JP4556464B2 - Control device for electric power steering device - Google Patents

Description

  The present invention relates to a control device for an electric power steering device that applies a steering assist force by a motor to a steering system of an automobile or a vehicle, and more particularly to a control device for an electric power steering device for reducing a torque step generated when a brushless motor rotates. .

  An electric power steering device that biases an automobile or a vehicle steering device with an auxiliary load by the rotational force of a motor assists the steering shaft or rack shaft with a transmission mechanism such as a gear or a belt via a reduction gear. The load is energized. Such a conventional electric power steering apparatus performs feedback control of motor current in order to accurately generate assist torque (steering assist torque). In the feedback control, the motor applied voltage is adjusted so that the difference between the current command value and the detected motor current is small. Generally, the adjustment of the motor applied voltage is a duty of PWM (pulse width modulation) control. This is done by adjusting the tee ratio.

  Here, the general configuration of the electric power steering apparatus will be described with reference to FIG. 5. The column shaft 2 of the steering handle 1 is connected to the steering wheel via the reduction gear 3, the universal joints 4 a and 4 b, and the pinion rack mechanism 5. Coupled to the tie rod 6. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the steering handle 1, and a motor 20 that assists the steering force of the steering handle 1 is coupled to the column shaft 2 via the reduction gear 3. ing. The control unit 30 that controls the power steering device is supplied with electric power from the battery 14 via the ignition key 11 and the relay 13, and the control unit 30 is detected by the steering torque T detected by the torque sensor 10 and the vehicle speed sensor 12. The steering assist command value I of the assist command is calculated based on the vehicle speed V, and the current supplied to the motor 20 is controlled based on the calculated steering assist command value I.

  The control unit 30 is mainly composed of a CPU (including an MPU). FIG. 6 shows general functions executed by a program inside the CPU. For example, the phase compensator 31 does not indicate a phase compensator as independent hardware, but indicates a phase compensation function executed by the CPU.

  The function and operation of the control unit 30 will be described. The steering torque T detected and input by the torque sensor 10 is phase-compensated by the phase compensator 31 in order to improve the stability of the steering system, and the phase-compensated steering torque. TA is input to the steering assist command value calculator 32. The vehicle speed V detected by the vehicle speed sensor 12 is also input to the steering assist command value calculator 32. The steering assist command value calculator 32 determines a steering assist command value I that is a control target value of the current supplied to the motor 20 based on the input steering torque TA and vehicle speed V. The steering assist command value I is input to the subtractor 30A, and is also input to the feedforward differential compensator 34 for increasing the response speed. The deviation (Ii) of the subtractor 30A is input to the proportional calculator 35. At the same time, it is input to an integration calculator 36 for improving the characteristics of the feedback system. Together with the output of the differential compensator 34, the outputs of the proportional calculator 35 and the integral calculator 36 are also added to the adder 30B, and the current control value E, which is the addition result of the adder 30B, is used as a motor drive signal as a motor drive circuit. 37. The current i of the motor 20 is detected by the motor current detection circuit 38 and fed back to the subtractor 30A.

  In such an electric power steering apparatus, a brushless motor having a variable speed and a feature that can be reduced in size is used as a conventional motor, and assist by the brushless motor is performed. The brushless motor has a structure for rotating the rotor by repeatedly switching the phase of the motor current and controlling the driving of the rotor. However, since the torque value decreases at the phase switching portion, that is, at the boundary portion of each phase, a concave step called a torque step is intermittently generated in the torque at the boundary portion of each phase, which is called a torque ripple. Torque pulsation occurs.

  FIGS. 3A and 3B are waveform diagrams showing a relationship between a current waveform supplied to a brushless motor that is driven and controlled by a rectangular wave motor current and a torque value generated by the current. As shown in FIG. 3A, the motor current is a plurality of phases such as three phases, and each phase is a rectangular wave having a square wave shape, side edges of adjacent waveforms overlap each other, and each upper side portion is It becomes almost a straight line and becomes a constant current. When such a current is supplied to the brushless motor, the torque of the brushless motor causes a torque step as shown in FIG. 3B at the boundary between the phases, causing torque ripple.

  Due to the torque ripple based on such a torque step, the electric power steering apparatus using the brushless motor has a problem of giving the driver an unpleasant feeling that the steering vibrates. Such a torque step is determined by the motor characteristics of the brushless motor, and the torque step and the torque ripple based thereon cannot be completely eliminated by improving the motor characteristics.

