JP2007008294A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of suppressing behavior of an assist motor in the event of failure by performing a failure diagnosis of a steering angle sensor etc. without adding a second steering angle sensor influencing largely the structure of a gear box. <P>SOLUTION: The electric power steering device is equipped with a failure diagnosing means 55 to calculate the motor rotating speed ω<SB>M</SB>and the back electromotive voltage V<SB>M</SB>of an assist motor M one by one from the steering angular velocity ω, presume the motor current I<SB>M</SB>from the difference between the inter-terminal voltage V<SB>T</SB>of the motor and the back electromotive voltage V<SB>M</SB>, and diagnose failure by comparing the presumed value I<SB>M</SB>of the motor current with the detected value I of the motor current detected by a motor current detection means 28, whereby the output of the feedback control amount Dfb is stopped when a failure determination is passed by the failure diagnosing means 55. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric power steering device that is mounted on an automobile and assists a steering force with an electric motor.

  Steering torque control of the electric power steering apparatus basically assists the steering force by applying an assisting force corresponding to the steering torque applied to the steering shaft from the motor to the steering mechanism when the steering wheel is steered.

  For example, in the electric power steering apparatus disclosed in Patent Document 1, the control unit ECU derives a target steering torque based on the steering angle and the vehicle speed, and based on the deviation between the target steering torque and the detected steering torque. The motor feedback control.

JP 2002-120743 A

  The steering angle required to derive the target steering torque is detected by the steering angle sensor. However, if this steering angle sensor fails, the correct target steering torque cannot be derived, and the steering steering force is appropriately assisted. Is impossible.

Therefore, it is conceivable to perform a failure diagnosis by adding a second steering angle sensor and comparing the signals of both steering angle sensors.
However, the addition of the second rudder angle sensor greatly affects the structure of the gear box that transmits the steering steering to the wheel steering, and the size of the device increases.

  The present invention has been made in view of such points, and the target process is to perform an abnormality diagnosis of the rudder angle sensor and the like without adding a second rudder angle sensor that greatly affects the structure of the gear box, It is in the point which provides the electric power steering device which can suppress the behavior of the assist motor at the time of abnormality.

  In order to achieve the above object, according to a first aspect of the present invention, there is provided an electric power steering apparatus in which a driving force of an assist motor assists a steering force, a torque sensor for detecting a steering torque, a vehicle speed sensor for detecting a vehicle speed, Steering angle detection means for detecting the steering angle of the steering, motor terminal voltage derivation means for deriving the inter-terminal voltage of the assist motor, motor current detection means for detecting the motor current of the assist motor, and the rudder Target steering torque calculation processing means for deriving a target steering torque based on the steering angle detected by the angle detection means and the vehicle speed detected by the vehicle speed sensor; the target steering torque calculated by the target steering torque calculation means; Calculate the feedback control amount based on the difference from the steering torque detected by the torque sensor Feedback control amount calculation means, steering angular speed calculation means for calculating the steering angular speed by time differentiation of the steering angle detected by the steering angle detection means, and the steering angular speed calculated by the steering angular speed calculation means as an assist motor Motor rotation speed calculation means for converting to the motor rotation speed, back electromotive force calculation means for calculating a counter electromotive voltage of the assist motor from the motor rotation speed calculated by the motor rotation speed calculation means, and the voltage between the motor terminals Motor current estimation processing means for estimating the motor current of the assist motor from the difference between the motor terminal voltage derived by the derivation means and the counter electromotive voltage calculated by the counter electromotive voltage calculation means; and the motor current estimation processing means The estimated motor current estimated by An abnormality diagnosis means for diagnosing an abnormality in comparison with the detected motor current value detected by the current detection means, and an output of the feedback control amount calculated by the feedback control amount calculation means when the abnormality diagnosis means diagnoses an abnormality. An electric power steering apparatus provided with output control processing means for stopping.

  According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the abnormality diagnosing means diagnoses an abnormality when the current difference between the estimated motor current value and the detected motor current value is equal to or greater than a predetermined value. It is characterized by.

