JP3433701B2 - Electric power steering device for vehicles - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for a vehicle, which assists a steering operation of a steering wheel by rotating an electric motor.

[0002]

2. Description of the Related Art Conventionally, an apparatus of this kind, for example, Japanese Patent Laid-Open No. 7-
As disclosed in Japanese Patent No. 329799, the control command value for controlling the operation of the electric motor is determined in accordance with the turning operation of the steering wheel, and the operation state of the electric motor is detected and detected. The operation state of the electric motor is fed back to control the operation of the electric motor to a state according to the determined control command value. Further, in this device, an attenuator or a low-pass filter for removing high frequency noise is inserted in the feedback path of the operating state of the electric motor to eliminate the influence of the noise on the operation of the electric motor.

[0003]

However, in the above-mentioned conventional device, since the steering feeling is not taken into consideration, when the steering wheel is slowly rotated while the vehicle is running at high speed, that is, Even in the area where the driver feels the steering feeling sharply, if feedback control of the electric motor is performed in the same way as in other cases, the followability of the electric motor to the control command value is emphasized too much and the steering wheel is affected by high frequency noise. The steering torque deteriorates because the assist torque for the turning operation of the electric motor fluctuates greatly, and the detection accuracy of the rotation angle and angular velocity of the electric motor deteriorates. As the steering feel deteriorates, the steering feel deteriorates, or the pulsating torque deteriorates the steering feel. There is. Further, when the control gain is constantly reduced so as to remove the influence of the high frequency noise or the control accompanied by a complicated calculation for removing the pulsating torque is performed, the electric motor follows the control command value. There is also a problem that it gets worse.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problem, and its object is to make the followability of an electric motor to a control command value determined according to a turning operation of a steering wheel unnecessary. An object of the present invention is to provide an electric power steering device that maintains a good driver's steering feeling without deteriorating.

In order to achieve the above-mentioned object, a structural feature of the present invention is that an electric motor for applying an assisting force to a turning operation of a steering handle and an electric motor according to the turning operation of the steering handle. Control command value determining means for determining a control command value for controlling the operation, state detecting means for detecting an operating state of the electric motor, and feedback of the detected operating state of the electric motor to operate the electric motor. In an electric power steering apparatus for a vehicle, comprising: a motor control means for controlling the state according to the determined control command value; a determining means for determining whether or not the traveling state of the vehicle belongs to a predetermined area; According to the judgment by means ,
It is a control mode of the electric motor by the motor control means.
Correction by the non-interference control correction value for the electric motor
The control mode changing means for controlling nothing is provided.

In this case, for example, the predetermined region is a region in which the driver feels the steering feeling sharply, and the judging means determines the traveling state of the vehicle according to the vehicle speed and the turning speed of the steering wheel. It is determined whether or not it belongs to the area.

In the present invention constructed as described above,
Due to the actions of the determination means and the control mode changing means, the electric motor is controlled by the motor control means depending on whether the traveling state of the vehicle belongs to a predetermined region (a region where the driver feels the steering feeling sharply) or not. The aspect is changed. That is, the running state of the vehicle is within the predetermined area.
If it belongs, the electric motor
By controlling the motor, when the electric motor rotates at low speed
In this case, the detection accuracy of the rotation angle and angular velocity in the
It is possible to avoid the disturbance control correction value from becoming a disturbance.
Steering by changing the assist torque of the electric motor
It is possible to avoid the deterioration of feeling. On the other hand, the running condition of the vehicle
If the condition does not belong to the predetermined area, the non-interference control compensation
By controlling the electric motor including the positive value, the control command value
The followability of the electric motor with respect to can be improved.

[0008]

[0009]

In another feature of the present invention, the above
The control mode changing means is a non-interference control for the electric motor.
Instead of the correction by the control value , the motor control means controls the electric motor according to the determination by the determination means.
It is an aspect of the present invention to control the presence / absence of correction by the pulsating torque correction value for the electric motor . According to this
When the traveling state of the vehicle belongs to the predetermined region, the pulsation torque correction value is included to control the electric motor to prevent the pulsation torque from being generated by the electric motor. It is possible to avoid the deterioration of the steering feeling. On the other hand, when the traveling state of the vehicle does not belong to the predetermined region, by controlling the electric motor not including the pulsation torque correction value, the time for calculating the pulsation torque correction value can be saved, and the control command value can be saved. The followability of the electric motor with respect to can be improved.

