CN111222201A - Multi-rotor damping simulation test combined design method - Google Patents
Multi-rotor damping simulation test combined design method Download PDFInfo
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- CN111222201A CN111222201A CN202010050870.5A CN202010050870A CN111222201A CN 111222201 A CN111222201 A CN 111222201A CN 202010050870 A CN202010050870 A CN 202010050870A CN 111222201 A CN111222201 A CN 111222201A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
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- B64F5/60—Testing or inspecting aircraft components or systems
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Abstract
The invention provides a multi-rotor damping simulation test combined design method, which comprises the following steps: carrying out simulation analysis through finite element software to obtain the natural frequency, the mode and the vibration mode of the structural system, and then carrying out test analysis; the test analysis part performs a frequency sweep vibration test on the sample piece on a vibration table to obtain time domain vibration data; carrying out a fixed frequency test by referring to a design standard to check whether the vibration level meets the requirement; carrying out fast Fourier transform on the test time domain data to obtain frequency domain data, and obtaining a frequency corresponding to a larger amplitude peak value in a frequency domain graph; then, the frequencies are compared with natural frequencies obtained by simulation analysis, and a simulation model is corrected to improve the precision of an analysis result; extracting a proper modal shape, modifying and optimizing the structure, and iterating the steps to finally obtain the vibration level meeting the design requirement. The invention optimizes the structure through simulation and test parallel analysis, thereby changing the rigidity of the structure and the natural frequency of the system and achieving the purpose of active vibration reduction.
Description
Technical Field
The invention belongs to the field of unmanned aerial vehicles, and particularly relates to a multi-rotor damping simulation test combined design method.
Background
The flight stability of the existing unmanned aerial vehicle is one of main technical indexes, the vibration during flight is an important influence factor, and especially the influence of the vibration level of a flight control sensor mounting surface on the stability operability of the aircraft is very important. Structural vibration must be considered and optimization iteration is constantly carried out in many rotor unmanned aerial vehicle design process.
At present, passive vibration isolation methods (such as adding high-damping rubber, vibration isolators and the like) are mainly used as main means. The method is simple and easy to implement, but the whole system is in weight increasing design, the unmanned aerial vehicle has extremely high requirements on quality control, and the structural design pursues light weight design.
Therefore, the method for optimizing the structure through simulation and test parallel analysis so as to change the rigidity of the structure and the natural frequency of the system achieves the purpose of active vibration reduction and has strong practical significance.
Disclosure of Invention
The invention aims to provide a multi-rotor damping simulation test combined design method, which is a method for changing the rigidity of a structure and the natural frequency of a system by optimizing the structure through simulation and test parallel analysis, and achieves the aim of active damping.
In order to achieve the purpose, the invention mainly provides the following technical scheme:
a multi-rotor damping simulation test combined design method comprises the following steps:
s1, carrying out simulation analysis through finite element software to obtain the natural frequency, the mode and the vibration mode of the body structure system, and then carrying out test analysis;
s2, during test analysis, performing a frequency sweep vibration test on the sample piece on a vibration table to obtain time domain vibration data;
s3, performing a fixed frequency test by referring to the working frequency of the engine and the rotor system, and checking the vibration level;
s4, performing fast Fourier transform on the time domain vibration data obtained through the test analysis in the S2 to obtain frequency domain data, and obtaining the frequency corresponding to the peak value of the typical resonance amplification frequency band in a frequency domain graph, namely obtaining the mode and the corresponding natural frequency in the sweep frequency interval through the peak value in the frequency domain graph;
s5, comparing the frequency obtained in S4 with the natural frequency obtained in the simulation analysis in S1, and correcting the simulation model, thereby improving the accuracy of the analysis result;
and S6, extracting the modal shape corresponding to the natural frequency close to the designed working frequency, modifying and optimizing the structure by referring to the corresponding shape, and repeating the steps S1-S5 to finally obtain the vibration level meeting the design requirement.
Further, the specific steps of obtaining the natural frequency of the body structure system in step S1 are as follows:
the strain energy of the body structure system in finite element analysis of the natural frequency of the body structure system is
Wherein E is the elastic modulus of the material; epsilonijIs the strain tensor,. epsilonklIs the strain tensor, dV is the differential volume;
the kinetic energy of the structural system of the body is
In the formula (I), the compound is shown in the specification,
is the velocity vector, ρ is the density;
discretizing into finite element model to form a multi-freedom-degree machine body structure system, and obtaining an undamped machine body matrix equation
In the formulaM is a mass matrix of the airframe structural system; k is a rigidity matrix of the machine body structure system;
a displacement array of a structural system of the body; f is an exciting force array acting on the machine body structure system;
without damping, the natural vibration generated by the structural system in the absence of any external excitation is given by the following equation
The natural vibration determined by it being in the form of harmonic vibration, i.e.
u＝u0eiωt(5)
Substituting it into equation (2) to obtain characteristic equation
Ku0＝ω2Mu0(6)
In the formula, omega is the natural vibration frequency of the body structure system; therefore, solving the natural frequency of the body structure system is solved into a generalized characteristic problem;
the characteristic value provided by the characteristic equation (4) is obtained by the following equation
From the characteristic value λiFinding omegaiSquare value of
In the formula, ωiIs the natural frequency of the ith order mode of the organism structural system.
