JP4089394B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor in accordance with an operation for steering the vehicle.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an electric power steering apparatus that applies a steering assist force to a steering mechanism by driving an electric motor in accordance with a steering torque applied to a steering wheel (steering wheel) by a driver has been used. In this electric power steering apparatus, a torque sensor for detecting a steering torque applied to the steering wheel is provided, and a target value of a current to be supplied to the electric motor is set based on the steering torque detected by the torque sensor. Based on the deviation between this target value and the current value that actually flows through the electric motor, a voltage command value to be given to the drive means of the electric motor is generated. The driving means of the electric motor includes, for example, a PWM signal generation circuit that generates a pulse width modulation signal (PWM signal) with a duty ratio corresponding to the voltage command value, and power that is turned on / off according to the duty ratio of the PWM signal It comprises a motor drive circuit configured using transistors, and a voltage corresponding to the duty ratio, that is, a voltage corresponding to a voltage command value is applied to the electric motor. A current flowing through the electric motor by this voltage application is detected by a current detector, and a difference between the detected value and the current target value is used as a deviation for generating the voltage command value. In the electric power steering apparatus, feedback control is performed in this manner so that a current having a target value set based on the steering torque flows to the electric motor. Then, the direction of the steered wheels is changed by an output torque that is a sum of torque (referred to as “assist torque”) as steering assist force generated by the electric motor and steering torque applied to the steering wheel.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-43058
[Patent Document 2]
Japanese Patent Laid-Open No. 10-147247
[Patent Document 3]
JP-A-6-171541
[0004]
[Problems to be solved by the invention]
By the way, in a vehicle equipped with a hydraulic power steering device, information on the road surface state (hereinafter referred to as “road surface information”) is transmitted to the driver by kickback or the like caused by road surface unevenness or the like. However, in a vehicle equipped with an electric power steering device, an electric motor is interposed between a tire as a steered wheel and a handle as an operation means for steering as described above. Road surface information is difficult to be transmitted to the driver due to inertia or the like. This is because even when there is an abnormality in the traveling device including the tire, such as when the tire as the steered wheel is unbalanced or the tire air pressure is reduced, information indicating the abnormality is difficult to be transmitted to the driver. Means that. Therefore, even if there is an abnormality in a traveling device such as a tire, the driver may not be able to recognize the abnormality.
[0005]
Therefore, an object of the present invention is to provide an electric power steering device that allows a driver to reliably recognize an abnormality in a traveling device including a tire as a steered wheel.
[0006]
[Means for Solving the Problems and Effects of the Invention]
  A first invention is an electric power steering device that applies a steering assist force to a steering mechanism of a vehicle by driving an electric motor in accordance with an operation by an operation means for steering the vehicle,
  Torque detecting means for detecting steering torque applied to the operating means and outputting a steering torque signal indicating the steering torque;
  An abnormality detecting means for detecting an abnormality in the traveling device including the steered wheels of the vehicle based on a specific frequency component included in the steering torque signal;
  Notification means for issuing a warning when an abnormality is detected by the abnormality detection means,
  The abnormality detection means includes
    Frequency calculating means for detecting a peak in the steering torque signal and calculating a frequency of the steering torque signal based on a time interval between the detected peaks;
    Determining means for determining the presence or absence of the abnormality according to whether or not the calculated frequency is in a frequency range corresponding to the specific frequency component;
It is characterized by including.
[0007]
  According to the first aspect of the present invention, when there is an abnormality in the traveling device including the steered wheels of the vehicle, the unsprung resonance that is difficult to be transmitted to the steering wheel (operation means for steering) in the conventional electric power steering device. The vibration caused by such an abnormality is detected based on the specific frequency component in the steering torque signal, and a warning is issued by the notification means. As a result, the driver can reliably recognize the abnormality.Further, when vibration such as unsprung resonance occurs due to an abnormality of the traveling device including the steered wheels, the presence / absence of the abnormality is determined from the frequency calculated based on the time interval between peaks in the steering torque signal. For this reason, since the processing load for detecting an abnormality is relatively light, the abnormality detecting means can be realized at low cost by software processing in a general-purpose microprocessor without using dedicated hardware.
[0008]
According to a second invention, in the first invention,
An abnormality control unit is further provided for reducing the steering assist force when an abnormality is detected by the abnormality detection unit.
