JP4012031B2 - Electric power steering device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric power steering apparatus, and more particularly, to an electric power steering apparatus that reduces the steering force of a driver by applying the power of a motor to a steering system.
[0002]
[Prior art]
The electric power steering device includes a motor in a steering system, and controls the power supplied from the motor by using a control device, thereby reducing the driver's steering force.
[0003]
FIG. 7 is a schematic structural diagram of the electric power steering apparatus. In the electric power steering apparatus 100, a steering shaft 102 provided integrally with a steering wheel (handle) 101 is connected to a pinion 105a of a rack and pinion mechanism 105 via a connecting shaft 103 having universal joints 103a and 103b. Thus, a manual steering torque generation mechanism 106 is configured.
[0004]
The rack shaft 107 having rack teeth 107a meshing with the pinion 105a and reciprocatingly converted in the axial direction by these meshing is connected to left and right front wheels 109 as rolling shafts via tie rods 108 at both ends thereof. Yes. By operating the handle 101, the driver can change the direction of the vehicle by swinging the front wheels via the manual steering torque generating mechanism 106 and a normal rack and pinion type steering device.
[0005]
In order to reduce the steering torque generated by the manual steering torque generating mechanism 106, a motor 110 for supplying assist torque (steering assist torque) is disposed coaxially with the rack shaft 107, for example, and substantially parallel to the rack shaft 107. The assist torque supplied by the rotational motion from the motor 110 via the provided ball screw mechanism 111 is converted into a force for linear motion and acts on the rack shaft 107.
[0006]
A driving side helical gear 110 a is integrally provided on the rotor of the motor 110. The helical gear 110a meshes with a helical gear 111b provided integrally with the shaft end of the screw shaft 111a of the ball screw mechanism 111. The nut of the ball screw mechanism 111 is connected to the rack shaft 107.
[0007]
FIG. 8 is a diagram illustrating a control device of the electric power steering device. In FIG. 7, in a steering gear box (not shown), a manual steering torque detector 112 that detects a manual steering torque T acting on the pinion 105a is provided. The manual steering torque detector 112 converts the detected manual steering torque T into a manual steering torque detection signal Td, and inputs the converted manual steering torque detection signal Td to the control device 114. The control device 114 operates the motor 110 using the manual steering torque detection signal Td as a main signal, and controls the power (steering assist torque) output by the motor 110.
[0008]
The control device 114 includes a target current determination unit 115 and a control unit 116. The target current determination unit 115 determines a target auxiliary torque based on the manual steering torque detection signal Td, and outputs a target current signal IT necessary for supplying the target auxiliary torque from the motor 110.
[0009]
FIG. 9 is a block configuration diagram of the control unit 116. The control unit 116 includes a deviation calculation unit 117, a motor operation control unit 118, a motor drive unit 119, and a motor current detection unit 120. Deviation calculation unit 117 calculates a deviation between target current signal IT output from target current determination unit 115 and motor current signal IM from motor current detection unit 120, and outputs the value as deviation signal 117a.
[0010]
The motor operation control unit 118 includes a deviation current control unit 121 and a PWM signal generation unit 122. The deviation current control unit 121 controls the motor current supplied to the motor 110 such that the value of the deviation signal 117a approaches zero by performing processing such as proportionality, integration, and differentiation on the input deviation signal 117a. Drive current signal 121a is generated and output.
[0011]
The PWM signal generation unit 122 generates a PWM (pulse width modulation) signal for performing PWM operation of the motor 110 based on the drive current signal 121a, and outputs the generated PWM signal as the drive control signal 122a.
[0012]
The motor drive unit 119 includes a gate drive circuit unit 123 and a motor drive circuit 124 in which four power field effect transistors are connected in an H-type bridge circuit configuration. Based on the drive control signal (PWM signal) 122a, the gate drive circuit unit 123 selects two field effect transistors according to the steering direction of the handle 101, and drives the gates of the selected two field effect transistors. The field effect transistor is switched.
[0013]
The motor current detection unit 120 detects a motor current (armature current) flowing through the motor 110 and outputs a motor current signal IM.
[0014]
As described above, the control device 114 performs PWM control on the current supplied from the battery power supply 126 to the motor 110 based on the manual steering torque T detected by the manual steering torque detection unit 112, and the power (steering assist torque) output from the motor 110. ) To control.
