阅读说明：本技术 电动机控制装置及电动助力转向装置 (Motor control device and electric power steering device ) 是由 折井将彦 家造坊勋 森辰也 藤井元气 于 2019-06-27 设计创作，主要内容包括：提供一种电动机控制装置,即使在电动机的电气特性具有误差或偏差的情况下,也能够抑制转矩脉动。包括：基本电流指令生成部(1)：其输出用于向具有突极性的电动机(7)输出基本转矩的d轴基本电流指令和q轴基本电流指令；位置依赖分量生成部(101),其根据电动机的旋转位置输出电动机的位置依赖分量；电流校正指令运算部(103),其根据d轴基本电流指令、q轴基本电流指令以及位置依赖分量来运算d轴电流校正指令和q轴电流校正指令；电流校正指令重叠部(2),其将d轴电流校正指令和q轴电流校正指令重叠到d轴基本电流指令和q轴基本电流指令,生成d轴电流指令和q轴电流指令；以及电流控制部(3),其基于d轴电流指令和q轴电流指令并经由逆变器(6)来控制流向电动机(7)的电流。(Provided is a motor control device capable of suppressing torque ripple even when the electric characteristics of a motor have errors or variations. The method comprises the following steps: basic current command generation unit (1): a d-axis basic current command and a q-axis basic current command for outputting a basic torque to a motor (7) having a salient polarity; a position-dependent component generating unit (101) that outputs a position-dependent component of the motor based on the rotational position of the motor; a current correction command calculation unit (103) that calculates a d-axis current correction command and a q-axis current correction command from the d-axis base current command, the q-axis base current command, and the position-dependent component; a current correction command superimposing unit (2) for superimposing a d-axis current correction command and a q-axis current correction command on the d-axis basic current command and the q-axis basic current command to generate a d-axis current command and a q-axis current command; and a current control unit (3) that controls the current flowing through the motor (7) via the inverter (6) on the basis of the d-axis current command and the q-axis current command.)

1. A control device for an electric motor is provided,

the motor control device controls a motor having a salient polarity by an inverter of a vector control method, and is characterized by comprising:

a basic current command generating unit that outputs a d-axis basic current command and a q-axis basic current command for outputting a basic torque to the motor;

a position-dependent component generating section that outputs a position-dependent component of the motor in accordance with a rotational position of the motor;

a current correction command calculation unit that calculates a d-axis current correction command and a q-axis current correction command from the d-axis base current command, the q-axis base current command, and the position-dependent component;

a current correction command superimposing unit that superimposes the d-axis current correction command on the d-axis base current command and superimposes the q-axis current correction command on the q-axis base current command to generate a d-axis current command and a q-axis current command; and

a current control unit that controls a current flowing to the motor via the inverter based on the d-axis current command and the q-axis current command,

in the current correction command calculation unit, magnitudes of the d-axis current correction command and the q-axis current correction command are calculated to a predetermined ratio, the ratio being specified in advance or according to a state of the motor.

2. The motor control device according to claim 1,

the position-dependent component generating unit outputs a position-dependent component of an armature interlinkage magnetic flux or an inductor of the motor in accordance with a rotational position of the motor.

3. The motor control device according to claim 1 or 2,

the current correction command calculation unit calculates the d-axis current correction command based on the armature interlinkage magnetic flux, the inductance, the d-axis base current command, the q-axis base current command, and the q-axis current correction command of the motor.

4. The motor control device according to any one of claims 1 to 3,

the ratio is a value of a sensitivity setting value that is a ratio of errors in the center values of the armature interlinkage magnetic flux and the inductance of the motor.

5. The motor control device of claim 4,

the current correction command calculation unit calculates the d-axis current correction command and the q-axis current correction command based on the sensitivity set value, the armature linkage flux of the motor, the inductance, the d-axis base current command, and the q-axis base current command.

6. The motor control device according to any one of claims 1 to 4,

the d-axis current correction command and the q-axis current correction command are equal in phase or 180 degrees out of phase.

7. An electric power steering apparatus characterized by comprising:

an electric motor having a salient polarity that generates an assist torque for assisting a driver in steering; and

the motor control device according to any one of claims 1 to 6.

Technical Field

The present application relates to a motor control device and an electric power steering device using the same.

Background

In recent years, PM motors (permanent magnet embedded motors) have been widely used in industrial equipment due to their small size and high efficiency. However, the PM motor has a spatial harmonic in its structure in a rotating magnetic field, and generates a harmonic component in an induced voltage, thereby generating torque ripple. Torque ripple may cause problems such as vibration, noise, and mechanical resonance, and therefore a related reduction technique is required. As a technique for reducing the torque ripple, a method is disclosed in which a current command value capable of suppressing the torque ripple is generated and the generated current command value is superimposed on a basic current command value to suppress the torque ripple (see, for example, patent document 1).

