JP6641247B2 - Electric motor control device and control method, electric power steering device - Google Patents

Description

  The present invention relates to a control device for a motor, and more particularly to a control device capable of realizing constant control performance even when the inductance of the motor changes.

  In conventional motor current control, the motor is analyzed by non-linear finite element analysis using a computer, the number of interlinkage magnetic fluxes of each winding at each current value is calculated and stored as table data, and the information in this table data is used. By controlling the electric current of the electric motor and optimizing the control parameters of the electric motor online during the control of the electric motor, highly accurate electric motor control is realized (for example, Patent Document 1 below).

  In the conventional current control, stable current control is performed by identifying the inductance of the motor as an inductance identification value or an inductance setting error ratio, and adjusting the control gain of the current control unit according to the obtained identification value. (For example, Patent Document 2 below).

JP 2008-141835 A JP-A-2003-339183

  In the conventional invention, stable current control is performed by adjusting control parameters using inductance values obtained by computer analysis, or control gain is adjusted by identifying inductances. When there is an error, an analysis error, an identification error, or the like, it is conceivable that the control parameters and the control gain cannot be adjusted correctly and the control performance deteriorates.

  The present invention has been made to solve the above-described problems.In current control of a motor in which inductance varies, the inductance changes during operation of the motor, and the inductance set value in control and the actual motor It is an object of the present invention to provide a control device and a control method for a motor capable of performing stable current control without changing the response of the current control even when an error occurs in the inductance value, and an electric power steering device.

The present invention provides a current command calculator that calculates a current command of a motor and outputs the current as a current command value, a current detector that detects the current of the motor and outputs the detected current as a current detection value, and a target for the current command value. A target response filter that calculates a target response current responding at a response speed and outputs the target response current as a target response current value, and calculates a compensation current by multiplying a difference between the target response current value and the current detection value by a target response gain. A target response compensator that outputs a compensation current value, and calculates a voltage command to the motor based on a sum of the compensation current value and a deviation between the current command value and the current detection value, and calculates the motor A current control unit that outputs a voltage command value for a power converter to be driven and controlled, wherein the target response compensating unit is configured to perform the compensation using the target response gain that is variable according to the current detection value. The current values are calculated, the target response gain is a function of the ratio of the inductance value set by the inductance value of the motor and the current controller, the ratio of the inductance value is a function of the current detection value, In the control device of the electric motor.

  According to the present invention, even when the inductance changes during the operation of the motor and an error occurs between the inductance setting value in the control and the actual inductance value of the motor, a stable current control is performed without changing the response of the current control. It is possible to provide a control device and a control method for an electric motor, and an electric power steering device.

FIG. 1 is a diagram showing an example of an overall configuration of a motor control device according to the present invention. FIG. 3 is a diagram showing an example of an internal configuration common to the d-axis current controller and the q-axis current controller of FIG. 1 according to Embodiment 1 of the present invention. FIG. 3 is a diagram in which a motor model is applied to the internal configuration of FIG. 2 according to Embodiment 1 of the present invention. FIG. 4 is a diagram modeling the shaft current controller of FIG. 3 according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing a gain of an open loop characteristic of current control common to the d-axis current controller and the q-axis current controller of FIG. 1 according to Embodiment 1 of the present invention. FIG. 6 is a diagram showing a change in current response to a step-like command current value when the present invention is not applied in each inductance error of FIG. 5. FIG. 3 is a diagram illustrating an example of a function model of inductance in the motor control device according to Embodiment 1 of the present invention; FIG. 14 is a diagram showing an example of table data of an inductance value in the electric motor control device according to Embodiment 2 of the present invention. FIG. 7 is a diagram showing a current response to a step-like command current value at the same inductance error as in FIG. 6 when the present invention according to Embodiment 1 of the present invention is applied. FIG. 5 is a diagram in which a voltage disturbance is added to the modeled shaft current controller of FIG. 4 according to the first embodiment of the present invention. FIG. 11 is a gain diagram from a voltage disturbance to a current detection value in the modeled shaft current controller of FIG. 10. FIG. 13 is a diagram schematically illustrating an example of a configuration of an electric power steering device according to Embodiment 3 of the present invention.