[0011]

DETAILED DESCRIPTION OF THE INVENTION a. First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows an electric power steering device for a vehicle according to the same embodiment.

This electric power steering apparatus is provided with a brushless motor 11 composed of a three-phase synchronous permanent magnet motor as an electric motor. Brushless motor 1
The reference numeral 1 applies an assisting force to the steering of the front wheels by the turning operation of the steering wheel 12, and drives the tie rod 13 connecting the front wheels at the outer end in the axial direction in accordance with the rotation. A steering torque sensor 15 is attached to a steering shaft 14 connected to the steering handle 12 at the upper end and to the tie rod 13 at the lower end. The sensor 15 detects the steering torque acting on the steering shaft 14. And outputs a detection signal representing the same torque. Further, the brushless motor 11 is assembled with a rotation angle sensor 16 composed of an encoder for detecting the rotation angle of the motor 11. The rotation angle sensor 16 has a phase difference of π / 2 depending on the rotation of the rotor of the brushless motor 11.
The phase pulse train signal and the zero phase pulse train signal indicating the reference rotation position are output.

The electric control device for controlling the rotation of the brushless motor 11 includes a basic assist force calculation unit 21, a return force calculation unit 22 and a calculation unit 23 for calculating the command torque T *. The basic assist force calculation unit 21 uses the steering torque and vehicle speed sensor 1 from the steering torque sensor 15.
The vehicle speed v detected by 7 is input, and the assist torque that increases as the steering torque increases and decreases as the vehicle speed v increases is calculated. The return force calculation unit 22 calculates the electric speed θ of the rotor, which will be described later, together with the vehicle speed v.
(Equivalent to the rotation angle) and the angular velocity ω are input, and the return torque corresponding to the return force of the steering shaft 14 to the basic position and the resistance force to the rotation of the steering shaft 14 is calculated based on these input values. The calculation unit 23 calculates the command torque T * by adding the assist torque and the return torque, and supplies the command torque T * to the command current determination unit 24.

The command current determining unit 24 is configured to control the command torque T.
Based on *, the two-phase command currents Id * and Iq * are calculated. The command currents Id * and Iq * respectively correspond to the d-axis in the same direction as the permanent magnet and the q-axis orthogonal thereto in the rotating coordinate system synchronized with the rotating magnetic flux generated by the permanent magnet on the rotor of the brushless motor 11. However, these command currents Id
* And Iq * are called d-axis and q-axis command currents, respectively. The command current determination unit 24 also inputs the detection values of various sensors and corrects and outputs both command currents Id * and Iq *. For example, the battery voltage value is input, and the d-axis and q-axis command currents Id * and Iq * are corrected for weakening magnetic flux control when the battery voltage value is low.

The corrected d-axis and q-axis command currents Id
* And Iq * are supplied to the arithmetic units 25 and 26, and
Reference numeral 26 calculates difference values ΔId, ΔIq by subtracting the d-axis and q-axis detection currents Id, Iq from the d-axis and q-axis command currents Id *, Iq *, respectively, and calculates the proportional-plus-integral control unit (PI control unit). ) 27, 28. Proportional integral control unit 27, 2
8 indicates that the d-axis and q-axis detection currents Id and Iq follow the d-axis and q-axis command currents Id * and Iq * by executing the operations of the following equations 1 and 2 using the difference values ΔId and ΔIq. d axis and q
The axis command voltages Vd * and Vq * are calculated respectively.

[0016]

[Formula 1] Vd * = − Kp · ΔId + Ki · ∫ΔId dt

[0017]

[Expression 2] Vq * =-Kp · ΔIq + Ki · ∫ΔIq dt

The coefficients Kp and Ki in the equations 1 and 2 are supplied from the coefficient generating section 32 to the proportional-plus-integral control sections 27 and 28, respectively, and have different values depending on the judgment result of the sensitive area judging section 31. Is set to. Sensitive area determination unit 31
Is a low region where the turning speed of the steering wheel is "0" when the vehicle is in a high-speed traveling state, that is, a region where the driver feels the steering feeling sharply (hereinafter referred to as a sensitive region).
First, it is determined whether or not the traveling state of the vehicle belongs. The sensitive area determination unit 31 stores a vehicle speed-angular velocity (steering speed) map representing the sensitive area as shown in FIG. 2 or a functional expression corresponding to the map, and stores the vehicle speed v and the vehicle speed v from the vehicle speed sensor 17. Brushless motor 11 described later
Based on the angular velocity ω, the signal indicating whether or not the traveling state of the vehicle is included in the sensitive area is output. Since the brushless motor 11 rotates in conjunction with the steering wheel 12, the angular velocity ω corresponds to the steering speed of the steering wheel 12.

