A method and device for obtaining modal parameters of a machine body through simulation analysis

Abstract

The application belongs to the field of helicopter structure strength design, and relates to a method and device for obtaining body modal parameters through simulation analysis. The method comprises the following steps: optimizing a full machine dynamics model based on the requirement of ground resonance and tail rotor tail beam coupling stability calculation; adding structural damping of the body in the existing full machine dynamics model for the requirement of tail rotor tail beam coupling stability calculation; for a typical state, carrying out complex modal calculation based on a dynamics model of the body on the landing gear to obtain modal frequency, modal damping ratio, modal mass, modal shape and modal vector of the body on the landing gear; obtaining a modal shape of a key point from the modal shape, and obtaining a modal vector of the key point from the modal vector according to the modal shape of the key point; converting the modal mass into normalized modal mass according to the modal vector of the key point ， so as to calculate corresponding modal stiffness and modal damping.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of helicopter structure strength design, and relates to a method and device for obtaining body modal parameters through simulation analysis. BACKGROUND

[0002] To ensure the safety of a helicopter, simulation calculation and analysis of stability are particularly important, and the key factor for the success of simulation calculation and analysis of stability is whether the input of body modal parameters is fast and accurate. Before a helicopter is subjected to stability test, it is of great significance to master the stability situation at the initial stage of type development and formulate a stability control plan to ensure the flight safety of the helicopter. On the one hand, stability test generally needs to consume a large cycle and cost, affecting the development progress of the type; on the other hand, to solve the stability problem or achieve the goal of predicting the unstable region, optimization design of the rotor system, the body structure and the landing gear system is often needed, and it is difficult to change the design or take stability control measures at the test and flight stage.

[0003] The traditional method is to obtain the body modal parameters through main hub center dynamic characteristic test or tail hub center dynamic characteristic test, and the main hub center dynamic characteristic test or the tail hub center dynamic characteristic test can be carried out only when there is a scientific research prototype at the trial production stage, and the acquisition of the body modal parameters is relatively lagging. At this time, if the ground resonance or the coupling characteristic of the tail boom is found to be unable to meet the requirements, the design needs to be repeated, more time cycle and development cost need to be consumed, and even a revolutionary improvement is brought, which brings great risk to the type development. SUMMARY

[0004] The present application aims to provide a method for quickly obtaining body modal parameters through simulation analysis, which is simpler, more direct and easier to operate than the traditional method for obtaining modal parameters, and can accurately predict the ground resonance and the tail boom coupling stability at the initial stage of type design.

[0005] TECHNICAL SCHEME

[0006] In a first aspect, a method for obtaining body modal parameters through simulation analysis is provided, comprising:

[0007] Based on the requirements of ground resonance and tail boom coupling stability calculation, the full machine dynamics model is optimized: for the requirement of ground resonance calculation, the stiffness and damping parameters of the landing gear are added to the existing full machine dynamics model according to the performance parameters of the landing gear; for the requirement of tail boom coupling stability calculation, the structural damping of the body is added to the existing full machine dynamics model;

[0008] For a typical state, the modal frequency, modal damping ratio, modal mass, modal shape and modal vector of the body on the landing gear are obtained through complex modal calculation based on the dynamics model of the body on the landing gear;

[0009] The modal shape of a key point is obtained from the modal shape, and the modal vector of the key point is obtained from the modal vector according to the modal shape of the key point; the key point is selected as the center of the main rotor hub and the center of the tail rotor hub, if the input is the ground resonance, the center of the main rotor hub is the key point, if the input is the tail rotor beam coupling stability calculation, the center of the tail rotor hub is the key point;

[0010] According to the modal vector of the key point, the modal mass is converted into the modal mass normalized according to the key point, so as to calculate the corresponding modal stiffness and modal damping.

[0011] Further, the modal mass calculation method comprises:

[0012] According to the modal frequency and damping ratio of the body on the landing gear, the modal mass and the modal shape are obtained.

[0013] Further, the method further comprises:

[0014] All modal parameters of the same key point in different typical states are obtained, and stability calculation is carried out; the modal parameters of the key point include: the modal mass normalized according to the key point, the modal damping, the modal stiffness, the modal frequency, the damping ratio and the modal shape of the key point.

[0015] Further, the calculation formula of the rth order modal mass M r normalized according to the key point is:

[0016] ;

[0017] Wherein, is the modal mass before conversion; is the rth order modal vector of the key point i.

[0018] Further, the calculation formula of the rth order modal stiffness K r normalized according to the key point is:

[0019] ;

[0020] Wherein, is the rth order modal frequency.