  Hereinafter, a control device and a control method for an electric motor according to the present invention, and an electric power steering device will be described with reference to the drawings according to each embodiment. In each embodiment, the same or corresponding portions are denoted by the same reference numerals, and overlapping description will be omitted.

Embodiment 1 FIG.
FIG. 1 is a diagram showing an example of the overall configuration of a motor control device according to the present invention. In FIG. 1, a current control unit 1 inputs currents iu and iv of a motor 4 detected by a current detector 3 and a rotation angle θ of the motor 4 detected by a rotation angle detector 5 to input a voltage command value. By calculating and outputting voltage command values v * u, v * v, v * w to the power converter 2, the current of the electric motor 4 is controlled.

  The power converter 2 converts power from a power supply (not shown) into power of a desired variable voltage and variable frequency based on a voltage command from the current control unit 1. The power converter 2 according to the present invention includes a converter and an inverter, which convert AC power into DC power by a converter and then convert DC power into AC power by an inverter, like a commonly sold inverter device. It refers to a power converter or a variable voltage variable frequency power converter including a power converter that directly converts AC power into AC variable voltage variable current AC power, such as a matrix converter. The present invention can be applied even if the power converter 2 is provided with a device for correcting the dead time or has a built-in correction function.

  The current detector 3 detects a current of the electric motor 4. When the motor 4 is a three-phase motor, two-phase currents such as U-phase and V-phase currents iu and iv are often measured as shown in FIG. 1, for example. The current may be measured. In FIG. 1, the current detector 3 measures the output current of the power converter 2, but the current detector 3 measures the bus current of the power converter 2 as in a current measurement method using a one-shunt resistor. Measurement may be made to estimate each phase current, and in this case, the present invention is applicable.

  The rotation angle detector 5 detects a rotation angle of the electric motor 4. The rotation angle detector 5 of the present invention is not limited as long as it can detect the rotation angle of the electric motor 4 such as an optical encoder, a resolver, or a magnetic sensor. Further, the configuration may be such that the rotation speed of the electric motor 4 is detected and the rotation angle of the electric motor 4 is obtained by time integration of the rotation speed.

  A current command calculator 11 in the current control unit 1 of FIG. 1 outputs current command values i * d and i * q on dq axes which are rotation coordinates of the electric motor 4. For example, when controlling the rotation speed of the motor 4, the current command calculator 11 includes a speed control function, and outputs a current command necessary for the rotation speed of the motor 4 to follow the command speed. . Further, the current command calculator 11 may calculate a current command according to the motor 4 or a signal related to the operation of the motor 4 input from outside the current control unit 1 and output a current command value.

  The d-axis current controller 12 and the q-axis current controller 13 provide voltage command values v * d, v * on the dq axes such that the detected current follows the current command value output from the current command calculator 11. Calculate and output q. A detailed description will be given later.

The three-phase / dq-axis converter 15 converts the currents iu and iv of the electric motor 4 detected by the current detector 3 into a current id on the d-axis and a current iq on the q-axis by the calculation of the equation (1). . Although FIG. 1 shows a configuration for detecting the u-phase and the v-phase among the three-phase currents of the electric motor 4, a configuration for detecting the other two phases may be employed. The three-phase / dq-axis converter 15 is not limited to the expression (1), and may be any converter that converts the detected current of the electric motor 4 onto the d-q axes.
The current id on the d-axis and the current iq on the q-axis are the detected current values on the d-axis and the q-axis, respectively.

  The dq-axis / 3-phase converter 14 calculates the d-axis voltage command value v * d and the q-axis current command value v * q output from the d-axis current controller 12 and the q-axis current controller 13 according to the equation (2). It is converted into three-phase voltage command values vu, vv, vw. The dq-axis / three-phase converter 14 is not limited to the expression (2), and may be any converter that converts a dq-axis voltage into a three-phase voltage.