The coefficient generator 32 stores two different values Kp0 and Kp1 (Kp0> Kp1) as the coefficient Kp and also two different values Ki0 and Ki1 (Ki0> Ki) as the coefficient Ki.
1) is stored, and when the sensitive area determination unit 31 determines that the traveling state of the vehicle belongs to the sensitive area, the proportional integral control units 27 and 2 are set to Kp1 and Ki1 as the coefficients Kp and Ki.
Supply to 8 respectively. If the sensitive area determination unit 31 determines that the traveling state of the vehicle does not belong to the sensitive area, Kp0 and Ki0 are supplied to the proportional-plus-integral control units 27 and 28 as the coefficients Kp and Ki, respectively.

The d-axis and q-axis command voltages Vd *, Vq * are calculated by the non-interference control correction value calculation section 33 and the calculation sections 34, 35.
2 after being corrected to the d-axis and q-axis correction command voltages Vd * 'and Vq *'
It is supplied to the three-phase / three-phase coordinate conversion unit 36. The non-interference control correction value calculation unit 33 calculates the d-axis and q-axis command voltage Vd based on the d-axis and q-axis detection currents Id and Iq and the angular velocity ω of the rotor.
*, Vq * non-interference control correction value ω ・ La ・ Iq, −ω ・
Calculate (φa + La · Id). The inductance La and the magnetic flux φa are predetermined constants. The arithmetic units 34 and 35 subtract the non-interference control correction values ω · La · Iq and −ω · (φa + La · Id) from the d-axis and q-axis command voltages Vd * and Vq *, respectively, to obtain the d-axis and q-axis. Axis correction command voltage Vd * '= Vd * -ω ・ La ・ Iq, Vq *' = Vq * + ω ・ (φa + La
-Id) is calculated and supplied to the two-phase / three-phase coordinate conversion unit 36.

The two-phase / three-phase coordinate conversion unit 36 has a d-axis and a q-axis.
Axis correction command voltages Vd * ', Vq *' are converted to three-phase command voltages Vu *, Vv
*, Vw * converted to the same three-phase command voltage Vu *, Vv
*, Vw * are supplied to the PWM voltage generator 37. The PWM voltage generator 37 outputs the PWM control voltage signals UU, VU, WU corresponding to the three-phase command voltages Vu *, Vv *, Vw * to the inverter circuit 3
Output to 8. The inverter circuit 38 includes a three-phase excitation voltage signal V corresponding to the PWM control voltage signals UU, VU, WU.
u, Vv, Vw are generated to generate the same excitation voltage signals Vu, Vv, Vw
Are supplied to the brushless motor 11 via the three-phase exciting current paths. Current sensors 41 and 42 are provided in two of the three-phase exciting current paths, and the current sensors 41 and 4 are provided.
2 is a three-phase exciting current I for the brushless motor 11.
Two exciting currents Iu and Iw of u, Iv, and Iw are detected and output to the three-phase / two-phase coordinate conversion unit 43. This 3 phase / 2
The phase coordinate converter 43 is also supplied with the exciting current Iv calculated by the calculator 44 based on the detected exciting currents Iu and Iw. The three-phase / two-phase coordinate conversion unit 43 converts these three-phase detection exciting currents Iu, Iv, Iw into two-phase d-axis and q-axis detection currents Id, Iq.

The two-phase pulse train signal and the zero-phase pulse train signal from the rotation angle sensor 16 are continuously supplied to the electrical angle converter 45 at a predetermined sampling cycle. The electrical angle conversion unit 45 calculates the electrical angle θ of the rotor of the brushless motor 11 with respect to the stator based on the pulse train signals, and supplies the calculated electrical angle θ to the angular velocity conversion unit 46. The angular velocity conversion unit 46 differentiates the electrical angle θ to calculate the angular velocity ω of the rotor with respect to the stator. It is assumed that the positive angular velocity ω represents rotation of the rotor in the positive direction, and the negative angular velocity ω represents rotation of the rotor in the negative direction. Also, the electrical angle θ calculated by the electrical angle conversion unit 45
Since the error includes an error due to the sampling period and the resolution of the rotation angle sensor 16, both errors may be corrected using the angular velocity ω calculated by the angular velocity conversion unit 46.

