JP2008154308A - Controller of motor-driven power steering system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize low noise in operation of a motor-driven power steering system. <P>SOLUTION: A non-interference control section 13 obtains an interlinked magnetic flux Ψ<SP>*</SP>, a d-axis inductance Ld<SP>*</SP>and a q-axis inductance Lq<SP>*</SP>from ϕ map 131, an Ld map 132 and an Lq map 133 on the basis of a motor electric angle θ, a d-axis detection current id and a q-axis detection current iq. The non-interference control section 13 corrects a d-axis command voltage vd<SP>*</SP>and a q-axis command voltage vq<SP>*</SP>on the basis of the interlinked magnetic flux Ψ<SP>*</SP>, d-axis inductance Ld<SP>*</SP>and q-axis Lq<SP>*</SP>obtained in this way so that an interference component between d- and q-axes can be removed from the d-axis command voltage vd<SP>*</SP>and the q-axis command voltage vq<SP>*</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electric power steering control device, and more particularly to an electric power steering control device that assists a steering operation of a steering wheel of a vehicle with a brushless motor.

  Conventionally, in electric power steering (EPS), there is a problem that noise is generated when the motor is operated. Causes of noise include, for example, uneven motor torque and vibrations of mechanical components such as gears.

By the way, when controlling a three-phase brushless motor, instead of controlling with three phases of UVW, the three phases of UVW are coordinate-converted into two-axis coordinates of d-axis and q-axis, and two of d-axis and q-axis are converted. It is common to control by phase. When the motor is regarded as a dq model, its electrical equation is expressed as follows.

  As shown in the above formula, the d-axis current includes a component (interference term) that depends on the q-axis current, and similarly, the q-axis current has a component (interference term) that depends on the d-axis current. As a result, the d-axis current and the q-axis current cannot be controlled independently. Therefore, in order to control the d-axis current and the q-axis current independently, control of subtracting these interference terms in advance by feedforward control is conventionally performed. Such control is called non-interference control.

As a conventional apparatus that performs non-interference control as described above, there is an apparatus disclosed in Patent Document 1. In this conventional apparatus, the non-interference control as described above is performed in the non-interference control correction value calculation unit. Specifically, in the non-interference control correction value calculation unit, ω · Lq · iq is calculated as a non-interference control correction value for correcting the d-axis command voltage vd ^* , and the q-axis command voltage vq ^* is corrected. -Ω (Ψ + Ld · id) is calculated as the non-interference control correction value of. Then, the d-axis command voltage vd ^* and the q-axis command voltage vq ^* are corrected based on the calculated non-interference control correction value (see FIG. 6).
JP 2001-18822 A

  By the way, in the conventional non-interference control as described above, Ld, Lq, and Ψ are treated as constant constants. In practice, however, these values pulsate or fluctuate depending on the current flowing through the motor and the angle of the rotor. Therefore, the operating range is low to high and low to high, as in EPS motors. When using a wide motor, there is a problem that the influence on noise due to such pulsation or fluctuation cannot be ignored.

  That is, when Ld, Lq, and Ψ are treated as constant constants, torque pulsation occurs due to the pulsation or fluctuation, and as a result, the current fed back (current flowing through the motor) fluctuates, and the fluctuation of this current becomes Ld , Lq, and Ψ, which lead to fluctuations in the actual values, thereby creating a vicious circle in which further torque pulsations are caused.

  Therefore, the present invention performs the operation of the electric power steering by performing the non-interference control in consideration of the fluctuation of the d-axis inductance Ld, the q-axis inductance Lq, and the linkage flux Ψ depending on the current flowing through the motor and the rotor angle. The objective is to reduce noise during the operation.

  In order to achieve the above object, the present invention employs the following configuration.

  The electric power steering control device of the present invention is an electric power steering control device that assists a steering operation of a steering wheel of a vehicle with a brushless motor. The electric power steering control device performs non-interference control for correcting the d-axis command voltage and the q-axis command voltage so that the interference component between the d-axis and the q-axis is removed from the d-axis command voltage and the q-axis command voltage. And an angle detection means for detecting the angle of the rotor of the brushless motor and / or a current detection means for detecting the current flowing through the brushless motor. The non-interference control unit calculates an interference component between the d-axis and the q-axis based on the angle detected by the angle detection unit and / or the current detected by the current detection unit.

