Torsional vibration analysis method for transmission chain torsional vibration system of bearingless rotor unmanned helicopter

Abstract

The invention belongs to the field of helicopter dynamics, and relates to a torsional vibration analysis method for a transmission chain torsional vibration system of a bearingless rotor unmanned helicopter. The method comprises the following steps: analyzing a bearingless rotor structure type and a structure connection mode thereof, and establishing a finite element analysis model of a blade of the bearingless rotor unmanned helicopter, so as to define an equivalent shimmy hinge position; based on the finite element analysis model and the equivalent shimmy hinge position, the shimmy modal frequency and the vibration mode of the isolated blade are obtained; analyzing the scheme of the power / transmission system of the bearingless rotor unmanned helicopter, and establishing a finite element analysis model of the power / transmission system so as to obtain the torsional vibration frequency and vibration mode of the power / transmission system; a rotor system composed of several bearingless rotor unmanned helicopter blades serves as a subsystem, a power / transmission system serves as a subsystem, finite element analysis models of the two subsystems are coupled at a main propeller hub, and the inherent characteristics of the rotor / power / transmission system in the coupled state are obtained; the result is the torsional vibration calculation result of the transmission chain torsional vibration system.

Description

Technical Field

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

[0002] The power transmission system composed of helicopter rotor / power / transmission, referred to as the power transmission chain, is an important aspect of helicopter dynamic design. It is necessary to solve the problem of the coupling dynamic stability of the transmission chain torsional vibration and the rotor and engine control system through special analysis and experiments. On the one hand, the main exciting force of the power transmission system is the alternating torque of the rotor. When the frequency of the exciting force is close to or even coincides with the natural frequency of the system, the system will be in danger of resonance, which will not only affect the premature fatigue damage of the helicopter torsional vibration system related structures and helicopter vibration, but also affect the safety of flight personnel in severe cases. The coupled dynamic stability problem of the rotor system requires that the natural frequency of the transmission chain torsional vibration is far enough away from the rotor pass frequency and its multiples; on the other hand, the coupled dynamic stability of the engine electronic control system requires that the control system will not cause the rotor speed (or engine power turbine speed) and its torque to fluctuate or even diverge during the control of the engine power or speed. Summary of the invention

[0003] Purpose of the invention: The torsional vibration analysis method of the transmission chain torsional vibration system of the bearingless rotor unmanned helicopter can be used for the torsional vibration analysis of the current domestic bearingless rotor unmanned helicopter, and provide guidance for the helicopter dynamics design.

[0004] Technical solution:

[0005] A torsional vibration analysis method for a transmission chain torsional vibration system of a bearingless rotor unmanned helicopter is provided, comprising:

[0006] Analyze the bearingless rotor structure type and its structural connection mode, establish a finite element analysis model of the bearingless rotor unmanned helicopter blade, and define the equivalent flap hinge position; based on the finite element analysis model and the equivalent flap hinge position, obtain the flap modal frequency and vibration shape of the isolated blade;

[0007] Analyze the power / transmission system of the bearingless rotor unmanned helicopter, establish the finite element analysis model of the power / transmission system, and obtain the torsional vibration frequency and vibration mode of the power / transmission system;

[0008] The rotor system composed of several bearingless rotor unmanned helicopter blades is taken as a subsystem, and the power / transmission system is taken as a subsystem. The finite element analysis models of the two subsystems are coupled at the main hub to obtain the inherent characteristics of the rotor / power / transmission system in the coupled state, that is, the torsional vibration calculation results of the transmission chain torsional vibration system; the torsional vibration calculation results of the transmission chain torsional vibration system give preliminary analysis conclusions and test frequencies, which provide a reference for the experiments in the subsequent detailed design.

[0009] Furthermore, the coupling considers the first two flap modes of the rotor and all modes of the power / transmission system.

[0010] Furthermore, the equivalent swing hinge position is defined, including:

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

[0012] Furthermore, stiffness parallel and series methods are used to process stiffness of different units, including:

[0013] The equivalent stiffness of the hub is connected in series with the unit where the flexible beam is exposed from the sleeve, the unit where the flexible beam is sleeved in the sleeve and the unit where the sleeve wraps the flexible beam are connected in parallel, and the remaining units of the sleeve are connected in series with the units connected to the root of the blade.

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

[0015] Analyze the power / transmission system scheme of bearingless rotor unmanned helicopter, and obtain the speed, torsional stiffness and moment of inertia of each component of the power / transmission system;

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

[0017] Furthermore, the bearingless rotor structure type and its structural connection method are analyzed, and a finite element analysis model of the bearingless rotor unmanned helicopter blade is established, including:

[0018] Analyze the bearingless rotor structure type and structural connection method of the bearingless rotor unmanned helicopter to obtain the overall parameters of the rotor;

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

[0020] Further, the rotor includes blades, flexible beams, sleeves, dampers, hub centerpieces and automatic tilt mechanism assemblies.