  According to a third aspect of the present invention, in the electric power steering apparatus according to any one of the first to third aspects, the target steering torque calculation processing means is a steering rudder angle detected by the steering rudder angle detecting means. And self-aligning torque calculating means for calculating self-aligning torque based on the vehicle speed detected by the vehicle speed sensor, steering based on the angular speed detected by the steering angular speed calculating means and the vehicle speed detected by the vehicle speed sensor. Friction torque calculating means for calculating the friction torque of the engine, and calculating the target steering torque by adding the friction torque calculated by the friction torque calculating means to the self-aligning torque calculated by the self-aligning torque calculating means. To do And features.

  According to the electric power steering device of the first aspect, since the motor current estimated value derived from the steering angle and the voltage between the motor terminals is compared with the detected motor current, the abnormality is diagnosed. Without adding a steering wheel, the abnormality diagnosis of the steering angle sensor, the motor current detection means, etc. can be performed, and the behavior of the assist motor at the time of abnormality can be suppressed.

  According to the electric power steering apparatus of the second aspect, since the abnormality is diagnosed when the current difference between the estimated motor current value and the detected motor current value is equal to or larger than the predetermined value, the abnormality diagnosis can be performed easily and quickly. .

  According to the electric power steering apparatus of the third aspect, the target steering torque is obtained by adding the friction torque calculated based on the angular velocity and the vehicle speed to the self-aligning torque calculated based on the steering angle and the vehicle speed. In addition, friction torque is added to compensate for the self-aligning torque that becomes smaller especially at low vehicle speeds, and the effect of tire friction on the road surface is covered while reflecting the road surface condition in feedback control, realizing a stable steering feeling at all times can do.

Hereinafter, an embodiment according to the present invention will be described with reference to FIGS.
FIG. 1 shows a schematic rear view of the entire electric power steering apparatus 1 according to the present embodiment.

  In the electric power steering apparatus 1, a rack shaft 3 is accommodated in a substantially cylindrical rack housing 2 oriented in the left-right direction of the vehicle (corresponding to the left-right direction in FIG. 1) so as to be slidable in the left-right axis direction.

  Tie rods are connected to both ends of the rack shaft 3 projecting from the openings at both ends of the rack housing 2 via joints, respectively, and the tie rod is moved by the movement of the rack shaft 3, and the steered wheels of the vehicle are rotated via the steering mechanism. Steered.

A steering gear box 4 is provided at the right end of the rack housing 2.
In the steering gear box 4, an input shaft 5 connected via a joint to a steering shaft to which a steering wheel (not shown) is integrally attached is rotatably supported via a bearing. As shown, the input shaft 5 is connected to the steering pinion shaft 7 via the torsion bar 6 in the steering gear box 4 so as to be capable of relative twisting.

The helical teeth 7 a of the steering pinion shaft 7 are engaged with the rack teeth 3 a of the rack shaft 3.
Therefore, the steering force transmitted to the input shaft 5 by the turning operation of the steering wheel rotates the steering pinion shaft 7 via the torsion bar 6 and meshes with the helical teeth 7a of the steering pinion shaft 7 and the rack teeth 3a. The rack shaft 3 is slid in the left-right axis direction.

  The rack shaft 3 is pressed from behind by a rack guide 9 biased by a rack guide spring 8.

  An assist motor M is attached to an upper portion of the steering gear box 4, and a worm reduction mechanism 10 that decelerates the driving force of the assist motor M and transmits it to the steering pinion shaft 7 is configured in the steering gear box 4.

The worm speed reduction mechanism 10 is configured such that a worm wheel 11 fitted on the steering pinion shaft 7 is engaged with a worm 12 coaxially connected to a drive shaft of the assist motor M.
The driving force of the assist motor M is applied to the steering pinion shaft 7 via the worm reduction mechanism 10 to assist steering.

  Although not shown in FIG. 2, the assist motor M is provided with a motor terminal voltage detecting device 27 for detecting the motor terminal voltages Vp and Vn and a motor current detecting device 28 for detecting the motor current I, and the steering pinion shaft. 7 is provided with a steering angle detection device 29 for detecting the steering angle θ.