Hereinafter, the d-axis current controller 12 and the q-axis current controller 13 of the current controller 1 will be described in particular. At least the d-axis current controller 12 and the q-axis current controller 13 of the current controller 1 are configured by a computer. be able to. The computer includes various programs for processing the target response filter 21, the target response compensator 22, the current controller 23, and the subtractors 24, 25, and the adder 26, which are shown in functional blocks in FIG. It is composed of a memory in which various kinds of setting information necessary for processing are stored, and a processor which executes processing in accordance with various programs and setting information.
Also, portions of the current control unit 1 shown in FIG. 1 other than the d-axis current controller 12 and the q-axis current controller 13 shown in FIG. 1 can be similarly configured by the same computer.
Further, the portions shown by the respective functional blocks may be constituted by digital circuits for executing the respective functions.

  FIG. 2 shows an example of an internal configuration common to the d-axis current controller 12 and the q-axis current controller 13, and shows specific processing contents. Since the d-axis current controller 12 and the q-axis current controller 13 have the same processing content, they will be described with reference to the same figure. That is, in FIG. 2, a current command value i * indicates a d-axis or q-axis current command, a current detection value i indicates a d-axis or q-axis current detection value, and a voltage command value v * indicates a d-axis or q-axis voltage. Indicates a command value.

2, a target response filter 21 receives a current command value i * and outputs a control response according to a design value to the current command value, that is, a target response current i21 responding at a target response speed. Details of this filter will be described later. The target response current value i21 responding with the control response value as the design value output from the target response filter 21 is compared with the current detection value i by the subtracter 25, and the deviation is output. The deviation i25 between the target response current value i21 and the current detection value i, which responds with the control response according to the design value calculated by the subtracter 25, is input to the target response compensator 22. The target response compensator 22 amplifies the deviation i25 output from the subtractor 25 by a target response gain associated with the current detection value i and outputs the result as a compensation current value i22. The compensation current value i22 is added by the adder 26 to the deviation i24 between the command current value i * calculated by the subtractor 24 and the current detection value i. The signal i26 output from the adder 26 is input to the current controller 23, and the current controller 23 calculates and outputs a voltage command value v * for the electric motor 4.
Note that the current controller 23, the subtractor 24, and the adder 26 constitute a current control unit. Further, the target response compensator 22 and the subtracter 25 constitute a target response compensator.

FIG. 3 shows a diagram in which a motor model is applied to the internal configuration of FIG. FIG. 3 is different from FIG. 2 in that an electric motor model 31 which is a model of the electric motor 4 is added. Therefore, the motor model 31 indicates a d-axis or q-axis motor model. In order to simplify the following description, FIG. 3 will be described according to a model converted from a symbol as shown in FIG. 4 and modeled. That is,
P (s): Motor model 31
C1 (s): current controller 23
K: target response compensator 22
C2 (s): target response filter 21
And In FIG. 4, a model 31 of the d-axis or q-axis motor 4 is expressed by Expression (3) if the d-axis and q-axis interference terms are ignored or non-interference control is applied.

Since the d-axis or q-axis motor model can be expressed by the same equation, it is expressed by equation (3). In equation (3),
Lm: d-axis inductance or q-axis inductance value of the motor 4;
Rm: winding resistance value of the motor 4
s: Indicates a Laplace operator. Since the present invention can be implemented with the same control system configuration for both the d-axis and the q-axis, the following description will be made based on the motor model of Expression (3). The current controller 23 applies PI control to the model of the motor 4 shown in Expression (3) as follows.

here,
ωc: design value of control response of the d-axis current controller 12 or the q-axis current controller 13,
L: d-axis or q-axis inductance value of the motor 4 set by the d-axis current controller 12 or the q-axis current controller 13;
R: a winding resistance value of the electric motor 4 set by the d-axis current controller 12 or the q-axis current controller 13.

  Next, a case is considered in which the d-axis current controller 12 or the q-axis current controller 13 is configured only with the control law shown in Expression (4). That is, the target response filter 21 and the target response compensator 22 are ignored from FIG. In this case, the open loop characteristics of the d-axis current controller 12 or the q-axis current controller 13 can be calculated as follows.