[0021] Further, the calculation formula of the rth order modal damping C r normalized according to the key point is:

[0022] ;

[0023] Wherein, is the rth order modal damping ratio.

[0024] In a second aspect, the application provides a device for obtaining modal parameters of a machine body through simulation analysis, comprising:

[0025] An optimization module is configured to optimize a full machine dynamics model based on requirements of ground resonance and tail rotor-tail boom coupling stability calculation, wherein, for the requirement of ground resonance calculation, the stiffness and damping parameters of the landing gear are added to the existing full machine dynamics model according to the performance parameters of the landing gear; and for the requirement of tail rotor-tail boom coupling stability calculation, the structural damping of the machine body is added to the existing full machine dynamics model.

[0026] A processing module is configured to perform complex modal calculation based on the dynamics model of the machine body on the landing gear to obtain modal frequency, modal damping ratio, modal mass, modal shape and modal vector of the machine body on the landing gear for a typical state.

[0027] An obtaining module is configured to obtain the modal shape of a key point from the modal shape and obtain the modal vector of the key point from the modal vector according to the modal shape of the key point, wherein the key point is selected as the center of the main rotor hub and the center of the tail rotor hub, and the center of the main rotor hub is selected as the key point if it is used as the input of the ground resonance, and the center of the tail rotor hub is selected as the key point if it is used as the input of the tail rotor-tail boom coupling stability calculation.

[0028] A conversion module is configured to convert the modal mass into normalized modal mass according to the modal vector of each order to calculate the corresponding modal stiffness and modal damping.

[0029] Further, the processing module is specifically configured to:

[0030] The modal mass and the modal shape are obtained according to the modal frequency and the damping ratio of the machine body on the landing gear.

[0031] Beneficial effects:

[0032] The application provides a method for quickly obtaining modal parameters of a machine body through simulation analysis, which meets the requirement of quickly and accurately evaluating stability in the early stage of type development, provides accurate and reliable modal parameters of the machine body for the stability strength design of the helicopter, and is of great significance to the flight safety of the helicopter.

[0033] The application can quickly obtain modal parameters of a machine body, ensures the requirement of stability simulation of the helicopter, provides an accurate and reliable simulation analysis method for the stability strength design, can more accurately carry out stability simulation strength design, and has high universality and engineering application value.

[0034] The application proposes to obtain modal parameters including modal mass, modal damping, modal stiffness, modal frequency, damping ratio and mode shape at key positions through a body dynamics model on the landing gear to perform stability calculation, thereby forming a method for rapid evaluation of helicopter stability, achieving the purpose of obtaining body modal parameters at the initial stage of type design as the input of ground resonance and tail rotor tail beam coupling to realize accurate design of ground resonance and tail rotor tail beam coupling, and accurately predicting the stability of ground resonance and tail rotor tail beam coupling, which has high engineering value in new machine stability analysis, vibration problem troubleshooting and vibration control plan. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a flowchart of a method for obtaining body modal parameters through simulation analysis.

[0036] Figure 2 It is a schematic diagram of a dynamics model of a typical weight state and a typical lift state. DETAILED DESCRIPTION

[0037] To make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiments of the present application will be described in more detail below with reference to the drawings. In the drawings, the same or similar notations represent the same or similar elements or elements with the same or similar functions throughout. The described embodiments are part of the embodiments of the present application, not all of the embodiments. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application. The embodiments of the present application will be described in detail below with reference to the drawings.

[0038] In the description of the present application, it should be understood that the terms "center", "axial", "vertical", "upper", "lower", "upper end", "bottom end", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the scope of protection of the present application.

[0039] The present application quickly obtains modal parameters including modal mass, modal damping, modal stiffness, modal frequency, damping ratio and mode shape at key positions based on a body dynamics model on the landing gear, and selects body modal parameters for stability calculation. The basic formula designed in the present application is as follows:

[0040] The motion equation is simplified as follows:

[0041] ;

[0042] where [M], [K], [C] are mass matrix, stiffness matrix and damping matrix respectively;

[0043] After solving, the natural frequency of the system is obtained ;

[0044] The matrix composed of each order modal vector is modal matrix ;

[0045] The modal matrix composed of the contribution of each order modal to the response ;

[0046] The response of the system is written in the following form using modal coordinates:

[0047] ;

[0048] ;

[0049] ;

[0050] where K r and M r represent the rth order modal stiffness and modal mass respectively;

[0051] After solving, the relationship between modal frequency and modal stiffness and modal damping can be expressed as:

[0052] ;

[0053] From the relationship between damping ratio and damping and frequency:

[0054] .

