JP7768041B2 - Motor control device, electric actuator, and electric power steering device - Google Patents

Description

The present invention relates to a motor control device, an electric actuator, and an electric power steering device.

2. Description of the Related Art Conventionally, motor control devices equipped with a disturbance suppressor that suppresses disturbances (noise) entering a motor control system are known.
For example, Patent Document 1 proposes a motor control device equipped with a disturbance observer that suppresses torque disturbances.

JP 2016-163370 A

However, if the disturbance suppression band is set to a high band so that the disturbance suppressor can suppress the disturbance even when the motor is rotating at high speed, while the disturbance is suppressed, the stability (phase margin) of the current control system decreases, and vibrations occur at the phase margin frequency.
Therefore, an object of the present invention is to suppress vibrations when suppressing disturbances in a high frequency band.

To solve the above problem, one aspect of the motor control device according to the present invention comprises a command value calculation unit that calculates a voltage command value based on the difference between a current command value and an actual current value; a disturbance suppression unit that calculates a suppression value to be added to the current command value based on the actual current value and the motor rotation angle in order to suppress at least torque disturbances; and a characteristic conversion unit that acts on the voltage command value to convert the electrical characteristics of the motor reflected in feedback control in the feedback control.

After detailed investigation by the inventors, it was found that the main factor affecting stability is the motor's electrical characteristics. The motor control device described above can change the motor's electrical characteristics to the desired electrical characteristics during control, thereby suppressing vibrations during disturbance suppression in the desired frequency range, including the high frequency range.

In the above motor control device, it is preferable that the command value calculation unit calculates a voltage command value for the q axis and a voltage command value for the d axis, and the characteristic conversion unit acts on each of the q axis and the d axis voltage command values. Because the influence of back electromotive force differs between the q axis and the d axis, the desired electrical characteristics are achieved by acting in accordance with the respective voltage command values.

In the motor control device, the characteristic conversion unit determines whether the gain G _LR acting on the q-axis voltage command value is:
G _LR ={(Ls+R)(Js+D)+K _E K _T }/{(L ₀ s+R ₀ )(Js+D)+K _E K _T }
however,
It is preferable to express it as follows: s: Laplace operator L[H]: inductance of the motor R[Ω]: resistance of the motor J[kgm ² ]: inertia of the motor D[Nm/(rad/s)]: viscosity of the motor K _E [V/(rad/s)]: EMF constant of the motor K _T [Nm/A]: torque constant of the motor L ₀ [H]: desired inductance R ₀ [Ω]: desired resistance.
The gain G _LR expressed by the above formula makes it possible to realize the desired inductance L ₀ and the desired resistance R ₀ in controlling the q axis.

In the motor control device, the characteristic conversion unit determines whether the gain G _LR acting on the d-axis voltage command value is:
G _LR =(Ls+R)/(L ₀ s+R ₀ )
however,
It is preferable to express it as follows: s: Laplace operator L[H]: inductance of the motor R[Ω]: resistance of the motor L ₀ [H]: desired inductance R ₀ [Ω]: desired resistance.
The gain G _LR expressed by the above formula makes it possible to realize the desired inductance L ₀ and the desired resistance R ₀ in controlling the d axis.

In order to solve the above problem, one aspect of the electric actuator according to the present invention includes any one of the motor control devices described above, and a motor to which a voltage controlled by the motor control device is applied.
With such an electric actuator, vibrations are suppressed when disturbances are suppressed in a high frequency range, so that an actual current flows through the motor in accordance with the current command value, thereby obtaining a desired output.

In order to solve the above problem, one aspect of an electric power steering device according to the present invention includes any of the motor control devices described above, a motor to which a voltage controlled by the motor control device is applied, and a power steering mechanism driven by the motor.
According to such an electric power steering device, an actual current flows to the motor in accordance with the current command value, and a desired output is obtained, so that the steering assist accuracy is high.

This invention makes it possible to suppress vibrations during disturbance suppression in high frequency bands.

