17 results about "Ground resonance" patented technology

The invention relates to the technical field of vibration tests, in particular to a ground resonance test suspension device and a test method. The ground resonance test suspension device is provided with a bearing frame body, a hoisting mechanism, a bearing mechanism and a suspension mechanism, the bearing frame body is composed of a bearing supporting column, a cross beam and a longitudinal beam, and the position of the cross beam can be adjusted; a bracket of the bearing mechanism is provided with a bottom beam, an auxiliary supporting beam and a supporting beam, and a flexible air cushion is arranged on the supporting beam. A flexible supporting unit of the suspension mechanism is provided with a main spring rope, an upper hanging scaffold, a lower hanging scaffold and an auxiliary spring rope, and an auxiliary spring rope connecting unit can control the state of the flexible supporting unit. The invention further provides a ground resonance test method which comprises the steps of suspension pretreatment, aircraft suspension and test, and the equivalent stiffness of the suspension mechanism can be adjusted. The aircraft suspension system can adapt to different aircraft sizes and weight distribution, and the equivalent stiffness of the whole suspension system can be adjusted to meet the test support frequency requirement.

The invention belongs to the field of structural strength design of helicopters, and relates to a method and a device for acquiring modal parameters of an airframe through simulation analysis. The method comprises the following steps: optimizing a full-aircraft dynamic model based on the requirements of ground resonance and tail rotor and tail beam coupling stability calculation; aiming at the requirement of tail rotor and tail beam coupling stability calculation, increasing the structural damping of a machine body in an existing full-machine dynamic model; for a typical state, performing complex modal calculation based on the kinetic model of the airframe on the undercarriage to obtain the modal frequency, the modal damping ratio, the modal mass, the modal shape and the modal vector of the airframe on the undercarriage; obtaining a modal shape of one key point from the modal shapes, and obtaining a modal vector of the key point from the modal vectors according to the modal shape of the key point; according to the modal vectors of the key points, the modal mass is converted into the modal mass normalized according to the key points, and therefore the corresponding modal rigidity and modal damping are calculated.

The application relates to a time domain and frequency domain mixed analysis method for ground resonance analysis when a pendulum damper fails. The method comprises the following steps: establishing a blade swing motion equation, obtaining a hub dynamics equation, combining the hub dynamics equation, applying external excitation to the blade swing motion equation to excite the response of a rotor swing back mode, removing the excitation, converting the response of the blade swing motion equation to a fixed coordinate system to obtain the attenuation response of the rotor swing back mode, performing fast Fourier transform on the attenuation response of the rotor swing back mode to obtain a response curve in the frequency domain, comparing and analyzing the frequency change of the rotor swing back mode before and after a single pendulum damper fails at a rated rotating speed, and identifying the damping of the rotor swing back mode by using a moving rectangular window method to judge the stability of the rotor swing back mode. Therefore, the result accuracy of the time domain and frequency domain mixed analysis for ground resonance when the pendulum damper fails is improved.

The invention discloses an air spring supporting system for an aircraft ground resonance test. The air spring supporting system comprises a shell, a working platform, a transmission module, a first vibration reduction module and a second vibration reduction module. The transmission module comprises a fixing ring, first to fourth sliding rods, and first to fourth pulley units. The first damping module comprises an air spring, a central connecting rod and first to fourth limiting pieces; the second vibration reduction module comprises a vibration reduction cylinder and first to fourth vibration reduction units; the first to fourth vibration reduction units are the same in structure and each comprise a guide rod, a linear bearing, a sleeve, a first fixing cylinder, a second fixing cylinder and a vibration reduction spring. Energy dissipation caused by non-linear friction can be inhibited, the dynamic stability of the system is improved, and the stability of geometric parameters in long-term use is ensured.