A steering torque sensor 20 is provided further above the worm reduction mechanism 10.
The twist of the torsion bar 6 is converted into the movement of the core 21 in the axial direction, and the movement of the core 21 is changed into the inductance change of the coils 22 and 23 to detect the steering torque T.
A torque sensor that optically detects torsion of the torsion bar 6 may be used.

  A control board on which a control system CPU and the like of the steering torque control device 30 that drives and controls the assist motor M as described above to assist the steering force is mounted in the steering gear box 4.

A schematic block diagram of the steering torque control device 30 is shown in FIG.
The steering torque control device 30 includes a steering torque T detected by the steering torque sensor 20, a vehicle speed v detected by the vehicle speed sensor 25, a steering angle θ detected by the steering angle detection device 29, and a motor terminal voltage detection device 27. The motor terminal voltages Vp and Vn detected by the above are input and processed, and the motor feedback control amount Dfb, which is a PWM control signal (duty signal, etc.), is output to the motor drive circuit 26. The motor drive circuit 26 The assist motor M is driven according to the PWM control signal.
The motor drive circuit 26, the motor terminal voltage detection device 27, and the motor current detection device 28 may be provided on the steering torque control device 30 side.

  The steering torque control device 30 mainly includes a target steering torque calculation processing means 40, a feedback control amount calculation means 57, and an output control processing means 58. In addition, a steering angular speed calculation means 50, a motor rotation speed calculation means 51, A back electromotive force calculation means 52, a motor terminal voltage calculation means 53, a motor current estimation means 54, an abnormality diagnosis means 55, and the like are provided.

The steering angular velocity calculation means 50 calculates the steering angular velocity ω by time differentiation of the steering angle θ detected by the steering angle detector 29.
Based on the steering angular velocity ω, the steering angle θ, and the vehicle speed v detected by the vehicle speed sensor 25, the target steering torque calculation processing means 40 calculates the target steering torque Tm.

The target steering torque calculation processing means 40 will be described with reference to FIGS.
FIG. 4 is a schematic block diagram of the target steering torque calculation processing means 40. As shown in FIG. 4, the target steering torque calculation processing means 40 includes two self-aligning torque calculation means 41 and friction torque calculation means 45. It consists of two computing means.

The self-aligning torque calculating unit 41 includes a self-aligning base torque extracting unit 42 and a self-aligning torque multiplication coefficient extracting unit 43.
The self-aligning base torque extracting means 42 is based on the steering angle θ from the self-aligning base torque (SABT) storage means 42a that stores the relationship of the self-aligning base torque with respect to the steering angle at the reference vehicle speed. To extract.

A relationship map of the self-aligning base torque Tsb with respect to the steering angle θ at the reference vehicle speed Vo stored in the self-aligning base torque storage means 42a is shown in the coordinates of FIG.
In FIG. 5, as for the steering angle θ on the horizontal axis, a positive value indicates a right steering angle (θ> 0), and a negative value indicates a left steering angle (θ <0).

Here, as for the self-aligning base torque Tsb on the vertical axis, the positive value is the right direction torque (Tsb> 0), the negative value is the left direction torque (Tsb <0), and the actual self-aligning torque ( This is the torque that the running wheel receives from the road surface, and is shown as the reaction force of the force that works to restore the running wheel to a straight running posture.
Therefore, for example, when the right steering angle θ (> 0) increases, the self-aligning base torque Tsb (> 0) in the right direction opposite to the actual direction increases.

  Another self-aligning torque multiplication coefficient extraction means 43 provided in the self-aligning torque calculation means 41 is changed from the self-aligning torque (SAT) multiplication coefficient storage means 43a for storing the self-aligning torque multiplication coefficient with respect to the vehicle speed to the vehicle speed v. Based on this, a self-aligning torque multiplication coefficient ks is extracted.

