A torsional vibration analysis method for a bearingless rotor unmanned helicopter transmission chain torsional vibration system

Abstract

The present application belongs to the field of helicopter dynamics, and relates to a torsional vibration analysis method for a bearingless rotor unmanned helicopter transmission chain torsional vibration system. The method comprises: analyzing the structure type and structure connection mode of the bearingless rotor, establishing a bearingless rotor unmanned helicopter blade finite element analysis model, thereby defining the equivalent flapping hinge position; based on the finite element analysis model and the equivalent flapping hinge position, obtaining the flapping modal frequency and mode shape of the isolated blade; analyzing the scheme of the bearingless rotor unmanned helicopter power / transmission system, establishing a power / transmission system finite element analysis model, thereby obtaining the power / transmission system torsional vibration frequency and mode shape; regarding the rotor system composed of several bearingless rotor unmanned helicopter blades as a subsystem, regarding the power / transmission system as a subsystem, coupling the finite element analysis models of the two subsystems at the main hub, obtaining the inherent characteristics of the coupled state rotor / power / transmission system, i.e. the torsional vibration calculation result of the transmission chain torsional vibration system.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of helicopter dynamics, and relates to a torsional vibration analysis method for a bearingless rotor unmanned helicopter transmission chain torsional vibration system. BACKGROUND

[0002] The power transmission system composed of the helicopter rotor / power / transmission, referred to as the power transmission chain, is an important aspect of helicopter dynamics design, and needs to solve the transmission chain torsional vibration and the rotor and the engine regulation system coupling dynamic stability problems through special analysis and test. On the one hand, the main excitation force of the power transmission system is the alternating torque of the rotor. When the frequency of the excitation force is close to or even coincides with the natural frequency of the system, the system will be in resonance danger, which will not only affect the advance fatigue damage of the relevant structure of the helicopter torsional vibration system and the helicopter vibration, but also will affect the flight personnel safety in serious cases. The rotor system coupling dynamic stability problem requires that the transmission chain torsional vibration natural frequency is far away from the rotor passing frequency and its multiple frequency; on the other hand, the engine electric regulation system coupling dynamic stability requires that the control process of the control system to the engine power or speed will not cause the rotor speed (or engine power turbine speed) and its torque to fluctuate greatly or even diverge. SUMMARY

[0003] The application aims to provide the torsional vibration analysis method for the bearingless rotor unmanned helicopter transmission chain torsional vibration system, which can be used for the torsional vibration analysis of the current domestic bearingless rotor unmanned helicopter and provide a guidance direction for the helicopter dynamics design.

[0004] TECHNICAL SCHEME

[0005] The application provides a torsional vibration analysis method for a bearingless rotor unmanned helicopter transmission chain torsional vibration system, which comprises the following steps:

[0006] analyzing a bearingless rotor structure type and a structure connection mode thereof, establishing a bearingless rotor unmanned helicopter blade finite element analysis model, and thereby defining an equivalent flapping hinge position;

[0007] analyzing a bearingless rotor unmanned helicopter power / transmission system scheme, establishing a power / transmission system finite element analysis model, and thereby obtaining power / transmission system torsional vibration frequency and mode;

[0008] regarding a rotor system composed of several bearingless rotor unmanned helicopter blades as a subsystem, regarding the power / transmission system as a subsystem, coupling the finite element analysis models of the two subsystems at a main rotor hub, obtaining inherent characteristics of the coupled state rotor / power / transmission system, i.e., transmission chain torsional vibration system torsional vibration calculation results; the transmission chain torsional vibration system torsional vibration calculation results give a preliminary analysis conclusion and a test frequency, which provide a reference for a subsequent test in detailed design.

[0009] Further, the coupling considers the first two order of the flapping mode and the total mode of the power / transmission system.

[0010] Further, the equivalent flapping hinge position is defined, including:

[0011] The isolated blade is divided into several units from the hub center to the blade tip, and the stiffness of different units is handled by the stiffness parallel and series method, the isolated blade unit stiffness is calculated, and the unit mass is calculated according to the mass distribution, and the equivalent flapping hinge position is defined according to the stiffness equivalence principle.