Hereinafter, assuming that R = Rm, that is, the resistance value of the motor 4 matches the resistance value set by the controller, the effect of the inductance error between the inductance value of the motor 4 and the inductance value set by the controller will be described. . FIG. 5 shows a gain diagram of the open-loop characteristic common to the d-axis current controller 12 and the q-axis current controller 13, that is, a gain diagram of Expression (5). In FIG.
A indicates that the d-axis or q-axis inductance of the motor 4 has an error of + 50% compared to the inductance set by the d-axis current controller 12 or the q-axis current controller 13;
B indicates that the d-axis or q-axis inductance of the motor 4 matches the inductance set by the d-axis current controller 12 or the q-axis current controller 13;
C is when the d-axis or q-axis inductance of the motor 4 has an error of −50% compared to the inductance set by the d-axis current controller 12 or the q-axis current controller 13.
Is shown.
It is assumed that the design value of the control response ωc of the d-axis current controller 12 or the q-axis current controller 13 in Expression (4) is set to 100 Hz.

In FIG. 5, the point where the open loop characteristic intersects with the gain 0 [dB] is the control response of the actual current control.
In the case of A, since the inductance error is + 50%, the control response ωA is 100 Hz × 1 / 1.5 = 66 Hz.
In the case of B, since there is no inductance error, the control response ωB is 100 Hz as designed.
In the case of C, since the inductance error is −50%, the control response ωC is 100 Hz × 1 / 0.5 = 200 Hz.
As described above, when there is an error between the inductance of the electric motor 4 and the inductance set in the d-axis current controller 12 or the q-axis current controller 13, a control response as designed cannot be achieved.

  FIG. 6 shows a change in current response to a step-like command current value in the case where the present invention is not applied at three types of inductance errors A, B, C in FIG. In FIG. 6, the response in the case of B is a response of 100 Hz as designed, but when the control response becomes smaller than the design value due to the inductance error as in the case of A, the rise of the step-like command current value X rises. It will be slow and the convergence time will be long. When the control response becomes larger than the design value due to an inductance error as shown in C, the rise is quicker and the time required to converge to the command current value X becomes shorter. Generation, vibration, and in the worst case, the current control loop may become unstable. Therefore, it is necessary to suppress the fluctuation of the control response due to the inductance error and to achieve the designed performance.

  If a supplementary explanation is added here, the current control response ωc indicates the band of current control, and the band is a measure of responsiveness, that is, quick response. As described above, the point where the gain becomes 0 [dB] when viewed from the open loop characteristics of the current control is the band. In the present invention, the responsiveness, that is, the quick response, indicates at what speed and time the detected current value follows the command current value. For example, the larger the control response, the shorter the time required for convergence. This is evaluated using a time constant (T = 1 / (2πω) (ω is a control band [Hz]) as an evaluation value.The time constant is a time until the detected current reaches 63% of the command current. The shorter this time, that is, the greater the control response, the shorter the time required for convergence, so that as described above, the response of the detected current unintentionally becomes faster or slower when the band changes. This is shown in the open-loop characteristic of FIG. 5, and the time response for easy understanding is shown in the current response of FIG.

  When the set inductance of the d-axis current controller 12 or the q-axis current controller 13 has no error with the inductance of the electric motor 4, that is, when L = Lm is satisfied, the open-loop characteristic Gop (s) shown in Expression (5) becomes The following equation is obtained.

  Therefore, the closed loop characteristic Gcl (s) in the ideal state where there is no error between the inductance of the motor 4 and the inductance set by the current controller is as follows.

  Therefore, when there is no error between the inductance of the motor 4 and the inductance set by the current controller, the current detection value follows the current command value with a first-order lag response. Equation (7) is a relational expression showing an ideal response in the conventional current control, and this transfer characteristic is set as the target response filter 21 (C2 (s)) in FIGS. As a result, the target response filter 21 outputs an ideal target response current value i21 for the current command value i * assuming that there is no inductance error between the set value of the current controller and the actual value of the motor.