[0055] As shown in Figure 1 , the specific steps are as follows:

[0056] [1] Based on the requirements of ground resonance and tail rotor tail beam coupling stability calculation, optimize the full aircraft dynamics model. For the calculation requirement of ground resonance, according to the performance parameters of the landing gear, the stiffness and damping parameters of the landing gear are added in the existing full aircraft dynamics model. For the requirement of tail rotor tail beam coupling stability calculation, the structural damping of the aircraft body is added in the existing full aircraft dynamics model.

[0057] [2] Based on step [1], the dynamics model of the de aircraft body on the landing gear is established, and the complex modal calculation is carried out according to the mass normalization.

[0058] 2.1 Select the dynamic model of the body on the landing gear in typical weight state and typical lift state to carry out complex modal calculation.

[0059] 2.2 Obtain the modal frequency and damping ratio of the body on the landing gear.

[0060] [3] Obtain the modal mass and mode shape according to the calculation result of step [2].

[0061] According to the use of modal parameters, the key point is generally selected as the center of the main rotor hub and the center of the tail rotor hub. If it is used as the input of ground resonance, the key point is selected as the center of the main rotor hub. If it is used as the input of tail rotor tail beam coupling stability calculation, the key point is selected as the center of the tail rotor hub.

[0062] [4] Obtain the modal mass normalized according to the mode shape of a certain key point through the modal mass; the rth order modal mass normalized according to the key point The calculation formula is:

[0063] ;

[0064] Wherein, is the rth order modal mass before conversion; is the rth order modal vector of the key point i.

[0065] [5] Obtain the modal stiffness K r through the modal mass M r ; The calculation formula of K r is:

[0066] ;

[0067] Wherein, is the rth order modal frequency.

[0068] [6] Obtain the modal damping through the damping ratio, modal mass and modal frequency; the calculation formula of the modal damping C r is:

[0069] ;

[0070] Wherein, is the rth order modal damping ratio.

[0071] [7] Obtain all the modal parameters of the typical weight state and the typical lift state according to steps [1] to [6], and carry out stability calculation.

[0072] Application example:

[0073] To prove the applicability and effectiveness of the present application, modal parameters are obtained by simulation analysis at the initial stage of design of a certain type of aircraft, and stability calculation is performed. The specific implementation is as follows.

[0074] S1: Based on the dynamic model of the body on the landing gear under the typical weight state and the typical lift state, the complex modal calculation is performed according to the mass normalization, and the modal frequency and the damping ratio of the body on the landing gear are obtained. The dynamic model of the typical weight state and the typical lift state is shown in Figure 2 , and the calculation results of the modal frequency and the damping ratio, the mass-normalized modal mass and the modal shape are shown in Table 1.

[0075] Table 1: Modal parameters obtained by simulation calculation

[0076] Mode name Mode mass (kg) Mode frequency (Hz) Damping ratio Mode shape X Mode shape Y Mode shape Z Yaw 1st order 1 0 0 0.0085 0.0000 0.0000 Lateral 1st order 1 0.5289 0.0848 0.0001 0.0140 0.0001 Yaw 2nd order 1 0.5605 0.0841 0.0055 0.0002 0.0047 Lateral 2nd order 1 3.2227 0.0989 0.0001 0.0106 0.0000

[0077] S2: According to the calculation results of step 1, the modal mass and the modal shape are obtained, and the calculation results of the modal shape are shown in Table 1.

[0078] S3: The mass-normalized modal mass is obtained according to the hub center modal shape, and the modal mass M r is obtained, and the calculation results are shown in Table 2.

[0079] Table 2: Modal parameters normalized according to the hub center

[0080] Mode name Mode mass (kg) Mode stiffness (N / m) Damping (Ns / m) Mode shape X Mode shape Y Mode shape Z Yaw 1st order 13776.84 0 0 1.00000 0.00000 0.00000 Lateral 1st order 5128.00 56641.72 2890.86 0.00668 1.00000 0.00440 Yaw 2nd order 33108.18 410636.11 19606.69 1.00000 0.04459 0.85631 Lateral 2nd order 8950.07 3669667.94 35864.54 0.00622 1.00000 0.00101

[0081] S4: The modal stiffness K r is obtained according to the modal mass M r , and the calculation results are shown in Table 2.

[0082] S5: The modal damping is obtained according to the damping ratio, the modal mass and the modal frequency, and the calculation results are shown in Table 2.

[0083] S6: According to S1-S6, the related modal parameters of the typical weight state and the typical lift state are obtained for stability calculation.