[0015]
Further, as shown in FIG. 9, the control device 114 detects the motor current that actually flows through the motor 110 in the control unit 116 as the motor current signal IM, and performs feedback control based on the motor current signal IM, thereby performing the motor 110. The control characteristics are improved.
[0016]
As described above, the manual steering torque T of the driver is detected by the manual steering torque detecting unit 112 of the manual steering torque generating mechanism 106, and the output of the motor 110 is driven and controlled by the control device 114 to control the steering gear box. Assists the force for the rack shaft 107 to move straight.
[0017]
Such an electric power steering apparatus is disclosed in several documents (for example, Patent Documents 1 to 3).
[0018]
[Patent Document 1]
Japanese Patent Laid-Open No. 07-208224 [Patent Document 2]
Japanese Patent No. 3133896 [Patent Document 3]
Japanese Patent Laid-Open No. 10-336886
[Problems to be solved by the invention]
In a conventional electric power steering device, when a failure occurs in a current sensor (motor current detection unit), a warning light is lit on a driver's seat display panel or the like based on fail-safe control, and steering force assist control can be performed completely. When there was not, it was made to return to the structure of the steering system by normal manual operation.
[0020]
In recent years, it is desired that the operating state of the electric power steering device can be continuously maintained even when the above-described failure occurs, and the driver's manual steering force can be assisted.
[0021]
In order to solve the above problems, an object of the present invention is to provide an electric power steering apparatus having a redundant system that can continue the assist of the manual steering force without interruption even if a failure occurs in the current sensor of the motor control apparatus. Is to provide.
[0022]
[Means and Actions for Solving the Problems]
The electric power steering apparatus according to the present invention is configured as follows to achieve the above object.
[0023]
A first electric power steering device (corresponding to claim 1) is provided between a motor, a power source, a motor and a power source, and performs a PWM control on a current flowing to the motor, and a current flowing to the motor. the electric power steering apparatus provided with a current sensor for detecting a differential voltage detecting means for detect the difference voltage between the input terminals of each of the two wires provided between the motor driving circuit and the power source, the and wiring resistance calculating means for calculating the wiring resistance of the wiring on the basis of the duty ratio of the current value and the PWM control from the difference between the voltage and current sensor detected by the differential voltage detecting means, the calculated wiring by the wiring resistance calculating means a motor current estimating means for estimating a current flowing through the motor based on the resistance, and the current detected by the current and the current sensor estimated by the motor current estimating means A failure detecting means for detecting a failure of the current sensor based on the provided, when the failure of the current sensor is detected by the failure detecting means, characterized by performing control by a current estimated by the motor current estimating means .
[0024]
According to a first electric power steering apparatus, and the differential voltage detecting means for detect a difference voltage between each of the input terminals of the two wires provided between the motor driving circuit and the power supply, the difference voltage detection and wiring resistance calculating means for calculating the wiring resistance of the wiring on the basis of the duty ratio of the current value and the PWM control from the detected differential voltage and current sensor by means based on the wiring resistance calculated by the wiring resistance calculation means Motor current estimation means for estimating the current flowing through the motor, and failure detection means for detecting a failure of the current sensor based on the current estimated by the motor current estimation means and the current detected by the current sensor. , when the failure of the current sensor is detected by the failure detecting means, for controlling the current estimated by the motor current estimating means, the current of the motor control device Se Even the failure in service has occurred, since estimates the current flowing from the wiring resistance of the wiring to the motor, without interrupting the assisted manual steering force on the basis of the current, it is possible to continue to Rukoto.
[0025]
The second electric power steering device (corresponding to claim 2) is provided between the motor, the power source, the motor and the power source, and performs a PWM control on the current flowing to the motor, and the current flowing to the motor. In an electric power steering apparatus provided with a current sensor to detect, a difference voltage detection means for detecting a difference voltage between each input terminal of two wires provided between a motor drive circuit and a power source, and the difference and wiring resistance calculating means for calculating the wiring resistance of the wiring on the basis of the duty ratio of the current value and the PWM control from the detected differential voltage and current sensor by the voltage detecting means, the wiring resistance calculated by the wiring resistance calculation means characterized by providing the failure determining means for determining a failure of the electric power steering apparatus, a based on.