Further, solving the natural vibration mode of the airframe structure system specifically includes: feature vector
Given modal displacement form, called the body structure systemThe ith order natural mode of the system.
Further, for an N degree of freedom airframe structural system, there are N pairs of features (ω and
) I.e. the index i in formula (7) is a value from 1 to N.
The invention has the beneficial effects that:
the invention optimizes the structure through simulation and test parallel analysis, thereby changing the rigidity of the structure and the natural frequency of the system and achieving the purpose of active vibration reduction.
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In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a multi-rotor damping simulation test combined design method of the present invention.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. It should be noted that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work based on the embodiments of the present invention belong to the protection scope of the present invention.
As shown in fig. 1, firstly, a dynamic simulation analysis is performed on an unmanned aerial vehicle structural system through commercially mature finite element software to obtain corresponding natural frequency, mode and vibration mode, and whether the mode natural frequency of the vibration mode with large displacement of the sensor mounting surface is close to the working frequency of the unmanned aerial vehicle is focused.
A multi-rotor damping simulation test combined design method comprises the following steps:
s1, carrying out simulation analysis through finite element software to obtain the natural frequency, the mode and the vibration mode of the body structure system, and then carrying out test analysis;
s2, during test analysis, performing a frequency sweep vibration test on the sample piece on a vibration table to obtain time domain vibration data;
s3, performing a fixed frequency test by referring to the working frequency of the engine and the rotor system, and checking the vibration level;
s4, performing fast Fourier transform on the time domain vibration data obtained through the test analysis in the S2 to obtain frequency domain data, and obtaining the frequency corresponding to the peak value of the typical resonance amplification frequency band in a frequency domain graph, namely obtaining the mode and the corresponding natural frequency in the sweep frequency interval through the peak value in the frequency domain graph;
s5, comparing the frequency obtained in S4 with the natural frequency obtained in the simulation analysis in S1, and correcting the simulation model, thereby improving the accuracy of the analysis result;
and S6, extracting the modal shape corresponding to the natural frequency close to the designed working frequency, modifying and optimizing the structure by referring to the corresponding shape, and repeating the steps S1-S5 to finally obtain the vibration level meeting the design requirement.
The specific steps of obtaining the natural frequency of the body structure system in step S1 are as follows:
the strain energy of the body structure system in finite element analysis of the natural frequency of the body structure system is
Wherein E is the elastic modulus of the material; epsilonijIs the strain tensor,. epsilonklIs the strain tensor, dV is the differential volume;
the kinetic energy of the structural system of the body is
In the formula (I), the compound is shown in the specification,
is the velocity vector, ρ is the density;
discretizing into finite element model to form a multi-freedom-degree machine body structure system, and obtaining an undamped machine body matrix equation
Wherein M is a mass matrix of the body structure system; k is a rigidity matrix of the machine body structure system;
a displacement array of a structural system of the body; f is an exciting force array acting on the machine body structure system;
without damping, the natural vibration generated by the structural system in the absence of any external excitation is given by the following equation
The natural vibration determined by it being in the form of harmonic vibration, i.e.
u＝u0eiωt(5)
Substituting it into equation (2) to obtain characteristic equation
Ku0＝ω2Mu0(6)
In the formula, omega is the natural vibration frequency of the body structure system; therefore, solving the natural frequency of the body structure system is solved into a generalized characteristic problem;
the characteristic value provided by the characteristic equation (4) is obtained by the following equation
From the characteristic value λiFinding omegaiSquare value of
In the formula, ωiIs the natural frequency of the ith order mode of the organism structural system.
Solving the natural vibration mode of the body structure system specifically comprises: feature vector
The displacement form of the given mode is called the ith order natural mode of the body structure system.
For an N degree of freedom airframe structural system, there are N pairs of features (ω and)
) I.e. the index i in formula (7) is a value from 1 to N.
