KR20160118665A - Apparatus for detecting and suppressing resonance in servo system and method thereof - Google Patents

Abstract

The present invention relates to a method of estimating and suppressing a resonance in real time when the resonance occurs in a servo-system having unknown resonance information. The method for automatically detecting and suppressing a resonance in a servo system according to embodiments of the present invention comprises the steps of: calculating a variance in a current command, which is outputted from a servo controller, and sensing a resonance using a magnitude of the current command; estimating a frequency of the current command by using an estimated frequency controller based on an adaptive notch filter; applying, when a resonance is detected, the adaptive notch filter having a filter frequency of the estimated frequency to the current command; replacing, when it is acknowledged that the resonance is suppressed by applying the adaptive notch filter, the applied adaptive notch filter with a fixed notch filter having a fixed filter frequency; and replacing, when the number of sensed resonances is bigger than the number of available fixed notch filters, a fixed notch filter, which suppresses a smallest resonance, with a fixed notch filter which suppresses a bigger resonance sensed later.

Description

TECHNICAL FIELD [0001] The present invention relates to an automatic resonance detection and suppression apparatus, and an automatic resonance detection and suppression method for a servo system,

More particularly, the present invention relates to a method and apparatus for automatically detecting a resonance occurring in a servo system using a frequency estimator, a resonance sensor, and a resonance suppressor, estimating a frequency of the resonance, .

As a method for suppressing the resonance phenomenon of the servo system, a method of applying the notch filter to the output current command is widely used. The notch filter is a filter that removes a component of a specific frequency band from the input signal. If it is used, the resonance effect of the servo system can be suppressed by removing the component causing resonance in the current command.

However, this resonance suppression method is a method capable of knowing the resonance frequency of the system, so it is difficult to apply the resonance frequency when the resonance frequency is unknown. In this case, the resonance frequency of the system can be determined using a separate estimation method. As a typical resonant frequency estimation method, there is a method of confirming a system response by analyzing a feedback signal generated after a specific input, for example, a frequency sweep or white noise is applied. However, there is a disadvantage in that it is not real time estimation but offline and non-real time estimation.

As a method for real-time estimation of the resonant frequency, there is a method of frequency-analyzing the output current command signal by a frequency estimator. If a resonance phenomenon occurs, the influence of the resonance phenomenon is reflected in the current command on the closed loop structure of the servo system. That is, there is a signal having a large resonance frequency band in the current command outputted during the occurrence of the resonance phenomenon. Fast Fourier transform method is most widely used as a method of analyzing the frequency characteristics of a signal. However, since more than a certain number of input samples are required, the time required for many samples is delayed, that is, The resonance suppression can not be performed. In addition, it has a disadvantage that it has a relatively high calculation amount.

On the other hand, when the adaptive notch filter is used, the resonance frequency can be estimated and suppressed at a smaller amount of computation than the fast Fourier transform. The adaptive notch filter is a notch filter that includes a frequency estimator that changes the filter frequency in the notch filter, and changes the frequency of the filter in real time. The mentioned frequency estimator adjusts the first derivative of the filter frequency so that the filter frequency is the fundamental frequency of the input signal. That is, as the filter frequency approaches the fundamental frequency of the input signal, the first derivative of the filter frequency is reduced to converge the filter frequency to the fundamental frequency of the input signal. The first derivative of the filter frequency includes the output signal of the notch filter. Since the output signal of the notch filter is minimized under the condition that the fundamental frequency of the input signal is the same as that of the filter frequency, The derivative value is also minimized. Under this principle, the filter frequency of the adaptive notch filter in the steady state becomes the fundamental frequency of the input signal, and the output signal is a signal from which the fundamental frequency component is removed from the input signal. When the resonance phenomenon occurs in the system, the fundamental frequency of the current command becomes the resonance frequency, so that the resonance frequency estimation and the resonance suppression occur simultaneously in the steady state by the principle of the above adaptive notch filter.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for suppressing resonance after detecting a resonance in real time by a servo system in which resonance information is not known and estimating the resonance frequency.

It is another object of the present invention to provide a method for effectively suppressing several resonances of a system by mixing an adaptive notch filter and a fixed notch filter,

The present invention provides a method of effectively using a limited number of notch filters by resetting a fixed notch filter in consideration of the magnitude of resonance generated when a resonance is detected in excess of the number of notch filters that can be operated by the servo system.