In patent document 1, a space harmonic of a rotating magnetic field generated in a motor is held as table data relating to a rotation position, a current command in which a torque ripple generated by the space harmonic becomes 0 is generated, and the current command is superimposed on a basic current command to suppress the torque ripple.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2007-267466

Disclosure of Invention

Technical problem to be solved by the invention

As described above, in the torque ripple suppression control device described in patent document 1, when the electric characteristics of the motor can be obtained with higher accuracy in advance, the torque ripple can be suppressed.

However, it is natural that the electric characteristics of the motor obtained in advance have an error in a design value or a measurement value with respect to the true value, and vary depending on the operating state of the motor or manufacturing variations. Therefore, when the obtained value of the electric characteristic of the motor deviates from the true value, there is a problem that the effect of suppressing the torque ripple cannot be obtained. Actually, patent document 1 does not have a configuration based on an error in the central value of an electrical parameter such as the armature interlinkage magnetic flux and inductance of the motor, and performs control using only the central value of the electrical parameter in addition to the pulsation term.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a motor control device capable of appropriately suppressing torque ripple even when an acquired value of an electric characteristic of a motor has an error.

Means for solving the problems

The motor control device disclosed in the present application includes: a basic current command generating unit that outputs a d-axis basic current command and a q-axis basic current command for outputting a basic torque to a motor having a salient polarity; a position-dependent component generating section that outputs a position-dependent component of the motor in accordance with a rotational position of the motor; a current correction command calculation unit that calculates a d-axis current correction command and a q-axis current correction command from the d-axis base current command, the q-axis base current command, and the position-dependent component; a current correction command superimposing unit that superimposes a d-axis current correction command on the d-axis base current command and superimposes a q-axis current correction command on the q-axis base current command to generate a d-axis current command and a q-axis current command; and a current control unit that controls a current flowing to the motor based on the d-axis current command and the q-axis current command, wherein the current correction command calculation unit calculates magnitudes of the d-axis current correction command and the q-axis current correction command to a predetermined ratio, the ratio being specified in advance or according to a state of the motor.

Effects of the invention

According to the motor control device disclosed in the present application, the magnitudes of the d-axis current correction command and the q-axis current correction command can be calculated to a predetermined ratio by the current correction command calculation unit. By specifying the magnitudes of the d-axis current correction command and the q-axis current correction command at a certain ratio and reducing the sensitivity of the torque ripple to an error in the electrical characteristic acquisition value of the motor, the torque ripple can be suppressed even when there is an error in the electrical characteristic of the motor.

Drawings

Fig. 1 is a block diagram showing a schematic configuration of a motor control device according to embodiment 1.

Fig. 2 is a diagram showing the position-dependent components in fig. 1.

Fig. 3 is a diagram showing error regions defined in the embodiment.

Fig. 4 is a diagram showing a pulsation suppression straight line in the error region.

Fig. 5 is a diagram showing the inside of the current correction calculation unit in the embodiment.

Fig. 6 is a diagram showing a current correction command in the embodiment.

Fig. 7 is a comparison of torque ripple in the embodiment and patent document 1.

Fig. 8 is a comparison of torque ripple in the embodiment and patent document 1.

Fig. 9 is a block diagram showing a schematic configuration of a motor control device according to embodiment 2.

Fig. 10 is a diagram showing a position-dependent component generation table in the embodiment.

Fig. 11 is a block diagram showing a schematic configuration of a motor control device according to embodiment 3.

Fig. 12 is a block diagram showing a schematic configuration of a motor control device according to embodiment 4.

Fig. 13 is a block diagram showing a schematic configuration of a modification of the motor control device according to embodiment 4.

Fig. 14 is a block diagram showing a schematic configuration of a modification of the motor control device according to embodiment 4.

Fig. 15 is a configuration diagram showing an electric power steering apparatus according to embodiment 5 to which a motor control apparatus according to an embodiment is applied.

Fig. 16 is a diagram showing an example of a hardware configuration of the motor control device according to the embodiment.

Detailed Description

Hereinafter, embodiments of the motor control device will be described with reference to the drawings, and the same or corresponding portions will be described with the same reference numerals in the drawings.

Embodiment 1.

Fig. 1 is a block diagram of a motor control device according to embodiment 1. In fig. 1, the motor control device includes a basic current command generating unit 1, a current correction command superimposing unit 2, a current control unit 3, a dq/3 phase coordinate converter 4, a 3 phase/dq coordinate converter 5, a vector control type inverter 6, and a current correction unit 100. The current correction unit 100 includes therein a motor position-dependent component generation unit 101, a motor electrical characteristic center value output unit 102, a current correction command calculation unit 103, and a sensitivity set value output unit 104. The motor control device inputs detection signals from the current detector 8 and the rotational position detector 9 to the motor 7 having the salient polarity.

