阅读说明：本技术 电动机控制装置和电动机控制方法 (Motor control device and motor control method ) 是由 藤原弘 田泽徹 三枝史岳 于 2018-05-18 设计创作，主要内容包括：一种电动机控制装置(300),其反馈控制系统的控制带宽能够变更,所述电动机控制装置用于对电动机或负载的状态量进行反馈控制,所述电动机控制装置(300)具备：滤波器系数能够变更的陷波滤波器(302),其配置于反馈控制系统内；陷波控制部(304),其变更陷波滤波器(302)的作为中心频率的陷波频率,使得去除由与电动机相关的机械共振引起的振动成分；以及控制系数设定部(305),其根据控制带宽和陷波频率来变更控制带宽和陷波滤波器(302)的滤波器系数中的至少一方,使得反馈控制系统稳定化。(A motor control device (300) capable of changing a control bandwidth of a feedback control system for feedback-controlling a state quantity of a motor or a load, the motor control device (300) comprising: a notch filter (302) capable of changing filter coefficients, which is disposed in the feedback control system; a notch control unit (304) that changes the notch frequency of the notch filter (302) as the center frequency so as to remove the vibration component caused by the mechanical resonance of the motor; and a control coefficient setting unit (305) for changing at least one of the control bandwidth and the filter coefficient of the notch filter (302) in accordance with the control bandwidth and the notch frequency, thereby stabilizing the feedback control system.)

1. A motor control device capable of changing a control bandwidth of a feedback control system for feedback-controlling a state quantity of a motor or a load, the motor control device comprising:

a notch filter having a changeable filter coefficient, which is disposed in the feedback control system;

a notch control unit that changes a notch frequency of the notch filter, which is a center frequency, so as to remove a vibration component caused by mechanical resonance related to the motor; and

and a control coefficient setting unit configured to change at least one of the control bandwidth and a filter coefficient of the notch filter in accordance with the control bandwidth and the notch frequency, thereby stabilizing the feedback control system.

2. The motor control device according to claim 1,

the control coefficient setting unit may change at least one of the control bandwidth and the notch frequency only when the notch frequency is lower than a predetermined reference value, so as to stabilize the feedback control system.

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

the notch control unit changes the notch frequency only within a predetermined notch frequency range.

4. The motor control device according to claim 3,

the predetermined range of notch frequencies is determined such that the notch frequencies do not overlap with a control bandwidth of the feedback control system.

5. A motor control device capable of changing a control bandwidth of a feedback control system for feedback-controlling a state quantity of a motor or a load, the motor control device comprising:

a first notch filter and a second notch filter having changeable filter coefficients, the first notch filter and the second notch filter being arranged in series in the feedback control system;

a first notch control unit that changes a first notch frequency, which is a center frequency of the first notch filter, so as to remove a vibration component caused by mechanical resonance related to the motor;

a second notch control unit that changes a second notch frequency, which is a center frequency of the second notch filter, so as to remove a vibration component caused by mechanical resonance related to the motor; and

and a control coefficient setting unit configured to change at least one of the control bandwidth, the filter coefficient of the first notch filter, and the filter coefficient of the second notch filter in accordance with the control bandwidth, the first notch frequency, and the second notch frequency, so as to stabilize the feedback control system.

6. A motor control method for feedback-controlling a state quantity of a motor or a load by a motor control device capable of changing a control bandwidth of a feedback control system, the motor control method comprising:

a notch control step of changing a notch frequency, which is a center frequency, of a notch filter that is disposed in the feedback control system and whose filter coefficient can be changed so as to remove a vibration component caused by mechanical resonance related to the motor; and

and a control coefficient setting step of changing at least one of the control bandwidth and a filter coefficient of the notch filter in accordance with the control bandwidth and the notch frequency so as to stabilize the feedback control system.

Technical Field

The present invention relates to a motor control device for controlling a driving operation such as a speed and a position of a motor and a mechanical load driven by the motor, and more particularly to a motor control device having a function of suppressing mechanical resonance generated during driving or the like.

Background

Conventionally, a motor control device capable of suppressing vibration due to mechanical resonance is known (for example, see patent document 1).

Disclosure of Invention

Problems to be solved by the invention

However, in the conventional motor control device, the mechanical resonance frequency may overlap with the control bandwidth of the feedback control system, and oscillation may occur due to instability of the feedback control system.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a motor control device and a motor control method that can prevent hunting due to an unstable feedback control system in advance, compared to the related art.

Means for solving the problems

A motor control device according to an aspect of the present invention is a motor control device capable of changing a control bandwidth of a feedback control system for feedback-controlling a state quantity of a motor or a load, the motor control device including: a notch filter having a changeable filter coefficient, which is disposed in the feedback control system; a notch control unit that changes a notch frequency of the notch filter, which is a center frequency, so as to remove a vibration component caused by mechanical resonance related to the motor; and a control coefficient setting unit that changes at least one of the control bandwidth and the filter coefficient of the notch filter in accordance with the control bandwidth and the notch frequency, thereby stabilizing the feedback control system.