As a conventional technique for solving such a problem, there is one disclosed in Japanese Patent Laid-Open No. 2001-18822 (Patent Document 1). In the electric power steering apparatus described in Patent Document 1, the brushless motor is driven and controlled by a sine wave, and a sensory region determination unit and a torque step compensation value calculation unit (pulsation torque correction value calculation unit) are provided. When the sensory region determination unit determines that the vehicle speed and the steering speed are slower than the predetermined speed, the torque step compensation value calculation unit calculates a torque step compensation value (pulsation torque correction value) Iqr by the following equation (1). .

Iqr = Kro ・ Fo (θ) / Kt + Krl ・ Fl (θ) ・ Iq / Kt − Kro ・ krl ・ Fo (θ) ・ Fl (θ) / Kt ²
... (1)
Where Kt is the torque coefficient, Kro and Krl are the torque step coefficient (pulsation torque coefficient), Fo (θ),
Fl (θ) is a torque step function (pulsation torque function).

The torque step compensation value Iqr calculated by the above equation (1) is used, and further, the torque step compensation is performed using vector control by dq conversion.
JP2001-18822

  However, in the control device for the electric power steering apparatus disclosed in Patent Document 1, the torque coefficient Kt and the torque step coefficients Kro and Krl are constants stored in advance in the torque step compensation value calculation unit, and the torque step The functions Fo (θ) and Fl (θ) are defined in a table or a function formula in the torque step compensation value calculation unit and are stored in advance, and are actual torque steps generated by actual vehicle travel. Does not necessarily meet. In addition, when the sensory region determination unit determines that the vehicle speed or the steering speed is equal to or higher than a predetermined speed, the torque step is not compensated at all, and thus the steering discomfort that is given to the steering operator is still not solved. is there.

  Furthermore, in order to compensate for the torque step in the control device for the electric power steering apparatus disclosed in Patent Document 1, it is necessary to accurately detect the motor rotation angle. For example, the detection accuracy is relatively low like a hall sensor. Inferior sensors cannot be used for the rotation angle detection means, and it is inevitably necessary to use an expensive and highly accurate rotation angle detection means, and there is a problem that the control device tends to be expensive. Further, the control device of the electric power steering device disclosed in Patent Document 1 compensates for a torque step with respect to the q-axis current Iq inside the vector control, and thus cannot be applied to a brushless motor that controls driving with a rectangular wave. There is also a problem.

  The present invention has been made under the circumstances as described above, and the object of the present invention is a simple configuration, does not require very high accuracy in the rotation angle detection means, and can be applied to a rectangular wave control motor, It is an object of the present invention to provide a control device for an electric power steering device that can sufficiently compensate for a torque step of a brushless motor and give a steering operator a smooth steering feeling.

The present invention relates to a control device for an electric power steering apparatus configured to apply an assist force by a brushless motor to a steering system of a vehicle, and the object of the present invention is to provide a compensation value for reducing a torque step of the brushless motor. Torque step compensation means is provided based on the timing of the rotation angle detection signal from the motor rotation angle detection means of the brushless motor. The torque step compensation means includes a low-pass filter, and the low-pass filter receives the rotation angle detection signal. The torque step compensation original signal for generating the compensation value is output .

The present invention also relates to a control device for an electric power steering apparatus, and the object of the present invention is to provide a brushless motor that applies a steering assist force to a steering handle, a drive circuit that drives the brushless motor, and a rotation angle of the brushless motor. A motor rotation angle detecting means for detecting the torque, a torque command value calculating means for outputting a current command value based on a torque value obtained by operating the steering handle, and a torque step compensation for the current command value at a specific rotation angle of the brushless motor. Torque step compensation means for outputting a compensation value, phase current command value calculation means for calculating each phase current command value based on a compensation current command value obtained by adding the compensation value to the current command value, supplied with the phase current command value and a drive circuit control means for outputting a command value for controlling the drive circuit, the torque step compensation means A low-pass filter, the low pass filter is achieved by outputting a torque step compensation original signal to generate the compensation value to input rotation angle detection signal from the motor rotation angle detecting means.

The above object of the present invention more be made proportional to the compensation value to the current command value, or a specific angle rotation angle at the time of commutation of the motor current the torque step compensation means detects that the motor rotation angle detection means This is achieved more effectively by using a Hall sensor as the motor rotation angle detection means.