1 is a configuration diagram schematically illustrating an embodiment of an electric power steering device. FIG. 2 is a functional block diagram illustrating an example of a functional configuration of a control unit. FIG. 2 is a functional block diagram showing an example of a functional configuration of a voltage command value calculation unit. FIG. 2 is a block diagram showing a specific functional configuration of a rotation speed estimation unit. FIG. 2 is a block diagram including an LR conversion unit and electrical, magnetic, and mechanical characteristics of a motor. FIG. 6 is a block diagram in which the electrical, magnetic, and mechanical characteristics shown in FIG. 5 are summarized in one block. FIG. 10 is a diagram showing post-conversion characteristics combining the LR conversion unit and the electric, magnetic, and mechanical characteristics of the motor. FIG. 10 is a diagram illustrating the characteristics of the LR conversion unit on the d axis. FIG. 10 is a diagram showing converted characteristics that combine the LR conversion unit and the electrical characteristics of the motor on the d axis. FIG. 4 is a diagram showing an approximation of a transfer function in the control system shown in FIG. 3 . 10 is a graph showing a change in stability of a control system due to a change in inductance. 10 is a graph showing a change in stability of a control system due to a change in resistance. 10 is a graph showing a change in stability of a control system when conversion of inductance and resistance is combined.

Embodiments of the present invention will be described below with reference to the drawings. However, to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art, more detailed descriptions than necessary may be omitted. For example, detailed descriptions of matters that are already well known or duplicate descriptions of substantially identical configurations may be omitted. Furthermore, elements shown in earlier-described figures may be referenced as appropriate in the descriptions of later figures.

In this specification, embodiments of the present disclosure will be described using as an example an electric actuator that supplies power from a power source to a three-phase motor with three-phase (A, B, and C) windings. However, the scope of the present disclosure also includes electric actuators that supply power from a power source to an n-phase motor with n-phase (n is an integer equal to or greater than 4) windings, such as four or five phases.

FIG. 1 is a schematic diagram showing the configuration of an embodiment of an electric power steering device.
The electric power steering device 100 of this embodiment is equipped with a steering mechanism having a steering wheel 1, a column shaft 2, a reduction gear 3, universal joints 4A and 4B, a pinion-rack mechanism 5, and a tie rod 6 for the steered wheels. The electric power steering device 100 also includes a torque sensor 10, a motor 20, a control unit 30, an ignition key 11, a vehicle speed sensor 12, and a battery 14. The combination of the motor 20 and the control unit 30 corresponds to one embodiment of the electric actuator of the present invention, and the control unit 30 corresponds to one embodiment of the motor control device of the present invention. The steering mechanism is driven by the motor 20.

A column shaft 2 of the steering wheel 1 is connected to a tie rod 6 of the steered wheels via a reduction gear 3, universal joints 4A and 4B, and a pinion rack mechanism 5. A torque sensor 10 that detects the steering torque of the steering wheel 1 is provided on the column shaft 2, and a motor 20 that assists the steering force of the steering wheel 1 is connected to the column shaft 2 via the reduction gear 3.
The torque sensor 10 detects the steering torque Th transmitted from the steering wheel 1 due to the driver's steering operation.

A control unit (ECU) 30 that controls the power steering device 100 is supplied with power from a battery 14, which is a power source, and also receives an ignition key signal from an ignition key 11. The control unit 30 calculates a steering assist torque using an assist map or the like based on the steering torque Th detected by the torque sensor 10 and the vehicle speed Vh detected by the vehicle speed sensor 12.
Then, the control unit 30 controls the current I supplied to the motor 20 so as to generate the calculated assist torque. A voltage controlled by the control unit 30 is applied to the motor 20, and the current I is controlled by the controlled voltage. The assist torque generated by driving the motor 20 is applied to the steering system as an assist force for the driver's steering operation (steering assist force), allowing the driver to operate the steering wheel with less force.

The quality of the steering feel is determined by the amount of assist torque generated from the steering torque Th output by steering and the vehicle speed Vh. Furthermore, the performance of the electric power steering device is greatly affected by the accuracy with which the current I required to generate the assist torque is passed to the motor 20.

The control unit 30 may be, for example, a computer including a processor and peripheral components such as a storage device. The processor may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit).
The storage device may include any of semiconductor storage devices, magnetic storage devices, and optical storage devices. The storage device may include memories such as registers, cache memories, and memory used as main storage devices, such as ROMs (Read Only Memory) and RAMs (Random Access Memory).