A motor control method according to an aspect of the present invention is a method for feedback-controlling a state quantity of a motor or a load by a motor control device capable of changing a control bandwidth of a feedback control system, the method including: a notch control step of changing a notch frequency, which is a center frequency, of a notch filter that is disposed in the feedback control system and whose filter coefficient can be changed so as to remove a vibration component caused by mechanical resonance related to the motor; and a control coefficient setting step of changing at least one of the control bandwidth and a filter coefficient of the notch filter in accordance with the control bandwidth and the notch frequency so as to stabilize the feedback control system.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the motor control device and the motor control method, it is possible to prevent hunting caused by an unstable feedback control system in advance as compared with the conventional one.

Drawings

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

Fig. 2 is a diagram showing an example of frequency characteristics of a notch filter.

Fig. 3 is a block diagram showing an example of the configuration of the notch control unit in embodiment 1.

Fig. 4 is a diagram showing an example of the configuration of the feedback control unit in embodiment 1.

Fig. 5 is a diagram showing an example of frequency characteristics of the motor speed with respect to the speed command in embodiment 1.

Fig. 6 is a block diagram showing an example of the configuration of a motor control device in embodiment 2.

Detailed Description

(original Commission to obtain one embodiment of the present invention)

Generally, a motor control device has a feedback control system configured therein for matching a motor operation with an operation command. A method is known in which a notch filter for attenuating a specific frequency component is provided in a feedback control system of a motor control device to prevent the occurrence of mechanical resonance vibration when there is mechanical resonance between a motor and a mechanical load. If the mechanical resonance frequency coincides with the notch frequency, which is the frequency attenuated by the notch filter, the mechanical resonance vibration component is attenuated by the notch filter, and the mechanical resonance vibration can be suppressed. However, when the mechanical resonance frequency changes due to long-term operation of the mechanical device, a shift occurs between the trap frequency and the mechanical resonance frequency, and it becomes impossible to suppress the mechanical resonance vibration. In order to suppress mechanical resonance vibration even when the mechanical resonance frequency changes greatly, it is necessary to always match the trap frequency with the mechanical resonance frequency.

Conventionally, as such a motor control device, there is a technique described in patent document 1. The technique is as follows: when mechanical resonance vibration occurs during operation of the motor, the mechanical resonance vibration component is extracted from the speed information of the motor, and the trap frequency is sequentially changed so that the amplitude of the extracted vibration component is reduced, thereby automatically adjusting the trap frequency to always coincide with the mechanical resonance frequency.

The inventors have found that the following problems occur in the conventional motor control device.

The notch filter used to suppress the mechanical resonance vibration has an effect of delaying the phase in a frequency band equal to or lower than the notch frequency. When the notch frequency overlaps with the control bandwidth of the feedback control system, the notch filter destabilizes the feedback control system, thereby causing oscillation. Therefore, in the case of using a notch filter, it is necessary to reduce the control bandwidth of the feedback control system with respect to the notch frequency so that the notch frequency does not overlap with the control bandwidth of the feedback control system. However, in the conventional motor control device, only consideration is given to making the notch frequency and the mechanical resonance frequency always coincide with each other, and therefore, when the mechanical resonance frequency falls to a degree that overlaps with the control bandwidth of the feedback control system due to deterioration of the mechanical components or the like caused by long-time operation of the mechanical equipment, the notch frequency also falls to a degree that overlaps with the control bandwidth of the feedback control system, and there is a possibility that an operation abnormality occurs with oscillation caused by instability of the feedback control system. When an abnormal operation occurs, the deteriorated mechanism member is replaced to repair the mechanical equipment, but unlike the opportunity of regular equipment maintenance, it takes time to prepare for replacement of the member, replacement work, and the like, and a large amount of time is required until the equipment is restarted. Therefore, in the mechanical equipment, it is desired to prevent operation abnormality such as oscillation in advance.

In view of the above problems, the present inventors have obtained a motor control device and a motor control method according to one embodiment of the present invention.

A motor control device according to an aspect of the present invention is a motor control device that can change a control bandwidth of a feedback control system and performs feedback control of a state quantity of a motor or a load, the motor control device including: a notch filter having a changeable filter coefficient, which is disposed in the feedback control system; a notch control unit that changes a notch frequency of the notch filter, which is a center frequency, so as to remove a vibration component caused by mechanical resonance related to the motor; and a control coefficient setting unit that changes at least one of the control bandwidth and the filter coefficient of the notch filter in accordance with the control bandwidth and the notch frequency, thereby stabilizing the feedback control system.

The motor control device changes at least one of a control bandwidth and a filter coefficient of a notch filter to stabilize a feedback control system.

Therefore, according to the motor control device, compared to the conventional device, it is possible to prevent the oscillation caused by the instability of the feedback control system.

For example, it is also possible to provide: the control coefficient setting unit may change at least one of the control bandwidth and the notch frequency only when the notch frequency is lower than a predetermined reference value, so as to stabilize the feedback control system.

In this way, by setting the predetermined reference value to a frequency value much higher than the control bandwidth of the feedback control system, it is possible to limit the change of at least one of the control bandwidth and the filter coefficient of the notch filter to a case where the frequency of the mechanical resonance is decreased to a degree that the frequency of the mechanical resonance is overlapped with the control bandwidth.

For example, it is also possible to provide: the notch control unit changes the notch frequency only within a predetermined notch frequency range.