  According to the present invention, the compensation value signal is output at a specific angle at which a torque step is generated in the drive control of the brushless motor, thereby greatly reducing the torque step of the brushless motor and greatly reducing the torque ripple. Therefore, a smooth steering feeling can be given to the steering wheel in the steering using the electric power steering.

  In addition, compensation for torque step is not performed using table data or function formulas, but compensation is performed according to the actual torque step generated by actual vehicle travel, so that the torque step suitable for an actual brushless motor is used. Therefore, it is possible to improve the performance of automobiles and vehicles at a low cost.

  The present invention is a control device for an electric power steering apparatus that applies a steering assist force to a steering system of an automobile or a vehicle using a brushless motor, and includes a torque step compensation means for reducing a torque step generated when the brushless motor rotates. Provided. Based on the timing of the output signal of the rotation angle detection means of the brushless motor (timing of reaching the specific rotation angle of the brushless motor, timing of phase switching of the brushless motor, timing of the Hall sensor edge signal, etc.), the torque of the brushless motor A compensation value for reducing the level difference is obtained and the torque level difference is compensated, and a smooth steering feeling can be given to the driver.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

In FIG. 1 showing the overall configuration of the present invention, a brushless motor 2 is a three-phase brushless DC motor that is driven and controlled by a rectangular wave as an example. The brushless motor 2 is a three-phase motor current I from an inverter 5 as a drive circuit. _A , I _B , and I _C are input, and driving control is performed by phase switching of motor currents I _A , I _B , and I _C and their timing. The inverter 5 is driven by PWM control signals Ua, Ub, Uc from the control means 7, and the vehicle speed V from the vehicle speed sensor 9 and the steering torque τ from the torque sensor 10 are input to the control means 7.

  Further, the brushless motor 2 is provided with a hall sensor 3 as a rotation angle detecting means for detecting a specific angle (phase switching position). The hall sensor 3 is a first sensor formed by a hall element. It comprises a part 3a, a second sensor part 3b, and a third sensor part 3c, and each sensor part 3a, 3b, 3c is disposed in the vicinity of a rotor (not shown) at approximately 120 ° intervals. The magnetism changes due to the rotation of the rotor of the brushless motor 2, and the first sensor unit 3a to the third sensor unit 3c of the hall sensor 3 output hall sensor signals Ha, Hb, Hc, respectively, corresponding to the magnetic change. Here, when the rotor rotation angle of the brushless motor 2 reaches a specific angle, the magnetism detected by the Hall sensor 3 is switched from N pole to S pole, for example, and the Hall sensor signals Ha, Hb, Each Hc outputs a pulse signal. Note that the switching timing of magnetism detected by the Hall sensor signals Ha, Hb, Hc coincides with the timing of phase switching of the motor current of the brushless motor 2.

  The hall sensor signals Ha, Hb, Hc are input to the edge detection means 21 and commutation setting means 22 in the control means 7, and the edge detection means 21 is formed at the timing of phase switching of the hall sensor signals Ha, Hb, Hc. The edge portion of the signal to be detected is detected, and the pulsed edge signal HSedg is input to the torque step compensation means 11. The commutation setting means 22 generates commutation signals Ca, Cb, and Cc for use in commutation control based on the hall sensor signals Ha, Hb, and Hc, and the commutation signals Ca, Cb, and Cc are rectangular waves. Input to the control unit 16.

The brushless motor 2 is connected to an inverter 5 that outputs motor currents I _A , I _B , and I _C through three-phase current paths 4 a, 4 b, and 4 c, and the inverter 5 receives a PWM control signal from the PWM control unit 20. Ua, Ub, Uc are input and converted to motor currents I _A , I _B , I _C and output to current paths 4a, 4b, 4c. The current paths 4a, 4b, and 4c are respectively provided with sensors 6a, 6b, and 6c that detect motor currents I _A , I _B , and I _C output from the inverter 5, and the detected current value Ia , Ib, Ic are subtracting sections 17a,
It is fed back to 17b and 17c.

  The torque command value calculation means 8 in the control means 7 receives the vehicle speed V from the vehicle speed sensor 9 and the steering torque τ from the torque sensor 10, and the torque command value calculation means 8 increases as the steering torque τ increases. An assist torque that decreases as the vehicle speed V increases is calculated, and a current command value Iref0 is calculated and output based on the assist torque or the like. The current command value Iref0 is input to the torque step compensation means 11 and also input to the adder 15. The torque step compensation means 11 outputs a compensation value K · Iref0 · Hsedgfil (where K is a constant) based on the current command value Iref0 and the edge signal Hsedg from the edge detection means 21 and inputs it to the adder 15.

