CN111949041A - Elastic vibration suppression method adaptive to large uncertainty frequency - Google Patents

Abstract

The invention discloses an elastic vibration suppression method suitable for large uncertainty frequency, which is based on the first-order elastic frequency range [ omega ] of an aircraft₁₁ω₁₂]Designing two filters in series, filter W₁₁(s) and W₁₂(s) have center frequencies of ω respectively₁₁And ω₁₂By adjusting the filter W₁₁(s) and W₁₂Parameter of(s) at [ omega ]₁₁ω₁₂]A required attenuation factor in the frequency range is met. Aiming at the first-order elastic frequency, the invention adopts a series connection form of double filters in the autopilot to form a notch filter with deeper filtering depth and wider width, thereby realizing stronger filtering effect on the aircraft in a larger uncertain frequency range. The invention can also be applied to the design of second-order and third-order filters of an aircraft, so as toThe effects of wider filtering frequency and larger filtering depth are obtained.

Description

Elastic vibration suppression method adaptive to 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 adaptive to large uncertain frequency. The invention is suitable for the aircraft with larger uncertainty of the elastic frequency.

Background

The 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 subsystem and the single machine to which the automatic pilot belongs, and ensures the reliable operation of the system.

The source of autopilot high frequency noise is primarily the aircraft's own elastic vibrations. For example, in the case of missiles, the positions of the missile cable covers cause the difference of elastic frequencies in the Y direction and the Z direction, and the elastic frequencies of every missile in mass production also have the difference. This requires a control system with strong elastic vibration suppression capability over a large uncertainty frequency range.

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

According to the technical scheme, aiming at the first-order elastic frequency, a trap filter with deeper filtering depth and wider width is formed by adopting a series connection form of double filters in the autopilot, and 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, aiming at the large uncertainty of the elastic frequency of an aircraft and achieving a strong filtering effect in a large uncertainty frequency range of the aircraft. The invention ensures stronger filtering effect in a wider frequency range by adopting a series connection form of the double filters.

In order to achieve the above object, the present invention provides an elastic vibration suppression method for large uncertainty frequency according to the first order elastic frequency range [ ω ] of the aircraft₁₁ω₁₂]Designing two filters in series, filter W₁₁(s) and W₁₂(s) have center frequencies of ω respectively₁₁And ω₁₂By adjusting the filter W₁₁(s) and W₁₂Parameter of(s) at [ omega ]₁₁ω₁₂]A required attenuation factor in the frequency range is met.

The elastic vibration suppression method for large uncertainty frequency is characterized in that the filter W is a filter with a frequency band of a large uncertainty₁₁(s) and W₁₂The formula of(s) is as follows:

in the formula, T_n11、T_d11Is a deterministic structure filter W₁₁(s) parameter of center frequency, ξ_n11、ξ_d11Is a deterministic structure filter W₁₁(s) parameters of notch width and depth; t is_n12、T_d12Is a deterministic structure filter W₁₂(s) parameter of center frequency, ξ_n12、ξ_d12Is a deterministic structure filter W₁₂(s) parameters of notch width and depth.

The elastic vibration suppression method for large uncertainty frequency is characterized in that the filter W is a filter with a frequency band of a large uncertainty₁₁(s) has a depth and width not greater than the filter W₁₂(s), the filter parameters satisfy the following formula:

ξ_d11≤ξ_d12

the elastic vibration suppression method for large uncertainty frequency is characterized in that the filter W is adjusted₁₁(s) and W₁₂(s) has a parameter in [ omega ]₁₁ω₁₂]The required attenuation factor in the frequency range is given by the formula:

A₁₁(ω₁₁)+A₁₂(ω₁₁)＜K

A₁₁(ω₁₂)+A₁₂(ω₁₂)＜K

in the formula: a. the₁₁(ω₁₁) Is a filter W₁₁(s) at ω₁₁Amplitude in dB; a. the₁₂(ω₁₂) Is a filter W₁₂(s) at ω₁₂Amplitude in dB; k is the desired attenuation amplitude, K<0, unit: dB.