[0021] Beneficial effects: According to the characteristics of a bearingless rotor unmanned helicopter, an exploratory torsional vibration analysis method for the torsional vibration system of the transmission chain of a bearingless rotor unmanned helicopter is proposed, which can effectively guide the design in the initial development stage and the later test planning, avoid increasing the risks of subsequent tests and design status, and eliminate the torsional vibration of the transmission chain of the bearingless rotor unmanned helicopter and its coupling dynamic stability problems with the engine electronic control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the blade analysis model diagram.

[0023] Figure 2 It is the vibration mode diagram of isolated blade.

[0024] Figure 3 It is the power / transmission system analysis model diagram. DETAILED DESCRIPTION

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

[0026] Step 1: Analyze the bearingless rotor structure type and main structural connection mode of the bearingless rotor unmanned helicopter, and obtain the overall parameters of the main rotor, including blades, flexible beams, sleeves, dampers, hub centerpieces and automatic tilt device components;

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

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

[0029] Stiffness equivalence principle: consider the blade as a rigid blade with a flap hinge, assume an overhang of the flap hinge, define the blade backswing as positive, and ignore the influence of the blade flap motion on the blade rotation speed. According to the small angle assumption, the blade is balanced under the action of centrifugal force, inertial force and aerodynamic force, and the blade flap motion equation is obtained. According to the extension line of the first-order vibration mode curve, the position of the equivalent flap hinge is obtained.

[0030] Step 3: Based on the established finite element analysis model of the bearingless rotor unmanned helicopter blade, obtain the swing modal frequency and vibration shape of the isolated blade.

[0031] Step 4: Analyze the power / transmission system of the bearingless rotor unmanned helicopter and obtain the rotation speed, torsional stiffness and moment of inertia of each component of the power / transmission system;

[0032] Step 5: According to the power / transmission system scheme, a finite element analysis model of the power / transmission system is established. The system is simplified into nodes with only rotational inertia and torsion elements with only torsional stiffness, and quantization is performed. 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 powertrain are simplified as follows: Figure 3 The torsional stiffness and moment of inertia of each unit of the model are shown in Table 1.

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

[0035] Node Number symbol Equivalent moment of inertia Twist Yuan No. symbol Equivalent torsional stiffness 1 <![CDATA[I MH ]]> <![CDATA[0.02kg.m 2 ]]> 1 <![CDATA[K MR ]]> 3.59E+05N.m / rad 2 <![CDATA[I MG ]]> <![CDATA[2.06kg.m 2 ]]> 2 <![CDATA[K E ]]> 7.73E+07N.m / rad 3 <![CDATA[I E ]]> <![CDATA[87.47kg.m 2 ]]> 3 <![CDATA[K S ]]> 9.79E+04N.m / rad 4 <![CDATA[I TG ]]> <![CDATA[0.28kg.m 2 ]]> 4 <![CDATA[K TR ]]> 9.97E+05N.m / rad 5 <![CDATA[I TR ]]> <![CDATA[18.59kg.m 2 ]]>

[0036] in:

[0037] 1) After the model is simplified, it consists of nodes with only rotational inertia and torsion elements with only torsional stiffness;

[0038] 2) Simplify gears and other components into nodes with only rotational inertia, where the stiffness of the gears is incorporated into the stiffness of the connected shafts;

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

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

[0041] 5) The engine node mainly refers to the engine power turbine part, taking into account the rotational inertia of the power shaft;

[0042] 6) The tail reducer node includes the tail reducer input and output gears, tail transmission shaft, related flanges, etc.

[0043] Step 6: Based on the established finite element analysis model of the power / transmission system, perform inherent characteristic analysis of the power / transmission system to obtain the torsional vibration frequency and vibration mode of the power / transmission system.

[0044] Step 7: Using the modal synthesis method, the rotor system is taken as a subsystem, the power / transmission system is taken as a subsystem, the two subsystems are coupled at the main hub, the rotor considers the first two swing modes and the power / transmission system takes all modes, and the inherent characteristics of the coupled rotor / power / transmission system are obtained; the rotor system is composed of several bearingless rotor unmanned helicopter blades;

[0045] Step 8: Analyze the torsional vibration calculation results of the transmission chain torsional vibration system of a bearingless rotor unmanned helicopter, give preliminary analysis conclusions and test frequencies, and provide reference for subsequent detailed design tests.