[0026]
According to the second electric power steering apparatus, the differential voltage detecting means for detecting the differential voltage between the input terminals of each of the two wires provided between the motor drive circuit and the power source, and the differential voltage detecting means and wiring resistance calculating means for calculating the wiring resistance of the wiring on the basis of the duty ratio of the current value and the PWM control of the difference voltage is detected and the current sensor by, on the basis of the wiring resistance calculated by the wiring resistance calculation means since it provided with failure judgment means for judging a failure of the electric power steering apparatus, and it is possible to reliably diagnose a failure of the electric power steering apparatus.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings.
[0028]
The structure of the electric power steering apparatus is basically the same as that shown in FIG. 7, and the structure and operation thereof are as described above.
[0029]
FIG. 1 is a diagram illustrating a power supply system of an electric power steering apparatus. The control device 10 is connected to the terminal 13 of the control device 10 from the power source 11 through the harness C10 and the fuse 12, is connected to the terminal 14 by the harness C11, and the motor 15 is connected to the control device 10 by the terminals 16 and 17. Further, the power supply 11 is wired by a harness C12 to a terminal 19 for a microcomputer in the control device 10 through a switch 18. The harness C10 has a wiring resistance RxH as shown in parentheses in the figure, the harness C11 has a wiring resistance RxL as shown in parentheses in the figure, and the harness C12 has a wiring resistance Rc. In the figure, Vdd is a value obtained by subtracting, from the power supply voltage Ve, a voltage drop when the average current Ie flows through the harness C10 and the harness C11. Ve1 is a value obtained by subtracting a voltage drop when the average current Icc flows through the harness C12 from the power supply voltage Ve. Vm is a motor voltage, and Im is a motor current.
[0030]
FIG. 2 shows the main functions inside the control device 10. The control device 10 basically has the function of the conventional control device shown in FIGS. 8 and 9, and besides that, a harness resistance calculation unit and a motor current estimation unit (motor current estimation means), which will be described later, A bridge circuit (motor drive circuit) 25, a current detection unit (current sensor) 26, a motor terminal internal voltage output amplifier 27, and a microcomputer each having a failure detection unit and comprising a microcomputer 20, four FETs 21, 22, 23, and 24. A power source 28 for use and a differential voltage detector 29 are provided. The microcomputer 20 inputs Vdd from the terminal 30, inputs Ve 1 from the terminal 31, and inputs the difference voltage (Ve 1 −Vdd) from the difference voltage detection unit 29 from the terminal 32. Then, they are A / D converted. A motor voltage is input from the terminal 33 and A / D converted. The terminal 34 is a terminal that outputs a PWM signal to the FETs 21, 22, 23, and 24 that constitute the H-type bridge, and the terminal 35 sends a signal related to the rotation direction of the motor 15 to the FETs 21, 22, 23, and 24 is a terminal to output to 24.
[0031]
With this configuration, there is provided a device that performs current control by regarding the resistances RxH and RxL of the power harness systems C10 and C11 through which the motor current flows as current detection shunt resistances. The differential voltage detector 29 subtracts the voltage drop due to the resistance (RxH + RxL) of the harness systems C10 and C11 from the power supply voltage Ve and the voltage drop due to the resistance (RxL + Rc) of the harnesses C11 and C12 from the power supply voltage Ve. The obtained value Ve1 is input to the control device, and the difference voltage between Vdd and Ve1 is taken into the microcomputer 20. Further, the microcomputer 20 calculates the battery take-out current (average current) Ie from the later-described differential voltage (Ve1-Vdd) from the motor current corresponding to the motor control state and the duty ratio of the PWM signal, and the calculation The motor current estimation unit includes a harness resistance calculation unit that calculates the resistances (RxL + RxH) of the harness systems C10 and C11 using the taken-out current.
[0032]
Next, a calculation method performed by the harness resistance calculation unit of the motor current estimation unit will be described.
[0033]
First, the take-out current (average current) Ie can be obtained from the motor current Im as follows. In FIG. 1, assuming that there is no power loss of the control device 10 (efficiency 100%), the power supplied from the power source is equal to the power at the motor, so the motor voltage is Vm, the motor current is Im, and the average current is If Ie, the equation (1) is established.
[0034]
[Expression 1]
Vdd × Ie = Im × Vm (1)
[0035]
In the equation (1), when the duty ratio of the PWM signal is DUTY, the motor voltage Vm is expressed by the following equation (2) by Vdd and DUTY.