According to embodiments of the present invention, a method of detecting and suppressing automatic resonance of a servo system includes: calculating a dispersion of a current command and sensing a resonance of the amplitude of the command; estimating a frequency of a current command using an adaptive notch filter- A step of applying an adaptive notch filter having an estimated frequency as a filter frequency to a current command when resonance is detected, a step of applying an adaptive notch filter to a fixed notch filter having a fixed filter frequency A fixed notch filter for suppressing the smallest resonance among the fixed notch filters in operation when the number of resonances greater than the number of operable fixed notch filters in the servo system is detected, . ≪ / RTI >

As an embodiment, the automatic resonance detection and suppressor of the servo system may include a resonance detector for calculating the dispersion of the current command output from the servo controller and sensing the resonance at the magnitude, a frequency estimator for estimating the resonance frequency using an adaptive notch filter- And a resonance suppressor that removes the resonance induced component in the current command using the adaptive notch filter and the fixed notch filter.

In one embodiment, the resonance sensor calculates the dispersion of the current command and senses resonance based on the magnitude of the magnitude of the current command, wherein the magnitude of the dispersion exceeds a simply set value for a period of time, When the magnitude of dispersion is smaller than the maximum value and the state where the magnitude of dispersion is larger than half of the maximum value is maintained for a predetermined time, two conditions are set as the resonance detection condition.

In one embodiment, the resonant frequency estimator estimates a frequency with a frequency estimator of an adaptive notch filter, wherein a frequency estimation gain used in the frequency estimator is a first frequency that is inversely proportional to the magnitude of dispersion, , And adjust the frequency estimation gain so that the frequency estimation gain has a second value different from the first value when the magnitude of variance is less than or equal to a certain value.

In an embodiment, the second value may be zero.

As an example, the frequency estimate of the resonant frequency estimator may have the same value as the frequency estimate of the previous control period.

In an embodiment, the resonance suppressor may be configured to perform resonance suppression by applying an adaptive notch filter having a frequency of the frequency estimator as a filter frequency to a current command when the resonance sensor senses resonance, wherein the current dispersion value after the application of the adaptive notch filter is The case where the resonance is suppressed at a certain rate or less of the maximum value of the current dispersion at the time of resonance detection is taken as a condition for resonance suppression. When the resonance suppression condition is satisfied, the adaptive notch filter at the time of satisfaction is converted into the fixed notch filter, and the maximum value of the current dispersion at the time of resonance detection is regarded as the size of the generated resonance and is stored.

In an embodiment, when the resonance suppressor generates additional resonance in a state where all of the fixed notch filters that can be operated by the servo system are used, the resonance is suppressed by the fixed notch filter, and the smallest resonance among the fixed notch filters operated is suppressed The notch filter that suppresses the smallest resonance in operation is changed to a fixed notch filter that suppresses resonance only when the maximum value of the current dispersion calculated at the time of additional resonance is larger than the maximum value of the current dispersion stored at the time of the notch filter setting.

According to embodiments of the present invention, it is possible to estimate and suppress, in real time, resonance occurring when a resonance phenomenon occurs in a servo system in which resonance information is not known.

In addition, since the resonance suppression function is performed using the fixed notch filter, it is possible to suppress a plurality of resonance components as many as the number of notch filters that can be operated by the servo system.

In addition, since the fixed notch filter is reset in consideration of the magnitude of the resonance generated when the servo system detects a larger number of resonances than the number of fixed notch filters that can be operated, a limited number of fixed notch filters necessary for resonance suppression can be efficiently used .

1 is a block diagram that schematically illustrates a servo system, in accordance with an embodiment of the present invention.
2 is a block diagram schematically showing a servo system including a fixed notch filter as an example of the servo system of Fig.
3 is a block diagram that schematically illustrates a servo system having a resonance sensor, a resonance frequency estimator, and a resonance suppressor, in accordance with one embodiment of the present invention.
4 is a block flow diagram schematically illustrating the operation of a fixed notch filter of a resonance suppressor according to an embodiment of the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of example, specific embodiments in which the invention may be practiced. Embodiments of the detailed description are provided to those skilled in the art for the purpose of disclosing the detailed description for carrying out the invention.

Each of the embodiments of the present invention can describe different cases, but it does not mean that the embodiments are mutually exclusive. For example, the specific shapes, structures, and characteristics described in connection with one embodiment of the detailed description may be implemented in other embodiments without departing from the spirit and scope of the present invention. It is also to be understood that the location or arrangement of the individual components of the embodiments disclosed herein may be varied without departing from the spirit and scope of the invention.