The electric control device having the above-mentioned structure is provided with various sensors 1.
4, 16, 17, 41, 42 and the inverter circuit 38 are included in the electronic circuit unit, and the circuit in the unit may be configured by a hard circuit that performs digital processing. Is composed of a microcomputer device. Each function of each part 21 to 28, 31 to 37, 43 to 46 in the electronic circuit unit is realized by the program processing. Therefore, various sensors 14, 16, 17, 41,
The detection signal from 42 is input to each part of the electronic circuit unit in the form of a detection value sampled at a predetermined sampling rate (sampling period).

Next, the operation of the first embodiment configured as described above will be described. When the driver turns the steering wheel 12, the turning operation is transmitted to the tie rod 13 and the front wheel is steered by the movement of the tie rod 13 in the axial direction. At the same time, the steering torque sensor 15 detects the steering torque applied to the steering shaft 14, and the brushless motor 11 is servo-controlled by the electric control device to drive the tie rod 13 with an assist torque corresponding to the steering torque. The front wheels are steered while being assisted by the driving force of the brushless motor 11.

In the servo control by this electric control device, the basic assist force calculating unit 21, the returning force calculating unit 22 and the calculating unit 23 are based on the detected steering torque, the vehicle speed v, the electrical angle θ and the angular velocity ω of the rotor. The command current determining unit 24 determines the d-axis and q-axis command currents Id *, Iq * based on the command torque T * and other various sensor values, as well as calculating the command torque T *. Then, the calculation unit 25,
26, proportional-plus-integral control units 27 and 28, 2-phase / 3-phase coordinate conversion unit 36, PWM voltage generation unit 37, and inverter circuit 38
Are the current sensors 41, 42 and the three-phase / two-phase coordinate conversion unit 43.
Using the d-axis and q-axis detection currents Id, Iq fed back by the calculation unit 44, the both detection currents Id, Iq are equal to the both command currents Id *, Iq *, that is, the brushless motor 11 has the command torque. The brushless motor 11 is controlled to rotate at a torque equal to T * (the corrected torque when the command torque T * is corrected by various sensor values). In this case, the non-interference control correction value calculation unit 33 and the calculation units 34, 35 use the proportional-plus-integral control unit 2 in order to cancel out the speed electromotive force that interferes between the d and q axes.
The d-axis and q-axis command voltages Vd * and Vq * from 7, 28 are corrected.

During the servo control as described above, the proportional-plus-integral control units 27 and 28 receive the difference value ΔId from the arithmetic units 25 and 26,
The command voltages Vd * and Vq * are obtained by executing the operations of the above-mentioned equations 1 and 2 using ΔIq and the coefficients Kp and Ki from the coefficient generator 32.
To calculate. On the other hand, the sensitive area determination unit 31 determines whether or not the traveling state of the vehicle belongs to the sensitive area based on the vehicle speed v and the angular velocity ω (steering speed). The coefficients Kp and Ki used for the calculation are supplied to the proportional-plus-integral control units 27 and 28. In this case, the values Kp1 and Ki1 are supplied as the coefficients Kp and Ki when the running state of the vehicle belongs to the sensitive region, and the values Kp0 and K when the running state of the vehicle does not belong to the sensitive region.
i0 is supplied as the coefficients Kp and Ki. These values Kp1,
Ki1, Kp0, and Ki0 have a relationship of Kp0> Kp1 and Ki0> Ki1.

Therefore, when the running state of the vehicle belongs to the sensitive area, the control gain for the brushless motor 11 is set low, and the variation of the assist torque by the brushless motor 11 due to disturbance such as high frequency noise occurs. Since it becomes smaller, the driver's steering feeling becomes good in the same-sensitivity region. Further, when the running state of the vehicle does not belong to the sensitive area, the brushless motor 11
The control gain for the brushless motor 11 is set high, and the followability of the brushless motor 11 with respect to the command torque T * becomes good.

In the first embodiment, the control gain for the brushless motor 11 is controlled to be switched between two types, a sensitive region and a region other than the sensitive region. However, the region where the steering feeling is most sensitive is sensed. The control gain may be switched to three or more types by determining three or more types of regions such as a region where the same feeling is sharply felt and a region other than that. In this case, a plurality of regions may be provided outside the sensitive region as shown by the broken line in FIG. 2, and the control gain may be reduced toward the region where the steering feeling is easily felt.