This can prevent the notch frequency from becoming an undesirable frequency band.

For example, it is also possible to provide: the predetermined range of notch frequencies is determined such that the notch frequencies do not overlap with a control bandwidth of the feedback control system.

This can prevent oscillation caused by the instability of the feedback control system due to the change of the notch frequency.

For example, it is also possible to provide: a motor control device for feedback-controlling a state quantity of a motor or a load, the control bandwidth of which can be changed in a feedback control system, includes: a first notch filter and a second notch filter having changeable filter coefficients, the first notch filter and the second notch filter being arranged in series in the feedback control system; a first notch control unit that changes a first notch frequency, which is a center frequency of the first notch filter, so as to remove a vibration component caused by mechanical resonance related to the motor; a second notch control unit that changes a second notch frequency, which is a center frequency of the second notch filter, so as to remove a vibration component caused by mechanical resonance related to the motor; and a control coefficient setting unit that changes at least one of the control bandwidth, the filter coefficient of the first notch filter, and the filter coefficient of the second notch filter in accordance with the control bandwidth, the first notch frequency, and the second notch frequency, thereby stabilizing the feedback control system.

Thus, even when there are 2 mechanical resonance frequencies, it is possible to prevent oscillation due to the instability of the feedback control system.

A motor control method according to an aspect of the present invention is a method for feedback-controlling a state quantity of a motor or a load by a motor control device capable of changing a control bandwidth of a feedback control system, the motor control method including: a notch control step of changing a notch frequency, which is a center frequency, of a notch filter that is disposed in the feedback control system and whose filter coefficient can be changed so as to remove a vibration component caused by mechanical resonance related to the motor; and a control coefficient setting step of changing at least one of the control bandwidth and a filter coefficient of the notch filter in accordance with the control bandwidth and the notch frequency so as to stabilize the feedback control system.

In the motor control method, at least one of the control bandwidth and the filter coefficient of the notch filter is changed to stabilize the feedback control system.

Therefore, according to this motor control method, compared to the conventional method, it is possible to prevent hunting caused by an unstable feedback control system.

The general or specific aspects can be realized by a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, and can be realized by any combination of a system, a method, an integrated circuit, a computer program, or a recording medium.

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below. The embodiments described below all show a preferred specific example of the present invention. The numerical values, shapes, materials, constituent elements, arrangement positions and connection modes of the constituent elements, steps, order of the steps, and the like shown in the following embodiments are examples, and the present invention is not limited thereto. The invention is limited only by the claims. Therefore, among the components in the following embodiments, those not described in the independent claims representing the most generic concept of the present invention are not necessarily essential to achieving the object of the present invention, and are described as a more preferable configuration.

(embodiment mode 1)

Fig. 1 is a block diagram showing an example of the configuration of a motor control device according to a first embodiment. The motor control device 300 is a motor control device for feedback-controlling the state quantity of the motor 100, in which the control bandwidth of the feedback control system can be changed.

As shown in fig. 1, the motor control device 300 is connected to the motor 100 and the speed detector 200, and receives an input of a speed command Vs indicating a desired operation of the motor 100 or the mechanical load 102 to be driven. The motor 100 is connected to a mechanical load 102 as a driving unit of a mechanical device via a joint 101. Further, speed detector 200 detects the rotational speed of motor 100 and outputs the detected rotational speed as motor speed Vm to motor control device 300.

Motor control device 300 includes a feedback control unit 301, a notch filter 302, a torque control unit 303, a notch control unit 304, and a control coefficient setting unit 305.

The feedback control unit 301 receives the motor speed Vm and the speed command Vs as input, and outputs a torque command τ M1 such that the difference between the two is 0. For example, a difference value between the speed command Vs and the motor speed Vm is calculated, and a value obtained by proportional-integrating the calculated difference value is multiplied by a changeable control coefficient indicating a control bandwidth of the feedback control system, and output as the torque command τ M1.

The notch filter 302 is a filter that can be changed in filter coefficient and is disposed in the feedback control system. That is, the notch filter 302 is a filter that applies attenuation to a signal component of an input signal having a frequency centered around a specific frequency and outputs the signal component, and the center frequency to which attenuation is applied is referred to as a notch frequency. The torque command τ M1 is input as an input signal, and a signal component of the torque command τ M1 having a frequency centered around the notch frequency is attenuated and output as a new torque command τ M2.

The torque control unit 303 controls, for example, the current flowing through the motor 100 so that the motor torque matches the torque command τ M2.

In this way, motor control device 300 internally configures a feedback control system so that speed command Vs matches motor speed Vm.

Further, motor control device 300 includes therein: notch control unit 304, when motor speed oscillates, notch control unit 304 sequentially changes the notch frequency of notch filter 302 so as to automatically match the oscillation frequency; and a control coefficient setting unit 305, wherein when the notch frequency is reduced to the control bandwidth of the feedback control system, the control coefficient setting unit 305 automatically changes the control coefficient of the feedback control unit 301 so that the feedback control system is always stable.