  The non-interference control unit may calculate a correction value for correcting the q-axis command voltage based on a φ map indicating the relationship between the rotor angle of the brushless motor and the flux linkage.

  Further, the non-interference control unit calculates a correction value for correcting the q-axis command voltage based on the Ld map indicating the relationship between the rotor angle of the brushless motor and the current flowing through the brushless motor and the d-axis inductance. May be.

  Further, the non-interference control unit calculates a correction value for correcting the d-axis command voltage based on the Lq map indicating the relationship between the rotor angle of the brushless motor and the current flowing through the brushless motor and the q-axis inductance. May be.

  In the present invention configured as described above, by performing non-interference control in consideration of fluctuations in the d-axis inductance Ld, the q-axis inductance Lq, and the linkage flux Ψ depending on the current flowing through the motor and the angle of the rotor, Noise during operation of the electric power steering can be suppressed.

  Hereinafter, an electric power steering control device according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the electric power steering control device of the present embodiment includes a d-axis PI control unit 11.
, Q-axis PI control unit 12, non-interference control unit 13, 2-phase / 3-phase conversion unit 14, PWM command value calculation unit 15, D / T compensation unit 16, PWM generation unit 17, inverter 18, current sensor 19, brushless A motor 20, a rotation angle sensor 22, an angle conversion unit 23, and a three-phase / two-phase conversion unit 21 are provided. However, since the configuration of the part for calculating the d-axis command current and the q-axis command current according to the steering operation of the steering wheel of the vehicle is a known technique (see, for example, Patent Document 1 described above), illustration is omitted. .

First, the d-axis command current id ^* and the q-axis command current iq ^* are determined based on the steering torque generated by the turning operation of the steering handle. The d-axis command current id ^* and the q-axis command current iq ^* are respectively applied to the d-axis in the same direction as the permanent magnet on the rotor and the q-axis orthogonal thereto in the rotating coordinate system synchronized with the rotor of the brushless motor 20. Correspond.

The d-axis PI control unit 11 receives a difference value Δid obtained by subtracting the d-axis detection current id output from the three-phase / two-phase conversion unit 21 from the d-axis command current id ^* . Similarly, the q-axis PI control unit 12 receives a difference value Δiq obtained by subtracting the q-axis detection current id output from the three-phase / two-phase conversion unit 21 from the q-axis command current iq ^*. The

The d-axis PI control unit 11 calculates the d-axis command voltage vd ^* based on the difference value Δid so that the d-axis detection current id follows the d-axis command current id ^* . Similarly, the q-axis PI control unit 12 calculates the q-axis command voltage vq ^* based on the difference value Δiq so that the q-axis detection current iq follows the q-axis command current iq ^* .

The d-axis command voltage vd ^* calculated by the d-axis PI control unit 11 and the q-axis command voltage vq ^* calculated by the q-axis PI control unit 12 are input to the non-interference control unit 13.

The non-interference control unit 13 removes the interference component between the d-axis and q-axis (that is, the speed electromotive force that interferes between the d-axis and q-axis ⁾ from the d-axis command voltage vd ^* and the q-axis command voltage vq ^*. The input d-axis command voltage and q-axis command voltage are corrected. Specifically, the non-interference control unit 13 determines the motor electrical angle θ output from the angle conversion unit 23, the d-axis detection current id output from the 3-phase / 2-phase conversion unit 21, and the q-axis detection current iq. Based on this, the correction values for correcting the d-axis command voltage vd ^* and the q-axis command voltage vq ^* are calculated, and the d-axis command voltage vd ^* and the q-axis command voltage vq ^* are respectively calculated using these correction values. It corrects and outputs d-axis correction command voltage vd ^* _new and q-axis correction command voltage vq ^* _new. Details of the non-interference control unit 13 will be described later.

The d-axis correction command voltage vd ^* _new and the q-axis correction command voltage vq ^* _new output from the non-interference control unit 13 are input to the 2-phase / 3-phase conversion unit 14.

The two-phase / three-phase converter 14 converts the d-axis correction command voltage vd ^* _new and the q-axis correction command voltage vq ^* _new into three-phase command voltages vu ^* , vv ^* , vw ^* . These three-phase command voltages vu ^* , vv ^* , vw ^* are input to the PWM command value calculation unit 15.