B. Second Embodiment Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 schematically shows an electric power steering device according to the second embodiment.

In the second embodiment, the coefficient generator 32 in the first embodiment is deleted, and the determination result by the sensitive area determiner 31 is used as the non-interference control correction value calculator 33.
I am trying to lead to. Non-interference control correction value calculation unit 33
Is d based on the determination result by the sensitive area determination unit 31.
Axis and q axis non-interference control correction value ω ・ La ・ Iq, −ω ・ (φ
It controls whether or not (a + La · Id) is added to the d-axis and q-axis command voltages Vd * and Vq * from the proportional-plus-integral control units 27 and 28. In this case, the coefficients Kp and Ki in the calculation of the d-axis and q-axis command voltages Vd * and Vq * in the proportional-plus-integral control units 27 and 28 are predetermined constants.

Specifically, when the running state of the vehicle belongs to the sensitive area, d by the non-interference control correction value calculation unit 33 is set.
Axis and q axis non-interference control correction value ω ・ La ・ Iq, −ω ・ (φ
The calculation of (a + La · Id) is prohibited and the two non-interference control correction values are set to “0” and “0”. As a result, the d-axis and q-axis correction command voltages Vd * 'and Vq *' supplied to the 2-phase / 3-phase coordinate conversion unit 36 are converted to the d-axis and q-axis command voltages Vd *, V.
It is equal to q * and is expressed by the following equations 3 and 4.
Actually, the subtraction processing by the arithmetic units 34 and 35 is also unnecessary.

[0032]

[Formula 3] Vd * ′ = Vd * = − Kp · ΔId + Ki · ∫ΔId dt

[0033]

[Expression 4] Vq * '= Vq * =-Kp · ΔIq + Ki · ∫ΔIq dt

On the other hand, when the running state of the vehicle does not belong to the sensitive area, the non-interference control correction value calculation unit 33 calculates the non-interference control correction values ω · La · Iq, −ω · for the d-axis and the q-axis. (φa + La
Id) is calculated, and the d-axis and q-axis command voltages Vd from the proportional-plus-integral control units 27 and 28 are calculated by the computing units 34 and 35.
* And Vq * are added respectively. As a result, the d-axis and q-axis correction command voltages Vd * 'and Vq *' supplied to the two-phase / three-phase coordinate conversion unit 36 are represented by the following equations 5 and 6.

[0035]

[Equation 5] Vd * '= Vd * -ω ・ La ・ Iq = -Kp ・ ΔId + Ki ・ ∫ΔId dt-ω ・ La ・ Iq

[0036]

[Equation 6] Vq * '= Vq * + ω ・ (φa + La ・ Id) = -Kp · ΔIq + Ki · ∫ ΔIq dt + ω · (φa + La · Id)

As described above, in the second embodiment, the non-interference control correction values ω · La · Iq and −ω · (φa + La · Id) are not included when the running state of the vehicle belongs to the sensitive area. The brushless motor 11 is controlled by. Further, when the traveling state of the vehicle does not belong to the sensitive area, the brushless motor 11 is controlled by including the non-interference control correction values ω · La · Iq and −ω · (φa + La · Id).

When the electrical angle θ is close to "0" and its absolute value | θ | is small, the rotation angle sensor 16
The electrical angle θ may include a large error due to an error due to the resolution and the sampling period, and the electrical angle θ slightly fluctuates in the vicinity of “0”. At the same time, the angular velocity ω obtained by differentiating the electrical angle θ May include a large error. On the other hand, the non-interference control correction value ω · La · Iq, −ω · (φa +
The angular velocity ω of the brushless motor 11 is used in the calculation of La · Id), and as described above, when a large error is included in the electrical angle θ and the angular velocity ω, the non-interference control correction value ω · La
・ Iq, -ω ・ (φa + La ・ Id) becomes a disturbance, and the d-axis and q-axis correction command voltages Vd * ', Vq * including the non-interference control correction value ω ・ La ・ Iq, -ω ・ (φa + La ・ Id) 'May cause hunting or may not be stable.

