CN105480431A - Method for avoiding excessive vibration of undercarriage in overhead state - Google Patents

Abstract

The invention provides a method for avoiding excessive vibration of an undercarriage in an overhead state, which is characterized by comprising the following steps: 1, simulating the rotating excitation of an airplane wheel of the undercarriage by using an eccentric runner, wherein the frequency of the rotating excitation changes with time; 2, changing the eccentric mass M3 of the eccentric runner, and simulating the change of a vibration excitation amplitude; 3, simulating main movement rules of the undercarriage by using a 2-DOF (Degree Of Freedom) model; and 4, changing and matching mass blocks M1 and M2 and springs K1 and K2 so as to realize the design of natural vibration frequencies f1 and f2 of the first and second orders of the undercarriage structure.

Description

A kind of method avoiding the liftoff state undue oscillation of alighting gear

Technical field

The invention belongs to undercarriage dynamics design field, particularly relate to aircraft liftoff process alighting gear wheel from high speed rotating to quiescing process in, avoid wheel rotating speed to be coupled with structure frequency and occur the method for undue oscillation.

Background technology

When undercarriage is liftoff, alighting gear wheel is in high speed rotating state.If wheel rotating speed exceedes the natural frequency of aircaft configuration, when rotation decays gradually, will be coupled with structure frequency and occur resonating, cause structure undue oscillation.

When there is this phenomenon, general employing wheel braking technology, but this needs to increase braking mechanism, causes structural weight to increase.From worst aspect, if braking mechanism lost efficacy, the generation of undue oscillation still can be there is.

Summary of the invention

The object of the invention is: a kind of method avoiding the liftoff state undue oscillation of alighting gear is provided.

Technical scheme of the present invention is: 1. avoid the method for the liftoff state undue oscillation of alighting gear for one kind, it is characterized in that, comprise the following steps:

1) use eccentric runner to simulate the rotation excitation of alighting gear wheel, the frequency of rotating excitation changes in time;

2) the eccentric mass M of eccentric runner is changed ₃, the change of analog vibration excitation amplitude;

3) the main movement rule of two-freedom model simulation alighting gear is used;

4) by the mass M to mass ₁, mass mass M ₂, spring stiffness K ₁and K ₂carry out changing and mating, according to the designing requirement avoiding undue oscillation, realize second order eigentone f before landing gear structure ₁, f ₂setting:

$f_1=\frac{1}{2^{3/2}\mathrm{\π}}{\{\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2}-{[{(\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2})}^2-\frac{{4K}_1{K}_2}{M_1{M}_2}]}^{1/2}\}}^{1/2}$

$f_2=\frac{1}{2^{3/2}\mathrm{\π}}{\{\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2}-{[{(\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2})}^2-\frac{{4K}_1{K}_2}{M_1{M}_2}]}^{1/2}\}}^{1/2}$

Further, also by coupling damping g ₁and g ₂, the damping distribution character of simulation alighting gear, avoids the designing requirement of undue oscillation.

Further, also by independent or combination adjustment: the eccentric mass M reducing runner ₃, shorten runner from moving to static rundown time t, to realize the control of the undue oscillation of the liftoff state of alighting gear.

Advantage of the present invention is:

The present invention proposes a kind of method avoiding the liftoff state undue oscillation of alighting gear.The present invention is directed to complicated Landing Gear System dynamics to simplify, extract main movement rule, set up two degrees of freedom vibration analysis model.The variable-speed motion of eccentric generation is utilized to produce variant-frequency vibration excitation, the motion process after simulation alighting gear wheel is liftoff.By the adjustment of design parameters, to realize the control of the undue oscillation of the liftoff state of alighting gear.Design parameters comprises: runner eccentric mass M ₃, runner from moving to static rundown time t, mass M ₁quality, mass M ₂quality, spring K ₁rigidity, spring K ₂rigidity, damper g ₁damping coefficient, damper g ₂damping coefficient.The vibrational excitation that energy accurate simulation of the present invention produces due to wheel eccentric rotary and find the vibration fault of alighting gear, for the Landing Gear Design initial stage conceptual design and there is the Analysis on Mechanism of vibration fault.Model of the present invention is simple, computational efficiency is high.

