stored steering torque value having a value or an average value calculation process for obtaining an average value of a plurality of read steering torque storage values is executed as a limit calculation (step B2). The calculated value obtained by such a limiting calculation is set as an abnormal-time steering torque value (step B3), and the target current value setting unit 21 sets the steering torque value (the initial value of the life extension control) when the target current value is set. Value).
[0030]
In this way, instead of using the steering torque stored value stored in the steering torque storage unit 23 as it is, the value subjected to the limit calculation is used as the abnormal-time steering torque value. Even if an abnormal value such as noise due to the abnormality is stored in the steering torque storage unit 23, an excessive value that causes self-steering may be set as the abnormal-time steering torque value, Thus, the steering assist that largely deviates from the intention of the vehicle is not performed, and therefore, the steering feeling when an abnormality occurs can be improved.
[0031]
FIG. 5 is a flowchart for explaining another example of the abnormal-time steering torque value calculation processing. First, a steering torque storage value corresponding to a detected steering torque value immediately before the abnormality determination unit 22 determines that an abnormality has occurred in the torque sensor system is read from the steering torque storage unit 23 (step C1). Next, the absolute value of the steering torque storage value read from the steering torque storage unit 23 is compared with a predetermined upper limit (> 0) by the operation of the limit calculation unit 25 (step C2). If the absolute value of the read steering torque storage value is equal to or less than the upper limit value (NO in step C2), the steering torque storage value is set as the abnormal-time steering torque value (step C3).
[0032]
If the absolute value of the stored steering torque value exceeds the upper limit value (YES in step C2), the sign of the stored steering torque value is further checked (step C4). If the stored steering torque value has a positive sign, the upper limit value having a positive value is set as the abnormal-time steering torque value (step C5). On the other hand, if the sign of the stored steering torque value is negative (NO in step C4), a value with a negative sign with respect to the upper limit is set as the abnormal-time steering torque value (step C6). .
[0033]
As described above, when an abnormality occurs in the torque sensor system, the life extension control is performed using the steering torque storage value stored in the steering torque storage unit 23 as an abnormal-time steering torque value within a range not exceeding a predetermined upper limit value. On the other hand, when the stored steering torque value exceeds the upper limit value, the absolute value of the abnormal-time steering torque value is limited to the upper limit value in order to avoid self-steering and undesired steering assistance. . As a result, the influence of noise or the like due to the failure of the torque sensor system can be eliminated, and the steering feeling when an abnormality occurs can be improved.
[0034]
FIG. 6 is a flowchart illustrating another example of the abnormal-time steering torque value calculation processing. The limit calculation unit 25 reads a steering torque storage value corresponding to a steering torque detection value immediately before the abnormality determination unit 22 detects an abnormality of the torque sensor system from the steering torque storage unit 23 (Step D1). The absolute value of the read steering torque storage value is compared with a predetermined upper limit (step D2). If the absolute value of the steering torque storage value is equal to or less than the upper limit (NO in step D2), the read steering torque storage value is set as the abnormal-time steering torque value (step D3).
[0035]
On the other hand, when the absolute value of the steering torque storage value exceeds the upper limit, the steering torque storage value is multiplied by 1 / n (n is a number greater than 1), and the value is used as the abnormal-time steering torque value. It is set (step D4).
In this way, when the absolute value of the steering torque storage value exceeds the upper limit, the value is multiplied by 1 / n to limit the abnormal-time steering torque value. Due to the noise caused, self-steering does not occur in the early stage of life extension control and excessive steering assistance is not provided, and the steering feeling can be improved.
[0036]
FIG. 7 is a flowchart for explaining still another example of the abnormal-time steering torque value calculation processing. In this example, one or a plurality of steering torque storage values (corresponding to a steering torque detection value immediately before abnormality detection) are read from the steering torque storage unit 23 by the limit calculation unit 25 (step E1), and the readout is performed. Limit calculation processing is performed on the output steering torque storage value (step E2). This limit calculation process may be any of the minimum absolute value calculation, the intermediate value calculation, and the average value calculation, may be the process shown in FIG. 5, or may be the process shown in FIG. It may be.
[0037]
Next, the stop control unit 24 determines whether the steering direction detected by the steering angle sensor 6 matches the steering assist direction (assist direction) based on the abnormal-state steering torque value after the limit calculation processing ( Step E3). If these directions match (YES in step E3), the calculated value obtained by the above-described limit value calculation process is set as the abnormal-time steering torque value (step E4). On the other hand, when the steering direction does not match the steering assist direction (NO in step E3), the abnormal-time steering torque value is forcibly set to zero (step E5).
[0038]
In this way, the limit calculation is performed on the stored steering torque value, and when the steering direction does not match the steering assist direction corresponding to the calculated value of the limit calculation, the electric motor M is immediately stopped. Therefore, undesired steering or steering assist when an abnormality occurs in the torque sensor system can be reliably avoided.
The embodiments of the present invention have been described above, but the present invention can be embodied in other forms. For example, the stop control unit 24 may perform a process of setting the target current value set by the target current value setting unit 21 to zero instead of setting the abnormal-time steering torque value to zero. Further, a voltage value may be used instead of the current value as the drive target value. In addition, various design changes can be made within the scope of the matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electric configuration of an electric power steering device according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining an operation of a target current value setting unit, and shows a relationship (assist characteristic) of a target current value with respect to a steering torque.
FIG. 3 is a flowchart for explaining the contents of processing repeatedly executed by the microcomputer for each control cycle.
FIG. 4 is a flowchart illustrating an example of an abnormal-time steering torque value calculation process.
FIG. 5 is a flowchart for explaining another example of the abnormal-time steering torque value calculation processing.
FIG. 6 is a flowchart illustrating another example of an abnormal-time steering torque value calculation process.
FIG. 7 is a flowchart for explaining still another example of the abnormal-time steering torque value calculation processing.
[Explanation of symbols]
Reference Signs List 1 steering wheel 2 steering shaft 3 steering mechanism 4 torsion bar 5 torque sensor 6 steering angle sensor 7 vehicle speed sensor 10 controller 20 microcomputer 21 target current value setting unit 22 abnormality determination unit 23 steering torque storage unit 24 stop control unit 25 limit calculation unit 30 Motor driver M Electric motor