A relationship map of the self-aligning torque multiplication coefficient ks with respect to the vehicle speed v stored in the self-aligning torque multiplication coefficient storage means 43a is shown in the coordinates of FIG.
In FIG. 6, the value of the self-aligning torque multiplication coefficient ks increases as the vehicle speed v increases.
At the reference vehicle speed Vo, the self-aligning torque multiplication coefficient ks = 1.0.

The self-aligning torque calculating means 41 extracts the self-aligning base torque Tsb extracted by the self-aligning base torque extracting means 42 based on the steering angle θ, and the self-aligning torque multiplication coefficient extracting means 43 extracts based on the vehicle speed v. The self-aligning torque multiplication coefficient ks is multiplied by the multiplication means 44 to calculate the self-aligning torque Ts.
The self-aligning torque Ts is a self-aligning torque as a reaction force of the actual self-aligning torque.

  By multiplying the self-aligning base torque Tsb by the self-aligning torque multiplication coefficient ks, the self-aligning torque Ts decreases as the vehicle speed v becomes lower than the reference vehicle speed Vo, and the reference vehicle speed Vo. The larger it is, the more it will be amplified.

On the other hand, the friction torque calculation means 45 includes a friction base torque extraction means 46 and a friction torque multiplication coefficient extraction means 47.
The friction base torque extraction means 46 extracts the friction base torque Tfb based on the angular speed ω from the friction base torque (FBT) storage means 46a that stores the relationship of the friction base torque to the angular speed when the vehicle is stopped.

A relationship map of the friction base torque Tfb with respect to the angular speed ω at the time of stopping (vehicle speed v = 0) stored in the friction base torque storage means 46a is shown in the coordinates of FIG.
In FIG. 7, as for the angular velocity ω on the horizontal axis, a positive value indicates an angular velocity in the right direction (ω> 0), and a negative value indicates an angular velocity in the left direction (ω <0).

The friction base torque Tfb on the vertical axis indicates a right direction torque (Tfb> 0) as a positive value and a left direction torque (Tfb <0) as a negative value. ing.
Therefore, for example, when the angular velocity ω (> 0) in the right direction increases, the friction base torque Tfb (> 0) in the right direction opposite to the actual direction increases, and the torque is lower than the self-aligning base torque Tsb. It becomes almost constant.

  Another friction torque multiplication coefficient extraction means 47 provided in the friction torque calculation means 45 obtains the friction torque multiplication coefficient kf based on the vehicle speed v from the friction torque (FT) multiplication coefficient storage means 47a for storing the friction torque multiplication coefficient for the vehicle speed. Extract.

A relationship map of the friction torque multiplication coefficient kf with respect to the vehicle speed v stored in the friction torque multiplication coefficient storage means 47a is shown in the coordinates of FIG.
In FIG. 8, when the vehicle speed v = 0 (when the vehicle is stopped), the value of the friction torque multiplication coefficient kf is 1.0, and the value of the friction torque multiplication coefficient kf decreases as the vehicle speed v increases from when the vehicle stops. The value is almost constant (about 0.5) from around / h.

The friction torque calculation means 45 multiplies the friction base torque Tfb extracted by the friction base torque extraction means 46 based on the angular velocity ω by the friction torque multiplication coefficient kf extracted by the friction torque multiplication coefficient extraction means 47 based on the vehicle speed v. Multiply by means 48 to calculate the friction torque Tf.
The friction torque Tf is a friction torque as a reaction force of the actual friction torque.

  By multiplying the friction base torque Tfb by the friction torque multiplication coefficient kf, the friction torque Tf gradually decreases until the vehicle speed v is about 20 km / h, and is substantially halved after about 20 km / h. The state continues.

  The self-aligning torque Ts calculated by the self-aligning torque calculating means 41 and the friction torque Tf calculated by the friction torque calculating means 45 are added by the adding means 49 to calculate the target steering torque Tm.

  The self-aligning torque Ts decreases particularly at low vehicle speeds, but the friction torque Tf exhibits a relatively large value so as to compensate for this at low vehicle speeds. Therefore, the friction torque Tf is added to the self-aligning torque Ts. The effect of tire friction on the road surface that appears greatly at low vehicle speeds can be compensated.