As a result, according to the second embodiment, when the running state of the vehicle belongs to the sensitive area, the non-interference control correction values ω · La · Iq, −ω · (φa + La · Id) as described above. )
Since the brushless motor 11 is controlled without including, the deterioration of the steering feeling due to the hunting and instability of the d-axis and q-axis correction command voltages Vd * ′ and Vq * ′ can be avoided. Further, in this case, the non-interference control correction value ω · La
Since the calculation related to Iq, −ω · (φa + La · Id) becomes unnecessary, the calculation efficiency can be improved. When the traveling state of the vehicle does not belong to the sensitive area, the brushless motor 11 is controlled by including the non-interference control correction values ω · La · Iq and −ω · (φa + La · Id) as described above. The followability of the brushless motor 11 to the command torque T * (d-axis and q-axis correction command currents Id *, Iq * ', d-axis and q-axis command voltages Vd *, Vq *) can be improved.

In the second embodiment, the coefficient K used for the calculation in the proportional-plus-integral control units 27 and 28.
Although p and Ki are constants, as in the case of the first embodiment, the coefficients Kp and Ki are made different depending on whether the traveling state of the vehicle belongs to the sensitive region or otherwise. Good. In this case, the coefficient generator 3 of the first embodiment described above
The coefficients Kp and Ki determined in 2 are set to the proportional-integral control unit 27,
28 may be supplied.

C. Third Embodiment Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 schematically shows an electric power steering device according to the third embodiment.

In the third embodiment, a pulsating torque correction value calculation unit 47 is provided in place of the coefficient generation unit 32 in the first embodiment, and the calculation unit 47 determines the determination result by the sensitive area determination unit 31. The pulsation torque correction value Iqr is calculated according to The pulsation torque correction value Iqr is calculated by the calculation unit 4
8 is supplied to the calculation unit 48, and the calculation unit 48 corrects the q-axis command current Iq * by subtracting the pulsating torque correction value Iqr from the q-axis command current Iq * from the command current determination unit 24.
Supply to 6. In this case, the proportional-plus-integral control unit 27,
The coefficients Kp and Ki in the calculation of the d-axis and q-axis command voltages Vd * and Vq * at 28 are predetermined constants.

The pulsation torque correction value calculation unit 47, in addition to the above determination result, receives the electrical angles θ and 3 from the electrical angle conversion unit 45.
When the q-axis detection current Iq from the two-phase / two-phase coordinate conversion unit 43 is input and the traveling state of the vehicle belongs to the sensitive area,
The pulsation torque correction value Iqr is calculated by executing the calculation of the following Expression 7. On the other hand, when the traveling state of the vehicle does not belong to the sensitive area, the pulsating torque correction value Iqr is set to "0".

[0044]

[Equation 7] Iqr = Kro · Fo (θ) / Kt + Kr1 · F1 (θ) · Iq
/ Kt-Kro ・ Kr1 ・ Fo (θ) ・ F1 (θ) / Kt ²

The torque coefficient Kt and the pulsating torque coefficients Kro and Kr1 in the equation 7 are constants which are obtained by an experiment and stored in advance in the pulsating torque correction value calculating section 47.
Further, the pulsating torque functions Fo (θ) and F1 (θ) are functions that are confirmed by experiments and are defined in the form of a table or a functional formula in the pulsating torque correction value calculation unit 47 and are stored in advance.

The pulsation torque correction value Iqr will be briefly described. The pulsating torque has a component (cogging torque) Kro · Fo (θ) when the q-axis current (torque current) Iq is “0” and a component (ripple torque) Kr1 · F1 (θ) · due to the q-axis current Iq. Iq and. Here, when both components Kro · Fo (θ) and Kr1 · F1 (θ) · Iq are used, the pulsating torque ΔT (θ) is expressed by the following equation 8.

[0047]

[Equation 8] ΔT (θ) = Kro · Fo (θ) + Kr1 · F1 (θ) · Iq

First, considering the compensation for the cogging torque Kro · Fo (θ), the output torque T (θ) is given by
Therefore, the cogging torque Kro · Fo (θ) can be removed by giving the current Iqo shown in the following formula 10 instead of the torque current Iq.

[0049]

[Equation 9] T (θ) = Kt · Iq + Kro · Fo (θ)

[0050]

[Equation 10] Iqo (θ) = Iq−Kro · Fo (θ) / Kt

Next, it will be considered to remove the ripple torque Kr1 · F1 (θ) · Iq. In this case, the output torque T (θ) is expressed by the following equation 11 using the current Iqo. Therefore, by giving the current Iq1 shown in the following equation 12 instead of the current Iqo, the relation of the position of the rotor is shown. Without pulsating torque.