[0036]
[Expression 2]
Vm = Vdd × DUTY (2)
[0037]
Therefore, the take-out current (average current) Ie is expressed by the equation (3) from the motor current Im and the duty ratio DUTY from the equations (1) and (2).
[0038]
[Equation 3]
Ie = Im × DUTY (3)
[0039]
The harness resistance calculation unit calculates the harness resistance as follows. That is, when focusing on Ve1 input to the terminal 31 and assuming that the current Icc is smaller than the current Ie, the voltage drop due to the harness C10 is RxH × Ie, and therefore, the following expression (4) is established.
[0040]
[Expression 4]
Ve1 = Vdd + RxH × Ie (4)
[0041]
Substituting equation (3) into equation (4) yields the following equation (5).
[0042]
[Equation 5]
Ve1 = Vdd + RxH × (Im × DUTY) (5)
[0043]
From the equation (5), the harness resistance RxH can be obtained by the following equation (6).
[0044]
[Formula 6]
RxH = (Ve1−Vdd) / (Im × DUTY) (6)
[0045]
From this equation (6), the harness resistance RxH can be obtained from the motor current Im and DUTY, and the average value Ie of the take-out current can be obtained from the equation (4). Therefore, when the current sensor is operating normally, the resistance RxH is obtained, and the average current Ie can be obtained from the resistance RxH and the difference voltage (Ve1-Vdd).
[0046]
The harness resistance calculation unit receives the value (Ve1-Vdd) from the differential voltage detection unit 29, the value Im from the motor current detection unit 26, and the duty ratio DUTY when the current sensor is operating normally, and (6 ), The harness resistance RxH is stored in the memory.
[0047]
The harness resistance may be a learning value or a design value.
[0048]
The motor current estimation unit inputs the harness resistance RxH and the difference voltage (Ve1-Vdd) stored in the memory, and the CPU calculates the carry-out current Ie according to the equation (4). If the sensor cannot be used when the current sensor fails, this RxH can be used for alternative control. The motor current Im ′ can be estimated from the following equation (7) from the carry-out current Ie.
[0049]
[Expression 7]
Im ′ = (Ve1−Vdd) / DUTY) / RxH (7)
[0050]
Thus, by obtaining the harness resistance RxH, even if a failure occurs in the current sensor (current detection unit) 26 that has been used for the control so far, an alternative value can be obtained from the equation (7), and the alternative control can be performed. Made possible.
[0051]
In addition, it was set as the description which detects the both-ends voltage including resistance components, such as a harness, a fuse, and a connector, so that the resistance of a harness system may be maximized and the voltage drop by current may become the maximum. Also, this time, in order to maximize the harness resistance, the length of the harness is increased and described in the immediate vicinity of the battery and inside the unit. Can be effective.
[0052]
Next, a control device for an electric power steering apparatus that can cope with a failure of a current sensor by estimating the motor current will be described.
[0053]
FIG. 3 is a block diagram of the control device 10 described above. The control device 10 includes a motor control unit 40, a harness resistance calculation unit 41, a motor current estimation unit 42, and a failure detection unit 43. In addition, a failure display unit 44 is connected to the failure detection unit 43. The motor control unit 40 is basically the same as that described in FIG. The failure detection unit 43 outputs “1” as a signal when a failure of the current sensor is determined, and outputs “zero” as a signal when the failure is not determined. When the signal is zero, the state is maintained as it is, and when the input from the failure detection unit 43 is 1, the signal of the current sensor 26 is cut off, and feedback control is performed by the input signal from the motor current estimation unit instead. An input signal switching unit 45 that can be switched as described above is provided.
[0054]
In FIG. 3, the motor current estimation unit 42 calculates a motor current estimation value Im ′ by dividing the difference voltage obtained by the difference voltage detection unit 29 by DUTY and the harness resistance RxH stored in the memory. A value is input to the failure detection unit 43.
[0055]
FIG. 4 is a block diagram showing the failure detection unit. The failure detection unit 43 includes an input unit 46, an output unit 47, a CPU 48, and a storage unit 49. The failure detection unit 43 compares the input of the motor current estimation unit 42 and the input from the current sensor 26, for example, takes a difference, determines that the difference is smaller than a predetermined value, determines that it is normal, and normal A value signal, for example, zero is output to the motor control unit 40 and the failure display unit 44. If the difference is greater than a predetermined value, it is determined that there is a failure, and a failure signal, for example, 1 is output to the motor control unit 40 and the failure display unit To do. The predetermined value here is stored in advance in the storage area 50 of the storage unit 49.