[0009]
According to the second aspect of the invention, when an abnormality occurs in the traveling device including the steered wheels, the steering assist force is reduced, so that the occurrence of unstable behavior of the vehicle due to the abnormality is suppressed. The
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
<1. Overall configuration>
FIG. 1 is a schematic diagram showing a configuration of an electric power steering apparatus according to an embodiment of the present invention, together with a vehicle configuration related thereto. This electric power steering apparatus includes a steering shaft 102 having one end fixed to a handle (steering wheel) 100 as an operation means for steering, a rack and pinion mechanism 104 connected to the other end of the steering shaft 102, a handle A torque sensor 3 for detecting a steering torque applied to the steering shaft 102 by an operation of 100, an electric motor 6 for generating a steering assist force for reducing a driver's load in the steering operation, and the steering assist force as a steering shaft. An electronic control unit (ECU) that receives power supply from the in-vehicle battery 8 via the ignition switch 9 and controls driving of the motor 6 based on sensor signals from the torque sensor 3 and the vehicle speed sensor 4. ) 5. When the driver operates the steering wheel 100 in a vehicle equipped with such an electric power steering device, the steering torque by the operation is detected by the torque sensor 3, and the detected steering torque and the vehicle speed detected by the vehicle speed sensor 4 are detected. Based on the above, the motor 6 is driven by the ECU 5. As a result, the motor 6 generates a steering assist force, and this steering assist force is applied to the steering shaft 102 via the reduction gear 7, thereby reducing the driver's load in the steering operation. That is, the sum of the steering torque applied by the steering operation and the torque due to the steering assist force generated by the motor 6 is given to the rack and pinion mechanism 104 via the steering shaft 102 as the output torque. Thus, when the pinion shaft rotates, the rotation is converted into a reciprocating motion of the rack shaft by the rack and pinion mechanism 104. Both ends of the rack shaft are connected to a wheel 108 via a connecting member 106 composed of a tie rod and a knuckle arm, and the direction of the wheel 108 changes according to the reciprocating motion of the rack shaft.
[0014]
In addition, the electric power steering apparatus according to the present embodiment includes a warning unit 50 as notification means for notifying the driver of an abnormality when the traveling apparatus including the tire 108 as a steered wheel has an abnormality. The warning unit 50 receives a warning signal Sa generated by the ECU 5 as described later. The warning unit 50 is configured by using a lamp, a sound generation device, and / or a display device, and when an input warning signal Sa becomes active, the driver is notified of an abnormality by lighting the lamp, sound, and / or display. To announce.
[0015]
<2. Configuration of control device>
FIG. 2 is a block diagram showing a hardware configuration of the ECU 5 in the electric power steering apparatus. The ECU 5 includes a microcomputer (hereinafter referred to as “microcomputer”) 10, a PWM signal generation circuit 32, a motor drive circuit 34, and a current detector 36, and the microcomputer 10 receives a steering torque signal from the torque sensor 3. Ts is input from the vehicle speed sensor 4 to the vehicle speed signal Vs. In the ECU 5, the current detector 36 detects a current supplied to the motor 6, that is, a motor current, and outputs the detection result as a current detection value Im. This detected current value Im is also input to the microcomputer 10. The microcomputer 10 functions as a motor control unit by executing a program stored in its internal memory. That is, based on the steering torque signal Ts, the vehicle speed signal Vs, and the current detection value Im, a voltage that is a value of a voltage to be applied to the motor 6 so that the motor 6 generates an appropriate steering assist force according to the steering torque and the vehicle speed. A command value Vd is calculated. The PWM signal generation circuit 32 generates a PWM signal whose duty ratio changes according to the voltage command value Vd, and supplies the PWM signal to the motor drive circuit 34. The motor drive circuit 34 is configured by using a plurality of power transistors as switching elements, and these switching elements are turned on / off by the PWM signal generated by the PWM signal generation circuit 32. Thereby, the motor drive circuit 34 generates a voltage according to the voltage command value Vd and applies it to the motor 6. Further, in parallel with the motor control operation, the microcomputer 10 detects an abnormality in the traveling device based on the steering torque signal Ts and generates a warning signal Sa indicating the presence or absence of the abnormality.
[0016]
Actually, in addition to the above-described components, the ECU 5 performs signal format conversion, level conversion, and so on as necessary to make a sensor signal or the like to be input to the microcomputer 10 suitable for input to the microcomputer 10. An input interface circuit that performs filter processing and the like, and a signal format and level conversion as necessary to make signals such as the voltage command value Vd and the warning signal Sa output from the microcomputer 10 suitable for the output destination circuit. However, components that are not directly related to the present invention, such as these interface circuits, are omitted in FIG.
