JP2006281882A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of realizing enhancement of responsiveness at rest swinging and low speed traveling and retrieval of responsiveness of feedback control lowered by influence of a back electro-motive voltage without raising gain of the feedback control. <P>SOLUTION: The electric power steering device is provided with a target steering torque operation processing means 40 for leading out target steering torque Tm based on a steering angle θ and a vehicle speed v; a feedback controlled variable operation means 51 for calculating a feedback controlled variable Dfb based on difference ΔT of the target steering torque Tm and the detected steering torque T; a reverse electro-motive voltage operation means 57 for calculating the reverse electro-motive voltage V<SB>M</SB>of an assist motor from a rotation angular velocity ω of the assist motor; a feed forward controlled variable operation means 52 for calculating a feed forward controlled variable Dff from the reverse electro-motive voltage V<SB>M</SB>calculated by the reverse electro-motive voltage operation means 57 and the detected power source voltage V<SB>B</SB>; and a motor drive means for driving the assist motor based on a motor controlled variable D<SB>M</SB>calculated by adding the feed forward controlled variable Dff to the feedback controlled variable Dfb. <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, a target steering torque is estimated based on a steering angle and a vehicle speed, and motor feedback is performed based on a deviation between the target steering torque and the detected steering torque. Control is in progress.

JP 2002-120743 A

  In this feedback control, the gain of the required steering torque with respect to the motor output is large, and the target steering torque gain in the feedback control cannot be set very high in order to suppress the generation of sound and vibration.

For this reason, the responsiveness may be deteriorated in a state where a large amount of assist is required, such as during stationary driving or low-speed traveling.
Further, during steering, the response of feedback control is lowered due to the influence of the counter electromotive voltage generated by the rotation of the motor.

  The present invention has been made in view of the above points, and the purpose of the present invention is to provide feedback that decreases due to the effect of back electromotive force and improved response during stationary driving and low-speed driving without increasing the gain of feedback control. The point is to provide an electric power steering device capable of recovering control responsiveness.

  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, The steering angle detection means for detecting the steering angle; the power supply voltage detection means for detecting the power supply voltage of the assist motor; the angular velocity detection means for detecting the rotational angular velocity of the assist motor; and the steering angle detection means. Target steering torque calculation processing means for deriving a target steering torque based on the steering angle and the vehicle speed detected by the vehicle speed sensor, target steering torque calculated by the target steering torque calculation means, and steering detected by the torque sensor A feedback control amount calculating means for calculating a feedback control amount based on a difference from the torque; A counter electromotive voltage calculating means for calculating a counter electromotive voltage of the assist motor from the rotational angular velocity of the assist motor detected by the degree detecting means, a counter electromotive voltage calculated by the counter electromotive voltage calculating means, and a power source detected by the power supply voltage detecting means Motor control by adding a feedforward control amount calculating means for calculating a feedforward control amount from the voltage, and adding the feedforward control amount calculated by the feedforward control amount calculating means to the feedback control amount calculated by the feedback control amount calculating means The electric power steering apparatus includes motor control amount calculation means for calculating the amount and motor drive means for driving the assist motor based on the motor control amount calculated by the motor control amount calculation means.

  According to a second aspect of the present invention, in the electric power steering apparatus according to the first aspect, the feedforward control amount calculating means is calculated by the counter electromotive voltage calculating means for the power supply voltage detected by the power supply voltage detecting means. The ratio of the back electromotive force is a feedforward control amount.

  According to a third aspect of the present invention, in the electric power steering apparatus according to the first or second aspect, the target steering torque calculation processing means includes an angular velocity detection means for detecting an angular velocity of a steering angle or a motor rotation angle, and the rudder Self-aligning torque calculation means for calculating self-aligning torque based on the steering angle detected by the angle detection means and the vehicle speed detected by the vehicle speed sensor, the angular velocity detected by the angular speed detection means, and the vehicle speed sensor Friction torque calculation means for calculating the friction torque of the steering based on the detected vehicle speed, and the friction torque calculated by the friction torque calculation means is added to the self-aligning torque calculated by the self-aligning torque calculation means. Add to calculate the target steering torque And wherein the Rukoto.

According to the electric power steering apparatus of the first aspect, the feedback control amount calculated by the feedback control amount calculation means based on the difference between the target steering torque and the steering torque is added to the feed calculated from the back electromotive voltage and the power supply voltage. Since the forward control amount is added to obtain the motor control amount, the feed forward control is supplemented without increasing the feedback control gain, improving the responsiveness in situations where a large amount of assist is required, such as during stationary or low-speed driving In addition, the responsiveness of the feedback control that is lowered due to the influence of the counter electromotive voltage can be recovered.
Furthermore, since the gain of the feedback control can be set as low as the amount compensated by the feedforward control, the generation of sound and vibration can be suppressed.

  According to the electric power steering apparatus of the second aspect, since the ratio of the counter electromotive voltage to the power supply voltage is used as the feedforward control amount, the response of feedback control is lowered due to the influence of the counter electromotive voltage generated by the rotation of the motor. Can be prevented to improve responsiveness.