The control unit 30 may be configured with dedicated hardware, which will be described below, for executing each information processing.
For example, the control unit 30 may include a functional logic circuit configured in a general-purpose semiconductor integrated circuit, or may include a programmable logic device (PLD) such as a field-programmable gate array (FPGA).

FIG. 2 is a functional block diagram showing an example of the functional configuration of the control unit 30.
The control unit 30 includes a current command value calculation unit 40, a voltage command value calculation unit 45, a two-phase/three-phase conversion unit 46, a PWM (Pulse Width Modulation) control unit 47, an inverter 48, and a three-phase/two-phase conversion unit 49, and drives the motor 20 by vector control. The motor 20 is, for example, a three-phase motor.
The functions of the current command value calculation unit 40, the voltage command value calculation unit 45, the two-phase/three-phase conversion unit 46, the PWM control unit 47, and the three-phase/two-phase conversion unit 49 are realized, for example, by the processor of the control unit 30 executing a computer program stored in a storage device.

The current command value calculation unit 40 calculates current command values Iq0 and Id0 that indicate the currents of the d and q axes that should be passed to the motor 20 based on the steering torque Th and the vehicle speed Vh.
On the other hand, the currents ia, ib, ic flowing in each phase of the motor 20 are detected by current sensors 60, 61, 62 provided in each layer, and the detected currents ia, ib, ic are converted into actual current values id, iq of the dq2 axes by the three-phase/two-phase conversion unit 49 and fed back.

The current command values Iq0, Id0 are input to the voltage command value calculation unit 45, and the fed-back actual current values id, iq are also input. The voltage command value calculation unit 45 calculates voltage command values vq, vd such that the difference between the current command values Iq0, Id0 and the actual current values id, iq is zero. The two-phase/three-phase conversion unit 46 converts the voltage command values vd, vq into three-phase voltage command values va, vb, vc.

The PWM control unit 47 generates PWM-controlled gate signals based on the three-phase voltage command values va, vb, and vc. The inverter 48 is driven by the gate signals generated by the PWM control unit 47 and applies voltages indicated by the three-phase voltage command values va, vb, and vc to each phase of the motor 20. As a result, currents indicated by the current command values Iq0 and Id0 are supplied to the motor 20.

The resolver 63 detects the motor angle (rotation angle) θ of the motor 20, and the detected motor angle θ is fed back to the current command value calculation unit 40 and used for vector control. A motor rotation angle sensor may be used instead of the resolver 63. Note that the rotation angular velocity ω of the motor 20 calculated based on changes in the motor angle θ may be input to the current command value calculation unit 40 together with the motor angle θ or instead of the motor angle θ.

Fig. 3 is a functional block diagram showing an example of the functional configuration of the voltage command value calculation unit 45. Fig. 3 also shows a model of the motor 20. Fig. 3 shows the control function of the q axis as a representative, but the voltage command value calculation unit 45 also has a similar control function for the d axis.
The function of the motor 20 is represented by a model having electrical characteristics 21, a torque constant _KT , mechanical characteristics 23, an integral element 24, and an EMF (back electromotive force) coefficient _KE .

An actual current is generated when a voltage is input to the electrical characteristic 21 of the motor 20. The voltage value input to the electrical characteristic 21 includes voltage noise. The gain of the electrical characteristic 21 is expressed as 1/(Ls+R) where L is an inductance [H] and R is a resistance [Ω]. The actual current is detected by current sensors 60, 61, and 62, and the detected value includes current detection noise.
A torque constant K _T [Nm/A] acts on the actual current to generate a motor torque.

The angular velocity of the motor 20 is generated by inputting the motor torque to the mechanical characteristic 23. The gain of the mechanical characteristic 23 is expressed as 1/(Js+D) where J is the inertia [kgm ² ] and D is the viscosity [Nm/(rad/s)].
The angular velocity of the motor 20 passes through an integral element 24 to become a motor angle θ. The motor angle θ is detected by a resolver 63 (or a motor rotation angle sensor), and the detected value contains angle detection noise.