[0017]
FIG. 3A is a block diagram showing an example of a functional configuration of the motor control unit (microcomputer) 10 in the ECU 5 (hereinafter referred to as “first configuration example”). The motor control unit 10 includes a target current setting unit 12, a subtractor 14, a control calculation unit 16, and an abnormality detection unit 20. The abnormality detection unit 20 includes a Fourier transform unit (hereinafter referred to as "FFT unit"). 21) and a determination unit 22. These components in the motor control unit 10 are realized by software by the microcomputer 10 executing a predetermined program.
[0018]
In the motor control unit 10, the steering torque signal Ts output from the torque sensor 3 is input to the target current setting unit 12 and the FFT unit 21, and the vehicle speed signal Vs output from the vehicle speed sensor 4 is input to the target current setting unit 12. Is done.
[0019]
Based on the steering torque signal Ts and the vehicle speed signal Vs, the target current setting unit 12 determines a current target value It that is a current value to be supplied to the motor 6 in order to generate an appropriate steering assist force.
[0020]
The electric motor 6 is driven by the drive control means comprising the subtractor 14, the control calculation unit 16, the PWM signal generation circuit 32, the motor drive circuit 34, and the current detector 36 based on the current target value It as follows. Be controlled.
[0021]
That is, the subtractor 14 calculates a deviation ΔI = It−Im between the current target value It output from the target current setting unit 12 and the current detection value Im output as the actual motor current value from the current detector 36. To do. This deviation ΔI is input to the control calculation unit 16. The control calculation unit 16 calculates the voltage command value Vd by a control calculation (usually a proportional integration calculation) based on the deviation ΔI. This voltage command value Vd is output from the microcomputer 10 as a motor control unit. The voltage command value Vd output from the microcomputer 10 is input to the PWM signal generation circuit 32, where a PWM signal having a duty ratio corresponding to the voltage command value Vd is generated. Then, the switching element in the motor drive circuit 34 is turned on / off by the PWM signal, so that a voltage corresponding to the voltage command value Vd is generated, and this voltage is applied to the motor 6. By applying this voltage, a current flows through the motor 6, and the motor 6 generates a torque corresponding to this current. The motor current at this time is detected by the current detector 36, and the current detection value Im which is the detection result is used to calculate the deviation ΔI = It−Im. In this way, feedback control is performed so that a current equal to the current target value It calculated by the motor control unit (microcomputer) 10 flows through the motor 6.
[0022]
On the other hand, the abnormality detection unit 20 including the FFT unit 21 and the determination unit 22 operates in parallel with the control operation for driving the electric motor 6 and includes a tire 108 as a steered wheel based on the steering torque signal Ts. An abnormality in the traveling device is detected, and a warning signal Sa indicating the detection result is output. That is, the FFT unit 21 calculates data indicating a frequency spectrum (hereinafter referred to as “spectrum data”) by performing a Fourier transform on the steering torque signal Ts, and the determination unit 22 performs an abnormality based on the spectrum data. The determination result is output as a warning signal Sa. The warning signal Sa is input to the warning unit 50 as described above.
[0023]
FIG. 3B is a block diagram showing another example of the functional configuration of the motor control unit (microcomputer) 10 in the ECU 5 (hereinafter referred to as “second configuration example”). The motor control unit 10 according to the second configuration example also includes a target current setting unit 12, a subtractor 14, a control calculation unit 16, an FFT unit 21, and a determination unit 22b having the same functions as those of the first configuration example. However, in the second configuration example, the multiplier 13 is interposed between the target current setting unit 12 and the subtractor 14, and the determination unit 22b determines whether the warning is in accordance with the determination result regarding the presence or absence of abnormality. A gain K is output in addition to the signal Sa. This gain K is input to the multiplier 13 together with the current target value It1 output from the target current setting unit 12 (hereinafter referred to as “current target basic value” in order to distinguish it from the current target value in the first configuration example). Is done. The multiplier 13 multiplies the current target basic value It1 and the gain K, and outputs K × It1 that is a result of the multiplication. The multiplication value K × It1 is input to the subtractor 14 as a current target value It2 for feedback control. Other operations of the motor control unit 10 according to the second configuration example are the same as those of the first configuration example, and thus the description thereof is omitted.