  The open-loop or closed-loop characteristics of the d-axis current controller 12 or the q-axis current controller 13 do not take the target response filter 21 and the target response compensator 22 into account. The effect will be described in consideration of the device 22. When the open-loop characteristics of the d-axis current controller 12 or the q-axis current controller 13 are determined in consideration of the target response filter 21 and the target response compensator 22, the following is obtained.

  The ideal open loop characteristic of the d-axis current controller 12 or the q-axis current controller 13 is as shown in Expression (6). In Expression (8), the actual value of the motor and the setting of the current controller are set. Due to the inductance error with the value, the ideal open loop characteristics are not obtained. Here, considering that equation (8) approaches equation (6) using K that can be set freely, if the target response gain K of the target response compensator 22 is selected to be sufficiently large, it is possible to open even if there is a parameter error. It can be seen that the loop characteristic can be approximated to the equation (6).

  Next, the target response gain K of the target response compensator 22 will be described. From the equation (8), if K is made infinitely large, the influence of the inductance error can be reduced to a negligible level, and the open-loop characteristics can be made closer to the ideal characteristics. However, if the target response gain K of the target response compensator 22 is too large, the difference between the target response current value (i21) output from the target response filter 21 and the current detection value i is excessively amplified, and the d-axis or q There is a possibility that the voltage command values v * d and v * q output by the shaft current controllers 12 and 13 are saturated, or current control becomes unstable due to an excessive voltage command. Further, if a small target response gain K is selected in order to prevent the saturation of the voltage command value and the instability of the current control, the influence of the inductance error cannot be reduced and the control response cannot be constant. Therefore, it is preferable that the target response gain K of the target response compensator 22 is set to an appropriate value such that the influence of the inductance error can be canceled in a desired current control band, that is, the current control response ωc in Expression (4). . Equation (8) can be modified as follows.

  Here, ΔL is represented by ΔL = Lm / L, and is the ratio of the inductance Lm of the electric motor 4 to L set by the current controller, that is, the ratio of the error of the inductance. When the inductance Lm of the motor 4 is 50% smaller than the design value, ΔL = 0.5, and when it is 50% larger, ΔL = 1.5. The transfer characteristics in parentheses in equation (9) are represented as in equation (10).

  If this transfer characteristic becomes 0 in a desired control band, that is, the current control response ωc, it is understood that the open-loop characteristic becomes the ideal characteristic shown in Expression (6). In order for the equation (10) to be 0, the ratio ΔL = 1 between the inductance Lm of the motor 4 and L set by the current controller is a condition from the numerator = 0, and this is the actual value of the motor 4. This is a condition under which there is no inductance error between the current and the set value in the current controller. Since only the target response gain K of the target response compensator 22 can be operated, the equation (10) cannot be completely set to zero. Therefore, the equation (10) is made closer to 0 by the target response gain K of the target response compensator 22. That is, equation (11) should be satisfied. Here, ε is a positive constant sufficiently smaller than 1. Ideally, equation (11) should be set to 0, but since it cannot be set to 0 for the above-mentioned reason, a sufficiently small positive value is used.

  When the frequency transfer function of Expression (11) is calculated and the gain in the current control response ωc is calculated, a relational expression such as Expression (12) is obtained.

  By solving the equation (12) for the target response gain K of the target response compensator 22, it is possible to obtain the target response gain K that brings the equation (8) closer to the ideal open loop characteristic in the current control response ωc. Here, the resistance value R, the inductance value L, and the control response ωc are values set in the current controller, and ε is a design value, all of which are constants. Therefore, the target response gain K obtained by the equation (12) is, as shown in the equation (13), a function f (ΔL) of a ratio ΔL between the inductance value Lm of the electric motor 4 and the inductance value L set by the current controller. Become.

  Therefore, if the ratio ΔL between the inductance Lm of the electric motor 4 and L set by the current controller is obtained, the target response gain K that brings the open loop characteristics closer to the ideal characteristics can be obtained. By using this target response gain K, the target response compensator 22 can calculate the compensation current value without any added or missing, the influence of the inductance error can be reduced, and a constant control response can be realized.