Claims (7)

An electric power steering device that transmits a driving force of an electric motor to a steering mechanism to assist in steering,
Steering state detection means for detecting a steering state and outputting a steering state detection signal;
Abnormality determining means for determining the presence or absence of an abnormality in the steering state detecting means;
Storage means for storing a steering state detection signal output by the steering state detection means before the abnormality determination means determines that an abnormality has occurred in the steering state detection means;
An abnormal steering state signal generating means for performing a predetermined limit operation on the steering state detection signal stored in the storage means to generate an abnormal steering state signal used when an abnormality occurs;
When the abnormality determination means determines that no abnormality has occurred in the steering state detection means, a drive target value for controlling the electric motor is determined based on a steering state detection signal output by the steering state detection means. When the abnormality determination means determines that an abnormality has occurred in the steering state detection means, the electric power is controlled based on the abnormality-time steering state signal generated by the abnormality-time steering state signal generation means. A drive target value setting unit for setting a drive target value for controlling the motor. The storage means stores a steering state detection signal output at a plurality of different times by the steering state detection means before the abnormality determination means determines that an abnormality has occurred in the steering state detection means,
The abnormal state steering state signal generating means performs a predetermined limit operation on the plurality of steering state detection signals stored in the storage means to obtain an abnormal state steering state signal. The electric power steering apparatus according to claim 1, wherein The abnormal state steering state signal generating means includes, as the limit operation, an absolute value minimum value which determines, as the abnormal state steering state signal, a signal having a minimum absolute value among the plurality of steering state detection signals stored in the storage means. 3. The electric power steering apparatus according to claim 2, further comprising absolute value minimum value calculation means for performing a value calculation. The abnormal state steering state signal generating means includes an intermediate value calculation for determining, as the limit operation, a signal having an intermediate value among the plurality of steering state detection signals stored in the storage means as the abnormal state steering state signal. 3. The electric power steering apparatus according to claim 2, further comprising an intermediate value calculating means for performing the following. The abnormal state steering state signal generating means calculates an average value of the plurality of steering state detection signals stored in the storage means as the limit calculation, and determines the average value as the abnormal state steering state signal. 3. The electric power steering apparatus according to claim 2, further comprising an average value calculating means for performing a calculation. The abnormal state steering state signal generating means compares the absolute value of the steering state detection signal stored in the storage means with a predetermined upper limit value as the limit calculation, and determines that the absolute value of the steering state detection signal is If it is equal to or less than the upper limit value, the steering state detection signal is determined as the abnormal state steering state signal, and if the absolute value of the steering state detection signal exceeds the upper limit value, the steering state detection signal is set to the upper limit value. 2. The electric power steering apparatus according to claim 1, further comprising means for assigning the same reference numerals as the reference signs and determining the same as an abnormal state steering state signal. The abnormal state steering state signal generating means compares the absolute value of the steering state detection signal stored in the storage means with a predetermined upper limit value as the limit calculation, and determines that the absolute value of the steering state detection signal is If the steering condition detection signal is less than or equal to the upper limit, the steering condition detection signal is determined as an abnormal condition steering condition signal. If the absolute value of the steering condition detection signal exceeds the upper limit, the steering condition detection signal is multiplied by 1 / n ( 2. The electric power steering apparatus according to claim 1, further comprising means for determining an abnormal state steering state signal by n being a number greater than 1.

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