Next, the compensation current command value Igp obtained by adding the current command value Iref0 and the compensation value K · Iref0 · HSedgfil by the addition unit 15 is supplied to the rectangular wave control unit 16 as each phase current command value calculation means. The The rectangular wave control unit 16 receives the compensation current command value Igp and also receives the commutation signals Ca, Cb, and Cc from the commutation setting means 22, and converts the compensation phase currents into values for each of the three phases of the brushless motor 2. The command values Ia _sref , Ib _sref , and Ic _sref are calculated and input to the subtraction units 17a, 17b, and 17c, respectively. Subtraction unit 17a,
Current values Ia, Ib, and Ic are input to 17b and 17c, respectively, and the subtraction result, that is, the deviation obtained by subtracting the current values Ia, Ib, and Ic from the compensation phase current command values Ia _sref , Ib _sref , and Ic _sref Input to the PI control unit 19. Compensation phase voltage command values va, vb, and vc that are respectively proportionally integrated by the PI control unit 19 are calculated for each phase, and the compensation phase voltage command values va, vb, and vc are input to the PWM control unit 20. The PWM control unit 20 performs PWM control on the compensation phase voltage command values va, vb, and vc for each phase, generates PWM control signals Ua, Ub, and Uc, respectively, and inputs them to the inverter 5.

  Next, the principle by which the torque step compensation means 11 of the present invention compensates for the torque step will be described.

As described above, when a current as shown in FIG. 3A is input to the brushless motor 2, the torque value of the brushless motor 2 causes a torque step at the phase switching timing as shown in FIG. 3B. . Here, since the torque value is proportional to the magnitude of the motor current, and the timing at which the torque step occurs coincides with the specific angle that is the phase switching timing, the current command value Iref0 is increased at the specific angle, and FIG. If the current value is raised in a convex shape as shown in FIG. 3, the torque step is compensated as shown in FIG. That is, the torque step compensation means 11 generates the current command value Iref0 based on the edge signal Hsedg from the edge detection means 21 as the compensation value K · Iref0 · Hsedgfil shown in FIG. By adding the value Iref0, a compensation current command value Igp for torque step compensation as shown in FIG. 3D is generated. FIG. 3D is a waveform diagram of the torque value of the brushless motor 2 when the motor currents I _A , I _B , and I _C are supplied. The timing at which the current value increases is the timing at which a torque step occurs. Since they coincide, the torque step is compensated around the latter half of the step.

  Next, as an example of increasing the current command value Iref0 at a specific angle of the brushless motor 2, the configuration of the torque step compensation means 11 shown in FIG. 2 will be described.

  As shown in FIG. 2, the torque step compensation means 11 includes a low-pass filter 12, a correction gain unit 13, and a multiplication unit 14. The low-pass filter 12 receives the pulse-shaped edge signal HSedg shown in FIG. 4A, outputs a torque step compensation original signal HSedgfil that forms the original signal to be compensated for the torque step, and the correction gain unit 13 The current command value Iref0 is input and a correction gain signal K · Iref0 multiplied by a constant correction value K is output. Here, the correction value K is a proportional constant that sets the ratio of the drop in torque step, and can be changed by tuning the correction gain unit 13. Further, the compensation value of the torque step can be adjusted according to the magnitude of the current command value. Then, the correction gain signal K · Iref0 and the torque step compensation original signal HSedgfil are input to the multiplication unit 14, and the multiplication unit 14 sets the signal amount of the torque step compensation original signal HSedgfil to the correction value K which is the torque step drop ratio and the motor. The compensation value K · Iref0 · HSedgfil adjusted with the current command value Iref0 which is the magnitude of the current is output.

As described above, the current command value Iref0 input to the torque step compensation unit 11, the torque step compensation original signal HSedgfil generated by the low-pass filter 12, the correction value K multiplied by the correction gain unit 13, and the torque step compensation unit. The relationship of the following equation (2) is established between the compensation values K, Iref0, and HSedgfil output by the terminal 11.

K ・ Iref0 ・ HSedgfil = Iref0 ・ Hsedgfil ・ K (2)

That is, the compensation values K · Iref0 · HSedgfil are generated as values proportional to the current command value Iref0 at the phase switching timing of the brushless motor 2 where the Hall sensor signals Ha, Hb, and Hc are output.