FIG. 9 is a flowchart showing a processing procedure until the above target steering torque Tm is calculated.
First, the steering angle θ detected by the rudder angle detecting means 29 is read (step 1), the angular speed ω is calculated by the angular speed calculating means 50 (step 2), and the vehicle speed v detected by the vehicle speed sensor 25 is read (step 3). .

  Next, the self-aligning base torque extraction means 42 extracts the self-aligning base torque Tsb based on the steering angle θ (step 4), and the self-aligning torque multiplication coefficient extraction means 43 extracts the self-aligning torque multiplication coefficient based on the vehicle speed v. ks is extracted (step 5), and the self-aligning base torque Tsb is multiplied by the self-aligning torque multiplication coefficient ks to calculate the self-aligning torque Ts (step 6).

  Next, the friction base torque extraction means 46 extracts the friction base torque Tfb based on the angular velocity ω (step 7), and the friction torque multiplication coefficient extraction means 47 extracts the friction torque multiplication coefficient kf based on the vehicle speed v (step 8). ), The friction torque Tf is calculated by multiplying the friction base torque Tfb by the friction torque multiplication coefficient kf (step 9).

In step 10, the target steering torque Tm is calculated by adding the friction torque Tf to the self-aligning torque Ts.
The processes of the above steps are repeatedly executed.

  With respect to the target steering torque Tm thus calculated, a deviation ΔT (= Tm−T) from the steering torque T detected by the steering torque sensor 20 is calculated by the subtracting means 56 with reference to FIG. Input to means 57.

  The feedback control amount calculating means 57 comprises PI (proportional / integral) control means and PWM control signal generating means, and P (proportional) is used for the PI control means to obtain the target steering torque Tm by setting the deviation ΔT to 0 from the deviation ΔT. ) The optimum control amount of feedback is calculated by combining the operation and the I (integration) operation, and the optimum control amount is converted into the feedback duty Dfb of the PWM control duty by the PWM control signal generating means and output.

On the other hand, the motor current estimated value _IM is estimated and calculated based on the steering angular velocity ω calculated by the steering angular velocity calculating means 50 and the motor terminal voltages Vp and Vn detected by the motor terminal voltage detector 27. The processing procedure will be described with reference to the flowchart of FIG.

First, the steering angular velocity ω is read (step 21), and the motor terminal voltages Vp and Vn are read (step 22).
Then, the motor terminal voltage V _T (= Vp−Vn) is calculated from the motor terminal voltages Vp and Vn by the motor terminal voltage calculation means 53 (step 23), and then the calculated motor terminal voltage V _T is low-pass filtered. Process (step 24).

In the next step 25, the motor rotation speed ω _M is calculated by the motor rotation speed calculation means 51 from the steering angular speed ω read in step 21.
The motor rotational speed ω _M (= ω × N) is calculated by multiplying the steering angular speed ω by the reduction ratio N (> 1) of the worm reduction mechanism 10.

In step 26, calculates the counter electromotive voltage V _M of the assist motor M by the counter electromotive voltage calculating unit 52 from the motor rotation speed omega _M.
The counter electromotive voltage V _M (= ω _M × k _E ) is calculated by multiplying the motor rotational speed ω _M by the induced voltage constant k _E.

Then, the motor current estimating means 54, the low-pass filtering the motor terminal voltage V _T and the counter electromotive voltage V assist from the difference between the _M motor M of execution voltage V (= V T _{-V M)} is calculated (Step 27 ), The execution voltage V is divided by the motor internal resistance Rm of the assist motor M, and a motor current estimated value I _M (= V / Rm) is estimated and calculated (step 28).

The estimated motor current value I _M is input to the abnormality diagnosis means 55 and compared with the motor current detection value I detected by the motor current detection device 28 separately input to the abnormality diagnosis means 55 to make an abnormality diagnosis. The
The abnormality diagnosis result by the abnormality diagnosis means 55 is input to the output control processing means 58, and the output of the feedback duty Dfb calculated by the feedback control amount calculation means 57 by the output control processing means 58 to the motor drive circuit 26 is stopped. Is done.