[0024]
In the second configuration example, the determination unit 22b outputs “1” as the gain K when no abnormality is detected, and outputs a predetermined value Kab smaller than “1” as the gain K when abnormality is detected. Therefore, when an abnormality is detected by the determination unit 22b, the absolute value of the current target value It2 for feedback control is smaller than that in the normal case, and as a result, the steering assist force generated by the motor 6 is reduced. In this way, in the second configuration example, the determination unit 22b and the multiplier 13 function as an abnormality control unit for driving control of the motor 6.
[0025]
<3. Software processing to realize motor control unit>
In the present embodiment, the motor control unit configured as described above causes the microcomputer 10 to execute a predetermined program, that is, the motor control process shown in FIG. 4A and the abnormality detection process shown in FIG. By executing the above, it is realized as software. Hereinafter, the processes shown in FIGS. 4A and 4B will be described. In the following description, it is assumed that the motor control unit is functionally configured as shown in FIG. 3B (second configuration example).
[0026]
In this embodiment, when the ignition switch 9 is turned on, the motor control process shown in FIG. 4A and the abnormality detection process shown in FIG. 4B are started as independent processes, and the microcomputer 10 in the ECU 5 These processes are executed in parallel. Among these, in the motor control process, the microcomputer 10 operates as follows.
[0027]
First, the steering torque signal Ts is received from the torque sensor 3, and the vehicle speed signal Vs is received from the vehicle speed sensor 4 (steps S12 and S14). Hereinafter, the value of the steering torque signal Ts received at this time is referred to as a steering torque detection value, and the value of the vehicle speed signal Vs received at this time is referred to as a vehicle speed detection value. Subsequently, the microcomputer 10 receives the current detection value Im from the current detector 36 (step S16).
[0028]
Next, a current target basic value It1 is calculated based on the steering torque detection value and the vehicle speed detection value (step S20). Specifically, a table (also referred to as a “map”) showing the relationship between the current target basic value, which is the value of the current to be supplied to the motor 6 to generate an appropriate steering assist force, and the steering torque using the vehicle speed as a parameter. Is previously stored in the memory in the microcomputer 10, and the current target basic value It1 is determined with reference to this table.
[0029]
Next, as described later, the gain K set in the abnormality detection process is multiplied by the current target basic value It1, and the multiplication value K × It1 obtained thereby is set as a current target value It2 for feedback control (step S22). ).
[0030]
When the current target value It2 is calculated as described above, a deviation ΔI = It2-Im between the current target value It2 and the current detection value Im output from the current detector 36 is calculated, and based on this deviation ΔI. The voltage command value Vd is calculated by feedback control calculation (usually proportional integration calculation) (step S24). And this voltage command value Vd is output from the microcomputer 10 as a motor control part (step S26), and it returns to step S12. Thereafter, the above motor control processing (steps S12 to S26) is repeatedly executed until the ignition switch 9 is turned off.
[0031]
The microcomputer 10 executes the abnormality detection process shown in FIG. 4B in parallel with the motor control process shown in FIG. In this abnormality detection process, the microcomputer 10 operates as follows.
[0032]
First, by receiving the steering torque signal Ts from the torque sensor 3 for a predetermined time, time-series data including a predetermined number of detected steering torque values is acquired (step S52). Next, spectrum data indicating the frequency spectrum of the steering torque signal Ts is calculated by performing fast Fourier transform (hereinafter referred to as “FFT”) on the time series data (step S54). Then, the frequency of vibration generated when there is an abnormality in the traveling device such as unbalance of the tire of the vehicle equipped with the electric power steering device according to the present embodiment or a decrease in tire air pressure (usually the frequency of unsprung resonance). ) Spectrum intensity SI of a frequency band set in advance as a band (hereinafter referred to as “determination frequency band”, typically 15 to 20 Hz) is obtained from the spectrum data (step S56).
[0033]
Next, it is determined whether or not the spectrum intensity SI of this determination frequency band is larger than a predetermined threshold value Sth (step S58). As a result of the determination, if the spectrum intensity SI of the determination frequency band is equal to or smaller than the threshold value Sth (when determined “No” in step S58), the warning signal Sa is made inactive because there is no abnormality (step S58). S60), “1” is set as the gain K to be multiplied by the current target basic value It1 in the motor control process (step S62). Thereafter, the process returns to step S52, and thereafter, steps S52 to S62 are repeatedly executed while the spectrum intensity SI of the determination frequency band is equal to or less than the threshold value Sth. During this time, if the spectral intensity SI of the determination frequency band becomes larger than the threshold value Sth, it is determined as “Yes” in step S58 and the process proceeds to step S64, the warning signal Sa is activated, and the predetermined value Kab is set as the gain K. Set (step S66). Here, the predetermined value Kab is a value smaller than “1” determined in advance as a gain when an abnormality occurs. Thereafter, the process returns to step S52, and the subsequent steps are repeatedly executed.