  Then, the current command value Iref0 and the compensation value K · Iref0 · HSedgfil output from the torque command value calculation means 8 are inputted to the adder 15, and the adder 15 adds the compensation value K · Iref0 · HSedgfil to the current command value Iref0. The compensation current command value Igp is generated by addition. That is, the compensation current command value Igp is generated as a signal obtained by adding the compensation value K · Iref0 · HSedgfil to the current command value Iref0 at the phase switching timing of the brushless motor 2.

  Next, a specification determination method for the low-pass filter 12 and a tuning method for the correction gain unit 13 in the torque step compensation means 11 will be described with reference to the drawings.

  First, the low-pass filter 12 cuts and outputs a component having a specific frequency or higher in the input signal, but the output with respect to the input of the pulse signal becomes an impulse response in which the signal amount gradually attenuates with time. Accordingly, as shown in FIG. 4A, the torque step compensation original signal HSedgfil output from the low-pass filter 12 by the input of the edge signal HSedg that increases or decreases substantially in a pulse shape at a specific angle as shown in FIG. The waveform gradually attenuates at a specific angle. As shown in the equation (2), the waveform of the compensation value K · Iref0 · HSedgfil added to the current command value Iref0 in the generation of the compensation current command value Igp is similar to the torque step compensation original signal HSedgfil, Accordingly, the shape of the compensated portion of the motor current after compensation shown in FIG. 4C is similar to the impulse response.

Here, the shape of the impulse response of the low-pass filter 12 is determined by the cutoff frequency of the low-pass filter 12. On the other hand, the impulse response of the low-pass filter 12 rises faster and has a maximum value as the order is lower. In this embodiment, the low-order low-pass filter such as the order 1 is used to compensate for the step mainly in the latter half of the torque step. A filter is suitable. In the case of a first-order low-pass filter, when the transfer function is F1, it is expressed by the following equation (3).

F1 = 1 / (T1 · s + 1) (3)

And considering the impulse response derived by inverse Laplace transform of the above equation (3), the impulse response shape that seems to be the closest to the torque step attenuation tendency as an example shown in FIG. When the cut-off frequency is about 100 Hz, a low-pass filter having such a cut-off frequency is most suitable. In this way, the waveform that is the original form of the torque step compensation original form signal HSedgfil is determined.

  On the other hand, the correction value K of the correction gain unit 13 determines the ratio of the compensation value K · Iref0 · HSedgfil. Here, as an example, the torque step is a ratio of about 15% of the maximum torque value corresponding to 1, as shown in FIG. As described above, the torque value is proportional to the current value. Therefore, the compensation value of the motor current is desirably about 15% of the original current command value Iref0 as shown in FIG. Therefore, it is desirable to tune the correction value K to a value at which the maximum value of the compensation values K, Iref0, and HSedgfil is about 15% of the ratio of the current command value Iref0. However, the magnitude of the torque step is basically determined by the individual static characteristics of the brushless motor 2 and the inverter 5, and the cutoff frequency of the low-pass filter 12 and the magnitude of the correction value K of the correction gain section 13 are always described above. Therefore, it is needless to say that the setting of the cut-off frequency and the tuning of the correction value K need to be adjusted according to the model of the brushless motor 2 and the inverter 5.

  As described above, the Hall sensor signals Ha, Hb, and Hc output from the first sensor unit 3a, the second sensor unit 3b, and the third sensor unit 3c as Hall sensors are phase switching timings at which a torque step occurs in the brushless motor 2. The torque step compensation means 11 to which the Hall sensor signals Ha, Hb, Hc are input outputs the compensation values K · Iref0 · HSedgfil at such timing. Further, since the compensation current command value Igp is generated by directly adding the compensation value K · Iref0 · HSedgfil to the current command value Iref0, the compensation current command value Igp can be applied to compensation of a torque step of a brushless motor of rectangular wave control.

  The compensation value K · Iref0 · HSedgfil is proportional to the current command value Iref0 before separation into each phase. For small torque, the compensation value K · Iref0 · HSedgfil is reduced and Therefore, the compensation values K, Iref0, and HSedgfil can be increased, so that even a large torque step when the torque is large can be sufficiently compensated.

  The fixed values used to generate the compensation current command value Igp are only the correction value K applied by the correction gain unit 12 and the filter constant of the low-pass filter 13, and neither of them uses a value that requires a large ROM capacity such as a table. Therefore, the cost of the control device can be reduced. The equation (2) for generating the compensation values K, Iref0, and HSedgfil is simple, and the current command value Igp can be generated by a simple algorithm. Can be given.