The ratio ΔL between the inductance Lm of the motor 4 and L set by the current controller is ΔL = Lm / L, and it is sufficient that the inductance value Lm of the motor is known. FIG. 7 is a diagram illustrating an example of a function model of inductance, showing a relationship between a current value and an inductance value. An inductance value obtained by an analysis of a motor by a computer or a characteristic measurement test of the motor is plotted, and an approximate value of a function obtained by linearly interpolating the analysis value or the measured value is shown. The inductance value Lm of the motor is calculated by a function approximation value based on such a functional expression, and L set by the current controller is known, so that the inductance Lm of the motor 4 and L set by the current controller are calculated. By calculating the ratio ΔL, the target response gain K shown in the equation (13) can be calculated, and the effect of the inductance error can be suppressed, and the control response can be made constant.
When the d-axis current controller 12 and the q-axis current controller 13 of the current control unit 1 are constituted by a computer, the function model of the inductance is stored in the memory, and the target response compensator 22 reads out from the memory and calculates the function. I do.

  Although FIG. 7 shows a diagram obtained by linearly interpolating the analysis values and the measurement values, the types of the functions are not limited, such as approximating a quadratic function or an exponential function. Any configuration can be used as long as the inductance value can be calculated using the current value as an input. Further, a function of the ratio ΔL between the inductance Lm of the motor 4 and L set by the current controller is stored in association with the current value, and the ratio ΔL between the inductance Lm and L set by the current controller is directly calculated. The present invention can be embodied in a configuration in which calculations are performed.

  As described above, the ratio ΔL between the inductance Lm and L set by the current controller can be considered as a function of the current value. Therefore, ΔL can be described as ΔL (i) using the current value i, and equation (13) can be written as follows.

    K = f (ΔL (i))

  The target response gain K is a function of the ratio ΔL between the inductance Lm and L set by the current controller. Since ΔL is given as a function of the current value, the target response gain K is also calculated as a function of the current value. be able to. For example, if ΔL can be described by a linear function of the current value i, then ΔL = a × i + b (a and b are constants). Substituting this into equation (13) gives, eventually, equation (13). K = f (i). Therefore, the target response compensator 22 shown in FIG. 2 has a configuration in which the current detection value i is input.

  Here, since an error is included in the inductance value obtained by the function, an error may occur in the target response gain K. However, by setting the design value ε of Expression (12) to a sufficiently small value, even if the target response gain K has an error, the gain of Expression (10) is set to a sufficiently small value at the frequency of the control response ωc. be able to. Therefore, even if there is an error in the inductance value obtained by the function, the control performance does not deteriorate.

  FIG. 9 shows a current response when the present invention is applied under the conditions shown in FIG. Under all conditions, the response is the same for the step-like command current value X, and the effect of the present invention can be confirmed. Therefore, even if the inductance of the motor 4 is different from the inductance set by the current control unit, the current detection value i is equal to the current command value i at the target response speed without changing the control response by applying the present invention. * Can be followed.

  Further, according to the present invention, it is possible to compensate for a voltage disturbance. FIG. 10 is a block diagram similar to FIG. 4 except that the voltage disturbance w is added to the voltage command value V * output from the current controller (C1 (s)) 23. In the above description, the explanation has been made on the assumption that the interference term is ignored or the interference term is canceled by the application of the non-interference control. In some cases, the non-interfering terms are not accurately canceled and act as voltage disturbances. At this time, when the transfer characteristic Gwi (s) from the voltage disturbance w to the current detection value i is obtained, Expression (14) is obtained.

FIG. 11 shows a gain diagram of Expression (14). In FIG.
A is a gain diagram of the equation (14) when the target response gain K = 0,
B is a gain diagram of Expression (14) when the target response gain K of Expression (13) is applied;
Is shown. It can be seen that the gain of B is smaller than that of A. Since the voltage disturbance w is generally treated as a low-frequency disturbance, it can be seen that the target response gain K has an effect of suppressing the voltage disturbance. Therefore, according to the present invention, it is possible to compensate for a change in response due to voltage disturbance.