[0084] Other embodiments of the present disclosure will be readily apparent to those skilled in the art upon considering the specification and practicing the disclosure disclosed herein. This application is intended to cover any variations, uses or adaptations of the present disclosure that follow the general principles of the present disclosure and include common general knowledge or conventional technical practices in the art not specifically disclosed. The specification and examples are to be regarded only as illustrative, and the true scope and spirit of the present disclosure are indicated by the following claims.

[0085] It should be understood that the present disclosure is not limited to the precise construction that has been described above and shown in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the present disclosure. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A method for obtaining modal parameters of a machine body by simulation analysis, characterized by, The method comprises the following steps: Based on the requirements of ground resonance and tail rotor tail boom coupling stability calculation, the full aircraft dynamics model is optimized: for the ground resonance calculation requirement, the stiffness and damping parameters of the landing gear are added to the existing full aircraft dynamics model according to the performance parameters of the landing gear; for the requirement of tail rotor tail boom coupling stability calculation, the structural damping of the aircraft is added to the existing full aircraft dynamics model; For a typical state, the modal frequency, modal damping ratio, modal mass, modal shape and modal vector of the aircraft on the landing gear are obtained by performing complex modal calculation based on the dynamics model of the aircraft on the landing gear; The modal shape of a key point is obtained from the modal shape, and the modal vector of the key point is obtained from the modal vector according to the modal shape of the key point; the key point is selected as the center of the main rotor hub and the center of the tail rotor hub, if it is used as the input of the ground resonance, the center of the main rotor hub is used as the key point, if it is used as the input of the tail rotor tail boom coupling stability calculation, the center of the tail rotor hub is used as the key point; According to the modal vector of the key point, the modal mass is converted into the normalized modal mass according to the key point, so as to calculate the corresponding modal stiffness and modal damping; The method further comprises the following steps: All modal parameters of the same key point under different typical states are obtained, and stability calculation is carried out; the modal parameters of the key point include: the normalized modal mass, modal damping, modal stiffness, modal frequency, modal damping ratio and modal shape of the key point according to the key point; rth order modal mass M normalized by key point r The formula for calculating is: ； wherein, is the pre-transform modal mass; is the rth modal vector of the key point i.

2. The method of claim 1, wherein, The modal mass calculation method comprises the following steps: According to the modal frequency and modal damping ratio of the aircraft on the landing gear, the modal mass and modal shape are obtained.

3. The method of claim 1, wherein, rth order modal stiffness K normalized by key point r The calculation formula is: ； wherein, is the rth modal frequency.

4. The method of claim 3, wherein, rth order modal damping C normalized by key point r The calculation formula is: ； wherein, is the rth modal damping ratio.

5. A device for obtaining modal parameters of an organism through simulation analysis, characterized in that, The method comprises the following steps: An optimization module is configured to optimize the full aircraft dynamics model based on the requirements of ground resonance and tail rotor tail boom coupling stability calculation: for the ground resonance calculation requirement, the stiffness and damping parameters of the landing gear are added to the existing full aircraft dynamics model according to the performance parameters of the landing gear; for the requirement of tail rotor tail boom coupling stability calculation, the structural damping of the aircraft is added to the existing full aircraft dynamics model; A processing module is configured to, for a typical state, perform complex modal calculation based on the dynamics model of the aircraft on the landing gear, and obtain the modal frequency, modal damping ratio, modal mass, modal shape and modal vector of the aircraft on the landing gear; An acquisition module is configured to obtain the modal shape of a key point from the modal shape, and obtain the modal vector of the key point from the modal vector according to the modal shape of the key point; the key point is selected as the center of the main rotor hub and the center of the tail rotor hub, if it is used as the input of the ground resonance, the center of the main rotor hub is used as the key point, if it is used as the input of the tail rotor tail boom coupling stability calculation, the center of the tail rotor hub is used as the key point; A conversion module is configured to convert the modal mass into the normalized modal mass according to the modal vector of each order, so as to calculate the corresponding modal stiffness and modal damping; The acquisition module is further configured to: obtain all modal parameters of the same key point under different typical states, and carry out stability calculation; the modal parameters of the key point include: the normalized modal mass, modal damping, modal stiffness, modal frequency, modal damping ratio and modal shape of the key point according to the key point; rth order modal mass M normalized by key point r The formula for calculating is: ； wherein, is the pre-transform modal mass; is the rth modal vector of the key point i.

6. The apparatus of claim 5, wherein, The processing module is specifically configured to: The modal mass and modal shape are obtained from the modal frequencies and modal damping ratios of the airframe on the landing gear.

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