Next, the functional operation of each of these components will be described.

The basic current command generating unit 1 calculates and outputs a d-axis basic current command id0 and a q-axis basic current command iq0 based on a torque command value T from the host control system. The calculation of the d-axis basic current command and the q-axis basic current command may be calculated according to the maximum torque control. Further, the calculation may be performed based on a known basic current command corresponding to the operating condition.

The current correction command superimposing unit 2 adds the output from the basic current command generating unit 1 to the current correction command, which is the output of the current correction command calculating unit 103.

The current control unit 3 calculates and outputs the dq-axis voltage command value in a control manner such that the d-axis real current and the q-axis real current follow the output from the current correction command superimposing unit 2, respectively. The control method may be PI control. In addition, other known control schemes may be used.

The dq/3-phase coordinate converter 4 converts the dq-axis voltage command output from the current control unit 3 into a voltage command on a 3-phase coordinate using the rotational position of the motor detected by the rotational position detector 9, and inputs the voltage command to the inverter 6. The inverter 6 applies 3-phase voltage to the motor 7.

The 3-phase/dq coordinate converter 5 converts the 3-phase real current detected by the current detector 8 into a dq-axis current using the rotational position of the motor detected by the rotational position detector 9.

The position-dependent component generating unit 101 outputs a position-dependent component Pd, which is a component of the electrical characteristics depending on the position of the motor, based on the rotational position of the motor detected by the rotational position detector 9.

The motor electrical characteristic central value output unit 102 outputs the central value of the electrical characteristic of the motor to be controlled to the current correction command calculation unit 103. The sensitivity set value output unit 104 outputs a value specified in advance by a designer or a value set according to an operating condition to the current correction command calculation unit 103 as the sensitivity of the torque ripple to the error in the electrical characteristics of the motor. The details of the current correction command calculation unit 103 will be described.

The current correction command calculation unit 103 calculates and outputs a dq-axis current correction command for suppressing torque ripple, based on the d-axis basic current command value, the q-axis basic current command value, the electric characteristic central value of the motor, the position-dependent component of the motor, and the sensitivity set value.

The principle of the current correction command calculation unit 103 and the effect of the dq-axis current correction command output from the current correction command calculation unit 103 will be described below.

The torque of the motor having the salient polarity is expressed by the following expression (1).

[ mathematical formula 1]

T＝P_m((L_d-L_q)i_di_q+i_qΦ_d-i_dΦ_q)···(1)

Here, T: torque, Pm: pole pair number of the motor, Ld: d-axis inductance, Lq: q-axis inductance, id: d-axis current, iq: q-axis current, Φ d: d-axis magnet flux, Φ q: q-axis magnet flux.

Since the difference between the inductances Ld and Lq contributes to the torque in the equation (1), the inductance L is defined as Ld-Lq, and the equation (1) is converted into the equation (2).

[ mathematical formula 2]

T＝P_m(Li_di_q+i_qΦ_d-i_dΦ_q)···(2)

The inductance and the magnet flux, which are electrical characteristics of the motor, are separated into a central value of the electrical characteristics and a position-dependent component in consideration of the position-dependent component relating to the rotational position of the motor, and are defined as follows.

[ mathematical formula 3]

Here, L0: center value of inductance, Lripple: position-dependent component of inductance, # d0: center value of d-axis magnet flux, # dripple: position-dependent component of d-axis magnet flux, [ phi ] q0: central value of q-axis magnet flux, [ phi ] qripple: a position dependent component of the q-axis magnet flux. By taking the position-dependent component into consideration by using equation (3), the torque ripple generated by the position-dependent component can be calculated, and therefore, the current correction command for suppressing the torque ripple can be calculated. As shown in fig. 2, the position-dependent component is set as a function having a value corresponding to the rotational position. For example, the position-dependent component having a frequency of 6 times the electrical angular frequency can be expressed as follows.

[ mathematical formula 4]

When the present embodiment is applied using the above equation (4), torque ripple having a frequency 6 times the electrical angular frequency can be suppressed. In addition, the position-dependent component having a frequency n times the electrical angular frequency, instead of having a frequency 6 times the electrical angular frequency, can be expressed as follows.

[ math figure 5]

As shown in the above equation (5), a position-dependent component of an arbitrary frequency can be targeted. When the present embodiment is applied using the above equation (5), torque ripple having a frequency n times the electrical angular frequency can be suppressed. In addition, when suppressing torque ripple at a plurality of frequencies, the current correction command at each frequency can be calculated by applying the present embodiment using equation (5) at each frequency, and superimposed on the basic current command.