Embodiment 2 FIG.
In the first embodiment, the inductance value is calculated by the function, and the target response gain K is obtained. In the second embodiment, the target response gain K is obtained from the inductance table data.
FIG. 8 shows an example of table data of a current value and an inductance value in the electric motor control device according to the second embodiment of the present invention. The inductance value obtained by the analysis of the motor by the computer or the characteristic measurement test of the motor is stored in the memory of the computer constituting the d-axis current controller 12 and the q-axis current controller 13 as table data in association with the current value as table data. Keep it. Then, the inductance value Lm of the motor is calculated, and L set by the current controller is known. Therefore, if the ratio ΔL between the inductance Lm of the motor 4 and L set by the current controller is calculated, the following equation is obtained. The target response gain K shown in 13) can be calculated, the influence of the inductance error can be reduced, and the control response can be kept constant.
Further, instead of calculating the inductance value of the motor based on the table data, the ratio ΔL between the inductance Lm of the motor 4 and L set by the current controller is stored in a data table, and the inductance Lm of the motor 4 and the current are stored. The configuration may be such that the ratio ΔL to L set by the controller is directly calculated using the current value as an input. Further, the table data is not limited to the table data shown in FIG. 8, but may be any table data that can calculate the motor inductance Lm or that can calculate the ratio ΔL between the inductance Lm of the motor 4 and L set by the current controller. Is not limited.

  As described above, the ratio ΔL between the inductance Lm and L set by the current controller is a value associated with the current value. Therefore, ΔL can be described as ΔL (i) using the current value i, and equation (13) can be written as follows.

  K = f (ΔL (i))

  The target response gain K is a function of the ratio ΔL between the inductance Lm and L set by the current controller. Since ΔL is given as a function of the current value, the target response gain K is also calculated as a function of the current value. be able to. Therefore, the target response compensator 22 shown in FIG. 2 has a configuration in which the current detection value i is input.

  Here, since the inductance value obtained from the table data includes an error, it is conceivable that an error also occurs in the target response gain K. However, by setting the design value ε of Expression (12) to a sufficiently small value, even if the target response gain K has an error, the gain of Expression (10) is set to a sufficiently small value at the frequency of the control response ωc. be able to. Therefore, even if there is an error in the inductance value obtained from the table data, the control performance does not deteriorate.

  Also in the present embodiment, a constant response shown in FIG. 9 can be obtained even if there is an inductance error. Further, needless to say, the same effect as the effect shown in the first embodiment can be obtained.

Embodiment 3 FIG.
FIG. 12 is a diagram schematically showing an example of a configuration of an electric power steering according to a third embodiment of the present invention to which the control device for the electric motor according to the first and second embodiments of the present invention is applied. In FIG. 12, the driver turns a steering wheel 1201 right and left to steer a steering wheel, for example, a front wheel 1203. Torque detector 1202 detects the steering torque of steering system ST including steering wheel 1201, and outputs the detected torque to control device 1205. The control device 1205 is a control device for the electric motor described in the first and second embodiments, and calculates a voltage to be applied to the electric motor 4 using the torque detected by the torque detector 1202 as a torque command. The electric motor 4 generates an assist torque for assisting the steering torque in the steering system ST including the steering wheel 1201 via the gear 1204.

  The torque command input to the control device 1205 is converted into a q-axis current command value i * q by the current command calculator 11 shown in FIG. When the motor 4 is a permanent magnet synchronous machine, the d-axis current command value i * d is set to zero from the viewpoint of motor efficiency. However, in a situation where the rotation speed of the motor 4 is high and voltage saturation occurs, a negative value is obtained. The current is caused to flow in a direction to eliminate the voltage saturation by the d-axis current command value i * d. In particular, when the load on the front wheel 1203 is large and high-speed steering is required, a negative d-axis current command value i * d is generated. The d-axis current command value i * d or q-axis current command value i * q generated as described above is input to the d-axis current controller 12 or the q-axis current controller 13. Then, the voltage command value v * is calculated and output by the current control calculation described in the first or second embodiment.