Notch control unit 304 changes the notch frequency of notch filter 302, which is the center frequency, so as to remove the vibration component caused by the mechanical resonance of motor 100. That is, motor speed Vm is input to this notch control unit 304, and when mechanical resonance oscillation occurs in motor speed Vm, this notch control unit 304 automatically and sequentially changes the notch frequency of notch filter 302 so that the amplitude of the oscillation decreases. Thereby, the notch frequency of notch filter 302 is changed to always coincide with the mechanical resonance frequency, and the mechanical resonance vibration can be suppressed.

The control coefficient setting unit 305 changes the control bandwidth based on the control bandwidth and the notch frequency, thereby stabilizing the feedback control system. More specifically, the control coefficient setting unit 305 receives a notch frequency ω n controlled by the notch control unit 304 to coincide with the mechanical resonance frequency and a control coefficient signal Sn indicating the current set value of the control coefficient of the feedback control unit 301. The control coefficient setting unit 305 determines whether or not the feedback control system is unstable by overlapping the notch frequency with the control bandwidth of the feedback control system based on the input information, and outputs a control coefficient setting signal Cn indicating that the control bandwidth of the feedback control system is reduced to the feedback control unit 301 when it is determined that the feedback control system is unstable. The feedback control unit 301 changes the internal control coefficient so as to reduce the control bandwidth of the feedback control system, based on the input control coefficient setting signal Cn. Thus, when the notch frequency is reduced to a degree that overlaps with the control bandwidth of the feedback control system, the control coefficient of the feedback control system is changed to stabilize the feedback control system, thereby making it possible to prevent oscillation due to the instability of the feedback control system.

Next, details of the notch filter 302 arranged in the feedback control system of the motor control device 300, in which the filter coefficient can be changed, will be described. The notch filter 302 is, for example, a quadratic recursive notch filter having a transfer function Gn1(s) shown in (equation 1) below.

[ numerical formula 1]

In (equation 1), ω n1 is a notch frequency coefficient of the notch filter 302, ζ n1 is an attenuation coefficient indicating the width of a frequency band to which attenuation is applied, and dn1 is a notch depth coefficient indicating the degree to which attenuation is applied. The notch depth coefficient dn1 is 0 ≦ dn1 ≦ 1, and when dn1 is 1, the gain characteristic at the notch frequency ω n1 of the notch filter 302 is 0[ dB ], and when dn1 is 0, the gain characteristic at the notch frequency ω n1 of the notch filter 302 is ∞ [ dB ].

As an example of characteristics of the notch filter 302, fig. 2 shows frequency characteristics of the transfer function Gn1(s) when dn1 is 0. As is apparent from fig. 2, notch filter 302 has a characteristic of attenuating the component of notch frequency ω n1, and its gain characteristic is ∞. When the input signal contains a vibration component, the amplitude of the input signal is not attenuated when the vibration frequency of the input signal is different from notch frequency ω n1, and the amplitude is attenuated when the vibration frequency of the input signal is equal to the notch frequency ω n 1.

When the notch frequency ω n1 of the notch filter 302 can be changed and the mechanical resonance oscillation occurs, the notch control unit 304 changes the notch frequency ω n1 so as to match the mechanical resonance frequency, thereby attenuating the mechanical resonance frequency component in the torque command τ M1 and suppressing the mechanical resonance oscillation.

FIG. 3 is a diagram showing an example of the configuration of the notch control unit 304. Notch control unit 304 includes oscillation extracting filter 3041, notch filter for detection 3042, and notch frequency changing unit 3043. When mechanical resonance oscillation occurs, notch control unit 304 changes notch frequency ω n1 of notch filter 302 in order to reduce the amplitude of oscillation, thereby changing notch frequency ω n1 to coincide with the mechanical resonance frequency.

The vibration extraction filter 3041 is a filter that extracts a component of a predetermined frequency band from an input signal and outputs the component, and extracts a mechanical resonance vibration component from the motor speed Vm and outputs the component as a vibration component Vb 1. Since the vibration extraction filter 3041 can extract the vibration component as described above, it may be a high-pass filter that passes a signal component of a predetermined frequency or higher, or a band-pass filter that passes a signal component in a predetermined frequency band.

Oscillation component Vb1 output from oscillation extracting filter 3041 is input to notch filter 3042 for detection and notch frequency changing unit 3043.

Notch filter for detection 3042 attenuates a frequency component of oscillation component Vb1 centered at the notch frequency as the center frequency, and outputs the attenuated frequency component as new oscillation component Vb 2.

In the present embodiment, as the characteristic of notch filter 3042 for detection, a predetermined value is given in advance to the width of the band to which attenuation is given, and the gain characteristic at the notch frequency is ∞ [ dB ]. For example, a quadratic recursive notch filter having a transfer function Gn2(s) shown in the following (equation 2) is used.

[ numerical formula 2]

Here, ω n2 is a notch frequency coefficient corresponding to the notch frequency of notch filter 3042 for detection, and ζ n2 is an attenuation coefficient. The frequency characteristic of notch filter 3042 for detection has the same characteristic as that shown in fig. 2, as in the case where dn1 is set to 0 in notch filter 302. That is, the notch frequency ω n2 has a characteristic of attenuating its component.