Next, when the electrical characteristics are divided into the central value and the position-dependent component and substituted into the torque equation, the above equation (2) is developed into equation (6).

[ mathematical formula 6]

T＝P_m((L₀+L_ripple)i_di_q+i_q(Φ_d0+Φ_dripple)-i_d(Φ_q0+Φ_qripple))···(6)

Further, if a harmonic correction command is applied to the dq-axis current, the above equation (6) is developed into equation (7).

[ math figure 7]

Here, id0 denotes a d-axis basic current command value, idripple denotes a d-axis current correction command value, iq0 denotes a q-axis basic current command value, and iqripple denotes a q-axis current correction command value.

In the above equation (7), the constant component of the torque is focused. The constant component of the torque represents a basic torque as an output of the motor. In the current control system, current control is performed so that a basic torque output as a motor follows a torque command value T. The basic torque T0 is expressed by the following equation (8) using the electric characteristics of the motor and the basic current commands id0 and iq 0.

[ mathematical formula 8]

T₀＝P_m(L₀i_d0i_q0+i_q0Φ_d0-i_d0Φ_q0)···(8)

The method of obtaining the base current commands id0 and iq0 from the base torque may use maximum torque/current (MTPA) control, or may use other known control methods. For example, in the case of using MTPA control, the basic current commands id0, iq0 are calculated so as to satisfy the following expression (9).

[ mathematical formula 9]

The basic current commands id0, iq0 are calculated from equations (8) and (9). Even if other known control methods are used, the basic current command is calculated based on equation (8) representing the basic torque.

Next, in equation (7), if the second or higher harmonic component is sufficiently small, the torque ripple as the torque harmonic component is expressed by equation (10) below.

[ mathematical formula 10]

Here, Tripple: the torque is pulsated.

When the center values of the magnetic flux and the inductance of the d-axis magnet have an error, expression (10) is expressed as expression (11).

[ mathematical formula 11]

Here, Δ L0: error in the center value of the inductance, Δ Φ d0 error in the center value of the d-axis magnet magnetic flux.

Next, the concept of the error region shown in fig. 3 is introduced into Δ L0 and Δ Φ d0, and a current correction command value for suppressing torque ripple will be described. In the error region shown in fig. 3, the horizontal axis represents Δ L0/| L0|, which is the ratio of Δ L0 to | L0|, and the vertical axis represents Δ Φ d0/Φ d0, which is the ratio of Δ Φ d0 to Φ d 0. Any errors Δ L0, Δ Φ d0 can be expressed as coordinates of points on the error region. For example, when both Δ L0 and Δ Φ d0 are 0, Δ L0 and Δ Φ d0 correspond to the origin (0, 0) of the error region. In addition, when the errors Δ L0 and Δ Φ d0 have a magnitude of + 10% with respect to the respective central values Me, Δ L0 and Δ Φ d0 correspond to coordinates (0.1 ) on the error region. Hereinafter, a point on the error region is referred to as an error point Ep.

Regarding the design of the current correction command, an error point Ep on one error region is selected, and the coordinates thereof are set to (eL, Ep). Next, the simultaneous equations are established such that the torque ripple represented by equation (11) at the selected error point Ep and the origin becomes 0.

[ mathematical formula 12]

Here, L0 is the central value Me of Ld-Lq, and in the motor having the reverse polarity, | L0| ═ L0. If the current correction commands idrapple and iqrapple of the simultaneous equations satisfying the above equation (12) are solved, the following formula of the current correction command can be obtained.

[ mathematical formula 13]

In the above equation (13), the ratio of the coordinates (eL, Ep) of the error point Ep is defined as follows.

[ mathematical formula 14]

In this case, equation (14) can be converted to equation (15) as described below.

[ mathematical formula 15]

As shown in fig. 5, equation (15) indicates that after iqrliple is obtained as in block 103a, idriple can be calculated as in block 103b using iqrliple. Thus, if iqripple can be calculated, idripple can be calculated easily. In equation (15), it is understood that the current correction command does not depend on the coordinates of the error point itself, but depends on the ratio of the coordinates, i.e., e. That is, if the error point is a point on a straight line having a slope e, the current correction command has exactly the same value regardless of which point is selected as the specific error point. Since the current correction command expressed by equation (15) is calculated with the torque ripple being 0 at a specific error point, it can be seen that the current correction command expressed by equation (15) is a current in which the torque ripple is 0 at all error points on a straight line having an inclination e. Therefore, the robustness against errors in the d-axis magnet magnetic flux and the inductance center value can be selected according to the setting of e.