Compared with the prior art, the invention has the technical beneficial effects that:

(1) and a double-filter series connection mode is adopted, so that compared with a single notch filter mode, the filtering depth near the first-order modal frequency is improved.

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

(3) Due to the notch filter W₁₁The center frequency of(s) is relatively low, the influence on the stability margin is large, and the designed depth and width are not more than the filter W₁₂And(s) depth and width to reduce the influence of the filter on the rigid stability margin and improve the system stability margin.

Drawings

The elastic vibration suppression method adapted to large uncertainty frequency of the present invention is provided by the following embodiments and the accompanying drawings.

FIG. 1 shows a filter W₁₁(s) bode plot;

FIG. 2 shows a filter W₁₂(s) bode plot;

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

An elastic vibration suppression method for large uncertainty frequency according to the present invention will be described in further detail with reference to the accompanying drawings.

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

the first-order modal frequency of a certain aircraft is assumed as 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 various aircrafts of the same model in the production process.

TABLE 1 aircraft modal frequencies

Modal frequency	First order modal frequency
		In the Y direction	35Hz
In the Z direction	40Hz

(1) According to aircraft first order elastic frequency range [3540 ]]Designing two filters in series, filter W₁₁(s) and W₁₂The center frequencies of(s) are 35Hz and 40Hz, respectively, for example, using the following parameters, as shown in fig. 1 and 2, and the filter center frequencies are 35Hz and 40Hz, respectively.

In the formula:

(2) designing a filter W₁₁The depth of filtering at the center frequency of(s) is about-17 dB (as in FIG. 1), design W₁₂The depth of filtering 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) filter W₁₁(s) and W₁₂(s) are connected in series, and the attenuation at 35Hz to 40Hz exceeds-30 dB (shown in figure 3). Compared with the conventional single filter, it can be seen that the filtering width around the first order frequency is significantly better than that of the single filter scheme (as shown in fig. 4) in the dual-filter scheme of the present invention, and the filtering effect is shown in table 2.

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

TABLE 2 Filter Effect comparison

Scheme(s)	The invention relates to a series connection scheme of double filters	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 designing second-order and third-order filters.

Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.

Claims (4)

1. An elastic vibration suppression method adapting to large uncertainty frequency is characterized in that according to a first-order elastic frequency range of an aircraftEnclose [ omega ]₁₁ ω₁₂]Designing two filters in series, filter W₁₁(s) and W₁₂(s) have center frequencies of ω respectively₁₁And ω₁₂By adjusting the filter W₁₁(s) and W₁₂Parameter of(s) at [ omega ]₁₁ ω₁₂]A required attenuation factor in the frequency range is met.

2. The method of claim 1, wherein the filter W is adapted to suppress elastic vibrations at frequencies of large uncertainty₁₁(s) and W₁₂The formula of(s) is as follows:

in the formula, T_n11、T_d11Is a deterministic structure filter W₁₁(s) parameter of center frequency, ξ_n11、ξ_d11Is a deterministic structure filter W₁₁(s) parameters of notch width and depth; t is_n12、T_d12Is a deterministic structure filter W₁₂(s) parameter of center frequency, ξ_n12、ξ_d12Is a deterministic structure filter W₁₂(s) parameters of notch width and depth.

3. The method of claim 1, wherein the filter W is adapted to suppress elastic vibrations at frequencies of large uncertainty₁₁(s) has a depth and width not greater than the filter W₁₂(s), the filter parameters satisfy the following formula:

ξ_d11≤ξ_d12

4. the method of claim 1, wherein said step of adjusting the filter W is performed by adjusting the filter W₁₁(s) and W₁₂(s) has a parameter in [ omega ]₁₁ω₁₂]The required attenuation factor in the frequency range is given by the formula:

A₁₁(ω₁₁)+A₁₂(ω₁₁)＜K

A₁₁(ω₁₂)+A₁₂(ω₁₂)＜K

in the formula: a. the₁₁(ω₁₁) Is a filter W₁₁(s) at ω₁₁Amplitude in dB; a. the₁₂(ω₁₂) Is a filter W₁₂(s) at ω₁₂Amplitude in dB; k is the desired attenuation amplitude, K<0, unit: dB.

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