[0056]
Next, the operation of this embodiment will be described with reference to the flowchart of FIG. The difference voltage (Ve1-Vdd) from the difference voltage detection unit 29 is output to the motor current estimation unit 42 (step ST10). The motor current estimation unit 42 calculates a motor current estimation value Im ′ based on the differential voltage, DUTY, and the harness resistance RxH stored in the memory (step ST11).
[0057]
The calculated motor current estimated value Im ′ is temporarily stored in the storage area A of the storage unit of the failure detection unit 43 (step ST12), and the output from the current sensor 26 is temporarily stored in the storage area B of the storage unit. (Step ST13). The CPU calculates a difference from the values in the storage areas A and B (step ST14), and stores the difference in the storage area C (step ST15). The CPU compares the difference with a predetermined value stored in the storage area 50 of the storage unit (step ST16). As a result, when the difference is smaller than the predetermined value, zero is output to the motor control unit 40 (step ST17). At that time, the motor control unit 40 maintains that state. And it returns to step ST10 again and processes.
[0058]
If the difference is greater than or equal to a predetermined value as a result of comparison by the CPU, signal 1 is output to the motor control unit 40 (step ST18). At that time, in the motor control unit 40, the input signal switching unit 45 is activated to cut off the signal from the current sensor 26, and at the same time, the control is switched to feedback control using the value Im ′ from the motor current estimation unit 42 (step ST19).
[0059]
Thus, normal control can be performed even when the current sensor 26 fails, and a failure of the current sensor 26 can be determined.
[0060]
In the present embodiment, it has been described that the failure of the current sensor is determined. However, the voltage of the wiring connecting the motor drive circuit and the power source is detected, and the current value from the voltage, the current sensor, and the duty ratio of the PWM control are detected. A failure determination unit that determines the resistance of the wiring based on the resistance and determines the failure of the electric power steering apparatus based on the change in resistance may be provided. The process flowchart in the failure determination part which determines the failure of the electric power steering apparatus at that time will be described with reference to FIG. First, in the harness resistance calculation unit, when the current sensor is operating normally, the value (Ve1-Vdd) from the differential voltage detection unit 29, the value Im from the motor current detection unit 26, and the duty ratio DUTY are input. The calculation according to the equation (6) is performed, and the harness resistance RxH is stored in the memory. This operation is performed several times, and the resistance value obtained each time is stored in the memory as Te2, Te3,... (Step ST30). Next, when the current sensor is operating normally again, the value (Ve1-Vdd) from the differential voltage detector 29, the value Im from the motor current detector 26, and the duty ratio DUTY are input (step ST31). Based on these values, calculation according to the equation (6) is performed to calculate the resistance Te1 (step ST32). The measurement count T is incremented by 1 (step ST33). It is determined whether the number of times of measurement T is n (step ST34). If the number of measurements T has not reached n, the process returns to step ST30. If the number of times of measurement T has reached n times, an average value Tea of values from n-1 resistance values Te2 to Ten is calculated (step ST35). It is determined whether or not the absolute value of the difference between the resistance value Te1 and the average value Tea is greater than a predetermined value a (step ST36). If the absolute value of the difference between the resistance value Te1 and the average value Tea is not greater than the predetermined value a, the process returns to step ST30. If the absolute value of the difference between the resistance value Te1 and the average value Tea is greater than the predetermined value a, the stored value of the resistor Te2 is changed to Te1, the stored value of Te3 is changed to Te2, and generally the stored value of Ten Is changed to Ten-1 (step ST37). When the current sensor is operating normally again, the value (Ve1-Vdd) from the differential voltage detector 29, the value Im from the motor current detector 26, and the duty ratio DUTY are input (step ST38). Based on these values, calculation according to the equation (6) is performed to calculate the resistance Te1 (step ST39). It is determined whether the absolute value of the difference between the resistance value Te1 and the average value Tea is greater than a predetermined value a (step ST40). If the absolute value of the difference between the resistance value Te1 and the average value Tea is not greater than the predetermined value a, the counter K is set to 0 and the process returns to step ST30. If the absolute value of the difference between the resistance value Te1 and the average value Tea is larger than the predetermined value a, 1 is added to the counter K (step ST41), and it is determined whether the counter K is larger than the predetermined value b (step ST42). . If the counter K is not greater than the predetermined value b, the process returns to step ST37. If the counter K is larger than the predetermined value b, it is determined that there is a failure (step ST43), and the failure is notified by a display device such as an LED.