Hereinafter, as shown in fig. 4, a straight line having an inclination e is referred to as a pulsation suppression straight line. When e is infinitely close to 0, the pulsation suppression straight line Rsl coincides with the axis of Δ L0/L0. In the current correction command at this time, torque ripple can be suppressed even if Δ L0 has any error. That is, robustness with respect to Δ L0 is shown by bringing e close to 0. By the same idea, if e is set to a large value, the pulsation suppression straight line Rsl coincides with the axis of Δ Φ d0/Φ d0, and the pulsation can be robustly suppressed with respect to Δ Φ d 0. When e is set to an arbitrary value, if the ratio of Δ L0 to Δ Φ d is e, the pulsation can be suppressed robustly. Above, e represents the sensitivity to Δ L0 and Δ Φ d0, and is referred to as a sensitivity setting value.

In equation (15), first, the q-axis current correction command iqripple is calculated, and the d-axis current correction command idripple is obtained from the value of iqripple, and can be easily calculated as a simple integer multiple of iqripple. In addition, iqripple may be calculated using idripple from the initial idripple calculation. Specifically, the following formula (16) is given.

[ mathematical formula 16]

From the above equation (16), if idripple can be calculated, iqripple can be simply calculated as a constant multiple of idripple. Thus, the d-axis current correction command and the q-axis current correction command of the present embodiment are characterized by being equal in phase or having a difference of 180 degrees. Therefore, if one is calculated, the other can be obtained by a simple calculation such as multiplying the calculated constant of one.

The current correction command in the present embodiment can also be applied to a positive salient pole motor having a feature that the d-axis inductance Ld is larger than the q-axis inductance Lq. In this case, if it is noted that | L0| ═ L0 in equation (12) is solved, the following equation can be obtained.

[ mathematical formula 17]

The above equation (17) is the same as when calculating the current correction command for the motor having the reverse polarity, and is the current indicated by the sensitivity setting value e, and if e is infinitely close to 0, robustness with respect to Δ L0 is achieved, and if e is set to a large value, robustness with respect to Δ Φ d0 is achieved.

Equation (17) first calculates the q-axis current correction command iqripple from the q-axis current correction command iqripple and calculates the d-axis current correction command idripple from the value of iqripple, but may calculate iqripple using idripple at the beginning. Specifically, the following formula (18) is obtained.

[ mathematical formula 18]

Next, the relationship between the sensitivity of the torque ripple and the magnitude of the current correction command will be described. The torque ripple expressed by equation (12) is calculated as follows if the gradient is calculated for Δ L0 and Δ Φ d 0.

[ math figure 19]

According to the above equation (19), in order to reduce the sensitivity of the torque ripple to Δ L0, idripple iq0+ iqripple id0 may be reduced. Further, to reduce the sensitivity of torque ripple to Δ Φ d0, iqripple may be reduced. Here, regarding the gradient of the torque ripple with respect to Δ L0, basically iq0 is larger than id0 except for id0 which is required to have a large reduction current at the time of high rotation, and therefore in order to reduce the sensitivity of the torque ripple to Δ L0, idripple can be reduced. The above is the relationship between the sensitivity of the torque ripple and the magnitude of the current correction command.

Fig. 6 shows current correction commands at that time, with the values of e, which are sensitivity setting values, set to 3 types (0.1, 1, 10). Fig. 6 (a) shows a case where e, which is a sensitivity setting value, is 0.1, fig. 6 (b) shows a case where e, which is a sensitivity setting value, is 1, and fig. 6 (c) shows a case where e, which is a sensitivity setting value, is 10. When the sensitivity setting e for which robustness with respect to Δ L0 is realized is small in design, it can be confirmed that the d-axis current correction command idripple is small by observing fig. 6. In addition, when the sensitivity setting value e for which robustness with respect to Δ Φ d0 is realized is large in design, it can be confirmed that the q-axis current correction command iqripple becomes small. As is clear from the above relationship, the sensitivity setting value e is a parameter for adjusting the magnitudes of the dq-axis current correction commands idripple and iqripple. That is, if the sensitivity set value e is decreased, the d-axis current correction command idrapple becomes small, and if the sensitivity set value e is increased, the q-axis current correction command iqrapple becomes small. Accordingly, the sensitivity setting value e is a parameter for determining the robustness of Δ L0 and Δ Φ d0 by operating the ratio of the magnitudes of the d-axis current correction command and the q-axis current correction command, and the torque ripple when the electric characteristics of the motor have errors can be made smaller than before by passing the current correction command of the present embodiment.