The PWM command value calculation unit 15 calculates and outputs a PWM command value corresponding to the three-phase command voltages vu ^* , vv ^* and vw ^* .

  The D / T compensator 16 performs dead time compensation control for preventing torque pulsation due to dead time in inverter control based on the motor electrical angle θ output from the angle converter 23.

The PWM generator 17 generates a P based on the PWM command value corrected by the D / T compensator 16.
A WM signal is generated and output to the inverter 18.

  The inverter 18 generates three-phase excitation voltage signals vu, vv, vw corresponding to the PWM signal output from the PWM generation unit 17 and outputs these excitation voltage signals vu, vv, vw to the three-phase excitation current path. Are respectively supplied to the brushless motor 20.

  The current sensor 19 detects and outputs the currents iu, iv, and iw (that is, the current that flows through the brushless motor 20) that flow through the three-phase excitation current paths to the three-phase / two-phase conversion unit 21, respectively. The current sensor 19 does not need to actually detect all the currents iu, iv, iw flowing through the three-phase excitation current paths, and only detects any two of the currents iu, iv, iw. Then, the remaining one can be calculated.

  The three-phase / two-phase converter 21 converts the currents iu, iv, iw detected by the current sensor 19 into a d-axis detection current id and a q-axis detection current iq.

  The brushless motor 20 is an electric motor composed of a three-phase synchronous permanent magnet motor. The brushless motor 20 is driven based on the three-phase excitation voltage signals vu, vv, vw output from the inverter 18 and applies assist force to the turning operation of the steering handle of the vehicle.

  The rotation angle sensor 22 detects the rotation angle (motor mechanical angle) of the rotor of the brushless motor 20.

  The angle conversion unit 23 converts the motor mechanical angle detected by the rotation angle sensor 22 into a motor electrical angle θ according to the number of pole pairs of the brushless motor 20.

As described above, in the electric power steering control device of the present embodiment, the d-axis detection current id and the q-axis detection current iq output from the three-phase / two-phase conversion unit 21 are the d-axis command current id ^* and the q-axis. By performing feedback control so as to be equal to the command current iq ^* , the brushless motor 20 is controlled to rotate at a desired torque.

  The electric brushless motor control device shown in FIG. 1 may be housed in an electronic circuit unit except for the inverter 18, the current sensor 19, the brushless motor 20, and the rotation angle sensor 22. And each part of an electric brushless motor control apparatus may be implement | achieved by the hardware circuit, and may be implement | achieved by the program processing by a microcomputer.

  Next, details of the non-interference control unit 13 will be described.

  FIG. 2 is a diagram illustrating the principle of non-interference control in the non-interference control unit 13, and FIG. 3 is a diagram illustrating a schematic configuration of the non-interference control unit 13.

  As described above, in the conventional non-interference control, the flux linkage Ψ, the d-axis inductance Ld, and the q-axis inductance Lq are treated as constant constants. On the other hand, in the non-interference control unit 13 of the present embodiment, the flux linkage Ψ is determined according to the motor electrical angle θ, and the d-axis inductance Ld is determined according to the combination of the motor electrical angle θ and the d-axis detection current id. The q-axis inductance Lq is determined according to the combination of the motor electrical angle θ and the q-axis detection current iq.

The φ map 131 is information indicating the relationship between the motor electrical angle θ and the flux linkage Ψ ^* . FIG. 4 shows a specific example of the φ map 131.

The Ld map 132 is information indicating the relationship between the combination of the motor electrical angle θ and the d-axis detection current id and the d-axis inductance Ld ^* . FIG. 5 shows a specific example of the Ld map 132.

The Lq map 133 is information indicating the relationship between the combination of the motor electrical angle θ and the q-axis detection current iq and the q-axis inductance Lq ^* . A specific example of the Lq map 133 is the same as that of the Ld map 132, and is not shown.