[0052]

[Equation 11] T (θ) = Kt ・ Iqo (θ) + Kr1 ・ F1 (θ) ・ Iqo (θ) = Kt ・ Iqo (θ) ・ {1 + Kr1 ・ F1 (θ) / Kt}

[0053]

[Equation 12] Iq1 (θ) = Iqo (θ) / {1 + Kr1 · F1 (θ) / Kt} ≒ Iqo (θ) ・ {1-Kr1 ・ F1 (θ) / Kt}

Then, by substituting Iqo (θ) shown in the above equation 10 into this equation 12, the following equation 13 is derived.

[0055]

[Equation 13] Iq1 (θ) = Iq−Kro · Fo (θ) / Kt−Kr1 ·
F1 (θ) ・ Iq / Kt ＋ Kro ・ Kr1 ・ Fo (θ) ・ F1 (θ) / Kt ²

Therefore, as the pulsating torque correction value for correcting the command current Iq *, the pulsating torque correction value Iqr shown in the equation 7 is derived. The pulsation torque correction value I
A detailed explanation of qr is introduced in the paper "To improve the torque ripple of the SR motor" in the Tokai Branch Joint Conference of the Electrical Association of Japan in 1988.

As a result, according to the third embodiment, when the running state of the vehicle belongs to the sensitive area, the brushless motor 11 is controlled by including the pulsating torque correction value Iqr. Generation of pulsating torque can be prevented, and deterioration of steering feeling due to variation of assist torque by the motor 11 can be avoided. on the other hand,
When the running state of the vehicle does not belong to the sensitive area, the brushless motor 11 is controlled without including the pulsation torque correction value Iqr, so that the pulsation torque correction value calculation unit 47 does not need to calculate the pulsation torque correction value Iqr. . In addition, the calculation unit 4
The calculation by 8 is also substantially unnecessary. Therefore, in this case, the time for calculating the pulsation torque correction value Iqr can be saved, and the followability of the brushless motor 11 to the command torque T * (command current Id *, Iq *) can be improved.

In the third embodiment as well, as in the second embodiment, the proportional-plus-integral control units 27, 2 are also provided.
Although the coefficients Kp and Ki used for the calculation in 8 are set to constants, the coefficient Kp depends on whether the running state of the vehicle belongs to the sensitive region or not, as in the case of the first embodiment. , Ki may be different. Also in this case, the coefficients Kp and Ki determined by the coefficient generator 32 of the first embodiment may be supplied to the proportional-plus-integral controllers 27 and 28.

Further, in the third embodiment, regarding the non-interference control, the control mode is not distinguished between the case where the running state of the vehicle belongs to the sensitive region and the case where the running state of the vehicle does not belong to the sensitive region. However, similar to the second embodiment. In addition, when the traveling state of the vehicle belongs to the sensitive region, the correction by the non-interference control correction value may not be performed, and the correction by the non-interference control correction value may be performed only when the traveling state does not belong to the same sensitive region. Further, the non-interference control may be omitted depending on the degree of demand.

D. Fourth Embodiment Next, a fourth embodiment of the present invention will be described with reference to the drawings. The fourth embodiment is configured almost the same as the third embodiment, but the calculation content in the pulsation torque correction value calculation unit 47 is different from that of the third embodiment.

In this case, the pulsating torque correction value calculation unit 47
Calculates the pulsating torque correction value Iqr based on the determination result of the sensitive area determination unit 31 and the angular velocity ω. When the running state of the vehicle belongs to the sensitive region, if the absolute value | ω | of the angular velocity ω is equal to or greater than a predetermined small value ε (| ω | ≧ ε), the pulsation torque correction value Iqr is expressed by the following formula 14 It is calculated by executing the operation of.

[0062]

[Equation 14] Iqr = -a · sign (ω)

However, in the equation 14, a is a positive constant, and sign (ω) is a function which becomes “+1” when the angular velocity ω is positive and “−1” when the angular velocity ω is negative. Further, even when the traveling state of the vehicle belongs to the sensitive region, the absolute value | ω | of the angular velocity ω is less than the predetermined minute value ε (| ω | <
If ε), the pulsation torque correction value Iqr is set to "0". This is because when the absolute value | ω | of the angular velocity ω becomes a small value near “0”, the angular velocity ω may fluctuate around “0” and the pulsating torque correction value Iqr may cause hunting. This is to avoid.