Regarding robustness against errors in the electrical characteristics of the motor and torque ripple suppression performance, fig. 7 and 8 show the magnitude of torque ripple generated when the current correction command in the present embodiment and the current correction command in patent document 1 are energized, respectively. Fig. 7 (a) and 8 (a) show cases where e is 0.1, fig. 7 (b) and 8 (b) show cases where e is 1, fig. 7 (c) and 8 (c) show cases where e is 10, and fig. 7 (d) and 8 (d) show cases of patent document 1. In fig. 7 and 8, the lower plane is an error region, the vertical axis is a torque ripple, and the magnitude of the torque ripple generated when the electric characteristics of the motor have an error in the error region is plotted. Fig. 7 shows a case where there is no pulsation of the q-axis magnet magnetic flux and the inductance but pulsation of the d-axis magnet magnetic flux. The current correction command of patent document 1 in fig. 7 (d) tends to be similar to the case where e of the current correction command of the present embodiment in fig. 7 (a) is 0.1, and has a feature that the torque ripple suppression effect is hardly reduced even if the inductance error Δ L0 is present. However, when the d-axis magnet magnetic flux error Δ Φ d0 exists, the torque ripple suppression effect will be reduced. Therefore, even for a motor in which Δ Φ d0 is likely to occur due to the manufacturing method or the measurement of the electrical characteristics of the motor, the torque ripple cannot be suppressed by the current correction command of patent document 1. In this regard, the current correction command of the present embodiment changes only the sensitivity setting value, i.e., e, and can suppress torque ripple even when Δ Φ d0 is likely to occur. Fig. 7 (b) shows that torque ripple can be suppressed when Δ L0 and Δ Φ d0 tend to have similar ratios to the respective median values, and fig. 7 (c) shows that torque ripple can be suppressed when Δ Φ d0 is likely to occur.

In addition, in any of the current correction commands shown in fig. 7, the maximum value of the torque ripple in the error region is 0.0167N · m, and the magnitude of the torque ripple when the torque ripple is not suppressed is 0.167N · m, so that the worst case can be reduced by 90%. When Δ L0 and Δ Φ d0 have any error in the error range, it can be seen from fig. 7 that the range in which the torque ripple suppression effect is higher in the case of the current correction command in which the energization e is 1 is larger than in the other cases. For comparison, in each current correction command, an error range of 0.0084N · m or less, which is half the maximum value of the torque ripple, is obtained, and this range is calculated as a ratio to the entire area of the error region. If the calculation is performed, the range of 0.0084N · m or less in patent document 1 is 48% of the error region, and in the current correction command of the present embodiment, it is 53% when e is 0.1, 74% when e is 1, and 53% when e is 10. From this, it is understood that when Δ L0 and Δ Φ d0 have an arbitrary error within the error range with the same probability, the probability of suppressing the torque ripple is highest. Thus, the current correction command according to the present embodiment can reduce the torque ripple when the electric characteristics of the motor have errors, as compared with the conventional case.

Next, fig. 8 shows a case where the q-axis magnet magnetic flux and the inductance pulsate in addition to the pulsation of the d-axis magnet magnetic flux. At this time, the magnitude of the torque ripple when the torque ripple is not suppressed is 0.1881N · m. According to fig. 8 (d), the magnitude of the torque ripple when the current correction command of patent document 1 is used is about 0.06N · m in any error, and the effect of suppressing the torque ripple as the original object is 68%. Although torque ripple can be reduced as compared with the case where torque ripple is not suppressed, the effect of torque ripple suppression is reduced as compared with the reduction rate when ripple of q-axis magnet magnetic flux and inductance is not present. On the other hand, the current correction command of the present embodiment has a high torque ripple suppression effect even if the q-axis magnet magnetic flux and the inductance ripple exist, and exhibits characteristics inherent in design in robustness against e, which is a sensitivity setting value, and errors. As described above, even when there are q-axis magnet magnetic flux and inductive ripple, the current correction command of the present embodiment can appropriately suppress torque ripple when there is an error in the electrical characteristics of the motor.

In the above description using fig. 7 and 8, the ranges in which the error of the center value of the inductance and armature interlinkage magnetic flux of the motor can be actually obtained are each set to 0.1 times, that is, the value obtained in practice by setting the ratio of the error of the center value to 1, and therefore, it is preferable that e be 1. Even when the ratio of the error between the inductance of the motor and the center value of the armature interlinkage magnetic flux is a value other than 1, the error region in which the amplitude of the torque ripple is small can be maximized by grasping the value in advance and adding the value to the sensitivity set value e. That is, with the configuration of the present embodiment, since the current correction command can be generated from the error region in which the center value of the electrical parameter can be obtained, it is possible to maximize the probability that the torque ripple is smaller than the estimated value when Δ L0 and Δ Φ d0 have any error within the error region with the same probability in the error region.

Embodiment 2.

Next, a motor control device according to embodiment 2 will be described with reference to fig. 9. Embodiment 2 is a case where, as shown in fig. 9, there is a table 105 having a position-dependent component of the motor with respect to the rotational position, and a current correction command is calculated by outputting the position-dependent component Pd based on the table.