Notch frequency changing unit 3043 receives as input oscillating component Vb1 and oscillating component Vb2 as the output of oscillating component Vb1 after passing through detection notch filter 3042. Then, a notch frequency ω n that matches the frequency of the vibration included in the motor speed Vm is generated. The notch frequency ω n is supplied to the notch filter 302 and the notch filter 3042 for detection, and ω n1 and ω n2 as notch frequencies of the notch filter 302 and the notch filter 3042 for detection are changed to ω n.

Here, in notch filter 3042 for detection, when the frequency of the oscillating component included in oscillating component Vb1 as an input is greatly different from notch frequency ω n2, the amplitude of oscillating component Vb1 is not attenuated. On the other hand, if they match, the amplitude of vibration component Vb1 is attenuated. Therefore, the amplitude of vibration component Vb2 becomes larger as the vibration frequency of vibration component Vb1 deviates from notch frequency ω n 2. That is, the amplitude of vibration component Vb2 can be said to indicate the degree of deviation between the vibration frequency of vibration component Vb1 and notch frequency ω n 2.

Notch frequency changing unit 3043 controls notch center frequency ω n2 of notch filter 3042 for detection by sequentially changing notch frequency ω n based on the amplitudes of oscillating component Vb1 and oscillating component Vb2 until the amplitude of oscillating component Vb2 becomes equal to or less than a predetermined value or 0. Such control of the notch filter can be realized by combining notch filter 3042 for detection with a directional filter and a notch filter coefficient correcting unit described in patent document 1, for example.

In this way, notch frequency ω n is controlled so as to coincide with the frequency of the vibration component included in vibration component Vb 1. The notch frequency ω n2 of the notch filter 3042 for detection and the notch frequency ω n1 of the notch filter 302 are both changed so as to coincide with the notch frequency ω n. That is, notch frequencies ω n1 and ω n2 are controlled so as to become frequencies of oscillation components included in oscillation component Vb 1.

As described above, when motor speed Vm includes a mechanical resonance vibration component, notch control unit 304 automatically and sequentially changes notch frequency ω n1 of notch filter 302 so as to match the frequency of the mechanical resonance vibration component, and therefore, in the motor control device of the present embodiment, mechanical resonance is always automatically suppressed.

Here, focusing on fig. 2 showing an example of the frequency characteristic of the notch filter 302 again, as described above, the gain characteristic of the notch filter 302 shows a characteristic of attenuating the component of the notch frequency ω n1, while the phase characteristic of the notch filter 302 has a value of-90 ° to 90 °. A negative value below the notch frequency has an effect of delaying the phase of the input signal. The notch filter 302 is disposed inside the feedback control system of the motor control device 300, and the phase delay of the feedback control system is caused by the phase delay effect of the notch filter 302 at the notch frequency or lower. Therefore, when the notch frequency overlaps the control bandwidth of the feedback control system, the notch filter 302 itself may destabilize the feedback control system, and may cause the operation to oscillate. In order to prevent oscillation due to instability of the feedback control system in advance while using the notch filter 302, it is necessary to reduce the control bandwidth of the feedback control system with respect to the notch frequency so that the notch frequency and the control bandwidth of the feedback control system do not overlap.

However, since the notch frequency of the notch filter 302 is automatically adjusted by the notch control unit 304 to always coincide with the mechanical resonance frequency, when the mechanical resonance frequency falls to a degree that overlaps with the control bandwidth of the feedback control system, the notch frequency also falls to a degree that overlaps with the control bandwidth of the feedback control system.

The control coefficient setting unit 305 receives a control coefficient signal Sn indicating the current control coefficient of the feedback control unit 301 and a notch frequency ω n automatically adjusted to match the mechanical resonance frequency by the notch control unit 304. Then, it is determined whether or not the feedback control system becomes unstable by overlapping the notch frequency with the control bandwidth of the feedback control system based on the input information. When it is determined that the feedback control system is unstable, a control coefficient setting signal Cn indicating a change in the control coefficient of the feedback control unit 301 is output to the feedback control unit 301 so that the control bandwidth of the feedback control system is reduced. The feedback control unit 301 changes the internal control coefficient so as to reduce the control bandwidth of the feedback control system, based on the input control coefficient setting signal Cn. Thus, even when the notch frequency falls to a level that overlaps the feedback control bandwidth, the control coefficient of the feedback control system is changed to stabilize the feedback control system, and oscillation due to instability of the feedback control system can be prevented in advance.

To describe the method of changing the control parameter of the feedback control unit 301 by the control coefficient setting unit 305, the configuration of the feedback control unit 301 will be described in detail first.