[0012] Further, the stiffness of different units is handled by the stiffness parallel and series method, including:

[0013] The equivalent stiffness of the hub is handled by the stiffness series with the units exposed to the sleeve of the flexible beam, the units of the flexible beam sleeve in the sleeve are handled by the stiffness parallel with the units of the flexible beam covered by the sleeve, and the remaining units of the sleeve are handled by the stiffness series with the units connected to the blade root.

[0014] Further, the scheme of the power / transmission system of the bearingless rotor unmanned helicopter is analyzed, and the finite element analysis model of the power / transmission system is established, including:

[0015] The scheme of the power / transmission system of the bearingless rotor unmanned helicopter is analyzed, and the rotation speed, torsional stiffness and moment of inertia of each component of the power / transmission system are obtained;

[0016] According to the scheme of the power / transmission system, the finite element analysis model of the power / transmission system is established, the system is simplified into nodes with only moment of inertia and torsional elements with only torsional stiffness, and is equivalent.

[0017] Further, the structure type and structure connection mode of the bearingless rotor are analyzed, and the finite element analysis model of the blade of the bearingless rotor unmanned helicopter is established, including:

[0018] The structure type and structure connection mode of the bearingless rotor of the bearingless rotor unmanned helicopter are analyzed, and the overall parameters of the rotor are obtained;

[0019] According to the structure type and structure connection mode of the bearingless rotor and the overall parameters of the rotor, the finite element analysis model of the blade of the bearingless rotor unmanned helicopter is established.

[0020] Further, the rotor includes a blade, a flexible beam, a sleeve, a damper, a hub central part and an automatic tilt assembly.

[0021] Beneficial effects: A bearingless rotor unmanned helicopter transmission chain torsional vibration system torsional vibration analysis method is exploratively proposed according to the characteristics of a bearingless rotor unmanned helicopter, which can effectively guide the design in the initial development stage and the test planning in the later stage, avoid increasing the risk of subsequent test and design state, and eliminate the bearingless rotor unmanned helicopter transmission chain torsional vibration and the coupling dynamic stability problem of the engine electric governor system. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a blade analysis model diagram.

[0023] Figure 2 is an isolated blade whirling mode shape diagram.

[0024] Figure 3 is a power transmission system analysis model diagram. DETAILED DESCRIPTION

[0025] The application provides a bearingless rotor unmanned helicopter transmission chain torsional vibration system torsional vibration analysis method, comprising the following steps:

[0026] Step 1: analyze the bearingless rotor unmanned helicopter bearingless rotor structure type and main structure connection mode, obtain the main rotor overall parameters, including blades, flexible beams, sleeves, dampers, hub central components and automatic tilting components;

[0027] Step 2: establish a bearingless rotor unmanned helicopter blade finite element analysis model, divide the isolated blade from the hub center to the blade tip into a plurality of units, calculate the isolated blade unit stiffness according to the stiffness parallel and series method, and calculate the unit mass according to the mass distribution, and define the equivalent whirling hinge position according to the stiffness equivalent principle;

[0028] As shown in Figure 1 , the equivalent stiffness of the hub is in series with the stiffness of the exposed section of the flexible beam in the sleeve, the section of the flexible beam in the sleeve is in parallel with the section of the sleeve covering the flexible beam, and the remaining section of the sleeve is in series with the hub root connection unit.

[0029] Stiffness equivalent principle: the blade is considered as a rigid blade with a whirling hinge, a whirling hinge extension is assumed, the blade after swing is defined as positive, the influence of the blade whirling motion on the blade rotation speed is not considered, the small angle assumption is made, the blade is balanced under the action of centrifugal force, inertia force and aerodynamic force, the whirling motion equation of the blade is obtained, and the position of the equivalent whirling hinge is obtained according to the first-order mode curve extension line.

[0030] Step 3: based on the established bearingless rotor unmanned helicopter blade finite element analysis model, obtain the whirling mode frequency and mode shape of the isolated blade.