A processing procedure of abnormality diagnosis by the abnormality diagnosis means 55 and output control by the output control processing means 58 will be described with reference to a flowchart of FIG.
First, read the motor current detection value I detected by the motor current detecting device 28 in step 31, the current difference in the next step 32 and the motor current detection value I and the motor current estimated value I _M ΔI (= | I- ΔI |) is calculated.

In step 33, it is determined whether or not the current difference ΔI is equal to or greater than a predetermined value A.
If the current difference ΔI is less than the predetermined value A, it is diagnosed that the current is normal, and this routine is exited and the routine returns to step 31, and no special signal is output to the output control processing means 58, and the output control processing means 58 performs feedback control. The feedback duty Dfb from the quantity calculating means 57 is not limited and is output to the motor drive circuit 26 as it is, and the assist motor M is feedback-controlled.

If it is determined in step 33 that the current difference ΔI is equal to or greater than the predetermined value A, the process proceeds to step 34, where the elapse of the predetermined time is determined, and until the current difference ΔI is equal to or greater than the predetermined value A and the predetermined time has elapsed This routine is exited as it is and no abnormality is diagnosed.
That is, even if the current difference ΔI exceeds the predetermined value A, it may be temporary, so it is awaited to diagnose it as abnormal.

When the current difference ΔI is equal to or greater than the predetermined value A and a predetermined time has elapsed, the process proceeds from step 34 to step 35, where an abnormality is diagnosed and an abnormality diagnosis signal is output to the output control processing means 58. Stops outputting the feedback duty Dfb from the feedback control amount calculation means 57 to the motor drive circuit 26.
That is, it is possible to stop the feedback control of the assist motor M and not to assist steering steering, and to suppress the behavior of the assist motor at the time of abnormality.

  Here, the cause of the abnormality when diagnosed as abnormal may be a failure of the steering angle detection device 29, the motor terminal voltage detection device 27, the motor current detection device 28, and the like. This failure is related to the calculation of the target steering torque Tm, which means that feedback control is impossible.

Even if such a steering angle sensor failure occurs, an abnormality diagnosis can be performed easily and quickly without adding a second steering angle sensor, and the behavior of the assist motor M due to the abnormality can be avoided in advance. Can do.
Since the second steering angle sensor is not added, the structure of the steering gear box 4 in which the normal steering angle sensor is arranged is not greatly affected, and the apparatus can be prevented from being enlarged.

  Further, in the present steering torque control device 30, the target steering torque calculation processing means 40 adds the friction torque Tf calculated by the friction torque calculation means 45 to the self-aligning torque Ts calculated by the self-aligning torque calculation means 41. Since the target steering torque Tm is obtained, the self-aligning torque Ts, which is reduced particularly at low vehicle speeds, is supplemented by the friction torque Tf, and the road surface condition appears on the road surface that appears greatly at low vehicle speeds while appropriately reflecting the road surface condition in the steering feeling Covering the effects of tire friction, etc., a stable steering feeling can be achieved at all times.

1 is a schematic rear view of an entire electric power steering apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure in a steering gear box. It is a schematic block diagram of a steering torque control device. It is a schematic block diagram of a target steering torque calculation processing means. It is a figure which shows the relationship map of the self-aligning base torque Tsb with respect to the steering angle (theta) in a reference | standard vehicle speed by a coordinate. It is a figure which shows the relationship map of the self-aligning torque multiplication coefficient ks with respect to the vehicle speed v by a coordinate. It is a figure which shows the relationship map of friction base torque Tfb with respect to angular velocity (omega) at the time of a stop by a coordinate. It is a figure which shows the relationship map of the friction torque multiplication coefficient kf with respect to the vehicle speed v by a coordinate. It is a flowchart which shows the calculation process sequence of target steering torque. It is a flowchart which shows the process sequence which estimates and calculates a motor current. It is a flowchart which shows the procedure of an abnormality diagnosis process.