Fig. 4 shows an example of the configuration of the feedback control unit 301. The feedback control unit 301 includes therein a subtractor 3011, a proportional controller 3012, an integrator 3013, an integral controller 3014, an adder 3015, and a control coefficient update unit 3016. The subtractor 3011 receives a speed command Vs and a motor speed Vm, subtracts the motor speed Vm from the speed command Vs, and outputs the result as a speed deviation Verr. The proportional controller 3012 multiplies the speed deviation Verr by a speed proportional gain as a weight coefficient to output a proportional control output τ vp. The integrator 3013 also receives the speed deviation Verr as an input, and outputs a speed deviation integrated value Vserr as an integrated value of the speed deviation Verr. The integral controller 3014 receives the speed deviation integral value Vserr as an input, multiplies the speed integral value by a speed integral gain which is a weight coefficient, and outputs an integral control output τ vi. The adder 3015 receives the proportional control output τ vp and the integral control output τ vi, and outputs the sum of the proportional control output τ vp and the integral control output τ vi as a torque command τ M1. The control coefficient update unit 3016 updates the control coefficient used by the feedback control unit 301 based on the control coefficient setting signal Cn input from the control coefficient setting unit 305. In this manner, the feedback control unit 301 internally has a proportional-integral control system so that the speed command Vs matches the motor speed Vm. The control bandwidth of the feedback control system configured inside the motor control device 300 is determined based on the values of the speed proportional gain and the speed integral gain. That is, the velocity proportional gain and the velocity integral gain are control coefficients relating to the control bandwidth of the feedback control system. The control coefficient update unit 3016 of the feedback control unit 301 outputs the current control coefficient to the control coefficient setting unit 305 as the control coefficient signal Sn, so that the control coefficient setting unit 305 can determine the control bandwidth of the feedback control system.

Control coefficient signal Sn and notch frequency ω n are input to control coefficient setting unit 305, and it is determined whether or not the feedback control system configured inside motor control device 300 is stable based on the input information. When it is determined that the feedback control system is unstable, a control coefficient setting signal Cn for changing the control coefficient of the feedback control unit 301 is output so that the control bandwidth of the feedback control system is reduced to such an extent that it can be determined that the feedback control system is stable.

Next, a method of changing the control coefficient of the feedback control unit 301 by the control coefficient setting unit 305 will be described in detail. First, details of the control bandwidth of the feedback control system will be described.

Fig. 5 shows an example of the frequency characteristic of the motor speed with respect to the speed command in the case where notch filter 302 is not used. The upper stage shows the gain characteristic, and the lower stage shows the phase characteristic. When focusing on the gain characteristic diagram of fig. 5, a value of 0dB is shown at the frequency value of w1 within the diagram. This means that the feedback control unit 301 controls the motor speed to be equal to the speed command when the change in the speed command is the frequency w 1. On the other hand, a value of-10 dB is shown at the frequency value of w2 within the graph. This indicates that, when the change in the speed command is the frequency w2, the motor speed is about-10 dB ≈ 0.32 times the size of the speed command, and the size of the motor speed does not match the size of the speed command. That is, on the gain characteristic diagram of the feedback control system, the feedback control unit 301 controls the operation so that the motor speed matches the speed command in a bandwidth indicating a value close to 0dB, which is the control bandwidth of the feedback control system.

Generally, as an index indicating the control bandwidth of the feedback control system, a frequency value (corresponding to wc in fig. 5) is used, which is a value at which the gain characteristic of the output with respect to the frequency characteristic of the input is at least-3 dB ≈ 0.71, and this frequency value is referred to as the cutoff frequency of the feedback control system. The control coefficient setting unit 305 calculates the cutoff frequency of the feedback control system from the input control coefficient signal Sn, and determines whether or not the feedback control system is unstable from the calculated values of the cutoff frequency and the notch frequency.

The upper limit of the ratio of the cut-off frequency to the notch frequency of the feedback control system is set in advance in the control coefficient setting unit 305. The control coefficient setting unit 305 determines that the feedback control system is stable if the ratio of the cut-off frequency to the notch frequency of the feedback control system is equal to or less than a predetermined value. When the trap frequency is lowered to such an extent that it overlaps with the control bandwidth of the feedback control system due to the lowering of the mechanical resonance frequency and the ratio of the cut-off frequency to the trap frequency of the feedback control system exceeds the upper limit value, it is determined that the feedback control system is unstable, and a control coefficient is calculated such that the ratio of the cut-off frequency to the trap frequency of the feedback control system is equal to or less than the preset upper limit value. The control coefficient setting unit 305 outputs a control coefficient setting signal Cn indicating that the control coefficient of the feedback control unit 301 is changed to the calculated value. Then, the feedback control unit 301 changes the control coefficient to the value indicated by the input control coefficient setting signal Cn.

In this way, even when the notch frequency falls to a level that overlaps the control bandwidth of the feedback control system, the control coefficient of the feedback control unit 301 is changed to a value determined to be stable by the control coefficient setting unit 305, so that the feedback control system configured inside the motor control device 300 is always stable, and oscillation due to instability of the feedback control system does not occur.

As described above, when the mechanical resonance frequency is reduced to such an extent that it overlaps the control bandwidth of the feedback control system, the motor control device 300 of the present embodiment can prevent oscillation due to instability of the feedback control system in advance by reducing the control bandwidth of the feedback control system.

In the present embodiment, the configuration in which the control coefficient setting unit 305 changes the control bandwidth based on the control bandwidth and the notch frequency to stabilize the feedback control system has been described, but the configuration in which the control coefficient setting unit 305 changes at least one of the control bandwidth and the filter coefficient of the notch filter 302 based on the control bandwidth and the notch frequency to stabilize the feedback control system may be employed. For example, the following configuration may be adopted: when the ratio of the notch frequency to the control bandwidth of the feedback control system is equal to or greater than a predetermined value, the control bandwidth is changed to be decreased, and the notch depth coefficient, which is one of the filter coefficients of the notch filter 302, is increased. By adopting such a configuration, when the mechanical resonance frequency is lowered to a level that overlaps the control bandwidth of the feedback control system, the degree of delay of the phase by the notch filter 302 can be reduced, and oscillation due to instability of the feedback control system can be prevented in advance without greatly lowering the control bandwidth of the feedback control system.