  According to the third aspect of the present invention, the target steering torque is obtained by adding the friction torque calculated based on the angular speed and the vehicle speed to the self-aligning torque calculated based on the steering angle and the vehicle speed. In particular, the friction torque is added so as to compensate for the self-aligning torque that is reduced at a low vehicle speed, and the influence of the tire friction on the road surface can be covered, so that a stable steering feeling can be realized at all times.

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.

  The assist motor M is provided with a rotation angle sensor 27 such as a rotary encoder or resolver that directly detects the rotation of the rotation drive shaft.

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.

FIG. 3 shows a schematic block diagram of the steering torque control device 30 that assists the steering force by driving and controlling the assist motor M as described above.
The steering torque control device 30 outputs a PWM control signal (duty signal or the like) to the motor drive circuit 26, and the motor drive circuit 26 drives the assist motor M according to the PWM control signal.

The assist motor M is provided with a rotation angle sensor 27 such as a rotary encoder or resolver that directly detects the rotation of the rotation drive shaft.
The power supply voltage sensor 29 that detects the power supply voltage V _B of the battery 28 applied to the assist motor M is provided.

The steering torque control device 30 includes a steering angle detection unit 55 and an angular velocity calculation unit 56, and the steering angle detection unit 55 detects the steering angle θ based on the motor rotation speed n detected by the rotation angle sensor 27. The angular velocity calculation means 56 calculates the rotational angular velocity ω of the assist motor M by differentiating the steering angle θ with respect to time.
Note that the steering angle θ may be obtained directly by a steering angle sensor provided with a separate steering angle sensor.

In addition to the steering torque T detected by the steering torque sensor 20, the steering torque control device 30 receives the vehicle speed v detected by the vehicle speed sensor 25 and the power supply voltage V _B detected by the power supply voltage sensor 29. .

  The steering torque control device 30 mainly includes target steering torque calculation processing means 40, feedback control amount calculation means 51, and feedforward control amount calculation means 52.

First, 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 is a 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. To 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 steering angle detection means 55 is read (step 1), the angular speed ω is calculated by the angular speed calculation means 56 (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 50 with reference to FIG. Input to means 51.

  The feedback control amount calculation means 51 includes PI (proportional / integral) control means and PWM control signal generation means. The PI control means sets P (proportional) in order 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 counter electromotive voltage calculating unit 57 the steering torque controller 30 comprises calculates the counter electromotive voltage V _M of the assist motor M from the rotational angular speed ω of the assist motor M, which is calculated by the angular velocity calculating means 56, a feedforward This is output to the control amount calculation means 52.
The counter electromotive voltage calculation means 57 estimates the counter electromotive voltage V _M (= ω × k _E ) by multiplying the rotational angular velocity ω of the assist motor M by the induced voltage constant k _E.

Feed forward control amount calculation means 52 calculates the duty of the counter electromotive voltage V _M corresponding the PWM control as a feedforward duty Dff.
That is, the ratio _V M / _{V B} of the counter electromotive voltage _{V M} with respect to the power supply voltage _{V B} of the battery 28, the feedforward duty Dff.
_{Dff = (V M / V B} ) × 100 (%) ......... (1)

Now, when the assist motor M is driven by PWM control with the duty D, the voltage V _B × D is applied to the assist motor M and the back electromotive voltage V _B is generated, so the motor current I (motor torque The following equation holds.
I = (V _B × D−V _M ) / Rm (2)
Here, Rm is an internal resistance of the assist motor M.

The relationship of the motor current I with respect to the duty D is shown in FIG.
The solid line in FIG. 10 shows the relationship of the motor current I to the duty D when the assist motor M is rotated at the duty D.
The formula (2) is established.

The two-dot chain line in FIG. 10 is in the motor lock state, and no back electromotive force is generated. Therefore, all of the voltage V _B × D applied by the PWM duty D becomes a current corresponding to the internal resistance Rm of the motor. Torque is generated.
In this case, the relationship of the motor current I with respect to the duty D is expressed by the following equation.
I = (V _B / Rm) × D (3)

When the assist motor M is driven to rotate, the back electromotive voltage V _M is generated, the applied voltage V _B × portion is offset motor torque i.e. the motor current I D has decreased as shown by the solid line in FIG. 10 .
To compensate for the decrease amount of the motor torque due to the counter electromotive voltage V _M, (1) by driving the assist motor M duty Dff as a feedforward duty in the expression, motor current (motor torque shown by the two-dot chain line in FIG. 10 ) Can be recovered.

Thus, feed forward control amount calculation means 52 calculates the supply voltage VB which counter electromotive voltage V _M and the power supply voltage sensor 29 that the counter electromotive voltage calculating unit 57 has calculated is detected in accordance with the equation (1), a feed forward duty Dff Is calculated.