Explanation of symbols

M: Assist motor, 1 ... Electric power steering device, 2 ... Rack housing, 3 ... Rack shaft, 4 ... Steering gear box, 5 ... Input shaft, 6 ... Torsion bar, 7 ... Steering pinion shaft, 8 ... Rack guide spring, DESCRIPTION OF SYMBOLS 9 ... Rack guide, 10 ... Worm deceleration mechanism, 11 ... Worm wheel, 12 ... Worm, 20 ... Steering torque sensor, 21 ... Core, 22, 23 ... Coil, 25 ... Vehicle speed sensor, 26 ... Motor drive circuit, 27 ... Motor Terminal voltage detection device, 28 ... motor current detection device, 29 ... steering steering angle detection device,
30 ... Steering torque control device,
40 ... Target steering torque calculation processing means, 41 ... Self-aligning torque calculation means, 42 ... Self-aligning base torque extraction means, 42a ... Self-aligning base torque storage means, 43 ... Self-aligning torque multiplication coefficient extraction means, 43a ... Self-aligning torque multiplication coefficient storage means 44 ... Multiplication means 45 ... Friction torque calculation means 46 ... Friction base torque extraction means 46a ... Friction base torque storage means 47 ... Friction torque multiplication coefficient extraction means 47a ... Friction Torque multiplication coefficient storage means, 48 ... multiplication means, 49 ... addition means,
50 ... steering angular velocity calculating means, 51 ... motor rotational speed calculating means, 52 ... back electromotive force calculating means, 53 ... voltage between motor terminals, 54 ... motor current estimating means, 55 ... abnormality diagnosing means, 56 ... subtracting means, 57 ... feedback control amount calculation means, 58 ... output control processing means.

Claims (3)

In the electric power steering device in which the driving force of the assist motor assists the steering force,
A torque sensor for detecting steering torque;
A vehicle speed sensor for detecting the vehicle speed;
Steering angle detection means for detecting the steering angle of the steering;
Motor terminal voltage deriving means for deriving the terminal voltage of the assist motor;
Motor current detection means for detecting the motor current of the assist motor;
Target steering torque calculation processing means for deriving a target steering torque based on the steering angle detected by the steering angle detection means and the vehicle speed detected by the vehicle speed sensor;
Feedback control amount calculation means for calculating a feedback control amount based on a difference between the target steering torque calculated by the target steering torque calculation means and the steering torque detected by the torque sensor;
Steering angular velocity calculating means for calculating a steering angular velocity by differentiating the steering angle detected by the steering angle detection means with respect to time;
Motor rotation speed calculation means for converting the steering angular speed calculated by the steering angular speed calculation means into the motor rotation speed of the assist motor;
Back electromotive force calculation means for calculating a back electromotive voltage of the assist motor from the motor rotation speed calculated by the motor rotation speed calculation means;
Motor current estimation processing means for estimating the motor current of the assist motor from the difference between the motor terminal voltage derived by the motor terminal voltage deriving means and the counter electromotive voltage calculated by the counter electromotive voltage calculation means;
An abnormality diagnosis means for diagnosing an abnormality by comparing the estimated motor current value estimated by the motor current estimation processing means with the detected motor current value detected by the motor current detection means;
An electric power steering apparatus comprising: output control processing means for stopping output of the feedback control amount calculated by the feedback control amount calculation means when the abnormality diagnosis means diagnoses an abnormality.   2. The electric power steering apparatus according to claim 1, wherein the abnormality diagnosis unit diagnoses an abnormality when a current difference between the estimated motor current value and the detected motor current value is a predetermined value or more. The target steering torque calculation processing means includes:
Self-aligning torque calculating means for calculating self-aligning torque based on the steering angle detected by the steering angle detecting means and the vehicle speed detected by the vehicle speed sensor;
Friction torque calculation means for calculating the friction torque of the steering based on the angular speed detected by the steering angular speed calculation means and the vehicle speed detected by the vehicle speed sensor;
4. The target steering torque is calculated by adding the friction torque calculated by the friction torque calculating means to the self-aligning torque calculated by the self-aligning torque calculating means. The electric power steering device according to any one of the items.

Images