In the present embodiment, the configuration in which the feedback control unit 301 is internally provided with a proportional-integral controller has been described, but the configuration may be such that: a notch filter 302 is used to suppress the low-frequency mechanical resonance vibration, and a low-pass filter for suppressing the high-frequency mechanical resonance vibration and the harmonic noise caused by the resolution roughness (japanese: decomposed energy さ) of the velocity detector 200 is connected in series to the post-stage of the proportional-integral controller. The cutoff band of the low-pass filter may be changed according to the control coefficient setting signal output from the control coefficient setting unit 305. Specifically, the control bandwidth of the feedback control system may be reduced and the cutoff band of the low-pass filter may be increased. The low-pass filter has an effect of delaying a phase equal to or lower than a cutoff frequency, as in the case of the notch filter. Therefore, the higher the cutoff frequency of the low-pass filter is, the smaller the phase delay of the feedback control system is, and the more stable the feedback control system is. By adopting a configuration in which the control bandwidth of the feedback control system is reduced and the cutoff band of the low-pass filter is increased, it is possible to prevent oscillation due to instability of the feedback control system in advance without significantly reducing the control bandwidth of the feedback control system while maintaining the degree of suppression of mechanical resonance vibration in the high frequency band.

In the present embodiment, the notch frequency of notch filter 302 arranged in the feedback control system is controlled to be always the frequency of the vibration included in the motor speed, but the following configuration may be adopted: only the notch frequency of the notch filter 302 arranged in the feedback control system is limited to the upper and lower limit values, and the control bandwidth of the feedback control system is prevented from overlapping the notch frequency of the notch filter 302 arranged in the feedback control system. That is, the following configuration may be adopted: notch control unit 304 changes the notch frequency of notch filter 302 only within a predetermined range of notch frequencies.

In the present embodiment, the presence or absence of vibration is determined based on the output of the vibration extraction filter 3041, which is composed of a low-pass filter or a band-pass filter, to which the motor speed Vm is input, but there are cases where: for example, when a temporary disturbance is applied to mechanical load 102, notch control unit 304 changes the notch frequency in response to the disturbance, and the notch frequency of notch filter 302 temporarily changes to a value that is largely different from the mechanical resonance frequency. When the notch frequency temporarily changes, the control bandwidth of the feedback control unit 301 is reduced by the action of the control coefficient setting unit 305, and the operation of the motor or the mechanical load extremely changes from the desired operation. With this configuration, even when a temporary disturbance is applied to the mechanical load, it is possible to prevent an extreme change in the operation of the motor or the mechanical load from a desired operation due to an inappropriate decrease in the notch frequency and the control bandwidth of the feedback control system.

In the present embodiment, the speed detector 200 is configured to detect the motor speed, and the speed detector 200 may be configured to detect the speed of the mechanical load 102 and output the speed to the feedback control unit 301.

By adopting such a configuration, the motor control device 300 controls the operation of the motor so that the speed command Vs coincides with the speed of the mechanical load, and therefore the difference between the speed command and the speed of the mechanical load is smaller.

(embodiment mode 2)

Fig. 6 is a diagram showing an example of the configuration of a motor control device according to embodiment 2. In fig. 6, the same functions and operations as those in fig. 1 showing the configuration of embodiment 1 described above are omitted. In motor control device 500, the number of notch filters and notch control units is increased from 1 to 2, respectively, compared to the configuration shown in fig. 1.

In motor control device 500, first notch filter 502a having notch frequency ω n1a and second notch filter 502b having notch frequency ω n1b are connected in series at the subsequent stage of feedback control unit 301, so that even when there are 2 mechanical resonances, it is possible to reduce the vibration caused by the 2 mechanical resonances in common.

The first notch filter 502a and the second notch filter 502b are the same as the notch filter 302 in embodiment 1.

The notch frequency ω n1a and the notch frequency ω n1b are set to different values so as to correspond to any of the 2 mechanical resonance frequencies. In order to change the notch frequency of each notch filter, a first notch controller 504a corresponding to the first notch filter 502a and a second notch controller 504b corresponding to the second notch filter 502b are provided.

The first notch controlling unit 504a and the second notch controlling unit 504b are the same as the notch controlling unit 304 in embodiment 1. More specifically, first notch control unit 504a changes the first notch frequency of first notch filter 502a, which is the center frequency, so as to remove the vibration component caused by the mechanical resonance of motor 100. Second notch control unit 504b changes the second notch frequency of second notch filter 502b, which is the center frequency, so as to remove the vibration component caused by the mechanical resonance of motor 100. That is, when 2 mechanical resonance frequencies change, the first notch controller 504a and the second notch controller 504b change the notch frequency of the corresponding notch filter to match the frequency of the generated oscillation component for the oscillation that occurs according to the change in the mechanical resonance frequency, and output the changed notch frequencies to the control coefficient setting unit 505 as ω na and ω nb, respectively.