Accompanying drawing explanation

Fig. 1 is two degrees of freedom model of vibration schematic diagram;

Fig. 2 alighting gear wheel rotational model schematic diagram;

Wherein, 1-rigid boundary, 2-runner, 3-rotary wheel frame, 4-mass M ₁, 5-spring K ₁, 6-spring K ₂, 7-damper g ₁, 8-damper g ₂, 9-rotating shaft, 10-runner eccentric mass M ₃;

Detailed description of the invention

Below in conjunction with accompanying drawing, the present invention is described in further details, refers to Fig. 1 to Fig. 2.

As shown in Figure 1, be two degrees of freedom model of vibration schematic diagram, comprise rigid boundary 1, runner 2, rotary wheel frame 3, mass 4, spring 5, damper 6 and 7, rotating shaft 9, runner eccentric mass 10.

As shown in Figure 2, be wheel rotational model schematic diagram, comprise runner 2, rotary wheel frame 3, rotating shaft 9, wheel eccentric mass 10.

Avoid a method for the liftoff state undue oscillation of alighting gear, comprising:

1, rotary wheel frame 3, runner 2, rotating shaft 9 and runner eccentric mass 10 form mass M jointly ₂;

2, wheel eccentric mass M is regulated ₃to change the amplitude of rotating excitation;

3, mass M is adjusted ₁, M ₂, spring stiffness K ₁, K ₂, second order oscillation frequency f before simulation alighting gear ₁, f ₂;

4, damper g is adjusted ₁, g ₂, the damping distribution character of simulation alighting gear;

5, apply initial speed to runner, rotating speed exceedes second order frequency peak before alighting gear, and release runner, makes rotatably mounted decay or force decay, observation quality block M ₁with the vibration of rotary wheel frame;

6, when alighting gear total mass is constant, mass M is changed ₁and M ₂proportionate relationship, or change Stiffness Distribution K ₁or K ₂, thus change alighting gear frequency f ₁and f ₂, the liftoff state undue oscillation of alighting gear can be avoided;

7, when alighting gear total mass is variable, mass distribution M is changed ₁or M ₂, or change Stiffness Distribution K ₁or K ₂, thus change alighting gear frequency f ₁and f ₂, the liftoff state undue oscillation of alighting gear can be avoided;

8, damper g is increased ₁or g ₂, the liftoff state undue oscillation of alighting gear can be avoided;

9, the eccentric mass M of runner is reduced ₃, the liftoff state undue oscillation of alighting gear can be avoided;

10, reduce runner from high speed rotating to static rundown time t, the liftoff state undue oscillation of alighting gear can be avoided.

Claims (3)

1. avoid a method for the liftoff state undue oscillation of alighting gear, it is characterized in that, comprise the following steps:

1) use eccentric runner to simulate the rotation excitation of alighting gear wheel, the frequency of rotating excitation changes in time;

2) the eccentric mass M of eccentric runner is changed ₃, the change of analog vibration excitation amplitude;

3) the main movement rule of two-freedom model simulation alighting gear is used;

4) by the mass M to mass ₁, mass mass M ₂, spring stiffness K ₁and K ₂carry out changing and mating, according to the designing requirement avoiding undue oscillation, realize second order eigentone f before landing gear structure ₁, f ₂setting:

$f_1=\frac{1}{2^{3/2}\mathrm{\π}}{\{\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2}-{[{(\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2})}^2-\frac{4K_1{K}_2}{M_1{M}_2}]}^{1/2}\}}^{1/2}$

$f_2=\frac{1}{2^{3/2}\mathrm{\π}}{\{\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2}+{[{(\frac{K_1+K_2}{M_1}+\frac{K_2}{M_2})}^2-\frac{4K_1{K}_2}{M_1{M}_2}]}^{1/2}\}}^{1/2}.$

2. the method avoiding the liftoff state undue oscillation of alighting gear according to claim 1, is characterized in that, also by coupling damping g ₁and g ₂, the damping distribution character of simulation alighting gear, avoids the designing requirement of undue oscillation.

3. the method avoiding the liftoff state undue oscillation of alighting gear according to claim 1, is characterized in that, also by independent or combination adjustment: the eccentric mass M reducing runner ₃, shorten runner from moving to static rundown time t, to realize the control of the undue oscillation of the liftoff state of alighting gear.