The non-interference control unit 13 generates a d-axis based on the motor electrical angle θ output from the angle conversion unit 23, the d-axis detection current id and the q-axis detection current iq output from the three-phase / 2-phase conversion unit 21. Correction values for correcting the command voltage vd ^* and the q-axis command voltage vq ^* are respectively calculated. Specifically, the non-interference control unit 13 refers to the Lq map 133 and calculates ω · Lq ^* · iq, which is a correction value for correcting the d-axis command voltage vd ^* . Then, the correction value is subtracted from the d-axis command voltage vd ^* output from the d-axis PI control unit 11 and output as a d-axis correction command voltage vd ^* _new. Similarly, the non-interference control unit 13 refers to the φ map 131 and the Ld map 132, and calculates ω (Ψ ^* + Ld ^* · id), which is a correction value for correcting the q-axis command voltage vq ^* . Then, this correction value is added to the q-axis command voltage vq ^* output from the q-axis PI control unit 12, and the result is output as the q-axis correction command voltage vq ^* _new. The angular velocity ω is calculated by differentiating the motor electrical angle θ.

  As described above, according to the present embodiment, the non-interference control unit 13 considers fluctuations in the d-axis inductance Ld, the q-axis inductance Lq, and the linkage flux Ψ depending on the current flowing through the motor and the rotor angle. Since non-interference control is performed, noise during operation of the electric power steering is suppressed.

  In this embodiment, the linkage flux Ψ is determined according to the motor electrical angle θ, the d-axis inductance Ld is determined according to the combination of the motor electrical angle θ and the d-axis detection current id, and the q-axis inductance is determined. Although the example in which Lq is determined according to the combination of the motor electrical angle θ and the q-axis detection current iq has been described, the present invention is not limited to this. That is, one or two of the flux linkage Ψ, the d-axis inductance Ld, and the q-axis inductance Lq may be treated as a constant. For example, the flux linkage Ψ may be determined according to the motor electrical angle θ, and the correction value may be calculated by regarding the remaining d-axis inductance Ld and q-axis inductance Lq as constant constants. Even in this case, as compared with the conventional non-interference control (as described above, the conventional non-interference control treats all of the flux linkage Ψ, the d-axis inductance Ld, and the q-axis inductance Lq as constant constants). Can be suppressed.

  According to the electric power steering control device of the present invention, since noise during operation of the electric power steering can be suppressed, the electric power steering control device is useful as an electric power steering control device that assists the steering operation of the steering wheel of the vehicle with a brushless motor.

The figure which shows schematic structure of the electric power steering control apparatus which concerns on one Embodiment of this invention. The figure which shows the principle of the non-interference control in the non-interference control part 13 which concerns on one Embodiment of this invention. The figure which shows schematic structure of the non-interference control part 13 which concerns on one Embodiment of this invention. Specific example of φ map 131 according to an embodiment of the present invention A specific example of the Ld map 132 according to an embodiment of the present invention Diagram showing the principle of conventional non-interference control

Explanation of symbols

11 d-axis PI control unit 12 q-axis PI control unit 13 non-interference control unit 14 2-phase / 3-phase conversion unit 15 PWM command value calculation unit 16 D / T compensation unit 17 PWM generation unit 18 inverter 19 current sensor 20 brushless motor 21 Three-phase / 2-phase converter 22 Rotation angle sensor 23 Angle converter 131 φ map 132 Ld map 133 Lq map

Claims (4)

An electric power steering control device that assists a steering operation of a steering wheel of a vehicle with a brushless motor,
a non-interference control unit that corrects the d-axis command voltage and the q-axis command voltage so that an interference component between the d-axis and q-axis is removed from the d-axis command voltage and the q-axis command voltage;
Angle detection means for detecting the angle of the rotor of the brushless motor and / or current detection means for detecting the current flowing through the brushless motor,
The non-interference control unit is an electric power steering control device that calculates an interference component between the d-axis and the q-axis based on the angle detected by the angle detection unit and / or the current detected by the current detection unit.   2. The electric power according to claim 1, wherein the non-interference control unit calculates a correction value for correcting the q-axis command voltage based on a φ map indicating a relationship between a rotor angle of the brushless motor and a flux linkage. Steering control device.   The non-interference control unit calculates a correction value for correcting the q-axis command voltage based on an Ld map indicating a relationship between a combination of the rotor angle of the brushless motor and the current flowing through the brushless motor and the d-axis inductance. The electric power steering control device according to claim 1 or 2.   The non-interference control unit calculates a correction value for correcting the d-axis command voltage based on an Lq map indicating the relationship between the combination of the rotor angle of the brushless motor and the current flowing through the brushless motor, and the q-axis inductance. The electric power steering control device according to any one of claims 1 to 3.

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