CN111949041B - Elastic vibration suppression method suitable for large uncertainty frequency - Google Patents

Abstract

The invention discloses an elastic vibration suppression method suitable for high uncertainty frequency, which is based on the first-order elastic frequency range [ omega ] of an aircraft ₁₁ ω ₁₂ ]Two filters connected in series are designed, and a filter W ₁₁ (s) and W ₁₂ (s) the center frequencies are ω ₁₁ And omega ₁₂ By adjusting the filter W ₁₁ (s) and W ₁₂ (s) parameters in [ omega ] ₁₁ ω ₁₂ ]The required attenuation times are satisfied in the frequency range. Aiming at the first-order elastic frequency, the notch filter with deeper filtering depth and wider width is formed by adopting a double-filter serial connection mode in the autopilot, so that a stronger filtering effect is achieved in a larger uncertain frequency range of the aircraft, and compared with the mode of adopting a single notch filter, the filtering depth near the first-order modal frequency is improved. The invention can also be applied to the design of the second-order filter and the third-order filter of the aircraft so as to obtain the effects of wider filtering frequency and larger filtering depth.

Description

Elastic vibration suppression method suitable for large uncertainty frequency

Technical Field

The invention relates to the field of elastic vibration suppression of aircrafts, in particular to an elastic vibration suppression method suitable for high uncertainty frequency. The method is suitable for the aircraft with larger elastic frequency uncertainty.

Background

Elastic vibration suppression is an important content of the design of the automatic pilot of the aircraft, can improve the stability of the system, provides a good working environment for the sub-system and the single machine of the automatic pilot, and ensures the reliable operation of the system.

The source of the high-frequency noise of the autopilot is mainly the elastic vibration of the aircraft. Taking a missile as an example, the difference between the Y-direction elastic frequency and the Z-direction elastic frequency can be caused by the position of a missile cable cover, and the difference exists between the elastic frequencies of each missile produced in batch. This requires the control system to have a strong elastic vibration suppression capability over a large uncertainty frequency range.

According to the traditional filter design method, a notch filter is designed for a first-order elastic frequency range, a frequency point is selected as a central frequency in a compromise mode, and the elastic frequency deviates from the central frequency of the filter due to large uncertainty of the elastic frequency, so that the filtering effect is obviously reduced.

According to the technical scheme, aiming at the first-order elastic frequency, a notch filter with deeper filtering depth and wider width is formed by adopting a double-filter serial connection mode in the autopilot, so that a stronger filtering effect is achieved in a larger uncertain frequency range of the aircraft.

Disclosure of Invention

The invention aims to provide an elastic vibration suppression method suitable for large uncertainty frequency, which aims at the large uncertainty of the elastic frequency of an aircraft and achieves a stronger filtering effect in a large uncertainty frequency range of the aircraft. The invention adopts the form of dual filters connected in series, thereby ensuring stronger filtering effect in a wider frequency range.

In order to achieve the above object, the present invention provides a method for suppressing elastic vibration adapted to a high uncertainty frequency according to a first-order elastic frequency range [ omega ] of an aircraft ₁₁ ω ₁₂ ]Two filters connected in series are designed, and a filter W ₁₁ (s) and W ₁₂ (s) the center frequencies are ω ₁₁ And omega ₁₂ By adjusting the filter W ₁₁ (s) and W ₁₂ (s) parameters in [ omega ] ₁₁ ω ₁₂ ]Is satisfied in the frequency rangeThe attenuation times are calculated.

The elastic vibration suppression method adapting to the frequency with large uncertainty, wherein the filter W ₁₁ (s) and W ₁₂ The formula of(s) is as follows:

wherein T is _n11 、T _d11 Is a deterministic structure filter W ₁₁ (s) parameters of center frequency, ζ _n11 、ξ _d11 Is a deterministic structure filter W ₁₁ Parameters of notch width and depth of(s); t (T) _n12 、T _d12 Is a deterministic structure filter W ₁₂ (s) parameters of center frequency, ζ _n12 、ξ _d12 Is a deterministic structure filter W ₁₂ Parameters of notch width and depth of(s).

The elastic vibration suppression method adapting to the frequency with large uncertainty, wherein the filter W ₁₁ (s) depth and width are not greater than the filter W ₁₂ (s) depth and width, the filter parameters satisfying the following formula:

ξ _d11 ≤ξ _d12

the elastic vibration suppression method adapting to the frequency of large uncertainty comprises the steps of adjusting a filter W ₁₁ (s) and W ₁₂ (s) the parameters are [ omega ] ₁₁ ω ₁₂ ]The attenuation factor meeting the requirement in the frequency range is expressed as follows:

A ₁₁ (ω ₁₁ )+A ₁₂ (ω ₁₁ )＜K

A ₁₁ (ω ₁₂ )+A ₁₂ (ω ₁₂ )＜K

wherein: a is that ₁₁ (ω ₁₁ ) Is a filter W ₁₁ (s) at ω ₁₁ Amplitude at, in dB; a is that ₁₂ (ω ₁₂ ) Is a filter W ₁₂ (s) at ω ₁₂ Amplitude at, in dB; k is the required attenuation amplitude, K<0, units: dB (dB).

Compared with the prior art, the invention has the technical advantages that:

(1) And compared with the mode of adopting a single notch filter, the filter depth near the first-order modal frequency is improved by adopting a dual-filter series connection mode.

(2) The method can also be applied to the design of second-order and third-order filters of the aircraft so as to obtain the effects of wider filtering frequency and larger filtering depth.

(3) Due to notch filter W ₁₁ (s) the center frequency is relatively low, the influence on the stability margin is large, and the depth and width of the design are not larger than those of the filter W ₁₂ And(s) depth and width to reduce the influence of the filter on the rigid body stability margin and improve the system stability margin.