The EMF coefficient K _E [V/(rad/s)] acts on the angular velocity to generate a back electromotive force, which is reflected in the input of the electrical characteristic 21 .
The voltage command value calculation unit 45 includes a control band setting unit 70, a PID (Proportional Integral Differential) control unit 71, a low-pass filter 72, a first delay element 73, an LR conversion unit 74, a second delay element 75, and a disturbance suppression unit 76.

The control band setting unit 70 receives the current command value Iq0 and applies a gain _Gref to the current command value, thereby setting a control band for current control of the motor 20 by the control unit 30. The gain _Gref of the control band setting unit 70 is expressed as follows:
G _ref =ω _ref /(s+ω _ref )
however,
s: Laplace operator ω _ref [rad/s]: current control band.

The PID control unit 71 receives a difference value Δq between the current command value Iq0 and the q-axis actual current value iq, and calculates a voltage command value vq by PID control based on the difference value Δq. The gain G _PID in the PID control unit 71 is expressed as follows:
G _PID = {ω _c L+(R/2)} [1+{ω _c /(2s)}+{s/(2ω _c )}]
however,
s: Laplace operator ω _c [rad/s]: disturbance suppression band L [H]: inductance of the motor R [Ω]: resistance of the motor.

The low-pass filter 72 cuts out current detection noise contained in the q-axis actual current value iq. The gain G _LPF of the low-pass filter 72 is expressed as follows:
G _LPF = ω _LPF / (s+ω _LPF )
however,
s: Laplace operator ω _LPF [rad/s]: Cutoff frequency.

The first delay element 73 functions as a back electromotive force suppressor by feedback with a delay. The gain G _dly in the first delay element 73 is expressed as follows:
G _dly = e ^-Tdly・s
however,
Tdly [μs]: Expressed as the current control period.

The LR conversion unit 74 acts on the voltage command value in order to convert the electrical characteristics of the motor 20 reflected in the feedback control into electrical characteristics desired for the feedback control. The gain _GLR in the LR conversion unit 74 will be described later.
The second delay element 75 represents a delay in the feedback loop. The gain G _DLY of the second delay element 75 is expressed as follows:
G _DLY = e ^-TDLY・s
however,
TDLY [μs]: represents the calculation time from current detection by the current sensors 60, 61, 62 to reflection of the duty in the output of the inverter 48.

The disturbance suppression unit 76 calculates a suppression value to be added to the current command value Iq0 to suppress control disturbances, based on the q-axis actual current value iq and the motor angle θ. The disturbance suppression unit 76 includes a rotation speed estimator 80, a torque disturbance estimator 81, a torque disturbance suppression unit 82, and a high-pass filter 83.
The rotation speed estimator 80 estimates the rotation speed of the motor 20 from the q-axis actual current value iq and the motor angle θ. The rotation speed estimator 80 provides a smooth estimated rotation speed value.

FIG. 4 is a block diagram showing a specific functional configuration of the rotation speed estimation unit 80.
The functional blocks shown in FIG. 4 correspond to the following formulas (1) and (2).


however,
z = Ce ^λs
λ: characteristic root j [kgm ² ]: inertia of motor under control d [Nm/(rad/s)]: viscosity of motor under control k _T [Nm/A]: torque constant of motor under control k: stiffness of motor under control i: actual q-axis current value x ₁ : motor angle.
That is, the q-axis actual current value i and the motor angle _x1 are input to the rotation speed estimator 80, and the rotation speed estimator 80 outputs an estimated rotation speed value _x2 (added with ^). The first block 51, the second block 52, and the third block 53 of the rotation speed estimator 80 correspond to the first term, the second term, and the third term of equation (1), respectively. The fourth block 54 of the rotation speed estimator 80 corresponds to the second term of equation (2). The rotation speed estimated value _x2 (added with ^) is input to the first block 51, the motor angle _x1 is input to the second block 52 and the fourth block 54, and the q-axis actual current value i is input to the third block 53. The outputs of the first block 51, the second block 52, and the third block 53 are added together and input to the integral element 55. The outputs of the integral element 55 and the fourth block 54 are added together to obtain the estimated rotation speed value _x2 (added with ^).

Returning to FIG. 3, the description will continue.
The transfer function Gω in the rotation speed estimation unit 80 is expressed by the matrix T in the following equation (3).

however,
ω _est [rad/s]: estimated rotation speed value ω _obs [rad/s]: cutoff angular frequency in rotation speed estimation.