[0046] Example:

[0047] The present invention is further described in detail below by taking the torsional vibration analysis of a transmission chain torsional vibration system of a bearingless rotor unmanned helicopter as an example:

[0048] The first step is to establish a finite element analysis model of the blade. The flexible beam, sleeve, blade, damper and torque-converting arm are simplified into a finite number of units. The coordination between the structural units is handled according to the force transmission route and coordination relationship as well as the series and parallel relationship of stiffness. The finite element model of the blade is as follows: Figure 1 As shown;

[0049] Step 2: Based on the established blade analysis model, perform isolated blade modal analysis to obtain the swing modal frequencies of isolated blades under different lift conditions as shown in Table 2, and the vibration modes as shown in Table 2. Figure 2 ;

[0050] Table 2 Isolated blade swing modal frequencies

[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 inherent characteristics of the dynamic system are analyzed, and the torsional vibration frequency and vibration mode of the power / transmission system are obtained as shown in Table 3;

[0053] Table 3 Calculation results of inherent characteristics of power / transmission system

[0054]

[0055] Step 5: Using the modal synthesis method, the rotor system is taken as a subsystem, the power / transmission system is taken as a subsystem, the two subsystems are coupled at the main hub, the rotor considers the first two swing modes, and the power / transmission system takes all modes for modal synthesis; the inherent characteristics of the coupled rotor / power / transmission system are obtained. Table 3 shows the calculation results of one state;

[0056] Table 3 Intrinsic characteristics of torsional vibration in coupled state (100% speed, 100% lift)

[0057]

[0058] Step 6: Based on the calculation results of the inherent characteristics of the transmission chain torsional vibration system of a certain bearingless rotor unmanned helicopter coupled with the front and rear rotors / power / transmission systems, it is analyzed to determine whether there is a dynamic stability problem of the transmission chain torsional vibration coupled with the rotor and the engine adjustment system of a certain bearingless rotor unmanned helicopter, and subsequent test guidance is given.

Claims

1. A torsional vibration analysis method for a bearingless rotor unmanned helicopter transmission chain torsional vibration system, characterized in that: include: Analyze the bearingless rotor structure and its structural connection mode, establish the finite element analysis model of the bearingless rotor unmanned helicopter blade, and define the equivalent flap hinge position; Based on the finite element analysis model and the equivalent flap hinge position, the flap modal frequency and vibration shape of the isolated blade are obtained; Analyze the power / transmission system of the bearingless rotor unmanned helicopter, establish the finite element analysis model of the power / transmission system, and obtain the torsional vibration frequency and vibration mode of the power / transmission system; The rotor system composed of several bearingless rotor unmanned helicopter blades is taken as a subsystem, and the power / transmission system is taken as a subsystem. The finite element analysis models of the two subsystems are coupled at the main hub to obtain the inherent characteristics of the rotor / power / transmission system in the coupled state, that is, the torsional vibration calculation results of the transmission chain torsional vibration system; the torsional vibration calculation results of the transmission chain torsional vibration system give preliminary analysis conclusions and test frequencies, which provide a reference for the experiments in the subsequent detailed design.

2. The method according to claim 1, characterized in that The coupling considers the first two swing modes of the rotor and all modes of the power / transmission system.

3. The method according to claim 1, characterized in that Define the equivalent swing hinge position, including: The isolated blade is divided into several units from the hub center to the blade tip. The stiffness of different units is processed by stiffness parallel and series methods. The stiffness of the isolated blade unit is calculated and the unit mass is calculated according to the mass distribution. According to the stiffness equivalence principle, the equivalent flap hinge position is defined.

4. The method according to claim 3, characterized in that The stiffness of different units is processed by using stiffness parallel and series methods, including: The equivalent stiffness of the hub is connected in series with the unit where the flexible beam is exposed from the sleeve, the unit where the flexible beam is sleeved in the sleeve and the unit where the sleeve wraps the flexible beam are connected in parallel, and the remaining units of the sleeve are connected in series with the units connected to the root of the blade.

5. The method according to claim 4, characterized in that Analyze the power / transmission system of the bearingless rotor unmanned helicopter and establish the finite element analysis model of the power / transmission system, including: Analyze the power / transmission system scheme of bearingless rotor unmanned helicopter, and obtain the speed, torsional stiffness and moment of inertia of each component of the power / transmission system; According to the power / transmission system scheme, a finite element analysis model of the power / transmission system is established, and the system is simplified into nodes with only rotational inertia and torsion elements with only torsional stiffness, and quantization is performed.

6. The method according to claim 1, characterized in that Analyze the bearingless rotor structure and its structural connection method, and establish a finite element analysis model of the bearingless rotor unmanned helicopter blade, including: Analyze the bearingless rotor structure type and structural connection method of the bearingless rotor unmanned helicopter to obtain the overall parameters of the rotor; According to the bearingless rotor structure type, structural connection mode and overall rotor parameters, a finite element analysis model of the bearingless rotor unmanned helicopter blade is established.

7. The method according to claim 1, characterized in that The rotor consists of blades, flex beams, sleeves, dampers, hub centerpiece and automatic tilter assembly.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

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