In order to allow the 2 notch filters to detect the change of the different mechanical resonance frequencies, for example, the pass bandwidths of the oscillation extracting filters existing inside the notch control units may be set to bandwidths that are centered around the 2 different mechanical resonance frequencies and do not overlap with each other. Thus, each of the 2 notch control units can be controlled so that the frequency of the oscillation generated by the change in the corresponding mechanical resonance frequency matches the notch frequency of the corresponding notch filter without being affected by the change in the other mechanical resonance frequency.

Control coefficient setting unit 505 changes at least one of the control bandwidth, the filter coefficient of first notch filter 502a, and the filter coefficient of second notch filter 502b in accordance with the control bandwidth, the first notch frequency, and the second notch frequency of the feedback control system, thereby stabilizing the feedback control system. More specifically, control coefficient signal Sn indicating the control coefficient of feedback control unit 301 and 2 notch frequencies ω na and ω nb are input to control coefficient setting unit 305, and control coefficient setting unit 30 determines whether or not the feedback control system configured inside motor control device 500 is unstable based on the input information. When it is determined that the feedback control system is unstable, the control coefficient setting signal Cn is a signal indicating that the control coefficient of the feedback control unit 301 is to be changed so that the control bandwidth of the feedback control system is reduced to such an extent that it can be determined that the feedback control system is stable.

Next, a method of changing the control coefficient of the feedback control unit 301 by the control coefficient setting unit 505 will be described in detail. An upper limit value indicating a ratio of a cut-off frequency and a notch frequency of a control bandwidth of the feedback control system is set in advance in the control coefficient setting unit 505. The control coefficient setting unit 505 calculates a cutoff frequency indicating a control bandwidth of the feedback control system from the control coefficient signal Sn, and determines that the feedback control system is stable if the ratio of the cutoff frequency of the feedback control system to the smaller one of the notch frequencies ω na and ω nb is equal to or less than a commonly set upper limit value. When the ratio of the cutoff frequency of the feedback control system to the smaller one of the notch frequencies ω na and ω nb exceeds the upper limit value, it is determined that the feedback control system is unstable, and a control coefficient is calculated such that the ratio of the cutoff frequency of the feedback control system to the smaller notch frequency is equal to or less than the preset upper limit value. The control coefficient setting unit 505 outputs a control coefficient setting signal Cn indicating that the control coefficient of the feedback control unit 301 is changed to the calculated value. Then, in the feedback control unit 301, the control coefficient is changed to a value indicated by the input control coefficient setting signal Cn.

As described above, when the smaller notch frequency of the 2 notch filters is reduced to a level that overlaps the control bandwidth of the feedback control system, the control coefficient of the feedback control unit 301 is changed by the control coefficient setting unit 505 to a value that is determined to be stable in the feedback control system, so that the feedback control system configured inside the motor control device 500 is always stable, and oscillation due to instability of the feedback control system does not occur.

By configuring to change the control coefficient of the feedback control unit 301 in this way, even when there are 2 mechanical resonances, the control coefficient setting unit 505 can prevent oscillation caused by instability of the feedback control system by reducing the control bandwidth of the feedback control system based on the notch frequency of the notch filter that further reduces the phase characteristics of the feedback control system among the 2 notch filters when at least one of the mechanical resonance frequencies falls to a degree that overlaps the control bandwidth of the feedback control system.

As described above, in the motor control device 500 of the present embodiment, even when there are 2 mechanical resonances, when the mechanical resonance frequency of at least one of the mechanical resonances falls to a degree that overlaps the control bandwidth of the feedback control system, it is possible to prevent oscillation due to the instability of the feedback control system by reducing the control bandwidth of the feedback control system.

In the present embodiment, the configuration is provided with 2 notch filters and notch control units, but there may be 3 or more. In this case, each notch filter and notch control unit may perform the same operation as in the present embodiment. With this configuration, even when there are 3 or more mechanical resonances, when at least one mechanical resonance frequency falls to a degree that overlaps with the control bandwidth of the feedback control system with respect to a change in each mechanical resonance frequency, it is possible to prevent oscillation due to instability of the feedback control system by reducing the control bandwidth of the feedback control system.

In embodiment 1 and embodiment 2, the motor control device has a feedback control unit that performs feedback control so that the motor speed follows the speed command, and may be configured as follows: the motor control device further includes a feedforward control unit that calculates a torque command for matching the motor speed with the speed command based on the speed command, in addition to the feedback control unit.

In embodiment 1 and embodiment 2, the motor control device is configured to control the motor speed, and may be configured to control the motor position.

Industrial applicability

The present invention can be widely applied to a control device for a motor that drives a machine device in which a mechanical resonance frequency changes.

Description of the reference numerals

100: an electric motor; 200: a speed detector; 300. 500: a motor control device; 301: a feedback control unit; 302: a notch filter; 303: a torque control unit; 304: a trap control unit; 305. 505: a control coefficient setting unit; 502 a: a first notch filter; 502 b: a second notch filter; 504 a: a first notch control unit; 504 b: a second notch control unit; 3011: a subtractor; 3012: a proportional controller; 3013: an integrator; 3014: an integral controller; 3015: an adder; 3016: a control coefficient update unit; 3041: a vibration extraction filter; 3042: a notch filter for detection; 3043: a notch frequency changing unit.