The torque disturbance estimator 81 estimates the torque disturbance from the q-axis actual current value iq and the estimated rotation speed value. The transfer function G _TRQ in the torque disturbance estimator 81 is expressed by the matrix T in the following equation (4).

where Δτ _est is an estimated torque disturbance value.

The torque disturbance suppression unit 82 calculates a suppression value for suppressing the estimated torque disturbance. The gain G _cmp in the torque disturbance suppression unit 82 is expressed by the following equation (5).

where ω _c is the disturbance suppression band.

The high-pass filter 83 acts on the torque disturbance suppression value to remove the DC component of the torque disturbance. The high-pass filter 83 functions like a notch filter to suppress disturbances of a specific frequency. The gain G _HPF of the high-pass filter 83 is expressed as G _HPF = s/(s + ω _HPF ) using the cutoff frequency ω _HPF .
The disturbance suppression unit 76 accurately suppresses torque disturbances by estimating the torque disturbances, and can also suppress voltage noise, current detection noise, and angle detection noise. When the disturbance suppression band _ωc is set to a high band, disturbance suppression by the disturbance suppression unit 76 can be achieved even in the high rotation range of the motor 20. On the other hand, when the disturbance suppression band _ωc is set to a high band, vibrations are more likely to occur in the feedback control of the voltage command value calculation unit 45, so a configuration that improves the stability of control is incorporated into the voltage command value calculation unit 45.

After detailed investigation by the inventors of the present invention, it was found that the main factor affecting the stability of the voltage command value calculation unit 45 is the electrical characteristics 21 of the motor 20. However, the electrical characteristics 21 of the motor 20 are inseparable from the specifications required of the motor 20, making it difficult to change the hardware of the motor 20. Therefore, an LR conversion unit 74 is incorporated to achieve the desired electrical characteristics in the feedback control of the voltage command value calculation unit 45. The voltage command value calculation unit 45 calculates the q-axis voltage command value vq and the d-axis voltage command value vd, and the LR conversion unit 74 acts on both the q-axis voltage command value vq and the d-axis voltage command value vd.

FIG. 5 is a block diagram including the LR conversion unit 74 and the electric, magnetic and mechanical characteristics 26 of the motor 20.
The motor 20 has the elements shown in Fig. 3 as electrical, magnetic, and mechanical characteristics 26. In q-axis control, a back electromotive force is added between the LR converter 74 and the electrical characteristics 21 of the motor 20, so the LR converter 74 must be designed with this back electromotive force taken into consideration. The back electromotive force added to the input side of the electrical characteristics 21 depends on the electrical characteristics 21, the torque constant _KT , the mechanical characteristics 23, and the EMF coefficient _KE , so all of these elements are related to the design of the LR converter 74.

FIG. 6 is a block diagram in which the electrical, magnetic and mechanical characteristics 26 shown in FIG. 5 are collected into one block.
The gain of the electric/magnetic/mechanical characteristic 26, which is a compilation of the electric characteristic 21, the torque constant _KT , the mechanical characteristic 23, and the _EMF coefficient _KE shown in Fig. 5, is expressed as _kT /{(Ls+R)(Js+D)+ _kEkT }. The corresponding gain of the LR conversion unit 74 is {(Ls+R)(Js+D)+ _{kEkT }}
/{(L ₀ s+R ₀ )(Js+D)+k _E k _T }.
That is, the gain G _LR acting on the q-axis voltage command value is
G _LR ={(Ls+R)(Js+D)+K _E K _T }/{(L ₀ s+R ₀ )(Js+D)+K _E K _T }
however,
It is expressed as follows: s: Laplace operator L[H]: inductance of the motor R[Ω]: resistance of the motor J[kgm ² ]: inertia of the motor D[Nm/(rad/s)]: viscosity of the motor K _E [V/(rad/s)]: EMF constant of the motor K _T [Nm/A]: torque constant of the motor L ₀ [H]: desired inductance R ₀ [Ω]: desired resistance.