The invention belongs to the technical field of structural strength design of helicopters, and particularly relates to a method for acquiring sliding or running state modal parameters of a helicopter. The method comprises the following steps: drawing a change curve of an undercarriage rigidity reduction coefficient and an additional damping coefficient along with the gliding / taxiing speed and the airframe frequency and a change curve of the rigidity reduction coefficient and the airframe modal frequency under the same coordinate system to obtain an intersection point of two groups of change curves so as to obtain a variable damping coefficient of the undercarriage under different gliding / taxiing speeds; the modal parameters of the aircraft body on the undercarriage are used as input to carry out ground resonance evaluation of the sliding and running state. The requirement of rapidly and accurately evaluating the ground resonance stability of the sliding state in the initial stage of model development is met, accurate and reliable body modal parameters are provided for helicopter stability design, and the method has great significance in guaranteeing the flight safety of helicopters.

The invention relates to the technical field of aircraft vibration experiments, and discloses aircraft ground resonance test equipment with visual entrance, comprising a fixing device; the fixing device comprises a rack, a lateral supporting frame, a forward supporting frame and a ground fixing mechanism. A lifting device; the lifting device is arranged in the rack and comprises lead screw lifting mechanisms, guide mechanisms and stroke limiting mechanisms, wherein the lead screw lifting mechanisms are installed at the four corners of the rack. A driving device; the driving device is arranged below the rack; the air spring device is arranged on the supporting plate; and the supporting device is arranged above the air spring device. According to the fixing device, the foldable extra supporting frame design is adopted, the lateral supporting frame prevents the situation that the aircraft is subjected to uneven lateral stress and rolls over together with the device, and the forward supporting frame prevents the situation that the aircraft is subjected to uneven forward and backward stress and rolls over together with the device.

This invention provides a skid landing gear with adjustable stiffness, comprising: two sets of slide tube assemblies, at least two cross tube assemblies, and bolt and nut assemblies; at least two cross tube assemblies are arranged front and rear along the flight direction; the two sets of slide tube assemblies are symmetrically connected to both sides of each cross tube assembly; in each set of slide tube assemblies, a spring plate angle adjuster and a spring plate mounting joint are embedded in the rear end of the slide tube and connected to a spring plate; multiple spring plate angle adjusters configured in each set of slide tube assemblies have end tilt planes with different angles, and by replacing spring plate angle adjusters with different end tilt plane angles, the mounting angle of the spring plate mounting joint and the spring plate is adjusted, thereby adjusting the stiffness of the skid landing gear. This invention solves the problem of ground resonance in helicopters caused by changes in the stiffness of rubber parts due to poor aircraft parameter matching, excessive onboard weight, and temperature changes in existing skid landing gear.

The application belongs to the technical field of structural dynamics test aircraft ground resonance test, and particularly relates to an aircraft ground resonance test sensor arrangement visualization auxiliary device and method. The device comprises: a three-dimensional adjustable fixing bracket for installing a laser range finder and a laser projector, and adjusting the visual angle of a measurement and projection integrated system; the laser range finder is used for calibrating the marked aircraft measurement points; the laser projector is used for projecting the solved sensor positions and numbers onto the aircraft body surface; a sensor arrangement solving system is used for: according to the aircraft measurement point geometric information obtained by the laser range finder calibration and the aircraft geometric shape, solving the matching relationship between the visual angle of the measurement and projection integrated system and the aircraft, generating a three-dimensional space combination for projecting the sensor arrangement points; and solving the sensor arrangement points in the three-dimensional space combination one by one according to the test task book, and sending the solved sensor positions and numbers to the laser projector.

The application provides a swing soft tilting rotor ship surface resonance modeling and analysis method, comprising the following steps: solving a landing gear vertical load static balance equation according to a right half span dynamics model to obtain a wheel vertical load; interpolating a wheel and a bumper compression amount according to data in a first test curve and the wheel vertical load; interpolating a wheel and a bumper stiffness and damping coefficient according to the wheel and the bumper compression amount and data of a second test curve; establishing a full span dynamics model of the aircraft according to the right half span dynamics model and the wheel and the bumper stiffness and damping coefficient; performing trimming analysis on rotor control to obtain a linearized mass, stiffness and damping matrix of the full span dynamics model; and performing eigenvalue analysis on the linearized mass, stiffness and damping matrix to obtain a stability analysis result of the full span dynamics model.