On the other hand, when the running state of the vehicle does not belong to the sensitive area, the pulsating torque correction value Iqr is set to "0".

Therefore, in the fourth embodiment, when the steering wheel 12 is being turned, and the running state of the vehicle is in the sensitive area, the command current determining section 24 outputs the current. The command current Iq * is calculated by the calculation unit 4
It is corrected to Iq * −Iqr (= Iq * + a · sign (ω)) at 8 and supplied to the calculation unit 26. By the way, in this type of control, the correction is performed by a.sign (ω), but this correction is executed to compensate the friction of the steering system. This makes it difficult for the driver to feel a dragging frictional force that occurs during steering, and thus it is possible to prevent deterioration of the steering feeling. On the other hand, when the traveling state of the vehicle does not belong to the sensitive region or the steering handle 12 is held, the brushless motor 11 is controlled without including the pulsation torque correction value Iqr. 47
Does not need to calculate the pulsation torque correction value Iqr. Further, the calculation by the calculation unit 48 is substantially unnecessary. Therefore, in this case, the time for calculating the pulsation torque correction value Iqr can be saved, and the command torque T * (command current Id
The followability of the brushless motor 11 with respect to *, Iq *) can be improved.

In the fourth embodiment as well, as in the case of the first embodiment, the coefficient K is determined depending on whether the traveling state of the vehicle belongs to the sensitive area or not.
The p and Ki may be different. Regarding the non-interference control, as in the second embodiment, the presence or absence of the correction based on the non-interference control correction value may be switched depending on whether the traveling state of the vehicle belongs to the sensitive region or not. . Further, also in this case, the non-interference control may be omitted depending on the degree of demand.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an electric power steering device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram for explaining a sensitive area and other areas.

FIG. 3 is a schematic diagram of an electric power steering device according to a second embodiment of the present invention.

FIG. 4 is a schematic diagram of an electric power steering device according to third and fourth embodiments of the present invention.

[Explanation of symbols]

11 ... Brushless motor, 12 ... Steering handle, 15 ...
Steering torque sensor, 16 ... Rotation angle sensor, 17 ... Vehicle speed sensor, 24 ... Command current determination unit, 27, 28 ... Proportional and integral control unit (PI control unit), 31 ... Sensitive area determination unit, 32 ... Coefficient generation unit, 33 ... Non-interference control correction value calculation unit, 36 ... Two-phase / 3-phase coordinate conversion unit, 37 ... PWM voltage generation unit, 38 ... Inverter circuit, 41, 42 ... Current sensor, 43 ... Three phases /
Two-phase coordinate conversion unit, 45 ... Electrical angle conversion unit, 46 ... Angular velocity conversion unit, 47 ... Pulsation torque correction value calculation unit, 48 ... Calculation unit.

Claims (2)

(57) [Claims] 1. An electric motor for applying an assisting force to a turning operation of a steering wheel, and a control for determining a control command value for controlling the operation of the electric motor according to the turning operation of the steering wheel. Command value determining means, state detecting means for detecting an operating state of the electric motor, and feedback of the detected operating state of the electric motor to control the operation of the electric motor to a state according to the determined control command value. An electric power steering device for a vehicle , comprising: a motor control unit that determines whether the traveling state of the vehicle belongs to a predetermined region; and the motor control unit according to the determination by the determination unit.
Is a control mode of an electric motor according to
An electric power steering apparatus for a vehicle, comprising: a control mode changing unit that controls the presence / absence of correction by a non-interference control correction value . 2.Assists in turning the steering wheel
An electric motor that applies power, In response to the turning operation of the steering handle, the electric motor
Control command value that determines the control command value for controlling the operation
Decision means, State detection means for detecting the operating state of the electric motor, Feedback of the detected operating state of the electric motor
The operation of the electric motor according to the determined control command value.
And a motor control means for controlling the closed state Vehicle power
In the dynamic power steering device,Determine if the driving state of the vehicle belongs to a predetermined area
Determination means, According to the judgment by the judgment means, the motor control means
Is a control mode of an electric motor according to
Control mode to control the presence / absence of correction by the pulsation torque correction value
It is characterized in that the change means is provided. Vehicle electric power
-Steering device.