[0034]
<4. Action and Effect>
As described above, in a vehicle equipped with an electric power steering device, even if there is an abnormality in a tire or the like as a steered wheel, vibration such as unsprung resonance caused by the abnormality causes frictional force or inertia of the motor 6 or the like. It is difficult to convey to the driver. However, since the vibration is sufficiently transmitted to the torsion bar inserted in the steering shaft 102 to detect the steering torque, the steering torque signal Ts output from the torque sensor 3 is caused by the abnormality. A frequency component corresponding to the unsprung resonance or the like is included. Therefore, according to the above-described embodiment, when an abnormality occurs in the traveling device including the tire 108 as a steered wheel, such as an unbalance of a tire of a vehicle equipped with an electric power steering device or a decrease in tire air pressure, the determination is performed. Based on the spectrum intensity SI in the frequency band, vibration such as unsprung resonance due to the abnormality is detected (step S58), the warning signal Sa is activated, and the gain K to be multiplied by the current target basic value It1 is “1”. Kab having a value smaller than "" is set (steps S64 and S66). Accordingly, the warning unit 50 issues a warning by voice, lamp lighting, and / or display, etc., so that the driver can reliably recognize the abnormality. As a result, the absolute value of the current target value It2 = K × It1 for driving control of the motor 6 is reduced, so that the steering assist force is reduced. As a result, the unstable behavior of the vehicle due to the abnormality occurs. Is suppressed.
[0035]
In the motor control process and the abnormality detection process (FIG. 4), the motor control unit (microcomputer) 10 is functionally configured as shown in the second configuration example of FIG. 3B. Although it is assumed that step S22 is omitted in the motor control process when the configuration is as shown in the first configuration example of FIG. 3A, the current target basic value It1 is the value of the drive control of the motor 6. Therefore, steps S62 and S66 are omitted in the abnormality detection process. In this case, the steering assist force does not change depending on whether there is an abnormality. However, as in the case of the second configuration example, when an abnormality occurs in the traveling device, vibrations such as unsprung resonance due to the abnormality are detected, and the warning unit 50 Since the warning is issued, the driver can surely recognize the abnormality.
[0036]
<5. Modification>
In the above embodiment, the microcomputer 10 performs Fourier transform (specifically FFT) on the steering torque signal Ts by software in order to calculate spectrum data necessary for determining whether there is an abnormality in the traveling device. When it is necessary to perform the Fourier transform in a shorter time, instead of this, dedicated hardware for executing FFT or a digital signal processor (DSP) may be provided in the ECU 5. Good.
[0037]
Moreover, in the said embodiment, in order to determine the presence or absence of abnormality in a traveling apparatus, the presence or absence of generation | occurrence | production of unsprung resonance etc. resulting from the said abnormality is determined based on the spectrum data calculated by a Fourier transform (FFT). (Steps S54 to S58) Instead of this, peaks P1, P2, P3,... Of the steering torque signal Ts as shown in FIG. 5 are detected, and the times t1, t2, t3,. The period may be calculated from the time interval, and the frequency may be calculated from the period. For example, a time t1 at which the steering torque signal Ts has a positive peak is detected, a time t2 at which the steering torque signal Ts has a negative peak is subsequently detected, and a time interval T1 = t2− between those times t1 and t2. Find t1. Since a half-cycle time is thus obtained, the frequency ft is obtained by ft = 1 / (2 · T1). Further, a time t3 at which the steering torque signal Ts again becomes a positive peak is detected, a time interval T2 = t3-t2 with respect to the time t2 is obtained, the sum T1 + T2 of these time intervals is regarded as a period, and the steering torque signal Ts The frequency ft = 1 / (T1 + T2) may be calculated.
[0038]
As described above, when the frequency is obtained by peak detection instead of calculating the spectrum data by FFT, the microcomputer 10 executes the abnormality detection process shown in FIG. 6 instead of the abnormality detection process shown in FIG. By doing so, the function similar to the said embodiment is realizable. In this case, the microcomputer 10 operates as follows in the abnormality detection process.