On the other hand, in various embodiments, the same or similar reference numerals refer to the same or similar components. In the accompanying drawings, the sizes of the respective components may be exaggerated for explanatory purposes and need not be equal to or similar to the actual applied size.

1 is a block diagram that schematically illustrates a servo system, in accordance with an embodiment of the present invention. Referring to FIG. 1, a servo system 100 includes a control unit 110 and a load unit 120.

The control unit 110 includes a servo controller 111 and a current controller 112. The load section 120 includes a plant 121 and an encoder 122. [ First, the servo controller 111 generates a current command for controlling the plant 121 of the load unit 120. When a current command is transmitted from the servo controller 111 to the current controller 112, the current controller 112 provides the drive 121 with a drive current corresponding to the current command. The encoder 122 encodes the parameters of the motor driven in the plant 121 and provides its angular displacement to the controller 111 as feedback. The controller 111 refers to the received feedback in the control of the plant 121 thereafter.

Although the example in which the feedback signal is an angular displacement is described here, the scope of the present invention is not limited thereto. For example, the feedback signal may further include the speed of the motor in addition to or in addition to the angular displacement.

The specific configuration and operation method of the current controller 112, the plant 121, and the encoder 122 are well known in the art, and a description thereof will be omitted here.

2 is a block diagram schematically showing a servo system including a fixed notch filter as an example of the servo system described above. Referring to FIG. 2, the servo system includes a control unit 210 and a load unit 220. The control unit 210 includes a servo controller 211, a fixed notch filter 212, and a current controller 213. The load section 220 includes a plant 221 and an encoder 222.

In the embodiment of FIG. 2, the fixed notch filter 212 serves to remove components corresponding to the filter frequency of the current command output from the servo controller 211. When the resonance frequency of the load is known, if the filter frequency of the fixed notch filter 212 is set to the resonance frequency, the resonance frequency component of the output current command of the servo controller 211 is suppressed, The resonance phenomenon of the plant 221 is not caused.

In the embodiment of FIG. 2, the servo controller 211, the current controller 213, the plant 221 and the encoder 222 of FIG. 2 correspond to the servo controller 111, the current controller 112, the plant 121 And the encoder 122 are substantially the same in construction and operation.

3 is a block diagram schematically showing a servo system having an automatic resonance detection and suppression section, according to an embodiment of the present invention. 3, the servo system 300 includes a control unit 310, an automatic resonance detection and suppression unit 320, and a load unit 330. The controller 310 includes a servo controller 311 and a current controller 312. The automatic resonance detection and suppression unit 320 includes a resonance sensor 321, a frequency estimator 322, an adaptive notch filter 323, and a fixed notch filter 324. [ The load section 330 includes a plant 331 and an encoder 332.

In the present invention, the automatic resonance detection and suppression unit 320 of FIG. 3 operates in the following process. First, the resonance sensor 321 calculates the variance of the current command output from the servo controller 311 to determine whether resonance of the system occurs. If one of the two conditions, Condition 1 and Condition 2, is satisfied from the calculated dispersion value, it is determined that resonance has occurred.

[Condition 1]

The calculated dispersion value exceeds the set first value for more than a certain period of time.

[Condition 2]

When the calculated dispersion value exceeds the set second value and the maximum value is not updated for a certain period of time after reaching the maximum value.

If one of the two conditions is satisfied and the occurrence of resonance is judged, the adaptive notch filter 323 having the estimated frequency of the frequency estimator 322 as the filter frequency is operated after storing the maximum value of the current dispersion at the judgment time, Try it. The adaptive notch filter 323 is designed as a second notch filter expressed by Equation (1).

는 필터 주파수,

는 필터의 감쇄비 (damping factor)를 나타낸다. 적응 노치 필터(323)의 필터 주파수인

는 주파수 추정기(322)의 추정 주파수로서 시간에 따라 변할 수 있다. 공진 억제의 판단 여부는 조건 3의 만족 여부로 결정된다.Where s is the Laplace operator,

The filter frequency,

Represents the damping factor of the filter. The filter frequency of the adaptive notch filter 323

May vary over time as an estimated frequency of the frequency estimator 322. [ Whether or not the resonance suppression is determined is determined by satisfaction of condition 3.

[Condition 3]

When the current dispersion value after the operation of the adaptive notch filter 323 is reduced to a certain ratio or less of the maximum value of the current dispersion at the resonance occurrence determination time.