  In the electric power steering apparatus as shown in FIG. 12, when there is an inductance error between the electric motor and the set value in the controller, the electric motor 4 responds to the torque steered by the driver with a delay, or excessive overshoot occurs. It is dangerous because it may occur or perform an operation unintended by the driver. However, by applying the present invention, an assist torque can be stably generated with a constant control response even when there is an inductance error between a motor and a set value in a controller, and a safe electric power steering apparatus is provided. Can be provided.

  As described above, the electric motor control device and the electric power steering device using the same according to the present invention have been described according to the embodiments, but the present invention is not limited to these embodiments.

1 current control unit, 2 power converter, 3 current detector, 4 motor, 5 rotation angle detector,
11 current command calculator, 12 d-axis current controller, 13 q-axis current controller,
14 dq-axis / 3-phase converter, 15 3-phase / dq-axis converter, 21 target response filter,
22 target response compensator, 23 current controller, 24, 25 subtractor, 26 adder,
31 motor model, 1201 steering wheel, 1202 torque detector, 1203 front wheel,
1204 gear, 1205 control device, ST steering system.

Claims (8)

A current command calculator that calculates a current command of the motor and outputs the current command value;
A current detector that detects the current of the electric motor and outputs it as a current detection value;
A target response filter that calculates a target response current that responds at a target response speed to the current command value and outputs the target response current as a target response current value;
A target response compensator that calculates a compensation current by multiplying a difference between the target response current value and the current detection value by a target response gain and outputs the result as a compensation current value;
A voltage command value for the power converter that calculates a voltage command to the motor based on a sum of the compensation current value and a deviation between the current command value and the current detection value, and controls the driving of the motor. A current control unit that outputs as
With
The target response compensator calculates the compensation current value by the target response gain that is variable according to the current detection value ,
The motor control device, wherein the target response gain is a function of a ratio between an inductance value of the motor and an inductance value set by the current control unit, and the ratio of the inductance values is a function of the detected current value .   The motor control device according to claim 1, wherein the target response filter calculates the target response current value based on a closed loop transfer characteristic configured when there is no parameter error between the current control unit and the motor.   The said target response compensation part calculates the said target response gain using the inductance value calculated | required by the function model of the inductance of the said motor which shows the relationship between the said detected current value and the inductance value of the said motor previously calculated. 3. The control device for an electric motor according to 1 or 2.   The motor control device according to claim 3, wherein the function model of the inductance is a function formula of the current detection value.   4. The motor control device according to claim 3, wherein the inductance function model is table data indicating a relationship between the detected current value and the inductance value of the motor determined in advance.   The control device for an electric motor according to any one of claims 1 to 5, wherein the target response gain is a value that causes a transfer characteristic portion in an open-loop transfer characteristic of the control device to approach 0 in a desired control band. A steering system including a steering wheel and a steering wheel;
A torque detector that detects the torque of the steering system;
An electric motor that generates assist torque to the steering system;
The motor control device according to any one of claims 1 to 6 , which controls the motor.
With
An electric power steering device, wherein a current command calculator of the control device inputs a detected torque from the torque detector and converts the torque into a current command value. Calculating a current command of the electric motor and outputting the current command value;
A step of detecting a current of the electric motor by a current detector and outputting the detected current as a current detection value;
A step of calculating a target response current that responds at a target response speed to the current command value and outputting the calculated target response current as a target response current value,
A step of calculating a compensation current by multiplying a difference between the target response current value and the current detection value by a target response gain, and outputting the result as a compensation current value;
A voltage command value for the power converter that calculates a voltage command to the motor based on a sum of the compensation current value and a deviation between the current command value and the current detection value, and controls the driving of the motor. Output as
With
The compensation current value is calculated by the target response gain that is variable according to the current detection value ,
The motor control method , wherein the target response gain is a function of a ratio between an inductance value of the motor and an inductance value when calculating the voltage command, and the ratio of the inductance values is a function of the current detection value .

Images