[0039]
First, similarly to the abnormality detection process shown in FIG. 4B, time series data including a predetermined number of detected steering torque values is acquired by receiving the steering torque signal Ts from the torque sensor 3 for a predetermined time (step) S72). Next, the frequency ft in the steering torque signal Ts is calculated by the above-described peak detection using the time series data (step S74). Then, it is determined whether or not the frequency ft is within a frequency range F1 to F2 set in advance as a frequency of unsprung resonance or the like that occurs when the traveling device is abnormal (step S76). Here, the preset frequency range (hereinafter referred to as “determination frequency range”) F1 to F2 corresponds to the determination frequency band set in the above embodiment, and the frequencies F1 and F2 are for determination. It corresponds to the lower limit and the upper limit of the frequency band, respectively.
[0040]
If the result of determination in step S76 is that the frequency ft is out of the determination frequency range (when “No” is determined in step S76), the warning signal Sa is deactivated, assuming that there is no abnormality ( In step S78), “1” is set as the gain K to be multiplied by the current target basic value It1 in the motor control process described above (step S80). Thereafter, the process returns to step S72, and thereafter, steps S72 to S80 are repeatedly executed while the calculated frequency ft is out of the determination frequency range. During this time, if the calculated frequency ft falls within the determination frequency range (F1 ≦ ft ≦ F2), “Yes” is determined in step S76, and the process proceeds to step S82 to activate the warning signal Sa and to generate an abnormality. A predetermined value Kab (<1) is set as the gain K as a gain at the time (step S84). Thereafter, the process returns to step S72, and the subsequent steps are repeatedly executed.
[0041]
As described above, even when the frequency of the steering torque signal Ts is obtained by peak detection instead of calculating the spectrum data of the steering torque signal Ts by FFT, if an abnormality occurs in the traveling device, unsprung due to the abnormality. A frequency ft (F1 ≦ ft ≦ F2) corresponding to vibration such as resonance is detected (steps S74 and S76), a warning is issued by the warning unit 50 and the steering assist force is reduced (steps S82 and S84). The same effect as the above embodiment can be obtained. In addition, in this case, since FFT processing is unnecessary and the burden of processing for abnormality detection is relatively light, an abnormality detection means is realized at low cost by software processing in the microcomputer 10 without using dedicated hardware or the like. can do.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a configuration of an electric power steering apparatus according to an embodiment of the present invention, together with a vehicle configuration related thereto.
FIG. 2 is a block diagram showing a hardware configuration of an ECU that is a control device in the electric power steering apparatus according to the embodiment.
FIG. 3 is a block diagram showing a functional configuration of a motor control unit in the electric power steering apparatus according to the embodiment.
FIG. 4 is a flowchart showing motor control processing and abnormality detection processing executed by a motor control unit in the embodiment.
FIG. 5 is a signal waveform diagram for explaining a method of calculating the frequency of the steering torque signal employed in the abnormality detection process in the modification of the present invention.
FIG. 6 is a flowchart showing an abnormality detection process in the modified example.
[Explanation of symbols]
3 ... Torque sensor
4 ... Vehicle speed sensor
5 ... Electronic control unit (ECU)
6 ... Motor
10 ... Microcomputer (motor control unit)
12 ... Target current setting section
13 ... Multiplier
14 ... Subtractor
16 ... Control calculation part
20, 20b ... abnormality detector
21 ... FFT section
22, 22b ... determination part
50 ... Warning section
Ts ... Steering torque signal
Vs ... Vehicle speed signal
Im ... current detection value
It, It2 ... Current target value
It1 ... Current target basic value
K: Gain
Sa ... Warning signal
Vd: Voltage command value

Claims (2)

An electric power steering device that applies a steering assist force to a steering mechanism of the vehicle by driving an electric motor in accordance with an operation by an operation means for steering the vehicle,
Torque detecting means for detecting steering torque applied to the operating means and outputting a steering torque signal indicating the steering torque;
An abnormality detecting means for detecting an abnormality in the traveling device including the steered wheels of the vehicle based on a specific frequency component included in the steering torque signal;
Notification means for issuing a warning when an abnormality is detected by the abnormality detection means ,
The abnormality detection means includes
Frequency calculating means for detecting a peak in the steering torque signal and calculating a frequency of the steering torque signal based on a time interval between the detected peaks;
Determining means for determining the presence or absence of the abnormality according to whether or not the calculated frequency is in a frequency range corresponding to the specific frequency component;
An electric power steering device comprising:   The electric power steering apparatus according to claim 1, further comprising an abnormality control unit that reduces the steering assist force when an abnormality is detected by the abnormality detection unit.

Images