In the present embodiment, the inductance and the magnet magnetic flux of the motor are measured in advance by a known method, and the average value is subtracted from each measured value to extract the position-dependent component. The extracted position-dependent component is set as table data for the rotational position shown in fig. 10, and the position-dependent component Pd corresponding to the rotational position is output to the current correction command calculation unit 103. The current correction command calculation unit 103 that outputs the dq-axis current correction command can calculate a current correction command that robustly suppresses the torque ripple with respect to the electrical characteristics of the motor by performing the same calculation as in embodiment 1, and superimposes the calculated current correction command on the dq-axis base current command, thereby suppressing the torque ripple. The table data in the present embodiment may include not only the 6f component but also table data including an arbitrary frequency component. By outputting the position-dependent component to the current correction command calculation unit 103 from the table data including the arbitrary frequency component, calculating the current correction command based on equation (15), and superimposing the current correction command on the dq-axis basic current command, it is possible to suppress torque ripple having the same frequency as the frequency component included in the table data. When a plurality of frequency components are included, torque ripple having the same frequency as those of the frequency components can be suppressed, and therefore, it is not necessary to calculate a current correction command separately for each frequency, and the amount of calculation can be reduced.

As described in embodiment 1, when the value of e is decreased, idripple becomes smaller, and the current becomes a current for suppressing the torque ripple robustly against the inductance median error Δ L0, and when the value of e is increased, iqripple becomes smaller, and the torque ripple can be suppressed robustly against the d-axis magnet magnetic flux median error Δ Φ d 0. Thus, in the present embodiment, the magnitude ratio of the dq-axis current correction command can be changed according to the sensitivity set value e, and thus torque ripple can be suppressed even when there is an error in the electrical characteristics of the motor.

Embodiment 3.

Next, a motor control device according to embodiment 3 will be described with reference to fig. 11. As shown in fig. 11, embodiment 3 includes a current correction command phase component generation unit 106, a current correction gain calculation unit 107, and a current correction gain multiplication unit 108.

In the present embodiment, the inductance and the magnet magnetic flux of the motor are measured in advance by a known method, and the average value is subtracted from each measured value to extract the position-dependent component. Next, a three-dimensional table of phase components f (θ, id0, iq0) of the dq-axis current correction command with respect to the rotational position of the motor and the dq-axis base current command is created as a current correction command phase component generating unit 106, based on the following equation (20) from which the molecular part of equation (15) is extracted.

[ mathematical formula 20]

f(θ,i_d0,i_q0)＝-(L_ripplei_d0i_q0+i_q0Φ_dripple-i_d0Φ_qripple)···(20)

The current correction gain multiplying unit 108 multiplies the output corresponding to the phase component f (θ, id0, iq0) from the prepared table by the current correction gain calculated by the current correction gain calculating unit 107, and the current correction command superimposing unit 2 superimposes the multiplied output with the basic current command. In the present embodiment, since the phase component of the current correction command is held as a table, it is not necessary to use each electrical characteristic of the motor as table data as in embodiment 2, and the amount of data can be reduced. Further, since the current correction command of the present embodiment is such that the phases of the d-axis current correction command and the q-axis current correction command are equal to each other or differ by 180 degrees, if there is a phase component represented by equation (20), the d-axis current correction command and the q-axis current correction command can be easily obtained as simple integer multiples of the phase component.

The current correction gain calculation unit 107 performs calculation according to the following expression (21).

[ mathematical formula 21]

As described in embodiment 1, the action of the sensitivity set value e in equation (21) is such that when the value of e is decreased, idripple becomes smaller and becomes a current for suppressing the torque ripple robustly against the inductance median error Δ L0, and when the value of e is increased, iqripple becomes smaller and becomes a current for suppressing the torque ripple robustly against the d-axis magnet magnetic flux median error Δ Φ d 0.

Thus, in the present embodiment, the magnitude ratio of the dq-axis current correction command can be changed in accordance with the sensitivity set value e, and thereby torque ripple can be suppressed even when there is an error in the electrical characteristics of the motor.

Alternatively, the molecular component of the current correction command may be calculated by applying the molecular component of the current correction command to a periodic function of a trigonometric function without using a table of the molecular component of the current correction command. In this case, for example, if a position-dependent component of the motor having a frequency n times the electrical angular frequency represented by equation (5) is targeted, the phase component of the current correction command becomes equation (22) below.

[ mathematical formula 22]

By using the above equation (22), the torque ripple of a specific frequency can be suppressed without creating table data. Therefore, in the present embodiment, it is also possible to distinguish between using table data and using equation (22) depending on the situation.

Embodiment 4.