  In the present embodiment, the compensation values K, Iref0, and HSedgfil are formed by using Hall sensor signals Ha, Hb, and Hc as pulse signals by using an impulse response in the low-pass filter 13, but the present invention is not limited to this. However, it can be formed by other means. In this embodiment, each phase current command value calculation means of the brushless motor 2 is rectangular wave control. However, the present invention is not limited to this. For example, a brushless motor using another calculation method such as vector control. It can also be applied to. Furthermore, since the means for detecting the rotation angle of the brushless motor 2 can compensate for the torque step even if it is not highly accurate, a general-purpose rotation angle detection means such as a Hall sensor is also applicable. For example, a resolver or an encoder can be used as a highly accurate device.

  In this embodiment, the brushless motor 2 has three phases. However, the present invention is not limited to this, and the present invention can be applied to a multiphase brushless motor having three or more phases.

  In this embodiment, all the components of the control means 7 are configured by hardware elements, but the present invention is not limited to this, and some or all of the components are processed by the CPU. It is also possible to do as.

  According to the present invention, the compensation signal is output at a specific angle at which a torque step is generated in the drive control of the brushless motor, whereby the torque step of the brushless motor can be greatly reduced, and the steering feel is smooth to the driver. And can be applied to high-performance electric power steering of automobiles and vehicles.

It is a block diagram which shows the structural example of the control apparatus of the electric power steering apparatus which concerns on this invention. It is a block diagram of the configuration of the torque step compensation means of the control device of the electric power steering device. It is a wave form diagram which shows the example of a relationship between the electric current supplied to the brushless motor of an electric power steering apparatus, and the torque value produced by a drive. It is a wave form diagram which shows the example of the correlation of the edge signal regarding the specification determination of the low-pass filter in the electric power steering device, and the determination of the correction value K of the correction gain unit, the torque step compensation original signal, the compensation current command value, and the torque value. It is a schematic block diagram of a general electric power steering device. It is a block block diagram of a general control unit.

Explanation of symbols

2 Brushless motor 3 Hall sensor 5 Inverter 8 Torque command value calculation means 9 Vehicle speed sensor 10 Torque sensor 11 Torque step compensation means 12 Low-pass filter 16 Rectangular wave control unit 18 as each phase current command value calculation means 18 Drive circuit control means 19 PI control Unit 20 PWM control unit 21 edge detection unit 22 commutation setting unit

Claims (6)

The control apparatus for an electric power steering apparatus of the assist force by the brushless motor is adapted to impart to the steering system of the vehicle, the compensation value for reducing the torque difference of the brushless motor, the motor rotation angle detecting means of the brushless motor Torque step compensation means for performing the rotation angle detection signal based on the timing of the rotation angle detection signal , wherein the torque step compensation means includes a low-pass filter, and the low-pass filter receives the rotation angle detection signal and generates the compensation value. A control device for an electric power steering device, wherein a compensation original signal is output . The control device for an electric power steering apparatus according to claim 1, wherein the motor rotation angle detection means is a Hall sensor. Based on a brushless motor that applies a steering assist force to the steering handle, a drive circuit that drives the brushless motor, motor rotation angle detection means that detects a rotation angle of the brushless motor, and a torque value obtained by operating the steering handle Torque command value calculating means for outputting a current command value; torque step compensating means for outputting a compensation value for applying a torque step compensation to the current command value at a specific rotation angle of the brushless motor; and the compensation value for the current command value. Each phase current command value calculation means for calculating each phase current command value based on the compensation current command value obtained by adding the value, and a drive for receiving the supply of each phase current command value and outputting a command value for controlling the drive circuit and a circuit control unit, the torque difference compensation means comprises a low pass filter, the low pass filter from the motor rotation angle detection means Control device for an electric power steering apparatus characterized by to input rotation angle detection signal and outputs a torque step compensation original signal to generate the compensation value. The control device for the electric power steering apparatus according to claim 3, wherein the compensation value is proportional to the current command value. 5. The control device for an electric power steering apparatus according to claim 3, wherein the torque step compensation means sets the rotation angle at the time of commutation of the motor current detected by the motor rotation angle detection means as a specific angle. 6. The control device for an electric power steering apparatus according to claim 3, wherein the motor rotation angle detection means is a hall sensor.

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