FIG. 7 is a diagram showing the converted characteristics obtained by combining the LR conversion unit 74 and the electric/magnetic/mechanical characteristics 26.
The gain of converted characteristic 27, which is a combination of LR conversion unit 74 and electric/magnetic/mechanical characteristic 26, is _kT /{( _L0s + _R0 )(Js+D)+ _{kEkT }} . It can be confirmed that the gain of converted characteristic 27 is a characteristic in which inductance L and resistance R in electric/magnetic/mechanical characteristic 26 shown in Figure 6 are converted into the desired inductance _L0 and resistance _R0 . In other words, the desired LR characteristic is realized in q-axis control by LR conversion unit 74 having the gain shown in Figure 6.

In the case of the LR conversion unit 74 on the d axis, it is not necessary to take the back electromotive force into consideration.
FIG. 8 is a diagram showing the characteristics of the LR converter 74 on the d axis, and FIG. 9 is a diagram showing the converted characteristics combining the LR converter 74 on the d axis and the electrical characteristics 21 of the motor 20.
In the control of the d-axis, since no back electromotive force is added to the input of the electrical characteristic 21 of the motor 20, the gain of the LR conversion unit 74 is calculated as (Ls+R)/(L ₀ s+R ₀ ) for the gain of the electrical characteristic 21, 1/(Ls+R).
That is, the gain G _LR acting on the d-axis voltage command value is
G _LR =(Ls+R)/(L ₀ s+R ₀ )
however,
s: Laplace operator L[H]: inductance of the motor R[Ω]: resistance of the motor L ₀ [H]: desired inductance R ₀ [Ω]: desired resistance.
As shown in Fig. 9, the converted characteristic 27 has a gain of 1/(L ₀ s + R ₀ ), which confirms that the inductance L and resistance R in the electrical characteristic 21 have been converted into the desired inductance L ₀ and resistance R _0. In other words, the desired LR characteristic is realized in the control of the d-axis by the LR conversion unit 74 having the gain shown in Fig. 8.

FIG. 10 is a diagram showing an approximation of the transfer function in the control system shown in FIG.
The transfer function in the control system is roughly divided into a characteristic compensation portion of the disturbance suppression unit 76, a loop transfer function portion of the current control system, and a sensitivity function portion. The characteristic compensation portion of the disturbance suppression unit 76 represents characteristic compensation of the mechanical system in the disturbance suppression unit 76, and includes a portion corresponding to the mechanical system on the actual machine side and a portion corresponding to the mechanical system on the control side. The mechanical system on the actual machine side is the mechanical characteristics 23 of the motor 20 itself, and the mechanical system on the control side is the mechanical characteristics set for control.

The open-loop transfer function portion of the current control system includes the actual portion of the motor 20 , the portion of the LR conversion portion 74 , and the main control portion from the PID control portion 71 to the second delay element 75 .
Since the LR conversion unit 74 is included in the open-loop transfer function of the current control system, the combination of the actual device part and the LR conversion unit 74 part becomes the actual device part in terms of control.
The sensitivity function portion is approximately zero for voltage noise Δv, and exhibits HPF characteristics for current detection noise Δi, torque disturbance Δτ, and angle detection noise Δθ. Therefore, it can be seen that the control system shown in Figure 3 achieves noise suppression for all types of noise. As will be explained below, the stability of the control system is improved by converting the motor characteristics in terms of control to desired characteristics, and noise suppression is achieved even in the high rotation speed range.

FIG. 11 is a graph showing the change in stability of the control system due to the change in inductance.
The horizontal axis in FIG. 11 is a logarithmic axis indicating frequency, and the vertical axis in FIG. 11 indicates amplitude in the upper graph and phase in the lower graph.
In the graph, the thin solid line shows the characteristics before conversion, the thick solid line shows the characteristics when the inductance is halved, and the dotted line shows the characteristics when the inductance is doubled. It can be seen that inductance is mainly sensitive to the resonant frequency of the hardware, and when the inductance is small, the phase advances and the stability of the control system (especially the phase margin) increases.

FIG. 12 is a graph showing the change in stability of the control system due to the change in resistance.
In FIG. 12, the horizontal axis is a pair of axes showing frequency, and the upper vertical axis shows amplitude and the lower vertical axis shows phase.
In the graph, the thin solid line shows the characteristics before conversion, the thick solid line shows the characteristics when the resistance is doubled, and the dotted line shows the characteristics when the inductance is halved. It can be seen that the inductance is mainly sensitive to the damping coefficient, and that a large resistance leads to a phase advance, increasing the stability of the control system.