[0031] Fourth step: analyze the scheme of the power transmission system of the bearingless rotor unmanned helicopter, and obtain the rotating speed, torsional stiffness and moment of inertia of each component of the power transmission system;

[0032] Fifth step: according to the scheme of the power transmission system, establish a finite element analysis model of the power transmission system, which is simplified into nodes with only moment of inertia and torsional elements with only torsional stiffness, and is equivalent; this step must include the hub node, which is the interface between the rotor subsystem and the power transmission subsystem;

[0033] The torsional stiffness and moment of inertia of each component in the power transmission system are simplified into a model as shown in Figure 3 Table 1 shows the torsional stiffness and moment of inertia of each unit,

[0034] Table 1 Finite element model of power transmission system

[0035] Node number Symbol Equivalent rotational inertia Torsional element number Symbol Equivalent torsional stiffness 1 I MH ]] 0.02 kg.m 2 ]] 1 K MR ]]> 3.59E+05 N.m / rad 2 I MG ]] 2.06 kg.m 2 ]] 2 K E ]]> 7.73E+07 N.m / rad 3 I E ]] 87.47 kg.m 2 ]] 3 K S ]]> 9.79E+04 N.m / rad 4 I TG ]] 0.28 kg.m 2 ]] 4 K TR ]]> 9.97E+05 N.m / rad 5 I TR ]]> 18.59 kg.m 2 ]]>

[0036] Wherein:

[0037] 1) After model simplification, it is composed of nodes with only moment of inertia and torsional elements with only torsional stiffness;

[0038] 2) Simplify gears and the like into nodes with only moment of inertia, wherein the stiffness of the gears is combined into the stiffness of the connected shaft;

[0039] 3) Simplify the shaft into a torsional element with only torsional stiffness;

[0040] 4) The main reduction node includes the sun gear, planetary gear and gear carrier, rotor shaft, double bevel gear, input gear, related flange, etc.;

[0041] 5) The engine node mainly refers to the power turbine part of the engine, considering the moment of inertia of the power shaft;

[0042] 6) The tail reduction gear node includes the tail reduction input and output gear, tail transmission shaft, related flange, etc.

[0043] Sixth step: based on the established finite element analysis model of the power transmission system, analyze the inherent characteristics of the power transmission system, and obtain the torsional vibration frequency and mode of the power transmission system.

[0044] Seventh step: using modal synthesis method, the rotor system is taken as a subsystem and the power transmission system is taken as a subsystem, the two subsystems are coupled at the main hub, the rotor considers the first two order modes of the rotor system and the power transmission system takes all the modes, and the inherent characteristics of the coupled rotor / power transmission system are obtained; the rotor system is composed of several blades of the bearingless rotor unmanned helicopter.

[0045] The eighth step is to analyze the torsional vibration calculation results of the transmission chain torsional vibration system of the bearingless rotor unmanned helicopter, and give the preliminary analysis conclusion and test frequency, which provides the reference for the subsequent detailed design test.

[0046] Embodiment:

[0047] The bearingless rotor unmanned helicopter transmission chain torsional vibration system is taken as an example to further illustrate the application:

[0048] The first step is to establish a blade finite element analysis model, and the flexible beam, sleeve, blade, damper and variable torque support arm are simplified as a finite number of units. The coordination between each structural unit is processed according to the force transmission route and coordination relationship, and the stiffness series and parallel relationship. The finite element model of the blade is as shown in Figure 1 ;

[0049] The second step is to perform isolated blade modal analysis based on the established blade analysis model to obtain the isolated blade's wobble modal frequency under different lift conditions as shown in Table 2, and the vibration mode as shown in Figure 2 ;

[0050] Table 2 Isolated blade wobble modal frequency

[0051] State 1st order frequency / Ω 2nd order frequency / Ω 100% speed 0% lift 0.82 6.53 100% speed 100% lift 0.76 6.53

[0052] The dynamic system inherent characteristic analysis obtains the power / drive system torsional vibration frequency and vibration mode as shown in Table 3.