Next, a motor control device according to embodiment 4 will be described with reference to fig. 12 to 14. Embodiment 4 includes an adjustment gain multiplying unit 110 for multiplying the adjustment gain generated by the adjustment gain generating unit 109 by the current correction command. The current correction command may be configured as shown in fig. 12 using equation (15) as described in embodiment 1, may be configured as a modification shown in fig. 13 using a current correction command calculated from a phase component table as described in embodiment 2, or may be configured as a modification shown in fig. 14 using a current correction command calculated from a current correction command phase component and a current correction gain as described in embodiment 3. The adjustment gain has a value from 0 to 1. In the present embodiment, the magnitude ratio of the dq-axis current correction command can be changed in accordance with the sensitivity set value e, and thereby torque ripple can be suppressed even when there is an error in the electrical characteristics of the motor.

Further, since the phases of the d-axis current correction command and the q-axis current correction command are equal to each other or differ by 180 degrees, the phase calculation of the current correction command may be performed only by one of the d-axis current correction command and the q-axis current correction command, and the other may be obtained only by multiplying the calculated constant by one of the d-axis current correction command and the q-axis current correction command.

In the present embodiment, the current correction command is smaller than the optimum design value of the current correction command calculated by the current correction command calculation unit 103. As a result, the torque ripple suppression effect when the electric characteristic of the motor becomes the central value is reduced, but as described in embodiment 1, the smaller the current correction command value is, the more robust the error of the electric characteristic central value of the motor is, and by applying this embodiment, the torque ripple can be reduced without deteriorating the torque ripple even when the electric characteristic deviation of the motor is large. This embodiment can be used separately from embodiment 1 in accordance with variations in electrical characteristics of the motor.

Embodiment 5.

In the above embodiment, the motor control device has been described, but the present invention can also be applied to an electric power steering device including the motor control device and a motor having a salient polarity that generates an assist torque for assisting a driver's steering.

Fig. 15 is a diagram showing a configuration of an electric power steering apparatus according to embodiment 5. In fig. 15, the electric power steering apparatus is provided with a steering wheel 301, a steering shaft 302, a rack-and-pinion gear 303, wheels 304, 305, a motor 7, a reduction gear 306, a rotational position detector 9, a torque sensor 307, a vehicle speed sensor 308, and a motor control apparatus 200.

In fig. 15, a steering torque applied to a steering wheel 301 by an unillustrated driver passes through a torsion bar of a torque sensor 307 and a steering shaft 302, and is transmitted to a rack via a rack-pinion gear 303, thereby steering wheels 304, 305.

The electric motor 7 is connected to the steering shaft 302 via a reduction gear 306. The output torque generated from the electric motor 7 is transmitted to the steering shaft 302 via the reduction gear 306, and the steering torque applied by the driver during steering is reduced.

The torque sensor 307 detects the steering torque applied to the torsion bar by the driver turning the steering wheel 301. Since torsion that is almost proportional to the steering torque is generated in the torsion bar based on the steering torque, the torsion angle is detected and converted into a steering torque signal. The vehicle speed sensor 308 outputs a vehicle speed, which is a signal for detecting the running speed of the vehicle.

The motor control device 200 is any of the embodiments described above, determines the direction and magnitude of a current command corresponding to the output torque output by the motor 7 based on the steering torque signal detected by the torque sensor 307, the rotational position θ obtained by the rotational position detector 9, and the vehicle speed detected by the vehicle speed sensor 308, and controls the current flowing from the power supply to the motor 7 based on the current command so that the motor 7 generates the output torque.

In such an electric power steering apparatus, as in embodiments 1 to 4, by reducing the sensitivity of the torque ripple to an error in the acquired value of the electric characteristic of the electric motor, the torque ripple can be suppressed even when there is an error in the electric characteristic of the electric motor.

The motor control device 200 is configured by a processor 2000 and a storage device 2001 as an example of hardware shown in fig. 16. Although not shown, the storage device includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory. In addition, an auxiliary storage device such as a hard disk may be provided instead of the flash memory. The processor 2000 executes programs input from the storage device 2001. In this case, the program is input to the processor 2000 from the auxiliary storage device via the volatile storage device. The processor 2000 may output data such as a calculation result to a volatile storage device of the storage device 2001, or may store the data in an auxiliary storage device via the volatile storage device.

While various exemplary embodiments and examples are described herein, the various features, aspects, and functions described in one or more embodiments are not limited in their application to a particular embodiment, but may be applied to embodiments alone or in various combinations.

Therefore, it is considered that numerous modifications not illustrated are also included in the technical scope disclosed in the present specification. For example, the present invention includes a case where at least one of the components is modified, added, or omitted, and a case where at least one of the components is extracted and combined with the components of the other embodiments.

Description of the reference symbols

1 basic current command generating part

2 current correction command overlap section

3 current control part

6 inverter

100 current correction unit

101 position-dependent component generating unit

103 current correction command calculation unit

200 motor control means.