The feedforward duty Dff calculated by the feedforward control amount calculation means 52 in this way is added to the feedback duty Dfb calculated by the feedback control amount calculation means 51 by the addition means (motor control amount calculation means) 53, and finally. duty _{D M} of PMW controlling the assist motor M is determined for.

FIG. 11 is a flowchart showing the procedure of the motor control amount calculation process.
First, the steering torque T detected by the steering torque sensor 20 is read (step 21), the target steering torque Tm calculated by the target steering torque calculation processing means 40 is read (step 22), and the power supply detected by the power supply voltage sensor 29 is read. The voltage VB is read, and the rotational angular velocity ω of the assist motor M calculated by the angular velocity calculating means 56 is read (step 24).

  In step 25, the feedback control amount calculation means 51 calculates the feedback control amount Dfb (feedback duty Dfb) based on the deviation ΔT (= Tm−T) between the target steering torque Tm and the steering torque T.

Then, calculates the counter electromotive voltage _{V M (= ω × k E} ) by the counter electromotive voltage calculating unit 57 in step 26, the counter electromotive voltage V _M and the power supply voltage VB by the feed forward control amount calculation means 52 in the next step 27 From the above, the feedforward duty Dff is calculated according to the equation (1).
In step 28, the feedforward duty Dff is added to the feedback duty Dfb to obtain the motor control amount D _M (the duty D _{M of the} PMW control signal).

Duty D _M of the PMW control signal is output to the motor driving circuit 26, a motor driving circuit 26, the voltage V _B × D _M in accordance with the duty of the PWM control signal is applied to the assist motor M to the assist motor M Drive to assist the steering force.

As described above, the steering torque controller 30, the feedback control amount Dfb calculated based on the deviation ΔT between the target steering torque Tm and the steering torque T, is calculated from the counter electromotive voltage V _M and the supply voltage V _B since being a by adding the feedforward control amount Dff motor control amount D _M, without increasing the gain of the feedback control, the assist amount is large necessary state as at the time of stationary steering and a low speed running is compensated feedforward control In addition, the responsiveness of the feedback control that is reduced by the influence of the back electromotive voltage can be recovered.
Furthermore, since the gain of the feedback control can be set as low as the amount compensated by the feedforward control, the generation of sound and vibration can be suppressed.

  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 friction torque Tf compensates for the self-aligning torque Ts, which is particularly small at low vehicle speeds, and is always stable, covering the effects of tire friction on the road surface that appears at low vehicle speeds. The steering feeling can be realized.

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. FIG. 6 is a diagram showing a relationship of motor current I with respect to PWM duty D. It is a flowchart which shows the procedure of the calculation process of a motor control amount.

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 reduction mechanism, 11 ... Worm wheel, 12 ... Worm, 20 ... Steering torque sensor, 21 ... Core, 22, 23 ... Coil, 25 ... Vehicle speed sensor, 26 ... Motor drive circuit, 27 ... Rotation Angle sensor, 28 ... Battery, 29 ... Power supply voltage sensor,
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 ... subtraction means, 51 ... feedback control amount calculation means, 52 ... feed forward control amount calculation means, 52a ... feed forward control amount storage means, 53 ... addition means, 55 ... steer angle detection means, 56 ... angular velocity calculation means, 57 ... back electromotive force calculation means.

Claims (3)

In the electric power steering apparatus in which the driving force of the assist motor assists the steering force, a torque sensor that detects steering torque;
A vehicle speed sensor for detecting the vehicle speed;
Rudder angle detecting means for detecting the rudder angle;
Power supply voltage detecting means for detecting the power supply voltage of the assist motor;
Angular velocity detection means for detecting the rotational angular velocity 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;
Back electromotive force calculation means for calculating a back electromotive voltage of the assist motor from the rotational angular speed of the assist motor detected by the angular speed detection means;
A feedforward control amount calculation means for calculating a feedforward control amount from the back electromotive voltage calculated by the back electromotive voltage calculation means and the power supply voltage detected by the power supply voltage detection means;
Motor control amount calculating means for calculating a motor control amount by adding the feedforward control amount calculated by the feedforward control amount calculating means to the feedback control amount calculated by the feedback control amount calculating means;
An electric power steering apparatus comprising: motor driving means for driving the assist motor based on the motor control amount calculated by the motor control amount calculating means. The feedforward control amount calculation means is
2. The electric power steering apparatus according to claim 1, wherein a ratio of the counter electromotive voltage calculated by the counter electromotive voltage calculation means to the power supply voltage detected by the power supply voltage detection means is a feedforward control amount. The target steering torque calculation processing means includes:
Angular velocity detection means for detecting the angular velocity of the rudder angle or motor rotation angle;
Self-aligning torque calculation means for calculating self-aligning torque based on the steering angle detected by the steering angle detection 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 angular speed detection means and the vehicle speed detected by the vehicle speed sensor;
3. The target steering torque is calculated by adding the friction torque calculated by the friction torque calculation means to the self-aligning torque calculated by the self-aligning torque calculation means. Electric power steering device.

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