[0053] Table 3 Power / drive system inherent characteristic calculation results

[0054]

[0055] The fifth step is to use the modal synthesis method, take the rotor system as a subsystem, and take the power / drive system as a subsystem. The two subsystems are coupled at the main rotor hub. The rotor considers the first two wobble modes, and the power / drive system takes all the modes to perform modal synthesis. The coupled state rotor / power / drive system inherent characteristics are obtained. The calculation results of one state are shown in Table 3.

[0056] Table 3 Coupled state torsional vibration inherent characteristics (100% speed, 100% lift)

[0057]

[0058] The sixth step is to analyze the coupled rotor / power / drive system inherent characteristic calculation results of the bearingless rotor unmanned helicopter transmission chain torsional vibration system before and after the coupling, to determine whether the bearingless rotor unmanned helicopter has the transmission chain torsional vibration and the rotor and engine regulation system coupling dynamic stability problem, and to give the subsequent test guidance.

Claims

1. A method of torsional vibration analysis of a bearingless rotor unmanned helicopter drive train torsional vibration system, characterized by, Comprising: Analyzing the structure type and connection mode of the bearingless rotor, establishing the finite element analysis model of the bearingless rotor unmanned helicopter blade, so as to define the equivalent flapping hinge position; Based on the finite element analysis model and the equivalent flapping hinge position, the flapping modal frequency and mode of the isolated blade are obtained; the scheme of the power / drive system of the bearingless rotor unmanned helicopter is analyzed, and the finite element analysis model of the power / drive system is established, so as to obtain the torsional vibration frequency and mode of the power / drive system; The rotor system composed of several bearingless rotor unmanned helicopter blades is taken as a subsystem, the power / drive system is taken as a subsystem, and the finite element analysis models of the two subsystems are coupled at the main hub, so as to obtain the inherent characteristics of the coupled rotor / power / drive system, i.e. the torsional vibration calculation result of the drive chain torsional vibration system; the torsional vibration calculation result of the drive chain torsional vibration system gives the preliminary analysis conclusion and test frequency, which provides a reference for the subsequent test in the detailed design; Defining the equivalent flapping hinge position, comprising: The isolated blade is divided into several units from the center of the hub to the blade tip, the stiffness of different units is handled by the stiffness parallel and series method, the unit stiffness of the isolated blade is calculated, and the unit mass is calculated according to the mass distribution; the equivalent flapping hinge position is defined according to the stiffness equivalent principle; The stiffness of different units is handled by the stiffness parallel and series method, comprising: The equivalent stiffness of the hub is handled in series with the unit of the flexible beam exposed to the sleeve, the unit of the flexible beam sleeve in the sleeve is handled in parallel with the unit of the sleeve covering the flexible beam, and the remaining unit of the sleeve is handled in series with the unit connected to the blade root; Analyzing the scheme of the power / drive system of the bearingless rotor unmanned helicopter, establishing the finite element analysis model of the power / drive system, comprising: Analyzing the scheme of the power / drive system of the bearingless rotor unmanned helicopter, obtaining the rotating speed, torsional stiffness and moment of inertia of each component of the power / drive system; According to the scheme of the power / drive system, the finite element analysis model of the power / drive system is established, which is simplified into nodes with only moment of inertia and torsional elements with only torsional stiffness, and is equivalent; Analyzing the structure type and connection mode of the bearingless rotor, establishing the finite element analysis model of the bearingless rotor unmanned helicopter blade, comprising: Analyzing the structure type and connection mode of the bearingless rotor of the bearingless rotor unmanned helicopter, obtaining the overall parameters of the rotor; According to the structure type and connection mode of the bearingless rotor and the overall parameters of the rotor, the finite element analysis model of the bearingless rotor unmanned helicopter blade is established.

2. The method of claim 1, wherein, The first two flapping modes of the rotor and all the modes of the power / drive system are considered in coupling.

3. The method of claim 1, wherein, The rotor includes blades, flexible beams, sleeves, dampers, hub central components and automatic tilt components.

4. A computer-readable storage medium storing a computer program, the computer program comprising instructions that, when executed by a computer, cause the computer to perform the method of any one of claims 1 to 3. The computer program is executed by a processor to implement the method of any one of claims 1-3.

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