[0061]
In this way, it is possible to determine the failure of the electric power steering apparatus from the change in resistance.
[0062]
【The invention's effect】
As is apparent from the above description, the present invention has the following effects.
[0063]
The voltage of the wiring that connects the motor drive circuit and the power supply is detected, the resistance of the wiring is determined based on the voltage, the current value from the current sensor, and the duty ratio of the PWM control. Therefore, even if a fault occurs in the current sensor of the motor control device, the current flowing to the motor is estimated from the resistance of the wiring. You can continue without interruption. In addition, by means of monitoring the voltage across the harness of the motor power supply system, alternative control is possible even if the current sensor normally used for motor control breaks down. Can supply a high system. Furthermore, by this means, it is possible to easily detect the failure of the current sensor by comparing the motor current and the current taken out from the battery. Also, the voltage of the wiring connecting the motor drive circuit and the power source is detected, the resistance of the wiring is determined based on the voltage, the current value from the current sensor, and the duty ratio of the PWM control, and the electric power steering by the change in resistance Since the failure of the device is determined, the failure of the electric power steering device can be reliably diagnosed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a power supply system of an electric power steering apparatus according to the present invention.
FIG. 2 is a diagram illustrating main functions inside the control device.
FIG. 3 is a block diagram of a control device.
FIG. 4 is a block configuration diagram showing a failure detection unit.
FIG. 5 is a flowchart illustrating the operation of the present embodiment.
FIG. 6 is a flowchart for diagnosing a failure of the electric power steering apparatus using a resistor.
FIG. 7 is a schematic structural diagram of an electric power steering apparatus.
FIG. 8 is a diagram showing a control device of the electric power steering device.
FIG. 9 is a block configuration diagram of a control unit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Control apparatus 11 Power supply 12 Fuse 13, 14 Terminal 15 Motor 16, 17 Terminal 18 Switch 19 Terminal 20 Microcomputer 21, 22, 23, 24 FET
25 Bridge circuit 26 Current detection unit 27 Motor terminal voltage output amplifier 28 Microcomputer power supply 29 Differential voltage detection unit 30, 31, 32, 33, 34, 35 Terminal 101 Harness resistance calculation unit 102 Motor current estimation unit C10, C11, C12 harness

Claims (2)

A motor, a power source, provided between said motor power supply, a motor drive circuit for PWM controlling the current supplied to the motor, an electric power steering equipped with a current sensor for sensing the current flowing through the motor In the device
Differential voltage detection means for detecting a differential voltage between the input terminals of each of the two wires provided between the motor drive circuit and the power source;
And wiring resistance calculating means for calculating the wiring resistance of the wiring on the basis of the duty ratio of the PWM control and current value from the current sensor and said detected difference voltage by the difference voltage detection means,
Motor current estimating means for estimating the current flowing through the motor based on the wiring resistance calculated by the wiring resistance calculating means ;
Failure detection means for detecting a failure of the current sensor based on the current estimated by the motor current estimation means and the current detected by the current sensor;
Provided,
It said failure when the failure of the current sensor is detected by the detecting means, the electric power steering apparatus characterized by performing control by the current estimated by the motor current estimating means. A motor, a power source, provided between said motor power supply, a motor drive circuit for PWM controlling the current supplied to the motor, an electric power steering equipped with a current sensor for sensing the current flowing through the motor In the device
Differential voltage detection means for detecting a differential voltage between the input terminals of each of the two wires provided between the motor drive circuit and the power source;
And wiring resistance calculating means for calculating the wiring resistance of the wiring on the basis of the duty ratio of the PWM control and current value from the current sensor and said detected difference voltage by the difference voltage detection means,
Failure determination means for determining a failure of the electric power steering device based on the wiring resistance calculated by the wiring resistance calculation means ;
An electric power steering apparatus comprising:

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