Drawings

An elastic vibration suppression method adapted to a large uncertainty frequency of the present invention is given by the following examples and drawings.

Fig. 1 shows a filter W ₁₁ A baud plot of(s);

FIG. 2 shows a filter W ₁₂ A baud plot of(s);

FIG. 3 is a Bode plot of two filters in series;

fig. 4 is a diagram comparing the present invention with a conventional single filter scheme.

Detailed Description

A method of elastic vibration suppression that accommodates large uncertainty frequencies of the present invention will be described in further detail below with reference to the accompanying drawings.

The implementation steps of the method are described by taking a certain aircraft as an example:

the first-order modal frequency of a certain aircraft is assumed in the following table, the filtering depth is required to be more than-30 dB within the range of 35 Hz-40 Hz, the filtering effect is improved as much as possible near the first-order modal frequency, and the method is suitable for the difference of each aircraft with the same model in the production process.

Table 1 modal frequencies of certain aircraft

Modal frequencies	First order modal frequencies
		Y-direction	35Hz
Z direction	40Hz

(1) According to the first-order elastic frequency range of the aircraft [3540 ]]Two filters connected in series are designed, and a filter W ₁₁ (s) and W ₁₂ The center frequencies of(s) are 35Hz and 40Hz, respectively, for example, using the following parameters, such as FIG. 1, FIG. 2, the filter center frequencies are 35Hz and 40Hz, respectively.

Wherein:

(2) Design filter W ₁₁ The filtering depth at the center frequency of(s) is about-17 dB (as in FIG. 1), design W ₁₂ The filter depth at the center frequency of(s) is about-20 dB (as in FIG. 2), and the filter parameters are as follows:

ξ _n11 ＝0.1

ξ _d11 ＝0.7

ξ _n12 ＝0.1

ξ _d12 ＝1.1

(3) Wave filter W ₁₁ (s) and W ₁₂ (s) in series, the attenuation at 35 Hz-40 Hz exceeds-30 dB (as shown in FIG. 3). As can be seen from comparison with the conventional single filter, the filtering width around the first order frequency is significantly better than that of the single filter scheme (as shown in fig. 4) under the dual filter scheme of the present invention, and the filtering effect is as shown in table 2.

For example, the actual Z-direction first-order modal frequency of a certain aircraft is 45Hz, the difference exists between the actual Z-direction first-order modal frequency and the design value, the filtering effect of the dual-filter series scheme is-25.8 dB, and the filtering effect of the single-filter scheme is only 18.8dB. The dual filter series scheme is more adaptable to modal frequency uncertainty.

Table 2 comparison of filtering effects

Scheme for the production of a semiconductor device	The dual filter series scheme of the invention	Single filter scheme
			-30dB frequency range	33Hz～42Hz	35Hz～38.7Hz
-20dB frequency range	28.5Hz～49.5Hz	30.5Hz～44Hz

The invention can also be used for the design of second-order and third-order filters.

What is not described in detail in the present specification is a well known technology to those skilled in the art.

Although the present invention has been described in terms of the preferred embodiments, it is not intended to be limited to the embodiments, and any person skilled in the art can make any possible variations and modifications to the technical solution of the present invention by using the methods and technical matters disclosed above without departing from the spirit and scope of the present invention, so any simple modifications, equivalent variations and modifications to the embodiments described above according to the technical matters of the present invention are within the scope of the technical matters of the present invention.

Claims (2)

1. A method for suppressing elastic vibration suitable for high-uncertainty frequency is characterized by comprising the following steps of according to a first-order elastic frequency range [ omega ] of an aircraft ₁₁ ω ₁₂ ]Two filters connected in series are designed, and a filter W ₁₁ (s) and W ₁₂ (s) the center frequencies are ω ₁₁ And omega ₁₂ By adjusting the filter W ₁₁ (s) and W ₁₂ (s) parameters in [ omega ] ₁₁ ω ₁₂ ]Attenuation times meeting requirements in a frequency range;

the filter W ₁₁ (s) and W ₁₂ The formula of(s) is as follows:

wherein T is _n11 、T _d11 Is a deterministic structure filter W ₁₁ (s) parameters of center frequency, ζ _n11 、ξ _d11 Is a deterministic structure filter W ₁₁ Parameters of notch width and depth of(s); t (T) _n12 、T _d12 Is a deterministic structure filter W ₁₂ (s) parameters of center frequency, ζ _n12 、ξ _d12 Is a deterministic structure filter W ₁₂ Parameters of notch width and depth of(s);

the filter W ₁₁ (s) depth and width are not greater than the filter W ₁₂ (s) depth and width, the filter parameters satisfying the following formula:

ξ _d11 ≤ξ _d12

2. a method of elastic vibration suppression for large uncertainty frequencies as defined in claim 1, wherein said adjusting said filter W ₁₁ (s) and W ₁₂ (s) the parameters are [ omega ] ₁₁ ω ₁₂ ]The attenuation factor meeting the requirement in the frequency range is expressed as follows:

A ₁₁ (ω ₁₁ )+A ₁₂ (ω ₁₁ )＜K

A ₁₁ (ω ₁₂ )+A ₁₂ (ω ₁₂ )＜K

wherein: a is that ₁₁ (ω ₁₁ ) Is a filter W ₁₁ (s) at ω ₁₁ Amplitude at, in dB; a is that ₁₂ (ω ₁₂ ) Is a filter W ₁₂ (s) at ω ₁₂ Amplitude at, in dB; k is the required attenuation amplitude, K<0, units: dB (dB).