FIG. 13 is a graph showing the change in stability of the control system when inductance and resistance conversion are combined.
In FIG. 13 as well, the horizontal axis is a pair of axes showing frequency, and the upper vertical axis shows amplitude and the lower vertical axis shows phase.
In the graph, the thin solid line shows the characteristics before conversion, and the thick solid line shows the characteristics when the inductance is halved and the resistance is doubled. It can be seen that the combination of inductance and resistance conversion further advances the phase, further increasing the stability of the control system.

By increasing the stability of the control system (particularly the phase margin), an electric actuator equipped with a motor 20 and a control unit 30 can obtain the desired output by allowing the actual current to flow through the motor 20 in accordance with the current command value, even during high-speed operation. Furthermore, the electric power steering device 100 shown in Figure 1 can obtain the desired output from the motor 20 even during high-speed operation, resulting in high steering assist accuracy.

Note that while the above description shows an example of application to a power steering device, the electric actuator and motor control device of the present invention can be applied to a wide range of fields, including vehicle drive systems and robots. In other words, the embodiments and scope of application of the present invention are not limited to power steering devices.

100... electric power steering device, 1... steering handle, 2... column shaft,
3...reduction gear, 4A, 4B...universal joint, 5...pinion rack mechanism,
6...steered wheel tie rod, 10...torque sensor, 11...ignition key,
12... vehicle speed sensor, 14... battery, 20... motor, 30... control unit,
40...current command value calculation unit, 45...voltage command value calculation unit, 46...two-phase/three-phase conversion unit,
47... PWM control unit, 48... inverter, 49... three-phase/two-phase conversion unit,
60, 61, 62...current sensors, 63...resolver, 70...control band setting unit,
71... PID control unit, 72... low-pass filter, 73... first delay element,
74... LR conversion unit, 75... second delay element, 76... disturbance suppression unit, 80... rotation speed estimation unit,
81...torque disturbance estimation unit, 82...torque disturbance suppression unit, 83...high-pass filter

Claims (5)

a command value calculation unit that calculates a voltage command value based on a difference between a current command value and an actual current value;
a disturbance suppression unit that calculates a suppression value to be added to the current command value based on the actual current value and a rotation angle of the motor in order to suppress at least torque disturbance;
a characteristic conversion unit that acts on the voltage command value to convert the electrical characteristics of the motor reflected in feedback control on the feedback control;
Equipped with
the command value calculation unit calculates a q-axis voltage command value and a d-axis voltage command value;
the characteristic conversion unit acts on each of the q-axis voltage command value and the d-axis voltage command value;
Motor control device. The characteristic conversion unit determines whether a gain G _LR acting on a q-axis voltage command value is:
G _LR ={(Ls+R)(Js+D)+K _E K _T }/{(L ₀ s+R ₀ )(Js+D)+K _E K _T }
however,
2. The motor control device of claim 1, wherein s is expressed as Laplace operator L[H]: inductance of the motor R[Ω]: resistance of the motor J[kgm ² ]: inertia of the motor D[Nm/(rad/s)]: viscosity of the motor K _E [V/(rad/s)]: EMF constant of the motor K _T [Nm/A]: torque constant of the motor L ₀ [H]: desired inductance R ₀ [Ω]: desired resistance. The characteristic conversion unit determines whether a gain G _LR acting on a d-axis voltage command value is:
G _LR =(Ls+R)/(L ₀ s+R ₀ )
however,
2. The motor control device according to claim 1, wherein s is expressed as a Laplace operator, L[H] is the inductance of the motor, and R[Ω] is the resistance of the motor. L ₀ [H] is the desired inductance, and R ₀ [Ω] is the desired resistance. The motor control device according to any one of claims 1 to 3 ;
a motor to which a voltage controlled by the motor control device is applied;
An electric actuator equipped with The motor control device according to any one of claims 1 to 3 ;
a motor to which a voltage controlled by the motor control device is applied;
a steering mechanism driven by the motor;
An electric power steering device equipped with