The invention relates to a large and small heterogeneous coaxial dual-rotor system, belongs to the technical field of aviation aircraft design, and solves the problems that in the prior art, upper and lower rotor vibration inherent frequencies of coaxial dual rotors are close, vibration loads are amplified through resonance, and helicopter fuselage vibration and ground resonance are caused. The propeller hub is used for connecting the upper rotor wing and the lower rotor wing with the fuselage; an inner sleeve and an outer sleeve are arranged in the propeller hub and connected with the upper rotor wing and the lower rotor wing correspondingly, and opposite rotation of the upper rotor wing and the lower rotor wing is achieved. The inner sleeve and the outer sleeve are respectively connected with a power system and a control system of the aircraft through a transmission mechanism to realize rotation speed and total distance adjustment; wherein the upper rotor wing and the lower rotor wing have different radiuses; the number of the blades of the upper rotor wing and the number of the blades of the lower rotor wing range from 2 to 6; the ratio of the distance between the upper rotor wing and the lower rotor wing in the vertical direction of the rotation axis to the radius of the upper rotor wing ranges from 0.1 to 1.00.

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.

An apparatus and method of preventing ground resonance of an aircraft, in which ground resonance may be prevented by detecting vibrations caused by rotation of a rotor in the aircraft and adjusting stiffness and damping performance of a landing gear, are provided. The apparatus for preventing ground resonance of an aircraft includes a at least one sensor for monitoring rolling of a fuselage of the aircraft according to rotation of a rotor; a vibration sensing unit installed on the fuselage and detecting vibrations of the fuselage; a damper installed on the fuselage, constituting landing gear, and varying a natural frequency of the fuselage; and a control unit controlling stiffness of the damper based on a phase difference between vibration signals and the rolling of the fuselage.

The invention belongs to the field of structural strength design of helicopters, and relates to a ground resonance calculation method of a helicopter based on multi-modal coupling. The method comprises the following steps: selecting a typical weight state and a typical lift state of a certain type of aircraft, and calculating to obtain compression stiffness and compression damping of a main aircraft wheel, a tail aircraft wheel and a buffer strut; simulating compression stiffness and compression damping of the main landing gear and the tail landing gear in the full-aircraft dynamics model, and establishing the full-aircraft dynamics model on the landing gear; carrying out aircraft body complex mode calculation on the full-aircraft dynamic model on the undercarriage, and selecting six rigid body modes, modal masses, damping ratios and modal shapes of the aircraft body on a main undercarriage and a tail undercarriage from calculation results; on the basis of machine body movement, under the condition of considering two directions of the center of a propeller hub and blade shimmy movement, several modalities are combined to carry out ground resonance stability calculation. According to the method, a more real ground resonance stability curve can be obtained, and an accurate and reliable calculation method is provided for ground resonance design.

The application belongs to the field of helicopter structure strength design, and relates to a helicopter multi-modal coupling ground resonance calculation method. The method comprises the following steps: selecting a typical weight state and a typical lift state of a certain type of helicopter, and calculating the compression stiffness and compression damping of the main landing gear, the tail landing gear and the buffer strut; simulating the compression stiffness and compression damping of the main landing gear and the tail landing gear in the full machine dynamics model, and establishing the full machine dynamics model on the landing gear; performing body complex modal calculation on the full machine dynamics model on the landing gear, and selecting six rigid body modes, modal mass, damping ratio and modal shape of the body on the main landing gear and the tail landing gear from the calculation results; and on the basis of the body motion, considering the hub center two directions and the blade oscillation motion, combining several modes to perform ground resonance stability calculation. The application can obtain more real ground resonance stability curve, and provides an accurate and reliable calculation method for ground resonance design.