When the condition is satisfied and the resonance suppression is judged, the fixed notch filter 324 having the estimated frequency at the judgment time as the filter frequency is operated, and at the same time, the operation of the adaptive notch filter 323 in operation is stopped. The fixed notch filter 324 is designed as a second notch filter expressed by Equation (2), which is similar to the adaptive notch filter 323.

는 필터 주파수,

는 필터의 감쇄비 (damping factor)를 나타낸다. 고정 노치 필터(324)의 필터 주파수인

는 고정된 주파수로서 시간에 따라 변하지 않는다.Where s is the Laplace operator,

The filter frequency,

Represents the damping factor of the filter. The filter frequency of the fixed notch filter 324

Is a fixed frequency and does not change with time.

The frequency estimator 322 is designed as a frequency estimator based on the adaptive notch filter 323 represented by Equation (3).

는 필터의 감쇄비,

는 추정 주파수,

는 주파수 추정 이득,u(t)는 입력 신호로 본 발명에서는 전류 명령을 나타낸다.Where x is the state of the filter,

The attenuation ratio of the filter,

Is the estimated frequency,

Is a frequency estimation gain, and u (t) is an input signal.

를 조절한다. 수학식 3의 주파수 추정 이득

는 수학식 4로 조절된다.If the input signal is very small, the frequency estimation gain is set so as not to perform the frequency estimation,

. The frequency estimation gain < RTI ID = 0.0 >

Is adjusted to Equation (4).

는 0 과 1 사이 상수를 나타낸다.In the present invention, var (u (t)) _lim is the variance of the current command, var (u (t)) _lim is the permissible dispersion,

Represents a constant between 0 and 1.

3, the servo controller 311, the current controller 312, the plant 331, and the encoder 332 in FIG. 3 correspond to the servo controller 111, the current controller 112, the plant 121 ) And the encoder 122 are substantially the same in construction and operation.

FIG. 4 is a process diagram showing a flow of a method of suppressing a resonance by a fixed notch filter when additional resonance occurs in a situation where all the fixed notch filters that can be operated by the servo system are used, according to an embodiment of the present invention.

The process of FIG. 4 operates in the following process. When suppressing the generated resonance with the fixed notch filter, first confirm that the servo system is using all the fixed notch filters that can be operated. If all of the fixed notch filters that can be operated are being used, a fixed notch filter that suppresses the smallest resonance among the fixed notch filters to be operated is selected. The size of the resonance suppressed by the operating fixed notch filter is based on the magnitude of the maximum value of the current dispersion stored by the resonance detector at the time of the resonance detection. A comparison is made between the maximum value of the current dispersion stored in the resonance detector and the maximum value of the stored current dispersion at the time of resonance detection at the time of resonance suppression suppressed by the selected fixed notch filter. If the former is smaller than the latter, the selected fixed notch filter is replaced by a fixed notch filter to suppress the currently occurring resonance. If the former is larger than the latter, do not set a fixed notch filter to suppress the resonance that is currently occurring.

Claims (3)

Calculating a variance of the current command to sense resonance;
Estimating a frequency of a current command using an adaptive notch filter-based frequency estimator;
Applying an adaptive notch filter having an estimated frequency as a filter frequency to a current command when resonance is sensed;
Changing the applied adaptive notch filter to a fixed notch filter having a fixed filter frequency if resonance suppression is confirmed by application of the adaptive notch filter; And
A step of converting a fixed notch filter for suppressing the smallest resonance among the fixed notch filters in operation into a fixed notch filter for suppressing a larger resonance that is detected when the number of resonances larger than the operable fixed notch filter number of the servo system is detected; Wherein the automatic resonance detection and suppression method comprises the steps of: The method according to claim 1,
Wherein the step of sensing resonance comprises:
The dispersion of the current command is detected and the resonance is detected based on the magnitude of the current command. When the magnitude of the dispersion exceeds the set value for a predetermined time, and when the magnitude of the dispersion becomes smaller than the maximum value And determining whether to hold the state larger than half of the maximum value for a predetermined period of time. The method according to claim 1,
The step of estimating the frequency comprises:
The frequency estimation gain used in the frequency estimator is adjusted by the frequency estimator of the adaptive notch filter so that the frequency estimation gain is adjusted to have a first value that is inversely proportional to the magnitude of dispersion when the magnitude of dispersion calculated by the resonance detector is more than a predetermined value And adjusting the frequency estimation gain so that the frequency estimation gain has a second value different from the first value when the magnitude of dispersion is less than a predetermined value.

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