The invention optimizes the structure through simulation and test parallel analysis, thereby changing the rigidity of the structure and the natural frequency of the system and achieving the purpose of active vibration reduction.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (4)
1. A multi-rotor damping simulation test combined design method is characterized by comprising the following steps:
s1, carrying out simulation analysis through finite element software to obtain the natural frequency, the mode and the vibration mode of the body structure system, and then carrying out test analysis;
s2, during test analysis, performing a frequency sweep vibration test on the sample piece on a vibration table to obtain time domain vibration data;
s3, performing a fixed frequency test by referring to the working frequency of the engine and the rotor system, and checking the vibration level;
s4, performing fast Fourier transform on the time domain vibration data obtained through the test analysis in the S2 to obtain frequency domain data, and obtaining the frequency corresponding to the peak value of the typical resonance amplification frequency band in a frequency domain graph, namely obtaining the mode and the corresponding natural frequency in the sweep frequency interval through the peak value in the frequency domain graph;
s5, comparing the frequency obtained in S4 with the natural frequency obtained in the simulation analysis in S1, and correcting the simulation model, thereby improving the accuracy of the analysis result;
and S6, extracting the modal shape corresponding to the natural frequency close to the designed working frequency, modifying and optimizing the structure by referring to the corresponding shape, and repeating the steps S1-S5 to finally obtain the vibration level meeting the design requirement.
2. The multi-rotor damping simulation test combined design method according to claim 1, wherein the specific steps of obtaining the natural frequency of the airframe structure system in step S1 are as follows:
the strain energy of the body structure system in finite element analysis of the natural frequency of the body structure system is
Wherein E is the elastic modulus of the material; epsilonijIs the strain tensor,. epsilonklIs the strain tensor, dV is the differential volume;
the kinetic energy of the structural system of the body is
In the formula (I), the compound is shown in the specification,
is the velocity vector, ρ is the density;
discretizing into finite element model to form a multi-freedom-degree machine body structure system, and obtaining an undamped machine body matrix equation
Wherein M is a mass matrix of the body structure system; k is a rigidity matrix of the machine body structure system;
a displacement array of a structural system of the body; f is an exciting force array acting on the machine body structure system;
without damping, the natural vibration generated by the structural system in the absence of any external excitation is given by the following equation
The natural vibration determined by it being in the form of harmonic vibration, i.e.
u＝u0eiωt(5)
Substituting it into equation (2) to obtain characteristic equation
Ku0＝ω2Mu0(6)
In the formula, omega is the natural vibration frequency of the body structure system; therefore, solving the natural frequency of the body structure system is solved into a generalized characteristic problem;
the characteristic value provided by the characteristic equation (4) is obtained by the following equation
From the characteristic value λiFinding omegaiSquare value of
In the formula, ωiIs the natural frequency of the ith order mode of the organism structural system.
3. Multi-spiral as claimed in claim 2The combined design method for the wing damping simulation test is characterized in that the solving of the natural vibration mode of the body structure system specifically comprises the following steps: feature vector
The displacement form of the given mode is called the ith order natural mode of the body structure system.
4. The multi-rotor damping simulation test combined design method according to claim 3, wherein: for an N degree of freedom airframe structural system, there are N pairs of features (ω and)
) I.e. the index i in formula (7) is a value from 1 to N.
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Cited By (5)
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| CN112861281A (en) * | 2021-02-02 | 2021-05-28 | 武汉船用电力推进装置研究所（中国船舶重工集团公司第七一二研究所） | Vibration reduction design method for mechanical equipment |
| CN113237746A (en) * | 2020-12-29 | 2021-08-10 | 中国航空工业集团公司西安飞机设计研究所 | Control surface manipulation test bench and strength analysis method for control surface simulation device of iron bird bench |
| US20220170818A1 (en) * | 2020-12-01 | 2022-06-02 | International Business Machines Corporation | Prioritization of maintenance activity based on computer analysis of machine data with digital vibration frequency simulation |
| CN117470752A (en) * | 2023-12-28 | 2024-01-30 | 广东省有色工业建筑质量检测站有限公司 | Method for detecting prestress grouting content in steel pipe truss body |
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| CN112861281B (en) * | 2021-02-02 | 2022-04-19 | 武汉船用电力推进装置研究所（中国船舶重工集团公司第七一二研究所） | Vibration reduction design method for mechanical equipment |
| CN117470752A (en) * | 2023-12-28 | 2024-01-30 | 广东省有色工业建筑质量检测站有限公司 | Method for detecting prestress grouting content in steel pipe truss body |
| CN117470752B (en) * | 2023-12-28 | 2024-05-07 | 广东省有色工业建筑质量检测站有限公司 | Method for detecting prestress grouting content in steel pipe truss body |
| CN118010365A (en) * | 2024-04-08 | 2024-05-10 | 青岛汽车散热器有限公司 | Heat dissipation vibration matching detection system and method for internal combustion engine |
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Inventor after: Li He Inventor after: Jin Shiwei Inventor after: Rao Dalin Inventor after: Chang Yanxiang Inventor after: Yan Xiaoqiang Inventor before: Li He Inventor before: Rao Dalin Inventor before: Chang Yanxiang Inventor before: Yan Xiaoqiang |